3305 files changed, 82154 insertions, 38192 deletions

diff --git a/spec/ruby/.mspec.constants b/spec/ruby/.mspec.constants
index 00198eb944..4da3633715 100644
--- a/spec/ruby/.mspec.constants
+++ b/spec/ruby/.mspec.constants
@@ -39,8 +39,11 @@ CodingUS_ASCII
 CodingUTF_8
 ComparisonTest
 ConstantSpecsIncludedModule
+ConstantSpecsTwo
+ConstantSpecsThree
 ConstantVisibility
 Coverage
+CoverageSpecs
 CustomArgumentError
 DRb
 DRbIdConv
@@ -55,6 +58,7 @@ DefSpecsLambdaVisibility
 DefineMethodByProcClass
 DefineMethodSpecClass
 DefineSingletonMethodSpecClass
+Delegator
 DescArray
 DescObjectTest
 Digest
@@ -71,6 +75,7 @@ EvalBindingProcA
 Exception2MessageMapper
 ExceptionForMatrix
 Fcntl
+Fiddle
 FileStat
 FileUtils
 Find
@@ -141,6 +146,7 @@ Prime
 Private
 ProcFromMethod
 Psych
+RactorLocalSingleton
 REXML
 RUBY_SIGNALS
 RbReadline
@@ -148,8 +154,10 @@ Readline
 ReceiverClass
 RegexpSpecsSubclass
 RegexpSpecsSubclassTwo
+Reline
 RescueInClassExample
 Resolv
+Ripper
 SHA1Constants
 SHA256Constants
 SHA384Constants
@@ -161,6 +169,7 @@ SecondClass
 SecureRandom
 Set
 Shellwords
+SimpleDelegator
 SingleForwardable
 Singleton
 Socket
@@ -171,6 +180,7 @@ SpecificExampleException
 Specs
 StrChild
 StrangeEach
+StringIO
 StringRefinement
 StringScanner
 StringSubclass
@@ -187,6 +197,7 @@ TimeoutError
 UDPSocket
 UNIXServer
 UNIXSocket
+URI
 UnaryMinusTest
 UnicodeNormalize
 UnloadableDumpableDir
@@ -194,6 +205,7 @@ UserArray
 UserCustomConstructorString
 UserDefined
 UserDefinedImmediate
+UserDefinedString
 UserDefinedWithIvar
 UserHash
 UserHashInitParams
diff --git a/spec/ruby/.rubocop.yml b/spec/ruby/.rubocop.yml
index cc31ff50b3..0b59a11512 100644
--- a/spec/ruby/.rubocop.yml
+++ b/spec/ruby/.rubocop.yml
@@ -1,20 +1,29 @@
 inherit_from: .rubocop_todo.yml
 
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 3.2
   DisplayCopNames: true
   Exclude:
     - command_line/fixtures/bad_syntax.rb
+    - core/exception/fixtures/syntax_error.rb
   DisabledByDefault: true
+  NewCops: disable
+
+Layout/IndentationConsistency:
+  Enabled: true
 
 Layout/TrailingWhitespace:
   Enabled: true
 
-Layout/TrailingBlankLines:
+Layout/TrailingEmptyLines:
   Enabled: true
   Exclude:
     - library/coverage/fixtures/some_class.rb
 
+Layout/SpaceInLambdaLiteral:
+  Enabled: true
+  EnforcedStyle: require_space
+
 Lint:
   Enabled: true
 
@@ -28,16 +37,31 @@ Lint/AssignmentInCondition:
 Lint/BooleanSymbol:
   Enabled: false
 
+Lint/DeprecatedOpenSSLConstant:
+  Exclude:
+    - library/openssl/digest/**/*.rb
+
 Lint/InterpolationCheck:
   Enabled: false
 
 Lint/LiteralAsCondition:
   Enabled: false
 
-Lint/UnneededRequireStatement:
+# Required to support Ruby 3.0
+Lint/RedundantRequireStatement:
+  Exclude:
+    - core/fiber/**/*.rb
+    - library/fiber/**/*.rb
+    - optional/capi/fiber_spec.rb
+
+Lint/RedundantSafeNavigation:
+  Exclude:
+    - language/safe_navigator_spec.rb
+
+Lint/RedundantSplatExpansion:
   Enabled: false
 
-Lint/UnneededSplatExpansion:
+Lint/RescueException:
   Enabled: false
 
 Lint/UnifiedInteger:
@@ -52,12 +76,58 @@ Lint/UnusedMethodArgument:
 Lint/UselessAssignment:
   Enabled: false
 
-Lint/UselessComparison:
+Lint/BinaryOperatorWithIdenticalOperands:
   Enabled: false
 
+Lint/EmptyConditionalBody:
+  Enabled: false # buggy
+
 Lint/Void:
   Enabled: false
 
+Lint/ConstantDefinitionInBlock:
+  Enabled: false
+
+Lint/RaiseException:
+  Enabled: false
+
+Lint/FloatComparison:
+  Enabled: false
+
+Lint/DeprecatedClassMethods:
+  Enabled: false
+
+Lint/UnreachableLoop:
+  Enabled: false
+
+Lint/MissingSuper:
+  Enabled: false
+
+Lint/UselessMethodDefinition:
+  Enabled: false
+
+Lint/UselessTimes:
+  Enabled: false
+
+Lint/MixedRegexpCaptureTypes:
+  Enabled: false
+
+Lint/DuplicateElsifCondition:
+  Enabled: false
+
+Lint/OutOfRangeRegexpRef:
+  Enabled: false
+
+Lint/InheritException:
+  Enabled: false
+
+Lint/SafeNavigationChain:
+  Enabled: false
+
+Lint/ElseLayout:
+  Exclude:
+    - 'language/if_spec.rb'
+
 Lint/EmptyExpression:
   Exclude:
     - 'language/**/*.rb'
@@ -67,6 +137,10 @@ Lint/EmptyWhen:
     - language/case_spec.rb
     - optional/capi/spec_helper.rb
 
+Lint/ErbNewArguments:
+  Exclude:
+    - 'library/erb/new_spec.rb'
+
 Lint/FormatParameterMismatch:
   Exclude:
     - 'core/kernel/shared/sprintf.rb'
@@ -77,12 +151,21 @@ Lint/NestedMethodDefinition:
     - language/def_spec.rb
     - language/fixtures/def.rb
 
+Lint/ShadowingOuterLocalVariable:
+  Exclude:
+    - 'core/binding/local_variables_spec.rb'
+    - 'core/kernel/local_variables_spec.rb'
+    - 'language/block_spec.rb'
+    - 'language/proc_spec.rb'
+
 Lint/UnreachableCode:
   Exclude:
     - 'core/enumerator/lazy/fixtures/classes.rb'
     - 'core/kernel/catch_spec.rb'
+    - 'core/kernel/raise_spec.rb'
     - 'core/kernel/throw_spec.rb'
     - 'language/break_spec.rb'
+    - 'language/optional_assignments_spec.rb'
     - 'language/fixtures/break.rb'
     - 'language/fixtures/break_lambda_toplevel.rb'
     - 'language/fixtures/break_lambda_toplevel_block.rb'
@@ -101,12 +184,20 @@ Lint/Debugger:
   Exclude:
     - 'core/binding/fixtures/irb.rb'
 
+Lint/Loop:
+  Enabled: false
+
+Style/BlockComments:
+  Enabled: true
+
 Style/Lambda:
   Enabled: true
   EnforcedStyle: literal
   Exclude:
     - 'language/lambda_spec.rb'
     - 'language/proc_spec.rb'
+    - 'language/numbered_parameters_spec.rb'
+    - 'language/it_parameter_spec.rb'
     - 'core/kernel/lambda_spec.rb'
 
 Style/EmptyLambdaParameter:
diff --git a/spec/ruby/.rubocop_todo.yml b/spec/ruby/.rubocop_todo.yml
index 261fde9e47..bd30f3f14a 100644
--- a/spec/ruby/.rubocop_todo.yml
+++ b/spec/ruby/.rubocop_todo.yml
@@ -1,6 +1,6 @@
 # This configuration was generated by
 # `rubocop --auto-gen-config`
-# on 2018-04-03 22:23:59 +0900 using RuboCop version 0.54.0.
+# on 2024-10-12 16:01:45 UTC using RuboCop version 1.66.1.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
@@ -20,7 +20,8 @@ Lint/DuplicateMethods:
     - 'core/unboundmethod/fixtures/classes.rb'
     - 'fixtures/class.rb'
 
-# Offense count: 5
+# Offense count: 8
+# This cop supports safe autocorrection (--autocorrect).
 Lint/EnsureReturn:
   Exclude:
     - 'language/fixtures/ensure.rb'
@@ -28,18 +29,22 @@ Lint/EnsureReturn:
     - 'language/return_spec.rb'
 
 # Offense count: 10
+Lint/FlipFlop:
+  Exclude:
+    - 'language/if_spec.rb'
+    - 'language/precedence_spec.rb'
+
+# Offense count: 10
 Lint/FloatOutOfRange:
   Exclude:
     - 'core/string/modulo_spec.rb'
 
-# Offense count: 29
-Lint/HandleExceptions:
-  Enabled: false
-
 # Offense count: 2
+# This cop supports safe autocorrection (--autocorrect).
 Lint/ImplicitStringConcatenation:
   Exclude:
     - 'language/string_spec.rb'
+    - 'core/string/chilled_string_spec.rb'
 
 # Offense count: 4
 Lint/IneffectiveAccessModifier:
@@ -48,88 +53,57 @@ Lint/IneffectiveAccessModifier:
     - 'core/module/fixtures/classes.rb'
     - 'language/fixtures/private.rb'
 
-# Offense count: 6
-# Cop supports --auto-correct.
-# Configuration parameters: EnforcedStyle.
-# SupportedStyles: runtime_error, standard_error
-Lint/InheritException:
-  Exclude:
-    - 'core/enumerator/lazy/fixtures/classes.rb'
-    - 'core/exception/fixtures/common.rb'
-    - 'core/module/fixtures/autoload_ex1.rb'
-
-# Offense count: 5
-# Cop supports --auto-correct.
+# Offense count: 71
+# This cop supports safe autocorrection (--autocorrect).
 Lint/LiteralInInterpolation:
   Exclude:
     - 'core/module/refine_spec.rb'
+    - 'core/regexp/shared/new.rb'
+    - 'core/string/shared/to_sym.rb'
+    - 'language/alias_spec.rb'
     - 'language/defined_spec.rb'
     - 'language/fixtures/squiggly_heredoc.rb'
-
-# Offense count: 16
-Lint/Loop:
-  Exclude:
-    - 'language/until_spec.rb'
-    - 'language/while_spec.rb'
+    - 'language/string_spec.rb'
+    - 'language/symbol_spec.rb'
+    - 'language/undef_spec.rb'
 
 # Offense count: 8
-# Cop supports --auto-correct.
-Lint/MultipleCompare:
+# This cop supports safe autocorrection (--autocorrect).
+Lint/MultipleComparison:
   Exclude:
     - 'language/precedence_spec.rb'
 
-# Offense count: 12
+# Offense count: 9
+# This cop supports safe autocorrection (--autocorrect).
 Lint/ParenthesesAsGroupedExpression:
   Exclude:
-    - 'core/string/fixtures/freeze_magic_comment.rb'
     - 'language/block_spec.rb'
-    - 'language/fixtures/send.rb'
     - 'language/method_spec.rb'
 
-# Offense count: 1
-# Cop supports --auto-correct.
-Lint/RedundantWithIndex:
+# Offense count: 2
+# This cop supports safe autocorrection (--autocorrect).
+Lint/RedundantStringCoercion:
   Exclude:
-    - 'core/enumerator/with_index_spec.rb'
+    - 'core/io/print_spec.rb'
 
-# Offense count: 26
-Lint/RescueException:
+# Offense count: 1
+Lint/SelfAssignment:
   Exclude:
-    - 'command_line/fixtures/debug_info.rb'
-    - 'core/dir/fileno_spec.rb'
-    - 'core/exception/cause_spec.rb'
-    - 'core/exception/no_method_error_spec.rb'
-    - 'core/kernel/fixtures/autoload_frozen.rb'
-    - 'core/module/autoload_spec.rb'
-    - 'core/mutex/sleep_spec.rb'
-    - 'core/process/euid_spec.rb'
-    - 'core/process/setsid_spec.rb'
-    - 'core/process/uid_spec.rb'
-    - 'core/thread/abort_on_exception_spec.rb'
-    - 'core/thread/shared/exit.rb'
-    - 'language/rescue_spec.rb'
-    - 'library/erb/filename_spec.rb'
+    - 'core/gc/auto_compact_spec.rb'
 
-# Offense count: 2
+# Offense count: 4
 # Configuration parameters: IgnoreImplicitReferences.
 Lint/ShadowedArgument:
   Exclude:
     - 'language/fixtures/super.rb'
 
-# Offense count: 10
-Lint/ShadowingOuterLocalVariable:
-  Exclude:
-    - 'core/binding/local_variables_spec.rb'
-    - 'language/block_spec.rb'
-    - 'language/proc_spec.rb'
-
-# Offense count: 2
-# Cop supports --auto-correct.
-Lint/StringConversionInInterpolation:
-  Exclude:
-    - 'core/io/print_spec.rb'
+# Offense count: 45
+# Configuration parameters: AllowComments, AllowNil.
+Lint/SuppressedException:
+  Enabled: false
 
 # Offense count: 9
+# Configuration parameters: AllowKeywordBlockArguments.
 Lint/UnderscorePrefixedVariableName:
   Exclude:
     - 'core/io/pipe_spec.rb'
@@ -137,20 +111,12 @@ Lint/UnderscorePrefixedVariableName:
     - 'language/block_spec.rb'
 
 # Offense count: 7
-# Configuration parameters: ContextCreatingMethods, MethodCreatingMethods.
+# This cop supports safe autocorrection (--autocorrect).
+# Configuration parameters: AutoCorrect, ContextCreatingMethods, MethodCreatingMethods.
 Lint/UselessAccessModifier:
   Exclude:
     - 'core/module/define_method_spec.rb'
     - 'core/module/fixtures/classes.rb'
     - 'core/module/module_function_spec.rb'
     - 'core/module/private_class_method_spec.rb'
-    - 'core/module/private_spec.rb'
-    - 'core/module/protected_spec.rb'
-    - 'core/module/public_spec.rb'
     - 'language/fixtures/send.rb'
-
-# Offense count: 6186
-# Configuration parameters: AllowHeredoc, AllowURI, URISchemes, IgnoreCopDirectives, IgnoredPatterns.
-# URISchemes: http, https
-Metrics/LineLength:
-  Max: 588
diff --git a/spec/ruby/.travis.yml b/spec/ruby/.travis.yml
deleted file mode 100644
index 467a5e9f68..0000000000
--- a/spec/ruby/.travis.yml
+++ /dev/null
@@ -1,28 +0,0 @@
-sudo: false
-language: ruby
-install:
-  - git clone https://github.com/ruby/mspec.git ../mspec
-script:
-  - CHECK_LEAKS=true ../mspec/bin/mspec
-matrix:
-  include:
-    - name: Running each spec twice
-      rvm: 2.5.5
-      script:
-        - CHECK_LEAKS=true ../mspec/bin/mspec -R2 -ff
-    - rvm: 2.4.6
-    - rvm: 2.5.5
-    - rvm: 2.6.3
-    - name: RuboCop Lint Checks
-      rvm: 2.4.6
-      script:
-        - gem install rubocop:0.61.0
-        - rubocop
-branches:
-  only:
-    - master
-    - /^try/
-notifications:
-  email:
-    on_success: change
-    on_failure: change
diff --git a/spec/ruby/CONTRIBUTING.md b/spec/ruby/CONTRIBUTING.md
index 2f9b138372..366b484bad 100644
--- a/spec/ruby/CONTRIBUTING.md
+++ b/spec/ruby/CONTRIBUTING.md
@@ -8,17 +8,19 @@ Spec are grouped in 5 separate top-level groups:
 
 * `command_line`: for the ruby executable command-line flags (`-v`, `-e`, etc)
 * `language`: for the language keywords and syntax constructs (`if`, `def`, `A::B`, etc)
-* `core`: for the core methods (`Fixnum#+`, `String#upcase`, no need to require anything)
+* `core`: for the core methods (`Integer#+`, `String#upcase`, no need to require anything)
 * `library`: for the standard libraries methods (`CSV.new`, `YAML.parse`, need to require the stdlib)
 * `optional/capi`: for functions available to the Ruby C-extension API
 
 The exact file for methods is decided by the `#owner` of a method, for instance for `#group_by`:
+
 ```ruby
 > [].method(:group_by)
 => #<Method: Array(Enumerable)#group_by>
 > [].method(:group_by).owner
 => Enumerable
 ```
+
 Which should therefore be specified in `core/enumerable/group_by_spec.rb`.
 
 ### MkSpec - a tool to generate the spec structure
@@ -53,12 +55,14 @@ which indicates the file was generated but the method unspecified.
 Here is a list of frequently-used matchers, which should be enough for most specs.
 There are a few extra specific matchers used in the couple specs that need it.
 
+#### Comparison matchers
+
 ```ruby
 (1 + 2).should == 3 # Calls #==
 (1 + 2).should_not == 5
 
-File.should equal(File) # Calls #equal? (tests identity)
-(1 + 2).should eql(3) # Calls #eql? (Hash equality)
+File.should.equal?(File) # Calls #equal? (tests identity)
+(1 + 2).should.eql?(3) # Calls #eql? (Hash equality)
 
 1.should < 2
 2.should <= 2
@@ -66,12 +70,19 @@ File.should equal(File) # Calls #equal? (tests identity)
 4.should > 3
 
 "Hello".should =~ /l{2}/ # Calls #=~ (Regexp match)
+```
 
-[].should be_empty # Calls #empty?
-[1,2,3].should include(2) # Calls #include?
+#### Predicate matchers
+
+```ruby
+[].should.empty?
+[1,2,3].should.include?(2)
+
+"hello".should.start_with?("h")
+"hello".should.end_with?("o")
 
 (0.1 + 0.2).should be_close(0.3, TOLERANCE) # (0.2-0.1).abs < TOLERANCE
-(0.0/0.0).should be_nan # Calls Float#nan?
+(0.0/0.0).should.nan?
 (1.0/0.0).should be_positive_infinity
 (-1.0/0.0).should be_negative_infinity
 
@@ -79,19 +90,41 @@ File.should equal(File) # Calls #equal? (tests identity)
 3.14.should be_kind_of(Numeric) # Calls #is_a?
 Numeric.should be_ancestor_of(Float) # Float.ancestors.include?(Numeric)
 
-3.14.should respond_to(:to_i) # Calls #respond_to?
-Fixnum.should have_instance_method(:+)
+3.14.should.respond_to?(:to_i)
+Integer.should have_instance_method(:+)
 Array.should have_method(:new)
-# Also have_constant, have_private_instance_method, have_singleton_method, etc
+```
+
+Also `have_constant`, `have_private_instance_method`, `have_singleton_method`, etc.
 
+#### Exception matchers
+
+```ruby
 -> {
   raise "oops"
 }.should raise_error(RuntimeError, /oops/)
 
-# To avoid! Instead, use an expectation testing what the code in the lambda does.
-# If an exception is raised, it will fail the example anyway.
+-> {
+  raise "oops"
+}.should raise_error(RuntimeError) { |e|
+  # Custom checks on the Exception object
+  e.message.should.include?("oops")
+  e.cause.should == nil
+}
+```
+
+##### `should_not raise_error`
+
+**Avoid this!** Instead, use an expectation testing what the code in the lambda does.
+If an exception is raised, it will fail the example anyway.
+
+```ruby
 -> { ... }.should_not raise_error
+```
+
+#### Warning matcher
 
+```ruby
 -> {
   Fixnum
 }.should complain(/constant ::Fixnum is deprecated/) # Expect a warning
@@ -102,15 +135,21 @@ Array.should have_method(:new)
 Different guards are available as defined by mspec.
 Here is a list of the most commonly-used guards:
 
+#### Version guards
+
 ```ruby
-ruby_version_is ""..."2.4" do
-  # Specs for RUBY_VERSION < 2.4
+ruby_version_is ""..."3.2" do
+  # Specs for RUBY_VERSION < 3.2
 end
 
-ruby_version_is "2.4" do
-  # Specs for RUBY_VERSION >= 2.4
+ruby_version_is "3.2" do
+  # Specs for RUBY_VERSION >= 3.2
 end
+```
 
+#### Platform guards
+
+```ruby
 platform_is :windows do
   # Specs only valid on Windows
 end
@@ -125,34 +164,48 @@ end
 platform_is_not :linux, :darwin do # Not Linux and not Darwin
 end
 
-platform_is wordsize: 64 do
+platform_is pointer_size: 64 do
   # 64-bit platform
 end
 
 big_endian do
   # Big-endian platform
 end
+```
+
+#### Guard for bug
 
-# In case there is a bug in MRI but the expected behavior is obvious
-# First file a bug at https://bugs.ruby-lang.org/
-# It is better to use a ruby_version_is guard if there was a release with the fix
-ruby_bug '#13669', ''...'2.5' do
+In case there is a bug in MRI and the fix will be backported to previous versions.
+If it is not backported or not likely, use `ruby_version_is` instead.
+First, file a bug at https://bugs.ruby-lang.org/.
+The problem is `ruby_bug` would make non-MRI implementations fail this spec while MRI itself does not pass it, so it should only be used if the bug is/will be fixed and backported.
+Otherwise, non-MRI implementations would have to choose between being incompatible with the latest release of MRI (which has the bug) to pass the spec, or behave the same as the latest release of MRI (which has the bug) and fail the spec, both which make no sense.
+
+IOW, `ruby_bug '#NN', ''...'X.Y' do` is equivalent to `guard_not { RUBY_ENGINE == "ruby" && ruby_version_is ''...'X.Y' } do`. So it skips tests on MRI on specified versions (where a bug is present) and runs tests on alternative implementations only.
+
+```ruby
+ruby_bug '#13669', ''...'3.2' do
   it "works like this" do
     # Specify the expected behavior here, not the bug
   end
 end
+```
 
+#### Combining guards
 
-# Combining guards
-guard -> { platform_is :windows and ruby_version_is ""..."2.5" } do
-  # Windows and RUBY_VERSION < 2.5
+```ruby
+guard -> { platform_is :windows and ruby_version_is ""..."3.2" } do
+  # Windows and RUBY_VERSION < 3.2
 end
 
-guard_not -> { platform_is :windows and ruby_version_is ""..."2.5" } do
+guard_not -> { platform_is :windows and ruby_version_is ""..."3.2" } do
   # The opposite
 end
+```
+
+#### Custom guard
 
-# Custom guard
+```ruby
 max_uint = (1 << 32) - 1
 guard -> { max_uint <= fixnum_max } do
 end
@@ -160,6 +213,8 @@ end
 
 Custom guards are better than a simple `if` as they allow [mspec commands](https://github.com/ruby/mspec/issues/30#issuecomment-312487779) to work properly.
 
+#### Implementation-specific behaviors
+
 In general, the usage of guards should be minimized as possible.
 
 There are no guards to define implementation-specific behavior because
@@ -171,7 +226,7 @@ If an implementation does not support some feature, simply tag the related specs
 ### Shared Specs
 
 Often throughout Ruby, identical functionality is used by different methods and modules. In order
-to avoid duplication of specs, we have shared specs that are re-used in other specs.  The use is a
+to avoid duplication of specs, we have shared specs that are re-used in other specs. The use is a
 bit tricky however, so let's go over it.
 
 Commonly, if a shared spec is only reused within its own module, the shared spec will live within a
@@ -183,7 +238,7 @@ An example of this is the `shared/file/socket.rb` which is used by `core/file/so
 `core/filetest/socket_spec.rb`, and `core/file/state/socket_spec.rb` and so it lives in the root `shared/`.
 
 Defining a shared spec involves adding a `shared: true` option to the top-level `describe` block. This
-will signal not to run the specs directly by the runner.  Shared specs have access to two instance
+will signal not to run the specs directly by the runner. Shared specs have access to two instance
 variables from the implementor spec: `@method` and `@object`, which the implementor spec will pass in.
 
 Here's an example of a snippet of a shared spec and two specs which integrates it:
@@ -208,12 +263,12 @@ end
 ```
 
 In the example, the first `describe` defines the shared spec `:hash_key_p`, which defines a spec that
-calls the `@method` method with an expectation.  In the implementor spec, we use `it_behaves_like` to
-integrate the shared spec.  `it_behaves_like` takes 3 parameters: the key of the shared spec, a method,
-and an object.  These last two parameters are accessible via `@method` and `@object` in the shared spec.
+calls the `@method` method with an expectation. In the implementor spec, we use `it_behaves_like` to
+integrate the shared spec. `it_behaves_like` takes 3 parameters: the key of the shared spec, a method,
+and an object. These last two parameters are accessible via `@method` and `@object` in the shared spec.
 
 Sometimes, shared specs require more context from the implementor class than a simple object. We can address
-this by passing a lambda as the method, which will have the scope of the implementor.  Here's an example of
+this by passing a lambda as the method, which will have the scope of the implementor. Here's an example of
 how this is used currently:
 
 ```ruby
@@ -224,13 +279,13 @@ describe :kernel_sprintf, shared: true do
 end
 
 describe "Kernel#sprintf" do
-  it_behaves_like :kernel_sprintf, -> (format, *args) {
+  it_behaves_like :kernel_sprintf, -> format, *args {
     sprintf(format, *args)
   }
 end
 
 describe "Kernel.sprintf" do
-  it_behaves_like :kernel_sprintf, -> (format, *args) {
+  it_behaves_like :kernel_sprintf, -> format, *args {
     Kernel.sprintf(format, *args)
   }
 end
diff --git a/spec/ruby/README.md b/spec/ruby/README.md
index 980eaf034f..674ada4c9e 100644
--- a/spec/ruby/README.md
+++ b/spec/ruby/README.md
@@ -1,11 +1,11 @@
 # The Ruby Spec Suite
 
-[![Build Status](https://travis-ci.org/ruby/spec.svg)](https://travis-ci.org/ruby/spec)
-[![Build Status](https://ci.appveyor.com/api/projects/status/1gs6f399320o44b1?svg=true)](https://ci.appveyor.com/project/eregon/spec-x948i)
-[![Gitter](https://badges.gitter.im/ruby/spec.svg)](https://gitter.im/ruby/spec)
+[![Actions Build Status](https://github.com/ruby/spec/workflows/CI/badge.svg)](https://github.com/ruby/spec/actions)
 
 The Ruby Spec Suite, abbreviated `ruby/spec`, is a test suite for the behavior of the Ruby programming language.
 
+### Description and Motivation
+
 It is not a standardized specification like the ISO one, and does not aim to become one.
 Instead, it is a practical tool to describe and test the behavior of Ruby with code.
 
@@ -17,39 +17,53 @@ Every example code has a textual description, which presents several advantages:
 
 The specs are written with syntax similar to RSpec 2.
 They are run with MSpec, the purpose-built framework for running the Ruby Spec Suite.
-For more information, see the [MSpec](http://github.com/ruby/mspec) project.
+For more information, see the [MSpec](https://github.com/ruby/mspec) project.
 
 The specs describe the [language syntax](language/), the [core library](core/), the [standard library](library/), the [C API for extensions](optional/capi) and the [command line flags](command_line/).
 The language specs are grouped by keyword while the core and standard library specs are grouped by class and method.
 
 ruby/spec is known to be tested in these implementations for every commit:
-* [MRI](http://rubyci.org/) on 30 platforms and 4 versions
+
+* [MRI](https://rubyci.org/) on 30 platforms and 4 versions
 * [JRuby](https://github.com/jruby/jruby/tree/master/spec/ruby) for both 1.7 and 9.x
-* [TruffleRuby](https://github.com/oracle/truffleruby/tree/master/spec/ruby)
+* [TruffleRuby](https://github.com/truffleruby/truffleruby/tree/master/spec/ruby)
 * [Opal](https://github.com/opal/opal/tree/master/spec)
+* [Artichoke](https://github.com/artichoke/spec/tree/artichoke-vendor)
 
-ruby/spec describes the behavior of Ruby 2.4 and more recent Ruby versions.
-More precisely, every latest stable MRI release should [pass](https://travis-ci.org/ruby/spec) all specs of ruby/spec (2.4.x, 2.5.x, 2.6.x, etc), and those are tested in TravisCI.
+ruby/spec describes the behavior of Ruby 3.2 and more recent Ruby versions.
+More precisely, every latest stable MRI release should [pass](https://github.com/ruby/spec/actions/workflows/ci.yml) all specs of ruby/spec (3.2.x, 3.3.x, etc), and those are tested in CI.
 
-The specs are synchronized both ways around once a month by @eregon between ruby/spec, MRI, JRuby and TruffleRuby.
+### Synchronization with Ruby Implementations
+
+The specs are synchronized both ways around once a month by @andrykonchin between ruby/spec, MRI, JRuby and TruffleRuby,
+using [this script](https://github.com/ruby/mspec/blob/master/tool/sync/sync-rubyspec.rb).
 Each of these repositories has a full copy of the specs under `spec/ruby` to ease editing specs.
 Any of these repositories can be used to add or edit specs, use what is most convenient for you.
 
-For *testing* a Ruby implementation, one should always test against the implementation's copy of the specs under `spec/ruby`, as that's what the Ruby implementation tests against in their CI.
+For *testing* the development version of a Ruby implementation, one should always test against that implementation's copy of the specs under `spec/ruby`, as that's what the Ruby implementation tests against in their CI.
 Also, this repository doesn't always contain the latest spec changes from MRI (it's synchronized monthly), and does not contain tags (specs marked as failing on that Ruby implementation).
-Running specs in a Ruby implementation can be done with:
+Running specs on a Ruby implementation can be done with:
 
-```
+```console
 $ cd ruby_implementation/spec/ruby
 # Add ../ruby_implementation/bin in PATH, or pass -t /path/to/bin/ruby
 $ ../mspec/bin/mspec
 ```
 
+### Specs for old Ruby versions
+
 For older specs try these commits:
+
 * Ruby 2.0.0-p647 - [Suite](https://github.com/ruby/spec/commit/245862558761d5abc676843ef74f86c9bcc8ea8d) using [MSpec](https://github.com/ruby/mspec/commit/f90efa068791064f955de7a843e96e2d7d3041c2) (may encounter 2 failures)
 * Ruby 2.1.9 - [Suite](https://github.com/ruby/spec/commit/f029e65241374386077ac500add557ae65069b55) using [MSpec](https://github.com/ruby/mspec/commit/55568ea3918c6380e64db8c567d732fa5781efed)
 * Ruby 2.2.10 - [Suite](https://github.com/ruby/spec/commit/cbaa0e412270c944df0c2532fc500c920dba0e92) using [MSpec](https://github.com/ruby/mspec/commit/d84d7668449e96856c5f6bac8cb1526b6d357ce3)
 * Ruby 2.3.8 - [Suite](https://github.com/ruby/spec/commit/dc733114d8ae66a3368ba3a98422c50147a76ba5) using [MSpec](https://github.com/ruby/mspec/commit/4599bc195fb109f2a482a01c32a7d659518369ea)
+* Ruby 2.4.10 - [Suite](https://github.com/ruby/spec/commit/bce4f2b81d6c31db67cf4d023a0625ceadde59bd) using [MSpec](https://github.com/ruby/mspec/commit/e7eb8aa4c26495b7b461e687d950b96eb08b3ff2)
+* Ruby 2.5.9 - [Suite](https://github.com/ruby/spec/commit/c503335d3d9f6ec6ef24de60a0716c34af69b64f) using [MSpec](https://github.com/ruby/mspec/commit/0091e8a62e954717cd54641f935eaf1403692041)
+* Ruby 2.6.10 - [Suite](https://github.com/ruby/spec/commit/aaf998fb8c92c4e63ad423a2e7ca6e6921818c6e) using [MSpec](https://github.com/ruby/mspec/commit/5e36c684e9e2b92b1187589bba1df22c640a8661)
+* Ruby 2.7.8 - [Suite](https://github.com/ruby/spec/commit/93787e6035c925b593a9c0c6fb0e7e07a6f1df1f) using [MSpec](https://github.com/ruby/mspec/commit/1d8cf64722d8a7529f7cd205be5f16a89b7a67fd)
+* Ruby 3.0.7 - [Suite](https://github.com/ruby/spec/commit/affef93d9940f615e4836f64b011da211f570913) using [MSpec](https://github.com/ruby/mspec/commit/0aabb3e548eb5ea6cad0125f8f46cee34542b6b7)
+* Ruby 3.1.6 - [Suite](https://github.com/ruby/spec/commit/ec960f2389d1c2265d32397fa8afa6d462014efc) using [MSpec](https://github.com/ruby/mspec/commit/484310dbed35b84c74484fd674602f88c42d063a)
 
 ### Running the specs
 
@@ -61,7 +75,7 @@ Then move to it:
 
     $ cd spec
 
-Clone [MSpec](http://github.com/ruby/mspec):
+Clone [MSpec](https://github.com/ruby/mspec):
 
     $ git clone https://github.com/ruby/mspec.git ../mspec
 
@@ -116,16 +130,31 @@ MSpec can automatically add new top-level constants in this file with:
 
     $ CHECK_LEAKS=save mspec ../mspec/bin/mspec file
 
+### Running Specs on S390x CPU Architecture
+
+Run the specs with `DFLTCC=0` if you see failing specs related to the zlib library on s390x CPU architecture. The failures can happen with the zlib library applying the patch madler/zlib#410 to enable the deflate algorithm producing a different compressed byte stream.
+
+    $ DFLTCC=0 ../mspec/bin/mspec
+
 ### Contributing and Writing Specs
 
 See [CONTRIBUTING.md](https://github.com/ruby/spec/blob/master/CONTRIBUTING.md) for documentation about contributing and writing specs (guards, matchers, etc).
 
+### Dependencies
+
+These command-line executables are needed to run the specs.
+
+* `echo`
+* `stat` for `core/file/*time_spec.rb`
+* `find` for `core/file/fixtures/file_types.rb` (package `findutils`, not needed on Windows)
+
+The file `/etc/services` is required for socket specs (package `netbase` on Debian, not needed on Windows).
+
 ### Socket specs from rubysl-socket
 
-Most specs under `library/socket` were imported from [the rubysl-socket project](https://github.com/rubysl/rubysl-socket).
+Most specs under `library/socket` were imported from the rubysl-socket project (which is no longer on GitHub).
 The 3 copyright holders of rubysl-socket, Yorick Peterse, Chuck Remes and
-Brian Shirai, [agreed to relicense those specs](https://github.com/rubysl/rubysl-socket/issues/15)
-under the MIT license in ruby/spec.
+Brian Shirai, agreed to relicense those specs under the MIT license in ruby/spec.
 
 ### History and RubySpec
 
@@ -133,5 +162,5 @@ This project was originally born from [Rubinius](https://github.com/rubinius/rub
 The revision history of these specs is available [here](https://github.com/ruby/spec/blob/2b886623/CHANGES.before-2008-05-10).
 These specs were later extracted to their own project, RubySpec, with a specific vision and principles.
 At the end of 2014, Brian Shirai, the creator of RubySpec, decided to [end RubySpec](http://rubinius.com/2014/12/31/matz-s-ruby-developers-don-t-use-rubyspec/).
-A couple months later, the different repositories were merged and [the project was revived](http://eregon.github.io/rubyspec/2015/07/29/rubyspec-is-reborn.html).
+A couple months later, the different repositories were merged and [the project was revived](https://eregon.github.io/rubyspec/2015/07/29/rubyspec-is-reborn.html).
 On 12 January 2016, the name was changed to "The Ruby Spec Suite" for clarity and to let the RubySpec ideology rest in peace.
diff --git a/spec/ruby/appveyor.yml b/spec/ruby/appveyor.yml
deleted file mode 100644
index 588172ee3d..0000000000
--- a/spec/ruby/appveyor.yml
+++ /dev/null
@@ -1,34 +0,0 @@
----
-version: "{build}"
-clone_depth: 100
-init:
-  # To avoid duplicated executables in PATH, see https://github.com/ruby/spec/pull/468
-  - set PATH=C:\Ruby%ruby_version%\bin;C:\Program Files\7-Zip;C:\Program Files\AppVeyor\BuildAgent;C:\Program Files\Git\cmd;C:\Windows\system32;C:\Program Files;C:\Windows
-  # Loads trunk build and updates MSYS2 / MinGW to most recent gcc compiler
-  - ps: |
-      if ($env:ruby_version -eq '_trunk') {
-        $trunk_uri = 'https://ci.appveyor.com/api/projects/MSP-Greg/ruby-loco/artifacts/ruby_trunk.7z'
-        (New-Object Net.WebClient).DownloadFile($trunk_uri, 'C:\ruby_trunk.7z')
-        7z.exe x C:\ruby_trunk.7z -oC:\Ruby_trunk
-      }
-
-environment:
-  matrix:
-    - ruby_version: 24-x64
-    - ruby_version: 25-x64
-    - ruby_version: _trunk # So the folder name is ruby_trunk
-install:
-  - git clone https://github.com/ruby/mspec.git ../mspec
-build: off
-test_script:
-  - SET CHECK_LEAKS=true
-  - ../mspec/bin/mspec -rdevkit -ff
-on_finish:
-  - ruby -v
-matrix:
-  allow_failures:
-    - ruby_version: _trunk
-branches:
-  only:
-    - master
-    - /^try/
diff --git a/spec/ruby/bin/rubocop b/spec/ruby/bin/rubocop
new file mode 100755
index 0000000000..38254f13e4
--- /dev/null
+++ b/spec/ruby/bin/rubocop
@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'bundler/inline'
+
+gemfile do
+  source 'https://rubygems.org'
+
+  gem 'rubocop', '1.66.1'
+end
+
+exec(Gem.bin_path('rubocop', 'rubocop'), *ARGV)
diff --git a/spec/ruby/command_line/backtrace_limit_spec.rb b/spec/ruby/command_line/backtrace_limit_spec.rb
new file mode 100644
index 0000000000..4d57bc268b
--- /dev/null
+++ b/spec/ruby/command_line/backtrace_limit_spec.rb
@@ -0,0 +1,93 @@
+require_relative '../spec_helper'
+
+describe "The --backtrace-limit command line option" do
+  ruby_version_is ""..."3.4" do
+    it "limits top-level backtraces to a given number of entries" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "top 2>&1", exit_status: 1)
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+top
+/fixtures/backtrace.rb:2:in `a': oops (RuntimeError)
+\tfrom /fixtures/backtrace.rb:6:in `b'
+\tfrom /fixtures/backtrace.rb:10:in `c'
+\t ... 2 levels...
+      MSG
+    end
+
+    it "affects Exception#full_message" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "full_message 2>&1")
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+full_message
+/fixtures/backtrace.rb:2:in `a': oops (RuntimeError)
+\tfrom /fixtures/backtrace.rb:6:in `b'
+\tfrom /fixtures/backtrace.rb:10:in `c'
+\t ... 2 levels...
+      MSG
+    end
+
+    it "does not affect Exception#backtrace" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "backtrace 2>&1")
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+backtrace
+/fixtures/backtrace.rb:2:in `a'
+/fixtures/backtrace.rb:6:in `b'
+/fixtures/backtrace.rb:10:in `c'
+/fixtures/backtrace.rb:14:in `d'
+/fixtures/backtrace.rb:29:in `<main>'
+      MSG
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "limits top-level backtraces to a given number of entries" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "top 2>&1", exit_status: 1)
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+top
+/fixtures/backtrace.rb:2:in 'Object#a': oops (RuntimeError)
+\tfrom /fixtures/backtrace.rb:6:in 'Object#b'
+\tfrom /fixtures/backtrace.rb:10:in 'Object#c'
+\t ... 2 levels...
+      MSG
+    end
+
+    it "affects Exception#full_message" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "full_message 2>&1")
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+full_message
+/fixtures/backtrace.rb:2:in 'Object#a': oops (RuntimeError)
+\tfrom /fixtures/backtrace.rb:6:in 'Object#b'
+\tfrom /fixtures/backtrace.rb:10:in 'Object#c'
+\t ... 2 levels...
+      MSG
+    end
+
+    it "does not affect Exception#backtrace" do
+      file = fixture(__FILE__ , "backtrace.rb")
+      out = ruby_exe(file, options: "--backtrace-limit=2", args: "backtrace 2>&1")
+      out = out.gsub(__dir__, '')
+
+      out.should == <<-MSG
+backtrace
+/fixtures/backtrace.rb:2:in 'Object#a'
+/fixtures/backtrace.rb:6:in 'Object#b'
+/fixtures/backtrace.rb:10:in 'Object#c'
+/fixtures/backtrace.rb:14:in 'Object#d'
+/fixtures/backtrace.rb:29:in '<main>'
+      MSG
+    end
+  end
+end
diff --git a/spec/ruby/command_line/dash_0_spec.rb b/spec/ruby/command_line/dash_0_spec.rb
new file mode 100755
index 0000000000..2ce4f49b5e
--- /dev/null
+++ b/spec/ruby/command_line/dash_0_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../spec_helper'
+
+describe "The -0 command line option" do
+  it "sets $/ and $-0" do
+    ruby_exe("puts $/, $-0", options: "-072").should == ":\n:\n"
+  end
+
+  ruby_version_is "4.0" do
+    it "sets $/ and $-0 as a frozen string" do
+      ruby_exe("puts $/.frozen?, $-0.frozen?", options: "-072").should == "true\ntrue\n"
+    end
+  end
+end
diff --git a/spec/ruby/command_line/dash_a_spec.rb b/spec/ruby/command_line/dash_a_spec.rb
index 9ea135dc76..43d923ce16 100644
--- a/spec/ruby/command_line/dash_a_spec.rb
+++ b/spec/ruby/command_line/dash_a_spec.rb
@@ -6,13 +6,13 @@ describe "The -a command line option" do
   end
 
   it "runs the code in loop conditional on Kernel.gets()" do
-    ruby_exe("puts $F.last", options: "-n -a", escape: true,
+    ruby_exe("puts $F.last", options: "-n -a",
                              args: " < #{@names}").should ==
       "jones\nfield\ngrey\n"
   end
 
   it "sets $-a" do
-    ruby_exe("puts $-a", options: "-n -a", escape: true,
+    ruby_exe("puts $-a", options: "-n -a",
                          args: " < #{@names}").should ==
       "true\ntrue\ntrue\n"
   end
diff --git a/spec/ruby/command_line/dash_e_spec.rb b/spec/ruby/command_line/dash_e_spec.rb
index 9f600eb414..24ed34376d 100644
--- a/spec/ruby/command_line/dash_e_spec.rb
+++ b/spec/ruby/command_line/dash_e_spec.rb
@@ -23,7 +23,7 @@ describe "The -e command line option" do
 
   #needs to test return => LocalJumpError
 
-  describe "with -n and a Fixnum range" do
+  describe "with -n and an Integer range" do
     before :each do
       @script = "-ne 'print if %s' #{fixture(__FILE__, "conditional_range.txt")}"
     end
diff --git a/spec/ruby/command_line/dash_encoding_spec.rb b/spec/ruby/command_line/dash_encoding_spec.rb
index 36ce55af5f..5803d328c1 100644
--- a/spec/ruby/command_line/dash_encoding_spec.rb
+++ b/spec/ruby/command_line/dash_encoding_spec.rb
@@ -25,6 +25,12 @@ describe "The --encoding command line option" do
   end
 
   it "does not accept a third encoding" do
-    ruby_exe(@test_string, options: "--disable-gems --encoding big5:#{@enc2}:utf-32le", args: "2>&1").should =~ /extra argument for --encoding: utf-32le/
+    options = {
+      options: "--disable-gems --encoding big5:#{@enc2}:utf-32le",
+      args: "2>&1",
+      exit_status: 1
+    }
+
+    ruby_exe(@test_string, options).should =~ /extra argument for --encoding: utf-32le/
   end
 end
diff --git a/spec/ruby/command_line/dash_l_spec.rb b/spec/ruby/command_line/dash_l_spec.rb
new file mode 100644
index 0000000000..44a98445f3
--- /dev/null
+++ b/spec/ruby/command_line/dash_l_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../spec_helper'
+
+describe "The -l command line option" do
+  before :each do
+    @names  = fixture __FILE__, "full_names.txt"
+  end
+
+  it "chomps lines with default separator" do
+    ruby_exe('puts $_.end_with?("\n")', options: "-n -l",
+             args: " < #{@names}").should ==
+        "false\nfalse\nfalse\n"
+  end
+
+  it "chomps last line based on $/" do
+    ruby_exe('BEGIN { $/ = "ones\n" }; puts $_', options: "-W0 -n -l",
+             args: " < #{@names}").should ==
+        "alice j\nbob field\njames grey\n"
+  end
+
+  it "sets $\\ to the value of $/" do
+    ruby_exe("puts $\\ == $/", options: "-W0 -n -l",
+             args: " < #{@names}").should ==
+        "true\ntrue\ntrue\n"
+  end
+
+  it "sets $-l" do
+    ruby_exe("puts $-l", options: "-n -l",
+                         args: " < #{@names}").should ==
+      "true\ntrue\ntrue\n"
+  end
+end
diff --git a/spec/ruby/command_line/dash_n_spec.rb b/spec/ruby/command_line/dash_n_spec.rb
index 9d331d6065..1dd9379259 100644
--- a/spec/ruby/command_line/dash_n_spec.rb
+++ b/spec/ruby/command_line/dash_n_spec.rb
@@ -6,19 +6,19 @@ describe "The -n command line option" do
   end
 
   it "runs the code in loop conditional on Kernel.gets()" do
-    ruby_exe("puts $_", options: "-n", escape: true,
+    ruby_exe("puts $_", options: "-n",
                         args: " < #{@names}").should ==
       "alice\nbob\njames\n"
   end
 
   it "only evaluates BEGIN blocks once" do
-    ruby_exe("BEGIN { puts \"hi\" }; puts $_", options: "-n", escape: true,
+    ruby_exe("BEGIN { puts \"hi\" }; puts $_", options: "-n",
                                                args: " < #{@names}").should ==
       "hi\nalice\nbob\njames\n"
   end
 
   it "only evaluates END blocks once" do
-    ruby_exe("puts $_; END {puts \"bye\"}", options: "-n", escape: true,
+    ruby_exe("puts $_; END {puts \"bye\"}", options: "-n",
                                             args: " < #{@names}").should ==
       "alice\nbob\njames\nbye\n"
   end
@@ -29,7 +29,7 @@ describe "The -n command line option" do
     $total += 1
     END { puts $total }
     script
-    ruby_exe(script, options: "-n", escape: true,
+    ruby_exe(script, options: "-n",
                      args: " < #{@names}").should ==
       "3\n"
   end
diff --git a/spec/ruby/command_line/dash_p_spec.rb b/spec/ruby/command_line/dash_p_spec.rb
index 39827c3868..967e3796de 100644
--- a/spec/ruby/command_line/dash_p_spec.rb
+++ b/spec/ruby/command_line/dash_p_spec.rb
@@ -6,13 +6,13 @@ describe "The -p command line option" do
   end
 
   it "runs the code in loop conditional on Kernel.gets() and prints $_" do
-    ruby_exe("$_ = $_.upcase", options: "-p", escape: true,
+    ruby_exe("$_ = $_.upcase", options: "-p",
                                args: " < #{@names}").should ==
       "ALICE\nBOB\nJAMES\n"
   end
 
   it "sets $-p" do
-    ruby_exe("$_ = $-p", options: "-p", escape: true,
+    ruby_exe("$_ = $-p", options: "-p",
                          args: " < #{@names}").should ==
       "truetruetrue"
   end
diff --git a/spec/ruby/command_line/dash_r_spec.rb b/spec/ruby/command_line/dash_r_spec.rb
index b29895bd26..9f673c53dc 100644
--- a/spec/ruby/command_line/dash_r_spec.rb
+++ b/spec/ruby/command_line/dash_r_spec.rb
@@ -7,7 +7,25 @@ describe "The -r command line option" do
   end
 
   it "requires the specified file" do
-    result = ruby_exe(@script, options: "-r #{@test_file}")
-    result.should include(@test_file + ".rb")
+    out = ruby_exe(@script, options: "-r #{@test_file}")
+    out.should include("REQUIRED")
+    out.should include(@test_file + ".rb")
+  end
+
+  it "requires the file before parsing the main script" do
+    out = ruby_exe(fixture(__FILE__, "bad_syntax.rb"), options: "-r #{@test_file}", args: "2>&1", exit_status: 1)
+    $?.should_not.success?
+    out.should include("REQUIRED")
+
+    # it's tempting not to rely on error message and rely only on exception class name,
+    # but CRuby before 3.2 doesn't print class name for syntax error
+    out.should include_any_of("syntax error", "SyntaxError")
+  end
+
+  it "does not require the file if the main script file does not exist" do
+    out = `#{ruby_exe.to_a.join(' ')} -r #{@test_file} #{fixture(__FILE__, "does_not_exist.rb")} 2>&1`
+    $?.should_not.success?
+    out.should_not.include?("REQUIRED")
+    out.should.include?("No such file or directory")
   end
 end
diff --git a/spec/ruby/command_line/dash_upper_e_spec.rb b/spec/ruby/command_line/dash_upper_e_spec.rb
index b3c6ce262b..5a83962583 100644
--- a/spec/ruby/command_line/dash_upper_e_spec.rb
+++ b/spec/ruby/command_line/dash_upper_e_spec.rb
@@ -31,6 +31,7 @@ describe "ruby -E" do
   it "raises a RuntimeError if used with -U" do
     ruby_exe("p 1",
              options: '-Eascii:ascii -U',
-             args: '2>&1').should =~ /RuntimeError/
+             args: '2>&1',
+             exit_status: 1).should =~ /RuntimeError/
   end
 end
diff --git a/spec/ruby/command_line/dash_upper_f_spec.rb b/spec/ruby/command_line/dash_upper_f_spec.rb
index 967acc2ece..5c10a7140d 100644
--- a/spec/ruby/command_line/dash_upper_f_spec.rb
+++ b/spec/ruby/command_line/dash_upper_f_spec.rb
@@ -6,7 +6,7 @@ describe "the -F command line option" do
   end
 
   it "specifies the field separator pattern for -a" do
-    ruby_exe("puts $F[0]", options: "-naF:", escape: true,
+    ruby_exe("puts $F[0]", options: "-naF:",
                            args: " < #{@passwd}").should ==
       "nobody\nroot\ndaemon\n"
   end
diff --git a/spec/ruby/command_line/dash_upper_k_spec.rb b/spec/ruby/command_line/dash_upper_k_spec.rb
index a060eab793..7e71532295 100644
--- a/spec/ruby/command_line/dash_upper_k_spec.rb
+++ b/spec/ruby/command_line/dash_upper_k_spec.rb
@@ -58,8 +58,8 @@ describe 'The -K command line option' do
   end
 
   it "ignores unknown codes" do
-    locale = Encoding.find('locale')
+    external = Encoding.find('external')
     ruby_exe(@test_string, options: '-KZ').should ==
-      [Encoding::UTF_8.name, locale.name, nil].inspect
+      [Encoding::UTF_8.name, external.name, nil].inspect
   end
 end
diff --git a/spec/ruby/command_line/dash_upper_s_spec.rb b/spec/ruby/command_line/dash_upper_s_spec.rb
index 3a28fa2ad2..17991503f1 100644
--- a/spec/ruby/command_line/dash_upper_s_spec.rb
+++ b/spec/ruby/command_line/dash_upper_s_spec.rb
@@ -21,7 +21,7 @@ describe 'The -S command line option' do
     end
 
     it "runs launcher found in PATH and sets the exit status to 1 if it fails" do
-      result = ruby_exe(nil, options: '-S dash_s_fail', env: { 'PATH' => @path }, args: '2>&1')
+      result = ruby_exe(nil, options: '-S dash_s_fail', env: { 'PATH' => @path }, args: '2>&1', exit_status: 1)
       result.should =~ /\bdie\b/
       $?.exitstatus.should == 1
     end
diff --git a/spec/ruby/command_line/dash_upper_u_spec.rb b/spec/ruby/command_line/dash_upper_u_spec.rb
index 2546b5b9f4..2c210eb603 100644
--- a/spec/ruby/command_line/dash_upper_u_spec.rb
+++ b/spec/ruby/command_line/dash_upper_u_spec.rb
@@ -2,42 +2,51 @@ require_relative '../spec_helper'
 
 describe "ruby -U" do
   it "sets Encoding.default_internal to UTF-8" do
-     ruby_exe('print Encoding.default_internal.name',
-              options: '-U').should == 'UTF-8'
+    ruby_exe('print Encoding.default_internal.name',
+             options: '-U').should == 'UTF-8'
+  end
+
+  it "sets Encoding.default_internal to UTF-8 when RUBYOPT is empty or only spaces" do
+    ruby_exe('p Encoding.default_internal',
+             options: '-U', env: { 'RUBYOPT' => '' }).should == "#<Encoding:UTF-8>\n"
+    ruby_exe('p Encoding.default_internal',
+             options: '-U', env: { 'RUBYOPT' => '  ' }).should == "#<Encoding:UTF-8>\n"
   end
 
   it "does nothing different if specified multiple times" do
-     ruby_exe('print Encoding.default_internal.name',
-              options: '-U -U').should == 'UTF-8'
+    ruby_exe('print Encoding.default_internal.name',
+             options: '-U -U').should == 'UTF-8'
   end
 
   it "is overruled by Encoding.default_internal=" do
-     ruby_exe('Encoding.default_internal="ascii"; print Encoding.default_internal.name',
-              options: '-U').should == 'US-ASCII'
+    ruby_exe('Encoding.default_internal="ascii"; print Encoding.default_internal.name',
+             options: '-U').should == 'US-ASCII'
   end
 
   it "does not affect the default external encoding" do
-     ruby_exe('Encoding.default_external="ascii"; print Encoding.default_external.name',
-              options: '-U').should == 'US-ASCII'
+    ruby_exe('Encoding.default_external="ascii"; print Encoding.default_external.name',
+             options: '-U').should == 'US-ASCII'
   end
 
   it "does not affect the source encoding" do
-     ruby_exe("print __ENCODING__.name",
-              options: '-U -KE').should == 'EUC-JP'
-     ruby_exe("print __ENCODING__.name",
-              options: '-KE -U').should == 'EUC-JP'
+    ruby_exe("print __ENCODING__.name",
+             options: '-U -KE').should == 'EUC-JP'
+    ruby_exe("print __ENCODING__.name",
+             options: '-KE -U').should == 'EUC-JP'
   end
 
   # I assume IO redirection will break on Windows...
   it "raises a RuntimeError if used with -Eext:int" do
     ruby_exe("p 1",
              options: '-U -Eascii:ascii',
-             args: '2>&1').should =~ /RuntimeError/
+             args: '2>&1',
+             exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError if used with -E:int" do
     ruby_exe("p 1",
              options: '-U -E:ascii',
-             args: '2>&1').should =~ /RuntimeError/
+             args: '2>&1',
+             exit_status: 1).should =~ /RuntimeError/
   end
 end
diff --git a/spec/ruby/command_line/dash_upper_w_spec.rb b/spec/ruby/command_line/dash_upper_w_spec.rb
index 31bb976ad2..4019510d42 100644
--- a/spec/ruby/command_line/dash_upper_w_spec.rb
+++ b/spec/ruby/command_line/dash_upper_w_spec.rb
@@ -18,3 +18,27 @@ end
 describe "The -W command line option with 2" do
   it_behaves_like :command_line_verbose, "-W2"
 end
+
+describe "The -W command line option with :deprecated" do
+  it "enables deprecation warnings" do
+    ruby_exe('p Warning[:deprecated]', options: '-W:deprecated').should == "true\n"
+  end
+end
+
+describe "The -W command line option with :no-deprecated" do
+  it "suppresses deprecation warnings" do
+    ruby_exe('p Warning[:deprecated]', options: '-w -W:no-deprecated').should == "false\n"
+  end
+end
+
+describe "The -W command line option with :experimental" do
+  it "enables experimental warnings" do
+    ruby_exe('p Warning[:experimental]', options: '-W:experimental').should == "true\n"
+  end
+end
+
+describe "The -W command line option with :no-experimental" do
+  it "suppresses experimental warnings" do
+    ruby_exe('p Warning[:experimental]', options: '-w -W:no-experimental').should == "false\n"
+  end
+end
diff --git a/spec/ruby/command_line/dash_v_spec.rb b/spec/ruby/command_line/dash_v_spec.rb
index 04d684fdad..b13350404c 100644
--- a/spec/ruby/command_line/dash_v_spec.rb
+++ b/spec/ruby/command_line/dash_v_spec.rb
@@ -6,7 +6,10 @@ describe "The -v command line option" do
 
   describe "when used alone" do
     it "prints version and ends" do
-      ruby_exe(nil, args: '-v').should include(RUBY_DESCRIPTION)
-    end
+      ruby_exe(nil, args: '-v').gsub("+PRISM ", "").should include(RUBY_DESCRIPTION.gsub("+PRISM ", ""))
+    end unless (defined?(RubyVM::YJIT) && RubyVM::YJIT.enabled?) ||
+               (defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled?) ||
+               (ENV['RUBY_GC_LIBRARY'] && ENV['RUBY_GC_LIBRARY'].length > 0) ||
+               (ENV['RUBY_MN_THREADS'] == '1')
   end
 end
diff --git a/spec/ruby/command_line/dash_w_spec.rb b/spec/ruby/command_line/dash_w_spec.rb
index 1d93e0347b..f310dca3ed 100644
--- a/spec/ruby/command_line/dash_w_spec.rb
+++ b/spec/ruby/command_line/dash_w_spec.rb
@@ -3,4 +3,8 @@ require_relative 'shared/verbose'
 
 describe "The -w command line option" do
   it_behaves_like :command_line_verbose, "-w"
+
+  it "enables both deprecated and experimental warnings" do
+    ruby_exe('p Warning[:deprecated]; p Warning[:experimental]', options: '-w').should == "true\ntrue\n"
+  end
 end
diff --git a/spec/ruby/command_line/dash_x_spec.rb b/spec/ruby/command_line/dash_x_spec.rb
index eb89db0144..ae14b61070 100644
--- a/spec/ruby/command_line/dash_x_spec.rb
+++ b/spec/ruby/command_line/dash_x_spec.rb
@@ -9,7 +9,7 @@ describe "The -x command line option" do
 
   it "fails when /\#!.*ruby.*/-ish line in target file is not found" do
     bad_embedded_ruby = fixture __FILE__, "bin/bad_embedded_ruby.txt"
-    result = ruby_exe(bad_embedded_ruby, options: '-x', args: '2>&1')
+    result = ruby_exe(bad_embedded_ruby, options: '-x', args: '2>&1', exit_status: 1)
     result.should include "no Ruby script found in input"
   end
 
diff --git a/spec/ruby/command_line/error_message_spec.rb b/spec/ruby/command_line/error_message_spec.rb
index 5fee3ead44..02150f30ce 100644
--- a/spec/ruby/command_line/error_message_spec.rb
+++ b/spec/ruby/command_line/error_message_spec.rb
@@ -2,10 +2,10 @@ require_relative '../spec_helper'
 
 describe "The error message caused by an exception" do
   it "is not printed to stdout" do
-    out = ruby_exe("this_does_not_exist", args: "2> #{File::NULL}")
-    out.chomp.empty?.should == true
+    out = ruby_exe("this_does_not_exist", args: "2> #{File::NULL}", exit_status: 1)
+    out.chomp.should.empty?
 
-    out = ruby_exe("end #syntax error", args: "2> #{File::NULL}")
-    out.chomp.empty?.should == true
+    out = ruby_exe("end #syntax error", args: "2> #{File::NULL}", exit_status: 1)
+    out.chomp.should.empty?
   end
 end
diff --git a/spec/ruby/command_line/feature_spec.rb b/spec/ruby/command_line/feature_spec.rb
index 02571ee8c6..838581d04a 100644
--- a/spec/ruby/command_line/feature_spec.rb
+++ b/spec/ruby/command_line/feature_spec.rb
@@ -1,6 +1,12 @@
 require_relative '../spec_helper'
 
 describe "The --enable and --disable flags" do
+  before :all do
+    # Since some specs disable reading RUBYOPT, we instead pass its contents as :options for those specs
+    rubyopt = [ENV["RUBYOPT"]]
+    rubyopt << ENV["#{RUBY_ENGINE.upcase}OPT"] unless RUBY_ENGINE == 'ruby'
+    @rubyopt = RUBY_ENGINE == "ruby" ? "" : rubyopt.compact.join(" ")
+  end
 
   it "can be used with gems" do
     ruby_exe("p defined?(Gem)", options: "--enable=gems").chomp.should == "\"constant\""
@@ -25,9 +31,9 @@ describe "The --enable and --disable flags" do
 
   it "can be used with rubyopt" do
     ruby_exe("p $VERBOSE", options: "--enable=rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "true"
-    ruby_exe("p $VERBOSE", options: "--disable=rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "false"
+    ruby_exe("p $VERBOSE", options: "#{@rubyopt} --disable=rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "false"
     ruby_exe("p $VERBOSE", options: "--enable-rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "true"
-    ruby_exe("p $VERBOSE", options: "--disable-rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "false"
+    ruby_exe("p $VERBOSE", options: "#{@rubyopt} --disable-rubyopt", env: {'RUBYOPT' => '-w'}).chomp.should == "false"
   end
 
   it "can be used with frozen-string-literal" do
@@ -37,13 +43,22 @@ describe "The --enable and --disable flags" do
     ruby_exe("p 'foo'.frozen?", options: "--disable-frozen-string-literal").chomp.should == "false"
   end
 
-  it "can be used with all" do
+  # frequently hangs for >60s on GitHub Actions macos-latest
+  # MinGW's YJIT support seems broken
+  platform_is_not :darwin, :mingw do
+    it "can be used with all for enable" do
+      e = "p [defined?(Gem), defined?(DidYouMean), $VERBOSE, 'foo'.frozen?]"
+      env = {'RUBYOPT' => '-w'}
+      # Use a single variant here because it can be quite slow as it might enable jit, etc
+      ruby_exe(e, options: "--enable-all", env: env).chomp.should == "[\"constant\", \"constant\", true, true]"
+    end unless defined?(RubyVM::YJIT) && defined?(RubyVM::ZJIT) && RubyVM::ZJIT.enabled? # You're not supposed to enable YJIT with --enable-all when ZJIT options are passed.
+  end
+
+  it "can be used with all for disable" do
     e = "p [defined?(Gem), defined?(DidYouMean), $VERBOSE, 'foo'.frozen?]"
     env = {'RUBYOPT' => '-w'}
-    ruby_exe(e, options: "--enable=all", env: env).chomp.should == "[\"constant\", \"constant\", true, true]"
-    ruby_exe(e, options: "--enable-all", env: env).chomp.should == "[\"constant\", \"constant\", true, true]"
-    ruby_exe(e, options: "--disable=all", env: env).chomp.should == "[nil, nil, false, false]"
-    ruby_exe(e, options: "--disable-all", env: env).chomp.should == "[nil, nil, false, false]"
+    ruby_exe(e, options: "#{@rubyopt} --disable=all", env: env).chomp.should == "[nil, nil, false, false]"
+    ruby_exe(e, options: "#{@rubyopt} --disable-all", env: env).chomp.should == "[nil, nil, false, false]"
   end
 
   it "prints a warning for unknown features" do
diff --git a/spec/ruby/command_line/fixtures/backtrace.rb b/spec/ruby/command_line/fixtures/backtrace.rb
new file mode 100644
index 0000000000..99acae95c8
--- /dev/null
+++ b/spec/ruby/command_line/fixtures/backtrace.rb
@@ -0,0 +1,35 @@
+def a
+  raise 'oops'
+end
+
+def b
+  a
+end
+
+def c
+  b
+end
+
+def d
+  c
+end
+
+arg = ARGV.first
+$stderr.puts arg
+
+case arg
+when 'full_message'
+  begin
+    d
+  rescue => exc
+    puts exc.full_message
+  end
+when 'backtrace'
+  begin
+    d
+  rescue => exc
+    puts exc.backtrace
+  end
+else
+  d
+end
diff --git a/spec/ruby/command_line/fixtures/bin/embedded_ruby.txt b/spec/ruby/command_line/fixtures/bin/embedded_ruby.txt
index c556bf0b71..1da779b1b9 100644
--- a/spec/ruby/command_line/fixtures/bin/embedded_ruby.txt
+++ b/spec/ruby/command_line/fixtures/bin/embedded_ruby.txt
@@ -1,3 +1,3 @@
 @@@This line is not value Ruby
 #!ruby
-puts 'success'
\ No newline at end of file
+puts 'success'
diff --git a/spec/ruby/command_line/fixtures/bin/hybrid_launcher.sh b/spec/ruby/command_line/fixtures/bin/hybrid_launcher.sh
index 0eede2a99f..fd3249f0e5 100644
--- a/spec/ruby/command_line/fixtures/bin/hybrid_launcher.sh
+++ b/spec/ruby/command_line/fixtures/bin/hybrid_launcher.sh
@@ -1,4 +1,4 @@
 #!/usr/bin/env bash
-exec somehow this file
+echo 'error' && exit 1
 #!ruby
 puts 'success'
diff --git a/spec/ruby/command_line/fixtures/debug_info.rb b/spec/ruby/command_line/fixtures/debug_info.rb
index ee607910c0..f02b041920 100644
--- a/spec/ruby/command_line/fixtures/debug_info.rb
+++ b/spec/ruby/command_line/fixtures/debug_info.rb
@@ -1,4 +1,3 @@
-# frozen_string_literal: true
 a = 'string'
 b = a
 c = b
diff --git a/spec/ruby/command_line/fixtures/freeze_flag_required_diff_enc.rb b/spec/ruby/command_line/fixtures/freeze_flag_required_diff_enc.rb
index fa348d59e7..df4b952c46 100644
--- a/spec/ruby/command_line/fixtures/freeze_flag_required_diff_enc.rb
+++ b/spec/ruby/command_line/fixtures/freeze_flag_required_diff_enc.rb
diff --git a/spec/ruby/command_line/fixtures/freeze_flag_two_literals.rb b/spec/ruby/command_line/fixtures/freeze_flag_two_literals.rb
index 074092c9d9..f5547a5bae 100644
--- a/spec/ruby/command_line/fixtures/freeze_flag_two_literals.rb
+++ b/spec/ruby/command_line/fixtures/freeze_flag_two_literals.rb
@@ -1 +1 @@
-p "abc".object_id == "abc".object_id
+p "abc".equal?("abc")
diff --git a/spec/ruby/command_line/fixtures/string_literal_frozen_comment.rb b/spec/ruby/command_line/fixtures/string_literal_frozen_comment.rb
new file mode 100644
index 0000000000..fb84b546c0
--- /dev/null
+++ b/spec/ruby/command_line/fixtures/string_literal_frozen_comment.rb
@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+frozen = "test".frozen?
+interned = "test".equal?("test")
+puts "frozen:#{frozen} interned:#{interned}"
diff --git a/spec/ruby/command_line/fixtures/string_literal_mutable_comment.rb b/spec/ruby/command_line/fixtures/string_literal_mutable_comment.rb
new file mode 100644
index 0000000000..381a742001
--- /dev/null
+++ b/spec/ruby/command_line/fixtures/string_literal_mutable_comment.rb
@@ -0,0 +1,4 @@
+# frozen_string_literal: false
+frozen = "test".frozen?
+interned = "test".equal?("test")
+puts "frozen:#{frozen} interned:#{interned}"
diff --git a/spec/ruby/command_line/fixtures/string_literal_raw.rb b/spec/ruby/command_line/fixtures/string_literal_raw.rb
new file mode 100644
index 0000000000..56b1841296
--- /dev/null
+++ b/spec/ruby/command_line/fixtures/string_literal_raw.rb
@@ -0,0 +1,3 @@
+frozen = "test".frozen?
+interned = "test".equal?("test")
+puts "frozen:#{frozen} interned:#{interned}"
diff --git a/spec/ruby/command_line/fixtures/test_file.rb b/spec/ruby/command_line/fixtures/test_file.rb
index 961e3c0b0c..30a832299e 100644
--- a/spec/ruby/command_line/fixtures/test_file.rb
+++ b/spec/ruby/command_line/fixtures/test_file.rb
@@ -1 +1 @@
-"test file"
+puts "REQUIRED"
diff --git a/spec/ruby/command_line/frozen_strings_spec.rb b/spec/ruby/command_line/frozen_strings_spec.rb
index 647b69daed..8acab5bc1d 100644
--- a/spec/ruby/command_line/frozen_strings_spec.rb
+++ b/spec/ruby/command_line/frozen_strings_spec.rb
@@ -19,11 +19,76 @@ describe "The --enable-frozen-string-literal flag causes string literals to" do
   end
 end
 
+describe "The --disable-frozen-string-literal flag causes string literals to" do
+
+  it "produce a different object each time" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_one_literal.rb"), options: "--disable-frozen-string-literal").chomp.should == "false"
+  end
+
+end
+
+describe "With neither --enable-frozen-string-literal nor --disable-frozen-string-literal flag set" do
+  before do
+    # disable --enable-frozen-string-literal and --disable-frozen-string-literal passed in $RUBYOPT
+    @rubyopt = ENV["RUBYOPT"]
+    ENV["RUBYOPT"] = ""
+  end
+
+  after do
+    ENV["RUBYOPT"] = @rubyopt
+  end
+
+  it "produce a different object each time" do
+    ruby_exe(fixture(__FILE__, "freeze_flag_one_literal.rb")).chomp.should == "false"
+  end
+
+  context "if file has no frozen_string_literal comment" do
+    it "produce different mutable strings each time" do
+      ruby_exe(fixture(__FILE__, "string_literal_raw.rb")).chomp.should == "frozen:false interned:false"
+    end
+
+    guard -> { ruby_version_is "3.4" and !"test".frozen? } do
+      it "complain about modification of produced mutable strings" do
+        -> { eval(<<~RUBY) }.should complain(/warning: literal string will be frozen in the future \(run with --debug-frozen-string-literal for more information\)/)
+          "test" << "!"
+        RUBY
+      end
+
+      it "does not complain about modification if Warning[:deprecated] is false" do
+        deprecated = Warning[:deprecated]
+        Warning[:deprecated] = false
+        -> { eval(<<~RUBY) }.should_not complain
+          "test" << "!"
+        RUBY
+      ensure
+        Warning[:deprecated] = deprecated
+      end
+    end
+  end
+
+  it "if file has frozen_string_literal:true comment produce same frozen strings each time" do
+    ruby_exe(fixture(__FILE__, "string_literal_frozen_comment.rb")).chomp.should == "frozen:true interned:true"
+  end
+
+  it "if file has frozen_string_literal:false comment produce different mutable strings each time" do
+    ruby_exe(fixture(__FILE__, "string_literal_mutable_comment.rb")).chomp.should == "frozen:false interned:false"
+  end
+end
+
 describe "The --debug flag produces" do
   it "debugging info on attempted frozen string modification" do
-    error_str = ruby_exe(fixture(__FILE__, 'debug_info.rb'), options: '--debug',  args: "2>&1")
+    error_str = ruby_exe(fixture(__FILE__, 'debug_info.rb'), options: '--enable-frozen-string-literal --debug',  args: "2>&1")
     error_str.should include("can't modify frozen String")
     error_str.should include("created at")
-    error_str.should include("command_line/fixtures/debug_info.rb:2")
+    error_str.should include("command_line/fixtures/debug_info.rb:1")
+  end
+
+  guard -> { ruby_version_is "3.4" and !"test".frozen? } do
+    it "debugging info on mutating chilled string" do
+      error_str = ruby_exe(fixture(__FILE__, 'debug_info.rb'), options: '-w --debug',  args: "2>&1")
+      error_str.should include("literal string will be frozen in the future")
+      error_str.should include("the string was created here")
+      error_str.should include("command_line/fixtures/debug_info.rb:1")
+    end
   end
 end
diff --git a/spec/ruby/command_line/rubyopt_spec.rb b/spec/ruby/command_line/rubyopt_spec.rb
index 2db42f77ef..eb297cd6fe 100644
--- a/spec/ruby/command_line/rubyopt_spec.rb
+++ b/spec/ruby/command_line/rubyopt_spec.rb
@@ -11,52 +11,70 @@ describe "Processing RUBYOPT" do
 
   it "adds the -I path to $LOAD_PATH" do
     ENV["RUBYOPT"] = "-Ioptrubyspecincl"
-    result = ruby_exe("puts $LOAD_PATH.grep(/byspecin/)", escape: true)
+    result = ruby_exe("puts $LOAD_PATH.grep(/byspecin/)")
     result.chomp[-15..-1].should == "optrubyspecincl"
   end
 
   it "sets $DEBUG to true for '-d'" do
     ENV["RUBYOPT"] = '-d'
     command = %[puts "value of $DEBUG is \#{$DEBUG}"]
-    result = ruby_exe(command, escape: true, args: "2>&1")
+    result = ruby_exe(command, args: "2>&1")
     result.should =~ /value of \$DEBUG is true/
   end
 
-  guard -> { not CROSS_COMPILING } do
+  guard -> { RbConfig::CONFIG["CROSS_COMPILING"] != "yes" } do
     it "prints the version number for '-v'" do
       ENV["RUBYOPT"] = '-v'
-      ruby_exe("")[/\A.*/].should == RUBY_DESCRIPTION
+      ruby_exe("")[/\A.*/].gsub(/\s\+(YJIT( \w+)?|ZJIT( \w+)?|PRISM|GC(\[\w+\])?)(?=\s)/, "").should == RUBY_DESCRIPTION.gsub(/\s\+(YJIT( \w+)?|ZJIT( \w+)?|PRISM|GC(\[\w+\])?)(?=\s)/, "")
     end
 
     it "ignores whitespace around the option" do
       ENV["RUBYOPT"] = ' -v '
-      ruby_exe("")[/\A.*/].should == RUBY_DESCRIPTION
+      ruby_exe("")[/\A.*/].gsub(/\s\+(YJIT( \w+)?|ZJIT( \w+)?|PRISM|GC(\[\w+\])?)(?=\s)/, "").should == RUBY_DESCRIPTION.gsub(/\s\+(YJIT( \w+)?|ZJIT( \w+)?|PRISM|GC(\[\w+\])?)(?=\s)/, "")
     end
   end
 
   it "sets $VERBOSE to true for '-w'" do
     ENV["RUBYOPT"] = '-w'
-    ruby_exe("p $VERBOSE", escape: true).chomp.should == "true"
+    ruby_exe("p $VERBOSE").chomp.should == "true"
   end
 
   it "sets $VERBOSE to true for '-W'" do
     ENV["RUBYOPT"] = '-W'
-    ruby_exe("p $VERBOSE", escape: true).chomp.should == "true"
+    ruby_exe("p $VERBOSE").chomp.should == "true"
   end
 
   it "sets $VERBOSE to nil for '-W0'" do
     ENV["RUBYOPT"] = '-W0'
-    ruby_exe("p $VERBOSE", escape: true).chomp.should == "nil"
+    ruby_exe("p $VERBOSE").chomp.should == "nil"
   end
 
   it "sets $VERBOSE to false for '-W1'" do
     ENV["RUBYOPT"] = '-W1'
-    ruby_exe("p $VERBOSE", escape: true).chomp.should == "false"
+    ruby_exe("p $VERBOSE").chomp.should == "false"
   end
 
   it "sets $VERBOSE to true for '-W2'" do
     ENV["RUBYOPT"] = '-W2'
-    ruby_exe("p $VERBOSE", escape: true).chomp.should == "true"
+    ruby_exe("p $VERBOSE").chomp.should == "true"
+  end
+
+  it "suppresses deprecation warnings for '-W:no-deprecated'" do
+    ENV["RUBYOPT"] = '-W:no-deprecated'
+    result = ruby_exe('$; = ""', args: '2>&1')
+    result.should == ""
+  end
+
+  it "suppresses experimental warnings for '-W:no-experimental'" do
+    ENV["RUBYOPT"] = '-W:no-experimental'
+    result = ruby_exe('case 0; in a; end', args: '2>&1')
+    result.should == ""
+  end
+
+  it "suppresses deprecation and experimental warnings for '-W:no-deprecated -W:no-experimental'" do
+    ENV["RUBYOPT"] = '-W:no-deprecated -W:no-experimental'
+    result = ruby_exe('case ($; = ""); in a; end', args: '2>&1')
+    result.should == ""
   end
 
   it "requires the file for '-r'" do
@@ -67,101 +85,101 @@ describe "Processing RUBYOPT" do
 
   it "raises a RuntimeError for '-a'" do
     ENV["RUBYOPT"] = '-a'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-p'" do
     ENV["RUBYOPT"] = '-p'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-n'" do
     ENV["RUBYOPT"] = '-n'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-y'" do
     ENV["RUBYOPT"] = '-y'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-c'" do
     ENV["RUBYOPT"] = '-c'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-s'" do
     ENV["RUBYOPT"] = '-s'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-h'" do
     ENV["RUBYOPT"] = '-h'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '--help'" do
     ENV["RUBYOPT"] = '--help'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-l'" do
     ENV["RUBYOPT"] = '-l'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-S'" do
     ENV["RUBYOPT"] = '-S irb'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-e'" do
     ENV["RUBYOPT"] = '-e0'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-i'" do
     ENV["RUBYOPT"] = '-i.bak'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-x'" do
     ENV["RUBYOPT"] = '-x'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-C'" do
     ENV["RUBYOPT"] = '-C'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-X'" do
     ENV["RUBYOPT"] = '-X.'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-F'" do
     ENV["RUBYOPT"] = '-F'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '-0'" do
     ENV["RUBYOPT"] = '-0'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '--copyright'" do
     ENV["RUBYOPT"] = '--copyright'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '--version'" do
     ENV["RUBYOPT"] = '--version'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 
   it "raises a RuntimeError for '--yydebug'" do
     ENV["RUBYOPT"] = '--yydebug'
-    ruby_exe("", args: '2>&1').should =~ /RuntimeError/
+    ruby_exe("", args: '2>&1', exit_status: 1).should =~ /RuntimeError/
   end
 end
diff --git a/spec/ruby/command_line/syntax_error_spec.rb b/spec/ruby/command_line/syntax_error_spec.rb
index f61cfe928d..9ba87b9e22 100644
--- a/spec/ruby/command_line/syntax_error_spec.rb
+++ b/spec/ruby/command_line/syntax_error_spec.rb
@@ -2,12 +2,18 @@ require_relative '../spec_helper'
 
 describe "The interpreter" do
   it "prints an error when given a file with invalid syntax" do
-    out = ruby_exe(fixture(__FILE__, "bad_syntax.rb"), args: "2>&1")
-    out.should include "syntax error"
+    out = ruby_exe(fixture(__FILE__, "bad_syntax.rb"), args: "2>&1", exit_status: 1)
+
+    # it's tempting not to rely on error message and rely only on exception class name,
+    # but CRuby before 3.2 doesn't print class name for syntax error
+    out.should include_any_of("syntax error", "SyntaxError")
   end
 
   it "prints an error when given code via -e with invalid syntax" do
-    out = ruby_exe(nil, args: "-e 'a{' 2>&1")
-    out.should include "syntax error"
+    out = ruby_exe(nil, args: "-e 'a{' 2>&1", exit_status: 1)
+
+    # it's tempting not to rely on error message and rely only on exception class name,
+    # but CRuby before 3.2 doesn't print class name for syntax error
+    out.should include_any_of("syntax error", "SyntaxError")
   end
 end
diff --git a/spec/ruby/core/argf/binmode_spec.rb b/spec/ruby/core/argf/binmode_spec.rb
index c2dd578d95..e083a30a27 100644
--- a/spec/ruby/core/argf/binmode_spec.rb
+++ b/spec/ruby/core/argf/binmode_spec.rb
@@ -22,7 +22,7 @@ describe "ARGF.binmode" do
       end
     end
 
-    it "puts alls subsequent stream reading through ARGF into binmode" do
+    it "puts all subsequent streams reading through ARGF into binmode" do
       argf [@bin_file, @bin_file] do
         @argf.binmode
         @argf.gets.should == "test\r\n"
@@ -34,7 +34,7 @@ describe "ARGF.binmode" do
   it "sets the file's encoding to BINARY" do
     argf [@bin_file, @file1] do
       @argf.binmode
-      @argf.binmode?.should == true
+      @argf.should.binmode?
       @argf.gets.encoding.should == Encoding::BINARY
       @argf.skip
       @argf.read.encoding.should == Encoding::BINARY
diff --git a/spec/ruby/core/argf/bytes_spec.rb b/spec/ruby/core/argf/bytes_spec.rb
deleted file mode 100644
index 71d07fabcb..0000000000
--- a/spec/ruby/core/argf/bytes_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/each_byte'
-
-describe "ARGF.bytes" do
-  it_behaves_like :argf_each_byte, :bytes
-end
diff --git a/spec/ruby/core/argf/chars_spec.rb b/spec/ruby/core/argf/chars_spec.rb
deleted file mode 100644
index ee79ea763b..0000000000
--- a/spec/ruby/core/argf/chars_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/each_char'
-
-describe "ARGF.chars" do
-  it_behaves_like :argf_each_char, :chars
-end
diff --git a/spec/ruby/core/argf/codepoints_spec.rb b/spec/ruby/core/argf/codepoints_spec.rb
deleted file mode 100644
index 7aa8a761fe..0000000000
--- a/spec/ruby/core/argf/codepoints_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/each_codepoint'
-
-describe "ARGF.codepoints" do
-  it_behaves_like :argf_each_codepoint, :codepoints
-end
diff --git a/spec/ruby/core/argf/lines_spec.rb b/spec/ruby/core/argf/lines_spec.rb
deleted file mode 100644
index 6ca6ff1256..0000000000
--- a/spec/ruby/core/argf/lines_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/each_line'
-
-describe "ARGF.lines" do
-  it_behaves_like :argf_each_line, :lines
-end
diff --git a/spec/ruby/core/argf/readpartial_spec.rb b/spec/ruby/core/argf/readpartial_spec.rb
index 5e284b3423..ea4301f25c 100644
--- a/spec/ruby/core/argf/readpartial_spec.rb
+++ b/spec/ruby/core/argf/readpartial_spec.rb
@@ -29,7 +29,7 @@ describe "ARGF.readpartial" do
 
   it "clears output buffer even if EOFError is raised because @argf is at end" do
     begin
-      output = "to be cleared"
+      output = +"to be cleared"
 
       argf [@file1_name] do
         @argf.read
@@ -69,7 +69,7 @@ describe "ARGF.readpartial" do
       print ARGF.readpartial(#{@stdin.size})
       ARGF.readpartial(1) rescue print $!.class
     STR
-    stdin = ruby_exe(ruby_str, args: "< #{@stdin_name}", escape: true)
+    stdin = ruby_exe(ruby_str, args: "< #{@stdin_name}")
     stdin.should == @stdin + "EOFError"
   end
 end
diff --git a/spec/ruby/core/argf/shared/fileno.rb b/spec/ruby/core/argf/shared/fileno.rb
index 5d674048e2..4350d43747 100644
--- a/spec/ruby/core/argf/shared/fileno.rb
+++ b/spec/ruby/core/argf/shared/fileno.rb
@@ -11,7 +11,7 @@ describe :argf_fileno, shared: true do
       # returns first current file even when not yet open
       result << @argf.send(@method) while @argf.gets
       # returns last current file even when closed
-      result.map { |d| d.class }.should == [Fixnum, Fixnum, Fixnum, Fixnum]
+      result.map { |d| d.class }.should == [Integer, Integer, Integer, Integer]
     end
   end
 
diff --git a/spec/ruby/core/argf/shared/getc.rb b/spec/ruby/core/argf/shared/getc.rb
index 8be39c60b6..d63372d9d7 100644
--- a/spec/ruby/core/argf/shared/getc.rb
+++ b/spec/ruby/core/argf/shared/getc.rb
@@ -9,7 +9,7 @@ describe :argf_getc, shared: true do
 
   it "reads each char of files" do
     argf [@file1, @file2] do
-      chars = ""
+      chars = +""
       @chars.size.times { chars << @argf.send(@method) }
       chars.should == @chars
     end
diff --git a/spec/ruby/core/argf/shared/read.rb b/spec/ruby/core/argf/shared/read.rb
index fe903983c0..e76d022139 100644
--- a/spec/ruby/core/argf/shared/read.rb
+++ b/spec/ruby/core/argf/shared/read.rb
@@ -15,7 +15,7 @@ describe :argf_read, shared: true do
 
   it "treats second argument as an output buffer" do
     argf [@file1_name] do
-      buffer = ""
+      buffer = +""
       @argf.send(@method, @file1.size, buffer)
       buffer.should == @file1
     end
@@ -23,7 +23,7 @@ describe :argf_read, shared: true do
 
   it "clears output buffer before appending to it" do
     argf [@file1_name] do
-      buffer = "to be cleared"
+      buffer = +"to be cleared"
       @argf.send(@method, @file1.size, buffer)
       buffer.should == @file1
     end
diff --git a/spec/ruby/core/array/all_spec.rb b/spec/ruby/core/array/all_spec.rb
new file mode 100644
index 0000000000..680e8c26fa
--- /dev/null
+++ b/spec/ruby/core/array/all_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#all?" do
+  @value_to_return = -> _ { true }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :all?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].all?(/bar/) { false }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/any_spec.rb b/spec/ruby/core/array/any_spec.rb
index 2fa5353e99..b51ce62f0f 100644
--- a/spec/ruby/core/array/any_spec.rb
+++ b/spec/ruby/core/array/any_spec.rb
@@ -1,24 +1,28 @@
 require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#any?" do
   describe 'with no block given (a default block of { |x| x } is implicit)' do
     it "is false if the array is empty" do
       empty_array = []
-      empty_array.any?.should == false
+      empty_array.should_not.any?
     end
 
     it "is false if the array is not empty, but all the members of the array are falsy" do
       falsy_array = [false, nil, false]
-      falsy_array.any?.should == false
+      falsy_array.should_not.any?
     end
 
     it "is true if the array has any truthy members" do
       not_empty_array = ['anything', nil]
-      not_empty_array.any?.should == true
+      not_empty_array.should.any?
     end
   end
 
   describe 'with a block given' do
+    @value_to_return = -> _ { false }
+    it_behaves_like :array_iterable_and_tolerating_size_increasing, :any?
+
     it 'is false if the array is empty' do
       empty_array = []
       empty_array.any? {|v| 1 == 1 }.should == false
@@ -34,4 +38,12 @@ describe "Array#any?" do
       array_with_members.any? {|v| v == 42 }.should == false
     end
   end
+
+  describe 'when given a pattern argument' do
+    it "ignores the block if there is an argument" do
+      -> {
+        ['bar', 'foobar'].any?(/bar/) { false }.should == true
+      }.should complain(/given block not used/)
+    end
+  end
 end
diff --git a/spec/ruby/core/array/append_spec.rb b/spec/ruby/core/array/append_spec.rb
index 302dc4a901..c12473dc07 100644
--- a/spec/ruby/core/array/append_spec.rb
+++ b/spec/ruby/core/array/append_spec.rb
@@ -30,13 +30,11 @@ describe "Array#<<" do
     a.should == [:foo]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array << 5 }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array << 5 }.should raise_error(FrozenError)
   end
 end
 
-ruby_version_is "2.5" do
-  describe "Array#append" do
-    it_behaves_like :array_push, :append
-  end
+describe "Array#append" do
+  it_behaves_like :array_push, :append
 end
diff --git a/spec/ruby/core/array/assoc_spec.rb b/spec/ruby/core/array/assoc_spec.rb
index f8479d763c..f0be3de795 100644
--- a/spec/ruby/core/array/assoc_spec.rb
+++ b/spec/ruby/core/array/assoc_spec.rb
@@ -6,7 +6,7 @@ describe "Array#assoc" do
     s1 = ["colors", "red", "blue", "green"]
     s2 = [:letters, "a", "b", "c"]
     s3 = [4]
-    s4 = ["colors", "cyan", "yellow", "magenda"]
+    s4 = ["colors", "cyan", "yellow", "magenta"]
     s5 = [:letters, "a", "i", "u"]
     s_nil = [nil, nil]
     a = [s1, s2, s3, s4, s5, s_nil]
@@ -37,4 +37,16 @@ describe "Array#assoc" do
     a.assoc(s1.first).should equal(s1)
     a.assoc(s2.first).should equal(s2)
   end
+
+  it "calls to_ary on non-array elements" do
+    s1 = [1, 2]
+    s2 = ArraySpecs::ArrayConvertible.new(2, 3)
+    a = [s1, s2]
+
+    s1.should_not_receive(:to_ary)
+    a.assoc(s1.first).should equal(s1)
+
+    a.assoc(2).should == [2, 3]
+    s2.called.should equal(:to_ary)
+  end
 end
diff --git a/spec/ruby/core/array/bsearch_index_spec.rb b/spec/ruby/core/array/bsearch_index_spec.rb
index aafded178d..94d85b37f3 100644
--- a/spec/ruby/core/array/bsearch_index_spec.rb
+++ b/spec/ruby/core/array/bsearch_index_spec.rb
@@ -63,10 +63,6 @@ describe "Array#bsearch_index" do
       @array.bsearch_index { |x| -1 }.should be_nil
     end
 
-    it "returns the middle element when block always returns zero" do
-      @array.bsearch_index { |x| 0 }.should == 2
-    end
-
     context "magnitude does not effect the result" do
       it "returns the index of any matched elements where element is between 4n <= xn < 8n" do
         [1, 2].should include(@array.bsearch_index { |x| (1 - x / 4) * (2**100) })
@@ -77,7 +73,7 @@ describe "Array#bsearch_index" do
         @array.bsearch_index { |x| (-1) * (2**100) }.should be_nil
       end
 
-      it "handles values from Bignum#coerce" do
+      it "handles values from Integer#coerce" do
         [1, 2].should include(@array.bsearch_index { |x| (2**100).coerce((1 - x / 4) * (2**100)).first })
       end
     end
diff --git a/spec/ruby/core/array/clear_spec.rb b/spec/ruby/core/array/clear_spec.rb
index 8f83a012b7..81ba56e01e 100644
--- a/spec/ruby/core/array/clear_spec.rb
+++ b/spec/ruby/core/array/clear_spec.rb
@@ -16,33 +16,17 @@ describe "Array#clear" do
   it "leaves the Array empty" do
     a = [1]
     a.clear
-    a.empty?.should == true
+    a.should.empty?
     a.size.should == 0
   end
 
-  it "keeps tainted status" do
-    a = [1]
-    a.taint
-    a.tainted?.should be_true
-    a.clear
-    a.tainted?.should be_true
-  end
-
   it "does not accept any arguments" do
     -> { [1].clear(true) }.should raise_error(ArgumentError)
   end
 
-  it "keeps untrusted status" do
-    a = [1]
-    a.untrust
-    a.untrusted?.should be_true
-    a.clear
-    a.untrusted?.should be_true
-  end
-
-  it "raises a #{frozen_error_class} on a frozen array" do
+  it "raises a FrozenError on a frozen array" do
     a = [1]
     a.freeze
-    -> { a.clear }.should raise_error(frozen_error_class)
+    -> { a.clear }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/clone_spec.rb b/spec/ruby/core/array/clone_spec.rb
index 803e746e02..e22a6c6d53 100644
--- a/spec/ruby/core/array/clone_spec.rb
+++ b/spec/ruby/core/array/clone_spec.rb
@@ -12,8 +12,8 @@ describe "Array#clone" do
     aa = a.clone
     bb = b.clone
 
-    aa.frozen?.should == true
-    bb.frozen?.should == false
+    aa.should.frozen?
+    bb.should_not.frozen?
   end
 
   it "copies singleton methods" do
diff --git a/spec/ruby/core/array/compact_spec.rb b/spec/ruby/core/array/compact_spec.rb
index ecccddeb9f..83b3fa2a89 100644
--- a/spec/ruby/core/array/compact_spec.rb
+++ b/spec/ruby/core/array/compact_spec.rb
@@ -21,18 +21,6 @@ describe "Array#compact" do
   it "does not return subclass instance for Array subclasses" do
     ArraySpecs::MyArray[1, 2, 3, nil].compact.should be_an_instance_of(Array)
   end
-
-  it "does not keep tainted status even if all elements are removed" do
-    a = [nil, nil]
-    a.taint
-    a.compact.tainted?.should be_false
-  end
-
-  it "does not keep untrusted status even if all elements are removed" do
-    a = [nil, nil]
-    a.untrust
-    a.compact.untrusted?.should be_false
-  end
 end
 
 describe "Array#compact!" do
@@ -57,21 +45,7 @@ describe "Array#compact!" do
     [1, 2, false, 3].compact!.should == nil
   end
 
-  it "keeps tainted status even if all elements are removed" do
-    a = [nil, nil]
-    a.taint
-    a.compact!
-    a.tainted?.should be_true
-  end
-
-  it "keeps untrusted status even if all elements are removed" do
-    a = [nil, nil]
-    a.untrust
-    a.compact!
-    a.untrusted?.should be_true
-  end
-
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.compact! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.compact! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/concat_spec.rb b/spec/ruby/core/array/concat_spec.rb
index cc707d9948..f3cab9c17c 100644
--- a/spec/ruby/core/array/concat_spec.rb
+++ b/spec/ruby/core/array/concat_spec.rb
@@ -32,69 +32,13 @@ describe "Array#concat" do
     [].concat(obj).should == [5, 6, 7]
   end
 
-  it "raises a #{frozen_error_class} when Array is frozen and modification occurs" do
-    -> { ArraySpecs.frozen_array.concat [1] }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when Array is frozen and modification occurs" do
+    -> { ArraySpecs.frozen_array.concat [1] }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} when Array is frozen and no modification occurs" do
-    -> { ArraySpecs.frozen_array.concat([]) }.should raise_error(frozen_error_class)
-  end
-
-  it "keeps tainted status" do
-    ary = [1, 2]
-    ary.taint
-    ary.concat([3])
-    ary.tainted?.should be_true
-    ary.concat([])
-    ary.tainted?.should be_true
-  end
-
-  it "is not infected by the other" do
-    ary = [1,2]
-    other = [3]; other.taint
-    ary.tainted?.should be_false
-    ary.concat(other)
-    ary.tainted?.should be_false
-  end
-
-  it "keeps the tainted status of elements" do
-    ary = [ Object.new, Object.new, Object.new ]
-    ary.each {|x| x.taint }
-
-    ary.concat([ Object.new ])
-    ary[0].tainted?.should be_true
-    ary[1].tainted?.should be_true
-    ary[2].tainted?.should be_true
-    ary[3].tainted?.should be_false
-  end
-
-  it "keeps untrusted status" do
-    ary = [1, 2]
-    ary.untrust
-    ary.concat([3])
-    ary.untrusted?.should be_true
-    ary.concat([])
-    ary.untrusted?.should be_true
-  end
-
-  it "is not infected untrustedness by the other" do
-    ary = [1,2]
-    other = [3]; other.untrust
-    ary.untrusted?.should be_false
-    ary.concat(other)
-    ary.untrusted?.should be_false
-  end
-
-  it "keeps the untrusted status of elements" do
-    ary = [ Object.new, Object.new, Object.new ]
-    ary.each {|x| x.untrust }
-
-    ary.concat([ Object.new ])
-    ary[0].untrusted?.should be_true
-    ary[1].untrusted?.should be_true
-    ary[2].untrusted?.should be_true
-    ary[3].untrusted?.should be_false
+  it "raises a FrozenError when Array is frozen and no modification occurs" do
+    -> { ArraySpecs.frozen_array.concat([]) }.should raise_error(FrozenError)
   end
 
   it "appends elements to an Array with enough capacity that has been shifted" do
diff --git a/spec/ruby/core/array/count_spec.rb b/spec/ruby/core/array/count_spec.rb
index eaf275aeb7..e778233c16 100644
--- a/spec/ruby/core/array/count_spec.rb
+++ b/spec/ruby/core/array/count_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#count" do
   it "returns the number of elements" do
@@ -12,4 +13,14 @@ describe "Array#count" do
   it "returns the number of element for which the block evaluates to true" do
     [:a, :b, :c].count { |s| s != :b }.should == 2
   end
+
+  it "ignores the block if there is an argument" do
+    -> {
+      [:a, :b, :b, :c].count(:b) { |e| e.size > 10 }.should == 2
+    }.should complain(/given block not used/)
+  end
+
+  context "when a block argument given" do
+    it_behaves_like :array_iterable_and_tolerating_size_increasing, :count
+  end
 end
diff --git a/spec/ruby/core/array/deconstruct_spec.rb b/spec/ruby/core/array/deconstruct_spec.rb
new file mode 100644
index 0000000000..ad67abe47b
--- /dev/null
+++ b/spec/ruby/core/array/deconstruct_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+
+describe "Array#deconstruct" do
+  it "returns self" do
+    array = [1]
+
+    array.deconstruct.should equal array
+  end
+end
diff --git a/spec/ruby/core/array/delete_at_spec.rb b/spec/ruby/core/array/delete_at_spec.rb
index c3111fe3d8..80ec643702 100644
--- a/spec/ruby/core/array/delete_at_spec.rb
+++ b/spec/ruby/core/array/delete_at_spec.rb
@@ -35,27 +35,7 @@ describe "Array#delete_at" do
     a.delete_at(-2).should == 1
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { [1,2,3].freeze.delete_at(0) }.should raise_error(frozen_error_class)
-  end
-
-  it "keeps tainted status" do
-    ary = [1, 2]
-    ary.taint
-    ary.tainted?.should be_true
-    ary.delete_at(0)
-    ary.tainted?.should be_true
-    ary.delete_at(0) # now empty
-    ary.tainted?.should be_true
-  end
-
-  it "keeps untrusted status" do
-    ary = [1, 2]
-    ary.untrust
-    ary.untrusted?.should be_true
-    ary.delete_at(0)
-    ary.untrusted?.should be_true
-    ary.delete_at(0) # now empty
-    ary.untrusted?.should be_true
+  it "raises a FrozenError on a frozen array" do
+    -> { [1,2,3].freeze.delete_at(0) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/delete_if_spec.rb b/spec/ruby/core/array/delete_if_spec.rb
index 9f22f7e086..10972eee0e 100644
--- a/spec/ruby/core/array/delete_if_spec.rb
+++ b/spec/ruby/core/array/delete_if_spec.rb
@@ -2,6 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/enumeratorize'
 require_relative 'shared/delete_if'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "Array#delete_if" do
@@ -39,28 +40,43 @@ describe "Array#delete_if" do
     @a.freeze.delete_if.should be_an_instance_of(Enumerator)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.delete_if {} }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.delete_if {} }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.delete_if {} }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.delete_if {} }.should raise_error(FrozenError)
   end
 
-  it "keeps tainted status" do
-    @a.taint
-    @a.tainted?.should be_true
-    @a.delete_if{ true }
-    @a.tainted?.should be_true
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.delete_if { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
   end
 
-  it "keeps untrusted status" do
-    @a.untrust
-    @a.untrusted?.should be_true
-    @a.delete_if{ true }
-    @a.untrusted?.should be_true
+  it "only removes elements for which the block returns true, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.delete_if do |e|
+        case e
+        when 2 then true
+        when 3 then raise StandardError, 'Oops'
+        else false
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [1, 3, 4]
   end
 
   it_behaves_like :enumeratorized_with_origin_size, :delete_if, [1,2,3]
   it_behaves_like :delete_if, :delete_if
+
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :delete_if
 end
diff --git a/spec/ruby/core/array/delete_spec.rb b/spec/ruby/core/array/delete_spec.rb
index c55f4ad672..dddbbe6bd3 100644
--- a/spec/ruby/core/array/delete_spec.rb
+++ b/spec/ruby/core/array/delete_spec.rb
@@ -40,27 +40,7 @@ describe "Array#delete" do
     [1, 2, 3].freeze.delete(0).should == nil
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { [1, 2, 3].freeze.delete(1) }.should raise_error(frozen_error_class)
-  end
-
-  it "keeps tainted status" do
-    a = [1, 2]
-    a.taint
-    a.tainted?.should be_true
-    a.delete(2)
-    a.tainted?.should be_true
-    a.delete(1) # now empty
-    a.tainted?.should be_true
-  end
-
-  it "keeps untrusted status" do
-    a = [1, 2]
-    a.untrust
-    a.untrusted?.should be_true
-    a.delete(2)
-    a.untrusted?.should be_true
-    a.delete(1) # now empty
-    a.untrusted?.should be_true
+  it "raises a FrozenError on a frozen array" do
+    -> { [1, 2, 3].freeze.delete(1) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/difference_spec.rb b/spec/ruby/core/array/difference_spec.rb
index a357657967..9f7d4c4a1a 100644
--- a/spec/ruby/core/array/difference_spec.rb
+++ b/spec/ruby/core/array/difference_spec.rb
@@ -2,23 +2,21 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/difference'
 
-ruby_version_is "2.6" do
-  describe "Array#difference" do
-    it_behaves_like :array_binary_difference, :difference
+describe "Array#difference" do
+  it_behaves_like :array_binary_difference, :difference
 
-    it "returns a copy when called without any parameter" do
-      x = [1, 2, 3, 2]
-      x.difference.should == x
-      x.difference.should_not equal x
-    end
+  it "returns a copy when called without any parameter" do
+    x = [1, 2, 3, 2]
+    x.difference.should == x
+    x.difference.should_not equal x
+  end
 
-    it "does not return subclass instances for Array subclasses" do
-      ArraySpecs::MyArray[1, 2, 3].difference.should be_an_instance_of(Array)
-    end
+  it "does not return subclass instances for Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3].difference.should be_an_instance_of(Array)
+  end
 
-    it "accepts multiple arguments" do
-      x = [1, 2, 3, 1]
-      x.difference([], [0, 1], [3, 4], [3]).should == [2]
-    end
+  it "accepts multiple arguments" do
+    x = [1, 2, 3, 1]
+    x.difference([], [0, 1], [3, 4], [3]).should == [2]
   end
 end
diff --git a/spec/ruby/core/array/drop_spec.rb b/spec/ruby/core/array/drop_spec.rb
index 89b8534af4..5926c291b8 100644
--- a/spec/ruby/core/array/drop_spec.rb
+++ b/spec/ruby/core/array/drop_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "Array#drop" do
   it "removes the specified number of elements from the start of the array" do
@@ -6,7 +7,7 @@ describe "Array#drop" do
   end
 
   it "raises an ArgumentError if the number of elements specified is negative" do
-   -> { [1, 2].drop(-3) }.should raise_error(ArgumentError)
+    -> { [1, 2].drop(-3) }.should raise_error(ArgumentError)
   end
 
   it "returns an empty Array if all elements are dropped" do
@@ -30,4 +31,26 @@ describe "Array#drop" do
     ary.shift
     ary.drop(1).should == [2]
   end
+
+  it "tries to convert the passed argument to an Integer using #to_int" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(2)
+
+    [1, 2, 3].drop(obj).should == [3]
+  end
+
+  it "raises a TypeError when the passed argument can't be coerced to Integer" do
+    -> { [1, 2].drop("cat") }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when the passed argument isn't an integer and #to_int returns non-Integer" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return("cat")
+
+    -> { [1, 2].drop(obj) }.should raise_error(TypeError)
+  end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].drop(1).should be_an_instance_of(Array)
+  end
 end
diff --git a/spec/ruby/core/array/drop_while_spec.rb b/spec/ruby/core/array/drop_while_spec.rb
index cfb6b1e267..bd46e8b882 100644
--- a/spec/ruby/core/array/drop_while_spec.rb
+++ b/spec/ruby/core/array/drop_while_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#drop_while" do
+  @value_to_return = -> _ { true }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :drop_while
+
   it "removes elements from the start of the array while the block evaluates to true" do
     [1, 2, 3, 4].drop_while { |n| n < 4 }.should == [4]
   end
@@ -12,4 +17,8 @@ describe "Array#drop_while" do
   it "removes elements from the start of the array until the block returns false" do
     [1, 2, 3, false, 5].drop_while { |n| n }.should == [false, 5]
   end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].drop_while { |n| n < 4 }.should be_an_instance_of(Array)
+  end
 end
diff --git a/spec/ruby/core/array/each_index_spec.rb b/spec/ruby/core/array/each_index_spec.rb
index 51af5842c4..3a4bca9251 100644
--- a/spec/ruby/core/array/each_index_spec.rb
+++ b/spec/ruby/core/array/each_index_spec.rb
@@ -5,7 +5,7 @@ require_relative '../enumerable/shared/enumeratorized'
 
 # Modifying a collection while the contents are being iterated
 # gives undefined behavior. See
-# http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/23633
+# https://blade.ruby-lang.org/ruby-core/23633
 
 describe "Array#each_index" do
   before :each do
@@ -40,3 +40,19 @@ describe "Array#each_index" do
   it_behaves_like :enumeratorize, :each_index
   it_behaves_like :enumeratorized_with_origin_size, :each_index, [1,2,3]
 end
+
+describe "Array#each_index" do
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.each_index do |index|
+      ScratchPad << index
+      array << i if i < 100
+      i += 1
+    end
+
+    ScratchPad.recorded.should == (0..102).to_a # element indices
+  end
+end
diff --git a/spec/ruby/core/array/each_spec.rb b/spec/ruby/core/array/each_spec.rb
index 256647d61e..f4b5b758d0 100644
--- a/spec/ruby/core/array/each_spec.rb
+++ b/spec/ruby/core/array/each_spec.rb
@@ -1,11 +1,13 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/enumeratorize'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 require_relative '../enumerable/shared/enumeratorized'
 
-# Modifying a collection while the contents are being iterated
-# gives undefined behavior. See
-# http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/23633
+# Mutating the array while it is being iterated is discouraged as it can result in confusing behavior.
+# Yet a Ruby implementation must not crash in such a case, and following the simple CRuby behavior makes sense.
+# CRuby simply reads the array storage and checks the size for every iteration;
+# like `i = 0; while i < size; yield self[i]; i += 1; end`
 
 describe "Array#each" do
   it "yields each element to the block" do
@@ -15,6 +17,34 @@ describe "Array#each" do
     a.should == [1, 2, 3]
   end
 
+  it "yields each element to the block even if the array is changed during iteration" do
+    a = [1, 2, 3, 4, 5]
+    iterated = []
+    a.each { |x| iterated << x; a << x+5 if x.even? }
+    iterated.should == [1, 2, 3, 4, 5, 7, 9]
+  end
+
+  it "yields only elements that are still in the array" do
+    a = [0, 1, 2, 3, 4]
+    iterated = []
+    a.each { |x| iterated << x; a.pop if x.even? }
+    iterated.should == [0, 1, 2]
+  end
+
+  it "yields elements based on an internal index" do
+    a = [0, 1, 2, 3, 4]
+    iterated = []
+    a.each { |x| iterated << x; a.shift if x.even? }
+    iterated.should == [0, 2, 4]
+  end
+
+  it "yields the same element multiple times if inserting while iterating" do
+    a = [1, 2]
+    iterated = []
+    a.each { |x| iterated << x; a.unshift(0) if a.size == 2 }
+    iterated.should == [1, 1, 2]
+  end
+
   it "yields each element to a block that takes multiple arguments" do
     a = [[1, 2], :a, [3, 4]]
     b = []
@@ -46,3 +76,7 @@ describe "Array#each" do
   it_behaves_like :enumeratorize, :each
   it_behaves_like :enumeratorized_with_origin_size, :each, [1,2,3]
 end
+
+describe "Array#each" do
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :each
+end
diff --git a/spec/ruby/core/array/element_set_spec.rb b/spec/ruby/core/array/element_set_spec.rb
index 9375ff9b80..df5ca9582e 100644
--- a/spec/ruby/core/array/element_set_spec.rb
+++ b/spec/ruby/core/array/element_set_spec.rb
@@ -36,6 +36,7 @@ describe "Array#[]=" do
     a[3, 2] = ['a', 'b', 'c', 'd']
     a.should == [2, 2, 3, "a", "b", "c", "d", 6]
   end
+
   it "replaces the section defined by [start,length] with the given values" do
     a = [1, 2, 3, 4, 5, 6]
     a[3, 2] = 'a', 'b', 'c', 'd'
@@ -94,8 +95,8 @@ describe "Array#[]=" do
 
   it "checks frozen before attempting to coerce arguments" do
     a = [1,2,3,4].freeze
-    -> {a[:foo] = 1}.should raise_error(frozen_error_class)
-    -> {a[:foo, :bar] = 1}.should raise_error(frozen_error_class)
+    -> {a[:foo] = 1}.should raise_error(FrozenError)
+    -> {a[:foo, :bar] = 1}.should raise_error(FrozenError)
   end
 
   it "sets elements in the range arguments when passed ranges" do
@@ -169,6 +170,7 @@ describe "Array#[]=" do
     ary[1...1] = []
     ary.should == [1, 2, 3]
   end
+
   it "does nothing if the section defined by range has negative width and the rhs is an empty array" do
     ary = [1, 2, 3, 4, 5]
     ary[1...0] = []
@@ -236,8 +238,8 @@ describe "Array#[]=" do
     ary.should == [5, 6, 7]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array[0, 0] = [] }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array[0, 0] = [] }.should raise_error(FrozenError)
   end
 end
 
@@ -284,6 +286,12 @@ describe "Array#[]= with [index, count]" do
     (a[2, 3] = [4, 5]).should == [4, 5]
   end
 
+  it "accepts a frozen String literal as RHS" do
+    a = ['a', 'b', 'c']
+    a[0, 2] = 'd'.freeze
+    a.should == ['d', 'c']
+  end
+
   it "just sets the section defined by [start,length] to nil even if the rhs is nil" do
     a = ['a', 'b', 'c', 'd', 'e']
     a[1, 3] = nil
@@ -323,6 +331,10 @@ describe "Array#[]= with [index, count]" do
     b = [1, 2, 3, 4, 5]
     b[10, 0] = [1]
     a.should == [1, 2, 3, 4, 5, nil, nil, nil, nil, nil, 1]
+
+    c = [1, 2, 3, 4, 5]
+    c[10, 0] = []
+    c.should == [1, 2, 3, 4, 5, nil, nil, nil, nil, nil]
   end
 
   it "inserts other section in place defined by idx" do
@@ -396,6 +408,14 @@ describe "Array#[]= with [m..n]" do
     a.should == [1, 2, 3, 8, 4, 5]
   end
 
+  it "inserts at the end if m > the array size" do
+    a = [1, 2, 3]
+    a[3..3] = [4]
+    a.should == [1, 2, 3, 4]
+    a[5..7] = [6]
+    a.should == [1, 2, 3, 4, nil, 6]
+  end
+
   describe "Range subclasses" do
     before :each do
       @range_incl = ArraySpecs::MyRange.new(1, 2)
@@ -425,6 +445,87 @@ describe "Array#[]= with [m..n]" do
   end
 end
 
+describe "Array#[]= with [m..]" do
+  it "just sets the section defined by range to nil even if the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(2..)")] = nil
+    a.should == [1, 2, nil]
+  end
+
+  it "just sets the section defined by range to nil if m and n < 0 and the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(-3..)")] = nil
+    a.should == [1, 2, nil]
+  end
+
+  it "replaces the section defined by range" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[eval("(3...)")] = 9
+    a.should == [6, 5, 4, 9]
+    a[eval("(2..)")] = [7, 7, 7]
+    a.should == [6, 5, 7, 7, 7]
+  end
+
+  it "replaces the section if m and n < 0" do
+    a = [1, 2, 3, 4, 5]
+    a[eval("(-3..)")] = [7, 8, 9]
+    a.should == [1, 2, 7, 8, 9]
+  end
+
+  it "inserts at the end if m > the array size" do
+    a = [1, 2, 3]
+    a[eval("(3..)")] = [4]
+    a.should == [1, 2, 3, 4]
+    a[eval("(5..)")] = [6]
+    a.should == [1, 2, 3, 4, nil, 6]
+  end
+end
+
+describe "Array#[]= with [..n] and [...n]" do
+  it "just sets the section defined by range to nil even if the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[(..2)] = nil
+    a.should == [nil, 4, 5]
+    a[(...2)] = nil
+    a.should == [nil, 5]
+  end
+
+  it "just sets the section defined by range to nil if n < 0 and the rhs is nil" do
+    a = [1, 2, 3, 4, 5]
+    a[(..-3)] = nil
+    a.should == [nil, 4, 5]
+    a[(...-1)] = [nil, 5]
+  end
+
+  it "replaces the section defined by range" do
+    a = [6, 5, 4, 3, 2, 1]
+    a[(...3)] = 9
+    a.should == [9, 3, 2, 1]
+    a[(..2)] = [7, 7, 7, 7, 7]
+    a.should == [7, 7, 7, 7, 7, 1]
+  end
+
+  it "replaces the section if n < 0" do
+    a = [1, 2, 3, 4, 5]
+    a[(..-2)] = [7, 8, 9]
+    a.should == [7, 8, 9, 5]
+  end
+
+  it "replaces everything if n > the array size" do
+    a = [1, 2, 3]
+    a[(...7)] = [4]
+    a.should == [4]
+  end
+
+  it "inserts at the beginning if n < negative the array size" do
+    a = [1, 2, 3]
+    a[(..-7)] = [4]
+    a.should == [4, 1, 2, 3]
+    a[(...-10)] = [6]
+    a.should == [6, 4, 1, 2, 3]
+  end
+end
+
 describe "Array#[] after a shift" do
   it "works for insertion" do
     a = [1,2]
diff --git a/spec/ruby/core/array/empty_spec.rb b/spec/ruby/core/array/empty_spec.rb
index b5f3e8ed48..f70b1b6ebe 100644
--- a/spec/ruby/core/array/empty_spec.rb
+++ b/spec/ruby/core/array/empty_spec.rb
@@ -3,8 +3,8 @@ require_relative 'fixtures/classes'
 
 describe "Array#empty?" do
   it "returns true if the array has no elements" do
-    [].empty?.should == true
-    [1].empty?.should == false
-    [1, 2].empty?.should == false
+    [].should.empty?
+    [1].should_not.empty?
+    [1, 2].should_not.empty?
   end
 end
diff --git a/spec/ruby/core/array/fetch_values_spec.rb b/spec/ruby/core/array/fetch_values_spec.rb
new file mode 100644
index 0000000000..cf377b3b71
--- /dev/null
+++ b/spec/ruby/core/array/fetch_values_spec.rb
@@ -0,0 +1,55 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Array#fetch_values" do
+  before :each do
+    @array = [:a, :b, :c]
+  end
+
+  ruby_version_is "3.4" do
+    describe "with matched indexes" do
+      it "returns the values for indexes" do
+        @array.fetch_values(0).should == [:a]
+        @array.fetch_values(0, 2).should == [:a, :c]
+        @array.fetch_values(-1).should == [:c]
+      end
+
+      it "returns the values for indexes ordered in the order of the requested indexes" do
+        @array.fetch_values(2, 0).should == [:c, :a]
+      end
+    end
+
+    describe "with unmatched indexes" do
+      it "raises a index error if no block is provided" do
+        -> { @array.fetch_values(0, 1, 44) }.should raise_error(IndexError, "index 44 outside of array bounds: -3...3")
+      end
+
+      it "returns the default value from block" do
+        @array.fetch_values(44) { |index| "`#{index}' is not found" }.should == ["`44' is not found"]
+        @array.fetch_values(0, 44) { |index| "`#{index}' is not found" }.should == [:a, "`44' is not found"]
+      end
+    end
+
+    describe "without keys" do
+      it "returns an empty Array" do
+        @array.fetch_values.should == []
+      end
+    end
+
+    it "tries to convert the passed argument to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(2)
+      @array.fetch_values(obj).should == [:c]
+    end
+
+    it "does not support a Range object as argument" do
+      -> {
+        @array.fetch_values(1..2)
+      }.should raise_error(TypeError, "no implicit conversion of Range into Integer")
+    end
+
+    it "raises a TypeError when the passed argument can't be coerced to Integer" do
+      -> { [].fetch_values("cat") }.should raise_error(TypeError, "no implicit conversion of String into Integer")
+    end
+  end
+end
diff --git a/spec/ruby/core/array/fill_spec.rb b/spec/ruby/core/array/fill_spec.rb
index 1c1beef25e..2c3b5d9e84 100644
--- a/spec/ruby/core/array/fill_spec.rb
+++ b/spec/ruby/core/array/fill_spec.rb
@@ -21,7 +21,7 @@ describe "Array#fill" do
 
   it "does not replicate the filler" do
     ary = [1, 2, 3, 4]
-    str = "x"
+    str = +"x"
     ary.fill(str).should == [str, str, str, str]
     str << "y"
     ary.should == [str, str, str, str]
@@ -43,20 +43,18 @@ describe "Array#fill" do
     [nil, nil, nil, nil].fill { |i| i * 2 }.should == [0, 2, 4, 6]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.fill('x') }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.fill('x') }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.fill('x') }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.fill('x') }.should raise_error(FrozenError)
   end
 
   it "raises an ArgumentError if 4 or more arguments are passed when no block given" do
-    -> { [].fill('a') }.should_not raise_error(ArgumentError)
-
-    -> { [].fill('a', 1) }.should_not raise_error(ArgumentError)
-
-    -> { [].fill('a', 1, 2) }.should_not raise_error(ArgumentError)
+    [].fill('a').should == []
+    [].fill('a', 1).should == []
+    [].fill('a', 1, 2).should == [nil, 'a', 'a']
     -> { [].fill('a', 1, 2, true) }.should raise_error(ArgumentError)
   end
 
@@ -65,12 +63,52 @@ describe "Array#fill" do
   end
 
   it "raises an ArgumentError if 3 or more arguments are passed when a block given" do
-    -> { [].fill() {|i|} }.should_not raise_error(ArgumentError)
+    [].fill() {|i|}.should == []
+    [].fill(1) {|i|}.should == []
+    [].fill(1, 2) {|i|}.should == [nil, nil, nil]
+    -> { [].fill(1, 2, true) {|i|} }.should raise_error(ArgumentError)
+  end
 
-    -> { [].fill(1) {|i|} }.should_not raise_error(ArgumentError)
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.fill { raise StandardError, 'Oops' }
+    rescue
+    end
 
-    -> { [].fill(1, 2) {|i|} }.should_not raise_error(ArgumentError)
-    -> { [].fill(1, 2, true) {|i|} }.should raise_error(ArgumentError)
+    a.should == [1, 2, 3]
+  end
+
+  it "only changes elements before error is raised, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.fill do |i|
+        case i
+        when 0 then -1
+        when 1 then -2
+        when 2 then raise StandardError, 'Oops'
+        else 0
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [-1, -2, 3, 4]
+  end
+
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.fill do |index|
+      ScratchPad << index
+      array << i if i < 100
+      i++
+      index
+    end
+
+    ScratchPad.recorded.should == [0, 1, 2]
   end
 end
 
@@ -169,25 +207,25 @@ describe "Array#fill with (filler, index, length)" do
     [1, 2, 3, 4, 5].fill(-2, -2, &@never_passed).should == [1, 2, 3, 4, 5]
   end
 
-  # See: http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/17481
+  # See: https://blade.ruby-lang.org/ruby-core/17481
   it "does not raise an exception if the given length is negative and its absolute value does not exceed the index" do
-    -> { [1, 2, 3, 4].fill('a', 3, -1)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill('a', 3, -2)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill('a', 3, -3)}.should_not raise_error(ArgumentError)
+    [1, 2, 3, 4].fill('a', 3, -1).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -2).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -3).should == [1, 2, 3, 4]
 
-    -> { [1, 2, 3, 4].fill(3, -1, &@never_passed)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill(3, -2, &@never_passed)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill(3, -3, &@never_passed)}.should_not raise_error(ArgumentError)
+    [1, 2, 3, 4].fill(3, -1, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -2, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -3, &@never_passed).should == [1, 2, 3, 4]
   end
 
   it "does not raise an exception even if the given length is negative and its absolute value exceeds the index" do
-    -> { [1, 2, 3, 4].fill('a', 3, -4)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill('a', 3, -5)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill('a', 3, -10000)}.should_not raise_error(ArgumentError)
+    [1, 2, 3, 4].fill('a', 3, -4).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -5).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill('a', 3, -10000).should == [1, 2, 3, 4]
 
-    -> { [1, 2, 3, 4].fill(3, -4, &@never_passed)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill(3, -5, &@never_passed)}.should_not raise_error(ArgumentError)
-    -> { [1, 2, 3, 4].fill(3, -10000, &@never_passed)}.should_not raise_error(ArgumentError)
+    [1, 2, 3, 4].fill(3, -4, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -5, &@never_passed).should == [1, 2, 3, 4]
+    [1, 2, 3, 4].fill(3, -10000, &@never_passed).should == [1, 2, 3, 4]
   end
 
   it "tries to convert the second and third arguments to Integers using #to_int" do
@@ -205,10 +243,17 @@ describe "Array#fill with (filler, index, length)" do
     -> { [].fill('a', obj) }.should raise_error(TypeError)
   end
 
+  it "raises a TypeError when the length is not numeric" do
+    -> { [1, 2, 3].fill("x", 1, "foo") }.should raise_error(TypeError, /no implicit conversion of String into Integer/)
+    -> { [1, 2, 3].fill("x", 1, :"foo") }.should raise_error(TypeError, /no implicit conversion of Symbol into Integer/)
+    -> { [1, 2, 3].fill("x", 1, Object.new) }.should raise_error(TypeError, /no implicit conversion of Object into Integer/)
+  end
+
   not_supported_on :opal do
     it "raises an ArgumentError or RangeError for too-large sizes" do
+      error_types = [RangeError, ArgumentError]
       arr = [1, 2, 3]
-      -> { arr.fill(10, 1, fixnum_max) }.should raise_error(ArgumentError)
+      -> { arr.fill(10, 1, fixnum_max) }.should raise_error { |err| error_types.should include(err.class) }
       -> { arr.fill(10, 1, bignum_value) }.should raise_error(RangeError)
     end
   end
@@ -314,4 +359,16 @@ describe "Array#fill with (filler, range)" do
     def obj.<=>(rhs); rhs == self ? 0 : nil end
     -> { [].fill('a', obj..obj) }.should raise_error(TypeError)
   end
+
+  it "works with endless ranges" do
+    [1, 2, 3, 4].fill('x', eval("(1..)")).should == [1, 'x', 'x', 'x']
+    [1, 2, 3, 4].fill('x', eval("(3...)")).should == [1, 2, 3, 'x']
+    [1, 2, 3, 4].fill(eval("(1..)")) { |x| x + 2 }.should == [1, 3, 4, 5]
+    [1, 2, 3, 4].fill(eval("(3...)")) { |x| x + 2 }.should == [1, 2, 3, 5]
+  end
+
+  it "works with beginless ranges" do
+    [1, 2, 3, 4].fill('x', (..2)).should == ["x", "x", "x", 4]
+    [1, 2, 3, 4].fill((...2)) { |x| x + 2 }.should == [2, 3, 3, 4]
+  end
 end
diff --git a/spec/ruby/core/array/filter_spec.rb b/spec/ruby/core/array/filter_spec.rb
index ee4f71ca28..156ad14f9c 100644
--- a/spec/ruby/core/array/filter_spec.rb
+++ b/spec/ruby/core/array/filter_spec.rb
@@ -1,16 +1,14 @@
 require_relative '../../spec_helper'
 require_relative 'shared/select'
 
-ruby_version_is "2.6" do
-  describe "Array#filter" do
-    it_behaves_like :array_select, :filter
-  end
-
-  describe "Array#filter!" do
-    it "returns nil if no changes were made in the array" do
-      [1, 2, 3].filter! { true }.should be_nil
-    end
+describe "Array#filter" do
+  it_behaves_like :array_select, :filter
+end
 
-    it_behaves_like :keep_if, :filter!
+describe "Array#filter!" do
+  it "returns nil if no changes were made in the array" do
+    [1, 2, 3].filter! { true }.should be_nil
   end
+
+  it_behaves_like :keep_if, :filter!
 end
diff --git a/spec/ruby/core/array/fixtures/classes.rb b/spec/ruby/core/array/fixtures/classes.rb
index 42071ed0cd..05283c0f74 100644
--- a/spec/ruby/core/array/fixtures/classes.rb
+++ b/spec/ruby/core/array/fixtures/classes.rb
@@ -40,6 +40,62 @@ module ArraySpecs
     a
   end
 
+  # Chi squared critical values for tests with n degrees of freedom at 99% confidence.
+  # Values obtained from NIST Engineering Statistic Handbook at
+  # https://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm
+
+  CHI_SQUARED_CRITICAL_VALUES = [
+    0,
+    6.635, 9.210, 11.345, 13.277, 15.086, 16.812, 18.475, 20.090, 21.666, 23.209,
+    24.725, 26.217, 27.688, 29.141, 30.578, 32.000, 33.409, 34.805, 36.191, 37.566,
+    38.932, 40.289, 41.638, 42.980, 44.314, 45.642, 46.963, 48.278, 49.588, 50.892,
+    52.191, 53.486, 54.776, 56.061, 57.342, 58.619, 59.893, 61.162, 62.428, 63.691,
+    64.950, 66.206, 67.459, 68.710, 69.957, 71.201, 72.443, 73.683, 74.919, 76.154,
+    77.386, 78.616, 79.843, 81.069, 82.292, 83.513, 84.733, 85.950, 87.166, 88.379,
+    89.591, 90.802, 92.010, 93.217, 94.422, 95.626, 96.828, 98.028, 99.228, 100.425,
+    101.621, 102.816, 104.010, 105.202, 106.393, 107.583, 108.771, 109.958, 111.144, 112.329,
+    113.512, 114.695, 115.876, 117.057, 118.236, 119.414, 120.591, 121.767, 122.942, 124.116,
+    125.289, 126.462, 127.633, 128.803, 129.973, 131.141, 132.309, 133.476, 134.642, 135.807,
+  ]
+
+  def self.measure_sample_fairness(size, samples, iters)
+    ary = Array.new(size) { |x| x }
+    expected = iters.fdiv size
+    (samples).times do |i|
+      chi_results = []
+      3.times do
+        counts = Array.new(size, 0)
+        iters.times do
+          x = ary.sample(samples)[i]
+          counts[x] += 1
+        end
+        chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
+        chi_results << chi_squared
+        break if chi_squared <= CHI_SQUARED_CRITICAL_VALUES[size]
+      end
+
+      chi_results.min.should <= CHI_SQUARED_CRITICAL_VALUES[size]
+    end
+  end
+
+  def self.measure_sample_fairness_large_sample_size(size, samples, iters)
+    ary = Array.new(size) { |x| x }
+    counts = Array.new(size, 0)
+    expected = (iters * samples).fdiv size
+    iters.times do
+      ary.sample(samples).each do |sample|
+        counts[sample] += 1
+      end
+    end
+    chi_squared = counts.sum {|count| (count - expected) ** 2} / expected
+
+    # Chi squared critical values for tests with 4 degrees of freedom
+    # Values obtained from NIST Engineering Statistic Handbook at
+    # https://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm
+
+    chi_squared.should <= CHI_SQUARED_CRITICAL_VALUES[size]
+  end
+
   class MyArray < Array
     # The #initialize method has a different signature than Array to help
     # catch places in the specs that do not assert the #initialize is not
@@ -98,6 +154,16 @@ module ArraySpecs
     end
   end
 
+  class ArrayMethodMissing
+    def initialize(*values, &block)
+      @values = values;
+    end
+
+    def method_missing(name, *args)
+      @values
+    end
+  end
+
   class SortSame
     def <=>(other); 0; end
     def ==(other); true; end
@@ -126,7 +192,7 @@ module ArraySpecs
     attr_accessor :order
   end
 
-  class ComparableWithFixnum
+  class ComparableWithInteger
     include Comparable
     def initialize(num)
       @num = num
@@ -144,373 +210,377 @@ module ArraySpecs
   end
 
   def self.universal_pack_object
-    obj = mock("string float int")
+    obj = mock("string float int".freeze)
     obj.stub!(:to_int).and_return(1)
     obj.stub!(:to_str).and_return("1")
     obj.stub!(:to_f).and_return(1.0)
     obj
   end
 
-  LargeArray = ["test_create_table_with_force_true_does_not_drop_nonexisting_table",
- "test_add_table",
- "assert_difference",
- "assert_operator",
- "instance_variables",
- "class",
- "instance_variable_get",
- "__class__",
- "expects",
- "assert_no_difference",
- "name",
- "assert_blank",
- "assert_not_same",
- "is_a?",
- "test_add_table_with_decimals",
- "test_create_table_with_timestamps_should_create_datetime_columns",
- "assert_present",
- "assert_no_match",
- "__instance_of__",
- "assert_deprecated",
- "assert",
- "assert_throws",
- "kind_of?",
- "try",
- "__instance_variable_get__",
- "object_id",
- "timeout",
- "instance_variable_set",
- "assert_nothing_thrown",
- "__instance_variable_set__",
- "copy_object",
- "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
- "assert_not_deprecated",
- "assert_in_delta",
- "id",
- "copy_metaclass",
- "test_create_table_without_a_block",
- "dup",
- "assert_not_nil",
- "send",
- "__instance_variables__",
- "to_sql",
- "mock",
- "assert_send",
- "instance_variable_defined?",
- "clone",
- "require",
- "test_migrator",
- "__instance_variable_defined_eh__",
- "frozen?",
- "test_add_column_not_null_with_default",
- "freeze",
- "test_migrator_one_up",
- "test_migrator_one_down",
- "singleton_methods",
- "method_exists?",
- "create_fixtures",
- "test_migrator_one_up_one_down",
- "test_native_decimal_insert_manual_vs_automatic",
- "instance_exec",
- "__is_a__",
- "test_migrator_double_up",
- "stub",
- "private_methods",
- "stubs",
- "test_migrator_double_down",
- "fixture_path",
- "private_singleton_methods",
- "stub_everything",
- "test_migrator_one_up_with_exception_and_rollback",
- "sequence",
- "protected_methods",
- "enum_for",
- "test_finds_migrations",
- "run_before_mocha",
- "states",
- "protected_singleton_methods",
- "to_json",
- "instance_values",
- "==",
- "mocha_setup",
- "public_methods",
- "test_finds_pending_migrations",
- "mocha_verify",
- "assert_kind_of",
- "===",
- "=~",
- "test_relative_migrations",
- "mocha_teardown",
- "gem",
- "mocha",
- "test_only_loads_pending_migrations",
- "test_add_column_with_precision_and_scale",
- "require_or_load",
- "eql?",
- "require_dependency",
- "test_native_types",
- "test_target_version_zero_should_run_only_once",
- "extend",
- "to_matcher",
- "unloadable",
- "require_association",
- "hash",
- "__id__",
- "load_dependency",
- "equals",
- "test_migrator_db_has_no_schema_migrations_table",
- "test_migrator_verbosity",
- "kind_of",
- "to_yaml",
- "to_bool",
- "test_migrator_verbosity_off",
- "taint",
- "test_migrator_going_down_due_to_version_target",
- "tainted?",
- "mocha_inspect",
- "test_migrator_rollback",
- "vim",
- "untaint",
- "taguri=",
- "test_migrator_forward",
- "test_schema_migrations_table_name",
- "test_proper_table_name",
- "all_of",
- "test_add_drop_table_with_prefix_and_suffix",
- "_setup_callbacks",
- "setup",
- "Not",
- "test_create_table_with_binary_column",
- "assert_not_equal",
- "enable_warnings",
- "acts_like?",
- "Rational",
- "_removed_setup_callbacks",
- "Table",
- "bind",
- "any_of",
- "__method__",
- "test_migrator_with_duplicates",
- "_teardown_callbacks",
- "method",
- "test_migrator_with_duplicate_names",
- "_removed_teardown_callbacks",
- "any_parameters",
- "test_migrator_with_missing_version_numbers",
- "test_add_remove_single_field_using_string_arguments",
- "test_create_table_with_custom_sequence_name",
- "test_add_remove_single_field_using_symbol_arguments",
- "_one_time_conditions_valid_14?",
- "_one_time_conditions_valid_16?",
- "run_callbacks",
- "anything",
- "silence_warnings",
- "instance_variable_names",
- "_fixture_path",
- "copy_instance_variables_from",
- "fixture_path?",
- "has_entry",
- "__marshal__",
- "_fixture_table_names",
- "__kind_of__",
- "fixture_table_names?",
- "test_add_rename",
- "assert_equal",
- "_fixture_class_names",
- "fixture_class_names?",
- "has_entries",
- "_use_transactional_fixtures",
- "people",
- "test_rename_column_using_symbol_arguments",
- "use_transactional_fixtures?",
- "instance_eval",
- "blank?",
- "with_warnings",
- "__nil__",
- "load",
- "metaclass",
- "_use_instantiated_fixtures",
- "has_key",
- "class_eval",
- "present?",
- "test_rename_column",
- "teardown",
- "use_instantiated_fixtures?",
- "method_name",
- "silence_stderr",
- "presence",
- "test_rename_column_preserves_default_value_not_null",
- "silence_stream",
- "_pre_loaded_fixtures",
- "__metaclass__",
- "__fixnum__",
- "pre_loaded_fixtures?",
- "has_value",
- "suppress",
- "to_yaml_properties",
- "test_rename_nonexistent_column",
- "test_add_index",
- "includes",
- "find_correlate_in",
- "equality_predicate_sql",
- "assert_nothing_raised",
- "let",
- "not_predicate_sql",
- "test_rename_column_with_sql_reserved_word",
- "singleton_class",
- "test_rename_column_with_an_index",
- "display",
- "taguri",
- "to_yaml_style",
- "test_remove_column_with_index",
- "size",
- "current_adapter?",
- "test_remove_column_with_multi_column_index",
- "respond_to?",
- "test_change_type_of_not_null_column",
- "is_a",
- "to_a",
- "test_rename_table_for_sqlite_should_work_with_reserved_words",
- "require_library_or_gem",
- "setup_fixtures",
- "equal?",
- "teardown_fixtures",
- "nil?",
- "fixture_table_names",
- "fixture_class_names",
- "test_create_table_without_id",
- "use_transactional_fixtures",
- "test_add_column_with_primary_key_attribute",
- "repair_validations",
- "use_instantiated_fixtures",
- "instance_of?",
- "test_create_table_adds_id",
- "test_rename_table",
- "pre_loaded_fixtures",
- "to_enum",
- "test_create_table_with_not_null_column",
- "instance_of",
- "test_change_column_nullability",
- "optionally",
- "test_rename_table_with_an_index",
- "run",
- "test_change_column",
- "default_test",
- "assert_raise",
- "test_create_table_with_defaults",
- "assert_nil",
- "flunk",
- "regexp_matches",
- "duplicable?",
- "reset_mocha",
- "stubba_method",
- "filter_backtrace",
- "test_create_table_with_limits",
- "responds_with",
- "stubba_object",
- "test_change_column_with_nil_default",
- "assert_block",
- "__show__",
- "assert_date_from_db",
- "__respond_to_eh__",
- "run_in_transaction?",
- "inspect",
- "assert_sql",
- "test_change_column_with_new_default",
- "yaml_equivalent",
- "build_message",
- "to_s",
- "test_change_column_default",
- "assert_queries",
- "pending",
- "as_json",
- "assert_no_queries",
- "test_change_column_quotes_column_names",
- "assert_match",
- "test_keeping_default_and_notnull_constraint_on_change",
- "methods",
- "connection_allow_concurrency_setup",
- "connection_allow_concurrency_teardown",
- "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
- "__send__",
- "make_connection",
- "assert_raises",
- "tap",
- "with_kcode",
- "assert_instance_of",
- "test_create_table_with_primary_key_prefix_as_table_name",
- "assert_respond_to",
- "test_change_column_default_to_null",
- "assert_same",
- "__extend__"]
-
-  LargeTestArraySorted = ["test_add_column_not_null_with_default",
- "test_add_column_with_precision_and_scale",
- "test_add_column_with_primary_key_attribute",
- "test_add_drop_table_with_prefix_and_suffix",
- "test_add_index",
- "test_add_remove_single_field_using_string_arguments",
- "test_add_remove_single_field_using_symbol_arguments",
- "test_add_rename",
- "test_add_table",
- "test_add_table_with_decimals",
- "test_change_column",
- "test_change_column_default",
- "test_change_column_default_to_null",
- "test_change_column_nullability",
- "test_change_column_quotes_column_names",
- "test_change_column_with_new_default",
- "test_change_column_with_nil_default",
- "test_change_type_of_not_null_column",
- "test_create_table_adds_id",
- "test_create_table_with_binary_column",
- "test_create_table_with_custom_sequence_name",
- "test_create_table_with_defaults",
- "test_create_table_with_force_true_does_not_drop_nonexisting_table",
- "test_create_table_with_limits",
- "test_create_table_with_not_null_column",
- "test_create_table_with_primary_key_prefix_as_table_name",
- "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
- "test_create_table_with_timestamps_should_create_datetime_columns",
- "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
- "test_create_table_without_a_block",
- "test_create_table_without_id",
- "test_finds_migrations",
- "test_finds_pending_migrations",
- "test_keeping_default_and_notnull_constraint_on_change",
- "test_migrator",
- "test_migrator_db_has_no_schema_migrations_table",
- "test_migrator_double_down",
- "test_migrator_double_up",
- "test_migrator_forward",
- "test_migrator_going_down_due_to_version_target",
- "test_migrator_one_down",
- "test_migrator_one_up",
- "test_migrator_one_up_one_down",
- "test_migrator_one_up_with_exception_and_rollback",
- "test_migrator_rollback",
- "test_migrator_verbosity",
- "test_migrator_verbosity_off",
- "test_migrator_with_duplicate_names",
- "test_migrator_with_duplicates",
- "test_migrator_with_missing_version_numbers",
- "test_native_decimal_insert_manual_vs_automatic",
- "test_native_types",
- "test_only_loads_pending_migrations",
- "test_proper_table_name",
- "test_relative_migrations",
- "test_remove_column_with_index",
- "test_remove_column_with_multi_column_index",
- "test_rename_column",
- "test_rename_column_preserves_default_value_not_null",
- "test_rename_column_using_symbol_arguments",
- "test_rename_column_with_an_index",
- "test_rename_column_with_sql_reserved_word",
- "test_rename_nonexistent_column",
- "test_rename_table",
- "test_rename_table_for_sqlite_should_work_with_reserved_words",
- "test_rename_table_with_an_index",
- "test_schema_migrations_table_name",
- "test_target_version_zero_should_run_only_once"]
+  LargeArray = [
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_add_table",
+    "assert_difference",
+    "assert_operator",
+    "instance_variables",
+    "class",
+    "instance_variable_get",
+    "__class__",
+    "expects",
+    "assert_no_difference",
+    "name",
+    "assert_blank",
+    "assert_not_same",
+    "is_a?",
+    "test_add_table_with_decimals",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "assert_present",
+    "assert_no_match",
+    "__instance_of__",
+    "assert_deprecated",
+    "assert",
+    "assert_throws",
+    "kind_of?",
+    "try",
+    "__instance_variable_get__",
+    "object_id",
+    "timeout",
+    "instance_variable_set",
+    "assert_nothing_thrown",
+    "__instance_variable_set__",
+    "copy_object",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "assert_not_deprecated",
+    "assert_in_delta",
+    "id",
+    "copy_metaclass",
+    "test_create_table_without_a_block",
+    "dup",
+    "assert_not_nil",
+    "send",
+    "__instance_variables__",
+    "to_sql",
+    "mock",
+    "assert_send",
+    "instance_variable_defined?",
+    "clone",
+    "require",
+    "test_migrator",
+    "__instance_variable_defined_eh__",
+    "frozen?",
+    "test_add_column_not_null_with_default",
+    "freeze",
+    "test_migrator_one_up",
+    "test_migrator_one_down",
+    "singleton_methods",
+    "method_exists?",
+    "create_fixtures",
+    "test_migrator_one_up_one_down",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "instance_exec",
+    "__is_a__",
+    "test_migrator_double_up",
+    "stub",
+    "private_methods",
+    "stubs",
+    "test_migrator_double_down",
+    "fixture_path",
+    "private_singleton_methods",
+    "stub_everything",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "sequence",
+    "protected_methods",
+    "enum_for",
+    "test_finds_migrations",
+    "run_before_mocha",
+    "states",
+    "protected_singleton_methods",
+    "to_json",
+    "instance_values",
+    "==",
+    "mocha_setup",
+    "public_methods",
+    "test_finds_pending_migrations",
+    "mocha_verify",
+    "assert_kind_of",
+    "===",
+    "=~",
+    "test_relative_migrations",
+    "mocha_teardown",
+    "gem",
+    "mocha",
+    "test_only_loads_pending_migrations",
+    "test_add_column_with_precision_and_scale",
+    "require_or_load",
+    "eql?",
+    "require_dependency",
+    "test_native_types",
+    "test_target_version_zero_should_run_only_once",
+    "extend",
+    "to_matcher",
+    "unloadable",
+    "require_association",
+    "hash",
+    "__id__",
+    "load_dependency",
+    "equals",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_verbosity",
+    "kind_of",
+    "to_yaml",
+    "to_bool",
+    "test_migrator_verbosity_off",
+    "taint",
+    "test_migrator_going_down_due_to_version_target",
+    "tainted?",
+    "mocha_inspect",
+    "test_migrator_rollback",
+    "vim",
+    "untaint",
+    "taguri=",
+    "test_migrator_forward",
+    "test_schema_migrations_table_name",
+    "test_proper_table_name",
+    "all_of",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "_setup_callbacks",
+    "setup",
+    "Not",
+    "test_create_table_with_binary_column",
+    "assert_not_equal",
+    "enable_warnings",
+    "acts_like?",
+    "Rational",
+    "_removed_setup_callbacks",
+    "Table",
+    "bind",
+    "any_of",
+    "__method__",
+    "test_migrator_with_duplicates",
+    "_teardown_callbacks",
+    "method",
+    "test_migrator_with_duplicate_names",
+    "_removed_teardown_callbacks",
+    "any_parameters",
+    "test_migrator_with_missing_version_numbers",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_create_table_with_custom_sequence_name",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "_one_time_conditions_valid_14?",
+    "_one_time_conditions_valid_16?",
+    "run_callbacks",
+    "anything",
+    "silence_warnings",
+    "instance_variable_names",
+    "_fixture_path",
+    "copy_instance_variables_from",
+    "fixture_path?",
+    "has_entry",
+    "__marshal__",
+    "_fixture_table_names",
+    "__kind_of__",
+    "fixture_table_names?",
+    "test_add_rename",
+    "assert_equal",
+    "_fixture_class_names",
+    "fixture_class_names?",
+    "has_entries",
+    "_use_transactional_fixtures",
+    "people",
+    "test_rename_column_using_symbol_arguments",
+    "use_transactional_fixtures?",
+    "instance_eval",
+    "blank?",
+    "with_warnings",
+    "__nil__",
+    "load",
+    "metaclass",
+    "_use_instantiated_fixtures",
+    "has_key",
+    "class_eval",
+    "present?",
+    "test_rename_column",
+    "teardown",
+    "use_instantiated_fixtures?",
+    "method_name",
+    "silence_stderr",
+    "presence",
+    "test_rename_column_preserves_default_value_not_null",
+    "silence_stream",
+    "_pre_loaded_fixtures",
+    "__metaclass__",
+    "__fixnum__",
+    "pre_loaded_fixtures?",
+    "has_value",
+    "suppress",
+    "to_yaml_properties",
+    "test_rename_nonexistent_column",
+    "test_add_index",
+    "includes",
+    "find_correlate_in",
+    "equality_predicate_sql",
+    "assert_nothing_raised",
+    "let",
+    "not_predicate_sql",
+    "test_rename_column_with_sql_reserved_word",
+    "singleton_class",
+    "test_rename_column_with_an_index",
+    "display",
+    "taguri",
+    "to_yaml_style",
+    "test_remove_column_with_index",
+    "size",
+    "current_adapter?",
+    "test_remove_column_with_multi_column_index",
+    "respond_to?",
+    "test_change_type_of_not_null_column",
+    "is_a",
+    "to_a",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "require_library_or_gem",
+    "setup_fixtures",
+    "equal?",
+    "teardown_fixtures",
+    "nil?",
+    "fixture_table_names",
+    "fixture_class_names",
+    "test_create_table_without_id",
+    "use_transactional_fixtures",
+    "test_add_column_with_primary_key_attribute",
+    "repair_validations",
+    "use_instantiated_fixtures",
+    "instance_of?",
+    "test_create_table_adds_id",
+    "test_rename_table",
+    "pre_loaded_fixtures",
+    "to_enum",
+    "test_create_table_with_not_null_column",
+    "instance_of",
+    "test_change_column_nullability",
+    "optionally",
+    "test_rename_table_with_an_index",
+    "run",
+    "test_change_column",
+    "default_test",
+    "assert_raise",
+    "test_create_table_with_defaults",
+    "assert_nil",
+    "flunk",
+    "regexp_matches",
+    "duplicable?",
+    "reset_mocha",
+    "stubba_method",
+    "filter_backtrace",
+    "test_create_table_with_limits",
+    "responds_with",
+    "stubba_object",
+    "test_change_column_with_nil_default",
+    "assert_block",
+    "__show__",
+    "assert_date_from_db",
+    "__respond_to_eh__",
+    "run_in_transaction?",
+    "inspect",
+    "assert_sql",
+    "test_change_column_with_new_default",
+    "yaml_equivalent",
+    "build_message",
+    "to_s",
+    "test_change_column_default",
+    "assert_queries",
+    "pending",
+    "as_json",
+    "assert_no_queries",
+    "test_change_column_quotes_column_names",
+    "assert_match",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "methods",
+    "connection_allow_concurrency_setup",
+    "connection_allow_concurrency_teardown",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "__send__",
+    "make_connection",
+    "assert_raises",
+    "tap",
+    "with_kcode",
+    "assert_instance_of",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "assert_respond_to",
+    "test_change_column_default_to_null",
+    "assert_same",
+    "__extend__",
+  ]
+
+  LargeTestArraySorted = [
+    "test_add_column_not_null_with_default",
+    "test_add_column_with_precision_and_scale",
+    "test_add_column_with_primary_key_attribute",
+    "test_add_drop_table_with_prefix_and_suffix",
+    "test_add_index",
+    "test_add_remove_single_field_using_string_arguments",
+    "test_add_remove_single_field_using_symbol_arguments",
+    "test_add_rename",
+    "test_add_table",
+    "test_add_table_with_decimals",
+    "test_change_column",
+    "test_change_column_default",
+    "test_change_column_default_to_null",
+    "test_change_column_nullability",
+    "test_change_column_quotes_column_names",
+    "test_change_column_with_new_default",
+    "test_change_column_with_nil_default",
+    "test_change_type_of_not_null_column",
+    "test_create_table_adds_id",
+    "test_create_table_with_binary_column",
+    "test_create_table_with_custom_sequence_name",
+    "test_create_table_with_defaults",
+    "test_create_table_with_force_true_does_not_drop_nonexisting_table",
+    "test_create_table_with_limits",
+    "test_create_table_with_not_null_column",
+    "test_create_table_with_primary_key_prefix_as_table_name",
+    "test_create_table_with_primary_key_prefix_as_table_name_with_underscore",
+    "test_create_table_with_timestamps_should_create_datetime_columns",
+    "test_create_table_with_timestamps_should_create_datetime_columns_with_options",
+    "test_create_table_without_a_block",
+    "test_create_table_without_id",
+    "test_finds_migrations",
+    "test_finds_pending_migrations",
+    "test_keeping_default_and_notnull_constraint_on_change",
+    "test_migrator",
+    "test_migrator_db_has_no_schema_migrations_table",
+    "test_migrator_double_down",
+    "test_migrator_double_up",
+    "test_migrator_forward",
+    "test_migrator_going_down_due_to_version_target",
+    "test_migrator_one_down",
+    "test_migrator_one_up",
+    "test_migrator_one_up_one_down",
+    "test_migrator_one_up_with_exception_and_rollback",
+    "test_migrator_rollback",
+    "test_migrator_verbosity",
+    "test_migrator_verbosity_off",
+    "test_migrator_with_duplicate_names",
+    "test_migrator_with_duplicates",
+    "test_migrator_with_missing_version_numbers",
+    "test_native_decimal_insert_manual_vs_automatic",
+    "test_native_types",
+    "test_only_loads_pending_migrations",
+    "test_proper_table_name",
+    "test_relative_migrations",
+    "test_remove_column_with_index",
+    "test_remove_column_with_multi_column_index",
+    "test_rename_column",
+    "test_rename_column_preserves_default_value_not_null",
+    "test_rename_column_using_symbol_arguments",
+    "test_rename_column_with_an_index",
+    "test_rename_column_with_sql_reserved_word",
+    "test_rename_nonexistent_column",
+    "test_rename_table",
+    "test_rename_table_for_sqlite_should_work_with_reserved_words",
+    "test_rename_table_with_an_index",
+    "test_schema_migrations_table_name",
+    "test_target_version_zero_should_run_only_once",
+  ]
 
   class PrivateToAry
     private
diff --git a/spec/ruby/core/array/fixtures/encoded_strings.rb b/spec/ruby/core/array/fixtures/encoded_strings.rb
index 5b85bd0e06..b5888d86ae 100644
--- a/spec/ruby/core/array/fixtures/encoded_strings.rb
+++ b/spec/ruby/core/array/fixtures/encoded_strings.rb
@@ -2,14 +2,14 @@
 module ArraySpecs
   def self.array_with_usascii_and_7bit_utf8_strings
     [
-      'foo'.force_encoding('US-ASCII'),
+      'foo'.dup.force_encoding('US-ASCII'),
       'bar'
     ]
   end
 
   def self.array_with_usascii_and_utf8_strings
     [
-      'foo'.force_encoding('US-ASCII'),
+      'foo'.dup.force_encoding('US-ASCII'),
       'báz'
     ]
   end
@@ -17,7 +17,7 @@ module ArraySpecs
   def self.array_with_7bit_utf8_and_usascii_strings
     [
       'bar',
-      'foo'.force_encoding('US-ASCII')
+      'foo'.dup.force_encoding('US-ASCII')
     ]
   end
 
@@ -25,13 +25,13 @@ module ArraySpecs
     [
       'báz',
       'bar',
-      'foo'.force_encoding('US-ASCII')
+      'foo'.dup.force_encoding('US-ASCII')
     ]
   end
 
   def self.array_with_usascii_and_utf8_strings
     [
-      'foo'.force_encoding('US-ASCII'),
+      'foo'.dup.force_encoding('US-ASCII'),
       'bar',
       'báz'
     ]
@@ -41,7 +41,7 @@ module ArraySpecs
     [
       'bar',
       'báz',
-      'foo'.force_encoding('BINARY')
+      'foo'.dup.force_encoding('BINARY')
     ]
   end
 
@@ -55,14 +55,14 @@ module ArraySpecs
 
   def self.array_with_usascii_and_7bit_binary_strings
     [
-      'bar'.force_encoding('US-ASCII'),
-      'foo'.force_encoding('BINARY')
+      'bar'.dup.force_encoding('US-ASCII'),
+      'foo'.dup.force_encoding('BINARY')
     ]
   end
 
   def self.array_with_usascii_and_binary_strings
     [
-      'bar'.force_encoding('US-ASCII'),
+      'bar'.dup.force_encoding('US-ASCII'),
       [255].pack('C').force_encoding('BINARY')
     ]
   end
diff --git a/spec/ruby/core/array/flatten_spec.rb b/spec/ruby/core/array/flatten_spec.rb
index b506f899b4..8c97000c79 100644
--- a/spec/ruby/core/array/flatten_spec.rb
+++ b/spec/ruby/core/array/flatten_spec.rb
@@ -75,11 +75,11 @@ describe "Array#flatten" do
     [[obj]].flatten(1)
   end
 
-  it "returns subclass instance for Array subclasses" do
-    ArraySpecs::MyArray[].flatten.should be_an_instance_of(ArraySpecs::MyArray)
-    ArraySpecs::MyArray[1, 2, 3].flatten.should be_an_instance_of(ArraySpecs::MyArray)
-    ArraySpecs::MyArray[1, [2], 3].flatten.should be_an_instance_of(ArraySpecs::MyArray)
-    ArraySpecs::MyArray[1, [2, 3], 4].flatten.should == ArraySpecs::MyArray[1, 2, 3, 4]
+  it "returns Array instance for Array subclasses" do
+    ArraySpecs::MyArray[].flatten.should be_an_instance_of(Array)
+    ArraySpecs::MyArray[1, 2, 3].flatten.should be_an_instance_of(Array)
+    ArraySpecs::MyArray[1, [2], 3].flatten.should be_an_instance_of(Array)
+    ArraySpecs::MyArray[1, [2, 3], 4].flatten.should == [1, 2, 3, 4]
     [ArraySpecs::MyArray[1, 2, 3]].flatten.should be_an_instance_of(Array)
   end
 
@@ -109,20 +109,10 @@ describe "Array#flatten" do
       -> { [@obj].flatten }.should raise_error(TypeError)
     end
 
-    ruby_version_is ""..."2.5" do
-      it "calls respond_to_missing?(:to_ary, false) to try coercing" do
-        def @obj.respond_to_missing?(*args) ScratchPad << args; false end
-        [@obj].flatten.should == [@obj]
-        ScratchPad.recorded.should == [[:to_ary, false]]
-      end
-    end
-
-    ruby_version_is "2.5" do
-      it "calls respond_to_missing?(:to_ary, true) to try coercing" do
-        def @obj.respond_to_missing?(*args) ScratchPad << args; false end
-        [@obj].flatten.should == [@obj]
-        ScratchPad.recorded.should == [[:to_ary, true]]
-      end
+    it "calls respond_to_missing?(:to_ary, true) to try coercing" do
+      def @obj.respond_to_missing?(*args) ScratchPad << args; false end
+      [@obj].flatten.should == [@obj]
+      ScratchPad.recorded.should == [[:to_ary, true]]
     end
 
     it "does not call #to_ary if not defined when #respond_to_missing? returns false" do
@@ -145,14 +135,6 @@ describe "Array#flatten" do
     end
   end
 
-  it "returns a tainted array if self is tainted" do
-    [].taint.flatten.tainted?.should be_true
-  end
-
-  it "returns an untrusted array if self is untrusted" do
-    [].untrust.flatten.untrusted?.should be_true
-  end
-
   it "performs respond_to? and method_missing-aware checks when coercing elements to array" do
     bo = BasicObject.new
     [bo].flatten.should == [bo]
@@ -270,15 +252,15 @@ describe "Array#flatten!" do
     ary.should == [1, 2, 3]
   end
 
-  it "raises a #{frozen_error_class} on frozen arrays when the array is modified" do
+  it "raises a FrozenError on frozen arrays when the array is modified" do
     nested_ary = [1, 2, []]
     nested_ary.freeze
-    -> { nested_ary.flatten! }.should raise_error(frozen_error_class)
+    -> { nested_ary.flatten! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23663]
-  it "raises a #{frozen_error_class} on frozen arrays when the array would not be modified" do
-    -> { ArraySpecs.frozen_array.flatten! }.should raise_error(frozen_error_class)
-    -> { ArraySpecs.empty_frozen_array.flatten! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on frozen arrays when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.flatten! }.should raise_error(FrozenError)
+    -> { ArraySpecs.empty_frozen_array.flatten! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/frozen_spec.rb b/spec/ruby/core/array/frozen_spec.rb
index bb4b2b4067..3ba54be46b 100644
--- a/spec/ruby/core/array/frozen_spec.rb
+++ b/spec/ruby/core/array/frozen_spec.rb
@@ -4,13 +4,13 @@ require_relative 'fixtures/classes'
 describe "Array#frozen?" do
   it "returns true if array is frozen" do
     a = [1, 2, 3]
-    a.frozen?.should == false
+    a.should_not.frozen?
     a.freeze
-    a.frozen?.should == true
+    a.should.frozen?
   end
 
   it "returns false for an array being sorted by #sort" do
     a = [1, 2, 3]
-    a.sort { |x,y| a.frozen?.should == false; x <=> y }
+    a.sort { |x,y| a.should_not.frozen?; x <=> y }
   end
 end
diff --git a/spec/ruby/core/array/hash_spec.rb b/spec/ruby/core/array/hash_spec.rb
index 8392253ae4..f3bcc83fce 100644
--- a/spec/ruby/core/array/hash_spec.rb
+++ b/spec/ruby/core/array/hash_spec.rb
@@ -7,7 +7,7 @@ describe "Array#hash" do
 
     [[], [1, 2, 3]].each do |ary|
       ary.hash.should == ary.dup.hash
-      ary.hash.should be_an_instance_of(Fixnum)
+      ary.hash.should be_an_instance_of(Integer)
     end
   end
 
diff --git a/spec/ruby/core/array/initialize_spec.rb b/spec/ruby/core/array/initialize_spec.rb
index dfc2ae3518..b9fa77b16e 100644
--- a/spec/ruby/core/array/initialize_spec.rb
+++ b/spec/ruby/core/array/initialize_spec.rb
@@ -32,13 +32,13 @@ describe "Array#initialize" do
     end.should raise_error(ArgumentError)
   end
 
-  it "raises a #{frozen_error_class} on frozen arrays" do
+  it "raises a FrozenError on frozen arrays" do
     -> do
       ArraySpecs.frozen_array.send :initialize
-    end.should raise_error(frozen_error_class)
+    end.should raise_error(FrozenError)
     -> do
       ArraySpecs.frozen_array.send :initialize, ArraySpecs.frozen_array
-    end.should raise_error(frozen_error_class)
+    end.should raise_error(FrozenError)
   end
 
   it "calls #to_ary to convert the value to an array, even if it's private" do
@@ -53,7 +53,9 @@ describe "Array#initialize with no arguments" do
   end
 
   it "does not use the given block" do
-    ->{ [1, 2, 3].send(:initialize) { raise } }.should_not raise_error
+    -> {
+      -> { [1, 2, 3].send(:initialize) { raise } }.should_not raise_error
+    }.should complain(/#{__FILE__}:#{__LINE__-1}: warning: given block not used/, verbose: true)
   end
 end
 
diff --git a/spec/ruby/core/array/insert_spec.rb b/spec/ruby/core/array/insert_spec.rb
index 7577a8f743..9e1757f68b 100644
--- a/spec/ruby/core/array/insert_spec.rb
+++ b/spec/ruby/core/array/insert_spec.rb
@@ -67,12 +67,12 @@ describe "Array#insert" do
     -> { [].insert() }.should raise_error(ArgumentError)
   end
 
-  it "raises a #{frozen_error_class} on frozen arrays when the array is modified" do
-    -> { ArraySpecs.frozen_array.insert(0, 'x') }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on frozen arrays when the array is modified" do
+    -> { ArraySpecs.frozen_array.insert(0, 'x') }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on frozen arrays when the array would not be modified" do
-    -> { ArraySpecs.frozen_array.insert(0) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on frozen arrays when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.insert(0) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/intersect_spec.rb b/spec/ruby/core/array/intersect_spec.rb
new file mode 100644
index 0000000000..456aa26c6e
--- /dev/null
+++ b/spec/ruby/core/array/intersect_spec.rb
@@ -0,0 +1,64 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe 'Array#intersect?' do
+  describe 'when at least one element in two Arrays is the same' do
+    it 'returns true' do
+      [1, 2].intersect?([2, 3, 4]).should == true
+      [2, 3, 4].intersect?([1, 2]).should == true
+    end
+  end
+
+  describe 'when there are no elements in common between two Arrays' do
+    it 'returns false' do
+      [0, 1, 2].intersect?([3, 4]).should == false
+      [3, 4].intersect?([0, 1, 2]).should == false
+      [3, 4].intersect?([]).should == false
+      [].intersect?([0, 1, 2]).should == false
+    end
+  end
+
+  it "tries to convert the passed argument to an Array using #to_ary" do
+    obj = mock('[1,2,3]')
+    obj.should_receive(:to_ary).and_return([1, 2, 3])
+
+    [1, 2].intersect?(obj).should == true
+  end
+
+  it "determines equivalence between elements in the sense of eql?" do
+    obj1 = mock('1')
+    obj2 = mock('2')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.stub!(:eql?).and_return(true)
+    obj2.stub!(:eql?).and_return(true)
+
+    [obj1].intersect?([obj2]).should == true
+
+    obj1 = mock('3')
+    obj2 = mock('4')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.stub!(:eql?).and_return(false)
+    obj2.stub!(:eql?).and_return(false)
+
+    [obj1].intersect?([obj2]).should == false
+  end
+
+  it "does not call to_ary on array subclasses" do
+    [5, 6].intersect?(ArraySpecs::ToAryArray[1, 2, 5, 6]).should == true
+  end
+
+  it "properly handles an identical item even when its #eql? isn't reflexive" do
+    x = mock('x')
+    x.stub!(:hash).and_return(42)
+    x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
+
+    [x].intersect?([x]).should == true
+  end
+
+  it "has semantic of !(a & b).empty?" do
+    [].intersect?([]).should == false
+    [nil].intersect?([nil]).should == true
+  end
+end
diff --git a/spec/ruby/core/array/intersection_spec.rb b/spec/ruby/core/array/intersection_spec.rb
index 7bf2ec4dbe..e01a68d389 100644
--- a/spec/ruby/core/array/intersection_spec.rb
+++ b/spec/ruby/core/array/intersection_spec.rb
@@ -1,87 +1,19 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/intersection'
 
 describe "Array#&" do
-  it "creates an array with elements common to both arrays (intersection)" do
-    ([] & []).should == []
-    ([1, 2] & []).should == []
-    ([] & [1, 2]).should == []
-    ([ 1, 3, 5 ] & [ 1, 2, 3 ]).should == [1, 3]
-  end
-
-  it "creates an array with no duplicates" do
-    ([ 1, 1, 3, 5 ] & [ 1, 2, 3 ]).uniq!.should == nil
-  end
-
-  it "creates an array with elements in order they are first encountered" do
-    ([ 1, 2, 3, 2, 5 ] & [ 5, 2, 3, 4 ]).should == [2, 3, 5]
-  end
-
-  it "does not modify the original Array" do
-    a = [1, 1, 3, 5]
-    (a & [1, 2, 3]).should == [1, 3]
-    a.should == [1, 1, 3, 5]
-  end
-
-  it "properly handles recursive arrays" do
-    empty = ArraySpecs.empty_recursive_array
-    (empty & empty).should == empty
-
-    (ArraySpecs.recursive_array & []).should == []
-    ([] & ArraySpecs.recursive_array).should == []
-
-    (ArraySpecs.recursive_array & ArraySpecs.recursive_array).should == [1, 'two', 3.0, ArraySpecs.recursive_array]
-  end
-
-  it "tries to convert the passed argument to an Array using #to_ary" do
-    obj = mock('[1,2,3]')
-    obj.should_receive(:to_ary).and_return([1, 2, 3])
-    ([1, 2] & obj).should == ([1, 2])
-  end
-
-  it "determines equivalence between elements in the sense of eql?" do
-    not_supported_on :opal do
-      ([5.0, 4.0] & [5, 4]).should == []
-    end
-
-    str = "x"
-    ([str] & [str.dup]).should == [str]
-
-    obj1 = mock('1')
-    obj2 = mock('2')
-    obj1.stub!(:hash).and_return(0)
-    obj2.stub!(:hash).and_return(0)
-    obj1.should_receive(:eql?).at_least(1).and_return(true)
-    obj2.stub!(:eql?).and_return(true)
-
-    ([obj1] & [obj2]).should == [obj1]
-    ([obj1, obj1, obj2, obj2] & [obj2]).should == [obj1]
-
-    obj1 = mock('3')
-    obj2 = mock('4')
-    obj1.stub!(:hash).and_return(0)
-    obj2.stub!(:hash).and_return(0)
-    obj1.should_receive(:eql?).at_least(1).and_return(false)
+  it_behaves_like :array_intersection, :&
+end
 
-    ([obj1] & [obj2]).should == []
-    ([obj1, obj1, obj2, obj2] & [obj2]).should == [obj2]
-  end
+describe "Array#intersection" do
+  it_behaves_like :array_intersection, :intersection
 
-  it "does return subclass instances for Array subclasses" do
-    (ArraySpecs::MyArray[1, 2, 3] & []).should be_an_instance_of(Array)
-    (ArraySpecs::MyArray[1, 2, 3] & ArraySpecs::MyArray[1, 2, 3]).should be_an_instance_of(Array)
-    ([] & ArraySpecs::MyArray[1, 2, 3]).should be_an_instance_of(Array)
+  it "accepts multiple arguments" do
+    [1, 2, 3, 4].intersection([1, 2, 3], [2, 3, 4]).should == [2, 3]
   end
 
-  it "does not call to_ary on array subclasses" do
-    ([5, 6] & ArraySpecs::ToAryArray[1, 2, 5, 6]).should == [5, 6]
-  end
-
-  it "properly handles an identical item even when its #eql? isn't reflexive" do
-    x = mock('x')
-    x.stub!(:hash).and_return(42)
-    x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
-
-    ([x] & [x]).should == [x]
+  it "preserves elements order from original array" do
+    [1, 2, 3, 4].intersection([3, 2, 1]).should == [1, 2, 3]
   end
 end
diff --git a/spec/ruby/core/array/keep_if_spec.rb b/spec/ruby/core/array/keep_if_spec.rb
index bf2bdeaf91..40f7329b7c 100644
--- a/spec/ruby/core/array/keep_if_spec.rb
+++ b/spec/ruby/core/array/keep_if_spec.rb
@@ -1,3 +1,4 @@
+require_relative '../../spec_helper'
 require_relative 'shared/keep_if'
 
 describe "Array#keep_if" do
diff --git a/spec/ruby/core/array/minmax_spec.rb b/spec/ruby/core/array/minmax_spec.rb
new file mode 100644
index 0000000000..e11fe63347
--- /dev/null
+++ b/spec/ruby/core/array/minmax_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/enumerable/minmax'
+
+describe "Array#minmax" do
+  before :each do
+    @enum = [6, 4, 5, 10, 8]
+    @empty_enum = []
+    @incomparable_enum = [BasicObject.new, BasicObject.new]
+    @incompatible_enum = [11, "22"]
+    @strs = ["333", "2", "60", "55555", "1010", "111"]
+  end
+
+  it_behaves_like :enumerable_minmax, :minmax
+end
diff --git a/spec/ruby/core/array/multiply_spec.rb b/spec/ruby/core/array/multiply_spec.rb
index ab654ce489..eca51142fb 100644
--- a/spec/ruby/core/array/multiply_spec.rb
+++ b/spec/ruby/core/array/multiply_spec.rb
@@ -76,10 +76,10 @@ describe "Array#* with an integer" do
       @array = ArraySpecs::MyArray[1, 2, 3, 4, 5]
     end
 
-    it "returns a subclass instance" do
-      (@array * 0).should be_an_instance_of(ArraySpecs::MyArray)
-      (@array * 1).should be_an_instance_of(ArraySpecs::MyArray)
-      (@array * 2).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns an Array instance" do
+      (@array * 0).should be_an_instance_of(Array)
+      (@array * 1).should be_an_instance_of(Array)
+      (@array * 2).should be_an_instance_of(Array)
     end
 
     it "does not call #initialize on the subclass instance" do
@@ -87,44 +87,6 @@ describe "Array#* with an integer" do
       ScratchPad.recorded.should be_nil
     end
   end
-
-  it "copies the taint status of the original array even if the passed count is 0" do
-    ary = [1, 2, 3]
-    ary.taint
-    (ary * 0).tainted?.should == true
-  end
-
-  it "copies the taint status of the original array even if the array is empty" do
-    ary = []
-    ary.taint
-    (ary * 3).tainted?.should == true
-  end
-
-  it "copies the taint status of the original array if the passed count is not 0" do
-    ary = [1, 2, 3]
-    ary.taint
-    (ary * 1).tainted?.should == true
-    (ary * 2).tainted?.should == true
-  end
-
-  it "copies the untrusted status of the original array even if the passed count is 0" do
-    ary = [1, 2, 3]
-    ary.untrust
-    (ary * 0).untrusted?.should == true
-  end
-
-  it "copies the untrusted status of the original array even if the array is empty" do
-    ary = []
-    ary.untrust
-    (ary * 3).untrusted?.should == true
-  end
-
-  it "copies the untrusted status of the original array if the passed count is not 0" do
-    ary = [1, 2, 3]
-    ary.untrust
-    (ary * 1).untrusted?.should == true
-    (ary * 2).untrusted?.should == true
-  end
 end
 
 describe "Array#* with a string" do
diff --git a/spec/ruby/core/array/new_spec.rb b/spec/ruby/core/array/new_spec.rb
index 96ec6b8198..b50a4857b0 100644
--- a/spec/ruby/core/array/new_spec.rb
+++ b/spec/ruby/core/array/new_spec.rb
@@ -26,7 +26,9 @@ describe "Array.new with no arguments" do
   end
 
   it "does not use the given block" do
-    ->{ Array.new { raise } }.should_not raise_error
+    -> {
+      -> { Array.new { raise } }.should_not raise_error
+    }.should complain(/warning: given block not used/, verbose: true)
   end
 end
 
diff --git a/spec/ruby/core/array/none_spec.rb b/spec/ruby/core/array/none_spec.rb
new file mode 100644
index 0000000000..31cd8c46d6
--- /dev/null
+++ b/spec/ruby/core/array/none_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#none?" do
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :none?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].none?(/baz/) { true }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/one_spec.rb b/spec/ruby/core/array/one_spec.rb
new file mode 100644
index 0000000000..0c61907881
--- /dev/null
+++ b/spec/ruby/core/array/one_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
+
+describe "Array#one?" do
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :one?
+
+  it "ignores the block if there is an argument" do
+    -> {
+      ['bar', 'foobar'].one?(/foo/) { false }.should == true
+    }.should complain(/given block not used/)
+  end
+end
diff --git a/spec/ruby/core/array/pack/a_spec.rb b/spec/ruby/core/array/pack/a_spec.rb
index 7af7a16c68..8245cd5470 100644
--- a/spec/ruby/core/array/pack/a_spec.rb
+++ b/spec/ruby/core/array/pack/a_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -12,11 +12,22 @@ describe "Array#pack with format 'A'" do
   it_behaves_like :array_pack_string, 'A'
   it_behaves_like :array_pack_taint, 'A'
 
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack A string")
+    obj.should_receive(:to_str).and_return("``abcdef")
+    [obj].pack("A*").should == "``abcdef"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('A') }.should raise_error(TypeError)
+    -> { [0].pack('a') }.should raise_error(TypeError)
+  end
+
   it "adds all the bytes to the output when passed the '*' modifier" do
     ["abc"].pack("A*").should == "abc"
   end
 
-  it "padds the output with spaces when the count exceeds the size of the String" do
+  it "pads the output with spaces when the count exceeds the size of the String" do
     ["abc"].pack("A6").should == "abc   "
   end
 
@@ -44,7 +55,7 @@ describe "Array#pack with format 'a'" do
     ["abc"].pack("a*").should == "abc"
   end
 
-  it "padds the output with NULL bytes when the count exceeds the size of the String" do
+  it "pads the output with NULL bytes when the count exceeds the size of the String" do
     ["abc"].pack("a6").should == "abc\x00\x00\x00"
   end
 
diff --git a/spec/ruby/core/array/pack/at_spec.rb b/spec/ruby/core/array/pack/at_spec.rb
index 3942677913..bb9801440a 100644
--- a/spec/ruby/core/array/pack/at_spec.rb
+++ b/spec/ruby/core/array/pack/at_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
diff --git a/spec/ruby/core/array/pack/b_spec.rb b/spec/ruby/core/array/pack/b_spec.rb
index 872c1b88d5..247a9ca023 100644
--- a/spec/ruby/core/array/pack/b_spec.rb
+++ b/spec/ruby/core/array/pack/b_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -13,11 +13,16 @@ describe "Array#pack with format 'B'" do
   it_behaves_like :array_pack_taint, 'B'
 
   it "calls #to_str to convert an Object to a String" do
-    obj = mock("pack H string")
+    obj = mock("pack B string")
     obj.should_receive(:to_str).and_return("``abcdef")
     [obj].pack("B*").should == "\x2a"
   end
 
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('B') }.should raise_error(TypeError)
+    -> { [0].pack('b') }.should raise_error(TypeError)
+  end
+
   it "encodes one bit for each character starting with the most significant bit" do
     [ [["0"], "\x00"],
       [["1"], "\x80"]
diff --git a/spec/ruby/core/array/pack/buffer_spec.rb b/spec/ruby/core/array/pack/buffer_spec.rb
index ecb40bfd06..b77b2d1efa 100644
--- a/spec/ruby/core/array/pack/buffer_spec.rb
+++ b/spec/ruby/core/array/pack/buffer_spec.rb
@@ -13,13 +13,13 @@ describe "Array#pack with :buffer option" do
   it "adds result at the end of buffer content" do
     n = [ 65, 66, 67 ] # result without buffer is "ABC"
 
-    buffer = ""
+    buffer = +""
     n.pack("ccc", buffer: buffer).should == "ABC"
 
-    buffer = "123"
+    buffer = +"123"
     n.pack("ccc", buffer: buffer).should == "123ABC"
 
-    buffer = "12345"
+    buffer = +"12345"
     n.pack("ccc", buffer: buffer).should == "12345ABC"
   end
 
@@ -28,22 +28,32 @@ describe "Array#pack with :buffer option" do
       TypeError, "buffer must be String, not Array")
   end
 
+  it "raise FrozenError if buffer is frozen" do
+    -> { [65].pack("c", buffer: "frozen-string".freeze) }.should raise_error(FrozenError)
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    [65, 66, 67].pack("ccc", buffer: buffer)
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
   context "offset (@) is specified" do
     it 'keeps buffer content if it is longer than offset' do
       n = [ 65, 66, 67 ]
-      buffer = "123456"
+      buffer = +"123456"
       n.pack("@3ccc", buffer: buffer).should == "123ABC"
     end
 
     it "fills the gap with \\0 if buffer content is shorter than offset" do
       n = [ 65, 66, 67 ]
-      buffer = "123"
+      buffer = +"123"
       n.pack("@6ccc", buffer: buffer).should == "123\0\0\0ABC"
     end
 
     it 'does not keep buffer content if it is longer than offset + result' do
       n = [ 65, 66, 67 ]
-      buffer = "1234567890"
+      buffer = +"1234567890"
       n.pack("@3ccc", buffer: buffer).should == "123ABC"
     end
   end
diff --git a/spec/ruby/core/array/pack/c_spec.rb b/spec/ruby/core/array/pack/c_spec.rb
index 7200830331..47b71b663d 100644
--- a/spec/ruby/core/array/pack/c_spec.rb
+++ b/spec/ruby/core/array/pack/c_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
@@ -45,8 +45,20 @@ describe :array_pack_8bit, shared: true do
     [1, 2, 3, 4, 5].pack(pack_format('*')).should == "\x01\x02\x03\x04\x05"
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack(pack_format("\000", 2)).should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [1, 2, 3].pack(pack_format("\000", 2)).should == "\x01\x02"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/comment_spec.rb b/spec/ruby/core/array/pack/comment_spec.rb
index 254c827ccc..daf1cff06a 100644
--- a/spec/ruby/core/array/pack/comment_spec.rb
+++ b/spec/ruby/core/array/pack/comment_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/core/array/pack/h_spec.rb b/spec/ruby/core/array/pack/h_spec.rb
index 85a875fc8b..ba188874ba 100644
--- a/spec/ruby/core/array/pack/h_spec.rb
+++ b/spec/ruby/core/array/pack/h_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -18,6 +18,11 @@ describe "Array#pack with format 'H'" do
     [obj].pack("H").should == "\xa0"
   end
 
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('H') }.should raise_error(TypeError)
+    -> { [0].pack('h') }.should raise_error(TypeError)
+  end
+
   it "encodes the first character as the most significant nibble when passed no count modifier" do
     ["ab"].pack("H").should == "\xa0"
   end
diff --git a/spec/ruby/core/array/pack/l_spec.rb b/spec/ruby/core/array/pack/l_spec.rb
index b446a7a36a..f6dfb1da83 100644
--- a/spec/ruby/core/array/pack/l_spec.rb
+++ b/spec/ruby/core/array/pack/l_spec.rb
@@ -29,7 +29,7 @@ describe "Array#pack with format 'L'" do
     it_behaves_like :array_pack_32bit_be, 'L>'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :array_pack_32bit_le, 'L<_'
       it_behaves_like :array_pack_32bit_le, 'L_<'
@@ -51,7 +51,7 @@ describe "Array#pack with format 'L'" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :array_pack_64bit_le, 'L<_'
       it_behaves_like :array_pack_64bit_le, 'L_<'
@@ -83,7 +83,7 @@ describe "Array#pack with format 'l'" do
     it_behaves_like :array_pack_32bit_be, 'l>'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :array_pack_32bit_le, 'l<_'
       it_behaves_like :array_pack_32bit_le, 'l_<'
@@ -105,7 +105,7 @@ describe "Array#pack with format 'l'" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :array_pack_64bit_le, 'l<_'
       it_behaves_like :array_pack_64bit_le, 'l_<'
@@ -137,7 +137,7 @@ little_endian do
     it_behaves_like :array_pack_32bit_le, 'l'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "Array#pack with format 'L' with modifier '_'" do
       it_behaves_like :array_pack_32bit_le, 'L_'
     end
@@ -155,7 +155,7 @@ little_endian do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "Array#pack with format 'L' with modifier '_'" do
       it_behaves_like :array_pack_64bit_le, 'L_'
     end
@@ -183,7 +183,7 @@ big_endian do
     it_behaves_like :array_pack_32bit_be, 'l'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "Array#pack with format 'L' with modifier '_'" do
       it_behaves_like :array_pack_32bit_be, 'L_'
     end
@@ -201,7 +201,7 @@ big_endian do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "Array#pack with format 'L' with modifier '_'" do
       it_behaves_like :array_pack_64bit_be, 'L_'
     end
diff --git a/spec/ruby/core/array/pack/m_spec.rb b/spec/ruby/core/array/pack/m_spec.rb
index 2b1a84abca..a80f91275c 100644
--- a/spec/ruby/core/array/pack/m_spec.rb
+++ b/spec/ruby/core/array/pack/m_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -80,8 +80,16 @@ describe "Array#pack with format 'M'" do
     ].should be_computed_by(:pack, "M")
   end
 
-  it "encodes a tab followed by a newline with an encoded newline" do
+  it "encodes a tab at the end of a line with an encoded newline" do
+    ["\t"].pack("M").should == "\t=\n"
     ["\t\n"].pack("M").should == "\t=\n\n"
+    ["abc\t\nxyz"].pack("M").should == "abc\t=\n\nxyz=\n"
+  end
+
+  it "encodes a space at the end of a line with an encoded newline" do
+    [" "].pack("M").should == " =\n"
+    [" \n"].pack("M").should == " =\n\n"
+    ["abc \nxyz"].pack("M").should == "abc =\n\nxyz=\n"
   end
 
   it "encodes 127..255 in hex format" do
diff --git a/spec/ruby/core/array/pack/p_spec.rb b/spec/ruby/core/array/pack/p_spec.rb
index 857d403313..b023bf9110 100644
--- a/spec/ruby/core/array/pack/p_spec.rb
+++ b/spec/ruby/core/array/pack/p_spec.rb
@@ -15,16 +15,6 @@ describe "Array#pack with format 'P'" do
     ["hello"].pack("P").unpack("P5").should == ["hello"]
   end
 
-  it "taints the input string" do
-    input_string = "hello"
-    [input_string].pack("P")
-    input_string.tainted?.should be_true
-  end
-
-  it "does not taint the output string in normal cases" do
-    ["hello"].pack("P").tainted?.should be_false
-  end
-
   it "with nil gives a null pointer" do
     [nil].pack("P").unpack("J").should == [0]
   end
@@ -42,16 +32,6 @@ describe "Array#pack with format 'p'" do
     ["hello"].pack("p").unpack("p").should == ["hello"]
   end
 
-  it "taints the input string" do
-    input_string = "hello"
-    [input_string].pack("p")
-    input_string.tainted?.should be_true
-  end
-
-  it "does not taint the output string in normal cases" do
-    ["hello"].pack("p").tainted?.should be_false
-  end
-
   it "with nil gives a null pointer" do
     [nil].pack("p").unpack("J").should == [0]
   end
diff --git a/spec/ruby/core/array/pack/shared/basic.rb b/spec/ruby/core/array/pack/shared/basic.rb
index bc366987c8..a63f64d296 100644
--- a/spec/ruby/core/array/pack/shared/basic.rb
+++ b/spec/ruby/core/array/pack/shared/basic.rb
@@ -27,15 +27,34 @@ describe :array_pack_basic_non_float, shared: true do
     [@obj, @obj].pack("a \t\n\v\f\r"+pack_format).should be_an_instance_of(String)
   end
 
+  it "ignores comments in the format string" do
+    # 2 additional directives ('a') are required for the X directive
+    [@obj, @obj, @obj, @obj].pack("aa #{pack_format} # some comment \n#{pack_format}").should be_an_instance_of(String)
+  end
+
+  ruby_version_is ""..."3.3" do
+    it "warns that a directive is unknown" do
+      # additional directive ('a') is required for the X directive
+      -> { [@obj, @obj].pack("a K" + pack_format) }.should complain(/unknown pack directive 'K' in 'a K#{pack_format}'/)
+      -> { [@obj, @obj].pack("a 0" + pack_format) }.should complain(/unknown pack directive '0' in 'a 0#{pack_format}'/)
+      -> { [@obj, @obj].pack("a :" + pack_format) }.should complain(/unknown pack directive ':' in 'a :#{pack_format}'/)
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError when a directive is unknown" do
+      # additional directive ('a') is required for the X directive
+      -> { [@obj, @obj].pack("a R" + pack_format) }.should raise_error(ArgumentError, /unknown pack directive 'R'/)
+      -> { [@obj, @obj].pack("a 0" + pack_format) }.should raise_error(ArgumentError, /unknown pack directive '0'/)
+      -> { [@obj, @obj].pack("a :" + pack_format) }.should raise_error(ArgumentError, /unknown pack directive ':'/)
+    end
+  end
+
   it "calls #to_str to coerce the directives string" do
     d = mock("pack directive")
     d.should_receive(:to_str).and_return("x"+pack_format)
     [@obj, @obj].pack(d).should be_an_instance_of(String)
   end
-
-  it "taints the output string if the format string is tainted" do
-    [@obj, @obj].pack("x"+pack_format.taint).tainted?.should be_true
-  end
 end
 
 describe :array_pack_basic_float, shared: true do
@@ -43,15 +62,15 @@ describe :array_pack_basic_float, shared: true do
     [9.3, 4.7].pack(" \t\n\v\f\r"+pack_format).should be_an_instance_of(String)
   end
 
+  it "ignores comments in the format string" do
+    [9.3, 4.7].pack(pack_format + "# some comment \n" + pack_format).should be_an_instance_of(String)
+  end
+
   it "calls #to_str to coerce the directives string" do
     d = mock("pack directive")
     d.should_receive(:to_str).and_return("x"+pack_format)
     [1.2, 4.7].pack(d).should be_an_instance_of(String)
   end
-
-  it "taints the output string if the format string is tainted" do
-    [3.2, 2.8].pack("x"+pack_format.taint).tainted?.should be_true
-  end
 end
 
 describe :array_pack_no_platform, shared: true do
diff --git a/spec/ruby/core/array/pack/shared/float.rb b/spec/ruby/core/array/pack/shared/float.rb
index c6b194007f..76c800b74d 100644
--- a/spec/ruby/core/array/pack/shared/float.rb
+++ b/spec/ruby/core/array/pack/shared/float.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :array_pack_float_le, shared: true do
   it "encodes a positive Float" do
@@ -25,8 +25,20 @@ describe :array_pack_float_le, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "\x9a\x999@33\xb3?33\x03A"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "\x9a\x99\xa9@33\x13A"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [5.3, 9.2].pack(pack_format("\000", 2)).should == "\x9a\x99\xa9@33\x13A"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -53,6 +65,14 @@ describe :array_pack_float_le, shared: true do
   it "encodes a negative Float outside the range of a single precision float" do
     [-1e150].pack(pack_format).should == "\x00\x00\x80\xff"
   end
+
+  it "encodes a bignum as a float" do
+    [2 ** 65].pack(pack_format).should == [(2 ** 65).to_f].pack(pack_format)
+  end
+
+  it "encodes a rational as a float" do
+    [Rational(3, 4)].pack(pack_format).should == [Rational(3, 4).to_f].pack(pack_format)
+  end
 end
 
 describe :array_pack_float_be, shared: true do
@@ -66,6 +86,11 @@ describe :array_pack_float_be, shared: true do
 
   it "converts an Integer to a Float" do
     [8].pack(pack_format).should == "A\x00\x00\x00"
+    [bignum_value].pack(pack_format).should == "_\x80\x00\x00"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "A\x00\x00\x00"
   end
 
   it "raises a TypeError if passed a String representation of a floating point number" do
@@ -80,8 +105,20 @@ describe :array_pack_float_be, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@9\x99\x9a?\xb333A\x0333"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\xa9\x99\x9aA\x1333"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\xa9\x99\x9aA\x1333"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -121,6 +158,11 @@ describe :array_pack_double_le, shared: true do
 
   it "converts an Integer to a Float" do
     [8].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\x20@"
+    [bignum_value].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00\xF0C"
+  end
+
+  it "converts a Rational to a Float" do
+    [Rational(8)].pack(pack_format).should == "\x00\x00\x00\x00\x00\x00 @"
   end
 
   it "raises a TypeError if passed a String representation of a floating point number" do
@@ -135,8 +177,20 @@ describe :array_pack_double_le, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "333333\x07@ffffff\xf6?ffffff\x20@"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "333333\x15@ffffff\x22@"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [5.3, 9.2].pack(pack_format("\000", 2)).should == "333333\x15@ffffff\x22@"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -194,8 +248,20 @@ describe :array_pack_double_be, shared: true do
     [2.9, 1.4, 8.2].pack(pack_format("*")).should == "@\x07333333?\xf6ffffff@\x20ffffff"
   end
 
-  it "ignores NULL bytes between directives" do
-    [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\x15333333@\x22ffffff"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [5.3, 9.2].pack(pack_format("\000", 2)).should == "@\x15333333@\x22ffffff"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [5.3, 9.2].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/shared/integer.rb b/spec/ruby/core/array/pack/shared/integer.rb
index 6592f85022..61f7cca184 100644
--- a/spec/ruby/core/array/pack/shared/integer.rb
+++ b/spec/ruby/core/array/pack/shared/integer.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :array_pack_16bit_le, shared: true do
   it "encodes the least significant 16 bits of a positive number" do
@@ -41,9 +41,21 @@ describe :array_pack_16bit_le, shared: true do
     str.should == "\x78\x65\xcd\xab\x21\x43"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x78\x65\xcd\xab"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+        str.should == "\x78\x65\xcd\xab"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -93,9 +105,21 @@ describe :array_pack_16bit_be, shared: true do
     str.should == "\x65\x78\xab\xcd\x43\x21"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x65\x78\xab\xcd"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+        str.should == "\x65\x78\xab\xcd"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -145,9 +169,21 @@ describe :array_pack_32bit_le, shared: true do
     str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde\x21\x43\x65\x78"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+        str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -197,9 +233,21 @@ describe :array_pack_32bit_be, shared: true do
     str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd\x78\x65\x43\x21"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
-    str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+        str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0x1243_6578, 0xdef0_abcd].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -225,7 +273,7 @@ describe :array_pack_32bit_le_platform, shared: true do
     str.should == "\x78\x65\x43\x12\xcd\xab\xf0\xde\x21\x43\x65\x78"
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     it "encodes the least significant 32 bits of a number that is greater than 32 bits" do
       [ [[0xff_7865_4321],  "\x21\x43\x65\x78"],
         [[-0xff_7865_4321], "\xdf\xbc\x9a\x87"]
@@ -251,7 +299,7 @@ describe :array_pack_32bit_be_platform, shared: true do
     str.should == "\x12\x43\x65\x78\xde\xf0\xab\xcd\x78\x65\x43\x21"
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     it "encodes the least significant 32 bits of a number that is greater than 32 bits" do
       [ [[0xff_7865_4321],  "\x78\x65\x43\x21"],
         [[-0xff_7865_4321], "\x87\x9a\xbc\xdf"]
@@ -309,9 +357,21 @@ describe :array_pack_64bit_le, shared: true do
     str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
-    str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+        str.should == "\x56\x78\x12\x34\xcd\xab\xf0\xde\xf0\xde\xba\xdc\x21\x43\x65\x78"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -369,9 +429,21 @@ describe :array_pack_64bit_be, shared: true do
     str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
   end
 
-  it "ignores NULL bytes between directives" do
-    str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
-    str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        str = [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+        str.should == "\xde\xf0\xab\xcd\x34\x12\x78\x56\x78\x65\x43\x21\xdc\xba\xde\xf0"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [0xdef0_abcd_3412_7856, 0x7865_4321_dcba_def0].pack(pack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/shared/numeric_basic.rb b/spec/ruby/core/array/pack/shared/numeric_basic.rb
index 7c36ba4a32..545e215e64 100644
--- a/spec/ruby/core/array/pack/shared/numeric_basic.rb
+++ b/spec/ruby/core/array/pack/shared/numeric_basic.rb
@@ -37,8 +37,14 @@ describe :array_pack_float, shared: true do
     -> { ["a"].pack(pack_format) }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError when the object does not respond to #to_f" do
-    obj = mock('not an float')
+  it "raises a TypeError when the object is not Numeric" do
+    obj = Object.new
+    -> { [obj].pack(pack_format) }.should raise_error(TypeError, /can't convert Object into Float/)
+  end
+
+  it "raises a TypeError when the Numeric object does not respond to #to_f" do
+    klass = Class.new(Numeric)
+    obj = klass.new
     -> { [obj].pack(pack_format) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/array/pack/shared/string.rb b/spec/ruby/core/array/pack/shared/string.rb
index 8c82e8c617..805f78b53b 100644
--- a/spec/ruby/core/array/pack/shared/string.rb
+++ b/spec/ruby/core/array/pack/shared/string.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :array_pack_string, shared: true do
   it "adds count bytes of a String to the output" do
     ["abc"].pack(pack_format(2)).should == "ab"
@@ -40,7 +40,7 @@ describe :array_pack_string, shared: true do
     f = pack_format("*")
     [ [["\u{3042 3044 3046 3048}", 0x2000B].pack(f+"U"),       Encoding::BINARY],
       [["abcde\xd1", "\xFF\xFe\x81\x82"].pack(f+"u"),          Encoding::BINARY],
-      [["a".force_encoding("ascii"), "\xFF\xFe\x81\x82"].pack(f+"u"), Encoding::BINARY],
+      [["a".dup.force_encoding("ascii"), "\xFF\xFe\x81\x82"].pack(f+"u"), Encoding::BINARY],
       # under discussion [ruby-dev:37294]
       [["\u{3042 3044 3046 3048}", 1].pack(f+"N"),             Encoding::BINARY]
     ].should be_computed_by(:encoding)
diff --git a/spec/ruby/core/array/pack/shared/taint.rb b/spec/ruby/core/array/pack/shared/taint.rb
index 88f349cb24..2c2b011c34 100644
--- a/spec/ruby/core/array/pack/shared/taint.rb
+++ b/spec/ruby/core/array/pack/shared/taint.rb
@@ -1,33 +1,2 @@
 describe :array_pack_taint, shared: true do
-  it "returns a tainted string when a pack argument is tainted" do
-    ["abcd".taint, 0x20].pack(pack_format("3C")).tainted?.should be_true
-  end
-
-  it "does not return a tainted string when the array is tainted" do
-    ["abcd", 0x20].taint.pack(pack_format("3C")).tainted?.should be_false
-  end
-
-  it "returns a tainted string when the format is tainted" do
-    ["abcd", 0x20].pack(pack_format("3C").taint).tainted?.should be_true
-  end
-
-  it "returns a tainted string when an empty format is tainted" do
-    ["abcd", 0x20].pack("".taint).tainted?.should be_true
-  end
-
-  it "returns a untrusted string when the format is untrusted" do
-    ["abcd", 0x20].pack(pack_format("3C").untrust).untrusted?.should be_true
-  end
-
-  it "returns a untrusted string when the empty format is untrusted" do
-    ["abcd", 0x20].pack("".untrust).untrusted?.should be_true
-  end
-
-  it "returns a untrusted string when a pack argument is untrusted" do
-    ["abcd".untrust, 0x20].pack(pack_format("3C")).untrusted?.should be_true
-  end
-
-  it "returns a trusted string when the array is untrusted" do
-    ["abcd", 0x20].untrust.pack(pack_format("3C")).untrusted?.should be_false
-  end
 end
diff --git a/spec/ruby/core/array/pack/shared/unicode.rb b/spec/ruby/core/array/pack/shared/unicode.rb
index dd0f8b38aa..4d8eaef323 100644
--- a/spec/ruby/core/array/pack/shared/unicode.rb
+++ b/spec/ruby/core/array/pack/shared/unicode.rb
@@ -67,8 +67,20 @@ describe :array_pack_unicode, shared: true do
     -> { [obj].pack("U") }.should raise_error(TypeError)
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack("U\x00U").should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [1, 2, 3].pack("U\x00U").should == "\x01\x02"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack("U\x00U")
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/u_spec.rb b/spec/ruby/core/array/pack/u_spec.rb
index fe969cbb2d..1f84095ac4 100644
--- a/spec/ruby/core/array/pack/u_spec.rb
+++ b/spec/ruby/core/array/pack/u_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -18,6 +18,16 @@ describe "Array#pack with format 'u'" do
   it_behaves_like :array_pack_arguments, 'u'
   it_behaves_like :array_pack_taint, 'u'
 
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack u string")
+    obj.should_receive(:to_str).and_return("``abcdef")
+    [obj].pack("u*").should == "(8&!A8F-D968`\n"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('u') }.should raise_error(TypeError)
+  end
+
   it "encodes an empty string as an empty string" do
     [""].pack("u").should == ""
   end
diff --git a/spec/ruby/core/array/pack/w_spec.rb b/spec/ruby/core/array/pack/w_spec.rb
index 439fa02198..e770288d67 100644
--- a/spec/ruby/core/array/pack/w_spec.rb
+++ b/spec/ruby/core/array/pack/w_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -24,8 +24,20 @@ describe "Array#pack with format 'w'" do
     [obj].pack("w").should == "\x05"
   end
 
-  it "ignores NULL bytes between directives" do
-    [1, 2, 3].pack("w\x00w").should == "\x01\x02"
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        [1, 2, 3].pack("w\x00w").should == "\x01\x02"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        [1, 2, 3].pack("w\x00w")
+      }.should raise_error(ArgumentError, /unknown pack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/array/pack/x_spec.rb b/spec/ruby/core/array/pack/x_spec.rb
index a28dd0bf21..012fe4567f 100644
--- a/spec/ruby/core/array/pack/x_spec.rb
+++ b/spec/ruby/core/array/pack/x_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -30,6 +30,7 @@ describe "Array#pack with format 'x'" do
 
   it "does not add a NULL byte when passed the '*' modifier" do
     [].pack("x*").should == ""
+    [1, 2].pack("Cx*C").should == "\x01\x02"
   end
 end
 
diff --git a/spec/ruby/core/array/pack/z_spec.rb b/spec/ruby/core/array/pack/z_spec.rb
index 82ce7b4a1c..60f8f7bf10 100644
--- a/spec/ruby/core/array/pack/z_spec.rb
+++ b/spec/ruby/core/array/pack/z_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -12,11 +12,21 @@ describe "Array#pack with format 'Z'" do
   it_behaves_like :array_pack_string, 'Z'
   it_behaves_like :array_pack_taint, 'Z'
 
+  it "calls #to_str to convert an Object to a String" do
+    obj = mock("pack Z string")
+    obj.should_receive(:to_str).and_return("``abcdef")
+    [obj].pack("Z*").should == "``abcdef\x00"
+  end
+
+  it "will not implicitly convert a number to a string" do
+    -> { [0].pack('Z') }.should raise_error(TypeError)
+  end
+
   it "adds all the bytes and appends a NULL byte when passed the '*' modifier" do
     ["abc"].pack("Z*").should == "abc\x00"
   end
 
-  it "padds the output with NULL bytes when the count exceeds the size of the String" do
+  it "pads the output with NULL bytes when the count exceeds the size of the String" do
     ["abc"].pack("Z6").should == "abc\x00\x00\x00"
   end
 
diff --git a/spec/ruby/core/array/plus_spec.rb b/spec/ruby/core/array/plus_spec.rb
index 7692163980..b7153fd3ef 100644
--- a/spec/ruby/core/array/plus_spec.rb
+++ b/spec/ruby/core/array/plus_spec.rb
@@ -14,10 +14,23 @@ describe "Array#+" do
     (ary + ary).should == [1, 2, 3, 1, 2, 3]
   end
 
-  it "tries to convert the passed argument to an Array using #to_ary" do
-    obj = mock('["x", "y"]')
-    obj.should_receive(:to_ary).and_return(["x", "y"])
-    ([1, 2, 3] + obj).should == [1, 2, 3, "x", "y"]
+  describe "converts the passed argument to an Array using #to_ary" do
+    it "successfully concatenates the resulting array from the #to_ary call" do
+      obj = mock('["x", "y"]')
+      obj.should_receive(:to_ary).and_return(["x", "y"])
+      ([1, 2, 3] + obj).should == [1, 2, 3, "x", "y"]
+    end
+
+    it "raises a TypeError if the given argument can't be converted to an array" do
+      -> { [1, 2, 3] + nil }.should raise_error(TypeError)
+      -> { [1, 2, 3] + "abc" }.should raise_error(TypeError)
+    end
+
+    it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to an Array" do
+      obj = mock("hello")
+      obj.should_receive(:to_ary).and_raise(NoMethodError)
+      -> { [1, 2, 3] + obj }.should raise_error(NoMethodError)
+    end
   end
 
   it "properly handles recursive arrays" do
@@ -40,18 +53,4 @@ describe "Array#+" do
   it "does not call to_ary on array subclasses" do
     ([5, 6] + ArraySpecs::ToAryArray[1, 2]).should == [5, 6, 1, 2]
   end
-
-  it "does not get infected even if an original array is tainted" do
-    ([1, 2] + [3, 4]).tainted?.should be_false
-    ([1, 2].taint + [3, 4]).tainted?.should be_false
-    ([1, 2] + [3, 4].taint).tainted?.should be_false
-    ([1, 2].taint + [3, 4].taint).tainted?.should be_false
-  end
-
-  it "does not infected even if an original array is untrusted" do
-    ([1, 2] + [3, 4]).untrusted?.should be_false
-    ([1, 2].untrust + [3, 4]).untrusted?.should be_false
-    ([1, 2] + [3, 4].untrust).untrusted?.should be_false
-    ([1, 2].untrust + [3, 4].untrust).untrusted?.should be_false
-  end
 end
diff --git a/spec/ruby/core/array/pop_spec.rb b/spec/ruby/core/array/pop_spec.rb
index 7dbd6cb3cc..2a19408660 100644
--- a/spec/ruby/core/array/pop_spec.rb
+++ b/spec/ruby/core/array/pop_spec.rb
@@ -30,28 +30,12 @@ describe "Array#pop" do
     array.pop.should == [1, 'two', 3.0, array, array, array, array]
   end
 
-  it "keeps taint status" do
-    a = [1, 2].taint
-    a.pop
-    a.tainted?.should be_true
-    a.pop
-    a.tainted?.should be_true
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.pop }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.pop }.should raise_error(frozen_error_class)
-  end
-
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.pop }.should raise_error(frozen_error_class)
-  end
-
-  it "keeps untrusted status" do
-    a = [1, 2].untrust
-    a.pop
-    a.untrusted?.should be_true
-    a.pop
-    a.untrusted?.should be_true
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.pop }.should raise_error(FrozenError)
   end
 
   describe "passed a number n as an argument" do
@@ -132,37 +116,9 @@ describe "Array#pop" do
       ArraySpecs::MyArray[1, 2, 3].pop(2).should be_an_instance_of(Array)
     end
 
-    it "returns an untainted array even if the array is tainted" do
-      ary = [1, 2].taint
-      ary.pop(2).tainted?.should be_false
-      ary.pop(0).tainted?.should be_false
-    end
-
-    it "keeps taint status" do
-      a = [1, 2].taint
-      a.pop(2)
-      a.tainted?.should be_true
-      a.pop(2)
-      a.tainted?.should be_true
-    end
-
-    it "returns a trusted array even if the array is untrusted" do
-      ary = [1, 2].untrust
-      ary.pop(2).untrusted?.should be_false
-      ary.pop(0).untrusted?.should be_false
-    end
-
-    it "raises a #{frozen_error_class} on a frozen array" do
-      -> { ArraySpecs.frozen_array.pop(2) }.should raise_error(frozen_error_class)
-      -> { ArraySpecs.frozen_array.pop(0) }.should raise_error(frozen_error_class)
-    end
-
-    it "keeps untrusted status" do
-      a = [1, 2].untrust
-      a.pop(2)
-      a.untrusted?.should be_true
-      a.pop(2)
-      a.untrusted?.should be_true
+    it "raises a FrozenError on a frozen array" do
+      -> { ArraySpecs.frozen_array.pop(2) }.should raise_error(FrozenError)
+      -> { ArraySpecs.frozen_array.pop(0) }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/array/prepend_spec.rb b/spec/ruby/core/array/prepend_spec.rb
index 22230ec300..368b8dcfcd 100644
--- a/spec/ruby/core/array/prepend_spec.rb
+++ b/spec/ruby/core/array/prepend_spec.rb
@@ -2,8 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/unshift'
 
-ruby_version_is "2.5" do
-  describe "Array#prepend" do
-    it_behaves_like :array_unshift, :prepend
-  end
+describe "Array#prepend" do
+  it_behaves_like :array_unshift, :prepend
 end
diff --git a/spec/ruby/core/array/product_spec.rb b/spec/ruby/core/array/product_spec.rb
index 07d2880a96..6fb3818508 100644
--- a/spec/ruby/core/array/product_spec.rb
+++ b/spec/ruby/core/array/product_spec.rb
@@ -9,6 +9,11 @@ describe "Array#product" do
     ar.called.should == :to_ary
   end
 
+  it "returns converted arguments using :method_missing" do
+    ar = ArraySpecs::ArrayMethodMissing.new(2,3)
+    [1].product(ar).should == [[1,2],[1,3]]
+  end
+
   it "returns the expected result" do
     [1,2].product([3,4,5],[6,8]).should == [[1, 3, 6], [1, 3, 8], [1, 4, 6], [1, 4, 8], [1, 5, 6], [1, 5, 8],
                                             [2, 3, 6], [2, 3, 8], [2, 4, 6], [2, 4, 8], [2, 5, 6], [2, 5, 8]]
diff --git a/spec/ruby/core/array/rassoc_spec.rb b/spec/ruby/core/array/rassoc_spec.rb
index 62fbd40611..632a05e8b3 100644
--- a/spec/ruby/core/array/rassoc_spec.rb
+++ b/spec/ruby/core/array/rassoc_spec.rb
@@ -35,4 +35,18 @@ describe "Array#rassoc" do
 
     [[1, :foobar, o], [2, o, 1], [3, mock('foo')]].rassoc(key).should == [2, o, 1]
   end
+
+  ruby_version_is "3.3" do
+    it "calls to_ary on non-array elements" do
+      s1 = [1, 2]
+      s2 = ArraySpecs::ArrayConvertible.new(2, 3)
+      a = [s1, s2]
+
+      s1.should_not_receive(:to_ary)
+      a.rassoc(2).should equal(s1)
+
+      a.rassoc(3).should == [2, 3]
+      s2.called.should equal(:to_ary)
+    end
+  end
 end
diff --git a/spec/ruby/core/array/reject_spec.rb b/spec/ruby/core/array/reject_spec.rb
index 1e9c296c8d..81a467e364 100644
--- a/spec/ruby/core/array/reject_spec.rb
+++ b/spec/ruby/core/array/reject_spec.rb
@@ -2,6 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/enumeratorize'
 require_relative 'shared/delete_if'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "Array#reject" do
@@ -47,6 +48,10 @@ describe "Array#reject" do
   it_behaves_like :enumeratorized_with_origin_size, :reject, [1,2,3]
 end
 
+describe "Array#reject" do
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :reject
+end
+
 describe "Array#reject!" do
   it "removes elements for which block is true" do
     a = [3, 4, 5, 6, 7, 8, 9, 10, 11]
@@ -103,12 +108,17 @@ describe "Array#reject!" do
     ArraySpecs.frozen_array.reject!.should be_an_instance_of(Enumerator)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.reject! {} }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.reject! {} }.should raise_error(FrozenError)
+  end
+
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.reject! {} }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.reject! {} }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array only during iteration if called without a block" do
+    enum = ArraySpecs.frozen_array.reject!
+    -> { enum.each {} }.should raise_error(FrozenError)
   end
 
   it "does not truncate the array is the block raises an exception" do
@@ -141,3 +151,8 @@ describe "Array#reject!" do
   it_behaves_like :enumeratorized_with_origin_size, :reject!, [1,2,3]
   it_behaves_like :delete_if, :reject!
 end
+
+describe "Array#reject!" do
+  @value_to_return = -> _ { false }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :reject!
+end
diff --git a/spec/ruby/core/array/reverse_each_spec.rb b/spec/ruby/core/array/reverse_each_spec.rb
index 28b8bfcb34..59dabcd33d 100644
--- a/spec/ruby/core/array/reverse_each_spec.rb
+++ b/spec/ruby/core/array/reverse_each_spec.rb
@@ -5,7 +5,7 @@ require_relative '../enumerable/shared/enumeratorized'
 
 # Modifying a collection while the contents are being iterated
 # gives undefined behavior. See
-# http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/23633
+# https://blade.ruby-lang.org/ruby-core/23633
 
 describe "Array#reverse_each" do
   before :each do
@@ -38,6 +38,20 @@ describe "Array#reverse_each" do
     [1, 2, 3].reverse_each.size.should == 3
   end
 
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.reverse_each do |e|
+      ScratchPad << e
+      array.prepend i if i < 100
+      i += 1
+    end
+
+    ScratchPad.recorded.should == [:c, :a, 1]
+  end
+
   it_behaves_like :enumeratorize, :reverse_each
   it_behaves_like :enumeratorized_with_origin_size, :reverse_each, [1,2,3]
 end
diff --git a/spec/ruby/core/array/reverse_spec.rb b/spec/ruby/core/array/reverse_spec.rb
index e738be6fe7..05dbd2efcf 100644
--- a/spec/ruby/core/array/reverse_spec.rb
+++ b/spec/ruby/core/array/reverse_spec.rb
@@ -36,7 +36,7 @@ describe "Array#reverse!" do
     array.reverse!.should == [array, array, array, array, array, 3.0, 'two', 1]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.reverse! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.reverse! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/rindex_spec.rb b/spec/ruby/core/array/rindex_spec.rb
index 175c7bcfe2..13de88818c 100644
--- a/spec/ruby/core/array/rindex_spec.rb
+++ b/spec/ruby/core/array/rindex_spec.rb
@@ -4,7 +4,7 @@ require_relative '../enumerable/shared/enumeratorized'
 
 # Modifying a collection while the contents are being iterated
 # gives undefined behavior. See
-# http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/23633
+# https://blade.ruby-lang.org/ruby-core/23633
 
 describe "Array#rindex" do
   it "returns the first index backwards from the end where element == to object" do
@@ -68,6 +68,21 @@ describe "Array#rindex" do
     seen.should == [3]
   end
 
+  it "tolerates increasing an array size during iteration" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.rindex do |e|
+      ScratchPad << e
+      array.prepend i if i < 100
+      i += 1
+      false
+    end
+
+    ScratchPad.recorded.should == [:c, :a, 1]
+  end
+
   describe "given no argument and no block" do
     it "produces an Enumerator" do
       enum = [4, 2, 1, 5, 1, 3].rindex
diff --git a/spec/ruby/core/array/rotate_spec.rb b/spec/ruby/core/array/rotate_spec.rb
index cc1aabf986..60dcc8b113 100644
--- a/spec/ruby/core/array/rotate_spec.rb
+++ b/spec/ruby/core/array/rotate_spec.rb
@@ -121,9 +121,9 @@ describe "Array#rotate!" do
     a.should == []
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { [1, 2, 3].freeze.rotate!(0) }.should raise_error(frozen_error_class)
-    -> { [1].freeze.rotate!(42) }.should raise_error(frozen_error_class)
-    -> { [].freeze.rotate! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { [1, 2, 3].freeze.rotate!(0) }.should raise_error(FrozenError)
+    -> { [1].freeze.rotate!(42) }.should raise_error(FrozenError)
+    -> { [].freeze.rotate! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/sample_spec.rb b/spec/ruby/core/array/sample_spec.rb
index 44be91ba18..d4e945152d 100644
--- a/spec/ruby/core/array/sample_spec.rb
+++ b/spec/ruby/core/array/sample_spec.rb
@@ -3,26 +3,36 @@ require_relative 'fixtures/classes'
 
 describe "Array#sample" do
   it "samples evenly" do
-    ary = [0, 1, 2, 3]
-    3.times do |i|
-      counts = [0, 0, 0, 0]
-      4000.times do
-        counts[ary.sample(3)[i]] += 1
-      end
-      counts.each do |count|
-        (800..1200).should include(count)
-      end
-    end
+    ArraySpecs.measure_sample_fairness(4, 1, 400)
+    ArraySpecs.measure_sample_fairness(4, 2, 400)
+    ArraySpecs.measure_sample_fairness(4, 3, 400)
+    ArraySpecs.measure_sample_fairness(40, 3, 400)
+    ArraySpecs.measure_sample_fairness(40, 4, 400)
+    ArraySpecs.measure_sample_fairness(40, 8, 400)
+    ArraySpecs.measure_sample_fairness(40, 16, 400)
+    ArraySpecs.measure_sample_fairness_large_sample_size(100, 80, 4000)
   end
 
   it "returns nil for an empty Array" do
     [].sample.should be_nil
   end
 
+  it "returns nil for an empty array when called without n and a Random is given" do
+    [].sample(random: Random.new(42)).should be_nil
+  end
+
   it "returns a single value when not passed a count" do
     [4].sample.should equal(4)
   end
 
+  it "returns a single value when not passed a count and a Random is given" do
+    [4].sample(random: Random.new(42)).should equal(4)
+  end
+
+  it "returns a single value when not passed a count and a Random class is given" do
+    [4].sample(random: Random).should equal(4)
+  end
+
   it "returns an empty Array when passed zero" do
     [4].sample(0).should == []
   end
@@ -65,28 +75,11 @@ describe "Array#sample" do
   end
 
   describe "with options" do
-    it "calls #to_hash to convert the passed Object" do
-      obj = mock("array_sample")
-      obj.should_receive(:to_hash).and_return({})
-      obj.should_not_receive(:to_int)
-
-      [1, 2].sample(obj).should be_an_instance_of(Fixnum)
-    end
-
-    it "calls #to_int on the first argument and #to_hash on the second when passed Objects" do
-      count = mock("array_sample_count")
-      count.should_receive(:to_int).and_return(2)
-      options = mock("array_sample_options")
-      options.should_receive(:to_hash).and_return({})
-
-      [1, 2].sample(count, options).size.should == 2
-    end
-
     it "calls #rand on the Object passed by the :random key in the arguments Hash" do
       obj = mock("array_sample_random")
       obj.should_receive(:rand).and_return(0.5)
 
-      [1, 2].sample(random: obj).should be_an_instance_of(Fixnum)
+      [1, 2].sample(random: obj).should be_an_instance_of(Integer)
     end
 
     it "raises a NoMethodError if an object passed for the RNG does not define #rand" do
@@ -95,8 +88,8 @@ describe "Array#sample" do
       -> { [1, 2].sample(random: obj) }.should raise_error(NoMethodError)
     end
 
-    describe "when the object returned by #rand is a Fixnum" do
-      it "uses the fixnum as index" do
+    describe "when the object returned by #rand is an Integer" do
+      it "uses the integer as index" do
         random = mock("array_sample_random_ret")
         random.should_receive(:rand).and_return(0)
 
@@ -121,10 +114,17 @@ describe "Array#sample" do
 
         -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
       end
+
+      it "raises a RangeError if the value is greater than the Array size" do
+        random = mock("array_sample_random")
+        random.should_receive(:rand).and_return(3)
+
+        -> { [1, 2].sample(random: random) }.should raise_error(RangeError)
+      end
     end
   end
 
-  describe "when the object returned by #rand is not a Fixnum but responds to #to_int" do
+  describe "when the object returned by #rand is not an Integer but responds to #to_int" do
     it "calls #to_int on the Object" do
       value = mock("array_sample_random_value")
       value.should_receive(:to_int).and_return(1)
diff --git a/spec/ruby/core/array/shared/clone.rb b/spec/ruby/core/array/shared/clone.rb
index 95d0d0a3d5..035b45ec99 100644
--- a/spec/ruby/core/array/shared/clone.rb
+++ b/spec/ruby/core/array/shared/clone.rb
@@ -17,26 +17,4 @@ describe :array_clone, shared: true do
     b.should == a
     b.__id__.should_not == a.__id__
   end
-
-  it "copies taint status from the original" do
-    a = [1, 2, 3, 4]
-    b = [1, 2, 3, 4]
-    a.taint
-    aa = a.send @method
-    bb = b.send @method
-
-    aa.tainted?.should == true
-    bb.tainted?.should == false
-  end
-
-  it "copies untrusted status from the original" do
-    a = [1, 2, 3, 4]
-    b = [1, 2, 3, 4]
-    a.untrust
-    aa = a.send @method
-    bb = b.send @method
-
-    aa.untrusted?.should == true
-    bb.untrusted?.should == false
-  end
 end
diff --git a/spec/ruby/core/array/shared/collect.rb b/spec/ruby/core/array/shared/collect.rb
index 80e2739893..030302ced6 100644
--- a/spec/ruby/core/array/shared/collect.rb
+++ b/spec/ruby/core/array/shared/collect.rb
@@ -1,4 +1,5 @@
 require_relative '../../enumerable/shared/enumeratorized'
+require_relative '../shared/iterable_and_tolerating_size_increasing'
 
 describe :array_collect, shared: true do
   it "returns a copy of array with each element replaced by the value returned by block" do
@@ -42,22 +43,12 @@ describe :array_collect, shared: true do
     }.should raise_error(ArgumentError)
   end
 
-  it "does not copy tainted status" do
-    a = [1, 2, 3]
-    a.taint
-    a.send(@method){|x| x}.tainted?.should be_false
-  end
-
-  it "does not copy untrusted status" do
-    a = [1, 2, 3]
-    a.untrust
-    a.send(@method){|x| x}.untrusted?.should be_false
-  end
-
   before :all do
     @object = [1, 2, 3, 4]
   end
   it_should_behave_like :enumeratorized_with_origin_size
+
+  it_should_behave_like :array_iterable_and_tolerating_size_increasing
 end
 
 describe :array_collect_b, shared: true do
@@ -94,43 +85,57 @@ describe :array_collect_b, shared: true do
     a.should == ["1!", "2!", "3!"]
   end
 
-  it "keeps tainted status" do
-    a = [1, 2, 3]
-    a.taint
-    a.tainted?.should be_true
-    a.send(@method){|x| x}
-    a.tainted?.should be_true
-  end
-
-  it "keeps untrusted status" do
-    a = [1, 2, 3]
-    a.untrust
-    a.send(@method){|x| x}
-    a.untrusted?.should be_true
-  end
-
   describe "when frozen" do
-    it "raises a #{frozen_error_class}" do
-      -> { ArraySpecs.frozen_array.send(@method) {} }.should raise_error(frozen_error_class)
+    it "raises a FrozenError" do
+      -> { ArraySpecs.frozen_array.send(@method) {} }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when empty" do
-      -> { ArraySpecs.empty_frozen_array.send(@method) {} }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when empty" do
+      -> { ArraySpecs.empty_frozen_array.send(@method) {} }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when calling #each on the returned Enumerator" do
+    it "raises a FrozenError when calling #each on the returned Enumerator" do
       enumerator = ArraySpecs.frozen_array.send(@method)
-      -> { enumerator.each {|x| x } }.should raise_error(frozen_error_class)
+      -> { enumerator.each {|x| x } }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when calling #each on the returned Enumerator when empty" do
+    it "raises a FrozenError when calling #each on the returned Enumerator when empty" do
       enumerator = ArraySpecs.empty_frozen_array.send(@method)
-      -> { enumerator.each {|x| x } }.should raise_error(frozen_error_class)
+      -> { enumerator.each {|x| x } }.should raise_error(FrozenError)
+    end
+  end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.send(@method) { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "only changes elements before error is raised, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.send(@method) do |e|
+        case e
+        when 1 then -1
+        when 2 then -2
+        when 3 then raise StandardError, 'Oops'
+        else 0
+        end
+      end
+    rescue StandardError
     end
+
+    a.should == [-1, -2, 3, 4]
   end
 
   before :all do
     @object = [1, 2, 3, 4]
   end
   it_should_behave_like :enumeratorized_with_origin_size
+
+  it_should_behave_like :array_iterable_and_tolerating_size_increasing
 end
diff --git a/spec/ruby/core/array/shared/index.rb b/spec/ruby/core/array/shared/index.rb
index a9896554f2..a4a0adbab6 100644
--- a/spec/ruby/core/array/shared/index.rb
+++ b/spec/ruby/core/array/shared/index.rb
@@ -1,3 +1,5 @@
+require_relative '../shared/iterable_and_tolerating_size_increasing'
+
 describe :array_index, shared: true do
   it "returns the index of the first element == to object" do
     x = mock('3')
@@ -34,4 +36,6 @@ describe :array_index, shared: true do
       [].send(@method).should be_an_instance_of(Enumerator)
     end
   end
+
+  it_should_behave_like :array_iterable_and_tolerating_size_increasing
 end
diff --git a/spec/ruby/core/array/shared/inspect.rb b/spec/ruby/core/array/shared/inspect.rb
index 434440c25b..af5128c645 100644
--- a/spec/ruby/core/array/shared/inspect.rb
+++ b/spec/ruby/core/array/shared/inspect.rb
@@ -19,7 +19,7 @@ describe :array_inspect, shared: true do
   end
 
   it "does not call #to_s on a String returned from #inspect" do
-    str = "abc"
+    str = +"abc"
     str.should_not_receive(:to_s)
 
     [str].send(@method).should == '["abc"]'
@@ -64,30 +64,6 @@ describe :array_inspect, shared: true do
     ArraySpecs.empty_recursive_array.send(@method).should == "[[...]]"
   end
 
-  it "taints the result if the Array is non-empty and tainted" do
-    [1, 2].taint.send(@method).tainted?.should be_true
-  end
-
-  it "does not taint the result if the Array is tainted but empty" do
-    [].taint.send(@method).tainted?.should be_false
-  end
-
-  it "taints the result if an element is tainted" do
-    ["str".taint].send(@method).tainted?.should be_true
-  end
-
-  it "untrusts the result if the Array is untrusted" do
-    [1, 2].untrust.send(@method).untrusted?.should be_true
-  end
-
-  it "does not untrust the result if the Array is untrusted but empty" do
-    [].untrust.send(@method).untrusted?.should be_false
-  end
-
-  it "untrusts the result if an element is untrusted" do
-    ["str".untrust].send(@method).untrusted?.should be_true
-  end
-
   describe "with encoding" do
     before :each do
       @default_external_encoding = Encoding.default_external
@@ -122,8 +98,8 @@ describe :array_inspect, shared: true do
     end
 
     it "does not raise if inspected result is not default external encoding" do
-      utf_16be = mock("utf_16be")
-      utf_16be.should_receive(:inspect).and_return(%<"utf_16be \u3042">.encode!(Encoding::UTF_16BE))
+      utf_16be = mock(+"utf_16be")
+      utf_16be.should_receive(:inspect).and_return(%<"utf_16be \u3042">.encode(Encoding::UTF_16BE))
 
       [utf_16be].send(@method).should == '["utf_16be \u3042"]'
     end
diff --git a/spec/ruby/core/array/shared/intersection.rb b/spec/ruby/core/array/shared/intersection.rb
new file mode 100644
index 0000000000..0b4166ab63
--- /dev/null
+++ b/spec/ruby/core/array/shared/intersection.rb
@@ -0,0 +1,85 @@
+describe :array_intersection, shared: true do
+  it "creates an array with elements common to both arrays (intersection)" do
+    [].send(@method, []).should == []
+    [1, 2].send(@method, []).should == []
+    [].send(@method, [1, 2]).should == []
+    [ 1, 3, 5 ].send(@method, [ 1, 2, 3 ]).should == [1, 3]
+  end
+
+  it "creates an array with no duplicates" do
+    [ 1, 1, 3, 5 ].send(@method, [ 1, 2, 3 ]).uniq!.should == nil
+  end
+
+  it "creates an array with elements in order they are first encountered" do
+    [ 1, 2, 3, 2, 5, 6, 7, 8 ].send(@method, [ 5, 2, 3, 4 ]).should == [2, 3, 5] # array > other
+    [ 5, 2, 3, 4 ].send(@method, [ 1, 2, 3, 2, 5, 6, 7, 8 ]).should == [5, 2, 3] # array < other
+  end
+
+  it "does not modify the original Array" do
+    a = [1, 1, 3, 5]
+    a.send(@method, [1, 2, 3]).should == [1, 3]
+    a.should == [1, 1, 3, 5]
+  end
+
+  it "properly handles recursive arrays" do
+    empty = ArraySpecs.empty_recursive_array
+    empty.send(@method, empty).should == empty
+
+    ArraySpecs.recursive_array.send(@method, []).should == []
+    [].send(@method, ArraySpecs.recursive_array).should == []
+
+    ArraySpecs.recursive_array.send(@method, ArraySpecs.recursive_array).should == [1, 'two', 3.0, ArraySpecs.recursive_array]
+  end
+
+  it "tries to convert the passed argument to an Array using #to_ary" do
+    obj = mock('[1,2,3]')
+    obj.should_receive(:to_ary).and_return([1, 2, 3])
+    [1, 2].send(@method, obj).should == ([1, 2])
+  end
+
+  it "determines equivalence between elements in the sense of eql?" do
+    not_supported_on :opal do
+      [5.0, 4.0].send(@method, [5, 4]).should == []
+    end
+
+    str = "x"
+    [str].send(@method, [str.dup]).should == [str]
+
+    obj1 = mock('1')
+    obj2 = mock('2')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.should_receive(:eql?).at_least(1).and_return(true)
+    obj2.stub!(:eql?).and_return(true)
+
+    [obj1].send(@method, [obj2]).should == [obj1]
+    [obj1, obj1, obj2, obj2].send(@method, [obj2]).should == [obj1]
+
+    obj1 = mock('3')
+    obj2 = mock('4')
+    obj1.stub!(:hash).and_return(0)
+    obj2.stub!(:hash).and_return(0)
+    obj1.should_receive(:eql?).at_least(1).and_return(false)
+
+    [obj1].send(@method, [obj2]).should == []
+    [obj1, obj1, obj2, obj2].send(@method, [obj2]).should == [obj2]
+  end
+
+  it "does return subclass instances for Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3].send(@method, []).should be_an_instance_of(Array)
+    ArraySpecs::MyArray[1, 2, 3].send(@method, ArraySpecs::MyArray[1, 2, 3]).should be_an_instance_of(Array)
+    [].send(@method, ArraySpecs::MyArray[1, 2, 3]).should be_an_instance_of(Array)
+  end
+
+  it "does not call to_ary on array subclasses" do
+    [5, 6].send(@method, ArraySpecs::ToAryArray[1, 2, 5, 6]).should == [5, 6]
+  end
+
+  it "properly handles an identical item even when its #eql? isn't reflexive" do
+    x = mock('x')
+    x.stub!(:hash).and_return(42)
+    x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
+
+    [x].send(@method, [x]).should == [x]
+  end
+end
diff --git a/spec/ruby/core/array/shared/iterable_and_tolerating_size_increasing.rb b/spec/ruby/core/array/shared/iterable_and_tolerating_size_increasing.rb
new file mode 100644
index 0000000000..3e73bad44b
--- /dev/null
+++ b/spec/ruby/core/array/shared/iterable_and_tolerating_size_increasing.rb
@@ -0,0 +1,25 @@
+describe :array_iterable_and_tolerating_size_increasing, shared: true do
+  before do
+    @value_to_return ||= -> _ { nil }
+  end
+
+  it "tolerates increasing an array size during iteration" do
+    # The goal is to trigger potential reallocation of internal array storage, so we:
+    # - use elements of different types, starting with the less generic (Integer)
+    # - add reasonably big number of new elements (~ 100)
+    array = [1, 2, 3] # to test some methods we need several uniq elements
+    array_to_join = [:a, :b, :c] + (4..100).to_a
+
+    ScratchPad.record []
+    i = 0
+
+    array.send(@method) do |e|
+      ScratchPad << e
+      array << array_to_join[i] if i < array_to_join.size
+      i += 1
+      @value_to_return.call(e)
+    end
+
+    ScratchPad.recorded.should == [1, 2, 3] + array_to_join
+  end
+end
diff --git a/spec/ruby/core/array/shared/join.rb b/spec/ruby/core/array/shared/join.rb
index 38bdde9502..507b13e3c8 100644
--- a/spec/ruby/core/array/shared/join.rb
+++ b/spec/ruby/core/array/shared/join.rb
@@ -58,34 +58,6 @@ describe :array_join_with_default_separator, shared: true do
     -> { ArraySpecs.empty_recursive_array.send(@method) }.should raise_error(ArgumentError)
   end
 
-  it "taints the result if the Array is tainted and non-empty" do
-    [1, 2].taint.send(@method).tainted?.should be_true
-  end
-
-  it "does not taint the result if the Array is tainted but empty" do
-    [].taint.send(@method).tainted?.should be_false
-  end
-
-  it "taints the result if the result of coercing an element is tainted" do
-    s = mock("taint")
-    s.should_receive(:to_s).and_return("str".taint)
-    [s].send(@method).tainted?.should be_true
-  end
-
-  it "untrusts the result if the Array is untrusted and non-empty" do
-    [1, 2].untrust.send(@method).untrusted?.should be_true
-  end
-
-  it "does not untrust the result if the Array is untrusted but empty" do
-    [].untrust.send(@method).untrusted?.should be_false
-  end
-
-  it "untrusts the result if the result of coercing an element is untrusted" do
-    s = mock("untrust")
-    s.should_receive(:to_s).and_return("str".untrust)
-    [s].send(@method).untrusted?.should be_true
-  end
-
   it "uses the first encoding when other strings are compatible" do
     ary1 = ArraySpecs.array_with_7bit_utf8_and_usascii_strings
     ary2 = ArraySpecs.array_with_usascii_and_7bit_utf8_strings
@@ -111,6 +83,19 @@ describe :array_join_with_default_separator, shared: true do
 
     -> { ary_utf8_bad_binary.send(@method) }.should raise_error(EncodingError)
   end
+
+  context "when $, is not nil" do
+    before do
+      suppress_warning do
+        $, = '*'
+      end
+    end
+
+    it "warns" do
+      -> { [].join }.should complain(/warning: \$, is set to non-nil value/)
+      -> { [].join(nil) }.should complain(/warning: \$, is set to non-nil value/)
+    end
+  end
 end
 
 describe :array_join_with_string_separator, shared: true do
@@ -124,40 +109,4 @@ describe :array_join_with_string_separator, shared: true do
     [1, [2, [3, 4], 5], 6].send(@method, ":").should == "1:2:3:4:5:6"
     [1, [2, ArraySpecs::MyArray[3, 4], 5], 6].send(@method, ":").should == "1:2:3:4:5:6"
   end
-
-  describe "with a tainted separator" do
-    before :each do
-      @sep = ":".taint
-    end
-
-    it "does not taint the result if the array is empty" do
-      [].send(@method, @sep).tainted?.should be_false
-    end
-
-    it "does not taint the result if the array has only one element" do
-      [1].send(@method, @sep).tainted?.should be_false
-    end
-
-    it "taints the result if the array has two or more elements" do
-      [1, 2].send(@method, @sep).tainted?.should be_true
-    end
-  end
-
-  describe "with an untrusted separator" do
-    before :each do
-      @sep = ":".untrust
-    end
-
-    it "does not untrust the result if the array is empty" do
-      [].send(@method, @sep).untrusted?.should be_false
-    end
-
-    it "does not untrust the result if the array has only one element" do
-      [1].send(@method, @sep).untrusted?.should be_false
-    end
-
-    it "untrusts the result if the array has two or more elements" do
-      [1, 2].send(@method, @sep).untrusted?.should be_true
-    end
-  end
 end
diff --git a/spec/ruby/core/array/shared/keep_if.rb b/spec/ruby/core/array/shared/keep_if.rb
index 2f1299c2b3..43a047c0a7 100644
--- a/spec/ruby/core/array/shared/keep_if.rb
+++ b/spec/ruby/core/array/shared/keep_if.rb
@@ -1,4 +1,5 @@
 require_relative '../../enumerable/shared/enumeratorized'
+require_relative '../shared/iterable_and_tolerating_size_increasing'
 
 describe :keep_if, shared: true do
   it "deletes elements for which the block returns a false value" do
@@ -41,8 +42,8 @@ describe :keep_if, shared: true do
         @frozen.should == @origin
       end
 
-      it "raises a #{frozen_error_class}" do
-        -> { @frozen.send(@method) { true } }.should raise_error(frozen_error_class)
+      it "raises a FrozenError" do
+        -> { @frozen.send(@method) { true } }.should raise_error(FrozenError)
       end
     end
 
@@ -52,9 +53,43 @@ describe :keep_if, shared: true do
         @frozen.should == @origin
       end
 
-      it "raises a #{frozen_error_class}" do
-        -> { @frozen.send(@method) { false } }.should raise_error(frozen_error_class)
+      it "raises a FrozenError" do
+        -> { @frozen.send(@method) { false } }.should raise_error(FrozenError)
       end
     end
+
+    it "raises a FrozenError on a frozen array only during iteration if called without a block" do
+      enum = @frozen.send(@method)
+      -> { enum.each {} }.should raise_error(FrozenError)
+    end
+  end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.send(@method) { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
   end
+
+  it "only changes elements before error is raised, keeping the element which raised an error." do
+    a = [1, 2, 3, 4]
+    begin
+      a.send(@method) do |e|
+        case e
+        when 2 then false
+        when 3 then raise StandardError, 'Oops'
+        else true
+        end
+      end
+    rescue StandardError
+    end
+
+    a.should == [1, 3, 4]
+  end
+
+  @value_to_return = -> _ { true }
+  it_should_behave_like :array_iterable_and_tolerating_size_increasing
 end
diff --git a/spec/ruby/core/array/shared/push.rb b/spec/ruby/core/array/shared/push.rb
index df307073cd..ac790fb6a4 100644
--- a/spec/ruby/core/array/shared/push.rb
+++ b/spec/ruby/core/array/shared/push.rb
@@ -26,8 +26,8 @@ describe :array_push, shared: true do
     array.send(@method, :last).should == [1, 'two', 3.0, array, array, array, array, array, :last]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.send(@method, 1) }.should raise_error(frozen_error_class)
-    -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.send(@method, 1) }.should raise_error(FrozenError)
+    -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/shared/replace.rb b/spec/ruby/core/array/shared/replace.rb
index b3474fad09..9a6e60c1b0 100644
--- a/spec/ruby/core/array/shared/replace.rb
+++ b/spec/ruby/core/array/shared/replace.rb
@@ -52,9 +52,9 @@ describe :array_replace, shared: true do
     [].send(@method, ArraySpecs::ToAryArray[5, 6, 7]).should == [5, 6, 7]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
+  it "raises a FrozenError on a frozen array" do
     -> {
       ArraySpecs.frozen_array.send(@method, ArraySpecs.frozen_array)
-    }.should raise_error(frozen_error_class)
+    }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/array/shared/select.rb b/spec/ruby/core/array/shared/select.rb
index 09101e8ab5..9c2cbf76c4 100644
--- a/spec/ruby/core/array/shared/select.rb
+++ b/spec/ruby/core/array/shared/select.rb
@@ -2,11 +2,14 @@ require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/enumeratorize'
 require_relative '../shared/keep_if'
+require_relative '../shared/iterable_and_tolerating_size_increasing'
 require_relative '../../enumerable/shared/enumeratorized'
 
 describe :array_select, shared: true do
   it_should_behave_like :enumeratorize
 
+  it_should_behave_like :array_iterable_and_tolerating_size_increasing
+
   before :each do
     @object = [1,2,3]
   end
diff --git a/spec/ruby/core/array/shared/slice.rb b/spec/ruby/core/array/shared/slice.rb
index 73456eb297..b80261d32f 100644
--- a/spec/ruby/core/array/shared/slice.rb
+++ b/spec/ruby/core/array/shared/slice.rb
@@ -117,6 +117,27 @@ describe :array_slice, shared: true do
     a.send(@method, 0, obj).should == [1, 2]
   end
 
+  it "raises TypeError if to_int returns non-integer" do
+    from = mock('from')
+    to = mock('to')
+
+    # So we can construct a range out of them...
+    def from.<=>(o) 0 end
+    def to.<=>(o) 0 end
+
+    a = [1, 2, 3, 4, 5]
+
+    def from.to_int() 'cat' end
+    def to.to_int() -2 end
+
+    -> { a.send(@method, from..to) }.should raise_error(TypeError)
+
+    def from.to_int() 1 end
+    def to.to_int() 'cat' end
+
+    -> { a.send(@method, from..to) }.should raise_error(TypeError)
+  end
+
   it "returns the elements specified by Range indexes with [m..n]" do
     [ "a", "b", "c", "d", "e" ].send(@method, 1..3).should == ["b", "c", "d"]
     [ "a", "b", "c", "d", "e" ].send(@method, 4..-1).should == ['e']
@@ -376,28 +397,28 @@ describe :array_slice, shared: true do
       @array = ArraySpecs::MyArray[1, 2, 3, 4, 5]
     end
 
-    it "returns a subclass instance with [n, m]" do
-      @array.send(@method, 0, 2).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [n, m]" do
+      @array.send(@method, 0, 2).should be_an_instance_of(Array)
     end
 
-    it "returns a subclass instance with [-n, m]" do
-      @array.send(@method, -3, 2).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [-n, m]" do
+      @array.send(@method, -3, 2).should be_an_instance_of(Array)
     end
 
-    it "returns a subclass instance with [n..m]" do
-      @array.send(@method, 1..3).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [n..m]" do
+      @array.send(@method, 1..3).should be_an_instance_of(Array)
     end
 
-    it "returns a subclass instance with [n...m]" do
-      @array.send(@method, 1...3).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [n...m]" do
+      @array.send(@method, 1...3).should be_an_instance_of(Array)
     end
 
-    it "returns a subclass instance with [-n..-m]" do
-      @array.send(@method, -3..-1).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [-n..-m]" do
+      @array.send(@method, -3..-1).should be_an_instance_of(Array)
     end
 
-    it "returns a subclass instance with [-n...-m]" do
-      @array.send(@method, -3...-1).should be_an_instance_of(ArraySpecs::MyArray)
+    it "returns a Array instance with [-n...-m]" do
+      @array.send(@method, -3...-1).should be_an_instance_of(Array)
     end
 
     it "returns an empty array when m == n with [m...n]" do
@@ -440,20 +461,397 @@ describe :array_slice, shared: true do
   it "raises a RangeError when the start index is out of range of Fixnum" do
     array = [1, 2, 3, 4, 5, 6]
     obj = mock('large value')
-    obj.should_receive(:to_int).and_return(0x8000_0000_0000_0000_0000)
+    obj.should_receive(:to_int).and_return(bignum_value)
     -> { array.send(@method, obj) }.should raise_error(RangeError)
 
     obj = 8e19
     -> { array.send(@method, obj) }.should raise_error(RangeError)
+
+    # boundary value when longs are 64 bits
+    -> { array.send(@method, 2.0**63) }.should raise_error(RangeError)
+
+    # just under the boundary value when longs are 64 bits
+    array.send(@method, max_long.to_f.prev_float).should == nil
   end
 
   it "raises a RangeError when the length is out of range of Fixnum" do
     array = [1, 2, 3, 4, 5, 6]
     obj = mock('large value')
-    obj.should_receive(:to_int).and_return(0x8000_0000_0000_0000_0000)
+    obj.should_receive(:to_int).and_return(bignum_value)
     -> { array.send(@method, 1, obj) }.should raise_error(RangeError)
 
     obj = 8e19
     -> { array.send(@method, 1, obj) }.should raise_error(RangeError)
   end
+
+  it "raises a type error if a range is passed with a length" do
+    ->{ [1, 2, 3].send(@method, 1..2, 1) }.should raise_error(TypeError)
+  end
+
+  it "raises a RangeError if passed a range with a bound that is too large" do
+    array = [1, 2, 3, 4, 5, 6]
+    -> { array.send(@method, bignum_value..(bignum_value + 1)) }.should raise_error(RangeError)
+    -> { array.send(@method, 0..bignum_value) }.should raise_error(RangeError)
+  end
+
+  it "can accept endless ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a.send(@method, eval("(2..)")).should == [2, 3, 4, 5]
+    a.send(@method, eval("(2...)")).should == [2, 3, 4, 5]
+    a.send(@method, eval("(-2..)")).should == [4, 5]
+    a.send(@method, eval("(-2...)")).should == [4, 5]
+    a.send(@method, eval("(9..)")).should == nil
+    a.send(@method, eval("(9...)")).should == nil
+    a.send(@method, eval("(-9..)")).should == nil
+    a.send(@method, eval("(-9...)")).should == nil
+  end
+
+  describe "can be sliced with Enumerator::ArithmeticSequence" do
+    before :each do
+      @array = [0, 1, 2, 3, 4, 5]
+    end
+
+    it "has endless range and positive steps" do
+      @array.send(@method, eval("(0..).step(1)")).should == [0, 1, 2, 3, 4, 5]
+      @array.send(@method, eval("(0..).step(2)")).should == [0, 2, 4]
+      @array.send(@method, eval("(0..).step(10)")).should == [0]
+
+      @array.send(@method, eval("(2..).step(1)")).should == [2, 3, 4, 5]
+      @array.send(@method, eval("(2..).step(2)")).should == [2, 4]
+      @array.send(@method, eval("(2..).step(10)")).should == [2]
+
+      @array.send(@method, eval("(-3..).step(1)")).should == [3, 4, 5]
+      @array.send(@method, eval("(-3..).step(2)")).should == [3, 5]
+      @array.send(@method, eval("(-3..).step(10)")).should == [3]
+    end
+
+    it "has beginless range and positive steps" do
+      # end with zero index
+      @array.send(@method, (..0).step(1)).should == [0]
+      @array.send(@method, (...0).step(1)).should == []
+
+      @array.send(@method, (..0).step(2)).should == [0]
+      @array.send(@method, (...0).step(2)).should == []
+
+      @array.send(@method, (..0).step(10)).should == [0]
+      @array.send(@method, (...0).step(10)).should == []
+
+      # end with positive index
+      @array.send(@method, (..3).step(1)).should == [0, 1, 2, 3]
+      @array.send(@method, (...3).step(1)).should == [0, 1, 2]
+
+      @array.send(@method, (..3).step(2)).should == [0, 2]
+      @array.send(@method, (...3).step(2)).should == [0, 2]
+
+      @array.send(@method, (..3).step(10)).should == [0]
+      @array.send(@method, (...3).step(10)).should == [0]
+
+      # end with negative index
+      @array.send(@method, (..-2).step(1)).should == [0, 1, 2, 3, 4,]
+      @array.send(@method, (...-2).step(1)).should == [0, 1, 2, 3]
+
+      @array.send(@method, (..-2).step(2)).should == [0, 2, 4]
+      @array.send(@method, (...-2).step(2)).should == [0, 2]
+
+      @array.send(@method, (..-2).step(10)).should == [0]
+      @array.send(@method, (...-2).step(10)).should == [0]
+    end
+
+    it "has endless range and negative steps" do
+      @array.send(@method, eval("(0..).step(-1)")).should == [0]
+      @array.send(@method, eval("(0..).step(-2)")).should == [0]
+      @array.send(@method, eval("(0..).step(-10)")).should == [0]
+
+      @array.send(@method, eval("(2..).step(-1)")).should == [2, 1, 0]
+      @array.send(@method, eval("(2..).step(-2)")).should == [2, 0]
+
+      @array.send(@method, eval("(-3..).step(-1)")).should == [3, 2, 1, 0]
+      @array.send(@method, eval("(-3..).step(-2)")).should == [3, 1]
+    end
+
+    it "has closed range and positive steps" do
+      # start and end with 0
+      @array.send(@method, eval("(0..0).step(1)")).should == [0]
+      @array.send(@method, eval("(0...0).step(1)")).should == []
+
+      @array.send(@method, eval("(0..0).step(2)")).should == [0]
+      @array.send(@method, eval("(0...0).step(2)")).should == []
+
+      @array.send(@method, eval("(0..0).step(10)")).should == [0]
+      @array.send(@method, eval("(0...0).step(10)")).should == []
+
+      # start and end with positive index
+      @array.send(@method, eval("(1..3).step(1)")).should == [1, 2, 3]
+      @array.send(@method, eval("(1...3).step(1)")).should == [1, 2]
+
+      @array.send(@method, eval("(1..3).step(2)")).should == [1, 3]
+      @array.send(@method, eval("(1...3).step(2)")).should == [1]
+
+      @array.send(@method, eval("(1..3).step(10)")).should == [1]
+      @array.send(@method, eval("(1...3).step(10)")).should == [1]
+
+      # start with positive index, end with negative index
+      @array.send(@method, eval("(1..-2).step(1)")).should == [1, 2, 3, 4]
+      @array.send(@method, eval("(1...-2).step(1)")).should == [1, 2, 3]
+
+      @array.send(@method, eval("(1..-2).step(2)")).should ==  [1, 3]
+      @array.send(@method, eval("(1...-2).step(2)")).should ==  [1, 3]
+
+      @array.send(@method, eval("(1..-2).step(10)")).should == [1]
+      @array.send(@method, eval("(1...-2).step(10)")).should == [1]
+
+      # start with negative index, end with positive index
+      @array.send(@method, eval("(-4..4).step(1)")).should == [2, 3, 4]
+      @array.send(@method, eval("(-4...4).step(1)")).should == [2, 3]
+
+      @array.send(@method, eval("(-4..4).step(2)")).should == [2, 4]
+      @array.send(@method, eval("(-4...4).step(2)")).should == [2]
+
+      @array.send(@method, eval("(-4..4).step(10)")).should == [2]
+      @array.send(@method, eval("(-4...4).step(10)")).should == [2]
+
+      # start with negative index, end with negative index
+      @array.send(@method, eval("(-4..-2).step(1)")).should == [2, 3, 4]
+      @array.send(@method, eval("(-4...-2).step(1)")).should == [2, 3]
+
+      @array.send(@method, eval("(-4..-2).step(2)")).should == [2, 4]
+      @array.send(@method, eval("(-4...-2).step(2)")).should == [2]
+
+      @array.send(@method, eval("(-4..-2).step(10)")).should == [2]
+      @array.send(@method, eval("(-4...-2).step(10)")).should == [2]
+    end
+
+    it "has closed range and negative steps" do
+      # start and end with 0
+      @array.send(@method, eval("(0..0).step(-1)")).should == [0]
+      @array.send(@method, eval("(0...0).step(-1)")).should == []
+
+      @array.send(@method, eval("(0..0).step(-2)")).should == [0]
+      @array.send(@method, eval("(0...0).step(-2)")).should == []
+
+      @array.send(@method, eval("(0..0).step(-10)")).should == [0]
+      @array.send(@method, eval("(0...0).step(-10)")).should == []
+
+      # start and end with positive index
+      @array.send(@method, eval("(1..3).step(-1)")).should == []
+      @array.send(@method, eval("(1...3).step(-1)")).should == []
+
+      @array.send(@method, eval("(1..3).step(-2)")).should == []
+      @array.send(@method, eval("(1...3).step(-2)")).should == []
+
+      @array.send(@method, eval("(1..3).step(-10)")).should == []
+      @array.send(@method, eval("(1...3).step(-10)")).should == []
+
+      # start with positive index, end with negative index
+      @array.send(@method, eval("(1..-2).step(-1)")).should == []
+      @array.send(@method, eval("(1...-2).step(-1)")).should == []
+
+      @array.send(@method, eval("(1..-2).step(-2)")).should ==  []
+      @array.send(@method, eval("(1...-2).step(-2)")).should ==  []
+
+      @array.send(@method, eval("(1..-2).step(-10)")).should == []
+      @array.send(@method, eval("(1...-2).step(-10)")).should == []
+
+      # start with negative index, end with positive index
+      @array.send(@method, eval("(-4..4).step(-1)")).should == []
+      @array.send(@method, eval("(-4...4).step(-1)")).should == []
+
+      @array.send(@method, eval("(-4..4).step(-2)")).should == []
+      @array.send(@method, eval("(-4...4).step(-2)")).should == []
+
+      @array.send(@method, eval("(-4..4).step(-10)")).should == []
+      @array.send(@method, eval("(-4...4).step(-10)")).should == []
+
+      # start with negative index, end with negative index
+      @array.send(@method, eval("(-4..-2).step(-1)")).should == []
+      @array.send(@method, eval("(-4...-2).step(-1)")).should == []
+
+      @array.send(@method, eval("(-4..-2).step(-2)")).should == []
+      @array.send(@method, eval("(-4...-2).step(-2)")).should == []
+
+      @array.send(@method, eval("(-4..-2).step(-10)")).should == []
+      @array.send(@method, eval("(-4...-2).step(-10)")).should == []
+    end
+
+    it "has inverted closed range and positive steps" do
+      # start and end with positive index
+      @array.send(@method, eval("(3..1).step(1)")).should == []
+      @array.send(@method, eval("(3...1).step(1)")).should == []
+
+      @array.send(@method, eval("(3..1).step(2)")).should == []
+      @array.send(@method, eval("(3...1).step(2)")).should == []
+
+      @array.send(@method, eval("(3..1).step(10)")).should == []
+      @array.send(@method, eval("(3...1).step(10)")).should == []
+
+      # start with negative index, end with positive index
+      @array.send(@method, eval("(-2..1).step(1)")).should == []
+      @array.send(@method, eval("(-2...1).step(1)")).should == []
+
+      @array.send(@method, eval("(-2..1).step(2)")).should ==  []
+      @array.send(@method, eval("(-2...1).step(2)")).should ==  []
+
+      @array.send(@method, eval("(-2..1).step(10)")).should == []
+      @array.send(@method, eval("(-2...1).step(10)")).should == []
+
+      # start with positive index, end with negative index
+      @array.send(@method, eval("(4..-4).step(1)")).should == []
+      @array.send(@method, eval("(4...-4).step(1)")).should == []
+
+      @array.send(@method, eval("(4..-4).step(2)")).should == []
+      @array.send(@method, eval("(4...-4).step(2)")).should == []
+
+      @array.send(@method, eval("(4..-4).step(10)")).should == []
+      @array.send(@method, eval("(4...-4).step(10)")).should == []
+
+      # start with negative index, end with negative index
+      @array.send(@method, eval("(-2..-4).step(1)")).should == []
+      @array.send(@method, eval("(-2...-4).step(1)")).should == []
+
+      @array.send(@method, eval("(-2..-4).step(2)")).should == []
+      @array.send(@method, eval("(-2...-4).step(2)")).should == []
+
+      @array.send(@method, eval("(-2..-4).step(10)")).should == []
+      @array.send(@method, eval("(-2...-4).step(10)")).should == []
+    end
+
+    it "has range with bounds outside of array" do
+      # end is equal to array's length
+      @array.send(@method, (0..6).step(1)).should == [0, 1, 2, 3, 4, 5]
+      -> { @array.send(@method, (0..6).step(2)) }.should raise_error(RangeError)
+
+      # end is greater than length with positive steps
+      @array.send(@method, (1..6).step(2)).should == [1, 3, 5]
+      @array.send(@method, (2..7).step(2)).should == [2, 4]
+      -> { @array.send(@method, (2..8).step(2)) }.should raise_error(RangeError)
+
+      # begin is greater than length with negative steps
+      @array.send(@method, (6..1).step(-2)).should == [5, 3, 1]
+      @array.send(@method, (7..2).step(-2)).should == [5, 3]
+      -> { @array.send(@method, (8..2).step(-2)) }.should raise_error(RangeError)
+    end
+
+    it "has endless range with start outside of array's bounds" do
+      @array.send(@method, eval("(6..).step(1)")).should == []
+      @array.send(@method, eval("(7..).step(1)")).should == nil
+
+      @array.send(@method, eval("(6..).step(2)")).should == []
+      -> { @array.send(@method, eval("(7..).step(2)")) }.should raise_error(RangeError)
+    end
+  end
+
+  it "can accept beginless ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a.send(@method, (..3)).should == [0, 1, 2, 3]
+    a.send(@method, (...3)).should == [0, 1, 2]
+    a.send(@method, (..-3)).should == [0, 1, 2, 3]
+    a.send(@method, (...-3)).should == [0, 1, 2]
+    a.send(@method, (..0)).should == [0]
+    a.send(@method, (...0)).should == []
+    a.send(@method, (..9)).should == [0, 1, 2, 3, 4, 5]
+    a.send(@method, (...9)).should == [0, 1, 2, 3, 4, 5]
+    a.send(@method, (..-9)).should == []
+    a.send(@method, (...-9)).should == []
+  end
+
+  describe "can be sliced with Enumerator::ArithmeticSequence" do
+    it "with infinite/inverted ranges and negative steps" do
+      @array = [0, 1, 2, 3, 4, 5]
+      @array.send(@method, (2..).step(-1)).should == [2, 1, 0]
+      @array.send(@method, (2..).step(-2)).should == [2, 0]
+      @array.send(@method, (2..).step(-3)).should == [2]
+      @array.send(@method, (2..).step(-4)).should == [2]
+
+      @array.send(@method, (-3..).step(-1)).should == [3, 2, 1, 0]
+      @array.send(@method, (-3..).step(-2)).should == [3, 1]
+      @array.send(@method, (-3..).step(-3)).should == [3, 0]
+      @array.send(@method, (-3..).step(-4)).should == [3]
+      @array.send(@method, (-3..).step(-5)).should == [3]
+
+      @array.send(@method, (..0).step(-1)).should == [5, 4, 3, 2, 1, 0]
+      @array.send(@method, (..0).step(-2)).should == [5, 3, 1]
+      @array.send(@method, (..0).step(-3)).should == [5, 2]
+      @array.send(@method, (..0).step(-4)).should == [5, 1]
+      @array.send(@method, (..0).step(-5)).should == [5, 0]
+      @array.send(@method, (..0).step(-6)).should == [5]
+      @array.send(@method, (..0).step(-7)).should == [5]
+
+      @array.send(@method, (...0).step(-1)).should == [5, 4, 3, 2, 1]
+      @array.send(@method, (...0).step(-2)).should == [5, 3, 1]
+      @array.send(@method, (...0).step(-3)).should == [5, 2]
+      @array.send(@method, (...0).step(-4)).should == [5, 1]
+      @array.send(@method, (...0).step(-5)).should == [5]
+      @array.send(@method, (...0).step(-6)).should == [5]
+
+      @array.send(@method, (...1).step(-1)).should == [5, 4, 3, 2]
+      @array.send(@method, (...1).step(-2)).should == [5, 3]
+      @array.send(@method, (...1).step(-3)).should == [5, 2]
+      @array.send(@method, (...1).step(-4)).should == [5]
+      @array.send(@method, (...1).step(-5)).should == [5]
+
+      @array.send(@method, (..-5).step(-1)).should == [5, 4, 3, 2, 1]
+      @array.send(@method, (..-5).step(-2)).should == [5, 3, 1]
+      @array.send(@method, (..-5).step(-3)).should == [5, 2]
+      @array.send(@method, (..-5).step(-4)).should == [5, 1]
+      @array.send(@method, (..-5).step(-5)).should == [5]
+      @array.send(@method, (..-5).step(-6)).should == [5]
+
+      @array.send(@method, (...-5).step(-1)).should == [5, 4, 3, 2]
+      @array.send(@method, (...-5).step(-2)).should == [5, 3]
+      @array.send(@method, (...-5).step(-3)).should == [5, 2]
+      @array.send(@method, (...-5).step(-4)).should == [5]
+      @array.send(@method, (...-5).step(-5)).should == [5]
+
+      @array.send(@method, (4..1).step(-1)).should == [4, 3, 2, 1]
+      @array.send(@method, (4..1).step(-2)).should == [4, 2]
+      @array.send(@method, (4..1).step(-3)).should == [4, 1]
+      @array.send(@method, (4..1).step(-4)).should == [4]
+      @array.send(@method, (4..1).step(-5)).should == [4]
+
+      @array.send(@method, (4...1).step(-1)).should == [4, 3, 2]
+      @array.send(@method, (4...1).step(-2)).should == [4, 2]
+      @array.send(@method, (4...1).step(-3)).should == [4]
+      @array.send(@method, (4...1).step(-4)).should == [4]
+
+      @array.send(@method, (-2..1).step(-1)).should == [4, 3, 2, 1]
+      @array.send(@method, (-2..1).step(-2)).should == [4, 2]
+      @array.send(@method, (-2..1).step(-3)).should == [4, 1]
+      @array.send(@method, (-2..1).step(-4)).should == [4]
+      @array.send(@method, (-2..1).step(-5)).should == [4]
+
+      @array.send(@method, (-2...1).step(-1)).should == [4, 3, 2]
+      @array.send(@method, (-2...1).step(-2)).should == [4, 2]
+      @array.send(@method, (-2...1).step(-3)).should == [4]
+      @array.send(@method, (-2...1).step(-4)).should == [4]
+
+      @array.send(@method, (4..-5).step(-1)).should == [4, 3, 2, 1]
+      @array.send(@method, (4..-5).step(-2)).should == [4, 2]
+      @array.send(@method, (4..-5).step(-3)).should == [4, 1]
+      @array.send(@method, (4..-5).step(-4)).should == [4]
+      @array.send(@method, (4..-5).step(-5)).should == [4]
+
+      @array.send(@method, (4...-5).step(-1)).should == [4, 3, 2]
+      @array.send(@method, (4...-5).step(-2)).should == [4, 2]
+      @array.send(@method, (4...-5).step(-3)).should == [4]
+      @array.send(@method, (4...-5).step(-4)).should == [4]
+
+      @array.send(@method, (-2..-5).step(-1)).should == [4, 3, 2, 1]
+      @array.send(@method, (-2..-5).step(-2)).should == [4, 2]
+      @array.send(@method, (-2..-5).step(-3)).should == [4, 1]
+      @array.send(@method, (-2..-5).step(-4)).should == [4]
+      @array.send(@method, (-2..-5).step(-5)).should == [4]
+
+      @array.send(@method, (-2...-5).step(-1)).should == [4, 3, 2]
+      @array.send(@method, (-2...-5).step(-2)).should == [4, 2]
+      @array.send(@method, (-2...-5).step(-3)).should == [4]
+      @array.send(@method, (-2...-5).step(-4)).should == [4]
+    end
+  end
+
+  it "can accept nil...nil ranges" do
+    a = [0, 1, 2, 3, 4, 5]
+    a.send(@method, eval("(nil...nil)")).should == a
+    a.send(@method, (...nil)).should == a
+    a.send(@method, eval("(nil..)")).should == a
+  end
 end
diff --git a/spec/ruby/core/array/shared/union.rb b/spec/ruby/core/array/shared/union.rb
index 12a98cc9fe..0b60df9ca4 100644
--- a/spec/ruby/core/array/shared/union.rb
+++ b/spec/ruby/core/array/shared/union.rb
@@ -31,7 +31,7 @@ describe :array_binary_union, shared: true do
     [0].send(@method, obj).should == ([0] | [1, 2, 3])
   end
 
-  # MRI follows hashing semantics here, so doesn't actually call eql?/hash for Fixnum/Symbol
+  # MRI follows hashing semantics here, so doesn't actually call eql?/hash for Integer/Symbol
   it "acts as if using an intermediate hash to collect values" do
     not_supported_on :opal do
       [5.0, 4.0].send(@method, [5, 4]).should == [5.0, 4.0, 5, 4]
diff --git a/spec/ruby/core/array/shared/unshift.rb b/spec/ruby/core/array/shared/unshift.rb
index be62084e95..9e0fe7556a 100644
--- a/spec/ruby/core/array/shared/unshift.rb
+++ b/spec/ruby/core/array/shared/unshift.rb
@@ -22,6 +22,11 @@ describe :array_unshift, shared: true do
     a.should == [3, 4]
   end
 
+  it "returns self" do
+    a = [1, 2, 3]
+    a.send(@method, "a").should.equal?(a)
+  end
+
   it "quietly ignores unshifting nothing" do
     [].send(@method).should == []
   end
@@ -35,12 +40,25 @@ describe :array_unshift, shared: true do
     array[0..5].should == [:new, 1, 'two', 3.0, array, array]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array when the array is modified" do
-    -> { ArraySpecs.frozen_array.send(@method, 1) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array when the array is modified" do
+    -> { ArraySpecs.frozen_array.send(@method, 1) }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen array when the array would not be modified" do
-    -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.send(@method) }.should raise_error(FrozenError)
+  end
+
+  # https://github.com/truffleruby/truffleruby/issues/2772
+  it "doesn't rely on Array#[]= so it can be overridden" do
+    subclass = Class.new(Array) do
+      def []=(*)
+        raise "[]= is called"
+      end
+    end
+
+    array = subclass.new
+    array.send(@method, 1)
+    array.should == [1]
   end
 end
diff --git a/spec/ruby/core/array/shift_spec.rb b/spec/ruby/core/array/shift_spec.rb
index ef3c9fe1cd..6b4ef39f77 100644
--- a/spec/ruby/core/array/shift_spec.rb
+++ b/spec/ruby/core/array/shift_spec.rb
@@ -30,11 +30,11 @@ describe "Array#shift" do
     array[0..2].should == ['two', 3.0, array]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.shift }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.shift }.should raise_error(FrozenError)
   end
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.shift }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.shift }.should raise_error(FrozenError)
   end
 
   describe "passed a number n as an argument" do
@@ -116,19 +116,5 @@ describe "Array#shift" do
     it "does not return subclass instances with Array subclass" do
       ArraySpecs::MyArray[1, 2, 3].shift(2).should be_an_instance_of(Array)
     end
-
-    it "returns an untainted array even if the array is tainted" do
-      ary = [1, 2].taint
-      ary.shift(2).tainted?.should be_false
-      ary.shift(0).tainted?.should be_false
-    end
-
-    it "keeps taint status" do
-      a = [1, 2].taint
-      a.shift(2)
-      a.tainted?.should be_true
-      a.shift(2)
-      a.tainted?.should be_true
-    end
   end
 end
diff --git a/spec/ruby/core/array/shuffle_spec.rb b/spec/ruby/core/array/shuffle_spec.rb
index 7a2fed7d50..b84394bcb5 100644
--- a/spec/ruby/core/array/shuffle_spec.rb
+++ b/spec/ruby/core/array/shuffle_spec.rb
@@ -25,12 +25,6 @@ describe "Array#shuffle" do
     ArraySpecs::MyArray[1, 2, 3].shuffle.should be_an_instance_of(Array)
   end
 
-  it "attempts coercion via #to_hash" do
-    obj = mock('hash')
-    obj.should_receive(:to_hash).once.and_return({})
-    [2, 3].shuffle(obj)
-  end
-
   it "calls #rand on the Object passed by the :random key in the arguments Hash" do
     obj = mock("array_shuffle_random")
     obj.should_receive(:rand).at_least(1).times.and_return(0.5)
@@ -53,6 +47,10 @@ describe "Array#shuffle" do
     [1, 2].shuffle(random: random).should be_an_instance_of(Array)
   end
 
+  it "accepts a Random class for the value for random: argument" do
+    [1, 2].shuffle(random: Random).should be_an_instance_of(Array)
+  end
+
   it "calls #to_int on the Object returned by #rand" do
     value = mock("array_shuffle_random_value")
     value.should_receive(:to_int).at_least(1).times.and_return(0)
@@ -71,9 +69,18 @@ describe "Array#shuffle" do
     -> { [1, 2].shuffle(random: random) }.should raise_error(RangeError)
   end
 
-  it "raises a RangeError if the value is equal to one" do
+  it "raises a RangeError if the value is equal to the Array size" do
     value = mock("array_shuffle_random_value")
-    value.should_receive(:to_int).at_least(1).times.and_return(1)
+    value.should_receive(:to_int).at_least(1).times.and_return(2)
+    random = mock("array_shuffle_random")
+    random.should_receive(:rand).at_least(1).times.and_return(value)
+
+    -> { [1, 2].shuffle(random: random) }.should raise_error(RangeError)
+  end
+
+  it "raises a RangeError if the value is greater than the Array size" do
+    value = mock("array_shuffle_random_value")
+    value.should_receive(:to_int).at_least(1).times.and_return(3)
     random = mock("array_shuffle_random")
     random.should_receive(:rand).at_least(1).times.and_return(value)
 
@@ -95,8 +102,18 @@ describe "Array#shuffle!" do
     a.should equal(original)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.shuffle! }.should raise_error(frozen_error_class)
-    -> { ArraySpecs.empty_frozen_array.shuffle! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.shuffle! }.should raise_error(FrozenError)
+    -> { ArraySpecs.empty_frozen_array.shuffle! }.should raise_error(FrozenError)
+  end
+
+  it "matches CRuby with random:" do
+    %w[a b c].shuffle(random: Random.new(1)).should == %w[a c b]
+    (0..10).to_a.shuffle(random: Random.new(10)).should == [2, 6, 8, 5, 7, 10, 3, 1, 0, 4, 9]
+  end
+
+  it "matches CRuby with srand" do
+    srand(123)
+    %w[a b c d e f g h i j k].shuffle.should == %w[a e f h i j d b g k c]
   end
 end
diff --git a/spec/ruby/core/array/slice_spec.rb b/spec/ruby/core/array/slice_spec.rb
index 16220bdf0d..731c129251 100644
--- a/spec/ruby/core/array/slice_spec.rb
+++ b/spec/ruby/core/array/slice_spec.rb
@@ -150,8 +150,66 @@ describe "Array#slice!" do
     a.should == [1, 2]
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.slice!(0, 0) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.slice!(0, 0) }.should raise_error(FrozenError)
+  end
+
+  it "works with endless ranges" do
+    a = [1, 2, 3]
+    a.slice!(eval("(1..)")).should == [2, 3]
+    a.should == [1]
+
+    a = [1, 2, 3]
+    a.slice!(eval("(2...)")).should == [3]
+    a.should == [1, 2]
+
+    a = [1, 2, 3]
+    a.slice!(eval("(-2..)")).should == [2, 3]
+    a.should == [1]
+
+    a = [1, 2, 3]
+    a.slice!(eval("(-1...)")).should == [3]
+    a.should == [1, 2]
+  end
+
+  it "works with beginless ranges" do
+    a = [0,1,2,3,4]
+    a.slice!((..3)).should == [0, 1, 2, 3]
+    a.should == [4]
+
+    a = [0,1,2,3,4]
+    a.slice!((...-2)).should == [0, 1, 2]
+    a.should == [3, 4]
+  end
+
+  describe "with a subclass of Array" do
+    before :each do
+      @array = ArraySpecs::MyArray[1, 2, 3, 4, 5]
+    end
+
+    it "returns a Array instance with [n, m]" do
+      @array.slice!(0, 2).should be_an_instance_of(Array)
+    end
+
+    it "returns a Array instance with [-n, m]" do
+      @array.slice!(-3, 2).should be_an_instance_of(Array)
+    end
+
+    it "returns a Array instance with [n..m]" do
+      @array.slice!(1..3).should be_an_instance_of(Array)
+    end
+
+    it "returns a Array instance with [n...m]" do
+      @array.slice!(1...3).should be_an_instance_of(Array)
+    end
+
+    it "returns a Array instance with [-n..-m]" do
+      @array.slice!(-3..-1).should be_an_instance_of(Array)
+    end
+
+    it "returns a Array instance with [-n...-m]" do
+      @array.slice!(-3...-1).should be_an_instance_of(Array)
+    end
   end
 end
 
diff --git a/spec/ruby/core/array/sort_by_spec.rb b/spec/ruby/core/array/sort_by_spec.rb
index 045051d307..0334f953f6 100644
--- a/spec/ruby/core/array/sort_by_spec.rb
+++ b/spec/ruby/core/array/sort_by_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "Array#sort_by!" do
@@ -23,12 +24,17 @@ describe "Array#sort_by!" do
     a.should be_an_instance_of(Array)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.sort_by! {}}.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.sort_by! {}}.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on an empty frozen array" do
-    -> { ArraySpecs.empty_frozen_array.sort_by! {}}.should raise_error(frozen_error_class)
+  it "raises a FrozenError on an empty frozen array" do
+    -> { ArraySpecs.empty_frozen_array.sort_by! {}}.should raise_error(FrozenError)
+  end
+
+  it "raises a FrozenError on a frozen array only during iteration if called without a block" do
+    enum = ArraySpecs.frozen_array.sort_by!
+    -> { enum.each {} }.should raise_error(FrozenError)
   end
 
   it "returns the specified value when it would break in the given block" do
@@ -48,5 +54,32 @@ describe "Array#sort_by!" do
     [1].sort_by!(&:to_s).should == [1]
   end
 
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.sort_by! { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "doesn't change array if error is raised" do
+    a = [4, 3, 2, 1]
+    begin
+      a.sort_by! do |e|
+        raise StandardError, 'Oops' if e == 1
+        e
+      end
+    rescue StandardError
+    end
+
+    a.should == [4, 3, 2, 1]
+  end
+
   it_behaves_like :enumeratorized_with_origin_size, :sort_by!, [1,2,3]
 end
+
+describe "Array#sort_by!" do
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :sort_by!
+end
diff --git a/spec/ruby/core/array/sort_spec.rb b/spec/ruby/core/array/sort_spec.rb
index 6b84a82a48..e20b650516 100644
--- a/spec/ruby/core/array/sort_spec.rb
+++ b/spec/ruby/core/array/sort_spec.rb
@@ -58,9 +58,9 @@ describe "Array#sort" do
     b = ArraySpecs::MockForCompared.new
     c = ArraySpecs::MockForCompared.new
 
-    ArraySpecs::MockForCompared.compared?.should == false
+    ArraySpecs::MockForCompared.should_not.compared?
     [a, b, c].sort.should == [c, b, a]
-    ArraySpecs::MockForCompared.compared?.should == true
+    ArraySpecs::MockForCompared.should.compared?
   end
 
   it "does not deal with exceptions raised by unimplemented or incorrect #<=>" do
@@ -104,17 +104,17 @@ describe "Array#sort" do
 
   it "does not freezes self during being sorted" do
     a = [1, 2, 3]
-    a.sort { |x,y| a.frozen?.should == false; x <=> y }
+    a.sort { |x,y| a.should_not.frozen?; x <=> y }
   end
 
   it "returns the specified value when it would break in the given block" do
     [1, 2, 3].sort{ break :a }.should == :a
   end
 
-  it "uses the sign of Bignum block results as the sort result" do
+  it "uses the sign of Integer block results as the sort result" do
     a = [1, 2, 5, 10, 7, -4, 12]
     begin
-      class Bignum;
+      class Integer
         alias old_spaceship <=>
         def <=>(other)
           raise
@@ -122,7 +122,7 @@ describe "Array#sort" do
       end
       a.sort {|n, m| (n - m) * (2 ** 200)}.should == [-4, 1, 2, 5, 7, 10, 12]
     ensure
-      class Bignum
+      class Integer
         alias <=> old_spaceship
       end
     end
@@ -132,7 +132,7 @@ describe "Array#sort" do
     a = [1, 2, 5, 10, 7, -4, 12]
     a.sort { |n, m| n - m }.should == [-4, 1, 2, 5, 7, 10, 12]
     a.sort { |n, m|
-      ArraySpecs::ComparableWithFixnum.new(n-m)
+      ArraySpecs::ComparableWithInteger.new(n-m)
     }.should == [-4, 1, 2, 5, 7, 10, 12]
     -> {
       a.sort { |n, m| (n - m).to_s }
@@ -207,9 +207,9 @@ describe "Array#sort!" do
     b = ArraySpecs::MockForCompared.new
     c = ArraySpecs::MockForCompared.new
 
-    ArraySpecs::MockForCompared.compared?.should == false
+    ArraySpecs::MockForCompared.should_not.compared?
     [a, b, c].sort!.should == [c, b, a]
-    ArraySpecs::MockForCompared.compared?.should == true
+    ArraySpecs::MockForCompared.should.compared?
   end
 
   it "does not call #<=> on contained objects when invoked with a block" do
@@ -233,8 +233,8 @@ describe "Array#sort!" do
     a.sort!{ -1 }.should be_an_instance_of(Array)
   end
 
-  it "raises a #{frozen_error_class} on a frozen array" do
-    -> { ArraySpecs.frozen_array.sort! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array" do
+    -> { ArraySpecs.frozen_array.sort! }.should raise_error(FrozenError)
   end
 
   it "returns the specified value when it would break in the given block" do
diff --git a/spec/ruby/core/array/sum_spec.rb b/spec/ruby/core/array/sum_spec.rb
index 39c769d328..06abe06135 100644
--- a/spec/ruby/core/array/sum_spec.rb
+++ b/spec/ruby/core/array/sum_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#sum" do
   it "returns the sum of elements" do
@@ -9,6 +10,39 @@ describe "Array#sum" do
     [1, 2, 3].sum { |i| i * 10 }.should == 60
   end
 
+  it "doesn't apply the block init" do
+    [1, 2, 3].sum(1) { |i| i * 10 }.should == 61
+  end
+
+  # https://bugs.ruby-lang.org/issues/12217
+  # https://github.com/ruby/ruby/blob/master/doc/ChangeLog/ChangeLog-2.4.0#L6208-L6214
+  it "uses Kahan's compensated summation algorithm for precise sum of float numbers" do
+    floats = [2.7800000000000002, 5.0, 2.5, 4.44, 3.89, 3.89, 4.44, 7.78, 5.0, 2.7800000000000002, 5.0, 2.5]
+    naive_sum = floats.reduce { |sum, e| sum + e }
+    naive_sum.should == 50.00000000000001
+    floats.sum.should == 50.0
+  end
+
+  it "handles infinite values and NaN" do
+    [1.0, Float::INFINITY].sum.should == Float::INFINITY
+    [1.0, -Float::INFINITY].sum.should == -Float::INFINITY
+    [1.0, Float::NAN].sum.should.nan?
+
+    [Float::INFINITY, 1.0].sum.should == Float::INFINITY
+    [-Float::INFINITY, 1.0].sum.should == -Float::INFINITY
+    [Float::NAN, 1.0].sum.should.nan?
+
+    [Float::NAN, Float::INFINITY].sum.should.nan?
+    [Float::INFINITY, Float::NAN].sum.should.nan?
+
+    [Float::INFINITY, -Float::INFINITY].sum.should.nan?
+    [-Float::INFINITY, Float::INFINITY].sum.should.nan?
+
+    [Float::INFINITY, Float::INFINITY].sum.should == Float::INFINITY
+    [-Float::INFINITY, -Float::INFINITY].sum.should == -Float::INFINITY
+    [Float::NAN, Float::NAN].sum.should.nan?
+  end
+
   it "returns init value if array is empty" do
     [].sum(-1).should == -1
   end
@@ -39,4 +73,18 @@ describe "Array#sum" do
     a.should_receive(:+).with(b).and_return(42)
     [b].sum(a).should == 42
   end
+
+  ruby_bug '#19530', ''...'3.3' do
+    it "calls + on the init value" do
+      a = mock("a")
+      b = mock("b")
+      a.should_receive(:+).with(42).and_return(b)
+      [42].sum(a).should == b
+    end
+  end
+end
+
+describe "Array#sum" do
+  @value_to_return = -> _ { 1 }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :sum
 end
diff --git a/spec/ruby/core/array/take_spec.rb b/spec/ruby/core/array/take_spec.rb
index 0de99b0a7e..c4f0ac9aa4 100644
--- a/spec/ruby/core/array/take_spec.rb
+++ b/spec/ruby/core/array/take_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "Array#take" do
   it "returns the first specified number of elements" do
@@ -24,4 +25,8 @@ describe "Array#take" do
   it "raises an ArgumentError when the argument is negative" do
     ->{ [1].take(-3) }.should raise_error(ArgumentError)
   end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].take(1).should be_an_instance_of(Array)
+  end
 end
diff --git a/spec/ruby/core/array/take_while_spec.rb b/spec/ruby/core/array/take_while_spec.rb
index f159e6f251..8f50260b42 100644
--- a/spec/ruby/core/array/take_while_spec.rb
+++ b/spec/ruby/core/array/take_while_spec.rb
@@ -1,4 +1,6 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#take_while" do
   it "returns all elements until the block returns false" do
@@ -12,4 +14,13 @@ describe "Array#take_while" do
   it "returns all elements until the block returns false" do
     [1, 2, false, 4].take_while{ |element| element }.should == [1, 2]
   end
+
+  it 'returns a Array instance for Array subclasses' do
+    ArraySpecs::MyArray[1, 2, 3, 4, 5].take_while { |n| n < 4 }.should be_an_instance_of(Array)
+  end
+end
+
+describe "Array#take_while" do
+  @value_to_return = -> _ { true }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :take_while
 end
diff --git a/spec/ruby/core/array/to_h_spec.rb b/spec/ruby/core/array/to_h_spec.rb
index 46a79ba58b..1c814f3d01 100644
--- a/spec/ruby/core/array/to_h_spec.rb
+++ b/spec/ruby/core/array/to_h_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#to_h" do
   it "converts empty array to empty hash" do
@@ -39,43 +40,52 @@ describe "Array#to_h" do
     [[:a, 1], [:b, 2]].to_h[:c].should be_nil
   end
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      it "converts [key, value] pairs returned by the block to a Hash" do
-        [:a, :b].to_h { |k| [k, k.to_s] }.should == { a: 'a', b: 'b' }
-      end
-
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          [:a, :b].to_h { |k| [k, k.to_s, 1] }
-        end.should raise_error(ArgumentError, /wrong array length at 0/)
-
-        -> do
-          [:a, :b].to_h { |k| [k] }
-        end.should raise_error(ArgumentError, /wrong array length at 0/)
-      end
-
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          [:a, :b].to_h { |k| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String at 0/)
-      end
-
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
-
-        [:a].to_h { |k| x }.should == { :b => 'b' }
-      end
-
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
-
-        -> do
-          [:a].to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject at 0/)
-      end
+  context "with block" do
+    it "converts [key, value] pairs returned by the block to a Hash" do
+      [:a, :b].to_h { |k| [k, k.to_s] }.should == { a: 'a', b: 'b' }
+    end
+
+    it "passes to a block each element as a single argument" do
+      ScratchPad.record []
+      [[:a, 1], [:b, 2]].to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[[:a, 1]], [[:b, 2]]]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        [:a, :b].to_h { |k| [k, k.to_s, 1] }
+      end.should raise_error(ArgumentError, /wrong array length at 0/)
+
+      -> do
+        [:a, :b].to_h { |k| [k] }
+      end.should raise_error(ArgumentError, /wrong array length at 0/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        [:a, :b].to_h { |k| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String at 0/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      [:a].to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        [:a].to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject at 0/)
     end
   end
 end
+
+describe "Array#to_h" do
+  @value_to_return = -> e { [e, e.to_s] }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :to_h
+end
diff --git a/spec/ruby/core/array/try_convert_spec.rb b/spec/ruby/core/array/try_convert_spec.rb
index 47b4722d80..bea8815006 100644
--- a/spec/ruby/core/array/try_convert_spec.rb
+++ b/spec/ruby/core/array/try_convert_spec.rb
@@ -39,7 +39,7 @@ describe "Array.try_convert" do
   it "sends #to_ary to the argument and raises TypeError if it's not a kind of Array" do
     obj = mock("to_ary")
     obj.should_receive(:to_ary).and_return(Object.new)
-    -> { Array.try_convert obj }.should raise_error(TypeError)
+    -> { Array.try_convert obj }.should raise_error(TypeError, "can't convert MockObject to Array (MockObject#to_ary gives Object)")
   end
 
   it "does not rescue exceptions raised by #to_ary" do
diff --git a/spec/ruby/core/array/union_spec.rb b/spec/ruby/core/array/union_spec.rb
index 1dca47696d..ba2cc0d6b7 100644
--- a/spec/ruby/core/array/union_spec.rb
+++ b/spec/ruby/core/array/union_spec.rb
@@ -6,22 +6,20 @@ describe "Array#|" do
   it_behaves_like :array_binary_union, :|
 end
 
-ruby_version_is "2.6" do
-  describe "Array#union" do
-    it_behaves_like :array_binary_union, :union
+describe "Array#union" do
+  it_behaves_like :array_binary_union, :union
 
-    it "returns unique elements when given no argument" do
-      x = [1, 2, 3, 2]
-      x.union.should == [1, 2, 3]
-    end
+  it "returns unique elements when given no argument" do
+    x = [1, 2, 3, 2]
+    x.union.should == [1, 2, 3]
+  end
 
-    it "does not return subclass instances for Array subclasses" do
-      ArraySpecs::MyArray[1, 2, 3].union.should be_an_instance_of(Array)
-    end
+  it "does not return subclass instances for Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3].union.should be_an_instance_of(Array)
+  end
 
-    it "accepts multiple arguments" do
-      x = [1, 2, 3]
-      x.union(x, x, x, x, [3, 4], x).should == [1, 2, 3, 4]
-    end
+  it "accepts multiple arguments" do
+    x = [1, 2, 3]
+    x.union(x, x, x, x, [3, 4], x).should == [1, 2, 3, 4]
   end
 end
diff --git a/spec/ruby/core/array/uniq_spec.rb b/spec/ruby/core/array/uniq_spec.rb
index c9bdd3dacd..d5d826db15 100644
--- a/spec/ruby/core/array/uniq_spec.rb
+++ b/spec/ruby/core/array/uniq_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/iterable_and_tolerating_size_increasing'
 
 describe "Array#uniq" do
   it "returns an array with no duplicates" do
@@ -45,10 +46,6 @@ describe "Array#uniq" do
       obj.should_receive(:hash).at_least(1).and_return(0)
 
       def obj.eql?(o)
-        # It's undefined whether the impl does a[0].eql?(a[1]) or
-        # a[1].eql?(a[0]) so we taint both.
-        taint
-        o.taint
         false
       end
 
@@ -56,18 +53,12 @@ describe "Array#uniq" do
     end
 
     a.uniq.should == a
-    a[0].tainted?.should == true
-    a[1].tainted?.should == true
 
     a = Array.new(2) do
       obj = mock('0')
       obj.should_receive(:hash).at_least(1).and_return(0)
 
       def obj.eql?(o)
-        # It's undefined whether the impl does a[0].eql?(a[1]) or
-        # a[1].eql?(a[0]) so we taint both.
-        taint
-        o.taint
         true
       end
 
@@ -75,8 +66,6 @@ describe "Array#uniq" do
     end
 
     a.uniq.size.should == 1
-    a[0].tainted?.should == true
-    a[1].tainted?.should == true
   end
 
   it "compares elements based on the value returned from the block" do
@@ -96,8 +85,8 @@ describe "Array#uniq" do
     [false, nil, 42].uniq { :bar }.should == [false]
   end
 
-  it "returns subclass instance on Array subclasses" do
-    ArraySpecs::MyArray[1, 2, 3].uniq.should be_an_instance_of(ArraySpecs::MyArray)
+  it "returns Array instance on Array subclasses" do
+    ArraySpecs::MyArray[1, 2, 3].uniq.should be_an_instance_of(Array)
   end
 
   it "properly handles an identical item even when its #eql? isn't reflexive" do
@@ -135,6 +124,11 @@ describe "Array#uniq" do
   end
 end
 
+describe "Array#uniq" do
+  @value_to_return = -> e { e }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :uniq
+end
+
 describe "Array#uniq!" do
   it "modifies the array in place" do
     a = [ "a", "a", "b", "b", "c" ]
@@ -188,20 +182,20 @@ describe "Array#uniq!" do
     [ "a", "b", "c" ].uniq!.should == nil
   end
 
-  it "raises a #{frozen_error_class} on a frozen array when the array is modified" do
+  it "raises a FrozenError on a frozen array when the array is modified" do
     dup_ary = [1, 1, 2]
     dup_ary.freeze
-    -> { dup_ary.uniq! }.should raise_error(frozen_error_class)
+    -> { dup_ary.uniq! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen array when the array would not be modified" do
-    -> { ArraySpecs.frozen_array.uniq!}.should raise_error(frozen_error_class)
-    -> { ArraySpecs.empty_frozen_array.uniq!}.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen array when the array would not be modified" do
+    -> { ArraySpecs.frozen_array.uniq!}.should raise_error(FrozenError)
+    -> { ArraySpecs.empty_frozen_array.uniq!}.should raise_error(FrozenError)
   end
 
   it "doesn't yield to the block on a frozen array" do
-    -> { ArraySpecs.frozen_array.uniq!{ raise RangeError, "shouldn't yield"}}.should raise_error(frozen_error_class)
+    -> { ArraySpecs.frozen_array.uniq!{ raise RangeError, "shouldn't yield"}}.should raise_error(FrozenError)
   end
 
   it "compares elements based on the value returned from the block" do
@@ -218,4 +212,32 @@ describe "Array#uniq!" do
     a.uniq!
     a.should == [x]
   end
+
+  it "does not truncate the array is the block raises an exception" do
+    a = [1, 2, 3]
+    begin
+      a.send(@method) { raise StandardError, 'Oops' }
+    rescue
+    end
+
+    a.should == [1, 2, 3]
+  end
+
+  it "doesn't change array if error is raised" do
+    a = [1, 1, 2, 2, 3, 3, 4, 4]
+    begin
+      a.send(@method) do |e|
+        raise StandardError, 'Oops' if e == 3
+        e
+      end
+    rescue StandardError
+    end
+
+    a.should == [1, 1, 2, 2, 3, 3, 4, 4]
+  end
+end
+
+describe "Array#uniq!" do
+  @value_to_return = -> e { e }
+  it_behaves_like :array_iterable_and_tolerating_size_increasing, :uniq!
 end
diff --git a/spec/ruby/core/array/values_at_spec.rb b/spec/ruby/core/array/values_at_spec.rb
index 13860150bb..e85bbee400 100644
--- a/spec/ruby/core/array/values_at_spec.rb
+++ b/spec/ruby/core/array/values_at_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+# Should be synchronized with core/struct/values_at_spec.rb
 describe "Array#values_at" do
   it "returns an array of elements at the indexes when passed indexes" do
     [1, 2, 3, 4, 5].values_at().should == []
@@ -60,4 +61,14 @@ describe "Array#values_at" do
   it "does not return subclass instance on Array subclasses" do
     ArraySpecs::MyArray[1, 2, 3].values_at(0, 1..2, 1).should be_an_instance_of(Array)
   end
+
+  it "works when given endless ranges" do
+    [1, 2, 3, 4].values_at(eval("(1..)")).should == [2, 3, 4]
+    [1, 2, 3, 4].values_at(eval("(3...)")).should == [4]
+  end
+
+  it "works when given beginless ranges" do
+    [1, 2, 3, 4].values_at((..2)).should == [1, 2, 3]
+    [1, 2, 3, 4].values_at((...2)).should == [1, 2]
+  end
 end
diff --git a/spec/ruby/core/array/zip_spec.rb b/spec/ruby/core/array/zip_spec.rb
index af4013debe..2a0f64cb49 100644
--- a/spec/ruby/core/array/zip_spec.rb
+++ b/spec/ruby/core/array/zip_spec.rb
@@ -62,4 +62,10 @@ describe "Array#zip" do
   it "does not return subclass instance on Array subclasses" do
     ArraySpecs::MyArray[1, 2, 3].zip(["a", "b"]).should be_an_instance_of(Array)
   end
+
+  it "raises TypeError when some argument isn't Array and doesn't respond to #to_ary and #to_enum" do
+    -> { [1, 2, 3].zip(Object.new) }.should raise_error(TypeError, "wrong argument type Object (must respond to :each)")
+    -> { [1, 2, 3].zip(1) }.should raise_error(TypeError, "wrong argument type Integer (must respond to :each)")
+    -> { [1, 2, 3].zip(true) }.should raise_error(TypeError, "wrong argument type TrueClass (must respond to :each)")
+  end
 end
diff --git a/spec/ruby/core/basicobject/equal_spec.rb b/spec/ruby/core/basicobject/equal_spec.rb
index 3c1ad56d4a..ce28eaed95 100644
--- a/spec/ruby/core/basicobject/equal_spec.rb
+++ b/spec/ruby/core/basicobject/equal_spec.rb
@@ -11,8 +11,10 @@ describe "BasicObject#equal?" do
   it "is unaffected by overriding __id__" do
     o1 = mock("object")
     o2 = mock("object")
-    def o1.__id__; 10; end
-    def o2.__id__; 10; end
+    suppress_warning {
+      def o1.__id__; 10; end
+      def o2.__id__; 10; end
+    }
     o1.equal?(o2).should be_false
   end
 
diff --git a/spec/ruby/core/basicobject/fixtures/classes.rb b/spec/ruby/core/basicobject/fixtures/classes.rb
index d1785afe31..ed5a2dda17 100644
--- a/spec/ruby/core/basicobject/fixtures/classes.rb
+++ b/spec/ruby/core/basicobject/fixtures/classes.rb
@@ -15,8 +15,231 @@ module BasicObjectSpecs
     include InstExec
   end
 
-  module InstEvalCVar
-    instance_eval { @@count = 2 }
+  module InstEval
+    module CVar
+      module Get
+        class ReceiverScope
+          @@cvar = :value_defined_in_receiver_scope
+        end
+
+        class BlockDefinitionScope
+          @@cvar = :value_defined_in_block_definition_scope
+
+          def block
+            -> * { @@cvar }
+          end
+        end
+
+        class CallerScope
+          @@cvar = :value_defined_in_caller_scope
+
+          def get_class_variable_with_string(obj)
+            obj.instance_eval("@@cvar")
+          end
+
+          def get_class_variable_with_block(obj, block)
+            obj.instance_eval(&block)
+          end
+        end
+
+        class CallerWithoutCVarScope
+          def get_class_variable_with_string(obj)
+            obj.instance_eval("@@cvar")
+          end
+        end
+
+        ReceiverWithCVarDefinedInSingletonClass = Class.new.new.tap do |obj|
+          obj.singleton_class.class_variable_set(:@@cvar, :value_defined_in_receiver_singleton_class)
+        end
+      end
+
+      module Set
+        class ReceiverScope
+        end
+
+        class BlockDefinitionScope
+          def self.get_class_variable
+            @@cvar
+          end
+
+          def block_to_assign(value)
+            -> * { @@cvar = value }
+          end
+        end
+
+        class CallerScope
+          def self.get_class_variable
+            @@cvar
+          end
+
+          def set_class_variable_with_string(obj, value)
+            obj.instance_eval("@@cvar=#{value.inspect}")
+          end
+
+          def set_class_variable_with_block(obj, block)
+            obj.instance_eval(&block)
+          end
+        end
+      end
+    end
+  end
+
+  module InstEval
+    module Constants
+      module ConstantInReceiverSingletonClass
+        module ReceiverScope
+          FOO = :ReceiverScope
+
+          class ReceiverParent
+            FOO = :ReceiverParent
+          end
+
+          class Receiver < ReceiverParent
+            FOO = :Receiver
+
+            def initialize
+              self.singleton_class.const_set(:FOO, :singleton_class)
+            end
+          end
+        end
+
+        module CallerScope
+          FOO = :CallerScope
+
+          class CallerParent
+            FOO = :CallerParent
+          end
+
+          class Caller < CallerParent
+            FOO = :Caller
+
+            def get_constant_with_string(receiver)
+              receiver.instance_eval("FOO")
+            end
+          end
+        end
+      end
+
+      module ConstantInReceiverClass
+        module ReceiverScope
+          FOO = :ReceiverScope
+
+          class ReceiverParent
+            FOO = :ReceiverParent
+          end
+
+          class Receiver < ReceiverParent
+            FOO = :Receiver
+          end
+        end
+
+        module CallerScope
+          FOO = :CallerScope
+
+          class CallerParent
+            FOO = :CallerParent
+          end
+
+          class Caller < CallerParent
+            FOO = :Caller
+
+            def get_constant_with_string(receiver)
+              receiver.instance_eval("FOO")
+            end
+          end
+        end
+      end
+
+      module ConstantInCallerClass
+        module ReceiverScope
+          FOO = :ReceiverScope
+
+          class ReceiverParent
+            FOO = :ReceiverParent
+          end
+
+          class Receiver < ReceiverParent
+            # FOO is not declared in a receiver class
+          end
+        end
+
+        module CallerScope
+          FOO = :CallerScope
+
+          class CallerParent
+            FOO = :CallerParent
+          end
+
+          class Caller < CallerParent
+            FOO = :Caller
+
+            def get_constant_with_string(receiver)
+              receiver.instance_eval("FOO")
+            end
+          end
+        end
+      end
+
+      module ConstantInCallerOuterScopes
+        module ReceiverScope
+          FOO = :ReceiverScope
+
+          class ReceiverParent
+            FOO = :ReceiverParent
+          end
+
+          class Receiver < ReceiverParent
+            # FOO is not declared in a receiver class
+          end
+        end
+
+        module CallerScope
+          FOO = :CallerScope
+
+          class CallerParent
+            FOO = :CallerParent
+          end
+
+          class Caller < CallerParent
+            # FOO is not declared in a caller class
+
+            def get_constant_with_string(receiver)
+              receiver.instance_eval("FOO")
+            end
+          end
+        end
+      end
+
+      module ConstantInReceiverParentClass
+        module ReceiverScope
+          FOO = :ReceiverScope
+
+          class ReceiverParent
+            FOO = :ReceiverParent
+          end
+
+          class Receiver < ReceiverParent
+            # FOO is not declared in a receiver class
+          end
+        end
+
+        module CallerScope
+          # FOO is not declared in a caller outer scopes
+
+          class CallerParent
+            FOO = :CallerParent
+          end
+
+          class Caller < CallerParent
+            # FOO is not declared in a caller class
+
+            def get_constant_with_string(receiver)
+              receiver.instance_eval("FOO")
+            end
+          end
+        end
+      end
+    end
   end
 
   class InstEvalConst
@@ -26,7 +249,6 @@ module BasicObjectSpecs
   module InstEvalOuter
     module Inner
       obj = InstEvalConst.new
-      X_BY_STR = obj.instance_eval("INST_EVAL_CONST_X") rescue nil
       X_BY_BLOCK = obj.instance_eval { INST_EVAL_CONST_X } rescue nil
     end
   end
diff --git a/spec/ruby/core/basicobject/instance_eval_spec.rb b/spec/ruby/core/basicobject/instance_eval_spec.rb
index d3dd05b745..633b5c2cb1 100644
--- a/spec/ruby/core/basicobject/instance_eval_spec.rb
+++ b/spec/ruby/core/basicobject/instance_eval_spec.rb
@@ -20,12 +20,18 @@ describe "BasicObject#instance_eval" do
     a.instance_eval('self').equal?(a).should be_true
   end
 
-  it "expects a block with no arguments" do
-    -> { "hola".instance_eval }.should raise_error(ArgumentError)
+  it "raises an ArgumentError when no arguments and no block are given" do
+    -> { "hola".instance_eval }.should raise_error(ArgumentError, "wrong number of arguments (given 0, expected 1..3)")
   end
 
-  it "takes no arguments with a block" do
-    -> { "hola".instance_eval(4, 5) {|a,b| a + b } }.should raise_error(ArgumentError)
+  it "raises an ArgumentError when a block and normal arguments are given" do
+    -> { "hola".instance_eval(4, 5) {|a,b| a + b } }.should raise_error(ArgumentError, "wrong number of arguments (given 2, expected 0)")
+  end
+
+  it "raises an ArgumentError when more than 3 arguments are given" do
+    -> {
+      "hola".instance_eval("1 + 1", "some file", 0, "bogus")
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 1..3)")
   end
 
   it "yields the object to the block" do
@@ -78,11 +84,30 @@ describe "BasicObject#instance_eval" do
 
   end
 
+  ruby_version_is "3.3" do
+    it "uses the caller location as default location" do
+      f = Object.new
+      f.instance_eval("[__FILE__, __LINE__]").should == ["(eval at #{__FILE__}:#{__LINE__})", 1]
+    end
+  end
+
   it "has access to receiver's instance variables" do
     BasicObjectSpecs::IVars.new.instance_eval { @secret }.should == 99
     BasicObjectSpecs::IVars.new.instance_eval("@secret").should == 99
   end
 
+  it "raises TypeError for frozen objects when tries to set receiver's instance variables" do
+    -> { nil.instance_eval { @foo = 42 } }.should raise_error(FrozenError, "can't modify frozen NilClass: nil")
+    -> { true.instance_eval { @foo = 42 } }.should raise_error(FrozenError, "can't modify frozen TrueClass: true")
+    -> { false.instance_eval { @foo = 42 } }.should raise_error(FrozenError, "can't modify frozen FalseClass: false")
+    -> { 1.instance_eval { @foo = 42 } }.should raise_error(FrozenError, "can't modify frozen Integer: 1")
+    -> { :symbol.instance_eval { @foo = 42 } }.should raise_error(FrozenError, "can't modify frozen Symbol: :symbol")
+
+    obj = Object.new
+    obj.freeze
+    -> { obj.instance_eval { @foo = 42 } }.should raise_error(FrozenError)
+  end
+
   it "treats block-local variables as local to the block" do
     prc = instance_eval <<-CODE
       proc do |x, prc|
@@ -99,11 +124,6 @@ describe "BasicObject#instance_eval" do
     prc.call(false, prc).should == 1
   end
 
-  it "sets class variables in the receiver" do
-    BasicObjectSpecs::InstEvalCVar.class_variables.should include(:@@count)
-    BasicObjectSpecs::InstEvalCVar.send(:class_variable_get, :@@count).should == 2
-  end
-
   it "makes the receiver metaclass the scoped class when used with a string" do
     obj = Object.new
     obj.instance_eval %{
@@ -113,8 +133,41 @@ describe "BasicObject#instance_eval" do
     obj.singleton_class.const_get(:B).should be_an_instance_of(Class)
   end
 
-  it "gets constants in the receiver if a string given" do
-    BasicObjectSpecs::InstEvalOuter::Inner::X_BY_STR.should == 2
+  describe "constants lookup when a String given" do
+    it "looks in the receiver singleton class first" do
+      receiver = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverSingletonClass::ReceiverScope::Receiver.new
+      caller = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverSingletonClass::CallerScope::Caller.new
+
+      caller.get_constant_with_string(receiver).should == :singleton_class
+    end
+
+    it "looks in the receiver class next" do
+      receiver = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverClass::ReceiverScope::Receiver.new
+      caller = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverClass::CallerScope::Caller.new
+
+      caller.get_constant_with_string(receiver).should == :Receiver
+    end
+
+    it "looks in the caller class next" do
+      receiver = BasicObjectSpecs::InstEval::Constants::ConstantInCallerClass::ReceiverScope::Receiver.new
+      caller = BasicObjectSpecs::InstEval::Constants::ConstantInCallerClass::CallerScope::Caller.new
+
+      caller.get_constant_with_string(receiver).should == :Caller
+    end
+
+    it "looks in the caller outer scopes next" do
+      receiver = BasicObjectSpecs::InstEval::Constants::ConstantInCallerOuterScopes::ReceiverScope::Receiver.new
+      caller = BasicObjectSpecs::InstEval::Constants::ConstantInCallerOuterScopes::CallerScope::Caller.new
+
+      caller.get_constant_with_string(receiver).should == :CallerScope
+    end
+
+    it "looks in the receiver class hierarchy next" do
+      receiver = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverParentClass::ReceiverScope::Receiver.new
+      caller = BasicObjectSpecs::InstEval::Constants::ConstantInReceiverParentClass::CallerScope::Caller.new
+
+      caller.get_constant_with_string(receiver).should == :ReceiverParent
+    end
   end
 
   it "doesn't get constants in the receiver if a block given" do
@@ -130,17 +183,51 @@ describe "BasicObject#instance_eval" do
     end.should raise_error(TypeError)
   end
 
-quarantine! do # Not clean, leaves cvars lying around to break other specs
-  it "scopes class var accesses in the caller when called on a Fixnum" do
-    # Fixnum can take instance vars
-    Fixnum.class_eval "@@__tmp_instance_eval_spec = 1"
-    (defined? @@__tmp_instance_eval_spec).should be_nil
+  describe "class variables lookup" do
+    it "gets class variables in the caller class when called with a String" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Get::ReceiverScope.new
+      caller = BasicObjectSpecs::InstEval::CVar::Get::CallerScope.new
+
+      caller.get_class_variable_with_string(receiver).should == :value_defined_in_caller_scope
+    end
+
+    it "gets class variables in the block definition scope when called with a block" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Get::ReceiverScope.new
+      caller = BasicObjectSpecs::InstEval::CVar::Get::CallerScope.new
+      block = BasicObjectSpecs::InstEval::CVar::Get::BlockDefinitionScope.new.block
+
+      caller.get_class_variable_with_block(receiver, block).should == :value_defined_in_block_definition_scope
+    end
+
+    it "sets class variables in the caller class when called with a String" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Set::ReceiverScope.new
+      caller = BasicObjectSpecs::InstEval::CVar::Set::CallerScope.new
 
-    @@__tmp_instance_eval_spec = 2
-    1.instance_eval { @@__tmp_instance_eval_spec }.should == 2
-    Fixnum.__send__(:remove_class_variable, :@@__tmp_instance_eval_spec)
+      caller.set_class_variable_with_string(receiver, 1)
+      BasicObjectSpecs::InstEval::CVar::Set::CallerScope.get_class_variable.should == 1
+    end
+
+    it "sets class variables in the block definition scope when called with a block" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Set::ReceiverScope.new
+      caller = BasicObjectSpecs::InstEval::CVar::Set::CallerScope.new
+      block = BasicObjectSpecs::InstEval::CVar::Set::BlockDefinitionScope.new.block_to_assign(1)
+
+      caller.set_class_variable_with_block(receiver, block)
+      BasicObjectSpecs::InstEval::CVar::Set::BlockDefinitionScope.get_class_variable.should == 1
+    end
+
+    it "does not have access to class variables in the receiver class when called with a String" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Get::ReceiverScope.new
+      caller = BasicObjectSpecs::InstEval::CVar::Get::CallerWithoutCVarScope.new
+      -> { caller.get_class_variable_with_string(receiver) }.should raise_error(NameError, /uninitialized class variable @@cvar/)
+    end
+
+    it "does not have access to class variables in the receiver's singleton class when called with a String" do
+      receiver = BasicObjectSpecs::InstEval::CVar::Get::ReceiverWithCVarDefinedInSingletonClass
+      caller = BasicObjectSpecs::InstEval::CVar::Get::CallerWithoutCVarScope.new
+      -> { caller.get_class_variable_with_string(receiver) }.should raise_error(NameError, /uninitialized class variable @@cvar/)
+    end
   end
-end
 
   it "raises a TypeError when defining methods on numerics" do
     -> do
@@ -185,4 +272,58 @@ end
 
     x.should == :value
   end
+
+  it "converts string argument with #to_str method" do
+    source_code = Object.new
+    def source_code.to_str() "1" end
+
+    a = BasicObject.new
+    a.instance_eval(source_code).should == 1
+  end
+
+  it "raises ArgumentError if returned value is not String" do
+    source_code = Object.new
+    def source_code.to_str() :symbol end
+
+    a = BasicObject.new
+    -> { a.instance_eval(source_code) }.should raise_error(TypeError, /can't convert Object to String/)
+  end
+
+  it "converts filename argument with #to_str method" do
+    filename = Object.new
+    def filename.to_str() "file.rb" end
+
+    err = begin
+            Object.new.instance_eval("raise", filename)
+          rescue => e
+            e
+          end
+    err.backtrace.first.split(":")[0].should == "file.rb"
+  end
+
+  it "raises ArgumentError if returned value is not String" do
+    filename = Object.new
+    def filename.to_str() :symbol end
+
+    -> { Object.new.instance_eval("raise", filename) }.should raise_error(TypeError, /can't convert Object to String/)
+  end
+
+  it "converts lineno argument with #to_int method" do
+    lineno = Object.new
+    def lineno.to_int() 15 end
+
+    err = begin
+            Object.new.instance_eval("raise", "file.rb", lineno)
+          rescue => e
+            e
+          end
+    err.backtrace.first.split(":")[1].should == "15"
+  end
+
+  it "raises ArgumentError if returned value is not Integer" do
+    lineno = Object.new
+    def lineno.to_int() :symbol end
+
+    -> { Object.new.instance_eval("raise", "file.rb", lineno) }.should raise_error(TypeError, /can't convert Object to Integer/)
+  end
 end
diff --git a/spec/ruby/core/basicobject/instance_exec_spec.rb b/spec/ruby/core/basicobject/instance_exec_spec.rb
index e25482d58a..370f03d33c 100644
--- a/spec/ruby/core/basicobject/instance_exec_spec.rb
+++ b/spec/ruby/core/basicobject/instance_exec_spec.rb
@@ -84,17 +84,17 @@ describe "BasicObject#instance_exec" do
     end.should raise_error(TypeError)
   end
 
-quarantine! do # Not clean, leaves cvars lying around to break other specs
-  it "scopes class var accesses in the caller when called on a Fixnum" do
-    # Fixnum can take instance vars
-    Fixnum.class_eval "@@__tmp_instance_exec_spec = 1"
-    (defined? @@__tmp_instance_exec_spec).should == nil
-
-    @@__tmp_instance_exec_spec = 2
-    1.instance_exec { @@__tmp_instance_exec_spec }.should == 2
-    Fixnum.__send__(:remove_class_variable, :@@__tmp_instance_exec_spec)
+  quarantine! do # Not clean, leaves cvars lying around to break other specs
+    it "scopes class var accesses in the caller when called on an Integer" do
+      # Integer can take instance vars
+      Integer.class_eval "@@__tmp_instance_exec_spec = 1"
+      (defined? @@__tmp_instance_exec_spec).should == nil
+
+      @@__tmp_instance_exec_spec = 2
+      1.instance_exec { @@__tmp_instance_exec_spec }.should == 2
+      Integer.__send__(:remove_class_variable, :@@__tmp_instance_exec_spec)
+    end
   end
-end
 
   it "raises a TypeError when defining methods on numerics" do
     -> do
diff --git a/spec/ruby/core/basicobject/method_missing_spec.rb b/spec/ruby/core/basicobject/method_missing_spec.rb
index b048780ee8..a29d4375bc 100644
--- a/spec/ruby/core/basicobject/method_missing_spec.rb
+++ b/spec/ruby/core/basicobject/method_missing_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative '../../shared/basicobject/method_missing'
 
 describe "BasicObject#method_missing" do
diff --git a/spec/ruby/core/basicobject/singleton_method_added_spec.rb b/spec/ruby/core/basicobject/singleton_method_added_spec.rb
index 8d256e22db..bd21458ea7 100644
--- a/spec/ruby/core/basicobject/singleton_method_added_spec.rb
+++ b/spec/ruby/core/basicobject/singleton_method_added_spec.rb
@@ -83,4 +83,65 @@ describe "BasicObject#singleton_method_added" do
     end
     ScratchPad.recorded.should == [:singleton_method_added, :new_method_with_define_method]
   end
+
+  describe "when singleton_method_added is undefined" do
+    it "raises NoMethodError for a metaclass" do
+      class BasicObjectSpecs::NoSingletonMethodAdded
+        class << self
+          undef_method :singleton_method_added
+        end
+
+        -> {
+          def self.foo
+          end
+        }.should raise_error(NoMethodError, /undefined method [`']singleton_method_added' for/)
+      end
+    ensure
+      BasicObjectSpecs.send(:remove_const, :NoSingletonMethodAdded)
+    end
+
+    it "raises NoMethodError for a singleton instance" do
+      object = Object.new
+      class << object
+        undef_method :singleton_method_added
+
+        -> {
+          def foo
+          end
+        }.should raise_error(NoMethodError, /undefined method [`']singleton_method_added' for #<Object:/)
+
+        -> {
+          define_method(:bar) {}
+        }.should raise_error(NoMethodError, /undefined method [`']singleton_method_added' for #<Object:/)
+      end
+
+      -> {
+        object.define_singleton_method(:baz) {}
+      }.should raise_error(NoMethodError, /undefined method [`']singleton_method_added' for #<Object:/)
+    end
+
+    it "calls #method_missing" do
+      ScratchPad.record []
+      object = Object.new
+      class << object
+        def method_missing(*args)
+          ScratchPad << args
+        end
+
+        undef_method :singleton_method_added
+
+        def foo
+        end
+
+        define_method(:bar) {}
+      end
+      object.define_singleton_method(:baz) {}
+
+      ScratchPad.recorded.should == [
+        [:singleton_method_added, :foo],
+        [:singleton_method_added, :bar],
+        [:singleton_method_added, :baz],
+      ]
+    end
+  end
 end
diff --git a/spec/ruby/core/binding/clone_spec.rb b/spec/ruby/core/binding/clone_spec.rb
index ebd40f5377..f1769ac6de 100644
--- a/spec/ruby/core/binding/clone_spec.rb
+++ b/spec/ruby/core/binding/clone_spec.rb
@@ -4,4 +4,10 @@ require_relative 'shared/clone'
 
 describe "Binding#clone" do
   it_behaves_like :binding_clone, :clone
+
+  it "preserves frozen status" do
+    bind = binding.freeze
+    bind.frozen?.should == true
+    bind.clone.frozen?.should == true
+  end
 end
diff --git a/spec/ruby/core/binding/dup_spec.rb b/spec/ruby/core/binding/dup_spec.rb
index 43968213c8..4eff66bd9a 100644
--- a/spec/ruby/core/binding/dup_spec.rb
+++ b/spec/ruby/core/binding/dup_spec.rb
@@ -4,4 +4,27 @@ require_relative 'shared/clone'
 
 describe "Binding#dup" do
   it_behaves_like :binding_clone, :dup
+
+  it "resets frozen status" do
+    bind = binding.freeze
+    bind.frozen?.should == true
+    bind.dup.frozen?.should == false
+  end
+
+  it "retains original binding variables but the list is distinct" do
+    bind1 = binding
+    eval "a = 1", bind1
+
+    bind2 = bind1.dup
+    eval("a = 2", bind2)
+    eval("a", bind1).should == 2
+    eval("a", bind2).should == 2
+
+    eval("b = 2", bind2)
+    -> { eval("b", bind1) }.should raise_error(NameError)
+    eval("b", bind2).should == 2
+
+    bind1.local_variables.sort.should == [:a, :bind1, :bind2]
+    bind2.local_variables.sort.should == [:a, :b, :bind1, :bind2]
+  end
 end
diff --git a/spec/ruby/core/binding/eval_spec.rb b/spec/ruby/core/binding/eval_spec.rb
index fff8c9cf44..bb2036f739 100644
--- a/spec/ruby/core/binding/eval_spec.rb
+++ b/spec/ruby/core/binding/eval_spec.rb
@@ -23,29 +23,29 @@ describe "Binding#eval" do
     bind2.local_variables.should == []
   end
 
-  it "inherits __LINE__ from the enclosing scope" do
+  it "starts with line 1 if single argument is given" do
     obj = BindingSpecs::Demo.new(1)
     bind = obj.get_binding
-    suppress_warning {bind.eval("__LINE__")}.should == obj.get_line_of_binding
+    bind.eval("__LINE__").should == 1
   end
 
   it "preserves __LINE__ across multiple calls to eval" do
     obj = BindingSpecs::Demo.new(1)
     bind = obj.get_binding
-    suppress_warning {bind.eval("__LINE__")}.should == obj.get_line_of_binding
-    suppress_warning {bind.eval("__LINE__")}.should == obj.get_line_of_binding
+    bind.eval("__LINE__").should == 1
+    bind.eval("__LINE__").should == 1
   end
 
   it "increments __LINE__ on each line of a multiline eval" do
     obj = BindingSpecs::Demo.new(1)
     bind = obj.get_binding
-    suppress_warning {bind.eval("#foo\n__LINE__")}.should == obj.get_line_of_binding + 1
+    bind.eval("#foo\n__LINE__").should == 2
   end
 
-  it "inherits __LINE__ from the enclosing scope even if the Binding is created with #send" do
+  it "starts with line 1 if the Binding is created with #send" do
     obj = BindingSpecs::Demo.new(1)
     bind, line = obj.get_binding_with_send_and_line
-    suppress_warning {bind.eval("__LINE__")}.should == line
+    bind.eval("__LINE__").should == 1
   end
 
   it "starts with a __LINE__ of 1 if a filename is passed" do
@@ -60,10 +60,18 @@ describe "Binding#eval" do
     bind.eval("#foo\n__LINE__", "(test)", 88).should == 89
   end
 
-  it "inherits __FILE__ from the enclosing scope" do
+  ruby_version_is ""..."3.3" do
+    it "uses (eval) as __FILE__ if single argument given" do
+      obj = BindingSpecs::Demo.new(1)
+      bind = obj.get_binding
+      bind.eval("__FILE__").should == '(eval)'
+    end
+  end
+
+  it "uses 1 as __LINE__" do
     obj = BindingSpecs::Demo.new(1)
     bind = obj.get_binding
-    suppress_warning {bind.eval("__FILE__")}.should == obj.get_file_of_binding
+    suppress_warning { bind.eval("__LINE__") }.should == 1
   end
 
   it "uses the __FILE__ that is passed in" do
@@ -92,4 +100,16 @@ describe "Binding#eval" do
     bind, meth = obj.get_binding_with_send_and_method
     bind.eval("__method__").should == meth
   end
+
+  it "reflects refinements activated in the binding scope" do
+    bind = BindingSpecs::Refined.refined_binding
+
+    bind.eval("'bar'.foo").should == "foo"
+  end
+
+  ruby_version_is "3.3" do
+    it "uses the caller location as default filename" do
+      binding.eval("[__FILE__, __LINE__]").should == ["(eval at #{__FILE__}:#{__LINE__})", 1]
+    end
+  end
 end
diff --git a/spec/ruby/core/binding/fixtures/classes.rb b/spec/ruby/core/binding/fixtures/classes.rb
index 43e32cacf6..b5f3ce9008 100644
--- a/spec/ruby/core/binding/fixtures/classes.rb
+++ b/spec/ruby/core/binding/fixtures/classes.rb
@@ -49,4 +49,18 @@ module BindingSpecs
       end
     end
   end
+
+  module AddFooToString
+    refine(String) do
+      def foo
+        "foo"
+      end
+    end
+  end
+  class Refined
+    using AddFooToString
+    def self.refined_binding
+      binding
+    end
+  end
 end
diff --git a/spec/ruby/core/binding/fixtures/irb.rb b/spec/ruby/core/binding/fixtures/irb.rb
deleted file mode 100644
index 5f305f2d5d..0000000000
--- a/spec/ruby/core/binding/fixtures/irb.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-a = 10
-
-binding.irb
diff --git a/spec/ruby/core/binding/fixtures/irbrc b/spec/ruby/core/binding/fixtures/irbrc
deleted file mode 100644
index 2bc12af2f7..0000000000
--- a/spec/ruby/core/binding/fixtures/irbrc
+++ /dev/null
@@ -1 +0,0 @@
-# empty configuration
diff --git a/spec/ruby/core/binding/irb_spec.rb b/spec/ruby/core/binding/irb_spec.rb
deleted file mode 100644
index bd37b419f9..0000000000
--- a/spec/ruby/core/binding/irb_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-
-ruby_version_is "2.5" do
-  describe "Binding#irb" do
-    it "creates an IRB session with the binding in scope" do
-      irb_fixture = fixture __FILE__, "irb.rb"
-      irbrc_fixture = fixture __FILE__, "irbrc"
-
-      out = IO.popen([{"IRBRC"=>irbrc_fixture}, *ruby_exe, irb_fixture], "r+") do |pipe|
-        pipe.puts "a ** 2"
-        pipe.puts "exit"
-        pipe.readlines.map(&:chomp)
-      end
-
-      out[-3..-1].should == ["a ** 2", "100", "exit"]
-    end
-  end
-end
diff --git a/spec/ruby/core/binding/shared/clone.rb b/spec/ruby/core/binding/shared/clone.rb
index 0e934ac1b5..2d854fce96 100644
--- a/spec/ruby/core/binding/shared/clone.rb
+++ b/spec/ruby/core/binding/shared/clone.rb
@@ -31,4 +31,26 @@ describe :binding_clone, shared: true do
       b2.local_variable_defined?(:x).should == false
     end
   end
+
+  ruby_version_is "3.4" do
+    it "copies instance variables" do
+      @b1.instance_variable_set(:@ivar, 1)
+      cl = @b1.send(@method)
+      cl.instance_variables.should == [:@ivar]
+    end
+
+    it "copies the finalizer" do
+      code = <<-'RUBY'
+        obj = binding
+
+        ObjectSpace.define_finalizer(obj, Proc.new { STDOUT.write "finalized\n" })
+
+        obj.clone
+
+        exit 0
+      RUBY
+
+      ruby_exe(code).lines.sort.should == ["finalized\n", "finalized\n"]
+    end
+  end
 end
diff --git a/spec/ruby/core/binding/source_location_spec.rb b/spec/ruby/core/binding/source_location_spec.rb
index e562bc65c8..d1c8191ea8 100644
--- a/spec/ruby/core/binding/source_location_spec.rb
+++ b/spec/ruby/core/binding/source_location_spec.rb
@@ -1,11 +1,14 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/location'
 
-ruby_version_is "2.6" do
-  describe "Binding#source_location" do
-    it "returns an [file, line] pair" do
-      b = BindingSpecs::LocationMethod::TEST_BINDING
-      b.source_location.should == [BindingSpecs::LocationMethod::FILE_PATH, 4]
-    end
+describe "Binding#source_location" do
+  it "returns an [file, line] pair" do
+    b = BindingSpecs::LocationMethod::TEST_BINDING
+    b.source_location.should == [BindingSpecs::LocationMethod::FILE_PATH, 4]
+  end
+
+  it "works for eval with a given line" do
+    b = eval('binding', nil, "foo", 100)
+    b.source_location.should == ["foo", 100]
   end
 end
diff --git a/spec/ruby/core/builtin_constants/builtin_constants_spec.rb b/spec/ruby/core/builtin_constants/builtin_constants_spec.rb
index a5141c3008..13e066cc7f 100644
--- a/spec/ruby/core/builtin_constants/builtin_constants_spec.rb
+++ b/spec/ruby/core/builtin_constants/builtin_constants_spec.rb
@@ -4,11 +4,15 @@ describe "RUBY_VERSION" do
   it "is a String" do
     RUBY_VERSION.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_VERSION.should.frozen?
+  end
 end
 
 describe "RUBY_PATCHLEVEL" do
-  it "is a Fixnum" do
-    RUBY_PATCHLEVEL.should be_kind_of(Fixnum)
+  it "is an Integer" do
+    RUBY_PATCHLEVEL.should be_kind_of(Integer)
   end
 end
 
@@ -16,42 +20,132 @@ describe "RUBY_COPYRIGHT" do
   it "is a String" do
     RUBY_COPYRIGHT.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_COPYRIGHT.should.frozen?
+  end
 end
 
 describe "RUBY_DESCRIPTION" do
   it "is a String" do
     RUBY_DESCRIPTION.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_DESCRIPTION.should.frozen?
+  end
 end
 
 describe "RUBY_ENGINE" do
   it "is a String" do
     RUBY_ENGINE.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_ENGINE.should.frozen?
+  end
+end
+
+describe "RUBY_ENGINE_VERSION" do
+  it "is a String" do
+    RUBY_ENGINE_VERSION.should be_kind_of(String)
+  end
+
+  it "is frozen" do
+    RUBY_ENGINE_VERSION.should.frozen?
+  end
 end
 
 describe "RUBY_PLATFORM" do
   it "is a String" do
     RUBY_PLATFORM.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_PLATFORM.should.frozen?
+  end
 end
 
 describe "RUBY_RELEASE_DATE" do
   it "is a String" do
     RUBY_RELEASE_DATE.should be_kind_of(String)
   end
+
+  it "is frozen" do
+    RUBY_RELEASE_DATE.should.frozen?
+  end
 end
 
 describe "RUBY_REVISION" do
-  ruby_version_is ""..."2.7" do
-    it "is an Integer" do
-      RUBY_REVISION.should be_kind_of(Fixnum)
-    end
+  it "is a String" do
+    RUBY_REVISION.should be_kind_of(String)
   end
 
-  ruby_version_is "2.7" do
-    it "is a String" do
-      RUBY_REVISION.should be_kind_of(String)
+  it "is frozen" do
+    RUBY_REVISION.should.frozen?
+  end
+end
+
+ruby_version_is "4.0" do
+  context "The constant" do
+    describe "Ruby" do
+      it "is a Module" do
+        Ruby.should.instance_of?(Module)
+      end
+    end
+
+    describe "Ruby::VERSION" do
+      it "is equal to RUBY_VERSION" do
+        Ruby::VERSION.should equal(RUBY_VERSION)
+      end
+    end
+
+    describe "RUBY::PATCHLEVEL" do
+      it "is equal to RUBY_PATCHLEVEL" do
+        Ruby::PATCHLEVEL.should equal(RUBY_PATCHLEVEL)
+      end
+    end
+
+    describe "Ruby::COPYRIGHT" do
+      it "is equal to RUBY_COPYRIGHT" do
+        Ruby::COPYRIGHT.should equal(RUBY_COPYRIGHT)
+      end
+    end
+
+    describe "Ruby::DESCRIPTION" do
+      it "is equal to RUBY_DESCRIPTION" do
+        Ruby::DESCRIPTION.should equal(RUBY_DESCRIPTION)
+      end
+    end
+
+    describe "Ruby::ENGINE" do
+      it "is equal to RUBY_ENGINE" do
+        Ruby::ENGINE.should equal(RUBY_ENGINE)
+      end
+    end
+
+    describe "Ruby::ENGINE_VERSION" do
+      it "is equal to RUBY_ENGINE_VERSION" do
+        Ruby::ENGINE_VERSION.should equal(RUBY_ENGINE_VERSION)
+      end
+    end
+
+    describe "Ruby::PLATFORM" do
+      it "is equal to RUBY_PLATFORM" do
+        Ruby::PLATFORM.should equal(RUBY_PLATFORM)
+      end
+    end
+
+    describe "Ruby::RELEASE_DATE" do
+      it "is equal to RUBY_RELEASE_DATE" do
+        Ruby::RELEASE_DATE.should equal(RUBY_RELEASE_DATE)
+      end
+    end
+
+    describe "Ruby::REVISION" do
+      it "is equal to RUBY_REVISION" do
+        Ruby::REVISION.should equal(RUBY_REVISION)
+      end
     end
   end
 end
diff --git a/spec/ruby/core/class/allocate_spec.rb b/spec/ruby/core/class/allocate_spec.rb
index c426c38ff9..b39622e06a 100644
--- a/spec/ruby/core/class/allocate_spec.rb
+++ b/spec/ruby/core/class/allocate_spec.rb
@@ -30,7 +30,7 @@ describe "Class#allocate" do
       end
     end
 
-    klass.allocate.initialized?.should == false
+    klass.allocate.should_not.initialized?
   end
 
   it "raises TypeError for #superclass" do
diff --git a/spec/ruby/core/class/attached_object_spec.rb b/spec/ruby/core/class/attached_object_spec.rb
new file mode 100644
index 0000000000..8f8a0734c6
--- /dev/null
+++ b/spec/ruby/core/class/attached_object_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../spec_helper'
+
+describe "Class#attached_object" do
+  it "returns the object that is attached to a singleton class" do
+    a = Class.new
+
+    a_obj = a.new
+    a_obj.singleton_class.attached_object.should == a_obj
+  end
+
+  it "returns the class object that is attached to a class's singleton class" do
+    a = Class.new
+    singleton_class = (class << a; self; end)
+
+    singleton_class.attached_object.should == a
+  end
+
+  it "raises TypeError if the class is not a singleton class" do
+    a = Class.new
+
+    -> { a.attached_object }.should raise_error(TypeError, /is not a singleton class/)
+  end
+
+  it "raises TypeError for special singleton classes" do
+    -> { nil.singleton_class.attached_object }.should raise_error(TypeError, /[`']NilClass' is not a singleton class/)
+    -> { true.singleton_class.attached_object }.should raise_error(TypeError, /[`']TrueClass' is not a singleton class/)
+    -> { false.singleton_class.attached_object }.should raise_error(TypeError, /[`']FalseClass' is not a singleton class/)
+  end
+end
diff --git a/spec/ruby/core/class/dup_spec.rb b/spec/ruby/core/class/dup_spec.rb
index 701fd72e19..1ff9abf7b4 100644
--- a/spec/ruby/core/class/dup_spec.rb
+++ b/spec/ruby/core/class/dup_spec.rb
@@ -59,6 +59,11 @@ describe "Class#dup" do
   it "stores the new name if assigned to a constant" do
     CoreClassSpecs::RecordCopy = CoreClassSpecs::Record.dup
     CoreClassSpecs::RecordCopy.name.should == "CoreClassSpecs::RecordCopy"
+  ensure
+    CoreClassSpecs.send(:remove_const, :RecordCopy)
   end
 
+  it "raises TypeError if called on BasicObject" do
+    -> { BasicObject.dup }.should raise_error(TypeError, "can't copy the root class")
+  end
 end
diff --git a/spec/ruby/core/class/inherited_spec.rb b/spec/ruby/core/class/inherited_spec.rb
index 8ef8bb8c35..2a8d1ff813 100644
--- a/spec/ruby/core/class/inherited_spec.rb
+++ b/spec/ruby/core/class/inherited_spec.rb
@@ -98,4 +98,21 @@ describe "Class.inherited" do
     -> { Class.new(top) }.should_not raise_error
   end
 
+  it "if the subclass is assigned to a constant, it is all set" do
+    ScratchPad.record []
+
+    parent = Class.new do
+      def self.inherited(subclass)
+        ScratchPad << defined?(self::C)
+        ScratchPad << const_defined?(:C)
+        ScratchPad << constants
+        ScratchPad << const_get(:C)
+        ScratchPad << subclass.name.match?(/\A#<Class:0x\w+>::C\z/)
+      end
+    end
+
+    class parent::C < parent; end
+
+    ScratchPad.recorded.should == ["constant", true, [:C], parent::C, true]
+  end
 end
diff --git a/spec/ruby/core/class/initialize_spec.rb b/spec/ruby/core/class/initialize_spec.rb
index 9678d7b373..6348758485 100644
--- a/spec/ruby/core/class/initialize_spec.rb
+++ b/spec/ruby/core/class/initialize_spec.rb
@@ -7,7 +7,7 @@ describe "Class#initialize" do
 
   it "raises a TypeError when called on already initialized classes" do
     ->{
-      Fixnum.send :initialize
+      Integer.send :initialize
     }.should raise_error(TypeError)
 
     ->{
diff --git a/spec/ruby/core/class/new_spec.rb b/spec/ruby/core/class/new_spec.rb
index 8191ce6a37..6fe54c3209 100644
--- a/spec/ruby/core/class/new_spec.rb
+++ b/spec/ruby/core/class/new_spec.rb
@@ -83,6 +83,8 @@ describe "Class.new" do
     a = Class.new
     MyClass::NestedClass = a
     MyClass::NestedClass.name.should == "MyClass::NestedClass"
+  ensure
+    Object.send(:remove_const, :MyClass)
   end
 
   it "sets the new class' superclass to the given class" do
@@ -95,12 +97,13 @@ describe "Class.new" do
   end
 
   it "raises a TypeError when given a non-Class" do
-    error_msg = /superclass must be a Class/
-    -> { Class.new("")         }.should raise_error(TypeError, error_msg)
-    -> { Class.new(1)          }.should raise_error(TypeError, error_msg)
-    -> { Class.new(:symbol)    }.should raise_error(TypeError, error_msg)
-    -> { Class.new(mock('o'))  }.should raise_error(TypeError, error_msg)
-    -> { Class.new(Module.new) }.should raise_error(TypeError, error_msg)
+    error_msg = /superclass must be a.*Class/
+    -> { Class.new("")              }.should raise_error(TypeError, error_msg)
+    -> { Class.new(1)               }.should raise_error(TypeError, error_msg)
+    -> { Class.new(:symbol)         }.should raise_error(TypeError, error_msg)
+    -> { Class.new(mock('o'))       }.should raise_error(TypeError, error_msg)
+    -> { Class.new(Module.new)      }.should raise_error(TypeError, error_msg)
+    -> { Class.new(BasicObject.new) }.should raise_error(TypeError, error_msg)
   end
 end
 
@@ -126,7 +129,7 @@ describe "Class#new" do
       end
     end
 
-    klass.new.initialized?.should == true
+    klass.new.should.initialized?
     klass.new(1, 2, 3).args.should == [1, 2, 3]
   end
 
diff --git a/spec/ruby/core/class/subclasses_spec.rb b/spec/ruby/core/class/subclasses_spec.rb
new file mode 100644
index 0000000000..f692152787
--- /dev/null
+++ b/spec/ruby/core/class/subclasses_spec.rb
@@ -0,0 +1,85 @@
+require_relative '../../spec_helper'
+require_relative '../module/fixtures/classes'
+
+describe "Class#subclasses" do
+  it "returns a list of classes directly inheriting from self" do
+    assert_subclasses(ModuleSpecs::Parent, [ModuleSpecs::Child, ModuleSpecs::Child2])
+  end
+
+  it "does not return included modules from the parent" do
+    parent = Class.new
+    child = Class.new(parent)
+    mod = Module.new
+    parent.include(mod)
+
+    assert_subclasses(parent, [child])
+  end
+
+  it "does not return included modules from the child" do
+    parent = Class.new
+    child = Class.new(parent)
+    mod = Module.new
+    parent.include(mod)
+
+    assert_subclasses(parent, [child])
+  end
+
+  it "does not return prepended modules from the parent" do
+    parent = Class.new
+    child = Class.new(parent)
+    mod = Module.new
+    parent.prepend(mod)
+
+    assert_subclasses(parent, [child])
+  end
+
+  it "does not return prepended modules from the child" do
+    parent = Class.new
+    child = Class.new(parent)
+    mod = Module.new
+    child.prepend(mod)
+
+    assert_subclasses(parent, [child])
+  end
+
+  it "does not return singleton classes" do
+    a = Class.new
+
+    a_obj = a.new
+    def a_obj.force_singleton_class
+      42
+    end
+
+    a.subclasses.should_not include(a_obj.singleton_class)
+  end
+
+  it "has 1 entry per module or class" do
+    ModuleSpecs::Parent.subclasses.should == ModuleSpecs::Parent.subclasses.uniq
+  end
+
+  it "works when creating subclasses concurrently" do
+    t = 16
+    n = 1000
+    go = false
+    superclass = Class.new
+
+    threads = t.times.map do
+      Thread.new do
+        Thread.pass until go
+        n.times.map do
+          Class.new(superclass)
+        end
+      end
+    end
+
+    go = true
+    classes = threads.map(&:value)
+
+    superclass.subclasses.size.should == t * n
+    superclass.subclasses.each { |c| c.should be_kind_of(Class) }
+  end
+
+  def assert_subclasses(mod,subclasses)
+    mod.subclasses.sort_by(&:inspect).should == subclasses.sort_by(&:inspect)
+  end
+end
diff --git a/spec/ruby/core/class/superclass_spec.rb b/spec/ruby/core/class/superclass_spec.rb
index deb5a45336..00579238a6 100644
--- a/spec/ruby/core/class/superclass_spec.rb
+++ b/spec/ruby/core/class/superclass_spec.rb
@@ -8,7 +8,7 @@ describe "Class#superclass" do
     Class.superclass.should == Module
     Class.new.superclass.should == Object
     Class.new(String).superclass.should == String
-    Class.new(Fixnum).superclass.should == Fixnum
+    Class.new(Integer).superclass.should == Integer
   end
 
   # redmine:567
diff --git a/spec/ruby/core/class/to_s_spec.rb b/spec/ruby/core/class/to_s_spec.rb
deleted file mode 100644
index 2055593a03..0000000000
--- a/spec/ruby/core/class/to_s_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-
-describe "Class#to_s" do
-  it 'regular class returns same name as Module#to_s' do
-    String.to_s.should == 'String'
-  end
-
-  describe 'singleton class' do
-    it 'for modules includes module name' do
-      CoreClassSpecs.singleton_class.to_s.should == '#<Class:CoreClassSpecs>'
-    end
-
-    it 'for classes includes class name' do
-      CoreClassSpecs::Record.singleton_class.to_s.should == '#<Class:CoreClassSpecs::Record>'
-    end
-
-    it 'for objects includes class name and object ID' do
-      obj = CoreClassSpecs::Record.new
-      obj.singleton_class.to_s.should =~ /#<Class:#<CoreClassSpecs::Record:0x[0-9a-f]+>>/
-    end
-  end
-end
diff --git a/spec/ruby/core/comparable/clamp_spec.rb b/spec/ruby/core/comparable/clamp_spec.rb
index 6d216220d4..18f616a997 100644
--- a/spec/ruby/core/comparable/clamp_spec.rb
+++ b/spec/ruby/core/comparable/clamp_spec.rb
@@ -2,12 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe 'Comparable#clamp' do
-  it 'raises an Argument error unless given 2 parameters' do
-    c = ComparableSpecs::Weird.new(0)
-    -> { c.clamp(c) }.should raise_error(ArgumentError)
-    -> { c.clamp(c, c, c) }.should raise_error(ArgumentError)
-  end
-
   it 'raises an Argument error unless the 2 parameters are correctly ordered' do
     one = ComparableSpecs::WithOnlyCompareDefined.new(1)
     two = ComparableSpecs::WithOnlyCompareDefined.new(2)
@@ -30,7 +24,7 @@ describe 'Comparable#clamp' do
     c.clamp(two, three).should equal(c)
   end
 
-  it 'returns the min parameter if smaller than it' do
+  it 'returns the min parameter if less than it' do
     one = ComparableSpecs::WithOnlyCompareDefined.new(1)
     two = ComparableSpecs::WithOnlyCompareDefined.new(2)
     c = ComparableSpecs::Weird.new(0)
@@ -45,4 +39,185 @@ describe 'Comparable#clamp' do
 
     c.clamp(one, two).should equal(two)
   end
+
+  context 'max is nil' do
+    it 'returns min if less than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(0)
+      c.clamp(one, nil).should equal(one)
+    end
+
+    it 'always returns self if greater than min' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(2)
+      c.clamp(one, nil).should equal(c)
+    end
+  end
+
+  context 'min is nil' do
+    it 'returns max if greater than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(2)
+      c.clamp(nil, one).should equal(one)
+    end
+
+    it 'always returns self if less than max' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(0)
+      c.clamp(nil, one).should equal(c)
+    end
+  end
+
+  it 'always returns self when min is nil and max is nil' do
+    c = ComparableSpecs::Weird.new(1)
+    c.clamp(nil, nil).should equal(c)
+  end
+
+  it 'returns self if within the given range parameters' do
+    one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+    two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+    three = ComparableSpecs::WithOnlyCompareDefined.new(3)
+    c = ComparableSpecs::Weird.new(2)
+
+    c.clamp(one..two).should equal(c)
+    c.clamp(two..two).should equal(c)
+    c.clamp(one..three).should equal(c)
+    c.clamp(two..three).should equal(c)
+  end
+
+  it 'returns the minimum value of the range parameters if less than it' do
+    one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+    two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+    c = ComparableSpecs::Weird.new(0)
+
+    c.clamp(one..two).should equal(one)
+  end
+
+  it 'returns the maximum value of the range parameters if greater than it' do
+    one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+    two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+    c = ComparableSpecs::Weird.new(3)
+
+    c.clamp(one..two).should equal(two)
+  end
+
+  it 'raises an Argument error if the range parameter is exclusive' do
+    one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+    two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+    c = ComparableSpecs::Weird.new(3)
+
+    -> { c.clamp(one...two) }.should raise_error(ArgumentError)
+  end
+
+  context 'with nil as the max argument' do
+    it 'returns min argument if less than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      zero = ComparableSpecs::WithOnlyCompareDefined.new(0)
+      c = ComparableSpecs::Weird.new(0)
+
+      c.clamp(one, nil).should equal(one)
+      c.clamp(zero, nil).should equal(c)
+    end
+
+    it 'always returns self if greater than min argument' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(one, nil).should equal(c)
+      c.clamp(two, nil).should equal(c)
+    end
+  end
+
+  context 'with endless range' do
+    it 'returns minimum value of the range parameters if less than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      zero = ComparableSpecs::WithOnlyCompareDefined.new(0)
+      c = ComparableSpecs::Weird.new(0)
+
+      c.clamp(one..).should equal(one)
+      c.clamp(zero..).should equal(c)
+    end
+
+    it 'always returns self if greater than minimum value of the range parameters' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      two = ComparableSpecs::WithOnlyCompareDefined.new(2)
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(one..).should equal(c)
+      c.clamp(two..).should equal(c)
+    end
+
+    it 'works with exclusive range' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(one...).should equal(c)
+    end
+  end
+
+  context 'with nil as the min argument' do
+    it 'returns max argument if greater than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(nil, one).should equal(one)
+    end
+
+    it 'always returns self if less than max argument' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      zero = ComparableSpecs::WithOnlyCompareDefined.new(0)
+      c = ComparableSpecs::Weird.new(0)
+
+      c.clamp(nil, one).should equal(c)
+      c.clamp(nil, zero).should equal(c)
+    end
+  end
+
+  context 'with beginless range' do
+    it 'returns maximum value of the range parameters if greater than it' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(..one).should equal(one)
+    end
+
+    it 'always returns self if less than maximum value of the range parameters' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      zero = ComparableSpecs::WithOnlyCompareDefined.new(0)
+      c = ComparableSpecs::Weird.new(0)
+
+      c.clamp(..one).should equal(c)
+      c.clamp(..zero).should equal(c)
+    end
+
+    it 'raises an Argument error if the range parameter is exclusive' do
+      one = ComparableSpecs::WithOnlyCompareDefined.new(1)
+      c = ComparableSpecs::Weird.new(0)
+
+      -> { c.clamp(...one) }.should raise_error(ArgumentError)
+    end
+  end
+
+  context 'with nil as the min and the max argument' do
+    it 'always returns self' do
+      c = ComparableSpecs::Weird.new(1)
+
+      c.clamp(nil, nil).should equal(c)
+    end
+  end
+
+  context 'with beginless-and-endless range' do
+    it 'always returns self' do
+      c = ComparableSpecs::Weird.new(1)
+
+      c.clamp(nil..nil).should equal(c)
+    end
+
+    it 'works with exclusive range' do
+      c = ComparableSpecs::Weird.new(2)
+
+      c.clamp(nil...nil).should equal(c)
+    end
+  end
 end
diff --git a/spec/ruby/core/comparable/fixtures/classes.rb b/spec/ruby/core/comparable/fixtures/classes.rb
index 4239a47d2f..2bdabbf014 100644
--- a/spec/ruby/core/comparable/fixtures/classes.rb
+++ b/spec/ruby/core/comparable/fixtures/classes.rb
@@ -7,6 +7,7 @@ module ComparableSpecs
     end
 
     def <=>(other)
+      return nil if other.nil?
       self.value <=> other.value
     end
   end
diff --git a/spec/ruby/core/comparable/lt_spec.rb b/spec/ruby/core/comparable/lt_spec.rb
index 4db92719e2..bca95f8d25 100644
--- a/spec/ruby/core/comparable/lt_spec.rb
+++ b/spec/ruby/core/comparable/lt_spec.rb
@@ -40,4 +40,10 @@ describe "Comparable#<" do
     a.should_receive(:<=>).any_number_of_times.and_return(nil)
     -> { (a < b) }.should raise_error(ArgumentError)
   end
+
+  it "raises an argument error with a message containing the value" do
+    -> { ("foo" < 7) }.should raise_error(ArgumentError) { |e|
+      e.message.should == "comparison of String with 7 failed"
+    }
+  end
 end
diff --git a/spec/ruby/core/complex/comparison_spec.rb b/spec/ruby/core/complex/comparison_spec.rb
new file mode 100644
index 0000000000..3a3142f234
--- /dev/null
+++ b/spec/ruby/core/complex/comparison_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+
+describe "Complex#<=>" do
+  it "returns nil if either self or argument has imaginary part" do
+    (Complex(5, 1) <=> Complex(2)).should be_nil
+    (Complex(1) <=> Complex(2, 1)).should be_nil
+    (5 <=> Complex(2, 1)).should be_nil
+  end
+
+  it "returns nil if argument is not numeric" do
+    (Complex(5, 1) <=> "cmp").should be_nil
+    (Complex(1) <=> "cmp").should be_nil
+    (Complex(1) <=> Object.new).should be_nil
+  end
+
+  it "returns 0, 1, or -1 if self and argument do not have imaginary part" do
+    (Complex(5) <=> Complex(2)).should == 1
+    (Complex(2) <=> Complex(3)).should == -1
+    (Complex(2) <=> Complex(2)).should == 0
+
+    (Complex(5) <=> 2).should == 1
+    (Complex(2) <=> 3).should == -1
+    (Complex(2) <=> 2).should == 0
+  end
+end
diff --git a/spec/ruby/core/complex/equal_value_spec.rb b/spec/ruby/core/complex/equal_value_spec.rb
index b1e4f9cfcd..97c486d820 100644
--- a/spec/ruby/core/complex/equal_value_spec.rb
+++ b/spec/ruby/core/complex/equal_value_spec.rb
@@ -53,7 +53,7 @@ describe "Complex#==" do
   end
 
   describe "with Object" do
-    # Fixnum#==, Float#== and Bignum#== only return booleans - Bug?
+    # Integer#== and Float#== only return booleans - Bug?
     it "calls other#== with self" do
       value = Complex(3, 0)
 
@@ -76,7 +76,7 @@ describe "Complex#==" do
       (Complex(real, 0) == @other).should be_true
     end
 
-    it "returns false when when the imaginary part is not zero" do
+    it "returns false when the imaginary part is not zero" do
       (Complex(3, 1) == @other).should be_false
     end
   end
diff --git a/spec/ruby/core/complex/exponent_spec.rb b/spec/ruby/core/complex/exponent_spec.rb
index bf07c90038..86f827aece 100644
--- a/spec/ruby/core/complex/exponent_spec.rb
+++ b/spec/ruby/core/complex/exponent_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Complex#**" do
-  describe "with Fixnum 0" do
+  describe "with Integer 0" do
     it "returns Complex(1)" do
       (Complex(3, 4) ** 0).should eql(Complex(1))
     end
diff --git a/spec/ruby/core/complex/finite_spec.rb b/spec/ruby/core/complex/finite_spec.rb
index 718848390c..7d9f82404e 100644
--- a/spec/ruby/core/complex/finite_spec.rb
+++ b/spec/ruby/core/complex/finite_spec.rb
@@ -2,31 +2,31 @@ require_relative '../../spec_helper'
 
 describe "Complex#finite?" do
   it "returns true if magnitude is finite" do
-    (1+1i).finite?.should == true
+    (1+1i).should.finite?
   end
 
   it "returns false for positive infinity" do
     value = Complex(Float::INFINITY, 42)
-    value.finite?.should == false
+    value.should_not.finite?
   end
 
   it "returns false for positive complex with infinite imaginary" do
     value = Complex(1, Float::INFINITY)
-    value.finite?.should == false
+    value.should_not.finite?
   end
 
   it "returns false for negative infinity" do
     value = -Complex(Float::INFINITY, 42)
-    value.finite?.should == false
+    value.should_not.finite?
   end
 
   it "returns false for negative complex with infinite imaginary" do
     value = -Complex(1, Float::INFINITY)
-    value.finite?.should == false
+    value.should_not.finite?
   end
 
   it "returns false for NaN" do
     value = Complex(Float::NAN, Float::NAN)
-    value.finite?.should == false
+    value.should_not.finite?
   end
 end
diff --git a/spec/ruby/core/complex/inspect_spec.rb b/spec/ruby/core/complex/inspect_spec.rb
index 71aabde5be..045be94b22 100644
--- a/spec/ruby/core/complex/inspect_spec.rb
+++ b/spec/ruby/core/complex/inspect_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative '../numeric/fixtures/classes'
 
 describe "Complex#inspect" do
   it "returns (${real}+${image}i) for positive imaginary parts" do
@@ -13,4 +14,24 @@ describe "Complex#inspect" do
     Complex(-1, -4).inspect.should == "(-1-4i)"
     Complex(-7, -6.7).inspect.should == "(-7-6.7i)"
   end
+
+  it "calls #inspect on real and imaginary" do
+    real = NumericSpecs::Subclass.new
+    # + because of https://bugs.ruby-lang.org/issues/20337
+    real.should_receive(:inspect).and_return(+"1")
+    imaginary = NumericSpecs::Subclass.new
+    imaginary.should_receive(:inspect).and_return("2")
+    imaginary.should_receive(:<).any_number_of_times.and_return(false)
+    Complex(real, imaginary).inspect.should == "(1+2i)"
+  end
+
+  it "adds an `*' before the `i' if the last character of the imaginary part is not numeric" do
+    real = NumericSpecs::Subclass.new
+    # + because of https://bugs.ruby-lang.org/issues/20337
+    real.should_receive(:inspect).and_return(+"(1)")
+    imaginary = NumericSpecs::Subclass.new
+    imaginary.should_receive(:inspect).and_return("(2)")
+    imaginary.should_receive(:<).any_number_of_times.and_return(false)
+    Complex(real, imaginary).inspect.should == "((1)+(2)*i)"
+  end
 end
diff --git a/spec/ruby/core/complex/polar_spec.rb b/spec/ruby/core/complex/polar_spec.rb
index 2a5d8ebd69..56335584ef 100644
--- a/spec/ruby/core/complex/polar_spec.rb
+++ b/spec/ruby/core/complex/polar_spec.rb
@@ -10,6 +10,20 @@ describe "Complex.polar" do
     ->{ Complex.polar(nil)      }.should raise_error(TypeError)
     ->{ Complex.polar(nil, nil) }.should raise_error(TypeError)
   end
+
+  it "computes the real values of the real & imaginary parts from the polar form" do
+    a = Complex.polar(1.0+0.0i, Math::PI/2+0.0i)
+    a.real.should be_close(0.0, TOLERANCE)
+    a.imag.should be_close(1.0, TOLERANCE)
+    a.real.real?.should be_true
+    a.imag.real?.should be_true
+
+    b = Complex.polar(1+0.0i)
+    b.real.should be_close(1.0, TOLERANCE)
+    b.imag.should be_close(0.0, TOLERANCE)
+    b.real.real?.should be_true
+    b.imag.real?.should be_true
+  end
 end
 
 describe "Complex#polar" do
diff --git a/spec/ruby/core/complex/shared/rect.rb b/spec/ruby/core/complex/shared/rect.rb
index 9f5de1ffeb..4ac294e771 100644
--- a/spec/ruby/core/complex/shared/rect.rb
+++ b/spec/ruby/core/complex/shared/rect.rb
@@ -24,15 +24,15 @@ describe :complex_rect, shared: true do
   end
 
   it "returns the real part of self as the first element" do
-   @numbers.each do |number|
-     number.send(@method).first.should == number.real
-   end
+    @numbers.each do |number|
+      number.send(@method).first.should == number.real
+    end
   end
 
   it "returns the imaginary part of self as the last element" do
-     @numbers.each do |number|
-       number.send(@method).last.should == number.imaginary
-     end
+    @numbers.each do |number|
+      number.send(@method).last.should == number.imaginary
+    end
   end
 
   it "raises an ArgumentError if given any arguments" do
diff --git a/spec/ruby/core/complex/spaceship_spec.rb b/spec/ruby/core/complex/spaceship_spec.rb
deleted file mode 100644
index 7b2849a86a..0000000000
--- a/spec/ruby/core/complex/spaceship_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Complex#<=>" do
-  ruby_version_is '2.7' do
-    it "returns nil if either self or argument has imaginary part" do
-      (Complex(5, 1) <=> Complex(2)).should be_nil
-      (Complex(1) <=> Complex(2, 1)).should be_nil
-      (5 <=> Complex(2, 1)).should be_nil
-    end
-
-    it "returns nil if argument is not numeric" do
-      (Complex(5, 1) <=> "cmp").should be_nil
-      (Complex(1) <=> "cmp").should be_nil
-      (Complex(1) <=> Object.new).should be_nil
-    end
-
-    it "returns 0, 1, or -1 if self and argument do not have imaginary part" do
-      (Complex(5) <=> Complex(2)).should == 1
-      (Complex(2) <=> Complex(3)).should == -1
-      (Complex(2) <=> Complex(2)).should == 0
-
-      (Complex(5) <=> 2).should == 1
-      (Complex(2) <=> 3).should == -1
-      (Complex(2) <=> 2).should == 0
-    end
-  end
-end
diff --git a/spec/ruby/core/complex/to_c_spec.rb b/spec/ruby/core/complex/to_c_spec.rb
new file mode 100644
index 0000000000..5ce01d9d4e
--- /dev/null
+++ b/spec/ruby/core/complex/to_c_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+
+describe "Complex#to_c" do
+  it "returns self" do
+    value = Complex(1, 5)
+    value.to_c.should equal(value)
+  end
+
+  it 'returns the same value' do
+    Complex(1, 5).to_c.should == Complex(1, 5)
+  end
+end
diff --git a/spec/ruby/core/complex/to_f_spec.rb b/spec/ruby/core/complex/to_f_spec.rb
index 78e6526491..b53471c1fc 100644
--- a/spec/ruby/core/complex/to_f_spec.rb
+++ b/spec/ruby/core/complex/to_f_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Complex#to_f" do
-  describe "when the imaginary part is Fixnum 0" do
+  describe "when the imaginary part is Integer 0" do
     it "returns the result of sending #to_f to the real part" do
       real = mock_numeric('real')
       real.should_receive(:to_f).and_return(:f)
diff --git a/spec/ruby/core/complex/to_i_spec.rb b/spec/ruby/core/complex/to_i_spec.rb
index 23134705ba..1e78f5ec0e 100644
--- a/spec/ruby/core/complex/to_i_spec.rb
+++ b/spec/ruby/core/complex/to_i_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Complex#to_i" do
-  describe "when the imaginary part is Fixnum 0" do
+  describe "when the imaginary part is Integer 0" do
     it "returns the result of sending #to_i to the real part" do
       real = mock_numeric('real')
       real.should_receive(:to_i).and_return(:i)
diff --git a/spec/ruby/core/complex/to_r_spec.rb b/spec/ruby/core/complex/to_r_spec.rb
index 76a69a0b93..788027a500 100644
--- a/spec/ruby/core/complex/to_r_spec.rb
+++ b/spec/ruby/core/complex/to_r_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Complex#to_r" do
-  describe "when the imaginary part is Fixnum 0" do
+  describe "when the imaginary part is Integer 0" do
     it "returns the result of sending #to_r to the real part" do
       real = mock_numeric('real')
       real.should_receive(:to_r).and_return(:r)
@@ -34,8 +34,16 @@ describe "Complex#to_r" do
   end
 
   describe "when the imaginary part is Float 0.0" do
-    it "raises RangeError" do
-      -> { Complex(0, 0.0).to_r }.should raise_error(RangeError)
+    ruby_version_is ''...'3.4' do
+      it "raises RangeError" do
+        -> { Complex(0, 0.0).to_r }.should raise_error(RangeError)
+      end
+    end
+
+    ruby_version_is '3.4' do
+      it "returns a Rational" do
+        Complex(0, 0.0).to_r.should == 0r
+      end
     end
   end
 end
diff --git a/spec/ruby/core/complex/to_s_spec.rb b/spec/ruby/core/complex/to_s_spec.rb
index 989a7ae0b7..ceccffe470 100644
--- a/spec/ruby/core/complex/to_s_spec.rb
+++ b/spec/ruby/core/complex/to_s_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative '../numeric/fixtures/classes'
 
 describe "Complex#to_s" do
   describe "when self's real component is 0" do
@@ -41,4 +42,14 @@ describe "Complex#to_s" do
   it "returns 1+NaN*i for Complex(1, NaN)" do
     Complex(1, nan_value).to_s.should == "1+NaN*i"
   end
+
+  it "treats real and imaginary parts as strings" do
+    real = NumericSpecs::Subclass.new
+    # + because of https://bugs.ruby-lang.org/issues/20337
+    real.should_receive(:to_s).and_return(+"1")
+    imaginary = NumericSpecs::Subclass.new
+    imaginary.should_receive(:to_s).and_return("2")
+    imaginary.should_receive(:<).any_number_of_times.and_return(false)
+    Complex(real, imaginary).to_s.should == "1+2i"
+  end
 end
diff --git a/spec/ruby/core/conditionvariable/broadcast_spec.rb b/spec/ruby/core/conditionvariable/broadcast_spec.rb
new file mode 100644
index 0000000000..55a7b89c72
--- /dev/null
+++ b/spec/ruby/core/conditionvariable/broadcast_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../spec_helper'
+
+describe "ConditionVariable#broadcast" do
+  it "releases all threads waiting in line for this resource" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    threads = []
+    r1 = []
+    r2 = []
+
+    # large number to attempt to cause race conditions
+    100.times do |i|
+      threads << Thread.new(i) do |tid|
+        m.synchronize do
+          r1 << tid
+          cv.wait(m)
+          r2 << tid
+        end
+      end
+    end
+
+    # wait for all threads to acquire the mutex the first time
+    Thread.pass until m.synchronize { r1.size == threads.size }
+    # wait until all threads are sleeping (ie waiting)
+    Thread.pass until threads.all?(&:stop?)
+
+    r2.should be_empty
+    m.synchronize do
+      cv.broadcast
+    end
+
+    threads.each {|t| t.join }
+
+    # ensure that all threads that enter cv.wait are released
+    r2.sort.should == r1.sort
+    # note that order is not specified as broadcast results in a race
+    # condition on regaining the lock m
+  end
+end
diff --git a/spec/ruby/core/conditionvariable/marshal_dump_spec.rb b/spec/ruby/core/conditionvariable/marshal_dump_spec.rb
new file mode 100644
index 0000000000..88b1cc38c1
--- /dev/null
+++ b/spec/ruby/core/conditionvariable/marshal_dump_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+
+describe "ConditionVariable#marshal_dump" do
+  it "raises a TypeError" do
+    cv = ConditionVariable.new
+    -> { cv.marshal_dump }.should raise_error(TypeError, /can't dump/)
+  end
+end
diff --git a/spec/ruby/core/conditionvariable/signal_spec.rb b/spec/ruby/core/conditionvariable/signal_spec.rb
new file mode 100644
index 0000000000..43a9cc611b
--- /dev/null
+++ b/spec/ruby/core/conditionvariable/signal_spec.rb
@@ -0,0 +1,76 @@
+require_relative '../../spec_helper'
+
+describe "ConditionVariable#signal" do
+  it "releases the first thread waiting in line for this resource" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    threads = []
+    r1 = []
+    r2 = []
+
+    # large number to attempt to cause race conditions
+    100.times do |i|
+      threads << Thread.new(i) do |tid|
+        m.synchronize do
+          r1 << tid
+          cv.wait(m)
+          r2 << tid
+        end
+      end
+    end
+
+    # wait for all threads to acquire the mutex the first time
+    Thread.pass until m.synchronize { r1.size == threads.size }
+    # wait until all threads are sleeping (ie waiting)
+    Thread.pass until threads.all?(&:stop?)
+
+    r2.should be_empty
+    100.times do |i|
+      m.synchronize do
+        cv.signal
+      end
+      Thread.pass until r2.size == i+1
+    end
+
+    threads.each {|t| t.join }
+
+    # ensure that all the threads that went into the cv.wait are
+    # released in the same order
+    r2.should == r1
+  end
+
+  it "allows control to be passed between a pair of threads" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    repeats = 100
+    in_synchronize = false
+
+    t1 = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        repeats.times do
+          cv.wait(m)
+          cv.signal
+        end
+      end
+    end
+
+    # Make sure t1 is waiting for a signal before launching t2.
+    Thread.pass until in_synchronize
+    Thread.pass until t1.stop?
+
+    t2 = Thread.new do
+      m.synchronize do
+        repeats.times do
+          cv.signal
+          cv.wait(m)
+        end
+      end
+    end
+
+    # Check that both threads terminated without exception
+    t1.join
+    t2.join
+    m.should_not.locked?
+  end
+end
diff --git a/spec/ruby/core/conditionvariable/wait_spec.rb b/spec/ruby/core/conditionvariable/wait_spec.rb
new file mode 100644
index 0000000000..fe73e513c0
--- /dev/null
+++ b/spec/ruby/core/conditionvariable/wait_spec.rb
@@ -0,0 +1,174 @@
+require_relative '../../spec_helper'
+
+describe "ConditionVariable#wait" do
+  it "calls #sleep on the given object" do
+    o = Object.new
+    o.should_receive(:sleep).with(1234)
+
+    cv = ConditionVariable.new
+
+    cv.wait(o, 1234)
+  end
+
+  it "can be woken up by ConditionVariable#signal" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    in_synchronize = false
+
+    th = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        cv.wait(m)
+      end
+      :success
+    end
+
+    # wait for m to acquire the mutex
+    Thread.pass until in_synchronize
+    # wait until th is sleeping (ie waiting)
+    Thread.pass until th.stop?
+
+    m.synchronize { cv.signal }
+    th.value.should == :success
+  end
+
+  it "can be interrupted by Thread#run" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    in_synchronize = false
+
+    th = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        cv.wait(m)
+      end
+      :success
+    end
+
+    # wait for m to acquire the mutex
+    Thread.pass until in_synchronize
+    # wait until th is sleeping (ie waiting)
+    Thread.pass until th.stop?
+
+    th.run
+    th.value.should == :success
+  end
+
+  it "can be interrupted by Thread#wakeup" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    in_synchronize = false
+
+    th = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        cv.wait(m)
+      end
+      :success
+    end
+
+    # wait for m to acquire the mutex
+    Thread.pass until in_synchronize
+    # wait until th is sleeping (ie waiting)
+    Thread.pass until th.stop?
+
+    th.wakeup
+    th.value.should == :success
+  end
+
+  it "reacquires the lock even if the thread is killed" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    in_synchronize = false
+    owned = nil
+
+    th = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        begin
+          cv.wait(m)
+        ensure
+          owned = m.owned?
+          $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
+        end
+      end
+    end
+
+    # wait for m to acquire the mutex
+    Thread.pass until in_synchronize
+    # wait until th is sleeping (ie waiting)
+    Thread.pass until th.stop?
+
+    th.kill
+    th.join
+
+    owned.should == true
+  end
+
+  it "reacquires the lock even if the thread is killed after being signaled" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    in_synchronize = false
+    owned = nil
+
+    th = Thread.new do
+      m.synchronize do
+        in_synchronize = true
+        begin
+          cv.wait(m)
+        ensure
+          owned = m.owned?
+          $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
+        end
+      end
+    end
+
+    # wait for m to acquire the mutex
+    Thread.pass until in_synchronize
+    # wait until th is sleeping (ie waiting)
+    Thread.pass until th.stop?
+
+    m.synchronize {
+      cv.signal
+      # Wait that the thread is blocked on acquiring the Mutex
+      sleep 0.001
+      # Kill the thread, yet the thread should first acquire the Mutex before going on
+      th.kill
+    }
+
+    th.join
+    owned.should == true
+  end
+
+  it "supports multiple Threads waiting on the same ConditionVariable and Mutex" do
+    m = Mutex.new
+    cv = ConditionVariable.new
+    n_threads = 4
+    events = []
+
+    threads = n_threads.times.map {
+      Thread.new {
+        m.synchronize {
+          events << :t_in_synchronize
+          cv.wait(m)
+        }
+      }
+    }
+
+    Thread.pass until m.synchronize { events.size } == n_threads
+    Thread.pass until threads.any?(&:stop?)
+    m.synchronize do
+      threads.each { |t|
+        # Cause interactions with the waiting threads.
+        # On TruffleRuby, this causes a safepoint which has interesting
+        # interactions with the ConditionVariable.
+        bt = t.backtrace
+        bt.should be_kind_of(Array)
+        bt.size.should >= 2
+      }
+    end
+
+    cv.broadcast
+    threads.each(&:join)
+  end
+end
diff --git a/spec/ruby/core/data/constants_spec.rb b/spec/ruby/core/data/constants_spec.rb
new file mode 100644
index 0000000000..ad0b1ddea7
--- /dev/null
+++ b/spec/ruby/core/data/constants_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+
+describe "Data" do
+  it "is a new constant" do
+    Data.superclass.should == Object
+  end
+
+  it "is not deprecated" do
+    -> { Data }.should_not complain
+  end
+end
diff --git a/spec/ruby/core/data/deconstruct_keys_spec.rb b/spec/ruby/core/data/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..df378f8b98
--- /dev/null
+++ b/spec/ruby/core/data/deconstruct_keys_spec.rb
@@ -0,0 +1,130 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#deconstruct_keys" do
+  it "returns a hash of attributes" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([:x, :y]).should == {x: 1, y: 2}
+  end
+
+  it "requires one argument" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    -> {
+      d.deconstruct_keys
+    }.should raise_error(ArgumentError, /wrong number of arguments \(given 0, expected 1\)/)
+  end
+
+  it "returns only specified keys" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([:x, :y]).should == {x: 1, y: 2}
+    d.deconstruct_keys([:x]    ).should == {x: 1}
+    d.deconstruct_keys([]      ).should == {}
+  end
+
+  it "accepts string attribute names" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys(['x', 'y']).should == {'x' => 1, 'y' => 2}
+  end
+
+  it "accepts argument position number as well but returns them as keys" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([0, 1]).should == {0 => 1, 1 => 2}
+    d.deconstruct_keys([0]   ).should == {0 => 1}
+    d.deconstruct_keys([-1]  ).should == {-1 => 2}
+  end
+
+  it "ignores incorrect position numbers" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([0, 3]).should == {0 => 1}
+  end
+
+  it "support mixing attribute names and argument position numbers" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([0, :x]).should == {0 => 1, :x => 1}
+  end
+
+  it "returns an empty hash when there are more keys than attributes" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([:x, :y, :x]).should == {}
+  end
+
+  it "returns at first not existing attribute name" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([:a, :x]).should == {}
+    d.deconstruct_keys([:x, :a]).should == {x: 1}
+  end
+
+  it "returns at first not existing argument position number" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys([3, 0]).should == {}
+    d.deconstruct_keys([0, 3]).should == {0 => 1}
+  end
+
+  it "accepts nil argument and return all the attributes" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    d.deconstruct_keys(nil).should == {x: 1, y: 2}
+  end
+
+  it "tries to convert a key with #to_int if index is not a String nor a Symbol, but responds to #to_int" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    key = mock("to_int")
+    key.should_receive(:to_int).and_return(1)
+
+    d.deconstruct_keys([key]).should == { key => 2 }
+  end
+
+  it "raises a TypeError if the conversion with #to_int does not return an Integer" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    key = mock("to_int")
+    key.should_receive(:to_int).and_return("not an Integer")
+
+    -> {
+      d.deconstruct_keys([key])
+    }.should raise_error(TypeError, /can't convert MockObject to Integer/)
+  end
+
+  it "raises TypeError if index is not a String, a Symbol and not convertible to Integer " do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    -> {
+      d.deconstruct_keys([0, []])
+    }.should raise_error(TypeError, "no implicit conversion of Array into Integer")
+  end
+
+  it "raise TypeError if passed anything except nil or array" do
+    klass = Data.define(:x, :y)
+    d = klass.new(1, 2)
+
+    -> { d.deconstruct_keys('x') }.should raise_error(TypeError, /expected Array or nil/)
+    -> { d.deconstruct_keys(1)   }.should raise_error(TypeError, /expected Array or nil/)
+    -> { d.deconstruct_keys(:x)  }.should raise_error(TypeError, /expected Array or nil/)
+    -> { d.deconstruct_keys({})  }.should raise_error(TypeError, /expected Array or nil/)
+  end
+end
diff --git a/spec/ruby/core/data/deconstruct_spec.rb b/spec/ruby/core/data/deconstruct_spec.rb
new file mode 100644
index 0000000000..4ca0b87039
--- /dev/null
+++ b/spec/ruby/core/data/deconstruct_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#deconstruct" do
+  it "returns an array of attribute values" do
+    DataSpecs::Measure.new(42, "km").deconstruct.should == [42, "km"]
+  end
+end
diff --git a/spec/ruby/core/data/define_spec.rb b/spec/ruby/core/data/define_spec.rb
new file mode 100644
index 0000000000..c0b4671e39
--- /dev/null
+++ b/spec/ruby/core/data/define_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data.define" do
+  it "accepts no arguments" do
+    empty_data = Data.define
+    empty_data.members.should == []
+  end
+
+  it "accepts symbols" do
+    movie = Data.define(:title, :year)
+    movie.members.should == [:title, :year]
+  end
+
+  it "accepts strings" do
+    movie = Data.define("title", "year")
+    movie.members.should == [:title, :year]
+  end
+
+  it "accepts a mix of strings and symbols" do
+    movie = Data.define("title", :year, "genre")
+    movie.members.should == [:title, :year, :genre]
+  end
+
+  it "accepts a block" do
+    movie = Data.define(:title, :year) do
+      def title_with_year
+        "#{title} (#{year})"
+      end
+    end
+    movie.members.should == [:title, :year]
+    movie.new("Matrix", 1999).title_with_year.should == "Matrix (1999)"
+  end
+end
diff --git a/spec/ruby/core/data/eql_spec.rb b/spec/ruby/core/data/eql_spec.rb
new file mode 100644
index 0000000000..6958d5de4a
--- /dev/null
+++ b/spec/ruby/core/data/eql_spec.rb
@@ -0,0 +1,63 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#eql?" do
+  it "returns true if the other is the same object" do
+    a = DataSpecs::Measure.new(42, "km")
+    a.should.eql?(a)
+  end
+
+  it "returns true if the other has all the same fields" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "km")
+    a.should.eql?(b)
+  end
+
+  it "returns false if the other is a different object or has different fields" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "mi")
+    a.should_not.eql?(b)
+  end
+
+  it "returns false if other is of a different class" do
+    a = DataSpecs::Measure.new(42, "km")
+    klass = Data.define(*DataSpecs::Measure.members)
+    b = klass.new(42, "km")
+    a.should_not.eql?(b)
+  end
+
+  it "returns false if any corresponding elements are not equal with #eql?" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42.0, "mi")
+    a.should_not.eql?(b)
+  end
+
+  context "recursive structure" do
+    it "returns true the other is the same object" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      a.should.eql?(a)
+    end
+
+    it "returns true if the other has all the same fields" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      b = DataSpecs::Measure.allocate
+      b.send(:initialize, amount: 42, unit: b)
+
+      a.should.eql?(b)
+    end
+
+    it "returns false if any corresponding elements are not equal with #eql?" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: a, unit: "km")
+
+      b = DataSpecs::Measure.allocate
+      b.send(:initialize, amount: b, unit: "mi")
+
+      a.should_not.eql?(b)
+    end
+  end
+end
diff --git a/spec/ruby/core/data/equal_value_spec.rb b/spec/ruby/core/data/equal_value_spec.rb
new file mode 100644
index 0000000000..d9a0dcff3e
--- /dev/null
+++ b/spec/ruby/core/data/equal_value_spec.rb
@@ -0,0 +1,63 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#==" do
+  it "returns true if the other is the same object" do
+    a = DataSpecs::Measure.new(42, "km")
+    a.should == a
+  end
+
+  it "returns true if the other has all the same fields" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "km")
+    a.should == b
+  end
+
+  it "returns false if the other is a different object or has different fields" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "mi")
+    a.should_not == b
+  end
+
+  it "returns false if other is of a different class" do
+    a = DataSpecs::Measure.new(42, "km")
+    klass = Data.define(*DataSpecs::Measure.members)
+    b = klass.new(42, "km")
+    a.should_not == b
+  end
+
+  it "returns false if any corresponding elements are not equal with #==" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42.0, "mi")
+    a.should_not == b
+  end
+
+  context "recursive structure" do
+    it "returns true the other is the same object" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      a.should == a
+    end
+
+    it "returns true if the other has all the same fields" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      b = DataSpecs::Measure.allocate
+      b.send(:initialize, amount: 42, unit: b)
+
+      a.should == b
+    end
+
+    it "returns false if any corresponding elements are not equal with #==" do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: a, unit: "km")
+
+      b = DataSpecs::Measure.allocate
+      b.send(:initialize, amount: b, unit: "mi")
+
+      a.should_not == b
+    end
+  end
+end
diff --git a/spec/ruby/core/data/fixtures/classes.rb b/spec/ruby/core/data/fixtures/classes.rb
new file mode 100644
index 0000000000..650c0b2a62
--- /dev/null
+++ b/spec/ruby/core/data/fixtures/classes.rb
@@ -0,0 +1,34 @@
+module DataSpecs
+  if Data.respond_to?(:define)
+    Measure = Data.define(:amount, :unit)
+
+    class MeasureWithOverriddenName < Measure
+      def self.name
+        "A"
+      end
+    end
+
+    class DataSubclass < Data; end
+
+    MeasureSubclass = Class.new(Measure) do
+      def initialize(amount:, unit:)
+        super
+      end
+    end
+
+    Empty = Data.define()
+
+    DataWithOverriddenInitialize = Data.define(:amount, :unit) do
+      def initialize(*rest, **kw)
+        super
+        ScratchPad.record [:initialize, rest, kw]
+      end
+    end
+
+    Area = Data.define(:width, :height, :area) do
+      def initialize(width:, height:)
+        super(width: width, height: height, area: width * height)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/data/hash_spec.rb b/spec/ruby/core/data/hash_spec.rb
new file mode 100644
index 0000000000..c23f08a71d
--- /dev/null
+++ b/spec/ruby/core/data/hash_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#hash" do
+  it "returns the same integer for objects with the same content" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "km")
+    a.hash.should == b.hash
+    a.hash.should be_an_instance_of(Integer)
+  end
+
+  it "returns different hashes for objects with different values" do
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(42, "ml")
+    a.hash.should_not == b.hash
+
+    a = DataSpecs::Measure.new(42, "km")
+    b = DataSpecs::Measure.new(13, "km")
+    a.hash.should_not == b.hash
+  end
+
+  it "returns different hashes for different classes" do
+    Data.define(:x).new(1).hash.should != Data.define(:x).new(1).hash
+  end
+end
diff --git a/spec/ruby/core/data/initialize_spec.rb b/spec/ruby/core/data/initialize_spec.rb
new file mode 100644
index 0000000000..010c73b91b
--- /dev/null
+++ b/spec/ruby/core/data/initialize_spec.rb
@@ -0,0 +1,124 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#initialize" do
+  it "accepts positional arguments" do
+    data = DataSpecs::Measure.new(42, "km")
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
+  it "accepts alternative positional arguments" do
+    data = DataSpecs::Measure[42, "km"]
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
+  it "accepts keyword arguments" do
+    data = DataSpecs::Measure.new(amount: 42, unit: "km")
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
+  it "accepts alternative keyword arguments" do
+    data = DataSpecs::Measure[amount: 42, unit: "km"]
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
+  it "accepts String keyword arguments" do
+    data = DataSpecs::Measure.new("amount" => 42, "unit" => "km")
+
+    data.amount.should == 42
+    data.unit.should == "km"
+  end
+
+  it "raises ArgumentError if no arguments are given" do
+    -> {
+      DataSpecs::Measure.new
+    }.should raise_error(ArgumentError) { |e|
+      e.message.should.include?("missing keywords: :amount, :unit")
+    }
+  end
+
+  it "raises ArgumentError if at least one argument is missing" do
+    -> {
+      DataSpecs::Measure.new(unit: "km")
+    }.should raise_error(ArgumentError) { |e|
+      e.message.should.include?("missing keyword: :amount")
+    }
+  end
+
+  it "raises ArgumentError if unknown keyword is given" do
+    -> {
+      DataSpecs::Measure.new(amount: 42, unit: "km", system: "metric")
+    }.should raise_error(ArgumentError) { |e|
+      e.message.should.include?("unknown keyword: :system")
+    }
+  end
+
+  it "supports super from a subclass" do
+    ms = DataSpecs::MeasureSubclass.new(amount: 1, unit: "km")
+
+    ms.amount.should == 1
+    ms.unit.should == "km"
+  end
+
+  it "supports Data with no fields" do
+    -> { DataSpecs::Empty.new }.should_not raise_error
+  end
+
+  it "can be overridden" do
+    ScratchPad.record []
+
+    measure_class = Data.define(:amount, :unit) do
+      def initialize(*, **)
+        super
+        ScratchPad << :initialize
+      end
+    end
+
+    measure_class.new(42, "m")
+    ScratchPad.recorded.should == [:initialize]
+  end
+
+  context "when it is overridden" do
+    it "is called with keyword arguments when given positional arguments" do
+      ScratchPad.clear
+      DataSpecs::DataWithOverriddenInitialize.new(42, "m")
+      ScratchPad.recorded.should == [:initialize, [], {amount: 42, unit: "m"}]
+    end
+
+    it "is called with keyword arguments when given keyword arguments" do
+      ScratchPad.clear
+      DataSpecs::DataWithOverriddenInitialize.new(amount: 42, unit: "m")
+      ScratchPad.recorded.should == [:initialize, [], {amount: 42, unit: "m"}]
+    end
+
+    it "is called with keyword arguments when given alternative positional arguments" do
+      ScratchPad.clear
+      DataSpecs::DataWithOverriddenInitialize[42, "m"]
+      ScratchPad.recorded.should == [:initialize, [], {amount: 42, unit: "m"}]
+    end
+
+    it "is called with keyword arguments when given alternative keyword arguments" do
+      ScratchPad.clear
+      DataSpecs::DataWithOverriddenInitialize[amount: 42, unit: "m"]
+      ScratchPad.recorded.should == [:initialize, [], {amount: 42, unit: "m"}]
+    end
+
+    # See https://github.com/ruby/psych/pull/765
+    it "can be deserialized by calling Data.instance_method(:initialize)" do
+      d1 = DataSpecs::Area.new(width: 2, height: 3)
+      d1.area.should == 6
+
+      d2 = DataSpecs::Area.allocate
+      Data.instance_method(:initialize).bind_call(d2, **d1.to_h)
+      d2.should == d1
+    end
+  end
+end
diff --git a/spec/ruby/core/data/inspect_spec.rb b/spec/ruby/core/data/inspect_spec.rb
new file mode 100644
index 0000000000..38642910a0
--- /dev/null
+++ b/spec/ruby/core/data/inspect_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/inspect'
+
+describe "Data#inspect" do
+  it_behaves_like :data_inspect, :inspect
+end
diff --git a/spec/ruby/core/data/members_spec.rb b/spec/ruby/core/data/members_spec.rb
new file mode 100644
index 0000000000..457a90a0d6
--- /dev/null
+++ b/spec/ruby/core/data/members_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#members" do
+  it "returns an array of attribute names" do
+    measure = DataSpecs::Measure.new(amount: 42, unit: 'km')
+    measure.members.should == [:amount, :unit]
+  end
+end
+
+describe "DataClass#members" do
+  it "returns an array of attribute names" do
+    DataSpecs::Measure.members.should == [:amount, :unit]
+  end
+
+  context "class inheriting Data" do
+    it "isn't available in a subclass" do
+      DataSpecs::DataSubclass.should_not.respond_to?(:members)
+    end
+  end
+end
diff --git a/spec/ruby/core/data/shared/inspect.rb b/spec/ruby/core/data/shared/inspect.rb
new file mode 100644
index 0000000000..6cd5664da7
--- /dev/null
+++ b/spec/ruby/core/data/shared/inspect.rb
@@ -0,0 +1,62 @@
+require_relative '../fixtures/classes'
+
+describe :data_inspect, shared: true do
+  it "returns a string representation showing members and values" do
+    a = DataSpecs::Measure.new(42, "km")
+    a.send(@method).should == '#<data DataSpecs::Measure amount=42, unit="km">'
+  end
+
+  it "returns a string representation without the class name for anonymous structs" do
+    Data.define(:a).new("").send(@method).should == '#<data a="">'
+  end
+
+  it "returns a string representation without the class name for structs nested in anonymous classes" do
+    c = Class.new
+    c.class_eval <<~DOC
+        Foo = Data.define(:a)
+      DOC
+
+    c::Foo.new("").send(@method).should == '#<data a="">'
+  end
+
+  it "returns a string representation without the class name for structs nested in anonymous modules" do
+    m = Module.new
+    m.class_eval <<~DOC
+        Foo = Data.define(:a)
+      DOC
+
+    m::Foo.new("").send(@method).should == '#<data a="">'
+  end
+
+  it "does not call #name method" do
+    struct = DataSpecs::MeasureWithOverriddenName.new(42, "km")
+    struct.send(@method).should == '#<data DataSpecs::MeasureWithOverriddenName amount=42, unit="km">'
+  end
+
+  it "does not call #name method when struct is anonymous" do
+    klass = Class.new(DataSpecs::Measure) do
+      def self.name
+        "A"
+      end
+    end
+    struct = klass.new(42, "km")
+    struct.send(@method).should == '#<data amount=42, unit="km">'
+  end
+
+  context "recursive structure" do
+    it "returns string representation with recursive attribute replaced with ..." do
+      a = DataSpecs::Measure.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      a.send(@method).should == "#<data DataSpecs::Measure amount=42, unit=#<data DataSpecs::Measure:...>>"
+    end
+
+    it "returns string representation with recursive attribute replaced with ... when an anonymous class" do
+      klass = Class.new(DataSpecs::Measure)
+      a = klass.allocate
+      a.send(:initialize, amount: 42, unit: a)
+
+      a.send(@method).should =~ /#<data amount=42, unit=#<data #<Class:0x.+?>:\.\.\.>>/
+    end
+  end
+end
diff --git a/spec/ruby/core/data/to_h_spec.rb b/spec/ruby/core/data/to_h_spec.rb
new file mode 100644
index 0000000000..64816b7251
--- /dev/null
+++ b/spec/ruby/core/data/to_h_spec.rb
@@ -0,0 +1,63 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#to_h" do
+  it "transforms the data object into a hash" do
+    data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+    data.to_h.should == { amount: 42, unit: 'km' }
+  end
+
+  context "with block" do
+    it "transforms [key, value] pairs returned by the block into a hash" do
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      data.to_h { |key, value| [value, key] }.should == { 42 => :amount, 'km' => :unit }
+    end
+
+    it "passes to a block each pair's key and value as separate arguments" do
+      ScratchPad.record []
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      data.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+      ScratchPad.recorded.sort.should == [[:amount, 42], [:unit, 'km']]
+
+      ScratchPad.record []
+      data.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[:amount, 42], [:unit, 'km']]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      -> do
+        data.to_h { |k, v| [k.to_s, v*v, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+
+      -> do
+        data.to_h { |k, v| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+      -> do
+        data.to_h { |k, v| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+
+      data.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+      data = DataSpecs::Measure.new(amount: 42, unit: 'km')
+
+      -> do
+        data.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
+    end
+  end
+end
diff --git a/spec/ruby/core/data/to_s_spec.rb b/spec/ruby/core/data/to_s_spec.rb
new file mode 100644
index 0000000000..2b4a670e8e
--- /dev/null
+++ b/spec/ruby/core/data/to_s_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/inspect'
+
+describe "Data#to_s" do
+  it_behaves_like :data_inspect, :to_s
+end
diff --git a/spec/ruby/core/data/with_spec.rb b/spec/ruby/core/data/with_spec.rb
new file mode 100644
index 0000000000..fd0a99d1fa
--- /dev/null
+++ b/spec/ruby/core/data/with_spec.rb
@@ -0,0 +1,57 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Data#with" do
+  it "returns self if given no arguments" do
+    data = DataSpecs::Measure.new(amount: 42, unit: "km")
+    data = data.with.should.equal?(data)
+  end
+
+  it "accepts keyword arguments" do
+    data = DataSpecs::Measure.new(amount: 42, unit: "km")
+    data = data.with(amount: 4, unit: "m")
+
+    data.amount.should == 4
+    data.unit.should == "m"
+  end
+
+  it "accepts String keyword arguments" do
+    data = DataSpecs::Measure.new(amount: 42, unit: "km")
+    data = data.with("amount" => 4, "unit" => "m")
+
+    data.amount.should == 4
+    data.unit.should == "m"
+  end
+
+  it "raises ArgumentError if no keyword arguments are given" do
+    data = DataSpecs::Measure.new(amount: 42, unit: "km")
+
+    -> {
+      data.with(4, "m")
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 2, expected 0)")
+  end
+
+  it "does not depend on the Data.new method" do
+    subclass = Class.new(DataSpecs::Measure)
+    data = subclass.new(amount: 42, unit: "km")
+
+    def subclass.new(*)
+      raise "Data.new is called"
+    end
+
+    data_copy = data.with(unit: "m")
+    data_copy.amount.should == 42
+    data_copy.unit.should == "m"
+  end
+
+  ruby_version_is "3.3" do
+    it "calls #initialize" do
+      data = DataSpecs::DataWithOverriddenInitialize.new(42, "m")
+      ScratchPad.clear
+
+      data.with(amount: 0)
+
+      ScratchPad.recorded.should == [:initialize, [], {amount: 0, unit: "m"}]
+    end
+  end
+end
diff --git a/spec/ruby/core/dir/chdir_spec.rb b/spec/ruby/core/dir/chdir_spec.rb
index e9b8274382..015386a902 100644
--- a/spec/ruby/core/dir/chdir_spec.rb
+++ b/spec/ruby/core/dir/chdir_spec.rb
@@ -19,14 +19,14 @@ describe "Dir.chdir" do
   end
 
   it "defaults to $HOME with no arguments" do
-    if ENV['HOME']
-      Dir.chdir
-      current_dir = Dir.pwd
+    skip "$HOME not valid directory" unless ENV['HOME'] && File.directory?(ENV['HOME'])
 
-      Dir.chdir(ENV['HOME'])
-      home = Dir.pwd
-      current_dir.should == home
-    end
+    Dir.chdir
+    current_dir = Dir.pwd
+
+    Dir.chdir(ENV['HOME'])
+    home = Dir.pwd
+    current_dir.should == home
   end
 
   it "changes to the specified directory" do
@@ -70,6 +70,8 @@ describe "Dir.chdir" do
   end
 
   it "defaults to the home directory when given a block but no argument" do
+    skip "$HOME not valid directory" unless ENV['HOME'] && File.directory?(ENV['HOME'])
+
     # Windows will return a path with forward slashes for ENV["HOME"] so we have
     # to compare the route representations returned by Dir.chdir.
     current_dir = ""
@@ -93,10 +95,10 @@ describe "Dir.chdir" do
   end
 
   it "raises an Errno::ENOENT if the original directory no longer exists" do
-    dir1 = tmp('/testdir1')
-    dir2 = tmp('/testdir2')
-    File.exist?(dir1).should == false
-    File.exist?(dir2).should == false
+    dir1 = tmp('testdir1')
+    dir2 = tmp('testdir2')
+    Dir.should_not.exist?(dir1)
+    Dir.should_not.exist?(dir2)
     Dir.mkdir dir1
     Dir.mkdir dir2
     begin
@@ -106,8 +108,8 @@ describe "Dir.chdir" do
         end
       }.should raise_error(Errno::ENOENT)
     ensure
-      Dir.unlink dir1 if File.exist?(dir1)
-      Dir.unlink dir2 if File.exist?(dir2)
+      Dir.unlink dir1 if Dir.exist?(dir1)
+      Dir.unlink dir2 if Dir.exist?(dir2)
     end
   end
 
@@ -122,3 +124,97 @@ describe "Dir.chdir" do
     Dir.pwd.should == @original
   end
 end
+
+ruby_version_is '3.3' do
+  describe "Dir#chdir" do
+    before :all do
+      DirSpecs.create_mock_dirs
+    end
+
+    after :all do
+      DirSpecs.delete_mock_dirs
+    end
+
+    before :each do
+      @original = Dir.pwd
+    end
+
+    after :each do
+      Dir.chdir(@original)
+    end
+
+    it "changes the current working directory to self" do
+      dir = Dir.new(DirSpecs.mock_dir)
+      dir.chdir
+      Dir.pwd.should == DirSpecs.mock_dir
+    ensure
+      dir.close
+    end
+
+    it "changes the current working directory to self for duration of the block when a block is given" do
+      dir = Dir.new(DirSpecs.mock_dir)
+      pwd_in_block = nil
+
+      dir.chdir { pwd_in_block = Dir.pwd }
+
+      pwd_in_block.should == DirSpecs.mock_dir
+      Dir.pwd.should == @original
+    ensure
+      dir.close
+    end
+
+    it "returns 0 when successfully changing directory" do
+      dir = Dir.new(DirSpecs.mock_dir)
+      dir.chdir.should == 0
+    ensure
+      dir.close
+    end
+
+    it "returns the value of the block when a block is given" do
+      dir = Dir.new(DirSpecs.mock_dir)
+      dir.chdir { :block_value }.should == :block_value
+    ensure
+      dir.close
+    end
+
+    platform_is_not :windows do
+      it "does not raise an Errno::ENOENT if the original directory no longer exists" do
+        dir_name1 = tmp('testdir1')
+        dir_name2 = tmp('testdir2')
+        Dir.should_not.exist?(dir_name1)
+        Dir.should_not.exist?(dir_name2)
+        Dir.mkdir dir_name1
+        Dir.mkdir dir_name2
+
+        dir2 = Dir.new(dir_name2)
+
+        begin
+          Dir.chdir(dir_name1) do
+            dir2.chdir { Dir.unlink dir_name1 }
+          end
+          Dir.pwd.should == @original
+        ensure
+          Dir.unlink dir_name1 if Dir.exist?(dir_name1)
+          Dir.unlink dir_name2 if Dir.exist?(dir_name2)
+        end
+      ensure
+        dir2.close
+      end
+    end
+
+    it "always returns to the original directory when given a block" do
+      dir = Dir.new(DirSpecs.mock_dir)
+
+      begin
+        dir.chdir do
+          raise StandardError, "something bad happened"
+        end
+      rescue StandardError
+      end
+
+      Dir.pwd.should == @original
+    ensure
+      dir.close
+    end
+  end
+end
diff --git a/spec/ruby/core/dir/children_spec.rb b/spec/ruby/core/dir/children_spec.rb
index 8f6e62b463..0ad3df4669 100644
--- a/spec/ruby/core/dir/children_spec.rb
+++ b/spec/ruby/core/dir/children_spec.rb
@@ -3,136 +3,145 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/common'
 
-ruby_version_is "2.5" do
-  describe "Dir.children" do
-    before :all do
-      DirSpecs.create_mock_dirs
-    end
+describe "Dir.children" do
+  before :all do
+    DirSpecs.create_mock_dirs
+  end
 
-    before :each do
-      @internal = Encoding.default_internal
-    end
+  before :each do
+    @internal = Encoding.default_internal
+  end
 
-    after :all do
-      DirSpecs.delete_mock_dirs
-    end
+  after :all do
+    DirSpecs.delete_mock_dirs
+  end
 
-    after :each do
-      Encoding.default_internal = @internal
-    end
+  after :each do
+    Encoding.default_internal = @internal
+  end
 
-    it "returns an Array of filenames in an existing directory including dotfiles" do
-      a = Dir.children(DirSpecs.mock_dir).sort
+  it "returns an Array of filenames in an existing directory including dotfiles" do
+    a = Dir.children(DirSpecs.mock_dir).sort
 
-      a.should == DirSpecs.expected_paths - %w[. ..]
+    a.should == DirSpecs.expected_paths - %w[. ..]
 
-      a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested").sort
-      a.should == %w|.dotfile.ext directory|
-    end
+    a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested").sort
+    a.should == %w|.dotfile.ext directory|
+  end
 
-    it "calls #to_path on non-String arguments" do
-      p = mock('path')
-      p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
-      Dir.children(p)
-    end
+  it "calls #to_path on non-String arguments" do
+    p = mock('path')
+    p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
+    Dir.children(p)
+  end
 
-    it "accepts an options Hash" do
-      a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").sort
-      a.should == %w|.dotfile.ext directory|
-    end
+  it "accepts an options Hash" do
+    a = Dir.children("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").sort
+    a.should == %w|.dotfile.ext directory|
+  end
 
-    it "returns children encoded with the filesystem encoding by default" do
-      # This spec depends on the locale not being US-ASCII because if it is, the
-      # children that are not ascii_only? will be BINARY encoded.
-      children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
-      encoding = Encoding.find("filesystem")
-      encoding = Encoding::BINARY if encoding == Encoding::US_ASCII
-      platform_is_not :windows do
-        children.should include("こんにちは.txt".force_encoding(encoding))
-      end
-      children.first.encoding.should equal(Encoding.find("filesystem"))
+  it "returns children encoded with the filesystem encoding by default" do
+    # This spec depends on the locale not being US-ASCII because if it is, the
+    # children that are not ascii_only? will be BINARY encoded.
+    children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
+    encoding = Encoding.find("filesystem")
+    encoding = Encoding::BINARY if encoding == Encoding::US_ASCII
+    platform_is_not :windows do
+      children.should include("こんにちは.txt".dup.force_encoding(encoding))
     end
+    children.first.encoding.should equal(Encoding.find("filesystem"))
+  end
 
-    it "returns children encoded with the specified encoding" do
-      dir = File.join(DirSpecs.mock_dir, 'special')
-      children = Dir.children(dir, encoding: "euc-jp").sort
-      children.first.encoding.should equal(Encoding::EUC_JP)
-    end
+  it "returns children encoded with the specified encoding" do
+    dir = File.join(DirSpecs.mock_dir, 'special')
+    children = Dir.children(dir, encoding: "euc-jp").sort
+    children.first.encoding.should equal(Encoding::EUC_JP)
+  end
 
-    it "returns children transcoded to the default internal encoding" do
-      Encoding.default_internal = Encoding::EUC_KR
-      children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
-      children.first.encoding.should equal(Encoding::EUC_KR)
-    end
+  it "returns children transcoded to the default internal encoding" do
+    Encoding.default_internal = Encoding::EUC_KR
+    children = Dir.children(File.join(DirSpecs.mock_dir, 'special')).sort
+    children.first.encoding.should equal(Encoding::EUC_KR)
+  end
 
-    it "raises a SystemCallError if called with a nonexistent directory" do
-      -> { Dir.children DirSpecs.nonexistent }.should raise_error(SystemCallError)
-    end
+  it "raises a SystemCallError if called with a nonexistent directory" do
+    -> { Dir.children DirSpecs.nonexistent }.should raise_error(SystemCallError)
   end
 end
 
-ruby_version_is "2.6" do
-  describe "Dir#children" do
-    before :all do
-      DirSpecs.create_mock_dirs
-    end
+describe "Dir#children" do
+  before :all do
+    DirSpecs.create_mock_dirs
+  end
 
-    before :each do
-      @internal = Encoding.default_internal
-    end
+  before :each do
+    @internal = Encoding.default_internal
+  end
 
-    after :all do
-      DirSpecs.delete_mock_dirs
-    end
+  after :all do
+    DirSpecs.delete_mock_dirs
+  end
 
-    after :each do
-      Encoding.default_internal = @internal
-      @dir.close if @dir
-    end
+  after :each do
+    Encoding.default_internal = @internal
+    @dir.close if @dir
+  end
 
-    it "returns an Array of filenames in an existing directory including dotfiles" do
-      @dir = Dir.new(DirSpecs.mock_dir)
-      a = @dir.children.sort
-      @dir.close
+  it "returns an Array of filenames in an existing directory including dotfiles" do
+    @dir = Dir.new(DirSpecs.mock_dir)
+    a = @dir.children.sort
+    @dir.close
 
-      a.should == DirSpecs.expected_paths - %w[. ..]
+    a.should == DirSpecs.expected_paths - %w[. ..]
 
-      @dir = Dir.new("#{DirSpecs.mock_dir}/deeply/nested")
-      a = @dir.children.sort
-      a.should == %w|.dotfile.ext directory|
-    end
+    @dir = Dir.new("#{DirSpecs.mock_dir}/deeply/nested")
+    a = @dir.children.sort
+    a.should == %w|.dotfile.ext directory|
+  end
 
-    it "accepts an options Hash" do
-      @dir = Dir.new("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8")
-      a = @dir.children.sort
-      a.should == %w|.dotfile.ext directory|
-    end
+  it "accepts an encoding keyword for the encoding of the entries" do
+    @dir = Dir.new("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8")
+    dirs = @dir.to_a.sort
+    dirs.each { |d| d.encoding.should == Encoding::UTF_8 }
+  end
 
-    it "returns children encoded with the filesystem encoding by default" do
-      # This spec depends on the locale not being US-ASCII because if it is, the
-      # children that are not ascii_only? will be BINARY encoded.
-      @dir = Dir.new(File.join(DirSpecs.mock_dir, 'special'))
-      children = @dir.children.sort
-      encoding = Encoding.find("filesystem")
-      encoding = Encoding::BINARY if encoding == Encoding::US_ASCII
-      platform_is_not :windows do
-        children.should include("こんにちは.txt".force_encoding(encoding))
-      end
-      children.first.encoding.should equal(Encoding.find("filesystem"))
-    end
+  it "returns children encoded with the filesystem encoding by default" do
+    # This spec depends on the locale not being US-ASCII because if it is, the
+    # children that are not ascii_only? will be BINARY encoded.
+    @dir = Dir.new(File.join(DirSpecs.mock_dir, 'special'))
+    children = @dir.children.sort
+    encoding = Encoding.find("filesystem")
+    encoding = Encoding::BINARY if encoding == Encoding::US_ASCII
+    platform_is_not :windows do
+      children.should include("こんにちは.txt".dup.force_encoding(encoding))
+    end
+    children.first.encoding.should equal(Encoding.find("filesystem"))
+  end
 
-    it "returns children encoded with the specified encoding" do
-      path = File.join(DirSpecs.mock_dir, 'special')
-      @dir = Dir.new(path, encoding: "euc-jp")
-      children = @dir.children.sort
-      children.first.encoding.should equal(Encoding::EUC_JP)
-    end
+  it "returns children encoded with the specified encoding" do
+    path = File.join(DirSpecs.mock_dir, 'special')
+    @dir = Dir.new(path, encoding: "euc-jp")
+    children = @dir.children.sort
+    children.first.encoding.should equal(Encoding::EUC_JP)
+  end
 
-    it "returns children transcoded to the default internal encoding" do
-      Encoding.default_internal = Encoding::EUC_KR
-      @dir = Dir.new(File.join(DirSpecs.mock_dir, 'special'))
-      children = @dir.children.sort
-      children.first.encoding.should equal(Encoding::EUC_KR)
-    end
+  it "returns children transcoded to the default internal encoding" do
+    Encoding.default_internal = Encoding::EUC_KR
+    @dir = Dir.new(File.join(DirSpecs.mock_dir, 'special'))
+    children = @dir.children.sort
+    children.first.encoding.should equal(Encoding::EUC_KR)
+  end
+
+  it "returns the same result when called repeatedly" do
+    @dir = Dir.open DirSpecs.mock_dir
+
+    a = []
+    @dir.each {|dir| a << dir}
+
+    b = []
+    @dir.each {|dir| b << dir}
+
+    a.sort.should == b.sort
+    a.sort.should == DirSpecs.expected_paths
   end
 end
diff --git a/spec/ruby/core/dir/close_spec.rb b/spec/ruby/core/dir/close_spec.rb
index 5fad5eecfb..f7cce318b8 100644
--- a/spec/ruby/core/dir/close_spec.rb
+++ b/spec/ruby/core/dir/close_spec.rb
@@ -11,9 +11,43 @@ describe "Dir#close" do
 
   it "does not raise an IOError even if the Dir instance is closed" do
     dir = Dir.open DirSpecs.mock_dir
-    dir.close
-    -> {
-      dir.close
-    }.should_not raise_error(IOError)
+    dir.close.should == nil
+    dir.close.should == nil
+
+    platform_is_not :windows do
+      -> { dir.fileno }.should raise_error(IOError, /closed directory/)
+    end
+  end
+
+  it "returns nil" do
+    dir = Dir.open DirSpecs.mock_dir
+    dir.close.should == nil
+  end
+
+  ruby_version_is '3.3'...'3.4' do
+    platform_is_not :windows do
+      it "does not raise an error even if the file descriptor is closed with another Dir instance" do
+        dir = Dir.open DirSpecs.mock_dir
+        dir_new = Dir.for_fd(dir.fileno)
+
+        dir.close
+        dir_new.close
+
+        -> { dir.fileno }.should raise_error(IOError, /closed directory/)
+        -> { dir_new.fileno }.should raise_error(IOError, /closed directory/)
+      end
+    end
+  end
+
+  ruby_version_is '3.4' do
+    platform_is_not :windows do
+      it "raises an error if the file descriptor is closed with another Dir instance" do
+        dir = Dir.open DirSpecs.mock_dir
+        dir_new = Dir.for_fd(dir.fileno)
+        dir.close
+
+        -> { dir_new.close }.should raise_error(Errno::EBADF, 'Bad file descriptor - closedir')
+      end
+    end
   end
 end
diff --git a/spec/ruby/core/dir/each_child_spec.rb b/spec/ruby/core/dir/each_child_spec.rb
index dcc9a456c7..7194273b95 100644
--- a/spec/ruby/core/dir/each_child_spec.rb
+++ b/spec/ruby/core/dir/each_child_spec.rb
@@ -1,103 +1,117 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/common'
 
-ruby_version_is "2.5" do
-  describe "Dir.each_child" do
-    before :all do
-      DirSpecs.create_mock_dirs
-    end
+describe "Dir.each_child" do
+  before :all do
+    DirSpecs.create_mock_dirs
+  end
 
-    after :all do
-      DirSpecs.delete_mock_dirs
-    end
+  after :all do
+    DirSpecs.delete_mock_dirs
+  end
 
-    it "yields all names in an existing directory to the provided block" do
-      a, b = [], []
+  it "accepts an encoding keyword for the encoding of the entries" do
+    dirs = Dir.each_child("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").to_a.sort
+    dirs.each {|dir| dir.encoding.should == Encoding::UTF_8}
+  end
 
-      Dir.each_child(DirSpecs.mock_dir) {|f| a << f}
-      Dir.each_child("#{DirSpecs.mock_dir}/deeply/nested") {|f| b << f}
+  it "yields all names in an existing directory to the provided block" do
+    a, b = [], []
 
-      a.sort.should == DirSpecs.expected_paths -  %w[. ..]
-      b.sort.should == %w|.dotfile.ext directory|
-    end
+    Dir.each_child(DirSpecs.mock_dir) {|f| a << f}
+    Dir.each_child("#{DirSpecs.mock_dir}/deeply/nested") {|f| b << f}
 
-    it "returns nil when successful" do
-      Dir.each_child(DirSpecs.mock_dir) {|f| f}.should == nil
-    end
+    a.sort.should == DirSpecs.expected_paths -  %w[. ..]
+    b.sort.should == %w|.dotfile.ext directory|
+  end
 
-    it "calls #to_path on non-String arguments" do
-      p = mock('path')
-      p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
-      Dir.each_child(p).to_a
-    end
+  it "returns nil when successful" do
+    Dir.each_child(DirSpecs.mock_dir) {|f| f}.should == nil
+  end
 
-    it "raises a SystemCallError if passed a nonexistent directory" do
-      -> { Dir.each_child(DirSpecs.nonexistent) {} }.should raise_error(SystemCallError)
-    end
+  it "calls #to_path on non-String arguments" do
+    p = mock('path')
+    p.should_receive(:to_path).and_return(DirSpecs.mock_dir)
+    Dir.each_child(p).to_a
+  end
 
-    describe "when no block is given" do
-      it "returns an Enumerator" do
-        Dir.each_child(DirSpecs.mock_dir).should be_an_instance_of(Enumerator)
-        Dir.each_child(DirSpecs.mock_dir).to_a.sort.should == DirSpecs.expected_paths - %w[. ..]
-      end
+  it "raises a SystemCallError if passed a nonexistent directory" do
+    -> { Dir.each_child(DirSpecs.nonexistent) {} }.should raise_error(SystemCallError)
+  end
 
-      describe "returned Enumerator" do
-        describe "size" do
-          it "should return nil" do
-            Dir.each_child(DirSpecs.mock_dir).size.should == nil
-          end
+  describe "when no block is given" do
+    it "returns an Enumerator" do
+      Dir.each_child(DirSpecs.mock_dir).should be_an_instance_of(Enumerator)
+      Dir.each_child(DirSpecs.mock_dir).to_a.sort.should == DirSpecs.expected_paths - %w[. ..]
+    end
+
+    describe "returned Enumerator" do
+      describe "size" do
+        it "should return nil" do
+          Dir.each_child(DirSpecs.mock_dir).size.should == nil
         end
       end
     end
   end
 end
 
-ruby_version_is "2.6" do
-  describe "Dir#each_child" do
-    before :all do
-      DirSpecs.create_mock_dirs
-    end
+describe "Dir#each_child" do
+  before :all do
+    DirSpecs.create_mock_dirs
+  end
 
-    after :all do
-      DirSpecs.delete_mock_dirs
-    end
+  after :all do
+    DirSpecs.delete_mock_dirs
+  end
 
-    after :each do
-      @dir.close if @dir
-    end
+  after :each do
+    @dir.close if @dir
+  end
 
-    it "yields all names in an existing directory to the provided block" do
-      a, b = [], []
-      @dir = Dir.new(DirSpecs.mock_dir)
-      @dir2 = Dir.new("#{DirSpecs.mock_dir}/deeply/nested")
+  it "yields all names in an existing directory to the provided block" do
+    a, b = [], []
+    @dir = Dir.new(DirSpecs.mock_dir)
+    @dir2 = Dir.new("#{DirSpecs.mock_dir}/deeply/nested")
 
-      @dir.each_child { |f| a << f }
-      @dir2.each_child { |f| b << f }
-      @dir2.close
+    @dir.each_child { |f| a << f }
+    @dir2.each_child { |f| b << f }
+    @dir2.close
 
-      a.sort.should == DirSpecs.expected_paths - %w|. ..|
-      b.sort.should == %w|.dotfile.ext directory|
-    end
+    a.sort.should == DirSpecs.expected_paths - %w|. ..|
+    b.sort.should == %w|.dotfile.ext directory|
+  end
 
-    it "returns self when successful" do
-      @dir = Dir.new(DirSpecs.mock_dir)
-      @dir.each_child { |f| f }.should == @dir
-    end
+  it "returns self when successful" do
+    @dir = Dir.new(DirSpecs.mock_dir)
+    @dir.each_child { |f| f }.should == @dir
+  end
 
-    describe "when no block is given" do
-      it "returns an Enumerator" do
-        @dir = Dir.new(DirSpecs.mock_dir)
+  it "returns the same result when called repeatedly" do
+    @dir = Dir.open DirSpecs.mock_dir
 
-        @dir.each_child.should be_an_instance_of(Enumerator)
-        @dir.each_child.to_a.sort.should == DirSpecs.expected_paths - %w|. ..|
-      end
+    a = []
+    @dir.each {|dir| a << dir}
+
+    b = []
+    @dir.each {|dir| b << dir}
+
+    a.sort.should == b.sort
+    a.sort.should == DirSpecs.expected_paths
+  end
+
+  describe "when no block is given" do
+    it "returns an Enumerator" do
+      @dir = Dir.new(DirSpecs.mock_dir)
+
+      @dir.each_child.should be_an_instance_of(Enumerator)
+      @dir.each_child.to_a.sort.should == DirSpecs.expected_paths - %w|. ..|
+    end
 
-      describe "returned Enumerator" do
-        describe "size" do
-          it "should return nil" do
-            @dir = Dir.new(DirSpecs.mock_dir)
-            @dir.each_child.size.should == nil
-          end
+    describe "returned Enumerator" do
+      describe "size" do
+        it "should return nil" do
+          @dir = Dir.new(DirSpecs.mock_dir)
+          @dir.each_child.size.should == nil
         end
       end
     end
diff --git a/spec/ruby/core/dir/each_spec.rb b/spec/ruby/core/dir/each_spec.rb
index 8c69a7212b..7674663d82 100644
--- a/spec/ruby/core/dir/each_spec.rb
+++ b/spec/ruby/core/dir/each_spec.rb
@@ -35,6 +35,17 @@ describe "Dir#each" do
     ls.should include(@dir.read)
   end
 
+  it "returns the same result when called repeatedly" do
+    a = []
+    @dir.each {|dir| a << dir}
+
+    b = []
+    @dir.each {|dir| b << dir}
+
+    a.sort.should == b.sort
+    a.sort.should == DirSpecs.expected_paths
+  end
+
   describe "when no block is given" do
     it "returns an Enumerator" do
       @dir.each.should be_an_instance_of(Enumerator)
diff --git a/spec/ruby/core/dir/entries_spec.rb b/spec/ruby/core/dir/entries_spec.rb
index 33568b6fc4..7462542acf 100644
--- a/spec/ruby/core/dir/entries_spec.rb
+++ b/spec/ruby/core/dir/entries_spec.rb
@@ -35,9 +35,9 @@ describe "Dir.entries" do
     Dir.entries(p)
   end
 
-  it "accepts an options Hash" do
-    a = Dir.entries("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").sort
-    a.should == %w|. .. .dotfile.ext directory|
+  it "accepts an encoding keyword for the encoding of the entries" do
+    dirs = Dir.entries("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").to_a.sort
+    dirs.each {|dir| dir.encoding.should == Encoding::UTF_8}
   end
 
   it "returns entries encoded with the filesystem encoding by default" do
@@ -47,7 +47,7 @@ describe "Dir.entries" do
     encoding = Encoding.find("filesystem")
     encoding = Encoding::BINARY if encoding == Encoding::US_ASCII
     platform_is_not :windows do
-      entries.should include("こんにちは.txt".force_encoding(encoding))
+      entries.should include("こんにちは.txt".dup.force_encoding(encoding))
     end
     entries.first.encoding.should equal(Encoding.find("filesystem"))
   end
diff --git a/spec/ruby/core/dir/exist_spec.rb b/spec/ruby/core/dir/exist_spec.rb
index 43987b0f32..0b8e521894 100644
--- a/spec/ruby/core/dir/exist_spec.rb
+++ b/spec/ruby/core/dir/exist_spec.rb
@@ -13,3 +13,9 @@ describe "Dir.exist?" do
 
   it_behaves_like :dir_exist, :exist?
 end
+
+describe "Dir.exists?" do
+  it "has been removed" do
+    Dir.should_not.respond_to?(:exists?)
+  end
+end
diff --git a/spec/ruby/core/dir/exists_spec.rb b/spec/ruby/core/dir/exists_spec.rb
deleted file mode 100644
index 2c6f145db2..0000000000
--- a/spec/ruby/core/dir/exists_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-require_relative 'shared/exist'
-
-describe "Dir.exists?" do
-  before :all do
-    DirSpecs.create_mock_dirs
-  end
-
-  after :all do
-    DirSpecs.delete_mock_dirs
-  end
-
-  it_behaves_like :dir_exist, :exists?
-end
diff --git a/spec/ruby/core/dir/fchdir_spec.rb b/spec/ruby/core/dir/fchdir_spec.rb
new file mode 100644
index 0000000000..52600a95f2
--- /dev/null
+++ b/spec/ruby/core/dir/fchdir_spec.rb
@@ -0,0 +1,73 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/common'
+
+ruby_version_is '3.3' do
+  platform_is_not :windows do
+    describe "Dir.fchdir" do
+      before :all do
+        DirSpecs.create_mock_dirs
+      end
+
+      after :all do
+        DirSpecs.delete_mock_dirs
+      end
+
+      before :each do
+        @original = Dir.pwd
+      end
+
+      after :each do
+        Dir.chdir(@original)
+      end
+
+      it "changes the current working directory to the directory specified by the integer file descriptor" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        Dir.fchdir dir.fileno
+        Dir.pwd.should == DirSpecs.mock_dir
+      ensure
+        dir.close
+      end
+
+      it "returns 0 when successfully changing directory" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        Dir.fchdir(dir.fileno).should == 0
+      ensure
+        dir.close
+      end
+
+      it "returns the value of the block when a block is given" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        Dir.fchdir(dir.fileno) { :block_value }.should == :block_value
+      ensure
+        dir.close
+      end
+
+      it "changes to the specified directory for the duration of the block" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        Dir.fchdir(dir.fileno) { Dir.pwd }.should == DirSpecs.mock_dir
+        Dir.pwd.should == @original
+      ensure
+        dir.close
+      end
+
+      it "raises a SystemCallError if the file descriptor given is not valid" do
+        -> { Dir.fchdir(-1) }.should raise_error(SystemCallError, "Bad file descriptor - fchdir")
+        -> { Dir.fchdir(-1) { } }.should raise_error(SystemCallError, "Bad file descriptor - fchdir")
+      end
+
+      it "raises a SystemCallError if the file descriptor given is not for a directory" do
+        -> { Dir.fchdir $stdout.fileno }.should raise_error(SystemCallError, /(Not a directory|Invalid argument) - fchdir/)
+        -> { Dir.fchdir($stdout.fileno) { } }.should raise_error(SystemCallError, /(Not a directory|Invalid argument) - fchdir/)
+      end
+    end
+  end
+
+  platform_is :windows do
+    describe "Dir.fchdir" do
+      it "raises NotImplementedError" do
+        -> { Dir.fchdir 1 }.should raise_error(NotImplementedError)
+        -> { Dir.fchdir(1) { } }.should raise_error(NotImplementedError)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/dir/fileno_spec.rb b/spec/ruby/core/dir/fileno_spec.rb
index 504e36d44b..bb84ef5378 100644
--- a/spec/ruby/core/dir/fileno_spec.rb
+++ b/spec/ruby/core/dir/fileno_spec.rb
@@ -27,7 +27,7 @@ describe "Dir#fileno" do
 
   if has_dir_fileno
     it "returns the file descriptor of the dir" do
-      @dir.fileno.should be_kind_of(Fixnum)
+      @dir.fileno.should be_kind_of(Integer)
     end
   else
     it "raises an error when not implemented on the platform" do
diff --git a/spec/ruby/core/dir/fixtures/common.rb b/spec/ruby/core/dir/fixtures/common.rb
index f6708b04f7..848656c9b9 100644
--- a/spec/ruby/core/dir/fixtures/common.rb
+++ b/spec/ruby/core/dir/fixtures/common.rb
@@ -22,7 +22,7 @@ module DirSpecs
       [0xe9].pack('U')
     ].each do |dir|
       begin
-        Dir.rmdir dir
+        Dir.rmdir mock_dir(dir)
       rescue
       end
     end
@@ -36,6 +36,8 @@ module DirSpecs
         .dotfile
         .dotsubdir/.dotfile
         .dotsubdir/nondotfile
+        nested/.dotsubir/.dotfile
+        nested/.dotsubir/nondotfile
 
         deeply/.dotfile
         deeply/nested/.dotfile.ext
@@ -79,6 +81,8 @@ module DirSpecs
         special/}
 
         special/test{1}/file[1]
+        special/{}/special
+        special/test\ +()[]{}/hello_world.erb
       ]
 
       platform_is_not :windows do
@@ -89,19 +93,39 @@ module DirSpecs
           special/|
 
           special/こんにちは.txt
+          special/\a
         ]
+        @mock_dir_files << "special/_\u{1f60e}.erb"
       end
     end
 
     @mock_dir_files
   end
 
+  def self.mock_dir_links
+    unless @mock_dir_links
+      @mock_dir_links = []
+      platform_is_not :windows do
+        @mock_dir_links += [
+          ['special/ln', 'subdir_one']
+        ]
+      end
+    end
+    @mock_dir_links
+  end
+
   def self.create_mock_dirs
     mock_dir_files.each do |name|
       file = File.join mock_dir, name
       mkdir_p File.dirname(file)
       touch file
     end
+    mock_dir_links.each do |link, target|
+      full_link = File.join mock_dir, link
+      full_target = File.join mock_dir, target
+
+      File.symlink full_target, full_link
+    end
   end
 
   def self.delete_mock_dirs
@@ -160,10 +184,15 @@ module DirSpecs
       dir_filename_ordering
       file_one.ext
       file_two.ext
+      nested
       nondotfile
       special
       subdir_one
       subdir_two
     ]
   end
+
+  def self.expected_glob_paths
+    expected_paths - ['..']
+  end
 end
diff --git a/spec/ruby/core/dir/for_fd_spec.rb b/spec/ruby/core/dir/for_fd_spec.rb
new file mode 100644
index 0000000000..ba467f2f86
--- /dev/null
+++ b/spec/ruby/core/dir/for_fd_spec.rb
@@ -0,0 +1,79 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/common'
+
+quarantine! do # leads to "Errno::EBADF: Bad file descriptor - closedir" in DirSpecs.delete_mock_dirs
+ruby_version_is '3.3' do
+  platform_is_not :windows do
+    describe "Dir.for_fd" do
+      before :all do
+        DirSpecs.create_mock_dirs
+      end
+
+      after :all do
+        DirSpecs.delete_mock_dirs
+      end
+
+      before :each do
+        @original = Dir.pwd
+      end
+
+      after :each do
+        Dir.chdir(@original)
+      end
+
+      it "returns a new Dir object representing the directory specified by the given integer directory file descriptor" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        dir_new = Dir.for_fd(dir.fileno)
+
+        dir_new.should.instance_of?(Dir)
+        dir_new.children.should == dir.children
+        dir_new.fileno.should == dir.fileno
+      ensure
+        dir.close
+      end
+
+      it "returns a new Dir object without associated path" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        dir_new = Dir.for_fd(dir.fileno)
+
+        dir_new.path.should == nil
+      ensure
+        dir.close
+      end
+
+      it "calls #to_int to convert a value to an Integer" do
+        dir = Dir.new(DirSpecs.mock_dir)
+        obj = mock("fd")
+        obj.should_receive(:to_int).and_return(dir.fileno)
+
+        dir_new = Dir.for_fd(obj)
+        dir_new.fileno.should == dir.fileno
+      ensure
+        dir.close
+      end
+
+      it "raises TypeError when value cannot be converted to Integer" do
+        -> {
+          Dir.for_fd(nil)
+        }.should raise_error(TypeError, "no implicit conversion from nil to integer")
+      end
+
+      it "raises a SystemCallError if the file descriptor given is not valid" do
+        -> { Dir.for_fd(-1) }.should raise_error(SystemCallError, "Bad file descriptor - fdopendir")
+      end
+
+      it "raises a SystemCallError if the file descriptor given is not for a directory" do
+        -> { Dir.for_fd $stdout.fileno }.should raise_error(SystemCallError, "Not a directory - fdopendir")
+      end
+    end
+  end
+
+  platform_is :windows do
+    describe "Dir.for_fd" do
+      it "raises NotImplementedError" do
+        -> { Dir.for_fd 1 }.should raise_error(NotImplementedError)
+      end
+    end
+  end
+end
+end
diff --git a/spec/ruby/core/dir/foreach_spec.rb b/spec/ruby/core/dir/foreach_spec.rb
index 1560b85f8a..9cf34b1d71 100644
--- a/spec/ruby/core/dir/foreach_spec.rb
+++ b/spec/ruby/core/dir/foreach_spec.rb
@@ -39,6 +39,18 @@ describe "Dir.foreach" do
     Dir.foreach(DirSpecs.mock_dir).to_a.sort.should == DirSpecs.expected_paths
   end
 
+  it "accepts an encoding keyword for the encoding of the entries" do
+    dirs = Dir.foreach("#{DirSpecs.mock_dir}/deeply/nested", encoding: "utf-8").to_a.sort
+    dirs.each { |dir| dir.encoding.should == Encoding::UTF_8 }
+
+    dirs = Dir.foreach("#{DirSpecs.mock_dir}/deeply/nested", encoding: Encoding::ISO_8859_1).to_a.sort
+    dirs.each { |dir| dir.encoding.should == Encoding::ISO_8859_1 }
+
+    Dir.foreach("#{DirSpecs.mock_dir}/deeply/nested", encoding: Encoding::ISO_8859_1) do |f|
+      f.encoding.should == Encoding::ISO_8859_1
+    end
+  end
+
   describe "when no block is given" do
     it "returns an Enumerator" do
       Dir.foreach(DirSpecs.mock_dir).should be_an_instance_of(Enumerator)
diff --git a/spec/ruby/core/dir/glob_spec.rb b/spec/ruby/core/dir/glob_spec.rb
index 4b437b0e24..a60b233bc0 100644
--- a/spec/ruby/core/dir/glob_spec.rb
+++ b/spec/ruby/core/dir/glob_spec.rb
@@ -29,6 +29,23 @@ describe "Dir.glob" do
                %w!file_one.ext file_two.ext!
   end
 
+  it 'returns matching file paths when supplied :base keyword argument' do
+    dir = tmp('dir_glob_base')
+    file_1 = "#{dir}/lib/bloop.rb"
+    file_2 = "#{dir}/lib/soup.rb"
+    file_3 = "#{dir}/lib/mismatched_file_type.txt"
+    file_4 = "#{dir}/mismatched_directory.rb"
+
+    touch file_1
+    touch file_2
+    touch file_3
+    touch file_4
+
+    Dir.glob('**/*.rb', base: "#{dir}/lib").sort.should == ["bloop.rb", "soup.rb"].sort
+  ensure
+    rm_r dir
+  end
+
   it "calls #to_path to convert multiple patterns" do
     pat1 = mock('file_one.ext')
     pat1.should_receive(:to_path).and_return('file_one.ext')
@@ -39,7 +56,7 @@ describe "Dir.glob" do
   end
 
   it "matches both dot and non-dotfiles with '*' and option File::FNM_DOTMATCH" do
-    Dir.glob('*', File::FNM_DOTMATCH).sort.should == DirSpecs.expected_paths
+    Dir.glob('*', File::FNM_DOTMATCH).sort.should == DirSpecs.expected_glob_paths
   end
 
   it "matches files with any beginning with '*<non-special characters>' and option File::FNM_DOTMATCH" do
@@ -47,7 +64,7 @@ describe "Dir.glob" do
   end
 
   it "matches any files in the current directory with '**' and option File::FNM_DOTMATCH" do
-    Dir.glob('**', File::FNM_DOTMATCH).sort.should == DirSpecs.expected_paths
+    Dir.glob('**', File::FNM_DOTMATCH).sort.should == DirSpecs.expected_glob_paths
   end
 
   it "recursively matches any subdirectories except './' or '../' with '**/' from the current directory and option File::FNM_DOTMATCH" do
@@ -59,8 +76,12 @@ describe "Dir.glob" do
       deeply/nested/directory/
       deeply/nested/directory/structure/
       dir/
+      nested/
+      nested/.dotsubir/
       special/
+      special/test\ +()[]{}/
       special/test{1}/
+      special/{}/
       subdir_one/
       subdir_two/
     ]
@@ -68,6 +89,17 @@ describe "Dir.glob" do
     Dir.glob('**/', File::FNM_DOTMATCH).sort.should == expected
   end
 
+  it "recursively matches files and directories in nested dot subdirectory except . with 'nested/**/*' from the current directory and option File::FNM_DOTMATCH" do
+    expected = %w[
+      nested/.
+      nested/.dotsubir
+      nested/.dotsubir/.dotfile
+      nested/.dotsubir/nondotfile
+    ]
+
+    Dir.glob('nested/**/*', File::FNM_DOTMATCH).sort.should == expected.sort
+  end
+
   # This is a separate case to check **/ coming after a constant
   # directory as well.
   it "recursively matches any subdirectories except './' or '../' with '**/' and option File::FNM_DOTMATCH" do
@@ -80,8 +112,12 @@ describe "Dir.glob" do
       ./deeply/nested/directory/
       ./deeply/nested/directory/structure/
       ./dir/
+      ./nested/
+      ./nested/.dotsubir/
       ./special/
+      ./special/test\ +()[]{}/
       ./special/test{1}/
+      ./special/{}/
       ./subdir_one/
       ./subdir_two/
     ]
@@ -102,6 +138,14 @@ describe "Dir.glob" do
     Dir.glob('{deeply/**/,subdir_two/*}').sort.should == expected
   end
 
+  it "preserves multiple /s before a **" do
+    expected = %w[
+      deeply//nested/directory/structure
+    ]
+
+    Dir.glob('{deeply//**/structure}').sort.should == expected
+  end
+
   it "accepts a block and yields it with each elements" do
     ary = []
     ret = Dir.glob(["file_o*", "file_t*"]) { |t| ary << t }
@@ -119,7 +163,132 @@ describe "Dir.glob" do
   end
 
   it "handles infinite directory wildcards" do
-    Dir.glob('**/**/**').empty?.should == false
+    Dir.glob('**/**/**').should_not.empty?
+  end
+
+  it "handles **/** with base keyword argument" do
+    Dir.glob('**/**', base: "dir").should == ["filename_ordering"]
+
+    expected = %w[
+      nested
+      nested/directory
+      nested/directory/structure
+      nested/directory/structure/bar
+      nested/directory/structure/baz
+      nested/directory/structure/file_one
+      nested/directory/structure/file_one.ext
+      nested/directory/structure/foo
+      nondotfile
+    ].sort
+
+    Dir.glob('**/**', base: "deeply").sort.should == expected
+  end
+
+  it "handles **/ with base keyword argument" do
+    expected = %w[
+      /
+      directory/
+      directory/structure/
+    ]
+    Dir.glob('**/', base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/nondotfile with base keyword argument" do
+    expected = %w[
+      deeply/nondotfile
+      nondotfile
+      subdir_one/nondotfile
+      subdir_two/nondotfile
+    ]
+    Dir.glob('**/nondotfile', base: ".").sort.should == expected
+  end
+
+  it "handles **/nondotfile with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .dotsubdir/nondotfile
+      deeply/nondotfile
+      nested/.dotsubir/nondotfile
+      nondotfile
+      subdir_one/nondotfile
+      subdir_two/nondotfile
+    ]
+    Dir.glob('**/nondotfile', File::FNM_DOTMATCH, base: ".").sort.should == expected
+  end
+
+  it "handles **/.dotfile with base keyword argument" do
+    expected = %w[
+      .dotfile
+      deeply/.dotfile
+      subdir_one/.dotfile
+    ]
+    Dir.glob('**/.dotfile', base: ".").sort.should == expected
+  end
+
+  it "handles **/.dotfile with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .dotfile
+      .dotsubdir/.dotfile
+      deeply/.dotfile
+      nested/.dotsubir/.dotfile
+      subdir_one/.dotfile
+    ]
+    Dir.glob('**/.dotfile', File::FNM_DOTMATCH, base: ".").sort.should == expected
+  end
+
+  it "handles **/.* with base keyword argument" do
+    expected = %w[
+      .dotfile.ext
+      directory/structure/.ext
+    ].sort
+
+    Dir.glob('**/.*', base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/.* with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .
+      .dotfile.ext
+      directory/structure/.ext
+    ].sort
+
+    Dir.glob('**/.*', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/** with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .
+      .dotfile.ext
+      directory
+      directory/structure
+      directory/structure/.ext
+      directory/structure/bar
+      directory/structure/baz
+      directory/structure/file_one
+      directory/structure/file_one.ext
+      directory/structure/foo
+    ].sort
+
+    Dir.glob('**/**', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/*pattern* with base keyword argument and FNM_DOTMATCH" do
+    expected = %w[
+      .dotfile.ext
+      directory/structure/file_one
+      directory/structure/file_one.ext
+    ]
+
+    Dir.glob('**/*file*', File::FNM_DOTMATCH, base: "deeply/nested").sort.should == expected
+  end
+
+  it "handles **/glob with base keyword argument and FNM_EXTGLOB" do
+    expected = %w[
+      directory/structure/bar
+      directory/structure/file_one
+      directory/structure/file_one.ext
+    ]
+
+    Dir.glob('**/*{file,bar}*', File::FNM_EXTGLOB, base: "deeply/nested").sort.should == expected
   end
 
   it "handles simple filename patterns" do
@@ -164,5 +333,30 @@ describe "Dir.glob" do
         Dir.rmdir('no_permission')
       end
     end
+
+    it "will follow symlinks when processing a `*/` pattern." do
+      expected = ['special/ln/nondotfile']
+      Dir.glob('special/*/nondotfile').should == expected
+    end
+
+    it "will not follow symlinks when recursively traversing directories" do
+      expected = %w[
+        deeply/nondotfile
+        nondotfile
+        subdir_one/nondotfile
+        subdir_two/nondotfile
+      ]
+      Dir.glob('**/nondotfile').sort.should == expected
+    end
+
+    it "will follow symlinks when testing directory after recursive directory in pattern" do
+      expected = %w[
+        deeply/nondotfile
+        special/ln/nondotfile
+        subdir_one/nondotfile
+        subdir_two/nondotfile
+      ]
+      Dir.glob('**/*/nondotfile').sort.should == expected
+    end
   end
 end
diff --git a/spec/ruby/core/dir/home_spec.rb b/spec/ruby/core/dir/home_spec.rb
index cdfc9346dc..966ac38af3 100644
--- a/spec/ruby/core/dir/home_spec.rb
+++ b/spec/ruby/core/dir/home_spec.rb
@@ -17,29 +17,69 @@ describe "Dir.home" do
     end
 
     it "returns a non-frozen string" do
-      Dir.home.frozen?.should == false
+      Dir.home.should_not.frozen?
     end
-  end
 
-  describe "when called with the current user name" do
-    platform_is :solaris do
-      it "returns the named user's home directory from the user database" do
-        Dir.home(ENV['USER']).should == `getent passwd #{ENV['USER']}|cut -d: -f6`.chomp
+    it "returns a string with the filesystem encoding" do
+      Dir.home.encoding.should == Encoding.find("filesystem")
+    end
+
+    platform_is_not :windows do
+      it "works even if HOME is unset" do
+        ENV.delete('HOME')
+        Dir.home.should.start_with?('/')
+        Dir.home.encoding.should == Encoding.find("filesystem")
+      end
+    end
+
+    platform_is :windows do
+      it "returns the home directory with forward slashs and as UTF-8" do
+        ENV['HOME'] = "C:\\rubyspäc\\home"
+        home = Dir.home
+        home.should == "C:/rubyspäc/home"
+        home.encoding.should == Encoding::UTF_8
+      end
+
+      it "retrieves the directory from HOME, USERPROFILE, HOMEDRIVE/HOMEPATH and the WinAPI in that order" do
+        old_dirs = [ENV.delete('HOME'), ENV.delete('USERPROFILE'), ENV.delete('HOMEDRIVE'), ENV.delete('HOMEPATH')]
+
+        Dir.home.should == old_dirs[1].gsub("\\", "/")
+        ENV['HOMEDRIVE'] = "C:"
+        ENV['HOMEPATH'] = "\\rubyspec\\home1"
+        Dir.home.should == "C:/rubyspec/home1"
+        ENV['USERPROFILE'] = "C:\\rubyspec\\home2"
+        Dir.home.should == "C:/rubyspec/home2"
+        ENV['HOME'] = "C:\\rubyspec\\home3"
+        Dir.home.should == "C:/rubyspec/home3"
+      ensure
+        ENV['HOME'], ENV['USERPROFILE'], ENV['HOMEDRIVE'], ENV['HOMEPATH'] = *old_dirs
       end
     end
+  end
 
-    platform_is_not :windows, :solaris do
+  describe "when called with the current user name" do
+    platform_is_not :windows, :android, :wasi do
       it "returns the named user's home directory, from the user database" do
         Dir.home(ENV['USER']).should == `echo ~#{ENV['USER']}`.chomp
       end
     end
 
     it "returns a non-frozen string" do
-      Dir.home(ENV['USER']).frozen?.should == false
+      Dir.home(ENV['USER']).should_not.frozen?
+    end
+
+    it "returns a string with the filesystem encoding" do
+      Dir.home(ENV['USER']).encoding.should == Encoding.find("filesystem")
     end
   end
 
   it "raises an ArgumentError if the named user doesn't exist" do
     -> { Dir.home('geuw2n288dh2k') }.should raise_error(ArgumentError)
   end
+
+  describe "when called with a nil user name" do
+    it "returns the current user's home directory, reading $HOME first" do
+      Dir.home(nil).should == "/rubyspec_home"
+    end
+  end
 end
diff --git a/spec/ruby/core/dir/mkdir_spec.rb b/spec/ruby/core/dir/mkdir_spec.rb
index 58767a5aa0..076ec19dd9 100644
--- a/spec/ruby/core/dir/mkdir_spec.rb
+++ b/spec/ruby/core/dir/mkdir_spec.rb
@@ -13,43 +13,63 @@ describe "Dir.mkdir" do
   it "creates the named directory with the given permissions" do
     DirSpecs.clear_dirs
 
+    nonexisting = DirSpecs.mock_dir('nonexisting')
+    default_perms = DirSpecs.mock_dir('default_perms')
+    reduced = DirSpecs.mock_dir('reduced')
     begin
-      File.exist?('nonexisting').should == false
-      Dir.mkdir 'nonexisting'
-      File.exist?('nonexisting').should == true
+      File.should_not.exist?(nonexisting)
+      Dir.mkdir nonexisting
+      File.should.exist?(nonexisting)
       platform_is_not :windows do
-        Dir.mkdir 'default_perms'
-        a = File.stat('default_perms').mode
-        Dir.mkdir 'reduced', (a - 1)
-        File.stat('reduced').mode.should_not == a
+        Dir.mkdir default_perms
+        a = File.stat(default_perms).mode
+        Dir.mkdir reduced, (a - 1)
+        File.stat(reduced).mode.should_not == a
       end
       platform_is :windows do
-        Dir.mkdir 'default_perms', 0666
-        a = File.stat('default_perms').mode
-        Dir.mkdir 'reduced', 0444
-        File.stat('reduced').mode.should_not == a
+        Dir.mkdir default_perms, 0666
+        a = File.stat(default_perms).mode
+        Dir.mkdir reduced, 0444
+        File.stat(reduced).mode.should_not == a
       end
 
-      Dir.mkdir('always_returns_0').should == 0
+      always_returns_0 = DirSpecs.mock_dir('always_returns_0')
+      Dir.mkdir(always_returns_0).should == 0
       platform_is_not(:windows) do
-        File.chmod(0777, "nonexisting","default_perms","reduced","always_returns_0")
+        File.chmod(0777, nonexisting, default_perms, reduced, always_returns_0)
       end
       platform_is_not(:windows) do
-        File.chmod(0644, "nonexisting","default_perms","reduced","always_returns_0")
+        File.chmod(0644, nonexisting, default_perms, reduced, always_returns_0)
       end
     ensure
       DirSpecs.clear_dirs
     end
   end
 
-  it "calls #to_path on non-String arguments" do
+  it "calls #to_path on non-String path arguments" do
     DirSpecs.clear_dirs
     p = mock('path')
-    p.should_receive(:to_path).and_return('nonexisting')
+    p.should_receive(:to_path).and_return(DirSpecs.mock_dir('nonexisting'))
     Dir.mkdir(p)
     DirSpecs.clear_dirs
   end
 
+  it "calls #to_int on non-Integer permissions argument" do
+    DirSpecs.clear_dirs
+    path = DirSpecs.mock_dir('nonexisting')
+    permissions = mock('permissions')
+    permissions.should_receive(:to_int).and_return(0666)
+    Dir.mkdir(path, permissions)
+    DirSpecs.clear_dirs
+  end
+
+  it "raises TypeError if non-Integer permissions argument does not have #to_int method" do
+    path = DirSpecs.mock_dir('nonexisting')
+    permissions = Object.new
+
+    -> { Dir.mkdir(path, permissions) }.should raise_error(TypeError, 'no implicit conversion of Object into Integer')
+  end
+
   it "raises a SystemCallError if any of the directories in the path before the last does not exist" do
     -> { Dir.mkdir "#{DirSpecs.nonexistent}/subdir" }.should raise_error(SystemCallError)
   end
diff --git a/spec/ruby/core/dir/read_spec.rb b/spec/ruby/core/dir/read_spec.rb
index 59de2e81cf..276930c6b7 100644
--- a/spec/ruby/core/dir/read_spec.rb
+++ b/spec/ruby/core/dir/read_spec.rb
@@ -39,5 +39,38 @@ describe "Dir#read" do
     entries.sort.should == DirSpecs.expected_paths
   end
 
+  platform_is_not :windows do
+    it "returns all directory entries even when encoding conversion will fail" do
+      dir = Dir.open(File.join(DirSpecs.mock_dir, 'special'))
+      utf8_entries = []
+      begin
+        while entry = dir.read
+          utf8_entries << entry
+        end
+      ensure
+        dir.close
+      end
+      old_internal_encoding = Encoding::default_internal
+      old_external_encoding = Encoding::default_external
+      Encoding.default_internal = Encoding::UTF_8
+      Encoding.default_external = Encoding::SHIFT_JIS
+      shift_jis_entries = []
+      begin
+        Dir.open(File.join(DirSpecs.mock_dir, 'special')) do |d|
+          -> {
+            while entry = d.read
+              shift_jis_entries << entry
+            end
+          }.should_not raise_error
+        end
+      ensure
+        Encoding.default_internal = old_internal_encoding
+        Encoding.default_external = old_external_encoding
+      end
+      shift_jis_entries.size.should == utf8_entries.size
+      shift_jis_entries.filter { |f| f.encoding == Encoding::SHIFT_JIS }.size.should == 1
+    end
+  end
+
   it_behaves_like :dir_closed, :read
 end
diff --git a/spec/ruby/core/dir/shared/chroot.rb b/spec/ruby/core/dir/shared/chroot.rb
index 93699f93be..a8f7c10a19 100644
--- a/spec/ruby/core/dir/shared/chroot.rb
+++ b/spec/ruby/core/dir/shared/chroot.rb
@@ -2,8 +2,8 @@ describe :dir_chroot_as_root, shared: true do
   before :all do
     DirSpecs.create_mock_dirs
 
-    @real_root = "../" * (File.dirname(__FILE__).count('/') - 1)
-    @ref_dir = File.join("/", Dir.new('/').entries.first)
+    @real_root = "../" * (__dir__.count('/') - 1)
+    @ref_dir = File.join("/", File.basename(Dir["/*"].first))
   end
 
   after :all do
@@ -14,10 +14,13 @@ describe :dir_chroot_as_root, shared: true do
     DirSpecs.delete_mock_dirs
   end
 
+  # Pending until https://github.com/ruby/ruby/runs/8075149420 is fixed
+  compilations_ci = ENV["GITHUB_WORKFLOW"] == "Compilations"
+
   it "can be used to change the process' root directory" do
-    -> { Dir.send(@method, File.dirname(__FILE__)) }.should_not raise_error
-    File.exist?("/#{File.basename(__FILE__)}").should be_true
-  end
+    -> { Dir.send(@method, __dir__) }.should_not raise_error
+    File.should.exist?("/#{File.basename(__FILE__)}")
+  end unless compilations_ci
 
   it "returns 0 if successful" do
     Dir.send(@method, '/').should == 0
@@ -29,9 +32,9 @@ describe :dir_chroot_as_root, shared: true do
 
   it "can be escaped from with ../" do
     Dir.send(@method, @real_root)
-    File.exist?(@ref_dir).should be_true
-    File.exist?("/#{File.basename(__FILE__)}").should be_false
-  end
+    File.should.exist?(@ref_dir)
+    File.should_not.exist?("/#{File.basename(__FILE__)}")
+  end unless compilations_ci
 
   it "calls #to_path on non-String argument" do
     p = mock('path')
diff --git a/spec/ruby/core/dir/shared/delete.rb b/spec/ruby/core/dir/shared/delete.rb
index 49e88360e8..a81b059759 100644
--- a/spec/ruby/core/dir/shared/delete.rb
+++ b/spec/ruby/core/dir/shared/delete.rb
@@ -17,20 +17,10 @@ describe :dir_delete, shared: true do
     Dir.send(@method, p)
   end
 
-  platform_is_not :solaris do
-    it "raises an Errno::ENOTEMPTY when trying to remove a nonempty directory" do
-      -> do
-        Dir.send @method, DirSpecs.mock_rmdir("nonempty")
-      end.should raise_error(Errno::ENOTEMPTY)
-    end
-  end
-
-  platform_is :solaris do
-    it "raises an Errno::EEXIST when trying to remove a nonempty directory" do
-      -> do
-        Dir.send @method, DirSpecs.mock_rmdir("nonempty")
-      end.should raise_error(Errno::EEXIST)
-    end
+  it "raises an Errno::ENOTEMPTY when trying to remove a nonempty directory" do
+    -> do
+      Dir.send @method, DirSpecs.mock_rmdir("nonempty")
+    end.should raise_error(Errno::ENOTEMPTY)
   end
 
   it "raises an Errno::ENOENT when trying to remove a non-existing directory" do
diff --git a/spec/ruby/core/dir/shared/exist.rb b/spec/ruby/core/dir/shared/exist.rb
index fbd2c9862d..3097f57715 100644
--- a/spec/ruby/core/dir/shared/exist.rb
+++ b/spec/ruby/core/dir/shared/exist.rb
@@ -1,6 +1,6 @@
 describe :dir_exist, shared: true do
   it "returns true if the given directory exists" do
-    Dir.send(@method, File.dirname(__FILE__)).should be_true
+    Dir.send(@method, __dir__).should be_true
   end
 
   it "returns true for '.'" do
@@ -20,7 +20,7 @@ describe :dir_exist, shared: true do
   end
 
   it "understands relative paths" do
-    Dir.send(@method, File.dirname(__FILE__) + '/../').should be_true
+    Dir.send(@method, __dir__ + '/../').should be_true
   end
 
   it "returns false if the given directory doesn't exist" do
@@ -28,18 +28,19 @@ describe :dir_exist, shared: true do
   end
 
   it "doesn't require the name to have a trailing slash" do
-    dir = File.dirname(__FILE__)
+    dir = __dir__
     dir.sub!(/\/$/,'')
     Dir.send(@method, dir).should be_true
   end
 
   it "doesn't expand paths" do
+    skip "$HOME not valid directory" unless ENV['HOME'] && File.directory?(ENV['HOME'])
     Dir.send(@method, File.expand_path('~')).should be_true
     Dir.send(@method, '~').should be_false
   end
 
   it "returns false if the argument exists but is a file" do
-    File.exist?(__FILE__).should be_true
+    File.should.exist?(__FILE__)
     Dir.send(@method, __FILE__).should be_false
   end
 
@@ -50,7 +51,7 @@ describe :dir_exist, shared: true do
 
   it "calls #to_path on non String arguments" do
     p = mock('path')
-    p.should_receive(:to_path).and_return(File.dirname(__FILE__))
+    p.should_receive(:to_path).and_return(__dir__)
     Dir.send(@method, p)
   end
 end
diff --git a/spec/ruby/core/dir/shared/glob.rb b/spec/ruby/core/dir/shared/glob.rb
index 62675145df..b1fc924f08 100644
--- a/spec/ruby/core/dir/shared/glob.rb
+++ b/spec/ruby/core/dir/shared/glob.rb
@@ -12,7 +12,7 @@ describe :dir_glob, shared: true do
   end
 
   it "raises an Encoding::CompatibilityError if the argument encoding is not compatible with US-ASCII" do
-    pattern = "file*".force_encoding Encoding::UTF_16BE
+    pattern = "files*".dup.force_encoding Encoding::UTF_16BE
     -> { Dir.send(@method, pattern) }.should raise_error(Encoding::CompatibilityError)
   end
 
@@ -23,26 +23,29 @@ describe :dir_glob, shared: true do
     Dir.send(@method, obj).should == %w[file_one.ext]
   end
 
-  ruby_version_is ""..."2.6" do
-    it "splits the string on \\0 if there is only one string given" do
-      Dir.send(@method, "file_o*\0file_t*").should ==
-        %w!file_one.ext file_two.ext!
-    end
+  it "raises an ArgumentError if the string contains \\0" do
+    -> {Dir.send(@method, "file_o*\0file_t*")}.should raise_error ArgumentError, /nul-separated/
   end
 
-  ruby_version_is "2.6"..."2.7" do
-    it "splits the string on \\0 if there is only one string given and warns" do
-      -> {
-        Dir.send(@method, "file_o*\0file_t*").should ==
-          %w!file_one.ext file_two.ext!
-      }.should complain(/warning: use glob patterns list instead of nul-separated patterns/)
-    end
+  it "result is sorted by default" do
+    result = Dir.send(@method, '*')
+    result.should == result.sort
   end
 
-  ruby_version_is "2.7" do
-    it "raises an ArgumentError if the string contains \\0" do
-      -> {Dir.send(@method, "file_o*\0file_t*")}.should raise_error ArgumentError, /nul-separated/
-    end
+  it "result is sorted with sort: true" do
+    result = Dir.send(@method, '*', sort: true)
+    result.should == result.sort
+  end
+
+  it "sort: false returns same files" do
+    result = Dir.send(@method,'*', sort: false)
+    result.sort.should == Dir.send(@method, '*').sort
+  end
+
+  it "raises an ArgumentError if sort: is not true or false" do
+    -> { Dir.send(@method, '*', sort: 0) }.should raise_error ArgumentError, /expected true or false/
+    -> { Dir.send(@method, '*', sort: nil) }.should raise_error ArgumentError, /expected true or false/
+    -> { Dir.send(@method, '*', sort: 'false') }.should raise_error ArgumentError, /expected true or false/
   end
 
   it "matches non-dotfiles with '*'" do
@@ -53,6 +56,7 @@ describe :dir_glob, shared: true do
       dir_filename_ordering
       file_one.ext
       file_two.ext
+      nested
       nondotfile
       special
       subdir_one
@@ -70,6 +74,10 @@ describe :dir_glob, shared: true do
     Dir.send(@method, 'special/+').should == ['special/+']
   end
 
+  it "matches directories with special characters when escaped" do
+    Dir.send(@method, 'special/\{}/special').should == ["special/{}/special"]
+  end
+
   platform_is_not :windows do
     it "matches regexp special *" do
       Dir.send(@method, 'special/\*').should == ['special/*']
@@ -82,6 +90,14 @@ describe :dir_glob, shared: true do
     it "matches regexp special |" do
       Dir.send(@method, 'special/|').should == ['special/|']
     end
+
+    it "matches files with backslashes in their name" do
+      Dir.glob('special/\\\\{a,b}').should == ['special/\a']
+    end
+
+    it "matches directory with special characters in their name in complex patterns" do
+      Dir.glob("special/test +()\\[\\]\\{\\}/hello_world{.{en},}{.{html},}{+{phone},}{.{erb},}").should == ['special/test +()[]{}/hello_world.erb']
+    end
   end
 
   it "matches regexp special ^" do
@@ -120,8 +136,8 @@ describe :dir_glob, shared: true do
     Dir.send(@method, 'special/test\{1\}/*').should == ['special/test{1}/file[1]']
   end
 
-  it "matches dotfiles with '.*'" do
-    Dir.send(@method, '.*').sort.should == %w|. .. .dotfile .dotsubdir|.sort
+  it "matches dotfiles except .. with '.*'" do
+    Dir.send(@method, '.*').sort.should == %w|. .dotfile .dotsubdir|.sort
   end
 
   it "matches non-dotfiles with '*<non-special characters>'" do
@@ -156,6 +172,7 @@ describe :dir_glob, shared: true do
       dir_filename_ordering
       file_one.ext
       file_two.ext
+      nested
       nondotfile
       special
       subdir_one
@@ -165,8 +182,8 @@ describe :dir_glob, shared: true do
     Dir.send(@method, '**').sort.should == expected
   end
 
-  it "matches dotfiles in the current directory with '.**'" do
-    Dir.send(@method, '.**').sort.should == %w|. .. .dotsubdir .dotfile|.sort
+  it "matches dotfiles in the current directory except .. with '.**'" do
+    Dir.send(@method, '.**').sort.should == %w|. .dotsubdir .dotfile|.sort
   end
 
   it "recursively matches any nondot subdirectories with '**/'" do
@@ -177,8 +194,11 @@ describe :dir_glob, shared: true do
       deeply/nested/directory/
       deeply/nested/directory/structure/
       dir/
+      nested/
       special/
+      special/test\ +()[]{}/
       special/test{1}/
+      special/{}/
       subdir_one/
       subdir_two/
     ]
@@ -186,9 +206,17 @@ describe :dir_glob, shared: true do
     Dir.send(@method, '**/').sort.should == expected
   end
 
-  it "recursively matches any subdirectories including ./ and ../ with '.**/'" do
+  it "recursively matches any subdirectories except './' or '../' with '**/' from the base directory if that is specified" do
+    expected = %w[
+      nested/directory
+    ]
+
+    Dir.send(@method, '**/*ory', base: 'deeply').sort.should == expected
+  end
+
+  it "recursively matches any subdirectories including ./ with '.**/'" do
     Dir.chdir("#{DirSpecs.mock_dir}/subdir_one") do
-      Dir.send(@method, '.**/').sort.should == %w|./ ../|.sort
+      Dir.send(@method, '.**/').should == ['./']
     end
   end
 
@@ -231,7 +259,7 @@ describe :dir_glob, shared: true do
   end
 
   it "matches dot or non-dotfiles with '{,.}*'" do
-    Dir.send(@method, '{,.}*').sort.should == DirSpecs.expected_paths
+    Dir.send(@method, '{,.}*').sort.should == DirSpecs.expected_glob_paths
   end
 
   it "respects the order of {} expressions, expanding left most first" do
@@ -291,74 +319,72 @@ describe :dir_glob, shared: true do
     end
   end
 
-  ruby_version_is "2.5" do
-    context ":base option passed" do
-      before :each do
-        @mock_dir = File.expand_path tmp('dir_glob_mock')
-
-        %w[
-          a/b/x
-          a/b/c/y
-          a/b/c/d/z
-        ].each do |path|
-          file = File.join @mock_dir, path
-          mkdir_p File.dirname(file)
-          touch file
-        end
-      end
+  context ":base option passed" do
+    before :each do
+      @mock_dir = File.expand_path tmp('dir_glob_mock')
 
-      after :each do
-        rm_r @mock_dir
+      %w[
+        a/b/x
+        a/b/c/y
+        a/b/c/d/z
+      ].each do |path|
+        file = File.join @mock_dir, path
+        mkdir_p File.dirname(file)
+        touch file
       end
+    end
 
-      it "matches entries only from within the specified directory" do
-        path = File.join(@mock_dir, "a/b/c")
-        Dir.send(@method, "*", base: path).sort.should == %w( d y )
-      end
+    after :each do
+      rm_r @mock_dir
+    end
 
-      it "accepts both relative and absolute paths" do
-        require 'pathname'
+    it "matches entries only from within the specified directory" do
+      path = File.join(@mock_dir, "a/b/c")
+      Dir.send(@method, "*", base: path).sort.should == %w( d y )
+    end
 
-        path_abs = File.join(@mock_dir, "a/b/c")
-        path_rel = Pathname.new(path_abs).relative_path_from(Pathname.new(Dir.pwd))
+    it "accepts both relative and absolute paths" do
+      require 'pathname'
 
-        result_abs = Dir.send(@method, "*", base: path_abs).sort
-        result_rel = Dir.send(@method, "*", base: path_rel).sort
+      path_abs = File.join(@mock_dir, "a/b/c")
+      path_rel = Pathname.new(path_abs).relative_path_from(Pathname.new(Dir.pwd))
 
-        result_abs.should == %w( d y )
-        result_rel.should == %w( d y )
-      end
+      result_abs = Dir.send(@method, "*", base: path_abs).sort
+      result_rel = Dir.send(@method, "*", base: path_rel).sort
 
-      it "returns [] if specified path does not exist" do
-        path = File.join(@mock_dir, "fake-name")
-        File.exist?(path).should == false
+      result_abs.should == %w( d y )
+      result_rel.should == %w( d y )
+    end
 
-        Dir.send(@method, "*", base: path).should == []
-      end
+    it "returns [] if specified path does not exist" do
+      path = File.join(@mock_dir, "fake-name")
+      File.should_not.exist?(path)
 
-      it "returns [] if specified path is a file" do
-        path = File.join(@mock_dir, "a/b/x")
-        File.exist?(path).should == true
+      Dir.send(@method, "*", base: path).should == []
+    end
 
-        Dir.send(@method, "*", base: path).should == []
-      end
+    it "returns [] if specified path is a file" do
+      path = File.join(@mock_dir, "a/b/x")
+      File.should.exist?(path)
 
-      it "raises TypeError when cannot convert value to string" do
-        -> {
-          Dir.send(@method, "*", base: [])
-        }.should raise_error(TypeError)
-      end
+      Dir.send(@method, "*", base: path).should == []
+    end
 
-      it "handles '' as current directory path" do
-        Dir.chdir @mock_dir do
-          Dir.send(@method, "*", base: "").should == %w( a )
-        end
+    it "raises TypeError when cannot convert value to string" do
+      -> {
+        Dir.send(@method, "*", base: [])
+      }.should raise_error(TypeError)
+    end
+
+    it "handles '' as current directory path" do
+      Dir.chdir @mock_dir do
+        Dir.send(@method, "*", base: "").should == %w( a )
       end
+    end
 
-      it "handles nil as current directory path" do
-        Dir.chdir @mock_dir do
-          Dir.send(@method, "*", base: nil).should == %w( a )
-        end
+    it "handles nil as current directory path" do
+      Dir.chdir @mock_dir do
+        Dir.send(@method, "*", base: nil).should == %w( a )
       end
     end
   end
diff --git a/spec/ruby/core/dir/shared/open.rb b/spec/ruby/core/dir/shared/open.rb
index fb2af71e05..920845cba1 100644
--- a/spec/ruby/core/dir/shared/open.rb
+++ b/spec/ruby/core/dir/shared/open.rb
@@ -52,7 +52,7 @@ describe :dir_open, shared: true do
     options = mock("dir_open")
     options.should_receive(:to_hash).and_return({ encoding: Encoding::UTF_8 })
 
-    dir = Dir.send(@method, DirSpecs.mock_dir, options) {|d| d }
+    dir = Dir.send(@method, DirSpecs.mock_dir, **options) {|d| d }
     dir.should be_kind_of(Dir)
   end
 
@@ -66,7 +66,7 @@ describe :dir_open, shared: true do
       Dir.send(@method, DirSpecs.mock_dir) do |dir|
         io = IO.for_fd(dir.fileno)
         io.autoclose = false
-        io.close_on_exec?.should == true
+        io.should.close_on_exec?
       end
     end
   end
diff --git a/spec/ruby/core/encoding/compatible_spec.rb b/spec/ruby/core/encoding/compatible_spec.rb
index dc47a6553a..31376a3b75 100644
--- a/spec/ruby/core/encoding/compatible_spec.rb
+++ b/spec/ruby/core/encoding/compatible_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require_relative '../../spec_helper'
 
@@ -7,7 +7,7 @@ require_relative '../../spec_helper'
 describe "Encoding.compatible? String, String" do
   describe "when the first's Encoding is valid US-ASCII" do
     before :each do
-      @str = "abc".force_encoding Encoding::US_ASCII
+      @str = "abc".dup.force_encoding Encoding::US_ASCII
     end
 
     it "returns US-ASCII when the second's is US-ASCII" do
@@ -33,28 +33,28 @@ describe "Encoding.compatible? String, String" do
 
   describe "when the first's Encoding is ASCII compatible and ASCII only" do
     it "returns the first's Encoding if the second is ASCII compatible and ASCII only" do
-      [ [Encoding, "abc".force_encoding("UTF-8"), "123".force_encoding("Shift_JIS"), Encoding::UTF_8],
-        [Encoding, "123".force_encoding("Shift_JIS"), "abc".force_encoding("UTF-8"), Encoding::Shift_JIS]
+      [ [Encoding, "abc".dup.force_encoding("UTF-8"), "123".dup.force_encoding("Shift_JIS"), Encoding::UTF_8],
+        [Encoding, "123".dup.force_encoding("Shift_JIS"), "abc".dup.force_encoding("UTF-8"), Encoding::Shift_JIS]
       ].should be_computed_by(:compatible?)
     end
 
     it "returns the first's Encoding if the second is ASCII compatible and ASCII only" do
-      [ [Encoding, "abc".force_encoding("BINARY"), "123".force_encoding("US-ASCII"), Encoding::BINARY],
-        [Encoding, "123".force_encoding("US-ASCII"), "abc".force_encoding("BINARY"), Encoding::US_ASCII]
+      [ [Encoding, "abc".dup.force_encoding("BINARY"), "123".dup.force_encoding("US-ASCII"), Encoding::BINARY],
+        [Encoding, "123".dup.force_encoding("US-ASCII"), "abc".dup.force_encoding("BINARY"), Encoding::US_ASCII]
       ].should be_computed_by(:compatible?)
     end
 
     it "returns the second's Encoding if the second is ASCII compatible but not ASCII only" do
-      [ [Encoding, "abc".force_encoding("UTF-8"), "\xff".force_encoding("Shift_JIS"), Encoding::Shift_JIS],
-        [Encoding, "123".force_encoding("Shift_JIS"), "\xff".force_encoding("UTF-8"), Encoding::UTF_8],
-        [Encoding, "abc".force_encoding("BINARY"), "\xff".force_encoding("US-ASCII"), Encoding::US_ASCII],
-        [Encoding, "123".force_encoding("US-ASCII"), "\xff".force_encoding("BINARY"), Encoding::BINARY],
+      [ [Encoding, "abc".dup.force_encoding("UTF-8"), "\xff".dup.force_encoding("Shift_JIS"), Encoding::Shift_JIS],
+        [Encoding, "123".dup.force_encoding("Shift_JIS"), "\xff".dup.force_encoding("UTF-8"), Encoding::UTF_8],
+        [Encoding, "abc".dup.force_encoding("BINARY"), "\xff".dup.force_encoding("US-ASCII"), Encoding::US_ASCII],
+        [Encoding, "123".dup.force_encoding("US-ASCII"), "\xff".dup.force_encoding("BINARY"), Encoding::BINARY],
       ].should be_computed_by(:compatible?)
     end
 
     it "returns nil if the second's Encoding is not ASCII compatible" do
-      a = "abc".force_encoding("UTF-8")
-      b = "123".force_encoding("UTF-16LE")
+      a = "abc".dup.force_encoding("UTF-8")
+      b = "1234".dup.force_encoding("UTF-16LE")
       Encoding.compatible?(a, b).should be_nil
     end
   end
@@ -75,7 +75,7 @@ describe "Encoding.compatible? String, String" do
 
   describe "when the first's Encoding is not ASCII compatible" do
     before :each do
-      @str = "abc".force_encoding Encoding::UTF_7
+      @str = "abc".dup.force_encoding Encoding::UTF_7
     end
 
     it "returns nil when the second String is US-ASCII" do
@@ -91,14 +91,14 @@ describe "Encoding.compatible? String, String" do
     end
 
     it "returns the Encoding when the second's Encoding is not ASCII compatible but the same as the first's Encoding" do
-      encoding = Encoding.compatible?(@str, "def".force_encoding("utf-7"))
+      encoding = Encoding.compatible?(@str, "def".dup.force_encoding("utf-7"))
       encoding.should == Encoding::UTF_7
     end
   end
 
   describe "when the first's Encoding is invalid" do
     before :each do
-      @str = "\xff".force_encoding Encoding::UTF_8
+      @str = "\xff".dup.force_encoding Encoding::UTF_8
     end
 
     it "returns the first's Encoding when the second's Encoding is US-ASCII" do
@@ -114,11 +114,11 @@ describe "Encoding.compatible? String, String" do
     end
 
     it "returns nil when the second's Encoding is invalid and ASCII only" do
-      Encoding.compatible?(@str, "\x7f".force_encoding("utf-16be")).should be_nil
+      Encoding.compatible?(@str, "\x7f\x7f".dup.force_encoding("utf-16be")).should be_nil
     end
 
     it "returns nil when the second's Encoding is invalid and not ASCII only" do
-      Encoding.compatible?(@str, "\xff".force_encoding("utf-16be")).should be_nil
+      Encoding.compatible?(@str, "\xff\xff".dup.force_encoding("utf-16be")).should be_nil
     end
 
     it "returns the Encoding when the second's Encoding is invalid but the same as the first" do
@@ -129,7 +129,7 @@ describe "Encoding.compatible? String, String" do
   describe "when the first String is empty and the second is not" do
     describe "and the first's Encoding is ASCII compatible" do
       before :each do
-        @str = "".force_encoding("utf-8")
+        @str = "".dup.force_encoding("utf-8")
       end
 
       it "returns the first's encoding when the second String is ASCII only" do
@@ -143,7 +143,7 @@ describe "Encoding.compatible? String, String" do
 
     describe "when the first's Encoding is not ASCII compatible" do
       before :each do
-        @str = "".force_encoding Encoding::UTF_7
+        @str = "".dup.force_encoding Encoding::UTF_7
       end
 
       it "returns the second string's encoding" do
@@ -154,18 +154,391 @@ describe "Encoding.compatible? String, String" do
 
   describe "when the second String is empty" do
     before :each do
-      @str = "abc".force_encoding("utf-7")
+      @str = "abc".dup.force_encoding("utf-7")
     end
 
     it "returns the first Encoding" do
       Encoding.compatible?(@str, "").should == Encoding::UTF_7
     end
   end
+
+  # Encoding negotiation depends on whether encodings are ASCII-compatible, empty
+  # and contain only ASCII characters (that take 7 bits). Check US-ASCII, UTF-8 and
+  # BINARY encodings (as most common) as well as an ASCII-compatible, a non-ASCII-compatible and a dummy
+  # encodings in all possible combinations.
+  describe "compatibility matrix" do
+
+#     Use the following script to regenerate the matrix:
+#
+#     ```
+#       # encoding: binary
+#
+#       ENCODINGS = [
+#         "US-ASCII",
+#         "UTF-8",
+#         "ASCII-8BIT",
+#         "ISO-8859-1",  # ASCII-compatible
+#         "UTF-16BE",    # non-ASCII-compatible
+#         "ISO-2022-JP"  # dummy
+#       ]
+#
+#       TYPES = [:empty, :"7bits", :non7bits]
+#
+#       VALUES = {
+#         empty: "",
+#         :"7bits" => "\x01\x01",
+#         non7bits: "\x01\x81"
+#       }
+#
+#       ENCODINGS.product(TYPES, ENCODINGS, TYPES).each do |encoding1, type1, encoding2, type2|
+#         value1 = VALUES[type1].dup.force_encoding(encoding1)
+#         value2 = VALUES[type2].dup.force_encoding(encoding2)
+#
+#         result_encoding = Encoding.compatible?(value1, value2)
+#
+#         puts "[#{encoding1.inspect}, #{value1.inspect}, #{encoding2.inspect}, #{value2.inspect}, #{result_encoding&.name.inspect}],"
+#       end
+#     ```
+
+    matrix = [
+      ["US-ASCII", "", "US-ASCII", "", "US-ASCII"],
+      ["US-ASCII", "", "US-ASCII", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["US-ASCII", "", "UTF-8", "", "US-ASCII"],
+      ["US-ASCII", "", "UTF-8", "\u0001\u0001", "US-ASCII"],
+      ["US-ASCII", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["US-ASCII", "", "ASCII-8BIT", "", "US-ASCII"],
+      ["US-ASCII", "", "ASCII-8BIT", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["US-ASCII", "", "ISO-8859-1", "", "US-ASCII"],
+      ["US-ASCII", "", "ISO-8859-1", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["US-ASCII", "", "UTF-16BE", "", "US-ASCII"],
+      ["US-ASCII", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["US-ASCII", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["US-ASCII", "", "ISO-2022-JP", "", "US-ASCII"],
+      ["US-ASCII", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["US-ASCII", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["US-ASCII", "\x01\x01", "US-ASCII", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "US-ASCII", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "UTF-8", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "UTF-8", "\u0001\u0001", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["US-ASCII", "\x01\x01", "ASCII-8BIT", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "ASCII-8BIT", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["US-ASCII", "\x01\x01", "ISO-8859-1", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "ISO-8859-1", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["US-ASCII", "\x01\x01", "UTF-16BE", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "UTF-16BE", "\u0101", nil],
+      ["US-ASCII", "\x01\x01", "UTF-16BE", "\u0181", nil],
+      ["US-ASCII", "\x01\x01", "ISO-2022-JP", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x01", "ISO-2022-JP", "\x01\x01", nil],
+      ["US-ASCII", "\x01\x01", "ISO-2022-JP", "\x01\x81", nil],
+      ["US-ASCII", "\x01\x81", "US-ASCII", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "US-ASCII", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "UTF-8", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "UTF-8", "\u0001\u0001", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "UTF-8", "\u0001\x81", nil],
+      ["US-ASCII", "\x01\x81", "ASCII-8BIT", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "ASCII-8BIT", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "ASCII-8BIT", "\x01\x81", nil],
+      ["US-ASCII", "\x01\x81", "ISO-8859-1", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "ISO-8859-1", "\x01\x01", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "ISO-8859-1", "\x01\x81", nil],
+      ["US-ASCII", "\x01\x81", "UTF-16BE", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "UTF-16BE", "\u0101", nil],
+      ["US-ASCII", "\x01\x81", "UTF-16BE", "\u0181", nil],
+      ["US-ASCII", "\x01\x81", "ISO-2022-JP", "", "US-ASCII"],
+      ["US-ASCII", "\x01\x81", "ISO-2022-JP", "\x01\x01", nil],
+      ["US-ASCII", "\x01\x81", "ISO-2022-JP", "\x01\x81", nil],
+      ["UTF-8", "", "US-ASCII", "", "UTF-8"],
+      ["UTF-8", "", "US-ASCII", "\x01\x01", "UTF-8"],
+      ["UTF-8", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["UTF-8", "", "UTF-8", "", "UTF-8"],
+      ["UTF-8", "", "UTF-8", "\u0001\u0001", "UTF-8"],
+      ["UTF-8", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["UTF-8", "", "ASCII-8BIT", "", "UTF-8"],
+      ["UTF-8", "", "ASCII-8BIT", "\x01\x01", "UTF-8"],
+      ["UTF-8", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["UTF-8", "", "ISO-8859-1", "", "UTF-8"],
+      ["UTF-8", "", "ISO-8859-1", "\x01\x01", "UTF-8"],
+      ["UTF-8", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["UTF-8", "", "UTF-16BE", "", "UTF-8"],
+      ["UTF-8", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["UTF-8", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["UTF-8", "", "ISO-2022-JP", "", "UTF-8"],
+      ["UTF-8", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["UTF-8", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["UTF-8", "\u0001\u0001", "US-ASCII", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "US-ASCII", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["UTF-8", "\u0001\u0001", "UTF-8", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "UTF-8", "\u0001\u0001", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ASCII-8BIT", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ASCII-8BIT", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["UTF-8", "\u0001\u0001", "ISO-8859-1", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ISO-8859-1", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["UTF-8", "\u0001\u0001", "UTF-16BE", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "UTF-16BE", "\u0101", nil],
+      ["UTF-8", "\u0001\u0001", "UTF-16BE", "\u0181", nil],
+      ["UTF-8", "\u0001\u0001", "ISO-2022-JP", "", "UTF-8"],
+      ["UTF-8", "\u0001\u0001", "ISO-2022-JP", "\x01\x01", nil],
+      ["UTF-8", "\u0001\u0001", "ISO-2022-JP", "\x01\x81", nil],
+      ["UTF-8", "\u0001\x81", "US-ASCII", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "US-ASCII", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "US-ASCII", "\x01\x81", nil],
+      ["UTF-8", "\u0001\x81", "UTF-8", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "UTF-8", "\u0001\u0001", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ASCII-8BIT", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ASCII-8BIT", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ASCII-8BIT", "\x01\x81", nil],
+      ["UTF-8", "\u0001\x81", "ISO-8859-1", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ISO-8859-1", "\x01\x01", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ISO-8859-1", "\x01\x81", nil],
+      ["UTF-8", "\u0001\x81", "UTF-16BE", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "UTF-16BE", "\u0101", nil],
+      ["UTF-8", "\u0001\x81", "UTF-16BE", "\u0181", nil],
+      ["UTF-8", "\u0001\x81", "ISO-2022-JP", "", "UTF-8"],
+      ["UTF-8", "\u0001\x81", "ISO-2022-JP", "\x01\x01", nil],
+      ["UTF-8", "\u0001\x81", "ISO-2022-JP", "\x01\x81", nil],
+      ["ASCII-8BIT", "", "US-ASCII", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "US-ASCII", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["ASCII-8BIT", "", "UTF-8", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "UTF-8", "\u0001\u0001", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["ASCII-8BIT", "", "ASCII-8BIT", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ASCII-8BIT", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ISO-8859-1", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ISO-8859-1", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ASCII-8BIT", "", "UTF-16BE", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["ASCII-8BIT", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["ASCII-8BIT", "", "ISO-2022-JP", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["ASCII-8BIT", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["ASCII-8BIT", "\x01\x01", "US-ASCII", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "US-ASCII", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["ASCII-8BIT", "\x01\x01", "UTF-8", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "UTF-8", "\u0001\u0001", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["ASCII-8BIT", "\x01\x01", "ASCII-8BIT", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ASCII-8BIT", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ISO-8859-1", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ISO-8859-1", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ASCII-8BIT", "\x01\x01", "UTF-16BE", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "UTF-16BE", "\u0101", nil],
+      ["ASCII-8BIT", "\x01\x01", "UTF-16BE", "\u0181", nil],
+      ["ASCII-8BIT", "\x01\x01", "ISO-2022-JP", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x01", "ISO-2022-JP", "\x01\x01", nil],
+      ["ASCII-8BIT", "\x01\x01", "ISO-2022-JP", "\x01\x81", nil],
+      ["ASCII-8BIT", "\x01\x81", "US-ASCII", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "US-ASCII", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "US-ASCII", "\x01\x81", nil],
+      ["ASCII-8BIT", "\x01\x81", "UTF-8", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "UTF-8", "\u0001\u0001", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "UTF-8", "\u0001\x81", nil],
+      ["ASCII-8BIT", "\x01\x81", "ASCII-8BIT", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ASCII-8BIT", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ISO-8859-1", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ISO-8859-1", "\x01\x01", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ISO-8859-1", "\x01\x81", nil],
+      ["ASCII-8BIT", "\x01\x81", "UTF-16BE", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "UTF-16BE", "\u0101", nil],
+      ["ASCII-8BIT", "\x01\x81", "UTF-16BE", "\u0181", nil],
+      ["ASCII-8BIT", "\x01\x81", "ISO-2022-JP", "", "ASCII-8BIT"],
+      ["ASCII-8BIT", "\x01\x81", "ISO-2022-JP", "\x01\x01", nil],
+      ["ASCII-8BIT", "\x01\x81", "ISO-2022-JP", "\x01\x81", nil],
+      ["ISO-8859-1", "", "US-ASCII", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "US-ASCII", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["ISO-8859-1", "", "UTF-8", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "UTF-8", "\u0001\u0001", "ISO-8859-1"],
+      ["ISO-8859-1", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["ISO-8859-1", "", "ASCII-8BIT", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "ASCII-8BIT", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ISO-8859-1", "", "ISO-8859-1", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "ISO-8859-1", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ISO-8859-1", "", "UTF-16BE", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["ISO-8859-1", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["ISO-8859-1", "", "ISO-2022-JP", "", "ISO-8859-1"],
+      ["ISO-8859-1", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["ISO-8859-1", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["ISO-8859-1", "\x01\x01", "US-ASCII", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "US-ASCII", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["ISO-8859-1", "\x01\x01", "UTF-8", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "UTF-8", "\u0001\u0001", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["ISO-8859-1", "\x01\x01", "ASCII-8BIT", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "ASCII-8BIT", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ISO-8859-1", "\x01\x01", "ISO-8859-1", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "ISO-8859-1", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "UTF-16BE", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "UTF-16BE", "\u0101", nil],
+      ["ISO-8859-1", "\x01\x01", "UTF-16BE", "\u0181", nil],
+      ["ISO-8859-1", "\x01\x01", "ISO-2022-JP", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x01", "ISO-2022-JP", "\x01\x01", nil],
+      ["ISO-8859-1", "\x01\x01", "ISO-2022-JP", "\x01\x81", nil],
+      ["ISO-8859-1", "\x01\x81", "US-ASCII", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "US-ASCII", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "US-ASCII", "\x01\x81", nil],
+      ["ISO-8859-1", "\x01\x81", "UTF-8", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "UTF-8", "\u0001\u0001", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "UTF-8", "\u0001\x81", nil],
+      ["ISO-8859-1", "\x01\x81", "ASCII-8BIT", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "ASCII-8BIT", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "ASCII-8BIT", "\x01\x81", nil],
+      ["ISO-8859-1", "\x01\x81", "ISO-8859-1", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "ISO-8859-1", "\x01\x01", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "UTF-16BE", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "UTF-16BE", "\u0101", nil],
+      ["ISO-8859-1", "\x01\x81", "UTF-16BE", "\u0181", nil],
+      ["ISO-8859-1", "\x01\x81", "ISO-2022-JP", "", "ISO-8859-1"],
+      ["ISO-8859-1", "\x01\x81", "ISO-2022-JP", "\x01\x01", nil],
+      ["ISO-8859-1", "\x01\x81", "ISO-2022-JP", "\x01\x81", nil],
+      ["UTF-16BE", "", "US-ASCII", "", "UTF-16BE"],
+      ["UTF-16BE", "", "US-ASCII", "\x01\x01", "US-ASCII"],
+      ["UTF-16BE", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["UTF-16BE", "", "UTF-8", "", "UTF-16BE"],
+      ["UTF-16BE", "", "UTF-8", "\u0001\u0001", "UTF-8"],
+      ["UTF-16BE", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["UTF-16BE", "", "ASCII-8BIT", "", "UTF-16BE"],
+      ["UTF-16BE", "", "ASCII-8BIT", "\x01\x01", "ASCII-8BIT"],
+      ["UTF-16BE", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["UTF-16BE", "", "ISO-8859-1", "", "UTF-16BE"],
+      ["UTF-16BE", "", "ISO-8859-1", "\x01\x01", "ISO-8859-1"],
+      ["UTF-16BE", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["UTF-16BE", "", "UTF-16BE", "", "UTF-16BE"],
+      ["UTF-16BE", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["UTF-16BE", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["UTF-16BE", "", "ISO-2022-JP", "", "UTF-16BE"],
+      ["UTF-16BE", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["UTF-16BE", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["UTF-16BE", "\u0101", "US-ASCII", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "US-ASCII", "\x01\x01", nil],
+      ["UTF-16BE", "\u0101", "US-ASCII", "\x01\x81", nil],
+      ["UTF-16BE", "\u0101", "UTF-8", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "UTF-8", "\u0001\u0001", nil],
+      ["UTF-16BE", "\u0101", "UTF-8", "\u0001\x81", nil],
+      ["UTF-16BE", "\u0101", "ASCII-8BIT", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "ASCII-8BIT", "\x01\x01", nil],
+      ["UTF-16BE", "\u0101", "ASCII-8BIT", "\x01\x81", nil],
+      ["UTF-16BE", "\u0101", "ISO-8859-1", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "ISO-8859-1", "\x01\x01", nil],
+      ["UTF-16BE", "\u0101", "ISO-8859-1", "\x01\x81", nil],
+      ["UTF-16BE", "\u0101", "UTF-16BE", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "ISO-2022-JP", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0101", "ISO-2022-JP", "\x01\x01", nil],
+      ["UTF-16BE", "\u0101", "ISO-2022-JP", "\x01\x81", nil],
+      ["UTF-16BE", "\u0181", "US-ASCII", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "US-ASCII", "\x01\x01", nil],
+      ["UTF-16BE", "\u0181", "US-ASCII", "\x01\x81", nil],
+      ["UTF-16BE", "\u0181", "UTF-8", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "UTF-8", "\u0001\u0001", nil],
+      ["UTF-16BE", "\u0181", "UTF-8", "\u0001\x81", nil],
+      ["UTF-16BE", "\u0181", "ASCII-8BIT", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "ASCII-8BIT", "\x01\x01", nil],
+      ["UTF-16BE", "\u0181", "ASCII-8BIT", "\x01\x81", nil],
+      ["UTF-16BE", "\u0181", "ISO-8859-1", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "ISO-8859-1", "\x01\x01", nil],
+      ["UTF-16BE", "\u0181", "ISO-8859-1", "\x01\x81", nil],
+      ["UTF-16BE", "\u0181", "UTF-16BE", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "ISO-2022-JP", "", "UTF-16BE"],
+      ["UTF-16BE", "\u0181", "ISO-2022-JP", "\x01\x01", nil],
+      ["UTF-16BE", "\u0181", "ISO-2022-JP", "\x01\x81", nil],
+      ["ISO-2022-JP", "", "US-ASCII", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "US-ASCII", "\x01\x01", "US-ASCII"],
+      ["ISO-2022-JP", "", "US-ASCII", "\x01\x81", "US-ASCII"],
+      ["ISO-2022-JP", "", "UTF-8", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "UTF-8", "\u0001\u0001", "UTF-8"],
+      ["ISO-2022-JP", "", "UTF-8", "\u0001\x81", "UTF-8"],
+      ["ISO-2022-JP", "", "ASCII-8BIT", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "ASCII-8BIT", "\x01\x01", "ASCII-8BIT"],
+      ["ISO-2022-JP", "", "ASCII-8BIT", "\x01\x81", "ASCII-8BIT"],
+      ["ISO-2022-JP", "", "ISO-8859-1", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "ISO-8859-1", "\x01\x01", "ISO-8859-1"],
+      ["ISO-2022-JP", "", "ISO-8859-1", "\x01\x81", "ISO-8859-1"],
+      ["ISO-2022-JP", "", "UTF-16BE", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "UTF-16BE", "\u0101", "UTF-16BE"],
+      ["ISO-2022-JP", "", "UTF-16BE", "\u0181", "UTF-16BE"],
+      ["ISO-2022-JP", "", "ISO-2022-JP", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["ISO-2022-JP", "", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "US-ASCII", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "US-ASCII", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x01", "US-ASCII", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x01", "UTF-8", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "UTF-8", "\u0001\u0001", nil],
+      ["ISO-2022-JP", "\x01\x01", "UTF-8", "\u0001\x81", nil],
+      ["ISO-2022-JP", "\x01\x01", "ASCII-8BIT", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "ASCII-8BIT", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x01", "ASCII-8BIT", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x01", "ISO-8859-1", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "ISO-8859-1", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x01", "ISO-8859-1", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x01", "UTF-16BE", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "UTF-16BE", "\u0101", nil],
+      ["ISO-2022-JP", "\x01\x01", "UTF-16BE", "\u0181", nil],
+      ["ISO-2022-JP", "\x01\x01", "ISO-2022-JP", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x01", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "US-ASCII", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "US-ASCII", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x81", "US-ASCII", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x81", "UTF-8", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "UTF-8", "\u0001\u0001", nil],
+      ["ISO-2022-JP", "\x01\x81", "UTF-8", "\u0001\x81", nil],
+      ["ISO-2022-JP", "\x01\x81", "ASCII-8BIT", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "ASCII-8BIT", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x81", "ASCII-8BIT", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x81", "ISO-8859-1", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "ISO-8859-1", "\x01\x01", nil],
+      ["ISO-2022-JP", "\x01\x81", "ISO-8859-1", "\x01\x81", nil],
+      ["ISO-2022-JP", "\x01\x81", "UTF-16BE", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "UTF-16BE", "\u0101", nil],
+      ["ISO-2022-JP", "\x01\x81", "UTF-16BE", "\u0181", nil],
+      ["ISO-2022-JP", "\x01\x81", "ISO-2022-JP", "", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "ISO-2022-JP", "\x01\x01", "ISO-2022-JP"],
+      ["ISO-2022-JP", "\x01\x81", "ISO-2022-JP", "\x01\x81", "ISO-2022-JP"],
+    ]
+
+    matrix.each do |encoding1, value1, encoding2, value2, compatible_encoding|
+      it "returns #{compatible_encoding} for #{value1.inspect} in #{encoding1} and #{value2.inspect} in #{encoding2}" do
+        actual_encoding = Encoding.compatible?(value1.dup.force_encoding(encoding1), value2.dup.force_encoding(encoding2))
+        actual_encoding&.name.should == compatible_encoding
+      end
+    end
+  end
 end
 
 describe "Encoding.compatible? String, Regexp" do
   it "returns US-ASCII if both are US-ASCII" do
-    str = "abc".force_encoding("us-ascii")
+    str = "abc".dup.force_encoding("us-ascii")
     Encoding.compatible?(str, /abc/).should == Encoding::US_ASCII
   end
 
@@ -180,15 +553,15 @@ describe "Encoding.compatible? String, Regexp" do
   it "returns the String's Encoding if the String is not ASCII only" do
     [ [Encoding, "\xff",                                  Encoding::BINARY],
       [Encoding, "\u3042".encode("utf-8"),                Encoding::UTF_8],
-      [Encoding, "\xa4\xa2".force_encoding("euc-jp"),     Encoding::EUC_JP],
-      [Encoding, "\x82\xa0".force_encoding("shift_jis"),  Encoding::Shift_JIS],
+      [Encoding, "\xa4\xa2".dup.force_encoding("euc-jp"),     Encoding::EUC_JP],
+      [Encoding, "\x82\xa0".dup.force_encoding("shift_jis"),  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, /abc/)
   end
 end
 
 describe "Encoding.compatible? String, Symbol" do
   it "returns US-ASCII if both are ASCII only" do
-    str = "abc".force_encoding("us-ascii")
+    str = "abc".dup.force_encoding("us-ascii")
     Encoding.compatible?(str, :abc).should == Encoding::US_ASCII
   end
 
@@ -203,8 +576,8 @@ describe "Encoding.compatible? String, Symbol" do
   it "returns the String's Encoding if the String is not ASCII only" do
     [ [Encoding, "\xff",                                  Encoding::BINARY],
       [Encoding, "\u3042".encode("utf-8"),                Encoding::UTF_8],
-      [Encoding, "\xa4\xa2".force_encoding("euc-jp"),     Encoding::EUC_JP],
-      [Encoding, "\x82\xa0".force_encoding("shift_jis"),  Encoding::Shift_JIS],
+      [Encoding, "\xa4\xa2".dup.force_encoding("euc-jp"),     Encoding::EUC_JP],
+      [Encoding, "\x82\xa0".dup.force_encoding("shift_jis"),  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, :abc)
   end
 end
@@ -221,8 +594,8 @@ describe "Encoding.compatible? String, Encoding" do
   it "returns the String's encoding if the Encoding is US-ASCII" do
     [ [Encoding, "\xff",                                  Encoding::BINARY],
       [Encoding, "\u3042".encode("utf-8"),                Encoding::UTF_8],
-      [Encoding, "\xa4\xa2".force_encoding("euc-jp"),     Encoding::EUC_JP],
-      [Encoding, "\x82\xa0".force_encoding("shift_jis"),  Encoding::Shift_JIS],
+      [Encoding, "\xa4\xa2".dup.force_encoding("euc-jp"),     Encoding::EUC_JP],
+      [Encoding, "\x82\xa0".dup.force_encoding("shift_jis"),  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, Encoding::US_ASCII)
   end
 
@@ -242,7 +615,7 @@ end
 
 describe "Encoding.compatible? Regexp, String" do
   it "returns US-ASCII if both are US-ASCII" do
-    str = "abc".force_encoding("us-ascii")
+    str = "abc".dup.force_encoding("us-ascii")
     Encoding.compatible?(/abc/, str).should == Encoding::US_ASCII
   end
 
@@ -256,8 +629,8 @@ describe "Encoding.compatible? Regexp, Regexp" do
   it "returns the first's Encoding if it is not US-ASCII and not ASCII only" do
     [ [Encoding, Regexp.new("\xff"),                                  Encoding::BINARY],
       [Encoding, Regexp.new("\u3042".encode("utf-8")),                Encoding::UTF_8],
-      [Encoding, Regexp.new("\xa4\xa2".force_encoding("euc-jp")),     Encoding::EUC_JP],
-      [Encoding, Regexp.new("\x82\xa0".force_encoding("shift_jis")),  Encoding::Shift_JIS],
+      [Encoding, Regexp.new("\xa4\xa2".dup.force_encoding("euc-jp")),     Encoding::EUC_JP],
+      [Encoding, Regexp.new("\x82\xa0".dup.force_encoding("shift_jis")),  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, /abc/)
   end
 end
@@ -270,15 +643,15 @@ describe "Encoding.compatible? Regexp, Symbol" do
   it "returns the first's Encoding if it is not US-ASCII and not ASCII only" do
     [ [Encoding, Regexp.new("\xff"),                                  Encoding::BINARY],
       [Encoding, Regexp.new("\u3042".encode("utf-8")),                Encoding::UTF_8],
-      [Encoding, Regexp.new("\xa4\xa2".force_encoding("euc-jp")),     Encoding::EUC_JP],
-      [Encoding, Regexp.new("\x82\xa0".force_encoding("shift_jis")),  Encoding::Shift_JIS],
+      [Encoding, Regexp.new("\xa4\xa2".dup.force_encoding("euc-jp")),     Encoding::EUC_JP],
+      [Encoding, Regexp.new("\x82\xa0".dup.force_encoding("shift_jis")),  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, /abc/)
   end
 end
 
 describe "Encoding.compatible? Symbol, String" do
   it "returns US-ASCII if both are ASCII only" do
-    str = "abc".force_encoding("us-ascii")
+    str = "abc".dup.force_encoding("us-ascii")
     Encoding.compatible?(str, :abc).should == Encoding::US_ASCII
   end
 end
@@ -291,8 +664,8 @@ describe "Encoding.compatible? Symbol, Regexp" do
   it "returns the Regexp's Encoding if it is not US-ASCII and not ASCII only" do
     a = Regexp.new("\xff")
     b = Regexp.new("\u3042".encode("utf-8"))
-    c = Regexp.new("\xa4\xa2".force_encoding("euc-jp"))
-    d = Regexp.new("\x82\xa0".force_encoding("shift_jis"))
+    c = Regexp.new("\xa4\xa2".dup.force_encoding("euc-jp"))
+    d = Regexp.new("\x82\xa0".dup.force_encoding("shift_jis"))
 
     [ [Encoding, :abc, a, Encoding::BINARY],
       [Encoding, :abc, b, Encoding::UTF_8],
@@ -310,8 +683,8 @@ describe "Encoding.compatible? Symbol, Symbol" do
   it "returns the first's Encoding if it is not ASCII only" do
     [ [Encoding, "\xff".to_sym,                                  Encoding::BINARY],
       [Encoding, "\u3042".encode("utf-8").to_sym,                Encoding::UTF_8],
-      [Encoding, "\xa4\xa2".force_encoding("euc-jp").to_sym,     Encoding::EUC_JP],
-      [Encoding, "\x82\xa0".force_encoding("shift_jis").to_sym,  Encoding::Shift_JIS],
+      [Encoding, "\xa4\xa2".dup.force_encoding("euc-jp").to_sym,     Encoding::EUC_JP],
+      [Encoding, "\x82\xa0".dup.force_encoding("shift_jis").to_sym,  Encoding::Shift_JIS],
     ].should be_computed_by(:compatible?, :abc)
   end
 end
@@ -377,3 +750,9 @@ describe "Encoding.compatible? Object, Object" do
     Encoding.compatible?(:sym, Object.new).should be_nil
   end
 end
+
+describe "Encoding.compatible? nil, nil" do
+  it "returns nil" do
+    Encoding.compatible?(nil, nil).should be_nil
+  end
+end
diff --git a/spec/ruby/core/encoding/converter/constants_spec.rb b/spec/ruby/core/encoding/converter/constants_spec.rb
index 57b6a4d4e7..7d29bdb278 100644
--- a/spec/ruby/core/encoding/converter/constants_spec.rb
+++ b/spec/ruby/core/encoding/converter/constants_spec.rb
@@ -5,8 +5,8 @@ describe "Encoding::Converter::INVALID_MASK" do
     Encoding::Converter.should have_constant(:INVALID_MASK)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::INVALID_MASK.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::INVALID_MASK.should be_an_instance_of(Integer)
   end
 end
 
@@ -15,8 +15,8 @@ describe "Encoding::Converter::INVALID_REPLACE" do
     Encoding::Converter.should have_constant(:INVALID_REPLACE)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::INVALID_REPLACE.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::INVALID_REPLACE.should be_an_instance_of(Integer)
   end
 end
 
@@ -25,8 +25,8 @@ describe "Encoding::Converter::UNDEF_MASK" do
     Encoding::Converter.should have_constant(:UNDEF_MASK)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::UNDEF_MASK.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::UNDEF_MASK.should be_an_instance_of(Integer)
   end
 end
 
@@ -35,8 +35,8 @@ describe "Encoding::Converter::UNDEF_REPLACE" do
     Encoding::Converter.should have_constant(:UNDEF_REPLACE)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::UNDEF_REPLACE.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::UNDEF_REPLACE.should be_an_instance_of(Integer)
   end
 end
 
@@ -45,8 +45,8 @@ describe "Encoding::Converter::UNDEF_HEX_CHARREF" do
     Encoding::Converter.should have_constant(:UNDEF_HEX_CHARREF)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::UNDEF_HEX_CHARREF.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::UNDEF_HEX_CHARREF.should be_an_instance_of(Integer)
   end
 end
 
@@ -55,8 +55,8 @@ describe "Encoding::Converter::PARTIAL_INPUT" do
     Encoding::Converter.should have_constant(:PARTIAL_INPUT)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::PARTIAL_INPUT.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::PARTIAL_INPUT.should be_an_instance_of(Integer)
   end
 end
 
@@ -65,8 +65,8 @@ describe "Encoding::Converter::AFTER_OUTPUT" do
     Encoding::Converter.should have_constant(:AFTER_OUTPUT)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::AFTER_OUTPUT.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::AFTER_OUTPUT.should be_an_instance_of(Integer)
   end
 end
 
@@ -75,8 +75,8 @@ describe "Encoding::Converter::UNIVERSAL_NEWLINE_DECORATOR" do
     Encoding::Converter.should have_constant(:UNIVERSAL_NEWLINE_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::UNIVERSAL_NEWLINE_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::UNIVERSAL_NEWLINE_DECORATOR.should be_an_instance_of(Integer)
   end
 end
 
@@ -85,8 +85,8 @@ describe "Encoding::Converter::CRLF_NEWLINE_DECORATOR" do
     Encoding::Converter.should have_constant(:CRLF_NEWLINE_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::CRLF_NEWLINE_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::CRLF_NEWLINE_DECORATOR.should be_an_instance_of(Integer)
   end
 end
 
@@ -95,8 +95,8 @@ describe "Encoding::Converter::CR_NEWLINE_DECORATOR" do
     Encoding::Converter.should have_constant(:CR_NEWLINE_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::CR_NEWLINE_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::CR_NEWLINE_DECORATOR.should be_an_instance_of(Integer)
   end
 end
 
@@ -105,8 +105,8 @@ describe "Encoding::Converter::XML_TEXT_DECORATOR" do
     Encoding::Converter.should have_constant(:XML_TEXT_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::XML_TEXT_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::XML_TEXT_DECORATOR.should be_an_instance_of(Integer)
   end
 end
 
@@ -115,8 +115,8 @@ describe "Encoding::Converter::XML_ATTR_CONTENT_DECORATOR" do
     Encoding::Converter.should have_constant(:XML_ATTR_CONTENT_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::XML_ATTR_CONTENT_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::XML_ATTR_CONTENT_DECORATOR.should be_an_instance_of(Integer)
   end
 end
 
@@ -125,7 +125,7 @@ describe "Encoding::Converter::XML_ATTR_QUOTE_DECORATOR" do
     Encoding::Converter.should have_constant(:XML_ATTR_QUOTE_DECORATOR)
   end
 
-  it "has a Fixnum value" do
-    Encoding::Converter::XML_ATTR_QUOTE_DECORATOR.should be_an_instance_of(Fixnum)
+  it "has an Integer value" do
+    Encoding::Converter::XML_ATTR_QUOTE_DECORATOR.should be_an_instance_of(Integer)
   end
 end
diff --git a/spec/ruby/core/encoding/converter/convert_spec.rb b/spec/ruby/core/encoding/converter/convert_spec.rb
index 95a9e0b758..8533af4565 100644
--- a/spec/ruby/core/encoding/converter/convert_spec.rb
+++ b/spec/ruby/core/encoding/converter/convert_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+# frozen_string_literal: true
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter#convert" do
@@ -9,31 +10,31 @@ describe "Encoding::Converter#convert" do
 
   it "sets the encoding of the result to the target encoding" do
     ec = Encoding::Converter.new('ascii', 'utf-8')
-    str = 'glark'.force_encoding('ascii')
+    str = 'glark'.dup.force_encoding('ascii')
     ec.convert(str).encoding.should == Encoding::UTF_8
   end
 
   it "transcodes the given String to the target encoding" do
     ec = Encoding::Converter.new("utf-8", "euc-jp")
-    ec.convert("\u3042".force_encoding('UTF-8')).should == \
-      "\xA4\xA2".force_encoding('EUC-JP')
+    ec.convert("\u3042".dup.force_encoding('UTF-8')).should == \
+      "\xA4\xA2".dup.force_encoding('EUC-JP')
   end
 
   it "allows Strings of different encodings to the source encoding" do
     ec = Encoding::Converter.new('ascii', 'utf-8')
-    str = 'glark'.force_encoding('SJIS')
+    str = 'glark'.dup.force_encoding('SJIS')
     ec.convert(str).encoding.should == Encoding::UTF_8
   end
 
   it "reuses the given encoding pair if called multiple times" do
     ec = Encoding::Converter.new('ascii', 'SJIS')
-    ec.convert('a'.force_encoding('ASCII')).should == 'a'.force_encoding('SJIS')
-    ec.convert('b'.force_encoding('ASCII')).should == 'b'.force_encoding('SJIS')
+    ec.convert('a'.dup.force_encoding('ASCII')).should == 'a'.dup.force_encoding('SJIS')
+    ec.convert('b'.dup.force_encoding('ASCII')).should == 'b'.dup.force_encoding('SJIS')
   end
 
   it "raises UndefinedConversionError if the String contains characters invalid for the target encoding" do
     ec = Encoding::Converter.new('UTF-8', Encoding.find('macCyrillic'))
-    -> { ec.convert("\u{6543}".force_encoding('UTF-8')) }.should \
+    -> { ec.convert("\u{6543}".dup.force_encoding('UTF-8')) }.should \
       raise_error(Encoding::UndefinedConversionError)
   end
 
diff --git a/spec/ruby/core/encoding/converter/convpath_spec.rb b/spec/ruby/core/encoding/converter/convpath_spec.rb
index 473f2db91e..23f1e5dc33 100644
--- a/spec/ruby/core/encoding/converter/convpath_spec.rb
+++ b/spec/ruby/core/encoding/converter/convpath_spec.rb
@@ -15,10 +15,10 @@ describe "Encoding::Converter#convpath" do
   end
 
   it "indicates if crlf_newline conversion would occur" do
-    ec = Encoding::Converter.new("ISo-8859-1", "EUC-JP", {crlf_newline: true})
+    ec = Encoding::Converter.new("ISo-8859-1", "EUC-JP", crlf_newline: true)
     ec.convpath.last.should == "crlf_newline"
 
-    ec = Encoding::Converter.new("ASCII", "UTF-8", {crlf_newline: false})
+    ec = Encoding::Converter.new("ASCII", "UTF-8", crlf_newline: false)
     ec.convpath.last.should_not == "crlf_newline"
   end
 end
diff --git a/spec/ruby/core/encoding/converter/finish_spec.rb b/spec/ruby/core/encoding/converter/finish_spec.rb
index 11ca7e8510..22e66df38c 100644
--- a/spec/ruby/core/encoding/converter/finish_spec.rb
+++ b/spec/ruby/core/encoding/converter/finish_spec.rb
@@ -16,8 +16,8 @@ describe "Encoding::Converter#finish" do
   end
 
   it "returns the last part of the converted String if it hasn't already" do
-     @ec.convert("\u{9999}").should == "\e$B9a".force_encoding('iso-2022-jp')
-     @ec.finish.should == "\e(B".force_encoding('iso-2022-jp')
+    @ec.convert("\u{9999}").should == "\e$B9a".dup.force_encoding('iso-2022-jp')
+    @ec.finish.should == "\e(B".dup.force_encoding('iso-2022-jp')
   end
 
   it "returns a String in the destination encoding" do
diff --git a/spec/ruby/core/encoding/converter/last_error_spec.rb b/spec/ruby/core/encoding/converter/last_error_spec.rb
index 68567737b7..ff2a2b4cbe 100644
--- a/spec/ruby/core/encoding/converter/last_error_spec.rb
+++ b/spec/ruby/core/encoding/converter/last_error_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter#last_error" do
@@ -9,45 +9,45 @@ describe "Encoding::Converter#last_error" do
 
   it "returns nil when the last conversion did not produce an error" do
     ec = Encoding::Converter.new('ascii','utf-8')
-    ec.convert('a'.force_encoding('ascii'))
+    ec.convert('a'.dup.force_encoding('ascii'))
     ec.last_error.should be_nil
   end
 
   it "returns nil when #primitive_convert last returned :destination_buffer_full" do
     ec = Encoding::Converter.new("utf-8", "iso-2022-jp")
-    ec.primitive_convert("\u{9999}", "", 0, 0, partial_input: false) \
+    ec.primitive_convert(+"\u{9999}", +"", 0, 0, partial_input: false) \
       .should == :destination_buffer_full
     ec.last_error.should be_nil
   end
 
   it "returns nil when #primitive_convert last returned :finished" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("glark".force_encoding('utf-8'),"").should == :finished
+    ec.primitive_convert("glark".dup.force_encoding('utf-8'), +"").should == :finished
     ec.last_error.should be_nil
   end
 
   it "returns nil if the last conversion succeeded but the penultimate failed" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\xf1abcd","").should == :invalid_byte_sequence
-    ec.primitive_convert("glark".force_encoding('utf-8'),"").should == :finished
+    ec.primitive_convert(+"\xf1abcd", +"").should == :invalid_byte_sequence
+    ec.primitive_convert("glark".dup.force_encoding('utf-8'), +"").should == :finished
     ec.last_error.should be_nil
   end
 
   it "returns an Encoding::InvalidByteSequenceError when #primitive_convert last returned :invalid_byte_sequence" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\xf1abcd","").should == :invalid_byte_sequence
+    ec.primitive_convert(+"\xf1abcd", +"").should == :invalid_byte_sequence
     ec.last_error.should be_an_instance_of(Encoding::InvalidByteSequenceError)
   end
 
   it "returns an Encoding::UndefinedConversionError when #primitive_convert last returned :undefined_conversion" do
     ec = Encoding::Converter.new("utf-8", "iso-8859-1")
-    ec.primitive_convert("\u{9876}","").should == :undefined_conversion
+    ec.primitive_convert(+"\u{9876}", +"").should == :undefined_conversion
     ec.last_error.should be_an_instance_of(Encoding::UndefinedConversionError)
   end
 
   it "returns an Encoding::InvalidByteSequenceError when #primitive_convert last returned :incomplete_input" do
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert("\xa4", "", nil, 10).should == :incomplete_input
+    ec.primitive_convert(+"\xa4", +"", nil, 10).should == :incomplete_input
     ec.last_error.should be_an_instance_of(Encoding::InvalidByteSequenceError)
   end
 
diff --git a/spec/ruby/core/encoding/converter/new_spec.rb b/spec/ruby/core/encoding/converter/new_spec.rb
index 6a6343012c..a7bef53809 100644
--- a/spec/ruby/core/encoding/converter/new_spec.rb
+++ b/spec/ruby/core/encoding/converter/new_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter.new" do
@@ -47,10 +47,10 @@ describe "Encoding::Converter.new" do
     conv.replacement.should == "fubar"
   end
 
-  it "calls #to_hash to convert the options argument to a Hash if not a Fixnum" do
+  it "calls #to_hash to convert the options argument to a Hash if not an Integer" do
     opts = mock("encoding converter options")
     opts.should_receive(:to_hash).and_return({ replace: "fubar" })
-    conv = Encoding::Converter.new("us-ascii", "utf-8", opts)
+    conv = Encoding::Converter.new("us-ascii", "utf-8", **opts)
     conv.replacement.should == "fubar"
   end
 
@@ -82,7 +82,7 @@ describe "Encoding::Converter.new" do
     end.should raise_error(TypeError)
   end
 
-  it "raises a TypeError if passed a Fixnum for the replacement object" do
+  it "raises a TypeError if passed an Integer for the replacement object" do
     -> do
       Encoding::Converter.new("us-ascii", "utf-8", replace: 1)
     end.should raise_error(TypeError)
@@ -107,7 +107,7 @@ describe "Encoding::Converter.new" do
 
       it "sets the replacement String to '\\uFFFD'" do
         conv = Encoding::Converter.new("us-ascii", "utf-8", replace: nil)
-        conv.replacement.should == "\u{fffd}".force_encoding("utf-8")
+        conv.replacement.should == "\u{fffd}".dup.force_encoding("utf-8")
       end
 
       it "sets the replacement String encoding to UTF-8" do
diff --git a/spec/ruby/core/encoding/converter/primitive_convert_spec.rb b/spec/ruby/core/encoding/converter/primitive_convert_spec.rb
index 4a22606375..e4aeed103e 100644
--- a/spec/ruby/core/encoding/converter/primitive_convert_spec.rb
+++ b/spec/ruby/core/encoding/converter/primitive_convert_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+# frozen_string_literal: false
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter#primitive_convert" do
@@ -14,6 +15,10 @@ describe "Encoding::Converter#primitive_convert" do
     -> { @ec.primitive_convert("","") }.should_not raise_error
   end
 
+  it "raises FrozenError when the destination buffer is a frozen String" do
+    -> { @ec.primitive_convert("", "".freeze) }.should raise_error(FrozenError)
+  end
+
   it "accepts nil for the destination byte offset" do
     -> { @ec.primitive_convert("","", nil) }.should_not raise_error
   end
@@ -85,7 +90,7 @@ describe "Encoding::Converter#primitive_convert" do
   end
 
   it "accepts an options hash" do
-    @ec.primitive_convert("","",nil,nil, {after_output: true}).should == :finished
+    @ec.primitive_convert("","",nil,nil, after_output: true).should == :finished
   end
 
   it "sets the destination buffer's encoding to the destination encoding if the conversion succeeded" do
diff --git a/spec/ruby/core/encoding/converter/primitive_errinfo_spec.rb b/spec/ruby/core/encoding/converter/primitive_errinfo_spec.rb
index 1f836b259f..5ee8b1fecd 100644
--- a/spec/ruby/core/encoding/converter/primitive_errinfo_spec.rb
+++ b/spec/ruby/core/encoding/converter/primitive_errinfo_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+# frozen_string_literal: false
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter#primitive_errinfo" do
diff --git a/spec/ruby/core/encoding/converter/putback_spec.rb b/spec/ruby/core/encoding/converter/putback_spec.rb
index 87495eaf3f..04bb565655 100644
--- a/spec/ruby/core/encoding/converter/putback_spec.rb
+++ b/spec/ruby/core/encoding/converter/putback_spec.rb
@@ -1,10 +1,10 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 
 describe "Encoding::Converter#putback" do
   before :each do
     @ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    @ret = @ec.primitive_convert(@src="abc\xa1def", @dst="", nil, 10)
+    @ret = @ec.primitive_convert(@src=+"abc\xa1def", @dst=+"", nil, 10)
   end
 
   it "returns a String" do
@@ -34,14 +34,23 @@ describe "Encoding::Converter#putback" do
     @ec.putback.should == ""
   end
 
+  it "returns the problematic bytes for UTF-16LE" do
+    ec = Encoding::Converter.new("utf-16le", "iso-8859-1")
+    src = +"\x00\xd8\x61\x00"
+    dst = +""
+    ec.primitive_convert(src, dst).should == :invalid_byte_sequence
+    ec.primitive_errinfo.should == [:invalid_byte_sequence, "UTF-16LE", "UTF-8", "\x00\xD8", "a\x00"]
+    ec.putback.should == "a\x00".dup.force_encoding("utf-16le")
+    ec.putback.should == ""
+  end
+
   it "accepts an integer argument corresponding to the number of bytes to be put back" do
     ec = Encoding::Converter.new("utf-16le", "iso-8859-1")
-    src = "\x00\xd8\x61\x00"
-    dst = ""
+    src = +"\x00\xd8\x61\x00"
+    dst = +""
     ec.primitive_convert(src, dst).should == :invalid_byte_sequence
     ec.primitive_errinfo.should == [:invalid_byte_sequence, "UTF-16LE", "UTF-8", "\x00\xD8", "a\x00"]
-    ec.putback(1).should == "\x00".force_encoding("utf-16le")
-    ec.putback.should == "a".force_encoding("utf-16le")
+    ec.putback(2).should == "a\x00".dup.force_encoding("utf-16le")
     ec.putback.should == ""
   end
 end
diff --git a/spec/ruby/core/encoding/converter/replacement_spec.rb b/spec/ruby/core/encoding/converter/replacement_spec.rb
index 5ca42e7e5a..ea514ca8dd 100644
--- a/spec/ruby/core/encoding/converter/replacement_spec.rb
+++ b/spec/ruby/core/encoding/converter/replacement_spec.rb
@@ -13,7 +13,7 @@ describe "Encoding::Converter#replacement" do
 
   it "returns \\uFFFD when the destination encoding is UTF-8" do
     ec = Encoding::Converter.new("us-ascii", "utf-8")
-    ec.replacement.should == "\u{fffd}".force_encoding('utf-8')
+    ec.replacement.should == "\u{fffd}".dup.force_encoding('utf-8')
     ec.replacement.encoding.should == Encoding::UTF_8
   end
 end
@@ -38,33 +38,33 @@ describe "Encoding::Converter#replacement=" do
 
   it "sets #replacement" do
     ec = Encoding::Converter.new("us-ascii", "utf-8")
-    ec.replacement.should == "\u{fffd}".force_encoding('utf-8')
+    ec.replacement.should == "\u{fffd}".dup.force_encoding('utf-8')
     ec.replacement = '?'.encode('utf-8')
-    ec.replacement.should == '?'.force_encoding('utf-8')
+    ec.replacement.should == '?'.dup.force_encoding('utf-8')
   end
 
   it "raises an UndefinedConversionError is the argument cannot be converted into the destination encoding" do
     ec = Encoding::Converter.new("sjis", "ascii")
-    utf8_q = "\u{986}".force_encoding('utf-8')
-    ec.primitive_convert(utf8_q.dup, "").should == :undefined_conversion
+    utf8_q = "\u{986}".dup.force_encoding('utf-8')
+    ec.primitive_convert(utf8_q.dup, +"").should == :undefined_conversion
     -> { ec.replacement = utf8_q }.should \
       raise_error(Encoding::UndefinedConversionError)
   end
 
   it "does not change the replacement character if the argument cannot be converted into the destination encoding" do
     ec = Encoding::Converter.new("sjis", "ascii")
-    utf8_q = "\u{986}".force_encoding('utf-8')
-    ec.primitive_convert(utf8_q.dup, "").should == :undefined_conversion
+    utf8_q = "\u{986}".dup.force_encoding('utf-8')
+    ec.primitive_convert(utf8_q.dup, +"").should == :undefined_conversion
     -> { ec.replacement = utf8_q }.should \
       raise_error(Encoding::UndefinedConversionError)
-    ec.replacement.should == "?".force_encoding('us-ascii')
+    ec.replacement.should == "?".dup.force_encoding('us-ascii')
   end
 
   it "uses the replacement character" do
     ec = Encoding::Converter.new("utf-8", "us-ascii", :invalid => :replace, :undef => :replace)
     ec.replacement = "!"
-    dest = ""
-    status = ec.primitive_convert "中文123", dest
+    dest = +""
+    status = ec.primitive_convert(+"中文123", dest)
 
     status.should == :finished
     dest.should == "!!123"
diff --git a/spec/ruby/core/encoding/converter/search_convpath_spec.rb b/spec/ruby/core/encoding/converter/search_convpath_spec.rb
index 0535e7bdc3..59fe4520c0 100644
--- a/spec/ruby/core/encoding/converter/search_convpath_spec.rb
+++ b/spec/ruby/core/encoding/converter/search_convpath_spec.rb
@@ -15,18 +15,16 @@ describe "Encoding::Converter.search_convpath" do
   end
 
   it "indicates if crlf_newline conversion would occur" do
-    cp = Encoding::Converter.search_convpath(
-      "ISO-8859-1", "EUC-JP", {crlf_newline: true})
+    cp = Encoding::Converter.search_convpath("ISO-8859-1", "EUC-JP", crlf_newline: true)
     cp.last.should == "crlf_newline"
 
-    cp = Encoding::Converter.search_convpath(
-      "ASCII", "UTF-8", {crlf_newline: false})
+    cp = Encoding::Converter.search_convpath("ASCII", "UTF-8", crlf_newline: false)
     cp.last.should_not == "crlf_newline"
   end
 
   it "raises an Encoding::ConverterNotFoundError if no conversion path exists" do
-   -> do
-     Encoding::Converter.search_convpath(Encoding::BINARY, Encoding::Emacs_Mule)
-   end.should raise_error(Encoding::ConverterNotFoundError)
+    -> do
+      Encoding::Converter.search_convpath(Encoding::BINARY, Encoding::Emacs_Mule)
+    end.should raise_error(Encoding::ConverterNotFoundError)
   end
 end
diff --git a/spec/ruby/core/encoding/default_external_spec.rb b/spec/ruby/core/encoding/default_external_spec.rb
index e2cb9b02f4..9aae4976e0 100644
--- a/spec/ruby/core/encoding/default_external_spec.rb
+++ b/spec/ruby/core/encoding/default_external_spec.rb
@@ -17,6 +17,12 @@ describe "Encoding.default_external" do
     Encoding.default_external = Encoding::SHIFT_JIS
     Encoding.default_external.should == Encoding::SHIFT_JIS
   end
+
+  platform_is :windows do
+    it 'is UTF-8 by default on Windows' do
+      Encoding.default_external.should == Encoding::UTF_8
+    end
+  end
 end
 
 describe "Encoding.default_external=" do
diff --git a/spec/ruby/core/encoding/find_spec.rb b/spec/ruby/core/encoding/find_spec.rb
index 8a0873070f..9c34fe0e77 100644
--- a/spec/ruby/core/encoding/find_spec.rb
+++ b/spec/ruby/core/encoding/find_spec.rb
@@ -50,7 +50,7 @@ describe "Encoding.find" do
   end
 
   it "raises an ArgumentError if the given encoding does not exist" do
-    -> { Encoding.find('dh2dh278d') }.should raise_error(ArgumentError)
+    -> { Encoding.find('dh2dh278d') }.should raise_error(ArgumentError, 'unknown encoding name - dh2dh278d')
   end
 
   # Not sure how to do a better test, since locale depends on weird platform-specific stuff
diff --git a/spec/ruby/core/encoding/fixtures/classes.rb b/spec/ruby/core/encoding/fixtures/classes.rb
index 12e9a4f348..943865e8d8 100644
--- a/spec/ruby/core/encoding/fixtures/classes.rb
+++ b/spec/ruby/core/encoding/fixtures/classes.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 module EncodingSpecs
   class UndefinedConversionError
     def self.exception
diff --git a/spec/ruby/core/encoding/inspect_spec.rb b/spec/ruby/core/encoding/inspect_spec.rb
index 9a930b2a77..df96141db9 100644
--- a/spec/ruby/core/encoding/inspect_spec.rb
+++ b/spec/ruby/core/encoding/inspect_spec.rb
@@ -5,9 +5,23 @@ describe "Encoding#inspect" do
     Encoding::UTF_8.inspect.should be_an_instance_of(String)
   end
 
-  it "returns #<Encoding:name> for a non-dummy encoding named 'name'" do
-    Encoding.list.to_a.reject {|e| e.dummy? }.each do |enc|
-      enc.inspect.should =~ /#<Encoding:#{enc.name}>/
+  ruby_version_is ""..."3.4" do
+    it "returns #<Encoding:name> for a non-dummy encoding named 'name'" do
+      Encoding.list.to_a.reject {|e| e.dummy? }.each do |enc|
+        enc.inspect.should =~ /#<Encoding:#{enc.name}>/
+      end
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "returns #<Encoding:name> for a non-dummy encoding named 'name'" do
+      Encoding.list.to_a.reject {|e| e.dummy? }.each do |enc|
+        if enc.name == "ASCII-8BIT"
+          enc.inspect.should == "#<Encoding:BINARY (ASCII-8BIT)>"
+        else
+          enc.inspect.should =~ /#<Encoding:#{enc.name}>/
+        end
+      end
     end
   end
 
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_name_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_name_spec.rb
index f5fa6f55e3..2b15fc1a0f 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_name_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::InvalidByteSequenceError#destination_encoding_name" do
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_spec.rb
index 43be3ddd71..c2ed6de1d8 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/destination_encoding_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::InvalidByteSequenceError#destination_encoding" do
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/error_bytes_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/error_bytes_spec.rb
index a8f7354b16..8b7e87960f 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/error_bytes_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/error_bytes_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::InvalidByteSequenceError#error_bytes" do
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/incomplete_input_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/incomplete_input_spec.rb
index e3ef3e4557..83606f77b4 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/incomplete_input_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/incomplete_input_spec.rb
@@ -1,15 +1,14 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 
 describe "Encoding::InvalidByteSequenceError#incomplete_input?" do
-
   it "returns nil by default" do
     Encoding::InvalidByteSequenceError.new.incomplete_input?.should be_nil
   end
 
   it "returns true if #primitive_convert returned :incomplete_input for the same data" do
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert("\xA1",'').should == :incomplete_input
+    ec.primitive_convert(+"\xA1", +'').should == :incomplete_input
     begin
       ec.convert("\xA1")
     rescue Encoding::InvalidByteSequenceError => e
@@ -19,7 +18,7 @@ describe "Encoding::InvalidByteSequenceError#incomplete_input?" do
 
   it "returns false if #primitive_convert returned :invalid_byte_sequence for the same data" do
     ec = Encoding::Converter.new("ascii", "utf-8")
-    ec.primitive_convert("\xfffffffff",'').should == :invalid_byte_sequence
+    ec.primitive_convert(+"\xfffffffff", +'').should == :invalid_byte_sequence
     begin
       ec.convert("\xfffffffff")
     rescue Encoding::InvalidByteSequenceError => e
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/readagain_bytes_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/readagain_bytes_spec.rb
index 93823b5db4..e5ad0a61bd 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/readagain_bytes_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/readagain_bytes_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::InvalidByteSequenceError#readagain_bytes" do
@@ -14,11 +15,11 @@ describe "Encoding::InvalidByteSequenceError#readagain_bytes" do
 
   it "returns the bytes to be read again" do
     @exception.readagain_bytes.size.should == 1
-    @exception.readagain_bytes.should == "a".force_encoding('binary')
+    @exception.readagain_bytes.should == "a".dup.force_encoding('binary')
     @exception.readagain_bytes.should == @errinfo[-1]
 
     @exception2.readagain_bytes.size.should == 1
-    @exception2.readagain_bytes.should == "\xFF".force_encoding('binary')
+    @exception2.readagain_bytes.should == "\xFF".dup.force_encoding('binary')
     @exception2.readagain_bytes.should == @errinfo2[-1]
   end
 
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_name_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_name_spec.rb
index bd3a51cbc5..a9464114a8 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_name_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#source_encoding_name" do
diff --git a/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_spec.rb b/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_spec.rb
index f43d6d5830..7fdc0a122b 100644
--- a/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_spec.rb
+++ b/spec/ruby/core/encoding/invalid_byte_sequence_error/source_encoding_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::InvalidByteSequenceError#source_encoding" do
diff --git a/spec/ruby/core/encoding/list_spec.rb b/spec/ruby/core/encoding/list_spec.rb
index 2a2078974e..bd3d5b7bc0 100644
--- a/spec/ruby/core/encoding/list_spec.rb
+++ b/spec/ruby/core/encoding/list_spec.rb
@@ -12,7 +12,7 @@ describe "Encoding.list" do
   end
 
   it "returns each encoding only once" do
-    orig = Encoding.list.map {|e| e.name}
+    orig = Encoding.list.map { |e| e.name }
     orig.should == orig.uniq
   end
 
@@ -33,7 +33,15 @@ describe "Encoding.list" do
   end
 
   it "includes dummy encodings" do
-    Encoding.list.select {|e| e.dummy?}.should_not == []
+    Encoding.list.select { |e| e.dummy? }.should_not == []
+  end
+
+  it 'includes UTF-8 encoding' do
+    Encoding.list.should.include?(Encoding::UTF_8)
+  end
+
+  it 'includes CESU-8 encoding' do
+    Encoding.list.should.include?(Encoding::CESU_8)
   end
 
   # TODO: Find example that illustrates this
diff --git a/spec/ruby/core/encoding/locale_charmap_spec.rb b/spec/ruby/core/encoding/locale_charmap_spec.rb
index 5963a8beb5..8143b9083a 100644
--- a/spec/ruby/core/encoding/locale_charmap_spec.rb
+++ b/spec/ruby/core/encoding/locale_charmap_spec.rb
@@ -7,11 +7,13 @@ describe "Encoding.locale_charmap" do
 
   # FIXME: Get this working on Windows
   platform_is :linux do
-    it "returns a value based on the LC_ALL environment variable" do
-      old_lc_all = ENV['LC_ALL']
-      ENV['LC_ALL'] = 'C'
-      ruby_exe("print Encoding.locale_charmap").should == 'ANSI_X3.4-1968'
-      ENV['LC_ALL'] = old_lc_all
+    platform_is_not :android do
+      it "returns a value based on the LC_ALL environment variable" do
+        old_lc_all = ENV['LC_ALL']
+        ENV['LC_ALL'] = 'C'
+        ruby_exe("print Encoding.locale_charmap").should == 'ANSI_X3.4-1968'
+        ENV['LC_ALL'] = old_lc_all
+      end
     end
   end
 
@@ -33,6 +35,15 @@ describe "Encoding.locale_charmap" do
     end
   end
 
+  platform_is :android do
+    it "always returns UTF-8" do
+      old_lc_all = ENV['LC_ALL']
+      ENV['LC_ALL'] = 'C'
+      ruby_exe("print Encoding.locale_charmap").should == 'UTF-8'
+      ENV['LC_ALL'] = old_lc_all
+    end
+  end
+
   platform_is :bsd, :darwin, :linux do
     it "is unaffected by assigning to ENV['LC_ALL'] in the same process" do
       old_charmap = Encoding.locale_charmap
diff --git a/spec/ruby/core/encoding/name_spec.rb b/spec/ruby/core/encoding/name_spec.rb
index 5eadb1d2f5..dce9347978 100644
--- a/spec/ruby/core/encoding/name_spec.rb
+++ b/spec/ruby/core/encoding/name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative 'shared/name'
 
 describe "Encoding#name" do
diff --git a/spec/ruby/core/encoding/replicate_spec.rb b/spec/ruby/core/encoding/replicate_spec.rb
index 717e9cea72..2da998837f 100644
--- a/spec/ruby/core/encoding/replicate_spec.rb
+++ b/spec/ruby/core/encoding/replicate_spec.rb
@@ -1,46 +1,88 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 
 describe "Encoding#replicate" do
-  before :all do
-    @i = 0
-  end
+  ruby_version_is ""..."3.3" do
+    before :all do
+      @i = 0
+    end
 
-  before :each do
-    @i += 1
-    @prefix = "RS#{@i}"
-  end
+    before :each do
+      @i += 1
+      @prefix = "RS#{@i}"
+    end
 
-  it "returns a replica of ASCII" do
-    name = @prefix + '-ASCII'
-    e = Encoding::ASCII.replicate(name)
-    e.name.should == name
-    "a".force_encoding(e).valid_encoding?.should be_true
-    "\x80".force_encoding(e).valid_encoding?.should be_false
-  end
+    it "returns a replica of ASCII" do
+      name = @prefix + '-ASCII'
+      e = suppress_warning { Encoding::ASCII.replicate(name) }
+      e.name.should == name
+      Encoding.find(name).should == e
+
+      "a".dup.force_encoding(e).valid_encoding?.should be_true
+      "\x80".dup.force_encoding(e).valid_encoding?.should be_false
+    end
+
+    it "returns a replica of UTF-8" do
+      name = @prefix + 'UTF-8'
+      e = suppress_warning { Encoding::UTF_8.replicate(name) }
+      e.name.should == name
+      Encoding.find(name).should == e
+
+      "a".dup.force_encoding(e).valid_encoding?.should be_true
+      "\u3042".dup.force_encoding(e).valid_encoding?.should be_true
+      "\x80".dup.force_encoding(e).valid_encoding?.should be_false
+    end
 
-  it "returns a replica of UTF-8" do
-    name = @prefix + 'UTF-8'
-    e = Encoding::UTF_8.replicate(name)
-    e.name.should == name
-    "a".force_encoding(e).valid_encoding?.should be_true
-    "\u3042".force_encoding(e).valid_encoding?.should be_true
-    "\x80".force_encoding(e).valid_encoding?.should be_false
+    it "returns a replica of UTF-16BE" do
+      name = @prefix + 'UTF-16-BE'
+      e = suppress_warning { Encoding::UTF_16BE.replicate(name) }
+      e.name.should == name
+      Encoding.find(name).should == e
+
+      "a".dup.force_encoding(e).valid_encoding?.should be_false
+      "\x30\x42".dup.force_encoding(e).valid_encoding?.should be_true
+      "\x80".dup.force_encoding(e).valid_encoding?.should be_false
+    end
+
+    it "returns a replica of ISO-2022-JP" do
+      name = @prefix + 'ISO-2022-JP'
+      e = suppress_warning { Encoding::ISO_2022_JP.replicate(name) }
+      Encoding.find(name).should == e
+
+      e.name.should == name
+      e.dummy?.should be_true
+    end
+
+    # NOTE: it's unclear of the value of this (for the complexity cost of it),
+    # but it is the current CRuby behavior.
+    it "can be associated with a String" do
+      name = @prefix + '-US-ASCII'
+      e = suppress_warning { Encoding::US_ASCII.replicate(name) }
+      e.name.should == name
+      Encoding.find(name).should == e
+
+      s = "abc".dup.force_encoding(e)
+      s.encoding.should == e
+      s.encoding.name.should == name
+    end
   end
 
-  it "returns a replica of UTF-16BE" do
-    name = @prefix + 'UTF-16-BE'
-    e = Encoding::UTF_16BE.replicate(name)
-    e.name.should == name
-    "a".force_encoding(e).valid_encoding?.should be_false
-    "\x30\x42".force_encoding(e).valid_encoding?.should be_true
-    "\x80".force_encoding(e).valid_encoding?.should be_false
+  ruby_version_is ""..."3.3" do
+    it "warns about deprecation" do
+      -> {
+        Encoding::US_ASCII.replicate('MY-US-ASCII')
+      }.should complain(/warning: Encoding#replicate is deprecated and will be removed in Ruby 3.3; use the original encoding instead/)
+    end
+
+    it "raises EncodingError if too many encodings" do
+      code = '1_000.times {|i| Encoding::US_ASCII.replicate("R_#{i}") }'
+      ruby_exe(code, args: "2>&1", exit_status: 1).should.include?('too many encoding (> 256) (EncodingError)')
+    end
   end
 
-  it "returns a replica of ISO-2022-JP" do
-    name = @prefix + 'ISO-2022-JP'
-    e = Encoding::ISO_2022_JP.replicate(name)
-    e.name.should == name
-    e.dummy?.should be_true
+  ruby_version_is "3.3" do
+    it "has been removed" do
+      Encoding::US_ASCII.should_not.respond_to?(:replicate, true)
+    end
   end
 end
diff --git a/spec/ruby/core/encoding/to_s_spec.rb b/spec/ruby/core/encoding/to_s_spec.rb
index 82d282386b..bab394a888 100644
--- a/spec/ruby/core/encoding/to_s_spec.rb
+++ b/spec/ruby/core/encoding/to_s_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative 'shared/name'
 
 describe "Encoding#to_s" do
diff --git a/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_name_spec.rb b/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_name_spec.rb
index 106fc7ecac..a51a9f46a0 100644
--- a/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_name_spec.rb
+++ b/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#destination_encoding_name" do
diff --git a/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_spec.rb b/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_spec.rb
index c6e24732fd..905556407c 100644
--- a/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_spec.rb
+++ b/spec/ruby/core/encoding/undefined_conversion_error/destination_encoding_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#destination_encoding" do
diff --git a/spec/ruby/core/encoding/undefined_conversion_error/error_char_spec.rb b/spec/ruby/core/encoding/undefined_conversion_error/error_char_spec.rb
index 780d81c1ee..9cb55e6d95 100644
--- a/spec/ruby/core/encoding/undefined_conversion_error/error_char_spec.rb
+++ b/spec/ruby/core/encoding/undefined_conversion_error/error_char_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#error_char" do
diff --git a/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_name_spec.rb b/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_name_spec.rb
index 3b697cb82f..d5e60e78db 100644
--- a/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_name_spec.rb
+++ b/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#source_encoding_name" do
diff --git a/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_spec.rb b/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_spec.rb
index 9101d51e11..de456a4b5a 100644
--- a/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_spec.rb
+++ b/spec/ruby/core/encoding/undefined_conversion_error/source_encoding_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative '../fixtures/classes'
 
 describe "Encoding::UndefinedConversionError#source_encoding" do
diff --git a/spec/ruby/core/enumerable/all_spec.rb b/spec/ruby/core/enumerable/all_spec.rb
index 8af80896a9..160cd52628 100644
--- a/spec/ruby/core/enumerable/all_spec.rb
+++ b/spec/ruby/core/enumerable/all_spec.rb
@@ -10,13 +10,13 @@ describe "Enumerable#all?" do
   end
 
   it "always returns true on empty enumeration" do
-    @empty.all?.should == true
+    @empty.should.all?
     @empty.all? { nil }.should == true
 
-    [].all?.should == true
+    [].should.all?
     [].all? { false }.should == true
 
-    {}.all?.should == true
+    {}.should.all?
     {}.all? { nil }.should == true
   end
 
@@ -26,15 +26,6 @@ describe "Enumerable#all?" do
     -> { {}.all?(1, 2, 3) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises an ArgumentError when any arguments provided" do
-      -> { @enum.all?(Proc.new {}) }.should raise_error(ArgumentError)
-      -> { @enum.all?(nil) }.should raise_error(ArgumentError)
-      -> { @empty.all?(1) }.should raise_error(ArgumentError)
-      -> { @enum1.all?(1) {} }.should raise_error(ArgumentError)
-    end
-  end
-
   it "does not hide exceptions out of #each" do
     -> {
       EnumerableSpecs::ThrowingEach.new.all?
@@ -47,24 +38,24 @@ describe "Enumerable#all?" do
 
   describe "with no block" do
     it "returns true if no elements are false or nil" do
-      @enum.all?.should == true
-      @enum1.all?.should == true
-      @enum2.all?.should == false
+      @enum.should.all?
+      @enum1.should.all?
+      @enum2.should_not.all?
 
-      EnumerableSpecs::Numerous.new('a','b','c').all?.should == true
-      EnumerableSpecs::Numerous.new(0, "x", true).all?.should == true
+      EnumerableSpecs::Numerous.new('a','b','c').should.all?
+      EnumerableSpecs::Numerous.new(0, "x", true).should.all?
     end
 
     it "returns false if there are false or nil elements" do
-      EnumerableSpecs::Numerous.new(false).all?.should == false
-      EnumerableSpecs::Numerous.new(false, false).all?.should == false
+      EnumerableSpecs::Numerous.new(false).should_not.all?
+      EnumerableSpecs::Numerous.new(false, false).should_not.all?
 
-      EnumerableSpecs::Numerous.new(nil).all?.should == false
-      EnumerableSpecs::Numerous.new(nil, nil).all?.should == false
+      EnumerableSpecs::Numerous.new(nil).should_not.all?
+      EnumerableSpecs::Numerous.new(nil, nil).should_not.all?
 
-      EnumerableSpecs::Numerous.new(1, nil, 2).all?.should == false
-      EnumerableSpecs::Numerous.new(0, "x", false, true).all?.should == false
-      @enum2.all?.should == false
+      EnumerableSpecs::Numerous.new(1, nil, 2).should_not.all?
+      EnumerableSpecs::Numerous.new(0, "x", false, true).should_not.all?
+      @enum2.should_not.all?
     end
 
     it "gathers whole arrays as elements when each yields multiple" do
@@ -133,69 +124,64 @@ describe "Enumerable#all?" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe 'when given a pattern argument' do
-      it "calls `===` on the pattern the return value " do
-        pattern = EnumerableSpecs::Pattern.new { |x| x >= 0 }
-        @enum1.all?(pattern).should == false
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-      end
-
-      # may raise an exception in future versions
-      ruby_version_is ""..."2.6" do
-        it "ignores block" do
-          @enum2.all?(NilClass) { raise }.should == false
-          [1, 2, nil].all?(NilClass) { raise }.should == false
-          {a: 1}.all?(Array) { raise }.should == true
-        end
-      end
-
-      it "always returns true on empty enumeration" do
-        @empty.all?(Integer).should == true
-        [].all?(Integer).should == true
-        {}.all?(NilClass).should == true
-      end
-
-      it "does not hide exceptions out of #each" do
-        -> {
-          EnumerableSpecs::ThrowingEach.new.all?(Integer)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "returns true if the pattern never returns false or nil" do
-        pattern = EnumerableSpecs::Pattern.new { |x| 42 }
-        @enum.all?(pattern).should == true
-
-        [1, 42, 3].all?(pattern).should == true
-
-        pattern = EnumerableSpecs::Pattern.new { |x| Array === x }
-        {a: 1, b: 2}.all?(pattern).should == true
-      end
-
-      it "returns false if the pattern ever returns false or nil" do
-        pattern = EnumerableSpecs::Pattern.new { |x| x >= 0 }
-        @enum1.all?(pattern).should == false
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-
-        [1, 2, 3, -1].all?(pattern).should == false
-
-        pattern = EnumerableSpecs::Pattern.new { |x| x[1] >= 0 }
-        {a: 1, b: -1}.all?(pattern).should == false
-      end
-
-      it "does not hide exceptions out of pattern#===" do
-        pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
-        -> {
-          @enum.all?(pattern)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "calls the pattern with gathered array when yielded with multiple arguments" do
-        multi = EnumerableSpecs::YieldsMulti.new
-        pattern = EnumerableSpecs::Pattern.new { true }
-        multi.all?(pattern).should == true
-        pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
-      end
+  describe 'when given a pattern argument' do
+    it "calls `===` on the pattern the return value " do
+      pattern = EnumerableSpecs::Pattern.new { |x| x >= 0 }
+      @enum1.all?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+    end
+
+    it "always returns true on empty enumeration" do
+      @empty.all?(Integer).should == true
+      [].all?(Integer).should == true
+      {}.all?(NilClass).should == true
+    end
+
+    it "does not hide exceptions out of #each" do
+      -> {
+        EnumerableSpecs::ThrowingEach.new.all?(Integer)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "returns true if the pattern never returns false or nil" do
+      pattern = EnumerableSpecs::Pattern.new { |x| 42 }
+      @enum.all?(pattern).should == true
+
+      [1, 42, 3].all?(pattern).should == true
+
+      pattern = EnumerableSpecs::Pattern.new { |x| Array === x }
+      {a: 1, b: 2}.all?(pattern).should == true
+    end
+
+    it "returns false if the pattern ever returns false or nil" do
+      pattern = EnumerableSpecs::Pattern.new { |x| x >= 0 }
+      @enum1.all?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+
+      [1, 2, 3, -1].all?(pattern).should == false
+
+      pattern = EnumerableSpecs::Pattern.new { |x| x[1] >= 0 }
+      {a: 1, b: -1}.all?(pattern).should == false
+    end
+
+    it "does not hide exceptions out of pattern#===" do
+      pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
+      -> {
+        @enum.all?(pattern)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "calls the pattern with gathered array when yielded with multiple arguments" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      pattern = EnumerableSpecs::Pattern.new { true }
+      multi.all?(pattern).should == true
+      pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
+    end
+
+    it "ignores the block if there is an argument" do
+      -> {
+        EnumerableSpecs::Numerous.new(1, 2, 3, 4, 5).all?(String) { true }.should == false
+      }.should complain(/given block not used/)
     end
   end
 end
diff --git a/spec/ruby/core/enumerable/any_spec.rb b/spec/ruby/core/enumerable/any_spec.rb
index c800fe2d4b..243f8735d5 100644
--- a/spec/ruby/core/enumerable/any_spec.rb
+++ b/spec/ruby/core/enumerable/any_spec.rb
@@ -10,13 +10,13 @@ describe "Enumerable#any?" do
   end
 
   it "always returns false on empty enumeration" do
-    @empty.any?.should == false
+    @empty.should_not.any?
     @empty.any? { nil }.should == false
 
-    [].any?.should == false
+    [].should_not.any?
     [].any? { false }.should == false
 
-    {}.any?.should == false
+    {}.should_not.any?
     {}.any? { nil }.should == false
   end
 
@@ -26,15 +26,6 @@ describe "Enumerable#any?" do
     -> { {}.any?(1, 2, 3) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises an ArgumentError when any arguments provided" do
-      -> { @enum.any?(Proc.new {}) }.should raise_error(ArgumentError)
-      -> { @enum.any?(nil) }.should raise_error(ArgumentError)
-      -> { @empty.any?(1) }.should raise_error(ArgumentError)
-      -> { @enum1.any?(1) {} }.should raise_error(ArgumentError)
-    end
-  end
-
   it "does not hide exceptions out of #each" do
     -> {
       EnumerableSpecs::ThrowingEach.new.any?
@@ -47,24 +38,24 @@ describe "Enumerable#any?" do
 
   describe "with no block" do
     it "returns true if any element is not false or nil" do
-      @enum.any?.should == true
-      @enum1.any?.should == true
-      @enum2.any?.should == true
-      EnumerableSpecs::Numerous.new(true).any?.should == true
-      EnumerableSpecs::Numerous.new('a','b','c').any?.should == true
-      EnumerableSpecs::Numerous.new('a','b','c', nil).any?.should == true
-      EnumerableSpecs::Numerous.new(1, nil, 2).any?.should == true
-      EnumerableSpecs::Numerous.new(1, false).any?.should == true
-      EnumerableSpecs::Numerous.new(false, nil, 1, false).any?.should == true
-      EnumerableSpecs::Numerous.new(false, 0, nil).any?.should == true
+      @enum.should.any?
+      @enum1.should.any?
+      @enum2.should.any?
+      EnumerableSpecs::Numerous.new(true).should.any?
+      EnumerableSpecs::Numerous.new('a','b','c').should.any?
+      EnumerableSpecs::Numerous.new('a','b','c', nil).should.any?
+      EnumerableSpecs::Numerous.new(1, nil, 2).should.any?
+      EnumerableSpecs::Numerous.new(1, false).should.any?
+      EnumerableSpecs::Numerous.new(false, nil, 1, false).should.any?
+      EnumerableSpecs::Numerous.new(false, 0, nil).should.any?
     end
 
     it "returns false if all elements are false or nil" do
-      EnumerableSpecs::Numerous.new(false).any?.should == false
-      EnumerableSpecs::Numerous.new(false, false).any?.should == false
-      EnumerableSpecs::Numerous.new(nil).any?.should == false
-      EnumerableSpecs::Numerous.new(nil, nil).any?.should == false
-      EnumerableSpecs::Numerous.new(nil, false, nil).any?.should == false
+      EnumerableSpecs::Numerous.new(false).should_not.any?
+      EnumerableSpecs::Numerous.new(false, false).should_not.any?
+      EnumerableSpecs::Numerous.new(nil).should_not.any?
+      EnumerableSpecs::Numerous.new(nil, nil).should_not.any?
+      EnumerableSpecs::Numerous.new(nil, false, nil).should_not.any?
     end
 
     it "gathers whole arrays as elements when each yields multiple" do
@@ -147,68 +138,63 @@ describe "Enumerable#any?" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe 'when given a pattern argument' do
-      it "calls `===` on the pattern the return value " do
-        pattern = EnumerableSpecs::Pattern.new { |x| x == 2 }
-        @enum1.any?(pattern).should == true
-        pattern.yielded.should == [[0], [1], [2]]
-      end
-
-      # may raise an exception in future versions
-      ruby_version_is ""..."2.6" do
-        it "ignores block" do
-          @enum2.any?(NilClass) { raise }.should == true
-          [1, 2, nil].any?(NilClass) { raise }.should == true
-          {a: 1}.any?(Array) { raise }.should == true
-        end
-      end
-
-      it "always returns false on empty enumeration" do
-        @empty.any?(Integer).should == false
-        [].any?(Integer).should == false
-        {}.any?(NilClass).should == false
-      end
-
-      it "does not hide exceptions out of #each" do
-        -> {
-          EnumerableSpecs::ThrowingEach.new.any?(Integer)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "returns true if the pattern ever returns a truthy value" do
-        @enum2.any?(NilClass).should == true
-        pattern = EnumerableSpecs::Pattern.new { |x| 42 }
-        @enum.any?(pattern).should == true
-
-        [1, 42, 3].any?(pattern).should == true
-
-        pattern = EnumerableSpecs::Pattern.new { |x| x == [:b, 2] }
-        {a: 1, b: 2}.any?(pattern).should == true
-      end
-
-      it "returns false if the block never returns other than false or nil" do
-        pattern = EnumerableSpecs::Pattern.new { |x| nil }
-        @enum1.any?(pattern).should == false
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-
-        [1, 2, 3].any?(pattern).should == false
-        {a: 1}.any?(pattern).should == false
-      end
-
-      it "does not hide exceptions out of pattern#===" do
-        pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
-        -> {
-          @enum.any?(pattern)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "calls the pattern with gathered array when yielded with multiple arguments" do
-        multi = EnumerableSpecs::YieldsMulti.new
-        pattern = EnumerableSpecs::Pattern.new { false }
-        multi.any?(pattern).should == false
-        pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
-      end
+  describe 'when given a pattern argument' do
+    it "calls `===` on the pattern the return value " do
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 2 }
+      @enum1.any?(pattern).should == true
+      pattern.yielded.should == [[0], [1], [2]]
+    end
+
+    it "always returns false on empty enumeration" do
+      @empty.any?(Integer).should == false
+      [].any?(Integer).should == false
+      {}.any?(NilClass).should == false
+    end
+
+    it "does not hide exceptions out of #each" do
+      -> {
+        EnumerableSpecs::ThrowingEach.new.any?(Integer)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "returns true if the pattern ever returns a truthy value" do
+      @enum2.any?(NilClass).should == true
+      pattern = EnumerableSpecs::Pattern.new { |x| 42 }
+      @enum.any?(pattern).should == true
+
+      [1, 42, 3].any?(pattern).should == true
+
+      pattern = EnumerableSpecs::Pattern.new { |x| x == [:b, 2] }
+      {a: 1, b: 2}.any?(pattern).should == true
+    end
+
+    it "returns false if the block never returns other than false or nil" do
+      pattern = EnumerableSpecs::Pattern.new { |x| nil }
+      @enum1.any?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+
+      [1, 2, 3].any?(pattern).should == false
+      {a: 1}.any?(pattern).should == false
+    end
+
+    it "does not hide exceptions out of pattern#===" do
+      pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
+      -> {
+        @enum.any?(pattern)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "calls the pattern with gathered array when yielded with multiple arguments" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      pattern = EnumerableSpecs::Pattern.new { false }
+      multi.any?(pattern).should == false
+      pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
+    end
+
+    it "ignores the block if there is an argument" do
+      -> {
+        EnumerableSpecs::Numerous.new(1, 2, 3, 4, 5).any?(String) { true }.should == false
+      }.should complain(/given block not used/)
     end
   end
 end
diff --git a/spec/ruby/core/enumerable/chain_spec.rb b/spec/ruby/core/enumerable/chain_spec.rb
index 85c0c03603..5e2105d294 100644
--- a/spec/ruby/core/enumerable/chain_spec.rb
+++ b/spec/ruby/core/enumerable/chain_spec.rb
@@ -1,25 +1,23 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is "2.6" do
-  describe "Enumerable#chain" do
-    before :each do
-      ScratchPad.record []
-    end
+describe "Enumerable#chain" do
+  before :each do
+    ScratchPad.record []
+  end
 
-    it "returns a chain of self and provided enumerables" do
-      one = EnumerableSpecs::Numerous.new(1)
-      two = EnumerableSpecs::Numerous.new(2, 3)
-      three = EnumerableSpecs::Numerous.new(4, 5, 6)
+  it "returns a chain of self and provided enumerables" do
+    one = EnumerableSpecs::Numerous.new(1)
+    two = EnumerableSpecs::Numerous.new(2, 3)
+    three = EnumerableSpecs::Numerous.new(4, 5, 6)
 
-      chain = one.chain(two, three)
+    chain = one.chain(two, three)
 
-      chain.each { |item| ScratchPad << item }
-      ScratchPad.recorded.should == [1, 2, 3, 4, 5, 6]
-    end
+    chain.each { |item| ScratchPad << item }
+    ScratchPad.recorded.should == [1, 2, 3, 4, 5, 6]
+  end
 
-    it "returns an Enumerator::Chain if given a block" do
-      EnumerableSpecs::Numerous.new.chain.should be_an_instance_of(Enumerator::Chain)
-    end
+  it "returns an Enumerator::Chain if given a block" do
+    EnumerableSpecs::Numerous.new.chain.should be_an_instance_of(Enumerator::Chain)
   end
 end
diff --git a/spec/ruby/core/enumerable/chunk_spec.rb b/spec/ruby/core/enumerable/chunk_spec.rb
index 548544f4e8..ed6304307f 100644
--- a/spec/ruby/core/enumerable/chunk_spec.rb
+++ b/spec/ruby/core/enumerable/chunk_spec.rb
@@ -29,12 +29,22 @@ describe "Enumerable#chunk" do
     result.should == [[1, [1, 2]], [0, [3]], [1, [2]], [0, [3]], [1, [2, 1]]]
   end
 
+  it "returns a partitioned Array of values" do
+    e = EnumerableSpecs::Numerous.new(1,2,3)
+    e.chunk { |x| x > 2 }.map(&:last).should == [[1, 2], [3]]
+  end
+
   it "returns elements for which the block returns :_alone in separate Arrays" do
     e = EnumerableSpecs::Numerous.new(1, 2, 3, 2, 1)
     result = e.chunk { |x| x < 2 && :_alone }.to_a
     result.should == [[:_alone, [1]], [false, [2, 3, 2]], [:_alone, [1]]]
   end
 
+  it "yields Arrays as a single argument to a rest argument" do
+    e = EnumerableSpecs::Numerous.new([1, 2])
+    result = e.chunk { |*x| x.should == [[1,2]] }.to_a
+  end
+
   it "does not return elements for which the block returns :_separator" do
     e = EnumerableSpecs::Numerous.new(1, 2, 3, 3, 2, 1)
     result = e.chunk { |x| x == 2 ? :_separator : 1 }.to_a
diff --git a/spec/ruby/core/enumerable/collect_concat_spec.rb b/spec/ruby/core/enumerable/collect_concat_spec.rb
index 6e34c9eb93..59317cfe34 100644
--- a/spec/ruby/core/enumerable/collect_concat_spec.rb
+++ b/spec/ruby/core/enumerable/collect_concat_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/collect_concat'
 
 describe "Enumerable#collect_concat" do
-  it_behaves_like :enumerable_collect_concat , :collect_concat
+  it_behaves_like :enumerable_collect_concat, :collect_concat
 end
diff --git a/spec/ruby/core/enumerable/collect_spec.rb b/spec/ruby/core/enumerable/collect_spec.rb
index 1016b67798..cfa2895cce 100644
--- a/spec/ruby/core/enumerable/collect_spec.rb
+++ b/spec/ruby/core/enumerable/collect_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/collect'
 
 describe "Enumerable#collect" do
-  it_behaves_like :enumerable_collect , :collect
+  it_behaves_like :enumerable_collect, :collect
 end
diff --git a/spec/ruby/core/enumerable/compact_spec.rb b/spec/ruby/core/enumerable/compact_spec.rb
new file mode 100644
index 0000000000..1895430c4e
--- /dev/null
+++ b/spec/ruby/core/enumerable/compact_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerable#compact" do
+  it 'returns array without nil elements' do
+    arr = EnumerableSpecs::Numerous.new(nil, 1, 2, nil, true)
+    arr.compact.should == [1, 2, true]
+  end
+end
diff --git a/spec/ruby/core/enumerable/detect_spec.rb b/spec/ruby/core/enumerable/detect_spec.rb
index e912134fed..6959aadc44 100644
--- a/spec/ruby/core/enumerable/detect_spec.rb
+++ b/spec/ruby/core/enumerable/detect_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/find'
 
 describe "Enumerable#detect" do
-  it_behaves_like :enumerable_find , :detect
+  it_behaves_like :enumerable_find, :detect
 end
diff --git a/spec/ruby/core/enumerable/each_cons_spec.rb b/spec/ruby/core/enumerable/each_cons_spec.rb
index 7d44f54f74..ed77741862 100644
--- a/spec/ruby/core/enumerable/each_cons_spec.rb
+++ b/spec/ruby/core/enumerable/each_cons_spec.rb
@@ -10,7 +10,7 @@ describe "Enumerable#each_cons" do
 
   it "passes element groups to the block" do
     acc = []
-    @enum.each_cons(3){|g| acc << g}.should be_nil
+    @enum.each_cons(3){|g| acc << g}
     acc.should == @in_threes
   end
 
@@ -27,7 +27,7 @@ describe "Enumerable#each_cons" do
 
   it "tries to convert n to an Integer using #to_int" do
     acc = []
-    @enum.each_cons(3.3){|g| acc << g}.should == nil
+    @enum.each_cons(3.3){|g| acc << g}
     acc.should == @in_threes
 
     obj = mock('to_int')
@@ -56,6 +56,10 @@ describe "Enumerable#each_cons" do
     multi.each_cons(2).to_a.should == [[[1, 2], [3, 4, 5]], [[3, 4, 5], [6, 7, 8, 9]]]
   end
 
+  it "returns self when a block is given" do
+    @enum.each_cons(3){}.should == @enum
+  end
+
   describe "when no block is given" do
     it "returns an enumerator" do
       e = @enum.each_cons(3)
diff --git a/spec/ruby/core/enumerable/each_slice_spec.rb b/spec/ruby/core/enumerable/each_slice_spec.rb
index ab3b79c344..47b8c9ba33 100644
--- a/spec/ruby/core/enumerable/each_slice_spec.rb
+++ b/spec/ruby/core/enumerable/each_slice_spec.rb
@@ -10,7 +10,7 @@ describe "Enumerable#each_slice" do
 
   it "passes element groups to the block" do
     acc = []
-    @enum.each_slice(3){|g| acc << g}.should be_nil
+    @enum.each_slice(3){|g| acc << g}
     acc.should == @sliced
   end
 
@@ -27,7 +27,7 @@ describe "Enumerable#each_slice" do
 
   it "tries to convert n to an Integer using #to_int" do
     acc = []
-    @enum.each_slice(3.3){|g| acc << g}.should == nil
+    @enum.each_slice(3.3){|g| acc << g}
     acc.should == @sliced
 
     obj = mock('to_int')
@@ -57,6 +57,10 @@ describe "Enumerable#each_slice" do
     e.to_a.should == @sliced
   end
 
+  it "returns self when a block is given" do
+    @enum.each_slice(3){}.should == @enum
+  end
+
   it "gathers whole arrays as elements when each yields multiple" do
     multi = EnumerableSpecs::YieldsMulti.new
     multi.each_slice(2).to_a.should == [[[1, 2], [3, 4, 5]], [[6, 7, 8, 9]]]
diff --git a/spec/ruby/core/enumerable/entries_spec.rb b/spec/ruby/core/enumerable/entries_spec.rb
index 83232cfa06..2de4fc756a 100644
--- a/spec/ruby/core/enumerable/entries_spec.rb
+++ b/spec/ruby/core/enumerable/entries_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/entries'
 
 describe "Enumerable#entries" do
-  it_behaves_like :enumerable_entries , :entries
+  it_behaves_like :enumerable_entries, :entries
 end
diff --git a/spec/ruby/core/enumerable/filter_map_spec.rb b/spec/ruby/core/enumerable/filter_map_spec.rb
index 31acc277b4..aa4894230b 100644
--- a/spec/ruby/core/enumerable/filter_map_spec.rb
+++ b/spec/ruby/core/enumerable/filter_map_spec.rb
@@ -1,26 +1,24 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is '2.7' do
-  describe 'Enumerable#filter_map' do
-    before :each do
-      @numerous = EnumerableSpecs::Numerous.new(*(1..8).to_a)
-    end
+describe 'Enumerable#filter_map' do
+  before :each do
+    @numerous = EnumerableSpecs::Numerous.new(*(1..8).to_a)
+  end
 
-    it 'returns an empty array if there are no elements' do
-      EnumerableSpecs::Empty.new.filter_map { true }.should == []
-    end
+  it 'returns an empty array if there are no elements' do
+    EnumerableSpecs::Empty.new.filter_map { true }.should == []
+  end
 
-    it 'returns an array with truthy results of passing each element to block' do
-      @numerous.filter_map { |i| i * 2 if i.even? }.should == [4, 8, 12, 16]
-      @numerous.filter_map { |i| i * 2 }.should == [2, 4, 6, 8, 10, 12, 14, 16]
-      @numerous.filter_map { 0 }.should == [0, 0, 0, 0, 0, 0, 0, 0]
-      @numerous.filter_map { false }.should == []
-      @numerous.filter_map { nil }.should == []
-    end
+  it 'returns an array with truthy results of passing each element to block' do
+    @numerous.filter_map { |i| i * 2 if i.even? }.should == [4, 8, 12, 16]
+    @numerous.filter_map { |i| i * 2 }.should == [2, 4, 6, 8, 10, 12, 14, 16]
+    @numerous.filter_map { 0 }.should == [0, 0, 0, 0, 0, 0, 0, 0]
+    @numerous.filter_map { false }.should == []
+    @numerous.filter_map { nil }.should == []
+  end
 
-    it 'returns an enumerator when no block given' do
-      @numerous.filter_map.should be_an_instance_of(Enumerator)
-    end
+  it 'returns an enumerator when no block given' do
+    @numerous.filter_map.should be_an_instance_of(Enumerator)
   end
 end
diff --git a/spec/ruby/core/enumerable/filter_spec.rb b/spec/ruby/core/enumerable/filter_spec.rb
index f2dc7a7b71..1c3a7e9ff5 100644
--- a/spec/ruby/core/enumerable/filter_spec.rb
+++ b/spec/ruby/core/enumerable/filter_spec.rb
@@ -2,8 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/find_all'
 
-ruby_version_is "2.6" do
-  describe "Enumerable#filter" do
-    it_behaves_like(:enumerable_find_all , :filter)
-  end
+describe "Enumerable#filter" do
+  it_behaves_like :enumerable_find_all, :filter
 end
diff --git a/spec/ruby/core/enumerable/find_all_spec.rb b/spec/ruby/core/enumerable/find_all_spec.rb
index ce9058fe77..9cd635f247 100644
--- a/spec/ruby/core/enumerable/find_all_spec.rb
+++ b/spec/ruby/core/enumerable/find_all_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/find_all'
 
 describe "Enumerable#find_all" do
-  it_behaves_like :enumerable_find_all , :find_all
+  it_behaves_like :enumerable_find_all, :find_all
 end
diff --git a/spec/ruby/core/enumerable/find_spec.rb b/spec/ruby/core/enumerable/find_spec.rb
index 25aa3bf103..5ddebc05f8 100644
--- a/spec/ruby/core/enumerable/find_spec.rb
+++ b/spec/ruby/core/enumerable/find_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/find'
 
 describe "Enumerable#find" do
-  it_behaves_like :enumerable_find , :find
+  it_behaves_like :enumerable_find, :find
 end
diff --git a/spec/ruby/core/enumerable/fixtures/classes.rb b/spec/ruby/core/enumerable/fixtures/classes.rb
index 5051196742..b5feafcfb7 100644
--- a/spec/ruby/core/enumerable/fixtures/classes.rb
+++ b/spec/ruby/core/enumerable/fixtures/classes.rb
@@ -38,12 +38,14 @@ module EnumerableSpecs
   class Empty
     include Enumerable
     def each
+      self
     end
   end
 
   class EmptyWithSize
     include Enumerable
     def each
+      self
     end
     def size
       0
@@ -251,7 +253,7 @@ module EnumerableSpecs
     end
   end
 
-  class ComparableWithFixnum
+  class ComparableWithInteger
     include Comparable
     def initialize(num)
       @num = num
@@ -342,4 +344,7 @@ module EnumerableSpecs
       @block.call(*args)
     end
   end
+
+  class SetSubclass < Set
+  end
 end # EnumerableSpecs utility classes
diff --git a/spec/ruby/core/enumerable/flat_map_spec.rb b/spec/ruby/core/enumerable/flat_map_spec.rb
index a294b9ddad..bd07eab6c5 100644
--- a/spec/ruby/core/enumerable/flat_map_spec.rb
+++ b/spec/ruby/core/enumerable/flat_map_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/collect_concat'
 
 describe "Enumerable#flat_map" do
-  it_behaves_like :enumerable_collect_concat , :flat_map
+  it_behaves_like :enumerable_collect_concat, :flat_map
 end
diff --git a/spec/ruby/core/enumerable/grep_spec.rb b/spec/ruby/core/enumerable/grep_spec.rb
index c9c0f34e27..989358f01b 100644
--- a/spec/ruby/core/enumerable/grep_spec.rb
+++ b/spec/ruby/core/enumerable/grep_spec.rb
@@ -40,15 +40,28 @@ describe "Enumerable#grep" do
     $~.should == nil
   end
 
-  it "sets $~ to the last match when given no block" do
+  it "does not set $~ when given no block" do
     "z" =~ /z/ # Reset $~
     ["abc", "def"].grep(/b/).should == ["abc"]
+    $&.should == "z"
+  end
 
-    # Set by the failed match of "def"
-    $~.should == nil
+  it "does not modify Regexp.last_match without block" do
+    "z" =~ /z/ # Reset last match
+    ["abc", "def"].grep(/b/).should == ["abc"]
+    Regexp.last_match[0].should == "z"
+  end
+
+  it "correctly handles non-string elements" do
+    'set last match' =~ /set last (.*)/
+    [:a, 'b', 'z', :c, 42, nil].grep(/[a-d]/).should == [:a, 'b', :c]
+    $1.should == 'match'
 
-    ["abc", "def"].grep(/e/)
-    $&.should == "e"
+    o = Object.new
+    def o.to_str
+      'hello'
+    end
+    [o].grep(/ll/).first.should.equal?(o)
   end
 
   describe "with a block" do
diff --git a/spec/ruby/core/enumerable/grep_v_spec.rb b/spec/ruby/core/enumerable/grep_v_spec.rb
index 6dec487065..ba19216968 100644
--- a/spec/ruby/core/enumerable/grep_v_spec.rb
+++ b/spec/ruby/core/enumerable/grep_v_spec.rb
@@ -20,15 +20,28 @@ describe "Enumerable#grep_v" do
     $&.should == "e"
   end
 
-  it "sets $~ to the last match when given no block" do
+  it "does not set $~ when given no block" do
     "z" =~ /z/ # Reset $~
     ["abc", "def"].grep_v(/e/).should == ["abc"]
+    $&.should == "z"
+  end
 
-    # Set by the match of "def"
-    $&.should == "e"
+  it "does not modify Regexp.last_match without block" do
+    "z" =~ /z/ # Reset last match
+    ["abc", "def"].grep_v(/e/).should == ["abc"]
+    Regexp.last_match[0].should == "z"
+  end
+
+  it "correctly handles non-string elements" do
+    'set last match' =~ /set last (.*)/
+    [:a, 'b', 'z', :c, 42, nil].grep_v(/[a-d]/).should == ['z', 42, nil]
+    $1.should == 'match'
 
-    ["abc", "def"].grep_v(/b/)
-    $&.should == nil
+    o = Object.new
+    def o.to_str
+      'hello'
+    end
+    [o].grep_v(/mm/).first.should.equal?(o)
   end
 
   describe "without block" do
diff --git a/spec/ruby/core/enumerable/group_by_spec.rb b/spec/ruby/core/enumerable/group_by_spec.rb
index 580a90cf0c..4fd1603819 100644
--- a/spec/ruby/core/enumerable/group_by_spec.rb
+++ b/spec/ruby/core/enumerable/group_by_spec.rb
@@ -33,13 +33,5 @@ describe "Enumerable#group_by" do
                   [3, 4, 5] => [[3, 4, 5]] }
   end
 
-  it "returns a tainted hash if self is tainted" do
-    EnumerableSpecs::Empty.new.taint.group_by {}.tainted?.should be_true
-  end
-
-  it "returns an untrusted hash if self is untrusted" do
-    EnumerableSpecs::Empty.new.untrust.group_by {}.untrusted?.should be_true
-  end
-
   it_behaves_like :enumerable_enumeratorized_with_origin_size, :group_by
 end
diff --git a/spec/ruby/core/enumerable/map_spec.rb b/spec/ruby/core/enumerable/map_spec.rb
index d65aec238c..98a70781cf 100644
--- a/spec/ruby/core/enumerable/map_spec.rb
+++ b/spec/ruby/core/enumerable/map_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/collect'
 
 describe "Enumerable#map" do
-  it_behaves_like :enumerable_collect , :map
+  it_behaves_like :enumerable_collect, :map
 end
diff --git a/spec/ruby/core/enumerable/minmax_spec.rb b/spec/ruby/core/enumerable/minmax_spec.rb
index 29f1ecf82c..f5f17ef079 100644
--- a/spec/ruby/core/enumerable/minmax_spec.rb
+++ b/spec/ruby/core/enumerable/minmax_spec.rb
@@ -1,41 +1,17 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../../shared/enumerable/minmax'
 
 describe "Enumerable#minmax" do
   before :each do
     @enum = EnumerableSpecs::Numerous.new(6, 4, 5, 10, 8)
-
+    @empty_enum = EnumerableSpecs::Empty.new
+    @incomparable_enum = EnumerableSpecs::Numerous.new(BasicObject.new, BasicObject.new)
+    @incompatible_enum = EnumerableSpecs::Numerous.new(11,"22")
     @strs = EnumerableSpecs::Numerous.new("333", "2", "60", "55555", "1010", "111")
   end
 
-  it "min should return the minimum element" do
-    @enum.minmax.should == [4, 10]
-    @strs.minmax.should == ["1010", "60" ]
-  end
-
-  it "returns [nil, nil] for an empty Enumerable" do
-    EnumerableSpecs::Empty.new.minmax.should == [nil, nil]
-  end
-
-  it "raises an ArgumentError when elements are incomparable" do
-    -> do
-      EnumerableSpecs::Numerous.new(11,"22").minmax
-    end.should raise_error(ArgumentError)
-    -> do
-      EnumerableSpecs::Numerous.new(11,12,22,33).minmax{|a, b| nil}
-    end.should raise_error(ArgumentError)
-  end
-
-  it "raises a NoMethodError for elements without #<=>" do
-    -> do
-      EnumerableSpecs::Numerous.new(BasicObject.new, BasicObject.new).minmax
-    end.should raise_error(NoMethodError)
-  end
-
-  it "returns the minimum when using a block rule" do
-    @enum.minmax {|a,b| b <=> a }.should == [10, 4]
-    @strs.minmax {|a,b| a.length <=> b.length }.should == ["2", "55555"]
-  end
+  it_behaves_like :enumerable_minmax, :minmax
 
   it "gathers whole arrays as elements when each yields multiple" do
     multi = EnumerableSpecs::YieldsMulti.new
diff --git a/spec/ruby/core/enumerable/none_spec.rb b/spec/ruby/core/enumerable/none_spec.rb
index 7c17e58a13..fb42f13386 100644
--- a/spec/ruby/core/enumerable/none_spec.rb
+++ b/spec/ruby/core/enumerable/none_spec.rb
@@ -10,7 +10,7 @@ describe "Enumerable#none?" do
   end
 
   it "always returns true on empty enumeration" do
-    @empty.none?.should == true
+    @empty.should.none?
     @empty.none? { true }.should == true
   end
 
@@ -20,15 +20,6 @@ describe "Enumerable#none?" do
     -> { {}.none?(1, 2, 3) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises an ArgumentError when any arguments provided" do
-      -> { @enum.none?(Proc.new {}) }.should raise_error(ArgumentError)
-      -> { @enum.none?(nil) }.should raise_error(ArgumentError)
-      -> { @empty.none?(1) }.should raise_error(ArgumentError)
-      -> { @enum.none?(1) {} }.should raise_error(ArgumentError)
-    end
-  end
-
   it "does not hide exceptions out of #each" do
     -> {
       EnumerableSpecs::ThrowingEach.new.none?
@@ -102,66 +93,61 @@ describe "Enumerable#none?" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe 'when given a pattern argument' do
-      it "calls `===` on the pattern the return value " do
-        pattern = EnumerableSpecs::Pattern.new { |x| x == 3 }
-        @enum1.none?(pattern).should == true
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-      end
-
-      # may raise an exception in future versions
-      ruby_version_is ""..."2.6" do
-        it "ignores block" do
-          @enum2.none?(Integer) { raise }.should == true
-          [1, 2, nil].none?(TrueClass) { raise }.should == true
-          {a: 1}.none?(Hash) { raise }.should == true
-        end
-      end
-
-      it "always returns true on empty enumeration" do
-        @empty.none?(Integer).should == true
-        [].none?(Integer).should == true
-        {}.none?(NilClass).should == true
-      end
-
-      it "does not hide exceptions out of #each" do
-        -> {
-          EnumerableSpecs::ThrowingEach.new.none?(Integer)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "returns true if the pattern never returns a truthy value" do
-        @enum2.none?(Integer).should == true
-        pattern = EnumerableSpecs::Pattern.new { |x| nil }
-        @enum.none?(pattern).should == true
-
-        [1, 42, 3].none?(pattern).should == true
-        {a: 1, b: 2}.none?(pattern).should == true
-      end
-
-      it "returns false if the pattern ever returns other than false or nil" do
-        pattern = EnumerableSpecs::Pattern.new { |x| x < 0 }
-        @enum1.none?(pattern).should == false
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-
-        [1, 2, 3, -1].none?(pattern).should == false
-        {a: 1}.none?(Array).should == false
-      end
-
-      it "does not hide exceptions out of pattern#===" do
-        pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
-        -> {
-          @enum.none?(pattern)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "calls the pattern with gathered array when yielded with multiple arguments" do
-        multi = EnumerableSpecs::YieldsMulti.new
-        pattern = EnumerableSpecs::Pattern.new { false }
-        multi.none?(pattern).should == true
-        pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
-      end
+  describe 'when given a pattern argument' do
+    it "calls `===` on the pattern the return value " do
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 3 }
+      @enum1.none?(pattern).should == true
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+    end
+
+    it "always returns true on empty enumeration" do
+      @empty.none?(Integer).should == true
+      [].none?(Integer).should == true
+      {}.none?(NilClass).should == true
+    end
+
+    it "does not hide exceptions out of #each" do
+      -> {
+        EnumerableSpecs::ThrowingEach.new.none?(Integer)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "returns true if the pattern never returns a truthy value" do
+      @enum2.none?(Integer).should == true
+      pattern = EnumerableSpecs::Pattern.new { |x| nil }
+      @enum.none?(pattern).should == true
+
+      [1, 42, 3].none?(pattern).should == true
+      {a: 1, b: 2}.none?(pattern).should == true
+    end
+
+    it "returns false if the pattern ever returns other than false or nil" do
+      pattern = EnumerableSpecs::Pattern.new { |x| x < 0 }
+      @enum1.none?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+
+      [1, 2, 3, -1].none?(pattern).should == false
+      {a: 1}.none?(Array).should == false
+    end
+
+    it "does not hide exceptions out of pattern#===" do
+      pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
+      -> {
+        @enum.none?(pattern)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "calls the pattern with gathered array when yielded with multiple arguments" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      pattern = EnumerableSpecs::Pattern.new { false }
+      multi.none?(pattern).should == true
+      pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
+    end
+
+    it "ignores the block if there is an argument" do
+      -> {
+        EnumerableSpecs::Numerous.new(1, 2, 3, 4, 5).none?(String) { true }.should == true
+      }.should complain(/given block not used/)
     end
   end
 end
diff --git a/spec/ruby/core/enumerable/one_spec.rb b/spec/ruby/core/enumerable/one_spec.rb
index 2ae8b3efa4..4bf8623d2e 100644
--- a/spec/ruby/core/enumerable/one_spec.rb
+++ b/spec/ruby/core/enumerable/one_spec.rb
@@ -10,7 +10,7 @@ describe "Enumerable#one?" do
   end
 
   it "always returns false on empty enumeration" do
-    @empty.one?.should == false
+    @empty.should_not.one?
     @empty.one? { true }.should == false
   end
 
@@ -20,15 +20,6 @@ describe "Enumerable#one?" do
     -> { {}.one?(1, 2, 3) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises an ArgumentError when any arguments provided" do
-      -> { @enum.one?(Proc.new {}) }.should raise_error(ArgumentError)
-      -> { @enum.one?(nil) }.should raise_error(ArgumentError)
-      -> { @empty.one?(1) }.should raise_error(ArgumentError)
-      -> { @enum.one?(1) {} }.should raise_error(ArgumentError)
-    end
-  end
-
   it "does not hide exceptions out of #each" do
     -> {
       EnumerableSpecs::ThrowingEach.new.one?
@@ -92,78 +83,72 @@ describe "Enumerable#one?" do
     end
   end
 
+  describe 'when given a pattern argument' do
+    it "calls `===` on the pattern the return value " do
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 1 }
+      @enum1.one?(pattern).should == true
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+    end
+
+    it "always returns false on empty enumeration" do
+      @empty.one?(Integer).should == false
+      [].one?(Integer).should == false
+      {}.one?(NilClass).should == false
+    end
+
+    it "does not hide exceptions out of #each" do
+      -> {
+        EnumerableSpecs::ThrowingEach.new.one?(Integer)
+      }.should raise_error(RuntimeError)
+    end
+
+    it "returns true if the pattern returns a truthy value only once" do
+      @enum2.one?(NilClass).should == true
+      pattern = EnumerableSpecs::Pattern.new { |x| x == 2 }
+      @enum1.one?(pattern).should == true
+
+      [1, 2, 42, 3].one?(pattern).should == true
+
+      pattern = EnumerableSpecs::Pattern.new { |x| x == [:b, 2] }
+      {a: 1, b: 2}.one?(pattern).should == true
+    end
+
+    it "returns false if the pattern returns a truthy value more than once" do
+      pattern = EnumerableSpecs::Pattern.new { |x| !x }
+      @enum2.one?(pattern).should == false
+      pattern.yielded.should == [[nil], [false]]
+
+      [1, 2, 3].one?(Integer).should == false
+      {a: 1, b: 2}.one?(Array).should == false
+    end
+
+    it "returns false if the pattern never returns a truthy value" do
+      pattern = EnumerableSpecs::Pattern.new { |x| nil }
+      @enum1.one?(pattern).should == false
+      pattern.yielded.should == [[0], [1], [2], [-1]]
+
+      [1, 2, 3].one?(pattern).should == false
+      {a: 1}.one?(pattern).should == false
+    end
+
+    it "does not hide exceptions out of pattern#===" do
+      pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
+      -> {
+        @enum.one?(pattern)
+      }.should raise_error(RuntimeError)
+    end
 
-  ruby_version_is "2.5" do
-    describe 'when given a pattern argument' do
-      it "calls `===` on the pattern the return value " do
-        pattern = EnumerableSpecs::Pattern.new { |x| x == 1 }
-        @enum1.one?(pattern).should == true
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-      end
-
-      # may raise an exception in future versions
-      ruby_version_is ""..."2.6" do
-        it "ignores block" do
-          @enum2.one?(NilClass) { raise }.should == true
-          [1, 2, nil].one?(NilClass) { raise }.should == true
-          {a: 1}.one?(Array) { raise }.should == true
-        end
-      end
-
-      it "always returns false on empty enumeration" do
-        @empty.one?(Integer).should == false
-        [].one?(Integer).should == false
-        {}.one?(NilClass).should == false
-      end
-
-      it "does not hide exceptions out of #each" do
-        -> {
-          EnumerableSpecs::ThrowingEach.new.one?(Integer)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "returns true if the pattern returns a truthy value only once" do
-        @enum2.one?(NilClass).should == true
-        pattern = EnumerableSpecs::Pattern.new { |x| x == 2 }
-        @enum1.one?(pattern).should == true
-
-        [1, 2, 42, 3].one?(pattern).should == true
-
-        pattern = EnumerableSpecs::Pattern.new { |x| x == [:b, 2] }
-        {a: 1, b: 2}.one?(pattern).should == true
-      end
-
-      it "returns false if the pattern returns a truthy value more than once" do
-        pattern = EnumerableSpecs::Pattern.new { |x| !x }
-        @enum2.one?(pattern).should == false
-        pattern.yielded.should == [[nil], [false]]
-
-        [1, 2, 3].one?(Integer).should == false
-        {a: 1, b: 2}.one?(Array).should == false
-      end
-
-      it "returns false if the pattern never returns a truthy value" do
-        pattern = EnumerableSpecs::Pattern.new { |x| nil }
-        @enum1.one?(pattern).should == false
-        pattern.yielded.should == [[0], [1], [2], [-1]]
-
-        [1, 2, 3].one?(pattern).should == false
-        {a: 1}.one?(pattern).should == false
-      end
-
-      it "does not hide exceptions out of pattern#===" do
-        pattern = EnumerableSpecs::Pattern.new { raise "from pattern" }
-        -> {
-          @enum.one?(pattern)
-        }.should raise_error(RuntimeError)
-      end
-
-      it "calls the pattern with gathered array when yielded with multiple arguments" do
-        multi = EnumerableSpecs::YieldsMulti.new
-        pattern = EnumerableSpecs::Pattern.new { false }
-        multi.one?(pattern).should == false
-        pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
-      end
+    it "calls the pattern with gathered array when yielded with multiple arguments" do
+      multi = EnumerableSpecs::YieldsMulti.new
+      pattern = EnumerableSpecs::Pattern.new { false }
+      multi.one?(pattern).should == false
+      pattern.yielded.should == [[[1, 2]], [[3, 4, 5]], [[6, 7, 8, 9]]]
+    end
+
+    it "ignores the block if there is an argument" do
+      -> {
+        EnumerableSpecs::Numerous.new(1, 2, 3, 4, "5").one?(String) { false }.should == true
+      }.should complain(/given block not used/)
     end
   end
 end
diff --git a/spec/ruby/core/enumerable/select_spec.rb b/spec/ruby/core/enumerable/select_spec.rb
index 11168eb42e..7fc61926f9 100644
--- a/spec/ruby/core/enumerable/select_spec.rb
+++ b/spec/ruby/core/enumerable/select_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/find_all'
 
 describe "Enumerable#select" do
-  it_behaves_like :enumerable_find_all , :select
+  it_behaves_like :enumerable_find_all, :select
 end
diff --git a/spec/ruby/core/enumerable/shared/collect.rb b/spec/ruby/core/enumerable/shared/collect.rb
index 16bf3f0d35..6df1a616eb 100644
--- a/spec/ruby/core/enumerable/shared/collect.rb
+++ b/spec/ruby/core/enumerable/shared/collect.rb
@@ -22,11 +22,86 @@ describe :enumerable_collect, shared: true do
     multi.send(@method) {|e| e}.should == [1,3,6]
   end
 
+  it "only yields increasing values for a Range" do
+    (1..0).send(@method) { |x| x }.should == []
+    (1..1).send(@method) { |x| x }.should == [1]
+    (1..2).send(@method) { |x| x }.should == [1, 2]
+  end
+
   it "returns an enumerator when no block given" do
     enum = EnumerableSpecs::Numerous.new.send(@method)
     enum.should be_an_instance_of(Enumerator)
     enum.each { |i| -i }.should == [-2, -5, -3, -6, -1, -4]
   end
 
+  it "reports the same arity as the given block" do
+    entries = [0, 1, 3, 4, 5, 6]
+    numerous = EnumerableSpecs::Numerous.new(*entries)
+
+    def numerous.each(&block)
+      ScratchPad << block.arity
+      super
+    end
+
+    numerous.send(@method) { |a, b| a % 2 }.should == [0, 1, 1, 0, 1, 0]
+    ScratchPad.recorded.should == [2]
+    ScratchPad.clear
+    ScratchPad.record []
+    numerous.send(@method) { |i| i }.should == entries
+    ScratchPad.recorded.should == [1]
+  end
+
+  it "yields an Array of 2 elements for a Hash when block arity is 1" do
+    c = Class.new do
+      def register(a)
+        ScratchPad << a
+      end
+    end
+    m = c.new.method(:register)
+
+    ScratchPad.record []
+    { 1 => 'a', 2 => 'b' }.map(&m)
+    ScratchPad.recorded.should == [[1, 'a'], [2, 'b']]
+  end
+
+  it "yields 2 arguments for a Hash when block arity is 2" do
+    c = Class.new do
+      def register(a, b)
+        ScratchPad << [a, b]
+      end
+    end
+    m = c.new.method(:register)
+
+    ScratchPad.record []
+    { 1 => 'a', 2 => 'b' }.map(&m)
+    ScratchPad.recorded.should == [[1, 'a'], [2, 'b']]
+  end
+
+  it "raises an error for a Hash when an arity enforcing block of arity >2 is passed in" do
+    c = Class.new do
+      def register(a, b, c)
+      end
+    end
+    m = c.new.method(:register)
+
+    -> do
+      { 1 => 'a', 2 => 'b' }.map(&m)
+    end.should raise_error(ArgumentError)
+  end
+
+  it "calls the each method on sub-classes" do
+    c = Class.new(Hash) do
+      def each
+        ScratchPad << 'in each'
+        super
+      end
+    end
+    h = c.new
+    h[1] = 'a'
+    ScratchPad.record []
+    h.send(@method) { |k,v| v }
+    ScratchPad.recorded.should == ['in each']
+  end
+
   it_should_behave_like :enumerable_enumeratorized_with_origin_size
 end
diff --git a/spec/ruby/core/enumerable/shared/entries.rb b/spec/ruby/core/enumerable/shared/entries.rb
index f52844cb45..e32eb23d2a 100644
--- a/spec/ruby/core/enumerable/shared/entries.rb
+++ b/spec/ruby/core/enumerable/shared/entries.rb
@@ -13,12 +13,4 @@ describe :enumerable_entries, shared: true do
     count.send(@method, :hello, "world").should == [1, 2, 3]
     count.arguments_passed.should == [:hello, "world"]
   end
-
-  it "returns a tainted array if self is tainted" do
-    EnumerableSpecs::Empty.new.taint.send(@method).tainted?.should be_true
-  end
-
-  it "returns an untrusted array if self is untrusted" do
-    EnumerableSpecs::Empty.new.untrust.send(@method).untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/enumerable/shared/inject.rb b/spec/ruby/core/enumerable/shared/inject.rb
index 12e0665dda..8fb7e98c2b 100644
--- a/spec/ruby/core/enumerable/shared/inject.rb
+++ b/spec/ruby/core/enumerable/shared/inject.rb
@@ -1,3 +1,5 @@
+require_relative '../../array/shared/iterable_and_tolerating_size_increasing'
+
 describe :enumerable_inject, shared: true do
   it "with argument takes a block with an accumulator (with argument as initial value) and the current element. Value of block becomes new accumulator" do
     a = []
@@ -14,14 +16,65 @@ describe :enumerable_inject, shared: true do
 
   it "can take two argument" do
     EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, :-).should == 4
+    EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, "-").should == 4
+
+    [1, 2, 3].send(@method, 10, :-).should == 4
+    [1, 2, 3].send(@method, 10, "-").should == 4
+  end
+
+  it "converts non-Symbol method name argument to String with #to_str if two arguments" do
+    name = Object.new
+    def name.to_str; "-"; end
+
+    EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, name).should == 4
+    [1, 2, 3].send(@method, 10, name).should == 4
+  end
+
+  it "raises TypeError when the second argument is not Symbol or String and it cannot be converted to String if two arguments" do
+    -> { EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, Object.new) }.should raise_error(TypeError, /is not a symbol nor a string/)
+    -> { [1, 2, 3].send(@method, 10, Object.new) }.should raise_error(TypeError, /is not a symbol nor a string/)
   end
 
   it "ignores the block if two arguments" do
-    EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, :-){ raise "we never get here"}.should == 4
+    -> {
+      EnumerableSpecs::Numerous.new(1, 2, 3).send(@method, 10, :-) { raise "we never get here"}.should == 4
+    }.should complain(/#{__FILE__}:#{__LINE__-1}: warning: given block not used/, verbose: true)
+
+    -> {
+      [1, 2, 3].send(@method, 10, :-) { raise "we never get here"}.should == 4
+    }.should complain(/#{__FILE__}:#{__LINE__-1}: warning: given block not used/, verbose: true)
+  end
+
+  it "does not warn when given a Symbol with $VERBOSE true" do
+    -> {
+      [1, 2].send(@method, 0, :+)
+      [1, 2].send(@method, :+)
+      EnumerableSpecs::Numerous.new(1, 2).send(@method, 0, :+)
+      EnumerableSpecs::Numerous.new(1, 2).send(@method, :+)
+    }.should_not complain(verbose: true)
   end
 
   it "can take a symbol argument" do
     EnumerableSpecs::Numerous.new(10, 1, 2, 3).send(@method, :-).should == 4
+    [10, 1, 2, 3].send(@method, :-).should == 4
+  end
+
+  it "can take a String argument" do
+    EnumerableSpecs::Numerous.new(10, 1, 2, 3).send(@method, "-").should == 4
+    [10, 1, 2, 3].send(@method, "-").should == 4
+  end
+
+  it "converts non-Symbol method name argument to String with #to_str" do
+    name = Object.new
+    def name.to_str; "-"; end
+
+    EnumerableSpecs::Numerous.new(10, 1, 2, 3).send(@method, name).should == 4
+    [10, 1, 2, 3].send(@method, name).should == 4
+  end
+
+  it "raises TypeError when passed not Symbol or String method name argument and it cannot be converted to String" do
+    -> { EnumerableSpecs::Numerous.new(10, 1, 2, 3).send(@method, Object.new) }.should raise_error(TypeError, /is not a symbol nor a string/)
+    -> { [10, 1, 2, 3].send(@method, Object.new) }.should raise_error(TypeError, /is not a symbol nor a string/)
   end
 
   it "without argument takes a block with an accumulator (with first element as initial value) and the current element. Value of block becomes new accumulator" do
@@ -30,10 +83,10 @@ describe :enumerable_inject, shared: true do
     a.should == [[2, 5], [5, 3], [3, 6], [6, 1], [1, 4]]
   end
 
-   it "gathers whole arrays as elements when each yields multiple" do
-     multi = EnumerableSpecs::YieldsMulti.new
-     multi.send(@method, []) {|acc, e| acc << e }.should == [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
-   end
+  it "gathers whole arrays as elements when each yields multiple" do
+    multi = EnumerableSpecs::YieldsMulti.new
+    multi.send(@method, []) {|acc, e| acc << e }.should == [[1, 2], [3, 4, 5], [6, 7, 8, 9]]
+  end
 
   it "with inject arguments(legacy rubycon)" do
     # with inject argument
@@ -50,7 +103,7 @@ describe :enumerable_inject, shared: true do
 
   it "without inject arguments(legacy rubycon)" do
     # no inject argument
-    EnumerableSpecs::EachDefiner.new(2).send(@method) {|acc,x| 999 } .should == 2
+    EnumerableSpecs::EachDefiner.new(2).send(@method) {|acc,x| 999 }.should == 2
     EnumerableSpecs::EachDefiner.new(2).send(@method) {|acc,x| acc }.should == 2
     EnumerableSpecs::EachDefiner.new(2).send(@method) {|acc,x| x }.should == 2
 
@@ -60,10 +113,30 @@ describe :enumerable_inject, shared: true do
     EnumerableSpecs::EachDefiner.new('a','b','c').send(@method) {|result, i| i+result}.should == "cba"
     EnumerableSpecs::EachDefiner.new(3, 4, 5).send(@method) {|result, i| result*i}.should == 60
     EnumerableSpecs::EachDefiner.new([1], 2, 'a','b').send(@method){|r,i| r<<i}.should == [1, 2, 'a', 'b']
-
   end
 
   it "returns nil when fails(legacy rubycon)" do
     EnumerableSpecs::EachDefiner.new().send(@method) {|acc,x| 999 }.should == nil
   end
+
+  it "tolerates increasing a collection size during iterating Array" do
+    array = [:a, :b, :c]
+    ScratchPad.record []
+    i = 0
+
+    array.send(@method, nil) do |_, e|
+      ScratchPad << e
+      array << i if i < 100
+      i += 1
+    end
+
+    actual = ScratchPad.recorded
+    expected = [:a, :b, :c] + (0..99).to_a
+    actual.sort_by(&:to_s).should == expected.sort_by(&:to_s)
+  end
+
+  it "raises an ArgumentError when no parameters or block is given" do
+    -> { [1,2].send(@method) }.should raise_error(ArgumentError)
+    -> { {one: 1, two: 2}.send(@method) }.should raise_error(ArgumentError)
+  end
 end
diff --git a/spec/ruby/core/enumerable/sort_spec.rb b/spec/ruby/core/enumerable/sort_spec.rb
index cff1a59986..6fc64f325e 100644
--- a/spec/ruby/core/enumerable/sort_spec.rb
+++ b/spec/ruby/core/enumerable/sort_spec.rb
@@ -31,7 +31,7 @@ describe "Enumerable#sort" do
   it "compare values returned by block with 0" do
     EnumerableSpecs::Numerous.new.sort { |n, m| -(n+m) * (n <=> m) }.should == [6, 5, 4, 3, 2, 1]
     EnumerableSpecs::Numerous.new.sort { |n, m|
-      EnumerableSpecs::ComparableWithFixnum.new(-(n+m) * (n <=> m))
+      EnumerableSpecs::ComparableWithInteger.new(-(n+m) * (n <=> m))
     }.should == [6, 5, 4, 3, 2, 1]
     -> {
       EnumerableSpecs::Numerous.new.sort { |n, m| (n <=> m).to_s }
diff --git a/spec/ruby/core/enumerable/sum_spec.rb b/spec/ruby/core/enumerable/sum_spec.rb
index c9d7017b45..2eb74db6ac 100644
--- a/spec/ruby/core/enumerable/sum_spec.rb
+++ b/spec/ruby/core/enumerable/sum_spec.rb
@@ -22,7 +22,29 @@ describe 'Enumerable#sum' do
     @enum.sum.should == 5/3r
   end
 
-  it 'takes a block to transform the elements' do
-    @enum.sum { |element| element * 2 }.should == 10/3r
+  context 'with a block' do
+    it 'transforms the elements' do
+      @enum.sum { |element| element * 2 }.should == 10/3r
+    end
+
+    it 'does not destructure array elements' do
+      class << @enum
+        def each
+          yield [1,2]
+          yield [3]
+        end
+      end
+
+      @enum.sum(&:last).should == 5
+    end
+  end
+
+  # https://bugs.ruby-lang.org/issues/12217
+  # https://github.com/ruby/ruby/blob/master/doc/ChangeLog/ChangeLog-2.4.0#L6208-L6214
+  it "uses Kahan's compensated summation algorithm for precise sum of float numbers" do
+    floats = [2.7800000000000002, 5.0, 2.5, 4.44, 3.89, 3.89, 4.44, 7.78, 5.0, 2.7800000000000002, 5.0, 2.5].to_enum
+    naive_sum = floats.reduce { |sum, e| sum + e }
+    naive_sum.should == 50.00000000000001
+    floats.sum.should == 50.0
   end
 end
diff --git a/spec/ruby/core/enumerable/tally_spec.rb b/spec/ruby/core/enumerable/tally_spec.rb
index 363b3def21..95c64c1294 100644
--- a/spec/ruby/core/enumerable/tally_spec.rb
+++ b/spec/ruby/core/enumerable/tally_spec.rb
@@ -1,35 +1,91 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is "2.7" do
-  describe "Enumerable#tally" do
-    before :each do
-      ScratchPad.record []
-    end
-
-    it "returns a hash with counts according to the value" do
-      enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
-      enum.tally.should == { 'foo' => 2, 'bar' => 1, 'baz' => 1}
-    end
-
-    it "returns a hash without default" do
-      hash = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz').tally
-      hash.default_proc.should be_nil
-      hash.default.should be_nil
-    end
-
-    it "returns an empty hash for empty enumerables" do
-      EnumerableSpecs::Empty.new.tally.should == {}
-    end
-
-    it "counts values as gathered array when yielded with multiple arguments" do
-      EnumerableSpecs::YieldsMixed2.new.tally.should == EnumerableSpecs::YieldsMixed2.gathered_yields.group_by(&:itself).transform_values(&:size)
-    end
-
-    it "does not call given block" do
-      enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
-      enum.tally { |v| ScratchPad << v }
-      ScratchPad.recorded.should == []
-    end
+describe "Enumerable#tally" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  it "returns a hash with counts according to the value" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally.should == { 'foo' => 2, 'bar' => 1, 'baz' => 1}
+  end
+
+  it "returns a hash without default" do
+    hash = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz').tally
+    hash.default_proc.should be_nil
+    hash.default.should be_nil
+  end
+
+  it "returns an empty hash for empty enumerables" do
+    EnumerableSpecs::Empty.new.tally.should == {}
+  end
+
+  it "counts values as gathered array when yielded with multiple arguments" do
+    EnumerableSpecs::YieldsMixed2.new.tally.should == EnumerableSpecs::YieldsMixed2.gathered_yields.group_by(&:itself).transform_values(&:size)
+  end
+
+  it "does not call given block" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally { |v| ScratchPad << v }
+    ScratchPad.recorded.should == []
+  end
+end
+
+describe "Enumerable#tally with a hash" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  it "returns a hash with counts according to the value" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally({ 'foo' => 1 }).should == { 'foo' => 3, 'bar' => 1, 'baz' => 1}
+  end
+
+  it "returns the given hash" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    hash = { 'foo' => 1 }
+    enum.tally(hash).should equal(hash)
+  end
+
+  it "calls #to_hash to convert argument to Hash implicitly if passed not a Hash" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    object = Object.new
+    def object.to_hash; { 'foo' => 1 }; end
+    enum.tally(object).should == { 'foo' => 3, 'bar' => 1, 'baz' => 1}
+  end
+
+  it "raises a FrozenError and does not update the given hash when the hash is frozen" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    hash = { 'foo' => 1 }.freeze
+    -> { enum.tally(hash) }.should raise_error(FrozenError)
+    hash.should == { 'foo' => 1 }
+  end
+
+  it "raises a FrozenError even if enumerable is empty" do
+    enum = EnumerableSpecs::Numerous.new()
+    hash = { 'foo' => 1 }.freeze
+    -> { enum.tally(hash) }.should raise_error(FrozenError)
+  end
+
+  it "does not call given block" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally({ 'foo' => 1 }) { |v| ScratchPad << v }
+    ScratchPad.recorded.should == []
+  end
+
+  it "ignores the default value" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally(Hash.new(100)).should == { 'foo' => 2, 'bar' => 1, 'baz' => 1}
+  end
+
+  it "ignores the default proc" do
+    enum = EnumerableSpecs::Numerous.new('foo', 'bar', 'foo', 'baz')
+    enum.tally(Hash.new {100}).should == { 'foo' => 2, 'bar' => 1, 'baz' => 1}
+  end
+
+  it "needs the values counting each elements to be an integer" do
+    enum = EnumerableSpecs::Numerous.new('foo')
+    -> { enum.tally({ 'foo' => 'bar' }) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/enumerable/to_a_spec.rb b/spec/ruby/core/enumerable/to_a_spec.rb
index 0f3060dc48..723f922574 100644
--- a/spec/ruby/core/enumerable/to_a_spec.rb
+++ b/spec/ruby/core/enumerable/to_a_spec.rb
@@ -3,5 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/entries'
 
 describe "Enumerable#to_a" do
-  it_behaves_like :enumerable_entries , :to_a
+  it_behaves_like :enumerable_entries, :to_a
 end
diff --git a/spec/ruby/core/enumerable/to_h_spec.rb b/spec/ruby/core/enumerable/to_h_spec.rb
index 63bfdf19af..11a4933c10 100644
--- a/spec/ruby/core/enumerable/to_h_spec.rb
+++ b/spec/ruby/core/enumerable/to_h_spec.rb
@@ -44,47 +44,53 @@ describe "Enumerable#to_h" do
     -> { enum.to_h }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      before do
-        @enum = EnumerableSpecs::EachDefiner.new(:a, :b)
-      end
-
-      it "converts [key, value] pairs returned by the block to a hash" do
-        @enum.to_h { |k| [k, k.to_s] }.should == { a: 'a', b: 'b' }
-      end
-
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          @enum.to_h { |k| [k, k.to_s, 1] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-
-        -> do
-          @enum.to_h { |k| [k] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-      end
-
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          @enum.to_h { |k| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String/)
-      end
-
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
-
-        @enum.to_h { |k| x }.should == { :b => 'b' }
-      end
-
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
-
-        -> do
-          @enum.to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject/)
-      end
+  context "with block" do
+    before do
+      @enum = EnumerableSpecs::EachDefiner.new(:a, :b)
+    end
+
+    it "converts [key, value] pairs returned by the block to a hash" do
+      @enum.to_h { |k| [k, k.to_s] }.should == { a: 'a', b: 'b' }
+    end
+
+    it "passes to a block each element as a single argument" do
+      enum_of_arrays = EnumerableSpecs::EachDefiner.new([:a, 1], [:b, 2])
+
+      ScratchPad.record []
+      enum_of_arrays.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[[:a, 1]], [[:b, 2]]]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        @enum.to_h { |k| [k, k.to_s, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+
+      -> do
+        @enum.to_h { |k| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        @enum.to_h { |k| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      @enum.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        @enum.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
     end
   end
 end
diff --git a/spec/ruby/core/enumerable/to_set_spec.rb b/spec/ruby/core/enumerable/to_set_spec.rb
new file mode 100644
index 0000000000..c02ead11fa
--- /dev/null
+++ b/spec/ruby/core/enumerable/to_set_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerable#to_set" do
+  it "returns a new Set created from self" do
+    [1, 2, 3].to_set.should == Set[1, 2, 3]
+    {a: 1, b: 2}.to_set.should == Set[[:b, 2], [:a, 1]]
+  end
+
+  it "passes down passed blocks" do
+    [1, 2, 3].to_set { |x| x * x }.should == Set[1, 4, 9]
+  end
+
+  ruby_version_is "4.0"..."4.1" do
+    it "instantiates an object of provided as the first argument set class" do
+      set = nil
+      proc{set = [1, 2, 3].to_set(EnumerableSpecs::SetSubclass)}.should complain(/Enumerable#to_set/)
+      set.should be_kind_of(EnumerableSpecs::SetSubclass)
+      set.to_a.sort.should == [1, 2, 3]
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "instantiates an object of provided as the first argument set class" do
+      set = [1, 2, 3].to_set(EnumerableSpecs::SetSubclass)
+      set.should be_kind_of(EnumerableSpecs::SetSubclass)
+      set.to_a.sort.should == [1, 2, 3]
+    end
+  end
+end
diff --git a/spec/ruby/core/enumerable/uniq_spec.rb b/spec/ruby/core/enumerable/uniq_spec.rb
index c286882e92..a1ed44796f 100644
--- a/spec/ruby/core/enumerable/uniq_spec.rb
+++ b/spec/ruby/core/enumerable/uniq_spec.rb
@@ -37,10 +37,6 @@ describe 'Enumerable#uniq' do
       obj.should_receive(:hash).at_least(1).and_return(0)
 
       def obj.eql?(o)
-        # It's undefined whether the impl does a[0].eql?(a[1]) or
-        # a[1].eql?(a[0]) so we taint both.
-        taint
-        o.taint
         false
       end
 
@@ -48,18 +44,12 @@ describe 'Enumerable#uniq' do
     end
 
     a.uniq.should == a
-    a[0].tainted?.should == true
-    a[1].tainted?.should == true
 
     a = Array.new(2) do
       obj = mock('0')
       obj.should_receive(:hash).at_least(1).and_return(0)
 
       def obj.eql?(o)
-        # It's undefined whether the impl does a[0].eql?(a[1]) or
-        # a[1].eql?(a[0]) so we taint both.
-        taint
-        o.taint
         true
       end
 
@@ -67,8 +57,6 @@ describe 'Enumerable#uniq' do
     end
 
     a.to_enum.uniq.size.should == 1
-    a[0].tainted?.should == true
-    a[1].tainted?.should == true
   end
 
   context 'when yielded with multiple arguments' do
diff --git a/spec/ruby/core/enumerable/zip_spec.rb b/spec/ruby/core/enumerable/zip_spec.rb
index 9ec15aa030..ab148f2a6e 100644
--- a/spec/ruby/core/enumerable/zip_spec.rb
+++ b/spec/ruby/core/enumerable/zip_spec.rb
@@ -38,4 +38,9 @@ describe "Enumerable#zip" do
     multi.zip(multi).should == [[[1, 2], [1, 2]], [[3, 4, 5], [3, 4, 5]], [[6, 7, 8, 9], [6, 7, 8, 9]]]
   end
 
+  it "raises TypeError when some argument isn't Array and doesn't respond to #to_ary and #to_enum" do
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(Object.new) }.should raise_error(TypeError, "wrong argument type Object (must respond to :each)")
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(1) }.should raise_error(TypeError, "wrong argument type Integer (must respond to :each)")
+    -> { EnumerableSpecs::Numerous.new(1,2,3).zip(true) }.should raise_error(TypeError, "wrong argument type TrueClass (must respond to :each)")
+  end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/begin_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/begin_spec.rb
index c8d91ebaec..bd243fa0b5 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/begin_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/begin_spec.rb
@@ -1,11 +1,16 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#begin" do
-    it "returns the begin of the sequence" do
-      1.step(10).begin.should == 1
-      (1..10).step.begin.should == 1
-      (1...10).step.begin.should == 1
+describe "Enumerator::ArithmeticSequence#begin" do
+  it "returns the begin of the sequence" do
+    1.step(10).begin.should == 1
+    (1..10).step.begin.should == 1
+    (1...10).step.begin.should == 1
+  end
+
+  context "with beginless" do
+    it "returns nil as begin of the sequence" do
+      (..10).step(1).begin.should == nil
+      (...10).step(1).begin.should == nil
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/each_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/each_spec.rb
index d7edf3a21f..d4fff3e01f 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/each_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/each_spec.rb
@@ -1,19 +1,17 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#each" do
-    before :each do
-      ScratchPad.record []
-      @seq = 1.step(10, 4)
-    end
+describe "Enumerator::ArithmeticSequence#each" do
+  before :each do
+    ScratchPad.record []
+    @seq = 1.step(10, 4)
+  end
 
-    it "calls given block on each item of the sequence" do
-      @seq.each { |item| ScratchPad << item }
-      ScratchPad.recorded.should == [1, 5, 9]
-    end
+  it "calls given block on each item of the sequence" do
+    @seq.each { |item| ScratchPad << item }
+    ScratchPad.recorded.should == [1, 5, 9]
+  end
 
-    it "returns self" do
-      @seq.each { |item| }.should equal(@seq)
-    end
+  it "returns self" do
+    @seq.each { |item| }.should equal(@seq)
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/end_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/end_spec.rb
index 5a436e8167..05429cac3e 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/end_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/end_spec.rb
@@ -1,11 +1,16 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#end" do
-    it "returns the end of the sequence" do
-      1.step(10).end.should == 10
-      (1..10).step.end.should == 10
-      (1...10).step(17).end.should == 10
+describe "Enumerator::ArithmeticSequence#end" do
+  it "returns the end of the sequence" do
+    1.step(10).end.should == 10
+    (1..10).step.end.should == 10
+    (1...10).step(17).end.should == 10
+  end
+
+  context "with endless" do
+    it "returns nil as end of the sequence" do
+      (1..).step(1).end.should == nil
+      (1...).step(1).end.should == nil
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/eq_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/eq_spec.rb
index 7895f98047..77eed02d8b 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/eq_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/eq_spec.rb
@@ -1,20 +1,18 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#==" do
-    it "returns true if begin, end, step and exclude_end? are equal" do
-      1.step(10).should == 1.step(10)
-      1.step(10, 5).should == 1.step(10, 5)
+describe "Enumerator::ArithmeticSequence#==" do
+  it "returns true if begin, end, step and exclude_end? are equal" do
+    1.step(10).should == 1.step(10)
+    1.step(10, 5).should == 1.step(10, 5)
 
-      (1..10).step.should == (1..10).step
-      (1...10).step(8).should == (1...10).step(8)
+    (1..10).step.should == (1..10).step
+    (1...10).step(8).should == (1...10).step(8)
 
-      # both have exclude_end? == false
-      (1..10).step(100).should == 1.step(10, 100)
+    # both have exclude_end? == false
+    (1..10).step(100).should == 1.step(10, 100)
 
-      ((1..10).step == (1..11).step).should == false
-      ((1..10).step == (1...10).step).should == false
-      ((1..10).step == (1..10).step(2)).should == false
-    end
+    ((1..10).step == (1..11).step).should == false
+    ((1..10).step == (1...10).step).should == false
+    ((1..10).step == (1..10).step(2)).should == false
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/exclude_end_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/exclude_end_spec.rb
index 8ce0ce0cd9..021fe7d90f 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/exclude_end_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/exclude_end_spec.rb
@@ -1,19 +1,17 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#exclude_end?" do
-    context "when created using Numeric#step" do
-      it "always returns false" do
-        1.step(10).exclude_end?.should == false
-        10.step(1).exclude_end?.should == false
-      end
+describe "Enumerator::ArithmeticSequence#exclude_end?" do
+  context "when created using Numeric#step" do
+    it "always returns false" do
+      1.step(10).should_not.exclude_end?
+      10.step(1).should_not.exclude_end?
     end
+  end
 
-    context "when created using Range#step" do
-      it "mirrors range.exclude_end?" do
-        (1...10).step.exclude_end?.should == true
-        (1..10).step.exclude_end?.should == false
-      end
+  context "when created using Range#step" do
+    it "mirrors range.exclude_end?" do
+      (1...10).step.should.exclude_end?
+      (1..10).step.should_not.exclude_end?
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/first_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/first_spec.rb
index 43c520d1f0..ccd02be020 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/first_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/first_spec.rb
@@ -1,11 +1,9 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#first" do
-    it "returns the first element of the sequence" do
-      1.step(10).first.should == 1
-      (1..10).step.first.should == 1
-      (1...10).step.first.should == 1
-    end
+describe "Enumerator::ArithmeticSequence#first" do
+  it "returns the first element of the sequence" do
+    1.step(10).first.should == 1
+    (1..10).step.first.should == 1
+    (1...10).step.first.should == 1
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/hash_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/hash_spec.rb
index 236f845f41..bdb308074b 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/hash_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/hash_spec.rb
@@ -1,22 +1,20 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#hash" do
-    it "is based on begin, end, step and exclude_end?" do
-      1.step(10).hash.should be_an_instance_of(Integer)
+describe "Enumerator::ArithmeticSequence#hash" do
+  it "is based on begin, end, step and exclude_end?" do
+    1.step(10).hash.should be_an_instance_of(Integer)
 
-      1.step(10).hash.should == 1.step(10).hash
-      1.step(10, 5).hash.should == 1.step(10, 5).hash
+    1.step(10).hash.should == 1.step(10).hash
+    1.step(10, 5).hash.should == 1.step(10, 5).hash
 
-      (1..10).step.hash.should == (1..10).step.hash
-      (1...10).step(8).hash.should == (1...10).step(8).hash
+    (1..10).step.hash.should == (1..10).step.hash
+    (1...10).step(8).hash.should == (1...10).step(8).hash
 
-      # both have exclude_end? == false
-      (1..10).step(100).hash.should == 1.step(10, 100).hash
+    # both have exclude_end? == false
+    (1..10).step(100).hash.should == 1.step(10, 100).hash
 
-      ((1..10).step.hash == (1..11).step.hash).should == false
-      ((1..10).step.hash == (1...10).step.hash).should == false
-      ((1..10).step.hash == (1..10).step(2).hash).should == false
-    end
+    ((1..10).step.hash == (1..11).step.hash).should == false
+    ((1..10).step.hash == (1...10).step.hash).should == false
+    ((1..10).step.hash == (1..10).step(2).hash).should == false
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/inspect_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/inspect_spec.rb
index 21e64a6b58..b73b49d272 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/inspect_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/inspect_spec.rb
@@ -1,22 +1,20 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#inspect" do
-    context 'when Numeric#step is used' do
-      it "returns '(begin.step(end{, step}))'" do
-        1.step(10).inspect.should == "(1.step(10))"
-        1.step(10, 3).inspect.should == "(1.step(10, 3))"
-      end
+describe "Enumerator::ArithmeticSequence#inspect" do
+  context 'when Numeric#step is used' do
+    it "returns '(begin.step(end{, step}))'" do
+      1.step(10).inspect.should == "(1.step(10))"
+      1.step(10, 3).inspect.should == "(1.step(10, 3))"
     end
+  end
 
-    context 'when Range#step is used' do
-      it "returns '((range).step{(step)})'" do
-        (1..10).step.inspect.should == "((1..10).step)"
-        (1..10).step(3).inspect.should == "((1..10).step(3))"
+  context 'when Range#step is used' do
+    it "returns '((range).step{(step)})'" do
+      (1..10).step.inspect.should == "((1..10).step)"
+      (1..10).step(3).inspect.should == "((1..10).step(3))"
 
-        (1...10).step.inspect.should == "((1...10).step)"
-        (1...10).step(3).inspect.should == "((1...10).step(3))"
-      end
+      (1...10).step.inspect.should == "((1...10).step)"
+      (1...10).step(3).inspect.should == "((1...10).step(3))"
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/last_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/last_spec.rb
index ebb20090fc..31f982b7c4 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/last_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/last_spec.rb
@@ -1,11 +1,9 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#last" do
-    it "returns the last element of the sequence" do
-      1.step(10).last.should == 10
-      (1..10).step.last.should == 10
-      (1...10).step(4).last.should == 9
-    end
+describe "Enumerator::ArithmeticSequence#last" do
+  it "returns the last element of the sequence" do
+    1.step(10).last.should == 10
+    (1..10).step.last.should == 10
+    (1...10).step(4).last.should == 9
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/new_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/new_spec.rb
index 7227581fb9..2015983826 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/new_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/new_spec.rb
@@ -1,19 +1,17 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence.new" do
-    it "is not defined" do
-      -> {
-        Enumerator::ArithmeticSequence.new
-      }.should raise_error(NoMethodError)
-    end
+describe "Enumerator::ArithmeticSequence.new" do
+  it "is not defined" do
+    -> {
+      Enumerator::ArithmeticSequence.new
+    }.should raise_error(NoMethodError)
   end
+end
 
-  describe "Enumerator::ArithmeticSequence.allocate" do
-    it "is not defined" do
-      -> {
-        Enumerator::ArithmeticSequence.allocate
-      }.should raise_error(TypeError, 'allocator undefined for Enumerator::ArithmeticSequence')
-    end
+describe "Enumerator::ArithmeticSequence.allocate" do
+  it "is not defined" do
+    -> {
+      Enumerator::ArithmeticSequence.allocate
+    }.should raise_error(TypeError, 'allocator undefined for Enumerator::ArithmeticSequence')
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/size_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/size_spec.rb
index 00403b0238..7e03edd961 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/size_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/size_spec.rb
@@ -1,19 +1,17 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#size" do
-    context "for finite sequence" do
-      it "returns the number of elements in this arithmetic sequence" do
-        1.step(10).size.should == 10
-        (1...10).step.size.should == 9
-      end
+describe "Enumerator::ArithmeticSequence#size" do
+  context "for finite sequence" do
+    it "returns the number of elements in this arithmetic sequence" do
+      1.step(10).size.should == 10
+      (1...10).step.size.should == 9
     end
+  end
 
-    context "for infinite sequence" do
-      it "returns Infinity" do
-        1.step(Float::INFINITY).size.should == Float::INFINITY
-        (1..Float::INFINITY).step.size.should == Float::INFINITY
-      end
+  context "for infinite sequence" do
+    it "returns Infinity" do
+      1.step(Float::INFINITY).size.should == Float::INFINITY
+      (1..Float::INFINITY).step.size.should == Float::INFINITY
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/arithmetic_sequence/step_spec.rb b/spec/ruby/core/enumerator/arithmetic_sequence/step_spec.rb
index 20a5cb6e7b..c1f2d9173f 100644
--- a/spec/ruby/core/enumerator/arithmetic_sequence/step_spec.rb
+++ b/spec/ruby/core/enumerator/arithmetic_sequence/step_spec.rb
@@ -1,15 +1,11 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::ArithmeticSequence#step" do
-    it "returns the original value given to step method" do
-      (1..10).step.step.should == 1
-      (1..10).step(3).step.should == 3
-      (1..10).step(0).step.should == 0
+describe "Enumerator::ArithmeticSequence#step" do
+  it "returns the original value given to step method" do
+    (1..10).step.step.should == 1
+    (1..10).step(3).step.should == 3
 
-      1.step(10).step.should == 1
-      1.step(10, 3).step.should == 3
-      1.step(10, 0).step.should == 0
-    end
+    1.step(10).step.should == 1
+    1.step(10, 3).step.should == 3
   end
 end
diff --git a/spec/ruby/core/enumerator/chain/each_spec.rb b/spec/ruby/core/enumerator/chain/each_spec.rb
index ab4d355f22..cc93cbac60 100644
--- a/spec/ruby/core/enumerator/chain/each_spec.rb
+++ b/spec/ruby/core/enumerator/chain/each_spec.rb
@@ -1,17 +1,15 @@
 require_relative '../../../spec_helper'
 require_relative '../../enumerable/fixtures/classes'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Chain#each" do
-    it "calls each on its constituents as needed" do
-      a = EnumerableSpecs::EachCounter.new(:a, :b)
-      b = EnumerableSpecs::EachCounter.new(:c, :d)
+describe "Enumerator::Chain#each" do
+  it "calls each on its constituents as needed" do
+    a = EnumerableSpecs::EachCounter.new(:a, :b)
+    b = EnumerableSpecs::EachCounter.new(:c, :d)
 
-      ScratchPad.record []
-      Enumerator::Chain.new(a, b).each do |elem|
-        ScratchPad << elem << b.times_yielded
-      end
-      ScratchPad.recorded.should == [:a, 0, :b, 0, :c, 1, :d, 2]
+    ScratchPad.record []
+    Enumerator::Chain.new(a, b).each do |elem|
+      ScratchPad << elem << b.times_yielded
     end
+    ScratchPad.recorded.should == [:a, 0, :b, 0, :c, 1, :d, 2]
   end
 end
diff --git a/spec/ruby/core/enumerator/chain/initialize_spec.rb b/spec/ruby/core/enumerator/chain/initialize_spec.rb
index e5aa32fd02..daa30351d7 100644
--- a/spec/ruby/core/enumerator/chain/initialize_spec.rb
+++ b/spec/ruby/core/enumerator/chain/initialize_spec.rb
@@ -1,33 +1,31 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Chain#initialize" do
-    before :each do
-      @uninitialized = Enumerator::Chain.allocate
-    end
+describe "Enumerator::Chain#initialize" do
+  before :each do
+    @uninitialized = Enumerator::Chain.allocate
+  end
 
-    it "is a private method" do
-      Enumerator::Chain.should have_private_instance_method(:initialize, false)
-    end
+  it "is a private method" do
+    Enumerator::Chain.should have_private_instance_method(:initialize, false)
+  end
 
-    it "returns self" do
-      @uninitialized.send(:initialize).should equal(@uninitialized)
-    end
+  it "returns self" do
+    @uninitialized.send(:initialize).should equal(@uninitialized)
+  end
 
-    it "accepts many arguments" do
-      @uninitialized.send(:initialize, 0..1, 2..3, 4..5).should equal(@uninitialized)
-    end
+  it "accepts many arguments" do
+    @uninitialized.send(:initialize, 0..1, 2..3, 4..5).should equal(@uninitialized)
+  end
 
-    it "accepts arguments that are not Enumerable nor responding to :each" do
-      @uninitialized.send(:initialize, Object.new).should equal(@uninitialized)
-    end
+  it "accepts arguments that are not Enumerable nor responding to :each" do
+    @uninitialized.send(:initialize, Object.new).should equal(@uninitialized)
+  end
 
-    describe "on frozen instance" do
-      it "raises a RuntimeError" do
-        -> {
-          @uninitialized.freeze.send(:initialize)
-        }.should raise_error(RuntimeError)
-      end
+  describe "on frozen instance" do
+    it "raises a FrozenError" do
+      -> {
+        @uninitialized.freeze.send(:initialize)
+      }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/chain/inspect_spec.rb b/spec/ruby/core/enumerator/chain/inspect_spec.rb
index a644d88c6f..9b5a442b75 100644
--- a/spec/ruby/core/enumerator/chain/inspect_spec.rb
+++ b/spec/ruby/core/enumerator/chain/inspect_spec.rb
@@ -1,16 +1,18 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Chain#inspect" do
-    it "shows a representation of the Enumerator" do
-      Enumerator::Chain.new.inspect.should == "#<Enumerator::Chain: []>"
-      Enumerator::Chain.new(1..2, 3..4).inspect.should == "#<Enumerator::Chain: [1..2, 3..4]>"
-    end
+describe "Enumerator::Chain#inspect" do
+  it "shows a representation of the Enumerator" do
+    Enumerator::Chain.new.inspect.should == "#<Enumerator::Chain: []>"
+    Enumerator::Chain.new(1..2, 3..4).inspect.should == "#<Enumerator::Chain: [1..2, 3..4]>"
+  end
+
+  it "calls inspect on its chain elements" do
+    obj = mock('inspect')
+    obj.should_receive(:inspect).and_return('some desc')
+    Enumerator::Chain.new(obj).inspect.should == "#<Enumerator::Chain: [some desc]>"
+  end
 
-    it "calls inspect on its chain elements" do
-      obj = mock('inspect')
-      obj.should_receive(:inspect).and_return('some desc')
-      Enumerator::Chain.new(obj).inspect.should == "#<Enumerator::Chain: [some desc]>"
-    end
+  it "returns a not initialized representation if #initialized is not called yet" do
+    Enumerator::Chain.allocate.inspect.should == "#<Enumerator::Chain: uninitialized>"
   end
 end
diff --git a/spec/ruby/core/enumerator/chain/rewind_spec.rb b/spec/ruby/core/enumerator/chain/rewind_spec.rb
index 951b364f07..5f51ce2cf1 100644
--- a/spec/ruby/core/enumerator/chain/rewind_spec.rb
+++ b/spec/ruby/core/enumerator/chain/rewind_spec.rb
@@ -1,53 +1,51 @@
 require_relative '../../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Chain#rewind" do
-    before(:each) do
-      @obj = mock('obj')
-      @obj.should_receive(:each).any_number_of_times.and_yield
-      @second = mock('obj')
-      @second.should_receive(:each).any_number_of_times.and_yield
-      @enum = Enumerator::Chain.new(@obj, @second)
-    end
-
-    it "returns self" do
-      @enum.rewind.should equal @enum
-    end
-
-    it "does nothing if receiver has not been iterated" do
-      @obj.should_not_receive(:rewind)
-      @obj.respond_to?(:rewind).should == true # sanity check
-      @enum.rewind
-    end
-
-    it "does nothing on objects that don't respond_to rewind" do
-      @obj.respond_to?(:rewind).should == false # sanity check
-      @enum.each {}
-      @enum.rewind
-    end
-
-    it "calls_rewind its objects" do
-      @obj.should_receive(:rewind)
-      @enum.each {}
-      @enum.rewind
-    end
-
-    it "calls_rewind in reverse order" do
-      @obj.should_not_receive(:rewind)
-      @second.should_receive(:rewind).and_raise(RuntimeError)
-      @enum.each {}
-      -> { @enum.rewind }.should raise_error(RuntimeError)
-    end
-
-    it "calls rewind only for objects that have actually been iterated on" do
-      @obj = mock('obj')
-      @obj.should_receive(:each).any_number_of_times.and_raise(RuntimeError)
-      @enum = Enumerator::Chain.new(@obj, @second)
-
-      @obj.should_receive(:rewind)
-      @second.should_not_receive(:rewind)
-      -> { @enum.each {} }.should raise_error(RuntimeError)
-      @enum.rewind
-    end
+describe "Enumerator::Chain#rewind" do
+  before(:each) do
+    @obj = mock('obj')
+    @obj.should_receive(:each).any_number_of_times.and_yield
+    @second = mock('obj')
+    @second.should_receive(:each).any_number_of_times.and_yield
+    @enum = Enumerator::Chain.new(@obj, @second)
+  end
+
+  it "returns self" do
+    @enum.rewind.should equal @enum
+  end
+
+  it "does nothing if receiver has not been iterated" do
+    @obj.should_not_receive(:rewind)
+    @obj.respond_to?(:rewind).should == true # sanity check
+    @enum.rewind
+  end
+
+  it "does nothing on objects that don't respond_to rewind" do
+    @obj.respond_to?(:rewind).should == false # sanity check
+    @enum.each {}
+    @enum.rewind
+  end
+
+  it "calls_rewind its objects" do
+    @obj.should_receive(:rewind)
+    @enum.each {}
+    @enum.rewind
+  end
+
+  it "calls_rewind in reverse order" do
+    @obj.should_not_receive(:rewind)
+    @second.should_receive(:rewind).and_raise(RuntimeError)
+    @enum.each {}
+    -> { @enum.rewind }.should raise_error(RuntimeError)
+  end
+
+  it "calls rewind only for objects that have actually been iterated on" do
+    @obj = mock('obj')
+    @obj.should_receive(:each).any_number_of_times.and_raise(RuntimeError)
+    @enum = Enumerator::Chain.new(@obj, @second)
+
+    @obj.should_receive(:rewind)
+    @second.should_not_receive(:rewind)
+    -> { @enum.each {} }.should raise_error(RuntimeError)
+    @enum.rewind
   end
 end
diff --git a/spec/ruby/core/enumerator/chain/size_spec.rb b/spec/ruby/core/enumerator/chain/size_spec.rb
index 42c31ac10b..d85b88ee8b 100644
--- a/spec/ruby/core/enumerator/chain/size_spec.rb
+++ b/spec/ruby/core/enumerator/chain/size_spec.rb
@@ -1,24 +1,22 @@
 require_relative '../../../spec_helper'
 require_relative '../../enumerable/fixtures/classes'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Chain#size" do
-    it "returns the sum of the sizes of the elements" do
+describe "Enumerator::Chain#size" do
+  it "returns the sum of the sizes of the elements" do
+    a = mock('size')
+    a.should_receive(:size).and_return(40)
+    Enumerator::Chain.new(a, [:a, :b]).size.should == 42
+  end
+
+  it "returns nil or Infinity for the first element of such a size" do
+    [nil, Float::INFINITY].each do |special|
       a = mock('size')
       a.should_receive(:size).and_return(40)
-      Enumerator::Chain.new(a, [:a, :b]).size.should == 42
-    end
-
-    it "returns nil or Infinity for the first element of such a size" do
-      [nil, Float::INFINITY].each do |special|
-        a = mock('size')
-        a.should_receive(:size).and_return(40)
-        b = mock('special')
-        b.should_receive(:size).and_return(special)
-        c = mock('not called')
-        c.should_not_receive(:size)
-        Enumerator::Chain.new(a, b, c).size.should == special
-      end
+      b = mock('special')
+      b.should_receive(:size).and_return(special)
+      c = mock('not called')
+      c.should_not_receive(:size)
+      Enumerator::Chain.new(a, b, c).size.should == special
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/each_spec.rb b/spec/ruby/core/enumerator/each_spec.rb
index d88c09cdb5..3af16e5587 100644
--- a/spec/ruby/core/enumerator/each_spec.rb
+++ b/spec/ruby/core/enumerator/each_spec.rb
@@ -10,41 +10,41 @@ describe "Enumerator#each" do
 
     @enum_with_arguments = object_each_with_arguments.to_enum(:each_with_arguments, :arg0, :arg1, :arg2)
 
-    @enum_with_yielder = Enumerator.new {|y| y.yield :ok}
+    @enum_with_yielder = Enumerator.new { |y| y.yield :ok }
   end
 
   it "yields each element of self to the given block" do
     acc = []
-    [1,2,3].to_enum.each {|e| acc << e }
-    acc.should == [1,2,3]
+    [1, 2, 3].to_enum.each { |e| acc << e }
+    acc.should == [1, 2, 3]
   end
 
   it "calls #each on the object given in the constructor by default" do
     each = mock('each')
     each.should_receive(:each)
-    each.to_enum.each {|e| e }
+    each.to_enum.each { |e| e }
   end
 
   it "calls #each on the underlying object until it's exhausted" do
     each = mock('each')
     each.should_receive(:each).and_yield(1).and_yield(2).and_yield(3)
     acc = []
-    each.to_enum.each {|e| acc << e }
-    acc.should == [1,2,3]
+    each.to_enum.each { |e| acc << e }
+    acc.should == [1, 2, 3]
   end
 
   it "calls the method given in the constructor instead of #each" do
     each = mock('peach')
     each.should_receive(:peach)
-    each.to_enum(:peach).each {|e| e }
+    each.to_enum(:peach).each { |e| e }
   end
 
   it "calls the method given in the constructor until it's exhausted" do
-    each = mock('each')
-    each.should_receive(:each).and_yield(1).and_yield(2).and_yield(3)
+    each = mock('peach')
+    each.should_receive(:peach).and_yield(1).and_yield(2).and_yield(3)
     acc = []
-    each.to_enum.each {|e| acc << e }
-    acc.should == [1,2,3]
+    each.to_enum(:peach).each { |e| acc << e }
+    acc.should == [1, 2, 3]
   end
 
   it "raises a NoMethodError if the object doesn't respond to #each" do
diff --git a/spec/ruby/core/enumerator/each_with_index_spec.rb b/spec/ruby/core/enumerator/each_with_index_spec.rb
index 96e53a2804..4898e86fa9 100644
--- a/spec/ruby/core/enumerator/each_with_index_spec.rb
+++ b/spec/ruby/core/enumerator/each_with_index_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/with_index'
+require_relative 'shared/with_index'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "Enumerator#each_with_index" do
@@ -21,16 +21,16 @@ describe "Enumerator#each_with_index" do
 
   it "passes on the given block's return value" do
     arr = [1,2,3]
-    arr.delete_if.with_index { |a,b| false }
+    arr.delete_if.each_with_index { |a,b| false }
     arr.should == [1,2,3]
   end
 
   it "returns the iterator's return value" do
-    [1,2,3].select.with_index { |a,b| false }.should == []
+    [1,2,3].select.each_with_index { |a,b| false }.should == []
+    [1,2,3].select.each_with_index { |a,b| true }.should == [1,2,3]
   end
 
   it "returns the correct value if chained with itself" do
     [:a].each_with_index.each_with_index.to_a.should == [[[:a,0],0]]
-    [:a].each.with_index.with_index.to_a.should == [[[:a,0],0]]
   end
 end
diff --git a/spec/ruby/core/enumerator/each_with_object_spec.rb b/spec/ruby/core/enumerator/each_with_object_spec.rb
index 68524dc74a..84a45ae89d 100644
--- a/spec/ruby/core/enumerator/each_with_object_spec.rb
+++ b/spec/ruby/core/enumerator/each_with_object_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/with_object'
+require_relative 'shared/with_object'
 
 describe "Enumerator#each_with_object" do
   it_behaves_like :enum_with_object, :each_with_object
diff --git a/spec/ruby/core/enumerator/enum_for_spec.rb b/spec/ruby/core/enumerator/enum_for_spec.rb
index fd33f463bf..fbdf98545a 100644
--- a/spec/ruby/core/enumerator/enum_for_spec.rb
+++ b/spec/ruby/core/enumerator/enum_for_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/enum_for'
+require_relative 'shared/enum_for'
 
 describe "Enumerator#enum_for" do
   it_behaves_like :enum_for, :enum_for
diff --git a/spec/ruby/fixtures/enumerator/classes.rb b/spec/ruby/core/enumerator/fixtures/classes.rb
index 6f285b8efa..6f285b8efa 100644
--- a/spec/ruby/fixtures/enumerator/classes.rb
+++ b/spec/ruby/core/enumerator/fixtures/classes.rb
diff --git a/spec/ruby/core/enumerator/generator/initialize_spec.rb b/spec/ruby/core/enumerator/generator/initialize_spec.rb
index f75c7d6f26..acc1174253 100644
--- a/spec/ruby/core/enumerator/generator/initialize_spec.rb
+++ b/spec/ruby/core/enumerator/generator/initialize_spec.rb
@@ -17,10 +17,10 @@ describe "Enumerator::Generator#initialize" do
   end
 
   describe "on frozen instance" do
-    it "raises a RuntimeError" do
+    it "raises a FrozenError" do
       -> {
         @uninitialized.freeze.send(:initialize) {}
-      }.should raise_error(RuntimeError)
+      }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/initialize_spec.rb b/spec/ruby/core/enumerator/initialize_spec.rb
index 53bf5d4ef2..5e0256ca46 100644
--- a/spec/ruby/core/enumerator/initialize_spec.rb
+++ b/spec/ruby/core/enumerator/initialize_spec.rb
@@ -11,10 +11,6 @@ describe "Enumerator#initialize" do
     Enumerator.should have_private_instance_method(:initialize, false)
   end
 
-  it "returns self when given an object" do
-    @uninitialized.send(:initialize, Object.new).should equal(@uninitialized)
-  end
-
   it "returns self when given a block" do
     @uninitialized.send(:initialize) {}.should equal(@uninitialized)
   end
@@ -43,7 +39,7 @@ describe "Enumerator#initialize" do
     @uninitialized.send(:initialize, Float::INFINITY) {}.size.should equal(Float::INFINITY)
   end
 
-  it "sets size to the given size if the given size is a Fixnum" do
+  it "sets size to the given size if the given size is an Integer" do
     @uninitialized.send(:initialize, 100) {}.size.should == 100
   end
 
@@ -52,10 +48,10 @@ describe "Enumerator#initialize" do
   end
 
   describe "on frozen instance" do
-    it "raises a RuntimeError" do
+    it "raises a FrozenError" do
       -> {
         @uninitialized.freeze.send(:initialize) {}
-      }.should raise_error(RuntimeError)
+      }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/inspect_spec.rb b/spec/ruby/core/enumerator/inspect_spec.rb
index 3bcf07e754..7e97864246 100644
--- a/spec/ruby/core/enumerator/inspect_spec.rb
+++ b/spec/ruby/core/enumerator/inspect_spec.rb
@@ -14,4 +14,9 @@ describe "Enumerator#inspect" do
       (1..3).each.each_slice(2).inspect.should == "#<Enumerator: #<Enumerator: 1..3:each>:each_slice(2)>"
     end
   end
+
+  it "returns a not initialized representation if #initialized is not called yet" do
+    Enumerator.allocate.inspect.should == "#<Enumerator: uninitialized>"
+    Enumerator::Lazy.allocate.inspect.should == "#<Enumerator::Lazy: uninitialized>"
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/chunk_while_spec.rb b/spec/ruby/core/enumerator/lazy/chunk_while_spec.rb
index d555089872..772bd42de9 100644
--- a/spec/ruby/core/enumerator/lazy/chunk_while_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/chunk_while_spec.rb
@@ -6,4 +6,9 @@ describe "Enumerator::Lazy#chunk_while" do
     s.lazy.chunk_while { |a, b| false }.first(100).should ==
       s.first(100).chunk_while { |a, b| false }.to_a
   end
+
+  it "should return a lazy enumerator" do
+    s = 0..Float::INFINITY
+    s.lazy.chunk_while { |a, b| false }.should be_kind_of(Enumerator::Lazy)
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/compact_spec.rb b/spec/ruby/core/enumerator/lazy/compact_spec.rb
new file mode 100644
index 0000000000..65c544f062
--- /dev/null
+++ b/spec/ruby/core/enumerator/lazy/compact_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerator::Lazy#compact" do
+  it 'returns array without nil elements' do
+    arr = [1, nil, 3, false, 5].to_enum.lazy.compact
+    arr.should be_an_instance_of(Enumerator::Lazy)
+    arr.force.should == [1, 3, false, 5]
+  end
+
+  it "sets #size to nil" do
+    Enumerator::Lazy.new(Object.new, 100) {}.compact.size.should == nil
+  end
+end
diff --git a/spec/ruby/core/enumerator/lazy/eager_spec.rb b/spec/ruby/core/enumerator/lazy/eager_spec.rb
new file mode 100644
index 0000000000..592da4fd8c
--- /dev/null
+++ b/spec/ruby/core/enumerator/lazy/eager_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Lazy#eager" do
+  it "returns a non-lazy Enumerator converted from the lazy enumerator" do
+    enum = [1, 2, 3].lazy
+
+    enum.class.should == Enumerator::Lazy
+    enum.eager.class.should == Enumerator
+  end
+
+  it "does not enumerate an enumerator" do
+    ScratchPad.record []
+
+    sequence = [1, 2, 3]
+    enum_lazy = Enumerator::Lazy.new(sequence) do |yielder, value|
+      yielder << value
+      ScratchPad << value
+    end
+
+    ScratchPad.recorded.should == []
+    enum = enum_lazy.eager
+    ScratchPad.recorded.should == []
+
+    enum.map { |i| i }.should == [1, 2, 3]
+    ScratchPad.recorded.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/enumerator/lazy/filter_map_spec.rb b/spec/ruby/core/enumerator/lazy/filter_map_spec.rb
new file mode 100644
index 0000000000..99dd59cebe
--- /dev/null
+++ b/spec/ruby/core/enumerator/lazy/filter_map_spec.rb
@@ -0,0 +1,14 @@
+# -*- encoding: us-ascii -*-
+
+require_relative '../../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerator::Lazy#filter_map" do
+  it "maps only truthy results" do
+    (1..Float::INFINITY).lazy.filter_map { |i| i if i.odd? }.first(4).should == [1, 3, 5, 7]
+  end
+
+  it "does not map false results" do
+    (1..Float::INFINITY).lazy.filter_map { |i| i.odd? ? i : false }.first(4).should == [1, 3, 5, 7]
+  end
+end
diff --git a/spec/ruby/core/enumerator/lazy/filter_spec.rb b/spec/ruby/core/enumerator/lazy/filter_spec.rb
index 2ababa69cc..43128241e0 100644
--- a/spec/ruby/core/enumerator/lazy/filter_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/filter_spec.rb
@@ -1,8 +1,6 @@
 require_relative '../../../spec_helper'
 require_relative 'shared/select'
 
-ruby_version_is "2.6" do
-  describe "Enumerator::Lazy#filter" do
-    it_behaves_like :enumerator_lazy_select, :filter
-  end
+describe "Enumerator::Lazy#filter" do
+  it_behaves_like :enumerator_lazy_select, :filter
 end
diff --git a/spec/ruby/core/enumerator/lazy/flat_map_spec.rb b/spec/ruby/core/enumerator/lazy/flat_map_spec.rb
index 6a3391a503..5dcaa8bfa1 100644
--- a/spec/ruby/core/enumerator/lazy/flat_map_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/flat_map_spec.rb
@@ -5,4 +5,12 @@ require_relative 'shared/collect_concat'
 
 describe "Enumerator::Lazy#flat_map" do
   it_behaves_like :enumerator_lazy_collect_concat, :flat_map
+
+  it "properly unwraps nested yields" do
+    s = Enumerator.new do |y| loop do y << [1, 2] end end
+
+    expected = s.take(3).flat_map { |x| x }.to_a
+    actual = s.lazy.take(3).flat_map{ |x| x }.force
+    actual.should == expected
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/initialize_spec.rb b/spec/ruby/core/enumerator/lazy/initialize_spec.rb
index 88c66530b9..e1e0b1d608 100644
--- a/spec/ruby/core/enumerator/lazy/initialize_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/initialize_spec.rb
@@ -43,7 +43,7 @@ describe "Enumerator::Lazy#initialize" do
     @uninitialized.send(:initialize, @receiver, Float::INFINITY) {}.size.should equal(Float::INFINITY)
   end
 
-  it "sets given size to own size if the given size is a Fixnum" do
+  it "sets given size to own size if the given size is an Integer" do
     @uninitialized.send(:initialize, @receiver, 100) {}.size.should == 100
   end
 
@@ -56,8 +56,8 @@ describe "Enumerator::Lazy#initialize" do
   end
 
   describe "on frozen instance" do
-    it "raises a RuntimeError" do
-      -> {  @uninitialized.freeze.send(:initialize, @receiver) {} }.should raise_error(RuntimeError)
+    it "raises a FrozenError" do
+      -> {  @uninitialized.freeze.send(:initialize, @receiver) {} }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/enumerator/lazy/lazy_spec.rb b/spec/ruby/core/enumerator/lazy/lazy_spec.rb
index cde9b31066..b43864b673 100644
--- a/spec/ruby/core/enumerator/lazy/lazy_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/lazy_spec.rb
@@ -9,12 +9,11 @@ describe "Enumerator::Lazy" do
 
   it "defines lazy versions of a whitelist of Enumerator methods" do
     lazy_methods = [
-      :chunk, :collect, :collect_concat, :drop, :drop_while, :enum_for,
+      :chunk, :chunk_while, :collect, :collect_concat, :compact, :drop, :drop_while, :enum_for,
       :find_all, :flat_map, :force, :grep, :grep_v, :lazy, :map, :reject,
       :select, :slice_after, :slice_before, :slice_when, :take, :take_while,
-      :to_enum, :zip
+      :to_enum, :uniq, :zip
     ]
-    lazy_methods += [:chunk_while, :uniq]
 
     Enumerator::Lazy.instance_methods(false).should include(*lazy_methods)
   end
diff --git a/spec/ruby/core/enumerator/lazy/slice_after_spec.rb b/spec/ruby/core/enumerator/lazy/slice_after_spec.rb
index 438df8d550..8b08a1ecfd 100644
--- a/spec/ruby/core/enumerator/lazy/slice_after_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/slice_after_spec.rb
@@ -6,4 +6,9 @@ describe "Enumerator::Lazy#slice_after" do
     s.lazy.slice_after { |n| true }.first(100).should ==
       s.first(100).slice_after { |n| true }.to_a
   end
+
+  it "should return a lazy enumerator" do
+    s = 0..Float::INFINITY
+    s.lazy.slice_after { |n| true }.should be_kind_of(Enumerator::Lazy)
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/slice_before_spec.rb b/spec/ruby/core/enumerator/lazy/slice_before_spec.rb
index 6c8660c1a1..9c1ec9ba4a 100644
--- a/spec/ruby/core/enumerator/lazy/slice_before_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/slice_before_spec.rb
@@ -6,4 +6,9 @@ describe "Enumerator::Lazy#slice_before" do
     s.lazy.slice_before { |n| true }.first(100).should ==
       s.first(100).slice_before { |n| true }.to_a
   end
+
+  it "should return a lazy enumerator" do
+    s = 0..Float::INFINITY
+    s.lazy.slice_before { |n| true }.should be_kind_of(Enumerator::Lazy)
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/slice_when_spec.rb b/spec/ruby/core/enumerator/lazy/slice_when_spec.rb
index e7673def47..f83403425d 100644
--- a/spec/ruby/core/enumerator/lazy/slice_when_spec.rb
+++ b/spec/ruby/core/enumerator/lazy/slice_when_spec.rb
@@ -6,4 +6,9 @@ describe "Enumerator::Lazy#slice_when" do
     s.lazy.slice_when { |a, b| true }.first(100).should ==
       s.first(100).slice_when { |a, b| true }.to_a
   end
+
+  it "should return a lazy enumerator" do
+    s = 0..Float::INFINITY
+    s.lazy.slice_when { |a, b| true }.should be_kind_of(Enumerator::Lazy)
+  end
 end
diff --git a/spec/ruby/core/enumerator/lazy/with_index_spec.rb b/spec/ruby/core/enumerator/lazy/with_index_spec.rb
new file mode 100644
index 0000000000..a6b5c38777
--- /dev/null
+++ b/spec/ruby/core/enumerator/lazy/with_index_spec.rb
@@ -0,0 +1,36 @@
+# -*- encoding: us-ascii -*-
+
+require_relative '../../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerator::Lazy#with_index" do
+  it "enumerates with an index" do
+    (0..Float::INFINITY).lazy.with_index.map { |i, idx| [i, idx] }.first(3).should == [[0, 0], [1, 1], [2, 2]]
+  end
+
+  it "enumerates with an index starting at a given offset" do
+    (0..Float::INFINITY).lazy.with_index(3).map { |i, idx| [i, idx] }.first(3).should == [[0, 3], [1, 4], [2, 5]]
+  end
+
+  it "enumerates with an index starting at 0 when offset is nil" do
+    (0..Float::INFINITY).lazy.with_index(nil).map { |i, idx| [i, idx] }.first(3).should == [[0, 0], [1, 1], [2, 2]]
+  end
+
+  it "raises TypeError when offset does not convert to Integer" do
+    -> { (0..Float::INFINITY).lazy.with_index(false).map { |i, idx| i }.first(3) }.should raise_error(TypeError)
+  end
+
+  it "enumerates with a given block" do
+    result = []
+    (0..Float::INFINITY).lazy.with_index { |i, idx| result << [i * 2, idx] }.first(3)
+    result.should == [[0,0],[2,1],[4,2]]
+  end
+
+  it "resets after a new call to each" do
+    enum = (0..2).lazy.with_index.map { |i, idx| [i, idx] }
+    result = []
+    enum.each { |i, idx| result << [i, idx] }
+    enum.each { |i, idx| result << [i, idx] }
+    result.should == [[0,0], [1,1], [2,2], [0,0], [1,1], [2,2]]
+  end
+end
diff --git a/spec/ruby/core/enumerator/new_spec.rb b/spec/ruby/core/enumerator/new_spec.rb
index 170809dbc1..671912224f 100644
--- a/spec/ruby/core/enumerator/new_spec.rb
+++ b/spec/ruby/core/enumerator/new_spec.rb
@@ -1,41 +1,76 @@
 require_relative '../../spec_helper'
 
 describe "Enumerator.new" do
-  it "creates a new custom enumerator with the given object, iterator and arguments" do
-    enum = Enumerator.new(1, :upto, 3)
-    enum.should be_an_instance_of(Enumerator)
+  context "no block given" do
+    it "raises" do
+      -> { Enumerator.new(1, :upto, 3) }.should raise_error(ArgumentError)
+    end
   end
 
-  it "creates a new custom enumerator that responds to #each" do
-    enum = Enumerator.new(1, :upto, 3)
-    enum.respond_to?(:each).should == true
-  end
+  context "when passed a block" do
+    it "defines iteration with block, yielder argument and calling << method" do
+      enum = Enumerator.new do |yielder|
+        a = 1
 
-  it "creates a new custom enumerator that runs correctly" do
-    Enumerator.new(1, :upto, 3).map{|x|x}.should == [1,2,3]
-  end
+        loop do
+          yielder << a
+          a = a + 1
+        end
+      end
 
-  it "aliases the second argument to :each" do
-    Enumerator.new(1..2).to_a.should == Enumerator.new(1..2, :each).to_a
-  end
+      enum.take(3).should == [1, 2, 3]
+    end
 
-  it "doesn't check for the presence of the iterator method" do
-    Enumerator.new(nil).should be_an_instance_of(Enumerator)
-  end
+    it "defines iteration with block, yielder argument and calling yield method" do
+      enum = Enumerator.new do |yielder|
+        a = 1
 
-  it "uses the latest define iterator method" do
-    class StrangeEach
-      def each
-        yield :foo
+        loop do
+          yielder.yield(a)
+          a = a + 1
+        end
       end
+
+      enum.take(3).should == [1, 2, 3]
     end
-    enum = Enumerator.new(StrangeEach.new)
-    enum.to_a.should == [:foo]
-    class StrangeEach
-      def each
-        yield :bar
+
+    it "defines iteration with block, yielder argument and treating it as a proc" do
+      enum = Enumerator.new do |yielder|
+        "a\nb\nc".each_line(&yielder)
+      end
+
+      enum.to_a.should == ["a\n", "b\n", "c"]
+    end
+
+    describe 'yielded values' do
+      it 'handles yield arguments properly' do
+        Enumerator.new { |y| y.yield(1) }.to_a.should == [1]
+        Enumerator.new { |y| y.yield(1) }.first.should == 1
+
+        Enumerator.new { |y| y.yield([1]) }.to_a.should == [[1]]
+        Enumerator.new { |y| y.yield([1]) }.first.should == [1]
+
+        Enumerator.new { |y| y.yield(1, 2) }.to_a.should == [[1, 2]]
+        Enumerator.new { |y| y.yield(1, 2) }.first.should == [1, 2]
+
+        Enumerator.new { |y| y.yield([1, 2]) }.to_a.should == [[1, 2]]
+        Enumerator.new { |y| y.yield([1, 2]) }.first.should == [1, 2]
+      end
+
+      it 'handles << arguments properly' do
+        Enumerator.new { |y| y.<<(1) }.to_a.should == [1]
+        Enumerator.new { |y| y.<<(1) }.first.should == 1
+
+        Enumerator.new { |y| y.<<([1]) }.to_a.should == [[1]]
+        Enumerator.new { |y| y.<<([1]) }.first.should == [1]
+
+        # << doesn't accept multiple arguments
+        # Enumerator.new { |y| y.<<(1, 2) }.to_a.should == [[1, 2]]
+        # Enumerator.new { |y| y.<<(1, 2) }.first.should == [1, 2]
+
+        Enumerator.new { |y| y.<<([1, 2]) }.to_a.should == [[1, 2]]
+        Enumerator.new { |y| y.<<([1, 2]) }.first.should == [1, 2]
       end
     end
-    enum.to_a.should == [:bar]
   end
 end
diff --git a/spec/ruby/core/enumerator/next_spec.rb b/spec/ruby/core/enumerator/next_spec.rb
index 3e9ed8b015..a5e01a399d 100644
--- a/spec/ruby/core/enumerator/next_spec.rb
+++ b/spec/ruby/core/enumerator/next_spec.rb
@@ -24,4 +24,15 @@ describe "Enumerator#next" do
     @enum.rewind
     @enum.next.should == 1
   end
+
+  it "restarts the enumerator if an exception terminated a previous iteration" do
+    exception = StandardError.new
+    enum = Enumerator.new do
+      raise exception
+    end
+
+    result = 2.times.map { enum.next rescue $! }
+
+    result.should == [exception, exception]
+  end
 end
diff --git a/spec/ruby/core/enumerator/next_values_spec.rb b/spec/ruby/core/enumerator/next_values_spec.rb
index 201b5d323f..2202700c58 100644
--- a/spec/ruby/core/enumerator/next_values_spec.rb
+++ b/spec/ruby/core/enumerator/next_values_spec.rb
@@ -11,6 +11,7 @@ describe "Enumerator#next_values" do
       yield :e1, :e2, :e3
       yield nil
       yield
+      yield [:f1, :f2]
     end
 
     @e = o.to_enum
@@ -48,8 +49,13 @@ describe "Enumerator#next_values" do
     @e.next_values.should == []
   end
 
-  it "raises StopIteration if called on a finished enumerator" do
+  it "returns an array of array if yield is called with an array" do
     7.times { @e.next }
+    @e.next_values.should == [[:f1, :f2]]
+  end
+
+  it "raises StopIteration if called on a finished enumerator" do
+    8.times { @e.next }
     -> { @e.next_values }.should raise_error(StopIteration)
   end
 end
diff --git a/spec/ruby/core/enumerator/peek_values_spec.rb b/spec/ruby/core/enumerator/peek_values_spec.rb
index 7865546515..8b84fc8afc 100644
--- a/spec/ruby/core/enumerator/peek_values_spec.rb
+++ b/spec/ruby/core/enumerator/peek_values_spec.rb
@@ -11,6 +11,7 @@ describe "Enumerator#peek_values" do
       yield :e1, :e2, :e3
       yield nil
       yield
+      yield [:f1, :f2]
     end
 
     @e = o.to_enum
@@ -50,8 +51,13 @@ describe "Enumerator#peek_values" do
     @e.peek_values.should == []
   end
 
-  it "raises StopIteration if called on a finished enumerator" do
+  it "returns an array of array if yield is called with an array" do
     7.times { @e.next }
+    @e.peek_values.should == [[:f1, :f2]]
+  end
+
+  it "raises StopIteration if called on a finished enumerator" do
+    8.times { @e.next }
     -> { @e.peek_values }.should raise_error(StopIteration)
   end
 end
diff --git a/spec/ruby/core/enumerator/plus_spec.rb b/spec/ruby/core/enumerator/plus_spec.rb
index c9bae08b04..755be5b4eb 100644
--- a/spec/ruby/core/enumerator/plus_spec.rb
+++ b/spec/ruby/core/enumerator/plus_spec.rb
@@ -1,35 +1,33 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Enumerator#+" do
-    before :each do
-      ScratchPad.record []
-    end
+describe "Enumerator#+" do
+  before :each do
+    ScratchPad.record []
+  end
 
-    it "returns a chain of self and provided enumerators" do
-      one   = Enumerator.new { |y| y << 1 }
-      two   = Enumerator.new { |y| y << 2 }
-      three = Enumerator.new { |y| y << 3 }
+  it "returns a chain of self and provided enumerators" do
+    one   = Enumerator.new { |y| y << 1 }
+    two   = Enumerator.new { |y| y << 2 }
+    three = Enumerator.new { |y| y << 3 }
 
-      chain = one + two + three
+    chain = one + two + three
 
-      chain.should be_an_instance_of(Enumerator::Chain)
-      chain.each { |item| ScratchPad << item }
-      ScratchPad.recorded.should == [1, 2, 3]
-    end
+    chain.should be_an_instance_of(Enumerator::Chain)
+    chain.each { |item| ScratchPad << item }
+    ScratchPad.recorded.should == [1, 2, 3]
+  end
 
-    it "calls #each on each argument" do
-      enum = Enumerator.new { |y| y << "one" }
+  it "calls #each on each argument" do
+    enum = Enumerator.new { |y| y << "one" }
 
-      obj1 = mock("obj1")
-      obj1.should_receive(:each).once.and_yield("two")
+    obj1 = mock("obj1")
+    obj1.should_receive(:each).once.and_yield("two")
 
-      obj2 = mock("obj2")
-      obj2.should_receive(:each).once.and_yield("three")
+    obj2 = mock("obj2")
+    obj2.should_receive(:each).once.and_yield("three")
 
-      chain = enum + obj1 + obj2
-      chain.each { |item| ScratchPad << item }
-      ScratchPad.recorded.should == ["one", "two", "three"]
-    end
+    chain = enum + obj1 + obj2
+    chain.each { |item| ScratchPad << item }
+    ScratchPad.recorded.should == ["one", "two", "three"]
   end
 end
diff --git a/spec/ruby/core/enumerator/produce_spec.rb b/spec/ruby/core/enumerator/produce_spec.rb
new file mode 100644
index 0000000000..c69fb49303
--- /dev/null
+++ b/spec/ruby/core/enumerator/produce_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+
+describe "Enumerator.produce" do
+  it "creates an infinite enumerator" do
+    enum = Enumerator.produce(0) { |prev| prev + 1 }
+    enum.take(5).should == [0, 1, 2, 3, 4]
+  end
+
+  it "terminates iteration when block raises StopIteration exception" do
+    enum = Enumerator.produce(0) do | prev|
+      raise StopIteration if prev >= 2
+      prev + 1
+    end
+
+    enum.to_a.should == [0, 1, 2]
+  end
+
+  context "when initial value skipped" do
+    it "uses nil instead" do
+      ScratchPad.record []
+      enum = Enumerator.produce { |prev| ScratchPad << prev; (prev || 0) + 1 }
+
+      enum.take(3).should == [1, 2, 3]
+      ScratchPad.recorded.should == [nil, 1, 2]
+    end
+
+    it "starts enumerable from result of first block call" do
+      array = "a\nb\nc\nd".lines
+      lines = Enumerator.produce { array.shift }.take_while { |s| s }
+
+      lines.should == ["a\n", "b\n", "c\n", "d"]
+    end
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/each_spec.rb b/spec/ruby/core/enumerator/product/each_spec.rb
new file mode 100644
index 0000000000..88f115a712
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/each_spec.rb
@@ -0,0 +1,71 @@
+require_relative '../../../spec_helper'
+require_relative '../../enumerable/shared/enumeratorized'
+
+describe "Enumerator::Product#each" do
+  it_behaves_like :enumeratorized_with_origin_size, :each, Enumerator::Product.new([1, 2], [:a, :b])
+
+  it "yields each element of Cartesian product of enumerators" do
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+    acc = []
+    enum.each { |e| acc << e }
+    acc.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "calls #each_entry method on enumerators" do
+    object1 = Object.new
+    def object1.each_entry
+      yield 1
+      yield 2
+    end
+
+    object2 = Object.new
+    def object2.each_entry
+      yield :a
+      yield :b
+    end
+
+    enum = Enumerator::Product.new(object1, object2)
+    acc = []
+    enum.each { |e| acc << e }
+    acc.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "raises a NoMethodError if the object doesn't respond to #each_entry" do
+    -> {
+      Enumerator::Product.new(Object.new).each {}
+    }.should raise_error(NoMethodError, /undefined method [`']each_entry' for/)
+  end
+
+  it "returns enumerator if not given a block" do
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+    enum.each.should.kind_of?(Enumerator)
+
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+    enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "returns self if given a block" do
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+    enum.each {}.should.equal?(enum)
+  end
+
+  it "doesn't accept arguments" do
+    Enumerator::Product.instance_method(:each).arity.should == 0
+  end
+
+  it "yields each element to a block that takes multiple arguments" do
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+
+    acc = []
+    enum.each { |x, y| acc << x }
+    acc.should == [1, 1, 2, 2]
+
+    acc = []
+    enum.each { |x, y| acc << y }
+    acc.should == [:a, :b, :a, :b]
+
+    acc = []
+    enum.each { |x, y, z| acc << z }
+    acc.should == [nil, nil, nil, nil]
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/initialize_copy_spec.rb b/spec/ruby/core/enumerator/product/initialize_copy_spec.rb
new file mode 100644
index 0000000000..b1b9f3ca9b
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/initialize_copy_spec.rb
@@ -0,0 +1,52 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Product#initialize_copy" do
+  it "replaces content of the receiver with content of the other object" do
+    enum = Enumerator::Product.new([true, false])
+    enum2 = Enumerator::Product.new([1, 2], [:a, :b])
+
+    enum.send(:initialize_copy, enum2)
+    enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "returns self" do
+    enum = Enumerator::Product.new([true, false])
+    enum2 = Enumerator::Product.new([1, 2], [:a, :b])
+
+    enum.send(:initialize_copy, enum2).should.equal?(enum)
+  end
+
+  it "is a private method" do
+    Enumerator::Product.should have_private_instance_method(:initialize_copy, false)
+  end
+
+  it "does nothing if the argument is the same as the receiver" do
+    enum = Enumerator::Product.new(1..2)
+    enum.send(:initialize_copy, enum).should.equal?(enum)
+
+    enum.freeze
+    enum.send(:initialize_copy, enum).should.equal?(enum)
+  end
+
+  it "raises FrozenError if the receiver is frozen" do
+    enum = Enumerator::Product.new(1..2)
+    enum2 = Enumerator::Product.new(3..4)
+
+    -> { enum.freeze.send(:initialize_copy, enum2) }.should raise_error(FrozenError)
+  end
+
+  it "raises TypeError if the objects are of different class" do
+    enum = Enumerator::Product.new(1..2)
+    enum2 = Class.new(Enumerator::Product).new(3..4)
+
+    -> { enum.send(:initialize_copy, enum2) }.should raise_error(TypeError, 'initialize_copy should take same class object')
+    -> { enum2.send(:initialize_copy, enum) }.should raise_error(TypeError, 'initialize_copy should take same class object')
+  end
+
+  it "raises ArgumentError if the argument is not initialized yet" do
+    enum = Enumerator::Product.new(1..2)
+    enum2 = Enumerator::Product.allocate
+
+    -> { enum.send(:initialize_copy, enum2) }.should raise_error(ArgumentError, 'uninitialized product')
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/initialize_spec.rb b/spec/ruby/core/enumerator/product/initialize_spec.rb
new file mode 100644
index 0000000000..ed2a8a2a13
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/initialize_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Product#initialize" do
+  before :each do
+    @uninitialized = Enumerator::Product.allocate
+  end
+
+  it "is a private method" do
+    Enumerator::Product.should have_private_instance_method(:initialize, false)
+  end
+
+  it "returns self" do
+    @uninitialized.send(:initialize).should equal(@uninitialized)
+  end
+
+  it "accepts many arguments" do
+    @uninitialized.send(:initialize, 0..1, 2..3, 4..5).should equal(@uninitialized)
+  end
+
+  it "accepts arguments that are not Enumerable nor responding to :each_entry" do
+    @uninitialized.send(:initialize, Object.new).should equal(@uninitialized)
+  end
+
+  describe "on frozen instance" do
+    it "raises a FrozenError" do
+      -> {
+        @uninitialized.freeze.send(:initialize, 0..1)
+      }.should raise_error(FrozenError)
+    end
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/inspect_spec.rb b/spec/ruby/core/enumerator/product/inspect_spec.rb
new file mode 100644
index 0000000000..e0d7441f26
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/inspect_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Product#inspect" do
+  it "returns a String including enumerators" do
+    enum = Enumerator::Product.new([1, 2], [:a, :b])
+    enum.inspect.should == "#<Enumerator::Product: [[1, 2], [:a, :b]]>"
+  end
+
+  it "represents a recursive element with '[...]'" do
+    enum = [1, 2]
+    enum_recursive = Enumerator::Product.new(enum)
+
+    enum << enum_recursive
+    enum_recursive.inspect.should == "#<Enumerator::Product: [[1, 2, #<Enumerator::Product: ...>]]>"
+  end
+
+  it "returns a not initialized representation if #initialized is not called yet" do
+    Enumerator::Product.allocate.inspect.should == "#<Enumerator::Product: uninitialized>"
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/rewind_spec.rb b/spec/ruby/core/enumerator/product/rewind_spec.rb
new file mode 100644
index 0000000000..2beffaf5c1
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/rewind_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Product#rewind" do
+  before :each do
+    @enum = Enumerator::Product.new([1, 2].each.to_enum, [:a, :b].each.to_enum)
+  end
+
+  it "resets the enumerator to its initial state" do
+    @enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+    @enum.rewind
+    @enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "returns self" do
+    @enum.rewind.should.equal? @enum
+  end
+
+  it "has no effect on a new enumerator" do
+    @enum.rewind
+    @enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "has no effect if called multiple, consecutive times" do
+    @enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+    @enum.rewind
+    @enum.rewind
+    @enum.each.to_a.should == [[1, :a], [1, :b], [2, :a], [2, :b]]
+  end
+
+  it "calls the enclosed object's rewind method if one exists" do
+    obj = mock('rewinder')
+    enum = Enumerator::Product.new(obj.to_enum)
+
+    obj.should_receive(:rewind)
+    enum.rewind
+  end
+
+  it "does nothing if the object doesn't have a #rewind method" do
+    obj = mock('rewinder')
+    enum = Enumerator::Product.new(obj.to_enum)
+
+    enum.rewind.should == enum
+  end
+
+  it "calls a rewind method on each enumerable in direct order" do
+    ScratchPad.record []
+
+    object1 = Object.new
+    def object1.rewind; ScratchPad << :object1; end
+
+    object2 = Object.new
+    def object2.rewind; ScratchPad << :object2; end
+
+    object3 = Object.new
+    def object3.rewind; ScratchPad << :object3; end
+
+    enum = Enumerator::Product.new(object1, object2, object3)
+    enum.rewind
+
+    ScratchPad.recorded.should == [:object1, :object2, :object3]
+  end
+end
diff --git a/spec/ruby/core/enumerator/product/size_spec.rb b/spec/ruby/core/enumerator/product/size_spec.rb
new file mode 100644
index 0000000000..96632d6eee
--- /dev/null
+++ b/spec/ruby/core/enumerator/product/size_spec.rb
@@ -0,0 +1,54 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Product#size" do
+  it "returns the total size of the enumerator product calculated by multiplying the sizes of enumerables in the product" do
+    product = Enumerator::Product.new(1..2, 1..3, 1..4)
+    product.size.should == 24 # 2 * 3 * 4
+  end
+
+  it "returns nil if any enumerable reports its size as nil" do
+    enum = Object.new
+    def enum.size; nil; end
+
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == nil
+  end
+
+  it "returns Float::INFINITY if any enumerable reports its size as Float::INFINITY" do
+    enum = Object.new
+    def enum.size; Float::INFINITY; end
+
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == Float::INFINITY
+  end
+
+  it "returns nil if any enumerable reports its size as Float::NAN" do
+    enum = Object.new
+    def enum.size; Float::NAN; end
+
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == nil
+  end
+
+  it "returns nil if any enumerable doesn't respond to #size" do
+    enum = Object.new
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == nil
+  end
+
+  it "returns nil if any enumerable reports a not-convertible to Integer" do
+    enum = Object.new
+    def enum.size; :symbol; end
+
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == nil
+  end
+
+  it "returns nil if any enumerable reports a non-Integer but convertible to Integer size" do
+    enum = Object.new
+    def enum.size; 1.0; end
+
+    product = Enumerator::Product.new(1..2, enum)
+    product.size.should == nil
+  end
+end
diff --git a/spec/ruby/core/enumerator/product_spec.rb b/spec/ruby/core/enumerator/product_spec.rb
new file mode 100644
index 0000000000..83c7cb8e0e
--- /dev/null
+++ b/spec/ruby/core/enumerator/product_spec.rb
@@ -0,0 +1,91 @@
+require_relative '../../spec_helper'
+
+describe "Enumerator.product" do
+  it "returns a Cartesian product of enumerators" do
+    enum = Enumerator.product(1..2, ["A", "B"])
+    enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
+  end
+
+  it "accepts a list of enumerators of any length" do
+    enum = Enumerator.product(1..2)
+    enum.to_a.should == [[1], [2]]
+
+    enum = Enumerator.product(1..2, ["A"])
+    enum.to_a.should == [[1, "A"], [2, "A"]]
+
+    enum = Enumerator.product(1..2, ["A"], ["B"])
+    enum.to_a.should == [[1, "A", "B"], [2, "A", "B"]]
+
+    enum = Enumerator.product(2..3, ["A"], ["B"], ["C"])
+    enum.to_a.should == [[2, "A", "B", "C"], [3, "A", "B", "C"]]
+  end
+
+  it "returns an enumerator with an empty array when no arguments passed" do
+    enum = Enumerator.product
+    enum.to_a.should == [[]]
+  end
+
+  it "returns an instance of Enumerator::Product" do
+    enum = Enumerator.product
+    enum.class.should == Enumerator::Product
+  end
+
+  it "accepts infinite enumerators and returns infinite enumerator" do
+    enum = Enumerator.product(1.., ["A", "B"])
+    enum.take(5).should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"], [3, "A"]]
+    enum.size.should == Float::INFINITY
+  end
+
+  it "accepts a block" do
+    elems = []
+    enum = Enumerator.product(1..2, ["X", "Y"]) { elems << _1 }
+
+    elems.should == [[1, "X"], [1, "Y"], [2, "X"], [2, "Y"]]
+  end
+
+  it "returns nil when a block passed" do
+    Enumerator.product(1..2) {}.should == nil
+  end
+
+  # https://bugs.ruby-lang.org/issues/19829
+  it "reject keyword arguments" do
+    -> {
+      Enumerator.product(1..3, foo: 1, bar: 2)
+    }.should raise_error(ArgumentError, "unknown keywords: :foo, :bar")
+  end
+
+  it "calls only #each_entry method on arguments" do
+    object = Object.new
+    def object.each_entry
+      yield 1
+      yield 2
+    end
+
+    enum = Enumerator.product(object, ["A", "B"])
+    enum.to_a.should == [[1, "A"], [1, "B"], [2, "A"], [2, "B"]]
+  end
+
+  it "raises NoMethodError when argument doesn't respond to #each_entry" do
+    -> {
+      Enumerator.product(Object.new).to_a
+    }.should raise_error(NoMethodError, /undefined method [`']each_entry' for/)
+  end
+
+  it "calls #each_entry lazily" do
+    Enumerator.product(Object.new).should be_kind_of(Enumerator)
+  end
+
+  it "iterates through consuming enumerator elements only once" do
+    a = [1, 2, 3]
+    i = 0
+
+    enum = Enumerator.new do |y|
+      while i < a.size
+        y << a[i]
+        i += 1
+      end
+    end
+
+    Enumerator.product(['a', 'b'], enum).to_a.should == [["a", 1], ["a", 2], ["a", 3]]
+  end
+end
diff --git a/spec/ruby/core/enumerator/rewind_spec.rb b/spec/ruby/core/enumerator/rewind_spec.rb
index a105f2c619..6ba0edf174 100644
--- a/spec/ruby/core/enumerator/rewind_spec.rb
+++ b/spec/ruby/core/enumerator/rewind_spec.rb
@@ -14,7 +14,7 @@ describe "Enumerator#rewind" do
   end
 
   it "returns self" do
-    @enum.rewind.should == @enum
+    @enum.rewind.should.equal? @enum
   end
 
   it "has no effect on a new enumerator" do
@@ -49,7 +49,7 @@ describe "Enumerator#rewind" do
     obj = mock('rewinder')
     enum = obj.to_enum
     obj.should_receive(:each).at_most(1)
-    -> { enum.rewind.should == enum }.should_not raise_error
+    enum.rewind.should == enum
   end
 end
 
diff --git a/spec/ruby/core/enumerator/shared/enum_for.rb b/spec/ruby/core/enumerator/shared/enum_for.rb
new file mode 100644
index 0000000000..a67a76c461
--- /dev/null
+++ b/spec/ruby/core/enumerator/shared/enum_for.rb
@@ -0,0 +1,57 @@
+describe :enum_for, shared: true do
+  it "is defined in Kernel" do
+    Kernel.method_defined?(@method).should be_true
+  end
+
+  it "returns a new enumerator" do
+    "abc".send(@method).should be_an_instance_of(Enumerator)
+  end
+
+  it "defaults the first argument to :each" do
+    enum = [1,2].send(@method)
+    enum.map { |v| v }.should == [1,2].each { |v| v }
+  end
+
+  it "sets regexp matches in the caller" do
+    "wawa".send(@method, :scan, /./).map {|o| $& }.should == ["w", "a", "w", "a"]
+    a = []
+    "wawa".send(@method, :scan, /./).each {|o| a << $& }
+    a.should == ["w", "a", "w", "a"]
+  end
+
+  it "exposes multi-arg yields as an array" do
+    o = Object.new
+    def o.each
+      yield :a
+      yield :b1, :b2
+      yield [:c]
+      yield :d1, :d2
+      yield :e1, :e2, :e3
+    end
+
+    enum = o.send(@method)
+    enum.next.should == :a
+    enum.next.should == [:b1, :b2]
+    enum.next.should == [:c]
+    enum.next.should == [:d1, :d2]
+    enum.next.should == [:e1, :e2, :e3]
+  end
+
+  it "uses the passed block's value to calculate the size of the enumerator" do
+    Object.new.enum_for { 100 }.size.should == 100
+  end
+
+  it "defers the evaluation of the passed block until #size is called" do
+    ScratchPad.record []
+
+    enum = Object.new.enum_for do
+      ScratchPad << :called
+      100
+    end
+
+    ScratchPad.recorded.should be_empty
+
+    enum.size
+    ScratchPad.recorded.should == [:called]
+  end
+end
diff --git a/spec/ruby/core/enumerator/shared/with_index.rb b/spec/ruby/core/enumerator/shared/with_index.rb
new file mode 100644
index 0000000000..78771ffe82
--- /dev/null
+++ b/spec/ruby/core/enumerator/shared/with_index.rb
@@ -0,0 +1,33 @@
+require_relative '../../../spec_helper'
+
+describe :enum_with_index, shared: true do
+
+  require_relative '../fixtures/classes'
+
+  before :each do
+    @origin = [1, 2, 3, 4]
+    @enum = @origin.to_enum
+  end
+
+  it "passes each element and its index to block" do
+    a = []
+    @enum.send(@method) { |o, i| a << [o, i] }
+    a.should == [[1, 0], [2, 1], [3, 2], [4, 3]]
+  end
+
+  it "returns the object being enumerated when given a block" do
+    @enum.send(@method) { |o, i| :glark }.should equal(@origin)
+  end
+
+  it "binds splat arguments properly" do
+    acc = []
+    @enum.send(@method) { |*b| c,d = b; acc << c; acc << d }
+    [1, 0, 2, 1, 3, 2, 4, 3].should == acc
+  end
+
+  it "returns an enumerator if no block is supplied" do
+    ewi = @enum.send(@method)
+    ewi.should be_an_instance_of(Enumerator)
+    ewi.to_a.should == [[1, 0], [2, 1], [3, 2], [4, 3]]
+  end
+end
diff --git a/spec/ruby/core/enumerator/shared/with_object.rb b/spec/ruby/core/enumerator/shared/with_object.rb
new file mode 100644
index 0000000000..d8e9d8e9f7
--- /dev/null
+++ b/spec/ruby/core/enumerator/shared/with_object.rb
@@ -0,0 +1,42 @@
+require_relative '../../../spec_helper'
+
+describe :enum_with_object, shared: true do
+  before :each do
+    @enum = [:a, :b].to_enum
+    @memo = ''
+    @block_params = @enum.send(@method, @memo).to_a
+  end
+
+  it "receives an argument" do
+    @enum.method(@method).arity.should == 1
+  end
+
+  context "with block" do
+    it "returns the given object" do
+      ret = @enum.send(@method, @memo) do |elm, memo|
+        # nothing
+      end
+      ret.should equal(@memo)
+    end
+
+    context "the block parameter" do
+      it "passes each element to first parameter" do
+        @block_params[0][0].should equal(:a)
+        @block_params[1][0].should equal(:b)
+      end
+
+      it "passes the given object to last parameter" do
+        @block_params[0][1].should equal(@memo)
+        @block_params[1][1].should equal(@memo)
+      end
+    end
+  end
+
+  context "without block" do
+    it "returns new Enumerator" do
+      ret = @enum.send(@method, @memo)
+      ret.should be_an_instance_of(Enumerator)
+      ret.should_not equal(@enum)
+    end
+  end
+end
diff --git a/spec/ruby/core/enumerator/to_enum_spec.rb b/spec/ruby/core/enumerator/to_enum_spec.rb
index cadfcf6314..7fb73d0c3c 100644
--- a/spec/ruby/core/enumerator/to_enum_spec.rb
+++ b/spec/ruby/core/enumerator/to_enum_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/enum_for'
+require_relative 'shared/enum_for'
 
 describe "Enumerator#to_enum" do
-  it_behaves_like :enum_for, :enum_for
+  it_behaves_like :enum_for, :to_enum
 end
diff --git a/spec/ruby/core/enumerator/with_index_spec.rb b/spec/ruby/core/enumerator/with_index_spec.rb
index ac37cee508..e49aa7a939 100644
--- a/spec/ruby/core/enumerator/with_index_spec.rb
+++ b/spec/ruby/core/enumerator/with_index_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/with_index'
+require_relative 'shared/with_index'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "Enumerator#with_index" do
@@ -69,4 +69,21 @@ describe "Enumerator#with_index" do
     @enum.with_index(-1) { |*x| res << x}
     res.should == [[1,-1], [2,0], [3,1], [4,2]]
   end
+
+  it "passes on the given block's return value" do
+    arr = [1,2,3]
+    arr.delete_if.with_index { |a,b| false }
+    arr.should == [1,2,3]
+
+    arr.delete_if.with_index { |a,b| true }
+    arr.should == []
+  end
+
+  it "returns the iterator's return value" do
+    @enum.select.with_index { |a,b| false }.should == []
+  end
+
+  it "returns the correct value if chained with itself" do
+    [:a].each.with_index.with_index.to_a.should == [[[:a,0],0]]
+  end
 end
diff --git a/spec/ruby/core/enumerator/with_object_spec.rb b/spec/ruby/core/enumerator/with_object_spec.rb
index e7ba83fd9f..58031fd765 100644
--- a/spec/ruby/core/enumerator/with_object_spec.rb
+++ b/spec/ruby/core/enumerator/with_object_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/enumerator/with_object'
+require_relative 'shared/with_object'
 
 describe "Enumerator#with_object" do
   it_behaves_like :enum_with_object, :with_object
diff --git a/spec/ruby/core/enumerator/yielder/append_spec.rb b/spec/ruby/core/enumerator/yielder/append_spec.rb
index dac66585a5..a36e5d64b6 100644
--- a/spec/ruby/core/enumerator/yielder/append_spec.rb
+++ b/spec/ruby/core/enumerator/yielder/append_spec.rb
@@ -21,4 +21,15 @@ describe "Enumerator::Yielder#<<" do
     y = Enumerator::Yielder.new {|x| x + 1}
     (y << 1).should equal(y)
   end
+
+  context "when multiple arguments passed" do
+    it "raises an ArgumentError" do
+      ary = []
+      y = Enumerator::Yielder.new { |*x| ary << x }
+
+      -> {
+        y.<<(1, 2)
+      }.should raise_error(ArgumentError, /wrong number of arguments/)
+    end
+  end
 end
diff --git a/spec/ruby/core/enumerator/yielder/to_proc_spec.rb b/spec/ruby/core/enumerator/yielder/to_proc_spec.rb
new file mode 100644
index 0000000000..1d3681ab50
--- /dev/null
+++ b/spec/ruby/core/enumerator/yielder/to_proc_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerator::Yielder#to_proc" do
+  it "returns a Proc object that takes an argument and yields it to the block" do
+    ScratchPad.record []
+    y = Enumerator::Yielder.new { |*args| ScratchPad << args; "foobar" }
+
+    callable = y.to_proc
+    callable.class.should == Proc
+
+    result = callable.call(1, 2)
+    ScratchPad.recorded.should == [[1, 2]]
+
+    result.should == "foobar"
+  end
+end
diff --git a/spec/ruby/core/enumerator/yielder/yield_spec.rb b/spec/ruby/core/enumerator/yielder/yield_spec.rb
index 58fc8e007a..acfdf114b6 100644
--- a/spec/ruby/core/enumerator/yielder/yield_spec.rb
+++ b/spec/ruby/core/enumerator/yielder/yield_spec.rb
@@ -20,4 +20,14 @@ describe "Enumerator::Yielder#yield" do
     y = Enumerator::Yielder.new {|x| x + 1}
     y.yield(1).should == 2
   end
+
+  context "when multiple arguments passed" do
+    it "yields the arguments list to the block" do
+      ary = []
+      y = Enumerator::Yielder.new { |*x| ary << x }
+      y.yield(1, 2)
+
+      ary.should == [[1, 2]]
+    end
+  end
 end
diff --git a/spec/ruby/core/env/assoc_spec.rb b/spec/ruby/core/env/assoc_spec.rb
index 853eca79a5..c7a388db75 100644
--- a/spec/ruby/core/env/assoc_spec.rb
+++ b/spec/ruby/core/env/assoc_spec.rb
@@ -1,8 +1,12 @@
 require_relative '../../spec_helper'
 
 describe "ENV.assoc" do
+  before :each do
+    @foo = ENV["foo"]
+  end
+
   after :each do
-    ENV.delete("foo")
+    ENV["foo"] = @foo
   end
 
   it "returns an array of the key and value of the environment variable with the given key" do
@@ -20,4 +24,8 @@ describe "ENV.assoc" do
     k.should_receive(:to_str).and_return("foo")
     ENV.assoc(k).should == ["foo", "bar"]
   end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> { ENV.assoc(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
 end
diff --git a/spec/ruby/core/env/clear_spec.rb b/spec/ruby/core/env/clear_spec.rb
index fd0984a220..48b034ba1d 100644
--- a/spec/ruby/core/env/clear_spec.rb
+++ b/spec/ruby/core/env/clear_spec.rb
@@ -4,7 +4,7 @@ describe "ENV.clear" do
   it "deletes all environment variables" do
     orig = ENV.to_hash
     begin
-      ENV.clear
+      ENV.clear.should equal(ENV)
 
       # This used 'env' the helper before. That shells out to 'env' which
       # itself sets up certain environment variables before it runs, because
diff --git a/spec/ruby/core/env/clone_spec.rb b/spec/ruby/core/env/clone_spec.rb
new file mode 100644
index 0000000000..01a29c6ab4
--- /dev/null
+++ b/spec/ruby/core/env/clone_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+
+describe "ENV#clone" do
+  it "raises ArgumentError when keyword argument 'freeze' is neither nil nor boolean" do
+    -> {
+      ENV.clone(freeze: 1)
+    }.should raise_error(ArgumentError)
+  end
+
+  it "raises ArgumentError when keyword argument is not 'freeze'" do
+    -> {
+      ENV.clone(foo: nil)
+    }.should raise_error(ArgumentError)
+  end
+
+  it "raises TypeError" do
+    -> {
+      ENV.clone
+    }.should raise_error(TypeError, /Cannot clone ENV, use ENV.to_h to get a copy of ENV as a hash/)
+  end
+end
diff --git a/spec/ruby/core/env/delete_if_spec.rb b/spec/ruby/core/env/delete_if_spec.rb
index d64443194e..d2de51c225 100644
--- a/spec/ruby/core/env/delete_if_spec.rb
+++ b/spec/ruby/core/env/delete_if_spec.rb
@@ -2,14 +2,31 @@ require_relative '../../spec_helper'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "ENV.delete_if" do
+  before :each do
+    @foo = ENV["foo"]
+    @bar = ENV["bar"]
+
+    ENV["foo"] = "0"
+    ENV["bar"] = "1"
+  end
+
+  after :each do
+    ENV["foo"] = @foo
+    ENV["bar"] = @bar
+  end
+
   it "deletes pairs if the block returns true" do
-    ENV["foo"] = "bar"
-    ENV.delete_if { |k, v| k == "foo" }
+    ENV.delete_if { |k, v| ["foo", "bar"].include?(k) }
     ENV["foo"].should == nil
+    ENV["bar"].should == nil
+  end
+
+  it "returns ENV when block given" do
+    ENV.delete_if { |k, v| ["foo", "bar"].include?(k) }.should equal(ENV)
   end
 
   it "returns ENV even if nothing deleted" do
-    ENV.delete_if { false }.should_not == nil
+    ENV.delete_if { false }.should equal(ENV)
   end
 
   it "returns an Enumerator if no block given" do
@@ -17,10 +34,20 @@ describe "ENV.delete_if" do
   end
 
   it "deletes pairs through enumerator" do
-    ENV["foo"] = "bar"
     enum = ENV.delete_if
-    enum.each { |k, v| k == "foo" }
+    enum.each { |k, v| ["foo", "bar"].include?(k) }
     ENV["foo"].should == nil
+    ENV["bar"].should == nil
+  end
+
+  it "returns ENV from enumerator" do
+    enum = ENV.delete_if
+    enum.each { |k, v| ["foo", "bar"].include?(k) }.should equal(ENV)
+  end
+
+  it "returns ENV from enumerator even if nothing deleted" do
+    enum = ENV.delete_if
+    enum.each { false }.should equal(ENV)
   end
 
   it_behaves_like :enumeratorized_with_origin_size, :delete_if, ENV
diff --git a/spec/ruby/core/env/delete_spec.rb b/spec/ruby/core/env/delete_spec.rb
index 1e677fb252..f28ac97911 100644
--- a/spec/ruby/core/env/delete_spec.rb
+++ b/spec/ruby/core/env/delete_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../spec_helper'
 
 describe "ENV.delete" do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
   after :each do
-    ENV.delete("foo")
+    ENV["foo"] = @saved_foo
   end
 
   it "removes the variable from the environment" do
@@ -16,9 +19,37 @@ describe "ENV.delete" do
     ENV.delete("foo").should == "bar"
   end
 
+  it "returns nil if the named environment variable does not exist and no block given" do
+    ENV.delete("foo")
+    ENV.delete("foo").should == nil
+  end
+
   it "yields the name to the given block if the named environment variable does not exist" do
     ENV.delete("foo")
     ENV.delete("foo") { |name| ScratchPad.record name }
     ScratchPad.recorded.should == "foo"
   end
+
+  it "returns the result of given block if the named environment variable does not exist" do
+    ENV.delete("foo")
+    ENV.delete("foo") { |name| "bar" }.should == "bar"
+  end
+
+  it "does not evaluate the block if the environment variable exists" do
+    ENV["foo"] = "bar"
+    ENV.delete("foo") { |name| fail "Should not happen" }
+    ENV["foo"].should == nil
+  end
+
+  it "removes the variable coerced with #to_str" do
+    ENV["foo"] = "bar"
+    k = mock('key')
+    k.should_receive(:to_str).and_return("foo")
+    ENV.delete(k)
+    ENV["foo"].should == nil
+  end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> { ENV.delete(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
 end
diff --git a/spec/ruby/core/env/dup_spec.rb b/spec/ruby/core/env/dup_spec.rb
new file mode 100644
index 0000000000..ac66b455cd
--- /dev/null
+++ b/spec/ruby/core/env/dup_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+
+describe "ENV#dup" do
+  it "raises TypeError" do
+    -> {
+      ENV.dup
+    }.should raise_error(TypeError, /Cannot dup ENV, use ENV.to_h to get a copy of ENV as a hash/)
+  end
+end
diff --git a/spec/ruby/core/env/each_key_spec.rb b/spec/ruby/core/env/each_key_spec.rb
index 294bf39912..0efcb09900 100644
--- a/spec/ruby/core/env/each_key_spec.rb
+++ b/spec/ruby/core/env/each_key_spec.rb
@@ -10,7 +10,7 @@ describe "ENV.each_key" do
       ENV.clear
       ENV["1"] = "3"
       ENV["2"] = "4"
-      ENV.each_key { |k| e << k }
+      ENV.each_key { |k| e << k }.should equal(ENV)
       e.should include("1")
       e.should include("2")
     ensure
@@ -19,7 +19,9 @@ describe "ENV.each_key" do
   end
 
   it "returns an Enumerator if called without a block" do
-    ENV.each_key.should be_an_instance_of(Enumerator)
+    enum = ENV.each_key
+    enum.should be_an_instance_of(Enumerator)
+    enum.to_a.should == ENV.keys
   end
 
   it "returns keys in the locale encoding" do
diff --git a/spec/ruby/core/env/each_pair_spec.rb b/spec/ruby/core/env/each_pair_spec.rb
index 01082dd419..2d7ed5faa0 100644
--- a/spec/ruby/core/env/each_pair_spec.rb
+++ b/spec/ruby/core/env/each_pair_spec.rb
@@ -1,4 +1,4 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 require_relative 'shared/each'
 
 describe "ENV.each_pair" do
diff --git a/spec/ruby/core/env/each_spec.rb b/spec/ruby/core/env/each_spec.rb
index 06d8be3124..d1e06f55b6 100644
--- a/spec/ruby/core/env/each_spec.rb
+++ b/spec/ruby/core/env/each_spec.rb
@@ -1,4 +1,4 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 require_relative 'shared/each'
 
 describe "ENV.each" do
diff --git a/spec/ruby/core/env/each_value_spec.rb b/spec/ruby/core/env/each_value_spec.rb
index 88f4bc49da..cc3c9ebfb8 100644
--- a/spec/ruby/core/env/each_value_spec.rb
+++ b/spec/ruby/core/env/each_value_spec.rb
@@ -1,4 +1,4 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "ENV.each_value" do
@@ -10,7 +10,7 @@ describe "ENV.each_value" do
       ENV.clear
       ENV["1"] = "3"
       ENV["2"] = "4"
-      ENV.each_value { |v| e << v }
+      ENV.each_value { |v| e << v }.should equal(ENV)
       e.should include("3")
       e.should include("4")
     ensure
@@ -19,12 +19,14 @@ describe "ENV.each_value" do
   end
 
   it "returns an Enumerator if called without a block" do
-    ENV.each_value.should be_an_instance_of(Enumerator)
+    enum = ENV.each_value
+    enum.should be_an_instance_of(Enumerator)
+    enum.to_a.should == ENV.values
   end
 
   it "uses the locale encoding" do
     ENV.each_value do |value|
-      value.encoding.should == Encoding.find('locale')
+      value.should.be_locale_env
     end
   end
 
diff --git a/spec/ruby/core/env/element_reference_spec.rb b/spec/ruby/core/env/element_reference_spec.rb
index 59b53fc4b1..66a9bc9690 100644
--- a/spec/ruby/core/env/element_reference_spec.rb
+++ b/spec/ruby/core/env/element_reference_spec.rb
@@ -1,5 +1,6 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
+require_relative 'fixtures/common'
 
 describe "ENV.[]" do
   before :each do
@@ -16,7 +17,18 @@ describe "ENV.[]" do
 
   it "returns only frozen values" do
     ENV[@variable] = "a non-frozen string"
-    ENV[@variable].frozen?.should == true
+    ENV[@variable].should.frozen?
+  end
+
+  it "coerces a non-string name with #to_str" do
+    ENV[@variable] = "bar"
+    k = mock('key')
+    k.should_receive(:to_str).and_return(@variable)
+    ENV[k].should == "bar"
+  end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> { ENV[Object.new] }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 
   platform_is :windows do
@@ -47,7 +59,7 @@ describe "ENV.[]" do
   it "uses the locale encoding if Encoding.default_internal is nil" do
     Encoding.default_internal = nil
 
-    locale = Encoding.find('locale')
+    locale = ENVSpecs.encoding
     locale = Encoding::BINARY if locale == Encoding::US_ASCII
     ENV[@variable] = "\xC3\xB8"
     ENV[@variable].encoding.should == locale
diff --git a/spec/ruby/core/env/empty_spec.rb b/spec/ruby/core/env/empty_spec.rb
index 7ef17d244f..afeb406a9e 100644
--- a/spec/ruby/core/env/empty_spec.rb
+++ b/spec/ruby/core/env/empty_spec.rb
@@ -4,12 +4,12 @@ describe "ENV.empty?" do
 
   it "returns true if the Environment is empty" do
     if ENV.keys.size > 0
-      ENV.empty?.should == false
+      ENV.should_not.empty?
     end
     orig = ENV.to_hash
     begin
       ENV.clear
-      ENV.empty?.should == true
+      ENV.should.empty?
     ensure
       ENV.replace orig
     end
@@ -17,7 +17,7 @@ describe "ENV.empty?" do
 
   it "returns false if not empty" do
     if ENV.keys.size > 0
-      ENV.empty?.should == false
+      ENV.should_not.empty?
     end
   end
 end
diff --git a/spec/ruby/core/env/except_spec.rb b/spec/ruby/core/env/except_spec.rb
new file mode 100644
index 0000000000..fb8f3b7536
--- /dev/null
+++ b/spec/ruby/core/env/except_spec.rb
@@ -0,0 +1,34 @@
+require_relative 'spec_helper'
+require_relative 'shared/to_hash'
+
+describe "ENV.except" do
+  before do
+    @orig_hash = ENV.to_hash
+  end
+
+  after do
+    ENV.replace @orig_hash
+  end
+
+  # Testing the method without arguments is covered via
+  it_behaves_like :env_to_hash, :except
+
+  it "returns a hash without the requested subset" do
+    ENV.clear
+
+    ENV['one'] = '1'
+    ENV['two'] = '2'
+    ENV['three'] = '3'
+
+    ENV.except('one', 'three').should == { 'two' => '2' }
+  end
+
+  it "ignores keys not present in the original hash" do
+    ENV.clear
+
+    ENV['one'] = '1'
+    ENV['two'] = '2'
+
+    ENV.except('one', 'three').should == { 'two' => '2' }
+  end
+end
diff --git a/spec/ruby/core/env/fetch_spec.rb b/spec/ruby/core/env/fetch_spec.rb
index eeaf290cf0..2c5d7cc3a0 100644
--- a/spec/ruby/core/env/fetch_spec.rb
+++ b/spec/ruby/core/env/fetch_spec.rb
@@ -1,15 +1,22 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/hash/key_error'
+require_relative 'fixtures/common'
 
 describe "ENV.fetch" do
+  before :each do
+    @foo_saved = ENV.delete("foo")
+  end
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "returns a value" do
     ENV["foo"] = "bar"
     ENV.fetch("foo").should == "bar"
-    ENV.delete "foo"
   end
 
   it "raises a TypeError if the key is not a String" do
-    -> { ENV.fetch :should_never_be_set }.should raise_error(TypeError)
+    -> { ENV.fetch Object.new }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 
   context "when the key is not found" do
@@ -23,20 +30,34 @@ describe "ENV.fetch" do
   end
 
   it "provides the given default parameter" do
-    ENV.fetch("should_never_be_set", "default").should == "default"
+    ENV.fetch("foo", "default").should == "default"
+  end
+
+  it "does not insist that the default be a String" do
+    ENV.fetch("foo", :default).should == :default
   end
 
   it "provides a default value from a block" do
-    ENV.fetch("should_never_be_set") { |k| "wanted #{k}" }.should == "wanted should_never_be_set"
+    ENV.fetch("foo") { |k| "wanted #{k}" }.should == "wanted foo"
+  end
+
+  it "does not insist that the block return a String" do
+    ENV.fetch("foo") { |k| k.to_sym }.should == :foo
   end
 
   it "warns on block and default parameter given" do
     -> do
-       ENV.fetch("should_never_be_set", "default") { 1 }.should == 1
+      ENV.fetch("foo", "default") { "bar" }.should == "bar"
     end.should complain(/block supersedes default value argument/)
   end
 
+  it "does not evaluate the block when key found" do
+    ENV["foo"] = "bar"
+    ENV.fetch("foo") { fail "should not get here"}.should == "bar"
+  end
+
   it "uses the locale encoding" do
-    ENV.fetch(ENV.keys.first).encoding.should == Encoding.find('locale')
+    ENV["foo"] = "bar"
+    ENV.fetch("foo").encoding.should == ENVSpecs.encoding
   end
 end
diff --git a/spec/ruby/core/env/filter_spec.rb b/spec/ruby/core/env/filter_spec.rb
index ba18a3b33b..52f8b79a0b 100644
--- a/spec/ruby/core/env/filter_spec.rb
+++ b/spec/ruby/core/env/filter_spec.rb
@@ -2,14 +2,12 @@ require_relative '../../spec_helper'
 require_relative '../enumerable/shared/enumeratorized'
 require_relative 'shared/select'
 
-ruby_version_is "2.6" do
-  describe "ENV.filter!" do
-    it_behaves_like :env_select!, :filter!
-    it_behaves_like :enumeratorized_with_origin_size, :filter!, ENV
-  end
+describe "ENV.filter!" do
+  it_behaves_like :env_select!, :filter!
+  it_behaves_like :enumeratorized_with_origin_size, :filter!, ENV
+end
 
-  describe "ENV.filter" do
-    it_behaves_like :env_select, :filter
-    it_behaves_like :enumeratorized_with_origin_size, :filter, ENV
-  end
+describe "ENV.filter" do
+  it_behaves_like :env_select, :filter
+  it_behaves_like :enumeratorized_with_origin_size, :filter, ENV
 end
diff --git a/spec/ruby/core/env/fixtures/common.rb b/spec/ruby/core/env/fixtures/common.rb
new file mode 100644
index 0000000000..8d5057614d
--- /dev/null
+++ b/spec/ruby/core/env/fixtures/common.rb
@@ -0,0 +1,9 @@
+module ENVSpecs
+  def self.encoding
+    locale = Encoding.find('locale')
+    if ruby_version_is '3' and platform_is :windows
+      locale = Encoding::UTF_8
+    end
+    locale
+  end
+end
diff --git a/spec/ruby/core/env/index_spec.rb b/spec/ruby/core/env/index_spec.rb
deleted file mode 100644
index 04986a0421..0000000000
--- a/spec/ruby/core/env/index_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/key'
-
-describe "ENV.index" do
-  it_behaves_like :env_key, :index
-end
diff --git a/spec/ruby/core/env/indexes_spec.rb b/spec/ruby/core/env/indexes_spec.rb
deleted file mode 100644
index e724feaa39..0000000000
--- a/spec/ruby/core/env/indexes_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../spec_helper'
diff --git a/spec/ruby/core/env/indices_spec.rb b/spec/ruby/core/env/indices_spec.rb
deleted file mode 100644
index e724feaa39..0000000000
--- a/spec/ruby/core/env/indices_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../spec_helper'
diff --git a/spec/ruby/core/env/inspect_spec.rb b/spec/ruby/core/env/inspect_spec.rb
index 3c611c24a1..7dd92b120f 100644
--- a/spec/ruby/core/env/inspect_spec.rb
+++ b/spec/ruby/core/env/inspect_spec.rb
@@ -4,7 +4,7 @@ describe "ENV.inspect" do
 
   it "returns a String that looks like a Hash with real data" do
     ENV["foo"] = "bar"
-    ENV.inspect.should =~ /\{.*"foo"=>"bar".*\}/
+    ENV.inspect.should =~ /\{.*"foo" *=> *"bar".*\}/
     ENV.delete "foo"
   end
 
diff --git a/spec/ruby/core/env/keep_if_spec.rb b/spec/ruby/core/env/keep_if_spec.rb
index cf8e27936e..64b6a207d0 100644
--- a/spec/ruby/core/env/keep_if_spec.rb
+++ b/spec/ruby/core/env/keep_if_spec.rb
@@ -3,20 +3,30 @@ require_relative '../enumerable/shared/enumeratorized'
 
 describe "ENV.keep_if" do
   before :each do
-    ENV["foo"] = "bar"
+    @foo = ENV["foo"]
+    @bar = ENV["bar"]
+
+    ENV["foo"] = "0"
+    ENV["bar"] = "1"
   end
 
   after :each do
-    ENV.delete "foo"
+    ENV["foo"] = @foo
+    ENV["bar"] = @bar
   end
 
   it "deletes pairs if the block returns false" do
-    ENV.keep_if { |k, v| k != "foo" }
+    ENV.keep_if { |k, v| !["foo", "bar"].include?(k) }
     ENV["foo"].should == nil
+    ENV["bar"].should == nil
+  end
+
+  it "returns ENV when block given" do
+    ENV.keep_if { |k, v| !["foo", "bar"].include?(k) }.should equal(ENV)
   end
 
   it "returns ENV even if nothing deleted" do
-    ENV.keep_if { true }.should_not == nil
+    ENV.keep_if { true }.should equal(ENV)
   end
 
   it "returns an Enumerator if no block given" do
@@ -25,8 +35,19 @@ describe "ENV.keep_if" do
 
   it "deletes pairs through enumerator" do
     enum = ENV.keep_if
-    enum.each { |k, v| k != "foo" }
+    enum.each { |k, v| !["foo", "bar"].include?(k) }
     ENV["foo"].should == nil
+    ENV["bar"].should == nil
+  end
+
+  it "returns ENV from enumerator" do
+    enum = ENV.keep_if
+    enum.each { |k, v| !["foo", "bar"].include?(k) }.should equal(ENV)
+  end
+
+  it "returns ENV from enumerator even if nothing deleted" do
+    enum = ENV.keep_if
+    enum.each { true }.should equal(ENV)
   end
 
   it_behaves_like :enumeratorized_with_origin_size, :keep_if, ENV
diff --git a/spec/ruby/core/env/key_spec.rb b/spec/ruby/core/env/key_spec.rb
index 82cfbefa39..cf70286409 100644
--- a/spec/ruby/core/env/key_spec.rb
+++ b/spec/ruby/core/env/key_spec.rb
@@ -1,11 +1,39 @@
 require_relative '../../spec_helper'
 require_relative 'shared/include'
-require_relative 'shared/key'
 
 describe "ENV.key?" do
   it_behaves_like :env_include, :key?
 end
 
 describe "ENV.key" do
-  it_behaves_like :env_key, :key
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
+  it "returns the index associated with the passed value" do
+    ENV["foo"] = "bar"
+    ENV.key("bar").should == "foo"
+  end
+
+  it "returns nil if the passed value is not found" do
+    ENV.delete("foo")
+    ENV.key("foo").should be_nil
+  end
+
+  it "coerces the key element with #to_str" do
+    ENV["foo"] = "bar"
+    k = mock('key')
+    k.should_receive(:to_str).and_return("bar")
+    ENV.key(k).should == "foo"
+  end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> {
+      ENV.key(Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
 end
diff --git a/spec/ruby/core/env/keys_spec.rb b/spec/ruby/core/env/keys_spec.rb
index 3699b2c225..b074a8f7c7 100644
--- a/spec/ruby/core/env/keys_spec.rb
+++ b/spec/ruby/core/env/keys_spec.rb
@@ -2,8 +2,8 @@ require_relative '../../spec_helper'
 
 describe "ENV.keys" do
 
-  it "returns all the keys" do
-    ENV.keys.sort.should == ENV.to_hash.keys.sort
+  it "returns an array of the keys" do
+    ENV.keys.should == ENV.to_hash.keys
   end
 
   it "returns the keys in the locale encoding" do
diff --git a/spec/ruby/core/env/length_spec.rb b/spec/ruby/core/env/length_spec.rb
index 536af9edf5..c6f9062892 100644
--- a/spec/ruby/core/env/length_spec.rb
+++ b/spec/ruby/core/env/length_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/length'
 
 describe "ENV.length" do
- it_behaves_like :env_length, :length
+  it_behaves_like :env_length, :length
 end
diff --git a/spec/ruby/core/env/merge_spec.rb b/spec/ruby/core/env/merge_spec.rb
index b418cd11f4..f10662cf79 100644
--- a/spec/ruby/core/env/merge_spec.rb
+++ b/spec/ruby/core/env/merge_spec.rb
@@ -1,8 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'shared/update'
 
-ruby_version_is "2.7" do
-  describe "ENV.merge!" do
-    it_behaves_like :env_update, :merge!
-  end
+describe "ENV.merge!" do
+  it_behaves_like :env_update, :merge!
 end
diff --git a/spec/ruby/core/env/rassoc_spec.rb b/spec/ruby/core/env/rassoc_spec.rb
index 4b839c15c7..ab9fe68088 100644
--- a/spec/ruby/core/env/rassoc_spec.rb
+++ b/spec/ruby/core/env/rassoc_spec.rb
@@ -1,8 +1,14 @@
 require_relative '../../spec_helper'
 
 describe "ENV.rassoc" do
+  before :each do
+    @foo = ENV["foo"]
+    @baz = ENV["baz"]
+  end
+
   after :each do
-    ENV.delete("foo")
+    ENV["foo"] = @foo
+    ENV["baz"] = @baz
   end
 
   it "returns an array of the key and value of the environment variable with the given value" do
@@ -10,6 +16,15 @@ describe "ENV.rassoc" do
     ENV.rassoc("bar").should == ["foo", "bar"]
   end
 
+  it "returns a single array even if there are multiple such environment variables" do
+    ENV["foo"] = "bar"
+    ENV["baz"] = "bar"
+    [
+        ["foo", "bar"],
+        ["baz", "bar"],
+    ].should include(ENV.rassoc("bar"))
+  end
+
   it "returns nil if no environment variable with the given value exists" do
     ENV.rassoc("bar").should == nil
   end
@@ -20,4 +35,8 @@ describe "ENV.rassoc" do
     v.should_receive(:to_str).and_return("bar")
     ENV.rassoc(v).should == ["foo", "bar"]
   end
+
+  it "returns nil if the argument is not a String and does not respond to #to_str" do
+    ENV.rassoc(Object.new).should == nil
+  end
 end
diff --git a/spec/ruby/core/env/rehash_spec.rb b/spec/ruby/core/env/rehash_spec.rb
index e724feaa39..3782e4b727 100644
--- a/spec/ruby/core/env/rehash_spec.rb
+++ b/spec/ruby/core/env/rehash_spec.rb
@@ -1 +1,7 @@
 require_relative '../../spec_helper'
+
+describe "ENV.rehash" do
+  it "returns nil" do
+    ENV.rehash.should == nil
+  end
+end
diff --git a/spec/ruby/core/env/reject_spec.rb b/spec/ruby/core/env/reject_spec.rb
index 1026c2f451..6a9794925d 100644
--- a/spec/ruby/core/env/reject_spec.rb
+++ b/spec/ruby/core/env/reject_spec.rb
@@ -2,6 +2,14 @@ require_relative '../../spec_helper'
 require_relative '../enumerable/shared/enumeratorized'
 
 describe "ENV.reject!" do
+  before :each do
+    @foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @foo
+  end
+
   it "rejects entries based on key" do
     ENV["foo"] = "bar"
     ENV.reject! { |k, v| k == "foo" }
@@ -17,12 +25,16 @@ describe "ENV.reject!" do
   it "returns itself or nil" do
     ENV.reject! { false }.should == nil
     ENV["foo"] = "bar"
-    ENV.reject! { |k, v| k == "foo" }.should == ENV
+    ENV.reject! { |k, v| k == "foo" }.should equal(ENV)
     ENV["foo"].should == nil
   end
 
   it "returns an Enumerator if called without a block" do
-    ENV.reject!.should be_an_instance_of(Enumerator)
+    ENV["foo"] = "bar"
+    enum = ENV.reject!
+    enum.should be_an_instance_of(Enumerator)
+    enum.each { |k, v| k == "foo" }.should equal(ENV)
+    ENV["foo"].should == nil
   end
 
   it "doesn't raise if empty" do
@@ -39,6 +51,14 @@ describe "ENV.reject!" do
 end
 
 describe "ENV.reject" do
+  before :each do
+    @foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @foo
+  end
+
   it "rejects entries based on key" do
     ENV["foo"] = "bar"
     e = ENV.reject { |k, v| k == "foo" }
@@ -60,7 +80,11 @@ describe "ENV.reject" do
   end
 
   it "returns an Enumerator if called without a block" do
-    ENV.reject.should be_an_instance_of(Enumerator)
+    ENV["foo"] = "bar"
+    enum = ENV.reject
+    enum.should be_an_instance_of(Enumerator)
+    enum.each { |k, v| k == "foo"}
+    ENV["foo"] = nil
   end
 
   it "doesn't raise if empty" do
diff --git a/spec/ruby/core/env/replace_spec.rb b/spec/ruby/core/env/replace_spec.rb
index 8837deea4a..9fc67643d1 100644
--- a/spec/ruby/core/env/replace_spec.rb
+++ b/spec/ruby/core/env/replace_spec.rb
@@ -1,15 +1,51 @@
 require_relative '../../spec_helper'
 
 describe "ENV.replace" do
+  before :each do
+    @orig = ENV.to_hash
+    ENV.delete("foo")
+  end
+
+  after :each do
+    ENV.replace(@orig)
+  end
 
   it "replaces ENV with a Hash" do
-    ENV["foo"] = "bar"
-    e = ENV.reject { |k, v| k == "foo" }
-    e["baz"] = "bam"
-    ENV.replace e
-    ENV["foo"].should == nil
-    ENV["baz"].should == "bam"
-    ENV.delete "baz"
+    ENV.replace("foo" => "0", "bar" => "1").should equal(ENV)
+    ENV.size.should == 2
+    ENV["foo"].should == "0"
+    ENV["bar"].should == "1"
+  end
+
+  it "raises TypeError if the argument is not a Hash" do
+    -> { ENV.replace(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into Hash")
+    ENV.to_hash.should == @orig
+  end
+
+  it "raises TypeError if a key is not a String" do
+    -> { ENV.replace(Object.new => "0") }.should raise_error(TypeError, "no implicit conversion of Object into String")
+    ENV.to_hash.should == @orig
+  end
+
+  it "raises TypeError if a value is not a String" do
+    -> { ENV.replace("foo" => Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
+    ENV.to_hash.should == @orig
+  end
+
+  it "raises Errno::EINVAL when the key contains the '=' character" do
+    -> { ENV.replace("foo=" =>"bar") }.should raise_error(Errno::EINVAL)
+  end
+
+  it "raises Errno::EINVAL when the key is an empty string" do
+    -> { ENV.replace("" => "bar") }.should raise_error(Errno::EINVAL)
+  end
+
+  it "does not accept good data preceding an error" do
+    -> { ENV.replace("foo" => "1", Object.new => Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 
+  it "does not accept good data following an error" do
+    -> { ENV.replace(Object.new => Object.new, "foo" => "0") }.should raise_error(TypeError, "no implicit conversion of Object into String")
+    ENV.to_hash.should == @orig
+  end
 end
diff --git a/spec/ruby/core/env/shared/each.rb b/spec/ruby/core/env/shared/each.rb
index 8a262e4862..d901b854c4 100644
--- a/spec/ruby/core/env/shared/each.rb
+++ b/spec/ruby/core/env/shared/each.rb
@@ -8,7 +8,7 @@ describe :env_each, shared: true do
       ENV.clear
       ENV["foo"] = "bar"
       ENV["baz"] = "boo"
-      ENV.send(@method) { |k, v| e << [k, v] }
+      ENV.send(@method) { |k, v| e << [k, v] }.should equal(ENV)
       e.should include(["foo", "bar"])
       e.should include(["baz", "boo"])
     ensure
@@ -17,7 +17,11 @@ describe :env_each, shared: true do
   end
 
   it "returns an Enumerator if called without a block" do
-    ENV.send(@method).should be_an_instance_of(Enumerator)
+    enum = ENV.send(@method)
+    enum.should be_an_instance_of(Enumerator)
+    enum.each do |name, value|
+      ENV[name].should == value
+    end
   end
 
   before :all do
@@ -31,8 +35,6 @@ describe :env_each, shared: true do
       @internal = Encoding.default_internal
 
       Encoding.default_external = Encoding::BINARY
-
-      @locale_encoding = Encoding.find "locale"
     end
 
     after :each do
@@ -44,8 +46,8 @@ describe :env_each, shared: true do
       Encoding.default_internal = nil
 
       ENV.send(@method) do |key, value|
-        key.encoding.should equal(@locale_encoding)
-        value.encoding.should equal(@locale_encoding)
+        key.should.be_locale_env
+        value.should.be_locale_env
       end
     end
 
diff --git a/spec/ruby/core/env/shared/include.rb b/spec/ruby/core/env/shared/include.rb
index 8d8311dcf2..70aa555301 100644
--- a/spec/ruby/core/env/shared/include.rb
+++ b/spec/ruby/core/env/shared/include.rb
@@ -1,11 +1,30 @@
 describe :env_include, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "returns true if ENV has the key" do
     ENV["foo"] = "bar"
     ENV.send(@method, "foo").should == true
-    ENV.delete "foo"
   end
 
   it "returns false if ENV doesn't include the key" do
-    ENV.send(@method, "should_never_be_set").should == false
+    ENV.delete("foo")
+    ENV.send(@method, "foo").should == false
+  end
+
+  it "coerces the key with #to_str" do
+    ENV["foo"] = "bar"
+    k = mock('key')
+    k.should_receive(:to_str).and_return("foo")
+    ENV.send(@method, k).should == true
+  end
+
+  it "raises TypeError if the argument is not a String and does not respond to #to_str" do
+    -> { ENV.send(@method, Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 end
diff --git a/spec/ruby/core/env/shared/key.rb b/spec/ruby/core/env/shared/key.rb
deleted file mode 100644
index 43299beadb..0000000000
--- a/spec/ruby/core/env/shared/key.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-describe :env_key, shared: true do
-  it "returns the index associated with the passed value" do
-    ENV["foo"] = "bar"
-    ENV.send(@method, "bar").should == "foo"
-    ENV.delete "foo"
-  end
-
-  it "returns nil if the passed value is not found" do
-    ENV.send(@method, "should_never_be_set").should be_nil
-  end
-end
diff --git a/spec/ruby/core/env/shared/select.rb b/spec/ruby/core/env/shared/select.rb
index a0b46a775a..75ba112a32 100644
--- a/spec/ruby/core/env/shared/select.rb
+++ b/spec/ruby/core/env/shared/select.rb
@@ -1,16 +1,38 @@
 describe :env_select, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "returns a Hash of names and values for which block return true" do
     ENV["foo"] = "bar"
     (ENV.send(@method) { |k, v| k == "foo" }).should == { "foo" => "bar" }
-    ENV.delete "foo"
   end
 
   it "returns an Enumerator when no block is given" do
-    ENV.send(@method).should be_an_instance_of(Enumerator)
+    enum = ENV.send(@method)
+    enum.should be_an_instance_of(Enumerator)
+  end
+
+  it "selects via the enumerator" do
+    enum = ENV.send(@method)
+    ENV["foo"] = "bar"
+    enum.each { |k, v| k == "foo" }.should == { "foo" => "bar"}
   end
 end
 
 describe :env_select!, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "removes environment variables for which the block returns true" do
     ENV["foo"] = "bar"
     ENV.send(@method) { |k, v| k != "foo" }
@@ -29,4 +51,11 @@ describe :env_select!, shared: true do
   it "returns an Enumerator if called without a block" do
     ENV.send(@method).should be_an_instance_of(Enumerator)
   end
+
+  it "selects via the enumerator" do
+    enum = ENV.send(@method)
+    ENV["foo"] = "bar"
+    enum.each { |k, v| k != "foo" }
+    ENV["foo"].should == nil
+  end
 end
diff --git a/spec/ruby/core/env/shared/store.rb b/spec/ruby/core/env/shared/store.rb
index 6ae91ef8fc..d6265c66a5 100644
--- a/spec/ruby/core/env/shared/store.rb
+++ b/spec/ruby/core/env/shared/store.rb
@@ -1,6 +1,10 @@
 describe :env_store, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
   after :each do
-    ENV.delete("foo")
+    ENV["foo"] = @saved_foo
   end
 
   it "sets the environment variable to the given value" do
@@ -34,11 +38,11 @@ describe :env_store, shared: true do
   end
 
   it "raises TypeError when the key is not coercible to String" do
-    -> { ENV.send(@method, Object.new, "bar") }.should raise_error(TypeError)
+    -> { ENV.send(@method, Object.new, "bar") }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 
   it "raises TypeError when the value is not coercible to String" do
-    -> { ENV.send(@method, "foo", Object.new) }.should raise_error(TypeError)
+    -> { ENV.send(@method, "foo", Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 
   it "raises Errno::EINVAL when the key contains the '=' character" do
diff --git a/spec/ruby/core/env/shared/to_hash.rb b/spec/ruby/core/env/shared/to_hash.rb
index 254054c14d..a0d4d7ce69 100644
--- a/spec/ruby/core/env/shared/to_hash.rb
+++ b/spec/ruby/core/env/shared/to_hash.rb
@@ -1,22 +1,33 @@
 describe :env_to_hash, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"]= @saved_foo
+  end
+
   it "returns the ENV as a hash" do
     ENV["foo"] = "bar"
     h = ENV.send(@method)
     h.should be_an_instance_of(Hash)
     h["foo"].should == "bar"
-    ENV.delete "foo"
   end
 
   it "uses the locale encoding for keys" do
-    ENV.send(@method).keys.all? {|k| k.encoding == Encoding.find('locale') }.should be_true
+    ENV.send(@method).keys.each {|k| k.should.be_locale_env }
   end
 
   it "uses the locale encoding for values" do
-    ENV.send(@method).values.all? {|v| v.encoding == Encoding.find('locale') }.should be_true
+    ENV.send(@method).values.each {|k| k.should.be_locale_env }
   end
 
   it "duplicates the ENV when converting to a Hash" do
     h = ENV.send(@method)
     h.should_not equal ENV
+    h.size.should == ENV.size
+    h.each_pair do |k, v|
+      ENV[k].should == v
+    end
   end
 end
diff --git a/spec/ruby/core/env/shared/update.rb b/spec/ruby/core/env/shared/update.rb
index cd09877243..e1b1c9c290 100644
--- a/spec/ruby/core/env/shared/update.rb
+++ b/spec/ruby/core/env/shared/update.rb
@@ -1,21 +1,104 @@
 describe :env_update, shared: true do
-  it "adds the parameter hash to ENV" do
-    ENV["foo"].should == nil
-    ENV.send @method, "foo" => "bar"
-    ENV["foo"].should == "bar"
-    ENV.delete "foo"
-  end
-
-  it "yields key, the old value and the new value when replacing entries" do
-    ENV.send @method, "foo" => "bar"
-    ENV["foo"].should == "bar"
-    ENV.send(@method, "foo" => "boo") do |key, old, new|
-      key.should == "foo"
-      old.should == "bar"
-      new.should == "boo"
-      "rab"
+  before :each do
+    @saved_foo = ENV["foo"]
+    @saved_bar = ENV["bar"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+    ENV["bar"] = @saved_bar
+  end
+
+  it "adds the parameter hash to ENV, returning ENV" do
+    ENV.send(@method, "foo" => "0", "bar" => "1").should equal(ENV)
+    ENV["foo"].should == "0"
+    ENV["bar"].should == "1"
+  end
+
+  it "adds the multiple parameter hashes to ENV, returning ENV" do
+    ENV.send(@method, {"foo" => "multi1"}, {"bar" => "multi2"}).should equal(ENV)
+    ENV["foo"].should == "multi1"
+    ENV["bar"].should == "multi2"
+  end
+
+  it "returns ENV when no block given" do
+    ENV.send(@method, {"foo" => "0", "bar" => "1"}).should equal(ENV)
+  end
+
+  it "yields key, the old value and the new value when replacing an entry" do
+    ENV.send @method, {"foo" => "0", "bar" => "3"}
+    a = []
+    ENV.send @method, {"foo" => "1", "bar" => "4"} do |key, old, new|
+      a << [key, old, new]
+      new
+    end
+    a[0].should == ["foo", "0", "1"]
+    a[1].should == ["bar", "3", "4"]
+  end
+
+  it "yields key, the old value and the new value when replacing an entry" do
+    ENV.send @method, {"foo" => "0", "bar" => "3"}
+    ENV.send @method, {"foo" => "1", "bar" => "4"} do |key, old, new|
+      (new.to_i + 1).to_s
+    end
+    ENV["foo"].should == "2"
+    ENV["bar"].should == "5"
+  end
+
+  # BUG: https://bugs.ruby-lang.org/issues/16192
+  it "does not evaluate the block when the name is new" do
+    ENV.delete("bar")
+    ENV.send @method, {"foo" => "0"}
+    ENV.send(@method, "bar" => "1") { |key, old, new| fail "Should not get here" }
+    ENV["bar"].should == "1"
+  end
+
+  # BUG: https://bugs.ruby-lang.org/issues/16192
+  it "does not use the block's return value as the value when the name is new" do
+    ENV.delete("bar")
+    ENV.send @method, {"foo" => "0"}
+    ENV.send(@method, "bar" => "1") { |key, old, new| "Should not use this value" }
+    ENV["foo"].should == "0"
+    ENV["bar"].should == "1"
+  end
+
+  it "returns ENV when block given" do
+    ENV.send(@method, {"foo" => "0", "bar" => "1"}){}.should equal(ENV)
+  end
+
+  it "raises TypeError when a name is not coercible to String" do
+    -> { ENV.send @method, Object.new => "0" }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
+
+  it "raises TypeError when a value is not coercible to String" do
+    -> { ENV.send @method, "foo" => Object.new }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
+
+  it "raises Errno::EINVAL when a name contains the '=' character" do
+    -> { ENV.send(@method, "foo=" => "bar") }.should raise_error(Errno::EINVAL)
+  end
+
+  it "raises Errno::EINVAL when a name is an empty string" do
+    -> { ENV.send(@method, "" => "bar") }.should raise_error(Errno::EINVAL)
+  end
+
+  it "updates good data preceding an error" do
+    ENV["foo"] = "0"
+    begin
+      ENV.send @method, {"foo" => "2", Object.new => "1"}
+    rescue TypeError
+    ensure
+      ENV["foo"].should == "2"
+    end
+  end
+
+  it "does not update good data following an error" do
+    ENV["foo"] = "0"
+    begin
+      ENV.send @method, {Object.new => "1", "foo" => "2"}
+    rescue TypeError
+    ensure
+      ENV["foo"].should == "0"
     end
-    ENV["foo"].should == "rab"
-    ENV.delete "foo"
   end
 end
diff --git a/spec/ruby/core/env/shared/value.rb b/spec/ruby/core/env/shared/value.rb
index d9ee90f12d..c2b5025465 100644
--- a/spec/ruby/core/env/shared/value.rb
+++ b/spec/ruby/core/env/shared/value.rb
@@ -1,11 +1,29 @@
 describe :env_value, shared: true do
+  before :each do
+    @saved_foo = ENV["foo"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+  end
+
   it "returns true if ENV has the value" do
     ENV["foo"] = "bar"
     ENV.send(@method, "bar").should == true
-    ENV["foo"] = nil
   end
 
   it "returns false if ENV doesn't have the value" do
-    ENV.send(@method, "this_value_should_never_exist").should == false
+    ENV.send(@method, "foo").should == false
+  end
+
+  it "coerces the value element with #to_str" do
+    ENV["foo"] = "bar"
+    v = mock('value')
+    v.should_receive(:to_str).and_return("bar")
+    ENV.send(@method, v).should == true
+  end
+
+  it "returns nil if the argument is not a String and does not respond to #to_str" do
+    ENV.send(@method, Object.new).should == nil
   end
 end
diff --git a/spec/ruby/core/env/shift_spec.rb b/spec/ruby/core/env/shift_spec.rb
index c03b5d50c5..1b92e5d1e4 100644
--- a/spec/ruby/core/env/shift_spec.rb
+++ b/spec/ruby/core/env/shift_spec.rb
@@ -1,28 +1,5 @@
 require_relative '../../spec_helper'
-
-describe "ENV.shift" do
-  it "returns a pair and deletes it" do
-    ENV.empty?.should == false
-    orig = ENV.to_hash
-    begin
-      pair = ENV.shift
-      ENV.has_key?(pair.first).should == false
-    ensure
-      ENV.replace orig
-    end
-    ENV.has_key?(pair.first).should == true
-  end
-
-  it "returns nil if ENV.empty?" do
-    orig = ENV.to_hash
-    begin
-      ENV.clear
-      ENV.shift.should == nil
-    ensure
-      ENV.replace orig
-    end
-  end
-end
+require_relative 'fixtures/common'
 
 describe "ENV.shift" do
   before :each do
@@ -31,6 +8,7 @@ describe "ENV.shift" do
     @internal = Encoding.default_internal
 
     Encoding.default_external = Encoding::BINARY
+    ENV.replace({"FOO"=>"BAR"})
   end
 
   after :each do
@@ -39,12 +17,24 @@ describe "ENV.shift" do
     ENV.replace @orig
   end
 
+  it "returns a pair and deletes it" do
+    ENV.should.has_key?("FOO")
+    pair = ENV.shift
+    pair.should == ["FOO", "BAR"]
+    ENV.should_not.has_key?("FOO")
+  end
+
+  it "returns nil if ENV.empty?" do
+    ENV.clear
+    ENV.shift.should == nil
+  end
+
   it "uses the locale encoding if Encoding.default_internal is nil" do
     Encoding.default_internal = nil
 
     pair = ENV.shift
-    pair.first.encoding.should equal(Encoding.find("locale"))
-    pair.last.encoding.should equal(Encoding.find("locale"))
+    pair.first.encoding.should equal(ENVSpecs.encoding)
+    pair.last.encoding.should equal(ENVSpecs.encoding)
   end
 
   it "transcodes from the locale encoding to Encoding.default_internal if set" do
diff --git a/spec/ruby/core/env/size_spec.rb b/spec/ruby/core/env/size_spec.rb
index f050e9e5a9..7c8072481e 100644
--- a/spec/ruby/core/env/size_spec.rb
+++ b/spec/ruby/core/env/size_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/length'
 
 describe "ENV.size" do
- it_behaves_like :env_length, :size
+  it_behaves_like :env_length, :size
 end
diff --git a/spec/ruby/core/env/slice_spec.rb b/spec/ruby/core/env/slice_spec.rb
new file mode 100644
index 0000000000..959239d2b2
--- /dev/null
+++ b/spec/ruby/core/env/slice_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+
+describe "ENV.slice" do
+  before :each do
+    @saved_foo = ENV["foo"]
+    @saved_bar = ENV["bar"]
+    ENV["foo"] = "0"
+    ENV["bar"] = "1"
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+    ENV["bar"] = @saved_bar
+  end
+
+  it "returns a hash of the given environment variable names and their values" do
+    ENV.slice("foo", "bar").should == {"foo" => "0", "bar" => "1"}
+  end
+
+  it "ignores each String that is not an environment variable name" do
+    ENV.slice("foo", "boo", "bar").should == {"foo" => "0", "bar" => "1"}
+  end
+
+  it "returns the values for the keys coerced with #to_str, but keeps the original objects as result keys" do
+    foo = mock('key 1')
+    foo.should_receive(:to_str).and_return("foo")
+    boo = mock('key 2')
+    boo.should_receive(:to_str).and_return("boo")
+    bar = mock('key 3')
+    bar.should_receive(:to_str).and_return("bar")
+    ENV.slice(foo, boo, bar).should == {foo => "0", bar => "1"}
+  end
+
+  it "raises TypeError if any argument is not a String and does not respond to #to_str" do
+    -> { ENV.slice(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
+end
diff --git a/spec/ruby/core/env/spec_helper.rb b/spec/ruby/core/env/spec_helper.rb
new file mode 100644
index 0000000000..470ffa58bc
--- /dev/null
+++ b/spec/ruby/core/env/spec_helper.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+locale_env_matcher = Class.new do
+  def initialize(name = 'locale')
+    encoding = Encoding.find(name)
+    @encodings = (encoding = Encoding::US_ASCII) ?
+                   [encoding, Encoding::ASCII_8BIT] : [encoding]
+  end
+
+  def matches?(actual)
+    @actual = actual = actual.encoding
+    @encodings.include?(actual)
+  end
+
+  def failure_message
+    ["Expected #{@actual} to be #{@encodings.join(' or ')}"]
+  end
+
+  def negative_failure_message
+    ["Expected #{@actual} not to be #{@encodings.join(' or ')}"]
+  end
+end
+
+String.__send__(:define_method, :be_locale_env) do |expected = 'locale'|
+  locale_env_matcher.new(expected)
+end
diff --git a/spec/ruby/core/env/to_a_spec.rb b/spec/ruby/core/env/to_a_spec.rb
index ed290a48a5..2b1649281f 100644
--- a/spec/ruby/core/env/to_a_spec.rb
+++ b/spec/ruby/core/env/to_a_spec.rb
@@ -1,19 +1,21 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 
 describe "ENV.to_a" do
 
   it "returns the ENV as an array" do
-    ENV["foo"] = "bar"
     a = ENV.to_a
     a.is_a?(Array).should == true
-    a.find { |e| e.first == "foo" }.should == ["foo", "bar"]
-    ENV.delete "foo"
+    a.size.should == ENV.size
+    a.each { |k,v| ENV[k].should == v }
+
+    a.first.should.is_a?(Array)
+    a.first.size.should == 2
   end
 
   it "returns the entries in the locale encoding" do
     ENV.to_a.each do |key, value|
-      key.encoding.should == Encoding.find('locale')
-      value.encoding.should == Encoding.find('locale')
+      key.should.be_locale_env
+      value.should.be_locale_env
     end
   end
 end
diff --git a/spec/ruby/core/env/to_h_spec.rb b/spec/ruby/core/env/to_h_spec.rb
index 81a17700e9..58ea2d2030 100644
--- a/spec/ruby/core/env/to_h_spec.rb
+++ b/spec/ruby/core/env/to_h_spec.rb
@@ -1,55 +1,70 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 require_relative 'shared/to_hash'
 
 describe "ENV.to_h" do
   it_behaves_like :env_to_hash, :to_h
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      before do
-        @orig_hash = ENV.to_hash
-      end
-
-      after do
-        ENV.replace @orig_hash
-      end
-
-      it "converts [key, value] pairs returned by the block to a hash" do
-        ENV.replace("a" => "b", "c" => "d")
-        ENV.to_h { |k, v| [k, v.upcase] }.should == { 'a' => "B", 'c' => "D" }
-      end
-
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          ENV.to_h { |k, v| [k, v.upcase, 1] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-
-        -> do
-          ENV.to_h { |k, v| [k] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-      end
-
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          ENV.to_h { |k, v| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String/)
-      end
-
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
-
-        ENV.to_h { |k| x }.should == { :b => 'b' }
-      end
-
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
-
-        -> do
-          ENV.to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject/)
-      end
+  context "with block" do
+    before do
+      @orig_hash = ENV.to_hash
+    end
+
+    after do
+      ENV.replace @orig_hash
+    end
+
+    it "converts [key, value] pairs returned by the block to a hash" do
+      ENV.replace("a" => "b", "c" => "d")
+      ENV.to_h { |k, v| [k, v.upcase] }.should == { 'a' => "B", 'c' => "D" }
+    end
+
+    it "passes to a block each pair's key and value as separate arguments" do
+      ENV.replace("a" => "b", "c" => "d")
+
+      ScratchPad.record []
+      ENV.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+      ScratchPad.recorded.sort.should == [["a", "b"], ["c", "d"]]
+
+      ScratchPad.record []
+      ENV.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [["a", "b"], ["c", "d"]]
+    end
+
+    it "does not require the array elements to be strings" do
+      ENV.replace("a" => "b", "c" => "d")
+      ENV.to_h { |k, v| [k.to_sym, v.to_sym] }.should == { :a => :b, :c => :d }
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        ENV.to_h { |k, v| [k, v.upcase, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+
+      -> do
+        ENV.to_h { |k, v| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        ENV.to_h { |k, v| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      ENV.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        ENV.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
     end
   end
 end
diff --git a/spec/ruby/core/env/to_hash_spec.rb b/spec/ruby/core/env/to_hash_spec.rb
index 4de0e077bb..306572c353 100644
--- a/spec/ruby/core/env/to_hash_spec.rb
+++ b/spec/ruby/core/env/to_hash_spec.rb
@@ -1,4 +1,4 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 require_relative 'shared/to_hash'
 
 describe "ENV.to_hash" do
diff --git a/spec/ruby/core/env/values_at_spec.rb b/spec/ruby/core/env/values_at_spec.rb
index 906d8b01f2..338680e820 100644
--- a/spec/ruby/core/env/values_at_spec.rb
+++ b/spec/ruby/core/env/values_at_spec.rb
@@ -1,17 +1,38 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/common'
 
 describe "ENV.values_at" do
+  before :each do
+    @saved_foo = ENV["foo"]
+    @saved_bar = ENV["bar"]
+  end
+
+  after :each do
+    ENV["foo"] = @saved_foo
+    ENV["bar"] = @saved_bar
+  end
 
-  it "returns an array of the values referenced by the parameters as keys" do
+  it "returns an array of the values corresponding to the given keys" do
     ENV["foo"] = "oof"
     ENV["bar"] = "rab"
-    ENV.values_at.should == []
     ENV.values_at("bar", "foo").should == ["rab", "oof"]
-    ENV.delete "foo"
-    ENV.delete "bar"
+  end
+
+  it "returns an empty array if no keys specified" do
+    ENV.values_at.should == []
+  end
+
+  it "returns nil for each key that is not a name" do
+    ENV["foo"] = "oof"
+    ENV["bar"] = "rab"
+    ENV.values_at("x", "bar", "y", "foo", "z").should == [nil, "rab", nil, "oof", nil]
   end
 
   it "uses the locale encoding" do
-    ENV.values_at(ENV.keys.first).first.encoding.should == Encoding.find('locale')
+    ENV.values_at(ENV.keys.first).first.encoding.should == ENVSpecs.encoding
+  end
+
+  it "raises TypeError when a key is not coercible to String" do
+    -> { ENV.values_at("foo", Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into String")
   end
 end
diff --git a/spec/ruby/core/env/values_spec.rb b/spec/ruby/core/env/values_spec.rb
index 2e4e69c23b..71bc877d31 100644
--- a/spec/ruby/core/env/values_spec.rb
+++ b/spec/ruby/core/env/values_spec.rb
@@ -1,21 +1,14 @@
-require_relative '../../spec_helper'
+require_relative 'spec_helper'
 
 describe "ENV.values" do
 
   it "returns an array of the values" do
-    orig = ENV.to_hash
-    begin
-      ENV.replace "a" => "b", "c" => "d"
-      a = ENV.values
-      a.sort.should == ["b", "d"]
-    ensure
-      ENV.replace orig
-    end
+    ENV.values.should == ENV.to_hash.values
   end
 
   it "uses the locale encoding" do
     ENV.values.each do |value|
-      value.encoding.should == Encoding.find('locale')
+      value.should.be_locale_env
     end
   end
 end
diff --git a/spec/ruby/core/exception/args_spec.rb b/spec/ruby/core/exception/args_spec.rb
deleted file mode 100644
index 005c2dd198..0000000000
--- a/spec/ruby/core/exception/args_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "NoMethodError#args" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/arguments_spec.rb b/spec/ruby/core/exception/arguments_spec.rb
deleted file mode 100644
index 0b283e9a54..0000000000
--- a/spec/ruby/core/exception/arguments_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ArgumentError" do
-  it "is a subclass of StandardError" do
-    StandardError.should be_ancestor_of(ArgumentError)
-  end
-
-  it "gives its own class name as message if it has no message" do
-    ArgumentError.new.message.should == "ArgumentError"
-  end
-end
diff --git a/spec/ruby/core/exception/backtrace_spec.rb b/spec/ruby/core/exception/backtrace_spec.rb
index 5e140f8d9b..9a65ea3820 100644
--- a/spec/ruby/core/exception/backtrace_spec.rb
+++ b/spec/ruby/core/exception/backtrace_spec.rb
@@ -27,7 +27,7 @@ describe "Exception#backtrace" do
   end
 
   it "includes the name of the method from where self raised in the first element" do
-    @backtrace.first.should =~ /in `backtrace'/
+    @backtrace.first.should =~ /in [`'](?:ExceptionSpecs::Backtrace\.)?backtrace'/
   end
 
   it "includes the filename of the location immediately prior to where self raised in the second element" do
@@ -38,16 +38,29 @@ describe "Exception#backtrace" do
     @backtrace[1].should =~ /:6(:in )?/
   end
 
-  it "contains lines of the same format for each prior position in the stack" do
-    @backtrace[2..-1].each do |line|
-      # This regexp is deliberately imprecise to account for the need to abstract out
-      # the paths of the included mspec files and the desire to avoid specifying in any
-      # detail what the in `...' portion looks like.
-      line.should =~ /^[^ ]+\:\d+(:in `[^`]+')?$/
+  ruby_version_is ""..."3.4" do
+    it "contains lines of the same format for each prior position in the stack" do
+      @backtrace[2..-1].each do |line|
+        # This regexp is deliberately imprecise to account for the need to abstract out
+        # the paths of the included mspec files and the desire to avoid specifying in any
+        # detail what the in `...' portion looks like.
+        line.should =~ /^.+:\d+:in `[^`]+'$/
+      end
     end
   end
 
-  it "produces a backtrace for an exception captured using $!" do
+  ruby_version_is "3.4" do
+    it "contains lines of the same format for each prior position in the stack" do
+      @backtrace[2..-1].each do |line|
+        # This regexp is deliberately imprecise to account for the need to abstract out
+        # the paths of the included mspec files and the desire to avoid specifying in any
+        # detail what the in '...' portion looks like.
+        line.should =~ /^.+:\d+:in '[^`]+'$/
+      end
+    end
+  end
+
+  it "captures the backtrace for an exception into $!" do
     exception = begin
       raise
     rescue RuntimeError
@@ -57,6 +70,16 @@ describe "Exception#backtrace" do
     exception.backtrace.first.should =~ /backtrace_spec/
   end
 
+  it "captures the backtrace for an exception into $@" do
+    backtrace = begin
+      raise
+    rescue RuntimeError
+      $@
+    end
+
+    backtrace.first.should =~ /backtrace_spec/
+  end
+
   it "returns an Array that can be updated" do
     begin
       raise
diff --git a/spec/ruby/core/exception/case_compare_spec.rb b/spec/ruby/core/exception/case_compare_spec.rb
index a4c9eaa6bf..5fd11ae741 100644
--- a/spec/ruby/core/exception/case_compare_spec.rb
+++ b/spec/ruby/core/exception/case_compare_spec.rb
@@ -1,5 +1,37 @@
 require_relative '../../spec_helper'
 
 describe "SystemCallError.===" do
-  it "needs to be reviewed for spec completeness"
+  before :all do
+    @example_errno_class = Errno::EINVAL
+    @example_errno = @example_errno_class::Errno
+  end
+
+  it "returns true for an instance of the same class" do
+    Errno::EINVAL.should === Errno::EINVAL.new
+  end
+
+  it "returns true if errnos same" do
+    e = SystemCallError.new('foo', @example_errno)
+    @example_errno_class.===(e).should == true
+  end
+
+  it "returns false if errnos different" do
+    e = SystemCallError.new('foo', @example_errno + 1)
+    @example_errno_class.===(e).should == false
+  end
+
+  it "returns false if arg is not kind of SystemCallError" do
+    e = Object.new
+    @example_errno_class.===(e).should == false
+  end
+
+  it "returns true if receiver is generic and arg is kind of SystemCallError" do
+    e = SystemCallError.new('foo', @example_errno)
+    SystemCallError.===(e).should == true
+  end
+
+  it "returns false if receiver is generic and arg is not kind of SystemCallError" do
+    e = Object.new
+    SystemCallError.===(e).should == false
+  end
 end
diff --git a/spec/ruby/core/exception/destination_encoding_name_spec.rb b/spec/ruby/core/exception/destination_encoding_name_spec.rb
deleted file mode 100644
index b6ffff8c9c..0000000000
--- a/spec/ruby/core/exception/destination_encoding_name_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::UndefinedConversionError#destination_encoding_name" do
-  it "needs to be reviewed for spec completeness"
-end
-
-describe "Encoding::InvalidByteSequenceError#destination_encoding_name" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/destination_encoding_spec.rb b/spec/ruby/core/exception/destination_encoding_spec.rb
deleted file mode 100644
index c3ad0342a1..0000000000
--- a/spec/ruby/core/exception/destination_encoding_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::UndefinedConversionError#destination_encoding" do
-  it "needs to be reviewed for spec completeness"
-end
-
-describe "Encoding::InvalidByteSequenceError#destination_encoding" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/detailed_message_spec.rb b/spec/ruby/core/exception/detailed_message_spec.rb
new file mode 100644
index 0000000000..9df164a1cf
--- /dev/null
+++ b/spec/ruby/core/exception/detailed_message_spec.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/common'
+
+describe "Exception#detailed_message" do
+  it "returns decorated message" do
+    RuntimeError.new("new error").detailed_message.should == "new error (RuntimeError)"
+  end
+
+  it "is called by #full_message to allow message customization" do
+    exception = Exception.new("new error")
+    def exception.detailed_message(**)
+      "<prefix>#{message}<suffix>"
+    end
+    exception.full_message(highlight: false).should.include? "<prefix>new error<suffix>"
+  end
+
+  it "returns just a message if exception class is anonymous" do
+    Class.new(RuntimeError).new("message").detailed_message.should == "message"
+  end
+
+  it "returns 'unhandled exception' for an instance of RuntimeError with empty message" do
+    RuntimeError.new("").detailed_message.should == "unhandled exception"
+  end
+
+  it "returns just class name for an instance other than RuntimeError with empty message" do
+    DetailedMessageSpec::C.new("").detailed_message.should == "DetailedMessageSpec::C"
+    StandardError.new("").detailed_message.should == "StandardError"
+  end
+
+  it "returns a generated class name for an instance of RuntimeError anonymous subclass with empty message" do
+    klass = Class.new(RuntimeError)
+    klass.new("").detailed_message.should =~ /\A#<Class:0x\h+>\z/
+  end
+
+  it "accepts highlight keyword argument and adds escape control sequences" do
+    RuntimeError.new("new error").detailed_message(highlight: true).should == "\e[1mnew error (\e[1;4mRuntimeError\e[m\e[1m)\e[m"
+  end
+
+  it "accepts highlight keyword argument and adds escape control sequences for an instance of RuntimeError with empty message" do
+    RuntimeError.new("").detailed_message(highlight: true).should == "\e[1;4munhandled exception\e[m"
+  end
+
+  it "accepts highlight keyword argument and adds escape control sequences for an instance other than RuntimeError with empty message" do
+    StandardError.new("").detailed_message(highlight: true).should == "\e[1;4mStandardError\e[m"
+  end
+
+  it "allows and ignores other keyword arguments" do
+    RuntimeError.new("new error").detailed_message(foo: true).should == "new error (RuntimeError)"
+  end
+end
diff --git a/spec/ruby/core/exception/equal_value_spec.rb b/spec/ruby/core/exception/equal_value_spec.rb
index 7f2065511a..e8f3ce0f8d 100644
--- a/spec/ruby/core/exception/equal_value_spec.rb
+++ b/spec/ruby/core/exception/equal_value_spec.rb
@@ -22,18 +22,18 @@ describe "Exception#==" do
 
   it "returns true if both exceptions have the same class, the same message, and the same backtrace" do
     one = TypeError.new("message")
-    one.set_backtrace [File.dirname(__FILE__)]
+    one.set_backtrace [__dir__]
     two = TypeError.new("message")
-    two.set_backtrace [File.dirname(__FILE__)]
+    two.set_backtrace [__dir__]
     one.should == two
   end
 
   it "returns false if the two exceptions inherit from Exception but have different classes" do
     one = RuntimeError.new("message")
-    one.set_backtrace [File.dirname(__FILE__)]
+    one.set_backtrace [__dir__]
     one.should be_kind_of(Exception)
     two = TypeError.new("message")
-    two.set_backtrace [File.dirname(__FILE__)]
+    two.set_backtrace [__dir__]
     two.should be_kind_of(Exception)
     one.should_not == two
   end
@@ -52,7 +52,7 @@ describe "Exception#==" do
 
   it "returns false if the two exceptions differ only in their backtrace" do
     one = RuntimeError.new("message")
-    one.set_backtrace [File.dirname(__FILE__)]
+    one.set_backtrace [__dir__]
     two = RuntimeError.new("message")
     two.set_backtrace nil
     one.should_not == two
@@ -60,9 +60,9 @@ describe "Exception#==" do
 
   it "returns false if the two exceptions differ only in their message" do
     one = RuntimeError.new("message")
-    one.set_backtrace [File.dirname(__FILE__)]
+    one.set_backtrace [__dir__]
     two = RuntimeError.new("message2")
-    two.set_backtrace [File.dirname(__FILE__)]
+    two.set_backtrace [__dir__]
     one.should_not == two
   end
 end
diff --git a/spec/ruby/core/exception/errno_spec.rb b/spec/ruby/core/exception/errno_spec.rb
index 9e0bf0086a..1ab4277700 100644
--- a/spec/ruby/core/exception/errno_spec.rb
+++ b/spec/ruby/core/exception/errno_spec.rb
@@ -1,10 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/common'
 
-describe "SystemCallError#errno" do
-  it "needs to be reviewed for spec completeness"
-end
-
 describe "Errno::EINVAL.new" do
   it "can be called with no arguments" do
     exc = Errno::EINVAL.new
@@ -33,6 +29,8 @@ describe "Errno::EMFILE" do
     ExceptionSpecs::EMFILESub = Class.new(Errno::EMFILE)
     exc = ExceptionSpecs::EMFILESub.new
     exc.should be_an_instance_of(ExceptionSpecs::EMFILESub)
+  ensure
+    ExceptionSpecs.send(:remove_const, :EMFILESub)
   end
 end
 
@@ -46,3 +44,26 @@ describe "Errno::EAGAIN" do
     end
   end
 end
+
+describe "Errno::ENOTSUP" do
+  it "is defined" do
+    Errno.should have_constant(:ENOTSUP)
+  end
+
+  it "is the same class as Errno::EOPNOTSUPP if they represent the same errno value" do
+    if Errno::ENOTSUP::Errno == Errno::EOPNOTSUPP::Errno
+      Errno::ENOTSUP.should == Errno::EOPNOTSUPP
+    else
+      Errno::ENOTSUP.should_not == Errno::EOPNOTSUPP
+    end
+  end
+end
+
+describe "Errno::ENOENT" do
+  it "lets subclasses inherit the default error message" do
+    c = Class.new(Errno::ENOENT)
+    raise c, "custom message"
+  rescue => e
+    e.message.should == "No such file or directory - custom message"
+  end
+end
diff --git a/spec/ruby/core/exception/error_bytes_spec.rb b/spec/ruby/core/exception/error_bytes_spec.rb
deleted file mode 100644
index 2a95bcfdf4..0000000000
--- a/spec/ruby/core/exception/error_bytes_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::InvalidByteSequenceError#error_bytes" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/error_char_spec.rb b/spec/ruby/core/exception/error_char_spec.rb
deleted file mode 100644
index c0256af03a..0000000000
--- a/spec/ruby/core/exception/error_char_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::UndefinedConversionError#error_char" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/exception_spec.rb b/spec/ruby/core/exception/exception_spec.rb
index 3a01366920..d6f5283bd9 100644
--- a/spec/ruby/core/exception/exception_spec.rb
+++ b/spec/ruby/core/exception/exception_spec.rb
@@ -6,48 +6,6 @@ describe "Exception.exception" do
   it_behaves_like :exception_new, :exception
 end
 
-describe "Exception" do
-  it "is a Class" do
-    Exception.should be_kind_of(Class)
-  end
-
-  it "is a superclass of NoMemoryError" do
-    Exception.should be_ancestor_of(NoMemoryError)
-  end
-
-  it "is a superclass of ScriptError" do
-    Exception.should be_ancestor_of(ScriptError)
-  end
-
-  it "is a superclass of SignalException" do
-    Exception.should be_ancestor_of(SignalException)
-  end
-
-  it "is a superclass of Interrupt" do
-    SignalException.should be_ancestor_of(Interrupt)
-  end
-
-  it "is a superclass of StandardError" do
-    Exception.should be_ancestor_of(StandardError)
-  end
-
-  it "is a superclass of SystemExit" do
-    Exception.should be_ancestor_of(SystemExit)
-  end
-
-  it "is a superclass of SystemStackError" do
-    Exception.should be_ancestor_of(SystemStackError)
-  end
-
-  it "is a superclass of SecurityError" do
-    Exception.should be_ancestor_of(SecurityError)
-  end
-
-  it "is a superclass of EncodingError" do
-    Exception.should be_ancestor_of(EncodingError)
-  end
-end
-
 describe "Exception#exception" do
   it "returns self when passed no argument" do
     e = RuntimeError.new
@@ -82,6 +40,18 @@ describe "Exception#exception" do
     raised_second.should == caught_second
   end
 
+  it "captures an exception into $!" do
+    exception = begin
+      raise
+    rescue RuntimeError
+      $!
+    end
+
+    exception.class.should == RuntimeError
+    exception.message.should == ""
+    exception.backtrace.first.should =~ /exception_spec/
+  end
+
   class CustomArgumentError < StandardError
     attr_reader :val
     def initialize(val)
diff --git a/spec/ruby/core/exception/exit_value_spec.rb b/spec/ruby/core/exception/exit_value_spec.rb
index 43de56af8b..99987dd1bc 100644
--- a/spec/ruby/core/exception/exit_value_spec.rb
+++ b/spec/ruby/core/exception/exit_value_spec.rb
@@ -1,5 +1,13 @@
 require_relative '../../spec_helper'
 
 describe "LocalJumpError#exit_value" do
-  it "needs to be reviewed for spec completeness"
+  def get_me_a_return
+    Proc.new { return 42 }
+  end
+
+  it "returns the value given to return" do
+    -> { get_me_a_return.call }.should raise_error(LocalJumpError) { |e|
+      e.exit_value.should == 42
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/fixtures/common.rb b/spec/ruby/core/exception/fixtures/common.rb
index 0ffb3ed855..3d8a3c3430 100644
--- a/spec/ruby/core/exception/fixtures/common.rb
+++ b/spec/ruby/core/exception/fixtures/common.rb
@@ -84,6 +84,9 @@ module NoMethodErrorSpecs
 
   class InstanceException < Exception
   end
+
+  class AClass; end
+  module AModule; end
 end
 
 class NameErrorSpecs
@@ -93,3 +96,7 @@ class NameErrorSpecs
     end
   end
 end
+
+module DetailedMessageSpec
+  C = Class.new(RuntimeError)
+end
diff --git a/spec/ruby/core/exception/fixtures/syntax_error.rb b/spec/ruby/core/exception/fixtures/syntax_error.rb
new file mode 100644
index 0000000000..ccec62f7a1
--- /dev/null
+++ b/spec/ruby/core/exception/fixtures/syntax_error.rb
@@ -0,0 +1,3 @@
+# rubocop:disable Lint/Syntax
+1+1=2
+# rubocop:enable Lint/Syntax
diff --git a/spec/ruby/core/exception/fixtures/thread_fiber_ensure.rb b/spec/ruby/core/exception/fixtures/thread_fiber_ensure.rb
new file mode 100644
index 0000000000..c109ec6247
--- /dev/null
+++ b/spec/ruby/core/exception/fixtures/thread_fiber_ensure.rb
@@ -0,0 +1,22 @@
+ready = false
+t = Thread.new do
+  f = Fiber.new do
+    begin
+      Fiber.yield
+    ensure
+      STDERR.puts "suspended fiber ensure"
+    end
+  end
+  f.resume
+
+  begin
+    ready = true
+    sleep
+  ensure
+    STDERR.puts "current fiber ensure"
+  end
+end
+
+Thread.pass until ready && t.stop?
+
+# let the program end, it's the same as #exit or an exception for this behavior
diff --git a/spec/ruby/core/exception/fixtures/thread_fiber_ensure_non_root_fiber.rb b/spec/ruby/core/exception/fixtures/thread_fiber_ensure_non_root_fiber.rb
new file mode 100644
index 0000000000..3364ed06d0
--- /dev/null
+++ b/spec/ruby/core/exception/fixtures/thread_fiber_ensure_non_root_fiber.rb
@@ -0,0 +1,25 @@
+ready = false
+t = Thread.new do
+  f = Fiber.new do
+    begin
+      Fiber.yield
+    ensure
+      STDERR.puts "suspended fiber ensure"
+    end
+  end
+  f.resume
+
+  f2 = Fiber.new do
+    begin
+      ready = true
+      sleep
+    ensure
+      STDERR.puts "current fiber ensure"
+    end
+  end
+  f2.resume
+end
+
+Thread.pass until ready && t.stop?
+
+# let the program end, it's the same as #exit or an exception for this behavior
diff --git a/spec/ruby/core/exception/frozen_error_spec.rb b/spec/ruby/core/exception/frozen_error_spec.rb
index 7b356253c4..af2e925661 100644
--- a/spec/ruby/core/exception/frozen_error_spec.rb
+++ b/spec/ruby/core/exception/frozen_error_spec.rb
@@ -1,34 +1,54 @@
 require_relative '../../spec_helper'
 
-describe "FrozenError" do
-  ruby_version_is "2.5" do
-    it "is a subclass of RuntimeError" do
-      RuntimeError.should be_ancestor_of(FrozenError)
-    end
+describe "FrozenError.new" do
+  it "should take optional receiver argument" do
+    o = Object.new
+    FrozenError.new("msg", receiver: o).receiver.should equal(o)
   end
 end
 
-describe "FrozenError.new" do
-  ruby_version_is "2.7" do
-    it "should take optional receiver argument" do
-      o = Object.new
-      FrozenError.new("msg", o).receiver.should equal(o)
+describe "FrozenError#receiver" do
+  it "should return frozen object that modification was attempted on" do
+    o = Object.new.freeze
+    begin
+      def o.x; end
+    rescue => e
+      e.should be_kind_of(FrozenError)
+      e.receiver.should equal(o)
+    else
+      raise
     end
   end
 end
 
-describe "FrozenError#receiver" do
-  ruby_version_is "2.7" do
-    it "should return frozen object that modification was attempted on" do
-      o = Object.new.freeze
-      begin
-        def o.x; end
-      rescue => e
-        e.should be_kind_of(FrozenError)
-        e.receiver.should equal(o)
-      else
-        raise
-      end
+describe "FrozenError#message" do
+  it "includes a receiver" do
+    object = Object.new
+    object.freeze
+
+    msg_class = ruby_version_is("4.0") ? "Object" : "object"
+
+    -> {
+      def object.x; end
+    }.should raise_error(FrozenError, "can't modify frozen #{msg_class}: #{object}")
+
+    object = [].freeze
+    -> { object << nil }.should raise_error(FrozenError, "can't modify frozen Array: []")
+  end
+end
+
+describe "Modifying a frozen object" do
+  context "#inspect is redefined and modifies the object" do
+    it "returns ... instead of String representation of object" do
+      object = Object.new
+      def object.inspect; @a = 1 end
+      def object.modify; @a = 2 end
+
+      object.freeze
+
+      # CRuby's message contains multiple whitespaces before '...'.
+      # So handle both multiple and single whitespace.
+      -> { object.modify }.should raise_error(FrozenError, /can't modify frozen .*?: \s*.../)
     end
   end
 end
diff --git a/spec/ruby/core/exception/full_message_spec.rb b/spec/ruby/core/exception/full_message_spec.rb
index 3df2d47f61..0761d2b40c 100644
--- a/spec/ruby/core/exception/full_message_spec.rb
+++ b/spec/ruby/core/exception/full_message_spec.rb
@@ -1,94 +1,226 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  describe "Exception#full_message" do
-    it "returns formatted string of exception using the same format that is used to print an uncaught exceptions to stderr" do
-      e = RuntimeError.new("Some runtime error")
-      e.set_backtrace(["a.rb:1", "b.rb:2"])
-
-      full_message = e.full_message
-      full_message.should include "RuntimeError"
-      full_message.should include "Some runtime error"
-      full_message.should include "a.rb:1"
-      full_message.should include "b.rb:2"
-    end
+describe "Exception#full_message" do
+  it "returns formatted string of exception using the same format that is used to print an uncaught exceptions to stderr" do
+    e = RuntimeError.new("Some runtime error")
+    e.set_backtrace(["a.rb:1", "b.rb:2"])
+
+    full_message = e.full_message
+    full_message.should include "RuntimeError"
+    full_message.should include "Some runtime error"
+    full_message.should include "a.rb:1"
+    full_message.should include "b.rb:2"
+  end
+
+  it "supports :highlight option and adds escape sequences to highlight some strings" do
+    e = RuntimeError.new("Some runtime error")
+
+    full_message = e.full_message(highlight: true, order: :top).lines
+    full_message[0].should.end_with? "\e[1mSome runtime error (\e[1;4mRuntimeError\e[m\e[1m)\e[m\n"
+
+    full_message = e.full_message(highlight: true, order: :bottom).lines
+    full_message[0].should == "\e[1mTraceback\e[m (most recent call last):\n"
+    full_message[-1].should.end_with? "\e[1mSome runtime error (\e[1;4mRuntimeError\e[m\e[1m)\e[m\n"
+
+    full_message = e.full_message(highlight: false, order: :top).lines
+    full_message[0].should.end_with? "Some runtime error (RuntimeError)\n"
+
+    full_message = e.full_message(highlight: false, order: :bottom).lines
+    full_message[0].should == "Traceback (most recent call last):\n"
+    full_message[-1].should.end_with? "Some runtime error (RuntimeError)\n"
+  end
+
+  it "supports :order option and places the error message and the backtrace at the top or the bottom" do
+    e = RuntimeError.new("Some runtime error")
+    e.set_backtrace(["a.rb:1", "b.rb:2"])
+
+    e.full_message(order: :top,    highlight: false).should =~ /a.rb:1.*b.rb:2/m
+    e.full_message(order: :bottom, highlight: false).should =~ /b.rb:2.*a.rb:1/m
+  end
 
-    ruby_version_is "2.5.1" do
-      it "supports :highlight option and adds escape sequences to highlight some strings" do
-        e = RuntimeError.new("Some runtime error")
+  it "shows the caller if the exception has no backtrace" do
+    e = RuntimeError.new("Some runtime error")
+    e.backtrace.should == nil
+    full_message = e.full_message(highlight: false, order: :top).lines
+    full_message[0].should.start_with?("#{__FILE__}:#{__LINE__-1}:in ")
+    full_message[0].should.end_with?("': Some runtime error (RuntimeError)\n")
+  end
 
-        full_message = e.full_message(highlight: true, order: :bottom)
-        full_message.should include "\e[1mTraceback\e[m (most recent call last)"
-        full_message.should include "\e[1mSome runtime error (\e[1;4mRuntimeError\e[m\e[1m)"
+  describe "includes details about whether an exception was handled" do
+    describe "RuntimeError" do
+      it "should report as unhandled if message is empty" do
+        err = RuntimeError.new("")
 
-        full_message = e.full_message(highlight: false, order: :bottom)
-        full_message.should include "Traceback (most recent call last)"
-        full_message.should include "Some runtime error (RuntimeError)"
+        err.full_message.should =~ /unhandled exception/
+        err.full_message(highlight: true).should =~ /unhandled exception/
+        err.full_message(highlight: false).should =~ /unhandled exception/
       end
 
-      it "supports :order option and places the error message and the backtrace at the top or the bottom" do
-        e = RuntimeError.new("Some runtime error")
-        e.set_backtrace(["a.rb:1", "b.rb:2"])
+      it "should not report as unhandled if the message is not empty" do
+        err = RuntimeError.new("non-empty")
 
-        e.full_message(order: :top,    highlight: false).should =~ /a.rb:1.*b.rb:2/m
-        e.full_message(order: :bottom, highlight: false).should =~ /b.rb:2.*a.rb:1/m
+        err.full_message.should !~ /unhandled exception/
+        err.full_message(highlight: true).should !~ /unhandled exception/
+        err.full_message(highlight: false).should !~ /unhandled exception/
       end
 
-      it "shows the caller if the exception has no backtrace" do
-        e = RuntimeError.new("Some runtime error")
-        e.backtrace.should == nil
-        full_message = e.full_message(highlight: false, order: :top)
-        full_message.should include("#{__FILE__}:#{__LINE__-1}:in `")
-        full_message.should include("': Some runtime error (RuntimeError)\n")
+      it "should not report as unhandled if the message is nil" do
+        err = RuntimeError.new(nil)
+
+        err.full_message.should !~ /unhandled exception/
+        err.full_message(highlight: true).should !~ /unhandled exception/
+        err.full_message(highlight: false).should !~ /unhandled exception/
       end
 
-      it "shows the exception class at the end of the first line of the message when the message contains multiple lines" do
-        begin
-          line = __LINE__; raise "first line\nsecond line"
-        rescue => e
-          full_message = e.full_message(highlight: false, order: :top).lines
-          full_message[0].should include("#{__FILE__}:#{line}:in `")
-          full_message[0].should include(": first line (RuntimeError)\n")
-          full_message[1].should == "second line\n"
-        end
+      it "should not report as unhandled if the message is not specified" do
+        err = RuntimeError.new()
+
+        err.full_message.should !~ /unhandled exception/
+        err.full_message(highlight: true).should !~ /unhandled exception/
+        err.full_message(highlight: false).should !~ /unhandled exception/
+      end
+
+      it "adds escape sequences to highlight some strings if the message is not specified and :highlight option is specified" do
+        e = RuntimeError.new("")
+
+        full_message = e.full_message(highlight: true, order: :top).lines
+        full_message[0].should.end_with? "\e[1;4munhandled exception\e[m\n"
+
+        full_message = e.full_message(highlight: true, order: :bottom).lines
+        full_message[0].should == "\e[1mTraceback\e[m (most recent call last):\n"
+        full_message[-1].should.end_with? "\e[1;4munhandled exception\e[m\n"
+
+        full_message = e.full_message(highlight: false, order: :top).lines
+        full_message[0].should.end_with? "unhandled exception\n"
+
+        full_message = e.full_message(highlight: false, order: :bottom).lines
+        full_message[0].should == "Traceback (most recent call last):\n"
+        full_message[-1].should.end_with? "unhandled exception\n"
       end
     end
 
-    ruby_version_is "2.6" do
-      it "contains cause of exception" do
-        begin
-          begin
-            raise 'the cause'
-          rescue
-            raise 'main exception'
-          end
-        rescue => e
-          exception = e
-        end
+    describe "generic Error" do
+      it "should not report as unhandled in any event" do
+        StandardError.new("").full_message.should !~ /unhandled exception/
+        StandardError.new("non-empty").full_message.should !~ /unhandled exception/
+      end
+    end
+  end
+
+  it "shows the exception class at the end of the first line of the message when the message contains multiple lines" do
+    begin
+      line = __LINE__; raise "first line\nsecond line"
+    rescue => e
+      full_message = e.full_message(highlight: false, order: :top).lines
+      full_message[0].should.start_with?("#{__FILE__}:#{line}:in ")
+      full_message[0].should.end_with?(": first line (RuntimeError)\n")
+      full_message[1].should == "second line\n"
+    end
+  end
 
-        exception.full_message.should include "main exception"
-        exception.full_message.should include "the cause"
+  it "highlights the entire message when the message contains multiple lines" do
+    begin
+      line = __LINE__; raise "first line\nsecond line\nthird line"
+    rescue => e
+      full_message = e.full_message(highlight: true, order: :top).lines
+      full_message[0].should.start_with?("#{__FILE__}:#{line}:in ")
+      full_message[0].should.end_with?(": \e[1mfirst line (\e[1;4mRuntimeError\e[m\e[1m)\e[m\n")
+      full_message[1].should == "\e[1msecond line\e[m\n"
+      full_message[2].should == "\e[1mthird line\e[m\n"
+    end
+  end
+
+  it "contains cause of exception" do
+    begin
+      begin
+        raise 'the cause'
+      rescue
+        raise 'main exception'
       end
+    rescue => e
+      exception = e
+    end
 
-      it 'contains all the chain of exceptions' do
+    exception.full_message.should include "main exception"
+    exception.full_message.should include "the cause"
+  end
+
+  it 'contains all the chain of exceptions' do
+    begin
+      begin
         begin
-          begin
-            begin
-              raise 'origin exception'
-            rescue
-              raise 'intermediate exception'
-            end
-          rescue
-            raise 'last exception'
-          end
-        rescue => e
-          exception = e
+          raise 'origin exception'
+        rescue
+          raise 'intermediate exception'
         end
-
-        exception.full_message.should include "last exception"
-        exception.full_message.should include "intermediate exception"
-        exception.full_message.should include "origin exception"
+      rescue
+        raise 'last exception'
       end
+    rescue => e
+      exception = e
+    end
+
+    exception.full_message.should include "last exception"
+    exception.full_message.should include "intermediate exception"
+    exception.full_message.should include "origin exception"
+  end
+
+  it "relies on #detailed_message" do
+    e = RuntimeError.new("new error")
+    e.define_singleton_method(:detailed_message) { |**| "DETAILED MESSAGE" }
+
+    e.full_message.lines.first.should =~ /DETAILED MESSAGE/
+  end
+
+  it "passes all its own keyword arguments (with :highlight default value and without :order default value) to #detailed_message" do
+    e = RuntimeError.new("new error")
+    options_passed = nil
+    e.define_singleton_method(:detailed_message) do |**options|
+      options_passed = options
+      "DETAILED MESSAGE"
+    end
+
+    e.full_message(foo: "bar")
+    options_passed.should == { foo: "bar", highlight: Exception.to_tty? }
+  end
+
+  it "converts #detailed_message returned value to String if it isn't a String" do
+    message = Object.new
+    def message.to_str; "DETAILED MESSAGE"; end
+
+    e = RuntimeError.new("new error")
+    e.define_singleton_method(:detailed_message) { |**| message }
+
+    e.full_message.lines.first.should =~ /DETAILED MESSAGE/
+  end
+
+  it "uses class name if #detailed_message returns nil" do
+    e = RuntimeError.new("new error")
+    e.define_singleton_method(:detailed_message) { |**| nil }
+
+    e.full_message(highlight: false).lines.first.should =~ /RuntimeError/
+    e.full_message(highlight: true).lines.first.should =~ /#{Regexp.escape("\e[1;4mRuntimeError\e[m")}/
+  end
+
+  it "uses class name if exception object doesn't respond to #detailed_message" do
+    e = RuntimeError.new("new error")
+    class << e
+      undef :detailed_message
     end
+
+    e.full_message(highlight: false).lines.first.should =~ /RuntimeError/
+    e.full_message(highlight: true).lines.first.should =~ /#{Regexp.escape("\e[1;4mRuntimeError\e[m")}/
+  end
+
+  it "allows cause with empty backtrace" do
+    begin
+      raise RuntimeError.new("Some runtime error"), cause: RuntimeError.new("Some other runtime error")
+    rescue => e
+    end
+
+    full_message = e.full_message
+    full_message.should include "RuntimeError"
+    full_message.should include "Some runtime error"
+    full_message.should include "Some other runtime error"
   end
 end
diff --git a/spec/ruby/core/exception/hierarchy_spec.rb b/spec/ruby/core/exception/hierarchy_spec.rb
new file mode 100644
index 0000000000..6514eb1994
--- /dev/null
+++ b/spec/ruby/core/exception/hierarchy_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../spec_helper'
+
+describe "Exception" do
+  it "has the right class hierarchy" do
+    hierarchy = {
+      Exception => {
+        NoMemoryError => nil,
+        ScriptError => {
+          LoadError => nil,
+          NotImplementedError => nil,
+          SyntaxError => nil,
+        },
+        SecurityError => nil,
+        SignalException => {
+          Interrupt => nil,
+        },
+        StandardError => {
+          ArgumentError => {
+            UncaughtThrowError => nil,
+          },
+          EncodingError => nil,
+          FiberError => nil,
+          IOError => {
+            EOFError => nil,
+          },
+          IndexError => {
+            KeyError => nil,
+            StopIteration => {
+              ClosedQueueError => nil,
+            },
+          },
+          LocalJumpError => nil,
+          NameError => {
+            NoMethodError => nil,
+          },
+          RangeError => {
+            FloatDomainError => nil,
+          },
+          RegexpError => nil,
+          RuntimeError => {
+            FrozenError => nil,
+          },
+          SystemCallError => nil,
+          ThreadError => nil,
+          TypeError => nil,
+          ZeroDivisionError => nil,
+        },
+        SystemExit => nil,
+        SystemStackError => nil,
+      },
+    }
+
+    traverse = -> parent_class, parent_subclass_hash {
+      parent_subclass_hash.each do |child_class, child_subclass_hash|
+        child_class.class.should == Class
+        child_class.superclass.should == parent_class
+        traverse.call(child_class, child_subclass_hash) if child_subclass_hash
+      end
+    }
+    traverse.call(Object, hierarchy)
+  end
+end
diff --git a/spec/ruby/core/exception/incomplete_input_spec.rb b/spec/ruby/core/exception/incomplete_input_spec.rb
deleted file mode 100644
index b033b33f56..0000000000
--- a/spec/ruby/core/exception/incomplete_input_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::InvalidByteSequenceError#incomplete_input?" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/initialize_spec.rb b/spec/ruby/core/exception/initialize_spec.rb
deleted file mode 100644
index e724feaa39..0000000000
--- a/spec/ruby/core/exception/initialize_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../spec_helper'
diff --git a/spec/ruby/core/exception/inspect_spec.rb b/spec/ruby/core/exception/inspect_spec.rb
index 519ce574ae..6f380a36c7 100644
--- a/spec/ruby/core/exception/inspect_spec.rb
+++ b/spec/ruby/core/exception/inspect_spec.rb
@@ -6,6 +6,10 @@ describe "Exception#inspect" do
     Exception.new.inspect.should == "#<Exception: Exception>"
   end
 
+  it "keeps message encoding" do
+    Exception.new('å').inspect.should == "#<Exception: å>"
+  end
+
   it "includes #to_s when the result is non-empty" do
     ExceptionSpecs::OverrideToS.new.inspect.should == "#<ExceptionSpecs::OverrideToS: this is from #to_s>"
   end
diff --git a/spec/ruby/core/exception/interrupt_spec.rb b/spec/ruby/core/exception/interrupt_spec.rb
index bc01b7b703..90d261e470 100644
--- a/spec/ruby/core/exception/interrupt_spec.rb
+++ b/spec/ruby/core/exception/interrupt_spec.rb
@@ -1,11 +1,5 @@
 require_relative '../../spec_helper'
 
-describe "Interrupt" do
-  it "is a subclass of SignalException" do
-    Interrupt.superclass.should == SignalException
-  end
-end
-
 describe "Interrupt.new" do
   it "returns an instance of interrupt with no message given" do
     e = Interrupt.new
@@ -35,7 +29,32 @@ describe "rescuing Interrupt" do
       sleep
     rescue Interrupt => e
       e.signo.should == Signal.list["INT"]
-      e.signm.should == ""
+      ["", "Interrupt"].should.include?(e.message)
+    end
+  end
+end
+
+describe "Interrupt" do
+  # This spec is basically the same as above,
+  # but it does not rely on Signal.trap(:INT, :SIG_DFL) which can be tricky
+  it "is raised on the main Thread by the default SIGINT handler" do
+    out = ruby_exe(<<-'RUBY', args: "2>&1")
+    begin
+      Process.kill :INT, Process.pid
+      sleep
+    rescue Interrupt => e
+      puts "Interrupt: #{e.signo}"
+    end
+    RUBY
+    out.should == "Interrupt: #{Signal.list["INT"]}\n"
+  end
+
+  platform_is_not :windows do
+    it "shows the backtrace and has a signaled exit status" do
+      err = IO.popen([*ruby_exe, '-e', 'Process.kill :INT, Process.pid; sleep'], err: [:child, :out], &:read)
+      $?.termsig.should == Signal.list.fetch('INT')
+      err.should.include? ': Interrupt'
+      err.should =~ /from -e:1:in [`']<main>'/
     end
   end
 end
diff --git a/spec/ruby/core/exception/io_error_spec.rb b/spec/ruby/core/exception/io_error_spec.rb
index 8dc10cc6ce..ab8a72518f 100644
--- a/spec/ruby/core/exception/io_error_spec.rb
+++ b/spec/ruby/core/exception/io_error_spec.rb
@@ -1,11 +1,5 @@
 require_relative '../../spec_helper'
 
-describe "IOError" do
-  it "is a superclass of EOFError" do
-    IOError.should be_ancestor_of(EOFError)
-  end
-end
-
 describe "IO::EAGAINWaitReadable" do
   it "combines Errno::EAGAIN and IO::WaitReadable" do
     IO::EAGAINWaitReadable.superclass.should == Errno::EAGAIN
diff --git a/spec/ruby/core/exception/key_error_spec.rb b/spec/ruby/core/exception/key_error_spec.rb
index ad280279d8..c5e2b1efbc 100644
--- a/spec/ruby/core/exception/key_error_spec.rb
+++ b/spec/ruby/core/exception/key_error_spec.rb
@@ -1,15 +1,19 @@
 require_relative '../../spec_helper'
 
 describe "KeyError" do
-  ruby_version_is "2.6" do
-    it "accepts :receiver and :key options" do
-      receiver = mock("receiver")
-      key = mock("key")
+  it "accepts :receiver and :key options" do
+    receiver = mock("receiver")
+    key = mock("key")
 
-      error = KeyError.new(receiver: receiver, key: key)
+    error = KeyError.new(receiver: receiver, key: key)
 
-      error.receiver.should == receiver
-      error.key.should == key
-    end
+    error.receiver.should == receiver
+    error.key.should == key
+
+    error = KeyError.new("message", receiver: receiver, key: key)
+
+    error.message.should == "message"
+    error.receiver.should == receiver
+    error.key.should == key
   end
 end
diff --git a/spec/ruby/core/exception/name_error_spec.rb b/spec/ruby/core/exception/name_error_spec.rb
index d0a810029b..ddd51a92e5 100644
--- a/spec/ruby/core/exception/name_error_spec.rb
+++ b/spec/ruby/core/exception/name_error_spec.rb
@@ -1,24 +1,28 @@
 require_relative '../../spec_helper'
 
-describe "NameError" do
-  it "is a superclass of NoMethodError" do
-    NameError.should be_ancestor_of(NoMethodError)
-  end
-end
-
 describe "NameError.new" do
   it "should take optional name argument" do
     NameError.new("msg","name").name.should == "name"
   end
 
-  ruby_version_is "2.6" do
-    it "accepts a :receiver keyword argument" do
-      receiver = mock("receiver")
+  it "accepts a :receiver keyword argument" do
+    receiver = mock("receiver")
 
-      error = NameError.new("msg", :name, receiver: receiver)
+    error = NameError.new("msg", :name, receiver: receiver)
+
+    error.receiver.should == receiver
+    error.name.should == :name
+  end
+end
 
-      error.receiver.should == receiver
-      error.name.should == :name
+describe "NameError#dup" do
+  it "copies the name and receiver" do
+    begin
+      foo
+    rescue NameError => ne
+      name_error_dup = ne.dup
+      name_error_dup.name.should == :foo
+      name_error_dup.receiver.should == self
     end
   end
 end
diff --git a/spec/ruby/core/exception/name_spec.rb b/spec/ruby/core/exception/name_spec.rb
index d1def51f24..c8a49b40e2 100644
--- a/spec/ruby/core/exception/name_spec.rb
+++ b/spec/ruby/core/exception/name_spec.rb
@@ -21,9 +21,7 @@ describe "NameError#name" do
 
   it "returns a class variable name as a symbol" do
     -> {
-      -> {
-        @@doesnt_exist
-      }.should complain(/class variable access from toplevel/)
+      eval("class singleton_class::A; @@doesnt_exist end", binding, __FILE__, __LINE__)
     }.should raise_error(NameError) { |e| e.name.should == :@@doesnt_exist }
   end
 
diff --git a/spec/ruby/core/exception/no_method_error_spec.rb b/spec/ruby/core/exception/no_method_error_spec.rb
index 28c3549562..772c569f67 100644
--- a/spec/ruby/core/exception/no_method_error_spec.rb
+++ b/spec/ruby/core/exception/no_method_error_spec.rb
@@ -10,15 +10,13 @@ describe "NoMethodError.new" do
     NoMethodError.new("msg").message.should == "msg"
   end
 
-  ruby_version_is "2.6" do
-    it "accepts a :receiver keyword argument" do
-      receiver = mock("receiver")
+  it "accepts a :receiver keyword argument" do
+    receiver = mock("receiver")
 
-      error = NoMethodError.new("msg", :name, receiver: receiver)
+    error = NoMethodError.new("msg", :name, receiver: receiver)
 
-      error.receiver.should == receiver
-      error.name.should == :name
-    end
+    error.receiver.should == receiver
+    error.name.should == :name
   end
 end
 
@@ -64,43 +62,222 @@ describe "NoMethodError#message" do
       NoMethodErrorSpecs::NoMethodErrorC.new.a_private_method
     rescue Exception => e
       e.should be_kind_of(NoMethodError)
-      e.message.match(/private method/).should_not == nil
+      e.message.lines[0].should =~ /private method [`']a_private_method' called for /
     end
   end
 
-  it "calls receiver.inspect only when calling Exception#message" do
-    ScratchPad.record []
-    test_class = Class.new do
-      def inspect
-        ScratchPad << :inspect_called
-        "<inspect>"
+  ruby_version_is ""..."3.3" do
+    it "calls #inspect when calling Exception#message" do
+      ScratchPad.record []
+      test_class = Class.new do
+        def inspect
+          ScratchPad << :inspect_called
+          "<inspect>"
+        end
+      end
+      instance = test_class.new
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']bar' for <inspect>:#<Class:0x\h+>$/
+        ScratchPad.recorded.should == [:inspect_called]
       end
     end
-    instance = test_class.new
-    begin
-      instance.bar
-    rescue Exception => e
-      e.name.should == :bar
-      ScratchPad.recorded.should == []
-      e.message.should =~ /undefined method.+\bbar\b/
-      ScratchPad.recorded.should == [:inspect_called]
+
+    it "fallbacks to a simpler representation of the receiver when receiver.inspect raises an exception" do
+      test_class = Class.new do
+        def inspect
+          raise NoMethodErrorSpecs::InstanceException
+        end
+      end
+      instance = test_class.new
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        message = error.message
+        message.should =~ /undefined method.+\bbar\b/
+        message.should include test_class.inspect
+      end
+    end
+
+    it "uses #name to display the receiver if it is a class" do
+      klass = Class.new { def self.name; "MyClass"; end }
+
+      begin
+        klass.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for MyClass:Class$/
+      end
+    end
+
+    it "uses #name to display the receiver if it is a module" do
+      mod = Module.new { def self.name; "MyModule"; end }
+
+      begin
+        mod.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for MyModule:Module$/
+      end
     end
   end
 
-  it "fallbacks to a simpler representation of the receiver when receiver.inspect raises an exception" do
-    test_class = Class.new do
-      def inspect
-        raise NoMethodErrorSpecs::InstanceException
+  ruby_version_is "3.3" do
+    it "uses a literal name when receiver is nil" do
+      begin
+        nil.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for nil\Z/
+      end
+    end
+
+    it "uses a literal name when receiver is true" do
+      begin
+        true.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for true\Z/
+      end
+    end
+
+    it "uses a literal name when receiver is false" do
+      begin
+        false.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for false\Z/
+      end
+    end
+
+    it "uses #name when receiver is a class" do
+      klass = Class.new { def self.name; "MyClass"; end }
+
+      begin
+        klass.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for class MyClass\Z/
+      end
+    end
+
+    it "uses class' string representation when receiver is an anonymous class" do
+      klass = Class.new
+
+      begin
+        klass.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for class #<Class:0x\h+>\Z/
+      end
+    end
+
+    it "uses class' string representation when receiver is a singleton class" do
+      obj = Object.new
+      singleton_class = obj.singleton_class
+
+      begin
+        singleton_class.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for class #<Class:#<Object:0x\h+>>\Z/
       end
     end
-    instance = test_class.new
+
+    it "uses #name when receiver is a module" do
+      mod = Module.new { def self.name; "MyModule"; end }
+
+      begin
+        mod.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for module MyModule\Z/
+      end
+    end
+
+    it "uses module's string representation when receiver is an anonymous module" do
+      m = Module.new
+
+      begin
+        m.foo
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for module #<Module:0x\h+>\Z/
+      end
+    end
+
+    it "uses class #name when receiver is an ordinary object" do
+      klass = Class.new { def self.name; "MyClass"; end }
+      instance = klass.new
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']bar' for an instance of MyClass\Z/
+      end
+    end
+
+    it "uses class string representation when receiver is an instance of anonymous class" do
+      klass = Class.new
+      instance = klass.new
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']bar' for an instance of #<Class:0x\h+>\Z/
+      end
+    end
+
+    it "uses class name when receiver has a singleton class" do
+      instance = NoMethodErrorSpecs::NoMethodErrorA.new
+      def instance.foo; end
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']bar' for #<NoMethodErrorSpecs::NoMethodErrorA:0x\h+>\Z/
+      end
+    end
+
+    it "does not call #inspect when calling Exception#message" do
+      ScratchPad.record []
+      test_class = Class.new do
+        def inspect
+          ScratchPad << :inspect_called
+          "<inspect>"
+        end
+      end
+      instance = test_class.new
+
+      begin
+        instance.bar
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']bar' for an instance of #<Class:0x\h+>\Z/
+        ScratchPad.recorded.should == []
+      end
+    end
+
+    it "does not truncate long class names" do
+      class_name = 'ExceptionSpecs::A' + 'a'*100
+
+      begin
+        eval <<~RUBY
+          class #{class_name}
+          end
+
+          obj = #{class_name}.new
+          obj.foo
+        RUBY
+      rescue NoMethodError => error
+        error.message.should =~ /\Aundefined method [`']foo' for an instance of #{class_name}\Z/
+      end
+    end
+  end
+end
+
+describe "NoMethodError#dup" do
+  it "copies the name, arguments and receiver" do
     begin
-      instance.bar
-    rescue Exception => e
-      e.name.should == :bar
-      message = e.message
-      message.should =~ /undefined method.+\bbar\b/
-      message.should include test_class.inspect
+      receiver = Object.new
+      receiver.foo(:one, :two)
+    rescue NoMethodError => nme
+      no_method_error_dup = nme.dup
+      no_method_error_dup.name.should == :foo
+      no_method_error_dup.receiver.should == receiver
+      no_method_error_dup.args.should == [:one, :two]
     end
   end
 end
diff --git a/spec/ruby/core/exception/range_error_spec.rb b/spec/ruby/core/exception/range_error_spec.rb
deleted file mode 100644
index 7cfbd0f1ec..0000000000
--- a/spec/ruby/core/exception/range_error_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "RangeError" do
-  it "is a superclass of FloatDomainError" do
-    RangeError.should be_ancestor_of(FloatDomainError)
-  end
-end
diff --git a/spec/ruby/core/exception/readagain_bytes_spec.rb b/spec/ruby/core/exception/readagain_bytes_spec.rb
deleted file mode 100644
index f7e8d9d1d3..0000000000
--- a/spec/ruby/core/exception/readagain_bytes_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::InvalidByteSequenceError#readagain_bytes" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/reason_spec.rb b/spec/ruby/core/exception/reason_spec.rb
index 6f18aaae13..210bbc9725 100644
--- a/spec/ruby/core/exception/reason_spec.rb
+++ b/spec/ruby/core/exception/reason_spec.rb
@@ -1,5 +1,13 @@
 require_relative '../../spec_helper'
 
 describe "LocalJumpError#reason" do
-  it "needs to be reviewed for spec completeness"
+  def get_me_a_return
+    Proc.new { return 42 }
+  end
+
+  it "returns 'return' for a return" do
+    -> { get_me_a_return.call }.should raise_error(LocalJumpError) { |e|
+      e.reason.should == :return
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/receiver_spec.rb b/spec/ruby/core/exception/receiver_spec.rb
index 7c57d63c3e..d1c23b67be 100644
--- a/spec/ruby/core/exception/receiver_spec.rb
+++ b/spec/ruby/core/exception/receiver_spec.rb
@@ -28,10 +28,8 @@ describe "NameError#receiver" do
 
   it "returns the Object class when an undefined class variable is called" do
     -> {
-      -> {
-        @@doesnt_exist
-      }.should complain(/class variable access from toplevel/)
-    }.should raise_error(NameError) {|e| e.receiver.should equal(Object) }
+      eval("class singleton_class::A; @@doesnt_exist end", binding, __FILE__, __LINE__)
+    }.should raise_error(NameError) {|e| e.receiver.should equal(singleton_class::A) }
   end
 
   it "returns a class when an undefined class variable is called in a subclass' namespace" do
diff --git a/spec/ruby/core/exception/result_spec.rb b/spec/ruby/core/exception/result_spec.rb
index 5ba26ebab1..d42fcdffcb 100644
--- a/spec/ruby/core/exception/result_spec.rb
+++ b/spec/ruby/core/exception/result_spec.rb
@@ -1,11 +1,5 @@
 require_relative '../../spec_helper'
 
-describe "StopIteration" do
-  it "is a subclass of IndexError" do
-    StopIteration.superclass.should equal(IndexError)
-  end
-end
-
 describe "StopIteration#result" do
   before :each do
     obj = Object.new
@@ -20,10 +14,8 @@ describe "StopIteration#result" do
   it "returns the method-returned-object from an Enumerator" do
     @enum.next
     @enum.next
-    -> { @enum.next }.should(
-      raise_error(StopIteration) do |error|
-        error.result.should equal(:method_returned)
-      end
-    )
+    -> { @enum.next }.should raise_error(StopIteration) { |error|
+      error.result.should equal(:method_returned)
+    }
   end
 end
diff --git a/spec/ruby/core/exception/script_error_spec.rb b/spec/ruby/core/exception/script_error_spec.rb
deleted file mode 100644
index e33a5d3a58..0000000000
--- a/spec/ruby/core/exception/script_error_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ScriptError" do
-   it "is a superclass of LoadError" do
-     ScriptError.should be_ancestor_of(LoadError)
-   end
-
-   it "is a superclass of NotImplementedError" do
-     ScriptError.should be_ancestor_of(NotImplementedError)
-   end
-
-   it "is a superclass of SyntaxError" do
-     ScriptError.should be_ancestor_of(SyntaxError)
-   end
-end
diff --git a/spec/ruby/core/exception/set_backtrace_spec.rb b/spec/ruby/core/exception/set_backtrace_spec.rb
index ba2e1bf7aa..2cd93326ec 100644
--- a/spec/ruby/core/exception/set_backtrace_spec.rb
+++ b/spec/ruby/core/exception/set_backtrace_spec.rb
@@ -1,56 +1,23 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/common'
+require_relative 'shared/set_backtrace'
 
 describe "Exception#set_backtrace" do
-  it "accepts an Array of Strings" do
-    err = RuntimeError.new
-    err.set_backtrace ["unhappy"]
-    err.backtrace.should == ["unhappy"]
-  end
-
   it "allows the user to set the backtrace from a rescued exception" do
     bt  = ExceptionSpecs::Backtrace.backtrace
     err = RuntimeError.new
+    err.backtrace.should == nil
+    err.backtrace_locations.should == nil
 
     err.set_backtrace bt
-    err.backtrace.should == bt
-  end
-
-  it "accepts an empty Array" do
-    err = RuntimeError.new
-    err.set_backtrace []
-    err.backtrace.should == []
-  end
-
-  it "accepts a String" do
-    err = RuntimeError.new
-    err.set_backtrace "unhappy"
-    err.backtrace.should == ["unhappy"]
-  end
 
-  it "accepts nil" do
-    err = RuntimeError.new
-    err.set_backtrace nil
-    err.backtrace.should be_nil
-  end
-
-  it "raises a TypeError when passed a Symbol" do
-    err = RuntimeError.new
-    -> { err.set_backtrace :unhappy }.should raise_error(TypeError)
+    err.backtrace.should == bt
+    err.backtrace_locations.should == nil
   end
 
-  it "raises a TypeError when the Array contains a Symbol" do
+  it_behaves_like :exception_set_backtrace, -> backtrace {
     err = RuntimeError.new
-    -> { err.set_backtrace ["String", :unhappy] }.should raise_error(TypeError)
-  end
-
-  it "raises a TypeError when the array contains nil" do
-    err = Exception.new
-    -> { err.set_backtrace ["String", nil] }.should raise_error(TypeError)
-  end
-
-  it "raises a TypeError when the argument is a nested array" do
-    err = Exception.new
-    -> { err.set_backtrace ["String", ["String"]] }.should raise_error(TypeError)
-  end
+    err.set_backtrace(backtrace)
+    err
+  }
 end
diff --git a/spec/ruby/core/exception/shared/set_backtrace.rb b/spec/ruby/core/exception/shared/set_backtrace.rb
new file mode 100644
index 0000000000..c6213b42b4
--- /dev/null
+++ b/spec/ruby/core/exception/shared/set_backtrace.rb
@@ -0,0 +1,64 @@
+require_relative '../fixtures/common'
+
+describe :exception_set_backtrace, shared: true do
+  it "accepts an Array of Strings" do
+    err = @method.call(["unhappy"])
+    err.backtrace.should == ["unhappy"]
+  end
+
+  it "allows the user to set the backtrace from a rescued exception" do
+    bt  = ExceptionSpecs::Backtrace.backtrace
+    err = @method.call(bt)
+    err.backtrace.should == bt
+  end
+
+  ruby_version_is "3.4" do
+    it "allows the user to set backtrace locations from a rescued exception" do
+      bt_locations = ExceptionSpecs::Backtrace.backtrace_locations
+      err = @method.call(bt_locations)
+      err.backtrace_locations.size.should == bt_locations.size
+      err.backtrace_locations.each_with_index do |loc, index|
+        other_loc = bt_locations[index]
+
+        loc.path.should == other_loc.path
+        loc.label.should == other_loc.label
+        loc.base_label.should == other_loc.base_label
+        loc.lineno.should == other_loc.lineno
+        loc.absolute_path.should == other_loc.absolute_path
+        loc.to_s.should == other_loc.to_s
+      end
+      err.backtrace.size.should == err.backtrace_locations.size
+    end
+  end
+
+  it "accepts an empty Array" do
+    err = @method.call([])
+    err.backtrace.should == []
+  end
+
+  it "accepts a String" do
+    err = @method.call("unhappy")
+    err.backtrace.should == ["unhappy"]
+  end
+
+  it "accepts nil" do
+    err = @method.call(nil)
+    err.backtrace.should be_nil
+  end
+
+  it "raises a TypeError when passed a Symbol" do
+    -> { @method.call(:unhappy) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when the Array contains a Symbol" do
+    -> { @method.call(["String", :unhappy]) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when the array contains nil" do
+    -> { @method.call(["String", nil]) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when the argument is a nested array" do
+    -> { @method.call(["String", ["String"]]) }.should raise_error(TypeError)
+  end
+end
diff --git a/spec/ruby/core/exception/signal_exception_spec.rb b/spec/ruby/core/exception/signal_exception_spec.rb
index e0b30236f7..1a0940743f 100644
--- a/spec/ruby/core/exception/signal_exception_spec.rb
+++ b/spec/ruby/core/exception/signal_exception_spec.rb
@@ -30,6 +30,10 @@ describe "SignalException.new" do
     -> { SignalException.new("NONEXISTENT") }.should raise_error(ArgumentError)
   end
 
+  it "raises an exception with an invalid first argument type" do
+    -> { SignalException.new(Object.new) }.should raise_error(ArgumentError)
+  end
+
   it "takes a signal symbol without SIG prefix as the first argument" do
     exc = SignalException.new(:INT)
     exc.signo.should == Signal.list["INT"]
@@ -72,3 +76,48 @@ describe "rescuing SignalException" do
     end
   end
 end
+
+describe "SignalException" do
+  it "can be rescued" do
+    ruby_exe(<<-RUBY)
+      begin
+        raise SignalException, 'SIGKILL'
+      rescue SignalException
+        exit(0)
+      end
+      exit(1)
+    RUBY
+
+    $?.exitstatus.should == 0
+  end
+
+  platform_is_not :windows do
+    it "runs after at_exit" do
+      output = ruby_exe(<<-RUBY, exit_status: :SIGKILL)
+        at_exit do
+          puts "hello"
+          $stdout.flush
+        end
+
+        raise SignalException, 'SIGKILL'
+      RUBY
+
+      $?.termsig.should == Signal.list.fetch("KILL")
+      output.should == "hello\n"
+    end
+
+    it "cannot be trapped with Signal.trap" do
+      ruby_exe(<<-RUBY, exit_status: :SIGPROF)
+        Signal.trap("PROF") {}
+        raise(SignalException, "PROF")
+      RUBY
+
+      $?.termsig.should == Signal.list.fetch("PROF")
+    end
+
+    it "self-signals for USR1" do
+      ruby_exe("raise(SignalException, 'USR1')", exit_status: :SIGUSR1)
+      $?.termsig.should == Signal.list.fetch('USR1')
+    end
+  end
+end
diff --git a/spec/ruby/core/exception/signm_spec.rb b/spec/ruby/core/exception/signm_spec.rb
index 8e3adcddae..4adff3b5ee 100644
--- a/spec/ruby/core/exception/signm_spec.rb
+++ b/spec/ruby/core/exception/signm_spec.rb
@@ -1,5 +1,9 @@
 require_relative '../../spec_helper'
 
 describe "SignalException#signm" do
-  it "needs to be reviewed for spec completeness"
+  it "returns the signal name" do
+    -> { Process.kill(:TERM, Process.pid) }.should raise_error(SignalException) { |e|
+      e.signm.should == 'SIGTERM'
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/signo_spec.rb b/spec/ruby/core/exception/signo_spec.rb
index 2d04cd7805..62fc321516 100644
--- a/spec/ruby/core/exception/signo_spec.rb
+++ b/spec/ruby/core/exception/signo_spec.rb
@@ -1,5 +1,9 @@
 require_relative '../../spec_helper'
 
 describe "SignalException#signo" do
-  it "needs to be reviewed for spec completeness"
+  it "returns the signal number" do
+    -> { Process.kill(:TERM, Process.pid) }.should raise_error(SignalException) { |e|
+      e.signo.should == Signal.list['TERM']
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/source_encoding_name_spec.rb b/spec/ruby/core/exception/source_encoding_name_spec.rb
deleted file mode 100644
index bd8bc359b6..0000000000
--- a/spec/ruby/core/exception/source_encoding_name_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::UndefinedConversionError#source_encoding_name" do
-  it "needs to be reviewed for spec completeness"
-end
-
-describe "Encoding::InvalidByteSequenceError#source_encoding_name" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/source_encoding_spec.rb b/spec/ruby/core/exception/source_encoding_spec.rb
deleted file mode 100644
index 65ac98d791..0000000000
--- a/spec/ruby/core/exception/source_encoding_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Encoding::UndefinedConversionError#source_encoding" do
-  it "needs to be reviewed for spec completeness"
-end
-
-describe "Encoding::InvalidByteSequenceError#source_encoding" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/exception/standard_error_spec.rb b/spec/ruby/core/exception/standard_error_spec.rb
index 1b469b5090..17e98ce7f0 100644
--- a/spec/ruby/core/exception/standard_error_spec.rb
+++ b/spec/ruby/core/exception/standard_error_spec.rb
@@ -1,56 +1,23 @@
 require_relative '../../spec_helper'
 
 describe "StandardError" do
-  it "is a superclass of ArgumentError" do
-    StandardError.should be_ancestor_of(ArgumentError)
-  end
-
-  it "is a superclass of IOError" do
-    StandardError.should be_ancestor_of(IOError)
-  end
-
-  it "is a superclass of IndexError" do
-    StandardError.should be_ancestor_of(IndexError)
-  end
-
-  it "is a superclass of LocalJumpError" do
-    StandardError.should be_ancestor_of(LocalJumpError)
-  end
-
-  it "is a superclass of NameError" do
-    StandardError.should be_ancestor_of(NameError)
-  end
-
-  it "is a superclass of RangeError" do
-    StandardError.should be_ancestor_of(RangeError)
-  end
-
-  it "is a superclass of RegexpError" do
-    StandardError.should be_ancestor_of(RegexpError)
-  end
-
-  it "is a superclass of RuntimeError" do
-    StandardError.should be_ancestor_of(RuntimeError)
-  end
-
-  it "is a superclass of SystemCallError" do
-    StandardError.should be_ancestor_of(SystemCallError.new("").class)
-  end
-  it "is a superclass of ThreadError" do
-    StandardError.should be_ancestor_of(ThreadError)
-  end
-
-  it "is a superclass of TypeError" do
-    StandardError.should be_ancestor_of(TypeError)
+  it "rescues StandardError" do
+    begin
+      raise StandardError
+    rescue => exception
+      exception.class.should == StandardError
+    end
   end
 
-  it "is a superclass of ZeroDivisionError" do
-    StandardError.should be_ancestor_of(ZeroDivisionError)
+  it "rescues subclass of StandardError" do
+    begin
+      raise RuntimeError
+    rescue => exception
+      exception.class.should == RuntimeError
+    end
   end
 
-  ruby_version_is '2.5' do
-    it "is a superclass of FrozenError" do
-      StandardError.should be_ancestor_of(FrozenError)
-    end
+  it "does not rescue superclass of StandardError" do
+    -> { begin; raise Exception; rescue; end }.should raise_error(Exception)
   end
 end
diff --git a/spec/ruby/core/exception/status_spec.rb b/spec/ruby/core/exception/status_spec.rb
index 1609bff3a5..8ace00fe10 100644
--- a/spec/ruby/core/exception/status_spec.rb
+++ b/spec/ruby/core/exception/status_spec.rb
@@ -1,5 +1,9 @@
 require_relative '../../spec_helper'
 
 describe "SystemExit#status" do
-  it "needs to be reviewed for spec completeness"
+  it "returns the exit status" do
+    -> { exit 42 }.should raise_error(SystemExit) { |e|
+      e.status.should == 42
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/success_spec.rb b/spec/ruby/core/exception/success_spec.rb
index 82e3df92c6..6f21743340 100644
--- a/spec/ruby/core/exception/success_spec.rb
+++ b/spec/ruby/core/exception/success_spec.rb
@@ -1,5 +1,15 @@
 require_relative '../../spec_helper'
 
 describe "SystemExit#success?" do
-  it "needs to be reviewed for spec completeness"
+  it "returns true if the process exited successfully" do
+    -> { exit 0 }.should raise_error(SystemExit) { |e|
+      e.should.success?
+    }
+  end
+
+  it "returns false if the process exited unsuccessfully" do
+    -> { exit(-1) }.should raise_error(SystemExit) { |e|
+      e.should_not.success?
+    }
+  end
 end
diff --git a/spec/ruby/core/exception/syntax_error_spec.rb b/spec/ruby/core/exception/syntax_error_spec.rb
new file mode 100644
index 0000000000..4c713a3507
--- /dev/null
+++ b/spec/ruby/core/exception/syntax_error_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+
+describe "SyntaxError#path" do
+  it "returns the file path provided to eval" do
+    filename = "speccing.rb"
+
+    -> {
+      eval("if true", TOPLEVEL_BINDING, filename)
+    }.should raise_error(SyntaxError) { |e|
+      e.path.should == filename
+    }
+  end
+
+  it "returns the file path that raised an exception" do
+    expected_path = fixture(__FILE__, "syntax_error.rb")
+
+    -> {
+      require_relative "fixtures/syntax_error"
+    }.should raise_error(SyntaxError) { |e| e.path.should == expected_path }
+  end
+
+  it "returns nil when constructed directly" do
+    SyntaxError.new.path.should == nil
+  end
+end
diff --git a/spec/ruby/core/exception/system_call_error_spec.rb b/spec/ruby/core/exception/system_call_error_spec.rb
index c07c8af72c..4fe51901c8 100644
--- a/spec/ruby/core/exception/system_call_error_spec.rb
+++ b/spec/ruby/core/exception/system_call_error_spec.rb
@@ -16,45 +16,111 @@ describe "SystemCallError" do
     exc = ExceptionSpecs::SCESub.new
     ScratchPad.recorded.should equal(:initialize)
     exc.should be_an_instance_of(ExceptionSpecs::SCESub)
+  ensure
+    ExceptionSpecs.send(:remove_const, :SCESub)
   end
 end
 
 describe "SystemCallError.new" do
+  before :all do
+    @example_errno = Errno::EINVAL::Errno
+    @example_errno_class = Errno::EINVAL
+    @last_known_errno = Errno.constants.size - 1
+    @unknown_errno = Errno.constants.size
+    @some_human_readable = /[[:graph:]]+/
+  end
+
   it "requires at least one argument" do
     -> { SystemCallError.new }.should raise_error(ArgumentError)
   end
 
-  it "accepts single Fixnum argument as errno" do
+  it "accepts single Integer argument as errno" do
     SystemCallError.new(-2**24).errno.should == -2**24
-    SystemCallError.new(42).errno.should == 42
+    SystemCallError.new(-1).errno.should == -1
+    SystemCallError.new(0).errno.should == 0
+    SystemCallError.new(@last_known_errno).errno.should == @last_known_errno
+    SystemCallError.new(@unknown_errno).errno.should == @unknown_errno
     SystemCallError.new(2**24).errno.should == 2**24
   end
 
+  it "constructs a SystemCallError for an unknown error number" do
+    SystemCallError.new(-2**24).should be_an_instance_of(SystemCallError)
+    SystemCallError.new(-1).should be_an_instance_of(SystemCallError)
+    SystemCallError.new(@unknown_errno).should be_an_instance_of(SystemCallError)
+    SystemCallError.new(2**24).should be_an_instance_of(SystemCallError)
+  end
+
   it "constructs the appropriate Errno class" do
-    # EINVAL should be more or less mortable across the platforms,
-    # so let's use it then.
-    SystemCallError.new(22).should be_kind_of(SystemCallError)
-    SystemCallError.new(22).should be_an_instance_of(Errno::EINVAL)
-    SystemCallError.new(2**28).should be_an_instance_of(SystemCallError)
+    e = SystemCallError.new(@example_errno)
+    e.should be_kind_of(SystemCallError)
+    e.should be_an_instance_of(@example_errno_class)
+  end
+
+  it "sets an error message corresponding to an appropriate Errno class" do
+    e = SystemCallError.new(@example_errno)
+    e.message.should == 'Invalid argument'
   end
 
   it "accepts an optional custom message preceding the errno" do
-    exc = SystemCallError.new("custom message", 22)
-    exc.should be_an_instance_of(Errno::EINVAL)
-    exc.errno.should == 22
-    exc.message.should == "Invalid argument - custom message"
+    exc = SystemCallError.new("custom message", @example_errno)
+    exc.should be_an_instance_of(@example_errno_class)
+    exc.errno.should == @example_errno
+    exc.message.should == 'Invalid argument - custom message'
   end
 
   it "accepts an optional third argument specifying the location" do
-    exc = SystemCallError.new("custom message", 22, "location")
-    exc.should be_an_instance_of(Errno::EINVAL)
-    exc.errno.should == 22
-    exc.message.should == "Invalid argument @ location - custom message"
+    exc = SystemCallError.new("custom message", @example_errno, "location")
+    exc.should be_an_instance_of(@example_errno_class)
+    exc.errno.should == @example_errno
+    exc.message.should == 'Invalid argument @ location - custom message'
+  end
+
+  it "coerces location if it is not a String" do
+    e = SystemCallError.new('foo', 1, :not_a_string)
+    e.message.should =~ /@ not_a_string - foo/
   end
 
   it "returns an arity of -1 for the initialize method" do
     SystemCallError.instance_method(:initialize).arity.should == -1
   end
+
+  it "converts to Integer if errno is a Float" do
+    SystemCallError.new('foo', 2.0).should == SystemCallError.new('foo', 2)
+    SystemCallError.new('foo', 2.9).should == SystemCallError.new('foo', 2)
+  end
+
+  it "treats nil errno as unknown error value" do
+    SystemCallError.new(nil).should be_an_instance_of(SystemCallError)
+  end
+
+  it "treats nil custom message as if it is not passed at all" do
+    exc = SystemCallError.new(nil, @example_errno)
+    exc.message.should == 'Invalid argument'
+  end
+
+  it "sets an 'unknown error' message when an unknown error number" do
+    SystemCallError.new(-1).message.should =~ @some_human_readable
+  end
+
+  it "adds a custom error message to an 'unknown error' message when an unknown error number and a custom message specified" do
+    SystemCallError.new("custom message", -1).message.should =~ /#{@some_human_readable}.* - custom message/
+  end
+
+  it "converts to Integer if errno is a Complex convertible to Integer" do
+    SystemCallError.new('foo', Complex(2.9, 0)).should == SystemCallError.new('foo', 2)
+  end
+
+  it "raises TypeError if message is not a String" do
+    -> { SystemCallError.new(:foo, 1) }.should raise_error(TypeError, /no implicit conversion of Symbol into String/)
+  end
+
+  it "raises TypeError if errno is not an Integer" do
+    -> { SystemCallError.new('foo', 'bar') }.should raise_error(TypeError, /no implicit conversion of String into Integer/)
+  end
+
+  it "raises RangeError if errno is a Complex not convertible to Integer" do
+    -> { SystemCallError.new('foo', Complex(2.9, 1)) }.should raise_error(RangeError, /can't convert/)
+  end
 end
 
 describe "SystemCallError#errno" do
@@ -74,12 +140,7 @@ end
 
 describe "SystemCallError#message" do
   it "returns the default message when no message is given" do
-    platform_is :aix do
-      SystemCallError.new(2**28).message.should =~ /Error .*occurred/i
-    end
-    platform_is_not :aix do
-      SystemCallError.new(2**28).message.should =~ /Unknown error/i
-    end
+    SystemCallError.new(2**28).message.should =~ @some_human_readable
   end
 
   it "returns the message given as an argument to new" do
@@ -87,3 +148,16 @@ describe "SystemCallError#message" do
     SystemCallError.new("XXX").message.should =~ /XXX/
   end
 end
+
+describe "SystemCallError#dup" do
+  it "copies the errno" do
+    dup_sce = SystemCallError.new("message", 42).dup
+    dup_sce.errno.should == 42
+  end
+end
+
+describe "SystemCallError#backtrace" do
+  it "is nil if not raised" do
+    SystemCallError.new("message", 42).backtrace.should == nil
+  end
+end
diff --git a/spec/ruby/core/exception/system_exit_spec.rb b/spec/ruby/core/exception/system_exit_spec.rb
new file mode 100644
index 0000000000..d899844c4e
--- /dev/null
+++ b/spec/ruby/core/exception/system_exit_spec.rb
@@ -0,0 +1,59 @@
+require_relative '../../spec_helper'
+
+describe "SystemExit" do
+  describe "#initialize" do
+    it "accepts a status and message" do
+      exc = SystemExit.new(42, "message")
+      exc.status.should == 42
+      exc.message.should == "message"
+
+      exc = SystemExit.new(true, "message")
+      exc.status.should == 0
+      exc.message.should == "message"
+
+      exc = SystemExit.new(false, "message")
+      exc.status.should == 1
+      exc.message.should == "message"
+    end
+
+    it "accepts a status only" do
+      exc = SystemExit.new(42)
+      exc.status.should == 42
+      exc.message.should == "SystemExit"
+
+      exc = SystemExit.new(true)
+      exc.status.should == 0
+      exc.message.should == "SystemExit"
+
+      exc = SystemExit.new(false)
+      exc.status.should == 1
+      exc.message.should == "SystemExit"
+    end
+
+    it "accepts a message only" do
+      exc = SystemExit.new("message")
+      exc.status.should == 0
+      exc.message.should == "message"
+    end
+
+    it "accepts no arguments" do
+      exc = SystemExit.new
+      exc.status.should == 0
+      exc.message.should == "SystemExit"
+    end
+  end
+
+  it "sets the exit status and exits silently when raised" do
+    code = 'raise SystemExit.new(7)'
+    result = ruby_exe(code, args: "2>&1", exit_status: 7)
+    result.should == ""
+    $?.exitstatus.should == 7
+  end
+
+  it "sets the exit status and exits silently when raised when subclassed" do
+    code = 'class CustomExit < SystemExit; end; raise CustomExit.new(8)'
+    result = ruby_exe(code, args: "2>&1", exit_status: 8)
+    result.should == ""
+    $?.exitstatus.should == 8
+  end
+end
diff --git a/spec/ruby/core/exception/system_stack_error_spec.rb b/spec/ruby/core/exception/system_stack_error_spec.rb
deleted file mode 100644
index 0343d2da59..0000000000
--- a/spec/ruby/core/exception/system_stack_error_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "SystemStackError" do
-  it "is a subclass of Exception" do
-    SystemStackError.superclass.should == Exception
-  end
-end
diff --git a/spec/ruby/core/exception/to_s_spec.rb b/spec/ruby/core/exception/to_s_spec.rb
index 8570b18cfd..65c0d73a98 100644
--- a/spec/ruby/core/exception/to_s_spec.rb
+++ b/spec/ruby/core/exception/to_s_spec.rb
@@ -19,5 +19,19 @@ describe "Exception#to_s" do
 end
 
 describe "NameError#to_s" do
-  it "needs to be reviewed for spec completeness"
+  it "raises its own message for an undefined variable" do
+    begin
+      puts not_defined
+    rescue => exception
+      exception.message.should =~ /undefined local variable or method [`']not_defined'/
+    end
+  end
+
+  it "raises its own message for an undefined constant" do
+    begin
+      puts NotDefined
+    rescue => exception
+      exception.message.should =~ /uninitialized constant NotDefined/
+    end
+  end
 end
diff --git a/spec/ruby/core/exception/top_level_spec.rb b/spec/ruby/core/exception/top_level_spec.rb
new file mode 100644
index 0000000000..cc961d06d5
--- /dev/null
+++ b/spec/ruby/core/exception/top_level_spec.rb
@@ -0,0 +1,65 @@
+require_relative '../../spec_helper'
+
+describe "An Exception reaching the top level" do
+  it "is printed on STDERR" do
+    ruby_exe('raise "foo"', args: "2>&1", exit_status: 1).should =~ /in [`']<main>': foo \(RuntimeError\)/
+  end
+
+  it "the Exception#cause is printed to STDERR with backtraces" do
+    code = <<-RUBY
+    def raise_cause
+      raise "the cause" # 2
+    end
+    def raise_wrapped
+      raise "wrapped" # 5
+    end
+    begin
+      raise_cause # 8
+    rescue
+      raise_wrapped # 10
+    end
+    RUBY
+    lines = ruby_exe(code, args: "2>&1", exit_status: 1).lines
+
+    lines.map! { |l| l.chomp[/:(\d+:in.+)/, 1] }
+    lines[0].should =~ /\A5:in [`'](?:Object#)?raise_wrapped': wrapped \(RuntimeError\)\z/
+    if lines[1].include? 'rescue in'
+      # CRuby < 3.4 has an extra 'rescue in' backtrace entry
+      lines[1].should =~ /\A10:in [`']rescue in <main>'\z/
+      lines.delete_at 1
+      lines[1].should =~ /\A7:in [`']<main>'\z/
+    else
+      lines[1].should =~ /\A10:in [`']<main>'\z/
+    end
+    lines[2].should =~ /\A2:in [`'](?:Object#)?raise_cause': the cause \(RuntimeError\)\z/
+    lines[3].should =~ /\A8:in [`']<main>'\z/
+    lines.size.should == 4
+  end
+
+  describe "with a custom backtrace" do
+    it "is printed on STDERR" do
+      code = <<-RUBY
+      raise RuntimeError, "foo", [
+        "/dir/foo.rb:10:in `raising'",
+        "/dir/bar.rb:20:in `caller'",
+      ]
+      RUBY
+      ruby_exe(code, args: "2>&1", exit_status: 1).should == <<-EOS
+/dir/foo.rb:10:in `raising': foo (RuntimeError)
+\tfrom /dir/bar.rb:20:in `caller'
+      EOS
+    end
+  end
+
+  describe "kills all threads and fibers, ensure clauses are only run for threads current fibers, not for suspended fibers" do
+    it "with ensure on the root fiber" do
+      file = fixture(__FILE__, "thread_fiber_ensure.rb")
+      ruby_exe(file, args: "2>&1", exit_status: 0).should == "current fiber ensure\n"
+    end
+
+    it "with ensure on non-root fiber" do
+      file = fixture(__FILE__, "thread_fiber_ensure_non_root_fiber.rb")
+      ruby_exe(file, args: "2>&1", exit_status: 0).should == "current fiber ensure\n"
+    end
+  end
+end
diff --git a/spec/ruby/core/exception/uncaught_throw_error_spec.rb b/spec/ruby/core/exception/uncaught_throw_error_spec.rb
index 57f391d755..9267df6670 100644
--- a/spec/ruby/core/exception/uncaught_throw_error_spec.rb
+++ b/spec/ruby/core/exception/uncaught_throw_error_spec.rb
@@ -1,11 +1,5 @@
 require_relative '../../spec_helper'
 
-describe "UncaughtThrowError" do
-  it "is a subclass of ArgumentError" do
-    ArgumentError.should be_ancestor_of(UncaughtThrowError)
-  end
-end
-
 describe "UncaughtThrowError#tag" do
   it "returns the object thrown" do
     begin
diff --git a/spec/ruby/core/false/case_compare_spec.rb b/spec/ruby/core/false/case_compare_spec.rb
new file mode 100644
index 0000000000..0bd0ab44ae
--- /dev/null
+++ b/spec/ruby/core/false/case_compare_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+
+describe "FalseClass#===" do
+  it "returns true for false" do
+    (false === false).should == true
+  end
+
+  it "returns false for non-false object" do
+    (false === 0).should == false
+    (false === "").should == false
+    (false === Object).should == false
+    (false === nil).should == false
+  end
+end
diff --git a/spec/ruby/core/false/singleton_method_spec.rb b/spec/ruby/core/false/singleton_method_spec.rb
new file mode 100644
index 0000000000..738794b46c
--- /dev/null
+++ b/spec/ruby/core/false/singleton_method_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+
+describe "FalseClass#singleton_method" do
+  ruby_version_is '3.3' do
+    it "raises regardless of whether FalseClass defines the method" do
+      -> { false.singleton_method(:foo) }.should raise_error(NameError)
+      begin
+        def (false).foo; end
+        -> { false.singleton_method(:foo) }.should raise_error(NameError)
+      ensure
+        FalseClass.send(:remove_method, :foo)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/false/to_s_spec.rb b/spec/ruby/core/false/to_s_spec.rb
index 40853da88b..62f67f6f55 100644
--- a/spec/ruby/core/false/to_s_spec.rb
+++ b/spec/ruby/core/false/to_s_spec.rb
@@ -4,4 +4,12 @@ describe "FalseClass#to_s" do
   it "returns the string 'false'" do
     false.to_s.should == "false"
   end
+
+  it "returns a frozen string" do
+    false.to_s.should.frozen?
+  end
+
+  it "always returns the same string" do
+    false.to_s.should equal(false.to_s)
+  end
 end
diff --git a/spec/ruby/core/fiber/alive_spec.rb b/spec/ruby/core/fiber/alive_spec.rb
new file mode 100644
index 0000000000..a1df582435
--- /dev/null
+++ b/spec/ruby/core/fiber/alive_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../spec_helper'
+
+describe "Fiber#alive?" do
+  it "returns true for a Fiber that hasn't had #resume called" do
+    fiber = Fiber.new { true }
+    fiber.alive?.should be_true
+  end
+
+  # FIXME: Better description?
+  it "returns true for a Fiber that's yielded to the caller" do
+    fiber = Fiber.new { Fiber.yield }
+    fiber.resume
+    fiber.alive?.should be_true
+  end
+
+  it "returns true when called from its Fiber" do
+    fiber = Fiber.new { fiber.alive?.should be_true }
+    fiber.resume
+  end
+
+  it "doesn't invoke the block associated with the Fiber" do
+    offthehook = mock('do not call')
+    offthehook.should_not_receive(:ring)
+    fiber = Fiber.new { offthehook.ring }
+    fiber.alive?
+  end
+
+  it "returns false for a Fiber that's dead" do
+    fiber = Fiber.new { true }
+    fiber.resume
+    -> { fiber.resume }.should raise_error(FiberError)
+    fiber.alive?.should be_false
+  end
+
+  it "always returns false for a dead Fiber" do
+    fiber = Fiber.new { true }
+    fiber.resume
+    -> { fiber.resume }.should raise_error(FiberError)
+    fiber.alive?.should be_false
+    -> { fiber.resume }.should raise_error(FiberError)
+    fiber.alive?.should be_false
+    fiber.alive?.should be_false
+  end
+end
diff --git a/spec/ruby/core/fiber/blocking_spec.rb b/spec/ruby/core/fiber/blocking_spec.rb
new file mode 100644
index 0000000000..d5caf81fbe
--- /dev/null
+++ b/spec/ruby/core/fiber/blocking_spec.rb
@@ -0,0 +1,73 @@
+require_relative '../../spec_helper'
+require_relative 'shared/blocking'
+
+describe "Fiber.blocking?" do
+  it_behaves_like :non_blocking_fiber, -> { Fiber.blocking? }
+
+  context "when fiber is blocking" do
+    context "root Fiber of the main thread" do
+      it "returns 1 for blocking: true" do
+        fiber = Fiber.new(blocking: true) { Fiber.blocking? }
+        blocking = fiber.resume
+
+        blocking.should == 1
+      end
+    end
+
+    context "root Fiber of a new thread" do
+      it "returns 1 for blocking: true" do
+        thread = Thread.new do
+          fiber = Fiber.new(blocking: true) { Fiber.blocking? }
+          blocking = fiber.resume
+
+          blocking.should == 1
+        end
+
+        thread.join
+      end
+    end
+  end
+end
+
+describe "Fiber#blocking?" do
+  it_behaves_like :non_blocking_fiber, -> { Fiber.current.blocking? }
+
+  context "when fiber is blocking" do
+    context "root Fiber of the main thread" do
+      it "returns true for blocking: true" do
+        fiber = Fiber.new(blocking: true) { Fiber.current.blocking? }
+        blocking = fiber.resume
+
+        blocking.should == true
+      end
+    end
+
+    context "root Fiber of a new thread" do
+      it "returns true for blocking: true" do
+        thread = Thread.new do
+          fiber = Fiber.new(blocking: true) { Fiber.current.blocking? }
+          blocking = fiber.resume
+
+          blocking.should == true
+        end
+
+        thread.join
+      end
+    end
+  end
+end
+
+describe "Fiber.blocking" do
+  context "when fiber is non-blocking" do
+    it "can become blocking" do
+      fiber = Fiber.new(blocking: false) do
+        Fiber.blocking do |f|
+          f.blocking? ? :blocking : :non_blocking
+        end
+      end
+
+      blocking = fiber.resume
+      blocking.should == :blocking
+    end
+  end
+end
diff --git a/spec/ruby/core/fiber/current_spec.rb b/spec/ruby/core/fiber/current_spec.rb
new file mode 100644
index 0000000000..b93df77a89
--- /dev/null
+++ b/spec/ruby/core/fiber/current_spec.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helper'
+
+describe "Fiber.current" do
+  it "returns the root Fiber when called outside of a Fiber" do
+    root = Fiber.current
+    root.should be_an_instance_of(Fiber)
+    # We can always transfer to the root Fiber; it will never die
+    5.times do
+      root.transfer.should be_nil
+      root.alive?.should be_true
+    end
+  end
+
+  it "returns the current Fiber when called from a Fiber" do
+    fiber = Fiber.new do
+      this = Fiber.current
+      this.should be_an_instance_of(Fiber)
+      this.should == fiber
+      this.alive?.should be_true
+    end
+    fiber.resume
+  end
+
+  it "returns the current Fiber when called from a Fiber that transferred to another" do
+    states = []
+    fiber = Fiber.new do
+      states << :fiber
+      this = Fiber.current
+      this.should be_an_instance_of(Fiber)
+      this.should == fiber
+      this.alive?.should be_true
+    end
+
+    fiber2 = Fiber.new do
+      states << :fiber2
+      fiber.transfer
+      flunk
+    end
+
+    fiber3 = Fiber.new do
+      states << :fiber3
+      fiber2.transfer
+      states << :fiber3_terminated
+    end
+
+    fiber3.resume
+
+    states.should == [:fiber3, :fiber2, :fiber, :fiber3_terminated]
+  end
+end
diff --git a/spec/ruby/core/fiber/fixtures/classes.rb b/spec/ruby/core/fiber/fixtures/classes.rb
new file mode 100644
index 0000000000..6b0e0fbc42
--- /dev/null
+++ b/spec/ruby/core/fiber/fixtures/classes.rb
@@ -0,0 +1,22 @@
+module FiberSpecs
+
+  class NewFiberToRaise
+    def self.raise(*args, **kwargs, &block)
+      fiber = Fiber.new do
+        if block_given?
+          block.call do
+            Fiber.yield
+          end
+        else
+          Fiber.yield
+        end
+      end
+
+      fiber.resume
+
+      fiber.raise(*args, **kwargs)
+    end
+  end
+
+  class CustomError < StandardError; end
+end
diff --git a/spec/ruby/core/fiber/fixtures/scheduler.rb b/spec/ruby/core/fiber/fixtures/scheduler.rb
new file mode 100644
index 0000000000..16bd2f6b44
--- /dev/null
+++ b/spec/ruby/core/fiber/fixtures/scheduler.rb
@@ -0,0 +1,35 @@
+module FiberSpecs
+
+  class LoggingScheduler
+    attr_reader :events
+    def initialize
+      @events = []
+    end
+
+    def block(*args)
+      @events << { event: :block, fiber: Fiber.current, args: args }
+      Fiber.yield
+    end
+
+    def io_wait(*args)
+      @events << { event: :io_wait, fiber: Fiber.current, args: args }
+      Fiber.yield
+    end
+
+    def kernel_sleep(*args)
+      @events << { event: :kernel_sleep, fiber: Fiber.current, args: args }
+      Fiber.yield
+    end
+
+    def unblock(*args)
+      @events << { event: :unblock, fiber: Fiber.current, args: args }
+      Fiber.yield
+    end
+
+    def fiber_interrupt(*args)
+      @events << { event: :fiber_interrupt, fiber: Fiber.current, args: args }
+      Fiber.yield
+    end
+  end
+
+end
diff --git a/spec/ruby/core/fiber/inspect_spec.rb b/spec/ruby/core/fiber/inspect_spec.rb
new file mode 100644
index 0000000000..fcfef20716
--- /dev/null
+++ b/spec/ruby/core/fiber/inspect_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../spec_helper'
+
+describe "Fiber#inspect" do
+  describe "status" do
+    it "is resumed for the root Fiber of a Thread" do
+      inspected = Thread.new { Fiber.current.inspect }.value
+      inspected.should =~ /\A#<Fiber:0x\h+ .*\(resumed\)>\z/
+    end
+
+    it "is created for a Fiber which did not run yet" do
+      inspected = Fiber.new {}.inspect
+      inspected.should =~ /\A#<Fiber:0x\h+ .+ \(created\)>\z/
+    end
+
+    it "is resumed for a Fiber which was resumed" do
+      inspected = Fiber.new { Fiber.current.inspect }.resume
+      inspected.should =~ /\A#<Fiber:0x\h+ .+ \(resumed\)>\z/
+    end
+
+    it "is resumed for a Fiber which was transferred" do
+      inspected = Fiber.new { Fiber.current.inspect }.transfer
+      inspected.should =~ /\A#<Fiber:0x\h+ .+ \(resumed\)>\z/
+    end
+
+    it "is suspended for a Fiber which was resumed and yielded" do
+      inspected = Fiber.new { Fiber.yield }.tap(&:resume).inspect
+      inspected.should =~ /\A#<Fiber:0x\h+ .+ \(suspended\)>\z/
+    end
+
+    it "is terminated for a Fiber which has terminated" do
+      inspected = Fiber.new {}.tap(&:resume).inspect
+      inspected.should =~ /\A#<Fiber:0x\h+ .+ \(terminated\)>\z/
+    end
+  end
+end
diff --git a/spec/ruby/core/fiber/kill_spec.rb b/spec/ruby/core/fiber/kill_spec.rb
new file mode 100644
index 0000000000..2f4c499280
--- /dev/null
+++ b/spec/ruby/core/fiber/kill_spec.rb
@@ -0,0 +1,90 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative '../../shared/kernel/raise'
+
+ruby_version_is "3.3" do
+  describe "Fiber#kill" do
+    it "kills a non-resumed fiber" do
+      fiber = Fiber.new{}
+
+      fiber.alive?.should == true
+
+      fiber.kill
+      fiber.alive?.should == false
+    end
+
+    it "kills a resumed fiber" do
+      fiber = Fiber.new{while true; Fiber.yield; end}
+      fiber.resume
+
+      fiber.alive?.should == true
+
+      fiber.kill
+      fiber.alive?.should == false
+    end
+
+    it "can kill itself" do
+      fiber = Fiber.new do
+        Fiber.current.kill
+      end
+
+      fiber.alive?.should == true
+
+      fiber.resume
+      fiber.alive?.should == false
+    end
+
+    it "kills a resumed fiber from a child" do
+      parent = Fiber.new do
+        child = Fiber.new do
+          parent.kill
+          parent.alive?.should == true
+        end
+
+        child.resume
+      end
+
+      parent.resume
+      parent.alive?.should == false
+    end
+
+    it "executes the ensure block" do
+      ensure_executed = false
+
+      fiber = Fiber.new do
+        while true; Fiber.yield; end
+      ensure
+        ensure_executed = true
+      end
+
+      fiber.resume
+      fiber.kill
+      ensure_executed.should == true
+    end
+
+    it "does not execute rescue block" do
+      rescue_executed = false
+
+      fiber = Fiber.new do
+        while true; Fiber.yield; end
+      rescue Exception
+        rescue_executed = true
+      end
+
+      fiber.resume
+      fiber.kill
+      rescue_executed.should == false
+    end
+
+    it "repeatedly kills a fiber" do
+      fiber = Fiber.new do
+        while true; Fiber.yield; end
+      ensure
+        while true; Fiber.yield; end
+      end
+
+      fiber.kill
+      fiber.alive?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/fiber/raise_spec.rb b/spec/ruby/core/fiber/raise_spec.rb
new file mode 100644
index 0000000000..896f760290
--- /dev/null
+++ b/spec/ruby/core/fiber/raise_spec.rb
@@ -0,0 +1,139 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative '../../shared/kernel/raise'
+
+describe "Fiber#raise" do
+  it_behaves_like :kernel_raise, :raise, FiberSpecs::NewFiberToRaise
+  it_behaves_like :kernel_raise_across_contexts, :raise, FiberSpecs::NewFiberToRaise
+end
+
+describe "Fiber#raise" do
+  it 'raises RuntimeError by default' do
+    -> { FiberSpecs::NewFiberToRaise.raise }.should raise_error(RuntimeError)
+  end
+
+  it "raises FiberError if Fiber is not born" do
+    fiber = Fiber.new { true }
+    -> { fiber.raise }.should raise_error(FiberError, "cannot raise exception on unborn fiber")
+  end
+
+  it "raises FiberError if Fiber is dead" do
+    fiber = Fiber.new { true }
+    fiber.resume
+    -> { fiber.raise }.should raise_error(FiberError, /dead fiber called|attempt to resume a terminated fiber/)
+  end
+
+  it 'accepts error class' do
+    -> { FiberSpecs::NewFiberToRaise.raise FiberSpecs::CustomError }.should raise_error(FiberSpecs::CustomError)
+  end
+
+  it 'accepts error message' do
+    -> { FiberSpecs::NewFiberToRaise.raise "error message" }.should raise_error(RuntimeError, "error message")
+  end
+
+  it 'does not accept array of backtrace information only' do
+    -> { FiberSpecs::NewFiberToRaise.raise ['foo'] }.should raise_error(TypeError)
+  end
+
+  it 'does not accept integer' do
+    -> { FiberSpecs::NewFiberToRaise.raise 100 }.should raise_error(TypeError)
+  end
+
+  it 'accepts error class with error message' do
+    -> { FiberSpecs::NewFiberToRaise.raise FiberSpecs::CustomError, 'test error' }.should raise_error(FiberSpecs::CustomError, 'test error')
+  end
+
+  it 'accepts error class with error message and backtrace information' do
+    -> {
+      FiberSpecs::NewFiberToRaise.raise FiberSpecs::CustomError, 'test error', ['foo', 'boo']
+    }.should raise_error(FiberSpecs::CustomError) { |e|
+      e.message.should == 'test error'
+      e.backtrace.should == ['foo', 'boo']
+    }
+  end
+
+  it 'does not accept only error message and backtrace information' do
+    -> { FiberSpecs::NewFiberToRaise.raise 'test error', ['foo', 'boo'] }.should raise_error(TypeError)
+  end
+
+  it "raises a FiberError if invoked from a different Thread" do
+    fiber = Fiber.new { Fiber.yield }
+    fiber.resume
+    Thread.new do
+      -> {
+        fiber.raise
+      }.should raise_error(FiberError, "fiber called across threads")
+    end.join
+  end
+
+  it "kills Fiber" do
+    fiber = Fiber.new { Fiber.yield :first; :second }
+    fiber.resume
+    -> { fiber.raise }.should raise_error
+    -> { fiber.resume }.should raise_error(FiberError, /dead fiber called|attempt to resume a terminated fiber/)
+  end
+
+  it "returns to calling fiber after raise" do
+    fiber_one = Fiber.new do
+      Fiber.yield :yield_one
+      :unreachable
+    end
+
+    fiber_two = Fiber.new do
+      results = []
+      results << fiber_one.resume
+      begin
+        fiber_one.raise
+      rescue
+        results << :rescued
+      end
+      results
+    end
+
+    fiber_two.resume.should == [:yield_one, :rescued]
+  end
+
+  ruby_version_is "3.4" do
+    it "raises on the resumed fiber" do
+      root_fiber = Fiber.current
+      f1 = Fiber.new { root_fiber.transfer }
+      f2 = Fiber.new { f1.resume }
+      f2.transfer
+
+      -> do
+        f2.raise(RuntimeError, "Expected error")
+      end.should raise_error(RuntimeError, "Expected error")
+    end
+
+    it "raises on itself" do
+      -> do
+        Fiber.current.raise(RuntimeError, "Expected error")
+      end.should raise_error(RuntimeError, "Expected error")
+    end
+
+    it "should raise on parent fiber" do
+      f2 = nil
+      f1 = Fiber.new do
+        # This is equivalent to Kernel#raise:
+        f2.raise(RuntimeError, "Expected error")
+      end
+      f2 = Fiber.new do
+        f1.resume
+      end
+
+      -> do
+        f2.resume
+      end.should raise_error(RuntimeError, "Expected error")
+    end
+  end
+end
+
+
+describe "Fiber#raise" do
+  it "transfers and raises on a transferring fiber" do
+    root = Fiber.current
+    fiber = Fiber.new { root.transfer }
+    fiber.transfer
+    -> { fiber.raise "msg" }.should raise_error(RuntimeError, "msg")
+  end
+end
diff --git a/spec/ruby/core/fiber/resume_spec.rb b/spec/ruby/core/fiber/resume_spec.rb
index 97495c5059..4b20f4b4bf 100644
--- a/spec/ruby/core/fiber/resume_spec.rb
+++ b/spec/ruby/core/fiber/resume_spec.rb
@@ -1,14 +1,36 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/fiber/resume'
+require_relative 'shared/resume'
 
 describe "Fiber#resume" do
   it_behaves_like :fiber_resume, :resume
 end
 
 describe "Fiber#resume" do
+  it "runs until Fiber.yield" do
+    obj = mock('obj')
+    obj.should_not_receive(:do)
+    fiber = Fiber.new { 1 + 2; Fiber.yield; obj.do }
+    fiber.resume
+  end
+
+  it "resumes from the last call to Fiber.yield on subsequent invocations" do
+    fiber = Fiber.new { Fiber.yield :first; :second }
+    fiber.resume.should == :first
+    fiber.resume.should == :second
+  end
+
+  it "sets the block parameters to its arguments on the first invocation" do
+    first = mock('first')
+    first.should_receive(:arg).with(:first).twice
+
+    fiber = Fiber.new { |arg| first.arg arg; Fiber.yield; first.arg arg; }
+    fiber.resume :first
+    fiber.resume :second
+  end
+
   it "raises a FiberError if the Fiber tries to resume itself" do
     fiber = Fiber.new { fiber.resume }
-    -> { fiber.resume }.should raise_error(FiberError, /double resume/)
+    -> { fiber.resume }.should raise_error(FiberError, /current fiber/)
   end
 
   it "returns control to the calling Fiber if called from one" do
@@ -45,4 +67,17 @@ describe "Fiber#resume" do
 
     ruby_exe(code).should == "ensure executed\n"
   end
+
+  it "can work with Fiber#transfer" do
+    fiber1 = Fiber.new { true }
+    fiber2 = Fiber.new { fiber1.transfer; Fiber.yield 10 ; Fiber.yield 20; raise }
+    fiber2.resume.should == 10
+    fiber2.resume.should == 20
+  end
+
+  it "raises a FiberError if the Fiber attempts to resume a resuming fiber" do
+    root_fiber = Fiber.current
+    fiber1 = Fiber.new { root_fiber.resume }
+    -> { fiber1.resume }.should raise_error(FiberError, /attempt to resume a resuming fiber/)
+  end
 end
diff --git a/spec/ruby/core/fiber/scheduler_spec.rb b/spec/ruby/core/fiber/scheduler_spec.rb
new file mode 100644
index 0000000000..15a03c1479
--- /dev/null
+++ b/spec/ruby/core/fiber/scheduler_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'shared/scheduler'
+
+require "fiber"
+
+describe "Fiber.scheduler" do
+  it_behaves_like :scheduler, :scheduler
+end
diff --git a/spec/ruby/core/fiber/set_scheduler_spec.rb b/spec/ruby/core/fiber/set_scheduler_spec.rb
new file mode 100644
index 0000000000..82f6acbe86
--- /dev/null
+++ b/spec/ruby/core/fiber/set_scheduler_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'shared/scheduler'
+
+require "fiber"
+
+describe "Fiber.scheduler" do
+  it_behaves_like :scheduler, :set_scheduler
+end
diff --git a/spec/ruby/core/fiber/shared/blocking.rb b/spec/ruby/core/fiber/shared/blocking.rb
new file mode 100644
index 0000000000..21707e1ea7
--- /dev/null
+++ b/spec/ruby/core/fiber/shared/blocking.rb
@@ -0,0 +1,41 @@
+describe :non_blocking_fiber, shared: true do
+  context "root Fiber of the main thread" do
+    it "returns false" do
+      fiber = Fiber.new { @method.call }
+      blocking = fiber.resume
+
+      blocking.should == false
+    end
+
+    it "returns false for blocking: false" do
+      fiber = Fiber.new(blocking: false) { @method.call }
+      blocking = fiber.resume
+
+      blocking.should == false
+    end
+  end
+
+  context "root Fiber of a new thread" do
+    it "returns false" do
+      thread = Thread.new do
+        fiber = Fiber.new { @method.call }
+        blocking = fiber.resume
+
+        blocking.should == false
+      end
+
+      thread.join
+    end
+
+    it "returns false for blocking: false" do
+      thread = Thread.new do
+        fiber = Fiber.new(blocking: false) { @method.call }
+        blocking = fiber.resume
+
+        blocking.should == false
+      end
+
+      thread.join
+    end
+  end
+end
diff --git a/spec/ruby/core/fiber/shared/resume.rb b/spec/ruby/core/fiber/shared/resume.rb
new file mode 100644
index 0000000000..5ee27d1d24
--- /dev/null
+++ b/spec/ruby/core/fiber/shared/resume.rb
@@ -0,0 +1,58 @@
+describe :fiber_resume, shared: true do
+  it "can be invoked from the root Fiber" do
+    fiber = Fiber.new { :fiber }
+    fiber.send(@method).should == :fiber
+  end
+
+  it "raises a FiberError if invoked from a different Thread" do
+    fiber = Fiber.new { 42 }
+    Thread.new do
+      -> {
+        fiber.send(@method)
+      }.should raise_error(FiberError)
+    end.join
+
+    # Check the Fiber can still be used
+    fiber.send(@method).should == 42
+  end
+
+  it "passes control to the beginning of the block on first invocation" do
+    invoked = false
+    fiber = Fiber.new { invoked = true }
+    fiber.send(@method)
+    invoked.should be_true
+  end
+
+  it "returns the last value encountered on first invocation" do
+    fiber = Fiber.new { 1+1; true }
+    fiber.send(@method).should be_true
+  end
+
+  it "runs until the end of the block" do
+    obj = mock('obj')
+    obj.should_receive(:do).once
+    fiber = Fiber.new { 1 + 2; a = "glark"; obj.do }
+    fiber.send(@method)
+  end
+
+  it "accepts any number of arguments" do
+    fiber = Fiber.new { |a| }
+    -> { fiber.send(@method, *(1..10).to_a) }.should_not raise_error
+  end
+
+  it "raises a FiberError if the Fiber is dead" do
+    fiber = Fiber.new { true }
+    fiber.send(@method)
+    -> { fiber.send(@method) }.should raise_error(FiberError)
+  end
+
+  it "raises a LocalJumpError if the block includes a return statement" do
+    fiber = Fiber.new { return; }
+    -> { fiber.send(@method) }.should raise_error(LocalJumpError)
+  end
+
+  it "raises a LocalJumpError if the block includes a break statement" do
+    fiber = Fiber.new { break; }
+    -> { fiber.send(@method) }.should raise_error(LocalJumpError)
+  end
+end
diff --git a/spec/ruby/core/fiber/shared/scheduler.rb b/spec/ruby/core/fiber/shared/scheduler.rb
new file mode 100644
index 0000000000..19bfb75e3e
--- /dev/null
+++ b/spec/ruby/core/fiber/shared/scheduler.rb
@@ -0,0 +1,51 @@
+describe :scheduler, shared: true do
+  it "validates the scheduler for required methods" do
+    required_methods = [:block, :unblock, :kernel_sleep, :io_wait]
+    required_methods.each do |missing_method|
+      scheduler = Object.new
+      required_methods.difference([missing_method]).each do |method|
+        scheduler.define_singleton_method(method) {}
+      end
+      -> {
+        suppress_warning { Fiber.set_scheduler(scheduler) }
+      }.should raise_error(ArgumentError, /Scheduler must implement ##{missing_method}/)
+    end
+  end
+
+  it "can set and get the scheduler" do
+    required_methods = [:block, :unblock, :kernel_sleep, :io_wait]
+    scheduler = Object.new
+    required_methods.each do |method|
+      scheduler.define_singleton_method(method) {}
+    end
+    suppress_warning { Fiber.set_scheduler(scheduler) }
+    Fiber.scheduler.should == scheduler
+  end
+
+  it "returns the scheduler after setting it" do
+    required_methods = [:block, :unblock, :kernel_sleep, :io_wait]
+    scheduler = Object.new
+    required_methods.each do |method|
+      scheduler.define_singleton_method(method) {}
+    end
+    result = suppress_warning { Fiber.set_scheduler(scheduler) }
+    result.should == scheduler
+  end
+
+  it "can remove the scheduler" do
+    required_methods = [:block, :unblock, :kernel_sleep, :io_wait]
+    scheduler = Object.new
+    required_methods.each do |method|
+      scheduler.define_singleton_method(method) {}
+    end
+    suppress_warning { Fiber.set_scheduler(scheduler) }
+    Fiber.set_scheduler(nil)
+    Fiber.scheduler.should be_nil
+  end
+
+  it "can assign a nil scheduler multiple times" do
+    Fiber.set_scheduler(nil)
+    Fiber.set_scheduler(nil)
+    Fiber.scheduler.should be_nil
+  end
+end
diff --git a/spec/ruby/core/fiber/storage_spec.rb b/spec/ruby/core/fiber/storage_spec.rb
new file mode 100644
index 0000000000..015caaf3bb
--- /dev/null
+++ b/spec/ruby/core/fiber/storage_spec.rb
@@ -0,0 +1,181 @@
+require_relative '../../spec_helper'
+
+describe "Fiber.new(storage:)" do
+  it "creates a Fiber with the given storage" do
+    storage = {life: 42}
+    fiber = Fiber.new(storage: storage) { Fiber.current.storage }
+    fiber.resume.should == storage
+  end
+
+  it "creates a fiber with lazily initialized storage" do
+    Fiber.new(storage: nil) { Fiber[:x] = 10; Fiber.current.storage }.resume.should == {x: 10}
+  end
+
+  it "creates a fiber by inheriting the storage of the parent fiber" do
+    fiber = Fiber.new(storage: {life: 42}) do
+      Fiber.new { Fiber.current.storage }.resume
+    end
+    fiber.resume.should == {life: 42}
+  end
+
+  it "cannot create a fiber with non-hash storage" do
+    -> { Fiber.new(storage: 42) {} }.should raise_error(TypeError)
+  end
+
+  it "cannot create a fiber with a frozen hash as storage" do
+    -> { Fiber.new(storage: {life: 43}.freeze) {} }.should raise_error(FrozenError)
+  end
+
+  it "cannot create a fiber with a storage hash with non-symbol keys" do
+    -> { Fiber.new(storage: {life: 43, Object.new => 44}) {} }.should raise_error(TypeError)
+  end
+end
+
+describe "Fiber#storage" do
+  it "cannot be accessed from a different fiber" do
+    f = Fiber.new(storage: {life: 42}) { nil }
+    -> {
+      f.storage
+    }.should raise_error(ArgumentError, /Fiber storage can only be accessed from the Fiber it belongs to/)
+  end
+end
+
+describe "Fiber#storage=" do
+  it "can clear the storage of the fiber" do
+    fiber = Fiber.new(storage: {life: 42}) do
+      Fiber.current.storage = nil
+      Fiber[:x] = 10
+      Fiber.current.storage
+    end
+    fiber.resume.should == {x: 10}
+  end
+
+  it "can set the storage of the fiber" do
+    fiber = Fiber.new(storage: {life: 42}) do
+      Fiber.current.storage = {life: 43}
+      Fiber.current.storage
+    end
+    fiber.resume.should == {life: 43}
+  end
+
+  it "can't set the storage of the fiber to non-hash" do
+    -> { Fiber.current.storage = 42 }.should raise_error(TypeError)
+  end
+
+  it "can't set the storage of the fiber to a frozen hash" do
+    -> { Fiber.current.storage = {life: 43}.freeze }.should raise_error(FrozenError)
+  end
+
+  it "can't set the storage of the fiber to a hash with non-symbol keys" do
+    -> { Fiber.current.storage = {life: 43, Object.new => 44} }.should raise_error(TypeError)
+  end
+end
+
+describe "Fiber.[]" do
+  it "returns the value of the given key in the storage of the current fiber" do
+    Fiber.new(storage: {life: 42}) { Fiber[:life] }.resume.should == 42
+  end
+
+  it "returns nil if the key is not present in the storage of the current fiber" do
+    Fiber.new(storage: {life: 42}) { Fiber[:death] }.resume.should be_nil
+  end
+
+  it "returns nil if the current fiber has no storage" do
+    Fiber.new { Fiber[:life] }.resume.should be_nil
+  end
+
+  ruby_version_is "3.2.3" do
+    it "can use dynamically defined keys" do
+      key = :"#{self.class.name}#.#{self.object_id}"
+      Fiber.new { Fiber[key] = 42; Fiber[key] }.resume.should == 42
+    end
+
+    it "can't use invalid keys" do
+      invalid_keys = [Object.new, 12]
+      invalid_keys.each do |key|
+        -> { Fiber[key] }.should raise_error(TypeError)
+      end
+    end
+  end
+
+  ruby_bug "#20978", ""..."3.4" do
+    it "can use keys as strings" do
+      key = Object.new
+      def key.to_str; "Foo"; end
+      Fiber.new { Fiber[key] = 42; Fiber["Foo"] }.resume.should == 42
+    end
+
+    it "converts a String key into a Symbol" do
+      Fiber.new { Fiber["key"] = 42; Fiber[:key] }.resume.should == 42
+      Fiber.new { Fiber[:key] = 42; Fiber["key"] }.resume.should == 42
+    end
+
+    it "can use any object that responds to #to_str as a key" do
+      key = mock("key")
+      key.should_receive(:to_str).twice.and_return("key")
+      Fiber.new { Fiber[key] = 42; Fiber[key] }.resume.should == 42
+    end
+  end
+
+  it "does not call #to_sym on the key" do
+    key = mock("key")
+    key.should_not_receive(:to_sym)
+    -> { Fiber[key] }.should raise_error(TypeError)
+  end
+
+  it "can access the storage of the parent fiber" do
+    f = Fiber.new(storage: {life: 42}) do
+      Fiber.new { Fiber[:life] }.resume
+    end
+    f.resume.should == 42
+  end
+
+  it "can't access the storage of the fiber with non-symbol keys" do
+    -> { Fiber[Object.new] }.should raise_error(TypeError)
+  end
+end
+
+describe "Fiber.[]=" do
+  it "sets the value of the given key in the storage of the current fiber" do
+    Fiber.new(storage: {life: 42}) { Fiber[:life] = 43; Fiber[:life] }.resume.should == 43
+  end
+
+  it "sets the value of the given key in the storage of the current fiber" do
+    Fiber.new(storage: {life: 42}) { Fiber[:death] = 43; Fiber[:death] }.resume.should == 43
+  end
+
+  it "sets the value of the given key in the storage of the current fiber" do
+    Fiber.new { Fiber[:life] = 43; Fiber[:life] }.resume.should == 43
+  end
+
+  it "does not overwrite the storage of the parent fiber" do
+    f = Fiber.new(storage: {life: 42}) do
+      Fiber.yield Fiber.new { Fiber[:life] = 43; Fiber[:life] }.resume
+      Fiber[:life]
+    end
+    f.resume.should == 43 # Value of the inner fiber
+    f.resume.should == 42 # Value of the outer fiber
+  end
+
+  it "can't access the storage of the fiber with non-symbol keys" do
+    -> { Fiber[Object.new] = 44 }.should raise_error(TypeError)
+  end
+
+  ruby_version_is "3.3" do
+    it "deletes the fiber storage key when assigning nil" do
+      Fiber.new(storage: {life: 42}) {
+        Fiber[:life] = nil
+        Fiber.current.storage
+      }.resume.should == {}
+    end
+  end
+end
+
+describe "Thread.new" do
+  it "creates a thread with the storage of the current fiber" do
+    fiber = Fiber.new(storage: {life: 42}) do
+      Thread.new { Fiber.current.storage }.value
+    end
+    fiber.resume.should == {life: 42}
+  end
+end
diff --git a/spec/ruby/core/fiber/transfer_spec.rb b/spec/ruby/core/fiber/transfer_spec.rb
new file mode 100644
index 0000000000..238721475d
--- /dev/null
+++ b/spec/ruby/core/fiber/transfer_spec.rb
@@ -0,0 +1,84 @@
+require_relative '../../spec_helper'
+require_relative 'shared/resume'
+
+describe "Fiber#transfer" do
+  it_behaves_like :fiber_resume, :transfer
+end
+
+describe "Fiber#transfer" do
+  it "transfers control from one Fiber to another when called from a Fiber" do
+    fiber1 = Fiber.new { :fiber1 }
+    fiber2 = Fiber.new { fiber1.transfer; :fiber2 }
+    fiber2.resume.should == :fiber2
+  end
+
+  it "returns to the root Fiber when finished" do
+    f1 = Fiber.new { :fiber_1 }
+    f2 = Fiber.new { f1.transfer; :fiber_2 }
+
+    f2.transfer.should == :fiber_1
+    f2.transfer.should == :fiber_2
+  end
+
+  it "can be invoked from the same Fiber it transfers control to" do
+    states = []
+    fiber = Fiber.new { states << :start; fiber.transfer; states << :end }
+    fiber.transfer
+    states.should == [:start, :end]
+
+    states = []
+    fiber = Fiber.new { states << :start; fiber.transfer; states << :end }
+    fiber.resume
+    states.should == [:start, :end]
+  end
+
+  it "can not transfer control to a Fiber that has suspended by Fiber.yield" do
+    states = []
+    fiber1 = Fiber.new { states << :fiber1 }
+    fiber2 = Fiber.new { states << :fiber2_start; Fiber.yield fiber1.transfer; states << :fiber2_end}
+    fiber2.resume.should == [:fiber2_start, :fiber1]
+    -> { fiber2.transfer }.should raise_error(FiberError)
+  end
+
+  it "raises a FiberError when transferring to a Fiber which resumes itself" do
+    fiber = Fiber.new { fiber.resume }
+    -> { fiber.transfer }.should raise_error(FiberError)
+  end
+
+  it "works if Fibers in different Threads each transfer to a Fiber in the same Thread" do
+    # This catches a bug where Fibers are running on a thread-pool
+    # and Fibers from a different Ruby Thread reuse the same native thread.
+    # Caching the Ruby Thread based on the native thread is not correct in that case,
+    # and the check for "fiber called across threads" in Fiber#transfer
+    # might be incorrect based on that.
+    2.times do
+      Thread.new do
+        io_fiber = Fiber.new do |calling_fiber|
+          calling_fiber.transfer
+        end
+        io_fiber.transfer(Fiber.current)
+        value = Object.new
+        io_fiber.transfer(value).should equal value
+      end.join
+    end
+  end
+
+  it "transfers control between a non-main thread's root fiber to a child fiber and back again" do
+    states = []
+    thread = Thread.new do
+      f1 = Fiber.new do |f0|
+        states << 0
+        value2 = f0.transfer(1)
+        states << value2
+        3
+      end
+
+      value1 = f1.transfer(Fiber.current)
+      states << value1
+      value3 = f1.transfer(2)
+      states << value3
+    end
+    thread.join
+    states.should == [0, 1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/file/absolute_path_spec.rb b/spec/ruby/core/file/absolute_path_spec.rb
index 52839cf1cc..315eead34f 100644
--- a/spec/ruby/core/file/absolute_path_spec.rb
+++ b/spec/ruby/core/file/absolute_path_spec.rb
@@ -1,54 +1,52 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.7" do
-  describe "File.absolute_path?" do
-    before :each do
-      @abs = File.expand_path(__FILE__)
-    end
+describe "File.absolute_path?" do
+  before :each do
+    @abs = File.expand_path(__FILE__)
+  end
 
-    it "returns true if it's an absolute pathname" do
-      File.absolute_path?(@abs).should be_true
-    end
+  it "returns true if it's an absolute pathname" do
+    File.absolute_path?(@abs).should be_true
+  end
 
-    it "returns false if it's a relative path" do
-      File.absolute_path?(File.basename(__FILE__)).should be_false
-    end
+  it "returns false if it's a relative path" do
+    File.absolute_path?(File.basename(__FILE__)).should be_false
+  end
 
-    it "returns false if it's a tricky relative path" do
-      File.absolute_path?("C:foo\\bar").should be_false
-    end
+  it "returns false if it's a tricky relative path" do
+    File.absolute_path?("C:foo\\bar").should be_false
+  end
 
-    it "does not expand '~' to a home directory." do
-      File.absolute_path?('~').should be_false
-    end
+  it "does not expand '~' to a home directory." do
+    File.absolute_path?('~').should be_false
+  end
 
-    it "does not expand '~user' to a home directory." do
-      path = File.dirname(@abs)
-      Dir.chdir(path) do
-        File.absolute_path?('~user').should be_false
-      end
+  it "does not expand '~user' to a home directory." do
+    path = File.dirname(@abs)
+    Dir.chdir(path) do
+      File.absolute_path?('~user').should be_false
     end
+  end
 
-    it "calls #to_path on its argument" do
-      mock = mock_to_path(File.expand_path(__FILE__))
+  it "calls #to_path on its argument" do
+    mock = mock_to_path(File.expand_path(__FILE__))
 
-      File.absolute_path?(mock).should be_true
-    end
+    File.absolute_path?(mock).should be_true
+  end
 
-    platform_is_not :windows do
-      it "takes into consideration the platform's root" do
-        File.absolute_path?("C:\\foo\\bar").should be_false
-        File.absolute_path?("C:/foo/bar").should be_false
-        File.absolute_path?("/foo/bar\\baz").should be_true
-      end
+  platform_is_not :windows do
+    it "takes into consideration the platform's root" do
+      File.absolute_path?("C:\\foo\\bar").should be_false
+      File.absolute_path?("C:/foo/bar").should be_false
+      File.absolute_path?("/foo/bar\\baz").should be_true
     end
+  end
 
-    platform_is :windows do
-      it "takes into consideration the platform path separator(s)" do
-        File.absolute_path?("C:\\foo\\bar").should be_true
-        File.absolute_path?("C:/foo/bar").should be_true
-        File.absolute_path?("/foo/bar\\baz").should be_false
-      end
+  platform_is :windows do
+    it "takes into consideration the platform path separator(s)" do
+      File.absolute_path?("C:\\foo\\bar").should be_true
+      File.absolute_path?("C:/foo/bar").should be_true
+      File.absolute_path?("/foo/bar\\baz").should be_false
     end
   end
 end
@@ -73,6 +71,12 @@ describe "File.absolute_path" do
     File.absolute_path('~').should_not == File.expand_path('~')
   end
 
+  platform_is_not :windows do
+    it "does not expand '~' when given dir argument" do
+      File.absolute_path('~', '/').should == '/~'
+    end
+  end
+
   it "does not expand '~user' to a home directory." do
     path = File.dirname(@abs)
     Dir.chdir(path) do
@@ -81,7 +85,7 @@ describe "File.absolute_path" do
   end
 
   it "accepts a second argument of a directory from which to resolve the path" do
-    File.absolute_path(__FILE__, File.dirname(__FILE__)).should == @abs
+    File.absolute_path(__FILE__, __dir__).should == @abs
   end
 
   it "calls #to_path on its argument" do
diff --git a/spec/ruby/core/file/atime_spec.rb b/spec/ruby/core/file/atime_spec.rb
index 02e8412722..e47e70e5ac 100644
--- a/spec/ruby/core/file/atime_spec.rb
+++ b/spec/ruby/core/file/atime_spec.rb
@@ -15,16 +15,21 @@ describe "File.atime" do
     File.atime(@file).should be_kind_of(Time)
   end
 
-  guard -> { platform_is :linux or (platform_is :windows and ruby_version_is '2.5') } do
-    ## NOTE also that some Linux systems disable atime (e.g. via mount params) for better filesystem speed.
-    it "returns the last access time for the named file with microseconds" do
-      supports_subseconds = Integer(`stat -c%x '#{__FILE__}'`[/\.(\d+)/, 1], 10)
-      if supports_subseconds != 0
-        expected_time = Time.at(Time.now.to_i + 0.123456)
-        File.utime expected_time, 0, @file
-        File.atime(@file).usec.should == expected_time.usec
-      else
-        File.atime(__FILE__).usec.should == 0
+  platform_is :linux, :windows do
+    unless ENV.key?('TRAVIS') # https://bugs.ruby-lang.org/issues/17926
+      ## NOTE also that some Linux systems disable atime (e.g. via mount params) for better filesystem speed.
+      it "returns the last access time for the named file with microseconds" do
+        supports_subseconds = Integer(`stat -c%x '#{__FILE__}'`[/\.(\d{1,6})/, 1], 10)
+        if supports_subseconds != 0
+          expected_time = Time.at(Time.now.to_i + 0.123456)
+          File.utime expected_time, 0, @file
+          File.atime(@file).usec.should == expected_time.usec
+        else
+          File.atime(__FILE__).usec.should == 0
+        end
+      rescue Errno::ENOENT => e
+        # Native Windows don't have stat command.
+        skip e.message
       end
     end
   end
diff --git a/spec/ruby/core/file/basename_spec.rb b/spec/ruby/core/file/basename_spec.rb
index 6d7e432086..87695ab97b 100644
--- a/spec/ruby/core/file/basename_spec.rb
+++ b/spec/ruby/core/file/basename_spec.rb
@@ -151,8 +151,34 @@ describe "File.basename" do
       File.basename("c:\\bar.txt", ".*").should == "bar"
       File.basename("c:\\bar.txt.exe", ".*").should == "bar.txt"
     end
+
+    it "handles Shift JIS 0x5C (\\) as second byte of a multi-byte sequence" do
+      # dir\fileソname.txt
+      path = "dir\\file\x83\x5cname.txt".b.force_encoding(Encoding::SHIFT_JIS)
+      path.valid_encoding?.should be_true
+      File.basename(path).should == "file\x83\x5cname.txt".b.force_encoding(Encoding::SHIFT_JIS)
+    end
   end
 
+  it "rejects strings encoded with non ASCII-compatible encodings" do
+    Encoding.list.reject(&:ascii_compatible?).reject(&:dummy?).each do |enc|
+      begin
+        path = "/foo/bar".encode(enc)
+      rescue Encoding::ConverterNotFoundError
+        next
+      end
+
+      -> {
+        File.basename(path)
+      }.should raise_error(Encoding::CompatibilityError)
+    end
+  end
+
+  it "works with all ASCII-compatible encodings" do
+    Encoding.list.select(&:ascii_compatible?).each do |enc|
+      File.basename("/foo/bar".encode(enc)).should == "bar".encode(enc)
+    end
+  end
 
   it "returns the extension for a multibyte filename" do
     File.basename('/path/Офис.m4a').should == "Офис.m4a"
@@ -164,5 +190,20 @@ describe "File.basename" do
     basename.encoding.should == Encoding::Windows_1250
   end
 
+  it "returns a new unfrozen String" do
+    exts = [nil, '.rb', '.*', '.txt']
+    ['foo.rb','//', '/test/', 'test'].each do |example|
+      exts.each do |ext|
+        original = example.freeze
+        result = if ext
+                   File.basename(original, ext)
+                 else
+                   File.basename(original)
+                 end
+        result.should_not equal(original)
+        result.frozen?.should == false
+      end
+    end
+  end
 
 end
diff --git a/spec/ruby/core/file/birthtime_spec.rb b/spec/ruby/core/file/birthtime_spec.rb
index 755601df64..f82eaf7cca 100644
--- a/spec/ruby/core/file/birthtime_spec.rb
+++ b/spec/ruby/core/file/birthtime_spec.rb
@@ -1,60 +1,56 @@
 require_relative '../../spec_helper'
 
-describe "File.birthtime" do
-  before :each do
-    @file = __FILE__
-  end
+platform_is :windows, :darwin, :freebsd, :netbsd, :linux do
+  not_implemented_messages = [
+    "birthtime() function is unimplemented", # unsupported OS/version
+    "birthtime is unimplemented",            # unsupported filesystem
+  ]
+
+  describe "File.birthtime" do
+    before :each do
+      @file = __FILE__
+    end
 
-  after :each do
-    @file = nil
-  end
+    after :each do
+      @file = nil
+    end
 
-  platform_is :windows, :darwin, :freebsd, :netbsd do
     it "returns the birth time for the named file as a Time object" do
       File.birthtime(@file)
       File.birthtime(@file).should be_kind_of(Time)
+    rescue NotImplementedError => e
+      e.message.should.start_with?(*not_implemented_messages)
     end
 
     it "accepts an object that has a #to_path method" do
+      File.birthtime(@file) # Avoid to failure of mock object with old Kernel and glibc
       File.birthtime(mock_to_path(@file))
+    rescue NotImplementedError => e
+      e.message.should.start_with?(*not_implemented_messages)
     end
 
     it "raises an Errno::ENOENT exception if the file is not found" do
       -> { File.birthtime('bogus') }.should raise_error(Errno::ENOENT)
+    rescue NotImplementedError => e
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
 
-  platform_is :openbsd do
-    it "raises an NotImplementedError" do
-      -> { File.birthtime(@file) }.should raise_error(NotImplementedError)
+  describe "File#birthtime" do
+    before :each do
+      @file = File.open(__FILE__)
     end
-  end
-
-  # TODO: depends on Linux kernel version
-end
 
-describe "File#birthtime" do
-  before :each do
-    @file = File.open(__FILE__)
-  end
-
-  after :each do
-    @file.close
-    @file = nil
-  end
+    after :each do
+      @file.close
+      @file = nil
+    end
 
-  platform_is :windows, :darwin, :freebsd, :netbsd do
     it "returns the birth time for self" do
       @file.birthtime
       @file.birthtime.should be_kind_of(Time)
+    rescue NotImplementedError => e
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
-
-  platform_is :openbsd do
-    it "raises an NotImplementedError" do
-      -> { @file.birthtime }.should raise_error(NotImplementedError)
-    end
-  end
-
-  # TODO: depends on Linux kernel version
 end
diff --git a/spec/ruby/core/file/chmod_spec.rb b/spec/ruby/core/file/chmod_spec.rb
index 86171691f6..5ca15c9748 100644
--- a/spec/ruby/core/file/chmod_spec.rb
+++ b/spec/ruby/core/file/chmod_spec.rb
@@ -105,7 +105,7 @@ describe "File.chmod" do
     File.chmod(0, mock_to_path(@file))
   end
 
-  it "throws a TypeError if the given path is not coercable into a string" do
+  it "throws a TypeError if the given path is not coercible into a string" do
     -> { File.chmod(0, []) }.should raise_error(TypeError)
   end
 
diff --git a/spec/ruby/core/file/chown_spec.rb b/spec/ruby/core/file/chown_spec.rb
index 8cc8f0d04b..4db0e3712c 100644
--- a/spec/ruby/core/file/chown_spec.rb
+++ b/spec/ruby/core/file/chown_spec.rb
@@ -78,15 +78,15 @@ describe "File.chown" do
 end
 
 describe "File#chown" do
-    before :each do
-      @fname = tmp('file_chown_test')
-      @file = File.open(@fname, 'w')
-    end
+  before :each do
+    @fname = tmp('file_chown_test')
+    @file = File.open(@fname, 'w')
+  end
 
-    after :each do
-      @file.close unless @file.closed?
-      rm_r @fname
-    end
+  after :each do
+    @file.close unless @file.closed?
+    rm_r @fname
+  end
 
   as_superuser do
     platform_is :windows do
diff --git a/spec/ruby/core/file/constants/constants_spec.rb b/spec/ruby/core/file/constants/constants_spec.rb
index 86946822c5..bba248c21e 100644
--- a/spec/ruby/core/file/constants/constants_spec.rb
+++ b/spec/ruby/core/file/constants/constants_spec.rb
@@ -4,7 +4,7 @@ require_relative '../../../spec_helper'
   "FNM_DOTMATCH", "FNM_EXTGLOB", "FNM_NOESCAPE", "FNM_PATHNAME",
   "FNM_SYSCASE", "LOCK_EX", "LOCK_NB", "LOCK_SH",
   "LOCK_UN", "NONBLOCK", "RDONLY",
-  "RDWR", "TRUNC", "WRONLY"].each do |const|
+  "RDWR", "TRUNC", "WRONLY", "SHARE_DELETE"].each do |const|
   describe "File::Constants::#{const}" do
     it "is defined" do
       File::Constants.const_defined?(const).should be_true
diff --git a/spec/ruby/core/file/ctime_spec.rb b/spec/ruby/core/file/ctime_spec.rb
index 68a9fa43cb..718f26d5cc 100644
--- a/spec/ruby/core/file/ctime_spec.rb
+++ b/spec/ruby/core/file/ctime_spec.rb
@@ -14,14 +14,17 @@ describe "File.ctime" do
     File.ctime(@file).should be_kind_of(Time)
   end
 
-  guard -> { platform_is :linux or (platform_is :windows and ruby_version_is '2.5') } do
+  platform_is :linux, :windows do
     it "returns the change time for the named file (the time at which directory information about the file was changed, not the file itself) with microseconds." do
-      supports_subseconds = Integer(`stat -c%z '#{__FILE__}'`[/\.(\d+)/, 1], 10)
+      supports_subseconds = Integer(`stat -c%z '#{__FILE__}'`[/\.(\d{1,6})/, 1], 10)
       if supports_subseconds != 0
         File.ctime(__FILE__).usec.should > 0
       else
         File.ctime(__FILE__).usec.should == 0
       end
+    rescue Errno::ENOENT => e
+      # Windows don't have stat command.
+      skip e.message
     end
   end
 
diff --git a/spec/ruby/core/file/dirname_spec.rb b/spec/ruby/core/file/dirname_spec.rb
index 2ef04a7b64..8e6016ce6f 100644
--- a/spec/ruby/core/file/dirname_spec.rb
+++ b/spec/ruby/core/file/dirname_spec.rb
@@ -11,6 +11,35 @@ describe "File.dirname" do
     File.dirname('/foo/foo').should == '/foo'
   end
 
+  context "when level is passed" do
+    it "returns all the components of filename except the last parts by the level" do
+      File.dirname('/home/jason', 2).should == '/'
+      File.dirname('/home/jason/poot.txt', 2).should == '/home'
+    end
+
+    it "returns the same String if the level is 0" do
+      File.dirname('poot.txt', 0).should == 'poot.txt'
+      File.dirname('/', 0).should == '/'
+    end
+
+    it "raises ArgumentError if the level is negative" do
+      -> {
+        File.dirname('/home/jason', -1)
+      }.should raise_error(ArgumentError, "negative level: -1")
+    end
+
+    it "returns '/' when level exceeds the number of segments in the path" do
+      File.dirname("/home/jason", 100).should == '/'
+    end
+
+    it "calls #to_int if passed not numeric value" do
+      object = Object.new
+      def object.to_int; 2; end
+
+      File.dirname("/a/b/c/d", object).should == '/a/b'
+    end
+  end
+
   it "returns a String" do
     File.dirname("foo").should be_kind_of(String)
   end
@@ -34,19 +63,19 @@ describe "File.dirname" do
   end
 
   it "returns all the components of filename except the last one (edge cases on all platforms)" do
-      File.dirname("").should == "."
-      File.dirname(".").should == "."
-      File.dirname("./").should == "."
-      File.dirname("./b/./").should == "./b"
-      File.dirname("..").should == "."
-      File.dirname("../").should == "."
-      File.dirname("/").should == "/"
-      File.dirname("/.").should == "/"
-      File.dirname("/foo/").should == "/"
-      File.dirname("/foo/.").should == "/foo"
-      File.dirname("/foo/./").should == "/foo"
-      File.dirname("/foo/../.").should == "/foo/.."
-      File.dirname("foo/../").should == "foo"
+    File.dirname("").should == "."
+    File.dirname(".").should == "."
+    File.dirname("./").should == "."
+    File.dirname("./b/./").should == "./b"
+    File.dirname("..").should == "."
+    File.dirname("../").should == "."
+    File.dirname("/").should == "/"
+    File.dirname("/.").should == "/"
+    File.dirname("/foo/").should == "/"
+    File.dirname("/foo/.").should == "/foo"
+    File.dirname("/foo/./").should == "/foo"
+    File.dirname("/foo/../.").should == "/foo/.."
+    File.dirname("foo/../").should == "foo"
   end
 
   platform_is_not :windows do
diff --git a/spec/ruby/core/file/empty_spec.rb b/spec/ruby/core/file/empty_spec.rb
index 77f132303e..e8c9941676 100644
--- a/spec/ruby/core/file/empty_spec.rb
+++ b/spec/ruby/core/file/empty_spec.rb
@@ -4,10 +4,4 @@ require_relative '../../shared/file/zero'
 describe "File.empty?" do
   it_behaves_like :file_zero, :empty?, File
   it_behaves_like :file_zero_missing, :empty?, File
-
-  platform_is :solaris do
-    it "returns false for /dev/null" do
-      File.empty?('/dev/null').should == true
-    end
-  end
 end
diff --git a/spec/ruby/core/file/exist_spec.rb b/spec/ruby/core/file/exist_spec.rb
index ddb5febcba..b5600e5b07 100644
--- a/spec/ruby/core/file/exist_spec.rb
+++ b/spec/ruby/core/file/exist_spec.rb
@@ -4,3 +4,9 @@ require_relative '../../shared/file/exist'
 describe "File.exist?" do
   it_behaves_like :file_exist, :exist?, File
 end
+
+describe "File.exists?" do
+  it "has been removed" do
+    File.should_not.respond_to?(:exists?)
+  end
+end
diff --git a/spec/ruby/core/file/exists_spec.rb b/spec/ruby/core/file/exists_spec.rb
deleted file mode 100644
index 31d0e4dd1e..0000000000
--- a/spec/ruby/core/file/exists_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../../shared/file/exist'
-
-describe "File.exists?" do
-  it_behaves_like :file_exist, :exists?, File
-end
diff --git a/spec/ruby/core/file/expand_path_spec.rb b/spec/ruby/core/file/expand_path_spec.rb
index 88078645ab..1abcf93900 100644
--- a/spec/ruby/core/file/expand_path_spec.rb
+++ b/spec/ruby/core/file/expand_path_spec.rb
@@ -137,7 +137,7 @@ describe "File.expand_path" do
   it "returns a String in the same encoding as the argument" do
     Encoding.default_external = Encoding::SHIFT_JIS
 
-    path = "./a".force_encoding Encoding::CP1251
+    path = "./a".dup.force_encoding Encoding::CP1251
     File.expand_path(path).encoding.should equal(Encoding::CP1251)
 
     weird_path = [222, 173, 190, 175].pack('C*')
@@ -203,9 +203,9 @@ platform_is_not :windows do
 
     it "does not return a frozen string" do
       home = "/rubyspec_home"
-      File.expand_path('~').frozen?.should == false
-      File.expand_path('~', '/tmp/gumby/ddd').frozen?.should == false
-      File.expand_path('~/a', '/tmp/gumby/ddd').frozen?.should == false
+      File.expand_path('~').should_not.frozen?
+      File.expand_path('~', '/tmp/gumby/ddd').should_not.frozen?
+      File.expand_path('~/a', '/tmp/gumby/ddd').should_not.frozen?
     end
   end
 
diff --git a/spec/ruby/core/file/extname_spec.rb b/spec/ruby/core/file/extname_spec.rb
index 358690b44a..d20cf813d9 100644
--- a/spec/ruby/core/file/extname_spec.rb
+++ b/spec/ruby/core/file/extname_spec.rb
@@ -2,7 +2,7 @@
 require_relative '../../spec_helper'
 
 describe "File.extname" do
-  it "returns the extension (the portion of file name in path after the period)." do
+  it "returns the extension (the portion of file name in path after the period)" do
     File.extname("foo.rb").should == ".rb"
     File.extname("/foo/bar.rb").should == ".rb"
     File.extname("/foo.rb/bar.c").should == ".c"
@@ -12,7 +12,17 @@ describe "File.extname" do
     File.extname(".app.conf").should == ".conf"
   end
 
-  it "returns the extension (the portion of file name in path after the period).(edge cases)" do
+  it "returns unfrozen strings" do
+    File.extname("foo.rb").frozen?.should == false
+    File.extname("/foo/bar.rb").frozen?.should == false
+    File.extname("/foo.rb/bar.c").frozen?.should == false
+    File.extname("bar").frozen?.should == false
+    File.extname(".bashrc").frozen?.should == false
+    File.extname("/foo.bar/baz").frozen?.should == false
+    File.extname(".app.conf").frozen?.should == false
+  end
+
+  it "returns the extension for edge cases" do
     File.extname("").should ==  ""
     File.extname(".").should ==  ""
     File.extname("/").should ==  ""
@@ -20,8 +30,22 @@ describe "File.extname" do
     File.extname("..").should ==  ""
     File.extname("...").should ==  ""
     File.extname("....").should ==  ""
-    File.extname(".foo.").should ==  ""
-    File.extname("foo.").should ==  ""
+  end
+
+  describe "for a filename ending with a dot" do
+    platform_is :windows do
+      it "returns ''" do
+        File.extname(".foo.").should == ""
+        File.extname("foo.").should == ""
+      end
+    end
+
+    platform_is_not :windows do
+      it "returns '.'" do
+        File.extname(".foo.").should == "."
+        File.extname("foo.").should == "."
+      end
+    end
   end
 
   it "returns only the last extension of a file with several dots" do
diff --git a/spec/ruby/core/file/flock_spec.rb b/spec/ruby/core/file/flock_spec.rb
index 751e99d994..23ddf89ed8 100644
--- a/spec/ruby/core/file/flock_spec.rb
+++ b/spec/ruby/core/file/flock_spec.rb
@@ -30,7 +30,7 @@ describe "File#flock" do
   it "returns false if trying to lock an exclusively locked file" do
     @file.flock File::LOCK_EX
 
-    ruby_exe(<<-END_OF_CODE, escape: true).should == "false"
+    ruby_exe(<<-END_OF_CODE).should == "false"
       File.open('#{@name}', "w") do |f2|
         print f2.flock(File::LOCK_EX | File::LOCK_NB).to_s
       end
@@ -40,7 +40,7 @@ describe "File#flock" do
   it "blocks if trying to lock an exclusively locked file" do
     @file.flock File::LOCK_EX
 
-    out = ruby_exe(<<-END_OF_CODE, escape: true)
+    out = ruby_exe(<<-END_OF_CODE)
       running = false
 
       t = Thread.new do
@@ -72,35 +72,3 @@ describe "File#flock" do
     end
   end
 end
-
-platform_is :solaris do
-  describe "File#flock on Solaris" do
-    before :each do
-      @name = tmp("flock_test")
-      touch(@name)
-
-      @read_file = File.open @name, "r"
-      @write_file = File.open @name, "w"
-    end
-
-    after :each do
-      @read_file.flock File::LOCK_UN
-      @read_file.close
-      @write_file.flock File::LOCK_UN
-      @write_file.close
-      rm_r @name
-    end
-
-    it "fails with EBADF acquiring exclusive lock on read-only File" do
-      -> do
-        @read_file.flock File::LOCK_EX
-      end.should raise_error(Errno::EBADF)
-    end
-
-    it "fails with EBADF acquiring shared lock on read-only File" do
-      -> do
-        @write_file.flock File::LOCK_SH
-      end.should raise_error(Errno::EBADF)
-    end
-  end
-end
diff --git a/spec/ruby/core/file/ftype_spec.rb b/spec/ruby/core/file/ftype_spec.rb
index 20e9af7e5f..cdddc404dc 100644
--- a/spec/ruby/core/file/ftype_spec.rb
+++ b/spec/ruby/core/file/ftype_spec.rb
@@ -12,8 +12,9 @@ describe "File.ftype" do
   end
 
   it "raises Errno::ENOENT if the file is not valid" do
-    l = -> { File.ftype("/#{$$}#{Time.now.to_f}") }
-    l.should raise_error(Errno::ENOENT)
+    -> {
+      File.ftype("/#{$$}#{Time.now.to_f}")
+    }.should raise_error(Errno::ENOENT)
   end
 
   it "returns a String" do
@@ -34,6 +35,14 @@ describe "File.ftype" do
     end
   end
 
+  it "uses to_path to convert arguments" do
+    FileSpecs.normal_file do |file|
+      obj = mock('path')
+      obj.should_receive(:to_path).and_return(file)
+      File.ftype(obj).should == 'file'
+    end
+  end
+
   # Both FreeBSD and Windows does not have block devices
   platform_is_not :freebsd, :windows do
     with_block_device do
diff --git a/spec/ruby/core/file/join_spec.rb b/spec/ruby/core/file/join_spec.rb
index f1eab02de0..0feedbae93 100644
--- a/spec/ruby/core/file/join_spec.rb
+++ b/spec/ruby/core/file/join_spec.rb
@@ -136,4 +136,13 @@ describe "File.join" do
     File.join(bin).should == "bin"
     File.join("usr", bin).should == "usr/bin"
   end
+
+  it "raises errors for null bytes" do
+    -> { File.join("\x00x", "metadata.gz") }.should raise_error(ArgumentError) { |e|
+      e.message.should == 'string contains null byte'
+    }
+    -> { File.join("metadata.gz", "\x00x") }.should raise_error(ArgumentError) { |e|
+      e.message.should == 'string contains null byte'
+    }
+  end
 end
diff --git a/spec/ruby/core/file/lchmod_spec.rb b/spec/ruby/core/file/lchmod_spec.rb
index 9490459a02..3c44374983 100644
--- a/spec/ruby/core/file/lchmod_spec.rb
+++ b/spec/ruby/core/file/lchmod_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "File.lchmod" do
-  platform_is_not :linux, :windows, :openbsd, :solaris, :aix do
+  platform_is_not :linux, :windows, :openbsd, :aix do
     before :each do
       @fname = tmp('file_chmod_test')
       @lname = @fname + '.lnk'
@@ -20,23 +20,13 @@ describe "File.lchmod" do
       File.chmod(0222, @lname).should == 1
       File.lchmod(0755, @lname).should == 1
 
-      File.lstat(@lname).executable?.should == true
-      File.lstat(@lname).readable?.should == true
-      File.lstat(@lname).writable?.should == true
+      File.lstat(@lname).should.executable?
+      File.lstat(@lname).should.readable?
+      File.lstat(@lname).should.writable?
 
-      File.stat(@lname).executable?.should == false
-      File.stat(@lname).readable?.should == false
-      File.stat(@lname).writable?.should == true
-    end
-  end
-
-  platform_is :linux, :openbsd, :aix do
-    it "returns false from #respond_to?" do
-      File.respond_to?(:lchmod).should be_false
-    end
-
-    it "raises a NotImplementedError when called" do
-      -> { File.lchmod 0 }.should raise_error(NotImplementedError)
+      File.stat(@lname).should_not.executable?
+      File.stat(@lname).should_not.readable?
+      File.stat(@lname).should.writable?
     end
   end
 end
diff --git a/spec/ruby/core/file/link_spec.rb b/spec/ruby/core/file/link_spec.rb
index 11d4c8d25b..a5d5b4815f 100644
--- a/spec/ruby/core/file/link_spec.rb
+++ b/spec/ruby/core/file/link_spec.rb
@@ -13,10 +13,10 @@ describe "File.link" do
     rm_r @link, @file
   end
 
-  platform_is_not :windows do
+  platform_is_not :windows, :android do
     it "link a file with another" do
       File.link(@file, @link).should == 0
-      File.exist?(@link).should == true
+      File.should.exist?(@link)
       File.identical?(@file, @link).should == true
     end
 
diff --git a/spec/ruby/core/file/lstat_spec.rb b/spec/ruby/core/file/lstat_spec.rb
index 918ed02163..a5ea9d15a5 100644
--- a/spec/ruby/core/file/lstat_spec.rb
+++ b/spec/ruby/core/file/lstat_spec.rb
@@ -22,8 +22,8 @@ describe "File.lstat" do
     it "returns a File::Stat object with symlink properties for a symlink" do
       st = File.lstat(@link)
 
-      st.symlink?.should == true
-      st.file?.should == false
+      st.should.symlink?
+      st.should_not.file?
     end
   end
 end
diff --git a/spec/ruby/core/file/lutime_spec.rb b/spec/ruby/core/file/lutime_spec.rb
new file mode 100644
index 0000000000..0f6df42ea3
--- /dev/null
+++ b/spec/ruby/core/file/lutime_spec.rb
@@ -0,0 +1,43 @@
+require_relative '../../spec_helper'
+require_relative 'shared/update_time'
+
+platform_is_not :windows do
+  describe "File.lutime" do
+    it_behaves_like :update_time, :lutime
+  end
+
+  describe "File.lutime" do
+    before :each do
+      @atime = Time.utc(2000)
+      @mtime = Time.utc(2001)
+      @file = tmp("specs_lutime_file")
+      @symlink = tmp("specs_lutime_symlink")
+      touch @file
+      File.symlink(@file, @symlink)
+    end
+
+    after :each do
+      rm_r @file, @symlink
+    end
+
+    it "sets the access and modification time for a regular file" do
+      File.lutime(@atime, @mtime, @file)
+      stat = File.stat(@file)
+      stat.atime.should == @atime
+      stat.mtime.should === @mtime
+    end
+
+    it "sets the access and modification time for a symlink" do
+      original = File.stat(@file)
+
+      File.lutime(@atime, @mtime, @symlink)
+      stat = File.lstat(@symlink)
+      stat.atime.should == @atime
+      stat.mtime.should === @mtime
+
+      file = File.stat(@file)
+      file.atime.should == original.atime
+      file.mtime.should == original.mtime
+    end
+  end
+end
diff --git a/spec/ruby/core/file/mtime_spec.rb b/spec/ruby/core/file/mtime_spec.rb
index 1941e2ff85..0e9c95caee 100644
--- a/spec/ruby/core/file/mtime_spec.rb
+++ b/spec/ruby/core/file/mtime_spec.rb
@@ -15,15 +15,20 @@ describe "File.mtime" do
     File.mtime(@filename).should be_close(@mtime, TIME_TOLERANCE)
   end
 
-  guard -> { platform_is :linux or (platform_is :windows and ruby_version_is '2.5') } do
-    it "returns the modification Time of the file with microseconds" do
-      supports_subseconds = Integer(`stat -c%y '#{__FILE__}'`[/\.(\d+)/, 1], 10)
-      if supports_subseconds != 0
-        expected_time = Time.at(Time.now.to_i + 0.123456)
-        File.utime 0, expected_time, @filename
-        File.mtime(@filename).usec.should == expected_time.usec
-      else
-        File.mtime(__FILE__).usec.should == 0
+  platform_is :linux, :windows do
+    unless ENV.key?('TRAVIS') # https://bugs.ruby-lang.org/issues/17926
+      it "returns the modification Time of the file with microseconds" do
+        supports_subseconds = Integer(`stat -c%y '#{__FILE__}'`[/\.(\d{1,6})/, 1], 10)
+        if supports_subseconds != 0
+          expected_time = Time.at(Time.now.to_i + 0.123456)
+          File.utime 0, expected_time, @filename
+          File.mtime(@filename).usec.should == expected_time.usec
+        else
+          File.mtime(__FILE__).usec.should == 0
+        end
+      rescue Errno::ENOENT => e
+        # Windows don't have stat command.
+        skip e.message
       end
     end
   end
diff --git a/spec/ruby/core/file/new_spec.rb b/spec/ruby/core/file/new_spec.rb
index e99f6ba72b..1e82a070b1 100644
--- a/spec/ruby/core/file/new_spec.rb
+++ b/spec/ruby/core/file/new_spec.rb
@@ -17,13 +17,13 @@ describe "File.new" do
   it "returns a new File with mode string" do
     @fh = File.new(@file, 'w')
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "returns a new File with mode num" do
     @fh = File.new(@file, @flags)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "returns a new File with modus num and permissions" do
@@ -34,7 +34,7 @@ describe "File.new" do
     platform_is_not :windows do
       File.stat(@file).mode.to_s(8).should == "100744"
     end
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "creates the file and returns writable descriptor when called with 'w' mode and r-o permissions" do
@@ -48,7 +48,7 @@ describe "File.new" do
     ensure
       f.close
     end
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
     File.read(@file).should == "test\n"
   end
 
@@ -75,62 +75,123 @@ describe "File.new" do
     fh_copy = File.new(@fh.fileno)
     fh_copy.autoclose = false
     fh_copy.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
+  end
+
+  it "returns a new read-only File when mode is not specified" do
+    @fh = File.new(@file)
+
+    -> { @fh.puts("test") }.should raise_error(IOError)
+    @fh.read.should == ""
+    File.should.exist?(@file)
+  end
+
+  it "returns a new read-only File when mode is not specified but flags option is present" do
+    @fh = File.new(@file, flags: File::CREAT)
+
+    -> { @fh.puts("test") }.should raise_error(IOError)
+    @fh.read.should == ""
+    File.should.exist?(@file)
   end
 
   it "creates a new file when use File::EXCL mode" do
     @fh = File.new(@file, File::EXCL)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
-  it "raises an Errorno::EEXIST if the file exists when create a new file with File::CREAT|File::EXCL" do
+  it "raises an Errno::EEXIST if the file exists when create a new file with File::CREAT|File::EXCL" do
     -> { @fh = File.new(@file, File::CREAT|File::EXCL) }.should raise_error(Errno::EEXIST)
   end
 
   it "creates a new file when use File::WRONLY|File::APPEND mode" do
     @fh = File.new(@file, File::WRONLY|File::APPEND)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "returns a new File when use File::APPEND mode" do
     @fh = File.new(@file, File::APPEND)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "returns a new File when use File::RDONLY|File::APPEND mode" do
     @fh = File.new(@file, File::RDONLY|File::APPEND)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "returns a new File when use File::RDONLY|File::WRONLY mode" do
     @fh = File.new(@file, File::RDONLY|File::WRONLY)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
-
   it "creates a new file when use File::WRONLY|File::TRUNC mode" do
     @fh = File.new(@file, File::WRONLY|File::TRUNC)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
+  end
+
+  it "returns a new read-only File when use File::RDONLY|File::CREAT mode" do
+    @fh = File.new(@file, File::RDONLY|File::CREAT)
+    @fh.should be_kind_of(File)
+    File.should.exist?(@file)
+
+    # it's read-only
+    -> { @fh.puts("test") }.should raise_error(IOError)
+    @fh.read.should == ""
+  end
+
+  it "returns a new read-only File when use File::CREAT mode" do
+    @fh = File.new(@file, File::CREAT)
+    @fh.should be_kind_of(File)
+    File.should.exist?(@file)
+
+    # it's read-only
+    -> { @fh.puts("test") }.should raise_error(IOError)
+    @fh.read.should == ""
   end
 
   it "coerces filename using to_str" do
     name = mock("file")
     name.should_receive(:to_str).and_return(@file)
     @fh = File.new(name, "w")
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "coerces filename using #to_path" do
     name = mock("file")
     name.should_receive(:to_path).and_return(@file)
     @fh = File.new(name, "w")
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
+  end
+
+  it "accepts options as a keyword argument" do
+    @fh = File.new(@file, 'w', 0755, flags: @flags)
+    @fh.should be_kind_of(File)
+    @fh.close
+
+    -> {
+      @fh = File.new(@file, 'w', 0755, {flags: @flags})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 1..3)")
+  end
+
+  it "bitwise-ORs mode and flags option" do
+    -> {
+      @fh = File.new(@file, 'w', flags: File::EXCL)
+    }.should raise_error(Errno::EEXIST, /File exists/)
+
+    -> {
+      @fh = File.new(@file, mode: 'w', flags: File::EXCL)
+    }.should raise_error(Errno::EEXIST, /File exists/)
+  end
+
+  it "does not use the given block and warns to use File::open" do
+    -> {
+      @fh = File.new(@file) { raise }
+    }.should complain(/warning: File::new\(\) does not take block; use File::open\(\) instead/)
   end
 
   it "raises a TypeError if the first parameter can't be coerced to a string" do
diff --git a/spec/ruby/core/file/open_spec.rb b/spec/ruby/core/file/open_spec.rb
index d946fc5ecf..6bfc16bbf9 100644
--- a/spec/ruby/core/file/open_spec.rb
+++ b/spec/ruby/core/file/open_spec.rb
@@ -28,7 +28,7 @@ describe "File.open" do
   describe "with a block" do
     it "does not raise error when file is closed inside the block" do
       @fh = File.open(@file) { |fh| fh.close; fh }
-      @fh.closed?.should == true
+      @fh.should.closed?
     end
 
     it "invokes close on an opened file when exiting the block" do
@@ -63,40 +63,40 @@ describe "File.open" do
   it "opens the file (basic case)" do
     @fh = File.open(@file)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens the file with unicode characters" do
     @fh = File.open(@unicode_path, "w")
     @fh.should be_kind_of(File)
-    File.exist?(@unicode_path).should == true
+    File.should.exist?(@unicode_path)
   end
 
   it "opens a file when called with a block" do
     File.open(@file) { |fh| }
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens with mode string" do
     @fh = File.open(@file, 'w')
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file with mode string and block" do
     File.open(@file, 'w') { |fh| }
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file with mode num" do
     @fh = File.open(@file, @flags)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file with mode num and block" do
     File.open(@file, 'w') { |fh| }
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file with mode and permission as nil" do
@@ -113,7 +113,7 @@ describe "File.open" do
     platform_is_not :windows do
       @fh.lstat.mode.to_s(8).should == "100744"
     end
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   # For this test we delete the file first to reset the perms
@@ -124,7 +124,7 @@ describe "File.open" do
     platform_is_not :windows do
       File.stat(@file).mode.to_s(8).should == "100755"
     end
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "creates the file and returns writable descriptor when called with 'w' mode and r-o permissions" do
@@ -162,7 +162,7 @@ describe "File.open" do
     fh_copy = File.open(@fh.fileno)
     fh_copy.autoclose = false
     fh_copy.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file that no exists when use File::WRONLY mode" do
@@ -206,19 +206,19 @@ describe "File.open" do
   it "opens a file that no exists when use File::CREAT mode" do
     @fh = File.open(@nonexistent, File::CREAT) { |f| f }
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file that no exists when use 'a' mode" do
     @fh = File.open(@nonexistent, 'a') { |f| f }
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file that no exists when use 'w' mode" do
     @fh = File.open(@nonexistent, 'w') { |f| f }
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   # Check the grants associated to the different open modes combinations.
@@ -314,7 +314,7 @@ describe "File.open" do
     end
   end
 
-  it "raises an IOError when read in a block opened with File::RDONLY|File::APPEND mode" do
+  it "raises an IOError when write in a block opened with File::RDONLY|File::APPEND mode" do
     -> {
       File.open(@file, File::RDONLY|File::APPEND ) do |f|
         f.puts("writing")
@@ -354,7 +354,7 @@ describe "File.open" do
     end
   end
 
-  it "raises an Errorno::EEXIST if the file exists when open with File::CREAT|File::EXCL" do
+  it "raises an Errno::EEXIST if the file exists when open with File::CREAT|File::EXCL" do
     -> {
       File.open(@file, File::CREAT|File::EXCL) do |f|
         f.puts("writing")
@@ -365,7 +365,7 @@ describe "File.open" do
   it "creates a new file when use File::WRONLY|File::APPEND mode" do
     @fh = File.open(@file, File::WRONLY|File::APPEND)
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file when use File::WRONLY|File::APPEND mode" do
@@ -408,7 +408,7 @@ describe "File.open" do
     begin
       @fh = File.open(@file, File::WRONLY|File::TRUNC)
       @fh.should be_kind_of(File)
-      File.exist?(@file).should == true
+      File.should.exist?(@file)
     ensure
       fh1.close
     end
@@ -423,7 +423,7 @@ describe "File.open" do
       }.should raise_error(IOError)
     end
 
-    it "raises an Errorno::EEXIST if the file exists when open with File::RDONLY|File::TRUNC" do
+    it "raises an Errno::EEXIST if the file exists when open with File::RDONLY|File::TRUNC" do
       -> {
         File.open(@file, File::RDONLY|File::TRUNC) do |f|
           f.puts("writing").should == nil
@@ -441,7 +441,7 @@ describe "File.open" do
       }.should raise_error(Errno::EINVAL)
     end
 
-    it "raises an Errorno::EEXIST if the file exists when open with File::RDONLY|File::TRUNC" do
+    it "raises an Errno::EEXIST if the file exists when open with File::RDONLY|File::TRUNC" do
       -> {
         File.open(@file, File::RDONLY|File::TRUNC) do |f|
           f.puts("writing").should == nil
@@ -471,13 +471,13 @@ describe "File.open" do
   it "opens a file for binary read" do
     @fh = File.open(@file, "rb")
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file for binary write" do
     @fh = File.open(@file, "wb")
     @fh.should be_kind_of(File)
-    File.exist?(@file).should == true
+    File.should.exist?(@file)
   end
 
   it "opens a file for read-write and truncate the file" do
@@ -485,7 +485,7 @@ describe "File.open" do
     File.size(@file).should > 0
     File.open(@file, "w+") do |f|
       f.pos.should == 0
-      f.eof?.should == true
+      f.should.eof?
     end
     File.size(@file).should == 0
   end
@@ -494,8 +494,16 @@ describe "File.open" do
     File.open(@file, "w") { |f| f.puts "testing" }
     File.size(@file).should > 0
     File.open(@file, "rb+") do |f|
+      f.binmode?.should == true
+      f.external_encoding.should == Encoding::ASCII_8BIT
       f.pos.should == 0
-      f.eof?.should == false
+      f.should_not.eof?
+    end
+    File.open(@file, "r+b") do |f|
+      f.binmode?.should == true
+      f.external_encoding.should == Encoding::ASCII_8BIT
+      f.pos.should == 0
+      f.should_not.eof?
     end
   end
 
@@ -504,7 +512,7 @@ describe "File.open" do
     File.size(@file).should > 0
     File.open(@file, "wb+") do |f|
       f.pos.should == 0
-      f.eof?.should == true
+      f.should.eof?
     end
     File.size(@file).should == 0
   end
@@ -523,10 +531,10 @@ describe "File.open" do
             io.read.should == "ruby"
             Dir["#{dir}/*"].should == []
           end
-        rescue Errno::EOPNOTSUPP, Errno::EINVAL, Errno::EISDIR
-          # EOPNOTSUPP: no support from the filesystem
-          # EINVAL: presumably bug in glibc
-          1.should == 1
+        rescue Errno::EOPNOTSUPP
+          skip "no support from the filesystem"
+        rescue Errno::EINVAL, Errno::EISDIR
+          skip "presumably bug in glibc"
         ensure
           rm_r dir
         end
@@ -557,6 +565,15 @@ describe "File.open" do
     File.open(@file, 'wb+') {|f| f.external_encoding.should == Encoding::BINARY}
   end
 
+  it "accepts options as a keyword argument" do
+    @fh = File.open(@file, 'w', 0755, flags: File::CREAT)
+    @fh.should be_an_instance_of(File)
+
+    -> {
+      File.open(@file, 'w', 0755, {flags: File::CREAT})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 1..3)")
+  end
+
   it "uses the second argument as an options Hash" do
     @fh = File.open(@file, mode: "r")
     @fh.should be_an_instance_of(File)
@@ -566,7 +583,7 @@ describe "File.open" do
     options = mock("file open options")
     options.should_receive(:to_hash).and_return({ mode: "r" })
 
-    @fh = File.open(@file, options)
+    @fh = File.open(@file, **options)
   end
 
   it "accepts extra flags as a keyword argument and combine with a string mode" do
@@ -623,31 +640,35 @@ describe "File.open" do
     end
   end
 
-  ruby_version_is "2.6" do
-    context "'x' flag" do
-      before :each do
-        @xfile = tmp("x-flag")
-        rm_r @xfile
-      end
+  it "raises ArgumentError if mixing :newline and binary mode" do
+    -> {
+      File.open(@file, "rb", newline: :universal) {}
+    }.should raise_error(ArgumentError, "newline decorator with binary mode")
+  end
 
-      after :each do
-        rm_r @xfile
-      end
+  context "'x' flag" do
+    before :each do
+      @xfile = tmp("x-flag")
+      rm_r @xfile
+    end
 
-      it "does nothing if the file doesn't exist" do
-        File.open(@xfile, "wx") { |f| f.write("content") }
-        File.read(@xfile).should == "content"
-      end
+    after :each do
+      rm_r @xfile
+    end
 
-      it "throws a Errno::EEXIST error if the file exists" do
-        touch @xfile
-        -> { File.open(@xfile, "wx") }.should raise_error(Errno::EEXIST)
-      end
+    it "does nothing if the file doesn't exist" do
+      File.open(@xfile, "wx") { |f| f.write("content") }
+      File.read(@xfile).should == "content"
+    end
 
-      it "can't be used with 'r' and 'a' flags" do
-        -> { File.open(@xfile, "rx") }.should raise_error(ArgumentError, 'invalid access mode rx')
-        -> { File.open(@xfile, "ax") }.should raise_error(ArgumentError, 'invalid access mode ax')
-      end
+    it "throws a Errno::EEXIST error if the file exists" do
+      touch @xfile
+      -> { File.open(@xfile, "wx") }.should raise_error(Errno::EEXIST)
+    end
+
+    it "can't be used with 'r' and 'a' flags" do
+      -> { File.open(@xfile, "rx") }.should raise_error(ArgumentError, 'invalid access mode rx')
+      -> { File.open(@xfile, "ax") }.should raise_error(ArgumentError, 'invalid access mode ax')
     end
   end
 end
diff --git a/spec/ruby/core/file/path_spec.rb b/spec/ruby/core/file/path_spec.rb
index dfa0c4ec02..726febcc2b 100644
--- a/spec/ruby/core/file/path_spec.rb
+++ b/spec/ruby/core/file/path_spec.rb
@@ -37,4 +37,45 @@ describe "File.path" do
     path.should_receive(:to_path).and_return("abc")
     File.path(path).should == "abc"
   end
+
+  it "raises TypeError when #to_path result is not a string" do
+    path = mock("path")
+    path.should_receive(:to_path).and_return(nil)
+    -> { File.path(path) }.should raise_error TypeError
+
+    path = mock("path")
+    path.should_receive(:to_path).and_return(42)
+    -> { File.path(path) }.should raise_error TypeError
+  end
+
+  it "raises ArgumentError for string argument contains NUL character" do
+    -> { File.path("\0") }.should raise_error ArgumentError
+    -> { File.path("a\0") }.should raise_error ArgumentError
+    -> { File.path("a\0c") }.should raise_error ArgumentError
+  end
+
+  it "raises ArgumentError when #to_path result contains NUL character" do
+    path = mock("path")
+    path.should_receive(:to_path).and_return("\0")
+    -> { File.path(path) }.should raise_error ArgumentError
+
+    path = mock("path")
+    path.should_receive(:to_path).and_return("a\0")
+    -> { File.path(path) }.should raise_error ArgumentError
+
+    path = mock("path")
+    path.should_receive(:to_path).and_return("a\0c")
+    -> { File.path(path) }.should raise_error ArgumentError
+  end
+
+  it "raises Encoding::CompatibilityError for ASCII-incompatible string argument" do
+    path = "abc".encode(Encoding::UTF_32BE)
+    -> { File.path(path) }.should raise_error Encoding::CompatibilityError
+  end
+
+  it "raises Encoding::CompatibilityError when #to_path result is ASCII-incompatible" do
+    path = mock("path")
+    path.should_receive(:to_path).and_return("abc".encode(Encoding::UTF_32BE))
+    -> { File.path(path) }.should raise_error Encoding::CompatibilityError
+  end
 end
diff --git a/spec/ruby/core/file/readlink_spec.rb b/spec/ruby/core/file/readlink_spec.rb
index eb3bfda30e..20741ba121 100644
--- a/spec/ruby/core/file/readlink_spec.rb
+++ b/spec/ruby/core/file/readlink_spec.rb
@@ -26,7 +26,7 @@ describe "File.readlink" do
 
       it "raises an Errno::ENOENT if there is no such file" do
         # TODO: missing_file
-        -> { File.readlink("/this/surely/doesnt/exist") }.should raise_error(Errno::ENOENT)
+        -> { File.readlink("/this/surely/does/not/exist") }.should raise_error(Errno::ENOENT)
       end
 
       it "raises an Errno::EINVAL if called with a normal file" do
diff --git a/spec/ruby/core/file/realpath_spec.rb b/spec/ruby/core/file/realpath_spec.rb
index 0c5d19287a..bd25bfdecf 100644
--- a/spec/ruby/core/file/realpath_spec.rb
+++ b/spec/ruby/core/file/realpath_spec.rb
@@ -54,6 +54,10 @@ platform_is_not :windows do
       File.realpath(@relative_symlink).should == @file
     end
 
+    it "removes the file element when going one level up" do
+      File.realpath('../', @file).should == @real_dir
+    end
+
     it "raises an Errno::ELOOP if the symlink points to itself" do
       File.unlink @link
       File.symlink(@link, @link)
@@ -67,6 +71,12 @@ platform_is_not :windows do
     it "raises Errno::ENOENT if the symlink points to an absent file" do
       -> { File.realpath(@fake_link) }.should raise_error(Errno::ENOENT)
     end
+
+    it "converts the argument with #to_path" do
+      path = mock("path")
+      path.should_receive(:to_path).and_return(__FILE__)
+      File.realpath(path).should == File.realpath(__FILE__ )
+    end
   end
 end
 
diff --git a/spec/ruby/core/file/rename_spec.rb b/spec/ruby/core/file/rename_spec.rb
index d903e7a0d5..f2c18d4905 100644
--- a/spec/ruby/core/file/rename_spec.rb
+++ b/spec/ruby/core/file/rename_spec.rb
@@ -14,11 +14,11 @@ describe "File.rename" do
   end
 
   it "renames a file" do
-    File.exist?(@old).should == true
-    File.exist?(@new).should == false
+    File.should.exist?(@old)
+    File.should_not.exist?(@new)
     File.rename(@old, @new)
-    File.exist?(@old).should == false
-    File.exist?(@new).should == true
+    File.should_not.exist?(@old)
+    File.should.exist?(@new)
   end
 
   it "raises an Errno::ENOENT if the source does not exist" do
diff --git a/spec/ruby/core/file/setuid_spec.rb b/spec/ruby/core/file/setuid_spec.rb
index 281ef01ab9..9e5e86df61 100644
--- a/spec/ruby/core/file/setuid_spec.rb
+++ b/spec/ruby/core/file/setuid_spec.rb
@@ -26,10 +26,6 @@ describe "File.setuid?" do
 
   platform_is_not :windows do
     it "returns true when the gid bit is set" do
-      platform_is :solaris do
-        # Solaris requires execute bit before setting suid
-        system "chmod u+x #{@name}"
-      end
       system "chmod u+s #{@name}"
 
       File.setuid?(@name).should == true
diff --git a/spec/ruby/core/file/shared/fnmatch.rb b/spec/ruby/core/file/shared/fnmatch.rb
index a8488fd30a..db4b5c5d8c 100644
--- a/spec/ruby/core/file/shared/fnmatch.rb
+++ b/spec/ruby/core/file/shared/fnmatch.rb
@@ -75,6 +75,14 @@ describe :file_fnmatch, shared: true do
     File.send(@method, 'c*t', 'c/a/b/t').should == true
   end
 
+  it "does not match unterminated range of characters" do
+    File.send(@method, 'abc[de', 'abcd').should == false
+  end
+
+  it "does not match unterminated range of characters as a literal" do
+    File.send(@method, 'abc[de', 'abc[de').should == false
+  end
+
   it "matches ranges of characters using bracket expression (e.g. [a-z])" do
     File.send(@method, 'ca[a-z]', 'cat').should == true
   end
@@ -94,6 +102,7 @@ describe :file_fnmatch, shared: true do
 
   it "matches ranges of characters using exclusive bracket expression (e.g. [^t] or [!t])" do
     File.send(@method, 'ca[^t]', 'cat').should == false
+    File.send(@method, 'ca[^t]', 'cas').should == true
     File.send(@method, 'ca[!t]', 'cat').should == false
   end
 
@@ -117,6 +126,13 @@ describe :file_fnmatch, shared: true do
     end
   end
 
+  it "matches wildcard with characters when flags includes FNM_PATHNAME" do
+    File.send(@method, '*a', 'aa', File::FNM_PATHNAME).should == true
+    File.send(@method, 'a*', 'aa', File::FNM_PATHNAME).should == true
+    File.send(@method, 'a*', 'aaa', File::FNM_PATHNAME).should == true
+    File.send(@method, '*a', 'aaa', File::FNM_PATHNAME).should == true
+  end
+
   it "does not match '/' characters with ? or * when flags includes FNM_PATHNAME" do
     File.send(@method, '?', '/', File::FNM_PATHNAME).should == false
     File.send(@method, '*', '/', File::FNM_PATHNAME).should == false
@@ -151,15 +167,25 @@ describe :file_fnmatch, shared: true do
   end
 
   it "does not match leading periods in filenames with wildcards by default" do
-    File.send(@method, '*', '.profile').should == false
-    File.send(@method, '*', 'home/.profile').should == true
-    File.send(@method, '*/*', 'home/.profile').should == true
-    File.send(@method, '*/*', 'dave/.profile', File::FNM_PATHNAME).should == false
+    File.should_not.send(@method, '*', '.profile')
+    File.should.send(@method, '*', 'home/.profile')
+    File.should.send(@method, '*/*', 'home/.profile')
+    File.should_not.send(@method, '*/*', 'dave/.profile', File::FNM_PATHNAME)
   end
 
-  it "matches patterns with leading periods to dotfiles by default" do
+  it "matches patterns with leading periods to dotfiles" do
     File.send(@method, '.*', '.profile').should == true
+    File.send(@method, '.*', '.profile', File::FNM_PATHNAME).should == true
     File.send(@method, ".*file", "nondotfile").should == false
+    File.send(@method, ".*file", "nondotfile", File::FNM_PATHNAME).should == false
+  end
+
+  it "does not match directories with leading periods by default with FNM_PATHNAME" do
+    File.send(@method, '.*', '.directory/nondotfile', File::FNM_PATHNAME).should == false
+    File.send(@method, '.*', '.directory/.profile', File::FNM_PATHNAME).should == false
+    File.send(@method, '.*', 'foo/.directory/nondotfile', File::FNM_PATHNAME).should == false
+    File.send(@method, '.*', 'foo/.directory/.profile', File::FNM_PATHNAME).should == false
+    File.send(@method, '**/.dotfile', '.dotsubdir/.dotfile', File::FNM_PATHNAME).should == false
   end
 
   it "matches leading periods in filenames when flags includes FNM_DOTMATCH" do
@@ -213,6 +239,33 @@ describe :file_fnmatch, shared: true do
     File.send(@method, pattern, 'a/.b/c/foo', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
   end
 
+  it "has special handling for ./ when using * and FNM_PATHNAME" do
+    File.send(@method, './*', '.', File::FNM_PATHNAME).should be_false
+    File.send(@method, './*', './', File::FNM_PATHNAME).should be_true
+    File.send(@method, './*/', './', File::FNM_PATHNAME).should be_false
+    File.send(@method, './**', './', File::FNM_PATHNAME).should be_true
+    File.send(@method, './**/', './', File::FNM_PATHNAME).should be_true
+    File.send(@method, './*', '.', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_false
+    File.send(@method, './*', './', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+    File.send(@method, './*/', './', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_false
+    File.send(@method, './**', './', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+    File.send(@method, './**/', './', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+  end
+
+  it "matches **/* with FNM_PATHNAME to recurse directories" do
+    File.send(@method, 'nested/**/*', 'nested/subdir', File::FNM_PATHNAME).should be_true
+    File.send(@method, 'nested/**/*', 'nested/subdir/file', File::FNM_PATHNAME).should be_true
+    File.send(@method, 'nested/**/*', 'nested/.dotsubdir', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+    File.send(@method, 'nested/**/*', 'nested/.dotsubir/.dotfile', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+  end
+
+  it "matches ** with FNM_PATHNAME only in current directory" do
+    File.send(@method, 'nested/**', 'nested/subdir', File::FNM_PATHNAME).should be_true
+    File.send(@method, 'nested/**', 'nested/subdir/file', File::FNM_PATHNAME).should be_false
+    File.send(@method, 'nested/**', 'nested/.dotsubdir', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_true
+    File.send(@method, 'nested/**', 'nested/.dotsubir/.dotfile', File::FNM_PATHNAME | File::FNM_DOTMATCH).should be_false
+  end
+
   it "accepts an object that has a #to_path method" do
     File.send(@method, '\*', mock_to_path('a')).should == false
   end
diff --git a/spec/ruby/core/file/shared/path.rb b/spec/ruby/core/file/shared/path.rb
index 9df3416c89..5a9fe1b0c5 100644
--- a/spec/ruby/core/file/shared/path.rb
+++ b/spec/ruby/core/file/shared/path.rb
@@ -1,7 +1,7 @@
 describe :file_path, shared: true do
   before :each do
-    @name = "file_to_path"
-    @path = tmp(@name)
+    @path = tmp("file_to_path")
+    @name = File.basename(@path)
     touch @path
   end
 
@@ -15,6 +15,23 @@ describe :file_path, shared: true do
     @file.send(@method).should be_an_instance_of(String)
   end
 
+  it "returns a different String on every call" do
+    @file = File.new @path
+    path1 = @file.send(@method)
+    path2 = @file.send(@method)
+    path1.should == path2
+    path1.should_not.equal?(path2)
+  end
+
+  it "returns a mutable String" do
+    @file = File.new @path.dup.freeze
+    path = @file.send(@method)
+    path.should == @path
+    path.should_not.frozen?
+    path << "test"
+    @file.send(@method).should == @path
+  end
+
   it "calls to_str on argument and returns exact value" do
     path = mock('path')
     path.should_receive(:to_str).and_return(@path)
@@ -50,28 +67,15 @@ describe :file_path, shared: true do
     @file.send(@method).encoding.should == Encoding.find("euc-jp")
   end
 
-  ruby_version_is "2.5" do
-    platform_is :linux do
-      guard -> { defined?(File::TMPFILE) } do
-        before :each do
-          @dir = tmp("tmpfilespec")
-          mkdir_p @dir
-        end
-
-        after :each do
-          rm_r @dir
-        end
+  platform_is :linux do
+    guard -> { defined?(File::TMPFILE) } do
+      before :each do
+        @dir = tmp("tmpfilespec")
+        mkdir_p @dir
+      end
 
-        it "raises IOError if file was opened with File::TMPFILE" do
-          begin
-            File.open(@dir, File::RDWR | File::TMPFILE) do |f|
-              -> { f.send(@method) }.should raise_error(IOError)
-            end
-          rescue Errno::EOPNOTSUPP, Errno::EINVAL, Errno::EISDIR
-            # EOPNOTSUPP: no support from the filesystem
-            1.should == 1
-          end
-        end
+      after :each do
+        rm_r @dir
       end
     end
   end
diff --git a/spec/ruby/core/file/shared/read.rb b/spec/ruby/core/file/shared/read.rb
index a2d479966d..f232235298 100644
--- a/spec/ruby/core/file/shared/read.rb
+++ b/spec/ruby/core/file/shared/read.rb
@@ -1,13 +1,13 @@
 require_relative '../../dir/fixtures/common'
 
 describe :file_read_directory, shared: true do
-  platform_is :darwin, :linux, :openbsd, :windows do
+  platform_is :darwin, :linux, :freebsd, :openbsd, :windows do
     it "raises an Errno::EISDIR when passed a path that is a directory" do
       -> { @object.send(@method, ".") }.should raise_error(Errno::EISDIR)
     end
   end
 
-  platform_is :freebsd, :netbsd do
+  platform_is :netbsd do
     it "does not raises any exception when passed a path that is a directory" do
       -> { @object.send(@method, ".") }.should_not raise_error
     end
diff --git a/spec/ruby/core/file/shared/unlink.rb b/spec/ruby/core/file/shared/unlink.rb
index d72ab4701f..e339e93271 100644
--- a/spec/ruby/core/file/shared/unlink.rb
+++ b/spec/ruby/core/file/shared/unlink.rb
@@ -21,13 +21,13 @@ describe :file_unlink, shared: true do
 
   it "deletes a single file" do
     File.send(@method, @file1).should == 1
-    File.exist?(@file1).should == false
+    File.should_not.exist?(@file1)
   end
 
   it "deletes multiple files" do
     File.send(@method, @file1, @file2).should == 2
-    File.exist?(@file1).should == false
-    File.exist?(@file2).should == false
+    File.should_not.exist?(@file1)
+    File.should_not.exist?(@file2)
   end
 
   it "raises a TypeError if not passed a String type" do
@@ -52,10 +52,10 @@ describe :file_unlink, shared: true do
     it "allows deleting an open file with File::SHARE_DELETE" do
       path = tmp("share_delete.txt")
       File.open(path, mode: File::CREAT | File::WRONLY | File::BINARY | File::SHARE_DELETE) do |f|
-        File.exist?(path).should be_true
+        File.should.exist?(path)
         File.send(@method, path)
       end
-      File.exist?(path).should be_false
+      File.should_not.exist?(path)
     end
   end
 end
diff --git a/spec/ruby/core/file/shared/update_time.rb b/spec/ruby/core/file/shared/update_time.rb
new file mode 100644
index 0000000000..3fe7266a00
--- /dev/null
+++ b/spec/ruby/core/file/shared/update_time.rb
@@ -0,0 +1,105 @@
+describe :update_time, shared: true do
+  before :all do
+    @time_is_float = platform_is :windows
+  end
+
+  before :each do
+    @atime = Time.now
+    @mtime = Time.now
+    @file1 = tmp("specs_file_utime1")
+    @file2 = tmp("specs_file_utime2")
+    touch @file1
+    touch @file2
+  end
+
+  after :each do
+    rm_r @file1, @file2
+  end
+
+  it "sets the access and modification time of each file" do
+    File.send(@method, @atime, @mtime, @file1, @file2)
+
+    if @time_is_float
+      File.atime(@file1).should be_close(@atime, 0.0001)
+      File.mtime(@file1).should be_close(@mtime, 0.0001)
+      File.atime(@file2).should be_close(@atime, 0.0001)
+      File.mtime(@file2).should be_close(@mtime, 0.0001)
+    else
+      File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+      File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+      File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+      File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+    end
+  end
+
+  it "uses the current times if two nil values are passed" do
+    tn = Time.now
+    File.send(@method, nil, nil, @file1, @file2)
+
+    if @time_is_float
+      File.atime(@file1).should be_close(tn, 0.050)
+      File.mtime(@file1).should be_close(tn, 0.050)
+      File.atime(@file2).should be_close(tn, 0.050)
+      File.mtime(@file2).should be_close(tn, 0.050)
+    else
+      File.atime(@file1).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
+      File.mtime(@file1).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
+      File.atime(@file2).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
+      File.mtime(@file2).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
+    end
+  end
+
+  it "accepts an object that has a #to_path method" do
+    File.send(@method, @atime, @mtime, mock_to_path(@file1), mock_to_path(@file2))
+  end
+
+  it "accepts numeric atime and mtime arguments" do
+    if @time_is_float
+      File.send(@method, @atime.to_f, @mtime.to_f, @file1, @file2)
+
+      File.atime(@file1).should be_close(@atime, 0.0001)
+      File.mtime(@file1).should be_close(@mtime, 0.0001)
+      File.atime(@file2).should be_close(@atime, 0.0001)
+      File.mtime(@file2).should be_close(@mtime, 0.0001)
+    else
+      File.send(@method, @atime.to_i, @mtime.to_i, @file1, @file2)
+
+      File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+      File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+      File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+      File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+    end
+  end
+
+  it "may set nanosecond precision" do
+    t = Time.utc(2007, 11, 1, 15, 25, 0, 123456.789r)
+    File.send(@method, t, t, @file1)
+
+    File.atime(@file1).nsec.should.between?(0, 123500000)
+    File.mtime(@file1).nsec.should.between?(0, 123500000)
+  end
+
+  it "returns the number of filenames in the arguments" do
+    File.send(@method, @atime.to_f, @mtime.to_f, @file1, @file2).should == 2
+  end
+
+  platform_is :linux do
+    platform_is pointer_size: 64 do
+      it "allows Time instances in the far future to set mtime and atime (but some filesystems limit it up to 2446-05-10 or 2038-01-19 or 2486-07-02)" do
+        # https://ext4.wiki.kernel.org/index.php/Ext4_Disk_Layout#Inode_Timestamps
+        # "Therefore, timestamps should not overflow until May 2446."
+        # https://lwn.net/Articles/804382/
+        # "On-disk timestamps hitting the y2038 limit..."
+        # The problem seems to be being improved, but currently it actually fails on XFS on RHEL8
+        # https://rubyci.org/logs/rubyci.s3.amazonaws.com/rhel8/ruby-master/log/20201112T123004Z.fail.html.gz
+        # Amazon Linux 2023 returns 2486-07-02 in this example
+        # http://rubyci.s3.amazonaws.com/amazon2023/ruby-master/log/20230322T063004Z.fail.html.gz
+        time = Time.at(1<<44)
+        File.send(@method, time, time, @file1)
+
+        [559444, 2486, 2446, 2038].should.include? File.atime(@file1).year
+        [559444, 2486, 2446, 2038].should.include? File.mtime(@file1).year
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/file/size_spec.rb b/spec/ruby/core/file/size_spec.rb
index a2bf408da1..11d20cbacb 100644
--- a/spec/ruby/core/file/size_spec.rb
+++ b/spec/ruby/core/file/size_spec.rb
@@ -59,8 +59,8 @@ describe "File#size" do
     @file.respond_to?(:size).should be_true
   end
 
-  it "returns the file's size as a Fixnum" do
-    @file.size.should be_an_instance_of(Fixnum)
+  it "returns the file's size as an Integer" do
+    @file.size.should be_an_instance_of(Integer)
   end
 
   it "returns the file's size in bytes" do
diff --git a/spec/ruby/core/file/socket_spec.rb b/spec/ruby/core/file/socket_spec.rb
index 5d12e21f55..d3f4eb013a 100644
--- a/spec/ruby/core/file/socket_spec.rb
+++ b/spec/ruby/core/file/socket_spec.rb
@@ -1,42 +1,10 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/file/socket'
-require 'socket'
 
 describe "File.socket?" do
   it_behaves_like :file_socket, :socket?, File
-end
 
-describe "File.socket?" do
   it "returns false if file does not exist" do
     File.socket?("I_am_a_bogus_file").should == false
   end
-
-  it "returns false if the file is not a socket" do
-    filename = tmp("i_exist")
-    touch(filename)
-
-    File.socket?(filename).should == false
-
-    rm_r filename
-  end
-end
-
-platform_is_not :windows do
-  describe "File.socket?" do
-    before :each do
-      # We need a really short name here.
-      # On Linux the path length is limited to 107, see unix(7).
-      @name = tmp("s")
-      @server = UNIXServer.new @name
-    end
-
-    after :each do
-      @server.close
-      rm_r @name
-    end
-
-    it "returns true if the file is a socket" do
-      File.socket?(@name).should == true
-    end
-  end
 end
diff --git a/spec/ruby/core/file/stat/birthtime_spec.rb b/spec/ruby/core/file/stat/birthtime_spec.rb
index a727bbe566..9aa39297b2 100644
--- a/spec/ruby/core/file/stat/birthtime_spec.rb
+++ b/spec/ruby/core/file/stat/birthtime_spec.rb
@@ -1,27 +1,29 @@
 require_relative '../../../spec_helper'
 
-describe "File::Stat#birthtime" do
-  before :each do
-    @file = tmp('i_exist')
-    touch(@file) { |f| f.write "rubinius" }
-  end
+platform_is(:windows, :darwin, :freebsd, :netbsd,
+            *ruby_version_is("4.0") { :linux },
+           ) do
+  not_implemented_messages = [
+    "birthtime() function is unimplemented", # unsupported OS/version
+    "birthtime is unimplemented",            # unsupported filesystem
+  ]
 
-  after :each do
-    rm_r @file
-  end
+  describe "File::Stat#birthtime" do
+    before :each do
+      @file = tmp('i_exist')
+      touch(@file) { |f| f.write "rubinius" }
+    end
+
+    after :each do
+      rm_r @file
+    end
 
-  platform_is :windows, :darwin, :freebsd, :netbsd do
     it "returns the birthtime of a File::Stat object" do
       st = File.stat(@file)
       st.birthtime.should be_kind_of(Time)
       st.birthtime.should <= Time.now
-    end
-  end
-
-  platform_is :linux, :openbsd do
-    it "raises an NotImplementedError" do
-      st = File.stat(@file)
-      -> { st.birthtime }.should raise_error(NotImplementedError)
+    rescue NotImplementedError => e
+      e.message.should.start_with?(*not_implemented_messages)
     end
   end
 end
diff --git a/spec/ruby/core/file/stat/nlink_spec.rb b/spec/ruby/core/file/stat/nlink_spec.rb
index 2dd0bff124..7143923cfc 100644
--- a/spec/ruby/core/file/stat/nlink_spec.rb
+++ b/spec/ruby/core/file/stat/nlink_spec.rb
@@ -11,7 +11,7 @@ describe "File::Stat#nlink" do
     rm_r @link, @file
   end
 
-  platform_is_not :windows do
+  platform_is_not :windows, :android do
     it "returns the number of links to a file" do
       File::Stat.new(@file).nlink.should == 1
       File.link(@file, @link)
diff --git a/spec/ruby/core/file/stat/owned_spec.rb b/spec/ruby/core/file/stat/owned_spec.rb
index 6f0c250f88..a23ad850c5 100644
--- a/spec/ruby/core/file/stat/owned_spec.rb
+++ b/spec/ruby/core/file/stat/owned_spec.rb
@@ -18,15 +18,15 @@ describe "File::Stat#owned?" do
 
   it "returns true if the file is owned by the user" do
     st = File.stat(@file)
-    st.owned?.should == true
+    st.should.owned?
   end
 
-  platform_is_not :windows do
+  platform_is_not :windows, :android do
     as_user do
       it "returns false if the file is not owned by the user" do
         system_file = '/etc/passwd'
         st = File.stat(system_file)
-        st.owned?.should == false
+        st.should_not.owned?
       end
     end
   end
diff --git a/spec/ruby/core/file/stat/pipe_spec.rb b/spec/ruby/core/file/stat/pipe_spec.rb
index 7abb6c742a..692dfbf42a 100644
--- a/spec/ruby/core/file/stat/pipe_spec.rb
+++ b/spec/ruby/core/file/stat/pipe_spec.rb
@@ -12,7 +12,7 @@ describe "File::Stat#pipe?" do
     touch(filename)
 
     st = File.stat(filename)
-    st.pipe?.should == false
+    st.should_not.pipe?
 
     rm_r filename
   end
@@ -23,7 +23,7 @@ describe "File::Stat#pipe?" do
       File.mkfifo(filename)
 
       st = File.stat(filename)
-      st.pipe?.should == true
+      st.should.pipe?
 
       rm_r filename
     end
diff --git a/spec/ruby/core/file/stat/rdev_major_spec.rb b/spec/ruby/core/file/stat/rdev_major_spec.rb
index f8a8d1b107..e08d19c03a 100644
--- a/spec/ruby/core/file/stat/rdev_major_spec.rb
+++ b/spec/ruby/core/file/stat/rdev_major_spec.rb
@@ -2,19 +2,12 @@ require_relative '../../../spec_helper'
 
 describe "File::Stat#rdev_major" do
   before :each do
-    platform_is :solaris do
-      @name = "/dev/zfs"
-    end
-    platform_is_not :solaris do
-      @name = tmp("file.txt")
-      touch(@name)
-    end
+    @name = tmp("file.txt")
+    touch(@name)
   end
 
   after :each do
-    platform_is_not :solaris do
-      rm_r @name
-    end
+    rm_r @name
   end
 
   platform_is_not :windows do
diff --git a/spec/ruby/core/file/stat/rdev_minor_spec.rb b/spec/ruby/core/file/stat/rdev_minor_spec.rb
index dc30c1f56c..ace5b8a732 100644
--- a/spec/ruby/core/file/stat/rdev_minor_spec.rb
+++ b/spec/ruby/core/file/stat/rdev_minor_spec.rb
@@ -2,19 +2,12 @@ require_relative '../../../spec_helper'
 
 describe "File::Stat#rdev_minor" do
   before :each do
-    platform_is :solaris do
-      @name = "/dev/zfs"
-    end
-    platform_is_not :solaris do
-      @name = tmp("file.txt")
-      touch(@name)
-    end
+    @name = tmp("file.txt")
+    touch(@name)
   end
 
   after :each do
-    platform_is_not :solaris do
-      rm_r @name
-    end
+    rm_r @name
   end
 
   platform_is_not :windows do
diff --git a/spec/ruby/core/file/stat_spec.rb b/spec/ruby/core/file/stat_spec.rb
index 31f9dc58af..6365500057 100644
--- a/spec/ruby/core/file/stat_spec.rb
+++ b/spec/ruby/core/file/stat_spec.rb
@@ -23,8 +23,8 @@ platform_is_not :windows do
 
         st = f.stat
 
-        st.file?.should == true
-        st.zero?.should == false
+        st.should.file?
+        st.should_not.zero?
         st.size.should == 8
         st.size?.should == 8
         st.blksize.should >= 0
@@ -38,8 +38,18 @@ platform_is_not :windows do
       File.symlink(@file, @link)
       st = File.stat(@link)
 
-      st.file?.should == true
-      st.symlink?.should == false
+      st.should.file?
+      st.should_not.symlink?
+    end
+
+    it "returns an error when given missing non-ASCII path" do
+      missing_path = "/missingfilepath\xE3E4".b
+      -> {
+        File.stat(missing_path)
+      }.should raise_error(SystemCallError) { |e|
+        [Errno::ENOENT, Errno::EILSEQ].should include(e.class)
+        e.message.should include(missing_path)
+      }
     end
   end
 end
diff --git a/spec/ruby/core/file/truncate_spec.rb b/spec/ruby/core/file/truncate_spec.rb
index 43b86b7382..b4a2e3e577 100644
--- a/spec/ruby/core/file/truncate_spec.rb
+++ b/spec/ruby/core/file/truncate_spec.rb
@@ -18,7 +18,7 @@ describe "File.truncate" do
 
     File.open(@name, "r") do |f|
       f.read(99).should == "12345"
-      f.eof?.should == true
+      f.should.eof?
     end
   end
 
@@ -120,7 +120,7 @@ describe "File#truncate" do
     File.size(@name).should == 5
     File.open(@name, "r") do |f|
       f.read(99).should == "12345"
-      f.eof?.should == true
+      f.should.eof?
     end
   end
 
@@ -161,7 +161,7 @@ describe "File#truncate" do
 
   it "raises an IOError if file is closed" do
     @file.close
-    @file.closed?.should == true
+    @file.should.closed?
     -> { @file.truncate(42) }.should raise_error(IOError)
   end
 
diff --git a/spec/ruby/core/file/umask_spec.rb b/spec/ruby/core/file/umask_spec.rb
index 2640e3c316..7f7e40abbc 100644
--- a/spec/ruby/core/file/umask_spec.rb
+++ b/spec/ruby/core/file/umask_spec.rb
@@ -12,8 +12,8 @@ describe "File.umask" do
     File.umask(@orig_umask)
   end
 
-  it "returns a Fixnum" do
-    File.umask.should be_kind_of(Fixnum)
+  it "returns an Integer" do
+    File.umask.should be_kind_of(Integer)
   end
 
   platform_is_not :windows do
diff --git a/spec/ruby/core/file/utime_spec.rb b/spec/ruby/core/file/utime_spec.rb
index 03adc76efe..d87626be50 100644
--- a/spec/ruby/core/file/utime_spec.rb
+++ b/spec/ruby/core/file/utime_spec.rb
@@ -1,83 +1,6 @@
 require_relative '../../spec_helper'
+require_relative 'shared/update_time'
 
 describe "File.utime" do
-
-  before :all do
-    @time_is_float = /mswin|mingw/ =~ RUBY_PLATFORM && RUBY_VERSION >= '2.5'
-  end
-
-  before :each do
-    @atime = Time.now
-    @mtime = Time.now
-    @file1 = tmp("specs_file_utime1")
-    @file2 = tmp("specs_file_utime2")
-    touch @file1
-    touch @file2
-  end
-
-  after :each do
-    rm_r @file1, @file2
-  end
-
-  it "sets the access and modification time of each file" do
-    File.utime(@atime, @mtime, @file1, @file2)
-    if @time_is_float
-      File.atime(@file1).should be_close(@atime, 0.0001)
-      File.mtime(@file1).should be_close(@mtime, 0.0001)
-      File.atime(@file2).should be_close(@atime, 0.0001)
-      File.mtime(@file2).should be_close(@mtime, 0.0001)
-    else
-      File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
-      File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
-    end
-  end
-
-  it "uses the current times if two nil values are passed" do
-    tn = Time.now
-    File.utime(nil, nil, @file1, @file2)
-    if @time_is_float
-      File.atime(@file1).should be_close(tn, 0.050)
-      File.mtime(@file1).should be_close(tn, 0.050)
-      File.atime(@file2).should be_close(tn, 0.050)
-      File.mtime(@file2).should be_close(tn, 0.050)
-    else
-      File.atime(@file1).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
-      File.mtime(@file1).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
-      File.atime(@file2).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
-      File.mtime(@file2).to_i.should be_close(Time.now.to_i, TIME_TOLERANCE)
-    end
-  end
-
-  it "accepts an object that has a #to_path method" do
-    File.utime(@atime, @mtime, mock_to_path(@file1), mock_to_path(@file2))
-  end
-
-  it "accepts numeric atime and mtime arguments" do
-    if @time_is_float
-      File.utime(@atime.to_f, @mtime.to_f, @file1, @file2)
-      File.atime(@file1).should be_close(@atime, 0.0001)
-      File.mtime(@file1).should be_close(@mtime, 0.0001)
-      File.atime(@file2).should be_close(@atime, 0.0001)
-      File.mtime(@file2).should be_close(@mtime, 0.0001)
-    else
-      File.utime(@atime.to_i, @mtime.to_i, @file1, @file2)
-      File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
-      File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
-    end
-  end
-
-  platform_is :linux do
-    platform_is wordsize: 64 do
-      it "allows Time instances in the far future to set mtime and atime" do
-        time = Time.at(1<<44)
-        File.utime(time, time, @file1)
-        File.atime(@file1).year.should == 559444
-        File.mtime(@file1).year.should == 559444
-      end
-    end
-  end
+  it_behaves_like :update_time, :utime
 end
diff --git a/spec/ruby/core/file/world_readable_spec.rb b/spec/ruby/core/file/world_readable_spec.rb
index 7e6c60b65c..11b8e67d0b 100644
--- a/spec/ruby/core/file/world_readable_spec.rb
+++ b/spec/ruby/core/file/world_readable_spec.rb
@@ -6,7 +6,7 @@ describe "File.world_readable?" do
 
   it "returns nil if the file does not exist" do
     file = rand.to_s + $$.to_s
-    File.exist?(file).should be_false
+    File.should_not.exist?(file)
     File.world_readable?(file).should be_nil
   end
 end
diff --git a/spec/ruby/core/file/world_writable_spec.rb b/spec/ruby/core/file/world_writable_spec.rb
index 00333a98ab..d378cf2eb9 100644
--- a/spec/ruby/core/file/world_writable_spec.rb
+++ b/spec/ruby/core/file/world_writable_spec.rb
@@ -6,7 +6,7 @@ describe "File.world_writable?" do
 
   it "returns nil if the file does not exist" do
     file = rand.to_s + $$.to_s
-    File.exist?(file).should be_false
+    File.should_not.exist?(file)
     File.world_writable?(file).should be_nil
   end
 end
diff --git a/spec/ruby/core/file/zero_spec.rb b/spec/ruby/core/file/zero_spec.rb
index 63dd85ee46..01c7505ef2 100644
--- a/spec/ruby/core/file/zero_spec.rb
+++ b/spec/ruby/core/file/zero_spec.rb
@@ -4,10 +4,4 @@ require_relative '../../shared/file/zero'
 describe "File.zero?" do
   it_behaves_like :file_zero, :zero?, File
   it_behaves_like :file_zero_missing, :zero?, File
-
-  platform_is :solaris do
-    it "returns false for /dev/null" do
-      File.zero?('/dev/null').should == true
-    end
-  end
 end
diff --git a/spec/ruby/core/filetest/exist_spec.rb b/spec/ruby/core/filetest/exist_spec.rb
index 4d14bea231..612ffa9fcb 100644
--- a/spec/ruby/core/filetest/exist_spec.rb
+++ b/spec/ruby/core/filetest/exist_spec.rb
@@ -4,3 +4,9 @@ require_relative '../../shared/file/exist'
 describe "FileTest.exist?" do
   it_behaves_like :file_exist, :exist?, FileTest
 end
+
+describe "FileTest.exists?" do
+  it "has been removed" do
+    FileTest.should_not.respond_to?(:exists?)
+  end
+end
diff --git a/spec/ruby/core/filetest/exists_spec.rb b/spec/ruby/core/filetest/exists_spec.rb
deleted file mode 100644
index d090d7d740..0000000000
--- a/spec/ruby/core/filetest/exists_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../../shared/file/exist'
-
-describe "FileTest.exists?" do
-  it_behaves_like :file_exist, :exists?, FileTest
-end
diff --git a/spec/ruby/core/filetest/socket_spec.rb b/spec/ruby/core/filetest/socket_spec.rb
index 63a6a31ecb..f274be6318 100644
--- a/spec/ruby/core/filetest/socket_spec.rb
+++ b/spec/ruby/core/filetest/socket_spec.rb
@@ -3,4 +3,8 @@ require_relative '../../shared/file/socket'
 
 describe "FileTest.socket?" do
   it_behaves_like :file_socket, :socket?, FileTest
+
+  it "returns false if file does not exist" do
+    FileTest.socket?("I_am_a_bogus_file").should == false
+  end
 end
diff --git a/spec/ruby/core/filetest/zero_spec.rb b/spec/ruby/core/filetest/zero_spec.rb
index dd6a164ec9..92cab67f1b 100644
--- a/spec/ruby/core/filetest/zero_spec.rb
+++ b/spec/ruby/core/filetest/zero_spec.rb
@@ -4,10 +4,4 @@ require_relative '../../shared/file/zero'
 describe "FileTest.zero?" do
   it_behaves_like :file_zero, :zero?, FileTest
   it_behaves_like :file_zero_missing, :zero?, FileTest
-
-  platform_is :solaris do
-    it "returns false for /dev/null" do
-      File.zero?('/dev/null').should == true
-    end
-  end
 end
diff --git a/spec/ruby/core/float/ceil_spec.rb b/spec/ruby/core/float/ceil_spec.rb
index 7fc18d304c..75f5610292 100644
--- a/spec/ruby/core/float/ceil_spec.rb
+++ b/spec/ruby/core/float/ceil_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
+require_relative '../integer/shared/integer_ceil_precision'
 
 describe "Float#ceil" do
+  context "with precision" do
+    it_behaves_like :integer_ceil_precision, :Float
+  end
+
   it "returns the smallest Integer greater than or equal to self" do
     -1.2.ceil.should eql( -1)
     -1.0.ceil.should eql( -1)
diff --git a/spec/ruby/core/float/coerce_spec.rb b/spec/ruby/core/float/coerce_spec.rb
index ea108f3303..baa831dcf6 100644
--- a/spec/ruby/core/float/coerce_spec.rb
+++ b/spec/ruby/core/float/coerce_spec.rb
@@ -9,10 +9,10 @@ describe "Float#coerce" do
     1.0.coerce(3.14).should == [3.14, 1.0]
 
     a, b = -0.0.coerce(bignum_value)
-    a.should be_close(9223372036854775808.0, TOLERANCE)
+    a.should be_close(18446744073709551616.0, TOLERANCE)
     b.should be_close(-0.0, TOLERANCE)
     a, b = 1.0.coerce(bignum_value)
-    a.should be_close(9223372036854775808.0, TOLERANCE)
+    a.should be_close(18446744073709551616.0, TOLERANCE)
     b.should be_close(1.0, TOLERANCE)
   end
 end
diff --git a/spec/ruby/core/float/comparison_spec.rb b/spec/ruby/core/float/comparison_spec.rb
index 4205d95c83..0cd290f4ad 100644
--- a/spec/ruby/core/float/comparison_spec.rb
+++ b/spec/ruby/core/float/comparison_spec.rb
@@ -7,30 +7,107 @@ describe "Float#<=>" do
     ((bignum_value*1.1) <=> bignum_value).should == 1
   end
 
-  it "returns nil when either argument is NaN" do
-    (nan_value <=> 71.2).should be_nil
-    (1771.176 <=> nan_value).should be_nil
+  it "returns nil if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value <=> n).should == nil
+      (n <=> nan_value).should == nil
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value <=> n).should == 1
+      (n <=> infinity_value).should == -1
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value <=> n).should == -1
+      (n <=> -infinity_value).should == 1
+    }
   end
 
   it "returns nil when the given argument is not a Float" do
     (1.0 <=> "1").should be_nil
+    (1.0 <=> "1".freeze).should be_nil
+    (1.0 <=> :one).should be_nil
+    (1.0 <=> true).should be_nil
   end
 
-  # The 4 tests below are taken from matz's revision 23730 for Ruby trunk
-  #
-  it "returns 1 when self is Infinity and other is a Bignum" do
-    (infinity_value <=> Float::MAX.to_i*2).should == 1
+  it "compares using #coerce when argument is not a Float" do
+    klass = Class.new do
+      attr_reader :call_count
+      def coerce(other)
+        @call_count ||= 0
+        @call_count += 1
+        [other, 42.0]
+      end
+    end
+
+    coercible = klass.new
+    (2.33 <=> coercible).should == -1
+    (42.0 <=> coercible).should == 0
+    (43.0 <=> coercible).should == 1
+    coercible.call_count.should == 3
   end
 
-  it "returns -1 when self is negative and other is Infinity" do
-    (-Float::MAX.to_i*2 <=> infinity_value).should == -1
+  it "raises TypeError when #coerce misbehaves" do
+    klass = Class.new do
+      def coerce(other)
+        :incorrect
+      end
+    end
+
+    bad_coercible = klass.new
+    -> {
+      4.2 <=> bad_coercible
+    }.should raise_error(TypeError, "coerce must return [x, y]")
   end
 
-  it "returns -1 when self is -Infinity and other is negative" do
+  it "returns the correct result when one side is infinite" do
+    (infinity_value <=> Float::MAX.to_i*2).should == 1
+    (-Float::MAX.to_i*2 <=> infinity_value).should == -1
     (-infinity_value <=> -Float::MAX.to_i*2).should == -1
+    (-Float::MAX.to_i*2 <=> -infinity_value).should == 1
   end
 
-  it "returns 1 when self is negative and other is -Infinity" do
-    (-Float::MAX.to_i*2 <=> -infinity_value).should == 1
+  it "returns 0 when self is Infinity and other is infinite?=1" do
+    obj = Object.new
+    def obj.infinite?
+      1
+    end
+    (infinity_value <=> obj).should == 0
+  end
+
+  it "returns 1 when self is Infinity and other is infinite?=-1" do
+    obj = Object.new
+    def obj.infinite?
+      -1
+    end
+    (infinity_value <=> obj).should == 1
+  end
+
+  it "returns 1 when self is Infinity and other is infinite?=nil (which means finite)" do
+    obj = Object.new
+    def obj.infinite?
+      nil
+    end
+    (infinity_value <=> obj).should == 1
+  end
+
+  it "returns 0 for -0.0 and 0.0" do
+    (-0.0 <=> 0.0).should == 0
+    (0.0 <=> -0.0).should == 0
+  end
+
+  it "returns 0 for -0.0 and 0" do
+    (-0.0 <=> 0).should == 0
+    (0 <=> -0.0).should == 0
+  end
+
+  it "returns 0 for 0.0 and 0" do
+    (0.0 <=> 0).should == 0
+    (0 <=> 0.0).should == 0
   end
 end
diff --git a/spec/ruby/core/float/divide_spec.rb b/spec/ruby/core/float/divide_spec.rb
index d8f71a6b98..72ab7527bd 100644
--- a/spec/ruby/core/float/divide_spec.rb
+++ b/spec/ruby/core/float/divide_spec.rb
@@ -36,4 +36,8 @@ describe "Float#/" do
     -> { 13.0 / "10"    }.should raise_error(TypeError)
     -> { 13.0 / :symbol }.should raise_error(TypeError)
   end
+
+  it "divides correctly by Rational numbers" do
+    (1.2345678901234567 / Rational(1, 10000000000000000000)).should == 1.2345678901234567e+19
+  end
 end
diff --git a/spec/ruby/core/float/divmod_spec.rb b/spec/ruby/core/float/divmod_spec.rb
index ec55dd3681..dad45a9b89 100644
--- a/spec/ruby/core/float/divmod_spec.rb
+++ b/spec/ruby/core/float/divmod_spec.rb
@@ -10,7 +10,7 @@ describe "Float#divmod" do
     values[1].should be_close(2.8284, TOLERANCE)
     values = -1.0.divmod(bignum_value)
     values[0].should eql(-1)
-    values[1].should be_close(9223372036854775808.000, TOLERANCE)
+    values[1].should be_close(18446744073709551616.0, TOLERANCE)
     values = -1.0.divmod(1)
     values[0].should eql(-1)
     values[1].should eql(0.0)
@@ -23,7 +23,7 @@ describe "Float#divmod" do
 
   # Behaviour established as correct in r23953
   it "raises a FloatDomainError if other is NaN" do
-    -> { 1.divmod(nan_value) }.should raise_error(FloatDomainError)
+    -> { 1.0.divmod(nan_value) }.should raise_error(FloatDomainError)
   end
 
   # Behaviour established as correct in r23953
diff --git a/spec/ruby/core/float/finite_spec.rb b/spec/ruby/core/float/finite_spec.rb
index c5fb3df849..d839b30e32 100644
--- a/spec/ruby/core/float/finite_spec.rb
+++ b/spec/ruby/core/float/finite_spec.rb
@@ -2,18 +2,18 @@ require_relative '../../spec_helper'
 
 describe "Float#finite?" do
   it "returns true for finite values" do
-    3.14159.finite?.should == true
+    3.14159.should.finite?
   end
 
   it "returns false for positive infinity" do
-    infinity_value.finite?.should == false
+    infinity_value.should_not.finite?
   end
 
   it "returns false for negative infinity" do
-    (-infinity_value).finite?.should == false
+    (-infinity_value).should_not.finite?
   end
 
   it "returns false for NaN" do
-    nan_value.finite?.should == false
+    nan_value.should_not.finite?
   end
 end
diff --git a/spec/ruby/core/float/floor_spec.rb b/spec/ruby/core/float/floor_spec.rb
index 046216d36d..8b492ef473 100644
--- a/spec/ruby/core/float/floor_spec.rb
+++ b/spec/ruby/core/float/floor_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
+require_relative '../integer/shared/integer_floor_precision'
 
 describe "Float#floor" do
+  context "with precision" do
+    it_behaves_like :integer_floor_precision, :Float
+  end
+
   it "returns the largest Integer less than or equal to self" do
     -1.2.floor.should eql( -2)
     -1.0.floor.should eql( -1)
diff --git a/spec/ruby/core/float/gt_spec.rb b/spec/ruby/core/float/gt_spec.rb
index 0d73f1c3df..33078e07ce 100644
--- a/spec/ruby/core/float/gt_spec.rb
+++ b/spec/ruby/core/float/gt_spec.rb
@@ -14,4 +14,25 @@ describe "Float#>" do
     -> { 5.0 > "4"       }.should raise_error(ArgumentError)
     -> { 5.0 > mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value > n).should == false
+      (n > nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value > n).should == true
+      (n > infinity_value).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value > n).should == false
+      (n > -infinity_value).should == true
+    }
+  end
 end
diff --git a/spec/ruby/core/float/gte_spec.rb b/spec/ruby/core/float/gte_spec.rb
index 98ec60b70b..44c0a81b43 100644
--- a/spec/ruby/core/float/gte_spec.rb
+++ b/spec/ruby/core/float/gte_spec.rb
@@ -14,4 +14,25 @@ describe "Float#>=" do
     -> { 5.0 >= "4"       }.should raise_error(ArgumentError)
     -> { 5.0 >= mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value >= n).should == false
+      (n >= nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value >= n).should == true
+      (n >= infinity_value).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value >= n).should == false
+      (n >= -infinity_value).should == true
+    }
+  end
 end
diff --git a/spec/ruby/core/float/inspect_spec.rb b/spec/ruby/core/float/inspect_spec.rb
new file mode 100644
index 0000000000..4be1927d84
--- /dev/null
+++ b/spec/ruby/core/float/inspect_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/to_s'
+
+describe "Float#inspect" do
+  it_behaves_like :float_to_s, :inspect
+end
diff --git a/spec/ruby/core/float/lt_spec.rb b/spec/ruby/core/float/lt_spec.rb
index c01b6e0e02..94dcfc42f8 100644
--- a/spec/ruby/core/float/lt_spec.rb
+++ b/spec/ruby/core/float/lt_spec.rb
@@ -14,4 +14,25 @@ describe "Float#<" do
     -> { 5.0 < "4"       }.should raise_error(ArgumentError)
     -> { 5.0 < mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value < n).should == false
+      (n < nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value < n).should == false
+      (n < infinity_value).should == true
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value < n).should == true
+      (n < -infinity_value).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/float/lte_spec.rb b/spec/ruby/core/float/lte_spec.rb
index 66f2ddc2c7..7b5a86ee76 100644
--- a/spec/ruby/core/float/lte_spec.rb
+++ b/spec/ruby/core/float/lte_spec.rb
@@ -15,4 +15,25 @@ describe "Float#<=" do
     -> { 5.0 <= "4"       }.should raise_error(ArgumentError)
     -> { 5.0 <= mock('x') }.should raise_error(ArgumentError)
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value <= n).should == false
+      (n <= nan_value).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value <= n).should == false
+      (n <= infinity_value).should == true
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (-infinity_value <= n).should == true
+      (n <= -infinity_value).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/float/magnitude_spec.rb b/spec/ruby/core/float/magnitude_spec.rb
index db577c15c5..7cdd8ef28a 100644
--- a/spec/ruby/core/float/magnitude_spec.rb
+++ b/spec/ruby/core/float/magnitude_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative 'shared/abs'
 
 describe "Float#magnitude" do
diff --git a/spec/ruby/core/float/minus_spec.rb b/spec/ruby/core/float/minus_spec.rb
index 5626cbdac2..a4281a397b 100644
--- a/spec/ruby/core/float/minus_spec.rb
+++ b/spec/ruby/core/float/minus_spec.rb
@@ -6,7 +6,7 @@ describe "Float#-" do
 
   it "returns self minus other" do
     (9_237_212.5280 - 5_280).should be_close(9231932.528, TOLERANCE)
-    (2_560_496.1691 - bignum_value).should be_close(-9223372036852215808.000, TOLERANCE)
+    (2_560_496.1691 - bignum_value).should be_close(-18446744073706991616.0, TOLERANCE)
     (5.5 - 5.5).should be_close(0.0,TOLERANCE)
   end
 end
diff --git a/spec/ruby/core/float/multiply_spec.rb b/spec/ruby/core/float/multiply_spec.rb
index eca0b52c4f..2adb8796cd 100644
--- a/spec/ruby/core/float/multiply_spec.rb
+++ b/spec/ruby/core/float/multiply_spec.rb
@@ -7,7 +7,7 @@ describe "Float#*" do
   it "returns self multiplied by other" do
     (4923.98221 * 2).should be_close(9847.96442, TOLERANCE)
     (6712.5 * 0.25).should be_close(1678.125, TOLERANCE)
-    (256.4096 * bignum_value).should be_close(2364961134621118431232.000, TOLERANCE)
+    (256.4096 * bignum_value).should be_close(4729922269242236862464.0, TOLERANCE)
   end
 
   it "raises a TypeError when given a non-Numeric" do
diff --git a/spec/ruby/core/float/nan_spec.rb b/spec/ruby/core/float/nan_spec.rb
index d09d25153c..c1043ef21b 100644
--- a/spec/ruby/core/float/nan_spec.rb
+++ b/spec/ruby/core/float/nan_spec.rb
@@ -2,8 +2,8 @@ require_relative '../../spec_helper'
 
 describe "Float#nan?" do
   it "returns true if self is not a valid IEEE floating-point number" do
-    0.0.nan?.should == false
-    -1.5.nan?.should == false
-    nan_value.nan?.should == true
+    0.0.should_not.nan?
+    -1.5.should_not.nan?
+    nan_value.should.nan?
   end
 end
diff --git a/spec/ruby/core/float/negative_spec.rb b/spec/ruby/core/float/negative_spec.rb
new file mode 100644
index 0000000000..511d92ade6
--- /dev/null
+++ b/spec/ruby/core/float/negative_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+
+describe "Float#negative?" do
+  describe "on positive numbers" do
+    it "returns false" do
+      0.1.negative?.should be_false
+    end
+  end
+
+  describe "on zero" do
+    it "returns false" do
+      0.0.negative?.should be_false
+    end
+  end
+
+  describe "on negative zero" do
+    it "returns false" do
+      -0.0.negative?.should be_false
+    end
+  end
+
+  describe "on negative numbers" do
+    it "returns true" do
+      -0.1.negative?.should be_true
+    end
+  end
+
+  describe "on NaN" do
+    it "returns false" do
+      nan_value.negative?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/core/float/next_float_spec.rb b/spec/ruby/core/float/next_float_spec.rb
index 2f0eff605a..29e2d31146 100644
--- a/spec/ruby/core/float/next_float_spec.rb
+++ b/spec/ruby/core/float/next_float_spec.rb
@@ -44,6 +44,6 @@ describe "Float#next_float" do
   end
 
   it "returns NAN if NAN was the receiver" do
-    Float::NAN.next_float.nan?.should == true
+    Float::NAN.next_float.should.nan?
   end
 end
diff --git a/spec/ruby/core/float/plus_spec.rb b/spec/ruby/core/float/plus_spec.rb
index 06b136a06b..e3e19d7f39 100644
--- a/spec/ruby/core/float/plus_spec.rb
+++ b/spec/ruby/core/float/plus_spec.rb
@@ -6,7 +6,7 @@ describe "Float#+" do
 
   it "returns self plus other" do
     (491.213 + 2).should be_close(493.213, TOLERANCE)
-    (9.99 + bignum_value).should be_close(9223372036854775808.000, TOLERANCE)
+    (9.99 + bignum_value).should be_close(18446744073709551616.0, TOLERANCE)
     (1001.99 + 5.219).should be_close(1007.209, TOLERANCE)
   end
 end
diff --git a/spec/ruby/core/float/positive_spec.rb b/spec/ruby/core/float/positive_spec.rb
new file mode 100644
index 0000000000..575f92a720
--- /dev/null
+++ b/spec/ruby/core/float/positive_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+
+describe "Float#positive?" do
+  describe "on positive numbers" do
+    it "returns true" do
+      0.1.positive?.should be_true
+    end
+  end
+
+  describe "on zero" do
+    it "returns false" do
+      0.0.positive?.should be_false
+    end
+  end
+
+  describe "on negative zero" do
+    it "returns false" do
+      -0.0.positive?.should be_false
+    end
+  end
+
+  describe "on negative numbers" do
+    it "returns false" do
+      -0.1.positive?.should be_false
+    end
+  end
+
+  describe "on NaN" do
+    it "returns false" do
+      nan_value.positive?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/core/float/prev_float_spec.rb b/spec/ruby/core/float/prev_float_spec.rb
index 40fcc25a6d..5e50269da7 100644
--- a/spec/ruby/core/float/prev_float_spec.rb
+++ b/spec/ruby/core/float/prev_float_spec.rb
@@ -44,6 +44,6 @@ describe "Float#prev_float" do
   end
 
   it "returns NAN if NAN was the receiver" do
-    Float::NAN.prev_float.nan?.should == true
+    Float::NAN.prev_float.should.nan?
   end
 end
diff --git a/spec/ruby/core/float/round_spec.rb b/spec/ruby/core/float/round_spec.rb
index e143682362..7e8c792051 100644
--- a/spec/ruby/core/float/round_spec.rb
+++ b/spec/ruby/core/float/round_spec.rb
@@ -30,6 +30,11 @@ describe "Float#round" do
     12.345678.round(3.999).should == 12.346
   end
 
+  it "correctly rounds exact floats with a numerous digits in a fraction part" do
+    0.8241000000000004.round(10).should == 0.8241
+    0.8241000000000002.round(10).should == 0.8241
+  end
+
   it "returns zero when passed a negative argument with magnitude greater than magnitude of the whole number portion of the Float" do
     0.8346268.round(-1).should eql(0)
   end
@@ -68,6 +73,10 @@ describe "Float#round" do
     0.42.round(2.0**30).should == 0.42
   end
 
+  it "returns rounded values for not so big argument" do
+    0.42.round(2.0**23).should == 0.42
+  end
+
   it "returns big values rounded to nearest" do
     +2.5e20.round(-20).should   eql( +3 * 10 ** 20  )
     -2.5e20.round(-20).should   eql( -3 * 10 ** 20  )
@@ -103,6 +112,70 @@ describe "Float#round" do
     5.55.round(1, half: :up).should eql(5.6)
     5.55.round(1, half: :down).should eql(5.5)
     5.55.round(1, half: :even).should eql(5.6)
+    -5.55.round(1, half: nil).should eql(-5.6)
+    -5.55.round(1, half: :up).should eql(-5.6)
+    -5.55.round(1, half: :down).should eql(-5.5)
+    -5.55.round(1, half: :even).should eql(-5.6)
+  end
+
+  it "preserves cases where neighbouring floating pointer number increase the decimal places" do
+    4.8100000000000005.round(5, half: nil).should eql(4.81)
+    4.8100000000000005.round(5, half: :up).should eql(4.81)
+    4.8100000000000005.round(5, half: :down).should eql(4.81)
+    4.8100000000000005.round(5, half: :even).should eql(4.81)
+    -4.8100000000000005.round(5, half: nil).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :up).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :down).should eql(-4.81)
+    -4.8100000000000005.round(5, half: :even).should eql(-4.81)
+    4.81.round(5, half: nil).should eql(4.81)
+    4.81.round(5, half: :up).should eql(4.81)
+    4.81.round(5, half: :down).should eql(4.81)
+    4.81.round(5, half: :even).should eql(4.81)
+    -4.81.round(5, half: nil).should eql(-4.81)
+    -4.81.round(5, half: :up).should eql(-4.81)
+    -4.81.round(5, half: :down).should eql(-4.81)
+    -4.81.round(5, half: :even).should eql(-4.81)
+    4.809999999999999.round(5, half: nil).should eql(4.81)
+    4.809999999999999.round(5, half: :up).should eql(4.81)
+    4.809999999999999.round(5, half: :down).should eql(4.81)
+    4.809999999999999.round(5, half: :even).should eql(4.81)
+    -4.809999999999999.round(5, half: nil).should eql(-4.81)
+    -4.809999999999999.round(5, half: :up).should eql(-4.81)
+    -4.809999999999999.round(5, half: :down).should eql(-4.81)
+    -4.809999999999999.round(5, half: :even).should eql(-4.81)
+  end
+
+  ruby_bug "#19318", ""..."3.3" do
+    # These numbers are neighbouring floating point numbers round a
+    # precise value. They test that the rounding modes work correctly
+    # round that value and precision is not lost which might cause
+    # incorrect results.
+    it "does not lose precision during the rounding process" do
+      767573.1875850001.round(5, half: nil).should eql(767573.18759)
+      767573.1875850001.round(5, half: :up).should eql(767573.18759)
+      767573.1875850001.round(5, half: :down).should eql(767573.18759)
+      767573.1875850001.round(5, half: :even).should eql(767573.18759)
+      -767573.1875850001.round(5, half: nil).should eql(-767573.18759)
+      -767573.1875850001.round(5, half: :up).should eql(-767573.18759)
+      -767573.1875850001.round(5, half: :down).should eql(-767573.18759)
+      -767573.1875850001.round(5, half: :even).should eql(-767573.18759)
+      767573.187585.round(5, half: nil).should eql(767573.18759)
+      767573.187585.round(5, half: :up).should eql(767573.18759)
+      767573.187585.round(5, half: :down).should eql(767573.18758)
+      767573.187585.round(5, half: :even).should eql(767573.18758)
+      -767573.187585.round(5, half: nil).should eql(-767573.18759)
+      -767573.187585.round(5, half: :up).should eql(-767573.18759)
+      -767573.187585.round(5, half: :down).should eql(-767573.18758)
+      -767573.187585.round(5, half: :even).should eql(-767573.18758)
+      767573.1875849998.round(5, half: nil).should eql(767573.18758)
+      767573.1875849998.round(5, half: :up).should eql(767573.18758)
+      767573.1875849998.round(5, half: :down).should eql(767573.18758)
+      767573.1875849998.round(5, half: :even).should eql(767573.18758)
+      -767573.1875849998.round(5, half: nil).should eql(-767573.18758)
+      -767573.1875849998.round(5, half: :up).should eql(-767573.18758)
+      -767573.1875849998.round(5, half: :down).should eql(-767573.18758)
+      -767573.1875849998.round(5, half: :even).should eql(-767573.18758)
+    end
   end
 
   it "raises FloatDomainError for exceptional values with a half option" do
@@ -114,4 +187,17 @@ describe "Float#round" do
   it "raise for a non-existent round mode" do
     -> { 14.2.round(half: :nonsense) }.should raise_error(ArgumentError, "invalid rounding mode: nonsense")
   end
+
+  describe "when 0.0 is given" do
+    it "returns self for positive ndigits" do
+      (0.0).round(5).inspect.should == "0.0"
+      (-0.0).round(1).inspect.should == "-0.0"
+    end
+
+    it "returns 0 for 0 or undefined ndigits" do
+      (0.0).round.should == 0
+      (-0.0).round(0).should == 0
+      (0.0).round(half: :up) == 0
+    end
+  end
 end
diff --git a/spec/ruby/core/float/shared/arithmetic_exception_in_coerce.rb b/spec/ruby/core/float/shared/arithmetic_exception_in_coerce.rb
index 19a02572d8..eec92d858f 100644
--- a/spec/ruby/core/float/shared/arithmetic_exception_in_coerce.rb
+++ b/spec/ruby/core/float/shared/arithmetic_exception_in_coerce.rb
@@ -1,33 +1,11 @@
 require_relative '../fixtures/classes'
 
 describe :float_arithmetic_exception_in_coerce, shared: true do
-  ruby_version_is ""..."2.5" do
-    it "rescues exception (StandardError and subclasses) raised in other#coerce and raises TypeError" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
+  it "does not rescue exception raised in other#coerce" do
+    b = mock("numeric with failed #coerce")
+    b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
 
-      # e.g. 1.0 > b
-      -> { 1.0.send(@method, b) }.should raise_error(TypeError, /MockObject can't be coerced into Float/)
-    end
-
-    it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-      [Exception, NoMemoryError].each do |exception|
-        b = mock("numeric with failed #coerce")
-        b.should_receive(:coerce).and_raise(exception)
-
-        # e.g. 1.0 > b
-        -> { 1.0.send(@method, b) }.should raise_error(exception)
-      end
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not rescue exception raised in other#coerce" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
-
-      # e.g. 1.0 > b
-      -> { 1.0.send(@method, b) }.should raise_error(FloatSpecs::CoerceError)
-    end
+    # e.g. 1.0 > b
+    -> { 1.0.send(@method, b) }.should raise_error(FloatSpecs::CoerceError)
   end
 end
diff --git a/spec/ruby/core/float/shared/comparison_exception_in_coerce.rb b/spec/ruby/core/float/shared/comparison_exception_in_coerce.rb
index f8ded53644..3e2c1e28dd 100644
--- a/spec/ruby/core/float/shared/comparison_exception_in_coerce.rb
+++ b/spec/ruby/core/float/shared/comparison_exception_in_coerce.rb
@@ -1,35 +1,11 @@
 require_relative '../fixtures/classes'
 
 describe :float_comparison_exception_in_coerce, shared: true do
-  ruby_version_is ""..."2.5" do
-    it "rescues exception (StandardError and subclasses) raised in other#coerce and raises ArgumentError" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
+  it "does not rescue exception raised in other#coerce" do
+    b = mock("numeric with failed #coerce")
+    b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
 
-      # e.g. 1.0 > b
-      -> {
-        -> { 1.0.send(@method, b) }.should raise_error(ArgumentError, /comparison of Float with MockObject failed/)
-      }.should complain(/Numerical comparison operators will no more rescue exceptions of #coerce/)
-    end
-
-    it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-      [Exception, NoMemoryError].each do |exception|
-        b = mock("numeric with failed #coerce")
-        b.should_receive(:coerce).and_raise(exception)
-
-        # e.g. 1.0 > b
-        -> { 1.0.send(@method, b) }.should raise_error(exception)
-      end
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not rescue exception raised in other#coerce" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(FloatSpecs::CoerceError)
-
-      # e.g. 1.0 > b
-      -> { 1.0.send(@method, b) }.should raise_error(FloatSpecs::CoerceError)
-    end
+    # e.g. 1.0 > b
+    -> { 1.0.send(@method, b) }.should raise_error(FloatSpecs::CoerceError)
   end
 end
diff --git a/spec/ruby/core/float/shared/equal.rb b/spec/ruby/core/float/shared/equal.rb
index 668aa069b5..4d524e1cf2 100644
--- a/spec/ruby/core/float/shared/equal.rb
+++ b/spec/ruby/core/float/shared/equal.rb
@@ -14,4 +14,25 @@ describe :float_equal, shared: true do
     1.0.send(@method, x).should == false
     2.0.send(@method, x).should == true
   end
+
+  it "returns false if one side is NaN" do
+    [1.0, 42, bignum_value].each { |n|
+      (nan_value.send(@method, n)).should == false
+      (n.send(@method, nan_value)).should == false
+    }
+  end
+
+  it "handles positive infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      (infinity_value.send(@method, n)).should == false
+      (n.send(@method, infinity_value)).should == false
+    }
+  end
+
+  it "handles negative infinity" do
+    [1.0, 42, bignum_value].each { |n|
+      ((-infinity_value).send(@method, n)).should == false
+      (n.send(@method, -infinity_value)).should == false
+    }
+  end
 end
diff --git a/spec/ruby/core/float/shared/quo.rb b/spec/ruby/core/float/shared/quo.rb
index 3487824f70..0c90171b87 100644
--- a/spec/ruby/core/float/shared/quo.rb
+++ b/spec/ruby/core/float/shared/quo.rb
@@ -1,9 +1,9 @@
 describe :float_quo, shared: true do
-  it "performs floating-point division between self and a Fixnum" do
+  it "performs floating-point division between self and an Integer" do
     8.9.send(@method, 7).should == 1.2714285714285716
   end
 
-  it "performs floating-point division between self and a Bignum" do
+  it "performs floating-point division between self and an Integer" do
     8.9.send(@method, 9999999999999**9).should == 8.900000000008011e-117
   end
 
diff --git a/spec/ruby/core/float/shared/to_i.rb b/spec/ruby/core/float/shared/to_i.rb
index 960295f095..33b32ca533 100644
--- a/spec/ruby/core/float/shared/to_i.rb
+++ b/spec/ruby/core/float/shared/to_i.rb
@@ -7,4 +7,8 @@ describe :float_to_i, shared: true do
     -9223372036854775808.1.send(@method).should eql(-9223372036854775808)
     9223372036854775808.1.send(@method).should eql(9223372036854775808)
   end
+
+  it "raises a FloatDomainError for NaN" do
+    -> { nan_value.send(@method) }.should raise_error(FloatDomainError)
+  end
 end
diff --git a/spec/ruby/core/float/shared/to_s.rb b/spec/ruby/core/float/shared/to_s.rb
new file mode 100644
index 0000000000..0925efc0f7
--- /dev/null
+++ b/spec/ruby/core/float/shared/to_s.rb
@@ -0,0 +1,308 @@
+describe :float_to_s, shared: true do
+  it "returns 'NaN' for NaN" do
+    nan_value().send(@method).should == 'NaN'
+  end
+
+  it "returns 'Infinity' for positive infinity" do
+    infinity_value().send(@method).should == 'Infinity'
+  end
+
+  it "returns '-Infinity' for negative infinity" do
+    (-infinity_value()).send(@method).should == '-Infinity'
+  end
+
+  it "returns '0.0' for 0.0" do
+    0.0.send(@method).should == "0.0"
+  end
+
+  platform_is_not :openbsd do
+    it "emits '-' for -0.0" do
+      -0.0.send(@method).should == "-0.0"
+    end
+  end
+
+  it "emits a '-' for negative values" do
+    -3.14.send(@method).should == "-3.14"
+  end
+
+  it "emits a trailing '.0' for a whole number" do
+    50.0.send(@method).should == "50.0"
+  end
+
+  it "emits a trailing '.0' for the mantissa in e format" do
+    1.0e20.send(@method).should == "1.0e+20"
+  end
+
+  it "uses non-e format for a positive value with fractional part having 5 significant figures" do
+    0.0001.send(@method).should == "0.0001"
+  end
+
+  it "uses non-e format for a negative value with fractional part having 5 significant figures" do
+    -0.0001.send(@method).should == "-0.0001"
+  end
+
+  it "uses e format for a positive value with fractional part having 6 significant figures" do
+    0.00001.send(@method).should == "1.0e-05"
+  end
+
+  it "uses e format for a negative value with fractional part having 6 significant figures" do
+    -0.00001.send(@method).should == "-1.0e-05"
+  end
+
+  it "uses non-e format for a positive value with whole part having 15 significant figures" do
+    10000000000000.0.send(@method).should == "10000000000000.0"
+  end
+
+  it "uses non-e format for a negative value with whole part having 15 significant figures" do
+    -10000000000000.0.send(@method).should == "-10000000000000.0"
+  end
+
+  it "uses non-e format for a positive value with whole part having 16 significant figures" do
+    100000000000000.0.send(@method).should == "100000000000000.0"
+  end
+
+  it "uses non-e format for a negative value with whole part having 16 significant figures" do
+    -100000000000000.0.send(@method).should == "-100000000000000.0"
+  end
+
+  it "uses e format for a positive value with whole part having 18 significant figures" do
+    10000000000000000.0.send(@method).should == "1.0e+16"
+  end
+
+  it "uses e format for a negative value with whole part having 18 significant figures" do
+    -10000000000000000.0.send(@method).should == "-1.0e+16"
+  end
+
+  it "uses e format for a positive value with whole part having 17 significant figures" do
+    1000000000000000.0.send(@method).should == "1.0e+15"
+  end
+
+  it "uses e format for a negative value with whole part having 17 significant figures" do
+    -1000000000000000.0.send(@method).should == "-1.0e+15"
+  end
+
+  # #3273
+  it "outputs the minimal, unique form necessary to recreate the value" do
+    value = 0.21611564636388508
+    string = "0.21611564636388508"
+
+    value.send(@method).should == string
+    string.to_f.should == value
+  end
+
+  it "outputs the minimal, unique form to represent the value" do
+    0.56.send(@method).should == "0.56"
+  end
+
+  describe "matches" do
+    it "random examples in all ranges" do
+      # 50.times do
+      #   bytes = (0...8).map { rand(256) }
+      #   string = bytes.pack('C8')
+      #   float = string.unpack('D').first
+      #   puts "#{'%.20g' % float}.send(@method).should == #{float.send(@method).inspect}"
+      # end
+
+      2.5540217314354050325e+163.send(@method).should == "2.554021731435405e+163"
+      2.5492588360356597544e-172.send(@method).should == "2.5492588360356598e-172"
+      1.742770260934704852e-82.send(@method).should == "1.7427702609347049e-82"
+      6.2108093676180883209e-104.send(@method).should == "6.210809367618088e-104"
+      -3.3448803488331067402e-143.send(@method).should == "-3.3448803488331067e-143"
+      -2.2740074343500832557e-168.send(@method).should == "-2.2740074343500833e-168"
+      7.0587971678048535732e+191.send(@method).should == "7.058797167804854e+191"
+      -284438.88327586348169.send(@method).should == "-284438.8832758635"
+      3.953272468476091301e+105.send(@method).should == "3.9532724684760913e+105"
+      -3.6361359552959847853e+100.send(@method).should == "-3.636135955295985e+100"
+      -1.3222325865575206185e-31.send(@method).should == "-1.3222325865575206e-31"
+      1.1440138916932761366e+130.send(@method).should == "1.1440138916932761e+130"
+      4.8750891560387561157e-286.send(@method).should == "4.875089156038756e-286"
+      5.6101113356591453525e-257.send(@method).should == "5.610111335659145e-257"
+      -3.829644279545809575e-100.send(@method).should == "-3.8296442795458096e-100"
+      1.5342839401396406117e-194.send(@method).should == "1.5342839401396406e-194"
+      2.2284972755169921402e-144.send(@method).should == "2.228497275516992e-144"
+      2.1825655917065601737e-61.send(@method).should == "2.1825655917065602e-61"
+      -2.6672271363524338322e-62.send(@method).should == "-2.667227136352434e-62"
+      -1.9257995160119059415e+21.send(@method).should == "-1.925799516011906e+21"
+      -8.9096732962887121718e-198.send(@method).should == "-8.909673296288712e-198"
+      2.0202075376548644959e-90.send(@method).should == "2.0202075376548645e-90"
+      -7.7341602581786258961e-266.send(@method).should == "-7.734160258178626e-266"
+      3.5134482598733635046e+98.send(@method).should == "3.5134482598733635e+98"
+      -2.124411722371029134e+154.send(@method).should == "-2.124411722371029e+154"
+      -4.573908787355718687e+110.send(@method).should == "-4.573908787355719e+110"
+      -1.9344425934170969879e-232.send(@method).should == "-1.934442593417097e-232"
+      -1.3274227399979271095e+171.send(@method).should == "-1.3274227399979271e+171"
+      9.3495270482104442383e-283.send(@method).should == "9.349527048210444e-283"
+      -4.2046059371986483233e+307.send(@method).should == "-4.2046059371986483e+307"
+      3.6133547278583543004e-117.send(@method).should == "3.613354727858354e-117"
+      4.9247416523566613499e-08.send(@method).should == "4.9247416523566613e-08"
+      1.6936145488250064007e-71.send(@method).should == "1.6936145488250064e-71"
+      2.4455483206829433098e+96.send(@method).should == "2.4455483206829433e+96"
+      7.9797449851436455384e+124.send(@method).should == "7.979744985143646e+124"
+      -1.3873689634457876774e-129.send(@method).should == "-1.3873689634457877e-129"
+      3.9761102037533483075e+284.send(@method).should == "3.976110203753348e+284"
+      -4.2819791952139402486e-303.send(@method).should == "-4.28197919521394e-303"
+      -5.7981017546689831298e-116.send(@method).should == "-5.798101754668983e-116"
+      -3.953266497860534199e-28.send(@method).should == "-3.953266497860534e-28"
+      -2.0659852720290440959e-243.send(@method).should == "-2.065985272029044e-243"
+      8.9670488995878688018e-05.send(@method).should == "8.967048899587869e-05"
+      -1.2317943708113061768e-98.send(@method).should == "-1.2317943708113062e-98"
+      -3.8930768307633080463e+248.send(@method).should == "-3.893076830763308e+248"
+      6.5854032671803925627e-239.send(@method).should == "6.5854032671803926e-239"
+      4.6257022188980878952e+177.send(@method).should == "4.625702218898088e+177"
+      -1.9397155125507235603e-187.send(@method).should == "-1.9397155125507236e-187"
+      8.5752156951245705056e+117.send(@method).should == "8.57521569512457e+117"
+      -2.4784875958162501671e-132.send(@method).should == "-2.4784875958162502e-132"
+      -4.4125691841230058457e-203.send(@method).should == "-4.412569184123006e-203"
+    end
+
+    it "random examples in human ranges" do
+      # 50.times do
+      #   formatted = ''
+      #   rand(1..3).times do
+      #     formatted << rand(10).to_s
+      #   end
+      #   formatted << '.'
+      #   rand(1..9).times do
+      #     formatted << rand(10).to_s
+      #   end
+      #   float = formatted.to_f
+      #   puts "#{'%.20f' % float}.send(@method).should == #{float.send(@method).inspect}"
+      # end
+
+      5.17869899999999994122.send(@method).should == "5.178699"
+      905.62695729999995819526.send(@method).should == "905.6269573"
+      62.75999999999999801048.send(@method).should == "62.76"
+      6.93856795800000014651.send(@method).should == "6.938567958"
+      4.95999999999999996447.send(@method).should == "4.96"
+      32.77993899999999882766.send(@method).should == "32.779939"
+      544.12756779999995160324.send(@method).should == "544.1275678"
+      66.25801119999999855281.send(@method).should == "66.2580112"
+      7.90000000000000035527.send(@method).should == "7.9"
+      5.93100000000000004974.send(@method).should == "5.931"
+      5.21229313600000043749.send(@method).should == "5.212293136"
+      503.44173809000000119340.send(@method).should == "503.44173809"
+      79.26000000000000511591.send(@method).should == "79.26"
+      8.51524999999999998579.send(@method).should == "8.51525"
+      174.00000000000000000000.send(@method).should == "174.0"
+      50.39580000000000126192.send(@method).should == "50.3958"
+      35.28999999999999914735.send(@method).should == "35.29"
+      5.43136675399999990788.send(@method).should == "5.431366754"
+      654.07680000000004838512.send(@method).should == "654.0768"
+      6.07423700000000010846.send(@method).should == "6.074237"
+      102.25779799999999397642.send(@method).should == "102.257798"
+      5.08129999999999970584.send(@method).should == "5.0813"
+      6.00000000000000000000.send(@method).should == "6.0"
+      8.30000000000000071054.send(@method).should == "8.3"
+      32.68345999999999662577.send(@method).should == "32.68346"
+      581.11170000000004165486.send(@method).should == "581.1117"
+      76.31342999999999676675.send(@method).should == "76.31343"
+      438.30826000000001840817.send(@method).should == "438.30826"
+      482.06631994000002805478.send(@method).should == "482.06631994"
+      55.92721026899999969828.send(@method).should == "55.927210269"
+      4.00000000000000000000.send(@method).should == "4.0"
+      55.86693999999999959982.send(@method).should == "55.86694"
+      787.98299999999994724931.send(@method).should == "787.983"
+      5.73810511000000023074.send(@method).should == "5.73810511"
+      74.51926810000000500622.send(@method).should == "74.5192681"
+      892.89999999999997726263.send(@method).should == "892.9"
+      68.27299999999999613465.send(@method).should == "68.273"
+      904.10000000000002273737.send(@method).should == "904.1"
+      5.23200000000000020606.send(@method).should == "5.232"
+      4.09628000000000014325.send(@method).should == "4.09628"
+      46.05152633699999853434.send(@method).should == "46.051526337"
+      142.12884990599999923688.send(@method).should == "142.128849906"
+      3.83057023500000015659.send(@method).should == "3.830570235"
+      11.81684594699999912848.send(@method).should == "11.816845947"
+      80.50000000000000000000.send(@method).should == "80.5"
+      382.18215010000000120272.send(@method).should == "382.1821501"
+      55.38444606899999911320.send(@method).should == "55.384446069"
+      5.78000000000000024869.send(@method).should == "5.78"
+      2.88244999999999995666.send(@method).should == "2.88245"
+      43.27709999999999723741.send(@method).should == "43.2771"
+    end
+
+    it "random values from divisions" do
+      (1.0 / 7).send(@method).should == "0.14285714285714285"
+
+      # 50.times do
+      #    a = rand(10)
+      #    b = rand(10)
+      #    c = rand(10)
+      #    d = rand(10)
+      #    expression = "#{a}.#{b} / #{c}.#{d}"
+      #    puts "      (#{expression}).send(@method).should == #{eval(expression).send(@method).inspect}"
+      #  end
+
+      (1.1 / 7.1).send(@method).should == "0.15492957746478875"
+      (6.5 / 8.8).send(@method).should == "0.7386363636363635"
+      (4.8 / 4.3).send(@method).should == "1.1162790697674418"
+      (4.0 / 1.9).send(@method).should == "2.1052631578947367"
+      (9.1 / 0.8).send(@method).should == "11.374999999999998"
+      (5.3 / 7.5).send(@method).should == "0.7066666666666667"
+      (2.8 / 1.8).send(@method).should == "1.5555555555555554"
+      (2.1 / 2.5).send(@method).should == "0.8400000000000001"
+      (3.5 / 6.0).send(@method).should == "0.5833333333333334"
+      (4.6 / 0.3).send(@method).should == "15.333333333333332"
+      (0.6 / 2.4).send(@method).should == "0.25"
+      (1.3 / 9.1).send(@method).should == "0.14285714285714288"
+      (0.3 / 5.0).send(@method).should == "0.06"
+      (5.0 / 4.2).send(@method).should == "1.1904761904761905"
+      (3.0 / 2.0).send(@method).should == "1.5"
+      (6.3 / 2.0).send(@method).should == "3.15"
+      (5.4 / 6.0).send(@method).should == "0.9"
+      (9.6 / 8.1).send(@method).should == "1.1851851851851851"
+      (8.7 / 1.6).send(@method).should == "5.437499999999999"
+      (1.9 / 7.8).send(@method).should == "0.24358974358974358"
+      (0.5 / 2.1).send(@method).should == "0.23809523809523808"
+      (9.3 / 5.8).send(@method).should == "1.6034482758620692"
+      (2.7 / 8.0).send(@method).should == "0.3375"
+      (9.7 / 7.8).send(@method).should == "1.2435897435897436"
+      (8.1 / 2.4).send(@method).should == "3.375"
+      (7.7 / 2.7).send(@method).should == "2.8518518518518516"
+      (7.9 / 1.7).send(@method).should == "4.647058823529412"
+      (6.5 / 8.2).send(@method).should == "0.7926829268292683"
+      (7.8 / 9.6).send(@method).should == "0.8125"
+      (2.2 / 4.6).send(@method).should == "0.47826086956521746"
+      (0.0 / 1.0).send(@method).should == "0.0"
+      (8.3 / 2.9).send(@method).should == "2.8620689655172415"
+      (3.1 / 6.1).send(@method).should == "0.5081967213114754"
+      (2.8 / 7.8).send(@method).should == "0.358974358974359"
+      (8.0 / 0.1).send(@method).should == "80.0"
+      (1.7 / 6.4).send(@method).should == "0.265625"
+      (1.8 / 5.4).send(@method).should == "0.3333333333333333"
+      (8.0 / 5.8).send(@method).should == "1.3793103448275863"
+      (5.2 / 4.1).send(@method).should == "1.2682926829268295"
+      (9.8 / 5.8).send(@method).should == "1.6896551724137934"
+      (5.4 / 9.5).send(@method).should == "0.5684210526315789"
+      (8.4 / 4.9).send(@method).should == "1.7142857142857142"
+      (1.7 / 3.5).send(@method).should == "0.4857142857142857"
+      (1.2 / 5.1).send(@method).should == "0.23529411764705882"
+      (1.4 / 2.0).send(@method).should == "0.7"
+      (4.8 / 8.0).send(@method).should == "0.6"
+      (9.0 / 2.5).send(@method).should == "3.6"
+      (0.2 / 0.6).send(@method).should == "0.33333333333333337"
+      (7.8 / 5.2).send(@method).should == "1.5"
+      (9.5 / 5.5).send(@method).should == "1.7272727272727273"
+    end
+  end
+
+  describe 'encoding' do
+    before :each do
+      @internal = Encoding.default_internal
+    end
+
+    after :each do
+      Encoding.default_internal = @internal
+    end
+
+    it "returns a String in US-ASCII encoding when Encoding.default_internal is nil" do
+      Encoding.default_internal = nil
+      1.23.send(@method).encoding.should equal(Encoding::US_ASCII)
+    end
+
+    it "returns a String in US-ASCII encoding when Encoding.default_internal is not nil" do
+      Encoding.default_internal = Encoding::IBM437
+      5.47.send(@method).encoding.should equal(Encoding::US_ASCII)
+    end
+  end
+end
diff --git a/spec/ruby/core/float/to_s_spec.rb b/spec/ruby/core/float/to_s_spec.rb
index ad04bc4fb6..6727a883f8 100644
--- a/spec/ruby/core/float/to_s_spec.rb
+++ b/spec/ruby/core/float/to_s_spec.rb
@@ -1,310 +1,6 @@
 require_relative '../../spec_helper'
+require_relative 'shared/to_s'
 
 describe "Float#to_s" do
-  it "returns 'NaN' for NaN" do
-    nan_value().to_s.should == 'NaN'
-  end
-
-  it "returns 'Infinity' for positive infinity" do
-    infinity_value().to_s.should == 'Infinity'
-  end
-
-  it "returns '-Infinity' for negative infinity" do
-    (-infinity_value()).to_s.should == '-Infinity'
-  end
-
-  it "returns '0.0' for 0.0" do
-    0.0.to_s.should == "0.0"
-  end
-
-  platform_is_not :openbsd do
-    it "emits '-' for -0.0" do
-      -0.0.to_s.should == "-0.0"
-    end
-  end
-
-  it "emits a '-' for negative values" do
-    -3.14.to_s.should == "-3.14"
-  end
-
-  it "emits a trailing '.0' for a whole number" do
-    50.0.to_s.should == "50.0"
-  end
-
-  it "emits a trailing '.0' for the mantissa in e format" do
-    1.0e20.to_s.should == "1.0e+20"
-  end
-
-  it "uses non-e format for a positive value with fractional part having 5 significant figures" do
-    0.0001.to_s.should == "0.0001"
-  end
-
-  it "uses non-e format for a negative value with fractional part having 5 significant figures" do
-    -0.0001.to_s.should == "-0.0001"
-  end
-
-  it "uses e format for a positive value with fractional part having 6 significant figures" do
-    0.00001.to_s.should == "1.0e-05"
-  end
-
-  it "uses e format for a negative value with fractional part having 6 significant figures" do
-    -0.00001.to_s.should == "-1.0e-05"
-  end
-
-  it "uses non-e format for a positive value with whole part having 15 significant figures" do
-    10000000000000.0.to_s.should == "10000000000000.0"
-  end
-
-  it "uses non-e format for a negative value with whole part having 15 significant figures" do
-    -10000000000000.0.to_s.should == "-10000000000000.0"
-  end
-
-  it "uses non-e format for a positive value with whole part having 16 significant figures" do
-    100000000000000.0.to_s.should == "100000000000000.0"
-  end
-
-  it "uses non-e format for a negative value with whole part having 16 significant figures" do
-    -100000000000000.0.to_s.should == "-100000000000000.0"
-  end
-
-  it "uses e format for a positive value with whole part having 18 significant figures" do
-    10000000000000000.0.to_s.should == "1.0e+16"
-  end
-
-  it "uses e format for a negative value with whole part having 18 significant figures" do
-    -10000000000000000.0.to_s.should == "-1.0e+16"
-  end
-
-  it "uses e format for a positive value with whole part having 17 significant figures" do
-    1000000000000000.0.to_s.should == "1.0e+15"
-  end
-
-  it "uses e format for a negative value with whole part having 17 significant figures" do
-    -1000000000000000.0.to_s.should == "-1.0e+15"
-  end
-
-  # #3273
-  it "outputs the minimal, unique form necessary to recreate the value" do
-    value = 0.21611564636388508
-    string = "0.21611564636388508"
-
-    value.to_s.should == string
-    string.to_f.should == value
-  end
-
-  it "outputs the minimal, unique form to represent the value" do
-    0.56.to_s.should == "0.56"
-  end
-
-  describe "matches" do
-    it "random examples in all ranges" do
-      # 50.times do
-      #   bytes = (0...8).map { rand(256) }
-      #   string = bytes.pack('C8')
-      #   float = string.unpack('D').first
-      #   puts "#{'%.20g' % float}.to_s.should == #{float.to_s.inspect}"
-      # end
-
-      2.5540217314354050325e+163.to_s.should == "2.554021731435405e+163"
-      2.5492588360356597544e-172.to_s.should == "2.5492588360356598e-172"
-      1.742770260934704852e-82.to_s.should == "1.7427702609347049e-82"
-      6.2108093676180883209e-104.to_s.should == "6.210809367618088e-104"
-      -3.3448803488331067402e-143.to_s.should == "-3.3448803488331067e-143"
-      -2.2740074343500832557e-168.to_s.should == "-2.2740074343500833e-168"
-      7.0587971678048535732e+191.to_s.should == "7.058797167804854e+191"
-      -284438.88327586348169.to_s.should == "-284438.8832758635"
-      3.953272468476091301e+105.to_s.should == "3.9532724684760913e+105"
-      -3.6361359552959847853e+100.to_s.should == "-3.636135955295985e+100"
-      -1.3222325865575206185e-31.to_s.should == "-1.3222325865575206e-31"
-      1.1440138916932761366e+130.to_s.should == "1.1440138916932761e+130"
-      4.8750891560387561157e-286.to_s.should == "4.875089156038756e-286"
-      5.6101113356591453525e-257.to_s.should == "5.610111335659145e-257"
-      -3.829644279545809575e-100.to_s.should == "-3.8296442795458096e-100"
-      1.5342839401396406117e-194.to_s.should == "1.5342839401396406e-194"
-      2.2284972755169921402e-144.to_s.should == "2.228497275516992e-144"
-      2.1825655917065601737e-61.to_s.should == "2.1825655917065602e-61"
-      -2.6672271363524338322e-62.to_s.should == "-2.667227136352434e-62"
-      -1.9257995160119059415e+21.to_s.should == "-1.925799516011906e+21"
-      -8.9096732962887121718e-198.to_s.should == "-8.909673296288712e-198"
-      2.0202075376548644959e-90.to_s.should == "2.0202075376548645e-90"
-      -7.7341602581786258961e-266.to_s.should == "-7.734160258178626e-266"
-      3.5134482598733635046e+98.to_s.should == "3.5134482598733635e+98"
-      -2.124411722371029134e+154.to_s.should == "-2.124411722371029e+154"
-      -4.573908787355718687e+110.to_s.should == "-4.573908787355719e+110"
-      -1.9344425934170969879e-232.to_s.should == "-1.934442593417097e-232"
-      -1.3274227399979271095e+171.to_s.should == "-1.3274227399979271e+171"
-      9.3495270482104442383e-283.to_s.should == "9.349527048210444e-283"
-      -4.2046059371986483233e+307.to_s.should == "-4.2046059371986483e+307"
-      3.6133547278583543004e-117.to_s.should == "3.613354727858354e-117"
-      4.9247416523566613499e-08.to_s.should == "4.9247416523566613e-08"
-      1.6936145488250064007e-71.to_s.should == "1.6936145488250064e-71"
-      2.4455483206829433098e+96.to_s.should == "2.4455483206829433e+96"
-      7.9797449851436455384e+124.to_s.should == "7.979744985143646e+124"
-      -1.3873689634457876774e-129.to_s.should == "-1.3873689634457877e-129"
-      3.9761102037533483075e+284.to_s.should == "3.976110203753348e+284"
-      -4.2819791952139402486e-303.to_s.should == "-4.28197919521394e-303"
-      -5.7981017546689831298e-116.to_s.should == "-5.798101754668983e-116"
-      -3.953266497860534199e-28.to_s.should == "-3.953266497860534e-28"
-      -2.0659852720290440959e-243.to_s.should == "-2.065985272029044e-243"
-      8.9670488995878688018e-05.to_s.should == "8.967048899587869e-05"
-      -1.2317943708113061768e-98.to_s.should == "-1.2317943708113062e-98"
-      -3.8930768307633080463e+248.to_s.should == "-3.893076830763308e+248"
-      6.5854032671803925627e-239.to_s.should == "6.5854032671803926e-239"
-      4.6257022188980878952e+177.to_s.should == "4.625702218898088e+177"
-      -1.9397155125507235603e-187.to_s.should == "-1.9397155125507236e-187"
-      8.5752156951245705056e+117.to_s.should == "8.57521569512457e+117"
-      -2.4784875958162501671e-132.to_s.should == "-2.4784875958162502e-132"
-      -4.4125691841230058457e-203.to_s.should == "-4.412569184123006e-203"
-    end
-
-    it "random examples in human ranges" do
-      # 50.times do
-      #   formatted = ''
-      #   rand(1..3).times do
-      #     formatted << rand(10).to_s
-      #   end
-      #   formatted << '.'
-      #   rand(1..9).times do
-      #     formatted << rand(10).to_s
-      #   end
-      #   float = formatted.to_f
-      #   puts "#{'%.20f' % float}.to_s.should == #{float.to_s.inspect}"
-      # end
-
-      5.17869899999999994122.to_s.should == "5.178699"
-      905.62695729999995819526.to_s.should == "905.6269573"
-      62.75999999999999801048.to_s.should == "62.76"
-      6.93856795800000014651.to_s.should == "6.938567958"
-      4.95999999999999996447.to_s.should == "4.96"
-      32.77993899999999882766.to_s.should == "32.779939"
-      544.12756779999995160324.to_s.should == "544.1275678"
-      66.25801119999999855281.to_s.should == "66.2580112"
-      7.90000000000000035527.to_s.should == "7.9"
-      5.93100000000000004974.to_s.should == "5.931"
-      5.21229313600000043749.to_s.should == "5.212293136"
-      503.44173809000000119340.to_s.should == "503.44173809"
-      79.26000000000000511591.to_s.should == "79.26"
-      8.51524999999999998579.to_s.should == "8.51525"
-      174.00000000000000000000.to_s.should == "174.0"
-      50.39580000000000126192.to_s.should == "50.3958"
-      35.28999999999999914735.to_s.should == "35.29"
-      5.43136675399999990788.to_s.should == "5.431366754"
-      654.07680000000004838512.to_s.should == "654.0768"
-      6.07423700000000010846.to_s.should == "6.074237"
-      102.25779799999999397642.to_s.should == "102.257798"
-      5.08129999999999970584.to_s.should == "5.0813"
-      6.00000000000000000000.to_s.should == "6.0"
-      8.30000000000000071054.to_s.should == "8.3"
-      32.68345999999999662577.to_s.should == "32.68346"
-      581.11170000000004165486.to_s.should == "581.1117"
-      76.31342999999999676675.to_s.should == "76.31343"
-      438.30826000000001840817.to_s.should == "438.30826"
-      482.06631994000002805478.to_s.should == "482.06631994"
-      55.92721026899999969828.to_s.should == "55.927210269"
-      4.00000000000000000000.to_s.should == "4.0"
-      55.86693999999999959982.to_s.should == "55.86694"
-      787.98299999999994724931.to_s.should == "787.983"
-      5.73810511000000023074.to_s.should == "5.73810511"
-      74.51926810000000500622.to_s.should == "74.5192681"
-      892.89999999999997726263.to_s.should == "892.9"
-      68.27299999999999613465.to_s.should == "68.273"
-      904.10000000000002273737.to_s.should == "904.1"
-      5.23200000000000020606.to_s.should == "5.232"
-      4.09628000000000014325.to_s.should == "4.09628"
-      46.05152633699999853434.to_s.should == "46.051526337"
-      142.12884990599999923688.to_s.should == "142.128849906"
-      3.83057023500000015659.to_s.should == "3.830570235"
-      11.81684594699999912848.to_s.should == "11.816845947"
-      80.50000000000000000000.to_s.should == "80.5"
-      382.18215010000000120272.to_s.should == "382.1821501"
-      55.38444606899999911320.to_s.should == "55.384446069"
-      5.78000000000000024869.to_s.should == "5.78"
-      2.88244999999999995666.to_s.should == "2.88245"
-      43.27709999999999723741.to_s.should == "43.2771"
-    end
-
-    it "random values from divisions" do
-      (1.0 / 7).to_s.should == "0.14285714285714285"
-
-      # 50.times do
-      #    a = rand(10)
-      #    b = rand(10)
-      #    c = rand(10)
-      #    d = rand(10)
-      #    expression = "#{a}.#{b} / #{c}.#{d}"
-      #    puts "      (#{expression}).to_s.should == #{eval(expression).to_s.inspect}"
-      #  end
-
-      (1.1 / 7.1).to_s.should == "0.15492957746478875"
-      (6.5 / 8.8).to_s.should == "0.7386363636363635"
-      (4.8 / 4.3).to_s.should == "1.1162790697674418"
-      (4.0 / 1.9).to_s.should == "2.1052631578947367"
-      (9.1 / 0.8).to_s.should == "11.374999999999998"
-      (5.3 / 7.5).to_s.should == "0.7066666666666667"
-      (2.8 / 1.8).to_s.should == "1.5555555555555554"
-      (2.1 / 2.5).to_s.should == "0.8400000000000001"
-      (3.5 / 6.0).to_s.should == "0.5833333333333334"
-      (4.6 / 0.3).to_s.should == "15.333333333333332"
-      (0.6 / 2.4).to_s.should == "0.25"
-      (1.3 / 9.1).to_s.should == "0.14285714285714288"
-      (0.3 / 5.0).to_s.should == "0.06"
-      (5.0 / 4.2).to_s.should == "1.1904761904761905"
-      (3.0 / 2.0).to_s.should == "1.5"
-      (6.3 / 2.0).to_s.should == "3.15"
-      (5.4 / 6.0).to_s.should == "0.9"
-      (9.6 / 8.1).to_s.should == "1.1851851851851851"
-      (8.7 / 1.6).to_s.should == "5.437499999999999"
-      (1.9 / 7.8).to_s.should == "0.24358974358974358"
-      (0.5 / 2.1).to_s.should == "0.23809523809523808"
-      (9.3 / 5.8).to_s.should == "1.6034482758620692"
-      (2.7 / 8.0).to_s.should == "0.3375"
-      (9.7 / 7.8).to_s.should == "1.2435897435897436"
-      (8.1 / 2.4).to_s.should == "3.375"
-      (7.7 / 2.7).to_s.should == "2.8518518518518516"
-      (7.9 / 1.7).to_s.should == "4.647058823529412"
-      (6.5 / 8.2).to_s.should == "0.7926829268292683"
-      (7.8 / 9.6).to_s.should == "0.8125"
-      (2.2 / 4.6).to_s.should == "0.47826086956521746"
-      (0.0 / 1.0).to_s.should == "0.0"
-      (8.3 / 2.9).to_s.should == "2.8620689655172415"
-      (3.1 / 6.1).to_s.should == "0.5081967213114754"
-      (2.8 / 7.8).to_s.should == "0.358974358974359"
-      (8.0 / 0.1).to_s.should == "80.0"
-      (1.7 / 6.4).to_s.should == "0.265625"
-      (1.8 / 5.4).to_s.should == "0.3333333333333333"
-      (8.0 / 5.8).to_s.should == "1.3793103448275863"
-      (5.2 / 4.1).to_s.should == "1.2682926829268295"
-      (9.8 / 5.8).to_s.should == "1.6896551724137934"
-      (5.4 / 9.5).to_s.should == "0.5684210526315789"
-      (8.4 / 4.9).to_s.should == "1.7142857142857142"
-      (1.7 / 3.5).to_s.should == "0.4857142857142857"
-      (1.2 / 5.1).to_s.should == "0.23529411764705882"
-      (1.4 / 2.0).to_s.should == "0.7"
-      (4.8 / 8.0).to_s.should == "0.6"
-      (9.0 / 2.5).to_s.should == "3.6"
-      (0.2 / 0.6).to_s.should == "0.33333333333333337"
-      (7.8 / 5.2).to_s.should == "1.5"
-      (9.5 / 5.5).to_s.should == "1.7272727272727273"
-    end
-  end
-end
-
-describe "Float#to_s" do
-  before :each do
-    @internal = Encoding.default_internal
-  end
-
-  after :each do
-    Encoding.default_internal = @internal
-  end
-
-  it "returns a String in US-ASCII encoding when Encoding.default_internal is nil" do
-    Encoding.default_internal = nil
-    1.23.to_s.encoding.should equal(Encoding::US_ASCII)
-  end
-
-  it "returns a String in US-ASCII encoding when Encoding.default_internal is not nil" do
-    Encoding.default_internal = Encoding::IBM437
-    5.47.to_s.encoding.should equal(Encoding::US_ASCII)
-  end
+  it_behaves_like :float_to_s, :to_s
 end
diff --git a/spec/ruby/core/float/uminus_spec.rb b/spec/ruby/core/float/uminus_spec.rb
index e676a26ada..57bae0fb4b 100644
--- a/spec/ruby/core/float/uminus_spec.rb
+++ b/spec/ruby/core/float/uminus_spec.rb
@@ -23,6 +23,6 @@ describe "Float#-@" do
   end
 
   it "returns NaN for NaN" do
-    nan_value.send(:-@).nan?.should == true
+    nan_value.send(:-@).should.nan?
   end
 end
diff --git a/spec/ruby/core/float/zero_spec.rb b/spec/ruby/core/float/zero_spec.rb
index e70edc422a..1f3de27793 100644
--- a/spec/ruby/core/float/zero_spec.rb
+++ b/spec/ruby/core/float/zero_spec.rb
@@ -2,8 +2,8 @@ require_relative '../../spec_helper'
 
 describe "Float#zero?" do
   it "returns true if self is 0.0" do
-    0.0.zero?.should == true
-    1.0.zero?.should == false
-    -1.0.zero?.should == false
+    0.0.should.zero?
+    1.0.should_not.zero?
+    -1.0.should_not.zero?
   end
 end
diff --git a/spec/ruby/core/gc/auto_compact_spec.rb b/spec/ruby/core/gc/auto_compact_spec.rb
new file mode 100644
index 0000000000..33ad1cb56c
--- /dev/null
+++ b/spec/ruby/core/gc/auto_compact_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+
+describe "GC.auto_compact" do
+  it "can set and get a boolean value" do
+    begin
+      GC.auto_compact = GC.auto_compact
+    rescue NotImplementedError # platform does not support autocompact
+      skip
+    end
+
+    original = GC.auto_compact
+    begin
+      GC.auto_compact = !original
+    rescue NotImplementedError # platform does not support autocompact
+      skip
+    end
+
+    begin
+      GC.auto_compact.should == !original
+    ensure
+      GC.auto_compact = original
+    end
+  end
+end
diff --git a/spec/ruby/core/gc/config_spec.rb b/spec/ruby/core/gc/config_spec.rb
new file mode 100644
index 0000000000..e20e8e4a16
--- /dev/null
+++ b/spec/ruby/core/gc/config_spec.rb
@@ -0,0 +1,83 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "GC.config" do
+    context "without arguments" do
+      it "returns a hash of current settings" do
+        GC.config.should be_kind_of(Hash)
+      end
+
+      it "includes the name of currently loaded GC implementation as a global key" do
+        GC.config.should include(:implementation)
+        GC.config[:implementation].should be_kind_of(String)
+      end
+    end
+
+    context "with a hash of options" do
+      it "allows to set GC implementation's options, returning the new config" do
+        config = GC.config({})
+        # Try to find a boolean setting to reliably test changing it.
+        key, _value = config.find { |_k, v| v == true }
+        skip unless key
+
+        GC.config(key => false).should == config.merge(key => false)
+        GC.config[key].should == false
+        GC.config(key => true).should == config
+        GC.config[key].should == true
+      ensure
+        GC.config(config.except(:implementation))
+      end
+
+      it "does not change settings that aren't present in the hash" do
+        previous = GC.config
+        GC.config({})
+        GC.config.should == previous
+      end
+
+      it "ignores unknown keys" do
+        previous = GC.config
+        GC.config(foo: "bar")
+        GC.config.should == previous
+      end
+
+      it "raises an ArgumentError if options include global keys" do
+        -> { GC.config(implementation: "default") }.should raise_error(ArgumentError, 'Attempting to set read-only key "Implementation"')
+      end
+    end
+
+    context "with a non-hash argument" do
+      it "returns current settings if argument is nil" do
+        GC.config(nil).should == GC.config
+      end
+
+      it "raises ArgumentError for all other arguments" do
+        -> { GC.config([]) }.should raise_error(ArgumentError)
+        -> { GC.config("default") }.should raise_error(ArgumentError)
+        -> { GC.config(1) }.should raise_error(ArgumentError)
+      end
+    end
+
+    guard -> { PlatformGuard.standard? && GC.config[:implementation] == "default" } do
+      context "with default GC implementation on MRI" do
+        before do
+          @default_config = GC.config({})
+        end
+
+        after do
+          GC.config(@default_config.except(:implementation))
+        end
+
+        it "includes :rgengc_allow_full_mark option, true by default" do
+          GC.config.should include(:rgengc_allow_full_mark)
+          GC.config[:rgengc_allow_full_mark].should be_true
+        end
+
+        it "allows to set :rgengc_allow_full_mark" do
+          # This key maps truthy and falsey values to true and false.
+          GC.config(rgengc_allow_full_mark: nil).should == @default_config.merge(rgengc_allow_full_mark: false)
+          GC.config(rgengc_allow_full_mark: 1.23).should == @default_config.merge(rgengc_allow_full_mark: true)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/gc/disable_spec.rb b/spec/ruby/core/gc/disable_spec.rb
index b0221d8520..f89a9d2768 100644
--- a/spec/ruby/core/gc/disable_spec.rb
+++ b/spec/ruby/core/gc/disable_spec.rb
@@ -5,7 +5,7 @@ describe "GC.disable" do
     GC.enable
   end
 
-  it "returns true iff the garbage collection was previously disabled" do
+  it "returns true if and only if the garbage collection was previously disabled" do
     GC.enable
     GC.disable.should == false
     GC.disable.should == true
diff --git a/spec/ruby/core/gc/enable_spec.rb b/spec/ruby/core/gc/enable_spec.rb
index eb8d572f46..ca4488547a 100644
--- a/spec/ruby/core/gc/enable_spec.rb
+++ b/spec/ruby/core/gc/enable_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "GC.enable" do
 
-  it "returns true iff the garbage collection was already disabled" do
+  it "returns true if and only if the garbage collection was already disabled" do
     GC.enable
     GC.enable.should == false
     GC.disable
diff --git a/spec/ruby/core/gc/measure_total_time_spec.rb b/spec/ruby/core/gc/measure_total_time_spec.rb
new file mode 100644
index 0000000000..f5377c18fd
--- /dev/null
+++ b/spec/ruby/core/gc/measure_total_time_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+
+describe "GC.measure_total_time" do
+  before :each do
+    @default = GC.measure_total_time
+  end
+
+  after :each do
+    GC.measure_total_time = @default
+  end
+
+  it "can set and get a boolean value" do
+    original = GC.measure_total_time
+    GC.measure_total_time = !original
+    GC.measure_total_time.should == !original
+  end
+end
diff --git a/spec/ruby/core/gc/profiler/disable_spec.rb b/spec/ruby/core/gc/profiler/disable_spec.rb
index 321a207deb..74089693eb 100644
--- a/spec/ruby/core/gc/profiler/disable_spec.rb
+++ b/spec/ruby/core/gc/profiler/disable_spec.rb
@@ -11,6 +11,6 @@ describe "GC::Profiler.disable" do
 
   it "disables the profiler" do
     GC::Profiler.disable
-    GC::Profiler.enabled?.should == false
+    GC::Profiler.should_not.enabled?
   end
 end
diff --git a/spec/ruby/core/gc/profiler/enable_spec.rb b/spec/ruby/core/gc/profiler/enable_spec.rb
index 1594511675..313ca3d949 100644
--- a/spec/ruby/core/gc/profiler/enable_spec.rb
+++ b/spec/ruby/core/gc/profiler/enable_spec.rb
@@ -12,6 +12,6 @@ describe "GC::Profiler.enable" do
 
   it "enables the profiler" do
     GC::Profiler.enable
-    GC::Profiler.enabled?.should == true
+    GC::Profiler.should.enabled?
   end
 end
diff --git a/spec/ruby/core/gc/start_spec.rb b/spec/ruby/core/gc/start_spec.rb
index fb6820db14..c941058969 100644
--- a/spec/ruby/core/gc/start_spec.rb
+++ b/spec/ruby/core/gc/start_spec.rb
@@ -5,4 +5,8 @@ describe "GC.start" do
     GC.start.should == nil
     GC.start.should == nil
   end
+
+  it "accepts keyword arguments" do
+    GC.start(full_mark: true, immediate_sweep: true).should == nil
+  end
 end
diff --git a/spec/ruby/core/gc/stat_spec.rb b/spec/ruby/core/gc/stat_spec.rb
new file mode 100644
index 0000000000..3b43b28a92
--- /dev/null
+++ b/spec/ruby/core/gc/stat_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../spec_helper'
+
+describe "GC.stat" do
+  it "returns hash of values" do
+    stat = GC.stat
+    stat.should be_kind_of(Hash)
+    stat.keys.should.include?(:count)
+  end
+
+  it "updates the given hash values" do
+    hash = { count: "hello", __other__: "world" }
+    stat = GC.stat(hash)
+
+    stat.should be_kind_of(Hash)
+    stat.should equal hash
+    stat[:count].should be_kind_of(Integer)
+    stat[:__other__].should == "world"
+  end
+
+  it "the values are all Integer since rb_gc_stat() returns size_t" do
+    GC.stat.values.each { |value| value.should be_kind_of(Integer) }
+  end
+
+  it "can return a single value" do
+    GC.stat(:count).should be_kind_of(Integer)
+  end
+
+  it "increases count after GC is run" do
+    count = GC.stat(:count)
+    GC.start
+    GC.stat(:count).should > count
+  end
+
+  it "increases major_gc_count after GC is run" do
+    count = GC.stat(:major_gc_count)
+    GC.start
+    GC.stat(:major_gc_count).should > count
+  end
+
+  it "provides some number for count" do
+    GC.stat(:count).should be_kind_of(Integer)
+    GC.stat[:count].should be_kind_of(Integer)
+  end
+
+  it "provides some number for heap_free_slots" do
+    GC.stat(:heap_free_slots).should be_kind_of(Integer)
+    GC.stat[:heap_free_slots].should be_kind_of(Integer)
+  end
+
+  it "provides some number for total_allocated_objects" do
+    GC.stat(:total_allocated_objects).should be_kind_of(Integer)
+    GC.stat[:total_allocated_objects].should be_kind_of(Integer)
+  end
+
+  it "raises an error if argument is not nil, a symbol, or a hash" do
+    -> { GC.stat(7) }.should raise_error(TypeError, "non-hash or symbol given")
+  end
+
+  it "raises an error if an unknown key is given" do
+    -> { GC.stat(:foo) }.should raise_error(ArgumentError, "unknown key: foo")
+  end
+end
diff --git a/spec/ruby/core/gc/total_time_spec.rb b/spec/ruby/core/gc/total_time_spec.rb
new file mode 100644
index 0000000000..a8430fbe9a
--- /dev/null
+++ b/spec/ruby/core/gc/total_time_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "GC.total_time" do
+  it "returns an Integer" do
+    GC.total_time.should be_kind_of(Integer)
+  end
+
+  it "increases as collections are run" do
+    time_before = GC.total_time
+    GC.start
+    GC.total_time.should >= time_before
+  end
+end
diff --git a/spec/ruby/core/hash/any_spec.rb b/spec/ruby/core/hash/any_spec.rb
index bd33e8cd8f..c26dfabde6 100644
--- a/spec/ruby/core/hash/any_spec.rb
+++ b/spec/ruby/core/hash/any_spec.rb
@@ -4,10 +4,10 @@ describe "Hash#any?" do
   describe 'with no block given' do
     it "checks if there are any members of a Hash" do
       empty_hash = {}
-      empty_hash.any?.should == false
+      empty_hash.should_not.any?
 
       hash_with_members = { 'key' => 'value' }
-      hash_with_members.any?.should == true
+      hash_with_members.should.any?
     end
   end
 
diff --git a/spec/ruby/core/hash/assoc_spec.rb b/spec/ruby/core/hash/assoc_spec.rb
index 64442918d1..62b2a11b30 100644
--- a/spec/ruby/core/hash/assoc_spec.rb
+++ b/spec/ruby/core/hash/assoc_spec.rb
@@ -22,11 +22,11 @@ describe "Hash#assoc" do
   end
 
   it "only returns the first matching key-value pair for identity hashes" do
-    # Avoid literal String keys in Hash#[]= due to https://bugs.ruby-lang.org/issues/12855
+    # Avoid literal String keys since string literals can be frozen and interned e.g. with --enable-frozen-string-literal
     h = {}.compare_by_identity
-    k1 = 'pear'
+    k1 = 'pear'.dup
     h[k1] = :red
-    k2 = 'pear'
+    k2 = 'pear'.dup
     h[k2] = :green
     h.size.should == 2
     h.keys.grep(/pear/).size.should == 2
diff --git a/spec/ruby/core/hash/clear_spec.rb b/spec/ruby/core/hash/clear_spec.rb
index e7816acbbc..cf05e36ac9 100644
--- a/spec/ruby/core/hash/clear_spec.rb
+++ b/spec/ruby/core/hash/clear_spec.rb
@@ -25,8 +25,8 @@ describe "Hash#clear" do
     h.default_proc.should_not == nil
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.clear  }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.clear }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.clear  }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.clear }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/compact_spec.rb b/spec/ruby/core/hash/compact_spec.rb
index ec9d4b5d79..13371bce43 100644
--- a/spec/ruby/core/hash/compact_spec.rb
+++ b/spec/ruby/core/hash/compact_spec.rb
@@ -18,6 +18,30 @@ describe "Hash#compact" do
     @hash.compact
     @hash.should == @initial_pairs
   end
+
+  ruby_version_is '3.3' do
+    it "retains the default value" do
+      hash = Hash.new(1)
+      hash.compact.default.should == 1
+      hash[:a] = 1
+      hash.compact.default.should == 1
+    end
+
+    it "retains the default_proc" do
+      pr = proc { |h, k| h[k] = [] }
+      hash = Hash.new(&pr)
+      hash.compact.default_proc.should == pr
+      hash[:a] = 1
+      hash.compact.default_proc.should == pr
+    end
+
+    it "retains compare_by_identity flag" do
+      hash = {}.compare_by_identity
+      hash.compact.compare_by_identity?.should == true
+      hash[:a] = 1
+      hash.compact.compare_by_identity?.should == true
+    end
+  end
 end
 
 describe "Hash#compact!" do
@@ -51,8 +75,8 @@ describe "Hash#compact!" do
       @hash.freeze
     end
 
-    it "keeps pairs and raises a #{frozen_error_class}" do
-      ->{ @hash.compact! }.should raise_error(frozen_error_class)
+    it "keeps pairs and raises a FrozenError" do
+      ->{ @hash.compact! }.should raise_error(FrozenError)
       @hash.should == @initial_pairs
     end
   end
diff --git a/spec/ruby/core/hash/compare_by_identity_spec.rb b/spec/ruby/core/hash/compare_by_identity_spec.rb
index 0658b4954a..2975526a97 100644
--- a/spec/ruby/core/hash/compare_by_identity_spec.rb
+++ b/spec/ruby/core/hash/compare_by_identity_spec.rb
@@ -33,7 +33,7 @@ describe "Hash#compare_by_identity" do
   it "has no effect on an already compare_by_identity hash" do
     @idh[:foo] = :bar
     @idh.compare_by_identity.should equal @idh
-    @idh.compare_by_identity?.should == true
+    @idh.should.compare_by_identity?
     @idh[:foo].should == :bar
   end
 
@@ -80,24 +80,26 @@ describe "Hash#compare_by_identity" do
     @h[o].should == :o
   end
 
-  it "raises a #{frozen_error_class} on frozen hashes" do
+  it "raises a FrozenError on frozen hashes" do
     @h = @h.freeze
-    -> { @h.compare_by_identity }.should raise_error(frozen_error_class)
+    -> { @h.compare_by_identity }.should raise_error(FrozenError)
   end
 
-  # Behaviour confirmed in bug #1871
+  # Behaviour confirmed in https://bugs.ruby-lang.org/issues/1871
   it "persists over #dups" do
-    @idh['foo'] = :bar
-    @idh['foo'] = :glark
+    @idh['foo'.dup] = :bar
+    @idh['foo'.dup] = :glark
     @idh.dup.should == @idh
     @idh.dup.size.should == @idh.size
+    @idh.dup.should.compare_by_identity?
   end
 
   it "persists over #clones" do
-    @idh['foo'] = :bar
-    @idh['foo'] = :glark
+    @idh['foo'.dup] = :bar
+    @idh['foo'.dup] = :glark
     @idh.clone.should == @idh
     @idh.clone.size.should == @idh.size
+    @idh.dup.should.compare_by_identity?
   end
 
   it "does not copy string keys" do
@@ -108,9 +110,16 @@ describe "Hash#compare_by_identity" do
     @idh.keys.first.should equal foo
   end
 
+  # Check `#[]=` call with a String literal.
+  # Don't use `#+` because with `#+` it's no longer a String literal.
+  #
+  # See https://bugs.ruby-lang.org/issues/12855
   it "gives different identity for string literals" do
+    eval <<~RUBY
+    # frozen_string_literal: false
     @idh['foo'] = 1
     @idh['foo'] = 2
+    RUBY
     @idh.values.should == [1, 2]
     @idh.size.should == 2
   end
diff --git a/spec/ruby/core/hash/constructor_spec.rb b/spec/ruby/core/hash/constructor_spec.rb
index ad67274802..0f97f7b40e 100644
--- a/spec/ruby/core/hash/constructor_spec.rb
+++ b/spec/ruby/core/hash/constructor_spec.rb
@@ -42,26 +42,13 @@ describe "Hash.[]" do
     Hash[ary].should == { a: :b }
   end
 
-  ruby_version_is "" ... "2.7" do
-    it "ignores elements that are not arrays" do
-      -> {
-        Hash[[:a]].should == {}
-      }.should complain(/ignoring wrong elements/)
-      -> {
-        Hash[[:nil]].should == {}
-      }.should complain(/ignoring wrong elements/)
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "raises for elements that are not arrays" do
-      -> {
-        Hash[[:a]].should == {}
-      }.should raise_error(ArgumentError)
-      -> {
-        Hash[[:nil]].should == {}
-      }.should raise_error(ArgumentError)
-    end
+  it "raises for elements that are not arrays" do
+    -> {
+      Hash[[:a]].should == {}
+    }.should raise_error(ArgumentError)
+    -> {
+      Hash[[:nil]].should == {}
+    }.should raise_error(ArgumentError)
   end
 
   it "raises an ArgumentError for arrays of more than 2 elements" do
@@ -116,8 +103,27 @@ describe "Hash.[]" do
     HashSpecs::MyInitializerHash[Hash[1, 2]].should be_an_instance_of(HashSpecs::MyInitializerHash)
   end
 
-  it "removes the default_proc" do
+  it "does not retain the default value" do
+    hash = Hash.new(1)
+    Hash[hash].default.should be_nil
+    hash[:a] = 1
+    Hash[hash].default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
     hash = Hash.new { |h, k| h[k] = [] }
     Hash[hash].default_proc.should be_nil
+    hash[:a] = 1
+    Hash[hash].default_proc.should be_nil
+  end
+
+  ruby_version_is '3.3' do
+    it "does not retain compare_by_identity flag" do
+      hash = { a: 1 }.compare_by_identity
+      Hash[hash].compare_by_identity?.should == false
+
+      hash = {}.compare_by_identity
+      Hash[hash].compare_by_identity?.should == false
+    end
   end
 end
diff --git a/spec/ruby/core/hash/deconstruct_keys_spec.rb b/spec/ruby/core/hash/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..bbcd8932e5
--- /dev/null
+++ b/spec/ruby/core/hash/deconstruct_keys_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+
+describe "Hash#deconstruct_keys" do
+  it "returns self" do
+    hash = {a: 1, b: 2}
+
+    hash.deconstruct_keys([:a, :b]).should equal hash
+  end
+
+  it "requires one argument" do
+    -> {
+      {a: 1}.deconstruct_keys
+    }.should raise_error(ArgumentError, /wrong number of arguments \(given 0, expected 1\)/)
+  end
+
+  it "ignores argument" do
+    hash = {a: 1, b: 2}
+
+    hash.deconstruct_keys([:a]).should == {a: 1, b: 2}
+    hash.deconstruct_keys(0   ).should == {a: 1, b: 2}
+    hash.deconstruct_keys(''  ).should == {a: 1, b: 2}
+  end
+end
diff --git a/spec/ruby/core/hash/default_proc_spec.rb b/spec/ruby/core/hash/default_proc_spec.rb
index 83ad98e5b6..f4e4803632 100644
--- a/spec/ruby/core/hash/default_proc_spec.rb
+++ b/spec/ruby/core/hash/default_proc_spec.rb
@@ -73,8 +73,8 @@ describe "Hash#default_proc=" do
     end.should raise_error(TypeError)
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { {}.freeze.default_proc = Proc.new {} }.should raise_error(frozen_error_class)
-    -> { {}.freeze.default_proc = nil }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { {}.freeze.default_proc = Proc.new {} }.should raise_error(FrozenError)
+    -> { {}.freeze.default_proc = nil }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/default_spec.rb b/spec/ruby/core/hash/default_spec.rb
index 6cad65bb62..d8b62ea196 100644
--- a/spec/ruby/core/hash/default_spec.rb
+++ b/spec/ruby/core/hash/default_spec.rb
@@ -39,8 +39,8 @@ describe "Hash#default=" do
     end
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.default = nil }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.default = nil }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.default = nil }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.default = nil }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/delete_if_spec.rb b/spec/ruby/core/hash/delete_if_spec.rb
index 345a24a726..c9e670ffc3 100644
--- a/spec/ruby/core/hash/delete_if_spec.rb
+++ b/spec/ruby/core/hash/delete_if_spec.rb
@@ -34,9 +34,9 @@ describe "Hash#delete_if" do
     each_pairs.should == delete_pairs
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.delete_if { false } }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.delete_if { true } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.delete_if { false } }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.delete_if { true } }.should raise_error(FrozenError)
   end
 
   it_behaves_like :hash_iteration_no_block, :delete_if
diff --git a/spec/ruby/core/hash/delete_spec.rb b/spec/ruby/core/hash/delete_spec.rb
index a69815c1d9..3e3479c69c 100644
--- a/spec/ruby/core/hash/delete_spec.rb
+++ b/spec/ruby/core/hash/delete_spec.rb
@@ -24,7 +24,7 @@ describe "Hash#delete" do
   it "allows removing a key while iterating" do
     h = { a: 1, b: 2 }
     visited = []
-    h.each_pair { |k,v|
+    h.each_pair { |k, v|
       visited << k
       h.delete(k)
     }
@@ -32,13 +32,27 @@ describe "Hash#delete" do
     h.should == {}
   end
 
+  it "allows removing a key while iterating for big hashes" do
+    h = { a: 1, b: 2, c: 3, d: 4, e: 5, f: 6, g: 7, h: 8, i: 9, j: 10,
+          k: 11, l: 12, m: 13, n: 14, o: 15, p: 16, q: 17, r: 18, s: 19, t: 20,
+          u: 21, v: 22, w: 23, x: 24, y: 25, z: 26 }
+    visited = []
+    h.each_pair { |k, v|
+      visited << k
+      h.delete(k)
+    }
+    visited.should == [:a, :b, :c, :d, :e, :f, :g, :h, :i, :j, :k, :l, :m,
+                       :n, :o, :p, :q, :r, :s, :t, :u, :v, :w, :x, :y, :z]
+    h.should == {}
+  end
+
   it "accepts keys with private #hash method" do
     key = HashSpecs::KeyWithPrivateHash.new
     { key => 5 }.delete(key).should == 5
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.delete("foo")  }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.delete("foo") }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.delete("foo") }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.delete("foo") }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/element_reference_spec.rb b/spec/ruby/core/hash/element_reference_spec.rb
index 2eb65d3789..d5859cb342 100644
--- a/spec/ruby/core/hash/element_reference_spec.rb
+++ b/spec/ruby/core/hash/element_reference_spec.rb
@@ -12,7 +12,7 @@ describe "Hash#[]" do
     h[[]].should == "baz"
   end
 
-  it "returns nil as default default value" do
+  it "returns nil as default value" do
     { 0 => 0 }[5].should == nil
   end
 
@@ -30,7 +30,7 @@ describe "Hash#[]" do
   end
 
   it "does not create copies of the immediate default value" do
-    str = "foo"
+    str = +"foo"
     h = Hash.new(str)
     a = h[:a]
     b = h[:b]
@@ -117,4 +117,18 @@ describe "Hash#[]" do
     key = HashSpecs::KeyWithPrivateHash.new
     { key => 42 }[key].should == 42
   end
+
+  it "does not dispatch to hash for Boolean, Integer, Float, String, or Symbol" do
+    code = <<-EOC
+      load '#{fixture __FILE__, "name.rb"}'
+      hash = { true => 42, false => 42, 1 => 42, 2.0 => 42, "hello" => 42, :ok => 42 }
+      [true, false, 1, 2.0, "hello", :ok].each do |value|
+        raise "incorrect value" unless hash[value] == 42
+      end
+      puts "Ok."
+    EOC
+    result = ruby_exe(code, args: "2>&1")
+    result.should == "Ok.\n"
+  end
+
 end
diff --git a/spec/ruby/core/hash/empty_spec.rb b/spec/ruby/core/hash/empty_spec.rb
index e9be44bab0..881e1cc34b 100644
--- a/spec/ruby/core/hash/empty_spec.rb
+++ b/spec/ruby/core/hash/empty_spec.rb
@@ -3,13 +3,13 @@ require_relative 'fixtures/classes'
 
 describe "Hash#empty?" do
   it "returns true if the hash has no entries" do
-    {}.empty?.should == true
-    { 1 => 1 }.empty?.should == false
+    {}.should.empty?
+    { 1 => 1 }.should_not.empty?
   end
 
   it "returns true if the hash has no entries and has a default value" do
-    Hash.new(5).empty?.should == true
-    Hash.new { 5 }.empty?.should == true
-    Hash.new { |hsh, k| hsh[k] = k }.empty?.should == true
+    Hash.new(5).should.empty?
+    Hash.new { 5 }.should.empty?
+    Hash.new { |hsh, k| hsh[k] = k }.should.empty?
   end
 end
diff --git a/spec/ruby/core/hash/except_spec.rb b/spec/ruby/core/hash/except_spec.rb
new file mode 100644
index 0000000000..026e454b13
--- /dev/null
+++ b/spec/ruby/core/hash/except_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+
+describe "Hash#except" do
+  before :each do
+    @hash = { a: 1, b: 2, c: 3 }
+  end
+
+  it "returns a new duplicate hash without arguments" do
+    ret = @hash.except
+    ret.should_not equal(@hash)
+    ret.should == @hash
+  end
+
+  it "returns a hash without the requested subset" do
+    @hash.except(:c, :a).should == { b: 2 }
+  end
+
+  it "ignores keys not present in the original hash" do
+    @hash.except(:a, :chunky_bacon).should == { b: 2, c: 3 }
+  end
+
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.except(:a).default.should be_nil
+    h[:a] = 1
+    h.except(:a).default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.except(:a).default_proc.should be_nil
+    h[:a] = 1
+    h.except(:a).default_proc.should be_nil
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.except(:a)
+    h2.compare_by_identity?.should == true
+  end
+end
diff --git a/spec/ruby/core/hash/fetch_spec.rb b/spec/ruby/core/hash/fetch_spec.rb
index 753167f709..6e0d207224 100644
--- a/spec/ruby/core/hash/fetch_spec.rb
+++ b/spec/ruby/core/hash/fetch_spec.rb
@@ -4,7 +4,7 @@ require_relative '../../shared/hash/key_error'
 
 describe "Hash#fetch" do
   context "when the key is not found" do
-    it_behaves_like :key_error, -> obj, key { obj.fetch(key) }, Hash.new(a: 5)
+    it_behaves_like :key_error, -> obj, key { obj.fetch(key) }, Hash.new({ a: 5 })
     it_behaves_like :key_error, -> obj, key { obj.fetch(key) }, {}
     it_behaves_like :key_error, -> obj, key { obj.fetch(key) }, Hash.new { 5 }
     it_behaves_like :key_error, -> obj, key { obj.fetch(key) }, Hash.new(5)
diff --git a/spec/ruby/core/hash/fetch_values_spec.rb b/spec/ruby/core/hash/fetch_values_spec.rb
index 041a3f07e9..0cd48565af 100644
--- a/spec/ruby/core/hash/fetch_values_spec.rb
+++ b/spec/ruby/core/hash/fetch_values_spec.rb
@@ -12,10 +12,14 @@ describe "Hash#fetch_values" do
       @hash.fetch_values(:a).should == [1]
       @hash.fetch_values(:a, :c).should == [1, 3]
     end
+
+    it "returns the values for keys ordered in the order of the requested keys" do
+      @hash.fetch_values(:c, :a).should == [3, 1]
+    end
   end
 
   describe "with unmatched keys" do
-    it_behaves_like :key_error, -> obj, key { obj.fetch_values(key) }, Hash.new(a: 5)
+    it_behaves_like :key_error, -> obj, key { obj.fetch_values(key) }, Hash.new({ a: 5 })
 
     it "returns the default value from block" do
       @hash.fetch_values(:z) { |key| "`#{key}' is not found" }.should == ["`z' is not found"]
diff --git a/spec/ruby/core/hash/filter_spec.rb b/spec/ruby/core/hash/filter_spec.rb
index 4382c94e62..7dabe44984 100644
--- a/spec/ruby/core/hash/filter_spec.rb
+++ b/spec/ruby/core/hash/filter_spec.rb
@@ -1,12 +1,10 @@
 require_relative '../../spec_helper'
 require_relative 'shared/select'
 
-ruby_version_is "2.6" do
-  describe "Hash#filter" do
-    it_behaves_like :hash_select, :filter
-  end
+describe "Hash#filter" do
+  it_behaves_like :hash_select, :filter
+end
 
-  describe "Hash#filter!" do
-    it_behaves_like :hash_select!, :filter!
-  end
+describe "Hash#filter!" do
+  it_behaves_like :hash_select!, :filter!
 end
diff --git a/spec/ruby/core/hash/fixtures/name.rb b/spec/ruby/core/hash/fixtures/name.rb
new file mode 100644
index 0000000000..b203bf6ae4
--- /dev/null
+++ b/spec/ruby/core/hash/fixtures/name.rb
@@ -0,0 +1,30 @@
+class TrueClass
+  def hash
+    raise "TrueClass#hash should not be called"
+  end
+end
+class FalseClass
+  def hash
+    raise "FalseClass#hash should not be called"
+  end
+end
+class Integer
+  def hash
+    raise "Integer#hash should not be called"
+  end
+end
+class Float
+  def hash
+    raise "Float#hash should not be called"
+  end
+end
+class String
+  def hash
+    raise "String#hash should not be called"
+  end
+end
+class Symbol
+  def hash
+    raise "Symbol#hash should not be called"
+  end
+end
diff --git a/spec/ruby/core/hash/hash_spec.rb b/spec/ruby/core/hash/hash_spec.rb
index 3649d4d8de..cd67f7a652 100644
--- a/spec/ruby/core/hash/hash_spec.rb
+++ b/spec/ruby/core/hash/hash_spec.rb
@@ -41,4 +41,11 @@ describe "Hash#hash" do
     h.hash.should == {x: [h]}.hash
     # Like above, because h.eql?(x: [h])
   end
+
+  it "allows omitting values" do
+    a = 1
+    b = 2
+
+    {a:, b:}.should == { a: 1, b: 2 }
+  end
 end
diff --git a/spec/ruby/core/hash/index_spec.rb b/spec/ruby/core/hash/index_spec.rb
deleted file mode 100644
index 2b52c69949..0000000000
--- a/spec/ruby/core/hash/index_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-require_relative 'shared/index'
-
-describe "Hash#index" do
-  it_behaves_like :hash_index, :index
-end
diff --git a/spec/ruby/core/hash/initialize_spec.rb b/spec/ruby/core/hash/initialize_spec.rb
index 00e1174ec8..d13496ba3b 100644
--- a/spec/ruby/core/hash/initialize_spec.rb
+++ b/spec/ruby/core/hash/initialize_spec.rb
@@ -45,17 +45,17 @@ describe "Hash#initialize" do
     h.send(:initialize).should equal(h)
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
+  it "raises a FrozenError if called on a frozen instance" do
     block = -> { HashSpecs.frozen_hash.instance_eval { initialize() }}
-    block.should raise_error(frozen_error_class)
+    block.should raise_error(FrozenError)
 
     block = -> { HashSpecs.frozen_hash.instance_eval { initialize(nil) }  }
-    block.should raise_error(frozen_error_class)
+    block.should raise_error(FrozenError)
 
     block = -> { HashSpecs.frozen_hash.instance_eval { initialize(5) }    }
-    block.should raise_error(frozen_error_class)
+    block.should raise_error(FrozenError)
 
     block = -> { HashSpecs.frozen_hash.instance_eval { initialize { 5 } } }
-    block.should raise_error(frozen_error_class)
+    block.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/invert_spec.rb b/spec/ruby/core/hash/invert_spec.rb
index 73377a9e97..c06e15ff7c 100644
--- a/spec/ruby/core/hash/invert_spec.rb
+++ b/spec/ruby/core/hash/invert_spec.rb
@@ -24,4 +24,25 @@ describe "Hash#invert" do
     HashSpecs::MyHash[1 => 2, 3 => 4].invert.class.should == Hash
     HashSpecs::MyHash[].invert.class.should == Hash
   end
+
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.invert.default.should be_nil
+    h[:a] = 1
+    h.invert.default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.invert.default_proc.should be_nil
+    h[:a] = 1
+    h.invert.default_proc.should be_nil
+  end
+
+  it "does not retain compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.invert
+    h2.compare_by_identity?.should == false
+  end
 end
diff --git a/spec/ruby/core/hash/keep_if_spec.rb b/spec/ruby/core/hash/keep_if_spec.rb
index 278eafc969..d50d969467 100644
--- a/spec/ruby/core/hash/keep_if_spec.rb
+++ b/spec/ruby/core/hash/keep_if_spec.rb
@@ -27,9 +27,9 @@ describe "Hash#keep_if" do
     h.keep_if { true }.should equal(h)
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.keep_if { true } }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.keep_if { false } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.keep_if { true } }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.keep_if { false } }.should raise_error(FrozenError)
   end
 
   it_behaves_like :hash_iteration_no_block, :keep_if
diff --git a/spec/ruby/core/hash/merge_spec.rb b/spec/ruby/core/hash/merge_spec.rb
index 91ded30eb7..6710d121ef 100644
--- a/spec/ruby/core/hash/merge_spec.rb
+++ b/spec/ruby/core/hash/merge_spec.rb
@@ -81,19 +81,40 @@ describe "Hash#merge" do
     merge_pairs.should == expected_pairs
   end
 
-  ruby_version_is "2.6" do
-    it "accepts multiple hashes" do
-      result = { a: 1 }.merge({ b: 2 }, { c: 3 }, { d: 4 })
-      result.should == { a: 1, b: 2, c: 3, d: 4 }
-    end
-
-    it "accepts zero arguments and returns a copy of self" do
-      hash = { a: 1 }
-      merged = hash.merge
-
-      merged.should eql(hash)
-      merged.should_not equal(hash)
-    end
+  it "accepts multiple hashes" do
+    result = { a: 1 }.merge({ b: 2 }, { c: 3 }, { d: 4 })
+    result.should == { a: 1, b: 2, c: 3, d: 4 }
+  end
+
+  it "accepts zero arguments and returns a copy of self" do
+    hash = { a: 1 }
+    merged = hash.merge
+
+    merged.should eql(hash)
+    merged.should_not equal(hash)
+  end
+
+  it "retains the default value" do
+    h = Hash.new(1)
+    h.merge(b: 1, d: 2).default.should == 1
+  end
+
+  it "retains the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.merge(b: 1, d: 2).default_proc.should == pr
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.merge(b: 1, d: 2)
+    h2.compare_by_identity?.should == true
+  end
+
+  it "ignores compare_by_identity flag of an argument" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = { b: 1, d: 2 }.merge(h)
+    h2.compare_by_identity?.should == false
   end
 end
 
diff --git a/spec/ruby/core/hash/new_spec.rb b/spec/ruby/core/hash/new_spec.rb
index 6054b69bdd..5ae3e1f98d 100644
--- a/spec/ruby/core/hash/new_spec.rb
+++ b/spec/ruby/core/hash/new_spec.rb
@@ -33,4 +33,35 @@ describe "Hash.new" do
     -> { Hash.new(5) { 0 }   }.should raise_error(ArgumentError)
     -> { Hash.new(nil) { 0 } }.should raise_error(ArgumentError)
   end
+
+  ruby_version_is "3.3"..."3.4" do
+    it "emits a deprecation warning if keyword arguments are passed" do
+      -> { Hash.new(unknown: true) }.should complain(
+        Regexp.new(Regexp.escape("Calling Hash.new with keyword arguments is deprecated and will be removed in Ruby 3.4; use Hash.new({ key: value }) instead"))
+      )
+
+      -> { Hash.new(1, unknown: true) }.should raise_error(ArgumentError)
+      -> { Hash.new(unknown: true) { 0 } }.should raise_error(ArgumentError)
+
+      Hash.new({ unknown: true }).default.should == { unknown: true }
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "accepts a capacity: argument" do
+      Hash.new(5, capacity: 42).default.should == 5
+      Hash.new(capacity: 42).default.should == nil
+      (Hash.new(capacity: 42) { 1 }).default_proc.should_not == nil
+    end
+
+    it "ignores negative capacity" do
+      -> { Hash.new(capacity: -42) }.should_not raise_error
+    end
+
+    it "raises an error if unknown keyword arguments are passed" do
+      -> { Hash.new(unknown: true) }.should raise_error(ArgumentError)
+      -> { Hash.new(1, unknown: true) }.should raise_error(ArgumentError)
+      -> { Hash.new(unknown: true) { 0 } }.should raise_error(ArgumentError)
+    end
+  end
 end
diff --git a/spec/ruby/core/hash/rehash_spec.rb b/spec/ruby/core/hash/rehash_spec.rb
index 587935fc43..db3e91b166 100644
--- a/spec/ruby/core/hash/rehash_spec.rb
+++ b/spec/ruby/core/hash/rehash_spec.rb
@@ -59,8 +59,56 @@ describe "Hash#rehash" do
     h.keys.should == [a]
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.rehash  }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.rehash }.should raise_error(frozen_error_class)
+  it "removes duplicate keys for large hashes" do
+    a = [1,2]
+    b = [1]
+
+    h = {}
+    h[a] = true
+    h[b] = true
+    100.times { |n| h[n] = true }
+    b << 2
+    h.size.should == 102
+    h.keys.should.include? a
+    h.keys.should.include? b
+    h.rehash
+    h.size.should == 101
+    h.keys.should.include? a
+    h.keys.should_not.include? [1]
+  end
+
+  it "iterates keys in insertion order" do
+    key = Class.new do
+      attr_reader :name
+
+      def initialize(name)
+        @name = name
+      end
+
+      def hash
+        123
+      end
+    end
+
+    a, b, c, d = key.new('a'), key.new('b'), key.new('c'), key.new('d')
+    h = { a => 1, b => 2, c => 3, d => 4 }
+    h.size.should == 4
+
+    key.class_exec do
+      def eql?(other)
+        true
+      end
+    end
+
+    h.rehash
+    h.size.should == 1
+    k, v = h.first
+    k.name.should == 'a'
+    v.should == 4
+  end
+
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.rehash  }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.rehash }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/hash/reject_spec.rb b/spec/ruby/core/hash/reject_spec.rb
index 8016be5e83..8381fc7fc1 100644
--- a/spec/ruby/core/hash/reject_spec.rb
+++ b/spec/ruby/core/hash/reject_spec.rb
@@ -31,11 +31,6 @@ describe "Hash#reject" do
       HashSpecs::MyHash[1 => 2, 3 => 4].reject { false }.should be_kind_of(Hash)
       HashSpecs::MyHash[1 => 2, 3 => 4].reject { true }.should be_kind_of(Hash)
     end
-
-    it "does not taint the resulting hash" do
-      h = { a: 1 }.taint
-      h.reject {false}.tainted?.should == false
-    end
   end
 
   it "processes entries with the same order as reject!" do
@@ -49,6 +44,27 @@ describe "Hash#reject" do
     reject_pairs.should == reject_bang_pairs
   end
 
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.reject { false }.default.should be_nil
+    h[:a] = 1
+    h.reject { false }.default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.reject { false }.default_proc.should be_nil
+    h[:a] = 1
+    h.reject { false }.default_proc.should be_nil
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.reject { |k, _| k == :a }
+    h2.compare_by_identity?.should == true
+  end
+
   it_behaves_like :hash_iteration_no_block, :reject
   it_behaves_like :enumeratorized_with_origin_size, :reject, { 1 => 2, 3 => 4, 5 => 6 }
 end
@@ -87,12 +103,12 @@ describe "Hash#reject!" do
     reject_bang_pairs.should == delete_if_pairs
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance that is modified" do
-    -> { HashSpecs.empty_frozen_hash.reject! { true } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance that is modified" do
+    -> { HashSpecs.empty_frozen_hash.reject! { true } }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance that would not be modified" do
-    -> { HashSpecs.frozen_hash.reject! { false } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance that would not be modified" do
+    -> { HashSpecs.frozen_hash.reject! { false } }.should raise_error(FrozenError)
   end
 
   it_behaves_like :hash_iteration_no_block, :reject!
diff --git a/spec/ruby/core/hash/replace_spec.rb b/spec/ruby/core/hash/replace_spec.rb
index 92b2118fd3..db30145e1a 100644
--- a/spec/ruby/core/hash/replace_spec.rb
+++ b/spec/ruby/core/hash/replace_spec.rb
@@ -1,7 +1,79 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
-require_relative 'shared/replace'
 
 describe "Hash#replace" do
-  it_behaves_like :hash_replace, :replace
+  it "replaces the contents of self with other" do
+    h = { a: 1, b: 2 }
+    h.replace(c: -1, d: -2).should equal(h)
+    h.should == { c: -1, d: -2 }
+  end
+
+  it "tries to convert the passed argument to a hash using #to_hash" do
+    obj = mock('{1=>2,3=>4}')
+    obj.should_receive(:to_hash).and_return({ 1 => 2, 3 => 4 })
+
+    h = {}
+    h.replace(obj)
+    h.should == { 1 => 2, 3 => 4 }
+  end
+
+  it "calls to_hash on hash subclasses" do
+    h = {}
+    h.replace(HashSpecs::ToHashHash[1 => 2])
+    h.should == { 1 => 2 }
+  end
+
+  it "does not retain the default value" do
+    hash = Hash.new(1)
+    hash.replace(b: 2).default.should be_nil
+  end
+
+  it "transfers the default value of an argument" do
+    hash = Hash.new(1)
+    { a: 1 }.replace(hash).default.should == 1
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    hash = Hash.new(&pr)
+    hash.replace(b: 2).default_proc.should be_nil
+  end
+
+  it "transfers the default_proc of an argument" do
+    pr = proc { |h, k| h[k] = [] }
+    hash = Hash.new(&pr)
+    { a: 1 }.replace(hash).default_proc.should == pr
+  end
+
+  it "does not call the default_proc of an argument" do
+    hash_a = Hash.new { |h, k| k * 5 }
+    hash_b = Hash.new(-> { raise "Should not invoke lambda" })
+    hash_a.replace(hash_b)
+    hash_a.default.should == hash_b.default
+  end
+
+  it "transfers compare_by_identity flag of an argument" do
+    h = { a: 1, c: 3 }
+    h2 = { b: 2, d: 4 }.compare_by_identity
+    h.replace(h2)
+    h.compare_by_identity?.should == true
+  end
+
+  it "does not retain compare_by_identity flag" do
+    h = { a: 1, c: 3 }.compare_by_identity
+    h.replace(b: 2, d: 4)
+    h.compare_by_identity?.should == false
+  end
+
+  it "raises a FrozenError if called on a frozen instance that would not be modified" do
+    -> do
+      HashSpecs.frozen_hash.replace(HashSpecs.frozen_hash)
+    end.should raise_error(FrozenError)
+  end
+
+  it "raises a FrozenError if called on a frozen instance that is modified" do
+    -> do
+      HashSpecs.frozen_hash.replace(HashSpecs.empty_frozen_hash)
+    end.should raise_error(FrozenError)
+  end
 end
diff --git a/spec/ruby/core/hash/ruby2_keywords_hash_spec.rb b/spec/ruby/core/hash/ruby2_keywords_hash_spec.rb
new file mode 100644
index 0000000000..7dbb9c0a98
--- /dev/null
+++ b/spec/ruby/core/hash/ruby2_keywords_hash_spec.rb
@@ -0,0 +1,83 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Hash.ruby2_keywords_hash?" do
+  it "returns false if the Hash is not a keywords Hash" do
+    Hash.ruby2_keywords_hash?({}).should == false
+  end
+
+  it "returns true if the Hash is a keywords Hash marked by Module#ruby2_keywords" do
+    obj = Class.new {
+      ruby2_keywords def m(*args)
+        args.last
+      end
+    }.new
+    Hash.ruby2_keywords_hash?(obj.m(a: 1)).should == true
+  end
+
+  it "raises TypeError for non-Hash" do
+    -> { Hash.ruby2_keywords_hash?(nil) }.should raise_error(TypeError)
+  end
+end
+
+describe "Hash.ruby2_keywords_hash" do
+  it "returns a copy of a Hash and marks the copy as a keywords Hash" do
+    h = {a: 1}.freeze
+    kw = Hash.ruby2_keywords_hash(h)
+    Hash.ruby2_keywords_hash?(h).should == false
+    Hash.ruby2_keywords_hash?(kw).should == true
+    kw.should == h
+  end
+
+  it "returns an instance of the subclass if called on an instance of a subclass of Hash" do
+    h = HashSpecs::MyHash.new
+    h[:a] = 1
+    kw = Hash.ruby2_keywords_hash(h)
+    kw.class.should == HashSpecs::MyHash
+    Hash.ruby2_keywords_hash?(h).should == false
+    Hash.ruby2_keywords_hash?(kw).should == true
+    kw.should == h
+  end
+
+  it "copies instance variables" do
+    h = {a: 1}
+    h.instance_variable_set(:@foo, 42)
+    kw = Hash.ruby2_keywords_hash(h)
+    kw.instance_variable_get(:@foo).should == 42
+  end
+
+  it "copies the hash internals" do
+    h = {a: 1}
+    kw = Hash.ruby2_keywords_hash(h)
+    h[:a] = 2
+    kw[:a].should == 1
+  end
+
+  it "raises TypeError for non-Hash" do
+    -> { Hash.ruby2_keywords_hash(nil) }.should raise_error(TypeError)
+  end
+
+  it "retains the default value" do
+    hash = Hash.new(1)
+    Hash.ruby2_keywords_hash(hash).default.should == 1
+    hash[:a] = 1
+    Hash.ruby2_keywords_hash(hash).default.should == 1
+  end
+
+  it "retains the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    hash = Hash.new(&pr)
+    Hash.ruby2_keywords_hash(hash).default_proc.should == pr
+    hash[:a] = 1
+    Hash.ruby2_keywords_hash(hash).default_proc.should == pr
+  end
+
+  ruby_version_is '3.3' do
+    it "retains compare_by_identity_flag" do
+      hash = {}.compare_by_identity
+      Hash.ruby2_keywords_hash(hash).compare_by_identity?.should == true
+      hash[:a] = 1
+      Hash.ruby2_keywords_hash(hash).compare_by_identity?.should == true
+    end
+  end
+end
diff --git a/spec/ruby/core/hash/shared/each.rb b/spec/ruby/core/hash/shared/each.rb
index d1f2e5f672..f9839ff58f 100644
--- a/spec/ruby/core/hash/shared/each.rb
+++ b/spec/ruby/core/hash/shared/each.rb
@@ -21,19 +21,39 @@ describe :hash_each, shared: true do
     ary.sort.should == ["a", "b", "c"]
   end
 
-  it "yields 2 values and not an Array of 2 elements when given a callable of arity 2" do
+  it "always yields an Array of 2 elements, even when given a callable of arity 2" do
     obj = Object.new
     def obj.foo(key, value)
-      ScratchPad << key << value
+    end
+
+    -> {
+      { "a" => 1 }.send(@method, &obj.method(:foo))
+    }.should raise_error(ArgumentError)
+
+    -> {
+      { "a" => 1 }.send(@method, &-> key, value { })
+    }.should raise_error(ArgumentError)
+  end
+
+  it "yields an Array of 2 elements when given a callable of arity 1" do
+    obj = Object.new
+    def obj.foo(key_value)
+      ScratchPad << key_value
     end
 
     ScratchPad.record([])
     { "a" => 1 }.send(@method, &obj.method(:foo))
-    ScratchPad.recorded.should == ["a", 1]
+    ScratchPad.recorded.should == [["a", 1]]
+  end
 
-    ScratchPad.record([])
-    { "a" => 1 }.send(@method, &-> key, value { ScratchPad << key << value })
-    ScratchPad.recorded.should == ["a", 1]
+  it "raises an error for a Hash when an arity enforcing callable of arity >2 is passed in" do
+    obj = Object.new
+    def obj.foo(key, value, extra)
+    end
+
+    -> {
+      { "a" => 1 }.send(@method, &obj.method(:foo))
+    }.should raise_error(ArgumentError)
   end
 
   it "uses the same order as keys() and values()" do
diff --git a/spec/ruby/core/hash/shared/eql.rb b/spec/ruby/core/hash/shared/eql.rb
index 1aed5f51fb..68db49f76d 100644
--- a/spec/ruby/core/hash/shared/eql.rb
+++ b/spec/ruby/core/hash/shared/eql.rb
@@ -118,7 +118,7 @@ describe :hash_eql_additional, shared: true do
     { 1.0 => "x" }.send(@method, { 1 => "x" }).should be_false
   end
 
-  it "returns true iff other Hash has the same number of keys and each key-value pair matches" do
+  it "returns true if and only if other Hash has the same number of keys and each key-value pair matches" do
     a = { a: 5 }
     b = {}
     a.send(@method, b).should be_false
@@ -155,12 +155,8 @@ describe :hash_eql_additional, shared: true do
       obj = mock('0')
       obj.should_receive(:hash).at_least(1).and_return(0)
 
-      # It's undefined whether the impl does a[0].eql?(a[1]) or
-      # a[1].eql?(a[0]) so we taint both.
       def obj.eql?(o)
         return true if self.equal?(o)
-        taint
-        o.taint
         false
       end
 
@@ -168,18 +164,12 @@ describe :hash_eql_additional, shared: true do
     end
 
     { a[0] => 1 }.send(@method, { a[1] => 1 }).should be_false
-    a[0].tainted?.should be_true
-    a[1].tainted?.should be_true
 
     a = Array.new(2) do
       obj = mock('0')
       obj.should_receive(:hash).at_least(1).and_return(0)
 
       def obj.eql?(o)
-        # It's undefined whether the impl does a[0].send(@method, a[1]) or
-        # a[1].send(@method, a[0]) so we taint both.
-        taint
-        o.taint
         true
       end
 
@@ -187,8 +177,6 @@ describe :hash_eql_additional, shared: true do
     end
 
     { a[0] => 1 }.send(@method, { a[1] => 1 }).should be_true
-    a[0].tainted?.should be_true
-    a[1].tainted?.should be_true
   end
 
   it "compares the values in self to values in other hash" do
diff --git a/spec/ruby/core/hash/shared/equal.rb b/spec/ruby/core/hash/shared/equal.rb
deleted file mode 100644
index 43606437fe..0000000000
--- a/spec/ruby/core/hash/shared/equal.rb
+++ /dev/null
@@ -1,90 +0,0 @@
-describe :hash_equal, shared: true do
-  it "does not compare values when keys don't match" do
-    value = mock('x')
-    value.should_not_receive(:==)
-    value.should_not_receive(:eql?)
-    { 1 => value }.send(@method, { 2 => value }).should be_false
-  end
-
-  it "returns false when the numbers of keys differ without comparing any elements" do
-    obj = mock('x')
-    h = { obj => obj }
-
-    obj.should_not_receive(:==)
-    obj.should_not_receive(:eql?)
-
-    {}.send(@method, h).should be_false
-    h.send(@method, {}).should be_false
-  end
-
-  it "first compares keys via hash" do
-    x = mock('x')
-    x.should_receive(:hash).and_return(0)
-    y = mock('y')
-    y.should_receive(:hash).and_return(0)
-
-    { x => 1 }.send(@method, { y => 1 }).should be_false
-  end
-
-  it "does not compare keys with different hash codes via eql?" do
-    x = mock('x')
-    y = mock('y')
-    x.should_not_receive(:eql?)
-    y.should_not_receive(:eql?)
-
-    x.should_receive(:hash).and_return(0)
-    y.should_receive(:hash).and_return(1)
-
-    def x.hash() 0 end
-    def y.hash() 1 end
-
-    { x => 1 }.send(@method, { y => 1 }).should be_false
-  end
-
-  it "computes equality for recursive hashes" do
-    h = {}
-    h[:a] = h
-    h.send(@method, h[:a]).should be_true
-    (h == h[:a]).should be_true
-  end
-
-  it "computes equality for complex recursive hashes" do
-    a, b = {}, {}
-    a.merge! self: a, other: b
-    b.merge! self: b, other: a
-    a.send(@method, b).should be_true # they both have the same structure!
-
-    c = {}
-    c.merge! other: c, self: c
-    c.send(@method, a).should be_true # subtle, but they both have the same structure!
-    a[:delta] = c[:delta] = a
-    c.send(@method, a).should be_false # not quite the same structure, as a[:other][:delta] = nil
-    c[:delta] = 42
-    c.send(@method, a).should be_false
-    a[:delta] = 42
-    c.send(@method, a).should be_false
-    b[:delta] = 42
-    c.send(@method, a).should be_true
-  end
-
-  it "computes equality for recursive hashes & arrays" do
-    x, y, z = [], [], []
-    a, b, c = {foo: x, bar: 42}, {foo: y, bar: 42}, {foo: z, bar: 42}
-    x << a
-    y << c
-    z << b
-    b.send(@method, c).should be_true # they clearly have the same structure!
-    y.send(@method, z).should be_true
-    a.send(@method, b).should be_true # subtle, but they both have the same structure!
-    x.send(@method, y).should be_true
-    y << x
-    y.send(@method, z).should be_false
-    z << x
-    y.send(@method, z).should be_true
-
-    a[:foo], a[:bar] = a[:bar], a[:foo]
-    a.send(@method, b).should be_false
-    b[:bar] = b[:foo]
-    b.send(@method, c).should be_false
-  end
-end
diff --git a/spec/ruby/core/hash/shared/index.rb b/spec/ruby/core/hash/shared/index.rb
index 4858ba85f5..7f6a186464 100644
--- a/spec/ruby/core/hash/shared/index.rb
+++ b/spec/ruby/core/hash/shared/index.rb
@@ -3,25 +3,35 @@ require_relative '../fixtures/classes'
 
 describe :hash_index, shared: true do
   it "returns the corresponding key for value" do
-    { 2 => 'a', 1 => 'b' }.send(@method, 'b').should == 1
+    suppress_warning do # for Hash#index
+      { 2 => 'a', 1 => 'b' }.send(@method, 'b').should == 1
+    end
   end
 
   it "returns nil if the value is not found" do
-    { a: -1, b: 3.14, c: 2.718 }.send(@method, 1).should be_nil
+    suppress_warning do # for Hash#index
+      { a: -1, b: 3.14, c: 2.718 }.send(@method, 1).should be_nil
+    end
   end
 
   it "doesn't return default value if the value is not found" do
-    Hash.new(5).send(@method, 5).should be_nil
+    suppress_warning do # for Hash#index
+      Hash.new(5).send(@method, 5).should be_nil
+    end
   end
 
   it "compares values using ==" do
-    { 1 => 0 }.send(@method, 0.0).should == 1
-    { 1 => 0.0 }.send(@method, 0).should == 1
+    suppress_warning do # for Hash#index
+      { 1 => 0 }.send(@method, 0.0).should == 1
+      { 1 => 0.0 }.send(@method, 0).should == 1
+    end
 
     needle = mock('needle')
     inhash = mock('inhash')
     inhash.should_receive(:==).with(needle).and_return(true)
 
-    { 1 => inhash }.send(@method, needle).should == 1
+    suppress_warning do # for Hash#index
+      { 1 => inhash }.send(@method, needle).should == 1
+    end
   end
 end
diff --git a/spec/ruby/core/hash/shared/replace.rb b/spec/ruby/core/hash/shared/replace.rb
deleted file mode 100644
index b3d098763b..0000000000
--- a/spec/ruby/core/hash/shared/replace.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-describe :hash_replace, shared: true do
-  it "replaces the contents of self with other" do
-    h = { a: 1, b: 2 }
-    h.send(@method, c: -1, d: -2).should equal(h)
-    h.should == { c: -1, d: -2 }
-  end
-
-  it "tries to convert the passed argument to a hash using #to_hash" do
-    obj = mock('{1=>2,3=>4}')
-    obj.should_receive(:to_hash).and_return({ 1 => 2, 3 => 4 })
-
-    h = {}
-    h.send(@method, obj)
-    h.should == { 1 => 2, 3 => 4 }
-  end
-
-  it "calls to_hash on hash subclasses" do
-    h = {}
-    h.send(@method, HashSpecs::ToHashHash[1 => 2])
-    h.should == { 1 => 2 }
-  end
-
-  it "does not transfer default values" do
-    hash_a = {}
-    hash_b = Hash.new(5)
-    hash_a.send(@method, hash_b)
-    hash_a.default.should == 5
-
-    hash_a = {}
-    hash_b = Hash.new { |h, k| k * 2 }
-    hash_a.send(@method, hash_b)
-    hash_a.default(5).should == 10
-
-    hash_a = Hash.new { |h, k| k * 5 }
-    hash_b = Hash.new(-> { raise "Should not invoke lambda" })
-    hash_a.send(@method, hash_b)
-    hash_a.default.should == hash_b.default
-  end
-
-  it "raises a #{frozen_error_class} if called on a frozen instance that would not be modified" do
-    -> do
-      HashSpecs.frozen_hash.send(@method, HashSpecs.frozen_hash)
-    end.should raise_error(frozen_error_class)
-  end
-
-  it "raises a #{frozen_error_class} if called on a frozen instance that is modified" do
-    -> do
-      HashSpecs.frozen_hash.send(@method, HashSpecs.empty_frozen_hash)
-    end.should raise_error(frozen_error_class)
-  end
-end
diff --git a/spec/ruby/core/hash/shared/select.rb b/spec/ruby/core/hash/shared/select.rb
index bb781817cb..fbeff07330 100644
--- a/spec/ruby/core/hash/shared/select.rb
+++ b/spec/ruby/core/hash/shared/select.rb
@@ -40,6 +40,27 @@ describe :hash_select, shared: true do
     @empty.send(@method).should be_an_instance_of(Enumerator)
   end
 
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.send(@method) { true }.default.should be_nil
+    h[:a] = 1
+    h.send(@method) { true }.default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.send(@method) { true }.default_proc.should be_nil
+    h[:a] = 1
+    h.send(@method) { true }.default_proc.should be_nil
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.send(@method) { |k, _| k == :a }
+    h2.compare_by_identity?.should == true
+  end
+
   it_should_behave_like :hash_iteration_no_block
 
   before :each do
@@ -74,12 +95,12 @@ describe :hash_select!, shared: true do
     { a: 1 }.send(@method) { |k,v| v <= 1 }.should == nil
   end
 
-  it "raises a #{frozen_error_class} if called on an empty frozen instance" do
-    -> { HashSpecs.empty_frozen_hash.send(@method) { false } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on an empty frozen instance" do
+    -> { HashSpecs.empty_frozen_hash.send(@method) { false } }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance that would not be modified" do
-    -> { HashSpecs.frozen_hash.send(@method) { true } }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance that would not be modified" do
+    -> { HashSpecs.frozen_hash.send(@method) { true } }.should raise_error(FrozenError)
   end
 
   it_should_behave_like :hash_iteration_no_block
diff --git a/spec/ruby/core/hash/shared/store.rb b/spec/ruby/core/hash/shared/store.rb
index ff40bef3ef..72a462a42f 100644
--- a/spec/ruby/core/hash/shared/store.rb
+++ b/spec/ruby/core/hash/shared/store.rb
@@ -9,7 +9,7 @@ describe :hash_store, shared: true do
 
   it "duplicates string keys using dup semantics" do
     # dup doesn't copy singleton methods
-    key = "foo"
+    key = +"foo"
     def key.reverse() "bar" end
     h = {}
     h.send(@method, key, 0)
@@ -36,7 +36,7 @@ describe :hash_store, shared: true do
     h[key].should == "foo"
   end
 
-  it " accepts keys with a Bignum hash" do
+  it " accepts keys with an Integer hash" do
     o = mock(hash: 1 << 100)
     h = {}
     h[o] = 1
@@ -44,13 +44,13 @@ describe :hash_store, shared: true do
   end
 
   it "duplicates and freezes string keys" do
-    key = "foo"
+    key = +"foo"
     h = {}
     h.send(@method, key, 0)
     key << "bar"
 
     h.should == { "foo" => 0 }
-    h.keys[0].frozen?.should == true
+    h.keys[0].should.frozen?
   end
 
   it "doesn't duplicate and freeze already frozen string keys" do
@@ -75,8 +75,8 @@ describe :hash_store, shared: true do
 
   it "keeps the existing String key in the hash if there is a matching one" do
     h = { "a" => 1, "b" => 2, "c" => 3, "d" => 4 }
-    key1 = "foo"
-    key2 = "foo"
+    key1 = "foo".dup
+    key2 = "foo".dup
     key1.should_not equal(key2)
     h[key1] = 41
     frozen_key = h.keys.last
@@ -86,13 +86,30 @@ describe :hash_store, shared: true do
     h.keys.last.should_not equal(key2)
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.send(@method, 1, 2) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.send(@method, 1, 2) }.should raise_error(FrozenError)
   end
 
   it "does not raise an exception if changing the value of an existing key during iteration" do
-      hash = {1 => 2, 3 => 4, 5 => 6}
-      hash.each { hash.send(@method, 1, :foo) }
-      hash.should == {1 => :foo, 3 => 4, 5 => 6}
+    hash = {1 => 2, 3 => 4, 5 => 6}
+    hash.each { hash.send(@method, 1, :foo) }
+    hash.should == {1 => :foo, 3 => 4, 5 => 6}
+  end
+
+  it "does not dispatch to hash for Boolean, Integer, Float, String, or Symbol" do
+    code = <<-EOC
+      load '#{fixture __FILE__, "name.rb"}'
+      hash = {}
+      [true, false, 1, 2.0, "hello", :ok].each do |value|
+        hash[value] = 42
+        raise "incorrect value" unless hash[value] == 42
+        hash[value] = 43
+        raise "incorrect value" unless hash[value] == 43
+      end
+      puts "OK"
+      puts hash.size
+    EOC
+    result = ruby_exe(code, args: "2>&1")
+    result.should == "OK\n6\n"
   end
 end
diff --git a/spec/ruby/core/hash/shared/to_s.rb b/spec/ruby/core/hash/shared/to_s.rb
index d180d08c2c..e116b8878b 100644
--- a/spec/ruby/core/hash/shared/to_s.rb
+++ b/spec/ruby/core/hash/shared/to_s.rb
@@ -2,17 +2,10 @@ require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
 describe :hash_to_s, shared: true do
-
   it "returns a string representation with same order as each()" do
     h = { a: [1, 2], b: -2, d: -6, nil => nil }
-
-    pairs = []
-    h.each do |key, value|
-      pairs << key.inspect + '=>' + value.inspect
-    end
-
-    str = '{' + pairs.join(', ') + '}'
-    h.send(@method).should == str
+    expected = ruby_version_is("3.4") ? "{a: [1, 2], b: -2, d: -6, nil => nil}" : "{:a=>[1, 2], :b=>-2, :d=>-6, nil=>nil}"
+    h.send(@method).should == expected
   end
 
   it "calls #inspect on keys and values" do
@@ -20,31 +13,31 @@ describe :hash_to_s, shared: true do
     val = mock('val')
     key.should_receive(:inspect).and_return('key')
     val.should_receive(:inspect).and_return('val')
-
-    { key => val }.send(@method).should == '{key=>val}'
+    expected = ruby_version_is("3.4") ? "{key => val}" : "{key=>val}"
+    { key => val }.send(@method).should == expected
   end
 
   it "does not call #to_s on a String returned from #inspect" do
-    str = "abc"
+    str = +"abc"
     str.should_not_receive(:to_s)
-
-    { a: str }.send(@method).should == '{:a=>"abc"}'
+    expected = ruby_version_is("3.4") ? '{a: "abc"}' : '{:a=>"abc"}'
+    { a: str }.send(@method).should == expected
   end
 
   it "calls #to_s on the object returned from #inspect if the Object isn't a String" do
     obj = mock("Hash#inspect/to_s calls #to_s")
     obj.should_receive(:inspect).and_return(obj)
     obj.should_receive(:to_s).and_return("abc")
-
-    { a: obj }.send(@method).should == "{:a=>abc}"
+    expected = ruby_version_is("3.4") ? "{a: abc}" : "{:a=>abc}"
+    { a: obj }.send(@method).should == expected
   end
 
   it "does not call #to_str on the object returned from #inspect when it is not a String" do
     obj = mock("Hash#inspect/to_s does not call #to_str")
     obj.should_receive(:inspect).and_return(obj)
     obj.should_not_receive(:to_str)
-
-    { a: obj }.send(@method).should =~ /^\{:a=>#<MockObject:0x[0-9a-f]+>\}$/
+    expected_pattern = ruby_version_is("3.4") ? /^\{a: #<MockObject:0x[0-9a-f]+>\}$/ : /^\{:a=>#<MockObject:0x[0-9a-f]+>\}$/
+    { a: obj }.send(@method).should =~ expected_pattern
   end
 
   it "does not call #to_str on the object returned from #to_s when it is not a String" do
@@ -52,8 +45,8 @@ describe :hash_to_s, shared: true do
     obj.should_receive(:inspect).and_return(obj)
     obj.should_receive(:to_s).and_return(obj)
     obj.should_not_receive(:to_str)
-
-    { a: obj }.send(@method).should =~ /^\{:a=>#<MockObject:0x[0-9a-f]+>\}$/
+    expected_pattern = ruby_version_is("3.4") ? /^\{a: #<MockObject:0x[0-9a-f]+>\}$/ : /^\{:a=>#<MockObject:0x[0-9a-f]+>\}$/
+    { a: obj }.send(@method).should =~ expected_pattern
   end
 
   it "does not swallow exceptions raised by #to_s" do
@@ -67,30 +60,34 @@ describe :hash_to_s, shared: true do
   it "handles hashes with recursive values" do
     x = {}
     x[0] = x
-    x.send(@method).should == '{0=>{...}}'
+    expected = ruby_version_is("3.4") ? '{0 => {...}}' : '{0=>{...}}'
+    x.send(@method).should == expected
 
     x = {}
     y = {}
     x[0] = y
     y[1] = x
-    x.send(@method).should == "{0=>{1=>{...}}}"
-    y.send(@method).should == "{1=>{0=>{...}}}"
+    expected_x = ruby_version_is("3.4") ? '{0 => {1 => {...}}}' : '{0=>{1=>{...}}}'
+    expected_y = ruby_version_is("3.4") ? '{1 => {0 => {...}}}' : '{1=>{0=>{...}}}'
+    x.send(@method).should == expected_x
+    y.send(@method).should == expected_y
   end
 
-  it "returns a tainted string if self is tainted and not empty" do
-    {}.taint.send(@method).tainted?.should be_false
-    { nil => nil }.taint.send(@method).tainted?.should be_true
+  it "does not raise if inspected result is not default external encoding" do
+    utf_16be = mock("utf_16be")
+    utf_16be.should_receive(:inspect).and_return(%<"utf_16be \u3042">.encode(Encoding::UTF_16BE))
+    expected = ruby_version_is("3.4") ? '{a: "utf_16be \u3042"}' : '{:a=>"utf_16be \u3042"}'
+    {a: utf_16be}.send(@method).should == expected
   end
 
-  it "returns an untrusted string if self is untrusted and not empty" do
-    {}.untrust.send(@method).untrusted?.should be_false
-    { nil => nil }.untrust.send(@method).untrusted?.should be_true
+  it "works for keys and values whose #inspect return a frozen String" do
+    expected = ruby_version_is("3.4") ? "{true => false}" : "{true=>false}"
+    { true => false }.to_s.should == expected
   end
 
-  it "does not raise if inspected result is not default external encoding" do
-    utf_16be = mock("utf_16be")
-    utf_16be.should_receive(:inspect).and_return(%<"utf_16be \u3042">.encode!(Encoding::UTF_16BE))
-
-    {a: utf_16be}.send(@method).should == '{:a=>"utf_16be \u3042"}'
+  ruby_version_is "3.4" do
+    it "adds quotes to symbol keys that are not valid symbol literals" do
+      { "needs-quotes": 1 }.send(@method).should == '{"needs-quotes": 1}'
+    end
   end
 end
diff --git a/spec/ruby/core/hash/shared/update.rb b/spec/ruby/core/hash/shared/update.rb
index 3af41c450a..1b0eb809bf 100644
--- a/spec/ruby/core/hash/shared/update.rb
+++ b/spec/ruby/core/hash/shared/update.rb
@@ -34,10 +34,10 @@ describe :hash_update, shared: true do
     merge_bang_pairs.should == merge_pairs
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
+  it "raises a FrozenError on a frozen instance that is modified" do
     -> do
       HashSpecs.frozen_hash.send(@method, 1 => 2)
-    end.should raise_error(frozen_error_class)
+    end.should raise_error(FrozenError)
   end
 
   it "checks frozen status before coercing an object with #to_hash" do
@@ -47,14 +47,14 @@ describe :hash_update, shared: true do
     def obj.to_hash() raise Exception, "should not receive #to_hash" end
     obj.freeze
 
-    -> { HashSpecs.frozen_hash.send(@method, obj) }.should raise_error(frozen_error_class)
+    -> { HashSpecs.frozen_hash.send(@method, obj) }.should raise_error(FrozenError)
   end
 
   # see redmine #1571
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
+  it "raises a FrozenError on a frozen instance that would not be modified" do
     -> do
       HashSpecs.frozen_hash.send(@method, HashSpecs.empty_frozen_hash)
-    end.should raise_error(frozen_error_class)
+    end.should raise_error(FrozenError)
   end
 
   it "does not raise an exception if changing the value of an existing key during iteration" do
@@ -64,15 +64,13 @@ describe :hash_update, shared: true do
     hash.should == {1 => :foo, 3 => :bar, 5 => 6}
   end
 
-  ruby_version_is "2.6" do
-    it "accepts multiple hashes" do
-      result = { a: 1 }.send(@method, { b: 2 }, { c: 3 }, { d: 4 })
-      result.should == { a: 1, b: 2, c: 3, d: 4 }
-    end
+  it "accepts multiple hashes" do
+    result = { a: 1 }.send(@method, { b: 2 }, { c: 3 }, { d: 4 })
+    result.should == { a: 1, b: 2, c: 3, d: 4 }
+  end
 
-    it "accepts zero arguments" do
-      hash = { a: 1 }
-      hash.send(@method).should eql(hash)
-    end
+  it "accepts zero arguments" do
+    hash = { a: 1 }
+    hash.send(@method).should eql(hash)
   end
 end
diff --git a/spec/ruby/core/hash/shift_spec.rb b/spec/ruby/core/hash/shift_spec.rb
index d9f121e38b..3f31b9864c 100644
--- a/spec/ruby/core/hash/shift_spec.rb
+++ b/spec/ruby/core/hash/shift_spec.rb
@@ -30,23 +30,22 @@ describe "Hash#shift" do
     h.should == {}
   end
 
-  it "calls #default with nil if the Hash is empty" do
+  it "returns nil if the Hash is empty" do
     h = {}
     def h.default(key)
-      key.should == nil
-      :foo
+      raise
     end
-    h.shift.should == :foo
+    h.shift.should == nil
   end
 
   it "returns nil from an empty hash" do
     {}.shift.should == nil
   end
 
-  it "returns (computed) default for empty hashes" do
-    Hash.new(5).shift.should == 5
+  it "returns nil for empty hashes with defaults and default procs" do
+    Hash.new(5).shift.should == nil
     h = Hash.new { |*args| args }
-    h.shift.should == [h, nil]
+    h.shift.should == nil
   end
 
   it "preserves Hash invariants when removing the last item" do
@@ -57,9 +56,9 @@ describe "Hash#shift" do
     h.should == {:c => 3}
   end
 
-  it "raises a #{frozen_error_class} if called on a frozen instance" do
-    -> { HashSpecs.frozen_hash.shift  }.should raise_error(frozen_error_class)
-    -> { HashSpecs.empty_frozen_hash.shift }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if called on a frozen instance" do
+    -> { HashSpecs.frozen_hash.shift  }.should raise_error(FrozenError)
+    -> { HashSpecs.empty_frozen_hash.shift }.should raise_error(FrozenError)
   end
 
   it "works when the hash is at capacity" do
diff --git a/spec/ruby/core/hash/slice_spec.rb b/spec/ruby/core/hash/slice_spec.rb
index f7717c9404..4fcc01f9a6 100644
--- a/spec/ruby/core/hash/slice_spec.rb
+++ b/spec/ruby/core/hash/slice_spec.rb
@@ -1,55 +1,74 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  describe "Hash#slice" do
-    before :each do
-      @hash = { a: 1, b: 2, c: 3 }
-    end
+describe "Hash#slice" do
+  before :each do
+    @hash = { a: 1, b: 2, c: 3 }
+  end
 
-    it "returns a new empty hash without arguments" do
-      ret = @hash.slice
-      ret.should_not equal(@hash)
-      ret.should be_an_instance_of(Hash)
-      ret.should == {}
-    end
+  it "returns a new empty hash without arguments" do
+    ret = @hash.slice
+    ret.should_not equal(@hash)
+    ret.should be_an_instance_of(Hash)
+    ret.should == {}
+  end
 
-    it "returns the requested subset" do
-      @hash.slice(:c, :a).should == { c: 3, a: 1 }
-    end
+  it "returns the requested subset" do
+    @hash.slice(:c, :a).should == { c: 3, a: 1 }
+  end
 
-    it "returns a hash ordered in the order of the requested keys" do
-      @hash.slice(:c, :a).keys.should == [:c, :a]
-    end
+  it "returns a hash ordered in the order of the requested keys" do
+    @hash.slice(:c, :a).keys.should == [:c, :a]
+  end
 
-    it "returns only the keys of the original hash" do
-      @hash.slice(:a, :chunky_bacon).should == { a: 1 }
-    end
+  it "returns only the keys of the original hash" do
+    @hash.slice(:a, :chunky_bacon).should == { a: 1 }
+  end
 
-    it "returns a Hash instance, even on subclasses" do
-      klass = Class.new(Hash)
-      h = klass.new
-      h[:bar] = 12
-      h[:foo] = 42
-      r = h.slice(:foo)
-      r.should == {foo: 42}
-      r.class.should == Hash
-    end
+  it "returns a Hash instance, even on subclasses" do
+    klass = Class.new(Hash)
+    h = klass.new
+    h[:bar] = 12
+    h[:foo] = 42
+    r = h.slice(:foo)
+    r.should == {foo: 42}
+    r.class.should == Hash
+  end
 
-    it "uses the regular Hash#[] method, even on subclasses that override it" do
-      ScratchPad.record []
-      klass = Class.new(Hash) do
-        def [](value)
-          ScratchPad << :used_subclassed_operator
-          super
-        end
+  it "uses the regular Hash#[] method, even on subclasses that override it" do
+    ScratchPad.record []
+    klass = Class.new(Hash) do
+      def [](value)
+        ScratchPad << :used_subclassed_operator
+        super
       end
+    end
 
-      h = klass.new
-      h[:bar] = 12
-      h[:foo] = 42
-      h.slice(:foo)
+    h = klass.new
+    h[:bar] = 12
+    h[:foo] = 42
+    h.slice(:foo)
 
-      ScratchPad.recorded.should == []
-    end
+    ScratchPad.recorded.should == []
+  end
+
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.slice(:a).default.should be_nil
+    h[:a] = 1
+    h.slice(:a).default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.slice(:a).default_proc.should be_nil
+    h[:a] = 1
+    h.slice(:a).default_proc.should be_nil
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.slice(:a)
+    h2.compare_by_identity?.should == true
   end
 end
diff --git a/spec/ruby/core/hash/to_a_spec.rb b/spec/ruby/core/hash/to_a_spec.rb
index 33ad7cdec9..5baf677929 100644
--- a/spec/ruby/core/hash/to_a_spec.rb
+++ b/spec/ruby/core/hash/to_a_spec.rb
@@ -26,12 +26,4 @@ describe "Hash#to_a" do
     ent.should be_kind_of(Array)
     ent.should == pairs
   end
-
-  it "returns a tainted array if self is tainted" do
-    {}.taint.to_a.tainted?.should be_true
-  end
-
-  it "returns an untrusted array if self is untrusted" do
-    {}.untrust.to_a.untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/hash/to_h_spec.rb b/spec/ruby/core/hash/to_h_spec.rb
index d6eaac9f33..f84fd7b503 100644
--- a/spec/ruby/core/hash/to_h_spec.rb
+++ b/spec/ruby/core/hash/to_h_spec.rb
@@ -19,56 +19,88 @@ describe "Hash#to_h" do
       @h[:foo].should == :bar
     end
 
-    it "copies the default" do
+    it "retains the default" do
       @h.default = 42
       @h.to_h.default.should == 42
       @h[:hello].should == 42
     end
 
-    it "copies the default_proc" do
+    it "retains the default_proc" do
       @h.default_proc = prc = Proc.new{ |h, k| h[k] = 2 * k }
       @h.to_h.default_proc.should == prc
       @h[42].should == 84
     end
+
+    it "retains compare_by_identity flag" do
+      @h.compare_by_identity
+      @h.to_h.compare_by_identity?.should == true
+    end
   end
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      it "converts [key, value] pairs returned by the block to a hash" do
-        { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v]}.should == { "a" => 1, "b" => 4 }
-      end
-
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v, 1] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-
-        -> do
-          { a: 1, b: 2 }.to_h { |k, v| [k] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-      end
-
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          { a: 1, b: 2 }.to_h { |k, v| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String/)
-      end
-
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
-
-        { a: 1 }.to_h { |k| x }.should == { :b => 'b' }
-      end
-
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
-
-        -> do
-          { a: 1 }.to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject/)
-      end
+  context "with block" do
+    it "converts [key, value] pairs returned by the block to a hash" do
+      { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v]}.should == { "a" => 1, "b" => 4 }
+    end
+
+    it "passes to a block each pair's key and value as separate arguments" do
+      ScratchPad.record []
+      { a: 1, b: 2 }.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+      ScratchPad.recorded.sort.should == [[:a, 1], [:b, 2]]
+
+      ScratchPad.record []
+      { a: 1, b: 2 }.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[:a, 1], [:b, 2]]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+
+      -> do
+        { a: 1, b: 2 }.to_h { |k, v| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        { a: 1, b: 2 }.to_h { |k, v| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      { a: 1 }.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        { a: 1 }.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
+    end
+
+    it "does not retain the default value" do
+      h = Hash.new(1)
+      h2 = h.to_h { |k, v| [k.to_s, v*v]}
+      h2.default.should be_nil
+    end
+
+    it "does not retain the default_proc" do
+      pr = proc { |h, k| h[k] = [] }
+      h = Hash.new(&pr)
+      h2 = h.to_h { |k, v| [k.to_s, v*v]}
+      h2.default_proc.should be_nil
+    end
+
+    it "does not retain compare_by_identity flag" do
+      h = { a: 9, c: 4 }.compare_by_identity
+      h2 = h.to_h { |k, v| [k.to_s, v*v]}
+      h2.compare_by_identity?.should == false
     end
   end
 end
diff --git a/spec/ruby/core/hash/to_proc_spec.rb b/spec/ruby/core/hash/to_proc_spec.rb
index 3e7e57d11f..9dbc79e5eb 100644
--- a/spec/ruby/core/hash/to_proc_spec.rb
+++ b/spec/ruby/core/hash/to_proc_spec.rb
@@ -19,8 +19,12 @@ describe "Hash#to_proc" do
       @proc = @hash.to_proc
     end
 
-    it "is not a lambda" do
-      @proc.lambda?.should == false
+    it "is a lambda" do
+      @proc.should.lambda?
+    end
+
+    it "has an arity of 1" do
+      @proc.arity.should == 1
     end
 
     it "raises ArgumentError if not passed exactly one argument" do
diff --git a/spec/ruby/core/hash/transform_keys_spec.rb b/spec/ruby/core/hash/transform_keys_spec.rb
index 32ac89b765..e2eeab1813 100644
--- a/spec/ruby/core/hash/transform_keys_spec.rb
+++ b/spec/ruby/core/hash/transform_keys_spec.rb
@@ -1,131 +1,149 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  describe "Hash#transform_keys" do
-    before :each do
-      @hash = { a: 1, b: 2, c: 3 }
-    end
+describe "Hash#transform_keys" do
+  before :each do
+    @hash = { a: 1, b: 2, c: 3 }
+  end
 
-    it "returns new hash" do
-      ret = @hash.transform_keys(&:succ)
-      ret.should_not equal(@hash)
-      ret.should be_an_instance_of(Hash)
-    end
+  it "returns new hash" do
+    ret = @hash.transform_keys(&:succ)
+    ret.should_not equal(@hash)
+    ret.should be_an_instance_of(Hash)
+  end
 
-    it "sets the result as transformed keys with the given block" do
-      @hash.transform_keys(&:succ).should ==  { b: 1, c: 2, d: 3 }
-    end
+  it "sets the result as transformed keys with the given block" do
+    @hash.transform_keys(&:succ).should ==  { b: 1, c: 2, d: 3 }
+  end
 
-    it "keeps last pair if new keys conflict" do
-      @hash.transform_keys { |_| :a }.should == { a: 3 }
-    end
+  it "keeps last pair if new keys conflict" do
+    @hash.transform_keys { |_| :a }.should == { a: 3 }
+  end
 
-    it "makes both hashes to share values" do
-      value = [1, 2, 3]
-      new_hash = { a: value }.transform_keys(&:upcase)
-      new_hash[:A].should equal(value)
-    end
+  it "makes both hashes to share values" do
+    value = [1, 2, 3]
+    new_hash = { a: value }.transform_keys(&:upcase)
+    new_hash[:A].should equal(value)
+  end
 
-    context "when no block is given" do
-      it "returns a sized Enumerator" do
-        enumerator = @hash.transform_keys
-        enumerator.should be_an_instance_of(Enumerator)
-        enumerator.size.should == @hash.size
-        enumerator.each(&:succ).should == { b: 1, c: 2, d: 3 }
-      end
+  context "when no block is given" do
+    it "returns a sized Enumerator" do
+      enumerator = @hash.transform_keys
+      enumerator.should be_an_instance_of(Enumerator)
+      enumerator.size.should == @hash.size
+      enumerator.each(&:succ).should == { b: 1, c: 2, d: 3 }
     end
+  end
 
-    it "returns a Hash instance, even on subclasses" do
-      klass = Class.new(Hash)
-      h = klass.new
-      h[:foo] = 42
-      r = h.transform_keys{|v| :"x#{v}"}
-      r.keys.should == [:xfoo]
-      r.class.should == Hash
-    end
+  it "returns a Hash instance, even on subclasses" do
+    klass = Class.new(Hash)
+    h = klass.new
+    h[:foo] = 42
+    r = h.transform_keys{|v| :"x#{v}"}
+    r.keys.should == [:xfoo]
+    r.class.should == Hash
   end
 
-  describe "Hash#transform_keys!" do
-    before :each do
-      @hash = { a: 1, b: 2, c: 3, d: 4 }
-      @initial_pairs = @hash.dup
-    end
+  it "allows a hash argument" do
+    @hash.transform_keys({ a: :A, b: :B, c: :C }).should == { A: 1, B: 2, C: 3 }
+  end
 
-    it "returns self" do
-      @hash.transform_keys!(&:succ).should equal(@hash)
-    end
+  it "allows a partial transformation of keys when using a hash argument" do
+    @hash.transform_keys({ a: :A, c: :C }).should == { A: 1, b: 2, C: 3 }
+  end
 
-    it "updates self as transformed values with the given block" do
-      @hash.transform_keys!(&:to_s)
-      @hash.should == { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4 }
-    end
+  it "allows a combination of hash and block argument" do
+    @hash.transform_keys({ a: :A }, &:to_s).should == { A: 1, 'b' => 2, 'c' => 3 }
+  end
 
-    # https://bugs.ruby-lang.org/issues/14380
-    ruby_version_is ""..."2.5.1" do
-      it "does not prevent conflicts between new keys and old ones" do
-        @hash.transform_keys!(&:succ)
-        @hash.should == { e: 1 }
-      end
-    end
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.transform_keys(&:succ).default.should be_nil
+    h[:a] = 1
+    h.transform_keys(&:succ).default.should be_nil
+  end
 
-    ruby_version_is "2.5.1" do
-      it "prevents conflicts between new keys and old ones" do
-        @hash.transform_keys!(&:succ)
-        @hash.should == { b: 1, c: 2, d: 3, e: 4 }
-      end
-    end
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.transform_values(&:succ).default_proc.should be_nil
+    h[:a] = 1
+    h.transform_values(&:succ).default_proc.should be_nil
+  end
 
-    ruby_version_is ""..."2.5.1" do
-      it "partially modifies the contents if we broke from the block" do
-        @hash.transform_keys! do |v|
-          break if v == :c
-          v.succ
-        end
-        @hash.should == { c: 1, d: 4 }
-      end
-    end
+  it "does not retain compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.transform_keys(&:succ)
+    h2.compare_by_identity?.should == false
+  end
+end
 
-    ruby_version_is "2.5.1" do
-      it "returns the processed keys if we broke from the block" do
-        @hash.transform_keys! do |v|
-          break if v == :c
-          v.succ
-        end
-        @hash.should == { b: 1, c: 2 }
-      end
+describe "Hash#transform_keys!" do
+  before :each do
+    @hash = { a: 1, b: 2, c: 3, d: 4 }
+    @initial_pairs = @hash.dup
+  end
+
+  it "returns self" do
+    @hash.transform_keys!(&:succ).should equal(@hash)
+  end
+
+  it "updates self as transformed values with the given block" do
+    @hash.transform_keys!(&:to_s)
+    @hash.should == { 'a' => 1, 'b' => 2, 'c' => 3, 'd' => 4 }
+  end
+
+  it "prevents conflicts between new keys and old ones" do
+    @hash.transform_keys!(&:succ)
+    @hash.should == { b: 1, c: 2, d: 3, e: 4 }
+  end
+
+  it "returns the processed keys and non evaluated keys if we break from the block" do
+    @hash.transform_keys! do |v|
+      break if v == :c
+      v.succ
     end
+    @hash.should == { b: 1, c: 2, d: 4 }
+  end
+
+  it "keeps later pair if new keys conflict" do
+    @hash.transform_keys! { |_| :a }.should == { a: 4 }
+  end
 
-    it "keeps later pair if new keys conflict" do
-      @hash.transform_keys! { |_| :a }.should == { a: 4 }
+  context "when no block is given" do
+    it "returns a sized Enumerator" do
+      enumerator = @hash.transform_keys!
+      enumerator.should be_an_instance_of(Enumerator)
+      enumerator.size.should == @hash.size
+      enumerator.each(&:upcase).should == { A: 1, B: 2, C: 3, D: 4 }
     end
+  end
 
-    context "when no block is given" do
-      it "returns a sized Enumerator" do
-        enumerator = @hash.transform_keys!
-        enumerator.should be_an_instance_of(Enumerator)
-        enumerator.size.should == @hash.size
-        enumerator.each(&:upcase).should == { A: 1, B: 2, C: 3, D: 4 }
-      end
+  it "allows a hash argument" do
+    @hash.transform_keys!({ a: :A, b: :B, c: :C, d: :D })
+    @hash.should == { A: 1, B: 2, C: 3, D: 4 }
+  end
+
+  describe "on frozen instance" do
+    before :each do
+      @hash.freeze
     end
 
-    describe "on frozen instance" do
-      before :each do
-        @hash.freeze
-      end
+    it "raises a FrozenError on an empty hash" do
+      ->{ {}.freeze.transform_keys!(&:upcase) }.should raise_error(FrozenError)
+    end
 
-      it "raises a #{frozen_error_class} on an empty hash" do
-        ->{ {}.freeze.transform_keys!(&:upcase) }.should raise_error(frozen_error_class)
-      end
+    it "keeps pairs and raises a FrozenError" do
+      ->{ @hash.transform_keys!(&:upcase) }.should raise_error(FrozenError)
+      @hash.should == @initial_pairs
+    end
 
-      it "keeps pairs and raises a #{frozen_error_class}" do
-        ->{ @hash.transform_keys!(&:upcase) }.should raise_error(frozen_error_class)
-        @hash.should == @initial_pairs
-      end
+    it "raises a FrozenError on hash argument" do
+      ->{ @hash.transform_keys!({ a: :A, b: :B, c: :C }) }.should raise_error(FrozenError)
+    end
 
-      context "when no block is given" do
-        it "does not raise an exception" do
-          @hash.transform_keys!.should be_an_instance_of(Enumerator)
-        end
+    context "when no block is given" do
+      it "does not raise an exception" do
+        @hash.transform_keys!.should be_an_instance_of(Enumerator)
       end
     end
   end
diff --git a/spec/ruby/core/hash/transform_values_spec.rb b/spec/ruby/core/hash/transform_values_spec.rb
index 8b53b7a522..4a0ae8a5a5 100644
--- a/spec/ruby/core/hash/transform_values_spec.rb
+++ b/spec/ruby/core/hash/transform_values_spec.rb
@@ -39,6 +39,27 @@ describe "Hash#transform_values" do
     r[:foo].should == 84
     r.class.should == Hash
   end
+
+  it "does not retain the default value" do
+    h = Hash.new(1)
+    h.transform_values(&:succ).default.should be_nil
+    h[:a] = 1
+    h.transform_values(&:succ).default.should be_nil
+  end
+
+  it "does not retain the default_proc" do
+    pr = proc { |h, k| h[k] = [] }
+    h = Hash.new(&pr)
+    h.transform_values(&:succ).default_proc.should be_nil
+    h[:a] = 1
+    h.transform_values(&:succ).default_proc.should be_nil
+  end
+
+  it "retains compare_by_identity flag" do
+    h = { a: 9, c: 4 }.compare_by_identity
+    h2 = h.transform_values(&:succ)
+    h2.compare_by_identity?.should == true
+  end
 end
 
 describe "Hash#transform_values!" do
@@ -79,12 +100,12 @@ describe "Hash#transform_values!" do
       @hash.freeze
     end
 
-    it "raises a #{frozen_error_class} on an empty hash" do
-      ->{ {}.freeze.transform_values!(&:succ) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError on an empty hash" do
+      ->{ {}.freeze.transform_values!(&:succ) }.should raise_error(FrozenError)
     end
 
-    it "keeps pairs and raises a #{frozen_error_class}" do
-      ->{ @hash.transform_values!(&:succ) }.should raise_error(frozen_error_class)
+    it "keeps pairs and raises a FrozenError" do
+      ->{ @hash.transform_values!(&:succ) }.should raise_error(FrozenError)
       @hash.should == @initial_pairs
     end
 
diff --git a/spec/ruby/core/hash/try_convert_spec.rb b/spec/ruby/core/hash/try_convert_spec.rb
index 44195c5010..d359ae49d8 100644
--- a/spec/ruby/core/hash/try_convert_spec.rb
+++ b/spec/ruby/core/hash/try_convert_spec.rb
@@ -39,7 +39,7 @@ describe "Hash.try_convert" do
   it "sends #to_hash to the argument and raises TypeError if it's not a kind of Hash" do
     obj = mock("to_hash")
     obj.should_receive(:to_hash).and_return(Object.new)
-    -> { Hash.try_convert obj }.should raise_error(TypeError)
+    -> { Hash.try_convert obj }.should raise_error(TypeError, "can't convert MockObject to Hash (MockObject#to_hash gives Object)")
   end
 
   it "does not rescue exceptions raised by #to_hash" do
diff --git a/spec/ruby/core/integer/allbits_spec.rb b/spec/ruby/core/integer/allbits_spec.rb
index f4a6fe9905..edce4b15e7 100644
--- a/spec/ruby/core/integer/allbits_spec.rb
+++ b/spec/ruby/core/integer/allbits_spec.rb
@@ -1,39 +1,37 @@
 require_relative '../../spec_helper'
 
-ruby_version_is '2.5' do
-  describe "Integer#allbits?" do
-    it "returns true iff all the bits of the argument are set in the receiver" do
-      42.allbits?(42).should == true
-      0b1010_1010.allbits?(0b1000_0010).should == true
-      0b1010_1010.allbits?(0b1000_0001).should == false
-      0b1000_0010.allbits?(0b1010_1010).should == false
-      (0b1010_1010 | bignum_value).allbits?(0b1000_0010 | bignum_value).should == true
-      (0b1010_1010 | bignum_value).allbits?(0b1000_0001 | bignum_value).should == false
-      (0b1000_0010 | bignum_value).allbits?(0b1010_1010 | bignum_value).should == false
-    end
+describe "Integer#allbits?" do
+  it "returns true if and only if all the bits of the argument are set in the receiver" do
+    42.allbits?(42).should == true
+    0b1010_1010.allbits?(0b1000_0010).should == true
+    0b1010_1010.allbits?(0b1000_0001).should == false
+    0b1000_0010.allbits?(0b1010_1010).should == false
+    (0b1010_1010 | bignum_value).allbits?(0b1000_0010 | bignum_value).should == true
+    (0b1010_1010 | bignum_value).allbits?(0b1000_0001 | bignum_value).should == false
+    (0b1000_0010 | bignum_value).allbits?(0b1010_1010 | bignum_value).should == false
+  end
 
-    it "handles negative values using two's complement notation" do
-      (~0b1).allbits?(42).should == true
-      (-42).allbits?(-42).should == true
-      (~0b1010_1010).allbits?(~0b1110_1011).should == true
-      (~0b1010_1010).allbits?(~0b1000_0010).should == false
-      (~(0b1010_1010 | bignum_value)).allbits?(~(0b1110_1011 | bignum_value)).should == true
-      (~(0b1010_1010 | bignum_value)).allbits?(~(0b1000_0010 | bignum_value)).should == false
-    end
+  it "handles negative values using two's complement notation" do
+    (~0b1).allbits?(42).should == true
+    (-42).allbits?(-42).should == true
+    (~0b1010_1010).allbits?(~0b1110_1011).should == true
+    (~0b1010_1010).allbits?(~0b1000_0010).should == false
+    (~(0b1010_1010 | bignum_value)).allbits?(~(0b1110_1011 | bignum_value)).should == true
+    (~(0b1010_1010 | bignum_value)).allbits?(~(0b1000_0010 | bignum_value)).should == false
+  end
 
-    it "coerces the rhs using to_int" do
-      obj = mock("the int 0b10")
-      obj.should_receive(:to_int).and_return(0b10)
-      0b110.allbits?(obj).should == true
-    end
+  it "coerces the rhs using to_int" do
+    obj = mock("the int 0b10")
+    obj.should_receive(:to_int).and_return(0b10)
+    0b110.allbits?(obj).should == true
+  end
 
-    it "raises a TypeError when given a non-Integer" do
-      -> {
-        (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
-        13.allbits?(obj)
-      }.should raise_error(TypeError)
-      -> { 13.allbits?("10")    }.should raise_error(TypeError)
-      -> { 13.allbits?(:symbol) }.should raise_error(TypeError)
-    end
+  it "raises a TypeError when given a non-Integer" do
+    -> {
+      (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
+      13.allbits?(obj)
+    }.should raise_error(TypeError)
+    -> { 13.allbits?("10")    }.should raise_error(TypeError)
+    -> { 13.allbits?(:symbol) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/integer/anybits_spec.rb b/spec/ruby/core/integer/anybits_spec.rb
index 91f349258a..e0449074a2 100644
--- a/spec/ruby/core/integer/anybits_spec.rb
+++ b/spec/ruby/core/integer/anybits_spec.rb
@@ -1,38 +1,36 @@
 require_relative '../../spec_helper'
 
-ruby_version_is '2.5' do
-  describe "Integer#anybits?" do
-    it "returns true iff all the bits of the argument are set in the receiver" do
-      42.anybits?(42).should == true
-      0b1010_1010.anybits?(0b1000_0010).should == true
-      0b1010_1010.anybits?(0b1000_0001).should == true
-      0b1000_0010.anybits?(0b0010_1100).should == false
-      different_bignum = (2 * bignum_value) & (~bignum_value)
-      (0b1010_1010 | different_bignum).anybits?(0b1000_0010 | bignum_value).should == true
-      (0b1010_1010 | different_bignum).anybits?(0b0010_1100 | bignum_value).should == true
-      (0b1000_0010 | different_bignum).anybits?(0b0010_1100 | bignum_value).should == false
-    end
+describe "Integer#anybits?" do
+  it "returns true if and only if all the bits of the argument are set in the receiver" do
+    42.anybits?(42).should == true
+    0b1010_1010.anybits?(0b1000_0010).should == true
+    0b1010_1010.anybits?(0b1000_0001).should == true
+    0b1000_0010.anybits?(0b0010_1100).should == false
+    different_bignum = (2 * bignum_value) & (~bignum_value)
+    (0b1010_1010 | different_bignum).anybits?(0b1000_0010 | bignum_value).should == true
+    (0b1010_1010 | different_bignum).anybits?(0b0010_1100 | bignum_value).should == true
+    (0b1000_0010 | different_bignum).anybits?(0b0010_1100 | bignum_value).should == false
+  end
 
-    it "handles negative values using two's complement notation" do
-      (~42).anybits?(42).should == false
-      (-42).anybits?(-42).should == true
-      (~0b100).anybits?(~0b1).should == true
-      (~(0b100 | bignum_value)).anybits?(~(0b1 | bignum_value)).should == true
-    end
+  it "handles negative values using two's complement notation" do
+    (~42).anybits?(42).should == false
+    (-42).anybits?(-42).should == true
+    (~0b100).anybits?(~0b1).should == true
+    (~(0b100 | bignum_value)).anybits?(~(0b1 | bignum_value)).should == true
+  end
 
-    it "coerces the rhs using to_int" do
-      obj = mock("the int 0b10")
-      obj.should_receive(:to_int).and_return(0b10)
-      0b110.anybits?(obj).should == true
-    end
+  it "coerces the rhs using to_int" do
+    obj = mock("the int 0b10")
+    obj.should_receive(:to_int).and_return(0b10)
+    0b110.anybits?(obj).should == true
+  end
 
-    it "raises a TypeError when given a non-Integer" do
-      -> {
-        (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
-        13.anybits?(obj)
-      }.should raise_error(TypeError)
-      -> { 13.anybits?("10")    }.should raise_error(TypeError)
-      -> { 13.anybits?(:symbol) }.should raise_error(TypeError)
-    end
+  it "raises a TypeError when given a non-Integer" do
+    -> {
+      (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
+      13.anybits?(obj)
+    }.should raise_error(TypeError)
+    -> { 13.anybits?("10")    }.should raise_error(TypeError)
+    -> { 13.anybits?(:symbol) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/integer/bit_and_spec.rb b/spec/ruby/core/integer/bit_and_spec.rb
index 15a8026855..e7face39ac 100644
--- a/spec/ruby/core/integer/bit_and_spec.rb
+++ b/spec/ruby/core/integer/bit_and_spec.rb
@@ -30,7 +30,7 @@ describe "Integer#&" do
 
     it "coerces the rhs and calls #coerce" do
       obj = mock("fixnum bit and")
-      obj.should_receive(:coerce).with(6).and_return([3, 6])
+      obj.should_receive(:coerce).with(6).and_return([6, 3])
       (6 & obj).should == 2
     end
 
@@ -55,24 +55,24 @@ describe "Integer#&" do
       @bignum = bignum_value(5)
       (@bignum & 3).should == 1
       (@bignum & 52).should == 4
-      (@bignum & bignum_value(9921)).should == 9223372036854775809
+      (@bignum & bignum_value(9921)).should == 18446744073709551617
 
       ((2*bignum_value) & 1).should == 0
-      ((2*bignum_value) & (2*bignum_value)).should == 18446744073709551616
+      ((2*bignum_value) & (2*bignum_value)).should == 36893488147419103232
     end
 
     it "returns self bitwise AND other when one operand is negative" do
       ((2*bignum_value) & -1).should == (2*bignum_value)
       ((4*bignum_value) & -1).should == (4*bignum_value)
-      (@bignum & -0xffffffffffffff5).should == 9223372036854775809
+      (@bignum & -0xffffffffffffff5).should == 18446744073709551617
       (@bignum & -@bignum).should == 1
-      (@bignum & -0x8000000000000000).should == 9223372036854775808
+      (@bignum & -0x8000000000000000).should == 18446744073709551616
     end
 
     it "returns self bitwise AND other when both operands are negative" do
-      (-@bignum & -0x4000000000000005).should == -13835058055282163717
-      (-@bignum & -@bignum).should == -9223372036854775813
-      (-@bignum & -0x4000000000000000).should == -13835058055282163712
+      (-@bignum & -0x4000000000000005).should == -23058430092136939525
+      (-@bignum & -@bignum).should == -18446744073709551621
+      (-@bignum & -0x4000000000000000).should == -23058430092136939520
     end
 
     it "returns self bitwise AND other when both are negative and a multiple in bitsize of Fixnum::MIN" do
diff --git a/spec/ruby/core/integer/bit_or_spec.rb b/spec/ruby/core/integer/bit_or_spec.rb
index e486eeec10..fdf8a191e5 100644
--- a/spec/ruby/core/integer/bit_or_spec.rb
+++ b/spec/ruby/core/integer/bit_or_spec.rb
@@ -7,13 +7,34 @@ describe "Integer#|" do
       (5 | 4).should == 5
       (5 | 6).should == 7
       (248 | 4096).should == 4344
-      (0xffff | bignum_value + 0xf0f0).should == 0x8000_0000_0000_ffff
+      (0xffff | bignum_value + 0xf0f0).should == 0x1_0000_0000_0000_ffff
+    end
+
+    it "returns self bitwise OR other when one operand is negative" do
+      ((1 << 33) | -1).should == -1
+      (-1 | (1 << 33)).should == -1
+
+      ((-(1<<33)-1) | 5).should == -8589934593
+      (5 | (-(1<<33)-1)).should == -8589934593
+    end
+
+    it "returns self bitwise OR other when both operands are negative" do
+      (-5 | -1).should == -1
+      (-3 | -4).should == -3
+      (-12 | -13).should == -9
+      (-13 | -12).should == -9
     end
 
     it "returns self bitwise OR a bignum" do
       (-1 | 2**64).should == -1
     end
 
+    it "coerces the rhs and calls #coerce" do
+      obj = mock("fixnum bit or")
+      obj.should_receive(:coerce).with(6).and_return([6, 3])
+      (6 | obj).should == 7
+    end
+
     it "raises a TypeError when passed a Float" do
       -> { (3 | 3.4) }.should raise_error(TypeError)
     end
@@ -32,20 +53,20 @@ describe "Integer#|" do
     end
 
     it "returns self bitwise OR other" do
-      (@bignum | 2).should == 9223372036854775819
-      (@bignum | 9).should == 9223372036854775819
-      (@bignum | bignum_value).should == 9223372036854775819
+      (@bignum | 2).should == 18446744073709551627
+      (@bignum | 9).should == 18446744073709551627
+      (@bignum | bignum_value).should == 18446744073709551627
     end
 
     it "returns self bitwise OR other when one operand is negative" do
-      (@bignum | -0x40000000000000000).should == -64563604257983430645
+      (@bignum | -0x40000000000000000).should == -55340232221128654837
       (@bignum | -@bignum).should == -1
       (@bignum | -0x8000000000000000).should == -9223372036854775797
     end
 
     it "returns self bitwise OR other when both operands are negative" do
       (-@bignum | -0x4000000000000005).should == -1
-      (-@bignum | -@bignum).should == -9223372036854775819
+      (-@bignum | -@bignum).should == -18446744073709551627
       (-@bignum | -0x4000000000000000).should == -11
     end
 
diff --git a/spec/ruby/core/integer/bit_xor_spec.rb b/spec/ruby/core/integer/bit_xor_spec.rb
index ac8826a52f..1f46bc52f3 100644
--- a/spec/ruby/core/integer/bit_xor_spec.rb
+++ b/spec/ruby/core/integer/bit_xor_spec.rb
@@ -5,13 +5,34 @@ describe "Integer#^" do
     it "returns self bitwise EXCLUSIVE OR other" do
       (3 ^ 5).should == 6
       (-2 ^ -255).should == 255
-      (5 ^ bignum_value + 0xffff_ffff).should == 0x8000_0000_ffff_fffa
+      (5 ^ bignum_value + 0xffff_ffff).should == 0x1_0000_0000_ffff_fffa
+    end
+
+    it "returns self bitwise XOR other when one operand is negative" do
+      ((1 << 33) ^ -1).should == -8589934593
+      (-1 ^ (1 << 33)).should == -8589934593
+
+      ((-(1<<33)-1) ^ 5).should == -8589934598
+      (5 ^ (-(1<<33)-1)).should == -8589934598
+    end
+
+    it "returns self bitwise XOR other when both operands are negative" do
+      (-5 ^ -1).should == 4
+      (-3 ^ -4).should == 1
+      (-12 ^ -13).should == 7
+      (-13 ^ -12).should == 7
     end
 
     it "returns self bitwise EXCLUSIVE OR a bignum" do
       (-1 ^ 2**64).should == -18446744073709551617
     end
 
+    it "coerces the rhs and calls #coerce" do
+      obj = mock("fixnum bit xor")
+      obj.should_receive(:coerce).with(6).and_return([6, 3])
+      (6 ^ obj).should == 5
+    end
+
     it "raises a TypeError when passed a Float" do
       -> { (3 ^ 3.4) }.should raise_error(TypeError)
     end
@@ -30,21 +51,21 @@ describe "Integer#^" do
     end
 
     it "returns self bitwise EXCLUSIVE OR other" do
-      (@bignum ^ 2).should == 9223372036854775824
+      (@bignum ^ 2).should == 18446744073709551632
       (@bignum ^ @bignum).should == 0
-      (@bignum ^ 14).should == 9223372036854775836
+      (@bignum ^ 14).should == 18446744073709551644
     end
 
     it "returns self bitwise EXCLUSIVE OR other when one operand is negative" do
-      (@bignum ^ -0x40000000000000000).should == -64563604257983430638
+      (@bignum ^ -0x40000000000000000).should == -55340232221128654830
       (@bignum ^ -@bignum).should == -4
-      (@bignum ^ -0x8000000000000000).should == -18446744073709551598
+      (@bignum ^ -0x8000000000000000).should == -27670116110564327406
     end
 
     it "returns self bitwise EXCLUSIVE OR other when both operands are negative" do
-      (-@bignum ^ -0x40000000000000000).should == 64563604257983430638
+      (-@bignum ^ -0x40000000000000000).should == 55340232221128654830
       (-@bignum ^ -@bignum).should == 0
-      (-@bignum ^ -0x4000000000000000).should == 13835058055282163694
+      (-@bignum ^ -0x4000000000000000).should == 23058430092136939502
     end
 
     it "returns self bitwise EXCLUSIVE OR other when all bits are 1 and other value is negative" do
diff --git a/spec/ruby/core/integer/ceil_spec.rb b/spec/ruby/core/integer/ceil_spec.rb
index 13bdaf838d..eb633fba78 100644
--- a/spec/ruby/core/integer/ceil_spec.rb
+++ b/spec/ruby/core/integer/ceil_spec.rb
@@ -1,11 +1,16 @@
 require_relative '../../spec_helper'
 require_relative 'shared/to_i'
 require_relative 'shared/integer_rounding'
+require_relative 'shared/integer_ceil_precision'
 
 describe "Integer#ceil" do
   it_behaves_like :integer_to_i, :ceil
   it_behaves_like :integer_rounding_positive_precision, :ceil
 
+  context "with precision" do
+    it_behaves_like :integer_ceil_precision, :Integer
+  end
+
   context "precision argument specified as part of the ceil method is negative" do
     it "returns the smallest integer greater than self with at least precision.abs trailing zeros" do
       18.ceil(-1).should eql(20)
diff --git a/spec/ruby/core/integer/ceildiv_spec.rb b/spec/ruby/core/integer/ceildiv_spec.rb
new file mode 100644
index 0000000000..c6e22a457d
--- /dev/null
+++ b/spec/ruby/core/integer/ceildiv_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../spec_helper'
+
+describe "Integer#ceildiv" do
+  it "returns a quotient of division which is rounded up to the nearest integer" do
+    0.ceildiv(3).should eql(0)
+    1.ceildiv(3).should eql(1)
+    3.ceildiv(3).should eql(1)
+    4.ceildiv(3).should eql(2)
+
+    4.ceildiv(-3).should eql(-1)
+    -4.ceildiv(3).should eql(-1)
+    -4.ceildiv(-3).should eql(2)
+
+    3.ceildiv(1.2).should eql(3)
+    3.ceildiv(6/5r).should eql(3)
+
+    (10**100-11).ceildiv(10**99-1).should eql(10)
+    (10**100-9).ceildiv(10**99-1).should eql(11)
+  end
+end
diff --git a/spec/ruby/core/integer/chr_spec.rb b/spec/ruby/core/integer/chr_spec.rb
index a8755eeb84..39cafe2874 100644
--- a/spec/ruby/core/integer/chr_spec.rb
+++ b/spec/ruby/core/integer/chr_spec.rb
@@ -10,8 +10,12 @@ describe "Integer#chr without argument" do
   end
 
   it "raises a RangeError is self is less than 0" do
-    -> { -1.chr }.should raise_error(RangeError)
-    -> { -bignum_value.chr }.should raise_error(RangeError)
+    -> { -1.chr }.should raise_error(RangeError, /-1 out of char range/)
+    -> { (-bignum_value).chr }.should raise_error(RangeError, /bignum out of char range/)
+  end
+
+  it "raises a RangeError if self is too large" do
+    -> { 2206368128.chr(Encoding::UTF_8) }.should raise_error(RangeError, /2206368128 out of char range/)
   end
 
   describe "when Encoding.default_internal is nil" do
@@ -44,8 +48,8 @@ describe "Integer#chr without argument" do
     end
 
     it "raises a RangeError is self is greater than 255" do
-      -> { 256.chr }.should raise_error(RangeError)
-      -> { bignum_value.chr }.should raise_error(RangeError)
+      -> { 256.chr }.should raise_error(RangeError, /256 out of char range/)
+      -> { bignum_value.chr }.should raise_error(RangeError, /bignum out of char range/)
     end
   end
 
@@ -133,7 +137,7 @@ describe "Integer#chr without argument" do
           [620,    "TIS-620"]
         ].each do |integer, encoding_name|
           Encoding.default_internal = Encoding.find(encoding_name)
-          -> { integer.chr }.should raise_error(RangeError)
+          -> { integer.chr }.should raise_error(RangeError, /(invalid codepoint|out of char range)/)
         end
       end
     end
@@ -161,12 +165,12 @@ describe "Integer#chr with an encoding argument" do
 
   # http://redmine.ruby-lang.org/issues/4869
   it "raises a RangeError is self is less than 0" do
-    -> { -1.chr(Encoding::UTF_8) }.should raise_error(RangeError)
-    -> { -bignum_value.chr(Encoding::EUC_JP) }.should raise_error(RangeError)
+    -> { -1.chr(Encoding::UTF_8) }.should raise_error(RangeError, /-1 out of char range/)
+    -> { (-bignum_value).chr(Encoding::EUC_JP) }.should raise_error(RangeError, /bignum out of char range/)
   end
 
   it "raises a RangeError if self is too large" do
-    -> { 2206368128.chr(Encoding::UTF_8) }.should raise_error(RangeError)
+    -> { 2206368128.chr(Encoding::UTF_8) }.should raise_error(RangeError, /2206368128 out of char range/)
   end
 
   it "returns a String with the specified encoding" do
@@ -219,25 +223,35 @@ describe "Integer#chr with an encoding argument" do
 
   # #5864
   it "raises RangeError if self is invalid as a codepoint in the specified encoding" do
-    [ [0x80,   "US-ASCII"],
-      [0x0100, "BINARY"],
-      [0x0100, "EUC-JP"],
-      [0xA1A0, "EUC-JP"],
-      [0xA1,   "EUC-JP"],
-      [0x80,   "SHIFT_JIS"],
-      [0xE0,   "SHIFT_JIS"],
-      [0x0100, "ISO-8859-9"],
-      [620,    "TIS-620"],
-      [0xD800, "UTF-8"],
-      [0xDBFF, "UTF-8"],
-      [0xDC00, "UTF-8"],
-      [0xDFFF, "UTF-8"],
-      [0xD800, "UTF-16"],
-      [0xDBFF, "UTF-16"],
-      [0xDC00, "UTF-16"],
-      [0xDFFF, "UTF-16"],
-    ].each do |integer, encoding_name|
-      -> { integer.chr(encoding_name) }.should raise_error(RangeError)
-    end
+    -> { 0x80.chr("US-ASCII") }.should raise_error(RangeError)
+    -> { 0x0100.chr("BINARY") }.should raise_error(RangeError)
+    -> { 0x0100.chr("EUC-JP") }.should raise_error(RangeError)
+    -> { 0xA1A0.chr("EUC-JP") }.should raise_error(RangeError)
+    -> { 0xA1.chr("EUC-JP") }.should raise_error(RangeError)
+    -> { 0x80.chr("SHIFT_JIS") }.should raise_error(RangeError)
+    -> { 0xE0.chr("SHIFT_JIS") }.should raise_error(RangeError)
+    -> { 0x0100.chr("ISO-8859-9") }.should raise_error(RangeError)
+    -> { 620.chr("TIS-620") }.should raise_error(RangeError)
+    # UTF-16 surrogate range
+    -> { 0xD800.chr("UTF-8") }.should raise_error(RangeError)
+    -> { 0xDBFF.chr("UTF-8") }.should raise_error(RangeError)
+    -> { 0xDC00.chr("UTF-8") }.should raise_error(RangeError)
+    -> { 0xDFFF.chr("UTF-8") }.should raise_error(RangeError)
+    # UTF-16 surrogate range
+    -> { 0xD800.chr("UTF-16") }.should raise_error(RangeError)
+    -> { 0xDBFF.chr("UTF-16") }.should raise_error(RangeError)
+    -> { 0xDC00.chr("UTF-16") }.should raise_error(RangeError)
+    -> { 0xDFFF.chr("UTF-16") }.should raise_error(RangeError)
+  end
+
+  it 'returns a String encoding self interpreted as a codepoint in the CESU-8 encoding' do
+    # see more details here https://en.wikipedia.org/wiki/CESU-8
+    # code points from U+0000 to U+FFFF is encoded in the same way as in UTF-8
+    0x0045.chr(Encoding::CESU_8).bytes.should == 0x0045.chr(Encoding::UTF_8).bytes
+
+    # code points in range from U+10000 to U+10FFFF is CESU-8 data containing a 6-byte surrogate pair,
+    # which decodes to a 4-byte UTF-8 string
+    0x10400.chr(Encoding::CESU_8).bytes.should != 0x10400.chr(Encoding::UTF_8).bytes
+    0x10400.chr(Encoding::CESU_8).bytes.to_a.should == [0xED, 0xA0, 0x81, 0xED, 0xB0, 0x80]
   end
 end
diff --git a/spec/ruby/core/integer/coerce_spec.rb b/spec/ruby/core/integer/coerce_spec.rb
index 9a19baf2ea..1d6dc9713f 100644
--- a/spec/ruby/core/integer/coerce_spec.rb
+++ b/spec/ruby/core/integer/coerce_spec.rb
@@ -1,13 +1,11 @@
 require_relative '../../spec_helper'
 
-require 'bigdecimal'
-
 describe "Integer#coerce" do
   context "fixnum" do
     describe "when given a Fixnum" do
       it "returns an array containing two Fixnums" do
         1.coerce(2).should == [2, 1]
-        1.coerce(2).map { |i| i.class }.should == [Fixnum, Fixnum]
+        1.coerce(2).map { |i| i.class }.should == [Integer, Integer]
       end
     end
 
@@ -46,8 +44,8 @@ describe "Integer#coerce" do
       a = bignum_value
       ary = a.coerce(2)
 
-      ary[0].should be_kind_of(Bignum)
-      ary[1].should be_kind_of(Bignum)
+      ary[0].should be_kind_of(Integer)
+      ary[1].should be_kind_of(Integer)
       ary.should == [2, a]
     end
 
@@ -56,8 +54,8 @@ describe "Integer#coerce" do
       b = bignum_value
       ary = a.coerce(b)
 
-      ary[0].should be_kind_of(Bignum)
-      ary[1].should be_kind_of(Bignum)
+      ary[0].should be_kind_of(Integer)
+      ary[1].should be_kind_of(Integer)
       ary.should == [b, a]
     end
 
@@ -90,15 +88,4 @@ describe "Integer#coerce" do
       ary.should == [1.2, a.to_f]
     end
   end
-
-  context "bigdecimal" do
-    it "produces Floats" do
-      x, y = 3.coerce(BigDecimal("3.4"))
-      x.class.should == Float
-      x.should == 3.4
-      y.class.should == Float
-      y.should == 3.0
-    end
-  end
-
 end
diff --git a/spec/ruby/core/integer/comparison_spec.rb b/spec/ruby/core/integer/comparison_spec.rb
index 762af51535..408c8e52ce 100644
--- a/spec/ruby/core/integer/comparison_spec.rb
+++ b/spec/ruby/core/integer/comparison_spec.rb
@@ -116,7 +116,7 @@ describe "Integer#<=>" do
     describe "with an Object" do
       before :each do
         @big = bignum_value
-        @num = mock("value for Bignum#<=>")
+        @num = mock("value for Integer#<=>")
       end
 
       it "calls #coerce on other" do
@@ -124,23 +124,11 @@ describe "Integer#<=>" do
         @big <=> @num
       end
 
-      ruby_version_is ""..."2.5" do
-        it "returns nil if #coerce raises an exception" do
-          @num.should_receive(:coerce).with(@big).and_raise(RuntimeError)
-          -> {
-            @result = (@big <=> @num)
-          }.should complain(/Numerical comparison operators will no more rescue exceptions/)
-          @result.should be_nil
-        end
-      end
-
-      ruby_version_is "2.5" do
-        it "lets the exception go through if #coerce raises an exception" do
-          @num.should_receive(:coerce).with(@big).and_raise(RuntimeError.new("my error"))
-          -> {
-            @big <=> @num
-          }.should raise_error(RuntimeError, "my error")
-        end
+      it "lets the exception go through if #coerce raises an exception" do
+        @num.should_receive(:coerce).with(@big).and_raise(RuntimeError.new("my error"))
+        -> {
+          @big <=> @num
+        }.should raise_error(RuntimeError, "my error")
       end
 
       it "raises an exception if #coerce raises a non-StandardError exception" do
@@ -174,7 +162,7 @@ describe "Integer#<=>" do
       (infinity_value <=> Float::MAX.to_i*2).should == 1
     end
 
-    it "returns -1 when self is negative and other is Infinty" do
+    it "returns -1 when self is negative and other is Infinity" do
       (-Float::MAX.to_i*2 <=> infinity_value).should == -1
     end
 
diff --git a/spec/ruby/core/integer/complement_spec.rb b/spec/ruby/core/integer/complement_spec.rb
index eafa5c263f..baf5e6c457 100644
--- a/spec/ruby/core/integer/complement_spec.rb
+++ b/spec/ruby/core/integer/complement_spec.rb
@@ -12,9 +12,9 @@ describe "Integer#~" do
 
   context "bignum" do
     it "returns self with each bit flipped" do
-      (~bignum_value(48)).should == -9223372036854775857
-      (~(-bignum_value(21))).should == 9223372036854775828
-      (~bignum_value(1)).should == -9223372036854775810
+      (~bignum_value(48)).should == -18446744073709551665
+      (~(-bignum_value(21))).should == 18446744073709551636
+      (~bignum_value(1)).should == -18446744073709551618
     end
   end
 end
diff --git a/spec/ruby/core/integer/constants_spec.rb b/spec/ruby/core/integer/constants_spec.rb
new file mode 100644
index 0000000000..937806c72f
--- /dev/null
+++ b/spec/ruby/core/integer/constants_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Fixnum" do
+  it "is no longer defined" do
+    Object.should_not.const_defined?(:Fixnum)
+  end
+end
+
+describe "Bignum" do
+  it "is no longer defined" do
+    Object.should_not.const_defined?(:Bignum)
+  end
+end
diff --git a/spec/ruby/core/integer/digits_spec.rb b/spec/ruby/core/integer/digits_spec.rb
index 4a8e33980c..3d0a64c25f 100644
--- a/spec/ruby/core/integer/digits_spec.rb
+++ b/spec/ruby/core/integer/digits_spec.rb
@@ -29,4 +29,13 @@ describe "Integer#digits" do
   it "raises Math::DomainError when calling digits on a negative number" do
     -> { -12345.digits(7) }.should raise_error(Math::DomainError)
   end
+
+  it "returns integer values > 9 when base is above 10" do
+    1234.digits(16).should == [2, 13, 4]
+  end
+
+  it "can be used with base > 37" do
+    1234.digits(100).should == [34, 12]
+    980099.digits(100).should == [99, 0, 98]
+  end
 end
diff --git a/spec/ruby/core/integer/div_spec.rb b/spec/ruby/core/integer/div_spec.rb
index 087d012fe0..2eb9c0623b 100644
--- a/spec/ruby/core/integer/div_spec.rb
+++ b/spec/ruby/core/integer/div_spec.rb
@@ -36,7 +36,7 @@ describe "Integer#div" do
       10.div(y).should == result
     end
 
-    it "coerces self and the given argument to Floats and returns self divided by other as Fixnum" do
+    it "coerces self and the given argument to Floats and returns self divided by other as Integer" do
       1.div(0.2).should == 5
       1.div(0.16).should == 6
       1.div(0.169).should == 5
@@ -70,8 +70,8 @@ describe "Integer#div" do
     end
 
     it "returns self divided by other" do
-      @bignum.div(4).should == 2305843009213693974
-      @bignum.div(Rational(4, 1)).should == 2305843009213693974
+      @bignum.div(4).should == 4611686018427387926
+      @bignum.div(Rational(4, 1)).should == 4611686018427387926
       @bignum.div(bignum_value(2)).should == 1
 
       (-(10**50)).div(-(10**40 + 1)).should == 9999999999
@@ -124,11 +124,11 @@ describe "Integer#div" do
     end
 
     it "returns a result of integer division of self by a float argument" do
-      @bignum.div(4294967295.5).should eql(2147483648)
+      @bignum.div(4294967295.5).should eql(4294967296)
       not_supported_on :opal do
-        @bignum.div(4294967295.0).should eql(2147483648)
+        @bignum.div(4294967295.0).should eql(4294967297)
         @bignum.div(bignum_value(88).to_f).should eql(1)
-        @bignum.div(-bignum_value(88).to_f).should eql(-1)
+        @bignum.div((-bignum_value(88)).to_f).should eql(-1)
       end
     end
 
@@ -143,4 +143,12 @@ describe "Integer#div" do
       -> { @bignum.div(-0) }.should raise_error(ZeroDivisionError)
     end
   end
+
+  context "rational" do
+    it "returns self divided by the given argument as an Integer" do
+      2.div(6/5r).should == 1
+      1.div(6/5r).should == 0
+      5.div(6/5r).should == 4
+    end
+  end
 end
diff --git a/spec/ruby/core/integer/divide_spec.rb b/spec/ruby/core/integer/divide_spec.rb
index a32d68c229..0d5e16e986 100644
--- a/spec/ruby/core/integer/divide_spec.rb
+++ b/spec/ruby/core/integer/divide_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/arithmetic_coerce'
 
 describe "Integer#/" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_arithmetic_coerce_rescue, :/
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_arithmetic_coerce_not_rescue, :/
-  end
+  it_behaves_like :integer_arithmetic_coerce_not_rescue, :/
 
   context "fixnum" do
     it "returns self divided by the given argument" do
@@ -18,6 +12,17 @@ describe "Integer#/" do
 
     it "supports dividing negative numbers" do
       (-1 / 10).should == -1
+      (-1 / 10**10).should == -1
+      (-1 / 10**20).should == -1
+    end
+
+    it "preservers sign correctly" do
+      (4 / 3).should == 1
+      (4 / -3).should == -2
+      (-4 / 3).should == -2
+      (-4 / -3).should == 1
+      (0 / -3).should == 0
+      (0 / 3).should == 0
     end
 
     it "returns result the same class as the argument" do
@@ -53,7 +58,7 @@ describe "Integer#/" do
     end
 
     it "returns self divided by other" do
-      (@bignum / 4).should == 2305843009213693974
+      (@bignum / 4).should == 4611686018427387926
 
       (@bignum / bignum_value(2)).should == 1
 
@@ -64,17 +69,26 @@ describe "Integer#/" do
       ((10**50) / -(10**40 + 1)).should == -10000000000
     end
 
+    it "preservers sign correctly" do
+      (4 / bignum_value).should == 0
+      (4 / -bignum_value).should == -1
+      (-4 / bignum_value).should == -1
+      (-4 / -bignum_value).should == 0
+      (0 / bignum_value).should == 0
+      (0 / -bignum_value).should == 0
+    end
+
     it "returns self divided by Float" do
       not_supported_on :opal do
-        (bignum_value(88) / 4294967295.0).should be_close(2147483648.5, TOLERANCE)
+        (bignum_value(88) / 4294967295.0).should be_close(4294967297.0, TOLERANCE)
       end
-      (bignum_value(88) / 4294967295.5).should be_close(2147483648.25, TOLERANCE)
+      (bignum_value(88) / 4294967295.5).should be_close(4294967296.5, TOLERANCE)
     end
 
     it "returns result the same class as the argument" do
-      (@bignum / 4).should == 2305843009213693974
-      (@bignum / 4.0).should be_close(2305843009213693974, TOLERANCE)
-      (@bignum / Rational(4, 1)).should == Rational(2305843009213693974, 1)
+      (@bignum / 4).should == 4611686018427387926
+      (@bignum / 4.0).should be_close(4611686018427387926, TOLERANCE)
+      (@bignum / Rational(4, 1)).should == Rational(4611686018427387926, 1)
     end
 
     it "does NOT raise ZeroDivisionError if other is zero and is a Float" do
@@ -92,4 +106,21 @@ describe "Integer#/" do
       -> { @bignum / :symbol }.should raise_error(TypeError)
     end
   end
+
+  it "coerces the RHS and calls #coerce" do
+    obj = mock("integer plus")
+    obj.should_receive(:coerce).with(6).and_return([6, 3])
+    (6 / obj).should == 2
+  end
+
+  it "coerces the RHS and calls #coerce even if it's private" do
+    obj = Object.new
+    class << obj
+      private def coerce(n)
+        [n, 3]
+      end
+    end
+
+    (6 / obj).should == 2
+  end
 end
diff --git a/spec/ruby/core/integer/divmod_spec.rb b/spec/ruby/core/integer/divmod_spec.rb
index d88925caad..7a489e9344 100644
--- a/spec/ruby/core/integer/divmod_spec.rb
+++ b/spec/ruby/core/integer/divmod_spec.rb
@@ -46,16 +46,16 @@ describe "Integer#divmod" do
     # assert(0 < b ? (0 <= r && r < b) : (b < r && r <= 0))
     # So, r is always between 0 and b.
     it "returns an Array containing quotient and modulus obtained from dividing self by the given argument" do
-      @bignum.divmod(4).should == [2305843009213693965, 3]
-      @bignum.divmod(13).should == [709490156681136604, 11]
+      @bignum.divmod(4).should == [4611686018427387917, 3]
+      @bignum.divmod(13).should == [1418980313362273205, 6]
 
-      @bignum.divmod(4.5).should == [2049638230412172288, 3.5]
+      @bignum.divmod(4.5).should == [4099276460824344576, 2.5]
 
       not_supported_on :opal do
-        @bignum.divmod(4.0).should == [2305843009213693952, 0.0]
-        @bignum.divmod(13.0).should == [709490156681136640, 8.0]
+        @bignum.divmod(4.0).should == [4611686018427387904, 0.0]
+        @bignum.divmod(13.0).should == [1418980313362273280, 3.0]
 
-        @bignum.divmod(2.0).should == [4611686018427387904, 0.0]
+        @bignum.divmod(2.0).should == [9223372036854775808, 0.0]
       end
 
       @bignum.divmod(bignum_value).should == [1, 55]
diff --git a/spec/ruby/core/integer/downto_spec.rb b/spec/ruby/core/integer/downto_spec.rb
index af7a7e36b9..987704b02e 100644
--- a/spec/ruby/core/integer/downto_spec.rb
+++ b/spec/ruby/core/integer/downto_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../../spec_helper'
 
-describe "Integer#downto [stop] when self and stop are Fixnums" do
+describe "Integer#downto [stop] when self and stop are Integers" do
   it "does not yield when stop is greater than self" do
     result = []
     5.downto(6) { |x| result << x }
diff --git a/spec/ruby/core/integer/element_reference_spec.rb b/spec/ruby/core/integer/element_reference_spec.rb
index 99283fac34..cb7e0dc9b0 100644
--- a/spec/ruby/core/integer/element_reference_spec.rb
+++ b/spec/ruby/core/integer/element_reference_spec.rb
@@ -78,6 +78,83 @@ describe "Integer#[]" do
     it "returns 0 when passed a Float in the range of a Bignum" do
       3[bignum_value.to_f].should == 0
     end
+
+    context "when index and length passed" do
+      it "returns specified number of bits from specified position" do
+        0b101001101[2, 4].should ==    0b0011
+        0b101001101[2, 5].should ==   0b10011
+        0b101001101[2, 7].should == 0b1010011
+      end
+
+      it "ensures n[i, len] equals to (n >> i) & ((1 << len) - 1)" do
+        n = 0b101001101; i = 2; len = 4
+        n[i, len].should == (n >> i) & ((1 << len) - 1)
+      end
+
+      it "moves start position to the most significant bits when negative index passed" do
+        0b000001[-1, 4].should == 0b10
+        0b000001[-2, 4].should == 0b100
+        0b000001[-3, 4].should == 0b1000
+      end
+
+      it "ignores negative length" do
+        0b101001101[1, -1].should == 0b10100110
+        0b101001101[2, -1].should == 0b1010011
+        0b101001101[3, -1].should == 0b101001
+
+        0b101001101[3,   -5].should == 0b101001
+        0b101001101[3,  -15].should == 0b101001
+        0b101001101[3, -125].should == 0b101001
+      end
+    end
+
+    context "when range passed" do
+      it "returns bits specified by range" do
+        0b101001101[2..5].should ==    0b0011
+        0b101001101[2..6].should ==   0b10011
+        0b101001101[2..8].should == 0b1010011
+      end
+
+      it "ensures n[i..j] equals to (n >> i) & ((1 << (j - i + 1)) - 1)" do
+        n = 0b101001101; i = 2; j = 5
+        n[i..j].should == (n >> i) & ((1 << (j - i + 1)) - 1)
+      end
+
+      it "ensures n[i..] equals to (n >> i)" do
+        eval("0b101001101[3..]").should == 0b101001101 >> 3
+      end
+
+      it "moves lower boundary to the most significant bits when negative value passed" do
+        0b000001[-1, 4].should == 0b10
+        0b000001[-2, 4].should == 0b100
+        0b000001[-3, 4].should == 0b1000
+      end
+
+      it "ignores upper boundary smaller than lower boundary" do
+        0b101001101[4..1].should == 0b10100
+        0b101001101[4..2].should == 0b10100
+        0b101001101[-4..-5].should == 0b1010011010000
+      end
+
+      it "raises FloatDomainError if any boundary is infinity" do
+        -> { 0x0001[3..Float::INFINITY] }.should raise_error(FloatDomainError, /Infinity/)
+        -> { 0x0001[-Float::INFINITY..3] }.should raise_error(FloatDomainError, /-Infinity/)
+      end
+
+      context "when passed (..i)" do
+        it "returns 0 if all i bits equal 0" do
+          eval("0b10000[..1]").should == 0
+          eval("0b10000[..2]").should == 0
+          eval("0b10000[..3]").should == 0
+        end
+
+        it "raises ArgumentError if any of i bit equals 1" do
+          -> {
+            eval("0b111110[..3]")
+          }.should raise_error(ArgumentError, /The beginless range for Integer#\[\] results in infinity/)
+        end
+      end
+    end
   end
 
   context "bignum" do
diff --git a/spec/ruby/core/integer/fdiv_spec.rb b/spec/ruby/core/integer/fdiv_spec.rb
index 6de170278f..d9ea2fdf8d 100644
--- a/spec/ruby/core/integer/fdiv_spec.rb
+++ b/spec/ruby/core/integer/fdiv_spec.rb
@@ -9,6 +9,57 @@ describe "Integer#fdiv" do
     8.fdiv(bignum_value).should be_close(8.673617379884035e-19, TOLERANCE)
   end
 
+  it "performs floating-point division between self bignum and a bignum" do
+    num = 1000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146010000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146010000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146009
+    den = 2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+    num.fdiv(den).should == 500.0
+  end
+
+  it "rounds to the correct value for bignums" do
+    den = 9 * 10**342
+
+    num = 1 * 10**344
+    num.fdiv(den).should == 11.11111111111111
+
+    num = 1 * 10**343
+    num.fdiv(den).should == 1.1111111111111112
+
+    num = 1 * 10**342
+    num.fdiv(den).should == 0.1111111111111111
+
+    num = 2 * 10**342
+    num.fdiv(den).should == 0.2222222222222222
+
+    num = 3 * 10**342
+    num.fdiv(den).should == 0.3333333333333333
+
+    num = 4 * 10**342
+    num.fdiv(den).should == 0.4444444444444444
+
+    num = 5 * 10**342
+    num.fdiv(den).should == 0.5555555555555556
+
+    num = 6 * 10**342
+    num.fdiv(den).should == 0.6666666666666666
+
+    num = 7 * 10**342
+    num.fdiv(den).should == 0.7777777777777778
+
+    num = 8 * 10**342
+    num.fdiv(den).should == 0.8888888888888888
+
+    num = 9 * 10**342
+    num.fdiv(den).should == 1.0
+
+    num = -5 * 10**342
+    num.fdiv(den).should == -0.5555555555555556
+  end
+
+  it "rounds to the correct float for bignum denominators" do
+    1.fdiv(10**324).should == 0.0
+    1.fdiv(10**323).should == 1.0e-323
+  end
+
   it "performs floating-point division between self and a Float" do
     8.fdiv(9.0).should be_close(0.888888888888889, TOLERANCE)
   end
diff --git a/spec/ruby/core/integer/floor_spec.rb b/spec/ruby/core/integer/floor_spec.rb
index aaa816fdc5..8fb84d58cb 100644
--- a/spec/ruby/core/integer/floor_spec.rb
+++ b/spec/ruby/core/integer/floor_spec.rb
@@ -1,19 +1,13 @@
 require_relative '../../spec_helper'
 require_relative 'shared/to_i'
 require_relative 'shared/integer_rounding'
+require_relative 'shared/integer_floor_precision'
 
 describe "Integer#floor" do
   it_behaves_like :integer_to_i, :floor
   it_behaves_like :integer_rounding_positive_precision, :floor
 
-  context "precision argument specified as part of the floor method is negative" do
-    it "returns the largest integer less than self with at least precision.abs trailing zeros" do
-      1832.floor(-1).should eql(1830)
-      1832.floor(-2).should eql(1800)
-      1832.floor(-3).should eql(1000)
-      -1832.floor(-1).should eql(-1840)
-      -1832.floor(-2).should eql(-1900)
-      -1832.floor(-3).should eql(-2000)
-    end
+  context "with precision" do
+    it_behaves_like :integer_floor_precision, :Integer
   end
 end
diff --git a/spec/ruby/core/integer/gcd_spec.rb b/spec/ruby/core/integer/gcd_spec.rb
index 8aa654a16a..961f1c5c2e 100644
--- a/spec/ruby/core/integer/gcd_spec.rb
+++ b/spec/ruby/core/integer/gcd_spec.rb
@@ -33,13 +33,13 @@ describe "Integer#gcd" do
 
   it "accepts a Bignum argument" do
     bignum = 9999**99
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     99.gcd(bignum).should == 99
   end
 
   it "works if self is a Bignum" do
     bignum = 9999**99
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     bignum.gcd(99).should == 99
   end
 
diff --git a/spec/ruby/core/integer/gcdlcm_spec.rb b/spec/ruby/core/integer/gcdlcm_spec.rb
index 5b3669e62a..ebf45e55a1 100644
--- a/spec/ruby/core/integer/gcdlcm_spec.rb
+++ b/spec/ruby/core/integer/gcdlcm_spec.rb
@@ -28,13 +28,13 @@ describe "Integer#gcdlcm" do
 
   it "accepts a Bignum argument" do
     bignum = 91999**99
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     99.gcdlcm(bignum).should == [99.gcd(bignum), 99.lcm(bignum)]
   end
 
   it "works if self is a Bignum" do
     bignum = 9999**89
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     bignum.gcdlcm(99).should == [bignum.gcd(99), bignum.lcm(99)]
   end
 
diff --git a/spec/ruby/core/integer/gt_spec.rb b/spec/ruby/core/integer/gt_spec.rb
index 428a6f6888..f0179e566d 100644
--- a/spec/ruby/core/integer/gt_spec.rb
+++ b/spec/ruby/core/integer/gt_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/comparison_coerce'
 
 describe "Integer#>" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_comparison_coerce_rescue, :>
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_comparison_coerce_not_rescue, :>
-  end
+  it_behaves_like :integer_comparison_coerce_not_rescue, :>
 
   context "fixnum" do
     it "returns true if self is greater than the given argument" do
diff --git a/spec/ruby/core/integer/gte_spec.rb b/spec/ruby/core/integer/gte_spec.rb
index ce1385c360..6237fc2c51 100644
--- a/spec/ruby/core/integer/gte_spec.rb
+++ b/spec/ruby/core/integer/gte_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/comparison_coerce'
 
 describe "Integer#>=" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_comparison_coerce_rescue, :>=
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_comparison_coerce_not_rescue, :>=
-  end
+  it_behaves_like :integer_comparison_coerce_not_rescue, :>=
 
   context "fixnum" do
     it "returns true if self is greater than or equal to the given argument" do
diff --git a/spec/ruby/core/integer/integer_spec.rb b/spec/ruby/core/integer/integer_spec.rb
index f8067cda06..2d5d2e3e92 100644
--- a/spec/ruby/core/integer/integer_spec.rb
+++ b/spec/ruby/core/integer/integer_spec.rb
@@ -13,8 +13,8 @@ end
 
 describe "Integer#integer?" do
   it "returns true for Integers" do
-    0.integer?.should == true
-    -1.integer?.should == true
-    bignum_value.integer?.should == true
+    0.should.integer?
+    -1.should.integer?
+    bignum_value.should.integer?
   end
 end
diff --git a/spec/ruby/core/integer/lcm_spec.rb b/spec/ruby/core/integer/lcm_spec.rb
index 77d3ad3488..296a001c8c 100644
--- a/spec/ruby/core/integer/lcm_spec.rb
+++ b/spec/ruby/core/integer/lcm_spec.rb
@@ -33,13 +33,13 @@ describe "Integer#lcm" do
 
   it "accepts a Bignum argument" do
     bignum = 9999**99
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     99.lcm(bignum).should == bignum
   end
 
   it "works if self is a Bignum" do
     bignum = 9999**99
-    bignum.should be_kind_of(Bignum)
+    bignum.should be_kind_of(Integer)
     bignum.lcm(99).should == bignum
   end
 
diff --git a/spec/ruby/core/integer/left_shift_spec.rb b/spec/ruby/core/integer/left_shift_spec.rb
index 4b5ef9386e..86c2b18ae2 100644
--- a/spec/ruby/core/integer/left_shift_spec.rb
+++ b/spec/ruby/core/integer/left_shift_spec.rb
@@ -56,23 +56,26 @@ describe "Integer#<< (with n << m)" do
       (3 << -bignum_value).should == 0
     end
 
-    it "returns an Bignum == fixnum_max * 2 when fixnum_max << 1 and n > 0" do
+    it "returns a Bignum == fixnum_max * 2 when fixnum_max << 1 and n > 0" do
       result = fixnum_max << 1
-      result.should be_an_instance_of(Bignum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_max * 2
     end
 
-    it "returns an Bignum == fixnum_min * 2 when fixnum_min << 1 and n < 0" do
+    it "returns a Bignum == fixnum_min * 2 when fixnum_min << 1 and n < 0" do
       result = fixnum_min << 1
-      result.should be_an_instance_of(Bignum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_min * 2
     end
 
     it "calls #to_int to convert the argument to an Integer" do
       obj = mock("4")
       obj.should_receive(:to_int).and_return(4)
-
       (3 << obj).should == 48
+
+      obj = mock("to_int_neg_bignum")
+      obj.should_receive(:to_int).and_return(-bignum_value)
+      (3 << obj).should == 0
     end
 
     it "raises a TypeError when #to_int does not return an Integer" do
@@ -93,7 +96,7 @@ describe "Integer#<< (with n << m)" do
 
   context "bignum" do
     before :each do
-      @bignum = bignum_value * 16
+      @bignum = bignum_value * 8 # 2 ** 67
     end
 
     it "returns n shifted left m bits when n > 0, m > 0" do
@@ -124,19 +127,15 @@ describe "Integer#<< (with n << m)" do
       (@bignum << -68).should == 0
     end
 
-    it "returns 0 when m < 0 and m is a Bignum" do
-      (@bignum << -bignum_value).should == 0
-    end
-
     it "returns a Fixnum == fixnum_max when (fixnum_max * 2) << -1 and n > 0" do
       result = (fixnum_max * 2) << -1
-      result.should be_an_instance_of(Fixnum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_max
     end
 
     it "returns a Fixnum == fixnum_min when (fixnum_min * 2) << -1 and n < 0" do
       result = (fixnum_min * 2) << -1
-      result.should be_an_instance_of(Fixnum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_min
     end
 
@@ -162,4 +161,51 @@ describe "Integer#<< (with n << m)" do
       -> { @bignum << "4" }.should raise_error(TypeError)
     end
   end
+
+  context "when m is a bignum or larger than int" do
+    it "returns -1 when m < 0 and n < 0" do
+      (-1 << -bignum_value).should == -1
+      (-1 << -(2**40)).should == -1
+
+      (-bignum_value << -bignum_value).should == -1
+      (-bignum_value << -(2**40)).should == -1
+    end
+
+    it "returns 0 when m < 0 and n >= 0" do
+      (0 << -bignum_value).should == 0
+      (1 << -bignum_value).should == 0
+      (bignum_value << -bignum_value).should == 0
+
+      (0 << -(2**40)).should == 0
+      (1 << -(2**40)).should == 0
+      (bignum_value << -(2**40)).should == 0
+    end
+
+    it "returns 0 when m > 0 long and n == 0" do
+      (0 << (2**40)).should == 0
+    end
+
+    it "returns 0 when m > 0 bignum and n == 0" do
+      (0 << bignum_value).should == 0
+    end
+
+    it "raises RangeError when m > 0 and n != 0" do
+      # https://bugs.ruby-lang.org/issues/18518#note-9
+      limit = RUBY_ENGINE == 'ruby' ? 2**67 : 2**32
+
+      coerce_long = mock("long")
+      coerce_long.stub!(:to_int).and_return(limit)
+      coerce_bignum = mock("bignum")
+      coerce_bignum.stub!(:to_int).and_return(bignum_value)
+      exps = [limit, coerce_long]
+      exps << bignum_value << coerce_bignum if bignum_value >= limit
+
+      exps.each { |exp|
+        -> { (1 << exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-1 << exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (bignum_value << exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-bignum_value << exp) }.should raise_error(RangeError, 'shift width too big')
+      }
+    end
+  end
 end
diff --git a/spec/ruby/core/integer/lt_spec.rb b/spec/ruby/core/integer/lt_spec.rb
index dfe2d9e369..c182f82555 100644
--- a/spec/ruby/core/integer/lt_spec.rb
+++ b/spec/ruby/core/integer/lt_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/comparison_coerce'
 
 describe "Integer#<" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_comparison_coerce_rescue, :<
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_comparison_coerce_not_rescue, :<
-  end
+  it_behaves_like :integer_comparison_coerce_not_rescue, :<
 
   context "fixnum" do
     it "returns true if self is less than the given argument" do
diff --git a/spec/ruby/core/integer/lte_spec.rb b/spec/ruby/core/integer/lte_spec.rb
index 3d843a5dd9..65b71d77f2 100644
--- a/spec/ruby/core/integer/lte_spec.rb
+++ b/spec/ruby/core/integer/lte_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/comparison_coerce'
 
 describe "Integer#<=" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_comparison_coerce_rescue, :<=
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_comparison_coerce_not_rescue, :<=
-  end
+  it_behaves_like :integer_comparison_coerce_not_rescue, :<=
 
   context "fixnum" do
     it "returns true if self is less than or equal to other" do
@@ -46,6 +40,11 @@ describe "Integer#<=" do
       (@bignum <= (@bignum + 0.5)).should == false
     end
 
+    it "returns true for bignums compare to a bigger float" do
+      (18446744073709551616 <= 1.8446744073709552e+19).should == true
+      (@bignum <= (@bignum + 9999.0)).should == true
+    end
+
     it "raises an ArgumentError when given a non-Integer" do
       -> { @bignum <= "4" }.should raise_error(ArgumentError)
       -> { @bignum <= mock('str') }.should raise_error(ArgumentError)
diff --git a/spec/ruby/core/integer/minus_spec.rb b/spec/ruby/core/integer/minus_spec.rb
index 34dd36c1a7..6072ba7c8b 100644
--- a/spec/ruby/core/integer/minus_spec.rb
+++ b/spec/ruby/core/integer/minus_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/arithmetic_coerce'
 
 describe "Integer#-" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_arithmetic_coerce_rescue, :-
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_arithmetic_coerce_not_rescue, :-
-  end
+  it_behaves_like :integer_arithmetic_coerce_not_rescue, :-
 
   context "fixnum" do
     it "returns self minus the given Integer" do
@@ -16,7 +10,7 @@ describe "Integer#-" do
       (9237212 - 5_280).should == 9231932
 
       (781 - 0.5).should == 780.5
-      (2_560_496 - bignum_value).should == -9223372036852215312
+      (2_560_496 - bignum_value).should == -18446744073706991120
     end
 
     it "raises a TypeError when given a non-Integer" do
@@ -35,8 +29,8 @@ describe "Integer#-" do
     end
 
     it "returns self minus the given Integer" do
-      (@bignum - 9).should == 9223372036854776113
-      (@bignum - 12.57).should be_close(9223372036854776109.43, TOLERANCE)
+      (@bignum - 9).should == 18446744073709551921
+      (@bignum - 12.57).should be_close(18446744073709551917.43, TOLERANCE)
       (@bignum - bignum_value(42)).should == 272
     end
 
@@ -46,4 +40,21 @@ describe "Integer#-" do
       -> { @bignum - :symbol }.should raise_error(TypeError)
     end
   end
+
+  it "coerces the RHS and calls #coerce" do
+    obj = mock("integer plus")
+    obj.should_receive(:coerce).with(5).and_return([5, 10])
+    (5 - obj).should == -5
+  end
+
+  it "coerces the RHS and calls #coerce even if it's private" do
+    obj = Object.new
+    class << obj
+      private def coerce(n)
+        [n, 10]
+      end
+    end
+
+    (5 - obj).should == -5
+  end
 end
diff --git a/spec/ruby/core/integer/multiply_spec.rb b/spec/ruby/core/integer/multiply_spec.rb
index 919786cbcc..5037d27458 100644
--- a/spec/ruby/core/integer/multiply_spec.rb
+++ b/spec/ruby/core/integer/multiply_spec.rb
@@ -2,13 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'shared/arithmetic_coerce'
 
 describe "Integer#*" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_arithmetic_coerce_rescue, :*
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_arithmetic_coerce_not_rescue, :*
-  end
+  it_behaves_like :integer_arithmetic_coerce_not_rescue, :*
 
   context "fixnum" do
     it "returns self multiplied by the given Integer" do
@@ -16,7 +10,7 @@ describe "Integer#*" do
       (1342177 * 800).should == 1073741600
       (65536 * 65536).should == 4294967296
 
-      (256 * bignum_value).should == 2361183241434822606848
+      (256 * bignum_value).should == 4722366482869645213696
       (6712 * 0.25).should == 1678.0
     end
 
@@ -38,8 +32,8 @@ describe "Integer#*" do
     it "returns self multiplied by the given Integer" do
       (@bignum * (1/bignum_value(0xffff).to_f)).should be_close(1.0, TOLERANCE)
       (@bignum * (1/bignum_value(0xffff).to_f)).should be_close(1.0, TOLERANCE)
-      (@bignum * 10).should == 92233720368547765800
-      (@bignum * (@bignum - 40)).should == 85070591730234629737795195287525433200
+      (@bignum * 10).should == 184467440737095523880
+      (@bignum * (@bignum - 40)).should == 340282366920938491207277694290934407024
     end
 
     it "raises a TypeError when given a non-Integer" do
diff --git a/spec/ruby/core/integer/nobits_spec.rb b/spec/ruby/core/integer/nobits_spec.rb
index af3b9e7db0..685759ffa3 100644
--- a/spec/ruby/core/integer/nobits_spec.rb
+++ b/spec/ruby/core/integer/nobits_spec.rb
@@ -1,38 +1,36 @@
 require_relative '../../spec_helper'
 
-ruby_version_is '2.5' do
-  describe "Integer#nobits?" do
-    it "returns true iff all no bits of the argument are set in the receiver" do
-      42.nobits?(42).should == false
-      0b1010_1010.nobits?(0b1000_0010).should == false
-      0b1010_1010.nobits?(0b1000_0001).should == false
-      0b0100_0101.nobits?(0b1010_1010).should == true
-      different_bignum = (2 * bignum_value) & (~bignum_value)
-      (0b1010_1010 | different_bignum).nobits?(0b1000_0010 | bignum_value).should == false
-      (0b1010_1010 | different_bignum).nobits?(0b1000_0001 | bignum_value).should == false
-      (0b0100_0101 | different_bignum).nobits?(0b1010_1010 | bignum_value).should == true
-    end
+describe "Integer#nobits?" do
+  it "returns true if and only if all no bits of the argument are set in the receiver" do
+    42.nobits?(42).should == false
+    0b1010_1010.nobits?(0b1000_0010).should == false
+    0b1010_1010.nobits?(0b1000_0001).should == false
+    0b0100_0101.nobits?(0b1010_1010).should == true
+    different_bignum = (2 * bignum_value) & (~bignum_value)
+    (0b1010_1010 | different_bignum).nobits?(0b1000_0010 | bignum_value).should == false
+    (0b1010_1010 | different_bignum).nobits?(0b1000_0001 | bignum_value).should == false
+    (0b0100_0101 | different_bignum).nobits?(0b1010_1010 | bignum_value).should == true
+  end
 
-    it "handles negative values using two's complement notation" do
-      (~0b1101).nobits?(0b1101).should == true
-      (-42).nobits?(-42).should == false
-      (~0b1101).nobits?(~0b10).should == false
-      (~(0b1101 | bignum_value)).nobits?(~(0b10 | bignum_value)).should == false
-    end
+  it "handles negative values using two's complement notation" do
+    (~0b1101).nobits?(0b1101).should == true
+    (-42).nobits?(-42).should == false
+    (~0b1101).nobits?(~0b10).should == false
+    (~(0b1101 | bignum_value)).nobits?(~(0b10 | bignum_value)).should == false
+  end
 
-    it "coerces the rhs using to_int" do
-      obj = mock("the int 0b10")
-      obj.should_receive(:to_int).and_return(0b10)
-      0b110.nobits?(obj).should == false
-    end
+  it "coerces the rhs using to_int" do
+    obj = mock("the int 0b10")
+    obj.should_receive(:to_int).and_return(0b10)
+    0b110.nobits?(obj).should == false
+  end
 
-    it "raises a TypeError when given a non-Integer" do
-      -> {
-        (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
-        13.nobits?(obj)
-      }.should raise_error(TypeError)
-      -> { 13.nobits?("10")    }.should raise_error(TypeError)
-      -> { 13.nobits?(:symbol) }.should raise_error(TypeError)
-    end
+  it "raises a TypeError when given a non-Integer" do
+    -> {
+      (obj = mock('10')).should_receive(:coerce).any_number_of_times.and_return([42,10])
+      13.nobits?(obj)
+    }.should raise_error(TypeError)
+    -> { 13.nobits?("10")    }.should raise_error(TypeError)
+    -> { 13.nobits?(:symbol) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/integer/plus_spec.rb b/spec/ruby/core/integer/plus_spec.rb
index 7e919a16db..38428e56c5 100644
--- a/spec/ruby/core/integer/plus_spec.rb
+++ b/spec/ruby/core/integer/plus_spec.rb
@@ -2,20 +2,14 @@ require_relative '../../spec_helper'
 require_relative 'shared/arithmetic_coerce'
 
 describe "Integer#+" do
-  ruby_version_is "2.4"..."2.5" do
-    it_behaves_like :integer_arithmetic_coerce_rescue, :+
-  end
-
-  ruby_version_is "2.5" do
-    it_behaves_like :integer_arithmetic_coerce_not_rescue, :+
-  end
+  it_behaves_like :integer_arithmetic_coerce_not_rescue, :+
 
   context "fixnum" do
     it "returns self plus the given Integer" do
       (491 + 2).should == 493
       (90210 + 10).should == 90220
 
-      (9 + bignum_value).should == 9223372036854775817
+      (9 + bignum_value).should == 18446744073709551625
       (1001 + 5.219).should == 1006.219
     end
 
@@ -35,9 +29,9 @@ describe "Integer#+" do
     end
 
     it "returns self plus the given Integer" do
-      (@bignum + 4).should == 9223372036854775888
-      (@bignum + 4.2).should be_close(9223372036854775888.2, TOLERANCE)
-      (@bignum + bignum_value(3)).should == 18446744073709551695
+      (@bignum + 4).should == 18446744073709551696
+      (@bignum + 4.2).should be_close(18446744073709551696.2, TOLERANCE)
+      (@bignum + bignum_value(3)).should == 36893488147419103311
     end
 
     it "raises a TypeError when given a non-Integer" do
@@ -46,4 +40,36 @@ describe "Integer#+" do
       -> { @bignum + :symbol}.should raise_error(TypeError)
     end
   end
+
+  it "can be redefined" do
+    code = <<~RUBY
+      class Integer
+        alias_method :old_plus, :+
+        def +(other)
+          self - other
+        end
+      end
+      result = 1 + 2
+      Integer.alias_method :+, :old_plus
+      print result
+    RUBY
+    ruby_exe(code).should == "-1"
+  end
+
+  it "coerces the RHS and calls #coerce" do
+    obj = mock("integer plus")
+    obj.should_receive(:coerce).with(6).and_return([6, 3])
+    (6 + obj).should == 9
+  end
+
+  it "coerces the RHS and calls #coerce even if it's private" do
+    obj = Object.new
+    class << obj
+      private def coerce(n)
+        [n, 3]
+      end
+    end
+
+    (6 + obj).should == 9
+  end
 end
diff --git a/spec/ruby/core/integer/pow_spec.rb b/spec/ruby/core/integer/pow_spec.rb
index ed14c40a27..ecaca01eff 100644
--- a/spec/ruby/core/integer/pow_spec.rb
+++ b/spec/ruby/core/integer/pow_spec.rb
@@ -2,48 +2,50 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/exponent'
 
-ruby_version_is "2.5" do
-  describe "Integer#pow" do
-    context "one argument is passed" do
-      it_behaves_like :integer_exponent, :pow
+describe "Integer#pow" do
+  context "one argument is passed" do
+    it_behaves_like :integer_exponent, :pow
+  end
+
+  context "two arguments are passed" do
+    it "returns modulo of self raised to the given power" do
+      2.pow(5, 12).should == 8
+      2.pow(6, 13).should == 12
+      2.pow(7, 14).should == 2
+      2.pow(8, 15).should == 1
+    end
+
+    it "works well with bignums" do
+      2.pow(61, 5843009213693951).should eql 3697379018277258
+      2.pow(62, 5843009213693952).should eql 1551748822859776
+      2.pow(63, 5843009213693953).should eql 3103497645717974
+      2.pow(64, 5843009213693954).should eql 363986077738838
+    end
+
+    it "handles sign like #divmod does" do
+      2.pow(5, 12).should == 8
+      2.pow(5, -12).should == -4
+      -2.pow(5, 12).should == 4
+      -2.pow(5, -12).should == -8
+    end
+
+    it "ensures all arguments are integers" do
+      -> { 2.pow(5, 12.0) }.should raise_error(TypeError, /2nd argument not allowed unless all arguments are integers/)
+      -> { 2.pow(5, Rational(12, 1)) }.should raise_error(TypeError, /2nd argument not allowed unless all arguments are integers/)
+    end
+
+    it "raises TypeError for non-numeric value" do
+      -> { 2.pow(5, "12") }.should raise_error(TypeError)
+      -> { 2.pow(5, []) }.should raise_error(TypeError)
+      -> { 2.pow(5, nil) }.should raise_error(TypeError)
+    end
+
+    it "raises a ZeroDivisionError when the given argument is 0" do
+      -> { 2.pow(5, 0) }.should raise_error(ZeroDivisionError)
     end
 
-    context "two arguments are passed" do
-      it "returns modulo of self raised to the given power" do
-        2.pow(5, 12).should == 8
-        2.pow(6, 13).should == 12
-        2.pow(7, 14).should == 2
-        2.pow(8, 15).should == 1
-      end
-
-      it "works well with bignums" do
-        2.pow(61, 5843009213693951).should eql 3697379018277258
-        2.pow(62, 5843009213693952).should eql 1551748822859776
-        2.pow(63, 5843009213693953).should eql 3103497645717974
-        2.pow(64, 5843009213693954).should eql  363986077738838
-      end
-
-      it "handles sign like #divmod does" do
-         2.pow(5,  12).should ==  8
-         2.pow(5, -12).should == -4
-        -2.pow(5,  12).should ==  4
-        -2.pow(5, -12).should == -8
-      end
-
-      it "ensures all arguments are integers" do
-        -> { 2.pow(5, 12.0) }.should raise_error(TypeError, /2nd argument not allowed unless all arguments are integers/)
-        -> { 2.pow(5, Rational(12, 1)) }.should raise_error(TypeError, /2nd argument not allowed unless all arguments are integers/)
-      end
-
-      it "raises TypeError for non-numeric value" do
-        -> { 2.pow(5, "12") }.should raise_error(TypeError)
-        -> { 2.pow(5, []) }.should raise_error(TypeError)
-        -> { 2.pow(5, nil) }.should raise_error(TypeError)
-      end
-
-      it "raises a ZeroDivisionError when the given argument is 0" do
-        -> { 2.pow(5, 0) }.should raise_error(ZeroDivisionError)
-      end
+    it "raises a RangeError when the first argument is negative and the second argument is present" do
+      -> { 2.pow(-5, 1) }.should raise_error(RangeError)
     end
   end
 end
diff --git a/spec/ruby/core/integer/remainder_spec.rb b/spec/ruby/core/integer/remainder_spec.rb
index cd10dad6f2..757e42fbe8 100644
--- a/spec/ruby/core/integer/remainder_spec.rb
+++ b/spec/ruby/core/integer/remainder_spec.rb
@@ -15,8 +15,8 @@ describe "Integer#remainder" do
     end
 
     it "keeps sign of self" do
-       5.remainder( 3).should ==  2
-       5.remainder(-3).should ==  2
+      5.remainder( 3).should == 2
+      5.remainder(-3).should == 2
       -5.remainder( 3).should == -2
       -5.remainder(-3).should == -2
     end
@@ -33,7 +33,7 @@ describe "Integer#remainder" do
     it "returns the remainder of dividing self by other" do
       a = bignum_value(79)
       a.remainder(2).should == 1
-      a.remainder(97.345).should be_close(46.5674996147722, TOLERANCE)
+      a.remainder(97.345).should be_close(93.1349992295444, TOLERANCE)
       a.remainder(bignum_value).should == 79
     end
 
diff --git a/spec/ruby/core/integer/right_shift_spec.rb b/spec/ruby/core/integer/right_shift_spec.rb
index 3eeaf3eb2f..c902674e2f 100644
--- a/spec/ruby/core/integer/right_shift_spec.rb
+++ b/spec/ruby/core/integer/right_shift_spec.rb
@@ -52,27 +52,26 @@ describe "Integer#>> (with n >> m)" do
       (-7 >> 64).should == -1
     end
 
-    it "returns 0 when m is a bignum" do
-      (3 >> bignum_value).should == 0
-    end
-
-    it "returns an Bignum == fixnum_max * 2 when fixnum_max >> -1 and n > 0" do
+    it "returns a Bignum == fixnum_max * 2 when fixnum_max >> -1 and n > 0" do
       result = fixnum_max >> -1
-      result.should be_an_instance_of(Bignum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_max * 2
     end
 
-    it "returns an Bignum == fixnum_min * 2 when fixnum_min >> -1 and n < 0" do
+    it "returns a Bignum == fixnum_min * 2 when fixnum_min >> -1 and n < 0" do
       result = fixnum_min >> -1
-      result.should be_an_instance_of(Bignum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_min * 2
     end
 
     it "calls #to_int to convert the argument to an Integer" do
       obj = mock("2")
       obj.should_receive(:to_int).and_return(2)
-
       (8 >> obj).should == 2
+
+      obj = mock("to_int_bignum")
+      obj.should_receive(:to_int).and_return(bignum_value)
+      (8 >> obj).should == 0
     end
 
     it "raises a TypeError when #to_int does not return an Integer" do
@@ -93,7 +92,7 @@ describe "Integer#>> (with n >> m)" do
 
   context "bignum" do
     before :each do
-      @bignum = bignum_value * 16
+      @bignum = bignum_value * 8 # 2 ** 67
     end
 
     it "returns n shifted right m bits when n > 0, m > 0" do
@@ -150,19 +149,15 @@ describe "Integer#>> (with n >> m)" do
       (@bignum >> 68).should == 0
     end
 
-    it "returns 0 when m is a Bignum" do
-      (@bignum >> bignum_value).should == 0
-    end
-
     it "returns a Fixnum == fixnum_max when (fixnum_max * 2) >> 1 and n > 0" do
       result = (fixnum_max * 2) >> 1
-      result.should be_an_instance_of(Fixnum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_max
     end
 
     it "returns a Fixnum == fixnum_min when (fixnum_min * 2) >> 1 and n < 0" do
       result = (fixnum_min * 2) >> 1
-      result.should be_an_instance_of(Fixnum)
+      result.should be_an_instance_of(Integer)
       result.should == fixnum_min
     end
 
@@ -188,4 +183,51 @@ describe "Integer#>> (with n >> m)" do
       -> { @bignum >> "4" }.should raise_error(TypeError)
     end
   end
+
+  context "when m is a bignum or larger than int" do
+    it "returns -1 when m > 0 and n < 0" do
+      (-1 >> bignum_value).should == -1
+      (-1 >> (2**40)).should == -1
+
+      (-bignum_value >> bignum_value).should == -1
+      (-bignum_value >> (2**40)).should == -1
+    end
+
+    it "returns 0 when m > 0 and n >= 0" do
+      (0 >> bignum_value).should == 0
+      (1 >> bignum_value).should == 0
+      (bignum_value >> bignum_value).should == 0
+
+      (0 >> (2**40)).should == 0
+      (1 >> (2**40)).should == 0
+      (bignum_value >> (2**40)).should == 0
+    end
+
+    it "returns 0 when m < 0 long and n == 0" do
+      (0 >> -(2**40)).should == 0
+    end
+
+    it "returns 0 when m < 0 bignum and n == 0" do
+      (0 >> -bignum_value).should == 0
+    end
+
+    it "raises RangeError when m < 0 and n != 0" do
+      # https://bugs.ruby-lang.org/issues/18518#note-9
+      limit = RUBY_ENGINE == 'ruby' ? 2**67 : 2**32
+
+      coerce_long = mock("long")
+      coerce_long.stub!(:to_int).and_return(-limit)
+      coerce_bignum = mock("bignum")
+      coerce_bignum.stub!(:to_int).and_return(-bignum_value)
+      exps = [-limit, coerce_long]
+      exps << -bignum_value << coerce_bignum if bignum_value >= limit
+
+      exps.each { |exp|
+        -> { (1 >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-1 >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (bignum_value >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-bignum_value >> exp) }.should raise_error(RangeError, 'shift width too big')
+      }
+    end
+  end
 end
diff --git a/spec/ruby/core/integer/round_spec.rb b/spec/ruby/core/integer/round_spec.rb
index feb6d475d3..189384f11a 100644
--- a/spec/ruby/core/integer/round_spec.rb
+++ b/spec/ruby/core/integer/round_spec.rb
@@ -6,14 +6,6 @@ describe "Integer#round" do
   it_behaves_like :integer_to_i, :round
   it_behaves_like :integer_rounding_positive_precision, :round
 
-  ruby_version_is ""..."2.5" do # Not just since 2.4
-    it "rounds itself as a float if passed a positive precision" do
-      [2, -4, 10**70, -10**100].each do |v|
-        v.round(42).should eql(v.to_f)
-      end
-    end
-  end
-
   # redmine:5228
   it "returns itself rounded if passed a negative value" do
     +249.round(-2).should eql(+200)
@@ -29,10 +21,8 @@ describe "Integer#round" do
     (-25 * 10**70).round(-71).should eql(-30 * 10**70)
   end
 
-  platform_is_not wordsize: 32 do
-    it "raises a RangeError when passed a big negative value" do
-      -> { 42.round(fixnum_min) }.should raise_error(RangeError)
-    end
+  it "raises a RangeError when passed a big negative value" do
+    -> { 42.round(min_long - 1) }.should raise_error(RangeError)
   end
 
   it "raises a RangeError when passed Float::INFINITY" do
@@ -78,20 +68,10 @@ describe "Integer#round" do
     (-25).round(-1, half: nil).should   eql(-30)
   end
 
-  ruby_version_is "2.4"..."2.5" do
-    it "returns itself as a float if passed a positive precision and the half option" do
-      35.round(1, half: :up).should      eql(35.0)
-      35.round(1, half: :down).should    eql(35.0)
-      35.round(1, half: :even).should    eql(35.0)
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns itself if passed a positive precision and the half option" do
-      35.round(1, half: :up).should      eql(35)
-      35.round(1, half: :down).should    eql(35)
-      35.round(1, half: :even).should    eql(35)
-    end
+  it "returns itself if passed a positive precision and the half option" do
+    35.round(1, half: :up).should      eql(35)
+    35.round(1, half: :down).should    eql(35)
+    35.round(1, half: :even).should    eql(35)
   end
 
   it "raises ArgumentError for an unknown rounding mode" do
diff --git a/spec/ruby/core/integer/shared/abs.rb b/spec/ruby/core/integer/shared/abs.rb
index 946aa21864..43844c9065 100644
--- a/spec/ruby/core/integer/shared/abs.rb
+++ b/spec/ruby/core/integer/shared/abs.rb
@@ -11,8 +11,8 @@ describe :integer_abs, shared: true do
 
   context "bignum" do
     it "returns the absolute bignum value" do
-      bignum_value(39).send(@method).should == 9223372036854775847
-      (-bignum_value(18)).send(@method).should == 9223372036854775826
+      bignum_value(39).send(@method).should == 18446744073709551655
+      (-bignum_value(18)).send(@method).should == 18446744073709551634
     end
   end
 end
diff --git a/spec/ruby/core/integer/shared/arithmetic_coerce.rb b/spec/ruby/core/integer/shared/arithmetic_coerce.rb
index 4c0cbcb999..1260192df1 100644
--- a/spec/ruby/core/integer/shared/arithmetic_coerce.rb
+++ b/spec/ruby/core/integer/shared/arithmetic_coerce.rb
@@ -1,25 +1,5 @@
 require_relative '../fixtures/classes'
 
-describe :integer_arithmetic_coerce_rescue, shared: true do
-  it "rescues exception (StandardError and subclasses) raised in other#coerce and raises TypeError" do
-    b = mock("numeric with failed #coerce")
-    b.should_receive(:coerce).and_raise(IntegerSpecs::CoerceError)
-
-    # e.g. 1 + b
-    -> { 1.send(@method, b) }.should raise_error(TypeError, /MockObject can't be coerced into Integer/)
-  end
-
-  it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-    [Exception, NoMemoryError].each do |exception|
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(exception)
-
-      # e.g. 1 + b
-      -> { 1.send(@method, b) }.should raise_error(exception)
-    end
-  end
-end
-
 describe :integer_arithmetic_coerce_not_rescue, shared: true do
   it "does not rescue exception raised in other#coerce" do
     b = mock("numeric with failed #coerce")
diff --git a/spec/ruby/core/integer/shared/comparison_coerce.rb b/spec/ruby/core/integer/shared/comparison_coerce.rb
index 50437f77f5..af52f5e99b 100644
--- a/spec/ruby/core/integer/shared/comparison_coerce.rb
+++ b/spec/ruby/core/integer/shared/comparison_coerce.rb
@@ -1,27 +1,5 @@
 require_relative '../fixtures/classes'
 
-describe :integer_comparison_coerce_rescue, shared: true do
-  it "rescues exception (StandardError and subclasses) raised in other#coerce and raises ArgumentError" do
-    b = mock("numeric with failed #coerce")
-    b.should_receive(:coerce).and_raise(IntegerSpecs::CoerceError)
-
-    # e.g. 1 > b
-    -> {
-      -> { 1.send(@method, b) }.should raise_error(ArgumentError, /comparison of Integer with MockObject failed/)
-    }.should complain(/Numerical comparison operators will no more rescue exceptions of #coerce/)
-  end
-
-  it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-    [Exception, NoMemoryError].each do |exception|
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(exception)
-
-      # e.g. 1 > b
-      -> { 1.send(@method, b) }.should raise_error(exception)
-    end
-  end
-end
-
 describe :integer_comparison_coerce_not_rescue, shared: true do
   it "does not rescue exception raised in other#coerce" do
     b = mock("numeric with failed #coerce")
diff --git a/spec/ruby/core/integer/shared/equal.rb b/spec/ruby/core/integer/shared/equal.rb
index 03416b60f5..ecee17831c 100644
--- a/spec/ruby/core/integer/shared/equal.rb
+++ b/spec/ruby/core/integer/shared/equal.rb
@@ -4,14 +4,14 @@ describe :integer_equal, shared: true do
       1.send(@method, 1).should == true
       9.send(@method, 5).should == false
 
-      # Actually, these call Float#==, Bignum#== etc.
+      # Actually, these call Float#==, Integer#== etc.
       9.send(@method, 9.0).should == true
       9.send(@method, 9.01).should == false
 
       10.send(@method, bignum_value).should == false
     end
 
-    it "calls 'other == self' if the given argument is not a Integer" do
+    it "calls 'other == self' if the given argument is not an Integer" do
       1.send(@method, '*').should == false
 
       obj = mock('one other')
diff --git a/spec/ruby/core/integer/shared/exponent.rb b/spec/ruby/core/integer/shared/exponent.rb
index f292cc2448..5ef6d686d8 100644
--- a/spec/ruby/core/integer/shared/exponent.rb
+++ b/spec/ruby/core/integer/shared/exponent.rb
@@ -30,11 +30,13 @@ describe :integer_exponent, shared: true do
       (-2).send(@method, 30).should eql(1073741824)
       (-2).send(@method, 31).should eql(-2147483648)
       (-2).send(@method, 32).should eql(4294967296)
+      (-2).send(@method, 33).should eql(-8589934592)
 
       (-2).send(@method, 61).should eql(-2305843009213693952)
       (-2).send(@method, 62).should eql(4611686018427387904)
       (-2).send(@method, 63).should eql(-9223372036854775808)
       (-2).send(@method, 64).should eql(18446744073709551616)
+      (-2).send(@method, 65).should eql(-36893488147419103232)
     end
 
     it "can raise 1 to a bignum safely" do
@@ -46,8 +48,18 @@ describe :integer_exponent, shared: true do
       (-1).send(@method, 4611686018427387905).should eql(-1)
     end
 
-    it "returns Float::INFINITY when the number is too big" do
-      2.send(@method, 427387904).should == Float::INFINITY
+    ruby_version_is ""..."3.4" do
+      it "returns Float::INFINITY when the number is too big" do
+        -> {
+          2.send(@method, 427387904).should == Float::INFINITY
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "raises an ArgumentError when the number is too big" do
+        -> { 100000000.send(@method, 1000000000) }.should raise_error(ArgumentError)
+      end
     end
 
     it "raises a ZeroDivisionError for 0 ** -1" do
@@ -94,8 +106,8 @@ describe :integer_exponent, shared: true do
     end
 
     it "returns self raised to other power" do
-      (@bignum.send(@method, 4)).should == 7237005577332262361485077344629993318496048279512298547155833600056910050625
-      (@bignum.send(@method, 1.2)).should be_close(57262152889751597425762.57804, TOLERANCE)
+      (@bignum.send(@method, 4)).should == 115792089237316196603666111261383895964500887398800252671052694326794607293761
+      (@bignum.send(@method, 1.3)).should be_close(11109528802438156839288832.0, TOLERANCE)
     end
 
     it "raises a TypeError when given a non-Integer" do
@@ -104,15 +116,29 @@ describe :integer_exponent, shared: true do
       -> { @bignum.send(@method, :symbol) }.should raise_error(TypeError)
     end
 
-    it "switch to a Float when the values is too big" do
-      flt = @bignum.send(@method, @bignum)
-      flt.should be_kind_of(Float)
-      flt.infinite?.should == 1
+    ruby_version_is ""..."3.4" do
+      it "switch to a Float when the values is too big" do
+        flt = nil
+        -> {
+          flt = @bignum.send(@method, @bignum)
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+        flt.should be_kind_of(Float)
+        flt.infinite?.should == 1
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "does not switch to a Float when the values is too big" do
+        -> {
+          @bignum.send(@method, @bignum)
+        }.should raise_error(ArgumentError)
+      end
     end
 
     it "returns a complex number when negative and raised to a fractional power" do
-      ((-@bignum).send(@method, (1.0/3)))      .should be_close(Complex(1048576,1816186.907597341), TOLERANCE)
-      ((-@bignum).send(@method, Rational(1,3))).should be_close(Complex(1048576,1816186.907597341), TOLERANCE)
+      (-bignum_value).send(@method, (1.0/2)).should be_close(Complex(0.0, 4294967296.0), TOLERANCE)
+      (-@bignum).send(@method, (1.0/3))      .should be_close(Complex(1321122.9748145656, 2288252.1154253655), TOLERANCE)
+      (-@bignum).send(@method, Rational(1,3)).should be_close(Complex(1321122.9748145656, 2288252.1154253655), TOLERANCE)
     end
   end
 end
diff --git a/spec/ruby/core/integer/shared/integer_ceil_precision.rb b/spec/ruby/core/integer/shared/integer_ceil_precision.rb
new file mode 100644
index 0000000000..9f31c2cf61
--- /dev/null
+++ b/spec/ruby/core/integer/shared/integer_ceil_precision.rb
@@ -0,0 +1,43 @@
+describe :integer_ceil_precision, shared: true do
+  context "precision is zero" do
+    it "returns integer self" do
+      send(@method, 0).ceil(0).should.eql?(0)
+      send(@method, 123).ceil(0).should.eql?(123)
+      send(@method, -123).ceil(0).should.eql?(-123)
+    end
+  end
+
+  context "precision is positive" do
+    it "returns self" do
+      send(@method, 0).ceil(1).should.eql?(send(@method, 0))
+      send(@method, 0).ceil(10).should.eql?(send(@method, 0))
+
+      send(@method, 123).ceil(10).should.eql?(send(@method, 123))
+      send(@method, -123).ceil(10).should.eql?(send(@method, -123))
+    end
+  end
+
+  context "precision is negative" do
+    it "always returns 0 when self is 0" do
+      send(@method, 0).ceil(-1).should.eql?(0)
+      send(@method, 0).ceil(-10).should.eql?(0)
+    end
+
+    it "returns largest integer less than self with at least precision.abs trailing zeros" do
+      send(@method, 123).ceil(-1).should.eql?(130)
+      send(@method, 123).ceil(-2).should.eql?(200)
+      send(@method, 123).ceil(-3).should.eql?(1000)
+
+      send(@method, -123).ceil(-1).should.eql?(-120)
+      send(@method, -123).ceil(-2).should.eql?(-100)
+      send(@method, -123).ceil(-3).should.eql?(0)
+    end
+
+    ruby_bug "#20654", ""..."3.4" do
+      it "returns 10**precision.abs when precision.abs is larger than the number digits of self" do
+        send(@method, 123).ceil(-20).should.eql?(100000000000000000000)
+        send(@method, 123).ceil(-50).should.eql?(100000000000000000000000000000000000000000000000000)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/integer/shared/integer_floor_precision.rb b/spec/ruby/core/integer/shared/integer_floor_precision.rb
new file mode 100644
index 0000000000..4c5888c6c4
--- /dev/null
+++ b/spec/ruby/core/integer/shared/integer_floor_precision.rb
@@ -0,0 +1,43 @@
+describe :integer_floor_precision, shared: true do
+  context "precision is zero" do
+    it "returns integer self" do
+      send(@method, 0).floor(0).should.eql?(0)
+      send(@method, 123).floor(0).should.eql?(123)
+      send(@method, -123).floor(0).should.eql?(-123)
+    end
+  end
+
+  context "precision is positive" do
+    it "returns self" do
+      send(@method, 0).floor(1).should.eql?(send(@method, 0))
+      send(@method, 0).floor(10).should.eql?(send(@method, 0))
+
+      send(@method, 123).floor(10).should.eql?(send(@method, 123))
+      send(@method, -123).floor(10).should.eql?(send(@method, -123))
+    end
+  end
+
+  context "precision is negative" do
+    it "always returns 0 when self is 0" do
+      send(@method, 0).floor(-1).should.eql?(0)
+      send(@method, 0).floor(-10).should.eql?(0)
+    end
+
+    it "returns largest integer less than self with at least precision.abs trailing zeros" do
+      send(@method, 123).floor(-1).should.eql?(120)
+      send(@method, 123).floor(-2).should.eql?(100)
+      send(@method, 123).floor(-3).should.eql?(0)
+
+      send(@method, -123).floor(-1).should.eql?(-130)
+      send(@method, -123).floor(-2).should.eql?(-200)
+      send(@method, -123).floor(-3).should.eql?(-1000)
+    end
+
+    ruby_bug "#20654", ""..."3.4" do
+      it "returns -(10**precision.abs) when self is negative and precision.abs is larger than the number digits of self" do
+        send(@method, -123).floor(-20).should.eql?(-100000000000000000000)
+        send(@method, -123).floor(-50).should.eql?(-100000000000000000000000000000000000000000000000000)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/integer/shared/integer_rounding.rb b/spec/ruby/core/integer/shared/integer_rounding.rb
index 3fb6e830ef..56d1819f84 100644
--- a/spec/ruby/core/integer/shared/integer_rounding.rb
+++ b/spec/ruby/core/integer/shared/integer_rounding.rb
@@ -11,19 +11,9 @@ describe :integer_rounding_positive_precision, shared: true do
     end
   end
 
-  ruby_version_is "2.4"..."2.5" do
-    it "returns itself as a float if passed a positive precision" do
-      [2, -4, 10**70, -10**100].each do |v|
-        v.send(@method, 42).should eql(v.to_f)
-      end
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns itself if passed a positive precision" do
-      [2, -4, 10**70, -10**100].each do |v|
-        v.send(@method, 42).should eql(v)
-      end
+  it "returns itself if passed a positive precision" do
+    [2, -4, 10**70, -10**100].each do |v|
+      v.send(@method, 42).should eql(v)
     end
   end
 end
diff --git a/spec/ruby/core/integer/shared/modulo.rb b/spec/ruby/core/integer/shared/modulo.rb
index b06d81e17d..d91af1e924 100644
--- a/spec/ruby/core/integer/shared/modulo.rb
+++ b/spec/ruby/core/integer/shared/modulo.rb
@@ -1,6 +1,12 @@
 describe :integer_modulo, shared: true do
   context "fixnum" do
     it "returns the modulus obtained from dividing self by the given argument" do
+      # test all possible combinations:
+      # - integer/double/bignum argument
+      # - positive/negative argument
+      # - positive/negative self
+      # - self greater/smaller than argument
+
       13.send(@method, 4).should == 1
       4.send(@method, 13).should == 4
 
@@ -16,8 +22,22 @@ describe :integer_modulo, shared: true do
       (200).send(@method, -256).should == -56
       (1000).send(@method, -512).should == -24
 
+      13.send(@method, -4.0).should == -3.0
+      4.send(@method, -13.0).should == -9.0
+
+      -13.send(@method, -4.0).should == -1.0
+      -4.send(@method, -13.0).should == -4.0
+
+      -13.send(@method, 4.0).should == 3.0
+      -4.send(@method, 13.0).should == 9.0
+
       1.send(@method, 2.0).should == 1.0
       200.send(@method, bignum_value).should == 200
+
+      4.send(@method, bignum_value(10)).should == 4
+      4.send(@method, -bignum_value(10)).should == -18446744073709551622
+      -4.send(@method, bignum_value(10)).should == 18446744073709551622
+      -4.send(@method, -bignum_value(10)).should == -4
     end
 
     it "raises a ZeroDivisionError when the given argument is 0" do
@@ -44,15 +64,35 @@ describe :integer_modulo, shared: true do
 
   context "bignum" do
     before :each do
-      @bignum = bignum_value
+      @bignum = bignum_value(10)
     end
 
     it "returns the modulus obtained from dividing self by the given argument" do
-      @bignum.send(@method, 5).should == 3
-      @bignum.send(@method, -5).should == -2
-      @bignum.send(@method, -100).should == -92
-      @bignum.send(@method, 2.22).should be_close(0.780180180180252, TOLERANCE)
-      @bignum.send(@method, bignum_value(10)).should == 9223372036854775808
+      # test all possible combinations:
+      # - integer/double/bignum argument
+      # - positive/negative argument
+      # - positive/negative self
+      # - self greater/smaller than argument
+
+      @bignum.send(@method, 5).should == 1
+      @bignum.send(@method, -5).should == -4
+      (-@bignum).send(@method, 5).should == 4
+      (-@bignum).send(@method, -5).should == -1
+
+      @bignum.send(@method, 2.22).should be_close(1.5603603603605034, TOLERANCE)
+      @bignum.send(@method, -2.22).should be_close(-0.6596396396394968, TOLERANCE)
+      (-@bignum).send(@method, 2.22).should be_close(0.6596396396394968, TOLERANCE)
+      (-@bignum).send(@method, -2.22).should be_close(-1.5603603603605034, TOLERANCE)
+
+      @bignum.send(@method, @bignum + 10).should == 18446744073709551626
+      @bignum.send(@method, -(@bignum + 10)).should == -10
+      (-@bignum).send(@method, @bignum + 10).should == 10
+      (-@bignum).send(@method, -(@bignum + 10)).should == -18446744073709551626
+
+      (@bignum + 10).send(@method, @bignum).should == 10
+      (@bignum + 10).send(@method, -@bignum).should == -18446744073709551616
+      (-(@bignum + 10)).send(@method, @bignum).should == 18446744073709551616
+      (-(@bignum + 10)).send(@method, -@bignum).should == -10
     end
 
     it "raises a ZeroDivisionError when the given argument is 0" do
diff --git a/spec/ruby/core/integer/size_spec.rb b/spec/ruby/core/integer/size_spec.rb
index a134e82384..725e9eb062 100644
--- a/spec/ruby/core/integer/size_spec.rb
+++ b/spec/ruby/core/integer/size_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Integer#size" do
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     it "returns the number of bytes in the machine representation of self" do
       -1.size.should == 4
       0.size.should == 4
@@ -9,7 +9,7 @@ describe "Integer#size" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     it "returns the number of bytes in the machine representation of self" do
       -1.size.should == 8
       0.size.should == 8
diff --git a/spec/ruby/core/integer/sqrt_spec.rb b/spec/ruby/core/integer/sqrt_spec.rb
index e56da058a0..4149ca2cc9 100644
--- a/spec/ruby/core/integer/sqrt_spec.rb
+++ b/spec/ruby/core/integer/sqrt_spec.rb
@@ -1,33 +1,31 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  describe "Integer.sqrt" do
-    it "returns an integer" do
-      Integer.sqrt(10).should be_kind_of(Integer)
-    end
+describe "Integer.sqrt" do
+  it "returns an integer" do
+    Integer.sqrt(10).should be_kind_of(Integer)
+  end
 
-    it "returns the integer square root of the argument" do
-      Integer.sqrt(0).should == 0
-      Integer.sqrt(1).should == 1
-      Integer.sqrt(24).should == 4
-      Integer.sqrt(25).should == 5
-      Integer.sqrt(10**400).should == 10**200
-    end
+  it "returns the integer square root of the argument" do
+    Integer.sqrt(0).should == 0
+    Integer.sqrt(1).should == 1
+    Integer.sqrt(24).should == 4
+    Integer.sqrt(25).should == 5
+    Integer.sqrt(10**400).should == 10**200
+  end
 
-    it "raises a Math::DomainError if the argument is negative" do
-      -> { Integer.sqrt(-4) }.should raise_error(Math::DomainError)
-    end
+  it "raises a Math::DomainError if the argument is negative" do
+    -> { Integer.sqrt(-4) }.should raise_error(Math::DomainError)
+  end
 
-    it "accepts any argument that can be coerced to Integer" do
-      Integer.sqrt(10.0).should == 3
-    end
+  it "accepts any argument that can be coerced to Integer" do
+    Integer.sqrt(10.0).should == 3
+  end
 
-    it "converts the argument with #to_int" do
-      Integer.sqrt(mock_int(10)).should == 3
-    end
+  it "converts the argument with #to_int" do
+    Integer.sqrt(mock_int(10)).should == 3
+  end
 
-    it "raises a TypeError if the argument cannot be coerced to Integer" do
-      -> { Integer.sqrt("test") }.should raise_error(TypeError)
-    end
+  it "raises a TypeError if the argument cannot be coerced to Integer" do
+    -> { Integer.sqrt("test") }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/core/integer/to_f_spec.rb b/spec/ruby/core/integer/to_f_spec.rb
index 06092eaa92..9f1df9ada9 100644
--- a/spec/ruby/core/integer/to_f_spec.rb
+++ b/spec/ruby/core/integer/to_f_spec.rb
@@ -11,9 +11,9 @@ describe "Integer#to_f" do
 
   context "bignum" do
     it "returns self converted to a Float" do
-      bignum_value(0x4000_0aa0_0bb0_0000).to_f.should eql(13_835_069_737_789_292_544.00)
-      bignum_value(0x8000_0000_0000_0ccc).to_f.should eql(18_446_744_073_709_555_712.00)
-      (-bignum_value(99)).to_f.should eql(-9_223_372_036_854_775_808.00)
+      bignum_value(0x4000_0aa0_0bb0_0000).to_f.should eql(23_058_441_774_644_068_352.0)
+      bignum_value(0x8000_0000_0000_0ccc).to_f.should eql(27_670_116_110_564_330_700.0)
+      (-bignum_value(99)).to_f.should eql(-18_446_744_073_709_551_715.0)
     end
 
     it "converts number close to Float::MAX without exceeding MAX or producing NaN" do
diff --git a/spec/ruby/core/integer/to_r_spec.rb b/spec/ruby/core/integer/to_r_spec.rb
index 4a40575b7f..7732bedca1 100644
--- a/spec/ruby/core/integer/to_r_spec.rb
+++ b/spec/ruby/core/integer/to_r_spec.rb
@@ -15,7 +15,7 @@ describe "Integer#to_r" do
 
   it "works even if self is a Bignum" do
     bignum = 99999**999
-    bignum.should be_an_instance_of(Bignum)
+    bignum.should be_an_instance_of(Integer)
     bignum.to_r.should == Rational(bignum, 1)
   end
 
diff --git a/spec/ruby/core/integer/to_s_spec.rb b/spec/ruby/core/integer/to_s_spec.rb
index 7988bfde7a..ca08dad95c 100644
--- a/spec/ruby/core/integer/to_s_spec.rb
+++ b/spec/ruby/core/integer/to_s_spec.rb
@@ -68,9 +68,9 @@ describe "Integer#to_s" do
 
     describe "when given no base" do
       it "returns self converted to a String using base 10" do
-        bignum_value(9).to_s.should == "9223372036854775817"
-        bignum_value.to_s.should == "9223372036854775808"
-        (-bignum_value(675)).to_s.should == "-9223372036854776483"
+        bignum_value(9).to_s.should == "18446744073709551625"
+        bignum_value.to_s.should == "18446744073709551616"
+        (-bignum_value(675)).to_s.should == "-18446744073709552291"
       end
     end
 
diff --git a/spec/ruby/core/integer/try_convert_spec.rb b/spec/ruby/core/integer/try_convert_spec.rb
new file mode 100644
index 0000000000..8a0ca671a9
--- /dev/null
+++ b/spec/ruby/core/integer/try_convert_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Integer.try_convert" do
+  it "returns the argument if it's an Integer" do
+    x = 42
+    Integer.try_convert(x).should equal(x)
+  end
+
+  it "returns nil when the argument does not respond to #to_int" do
+    Integer.try_convert(Object.new).should be_nil
+  end
+
+  it "sends #to_int to the argument and returns the result if it's nil" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(nil)
+    Integer.try_convert(obj).should be_nil
+  end
+
+  it "sends #to_int to the argument and returns the result if it's an Integer" do
+    x = 234
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(x)
+    Integer.try_convert(obj).should equal(x)
+  end
+
+  it "sends #to_int to the argument and raises TypeError if it's not a kind of Integer" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return(Object.new)
+    -> {
+      Integer.try_convert obj
+    }.should raise_error(TypeError, "can't convert MockObject to Integer (MockObject#to_int gives Object)")
+  end
+
+  it "responds with a different error message when it raises a TypeError, depending on the type of the non-Integer object :to_int returns" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_return("A String")
+    -> {
+      Integer.try_convert obj
+    }.should raise_error(TypeError, "can't convert MockObject to Integer (MockObject#to_int gives String)")
+  end
+
+  it "does not rescue exceptions raised by #to_int" do
+    obj = mock("to_int")
+    obj.should_receive(:to_int).and_raise(RuntimeError)
+    -> { Integer.try_convert obj }.should raise_error(RuntimeError)
+  end
+end
diff --git a/spec/ruby/core/integer/uminus_spec.rb b/spec/ruby/core/integer/uminus_spec.rb
index b6b110dec4..7a9cfe89bf 100644
--- a/spec/ruby/core/integer/uminus_spec.rb
+++ b/spec/ruby/core/integer/uminus_spec.rb
@@ -20,11 +20,11 @@ describe "Integer#-@" do
 
   context "bignum" do
     it "returns self as a negative value" do
-      bignum_value.send(:-@).should == -9223372036854775808
-      (-bignum_value).send(:-@).should == 9223372036854775808
+      bignum_value.send(:-@).should == -18446744073709551616
+      (-bignum_value).send(:-@).should == 18446744073709551616
 
-      bignum_value(921).send(:-@).should == -9223372036854776729
-      (-bignum_value(921).send(:-@)).should == 9223372036854776729
+      bignum_value(921).send(:-@).should == -18446744073709552537
+      (-bignum_value(921).send(:-@)).should == 18446744073709552537
     end
   end
 end
diff --git a/spec/ruby/core/integer/upto_spec.rb b/spec/ruby/core/integer/upto_spec.rb
index 6049eb173e..dd6995e94b 100644
--- a/spec/ruby/core/integer/upto_spec.rb
+++ b/spec/ruby/core/integer/upto_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../../spec_helper'
 
-describe "Integer#upto [stop] when self and stop are Fixnums" do
+describe "Integer#upto [stop] when self and stop are Integers" do
   it "does not yield when stop is less than self" do
     result = []
     5.upto(4) { |x| result << x }
diff --git a/spec/ruby/core/integer/zero_spec.rb b/spec/ruby/core/integer/zero_spec.rb
new file mode 100644
index 0000000000..bd362c4181
--- /dev/null
+++ b/spec/ruby/core/integer/zero_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Integer#zero?" do
+  it "returns true if self is 0" do
+    0.should.zero?
+    1.should_not.zero?
+    -1.should_not.zero?
+  end
+
+  it "Integer#zero? overrides Numeric#zero?" do
+    42.method(:zero?).owner.should == Integer
+  end
+end
diff --git a/spec/ruby/core/io/advise_spec.rb b/spec/ruby/core/io/advise_spec.rb
index 59469fa164..651fc52378 100644
--- a/spec/ruby/core/io/advise_spec.rb
+++ b/spec/ruby/core/io/advise_spec.rb
@@ -73,20 +73,9 @@ describe "IO#advise" do
     end
   end
 
-  platform_is :linux do
+  guard -> { platform_is :linux and kernel_version_is '3.6' } do # [ruby-core:65355] tmpfs is not supported
     it "supports the willneed advice type" do
-      require 'etc'
-      uname = if Etc.respond_to?(:uname)
-                Etc.uname[:release]
-              else
-                `uname -r`.chomp
-              end
-      if (uname.split('.').map(&:to_i) <=> [3,6]) < 0
-        # [ruby-core:65355] tmpfs is not supported
-        1.should == 1
-      else
-        @io.advise(:willneed).should be_nil
-      end
+      @io.advise(:willneed).should be_nil
     end
   end
 
diff --git a/spec/ruby/core/io/autoclose_spec.rb b/spec/ruby/core/io/autoclose_spec.rb
new file mode 100644
index 0000000000..715ada7c93
--- /dev/null
+++ b/spec/ruby/core/io/autoclose_spec.rb
@@ -0,0 +1,77 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "IO#autoclose?" do
+  before :each do
+    @io = IOSpecs.io_fixture "lines.txt"
+  end
+
+  after :each do
+    @io.autoclose = true unless @io.closed?
+    @io.close unless @io.closed?
+  end
+
+  it "is set to true by default" do
+    @io.should.autoclose?
+  end
+
+  it "cannot be queried on a closed IO object" do
+    @io.close
+    -> { @io.autoclose? }.should raise_error(IOError, /closed stream/)
+  end
+end
+
+describe "IO#autoclose=" do
+  before :each do
+    @io = IOSpecs.io_fixture "lines.txt"
+  end
+
+  after :each do
+    @io.autoclose = true unless @io.closed?
+    @io.close unless @io.closed?
+  end
+
+  it "can be set to true" do
+    @io.autoclose = false
+    @io.autoclose = true
+    @io.should.autoclose?
+  end
+
+  it "can be set to false" do
+    @io.autoclose = true
+    @io.autoclose = false
+    @io.should_not.autoclose?
+  end
+
+  it "can be set to any truthy value" do
+    @io.autoclose = false
+    @io.autoclose = 42
+    @io.should.autoclose?
+
+    @io.autoclose = false
+    @io.autoclose = Object.new
+    @io.should.autoclose?
+  end
+
+  it "can be set to any falsy value" do
+    @io.autoclose = true
+    @io.autoclose = nil
+    @io.should_not.autoclose?
+  end
+
+  it "can be set multiple times" do
+    @io.autoclose = true
+    @io.should.autoclose?
+
+    @io.autoclose = false
+    @io.should_not.autoclose?
+
+    @io.autoclose = true
+    @io.should.autoclose?
+  end
+
+  it "cannot be set on a closed IO object" do
+    @io.close
+    -> { @io.autoclose = false }.should raise_error(IOError, /closed stream/)
+  end
+end
diff --git a/spec/ruby/core/io/binmode_spec.rb b/spec/ruby/core/io/binmode_spec.rb
index b698777cad..342cac2a9b 100644
--- a/spec/ruby/core/io/binmode_spec.rb
+++ b/spec/ruby/core/io/binmode_spec.rb
@@ -57,4 +57,8 @@ describe "IO#binmode?" do
     @duped = @file.dup
     @duped.binmode?.should == @file.binmode?
   end
+
+  it "raises an IOError on closed stream" do
+    -> { IOSpecs.closed_io.binmode? }.should raise_error(IOError)
+  end
 end
diff --git a/spec/ruby/core/io/binread_spec.rb b/spec/ruby/core/io/binread_spec.rb
index a3f752d8f9..9e36b84da9 100644
--- a/spec/ruby/core/io/binread_spec.rb
+++ b/spec/ruby/core/io/binread_spec.rb
@@ -44,4 +44,14 @@ describe "IO.binread" do
   it "raises an Errno::EINVAL when not passed a valid offset" do
     -> { IO.binread @fname, 0, -1  }.should raise_error(Errno::EINVAL)
   end
+
+  ruby_version_is "3.3"..."4.0" do
+    # https://bugs.ruby-lang.org/issues/19630
+    it "warns about deprecation given a path with a pipe" do
+      cmd = "|echo ok"
+      -> {
+        IO.binread(cmd)
+      }.should complain(/IO process creation with a leading '\|'/)
+    end
+  end
 end
diff --git a/spec/ruby/core/io/buffer/empty_spec.rb b/spec/ruby/core/io/buffer/empty_spec.rb
new file mode 100644
index 0000000000..e1fd4ab6a2
--- /dev/null
+++ b/spec/ruby/core/io/buffer/empty_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/null_and_empty'
+
+describe "IO::Buffer#empty?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  it_behaves_like :io_buffer_null_and_empty, :empty?
+
+  it "is true for a 0-length String-backed buffer created with .for" do
+    @buffer = IO::Buffer.for("")
+    @buffer.empty?.should be_true
+  end
+
+  ruby_version_is "3.3" do
+    it "is true for a 0-length String-backed buffer created with .string" do
+      IO::Buffer.string(0) do |buffer|
+        buffer.empty?.should be_true
+      end
+    end
+  end
+
+  it "is true for a 0-length slice of a buffer with size > 0" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.slice(3, 0).empty?.should be_true
+  end
+end
diff --git a/spec/ruby/core/io/buffer/external_spec.rb b/spec/ruby/core/io/buffer/external_spec.rb
new file mode 100644
index 0000000000..4377a38357
--- /dev/null
+++ b/spec/ruby/core/io/buffer/external_spec.rb
@@ -0,0 +1,108 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#external?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is false for an internal buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.external?.should be_false
+    end
+
+    it "is false for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.external?.should be_false
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is true for a regular mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.external?.should be_true
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is false for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.external?.should be_false
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is true for a buffer created without a block" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.external?.should be_true
+    end
+
+    it "is true for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.external?.should be_true
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is true" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.external?.should be_true
+        end
+      end
+    end
+  end
+
+  # Always false for slices
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.external?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.external?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.external?.should be_false
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is false when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.slice.external?.should be_false
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.external?.should be_false
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.external?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/free_spec.rb b/spec/ruby/core/io/buffer/free_spec.rb
new file mode 100644
index 0000000000..f3a4918978
--- /dev/null
+++ b/spec/ruby/core/io/buffer/free_spec.rb
@@ -0,0 +1,104 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#free" do
+  context "with a buffer created with .new" do
+    it "frees internal memory and nullifies the buffer" do
+      buffer = IO::Buffer.new(4)
+      buffer.free
+      buffer.null?.should be_true
+    end
+
+    it "frees mapped memory and nullifies the buffer" do
+      buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      buffer.free
+      buffer.null?.should be_true
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "frees mapped memory and nullifies the buffer" do
+      File.open(__FILE__, "r") do |file|
+        buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        buffer.free
+        buffer.null?.should be_true
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    context "without a block" do
+      it "disassociates the buffer from the string and nullifies the buffer" do
+        string = +"test"
+        buffer = IO::Buffer.for(string)
+        # Read-only buffer, can't modify the string.
+        buffer.free
+        buffer.null?.should be_true
+      end
+    end
+
+    context "with a block" do
+      it "disassociates the buffer from the string and nullifies the buffer" do
+        string = +"test"
+        IO::Buffer.for(string) do |buffer|
+          buffer.set_string("meat")
+          buffer.free
+          buffer.null?.should be_true
+        end
+        string.should == "meat"
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "disassociates the buffer from the string and nullifies the buffer" do
+        string =
+          IO::Buffer.string(4) do |buffer|
+            buffer.set_string("meat")
+            buffer.free
+            buffer.null?.should be_true
+          end
+        string.should == "meat"
+      end
+    end
+  end
+
+  it "can be called repeatedly without an error" do
+    buffer = IO::Buffer.new(4)
+    buffer.free
+    buffer.null?.should be_true
+    buffer.free
+    buffer.null?.should be_true
+  end
+
+  it "is disallowed while locked, raising IO::Buffer::LockedError" do
+    buffer = IO::Buffer.new(4)
+    buffer.locked do
+      -> { buffer.free }.should raise_error(IO::Buffer::LockedError, "Buffer is locked!")
+    end
+    buffer.free
+    buffer.null?.should be_true
+  end
+
+  context "with a slice of a buffer" do
+    it "nullifies the slice, not touching the buffer" do
+      buffer = IO::Buffer.new(4)
+      slice = buffer.slice(0, 2)
+
+      slice.free
+      slice.null?.should be_true
+      buffer.null?.should be_false
+
+      buffer.free
+    end
+
+    it "nullifies buffer, invalidating the slice" do
+      buffer = IO::Buffer.new(4)
+      slice = buffer.slice(0, 2)
+
+      buffer.free
+      slice.null?.should be_false
+      slice.valid?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/initialize_spec.rb b/spec/ruby/core/io/buffer/initialize_spec.rb
new file mode 100644
index 0000000000..c86d1e7f1d
--- /dev/null
+++ b/spec/ruby/core/io/buffer/initialize_spec.rb
@@ -0,0 +1,103 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#initialize" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  it "creates a new zero-filled buffer with default size" do
+    @buffer = IO::Buffer.new
+    @buffer.size.should == IO::Buffer::DEFAULT_SIZE
+    @buffer.each(:U8).should.all? { |_offset, value| value.eql?(0) }
+  end
+
+  it "creates a buffer with default state" do
+    @buffer = IO::Buffer.new
+    @buffer.should_not.shared?
+    @buffer.should_not.readonly?
+
+    @buffer.should_not.empty?
+    @buffer.should_not.null?
+
+    # This is run-time state, set by #locked.
+    @buffer.should_not.locked?
+  end
+
+  context "with size argument" do
+    it "creates a new internal buffer if size is less than IO::Buffer::PAGE_SIZE" do
+      size = IO::Buffer::PAGE_SIZE - 1
+      @buffer = IO::Buffer.new(size)
+      @buffer.size.should == size
+      @buffer.should.internal?
+      @buffer.should_not.mapped?
+      @buffer.should_not.empty?
+    end
+
+    it "creates a new mapped buffer if size is greater than or equal to IO::Buffer::PAGE_SIZE" do
+      size = IO::Buffer::PAGE_SIZE
+      @buffer = IO::Buffer.new(size)
+      @buffer.size.should == size
+      @buffer.should_not.internal?
+      @buffer.should.mapped?
+      @buffer.should_not.empty?
+    end
+
+    it "creates a null buffer if size is 0" do
+      @buffer = IO::Buffer.new(0)
+      @buffer.size.should.zero?
+      @buffer.should_not.internal?
+      @buffer.should_not.mapped?
+      @buffer.should.null?
+      @buffer.should.empty?
+    end
+
+    it "raises TypeError if size is not an Integer" do
+      -> { IO::Buffer.new(nil) }.should raise_error(TypeError, "not an Integer")
+      -> { IO::Buffer.new(10.0) }.should raise_error(TypeError, "not an Integer")
+    end
+
+    it "raises ArgumentError if size is negative" do
+      -> { IO::Buffer.new(-1) }.should raise_error(ArgumentError, "Size can't be negative!")
+    end
+  end
+
+  context "with size and flags arguments" do
+    it "forces mapped buffer with IO::Buffer::MAPPED flag" do
+      @buffer = IO::Buffer.new(IO::Buffer::PAGE_SIZE - 1, IO::Buffer::MAPPED)
+      @buffer.should.mapped?
+      @buffer.should_not.internal?
+      @buffer.should_not.empty?
+    end
+
+    it "forces internal buffer with IO::Buffer::INTERNAL flag" do
+      @buffer = IO::Buffer.new(IO::Buffer::PAGE_SIZE, IO::Buffer::INTERNAL)
+      @buffer.should.internal?
+      @buffer.should_not.mapped?
+      @buffer.should_not.empty?
+    end
+
+    it "raises IO::Buffer::AllocationError if neither IO::Buffer::MAPPED nor IO::Buffer::INTERNAL is given" do
+      -> { IO::Buffer.new(10, IO::Buffer::READONLY) }.should raise_error(IO::Buffer::AllocationError, "Could not allocate buffer!")
+      -> { IO::Buffer.new(10, 0) }.should raise_error(IO::Buffer::AllocationError, "Could not allocate buffer!")
+    end
+
+    ruby_version_is "3.3" do
+      it "raises ArgumentError if flags is negative" do
+        -> { IO::Buffer.new(10, -1) }.should raise_error(ArgumentError, "Flags can't be negative!")
+      end
+    end
+
+    ruby_version_is ""..."3.3" do
+      it "raises IO::Buffer::AllocationError with non-Integer flags" do
+        -> { IO::Buffer.new(10, 0.0) }.should raise_error(IO::Buffer::AllocationError, "Could not allocate buffer!")
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "raises TypeError with non-Integer flags" do
+        -> { IO::Buffer.new(10, 0.0) }.should raise_error(TypeError, "not an Integer")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/internal_spec.rb b/spec/ruby/core/io/buffer/internal_spec.rb
new file mode 100644
index 0000000000..409699cc3c
--- /dev/null
+++ b/spec/ruby/core/io/buffer/internal_spec.rb
@@ -0,0 +1,108 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#internal?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is true for an internal buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.internal?.should be_true
+    end
+
+    it "is false for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.internal?.should be_false
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is false for a regular mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.internal?.should be_false
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is false for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.internal?.should be_false
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is false for a buffer created without a block" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.internal?.should be_false
+    end
+
+    it "is false for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.internal?.should be_false
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.internal?.should be_false
+        end
+      end
+    end
+  end
+
+  # Always false for slices
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.internal?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.internal?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.internal?.should be_false
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is false when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.slice.internal?.should be_false
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.internal?.should be_false
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.internal?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/locked_spec.rb b/spec/ruby/core/io/buffer/locked_spec.rb
new file mode 100644
index 0000000000..4ffa569fd2
--- /dev/null
+++ b/spec/ruby/core/io/buffer/locked_spec.rb
@@ -0,0 +1,75 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#locked" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "when buffer is locked" do
+    it "allows reading and writing operations on the buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.set_string("test")
+      @buffer.locked do
+        @buffer.get_string.should == "test"
+        @buffer.set_string("meat")
+      end
+      @buffer.get_string.should == "meat"
+    end
+
+    it "disallows operations changing buffer itself, raising IO::Buffer::LockedError" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.locked do
+        # Just an example, each method is responsible for checking the lock state.
+        -> { @buffer.resize(8) }.should raise_error(IO::Buffer::LockedError)
+      end
+    end
+  end
+
+  it "disallows reentrant locking, raising IO::Buffer::LockedError" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.locked do
+      -> { @buffer.locked {} }.should raise_error(IO::Buffer::LockedError, "Buffer already locked!")
+    end
+  end
+
+  it "does not propagate to buffer's slices" do
+    @buffer = IO::Buffer.new(4)
+    slice = @buffer.slice(0, 2)
+    @buffer.locked do
+      @buffer.locked?.should be_true
+      slice.locked?.should be_false
+      slice.locked { slice.locked?.should be_true }
+    end
+  end
+
+  it "does not propagate backwards from buffer's slices" do
+    @buffer = IO::Buffer.new(4)
+    slice = @buffer.slice(0, 2)
+    slice.locked do
+      slice.locked?.should be_true
+      @buffer.locked?.should be_false
+      @buffer.locked { @buffer.locked?.should be_true }
+    end
+  end
+end
+
+describe "IO::Buffer#locked?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  it "is false by default" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.locked?.should be_false
+  end
+
+  it "is true only inside of #locked block" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.locked do
+      @buffer.locked?.should be_true
+    end
+    @buffer.locked?.should be_false
+  end
+end
diff --git a/spec/ruby/core/io/buffer/mapped_spec.rb b/spec/ruby/core/io/buffer/mapped_spec.rb
new file mode 100644
index 0000000000..b3610207ff
--- /dev/null
+++ b/spec/ruby/core/io/buffer/mapped_spec.rb
@@ -0,0 +1,108 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#mapped?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is false for an internal buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.mapped?.should be_false
+    end
+
+    it "is true for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.mapped?.should be_true
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is true for a regular mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.mapped?.should be_true
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is true for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.mapped?.should be_true
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is false for a buffer created without a block" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.mapped?.should be_false
+    end
+
+    it "is false for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.mapped?.should be_false
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.mapped?.should be_false
+        end
+      end
+    end
+  end
+
+  # Always false for slices
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.mapped?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.mapped?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.mapped?.should be_false
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is false when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.slice.mapped?.should be_false
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.mapped?.should be_false
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.mapped?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/null_spec.rb b/spec/ruby/core/io/buffer/null_spec.rb
new file mode 100644
index 0000000000..3fb1144d0e
--- /dev/null
+++ b/spec/ruby/core/io/buffer/null_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/null_and_empty'
+
+describe "IO::Buffer#null?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  it_behaves_like :io_buffer_null_and_empty, :null?
+
+  it "is false for a 0-length String-backed buffer created with .for" do
+    @buffer = IO::Buffer.for("")
+    @buffer.null?.should be_false
+  end
+
+  ruby_version_is "3.3" do
+    it "is false for a 0-length String-backed buffer created with .string" do
+      IO::Buffer.string(0) do |buffer|
+        buffer.null?.should be_false
+      end
+    end
+  end
+
+  it "is false for a 0-length slice of a buffer with size > 0" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.slice(3, 0).null?.should be_false
+  end
+end
diff --git a/spec/ruby/core/io/buffer/private_spec.rb b/spec/ruby/core/io/buffer/private_spec.rb
new file mode 100644
index 0000000000..7aa308997b
--- /dev/null
+++ b/spec/ruby/core/io/buffer/private_spec.rb
@@ -0,0 +1,111 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "IO::Buffer#private?" do
+    after :each do
+      @buffer&.free
+      @buffer = nil
+    end
+
+    context "with a buffer created with .new" do
+      it "is false for an internal buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::INTERNAL)
+        @buffer.private?.should be_false
+      end
+
+      it "is false for a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.private?.should be_false
+      end
+    end
+
+    context "with a file-backed buffer created with .map" do
+      it "is false for a regular mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.private?.should be_false
+        end
+      end
+
+      it "is true for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.private?.should be_true
+        end
+      end
+    end
+
+    context "with a String-backed buffer created with .for" do
+      it "is false for a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.private?.should be_false
+      end
+
+      it "is false for a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.private?.should be_false
+        end
+      end
+    end
+
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.private?.should be_false
+        end
+      end
+    end
+
+    # Always false for slices
+    context "with a slice of a buffer" do
+      context "created with .new" do
+        it "is false when slicing an internal buffer" do
+          @buffer = IO::Buffer.new(4)
+          @buffer.slice.private?.should be_false
+        end
+
+        it "is false when slicing a mapped buffer" do
+          @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+          @buffer.slice.private?.should be_false
+        end
+      end
+
+      context "created with .map" do
+        it "is false when slicing a regular file-backed buffer" do
+          File.open(__FILE__, "r") do |file|
+            @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+            @buffer.slice.private?.should be_false
+          end
+        end
+
+        it "is false when slicing a private file-backed buffer" do
+          File.open(__FILE__, "r") do |file|
+            @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+            @buffer.slice.private?.should be_false
+          end
+        end
+      end
+
+      context "created with .for" do
+        it "is false when slicing a buffer created without a block" do
+          @buffer = IO::Buffer.for("test")
+          @buffer.slice.private?.should be_false
+        end
+
+        it "is false when slicing a buffer created with a block" do
+          IO::Buffer.for(+"test") do |buffer|
+            buffer.slice.private?.should be_false
+          end
+        end
+      end
+
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.private?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/readonly_spec.rb b/spec/ruby/core/io/buffer/readonly_spec.rb
new file mode 100644
index 0000000000..0014a876ed
--- /dev/null
+++ b/spec/ruby/core/io/buffer/readonly_spec.rb
@@ -0,0 +1,143 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#readonly?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is false for an internal buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::INTERNAL)
+      @buffer.readonly?.should be_false
+    end
+
+    it "is false for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.readonly?.should be_false
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is false for a writable mapping" do
+      File.open(__FILE__, "r+") do |file|
+        @buffer = IO::Buffer.map(file)
+        @buffer.readonly?.should be_false
+      end
+    end
+
+    it "is true for a readonly mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.readonly?.should be_true
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is false for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::PRIVATE)
+          @buffer.readonly?.should be_false
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is true for a buffer created without a block" do
+      @buffer = IO::Buffer.for(+"test")
+      @buffer.readonly?.should be_true
+    end
+
+    it "is false for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.readonly?.should be_false
+      end
+    end
+
+    it "is true for a buffer created with a block from a frozen string" do
+      IO::Buffer.for(-"test") do |buffer|
+        buffer.readonly?.should be_true
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.readonly?.should be_false
+        end
+      end
+    end
+  end
+
+  # This seems to be the only flag propagated from the source buffer to the slice.
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.readonly?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.readonly?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false when slicing a read-write file-backed buffer" do
+        File.open(__FILE__, "r+") do |file|
+          @buffer = IO::Buffer.map(file)
+          @buffer.slice.readonly?.should be_false
+        end
+      end
+
+      it "is true when slicing a readonly file-backed buffer" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.readonly?.should be_true
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "is false when slicing a private file-backed buffer" do
+          File.open(__FILE__, "r") do |file|
+            @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::PRIVATE)
+            @buffer.slice.readonly?.should be_false
+          end
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is true when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for(+"test")
+        @buffer.slice.readonly?.should be_true
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.readonly?.should be_false
+        end
+      end
+
+      it "is true when slicing a buffer created with a block from a frozen string" do
+        IO::Buffer.for(-"test") do |buffer|
+          buffer.slice.readonly?.should be_true
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.readonly?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/resize_spec.rb b/spec/ruby/core/io/buffer/resize_spec.rb
new file mode 100644
index 0000000000..0da3a23356
--- /dev/null
+++ b/spec/ruby/core/io/buffer/resize_spec.rb
@@ -0,0 +1,155 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#resize" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "resizes internal buffer, preserving type" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.resize(IO::Buffer::PAGE_SIZE)
+      @buffer.size.should == IO::Buffer::PAGE_SIZE
+      @buffer.internal?.should be_true
+      @buffer.mapped?.should be_false
+    end
+
+    platform_is :linux do
+      it "resizes mapped buffer, preserving type" do
+        @buffer = IO::Buffer.new(IO::Buffer::PAGE_SIZE, IO::Buffer::MAPPED)
+        @buffer.resize(4)
+        @buffer.size.should == 4
+        @buffer.internal?.should be_false
+        @buffer.mapped?.should be_true
+      end
+    end
+
+    platform_is_not :linux do
+      it "resizes mapped buffer, changing type to internal" do
+        @buffer = IO::Buffer.new(IO::Buffer::PAGE_SIZE, IO::Buffer::MAPPED)
+        @buffer.resize(4)
+        @buffer.size.should == 4
+        @buffer.internal?.should be_true
+        @buffer.mapped?.should be_false
+      end
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "disallows resizing shared buffer, raising IO::Buffer::AccessError" do
+      File.open(__FILE__, "r+") do |file|
+        @buffer = IO::Buffer.map(file)
+        -> { @buffer.resize(10) }.should raise_error(IO::Buffer::AccessError, "Cannot resize external buffer!")
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "resizes private buffer, discarding excess contents" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::PRIVATE)
+          @buffer.resize(10)
+          @buffer.size.should == 10
+          @buffer.get_string.should == "require_re"
+          @buffer.resize(12)
+          @buffer.size.should == 12
+          @buffer.get_string.should == "require_re\0\0"
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    context "without a block" do
+      it "disallows resizing, raising IO::Buffer::AccessError" do
+        @buffer = IO::Buffer.for(+"test")
+        -> { @buffer.resize(10) }.should raise_error(IO::Buffer::AccessError, "Cannot resize external buffer!")
+      end
+    end
+
+    context "with a block" do
+      it "disallows resizing, raising IO::Buffer::AccessError" do
+        IO::Buffer.for(+'test') do |buffer|
+          -> { buffer.resize(10) }.should raise_error(IO::Buffer::AccessError, "Cannot resize external buffer!")
+        end
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "disallows resizing, raising IO::Buffer::AccessError" do
+        IO::Buffer.string(4) do |buffer|
+          -> { buffer.resize(10) }.should raise_error(IO::Buffer::AccessError, "Cannot resize external buffer!")
+        end
+      end
+    end
+  end
+
+  context "with a null buffer" do
+    it "allows resizing a 0-sized buffer, creating a regular buffer according to new size" do
+      @buffer = IO::Buffer.new(0)
+      @buffer.resize(IO::Buffer::PAGE_SIZE)
+      @buffer.size.should == IO::Buffer::PAGE_SIZE
+      @buffer.internal?.should be_false
+      @buffer.mapped?.should be_true
+    end
+
+    it "allows resizing after a free, creating a regular buffer according to new size" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.free
+      @buffer.resize(10)
+      @buffer.size.should == 10
+      @buffer.internal?.should be_true
+      @buffer.mapped?.should be_false
+    end
+  end
+
+  it "allows resizing to 0, freeing memory" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.resize(0)
+    @buffer.null?.should be_true
+  end
+
+  it "can be called repeatedly" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.resize(10)
+    @buffer.resize(27)
+    @buffer.resize(1)
+    @buffer.size.should == 1
+  end
+
+  it "always clears extra memory" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.set_string("test")
+    # This should not cause a re-allocation, just a technical resizing,
+    # even with very aggressive memory allocation.
+    @buffer.resize(2)
+    @buffer.resize(4)
+    @buffer.get_string.should == "te\0\0"
+  end
+
+  it "is disallowed while locked, raising IO::Buffer::LockedError" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.locked do
+      -> { @buffer.resize(10) }.should raise_error(IO::Buffer::LockedError, "Cannot resize locked buffer!")
+    end
+  end
+
+  it "raises ArgumentError if size is negative" do
+    @buffer = IO::Buffer.new(4)
+    -> { @buffer.resize(-1) }.should raise_error(ArgumentError, "Size can't be negative!")
+  end
+
+  it "raises TypeError if size is not an Integer" do
+    @buffer = IO::Buffer.new(4)
+    -> { @buffer.resize(nil) }.should raise_error(TypeError, "not an Integer")
+    -> { @buffer.resize(10.0) }.should raise_error(TypeError, "not an Integer")
+  end
+
+  context "with a slice of a buffer" do
+    # Current behavior of slice resizing seems unintended (it's undocumented, too).
+    # It either creates a completely new buffer, or breaks the slice on size 0.
+    it "needs to be reviewed for spec completeness"
+  end
+end
diff --git a/spec/ruby/core/io/buffer/shared/null_and_empty.rb b/spec/ruby/core/io/buffer/shared/null_and_empty.rb
new file mode 100644
index 0000000000..c8fe9e5e46
--- /dev/null
+++ b/spec/ruby/core/io/buffer/shared/null_and_empty.rb
@@ -0,0 +1,59 @@
+describe :io_buffer_null_and_empty, shared: true do
+  it "is false for a buffer with size > 0" do
+    @buffer = IO::Buffer.new(1)
+    @buffer.send(@method).should be_false
+  end
+
+  it "is false for a slice with length > 0" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.slice(1, 2).send(@method).should be_false
+  end
+
+  it "is false for a file-mapped buffer" do
+    File.open(__FILE__, "rb") do |file|
+      @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+      @buffer.send(@method).should be_false
+    end
+  end
+
+  it "is false for a non-empty String-backed buffer created with .for" do
+    @buffer = IO::Buffer.for("test")
+    @buffer.send(@method).should be_false
+  end
+
+  ruby_version_is "3.3" do
+    it "is false for a non-empty String-backed buffer created with .string" do
+      IO::Buffer.string(4) do |buffer|
+        buffer.send(@method).should be_false
+      end
+    end
+  end
+
+  it "is true for a 0-sized buffer" do
+    @buffer = IO::Buffer.new(0)
+    @buffer.send(@method).should be_true
+  end
+
+  it "is true for a slice of a 0-sized buffer" do
+    @buffer = IO::Buffer.new(0)
+    @buffer.slice(0, 0).send(@method).should be_true
+  end
+
+  it "is true for a freed buffer" do
+    @buffer = IO::Buffer.new(1)
+    @buffer.free
+    @buffer.send(@method).should be_true
+  end
+
+  it "is true for a buffer resized to 0" do
+    @buffer = IO::Buffer.new(1)
+    @buffer.resize(0)
+    @buffer.send(@method).should be_true
+  end
+
+  it "is true for a buffer whose memory was transferred" do
+    buffer = IO::Buffer.new(1)
+    @buffer = buffer.transfer
+    buffer.send(@method).should be_true
+  end
+end
diff --git a/spec/ruby/core/io/buffer/shared_spec.rb b/spec/ruby/core/io/buffer/shared_spec.rb
new file mode 100644
index 0000000000..f2a638cf39
--- /dev/null
+++ b/spec/ruby/core/io/buffer/shared_spec.rb
@@ -0,0 +1,117 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#shared?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "is false for an internal buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::INTERNAL)
+      @buffer.shared?.should be_false
+    end
+
+    it "is false for a mapped buffer" do
+      @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      @buffer.shared?.should be_false
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "is true for a regular mapping" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.shared?.should be_true
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "is false for a private mapping" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+          @buffer.shared?.should be_false
+        end
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    it "is false for a buffer created without a block" do
+      @buffer = IO::Buffer.for("test")
+      @buffer.shared?.should be_false
+    end
+
+    it "is false for a buffer created with a block" do
+      IO::Buffer.for(+"test") do |buffer|
+        buffer.shared?.should be_false
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "is false" do
+        IO::Buffer.string(4) do |buffer|
+          buffer.shared?.should be_false
+        end
+      end
+    end
+  end
+
+  # Always false for slices
+  context "with a slice of a buffer" do
+    context "created with .new" do
+      it "is false when slicing an internal buffer" do
+        @buffer = IO::Buffer.new(4)
+        @buffer.slice.shared?.should be_false
+      end
+
+      it "is false when slicing a mapped buffer" do
+        @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+        @buffer.slice.shared?.should be_false
+      end
+    end
+
+    context "created with .map" do
+      it "is false when slicing a regular file-backed buffer" do
+        File.open(__FILE__, "r") do |file|
+          @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+          @buffer.slice.shared?.should be_false
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "is false when slicing a private file-backed buffer" do
+          File.open(__FILE__, "r") do |file|
+            @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY | IO::Buffer::PRIVATE)
+            @buffer.slice.shared?.should be_false
+          end
+        end
+      end
+    end
+
+    context "created with .for" do
+      it "is false when slicing a buffer created without a block" do
+        @buffer = IO::Buffer.for("test")
+        @buffer.slice.shared?.should be_false
+      end
+
+      it "is false when slicing a buffer created with a block" do
+        IO::Buffer.for(+"test") do |buffer|
+          buffer.slice.shared?.should be_false
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      context "created with .string" do
+        it "is false" do
+          IO::Buffer.string(4) do |buffer|
+            buffer.slice.shared?.should be_false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/transfer_spec.rb b/spec/ruby/core/io/buffer/transfer_spec.rb
new file mode 100644
index 0000000000..cb8c843ff2
--- /dev/null
+++ b/spec/ruby/core/io/buffer/transfer_spec.rb
@@ -0,0 +1,118 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#transfer" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  context "with a buffer created with .new" do
+    it "transfers internal memory to a new buffer, nullifying the original" do
+      buffer = IO::Buffer.new(4)
+      info = buffer.to_s
+      @buffer = buffer.transfer
+      @buffer.to_s.should == info
+      buffer.null?.should be_true
+    end
+
+    it "transfers mapped memory to a new buffer, nullifying the original" do
+      buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+      info = buffer.to_s
+      @buffer = buffer.transfer
+      @buffer.to_s.should == info
+      buffer.null?.should be_true
+    end
+  end
+
+  context "with a file-backed buffer created with .map" do
+    it "transfers mapped memory to a new buffer, nullifying the original" do
+      File.open(__FILE__, "r") do |file|
+        buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        info = buffer.to_s
+        @buffer = buffer.transfer
+        @buffer.to_s.should == info
+        buffer.null?.should be_true
+      end
+    end
+  end
+
+  context "with a String-backed buffer created with .for" do
+    context "without a block" do
+      it "transfers memory to a new buffer, nullifying the original" do
+        buffer = IO::Buffer.for("test")
+        info = buffer.to_s
+        @buffer = buffer.transfer
+        @buffer.to_s.should == info
+        buffer.null?.should be_true
+      end
+    end
+
+    context "with a block" do
+      it "transfers memory to a new buffer, breaking the transaction by nullifying the original" do
+        IO::Buffer.for(+"test") do |buffer|
+          info = buffer.to_s
+          @buffer = buffer.transfer
+          @buffer.to_s.should == info
+          buffer.null?.should be_true
+        end
+        @buffer.null?.should be_false
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    context "with a String-backed buffer created with .string" do
+      it "transfers memory to a new buffer, breaking the transaction by nullifying the original" do
+        IO::Buffer.string(4) do |buffer|
+          info = buffer.to_s
+          @buffer = buffer.transfer
+          @buffer.to_s.should == info
+          buffer.null?.should be_true
+        end
+        @buffer.null?.should be_false
+      end
+    end
+  end
+
+  it "allows multiple transfers" do
+    buffer_1 = IO::Buffer.new(4)
+    buffer_2 = buffer_1.transfer
+    @buffer = buffer_2.transfer
+    buffer_1.null?.should be_true
+    buffer_2.null?.should be_true
+    @buffer.null?.should be_false
+  end
+
+  it "is disallowed while locked, raising IO::Buffer::LockedError" do
+    @buffer = IO::Buffer.new(4)
+    @buffer.locked do
+      -> { @buffer.transfer }.should raise_error(IO::Buffer::LockedError, "Cannot transfer ownership of locked buffer!")
+    end
+  end
+
+  context "with a slice of a buffer" do
+    it "transfers source to a new slice, not touching the buffer" do
+      @buffer = IO::Buffer.new(4)
+      slice = @buffer.slice(0, 2)
+      @buffer.set_string("test")
+
+      new_slice = slice.transfer
+      slice.null?.should be_true
+      new_slice.null?.should be_false
+      @buffer.null?.should be_false
+
+      new_slice.set_string("ea")
+      @buffer.get_string.should == "east"
+    end
+
+    it "nullifies buffer, invalidating the slice" do
+      buffer = IO::Buffer.new(4)
+      slice = buffer.slice(0, 2)
+      @buffer = buffer.transfer
+
+      slice.null?.should be_false
+      slice.valid?.should be_false
+      -> { slice.get_string }.should raise_error(IO::Buffer::InvalidatedError, "Buffer has been invalidated!")
+    end
+  end
+end
diff --git a/spec/ruby/core/io/buffer/valid_spec.rb b/spec/ruby/core/io/buffer/valid_spec.rb
new file mode 100644
index 0000000000..680a35ae9a
--- /dev/null
+++ b/spec/ruby/core/io/buffer/valid_spec.rb
@@ -0,0 +1,110 @@
+require_relative '../../../spec_helper'
+
+describe "IO::Buffer#valid?" do
+  after :each do
+    @buffer&.free
+    @buffer = nil
+  end
+
+  # Non-slices are always valid
+  context "with a non-slice buffer" do
+    it "is true for a regular buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a 0-size buffer" do
+      @buffer = IO::Buffer.new(0)
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a freed buffer" do
+      @buffer = IO::Buffer.new(4)
+      @buffer.free
+      @buffer.valid?.should be_true
+    end
+
+    it "is true for a freed file-backed buffer" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        @buffer.valid?.should be_true
+        @buffer.free
+        @buffer.valid?.should be_true
+      end
+    end
+
+    it "is true for a freed string-backed buffer" do
+      @buffer = IO::Buffer.for("hello")
+      @buffer.valid?.should be_true
+      @buffer.free
+      @buffer.valid?.should be_true
+    end
+  end
+
+  # "A buffer becomes invalid if it is a slice of another buffer (or string)
+  # which has been freed or re-allocated at a different address."
+  context "with a slice" do
+    it "is true for a slice of a live buffer" do
+      @buffer = IO::Buffer.new(4)
+      slice = @buffer.slice(0, 2)
+      slice.valid?.should be_true
+    end
+
+    context "when buffer is resized" do
+      it "is false when slice becomes outside the buffer" do
+        @buffer = IO::Buffer.new(4)
+        slice = @buffer.slice(2, 2)
+        @buffer.resize(3)
+        slice.valid?.should be_false
+      end
+
+      platform_is_not :linux do
+        # This test does not cause a copy-resize on Linux.
+        # `#resize` MAY cause the buffer to move, but there is no guarantee.
+        it "is false when buffer is copied on resize" do
+          @buffer = IO::Buffer.new(4, IO::Buffer::MAPPED)
+          slice = @buffer.slice(0, 2)
+          @buffer.resize(8)
+          slice.valid?.should be_false
+        end
+      end
+    end
+
+    it "is false for a slice of a transferred buffer" do
+      buffer = IO::Buffer.new(4)
+      slice = buffer.slice(0, 2)
+      @buffer = buffer.transfer
+      slice.valid?.should be_false
+    end
+
+    it "is false for a slice of a freed buffer" do
+      @buffer = IO::Buffer.new(4)
+      slice = @buffer.slice(0, 2)
+      @buffer.free
+      slice.valid?.should be_false
+    end
+
+    it "is false for a slice of a freed file-backed buffer" do
+      File.open(__FILE__, "r") do |file|
+        @buffer = IO::Buffer.map(file, nil, 0, IO::Buffer::READONLY)
+        slice = @buffer.slice(0, 2)
+        slice.valid?.should be_true
+        @buffer.free
+        slice.valid?.should be_false
+      end
+    end
+
+    it "is true for a slice of a freed string-backed buffer while string is alive" do
+      @buffer = IO::Buffer.for("alive")
+      slice = @buffer.slice(0, 2)
+      slice.valid?.should be_true
+      @buffer.free
+      slice.valid?.should be_true
+    end
+
+    # There probably should be a test with a garbage-collected string,
+    # but it's not clear how to force that.
+
+    it "needs to be reviewed for spec completeness"
+  end
+end
diff --git a/spec/ruby/core/io/bytes_spec.rb b/spec/ruby/core/io/bytes_spec.rb
deleted file mode 100644
index feeb493566..0000000000
--- a/spec/ruby/core/io/bytes_spec.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-# -*- encoding: utf-8 -*-
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-
-describe "IO#bytes" do
-  before :each do
-    @io = IOSpecs.io_fixture "lines.txt"
-  end
-
-  after :each do
-    @io.close unless @io.closed?
-  end
-
-  it "returns an enumerator of the next bytes from the stream" do
-    enum = @io.bytes
-    enum.should be_an_instance_of(Enumerator)
-    @io.readline.should == "Voici la ligne une.\n"
-    enum.first(5).should == [81, 117, 105, 32, 195]
-  end
-
-  it "yields each byte" do
-    count = 0
-    ScratchPad.record []
-    @io.each_byte do |byte|
-      ScratchPad << byte
-      break if 4 < count += 1
-    end
-
-    ScratchPad.recorded.should == [86, 111, 105, 99, 105]
-  end
-
-  it "raises an IOError on closed stream" do
-    enum = IOSpecs.closed_io.bytes
-    -> { enum.first }.should raise_error(IOError)
-  end
-
-  it "raises an IOError on an enumerator for a stream that has been closed" do
-    enum = @io.bytes
-    enum.first.should == 86
-    @io.close
-    -> { enum.first }.should raise_error(IOError)
-  end
-end
diff --git a/spec/ruby/core/io/chars_spec.rb b/spec/ruby/core/io/chars_spec.rb
deleted file mode 100644
index cd5dbbce4f..0000000000
--- a/spec/ruby/core/io/chars_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-# -*- encoding: utf-8 -*-
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-require_relative 'shared/chars'
-
-describe "IO#chars" do
-  it_behaves_like :io_chars, :chars
-end
-
-describe "IO#chars" do
-  it_behaves_like :io_chars_empty, :chars
-end
diff --git a/spec/ruby/core/io/close_on_exec_spec.rb b/spec/ruby/core/io/close_on_exec_spec.rb
index f837bb56af..4e89e08d61 100644
--- a/spec/ruby/core/io/close_on_exec_spec.rb
+++ b/spec/ruby/core/io/close_on_exec_spec.rb
@@ -14,24 +14,24 @@ describe "IO#close_on_exec=" do
   guard -> { platform_is_not :windows } do
     it "sets the close-on-exec flag if true" do
       @io.close_on_exec = true
-      @io.close_on_exec?.should == true
+      @io.should.close_on_exec?
     end
 
     it "sets the close-on-exec flag if non-false" do
       @io.close_on_exec = :true
-      @io.close_on_exec?.should == true
+      @io.should.close_on_exec?
     end
 
     it "unsets the close-on-exec flag if false" do
       @io.close_on_exec = true
       @io.close_on_exec = false
-      @io.close_on_exec?.should == false
+      @io.should_not.close_on_exec?
     end
 
     it "unsets the close-on-exec flag if nil" do
       @io.close_on_exec = true
       @io.close_on_exec = nil
-      @io.close_on_exec?.should == false
+      @io.should_not.close_on_exec?
     end
 
     it "ensures the IO's file descriptor is closed in exec'ed processes" do
@@ -44,10 +44,6 @@ describe "IO#close_on_exec=" do
       @io.close
       -> { @io.close_on_exec = true }.should raise_error(IOError)
     end
-
-    it "returns nil" do
-      @io.send(:close_on_exec=, true).should be_nil
-    end
   end
 end
 
@@ -64,12 +60,12 @@ describe "IO#close_on_exec?" do
 
   guard -> { platform_is_not :windows } do
     it "returns true by default" do
-      @io.close_on_exec?.should == true
+      @io.should.close_on_exec?
     end
 
     it "returns true if set" do
       @io.close_on_exec = true
-      @io.close_on_exec?.should == true
+      @io.should.close_on_exec?
     end
 
     it "raises IOError if called on a closed IO" do
diff --git a/spec/ruby/core/io/close_read_spec.rb b/spec/ruby/core/io/close_read_spec.rb
index 6fa4fc8ff8..e700e85bd9 100644
--- a/spec/ruby/core/io/close_read_spec.rb
+++ b/spec/ruby/core/io/close_read_spec.rb
@@ -4,7 +4,8 @@ require_relative 'fixtures/classes'
 describe "IO#close_read" do
 
   before :each do
-    @io = IO.popen 'cat', "r+"
+    cmd = platform_is(:windows) ? 'rem' : 'cat'
+    @io = IO.popen cmd, "r+"
     @path = tmp('io.close.txt')
   end
 
@@ -49,7 +50,7 @@ describe "IO#close_read" do
 
     io.close_read
 
-    io.closed?.should == true
+    io.should.closed?
   end
 
   it "does nothing on closed stream" do
diff --git a/spec/ruby/core/io/close_spec.rb b/spec/ruby/core/io/close_spec.rb
index 21bba32cd8..3a44cc8b17 100644
--- a/spec/ruby/core/io/close_spec.rb
+++ b/spec/ruby/core/io/close_spec.rb
@@ -14,7 +14,7 @@ describe "IO#close" do
 
   it "closes the stream" do
     @io.close
-    @io.closed?.should == true
+    @io.should.closed?
   end
 
   it "returns nil" do
@@ -44,22 +44,43 @@ describe "IO#close" do
     @io.close.should be_nil
   end
 
-  ruby_version_is '2.5' do
-    it 'raises an IOError with a clear message' do
-      read_io, write_io = IO.pipe
-      going_to_read = false
-      thread = Thread.new do
-        -> do
-          going_to_read = true
-          read_io.read
-        end.should raise_error(IOError, 'stream closed in another thread')
-      end
+  it "does not call the #flush method but flushes the stream internally" do
+    @io.should_not_receive(:flush)
+    @io.close
+    @io.should.closed?
+  end
 
-      Thread.pass until going_to_read && thread.stop?
-      read_io.close
-      thread.join
-      write_io.close
-    end
+  it 'raises an IOError with a clear message' do
+    matching_exception = nil
+
+    -> do
+      IOSpecs::THREAD_CLOSE_RETRIES.times do
+        read_io, write_io = IO.pipe
+        going_to_read = false
+
+        thread = Thread.new do
+          begin
+            going_to_read = true
+            read_io.read
+          rescue IOError => ioe
+            if ioe.message == IOSpecs::THREAD_CLOSE_ERROR_MESSAGE
+              matching_exception = ioe
+            end
+            # try again
+          end
+        end
+
+        # best attempt to ensure the thread is actually blocked on read
+        Thread.pass until going_to_read && thread.stop?
+        sleep(0.001)
+
+        read_io.close
+        thread.join
+        write_io.close
+
+        matching_exception&.tap {|ex| raise ex}
+      end
+    end.should raise_error(IOError, IOSpecs::THREAD_CLOSE_ERROR_MESSAGE)
   end
 end
 
diff --git a/spec/ruby/core/io/close_write_spec.rb b/spec/ruby/core/io/close_write_spec.rb
index 75e1577654..70610a3e9d 100644
--- a/spec/ruby/core/io/close_write_spec.rb
+++ b/spec/ruby/core/io/close_write_spec.rb
@@ -3,7 +3,8 @@ require_relative 'fixtures/classes'
 
 describe "IO#close_write" do
   before :each do
-    @io = IO.popen 'cat', 'r+'
+    cmd = platform_is(:windows) ? 'rem' : 'cat'
+    @io = IO.popen cmd, 'r+'
     @path = tmp('io.close.txt')
   end
 
@@ -45,15 +46,18 @@ describe "IO#close_write" do
 
     io.close_write
 
-    io.closed?.should == true
+    io.should.closed?
   end
 
-  it "flushes and closes the write stream" do
-    @io.puts '12345'
+  # Windows didn't have command like cat
+  platform_is_not :windows do
+    it "flushes and closes the write stream" do
+      @io.puts '12345'
 
-    @io.close_write
+      @io.close_write
 
-    @io.read.should == "12345\n"
+      @io.read.should == "12345\n"
+    end
   end
 
   it "does nothing on closed stream" do
diff --git a/spec/ruby/core/io/codepoints_spec.rb b/spec/ruby/core/io/codepoints_spec.rb
deleted file mode 100644
index 915d99c027..0000000000
--- a/spec/ruby/core/io/codepoints_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-require_relative 'shared/codepoints'
-
-# See redmine #1667
-describe "IO#codepoints" do
-  it_behaves_like :io_codepoints, :codepoints
-end
-
-describe "IO#codepoints" do
-  before :each do
-    @io = IOSpecs.io_fixture "lines.txt"
-  end
-
-  after :each do
-    @io.close unless @io.closed?
-  end
-
-  it "calls the given block" do
-    r = []
-    @io.codepoints { |c| r << c }
-    r[24].should == 232
-    r.last.should == 10
-  end
-end
diff --git a/spec/ruby/core/io/copy_stream_spec.rb b/spec/ruby/core/io/copy_stream_spec.rb
index c541e96e14..ffa2ea992c 100644
--- a/spec/ruby/core/io/copy_stream_spec.rb
+++ b/spec/ruby/core/io/copy_stream_spec.rb
@@ -69,9 +69,12 @@ describe :io_copy_stream_to_io, shared: true do
   end
 
   it "raises an IOError if the destination IO is not open for writing" do
-    @to_io.close
-    @to_io = new_io @to_name, "r"
-    -> { IO.copy_stream @object.from, @to_io }.should raise_error(IOError)
+    to_io = new_io __FILE__, "r"
+    begin
+      -> { IO.copy_stream @object.from, to_io }.should raise_error(IOError)
+    ensure
+      to_io.close
+    end
   end
 
   it "does not close the destination IO" do
@@ -109,7 +112,8 @@ describe "IO.copy_stream" do
   end
 
   after :each do
-    rm_r @to_name, @from_bigfile
+    rm_r @to_name if @to_name
+    rm_r @from_bigfile
   end
 
   describe "from an IO" do
@@ -164,6 +168,25 @@ describe "IO.copy_stream" do
       it_behaves_like :io_copy_stream_to_io, nil, IOSpecs::CopyStream
       it_behaves_like :io_copy_stream_to_io_with_offset, nil, IOSpecs::CopyStream
     end
+
+    describe "to a Tempfile" do
+      before :all do
+        require 'tempfile'
+      end
+
+      before :each do
+        @to_io = Tempfile.new("rubyspec_copy_stream", encoding: Encoding::BINARY, mode: File::RDONLY)
+        @to_name = @to_io.path
+      end
+
+      after :each do
+        @to_io.close!
+        @to_name = nil # do not rm_r it, already done by Tempfile#close!
+      end
+
+      it_behaves_like :io_copy_stream_to_io, nil, IOSpecs::CopyStream
+      it_behaves_like :io_copy_stream_to_io_with_offset, nil, IOSpecs::CopyStream
+    end
   end
 
   describe "from a file name" do
@@ -277,6 +300,44 @@ describe "IO.copy_stream" do
       @io.should_not_receive(:pos)
       IO.copy_stream(@io, @to_name)
     end
+  end
+
+  describe "with a destination that does partial reads" do
+    before do
+      @from_out, @from_in = IO.pipe
+      @to_out, @to_in = IO.pipe
+    end
 
+    after do
+      [@from_out, @from_in, @to_out, @to_in].each {|io| io.close rescue nil}
+    end
+
+    it "calls #write repeatedly on the destination Object" do
+      @from_in.write "1234"
+      @from_in.close
+
+      th = Thread.new do
+        IO.copy_stream(@from_out, @to_in)
+      end
+
+      copied = ""
+      4.times do
+        copied += @to_out.read(1)
+      end
+
+      th.join
+
+      copied.should == "1234"
+    end
+
+  end
+end
+
+describe "IO.copy_stream" do
+  it "does not use buffering when writing to STDOUT" do
+    IO.popen([*ruby_exe, fixture(__FILE__ , "copy_in_out.rb")], "r+") do |io|
+      io.write("bar")
+      io.read(3).should == "bar"
+    end
   end
 end
diff --git a/spec/ruby/core/io/dup_spec.rb b/spec/ruby/core/io/dup_spec.rb
index de32c5e347..564e007438 100644
--- a/spec/ruby/core/io/dup_spec.rb
+++ b/spec/ruby/core/io/dup_spec.rb
@@ -25,42 +25,42 @@ describe "IO#dup" do
     @i.fileno.should_not == @f.fileno
   end
 
-quarantine! do # This does not appear to be consistent across platforms
-  it "shares the original stream between the two IOs" do
-    start = @f.pos
-    @i.pos.should == start
+  quarantine! do # This does not appear to be consistent across platforms
+    it "shares the original stream between the two IOs" do
+      start = @f.pos
+      @i.pos.should == start
 
-    s =  "Hello, wo.. wait, where am I?\n"
-    s2 = "<evil voice>       Muhahahaa!"
+      s =  "Hello, wo.. wait, where am I?\n"
+      s2 = "<evil voice>       Muhahahaa!"
 
-    @f.write s
-    @i.pos.should == @f.pos
+      @f.write s
+      @i.pos.should == @f.pos
 
-    @i.rewind
-    @i.gets.should == s
+      @i.rewind
+      @i.gets.should == s
 
-    @i.rewind
-    @i.write s2
+      @i.rewind
+      @i.write s2
 
-    @f.rewind
-    @f.gets.should == "#{s2}\n"
+      @f.rewind
+      @f.gets.should == "#{s2}\n"
+    end
   end
-end
 
   it "allows closing the new IO without affecting the original" do
     @i.close
     -> { @f.gets }.should_not raise_error(Exception)
 
-    @i.closed?.should == true
-    @f.closed?.should == false
+    @i.should.closed?
+    @f.should_not.closed?
   end
 
   it "allows closing the original IO without affecting the new one" do
     @f.close
     -> { @i.gets }.should_not raise_error(Exception)
 
-    @i.closed?.should == false
-    @f.closed?.should == true
+    @i.should_not.closed?
+    @f.should.closed?
   end
 
   it "raises IOError on closed stream" do
@@ -71,7 +71,7 @@ end
     @f.close_on_exec = true
     dup = @f.dup
     begin
-      dup.close_on_exec?.should == true
+      dup.should.close_on_exec?
     ensure
       dup.close
     end
@@ -79,9 +79,28 @@ end
     @f.close_on_exec = false
     dup = @f.dup
     begin
-      dup.close_on_exec?.should == true
+      dup.should.close_on_exec?
+    ensure
+      dup.close
+    end
+  end
+
+  it "always sets the autoclose flag for the new IO object" do
+    @f.autoclose = true
+    dup = @f.dup
+    begin
+      dup.should.autoclose?
+    ensure
+      dup.close
+    end
+
+    @f.autoclose = false
+    dup = @f.dup
+    begin
+      dup.should.autoclose?
     ensure
       dup.close
+      @f.autoclose = true
     end
   end
 end
diff --git a/spec/ruby/core/io/each_codepoint_spec.rb b/spec/ruby/core/io/each_codepoint_spec.rb
index cddc6b4662..07a4037c8a 100644
--- a/spec/ruby/core/io/each_codepoint_spec.rb
+++ b/spec/ruby/core/io/each_codepoint_spec.rb
@@ -4,7 +4,7 @@ require_relative 'shared/codepoints'
 
 # See redmine #1667
 describe "IO#each_codepoint" do
-  it_behaves_like :io_codepoints, :codepoints
+  it_behaves_like :io_codepoints, :each_codepoint
 end
 
 describe "IO#each_codepoint" do
diff --git a/spec/ruby/core/io/eof_spec.rb b/spec/ruby/core/io/eof_spec.rb
index 8fd3c37132..b4850df437 100644
--- a/spec/ruby/core/io/eof_spec.rb
+++ b/spec/ruby/core/io/eof_spec.rb
@@ -12,7 +12,7 @@ describe "IO#eof?" do
   end
 
   it "returns true on an empty stream that has just been opened" do
-    File.open(@name) { |empty| empty.eof?.should == true }
+    File.open(@name) { |empty| empty.should.eof? }
   end
 
   it "raises IOError on stream not opened for reading" do
@@ -34,35 +34,35 @@ describe "IO#eof?" do
 
   it "returns false when not at end of file" do
     @io.read 1
-    @io.eof?.should == false
+    @io.should_not.eof?
   end
 
   it "returns true after reading with read with no parameters" do
     @io.read()
-    @io.eof?.should == true
+    @io.should.eof?
   end
 
   it "returns true after reading with read" do
     @io.read(File.size(@name))
-    @io.eof?.should == true
+    @io.should.eof?
   end
 
   it "returns true after reading with sysread" do
     @io.sysread(File.size(@name))
-    @io.eof?.should == true
+    @io.should.eof?
   end
 
   it "returns true after reading with readlines" do
     @io.readlines
-    @io.eof?.should == true
+    @io.should.eof?
   end
 
   it "returns false on just opened non-empty stream" do
-    @io.eof?.should == false
+    @io.should_not.eof?
   end
 
   it "does not consume the data from the stream" do
-    @io.eof?.should == false
+    @io.should_not.eof?
     @io.getc.should == 'V'
   end
 
@@ -76,9 +76,9 @@ describe "IO#eof?" do
   end
 
   it "returns true on one-byte stream after single-byte read" do
-    File.open(File.dirname(__FILE__) + '/fixtures/one_byte.txt') { |one_byte|
+    File.open(__dir__ + '/fixtures/one_byte.txt') { |one_byte|
       one_byte.read(1)
-      one_byte.eof?.should == true
+      one_byte.should.eof?
     }
   end
 end
@@ -92,16 +92,16 @@ describe "IO#eof?" do
   it "returns true on receiving side of Pipe when writing side is closed" do
     @r, @w = IO.pipe
     @w.close
-    @r.eof?.should == true
+    @r.should.eof?
   end
 
   it "returns false on receiving side of Pipe when writing side wrote some data" do
     @r, @w = IO.pipe
     @w.puts "hello"
-    @r.eof?.should == false
+    @r.should_not.eof?
     @w.close
-    @r.eof?.should == false
+    @r.should_not.eof?
     @r.read
-    @r.eof?.should == true
+    @r.should.eof?
   end
 end
diff --git a/spec/ruby/core/io/external_encoding_spec.rb b/spec/ruby/core/io/external_encoding_spec.rb
index 9666974647..7765c6c0f5 100644
--- a/spec/ruby/core/io/external_encoding_spec.rb
+++ b/spec/ruby/core/io/external_encoding_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe :io_external_encoding_write, shared: true do
   describe "when Encoding.default_internal is nil" do
@@ -93,6 +94,12 @@ describe "IO#external_encoding" do
     rm_r @name
   end
 
+  it "can be retrieved from a closed stream" do
+    io = IOSpecs.io_fixture("lines.txt", "r")
+    io.close
+    io.external_encoding.should equal(Encoding.default_external)
+  end
+
   describe "with 'r' mode" do
     describe "when Encoding.default_internal is nil" do
       before :each do
diff --git a/spec/ruby/core/io/fixtures/classes.rb b/spec/ruby/core/io/fixtures/classes.rb
index 460dd62387..204a2a101b 100644
--- a/spec/ruby/core/io/fixtures/classes.rb
+++ b/spec/ruby/core/io/fixtures/classes.rb
@@ -1,9 +1,24 @@
 # -*- encoding: utf-8 -*-
 
 module IOSpecs
+  THREAD_CLOSE_RETRIES = 10
+  THREAD_CLOSE_ERROR_MESSAGE = 'stream closed in another thread'
+
   class SubIO < IO
   end
 
+  class SubIOWithRedefinedNew < IO
+    def self.new(...)
+      ScratchPad << :redefined_new_called
+      super
+    end
+
+    def initialize(...)
+      ScratchPad << :call_original_initialize
+      super
+    end
+  end
+
   def self.collector
     Proc.new { |x| ScratchPad << x }
   end
@@ -105,6 +120,14 @@ module IOSpecs
       "linha ", "cinco.\nHere ", "is ", "line ", "six.\n" ]
   end
 
+  def self.lines_space_separator_without_trailing_spaces
+    [ "Voici", "la", "ligne", "une.\nQui",
+      "\303\250", "la", "linea", "due.\n\n\nAqu\303\255",
+      "est\303\241", "la", "l\303\255nea", "tres.\nHier",
+      "ist", "Zeile", "vier.\n\nEst\303\241", "aqui", "a",
+      "linha", "cinco.\nHere", "is", "line", "six.\n" ]
+  end
+
   def self.lines_arbitrary_separator
     [ "Voici la ligne une.\nQui \303\250",
       " la linea due.\n\n\nAqu\303\255 est\303\241 la l\303\255nea tres.\nHier ist Zeile vier.\n\nEst\303\241 aqui a linha cinco.\nHere is line six.\n" ]
@@ -116,6 +139,12 @@ module IOSpecs
       "Est\303\241 aqui a linha cinco.\nHere is line six.\n" ]
   end
 
+  def self.paragraphs_without_trailing_new_line_characters
+    [ "Voici la ligne une.\nQui \303\250 la linea due.",
+      "Aqu\303\255 est\303\241 la l\303\255nea tres.\nHier ist Zeile vier.",
+      "Est\303\241 aqui a linha cinco.\nHere is line six.\n" ]
+  end
+
   # Creates an IO instance for an existing fixture file. The
   # file should obviously not be deleted.
   def self.io_fixture(name, mode = "r:utf-8")
@@ -164,7 +193,7 @@ module IOSpecs
       @io = io
     end
 
-    def read(size, buf=nil)
+    def read(size, buf)
       @io.read size, buf
     end
 
@@ -178,7 +207,7 @@ module IOSpecs
       @io = io
     end
 
-    def readpartial(size, buf=nil)
+    def readpartial(size, buf)
       @io.readpartial size, buf
     end
 
diff --git a/spec/ruby/core/io/fixtures/copy_in_out.rb b/spec/ruby/core/io/fixtures/copy_in_out.rb
new file mode 100644
index 0000000000..b9d4085a47
--- /dev/null
+++ b/spec/ruby/core/io/fixtures/copy_in_out.rb
@@ -0,0 +1,2 @@
+STDOUT.sync = false
+IO.copy_stream(STDIN, STDOUT)
diff --git a/spec/ruby/core/io/flush_spec.rb b/spec/ruby/core/io/flush_spec.rb
index 34cf42c425..f7d5ba77fc 100644
--- a/spec/ruby/core/io/flush_spec.rb
+++ b/spec/ruby/core/io/flush_spec.rb
@@ -19,11 +19,11 @@ describe "IO#flush" do
       end
     end
 
-    # [ruby-core:90895] MJIT worker may leave fd open in a forked child.
-    # For instance, MJIT creates a worker before @r.close with fork(), @r.close happens,
-    # and the MJIT worker keeps the pipe open until the worker execve().
-    # TODO: consider acquiring GVL from MJIT worker.
-    guard_not -> { defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? } do
+    # [ruby-core:90895] RJIT worker may leave fd open in a forked child.
+    # For instance, RJIT creates a worker before @r.close with fork(), @r.close happens,
+    # and the RJIT worker keeps the pipe open until the worker execve().
+    # TODO: consider acquiring GVL from RJIT worker.
+    guard_not -> { defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled? } do
       it "raises Errno::EPIPE if sync=false and the read end is closed" do
         @w.sync = false
         @w.write "foo"
diff --git a/spec/ruby/core/io/foreach_spec.rb b/spec/ruby/core/io/foreach_spec.rb
index c2276cf544..6abe8901ba 100644
--- a/spec/ruby/core/io/foreach_spec.rb
+++ b/spec/ruby/core/io/foreach_spec.rb
@@ -14,31 +14,48 @@ describe "IO.foreach" do
     IO.foreach(@name) { $..should == @count += 1 }
   end
 
-  describe "when the filename starts with |" do
-    it "gets data from the standard out of the subprocess" do
-      cmd = "|sh -c 'echo hello;echo line2'"
-      platform_is :windows do
-        cmd = "|cmd.exe /C echo hello&echo line2"
+  ruby_version_is ""..."4.0" do
+    describe "when the filename starts with |" do
+      it "gets data from the standard out of the subprocess" do
+        cmd = "|sh -c 'echo hello;echo line2'"
+        platform_is :windows do
+          cmd = "|cmd.exe /C echo hello&echo line2"
+        end
+
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          IO.foreach(cmd) { |l| ScratchPad << l }
+        end
+        ScratchPad.recorded.should == ["hello\n", "line2\n"]
       end
-      IO.foreach(cmd) { |l| ScratchPad << l }
-      ScratchPad.recorded.should == ["hello\n", "line2\n"]
-    end
 
-    platform_is_not :windows do
-      it "gets data from a fork when passed -" do
-        parent_pid = $$
+      platform_is_not :windows do
+        it "gets data from a fork when passed -" do
+          parent_pid = $$
 
-        IO.foreach("|-") { |l| ScratchPad << l }
+          suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+            IO.foreach("|-") { |l| ScratchPad << l }
+          end
 
-        if $$ == parent_pid
-          ScratchPad.recorded.should == ["hello\n", "from a fork\n"]
-        else # child
-          puts "hello"
-          puts "from a fork"
-          exit!
+          if $$ == parent_pid
+            ScratchPad.recorded.should == ["hello\n", "from a fork\n"]
+          else # child
+            puts "hello"
+            puts "from a fork"
+            exit!
+          end
         end
       end
     end
+
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        cmd = "|echo ok"
+        -> {
+          IO.foreach(cmd).to_a
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
+    end
   end
 end
 
diff --git a/spec/ruby/core/io/getbyte_spec.rb b/spec/ruby/core/io/getbyte_spec.rb
index 6ba8f0a3e0..b4351160e6 100644
--- a/spec/ruby/core/io/getbyte_spec.rb
+++ b/spec/ruby/core/io/getbyte_spec.rb
@@ -40,3 +40,19 @@ describe "IO#getbyte" do
     @io.getbyte.should == nil
   end
 end
+
+describe "IO#getbyte" do
+  before :each do
+    @name = tmp("io_getbyte.txt")
+    @io = new_io(@name, 'w')
+  end
+
+  after :each do
+    @io.close if @io
+    rm_r @name if @name
+  end
+
+  it "raises an IOError if the stream is not readable" do
+    -> { @io.getbyte }.should raise_error(IOError)
+  end
+end
diff --git a/spec/ruby/core/io/gets_spec.rb b/spec/ruby/core/io/gets_spec.rb
index 8f6ec0dfc7..ca64bf860e 100644
--- a/spec/ruby/core/io/gets_spec.rb
+++ b/spec/ruby/core/io/gets_spec.rb
@@ -24,6 +24,12 @@ describe "IO#gets" do
     end
   end
 
+  it "sets $_ to nil after the last line has been read" do
+    while @io.gets
+    end
+    $_.should be_nil
+  end
+
   it "returns nil if called at the end of the stream" do
     IOSpecs.lines.length.times { @io.gets }
     @io.gets.should == nil
@@ -38,12 +44,6 @@ describe "IO#gets" do
       IOSpecs.lines.each { |line| line.should == @io.gets }
     end
 
-    it "returns tainted strings" do
-      while line = @io.gets
-        line.tainted?.should == true
-      end
-    end
-
     it "updates lineno with each invocation" do
       while @io.gets
         @io.lineno.should == @count += 1
@@ -62,12 +62,6 @@ describe "IO#gets" do
       @io.gets(nil).should == IOSpecs.lines.join("")
     end
 
-    it "returns tainted strings" do
-      while line = @io.gets(nil)
-        line.tainted?.should == true
-      end
-    end
-
     it "updates lineno with each invocation" do
       while @io.gets(nil)
         @io.lineno.should == @count += 1
@@ -96,12 +90,6 @@ describe "IO#gets" do
       @io.gets.should == IOSpecs.lines[4]
     end
 
-    it "returns tainted strings" do
-      while line = @io.gets("")
-        line.tainted?.should == true
-      end
-    end
-
     it "updates lineno with each invocation" do
       while @io.gets("")
         @io.lineno.should == @count += 1
@@ -120,12 +108,6 @@ describe "IO#gets" do
       @io.gets("la linea").should == "Voici la ligne une.\nQui \303\250 la linea"
     end
 
-    it "returns tainted strings" do
-      while line = @io.gets("la")
-        line.tainted?.should == true
-      end
-    end
-
     it "updates lineno with each invocation" do
       while (@io.gets("la"))
         @io.lineno.should == @count += 1
@@ -137,12 +119,49 @@ describe "IO#gets" do
         $..should == @count += 1
       end
     end
+
+    describe "that consists of multiple bytes" do
+      platform_is_not :windows do
+        it "should match the separator even if the buffer is filled over successive reads" do
+          IO.pipe do |read, write|
+
+            # Write part of the string with the separator split between two write calls. We want
+            # the read to intertwine such that when the read starts the full data isn't yet
+            # available in the buffer.
+            write.write("Aquí está la línea tres\r\n")
+
+            t = Thread.new do
+              # Continue reading until the separator is encountered or the pipe is closed.
+              read.gets("\r\n\r\n")
+            end
+
+            # Write the other half of the separator, which should cause the `gets` call to now
+            # match. Explicitly close the pipe for good measure so a bug in `gets` doesn't block forever.
+            Thread.pass until t.stop?
+
+            write.write("\r\nelse\r\n\r\n")
+            write.close
+
+            t.value.bytes.should == "Aquí está la línea tres\r\n\r\n".bytes
+            read.read(8).bytes.should == "else\r\n\r\n".bytes
+          end
+        end
+      end
+    end
   end
 
   describe "when passed chomp" do
     it "returns the first line without a trailing newline character" do
       @io.gets(chomp: true).should == IOSpecs.lines_without_newline_characters[0]
     end
+
+    it "raises exception when options passed as Hash" do
+      -> { @io.gets({ chomp: true }) }.should raise_error(TypeError)
+
+      -> {
+        @io.gets("\n", 1, { chomp: true })
+      }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
+    end
   end
 end
 
@@ -224,6 +243,16 @@ describe "IO#gets" do
   it "reads all bytes when pass a separator and reading more than all bytes" do
     @io.gets("\t", 100).should == "one\n\ntwo\n\nthree\nfour\n"
   end
+
+  it "returns empty string when 0 passed as a limit" do
+    @io.gets(0).should == ""
+    @io.gets(nil, 0).should == ""
+    @io.gets("", 0).should == ""
+  end
+
+  it "does not accept limit that doesn't fit in a C off_t" do
+    -> { @io.gets(2**128) }.should raise_error(RangeError)
+  end
 end
 
 describe "IO#gets" do
@@ -309,11 +338,23 @@ describe "IO#gets" do
     @io.gets.encoding.should == Encoding::BINARY
   end
 
-  it "transcodes to internal encoding if the IO object's external encoding is BINARY" do
-    Encoding.default_external = Encoding::BINARY
-    Encoding.default_internal = Encoding::UTF_8
-    @io = new_io @name, 'r'
-    @io.set_encoding Encoding::BINARY, Encoding::UTF_8
-    @io.gets.encoding.should == Encoding::UTF_8
+  ruby_version_is ''...'3.3' do
+    it "transcodes to internal encoding if the IO object's external encoding is BINARY" do
+      Encoding.default_external = Encoding::BINARY
+      Encoding.default_internal = Encoding::UTF_8
+      @io = new_io @name, 'r'
+      @io.set_encoding Encoding::BINARY, Encoding::UTF_8
+      @io.gets.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  ruby_version_is '3.3' do
+    it "ignores the internal encoding if the IO object's external encoding is BINARY" do
+      Encoding.default_external = Encoding::BINARY
+      Encoding.default_internal = Encoding::UTF_8
+      @io = new_io @name, 'r'
+      @io.set_encoding Encoding::BINARY, Encoding::UTF_8
+      @io.gets.encoding.should == Encoding::BINARY
+    end
   end
 end
diff --git a/spec/ruby/core/io/initialize_spec.rb b/spec/ruby/core/io/initialize_spec.rb
index c8f3faf110..026252a13d 100644
--- a/spec/ruby/core/io/initialize_spec.rb
+++ b/spec/ruby/core/io/initialize_spec.rb
@@ -4,7 +4,7 @@ require_relative 'fixtures/classes'
 describe "IO#initialize" do
   before :each do
     @name = tmp("io_initialize.txt")
-    @io = new_io @name
+    @io = IO.new(new_fd(@name))
     @fd = @io.fileno
   end
 
@@ -13,7 +13,7 @@ describe "IO#initialize" do
     rm_r @name
   end
 
-  it "reassociates the IO instance with the new descriptor when passed a Fixnum" do
+  it "reassociates the IO instance with the new descriptor when passed an Integer" do
     fd = new_fd @name, "r:utf-8"
     @io.send :initialize, fd, 'r'
     @io.fileno.should == fd
@@ -27,6 +27,17 @@ describe "IO#initialize" do
     @io.fileno.should == fd
   end
 
+  it "accepts options as keyword arguments" do
+    fd = new_fd @name, "w:utf-8"
+
+    @io.send(:initialize, fd, "w", flags: File::CREAT)
+    @io.fileno.should == fd
+
+    -> {
+      @io.send(:initialize, fd, "w", {flags: File::CREAT})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 1..2)")
+  end
+
   it "raises a TypeError when passed an IO" do
     -> { @io.send :initialize, STDOUT, 'w' }.should raise_error(TypeError)
   end
diff --git a/spec/ruby/core/io/internal_encoding_spec.rb b/spec/ruby/core/io/internal_encoding_spec.rb
index 10ebf28707..7a583d4bcb 100644
--- a/spec/ruby/core/io/internal_encoding_spec.rb
+++ b/spec/ruby/core/io/internal_encoding_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe :io_internal_encoding, shared: true do
   describe "when Encoding.default_internal is not set" do
@@ -112,6 +113,12 @@ describe "IO#internal_encoding" do
     Encoding.default_internal = @internal
   end
 
+  it "can be retrieved from a closed stream" do
+    io = IOSpecs.io_fixture("lines.txt", "r")
+    io.close
+    io.internal_encoding.should equal(Encoding.default_internal)
+  end
+
   describe "with 'r' mode" do
     it_behaves_like :io_internal_encoding, nil, "r"
   end
diff --git a/spec/ruby/core/io/ioctl_spec.rb b/spec/ruby/core/io/ioctl_spec.rb
index e819a217a8..3f7b5ad5d7 100644
--- a/spec/ruby/core/io/ioctl_spec.rb
+++ b/spec/ruby/core/io/ioctl_spec.rb
@@ -12,7 +12,7 @@ describe "IO#ioctl" do
     guard -> { RUBY_PLATFORM.include?("86") } do # x86 / x86_64
       it "resizes an empty String to match the output size" do
         File.open(__FILE__, 'r') do |f|
-          buffer = ''
+          buffer = +''
           # FIONREAD in /usr/include/asm-generic/ioctls.h
           f.ioctl 0x541B, buffer
           buffer.unpack('I').first.should be_kind_of(Integer)
@@ -20,12 +20,12 @@ describe "IO#ioctl" do
       end
     end
 
-    it "raises an Errno error when ioctl fails" do
+    it "raises a system call error when ioctl fails" do
       File.open(__FILE__, 'r') do |f|
         -> {
           # TIOCGWINSZ in /usr/include/asm-generic/ioctls.h
           f.ioctl 0x5413, nil
-        }.should raise_error(Errno::ENOTTY)
+        }.should raise_error(SystemCallError)
       end
     end
   end
diff --git a/spec/ruby/core/io/lineno_spec.rb b/spec/ruby/core/io/lineno_spec.rb
index 3d1b2275cc..e82cdd9f17 100644
--- a/spec/ruby/core/io/lineno_spec.rb
+++ b/spec/ruby/core/io/lineno_spec.rb
@@ -14,6 +14,25 @@ describe "IO#lineno" do
     -> { IOSpecs.closed_io.lineno }.should raise_error(IOError)
   end
 
+  it "raises an IOError on a write-only stream" do
+    name = tmp("io_lineno.txt")
+    begin
+      File.open(name, 'w') do |f|
+        -> { f.lineno }.should raise_error(IOError)
+      end
+    ensure
+      rm_r name
+    end
+  end
+
+  it "raises an IOError on a duplexed stream with the read side closed" do
+    cmd = platform_is(:windows) ? 'rem' : 'cat'
+    IO.popen(cmd, 'r+') do |p|
+      p.close_read
+      -> { p.lineno }.should raise_error(IOError)
+    end
+  end
+
   it "returns the current line number" do
     @io.lineno.should == 0
 
@@ -40,6 +59,25 @@ describe "IO#lineno=" do
     -> { IOSpecs.closed_io.lineno = 5 }.should raise_error(IOError)
   end
 
+  it "raises an IOError on a write-only stream" do
+    name = tmp("io_lineno.txt")
+    begin
+      File.open(name, 'w') do |f|
+        -> { f.lineno = 0 }.should raise_error(IOError)
+      end
+    ensure
+      rm_r name
+    end
+  end
+
+  it "raises an IOError on a duplexed stream with the read side closed" do
+    cmd = platform_is(:windows) ? 'rem' : 'cat'
+    IO.popen(cmd, 'r+') do |p|
+      p.close_read
+      -> { p.lineno = 0 }.should raise_error(IOError)
+    end
+  end
+
   it "calls #to_int on a non-numeric argument" do
     obj = mock('123')
     obj.should_receive(:to_int).and_return(123)
@@ -56,8 +94,13 @@ describe "IO#lineno=" do
     @io.lineno.should == 92233
   end
 
-  it "raises TypeError on nil argument" do
-    -> { @io.lineno = nil }.should raise_error(TypeError)
+  it "raises TypeError if cannot convert argument to Integer implicitly" do
+    -> { @io.lineno = "1" }.should raise_error(TypeError, 'no implicit conversion of String into Integer')
+    -> { @io.lineno = nil }.should raise_error(TypeError, 'no implicit conversion from nil to integer')
+  end
+
+  it "does not accept Integers that don't fit in a C int" do
+    -> { @io.lineno = 2**32 }.should raise_error(RangeError)
   end
 
   it "sets the current line number to the given value" do
diff --git a/spec/ruby/core/io/lines_spec.rb b/spec/ruby/core/io/lines_spec.rb
deleted file mode 100644
index a8b8023a2a..0000000000
--- a/spec/ruby/core/io/lines_spec.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-# -*- encoding: utf-8 -*-
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-
-describe "IO#lines" do
-  before :each do
-    @io = IOSpecs.io_fixture "lines.txt"
-  end
-
-  after :each do
-    @io.close if @io
-  end
-
-  it "returns an Enumerator" do
-    @io.lines.should be_an_instance_of(Enumerator)
-  end
-
-  describe "when no block is given" do
-    it "returns an Enumerator" do
-      @io.lines.should be_an_instance_of(Enumerator)
-    end
-
-    describe "returned Enumerator" do
-      describe "size" do
-        it "should return nil" do
-          @io.lines.size.should == nil
-        end
-      end
-    end
-  end
-
-  it "returns a line when accessed" do
-    enum = @io.lines
-    enum.first.should == IOSpecs.lines[0]
-  end
-
-  it "yields each line to the passed block" do
-    ScratchPad.record []
-    @io.lines { |s| ScratchPad << s }
-    ScratchPad.recorded.should == IOSpecs.lines
-  end
-end
diff --git a/spec/ruby/core/io/new_spec.rb b/spec/ruby/core/io/new_spec.rb
index 3597098caf..979ac0efcb 100644
--- a/spec/ruby/core/io/new_spec.rb
+++ b/spec/ruby/core/io/new_spec.rb
@@ -1,8 +1,16 @@
 require_relative '../../spec_helper'
 require_relative 'shared/new'
 
+# NOTE: should be synchronized with library/stringio/initialize_spec.rb
+
 describe "IO.new" do
   it_behaves_like :io_new, :new
+
+  it "does not use the given block and warns to use IO::open" do
+    -> {
+      @io = IO.send(@method, @fd) { raise }
+    }.should complain(/warning: IO::new\(\) does not take block; use IO::open\(\) instead/)
+  end
 end
 
 describe "IO.new" do
diff --git a/spec/ruby/core/io/nonblock_spec.rb b/spec/ruby/core/io/nonblock_spec.rb
new file mode 100644
index 0000000000..99dc0cafd0
--- /dev/null
+++ b/spec/ruby/core/io/nonblock_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../spec_helper'
+
+platform_is_not :windows do
+  describe "IO#nonblock?" do
+    before :all do
+      require 'io/nonblock'
+    end
+
+    it "returns false for a file by default" do
+      File.open(__FILE__) do |f|
+        f.nonblock?.should == false
+      end
+    end
+
+    it "returns true for pipe by default" do
+      r, w = IO.pipe
+      begin
+        r.nonblock?.should == true
+        w.nonblock?.should == true
+      ensure
+        r.close
+        w.close
+      end
+    end
+
+    it "returns true for socket by default" do
+      require 'socket'
+      TCPServer.open(0) do |socket|
+        socket.nonblock?.should == true
+      end
+    end
+  end
+
+  describe "IO#nonblock=" do
+    before :all do
+      require 'io/nonblock'
+    end
+
+    it "changes the IO to non-blocking mode" do
+      File.open(__FILE__) do |f|
+        f.nonblock = true
+        f.nonblock?.should == true
+        f.nonblock = false
+        f.nonblock?.should == false
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/io/open_spec.rb b/spec/ruby/core/io/open_spec.rb
index 94df5a5ef6..d151da9ce5 100644
--- a/spec/ruby/core/io/open_spec.rb
+++ b/spec/ruby/core/io/open_spec.rb
@@ -37,6 +37,19 @@ describe "IO.open" do
     ScratchPad.recorded.should == :called
   end
 
+  it "propagate an exception in the block after calling #close" do
+    -> do
+      IO.open(@fd, "w") do |io|
+        IOSpecs.io_mock(io, :close) do
+          super()
+          ScratchPad.record :called
+        end
+        raise Exception
+      end
+    end.should raise_error(Exception)
+    ScratchPad.recorded.should == :called
+  end
+
   it "propagates an exception raised by #close that is not a StandardError" do
     -> do
       IO.open(@fd, "w") do |io|
@@ -63,7 +76,7 @@ describe "IO.open" do
     ScratchPad.recorded.should == :called
   end
 
-  it "does not propagate a IOError with 'closed stream' message raised by #close" do
+  it "does not propagate an IOError with 'closed stream' message raised by #close" do
     IO.open(@fd, "w") do |io|
       IOSpecs.io_mock(io, :close) do
         super()
@@ -74,7 +87,7 @@ describe "IO.open" do
     ScratchPad.recorded.should == :called
   end
 
-  it "does not set last error when a IOError with 'closed stream' raised by #close" do
+  it "does not set last error when an IOError with 'closed stream' raised by #close" do
     IO.open(@fd, "w") do |io|
       IOSpecs.io_mock(io, :close) do
         super()
diff --git a/spec/ruby/core/io/path_spec.rb b/spec/ruby/core/io/path_spec.rb
new file mode 100644
index 0000000000..798adb2163
--- /dev/null
+++ b/spec/ruby/core/io/path_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+
+describe "IO#path" do
+  it "returns the path of the file associated with the IO object" do
+    path = tmp("io_path.txt")
+    File.open(path, "w") do |file|
+      IO.new(file.fileno, path: file.path, autoclose: false).path.should == file.path
+    end
+  ensure
+    File.unlink(path)
+  end
+end
diff --git a/spec/ruby/core/io/pipe_spec.rb b/spec/ruby/core/io/pipe_spec.rb
index 5b2f18d836..aee0d9003f 100644
--- a/spec/ruby/core/io/pipe_spec.rb
+++ b/spec/ruby/core/io/pipe_spec.rb
@@ -25,6 +25,17 @@ describe "IO.pipe" do
     @r.should be_an_instance_of(IOSpecs::SubIO)
     @w.should be_an_instance_of(IOSpecs::SubIO)
   end
+
+  it "does not use IO.new method to create pipes and allows its overriding" do
+    ScratchPad.record []
+
+    # so redefined .new is not called, but original #initialize is
+    @r, @w = IOSpecs::SubIOWithRedefinedNew.pipe
+    ScratchPad.recorded.should == [:call_original_initialize, :call_original_initialize] # called 2 times - for each pipe (r and w)
+
+    @r.should be_an_instance_of(IOSpecs::SubIOWithRedefinedNew)
+    @w.should be_an_instance_of(IOSpecs::SubIOWithRedefinedNew)
+  end
 end
 
 describe "IO.pipe" do
@@ -44,8 +55,8 @@ describe "IO.pipe" do
       r, w = IO.pipe do |_r, _w|
         [_r, _w]
       end
-      r.closed?.should == true
-      w.closed?.should == true
+      r.should.closed?
+      w.should.closed?
     end
 
     it "closes both IO objects when the block raises" do
@@ -57,8 +68,8 @@ describe "IO.pipe" do
           raise RuntimeError
         end
       end.should raise_error(RuntimeError)
-      r.closed?.should == true
-      w.closed?.should == true
+      r.should.closed?
+      w.should.closed?
     end
 
     it "allows IO objects to be closed within the block" do
@@ -67,8 +78,8 @@ describe "IO.pipe" do
         _w.close
         [_r, _w]
       end
-      r.closed?.should == true
-      w.closed?.should == true
+      r.should.closed?
+      w.should.closed?
     end
   end
 end
@@ -179,7 +190,7 @@ describe "IO.pipe" do
   it "calls #to_hash to convert an options argument" do
     options = mock("io pipe encoding options")
     options.should_receive(:to_hash).and_return({ invalid: :replace })
-    IO.pipe("UTF-8", "ISO-8859-1", options) { |r, w| }
+    IO.pipe("UTF-8", "ISO-8859-1", **options) { |r, w| }
   end
 
   it "calls #to_str to convert the first argument to a String" do
diff --git a/spec/ruby/core/io/popen_spec.rb b/spec/ruby/core/io/popen_spec.rb
index 622b3a9394..6043862614 100644
--- a/spec/ruby/core/io/popen_spec.rb
+++ b/spec/ruby/core/io/popen_spec.rb
@@ -1,13 +1,22 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../process/fixtures/common'
 
 describe "IO.popen" do
+  ProcessSpecs.use_system_ruby(self)
+
   before :each do
+    @fname = tmp("IO_popen_spec")
     @io = nil
+    @var = "$FOO"
+    platform_is :windows do
+      @var = "%FOO%"
+    end
   end
 
   after :each do
-    @io.close if @io
+    @io.close if @io and !@io.closed?
+    rm_r @fname
   end
 
   it "returns an open IO" do
@@ -16,27 +25,15 @@ describe "IO.popen" do
   end
 
   it "reads a read-only pipe" do
-    @io = IO.popen(ruby_cmd('puts "foo"'), "r")
+    @io = IO.popen('echo foo', "r")
     @io.read.should == "foo\n"
   end
 
   it "raises IOError when writing a read-only pipe" do
-    @io = IO.popen(ruby_cmd('puts "foo"'), "r")
+    @io = IO.popen('echo foo', "r")
     -> { @io.write('bar') }.should raise_error(IOError)
     @io.read.should == "foo\n"
   end
-end
-
-describe "IO.popen" do
-  before :each do
-    @fname = tmp("IO_popen_spec")
-    @io = nil
-  end
-
-  after :each do
-    @io.close if @io and !@io.closed?
-    rm_r @fname
-  end
 
   it "sees an infinitely looping subprocess exit when read pipe is closed" do
     io = IO.popen ruby_cmd('r = loop{puts "y"; 0} rescue 1; exit r'), 'r'
@@ -80,10 +77,10 @@ describe "IO.popen" do
     Process.kill "KILL", pid
     @io.close
     platform_is_not :windows do
-      $?.signaled?.should == true
+      $?.should.signaled?
     end
     platform_is :windows do
-      $?.exited?.should == true
+      $?.should.exited?
     end
   end
 
@@ -97,15 +94,21 @@ describe "IO.popen" do
     mode.should_receive(:to_str).and_return("r")
     @io = IO.popen(ruby_cmd('exit 0'), mode)
   end
-end
 
-describe "IO.popen" do
-  before :each do
-    @io = nil
+  it "accepts a path using the chdir: keyword argument" do
+    path = File.dirname(@fname)
+
+    @io = IO.popen(ruby_cmd("puts Dir.pwd"), "r", chdir: path)
+    @io.read.chomp.should == path
   end
 
-  after :each do
-    @io.close if @io
+  it "accepts a path using the chdir: keyword argument and a coercible path" do
+    path = File.dirname(@fname)
+    object = mock("path")
+    object.should_receive(:to_path).and_return(path)
+
+    @io = IO.popen(ruby_cmd("puts Dir.pwd"), "r", chdir: object)
+    @io.read.chomp.should == path
   end
 
   describe "with a block" do
@@ -171,13 +174,13 @@ describe "IO.popen" do
 
   context "with a leading ENV Hash" do
     it "accepts a single String command" do
-      IO.popen({"FOO" => "bar"}, ruby_cmd('puts ENV["FOO"]')) do |io|
+      IO.popen({"FOO" => "bar"}, "echo #{@var}") do |io|
         io.read.should == "bar\n"
       end
     end
 
     it "accepts a single String command, and an IO mode" do
-      IO.popen({"FOO" => "bar"}, ruby_cmd('puts ENV["FOO"]'), "r") do |io|
+      IO.popen({"FOO" => "bar"}, "echo #{@var}", "r") do |io|
         io.read.should == "bar\n"
       end
     end
diff --git a/spec/ruby/core/io/pread_spec.rb b/spec/ruby/core/io/pread_spec.rb
index bfe6472fef..dc7bcedf3e 100644
--- a/spec/ruby/core/io/pread_spec.rb
+++ b/spec/ruby/core/io/pread_spec.rb
@@ -1,52 +1,140 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  platform_is_not :windows do
-    describe "IO#pread" do
-      before :each do
-        @fname = tmp("io_pread.txt")
-        @contents = "1234567890"
-        touch(@fname) { |f| f.write @contents }
-        @file = File.open(@fname, "r+")
-      end
+guard -> { platform_is_not :windows or ruby_version_is "3.3" } do
+  describe "IO#pread" do
+    before :each do
+      @fname = tmp("io_pread.txt")
+      @contents = "1234567890"
+      touch(@fname) { |f| f.write @contents }
+      @file = File.open(@fname, "r+")
+    end
 
-      after :each do
-        @file.close
-        rm_r @fname
-      end
+    after :each do
+      @file.close
+      rm_r @fname
+    end
 
-      it "accepts a length, and an offset" do
-        @file.pread(4, 0).should == "1234"
-        @file.pread(3, 4).should == "567"
-      end
+    it "accepts a length, and an offset" do
+      @file.pread(4, 0).should == "1234"
+      @file.pread(3, 4).should == "567"
+    end
 
-      it "accepts a length, an offset, and an output buffer" do
-        buffer = "foo"
-        @file.pread(3, 4, buffer)
-        buffer.should == "567"
-      end
+    it "accepts a length, an offset, and an output buffer" do
+      buffer = +"foo"
+      @file.pread(3, 4, buffer).should.equal?(buffer)
+      buffer.should == "567"
+    end
 
-      it "does not advance the file pointer" do
-        @file.pread(4, 0).should == "1234"
-        @file.read.should == "1234567890"
-      end
+    it "shrinks the buffer in case of less bytes read" do
+      buffer = +"foo"
+      @file.pread(1, 0, buffer)
+      buffer.should == "1"
+    end
 
-      it "raises EOFError if end-of-file is reached" do
-        -> { @file.pread(1, 10) }.should raise_error(EOFError)
-      end
+    it "grows the buffer in case of more bytes read" do
+      buffer = +"foo"
+      @file.pread(5, 0, buffer)
+      buffer.should == "12345"
+    end
 
-      it "raises IOError when file is not open in read mode" do
-        File.open(@fname, "w") do |file|
-          -> { file.pread(1, 1) }.should raise_error(IOError)
-        end
-      end
+    it "preserves the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @file.pread(10, 0, buffer)
+
+      buffer.encoding.should == Encoding::ISO_8859_1
+    end
+
+    it "does not advance the file pointer" do
+      @file.pread(4, 0).should == "1234"
+      @file.read.should == "1234567890"
+    end
+
+    it "ignores the current offset" do
+      @file.pos = 3
+      @file.pread(4, 0).should == "1234"
+    end
+
+    it "returns an empty string for maxlen = 0" do
+      @file.pread(0, 4).should == ""
+    end
+
+    it "returns a buffer for maxlen = 0 when buffer specified" do
+      buffer = +"foo"
+      @file.pread(0, 4, buffer).should.equal?(buffer)
+      buffer.should == "foo"
+    end
+
+    it "ignores the offset for maxlen = 0, even if it is out of file bounds" do
+      @file.pread(0, 400).should == ""
+    end
+
+    it "does not reset the buffer when reading with maxlen = 0" do
+      buffer = +"foo"
+      @file.pread(0, 4, buffer)
+      buffer.should == "foo"
+
+      @file.pread(0, 400, buffer)
+      buffer.should == "foo"
+    end
+
+    it "converts maxlen to Integer using #to_int" do
+      maxlen = mock('maxlen')
+      maxlen.should_receive(:to_int).and_return(4)
+      @file.pread(maxlen, 0).should == "1234"
+    end
+
+    it "converts offset to Integer using #to_int" do
+      offset = mock('offset')
+      offset.should_receive(:to_int).and_return(0)
+      @file.pread(4, offset).should == "1234"
+    end
+
+    it "converts a buffer to String using to_str" do
+      buffer = mock('buffer')
+      buffer.should_receive(:to_str).at_least(1).and_return(+"foo")
+      @file.pread(4, 0, buffer)
+      buffer.should_not.is_a?(String)
+      buffer.to_str.should == "1234"
+    end
+
+    it "raises TypeError if maxlen is not an Integer and cannot be coerced into Integer" do
+      maxlen = Object.new
+      -> { @file.pread(maxlen, 0) }.should raise_error(TypeError, 'no implicit conversion of Object into Integer')
+    end
 
-      it "raises IOError when file is closed" do
-        file = File.open(@fname, "r+")
-        file.close
+    it "raises TypeError if offset is not an Integer and cannot be coerced into Integer" do
+      offset = Object.new
+      -> { @file.pread(4, offset) }.should raise_error(TypeError, 'no implicit conversion of Object into Integer')
+    end
+
+    it "raises ArgumentError for negative values of maxlen" do
+      -> { @file.pread(-4, 0) }.should raise_error(ArgumentError, 'negative string size (or size too big)')
+    end
+
+    it "raised Errno::EINVAL for negative values of offset" do
+      -> { @file.pread(4, -1) }.should raise_error(Errno::EINVAL, /Invalid argument/)
+    end
+
+    it "raises TypeError if the buffer is not a String and cannot be coerced into String" do
+      buffer = Object.new
+      -> { @file.pread(4, 0, buffer) }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+    end
+
+    it "raises EOFError if end-of-file is reached" do
+      -> { @file.pread(1, 10) }.should raise_error(EOFError)
+    end
+
+    it "raises IOError when file is not open in read mode" do
+      File.open(@fname, "w") do |file|
         -> { file.pread(1, 1) }.should raise_error(IOError)
       end
     end
+
+    it "raises IOError when file is closed" do
+      file = File.open(@fname, "r+")
+      file.close
+      -> { file.pread(1, 1) }.should raise_error(IOError)
+    end
   end
 end
diff --git a/spec/ruby/core/io/print_spec.rb b/spec/ruby/core/io/print_spec.rb
index 2021cd5420..085852024c 100644
--- a/spec/ruby/core/io/print_spec.rb
+++ b/spec/ruby/core/io/print_spec.rb
@@ -1,18 +1,29 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe IO, "#print" do
+describe "IO#print" do
   before :each do
-    @old_separator = $\
-    $\ = '->'
+    @old_record_separator = $\
+    @old_field_separator = $,
+    suppress_warning {
+      $\ = '->'
+      $, = '^^'
+    }
     @name = tmp("io_print")
   end
 
   after :each do
-    $\ = @old_separator
+    suppress_warning {
+      $\ = @old_record_separator
+      $, = @old_field_separator
+    }
     rm_r @name
   end
 
+  it "returns nil" do
+    touch(@name) { |f| f.print.should be_nil }
+  end
+
   it "writes $_.to_s followed by $\\ (if any) to the stream if no arguments given" do
     o = mock('o')
     o.should_receive(:to_s).and_return("mockmockmock")
@@ -38,13 +49,15 @@ describe IO, "#print" do
     IO.read(@name).should == "hello#{$\}"
   end
 
-  it "writes each obj.to_s to the stream and appends $\\ (if any) given multiple objects" do
+  it "writes each obj.to_s to the stream separated by $, (if any) and appends $\\ (if any) given multiple objects" do
     o, o2 = Object.new, Object.new
     def o.to_s(); 'o'; end
     def o2.to_s(); 'o2'; end
 
-    touch(@name) { |f| f.print(o, o2) }
-    IO.read(@name).should == "#{o.to_s}#{o2.to_s}#{$\}"
+    suppress_warning {
+      touch(@name) { |f| f.print(o, o2) }
+    }
+    IO.read(@name).should == "#{o.to_s}#{$,}#{o2.to_s}#{$\}"
   end
 
   it "raises IOError on closed stream" do
diff --git a/spec/ruby/core/io/puts_spec.rb b/spec/ruby/core/io/puts_spec.rb
index 3e4b877b7f..a186ddaa5d 100644
--- a/spec/ruby/core/io/puts_spec.rb
+++ b/spec/ruby/core/io/puts_spec.rb
@@ -6,7 +6,7 @@ describe "IO#puts" do
     @before_separator = $/
     @name = tmp("io_puts.txt")
     @io = new_io @name
-    ScratchPad.record ""
+    ScratchPad.record(+"")
     def @io.write(str)
       ScratchPad << str
     end
@@ -16,7 +16,7 @@ describe "IO#puts" do
     ScratchPad.clear
     @io.close if @io
     rm_r @name
-    $/ = @before_separator
+    suppress_warning {$/ = @before_separator}
   end
 
   it "writes just a newline when given no args" do
@@ -25,7 +25,7 @@ describe "IO#puts" do
   end
 
   it "writes just a newline when given just a newline" do
-    -> { $stdout.puts "\n" }.should output_to_fd("\n", STDOUT)
+    -> { $stdout.puts "\n" }.should output_to_fd("\n", $stdout)
   end
 
   it "writes empty string with a newline when given nil as an arg" do
@@ -33,7 +33,7 @@ describe "IO#puts" do
     ScratchPad.recorded.should == "\n"
   end
 
-  it "writes empty string with a newline when when given nil as multiple args" do
+  it "writes empty string with a newline when given nil as multiple args" do
     @io.puts(nil, nil).should == nil
     ScratchPad.recorded.should == "\n\n"
   end
@@ -105,7 +105,7 @@ describe "IO#puts" do
   end
 
   it "ignores the $/ separator global" do
-    $/ = ":"
+    suppress_warning {$/ = ":"}
     @io.puts(5).should == nil
     ScratchPad.recorded.should == "5\n"
   end
diff --git a/spec/ruby/core/io/pwrite_spec.rb b/spec/ruby/core/io/pwrite_spec.rb
index 929ed08698..2bc508b37d 100644
--- a/spec/ruby/core/io/pwrite_spec.rb
+++ b/spec/ruby/core/io/pwrite_spec.rb
@@ -1,45 +1,69 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  platform_is_not :windows do
-    describe "IO#pwrite" do
-      before :each do
-        @fname = tmp("io_pwrite.txt")
-        @file = File.open(@fname, "w+")
-      end
+guard -> { platform_is_not :windows or ruby_version_is "3.3" } do
+  describe "IO#pwrite" do
+    before :each do
+      @fname = tmp("io_pwrite.txt")
+      @file = File.open(@fname, "w+")
+    end
 
-      after :each do
-        @file.close
-        rm_r @fname
-      end
+    after :each do
+      @file.close
+      rm_r @fname
+    end
 
-      it "returns the number of bytes written" do
-        @file.pwrite("foo", 0).should == 3
-      end
+    it "returns the number of bytes written" do
+      @file.pwrite("foo", 0).should == 3
+    end
 
-      it "accepts a string and an offset"  do
-        @file.pwrite("foo", 2)
-        @file.pread(3, 2).should == "foo"
-      end
+    it "accepts a string and an offset"  do
+      @file.pwrite("foo", 2)
+      @file.pread(3, 2).should == "foo"
+    end
 
-      it "does not advance the pointer in the file" do
-        @file.pwrite("bar", 3)
-        @file.write("foo")
-        @file.pread(6, 0).should == "foobar"
-      end
+    it "does not advance the pointer in the file" do
+      @file.pwrite("bar", 3)
+      @file.write("foo")
+      @file.pread(6, 0).should == "foobar"
+    end
 
-      it "raises IOError when file is not open in write mode" do
-        File.open(@fname, "r") do |file|
-          -> { file.pwrite("foo", 1) }.should raise_error(IOError)
-        end
-      end
+    it "calls #to_s on the object to be written" do
+      object = mock("to_s")
+      object.should_receive(:to_s).and_return("foo")
+      @file.pwrite(object, 0)
+      @file.pread(3, 0).should == "foo"
+    end
 
-      it "raises IOError when file is closed" do
-        file = File.open(@fname, "w+")
-        file.close
-        -> { file.pwrite("foo", 1) }.should raise_error(IOError)
+    it "calls #to_int on the offset" do
+      offset = mock("to_int")
+      offset.should_receive(:to_int).and_return(2)
+      @file.pwrite("foo", offset)
+      @file.pread(3, 2).should == "foo"
+    end
+
+    it "raises IOError when file is not open in write mode" do
+      File.open(@fname, "r") do |file|
+        -> { file.pwrite("foo", 1) }.should raise_error(IOError, "not opened for writing")
       end
     end
+
+    it "raises IOError when file is closed" do
+      file = File.open(@fname, "w+")
+      file.close
+      -> { file.pwrite("foo", 1) }.should raise_error(IOError, "closed stream")
+    end
+
+    it "raises a NoMethodError if object does not respond to #to_s" do
+      -> {
+        @file.pwrite(BasicObject.new, 0)
+      }.should raise_error(NoMethodError, /undefined method [`']to_s'/)
+    end
+
+    it "raises a TypeError if the offset cannot be converted to an Integer" do
+      -> {
+        @file.pwrite("foo", Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
   end
 end
diff --git a/spec/ruby/core/io/read_nonblock_spec.rb b/spec/ruby/core/io/read_nonblock_spec.rb
index 63ccab5a44..51e7cd6bd2 100644
--- a/spec/ruby/core/io/read_nonblock_spec.rb
+++ b/spec/ruby/core/io/read_nonblock_spec.rb
@@ -46,7 +46,7 @@ describe "IO#read_nonblock" do
       require 'io/nonblock'
       @write.write "abc"
       @read.read_nonblock(1).should == "a"
-      @read.nonblock?.should == true
+      @read.should.nonblock?
     end
   end
 
@@ -55,6 +55,27 @@ describe "IO#read_nonblock" do
     @read.read_nonblock(4).should == "hell"
   end
 
+  it "reads after ungetc with data in the buffer" do
+    @write.write("foobar")
+    @read.set_encoding(
+      'utf-8', universal_newline: false
+    )
+    c = @read.getc
+    @read.ungetc(c)
+    @read.read_nonblock(3).should == "foo"
+    @read.read_nonblock(3).should == "bar"
+  end
+
+  it "raises an exception after ungetc with data in the buffer and character conversion enabled" do
+    @write.write("foobar")
+    @read.set_encoding(
+      'utf-8', universal_newline: true
+    )
+    c = @read.getc
+    @read.ungetc(c)
+    -> { @read.read_nonblock(3).should == "foo" }.should raise_error(IOError)
+  end
+
   it "returns less data if that is all that is available" do
     @write << "hello"
     @read.read_nonblock(10).should == "hello"
@@ -70,20 +91,39 @@ describe "IO#read_nonblock" do
     @read.read_nonblock(1).should == "1"
   end
 
+  it "raises ArgumentError when length is less than 0" do
+    -> { @read.read_nonblock(-1) }.should raise_error(ArgumentError)
+  end
+
   it "reads into the passed buffer" do
-    buffer = ""
+    buffer = +""
     @write.write("1")
     @read.read_nonblock(1, buffer)
     buffer.should == "1"
   end
 
   it "returns the passed buffer" do
-    buffer = ""
+    buffer = +""
     @write.write("1")
     output = @read.read_nonblock(1, buffer)
     output.should equal(buffer)
   end
 
+  it "discards the existing buffer content upon successful read" do
+    buffer = +"existing content"
+    @write.write("hello world")
+    @write.close
+    @read.read_nonblock(11, buffer)
+    buffer.should == "hello world"
+  end
+
+  it "discards the existing buffer content upon error" do
+    buffer = +"existing content"
+    @write.close
+    -> { @read.read_nonblock(1, buffer) }.should raise_error(EOFError)
+    buffer.should be_empty
+  end
+
   it "raises IOError on closed stream" do
     -> { IOSpecs.closed_io.read_nonblock(5) }.should raise_error(IOError)
   end
@@ -96,4 +136,13 @@ describe "IO#read_nonblock" do
 
     -> { @read.read_nonblock(5) }.should raise_error(EOFError)
   end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @write.write("abc")
+    @write.close
+    @read.read_nonblock(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
 end
diff --git a/spec/ruby/core/io/read_spec.rb b/spec/ruby/core/io/read_spec.rb
index 267d840cd3..988ec2ce30 100644
--- a/spec/ruby/core/io/read_spec.rb
+++ b/spec/ruby/core/io/read_spec.rb
@@ -23,36 +23,72 @@ describe "IO.read" do
     IO.read(p)
   end
 
+  # https://bugs.ruby-lang.org/issues/19354
+  it "accepts options as keyword arguments" do
+    IO.read(@fname, 3, 0, mode: "r+").should == @contents[0, 3]
+
+    -> {
+      IO.read(@fname, 3, 0, {mode: "r+"})
+    }.should raise_error(ArgumentError, /wrong number of arguments/)
+  end
+
   it "accepts an empty options Hash" do
-    IO.read(@fname, {}).should == @contents
+    IO.read(@fname, **{}).should == @contents
   end
 
   it "accepts a length, and empty options Hash" do
-    IO.read(@fname, 3, {}).should == @contents[0, 3]
+    IO.read(@fname, 3, **{}).should == @contents[0, 3]
   end
 
   it "accepts a length, offset, and empty options Hash" do
-    IO.read(@fname, 3, 0, {}).should == @contents[0, 3]
+    IO.read(@fname, 3, 0, **{}).should == @contents[0, 3]
   end
 
   it "raises an IOError if the options Hash specifies write mode" do
-    -> { IO.read(@fname, 3, 0, {mode: "w"}) }.should raise_error(IOError)
+    -> { IO.read(@fname, 3, 0, mode: "w") }.should raise_error(IOError)
   end
 
   it "raises an IOError if the options Hash specifies append only mode" do
-    -> { IO.read(@fname, {mode: "a"}) }.should raise_error(IOError)
+    -> { IO.read(@fname, mode: "a") }.should raise_error(IOError)
   end
 
   it "reads the file if the options Hash includes read mode" do
-    IO.read(@fname, {mode: "r"}).should == @contents
+    IO.read(@fname, mode: "r").should == @contents
   end
 
   it "reads the file if the options Hash includes read/write mode" do
-    IO.read(@fname, {mode: "r+"}).should == @contents
+    IO.read(@fname, mode: "r+").should == @contents
   end
 
   it "reads the file if the options Hash includes read/write append mode" do
-    IO.read(@fname, {mode: "a+"}).should == @contents
+    IO.read(@fname, mode: "a+").should == @contents
+  end
+
+  platform_is_not :windows do
+    ruby_version_is ""..."3.3" do
+      it "uses an :open_args option" do
+        string = IO.read(@fname, nil, 0, open_args: ["r", nil, {encoding: Encoding::US_ASCII}])
+        string.encoding.should == Encoding::US_ASCII
+
+        string = IO.read(@fname, nil, 0, open_args: ["r", nil, {}])
+        string.encoding.should == Encoding::UTF_8
+      end
+    end
+  end
+
+  it "disregards other options if :open_args is given" do
+    string = IO.read(@fname,mode: "w", encoding: Encoding::UTF_32LE, open_args: ["r", encoding: Encoding::UTF_8])
+    string.encoding.should == Encoding::UTF_8
+  end
+
+  it "doesn't require mode to be specified in :open_args" do
+    string = IO.read(@fname, nil, 0, open_args: [{encoding: Encoding::US_ASCII}])
+    string.encoding.should == Encoding::US_ASCII
+  end
+
+  it "doesn't require mode to be specified in :open_args even if flags option passed" do
+    string = IO.read(@fname, nil, 0, open_args: [{encoding: Encoding::US_ASCII, flags: File::CREAT}])
+    string.encoding.should == Encoding::US_ASCII
   end
 
   it "treats second nil argument as no length limit" do
@@ -77,6 +113,15 @@ describe "IO.read" do
     IO.read(@fname, 1, 10).should == nil
   end
 
+  it "returns an empty string when reading zero bytes" do
+    IO.read(@fname, 0).should == ''
+  end
+
+  it "returns a String in BINARY when passed a size" do
+    IO.read(@fname, 1).encoding.should == Encoding::BINARY
+    IO.read(@fname, 0).encoding.should == Encoding::BINARY
+  end
+
   it "raises an Errno::ENOENT when the requested file does not exist" do
     rm_r @fname
     -> { IO.read @fname }.should raise_error(Errno::ENOENT)
@@ -90,9 +135,18 @@ describe "IO.read" do
     -> { IO.read @fname, -1 }.should raise_error(ArgumentError)
   end
 
-  it "raises an Errno::EINVAL when not passed a valid offset" do
-    -> { IO.read @fname, 0, -1  }.should raise_error(Errno::EINVAL)
-    -> { IO.read @fname, -1, -1 }.should raise_error(Errno::EINVAL)
+  ruby_version_is ''...'3.3' do
+    it "raises an Errno::EINVAL when not passed a valid offset" do
+      -> { IO.read @fname, 0, -1  }.should raise_error(Errno::EINVAL)
+      -> { IO.read @fname, -1, -1 }.should raise_error(Errno::EINVAL)
+    end
+  end
+
+  ruby_version_is '3.3' do
+    it "raises an ArgumentError when not passed a valid offset" do
+      -> { IO.read @fname, 0, -1  }.should raise_error(ArgumentError)
+      -> { IO.read @fname, -1, -1 }.should raise_error(ArgumentError)
+    end
   end
 
   it "uses the external encoding specified via the :external_encoding option" do
@@ -104,57 +158,91 @@ describe "IO.read" do
     str = IO.read(@fname, encoding: Encoding::ISO_8859_1)
     str.encoding.should == Encoding::ISO_8859_1
   end
-end
 
-describe "IO.read from a pipe" do
-  it "runs the rest as a subprocess and returns the standard output" do
-    cmd = "|sh -c 'echo hello'"
-    platform_is :windows do
-      cmd = "|cmd.exe /C echo hello"
+  platform_is :windows do
+    it "reads the file in text mode" do
+      # 0x1A is CTRL+Z and is EOF in Windows text mode.
+      File.binwrite(@fname, "\x1Abbb")
+      IO.read(@fname).should.empty?
     end
-    IO.read(cmd).should == "hello\n"
   end
+end
 
-  platform_is_not :windows do
-    it "opens a pipe to a fork if the rest is -" do
-      str = IO.read("|-")
-      if str # parent
-        str.should == "hello from child\n"
-      else #child
-        puts "hello from child"
-        exit!
+ruby_version_is ""..."4.0" do
+  describe "IO.read from a pipe" do
+    it "runs the rest as a subprocess and returns the standard output" do
+      cmd = "|sh -c 'echo hello'"
+      platform_is :windows do
+        cmd = "|cmd.exe /C echo hello"
+      end
+
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        IO.read(cmd).should == "hello\n"
       end
     end
-  end
 
-  it "reads only the specified number of bytes requested" do
-    cmd = "|sh -c 'echo hello'"
-    platform_is :windows do
-      cmd = "|cmd.exe /C echo hello"
+    platform_is_not :windows do
+      it "opens a pipe to a fork if the rest is -" do
+        str = nil
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          str = IO.read("|-")
+        end
+
+        if str # parent
+          str.should == "hello from child\n"
+        else #child
+          puts "hello from child"
+          exit!
+        end
+      end
     end
-    IO.read(cmd, 1).should == "h"
-  end
 
-  platform_is_not :windows do
-    it "raises Errno::ESPIPE if passed an offset" do
-      -> {
-        IO.read("|sh -c 'echo hello'", 1, 1)
-      }.should raise_error(Errno::ESPIPE)
+    it "reads only the specified number of bytes requested" do
+      cmd = "|sh -c 'echo hello'"
+      platform_is :windows do
+        cmd = "|cmd.exe /C echo hello"
+      end
+
+      suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+        IO.read(cmd, 1).should == "h"
+      end
     end
-  end
 
-quarantine! do # The process tried to write to a nonexistent pipe.
-  platform_is :windows do
-    # TODO: It should raise Errno::ESPIPE on Windows as well
-    # once https://bugs.ruby-lang.org/issues/12230 is fixed.
-    it "raises Errno::EINVAL if passed an offset" do
-      -> {
-        IO.read("|cmd.exe /C echo hello", 1, 1)
-      }.should raise_error(Errno::EINVAL)
+    platform_is_not :windows do
+      it "raises Errno::ESPIPE if passed an offset" do
+        -> {
+          suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+            IO.read("|sh -c 'echo hello'", 1, 1)
+          end
+        }.should raise_error(Errno::ESPIPE)
+      end
+    end
+
+    quarantine! do # The process tried to write to a nonexistent pipe.
+      platform_is :windows do
+        # TODO: It should raise Errno::ESPIPE on Windows as well
+        # once https://bugs.ruby-lang.org/issues/12230 is fixed.
+        it "raises Errno::EINVAL if passed an offset" do
+          -> {
+            suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+              IO.read("|cmd.exe /C echo hello", 1, 1)
+            end
+          }.should raise_error(Errno::EINVAL)
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation" do
+        cmd = "|echo ok"
+        -> {
+          IO.read(cmd)
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
     end
   end
 end
-end
 
 describe "IO.read on an empty file" do
   before :each do
@@ -197,26 +285,60 @@ describe "IO#read" do
     @io.read(4).should == '7890'
   end
 
+  it "treats first nil argument as no length limit" do
+    @io.read(nil).should == @contents
+  end
+
+  it "raises an ArgumentError when not passed a valid length" do
+    -> { @io.read(-1) }.should raise_error(ArgumentError)
+  end
+
   it "clears the output buffer if there is nothing to read" do
     @io.pos = 10
 
-    buf = 'non-empty string'
+    buf = +'non-empty string'
 
     @io.read(10, buf).should == nil
 
     buf.should == ''
+
+    buf = +'non-empty string'
+
+    @io.read(nil, buf).should == ""
+
+    buf.should == ''
+
+    buf = +'non-empty string'
+
+    @io.read(0, buf).should == ""
+
+    buf.should == ''
+  end
+
+  it "raise FrozenError if the output buffer is frozen" do
+    @io.read
+    -> { @io.read(0, 'frozen-string'.freeze) }.should raise_error(FrozenError)
+    -> { @io.read(1, 'frozen-string'.freeze) }.should raise_error(FrozenError)
+    -> { @io.read(nil, 'frozen-string'.freeze) }.should raise_error(FrozenError)
+  end
+
+  ruby_bug "", ""..."3.3" do
+    it "raise FrozenError if the output buffer is frozen (2)" do
+      @io.read
+      -> { @io.read(1, ''.freeze) }.should raise_error(FrozenError)
+    end
   end
 
   it "consumes zero bytes when reading zero bytes" do
     @io.read(0).should == ''
     @io.pos.should == 0
 
-    @io.getc.chr.should == '1'
+    @io.getc.should == '1'
   end
 
   it "is at end-of-file when everything has been read" do
     @io.read
-    @io.eof?.should == true
+    @io.should.eof?
   end
 
   it "reads the contents of a file" do
@@ -224,46 +346,68 @@ describe "IO#read" do
   end
 
   it "places the specified number of bytes in the buffer" do
-    buf = ""
+    buf = +""
     @io.read 5, buf
 
     buf.should == "12345"
   end
 
   it "expands the buffer when too small" do
-    buf = "ABCDE"
+    buf = +"ABCDE"
     @io.read nil, buf
 
     buf.should == @contents
   end
 
   it "overwrites the buffer" do
-    buf = "ABCDEFGHIJ"
+    buf = +"ABCDEFGHIJ"
     @io.read nil, buf
 
     buf.should == @contents
   end
 
   it "truncates the buffer when too big" do
-    buf = "ABCDEFGHIJKLMNO"
+    buf = +"ABCDEFGHIJKLMNO"
     @io.read nil, buf
     buf.should == @contents
 
     @io.rewind
 
-    buf = "ABCDEFGHIJKLMNO"
+    buf = +"ABCDEFGHIJKLMNO"
     @io.read 5, buf
     buf.should == @contents[0..4]
   end
 
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @io.read(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
+  # https://bugs.ruby-lang.org/issues/20416
+  it "does not preserve the encoding of the given buffer when max length is not provided" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @io.read(nil, buffer)
+
+    buffer.encoding.should_not == Encoding::ISO_8859_1
+  end
+
   it "returns the given buffer" do
-    buf = ""
+    buf = +""
 
     @io.read(nil, buf).should equal buf
   end
 
+  it "returns the given buffer when there is nothing to read" do
+    buf = +""
+
+    @io.read
+    @io.read(nil, buf).should equal buf
+  end
+
   it "coerces the second argument to string and uses it as a buffer" do
-    buf = "ABCDE"
+    buf = +"ABCDE"
     obj = mock("buff")
     obj.should_receive(:to_str).any_number_of_times.and_return(buf)
 
@@ -304,6 +448,9 @@ describe "IO#read" do
     -> { IOSpecs.closed_io.read }.should raise_error(IOError)
   end
 
+  it "raises ArgumentError when length is less than 0" do
+    -> { @io.read(-1) }.should raise_error(ArgumentError)
+  end
 
   platform_is_not :windows do
     it "raises IOError when stream is closed by another thread" do
@@ -384,13 +531,6 @@ describe "IO#read in binary mode" do
     xE2 = [226].pack('C*')
     result.should == ("abc" + xE2 + "def").force_encoding(Encoding::BINARY)
   end
-
-  it "does not transcode file contents when an internal encoding is specified" do
-    result = File.open(@name, "r:binary:utf-8") { |f| f.read }.chomp
-    result.encoding.should == Encoding::BINARY
-    xE2 = [226].pack('C*')
-    result.should == ("abc" + xE2 + "def").force_encoding(Encoding::BINARY)
-  end
 end
 
 describe "IO#read in text mode" do
@@ -465,13 +605,13 @@ describe :io_read_internal_encoding, shared: true do
 
   describe "when passed nil for limit" do
     it "sets the buffer to a transcoded String" do
-      result = @io.read(nil, buf = "")
+      result = @io.read(nil, buf = +"")
       buf.should equal(result)
       buf.should == "ありがとう\n"
     end
 
     it "sets the buffer's encoding to the internal encoding" do
-      buf = "".force_encoding Encoding::ISO_8859_1
+      buf = "".dup.force_encoding Encoding::ISO_8859_1
       @io.read(nil, buf)
       buf.encoding.should equal(Encoding::UTF_8)
     end
@@ -485,17 +625,18 @@ describe :io_read_size_internal_encoding, shared: true do
 
   it "returns a String in BINARY when passed a size" do
     @io.read(4).encoding.should equal(Encoding::BINARY)
+    @io.read(0).encoding.should equal(Encoding::BINARY)
   end
 
   it "does not change the buffer's encoding when passed a limit" do
-    buf = "".force_encoding Encoding::ISO_8859_1
+    buf = "".dup.force_encoding Encoding::ISO_8859_1
     @io.read(4, buf)
     buf.should == [164, 162, 164, 234].pack('C*').force_encoding(Encoding::ISO_8859_1)
     buf.encoding.should equal(Encoding::ISO_8859_1)
   end
 
   it "truncates the buffer but does not change the buffer's encoding when no data remains" do
-    buf = "abc".force_encoding Encoding::ISO_8859_1
+    buf = "abc".dup.force_encoding Encoding::ISO_8859_1
     @io.read
 
     @io.read(1, buf).should be_nil
diff --git a/spec/ruby/core/io/readchar_spec.rb b/spec/ruby/core/io/readchar_spec.rb
index b5f762a846..a66773851a 100644
--- a/spec/ruby/core/io/readchar_spec.rb
+++ b/spec/ruby/core/io/readchar_spec.rb
@@ -1,6 +1,16 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+describe :io_readchar_internal_encoding, shared: true do
+  it "returns a transcoded String" do
+    @io.readchar.should == "あ"
+  end
+
+  it "sets the String encoding to the internal encoding" do
+    @io.readchar.encoding.should equal(Encoding::UTF_8)
+  end
+end
+
 describe "IO#readchar" do
   before :each do
     @io = IOSpecs.io_fixture "lines.txt"
@@ -29,6 +39,62 @@ describe "IO#readchar" do
   end
 end
 
+describe "IO#readchar with internal encoding" do
+  after :each do
+    @io.close if @io
+  end
+
+  describe "not specified" do
+    before :each do
+      @io = IOSpecs.io_fixture "read_euc_jp.txt", "r:euc-jp"
+    end
+
+    it "does not transcode the String" do
+      @io.readchar.should == ("あ").encode(Encoding::EUC_JP)
+    end
+
+    it "sets the String encoding to the external encoding" do
+      @io.readchar.encoding.should equal(Encoding::EUC_JP)
+    end
+  end
+
+  describe "specified by open mode" do
+    before :each do
+      @io = IOSpecs.io_fixture "read_euc_jp.txt", "r:euc-jp:utf-8"
+    end
+
+    it_behaves_like :io_readchar_internal_encoding, nil
+  end
+
+  describe "specified by mode: option" do
+    before :each do
+      @io = IOSpecs.io_fixture "read_euc_jp.txt", mode: "r:euc-jp:utf-8"
+    end
+
+    it_behaves_like :io_readchar_internal_encoding, nil
+  end
+
+  describe "specified by internal_encoding: option" do
+    before :each do
+      options = { mode: "r",
+                  internal_encoding: "utf-8",
+                  external_encoding: "euc-jp" }
+      @io = IOSpecs.io_fixture "read_euc_jp.txt", options
+    end
+
+    it_behaves_like :io_readchar_internal_encoding, nil
+  end
+
+  describe "specified by encoding: option" do
+    before :each do
+      options = { mode: "r", encoding: "euc-jp:utf-8" }
+      @io = IOSpecs.io_fixture "read_euc_jp.txt", options
+    end
+
+    it_behaves_like :io_readchar_internal_encoding, nil
+  end
+end
+
 describe "IO#readchar" do
   before :each do
     @io = IOSpecs.io_fixture "empty.txt"
diff --git a/spec/ruby/core/io/readline_spec.rb b/spec/ruby/core/io/readline_spec.rb
index 7cb1601816..a814c1be90 100644
--- a/spec/ruby/core/io/readline_spec.rb
+++ b/spec/ruby/core/io/readline_spec.rb
@@ -43,9 +43,42 @@ describe "IO#readline" do
     end
   end
 
+  describe "when passed limit" do
+    it "reads limit bytes" do
+      @io.readline(3).should == "Voi"
+    end
+
+    it "returns an empty string when passed 0 as a limit" do
+      @io.readline(0).should == ""
+    end
+
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.readline(2**128) }.should raise_error(RangeError)
+    end
+  end
+
+  describe "when passed separator and limit" do
+    it "reads limit bytes till the separator" do
+      # Voici la ligne une.\
+      @io.readline(" ", 4).should == "Voic"
+      @io.readline(" ", 4).should == "i "
+      @io.readline(" ", 4).should == "la "
+      @io.readline(" ", 4).should == "lign"
+      @io.readline(" ", 4).should == "e "
+    end
+  end
+
   describe "when passed chomp" do
     it "returns the first line without a trailing newline character" do
       @io.readline(chomp: true).should == IOSpecs.lines_without_newline_characters[0]
     end
+
+    it "raises exception when options passed as Hash" do
+      -> { @io.readline({ chomp: true }) }.should raise_error(TypeError)
+
+      -> {
+        @io.readline("\n", 1, { chomp: true })
+      }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
+    end
   end
 end
diff --git a/spec/ruby/core/io/readlines_spec.rb b/spec/ruby/core/io/readlines_spec.rb
index 0d4f002972..b4770775d1 100644
--- a/spec/ruby/core/io/readlines_spec.rb
+++ b/spec/ruby/core/io/readlines_spec.rb
@@ -22,11 +22,11 @@ describe "IO#readlines" do
 
   describe "when passed no arguments" do
     before :each do
-      @sep, $/ = $/, " "
+      suppress_warning {@sep, $/ = $/, " "}
     end
 
     after :each do
-      $/ = @sep
+      suppress_warning {$/ = @sep}
     end
 
     it "returns an Array containing lines based on $/" do
@@ -102,28 +102,33 @@ describe "IO#readlines" do
     end
   end
 
-  describe "when passed a string that starts with a |" do
-    it "gets data from the standard out of the subprocess" do
-      cmd = "|sh -c 'echo hello;echo line2'"
-      platform_is :windows do
-        cmd = "|cmd.exe /C echo hello&echo line2"
-      end
-      lines = IO.readlines(cmd)
-      lines.should == ["hello\n", "line2\n"]
+  describe "when passed limit" do
+    it "raises ArgumentError when passed 0 as a limit" do
+      -> { @io.readlines(0) }.should raise_error(ArgumentError)
     end
 
-    platform_is_not :windows do
-      it "gets data from a fork when passed -" do
-        lines = IO.readlines("|-")
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.readlines(2**128) }.should raise_error(RangeError)
+    end
+  end
 
-        if lines # parent
-          lines.should == ["hello\n", "from a fork\n"]
-        else
-          puts "hello"
-          puts "from a fork"
-          exit!
-        end
-      end
+  describe "when passed chomp" do
+    it "returns the first line without a trailing newline character" do
+      @io.readlines(chomp: true).should == IOSpecs.lines_without_newline_characters
+    end
+
+    it "raises exception when options passed as Hash" do
+      -> { @io.readlines({ chomp: true }) }.should raise_error(TypeError)
+
+      -> {
+        @io.readlines("\n", 1, { chomp: true })
+      }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
+    end
+  end
+
+  describe "when passed arbitrary keyword argument" do
+    it "tolerates it" do
+      @io.readlines(chomp: true, foo: :bar).should == IOSpecs.lines_without_newline_characters
     end
   end
 end
@@ -169,6 +174,50 @@ describe "IO.readlines" do
     $_.should == "test"
   end
 
+  ruby_version_is ""..."4.0" do
+    describe "when passed a string that starts with a |" do
+      it "gets data from the standard out of the subprocess" do
+        cmd = "|sh -c 'echo hello;echo line2'"
+        platform_is :windows do
+          cmd = "|cmd.exe /C echo hello&echo line2"
+        end
+
+        lines = nil
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          lines = IO.readlines(cmd)
+        end
+        lines.should == ["hello\n", "line2\n"]
+      end
+
+      platform_is_not :windows do
+        it "gets data from a fork when passed -" do
+          lines = nil
+          suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+            lines = IO.readlines("|-")
+          end
+
+          if lines # parent
+            lines.should == ["hello\n", "from a fork\n"]
+          else
+            puts "hello"
+            puts "from a fork"
+            exit!
+          end
+        end
+      end
+    end
+
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        cmd = "|echo ok"
+        -> {
+          IO.readlines(cmd)
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
+    end
+  end
+
   it_behaves_like :io_readlines, :readlines
   it_behaves_like :io_readlines_options_19, :readlines
 end
@@ -184,7 +233,7 @@ describe "IO.readlines" do
   after :each do
     Encoding.default_external = @external
     Encoding.default_internal = @internal
-    $/ = @dollar_slash
+    suppress_warning {$/ = @dollar_slash}
   end
 
   it "encodes lines using the default external encoding" do
@@ -196,7 +245,7 @@ describe "IO.readlines" do
   it "encodes lines using the default internal encoding, when set" do
     Encoding.default_external = Encoding::UTF_8
     Encoding.default_internal = Encoding::UTF_16
-    $/ = $/.encode Encoding::UTF_16
+    suppress_warning {$/ = $/.encode Encoding::UTF_16}
     lines = IO.readlines(@name)
     lines.all? { |s| s.encoding == Encoding::UTF_16 }.should be_true
   end
diff --git a/spec/ruby/core/io/readpartial_spec.rb b/spec/ruby/core/io/readpartial_spec.rb
index 2b33a0d5b1..176c33cf9e 100644
--- a/spec/ruby/core/io/readpartial_spec.rb
+++ b/spec/ruby/core/io/readpartial_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -59,10 +59,10 @@ describe "IO#readpartial" do
   end
 
   it "discards the existing buffer content upon successful read" do
-    buffer = "existing"
+    buffer = +"existing content"
     @wr.write("hello world")
     @wr.close
-    @rd.readpartial(11, buffer)
+    @rd.readpartial(11, buffer).should.equal?(buffer)
     buffer.should == "hello world"
   end
 
@@ -74,7 +74,7 @@ describe "IO#readpartial" do
   end
 
   it "discards the existing buffer content upon error" do
-    buffer = 'hello'
+    buffer = +'hello'
     @wr.close
     -> { @rd.readpartial(1, buffer) }.should raise_error(EOFError)
     buffer.should be_empty
@@ -93,4 +93,23 @@ describe "IO#readpartial" do
     @rd.readpartial(0).should == ""
   end
 
+  it "raises IOError if the stream is closed and the length argument is 0" do
+    @rd.close
+    -> { @rd.readpartial(0) }.should raise_error(IOError, "closed stream")
+  end
+
+  it "clears and returns the given buffer if the length argument is 0" do
+    buffer = +"existing content"
+    @rd.readpartial(0, buffer).should == buffer
+    buffer.should == ""
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    @wr.write("abc")
+    @wr.close
+    @rd.readpartial(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
 end
diff --git a/spec/ruby/core/io/reopen_spec.rb b/spec/ruby/core/io/reopen_spec.rb
index 133ff03ea5..8ff0f217f4 100644
--- a/spec/ruby/core/io/reopen_spec.rb
+++ b/spec/ruby/core/io/reopen_spec.rb
@@ -150,25 +150,25 @@ describe "IO#reopen with a String" do
 
     @io.close_on_exec = true
     @io.reopen @other_name
-    @io.close_on_exec?.should == true
+    @io.should.close_on_exec?
 
     @io.close_on_exec = false
     @io.reopen @other_name
-    @io.close_on_exec?.should == true
+    @io.should.close_on_exec?
   end
 
   it "creates the file if it doesn't exist if the IO is opened in write mode" do
     @io = new_io @name, "w"
 
     @io.reopen(@other_name)
-    File.exist?(@other_name).should be_true
+    File.should.exist?(@other_name)
   end
 
   it "creates the file if it doesn't exist if the IO is opened in write mode" do
     @io = new_io @name, "a"
 
     @io.reopen(@other_name)
-    File.exist?(@other_name).should be_true
+    File.should.exist?(@other_name)
   end
 end
 
@@ -230,7 +230,7 @@ describe "IO#reopen with an IO" do
     end
 
     @io = new_io @name
-    @other_io = new_io @other_name, "r"
+    @other_io = IO.new(new_fd(@other_name, "r"), "r")
   end
 
   after :each do
@@ -293,12 +293,12 @@ describe "IO#reopen with an IO" do
     @other_io.close_on_exec = true
     @io.close_on_exec = true
     @io.reopen @other_io
-    @io.close_on_exec?.should == true
+    @io.should.close_on_exec?
 
     @other_io.close_on_exec = false
     @io.close_on_exec = false
     @io.reopen @other_io
-    @io.close_on_exec?.should == true
+    @io.should.close_on_exec?
   end
 
   it "may change the class of the instance" do
diff --git a/spec/ruby/core/io/rewind_spec.rb b/spec/ruby/core/io/rewind_spec.rb
index 954d56d30c..5579cbd988 100644
--- a/spec/ruby/core/io/rewind_spec.rb
+++ b/spec/ruby/core/io/rewind_spec.rb
@@ -18,10 +18,21 @@ describe "IO#rewind" do
     @io.readline.should == "Voici la ligne une.\n"
   end
 
+  it "positions the instance to the beginning of output for write-only IO" do
+    name = tmp("io_rewind_spec")
+    io = File.open(name, "w")
+    io.write("Voici la ligne une.\n")
+    io.rewind
+    io.pos.should == 0
+  ensure
+    io.close
+    rm_r name
+  end
+
   it "positions the instance to the beginning of input and clears EOF" do
     value = @io.read
     @io.rewind
-    @io.eof?.should == false
+    @io.should_not.eof?
     value.should == @io.read
   end
 
@@ -32,6 +43,10 @@ describe "IO#rewind" do
     @io.lineno.should == 0
   end
 
+  it "returns 0" do
+    @io.rewind.should == 0
+  end
+
   it "raises IOError on closed stream" do
     -> { IOSpecs.closed_io.rewind }.should raise_error(IOError)
   end
diff --git a/spec/ruby/core/io/seek_spec.rb b/spec/ruby/core/io/seek_spec.rb
index 7e9c308272..2fa4a73ac9 100644
--- a/spec/ruby/core/io/seek_spec.rb
+++ b/spec/ruby/core/io/seek_spec.rb
@@ -44,21 +44,21 @@ describe "IO#seek" do
   it "moves the read position and clears EOF with SEEK_SET" do
     value = @io.read
     @io.seek(0, IO::SEEK_SET)
-    @io.eof?.should == false
+    @io.should_not.eof?
     value.should == @io.read
   end
 
   it "moves the read position and clears EOF with SEEK_CUR" do
     value = @io.read
     @io.seek(-1, IO::SEEK_CUR)
-    @io.eof?.should == false
+    @io.should_not.eof?
     value[-1].should == @io.read[0]
   end
 
   it "moves the read position and clears EOF with SEEK_END" do
     value = @io.read
     @io.seek(-1, IO::SEEK_END)
-    @io.eof?.should == false
+    @io.should_not.eof?
     value[-1].should == @io.read[0]
   end
 
diff --git a/spec/ruby/core/io/select_spec.rb b/spec/ruby/core/io/select_spec.rb
index 4603c1fbbc..3893e7620f 100644
--- a/spec/ruby/core/io/select_spec.rb
+++ b/spec/ruby/core/io/select_spec.rb
@@ -55,8 +55,8 @@ describe "IO.select" do
     end
   end
 
-  it "returns supplied objects correctly even when monitoring the same object in different arrays" do
-    filename = tmp("IO_select_pipe_file") + $$.to_s
+  it "returns supplied objects correctly when monitoring the same object in different arrays" do
+    filename = tmp("IO_select_pipe_file")
     io = File.open(filename, 'w+')
     result = IO.select [io], [io], nil, 0
     result.should == [[io], [io], []]
@@ -64,6 +64,17 @@ describe "IO.select" do
     rm_r filename
   end
 
+  it "returns the pipe read end in read set if the pipe write end is closed concurrently" do
+    main = Thread.current
+    t = Thread.new {
+      Thread.pass until main.stop?
+      @wr.close
+    }
+    IO.select([@rd]).should == [[@rd], [], []]
+  ensure
+    t.join
+  end
+
   it "invokes to_io on supplied objects that are not IO and returns the supplied objects" do
     # make some data available
     @wr.write("foobar")
@@ -103,6 +114,39 @@ describe "IO.select" do
   it "raises an ArgumentError when passed a negative timeout" do
     -> { IO.select(nil, nil, nil, -5)}.should raise_error(ArgumentError)
   end
+
+  describe "returns the available descriptors when the file descriptor" do
+    it "is in both read and error arrays" do
+      @wr.write("foobar")
+      result = IO.select([@rd], nil, [@rd])
+      result.should == [[@rd], [], []]
+    end
+
+    it "is in both write and error arrays" do
+      result = IO.select(nil, [@wr], [@wr])
+      result.should == [[], [@wr], []]
+    end
+
+    it "is in both read and write arrays" do
+      filename = tmp("IO_select_read_write_file")
+      w = File.open(filename, 'w+')
+      begin
+        IO.select([w], [w], []).should == [[w], [w], []]
+      ensure
+        w.close
+        rm_r filename
+      end
+
+      IO.select([@wr], [@wr], []).should == [[], [@wr], []]
+
+      @wr.write("foobar")
+      # CRuby on macOS returns [[@rd], [@rd], []], weird but we accept it here, probably only for pipe read-end
+      [
+        [[@rd], [], []],
+        [[@rd], [@rd], []]
+      ].should.include? IO.select([@rd], [@rd], [])
+    end
+  end
 end
 
 describe "IO.select when passed nil for timeout" do
diff --git a/spec/ruby/core/io/set_encoding_by_bom_spec.rb b/spec/ruby/core/io/set_encoding_by_bom_spec.rb
new file mode 100644
index 0000000000..30d5ce5a5a
--- /dev/null
+++ b/spec/ruby/core/io/set_encoding_by_bom_spec.rb
@@ -0,0 +1,262 @@
+require_relative '../../spec_helper'
+
+describe "IO#set_encoding_by_bom" do
+  before :each do
+    @name = tmp('io_set_encoding_by_bom.txt')
+    touch(@name)
+    @io = new_io(@name, 'rb')
+  end
+
+  after :each do
+    @io.close unless @io.closed?
+    rm_r @name
+  end
+
+  it "returns nil if not readable" do
+    not_readable_io = new_io(@name, 'wb')
+
+    not_readable_io.set_encoding_by_bom.should be_nil
+    not_readable_io.external_encoding.should == Encoding::ASCII_8BIT
+  ensure
+    not_readable_io.close
+  end
+
+  it "returns the result encoding if found BOM UTF-8 sequence" do
+    File.binwrite(@name, "\u{FEFF}")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_8
+    @io.external_encoding.should == Encoding::UTF_8
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\u{FEFF}abc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_8
+    @io.external_encoding.should == Encoding::UTF_8
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16LE sequence" do
+    File.binwrite(@name, "\xFF\xFE")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFF\xFEabc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16BE sequence" do
+    File.binwrite(@name, "\xFE\xFF")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    @io.external_encoding.should == Encoding::UTF_16BE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFE\xFFabcd")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    @io.external_encoding.should == Encoding::UTF_16BE
+    @io.read.b.should == "abcd".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32LE sequence" do
+    File.binwrite(@name, "\xFF\xFE\x00\x00")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    @io.external_encoding.should == Encoding::UTF_32LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\xFF\xFE\x00\x00abc")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    @io.external_encoding.should == Encoding::UTF_32LE
+    @io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32BE sequence" do
+    File.binwrite(@name, "\x00\x00\xFE\xFF")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    @io.external_encoding.should == Encoding::UTF_32BE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.binwrite(@name, "\x00\x00\xFE\xFFabcd")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    @io.external_encoding.should == Encoding::UTF_32BE
+    @io.read.b.should == "abcd".b
+  end
+
+  it "returns nil if io is empty" do
+    @io.set_encoding_by_bom.should be_nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+  end
+
+  it "returns nil if UTF-8 BOM sequence is incomplete" do
+    File.write(@name, "\xEF")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF".b
+    @io.rewind
+
+    File.write(@name, "\xEFa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEFa".b
+    @io.rewind
+
+    File.write(@name, "\xEF\xBB")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF\xBB".b
+    @io.rewind
+
+    File.write(@name, "\xEF\xBBa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xEF\xBBa".b
+  end
+
+  it "returns nil if UTF-16BE BOM sequence is incomplete" do
+    File.write(@name, "\xFE")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFE".b
+    @io.rewind
+
+    File.write(@name, "\xFEa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFEa".b
+  end
+
+  it "returns nil if UTF-16LE/UTF-32LE BOM sequence is incomplete" do
+    File.write(@name, "\xFF")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFF".b
+    @io.rewind
+
+    File.write(@name, "\xFFa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\xFFa".b
+  end
+
+  it "returns UTF-16LE if UTF-32LE BOM sequence is incomplete" do
+    File.write(@name, "\xFF\xFE")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.write(@name, "\xFF\xFE\x00")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "\x00".b
+    @io.rewind
+    @io.set_encoding(Encoding::ASCII_8BIT)
+
+    File.write(@name, "\xFF\xFE\x00a")
+
+    @io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    @io.external_encoding.should == Encoding::UTF_16LE
+    @io.read.b.should == "\x00a".b
+  end
+
+  it "returns nil if UTF-32BE BOM sequence is incomplete" do
+    File.write(@name, "\x00")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00".b
+    @io.rewind
+
+    File.write(@name, "\x00a")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00a".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00a")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00a".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00\xFE")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00\xFE".b
+    @io.rewind
+
+    File.write(@name, "\x00\x00\xFEa")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read.b.should == "\x00\x00\xFEa".b
+  end
+
+  it "returns nil if found BOM sequence not provided" do
+    File.write(@name, "abc")
+
+    @io.set_encoding_by_bom.should == nil
+    @io.external_encoding.should == Encoding::ASCII_8BIT
+    @io.read(3).should == "abc".b
+  end
+
+  it 'returns exception if io not in binary mode' do
+    not_binary_io = new_io(@name, 'r')
+
+    -> { not_binary_io.set_encoding_by_bom }.should raise_error(ArgumentError, 'ASCII incompatible encoding needs binmode')
+  ensure
+    not_binary_io.close
+  end
+
+  it 'returns exception if encoding already set' do
+    @io.set_encoding("utf-8")
+
+    -> { @io.set_encoding_by_bom }.should raise_error(ArgumentError, 'encoding is set to UTF-8 already')
+  end
+
+  it 'returns exception if encoding conversion is already set' do
+    @io.set_encoding(Encoding::UTF_8, Encoding::UTF_16BE)
+
+    -> { @io.set_encoding_by_bom }.should raise_error(ArgumentError, 'encoding conversion is set')
+  end
+end
diff --git a/spec/ruby/core/io/set_encoding_spec.rb b/spec/ruby/core/io/set_encoding_spec.rb
index 5aec6a96c3..22d9017635 100644
--- a/spec/ruby/core/io/set_encoding_spec.rb
+++ b/spec/ruby/core/io/set_encoding_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe :io_set_encoding_write, shared: true do
-  it "sets the encodings to nil" do
+  it "sets the encodings to nil when they were set previously" do
     @io = new_io @name, "#{@object}:ibm437:ibm866"
     @io.set_encoding nil, nil
 
@@ -9,6 +9,19 @@ describe :io_set_encoding_write, shared: true do
     @io.internal_encoding.should be_nil
   end
 
+  it "sets the encodings to nil when the IO is built with no explicit encoding" do
+    @io = new_io @name, @object
+
+    # Checking our assumptions first
+    @io.external_encoding.should be_nil
+    @io.internal_encoding.should be_nil
+
+    @io.set_encoding nil, nil
+
+    @io.external_encoding.should be_nil
+    @io.internal_encoding.should be_nil
+  end
+
   it "prevents the encodings from changing when Encoding defaults are changed" do
     @io = new_io @name, "#{@object}:utf-8:us-ascii"
     @io.set_encoding nil, nil
@@ -38,6 +51,7 @@ describe "IO#set_encoding when passed nil, nil" do
     @external = Encoding.default_external
     @internal = Encoding.default_internal
 
+    # The defaults
     Encoding.default_external = Encoding::UTF_8
     Encoding.default_internal = nil
 
@@ -113,6 +127,22 @@ describe "IO#set_encoding when passed nil, nil" do
   describe "with 'a+' mode" do
     it_behaves_like :io_set_encoding_write, nil, "a+"
   end
+
+  describe "with standard IOs" do
+    it "correctly resets them" do
+      STDOUT.external_encoding.should == nil
+      STDOUT.internal_encoding.should == nil
+
+      begin
+        STDOUT.set_encoding(Encoding::US_ASCII, Encoding::ISO_8859_1)
+      ensure
+        STDOUT.set_encoding(nil, nil)
+      end
+
+      STDOUT.external_encoding.should == nil
+      STDOUT.internal_encoding.should == nil
+    end
+  end
 end
 
 describe "IO#set_encoding" do
@@ -188,4 +218,21 @@ describe "IO#set_encoding" do
     @io.external_encoding.should == Encoding::UTF_8
     @io.internal_encoding.should == Encoding::UTF_16BE
   end
+
+  it "saves encoding options passed as a hash in the last argument" do
+    File.write(@name, "\xff")
+    io = File.open(@name)
+    io.set_encoding(Encoding::EUC_JP, Encoding::SHIFT_JIS, invalid: :replace, replace: ".")
+    io.read.should == "."
+  ensure
+    io.close
+  end
+
+  it "raises ArgumentError when no arguments are given" do
+    -> { @io.set_encoding() }.should raise_error(ArgumentError)
+  end
+
+  it "raises ArgumentError when too many arguments are given" do
+    -> { @io.set_encoding(1, 2, 3) }.should raise_error(ArgumentError)
+  end
 end
diff --git a/spec/ruby/core/io/shared/binwrite.rb b/spec/ruby/core/io/shared/binwrite.rb
index 17682a1a93..e51093329b 100644
--- a/spec/ruby/core/io/shared/binwrite.rb
+++ b/spec/ruby/core/io/shared/binwrite.rb
@@ -21,12 +21,20 @@ describe :io_binwrite, shared: true do
     IO.send(@method, @filename, "abcde").should == 5
   end
 
+  it "accepts options as a keyword argument" do
+    IO.send(@method, @filename, "hi", 0, flags: File::CREAT).should == 2
+
+    -> {
+      IO.send(@method, @filename, "hi", 0, {flags: File::CREAT})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 2..3)")
+  end
+
   it "creates a file if missing" do
     fn = @filename + "xxx"
     begin
-      File.exist?(fn).should be_false
+      File.should_not.exist?(fn)
       IO.send(@method, fn, "test")
-      File.exist?(fn).should be_true
+      File.should.exist?(fn)
     ensure
       rm_r fn
     end
@@ -35,9 +43,9 @@ describe :io_binwrite, shared: true do
   it "creates file if missing even if offset given" do
     fn = @filename + "xxx"
     begin
-      File.exist?(fn).should be_false
+      File.should_not.exist?(fn)
       IO.send(@method, fn, "test", 0)
-      File.exist?(fn).should be_true
+      File.should.exist?(fn)
     ensure
       rm_r fn
     end
@@ -56,7 +64,7 @@ describe :io_binwrite, shared: true do
   end
 
   it "doesn't truncate and writes at the given offset after passing empty opts" do
-    IO.send(@method, @filename, "hello world!", 1, {})
+    IO.send(@method, @filename, "hello world!", 1, **{})
     File.read(@filename).should == "0hello world!34567890123456789"
   end
 
@@ -67,12 +75,17 @@ describe :io_binwrite, shared: true do
     File.read(@filename).should == "\0\0foo"
   end
 
+  it "accepts a :flags option without :mode one" do
+    IO.send(@method, @filename, "hello, world!", flags: File::CREAT)
+    File.read(@filename).should == "hello, world!"
+  end
+
   it "raises an error if readonly mode is specified" do
     -> { IO.send(@method, @filename, "abcde", mode: "r") }.should raise_error(IOError)
   end
 
   it "truncates if empty :opts provided and offset skipped" do
-    IO.send(@method, @filename, "hello, world!", {})
+    IO.send(@method, @filename, "hello, world!", **{})
     File.read(@filename).should == "hello, world!"
   end
 end
diff --git a/spec/ruby/core/io/shared/each.rb b/spec/ruby/core/io/shared/each.rb
index 0b2dfa3548..0747f31b8a 100644
--- a/spec/ruby/core/io/shared/each.rb
+++ b/spec/ruby/core/io/shared/each.rb
@@ -33,10 +33,6 @@ describe :io_each, shared: true do
       $_.should == "test"
     end
 
-    it "returns self" do
-      @io.send(@method) { |l| l }.should equal(@io)
-    end
-
     it "raises an IOError when self is not readable" do
       -> { IOSpecs.closed_io.send(@method) {} }.should raise_error(IOError)
     end
@@ -77,6 +73,10 @@ describe :io_each, shared: true do
         -> { @io.send(@method, 0){} }.should raise_error(ArgumentError)
       end
     end
+
+    it "does not accept Integers that don't fit in a C off_t" do
+      -> { @io.send(@method, 2**128){} }.should raise_error(RangeError)
+    end
   end
 
   describe "when passed a String containing one space as a separator" do
@@ -113,6 +113,13 @@ describe :io_each, shared: true do
       @io.send(@method, "") { |s| ScratchPad << s }
       ScratchPad.recorded.should == IOSpecs.paragraphs
     end
+
+    it "discards leading newlines" do
+      @io.readline
+      @io.readline
+      @io.send(@method, "") { |s| ScratchPad << s }
+      ScratchPad.recorded.should == IOSpecs.paragraphs[1..-1]
+    end
   end
 
   describe "with both separator and limit" do
@@ -152,6 +159,13 @@ describe :io_each, shared: true do
           @io.send(@method, "", 1024) { |s| ScratchPad << s }
           ScratchPad.recorded.should == IOSpecs.paragraphs
         end
+
+        it "discards leading newlines" do
+          @io.readline
+          @io.readline
+          @io.send(@method, "", 1024) { |s| ScratchPad << s }
+          ScratchPad.recorded.should == IOSpecs.paragraphs[1..-1]
+        end
       end
     end
   end
@@ -161,6 +175,60 @@ describe :io_each, shared: true do
       @io.send(@method, chomp: true) { |s| ScratchPad << s }
       ScratchPad.recorded.should == IOSpecs.lines_without_newline_characters
     end
+
+    it "raises exception when options passed as Hash" do
+      -> {
+        @io.send(@method, { chomp: true }) { |s| }
+      }.should raise_error(TypeError)
+
+      -> {
+        @io.send(@method, "\n", 1, { chomp: true }) { |s| }
+      }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 0..2)")
+    end
+  end
+
+  describe "when passed chomp and a separator" do
+    it "yields each line without separator to the passed block" do
+      @io.send(@method, " ", chomp: true) { |s| ScratchPad << s }
+      ScratchPad.recorded.should == IOSpecs.lines_space_separator_without_trailing_spaces
+    end
+  end
+
+  describe "when passed chomp and empty line as a separator" do
+    it "yields each paragraph without trailing new line characters" do
+      @io.send(@method, "", 1024, chomp: true) { |s| ScratchPad << s }
+      ScratchPad.recorded.should == IOSpecs.paragraphs_without_trailing_new_line_characters
+    end
+  end
+
+  describe "when passed chomp and nil as a separator" do
+    it "yields self's content" do
+      @io.pos = 100
+      @io.send(@method, nil, chomp: true) { |s| ScratchPad << s }
+      ScratchPad.recorded.should == ["qui a linha cinco.\nHere is line six.\n"]
+    end
+  end
+
+  describe "when passed chomp, nil as a separator, and a limit" do
+    it "yields each line of limit size without truncating trailing new line character" do
+      # 43 - is a size of the 1st paragraph in the file
+      @io.send(@method, nil, 43, chomp: true) { |s| ScratchPad << s }
+
+      ScratchPad.recorded.should == [
+        "Voici la ligne une.\nQui è la linea due.\n\n\n",
+        "Aquí está la línea tres.\n" + "Hier ist Zeile ",
+        "vier.\n\nEstá aqui a linha cinco.\nHere is li",
+        "ne six.\n"
+      ]
+    end
+  end
+
+  describe "when passed too many arguments" do
+    it "raises ArgumentError" do
+      -> {
+        @io.send(@method, "", 1, "excess argument", chomp: true) {}
+      }.should raise_error(ArgumentError)
+    end
   end
 end
 
@@ -168,12 +236,12 @@ describe :io_each_default_separator, shared: true do
   before :each do
     @io = IOSpecs.io_fixture "lines.txt"
     ScratchPad.record []
-    @sep, $/ = $/, " "
+    suppress_warning {@sep, $/ = $/, " "}
   end
 
   after :each do
     @io.close if @io
-    $/ = @sep
+    suppress_warning {$/ = @sep}
   end
 
   it "uses $/ as the default line separator" do
diff --git a/spec/ruby/core/io/shared/gets_ascii.rb b/spec/ruby/core/io/shared/gets_ascii.rb
index 2a8fe3c9a5..2bd5470d99 100644
--- a/spec/ruby/core/io/shared/gets_ascii.rb
+++ b/spec/ruby/core/io/shared/gets_ascii.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :io_gets_ascii, shared: true do
   describe "with ASCII separator" do
     before :each do
diff --git a/spec/ruby/core/io/shared/new.rb b/spec/ruby/core/io/shared/new.rb
index 2101958170..e84133493c 100644
--- a/spec/ruby/core/io/shared/new.rb
+++ b/spec/ruby/core/io/shared/new.rb
@@ -1,5 +1,7 @@
 require_relative '../fixtures/classes'
 
+# NOTE: should be synchronized with library/stringio/initialize_spec.rb
+
 # This group of specs may ONLY contain specs that do successfully create
 # an IO instance from the file descriptor returned by #new_fd helper.
 describe :io_new, shared: true do
@@ -18,50 +20,59 @@ describe :io_new, shared: true do
     rm_r @name
   end
 
-  it "creates an IO instance from a Fixnum argument" do
+  it "creates an IO instance from an Integer argument" do
     @io = IO.send(@method, @fd, "w")
     @io.should be_an_instance_of(IO)
   end
 
   it "creates an IO instance when STDOUT is closed" do
-    verbose, $VERBOSE = $VERBOSE, nil
-    stdout = STDOUT
-    stdout_file = tmp("stdout.txt")
-
-    begin
-      @io = IO.send(@method, @fd, "w")
-      @io.should be_an_instance_of(IO)
-    ensure
-      STDOUT = stdout
-      $VERBOSE = verbose
-      rm_r stdout_file
+    suppress_warning do
+      stdout = STDOUT
+      stdout_file = tmp("stdout.txt")
+
+      begin
+        @io = IO.send(@method, @fd, "w")
+        @io.should be_an_instance_of(IO)
+      ensure
+        STDOUT = stdout
+        rm_r stdout_file
+      end
     end
   end
 
   it "creates an IO instance when STDERR is closed" do
-    verbose, $VERBOSE = $VERBOSE, nil
-    stderr = STDERR
-    stderr_file = tmp("stderr.txt")
-    STDERR = new_io stderr_file
-    STDERR.close
-
-    begin
-      @io = IO.send(@method, @fd, "w")
-      @io.should be_an_instance_of(IO)
-    ensure
-      STDERR = stderr
-      $VERBOSE = verbose
-      rm_r stderr_file
+    suppress_warning do
+      stderr = STDERR
+      stderr_file = tmp("stderr.txt")
+      STDERR = new_io stderr_file
+      STDERR.close
+
+      begin
+        @io = IO.send(@method, @fd, "w")
+        @io.should be_an_instance_of(IO)
+      ensure
+        STDERR = stderr
+        rm_r stderr_file
+      end
     end
   end
 
-  it "calls #to_int on an object to convert to a Fixnum" do
+  it "calls #to_int on an object to convert to an Integer" do
     obj = mock("file descriptor")
     obj.should_receive(:to_int).and_return(@fd)
     @io = IO.send(@method, obj, "w")
     @io.should be_an_instance_of(IO)
   end
 
+  it "accepts options as keyword arguments" do
+    @io = IO.send(@method, @fd, "w", flags: File::CREAT)
+    @io.write("foo").should == 3
+
+    -> {
+      IO.send(@method, @fd, "w", {flags: File::CREAT})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 3, expected 1..2)")
+  end
+
   it "accepts a :mode option" do
     @io = IO.send(@method, @fd, mode: "w")
     @io.write("foo").should == 3
@@ -89,81 +100,81 @@ describe :io_new, shared: true do
   end
 
   it "uses the external encoding specified via the :external_encoding option" do
-    @io = IO.send(@method, @fd, 'w', {external_encoding: 'utf-8'})
+    @io = IO.send(@method, @fd, 'w', external_encoding: 'utf-8')
     @io.external_encoding.to_s.should == 'UTF-8'
   end
 
   it "uses the internal encoding specified via the :internal_encoding option" do
-    @io = IO.send(@method, @fd, 'w', {internal_encoding: 'ibm866'})
+    @io = IO.send(@method, @fd, 'w', internal_encoding: 'ibm866')
     @io.internal_encoding.to_s.should == 'IBM866'
   end
 
   it "uses the colon-separated encodings specified via the :encoding option" do
-    @io = IO.send(@method, @fd, 'w', {encoding: 'utf-8:ISO-8859-1'})
+    @io = IO.send(@method, @fd, 'w', encoding: 'utf-8:ISO-8859-1')
     @io.external_encoding.to_s.should == 'UTF-8'
     @io.internal_encoding.to_s.should == 'ISO-8859-1'
   end
 
   it "uses the :encoding option as the external encoding when only one is given" do
-    @io = IO.send(@method, @fd, 'w', {encoding: 'ISO-8859-1'})
+    @io = IO.send(@method, @fd, 'w', encoding: 'ISO-8859-1')
     @io.external_encoding.to_s.should == 'ISO-8859-1'
   end
 
   it "uses the :encoding options as the external encoding when it's an Encoding object" do
-    @io = IO.send(@method, @fd, 'w', {encoding: Encoding::ISO_8859_1})
+    @io = IO.send(@method, @fd, 'w', encoding: Encoding::ISO_8859_1)
     @io.external_encoding.should == Encoding::ISO_8859_1
   end
 
   it "ignores the :encoding option when the :external_encoding option is present" do
     -> {
-      @io = IO.send(@method, @fd, 'w', {external_encoding: 'utf-8', encoding: 'iso-8859-1:iso-8859-1'})
+      @io = IO.send(@method, @fd, 'w', external_encoding: 'utf-8', encoding: 'iso-8859-1:iso-8859-1')
     }.should complain(/Ignoring encoding parameter/)
     @io.external_encoding.to_s.should == 'UTF-8'
   end
 
   it "ignores the :encoding option when the :internal_encoding option is present" do
     -> {
-      @io = IO.send(@method, @fd, 'w', {internal_encoding: 'ibm866', encoding: 'iso-8859-1:iso-8859-1'})
+      @io = IO.send(@method, @fd, 'w', internal_encoding: 'ibm866', encoding: 'iso-8859-1:iso-8859-1')
     }.should complain(/Ignoring encoding parameter/)
     @io.internal_encoding.to_s.should == 'IBM866'
   end
 
   it "uses the encoding specified via the :mode option hash" do
-    @io = IO.send(@method, @fd, {mode: 'w:utf-8:ISO-8859-1'})
+    @io = IO.send(@method, @fd, mode: 'w:utf-8:ISO-8859-1')
     @io.external_encoding.to_s.should == 'UTF-8'
     @io.internal_encoding.to_s.should == 'ISO-8859-1'
   end
 
   it "ignores the :internal_encoding option when the same as the external encoding" do
-    @io = IO.send(@method, @fd, 'w', {external_encoding: 'utf-8', internal_encoding: 'utf-8'})
+    @io = IO.send(@method, @fd, 'w', external_encoding: 'utf-8', internal_encoding: 'utf-8')
     @io.external_encoding.to_s.should == 'UTF-8'
     @io.internal_encoding.to_s.should == ''
   end
 
   it "sets internal encoding to nil when passed '-'" do
-    @io = IO.send(@method, @fd, 'w', {external_encoding: 'utf-8', internal_encoding: '-'})
+    @io = IO.send(@method, @fd, 'w', external_encoding: 'utf-8', internal_encoding: '-')
     @io.external_encoding.to_s.should == 'UTF-8'
     @io.internal_encoding.to_s.should == ''
   end
 
   it "sets binmode from mode string" do
     @io = IO.send(@method, @fd, 'wb')
-    @io.binmode?.should == true
+    @io.should.binmode?
   end
 
   it "does not set binmode without being asked" do
     @io = IO.send(@method, @fd, 'w')
-    @io.binmode?.should == false
+    @io.should_not.binmode?
   end
 
   it "sets binmode from :binmode option" do
-    @io = IO.send(@method, @fd, 'w', {binmode: true})
-    @io.binmode?.should == true
+    @io = IO.send(@method, @fd, 'w', binmode: true)
+    @io.should.binmode?
   end
 
   it "does not set binmode from false :binmode" do
-    @io = IO.send(@method, @fd, 'w', {binmode: false})
-    @io.binmode?.should == false
+    @io = IO.send(@method, @fd, 'w', binmode: false)
+    @io.should_not.binmode?
   end
 
   it "sets external encoding to binary with binmode in mode string" do
@@ -173,7 +184,7 @@ describe :io_new, shared: true do
 
   # #5917
   it "sets external encoding to binary with :binmode option" do
-    @io = IO.send(@method, @fd, 'w', {binmode: true})
+    @io = IO.send(@method, @fd, 'w', binmode: true)
     @io.external_encoding.should == Encoding::BINARY
   end
 
@@ -197,9 +208,30 @@ describe :io_new, shared: true do
     @io.internal_encoding.to_s.should == 'IBM866'
   end
 
-  it "accepts nil options" do
-    @io = IO.send(@method, @fd, 'w', nil)
-    @io.write("foo").should == 3
+  it "does not use binary encoding when mode encoding is specified along with binmode: true option" do
+    @io = IO.send(@method, @fd, 'w:iso-8859-1', binmode: true)
+    @io.external_encoding.to_s.should == 'ISO-8859-1'
+  end
+
+  it "does not use textmode argument when mode encoding is specified" do
+    @io = IO.send(@method, @fd, 'w:ascii-8bit', textmode: true)
+    @io.external_encoding.to_s.should == 'ASCII-8BIT'
+  end
+
+  it "does not use binmode argument when external encoding is specified via the :external_encoding option" do
+    @io = IO.send(@method, @fd, 'w', binmode: true, external_encoding: 'iso-8859-1')
+    @io.external_encoding.to_s.should == 'ISO-8859-1'
+  end
+
+  it "does not use textmode argument when external encoding is specified via the :external_encoding option" do
+    @io = IO.send(@method, @fd, 'w', textmode: true, external_encoding: 'ascii-8bit')
+    @io.external_encoding.to_s.should == 'ASCII-8BIT'
+  end
+
+  it "raises ArgumentError for nil options" do
+    -> {
+      IO.send(@method, @fd, 'w', nil)
+    }.should raise_error(ArgumentError)
   end
 
   it "coerces mode with #to_str" do
@@ -247,24 +279,24 @@ describe :io_new, shared: true do
   it "coerces options as third argument with #to_hash" do
     options = mock("options")
     options.should_receive(:to_hash).and_return({})
-    @io = IO.send(@method, @fd, 'w', options)
+    @io = IO.send(@method, @fd, 'w', **options)
   end
 
   it "coerces options as second argument with #to_hash" do
     options = mock("options")
     options.should_receive(:to_hash).and_return({})
-    @io = IO.send(@method, @fd, options)
+    @io = IO.send(@method, @fd, **options)
   end
 
   it "accepts an :autoclose option" do
     @io = IO.send(@method, @fd, 'w', autoclose: false)
-    @io.autoclose?.should == false
+    @io.should_not.autoclose?
     @io.autoclose = true
   end
 
   it "accepts any truthy option :autoclose" do
     @io = IO.send(@method, @fd, 'w', autoclose: 42)
-    @io.autoclose?.should == true
+    @io.should.autoclose?
   end
 end
 
@@ -307,13 +339,16 @@ describe :io_new_errors, shared: true do
 
   it "raises an error if passed encodings two ways" do
     -> {
-      @io = IO.send(@method, @fd, 'w:ISO-8859-1', {encoding: 'ISO-8859-1'})
+      @io = IO.send(@method, @fd, 'w:ISO-8859-1', encoding: 'ISO-8859-1')
     }.should raise_error(ArgumentError)
     -> {
-      @io = IO.send(@method, @fd, 'w:ISO-8859-1', {external_encoding: 'ISO-8859-1'})
+      @io = IO.send(@method, @fd, 'w:ISO-8859-1', external_encoding: 'ISO-8859-1')
     }.should raise_error(ArgumentError)
     -> {
-      @io = IO.send(@method, @fd, 'w:ISO-8859-1:UTF-8', {internal_encoding: 'ISO-8859-1'})
+      @io = IO.send(@method, @fd, 'w:ISO-8859-1', internal_encoding: 'ISO-8859-1')
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = IO.send(@method, @fd, 'w:ISO-8859-1:UTF-8', internal_encoding: 'ISO-8859-1')
     }.should raise_error(ArgumentError)
   end
 
@@ -370,9 +405,9 @@ describe :io_new_errors, shared: true do
     }.should raise_error(ArgumentError)
   end
 
-  it "raises TypeError if passed a hash for mode and nil for options" do
+  it "raises ArgumentError if passed a hash for mode and nil for options" do
     -> {
       @io = IO.send(@method, @fd, {mode: 'w'}, nil)
-    }.should raise_error(TypeError)
+    }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/core/io/shared/pos.rb b/spec/ruby/core/io/shared/pos.rb
index fb6d8087bc..3fdd3eb2b3 100644
--- a/spec/ruby/core/io/shared/pos.rb
+++ b/spec/ruby/core/io/shared/pos.rb
@@ -27,7 +27,7 @@ describe :io_pos, shared: true do
       io.read 1
       io.read 1
       io.send(@method)
-      io.eof?.should == false
+      io.should_not.eof?
     end
   end
 end
@@ -60,7 +60,13 @@ describe :io_set_pos, shared: true do
     end
   end
 
-  it "does not accept Bignums that don't fit in a C long" do
+  it "raises TypeError when cannot convert implicitly argument to Integer" do
+    File.open @fname do |io|
+      -> { io.send @method, Object.new }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+  end
+
+  it "does not accept Integers that don't fit in a C off_t" do
     File.open @fname do |io|
       -> { io.send @method, 2**128 }.should raise_error(RangeError)
     end
diff --git a/spec/ruby/core/io/shared/readlines.rb b/spec/ruby/core/io/shared/readlines.rb
index 9bc02da0bd..6c1fa11a59 100644
--- a/spec/ruby/core/io/shared/readlines.rb
+++ b/spec/ruby/core/io/shared/readlines.rb
@@ -54,25 +54,42 @@ describe :io_readlines_options_19, shared: true do
       (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator
     end
 
-    describe "when the object is a Fixnum" do
+    describe "when the object is an Integer" do
       before :each do
         @sep = $/
       end
 
       after :each do
-        $/ = @sep
+        suppress_warning {$/ = @sep}
       end
 
       it "defaults to $/ as the separator" do
-        $/ = " "
+        suppress_warning {$/ = " "}
         result = IO.send(@method, @name, 10, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
 
-      it "uses the object as a limit if it is a Fixnum" do
+      it "uses the object as a limit if it is an Integer" do
         result = IO.send(@method, @name, 10, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_limit
       end
+
+      it "ignores the object as a limit if it is negative" do
+        result = IO.send(@method, @name, -2, &@object)
+        (result ? result : ScratchPad.recorded).should == IOSpecs.lines
+      end
+
+      it "does not accept Integers that don't fit in a C off_t" do
+        -> { IO.send(@method, @name, 2**128, &@object) }.should raise_error(RangeError)
+      end
+
+      ruby_bug "#18767", ""..."3.3" do
+        describe "when passed limit" do
+          it "raises ArgumentError when passed 0 as a limit" do
+            -> { IO.send(@method, @name, 0, &@object) }.should raise_error(ArgumentError)
+          end
+        end
+      end
     end
 
     describe "when the object is a String" do
@@ -82,38 +99,40 @@ describe :io_readlines_options_19, shared: true do
       end
 
       it "accepts non-ASCII data as separator" do
-        result = IO.send(@method, @name, "\303\250".force_encoding("utf-8"), &@object)
+        result = IO.send(@method, @name, "\303\250".dup.force_encoding("utf-8"), &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_arbitrary_separator
       end
     end
 
-    describe "when the object is a Hash" do
-      it "uses the value as the options hash" do
-        result = IO.send(@method, @name, mode: "r", &@object)
-        (result ? result : ScratchPad.recorded).should == IOSpecs.lines
+    describe "when the object is an options Hash" do
+      it "raises TypeError exception" do
+        -> {
+          IO.send(@method, @name, { chomp: true }, &@object)
+        }.should raise_error(TypeError)
       end
     end
-  end
 
-  describe "when passed name, object, object" do
-    describe "when the first object is a Fixnum" do
-      it "uses the second object as an options Hash" do
-        -> do
-          IO.send(@method, @filename, 10, mode: "w", &@object)
-        end.should raise_error(IOError)
-      end
+    describe "when the object is neither Integer nor String" do
+      it "raises TypeError exception" do
+        obj = mock("not io readlines limit")
 
-      it "calls #to_hash to convert the second object to a Hash" do
-        options = mock("io readlines options Hash")
-        options.should_receive(:to_hash).and_return({ mode: "w" })
-        -> do
-          IO.send(@method, @filename, 10, options, &@object)
-        end.should raise_error(IOError)
+        -> {
+          IO.send(@method, @name, obj, &@object)
+        }.should raise_error(TypeError)
       end
     end
+  end
+
+  describe "when passed name, keyword arguments" do
+    it "uses the keyword arguments as options" do
+      result = IO.send(@method, @name, mode: "r", &@object)
+      (result ? result : ScratchPad.recorded).should == IOSpecs.lines
+    end
+  end
 
+  describe "when passed name, object, object" do
     describe "when the first object is a String" do
-      it "uses the second object as a limit if it is a Fixnum" do
+      it "uses the second object as a limit if it is an Integer" do
         result = IO.send(@method, @name, " ", 10, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
@@ -124,32 +143,18 @@ describe :io_readlines_options_19, shared: true do
         result = IO.send(@method, @name, " ", limit, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
-
-      it "uses the second object as an options Hash" do
-        -> do
-          IO.send(@method, @filename, " ", mode: "w", &@object)
-        end.should raise_error(IOError)
-      end
-
-      it "calls #to_hash to convert the second object to a Hash" do
-        options = mock("io readlines options Hash")
-        options.should_receive(:to_hash).and_return({ mode: "w" })
-        -> do
-          IO.send(@method, @filename, " ", options, &@object)
-        end.should raise_error(IOError)
-      end
     end
 
-    describe "when the first object is not a String or Fixnum" do
+    describe "when the first object is not a String or Integer" do
       it "calls #to_str to convert the object to a String" do
         sep = mock("io readlines separator")
         sep.should_receive(:to_str).at_least(1).and_return(" ")
-        result = IO.send(@method, @name, sep, 10, mode: "r", &@object)
+        result = IO.send(@method, @name, sep, 10, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
 
-      it "uses the second object as a limit if it is a Fixnum" do
-        result = IO.send(@method, @name, " ", 10, mode: "r", &@object)
+      it "uses the second object as a limit if it is an Integer" do
+        result = IO.send(@method, @name, " ", 10, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
 
@@ -159,24 +164,57 @@ describe :io_readlines_options_19, shared: true do
         result = IO.send(@method, @name, " ", limit, &@object)
         (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
       end
+    end
+
+    describe "when the second object is neither Integer nor String" do
+      it "raises TypeError exception" do
+        obj = mock("not io readlines limit")
+
+        -> {
+          IO.send(@method, @name, " ", obj, &@object)
+        }.should raise_error(TypeError)
+      end
+    end
+
+    describe "when the second object is an options Hash" do
+      it "raises TypeError exception" do
+        -> {
+          IO.send(@method, @name, "", { chomp: true }, &@object)
+        }.should raise_error(TypeError)
+      end
+    end
+  end
+
+  describe "when passed name, object, keyword arguments" do
+    describe "when the first object is an Integer" do
+      it "uses the keyword arguments as options" do
+        -> do
+          IO.send(@method, @filename, 10, mode: "w", &@object)
+        end.should raise_error(IOError)
+      end
+    end
 
-      it "uses the second object as an options Hash" do
+    describe "when the first object is a String" do
+      it "uses the keyword arguments as options" do
         -> do
           IO.send(@method, @filename, " ", mode: "w", &@object)
         end.should raise_error(IOError)
       end
+    end
+
+    describe "when the first object is not a String or Integer" do
+      it "uses the keyword arguments as options" do
+        sep = mock("io readlines separator")
+        sep.should_receive(:to_str).at_least(1).and_return(" ")
 
-      it "calls #to_hash to convert the second object to a Hash" do
-        options = mock("io readlines options Hash")
-        options.should_receive(:to_hash).and_return({ mode: "w" })
         -> do
-          IO.send(@method, @filename, " ", options, &@object)
+          IO.send(@method, @filename, sep, mode: "w", &@object)
         end.should raise_error(IOError)
       end
     end
   end
 
-  describe "when passed name, separator, limit, options" do
+  describe "when passed name, separator, limit, keyword arguments" do
     it "calls #to_path to convert the name object" do
       name = mock("io name to_path")
       name.should_receive(:to_path).and_return(@name)
@@ -198,12 +236,24 @@ describe :io_readlines_options_19, shared: true do
       (result ? result : ScratchPad.recorded).should == IOSpecs.lines_space_separator_limit
     end
 
-    it "calls #to_hash to convert the options object" do
-      options = mock("io readlines options Hash")
-      options.should_receive(:to_hash).and_return({ mode: "w" })
+    it "uses the keyword arguments as options" do
       -> do
-        IO.send(@method, @filename, " ", 10, options, &@object)
+        IO.send(@method, @filename, " ", 10, mode: "w", &@object)
       end.should raise_error(IOError)
     end
+
+    describe "when passed chomp, nil as a separator, and a limit" do
+      it "yields each line of limit size without truncating trailing new line character" do
+        # 43 - is a size of the 1st paragraph in the file
+        result = IO.send(@method, @name, nil, 43, chomp: true, &@object)
+
+        (result ? result : ScratchPad.recorded).should == [
+          "Voici la ligne une.\nQui è la linea due.\n\n\n",
+          "Aquí está la línea tres.\n" + "Hier ist Zeile ",
+          "vier.\n\nEstá aqui a linha cinco.\nHere is li",
+          "ne six.\n"
+        ]
+      end
+    end
   end
 end
diff --git a/spec/ruby/core/io/shared/tty.rb b/spec/ruby/core/io/shared/tty.rb
index 82a780a9f3..89ac08ec86 100644
--- a/spec/ruby/core/io/shared/tty.rb
+++ b/spec/ruby/core/io/shared/tty.rb
@@ -7,8 +7,7 @@ describe :io_tty, shared: true do
         # check to enabled tty
         File.open('/dev/tty') {}
       rescue Errno::ENXIO
-        # workaround for not configured environment like OS X
-        1.should == 1
+        skip "workaround for not configured environment like OS X"
       else
         File.open('/dev/tty') { |f| f.send(@method) }.should == true
       end
diff --git a/spec/ruby/core/io/shared/write.rb b/spec/ruby/core/io/shared/write.rb
index 270b84ac39..964064746a 100644
--- a/spec/ruby/core/io/shared/write.rb
+++ b/spec/ruby/core/io/shared/write.rb
@@ -69,16 +69,6 @@ describe :io_write, shared: true do
     -> { IOSpecs.closed_io.send(@method, "hello") }.should raise_error(IOError)
   end
 
-  it "does not modify the passed argument" do
-    File.open(@filename, "w") do |f|
-      f.set_encoding(Encoding::IBM437)
-      # A character whose codepoint differs between UTF-8 and IBM437
-      f.write "ƒ".freeze
-    end
-
-    File.binread(@filename).bytes.should == [159]
-  end
-
   describe "on a pipe" do
     before :each do
       @r, @w = IO.pipe
@@ -95,11 +85,11 @@ describe :io_write, shared: true do
       @r.read.should == "foo"
     end
 
-    # [ruby-core:90895] MJIT worker may leave fd open in a forked child.
-    # For instance, MJIT creates a worker before @r.close with fork(), @r.close happens,
-    # and the MJIT worker keeps the pipe open until the worker execve().
-    # TODO: consider acquiring GVL from MJIT worker.
-    guard_not -> { defined?(RubyVM::MJIT) && RubyVM::MJIT.enabled? } do
+    # [ruby-core:90895] RJIT worker may leave fd open in a forked child.
+    # For instance, RJIT creates a worker before @r.close with fork(), @r.close happens,
+    # and the RJIT worker keeps the pipe open until the worker execve().
+    # TODO: consider acquiring GVL from RJIT worker.
+    guard_not -> { defined?(RubyVM::RJIT) && RubyVM::RJIT.enabled? } do
       it "raises Errno::EPIPE if the read end is closed and does not die from SIGPIPE" do
         @r.close
         -> { @w.send(@method, "foo") }.should raise_error(Errno::EPIPE, /Broken pipe/)
@@ -107,3 +97,58 @@ describe :io_write, shared: true do
     end
   end
 end
+
+describe :io_write_transcode, shared: true do
+  before :each do
+    @transcode_filename = tmp("io_write_transcode")
+  end
+
+  after :each do
+    rm_r @transcode_filename
+  end
+
+  it "transcodes the given string when the external encoding is set and neither is BINARY" do
+    utf8_str = "hello"
+
+    File.open(@transcode_filename, "w", external_encoding: Encoding::UTF_16BE) do |file|
+      file.external_encoding.should == Encoding::UTF_16BE
+      file.send(@method, utf8_str)
+    end
+
+    result = File.binread(@transcode_filename)
+    expected = [0, 104, 0, 101, 0, 108, 0, 108, 0, 111] # UTF-16BE bytes for "hello"
+
+    result.bytes.should == expected
+  end
+
+  it "transcodes the given string when the external encoding is set and the string encoding is BINARY" do
+    str = "été".b
+
+    File.open(@transcode_filename, "w", external_encoding: Encoding::UTF_16BE) do |file|
+      file.external_encoding.should == Encoding::UTF_16BE
+      -> { file.send(@method, str) }.should raise_error(Encoding::UndefinedConversionError)
+    end
+  end
+end
+
+describe :io_write_no_transcode, shared: true do
+  before :each do
+    @transcode_filename = tmp("io_write_no_transcode")
+  end
+
+  after :each do
+    rm_r @transcode_filename
+  end
+
+  it "does not transcode the given string even when the external encoding is set" do
+    utf8_str = "hello"
+
+    File.open(@transcode_filename, "w", external_encoding: Encoding::UTF_16BE) do |file|
+      file.external_encoding.should == Encoding::UTF_16BE
+      file.send(@method, utf8_str)
+    end
+
+    result = File.binread(@transcode_filename)
+    result.bytes.should == utf8_str.bytes
+  end
+end
diff --git a/spec/ruby/core/io/stat_spec.rb b/spec/ruby/core/io/stat_spec.rb
index 58eba02b8f..717c45d0a3 100644
--- a/spec/ruby/core/io/stat_spec.rb
+++ b/spec/ruby/core/io/stat_spec.rb
@@ -3,7 +3,8 @@ require_relative 'fixtures/classes'
 
 describe "IO#stat" do
   before :each do
-    @io = IO.popen 'cat', "r+"
+    cmd = platform_is(:windows) ? 'rem' : 'cat'
+    @io = IO.popen cmd, "r+"
   end
 
   after :each do
diff --git a/spec/ruby/core/io/sysopen_spec.rb b/spec/ruby/core/io/sysopen_spec.rb
index 4607d13687..7ad379df3a 100644
--- a/spec/ruby/core/io/sysopen_spec.rb
+++ b/spec/ruby/core/io/sysopen_spec.rb
@@ -13,7 +13,7 @@ describe "IO.sysopen" do
 
   it "returns the file descriptor for a given path" do
     @fd = IO.sysopen(@filename, "w")
-    @fd.should be_kind_of(Fixnum)
+    @fd.should be_kind_of(Integer)
     @fd.should_not equal(0)
   end
 
@@ -21,7 +21,7 @@ describe "IO.sysopen" do
   platform_is_not :windows do
     it "works on directories" do
       @fd = IO.sysopen(tmp(""))    # /tmp
-      @fd.should be_kind_of(Fixnum)
+      @fd.should be_kind_of(Integer)
       @fd.should_not equal(0)
     end
   end
diff --git a/spec/ruby/core/io/sysread_spec.rb b/spec/ruby/core/io/sysread_spec.rb
index 024200efea..d56a27b3af 100644
--- a/spec/ruby/core/io/sysread_spec.rb
+++ b/spec/ruby/core/io/sysread_spec.rb
@@ -6,7 +6,7 @@ describe "IO#sysread on a file" do
     @file_name = tmp("IO_sysread_file") + $$.to_s
     File.open(@file_name, "w") do |f|
       # write some stuff
-      f.write("012345678901234567890123456789")
+      f.write("012345678901234567890123456789\nabcdef")
     end
     @file = File.open(@file_name, "r+")
   end
@@ -21,25 +21,25 @@ describe "IO#sysread on a file" do
   end
 
   it "reads the specified number of bytes from the file to the buffer" do
-    buf = "" # empty buffer
+    buf = +"" # empty buffer
     @file.sysread(15, buf).should == buf
     buf.should == "012345678901234"
 
     @file.rewind
 
-    buf = "ABCDE" # small buffer
+    buf = +"ABCDE" # small buffer
     @file.sysread(15, buf).should == buf
     buf.should == "012345678901234"
 
     @file.rewind
 
-    buf = "ABCDE" * 5 # large buffer
+    buf = +"ABCDE" * 5 # large buffer
     @file.sysread(15, buf).should == buf
     buf.should == "012345678901234"
   end
 
   it "coerces the second argument to string and uses it as a buffer" do
-    buf = "ABCDE"
+    buf = +"ABCDE"
     (obj = mock("buff")).should_receive(:to_str).any_number_of_times.and_return(buf)
     @file.sysread(15, obj).should == buf
     buf.should == "012345678901234"
@@ -50,6 +50,11 @@ describe "IO#sysread on a file" do
     @file.sysread(5).should == "56789"
   end
 
+  it "raises an error when called after buffered reads" do
+    @file.readline
+    -> { @file.sysread(5) }.should raise_error(IOError)
+  end
+
   it "reads normally even when called immediately after a buffered IO#read" do
     @file.read(15)
     @file.sysread(5).should == "56789"
@@ -79,6 +84,36 @@ describe "IO#sysread on a file" do
   it "raises IOError on closed stream" do
     -> { IOSpecs.closed_io.sysread(5) }.should raise_error(IOError)
   end
+
+  it "immediately returns an empty string if the length argument is 0" do
+    @file.sysread(0).should == ""
+  end
+
+  it "immediately returns the given buffer if the length argument is 0" do
+    buffer = +"existing content"
+    @file.sysread(0, buffer).should == buffer
+    buffer.should == "existing content"
+  end
+
+  it "discards the existing buffer content upon successful read" do
+    buffer = +"existing content"
+    @file.sysread(11, buffer).should.equal?(buffer)
+    buffer.should == "01234567890"
+  end
+
+  it "discards the existing buffer content upon error" do
+    buffer = +"existing content"
+    @file.seek(0, :END)
+    -> { @file.sysread(1, buffer) }.should raise_error(EOFError)
+    buffer.should be_empty
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    string = @file.sysread(10, buffer)
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
 end
 
 describe "IO#sysread" do
@@ -95,4 +130,8 @@ describe "IO#sysread" do
     @write.syswrite "ab"
     @read.sysread(3).should == "ab"
   end
+
+  it "raises ArgumentError when length is less than 0" do
+    -> { @read.sysread(-1) }.should raise_error(ArgumentError)
+  end
 end
diff --git a/spec/ruby/core/io/sysseek_spec.rb b/spec/ruby/core/io/sysseek_spec.rb
index df894734e3..002f2a14eb 100644
--- a/spec/ruby/core/io/sysseek_spec.rb
+++ b/spec/ruby/core/io/sysseek_spec.rb
@@ -4,7 +4,7 @@ require_relative 'fixtures/classes'
 require_relative 'shared/pos'
 
 describe "IO#sysseek" do
-  it_behaves_like :io_set_pos, :seek
+  it_behaves_like :io_set_pos, :sysseek
 end
 
 describe "IO#sysseek" do
@@ -26,6 +26,11 @@ describe "IO#sysseek" do
     -> { @io.sysseek(-5, IO::SEEK_CUR) }.should raise_error(IOError)
   end
 
+  it "seeks normally even when called immediately after a buffered IO#read" do
+    @io.read(15)
+    @io.sysseek(-5, IO::SEEK_CUR).should == 10
+  end
+
   it "moves the read position relative to the start with SEEK_SET" do
     @io.sysseek(43, IO::SEEK_SET)
     @io.readline.should == "Aquí está la línea tres.\n"
diff --git a/spec/ruby/core/io/syswrite_spec.rb b/spec/ruby/core/io/syswrite_spec.rb
index a28cc62174..8bf61a27c3 100644
--- a/spec/ruby/core/io/syswrite_spec.rb
+++ b/spec/ruby/core/io/syswrite_spec.rb
@@ -29,6 +29,16 @@ describe "IO#syswrite on a file" do
     end
   end
 
+  it "does not modify the passed argument" do
+    File.open(@filename, "w") do |f|
+      f.set_encoding(Encoding::IBM437)
+      # A character whose codepoint differs between UTF-8 and IBM437
+      f.syswrite("ƒ".freeze)
+    end
+
+    File.binread(@filename).bytes.should == [198, 146]
+  end
+
   it "warns if called immediately after a buffered IO#write" do
     @file.write("abcde")
     -> { @file.syswrite("fghij") }.should complain(/syswrite/)
@@ -68,4 +78,5 @@ end
 
 describe "IO#syswrite" do
   it_behaves_like :io_write, :syswrite
+  it_behaves_like :io_write_no_transcode, :syswrite
 end
diff --git a/spec/ruby/core/io/try_convert_spec.rb b/spec/ruby/core/io/try_convert_spec.rb
index 5fbd10b6fa..a9e99de7aa 100644
--- a/spec/ruby/core/io/try_convert_spec.rb
+++ b/spec/ruby/core/io/try_convert_spec.rb
@@ -38,7 +38,7 @@ describe "IO.try_convert" do
   it "raises a TypeError if the object does not return an IO from #to_io" do
     obj = mock("io")
     obj.should_receive(:to_io).and_return("io")
-    -> { IO.try_convert(obj) }.should raise_error(TypeError)
+    -> { IO.try_convert(obj) }.should raise_error(TypeError, "can't convert MockObject to IO (MockObject#to_io gives String)")
   end
 
   it "propagates an exception raised by #to_io" do
diff --git a/spec/ruby/core/io/ungetbyte_spec.rb b/spec/ruby/core/io/ungetbyte_spec.rb
index 1971dee534..716743a6af 100644
--- a/spec/ruby/core/io/ungetbyte_spec.rb
+++ b/spec/ruby/core/io/ungetbyte_spec.rb
@@ -36,34 +36,15 @@ describe "IO#ungetbyte" do
     @io.getbyte.should == 97
   end
 
-  ruby_version_is ''...'2.6' do
-    it "puts back one byte for a Fixnum argument..." do
-      @io.ungetbyte(4095).should be_nil
+  it "never raises RangeError" do
+    for i in [4095, 0x4f7574206f6620636861722072616e67ff] do
+      @io.ungetbyte(i).should be_nil
       @io.getbyte.should == 255
     end
-
-    it "... but not for Bignum argument (eh?)" do
-      -> {
-        @io.ungetbyte(0x4f7574206f6620636861722072616e6765)
-      }.should raise_error(TypeError)
-    end
-  end
-
-  ruby_version_is '2.6'...'2.6.1' do
-    it "is an RangeError if the integer is not in 8bit" do
-      for i in [4095, 0x4f7574206f6620636861722072616e6765] do
-        -> { @io.ungetbyte(i) }.should raise_error(RangeError)
-      end
-    end
   end
 
-  ruby_version_is '2.6.1' do
-    it "never raises RangeError" do
-      for i in [4095, 0x4f7574206f6620636861722072616e67ff] do
-        @io.ungetbyte(i).should be_nil
-        @io.getbyte.should == 255
-      end
-    end
+  it "raises IOError on stream not opened for reading" do
+    -> { STDOUT.ungetbyte(42) }.should raise_error(IOError, "not opened for reading")
   end
 
   it "raises an IOError if the IO is closed" do
diff --git a/spec/ruby/core/io/ungetc_spec.rb b/spec/ruby/core/io/ungetc_spec.rb
index 34d4caf745..47a4e99ebf 100644
--- a/spec/ruby/core/io/ungetc_spec.rb
+++ b/spec/ruby/core/io/ungetc_spec.rb
@@ -74,10 +74,10 @@ describe "IO#ungetc" do
     touch(@empty)
 
     File.open(@empty) { |empty|
-      empty.eof?.should == true
+      empty.should.eof?
       empty.getc.should == nil
       empty.ungetc(100)
-      empty.eof?.should == false
+      empty.should_not.eof?
     }
   end
 
@@ -103,10 +103,9 @@ describe "IO#ungetc" do
     -> { @io.sysread(1) }.should raise_error(IOError)
   end
 
-  it "does not affect the stream and returns nil when passed nil" do
+  it "raises TypeError if passed nil" do
     @io.getc.should == ?V
-    @io.ungetc(nil)
-    @io.getc.should == ?o
+    proc{@io.ungetc(nil)}.should raise_error(TypeError)
   end
 
   it "puts one or more characters back in the stream" do
@@ -127,6 +126,10 @@ describe "IO#ungetc" do
     @io.ungetc(100).should be_nil
   end
 
+  it "raises IOError on stream not opened for reading" do
+    -> { STDOUT.ungetc(100) }.should raise_error(IOError, "not opened for reading")
+  end
+
   it "raises IOError on closed stream" do
     @io.getc
     @io.close
diff --git a/spec/ruby/core/io/write_nonblock_spec.rb b/spec/ruby/core/io/write_nonblock_spec.rb
index 18adfcfc4a..5bfc690f9b 100644
--- a/spec/ruby/core/io/write_nonblock_spec.rb
+++ b/spec/ruby/core/io/write_nonblock_spec.rb
@@ -31,15 +31,26 @@ platform_is_not :windows do
       end
     end
 
+    it "does not modify the passed argument" do
+      File.open(@filename, "w") do |f|
+        f.set_encoding(Encoding::IBM437)
+        # A character whose codepoint differs between UTF-8 and IBM437
+        f.write_nonblock("ƒ".freeze)
+      end
+
+      File.binread(@filename).bytes.should == [198, 146]
+    end
+
     it "checks if the file is writable if writing zero bytes" do
       -> {
-         @readonly_file.write_nonblock("")
+        @readonly_file.write_nonblock("")
       }.should raise_error(IOError)
     end
   end
 
   describe "IO#write_nonblock" do
     it_behaves_like :io_write, :write_nonblock
+    it_behaves_like :io_write_no_transcode, :write_nonblock
   end
 end
 
@@ -68,8 +79,10 @@ describe 'IO#write_nonblock' do
 
   context "when exception option is set to false" do
     it "returns :wait_writable when the operation would block" do
-      loop { break if @write.write_nonblock("a" * 10_000, exception: false) == :wait_writable }
-      1.should == 1
+      loop {
+        break if @write.write_nonblock("a" * 10_000, exception: false) == :wait_writable
+      }
+      @write.write_nonblock("a" * 10_000, exception: false).should == :wait_writable
     end
   end
 
@@ -77,7 +90,7 @@ describe 'IO#write_nonblock' do
     it 'sets the IO in nonblock mode' do
       require 'io/nonblock'
       @write.write_nonblock('a')
-      @write.nonblock?.should == true
+      @write.should.nonblock?
     end
   end
 end
diff --git a/spec/ruby/core/io/write_spec.rb b/spec/ruby/core/io/write_spec.rb
index b28b582019..e58100f846 100644
--- a/spec/ruby/core/io/write_spec.rb
+++ b/spec/ruby/core/io/write_spec.rb
@@ -24,10 +24,6 @@ describe "IO#write on a file" do
     -> { @readonly_file.write("") }.should_not raise_error
   end
 
-  it "returns a length of 0 when writing a blank string" do
-    @file.write('').should == 0
-  end
-
   before :each do
     @external = Encoding.default_external
     @internal = Encoding.default_internal
@@ -40,10 +36,44 @@ describe "IO#write on a file" do
     Encoding.default_internal = @internal
   end
 
+  it "returns a length of 0 when writing a blank string" do
+    @file.write('').should == 0
+  end
+
+  it "returns a length of 0 when writing blank strings" do
+    @file.write('', '', '').should == 0
+  end
+
+  it "returns a length of 0 when passed no arguments" do
+    @file.write().should == 0
+  end
+
   it "returns the number of bytes written" do
     @file.write("hellø").should == 6
   end
 
+  it "does not modify the passed argument" do
+    File.open(@filename, "w") do |f|
+      f.set_encoding(Encoding::IBM437)
+      # A character whose codepoint differs between UTF-8 and IBM437
+      f.write("ƒ".freeze)
+    end
+
+    File.binread(@filename).bytes.should == [159]
+  end
+
+  it "does not modify arguments when passed multiple arguments and external encoding not set" do
+    a, b = "a".freeze, "b".freeze
+
+    File.open(@filename, "w") do |f|
+      f.write(a, b)
+    end
+
+    File.binread(@filename).bytes.should == [97, 98]
+    a.encoding.should == Encoding::UTF_8
+    b.encoding.should == Encoding::UTF_8
+  end
+
   it "uses the encoding from the given option for non-ascii encoding" do
     File.open(@filename, "w", encoding: Encoding::UTF_32LE) do |file|
       file.write("hi").should == 8
@@ -51,8 +81,25 @@ describe "IO#write on a file" do
     File.binread(@filename).should == "h\u0000\u0000\u0000i\u0000\u0000\u0000"
   end
 
-  it "uses an :open_args option" do
-    IO.write(@filename, 'hi', open_args: ["w", nil, {encoding: Encoding::UTF_32LE}]).should == 8
+  it "uses the encoding from the given option for non-ascii encoding even if in binary mode" do
+    File.open(@filename, "w", encoding: Encoding::UTF_32LE, binmode: true) do |file|
+      file.should.binmode?
+      file.write("hi").should == 8
+    end
+    File.binread(@filename).should == "h\u0000\u0000\u0000i\u0000\u0000\u0000"
+
+    File.open(@filename, "wb", encoding: Encoding::UTF_32LE) do |file|
+      file.should.binmode?
+      file.write("hi").should == 8
+    end
+    File.binread(@filename).should == "h\u0000\u0000\u0000i\u0000\u0000\u0000"
+  end
+
+  it "uses the encoding from the given option for non-ascii encoding when multiple arguments passes" do
+    File.open(@filename, "w", encoding: Encoding::UTF_32LE) do |file|
+      file.write("h", "i").should == 8
+    end
+    File.binread(@filename).should == "h\u0000\u0000\u0000i\u0000\u0000\u0000"
   end
 
   it "raises a invalid byte sequence error if invalid bytes are being written" do
@@ -72,6 +119,20 @@ describe "IO#write on a file" do
     res = "H#{ë}ll#{ö}"
     File.binread(@filename).should == res.force_encoding(Encoding::BINARY)
   end
+
+  platform_is_not :windows do
+    it "writes binary data if no encoding is given and multiple arguments passed" do
+      File.open(@filename, "w") do |file|
+        file.write("\x87".b, "ą") # 0x87 isn't a valid UTF-8 binary representation of a character
+      end
+      File.binread(@filename).bytes.should == [0x87, 0xC4, 0x85]
+
+      File.open(@filename, "w") do |file|
+        file.write("\x61".encode("utf-32le"), "ą")
+      end
+      File.binread(@filename).bytes.should == [0x61, 0x00, 0x00, 0x00, 0xC4, 0x85]
+    end
+  end
 end
 
 describe "IO.write" do
@@ -86,10 +147,44 @@ describe "IO.write" do
     File.read(@filename).should == "\0\0hi"
   end
 
+  it "requires mode to be specified in :open_args" do
+    -> {
+      IO.write(@filename, 'hi', open_args: [{encoding: Encoding::UTF_32LE, binmode: true}])
+    }.should raise_error(IOError, "not opened for writing")
+
+    IO.write(@filename, 'hi', open_args: ["w", {encoding: Encoding::UTF_32LE, binmode: true}]).should == 8
+    IO.write(@filename, 'hi', open_args: [{encoding: Encoding::UTF_32LE, binmode: true, mode: "w"}]).should == 8
+  end
+
+  it "requires mode to be specified in :open_args even if flags option passed" do
+    -> {
+      IO.write(@filename, 'hi', open_args: [{encoding: Encoding::UTF_32LE, binmode: true, flags: File::CREAT}])
+    }.should raise_error(IOError, "not opened for writing")
+
+    IO.write(@filename, 'hi', open_args: ["w", {encoding: Encoding::UTF_32LE, binmode: true, flags: File::CREAT}]).should == 8
+    IO.write(@filename, 'hi', open_args: [{encoding: Encoding::UTF_32LE, binmode: true, flags: File::CREAT, mode: "w"}]).should == 8
+  end
+
   it "uses the given encoding and returns the number of bytes written" do
     IO.write(@filename, 'hi', mode: "w", encoding: Encoding::UTF_32LE).should == 8
   end
 
+  it "raises ArgumentError if encoding is specified in mode parameter and is given as :encoding option" do
+    -> {
+      IO.write(@filename, 'hi', mode: "w:UTF-16LE:UTF-16BE", encoding: Encoding::UTF_32LE)
+    }.should raise_error(ArgumentError, "encoding specified twice")
+
+    -> {
+      IO.write(@filename, 'hi', mode: "w:UTF-16BE", encoding: Encoding::UTF_32LE)
+    }.should raise_error(ArgumentError, "encoding specified twice")
+  end
+
+  it "writes the file with the permissions in the :perm parameter" do
+    rm_r @filename
+    IO.write(@filename, 'write :perm spec', mode: "w", perm: 0o755).should == 16
+    (File.stat(@filename).mode & 0o777) == 0o755
+  end
+
   it "writes binary data if no encoding is given" do
     IO.write(@filename, 'Hëllö'.encode('ISO-8859-1'))
     xEB = [235].pack('C*')
@@ -108,32 +203,46 @@ describe "IO.write" do
         rm_r @fifo
       end
 
-      it "writes correctly" do
-        thr = Thread.new do
-          IO.read(@fifo)
-        end
-        begin
-          string = "hi"
-          IO.write(@fifo, string).should == string.length
-        ensure
-          thr.join
+      # rb_cloexec_open() is currently missing a retry on EINTR.
+      # @ioquatix is looking into fixing it. Quarantined until it's done.
+      quarantine! do
+        it "writes correctly" do
+          thr = Thread.new do
+            IO.read(@fifo)
+          end
+          begin
+            string = "hi"
+            IO.write(@fifo, string).should == string.length
+          ensure
+            thr.join
+          end
         end
       end
     end
+
+    ruby_version_is "3.3"..."4.0" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        -> {
+          -> {
+            IO.write("|cat", "xxx")
+          }.should output_to_fd("xxx")
+        }.should complain(/IO process creation with a leading '\|'/)
+      end
+    end
   end
 end
 
 describe "IO#write" do
   it_behaves_like :io_write, :write
+  it_behaves_like :io_write_transcode, :write
 
-  ruby_version_is "2.5" do
-    it "accepts multiple arguments" do
-      IO.pipe do |r, w|
-        w.write("foo", "bar")
-        w.close
+  it "accepts multiple arguments" do
+    IO.pipe do |r, w|
+      w.write("foo", "bar")
+      w.close
 
-        r.read.should == "foobar"
-      end
+      r.read.should == "foobar"
     end
   end
 end
@@ -164,3 +273,25 @@ platform_is :windows do
     end
   end
 end
+
+describe "IO#write on STDOUT" do
+  # https://bugs.ruby-lang.org/issues/14413
+  platform_is_not :windows do
+    it "raises SignalException SIGPIPE if the stream is closed instead of Errno::EPIPE like other IOs" do
+      stderr_file = tmp("stderr")
+      begin
+        IO.popen([*ruby_exe, "-e", "loop { puts :ok }"], "r", err: stderr_file) do |io|
+          io.gets.should == "ok\n"
+          io.close
+        end
+        status = $?
+        status.should_not.success?
+        status.should.signaled?
+        Signal.signame(status.termsig).should == 'PIPE'
+        File.read(stderr_file).should.empty?
+      ensure
+        rm_r stderr_file
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/kernel/Complex_spec.rb b/spec/ruby/core/kernel/Complex_spec.rb
index 37f9843931..346d50ab5e 100644
--- a/spec/ruby/core/kernel/Complex_spec.rb
+++ b/spec/ruby/core/kernel/Complex_spec.rb
@@ -1,4 +1,6 @@
 require_relative '../../spec_helper'
+require_relative '../../shared/kernel/complex'
+require_relative 'fixtures/Complex'
 
 describe "Kernel.Complex()" do
   describe "when passed [Complex, Complex]" do
@@ -58,7 +60,92 @@ describe "Kernel.Complex()" do
     end
   end
 
-  describe "when passed a String" do
+  describe "when passed [String]" do
+    it_behaves_like :kernel_complex, :Complex_method, KernelSpecs
+
+    context "invalid argument" do
+      it "raises Encoding::CompatibilityError if String is in not ASCII-compatible encoding" do
+        -> {
+          Complex("79+4i".encode("UTF-16"))
+        }.should raise_error(Encoding::CompatibilityError, "ASCII incompatible encoding: UTF-16")
+      end
+
+      it "raises ArgumentError for unrecognised Strings" do
+        -> {
+          Complex("ruby")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "ruby"')
+      end
+
+      it "raises ArgumentError for trailing garbage" do
+        -> {
+          Complex("79+4iruby")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "79+4iruby"')
+      end
+
+      it "does not understand Float::INFINITY" do
+        -> {
+          Complex("Infinity")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "Infinity"')
+
+        -> {
+          Complex("-Infinity")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "-Infinity"')
+      end
+
+      it "does not understand Float::NAN" do
+        -> {
+          Complex("NaN")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "NaN"')
+      end
+
+      it "does not understand a sequence of _" do
+        -> {
+          Complex("7__9+4__0i")
+        }.should raise_error(ArgumentError, 'invalid value for convert(): "7__9+4__0i"')
+      end
+
+      it "does not allow null-byte" do
+        -> {
+          Complex("1-2i\0")
+        }.should raise_error(ArgumentError, "string contains null byte")
+      end
+    end
+
+    context "invalid argument and exception: false passed" do
+      it "raises Encoding::CompatibilityError if String is in not ASCII-compatible encoding" do
+        -> {
+          Complex("79+4i".encode("UTF-16"), exception: false)
+        }.should raise_error(Encoding::CompatibilityError, "ASCII incompatible encoding: UTF-16")
+      end
+
+      it "returns nil for unrecognised Strings" do
+        Complex("ruby", exception: false).should == nil
+      end
+
+      it "returns nil when trailing garbage" do
+        Complex("79+4iruby", exception: false).should == nil
+      end
+
+      it "returns nil for Float::INFINITY" do
+        Complex("Infinity", exception: false).should == nil
+        Complex("-Infinity", exception: false).should == nil
+      end
+
+      it "returns nil for Float::NAN" do
+        Complex("NaN", exception: false).should == nil
+      end
+
+      it "returns nil when there is a sequence of _" do
+        Complex("7__9+4__0i", exception: false).should == nil
+      end
+
+      it "returns nil when String contains null-byte" do
+        Complex("1-2i\0", exception: false).should == nil
+      end
+    end
+  end
+
+  describe "when passes [String, String]" do
     it "needs to be reviewed for spec completeness"
   end
 
@@ -139,49 +226,51 @@ describe "Kernel.Complex()" do
     end
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and [Numeric]" do
-        it "returns a complex number" do
-          Complex("123", exception: false).should == Complex(123)
-        end
+  describe "when passed exception: false" do
+    describe "and [Numeric]" do
+      it "returns a complex number" do
+        Complex("123", exception: false).should == Complex(123)
       end
+    end
 
-      describe "and [non-Numeric]" do
-        it "swallows an error" do
-          Complex(:sym, exception: false).should == nil
-        end
+    describe "and [non-Numeric]" do
+      it "swallows an error" do
+        Complex(:sym, exception: false).should == nil
       end
+    end
 
-      describe "and [non-Numeric, Numeric] argument" do
-        it "throws a TypeError" do
-          -> { Complex(:sym, 0, exception: false) }.should raise_error(TypeError, "not a real")
-        end
+    describe "and [non-Numeric, Numeric] argument" do
+      it "throws a TypeError" do
+        -> { Complex(:sym, 0, exception: false) }.should raise_error(TypeError, "not a real")
       end
+    end
 
-      describe "and [anything, non-Numeric] argument" do
-        it "swallows an error" do
-          Complex("a",  :sym, exception: false).should == nil
-          Complex(:sym, :sym, exception: false).should == nil
-          Complex(0,    :sym, exception: false).should == nil
-        end
+    describe "and [anything, non-Numeric] argument" do
+      it "swallows an error" do
+        Complex("a",  :sym, exception: false).should == nil
+        Complex(:sym, :sym, exception: false).should == nil
+        Complex(0,    :sym, exception: false).should == nil
       end
+    end
 
-      describe "and non-numeric String arguments" do
-        it "swallows an error" do
-          Complex("a", "b", exception: false).should == nil
-          Complex("a", 0, exception: false).should == nil
-          Complex(0, "b", exception: false).should == nil
-        end
+    describe "and non-numeric String arguments" do
+      it "swallows an error" do
+        Complex("a", "b", exception: false).should == nil
+        Complex("a", 0, exception: false).should == nil
+        Complex(0, "b", exception: false).should == nil
       end
+    end
 
-      describe "and nil arguments" do
-        it "swallows an error" do
-          Complex(nil, exception: false).should == nil
-          Complex(0, nil, exception: false).should == nil
-          Complex(nil, 0, exception: false).should == nil
-        end
+    describe "and nil arguments" do
+      it "swallows an error" do
+        Complex(nil, exception: false).should == nil
+        Complex(0, nil, exception: false).should == nil
+        Complex(nil, 0, exception: false).should == nil
       end
     end
   end
+
+  it "freezes its result" do
+    Complex(1).frozen?.should == true
+  end
 end
diff --git a/spec/ruby/core/kernel/Float_spec.rb b/spec/ruby/core/kernel/Float_spec.rb
index 6580c38137..9c436b05f7 100644
--- a/spec/ruby/core/kernel/Float_spec.rb
+++ b/spec/ruby/core/kernel/Float_spec.rb
@@ -41,7 +41,7 @@ describe :kernel_float, shared: true do
   end
 
   it "converts Strings to floats without calling #to_f" do
-    string = "10"
+    string = +"10"
     string.should_not_receive(:to_f)
     @object.send(:Float, string).should == 10.0
   end
@@ -54,6 +54,12 @@ describe :kernel_float, shared: true do
     -> { @object.send(:Float, "float") }.should raise_error(ArgumentError)
   end
 
+  it "raises an ArgumentError for a String with string in error message" do
+    -> { @object.send(:Float, "foo") }.should raise_error(ArgumentError) { |e|
+      e.message.should == 'invalid value for Float(): "foo"'
+    }
+  end
+
   it "raises an ArgumentError if there are two decimal points in the String" do
     -> { @object.send(:Float, "10.0.0") }.should raise_error(ArgumentError)
   end
@@ -151,6 +157,26 @@ describe :kernel_float, shared: true do
     @object.send(:Float, "1\t\n").should == 1.0
   end
 
+  ruby_version_is ""..."3.4" do
+    it "raises ArgumentError if a fractional part is missing" do
+      -> { @object.send(:Float, "1.") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "+1.") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "-1.") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "1.e+0") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "1.e-2") }.should raise_error(ArgumentError)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "allows String representation without a fractional part" do
+      @object.send(:Float, "1.").should == 1.0
+      @object.send(:Float, "+1.").should == 1.0
+      @object.send(:Float, "-1.").should == -1.0
+      @object.send(:Float, "1.e+0").should == 1.0
+      @object.send(:Float, "1.e-2").should be_close(0.01, TOLERANCE)
+    end
+  end
+
   %w(e E).each do |e|
     it "raises an ArgumentError if #{e} is the trailing character" do
       -> { @object.send(:Float, "2#{e}") }.should raise_error(ArgumentError)
@@ -198,59 +224,107 @@ describe :kernel_float, shared: true do
     end
   end
 
-  describe "for hexadecimal literals with binary exponent" do
-    %w(p P).each do |p|
-      it "interprets the fractional part (on the left side of '#{p}') in hexadecimal" do
-        @object.send(:Float, "0x10#{p}0").should == 16.0
-      end
+  context "for hexadecimal literals" do
+    it "interprets the 0x prefix as hexadecimal" do
+      @object.send(:Float, "0x10").should == 16.0
+      @object.send(:Float, "0x0F").should == 15.0
+      @object.send(:Float, "0x0f").should == 15.0
+    end
 
-      it "interprets the exponent (on the right of '#{p}') in decimal" do
-        @object.send(:Float, "0x1#{p}10").should == 1024.0
-      end
+    it "interprets negative hex value" do
+      @object.send(:Float, "-0x10").should == -16.0
+    end
 
-      it "raises an ArgumentError if #{p} is the trailing character" do
-        -> { @object.send(:Float, "0x1#{p}") }.should raise_error(ArgumentError)
-      end
+    it "accepts embedded _ if the number does not contain a-f" do
+      @object.send(:Float, "0x1_0").should == 16.0
+    end
 
-      it "raises an ArgumentError if #{p} is the leading character" do
-        -> { @object.send(:Float, "0x#{p}1") }.should raise_error(ArgumentError)
+    ruby_version_is ""..."3.4.3" do
+      it "does not accept embedded _ if the number contains a-f" do
+        -> { @object.send(:Float, "0x1_0a") }.should raise_error(ArgumentError)
+        @object.send(:Float, "0x1_0a", exception: false).should be_nil
       end
+    end
 
-      it "returns Infinity for '0x1#{p}10000'" do
-        @object.send(:Float, "0x1#{p}10000").should == Float::INFINITY
+    ruby_version_is "3.4.3" do
+      it "accepts embedded _ if the number contains a-f" do
+        @object.send(:Float, "0x1_0a").should == 0x10a.to_f
       end
+    end
 
-      it "returns 0 for '0x1#{p}-10000'" do
-        @object.send(:Float, "0x1#{p}-10000").should == 0
-      end
+    it "does not accept _ before, after or inside the 0x prefix" do
+      -> { @object.send(:Float, "_0x10") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "0_x10") }.should raise_error(ArgumentError)
+      -> { @object.send(:Float, "0x_10") }.should raise_error(ArgumentError)
+      @object.send(:Float, "_0x10", exception: false).should be_nil
+      @object.send(:Float, "0_x10", exception: false).should be_nil
+      @object.send(:Float, "0x_10", exception: false).should be_nil
+    end
 
-      it "allows embedded _ in a number on either side of the #{p}" do
-        @object.send(:Float, "0x1_0#{p}10").should == 16384.0
-        @object.send(:Float, "0x10#{p}1_0").should == 16384.0
-        @object.send(:Float, "0x1_0#{p}1_0").should == 16384.0
-      end
+    it "parses negative hexadecimal string as negative float" do
+      @object.send(:Float, "-0x7b").should == -123.0
+    end
 
-      it "raises an exception if a space is embedded on either side of the '#{p}'" do
-        -> { @object.send(:Float, "0x1 0#{p}10") }.should raise_error(ArgumentError)
-        -> { @object.send(:Float, "0x10#{p}1 0") }.should raise_error(ArgumentError)
+    ruby_version_is "3.4" do
+      it "accepts a fractional part" do
+        @object.send(:Float, "0x0.8").should == 0.5
       end
+    end
 
-      it "raises an exception if there's a leading _ on either side of the '#{p}'" do
-        -> { @object.send(:Float, "0x_10#{p}10") }.should raise_error(ArgumentError)
-        -> { @object.send(:Float, "0x10#{p}_10") }.should raise_error(ArgumentError)
-      end
+    describe "with binary exponent" do
+      %w(p P).each do |p|
+        it "interprets the fractional part (on the left side of '#{p}') in hexadecimal" do
+          @object.send(:Float, "0x10#{p}0").should == 16.0
+        end
 
-      it "raises an exception if there's a trailing _ on either side of the '#{p}'" do
-        -> { @object.send(:Float, "0x10_#{p}10") }.should raise_error(ArgumentError)
-        -> { @object.send(:Float, "0x10#{p}10_") }.should raise_error(ArgumentError)
-      end
+        it "interprets the exponent (on the right of '#{p}') in decimal" do
+          @object.send(:Float, "0x1#{p}10").should == 1024.0
+        end
 
-      it "allows hexadecimal points on the left side of the '#{p}'" do
-        @object.send(:Float, "0x1.8#{p}0").should == 1.5
-      end
+        it "raises an ArgumentError if #{p} is the trailing character" do
+          -> { @object.send(:Float, "0x1#{p}") }.should raise_error(ArgumentError)
+        end
+
+        it "raises an ArgumentError if #{p} is the leading character" do
+          -> { @object.send(:Float, "0x#{p}1") }.should raise_error(ArgumentError)
+        end
+
+        it "returns Infinity for '0x1#{p}10000'" do
+          @object.send(:Float, "0x1#{p}10000").should == Float::INFINITY
+        end
+
+        it "returns 0 for '0x1#{p}-10000'" do
+          @object.send(:Float, "0x1#{p}-10000").should == 0
+        end
+
+        it "allows embedded _ in a number on either side of the #{p}" do
+          @object.send(:Float, "0x1_0#{p}10").should == 16384.0
+          @object.send(:Float, "0x10#{p}1_0").should == 16384.0
+          @object.send(:Float, "0x1_0#{p}1_0").should == 16384.0
+        end
+
+        it "raises an exception if a space is embedded on either side of the '#{p}'" do
+          -> { @object.send(:Float, "0x1 0#{p}10") }.should raise_error(ArgumentError)
+          -> { @object.send(:Float, "0x10#{p}1 0") }.should raise_error(ArgumentError)
+        end
 
-      it "raises an ArgumentError if there's a decimal point on the right side of the '#{p}'" do
-        -> { @object.send(:Float, "0x1#{p}1.0") }.should raise_error(ArgumentError)
+        it "raises an exception if there's a leading _ on either side of the '#{p}'" do
+          -> { @object.send(:Float, "0x_10#{p}10") }.should raise_error(ArgumentError)
+          -> { @object.send(:Float, "0x10#{p}_10") }.should raise_error(ArgumentError)
+        end
+
+        it "raises an exception if there's a trailing _ on either side of the '#{p}'" do
+          -> { @object.send(:Float, "0x10_#{p}10") }.should raise_error(ArgumentError)
+          -> { @object.send(:Float, "0x10#{p}10_") }.should raise_error(ArgumentError)
+        end
+
+        it "allows hexadecimal points on the left side of the '#{p}'" do
+          @object.send(:Float, "0x1.8#{p}0").should == 1.5
+        end
+
+        it "raises an ArgumentError if there's a decimal point on the right side of the '#{p}'" do
+          -> { @object.send(:Float, "0x1#{p}1.0") }.should raise_error(ArgumentError)
+        end
       end
     end
   end
@@ -274,7 +348,7 @@ describe :kernel_float, shared: true do
     nan2.should equal(nan)
   end
 
-  it "returns the identical Infinity if to_f is called and it returns Infinity" do
+  it "returns the identical Infinity if #to_f is called and it returns Infinity" do
     infinity = infinity_value
     (infinity_to_f = mock('Infinity')).should_receive(:to_f).once.and_return(infinity)
     infinity2 = @object.send(:Float, infinity_to_f)
@@ -300,27 +374,25 @@ describe :kernel_float, shared: true do
     -> { @object.send(:Float, c) }.should raise_error(RangeError)
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and valid input" do
-        it "returns a Float number" do
-          @object.send(:Float, 1, exception: false).should == 1.0
-          @object.send(:Float, "1", exception: false).should == 1.0
-          @object.send(:Float, "1.23", exception: false).should == 1.23
-        end
+  describe "when passed exception: false" do
+    describe "and valid input" do
+      it "returns a Float number" do
+        @object.send(:Float, 1, exception: false).should == 1.0
+        @object.send(:Float, "1", exception: false).should == 1.0
+        @object.send(:Float, "1.23", exception: false).should == 1.23
       end
+    end
 
-      describe "and invalid input" do
-        it "swallows an error" do
-          @object.send(:Float, "abc", exception: false).should == nil
-          @object.send(:Float, :sym, exception: false).should == nil
-        end
+    describe "and invalid input" do
+      it "swallows an error" do
+        @object.send(:Float, "abc", exception: false).should == nil
+        @object.send(:Float, :sym, exception: false).should == nil
       end
+    end
 
-      describe "and nil" do
-        it "swallows it" do
-          @object.send(:Float, nil, exception: false).should == nil
-        end
+    describe "and nil" do
+      it "swallows it" do
+        @object.send(:Float, nil, exception: false).should == nil
       end
     end
   end
diff --git a/spec/ruby/core/kernel/Integer_spec.rb b/spec/ruby/core/kernel/Integer_spec.rb
index 59b41d37e6..74dd3e0dd2 100644
--- a/spec/ruby/core/kernel/Integer_spec.rb
+++ b/spec/ruby/core/kernel/Integer_spec.rb
@@ -10,38 +10,27 @@ describe :kernel_integer, shared: true do
     Integer(100).should == 100
   end
 
-  ruby_version_is ""..."2.6" do
-    it "uncritically return the value of to_int even if it is not an Integer" do
-      obj = mock("object")
-      obj.should_receive(:to_int).and_return("1")
-      obj.should_not_receive(:to_i)
-      Integer(obj).should == "1"
-    end
+  it "raises a TypeError when to_int returns not-an-Integer object and to_i returns nil" do
+    obj = mock("object")
+    obj.should_receive(:to_int).and_return("1")
+    obj.should_receive(:to_i).and_return(nil)
+    -> { Integer(obj) }.should raise_error(TypeError)
   end
 
-  ruby_version_is "2.6" do
-    it "raises a TypeError when to_int returns not-an-Integer object and to_i returns nil" do
-      obj = mock("object")
-      obj.should_receive(:to_int).and_return("1")
-      obj.should_receive(:to_i).and_return(nil)
-      -> { Integer(obj) }.should raise_error(TypeError)
-    end
-
-    it "return a result of to_i when to_int does not return an Integer" do
-      obj = mock("object")
-      obj.should_receive(:to_int).and_return("1")
-      obj.should_receive(:to_i).and_return(42)
-      Integer(obj).should == 42
-    end
+  it "return a result of to_i when to_int does not return an Integer" do
+    obj = mock("object")
+    obj.should_receive(:to_int).and_return("1")
+    obj.should_receive(:to_i).and_return(42)
+    Integer(obj).should == 42
   end
 
   it "raises a TypeError when passed nil" do
     -> { Integer(nil) }.should raise_error(TypeError)
   end
 
-  it "returns a Fixnum or Bignum object" do
-    Integer(2).should be_an_instance_of(Fixnum)
-    Integer(9**99).should be_an_instance_of(Bignum)
+  it "returns an Integer object" do
+    Integer(2).should be_an_instance_of(Integer)
+    Integer(9**99).should be_an_instance_of(Integer)
   end
 
   it "truncates Floats" do
@@ -100,65 +89,63 @@ describe :kernel_integer, shared: true do
     -> { Integer(infinity_value) }.should raise_error(FloatDomainError)
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and to_i returns a value that is not an Integer" do
-        it "swallows an error" do
-          obj = mock("object")
-          obj.should_receive(:to_i).and_return("1")
-          Integer(obj, exception: false).should == nil
-        end
+  describe "when passed exception: false" do
+    describe "and to_i returns a value that is not an Integer" do
+      it "swallows an error" do
+        obj = mock("object")
+        obj.should_receive(:to_i).and_return("1")
+        Integer(obj, exception: false).should == nil
       end
+    end
 
-      describe "and no to_int or to_i methods exist" do
-        it "swallows an error" do
-          obj = mock("object")
-          Integer(obj, exception: false).should == nil
-        end
+    describe "and no to_int or to_i methods exist" do
+      it "swallows an error" do
+        obj = mock("object")
+        Integer(obj, exception: false).should == nil
       end
+    end
 
-      describe "and to_int returns nil and no to_i exists" do
-        it "swallows an error" do
-          obj = mock("object")
-          obj.should_receive(:to_i).and_return(nil)
-          Integer(obj, exception: false).should == nil
-        end
+    describe "and to_int returns nil and no to_i exists" do
+      it "swallows an error" do
+        obj = mock("object")
+        obj.should_receive(:to_i).and_return(nil)
+        Integer(obj, exception: false).should == nil
       end
+    end
 
-      describe "and passed NaN" do
-        it "swallows an error" do
-          Integer(nan_value, exception: false).should == nil
-        end
+    describe "and passed NaN" do
+      it "swallows an error" do
+        Integer(nan_value, exception: false).should == nil
       end
+    end
 
-      describe "and passed Infinity" do
-        it "swallows an error" do
-          Integer(infinity_value, exception: false).should == nil
-        end
+    describe "and passed Infinity" do
+      it "swallows an error" do
+        Integer(infinity_value, exception: false).should == nil
       end
+    end
 
-      describe "and passed nil" do
-        it "swallows an error" do
-          Integer(nil, exception: false).should == nil
-        end
+    describe "and passed nil" do
+      it "swallows an error" do
+        Integer(nil, exception: false).should == nil
       end
+    end
 
-      describe "and passed a String that contains numbers" do
-        it "normally parses it and returns an Integer" do
-          Integer("42", exception: false).should == 42
-        end
+    describe "and passed a String that contains numbers" do
+      it "normally parses it and returns an Integer" do
+        Integer("42", exception: false).should == 42
       end
+    end
 
-      describe "and passed a String that can't be converted to an Integer" do
-        it "swallows an error" do
-          Integer("abc", exception: false).should == nil
-        end
+    describe "and passed a String that can't be converted to an Integer" do
+      it "swallows an error" do
+        Integer("abc", exception: false).should == nil
       end
     end
   end
 end
 
-describe "Integer() given a String", shared: true do
+describe :kernel_integer_string, shared: true do
   it "raises an ArgumentError if the String is a null byte" do
     -> { Integer("\0") }.should raise_error(ArgumentError)
   end
@@ -246,30 +233,28 @@ describe "Integer() given a String", shared: true do
     -> { Integer("") }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and multiple leading -s" do
-        it "swallows an error" do
-          Integer("---1", exception: false).should == nil
-        end
+  describe "when passed exception: false" do
+    describe "and multiple leading -s" do
+      it "swallows an error" do
+        Integer("---1", exception: false).should == nil
       end
+    end
 
-      describe "and multiple trailing -s" do
-        it "swallows an error" do
-          Integer("1---", exception: false).should == nil
-        end
+    describe "and multiple trailing -s" do
+      it "swallows an error" do
+        Integer("1---", exception: false).should == nil
       end
+    end
 
-      describe "and an argument that contains a period" do
-        it "swallows an error" do
-          Integer("0.0", exception: false).should == nil
-        end
+    describe "and an argument that contains a period" do
+      it "swallows an error" do
+        Integer("0.0", exception: false).should == nil
       end
+    end
 
-      describe "and an empty string" do
-        it "swallows an error" do
-          Integer("", exception: false).should == nil
-        end
+    describe "and an empty string" do
+      it "swallows an error" do
+        Integer("", exception: false).should == nil
       end
     end
   end
@@ -363,7 +348,7 @@ describe "Integer() given a String", shared: true do
   end
 end
 
-describe "Integer() given a String and base", shared: true do
+describe :kernel_integer_string_base, shared: true do
   it "raises an ArgumentError if the String is a null byte" do
     -> { Integer("\0", 2) }.should raise_error(ArgumentError)
   end
@@ -588,26 +573,46 @@ describe "Integer() given a String and base", shared: true do
         -> { Integer("0#{d}1", base) }.should raise_error(ArgumentError)
       end
     end
+  end
+
+  it "raises an ArgumentError if a base is given for a non-String value" do
+    -> { Integer(98, 15) }.should raise_error(ArgumentError)
+  end
+
+  it "tries to convert the base to an integer using to_int" do
+    obj = mock('8')
+    obj.should_receive(:to_int).and_return(8)
+
+    Integer("777", obj).should == 0777
+  end
+
+  # https://bugs.ruby-lang.org/issues/19349
+  ruby_version_is ''...'3.3' do
+    it "ignores the base if it is not an integer and does not respond to #to_i" do
+      Integer("777", "8").should == 777
+    end
+  end
 
-    it "raises an ArgumentError if a base is given for a non-String value" do
-      -> { Integer(98, 15) }.should raise_error(ArgumentError)
+  ruby_version_is '3.3' do
+    it "raises a TypeError if it is not an integer and does not respond to #to_i" do
+      -> {
+        Integer("777", "8")
+      }.should raise_error(TypeError, "no implicit conversion of String into Integer")
     end
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and valid argument" do
-        it "returns an Integer number" do
-          Integer("100", 10, exception: false).should == 100
-          Integer("100", 2, exception: false).should == 4
-        end
+  describe "when passed exception: false" do
+    describe "and valid argument" do
+      it "returns an Integer number" do
+        Integer("100", 10, exception: false).should == 100
+        Integer("100", 2, exception: false).should == 4
       end
+    end
 
-      describe "and invalid argument" do
-        it "swallows an error" do
-          Integer("999", 2, exception: false).should == nil
-          Integer("abc", 10, exception: false).should == nil
-        end
+    describe "and invalid argument" do
+      it "swallows an error" do
+        Integer("999", 2, exception: false).should == nil
+        Integer("abc", 10, exception: false).should == nil
       end
     end
   end
@@ -794,9 +799,9 @@ describe "Kernel.Integer" do
 
   # TODO: fix these specs
   it_behaves_like :kernel_integer, :Integer, Kernel
-  it_behaves_like "Integer() given a String", :Integer
+  it_behaves_like :kernel_integer_string, :Integer
 
-  it_behaves_like "Integer() given a String and base", :Integer
+  it_behaves_like :kernel_integer_string_base, :Integer
 
   it "is a public method" do
     Kernel.Integer(10).should == 10
@@ -808,9 +813,9 @@ describe "Kernel#Integer" do
 
   # TODO: fix these specs
   it_behaves_like :kernel_integer, :Integer, Object.new
-  it_behaves_like "Integer() given a String", :Integer
+  it_behaves_like :kernel_integer_string, :Integer
 
-  it_behaves_like "Integer() given a String and base", :Integer
+  it_behaves_like :kernel_integer_string_base, :Integer
 
   it "is a private method" do
     Kernel.should have_private_instance_method(:Integer)
diff --git a/spec/ruby/core/kernel/Rational_spec.rb b/spec/ruby/core/kernel/Rational_spec.rb
index 2d1051db7f..cc11a35451 100644
--- a/spec/ruby/core/kernel/Rational_spec.rb
+++ b/spec/ruby/core/kernel/Rational_spec.rb
@@ -1,6 +1,236 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/rational/Rational'
+require_relative '../rational/fixtures/rational'
 
 describe "Kernel.Rational" do
-  it_behaves_like :kernel_Rational, :Rational
+  describe "passed Integer" do
+    # Guard against the Mathn library
+    guard -> { !defined?(Math.rsqrt) } do
+      it "returns a new Rational number with 1 as the denominator" do
+        Rational(1).should eql(Rational(1, 1))
+        Rational(-3).should eql(Rational(-3, 1))
+        Rational(bignum_value).should eql(Rational(bignum_value, 1))
+      end
+    end
+  end
+
+  describe "passed two integers" do
+    it "returns a new Rational number" do
+      rat = Rational(1, 2)
+      rat.numerator.should == 1
+      rat.denominator.should == 2
+      rat.should be_an_instance_of(Rational)
+
+      rat = Rational(-3, -5)
+      rat.numerator.should == 3
+      rat.denominator.should == 5
+      rat.should be_an_instance_of(Rational)
+
+      rat = Rational(bignum_value, 3)
+      rat.numerator.should == bignum_value
+      rat.denominator.should == 3
+      rat.should be_an_instance_of(Rational)
+    end
+
+    it "reduces the Rational" do
+      rat = Rational(2, 4)
+      rat.numerator.should == 1
+      rat.denominator.should == 2
+
+      rat = Rational(3, 9)
+      rat.numerator.should == 1
+      rat.denominator.should == 3
+    end
+  end
+
+  describe "when passed a String" do
+    it "converts the String to a Rational using the same method as String#to_r" do
+      r = Rational(13, 25)
+      s_r = ".52".to_r
+      r_s = Rational(".52")
+
+      r_s.should == r
+      r_s.should == s_r
+    end
+
+    it "scales the Rational value of the first argument by the Rational value of the second" do
+      Rational(".52", ".6").should == Rational(13, 15)
+      Rational(".52", "1.6").should == Rational(13, 40)
+    end
+
+    it "does not use the same method as Float#to_r" do
+      r = Rational(3, 5)
+      f_r = 0.6.to_r
+      r_s = Rational("0.6")
+
+      r_s.should == r
+      r_s.should_not == f_r
+    end
+  end
+
+  describe "when passed a Numeric" do
+    it "calls #to_r to convert the first argument to a Rational" do
+      num = RationalSpecs::SubNumeric.new(2)
+
+      Rational(num).should == Rational(2)
+    end
+  end
+
+  describe "when passed a Complex" do
+    context "[Complex]" do
+      it "returns a Rational from the real part if the imaginary part is 0" do
+        Rational(Complex(1, 0)).should == Rational(1)
+      end
+
+      it "raises a RangeError if the imaginary part is not 0" do
+        -> { Rational(Complex(1, 2)) }.should raise_error(RangeError, "can't convert 1+2i into Rational")
+      end
+    end
+
+    context "[Numeric, Complex]" do
+      it "uses the real part if the imaginary part is 0" do
+        Rational(1, Complex(2, 0)).should == Rational(1, 2)
+      end
+
+      it "divides a numerator by the Complex denominator if the imaginary part is not 0" do
+        Rational(1, Complex(2, 1)).should == Complex(2/5r, -1/5r)
+      end
+    end
+  end
+
+  context "when passed neither a Numeric nor a String" do
+    it "converts to Rational with #to_r method" do
+      obj = Object.new
+      def obj.to_r; 1/2r; end
+
+      Rational(obj).should == 1/2r
+    end
+
+    it "tries to convert to Integer with #to_int method if it does not respond to #to_r" do
+      obj = Object.new
+      def obj.to_int; 1; end
+
+      Rational(obj).should == 1r
+    end
+
+    it "raises TypeError if it neither responds to #to_r nor #to_int method" do
+      -> { Rational([]) }.should raise_error(TypeError, "can't convert Array into Rational")
+      -> { Rational({}) }.should raise_error(TypeError, "can't convert Hash into Rational")
+      -> { Rational(nil) }.should raise_error(TypeError, "can't convert nil into Rational")
+    end
+
+    it "swallows exception raised in #to_int method" do
+      object = Object.new
+      def object.to_int() raise NoMethodError; end
+
+      -> { Rational(object) }.should raise_error(TypeError)
+      -> { Rational(object, 1) }.should raise_error(TypeError)
+      -> { Rational(1, object) }.should raise_error(TypeError)
+    end
+
+    it "raises TypeError if #to_r does not return Rational" do
+      obj = Object.new
+      def obj.to_r; []; end
+
+      -> { Rational(obj) }.should raise_error(TypeError, "can't convert Object to Rational (Object#to_r gives Array)")
+    end
+  end
+
+  it "raises a ZeroDivisionError if the second argument is 0" do
+    -> { Rational(1, 0) }.should raise_error(ZeroDivisionError, "divided by 0")
+    -> { Rational(1, 0.0) }.should raise_error(ZeroDivisionError, "divided by 0")
+  end
+
+  it "raises a TypeError if the first argument is nil" do
+    -> { Rational(nil) }.should raise_error(TypeError, "can't convert nil into Rational")
+  end
+
+  it "raises a TypeError if the second argument is nil" do
+    -> { Rational(1, nil) }.should raise_error(TypeError, "can't convert nil into Rational")
+  end
+
+  it "raises a TypeError if the first argument is a Symbol" do
+    -> { Rational(:sym) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError if the second argument is a Symbol" do
+    -> { Rational(1, :sym) }.should raise_error(TypeError)
+  end
+
+  describe "when passed exception: false" do
+    describe "and [non-Numeric]" do
+      it "swallows an error" do
+        Rational(:sym, exception: false).should == nil
+        Rational("abc", exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_r" do
+        obj = Object.new
+        def obj.to_r; raise; end
+        Rational(obj, exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_int" do
+        obj = Object.new
+        def obj.to_int; raise; end
+        Rational(obj, exception: false).should == nil
+      end
+    end
+
+    describe "and [non-Numeric, Numeric]" do
+      it "swallows an error" do
+        Rational(:sym, 1, exception: false).should == nil
+        Rational("abc", 1, exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_r" do
+        obj = Object.new
+        def obj.to_r; raise; end
+        Rational(obj, 1, exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_int" do
+        obj = Object.new
+        def obj.to_int; raise; end
+        Rational(obj, 1, exception: false).should == nil
+      end
+    end
+
+    describe "and [anything, non-Numeric]" do
+      it "swallows an error" do
+        Rational(:sym, :sym, exception: false).should == nil
+        Rational("abc", :sym, exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_r" do
+        obj = Object.new
+        def obj.to_r; raise; end
+        Rational(obj, obj, exception: false).should == nil
+      end
+
+      it "swallows an exception raised in #to_int" do
+        obj = Object.new
+        def obj.to_int; raise; end
+        Rational(obj, obj, exception: false).should == nil
+      end
+    end
+
+    describe "and non-Numeric String arguments" do
+      it "swallows an error" do
+        Rational("a", "b", exception: false).should == nil
+        Rational("a", 0, exception: false).should == nil
+        Rational(0, "b", exception: false).should == nil
+      end
+    end
+
+    describe "and nil arguments" do
+      it "swallows an error" do
+        Rational(nil, exception: false).should == nil
+        Rational(nil, nil, exception: false).should == nil
+      end
+    end
+  end
+
+  it "freezes its result" do
+    Rational(1).frozen?.should == true
+  end
 end
diff --git a/spec/ruby/core/kernel/String_spec.rb b/spec/ruby/core/kernel/String_spec.rb
index 47ee797be5..7caec6eda5 100644
--- a/spec/ruby/core/kernel/String_spec.rb
+++ b/spec/ruby/core/kernel/String_spec.rb
@@ -78,7 +78,7 @@ describe :kernel_String, shared: true do
   end
 
   it "returns the same object if it is already a String" do
-    string = "Hello"
+    string = +"Hello"
     string.should_not_receive(:to_s)
     string2 = @object.send(@method, string)
     string.should equal(string2)
diff --git a/spec/ruby/core/kernel/__dir___spec.rb b/spec/ruby/core/kernel/__dir___spec.rb
index 3c34277277..242adbf48b 100644
--- a/spec/ruby/core/kernel/__dir___spec.rb
+++ b/spec/ruby/core/kernel/__dir___spec.rb
@@ -5,6 +5,13 @@ describe "Kernel#__dir__" do
     __dir__.should == File.realpath(File.dirname(__FILE__))
   end
 
+  it "returns the expanded path of the directory when used in the main script" do
+    fixtures_dir = File.dirname(fixture(__FILE__, '__dir__.rb'))
+    Dir.chdir(fixtures_dir) do
+      ruby_exe("__dir__.rb").should == "__dir__.rb\n#{fixtures_dir}\n"
+    end
+  end
+
   context "when used in eval with a given filename" do
     it "returns File.dirname(filename)" do
       eval("__dir__", nil, "foo.rb").should == "."
@@ -13,8 +20,8 @@ describe "Kernel#__dir__" do
   end
 
   context "when used in eval with top level binding" do
-    it "returns the real name of the directory containing the currently-executing file" do
-      eval("__dir__", binding).should == File.realpath(File.dirname(__FILE__))
+    it "returns nil" do
+      eval("__dir__", binding).should == nil
     end
   end
 end
diff --git a/spec/ruby/core/kernel/at_exit_spec.rb b/spec/ruby/core/kernel/at_exit_spec.rb
index 21149f965b..ebd9a71d15 100644
--- a/spec/ruby/core/kernel/at_exit_spec.rb
+++ b/spec/ruby/core/kernel/at_exit_spec.rb
@@ -1,42 +1,17 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../../shared/kernel/at_exit'
 
 describe "Kernel.at_exit" do
+  it_behaves_like :kernel_at_exit, :at_exit
+
   it "is a private method" do
     Kernel.should have_private_instance_method(:at_exit)
   end
 
-  it "runs after all other code" do
-    ruby_exe("at_exit {print 5}; print 6").should == "65"
-  end
-
-  it "runs in reverse order of registration" do
-    code = "at_exit {print 4};at_exit {print 5}; print 6; at_exit {print 7}"
-    ruby_exe(code).should == "6754"
-  end
-
-  it "allows calling exit inside at_exit handler" do
-    code = "at_exit {print 3}; at_exit {print 4; exit; print 5}; at_exit {print 6}"
-    ruby_exe(code).should == "643"
+  it "raises ArgumentError if called without a block" do
+    -> { at_exit }.should raise_error(ArgumentError, "called without a block")
   end
-
-  it "gives access to the last raised exception" do
-    code = <<-EOC
-      at_exit do
-        puts "The exception matches: \#{$! == $exception}"
-      end
-
-      begin
-        raise "foo"
-      rescue => $exception
-        raise
-      end
-    EOC
-
-    result = ruby_exe(code, args: "2>&1", escape: true)
-    result.should =~ /The exception matches: true/
-  end
-
 end
 
 describe "Kernel#at_exit" do
diff --git a/spec/ruby/core/kernel/autoload_spec.rb b/spec/ruby/core/kernel/autoload_spec.rb
index 68732a69ef..5edb70541d 100644
--- a/spec/ruby/core/kernel/autoload_spec.rb
+++ b/spec/ruby/core/kernel/autoload_spec.rb
@@ -7,7 +7,9 @@ require_relative 'fixtures/classes'
 
 autoload :KSAutoloadA, "autoload_a.rb"
 autoload :KSAutoloadB, fixture(__FILE__, "autoload_b.rb")
-autoload :KSAutoloadCallsRequire, "main_autoload_not_exist.rb"
+define_autoload_KSAutoloadCallsRequire = -> {
+  autoload :KSAutoloadCallsRequire, "main_autoload_not_exist.rb"
+}
 
 def check_autoload(const)
   autoload? const
@@ -43,6 +45,7 @@ describe "Kernel#autoload" do
   end
 
   it "calls main.require(path) to load the file" do
+    define_autoload_KSAutoloadCallsRequire.call
     main = TOPLEVEL_BINDING.eval("self")
     main.should_receive(:require).with("main_autoload_not_exist.rb")
     # The constant won't be defined since require is mocked to do nothing
@@ -56,9 +59,24 @@ describe "Kernel#autoload" do
     end
   end
 
+  describe "inside a Class.new method body" do
+    # NOTE: this spec is being discussed in https://github.com/ruby/spec/pull/839
+    it "should define on the new anonymous class" do
+      cls = Class.new do
+        def go
+          autoload :Object, 'bogus'
+          autoload? :Object
+        end
+      end
+
+      cls.new.go.should == 'bogus'
+      cls.autoload?(:Object).should == 'bogus'
+    end
+  end
+
   describe "when Object is frozen" do
-    it "raises a #{frozen_error_class} before defining the constant" do
-      ruby_exe(fixture(__FILE__, "autoload_frozen.rb")).should == "#{frozen_error_class} - nil"
+    it "raises a FrozenError before defining the constant" do
+      ruby_exe(fixture(__FILE__, "autoload_frozen.rb")).should == "FrozenError - nil"
     end
   end
 
diff --git a/spec/ruby/core/kernel/backtick_spec.rb b/spec/ruby/core/kernel/backtick_spec.rb
index 5ab0fb0eea..834d5636c1 100644
--- a/spec/ruby/core/kernel/backtick_spec.rb
+++ b/spec/ruby/core/kernel/backtick_spec.rb
@@ -36,20 +36,24 @@ describe "Kernel#`" do
   end
 
   platform_is_not :windows do
+    it "handles invalid UTF-8 bytes in command" do
+      `echo "testing\xC2 a non UTF-8 string"`.b.should == "testing\xC2 a non UTF-8 string\n".b
+    end
+
     it "sets $? to the exit status of the executed sub-process" do
       ip = 'world'
       `echo disc #{ip}`
       $?.should be_kind_of(Process::Status)
-      $?.stopped?.should == false
-      $?.exited?.should == true
+      $?.should_not.stopped?
+      $?.should.exited?
       $?.exitstatus.should == 0
-      $?.success?.should == true
+      $?.should.success?
       `echo disc #{ip}; exit 99`
       $?.should be_kind_of(Process::Status)
-      $?.stopped?.should == false
-      $?.exited?.should == true
+      $?.should_not.stopped?
+      $?.should.exited?
       $?.exitstatus.should == 99
-      $?.success?.should == false
+      $?.should_not.success?
     end
   end
 
@@ -58,16 +62,16 @@ describe "Kernel#`" do
       ip = 'world'
       `echo disc #{ip}`
       $?.should be_kind_of(Process::Status)
-      $?.stopped?.should == false
-      $?.exited?.should == true
+      $?.should_not.stopped?
+      $?.should.exited?
       $?.exitstatus.should == 0
-      $?.success?.should == true
+      $?.should.success?
       `echo disc #{ip}& exit 99`
       $?.should be_kind_of(Process::Status)
-      $?.stopped?.should == false
-      $?.exited?.should == true
+      $?.should_not.stopped?
+      $?.should.exited?
       $?.exitstatus.should == 99
-      $?.success?.should == false
+      $?.should_not.success?
     end
   end
 end
diff --git a/spec/ruby/core/kernel/block_given_spec.rb b/spec/ruby/core/kernel/block_given_spec.rb
index b00bfabfc3..aece4c821d 100644
--- a/spec/ruby/core/kernel/block_given_spec.rb
+++ b/spec/ruby/core/kernel/block_given_spec.rb
@@ -5,15 +5,20 @@ describe :kernel_block_given, shared: true do
   it "returns true if and only if a block is supplied" do
     @object.accept_block {}.should == true
     @object.accept_block_as_argument {}.should == true
+    @object.accept_block_inside_block {}.should == true
+    @object.accept_block_as_argument_inside_block {}.should == true
 
     @object.accept_block.should == false
     @object.accept_block_as_argument.should == false
+    @object.accept_block_inside_block.should == false
+    @object.accept_block_as_argument_inside_block.should == false
   end
 
   # Clarify: Based on http://www.ruby-forum.com/topic/137822 it appears
   # that Matz wanted this to be true in 1.9.
   it "returns false when a method defined by define_method is called with a block" do
     @object.defined_block {}.should == false
+    @object.defined_block_inside_block {}.should == false
   end
 end
 
diff --git a/spec/ruby/core/kernel/caller_locations_spec.rb b/spec/ruby/core/kernel/caller_locations_spec.rb
index 03c05883d1..a917dba504 100644
--- a/spec/ruby/core/kernel/caller_locations_spec.rb
+++ b/spec/ruby/core/kernel/caller_locations_spec.rb
@@ -7,13 +7,13 @@ describe 'Kernel#caller_locations' do
   end
 
   it 'returns an Array of caller locations' do
-    KernelSpecs::CallerLocationsTest.locations.empty?.should == false
+    KernelSpecs::CallerLocationsTest.locations.should_not.empty?
   end
 
   it 'returns an Array of caller locations using a custom offset' do
     locations = KernelSpecs::CallerLocationsTest.locations(2)
 
-    locations[0].absolute_path.end_with?('mspec.rb').should == true
+    locations[0].absolute_path.should.end_with?('mspec.rb')
   end
 
   it 'returns an Array of caller locations using a custom limit' do
@@ -22,6 +22,42 @@ describe 'Kernel#caller_locations' do
     locations.length.should == 1
   end
 
+  it "can be called with a range" do
+    locations1 = caller_locations(0)
+    locations2 = caller_locations(2..4)
+    locations1[2..4].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "works with endless ranges" do
+    locations1 = caller_locations(0)
+    locations2 = caller_locations(eval("(2..)"))
+    locations2.map(&:to_s).should == locations1[2..-1].map(&:to_s)
+  end
+
+  it "works with beginless ranges" do
+    locations1 = caller_locations(0)
+    locations2 = caller_locations((...5))
+    locations2.map(&:to_s)[eval("(2..)")].should == locations1[(...5)].map(&:to_s)[eval("(2..)")]
+  end
+
+  it "can be called with a range whose end is negative" do
+    locations1 = caller_locations(0)
+    locations2 = caller_locations(2..-1)
+    locations3 = caller_locations(2..-2)
+    locations1[2..-1].map(&:to_s).should == locations2.map(&:to_s)
+    locations1[2..-2].map(&:to_s).should == locations3.map(&:to_s)
+  end
+
+  it "must return nil if omitting more locations than available" do
+    caller_locations(100).should == nil
+    caller_locations(100..-1).should == nil
+  end
+
+  it "must return [] if omitting exactly the number of locations available" do
+    omit = caller_locations(0).length
+    caller_locations(omit).should == []
+  end
+
   it 'returns the locations as Thread::Backtrace::Location instances' do
     locations = KernelSpecs::CallerLocationsTest.locations
 
@@ -29,4 +65,46 @@ describe 'Kernel#caller_locations' do
       location.kind_of?(Thread::Backtrace::Location).should == true
     end
   end
+
+  it "must return the same locations when called with 1..-1 and when called with no arguments" do
+    caller_locations.map(&:to_s).should == caller_locations(1..-1).map(&:to_s)
+  end
+
+  guard -> { Kernel.instance_method(:tap).source_location } do
+    ruby_version_is ""..."3.4" do
+      it "includes core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
+
+        loc = nil
+        tap { loc = caller_locations(1, 1)[0] }
+        loc.label.should == "tap"
+        loc.path.should.start_with? "<internal:"
+      end
+    end
+
+    ruby_version_is "3.4"..."4.0" do
+      it "includes core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
+
+        loc = nil
+        tap { loc = caller_locations(1, 1)[0] }
+        loc.label.should == "Kernel#tap"
+        loc.path.should.start_with? "<internal:"
+      end
+    end
+
+    ruby_version_is "4.0" do
+      it "does not include core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
+
+        loc = nil
+        tap { loc = caller_locations(1, 1)[0] }
+        loc.label.should == "Kernel#tap"
+        loc.path.should == __FILE__
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/caller_spec.rb b/spec/ruby/core/kernel/caller_spec.rb
index 8469319c94..7cd703de5a 100644
--- a/spec/ruby/core/kernel/caller_spec.rb
+++ b/spec/ruby/core/kernel/caller_spec.rb
@@ -7,7 +7,7 @@ describe 'Kernel#caller' do
   end
 
   it 'returns an Array of caller locations' do
-    KernelSpecs::CallerTest.locations.empty?.should == false
+    KernelSpecs::CallerTest.locations.should_not.empty?
   end
 
   it 'returns an Array of caller locations using a custom offset' do
@@ -38,9 +38,72 @@ describe 'Kernel#caller' do
   it "returns an Array with the block given to #at_exit at the base of the stack" do
     path = fixture(__FILE__, "caller_at_exit.rb")
     lines = ruby_exe(path).lines
-    lines.should == [
-      "#{path}:6:in `foo'\n",
-      "#{path}:2:in `block in <main>'\n"
-    ]
+    lines.size.should == 2
+    lines[0].should =~ /\A#{path}:6:in [`'](?:Object#)?foo'\n\z/
+    lines[1].should =~ /\A#{path}:2:in [`']block in <main>'\n\z/
+  end
+
+  it "can be called with a range" do
+    locations1 = caller(0)
+    locations2 = caller(2..4)
+    locations1[2..4].should == locations2
+  end
+
+  it "works with endless ranges" do
+    locations1 = KernelSpecs::CallerTest.locations(0)
+    locations2 = KernelSpecs::CallerTest.locations(eval("(2..)"))
+    locations2.should == locations1[2..-1]
+  end
+
+  it "works with beginless ranges" do
+    locations1 = KernelSpecs::CallerTest.locations(0)
+    locations2 = KernelSpecs::CallerTest.locations((..5))
+    locations2[eval("(2..)")].should == locations1[(..5)][eval("(2..)")]
+  end
+
+  it "can be called with a range whose end is negative" do
+    locations1 = caller(0)
+    locations2 = caller(2..-1)
+    locations3 = caller(2..-2)
+    locations1[2..-1].should == locations2
+    locations1[2..-2].should == locations3
+  end
+
+  it "must return nil if omitting more locations than available" do
+    caller(100).should == nil
+    caller(100..-1).should == nil
+  end
+
+  it "must return [] if omitting exactly the number of locations available" do
+    omit = caller(0).length
+    caller(omit).should == []
+  end
+
+  it "must return the same locations when called with 1..-1 and when called with no arguments" do
+    caller.should == caller(1..-1)
+  end
+
+  guard -> { Kernel.instance_method(:tap).source_location } do
+    ruby_version_is ""..."4.0" do
+      it "includes core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
+
+        loc = nil
+        tap { loc = caller(1, 1)[0] }
+        loc.should =~ /\A<internal:.*in [`'](?:Kernel#)?tap'\z/
+      end
+    end
+
+    ruby_version_is "4.0" do
+      it "includes core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
+
+        loc = nil
+        tap { loc = caller(1, 1)[0] }
+        loc.should =~ /\A#{ __FILE__ }:.*in [`'](?:Kernel#)?tap'\z/
+      end
+    end
   end
 end
diff --git a/spec/ruby/core/kernel/catch_spec.rb b/spec/ruby/core/kernel/catch_spec.rb
index 4060172429..9f59d3b384 100644
--- a/spec/ruby/core/kernel/catch_spec.rb
+++ b/spec/ruby/core/kernel/catch_spec.rb
@@ -35,7 +35,7 @@ describe "Kernel.catch" do
   end
 
   it "raises an ArgumentError if a String with different identity is thrown" do
-    -> { catch("exit") { throw "exit" } }.should raise_error(ArgumentError)
+    -> { catch("exit".dup) { throw "exit".dup } }.should raise_error(ArgumentError)
   end
 
   it "catches a Symbol when thrown a matching Symbol" do
diff --git a/spec/ruby/core/kernel/class_spec.rb b/spec/ruby/core/kernel/class_spec.rb
index 4d3b4e549b..b1d9df1671 100644
--- a/spec/ruby/core/kernel/class_spec.rb
+++ b/spec/ruby/core/kernel/class_spec.rb
@@ -5,7 +5,7 @@ describe "Kernel#class" do
   it "returns the class of the object" do
     Object.new.class.should equal(Object)
 
-    1.class.should equal(Fixnum)
+    1.class.should equal(Integer)
     3.14.class.should equal(Float)
     :hello.class.should equal(Symbol)
     "hello".class.should equal(String)
@@ -19,7 +19,7 @@ describe "Kernel#class" do
   end
 
   it "returns the first non-singleton class" do
-    a = "hello"
+    a = +"hello"
     def a.my_singleton_method; end
     a.class.should equal(String)
   end
diff --git a/spec/ruby/core/kernel/clone_spec.rb b/spec/ruby/core/kernel/clone_spec.rb
index eb8739d571..5adcbbe603 100644
--- a/spec/ruby/core/kernel/clone_spec.rb
+++ b/spec/ruby/core/kernel/clone_spec.rb
@@ -28,21 +28,88 @@ describe "Kernel#clone" do
     clone.class.should equal klass
   end
 
-  it "copies frozen state from the original" do
-    o2 = @obj.clone
-    @obj.freeze
-    o3 = @obj.clone
+  describe "with no arguments" do
+    it "copies frozen state from the original" do
+      o2 = @obj.clone
+      o2.should_not.frozen?
+
+      @obj.freeze
+      o3 = @obj.clone
+      o3.should.frozen?
+    end
+
+    it 'copies frozen?' do
+      o = ''.freeze.clone
+      o.frozen?.should be_true
+    end
+  end
 
-    o2.frozen?.should == false
-    o3.frozen?.should == true
+  describe "with freeze: nil" do
+    it "copies frozen state from the original, like #clone without arguments" do
+      o2 = @obj.clone(freeze: nil)
+      o2.should_not.frozen?
+
+      @obj.freeze
+      o3 = @obj.clone(freeze: nil)
+      o3.should.frozen?
+    end
+
+    it "copies frozen?" do
+      o = "".freeze.clone(freeze: nil)
+      o.frozen?.should be_true
+    end
   end
 
-  it 'takes an option to copy freeze state or not' do
-    @obj.clone(freeze: true).frozen?.should == false
-    @obj.clone(freeze: false).frozen?.should == false
-    @obj.freeze
-    @obj.clone(freeze: true).frozen?.should == true
-    @obj.clone(freeze: false).frozen?.should == false
+  describe "with freeze: true" do
+    it 'makes a frozen copy if the original is frozen' do
+      @obj.freeze
+      @obj.clone(freeze: true).should.frozen?
+    end
+
+    it 'freezes the copy even if the original was not frozen' do
+      @obj.clone(freeze: true).should.frozen?
+    end
+
+    it "calls #initialize_clone with kwargs freeze: true" do
+      obj = KernelSpecs::CloneFreeze.new
+      obj.clone(freeze: true)
+      ScratchPad.recorded.should == [obj, { freeze: true }]
+    end
+
+    it "calls #initialize_clone with kwargs freeze: true even if #initialize_clone only takes a single argument" do
+      obj = KernelSpecs::Clone.new
+      -> { obj.clone(freeze: true) }.should raise_error(ArgumentError, 'wrong number of arguments (given 2, expected 1)')
+    end
+  end
+
+  describe "with freeze: false" do
+    it 'does not freeze the copy if the original is frozen' do
+      @obj.freeze
+      @obj.clone(freeze: false).should_not.frozen?
+    end
+
+    it 'does not freeze the copy if the original is not frozen' do
+      @obj.clone(freeze: false).should_not.frozen?
+    end
+
+    it "calls #initialize_clone with kwargs freeze: false" do
+      obj = KernelSpecs::CloneFreeze.new
+      obj.clone(freeze: false)
+      ScratchPad.recorded.should == [obj, { freeze: false }]
+    end
+
+    it "calls #initialize_clone with kwargs freeze: false even if #initialize_clone only takes a single argument" do
+      obj = KernelSpecs::Clone.new
+      -> { obj.clone(freeze: false) }.should raise_error(ArgumentError, 'wrong number of arguments (given 2, expected 1)')
+    end
+  end
+
+  describe "with freeze: anything else" do
+    it 'raises ArgumentError when passed not true/false/nil' do
+      -> { @obj.clone(freeze: 1) }.should raise_error(ArgumentError, /unexpected value for freeze: Integer/)
+      -> { @obj.clone(freeze: "") }.should raise_error(ArgumentError, /unexpected value for freeze: String/)
+      -> { @obj.clone(freeze: Object.new) }.should raise_error(ArgumentError, /unexpected value for freeze: Object/)
+    end
   end
 
   it "copies instance variables" do
@@ -107,10 +174,4 @@ describe "Kernel#clone" do
 
     cloned.bar.should == ['a']
   end
-
-  it 'copies frozen? and tainted?' do
-    o = ''.taint.freeze.clone
-    o.frozen?.should be_true
-    o.tainted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/kernel/define_singleton_method_spec.rb b/spec/ruby/core/kernel/define_singleton_method_spec.rb
index dc77c3e6f8..24acec84f5 100644
--- a/spec/ruby/core/kernel/define_singleton_method_spec.rb
+++ b/spec/ruby/core/kernel/define_singleton_method_spec.rb
@@ -96,4 +96,25 @@ describe "Kernel#define_singleton_method" do
       o.define(:foo) { raise "not used" }
     }.should raise_error(ArgumentError)
   end
+
+  it "always defines the method with public visibility" do
+    cls = Class.new
+    def cls.define(name, &block)
+      private
+      define_singleton_method(name, &block)
+    end
+
+    -> {
+      suppress_warning do
+        cls.define(:foo) { :ok }
+      end
+      cls.foo.should == :ok
+    }.should_not raise_error(NoMethodError)
+  end
+
+  it "cannot define a singleton method with a frozen singleton class" do
+    o = Object.new
+    o.freeze
+    -> { o.define_singleton_method(:foo) { 1 } }.should raise_error(FrozenError)
+  end
 end
diff --git a/spec/ruby/core/kernel/dup_spec.rb b/spec/ruby/core/kernel/dup_spec.rb
index fe0a269d69..70198abdb7 100644
--- a/spec/ruby/core/kernel/dup_spec.rb
+++ b/spec/ruby/core/kernel/dup_spec.rb
@@ -32,7 +32,7 @@ describe "Kernel#dup" do
     @obj.freeze
     dup = @obj.dup
 
-    dup.frozen?.should == false
+    dup.should_not.frozen?
   end
 
   it "copies instance variables" do
diff --git a/spec/ruby/core/kernel/eval_spec.rb b/spec/ruby/core/kernel/eval_spec.rb
index 02f7ae87e9..e027294347 100644
--- a/spec/ruby/core/kernel/eval_spec.rb
+++ b/spec/ruby/core/kernel/eval_spec.rb
@@ -135,7 +135,7 @@ describe "Kernel#eval" do
   it "includes file and line information in syntax error" do
     expected = 'speccing.rb'
     -> {
-      eval('if true',TOPLEVEL_BINDING, expected)
+      eval('if true', TOPLEVEL_BINDING, expected)
     }.should raise_error(SyntaxError) { |e|
       e.message.should =~ /#{expected}:1:.+/
     }
@@ -144,7 +144,7 @@ describe "Kernel#eval" do
   it "evaluates string with given filename and negative linenumber" do
     expected_file = 'speccing.rb'
     -> {
-      eval('if true',TOPLEVEL_BINDING, expected_file, -100)
+      eval('if true', TOPLEVEL_BINDING, expected_file, -100)
     }.should raise_error(SyntaxError) { |e|
       e.message.should =~ /#{expected_file}:-100:.+/
     }
@@ -159,15 +159,106 @@ describe "Kernel#eval" do
     end
   end
 
-  it "uses the filename of the binding if none is provided" do
-    eval("__FILE__").should == "(eval)"
-    suppress_warning {eval("__FILE__", binding)}.should == __FILE__
-    eval("__FILE__", binding, "success").should == "success"
-    suppress_warning {eval("eval '__FILE__', binding")}.should == "(eval)"
-    suppress_warning {eval("eval '__FILE__', binding", binding)}.should == __FILE__
-    suppress_warning {eval("eval '__FILE__', binding", binding, 'success')}.should == 'success'
+  ruby_version_is ""..."3.3" do
+    it "uses (eval) filename if none is provided" do
+      eval("__FILE__").should == "(eval)"
+      eval("__FILE__", binding).should == "(eval)"
+      eval("__FILE__", binding, "success").should == "success"
+      eval("eval '__FILE__', binding").should == "(eval)"
+      eval("eval '__FILE__', binding", binding).should == "(eval)"
+      eval("eval '__FILE__', binding", binding, 'success').should == '(eval)'
+      eval("eval '__FILE__', binding, 'success'", binding).should == 'success'
+    end
+
+    it 'uses (eval) for __FILE__ and 1 for __LINE__ with a binding argument' do
+      eval("[__FILE__, __LINE__]", binding).should == ["(eval)", 1]
+    end
   end
 
+  context "parameter forwarding" do
+    it "allows anonymous rest parameter forwarding" do
+      object = Object.new
+      def object.foo(a, b, c)
+        [a, b, c]
+      end
+      def object.bar(*)
+        eval "foo(*)"
+      end
+
+      object.bar(1, 2, 3).should == [1, 2, 3]
+    end
+
+    it "allows anonymous keyword parameters forwarding" do
+      object = Object.new
+      def object.foo(a:, b:, c:)
+        [a, b, c]
+      end
+      def object.bar(**)
+        eval "foo(**)"
+      end
+
+      object.bar(a: 1, b: 2, c: 3).should == [1, 2, 3]
+    end
+
+    it "allows anonymous block parameter forwarding" do
+      object = Object.new
+      def object.foo(&block)
+        block.call
+      end
+      def object.bar(&)
+        eval "foo(&)"
+      end
+
+      object.bar { :foobar }.should == :foobar
+    end
+
+    it "allows ... forwarding" do
+      object = Object.new
+      def object.foo(a, b:, &block)
+        [a, b, block.call]
+      end
+      def object.bar(...)
+        eval "foo(...)"
+      end
+
+      object.bar(1, b: 2) { 3 }.should == [1, 2, 3]
+    end
+
+    it "allows parameter forwarding to super" do
+      m = Module.new do
+        def foo(a, b:, &block)
+          [a, b, block.call]
+        end
+      end
+
+      c = Class.new do
+        include m
+
+        def foo(a, b:, &block)
+          eval "super"
+        end
+      end
+
+      object = c.new
+      object.foo(1, b: 2) { 3 }.should == [1, 2, 3]
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "uses (eval at __FILE__:__LINE__) if none is provided" do
+      eval("__FILE__").should == "(eval at #{__FILE__}:#{__LINE__})"
+      eval("__FILE__", binding).should == "(eval at #{__FILE__}:#{__LINE__})"
+      eval("__FILE__", binding, "success").should == "success"
+      eval("eval '__FILE__', binding").should == "(eval at (eval at #{__FILE__}:#{__LINE__}):1)"
+      eval("eval '__FILE__', binding", binding).should == "(eval at (eval at #{__FILE__}:#{__LINE__}):1)"
+      eval("eval '__FILE__', binding", binding, 'success').should == "(eval at success:1)"
+      eval("eval '__FILE__', binding, 'success'", binding).should == 'success'
+    end
+
+    it 'uses (eval at __FILE__:__LINE__) for __FILE__ and 1 for __LINE__ with a binding argument' do
+      eval("[__FILE__, __LINE__]", binding).should == ["(eval at #{__FILE__}:#{__LINE__})", 1]
+    end
+  end
   # Found via Rubinius bug github:#149
   it "does not alter the value of __FILE__ in the binding" do
     first_time =  EvalSpecs.call_eval
@@ -204,6 +295,20 @@ describe "Kernel#eval" do
     -> { eval("return :eval") }.call.should == :eval
   end
 
+  it "returns from the method calling #eval when evaluating 'return'" do
+    def eval_return(n)
+      eval("return n*2")
+    end
+    -> { eval_return(3) }.call.should == 6
+  end
+
+  it "returns from the method calling #eval when evaluating 'return' in BEGIN" do
+    def eval_return(n)
+      eval("BEGIN {return n*3}")
+    end
+    -> { eval_return(4) }.call.should == 12
+  end
+
   it "unwinds through a Proc-style closure and returns from a lambda-style closure in the closure chain" do
     code = fixture __FILE__, "eval_return_with_lambda.rb"
     ruby_exe(code).chomp.should == "a,b,c,eval,f"
@@ -214,6 +319,50 @@ describe "Kernel#eval" do
     ruby_exe(code).chomp.should == "a,b,c,e,LocalJumpError,f"
   end
 
+  it "can be called with Method#call" do
+    method(:eval).call("2 * 3").should == 6
+  end
+
+  it "has the correct default definee when called through Method#call" do
+    class EvalSpecs
+      method(:eval).call("def eval_spec_method_call; end")
+      EvalSpecs.should have_instance_method(:eval_spec_method_call)
+    end
+  end
+
+  it "makes flip-flop operator work correctly" do
+    ScratchPad.record []
+
+    eval "10.times { |i| ScratchPad << i if (i == 4)...(i == 4) }"
+    ScratchPad.recorded.should == [4, 5, 6, 7, 8, 9]
+
+    ScratchPad.clear
+  end
+
+  it "returns nil if given an empty string" do
+    eval("").should == nil
+  end
+
+  context "with shebang" do
+    it "ignores shebang with ruby interpreter" do
+      pid = eval(<<~CODE.b)
+        #!/usr/bin/env ruby
+        Process.pid
+      CODE
+
+      pid.should == Process.pid
+    end
+
+    it "ignores shebang with non-ruby interpreter" do
+      pid = eval(<<~CODE.b)
+        #!/usr/bin/env puma
+        Process.pid
+      CODE
+
+      pid.should == Process.pid
+    end
+  end
+
   # See language/magic_comment_spec.rb for more magic comments specs
   describe "with a magic encoding comment" do
     it "uses the magic comment encoding for the encoding of literal strings" do
@@ -233,6 +382,8 @@ CODE
       eval(code)
       EvalSpecs.constants(false).should include(:"Vπ")
       EvalSpecs::Vπ.should == 3.14
+    ensure
+      EvalSpecs.send(:remove_const, :Vπ)
     end
 
     it "allows an emacs-style magic comment encoding" do
@@ -246,6 +397,8 @@ CODE
       eval(code)
       EvalSpecs.constants(false).should include(:"Vπemacs")
       EvalSpecs::Vπemacs.should == 3.14
+    ensure
+      EvalSpecs.send(:remove_const, :Vπemacs)
     end
 
     it "allows spaces before the magic encoding comment" do
@@ -259,6 +412,8 @@ CODE
       eval(code)
       EvalSpecs.constants(false).should include(:"Vπspaces")
       EvalSpecs::Vπspaces.should == 3.14
+    ensure
+      EvalSpecs.send(:remove_const, :Vπspaces)
     end
 
     it "allows a shebang line before the magic encoding comment" do
@@ -273,6 +428,8 @@ CODE
       eval(code)
       EvalSpecs.constants(false).should include(:"Vπshebang")
       EvalSpecs::Vπshebang.should == 3.14
+    ensure
+      EvalSpecs.send(:remove_const, :Vπshebang)
     end
 
     it "allows a shebang line and some spaces before the magic encoding comment" do
@@ -287,15 +444,16 @@ CODE
       eval(code)
       EvalSpecs.constants(false).should include(:"Vπshebang_spaces")
       EvalSpecs::Vπshebang_spaces.should == 3.14
+    ensure
+      EvalSpecs.send(:remove_const, :Vπshebang_spaces)
     end
 
     it "allows a magic encoding comment and a subsequent frozen_string_literal magic comment" do
-      # Make sure frozen_string_literal is not default true
-      eval("'foo'".b).frozen?.should be_false
+      frozen_string_default = "test".frozen?
 
       code = <<CODE.b
 # encoding: UTF-8
-# frozen_string_literal: true
+# frozen_string_literal: #{!frozen_string_default}
 class EvalSpecs
   Vπstring = "frozen"
 end
@@ -305,7 +463,9 @@ CODE
       EvalSpecs.constants(false).should include(:"Vπstring")
       EvalSpecs::Vπstring.should == "frozen"
       EvalSpecs::Vπstring.encoding.should == Encoding::UTF_8
-      EvalSpecs::Vπstring.frozen?.should be_true
+      EvalSpecs::Vπstring.frozen?.should == !frozen_string_default
+    ensure
+      EvalSpecs.send(:remove_const, :Vπstring)
     end
 
     it "allows a magic encoding comment and a frozen_string_literal magic comment on the same line in emacs style" do
@@ -321,11 +481,14 @@ CODE
       EvalSpecs::Vπsame_line.should == "frozen"
       EvalSpecs::Vπsame_line.encoding.should == Encoding::UTF_8
       EvalSpecs::Vπsame_line.frozen?.should be_true
+    ensure
+      EvalSpecs.send(:remove_const, :Vπsame_line)
     end
 
     it "ignores the magic encoding comment if it is after a frozen_string_literal magic comment" do
+      frozen_string_default = "test".frozen?
       code = <<CODE.b
-# frozen_string_literal: true
+# frozen_string_literal: #{!frozen_string_default}
 # encoding: UTF-8
 class EvalSpecs
   Vπfrozen_first = "frozen"
@@ -339,7 +502,69 @@ CODE
       value = EvalSpecs.const_get(binary_constant)
       value.should == "frozen"
       value.encoding.should == Encoding::BINARY
-      value.frozen?.should be_true
+      value.frozen?.should == !frozen_string_default
+    ensure
+      EvalSpecs.send(:remove_const, binary_constant)
+    end
+
+    it "ignores the frozen_string_literal magic comment if it appears after a token and warns if $VERBOSE is true" do
+      frozen_string_default = "test".frozen?
+      code = <<CODE
+some_token_before_magic_comment = :anything
+# frozen_string_literal: #{!frozen_string_default}
+class EvalSpecs
+  Vπstring_not_frozen = "not frozen"
+end
+CODE
+      -> { eval(code) }.should complain(/warning: [`']frozen_string_literal' is ignored after any tokens/, verbose: true)
+      EvalSpecs::Vπstring_not_frozen.frozen?.should == frozen_string_default
+      EvalSpecs.send :remove_const, :Vπstring_not_frozen
+
+      -> { eval(code) }.should_not complain(verbose: false)
+      EvalSpecs::Vπstring_not_frozen.frozen?.should == frozen_string_default
+      EvalSpecs.send :remove_const, :Vπstring_not_frozen
+    end
+  end
+
+  describe 'with refinements' do
+    it "activates refinements from the eval scope" do
+      refinery = Module.new do
+        refine EvalSpecs::A do
+          def foo
+            "bar"
+          end
+        end
+      end
+
+      result = nil
+
+      Module.new do
+        using refinery
+
+        result = eval "EvalSpecs::A.new.foo"
+      end
+
+      result.should == "bar"
+    end
+
+    it "activates refinements from the binding" do
+      refinery = Module.new do
+        refine EvalSpecs::A do
+          def foo
+            "bar"
+          end
+        end
+      end
+
+      b = nil
+      m = Module.new do
+        using refinery
+        b = binding
+      end
+
+      result = eval "EvalSpecs::A.new.foo", b
+
+      result.should == "bar"
     end
   end
 end
diff --git a/spec/ruby/core/kernel/exec_spec.rb b/spec/ruby/core/kernel/exec_spec.rb
index 1b4a7ae6f4..3d9520ad67 100644
--- a/spec/ruby/core/kernel/exec_spec.rb
+++ b/spec/ruby/core/kernel/exec_spec.rb
@@ -7,12 +7,12 @@ describe "Kernel#exec" do
   end
 
   it "runs the specified command, replacing current process" do
-    ruby_exe('exec "echo hello"; puts "fail"', escape: true).should == "hello\n"
+    ruby_exe('exec "echo hello"; puts "fail"').should == "hello\n"
   end
 end
 
 describe "Kernel.exec" do
   it "runs the specified command, replacing current process" do
-    ruby_exe('Kernel.exec "echo hello"; puts "fail"', escape: true).should == "hello\n"
+    ruby_exe('Kernel.exec "echo hello"; puts "fail"').should == "hello\n"
   end
 end
diff --git a/spec/ruby/core/kernel/exit_spec.rb b/spec/ruby/core/kernel/exit_spec.rb
index f168cb375e..93cec3fee5 100644
--- a/spec/ruby/core/kernel/exit_spec.rb
+++ b/spec/ruby/core/kernel/exit_spec.rb
@@ -10,6 +10,10 @@ describe "Kernel#exit" do
   it_behaves_like :process_exit, :exit, KernelSpecs::Method.new
 end
 
+describe "Kernel.exit" do
+  it_behaves_like :process_exit, :exit, Kernel
+end
+
 describe "Kernel#exit!" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:exit!)
@@ -18,10 +22,6 @@ describe "Kernel#exit!" do
   it_behaves_like :process_exit!, :exit!, "self"
 end
 
-describe "Kernel.exit" do
-  it_behaves_like :process_exit, :exit, Kernel
-end
-
 describe "Kernel.exit!" do
-  it_behaves_like :process_exit!, :exit!, Kernel
+  it_behaves_like :process_exit!, :exit!, "Kernel"
 end
diff --git a/spec/ruby/core/kernel/extend_spec.rb b/spec/ruby/core/kernel/extend_spec.rb
index 9f98b3681f..6342d8cae1 100644
--- a/spec/ruby/core/kernel/extend_spec.rb
+++ b/spec/ruby/core/kernel/extend_spec.rb
@@ -72,8 +72,20 @@ describe "Kernel#extend" do
       -> { @frozen.extend }.should raise_error(ArgumentError)
     end
 
-    it "raises a #{frozen_error_class}" do
-      -> { @frozen.extend @module }.should raise_error(frozen_error_class)
+    it "raises a FrozenError" do
+      -> { @frozen.extend @module }.should raise_error(FrozenError)
     end
   end
+
+  it "updated class methods of a module when it extends self and includes another module" do
+    a = Module.new do
+      extend self
+    end
+    b = Module.new do
+      def foo; :foo; end
+    end
+
+    a.include b
+    a.foo.should == :foo
+  end
 end
diff --git a/spec/ruby/core/kernel/fixtures/Complex.rb b/spec/ruby/core/kernel/fixtures/Complex.rb
new file mode 100644
index 0000000000..bf14d55ad5
--- /dev/null
+++ b/spec/ruby/core/kernel/fixtures/Complex.rb
@@ -0,0 +1,5 @@
+module KernelSpecs
+  def self.Complex_method(string)
+    Complex(string)
+  end
+end
diff --git a/spec/ruby/core/kernel/fixtures/__dir__.rb b/spec/ruby/core/kernel/fixtures/__dir__.rb
new file mode 100644
index 0000000000..bf9a15e3c8
--- /dev/null
+++ b/spec/ruby/core/kernel/fixtures/__dir__.rb
@@ -0,0 +1,2 @@
+puts __FILE__
+puts __dir__
diff --git a/spec/ruby/core/kernel/fixtures/classes.rb b/spec/ruby/core/kernel/fixtures/classes.rb
index 2909a621a9..0e2b81988f 100644
--- a/spec/ruby/core/kernel/fixtures/classes.rb
+++ b/spec/ruby/core/kernel/fixtures/classes.rb
@@ -49,7 +49,7 @@ module KernelSpecs
 
   def self.chomp(str, method, sep="\n")
     code = "$_ = #{str.inspect}; $/ = #{sep.inspect}; #{method}; print $_"
-    IO.popen([*ruby_exe, "-n", "-e", code], "r+") do |io|
+    IO.popen([*ruby_exe, "-W0", "-n", "-e", code], "r+") do |io|
       io.puts
       io.close_write
       io.read
@@ -219,10 +219,28 @@ module KernelSpecs
       block_given?
     end
 
+    def self.accept_block_inside_block()
+      yield_self {
+        block_given?
+      }
+    end
+
+    def self.accept_block_as_argument_inside_block(&block)
+      yield_self {
+        block_given?
+      }
+    end
+
     class << self
       define_method(:defined_block) do
         block_given?
       end
+
+      define_method(:defined_block_inside_block) do
+        yield_self {
+          block_given?
+        }
+      end
     end
   end
 
@@ -235,10 +253,28 @@ module KernelSpecs
       self.send(:block_given?)
     end
 
+    def self.accept_block_inside_block
+      yield_self {
+        self.send(:block_given?)
+      }
+    end
+
+    def self.accept_block_as_argument_inside_block(&block)
+      yield_self {
+        self.send(:block_given?)
+      }
+    end
+
     class << self
       define_method(:defined_block) do
         self.send(:block_given?)
       end
+
+      define_method(:defined_block_inside_block) do
+        yield_self {
+          self.send(:block_given?)
+        }
+      end
     end
   end
 
@@ -251,10 +287,28 @@ module KernelSpecs
       Kernel.block_given?
     end
 
+    def self.accept_block_inside_block
+      yield_self {
+        Kernel.block_given?
+      }
+    end
+
+    def self.accept_block_as_argument_inside_block(&block)
+      yield_self {
+        Kernel.block_given?
+      }
+    end
+
     class << self
       define_method(:defined_block) do
         Kernel.block_given?
       end
+
+      define_method(:defined_block_inside_block) do
+        yield_self {
+          Kernel.block_given?
+        }
+      end
     end
   end
 
@@ -281,14 +335,25 @@ module KernelSpecs
       @two = two
     end
 
-    def initialize_copy(other)
+    def initialize_copy(other, **kw)
       ScratchPad.record object_id
     end
+
+    # define to support calling #clone with optional :freeze keyword argument
+    def initialize_clone(other, **kw)
+      super(other) # to call #initialize_copy
+    end
   end
 
   class Clone
     def initialize_clone(other)
-      ScratchPad.record other.object_id
+      ScratchPad.record other
+    end
+  end
+
+  class CloneFreeze
+    def initialize_clone(other, **kwargs)
+      ScratchPad.record([other, kwargs])
     end
   end
 
@@ -337,21 +402,44 @@ module KernelSpecs
     end
   end
 
+  module LambdaSpecs
+    module ZSuper
+      def lambda
+        super
+      end
+    end
+
+    class ForwardBlockWithZSuper
+      prepend(ZSuper)
+    end
+
+    module Ampersand
+      def lambda(&block)
+        suppress_warning {super(&block)}
+      end
+    end
+
+    class SuperAmpersand
+      prepend(Ampersand)
+    end
+  end
+
   class RespondViaMissing
     def respond_to_missing?(method, priv=false)
       case method
-        when :handled_publicly
-          true
-        when :handled_privately
-          priv
-        when :not_handled
-          false
-        else
-          raise "Typo in method name"
+      when :handled_publicly
+        true
+      when :handled_privately
+        priv
+      when :not_handled
+        false
+      else
+        raise "Typo in method name: #{method.inspect}"
       end
     end
 
     def method_missing(method, *args)
+      raise "the method name should be a Symbol" unless Symbol === method
       "Done #{method}(#{args})"
     end
   end
diff --git a/spec/ruby/core/kernel/fixtures/warn_core_method.rb b/spec/ruby/core/kernel/fixtures/warn_core_method.rb
new file mode 100644
index 0000000000..fd82562404
--- /dev/null
+++ b/spec/ruby/core/kernel/fixtures/warn_core_method.rb
@@ -0,0 +1,14 @@
+raise 'should be run without RubyGems' if defined?(Gem)
+
+public def deprecated(n=1)
+  # puts nil, caller(0), nil
+  warn "use X instead", uplevel: n
+end
+
+1.times do # to test with a non-empty stack above the reported locations
+  deprecated
+  tap(&:deprecated)
+  tap { deprecated(2) }
+  # eval sources with a <internal: file are also ignored
+  eval "tap(&:deprecated)", nil, "<internal:should-be-skipped-by-warn-uplevel>"
+end
diff --git a/spec/ruby/core/kernel/fixtures/warn_require.rb b/spec/ruby/core/kernel/fixtures/warn_require.rb
new file mode 100644
index 0000000000..c4b0733233
--- /dev/null
+++ b/spec/ruby/core/kernel/fixtures/warn_require.rb
@@ -0,0 +1 @@
+warn 'warn-require-warning', uplevel: 1
diff --git a/spec/ruby/core/kernel/fixtures/warn_require_caller.rb b/spec/ruby/core/kernel/fixtures/warn_require_caller.rb
new file mode 100644
index 0000000000..35a0f969f9
--- /dev/null
+++ b/spec/ruby/core/kernel/fixtures/warn_require_caller.rb
@@ -0,0 +1,2 @@
+# Use a different line than just 1
+require "#{__dir__}/warn_require"
diff --git a/spec/ruby/core/kernel/format_spec.rb b/spec/ruby/core/kernel/format_spec.rb
index 72fd40b952..1d0c000c15 100644
--- a/spec/ruby/core/kernel/format_spec.rb
+++ b/spec/ruby/core/kernel/format_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+# NOTE: most specs are in sprintf_spec.rb, this is just an alias
 describe "Kernel#format" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:format)
@@ -11,4 +12,36 @@ describe "Kernel.format" do
   it "is accessible as a module function" do
     Kernel.format("%s", "hello").should == "hello"
   end
+
+  describe "when $VERBOSE is true" do
+    it "warns if too many arguments are passed" do
+      code = <<~RUBY
+        $VERBOSE = true
+        format("test", 1)
+      RUBY
+
+      ruby_exe(code, args: "2>&1").should include("warning: too many arguments for format string")
+    end
+
+    it "does not warns if too many keyword arguments are passed" do
+      code = <<~RUBY
+        $VERBOSE = true
+        format("test %{test}", test: 1, unused: 2)
+      RUBY
+
+      ruby_exe(code, args: "2>&1").should_not include("warning")
+    end
+
+    ruby_bug "#20593", ""..."3.4" do
+      it "doesn't warns if keyword arguments are passed and none are used" do
+        code = <<~RUBY
+          $VERBOSE = true
+          format("test", test: 1)
+          format("test", {})
+        RUBY
+
+        ruby_exe(code, args: "2>&1").should_not include("warning")
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/freeze_spec.rb b/spec/ruby/core/kernel/freeze_spec.rb
index 214b619f9f..fa32d321cf 100644
--- a/spec/ruby/core/kernel/freeze_spec.rb
+++ b/spec/ruby/core/kernel/freeze_spec.rb
@@ -51,21 +51,19 @@ describe "Kernel#freeze" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe "on a Complex" do
-      it "has no effect since it is already frozen" do
-        c = Complex(1.3, 3.1)
-        c.frozen?.should be_true
-        c.freeze
-      end
+  describe "on a Complex" do
+    it "has no effect since it is already frozen" do
+      c = Complex(1.3, 3.1)
+      c.frozen?.should be_true
+      c.freeze
     end
+  end
 
-    describe "on a Rational" do
-      it "has no effect since it is already frozen" do
-        r = Rational(1, 3)
-        r.frozen?.should be_true
-        r.freeze
-      end
+  describe "on a Rational" do
+    it "has no effect since it is already frozen" do
+      r = Rational(1, 3)
+      r.frozen?.should be_true
+      r.freeze
     end
   end
 
@@ -82,4 +80,12 @@ describe "Kernel#freeze" do
     o.freeze
     -> {o.instance_variable_set(:@foo, 1)}.should raise_error(RuntimeError)
   end
+
+  it "freezes an object's singleton class" do
+    o = Object.new
+    c = o.singleton_class
+    c.frozen?.should == false
+    o.freeze
+    c.frozen?.should == true
+  end
 end
diff --git a/spec/ruby/core/kernel/frozen_spec.rb b/spec/ruby/core/kernel/frozen_spec.rb
index 5887ed75ba..a4cec4263d 100644
--- a/spec/ruby/core/kernel/frozen_spec.rb
+++ b/spec/ruby/core/kernel/frozen_spec.rb
@@ -6,8 +6,8 @@ describe "Kernel#frozen?" do
     o = mock('o')
     p = mock('p')
     p.freeze
-    o.frozen?.should == false
-    p.frozen?.should == true
+    o.should_not.frozen?
+    p.should.frozen?
   end
 
   describe "on true, false and nil" do
@@ -50,29 +50,27 @@ describe "Kernel#frozen?" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe "on a Complex" do
-      it "returns true" do
-        c = Complex(1.3, 3.1)
-        c.frozen?.should be_true
-      end
+  describe "on a Complex" do
+    it "returns true" do
+      c = Complex(1.3, 3.1)
+      c.frozen?.should be_true
+    end
 
-      it "literal returns true" do
-        c = eval "1.3i"
-        c.frozen?.should be_true
-      end
+    it "literal returns true" do
+      c = eval "1.3i"
+      c.frozen?.should be_true
     end
+  end
 
-    describe "on a Rational" do
-      it "returns true" do
-        r = Rational(1, 3)
-        r.frozen?.should be_true
-      end
+  describe "on a Rational" do
+    it "returns true" do
+      r = Rational(1, 3)
+      r.frozen?.should be_true
+    end
 
-      it "literal returns true" do
-        r = eval "1/3r"
-        r.frozen?.should be_true
-      end
+    it "literal returns true" do
+      r = eval "1/3r"
+      r.frozen?.should be_true
     end
   end
 end
diff --git a/spec/ruby/core/kernel/initialize_clone_spec.rb b/spec/ruby/core/kernel/initialize_clone_spec.rb
new file mode 100644
index 0000000000..21a90c19f0
--- /dev/null
+++ b/spec/ruby/core/kernel/initialize_clone_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+describe "Kernel#initialize_clone" do
+  it "is a private instance method" do
+    Kernel.should have_private_instance_method(:initialize_clone)
+  end
+
+  it "returns the receiver" do
+    a = Object.new
+    b = Object.new
+    a.send(:initialize_clone, b).should == a
+  end
+
+  it "calls #initialize_copy" do
+    a = Object.new
+    b = Object.new
+    a.should_receive(:initialize_copy).with(b)
+    a.send(:initialize_clone, b)
+  end
+
+  it "accepts a :freeze keyword argument for obj.clone(freeze: value)" do
+    a = Object.new
+    b = Object.new
+    a.send(:initialize_clone, b, freeze: true).should == a
+  end
+end
diff --git a/spec/ruby/core/kernel/initialize_copy_spec.rb b/spec/ruby/core/kernel/initialize_copy_spec.rb
new file mode 100644
index 0000000000..d71ca9f60f
--- /dev/null
+++ b/spec/ruby/core/kernel/initialize_copy_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../spec_helper'
+
+describe "Kernel#initialize_copy" do
+  it "returns self" do
+    obj = Object.new
+    obj.send(:initialize_copy, obj).should.equal?(obj)
+  end
+
+  it "does nothing if the argument is the same as the receiver" do
+    obj = Object.new
+    obj.send(:initialize_copy, obj).should.equal?(obj)
+
+    obj = Object.new.freeze
+    obj.send(:initialize_copy, obj).should.equal?(obj)
+
+    1.send(:initialize_copy, 1).should.equal?(1)
+  end
+
+  it "raises FrozenError if the receiver is frozen" do
+    -> { Object.new.freeze.send(:initialize_copy, Object.new) }.should raise_error(FrozenError)
+    -> { 1.send(:initialize_copy, Object.new) }.should raise_error(FrozenError)
+  end
+
+  it "raises TypeError if the objects are of different class" do
+    klass = Class.new
+    sub = Class.new(klass)
+    a = klass.new
+    b = sub.new
+    message = 'initialize_copy should take same class object'
+    -> { a.send(:initialize_copy, b) }.should raise_error(TypeError, message)
+    -> { b.send(:initialize_copy, a) }.should raise_error(TypeError, message)
+
+    -> { a.send(:initialize_copy, 1) }.should raise_error(TypeError, message)
+    -> { a.send(:initialize_copy, 1.0) }.should raise_error(TypeError, message)
+  end
+end
diff --git a/spec/ruby/core/kernel/initialize_dup_spec.rb b/spec/ruby/core/kernel/initialize_dup_spec.rb
new file mode 100644
index 0000000000..6dff34b7ad
--- /dev/null
+++ b/spec/ruby/core/kernel/initialize_dup_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../spec_helper'
+
+describe "Kernel#initialize_dup" do
+  it "is a private instance method" do
+    Kernel.should have_private_instance_method(:initialize_dup)
+  end
+
+  it "returns the receiver" do
+    a = Object.new
+    b = Object.new
+    a.send(:initialize_dup, b).should == a
+  end
+
+  it "calls #initialize_copy" do
+    a = Object.new
+    b = Object.new
+    a.should_receive(:initialize_copy).with(b)
+    a.send(:initialize_dup, b)
+  end
+end
diff --git a/spec/ruby/core/kernel/inspect_spec.rb b/spec/ruby/core/kernel/inspect_spec.rb
index b5ba1a3903..1fa66cab98 100644
--- a/spec/ruby/core/kernel/inspect_spec.rb
+++ b/spec/ruby/core/kernel/inspect_spec.rb
@@ -6,14 +6,6 @@ describe "Kernel#inspect" do
     Object.new.inspect.should be_an_instance_of(String)
   end
 
-  it "returns a tainted string if self is tainted" do
-    Object.new.taint.inspect.tainted?.should be_true
-  end
-
-  it "returns an untrusted string if self is untrusted" do
-    Object.new.untrust.inspect.untrusted?.should be_true
-  end
-
   it "does not call #to_s if it is defined" do
     # We must use a bare Object here
     obj = Object.new
@@ -28,4 +20,71 @@ describe "Kernel#inspect" do
     obj = Object.new
     obj.inspect.should =~ /^#<Object:0x[0-9a-f]+>$/
   end
+
+  it "returns a String for an object without #class method" do
+    obj = Object.new
+    class << obj
+      undef_method :class
+    end
+    obj.inspect.should be_kind_of(String)
+  end
+
+  ruby_version_is "4.0" do
+    it "calls #instance_variables_to_inspect private method to know which variables to display" do
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = %i[@host @user @does_not_exist]
+      end
+
+      inspected = obj.inspect.sub(/^#<Object:0x[0-9a-f]+/, '#<Object:0x00')
+      inspected.should == '#<Object:0x00 @host="localhost", @user="root">'
+
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = []
+      end
+
+      inspected = obj.inspect.sub(/^#<Object:0x[0-9a-f]+/, '#<Object:0x00')
+      inspected.should == "#<Object:0x00>"
+    end
+
+    it "displays all instance variables if #instance_variables_to_inspect returns nil" do
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = nil
+      end
+
+      inspected = obj.inspect.sub(/^#<Object:0x[0-9a-f]+/, '#<Object:0x00')
+      inspected.should ==  %{#<Object:0x00 @host="localhost", @user="root", @password="hunter2">}
+    end
+
+    it "raises an error if #instance_variables_to_inspect returns an invalid value" do
+      obj = Object.new
+      obj.instance_eval do
+        @host = "localhost"
+        @user = "root"
+        @password = "hunter2"
+      end
+      obj.singleton_class.class_eval do
+        private def instance_variables_to_inspect = {}
+      end
+
+      ->{ obj.inspect }.should raise_error(TypeError, "Expected #instance_variables_to_inspect to return an Array or nil, but it returned Hash")
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/instance_of_spec.rb b/spec/ruby/core/kernel/instance_of_spec.rb
index 40e856b0d9..d1170d5047 100644
--- a/spec/ruby/core/kernel/instance_of_spec.rb
+++ b/spec/ruby/core/kernel/instance_of_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe Kernel, "#instance_of?" do
+describe "Kernel#instance_of?" do
   before :each do
     @o = KernelSpecs::InstanceClass.new
   end
diff --git a/spec/ruby/core/kernel/instance_variable_get_spec.rb b/spec/ruby/core/kernel/instance_variable_get_spec.rb
index 84d3188f07..f1d2a45df8 100644
--- a/spec/ruby/core/kernel/instance_variable_get_spec.rb
+++ b/spec/ruby/core/kernel/instance_variable_get_spec.rb
@@ -67,6 +67,12 @@ describe "Kernel#instance_variable_get when passed Symbol" do
   it "raises a NameError when the passed Symbol is an invalid instance variable name" do
     -> { @obj.instance_variable_get(:"@0") }.should raise_error(NameError)
   end
+
+  it "returns nil or raises for frozen objects" do
+    nil.instance_variable_get(:@foo).should == nil
+    -> { nil.instance_variable_get(:foo) }.should raise_error(NameError)
+    :foo.instance_variable_get(:@foo).should == nil
+  end
 end
 
 describe "Kernel#instance_variable_get when passed String" do
@@ -92,7 +98,7 @@ describe "Kernel#instance_variable_get when passed String" do
   end
 end
 
-describe "Kernel#instance_variable_get when passed Fixnum" do
+describe "Kernel#instance_variable_get when passed Integer" do
   before :each do
     @obj = Object.new
     @obj.instance_variable_set("@test", :test)
diff --git a/spec/ruby/core/kernel/instance_variable_set_spec.rb b/spec/ruby/core/kernel/instance_variable_set_spec.rb
index c5a4085530..2c25f4366f 100644
--- a/spec/ruby/core/kernel/instance_variable_set_spec.rb
+++ b/spec/ruby/core/kernel/instance_variable_set_spec.rb
@@ -31,7 +31,7 @@ describe "Kernel#instance_variable_set" do
     -> { dog_at.new.instance_variable_set(:"@", "cat") }.should raise_error(NameError)
   end
 
-  it "raises a TypeError if the instance variable name is a Fixnum" do
+  it "raises a TypeError if the instance variable name is an Integer" do
     -> { "".instance_variable_set(1, 2) }.should raise_error(TypeError)
   end
 
@@ -82,12 +82,24 @@ describe "Kernel#instance_variable_set" do
       @frozen.ivar.should equal(:origin)
     end
 
-    it "raises a #{frozen_error_class} when passed replacement is identical to stored object" do
-      -> { @frozen.instance_variable_set(:@ivar, :origin) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed replacement is identical to stored object" do
+      -> { @frozen.instance_variable_set(:@ivar, :origin) }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when passed replacement is different from stored object" do
-      -> { @frozen.instance_variable_set(:@ivar, :replacement) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed replacement is different from stored object" do
+      -> { @frozen.instance_variable_set(:@ivar, :replacement) }.should raise_error(FrozenError)
+    end
+
+    it "accepts unicode instance variable names" do
+      o = Object.new
+      o.instance_variable_set(:@💙, 42)
+      o.instance_variable_get(:@💙).should == 42
+    end
+
+    it "raises for frozen objects" do
+      -> { nil.instance_variable_set(:@foo, 42) }.should raise_error(FrozenError)
+      -> { nil.instance_variable_set(:foo, 42) }.should raise_error(NameError)
+      -> { :foo.instance_variable_set(:@foo, 42) }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/kernel/instance_variables_spec.rb b/spec/ruby/core/kernel/instance_variables_spec.rb
index b6d6e27772..677d8bb7b2 100644
--- a/spec/ruby/core/kernel/instance_variables_spec.rb
+++ b/spec/ruby/core/kernel/instance_variables_spec.rb
@@ -4,7 +4,9 @@ require_relative 'fixtures/classes'
 describe "Kernel#instance_variables" do
   describe "immediate values" do
     it "returns an empty array if no instance variables are defined" do
-      0.instance_variables.should == []
+      [0, 0.5, true, false, nil].each do |value|
+        value.instance_variables.should == []
+      end
     end
 
     it "returns the correct array if an instance variable is added" do
@@ -23,5 +25,16 @@ describe "Kernel#instance_variables" do
       a.instance_variable_set("@test", 1)
       a.instance_variables.should == [:@test]
     end
+
+    it "returns the instances variables in the order declared" do
+      c = Class.new do
+        def initialize
+          @c = 1
+          @a = 2
+          @b = 3
+        end
+      end
+      c.new.instance_variables.should == [:@c, :@a, :@b]
+    end
   end
 end
diff --git a/spec/ruby/core/kernel/is_a_spec.rb b/spec/ruby/core/kernel/is_a_spec.rb
index dc69766f83..bd8c96529a 100644
--- a/spec/ruby/core/kernel/is_a_spec.rb
+++ b/spec/ruby/core/kernel/is_a_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/kind_of'
 
 describe "Kernel#is_a?" do
-  it_behaves_like :kernel_kind_of , :is_a?
+  it_behaves_like :kernel_kind_of, :is_a?
 end
diff --git a/spec/ruby/core/kernel/iterator_spec.rb b/spec/ruby/core/kernel/iterator_spec.rb
deleted file mode 100644
index 7fbdade9dc..0000000000
--- a/spec/ruby/core/kernel/iterator_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-
-describe "Kernel#iterator?" do
-  it "is a private method" do
-    Kernel.should have_private_instance_method(:iterator?)
-  end
-end
-
-describe "Kernel.iterator?" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/kernel/kind_of_spec.rb b/spec/ruby/core/kernel/kind_of_spec.rb
index 734035620c..c988edccb5 100644
--- a/spec/ruby/core/kernel/kind_of_spec.rb
+++ b/spec/ruby/core/kernel/kind_of_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/kind_of'
 
 describe "Kernel#kind_of?" do
-  it_behaves_like :kernel_kind_of , :kind_of?
+  it_behaves_like :kernel_kind_of, :kind_of?
 end
diff --git a/spec/ruby/core/kernel/lambda_spec.rb b/spec/ruby/core/kernel/lambda_spec.rb
index 4796d65352..565536ac0d 100644
--- a/spec/ruby/core/kernel/lambda_spec.rb
+++ b/spec/ruby/core/kernel/lambda_spec.rb
@@ -26,16 +26,44 @@ describe "Kernel.lambda" do
     l.lambda?.should be_true
   end
 
-  it "creates a lambda-style Proc if given a literal block via Kernel.public_send" do
-    l = Kernel.public_send(:lambda) { 42 }
-    l.lambda?.should be_true
-  end
+  ruby_version_is ""..."3.3" do
+    it "creates a lambda-style Proc if given a literal block via Kernel.public_send" do
+      suppress_warning do
+        l = Kernel.public_send(:lambda) { 42 }
+        l.lambda?.should be_true
+      end
+    end
+
+    it "returns the passed Proc if given an existing Proc" do
+      some_proc = proc {}
+      l = suppress_warning {lambda(&some_proc)}
+      l.should equal(some_proc)
+      l.lambda?.should be_false
+    end
+
+    it "creates a lambda-style Proc when called with zsuper" do
+      suppress_warning do
+        l = KernelSpecs::LambdaSpecs::ForwardBlockWithZSuper.new.lambda { 42 }
+        l.lambda?.should be_true
+        l.call.should == 42
 
-  it "returned the passed Proc if given an existing Proc" do
-    some_proc = proc {}
-    l = lambda(&some_proc)
-    l.should equal(some_proc)
-    l.lambda?.should be_false
+        lambda { l.call(:extra) }.should raise_error(ArgumentError)
+      end
+    end
+
+    it "returns the passed Proc if given an existing Proc through super" do
+      some_proc = proc { }
+      l = KernelSpecs::LambdaSpecs::SuperAmpersand.new.lambda(&some_proc)
+      l.should equal(some_proc)
+      l.lambda?.should be_false
+    end
+
+    it "does not create lambda-style Procs when captured with #method" do
+      kernel_lambda = method(:lambda)
+      l = suppress_warning {kernel_lambda.call { 42 }}
+      l.lambda?.should be_false
+      l.call(:extra).should == 42
+    end
   end
 
   it "checks the arity of the call when no args are specified" do
@@ -97,4 +125,34 @@ describe "Kernel.lambda" do
   it "allows long returns to flow through it" do
     KernelSpecs::Lambda.new.outer.should == :good
   end
+
+  it "treats the block as a Proc when lambda is re-defined" do
+    klass = Class.new do
+      def lambda (&block); block; end
+      def ret
+        lambda { return 1 }.call
+        2
+      end
+    end
+    klass.new.lambda { 42 }.should be_an_instance_of Proc
+    klass.new.ret.should == 1
+  end
+
+  context "when called without a literal block" do
+    ruby_version_is ""..."3.3" do
+      it "warns when proc isn't a lambda" do
+        -> { lambda(&proc{}) }.should complain("#{__FILE__}:#{__LINE__}: warning: lambda without a literal block is deprecated; use the proc without lambda instead\n")
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "raises when proc isn't a lambda" do
+        -> { lambda(&proc{}) }.should raise_error(ArgumentError, /the lambda method requires a literal block/)
+      end
+    end
+
+    it "doesn't warn when proc is lambda" do
+      -> { lambda(&lambda{}) }.should_not complain(verbose: true)
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/local_variables_spec.rb b/spec/ruby/core/kernel/local_variables_spec.rb
index d0f09943bd..f6f1e15f52 100644
--- a/spec/ruby/core/kernel/local_variables_spec.rb
+++ b/spec/ruby/core/kernel/local_variables_spec.rb
@@ -34,4 +34,15 @@ describe "Kernel#local_variables" do
     ScratchPad.recorded.should include(:a, :b)
     ScratchPad.recorded.length.should == 2
   end
+
+  it "includes only unique variable names" do
+    def local_var_method
+      a = 1
+      1.times do |;a|
+        return local_variables
+      end
+    end
+
+    local_var_method.should == [:a]
+  end
 end
diff --git a/spec/ruby/core/kernel/match_spec.rb b/spec/ruby/core/kernel/match_spec.rb
index 6dc1eb7de8..cd6330fe91 100644
--- a/spec/ruby/core/kernel/match_spec.rb
+++ b/spec/ruby/core/kernel/match_spec.rb
@@ -1,24 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Kernel#=~" do
-  it "returns nil matching any object" do
-    o = Object.new
-
-    suppress_warning do
-      (o =~ /Object/).should   be_nil
-      (o =~ 'Object').should   be_nil
-      (o =~ Object).should     be_nil
-      (o =~ Object.new).should be_nil
-      (o =~ nil).should        be_nil
-      (o =~ true).should       be_nil
-    end
-  end
-
-  ruby_version_is "2.6" do
-    it "is deprecated" do
-      -> do
-        Object.new =~ /regexp/
-      end.should complain(/deprecated Object#=~ is called on Object/, verbose: true)
-    end
+  it "is no longer defined" do
+    Object.new.should_not.respond_to?(:=~)
   end
 end
diff --git a/spec/ruby/core/kernel/method_spec.rb b/spec/ruby/core/kernel/method_spec.rb
index 25c6691e10..3fc566d6a6 100644
--- a/spec/ruby/core/kernel/method_spec.rb
+++ b/spec/ruby/core/kernel/method_spec.rb
@@ -29,9 +29,52 @@ describe "Kernel#method" do
     m.call.should == :defined
   end
 
-  it "can be called even if we only repond_to_missing? method, true" do
+  it "can be called even if we only respond_to_missing? method, true" do
     m = KernelSpecs::RespondViaMissing.new.method(:handled_privately)
     m.should be_an_instance_of(Method)
     m.call(1, 2, 3).should == "Done handled_privately([1, 2, 3])"
   end
+
+  it "can call a #method_missing accepting zero or one arguments" do
+    cls = Class.new do
+      def respond_to_missing?(name, *)
+        name == :foo or super
+      end
+      def method_missing
+        :no_args
+      end
+    end
+    m = cls.new.method(:foo)
+    -> { m.call }.should raise_error(ArgumentError)
+
+    cls = Class.new do
+      def respond_to_missing?(name, *)
+        name == :bar or super
+      end
+      def method_missing(m)
+        m
+      end
+    end
+    m = cls.new.method(:bar)
+    m.call.should == :bar
+  end
+
+  describe "converts the given name to a String using #to_str" do
+    it "calls #to_str to convert the given name to a String" do
+      name = mock("method-name")
+      name.should_receive(:to_str).and_return("hash")
+      Object.method(name).should == Object.method(:hash)
+    end
+
+    it "raises a TypeError if the given name can't be converted to a String" do
+      -> { Object.method(nil) }.should raise_error(TypeError)
+      -> { Object.method([])  }.should raise_error(TypeError)
+    end
+
+    it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to a String" do
+      name = mock("method-name")
+      name.should_receive(:to_str).and_raise(NoMethodError)
+      -> { Object.method(name) }.should raise_error(NoMethodError)
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/nil_spec.rb b/spec/ruby/core/kernel/nil_spec.rb
index b63705f7bc..7418245f26 100644
--- a/spec/ruby/core/kernel/nil_spec.rb
+++ b/spec/ruby/core/kernel/nil_spec.rb
@@ -1,6 +1,12 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe "Kernel#nil?" do
-  it "needs to be reviewed for spec completeness"
+describe 'Kernel#nil?' do
+  it 'returns false' do
+    Object.should_not.nil?
+    Object.new.should_not.nil?
+    ''.should_not.nil?
+    [].should_not.nil?
+    {}.should_not.nil?
+  end
 end
diff --git a/spec/ruby/core/kernel/not_match_spec.rb b/spec/ruby/core/kernel/not_match_spec.rb
index 906f18df2c..082e56fed7 100644
--- a/spec/ruby/core/kernel/not_match_spec.rb
+++ b/spec/ruby/core/kernel/not_match_spec.rb
@@ -14,6 +14,10 @@ describe "Kernel#!~" do
     (obj !~ :foo).should == false
   end
 
+  it "raises NoMethodError if self does not respond to #=~" do
+    -> { Object.new !~ :foo }.should raise_error(NoMethodError)
+  end
+
   it 'can be overridden in subclasses' do
     obj = KernelSpecs::NotMatch.new
     (obj !~ :bar).should == :foo
diff --git a/spec/ruby/core/kernel/open_spec.rb b/spec/ruby/core/kernel/open_spec.rb
index 981b5291b3..b967d5044b 100644
--- a/spec/ruby/core/kernel/open_spec.rb
+++ b/spec/ruby/core/kernel/open_spec.rb
@@ -2,7 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#open" do
-
   before :each do
     @name = tmp("kernel_open.txt")
     @content = "This is a test"
@@ -28,44 +27,66 @@ describe "Kernel#open" do
     open(@name, "r") { |f| f.gets }.should == @content
   end
 
-  platform_is_not :windows do
-    it "opens an io when path starts with a pipe" do
-      @io = open("|date")
-      begin
-        @io.should be_kind_of(IO)
-        @io.read
-      ensure
-        @io.close
+  ruby_version_is ""..."4.0" do
+    platform_is_not :windows, :wasi do
+      it "opens an io when path starts with a pipe" do
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          @io = open("|date")
+        end
+        begin
+          @io.should be_kind_of(IO)
+          @io.read
+        ensure
+          @io.close
+        end
       end
-    end
 
-    it "opens an io when called with a block" do
-      @output = open("|date") { |f| f.read }
-      @output.should_not == ''
-    end
+      it "opens an io when called with a block" do
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          @output = open("|date") { |f| f.read }
+        end
+        @output.should_not == ''
+      end
 
-    it "opens an io for writing" do
-      -> do
-        bytes = open("|cat", "w") { |io| io.write(".") }
-        bytes.should == 1
-      end.should output_to_fd(".")
+      it "opens an io for writing" do
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          -> {
+            bytes = open("|cat", "w") { |io| io.write(".") }
+            bytes.should == 1
+          }.should output_to_fd(".")
+        end
+      end
     end
-  end
 
-  platform_is :windows do
-    it "opens an io when path starts with a pipe" do
-      @io = open("|date /t")
-      begin
-        @io.should be_kind_of(IO)
-        @io.read
-      ensure
-        @io.close
+    platform_is :windows do
+      it "opens an io when path starts with a pipe" do
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          @io = open("|date /t")
+        end
+        begin
+          @io.should be_kind_of(IO)
+          @io.read
+        ensure
+          @io.close
+        end
+      end
+
+      it "opens an io when called with a block" do
+        suppress_warning do # https://bugs.ruby-lang.org/issues/19630
+          @output = open("|date /t") { |f| f.read }
+        end
+        @output.should_not == ''
       end
     end
 
-    it "opens an io when called with a block" do
-      @output = open("|date /t") { |f| f.read }
-      @output.should_not == ''
+    ruby_version_is "3.3" do
+      # https://bugs.ruby-lang.org/issues/19630
+      it "warns about deprecation given a path with a pipe" do
+        cmd = "|echo ok"
+        -> {
+          open(cmd) { |f| f.read }
+        }.should complain(/Kernel#open with a leading '\|'/)
+      end
     end
   end
 
@@ -73,12 +94,21 @@ describe "Kernel#open" do
     -> { open }.should raise_error(ArgumentError)
   end
 
+  it "accepts options as keyword arguments" do
+    @file = open(@name, "r", 0666, flags: File::CREAT)
+    @file.should be_kind_of(File)
+
+    -> {
+      open(@name, "r", 0666, {flags: File::CREAT})
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 1..3)")
+  end
+
   describe "when given an object that responds to to_open" do
     before :each do
       ScratchPad.clear
     end
 
-    it "calls #to_path to covert the argument to a String before calling #to_str" do
+    it "calls #to_path to convert the argument to a String before calling #to_str" do
       obj = mock("open to_path")
       obj.should_receive(:to_path).at_least(1).times.and_return(@name)
       obj.should_not_receive(:to_str)
@@ -110,11 +140,21 @@ describe "Kernel#open" do
 
     it "passes its arguments onto #to_open" do
       obj = mock('to_open')
-      obj.should_receive(:to_open).with(1,2,3)
-
+      obj.should_receive(:to_open).with(1, 2, 3)
       open(obj, 1, 2, 3)
     end
 
+    it "passes keyword arguments onto #to_open as keyword arguments if to_open accepts them" do
+      obj = Object.new
+      def obj.to_open(*args, **kw)
+        ScratchPad << {args: args, kw: kw}
+      end
+
+      ScratchPad.record []
+      open(obj, 1, 2, 3, a: "b")
+      ScratchPad.recorded.should == [args: [1, 2, 3], kw: {a: "b"}]
+    end
+
     it "passes the return value from #to_open to a block" do
       obj = mock('to_open')
       obj.should_receive(:to_open).and_return(:value)
@@ -137,6 +177,16 @@ describe "Kernel#open" do
   it "accepts nil for mode and permission" do
     open(@name, nil, nil) { |f| f.gets }.should == @content
   end
+
+  it "is not redefined by open-uri" do
+    code = <<~RUBY
+      before = Kernel.instance_method(:open)
+      require 'open-uri'
+      after = Kernel.instance_method(:open)
+      p before == after
+    RUBY
+    ruby_exe(code, args: "2>&1").should == "true\n"
+  end
 end
 
 describe "Kernel.open" do
diff --git a/spec/ruby/core/kernel/p_spec.rb b/spec/ruby/core/kernel/p_spec.rb
index 798bd47b34..eae191aa54 100644
--- a/spec/ruby/core/kernel/p_spec.rb
+++ b/spec/ruby/core/kernel/p_spec.rb
@@ -57,10 +57,14 @@ describe "Kernel#p" do
     }
     -> { p(o) }.should output_to_fd("Next time, Gadget, NEXT TIME!\n")
 
-    $\ = " *helicopter sound*\n"
+    suppress_warning {
+      $\ = " *helicopter sound*\n"
+    }
     -> { p(o) }.should output_to_fd("Next time, Gadget, NEXT TIME!\n")
 
-    $/ = " *helicopter sound*\n"
+    suppress_warning {
+      $/ = " *helicopter sound*\n"
+    }
     -> { p(o) }.should output_to_fd("Next time, Gadget, NEXT TIME!\n")
   end
 
@@ -72,10 +76,8 @@ describe "Kernel#p" do
     -> { p(*[]) }.should output("")
   end
 
-=begin Not sure how to spec this, but wanted to note the behavior here
-  it "does not flush if receiver is not a TTY or a File" do
-  end
-=end
+  # Not sure how to spec this, but wanted to note the behavior here
+  it "does not flush if receiver is not a TTY or a File"
 end
 
 describe "Kernel.p" do
diff --git a/spec/ruby/core/kernel/pp_spec.rb b/spec/ruby/core/kernel/pp_spec.rb
index e19dc64caf..b5b1c98d38 100644
--- a/spec/ruby/core/kernel/pp_spec.rb
+++ b/spec/ruby/core/kernel/pp_spec.rb
@@ -1,11 +1,9 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.5" do
-  describe "Kernel#pp" do
-    it "lazily loads the 'pp' library and delegates the call to that library" do
-      # Run in child process to ensure 'pp' hasn't been loaded yet.
-      output = ruby_exe("pp [1, 2, 3]")
-      output.should == "[1, 2, 3]\n"
-    end
+describe "Kernel#pp" do
+  it "lazily loads the 'pp' library and delegates the call to that library" do
+    # Run in child process to ensure 'pp' hasn't been loaded yet.
+    output = ruby_exe("pp [1, 2, 3]")
+    output.should == "[1, 2, 3]\n"
   end
 end
diff --git a/spec/ruby/core/kernel/print_spec.rb b/spec/ruby/core/kernel/print_spec.rb
index c8c4453d1e..7e7c9b822d 100644
--- a/spec/ruby/core/kernel/print_spec.rb
+++ b/spec/ruby/core/kernel/print_spec.rb
@@ -5,6 +5,18 @@ describe "Kernel#print" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:print)
   end
+
+  it "delegates to $stdout" do
+    -> { print :arg }.should output("arg")
+  end
+
+  it "prints $_ when no arguments are given" do
+    orig_value = $_
+    $_ = 'foo'
+    -> { print }.should output("foo")
+  ensure
+    $_ = orig_value
+  end
 end
 
 describe "Kernel.print" do
diff --git a/spec/ruby/core/kernel/printf_spec.rb b/spec/ruby/core/kernel/printf_spec.rb
index 5d68c0a13c..61bf955c25 100644
--- a/spec/ruby/core/kernel/printf_spec.rb
+++ b/spec/ruby/core/kernel/printf_spec.rb
@@ -1,7 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/sprintf'
-require "stringio"
 
 describe "Kernel#printf" do
   it "is a private method" do
@@ -10,7 +9,6 @@ describe "Kernel#printf" do
 end
 
 describe "Kernel.printf" do
-
   before :each do
     @stdout = $stdout
     @name = tmp("kernel_puts.txt")
@@ -34,11 +32,24 @@ describe "Kernel.printf" do
     Kernel.printf(object, "%s", "string")
   end
 
+  it "calls #to_str to convert the format object to a String" do
+    object = mock('format string')
+    object.should_receive(:to_str).and_return("to_str: %i")
+    $stdout.should_receive(:write).with("to_str: 42")
+    Kernel.printf($stdout, object, 42)
+  end
+end
+
+describe "Kernel.printf" do
   describe "formatting" do
+    before :each do
+      require "stringio"
+    end
+
     context "io is specified" do
       it_behaves_like :kernel_sprintf, -> format, *args {
-        io = StringIO.new
-        printf(io, format, *args)
+        io = StringIO.new(+"")
+        Kernel.printf(io, format, *args)
         io.string
       }
     end
@@ -46,10 +57,9 @@ describe "Kernel.printf" do
     context "io is not specified" do
       it_behaves_like :kernel_sprintf, -> format, *args {
         stdout = $stdout
-
         begin
-          $stdout = io = StringIO.new
-          printf(format, *args)
+          $stdout = io = StringIO.new(+"")
+          Kernel.printf(format, *args)
           io.string
         ensure
           $stdout = stdout
diff --git a/spec/ruby/core/kernel/proc_spec.rb b/spec/ruby/core/kernel/proc_spec.rb
index ded2cec3fd..6553b8fd04 100644
--- a/spec/ruby/core/kernel/proc_spec.rb
+++ b/spec/ruby/core/kernel/proc_spec.rb
@@ -36,27 +36,13 @@ describe "Kernel.proc" do
 end
 
 describe "Kernel#proc" do
-  ruby_version_is ""..."2.7" do
-    it "uses the implicit block from an enclosing method" do
-      def some_method
-        proc
-      end
-
-      prc = some_method { "hello" }
-
-      prc.call.should == "hello"
-    end
+  def some_method
+    proc
   end
 
-  ruby_version_is "2.7" do
-    it "can be created when called with no block" do
-      def some_method
-        proc
-      end
-
-      -> {
-        some_method { "hello" }
-      }.should complain(/Capturing the given block using Proc.new is deprecated/)
-    end
+  it "raises an ArgumentError when passed no block" do
+    -> {
+      some_method { "hello" }
+    }.should raise_error(ArgumentError, 'tried to create Proc object without a block')
   end
 end
diff --git a/spec/ruby/core/kernel/public_send_spec.rb b/spec/ruby/core/kernel/public_send_spec.rb
index 6b942a2e4b..b684b1729c 100644
--- a/spec/ruby/core/kernel/public_send_spec.rb
+++ b/spec/ruby/core/kernel/public_send_spec.rb
@@ -104,5 +104,13 @@ describe "Kernel#public_send" do
     }.should raise_error(NoMethodError)
   end
 
+  it "includes `public_send` in the backtrace when passed not enough arguments" do
+    -> { public_send() }.should raise_error(ArgumentError) { |e| e.backtrace[0].should =~ /[`'](?:Kernel#)?public_send'/ }
+  end
+
+  it "includes `public_send` in the backtrace when passed a single incorrect argument" do
+    -> { public_send(Object.new) }.should raise_error(TypeError) { |e| e.backtrace[0].should =~ /[`'](?:Kernel#)?public_send'/ }
+  end
+
   it_behaves_like :basicobject_send, :public_send
 end
diff --git a/spec/ruby/core/kernel/raise_spec.rb b/spec/ruby/core/kernel/raise_spec.rb
index bf26560246..fcd011d4e6 100644
--- a/spec/ruby/core/kernel/raise_spec.rb
+++ b/spec/ruby/core/kernel/raise_spec.rb
@@ -6,6 +6,281 @@ describe "Kernel#raise" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:raise)
   end
+
+  it "re-raises the previously rescued exception if no exception is specified" do
+    ScratchPad.record nil
+
+    -> do
+      begin
+        raise Exception, "outer"
+        ScratchPad.record :no_abort
+      rescue Exception
+        begin
+          raise StandardError, "inner"
+        rescue StandardError
+        end
+
+        raise
+        ScratchPad.record :no_reraise
+      end
+    end.should raise_error(Exception, "outer")
+
+    ScratchPad.recorded.should be_nil
+  end
+
+  it "accepts a cause keyword argument that sets the cause" do
+    cause = StandardError.new
+    -> { raise("error", cause: cause) }.should raise_error(RuntimeError) { |e| e.cause.should == cause }
+  end
+
+  it "accepts a cause keyword argument that overrides the last exception" do
+    begin
+      raise "first raise"
+    rescue => ignored
+      cause = StandardError.new
+      -> { raise("error", cause: cause) }.should raise_error(RuntimeError) { |e| e.cause.should == cause }
+    end
+  end
+
+  it "raises an ArgumentError when only cause is given" do
+    cause = StandardError.new
+    -> { raise(cause: cause) }.should raise_error(ArgumentError, "only cause is given with no arguments")
+  end
+
+  it "raises an ArgumentError when only cause is given even if it has nil value" do
+    -> { raise(cause: nil) }.should raise_error(ArgumentError, "only cause is given with no arguments")
+  end
+
+  it "raises a TypeError when given cause is not an instance of Exception" do
+    -> { raise "message", cause: Object.new }.should raise_error(TypeError, "exception object expected")
+  end
+
+  it "doesn't raise a TypeError when given cause is nil" do
+    -> { raise "message", cause: nil }.should raise_error(RuntimeError, "message")
+  end
+
+  it "allows cause equal an exception" do
+    e = RuntimeError.new("message")
+    -> { raise e, cause: e }.should raise_error(e)
+  end
+
+  it "doesn't set given cause when it equals an exception" do
+    e = RuntimeError.new("message")
+
+    begin
+      raise e, cause: e
+    rescue
+    end
+
+    e.cause.should == nil
+  end
+
+  it "raises ArgumentError when exception is part of the cause chain" do
+    -> {
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          raise "Error 2"
+        rescue => e2
+          begin
+            raise "Error 3"
+          rescue => e3
+            raise e1, cause: e3
+          end
+        end
+      end
+    }.should raise_error(ArgumentError, "circular causes")
+  end
+
+  it "re-raises a rescued exception" do
+    -> do
+      begin
+        raise StandardError, "aaa"
+      rescue Exception
+        begin
+          raise ArgumentError
+        rescue ArgumentError
+        end
+
+        # should raise StandardError "aaa"
+        raise
+      end
+    end.should raise_error(StandardError, "aaa")
+  end
+
+  it "re-raises a previously rescued exception without overwriting the cause" do
+    begin
+      begin
+        begin
+          begin
+            raise "Error 1"
+          rescue => e1
+            raise "Error 2"
+          end
+        rescue => e2
+          raise "Error 3"
+        end
+      rescue
+        e2.cause.should == e1
+        raise e2
+      end
+    rescue => e
+      e.cause.should == e1
+    end
+  end
+
+  it "re-raises a previously rescued exception with overwriting the cause when it's explicitly specified with :cause option" do
+    e4 = RuntimeError.new("Error 4")
+
+    begin
+      begin
+        begin
+          begin
+            raise "Error 1"
+          rescue => e1
+            raise "Error 2"
+          end
+        rescue => e2
+          raise "Error 3"
+        end
+      rescue
+        e2.cause.should == e1
+        raise e2, cause: e4
+      end
+    rescue => e
+      e.cause.should == e4
+    end
+  end
+
+  it "re-raises a previously rescued exception without overwriting the cause when it's explicitly specified with :cause option and has nil value" do
+    begin
+      begin
+        begin
+          begin
+            raise "Error 1"
+          rescue => e1
+            raise "Error 2"
+          end
+        rescue => e2
+          raise "Error 3"
+        end
+      rescue
+        e2.cause.should == e1
+        raise e2, cause: nil
+      end
+    rescue => e
+      e.cause.should == e1
+    end
+  end
+
+  it "re-raises a previously rescued exception without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        raise
+      end
+    rescue => e
+      e.should == e1
+      e.cause.should == nil
+    end
+  end
+
+  it "re-raises a previously rescued exception that has a cause without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          raise "Error 2"
+        rescue => e2
+          raise
+        end
+      end
+    rescue => e
+      e.should == e2
+      e.cause.should == e1
+    end
+  end
+
+  it "re-raises a previously rescued exception that doesn't have a cause and isn't a cause of any other exception with setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          raise "Error 2"
+        rescue => e2
+          raise "Error 3"
+        end
+      end
+    rescue => e
+      e.message.should == "Error 3"
+      e.cause.should == e2
+    end
+  end
+
+  it "re-raises a previously rescued exception that doesn't have a cause and is a cause of other exception without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          raise "Error 2"
+        rescue => e2
+          e1.cause.should == nil
+          e2.cause.should == e1
+          raise e1
+        end
+      end
+    rescue => e
+      e.should == e1
+      e.cause.should == nil
+    end
+  end
+
+  it "re-raises a previously rescued exception that doesn't have a cause and is a cause of other exception (that wasn't raised explicitly) without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          foo # raises NameError
+        rescue => e2
+          e1.cause.should == nil
+          e2.cause.should == e1
+          raise e1
+        end
+      end
+    rescue => e
+      e.should == e1
+      e.cause.should == nil
+    end
+  end
+
+  it "re-raises a previously rescued exception that has a cause but isn't a cause of any other exception without setting a cause implicitly" do
+    begin
+      begin
+        raise "Error 1"
+      rescue => e1
+        begin
+          raise "Error 2"
+        rescue => e2
+          begin
+            raise "Error 3", cause: RuntimeError.new("Error 4")
+          rescue => e3
+            e2.cause.should == e1
+            e3.cause.should_not == e2
+            raise e2
+          end
+        end
+      end
+    rescue => e
+      e.should == e2
+      e.cause.should == e1
+    end
+  end
 end
 
 describe "Kernel#raise" do
diff --git a/spec/ruby/core/kernel/rand_spec.rb b/spec/ruby/core/kernel/rand_spec.rb
index 843b5d10a2..355e425792 100644
--- a/spec/ruby/core/kernel/rand_spec.rb
+++ b/spec/ruby/core/kernel/rand_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe "Kernel.rand" do
+describe "Kernel#rand" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:rand)
   end
@@ -117,6 +117,48 @@ describe "Kernel.rand" do
     end
   end
 
+  context "given an inclusive range between 0 and 1" do
+    it "returns an Integer between the two Integers" do
+      x = rand(0..1)
+      x.should be_kind_of(Integer)
+      (0..1).should include(x)
+    end
+
+    it "returns a Float if at least one side is Float" do
+      seed = 42
+      x1 = Random.new(seed).rand(0..1.0)
+      x2 = Random.new(seed).rand(0.0..1.0)
+      x3 = Random.new(seed).rand(0.0..1)
+
+      x3.should be_kind_of(Float)
+      x1.should eql(x3)
+      x2.should eql(x3)
+
+      (0.0..1.0).should include(x3)
+    end
+  end
+
+  context "given an exclusive range between 0 and 1" do
+    it "returns zero as an Integer" do
+      x = rand(0...1)
+      x.should be_kind_of(Integer)
+      x.should eql(0)
+    end
+
+    it "returns a Float if at least one side is Float" do
+      seed = 42
+      x1 = Random.new(seed).rand(0...1.0)
+      x2 = Random.new(seed).rand(0.0...1.0)
+      x3 = Random.new(seed).rand(0.0...1)
+
+      x3.should be_kind_of(Float)
+      x1.should eql(x3)
+      x2.should eql(x3)
+
+      (0.0...1.0).should include(x3)
+    end
+  end
+
   it "returns a numeric for an range argument where max is < 1" do
     rand(0.25..0.75).should be_kind_of(Numeric)
   end
@@ -138,8 +180,18 @@ describe "Kernel.rand" do
     rand(KernelSpecs::CustomRangeFloat.new(1.0)..KernelSpecs::CustomRangeFloat.new(42.0)).should be_an_instance_of(KernelSpecs::CustomRangeFloat)
     rand(Time.now..Time.now).should be_an_instance_of(Time)
   end
+
+  it "is random on boot" do
+    results = 2.times.map {
+      out = ruby_exe('p rand', options: '--disable-gems')
+      Float(out)
+    }
+    results.size.should == 2
+    # this is technically flaky, but very unlikely in a good distribution
+    results[0].should_not == results[1]
+  end
 end
 
-describe "Kernel#rand" do
+describe "Kernel.rand" do
   it "needs to be reviewed for spec completeness"
 end
diff --git a/spec/ruby/core/kernel/remove_instance_variable_spec.rb b/spec/ruby/core/kernel/remove_instance_variable_spec.rb
index e90efc8aed..4e5ba5e018 100644
--- a/spec/ruby/core/kernel/remove_instance_variable_spec.rb
+++ b/spec/ruby/core/kernel/remove_instance_variable_spec.rb
@@ -41,6 +41,19 @@ describe "Kernel#remove_instance_variable" do
     end.should raise_error(TypeError)
   end
 
+  it "raises a FrozenError if self is frozen" do
+    o = Object.new
+    o.freeze
+    -> { o.remove_instance_variable(:@foo) }.should raise_error(FrozenError)
+    -> { o.remove_instance_variable(:foo) }.should raise_error(NameError)
+  end
+
+  it "raises for frozen objects" do
+    -> { nil.remove_instance_variable(:@foo) }.should raise_error(FrozenError)
+    -> { nil.remove_instance_variable(:foo) }.should raise_error(NameError)
+    -> { :foo.remove_instance_variable(:@foo) }.should raise_error(FrozenError)
+  end
+
   describe "when passed a String" do
     it_behaves_like :kernel_remove_instance_variable, nil, "@greeting"
   end
diff --git a/spec/ruby/core/kernel/require_relative_spec.rb b/spec/ruby/core/kernel/require_relative_spec.rb
index b292a46c63..6188d13a4e 100644
--- a/spec/ruby/core/kernel/require_relative_spec.rb
+++ b/spec/ruby/core/kernel/require_relative_spec.rb
@@ -5,9 +5,9 @@ describe "Kernel#require_relative with a relative path" do
   before :each do
     CodeLoadingSpecs.spec_setup
     @dir = "../../fixtures/code"
-    @abs_dir = File.realpath(@dir, File.dirname(__FILE__))
+    @abs_dir = File.realpath(@dir, __dir__)
     @path = "#{@dir}/load_fixture.rb"
-    @abs_path = File.realpath(@path, File.dirname(__FILE__))
+    @abs_path = File.realpath(@path, __dir__)
   end
 
   after :each do
@@ -90,6 +90,16 @@ describe "Kernel#require_relative with a relative path" do
     ScratchPad.recorded.should == []
   end
 
+  it "raises a LoadError that includes the missing path" do
+    missing_path = "#{@dir}/nonexistent.rb"
+    expanded_missing_path = File.expand_path(missing_path, __dir__)
+    -> { require_relative(missing_path) }.should raise_error(LoadError) { |e|
+      e.message.should include(expanded_missing_path)
+      e.path.should == expanded_missing_path
+    }
+    ScratchPad.recorded.should == []
+  end
+
   it "raises a LoadError if basepath does not exist" do
     -> { eval("require_relative('#{@dir}/nonexistent.rb')") }.should raise_error(LoadError)
   end
@@ -197,7 +207,7 @@ describe "Kernel#require_relative with a relative path" do
       $LOADED_FEATURES.should include(@abs_path)
     end
 
-    platform_is_not :windows do
+    platform_is_not :windows, :wasi do
       describe "with symlinks" do
         before :each do
           @symlink_to_code_dir = tmp("codesymlink")
@@ -267,7 +277,7 @@ end
 describe "Kernel#require_relative with an absolute path" do
   before :each do
     CodeLoadingSpecs.spec_setup
-    @dir = File.expand_path "../../fixtures/code", File.dirname(__FILE__)
+    @dir = File.expand_path "../../fixtures/code", __dir__
     @abs_dir = @dir
     @path = File.join @dir, "load_fixture.rb"
     @abs_path = @path
diff --git a/spec/ruby/core/kernel/require_spec.rb b/spec/ruby/core/kernel/require_spec.rb
index dc3da4b7e6..60d17242fe 100644
--- a/spec/ruby/core/kernel/require_spec.rb
+++ b/spec/ruby/core/kernel/require_spec.rb
@@ -16,6 +16,32 @@ describe "Kernel#require" do
     Kernel.should have_private_instance_method(:require)
   end
 
+  provided = %w[complex enumerator fiber rational thread ruby2_keywords]
+  ruby_version_is "4.0" do
+    provided << "set"
+    provided << "pathname"
+  end
+
+  it "#{provided.join(', ')} are already required" do
+    out = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems --disable-did-you-mean')
+    features = out.lines.map { |line| File.basename(line.chomp, '.*') }
+
+    # Ignore CRuby internals
+    features -= %w[encdb transdb windows_1252 windows_31j]
+    features.reject! { |feature| feature.end_with?('-fake') }
+
+    features.sort.should == provided.sort
+
+    requires = provided
+    ruby_version_is "4.0" do
+      requires = requires.map { |f| f == "pathname" ? "pathname.so" : f }
+    end
+
+    code = requires.map { |f| "puts require #{f.inspect}\n" }.join
+    required = ruby_exe(code, options: '--disable-gems')
+    required.should == "false\n" * requires.size
+  end
+
   it_behaves_like :kernel_require_basic, :require, CodeLoadingSpecs::Method.new
   it_behaves_like :kernel_require, :require, CodeLoadingSpecs::Method.new
 end
diff --git a/spec/ruby/core/kernel/respond_to_spec.rb b/spec/ruby/core/kernel/respond_to_spec.rb
index e7efc9f275..5b3ea3f651 100644
--- a/spec/ruby/core/kernel/respond_to_spec.rb
+++ b/spec/ruby/core/kernel/respond_to_spec.rb
@@ -25,7 +25,7 @@ describe "Kernel#respond_to?" do
   end
 
   it "throws a type error if argument can't be coerced into a Symbol" do
-    -> { @a.respond_to?(Object.new) }.should raise_error(TypeError)
+    -> { @a.respond_to?(Object.new) }.should raise_error(TypeError, /is not a symbol nor a string/)
   end
 
   it "returns false if obj responds to the given protected method" do
@@ -69,5 +69,4 @@ describe "Kernel#respond_to?" do
     KernelSpecs::Foo.new.respond_to?(:bar).should == true
     KernelSpecs::Foo.new.respond_to?(:invalid_and_silly_method_name).should == false
   end
-
 end
diff --git a/spec/ruby/core/kernel/select_spec.rb b/spec/ruby/core/kernel/select_spec.rb
index e0d82f3079..df23414b28 100644
--- a/spec/ruby/core/kernel/select_spec.rb
+++ b/spec/ruby/core/kernel/select_spec.rb
@@ -10,9 +10,9 @@ end
 describe "Kernel.select" do
   it 'does not block when timeout is 0' do
     IO.pipe do |read, write|
-      IO.select([read], [], [], 0).should == nil
+      select([read], [], [], 0).should == nil
       write.write 'data'
-      IO.select([read], [], [], 0).should == [[read], [], []]
+      select([read], [], [], 0).should == [[read], [], []]
     end
   end
 end
diff --git a/spec/ruby/core/kernel/shared/dup_clone.rb b/spec/ruby/core/kernel/shared/dup_clone.rb
index d1ee64bd09..4fac6006e1 100644
--- a/spec/ruby/core/kernel/shared/dup_clone.rb
+++ b/spec/ruby/core/kernel/shared/dup_clone.rb
@@ -52,16 +52,6 @@ describe :kernel_dup_clone, shared: true do
     o2.original.should equal(o)
   end
 
-  it "preserves tainted state from the original" do
-    o = ObjectSpecDupInitCopy.new
-    o2 = o.send(@method)
-    o.taint
-    o3 = o.send(@method)
-
-    o2.tainted?.should == false
-    o3.tainted?.should == true
-  end
-
   it "does not preserve the object_id" do
     o1 = ObjectSpecDupInitCopy.new
     old_object_id = o1.object_id
@@ -69,16 +59,6 @@ describe :kernel_dup_clone, shared: true do
     o2.object_id.should_not == old_object_id
   end
 
-  it "preserves untrusted state from the original" do
-    o = ObjectSpecDupInitCopy.new
-    o2 = o.send(@method)
-    o.untrust
-    o3 = o.send(@method)
-
-    o2.untrusted?.should == false
-    o3.untrusted?.should == true
-  end
-
   it "returns nil for NilClass" do
     nil.send(@method).should == nil
   end
@@ -99,27 +79,13 @@ describe :kernel_dup_clone, shared: true do
     :my_symbol.send(@method).should == :my_symbol
   end
 
-  ruby_version_is ''...'2.5' do
-    it "raises a TypeError for Complex" do
-      c = Complex(1.3, 3.1)
-      -> { c.send(@method) }.should raise_error(TypeError)
-    end
-
-    it "raises a TypeError for Rational" do
-      r = Rational(1, 3)
-      -> { r.send(@method) }.should raise_error(TypeError)
-    end
+  it "returns self for Complex" do
+    c = Complex(1.3, 3.1)
+    c.send(@method).should equal c
   end
 
-  ruby_version_is '2.5' do
-    it "returns self for Complex" do
-      c = Complex(1.3, 3.1)
-      c.send(@method).should equal c
-    end
-
-    it "returns self for Rational" do
-      r = Rational(1, 3)
-      r.send(@method).should equal r
-    end
+  it "returns self for Rational" do
+    r = Rational(1, 3)
+    r.send(@method).should equal r
   end
 end
diff --git a/spec/ruby/core/kernel/shared/lambda.rb b/spec/ruby/core/kernel/shared/lambda.rb
index c7180e1442..c70640082a 100644
--- a/spec/ruby/core/kernel/shared/lambda.rb
+++ b/spec/ruby/core/kernel/shared/lambda.rb
@@ -4,6 +4,8 @@ describe :kernel_lambda, shared: true do
   end
 
   it "raises an ArgumentError when no block is given" do
-    -> { send(@method) }.should raise_error(ArgumentError)
+    suppress_warning do
+      -> { send(@method) }.should raise_error(ArgumentError)
+    end
   end
 end
diff --git a/spec/ruby/core/kernel/shared/load.rb b/spec/ruby/core/kernel/shared/load.rb
index 14bf5f27da..62c5c7be9b 100644
--- a/spec/ruby/core/kernel/shared/load.rb
+++ b/spec/ruby/core/kernel/shared/load.rb
@@ -1,3 +1,6 @@
+main = self
+
+# The big difference is Kernel#load does not attempt to add an extension to the passed path, unlike Kernel#require
 describe :kernel_load, shared: true do
   before :each do
     CodeLoadingSpecs.spec_setup
@@ -8,22 +11,31 @@ describe :kernel_load, shared: true do
     CodeLoadingSpecs.spec_cleanup
   end
 
-  it "loads a non-extensioned file as a Ruby source file" do
-    path = File.expand_path "load_fixture", CODE_LOADING_DIR
-    @object.load(path).should be_true
-    ScratchPad.recorded.should == [:no_ext]
-  end
+  describe "(path resolution)" do
+    # This behavior is specific to Kernel#load, it differs for Kernel#require
+    it "loads a non-extensioned file as a Ruby source file" do
+      path = File.expand_path "load_fixture", CODE_LOADING_DIR
+      @object.load(path).should be_true
+      ScratchPad.recorded.should == [:no_ext]
+    end
 
-  it "loads a non .rb extensioned file as a Ruby source file" do
-    path = File.expand_path "load_fixture.ext", CODE_LOADING_DIR
-    @object.load(path).should be_true
-    ScratchPad.recorded.should == [:no_rb_ext]
-  end
+    it "loads a non .rb extensioned file as a Ruby source file" do
+      path = File.expand_path "load_fixture.ext", CODE_LOADING_DIR
+      @object.load(path).should be_true
+      ScratchPad.recorded.should == [:no_rb_ext]
+    end
 
-  it "loads from the current working directory" do
-    Dir.chdir CODE_LOADING_DIR do
-      @object.load("load_fixture.rb").should be_true
-      ScratchPad.recorded.should == [:loaded]
+    it "loads from the current working directory" do
+      Dir.chdir CODE_LOADING_DIR do
+        @object.load("load_fixture.rb").should be_true
+        ScratchPad.recorded.should == [:loaded]
+      end
+    end
+
+    # This behavior is specific to Kernel#load, it differs for Kernel#require
+    it "does not look for a c-extension file when passed a path without extension (when no .rb is present)" do
+      path = File.join CODE_LOADING_DIR, "a", "load_fixture"
+      -> { @object.send(@method, path) }.should raise_error(LoadError)
     end
   end
 
@@ -86,22 +98,54 @@ describe :kernel_load, shared: true do
 
   describe "when passed true for 'wrap'" do
     it "loads from an existing path" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true).should be_true
     end
 
     it "sets the enclosing scope to an anonymous module" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
       Object.const_defined?(:LoadSpecWrap).should be_false
+
+      wrap_module = ScratchPad.recorded[1]
+      wrap_module.should be_an_instance_of(Module)
     end
 
     it "allows referencing outside namespaces" do
-      path = File.expand_path "wrap_fixture.rb", CODE_LOADING_DIR
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
       @object.load(path, true)
 
-      ScratchPad.recorded.first.should be_an_instance_of(Class)
+      ScratchPad.recorded[0].should equal(String)
+    end
+
+    it "sets self as a copy of the top-level main" do
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+      @object.load(path, true)
+
+      top_level = ScratchPad.recorded[2]
+      top_level.to_s.should == "main"
+      top_level.method(:to_s).owner.should == top_level.singleton_class
+      top_level.should_not equal(main)
+      top_level.should be_an_instance_of(Object)
+    end
+
+    it "includes modules included in main's singleton class in self's class" do
+      mod = Module.new
+      main.extend(mod)
+
+      main_ancestors = main.singleton_class.ancestors[1..-1]
+      main_ancestors.first.should == mod
+
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+      @object.load(path, true)
+
+      top_level = ScratchPad.recorded[2]
+      top_level_ancestors = top_level.singleton_class.ancestors[-main_ancestors.size..-1]
+      top_level_ancestors.should == main_ancestors
+
+      wrap_module = ScratchPad.recorded[1]
+      top_level.singleton_class.ancestors.should == [top_level.singleton_class, wrap_module, *main_ancestors]
     end
 
     describe "with top-level methods" do
@@ -120,6 +164,39 @@ describe :kernel_load, shared: true do
     end
   end
 
+  describe "when passed a module for 'wrap'" do
+    it "sets the enclosing scope to the supplied module" do
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+      mod = Module.new
+      @object.load(path, mod)
+
+      Object.const_defined?(:LoadSpecWrap).should be_false
+      mod.const_defined?(:LoadSpecWrap).should be_true
+
+      wrap_module = ScratchPad.recorded[1]
+      wrap_module.should == mod
+    end
+
+    it "makes constants and instance methods in the source file reachable with the supplied module" do
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+      mod = Module.new
+      @object.load(path, mod)
+
+      mod::LOAD_WRAP_SPECS_TOP_LEVEL_CONSTANT.should == 1
+      obj = Object.new
+      obj.extend(mod)
+      obj.send(:load_wrap_specs_top_level_method).should == :load_wrap_specs_top_level_method
+    end
+
+    it "makes instance methods in the source file private" do
+      path = File.expand_path "load_wrap_fixture.rb", CODE_LOADING_DIR
+      mod = Module.new
+      @object.load(path, mod)
+
+      mod.private_instance_methods.include?(:load_wrap_specs_top_level_method).should == true
+    end
+  end
+
   describe "(shell expansion)" do
     before :each do
       @env_home = ENV["HOME"]
diff --git a/spec/ruby/core/kernel/shared/method.rb b/spec/ruby/core/kernel/shared/method.rb
index 3418966b1b..8b6ab23fd3 100644
--- a/spec/ruby/core/kernel/shared/method.rb
+++ b/spec/ruby/core/kernel/shared/method.rb
@@ -15,12 +15,18 @@ describe :kernel_method, shared: true do
     m.call.should == 'class done'
   end
 
-  it "returns a method object if we repond_to_missing? method" do
+  it "returns a method object if respond_to_missing?(method) is true" do
     m = KernelSpecs::RespondViaMissing.new.send(@method, :handled_publicly)
     m.should be_an_instance_of Method
     m.call(42).should == "Done handled_publicly([42])"
   end
 
+  it "the returned method object if respond_to_missing?(method) calls #method_missing with a Symbol name" do
+    m = KernelSpecs::RespondViaMissing.new.send(@method, "handled_publicly")
+    m.should be_an_instance_of Method
+    m.call(42).should == "Done handled_publicly([42])"
+  end
+
   it "raises a NameError for an invalid method name" do
     class KernelSpecs::Foo; def bar; 'done'; end; end
     -> {
diff --git a/spec/ruby/core/kernel/shared/require.rb b/spec/ruby/core/kernel/shared/require.rb
index cfa1a4bbbd..52f86f73e5 100644
--- a/spec/ruby/core/kernel/shared/require.rb
+++ b/spec/ruby/core/kernel/shared/require.rb
@@ -20,7 +20,7 @@ describe :kernel_require_basic, shared: true do
 
     it "raises a LoadError if the file does not exist" do
       path = File.expand_path "nonexistent.rb", CODE_LOADING_DIR
-      File.exist?(path).should be_false
+      File.should_not.exist?(path)
       -> { @object.send(@method, path) }.should raise_error(LoadError)
       ScratchPad.recorded.should == []
     end
@@ -41,7 +41,7 @@ describe :kernel_require_basic, shared: true do
           end
 
           it "raises a LoadError" do
-            File.exist?(@path).should be_true
+            File.should.exist?(@path)
             -> { @object.send(@method, @path) }.should raise_error(LoadError)
           end
         end
@@ -60,7 +60,7 @@ describe :kernel_require_basic, shared: true do
       -> { @object.send(@method, nil) }.should raise_error(TypeError)
     end
 
-    it "raises a TypeError if passed a Fixnum" do
+    it "raises a TypeError if passed an Integer" do
       -> { @object.send(@method, 42) }.should raise_error(TypeError)
     end
 
@@ -160,6 +160,14 @@ describe :kernel_require_basic, shared: true do
       ScratchPad.recorded.should == [:loaded]
     end
 
+    it "accepts an Object with #to_path in $LOAD_PATH" do
+      obj = mock("to_path")
+      obj.should_receive(:to_path).at_least(:once).and_return(CODE_LOADING_DIR)
+      $LOAD_PATH << obj
+      @object.send(@method, "load_fixture.rb").should be_true
+      ScratchPad.recorded.should == [:loaded]
+    end
+
     it "does not require file twice after $LOAD_PATH change" do
       $LOAD_PATH << CODE_LOADING_DIR
       @object.require("load_fixture.rb").should be_true
@@ -204,6 +212,34 @@ end
 
 describe :kernel_require, shared: true do
   describe "(path resolution)" do
+    it "loads .rb file when passed absolute path without extension" do
+      path = File.expand_path "load_fixture", CODE_LOADING_DIR
+      @object.send(@method, path).should be_true
+      # This should _not_ be [:no_ext]
+      ScratchPad.recorded.should == [:loaded]
+    end
+
+    platform_is :linux, :darwin do
+      it "loads c-extension file when passed absolute path without extension when no .rb is present" do
+        # the error message is specific to what dlerror() returns
+        path = File.join CODE_LOADING_DIR, "a", "load_fixture"
+        -> { @object.send(@method, path) }.should raise_error(LoadError)
+      end
+    end
+
+    platform_is :darwin do
+      it "loads .bundle file when passed absolute path with .so" do
+        # the error message is specific to what dlerror() returns
+        path = File.join CODE_LOADING_DIR, "a", "load_fixture.so"
+        -> { @object.send(@method, path) }.should raise_error(LoadError)
+      end
+    end
+
+    it "does not try an extra .rb if the path already ends in .rb" do
+      path = File.join CODE_LOADING_DIR, "d", "load_fixture.rb"
+      -> { @object.send(@method, path) }.should raise_error(LoadError)
+    end
+
     # For reference see [ruby-core:24155] in which matz confirms this feature is
     # intentional for security reasons.
     it "does not load a bare filename unless the current working directory is in $LOAD_PATH" do
@@ -229,6 +265,17 @@ describe :kernel_require, shared: true do
       }.should complain(/circular require considered harmful/, verbose: true)
       ScratchPad.recorded.should == [:loaded]
     end
+
+    ruby_bug "#17340", ''...'3.3' do
+      it "loads a file concurrently" do
+        path = File.expand_path "concurrent_require_fixture.rb", CODE_LOADING_DIR
+        ScratchPad.record(@object)
+        -> {
+          @object.require(path)
+        }.should_not complain(/circular require considered harmful/, verbose: true)
+        ScratchPad.recorded.join
+      end
+    end
   end
 
   describe "(non-extensioned path)" do
@@ -242,12 +289,29 @@ describe :kernel_require, shared: true do
       @object.require("load_fixture").should be_true
       ScratchPad.recorded.should == [:loaded]
     end
+
+    it "does not load a feature twice when $LOAD_PATH has been modified" do
+      $LOAD_PATH.replace [CODE_LOADING_DIR]
+      @object.require("load_fixture").should be_true
+      $LOAD_PATH.replace [File.expand_path("b", CODE_LOADING_DIR), CODE_LOADING_DIR]
+      @object.require("load_fixture").should be_false
+    end
+
+    it "stores the missing path in a LoadError object" do
+      path = "abcd1234"
+
+      -> {
+        @object.send(@method, path)
+      }.should raise_error(LoadError) { |e|
+        e.path.should == path
+      }
+    end
   end
 
   describe "(file extensions)" do
     it "loads a .rb extensioned file when passed a non-extensioned path" do
       path = File.expand_path "load_fixture", CODE_LOADING_DIR
-      File.exist?(path).should be_true
+      File.should.exist?(path)
       @object.require(path).should be_true
       ScratchPad.recorded.should == [:loaded]
     end
@@ -271,7 +335,7 @@ describe :kernel_require, shared: true do
 
     it "loads a .rb extensioned file when passed a non-.rb extensioned path" do
       path = File.expand_path "load_fixture.ext", CODE_LOADING_DIR
-      File.exist?(path).should be_true
+      File.should.exist?(path)
       @object.require(path).should be_true
       ScratchPad.recorded.should == [:loaded]
     end
@@ -335,6 +399,21 @@ describe :kernel_require, shared: true do
           loaded_feature = $LOADED_FEATURES.last
           ScratchPad.recorded.should == [loaded_feature]
         end
+
+        it "requires only once when a new matching file added to path" do
+          @object.require('load_fixture').should be_true
+          ScratchPad.recorded.should == [:loaded]
+
+          symlink_to_code_dir_two = tmp("codesymlinktwo")
+          File.symlink("#{CODE_LOADING_DIR}/b", symlink_to_code_dir_two)
+          begin
+            $LOAD_PATH.unshift(symlink_to_code_dir_two)
+
+            @object.require('load_fixture').should be_false
+          ensure
+            rm_r symlink_to_code_dir_two
+          end
+        end
       end
 
       describe "with symlinks in the required feature and $LOAD_PATH" do
@@ -354,26 +433,13 @@ describe :kernel_require, shared: true do
           rm_r @dir, @symlink_to_dir
         end
 
-        ruby_version_is ""..."2.4.4" do
-          it "canonicalizes neither the entry in $LOAD_PATH nor the filename passed to #require" do
-            $LOAD_PATH.unshift(@symlink_to_dir)
-            @object.require("symfile").should be_true
-            loaded_feature = "#{@symlink_to_dir}/symfile.rb"
-            ScratchPad.recorded.should == [loaded_feature]
-            $".last.should == loaded_feature
-            $LOAD_PATH[0].should == @symlink_to_dir
-          end
-        end
-
-        ruby_version_is "2.4.4" do
-          it "canonicalizes the entry in $LOAD_PATH but not the filename passed to #require" do
-            $LOAD_PATH.unshift(@symlink_to_dir)
-            @object.require("symfile").should be_true
-            loaded_feature = "#{@dir}/symfile.rb"
-            ScratchPad.recorded.should == [loaded_feature]
-            $".last.should == loaded_feature
-            $LOAD_PATH[0].should == @symlink_to_dir
-          end
+        it "canonicalizes the entry in $LOAD_PATH but not the filename passed to #require" do
+          $LOAD_PATH.unshift(@symlink_to_dir)
+          @object.require("symfile").should be_true
+          loaded_feature = "#{@dir}/symfile.rb"
+          ScratchPad.recorded.should == [loaded_feature]
+          $".last.should == loaded_feature
+          $LOAD_PATH[0].should == @symlink_to_dir
         end
       end
     end
@@ -527,41 +593,30 @@ describe :kernel_require, shared: true do
       ScratchPad.recorded.should == []
     end
 
-    ruby_version_is ""..."2.5" do
-      it "complex, enumerator, rational, thread and unicode_normalize are already required" do
-        provided = %w[complex enumerator rational thread unicode_normalize]
-        features = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems')
-        provided.each { |feature|
-          features.should =~ /\b#{feature}\.(rb|so|jar)$/
-        }
+    it "unicode_normalize is part of core and not $LOADED_FEATURES" do
+      features = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems')
+      features.lines.each { |feature|
+        feature.should_not include("unicode_normalize")
+      }
 
-        code = provided.map { |f| "puts require #{f.inspect}\n" }.join
-        required = ruby_exe(code, options: '--disable-gems')
-        required.should == "false\n" * provided.size
-      end
+      -> { @object.require("unicode_normalize") }.should raise_error(LoadError)
     end
 
-    ruby_version_is "2.5" do
-      it "complex, enumerator, rational and thread are already required" do
-        provided = %w[complex enumerator rational thread]
-        features = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems')
-        provided.each { |feature|
-          features.should =~ /\b#{feature}\.(rb|so|jar)$/
-        }
-
-        code = provided.map { |f| "puts require #{f.inspect}\n" }.join
-        required = ruby_exe(code, options: '--disable-gems')
-        required.should == "false\n" * provided.size
+    it "does not load a file earlier on the $LOAD_PATH when other similar features were already loaded" do
+      Dir.chdir CODE_LOADING_DIR do
+        @object.send(@method, "../code/load_fixture").should be_true
       end
+      ScratchPad.recorded.should == [:loaded]
 
-      it "unicode_normalize is part of core and not $LOADED_FEATURES" do
-        features = ruby_exe("puts $LOADED_FEATURES", options: '--disable-gems')
-        features.lines.each { |feature|
-          feature.should_not include("unicode_normalize")
-        }
+      $LOAD_PATH.unshift "#{CODE_LOADING_DIR}/b"
+      # This loads because the above load was not on the $LOAD_PATH
+      @object.send(@method, "load_fixture").should be_true
+      ScratchPad.recorded.should == [:loaded, :loaded]
 
-        -> { @object.require("unicode_normalize") }.should raise_error(LoadError)
-      end
+      $LOAD_PATH.unshift "#{CODE_LOADING_DIR}/c"
+      # This does not load because the above load was on the $LOAD_PATH
+      @object.send(@method, "load_fixture").should be_false
+      ScratchPad.recorded.should == [:loaded, :loaded]
     end
   end
 
@@ -770,4 +825,24 @@ describe :kernel_require, shared: true do
       e.path.should == path
     }
   end
+
+  platform_is :linux, :darwin do
+    it "does not store the missing path in a LoadError object when c-extension file exists but loading fails and passed absolute path without extension" do
+      # the error message is specific to what dlerror() returns
+      path = File.join CODE_LOADING_DIR, "a", "load_fixture"
+      -> { @object.send(@method, path) }.should raise_error(LoadError) { |e|
+        e.path.should == nil
+      }
+    end
+  end
+
+  platform_is :darwin do
+    it "does not store the missing path in a LoadError object when c-extension file exists but loading fails and passed absolute path with extension" do
+      # the error message is specific to what dlerror() returns
+      path = File.join CODE_LOADING_DIR, "a", "load_fixture.bundle"
+      -> { @object.send(@method, path) }.should raise_error(LoadError) { |e|
+        e.path.should == nil
+      }
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/shared/sprintf.rb b/spec/ruby/core/kernel/shared/sprintf.rb
index 9899684284..2b2c6c9b63 100644
--- a/spec/ruby/core/kernel/shared/sprintf.rb
+++ b/spec/ruby/core/kernel/shared/sprintf.rb
@@ -1,10 +1,4 @@
-require_relative '../../../shared/hash/key_error'
-
 describe :kernel_sprintf, shared: true do
-  def format(*args)
-    @method.call(*args)
-  end
-
   describe "integer formats" do
     it "converts argument into Integer with to_int" do
       obj = Object.new
@@ -12,7 +6,7 @@ describe :kernel_sprintf, shared: true do
       def obj.to_int; 10; end
 
       obj.should_receive(:to_int).and_return(10)
-      format("%b", obj).should == "1010"
+      @method.call("%b", obj).should == "1010"
     end
 
     it "converts argument into Integer with to_i if to_int isn't available" do
@@ -20,35 +14,36 @@ describe :kernel_sprintf, shared: true do
       def obj.to_i; 10; end
 
       obj.should_receive(:to_i).and_return(10)
-      format("%b", obj).should == "1010"
+      @method.call("%b", obj).should == "1010"
     end
 
     it "converts String argument with Kernel#Integer" do
-      format("%d", "0b1010").should == "10"
-      format("%d", "112").should == "112"
-      format("%d", "0127").should == "87"
-      format("%d", "0xc4").should == "196"
+      @method.call("%d", "0b1010").should == "10"
+      @method.call("%d", "112").should == "112"
+      @method.call("%d", "0127").should == "87"
+      @method.call("%d", "0xc4").should == "196"
+      @method.call("%d", "0").should == "0"
     end
 
     it "raises TypeError exception if cannot convert to Integer" do
       -> {
-        format("%b", Object.new)
+        @method.call("%b", Object.new)
       }.should raise_error(TypeError)
     end
 
     ["b", "B"].each do |f|
       describe f do
         it "converts argument as a binary number" do
-          format("%#{f}", 10).should == "1010"
+          @method.call("%#{f}", 10).should == "1010"
         end
 
         it "displays negative number as a two's complement prefixed with '..1'" do
-          format("%#{f}", -10).should == "..1" + "0110"
+          @method.call("%#{f}", -10).should == "..1" + "0110"
         end
 
         it "collapse negative number representation if it equals 1" do
-          format("%#{f}", -1).should_not == "..11"
-          format("%#{f}", -1).should == "..1"
+          @method.call("%#{f}", -1).should_not == "..11"
+          @method.call("%#{f}", -1).should == "..1"
         end
       end
     end
@@ -56,58 +51,63 @@ describe :kernel_sprintf, shared: true do
     ["d", "i", "u"].each do |f|
       describe f do
         it "converts argument as a decimal number" do
-          format("%#{f}", 112).should == "112"
-          format("%#{f}", -112).should == "-112"
+          @method.call("%#{f}", 112).should == "112"
+          @method.call("%#{f}", -112).should == "-112"
         end
 
         it "works well with large numbers" do
-          format("%#{f}", 1234567890987654321).should == "1234567890987654321"
+          @method.call("%#{f}", 1234567890987654321).should == "1234567890987654321"
+        end
+
+        it "converts to the empty string if precision is 0 and value is 0" do
+          @method.call("%.#{f}", 0).should == ""
+          @method.call("%.0#{f}", 0).should == ""
         end
       end
     end
 
     describe "o" do
       it "converts argument as an octal number" do
-        format("%o", 87).should == "127"
+        @method.call("%o", 87).should == "127"
       end
 
       it "displays negative number as a two's complement prefixed with '..7'" do
-        format("%o", -87).should == "..7" + "651"
+        @method.call("%o", -87).should == "..7" + "651"
       end
 
       it "collapse negative number representation if it equals 7" do
-        format("%o", -1).should_not == "..77"
-        format("%o", -1).should == "..7"
+        @method.call("%o", -1).should_not == "..77"
+        @method.call("%o", -1).should == "..7"
       end
     end
 
     describe "x" do
       it "converts argument as a hexadecimal number" do
-        format("%x", 196).should == "c4"
+        @method.call("%x", 196).should == "c4"
       end
 
       it "displays negative number as a two's complement prefixed with '..f'" do
-        format("%x", -196).should == "..f" + "3c"
+        @method.call("%x", -196).should == "..f" + "3c"
       end
 
       it "collapse negative number representation if it equals f" do
-        format("%x", -1).should_not == "..ff"
-        format("%x", -1).should == "..f"
+        @method.call("%x", -1).should_not == "..ff"
+        @method.call("%x", -1).should == "..f"
       end
     end
 
     describe "X" do
       it "converts argument as a hexadecimal number with uppercase letters" do
-        format("%X", 196).should == "C4"
+        @method.call("%X", 196).should == "C4"
       end
 
       it "displays negative number as a two's complement prefixed with '..f'" do
-        format("%X", -196).should == "..F" + "3C"
+        @method.call("%X", -196).should == "..F" + "3C"
       end
 
       it "collapse negative number representation if it equals F" do
-        format("%X", -1).should_not == "..FF"
-        format("%X", -1).should == "..F"
+        @method.call("%X", -1).should_not == "..FF"
+        @method.call("%X", -1).should == "..F"
       end
     end
   end
@@ -116,70 +116,70 @@ describe :kernel_sprintf, shared: true do
     it "converts argument into Float" do
       obj = mock("float")
       obj.should_receive(:to_f).and_return(9.6)
-      format("%f", obj).should == "9.600000"
+      @method.call("%f", obj).should == "9.600000"
     end
 
     it "raises TypeError exception if cannot convert to Float" do
       -> {
-        format("%f", Object.new)
+        @method.call("%f", Object.new)
       }.should raise_error(TypeError)
     end
 
     {"e" => "e", "E" => "E"}.each_pair do |f, exp|
       describe f do
         it "converts argument into exponential notation [-]d.dddddde[+-]dd" do
-          format("%#{f}", 109.52).should == "1.095200#{exp}+02"
-          format("%#{f}", -109.52).should == "-1.095200#{exp}+02"
-          format("%#{f}", 0.10952).should == "1.095200#{exp}-01"
-          format("%#{f}", -0.10952).should == "-1.095200#{exp}-01"
+          @method.call("%#{f}", 109.52).should == "1.095200#{exp}+02"
+          @method.call("%#{f}", -109.52).should == "-1.095200#{exp}+02"
+          @method.call("%#{f}", 0.10952).should == "1.095200#{exp}-01"
+          @method.call("%#{f}", -0.10952).should == "-1.095200#{exp}-01"
         end
 
         it "cuts excessive digits and keeps only 6 ones" do
-          format("%#{f}", 1.123456789).should == "1.123457#{exp}+00"
+          @method.call("%#{f}", 1.123456789).should == "1.123457#{exp}+00"
         end
 
         it "rounds the last significant digit to the closest one" do
-          format("%#{f}", 1.555555555).should == "1.555556#{exp}+00"
-          format("%#{f}", -1.555555555).should == "-1.555556#{exp}+00"
-          format("%#{f}", 1.444444444).should == "1.444444#{exp}+00"
+          @method.call("%#{f}", 1.555555555).should == "1.555556#{exp}+00"
+          @method.call("%#{f}", -1.555555555).should == "-1.555556#{exp}+00"
+          @method.call("%#{f}", 1.444444444).should == "1.444444#{exp}+00"
         end
 
         it "displays Float::INFINITY as Inf" do
-          format("%#{f}", Float::INFINITY).should == "Inf"
-          format("%#{f}", -Float::INFINITY).should == "-Inf"
+          @method.call("%#{f}", Float::INFINITY).should == "Inf"
+          @method.call("%#{f}", -Float::INFINITY).should == "-Inf"
         end
 
         it "displays Float::NAN as NaN" do
-          format("%#{f}", Float::NAN).should == "NaN"
-          format("%#{f}", -Float::NAN).should == "NaN"
+          @method.call("%#{f}", Float::NAN).should == "NaN"
+          @method.call("%#{f}", -Float::NAN).should == "NaN"
         end
       end
     end
 
     describe "f" do
       it "converts floating point argument as [-]ddd.dddddd" do
-        format("%f", 10.952).should == "10.952000"
-        format("%f", -10.952).should == "-10.952000"
+        @method.call("%f", 10.952).should == "10.952000"
+        @method.call("%f", -10.952).should == "-10.952000"
       end
 
       it "cuts excessive digits and keeps only 6 ones" do
-        format("%f", 1.123456789).should == "1.123457"
+        @method.call("%f", 1.123456789).should == "1.123457"
       end
 
       it "rounds the last significant digit to the closest one" do
-        format("%f", 1.555555555).should == "1.555556"
-        format("%f", -1.555555555).should == "-1.555556"
-        format("%f", 1.444444444).should == "1.444444"
+        @method.call("%f", 1.555555555).should == "1.555556"
+        @method.call("%f", -1.555555555).should == "-1.555556"
+        @method.call("%f", 1.444444444).should == "1.444444"
       end
 
       it "displays Float::INFINITY as Inf" do
-        format("%f", Float::INFINITY).should == "Inf"
-        format("%f", -Float::INFINITY).should == "-Inf"
+        @method.call("%f", Float::INFINITY).should == "Inf"
+        @method.call("%f", -Float::INFINITY).should == "-Inf"
       end
 
       it "displays Float::NAN as NaN" do
-        format("%f", Float::NAN).should == "NaN"
-        format("%f", -Float::NAN).should == "NaN"
+        @method.call("%f", Float::NAN).should == "NaN"
+        @method.call("%f", -Float::NAN).should == "NaN"
       end
     end
 
@@ -187,100 +187,100 @@ describe :kernel_sprintf, shared: true do
       describe f do
         context "the exponent is less than -4" do
           it "converts a floating point number using exponential form" do
-            format("%#{f}", 0.0000123456).should == "1.23456#{exp}-05"
-            format("%#{f}", -0.0000123456).should == "-1.23456#{exp}-05"
+            @method.call("%#{f}", 0.0000123456).should == "1.23456#{exp}-05"
+            @method.call("%#{f}", -0.0000123456).should == "-1.23456#{exp}-05"
 
-            format("%#{f}", 0.000000000123456).should == "1.23456#{exp}-10"
-            format("%#{f}", -0.000000000123456).should == "-1.23456#{exp}-10"
+            @method.call("%#{f}", 0.000000000123456).should == "1.23456#{exp}-10"
+            @method.call("%#{f}", -0.000000000123456).should == "-1.23456#{exp}-10"
           end
         end
 
         context "the exponent is greater than or equal to the precision (6 by default)" do
           it "converts a floating point number using exponential form" do
-            format("%#{f}", 1234567).should == "1.23457#{exp}+06"
-            format("%#{f}", 1234567890123).should == "1.23457#{exp}+12"
-            format("%#{f}", -1234567).should == "-1.23457#{exp}+06"
+            @method.call("%#{f}", 1234567).should == "1.23457#{exp}+06"
+            @method.call("%#{f}", 1234567890123).should == "1.23457#{exp}+12"
+            @method.call("%#{f}", -1234567).should == "-1.23457#{exp}+06"
           end
         end
 
         context "otherwise" do
           it "converts a floating point number in dd.dddd form" do
-            format("%#{f}", 0.0001).should == "0.0001"
-            format("%#{f}", -0.0001).should == "-0.0001"
-            format("%#{f}", 123456).should == "123456"
-            format("%#{f}", -123456).should == "-123456"
+            @method.call("%#{f}", 0.0001).should == "0.0001"
+            @method.call("%#{f}", -0.0001).should == "-0.0001"
+            @method.call("%#{f}", 123456).should == "123456"
+            @method.call("%#{f}", -123456).should == "-123456"
           end
 
           it "cuts excessive digits in fractional part and keeps only 4 ones" do
-            format("%#{f}", 12.12341111).should == "12.1234"
-            format("%#{f}", -12.12341111).should == "-12.1234"
+            @method.call("%#{f}", 12.12341111).should == "12.1234"
+            @method.call("%#{f}", -12.12341111).should == "-12.1234"
           end
 
           it "rounds the last significant digit to the closest one in fractional part" do
-            format("%#{f}", 1.555555555).should == "1.55556"
-            format("%#{f}", -1.555555555).should == "-1.55556"
-            format("%#{f}", 1.444444444).should == "1.44444"
+            @method.call("%#{f}", 1.555555555).should == "1.55556"
+            @method.call("%#{f}", -1.555555555).should == "-1.55556"
+            @method.call("%#{f}", 1.444444444).should == "1.44444"
           end
 
           it "cuts fraction part to have only 6 digits at all" do
-            format("%#{f}", 1.1234567).should == "1.12346"
-            format("%#{f}", 12.1234567).should == "12.1235"
-            format("%#{f}", 123.1234567).should == "123.123"
-            format("%#{f}", 1234.1234567).should == "1234.12"
-            format("%#{f}", 12345.1234567).should == "12345.1"
-            format("%#{f}", 123456.1234567).should == "123456"
+            @method.call("%#{f}", 1.1234567).should == "1.12346"
+            @method.call("%#{f}", 12.1234567).should == "12.1235"
+            @method.call("%#{f}", 123.1234567).should == "123.123"
+            @method.call("%#{f}", 1234.1234567).should == "1234.12"
+            @method.call("%#{f}", 12345.1234567).should == "12345.1"
+            @method.call("%#{f}", 123456.1234567).should == "123456"
           end
         end
 
         it "displays Float::INFINITY as Inf" do
-          format("%#{f}", Float::INFINITY).should == "Inf"
-          format("%#{f}", -Float::INFINITY).should == "-Inf"
+          @method.call("%#{f}", Float::INFINITY).should == "Inf"
+          @method.call("%#{f}", -Float::INFINITY).should == "-Inf"
         end
 
         it "displays Float::NAN as NaN" do
-          format("%#{f}", Float::NAN).should == "NaN"
-          format("%#{f}", -Float::NAN).should == "NaN"
+          @method.call("%#{f}", Float::NAN).should == "NaN"
+          @method.call("%#{f}", -Float::NAN).should == "NaN"
         end
       end
     end
 
     describe "a" do
       it "converts floating point argument as [-]0xh.hhhhp[+-]dd" do
-        format("%a", 196).should == "0x1.88p+7"
-        format("%a", -196).should == "-0x1.88p+7"
-        format("%a", 196.1).should == "0x1.8833333333333p+7"
-        format("%a", 0.01).should == "0x1.47ae147ae147bp-7"
-        format("%a", -0.01).should == "-0x1.47ae147ae147bp-7"
+        @method.call("%a", 196).should == "0x1.88p+7"
+        @method.call("%a", -196).should == "-0x1.88p+7"
+        @method.call("%a", 196.1).should == "0x1.8833333333333p+7"
+        @method.call("%a", 0.01).should == "0x1.47ae147ae147bp-7"
+        @method.call("%a", -0.01).should == "-0x1.47ae147ae147bp-7"
       end
 
       it "displays Float::INFINITY as Inf" do
-        format("%a", Float::INFINITY).should == "Inf"
-        format("%a", -Float::INFINITY).should == "-Inf"
+        @method.call("%a", Float::INFINITY).should == "Inf"
+        @method.call("%a", -Float::INFINITY).should == "-Inf"
       end
 
       it "displays Float::NAN as NaN" do
-        format("%a", Float::NAN).should == "NaN"
-        format("%a", -Float::NAN).should == "NaN"
+        @method.call("%a", Float::NAN).should == "NaN"
+        @method.call("%a", -Float::NAN).should == "NaN"
       end
     end
 
     describe "A" do
       it "converts floating point argument as [-]0xh.hhhhp[+-]dd and use uppercase X and P" do
-        format("%A", 196).should == "0X1.88P+7"
-        format("%A", -196).should == "-0X1.88P+7"
-        format("%A", 196.1).should == "0X1.8833333333333P+7"
-        format("%A", 0.01).should == "0X1.47AE147AE147BP-7"
-        format("%A", -0.01).should == "-0X1.47AE147AE147BP-7"
+        @method.call("%A", 196).should == "0X1.88P+7"
+        @method.call("%A", -196).should == "-0X1.88P+7"
+        @method.call("%A", 196.1).should == "0X1.8833333333333P+7"
+        @method.call("%A", 0.01).should == "0X1.47AE147AE147BP-7"
+        @method.call("%A", -0.01).should == "-0X1.47AE147AE147BP-7"
       end
 
       it "displays Float::INFINITY as Inf" do
-        format("%A", Float::INFINITY).should == "Inf"
-        format("%A", -Float::INFINITY).should == "-Inf"
+        @method.call("%A", Float::INFINITY).should == "Inf"
+        @method.call("%A", -Float::INFINITY).should == "-Inf"
       end
 
       it "displays Float::NAN as NaN" do
-        format("%A", Float::NAN).should == "NaN"
-        format("%A", -Float::NAN).should == "NaN"
+        @method.call("%A", Float::NAN).should == "NaN"
+        @method.call("%A", -Float::NAN).should == "NaN"
       end
     end
   end
@@ -288,28 +288,71 @@ describe :kernel_sprintf, shared: true do
   describe "other formats" do
     describe "c" do
       it "displays character if argument is a numeric code of character" do
-        format("%c", 97).should == "a"
+        @method.call("%c", 97).should == "a"
       end
 
       it "displays character if argument is a single character string" do
-        format("%c", "a").should == "a"
+        @method.call("%c", "a").should == "a"
+      end
+
+      it "displays only the first character if argument is a string of several characters" do
+        @method.call("%c", "abc").should == "a"
+      end
+
+      it "displays no characters if argument is an empty string" do
+        @method.call("%c", "").should == ""
       end
 
-      it "raises ArgumentError if argument is a string of several characters" do
+      it "raises TypeError if argument is not String or Integer and cannot be converted to them" do
         -> {
-          format("%c", "abc")
-        }.should raise_error(ArgumentError)
+          @method.call("%c", [])
+        }.should raise_error(TypeError, /no implicit conversion of Array into Integer/)
       end
 
-      it "raises ArgumentError if argument is an empty string" do
+      it "raises TypeError if argument is nil" do
         -> {
-          format("%c", "")
-        }.should raise_error(ArgumentError)
+          @method.call("%c", nil)
+        }.should raise_error(TypeError, /no implicit conversion from nil to integer/)
+      end
+
+      it "tries to convert argument to String with to_str" do
+        obj = BasicObject.new
+        def obj.to_str
+          "a"
+        end
+
+        @method.call("%c", obj).should == "a"
+      end
+
+      it "tries to convert argument to Integer with to_int" do
+        obj = BasicObject.new
+        def obj.to_int
+          90
+        end
+
+        @method.call("%c", obj).should == "Z"
+      end
+
+      it "raises TypeError if converting to String with to_str returns non-String" do
+        obj = BasicObject.new
+        def obj.to_str
+          :foo
+        end
+
+        -> {
+          @method.call("%c", obj)
+        }.should raise_error(TypeError, /can't convert BasicObject to String/)
       end
 
-      it "supports Unicode characters" do
-        format("%c", 1286).should == "Ԇ"
-        format("%c", "ش").should == "ش"
+      it "raises TypeError if converting to Integer with to_int returns non-Integer" do
+        obj = BasicObject.new
+        def obj.to_int
+          :foo
+        end
+
+        -> {
+          @method.call("%c", obj)
+        }.should raise_error(TypeError, /can't convert BasicObject to Integer/)
       end
     end
 
@@ -317,19 +360,27 @@ describe :kernel_sprintf, shared: true do
       it "displays argument.inspect value" do
         obj = mock("object")
         obj.should_receive(:inspect).and_return("<inspect-result>")
-        format("%p", obj).should == "<inspect-result>"
+        @method.call("%p", obj).should == "<inspect-result>"
+      end
+
+      it "substitutes 'nil' for nil" do
+        @method.call("%p", nil).should == "nil"
       end
     end
 
     describe "s" do
       it "substitute argument passes as a string" do
-        format("%s", "abc").should == "abc"
+        @method.call("%s", "abc").should == "abc"
+      end
+
+      it "substitutes '' for nil" do
+        @method.call("%s", nil).should == ""
       end
 
       it "converts argument to string with to_s" do
         obj = mock("string")
         obj.should_receive(:to_s).and_return("abc")
-        format("%s", obj).should == "abc"
+        @method.call("%s", obj).should == "abc"
       end
 
       it "does not try to convert with to_str" do
@@ -339,29 +390,66 @@ describe :kernel_sprintf, shared: true do
         end
 
         -> {
-          format("%s", obj)
+          @method.call("%s", obj)
         }.should raise_error(NoMethodError)
       end
-    end
 
-    describe "%" do
-      ruby_version_is ""..."2.5" do
-        it "alone displays the percent sign" do
-          format("%").should == "%"
-        end
+      it "formats a partial substring without including omitted characters" do
+        long_string = "aabbccddhelloddccbbaa"
+        sub_string = long_string[8, 5]
+        sprintf("%.#{1 * 3}s", sub_string).should == "hel"
       end
 
-      ruby_version_is "2.5" do
-        it "alone raises an ArgumentError" do
-          -> {
-            format("%")
-          }.should raise_error(ArgumentError)
-        end
+      it "formats string with precision" do
+        Kernel.format("%.3s", "hello").should == "hel"
+        Kernel.format("%-3.3s", "hello").should == "hel"
+      end
+
+      it "formats string with width" do
+        @method.call("%6s", "abc").should == "   abc"
+        @method.call("%6s", "abcdefg").should == "abcdefg"
+      end
+
+      it "formats string with width and precision" do
+        @method.call("%4.6s", "abc").should == " abc"
+        @method.call("%4.6s", "abcdefg").should == "abcdef"
+      end
+
+      it "formats nil with width" do
+        @method.call("%6s", nil).should == "      "
+      end
+
+      it "formats nil with precision" do
+        @method.call("%.6s", nil).should == ""
+      end
+
+      it "formats nil with width and precision" do
+        @method.call("%4.6s", nil).should == "    "
+      end
+
+      it "formats multibyte string with precision" do
+        Kernel.format("%.2s", "été").should == "ét"
+      end
+
+      it "preserves encoding of the format string" do
+        str = format('%s'.encode(Encoding::UTF_8), 'foobar')
+        str.encoding.should == Encoding::UTF_8
+
+        str = format('%s'.encode(Encoding::US_ASCII), 'foobar')
+        str.encoding.should == Encoding::US_ASCII
+      end
+    end
+
+    describe "%" do
+      it "alone raises an ArgumentError" do
+        -> {
+          @method.call("%")
+        }.should raise_error(ArgumentError)
       end
 
       it "is escaped by %" do
-        format("%%").should == "%"
-        format("%%d", 10).should == "%d"
+        @method.call("%%").should == "%"
+        @method.call("%%d").should == "%d"
       end
     end
   end
@@ -370,110 +458,110 @@ describe :kernel_sprintf, shared: true do
     describe "space" do
       context "applies to numeric formats bBdiouxXeEfgGaA" do
         it "leaves a space at the start of non-negative numbers" do
-          format("% b", 10).should == " 1010"
-          format("% B", 10).should == " 1010"
-          format("% d", 112).should == " 112"
-          format("% i", 112).should == " 112"
-          format("% o", 87).should == " 127"
-          format("% u", 112).should == " 112"
-          format("% x", 196).should == " c4"
-          format("% X", 196).should == " C4"
-
-          format("% e", 109.52).should == " 1.095200e+02"
-          format("% E", 109.52).should == " 1.095200E+02"
-          format("% f", 10.952).should == " 10.952000"
-          format("% g", 12.1234).should == " 12.1234"
-          format("% G", 12.1234).should == " 12.1234"
-          format("% a", 196).should == " 0x1.88p+7"
-          format("% A", 196).should == " 0X1.88P+7"
+          @method.call("% b", 10).should == " 1010"
+          @method.call("% B", 10).should == " 1010"
+          @method.call("% d", 112).should == " 112"
+          @method.call("% i", 112).should == " 112"
+          @method.call("% o", 87).should == " 127"
+          @method.call("% u", 112).should == " 112"
+          @method.call("% x", 196).should == " c4"
+          @method.call("% X", 196).should == " C4"
+
+          @method.call("% e", 109.52).should == " 1.095200e+02"
+          @method.call("% E", 109.52).should == " 1.095200E+02"
+          @method.call("% f", 10.952).should == " 10.952000"
+          @method.call("% g", 12.1234).should == " 12.1234"
+          @method.call("% G", 12.1234).should == " 12.1234"
+          @method.call("% a", 196).should == " 0x1.88p+7"
+          @method.call("% A", 196).should == " 0X1.88P+7"
         end
 
         it "does not leave a space at the start of negative numbers" do
-          format("% b", -10).should == "-1010"
-          format("% B", -10).should == "-1010"
-          format("% d", -112).should == "-112"
-          format("% i", -112).should == "-112"
-          format("% o", -87).should == "-127"
-          format("% u", -112).should == "-112"
-          format("% x", -196).should == "-c4"
-          format("% X", -196).should == "-C4"
-
-          format("% e", -109.52).should == "-1.095200e+02"
-          format("% E", -109.52).should == "-1.095200E+02"
-          format("% f", -10.952).should == "-10.952000"
-          format("% g", -12.1234).should == "-12.1234"
-          format("% G", -12.1234).should == "-12.1234"
-          format("% a", -196).should == "-0x1.88p+7"
-          format("% A", -196).should == "-0X1.88P+7"
+          @method.call("% b", -10).should == "-1010"
+          @method.call("% B", -10).should == "-1010"
+          @method.call("% d", -112).should == "-112"
+          @method.call("% i", -112).should == "-112"
+          @method.call("% o", -87).should == "-127"
+          @method.call("% u", -112).should == "-112"
+          @method.call("% x", -196).should == "-c4"
+          @method.call("% X", -196).should == "-C4"
+
+          @method.call("% e", -109.52).should == "-1.095200e+02"
+          @method.call("% E", -109.52).should == "-1.095200E+02"
+          @method.call("% f", -10.952).should == "-10.952000"
+          @method.call("% g", -12.1234).should == "-12.1234"
+          @method.call("% G", -12.1234).should == "-12.1234"
+          @method.call("% a", -196).should == "-0x1.88p+7"
+          @method.call("% A", -196).should == "-0X1.88P+7"
         end
 
         it "prevents converting negative argument to two's complement form" do
-          format("% b", -10).should == "-1010"
-          format("% B", -10).should == "-1010"
-          format("% o", -87).should == "-127"
-          format("% x", -196).should == "-c4"
-          format("% X", -196).should == "-C4"
+          @method.call("% b", -10).should == "-1010"
+          @method.call("% B", -10).should == "-1010"
+          @method.call("% o", -87).should == "-127"
+          @method.call("% x", -196).should == "-c4"
+          @method.call("% X", -196).should == "-C4"
         end
 
         it "treats several white spaces as one" do
-          format("%     b", 10).should == " 1010"
-          format("%     B", 10).should == " 1010"
-          format("%     d", 112).should == " 112"
-          format("%     i", 112).should == " 112"
-          format("%     o", 87).should == " 127"
-          format("%     u", 112).should == " 112"
-          format("%     x", 196).should == " c4"
-          format("%     X", 196).should == " C4"
+          @method.call("%     b", 10).should == " 1010"
+          @method.call("%     B", 10).should == " 1010"
+          @method.call("%     d", 112).should == " 112"
+          @method.call("%     i", 112).should == " 112"
+          @method.call("%     o", 87).should == " 127"
+          @method.call("%     u", 112).should == " 112"
+          @method.call("%     x", 196).should == " c4"
+          @method.call("%     X", 196).should == " C4"
 
-          format("%     e", 109.52).should == " 1.095200e+02"
-          format("%     E", 109.52).should == " 1.095200E+02"
-          format("%     f", 10.952).should == " 10.952000"
-          format("%     g", 12.1234).should == " 12.1234"
-          format("%     G", 12.1234).should == " 12.1234"
-          format("%     a", 196).should == " 0x1.88p+7"
-          format("%     A", 196).should == " 0X1.88P+7"
+          @method.call("%     e", 109.52).should == " 1.095200e+02"
+          @method.call("%     E", 109.52).should == " 1.095200E+02"
+          @method.call("%     f", 10.952).should == " 10.952000"
+          @method.call("%     g", 12.1234).should == " 12.1234"
+          @method.call("%     G", 12.1234).should == " 12.1234"
+          @method.call("%     a", 196).should == " 0x1.88p+7"
+          @method.call("%     A", 196).should == " 0X1.88P+7"
         end
       end
     end
 
     describe "(digit)$" do
       it "specifies the absolute argument number for this field" do
-        format("%2$b", 0, 10).should == "1010"
-        format("%2$B", 0, 10).should == "1010"
-        format("%2$d", 0, 112).should == "112"
-        format("%2$i", 0, 112).should == "112"
-        format("%2$o", 0, 87).should == "127"
-        format("%2$u", 0, 112).should == "112"
-        format("%2$x", 0, 196).should == "c4"
-        format("%2$X", 0, 196).should == "C4"
-
-        format("%2$e", 0, 109.52).should == "1.095200e+02"
-        format("%2$E", 0, 109.52).should == "1.095200E+02"
-        format("%2$f", 0, 10.952).should == "10.952000"
-        format("%2$g", 0, 12.1234).should == "12.1234"
-        format("%2$G", 0, 12.1234).should == "12.1234"
-        format("%2$a", 0, 196).should == "0x1.88p+7"
-        format("%2$A", 0, 196).should == "0X1.88P+7"
-
-        format("%2$c", 1, 97).should == "a"
-        format("%2$p", "a", []).should == "[]"
-        format("%2$s", "-", "abc").should == "abc"
+        @method.call("%2$b", 0, 10).should == "1010"
+        @method.call("%2$B", 0, 10).should == "1010"
+        @method.call("%2$d", 0, 112).should == "112"
+        @method.call("%2$i", 0, 112).should == "112"
+        @method.call("%2$o", 0, 87).should == "127"
+        @method.call("%2$u", 0, 112).should == "112"
+        @method.call("%2$x", 0, 196).should == "c4"
+        @method.call("%2$X", 0, 196).should == "C4"
+
+        @method.call("%2$e", 0, 109.52).should == "1.095200e+02"
+        @method.call("%2$E", 0, 109.52).should == "1.095200E+02"
+        @method.call("%2$f", 0, 10.952).should == "10.952000"
+        @method.call("%2$g", 0, 12.1234).should == "12.1234"
+        @method.call("%2$G", 0, 12.1234).should == "12.1234"
+        @method.call("%2$a", 0, 196).should == "0x1.88p+7"
+        @method.call("%2$A", 0, 196).should == "0X1.88P+7"
+
+        @method.call("%2$c", 1, 97).should == "a"
+        @method.call("%2$p", "a", []).should == "[]"
+        @method.call("%2$s", "-", "abc").should == "abc"
       end
 
       it "raises exception if argument number is bigger than actual arguments list" do
         -> {
-          format("%4$d", 1, 2, 3)
+          @method.call("%4$d", 1, 2, 3)
         }.should raise_error(ArgumentError)
       end
 
       it "ignores '-' sign" do
-        format("%2$d", 1, 2, 3).should == "2"
-        format("%-2$d", 1, 2, 3).should == "2"
+        @method.call("%2$d", 1, 2, 3).should == "2"
+        @method.call("%-2$d", 1, 2, 3).should == "2"
       end
 
       it "raises ArgumentError exception when absolute and relative argument numbers are mixed" do
         -> {
-          format("%1$d %d", 1, 2)
+          @method.call("%1$d %d", 1, 2)
         }.should raise_error(ArgumentError)
       end
     end
@@ -481,62 +569,62 @@ describe :kernel_sprintf, shared: true do
     describe "#" do
       context "applies to format o" do
         it "increases the precision until the first digit will be `0' if it is not formatted as complements" do
-          format("%#o", 87).should == "0127"
+          @method.call("%#o", 87).should == "0127"
         end
 
         it "does nothing for negative argument" do
-          format("%#o", -87).should == "..7651"
+          @method.call("%#o", -87).should == "..7651"
         end
       end
 
       context "applies to formats bBxX" do
         it "prefixes the result with 0x, 0X, 0b and 0B respectively for non-zero argument" do
-          format("%#b", 10).should == "0b1010"
-          format("%#b", -10).should == "0b..10110"
-          format("%#B", 10).should == "0B1010"
-          format("%#B", -10).should == "0B..10110"
+          @method.call("%#b", 10).should == "0b1010"
+          @method.call("%#b", -10).should == "0b..10110"
+          @method.call("%#B", 10).should == "0B1010"
+          @method.call("%#B", -10).should == "0B..10110"
 
-          format("%#x", 196).should == "0xc4"
-          format("%#x", -196).should == "0x..f3c"
-          format("%#X", 196).should == "0XC4"
-          format("%#X", -196).should == "0X..F3C"
+          @method.call("%#x", 196).should == "0xc4"
+          @method.call("%#x", -196).should == "0x..f3c"
+          @method.call("%#X", 196).should == "0XC4"
+          @method.call("%#X", -196).should == "0X..F3C"
         end
 
         it "does nothing for zero argument" do
-          format("%#b", 0).should == "0"
-          format("%#B", 0).should == "0"
+          @method.call("%#b", 0).should == "0"
+          @method.call("%#B", 0).should == "0"
 
-          format("%#o", 0).should == "0"
+          @method.call("%#o", 0).should == "0"
 
-          format("%#x", 0).should == "0"
-          format("%#X", 0).should == "0"
+          @method.call("%#x", 0).should == "0"
+          @method.call("%#X", 0).should == "0"
         end
       end
 
       context "applies to formats aAeEfgG" do
         it "forces a decimal point to be added, even if no digits follow" do
-          format("%#.0a", 16.25).should == "0x1.p+4"
-          format("%#.0A", 16.25).should == "0X1.P+4"
+          @method.call("%#.0a", 16.25).should == "0x1.p+4"
+          @method.call("%#.0A", 16.25).should == "0X1.P+4"
 
-          format("%#.0e", 100).should == "1.e+02"
-          format("%#.0E", 100).should == "1.E+02"
+          @method.call("%#.0e", 100).should == "1.e+02"
+          @method.call("%#.0E", 100).should == "1.E+02"
 
-          format("%#.0f", 123.4).should == "123."
+          @method.call("%#.0f", 123.4).should == "123."
 
-          format("%#g", 123456).should == "123456."
-          format("%#G", 123456).should == "123456."
+          @method.call("%#g", 123456).should == "123456."
+          @method.call("%#G", 123456).should == "123456."
         end
 
         it "changes format from dd.dddd to exponential form for gG" do
-          format("%#.0g", 123.4).should_not == "123."
-          format("%#.0g", 123.4).should == "1.e+02"
+          @method.call("%#.0g", 123.4).should_not == "123."
+          @method.call("%#.0g", 123.4).should == "1.e+02"
         end
       end
 
       context "applies to gG" do
         it "does not remove trailing zeros" do
-          format("%#g", 123.4).should == "123.400"
-          format("%#g", 123.4).should == "123.400"
+          @method.call("%#g", 123.4).should == "123.400"
+          @method.call("%#g", 123.4).should == "123.400"
         end
       end
     end
@@ -544,186 +632,186 @@ describe :kernel_sprintf, shared: true do
     describe "+" do
       context "applies to numeric formats bBdiouxXaAeEfgG" do
         it "adds a leading plus sign to non-negative numbers" do
-          format("%+b", 10).should == "+1010"
-          format("%+B", 10).should == "+1010"
-          format("%+d", 112).should == "+112"
-          format("%+i", 112).should == "+112"
-          format("%+o", 87).should == "+127"
-          format("%+u", 112).should == "+112"
-          format("%+x", 196).should == "+c4"
-          format("%+X", 196).should == "+C4"
-
-          format("%+e", 109.52).should == "+1.095200e+02"
-          format("%+E", 109.52).should == "+1.095200E+02"
-          format("%+f", 10.952).should == "+10.952000"
-          format("%+g", 12.1234).should == "+12.1234"
-          format("%+G", 12.1234).should == "+12.1234"
-          format("%+a", 196).should == "+0x1.88p+7"
-          format("%+A", 196).should == "+0X1.88P+7"
+          @method.call("%+b", 10).should == "+1010"
+          @method.call("%+B", 10).should == "+1010"
+          @method.call("%+d", 112).should == "+112"
+          @method.call("%+i", 112).should == "+112"
+          @method.call("%+o", 87).should == "+127"
+          @method.call("%+u", 112).should == "+112"
+          @method.call("%+x", 196).should == "+c4"
+          @method.call("%+X", 196).should == "+C4"
+
+          @method.call("%+e", 109.52).should == "+1.095200e+02"
+          @method.call("%+E", 109.52).should == "+1.095200E+02"
+          @method.call("%+f", 10.952).should == "+10.952000"
+          @method.call("%+g", 12.1234).should == "+12.1234"
+          @method.call("%+G", 12.1234).should == "+12.1234"
+          @method.call("%+a", 196).should == "+0x1.88p+7"
+          @method.call("%+A", 196).should == "+0X1.88P+7"
         end
 
         it "does not use two's complement form for negative numbers for formats bBoxX" do
-          format("%+b", -10).should == "-1010"
-          format("%+B", -10).should == "-1010"
-          format("%+o", -87).should == "-127"
-          format("%+x", -196).should == "-c4"
-          format("%+X", -196).should == "-C4"
+          @method.call("%+b", -10).should == "-1010"
+          @method.call("%+B", -10).should == "-1010"
+          @method.call("%+o", -87).should == "-127"
+          @method.call("%+x", -196).should == "-c4"
+          @method.call("%+X", -196).should == "-C4"
         end
       end
     end
 
     describe "-" do
       it "left-justifies the result of conversion if width is specified" do
-        format("%-10b", 10).should == "1010      "
-        format("%-10B", 10).should == "1010      "
-        format("%-10d", 112).should == "112       "
-        format("%-10i", 112).should == "112       "
-        format("%-10o", 87).should == "127       "
-        format("%-10u", 112).should == "112       "
-        format("%-10x", 196).should == "c4        "
-        format("%-10X", 196).should == "C4        "
+        @method.call("%-10b", 10).should == "1010      "
+        @method.call("%-10B", 10).should == "1010      "
+        @method.call("%-10d", 112).should == "112       "
+        @method.call("%-10i", 112).should == "112       "
+        @method.call("%-10o", 87).should == "127       "
+        @method.call("%-10u", 112).should == "112       "
+        @method.call("%-10x", 196).should == "c4        "
+        @method.call("%-10X", 196).should == "C4        "
 
-        format("%-20e", 109.52).should == "1.095200e+02        "
-        format("%-20E", 109.52).should == "1.095200E+02        "
-        format("%-20f", 10.952).should == "10.952000           "
-        format("%-20g", 12.1234).should == "12.1234             "
-        format("%-20G", 12.1234).should == "12.1234             "
-        format("%-20a", 196).should == "0x1.88p+7           "
-        format("%-20A", 196).should == "0X1.88P+7           "
+        @method.call("%-20e", 109.52).should == "1.095200e+02        "
+        @method.call("%-20E", 109.52).should == "1.095200E+02        "
+        @method.call("%-20f", 10.952).should == "10.952000           "
+        @method.call("%-20g", 12.1234).should == "12.1234             "
+        @method.call("%-20G", 12.1234).should == "12.1234             "
+        @method.call("%-20a", 196).should == "0x1.88p+7           "
+        @method.call("%-20A", 196).should == "0X1.88P+7           "
 
-        format("%-10c", 97).should == "a         "
-        format("%-10p", []).should == "[]        "
-        format("%-10s", "abc").should == "abc       "
+        @method.call("%-10c", 97).should == "a         "
+        @method.call("%-10p", []).should == "[]        "
+        @method.call("%-10s", "abc").should == "abc       "
       end
     end
 
     describe "0 (zero)" do
       context "applies to numeric formats bBdiouxXaAeEfgG and width is specified" do
         it "pads with zeros, not spaces" do
-          format("%010b", 10).should == "0000001010"
-          format("%010B", 10).should == "0000001010"
-          format("%010d", 112).should == "0000000112"
-          format("%010i", 112).should == "0000000112"
-          format("%010o", 87).should == "0000000127"
-          format("%010u", 112).should == "0000000112"
-          format("%010x", 196).should == "00000000c4"
-          format("%010X", 196).should == "00000000C4"
-
-          format("%020e", 109.52).should == "000000001.095200e+02"
-          format("%020E", 109.52).should == "000000001.095200E+02"
-          format("%020f", 10.952).should == "0000000000010.952000"
-          format("%020g", 12.1234).should == "000000000000012.1234"
-          format("%020G", 12.1234).should == "000000000000012.1234"
-          format("%020a", 196).should == "0x000000000001.88p+7"
-          format("%020A", 196).should == "0X000000000001.88P+7"
+          @method.call("%010b", 10).should == "0000001010"
+          @method.call("%010B", 10).should == "0000001010"
+          @method.call("%010d", 112).should == "0000000112"
+          @method.call("%010i", 112).should == "0000000112"
+          @method.call("%010o", 87).should == "0000000127"
+          @method.call("%010u", 112).should == "0000000112"
+          @method.call("%010x", 196).should == "00000000c4"
+          @method.call("%010X", 196).should == "00000000C4"
+
+          @method.call("%020e", 109.52).should == "000000001.095200e+02"
+          @method.call("%020E", 109.52).should == "000000001.095200E+02"
+          @method.call("%020f", 10.952).should == "0000000000010.952000"
+          @method.call("%020g", 12.1234).should == "000000000000012.1234"
+          @method.call("%020G", 12.1234).should == "000000000000012.1234"
+          @method.call("%020a", 196).should == "0x000000000001.88p+7"
+          @method.call("%020A", 196).should == "0X000000000001.88P+7"
         end
 
         it "uses radix-1 when displays negative argument as a two's complement" do
-          format("%010b", -10).should == "..11110110"
-          format("%010B", -10).should == "..11110110"
-          format("%010o", -87).should == "..77777651"
-          format("%010x", -196).should == "..ffffff3c"
-          format("%010X", -196).should == "..FFFFFF3C"
+          @method.call("%010b", -10).should == "..11110110"
+          @method.call("%010B", -10).should == "..11110110"
+          @method.call("%010o", -87).should == "..77777651"
+          @method.call("%010x", -196).should == "..ffffff3c"
+          @method.call("%010X", -196).should == "..FFFFFF3C"
         end
       end
     end
 
     describe "*" do
       it "uses the previous argument as the field width" do
-        format("%*b", 10, 10).should == "      1010"
-        format("%*B", 10, 10).should == "      1010"
-        format("%*d", 10, 112).should == "       112"
-        format("%*i", 10, 112).should == "       112"
-        format("%*o", 10, 87).should == "       127"
-        format("%*u", 10, 112).should == "       112"
-        format("%*x", 10, 196).should == "        c4"
-        format("%*X", 10, 196).should == "        C4"
-
-        format("%*e", 20, 109.52).should == "        1.095200e+02"
-        format("%*E", 20, 109.52).should == "        1.095200E+02"
-        format("%*f", 20, 10.952).should == "           10.952000"
-        format("%*g", 20, 12.1234).should == "             12.1234"
-        format("%*G", 20, 12.1234).should == "             12.1234"
-        format("%*a", 20, 196).should == "           0x1.88p+7"
-        format("%*A", 20, 196).should == "           0X1.88P+7"
-
-        format("%*c", 10, 97).should == "         a"
-        format("%*p", 10, []).should == "        []"
-        format("%*s", 10, "abc").should == "       abc"
+        @method.call("%*b", 10, 10).should == "      1010"
+        @method.call("%*B", 10, 10).should == "      1010"
+        @method.call("%*d", 10, 112).should == "       112"
+        @method.call("%*i", 10, 112).should == "       112"
+        @method.call("%*o", 10, 87).should == "       127"
+        @method.call("%*u", 10, 112).should == "       112"
+        @method.call("%*x", 10, 196).should == "        c4"
+        @method.call("%*X", 10, 196).should == "        C4"
+
+        @method.call("%*e", 20, 109.52).should == "        1.095200e+02"
+        @method.call("%*E", 20, 109.52).should == "        1.095200E+02"
+        @method.call("%*f", 20, 10.952).should == "           10.952000"
+        @method.call("%*g", 20, 12.1234).should == "             12.1234"
+        @method.call("%*G", 20, 12.1234).should == "             12.1234"
+        @method.call("%*a", 20, 196).should == "           0x1.88p+7"
+        @method.call("%*A", 20, 196).should == "           0X1.88P+7"
+
+        @method.call("%*c", 10, 97).should == "         a"
+        @method.call("%*p", 10, []).should == "        []"
+        @method.call("%*s", 10, "abc").should == "       abc"
       end
 
       it "left-justifies the result if width is negative" do
-        format("%*b", -10, 10).should == "1010      "
-        format("%*B", -10, 10).should == "1010      "
-        format("%*d", -10, 112).should == "112       "
-        format("%*i", -10, 112).should == "112       "
-        format("%*o", -10, 87).should == "127       "
-        format("%*u", -10, 112).should == "112       "
-        format("%*x", -10, 196).should == "c4        "
-        format("%*X", -10, 196).should == "C4        "
-
-        format("%*e", -20, 109.52).should == "1.095200e+02        "
-        format("%*E", -20, 109.52).should == "1.095200E+02        "
-        format("%*f", -20, 10.952).should == "10.952000           "
-        format("%*g", -20, 12.1234).should == "12.1234             "
-        format("%*G", -20, 12.1234).should == "12.1234             "
-        format("%*a", -20, 196).should == "0x1.88p+7           "
-        format("%*A", -20, 196).should == "0X1.88P+7           "
-
-        format("%*c", -10, 97).should == "a         "
-        format("%*p", -10, []).should == "[]        "
-        format("%*s", -10, "abc").should == "abc       "
+        @method.call("%*b", -10, 10).should == "1010      "
+        @method.call("%*B", -10, 10).should == "1010      "
+        @method.call("%*d", -10, 112).should == "112       "
+        @method.call("%*i", -10, 112).should == "112       "
+        @method.call("%*o", -10, 87).should == "127       "
+        @method.call("%*u", -10, 112).should == "112       "
+        @method.call("%*x", -10, 196).should == "c4        "
+        @method.call("%*X", -10, 196).should == "C4        "
+
+        @method.call("%*e", -20, 109.52).should == "1.095200e+02        "
+        @method.call("%*E", -20, 109.52).should == "1.095200E+02        "
+        @method.call("%*f", -20, 10.952).should == "10.952000           "
+        @method.call("%*g", -20, 12.1234).should == "12.1234             "
+        @method.call("%*G", -20, 12.1234).should == "12.1234             "
+        @method.call("%*a", -20, 196).should == "0x1.88p+7           "
+        @method.call("%*A", -20, 196).should == "0X1.88P+7           "
+
+        @method.call("%*c", -10, 97).should == "a         "
+        @method.call("%*p", -10, []).should == "[]        "
+        @method.call("%*s", -10, "abc").should == "abc       "
       end
 
       it "uses the specified argument as the width if * is followed by a number and $" do
-        format("%1$*2$b", 10, 10).should == "      1010"
-        format("%1$*2$B", 10, 10).should == "      1010"
-        format("%1$*2$d", 112, 10).should == "       112"
-        format("%1$*2$i", 112, 10).should == "       112"
-        format("%1$*2$o", 87, 10).should == "       127"
-        format("%1$*2$u", 112, 10).should == "       112"
-        format("%1$*2$x", 196, 10).should == "        c4"
-        format("%1$*2$X", 196, 10).should == "        C4"
-
-        format("%1$*2$e", 109.52, 20).should == "        1.095200e+02"
-        format("%1$*2$E", 109.52, 20).should == "        1.095200E+02"
-        format("%1$*2$f", 10.952, 20).should == "           10.952000"
-        format("%1$*2$g", 12.1234, 20).should == "             12.1234"
-        format("%1$*2$G", 12.1234, 20).should == "             12.1234"
-        format("%1$*2$a", 196, 20).should == "           0x1.88p+7"
-        format("%1$*2$A", 196, 20).should == "           0X1.88P+7"
-
-        format("%1$*2$c", 97, 10).should == "         a"
-        format("%1$*2$p", [], 10).should == "        []"
-        format("%1$*2$s", "abc", 10).should == "       abc"
+        @method.call("%1$*2$b", 10, 10).should == "      1010"
+        @method.call("%1$*2$B", 10, 10).should == "      1010"
+        @method.call("%1$*2$d", 112, 10).should == "       112"
+        @method.call("%1$*2$i", 112, 10).should == "       112"
+        @method.call("%1$*2$o", 87, 10).should == "       127"
+        @method.call("%1$*2$u", 112, 10).should == "       112"
+        @method.call("%1$*2$x", 196, 10).should == "        c4"
+        @method.call("%1$*2$X", 196, 10).should == "        C4"
+
+        @method.call("%1$*2$e", 109.52, 20).should == "        1.095200e+02"
+        @method.call("%1$*2$E", 109.52, 20).should == "        1.095200E+02"
+        @method.call("%1$*2$f", 10.952, 20).should == "           10.952000"
+        @method.call("%1$*2$g", 12.1234, 20).should == "             12.1234"
+        @method.call("%1$*2$G", 12.1234, 20).should == "             12.1234"
+        @method.call("%1$*2$a", 196, 20).should == "           0x1.88p+7"
+        @method.call("%1$*2$A", 196, 20).should == "           0X1.88P+7"
+
+        @method.call("%1$*2$c", 97, 10).should == "         a"
+        @method.call("%1$*2$p", [], 10).should == "        []"
+        @method.call("%1$*2$s", "abc", 10).should == "       abc"
       end
 
       it "left-justifies the result if specified with $ argument is negative" do
-        format("%1$*2$b", 10, -10).should == "1010      "
-        format("%1$*2$B", 10, -10).should == "1010      "
-        format("%1$*2$d", 112, -10).should == "112       "
-        format("%1$*2$i", 112, -10).should == "112       "
-        format("%1$*2$o", 87, -10).should == "127       "
-        format("%1$*2$u", 112, -10).should == "112       "
-        format("%1$*2$x", 196, -10).should == "c4        "
-        format("%1$*2$X", 196, -10).should == "C4        "
-
-        format("%1$*2$e", 109.52, -20).should == "1.095200e+02        "
-        format("%1$*2$E", 109.52, -20).should == "1.095200E+02        "
-        format("%1$*2$f", 10.952, -20).should == "10.952000           "
-        format("%1$*2$g", 12.1234, -20).should == "12.1234             "
-        format("%1$*2$G", 12.1234, -20).should == "12.1234             "
-        format("%1$*2$a", 196, -20).should == "0x1.88p+7           "
-        format("%1$*2$A", 196, -20).should == "0X1.88P+7           "
-
-        format("%1$*2$c", 97, -10).should == "a         "
-        format("%1$*2$p", [], -10).should == "[]        "
-        format("%1$*2$s", "abc", -10).should == "abc       "
+        @method.call("%1$*2$b", 10, -10).should == "1010      "
+        @method.call("%1$*2$B", 10, -10).should == "1010      "
+        @method.call("%1$*2$d", 112, -10).should == "112       "
+        @method.call("%1$*2$i", 112, -10).should == "112       "
+        @method.call("%1$*2$o", 87, -10).should == "127       "
+        @method.call("%1$*2$u", 112, -10).should == "112       "
+        @method.call("%1$*2$x", 196, -10).should == "c4        "
+        @method.call("%1$*2$X", 196, -10).should == "C4        "
+
+        @method.call("%1$*2$e", 109.52, -20).should == "1.095200e+02        "
+        @method.call("%1$*2$E", 109.52, -20).should == "1.095200E+02        "
+        @method.call("%1$*2$f", 10.952, -20).should == "10.952000           "
+        @method.call("%1$*2$g", 12.1234, -20).should == "12.1234             "
+        @method.call("%1$*2$G", 12.1234, -20).should == "12.1234             "
+        @method.call("%1$*2$a", 196, -20).should == "0x1.88p+7           "
+        @method.call("%1$*2$A", 196, -20).should == "0X1.88P+7           "
+
+        @method.call("%1$*2$c", 97, -10).should == "a         "
+        @method.call("%1$*2$p", [], -10).should == "[]        "
+        @method.call("%1$*2$s", "abc", -10).should == "abc       "
       end
 
       it "raises ArgumentError when is mixed with width" do
         -> {
-          format("%*10d", 10, 112)
+          @method.call("%*10d", 10, 112)
         }.should raise_error(ArgumentError)
       end
     end
@@ -731,74 +819,74 @@ describe :kernel_sprintf, shared: true do
 
   describe "width" do
     it "specifies the minimum number of characters that will be written to the result" do
-      format("%10b", 10).should == "      1010"
-      format("%10B", 10).should == "      1010"
-      format("%10d", 112).should == "       112"
-      format("%10i", 112).should == "       112"
-      format("%10o", 87).should == "       127"
-      format("%10u", 112).should == "       112"
-      format("%10x", 196).should == "        c4"
-      format("%10X", 196).should == "        C4"
-
-      format("%20e", 109.52).should == "        1.095200e+02"
-      format("%20E", 109.52).should == "        1.095200E+02"
-      format("%20f", 10.952).should == "           10.952000"
-      format("%20g", 12.1234).should == "             12.1234"
-      format("%20G", 12.1234).should == "             12.1234"
-      format("%20a", 196).should == "           0x1.88p+7"
-      format("%20A", 196).should == "           0X1.88P+7"
-
-      format("%10c", 97).should == "         a"
-      format("%10p", []).should == "        []"
-      format("%10s", "abc").should == "       abc"
+      @method.call("%10b", 10).should == "      1010"
+      @method.call("%10B", 10).should == "      1010"
+      @method.call("%10d", 112).should == "       112"
+      @method.call("%10i", 112).should == "       112"
+      @method.call("%10o", 87).should == "       127"
+      @method.call("%10u", 112).should == "       112"
+      @method.call("%10x", 196).should == "        c4"
+      @method.call("%10X", 196).should == "        C4"
+
+      @method.call("%20e", 109.52).should == "        1.095200e+02"
+      @method.call("%20E", 109.52).should == "        1.095200E+02"
+      @method.call("%20f", 10.952).should == "           10.952000"
+      @method.call("%20g", 12.1234).should == "             12.1234"
+      @method.call("%20G", 12.1234).should == "             12.1234"
+      @method.call("%20a", 196).should == "           0x1.88p+7"
+      @method.call("%20A", 196).should == "           0X1.88P+7"
+
+      @method.call("%10c", 97).should == "         a"
+      @method.call("%10p", []).should == "        []"
+      @method.call("%10s", "abc").should == "       abc"
     end
 
     it "is ignored if argument's actual length is greater" do
-      format("%5d", 1234567890).should == "1234567890"
+      @method.call("%5d", 1234567890).should == "1234567890"
     end
   end
 
   describe "precision" do
     context "integer types" do
       it "controls the number of decimal places displayed" do
-        format("%.6b", 10).should == "001010"
-        format("%.6B", 10).should == "001010"
-        format("%.5d", 112).should == "00112"
-        format("%.5i", 112).should == "00112"
-        format("%.5o", 87).should == "00127"
-        format("%.5u", 112).should == "00112"
+        @method.call("%.6b", 10).should == "001010"
+        @method.call("%.6B", 10).should == "001010"
+        @method.call("%.5d", 112).should == "00112"
+        @method.call("%.5i", 112).should == "00112"
+        @method.call("%.5o", 87).should == "00127"
+        @method.call("%.5u", 112).should == "00112"
 
-        format("%.5x", 196).should == "000c4"
-        format("%.5X", 196).should == "000C4"
+        @method.call("%.5x", 196).should == "000c4"
+        @method.call("%.5X", 196).should == "000C4"
       end
     end
 
     context "float types" do
       it "controls the number of decimal places displayed in fraction part" do
-        format("%.10e", 109.52).should == "1.0952000000e+02"
-        format("%.10E", 109.52).should == "1.0952000000E+02"
-        format("%.10f", 10.952).should == "10.9520000000"
-        format("%.10a", 196).should == "0x1.8800000000p+7"
-        format("%.10A", 196).should == "0X1.8800000000P+7"
+        @method.call("%.10e", 109.52).should == "1.0952000000e+02"
+        @method.call("%.10E", 109.52).should == "1.0952000000E+02"
+        @method.call("%.10f", 10.952).should == "10.9520000000"
+        @method.call("%.10a", 196).should == "0x1.8800000000p+7"
+        @method.call("%.10A", 196).should == "0X1.8800000000P+7"
       end
 
       it "does not affect G format" do
-        format("%.10g", 12.1234).should == "12.1234"
-        format("%.10g", 123456789).should == "123456789"
+        @method.call("%.10g", 12.1234).should == "12.1234"
+        @method.call("%.10g", 123456789).should == "123456789"
       end
     end
 
     context "string formats" do
       it "determines the maximum number of characters to be copied from the string" do
-        format("%.1p", [1]).should == "["
-        format("%.2p", [1]).should == "[1"
-        format("%.10p", [1]).should == "[1]"
-        format("%.0p", [1]).should == ""
+        @method.call("%.1p", [1]).should == "["
+        @method.call("%.2p", [1]).should == "[1"
+        @method.call("%.10p", [1]).should == "[1]"
+        @method.call("%.0p", [1]).should == ""
 
-        format("%.1s", "abc").should == "a"
-        format("%.2s", "abc").should == "ab"
-        format("%.10s", "abc").should == "abc"
-        format("%.0s", "abc").should == ""
+        @method.call("%.1s", "abc").should == "a"
+        @method.call("%.2s", "abc").should == "ab"
+        @method.call("%.10s", "abc").should == "abc"
+        @method.call("%.0s", "abc").should == ""
       end
     end
   end
@@ -806,49 +894,49 @@ describe :kernel_sprintf, shared: true do
   describe "reference by name" do
     describe "%<name>s style" do
       it "uses value passed in a hash argument" do
-        format("%<foo>d", foo: 123).should == "123"
+        @method.call("%<foo>d", foo: 123).should == "123"
       end
 
       it "supports flags, width, precision and type" do
-        format("%+20.10<foo>f", foo: 10.952).should == "      +10.9520000000"
+        @method.call("%+20.10<foo>f", foo: 10.952).should == "      +10.9520000000"
       end
 
       it "allows to place name in any position" do
-        format("%+15.5<foo>f", foo: 10.952).should == "      +10.95200"
-        format("%+15<foo>.5f", foo: 10.952).should == "      +10.95200"
-        format("%+<foo>15.5f", foo: 10.952).should == "      +10.95200"
-        format("%<foo>+15.5f", foo: 10.952).should == "      +10.95200"
+        @method.call("%+15.5<foo>f", foo: 10.952).should == "      +10.95200"
+        @method.call("%+15<foo>.5f", foo: 10.952).should == "      +10.95200"
+        @method.call("%+<foo>15.5f", foo: 10.952).should == "      +10.95200"
+        @method.call("%<foo>+15.5f", foo: 10.952).should == "      +10.95200"
       end
 
       it "cannot be mixed with unnamed style" do
         -> {
-          format("%d %<foo>d", 1, foo: "123")
+          @method.call("%d %<foo>d", 1, foo: "123")
         }.should raise_error(ArgumentError)
       end
     end
 
     describe "%{name} style" do
       it "uses value passed in a hash argument" do
-        format("%{foo}", foo: 123).should == "123"
+        @method.call("%{foo}", foo: 123).should == "123"
       end
 
       it "does not support type style" do
-        format("%{foo}d", foo: 123).should == "123d"
+        @method.call("%{foo}d", foo: 123).should == "123d"
       end
 
       it "supports flags, width and precision" do
-        format("%-20.5{foo}", foo: "123456789").should == "12345               "
+        @method.call("%-20.5{foo}", foo: "123456789").should == "12345               "
       end
 
       it "cannot be mixed with unnamed style" do
         -> {
-          format("%d %{foo}", 1, foo: "123")
+          @method.call("%d %{foo}", 1, foo: "123")
         }.should raise_error(ArgumentError)
       end
 
       it "raises KeyError when there is no matching key" do
         -> {
-          format("%{foo}", {})
+          @method.call("%{foo}", {})
         }.should raise_error(KeyError)
       end
 
@@ -860,18 +948,40 @@ describe :kernel_sprintf, shared: true do
         obj.should_receive(:to_s).and_return("42")
         obj.should_not_receive(:to_str)
 
-        format("%{foo}", foo: obj).should == "42"
+        @method.call("%{foo}", foo: obj).should == "42"
       end
     end
   end
 
   describe "faulty key" do
-    before :all do
-      @base_method = @method
+    before :each do
+      @object = { foooo: 1 }
+    end
+
+    it "raises a KeyError" do
+      -> {
+        @method.call("%<foo>s", @object)
+      }.should raise_error(KeyError)
+    end
+
+    it "sets the Hash as the receiver of KeyError" do
+      -> {
+        @method.call("%<foo>s", @object)
+      }.should raise_error(KeyError) { |err|
+        err.receiver.should equal(@object)
+      }
     end
 
-    it_behaves_like :key_error, -> obj, key {
-      @base_method.call("%<#{key}>s", obj)
-    }, { foooo: 1 }
+    it "sets the unmatched key as the key of KeyError" do
+      -> {
+        @method.call("%<foo>s", @object)
+      }.should raise_error(KeyError) { |err|
+        err.key.to_s.should == 'foo'
+      }
+    end
+  end
+
+  it "does not raise error when passed more arguments than needed" do
+    sprintf("%s %d %c", "string", 2, "c", []).should == "string 2 c"
   end
 end
diff --git a/spec/ruby/core/kernel/shared/sprintf_encoding.rb b/spec/ruby/core/kernel/shared/sprintf_encoding.rb
index c3d62bf3bb..7ec0fe4c48 100644
--- a/spec/ruby/core/kernel/shared/sprintf_encoding.rb
+++ b/spec/ruby/core/kernel/shared/sprintf_encoding.rb
@@ -1,28 +1,67 @@
+# Keep encoding-related specs in a separate shared example to be able to skip them in IO/File/StringIO specs.
+# It's difficult to check result's encoding in the test after writing to a file/io buffer.
 describe :kernel_sprintf_encoding, shared: true do
-  def format(*args)
-    @method.call(*args)
+  it "can produce a string with valid encoding" do
+    string = @method.call("good day %{valid}", valid: "e")
+    string.encoding.should == Encoding::UTF_8
+    string.valid_encoding?.should be_true
+  end
+
+  it "can produce a string with invalid encoding" do
+    string = @method.call("good day %{invalid}", invalid: "\x80")
+    string.encoding.should == Encoding::UTF_8
+    string.valid_encoding?.should be_false
   end
 
   it "returns a String in the same encoding as the format String if compatible" do
-    string = "%s".force_encoding(Encoding::KOI8_U)
-    result = format(string, "dogs")
+    string = "%s".dup.force_encoding(Encoding::KOI8_U)
+    result = @method.call(string, "dogs")
     result.encoding.should equal(Encoding::KOI8_U)
   end
 
   it "returns a String in the argument's encoding if format encoding is more restrictive" do
-    string = "foo %s".force_encoding(Encoding::US_ASCII)
-    argument = "b\303\274r".force_encoding(Encoding::UTF_8)
+    string = "foo %s".dup.force_encoding(Encoding::US_ASCII)
+    argument = "b\303\274r".dup.force_encoding(Encoding::UTF_8)
 
-    result = format(string, argument)
+    result = @method.call(string, argument)
     result.encoding.should equal(Encoding::UTF_8)
   end
 
-  it "raises Encoding::CompatibilityError if both encodings are ASCII compatible and there ano not ASCII characters" do
+  it "raises Encoding::CompatibilityError if both encodings are ASCII compatible and there are not ASCII characters" do
     string = "Ä %s".encode('windows-1252')
     argument = "Ђ".encode('windows-1251')
 
     -> {
-      format(string, argument)
+      @method.call(string, argument)
     }.should raise_error(Encoding::CompatibilityError)
   end
+
+  describe "%c" do
+    it "supports Unicode characters" do
+      result = @method.call("%c", 1286)
+      result.should == "Ԇ"
+      result.bytes.should == [212, 134]
+
+      result = @method.call("%c", "ش")
+      result.should == "ش"
+      result.bytes.should == [216, 180]
+    end
+
+    it "raises error when a codepoint isn't representable in an encoding of a format string" do
+      format = "%c".encode("ASCII")
+
+      -> {
+        @method.call(format, 1286)
+      }.should raise_error(RangeError, /out of char range/)
+    end
+
+    it "uses the encoding of the format string to interpret codepoints" do
+      format = "%c".dup.force_encoding("euc-jp")
+      result = @method.call(format, 9415601)
+
+      result.encoding.should == Encoding::EUC_JP
+      result.should == "é".encode(Encoding::EUC_JP)
+      result.bytes.should == [143, 171, 177]
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/singleton_class_spec.rb b/spec/ruby/core/kernel/singleton_class_spec.rb
index 5dbb4f8c05..23c400f9bd 100644
--- a/spec/ruby/core/kernel/singleton_class_spec.rb
+++ b/spec/ruby/core/kernel/singleton_class_spec.rb
@@ -1,3 +1,6 @@
+# truffleruby_primitives: true
+require_relative '../../spec_helper'
+
 describe "Kernel#singleton_class" do
   it "returns class extended from an object" do
     x = Object.new
@@ -17,11 +20,55 @@ describe "Kernel#singleton_class" do
     false.singleton_class.should == FalseClass
   end
 
-  it "raises TypeError for Fixnum" do
-    -> { 123.singleton_class }.should raise_error(TypeError)
+  it "raises TypeError for Integer" do
+    -> { 123.singleton_class }.should raise_error(TypeError, "can't define singleton")
+  end
+
+  it "raises TypeError for Float" do
+    -> { 3.14.singleton_class }.should raise_error(TypeError, "can't define singleton")
   end
 
   it "raises TypeError for Symbol" do
-    -> { :foo.singleton_class }.should raise_error(TypeError)
+    -> { :foo.singleton_class }.should raise_error(TypeError, "can't define singleton")
+  end
+
+  it "raises TypeError for a frozen deduplicated String" do
+    -> { (-"string").singleton_class }.should raise_error(TypeError, "can't define singleton")
+    -> { a = -"string"; a.singleton_class }.should raise_error(TypeError, "can't define singleton")
+    -> { a = "string"; (-a).singleton_class }.should raise_error(TypeError, "can't define singleton")
+  end
+
+  it "returns a frozen singleton class if object is frozen" do
+    obj = Object.new
+    obj.freeze
+    obj.singleton_class.frozen?.should be_true
+  end
+
+  context "for an IO object with a replaced singleton class" do
+    it "looks up singleton methods from the fresh singleton class after an object instance got a new one" do
+      proxy = -> io { io.foo }
+      if RUBY_ENGINE == 'truffleruby'
+        # We need an inline cache with only this object seen, the best way to do that is to use a Primitive
+        sclass = -> io { Primitive.singleton_class(io) }
+      else
+        sclass = -> io { io.singleton_class }
+      end
+
+      io = File.new(__FILE__)
+      io.define_singleton_method(:foo) { "old" }
+      sclass1 = sclass.call(io)
+      proxy.call(io).should == "old"
+
+      # IO#reopen is the only method which can replace an object's singleton class
+      io2 = File.new(__FILE__)
+      io.reopen(io2)
+      io.define_singleton_method(:foo) { "new" }
+      sclass2 = sclass.call(io)
+      sclass2.should_not.equal?(sclass1)
+      proxy.call(io).should == "new"
+    ensure
+      io2.close
+      io.close
+    end
   end
 end
diff --git a/spec/ruby/core/kernel/singleton_method_spec.rb b/spec/ruby/core/kernel/singleton_method_spec.rb
index 0bdf125ad8..7d63fa7cc6 100644
--- a/spec/ruby/core/kernel/singleton_method_spec.rb
+++ b/spec/ruby/core/kernel/singleton_method_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Kernel#singleton_method" do
-  it "find a method defined on the singleton class" do
+  it "finds a method defined on the singleton class" do
     obj = Object.new
     def obj.foo; end
     obj.singleton_method(:foo).should be_an_instance_of(Method)
@@ -38,4 +38,48 @@ describe "Kernel#singleton_method" do
       e.class.should == NameError
     }
   end
+
+  ruby_bug "#20620", ""..."3.4" do
+    it "finds a method defined in a module included in the singleton class" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.singleton_class.include(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+
+    it "finds a method defined in a module prepended in the singleton class" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.singleton_class.prepend(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+
+    it "finds a method defined in a module that an object is extended with" do
+      m = Module.new do
+        def foo
+          :foo
+        end
+      end
+
+      obj = Object.new
+      obj.extend(m)
+
+      obj.singleton_method(:foo).should be_an_instance_of(Method)
+      obj.singleton_method(:foo).call.should == :foo
+    end
+  end
 end
diff --git a/spec/ruby/core/kernel/singleton_methods_spec.rb b/spec/ruby/core/kernel/singleton_methods_spec.rb
index eb4cede110..a127a439de 100644
--- a/spec/ruby/core/kernel/singleton_methods_spec.rb
+++ b/spec/ruby/core/kernel/singleton_methods_spec.rb
@@ -52,7 +52,7 @@ describe :kernel_singleton_methods_modules, shared: true do
 end
 
 describe :kernel_singleton_methods_supers, shared: true do
-  it "returns the names of singleton methods for an object extented with a module" do
+  it "returns the names of singleton methods for an object extended with a module" do
     ReflectSpecs.oe.singleton_methods(*@object).should include(:m_pro, :m_pub)
   end
 
@@ -62,11 +62,11 @@ describe :kernel_singleton_methods_supers, shared: true do
     r.should == [:pro, :pub]
   end
 
-  it "returns the names of singleton methods for an object extented with two modules" do
+  it "returns the names of singleton methods for an object extended with two modules" do
     ReflectSpecs.oee.singleton_methods(*@object).should include(:m_pro, :m_pub, :n_pro, :n_pub)
   end
 
-  it "returns the names of singleton methods for an object extented with a module including a module" do
+  it "returns the names of singleton methods for an object extended with a module including a module" do
     ReflectSpecs.oei.singleton_methods(*@object).should include(:n_pro, :n_pub, :m_pro, :m_pub)
   end
 
@@ -112,7 +112,7 @@ describe :kernel_singleton_methods_private_supers, shared: true do
     ReflectSpecs.oee.singleton_methods(*@object).should_not include(:m_pri)
   end
 
-  it "does not return private singleton methods for an object extented with a module including a module" do
+  it "does not return private singleton methods for an object extended with a module including a module" do
     ReflectSpecs.oei.singleton_methods(*@object).should_not include(:n_pri, :m_pri)
   end
 
@@ -165,11 +165,11 @@ describe "Kernel#singleton_methods" do
     it_behaves_like :kernel_singleton_methods_modules, nil, false
     it_behaves_like :kernel_singleton_methods_private_supers, nil, false
 
-    it "returns an empty Array for an object extented with a module" do
+    it "returns an empty Array for an object extended with a module" do
       ReflectSpecs.oe.singleton_methods(false).should == []
     end
 
-    it "returns an empty Array for an object extented with two modules" do
+    it "returns an empty Array for an object extended with two modules" do
       ReflectSpecs.oee.singleton_methods(false).should == []
     end
 
diff --git a/spec/ruby/core/kernel/sleep_spec.rb b/spec/ruby/core/kernel/sleep_spec.rb
index 387dc4787b..e9c600aac4 100644
--- a/spec/ruby/core/kernel/sleep_spec.rb
+++ b/spec/ruby/core/kernel/sleep_spec.rb
@@ -1,5 +1,5 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
+require_relative '../fiber/fixtures/scheduler'
 
 describe "Kernel#sleep" do
   it "is a private method" do
@@ -14,7 +14,7 @@ describe "Kernel#sleep" do
     sleep(0.001).should >= 0
   end
 
-  it "accepts a Fixnum" do
+  it "accepts an Integer" do
     sleep(0).should >= 0
   end
 
@@ -22,15 +22,17 @@ describe "Kernel#sleep" do
     sleep(Rational(1, 999)).should >= 0
   end
 
+  it "accepts any Object that responds to divmod" do
+    o = Object.new
+    def o.divmod(*); [0, 0.001]; end
+    sleep(o).should >= 0
+  end
+
   it "raises an ArgumentError when passed a negative duration" do
     -> { sleep(-0.1) }.should raise_error(ArgumentError)
     -> { sleep(-1) }.should raise_error(ArgumentError)
   end
 
-  it "raises a TypeError when passed nil" do
-    -> { sleep(nil)   }.should raise_error(TypeError)
-  end
-
   it "raises a TypeError when passed a String" do
     -> { sleep('2')   }.should raise_error(TypeError)
   end
@@ -49,6 +51,74 @@ describe "Kernel#sleep" do
     t.wakeup
     t.value.should == 5
   end
+
+  it "sleeps with nanosecond precision" do
+    start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    100.times do
+      sleep(0.0001)
+    end
+    end_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+    actual_duration = end_time - start_time
+    actual_duration.should > 0.01 # 100 * 0.0001 => 0.01
+  end
+
+  ruby_version_is ""..."3.3" do
+    it "raises a TypeError when passed nil" do
+      -> { sleep(nil)   }.should raise_error(TypeError)
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "accepts a nil duration" do
+      running = false
+      t = Thread.new do
+        running = true
+        sleep(nil)
+        5
+      end
+
+      Thread.pass until running
+      Thread.pass while t.status and t.status != "sleep"
+
+      t.wakeup
+      t.value.should == 5
+    end
+  end
+
+  context "Kernel.sleep with Fiber scheduler" do
+    before :each do
+      Fiber.set_scheduler(FiberSpecs::LoggingScheduler.new)
+    end
+
+    after :each do
+      Fiber.set_scheduler(nil)
+    end
+
+    it "calls the scheduler without arguments when no duration is given" do
+      sleeper = Fiber.new(blocking: false) do
+        sleep
+      end
+      sleeper.resume
+      Fiber.scheduler.events.should == [{ event: :kernel_sleep, fiber: sleeper, args: [] }]
+    end
+
+    it "calls the scheduler with the given duration" do
+      sleeper = Fiber.new(blocking: false) do
+        sleep(0.01)
+      end
+      sleeper.resume
+      Fiber.scheduler.events.should == [{ event: :kernel_sleep, fiber: sleeper, args: [0.01] }]
+    end
+
+    it "does not call the scheduler if the fiber is blocking" do
+      sleeper = Fiber.new(blocking: true) do
+        sleep(0.01)
+      end
+      sleeper.resume
+      Fiber.scheduler.events.should == []
+    end
+  end
 end
 
 describe "Kernel.sleep" do
diff --git a/spec/ruby/core/kernel/sprintf_spec.rb b/spec/ruby/core/kernel/sprintf_spec.rb
index 7adf71be76..5a4a90ff7a 100644
--- a/spec/ruby/core/kernel/sprintf_spec.rb
+++ b/spec/ruby/core/kernel/sprintf_spec.rb
@@ -3,22 +3,62 @@ require_relative 'fixtures/classes'
 require_relative 'shared/sprintf'
 require_relative 'shared/sprintf_encoding'
 
+describe :kernel_sprintf_to_str, shared: true do
+  it "calls #to_str to convert the format object to a String" do
+    obj = mock('format string')
+    obj.should_receive(:to_str).and_return("to_str: %i")
+    @method.call(obj, 42).should == "to_str: 42"
+  end
+end
+
 describe "Kernel#sprintf" do
   it_behaves_like :kernel_sprintf, -> format, *args {
-    sprintf(format, *args)
+    r = nil
+    -> {
+      r = sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
   }
 
   it_behaves_like :kernel_sprintf_encoding, -> format, *args {
-    sprintf(format, *args)
+    r = nil
+    -> {
+      r = sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
+  }
+
+  it_behaves_like :kernel_sprintf_to_str, -> format, *args {
+    r = nil
+    -> {
+      r = sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
   }
 end
 
 describe "Kernel.sprintf" do
   it_behaves_like :kernel_sprintf, -> format, *args {
-    Kernel.sprintf(format, *args)
+    r = nil
+    -> {
+      r = Kernel.sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
   }
 
   it_behaves_like :kernel_sprintf_encoding, -> format, *args {
-    Kernel.sprintf(format, *args)
+    r = nil
+    -> {
+      r = Kernel.sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
+  }
+
+  it_behaves_like :kernel_sprintf_to_str, -> format, *args {
+    r = nil
+    -> {
+      r = Kernel.sprintf(format, *args)
+    }.should_not complain(verbose: true)
+    r
   }
 end
diff --git a/spec/ruby/core/kernel/srand_spec.rb b/spec/ruby/core/kernel/srand_spec.rb
index 5454aae8cf..95bb406f46 100644
--- a/spec/ruby/core/kernel/srand_spec.rb
+++ b/spec/ruby/core/kernel/srand_spec.rb
@@ -1,7 +1,15 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe "Kernel.srand" do
+describe "Kernel#srand" do
+  before :each do
+    @seed = srand
+  end
+
+  after :each do
+    srand(@seed)
+  end
+
   it "is a private method" do
     Kernel.should have_private_instance_method(:srand)
   end
@@ -11,6 +19,10 @@ describe "Kernel.srand" do
     srand(20).should == 10
   end
 
+  it "returns the system-initialized seed value on the first call" do
+    ruby_exe('print srand(10)', options: '--disable-gems').should =~ /\A\d+\z/
+  end
+
   it "seeds the RNG correctly and repeatably" do
     srand(10)
     x = rand
@@ -33,7 +45,7 @@ describe "Kernel.srand" do
     srand.should == -17
   end
 
-  it "accepts a Bignum as a seed" do
+  it "accepts an Integer as a seed" do
     srand(0x12345678901234567890)
     srand.should == 0x12345678901234567890
   end
@@ -56,6 +68,6 @@ describe "Kernel.srand" do
   end
 end
 
-describe "Kernel#srand" do
+describe "Kernel.srand" do
   it "needs to be reviewed for spec completeness"
 end
diff --git a/spec/ruby/core/kernel/system_spec.rb b/spec/ruby/core/kernel/system_spec.rb
index 96c0496dd6..9bc03924dd 100644
--- a/spec/ruby/core/kernel/system_spec.rb
+++ b/spec/ruby/core/kernel/system_spec.rb
@@ -6,14 +6,14 @@ describe :kernel_system, shared: true do
     -> { @object.system("echo a") }.should output_to_fd("a\n")
 
     $?.should be_an_instance_of Process::Status
-    $?.success?.should == true
+    $?.should.success?
   end
 
   it "returns true when the command exits with a zero exit status" do
     @object.system(ruby_cmd('exit 0')).should == true
 
     $?.should be_an_instance_of Process::Status
-    $?.success?.should == true
+    $?.should.success?
     $?.exitstatus.should == 0
   end
 
@@ -21,18 +21,16 @@ describe :kernel_system, shared: true do
     @object.system(ruby_cmd('exit 1')).should == false
 
     $?.should be_an_instance_of Process::Status
-    $?.success?.should == false
+    $?.should_not.success?
     $?.exitstatus.should == 1
   end
 
-  ruby_version_is "2.6" do
-    it "raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status" do
-      -> { @object.system(ruby_cmd('exit 1'), exception: true) }.should raise_error(RuntimeError)
-    end
+  it "raises RuntimeError when `exception: true` is given and the command exits with a non-zero exit status" do
+    -> { @object.system(ruby_cmd('exit 1'), exception: true) }.should raise_error(RuntimeError)
+  end
 
-    it "raises Errno::ENOENT when `exception: true` is given and the specified command does not exist" do
-      -> { @object.system('feature_14386', exception: true) }.should raise_error(Errno::ENOENT)
-    end
+  it "raises Errno::ENOENT when `exception: true` is given and the specified command does not exist" do
+    -> { @object.system('feature_14386', exception: true) }.should raise_error(Errno::ENOENT)
   end
 
   it "returns nil when command execution fails" do
@@ -40,7 +38,7 @@ describe :kernel_system, shared: true do
 
     $?.should be_an_instance_of Process::Status
     $?.pid.should be_kind_of(Integer)
-    $?.exitstatus.should == 127
+    $?.should_not.success?
   end
 
   it "does not write to stderr when command execution fails" do
@@ -66,6 +64,23 @@ describe :kernel_system, shared: true do
     end
   end
 
+  platform_is_not :windows do
+    before :each do
+      require 'tmpdir'
+      @shell_command = File.join(Dir.mktmpdir, "noshebang.cmd")
+      File.write(@shell_command, %[echo "$PATH"\n], perm: 0o700)
+    end
+
+    after :each do
+      File.unlink(@shell_command)
+      Dir.rmdir(File.dirname(@shell_command))
+    end
+
+    it "executes with `sh` if the command is executable but not binary and there is no shebang" do
+      -> { @object.system(@shell_command) }.should output_to_fd(ENV['PATH'] + "\n")
+    end
+  end
+
   before :each do
     ENV['TEST_SH_EXPANSION'] = 'foo'
     @shell_var = '$TEST_SH_EXPANSION'
diff --git a/spec/ruby/core/kernel/taint_spec.rb b/spec/ruby/core/kernel/taint_spec.rb
index 000295f6d2..9a2efbaea0 100644
--- a/spec/ruby/core/kernel/taint_spec.rb
+++ b/spec/ruby/core/kernel/taint_spec.rb
@@ -2,44 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#taint" do
-  it "returns self" do
-    o = Object.new
-    o.taint.should equal(o)
-  end
-
-  it "sets the tainted bit" do
-    o = Object.new
-    o.taint
-    o.tainted?.should == true
-  end
-
-  it "raises #{frozen_error_class} on an untainted, frozen object" do
-    o = Object.new.freeze
-    -> { o.taint }.should raise_error(frozen_error_class)
-  end
-
-  it "does not raise an error on a tainted, frozen object" do
-    o = Object.new.taint.freeze
-    o.taint.should equal(o)
-  end
-
-  it "has no effect on immediate values" do
-    [nil, true, false].each do |v|
-      v.taint
-      v.tainted?.should == false
-    end
-  end
-
-  it "no raises a RuntimeError on symbols" do
-    v = :sym
-    -> { v.taint }.should_not raise_error(RuntimeError)
-    v.tainted?.should == false
-  end
-
-  it "no raises error on fixnum values" do
-    [1].each do |v|
-      -> { v.taint }.should_not raise_error(RuntimeError)
-      v.tainted?.should == false
-    end
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:taint)
   end
 end
diff --git a/spec/ruby/core/kernel/tainted_spec.rb b/spec/ruby/core/kernel/tainted_spec.rb
index c024756110..837eb1dafb 100644
--- a/spec/ruby/core/kernel/tainted_spec.rb
+++ b/spec/ruby/core/kernel/tainted_spec.rb
@@ -2,11 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#tainted?" do
-  it "returns true if Object is tainted" do
-    o = mock('o')
-    p = mock('p')
-    p.taint
-    o.tainted?.should == false
-    p.tainted?.should == true
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:tainted?)
   end
 end
diff --git a/spec/ruby/core/kernel/test_spec.rb b/spec/ruby/core/kernel/test_spec.rb
index abb365aed2..d26dc06361 100644
--- a/spec/ruby/core/kernel/test_spec.rb
+++ b/spec/ruby/core/kernel/test_spec.rb
@@ -3,8 +3,8 @@ require_relative 'fixtures/classes'
 
 describe "Kernel#test" do
   before :all do
-    @file = File.dirname(__FILE__) + '/fixtures/classes.rb'
-    @dir = File.dirname(__FILE__) + '/fixtures'
+    @file = __dir__ + '/fixtures/classes.rb'
+    @dir = __dir__ + '/fixtures'
   end
 
   it "is a private method" do
diff --git a/spec/ruby/core/kernel/then_spec.rb b/spec/ruby/core/kernel/then_spec.rb
index fa896b52b1..8109a2960a 100644
--- a/spec/ruby/core/kernel/then_spec.rb
+++ b/spec/ruby/core/kernel/then_spec.rb
@@ -1,8 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'shared/then'
 
-ruby_version_is "2.6" do
-  describe "Kernel#then" do
-    it_behaves_like :kernel_then, :then
-  end
+describe "Kernel#then" do
+  it_behaves_like :kernel_then, :then
 end
diff --git a/spec/ruby/core/kernel/to_s_spec.rb b/spec/ruby/core/kernel/to_s_spec.rb
index 4b59520ce7..ea4b00151e 100644
--- a/spec/ruby/core/kernel/to_s_spec.rb
+++ b/spec/ruby/core/kernel/to_s_spec.rb
@@ -5,12 +5,4 @@ describe "Kernel#to_s" do
   it "returns a String containing the name of self's class" do
     Object.new.to_s.should =~ /Object/
   end
-
-  it "returns a tainted result if self is tainted" do
-    Object.new.taint.to_s.tainted?.should be_true
-  end
-
-  it "returns an untrusted result if self is untrusted" do
-    Object.new.untrust.to_s.untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/kernel/trap_spec.rb b/spec/ruby/core/kernel/trap_spec.rb
index 465aacb0fb..4c801a7215 100644
--- a/spec/ruby/core/kernel/trap_spec.rb
+++ b/spec/ruby/core/kernel/trap_spec.rb
@@ -1,12 +1,9 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
 
 describe "Kernel#trap" do
   it "is a private method" do
     Kernel.should have_private_instance_method(:trap)
   end
-end
 
-describe "Kernel.trap" do
-  it "needs to be reviewed for spec completeness"
+  # Behaviour is specified for Signal.trap
 end
diff --git a/spec/ruby/core/kernel/trust_spec.rb b/spec/ruby/core/kernel/trust_spec.rb
index d34aa293ec..ef3fa9a3e1 100644
--- a/spec/ruby/core/kernel/trust_spec.rb
+++ b/spec/ruby/core/kernel/trust_spec.rb
@@ -2,24 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#trust" do
-  it "returns self" do
-    o = Object.new
-    o.trust.should equal(o)
-  end
-
-  it "clears the untrusted bit" do
-    o = Object.new.untrust
-    o.trust
-    o.untrusted?.should == false
-  end
-
-  it "raises #{frozen_error_class} on an untrusted, frozen object" do
-    o = Object.new.untrust.freeze
-    -> { o.trust }.should raise_error(frozen_error_class)
-  end
-
-  it "does not raise an error on a trusted, frozen object" do
-    o = Object.new.freeze
-    o.trust.should equal(o)
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:trust)
   end
 end
diff --git a/spec/ruby/core/kernel/untaint_spec.rb b/spec/ruby/core/kernel/untaint_spec.rb
index 94e4a8fd44..47e8544bd4 100644
--- a/spec/ruby/core/kernel/untaint_spec.rb
+++ b/spec/ruby/core/kernel/untaint_spec.rb
@@ -2,24 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#untaint" do
-  it "returns self" do
-    o = Object.new
-    o.untaint.should equal(o)
-  end
-
-  it "clears the tainted bit" do
-    o = Object.new.taint
-    o.untaint
-    o.tainted?.should == false
-  end
-
-  it "raises #{frozen_error_class} on a tainted, frozen object" do
-    o = Object.new.taint.freeze
-    -> { o.untaint }.should raise_error(frozen_error_class)
-  end
-
-  it "does not raise an error on an untainted, frozen object" do
-    o = Object.new.freeze
-    o.untaint.should equal(o)
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:untaint)
   end
 end
diff --git a/spec/ruby/core/kernel/untrust_spec.rb b/spec/ruby/core/kernel/untrust_spec.rb
index 2ee3dbb170..8787ab3fc9 100644
--- a/spec/ruby/core/kernel/untrust_spec.rb
+++ b/spec/ruby/core/kernel/untrust_spec.rb
@@ -2,24 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#untrust" do
-  it "returns self" do
-    o = Object.new
-    o.untrust.should equal(o)
-  end
-
-  it "sets the untrusted bit" do
-    o = Object.new
-    o.untrust
-    o.untrusted?.should == true
-  end
-
-  it "raises #{frozen_error_class} on a trusted, frozen object" do
-    o = Object.new.freeze
-    -> { o.untrust }.should raise_error(frozen_error_class)
-  end
-
-  it "does not raise an error on an untrusted, frozen object" do
-    o = Object.new.untrust.freeze
-    o.untrust.should equal(o)
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:untrust)
   end
 end
diff --git a/spec/ruby/core/kernel/untrusted_spec.rb b/spec/ruby/core/kernel/untrusted_spec.rb
index 3f894b0bab..29261be9c4 100644
--- a/spec/ruby/core/kernel/untrusted_spec.rb
+++ b/spec/ruby/core/kernel/untrusted_spec.rb
@@ -2,27 +2,7 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Kernel#untrusted?" do
-  it "returns the untrusted status of an object" do
-    o = mock('o')
-    o.untrusted?.should == false
-    o.untrust
-    o.untrusted?.should == true
-  end
-
-  it "has no effect on immediate values" do
-    a = nil
-    b = true
-    c = false
-    a.untrust
-    b.untrust
-    c.untrust
-    a.untrusted?.should == false
-    b.untrusted?.should == false
-    c.untrusted?.should == false
-  end
-
-  it "has effect on immediate values" do
-    d = 1
-    -> { d.untrust }.should_not raise_error(RuntimeError)
+  it "has been removed" do
+    Object.new.should_not.respond_to?(:untrusted?)
   end
 end
diff --git a/spec/ruby/core/kernel/warn_spec.rb b/spec/ruby/core/kernel/warn_spec.rb
index d05a37958d..e03498c6dc 100644
--- a/spec/ruby/core/kernel/warn_spec.rb
+++ b/spec/ruby/core/kernel/warn_spec.rb
@@ -8,15 +8,16 @@ describe "Kernel#warn" do
   end
 
   after :each do
-    $VERBOSE = @before_verbose
+    $VERBOSE = nil
     $/ = @before_separator
+    $VERBOSE = @before_verbose
   end
 
   it "is a private method" do
     Kernel.should have_private_instance_method(:warn)
   end
 
-  it "requires multiple arguments" do
+  it "accepts multiple arguments" do
     Kernel.method(:warn).arity.should < 0
   end
 
@@ -86,55 +87,212 @@ describe "Kernel#warn" do
     }.should output(nil, "to_s called\n")
   end
 
-  ruby_version_is "2.5" do
-    describe ":uplevel keyword argument" do
-      before :each do
-        $VERBOSE = true
-      end
+  describe ":uplevel keyword argument" do
+    before :each do
+      $VERBOSE = true
+    end
 
-      it "prepends a message with specified line from the backtrace" do
-        w = KernelSpecs::WarnInNestedCall.new
+    it "prepends a message with specified line from the backtrace" do
+      w = KernelSpecs::WarnInNestedCall.new
 
-        -> { w.f4("foo", 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: foo|)
-        -> { w.f4("foo", 1) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f1_call_lineno}: warning: foo|)
-        -> { w.f4("foo", 2) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f2_call_lineno}: warning: foo|)
-        -> { w.f4("foo", 3) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f3_call_lineno}: warning: foo|)
-      end
+      -> { w.f4("foo", 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: foo|)
+      -> { w.f4("foo", 1) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f1_call_lineno}: warning: foo|)
+      -> { w.f4("foo", 2) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f2_call_lineno}: warning: foo|)
+      -> { w.f4("foo", 3) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f3_call_lineno}: warning: foo|)
+    end
 
-      it "does not prepend caller information if line number is too big" do
-        w = KernelSpecs::WarnInNestedCall.new
-        -> { w.f4("foo", 100) }.should output(nil, "warning: foo\n")
-      end
+    # Test both explicitly without and with RubyGems as RubyGems overrides Kernel#warn
+    it "shows the caller of #require and not #require itself without RubyGems" do
+      file = fixture(__FILE__ , "warn_require_caller.rb")
+      ruby_exe(file, options: "--disable-gems", args: "2>&1").should == "#{file}:2: warning: warn-require-warning\n"
+    end
 
-      it "prepends even if a message is empty or nil" do
-        w = KernelSpecs::WarnInNestedCall.new
+    it "shows the caller of #require and not #require itself with RubyGems loaded" do
+      file = fixture(__FILE__ , "warn_require_caller.rb")
+      ruby_exe(file, options: "-rrubygems", args: "2>&1").should == "#{file}:2: warning: warn-require-warning\n"
+    end
 
-        -> { w.f4("", 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: \n$|)
-        -> { w.f4(nil, 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: \n$|)
-      end
+    it "doesn't show the caller when the uplevel is `nil`" do
+      w = KernelSpecs::WarnInNestedCall.new
 
-      it "converts value to Integer" do
-        w = KernelSpecs::WarnInNestedCall.new
+      -> { w.f4("foo", nil) }.should output(nil, "foo\n")
+    end
+
+    guard -> { Kernel.instance_method(:tap).source_location } do
+      it "skips <internal: core library methods defined in Ruby" do
+        file, line = Kernel.instance_method(:tap).source_location
+        file.should.start_with?('<internal:')
 
-        -> { w.f4(0.1) }.should output(nil, %r|classes.rb:#{w.warn_call_lineno}:|)
-        -> { w.f4(Rational(1, 2)) }.should output(nil, %r|classes.rb:#{w.warn_call_lineno}:|)
+        file = fixture(__FILE__ , "warn_core_method.rb")
+        n = 9
+        ruby_exe(file, options: "--disable-gems", args: "2>&1").lines.should == [
+          "#{file}:#{n+0}: warning: use X instead\n",
+          "#{file}:#{n+1}: warning: use X instead\n",
+          "#{file}:#{n+2}: warning: use X instead\n",
+          "#{file}:#{n+4}: warning: use X instead\n",
+        ]
       end
+    end
+
+    it "accepts :category keyword with a symbol" do
+      -> {
+        $VERBOSE = true
+        warn("message", category: :deprecated)
+      }.should output(nil, "message\n")
+    end
+
+    it "accepts :category keyword with nil" do
+      -> {
+        $VERBOSE = true
+        warn("message", category: nil)
+      }.should output(nil, "message\n")
+    end
+
+    it "accepts :category keyword with object convertible to symbol" do
+      o = Object.new
+      def o.to_sym; :deprecated; end
+      -> {
+        $VERBOSE = true
+        warn("message", category: o)
+      }.should output(nil, "message\n")
+    end
+
+    it "raises if :category keyword is not nil and not convertible to symbol" do
+      -> {
+        $VERBOSE = true
+        warn("message", category: Object.new)
+      }.should raise_error(TypeError)
+    end
+
+    it "converts first arg using to_s" do
+      w = KernelSpecs::WarnInNestedCall.new
+
+      -> { w.f4(false, 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: false|)
+      -> { w.f4(nil, 1) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f1_call_lineno}: warning: |)
+      obj = mock("obj")
+      obj.should_receive(:to_s).and_return("to_s called")
+      -> { w.f4(obj, 2) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.f2_call_lineno}: warning: to_s called|)
+    end
 
-      it "raises ArgumentError if passed negative value" do
-        -> { warn "", uplevel: -2 }.should raise_error(ArgumentError)
-        -> { warn "", uplevel: -100 }.should raise_error(ArgumentError)
+    it "does not prepend caller information if the uplevel argument is too large" do
+      w = KernelSpecs::WarnInNestedCall.new
+      -> { w.f4("foo", 100) }.should output(nil, "warning: foo\n")
+    end
+
+    it "prepends even if a message is empty or nil" do
+      w = KernelSpecs::WarnInNestedCall.new
+
+      -> { w.f4("", 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: \n$|)
+      -> { w.f4(nil, 0) }.should output(nil, %r|core/kernel/fixtures/classes.rb:#{w.warn_call_lineno}: warning: \n$|)
+    end
+
+    it "converts value to Integer" do
+      w = KernelSpecs::WarnInNestedCall.new
+
+      -> { w.f4(0.1) }.should output(nil, %r|classes.rb:#{w.warn_call_lineno}:|)
+      -> { w.f4(Rational(1, 2)) }.should output(nil, %r|classes.rb:#{w.warn_call_lineno}:|)
+    end
+
+    it "raises ArgumentError if passed negative value" do
+      -> { warn "", uplevel: -2 }.should raise_error(ArgumentError)
+      -> { warn "", uplevel: -100 }.should raise_error(ArgumentError)
+    end
+
+    it "raises ArgumentError if passed -1" do
+      -> { warn "", uplevel: -1 }.should raise_error(ArgumentError)
+    end
+
+    it "raises TypeError if passed not Integer" do
+      -> { warn "", uplevel: "" }.should raise_error(TypeError)
+      -> { warn "", uplevel: [] }.should raise_error(TypeError)
+      -> { warn "", uplevel: {} }.should raise_error(TypeError)
+      -> { warn "", uplevel: Object.new }.should raise_error(TypeError)
+    end
+  end
+
+  it "treats empty hash as no keyword argument" do
+    h = {}
+    -> { warn(**h) }.should_not complain(verbose: true)
+    -> { warn('foo', **h) }.should complain("foo\n")
+  end
+
+  it "calls Warning.warn without keyword arguments if Warning.warn does not accept keyword arguments" do
+    verbose = $VERBOSE
+    $VERBOSE = false
+    class << Warning
+      alias_method :_warn, :warn
+      def warn(message)
+        ScratchPad.record(message)
       end
+    end
+
+    begin
+      ScratchPad.clear
+      Kernel.warn("Chunky bacon!")
+      ScratchPad.recorded.should == "Chunky bacon!\n"
 
-      it "raises ArgumentError if passed -1" do
-        -> { warn "", uplevel: -1 }.should raise_error(ArgumentError)
+      Kernel.warn("Deprecated bacon!", category: :deprecated)
+      ScratchPad.recorded.should == "Deprecated bacon!\n"
+    ensure
+      class << Warning
+        remove_method :warn
+        alias_method :warn, :_warn
+        remove_method :_warn
       end
+      $VERBOSE = verbose
+    end
+  end
+
+  it "calls Warning.warn with category: nil if Warning.warn accepts keyword arguments" do
+    Warning.should_receive(:warn).with("Chunky bacon!\n", category: nil)
+    verbose = $VERBOSE
+    $VERBOSE = false
+    begin
+      Kernel.warn("Chunky bacon!")
+    ensure
+      $VERBOSE = verbose
+    end
+  end
+
+  it "calls Warning.warn with given category keyword converted to a symbol" do
+    Warning.should_receive(:warn).with("Chunky bacon!\n", category: :deprecated)
+    verbose = $VERBOSE
+    $VERBOSE = false
+    begin
+      Kernel.warn("Chunky bacon!", category: 'deprecated')
+    ensure
+      $VERBOSE = verbose
+    end
+  end
+
+  it "does not call Warning.warn if self is the Warning module" do
+    # RubyGems redefines Kernel#warn so we need to use a subprocess and disable RubyGems here
+    code = <<-RUBY
+    def Warning.warn(*args, **kwargs)
+      raise 'should not be called'
+    end
+    Kernel.instance_method(:warn).bind(Warning).call('Kernel#warn spec edge case')
+    RUBY
+    out = ruby_exe(code, args: "2>&1", options: "--disable-gems")
+    out.should == "Kernel#warn spec edge case\n"
+    $?.should.success?
+  end
 
-      it "raises TypeError if passed not Integer" do
-        -> { warn "", uplevel: "" }.should raise_error(TypeError)
-        -> { warn "", uplevel: [] }.should raise_error(TypeError)
-        -> { warn "", uplevel: {} }.should raise_error(TypeError)
-        -> { warn "", uplevel: Object.new }.should raise_error(TypeError)
+  it "avoids recursion if Warning#warn is redefined and calls super" do
+    # This works because of the spec above, which is the workaround for it.
+    # Note that redefining Warning#warn is a mistake which would naturally end in infinite recursion,
+    # Warning.extend Module.new { def warn } should be used instead.
+    # RubyGems redefines Kernel#warn so we need to use a subprocess and disable RubyGems here
+    code = <<-RUBY
+    module Warning
+      def warn(*args, **kwargs)
+        super
       end
     end
+    warn "avoid infinite recursion"
+    RUBY
+    out = ruby_exe(code, args: "2>&1", options: "--disable-gems")
+    out.should == "avoid infinite recursion\n"
+    $?.should.success?
   end
 end
diff --git a/spec/ruby/core/kernel/yield_self_spec.rb b/spec/ruby/core/kernel/yield_self_spec.rb
index affedae144..e311dcee47 100644
--- a/spec/ruby/core/kernel/yield_self_spec.rb
+++ b/spec/ruby/core/kernel/yield_self_spec.rb
@@ -1,8 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'shared/then'
 
-ruby_version_is "2.5" do
-  describe "Kernel#yield_self" do
-    it_behaves_like :kernel_then, :yield_self
-  end
+describe "Kernel#yield_self" do
+  it_behaves_like :kernel_then, :yield_self
 end
diff --git a/spec/ruby/core/main/fixtures/classes.rb b/spec/ruby/core/main/fixtures/classes.rb
index 6aba948ce0..757cee4e4a 100644
--- a/spec/ruby/core/main/fixtures/classes.rb
+++ b/spec/ruby/core/main/fixtures/classes.rb
@@ -13,6 +13,14 @@ def main_public_method
 end
 public :main_public_method
 
+def main_public_method2
+end
+public :main_public_method2
+
 def main_private_method
 end
 private :main_private_method
+
+def main_private_method2
+end
+private :main_private_method2
diff --git a/spec/ruby/core/main/fixtures/using.rb b/spec/ruby/core/main/fixtures/using.rb
new file mode 100644
index 0000000000..30713ef309
--- /dev/null
+++ b/spec/ruby/core/main/fixtures/using.rb
@@ -0,0 +1 @@
+using Module.new
diff --git a/spec/ruby/core/main/fixtures/using_in_main.rb b/spec/ruby/core/main/fixtures/using_in_main.rb
new file mode 100644
index 0000000000..a4a71c89cc
--- /dev/null
+++ b/spec/ruby/core/main/fixtures/using_in_main.rb
@@ -0,0 +1,5 @@
+MAIN = self
+
+module X
+  MAIN.send(:using, Module.new)
+end
diff --git a/spec/ruby/core/main/fixtures/using_in_method.rb b/spec/ruby/core/main/fixtures/using_in_method.rb
new file mode 100644
index 0000000000..d9ea2e9ef0
--- /dev/null
+++ b/spec/ruby/core/main/fixtures/using_in_method.rb
@@ -0,0 +1,5 @@
+def foo
+  using Module.new
+end
+
+foo
diff --git a/spec/ruby/core/main/private_spec.rb b/spec/ruby/core/main/private_spec.rb
index e34e0c7b7b..76895fd649 100644
--- a/spec/ruby/core/main/private_spec.rb
+++ b/spec/ruby/core/main/private_spec.rb
@@ -4,20 +4,39 @@ require_relative 'fixtures/classes'
 describe "main#private" do
   after :each do
     Object.send(:public, :main_public_method)
+    Object.send(:public, :main_public_method2)
   end
 
-  it "sets the visibility of the given method to private" do
-    eval "private :main_public_method", TOPLEVEL_BINDING
-    Object.should have_private_method(:main_public_method)
+  context "when single argument is passed and it is not an array" do
+    it "sets the visibility of the given methods to private" do
+      eval "private :main_public_method", TOPLEVEL_BINDING
+      Object.should have_private_method(:main_public_method)
+    end
   end
 
-  it "returns Object" do
-    eval("private :main_public_method", TOPLEVEL_BINDING).should equal(Object)
+  context "when multiple arguments are passed" do
+    it "sets the visibility of the given methods to private" do
+      eval "private :main_public_method, :main_public_method2", TOPLEVEL_BINDING
+      Object.should have_private_method(:main_public_method)
+      Object.should have_private_method(:main_public_method2)
+    end
   end
 
-  it "raises a NameError when given an undefined name" do
+  context "when single argument is passed and is an array" do
+    it "sets the visibility of the given methods to private" do
+      eval "private [:main_public_method, :main_public_method2]", TOPLEVEL_BINDING
+      Object.should have_private_method(:main_public_method)
+      Object.should have_private_method(:main_public_method2)
+    end
+  end
+
+  it "returns argument" do
+    eval("private :main_public_method", TOPLEVEL_BINDING).should equal(:main_public_method)
+  end
+
+  it "raises a NameError when at least one of given method names is undefined" do
     -> do
-      eval "private :main_undefined_method", TOPLEVEL_BINDING
+      eval "private :main_public_method, :main_undefined_method", TOPLEVEL_BINDING
     end.should raise_error(NameError)
   end
 end
diff --git a/spec/ruby/core/main/public_spec.rb b/spec/ruby/core/main/public_spec.rb
index afe25c705a..3c77798fbc 100644
--- a/spec/ruby/core/main/public_spec.rb
+++ b/spec/ruby/core/main/public_spec.rb
@@ -4,17 +4,37 @@ require_relative 'fixtures/classes'
 describe "main#public" do
   after :each do
     Object.send(:private, :main_private_method)
+    Object.send(:private, :main_private_method2)
   end
 
-  it "sets the visibility of the given method to public" do
-    eval "public :main_private_method", TOPLEVEL_BINDING
-    Object.should_not have_private_method(:main_private_method)
+  context "when single argument is passed and it is not an array" do
+    it "sets the visibility of the given methods to public" do
+      eval "public :main_private_method", TOPLEVEL_BINDING
+      Object.should_not have_private_method(:main_private_method)
+    end
   end
 
-  it "returns Object" do
-    eval("public :main_private_method", TOPLEVEL_BINDING).should equal(Object)
+  context "when multiple arguments are passed" do
+    it "sets the visibility of the given methods to public" do
+      eval "public :main_private_method, :main_private_method2", TOPLEVEL_BINDING
+      Object.should_not have_private_method(:main_private_method)
+      Object.should_not have_private_method(:main_private_method2)
+    end
   end
 
+  context "when single argument is passed and is an array" do
+    it "sets the visibility of the given methods to public" do
+      eval "public [:main_private_method, :main_private_method2]", TOPLEVEL_BINDING
+      Object.should_not have_private_method(:main_private_method)
+      Object.should_not have_private_method(:main_private_method2)
+    end
+  end
+
+  it "returns argument" do
+    eval("public :main_private_method", TOPLEVEL_BINDING).should equal(:main_private_method)
+  end
+
+
   it "raises a NameError when given an undefined name" do
     -> do
       eval "public :main_undefined_method", TOPLEVEL_BINDING
diff --git a/spec/ruby/core/main/ruby2_keywords_spec.rb b/spec/ruby/core/main/ruby2_keywords_spec.rb
new file mode 100644
index 0000000000..27ceae3253
--- /dev/null
+++ b/spec/ruby/core/main/ruby2_keywords_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "main.ruby2_keywords" do
+  it "is the same as Object.ruby2_keywords" do
+    main = TOPLEVEL_BINDING.receiver
+    main.should have_private_method(:ruby2_keywords)
+  end
+end
diff --git a/spec/ruby/core/main/using_spec.rb b/spec/ruby/core/main/using_spec.rb
index f9f709f7dc..5b9a751595 100644
--- a/spec/ruby/core/main/using_spec.rb
+++ b/spec/ruby/core/main/using_spec.rb
@@ -129,4 +129,22 @@ describe "main.using" do
 
     x.call_bar(cls2.new).should == 'bar'
   end
+
+  it "raises error when called from method in wrapped script" do
+    -> do
+      load File.expand_path('../fixtures/using_in_method.rb', __FILE__), true
+    end.should raise_error(RuntimeError)
+  end
+
+  it "raises error when called on toplevel from module" do
+    -> do
+      load File.expand_path('../fixtures/using_in_main.rb', __FILE__), true
+    end.should raise_error(RuntimeError)
+  end
+
+  it "does not raise error when wrapped with module" do
+    -> do
+      load File.expand_path('../fixtures/using.rb', __FILE__), true
+    end.should_not raise_error
+  end
 end
diff --git a/spec/ruby/core/marshal/dump_spec.rb b/spec/ruby/core/marshal/dump_spec.rb
index 700f090a2f..ff9b9214fa 100644
--- a/spec/ruby/core/marshal/dump_spec.rb
+++ b/spec/ruby/core/marshal/dump_spec.rb
@@ -1,5 +1,6 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 require_relative 'fixtures/marshal_data'
 
 describe "Marshal.dump" do
@@ -37,7 +38,7 @@ describe "Marshal.dump" do
       ].should be_computed_by(:dump)
     end
 
-    platform_is wordsize: 64 do
+    platform_is c_long_size: 64 do
       it "dumps a positive Fixnum > 31 bits as a Bignum" do
         Marshal.dump(2**31 + 1).should == "\x04\bl+\a\x01\x00\x00\x80"
       end
@@ -46,6 +47,11 @@ describe "Marshal.dump" do
         Marshal.dump(-2**31 - 1).should == "\x04\bl-\a\x01\x00\x00\x80"
       end
     end
+
+    it "does not use object links for objects repeatedly dumped" do
+      Marshal.dump([0, 0]).should == "\x04\b[\ai\x00i\x00"
+      Marshal.dump([2**16, 2**16]).should == "\x04\b[\ai\x03\x00\x00\x01i\x03\x00\x00\x01"
+    end
   end
 
   describe "with a Symbol" do
@@ -75,9 +81,28 @@ describe "Marshal.dump" do
     end
 
     it "dumps a binary encoded Symbol" do
-      s = "\u2192".force_encoding("binary").to_sym
+      s = "\u2192".dup.force_encoding("binary").to_sym
       Marshal.dump(s).should == "\x04\b:\b\xE2\x86\x92"
     end
+
+    it "dumps multiple Symbols sharing the same encoding" do
+      # Note that the encoding is a link for the second Symbol
+      symbol1 = "I:\t\xE2\x82\xACa\x06:\x06ET"
+      symbol2 = "I:\t\xE2\x82\xACb\x06;\x06T"
+      value = [
+        "€a".dup.force_encoding(Encoding::UTF_8).to_sym,
+        "€b".dup.force_encoding(Encoding::UTF_8).to_sym
+      ]
+      Marshal.dump(value).should == "\x04\b[\a#{symbol1}#{symbol2}"
+
+      value = [*value, value[0]]
+      Marshal.dump(value).should == "\x04\b[\b#{symbol1}#{symbol2};\x00"
+    end
+
+    it "uses symbol links for objects repeatedly dumped" do
+      symbol = :foo
+      Marshal.dump([symbol, symbol]).should == "\x04\b[\a:\bfoo;\x00" # ;\x00 is a link to the symbol object
+    end
   end
 
   describe "with an object responding to #marshal_dump" do
@@ -89,25 +114,104 @@ describe "Marshal.dump" do
       UserMarshal.should_not_receive(:name)
       Marshal.dump(UserMarshal.new)
     end
+
+    it "raises TypeError if an Object is an instance of an anonymous class" do
+      -> { Marshal.dump(Class.new(UserMarshal).new) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      obj = UserMarshal.new
+      Marshal.dump([obj, obj]).should == "\x04\b[\aU:\x10UserMarshal:\tdata@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables of a dumped object after the object itself into the objects table" do
+      value = "<foo>"
+      obj = MarshalSpec::UserMarshalDumpWithIvar.new("string", value)
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\t, that means Integer 4)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bU:)MarshalSpec::UserMarshalDumpWithIvarI[\x06\"\vstring\x06:\t@foo\"\n<foo>@\x06@\t"
+    end
   end
 
   describe "with an object responding to #_dump" do
-    it "dumps the object returned by #marshal_dump" do
+    it "dumps the String returned by #_dump" do
       Marshal.dump(UserDefined.new).should == "\004\bu:\020UserDefined\022\004\b[\a:\nstuff;\000"
     end
 
+    it "dumps the String in non US-ASCII and non UTF-8 encoding" do
+      object = UserDefinedString.new("a".encode("windows-1251"))
+      Marshal.dump(object).should == "\x04\bIu:\x16UserDefinedString\x06a\x06:\rencoding\"\x11Windows-1251"
+    end
+
+    it "dumps the String in multibyte encoding" do
+      object = UserDefinedString.new("a".encode("utf-32le"))
+      Marshal.dump(object).should == "\x04\bIu:\x16UserDefinedString\ta\x00\x00\x00\x06:\rencoding\"\rUTF-32LE"
+    end
+
+    it "ignores overridden name method" do
+      obj = MarshalSpec::UserDefinedWithOverriddenName.new
+      Marshal.dump(obj).should == "\x04\bu:/MarshalSpec::UserDefinedWithOverriddenName\x12\x04\b[\a:\nstuff;\x00"
+    end
+
     it "raises a TypeError if _dump returns a non-string" do
       m = mock("marshaled")
       m.should_receive(:_dump).and_return(0)
       -> { Marshal.dump(m) }.should raise_error(TypeError)
     end
 
+    it "raises TypeError if an Object is an instance of an anonymous class" do
+      -> { Marshal.dump(Class.new(UserDefined).new) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
+
     it "favors marshal_dump over _dump" do
       m = mock("marshaled")
       m.should_receive(:marshal_dump).and_return(0)
       m.should_not_receive(:_dump)
       Marshal.dump(m)
     end
+
+    it "indexes instance variables of a String returned by #_dump at first and then indexes the object itself" do
+      class MarshalSpec::M1::A
+        def _dump(level)
+          s = +"<dump>"
+          s.instance_variable_set(:@foo, "bar")
+          s
+        end
+      end
+
+      a = MarshalSpec::M1::A.new
+
+      # 0-based index of the object a = 2, that is encoded as \x07 and printed as "\a" character.
+      # Objects are serialized in the following order: Array, a, "bar".
+      # But they are indexed in different order: Array (index=0), "bar" (index=1), a (index=2)
+      # So the second occurenc of the object a is encoded as an index 2.
+      reference = "@\a"
+      Marshal.dump([a, a]).should == "\x04\b[\aIu:\x17MarshalSpec::M1::A\v<dump>\x06:\t@foo\"\bbar#{reference}"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      obj = UserDefined.new
+      Marshal.dump([obj, obj]).should == "\x04\b[\au:\x10UserDefined\x12\x04\b[\a:\nstuff;\x00@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables of a dumped String before the object itself into the objects table" do
+      value = "<foo>"
+      obj = MarshalSpec::UserDefinedDumpWithIVars.new(+"string", value)
+
+      # expect a link to the object (@\a, that means Integer 2) is greater than a link
+      # to the instance variable value (@\x06, that means Integer 1)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bIu:*MarshalSpec::UserDefinedDumpWithIVars\vstring\x06:\t@foo\"\n<foo>@\a@\x06"
+    end
+
+    describe "Core library classes with #_dump returning a String with instance variables" do
+      it "indexes instance variables and then a Time object itself" do
+        t = Time.utc(2022)
+        reference = "@\a"
+
+        Marshal.dump([t, t]).should == "\x04\b[\aIu:\tTime\r \x80\x1E\xC0\x00\x00\x00\x00\x06:\tzoneI\"\bUTC\x06:\x06EF#{reference}"
+      end
+    end
   end
 
   describe "with a Class" do
@@ -123,8 +227,24 @@ describe "Marshal.dump" do
       Marshal.dump(UserDefined::Nested).should == "\004\bc\030UserDefined::Nested"
     end
 
+    it "ignores overridden name method" do
+      Marshal.dump(MarshalSpec::ClassWithOverriddenName).should == "\x04\bc)MarshalSpec::ClassWithOverriddenName"
+    end
+
+    ruby_version_is "4.0" do
+      it "dumps a class with multibyte characters in name" do
+        source_object = eval("MarshalSpec::MultibyteぁあぃいClass".dup.force_encoding(Encoding::UTF_8))
+        Marshal.dump(source_object).should == "\x04\bIc,MarshalSpec::Multibyte\xE3\x81\x81\xE3\x81\x82\xE3\x81\x83\xE3\x81\x84Class\x06:\x06ET"
+        Marshal.load(Marshal.dump(source_object)) == source_object
+      end
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      Marshal.dump([String, String]).should == "\x04\b[\ac\vString@\x06" # @\x06 is a link to the object
+    end
+
     it "raises TypeError with an anonymous Class" do
-      -> { Marshal.dump(Class.new) }.should raise_error(TypeError)
+      -> { Marshal.dump(Class.new) }.should raise_error(TypeError, /can't dump anonymous class/)
     end
 
     it "raises TypeError with a singleton Class" do
@@ -137,8 +257,24 @@ describe "Marshal.dump" do
       Marshal.dump(Marshal).should == "\004\bm\fMarshal"
     end
 
+    it "ignores overridden name method" do
+      Marshal.dump(MarshalSpec::ModuleWithOverriddenName).should == "\x04\bc*MarshalSpec::ModuleWithOverriddenName"
+    end
+
+    ruby_version_is "4.0" do
+      it "dumps a module with multibyte characters in name" do
+        source_object = eval("MarshalSpec::MultibyteけげこごModule".dup.force_encoding(Encoding::UTF_8))
+        Marshal.dump(source_object).should == "\x04\bIm-MarshalSpec::Multibyte\xE3\x81\x91\xE3\x81\x92\xE3\x81\x93\xE3\x81\x94Module\x06:\x06ET"
+        Marshal.load(Marshal.dump(source_object)) == source_object
+      end
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      Marshal.dump([Marshal, Marshal]).should == "\x04\b[\am\fMarshal@\x06" # @\x06 is a link to the object
+    end
+
     it "raises TypeError with an anonymous Module" do
-      -> { Marshal.dump(Module.new) }.should raise_error(TypeError)
+      -> { Marshal.dump(Module.new) }.should raise_error(TypeError, /can't dump anonymous module/)
     end
   end
 
@@ -155,6 +291,23 @@ describe "Marshal.dump" do
         [Marshal,  nan_value,      "\004\bf\bnan"],
       ].should be_computed_by(:dump)
     end
+
+    it "may or may not use object links for objects repeatedly dumped" do
+      # it's an MRI implementation detail - on x86 architecture object links
+      # aren't used for Float values but on amd64 - object links are used
+
+      dump = Marshal.dump([0.0, 0.0])
+      ["\x04\b[\af\x060@\x06", "\x04\b[\af\x060f\x060"].should.include?(dump)
+
+      # if object links aren't used - entries in the objects table are still
+      # occupied by Float values
+      if dump == "\x04\b[\af\x060f\x060"
+        s = "string"
+        # an index of "string" ("@\b") in the object table equals 3 (`"\b".ord - 5`),
+        # so `0.0, 0,0` elements occupied indices 1 and 2
+        Marshal.dump([0.0, 0.0, s, s]).should == "\x04\b[\tf\x060f\x060\"\vstring@\b"
+      end
+    end
   end
 
   describe "with a Bignum" do
@@ -171,15 +324,81 @@ describe "Marshal.dump" do
         [Marshal, -2**64, "\004\bl-\n\000\000\000\000\000\000\000\000\001\000"],
       ].should be_computed_by(:dump)
     end
+
+    it "uses object links for objects repeatedly dumped" do
+      n = 2**64
+      Marshal.dump([n, n]).should == "\x04\b[\al+\n\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00@\x06" # @\x06 is a link to the object
+    end
+
+    it "increases the object links counter" do
+      obj = Object.new
+      object_1_link = "\x06" # representing of (0-based) index=1 (by adding 5 for small Integers)
+      object_2_link = "\x07" # representing of index=2
+
+      # objects: Array, Object, Object
+      Marshal.dump([obj, obj]).should == "\x04\b[\ao:\vObject\x00@#{object_1_link}"
+
+      # objects: Array, Bignum, Object, Object
+      Marshal.dump([2**64, obj, obj]).should == "\x04\b[\bl+\n\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+      Marshal.dump([2**48, obj, obj]).should == "\x04\b[\bl+\t\x00\x00\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+      Marshal.dump([2**32, obj, obj]).should == "\x04\b[\bl+\b\x00\x00\x00\x00\x01\x00o:\vObject\x00@#{object_2_link}"
+    end
+  end
+
+  describe "with a Rational" do
+    it "dumps a Rational" do
+      Marshal.dump(Rational(2, 3)).should == "\x04\bU:\rRational[\ai\ai\b"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      r = Rational(2, 3)
+      Marshal.dump([r, r]).should == "\x04\b[\aU:\rRational[\ai\ai\b@\x06" # @\x06 is a link to the object
+    end
+  end
+
+  describe "with a Complex" do
+    it "dumps a Complex" do
+      Marshal.dump(Complex(2, 3)).should == "\x04\bU:\fComplex[\ai\ai\b"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      c = Complex(2, 3)
+      Marshal.dump([c, c]).should == "\x04\b[\aU:\fComplex[\ai\ai\b@\x06" # @\x06 is a link to the object
+    end
+  end
+
+  describe "with a Data" do
+    it "dumps a Data" do
+      Marshal.dump(MarshalSpec::DataSpec::Measure.new(100, 'km')).should == "\x04\bS:#MarshalSpec::DataSpec::Measure\a:\vamountii:\tunit\"\akm"
+    end
+
+    it "dumps an extended Data" do
+      obj = MarshalSpec::DataSpec::MeasureExtended.new(100, "km")
+      Marshal.dump(obj).should == "\x04\bS:+MarshalSpec::DataSpec::MeasureExtended\a:\vamountii:\tunit\"\akm"
+    end
+
+    it "ignores overridden name method" do
+      obj = MarshalSpec::DataSpec::MeasureWithOverriddenName.new(100, "km")
+      Marshal.dump(obj).should == "\x04\bS:5MarshalSpec::DataSpec::MeasureWithOverriddenName\a:\vamountii:\tunit\"\akm"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      d = MarshalSpec::DataSpec::Measure.new(100, 'km')
+      Marshal.dump([d, d]).should == "\x04\b[\aS:#MarshalSpec::DataSpec::Measure\a:\vamountii:\tunit\"\akm@\x06" # @\x06 is a link to the object
+    end
+
+    it "raises TypeError with an anonymous Struct" do
+      -> { Marshal.dump(Data.define(:a).new(1)) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
   end
 
   describe "with a String" do
     it "dumps a blank String" do
-      Marshal.dump("".force_encoding("binary")).should == "\004\b\"\000"
+      Marshal.dump("".dup.force_encoding("binary")).should == "\004\b\"\000"
     end
 
     it "dumps a short String" do
-      Marshal.dump("short".force_encoding("binary")).should == "\004\b\"\012short"
+      Marshal.dump("short".dup.force_encoding("binary")).should == "\004\b\"\012short"
     end
 
     it "dumps a long String" do
@@ -187,7 +406,7 @@ describe "Marshal.dump" do
     end
 
     it "dumps a String extended with a Module" do
-      Marshal.dump("".extend(Meths).force_encoding("binary")).should == "\004\be:\nMeths\"\000"
+      Marshal.dump("".dup.extend(Meths).force_encoding("binary")).should == "\004\be:\nMeths\"\000"
     end
 
     it "dumps a String subclass" do
@@ -198,24 +417,29 @@ describe "Marshal.dump" do
       Marshal.dump(UserString.new.extend(Meths).force_encoding("binary")).should == "\004\be:\nMethsC:\017UserString\"\000"
     end
 
+    it "ignores overridden name method when dumps a String subclass" do
+      obj = MarshalSpec::StringWithOverriddenName.new
+      Marshal.dump(obj).should == "\x04\bC:*MarshalSpec::StringWithOverriddenName\"\x00"
+    end
+
     it "dumps a String with instance variables" do
-      str = ""
+      str = +""
       str.instance_variable_set("@foo", "bar")
       Marshal.dump(str.force_encoding("binary")).should == "\x04\bI\"\x00\x06:\t@foo\"\bbar"
     end
 
     it "dumps a US-ASCII String" do
-      str = "abc".force_encoding("us-ascii")
+      str = "abc".dup.force_encoding("us-ascii")
       Marshal.dump(str).should == "\x04\bI\"\babc\x06:\x06EF"
     end
 
     it "dumps a UTF-8 String" do
-      str = "\x6d\xc3\xb6\x68\x72\x65".force_encoding("utf-8")
+      str = "\x6d\xc3\xb6\x68\x72\x65".dup.force_encoding("utf-8")
       Marshal.dump(str).should == "\x04\bI\"\vm\xC3\xB6hre\x06:\x06ET"
     end
 
     it "dumps a String in another encoding" do
-      str = "\x6d\x00\xf6\x00\x68\x00\x72\x00\x65\x00".force_encoding("utf-16le")
+      str = "\x6d\x00\xf6\x00\x68\x00\x72\x00\x65\x00".dup.force_encoding("utf-16le")
       result = "\x04\bI\"\x0Fm\x00\xF6\x00h\x00r\x00e\x00\x06:\rencoding\"\rUTF-16LE"
       Marshal.dump(str).should == result
     end
@@ -223,6 +447,21 @@ describe "Marshal.dump" do
     it "dumps multiple strings using symlinks for the :E (encoding) symbol" do
       Marshal.dump(["".encode("us-ascii"), "".encode("utf-8")]).should == "\x04\b[\aI\"\x00\x06:\x06EFI\"\x00\x06;\x00T"
     end
+
+    it "uses object links for objects repeatedly dumped" do
+      s = "string"
+      Marshal.dump([s, s]).should == "\x04\b[\a\"\vstring@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = +"string"
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bI\"\vstring\x06:\t@foo\"\n<foo>@\x06@\a"
+    end
   end
 
   describe "with a Regexp" do
@@ -235,13 +474,13 @@ describe "Marshal.dump" do
     end
 
     it "dumps a Regexp with instance variables" do
-      o = //
+      o = Regexp.new("")
       o.instance_variable_set(:@ivar, :ivar)
       Marshal.dump(o).should == "\x04\bI/\x00\x00\a:\x06EF:\n@ivar:\tivar"
     end
 
     it "dumps an extended Regexp" do
-      Marshal.dump(//.extend(Meths)).should == "\x04\bIe:\nMeths/\x00\x00\x06:\x06EF"
+      Marshal.dump(Regexp.new("").extend(Meths)).should == "\x04\bIe:\nMeths/\x00\x00\x06:\x06EF"
     end
 
     it "dumps a Regexp subclass" do
@@ -249,18 +488,51 @@ describe "Marshal.dump" do
     end
 
     it "dumps a binary Regexp" do
-      o = Regexp.new("".force_encoding("binary"), Regexp::FIXEDENCODING)
+      o = Regexp.new("".dup.force_encoding("binary"), Regexp::FIXEDENCODING)
       Marshal.dump(o).should == "\x04\b/\x00\x10"
     end
 
+    it "dumps an ascii-compatible Regexp" do
+      o = Regexp.new("a".encode("us-ascii"), Regexp::FIXEDENCODING)
+      Marshal.dump(o).should == "\x04\bI/\x06a\x10\x06:\x06EF"
+
+      o = Regexp.new("a".encode("us-ascii"))
+      Marshal.dump(o).should == "\x04\bI/\x06a\x00\x06:\x06EF"
+
+      o = Regexp.new("a".encode("windows-1251"), Regexp::FIXEDENCODING)
+      Marshal.dump(o).should == "\x04\bI/\x06a\x10\x06:\rencoding\"\x11Windows-1251"
+
+      o = Regexp.new("a".encode("windows-1251"))
+      Marshal.dump(o).should == "\x04\bI/\x06a\x00\x06:\x06EF"
+    end
+
     it "dumps a UTF-8 Regexp" do
-      o = Regexp.new("".force_encoding("utf-8"), Regexp::FIXEDENCODING)
+      o = Regexp.new("".dup.force_encoding("utf-8"), Regexp::FIXEDENCODING)
       Marshal.dump(o).should == "\x04\bI/\x00\x10\x06:\x06ET"
+
+      o = Regexp.new("a".dup.force_encoding("utf-8"), Regexp::FIXEDENCODING)
+      Marshal.dump(o).should == "\x04\bI/\x06a\x10\x06:\x06ET"
+
+      o = Regexp.new("\u3042".dup.force_encoding("utf-8"), Regexp::FIXEDENCODING)
+      Marshal.dump(o).should == "\x04\bI/\b\xE3\x81\x82\x10\x06:\x06ET"
     end
 
     it "dumps a Regexp in another encoding" do
-      o = Regexp.new("".force_encoding("utf-16le"), Regexp::FIXEDENCODING)
+      o = Regexp.new("".dup.force_encoding("utf-16le"), Regexp::FIXEDENCODING)
       Marshal.dump(o).should == "\x04\bI/\x00\x10\x06:\rencoding\"\rUTF-16LE"
+
+      o = Regexp.new("a".encode("utf-16le"), Regexp::FIXEDENCODING)
+      Marshal.dump(o).should == "\x04\bI/\aa\x00\x10\x06:\rencoding\"\rUTF-16LE"
+    end
+
+    it "ignores overridden name method when dumps a Regexp subclass" do
+      obj = MarshalSpec::RegexpWithOverriddenName.new("")
+      Marshal.dump(obj).should == "\x04\bIC:*MarshalSpec::RegexpWithOverriddenName/\x00\x00\x06:\x06EF"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      r = /\A.\Z/
+      Marshal.dump([r, r]).should == "\x04\b[\aI/\n\\A.\\Z\x00\x06:\x06EF@\x06" # @\x06 is a link to the object
     end
   end
 
@@ -292,6 +564,26 @@ describe "Marshal.dump" do
     it "dumps an extended Array" do
       Marshal.dump([].extend(Meths)).should == "\004\be:\nMeths[\000"
     end
+
+    it "ignores overridden name method when dumps an Array subclass" do
+      obj = MarshalSpec::ArrayWithOverriddenName.new
+      Marshal.dump(obj).should == "\x04\bC:)MarshalSpec::ArrayWithOverriddenName[\x00"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      a = [1]
+      Marshal.dump([a, a]).should == "\x04\b[\a[\x06i\x06@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = []
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bI[\x00\x06:\t@foo\"\n<foo>@\x06@\a"
+    end
   end
 
   describe "with a Hash" do
@@ -299,6 +591,10 @@ describe "Marshal.dump" do
       Marshal.dump({}).should == "\004\b{\000"
     end
 
+    it "dumps a non-empty Hash" do
+      Marshal.dump({a: 1}).should == "\x04\b{\x06:\x06ai\x06"
+    end
+
     it "dumps a Hash subclass" do
       Marshal.dump(UserHash.new).should == "\004\bC:\rUserHash{\000"
     end
@@ -307,8 +603,22 @@ describe "Marshal.dump" do
       Marshal.dump(Hash.new(1)).should == "\004\b}\000i\006"
     end
 
+    it "dumps a Hash with compare_by_identity" do
+      h = {}
+      h.compare_by_identity
+
+      Marshal.dump(h).should == "\004\bC:\tHash{\x00"
+    end
+
+    it "dumps a Hash subclass with compare_by_identity" do
+      h = UserHash.new
+      h.compare_by_identity
+
+      Marshal.dump(h).should == "\x04\bC:\rUserHashC:\tHash{\x00"
+    end
+
     it "raises a TypeError with hash having default proc" do
-      -> { Marshal.dump(Hash.new {}) }.should raise_error(TypeError)
+      -> { Marshal.dump(Hash.new {}) }.should raise_error(TypeError, "can't dump hash with default proc")
     end
 
     it "dumps a Hash with instance variables" do
@@ -324,6 +634,26 @@ describe "Marshal.dump" do
     it "dumps an Hash subclass with a parameter to initialize" do
       Marshal.dump(UserHashInitParams.new(1)).should == "\004\bIC:\027UserHashInitParams{\000\006:\a@ai\006"
     end
+
+    it "ignores overridden name method when dumps a Hash subclass" do
+      obj = MarshalSpec::HashWithOverriddenName.new
+      Marshal.dump(obj).should == "\x04\bC:(MarshalSpec::HashWithOverriddenName{\x00"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      h = {a: 1}
+      Marshal.dump([h, h]).should == "\x04\b[\a{\x06:\x06ai\x06@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = {}
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bI{\x00\x06:\t@foo\"\n<foo>@\x06@\a"
+    end
   end
 
   describe "with a Struct" do
@@ -343,10 +673,39 @@ describe "Marshal.dump" do
     end
 
     it "dumps an extended Struct" do
-      st = Struct.new("Extended", :a, :b).new
-      Marshal.dump(st.extend(Meths)).should == "\004\be:\nMethsS:\025Struct::Extended\a:\006a0:\006b0"
+      obj = Struct.new("Extended", :a, :b).new.extend(Meths)
+      Marshal.dump(obj).should == "\004\be:\nMethsS:\025Struct::Extended\a:\006a0:\006b0"
+
+      s = 'hi'
+      obj.a = [:a, s]
+      obj.b = [:Meths, s]
+      Marshal.dump(obj).should == "\004\be:\nMethsS:\025Struct::Extended\a:\006a[\a;\a\"\ahi:\006b[\a;\000@\a"
       Struct.send(:remove_const, :Extended)
     end
+
+    it "ignores overridden name method" do
+      obj = MarshalSpec::StructWithOverriddenName.new("member")
+      Marshal.dump(obj).should == "\x04\bS:*MarshalSpec::StructWithOverriddenName\x06:\x06a\"\vmember"
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      s = Struct::Pyramid.new
+      Marshal.dump([s, s]).should == "\x04\b[\aS:\x14Struct::Pyramid\x00@\x06" # @\x06 is a link to the object
+    end
+
+    it "raises TypeError with an anonymous Struct" do
+      -> { Marshal.dump(Struct.new(:a).new(1)) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = Struct::Pyramid.new
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bIS:\x14Struct::Pyramid\x00\x06:\t@foo\"\n<foo>@\x06@\a"
+    end
   end
 
   describe "with an Object" do
@@ -366,7 +725,7 @@ describe "Marshal.dump" do
 
     it "dumps an Object with a non-US-ASCII instance variable" do
       obj = Object.new
-      ivar = "@é".force_encoding(Encoding::UTF_8).to_sym
+      ivar = "@é".dup.force_encoding(Encoding::UTF_8).to_sym
       obj.instance_variable_set(ivar, 1)
       Marshal.dump(obj).should == "\x04\bo:\vObject\x06I:\b@\xC3\xA9\x06:\x06ETi\x06"
     end
@@ -378,13 +737,18 @@ describe "Marshal.dump" do
       Marshal.dump(obj).should == "\004\bo:\x0BObject\x00"
     end
 
-    it "dumps an Object if it has a singleton class but no singleton methods" do
+    it "dumps an Object if it has a singleton class but no singleton methods and no singleton instance variables" do
       obj = Object.new
       obj.singleton_class
       Marshal.dump(obj).should == "\004\bo:\x0BObject\x00"
     end
 
-    it "raises if an Object has a singleton class and singleton methods" do
+    it "ignores overridden name method" do
+      obj = MarshalSpec::ClassWithOverriddenName.new
+      Marshal.dump(obj).should == "\x04\bo:)MarshalSpec::ClassWithOverriddenName\x00"
+    end
+
+    it "raises TypeError if an Object has a singleton class and singleton methods" do
       obj = Object.new
       def obj.foo; end
       -> {
@@ -392,32 +756,86 @@ describe "Marshal.dump" do
       }.should raise_error(TypeError, "singleton can't be dumped")
     end
 
+    it "raises TypeError if an Object has a singleton class and singleton instance variables" do
+      obj = Object.new
+      class << obj
+        @v = 1
+      end
+
+      -> {
+        Marshal.dump(obj)
+      }.should raise_error(TypeError, "singleton can't be dumped")
+    end
+
+    it "raises TypeError if an Object is an instance of an anonymous class" do
+      anonymous_class = Class.new
+      obj = anonymous_class.new
+
+      -> { Marshal.dump(obj) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
+
+    it "raises TypeError if an Object extends an anonymous module" do
+      anonymous_module = Module.new
+      obj = Object.new
+      obj.extend(anonymous_module)
+
+      -> { Marshal.dump(obj) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
+
     it "dumps a BasicObject subclass if it defines respond_to?" do
       obj = MarshalSpec::BasicObjectSubWithRespondToFalse.new
       Marshal.dump(obj).should == "\x04\bo:2MarshalSpec::BasicObjectSubWithRespondToFalse\x00"
     end
+
+    it "dumps without marshaling any attached finalizer" do
+      obj = Object.new
+      finalizer = Object.new
+      def finalizer.noop(_)
+      end
+      ObjectSpace.define_finalizer(obj, finalizer.method(:noop))
+      Marshal.load(Marshal.dump(obj)).class.should == Object
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      obj = Object.new
+      Marshal.dump([obj, obj]).should == "\x04\b[\ao:\vObject\x00@\x06" # @\x06 is a link to the object
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = Object.new
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bo:\vObject\x06:\t@foo\"\n<foo>@\x06@\a"
+    end
   end
 
   describe "with a Range" do
-    it "dumps a Range inclusive of end (with indeterminant order)" do
+    it "dumps a Range inclusive of end" do
       dump = Marshal.dump(1..2)
+      dump.should == "\x04\bo:\nRange\b:\texclF:\nbegini\x06:\bendi\a"
+
       load = Marshal.load(dump)
       load.should == (1..2)
     end
 
-    it "dumps a Range exclusive of end (with indeterminant order)" do
+    it "dumps a Range exclusive of end" do
       dump = Marshal.dump(1...2)
+      dump.should == "\x04\bo:\nRange\b:\texclT:\nbegini\x06:\bendi\a"
+
       load = Marshal.load(dump)
       load.should == (1...2)
     end
 
-    it "dumps a Range with extra instance variables" do
-      range = (1...3)
-      range.instance_variable_set :@foo, 42
-      dump = Marshal.dump(range)
-      load = Marshal.load(dump)
-      load.should == range
-      load.instance_variable_get(:@foo).should == 42
+    it "uses object links for objects repeatedly dumped" do
+      r = 1..2
+      Marshal.dump([r, r]).should == "\x04\b[\ao:\nRange\b:\texclF:\nbegini\x06:\bendi\a@\x06" # @\x06 is a link to the object
+    end
+
+    it "raises TypeError with an anonymous Range subclass" do
+      -> { Marshal.dump(Class.new(Range).new(1, 2)) }.should raise_error(TypeError, /can't dump anonymous class/)
     end
   end
 
@@ -456,6 +874,43 @@ describe "Marshal.dump" do
       zone = ":\tzoneI\"\bUTC\x06:\x06EF" # Last is 'F' (US-ASCII)
       dump.should == "\x04\bIu:\tTime\r#{@utc_dump}\x06#{zone}"
     end
+
+    it "ignores overridden name method" do
+      obj = MarshalSpec::TimeWithOverriddenName.new
+      Marshal.dump(obj).should include("MarshalSpec::TimeWithOverriddenName")
+    end
+
+    ruby_version_is "4.0" do
+      it "dumps a Time subclass with multibyte characters in name" do
+        source_object = eval("MarshalSpec::MultibyteぁあぃいTime".dup.force_encoding(Encoding::UTF_8))
+        Marshal.dump(source_object).should == "\x04\bIc+MarshalSpec::Multibyte\xE3\x81\x81\xE3\x81\x82\xE3\x81\x83\xE3\x81\x84Time\x06:\x06ET"
+        Marshal.load(Marshal.dump(source_object)) == source_object
+      end
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      # order of the offset and zone instance variables is a subject to change
+      # and may be different on different CRuby versions
+      base = Regexp.quote("\x04\b[\aIu:\tTime\r\xF5\xEF\e\x80\x00\x00\x00\x00\a")
+      offset = Regexp.quote(":\voffseti\x020*:\tzoneI\"\bAST\x06:\x06EF")
+      zone = Regexp.quote(":\tzoneI\"\bAST\x06:\x06EF:\voffseti\x020*")
+      instance_variables = /#{offset}|#{zone}/
+      Marshal.dump([@t, @t]).should =~ /\A#{base}#{instance_variables}@\a\Z/ # @\a is a link to the object
+    end
+
+    it "adds instance variables before the object itself into the objects table" do
+      obj = @utc
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\b, that means Integer 3) is greater than a link
+      # to the instance variable value (@\x06, that means Integer 1)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bIu:\tTime\r \x00\x1C\xC0\x00\x00\x00\x00\a:\t@foo\"\n<foo>:\tzoneI\"\bUTC\x06:\x06EF@\b@\x06"
+    end
+
+    it "raises TypeError with an anonymous Time subclass" do
+      -> { Marshal.dump(Class.new(Time).now) }.should raise_error(TypeError)
+    end
   end
 
   describe "with an Exception" do
@@ -473,6 +928,12 @@ describe "Marshal.dump" do
       Marshal.dump(obj).should == "\x04\bo:\x0EException\a:\tmesg\"\bfoo:\abt[\x06\"\x12foo/bar.rb:10"
     end
 
+    it "dumps instance variables if they exist" do
+      obj = Exception.new("foo")
+      obj.instance_variable_set(:@ivar, 1)
+      Marshal.dump(obj).should == "\x04\bo:\x0EException\b:\tmesg\"\bfoo:\abt0:\n@ivari\x06"
+    end
+
     it "dumps the cause for the exception" do
       exc = nil
       begin
@@ -490,6 +951,38 @@ describe "Marshal.dump" do
       reloaded.cause.should be_an_instance_of(StandardError)
       reloaded.cause.message.should == "the cause"
     end
+
+    # NoMethodError uses an exception formatter on TruffleRuby and computes a message lazily
+    it "dumps the message for the raised NoMethodError exception" do
+      begin
+        "".foo
+      rescue => e
+      end
+
+      Marshal.dump(e).should =~ /undefined method [`']foo' for ("":String|an instance of String)/
+    end
+
+    it "uses object links for objects repeatedly dumped" do
+      e = Exception.new
+      Marshal.dump([e, e]).should == "\x04\b[\ao:\x0EException\a:\tmesg0:\abt0@\x06" # @\x\a is a link to the object
+    end
+
+    it "adds instance variables after the object itself into the objects table" do
+      obj = Exception.new
+      value = "<foo>"
+      obj.instance_variable_set :@foo, value
+
+      # expect a link to the object (@\x06, that means Integer 1) is smaller than a link
+      # to the instance variable value (@\a, that means Integer 2)
+      Marshal.dump([obj, obj, value]).should == "\x04\b[\bo:\x0EException\b:\tmesg0:\abt0:\t@foo\"\n<foo>@\x06@\a"
+    end
+
+    it "raises TypeError if an Object is an instance of an anonymous class" do
+      anonymous_class = Class.new(Exception)
+      obj = anonymous_class.new
+
+      -> { Marshal.dump(obj) }.should raise_error(TypeError, /can't dump anonymous class/)
+    end
   end
 
   it "dumps subsequent appearances of a symbol as a link" do
@@ -522,7 +1015,6 @@ describe "Marshal.dump" do
   end
 
   describe "when passed an IO" do
-
     it "writes the serialized data to the IO-Object" do
       (obj = mock('test')).should_receive(:write).at_least(1)
       Marshal.dump("test", obj)
@@ -545,18 +1037,13 @@ describe "Marshal.dump" do
       obj.should_receive(:binmode).at_least(1)
       Marshal.dump("test", obj)
     end
-
-
   end
 
   describe "when passed a StringIO" do
-
     it "should raise an error" do
       require "stringio"
-
       -> { Marshal.dump(StringIO.new) }.should raise_error(TypeError)
     end
-
   end
 
   it "raises a TypeError if marshalling a Method instance" do
@@ -580,28 +1067,4 @@ describe "Marshal.dump" do
     m = Mutex.new
     -> { Marshal.dump(m) }.should raise_error(TypeError)
   end
-
-  it "returns an untainted string if object is untainted" do
-    Marshal.dump(Object.new).tainted?.should be_false
-  end
-
-  it "returns a tainted string if object is tainted" do
-    Marshal.dump(Object.new.taint).tainted?.should be_true
-  end
-
-  it "returns a tainted string if nested object is tainted" do
-    Marshal.dump([[Object.new.taint]]).tainted?.should be_true
-  end
-
-  it "returns a trusted string if object is trusted" do
-    Marshal.dump(Object.new).untrusted?.should be_false
-  end
-
-  it "returns an untrusted string if object is untrusted" do
-    Marshal.dump(Object.new.untrust).untrusted?.should be_true
-  end
-
-  it "returns an untrusted string if nested object is untrusted" do
-    Marshal.dump([[Object.new.untrust]]).untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/marshal/fixtures/classes.rb b/spec/ruby/core/marshal/fixtures/classes.rb
new file mode 100644
index 0000000000..7c81c64927
--- /dev/null
+++ b/spec/ruby/core/marshal/fixtures/classes.rb
@@ -0,0 +1,4 @@
+module MarshalSpec
+  # empty modules
+  module M1 end
+end
diff --git a/spec/ruby/core/marshal/fixtures/marshal_data.rb b/spec/ruby/core/marshal/fixtures/marshal_data.rb
index 2931278290..c16d9e4bb6 100644
--- a/spec/ruby/core/marshal/fixtures/marshal_data.rb
+++ b/spec/ruby/core/marshal/fixtures/marshal_data.rb
@@ -1,4 +1,7 @@
-# -*- encoding: binary -*-
+# encoding: binary
+
+require_relative 'marshal_multibyte_data'
+
 class UserDefined
   class Nested
     def ==(other)
@@ -38,7 +41,7 @@ class UserDefinedWithIvar
   attr_reader :a, :b, :c
 
   def initialize
-    @a = 'stuff'
+    @a = +'stuff'
     @a.instance_variable_set :@foo, :UserDefinedWithIvar
     @b = 'more'
     @c = @b
@@ -78,12 +81,47 @@ class UserDefinedImmediate
   end
 end
 
+class UserDefinedString
+  attr_reader :string
+
+  def initialize(string)
+    @string = string
+  end
+
+  def _dump(depth)
+    @string
+  end
+
+  def self._load(data)
+    new(data)
+  end
+end
+
+module MarshalSpec
+  class UserDefinedDumpWithIVars
+    attr_reader :string
+
+    def initialize(string, ivar_value)
+      @string = string
+      @string.instance_variable_set(:@foo, ivar_value)
+    end
+
+    def _dump(depth)
+      @string
+    end
+
+    def self._load(data)
+      new(data)
+    end
+  end
+end
+
 class UserPreviouslyDefinedWithInitializedIvar
   attr_accessor :field1, :field2
 end
 
 class UserMarshal
-  attr_reader :data
+  attr_accessor :data
 
   def initialize
     @data = 'stuff'
@@ -120,6 +158,32 @@ class UserMarshalWithIvar
   end
 end
 
+module MarshalSpec
+  class UserMarshalDumpWithIvar
+    attr_reader :data
+
+    def initialize(data, ivar_value)
+      @data = data
+      @ivar_value = ivar_value
+    end
+
+    def marshal_dump
+      obj = [data]
+      obj.instance_variable_set(:@foo, @ivar_value)
+      obj
+    end
+
+    def marshal_load(o)
+      @data = o[0]
+    end
+
+    def ==(other)
+      self.class === other and
+        @data = other.data
+    end
+  end
+end
+
 class UserArray < Array
 end
 
@@ -167,12 +231,17 @@ module MarshalSpec
     end
   end
 
+  StructToDump = Struct.new(:a, :b)
+
   class BasicObjectSubWithRespondToFalse < BasicObject
     def respond_to?(method_name, include_all=false)
       false
     end
   end
 
+  module ModuleToExtendBy
+  end
+
   def self.random_data
     randomizer = Random.new(42)
     1000.times{randomizer.rand} # Make sure we exhaust his first state of 624 random words
@@ -192,6 +261,70 @@ module MarshalSpec
     set_swapped_class(nil)
   end
 
+  class ClassWithOverriddenName
+    def self.name
+      "Foo"
+    end
+  end
+
+  class ModuleWithOverriddenName
+    def self.name
+      "Foo"
+    end
+  end
+
+  class TimeWithOverriddenName < Time
+    def self.name
+      "Foo"
+    end
+  end
+
+  class StructWithOverriddenName < Struct.new(:a)
+    def self.name
+      "Foo"
+    end
+  end
+
+  class UserDefinedWithOverriddenName < UserDefined
+    def self.name
+      "Foo"
+    end
+  end
+
+  class StringWithOverriddenName < String
+    def self.name
+      "Foo"
+    end
+  end
+
+  class ArrayWithOverriddenName < Array
+    def self.name
+      "Foo"
+    end
+  end
+
+  class HashWithOverriddenName < Hash
+    def self.name
+      "Foo"
+    end
+  end
+
+  class RegexpWithOverriddenName < Regexp
+    def self.name
+      "Foo"
+    end
+  end
+
+  class ObjectWithFreezeRaisingException < Object
+    def freeze
+      raise
+    end
+  end
+
+  class ObjectWithoutFreeze < Object
+    undef freeze
+  end
+
   DATA = {
     "nil" => [nil, "\004\b0"],
     "1..2" => [(1..2),
@@ -217,7 +350,7 @@ module MarshalSpec
                        "\004\b\"\012small"],
     "String big" => ['big' * 100,
                      "\004\b\"\002,\001#{'big' * 100}"],
-    "String extended" => [''.extend(Meths), # TODO: check for module on load
+    "String extended" => [''.dup.extend(Meths), # TODO: check for module on load
                           "\004\be:\nMeths\"\000"],
     "String subclass" => [UserString.new,
                           "\004\bC:\017UserString\"\000"],
@@ -227,36 +360,36 @@ module MarshalSpec
                        "\004\b:\010big"],
     "Symbol big" => [('big' * 100).to_sym,
                                "\004\b:\002,\001#{'big' * 100}"],
-    "Bignum -2**64" => [-2**64,
+    "Integer -2**64" => [-2**64,
                         "\004\bl-\n\000\000\000\000\000\000\000\000\001\000"],
-    "Bignum -2**63" => [-2**63,
+    "Integer -2**63" => [-2**63,
                         "\004\bl-\t\000\000\000\000\000\000\000\200"],
-    "Fixnum -2**24" => [-2**24,
+    "Integer -2**24" => [-2**24,
                         "\004\bi\375\000\000\000"],
-    "Fixnum -4516727" => [-4516727,
+    "Integer -4516727" => [-4516727,
                           "\004\bi\375\211\024\273"],
-    "Fixnum -2**16" => [-2**16,
+    "Integer -2**16" => [-2**16,
                         "\004\bi\376\000\000"],
-    "Fixnum -2**8" => [-2**8,
+    "Integer -2**8" => [-2**8,
                        "\004\bi\377\000"],
-    "Fixnum -123" => [-123,
+    "Integer -123" => [-123,
                       "\004\bi\200"],
-    "Fixnum -124" => [-124, "\004\bi\377\204"],
-    "Fixnum 0" => [0,
+    "Integer -124" => [-124, "\004\bi\377\204"],
+    "Integer 0" => [0,
                    "\004\bi\000"],
-    "Fixnum 5" => [5,
+    "Integer 5" => [5,
                    "\004\bi\n"],
-    "Fixnum 122" => [122, "\004\bi\177"],
-    "Fixnum 123" => [123, "\004\bi\001{"],
-    "Fixnum 2**8" => [2**8,
+    "Integer 122" => [122, "\004\bi\177"],
+    "Integer 123" => [123, "\004\bi\001{"],
+    "Integer 2**8" => [2**8,
                       "\004\bi\002\000\001"],
-    "Fixnum 2**16" => [2**16,
+    "Integer 2**16" => [2**16,
                        "\004\bi\003\000\000\001"],
-    "Fixnum 2**24" => [2**24,
+    "Integer 2**24" => [2**24,
                        "\004\bi\004\000\000\000\001"],
-    "Bignum 2**64" => [2**64,
+    "Integer 2**64" => [2**64,
                        "\004\bl+\n\000\000\000\000\000\000\000\000\001\000"],
-    "Bignum 2**90" => [2**90,
+    "Integer 2**90" => [2**90,
                        "\004\bl+\v#{"\000" * 11}\004"],
     "Class String" => [String,
                        "\004\bc\vString"],
@@ -324,7 +457,7 @@ module MarshalSpec
                     "\x04\bI\"\nsmall\x06:\x06EF"],
     "String big" => ['big' * 100,
                     "\x04\bI\"\x02,\x01bigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbigbig\x06:\x06EF"],
-    "String extended" => [''.extend(Meths), # TODO: check for module on load
+    "String extended" => [''.dup.extend(Meths), # TODO: check for module on load
                           "\x04\bIe:\nMeths\"\x00\x06:\x06EF"],
     "String subclass" => [UserString.new,
                           "\004\bC:\017UserString\"\000"],
@@ -334,31 +467,31 @@ module MarshalSpec
                        "\004\b:\010big"],
     "Symbol big" => [('big' * 100).to_sym,
                                "\004\b:\002,\001#{'big' * 100}"],
-    "Bignum -2**64" => [-2**64,
+    "Integer -2**64" => [-2**64,
                         "\004\bl-\n\000\000\000\000\000\000\000\000\001\000"],
-    "Bignum -2**63" => [-2**63,
+    "Integer -2**63" => [-2**63,
                         "\004\bl-\t\000\000\000\000\000\000\000\200"],
-    "Fixnum -2**24" => [-2**24,
+    "Integer -2**24" => [-2**24,
                         "\004\bi\375\000\000\000"],
-    "Fixnum -2**16" => [-2**16,
+    "Integer -2**16" => [-2**16,
                         "\004\bi\376\000\000"],
-    "Fixnum -2**8" => [-2**8,
+    "Integer -2**8" => [-2**8,
                        "\004\bi\377\000"],
-    "Fixnum -123" => [-123,
+    "Integer -123" => [-123,
                       "\004\bi\200"],
-    "Fixnum 0" => [0,
+    "Integer 0" => [0,
                    "\004\bi\000"],
-    "Fixnum 5" => [5,
+    "Integer 5" => [5,
                    "\004\bi\n"],
-    "Fixnum 2**8" => [2**8,
+    "Integer 2**8" => [2**8,
                       "\004\bi\002\000\001"],
-    "Fixnum 2**16" => [2**16,
+    "Integer 2**16" => [2**16,
                        "\004\bi\003\000\000\001"],
-    "Fixnum 2**24" => [2**24,
+    "Integer 2**24" => [2**24,
                        "\004\bi\004\000\000\000\001"],
-    "Bignum 2**64" => [2**64,
+    "Integer 2**64" => [2**64,
                        "\004\bl+\n\000\000\000\000\000\000\000\000\001\000"],
-    "Bignum 2**90" => [2**90,
+    "Integer 2**90" => [2**90,
                        "\004\bl+\v#{"\000" * 11}\004"],
     "Class String" => [String,
                        "\004\bc\vString"],
@@ -398,6 +531,20 @@ module MarshalSpec
                  "\004\bS:\024Struct::Pyramid\000"],
     "Random" => random_data,
   }
+
+  module DataSpec
+    Measure = Data.define(:amount, :unit)
+    Empty = Data.define
+
+    MeasureExtended = Class.new(Measure)
+    MeasureExtended.extend(Enumerable)
+
+    class MeasureWithOverriddenName < Measure
+      def self.name
+        "Foo"
+      end
+    end
+  end
 end
 
 class ArraySub < Array
diff --git a/spec/ruby/core/marshal/fixtures/marshal_multibyte_data.rb b/spec/ruby/core/marshal/fixtures/marshal_multibyte_data.rb
new file mode 100644
index 0000000000..98a0d43392
--- /dev/null
+++ b/spec/ruby/core/marshal/fixtures/marshal_multibyte_data.rb
@@ -0,0 +1,12 @@
+# -*- encoding: utf-8 -*-
+
+module MarshalSpec
+  class MultibyteぁあぃいClass
+  end
+
+  module MultibyteけげこごModule
+  end
+
+  class MultibyteぁあぃいTime < Time
+  end
+end
diff --git a/spec/ruby/core/marshal/shared/load.rb b/spec/ruby/core/marshal/shared/load.rb
index f92d49c68c..204a4d34e3 100644
--- a/spec/ruby/core/marshal/shared/load.rb
+++ b/spec/ruby/core/marshal/shared/load.rb
@@ -1,6 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../fixtures/marshal_data'
-require 'stringio'
 
 describe :marshal_load, shared: true do
   before :all do
@@ -9,7 +8,11 @@ describe :marshal_load, shared: true do
 
   it "raises an ArgumentError when the dumped data is truncated" do
     obj = {first: 1, second: 2, third: 3}
-    -> { Marshal.send(@method, Marshal.dump(obj)[0, 5]) }.should raise_error(ArgumentError)
+    -> { Marshal.send(@method, Marshal.dump(obj)[0, 5]) }.should raise_error(ArgumentError, "marshal data too short")
+  end
+
+  it "raises an ArgumentError when the argument is empty String" do
+    -> { Marshal.send(@method, "") }.should raise_error(ArgumentError, "marshal data too short")
   end
 
   it "raises an ArgumentError when the dumped class is missing" do
@@ -20,7 +23,230 @@ describe :marshal_load, shared: true do
     -> { Marshal.send(@method, kaboom) }.should raise_error(ArgumentError)
   end
 
+  describe "when called with freeze: true" do
+    it "returns frozen strings" do
+      string = Marshal.send(@method, Marshal.dump("foo"), freeze: true)
+      string.should == "foo"
+      string.should.frozen?
+
+      utf8_string = "foo".encode(Encoding::UTF_8)
+      string = Marshal.send(@method, Marshal.dump(utf8_string), freeze: true)
+      string.should == utf8_string
+      string.should.frozen?
+    end
+
+    it "returns frozen arrays" do
+      array = Marshal.send(@method, Marshal.dump([1, 2, 3]), freeze: true)
+      array.should == [1, 2, 3]
+      array.should.frozen?
+    end
+
+    it "returns frozen hashes" do
+      hash = Marshal.send(@method, Marshal.dump({foo: 42}), freeze: true)
+      hash.should == {foo: 42}
+      hash.should.frozen?
+    end
+
+    it "returns frozen regexps" do
+      regexp = Marshal.send(@method, Marshal.dump(/foo/), freeze: true)
+      regexp.should == /foo/
+      regexp.should.frozen?
+    end
+
+    it "returns frozen structs" do
+      struct = Marshal.send(@method, Marshal.dump(MarshalSpec::StructToDump.new(1, 2)), freeze: true)
+      struct.should == MarshalSpec::StructToDump.new(1, 2)
+      struct.should.frozen?
+    end
+
+    it "returns frozen objects" do
+      source_object = Object.new
+
+      object = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+      object.should.frozen?
+    end
+
+    describe "deep freezing" do
+      it "returns hashes with frozen keys and values" do
+        key = Object.new
+        value = Object.new
+        source_object = {key => value}
+
+        hash = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+        hash.size.should == 1
+        hash.keys[0].should.frozen?
+        hash.values[0].should.frozen?
+      end
+
+      it "returns arrays with frozen elements" do
+        object = Object.new
+        source_object = [object]
+
+        array = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+        array.size.should == 1
+        array[0].should.frozen?
+      end
+
+      it "returns structs with frozen members" do
+        object1 = Object.new
+        object2 = Object.new
+        source_object = MarshalSpec::StructToDump.new(object1, object2)
+
+        struct = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+        struct.a.should.frozen?
+        struct.b.should.frozen?
+      end
+
+      it "returns objects with frozen instance variables" do
+        source_object = Object.new
+        instance_variable = Object.new
+        source_object.instance_variable_set(:@a, instance_variable)
+
+        object = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+        object.instance_variable_get(:@a).should != nil
+        object.instance_variable_get(:@a).should.frozen?
+      end
+
+      it "deduplicates frozen strings" do
+        source_object = ["foo" + "bar", "foobar"]
+        object = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+
+        object[0].should equal(object[1])
+      end
+    end
+
+    it "does not freeze modules" do
+      object = Marshal.send(@method, Marshal.dump(Kernel), freeze: true)
+      object.should_not.frozen?
+      Kernel.should_not.frozen?
+    end
+
+    it "does not freeze classes" do
+      object = Marshal.send(@method, Marshal.dump(Object), freeze: true)
+      object.should_not.frozen?
+      Object.should_not.frozen?
+    end
+
+    ruby_bug "#19427", ""..."3.3" do
+      it "does freeze extended objects" do
+        object = Marshal.load("\x04\be:\x0FEnumerableo:\vObject\x00", freeze: true)
+        object.should.frozen?
+      end
+
+      it "does freeze extended objects with instance variables" do
+        object = Marshal.load("\x04\be:\x0FEnumerableo:\vObject\x06:\n@ivarT", freeze: true)
+        object.should.frozen?
+      end
+    end
+
+    ruby_bug "#19427", ""..."3.3" do
+      it "returns frozen object having #_dump method" do
+        object = Marshal.send(@method, Marshal.dump(UserDefined.new), freeze: true)
+        object.should.frozen?
+      end
+
+      it "returns frozen object responding to #marshal_dump and #marshal_load" do
+        object = Marshal.send(@method, Marshal.dump(UserMarshal.new), freeze: true)
+        object.should.frozen?
+      end
+
+      it "returns frozen object extended by a module" do
+        object = Object.new
+        object.extend(MarshalSpec::ModuleToExtendBy)
+
+        object = Marshal.send(@method, Marshal.dump(object), freeze: true)
+        object.should.frozen?
+      end
+    end
+
+    it "does not call freeze method" do
+      object = MarshalSpec::ObjectWithFreezeRaisingException.new
+      object = Marshal.send(@method, Marshal.dump(object), freeze: true)
+      object.should.frozen?
+    end
+
+    it "returns frozen object even if object does not respond to freeze method" do
+      object = MarshalSpec::ObjectWithoutFreeze.new
+      object = Marshal.send(@method, Marshal.dump(object), freeze: true)
+      object.should.frozen?
+    end
+
+    it "returns a frozen object when is an instance of String/Array/Regexp/Hash subclass and has instance variables" do
+      source_object = UserString.new
+      source_object.instance_variable_set(:@foo, "bar")
+
+      object = Marshal.send(@method, Marshal.dump(source_object), freeze: true)
+      object.should.frozen?
+    end
+
+    describe "when called with a proc" do
+      it "call the proc with frozen objects" do
+        arr = []
+        s = +'hi'
+        s.instance_variable_set(:@foo, 5)
+        st = Struct.new("Brittle", :a).new
+        st.instance_variable_set(:@clue, 'none')
+        st.a = 0.0
+        h = Hash.new('def')
+        h['nine'] = 9
+        a = [:a, :b, :c]
+        a.instance_variable_set(:@two, 2)
+        obj = [s, 10, s, s, st, a]
+        obj.instance_variable_set(:@zoo, 'ant')
+        proc = Proc.new { |o| arr << o; o}
+
+        Marshal.send(
+          @method,
+          "\x04\bI[\vI\"\ahi\a:\x06EF:\t@fooi\ni\x0F@\x06@\x06IS:\x14Struct::Brittle\x06:\x06af\x060\x06:\n@clueI\"\tnone\x06;\x00FI[\b;\b:\x06b:\x06c\x06:\t@twoi\a\x06:\t@zooI\"\bant\x06;\x00F",
+          proc,
+          freeze: true,
+        )
+
+        arr.should == [
+          false, 5, "hi", 10, "hi", "hi", 0.0, false, "none", st,
+          :b, :c, 2, a, false, "ant", ["hi", 10, "hi", "hi", st, [:a, :b, :c]],
+        ]
+
+        arr.each do |v|
+          v.should.frozen?
+        end
+
+        Struct.send(:remove_const, :Brittle)
+      end
+
+      it "does not freeze the object returned by the proc" do
+        string = Marshal.send(@method, Marshal.dump("foo"), proc { |o| o.upcase }, freeze: true)
+        string.should == "FOO"
+        string.should_not.frozen?
+      end
+    end
+  end
+
   describe "when called with a proc" do
+    it "call the proc with fully initialized strings" do
+      utf8_string = "foo".encode(Encoding::UTF_8)
+      Marshal.send(@method, Marshal.dump(utf8_string), proc { |arg|
+        if arg.is_a?(String)
+          arg.should == utf8_string
+          arg.encoding.should == Encoding::UTF_8
+        end
+        arg
+      })
+    end
+
+    it "no longer mutate the object after it was passed to the proc" do
+      string = Marshal.load(Marshal.dump("foo"), :freeze.to_proc)
+      string.should.frozen?
+    end
+
+    ruby_bug "#19427", ""..."3.3" do
+      it "call the proc with extended objects" do
+        objs = []
+        obj = Marshal.load("\x04\be:\x0FEnumerableo:\vObject\x00", Proc.new { |o| objs << o; o })
+        objs.should == [obj]
+      end
+    end
+
     it "returns the value of the proc" do
       Marshal.send(@method, Marshal.dump([1,2]), proc { [3,4] }).should ==  [3,4]
     end
@@ -29,16 +255,15 @@ describe :marshal_load, shared: true do
       a = [1]
       a << a
       ret = []
-      Marshal.send(@method, Marshal.dump(a), proc { |arg| ret << arg; arg })
-      ret.first.should == 1
-      ret[1].should == [1,a]
-      ret[2].should == a
-      ret.size.should == 3
+      Marshal.send(@method, Marshal.dump(a), proc { |arg| ret << arg.inspect; arg })
+      ret[0].should == 1.inspect
+      ret[1].should == a.inspect
+      ret.size.should == 2
     end
 
     it "loads an Array with proc" do
       arr = []
-      s = 'hi'
+      s = +'hi'
       s.instance_variable_set(:@foo, 5)
       st = Struct.new("Brittle", :a).new
       st.instance_variable_set(:@clue, 'none')
@@ -49,13 +274,14 @@ describe :marshal_load, shared: true do
       a.instance_variable_set(:@two, 2)
       obj = [s, 10, s, s, st, a]
       obj.instance_variable_set(:@zoo, 'ant')
-      proc = Proc.new { |o| arr << o; o}
+      proc = Proc.new { |o| arr << o.dup; o}
 
       Marshal.send(@method, "\x04\bI[\vI\"\ahi\a:\x06EF:\t@fooi\ni\x0F@\x06@\x06IS:\x14Struct::Brittle\x06:\x06af\x060\x06:\n@clueI\"\tnone\x06;\x00FI[\b;\b:\x06b:\x06c\x06:\t@twoi\a\x06:\t@zooI\"\bant\x06;\x00F", proc)
 
-      arr.should == ["hi", false, 5, 10, "hi", "hi", 0.0, st, "none", false,
-                     :b, :c, a, 2, ["hi", 10, "hi", "hi", st, [:a, :b, :c]], "ant", false]
-
+      arr.should == [
+        false, 5, "hi", 10, "hi", "hi", 0.0, false, "none", st,
+        :b, :c, 2, a, false, "ant", ["hi", 10, "hi", "hi", st, [:a, :b, :c]],
+      ]
       Struct.send(:remove_const, :Brittle)
     end
   end
@@ -82,7 +308,19 @@ describe :marshal_load, shared: true do
       marshaled_obj.field2.should be_nil
     end
 
-    describe "that return an immediate value" do
+    it "loads the String in non US-ASCII and non UTF-8 encoding" do
+      source_object = UserDefinedString.new("a".encode("windows-1251"))
+      object = Marshal.send(@method, Marshal.dump(source_object))
+      object.string.should == "a".encode("windows-1251")
+    end
+
+    it "loads the String in multibyte encoding" do
+      source_object = UserDefinedString.new("a".encode("utf-32le"))
+      object = Marshal.send(@method, Marshal.dump(source_object))
+      object.string.should == "a".encode("utf-32le")
+    end
+
+    describe "that returns an immediate value" do
       it "loads an array containing an instance of the object, followed by multiple instances of another object" do
         str = "string"
 
@@ -122,26 +360,35 @@ describe :marshal_load, shared: true do
 
   it "loads an array containing objects having _dump method, and with proc" do
     arr = []
-    myproc = Proc.new { |o| arr << o; o }
+    myproc = Proc.new { |o| arr << o.dup; o }
     o1 = UserDefined.new;
     o2 = UserDefinedWithIvar.new
     obj = [o1, o2, o1, o2]
 
     Marshal.send(@method, "\x04\b[\tu:\x10UserDefined\x18\x04\b[\aI\"\nstuff\x06:\x06EF@\x06u:\x18UserDefinedWithIvar>\x04\b[\bI\"\nstuff\a:\x06EF:\t@foo:\x18UserDefinedWithIvarI\"\tmore\x06;\x00F@\a@\x06@\a", myproc)
 
-    arr.should == [o1, o2, o1, o2, obj]
+    arr[0].should == o1
+    arr[1].should == o2
+    arr[2].should == obj
+    arr.size.should == 3
   end
 
   it "loads an array containing objects having marshal_dump method, and with proc" do
     arr = []
-    proc = Proc.new { |o| arr << o; o }
+    proc = Proc.new { |o| arr << o.dup; o }
     o1 = UserMarshal.new
     o2 = UserMarshalWithIvar.new
-    obj = [o1, o2, o1, o2]
 
     Marshal.send(@method, "\004\b[\tU:\020UserMarshal\"\nstuffU:\030UserMarshalWithIvar[\006\"\fmy data@\006@\b", proc)
 
-    arr.should == ['stuff', o1, 'my data', ['my data'], o2, o1, o2, obj]
+    arr[0].should == 'stuff'
+    arr[1].should == o1
+    arr[2].should == 'my data'
+    arr[3].should == ['my data']
+    arr[4].should == o2
+    arr[5].should == [o1, o2, o1, o2]
+
+    arr.size.should == 6
   end
 
   it "assigns classes to nested subclasses of Array correctly" do
@@ -158,13 +405,13 @@ describe :marshal_load, shared: true do
   end
 
   it "raises a TypeError with bad Marshal version" do
-    marshal_data = '\xff\xff'
+    marshal_data = +'\xff\xff'
     marshal_data[0] = (Marshal::MAJOR_VERSION).chr
     marshal_data[1] = (Marshal::MINOR_VERSION + 1).chr
 
     -> { Marshal.send(@method, marshal_data) }.should raise_error(TypeError)
 
-    marshal_data = '\xff\xff'
+    marshal_data = +'\xff\xff'
     marshal_data[0] = (Marshal::MAJOR_VERSION - 1).chr
     marshal_data[1] = (Marshal::MINOR_VERSION).chr
 
@@ -182,87 +429,6 @@ describe :marshal_load, shared: true do
     end
   end
 
-  it "returns an untainted object if source is untainted" do
-    x = Object.new
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.tainted?.should be_false
-  end
-
-  describe "when source is tainted" do
-    it "returns a tainted object" do
-      x = Object.new
-      x.taint
-      s = Marshal.dump(x)
-      y = Marshal.send(@method, s)
-      y.tainted?.should be_true
-
-      # note that round-trip via Marshal does not preserve
-      # the taintedness at each level of the nested structure
-      y = Marshal.send(@method, Marshal.dump([[x]]))
-      y.tainted?.should be_true
-      y.first.tainted?.should be_true
-      y.first.first.tainted?.should be_true
-    end
-
-    it "does not taint Symbols" do
-      x = [:x]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-
-    it "does not taint Fixnums" do
-      x = [1]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-
-    it "does not taint Bignums" do
-      x = [bignum_value]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-
-    it "does not taint Floats" do
-      x = [1.2]
-      y = Marshal.send(@method, Marshal.dump(x).taint)
-      y.tainted?.should be_true
-      y.first.tainted?.should be_false
-    end
-  end
-
-  it "preserves taintedness of nested structure" do
-    x = Object.new
-    a = [[x]]
-    x.taint
-    y = Marshal.send(@method, Marshal.dump(a))
-    y.tainted?.should be_true
-    y.first.tainted?.should be_true
-    y.first.first.tainted?.should be_true
-  end
-
-  it "returns a trusted object if source is trusted" do
-    x = Object.new
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.untrusted?.should be_false
-  end
-
-  it "returns an untrusted object if source is untrusted" do
-    x = Object.new
-    x.untrust
-    y = Marshal.send(@method, Marshal.dump(x))
-    y.untrusted?.should be_true
-
-    # note that round-trip via Marshal does not preserve
-    # the untrustedness at each level of the nested structure
-    y = Marshal.send(@method, Marshal.dump([[x]]))
-    y.untrusted?.should be_true
-    y.first.untrusted?.should be_true
-    y.first.first.untrusted?.should be_true
-  end
-
   # Note: Ruby 1.9 should be compatible with older marshal format
   MarshalSpec::DATA.each do |description, (object, marshal, attributes)|
     it "loads a #{description}" do
@@ -296,7 +462,7 @@ describe :marshal_load, shared: true do
     end
 
     it "loads an array having ivar" do
-      s = 'well'
+      s = +'well'
       s.instance_variable_set(:@foo, 10)
       obj = ['5', s, 'hi'].extend(Meths, MethsMore)
       obj.instance_variable_set(:@mix, s)
@@ -308,7 +474,8 @@ describe :marshal_load, shared: true do
 
     it "loads an extended Array object containing a user-marshaled object" do
       obj = [UserMarshal.new, UserMarshal.new].extend(Meths)
-      new_obj = Marshal.send(@method, "\x04\be:\nMeths[\ao:\x10UserMarshal\x06:\n@dataI\"\nstuff\x06:\x06ETo;\x06\x06;\aI\"\nstuff\x06;\bT")
+      dump = "\x04\be:\nMeths[\ao:\x10UserMarshal\x06:\n@dataI\"\nstuff\x06:\x06ETo;\x06\x06;\aI\"\nstuff\x06;\bT"
+      new_obj = Marshal.send(@method, dump)
 
       new_obj.should == obj
       obj_ancestors = class << obj; ancestors[1..-1]; end
@@ -341,7 +508,7 @@ describe :marshal_load, shared: true do
     end
 
     it "preserves hash ivars when hash contains a string having ivar" do
-      s = 'string'
+      s = +'string'
       s.instance_variable_set :@string_ivar, 'string ivar'
       h = { key: s }
       h.instance_variable_set :@hash_ivar, 'hash ivar'
@@ -350,6 +517,36 @@ describe :marshal_load, shared: true do
       unmarshalled.instance_variable_get(:@hash_ivar).should == 'hash ivar'
       unmarshalled[:key].instance_variable_get(:@string_ivar).should == 'string ivar'
     end
+
+    it "preserves compare_by_identity behaviour" do
+      h = { a: 1 }
+      h.compare_by_identity
+      unmarshalled = Marshal.send(@method, Marshal.dump(h))
+      unmarshalled.should.compare_by_identity?
+
+      h = { a: 1 }
+      unmarshalled = Marshal.send(@method, Marshal.dump(h))
+      unmarshalled.should_not.compare_by_identity?
+    end
+
+    it "preserves compare_by_identity behaviour for a Hash subclass" do
+      h = UserHash.new({ a: 1 })
+      h.compare_by_identity
+      unmarshalled = Marshal.send(@method, Marshal.dump(h))
+      unmarshalled.should.compare_by_identity?
+
+      h = UserHash.new({ a: 1 })
+      unmarshalled = Marshal.send(@method, Marshal.dump(h))
+      unmarshalled.should_not.compare_by_identity?
+    end
+
+    it "allocates an instance of the proper class when Hash subclass with compare_by_identity behaviour" do
+      h = UserHash.new({ a: 1 })
+      h.compare_by_identity
+
+      unmarshalled = Marshal.send(@method, Marshal.dump(h))
+      unmarshalled.should.kind_of?(UserHash)
+    end
   end
 
   describe "for a Symbol" do
@@ -393,23 +590,56 @@ describe :marshal_load, shared: true do
     end
 
     it "loads a binary encoded Symbol" do
-      s = "\u2192".force_encoding("binary").to_sym
+      s = "\u2192".dup.force_encoding("binary").to_sym
       sym = Marshal.send(@method, "\x04\b:\b\xE2\x86\x92")
       sym.should == s
       sym.encoding.should == Encoding::BINARY
     end
+
+    it "loads multiple Symbols sharing the same encoding" do
+      # Note that the encoding is a link for the second Symbol
+      symbol1 = "I:\t\xE2\x82\xACa\x06:\x06ET"
+      symbol2 = "I:\t\xE2\x82\xACb\x06;\x06T"
+      dump = "\x04\b[\a#{symbol1}#{symbol2}"
+      value = Marshal.send(@method, dump)
+      value.map(&:encoding).should == [Encoding::UTF_8, Encoding::UTF_8]
+      expected = [
+        "€a".dup.force_encoding(Encoding::UTF_8).to_sym,
+        "€b".dup.force_encoding(Encoding::UTF_8).to_sym
+      ]
+      value.should == expected
+
+      value = Marshal.send(@method, "\x04\b[\b#{symbol1}#{symbol2};\x00")
+      value.map(&:encoding).should == [Encoding::UTF_8, Encoding::UTF_8, Encoding::UTF_8]
+      value.should == [*expected, expected[0]]
+    end
+
+    it "raises ArgumentError when end of byte sequence reached before symbol characters end" do
+      Marshal.dump(:hello).should == "\x04\b:\nhello"
+
+      -> {
+        Marshal.send(@method, "\x04\b:\nhel")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
   describe "for a String" do
     it "loads a string having ivar with ref to self" do
-      obj = 'hi'
+      obj = +'hi'
       obj.instance_variable_set(:@self, obj)
       Marshal.send(@method, "\004\bI\"\ahi\006:\n@self@\000").should == obj
     end
 
     it "loads a string through StringIO stream" do
-        obj = "This is a string which should be unmarshalled through StringIO stream!"
-        Marshal.send(@method, StringIO.new(Marshal.dump(obj))).should == obj
+      require 'stringio'
+      obj = "This is a string which should be unmarshalled through StringIO stream!"
+      Marshal.send(@method, StringIO.new(Marshal.dump(obj))).should == obj
+    end
+
+    it "sets binmode if it is loading through StringIO stream" do
+      io = StringIO.new("\004\b:\vsymbol")
+      def io.binmode; raise "binmode"; end
+      -> { Marshal.load(io) }.should raise_error(RuntimeError, "binmode")
     end
 
     it "loads a string with an ivar" do
@@ -423,7 +653,7 @@ describe :marshal_load, shared: true do
     end
 
     it "loads a US-ASCII String" do
-      str = "abc".force_encoding("us-ascii")
+      str = "abc".dup.force_encoding("us-ascii")
       data = "\x04\bI\"\babc\x06:\x06EF"
       result = Marshal.send(@method, data)
       result.should == str
@@ -431,7 +661,7 @@ describe :marshal_load, shared: true do
     end
 
     it "loads a UTF-8 String" do
-      str = "\x6d\xc3\xb6\x68\x72\x65".force_encoding("utf-8")
+      str = "\x6d\xc3\xb6\x68\x72\x65".dup.force_encoding("utf-8")
       data = "\x04\bI\"\vm\xC3\xB6hre\x06:\x06ET"
       result = Marshal.send(@method, data)
       result.should == str
@@ -439,7 +669,7 @@ describe :marshal_load, shared: true do
     end
 
     it "loads a String in another encoding" do
-      str = "\x6d\x00\xf6\x00\x68\x00\x72\x00\x65\x00".force_encoding("utf-16le")
+      str = "\x6d\x00\xf6\x00\x68\x00\x72\x00\x65\x00".dup.force_encoding("utf-16le")
       data = "\x04\bI\"\x0Fm\x00\xF6\x00h\x00r\x00e\x00\x06:\rencoding\"\rUTF-16LE"
       result = Marshal.send(@method, data)
       result.should == str
@@ -447,31 +677,42 @@ describe :marshal_load, shared: true do
     end
 
     it "loads a String as BINARY if no encoding is specified at the end" do
-      str = "\xC3\xB8".force_encoding("BINARY")
-      data = "\x04\b\"\a\xC3\xB8".force_encoding("UTF-8")
+      str = "\xC3\xB8".dup.force_encoding("BINARY")
+      data = "\x04\b\"\a\xC3\xB8".dup.force_encoding("UTF-8")
       result = Marshal.send(@method, data)
       result.encoding.should == Encoding::BINARY
       result.should == str
     end
+
+    it "raises ArgumentError when end of byte sequence reached before string characters end" do
+      Marshal.dump("hello").should == "\x04\b\"\nhello"
+
+      -> {
+        Marshal.send(@method, "\x04\b\"\nhel")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
   describe "for a Struct" do
     it "loads a extended_struct having fields with same objects" do
       s = 'hi'
-      obj = Struct.new("Ure2", :a, :b).new.extend(Meths)
+      obj = Struct.new("Extended", :a, :b).new.extend(Meths)
+      dump = "\004\be:\nMethsS:\025Struct::Extended\a:\006a0:\006b0"
+      Marshal.send(@method, dump).should == obj
+
       obj.a = [:a, s]
       obj.b = [:Meths, s]
-
-      Marshal.send(@method,
-        "\004\be:\nMethsS:\021Struct::Ure2\a:\006a[\a;\a\"\ahi:\006b[\a;\000@\a"
-        ).should == obj
-      Struct.send(:remove_const, :Ure2)
+      dump = "\004\be:\nMethsS:\025Struct::Extended\a:\006a[\a;\a\"\ahi:\006b[\a;\000@\a"
+      Marshal.send(@method, dump).should == obj
+      Struct.send(:remove_const, :Extended)
     end
 
     it "loads a struct having ivar" do
       obj = Struct.new("Thick").new
       obj.instance_variable_set(:@foo, 5)
-      Marshal.send(@method, "\004\bIS:\022Struct::Thick\000\006:\t@fooi\n").should == obj
+      reloaded = Marshal.send(@method, "\004\bIS:\022Struct::Thick\000\006:\t@fooi\n")
+      reloaded.should == obj
+      reloaded.instance_variable_get(:@foo).should == 5
       Struct.send(:remove_const, :Thick)
     end
 
@@ -498,6 +739,32 @@ describe :marshal_load, shared: true do
     end
   end
 
+  describe "for a Data" do
+    it "loads a Data" do
+      obj = MarshalSpec::DataSpec::Measure.new(100, 'km')
+      dumped = "\x04\bS:#MarshalSpec::DataSpec::Measure\a:\vamountii:\tunit\"\akm"
+      Marshal.dump(obj).should == dumped
+
+      Marshal.send(@method, dumped).should == obj
+    end
+
+    it "loads an extended Data" do
+      obj = MarshalSpec::DataSpec::MeasureExtended.new(100, "km")
+      dumped = "\x04\bS:+MarshalSpec::DataSpec::MeasureExtended\a:\vamountii:\tunit\"\akm"
+      Marshal.dump(obj).should == dumped
+
+      Marshal.send(@method, dumped).should == obj
+    end
+
+    it "returns a frozen object" do
+      obj = MarshalSpec::DataSpec::Measure.new(100, 'km')
+      dumped = "\x04\bS:#MarshalSpec::DataSpec::Measure\a:\vamountii:\tunit\"\akm"
+      Marshal.dump(obj).should == dumped
+
+      Marshal.send(@method, dumped).should.frozen?
+    end
+  end
+
   describe "for an Exception" do
     it "loads a marshalled exception with no message" do
       obj = Exception.new
@@ -529,6 +796,19 @@ describe :marshal_load, shared: true do
       loaded.message.should == obj.message
       loaded.backtrace.should == obj.backtrace
     end
+
+    it "loads an marshalled exception with ivars" do
+      s = 'hi'
+      arr = [:so, :so, s, s]
+      obj = Exception.new("foo")
+      obj.instance_variable_set :@arr, arr
+
+      loaded = Marshal.send(@method, "\x04\bo:\x0EException\b:\tmesg\"\bfoo:\abt0:\t@arr[\t:\aso;\t\"\ahi@\b")
+      new_arr = loaded.instance_variable_get :@arr
+
+      loaded.message.should == obj.message
+      new_arr.should == arr
+    end
   end
 
   describe "for an Object" do
@@ -559,7 +839,7 @@ describe :marshal_load, shared: true do
     end
 
     it "loads an Object with a non-US-ASCII instance variable" do
-      ivar = "@é".force_encoding(Encoding::UTF_8).to_sym
+      ivar = "@é".dup.force_encoding(Encoding::UTF_8).to_sym
       obj = Marshal.send(@method, "\x04\bo:\vObject\x06I:\b@\xC3\xA9\x06:\x06ETi\x06")
       obj.instance_variables.should == [ivar]
       obj.instance_variables[0].encoding.should == Encoding::UTF_8
@@ -571,6 +851,26 @@ describe :marshal_load, shared: true do
         Marshal.send(@method, "\x04\bo:\tFile\001\001:\001\005@path\"\x10/etc/passwd")
       end.should raise_error(ArgumentError)
     end
+
+    it "raises ArgumentError when end of byte sequence reached before class name end" do
+      Marshal.dump(Object.new).should == "\x04\bo:\vObject\x00"
+
+      -> {
+        Marshal.send(@method, "\x04\bo:\vObj")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
+  end
+
+  describe "for an object responding to #marshal_dump and #marshal_load" do
+    it "loads a user-marshaled object" do
+      obj = UserMarshal.new
+      obj.data = :data
+      value = [obj, :data]
+      dump = Marshal.dump(value)
+      dump.should == "\x04\b[\aU:\x10UserMarshal:\tdata;\x06"
+      reloaded = Marshal.load(dump)
+      reloaded.should == value
+    end
   end
 
   describe "for a user object" do
@@ -608,7 +908,7 @@ describe :marshal_load, shared: true do
 
   describe "for a Regexp" do
     it "loads an extended Regexp" do
-      obj = /[a-z]/.extend(Meths, MethsMore)
+      obj = /[a-z]/.dup.extend(Meths, MethsMore)
       new_obj = Marshal.send(@method, "\004\be:\nMethse:\016MethsMore/\n[a-z]\000")
 
       new_obj.should == obj
@@ -617,7 +917,7 @@ describe :marshal_load, shared: true do
         [Meths, MethsMore, Regexp]
     end
 
-    it "loads a extended_user_regexp having ivar" do
+    it "loads a Regexp subclass instance variables when it is extended with a module" do
       obj = UserRegexp.new('').extend(Meths)
       obj.instance_variable_set(:@noise, 'much')
 
@@ -629,6 +929,33 @@ describe :marshal_load, shared: true do
       new_obj_metaclass_ancestors[@num_self_class, 3].should ==
         [Meths, UserRegexp, Regexp]
     end
+
+    ruby_bug "#19439", ""..."3.3" do
+      it "restore the regexp instance variables" do
+        obj = Regexp.new("hello")
+        obj.instance_variable_set(:@regexp_ivar, [42])
+
+        new_obj = Marshal.send(@method, "\x04\bI/\nhello\x00\a:\x06EF:\x11@regexp_ivar[\x06i/")
+        new_obj.instance_variables.should == [:@regexp_ivar]
+        new_obj.instance_variable_get(:@regexp_ivar).should == [42]
+      end
+    end
+
+    it "preserves Regexp encoding" do
+      source_object = Regexp.new("a".encode("utf-32le"))
+      regexp = Marshal.send(@method, Marshal.dump(source_object))
+
+      regexp.encoding.should == Encoding::UTF_32LE
+      regexp.source.should == "a".encode("utf-32le")
+    end
+
+    it "raises ArgumentError when end of byte sequence reached before source string end" do
+      Marshal.dump(/hello world/).should == "\x04\bI/\x10hello world\x00\x06:\x06EF"
+
+      -> {
+        Marshal.send(@method, "\x04\bI/\x10hel")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
   describe "for a Float" do
@@ -650,9 +977,17 @@ describe :marshal_load, shared: true do
       obj = 1.1867345e+22
       Marshal.send(@method, "\004\bf\0361.1867344999999999e+22\000\344@").should == obj
     end
+
+    it "raises ArgumentError when end of byte sequence reached before float string representation end" do
+      Marshal.dump(1.3).should == "\x04\bf\b1.3"
+
+      -> {
+        Marshal.send(@method, "\004\bf\v1")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
-  describe "for a Integer" do
+  describe "for an Integer" do
     it "loads 0" do
       Marshal.send(@method, "\004\bi\000").should == 0
       Marshal.send(@method, "\004\bi\005").should == 0
@@ -715,29 +1050,33 @@ describe :marshal_load, shared: true do
 
   describe "for a Rational" do
     it "loads" do
-      Marshal.send(@method, Marshal.dump(Rational(1, 3))).should == Rational(1, 3)
+      r = Marshal.send(@method, Marshal.dump(Rational(1, 3)))
+      r.should == Rational(1, 3)
+      r.should.frozen?
     end
   end
 
   describe "for a Complex" do
     it "loads" do
-      Marshal.send(@method, Marshal.dump(Complex(4, 3))).should == Complex(4, 3)
+      c = Marshal.send(@method, Marshal.dump(Complex(4, 3)))
+      c.should == Complex(4, 3)
+      c.should.frozen?
     end
   end
 
   describe "for a Bignum" do
-    platform_is wordsize: 64 do
+    platform_is c_long_size: 64 do
       context "that is Bignum on 32-bit platforms but Fixnum on 64-bit" do
         it "dumps a Fixnum" do
           val = Marshal.send(@method, "\004\bl+\ab:wU")
           val.should == 1433877090
-          val.class.should == Fixnum
+          val.class.should == Integer
         end
 
         it "dumps an array containing multiple references to the Bignum as an array of Fixnum" do
           arr = Marshal.send(@method, "\004\b[\al+\a\223BwU@\006")
           arr.should == [1433879187, 1433879187]
-          arr.each { |v| v.class.should == Fixnum }
+          arr.each { |v| v.class.should == Integer }
         end
       end
     end
@@ -762,17 +1101,47 @@ describe :marshal_load, shared: true do
       t1.should equal t2
     end
 
-    it "loads the zone" do
+    it "keeps the local zone" do
       with_timezone 'AST', 3 do
         t = Time.local(2012, 1, 1)
         Marshal.send(@method, Marshal.dump(t)).zone.should == t.zone
       end
     end
 
-    it "loads nanoseconds" do
+    it "keeps UTC zone" do
+      t = Time.now.utc
+      t2 = Marshal.send(@method, Marshal.dump(t))
+      t2.should.utc?
+    end
+
+    it "keeps the zone" do
+      t = nil
+
+      with_timezone 'AST', 4 do
+        t = Time.local(2012, 1, 1)
+      end
+
+      with_timezone 'EET', -2 do
+        Marshal.send(@method, Marshal.dump(t)).zone.should == 'AST'
+      end
+    end
+
+    it "keeps utc offset" do
+      t = Time.new(2007,11,1,15,25,0, "+09:00")
+      t2 = Marshal.send(@method, Marshal.dump(t))
+      t2.utc_offset.should == 32400
+    end
+
+    it "keeps nanoseconds" do
       t = Time.now
       Marshal.send(@method, Marshal.dump(t)).nsec.should == t.nsec
     end
+
+    it "does not add any additional instance variable" do
+      t = Time.now
+      t2 = Marshal.send(@method, Marshal.dump(t))
+      t2.instance_variables.should.empty?
+    end
   end
 
   describe "for nil" do
@@ -805,6 +1174,14 @@ describe :marshal_load, shared: true do
     it "raises ArgumentError if given a nonexistent class" do
       -> { Marshal.send(@method, "\x04\bc\vStrung") }.should raise_error(ArgumentError)
     end
+
+    it "raises ArgumentError when end of byte sequence reached before class name end" do
+      Marshal.dump(String).should == "\x04\bc\vString"
+
+      -> {
+        Marshal.send(@method, "\x04\bc\vStr")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
   describe "for a Module" do
@@ -819,6 +1196,14 @@ describe :marshal_load, shared: true do
     it "loads an old module" do
       Marshal.send(@method, "\x04\bM\vKernel").should == Kernel
     end
+
+    it "raises ArgumentError when end of byte sequence reached before module name end" do
+      Marshal.dump(Kernel).should == "\x04\bm\vKernel"
+
+      -> {
+        Marshal.send(@method, "\x04\bm\vKer")
+      }.should raise_error(ArgumentError, "marshal data too short")
+    end
   end
 
   describe "for a wrapped C pointer" do
diff --git a/spec/ruby/core/matchdata/allocate_spec.rb b/spec/ruby/core/matchdata/allocate_spec.rb
new file mode 100644
index 0000000000..142ce639c2
--- /dev/null
+++ b/spec/ruby/core/matchdata/allocate_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+
+describe "MatchData.allocate" do
+  it "is undefined" do
+    # https://bugs.ruby-lang.org/issues/16294
+    -> { MatchData.allocate }.should raise_error(NoMethodError)
+  end
+end
diff --git a/spec/ruby/core/matchdata/begin_spec.rb b/spec/ruby/core/matchdata/begin_spec.rb
index 85c454da56..54b4e0a33f 100644
--- a/spec/ruby/core/matchdata/begin_spec.rb
+++ b/spec/ruby/core/matchdata/begin_spec.rb
@@ -36,6 +36,18 @@ describe "MatchData#begin" do
       match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
       match_data.begin(obj).should == 2
     end
+
+    it "raises IndexError if index is out of bounds" do
+      match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+      -> {
+        match_data.begin(-1)
+      }.should raise_error(IndexError, "index -1 out of matches")
+
+      -> {
+        match_data.begin(3)
+      }.should raise_error(IndexError, "index 3 out of matches")
+    end
   end
 
   context "when passed a String argument" do
@@ -68,6 +80,14 @@ describe "MatchData#begin" do
       match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
       match_data.begin("æ").should == 1
     end
+
+    it "raises IndexError if there is no group with the provided name" do
+      match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+      -> {
+        match_data.begin("y")
+      }.should raise_error(IndexError, "undefined group name reference: y")
+    end
   end
 
   context "when passed a Symbol argument" do
@@ -100,5 +120,13 @@ describe "MatchData#begin" do
       match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
       match_data.begin(:æ).should == 1
     end
+
+    it "raises IndexError if there is no group with the provided name" do
+      match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+      -> {
+        match_data.begin(:y)
+      }.should raise_error(IndexError, "undefined group name reference: y")
+    end
   end
 end
diff --git a/spec/ruby/core/matchdata/bytebegin_spec.rb b/spec/ruby/core/matchdata/bytebegin_spec.rb
new file mode 100644
index 0000000000..08c1fd6d1e
--- /dev/null
+++ b/spec/ruby/core/matchdata/bytebegin_spec.rb
@@ -0,0 +1,132 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "MatchData#bytebegin" do
+    context "when passed an integer argument" do
+      it "returns the byte-based offset of the start of the nth element" do
+        match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin(0).should == 1
+        match_data.bytebegin(2).should == 2
+      end
+
+      it "returns nil when the nth match isn't found" do
+        match_data = /something is( not)? (right)/.match("something is right")
+        match_data.bytebegin(1).should be_nil
+      end
+
+      it "returns the byte-based offset for multi-byte strings" do
+        match_data = /(.)(.)(\d+)(\d)/.match("TñX1138.")
+        match_data.bytebegin(0).should == 1
+        match_data.bytebegin(2).should == 3
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi-byte strings with unicode regexp" do
+          match_data = /(.)(.)(\d+)(\d)/u.match("TñX1138.")
+          match_data.bytebegin(0).should == 1
+          match_data.bytebegin(2).should == 3
+        end
+      end
+
+      it "tries to convert the passed argument to an Integer using #to_int" do
+        obj = mock('to_int')
+        obj.should_receive(:to_int).and_return(2)
+
+        match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin(obj).should == 2
+      end
+
+      it "raises IndexError if index is out of bounds" do
+        match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+        -> {
+          match_data.bytebegin(-1)
+        }.should raise_error(IndexError, "index -1 out of matches")
+
+        -> {
+          match_data.bytebegin(3)
+        }.should raise_error(IndexError, "index 3 out of matches")
+      end
+    end
+
+    context "when passed a String argument" do
+      it "return the byte-based offset of the start of the named capture" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin("a").should == 1
+        match_data.bytebegin("b").should == 3
+      end
+
+      it "returns the byte-based offset for multi byte strings" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("TñX1138.")
+        match_data.bytebegin("a").should == 1
+        match_data.bytebegin("b").should == 4
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi byte strings with unicode regexp" do
+          match_data = /(?<a>.)(.)(?<b>\d+)(\d)/u.match("TñX1138.")
+          match_data.bytebegin("a").should == 1
+          match_data.bytebegin("b").should == 4
+        end
+      end
+
+      it "returns the byte-based offset for the farthest match when multiple named captures use the same name" do
+        match_data = /(?<a>.)(.)(?<a>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin("a").should == 3
+      end
+
+      it "returns the byte-based offset for multi-byte names" do
+        match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin("æ").should == 1
+      end
+
+      it "raises IndexError if there is no group with the provided name" do
+        match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+        -> {
+          match_data.bytebegin("y")
+        }.should raise_error(IndexError, "undefined group name reference: y")
+      end
+    end
+
+    context "when passed a Symbol argument" do
+      it "return the byte-based offset of the start of the named capture" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin(:a).should == 1
+        match_data.bytebegin(:b).should == 3
+      end
+
+      it "returns the byte-based offset for multi byte strings" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("TñX1138.")
+        match_data.bytebegin(:a).should == 1
+        match_data.bytebegin(:b).should == 4
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi byte strings with unicode regexp" do
+          match_data = /(?<a>.)(.)(?<b>\d+)(\d)/u.match("TñX1138.")
+          match_data.bytebegin(:a).should == 1
+          match_data.bytebegin(:b).should == 4
+        end
+      end
+
+      it "returns the byte-based offset for the farthest match when multiple named captures use the same name" do
+        match_data = /(?<a>.)(.)(?<a>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin(:a).should == 3
+      end
+
+      it "returns the byte-based offset for multi-byte names" do
+        match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.bytebegin(:æ).should == 1
+      end
+
+      it "raises IndexError if there is no group with the provided name" do
+        match_data = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+        -> {
+          match_data.bytebegin(:y)
+        }.should raise_error(IndexError, "undefined group name reference: y")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/matchdata/byteend_spec.rb b/spec/ruby/core/matchdata/byteend_spec.rb
new file mode 100644
index 0000000000..98015e287d
--- /dev/null
+++ b/spec/ruby/core/matchdata/byteend_spec.rb
@@ -0,0 +1,104 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "MatchData#byteend" do
+    context "when passed an integer argument" do
+      it "returns the byte-based offset of the end of the nth element" do
+        match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
+        match_data.byteend(0).should == 7
+        match_data.byteend(2).should == 3
+      end
+
+      it "returns nil when the nth match isn't found" do
+        match_data = /something is( not)? (right)/.match("something is right")
+        match_data.byteend(1).should be_nil
+      end
+
+      it "returns the byte-based offset for multi-byte strings" do
+        match_data = /(.)(.)(\d+)(\d)/.match("TñX1138.")
+        match_data.byteend(0).should == 8
+        match_data.byteend(2).should == 4
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi-byte strings with unicode regexp" do
+          match_data = /(.)(.)(\d+)(\d)/u.match("TñX1138.")
+          match_data.byteend(0).should == 8
+          match_data.byteend(2).should == 4
+        end
+      end
+
+      it "tries to convert the passed argument to an Integer using #to_int" do
+        obj = mock('to_int')
+        obj.should_receive(:to_int).and_return(2)
+
+        match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
+        match_data.byteend(obj).should == 3
+      end
+    end
+
+    context "when passed a String argument" do
+      it "return the byte-based offset of the start of the named capture" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.byteend("a").should == 2
+        match_data.byteend("b").should == 6
+      end
+
+      it "returns the byte-based offset for multi byte strings" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("TñX1138.")
+        match_data.byteend("a").should == 3
+        match_data.byteend("b").should == 7
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi byte strings with unicode regexp" do
+          match_data = /(?<a>.)(.)(?<b>\d+)(\d)/u.match("TñX1138.")
+          match_data.byteend("a").should == 3
+          match_data.byteend("b").should == 7
+        end
+      end
+
+      it "returns the byte-based offset for the farthest match when multiple named captures use the same name" do
+        match_data = /(?<a>.)(.)(?<a>\d+)(\d)/.match("THX1138.")
+        match_data.byteend("a").should == 6
+      end
+
+      it "returns the byte-based offset for multi-byte names" do
+        match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.byteend("æ").should == 2
+      end
+    end
+
+    context "when passed a Symbol argument" do
+      it "return the byte-based offset of the start of the named capture" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.byteend(:a).should == 2
+        match_data.byteend(:b).should == 6
+      end
+
+      it "returns the byte-based offset for multi byte strings" do
+        match_data = /(?<a>.)(.)(?<b>\d+)(\d)/.match("TñX1138.")
+        match_data.byteend(:a).should == 3
+        match_data.byteend(:b).should == 7
+      end
+
+      not_supported_on :opal do
+        it "returns the byte-based offset for multi byte strings with unicode regexp" do
+          match_data = /(?<a>.)(.)(?<b>\d+)(\d)/u.match("TñX1138.")
+          match_data.byteend(:a).should == 3
+          match_data.byteend(:b).should == 7
+        end
+      end
+
+      it "returns the byte-based offset for the farthest match when multiple named captures use the same name" do
+        match_data = /(?<a>.)(.)(?<a>\d+)(\d)/.match("THX1138.")
+        match_data.byteend(:a).should == 6
+      end
+
+      it "returns the byte-based offset for multi-byte names" do
+        match_data = /(?<æ>.)(.)(?<b>\d+)(\d)/.match("THX1138.")
+        match_data.byteend(:æ).should == 2
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/matchdata/byteoffset_spec.rb b/spec/ruby/core/matchdata/byteoffset_spec.rb
new file mode 100644
index 0000000000..fb8f5fb67d
--- /dev/null
+++ b/spec/ruby/core/matchdata/byteoffset_spec.rb
@@ -0,0 +1,93 @@
+require_relative '../../spec_helper'
+
+describe "MatchData#byteoffset" do
+  it "returns beginning and ending byte-based offset of whole matched substring for 0 element" do
+    m = /(.)(.)(\d+)(\d)/.match("THX1138.")
+    m.byteoffset(0).should == [1, 7]
+  end
+
+  it "returns beginning and ending byte-based offset of n-th match, all the subsequent elements are capturing groups" do
+    m = /(.)(.)(\d+)(\d)/.match("THX1138.")
+
+    m.byteoffset(2).should == [2, 3]
+    m.byteoffset(3).should == [3, 6]
+    m.byteoffset(4).should == [6, 7]
+  end
+
+  it "accepts String as a reference to a named capture" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.byteoffset("f").should == [0, 3]
+    m.byteoffset("b").should == [3, 6]
+  end
+
+  it "accepts Symbol as a reference to a named capture" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.byteoffset(:f).should == [0, 3]
+    m.byteoffset(:b).should == [3, 6]
+  end
+
+  it "returns [nil, nil] if a capturing group is optional and doesn't match" do
+    m = /(?<x>q..)?/.match("foobarbaz")
+
+    m.byteoffset("x").should == [nil, nil]
+    m.byteoffset(1).should == [nil, nil]
+  end
+
+  it "returns correct beginning and ending byte-based offset for multi-byte strings" do
+    m = /\A\u3042(.)(.)?(.)\z/.match("\u3042\u3043\u3044")
+
+    m.byteoffset(1).should == [3, 6]
+    m.byteoffset(3).should == [6, 9]
+  end
+
+  it "returns [nil, nil] if a capturing group is optional and doesn't match for multi-byte string" do
+    m = /\A\u3042(.)(.)?(.)\z/.match("\u3042\u3043\u3044")
+
+    m.byteoffset(2).should == [nil, nil]
+  end
+
+  it "converts argument into integer if is not String nor Symbol" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    obj = Object.new
+    def obj.to_int; 2; end
+
+    m.byteoffset(1r).should == [0, 3]
+    m.byteoffset(1.1).should == [0, 3]
+    m.byteoffset(obj).should == [3, 6]
+  end
+
+  it "raises IndexError if there is no group with the provided name" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.byteoffset("y")
+    }.should raise_error(IndexError, "undefined group name reference: y")
+
+    -> {
+      m.byteoffset(:y)
+    }.should raise_error(IndexError, "undefined group name reference: y")
+  end
+
+  it "raises IndexError if index is out of bounds" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.byteoffset(-1)
+    }.should raise_error(IndexError, "index -1 out of matches")
+
+    -> {
+      m.byteoffset(3)
+    }.should raise_error(IndexError, "index 3 out of matches")
+  end
+
+  it "raises TypeError if can't convert argument into Integer" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.byteoffset([])
+    }.should raise_error(TypeError, "no implicit conversion of Array into Integer")
+  end
+end
diff --git a/spec/ruby/core/matchdata/captures_spec.rb b/spec/ruby/core/matchdata/captures_spec.rb
index 8c0d2978b7..f829a25481 100644
--- a/spec/ruby/core/matchdata/captures_spec.rb
+++ b/spec/ruby/core/matchdata/captures_spec.rb
@@ -1,7 +1,6 @@
 require_relative '../../spec_helper'
+require_relative 'shared/captures'
 
 describe "MatchData#captures" do
-  it "returns an array of the match captures" do
-    /(.)(.)(\d+)(\d)/.match("THX1138.").captures.should == ["H","X","113","8"]
-  end
+  it_behaves_like :matchdata_captures, :captures
 end
diff --git a/spec/ruby/core/matchdata/deconstruct_keys_spec.rb b/spec/ruby/core/matchdata/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..bf22bc33ff
--- /dev/null
+++ b/spec/ruby/core/matchdata/deconstruct_keys_spec.rb
@@ -0,0 +1,63 @@
+require_relative '../../spec_helper'
+
+describe "MatchData#deconstruct_keys" do
+  it "returns whole hash for nil as an argument" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.deconstruct_keys(nil).should == { f: "foo", b: "bar" }
+  end
+
+  it "returns only specified keys" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.deconstruct_keys([:f]).should == { f: "foo" }
+  end
+
+  it "requires one argument" do
+    m = /l/.match("l")
+
+    -> {
+      m.deconstruct_keys
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 0, expected 1)")
+  end
+
+  it "it raises error when argument is neither nil nor array" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> { m.deconstruct_keys(1) }.should raise_error(TypeError, "wrong argument type Integer (expected Array)")
+    -> { m.deconstruct_keys("asd") }.should raise_error(TypeError, "wrong argument type String (expected Array)")
+    -> { m.deconstruct_keys(:x) }.should raise_error(TypeError, "wrong argument type Symbol (expected Array)")
+    -> { m.deconstruct_keys({}) }.should raise_error(TypeError, "wrong argument type Hash (expected Array)")
+  end
+
+  it "returns {} when passed []" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.deconstruct_keys([]).should == {}
+  end
+
+  it "does not accept non-Symbol keys" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.deconstruct_keys(['year', :foo])
+    }.should raise_error(TypeError, "wrong argument type String (expected Symbol)")
+  end
+
+  it "process keys till the first non-existing one" do
+    m = /(?<f>foo)(?<b>bar)(?<c>baz)/.match("foobarbaz")
+
+    m.deconstruct_keys([:f, :a, :b]).should == { f: "foo" }
+  end
+
+  it "returns {} when there are no named captured groups at all" do
+    m = /foo.+/.match("foobar")
+
+    m.deconstruct_keys(nil).should == {}
+  end
+
+  it "returns {} when passed more keys than named captured groups" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+    m.deconstruct_keys([:f, :b, :c]).should == {}
+  end
+end
diff --git a/spec/ruby/core/matchdata/deconstruct_spec.rb b/spec/ruby/core/matchdata/deconstruct_spec.rb
new file mode 100644
index 0000000000..c55095665d
--- /dev/null
+++ b/spec/ruby/core/matchdata/deconstruct_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/captures'
+
+describe "MatchData#deconstruct" do
+  it_behaves_like :matchdata_captures, :deconstruct
+end
diff --git a/spec/ruby/core/matchdata/dup_spec.rb b/spec/ruby/core/matchdata/dup_spec.rb
new file mode 100644
index 0000000000..70877f07eb
--- /dev/null
+++ b/spec/ruby/core/matchdata/dup_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+
+describe "MatchData#dup" do
+  it "duplicates the match data" do
+    original = /ll/.match("hello")
+    original.instance_variable_set(:@custom_ivar, 42)
+    duplicate = original.dup
+
+    duplicate.instance_variable_get(:@custom_ivar).should == 42
+    original.regexp.should == duplicate.regexp
+    original.string.should == duplicate.string
+    original.offset(0).should == duplicate.offset(0)
+  end
+end
diff --git a/spec/ruby/core/matchdata/element_reference_spec.rb b/spec/ruby/core/matchdata/element_reference_spec.rb
index 26550ac94d..0924be0aae 100644
--- a/spec/ruby/core/matchdata/element_reference_spec.rb
+++ b/spec/ruby/core/matchdata/element_reference_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "MatchData#[]" do
   it "acts as normal array indexing [index]" do
@@ -15,10 +16,46 @@ describe "MatchData#[]" do
   it "supports accessors [start, length]" do
     /(.)(.)(\d+)(\d)/.match("THX1138.")[1, 2].should == %w|H X|
     /(.)(.)(\d+)(\d)/.match("THX1138.")[-3, 2].should == %w|X 113|
+
+    # negative index is larger than the number of match values
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[-30, 2].should == nil
+
+    # positive index larger than number of match values
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[5, 2].should == []
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[6, 2].should == nil
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[30, 2].should == nil
+
+    # length argument larger than number of match values is capped to match value length
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3, 10].should == %w|113 8|
+
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3, 0].should == []
+
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3, -1].should == nil
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3, -30].should == nil
   end
 
   it "supports ranges [start..end]" do
     /(.)(.)(\d+)(\d)/.match("THX1138.")[1..3].should == %w|H X 113|
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3..10].should == %w|113 8|
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[-30..2].should == nil
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3..1].should == []
+  end
+
+  it "supports endless ranges [start..]" do
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[3..].should == %w|113 8|
+  end
+
+  it "supports beginningless ranges [..end]" do
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[..1].should == %w|HX1138 H|
+  end
+
+  it "supports beginningless endless ranges [nil..nil]" do
+    /(.)(.)(\d+)(\d)/.match("THX1138.")[nil..nil].should == %w|HX1138 H X 113 8|
+  end
+
+  it "returns instances of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138.")
+    /(.)(.)(\d+)(\d)/.match(str)[0..-1].each { |m| m.should be_an_instance_of(String) }
   end
 end
 
@@ -81,7 +118,7 @@ describe "MatchData#[Symbol]" do
 
   it "returns matches in the String's encoding" do
     rex = /(?<t>t(?<a>ack))/u
-    md = 'haystack'.force_encoding('euc-jp').match(rex)
+    md = 'haystack'.dup.force_encoding('euc-jp').match(rex)
     md[:t].encoding.should == Encoding::EUC_JP
   end
 end
diff --git a/spec/ruby/core/matchdata/fixtures/classes.rb b/spec/ruby/core/matchdata/fixtures/classes.rb
new file mode 100644
index 0000000000..54795636e5
--- /dev/null
+++ b/spec/ruby/core/matchdata/fixtures/classes.rb
@@ -0,0 +1,3 @@
+module MatchDataSpecs
+  class MyString < String; end
+end
diff --git a/spec/ruby/core/matchdata/match_length_spec.rb b/spec/ruby/core/matchdata/match_length_spec.rb
new file mode 100644
index 0000000000..824f94a397
--- /dev/null
+++ b/spec/ruby/core/matchdata/match_length_spec.rb
@@ -0,0 +1,32 @@
+# -*- encoding: utf-8 -*-
+
+require_relative '../../spec_helper'
+
+describe "MatchData#match_length" do
+  it "returns the length of the corresponding match when given an Integer" do
+    md = /(.)(.)(\d+)(\d)/.match("THX1138.")
+
+    md.match_length(0).should == 6
+    md.match_length(1).should == 1
+    md.match_length(2).should == 1
+    md.match_length(3).should == 3
+    md.match_length(4).should == 1
+  end
+
+  it "returns nil on non-matching index matches" do
+    md = /\d+(\w)?/.match("THX1138.")
+    md.match_length(1).should == nil
+  end
+
+  it "returns the length of the corresponding named match when given a Symbol" do
+    md = 'haystack'.match(/(?<t>t(?<a>ack))/)
+    md.match_length(:a).should == 3
+    md.match_length(:t).should == 4
+  end
+
+  it "returns nil on non-matching index matches" do
+    md = 'haystack'.match(/(?<t>t)(?<a>all)?/)
+    md.match_length(:t).should == 1
+    md.match_length(:a).should == nil
+  end
+end
diff --git a/spec/ruby/core/matchdata/match_spec.rb b/spec/ruby/core/matchdata/match_spec.rb
new file mode 100644
index 0000000000..a16914ea15
--- /dev/null
+++ b/spec/ruby/core/matchdata/match_spec.rb
@@ -0,0 +1,32 @@
+# -*- encoding: utf-8 -*-
+
+require_relative '../../spec_helper'
+
+describe "MatchData#match" do
+  it "returns the corresponding match when given an Integer" do
+    md = /(.)(.)(\d+)(\d)/.match("THX1138.")
+
+    md.match(0).should == 'HX1138'
+    md.match(1).should == 'H'
+    md.match(2).should == 'X'
+    md.match(3).should == '113'
+    md.match(4).should == '8'
+  end
+
+  it "returns nil on non-matching index matches" do
+    md = /\d+(\w)?/.match("THX1138.")
+    md.match(1).should == nil
+  end
+
+  it "returns the corresponding named match when given a Symbol" do
+    md = 'haystack'.match(/(?<t>t(?<a>ack))/)
+    md.match(:a).should == 'ack'
+    md.match(:t).should == 'tack'
+  end
+
+  it "returns nil on non-matching index matches" do
+    md = 'haystack'.match(/(?<t>t)(?<a>all)?/)
+    md.match(:t).should == 't'
+    md.match(:a).should == nil
+  end
+end
diff --git a/spec/ruby/core/matchdata/named_captures_spec.rb b/spec/ruby/core/matchdata/named_captures_spec.rb
index 9b1e324a24..5e4693d62d 100644
--- a/spec/ruby/core/matchdata/named_captures_spec.rb
+++ b/spec/ruby/core/matchdata/named_captures_spec.rb
@@ -12,4 +12,16 @@ describe 'MatchData#named_captures' do
   it 'returns the latest matched capture, even if a later one that does not match exists' do
     /\A(?<a>.)(?<b>.)(?<b>.)(?<a>.)?\z/.match('012').named_captures.should == { 'a' => '0', 'b' => '2' }
   end
+
+  ruby_version_is "3.3" do
+    it 'returns a Hash with Symbol keys when symbolize_names is provided a true value' do
+      /(?<a>.)(?<b>.)?/.match('0').named_captures(symbolize_names: true).should == { a: '0', b: nil }
+      /(?<a>.)(?<b>.)?/.match('0').named_captures(symbolize_names: "truly").should == { a: '0', b: nil }
+    end
+
+    it 'returns a Hash with String keys when symbolize_names is provided a false value' do
+      /(?<a>.)(?<b>.)?/.match('02').named_captures(symbolize_names: false).should == { 'a' => '0', 'b' => '2' }
+      /(?<a>.)(?<b>.)?/.match('02').named_captures(symbolize_names: nil).should == { 'a' => '0', 'b' => '2' }
+    end
+  end
 end
diff --git a/spec/ruby/core/matchdata/offset_spec.rb b/spec/ruby/core/matchdata/offset_spec.rb
index 1ccb54b7a7..a03d58aad1 100644
--- a/spec/ruby/core/matchdata/offset_spec.rb
+++ b/spec/ruby/core/matchdata/offset_spec.rb
@@ -1,30 +1,102 @@
-# -*- encoding: utf-8 -*-
-
 require_relative '../../spec_helper'
 
 describe "MatchData#offset" do
-  it "returns a two element array with the begin and end of the nth match" do
-    match_data = /(.)(.)(\d+)(\d)/.match("THX1138.")
-    match_data.offset(0).should == [1, 7]
-    match_data.offset(4).should == [6, 7]
+  it "returns beginning and ending character offset of whole matched substring for 0 element" do
+    m = /(.)(.)(\d+)(\d)/.match("THX1138.")
+    m.offset(0).should == [1, 7]
+  end
+
+  it "returns beginning and ending character offset of n-th match, all the subsequent elements are capturing groups" do
+    m = /(.)(.)(\d+)(\d)/.match("THX1138.")
+
+    m.offset(2).should == [2, 3]
+    m.offset(3).should == [3, 6]
+    m.offset(4).should == [6, 7]
+  end
+
+  it "accepts String as a reference to a named capture" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.offset("f").should == [0, 3]
+    m.offset("b").should == [3, 6]
+  end
+
+  it "accepts Symbol as a reference to a named capture" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    m.offset(:f).should == [0, 3]
+    m.offset(:b).should == [3, 6]
   end
 
-  it "returns [nil, nil] when the nth match isn't found" do
-    match_data = /something is( not)? (right)/.match("something is right")
-    match_data.offset(1).should == [nil, nil]
+  it "returns [nil, nil] if a capturing group is optional and doesn't match" do
+    m = /(?<x>q..)?/.match("foobarbaz")
+
+    m.offset("x").should == [nil, nil]
+    m.offset(1).should == [nil, nil]
   end
 
-  it "returns the offset for multi byte strings" do
-    match_data = /(.)(.)(\d+)(\d)/.match("TñX1138.")
-    match_data.offset(0).should == [1, 7]
-    match_data.offset(4).should == [6, 7]
+  it "returns correct beginning and ending character offset for multi-byte strings" do
+    m = /\A\u3042(.)(.)?(.)\z/.match("\u3042\u3043\u3044")
+
+    m.offset(1).should == [1, 2]
+    m.offset(3).should == [2, 3]
   end
 
   not_supported_on :opal do
-    it "returns the offset for multi byte strings with unicode regexp" do
-      match_data = /(.)(.)(\d+)(\d)/u.match("TñX1138.")
-      match_data.offset(0).should == [1, 7]
-      match_data.offset(4).should == [6, 7]
+    it "returns correct character offset for multi-byte strings with unicode regexp" do
+      m = /\A\u3042(.)(.)?(.)\z/u.match("\u3042\u3043\u3044")
+
+      m.offset(1).should == [1, 2]
+      m.offset(3).should == [2, 3]
     end
   end
+
+  it "returns [nil, nil] if a capturing group is optional and doesn't match for multi-byte string" do
+    m = /\A\u3042(.)(.)?(.)\z/.match("\u3042\u3043\u3044")
+
+    m.offset(2).should == [nil, nil]
+  end
+
+  it "converts argument into integer if is not String nor Symbol" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    obj = Object.new
+    def obj.to_int; 2; end
+
+    m.offset(1r).should == [0, 3]
+    m.offset(1.1).should == [0, 3]
+    m.offset(obj).should == [3, 6]
+  end
+
+  it "raises IndexError if there is no group with the provided name" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.offset("y")
+    }.should raise_error(IndexError, "undefined group name reference: y")
+
+    -> {
+      m.offset(:y)
+    }.should raise_error(IndexError, "undefined group name reference: y")
+  end
+
+  it "raises IndexError if index is out of bounds" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.offset(-1)
+    }.should raise_error(IndexError, "index -1 out of matches")
+
+    -> {
+      m.offset(3)
+    }.should raise_error(IndexError, "index 3 out of matches")
+  end
+
+  it "raises TypeError if can't convert argument into Integer" do
+    m = /(?<f>foo)(?<b>bar)/.match("foobar")
+
+    -> {
+      m.offset([])
+    }.should raise_error(TypeError, "no implicit conversion of Array into Integer")
+  end
 end
diff --git a/spec/ruby/core/matchdata/post_match_spec.rb b/spec/ruby/core/matchdata/post_match_spec.rb
index 6e13438124..7bfe6df119 100644
--- a/spec/ruby/core/matchdata/post_match_spec.rb
+++ b/spec/ruby/core/matchdata/post_match_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "MatchData#post_match" do
   it "returns the string after the match equiv. special var $'" do
@@ -6,29 +7,18 @@ describe "MatchData#post_match" do
     $'.should == ': The Movie'
   end
 
-  it "keeps taint status from the source string" do
-    str = "THX1138: The Movie"
-    str.taint
-    res = /(.)(.)(\d+)(\d)/.match(str).post_match
-    res.tainted?.should be_true
-    $'.tainted?.should be_true
-  end
-
-  it "keeps untrusted status from the source string" do
-    str = "THX1138: The Movie"
-    str.untrust
-    res = /(.)(.)(\d+)(\d)/.match(str).post_match
-    res.untrusted?.should be_true
-    $'.untrusted?.should be_true
-  end
-
   it "sets the encoding to the encoding of the source String" do
-    str = "abc".force_encoding Encoding::EUC_JP
+    str = "abc".dup.force_encoding Encoding::EUC_JP
     str.match(/b/).post_match.encoding.should equal(Encoding::EUC_JP)
   end
 
   it "sets an empty result to the encoding of the source String" do
-    str = "abc".force_encoding Encoding::ISO_8859_1
+    str = "abc".dup.force_encoding Encoding::ISO_8859_1
     str.match(/c/).post_match.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "returns an instance of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138: The Movie")
+    /(.)(.)(\d+)(\d)/.match(str).post_match.should be_an_instance_of(String)
+  end
 end
diff --git a/spec/ruby/core/matchdata/pre_match_spec.rb b/spec/ruby/core/matchdata/pre_match_spec.rb
index 816cc91eb2..2f1ba9b8f6 100644
--- a/spec/ruby/core/matchdata/pre_match_spec.rb
+++ b/spec/ruby/core/matchdata/pre_match_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "MatchData#pre_match" do
   it "returns the string before the match, equiv. special var $`" do
@@ -6,29 +7,18 @@ describe "MatchData#pre_match" do
     $`.should == 'T'
   end
 
-  it "keeps taint status from the source string" do
-    str = "THX1138: The Movie"
-    str.taint
-    res = /(.)(.)(\d+)(\d)/.match(str).pre_match
-    res.tainted?.should be_true
-    $`.tainted?.should be_true
-  end
-
-  it "keeps untrusted status from the source string" do
-    str = "THX1138: The Movie"
-    str.untrust
-    res = /(.)(.)(\d+)(\d)/.match(str).pre_match
-    res.untrusted?.should be_true
-    $`.untrusted?.should be_true
-  end
-
   it "sets the encoding to the encoding of the source String" do
-    str = "abc".force_encoding Encoding::EUC_JP
+    str = "abc".dup.force_encoding Encoding::EUC_JP
     str.match(/b/).pre_match.encoding.should equal(Encoding::EUC_JP)
   end
 
   it "sets an empty result to the encoding of the source String" do
-    str = "abc".force_encoding Encoding::ISO_8859_1
+    str = "abc".dup.force_encoding Encoding::ISO_8859_1
     str.match(/a/).pre_match.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "returns an instance of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138: The Movie")
+    /(.)(.)(\d+)(\d)/.match(str).pre_match.should be_an_instance_of(String)
+  end
 end
diff --git a/spec/ruby/core/matchdata/regexp_spec.rb b/spec/ruby/core/matchdata/regexp_spec.rb
index 05a8e80567..099b59c559 100644
--- a/spec/ruby/core/matchdata/regexp_spec.rb
+++ b/spec/ruby/core/matchdata/regexp_spec.rb
@@ -10,4 +10,15 @@ describe "MatchData#regexp" do
     m = 'haystack'.match(/hay/)
     m.regexp.should == /hay/
   end
+
+  it "returns the same Regexp used to match" do
+    r = /hay/
+    m = 'haystack'.match(r)
+    m.regexp.object_id.should == r.object_id
+  end
+
+  it "returns a Regexp for the result of gsub(String)" do
+    'he[[o'.gsub('[', ']')
+    $~.regexp.should == /\[/
+  end
 end
diff --git a/spec/ruby/core/matchdata/shared/captures.rb b/spec/ruby/core/matchdata/shared/captures.rb
new file mode 100644
index 0000000000..33f834561a
--- /dev/null
+++ b/spec/ruby/core/matchdata/shared/captures.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe :matchdata_captures, shared: true do
+  it "returns an array of the match captures" do
+    /(.)(.)(\d+)(\d)/.match("THX1138.").send(@method).should == ["H","X","113","8"]
+  end
+
+  it "returns instances of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138: The Movie")
+    /(.)(.)(\d+)(\d)/.match(str).send(@method).each { |c| c.should be_an_instance_of(String) }
+  end
+end
diff --git a/spec/ruby/core/matchdata/string_spec.rb b/spec/ruby/core/matchdata/string_spec.rb
index ff1b4eab5b..952e953318 100644
--- a/spec/ruby/core/matchdata/string_spec.rb
+++ b/spec/ruby/core/matchdata/string_spec.rb
@@ -9,6 +9,18 @@ describe "MatchData#string" do
   it "returns a frozen copy of the match string" do
     str = /(.)(.)(\d+)(\d)/.match("THX1138.").string
     str.should == "THX1138."
-    str.frozen?.should == true
+    str.should.frozen?
+  end
+
+  it "returns the same frozen string for every call" do
+    md = /(.)(.)(\d+)(\d)/.match("THX1138.")
+    md.string.should equal(md.string)
+  end
+
+  it "returns a frozen copy of the matched string for gsub!(String)" do
+    s = +'he[[o'
+    s.gsub!('[', ']')
+    $~.string.should == 'he[[o'
+    $~.string.should.frozen?
   end
 end
diff --git a/spec/ruby/core/matchdata/to_a_spec.rb b/spec/ruby/core/matchdata/to_a_spec.rb
index 6231d096fb..4fa11ff604 100644
--- a/spec/ruby/core/matchdata/to_a_spec.rb
+++ b/spec/ruby/core/matchdata/to_a_spec.rb
@@ -1,7 +1,13 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "MatchData#to_a" do
   it "returns an array of matches" do
     /(.)(.)(\d+)(\d)/.match("THX1138.").to_a.should == ["HX1138", "H", "X", "113", "8"]
   end
+
+  it "returns instances of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138.")
+    /(.)(.)(\d+)(\d)/.match(str)[0..-1].to_a.each { |m| m.should be_an_instance_of(String) }
+  end
 end
diff --git a/spec/ruby/core/matchdata/to_s_spec.rb b/spec/ruby/core/matchdata/to_s_spec.rb
index 9e213bb342..cd1c4dbca2 100644
--- a/spec/ruby/core/matchdata/to_s_spec.rb
+++ b/spec/ruby/core/matchdata/to_s_spec.rb
@@ -1,7 +1,13 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "MatchData#to_s" do
   it "returns the entire matched string" do
     /(.)(.)(\d+)(\d)/.match("THX1138.").to_s.should == "HX1138"
   end
+
+  it "returns an instance of String when given a String subclass" do
+    str = MatchDataSpecs::MyString.new("THX1138.")
+    /(.)(.)(\d+)(\d)/.match(str).to_s.should be_an_instance_of(String)
+  end
 end
diff --git a/spec/ruby/core/matchdata/values_at_spec.rb b/spec/ruby/core/matchdata/values_at_spec.rb
index 8f7fdf557c..535719a2ee 100644
--- a/spec/ruby/core/matchdata/values_at_spec.rb
+++ b/spec/ruby/core/matchdata/values_at_spec.rb
@@ -1,21 +1,76 @@
 require_relative '../../spec_helper'
 
 describe "MatchData#values_at" do
-  it "returns an array of the matching value" do
-    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+  # Should be synchronized with core/array/values_at_spec.rb and core/struct/values_at_spec.rb
+  #
+  # /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").to_a # => ["HX1138", "H", "X", "113", "8"]
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0, 2, -2).should == ["HX1138", "X", "113"]
+    end
+
+    it "returns nil value for any integer that is out of range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(5).should == [nil]
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6).should == [nil]
+    end
   end
 
-  describe "when passed a Range" do
-    it "returns an array of the matching value" do
-      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..4, 0..1).should == ["X", "113", "8", "HX1138", "H"]
+  context "when passed an integer Range" do
+    it "returns an array containing each value given by the elements of the range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "fills with nil values for range elements larger than the captured values number" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..5).should == ["HX1138", "H", "X", "113", "8", nil]
+    end
+
+    it "raises RangeError if any element of the range is negative and out of range" do
+      -> { /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(-6..3) }.should raise_error(RangeError, "-6..3 out of range")
+    end
+
+    it "supports endless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(0..).should == ["HX1138", "H", "X", "113", "8"]
+    end
+
+    it "supports beginningless Range" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(..2).should == ["HX1138", "H", "X"]
+    end
+
+    it "returns an empty Array when Range is empty" do
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(2..0).should == []
+    end
+  end
+
+  context "when passed names" do
+    it 'slices captures with the given names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+    end
+
+    it 'slices captures with the given String names' do
+      /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at('c', 'a').should == ['2', '0']
     end
   end
 
-  it 'slices captures with the given names' do
-    /(?<a>.)(?<b>.)(?<c>.)/.match('012').values_at(:c, :a).should == ['2', '0']
+  it "supports multiple integer Ranges" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 2..3).should == ["H", "X", "X", "113"]
   end
 
-  it 'takes names and indices' do
+  it "supports mixing integer Ranges and Integers" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(1..2, 4).should == ["H", "X", "8"]
+  end
+
+  it 'supports mixing of names and indices' do
     /\A(?<a>.)(?<b>.)\z/.match('01').values_at(0, 1, 2, :a, :b).should == ['01', '0', '1', '0', '1']
   end
+
+  it "returns a new empty Array if no arguments given" do
+    /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at().should == []
+  end
+
+  it "fails when passed arguments of unsupported types" do
+    -> {
+      /(.)(.)(\d+)(\d)/.match("THX1138: The Movie").values_at(Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+  end
 end
diff --git a/spec/ruby/core/math/atanh_spec.rb b/spec/ruby/core/math/atanh_spec.rb
index 21fb209941..edcb8f2e52 100644
--- a/spec/ruby/core/math/atanh_spec.rb
+++ b/spec/ruby/core/math/atanh_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../../spec_helper'
-require_relative '../../fixtures/math/common'
-require_relative '../../shared/math/atanh'
+require_relative 'fixtures/common'
+require_relative 'shared/atanh'
 
 describe "Math.atanh" do
   it_behaves_like :math_atanh_base, :atanh, Math
diff --git a/spec/ruby/core/math/cos_spec.rb b/spec/ruby/core/math/cos_spec.rb
index 3ba7a54c38..006afeb2cc 100644
--- a/spec/ruby/core/math/cos_spec.rb
+++ b/spec/ruby/core/math/cos_spec.rb
@@ -15,7 +15,6 @@ describe "Math.cos" do
     Math.cos(2*Math::PI).should be_close(1.0, TOLERANCE)
   end
 
-
   it "raises a TypeError unless the argument is Numeric and has #to_f" do
     -> { Math.cos("test") }.should raise_error(TypeError)
   end
@@ -24,14 +23,23 @@ describe "Math.cos" do
     Math.cos(nan_value).nan?.should be_true
   end
 
-  it "raises a TypeError if the argument is nil" do
-    -> { Math.cos(nil) }.should raise_error(TypeError)
-  end
-
-  it "coerces its argument with #to_f" do
-    f = mock_numeric('8.2')
-    f.should_receive(:to_f).and_return(8.2)
-    Math.cos(f).should == Math.cos(8.2)
+  describe "coerces its argument with #to_f" do
+    it "coerces its argument with #to_f" do
+      f = mock_numeric('8.2')
+      f.should_receive(:to_f).and_return(8.2)
+      Math.cos(f).should == Math.cos(8.2)
+    end
+
+    it "raises a TypeError if the given argument can't be converted to a Float" do
+      -> { Math.cos(nil) }.should raise_error(TypeError)
+      -> { Math.cos(:abc) }.should raise_error(TypeError)
+    end
+
+    it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to a Float" do
+      object = mock_numeric('mock-float')
+      object.should_receive(:to_f).and_raise(NoMethodError)
+      -> { Math.cos(object) }.should raise_error(NoMethodError)
+    end
   end
 end
 
diff --git a/spec/ruby/core/math/expm1_spec.rb b/spec/ruby/core/math/expm1_spec.rb
new file mode 100644
index 0000000000..5725319abb
--- /dev/null
+++ b/spec/ruby/core/math/expm1_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "4.0" do
+  describe "Math.expm1" do
+    it "calculates Math.exp(arg) - 1" do
+      Math.expm1(3).should == Math.exp(3) - 1
+    end
+
+    it "preserves precision that can be lost otherwise" do
+      Math.expm1(1.0e-16).should be_close(1.0e-16, TOLERANCE)
+      Math.expm1(1.0e-16).should != 0.0
+    end
+
+    it "raises a TypeError if the argument cannot be coerced with Float()" do
+      -> { Math.expm1("test") }.should raise_error(TypeError, "can't convert String into Float")
+    end
+
+    it "returns NaN given NaN" do
+      Math.expm1(nan_value).nan?.should be_true
+    end
+
+    it "raises a TypeError if the argument is nil" do
+      -> { Math.expm1(nil) }.should raise_error(TypeError, "can't convert nil into Float")
+    end
+
+    it "accepts any argument that can be coerced with Float()" do
+      Math.expm1(MathSpecs::Float.new).should be_close(Math::E - 1, TOLERANCE)
+    end
+  end
+
+  describe "Math#expm1" do
+    it "is accessible as a private instance method" do
+      IncludesMath.new.send(:expm1, 23.1415).should be_close(11226018483.0012, TOLERANCE)
+    end
+  end
+end
diff --git a/spec/ruby/fixtures/math/common.rb b/spec/ruby/core/math/fixtures/common.rb
index 024732fa7a..024732fa7a 100644
--- a/spec/ruby/fixtures/math/common.rb
+++ b/spec/ruby/core/math/fixtures/common.rb
diff --git a/spec/ruby/core/math/ldexp_spec.rb b/spec/ruby/core/math/ldexp_spec.rb
index fb7799cf26..6dcf94a663 100644
--- a/spec/ruby/core/math/ldexp_spec.rb
+++ b/spec/ruby/core/math/ldexp_spec.rb
@@ -45,6 +45,12 @@ describe "Math.ldexp" do
   it "accepts any second argument that can be coerced with Integer()" do
     Math.ldexp(3.23, MathSpecs::Integer.new).should be_close(12.92, TOLERANCE)
   end
+
+  it "returns correct value that closes to the max value of double type" do
+    Math.ldexp(0.5122058490966879, 1024).should == 9.207889385574391e+307
+    Math.ldexp(0.9999999999999999, 1024).should == 1.7976931348623157e+308
+    Math.ldexp(0.99999999999999999, 1024).should == Float::INFINITY
+  end
 end
 
 describe "Math#ldexp" do
diff --git a/spec/ruby/core/math/lgamma_spec.rb b/spec/ruby/core/math/lgamma_spec.rb
index 33e7836448..2bf350993e 100644
--- a/spec/ruby/core/math/lgamma_spec.rb
+++ b/spec/ruby/core/math/lgamma_spec.rb
@@ -5,10 +5,8 @@ describe "Math.lgamma" do
     Math.lgamma(0).should == [infinity_value, 1]
   end
 
-  platform_is_not :windows do
-    it "returns [Infinity, 1] when passed -1" do
-      Math.lgamma(-1).should == [infinity_value, 1]
-    end
+  it "returns [Infinity, ...] when passed -1" do
+    Math.lgamma(-1)[0].should == infinity_value
   end
 
   it "returns [Infinity, -1] when passed -0.0" do
@@ -47,8 +45,7 @@ describe "Math.lgamma" do
     Math.lgamma(infinity_value).should == [infinity_value, 1]
   end
 
-  it "returns [NaN, 1] when passed NaN" do
-    Math.lgamma(nan_value)[0].nan?.should be_true
-    Math.lgamma(nan_value)[1].should == 1
+  it "returns [NaN, ...] when passed NaN" do
+    Math.lgamma(nan_value)[0].should.nan?
   end
 end
diff --git a/spec/ruby/core/math/log1p_spec.rb b/spec/ruby/core/math/log1p_spec.rb
new file mode 100644
index 0000000000..216358a3c4
--- /dev/null
+++ b/spec/ruby/core/math/log1p_spec.rb
@@ -0,0 +1,49 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "4.0" do
+  describe "Math.log1p" do
+    it "calculates Math.log(1 + arg)" do
+      Math.log1p(3).should == Math.log(1 + 3)
+    end
+
+    it "preserves precision that can be lost otherwise" do
+      Math.log1p(1e-16).should be_close(1.0e-16, TOLERANCE)
+      Math.log1p(1e-16).should != 0.0
+    end
+
+    it "raises an Math::DomainError if the argument is less than 1" do
+      -> { Math.log1p(-1-1e-15) }.should raise_error(Math::DomainError, "Numerical argument is out of domain - log1p")
+    end
+
+    it "raises a TypeError if the argument cannot be coerced with Float()" do
+      -> { Math.log1p("test") }.should raise_error(TypeError, "can't convert String into Float")
+    end
+
+    it "raises a TypeError for numerical values passed as string" do
+      -> { Math.log1p("10") }.should raise_error(TypeError, "can't convert String into Float")
+    end
+
+    it "does not accept a second argument for the base" do
+      -> { Math.log1p(9, 3) }.should raise_error(ArgumentError, "wrong number of arguments (given 2, expected 1)")
+    end
+
+    it "returns NaN given NaN" do
+      Math.log1p(nan_value).nan?.should be_true
+    end
+
+    it "raises a TypeError if the argument is nil" do
+      -> { Math.log1p(nil) }.should raise_error(TypeError, "can't convert nil into Float")
+    end
+
+    it "accepts any argument that can be coerced with Float()" do
+      Math.log1p(MathSpecs::Float.new).should be_close(0.6931471805599453, TOLERANCE)
+    end
+  end
+
+  describe "Math#log1p" do
+    it "is accessible as a private instance method" do
+      IncludesMath.new.send(:log1p, 4.21).should be_close(1.65057985576528, TOLERANCE)
+    end
+  end
+end
diff --git a/spec/ruby/core/math/log2_spec.rb b/spec/ruby/core/math/log2_spec.rb
index 1594f2d7af..3d4d41d130 100644
--- a/spec/ruby/core/math/log2_spec.rb
+++ b/spec/ruby/core/math/log2_spec.rb
@@ -15,7 +15,7 @@ describe "Math.log2" do
     Math.log2((2**301+45677544234809571)).should == 301.0
   end
 
-  it "raises an Errno::EDOM if the argument is less than 0" do
+  it "raises Math::DomainError if the argument is less than 0" do
     -> { Math.log2(-1e-15) }.should raise_error( Math::DomainError)
   end
 
diff --git a/spec/ruby/shared/math/atanh.rb b/spec/ruby/core/math/shared/atanh.rb
index 3fb64153a0..3fb64153a0 100644
--- a/spec/ruby/shared/math/atanh.rb
+++ b/spec/ruby/core/math/shared/atanh.rb
diff --git a/spec/ruby/core/math/sqrt_spec.rb b/spec/ruby/core/math/sqrt_spec.rb
index 779aea2a0a..918e7c3a17 100644
--- a/spec/ruby/core/math/sqrt_spec.rb
+++ b/spec/ruby/core/math/sqrt_spec.rb
@@ -27,6 +27,10 @@ describe "Math.sqrt" do
   it "accepts any argument that can be coerced with Float()" do
     Math.sqrt(MathSpecs::Float.new).should be_close(1.0, TOLERANCE)
   end
+
+  it "raises a Math::DomainError when given a negative number" do
+    -> { Math.sqrt(-1) }.should raise_error(Math::DomainError)
+  end
 end
 
 describe "Math#sqrt" do
diff --git a/spec/ruby/core/math/tan_spec.rb b/spec/ruby/core/math/tan_spec.rb
index c7b188cd81..67307f1e6e 100644
--- a/spec/ruby/core/math/tan_spec.rb
+++ b/spec/ruby/core/math/tan_spec.rb
@@ -14,8 +14,8 @@ describe "Math.tan" do
   end
 
   it "returns NaN if called with +-Infinity" do
-    Math.tan(infinity_value).nan?.should == true
-    Math.tan(-infinity_value).nan?.should == true
+    Math.tan(infinity_value).should.nan?
+    Math.tan(-infinity_value).should.nan?
   end
 
   it "raises a TypeError if the argument cannot be coerced with Float()" do
diff --git a/spec/ruby/core/method/case_compare_spec.rb b/spec/ruby/core/method/case_compare_spec.rb
index 17785b5c1d..a78953e8ad 100644
--- a/spec/ruby/core/method/case_compare_spec.rb
+++ b/spec/ruby/core/method/case_compare_spec.rb
@@ -2,8 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/call'
 
-ruby_version_is "2.5" do
-  describe "Method#===" do
-    it_behaves_like :method_call, :===
-  end
+describe "Method#===" do
+  it_behaves_like :method_call, :===
 end
diff --git a/spec/ruby/core/method/clone_spec.rb b/spec/ruby/core/method/clone_spec.rb
index 3fe4000fb7..b0eb5751a9 100644
--- a/spec/ruby/core/method/clone_spec.rb
+++ b/spec/ruby/core/method/clone_spec.rb
@@ -1,14 +1,13 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
+require_relative 'shared/dup'
 
 describe "Method#clone" do
-  it "returns a copy of the method" do
-    m1 = MethodSpecs::Methods.new.method(:foo)
-    m2 = m1.clone
+  it_behaves_like :method_dup, :clone
 
-    m1.should == m2
-    m1.should_not equal(m2)
-
-    m1.call.should == m2.call
+  it "preserves frozen status" do
+    method = Object.new.method(:method)
+    method.freeze
+    method.frozen?.should == true
+    method.clone.frozen?.should == true
   end
 end
diff --git a/spec/ruby/core/method/compose_spec.rb b/spec/ruby/core/method/compose_spec.rb
index aa0aded775..7506e33ea8 100644
--- a/spec/ruby/core/method/compose_spec.rb
+++ b/spec/ruby/core/method/compose_spec.rb
@@ -2,100 +2,98 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative '../proc/shared/compose'
 
-ruby_version_is "2.6" do
-  describe "Method#<<" do
-    it "returns a Proc that is the composition of self and the passed Proc" do
-      succ = MethodSpecs::Composition.new.method(:succ)
-      upcase = proc { |s| s.upcase }
+describe "Method#<<" do
+  it "returns a Proc that is the composition of self and the passed Proc" do
+    succ = MethodSpecs::Composition.new.method(:succ)
+    upcase = proc { |s| s.upcase }
 
-      (succ << upcase).call('Ruby').should == "RUBZ"
-    end
+    (succ << upcase).call('Ruby').should == "RUBZ"
+  end
 
-    it "calls passed Proc with arguments and then calls self with result" do
-      pow_2_proc = proc { |x| x * x }
-      double_proc = proc { |x| x + x }
+  it "calls passed Proc with arguments and then calls self with result" do
+    pow_2_proc = proc { |x| x * x }
+    double_proc = proc { |x| x + x }
 
-      pow_2_method = MethodSpecs::Composition.new.method(:pow_2)
-      double_method = MethodSpecs::Composition.new.method(:double)
+    pow_2_method = MethodSpecs::Composition.new.method(:pow_2)
+    double_method = MethodSpecs::Composition.new.method(:double)
 
-      (pow_2_method << double_proc).call(2).should == 16
-      (double_method << pow_2_proc).call(2).should == 8
-    end
+    (pow_2_method << double_proc).call(2).should == 16
+    (double_method << pow_2_proc).call(2).should == 8
+  end
 
-    it "accepts any callable object" do
-      inc = MethodSpecs::Composition.new.method(:inc)
+  it "accepts any callable object" do
+    inc = MethodSpecs::Composition.new.method(:inc)
 
-      double = Object.new
-      def double.call(n); n * 2; end
+    double = Object.new
+    def double.call(n); n * 2; end
 
-      (inc << double).call(3).should == 7
-    end
+    (inc << double).call(3).should == 7
+  end
 
-    it_behaves_like :proc_compose, :<<, -> { MethodSpecs::Composition.new.method(:upcase) }
+  it_behaves_like :proc_compose, :<<, -> { MethodSpecs::Composition.new.method(:upcase) }
 
-    describe "composition" do
-      it "is a lambda" do
-        pow_2 = MethodSpecs::Composition.new.method(:pow_2)
-        double = proc { |x| x + x }
+  describe "composition" do
+    it "is a lambda" do
+      pow_2 = MethodSpecs::Composition.new.method(:pow_2)
+      double = proc { |x| x + x }
 
-        (pow_2 << double).is_a?(Proc).should == true
-        (pow_2 << double).lambda?.should == true
-      end
+      (pow_2 << double).is_a?(Proc).should == true
+      (pow_2 << double).should_not.lambda?
+    end
 
-      it "may accept multiple arguments" do
-        inc = MethodSpecs::Composition.new.method(:inc)
-        mul = proc { |n, m| n * m }
+    it "may accept multiple arguments" do
+      inc = MethodSpecs::Composition.new.method(:inc)
+      mul = proc { |n, m| n * m }
 
-        (inc << mul).call(2, 3).should == 7
-      end
+      (inc << mul).call(2, 3).should == 7
     end
   end
+end
 
-  describe "Method#>>" do
-    it "returns a Proc that is the composition of self and the passed Proc" do
-      upcase = proc { |s| s.upcase }
-      succ = MethodSpecs::Composition.new.method(:succ)
+describe "Method#>>" do
+  it "returns a Proc that is the composition of self and the passed Proc" do
+    upcase = proc { |s| s.upcase }
+    succ = MethodSpecs::Composition.new.method(:succ)
 
-      (succ >> upcase).call('Ruby').should == "RUBZ"
-    end
+    (succ >> upcase).call('Ruby').should == "RUBZ"
+  end
 
-    it "calls passed Proc with arguments and then calls self with result" do
-      pow_2_proc = proc { |x| x * x }
-      double_proc = proc { |x| x + x }
+  it "calls passed Proc with arguments and then calls self with result" do
+    pow_2_proc = proc { |x| x * x }
+    double_proc = proc { |x| x + x }
 
-      pow_2_method = MethodSpecs::Composition.new.method(:pow_2)
-      double_method = MethodSpecs::Composition.new.method(:double)
+    pow_2_method = MethodSpecs::Composition.new.method(:pow_2)
+    double_method = MethodSpecs::Composition.new.method(:double)
 
-      (pow_2_method >> double_proc).call(2).should == 8
-      (double_method >> pow_2_proc).call(2).should == 16
-    end
+    (pow_2_method >> double_proc).call(2).should == 8
+    (double_method >> pow_2_proc).call(2).should == 16
+  end
 
-    it "accepts any callable object" do
-      inc = MethodSpecs::Composition.new.method(:inc)
+  it "accepts any callable object" do
+    inc = MethodSpecs::Composition.new.method(:inc)
 
-      double = Object.new
-      def double.call(n); n * 2; end
+    double = Object.new
+    def double.call(n); n * 2; end
 
-      (inc >> double).call(3).should == 8
-    end
+    (inc >> double).call(3).should == 8
+  end
 
-    it_behaves_like :proc_compose, :>>, -> { MethodSpecs::Composition.new.method(:upcase) }
+  it_behaves_like :proc_compose, :>>, -> { MethodSpecs::Composition.new.method(:upcase) }
 
-    describe "composition" do
-      it "is a lambda" do
-        pow_2 = MethodSpecs::Composition.new.method(:pow_2)
-        double = proc { |x| x + x }
+  describe "composition" do
+    it "is a lambda" do
+      pow_2 = MethodSpecs::Composition.new.method(:pow_2)
+      double = proc { |x| x + x }
 
-        (pow_2 >> double).is_a?(Proc).should == true
-        (pow_2 >> double).lambda?.should == true
-      end
+      (pow_2 >> double).is_a?(Proc).should == true
+      (pow_2 >> double).should.lambda?
+    end
 
-      it "may accept multiple arguments" do
-        mul = MethodSpecs::Composition.new.method(:mul)
-        inc = proc { |n| n + 1 }
+    it "may accept multiple arguments" do
+      mul = MethodSpecs::Composition.new.method(:mul)
+      inc = proc { |n| n + 1 }
 
-        (mul >> inc).call(2, 3).should == 7
-      end
+      (mul >> inc).call(2, 3).should == 7
     end
   end
 end
diff --git a/spec/ruby/core/method/dup_spec.rb b/spec/ruby/core/method/dup_spec.rb
new file mode 100644
index 0000000000..e3e29d8a68
--- /dev/null
+++ b/spec/ruby/core/method/dup_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+require_relative 'shared/dup'
+
+describe "Method#dup" do
+  ruby_version_is "3.4" do
+    it_behaves_like :method_dup, :dup
+
+    it "resets frozen status" do
+      method = Object.new.method(:method)
+      method.freeze
+      method.frozen?.should == true
+      method.dup.frozen?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/method/fixtures/classes.rb b/spec/ruby/core/method/fixtures/classes.rb
index 315672c6e0..464a519aea 100644
--- a/spec/ruby/core/method/fixtures/classes.rb
+++ b/spec/ruby/core/method/fixtures/classes.rb
@@ -26,6 +26,7 @@ module MethodSpecs
     end
 
     alias bar foo
+    alias baz bar
 
     def same_as_foo
       true
@@ -49,6 +50,8 @@ module MethodSpecs
     def one_req(a); end
     def two_req(a, b); end
 
+    def one_req_named(a:); end
+
     def zero_with_block(&blk); end
     def one_req_with_block(a, &blk); end
     def two_req_with_block(a, b, &blk); end
@@ -58,6 +61,8 @@ module MethodSpecs
     def one_req_two_opt(a, b=nil, c=nil); end
     def two_req_one_opt(a, b, c=nil); end
 
+    def one_opt_named(a: nil); end
+
     def one_opt_with_block(a=nil, &blk); end
     def one_req_one_opt_with_block(a, b=nil, &blk); end
     def one_req_two_opt_with_block(a, b=nil, c=nil, &blk); end
@@ -70,6 +75,8 @@ module MethodSpecs
     def two_req_one_opt_with_splat(a, b, c=nil, *d); end
     def one_req_two_opt_with_splat(a, b=nil, c=nil, *d); end
 
+    def zero_with_double_splat(**a); end
+
     def zero_with_splat_and_block(*a, &blk); end
     def one_req_with_splat_and_block(a, *b, &blk); end
     def two_req_with_splat_and_block(a, b, *c, &blk); end
@@ -77,6 +84,12 @@ module MethodSpecs
     def two_req_one_opt_with_splat_and_block(a, b, c=nil, *d, &blk); end
     def one_req_two_opt_with_splat_and_block(a, b=nil, c=nil, *d, &blk); end
 
+    def my_public_method; end
+    def my_protected_method; end
+    def my_private_method; end
+    protected :my_protected_method
+    private :my_private_method
+
     define_method(:zero_defined_method, Proc.new {||})
     define_method(:zero_with_splat_defined_method, Proc.new {|*x|})
     define_method(:one_req_defined_method, Proc.new {|x|})
@@ -206,4 +219,28 @@ module MethodSpecs
       n * m
     end
   end
+
+  module InheritedMethods
+    module A
+      private
+      def derp(message)
+        'A'
+      end
+    end
+
+    module B
+      private
+      def derp
+        'B' + super('superclass')
+      end
+    end
+
+    class C
+      include A
+      include B
+
+      public :derp
+      alias_method :meow, :derp
+    end
+  end
 end
diff --git a/spec/ruby/core/method/original_name_spec.rb b/spec/ruby/core/method/original_name_spec.rb
new file mode 100644
index 0000000000..676fdaedb4
--- /dev/null
+++ b/spec/ruby/core/method/original_name_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Method#original_name" do
+  it "returns the name of the method" do
+    "abc".method(:upcase).original_name.should == :upcase
+  end
+
+  it "returns the original name when aliased" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:foo).original_name.should == :foo
+    obj.method(:bar).original_name.should == :foo
+    obj.method(:bar).unbind.bind(obj).original_name.should == :foo
+  end
+
+  it "returns the original name even when aliased twice" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:foo).original_name.should == :foo
+    obj.method(:baz).original_name.should == :foo
+    obj.method(:baz).unbind.bind(obj).original_name.should == :foo
+  end
+end
diff --git a/spec/ruby/core/method/owner_spec.rb b/spec/ruby/core/method/owner_spec.rb
index ca5dff7295..1cdc4edfa7 100644
--- a/spec/ruby/core/method/owner_spec.rb
+++ b/spec/ruby/core/method/owner_spec.rb
@@ -23,4 +23,8 @@ describe "Method#owner" do
       @m.method(:handled_via_method_missing).owner.should == MethodSpecs::Methods
     end
   end
+
+  it "returns the class on which public was called for a private method in ancestor" do
+    MethodSpecs::InheritedMethods::C.new.method(:derp).owner.should == MethodSpecs::InheritedMethods::C
+  end
 end
diff --git a/spec/ruby/core/method/parameters_spec.rb b/spec/ruby/core/method/parameters_spec.rb
index 3fdaf9ce6f..f1c2523cf0 100644
--- a/spec/ruby/core/method/parameters_spec.rb
+++ b/spec/ruby/core/method/parameters_spec.rb
@@ -7,6 +7,7 @@ describe "Method#parameters" do
     def one_keyrest(**a); end
 
     def one_keyreq(a:); end
+    def one_nokey(**nil); end
 
     def one_splat_one_req(*a,b); end
     def one_splat_two_req(*a,b,c); end
@@ -15,11 +16,16 @@ describe "Method#parameters" do
     def one_opt_with_stabby(a=-> b { true }); end
 
     def one_unnamed_splat(*); end
+    def one_unnamed_keyrest(**); end
 
     def one_splat_one_block(*args, &block)
       local_is_not_parameter = {}
     end
 
+    def forward_parameters(...) end
+
+    def underscore_parameters(_, _, _ = 1, *_, _:, _: 2, **_, &_); end
+
     define_method(:one_optional_defined_method) {|x = 1|}
   end
 
@@ -176,6 +182,11 @@ describe "Method#parameters" do
     m.parameters.should == [[:keyreq,:a]]
   end
 
+  it "returns [[:nokey]] for a method with a single **nil parameter" do
+    m = MethodSpecs::Methods.instance_method(:one_nokey)
+    m.parameters.should == [[:nokey]]
+  end
+
   it "works with ->(){} as the value of an optional argument" do
     m = MethodSpecs::Methods.instance_method(:one_opt_with_stabby)
     m.parameters.should == [[:opt,:a]]
@@ -222,9 +233,27 @@ describe "Method#parameters" do
     m.method(:handled_via_method_missing).parameters.should == [[:rest]]
   end
 
-  it "adds nameless rest arg for \"star\" argument" do
+  it "adds rest arg with name * for \"star\" argument" do
+    m = MethodSpecs::Methods.new
+    m.method(:one_unnamed_splat).parameters.should == [[:rest, :*]]
+  end
+
+  it "adds keyrest arg with ** as a name for \"double star\" argument" do
+    m = MethodSpecs::Methods.new
+    m.method(:one_unnamed_keyrest).parameters.should == [[:keyrest, :**]]
+  end
+
+  it "adds block arg with name & for anonymous block argument" do
+    object = Object.new
+    def object.foo(&)
+    end
+
+    object.method(:foo).parameters.should == [[:block, :&]]
+  end
+
+  it "returns [:rest, :*], [:keyrest, :**], [:block, :&] for forward parameters operator" do
     m = MethodSpecs::Methods.new
-    m.method(:one_unnamed_splat).parameters.should == [[:rest]]
+    m.method(:forward_parameters).parameters.should == [[:rest, :*], [:keyrest, :**], [:block, :&]]
   end
 
   it "returns the args and block for a splat and block argument" do
@@ -242,6 +271,20 @@ describe "Method#parameters" do
     m.method(:writer=).parameters.should == [[:req]]
   end
 
+  it "returns all parameters defined with the name _ as _" do
+    m = MethodSpecs::Methods.instance_method(:underscore_parameters)
+    m.parameters.should == [
+      [:req, :_],
+      [:req, :_],
+      [:opt, :_],
+      [:rest, :_],
+      [:keyreq, :_],
+      [:key, :_],
+      [:keyrest, :_],
+      [:block, :_]
+    ]
+  end
+
   it "returns [[:rest]] for core methods with variable-length argument lists" do
     # delete! takes rest args
     "foo".method(:delete!).parameters.should == [[:rest]]
diff --git a/spec/ruby/core/method/private_spec.rb b/spec/ruby/core/method/private_spec.rb
new file mode 100644
index 0000000000..e708542b2e
--- /dev/null
+++ b/spec/ruby/core/method/private_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Method#private?" do
+  it "has been removed" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:my_private_method).should_not.respond_to?(:private?)
+  end
+end
diff --git a/spec/ruby/core/method/protected_spec.rb b/spec/ruby/core/method/protected_spec.rb
new file mode 100644
index 0000000000..f9e422ae3d
--- /dev/null
+++ b/spec/ruby/core/method/protected_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Method#protected?" do
+  it "has been removed" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:my_protected_method).should_not.respond_to?(:protected?)
+  end
+end
diff --git a/spec/ruby/core/method/public_spec.rb b/spec/ruby/core/method/public_spec.rb
new file mode 100644
index 0000000000..4cb23f4cf1
--- /dev/null
+++ b/spec/ruby/core/method/public_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Method#public?" do
+  it "has been removed" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:my_public_method).should_not.respond_to?(:public?)
+  end
+end
diff --git a/spec/ruby/core/method/shared/dup.rb b/spec/ruby/core/method/shared/dup.rb
new file mode 100644
index 0000000000..c74847083f
--- /dev/null
+++ b/spec/ruby/core/method/shared/dup.rb
@@ -0,0 +1,32 @@
+describe :method_dup, shared: true do
+  it "returns a copy of self" do
+    a = Object.new.method(:method)
+    b = a.send(@method)
+
+    a.should == b
+    a.should_not equal(b)
+  end
+
+  ruby_version_is "3.4" do
+    it "copies instance variables" do
+      method = Object.new.method(:method)
+      method.instance_variable_set(:@ivar, 1)
+      cl = method.send(@method)
+      cl.instance_variables.should == [:@ivar]
+    end
+
+    it "copies the finalizer" do
+      code = <<-'RUBY'
+        obj = Object.new.method(:method)
+
+        ObjectSpace.define_finalizer(obj, Proc.new { STDOUT.write "finalized\n" })
+
+        obj.clone
+
+        exit 0
+      RUBY
+
+      ruby_exe(code).lines.sort.should == ["finalized\n", "finalized\n"]
+    end
+  end
+end
diff --git a/spec/ruby/core/method/shared/to_s.rb b/spec/ruby/core/method/shared/to_s.rb
index 373398a785..b2d27d370f 100644
--- a/spec/ruby/core/method/shared/to_s.rb
+++ b/spec/ruby/core/method/shared/to_s.rb
@@ -4,7 +4,7 @@ require_relative '../fixtures/classes'
 describe :method_to_s, shared: true do
   before :each do
     @m = MethodSpecs::MySub.new.method :bar
-    @string = @m.send(@method).sub(/0x\w+/, '0xXXXXXX')
+    @string = @m.send(@method)
   end
 
   it "returns a String" do
@@ -24,6 +24,19 @@ describe :method_to_s, shared: true do
     @string.should =~ /\#bar/
   end
 
+  it "returns a String containing method arguments" do
+    obj = MethodSpecs::Methods.new
+    obj.method(:zero).send(@method).should.include?("()")
+    obj.method(:one_req).send(@method).should.include?("(a)")
+    obj.method(:one_req_named).send(@method).should.include?("(a:)")
+    obj.method(:zero_with_block).send(@method).should.include?("(&blk)")
+    obj.method(:one_opt).send(@method).should.include?("(a=...)")
+    obj.method(:one_opt_named).send(@method).should.include?("(a: ...)")
+    obj.method(:zero_with_splat).send(@method).should.include?("(*a)")
+    obj.method(:zero_with_double_splat).send(@method).should.include?("(**a)")
+    obj.method(:one_req_one_opt_with_splat_and_block).send(@method).should.include?("(a, b=..., *c, &blk)")
+  end
+
   it "returns a String containing the Module the method is defined in" do
     @string.should =~ /MethodSpecs::MyMod/
   end
@@ -31,4 +44,38 @@ describe :method_to_s, shared: true do
   it "returns a String containing the Module the method is referenced from" do
     @string.should =~ /MethodSpecs::MySub/
   end
+
+  it "returns a String including all details" do
+    @string.should.start_with? "#<Method: MethodSpecs::MySub(MethodSpecs::MyMod)#bar"
+  end
+
+  it "does not show the defining module if it is the same as the receiver class" do
+    MethodSpecs::A.new.method(:baz).send(@method).should.start_with? "#<Method: MethodSpecs::A#baz"
+  end
+
+  it "returns a String containing the Module containing the method if object has a singleton class but method is not defined in the singleton class" do
+    obj = MethodSpecs::MySub.new
+    obj.singleton_class
+    @m = obj.method(:bar)
+    @string = @m.send(@method)
+    @string.should.start_with? "#<Method: MethodSpecs::MySub(MethodSpecs::MyMod)#bar"
+
+    c = MethodSpecs::MySub.dup
+    m = Module.new{def bar; end}
+    c.extend(m)
+    @string = c.method(:bar).send(@method)
+    @string.should.start_with? "#<Method: #<Class:#{c.inspect}>(#{m.inspect})#bar"
+  end
+
+  it "returns a String containing the singleton class if method is defined in the singleton class" do
+    obj = MethodSpecs::MySub.new
+    def obj.bar; end
+    @m = obj.method(:bar)
+    @string = @m.send(@method).sub(/0x\h+/, '0xXXXXXX')
+    @string.should.start_with? "#<Method: #<MethodSpecs::MySub:0xXXXXXX>.bar"
+  end
+
+  it "shows the metaclass and the owner for a Module instance method retrieved from a class" do
+    String.method(:include).inspect.should.start_with?("#<Method: #<Class:String>(Module)#include")
+  end
 end
diff --git a/spec/ruby/core/method/source_location_spec.rb b/spec/ruby/core/method/source_location_spec.rb
index dd81b02c77..87413a2ab6 100644
--- a/spec/ruby/core/method/source_location_spec.rb
+++ b/spec/ruby/core/method/source_location_spec.rb
@@ -11,23 +11,23 @@ describe "Method#source_location" do
   end
 
   it "sets the first value to the path of the file in which the method was defined" do
-    file = @method.source_location.first
+    file = @method.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/classes.rb', __FILE__)
+    file.should == File.realpath('fixtures/classes.rb', __dir__)
   end
 
-  it "sets the last value to a Fixnum representing the line on which the method was defined" do
-    line = @method.source_location.last
-    line.should be_an_instance_of(Fixnum)
+  it "sets the last value to an Integer representing the line on which the method was defined" do
+    line = @method.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 5
   end
 
   it "returns the last place the method was defined" do
-    MethodSpecs::SourceLocation.method(:redefined).source_location.last.should == 13
+    MethodSpecs::SourceLocation.method(:redefined).source_location[1].should == 13
   end
 
   it "returns the location of the original method even if it was aliased" do
-    MethodSpecs::SourceLocation.new.method(:aka).source_location.last.should == 17
+    MethodSpecs::SourceLocation.new.method(:aka).source_location[1].should == 17
   end
 
   it "works for methods defined with a block" do
@@ -86,6 +86,37 @@ describe "Method#source_location" do
     method.source_location[1].should == line
   end
 
+  it "works for core methods where it returns nil or <internal:" do
+    loc = method(:__id__).source_location
+    if loc == nil
+      loc.should == nil
+    else
+      loc[0].should.start_with?('<internal:')
+      loc[1].should be_kind_of(Integer)
+    end
+
+    loc = method(:tap).source_location
+    if loc == nil
+      loc.should == nil
+    else
+      loc[0].should.start_with?('<internal:')
+      loc[1].should be_kind_of(Integer)
+    end
+  end
+
+  it "works for eval with a given line" do
+    c = Class.new do
+      eval('def self.m; end', nil, "foo", 100)
+    end
+    location = c.method(:m).source_location
+    ruby_version_is(""..."4.1") do
+      location.should == ["foo", 100]
+    end
+    ruby_version_is("4.1") do
+      location.should == ["foo", 100, 0, 100, 15]
+    end
+  end
+
   describe "for a Method generated by respond_to_missing?" do
     it "returns nil" do
       m = MethodSpecs::Methods.new
diff --git a/spec/ruby/core/method/super_method_spec.rb b/spec/ruby/core/method/super_method_spec.rb
index e5d8b87a06..c63a7aaa0f 100644
--- a/spec/ruby/core/method/super_method_spec.rb
+++ b/spec/ruby/core/method/super_method_spec.rb
@@ -42,4 +42,23 @@ describe "Method#super_method" do
 
     method.super_method.should == nil
   end
+
+  # https://github.com/jruby/jruby/issues/7240
+  context "after changing an inherited methods visibility" do
+    it "calls the proper super method" do
+      MethodSpecs::InheritedMethods::C.new.derp.should == 'BA'
+    end
+
+    it "returns the expected super_method" do
+      method = MethodSpecs::InheritedMethods::C.new.method(:derp)
+      method.super_method.owner.should == MethodSpecs::InheritedMethods::A
+    end
+  end
+
+  context "after aliasing an inherited method" do
+    it "returns the expected super_method" do
+      method = MethodSpecs::InheritedMethods::C.new.method(:meow)
+      method.super_method.owner.should == MethodSpecs::InheritedMethods::A
+    end
+  end
 end
diff --git a/spec/ruby/core/method/to_proc_spec.rb b/spec/ruby/core/method/to_proc_spec.rb
index 29b7bec2b3..4993cce239 100644
--- a/spec/ruby/core/method/to_proc_spec.rb
+++ b/spec/ruby/core/method/to_proc_spec.rb
@@ -35,7 +35,7 @@ describe "Method#to_proc" do
   end
 
   it "returns a proc that can be used by define_method" do
-    x = 'test'
+    x = +'test'
     to_s = class << x
       define_method :foo, method(:to_s).to_proc
       to_s
diff --git a/spec/ruby/core/method/unbind_spec.rb b/spec/ruby/core/method/unbind_spec.rb
index 3d36c6d675..0b630e4d88 100644
--- a/spec/ruby/core/method/unbind_spec.rb
+++ b/spec/ruby/core/method/unbind_spec.rb
@@ -14,20 +14,29 @@ describe "Method#unbind" do
     @normal_um.should be_kind_of(UnboundMethod)
   end
 
-  it "returns a String containing 'UnboundMethod'" do
-    @string.should =~ /\bUnboundMethod\b/
-  end
+  describe "#inspect" do
+    it "returns a String containing 'UnboundMethod'" do
+      @string.should =~ /\bUnboundMethod\b/
+    end
 
-  it "returns a String containing the method name" do
-    @string.should =~ /\#bar/
-  end
+    it "returns a String containing the method name" do
+      @string.should =~ /\#bar/
+    end
+
+    it "returns a String containing the Module the method is defined in" do
+      @string.should =~ /MethodSpecs::MyMod/
+    end
 
-  it "returns a String containing the Module the method is defined in" do
-    @string.should =~ /MethodSpecs::MyMod/
+    it "returns a String containing the Module the method is referenced from" do
+      @string.should =~ /MethodSpecs::MyMod/
+    end
   end
 
-  it "returns a String containing the Module the method is referenced from" do
-    @string.should =~ /MethodSpecs::MySub/
+  it "keeps the origin singleton class if there is one" do
+    obj = Object.new
+    def obj.foo
+    end
+    obj.method(:foo).unbind.inspect.should.start_with?("#<UnboundMethod: #{obj.singleton_class}#foo")
   end
 
   specify "rebinding UnboundMethod to Method's obj produces exactly equivalent Methods" do
diff --git a/spec/ruby/core/module/alias_method_spec.rb b/spec/ruby/core/module/alias_method_spec.rb
index b14f5430a8..c36dedd2d8 100644
--- a/spec/ruby/core/module/alias_method_spec.rb
+++ b/spec/ruby/core/module/alias_method_spec.rb
@@ -14,7 +14,7 @@ describe "Module#alias_method" do
     @object.double(12).should == @object.public_two(12)
   end
 
-  it "creates methods that are == to eachother" do
+  it "creates methods that are == to each other" do
     @class.make_alias :uno, :public_one
     @object.method(:uno).should == @object.method(:public_one)
   end
@@ -42,6 +42,18 @@ describe "Module#alias_method" do
     @object.was_private_one.should == 1
   end
 
+  it "handles aliasing a method only present in a refinement" do
+    c = @class
+    Module.new do
+      refine c do
+        def uno_refined_method
+        end
+        alias_method :double_refined_method, :uno_refined_method
+        instance_method(:uno_refined_method).should == instance_method(:double_refined_method)
+      end
+    end
+  end
+
   it "fails if origin method not found" do
     -> { @class.make_alias :ni, :san }.should raise_error(NameError) { |e|
       # a NameError and not a NoMethodError
@@ -49,9 +61,9 @@ describe "Module#alias_method" do
     }
   end
 
-  it "raises #{frozen_error_class} if frozen" do
+  it "raises FrozenError if frozen" do
     @class.freeze
-    -> { @class.make_alias :uno, :public_one }.should raise_error(frozen_error_class)
+    -> { @class.make_alias :uno, :public_one }.should raise_error(FrozenError)
   end
 
   it "converts the names using #to_str" do
@@ -69,19 +81,21 @@ describe "Module#alias_method" do
     -> { @class.make_alias mock('x'), :public_one }.should raise_error(TypeError)
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      -> { @class.alias_method :ichi, :public_one }.should raise_error(NoMethodError)
-    end
+  it "raises a NoMethodError if the given name raises a NoMethodError during type coercion using to_str" do
+    obj = mock("mock-name")
+    obj.should_receive(:to_str).and_raise(NoMethodError)
+    -> { @class.make_alias obj, :public_one }.should raise_error(NoMethodError)
   end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:alias_method, false)
-    end
+
+  it "is a public method" do
+    Module.should have_public_instance_method(:alias_method, false)
   end
 
-  it "returns self" do
-    @class.send(:alias_method, :checking_return_value, :public_one).should equal(@class)
+  describe "returned value" do
+    it "returns symbol of the defined method name" do
+      @class.send(:alias_method, :checking_return_value, :public_one).should equal(:checking_return_value)
+      @class.send(:alias_method, 'checking_return_value', :public_one).should equal(:checking_return_value)
+    end
   end
 
   it "works in module" do
diff --git a/spec/ruby/core/module/allocate_spec.rb b/spec/ruby/core/module/allocate_spec.rb
deleted file mode 100644
index 3b2c4119c3..0000000000
--- a/spec/ruby/core/module/allocate_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Module.allocate" do
-  it "returns an instance of Module" do
-    mod = Module.allocate
-    mod.should be_an_instance_of(Module)
-  end
-
-  it "returns a fully-formed instance of Module" do
-    mod = Module.allocate
-    mod.constants.should_not == nil
-    mod.methods.should_not == nil
-  end
-end
diff --git a/spec/ruby/core/module/ancestors_spec.rb b/spec/ruby/core/module/ancestors_spec.rb
index 5e4c196206..90c26941d1 100644
--- a/spec/ruby/core/module/ancestors_spec.rb
+++ b/spec/ruby/core/module/ancestors_spec.rb
@@ -7,10 +7,17 @@ describe "Module#ancestors" do
     ModuleSpecs.ancestors.should == [ModuleSpecs]
     ModuleSpecs::Basic.ancestors.should == [ModuleSpecs::Basic]
     ModuleSpecs::Super.ancestors.should == [ModuleSpecs::Super, ModuleSpecs::Basic]
-    ModuleSpecs.without_test_modules(ModuleSpecs::Parent.ancestors).should ==
-      [ModuleSpecs::Parent, Object, Kernel, BasicObject]
-    ModuleSpecs.without_test_modules(ModuleSpecs::Child.ancestors).should ==
-      [ModuleSpecs::Child, ModuleSpecs::Super, ModuleSpecs::Basic, ModuleSpecs::Parent, Object, Kernel, BasicObject]
+    if defined?(Ruby::Box) && Ruby::Box.enabled?
+      ModuleSpecs.without_test_modules(ModuleSpecs::Parent.ancestors).should ==
+        [ModuleSpecs::Parent, Object, Ruby::Box::Loader, Kernel, BasicObject]
+      ModuleSpecs.without_test_modules(ModuleSpecs::Child.ancestors).should ==
+        [ModuleSpecs::Child, ModuleSpecs::Super, ModuleSpecs::Basic, ModuleSpecs::Parent, Object, Ruby::Box::Loader, Kernel, BasicObject]
+    else
+      ModuleSpecs.without_test_modules(ModuleSpecs::Parent.ancestors).should ==
+        [ModuleSpecs::Parent, Object, Kernel, BasicObject]
+      ModuleSpecs.without_test_modules(ModuleSpecs::Child.ancestors).should ==
+        [ModuleSpecs::Child, ModuleSpecs::Super, ModuleSpecs::Basic, ModuleSpecs::Parent, Object, Kernel, BasicObject]
+    end
   end
 
   it "returns only modules and classes" do
@@ -21,6 +28,17 @@ describe "Module#ancestors" do
     ModuleSpecs::Parent.ancestors.should == ModuleSpecs::Parent.ancestors.uniq
   end
 
+  it "returns a module that is included later into a nested module as well" do
+    m1 = Module.new
+    m2 = Module.new
+    m3 = Module.new do
+      include m2
+    end
+    m2.include m1 # should be after m3 includes m2
+
+    m3.ancestors.should == [m3, m2, m1]
+  end
+
   describe "when called on a singleton class" do
     it "includes the singleton classes of ancestors" do
       parent  = Class.new
diff --git a/spec/ruby/core/module/append_features_spec.rb b/spec/ruby/core/module/append_features_spec.rb
index 584aa11dfa..1724cde5d6 100644
--- a/spec/ruby/core/module/append_features_spec.rb
+++ b/spec/ruby/core/module/append_features_spec.rb
@@ -47,26 +47,14 @@ describe "Module#append_features" do
 
   end
 
-  it "copies own tainted status to the given module" do
-    other = Module.new
-    Module.new.taint.send :append_features, other
-    other.tainted?.should be_true
-  end
-
-  it "copies own untrusted status to the given module" do
-    other = Module.new
-    Module.new.untrust.send :append_features, other
-    other.untrusted?.should be_true
-  end
-
   describe "when other is frozen" do
     before :each do
       @receiver = Module.new
       @other = Module.new.freeze
     end
 
-    it "raises a #{frozen_error_class} before appending self" do
-      -> { @receiver.send(:append_features, @other) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError before appending self" do
+      -> { @receiver.send(:append_features, @other) }.should raise_error(FrozenError)
       @other.ancestors.should_not include(@receiver)
     end
   end
diff --git a/spec/ruby/core/module/attr_accessor_spec.rb b/spec/ruby/core/module/attr_accessor_spec.rb
index ce95ccd487..503dccc61e 100644
--- a/spec/ruby/core/module/attr_accessor_spec.rb
+++ b/spec/ruby/core/module/attr_accessor_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/attr_added'
 
 describe "Module#attr_accessor" do
   it "creates a getter and setter for each given attribute name" do
@@ -33,10 +34,23 @@ describe "Module#attr_accessor" do
       attr_accessor :spec_attr_accessor
     end
 
-    -> { true.spec_attr_accessor = "a" }.should raise_error(RuntimeError)
+    -> { true.spec_attr_accessor = "a" }.should raise_error(FrozenError)
   end
 
-  it "converts non string/symbol/fixnum names to strings using to_str" do
+  it "raises FrozenError if the receiver if frozen" do
+    c = Class.new do
+      attr_accessor :foo
+    end
+    obj = c.new
+    obj.foo = 1
+    obj.foo.should == 1
+
+    obj.freeze
+    -> { obj.foo = 42 }.should raise_error(FrozenError)
+    obj.foo.should == 1
+  end
+
+  it "converts non string/symbol names to strings using to_str" do
     (o = mock('test')).should_receive(:to_str).any_number_of_times.and_return("test")
     c = Class.new do
       attr_accessor o
@@ -63,30 +77,29 @@ describe "Module#attr_accessor" do
     -> { c.new.foo=1 }.should raise_error(NoMethodError)
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:attr_accessor, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:attr_accessor, false)
   end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:attr_accessor, false)
+
+  it "returns an array of defined method names as symbols" do
+    Class.new do
+      (attr_accessor :foo, 'bar').should == [:foo, :foo=, :bar, :bar=]
     end
   end
 
   describe "on immediates" do
     before :each do
-      class Fixnum
+      class Integer
         attr_accessor :foobar
       end
     end
 
     after :each do
-      if Fixnum.method_defined?(:foobar)
-        Fixnum.send(:remove_method, :foobar)
+      if Integer.method_defined?(:foobar)
+        Integer.send(:remove_method, :foobar)
       end
-      if Fixnum.method_defined?(:foobar=)
-        Fixnum.send(:remove_method, :foobar=)
+      if Integer.method_defined?(:foobar=)
+        Integer.send(:remove_method, :foobar=)
       end
     end
 
@@ -94,4 +107,6 @@ describe "Module#attr_accessor" do
       1.foobar.should be_nil
     end
   end
+
+  it_behaves_like :module_attr_added, :attr_accessor
 end
diff --git a/spec/ruby/core/module/attr_reader_spec.rb b/spec/ruby/core/module/attr_reader_spec.rb
index 082bc03b60..37fd537ff5 100644
--- a/spec/ruby/core/module/attr_reader_spec.rb
+++ b/spec/ruby/core/module/attr_reader_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/attr_added'
 
 describe "Module#attr_reader" do
   it "creates a getter for each given attribute name" do
@@ -32,7 +33,7 @@ describe "Module#attr_reader" do
     -> { true.instance_variable_set("@spec_attr_reader", "a") }.should raise_error(RuntimeError)
   end
 
-  it "converts non string/symbol/fixnum names to strings using to_str" do
+  it "converts non string/symbol names to strings using to_str" do
     (o = mock('test')).should_receive(:to_str).any_number_of_times.and_return("test")
     c = Class.new do
       attr_reader o
@@ -58,14 +59,15 @@ describe "Module#attr_reader" do
     -> { c.new.foo }.should raise_error(NoMethodError)
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:attr_reader, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:attr_reader, false)
   end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:attr_reader, false)
+
+  it "returns an array of defined method names as symbols" do
+    Class.new do
+      (attr_reader :foo, 'bar').should == [:foo, :bar]
     end
   end
+
+  it_behaves_like :module_attr_added, :attr_reader
 end
diff --git a/spec/ruby/core/module/attr_spec.rb b/spec/ruby/core/module/attr_spec.rb
index 20316a3d39..2f9f4e26dc 100644
--- a/spec/ruby/core/module/attr_spec.rb
+++ b/spec/ruby/core/module/attr_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/attr_added'
 
 describe "Module#attr" do
   before :each do
@@ -124,7 +125,7 @@ describe "Module#attr" do
     -> { c.new.bar }.should raise_error(NoMethodError)
   end
 
-  it "converts non string/symbol/fixnum names to strings using to_str" do
+  it "converts non string/symbol names to strings using to_str" do
     (o = mock('test')).should_receive(:to_str).any_number_of_times.and_return("test")
     Class.new { attr o }.new.respond_to?("test").should == true
   end
@@ -142,14 +143,17 @@ describe "Module#attr" do
     }.should complain(/boolean argument is obsoleted/, verbose: true)
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:attr, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:attr, false)
   end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:attr, false)
+
+  it "returns an array of defined method names as symbols" do
+    Class.new do
+      (attr :foo, 'bar').should == [:foo, :bar]
+      (attr :baz, false).should == [:baz]
+      (attr :qux, true).should == [:qux, :qux=]
     end
   end
+
+  it_behaves_like :module_attr_added, :attr
 end
diff --git a/spec/ruby/core/module/attr_writer_spec.rb b/spec/ruby/core/module/attr_writer_spec.rb
index 3b110cecf7..5b863ef88c 100644
--- a/spec/ruby/core/module/attr_writer_spec.rb
+++ b/spec/ruby/core/module/attr_writer_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/attr_added'
 
 describe "Module#attr_writer" do
   it "creates a setter for each given attribute name" do
@@ -29,10 +30,20 @@ describe "Module#attr_writer" do
       attr_writer :spec_attr_writer
     end
 
-    -> { true.spec_attr_writer = "a" }.should raise_error(RuntimeError)
+    -> { true.spec_attr_writer = "a" }.should raise_error(FrozenError)
   end
 
-  it "converts non string/symbol/fixnum names to strings using to_str" do
+  it "raises FrozenError if the receiver if frozen" do
+    c = Class.new do
+      attr_writer :foo
+    end
+    obj = c.new
+    obj.freeze
+
+    -> { obj.foo = 42 }.should raise_error(FrozenError)
+  end
+
+  it "converts non string/symbol names to strings using to_str" do
     (o = mock('test')).should_receive(:to_str).any_number_of_times.and_return("test")
     c = Class.new do
       attr_writer o
@@ -58,14 +69,15 @@ describe "Module#attr_writer" do
     -> { c.new.foo=1 }.should raise_error(NoMethodError)
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:attr_writer, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:attr_writer, false)
   end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:attr_writer, false)
+
+  it "returns an array of defined method names as symbols" do
+    Class.new do
+      (attr_writer :foo, 'bar').should == [:foo=, :bar=]
     end
   end
+
+  it_behaves_like :module_attr_added, :attr_writer
 end
diff --git a/spec/ruby/core/module/autoload_spec.rb b/spec/ruby/core/module/autoload_spec.rb
index df434e8e60..625d945686 100644
--- a/spec/ruby/core/module/autoload_spec.rb
+++ b/spec/ruby/core/module/autoload_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../../spec_helper'
+require_relative '../../fixtures/code_loading'
 require_relative 'fixtures/classes'
-require 'thread'
 
 describe "Module#autoload?" do
   it "returns the name of the file that will be autoloaded" do
@@ -17,30 +17,21 @@ describe "Module#autoload?" do
     ModuleSpecs::Autoload::Child.autoload?(:AnotherAutoload).should == "another_autoload.rb"
   end
 
-  ruby_version_is "2.7" do
-    it "returns nil if an ancestor defined that autoload but recursion is disabled" do
-      ModuleSpecs::Autoload::Parent.autoload :InheritedAutoload, "inherited_autoload.rb"
-      ModuleSpecs::Autoload::Child.autoload?(:InheritedAutoload, false).should be_nil
-    end
+  it "returns nil if an ancestor defined that autoload but recursion is disabled" do
+    ModuleSpecs::Autoload::Parent.autoload :InheritedAutoload, "inherited_autoload.rb"
+    ModuleSpecs::Autoload::Child.autoload?(:InheritedAutoload, false).should be_nil
+  end
 
-    it "returns the name of the file that will be loaded if recursion is disabled but the autoload is defined on the classs itself" do
-      ModuleSpecs::Autoload::Child.autoload :ChildAutoload, "child_autoload.rb"
-      ModuleSpecs::Autoload::Child.autoload?(:ChildAutoload, false).should == "child_autoload.rb"
-    end
+  it "returns the name of the file that will be loaded if recursion is disabled but the autoload is defined on the class itself" do
+    ModuleSpecs::Autoload::Child.autoload :ChildAutoload, "child_autoload.rb"
+    ModuleSpecs::Autoload::Child.autoload?(:ChildAutoload, false).should == "child_autoload.rb"
   end
 end
 
 describe "Module#autoload" do
   before :all do
     @non_existent = fixture __FILE__, "no_autoload.rb"
-
-    # Require RubyGems eagerly, to ensure #require is already the RubyGems
-    # version, before starting #autoload specs which snapshot #require, and
-    # could end up redefining #require as the original core Kernel#require.
-    begin
-      require "rubygems"
-    rescue LoadError
-    end
+    CodeLoadingSpecs.preload_rubygems
   end
 
   before :each do
@@ -210,6 +201,13 @@ describe "Module#autoload" do
     ModuleSpecs::Autoload.use_ex1.should == :good
   end
 
+  it "considers an autoload constant as loaded when autoload is called for/from the current file" do
+    filename = fixture(__FILE__, "autoload_during_require_current_file.rb")
+    require filename
+
+    ScratchPad.recorded.should be_nil
+  end
+
   describe "interacting with defined?" do
     it "does not load the file when referring to the constant in defined?" do
       module ModuleSpecs::Autoload::Dog
@@ -294,6 +292,32 @@ describe "Module#autoload" do
       ScratchPad.recorded.should == [nil, nil]
       @check.call.should == ["constant", nil]
     end
+
+    it "does not raise an error if the autoload constant was not defined" do
+      module ModuleSpecs::Autoload
+        autoload :RequiredDirectlyNoConstant, fixture(__FILE__, "autoload_required_directly_no_constant.rb")
+      end
+      @path = fixture(__FILE__, "autoload_required_directly_no_constant.rb")
+      @remove << :RequiredDirectlyNoConstant
+      @check = -> {
+        [
+            defined?(ModuleSpecs::Autoload::RequiredDirectlyNoConstant),
+            ModuleSpecs::Autoload.constants(false).include?(:RequiredDirectlyNoConstant),
+            ModuleSpecs::Autoload.const_defined?(:RequiredDirectlyNoConstant),
+            ModuleSpecs::Autoload.autoload?(:RequiredDirectlyNoConstant)
+        ]
+      }
+      ScratchPad.record @check
+      @check.call.should == ["constant", true, true, @path]
+      $:.push File.dirname(@path)
+      begin
+        require "autoload_required_directly_no_constant.rb"
+      ensure
+        $:.pop
+      end
+      ScratchPad.recorded.should == [nil, true, false, nil]
+      @check.call.should == [nil, true, false, nil]
+    end
   end
 
   describe "after the autoload is triggered by require" do
@@ -318,6 +342,29 @@ describe "Module#autoload" do
     end
   end
 
+  def check_before_during_thread_after(const, &check)
+    before = check.call
+    to_autoload_thread, from_autoload_thread = Queue.new, Queue.new
+    ScratchPad.record -> {
+      from_autoload_thread.push check.call
+      to_autoload_thread.pop
+    }
+    t = Thread.new {
+      in_loading_thread = from_autoload_thread.pop
+      in_other_thread = check.call
+      to_autoload_thread.push :done
+      [in_loading_thread, in_other_thread]
+    }
+    in_loading_thread, in_other_thread = nil
+    begin
+      ModuleSpecs::Autoload.const_get(const)
+    ensure
+      in_loading_thread, in_other_thread = t.value
+    end
+    after = check.call
+    [before, in_loading_thread, in_other_thread, after]
+  end
+
   describe "during the autoload before the constant is assigned" do
     before :each do
       @path = fixture(__FILE__, "autoload_during_autoload.rb")
@@ -326,58 +373,83 @@ describe "Module#autoload" do
       raise unless ModuleSpecs::Autoload.autoload?(:DuringAutoload) == @path
     end
 
-    def check_before_during_thread_after(&check)
-      before = check.call
-      to_autoload_thread, from_autoload_thread = Queue.new, Queue.new
-      ScratchPad.record -> {
-        from_autoload_thread.push check.call
-        to_autoload_thread.pop
-      }
-      t = Thread.new {
-        in_loading_thread = from_autoload_thread.pop
-        in_other_thread = check.call
-        to_autoload_thread.push :done
-        [in_loading_thread, in_other_thread]
-      }
-      in_loading_thread, in_other_thread = nil
-      begin
-        ModuleSpecs::Autoload::DuringAutoload
-      ensure
-        in_loading_thread, in_other_thread = t.value
-      end
-      after = check.call
-      [before, in_loading_thread, in_other_thread, after]
-    end
-
     it "returns nil in autoload thread and 'constant' otherwise for defined?" do
-      results = check_before_during_thread_after {
+      results = check_before_during_thread_after(:DuringAutoload) {
         defined?(ModuleSpecs::Autoload::DuringAutoload)
       }
       results.should == ['constant', nil, 'constant', 'constant']
     end
 
     it "keeps the constant in Module#constants" do
-      results = check_before_during_thread_after {
+      results = check_before_during_thread_after(:DuringAutoload) {
         ModuleSpecs::Autoload.constants(false).include?(:DuringAutoload)
       }
       results.should == [true, true, true, true]
     end
 
     it "returns false in autoload thread and true otherwise for Module#const_defined?" do
-      results = check_before_during_thread_after {
+      results = check_before_during_thread_after(:DuringAutoload) {
         ModuleSpecs::Autoload.const_defined?(:DuringAutoload, false)
       }
       results.should == [true, false, true, true]
     end
 
     it "returns nil in autoload thread and returns the path in other threads for Module#autoload?" do
-      results = check_before_during_thread_after {
+      results = check_before_during_thread_after(:DuringAutoload) {
         ModuleSpecs::Autoload.autoload?(:DuringAutoload)
       }
       results.should == [@path, nil, @path, nil]
     end
   end
 
+  describe "during the autoload after the constant is assigned" do
+    before :each do
+      @path = fixture(__FILE__, "autoload_during_autoload_after_define.rb")
+      ModuleSpecs::Autoload.autoload :DuringAutoloadAfterDefine, @path
+      @autoload_location = [__FILE__, __LINE__ - 1]
+      @const_location = [@path, 2]
+      @remove << :DuringAutoloadAfterDefine
+      raise unless ModuleSpecs::Autoload.autoload?(:DuringAutoloadAfterDefine) == @path
+    end
+
+    it "returns 'constant' in both threads" do
+      results = check_before_during_thread_after(:DuringAutoloadAfterDefine) {
+        defined?(ModuleSpecs::Autoload::DuringAutoloadAfterDefine)
+      }
+      results.should == ['constant', 'constant', 'constant', 'constant']
+    end
+
+    it "Module#constants include the autoloaded in both threads" do
+      results = check_before_during_thread_after(:DuringAutoloadAfterDefine) {
+        ModuleSpecs::Autoload.constants(false).include?(:DuringAutoloadAfterDefine)
+      }
+      results.should == [true, true, true, true]
+    end
+
+    it "Module#const_defined? returns true in both threads" do
+      results = check_before_during_thread_after(:DuringAutoloadAfterDefine) {
+        ModuleSpecs::Autoload.const_defined?(:DuringAutoloadAfterDefine, false)
+      }
+      results.should == [true, true, true, true]
+    end
+
+    it "returns nil in autoload thread and returns the path in other threads for Module#autoload?" do
+      results = check_before_during_thread_after(:DuringAutoloadAfterDefine) {
+        ModuleSpecs::Autoload.autoload?(:DuringAutoloadAfterDefine)
+      }
+      results.should == [@path, nil, @path, nil]
+    end
+
+    ruby_bug("#20188", ""..."3.4") do
+      it "returns the real constant location in autoload thread and returns the autoload location in other threads for Module#const_source_location" do
+        results = check_before_during_thread_after(:DuringAutoloadAfterDefine) {
+          ModuleSpecs::Autoload.const_source_location(:DuringAutoloadAfterDefine)
+        }
+        results.should == [@autoload_location, @const_location, @autoload_location, @const_location]
+      end
+    end
+  end
+
   it "does not remove the constant from Module#constants if load fails and keeps it as an autoload" do
     ModuleSpecs::Autoload.autoload :Fail, @non_existent
 
@@ -414,7 +486,7 @@ describe "Module#autoload" do
     ScratchPad.recorded.should == [:raise, :raise]
   end
 
-  it "does not remove the constant from Module#constants if the loaded file does not define it, but leaves it as 'undefined'" do
+  it "removes the constant from Module#constants if the loaded file does not define it" do
     path = fixture(__FILE__, "autoload_o.rb")
     ScratchPad.record []
     ModuleSpecs::Autoload.autoload :O, path
@@ -425,8 +497,8 @@ describe "Module#autoload" do
 
     -> { ModuleSpecs::Autoload::O }.should raise_error(NameError)
 
-    ModuleSpecs::Autoload.should have_constant(:O)
     ModuleSpecs::Autoload.const_defined?(:O).should == false
+    ModuleSpecs::Autoload.should_not have_constant(:O)
     ModuleSpecs::Autoload.autoload?(:O).should == nil
     -> { ModuleSpecs::Autoload.const_get(:O) }.should raise_error(NameError)
   end
@@ -466,9 +538,7 @@ describe "Module#autoload" do
   it "does not load the file when accessing the constants table of the module" do
     ModuleSpecs::Autoload.autoload :P, @non_existent
     ModuleSpecs::Autoload.const_defined?(:P).should be_true
-    ruby_bug "[Bug #15780]", ""..."2.7" do
-      ModuleSpecs::Autoload.const_defined?("P").should be_true
-    end
+    ModuleSpecs::Autoload.const_defined?("P").should be_true
   end
 
   it "loads the file when opening a module that is the autoloaded constant" do
@@ -527,14 +597,41 @@ describe "Module#autoload" do
         # Basically, the parent autoload constant remains in a "undefined" state
         self.autoload?(:DeclaredInParentDefinedInCurrent).should == nil
         const_defined?(:DeclaredInParentDefinedInCurrent).should == false
-        self.should have_constant(:DeclaredInParentDefinedInCurrent)
         -> { DeclaredInParentDefinedInCurrent }.should raise_error(NameError)
 
         ModuleSpecs::Autoload::LexicalScope.send(:remove_const, :DeclaredInParentDefinedInCurrent)
       end
     end
 
-    it "and fails when finding the undefined autoload constant in the current scope when declared in current and defined in parent" do
+    it "warns once in verbose mode if the constant was defined in a parent scope" do
+      ScratchPad.record -> {
+        ModuleSpecs::DeclaredInCurrentDefinedInParent = :declared_in_current_defined_in_parent
+      }
+
+      module ModuleSpecs
+        module Autoload
+          autoload :DeclaredInCurrentDefinedInParent, fixture(__FILE__, "autoload_callback.rb")
+          self.autoload?(:DeclaredInCurrentDefinedInParent).should == fixture(__FILE__, "autoload_callback.rb")
+          const_defined?(:DeclaredInCurrentDefinedInParent).should == true
+
+          -> {
+            DeclaredInCurrentDefinedInParent
+          }.should complain(
+            /Expected .*autoload_callback.rb to define ModuleSpecs::Autoload::DeclaredInCurrentDefinedInParent but it didn't/,
+            verbose: true,
+          )
+
+          -> {
+            DeclaredInCurrentDefinedInParent
+          }.should_not complain(/.*/, verbose: true)
+          self.autoload?(:DeclaredInCurrentDefinedInParent).should == nil
+          const_defined?(:DeclaredInCurrentDefinedInParent).should == false
+          ModuleSpecs.const_defined?(:DeclaredInCurrentDefinedInParent).should == true
+        end
+      end
+    end
+
+    it "looks up in parent scope after failed autoload" do
       @remove << :DeclaredInCurrentDefinedInParent
       module ModuleSpecs::Autoload
         ScratchPad.record -> {
@@ -543,11 +640,10 @@ describe "Module#autoload" do
 
         class LexicalScope
           autoload :DeclaredInCurrentDefinedInParent, fixture(__FILE__, "autoload_callback.rb")
-          -> { DeclaredInCurrentDefinedInParent }.should raise_error(NameError)
+          -> { DeclaredInCurrentDefinedInParent }.should_not raise_error(NameError)
           # Basically, the autoload constant remains in a "undefined" state
           self.autoload?(:DeclaredInCurrentDefinedInParent).should == nil
           const_defined?(:DeclaredInCurrentDefinedInParent).should == false
-          self.should have_constant(:DeclaredInCurrentDefinedInParent)
           -> { const_get(:DeclaredInCurrentDefinedInParent) }.should raise_error(NameError)
         end
 
@@ -622,6 +718,21 @@ describe "Module#autoload" do
     end
   end
 
+  it "should trigger the autoload when using `private_constant`" do
+    @remove << :DynClass
+    module ModuleSpecs::Autoload
+      autoload :DynClass, fixture(__FILE__, "autoload_c.rb")
+      private_constant :DynClass
+
+      ScratchPad.recorded.should be_nil
+
+      DynClass::C.new.loaded.should == :dynclass_c
+      ScratchPad.recorded.should == :loaded
+    end
+
+    -> { ModuleSpecs::Autoload::DynClass }.should raise_error(NameError, /private constant/)
+  end
+
   # [ruby-core:19127] [ruby-core:29941]
   it "does NOT raise a NameError when the autoload file did not define the constant and a module is opened with the same name" do
     module ModuleSpecs::Autoload
@@ -652,6 +763,27 @@ describe "Module#autoload" do
     ModuleSpecs::Autoload::AutoloadDuringRequire.should be_kind_of(Class)
   end
 
+  it "does not call #require a second time and does not warn if feature sets and trigger autoload on itself" do
+    main = TOPLEVEL_BINDING.eval("self")
+    main.should_not_receive(:require)
+
+    -> {
+      Kernel.require fixture(__FILE__, "autoload_self_during_require.rb")
+    }.should_not complain(verbose: true)
+    ModuleSpecs::Autoload::AutoloadSelfDuringRequire.should be_kind_of(Class)
+  end
+
+  it "handles multiple autoloads in the same file" do
+    $LOAD_PATH.unshift(File.expand_path('../fixtures/multi', __FILE__))
+    begin
+      require 'foo/bar_baz'
+      ModuleSpecs::Autoload::Foo::Bar.should be_kind_of(Class)
+      ModuleSpecs::Autoload::Foo::Baz.should be_kind_of(Class)
+    ensure
+      $LOAD_PATH.shift
+    end
+  end
+
   it "calls #to_path on non-string filenames" do
     p = mock('path')
     p.should_receive(:to_path).and_return @non_existent
@@ -716,9 +848,9 @@ describe "Module#autoload" do
   end
 
   describe "on a frozen module" do
-    it "raises a #{frozen_error_class} before setting the name" do
+    it "raises a FrozenError before setting the name" do
       frozen_module = Module.new.freeze
-      -> { frozen_module.autoload :Foo, @non_existent }.should raise_error(frozen_error_class)
+      -> { frozen_module.autoload :Foo, @non_existent }.should raise_error(FrozenError)
       frozen_module.should_not have_constant(:Foo)
     end
   end
diff --git a/spec/ruby/core/module/class_variable_defined_spec.rb b/spec/ruby/core/module/class_variable_defined_spec.rb
index f867d383c3..c0f2072a37 100644
--- a/spec/ruby/core/module/class_variable_defined_spec.rb
+++ b/spec/ruby/core/module/class_variable_defined_spec.rb
@@ -51,7 +51,7 @@ describe "Module#class_variable_defined?" do
     }.should raise_error(NameError)
   end
 
-  it "converts a non string/symbol/fixnum name to string using to_str" do
+  it "converts a non string/symbol name to string using to_str" do
     c = Class.new { class_variable_set :@@class_var, "test" }
     (o = mock('@@class_var')).should_receive(:to_str).and_return("@@class_var")
     c.class_variable_defined?(o).should == true
diff --git a/spec/ruby/core/module/class_variable_get_spec.rb b/spec/ruby/core/module/class_variable_get_spec.rb
index 79d22a506b..e5d06731ec 100644
--- a/spec/ruby/core/module/class_variable_get_spec.rb
+++ b/spec/ruby/core/module/class_variable_get_spec.rb
@@ -60,7 +60,7 @@ describe "Module#class_variable_get" do
     -> { c.send(:class_variable_get, "@invalid_name") }.should raise_error(NameError)
   end
 
-  it "converts a non string/symbol/fixnum name to string using to_str" do
+  it "converts a non string/symbol name to string using to_str" do
     c = Class.new { class_variable_set :@@class_var, "test" }
     (o = mock('@@class_var')).should_receive(:to_str).and_return("@@class_var")
     c.send(:class_variable_get, o).should == "test"
diff --git a/spec/ruby/core/module/class_variable_set_spec.rb b/spec/ruby/core/module/class_variable_set_spec.rb
index 204bbaf75e..63f32f5389 100644
--- a/spec/ruby/core/module/class_variable_set_spec.rb
+++ b/spec/ruby/core/module/class_variable_set_spec.rb
@@ -25,13 +25,13 @@ describe "Module#class_variable_set" do
     c.send(:class_variable_get, "@@mvar").should == :new_mvar
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     -> {
       Class.new.freeze.send(:class_variable_set, :@@test, "test")
-    }.should raise_error(frozen_error_class)
+    }.should raise_error(FrozenError)
     -> {
       Module.new.freeze.send(:class_variable_set, :@@test, "test")
-    }.should raise_error(frozen_error_class)
+    }.should raise_error(FrozenError)
   end
 
   it "raises a NameError when the given name is not allowed" do
@@ -45,7 +45,7 @@ describe "Module#class_variable_set" do
     }.should raise_error(NameError)
   end
 
-  it "converts a non string/symbol/fixnum name to string using to_str" do
+  it "converts a non string/symbol name to string using to_str" do
     (o = mock('@@class_var')).should_receive(:to_str).and_return("@@class_var")
     c = Class.new
     c.send(:class_variable_set, o, "test")
diff --git a/spec/ruby/core/module/class_variables_spec.rb b/spec/ruby/core/module/class_variables_spec.rb
index fd7aa93aa8..e155f1deac 100644
--- a/spec/ruby/core/module/class_variables_spec.rb
+++ b/spec/ruby/core/module/class_variables_spec.rb
@@ -23,4 +23,12 @@ describe "Module#class_variables" do
     c.extend ModuleSpecs::MVars
     c.class_variables.should_not include(:@@mvar)
   end
+
+  it "returns the correct class variables when inherit is given" do
+    ModuleSpecs::SubCVars.class_variables(false).should == [:@@sub]
+    ModuleSpecs::SubCVars.new.singleton_class.class_variables(false).should == []
+
+    ModuleSpecs::SubCVars.class_variables(true).should == [:@@sub, :@@cls, :@@meta]
+    ModuleSpecs::SubCVars.new.singleton_class.class_variables(true).should ==  [:@@sub, :@@cls, :@@meta]
+  end
 end
diff --git a/spec/ruby/core/module/const_added_spec.rb b/spec/ruby/core/module/const_added_spec.rb
new file mode 100644
index 0000000000..90cd36551a
--- /dev/null
+++ b/spec/ruby/core/module/const_added_spec.rb
@@ -0,0 +1,238 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'fixtures/const_added'
+
+describe "Module#const_added" do
+  it "is a private instance method" do
+    Module.should have_private_instance_method(:const_added)
+  end
+
+  it "returns nil in the default implementation" do
+    Module.new do
+      const_added(:TEST).should == nil
+    end
+  end
+
+  it "for a class defined with the `class` keyword, const_added runs before inherited" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(_)
+        ScratchPad << :const_added
+      end
+    end
+
+    parent = Class.new do
+      def self.inherited(_)
+        ScratchPad << :inherited
+      end
+    end
+
+    class mod::C < parent; end
+
+    ScratchPad.recorded.should == [:const_added, :inherited]
+  end
+
+  it "the superclass of a class assigned to a constant is set before const_added is called" do
+    ScratchPad.record []
+
+    parent = Class.new do
+      def self.const_added(name)
+        ScratchPad << name
+        ScratchPad << const_get(name).superclass
+      end
+    end
+
+    class parent::C < parent; end
+
+    ScratchPad.recorded.should == [:C, parent]
+  end
+
+  it "is called when a new constant is assigned on self" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+    end
+
+    mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+      TEST = 1
+    RUBY
+
+    ScratchPad.recorded.should == [:TEST]
+  end
+
+  it "is called when a new constant is assigned on self through const_set" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+    end
+
+    mod.const_set(:TEST, 1)
+
+    ScratchPad.recorded.should == [:TEST]
+  end
+
+  it "is called when a new module is defined under self" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+    end
+
+    mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+      module SubModule
+      end
+
+      module SubModule
+      end
+    RUBY
+
+    ScratchPad.recorded.should == [:SubModule]
+  end
+
+  it "is called when a new module is defined under a named module (assigned to a constant)" do
+    ScratchPad.record []
+
+    ModuleSpecs::ConstAddedSpecs::NamedModule = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+
+      module self::A
+        def self.const_added(name)
+          ScratchPad << name
+        end
+
+        module self::B
+        end
+      end
+    end
+
+    ScratchPad.recorded.should == [:A, :B]
+    ModuleSpecs::ConstAddedSpecs.send :remove_const, :NamedModule
+  end
+
+  it "is called when a new class is defined under self" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+    end
+
+    mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+      class SubClass
+      end
+
+      class SubClass
+      end
+    RUBY
+
+    ScratchPad.recorded.should == [:SubClass]
+  end
+
+  it "is called when a new class is defined under a named module (assigned to a constant)" do
+    ScratchPad.record []
+
+    ModuleSpecs::ConstAddedSpecs::NamedModuleB = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+
+      class self::A
+        def self.const_added(name)
+          ScratchPad << name
+        end
+
+        class self::B
+        end
+      end
+    end
+
+    ScratchPad.recorded.should == [:A, :B]
+    ModuleSpecs::ConstAddedSpecs.send :remove_const, :NamedModuleB
+  end
+
+  it "is called when an autoload is defined" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << name
+      end
+    end
+
+    mod.autoload :Autoload, "foo"
+    ScratchPad.recorded.should == [:Autoload]
+  end
+
+  it "is called with a precise caller location with the line of definition" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        location = caller_locations(1, 1)[0]
+        ScratchPad << location.lineno
+      end
+    end
+
+    line = __LINE__
+    mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+      TEST = 1
+
+      module SubModule
+      end
+
+      class SubClass
+      end
+    RUBY
+
+    mod.const_set(:CONST_SET, 1)
+
+    ScratchPad.recorded.should == [line + 2, line + 4, line + 7, line + 11]
+  end
+
+  it "is called when the constant is already assigned a value" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad.record const_get(name)
+      end
+    end
+
+    mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+      TEST = 123
+    RUBY
+
+    ScratchPad.recorded.should == 123
+  end
+
+  it "records re-definition of existing constants" do
+    ScratchPad.record []
+
+    mod = Module.new do
+      def self.const_added(name)
+        ScratchPad << const_get(name)
+      end
+    end
+
+    -> {
+      mod.module_eval(<<-RUBY, __FILE__, __LINE__ + 1)
+        TEST = 123
+        TEST = 456
+      RUBY
+    }.should complain(/warning: already initialized constant .+::TEST/)
+
+    ScratchPad.recorded.should == [123, 456]
+  end
+end
diff --git a/spec/ruby/core/module/const_defined_spec.rb b/spec/ruby/core/module/const_defined_spec.rb
index 0673adca3d..8b137cd134 100644
--- a/spec/ruby/core/module/const_defined_spec.rb
+++ b/spec/ruby/core/module/const_defined_spec.rb
@@ -17,11 +17,16 @@ describe "Module#const_defined?" do
     ConstantSpecs::ContainerA::ChildA.const_defined?(:CS_CONST4).should be_true
   end
 
-  it "returns true if the constant is defined in a mixed-in module of the receiver" do
+  it "returns true if the constant is defined in a mixed-in module of the receiver's parent" do
     # CS_CONST10 is defined in a module included by ChildA
     ConstantSpecs::ContainerA::ChildA.const_defined?(:CS_CONST10).should be_true
   end
 
+  it "returns true if the constant is defined in a mixed-in module (with prepends) of the receiver" do
+    # CS_CONST11 is defined in the module included by ContainerPrepend
+    ConstantSpecs::ContainerPrepend.const_defined?(:CS_CONST11).should be_true
+  end
+
   it "returns true if the constant is defined in Object and the receiver is a module" do
     # CS_CONST1 is defined in Object
     ConstantSpecs::ModuleA.const_defined?(:CS_CONST1).should be_true
@@ -40,6 +45,11 @@ describe "Module#const_defined?" do
     ConstantSpecs::ContainerA::ChildA.const_defined?(:CS_CONST4, true).should be_true
   end
 
+  it "coerces the inherit flag to a boolean" do
+    ConstantSpecs::ContainerA::ChildA.const_defined?(:CS_CONST4, nil).should be_false
+    ConstantSpecs::ContainerA::ChildA.const_defined?(:CS_CONST4, :true).should be_true
+  end
+
   it "returns true if the given String names a constant defined in the receiver" do
     ConstantSpecs.const_defined?("CS_CONST2").should == true
     ConstantSpecs.const_defined?("ModuleA").should == true
@@ -55,6 +65,8 @@ describe "Module#const_defined?" do
     str = "CS_CONSTλ".encode("euc-jp")
     ConstantSpecs.const_set str, 1
     ConstantSpecs.const_defined?(str).should be_true
+  ensure
+    ConstantSpecs.send(:remove_const, str)
   end
 
   it "returns false if the constant is not defined in the receiver, its superclass, or any included modules" do
@@ -70,10 +82,23 @@ describe "Module#const_defined?" do
     ConstantSpecs::ClassA.const_defined?(:CS_CONSTX).should == false
   end
 
-  it "calls #to_str to convert the given name to a String" do
-    name = mock("ClassA")
-    name.should_receive(:to_str).and_return("ClassA")
-    ConstantSpecs.const_defined?(name).should == true
+  describe "converts the given name to a String using #to_str" do
+    it "calls #to_str to convert the given name to a String" do
+      name = mock("ClassA")
+      name.should_receive(:to_str).and_return("ClassA")
+      ConstantSpecs.const_defined?(name).should == true
+    end
+
+    it "raises a TypeError if the given name can't be converted to a String" do
+      -> { ConstantSpecs.const_defined?(nil) }.should raise_error(TypeError)
+      -> { ConstantSpecs.const_defined?([])  }.should raise_error(TypeError)
+    end
+
+    it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to a String" do
+      name = mock("classA")
+      name.should_receive(:to_str).and_raise(NoMethodError)
+      -> { ConstantSpecs.const_defined?(name) }.should raise_error(NoMethodError)
+    end
   end
 
   it "special cases Object and checks it's included Modules" do
diff --git a/spec/ruby/core/module/const_get_spec.rb b/spec/ruby/core/module/const_get_spec.rb
index 0a6702903f..4b53cbe7b3 100644
--- a/spec/ruby/core/module/const_get_spec.rb
+++ b/spec/ruby/core/module/const_get_spec.rb
@@ -88,10 +88,28 @@ describe "Module#const_get" do
     end.should raise_error(NameError)
   end
 
+  it "coerces the inherit flag to a boolean" do
+    ConstantSpecs::ContainerA::ChildA.const_get(:CS_CONST4, :true).should == :const4
+
+    -> do
+      ConstantSpecs::ContainerA::ChildA.const_get(:CS_CONST1, nil)
+    end.should raise_error(NameError)
+  end
+
   it "accepts a toplevel scope qualifier" do
     ConstantSpecs.const_get("::CS_CONST1").should == :const1
   end
 
+  it "accepts a toplevel scope qualifier when inherit is false" do
+    ConstantSpecs.const_get("::CS_CONST1", false).should == :const1
+    -> { ConstantSpecs.const_get("CS_CONST1", false) }.should raise_error(NameError)
+  end
+
+  it "returns a constant whose module is defined the toplevel" do
+    ConstantSpecs.const_get("ConstantSpecsTwo::Foo").should == :cs_two_foo
+    ConstantSpecsThree.const_get("ConstantSpecsTwo::Foo").should == :cs_three_foo
+  end
+
   it "accepts a scoped constant name" do
     ConstantSpecs.const_get("ClassA::CS_CONST10").should == :const10_10
   end
@@ -113,7 +131,7 @@ describe "Module#const_get" do
   end
 
   it "does read private constants" do
-     ConstantSpecs.const_get(:CS_PRIVATE).should == :cs_private
+    ConstantSpecs.const_get(:CS_PRIVATE).should == :cs_private
   end
 
   it 'does autoload a constant' do
@@ -132,6 +150,10 @@ describe "Module#const_get" do
     Object.const_get('CSAutoloadD::InnerModule').name.should == 'CSAutoloadD::InnerModule'
   end
 
+  it "raises a NameError when the nested constant does not exist on the module but exists in Object" do
+    -> { Object.const_get('ConstantSpecs::CS_CONST1') }.should raise_error(NameError)
+  end
+
   describe "with statically assigned constants" do
     it "searches the immediate class or module first" do
       ConstantSpecs::ClassA.const_get(:CS_CONST10).should == :const10_10
@@ -180,40 +202,60 @@ describe "Module#const_get" do
 
       ConstantSpecs::ContainerA::ChildA::CS_CONST301 = :const301_5
       ConstantSpecs::ContainerA::ChildA.const_get(:CS_CONST301).should == :const301_5
+    ensure
+      ConstantSpecs::ClassA.send(:remove_const, :CS_CONST301)
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST301)
+      ConstantSpecs::ParentA.send(:remove_const, :CS_CONST301)
+      ConstantSpecs::ContainerA::ChildA.send(:remove_const, :CS_CONST301)
     end
 
     it "searches a module included in the immediate class before the superclass" do
       ConstantSpecs::ParentB::CS_CONST302 = :const302_1
       ConstantSpecs::ModuleF::CS_CONST302 = :const302_2
       ConstantSpecs::ContainerB::ChildB.const_get(:CS_CONST302).should == :const302_2
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST302)
+      ConstantSpecs::ModuleF.send(:remove_const, :CS_CONST302)
     end
 
     it "searches the superclass before a module included in the superclass" do
       ConstantSpecs::ModuleE::CS_CONST303 = :const303_1
       ConstantSpecs::ParentB::CS_CONST303 = :const303_2
       ConstantSpecs::ContainerB::ChildB.const_get(:CS_CONST303).should == :const303_2
+    ensure
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST303)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST303)
     end
 
     it "searches a module included in the superclass" do
       ConstantSpecs::ModuleA::CS_CONST304 = :const304_1
       ConstantSpecs::ModuleE::CS_CONST304 = :const304_2
       ConstantSpecs::ContainerB::ChildB.const_get(:CS_CONST304).should == :const304_2
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST304)
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST304)
     end
 
     it "searches the superclass chain" do
       ConstantSpecs::ModuleA::CS_CONST305 = :const305
       ConstantSpecs::ContainerB::ChildB.const_get(:CS_CONST305).should == :const305
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST305)
     end
 
     it "returns a toplevel constant when the receiver is a Class" do
       Object::CS_CONST306 = :const306
       ConstantSpecs::ContainerB::ChildB.const_get(:CS_CONST306).should == :const306
+    ensure
+      Object.send(:remove_const, :CS_CONST306)
     end
 
     it "returns a toplevel constant when the receiver is a Module" do
       Object::CS_CONST308 = :const308
       ConstantSpecs.const_get(:CS_CONST308).should == :const308
       ConstantSpecs::ModuleA.const_get(:CS_CONST308).should == :const308
+    ensure
+      Object.send(:remove_const, :CS_CONST308)
     end
 
     it "returns the updated value of a constant" do
@@ -224,6 +266,8 @@ describe "Module#const_get" do
         ConstantSpecs::ClassB::CS_CONST309 = :const309_2
       }.should complain(/already initialized constant/)
       ConstantSpecs::ClassB.const_get(:CS_CONST309).should == :const309_2
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST309)
     end
   end
 end
diff --git a/spec/ruby/core/module/const_set_spec.rb b/spec/ruby/core/module/const_set_spec.rb
index 1b8b86dd04..823768b882 100644
--- a/spec/ruby/core/module/const_set_spec.rb
+++ b/spec/ruby/core/module/const_set_spec.rb
@@ -8,22 +8,29 @@ describe "Module#const_set" do
 
     ConstantSpecs.const_set "CS_CONST402", :const402
     ConstantSpecs.const_get(:CS_CONST402).should == :const402
+  ensure
+    ConstantSpecs.send(:remove_const, :CS_CONST401)
+    ConstantSpecs.send(:remove_const, :CS_CONST402)
   end
 
   it "returns the value set" do
     ConstantSpecs.const_set(:CS_CONST403, :const403).should == :const403
+  ensure
+    ConstantSpecs.send(:remove_const, :CS_CONST403)
   end
 
   it "sets the name of an anonymous module" do
     m = Module.new
     ConstantSpecs.const_set(:CS_CONST1000, m)
     m.name.should == "ConstantSpecs::CS_CONST1000"
+  ensure
+    ConstantSpecs.send(:remove_const, :CS_CONST1000)
   end
 
-  it "does not set the name of a module scoped by an anonymous module" do
+  it "sets the name of a module scoped by an anonymous module" do
     a, b = Module.new, Module.new
     a.const_set :B, b
-    b.name.should be_nil
+    b.name.should.end_with? '::B'
   end
 
   it "sets the name of contained modules when assigning a toplevel anonymous module" do
@@ -38,6 +45,8 @@ describe "Module#const_set" do
     b.name.should == "ModuleSpecs_CS3::B"
     c.name.should == "ModuleSpecs_CS3::B::C"
     d.name.should == "ModuleSpecs_CS3::D"
+  ensure
+    Object.send(:remove_const, :ModuleSpecs_CS3)
   end
 
   it "raises a NameError if the name does not start with a capital letter" do
@@ -55,6 +64,8 @@ describe "Module#const_set" do
     ConstantSpecs.const_set("CS_CONST404", :const404).should == :const404
     -> { ConstantSpecs.const_set "Name=", 1 }.should raise_error(NameError)
     -> { ConstantSpecs.const_set "Name?", 1 }.should raise_error(NameError)
+  ensure
+    ConstantSpecs.send(:remove_const, :CS_CONST404)
   end
 
   it "calls #to_str to convert the given name to a String" do
@@ -62,6 +73,8 @@ describe "Module#const_set" do
     name.should_receive(:to_str).and_return("CS_CONST405")
     ConstantSpecs.const_set(name, :const405).should == :const405
     ConstantSpecs::CS_CONST405.should == :const405
+  ensure
+    ConstantSpecs.send(:remove_const, :CS_CONST405)
   end
 
   it "raises a TypeError if conversion to a String by calling #to_str fails" do
@@ -91,7 +104,7 @@ describe "Module#const_set" do
       mod.const_get(:Foo).should == 1
     end
 
-    it "does not warn if the previous value was undefined" do
+    it "does not warn after a failed autoload" do
       path = fixture(__FILE__, "autoload_o.rb")
       ScratchPad.record []
       mod = Module.new
@@ -99,7 +112,6 @@ describe "Module#const_set" do
       mod.autoload :Foo, path
       -> { mod::Foo }.should raise_error(NameError)
 
-      mod.should have_constant(:Foo)
       mod.const_defined?(:Foo).should == false
       mod.autoload?(:Foo).should == nil
 
@@ -125,8 +137,8 @@ describe "Module#const_set" do
       @name = :Foo
     end
 
-    it "raises a #{frozen_error_class} before setting the name" do
-      -> { @frozen.const_set @name, nil }.should raise_error(frozen_error_class)
+    it "raises a FrozenError before setting the name" do
+      -> { @frozen.const_set @name, nil }.should raise_error(FrozenError)
       @frozen.should_not have_constant(@name)
     end
   end
diff --git a/spec/ruby/core/module/const_source_location_spec.rb b/spec/ruby/core/module/const_source_location_spec.rb
new file mode 100644
index 0000000000..96649ea10b
--- /dev/null
+++ b/spec/ruby/core/module/const_source_location_spec.rb
@@ -0,0 +1,281 @@
+require_relative '../../spec_helper'
+require_relative '../../fixtures/constants'
+
+describe "Module#const_source_location" do
+  before do
+    @constants_fixture_path = File.expand_path('../../fixtures/constants.rb', __dir__)
+  end
+
+  describe "with dynamically assigned constants" do
+    it "searches a path in the immediate class or module first" do
+      ConstantSpecs::ClassA::CSL_CONST301 = :const301_1
+      ConstantSpecs::ClassA.const_source_location(:CSL_CONST301).should == [__FILE__, __LINE__ - 1]
+
+      ConstantSpecs::ModuleA::CSL_CONST301 = :const301_2
+      ConstantSpecs::ModuleA.const_source_location(:CSL_CONST301).should == [__FILE__, __LINE__ - 1]
+
+      ConstantSpecs::ParentA::CSL_CONST301 = :const301_3
+      ConstantSpecs::ParentA.const_source_location(:CSL_CONST301).should == [__FILE__, __LINE__ - 1]
+
+      ConstantSpecs::ContainerA::ChildA::CSL_CONST301 = :const301_5
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CSL_CONST301).should == [__FILE__, __LINE__ - 1]
+    ensure
+      ConstantSpecs::ClassA.send(:remove_const, :CSL_CONST301)
+      ConstantSpecs::ModuleA.send(:remove_const, :CSL_CONST301)
+      ConstantSpecs::ParentA.send(:remove_const, :CSL_CONST301)
+      ConstantSpecs::ContainerA::ChildA.send(:remove_const, :CSL_CONST301)
+    end
+
+    it "searches a path in a module included in the immediate class before the superclass" do
+      ConstantSpecs::ParentB::CSL_CONST302 = :const302_1
+      ConstantSpecs::ModuleF::CSL_CONST302 = :const302_2
+      ConstantSpecs::ContainerB::ChildB.const_source_location(:CSL_CONST302).should == [__FILE__, __LINE__ - 1]
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CSL_CONST302)
+      ConstantSpecs::ModuleF.send(:remove_const, :CSL_CONST302)
+    end
+
+    it "searches a path in the superclass before a module included in the superclass" do
+      ConstantSpecs::ModuleE::CSL_CONST303 = :const303_1
+      ConstantSpecs::ParentB::CSL_CONST303 = :const303_2
+      ConstantSpecs::ContainerB::ChildB.const_source_location(:CSL_CONST303).should == [__FILE__, __LINE__ - 1]
+    ensure
+      ConstantSpecs::ModuleE.send(:remove_const, :CSL_CONST303)
+      ConstantSpecs::ParentB.send(:remove_const, :CSL_CONST303)
+    end
+
+    it "searches a path in a module included in the superclass" do
+      ConstantSpecs::ModuleA::CSL_CONST304 = :const304_1
+      ConstantSpecs::ModuleE::CSL_CONST304 = :const304_2
+      ConstantSpecs::ContainerB::ChildB.const_source_location(:CSL_CONST304).should == [__FILE__, __LINE__ - 1]
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CSL_CONST304)
+      ConstantSpecs::ModuleE.send(:remove_const, :CSL_CONST304)
+    end
+
+    it "searches a path in the superclass chain" do
+      ConstantSpecs::ModuleA::CSL_CONST305 = :const305
+      ConstantSpecs::ContainerB::ChildB.const_source_location(:CSL_CONST305).should == [__FILE__, __LINE__ - 1]
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CSL_CONST305)
+    end
+
+    it "returns path to a toplevel constant when the receiver is a Class" do
+      Object::CSL_CONST306 = :const306
+      ConstantSpecs::ContainerB::ChildB.const_source_location(:CSL_CONST306).should == [__FILE__, __LINE__ - 1]
+    ensure
+      Object.send(:remove_const, :CSL_CONST306)
+    end
+
+    it "returns path to a toplevel constant when the receiver is a Module" do
+      Object::CSL_CONST308 = :const308
+      ConstantSpecs.const_source_location(:CSL_CONST308).should == [__FILE__, __LINE__ - 1]
+      ConstantSpecs::ModuleA.const_source_location(:CSL_CONST308).should == [__FILE__, __LINE__ - 2]
+    ensure
+      Object.send(:remove_const, :CSL_CONST308)
+    end
+
+    it "returns path to the updated value of a constant" do
+      ConstantSpecs::ClassB::CSL_CONST309 = :const309_1
+      ConstantSpecs::ClassB.const_source_location(:CSL_CONST309).should == [__FILE__, __LINE__ - 1]
+
+      -> {
+        ConstantSpecs::ClassB::CSL_CONST309 = :const309_2
+      }.should complain(/already initialized constant/)
+      ConstantSpecs::ClassB.const_source_location(:CSL_CONST309).should == [__FILE__, __LINE__ - 2]
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CSL_CONST309)
+    end
+  end
+
+  describe "with statically assigned constants" do
+    it "works for the module and class keywords" do
+      ConstantSpecs.const_source_location(:ModuleB).should == [@constants_fixture_path, ConstantSpecs::ModuleB::LINE]
+      ConstantSpecs.const_source_location(:ClassA).should == [@constants_fixture_path, ConstantSpecs::ClassA::LINE]
+    end
+
+    it "searches location path the immediate class or module first" do
+      ConstantSpecs::ClassA.const_source_location(:CS_CONST10).should == [@constants_fixture_path, ConstantSpecs::ClassA::CS_CONST10_LINE]
+      ConstantSpecs::ModuleA.const_source_location(:CS_CONST10).should == [@constants_fixture_path, ConstantSpecs::ModuleA::CS_CONST10_LINE]
+      ConstantSpecs::ParentA.const_source_location(:CS_CONST10).should == [@constants_fixture_path, ConstantSpecs::ParentA::CS_CONST10_LINE]
+      ConstantSpecs::ContainerA.const_source_location(:CS_CONST10).should == [@constants_fixture_path, ConstantSpecs::ContainerA::CS_CONST10_LINE]
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST10).should == [@constants_fixture_path, ConstantSpecs::ContainerA::ChildA::CS_CONST10_LINE]
+    end
+
+    it "searches location path a module included in the immediate class before the superclass" do
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST15).should == [@constants_fixture_path, ConstantSpecs::ModuleC::CS_CONST15_LINE]
+    end
+
+    it "searches location path the superclass before a module included in the superclass" do
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST11).should == [@constants_fixture_path, ConstantSpecs::ParentA::CS_CONST11_LINE]
+    end
+
+    it "searches location path a module included in the superclass" do
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST12).should == [@constants_fixture_path, ConstantSpecs::ModuleB::CS_CONST12_LINE]
+    end
+
+    it "searches location path the superclass chain" do
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST13).should == [@constants_fixture_path, ConstantSpecs::ModuleA::CS_CONST13_LINE]
+    end
+
+    it "returns location path a toplevel constant when the receiver is a Class" do
+      ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST1).should == [@constants_fixture_path, CS_CONST1_LINE]
+    end
+
+    it "returns location path a toplevel constant when the receiver is a Module" do
+      ConstantSpecs.const_source_location(:CS_CONST1).should == [@constants_fixture_path, CS_CONST1_LINE]
+      ConstantSpecs::ModuleA.const_source_location(:CS_CONST1).should == [@constants_fixture_path, CS_CONST1_LINE]
+    end
+  end
+
+  it "return empty path if constant defined in C code" do
+    Object.const_source_location(:String).should == []
+  end
+
+  it "accepts a String or Symbol name" do
+    Object.const_source_location(:CS_CONST1).should == [@constants_fixture_path, CS_CONST1_LINE]
+    Object.const_source_location("CS_CONST1").should == [@constants_fixture_path, CS_CONST1_LINE]
+  end
+
+  it "returns nil if no constant is defined in the search path" do
+    ConstantSpecs.const_source_location(:CS_CONSTX).should == nil
+  end
+
+  it "raises a NameError if the name does not start with a capital letter" do
+    -> { ConstantSpecs.const_source_location "name" }.should raise_error(NameError)
+  end
+
+  it "raises a NameError if the name starts with a non-alphabetic character" do
+    -> { ConstantSpecs.const_source_location "__CONSTX__" }.should raise_error(NameError)
+    -> { ConstantSpecs.const_source_location "@CS_CONST1" }.should raise_error(NameError)
+    -> { ConstantSpecs.const_source_location "!CS_CONST1" }.should raise_error(NameError)
+  end
+
+  it "raises a NameError if the name contains non-alphabetic characters except '_'" do
+    Object.const_source_location("CS_CONST1").should == [@constants_fixture_path, CS_CONST1_LINE]
+    -> { ConstantSpecs.const_source_location "CS_CONST1=" }.should raise_error(NameError)
+    -> { ConstantSpecs.const_source_location "CS_CONST1?" }.should raise_error(NameError)
+  end
+
+  it "calls #to_str to convert the given name to a String" do
+    name = mock("ClassA")
+    name.should_receive(:to_str).and_return("ClassA")
+    ConstantSpecs.const_source_location(name).should == [@constants_fixture_path, ConstantSpecs::ClassA::LINE]
+  end
+
+  it "raises a TypeError if conversion to a String by calling #to_str fails" do
+    name = mock('123')
+    -> { ConstantSpecs.const_source_location(name) }.should raise_error(TypeError)
+
+    name.should_receive(:to_str).and_return(123)
+    -> { ConstantSpecs.const_source_location(name) }.should raise_error(TypeError)
+  end
+
+  it "does not search the singleton class of a Class or Module" do
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST14).should == nil
+    ConstantSpecs.const_source_location(:CS_CONST14).should == nil
+  end
+
+  it "does not search the containing scope" do
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST20).should == [@constants_fixture_path, ConstantSpecs::ParentA::CS_CONST20_LINE]
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST5) == nil
+  end
+
+  it "returns nil if the constant is defined in the receiver's superclass and the inherit flag is false" do
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST4, false).should == nil
+  end
+
+  it "searches into the receiver superclasses if the inherit flag is true" do
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST4, true).should == [@constants_fixture_path, ConstantSpecs::ParentA::CS_CONST4_LINE]
+  end
+
+  it "returns nil when the receiver is a Module, the constant is defined at toplevel and the inherit flag is false" do
+    ConstantSpecs::ModuleA.const_source_location(:CS_CONST1, false).should == nil
+  end
+
+  it "returns nil when the receiver is a Class, the constant is defined at toplevel and the inherit flag is false" do
+    ConstantSpecs::ContainerA::ChildA.const_source_location(:CS_CONST1, false).should == nil
+  end
+
+  it "accepts a toplevel scope qualifier" do
+    ConstantSpecs.const_source_location("::CS_CONST1").should == [@constants_fixture_path, CS_CONST1_LINE]
+  end
+
+  it "accepts a scoped constant name" do
+    ConstantSpecs.const_source_location("ClassA::CS_CONST10").should == [@constants_fixture_path, ConstantSpecs::ClassA::CS_CONST10_LINE]
+  end
+
+  it "returns updated location from const_set" do
+    mod = Module.new
+    const_line = __LINE__ + 1
+    mod.const_set :Foo, 1
+    mod.const_source_location(:Foo).should == [__FILE__, const_line]
+  end
+
+  it "raises a NameError if the name includes two successive scope separators" do
+    -> { ConstantSpecs.const_source_location("ClassA::::CS_CONST10") }.should raise_error(NameError)
+  end
+
+  it "raises a NameError if only '::' is passed" do
+    -> { ConstantSpecs.const_source_location("::") }.should raise_error(NameError)
+  end
+
+  it "raises a NameError if a Symbol has a toplevel scope qualifier" do
+    -> { ConstantSpecs.const_source_location(:'::CS_CONST1') }.should raise_error(NameError)
+  end
+
+  it "raises a NameError if a Symbol is a scoped constant name" do
+    -> { ConstantSpecs.const_source_location(:'ClassA::CS_CONST10') }.should raise_error(NameError)
+  end
+
+  it "does search private constants path" do
+    ConstantSpecs.const_source_location(:CS_PRIVATE).should == [@constants_fixture_path, ConstantSpecs::CS_PRIVATE_LINE]
+  end
+
+  it "works for eval with a given line" do
+    c = Class.new do
+      eval('self::C = 1', nil, "foo", 100)
+    end
+    c.const_source_location(:C).should == ["foo", 100]
+  end
+
+  context 'autoload' do
+    before :all do
+      ConstantSpecs.autoload :CSL_CONST1, "#{__dir__}/notexisting.rb"
+      @line = __LINE__ - 1
+    end
+
+    before :each do
+      @loaded_features = $".dup
+    end
+
+    after :each do
+      $".replace @loaded_features
+    end
+
+    it 'returns the autoload location while not resolved' do
+      ConstantSpecs.const_source_location('CSL_CONST1').should == [__FILE__, @line]
+    end
+
+    it 'returns where the constant was resolved when resolved' do
+      file = fixture(__FILE__, 'autoload_location.rb')
+      ConstantSpecs.autoload :CONST_LOCATION, file
+      line = ConstantSpecs::CONST_LOCATION
+      ConstantSpecs.const_source_location('CONST_LOCATION').should == [file, line]
+    end
+
+    ruby_bug("#20188", ""..."3.4") do
+      it 'returns the real constant location as soon as it is defined' do
+        file = fixture(__FILE__, 'autoload_const_source_location.rb')
+        ConstantSpecs.autoload :ConstSource, file
+        autoload_location = [__FILE__, __LINE__ - 1]
+
+        ConstantSpecs.const_source_location(:ConstSource).should == autoload_location
+        ConstantSpecs::ConstSource::LOCATION.should == ConstantSpecs.const_source_location(:ConstSource)
+        ConstantSpecs::BEFORE_DEFINE_LOCATION.should == autoload_location
+        ConstantSpecs.send :remove_const, :ConstSource
+        ConstantSpecs.send :remove_const, :BEFORE_DEFINE_LOCATION
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/module/constants_spec.rb b/spec/ruby/core/module/constants_spec.rb
index 4538e828dd..330da1cc88 100644
--- a/spec/ruby/core/module/constants_spec.rb
+++ b/spec/ruby/core/module/constants_spec.rb
@@ -13,9 +13,9 @@ describe "Module.constants" do
 
   it "returns an array of Symbol names" do
     # This in NOT an exhaustive list
-    Module.constants.should include(:Array, :Bignum, :Class, :Comparable, :Dir,
+    Module.constants.should include(:Array, :Class, :Comparable, :Dir,
                                     :Enumerable, :ENV, :Exception, :FalseClass,
-                                    :File, :Fixnum, :Float, :Hash, :Integer, :IO,
+                                    :File, :Float, :Hash, :Integer, :IO,
                                     :Kernel, :Math, :Method, :Module, :NilClass,
                                     :Numeric, :Object, :Range, :Regexp, :String,
                                     :Symbol, :Thread, :Time, :TrueClass)
@@ -43,37 +43,43 @@ end
 describe "Module#constants" do
   it "returns an array of Symbol names of all constants defined in the module and all included modules" do
     ConstantSpecs::ContainerA.constants.sort.should == [
-      :CS_CONST10, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
+      :CS_CONST10, :CS_CONST10_LINE, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
     ]
   end
 
   it "returns all constants including inherited when passed true" do
     ConstantSpecs::ContainerA.constants(true).sort.should == [
-      :CS_CONST10, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
+      :CS_CONST10, :CS_CONST10_LINE, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
     ]
   end
 
   it "returns all constants including inherited when passed some object" do
     ConstantSpecs::ContainerA.constants(Object.new).sort.should == [
-      :CS_CONST10, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
+      :CS_CONST10, :CS_CONST10_LINE, :CS_CONST23, :CS_CONST24, :CS_CONST5, :ChildA
     ]
   end
 
   it "doesn't returns inherited constants when passed false" do
     ConstantSpecs::ContainerA.constants(false).sort.should == [
-      :CS_CONST10, :CS_CONST23, :CS_CONST5, :ChildA
+      :CS_CONST10, :CS_CONST10_LINE, :CS_CONST23, :CS_CONST5, :ChildA
     ]
   end
 
   it "doesn't returns inherited constants when passed nil" do
     ConstantSpecs::ContainerA.constants(nil).sort.should == [
-      :CS_CONST10, :CS_CONST23, :CS_CONST5, :ChildA
+      :CS_CONST10, :CS_CONST10_LINE, :CS_CONST23, :CS_CONST5, :ChildA
     ]
   end
 
   it "returns only public constants" do
     ModuleSpecs::PrivConstModule.constants.should == [:PUBLIC_CONSTANT]
   end
+
+  it "returns only constants starting with an uppercase letter" do
+    # e.g. fatal, IO::generic_readable and IO::generic_writable should not be returned by Module#constants
+    Object.constants.each { |c| c[0].should == c[0].upcase }
+    IO.constants.each { |c| c[0].should == c[0].upcase }
+  end
 end
 
 describe "Module#constants" do
diff --git a/spec/ruby/core/module/define_method_spec.rb b/spec/ruby/core/module/define_method_spec.rb
index 29394e5b92..c5dfc53764 100644
--- a/spec/ruby/core/module/define_method_spec.rb
+++ b/spec/ruby/core/module/define_method_spec.rb
@@ -88,6 +88,23 @@ describe "Module#define_method when given an UnboundMethod" do
   end
 end
 
+describe "Module#define_method" do
+  describe "when the default definee is not the same as the module" do
+    it "sets the visibility of the method to public" do
+      klass = Class.new
+      class << klass
+        private
+        define_method(:meta) do
+          define_method(:foo) { :foo }
+        end
+      end
+
+      klass.send :meta
+      klass.new.foo.should == :foo
+    end
+  end
+end
+
 describe "Module#define_method when name is not a special private name" do
   describe "given an UnboundMethod" do
     describe "and called from the target module" do
@@ -116,6 +133,17 @@ describe "Module#define_method when name is not a special private name" do
         klass.should have_public_instance_method(:baz)
       end
     end
+
+    it "sets the method owner for a dynamically added method with a different original owner" do
+      mixin_module = Module.new do
+        def bar; end
+      end
+
+      foo = Object.new
+      foo.singleton_class.define_method(:bar, mixin_module.instance_method(:bar))
+
+      foo.method(:bar).owner.should == foo.singleton_class
+    end
   end
 
   describe "passed a block" do
@@ -202,18 +230,55 @@ describe "Module#define_method" do
     o.block_test2.should == o
   end
 
+  it "raises TypeError if name cannot converted to String" do
+    -> {
+      Class.new { define_method(1001, -> {}) }
+    }.should raise_error(TypeError, /is not a symbol nor a string/)
+
+    -> {
+      Class.new { define_method([], -> {}) }
+    }.should raise_error(TypeError, /is not a symbol nor a string/)
+  end
+
+  it "converts non-String name to String with #to_str" do
+    obj = Object.new
+    def obj.to_str() "foo" end
+
+    new_class = Class.new { define_method(obj, -> { :called }) }
+    new_class.new.foo.should == :called
+  end
+
+  it "raises TypeError when #to_str called on non-String name returns non-String value" do
+    obj = Object.new
+    def obj.to_str() [] end
+
+    -> {
+      Class.new { define_method(obj, -> {}) }
+    }.should raise_error(TypeError, /can't convert Object to String/)
+  end
+
   it "raises a TypeError when the given method is no Method/Proc" do
     -> {
       Class.new { define_method(:test, "self") }
-    }.should raise_error(TypeError)
+    }.should raise_error(TypeError, "wrong argument type String (expected Proc/Method/UnboundMethod)")
 
     -> {
       Class.new { define_method(:test, 1234) }
-    }.should raise_error(TypeError)
+    }.should raise_error(TypeError, "wrong argument type Integer (expected Proc/Method/UnboundMethod)")
 
     -> {
       Class.new { define_method(:test, nil) }
-    }.should raise_error(TypeError)
+    }.should raise_error(TypeError, "wrong argument type NilClass (expected Proc/Method/UnboundMethod)")
+  end
+
+  it "uses provided Method/Proc even if block is specified" do
+    new_class = Class.new do
+      define_method(:test, -> { :method_is_called }) do
+        :block_is_called
+      end
+    end
+
+    new_class.new.test.should == :method_is_called
   end
 
   it "raises an ArgumentError when no block is given" do
@@ -245,10 +310,10 @@ describe "Module#define_method" do
     -> { obj.proc_style_test :arg }.should raise_error(ArgumentError)
   end
 
-  it "raises a #{frozen_error_class} if frozen" do
+  it "raises a FrozenError if frozen" do
     -> {
       Class.new { freeze; define_method(:foo) {} }
-    }.should raise_error(frozen_error_class)
+    }.should raise_error(FrozenError)
   end
 
   it "accepts a Method (still bound)" do
@@ -333,6 +398,14 @@ describe "Module#define_method" do
     object2.other_cool_method.should == "data is foo"
   end
 
+  it "accepts a proc from a Symbol" do
+    symbol_proc = :+.to_proc
+    klass = Class.new do
+      define_method :foo, &symbol_proc
+    end
+    klass.new.foo(1, 2).should == 3
+  end
+
   it "maintains the Proc's scope" do
     class DefineMethodByProcClass
       in_scope = true
@@ -355,15 +428,8 @@ describe "Module#define_method" do
     klass.new.string_test.should == "string_test result"
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:define_method)
-    end
-  end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:define_method)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:define_method)
   end
 
   it "returns its symbol" do
@@ -410,6 +476,9 @@ describe "Module#define_method" do
       ChildClass = Class.new(ParentClass) { define_method(:foo) { :baz } }
       ParentClass.send :define_method, :foo, ChildClass.instance_method(:foo)
     }.should raise_error(TypeError, /bind argument must be a subclass of ChildClass/)
+  ensure
+    Object.send(:remove_const, :ParentClass)
+    Object.send(:remove_const, :ChildClass)
   end
 
   it "raises a TypeError when an UnboundMethod from one class is defined on an unrelated class" do
@@ -433,6 +502,33 @@ describe "Module#define_method" do
       Class.new { define_method :bar, m }
     }.should raise_error(TypeError, /can't bind singleton method to a different class/)
   end
+
+  it "defines a new method with public visibility when a Method passed and the class/module of the context isn't equal to the receiver of #define_method" do
+    c = Class.new do
+      private def foo
+        "public"
+      end
+    end
+
+    object = c.new
+    object.singleton_class.define_method(:bar, object.method(:foo))
+
+    object.bar.should == "public"
+  end
+
+  it "defines the new method according to the scope visibility when a Method passed and the class/module of the context is equal to the receiver of #define_method" do
+    c = Class.new do
+      def foo; end
+    end
+
+    object = c.new
+    object.singleton_class.class_eval do
+      private
+      define_method(:bar, c.new.method(:foo))
+    end
+
+    -> { object.bar }.should raise_error(NoMethodError)
+  end
 end
 
 describe "Module#define_method" do
@@ -498,7 +594,36 @@ describe "Module#define_method" do
     it "receives the value passed as the argument when passed one argument" do
       @klass.new.m(1).should == 1
     end
+  end
+
+  describe "passed { |a,|  } creates a method that" do
+    before :each do
+      @klass = Class.new do
+        define_method(:m) { |a,| a }
+      end
+    end
+
+    it "raises an ArgumentError when passed zero arguments" do
+      -> { @klass.new.m }.should raise_error(ArgumentError)
+    end
+
+    it "raises an ArgumentError when passed zero arguments and a block" do
+      -> { @klass.new.m { :computed } }.should raise_error(ArgumentError)
+    end
+
+    it "raises an ArgumentError when passed two arguments" do
+      -> { @klass.new.m 1, 2 }.should raise_error(ArgumentError)
+    end
+
+    it "receives the value passed as the argument when passed one argument" do
+      @klass.new.m(1).should == 1
+    end
 
+    it "does not destructure the passed argument" do
+      @klass.new.m([1, 2]).should == [1, 2]
+      # for comparison:
+      proc { |a,| a }.call([1, 2]).should == 1
+    end
   end
 
   describe "passed { |*a|  } creates a method that" do
@@ -602,7 +727,7 @@ describe "Module#define_method" do
   end
 end
 
-describe "Method#define_method when passed a Method object" do
+describe "Module#define_method when passed a Method object" do
   before :each do
     @klass = Class.new do
       def m(a, b, *c)
@@ -627,7 +752,7 @@ describe "Method#define_method when passed a Method object" do
   end
 end
 
-describe "Method#define_method when passed an UnboundMethod object" do
+describe "Module#define_method when passed an UnboundMethod object" do
   before :each do
     @klass = Class.new do
       def m(a, b, *c)
@@ -652,7 +777,7 @@ describe "Method#define_method when passed an UnboundMethod object" do
   end
 end
 
-describe "Method#define_method when passed a Proc object" do
+describe "Module#define_method when passed a Proc object" do
   describe "and a method is defined inside" do
     it "defines the nested method in the default definee where the Proc was created" do
       prc = nil
@@ -676,3 +801,46 @@ describe "Method#define_method when passed a Proc object" do
     end
   end
 end
+
+describe "Module#define_method when passed a block" do
+  describe "behaves exactly like a lambda" do
+    it "for return" do
+      Class.new do
+        define_method(:foo) do
+          return 42
+        end
+      end.new.foo.should == 42
+    end
+
+    it "for break" do
+      Class.new do
+        define_method(:foo) do
+          break 42
+        end
+      end.new.foo.should == 42
+    end
+
+    it "for next" do
+      Class.new do
+        define_method(:foo) do
+          next 42
+        end
+      end.new.foo.should == 42
+    end
+
+    it "for redo" do
+      Class.new do
+        result = []
+        define_method(:foo) do
+          if result.empty?
+            result << :first
+            redo
+          else
+            result << :second
+            result
+          end
+        end
+      end.new.foo.should == [:first, :second]
+    end
+  end
+end
diff --git a/spec/ruby/core/module/deprecate_constant_spec.rb b/spec/ruby/core/module/deprecate_constant_spec.rb
index 7bcced981b..ec0de6782f 100644
--- a/spec/ruby/core/module/deprecate_constant_spec.rb
+++ b/spec/ruby/core/module/deprecate_constant_spec.rb
@@ -9,7 +9,6 @@ describe "Module#deprecate_constant" do
     @module::PRIVATE = @value
     @module.private_constant :PRIVATE
     @module.deprecate_constant :PRIVATE
-    @pattern = /deprecated/
   end
 
   describe "when accessing the deprecated module" do
@@ -19,7 +18,7 @@ describe "Module#deprecate_constant" do
       value = nil
       -> {
         value = @module::PUBLIC1
-      }.should complain(@pattern)
+      }.should complain(/warning: constant .+::PUBLIC1 is deprecated/)
       value.should equal(@value)
 
       -> { @module::PRIVATE }.should raise_error(NameError)
@@ -28,16 +27,37 @@ describe "Module#deprecate_constant" do
     it "warns with a message" do
       @module.deprecate_constant :PUBLIC1
 
-      -> { @module::PUBLIC1 }.should complain(@pattern)
-      -> { @module.const_get :PRIVATE }.should complain(@pattern)
+      -> { @module::PUBLIC1 }.should complain(/warning: constant .+::PUBLIC1 is deprecated/)
+      -> { @module.const_get :PRIVATE }.should complain(/warning: constant .+::PRIVATE is deprecated/)
+    end
+
+    it "does not warn if Warning[:deprecated] is false" do
+      @module.deprecate_constant :PUBLIC1
+
+      deprecated = Warning[:deprecated]
+      begin
+        Warning[:deprecated] = false
+        -> { @module::PUBLIC1 }.should_not complain
+      ensure
+        Warning[:deprecated] = deprecated
+      end
+    end
+  end
+
+  ruby_bug '#20900', ''...'3.4' do
+    describe "when removing the deprecated module" do
+      it "warns with a message" do
+        @module.deprecate_constant :PUBLIC1
+        -> { @module.module_eval {remove_const :PUBLIC1} }.should complain(/warning: constant .+::PUBLIC1 is deprecated/)
+      end
     end
   end
 
   it "accepts multiple symbols and strings as constant names" do
     @module.deprecate_constant "PUBLIC1", :PUBLIC2
 
-    -> { @module::PUBLIC1 }.should complain(@pattern)
-    -> { @module::PUBLIC2 }.should complain(@pattern)
+    -> { @module::PUBLIC1 }.should complain(/warning: constant .+::PUBLIC1 is deprecated/)
+    -> { @module::PUBLIC2 }.should complain(/warning: constant .+::PUBLIC2 is deprecated/)
   end
 
   it "returns self" do
diff --git a/spec/ruby/core/module/extend_object_spec.rb b/spec/ruby/core/module/extend_object_spec.rb
index bc97a55e7c..1fd1abc0b5 100644
--- a/spec/ruby/core/module/extend_object_spec.rb
+++ b/spec/ruby/core/module/extend_object_spec.rb
@@ -42,18 +42,6 @@ describe "Module#extend_object" do
     ScratchPad.recorded.should == :extended
   end
 
-  it "does not copy own tainted status to the given object" do
-    other = Object.new
-    Module.new.taint.send :extend_object, other
-    other.tainted?.should be_false
-  end
-
-  it "does not copy own untrusted status to the given object" do
-    other = Object.new
-    Module.new.untrust.send :extend_object, other
-    other.untrusted?.should be_false
-  end
-
   describe "when given a frozen object" do
     before :each do
       @receiver = Module.new
diff --git a/spec/ruby/core/module/fixtures/autoload_const_source_location.rb b/spec/ruby/core/module/fixtures/autoload_const_source_location.rb
new file mode 100644
index 0000000000..ee0e5a689f
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_const_source_location.rb
@@ -0,0 +1,6 @@
+module ConstantSpecs
+  BEFORE_DEFINE_LOCATION = const_source_location(:ConstSource)
+  module ConstSource
+    LOCATION = Object.const_source_location(name)
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/autoload_during_autoload_after_define.rb b/spec/ruby/core/module/fixtures/autoload_during_autoload_after_define.rb
new file mode 100644
index 0000000000..a9d886dfd6
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_during_autoload_after_define.rb
@@ -0,0 +1,6 @@
+module ModuleSpecs::Autoload
+  class DuringAutoloadAfterDefine
+    block = ScratchPad.recorded
+    ScratchPad.record(block.call)
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/autoload_during_require_current_file.rb b/spec/ruby/core/module/fixtures/autoload_during_require_current_file.rb
new file mode 100644
index 0000000000..5aa8595065
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_during_require_current_file.rb
@@ -0,0 +1,5 @@
+module ModuleSpecs::Autoload
+  autoload(:AutoloadCurrentFile, __FILE__)
+
+  ScratchPad.record autoload?(:AutoloadCurrentFile)
+end
diff --git a/spec/ruby/core/module/fixtures/autoload_location.rb b/spec/ruby/core/module/fixtures/autoload_location.rb
new file mode 100644
index 0000000000..318851b2df
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_location.rb
@@ -0,0 +1,3 @@
+module ConstantSpecs
+  CONST_LOCATION = __LINE__
+end
diff --git a/spec/ruby/core/module/fixtures/autoload_required_directly_no_constant.rb b/spec/ruby/core/module/fixtures/autoload_required_directly_no_constant.rb
new file mode 100644
index 0000000000..25e08c1129
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_required_directly_no_constant.rb
@@ -0,0 +1,2 @@
+block = ScratchPad.recorded
+ScratchPad.record(block.call)
diff --git a/spec/ruby/core/module/fixtures/autoload_self_during_require.rb b/spec/ruby/core/module/fixtures/autoload_self_during_require.rb
new file mode 100644
index 0000000000..f4a514a807
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/autoload_self_during_require.rb
@@ -0,0 +1,5 @@
+module ModuleSpecs::Autoload
+  autoload :AutoloadSelfDuringRequire, __FILE__
+  class AutoloadSelfDuringRequire
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/classes.rb b/spec/ruby/core/module/fixtures/classes.rb
index ef70eaf9cf..964f64c593 100644
--- a/spec/ruby/core/module/fixtures/classes.rb
+++ b/spec/ruby/core/module/fixtures/classes.rb
@@ -1,11 +1,14 @@
 module ModuleSpecs
   def self.without_test_modules(modules)
-    ignore = %w[MSpecRSpecAdapter PP::ObjectMixin ModuleSpecs::IncludedInObject MainSpecs::Module ConstantSpecs::ModuleA]
+    ignore = %w[MSpecRSpecAdapter PP::ObjectMixin MainSpecs::Module ConstantSpecs::ModuleA]
     modules.reject { |k| ignore.include?(k.name) }
   end
 
   CONST = :plain_constant
 
+  class NamedClass
+  end
+
   module PrivConstModule
     PRIVATE_CONSTANT = 1
     private_constant :PRIVATE_CONSTANT
@@ -39,6 +42,14 @@ module ModuleSpecs
   class LookupChild < Lookup
   end
 
+  module ModuleWithPrepend
+    prepend LookupMod
+  end
+
+  class WithPrependedModule
+    include ModuleWithPrepend
+  end
+
   class Parent
     # For private_class_method spec
     def self.private_method; end
@@ -349,6 +360,10 @@ module ModuleSpecs
     end
   end
 
+  class SubCVars < CVars
+    @@sub = :sub
+  end
+
   module MVars
     @@mvar = :mvar
   end
@@ -373,6 +388,7 @@ module ModuleSpecs
   # empty modules
   module M1; end
   module M2; end
+  module M3; end
 
   module Autoload
     def self.use_ex1
@@ -580,6 +596,32 @@ module ModuleSpecs
     private :foo
   end
   EmptyFooMethod = m.instance_method(:foo)
+
+  # for undefined_instance_methods spec
+  module UndefinedInstanceMethods
+    module Super
+      def super_included_method; end
+    end
+
+    class Parent
+      def undefed_method; end
+      undef_method :undefed_method
+
+      def parent_method; end
+      def another_parent_method; end
+    end
+
+    class Child < Parent
+      include Super
+
+      undef_method :parent_method
+      undef_method :another_parent_method
+    end
+
+    class Grandchild < Child
+      undef_method :super_included_method
+    end
+  end
 end
 
 class Object
diff --git a/spec/ruby/core/module/fixtures/const_added.rb b/spec/ruby/core/module/fixtures/const_added.rb
new file mode 100644
index 0000000000..0f5baad65d
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/const_added.rb
@@ -0,0 +1,4 @@
+module ModuleSpecs
+  module ConstAddedSpecs
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/module.rb b/spec/ruby/core/module/fixtures/module.rb
index 9050a272ec..34543ca2b4 100644
--- a/spec/ruby/core/module/fixtures/module.rb
+++ b/spec/ruby/core/module/fixtures/module.rb
@@ -1,4 +1,8 @@
 module ModuleSpecs
   module Anonymous
+    module Child
+    end
+
+    SameChild = Child
   end
 end
diff --git a/spec/ruby/core/module/fixtures/multi/foo.rb b/spec/ruby/core/module/fixtures/multi/foo.rb
new file mode 100644
index 0000000000..549996f08f
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/multi/foo.rb
@@ -0,0 +1,6 @@
+module ModuleSpecs::Autoload
+  module Foo
+    autoload :Bar, 'foo/bar_baz'
+    autoload :Baz, 'foo/bar_baz'
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/multi/foo/bar_baz.rb b/spec/ruby/core/module/fixtures/multi/foo/bar_baz.rb
new file mode 100644
index 0000000000..53d3849e1f
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/multi/foo/bar_baz.rb
@@ -0,0 +1,11 @@
+require 'foo'
+
+module ModuleSpecs::Autoload
+  module Foo
+    class Bar
+    end
+
+    class Baz
+    end
+  end
+end
diff --git a/spec/ruby/core/module/fixtures/name.rb b/spec/ruby/core/module/fixtures/name.rb
index fb9e66c309..25c74d3944 100644
--- a/spec/ruby/core/module/fixtures/name.rb
+++ b/spec/ruby/core/module/fixtures/name.rb
@@ -7,4 +7,7 @@ module ModuleSpecs
       Cß.name
     end
   end
+
+  module NameSpecs
+  end
 end
diff --git a/spec/ruby/core/module/fixtures/refine.rb b/spec/ruby/core/module/fixtures/refine.rb
index 46975361dd..e8215aa640 100644
--- a/spec/ruby/core/module/fixtures/refine.rb
+++ b/spec/ruby/core/module/fixtures/refine.rb
@@ -3,6 +3,10 @@ module ModuleSpecs
     def foo; "foo" end
   end
 
+  class ClassWithSuperFoo
+    def foo; [:C] end
+  end
+
   module PrependedModule
     def foo; "foo from prepended module"; end
   end
@@ -10,4 +14,12 @@ module ModuleSpecs
   module IncludedModule
     def foo; "foo from included module"; end
   end
+
+  def self.build_refined_class(for_super: false)
+    if for_super
+      Class.new(ClassWithSuperFoo)
+    else
+      Class.new(ClassWithFoo)
+    end
+  end
 end
diff --git a/spec/ruby/core/module/fixtures/set_temporary_name.rb b/spec/ruby/core/module/fixtures/set_temporary_name.rb
new file mode 100644
index 0000000000..901b3b94d1
--- /dev/null
+++ b/spec/ruby/core/module/fixtures/set_temporary_name.rb
@@ -0,0 +1,4 @@
+module ModuleSpecs
+  module SetTemporaryNameSpec
+  end
+end
diff --git a/spec/ruby/core/module/include_spec.rb b/spec/ruby/core/module/include_spec.rb
index e7f99a5981..210918b2e7 100644
--- a/spec/ruby/core/module/include_spec.rb
+++ b/spec/ruby/core/module/include_spec.rb
@@ -44,7 +44,23 @@ describe "Module#include" do
   end
 
   it "does not raise a TypeError when the argument is an instance of a subclass of Module" do
-    -> { ModuleSpecs::SubclassSpec.include(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
+    class ModuleSpecs::SubclassSpec::AClass
+    end
+    -> { ModuleSpecs::SubclassSpec::AClass.include(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
+  ensure
+    ModuleSpecs::SubclassSpec.send(:remove_const, :AClass)
+  end
+
+  it "raises a TypeError when the argument is a refinement" do
+    refinement = nil
+
+    Module.new do
+      refine String do
+        refinement = self
+      end
+    end
+
+    -> { ModuleSpecs::Basic.include(refinement) }.should raise_error(TypeError, "Cannot include refinement")
   end
 
   it "imports constants to modules and classes" do
@@ -104,9 +120,9 @@ describe "Module#include" do
       class A; include M; end
       class B < A; include M; end
 
-      all = [A,B,M]
+      all = [A, B, M]
 
-      (B.ancestors & all).should == [B, A, M]
+      (B.ancestors.filter { |a| all.include?(a) }).should == [B, A, M]
     end
   end
 
@@ -234,6 +250,360 @@ describe "Module#include" do
       remove_const :C
     end
   end
+
+  it "updates the method when an included module is updated" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    m_module = Module.new
+
+    b_class = Class.new(a_class) do
+      include m_module
+    end
+
+    b = b_class.new
+
+    foo = -> { b.foo }
+
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        'm'
+      end
+    end
+
+    foo.call.should == 'm'
+  end
+
+
+  it "updates the method when a module included after a call is later updated" do
+    m_module = Module.new
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+    b_class = Class.new(a_class)
+    b = b_class.new
+    foo = -> { b.foo }
+    foo.call.should == 'a'
+
+    b_class.include m_module
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a nested included module is updated" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    n_module = Module.new
+
+    m_module = Module.new  do
+      include n_module
+    end
+
+    b_class = Class.new(a_class) do
+      include m_module
+    end
+
+    b = b_class.new
+
+    foo = -> { b.foo }
+
+    foo.call.should == 'a'
+
+    n_module.module_eval do
+      def foo
+        'n'
+      end
+    end
+
+    foo.call.should == 'n'
+  end
+
+  it "updates the method when a new module is included" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    m_module = Module.new do
+      def foo
+        'm'
+      end
+    end
+
+    b_class = Class.new(a_class)
+    b = b_class.new
+
+    foo = -> { b.foo }
+
+    foo.call.should == 'a'
+
+    b_class.class_eval do
+      include m_module
+    end
+
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a new module with nested module is included" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    n_module = Module.new do
+      def foo
+        'n'
+      end
+    end
+
+    m_module = Module.new  do
+      include n_module
+    end
+
+    b_class = Class.new(a_class)
+    b = b_class.new
+
+    foo = -> { b.foo }
+
+    foo.call.should == 'a'
+
+    b_class.class_eval do
+      include m_module
+    end
+
+    foo.call.should == 'n'
+  end
+
+  it "updates the constant when an included module is updated" do
+    module ModuleSpecs::ConstUpdated
+      module A
+        FOO = 'a'
+      end
+
+      module M
+      end
+
+      module B
+        include A
+        include M
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdated)
+  end
+
+  it "updates the constant when a module included after a call is later updated" do
+    module ModuleSpecs::ConstLaterUpdated
+      module A
+        FOO = 'a'
+      end
+
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      module M
+      end
+      B.include M
+
+      B.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstLaterUpdated)
+  end
+
+  it "updates the constant when a module included in another module after a call is later updated" do
+    module ModuleSpecs::ConstModuleLaterUpdated
+      module A
+        FOO = 'a'
+      end
+
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      module M
+      end
+      B.include M
+
+      B.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstModuleLaterUpdated)
+  end
+
+  it "updates the constant when a nested included module is updated" do
+    module ModuleSpecs::ConstUpdatedNestedIncludeUpdated
+      module A
+        FOO = 'a'
+      end
+
+      module N
+      end
+
+      module M
+        include N
+      end
+
+      module B
+        include A
+        include M
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      N.const_set(:FOO, 'n')
+      B.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedNestedIncludeUpdated)
+  end
+
+  it "updates the constant when a new module is included" do
+    module ModuleSpecs::ConstUpdatedNewInclude
+      module A
+        FOO = 'a'
+      end
+
+      module M
+        FOO = 'm'
+      end
+
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      B.include(M)
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedNewInclude)
+  end
+
+  it "updates the constant when a new module with nested module is included" do
+    module ModuleSpecs::ConstUpdatedNestedIncluded
+      module A
+        FOO = 'a'
+      end
+
+      module N
+        FOO = 'n'
+      end
+
+      module M
+        include N
+      end
+
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+
+      B.include M
+      B.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedNestedIncluded)
+  end
+
+  it "overrides a previous super method call" do
+    c1 = Class.new do
+      def foo
+        [:c1]
+      end
+    end
+    c2 = Class.new(c1) do
+      def foo
+        [:c2] + super
+      end
+    end
+    c2.new.foo.should == [:c2, :c1]
+    m = Module.new do
+      def foo
+        [:m1]
+      end
+    end
+    c2.include(m)
+    c2.new.foo.should == [:c2, :m1]
+  end
+
+  it "update a module when a nested module is updated and includes a module on its own" do
+    m1 = Module.new
+    m2 = Module.new do
+      def m2; [:m2]; end
+    end
+    m3 = Module.new do
+      def m3; [:m3]; end
+    end
+    m4 = Module.new do
+      def m4; [:m4]; end
+    end
+    c = Class.new
+
+    c.include(m1)
+    m1.include(m2)
+    m2.include(m3)
+    m3.include(m4)
+
+    c.new.m2.should == [:m2]
+    c.new.m3.should == [:m3]
+    c.new.m4.should == [:m4]
+  end
 end
 
 describe "Module#include?" do
diff --git a/spec/ruby/core/module/included_modules_spec.rb b/spec/ruby/core/module/included_modules_spec.rb
index 40e20953f4..ce94ed1285 100644
--- a/spec/ruby/core/module/included_modules_spec.rb
+++ b/spec/ruby/core/module/included_modules_spec.rb
@@ -4,9 +4,11 @@ require_relative 'fixtures/classes'
 describe "Module#included_modules" do
   it "returns a list of modules included in self" do
     ModuleSpecs.included_modules.should == []
+
     ModuleSpecs::Child.included_modules.should include(ModuleSpecs::Super, ModuleSpecs::Basic, Kernel)
     ModuleSpecs::Parent.included_modules.should include(Kernel)
     ModuleSpecs::Basic.included_modules.should == []
     ModuleSpecs::Super.included_modules.should include(ModuleSpecs::Basic)
+    ModuleSpecs::WithPrependedModule.included_modules.should include(ModuleSpecs::ModuleWithPrepend)
   end
 end
diff --git a/spec/ruby/core/module/included_spec.rb b/spec/ruby/core/module/included_spec.rb
index f8dbad1d31..2fdd4325f2 100644
--- a/spec/ruby/core/module/included_spec.rb
+++ b/spec/ruby/core/module/included_spec.rb
@@ -39,6 +39,6 @@ describe "Module#included" do
 
   it "works with super using a singleton class" do
     ModuleSpecs::SingletonOnModuleCase::Bar.include ModuleSpecs::SingletonOnModuleCase::Foo
-    ModuleSpecs::SingletonOnModuleCase::Bar.included_called?.should == true
+    ModuleSpecs::SingletonOnModuleCase::Bar.should.included_called?
   end
 end
diff --git a/spec/ruby/core/module/instance_method_spec.rb b/spec/ruby/core/module/instance_method_spec.rb
index b4d6a0d8c8..182cdf5c54 100644
--- a/spec/ruby/core/module/instance_method_spec.rb
+++ b/spec/ruby/core/module/instance_method_spec.rb
@@ -45,20 +45,41 @@ describe "Module#instance_method" do
     @parent_um.inspect.should =~ /\bModuleSpecs::InstanceMeth\b/
     @child_um.inspect.should =~ /\bfoo\b/
     @child_um.inspect.should =~ /\bModuleSpecs::InstanceMeth\b/
-    @child_um.inspect.should =~ /\bModuleSpecs::InstanceMethChild\b/
+
     @mod_um.inspect.should =~ /\bbar\b/
     @mod_um.inspect.should =~ /\bModuleSpecs::InstanceMethMod\b/
-    @mod_um.inspect.should =~ /\bModuleSpecs::InstanceMethChild\b/
   end
 
-  it "raises a TypeError if not passed a symbol" do
-    -> { Object.instance_method([]) }.should raise_error(TypeError)
-    -> { Object.instance_method(0)  }.should raise_error(TypeError)
+  it "raises a TypeError if the given name is not a String/Symbol" do
+    -> { Object.instance_method([]) }.should raise_error(TypeError, /is not a symbol nor a string/)
+    -> { Object.instance_method(0) }.should raise_error(TypeError, /is not a symbol nor a string/)
+    -> { Object.instance_method(nil) }.should raise_error(TypeError, /is not a symbol nor a string/)
+    -> { Object.instance_method(mock('x')) }.should raise_error(TypeError, /is not a symbol nor a string/)
+  end
+
+  it "accepts String name argument" do
+    method = ModuleSpecs::InstanceMeth.instance_method(:foo)
+    method.should be_kind_of(UnboundMethod)
+  end
+
+  it "accepts Symbol name argument"  do
+    method = ModuleSpecs::InstanceMeth.instance_method("foo")
+    method.should be_kind_of(UnboundMethod)
   end
 
-  it "raises a TypeError if the given name is not a string/symbol" do
-    -> { Object.instance_method(nil)       }.should raise_error(TypeError)
-    -> { Object.instance_method(mock('x')) }.should raise_error(TypeError)
+  it "converts non-String name by calling #to_str method" do
+    obj = Object.new
+    def obj.to_str() "foo" end
+
+    method = ModuleSpecs::InstanceMeth.instance_method(obj)
+    method.should be_kind_of(UnboundMethod)
+  end
+
+  it "raises TypeError when passed non-String name and #to_str returns non-String value" do
+    obj = Object.new
+    def obj.to_str() [] end
+
+    -> { ModuleSpecs::InstanceMeth.instance_method(obj) }.should raise_error(TypeError, /can't convert Object to String/)
   end
 
   it "raises a NameError if the method has been undefined" do
diff --git a/spec/ruby/core/module/method_added_spec.rb b/spec/ruby/core/module/method_added_spec.rb
index e1b1eda430..ec92cddc1e 100644
--- a/spec/ruby/core/module/method_added_spec.rb
+++ b/spec/ruby/core/module/method_added_spec.rb
@@ -2,6 +2,10 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Module#method_added" do
+  before :each do
+    ScratchPad.record []
+  end
+
   it "is a private instance method" do
     Module.should have_private_instance_method(:method_added)
   end
@@ -13,8 +17,6 @@ describe "Module#method_added" do
   end
 
   it "is called when a new instance method is defined in self" do
-    ScratchPad.record []
-
     Module.new do
       def self.method_added(name)
         ScratchPad << name
@@ -32,8 +34,6 @@ describe "Module#method_added" do
 
   it "is not called when a singleton method is added" do
     # obj.singleton_method_added is called instead
-    ScratchPad.record []
-
     klass = Class.new
     def klass.method_added(name)
       ScratchPad << name
@@ -59,4 +59,88 @@ describe "Module#method_added" do
     end
     m.should_not have_method(:method_to_undef)
   end
+
+  it "is not called when a method changes visibility" do
+    Module.new do
+      def public_method
+      end
+
+      def private_method
+      end
+
+      def self.method_added(name)
+        ScratchPad << name
+      end
+
+      public :public_method
+      private :public_method
+
+      private :private_method
+      public :private_method
+    end
+
+    ScratchPad.recorded.should == []
+  end
+
+  it "is called when using #private in a subclass" do
+    parent = Class.new do
+      def foo
+      end
+    end
+
+    Class.new(parent) do
+      def self.method_added(name)
+        ScratchPad << name
+      end
+
+      # Create an instance as that might initialize some method lookup caches, which is interesting to test
+      self.new.foo
+
+      private :foo
+      public :foo
+    end
+
+    ScratchPad.recorded.should == [:foo]
+  end
+
+  it "is not called when a method is copied via module_function, rather #singleton_method_added is called" do
+    Module.new do
+      def mod_function
+      end
+
+      def self.method_added(name)
+        ScratchPad << [:method_added, name]
+      end
+
+      def self.singleton_method_added(name)
+        ScratchPad << [:singleton_method_added, name]
+      end
+
+      ScratchPad.record []
+
+      module_function :mod_function
+    end
+
+    ScratchPad.recorded.should == [[:singleton_method_added, :mod_function]]
+  end
+
+  it "is called with a precise caller location with the line of the 'def'" do
+    line = nil
+
+    Module.new do
+      def self.method_added(name)
+        location = caller_locations(1, 1)[0]
+        ScratchPad << location.lineno
+      end
+
+      line = __LINE__
+      def first
+      end
+
+      def second
+      end
+    end
+
+    ScratchPad.recorded.should == [line + 1, line + 4]
+  end
 end
diff --git a/spec/ruby/core/module/method_defined_spec.rb b/spec/ruby/core/module/method_defined_spec.rb
index c2a8702d97..bc5b420e11 100644
--- a/spec/ruby/core/module/method_defined_spec.rb
+++ b/spec/ruby/core/module/method_defined_spec.rb
@@ -30,7 +30,7 @@ describe "Module#method_defined?" do
     m.method_defined?(:module_specs_public_method_on_kernel).should be_false
   end
 
-  it "raises a TypeError when the given object is not a string/symbol/fixnum" do
+  it "raises a TypeError when the given object is not a string/symbol" do
     c = Class.new
     o = mock('123')
 
@@ -47,54 +47,52 @@ describe "Module#method_defined?" do
     c.method_defined?(o).should == true
   end
 
-  ruby_version_is "2.6" do
-    # works as method_defined?(method_name)
-    describe "when passed true as a second optional argument" do
-      it "performs a lookup in ancestors" do
-        ModuleSpecs::Child.method_defined?(:public_child, true).should == true
-        ModuleSpecs::Child.method_defined?(:protected_child, true).should == true
-        ModuleSpecs::Child.method_defined?(:accessor_method, true).should == true
-        ModuleSpecs::Child.method_defined?(:private_child, true).should == false
-
-        # Defined in Parent
-        ModuleSpecs::Child.method_defined?(:public_parent, true).should == true
-        ModuleSpecs::Child.method_defined?(:protected_parent, true).should == true
-        ModuleSpecs::Child.method_defined?(:private_parent, true).should == false
-
-        # Defined in Module
-        ModuleSpecs::Child.method_defined?(:public_module, true).should == true
-        ModuleSpecs::Child.method_defined?(:protected_module, true).should == true
-        ModuleSpecs::Child.method_defined?(:private_module, true).should == false
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.method_defined?(:public_super_module, true).should == true
-        ModuleSpecs::Child.method_defined?(:protected_super_module, true).should == true
-        ModuleSpecs::Child.method_defined?(:private_super_module, true).should == false
-      end
+  # works as method_defined?(method_name)
+  describe "when passed true as a second optional argument" do
+    it "performs a lookup in ancestors" do
+      ModuleSpecs::Child.method_defined?(:public_child, true).should == true
+      ModuleSpecs::Child.method_defined?(:protected_child, true).should == true
+      ModuleSpecs::Child.method_defined?(:accessor_method, true).should == true
+      ModuleSpecs::Child.method_defined?(:private_child, true).should == false
+
+      # Defined in Parent
+      ModuleSpecs::Child.method_defined?(:public_parent, true).should == true
+      ModuleSpecs::Child.method_defined?(:protected_parent, true).should == true
+      ModuleSpecs::Child.method_defined?(:private_parent, true).should == false
+
+      # Defined in Module
+      ModuleSpecs::Child.method_defined?(:public_module, true).should == true
+      ModuleSpecs::Child.method_defined?(:protected_module, true).should == true
+      ModuleSpecs::Child.method_defined?(:private_module, true).should == false
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.method_defined?(:public_super_module, true).should == true
+      ModuleSpecs::Child.method_defined?(:protected_super_module, true).should == true
+      ModuleSpecs::Child.method_defined?(:private_super_module, true).should == false
     end
+  end
 
-    describe "when passed false as a second optional argument" do
-      it "checks only the class itself" do
-        ModuleSpecs::Child.method_defined?(:public_child, false).should == true
-        ModuleSpecs::Child.method_defined?(:protected_child, false).should == true
-        ModuleSpecs::Child.method_defined?(:accessor_method, false).should == true
-        ModuleSpecs::Child.method_defined?(:private_child, false).should == false
-
-        # Defined in Parent
-        ModuleSpecs::Child.method_defined?(:public_parent, false).should == false
-        ModuleSpecs::Child.method_defined?(:protected_parent, false).should == false
-        ModuleSpecs::Child.method_defined?(:private_parent, false).should == false
-
-        # Defined in Module
-        ModuleSpecs::Child.method_defined?(:public_module, false).should == false
-        ModuleSpecs::Child.method_defined?(:protected_module, false).should == false
-        ModuleSpecs::Child.method_defined?(:private_module, false).should == false
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.method_defined?(:public_super_module, false).should == false
-        ModuleSpecs::Child.method_defined?(:protected_super_module, false).should == false
-        ModuleSpecs::Child.method_defined?(:private_super_module, false).should == false
-      end
+  describe "when passed false as a second optional argument" do
+    it "checks only the class itself" do
+      ModuleSpecs::Child.method_defined?(:public_child, false).should == true
+      ModuleSpecs::Child.method_defined?(:protected_child, false).should == true
+      ModuleSpecs::Child.method_defined?(:accessor_method, false).should == true
+      ModuleSpecs::Child.method_defined?(:private_child, false).should == false
+
+      # Defined in Parent
+      ModuleSpecs::Child.method_defined?(:public_parent, false).should == false
+      ModuleSpecs::Child.method_defined?(:protected_parent, false).should == false
+      ModuleSpecs::Child.method_defined?(:private_parent, false).should == false
+
+      # Defined in Module
+      ModuleSpecs::Child.method_defined?(:public_module, false).should == false
+      ModuleSpecs::Child.method_defined?(:protected_module, false).should == false
+      ModuleSpecs::Child.method_defined?(:private_module, false).should == false
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.method_defined?(:public_super_module, false).should == false
+      ModuleSpecs::Child.method_defined?(:protected_super_module, false).should == false
+      ModuleSpecs::Child.method_defined?(:private_super_module, false).should == false
     end
   end
 end
diff --git a/spec/ruby/core/module/module_function_spec.rb b/spec/ruby/core/module/module_function_spec.rb
index 407237d48f..51f647142e 100644
--- a/spec/ruby/core/module/module_function_spec.rb
+++ b/spec/ruby/core/module/module_function_spec.rb
@@ -38,14 +38,12 @@ describe "Module#module_function with specific method names" do
     m.respond_to?(:test3).should == false
   end
 
-  it "returns the current module" do
-    x = nil
-    m = Module.new do
-      def test()  end
-      x = module_function :test
+  it "returns argument or arguments if given" do
+    Module.new do
+      def foo; end
+      module_function(:foo).should equal(:foo)
+      module_function(:foo, :foo).should == [:foo, :foo]
     end
-
-    x.should == m
   end
 
   it "creates an independent copy of the method, not a redirect" do
@@ -146,38 +144,82 @@ describe "Module#module_function with specific method names" do
 
     m.foo.should == ["m", "super_m"]
   end
+
+  context "methods created with define_method" do
+    context "passed a block" do
+      it "creates duplicates of the given instance methods" do
+        m = Module.new do
+          define_method :test1 do; end
+          module_function :test1
+        end
+
+        m.respond_to?(:test1).should == true
+      end
+    end
+
+    context "passed a method" do
+      it "creates duplicates of the given instance methods" do
+        module_with_method = Module.new do
+          def test1; end
+        end
+
+        c = Class.new do
+          extend module_with_method
+        end
+
+        m = Module.new do
+          define_method :test2, c.method(:test1)
+          module_function :test2
+        end
+
+        m.respond_to?(:test2).should == true
+      end
+    end
+
+    context "passed an unbound method" do
+      it "creates duplicates of the given instance methods" do
+        module_with_method = Module.new do
+          def test1; end
+        end
+
+        m = Module.new do
+          define_method :test2, module_with_method.instance_method(:test1)
+          module_function :test2
+        end
+
+        m.respond_to?(:test2).should == true
+      end
+    end
+  end
 end
 
 describe "Module#module_function as a toggle (no arguments) in a Module body" do
   it "makes any subsequently defined methods module functions with the normal semantics" do
-    m = Module.new {
+    m = Module.new do
       module_function
       def test1() end
       def test2() end
-    }
+    end
 
     m.respond_to?(:test1).should == true
     m.respond_to?(:test2).should == true
   end
 
-  it "returns the current module" do
-    x = nil
-    m = Module.new {
-      x = module_function
-    }
-
-    x.should == m
+  it "returns nil" do
+    Module.new do
+      module_function.should equal(nil)
+    end
   end
 
   it "stops creating module functions if the body encounters another toggle " \
      "like public/protected/private without arguments" do
-    m = Module.new {
+    m = Module.new do
       module_function
       def test1() end
       def test2() end
       public
       def test3() end
-    }
+    end
 
     m.respond_to?(:test1).should == true
     m.respond_to?(:test2).should == true
@@ -186,14 +228,14 @@ describe "Module#module_function as a toggle (no arguments) in a Module body" do
 
   it "does not stop creating module functions if the body encounters " \
      "public/protected/private WITH arguments" do
-    m = Module.new {
+    m = Module.new do
       def foo() end
       module_function
       def test1() end
       def test2() end
       public :foo
       def test3() end
-    }
+    end
 
     m.respond_to?(:test1).should == true
     m.respond_to?(:test2).should == true
@@ -201,69 +243,116 @@ describe "Module#module_function as a toggle (no arguments) in a Module body" do
   end
 
   it "does not affect module_evaled method definitions also if outside the eval itself" do
-    m = Module.new {
+    m = Module.new do
       module_function
       module_eval { def test1() end }
       module_eval " def test2() end "
-    }
+    end
 
     m.respond_to?(:test1).should == false
     m.respond_to?(:test2).should == false
   end
 
   it "has no effect if inside a module_eval if the definitions are outside of it" do
-    m = Module.new {
+    m = Module.new do
       module_eval { module_function }
       def test1() end
       def test2() end
-    }
+    end
 
     m.respond_to?(:test1).should == false
     m.respond_to?(:test2).should == false
   end
 
   it "functions normally if both toggle and definitions inside a module_eval" do
-    m = Module.new {
-      module_eval {
+    m = Module.new do
+      module_eval do
         module_function
         def test1() end
         def test2() end
-      }
-    }
+      end
+    end
 
     m.respond_to?(:test1).should == true
     m.respond_to?(:test2).should == true
   end
 
-  it "affects evaled method definitions also even when outside the eval itself" do
-    m = Module.new {
+  it "affects eval'ed method definitions also even when outside the eval itself" do
+    m = Module.new do
       module_function
       eval "def test1() end"
-    }
+    end
 
     m.respond_to?(:test1).should == true
   end
 
   it "doesn't affect definitions when inside an eval even if the definitions are outside of it" do
-    m = Module.new {
+    m = Module.new do
       eval "module_function"
       def test1() end
-    }
+    end
 
     m.respond_to?(:test1).should == false
   end
 
   it "functions normally if both toggle and definitions inside a eval" do
-    m = Module.new {
+    m = Module.new do
       eval <<-CODE
         module_function
 
         def test1() end
         def test2() end
       CODE
-    }
+    end
 
     m.respond_to?(:test1).should == true
     m.respond_to?(:test2).should == true
   end
+
+  context "methods are defined with define_method" do
+    context "passed a block" do
+      it "makes any subsequently defined methods module functions with the normal semantics" do
+        m = Module.new do
+          module_function
+          define_method :test1 do; end
+        end
+
+        m.respond_to?(:test1).should == true
+      end
+    end
+
+    context "passed a method" do
+      it "makes any subsequently defined methods module functions with the normal semantics" do
+        module_with_method = Module.new do
+          def test1; end
+        end
+
+        c = Class.new do
+          extend module_with_method
+        end
+
+        m = Module.new do
+          module_function
+          define_method :test2, c.method(:test1)
+        end
+
+        m.respond_to?(:test2).should == true
+      end
+    end
+
+    context "passed an unbound method" do
+      it "makes any subsequently defined methods module functions with the normal semantics" do
+        module_with_method = Module.new do
+          def test1; end
+        end
+
+        m = Module.new do
+          module_function
+          define_method :test2, module_with_method.instance_method(:test1)
+        end
+
+        m.respond_to?(:test2).should == true
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/module/name_spec.rb b/spec/ruby/core/module/name_spec.rb
index d64684319c..d3318e1645 100644
--- a/spec/ruby/core/module/name_spec.rb
+++ b/spec/ruby/core/module/name_spec.rb
@@ -6,10 +6,10 @@ describe "Module#name" do
     Module.new.name.should be_nil
   end
 
-  it "is nil when assigned to a constant in an anonymous module" do
+  it "is not nil when assigned to a constant in an anonymous module" do
     m = Module.new
     m::N = Module.new
-    m::N.name.should be_nil
+    m::N.name.should.end_with? '::N'
   end
 
   it "is not nil for a nested module created with the module keyword" do
@@ -18,12 +18,33 @@ describe "Module#name" do
     m::N.name.should =~ /\A#<Module:0x[0-9a-f]+>::N\z/
   end
 
+  it "returns nil for a singleton class" do
+    Module.new.singleton_class.name.should be_nil
+    String.singleton_class.name.should be_nil
+    Object.new.singleton_class.name.should be_nil
+  end
+
   it "changes when the module is reachable through a constant path" do
     m = Module.new
     module m::N; end
     m::N.name.should =~ /\A#<Module:0x\h+>::N\z/
     ModuleSpecs::Anonymous::WasAnnon = m::N
     m::N.name.should == "ModuleSpecs::Anonymous::WasAnnon"
+  ensure
+    ModuleSpecs::Anonymous.send(:remove_const, :WasAnnon)
+  end
+
+  it "may be the repeated in different module objects" do
+    m = Module.new
+    n = Module.new
+
+    suppress_warning do
+      ModuleSpecs::Anonymous::SameName = m
+      ModuleSpecs::Anonymous::SameName = n
+    end
+
+    m.name.should == "ModuleSpecs::Anonymous::SameName"
+    n.name.should == "ModuleSpecs::Anonymous::SameName"
   end
 
   it "is set after it is removed from a constant" do
@@ -53,10 +74,20 @@ describe "Module#name" do
     ModuleSpecs::Anonymous.name.should == "ModuleSpecs::Anonymous"
   end
 
-  it "is set when assigning to a constant" do
+  it "is set when assigning to a constant (constant path matches outer module name)" do
     m = Module.new
     ModuleSpecs::Anonymous::A = m
     m.name.should == "ModuleSpecs::Anonymous::A"
+  ensure
+    ModuleSpecs::Anonymous.send(:remove_const, :A)
+  end
+
+  it "is set when assigning to a constant (constant path does not match outer module name)" do
+    m = Module.new
+    ModuleSpecs::Anonymous::SameChild::A = m
+    m.name.should == "ModuleSpecs::Anonymous::Child::A"
+  ensure
+    ModuleSpecs::Anonymous::SameChild.send(:remove_const, :A)
   end
 
   it "is not modified when assigning to a new constant after it has been accessed" do
@@ -65,6 +96,9 @@ describe "Module#name" do
     m.name.should == "ModuleSpecs::Anonymous::B"
     ModuleSpecs::Anonymous::C = m
     m.name.should == "ModuleSpecs::Anonymous::B"
+  ensure
+    ModuleSpecs::Anonymous.send(:remove_const, :B)
+    ModuleSpecs::Anonymous.send(:remove_const, :C)
   end
 
   it "is not modified when assigned to a different anonymous module" do
@@ -95,20 +129,77 @@ describe "Module#name" do
     ModuleSpecs::NameEncoding.new.name.encoding.should == Encoding::UTF_8
   end
 
-  it "is set when the anonymous outer module name is set" do
+  it "is set when the anonymous outer module name is set (module in one single constant)" do
     m = Module.new
     m::N = Module.new
     ModuleSpecs::Anonymous::E = m
     m::N.name.should == "ModuleSpecs::Anonymous::E::N"
+  ensure
+    ModuleSpecs::Anonymous.send(:remove_const, :E)
+  end
+
+  # https://bugs.ruby-lang.org/issues/19681
+  it "is set when the anonymous outer module name is set (module in several constants)" do
+    m = Module.new
+    m::N = Module.new
+    m::O = m::N
+    ModuleSpecs::Anonymous::StoredInMultiplePlaces = m
+    valid_names = [
+      "ModuleSpecs::Anonymous::StoredInMultiplePlaces::N",
+      "ModuleSpecs::Anonymous::StoredInMultiplePlaces::O"
+    ]
+    valid_names.should include(m::N.name) # You get one of the two, but you don't know which one.
+  ensure
+    ModuleSpecs::Anonymous.send(:remove_const, :StoredInMultiplePlaces)
+  end
+
+  it "is set in #const_added callback when a module defined in the top-level scope" do
+    ruby_exe(<<~RUBY, args: "2>&1").chomp.should == "TEST1\nTEST2"
+      class Module
+        def const_added(name)
+          puts const_get(name).name
+        end
+      end
+
+      # module with name
+      module TEST1
+      end
+
+      # anonymous module
+      TEST2 = Module.new
+    RUBY
   end
 
-  it "returns a mutable string" do
-    ModuleSpecs.name.frozen?.should be_false
+  it "is set in #const_added callback for a nested module when an outer module defined in the top-level scope" do
+    ScratchPad.record []
+
+    ModuleSpecs::NameSpecs::NamedModule = Module.new do
+      def self.const_added(name)
+        ScratchPad << const_get(name).name
+      end
+
+      module self::A
+        def self.const_added(name)
+          ScratchPad << const_get(name).name
+        end
+
+        module self::B
+        end
+      end
+    end
+
+    ScratchPad.recorded.should.one?(/#<Module.+>::A$/)
+    ScratchPad.recorded.should.one?(/#<Module.+>::A::B$/)
+    ModuleSpecs::NameSpecs.send :remove_const, :NamedModule
   end
 
-  it "returns a mutable string that when mutated does not modify the original module name" do
-    ModuleSpecs.name << "foo"
+  it "returns a frozen String" do
+    ModuleSpecs.name.should.frozen?
+  end
 
-    ModuleSpecs.name.should == "ModuleSpecs"
+  it "always returns the same String for a given Module" do
+    s1 = ModuleSpecs.name
+    s2 = ModuleSpecs.name
+    s1.should equal(s2)
   end
 end
diff --git a/spec/ruby/core/module/new_spec.rb b/spec/ruby/core/module/new_spec.rb
index da7f3b8720..ec521360bd 100644
--- a/spec/ruby/core/module/new_spec.rb
+++ b/spec/ruby/core/module/new_spec.rb
@@ -6,6 +6,10 @@ describe "Module.new" do
     Module.new.is_a?(Module).should == true
   end
 
+  it "creates a module without a name" do
+    Module.new.name.should be_nil
+  end
+
   it "creates a new Module and passes it to the provided block" do
     test_mod = nil
     m = Module.new do |mod|
diff --git a/spec/ruby/core/module/prepend_features_spec.rb b/spec/ruby/core/module/prepend_features_spec.rb
index b6fce9aba0..09c15c5c15 100644
--- a/spec/ruby/core/module/prepend_features_spec.rb
+++ b/spec/ruby/core/module/prepend_features_spec.rb
@@ -28,18 +28,6 @@ describe "Module#prepend_features" do
     }.should raise_error(ArgumentError)
   end
 
-  it "copies own tainted status to the given module" do
-    other = Module.new
-    Module.new.taint.send :prepend_features, other
-    other.tainted?.should be_true
-  end
-
-  it "copies own untrusted status to the given module" do
-    other = Module.new
-    Module.new.untrust.send :prepend_features, other
-    other.untrusted?.should be_true
-  end
-
   it "clears caches of the given module" do
     parent = Class.new do
       def bar; :bar; end
diff --git a/spec/ruby/core/module/prepend_spec.rb b/spec/ruby/core/module/prepend_spec.rb
index e143f51673..71e82c513e 100644
--- a/spec/ruby/core/module/prepend_spec.rb
+++ b/spec/ruby/core/module/prepend_spec.rb
@@ -36,12 +36,435 @@ describe "Module#prepend" do
     ScratchPad.recorded.should == [ [ m3, c], [ m2, c ], [ m, c ] ]
   end
 
+  it "updates the method when a module is prepended" do
+    m_module = Module.new do
+      def foo
+        "m"
+      end
+    end
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+    a_class.class_eval do
+      prepend m_module
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a prepended module is updated" do
+    m_module = Module.new
+    a_class = Class.new do
+      prepend m_module
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the optimized method when a prepended module is updated" do
+    out = ruby_exe(<<~RUBY)
+    module M; end
+    class Integer
+      prepend M
+    end
+    l = -> { 1 + 2 }
+    p l.call
+    M.module_eval do
+      def +(o)
+        $called = true
+        super(o)
+      end
+    end
+    p l.call
+    p $called
+    RUBY
+    out.should == "3\n3\ntrue\n"
+  end
+
+  it "updates the method when there is a base included method and the prepended module overrides it" do
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new do
+      include base_module
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new do
+      def foo
+        "m"
+      end
+    end
+    a_class.prepend m_module
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when there is a base included method and the prepended module is later updated" do
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new do
+      include base_module
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new
+    a_class.prepend m_module
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a module prepended after a call is later updated" do
+    m_module = Module.new
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    a_class.prepend m_module
+    foo.call.should == 'a'
+
+    m_module.module_eval do
+      def foo
+        "m"
+      end
+    end
+    foo.call.should == 'm'
+  end
+
+  it "updates the method when a module is prepended after another and the method is defined later on that module" do
+    m_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class = Class.new
+    a_class.prepend m_module
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    n_module = Module.new
+    a_class.prepend n_module
+    foo.call.should == 'a'
+
+    n_module.module_eval do
+      def foo
+        "n"
+      end
+    end
+    foo.call.should == 'n'
+  end
+
+  it "updates the method when a module is included in a prepended module and the method is defined later" do
+    a_class = Class.new
+    base_module = Module.new do
+      def foo
+        'a'
+      end
+    end
+    a_class.prepend base_module
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+
+    m_module = Module.new
+    n_module = Module.new
+    m_module.include n_module
+    a_class.prepend m_module
+
+    n_module.module_eval do
+      def foo
+        "n"
+      end
+    end
+    foo.call.should == 'n'
+  end
+
+  it "updates the method when a new module with an included module is prepended" do
+    a_class = Class.new do
+      def foo
+        'a'
+      end
+    end
+
+    n_module = Module.new do
+      def foo
+        'n'
+      end
+    end
+
+    m_module = Module.new  do
+      include n_module
+    end
+
+    a = a_class.new
+    foo = -> { a.foo }
+
+    foo.call.should == 'a'
+
+    a_class.class_eval do
+      prepend m_module
+    end
+
+    foo.call.should == 'n'
+  end
+
+  it "updates the constant when a module is prepended" do
+    module ModuleSpecs::ConstUpdatePrepended
+      module M
+        FOO = 'm'
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+
+      B.foo.should == 'a'
+      B.prepend M
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatePrepended)
+  end
+
+  it "updates the constant when a prepended module is updated" do
+    module ModuleSpecs::ConstPrependedUpdated
+      module M
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        prepend M
+        def self.foo
+          FOO
+        end
+      end
+      B.foo.should == 'a'
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstPrependedUpdated)
+  end
+
+  it "updates the constant when there is a base included constant and the prepended module overrides it" do
+    module ModuleSpecs::ConstIncludedPrependedOverride
+      module Base
+        FOO = 'a'
+      end
+      module A
+        include Base
+        def self.foo
+          FOO
+        end
+      end
+      A.foo.should == 'a'
+
+      module M
+        FOO = 'm'
+      end
+      A.prepend M
+      A.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstIncludedPrependedOverride)
+  end
+
+  it "updates the constant when there is a base included constant and the prepended module is later updated" do
+    module ModuleSpecs::ConstIncludedPrependedLaterUpdated
+      module Base
+        FOO = 'a'
+      end
+      module A
+        include Base
+        def self.foo
+          FOO
+        end
+      end
+      A.foo.should == 'a'
+
+      module M
+      end
+      A.prepend M
+      A.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      A.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstIncludedPrependedLaterUpdated)
+  end
+
+  it "updates the constant when a module prepended after a constant is later updated" do
+    module ModuleSpecs::ConstUpdatedPrependedAfterLaterUpdated
+      module M
+      end
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+      B.foo.should == 'a'
+
+      B.prepend M
+      B.foo.should == 'a'
+
+      M.const_set(:FOO, 'm')
+      B.foo.should == 'm'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedPrependedAfterLaterUpdated)
+  end
+
+  it "updates the constant when a module is prepended after another and the constant is defined later on that module" do
+    module ModuleSpecs::ConstUpdatedPrependedAfterConstDefined
+      module M
+        FOO = 'm'
+      end
+      module A
+        prepend M
+        def self.foo
+          FOO
+        end
+      end
+
+      A.foo.should == 'm'
+
+      module N
+      end
+      A.prepend N
+      A.foo.should == 'm'
+
+      N.const_set(:FOO, 'n')
+      A.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedPrependedAfterConstDefined)
+  end
+
+  it "updates the constant when a module is included in a prepended module and the constant is defined later" do
+    module ModuleSpecs::ConstUpdatedIncludedInPrependedConstDefinedLater
+      module A
+        def self.foo
+          FOO
+        end
+      end
+      module Base
+        FOO = 'a'
+      end
+
+      A.prepend Base
+      A.foo.should == 'a'
+
+      module N
+      end
+      module M
+        include N
+      end
+
+      A.prepend M
+
+      N.const_set(:FOO, 'n')
+      A.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedIncludedInPrependedConstDefinedLater)
+  end
+
+  it "updates the constant when a new module with an included module is prepended" do
+    module ModuleSpecs::ConstUpdatedNewModuleIncludedPrepended
+      module A
+        FOO = 'a'
+      end
+      module B
+        include A
+        def self.foo
+          FOO
+        end
+      end
+      module N
+        FOO = 'n'
+      end
+
+      module M
+        include N
+      end
+
+      B.foo.should == 'a'
+
+      B.prepend M
+      B.foo.should == 'n'
+    end
+  ensure
+    ModuleSpecs.send(:remove_const, :ConstUpdatedNewModuleIncludedPrepended)
+  end
+
   it "raises a TypeError when the argument is not a Module" do
     -> { ModuleSpecs::Basic.prepend(Class.new) }.should raise_error(TypeError)
   end
 
   it "does not raise a TypeError when the argument is an instance of a subclass of Module" do
-    -> { ModuleSpecs::SubclassSpec.prepend(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
+    class ModuleSpecs::SubclassSpec::AClass
+    end
+    -> { ModuleSpecs::SubclassSpec::AClass.prepend(ModuleSpecs::Subclass.new) }.should_not raise_error(TypeError)
+  ensure
+    ModuleSpecs::SubclassSpec.send(:remove_const, :AClass)
+  end
+
+  it "raises a TypeError when the argument is a refinement" do
+    refinement = nil
+
+    Module.new do
+      refine String do
+        refinement = self
+      end
+    end
+
+    -> { ModuleSpecs::Basic.prepend(refinement) }.should raise_error(TypeError, "Cannot prepend refinement")
   end
 
   it "imports constants" do
@@ -128,16 +551,16 @@ describe "Module#prepend" do
     c.dup.new.should be_kind_of(m)
   end
 
-  it "keeps the module in the chain when dupping an intermediate module" do
+  it "uses only new module when dupping the module" do
     m1 = Module.new { def calc(x) x end }
     m2 = Module.new { prepend(m1) }
     c1 = Class.new { prepend(m2) }
     m2dup = m2.dup
-    m2dup.ancestors.should == [m2dup,m1,m2]
+    m2dup.ancestors.should == [m1,m2dup]
     c2 = Class.new { prepend(m2dup) }
     c1.ancestors[0,3].should == [m1,m2,c1]
     c1.new.should be_kind_of(m1)
-    c2.ancestors[0,4].should == [m2dup,m1,m2,c2]
+    c2.ancestors[0,3].should == [m1,m2dup,c2]
     c2.new.should be_kind_of(m1)
   end
 
@@ -223,6 +646,18 @@ describe "Module#prepend" do
     ScratchPad.recorded.should == [[:prepend_features, c], [:prepended, c]]
   end
 
+  it "prepends a module if it is included in a super class" do
+    module ModuleSpecs::M3
+      module M; end
+      class A; include M; end
+      class B < A; prepend M; end
+
+      all = [A, B, M]
+
+      (B.ancestors.filter { |a| all.include?(a) }).should == [M, B, A, M]
+    end
+  end
+
   it "detects cyclic prepends" do
     -> {
       module ModuleSpecs::P
@@ -343,6 +778,33 @@ describe "Module#prepend" do
     ary.should == [3, 2, 1]
   end
 
+  it "does not prepend a second copy if the module already indirectly exists in the hierarchy" do
+    mod = Module.new do; end
+    submod = Module.new do; end
+    klass = Class.new do; end
+    klass.include(mod)
+    mod.prepend(submod)
+    klass.include(mod)
+
+    klass.ancestors.take(4).should == [klass, submod, mod, Object]
+  end
+
+  # https://bugs.ruby-lang.org/issues/17423
+  describe "when module already exists in ancestor chain" do
+    it "modifies the ancestor chain" do
+      m = Module.new do; end
+      a = Module.new do; end
+      b = Class.new do; end
+
+      b.include(a)
+      a.prepend(m)
+      b.ancestors.take(4).should == [b, m, a, Object]
+
+      b.prepend(m)
+      b.ancestors.take(5).should == [m, b, m, a, Object]
+    end
+  end
+
   describe "called on a module" do
     describe "included into a class"
     it "does not obscure the module's methods from reflective access" do
diff --git a/spec/ruby/core/module/private_class_method_spec.rb b/spec/ruby/core/module/private_class_method_spec.rb
index e35b50d986..f899c71a57 100644
--- a/spec/ruby/core/module/private_class_method_spec.rb
+++ b/spec/ruby/core/module/private_class_method_spec.rb
@@ -78,4 +78,14 @@ describe "Module#private_class_method" do
       end
     end.should raise_error(NameError)
   end
+
+  context "when single argument is passed and is an array" do
+    it "sets the visibility of the given methods to private" do
+      c = Class.new do
+        def self.foo() "foo" end
+        private_class_method [:foo]
+      end
+      -> { c.foo }.should raise_error(NoMethodError)
+    end
+  end
 end
diff --git a/spec/ruby/core/module/private_method_defined_spec.rb b/spec/ruby/core/module/private_method_defined_spec.rb
index 515542d9df..01fc8f8fb9 100644
--- a/spec/ruby/core/module/private_method_defined_spec.rb
+++ b/spec/ruby/core/module/private_method_defined_spec.rb
@@ -31,7 +31,7 @@ describe "Module#private_method_defined?" do
     ModuleSpecs::CountsMixin.private_method_defined?(:private_3).should == true
   end
 
-  it "raises a TypeError if passed a Fixnum" do
+  it "raises a TypeError if passed an Integer" do
     -> do
       ModuleSpecs::CountsMixin.private_method_defined?(1)
     end.should raise_error(TypeError)
@@ -70,53 +70,51 @@ describe "Module#private_method_defined?" do
     ModuleSpecs::CountsMixin.private_method_defined?(str).should == true
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed true as a second optional argument" do
-      it "performs a lookup in ancestors" do
-        ModuleSpecs::Child.private_method_defined?(:public_child, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_child, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:accessor_method, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_child, true).should == true
-
-        # Defined in Parent
-        ModuleSpecs::Child.private_method_defined?(:public_parent, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_parent, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_parent, true).should == true
-
-        # Defined in Module
-        ModuleSpecs::Child.private_method_defined?(:public_module, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_module, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_module, true).should == true
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.private_method_defined?(:public_super_module, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_super_module, true).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_super_module, true).should == true
-      end
+  describe "when passed true as a second optional argument" do
+    it "performs a lookup in ancestors" do
+      ModuleSpecs::Child.private_method_defined?(:public_child, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_child, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:accessor_method, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_child, true).should == true
+
+      # Defined in Parent
+      ModuleSpecs::Child.private_method_defined?(:public_parent, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_parent, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_parent, true).should == true
+
+      # Defined in Module
+      ModuleSpecs::Child.private_method_defined?(:public_module, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_module, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_module, true).should == true
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.private_method_defined?(:public_super_module, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_super_module, true).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_super_module, true).should == true
     end
+  end
 
-    describe "when passed false as a second optional argument" do
-      it "checks only the class itself" do
-        ModuleSpecs::Child.private_method_defined?(:public_child, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_child, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:accessor_method, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_child, false).should == true
-
-        # Defined in Parent
-        ModuleSpecs::Child.private_method_defined?(:public_parent, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_parent, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_parent, false).should == false
-
-        # Defined in Module
-        ModuleSpecs::Child.private_method_defined?(:public_module, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_module, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_module, false).should == false
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.private_method_defined?(:public_super_module, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:protected_super_module, false).should == false
-        ModuleSpecs::Child.private_method_defined?(:private_super_module, false).should == false
-      end
+  describe "when passed false as a second optional argument" do
+    it "checks only the class itself" do
+      ModuleSpecs::Child.private_method_defined?(:public_child, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_child, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:accessor_method, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_child, false).should == true
+
+      # Defined in Parent
+      ModuleSpecs::Child.private_method_defined?(:public_parent, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_parent, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_parent, false).should == false
+
+      # Defined in Module
+      ModuleSpecs::Child.private_method_defined?(:public_module, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_module, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_module, false).should == false
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.private_method_defined?(:public_super_module, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:protected_super_module, false).should == false
+      ModuleSpecs::Child.private_method_defined?(:private_super_module, false).should == false
     end
   end
 end
diff --git a/spec/ruby/core/module/private_spec.rb b/spec/ruby/core/module/private_spec.rb
index e893c24f38..9e1a297eea 100644
--- a/spec/ruby/core/module/private_spec.rb
+++ b/spec/ruby/core/module/private_spec.rb
@@ -38,11 +38,13 @@ describe "Module#private" do
                   :module_specs_public_method_on_object_for_kernel_private)
   end
 
-  it "returns self" do
+  it "returns argument or arguments if given" do
     (class << Object.new; self; end).class_eval do
       def foo; end
-      private(:foo).should equal(self)
-      private.should equal(self)
+      private(:foo).should equal(:foo)
+      private([:foo, :foo]).should == [:foo, :foo]
+      private(:foo, :foo).should == [:foo, :foo]
+      private.should equal(nil)
     end
   end
 
diff --git a/spec/ruby/core/module/protected_method_defined_spec.rb b/spec/ruby/core/module/protected_method_defined_spec.rb
index 7be7bdd3c9..31e24a16c1 100644
--- a/spec/ruby/core/module/protected_method_defined_spec.rb
+++ b/spec/ruby/core/module/protected_method_defined_spec.rb
@@ -31,7 +31,7 @@ describe "Module#protected_method_defined?" do
     ModuleSpecs::CountsMixin.protected_method_defined?(:protected_3).should == true
   end
 
-  it "raises a TypeError if passed a Fixnum" do
+  it "raises a TypeError if passed an Integer" do
     -> do
       ModuleSpecs::CountsMixin.protected_method_defined?(1)
     end.should raise_error(TypeError)
@@ -70,53 +70,51 @@ describe "Module#protected_method_defined?" do
     ModuleSpecs::CountsMixin.protected_method_defined?(str).should == true
   end
 
-  ruby_version_is "2.6" do
-    describe "when passed true as a second optional argument" do
-      it "performs a lookup in ancestors" do
-        ModuleSpecs::Child.protected_method_defined?(:public_child, true).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_child, true).should == true
-        ModuleSpecs::Child.protected_method_defined?(:accessor_method, true).should == false
-        ModuleSpecs::Child.protected_method_defined?(:private_child, true).should == false
-
-        # Defined in Parent
-        ModuleSpecs::Child.protected_method_defined?(:public_parent, true).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_parent, true).should == true
-        ModuleSpecs::Child.protected_method_defined?(:private_parent, true).should == false
-
-        # Defined in Module
-        ModuleSpecs::Child.protected_method_defined?(:public_module, true).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_module, true).should == true
-        ModuleSpecs::Child.protected_method_defined?(:private_module, true).should == false
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.protected_method_defined?(:public_super_module, true).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_super_module, true).should == true
-        ModuleSpecs::Child.protected_method_defined?(:private_super_module, true).should == false
-      end
+  describe "when passed true as a second optional argument" do
+    it "performs a lookup in ancestors" do
+      ModuleSpecs::Child.protected_method_defined?(:public_child, true).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_child, true).should == true
+      ModuleSpecs::Child.protected_method_defined?(:accessor_method, true).should == false
+      ModuleSpecs::Child.protected_method_defined?(:private_child, true).should == false
+
+      # Defined in Parent
+      ModuleSpecs::Child.protected_method_defined?(:public_parent, true).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_parent, true).should == true
+      ModuleSpecs::Child.protected_method_defined?(:private_parent, true).should == false
+
+      # Defined in Module
+      ModuleSpecs::Child.protected_method_defined?(:public_module, true).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_module, true).should == true
+      ModuleSpecs::Child.protected_method_defined?(:private_module, true).should == false
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.protected_method_defined?(:public_super_module, true).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_super_module, true).should == true
+      ModuleSpecs::Child.protected_method_defined?(:private_super_module, true).should == false
     end
+  end
 
-    describe "when passed false as a second optional argument" do
-      it "checks only the class itself" do
-        ModuleSpecs::Child.protected_method_defined?(:public_child, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_child, false).should == true
-        ModuleSpecs::Child.protected_method_defined?(:accessor_method, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:private_child, false).should == false
-
-        # Defined in Parent
-        ModuleSpecs::Child.protected_method_defined?(:public_parent, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_parent, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:private_parent, false).should == false
-
-        # Defined in Module
-        ModuleSpecs::Child.protected_method_defined?(:public_module, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_module, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:private_module, false).should == false
-
-        # Defined in SuperModule
-        ModuleSpecs::Child.protected_method_defined?(:public_super_module, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:protected_super_module, false).should == false
-        ModuleSpecs::Child.protected_method_defined?(:private_super_module, false).should == false
-      end
+  describe "when passed false as a second optional argument" do
+    it "checks only the class itself" do
+      ModuleSpecs::Child.protected_method_defined?(:public_child, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_child, false).should == true
+      ModuleSpecs::Child.protected_method_defined?(:accessor_method, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:private_child, false).should == false
+
+      # Defined in Parent
+      ModuleSpecs::Child.protected_method_defined?(:public_parent, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_parent, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:private_parent, false).should == false
+
+      # Defined in Module
+      ModuleSpecs::Child.protected_method_defined?(:public_module, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_module, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:private_module, false).should == false
+
+      # Defined in SuperModule
+      ModuleSpecs::Child.protected_method_defined?(:public_super_module, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:protected_super_module, false).should == false
+      ModuleSpecs::Child.protected_method_defined?(:private_super_module, false).should == false
     end
   end
 end
diff --git a/spec/ruby/core/module/protected_spec.rb b/spec/ruby/core/module/protected_spec.rb
index aa04a42fb8..9e37223e18 100644
--- a/spec/ruby/core/module/protected_spec.rb
+++ b/spec/ruby/core/module/protected_spec.rb
@@ -39,11 +39,13 @@ describe "Module#protected" do
                   :module_specs_public_method_on_object_for_kernel_protected)
   end
 
-  it "returns self" do
+  it "returns argument or arguments if given" do
     (class << Object.new; self; end).class_eval do
       def foo; end
-      protected(:foo).should equal(self)
-      protected.should equal(self)
+      protected(:foo).should equal(:foo)
+      protected([:foo, :foo]).should == [:foo, :foo]
+      protected(:foo, :foo).should == [:foo, :foo]
+      protected.should equal(nil)
     end
   end
 
diff --git a/spec/ruby/core/module/public_class_method_spec.rb b/spec/ruby/core/module/public_class_method_spec.rb
index c09cc64863..71b20acda5 100644
--- a/spec/ruby/core/module/public_class_method_spec.rb
+++ b/spec/ruby/core/module/public_class_method_spec.rb
@@ -77,4 +77,18 @@ describe "Module#public_class_method" do
       end
     end.should raise_error(NameError)
   end
+
+  context "when single argument is passed and is an array" do
+    it "makes a class method public" do
+      c = Class.new do
+        class << self
+          private
+          def foo() "foo" end
+        end
+        public_class_method [:foo]
+      end
+
+      c.foo.should == "foo"
+    end
+  end
 end
diff --git a/spec/ruby/core/module/public_method_defined_spec.rb b/spec/ruby/core/module/public_method_defined_spec.rb
index d2fcfd1e72..5c9bdf1ccc 100644
--- a/spec/ruby/core/module/public_method_defined_spec.rb
+++ b/spec/ruby/core/module/public_method_defined_spec.rb
@@ -31,7 +31,7 @@ describe "Module#public_method_defined?" do
     ModuleSpecs::CountsMixin.public_method_defined?(:public_3).should == true
   end
 
-  it "raises a TypeError if passed a Fixnum" do
+  it "raises a TypeError if passed an Integer" do
     -> do
       ModuleSpecs::CountsMixin.public_method_defined?(1)
     end.should raise_error(TypeError)
diff --git a/spec/ruby/core/module/public_spec.rb b/spec/ruby/core/module/public_spec.rb
index e7059f6aa6..ce31eb5d0e 100644
--- a/spec/ruby/core/module/public_spec.rb
+++ b/spec/ruby/core/module/public_spec.rb
@@ -27,12 +27,13 @@ describe "Module#public" do
                   :module_specs_private_method_on_object_for_kernel_public)
   end
 
-  it "returns self" do
+  it "returns argument or arguments if given" do
     (class << Object.new; self; end).class_eval do
       def foo; end
-      private :foo
-      public(:foo).should equal(self)
-      public.should equal(self)
+      public(:foo).should equal(:foo)
+      public([:foo, :foo]).should == [:foo, :foo]
+      public(:foo, :foo).should == [:foo, :foo]
+      public.should equal(nil)
     end
   end
 
diff --git a/spec/ruby/core/module/refine_spec.rb b/spec/ruby/core/module/refine_spec.rb
index 66c19ddb66..d219b98825 100644
--- a/spec/ruby/core/module/refine_spec.rb
+++ b/spec/ruby/core/module/refine_spec.rb
@@ -71,7 +71,7 @@ describe "Module#refine" do
       Module.new do
         refine("foo") {}
       end
-    end.should raise_error(TypeError)
+    end.should raise_error(TypeError, "wrong argument type String (expected Class or Module)")
   end
 
   it "accepts a module as argument" do
@@ -87,6 +87,31 @@ describe "Module#refine" do
     inner_self.public_instance_methods.should include(:blah)
   end
 
+  it "applies refinements to the module" do
+    refinement = Module.new do
+      refine(Enumerable) do
+        def foo?
+          self.any? ? "yes" : "no"
+        end
+      end
+    end
+
+    foo = Class.new do
+      using refinement
+
+      def initialize(items)
+        @items = items
+      end
+
+      def result
+        @items.foo?
+      end
+    end
+
+    foo.new([]).result.should == "no"
+    foo.new([1]).result.should == "yes"
+  end
+
   it "raises ArgumentError if not given a block" do
     -> do
       Module.new do
@@ -196,8 +221,10 @@ describe "Module#refine" do
   #   * The included modules of C
   describe "method lookup" do
     it "looks in the object singleton class first" do
+      refined_class = ModuleSpecs.build_refined_class
+
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
+        refine refined_class do
           def foo; "foo from refinement"; end
         end
       end
@@ -206,7 +233,7 @@ describe "Module#refine" do
       Module.new do
         using refinement
 
-        obj = ModuleSpecs::ClassWithFoo.new
+        obj = refined_class.new
         class << obj
           def foo; "foo from singleton class"; end
         end
@@ -216,68 +243,48 @@ describe "Module#refine" do
       result.should == "foo from singleton class"
     end
 
-    it "looks in prepended modules from the refinement first" do
-      refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
-          include ModuleSpecs::IncludedModule
-          prepend ModuleSpecs::PrependedModule
-
-          def foo; "foo from refinement"; end
+    it "looks in later included modules of the refined module first" do
+      a = Module.new do
+        def foo
+          "foo from A"
         end
       end
 
-      result = nil
-      Module.new do
-        using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
-      end
-
-      result.should == "foo from prepended module"
-    end
-
-    it "looks in refinement then" do
-      refinement = Module.new do
-        refine(ModuleSpecs::ClassWithFoo) do
-          include ModuleSpecs::IncludedModule
-
-          def foo; "foo from refinement"; end
+      include_me_later = Module.new do
+        def foo
+          "foo from IncludeMeLater"
         end
       end
 
-      result = nil
-      Module.new do
-        using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
+      c = Class.new do
+        include a
       end
 
-      result.should == "foo from refinement"
-    end
-
-    it "looks in included modules from the refinement then" do
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
-          include ModuleSpecs::IncludedModule
-        end
-      end
+         refine c do; end
+       end
 
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
+        c.include include_me_later
+        result = c.new.foo
       end
 
-      result.should == "foo from included module"
+      result.should == "foo from IncludeMeLater"
     end
 
     it "looks in the class then" do
+      refined_class = ModuleSpecs.build_refined_class
+
       refinement = Module.new do
-        refine(ModuleSpecs::ClassWithFoo) { }
+        refine(refined_class) { }
       end
 
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
+        result = refined_class.new.foo
       end
 
       result.should == "foo"
@@ -287,12 +294,14 @@ describe "Module#refine" do
 
   # methods in a subclass have priority over refinements in a superclass
   it "does not override methods in subclasses" do
-    subclass = Class.new(ModuleSpecs::ClassWithFoo) do
+    refined_class = ModuleSpecs.build_refined_class
+
+    subclass = Class.new(refined_class) do
       def foo; "foo from subclass"; end
     end
 
     refinement = Module.new do
-      refine ModuleSpecs::ClassWithFoo do
+      refine refined_class do
         def foo; "foo from refinement"; end
       end
     end
@@ -308,8 +317,10 @@ describe "Module#refine" do
 
   context "for methods accessed indirectly" do
     it "is honored by Kernel#send" do
+      refined_class = ModuleSpecs.build_refined_class
+
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo do
+        refine refined_class do
           def foo; "foo from refinement"; end
         end
       end
@@ -317,15 +328,17 @@ describe "Module#refine" do
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.send :foo
+        result = refined_class.new.send :foo
       end
 
       result.should == "foo from refinement"
     end
 
     it "is honored by BasicObject#__send__" do
+      refined_class = ModuleSpecs.build_refined_class
+
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo do
+        refine refined_class do
           def foo; "foo from refinement"; end
         end
       end
@@ -333,7 +346,7 @@ describe "Module#refine" do
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.__send__ :foo
+        result = refined_class.new.__send__ :foo
       end
 
       result.should == "foo from refinement"
@@ -357,80 +370,40 @@ describe "Module#refine" do
       result.should == ["(1)", "(2)", "(3)"]
     end
 
-    ruby_version_is "" ... "2.6" do
-      it "is not honored by Kernel#public_send" do
-        refinement = Module.new do
-          refine ModuleSpecs::ClassWithFoo do
-            def foo; "foo from refinement"; end
-          end
-        end
+    it "is honored by Kernel#public_send" do
+      refined_class = ModuleSpecs.build_refined_class
 
-        result = nil
-        Module.new do
-          using refinement
-          result = ModuleSpecs::ClassWithFoo.new.public_send :foo
+      refinement = Module.new do
+        refine refined_class do
+          def foo; "foo from refinement"; end
         end
-
-        result.should == "foo"
       end
-    end
 
-    ruby_version_is "2.6" do
-      it "is honored by Kernel#public_send" do
-        refinement = Module.new do
-          refine ModuleSpecs::ClassWithFoo do
-            def foo; "foo from refinement"; end
-          end
-        end
-
-        result = nil
-        Module.new do
-          using refinement
-          result = ModuleSpecs::ClassWithFoo.new.public_send :foo
-        end
-
-        result.should == "foo from refinement"
+      result = nil
+      Module.new do
+        using refinement
+        result = refined_class.new.public_send :foo
       end
-    end
-
-    ruby_version_is "" ... "2.5" do
-      it "is not honored by string interpolation" do
-        refinement = Module.new do
-          refine Integer do
-            def to_s
-              "foo"
-            end
-          end
-        end
 
-        result = nil
-        Module.new do
-          using refinement
-          result = "#{1}"
-        end
-
-        result.should == "1"
-      end
+      result.should == "foo from refinement"
     end
 
-    ruby_version_is "2.5" do
-      it "is honored by string interpolation" do
-        refinement = Module.new do
-          refine Integer do
-            def to_s
-              "foo"
-            end
+    it "is honored by string interpolation" do
+      refinement = Module.new do
+        refine Integer do
+          def to_s
+            "foo"
           end
         end
+      end
 
-        result = nil
-        Module.new do
-          using refinement
-          result = "#{1}"
-        end
-
-        result.should == "foo"
+      result = nil
+      Module.new do
+        using refinement
+        result = "#{1}"
       end
+
+      result.should == "foo"
     end
 
     it "is honored by Kernel#binding" do
@@ -458,166 +431,79 @@ describe "Module#refine" do
       result.should == "hello from refinement"
     end
 
-    ruby_version_is "" ... "2.7" do
-      it "is not honored by Kernel#method" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
+    it "is honored by Kernel#method" do
+      klass = Class.new
+      refinement = Module.new do
+        refine klass do
+          def foo; end
         end
-
-        -> {
-          Module.new do
-            using refinement
-            klass.new.method(:foo)
-          end
-        }.should raise_error(NameError, /undefined method `foo'/)
       end
-    end
-
-    ruby_version_is "2.7" do
-      it "is honored by Kernel#method" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
-        end
-
-        result = nil
-        Module.new do
-          using refinement
-          result = klass.new.method(:foo).class
-        end
 
-        result.should == Method
+      result = nil
+      Module.new do
+        using refinement
+        result = klass.new.method(:foo).class
       end
-    end
 
-    ruby_version_is "" ... "2.7" do
-      it "is not honored by Kernel#instance_method" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
-        end
-
-        -> {
-          Module.new do
-            using refinement
-            klass.instance_method(:foo)
-          end
-        }.should raise_error(NameError, /undefined method `foo'/)
-      end
+      result.should == Method
     end
 
-    ruby_version_is "2.7" do
-      it "is honored by Kernel#method" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
-        end
-
-        result = nil
-        Module.new do
-          using refinement
-          result = klass.instance_method(:foo).class
+    it "is honored by Kernel#public_method" do
+      klass = Class.new
+      refinement = Module.new do
+        refine klass do
+          def foo; end
         end
-
-        result.should == UnboundMethod
       end
-    end
 
-    ruby_version_is "" ... "2.6" do
-      it "is not honored by Kernel#respond_to?" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
-        end
-
-        result = nil
-        Module.new do
-          using refinement
-          result = klass.new.respond_to?(:foo)
-        end
-
-        result.should == false
+      result = nil
+      Module.new do
+        using refinement
+        result = klass.new.public_method(:foo).class
       end
-    end
-
-    ruby_version_is "2.6" do
-      it "is honored by Kernel#respond_to?" do
-        klass = Class.new
-        refinement = Module.new do
-          refine klass do
-            def foo; end
-          end
-        end
 
-        result = nil
-        Module.new do
-          using refinement
-          result = klass.new.respond_to?(:foo)
-        end
-
-        result.should == true
-      end
+      result.should == Method
     end
 
-    ruby_version_is ""..."2.6" do
-      it "is not honored by &" do
-        refinement = Module.new do
-          refine String do
-            def to_proc(*args)
-              -> * { 'foo' }
-            end
-          end
+    it "is honored by Kernel#instance_method" do
+      klass = Class.new
+      refinement = Module.new do
+        refine klass do
+          def foo; end
         end
+      end
 
-        -> do
-          Module.new do
-            using refinement
-            ["hola"].map(&"upcase")
-          end
-        end.should raise_error(TypeError, /wrong argument type String \(expected Proc\)/)
+      result = nil
+      Module.new do
+        using refinement
+        result = klass.instance_method(:foo).class
       end
-    end
 
-    ruby_version_is "2.6" do
-      it "is honored by &" do
-        refinement = Module.new do
-          refine String do
-            def to_proc(*args)
-              -> * { 'foo' }
-            end
-          end
-        end
+      result.should == UnboundMethod
+    end
 
-        result = nil
-        Module.new do
-          using refinement
-          result = ["hola"].map(&"upcase")
+    it "is honored by Kernel#respond_to?" do
+      klass = Class.new
+      refinement = Module.new do
+        refine klass do
+          def foo; end
         end
+      end
 
-        result.should == ['foo']
+      result = nil
+      Module.new do
+        using refinement
+        result = klass.new.respond_to?(:foo)
       end
+
+      result.should == true
     end
-  end
 
-  context "when super is called in a refinement" do
-    it "looks in the included to refinery module" do
+    it "is honored by &" do
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
-          include ModuleSpecs::IncludedModule
-
-          def foo
-            super
+        refine String do
+          def to_proc(*args)
+            -> * { 'foo' }
           end
         end
       end
@@ -625,15 +511,19 @@ describe "Module#refine" do
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
+        result = ["hola"].map(&"upcase")
       end
 
-      result.should == "foo from included module"
+      result.should == ['foo']
     end
+  end
 
+  context "when super is called in a refinement" do
     it "looks in the refined class" do
+      refined_class = ModuleSpecs.build_refined_class
+
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
+        refine refined_class do
           def foo
             super
           end
@@ -643,7 +533,7 @@ describe "Module#refine" do
       result = nil
       Module.new do
         using refinement
-        result = ModuleSpecs::ClassWithFoo.new.foo
+        result = refined_class.new.foo
       end
 
       result.should == "foo"
@@ -652,19 +542,21 @@ describe "Module#refine" do
     # super in a method of a refinement invokes the method in the refined
     # class even if there is another refinement which has been activated
     # in the same context.
-    it "looks in the refined class even if there is another active refinement" do
+    it "looks in the refined class first if called from refined method" do
+      refined_class = ModuleSpecs.build_refined_class(for_super: true)
+
       refinement = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
+        refine refined_class do
           def foo
-            "foo from refinement"
+            [:R1]
           end
         end
       end
 
       refinement_with_super = Module.new do
-        refine ModuleSpecs::ClassWithFoo  do
+        refine refined_class do
           def foo
-            super
+            [:R2] + super
           end
         end
       end
@@ -673,10 +565,39 @@ describe "Module#refine" do
       Module.new do
         using refinement
         using refinement_with_super
-        result = ModuleSpecs::ClassWithFoo.new.foo
+        result = refined_class.new.foo
       end
 
-      result.should == "foo"
+      result.should == [:R2, :C]
+    end
+
+    it "looks only in the refined class even if there is another active refinement" do
+      refined_class = ModuleSpecs.build_refined_class(for_super: true)
+
+      refinement = Module.new do
+        refine refined_class do
+          def bar
+            "you cannot see me from super because I belong to another active R"
+          end
+        end
+      end
+
+      refinement_with_super = Module.new do
+        refine refined_class do
+          def bar
+            super
+          end
+        end
+      end
+
+
+      Module.new do
+        using refinement
+        using refinement_with_super
+        -> {
+          refined_class.new.bar
+        }.should raise_error(NoMethodError)
+      end
     end
   end
 
@@ -704,6 +625,17 @@ describe "Module#refine" do
     -> { [1,2].orig_count }.should raise_error(NoMethodError)
   end
 
+  it "and instance_methods returns a list of methods including those of the refined module" do
+    methods = Array.instance_methods
+    methods_2 = []
+    Module.new do
+      refine Array do
+        methods_2 = instance_methods
+      end
+    end
+    methods.should == methods_2
+  end
+
   # Refinements are inherited by module inclusion.
   # That is, using activates all refinements in the ancestors of the specified module.
   # Refinements in a descendant have priority over refinements in an ancestor.
diff --git a/spec/ruby/core/module/refinements_spec.rb b/spec/ruby/core/module/refinements_spec.rb
new file mode 100644
index 0000000000..05658a8b0e
--- /dev/null
+++ b/spec/ruby/core/module/refinements_spec.rb
@@ -0,0 +1,43 @@
+require_relative '../../spec_helper'
+
+describe "Module#refinements" do
+  it "returns refinements defined in a module" do
+    ScratchPad.record []
+
+    m = Module.new do
+      refine String do
+        ScratchPad << self
+      end
+
+      refine Array do
+        ScratchPad << self
+      end
+    end
+
+    m.refinements.sort_by(&:object_id).should == ScratchPad.recorded.sort_by(&:object_id)
+  end
+
+  it "does not return refinements defined in the included module" do
+    ScratchPad.record []
+
+    m1 = Module.new do
+      refine Integer do
+        nil
+      end
+    end
+
+    m2 = Module.new do
+      include m1
+
+      refine String do
+        ScratchPad << self
+      end
+    end
+
+    m2.refinements.should == ScratchPad.recorded
+  end
+
+  it "returns an empty array if no refinements defined in a module" do
+    Module.new.refinements.should == []
+  end
+end
diff --git a/spec/ruby/core/module/remove_const_spec.rb b/spec/ruby/core/module/remove_const_spec.rb
index 20eb2dc3ed..35a9d65105 100644
--- a/spec/ruby/core/module/remove_const_spec.rb
+++ b/spec/ruby/core/module/remove_const_spec.rb
@@ -81,4 +81,27 @@ describe "Module#remove_const" do
     ConstantSpecs.autoload :AutoloadedConstant, 'a_file'
     ConstantSpecs.send(:remove_const, :AutoloadedConstant).should be_nil
   end
+
+  it "updates the constant value" do
+    module ConstantSpecs::RemovedConstantUpdate
+      module M
+        FOO = 'm'
+      end
+
+      module A
+        include M
+        FOO = 'a'
+        def self.foo
+          FOO
+        end
+      end
+
+      A.foo.should == 'a'
+
+      A.send(:remove_const,:FOO)
+      A.foo.should == 'm'
+    end
+  ensure
+    ConstantSpecs.send(:remove_const, :RemovedConstantUpdate)
+  end
 end
diff --git a/spec/ruby/core/module/remove_method_spec.rb b/spec/ruby/core/module/remove_method_spec.rb
index ba08cc9b44..94b255df62 100644
--- a/spec/ruby/core/module/remove_method_spec.rb
+++ b/spec/ruby/core/module/remove_method_spec.rb
@@ -20,15 +20,8 @@ describe "Module#remove_method" do
     @module = Module.new { def method_to_remove; end }
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:remove_method, false)
-    end
-  end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:remove_method, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:remove_method, false)
   end
 
   it "removes the method from a class" do
@@ -50,6 +43,28 @@ describe "Module#remove_method" do
     x.method_to_remove.should == 1
   end
 
+  it "updates the method implementation" do
+    m_module = Module.new do
+      def foo
+        'm'
+      end
+    end
+
+    a_class = Class.new do
+      include m_module
+
+      def foo
+        'a'
+      end
+    end
+
+    a = a_class.new
+    foo = -> { a.foo }
+    foo.call.should == 'a'
+    a_class.remove_method(:foo)
+    foo.call.should == 'm'
+  end
+
   it "removes multiple methods with 1 call" do
     klass = Class.new do
       def method_to_remove_1; 1; end
@@ -97,12 +112,12 @@ describe "Module#remove_method" do
       @frozen = @module.dup.freeze
     end
 
-    it "raises a #{frozen_error_class} when passed a name" do
-      -> { @frozen.send :remove_method, :method_to_remove }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed a name" do
+      -> { @frozen.send :remove_method, :method_to_remove }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when passed a missing name" do
-      -> { @frozen.send :remove_method, :not_exist }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed a missing name" do
+      -> { @frozen.send :remove_method, :not_exist }.should raise_error(FrozenError)
     end
 
     it "raises a TypeError when passed a not name" do
diff --git a/spec/ruby/core/module/ruby2_keywords_spec.rb b/spec/ruby/core/module/ruby2_keywords_spec.rb
new file mode 100644
index 0000000000..652f9f7083
--- /dev/null
+++ b/spec/ruby/core/module/ruby2_keywords_spec.rb
@@ -0,0 +1,248 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Module#ruby2_keywords" do
+  class << self
+    ruby2_keywords def mark(*args)
+      args
+    end
+  end
+
+  it "marks the final hash argument as keyword hash" do
+    last = mark(1, 2, a: "a").last
+    Hash.ruby2_keywords_hash?(last).should == true
+  end
+
+  it "makes a copy of the hash and only marks the copy as keyword hash" do
+    obj = Object.new
+    obj.singleton_class.class_exec do
+      def regular(*args)
+        args.last
+      end
+    end
+
+    h = {a: 1}
+
+    last = mark(**h).last
+    Hash.ruby2_keywords_hash?(last).should == true
+    Hash.ruby2_keywords_hash?(h).should == false
+
+    last2 = mark(**last).last # last is already marked
+    Hash.ruby2_keywords_hash?(last2).should == true
+    Hash.ruby2_keywords_hash?(last).should == true
+    last2.should_not.equal?(last)
+    Hash.ruby2_keywords_hash?(h).should == false
+  end
+
+  it "makes a copy and unmark the Hash when calling a method taking (arg)" do
+    obj = Object.new
+    obj.singleton_class.class_exec do
+      def single(arg)
+        arg
+      end
+    end
+
+    h = { a: 1 }
+    args = mark(**h)
+    marked = args.last
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    after_usage = obj.single(*args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+  end
+
+  it "makes a copy and unmark the Hash when calling a method taking (**kw)" do
+    obj = Object.new
+    obj.singleton_class.class_exec do
+      def kwargs(**kw)
+        kw
+      end
+    end
+
+    h = { a: 1 }
+    args = mark(**h)
+    marked = args.last
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    after_usage = obj.kwargs(*args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+  end
+
+  it "makes a copy and unmark the Hash when calling a method taking (*args)" do
+    obj = Object.new
+    obj.singleton_class.class_exec do
+      def splat(*args)
+        args.last
+      end
+
+      def splat1(arg, *args)
+        args.last
+      end
+
+      def proc_call(*args)
+        -> *a { a.last }.call(*args)
+      end
+    end
+
+    h = { a: 1 }
+    args = mark(**h)
+    marked = args.last
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    after_usage = obj.splat(*args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    args = mark(1, **h)
+    marked = args.last
+    after_usage = obj.splat1(*args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    args = mark(**h)
+    marked = args.last
+    after_usage = obj.proc_call(*args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+
+    args = mark(**h)
+    marked = args.last
+    after_usage = obj.send(:splat, *args)
+    after_usage.should == h
+    after_usage.should_not.equal?(h)
+    after_usage.should_not.equal?(marked)
+    Hash.ruby2_keywords_hash?(after_usage).should == false
+    Hash.ruby2_keywords_hash?(marked).should == true
+  end
+
+  it "applies to the underlying method and applies across aliasing" do
+    obj = Object.new
+
+    obj.singleton_class.class_exec do
+      def foo(*a) a.last end
+      alias_method :bar, :foo
+      ruby2_keywords :foo
+
+      def baz(*a) a.last end
+      ruby2_keywords :baz
+      alias_method :bob, :baz
+    end
+
+    last = obj.foo(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+
+    last = obj.bar(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+
+    last = obj.baz(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+
+    last = obj.bob(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+  end
+
+  it "returns nil" do
+    obj = Object.new
+
+    obj.singleton_class.class_exec do
+      def foo(*a) end
+
+      ruby2_keywords(:foo).should == nil
+    end
+  end
+
+  it "raises NameError when passed not existing method name" do
+    obj = Object.new
+
+    -> {
+      obj.singleton_class.class_exec do
+        ruby2_keywords :not_existing
+      end
+    }.should raise_error(NameError, /undefined method [`']not_existing'/)
+  end
+
+  it "accepts String as well" do
+    obj = Object.new
+
+    obj.singleton_class.class_exec do
+      def foo(*a) a.last end
+      ruby2_keywords "foo"
+    end
+
+    last = obj.foo(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+  end
+
+  it "raises TypeError when passed not Symbol or String" do
+    obj = Object.new
+
+    -> {
+      obj.singleton_class.class_exec do
+        ruby2_keywords Object.new
+      end
+    }.should raise_error(TypeError, /is not a symbol nor a string/)
+  end
+
+  it "prints warning when a method does not accept argument splat" do
+    obj = Object.new
+    def obj.foo(a, b, c) end
+
+    -> {
+      obj.singleton_class.class_exec do
+        ruby2_keywords :foo
+      end
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  it "prints warning when a method accepts keywords" do
+    obj = Object.new
+    def obj.foo(*a, b:) end
+
+    -> {
+      obj.singleton_class.class_exec do
+        ruby2_keywords :foo
+      end
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  it "prints warning when a method accepts keyword splat" do
+    obj = Object.new
+    def obj.foo(*a, **b) end
+
+    -> {
+      obj.singleton_class.class_exec do
+        ruby2_keywords :foo
+      end
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  ruby_version_is "4.0" do
+    it "prints warning when a method accepts post arguments" do
+      obj = Object.new
+      def obj.foo(*a, b) end
+
+      -> {
+        obj.singleton_class.class_exec do
+          ruby2_keywords :foo
+        end
+      }.should complain(/Skipping set of ruby2_keywords flag for/)
+    end
+  end
+end
diff --git a/spec/ruby/core/module/set_temporary_name_spec.rb b/spec/ruby/core/module/set_temporary_name_spec.rb
new file mode 100644
index 0000000000..46605ed675
--- /dev/null
+++ b/spec/ruby/core/module/set_temporary_name_spec.rb
@@ -0,0 +1,147 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_temporary_name'
+
+ruby_version_is "3.3" do
+  describe "Module#set_temporary_name" do
+    it "can assign a temporary name" do
+      m = Module.new
+      m.name.should be_nil
+
+      m.set_temporary_name("fake_name")
+      m.name.should == "fake_name"
+
+      m.set_temporary_name(nil)
+      m.name.should be_nil
+    end
+
+    it "returns self" do
+      m = Module.new
+      m.set_temporary_name("fake_name").should.equal? m
+    end
+
+    it "can assign a temporary name which is not a valid constant path" do
+      m = Module.new
+
+      m.set_temporary_name("name")
+      m.name.should == "name"
+
+      m.set_temporary_name("Template['foo.rb']")
+      m.name.should == "Template['foo.rb']"
+
+      m.set_temporary_name("a::B")
+      m.name.should == "a::B"
+
+      m.set_temporary_name("A::b")
+      m.name.should == "A::b"
+
+      m.set_temporary_name("A::B::")
+      m.name.should == "A::B::"
+
+      m.set_temporary_name("A::::B")
+      m.name.should == "A::::B"
+
+      m.set_temporary_name("A=")
+      m.name.should == "A="
+    end
+
+    it "can't assign empty string as name" do
+      m = Module.new
+      -> { m.set_temporary_name("") }.should raise_error(ArgumentError, "empty class/module name")
+    end
+
+    it "can't assign a constant name as a temporary name" do
+      m = Module.new
+      -> { m.set_temporary_name("Object") }.should raise_error(ArgumentError, "the temporary name must not be a constant path to avoid confusion")
+    end
+
+    it "can't assign a constant path as a temporary name" do
+      m = Module.new
+      -> { m.set_temporary_name("A::B") }.should raise_error(ArgumentError, "the temporary name must not be a constant path to avoid confusion")
+      -> { m.set_temporary_name("::A") }.should raise_error(ArgumentError, "the temporary name must not be a constant path to avoid confusion")
+      -> { m.set_temporary_name("::A::B") }.should raise_error(ArgumentError, "the temporary name must not be a constant path to avoid confusion")
+    end
+
+    it "can't assign name to permanent module" do
+      -> { Object.set_temporary_name("fake_name") }.should raise_error(RuntimeError, "can't change permanent name")
+    end
+
+    it "can assign a temporary name to a module nested into an anonymous module" do
+      m = Module.new
+      module m::N; end
+      m::N.name.should =~ /\A#<Module:0x\h+>::N\z/
+
+      m::N.set_temporary_name("fake_name")
+      m::N.name.should == "fake_name"
+
+      m::N.set_temporary_name(nil)
+      m::N.name.should be_nil
+    end
+
+    it "discards a temporary name when an outer anonymous module gets a permanent name" do
+      m = Module.new
+      module m::N; end
+
+      m::N.set_temporary_name("fake_name")
+      m::N.name.should == "fake_name"
+
+      ModuleSpecs::SetTemporaryNameSpec::M = m
+      m::N.name.should == "ModuleSpecs::SetTemporaryNameSpec::M::N"
+      ModuleSpecs::SetTemporaryNameSpec.send :remove_const, :M
+    end
+
+    it "can update the name when assigned to a constant" do
+      m = Module.new
+      m::N = Module.new
+      m::N.name.should =~ /\A#<Module:0x\h+>::N\z/
+      m::N.set_temporary_name(nil)
+
+      m::M = m::N
+      m::M.name.should =~ /\A#<Module:0x\h+>::M\z/m
+    end
+
+    it "can reassign a temporary name repeatedly" do
+      m = Module.new
+
+      m.set_temporary_name("fake_name")
+      m.name.should == "fake_name"
+
+      m.set_temporary_name("fake_name_2")
+      m.name.should == "fake_name_2"
+    end
+
+    ruby_bug "#21094", ""..."4.0" do
+      it "also updates a name of a nested module" do
+        m = Module.new
+        m::N = Module.new
+        m::N.name.should =~ /\A#<Module:0x\h+>::N\z/
+
+        m.set_temporary_name "m"
+        m::N.name.should == "m::N"
+
+        m.set_temporary_name nil
+        m::N.name.should == nil
+      end
+    end
+
+    it "keeps temporary name when assigned in an anonymous module" do
+      outer = Module.new
+      m = Module.new
+      m.set_temporary_name "m"
+      m.name.should == "m"
+      outer::M = m
+      m.name.should == "m"
+      m.inspect.should == "m"
+    end
+
+    it "keeps temporary name when assigned in an anonymous module and nested before" do
+      outer = Module.new
+      m = Module.new
+      outer::A = m
+      m.set_temporary_name "m"
+      m.name.should == "m"
+      outer::M = m
+      m.name.should == "m"
+      m.inspect.should == "m"
+    end
+  end
+end
diff --git a/spec/ruby/core/module/shared/attr_added.rb b/spec/ruby/core/module/shared/attr_added.rb
new file mode 100644
index 0000000000..ce832cdcff
--- /dev/null
+++ b/spec/ruby/core/module/shared/attr_added.rb
@@ -0,0 +1,34 @@
+describe :module_attr_added, shared: true do
+  it "calls method_added for normal classes" do
+    ScratchPad.record []
+
+    cls = Class.new do
+      class << self
+        def method_added(name)
+          ScratchPad.recorded << name
+        end
+      end
+    end
+
+    cls.send(@method, :foo)
+
+    ScratchPad.recorded.each {|name| name.to_s.should =~ /foo[=]?/}
+  end
+
+  it "calls singleton_method_added for singleton classes" do
+    ScratchPad.record []
+    cls = Class.new do
+      class << self
+        def singleton_method_added(name)
+          # called for this def so ignore it
+          return if name == :singleton_method_added
+          ScratchPad.recorded << name
+        end
+      end
+    end
+
+    cls.singleton_class.send(@method, :foo)
+
+    ScratchPad.recorded.each {|name| name.to_s.should =~ /foo[=]?/}
+  end
+end
diff --git a/spec/ruby/core/module/shared/class_eval.rb b/spec/ruby/core/module/shared/class_eval.rb
index 08f8ff7597..b1d5cb3814 100644
--- a/spec/ruby/core/module/shared/class_eval.rb
+++ b/spec/ruby/core/module/shared/class_eval.rb
@@ -52,43 +52,58 @@ describe :module_class_eval, shared: true do
     ModuleSpecs.send(@method, "[__FILE__, __LINE__]", "test", 102).should == ["test", 102]
   end
 
+  ruby_version_is "3.3" do
+    it "uses the caller location as default filename" do
+      ModuleSpecs.send(@method, "[__FILE__, __LINE__]").should == ["(eval at #{__FILE__}:#{__LINE__})", 1]
+    end
+  end
+
   it "converts a non-string filename to a string using to_str" do
     (file = mock(__FILE__)).should_receive(:to_str).and_return(__FILE__)
     ModuleSpecs.send(@method, "1+1", file)
+
+    (file = mock(__FILE__)).should_receive(:to_str).and_return(__FILE__)
+    ModuleSpecs.send(@method, "1+1", file, 15)
   end
 
   it "raises a TypeError when the given filename can't be converted to string using to_str" do
     (file = mock('123')).should_receive(:to_str).and_return(123)
-    -> { ModuleSpecs.send(@method, "1+1", file) }.should raise_error(TypeError)
+    -> { ModuleSpecs.send(@method, "1+1", file) }.should raise_error(TypeError, /can't convert MockObject to String/)
   end
 
   it "converts non string eval-string to string using to_str" do
     (o = mock('1 + 1')).should_receive(:to_str).and_return("1 + 1")
     ModuleSpecs.send(@method, o).should == 2
+
+    (o = mock('1 + 1')).should_receive(:to_str).and_return("1 + 1")
+    ModuleSpecs.send(@method, o, "file.rb").should == 2
+
+    (o = mock('1 + 1')).should_receive(:to_str).and_return("1 + 1")
+    ModuleSpecs.send(@method, o, "file.rb", 15).should == 2
   end
 
   it "raises a TypeError when the given eval-string can't be converted to string using to_str" do
     o = mock('x')
-    -> { ModuleSpecs.send(@method, o) }.should raise_error(TypeError)
+    -> { ModuleSpecs.send(@method, o) }.should raise_error(TypeError, "no implicit conversion of MockObject into String")
 
     (o = mock('123')).should_receive(:to_str).and_return(123)
-    -> { ModuleSpecs.send(@method, o) }.should raise_error(TypeError)
+    -> { ModuleSpecs.send(@method, o) }.should raise_error(TypeError, /can't convert MockObject to String/)
   end
 
   it "raises an ArgumentError when no arguments and no block are given" do
-    -> { ModuleSpecs.send(@method) }.should raise_error(ArgumentError)
+    -> { ModuleSpecs.send(@method) }.should raise_error(ArgumentError, "wrong number of arguments (given 0, expected 1..3)")
   end
 
   it "raises an ArgumentError when more than 3 arguments are given" do
     -> {
       ModuleSpecs.send(@method, "1 + 1", "some file", 0, "bogus")
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 1..3)")
   end
 
   it "raises an ArgumentError when a block and normal arguments are given" do
     -> {
       ModuleSpecs.send(@method, "1 + 1") { 1 + 1 }
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, "wrong number of arguments (given 1, expected 0)")
   end
 
   # This case was found because Rubinius was caching the compiled
@@ -112,4 +127,48 @@ describe :module_class_eval, shared: true do
     a.attribute.should == "A"
     b.attribute.should == "B"
   end
+
+  it "activates refinements from the eval scope" do
+    refinery = Module.new do
+      refine ModuleSpecs::NamedClass do
+        def foo
+          "bar"
+        end
+      end
+    end
+
+    mid = @method
+    result = nil
+
+    Class.new do
+      using refinery
+
+      result = send(mid, "ModuleSpecs::NamedClass.new.foo")
+    end
+
+    result.should == "bar"
+  end
+
+  it "activates refinements from the eval scope with block" do
+    refinery = Module.new do
+      refine ModuleSpecs::NamedClass do
+        def foo
+          "bar"
+        end
+      end
+    end
+
+    mid = @method
+    result = nil
+
+    Class.new do
+      using refinery
+
+      result = send(mid) do
+        ModuleSpecs::NamedClass.new.foo
+      end
+    end
+
+    result.should == "bar"
+  end
 end
diff --git a/spec/ruby/core/module/shared/set_visibility.rb b/spec/ruby/core/module/shared/set_visibility.rb
index c39d59e05d..a1586dd2bd 100644
--- a/spec/ruby/core/module/shared/set_visibility.rb
+++ b/spec/ruby/core/module/shared/set_visibility.rb
@@ -5,6 +5,55 @@ describe :set_visibility, shared: true do
     Module.should have_private_instance_method(@method, false)
   end
 
+  describe "with argument" do
+    describe "one or more arguments" do
+      it "sets visibility of given method names" do
+        visibility = @method
+        old_visibility = [:protected, :private].find {|vis| vis != visibility }
+
+        mod = Module.new {
+          send old_visibility
+          def test1() end
+          def test2() end
+          send visibility, :test1, :test2
+        }
+        mod.should send(:"have_#{visibility}_instance_method", :test1, false)
+        mod.should send(:"have_#{visibility}_instance_method", :test2, false)
+      end
+    end
+
+    describe "array as a single argument" do
+      it "sets visibility of given method names" do
+        visibility = @method
+        old_visibility = [:protected, :private].find {|vis| vis != visibility }
+
+        mod = Module.new {
+          send old_visibility
+          def test1() end
+          def test2() end
+          send visibility, [:test1, :test2]
+        }
+        mod.should send(:"have_#{visibility}_instance_method", :test1, false)
+        mod.should send(:"have_#{visibility}_instance_method", :test2, false)
+      end
+    end
+
+    it "does not clone method from the ancestor when setting to the same visibility in a child" do
+      visibility = @method
+      parent = Module.new {
+        def test_method; end
+        send(visibility, :test_method)
+      }
+
+      child = Module.new {
+        include parent
+        send(visibility, :test_method)
+      }
+
+      child.should_not send(:"have_#{visibility}_instance_method", :test_method, false)
+    end
+  end
+
   describe "without arguments" do
     it "sets visibility to following method definitions" do
       visibility = @method
diff --git a/spec/ruby/core/module/singleton_class_spec.rb b/spec/ruby/core/module/singleton_class_spec.rb
index b9f78eeb21..052755b73b 100644
--- a/spec/ruby/core/module/singleton_class_spec.rb
+++ b/spec/ruby/core/module/singleton_class_spec.rb
@@ -3,25 +3,25 @@ require_relative '../../spec_helper'
 describe "Module#singleton_class?" do
   it "returns true for singleton classes" do
     xs = self.singleton_class
-    xs.singleton_class?.should == true
+    xs.should.singleton_class?
   end
 
   it "returns false for other classes" do
     c = Class.new
-    c.singleton_class?.should == false
+    c.should_not.singleton_class?
   end
 
   describe "with singleton values" do
     it "returns false for nil's singleton class" do
-      NilClass.singleton_class?.should == false
+      NilClass.should_not.singleton_class?
     end
 
     it "returns false for true's singleton class" do
-      TrueClass.singleton_class?.should == false
+      TrueClass.should_not.singleton_class?
     end
 
     it "returns false for false's singleton class" do
-      FalseClass.singleton_class?.should == false
+      FalseClass.should_not.singleton_class?
     end
   end
 end
diff --git a/spec/ruby/core/module/to_s_spec.rb b/spec/ruby/core/module/to_s_spec.rb
index bebdcf6e1b..83c0ae0825 100644
--- a/spec/ruby/core/module/to_s_spec.rb
+++ b/spec/ruby/core/module/to_s_spec.rb
@@ -2,17 +2,69 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "Module#to_s" do
+  it 'returns the name of the module if it has a name' do
+    Enumerable.to_s.should == 'Enumerable'
+    String.to_s.should == 'String'
+  end
+
   it "returns the full constant path leading to the module" do
     ModuleSpecs::LookupMod.to_s.should == "ModuleSpecs::LookupMod"
   end
 
   it "works with an anonymous module" do
     m = Module.new
-    m.to_s.should =~ /#<Module:0x[0-9a-f]+>/
+    m.to_s.should =~ /\A#<Module:0x\h+>\z/
   end
 
   it "works with an anonymous class" do
     c = Class.new
-    c.to_s.should =~ /#<Class:0x[0-9a-f]+>/
+    c.to_s.should =~ /\A#<Class:0x\h+>\z/
+  end
+
+  it 'for the singleton class of an object of an anonymous class' do
+    klass = Class.new
+    obj = klass.new
+    sclass = obj.singleton_class
+    sclass.to_s.should == "#<Class:#{obj}>"
+    sclass.to_s.should =~ /\A#<Class:#<#{klass}:0x\h+>>\z/
+    sclass.to_s.should =~ /\A#<Class:#<#<Class:0x\h+>:0x\h+>>\z/
+  end
+
+  it 'for a singleton class of a module includes the module name' do
+    ModuleSpecs.singleton_class.to_s.should == '#<Class:ModuleSpecs>'
+  end
+
+  it 'for a metaclass includes the class name' do
+    ModuleSpecs::NamedClass.singleton_class.to_s.should == '#<Class:ModuleSpecs::NamedClass>'
+  end
+
+  it 'for objects includes class name and object ID' do
+    obj = ModuleSpecs::NamedClass.new
+    obj.singleton_class.to_s.should =~ /\A#<Class:#<ModuleSpecs::NamedClass:0x\h+>>\z/
+  end
+
+  it "always show the refinement name, even if the module is named" do
+    module ModuleSpecs::RefinementInspect
+      R = refine String do
+      end
+    end
+
+    ModuleSpecs::RefinementInspect::R.name.should == 'ModuleSpecs::RefinementInspect::R'
+    ModuleSpecs::RefinementInspect::R.to_s.should == '#<refinement:String@ModuleSpecs::RefinementInspect>'
+  ensure
+    ModuleSpecs.send(:remove_const, :RefinementInspect)
+  end
+
+  it 'does not call #inspect or #to_s for singleton classes' do
+    klass = Class.new
+    obj = klass.new
+    def obj.to_s
+      "to_s"
+    end
+    def obj.inspect
+      "inspect"
+    end
+    sclass = obj.singleton_class
+    sclass.to_s.should =~ /\A#<Class:#<#{Regexp.escape klass.to_s}:0x\h+>>\z/
   end
 end
diff --git a/spec/ruby/core/module/undef_method_spec.rb b/spec/ruby/core/module/undef_method_spec.rb
index 9b2c9240f4..d4efcd51cb 100644
--- a/spec/ruby/core/module/undef_method_spec.rb
+++ b/spec/ruby/core/module/undef_method_spec.rb
@@ -18,15 +18,8 @@ describe "Module#undef_method" do
     @module = Module.new { def method_to_undef; end }
   end
 
-  ruby_version_is ''...'2.5' do
-    it "is a private method" do
-      Module.should have_private_instance_method(:undef_method, false)
-    end
-  end
-  ruby_version_is '2.5' do
-    it "is a public method" do
-      Module.should have_public_instance_method(:undef_method, false)
-    end
+  it "is a public method" do
+    Module.should have_public_instance_method(:undef_method, false)
   end
 
   it "requires multiple arguments" do
@@ -56,8 +49,37 @@ describe "Module#undef_method" do
     @module.send(:undef_method, :method_to_undef).should equal(@module)
   end
 
-  it "raises a NameError when passed a missing name" do
-    -> { @module.send :undef_method, :not_exist }.should raise_error(NameError) { |e|
+  it "raises a NameError when passed a missing name for a module" do
+    -> { @module.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method [`']not_exist' for module [`']#{@module}'/) { |e|
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError when passed a missing name for a class" do
+    klass = Class.new
+    -> { klass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method [`']not_exist' for class [`']#{klass}'/) { |e|
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError when passed a missing name for a singleton class" do
+    klass = Class.new
+    obj = klass.new
+    sclass = obj.singleton_class
+
+    -> { sclass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method [`']not_exist' for class [`']#{sclass}'/) { |e|
+      e.message.should =~ /[`']#<Class:#<#<Class:/
+
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError when passed a missing name for a metaclass" do
+    klass = String.singleton_class
+    -> { klass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method [`']not_exist' for class [`']String'/) { |e|
       # a NameError and not a NoMethodError
       e.class.should == NameError
     }
@@ -68,12 +90,12 @@ describe "Module#undef_method" do
       @frozen = @module.dup.freeze
     end
 
-    it "raises a #{frozen_error_class} when passed a name" do
-      -> { @frozen.send :undef_method, :method_to_undef }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed a name" do
+      -> { @frozen.send :undef_method, :method_to_undef }.should raise_error(FrozenError)
     end
 
-    it "raises a #{frozen_error_class} when passed a missing name" do
-      -> { @frozen.send :undef_method, :not_exist }.should raise_error(frozen_error_class)
+    it "raises a FrozenError when passed a missing name" do
+      -> { @frozen.send :undef_method, :not_exist }.should raise_error(FrozenError)
     end
 
     it "raises a TypeError when passed a not name" do
diff --git a/spec/ruby/core/module/undefined_instance_methods_spec.rb b/spec/ruby/core/module/undefined_instance_methods_spec.rb
new file mode 100644
index 0000000000..d33ee93fc1
--- /dev/null
+++ b/spec/ruby/core/module/undefined_instance_methods_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Module#undefined_instance_methods" do
+  it "returns methods undefined in the class" do
+    methods = ModuleSpecs::UndefinedInstanceMethods::Parent.undefined_instance_methods
+    methods.should == [:undefed_method]
+  end
+
+  it "returns inherited methods undefined in the class" do
+    methods = ModuleSpecs::UndefinedInstanceMethods::Child.undefined_instance_methods
+    methods.should include(:parent_method, :another_parent_method)
+  end
+
+  it "returns methods from an included module that are undefined in the class" do
+    methods = ModuleSpecs::UndefinedInstanceMethods::Grandchild.undefined_instance_methods
+    methods.should include(:super_included_method)
+  end
+
+  it "does not returns ancestors undefined methods" do
+    methods = ModuleSpecs::UndefinedInstanceMethods::Grandchild.undefined_instance_methods
+    methods.should_not include(:parent_method, :another_parent_method)
+  end
+end
diff --git a/spec/ruby/core/module/used_refinements_spec.rb b/spec/ruby/core/module/used_refinements_spec.rb
new file mode 100644
index 0000000000..40dd4a444e
--- /dev/null
+++ b/spec/ruby/core/module/used_refinements_spec.rb
@@ -0,0 +1,85 @@
+require_relative '../../spec_helper'
+
+describe "Module.used_refinements" do
+  it "returns list of all refinements imported in the current scope" do
+    refinement_int = nil
+    refinement_str = nil
+    ScratchPad.record []
+
+    m1 = Module.new do
+      refine Integer do
+        refinement_int = self
+      end
+    end
+
+    m2 = Module.new do
+      refine String do
+        refinement_str = self
+      end
+    end
+
+    Module.new do
+      using m1
+      using m2
+
+      Module.used_refinements.each { |r| ScratchPad << r }
+    end
+
+    ScratchPad.recorded.sort_by(&:object_id).should == [refinement_int, refinement_str].sort_by(&:object_id)
+  end
+
+  it "returns empty array if does not have any refinements imported" do
+    used_refinements = nil
+
+    Module.new do
+      used_refinements = Module.used_refinements
+    end
+
+    used_refinements.should == []
+  end
+
+  it "ignores refinements imported in a module that is included into the current one" do
+    used_refinements = nil
+
+    m1 = Module.new do
+      refine Integer do
+        nil
+      end
+    end
+
+    m2 = Module.new do
+      using m1
+    end
+
+    Module.new do
+      include m2
+
+      used_refinements = Module.used_refinements
+    end
+
+    used_refinements.should == []
+  end
+
+  it "returns refinements even not defined directly in a module refinements are imported from" do
+    used_refinements = nil
+    ScratchPad.record []
+
+    m1 = Module.new do
+      refine Integer do
+        ScratchPad << self
+      end
+    end
+
+    m2 = Module.new do
+      include m1
+    end
+
+    Module.new do
+      using m2
+
+      used_refinements = Module.used_refinements
+    end
+
+    used_refinements.should == ScratchPad.recorded
+  end
+end
diff --git a/spec/ruby/core/module/using_spec.rb b/spec/ruby/core/module/using_spec.rb
index 533d87d080..a908363c96 100644
--- a/spec/ruby/core/module/using_spec.rb
+++ b/spec/ruby/core/module/using_spec.rb
@@ -243,6 +243,96 @@ describe "Module#using" do
       mod.call_foo(c).should == "foo from refinement"
     end
 
+    it "is active for module defined via Module.new {}" do
+      refinement = Module.new do
+        refine Integer do
+          def foo; "foo from refinement"; end
+        end
+      end
+
+      result = nil
+
+      Module.new do
+        using refinement
+
+        Module.new do
+          result = 1.foo
+        end
+      end
+
+      result.should == "foo from refinement"
+    end
+
+    it "is active for class defined via Class.new {}" do
+      refinement = Module.new do
+        refine Integer do
+          def foo; "foo from refinement"; end
+        end
+      end
+
+      result = nil
+
+      Module.new do
+        using refinement
+
+        Class.new do
+          result = 1.foo
+        end
+      end
+
+      result.should == "foo from refinement"
+    end
+
+    it "is active for block called via instance_exec" do
+      refinement = Module.new do
+        refine Integer do
+          def foo; "foo from refinement"; end
+        end
+      end
+
+      c = Class.new do
+        using refinement
+
+        def abc
+          block = -> {
+            1.foo
+          }
+
+          self.instance_exec(&block)
+        end
+      end
+
+      c.new.abc.should == "foo from refinement"
+    end
+
+    it "is active for block called via instance_eval" do
+      refinement = Module.new do
+        refine String do
+          def foo; "foo from refinement"; end
+        end
+      end
+
+      c = Class.new do
+        using refinement
+
+        def initialize
+          @a = +"1703"
+
+          @a.instance_eval do
+            def abc
+              "#{self}: #{self.foo}"
+            end
+          end
+        end
+
+        def abc
+          @a.abc
+        end
+      end
+
+      c.new.abc.should == "1703: foo from refinement"
+    end
+
     it "is not active if `using` call is not evaluated" do
       result = nil
 
diff --git a/spec/ruby/core/mutex/lock_spec.rb b/spec/ruby/core/mutex/lock_spec.rb
index 7a39817b11..e9d33f5fd9 100644
--- a/spec/ruby/core/mutex/lock_spec.rb
+++ b/spec/ruby/core/mutex/lock_spec.rb
@@ -1,10 +1,6 @@
 require_relative '../../spec_helper'
 
 describe "Mutex#lock" do
-  before :each do
-    ScratchPad.clear
-  end
-
   it "returns self" do
     m = Mutex.new
     m.lock.should == m
diff --git a/spec/ruby/core/mutex/owned_spec.rb b/spec/ruby/core/mutex/owned_spec.rb
index e66062534e..7bfc7d8f83 100644
--- a/spec/ruby/core/mutex/owned_spec.rb
+++ b/spec/ruby/core/mutex/owned_spec.rb
@@ -40,4 +40,14 @@ describe "Mutex#owned?" do
       m.owned?.should be_false
     end
   end
+
+  it "is held per Fiber" do
+    m = Mutex.new
+    m.lock
+
+    Fiber.new do
+      m.locked?.should == true
+      m.owned?.should == false
+    end.resume
+  end
 end
diff --git a/spec/ruby/core/mutex/sleep_spec.rb b/spec/ruby/core/mutex/sleep_spec.rb
index 477f9278c8..9832e3125e 100644
--- a/spec/ruby/core/mutex/sleep_spec.rb
+++ b/spec/ruby/core/mutex/sleep_spec.rb
@@ -24,12 +24,12 @@ describe "Mutex#sleep" do
   it "pauses execution for approximately the duration requested" do
     m = Mutex.new
     m.lock
-    duration = 0.1
+    duration = 0.001
     start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
     m.sleep duration
     now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
-    (now - start).should > 0
-    (now - start).should < 2.0
+    (now - start).should >= 0
+    (now - start).should < (duration + TIME_TOLERANCE)
   end
 
   it "unlocks the mutex while sleeping" do
@@ -37,7 +37,7 @@ describe "Mutex#sleep" do
     locked = false
     th = Thread.new { m.lock; locked = true; m.sleep }
     Thread.pass until locked
-    Thread.pass while th.status and th.status != "sleep"
+    Thread.pass until th.stop?
     m.locked?.should be_false
     th.run
     th.join
@@ -46,7 +46,7 @@ describe "Mutex#sleep" do
   it "relocks the mutex when woken" do
     m = Mutex.new
     m.lock
-    m.sleep(0.01)
+    m.sleep(0.001)
     m.locked?.should be_true
   end
 
@@ -63,15 +63,23 @@ describe "Mutex#sleep" do
       end
     end
     Thread.pass until locked
-    Thread.pass while th.status and th.status != "sleep"
+    Thread.pass until th.stop?
     th.raise(Exception)
     th.value.should be_true
   end
 
   it "returns the rounded number of seconds asleep" do
     m = Mutex.new
-    m.lock
-    m.sleep(0.01).should be_kind_of(Integer)
+    locked = false
+    th = Thread.start do
+      m.lock
+      locked = true
+      m.sleep
+    end
+    Thread.pass until locked
+    Thread.pass until th.stop?
+    th.wakeup
+    th.value.should be_kind_of(Integer)
   end
 
   it "wakes up when requesting sleep times near or equal to zero" do
@@ -89,7 +97,7 @@ describe "Mutex#sleep" do
     m.lock
     times.each do |time|
       # just testing that sleep completes
-      m.sleep(time).should_not == nil
+      -> {m.sleep(time)}.should_not raise_error
     end
   end
 end
diff --git a/spec/ruby/core/mutex/unlock_spec.rb b/spec/ruby/core/mutex/unlock_spec.rb
index c9c3bfe14f..d999e66842 100644
--- a/spec/ruby/core/mutex/unlock_spec.rb
+++ b/spec/ruby/core/mutex/unlock_spec.rb
@@ -17,7 +17,7 @@ describe "Mutex#unlock" do
 
     # avoid race on mutex.lock
     Thread.pass until mutex.locked?
-    Thread.pass while th.status and th.status != "sleep"
+    Thread.pass until th.stop?
 
     -> { mutex.unlock }.should raise_error(ThreadError)
 
diff --git a/spec/ruby/core/nil/case_compare_spec.rb b/spec/ruby/core/nil/case_compare_spec.rb
new file mode 100644
index 0000000000..142560c6f5
--- /dev/null
+++ b/spec/ruby/core/nil/case_compare_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "NilClass#===" do
+  it "returns true for nil" do
+    (nil === nil).should == true
+  end
+
+  it "returns false for non-nil object" do
+    (nil === 1).should == false
+    (nil === "").should == false
+    (nil === Object).should == false
+  end
+end
diff --git a/spec/ruby/core/nil/match_spec.rb b/spec/ruby/core/nil/match_spec.rb
index 3f69312bfe..bc1c591793 100644
--- a/spec/ruby/core/nil/match_spec.rb
+++ b/spec/ruby/core/nil/match_spec.rb
@@ -1,19 +1,21 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "NilClass#=~" do
-    it "returns nil matching any object" do
-      o = Object.new
+describe "NilClass#=~" do
+  it "returns nil matching any object" do
+    o = nil
 
-      suppress_warning do
-        (o =~ /Object/).should   be_nil
-        (o =~ 'Object').should   be_nil
-        (o =~ Object).should     be_nil
-        (o =~ Object.new).should be_nil
-        (o =~ nil).should        be_nil
-        (o =~ false).should      be_nil
-        (o =~ true).should       be_nil
-      end
+    suppress_warning do
+      (o =~ /Object/).should   be_nil
+      (o =~ 'Object').should   be_nil
+      (o =~ Object).should     be_nil
+      (o =~ Object.new).should be_nil
+      (o =~ nil).should        be_nil
+      (o =~ false).should      be_nil
+      (o =~ true).should       be_nil
     end
   end
+
+  it "should not warn" do
+    -> { nil =~ /a/ }.should_not complain(verbose: true)
+  end
 end
diff --git a/spec/ruby/core/nil/nil_spec.rb b/spec/ruby/core/nil/nil_spec.rb
index 47db0c5cf0..2cf97621c6 100644
--- a/spec/ruby/core/nil/nil_spec.rb
+++ b/spec/ruby/core/nil/nil_spec.rb
@@ -2,6 +2,6 @@ require_relative '../../spec_helper'
 
 describe "NilClass#nil?" do
   it "returns true" do
-    nil.nil?.should == true
+    nil.should.nil?
   end
 end
diff --git a/spec/ruby/core/nil/singleton_method_spec.rb b/spec/ruby/core/nil/singleton_method_spec.rb
new file mode 100644
index 0000000000..8d898b1cc9
--- /dev/null
+++ b/spec/ruby/core/nil/singleton_method_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+
+describe "NilClass#singleton_method" do
+  ruby_version_is '3.3' do
+    it "raises regardless of whether NilClass defines the method" do
+      -> { nil.singleton_method(:foo) }.should raise_error(NameError)
+      begin
+        def (nil).foo; end
+        -> { nil.singleton_method(:foo) }.should raise_error(NameError)
+      ensure
+        NilClass.send(:remove_method, :foo)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/nil/to_i_spec.rb b/spec/ruby/core/nil/to_i_spec.rb
index 099792ef68..d3d088e999 100644
--- a/spec/ruby/core/nil/to_i_spec.rb
+++ b/spec/ruby/core/nil/to_i_spec.rb
@@ -5,7 +5,7 @@ describe "NilClass#to_i" do
     nil.to_i.should == 0
   end
 
-  it "does not cause NilClass to be coerced to Fixnum" do
+  it "does not cause NilClass to be coerced to Integer" do
     (0 == nil).should == false
   end
 end
diff --git a/spec/ruby/core/nil/to_s_spec.rb b/spec/ruby/core/nil/to_s_spec.rb
index c7a18e2527..fa0b929677 100644
--- a/spec/ruby/core/nil/to_s_spec.rb
+++ b/spec/ruby/core/nil/to_s_spec.rb
@@ -4,4 +4,12 @@ describe "NilClass#to_s" do
   it "returns the string ''" do
     nil.to_s.should == ""
   end
+
+  it "returns a frozen string" do
+    nil.to_s.should.frozen?
+  end
+
+  it "always returns the same string" do
+    nil.to_s.should equal(nil.to_s)
+  end
 end
diff --git a/spec/ruby/core/numeric/clone_spec.rb b/spec/ruby/core/numeric/clone_spec.rb
new file mode 100644
index 0000000000..423cec85dd
--- /dev/null
+++ b/spec/ruby/core/numeric/clone_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+
+describe "Numeric#clone" do
+  it "returns self" do
+    value = 1
+    value.clone.should equal(value)
+
+    subclass = Class.new(Numeric)
+    value = subclass.new
+    value.clone.should equal(value)
+  end
+
+  it "does not change frozen status" do
+    1.clone.frozen?.should == true
+  end
+
+  it "accepts optional keyword argument :freeze" do
+    value = 1
+    value.clone(freeze: true).should equal(value)
+  end
+
+  it "raises ArgumentError if passed freeze: false" do
+    -> { 1.clone(freeze: false) }.should raise_error(ArgumentError, /can't unfreeze/)
+  end
+
+  it "does not change frozen status if passed freeze: nil" do
+    value = 1
+    value.clone(freeze: nil).should equal(value)
+  end
+end
diff --git a/spec/ruby/core/numeric/dup_spec.rb b/spec/ruby/core/numeric/dup_spec.rb
new file mode 100644
index 0000000000..189a7ef44d
--- /dev/null
+++ b/spec/ruby/core/numeric/dup_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+
+describe "Numeric#dup" do
+  it "returns self" do
+    value = 1
+    value.dup.should equal(value)
+
+    subclass = Class.new(Numeric)
+    value = subclass.new
+    value.dup.should equal(value)
+  end
+
+  it "does not change frozen status" do
+    1.dup.frozen?.should == true
+  end
+end
diff --git a/spec/ruby/core/numeric/fdiv_spec.rb b/spec/ruby/core/numeric/fdiv_spec.rb
index 907e5d343c..e97fa77f79 100644
--- a/spec/ruby/core/numeric/fdiv_spec.rb
+++ b/spec/ruby/core/numeric/fdiv_spec.rb
@@ -1,5 +1,4 @@
 require_relative '../../spec_helper'
-require_relative 'shared/quo'
 
 describe "Numeric#fdiv" do
   it "coerces self with #to_f" do
diff --git a/spec/ruby/core/numeric/integer_spec.rb b/spec/ruby/core/numeric/integer_spec.rb
index 5d4bf00360..adbac4d7aa 100644
--- a/spec/ruby/core/numeric/integer_spec.rb
+++ b/spec/ruby/core/numeric/integer_spec.rb
@@ -3,6 +3,6 @@ require_relative 'fixtures/classes'
 
 describe "Numeric#integer?" do
   it "returns false" do
-    NumericSpecs::Subclass.new.integer?.should == false
+    NumericSpecs::Subclass.new.should_not.integer?
   end
 end
diff --git a/spec/ruby/core/numeric/magnitude_spec.rb b/spec/ruby/core/numeric/magnitude_spec.rb
index 7a3290b036..1371dff21f 100644
--- a/spec/ruby/core/numeric/magnitude_spec.rb
+++ b/spec/ruby/core/numeric/magnitude_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative 'shared/abs'
 
 describe "Numeric#magnitude" do
diff --git a/spec/ruby/core/numeric/negative_spec.rb b/spec/ruby/core/numeric/negative_spec.rb
index da464a9094..9c6f95fd87 100644
--- a/spec/ruby/core/numeric/negative_spec.rb
+++ b/spec/ruby/core/numeric/negative_spec.rb
@@ -31,11 +31,11 @@ describe "Numeric#negative?" do
 
   it "returns true if self is less than 0" do
     @obj.should_receive(:<).with(0).and_return(true)
-    @obj.negative?.should == true
+    @obj.should.negative?
   end
 
   it "returns false if self is greater than 0" do
     @obj.should_receive(:<).with(0).and_return(false)
-    @obj.negative?.should == false
+    @obj.should_not.negative?
   end
 end
diff --git a/spec/ruby/core/numeric/positive_spec.rb b/spec/ruby/core/numeric/positive_spec.rb
index 8f98fbfa26..3b831b4d34 100644
--- a/spec/ruby/core/numeric/positive_spec.rb
+++ b/spec/ruby/core/numeric/positive_spec.rb
@@ -31,11 +31,11 @@ describe "Numeric#positive?" do
 
   it "returns true if self is greater than 0" do
     @obj.should_receive(:>).with(0).and_return(true)
-    @obj.positive?.should == true
+    @obj.should.positive?
   end
 
   it "returns false if self is less than 0" do
     @obj.should_receive(:>).with(0).and_return(false)
-    @obj.positive?.should == false
+    @obj.should_not.positive?
   end
 end
diff --git a/spec/ruby/core/numeric/quo_spec.rb b/spec/ruby/core/numeric/quo_spec.rb
index 5c952b11a9..6e3ce7a374 100644
--- a/spec/ruby/core/numeric/quo_spec.rb
+++ b/spec/ruby/core/numeric/quo_spec.rb
@@ -1,6 +1,5 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
-require_relative 'shared/quo'
 
 describe "Numeric#quo" do
   it "returns the result of self divided by the given Integer as a Rational" do
@@ -20,7 +19,7 @@ describe "Numeric#quo" do
     -> { 10.quo(0) }.should raise_error(ZeroDivisionError)
     -> { -10.quo(0) }.should raise_error(ZeroDivisionError)
     -> { bignum_value.quo(0) }.should raise_error(ZeroDivisionError)
-    -> { -bignum_value.quo(0) }.should raise_error(ZeroDivisionError)
+    -> { (-bignum_value).quo(0) }.should raise_error(ZeroDivisionError)
   end
 
   it "calls #to_r to convert the object to a Rational" do
@@ -52,4 +51,13 @@ describe "Numeric#quo" do
 
     obj.quo(19).should == 1.quo(20)
   end
+
+  it "raises a ZeroDivisionError if the given argument is zero and not a Float" do
+    -> { 1.quo(0) }.should raise_error(ZeroDivisionError)
+  end
+
+  it "returns infinity if the given argument is zero and is a Float" do
+    (1.quo(0.0)).to_s.should == 'Infinity'
+    (-1.quo(0.0)).to_s.should == '-Infinity'
+  end
 end
diff --git a/spec/ruby/core/numeric/real_spec.rb b/spec/ruby/core/numeric/real_spec.rb
index caa8dcec6d..2d2499bcce 100644
--- a/spec/ruby/core/numeric/real_spec.rb
+++ b/spec/ruby/core/numeric/real_spec.rb
@@ -32,6 +32,6 @@ end
 
 describe "Numeric#real?" do
   it "returns true" do
-    NumericSpecs::Subclass.new.real?.should == true
+    NumericSpecs::Subclass.new.should.real?
   end
 end
diff --git a/spec/ruby/core/numeric/remainder_spec.rb b/spec/ruby/core/numeric/remainder_spec.rb
index 1e2f5f3a96..674fa22d8e 100644
--- a/spec/ruby/core/numeric/remainder_spec.rb
+++ b/spec/ruby/core/numeric/remainder_spec.rb
@@ -6,6 +6,9 @@ describe "Numeric#remainder" do
     @obj    = NumericSpecs::Subclass.new
     @result = mock("Numeric#% result")
     @other  = mock("Passed Object")
+    ruby_version_is "3.3" do
+      @other.should_receive(:coerce).with(@obj).and_return([@obj, @other])
+    end
   end
 
   it "returns the result of calling self#% with other if self is 0" do
diff --git a/spec/ruby/core/numeric/shared/imag.rb b/spec/ruby/core/numeric/shared/imag.rb
index ac2da40a3b..4f117e243a 100644
--- a/spec/ruby/core/numeric/shared/imag.rb
+++ b/spec/ruby/core/numeric/shared/imag.rb
@@ -19,8 +19,8 @@ describe :numeric_imag, shared: true do
   end
 
   it "raises an ArgumentError if given any arguments" do
-   @numbers.each do |number|
-     -> { number.send(@method, number) }.should raise_error(ArgumentError)
-   end
+    @numbers.each do |number|
+      -> { number.send(@method, number) }.should raise_error(ArgumentError)
+    end
   end
 end
diff --git a/spec/ruby/core/numeric/shared/quo.rb b/spec/ruby/core/numeric/shared/quo.rb
deleted file mode 100644
index 2392636fe7..0000000000
--- a/spec/ruby/core/numeric/shared/quo.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-describe :numeric_quo_18, shared: true do
-  it "returns the result of calling self#/ with other" do
-    obj = mock_numeric('numeric')
-    obj.should_receive(:/).with(19).and_return(:result)
-    obj.send(@method, 19).should == :result
-  end
-end
diff --git a/spec/ruby/core/numeric/shared/rect.rb b/spec/ruby/core/numeric/shared/rect.rb
index 9cde19a398..120a69b1c4 100644
--- a/spec/ruby/core/numeric/shared/rect.rb
+++ b/spec/ruby/core/numeric/shared/rect.rb
@@ -25,24 +25,24 @@ describe :numeric_rect, shared: true do
   end
 
   it "returns self as the first element" do
-   @numbers.each do |number|
-     if Float === number and number.nan?
-       number.send(@method).first.nan?.should be_true
-     else
-       number.send(@method).first.should == number
-     end
-   end
+    @numbers.each do |number|
+      if Float === number and number.nan?
+        number.send(@method).first.nan?.should be_true
+      else
+        number.send(@method).first.should == number
+      end
+    end
   end
 
   it "returns 0 as the last element" do
-   @numbers.each do |number|
-     number.send(@method).last.should == 0
-   end
+    @numbers.each do |number|
+      number.send(@method).last.should == 0
+    end
   end
 
   it "raises an ArgumentError if given any arguments" do
-   @numbers.each do |number|
-     -> { number.send(@method, number) }.should raise_error(ArgumentError)
-   end
+    @numbers.each do |number|
+      -> { number.send(@method, number) }.should raise_error(ArgumentError)
+    end
   end
 end
diff --git a/spec/ruby/core/numeric/shared/step.rb b/spec/ruby/core/numeric/shared/step.rb
index b0cbbd0585..977ec6de02 100644
--- a/spec/ruby/core/numeric/shared/step.rb
+++ b/spec/ruby/core/numeric/shared/step.rb
@@ -2,17 +2,17 @@ require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
 # Describes Numeric#step shared specs between different argument styles.
-# To be able to do it, the @step_args var must contain a Proc that transforms
+# To be able to do it, the @step ivar must contain a Proc that transforms
 # the step call arguments passed as positional arguments to the style of
 # arguments pretended to test.
-describe :numeric_step, :shared => true do
+describe :numeric_step, shared: true do
   before :each do
     ScratchPad.record []
     @prc = -> x { ScratchPad << x }
   end
 
   it "defaults to step = 1" do
-    1.send(@method, *@step_args.call(5), &@prc)
+    @step.call(1, 5, &@prc)
     ScratchPad.recorded.should eql [1, 2, 3, 4, 5]
   end
 
@@ -24,41 +24,41 @@ describe :numeric_step, :shared => true do
     1.0.step.first(5).should == [1.0, 2.0, 3.0, 4.0, 5.0]
   end
 
-  describe "when self, stop and step are Fixnums" do
-    it "yields only Fixnums" do
-      1.send(@method, *@step_args.call(5, 1)) { |x| x.should be_an_instance_of(Fixnum) }
+  describe "when self, stop and step are Integers" do
+    it "yields only Integers" do
+      @step.call(1, 5, 1) { |x| x.should be_an_instance_of(Integer) }
     end
 
     describe "with a positive step" do
       it "yields while increasing self by step until stop is reached" do
-        1.send(@method, *@step_args.call(5, 1), &@prc)
+        @step.call(1, 5, 1, &@prc)
         ScratchPad.recorded.should eql [1, 2, 3, 4, 5]
       end
 
       it "yields once when self equals stop" do
-        1.send(@method, *@step_args.call(1, 1), &@prc)
+        @step.call(1, 1, 1, &@prc)
         ScratchPad.recorded.should eql [1]
       end
 
       it "does not yield when self is greater than stop" do
-        2.send(@method, *@step_args.call(1, 1), &@prc)
+        @step.call(2, 1, 1, &@prc)
         ScratchPad.recorded.should eql []
       end
     end
 
     describe "with a negative step" do
       it "yields while decreasing self by step until stop is reached" do
-        5.send(@method, *@step_args.call(1, -1), &@prc)
+        @step.call(5, 1, -1, &@prc)
         ScratchPad.recorded.should eql [5, 4, 3, 2, 1]
       end
 
       it "yields once when self equals stop" do
-        5.send(@method, *@step_args.call(5, -1), &@prc)
+        @step.call(5, 5, -1, &@prc)
         ScratchPad.recorded.should eql [5]
       end
 
       it "does not yield when self is less than stop" do
-        1.send(@method, *@step_args.call(5, -1), &@prc)
+        @step.call(1, 5, -1, &@prc)
         ScratchPad.recorded.should == []
       end
     end
@@ -66,156 +66,157 @@ describe :numeric_step, :shared => true do
 
   describe "when at least one of self, stop or step is a Float" do
     it "yields Floats even if only self is a Float" do
-      1.5.send(@method, *@step_args.call(5, 1)) { |x| x.should be_an_instance_of(Float) }
+      @step.call(1.5, 5, 1) { |x| x.should be_an_instance_of(Float) }
     end
 
     it "yields Floats even if only stop is a Float" do
-      1.send(@method, *@step_args.call(5.0, 1)) { |x| x.should be_an_instance_of(Float) }
+      @step.call(1, 5.0, 1) { |x| x.should be_an_instance_of(Float) }
     end
 
     it "yields Floats even if only step is a Float" do
-      1.send(@method, *@step_args.call(5, 1.0)) { |x| x.should be_an_instance_of(Float) }
+      @step.call(1, 5, 1.0) { |x| x.should be_an_instance_of(Float) }
     end
 
     describe "with a positive step" do
       it "yields while increasing self by step while < stop" do
-        1.5.send(@method, *@step_args.call(5, 1), &@prc)
+        @step.call(1.5, 5, 1, &@prc)
         ScratchPad.recorded.should eql [1.5, 2.5, 3.5, 4.5]
       end
 
       it "yields once when self equals stop" do
-        1.5.send(@method, *@step_args.call(1.5, 1), &@prc)
+        @step.call(1.5, 1.5, 1, &@prc)
         ScratchPad.recorded.should eql [1.5]
       end
 
       it "does not yield when self is greater than stop" do
-        2.5.send(@method, *@step_args.call(1.5, 1), &@prc)
+        @step.call(2.5, 1.5, 1, &@prc)
         ScratchPad.recorded.should == []
       end
 
       it "is careful about not yielding a value greater than limit" do
         # As 9*1.3+1.0 == 12.700000000000001 > 12.7, we test:
-        1.0.send(@method, *@step_args.call(12.7, 1.3), &@prc)
+        @step.call(1.0, 12.7, 1.3, &@prc)
         ScratchPad.recorded.should eql [1.0, 2.3, 3.6, 4.9, 6.2, 7.5, 8.8, 10.1, 11.4, 12.7]
       end
     end
 
     describe "with a negative step" do
       it "yields while decreasing self by step while self > stop" do
-        5.send(@method, *@step_args.call(1.5, -1), &@prc)
+        @step.call(5, 1.5, -1, &@prc)
         ScratchPad.recorded.should eql [5.0, 4.0, 3.0, 2.0]
       end
 
       it "yields once when self equals stop" do
-        1.5.send(@method, *@step_args.call(1.5, -1), &@prc)
+        @step.call(1.5, 1.5, -1, &@prc)
         ScratchPad.recorded.should eql [1.5]
       end
 
       it "does not yield when self is less than stop" do
-        1.send(@method, *@step_args.call(5, -1.5), &@prc)
+        @step.call(1, 5, -1.5, &@prc)
         ScratchPad.recorded.should == []
       end
 
       it "is careful about not yielding a value smaller than limit" do
         # As -9*1.3-1.0 == -12.700000000000001 < -12.7, we test:
-        -1.0.send(@method, *@step_args.call(-12.7, -1.3), &@prc)
+        @step.call(-1.0, -12.7, -1.3, &@prc)
         ScratchPad.recorded.should eql [-1.0, -2.3, -3.6, -4.9, -6.2, -7.5, -8.8, -10.1, -11.4, -12.7]
       end
     end
 
     describe "with a positive Infinity step" do
       it "yields once if self < stop" do
-        42.send(@method, *@step_args.call(100, infinity_value), &@prc)
+        @step.call(42, 100, infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once when stop is Infinity" do
-        42.send(@method, *@step_args.call(infinity_value, infinity_value), &@prc)
+        @step.call(42, infinity_value, infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once when self equals stop" do
-        42.send(@method, *@step_args.call(42, infinity_value), &@prc)
+        @step.call(42, 42, infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once when self and stop are Infinity" do
-        (infinity_value).send(@method, *@step_args.call(infinity_value, infinity_value), &@prc)
+        # @step.call(infinity_value, infinity_value, infinity_value, &@prc)
+        @step.call(infinity_value, infinity_value, infinity_value, &@prc)
         ScratchPad.recorded.should == [infinity_value]
       end
 
       it "does not yield when self > stop" do
-        100.send(@method, *@step_args.call(42, infinity_value), &@prc)
+        @step.call(100, 42, infinity_value, &@prc)
         ScratchPad.recorded.should == []
       end
 
       it "does not yield when stop is -Infinity" do
-        42.send(@method, *@step_args.call(-infinity_value, infinity_value), &@prc)
+        @step.call(42, -infinity_value, infinity_value, &@prc)
         ScratchPad.recorded.should == []
       end
     end
 
     describe "with a negative Infinity step" do
       it "yields once if self > stop" do
-        42.send(@method, *@step_args.call(6, -infinity_value), &@prc)
+        @step.call(42, 6, -infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once if stop is -Infinity" do
-        42.send(@method, *@step_args.call(-infinity_value, -infinity_value), &@prc)
+        @step.call(42, -infinity_value, -infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once when self equals stop" do
-        42.send(@method, *@step_args.call(42, -infinity_value), &@prc)
+        @step.call(42, 42, -infinity_value, &@prc)
         ScratchPad.recorded.should eql [42.0]
       end
 
       it "yields once when self and stop are Infinity" do
-        (infinity_value).send(@method, *@step_args.call(infinity_value, -infinity_value), &@prc)
+        @step.call(infinity_value, infinity_value, -infinity_value, &@prc)
         ScratchPad.recorded.should == [infinity_value]
       end
 
       it "does not yield when self > stop" do
-        42.send(@method, *@step_args.call(100, -infinity_value), &@prc)
+        @step.call(42, 100, -infinity_value, &@prc)
         ScratchPad.recorded.should == []
       end
 
       it "does not yield when stop is Infinity" do
-        42.send(@method, *@step_args.call(infinity_value, -infinity_value), &@prc)
+        @step.call(42, infinity_value, -infinity_value, &@prc)
         ScratchPad.recorded.should == []
       end
     end
 
     describe "with a Infinity stop and a positive step" do
       it "does not yield when self is infinity" do
-        (infinity_value).send(@method, *@step_args.call(infinity_value, 1), &@prc)
+        @step.call(infinity_value, infinity_value, 1, &@prc)
         ScratchPad.recorded.should == []
       end
     end
 
     describe "with a Infinity stop and a negative step" do
       it "does not yield when self is negative infinity" do
-        (-infinity_value).send(@method, *@step_args.call(infinity_value, -1), &@prc)
+        @step.call(-infinity_value, infinity_value, -1, &@prc)
         ScratchPad.recorded.should == []
       end
 
       it "does not yield when self is positive infinity" do
-        infinity_value.send(@method, *@step_args.call(infinity_value, -1), &@prc)
+        @step.call(infinity_value, infinity_value, -1, &@prc)
         ScratchPad.recorded.should == []
       end
     end
 
     describe "with a negative Infinity stop and a positive step" do
       it "does not yield when self is negative infinity" do
-        (-infinity_value).send(@method, *@step_args.call(-infinity_value, 1), &@prc)
+        @step.call(-infinity_value, -infinity_value, 1, &@prc)
         ScratchPad.recorded.should == []
       end
     end
 
     describe "with a negative Infinity stop and a negative step" do
       it "does not yield when self is negative infinity" do
-        (-infinity_value).send(@method, *@step_args.call(-infinity_value, -1), &@prc)
+        @step.call(-infinity_value, -infinity_value, -1, &@prc)
         ScratchPad.recorded.should == []
       end
     end
@@ -223,77 +224,62 @@ describe :numeric_step, :shared => true do
   end
 
   describe "when step is a String" do
-    error = nil
-    ruby_version_is "2.4"..."2.5" do
-      error = TypeError
-    end
-    ruby_version_is "2.5" do
-      error = ArgumentError
-    end
-
-    describe "with self and stop as Fixnums" do
-      it "raises an #{error} when step is a numeric representation" do
-        -> { 1.send(@method, *@step_args.call(5, "1")) {} }.should raise_error(error)
-        -> { 1.send(@method, *@step_args.call(5, "0.1")) {} }.should raise_error(error)
-        -> { 1.send(@method, *@step_args.call(5, "1/3")) {} }.should raise_error(error)
+    describe "with self and stop as Integers" do
+      it "raises an ArgumentError when step is a numeric representation" do
+        -> { @step.call(1, 5, "1") {} }.should raise_error(ArgumentError)
+        -> { @step.call(1, 5, "0.1") {} }.should raise_error(ArgumentError)
+        -> { @step.call(1, 5, "1/3") {} }.should raise_error(ArgumentError)
       end
-      it "raises an #{error} with step as an alphanumeric string" do
-        -> { 1.send(@method, *@step_args.call(5, "foo")) {} }.should raise_error(error)
+      it "raises an ArgumentError with step as an alphanumeric string" do
+        -> { @step.call(1, 5, "foo") {} }.should raise_error(ArgumentError)
       end
     end
 
     describe "with self and stop as Floats" do
-      it "raises an #{error} when step is a numeric representation" do
-        -> { 1.1.send(@method, *@step_args.call(5.1, "1")) {} }.should raise_error(error)
-        -> { 1.1.send(@method, *@step_args.call(5.1, "0.1")) {} }.should raise_error(error)
-        -> { 1.1.send(@method, *@step_args.call(5.1, "1/3")) {} }.should raise_error(error)
+      it "raises an ArgumentError when step is a numeric representation" do
+        -> { @step.call(1.1, 5.1, "1") {} }.should raise_error(ArgumentError)
+        -> { @step.call(1.1, 5.1, "0.1") {} }.should raise_error(ArgumentError)
+        -> { @step.call(1.1, 5.1, "1/3") {} }.should raise_error(ArgumentError)
       end
-      it "raises an #{error} with step as an alphanumeric string" do
-        -> { 1.1.send(@method, *@step_args.call(5.1, "foo")) {} }.should raise_error(error)
+      it "raises an ArgumentError with step as an alphanumeric string" do
+        -> { @step.call(1.1, 5.1, "foo") {} }.should raise_error(ArgumentError)
       end
     end
   end
 
   it "does not rescue ArgumentError exceptions" do
-    -> { 1.send(@method, *@step_args.call(2)) { raise ArgumentError, "" }}.should raise_error(ArgumentError)
+    -> { @step.call(1, 2) { raise ArgumentError, "" }}.should raise_error(ArgumentError)
   end
 
   it "does not rescue TypeError exceptions" do
-    -> { 1.send(@method, *@step_args.call(2)) { raise TypeError, "" } }.should raise_error(TypeError)
+    -> { @step.call(1, 2) { raise TypeError, "" } }.should raise_error(TypeError)
   end
 
   describe "when no block is given" do
-    step_enum_class = Enumerator
-    ruby_version_is "2.6" do
-      step_enum_class = Enumerator::ArithmeticSequence
-    end
-
-    it "returns an #{step_enum_class} when step is 0" do
-      1.send(@method, *@step_args.call(2, 0)).should be_an_instance_of(step_enum_class)
-    end
+    step_enum_class = Enumerator::ArithmeticSequence
 
     it "returns an #{step_enum_class} when not passed a block and self > stop" do
-      1.send(@method, *@step_args.call(0, 2)).should be_an_instance_of(step_enum_class)
+      @step.call(1, 0, 2).should be_an_instance_of(step_enum_class)
     end
 
     it "returns an #{step_enum_class} when not passed a block and self < stop" do
-      1.send(@method, *@step_args.call(2, 3)).should be_an_instance_of(step_enum_class)
+      @step.call(1, 2, 3).should be_an_instance_of(step_enum_class)
     end
 
     it "returns an #{step_enum_class} that uses the given step" do
-      0.send(@method, *@step_args.call(5, 2)).to_a.should eql [0, 2, 4]
+      @step.call(0, 5, 2).to_a.should eql [0, 2, 4]
     end
 
     describe "when step is a String" do
-      describe "with self and stop as Fixnums" do
+      describe "with self and stop as Integers" do
         it "returns an Enumerator" do
-          1.send(@method, *@step_args.call(5, "foo")).should be_an_instance_of(Enumerator)
+          @step.call(1, 5, "foo").should be_an_instance_of(Enumerator)
         end
       end
 
       describe "with self and stop as Floats" do
         it "returns an Enumerator" do
-          1.1.send(@method, *@step_args.call(5.1, "foo")).should be_an_instance_of(Enumerator)
+          @step.call(1.1, 5.1, "foo").should be_an_instance_of(Enumerator)
         end
       end
     end
@@ -301,129 +287,121 @@ describe :numeric_step, :shared => true do
     describe "returned Enumerator" do
       describe "size" do
         describe "when step is a String" do
-          error = nil
-          ruby_version_is "2.4"..."2.5" do
-            error = TypeError
-          end
-          ruby_version_is "2.5" do
-            error = ArgumentError
-          end
-
-          describe "with self and stop as Fixnums" do
-            it "raises an #{error} when step is a numeric representation" do
-              -> { 1.send(@method, *@step_args.call(5, "1")).size }.should raise_error(error)
-              -> { 1.send(@method, *@step_args.call(5, "0.1")).size }.should raise_error(error)
-              -> { 1.send(@method, *@step_args.call(5, "1/3")).size }.should raise_error(error)
+          describe "with self and stop as Integers" do
+            it "raises an ArgumentError when step is a numeric representation" do
+              -> { @step.call(1, 5, "1").size }.should raise_error(ArgumentError)
+              -> { @step.call(1, 5, "0.1").size }.should raise_error(ArgumentError)
+              -> { @step.call(1, 5, "1/3").size }.should raise_error(ArgumentError)
             end
-            it "raises an #{error} with step as an alphanumeric string" do
-              -> { 1.send(@method, *@step_args.call(5, "foo")).size }.should raise_error(error)
+            it "raises an ArgumentError with step as an alphanumeric string" do
+              -> { @step.call(1, 5, "foo").size }.should raise_error(ArgumentError)
             end
           end
 
           describe "with self and stop as Floats" do
-            it "raises an #{error} when step is a numeric representation" do
-              -> { 1.1.send(@method, *@step_args.call(5.1, "1")).size }.should raise_error(error)
-              -> { 1.1.send(@method, *@step_args.call(5.1, "0.1")).size }.should raise_error(error)
-              -> { 1.1.send(@method, *@step_args.call(5.1, "1/3")).size }.should raise_error(error)
+            it "raises an ArgumentError when step is a numeric representation" do
+              -> { @step.call(1.1, 5.1, "1").size }.should raise_error(ArgumentError)
+              -> { @step.call(1.1, 5.1, "0.1").size }.should raise_error(ArgumentError)
+              -> { @step.call(1.1, 5.1, "1/3").size }.should raise_error(ArgumentError)
             end
-            it "raises an #{error} with step as an alphanumeric string" do
-              -> { 1.1.send(@method, *@step_args.call(5.1, "foo")).size }.should raise_error(error)
+            it "raises an ArgumentError with step as an alphanumeric string" do
+              -> { @step.call(1.1, 5.1, "foo").size }.should raise_error(ArgumentError)
             end
           end
         end
 
-        describe "when self, stop and step are Fixnums and step is positive" do
+        describe "when self, stop and step are Integers and step is positive" do
           it "returns the difference between self and stop divided by the number of steps" do
-            5.send(@method, *@step_args.call(10, 11)).size.should == 1
-            5.send(@method, *@step_args.call(10, 6)).size.should == 1
-            5.send(@method, *@step_args.call(10, 5)).size.should == 2
-            5.send(@method, *@step_args.call(10, 4)).size.should == 2
-            5.send(@method, *@step_args.call(10, 2)).size.should == 3
-            5.send(@method, *@step_args.call(10, 1)).size.should == 6
-            5.send(@method, *@step_args.call(10)).size.should == 6
-            10.send(@method, *@step_args.call(10, 1)).size.should == 1
+            @step.call(5, 10, 11).size.should == 1
+            @step.call(5, 10, 6).size.should == 1
+            @step.call(5, 10, 5).size.should == 2
+            @step.call(5, 10, 4).size.should == 2
+            @step.call(5, 10, 2).size.should == 3
+            @step.call(5, 10, 1).size.should == 6
+            @step.call(5, 10).size.should == 6
+            @step.call(10, 10, 1).size.should == 1
           end
 
           it "returns 0 if value > limit" do
-            11.send(@method, *@step_args.call(10, 1)).size.should == 0
+            @step.call(11, 10, 1).size.should == 0
           end
         end
 
-        describe "when self, stop and step are Fixnums and step is negative" do
+        describe "when self, stop and step are Integers and step is negative" do
           it "returns the difference between self and stop divided by the number of steps" do
-            10.send(@method, *@step_args.call(5, -11)).size.should == 1
-            10.send(@method, *@step_args.call(5, -6)).size.should == 1
-            10.send(@method, *@step_args.call(5, -5)).size.should == 2
-            10.send(@method, *@step_args.call(5, -4)).size.should == 2
-            10.send(@method, *@step_args.call(5, -2)).size.should == 3
-            10.send(@method, *@step_args.call(5, -1)).size.should == 6
-            10.send(@method, *@step_args.call(10, -1)).size.should == 1
+            @step.call(10, 5, -11).size.should == 1
+            @step.call(10, 5, -6).size.should == 1
+            @step.call(10, 5, -5).size.should == 2
+            @step.call(10, 5, -4).size.should == 2
+            @step.call(10, 5, -2).size.should == 3
+            @step.call(10, 5, -1).size.should == 6
+            @step.call(10, 10, -1).size.should == 1
           end
 
           it "returns 0 if value < limit" do
-            10.send(@method, *@step_args.call(11, -1)).size.should == 0
+            @step.call(10, 11, -1).size.should == 0
           end
         end
 
         describe "when self, stop or step is a Float" do
           describe "and step is positive" do
             it "returns the difference between self and stop divided by the number of steps" do
-              5.send(@method, *@step_args.call(10, 11.0)).size.should == 1
-              5.send(@method, *@step_args.call(10, 6.0)).size.should == 1
-              5.send(@method, *@step_args.call(10, 5.0)).size.should == 2
-              5.send(@method, *@step_args.call(10, 4.0)).size.should == 2
-              5.send(@method, *@step_args.call(10, 2.0)).size.should == 3
-              5.send(@method, *@step_args.call(10, 0.5)).size.should == 11
-              5.send(@method, *@step_args.call(10, 1.0)).size.should == 6
-              5.send(@method, *@step_args.call(10.5)).size.should == 6
-              10.send(@method, *@step_args.call(10, 1.0)).size.should == 1
+              @step.call(5, 10, 11.0).size.should == 1
+              @step.call(5, 10, 6.0).size.should == 1
+              @step.call(5, 10, 5.0).size.should == 2
+              @step.call(5, 10, 4.0).size.should == 2
+              @step.call(5, 10, 2.0).size.should == 3
+              @step.call(5, 10, 0.5).size.should == 11
+              @step.call(5, 10, 1.0).size.should == 6
+              @step.call(5, 10.5).size.should == 6
+              @step.call(10, 10, 1.0).size.should == 1
             end
 
             it "returns 0 if value > limit" do
-              10.send(@method, *@step_args.call(5.5)).size.should == 0
-              11.send(@method, *@step_args.call(10, 1.0)).size.should == 0
-              11.send(@method, *@step_args.call(10, 1.5)).size.should == 0
-              10.send(@method, *@step_args.call(5, infinity_value)).size.should == 0
+              @step.call(10, 5.5).size.should == 0
+              @step.call(11, 10, 1.0).size.should == 0
+              @step.call(11, 10, 1.5).size.should == 0
+              @step.call(10, 5, infinity_value).size.should == 0
             end
 
             it "returns 1 if step is infinity_value" do
-              5.send(@method, *@step_args.call(10, infinity_value)).size.should == 1
+              @step.call(5, 10, infinity_value).size.should == 1
             end
           end
 
           describe "and step is negative" do
             it "returns the difference between self and stop divided by the number of steps" do
-              10.send(@method, *@step_args.call(5, -11.0)).size.should == 1
-              10.send(@method, *@step_args.call(5, -6.0)).size.should == 1
-              10.send(@method, *@step_args.call(5, -5.0)).size.should == 2
-              10.send(@method, *@step_args.call(5, -4.0)).size.should == 2
-              10.send(@method, *@step_args.call(5, -2.0)).size.should == 3
-              10.send(@method, *@step_args.call(5, -0.5)).size.should == 11
-              10.send(@method, *@step_args.call(5, -1.0)).size.should == 6
-              10.send(@method, *@step_args.call(10, -1.0)).size.should == 1
+              @step.call(10, 5, -11.0).size.should == 1
+              @step.call(10, 5, -6.0).size.should == 1
+              @step.call(10, 5, -5.0).size.should == 2
+              @step.call(10, 5, -4.0).size.should == 2
+              @step.call(10, 5, -2.0).size.should == 3
+              @step.call(10, 5, -0.5).size.should == 11
+              @step.call(10, 5, -1.0).size.should == 6
+              @step.call(10, 10, -1.0).size.should == 1
             end
 
             it "returns 0 if value < limit" do
-              10.send(@method, *@step_args.call(11, -1.0)).size.should == 0
-              10.send(@method, *@step_args.call(11, -1.5)).size.should == 0
-              5.send(@method, *@step_args.call(10, -infinity_value)).size.should == 0
+              @step.call(10, 11, -1.0).size.should == 0
+              @step.call(10, 11, -1.5).size.should == 0
+              @step.call(5, 10, -infinity_value).size.should == 0
             end
 
             it "returns 1 if step is infinity_value" do
-              10.send(@method, *@step_args.call(5, -infinity_value)).size.should == 1
+              @step.call(10, 5, -infinity_value).size.should == 1
             end
           end
         end
 
         describe "when stop is not passed" do
           it "returns infinity_value" do
-            1.send(@method, *@step_args.call()).size.should == infinity_value
+            @step.call(1).size.should == infinity_value
           end
         end
 
         describe "when stop is nil" do
           it "returns infinity_value" do
-            1.send(@method, *@step_args.call(nil, 5)).size.should == infinity_value
+            @step.call(1, nil, 5).size.should == infinity_value
           end
         end
       end
diff --git a/spec/ruby/core/numeric/step_spec.rb b/spec/ruby/core/numeric/step_spec.rb
index fc80cc4ab0..1705fb1b4e 100644
--- a/spec/ruby/core/numeric/step_spec.rb
+++ b/spec/ruby/core/numeric/step_spec.rb
@@ -16,51 +16,15 @@ describe "Numeric#step" do
     before :all do
       # This lambda definition limits to return the arguments it receives.
       # It's needed to test numeric_step behaviour with positional arguments.
-      @step_args = -> *args { args }
+      @step = -> receiver, *args, &block { receiver.step(*args, &block) }
     end
-
     it_behaves_like :numeric_step, :step
 
     describe "when no block is given" do
-      step_enum_class = Enumerator
-      ruby_version_is "2.6" do
-        step_enum_class = Enumerator::ArithmeticSequence
-      end
-
-      it "returns an #{step_enum_class} when step is 0" do
-        1.step(5, 0).should be_an_instance_of(step_enum_class)
-      end
-
-      it "returns an #{step_enum_class} when step is 0.0" do
-        1.step(2, 0.0).should be_an_instance_of(step_enum_class)
-      end
+      step_enum_class = Enumerator::ArithmeticSequence
 
       describe "returned #{step_enum_class}" do
         describe "size" do
-          ruby_version_is ""..."2.6" do
-            it "raises an ArgumentError when step is 0" do
-              enum = 1.step(5, 0)
-              -> { enum.size }.should raise_error(ArgumentError)
-            end
-
-            it "raises an ArgumentError when step is 0.0" do
-              enum = 1.step(2, 0.0)
-              -> { enum.size }.should raise_error(ArgumentError)
-            end
-          end
-
-          ruby_version_is "2.6" do
-            it "is infinity when step is 0" do
-              enum = 1.step(5, 0)
-              enum.size.should == Float::INFINITY
-            end
-
-            it "is infinity when step is 0.0" do
-              enum = 1.step(2, 0.0)
-              enum.size.should == Float::INFINITY
-            end
-          end
-
           it "defaults to an infinite size" do
             enum = 1.step
             enum.size.should == Float::INFINITY
@@ -68,38 +32,15 @@ describe "Numeric#step" do
         end
 
         describe "type" do
-          ruby_version_is ""..."2.6" do
-            it "returns an instance of Enumerator" do
-              1.step(10).class.should == Enumerator
-            end
-          end
-
-          ruby_version_is "2.6" do
-            it "returns an instance of Enumerator::ArithmeticSequence" do
-              1.step(10).class.should == Enumerator::ArithmeticSequence
-            end
+          it "returns an instance of Enumerator::ArithmeticSequence" do
+            1.step(10).class.should == Enumerator::ArithmeticSequence
           end
         end
       end
     end
-
   end
 
   describe 'with keyword arguments' do
-    it "doesn't raise an error when step is 0" do
-      -> { 1.step(to: 5, by: 0) { break } }.should_not raise_error
-    end
-
-    it "doesn't raise an error when step is 0.0" do
-      -> { 1.step(to: 2, by: 0.0) { break } }.should_not raise_error
-    end
-
-    it "should loop over self when step is 0 or 0.0" do
-      1.step(to: 2, by: 0.0).take(5).should eql [1.0, 1.0, 1.0, 1.0, 1.0]
-      1.step(to: 2, by: 0).take(5).should eql [1, 1, 1, 1, 1]
-      1.1.step(to: 2, by: 0).take(5).should eql [1.1, 1.1, 1.1, 1.1, 1.1]
-    end
-
     describe "when no block is given" do
       describe "returned Enumerator" do
         describe "size" do
@@ -107,14 +48,6 @@ describe "Numeric#step" do
             1.step(by: 42).size.should == infinity_value
           end
 
-          it "should return infinity_value when step is 0" do
-            1.step(to: 5, by: 0).size.should == infinity_value
-          end
-
-          it "should return infinity_value when step is 0.0" do
-            1.step(to: 2, by: 0.0).size.should == infinity_value
-          end
-
           it "should return infinity_value when ascending towards a limit of Float::INFINITY" do
             1.step(to: Float::INFINITY, by: 42).size.should == infinity_value
           end
@@ -135,25 +68,24 @@ describe "Numeric#step" do
     end
 
     before :all do
-      # This lambda transforms a positional step method args into
-      # keyword arguments.
+      # This lambda transforms a positional step method args into  keyword arguments.
       # It's needed to test numeric_step behaviour with keyword arguments.
-      @step_args = -> *args do
-        kw_args = {to: args[0]}
+      @step = -> receiver, *args, &block do
+        kw_args = { to: args[0] }
         kw_args[:by] = args[1] if args.size == 2
-        [kw_args]
+        receiver.step(**kw_args, &block)
       end
     end
     it_behaves_like :numeric_step, :step
   end
 
   describe 'with mixed arguments' do
-    it "doesn't raise an error when step is 0" do
-      -> { 1.step(5, by: 0) { break } }.should_not raise_error
+    it " raises an ArgumentError when step is 0" do
+      -> { 1.step(5, by: 0) { break } }.should raise_error(ArgumentError)
     end
 
-    it "doesn't raise an error when step is 0.0" do
-      -> { 1.step(2, by: 0.0) { break } }.should_not raise_error
+    it "raises an ArgumentError when step is 0.0" do
+      -> { 1.step(2, by: 0.0) { break } }.should raise_error(ArgumentError)
     end
 
     it "raises a ArgumentError when limit and to are defined" do
@@ -164,35 +96,23 @@ describe "Numeric#step" do
       -> { 1.step(5, 1, by: 5) { break } }.should raise_error(ArgumentError)
     end
 
-    it "should loop over self when step is 0 or 0.0" do
-      1.step(2, by: 0.0).take(5).should eql [1.0, 1.0, 1.0, 1.0, 1.0]
-      1.step(2, by: 0).take(5).should eql [1, 1, 1, 1, 1]
-      1.1.step(2, by: 0).take(5).should eql [1.1, 1.1, 1.1, 1.1, 1.1]
-    end
-
     describe "when no block is given" do
       describe "returned Enumerator" do
         describe "size" do
-          it "should return infinity_value when step is 0" do
-            1.step(5, by: 0).size.should == infinity_value
-          end
-
-          it "should return infinity_value when step is 0.0" do
-            1.step(2, by: 0.0).size.should == infinity_value
-          end
         end
       end
     end
+
     before :all do
       # This lambda definition transforms a positional step method args into
       # a mix of positional and keyword arguments.
       # It's needed to test numeric_step behaviour with positional mixed with
       # keyword arguments.
-      @step_args = -> *args do
+      @step = -> receiver, *args, &block do
         if args.size == 2
-          [args[0], {by: args[1]}]
+          receiver.step(args[0], by: args[1], &block)
         else
-          args
+          receiver.step(*args, &block)
         end
       end
     end
diff --git a/spec/ruby/core/numeric/zero_spec.rb b/spec/ruby/core/numeric/zero_spec.rb
index 9de71d1dc9..0fb7619bcd 100644
--- a/spec/ruby/core/numeric/zero_spec.rb
+++ b/spec/ruby/core/numeric/zero_spec.rb
@@ -8,11 +8,11 @@ describe "Numeric#zero?" do
 
   it "returns true if self is 0" do
     @obj.should_receive(:==).with(0).and_return(true)
-    @obj.zero?.should == true
+    @obj.should.zero?
   end
 
   it "returns false if self is not 0" do
     @obj.should_receive(:==).with(0).and_return(false)
-    @obj.zero?.should == false
+    @obj.should_not.zero?
   end
 end
diff --git a/spec/ruby/core/objectspace/_id2ref_spec.rb b/spec/ruby/core/objectspace/_id2ref_spec.rb
index 1d8ad02deb..1ae3230bdf 100644
--- a/spec/ruby/core/objectspace/_id2ref_spec.rb
+++ b/spec/ruby/core/objectspace/_id2ref_spec.rb
@@ -1,25 +1,65 @@
 require_relative '../../spec_helper'
 
-describe "ObjectSpace._id2ref" do
-  it "converts an object id to a reference to the object" do
-    s = "I am a string"
-    r = ObjectSpace._id2ref(s.object_id)
-    r.should == s
+ruby_version_is "4.0" do
+  describe "ObjectSpace._id2ref" do
+    it "is deprecated" do
+      id = nil.object_id
+      -> {
+        ObjectSpace._id2ref(id)
+      }.should complain(/warning: ObjectSpace\._id2ref is deprecated/)
+    end
   end
+end
 
-  it "retrieves a Fixnum by object_id" do
-    f = 1
-    r = ObjectSpace._id2ref(f.object_id)
-    r.should == f
-  end
+ruby_version_is ""..."4.0" do
+  describe "ObjectSpace._id2ref" do
+    it "converts an object id to a reference to the object" do
+      s = "I am a string"
+      r = ObjectSpace._id2ref(s.object_id)
+      r.should == s
+    end
 
-  it "retrieves a Symbol by object_id" do
-    s = :sym
-    r = ObjectSpace._id2ref(s.object_id)
-    r.should == s
-  end
+    it "retrieves true by object_id" do
+      ObjectSpace._id2ref(true.object_id).should == true
+    end
+
+    it "retrieves false by object_id" do
+      ObjectSpace._id2ref(false.object_id).should == false
+    end
+
+    it "retrieves nil by object_id" do
+      ObjectSpace._id2ref(nil.object_id).should == nil
+    end
+
+    it "retrieves a small Integer by object_id" do
+      ObjectSpace._id2ref(1.object_id).should == 1
+      ObjectSpace._id2ref((-42).object_id).should == -42
+    end
+
+    it "retrieves a large Integer by object_id" do
+      obj = 1 << 88
+      ObjectSpace._id2ref(obj.object_id).should.equal?(obj)
+    end
+
+    it "retrieves a Symbol by object_id" do
+      ObjectSpace._id2ref(:sym.object_id).should.equal?(:sym)
+    end
+
+    it "retrieves a String by object_id" do
+      obj = "str"
+      ObjectSpace._id2ref(obj.object_id).should.equal?(obj)
+    end
+
+    it "retrieves a frozen literal String by object_id" do
+      ObjectSpace._id2ref("frozen string literal _id2ref".freeze.object_id).should.equal?("frozen string literal _id2ref".freeze)
+    end
+
+    it "retrieves an Encoding by object_id" do
+      ObjectSpace._id2ref(Encoding::UTF_8.object_id).should.equal?(Encoding::UTF_8)
+    end
 
-  it 'raises RangeError when an object could not be found' do
-    proc { ObjectSpace._id2ref(1 << 60) }.should raise_error(RangeError)
+    it 'raises RangeError when an object could not be found' do
+      proc { ObjectSpace._id2ref(1 << 60) }.should raise_error(RangeError)
+    end
   end
 end
diff --git a/spec/ruby/core/objectspace/add_finalizer_spec.rb b/spec/ruby/core/objectspace/add_finalizer_spec.rb
deleted file mode 100644
index 3540ac0413..0000000000
--- a/spec/ruby/core/objectspace/add_finalizer_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ObjectSpace.add_finalizer" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/objectspace/call_finalizer_spec.rb b/spec/ruby/core/objectspace/call_finalizer_spec.rb
deleted file mode 100644
index 6dce92ddd6..0000000000
--- a/spec/ruby/core/objectspace/call_finalizer_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ObjectSpace.call_finalizer" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/objectspace/define_finalizer_spec.rb b/spec/ruby/core/objectspace/define_finalizer_spec.rb
index 3f7b1ae576..0f4b54c345 100644
--- a/spec/ruby/core/objectspace/define_finalizer_spec.rb
+++ b/spec/ruby/core/objectspace/define_finalizer_spec.rb
@@ -1,24 +1,42 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-# NOTE: A call to define_finalizer does not guarantee that the
-# passed proc or callable will be called at any particular time.
+# Why do we not test that finalizers are run by the GC? The documentation
+# says that finalizers are never guaranteed to be run, so we can't
+# spec that they are. On some implementations of Ruby the finalizers may
+# run asynchronously, meaning that we can't predict when they'll run,
+# even if they were guaranteed to do so. Even on MRI finalizers can be
+# very unpredictable, due to conservative stack scanning and references
+# left in unused memory.
+
 describe "ObjectSpace.define_finalizer" do
   it "raises an ArgumentError if the action does not respond to call" do
     -> {
-      ObjectSpace.define_finalizer("", mock("ObjectSpace.define_finalizer no #call"))
+      ObjectSpace.define_finalizer(Object.new, mock("ObjectSpace.define_finalizer no #call"))
     }.should raise_error(ArgumentError)
   end
 
   it "accepts an object and a proc" do
-    handler = -> obj { obj }
-    ObjectSpace.define_finalizer("garbage", handler).should == [0, handler]
+    handler = -> id { id }
+    ObjectSpace.define_finalizer(Object.new, handler).should == [0, handler]
+  end
+
+  it "accepts an object and a bound method" do
+    handler = mock("callable")
+    def handler.finalize(id) end
+    finalize = handler.method(:finalize)
+    ObjectSpace.define_finalizer(Object.new, finalize).should == [0, finalize]
   end
 
   it "accepts an object and a callable" do
     handler = mock("callable")
-    def handler.call(obj) end
-    ObjectSpace.define_finalizer("garbage", handler).should == [0, handler]
+    def handler.call(id) end
+    ObjectSpace.define_finalizer(Object.new, handler).should == [0, handler]
+  end
+
+  it "accepts an object and a block" do
+    handler = -> id { id }
+    ObjectSpace.define_finalizer(Object.new, &handler).should == [0, handler]
   end
 
   it "raises ArgumentError trying to define a finalizer on a non-reference" do
@@ -31,30 +49,114 @@ describe "ObjectSpace.define_finalizer" do
   it "calls finalizer on process termination" do
     code = <<-RUBY
       def scoped
-        Proc.new { puts "finalized" }
+        Proc.new { puts "finalizer run" }
       end
       handler = scoped
-      obj = "Test"
+      obj = +"Test"
       ObjectSpace.define_finalizer(obj, handler)
       exit 0
     RUBY
 
-    ruby_exe(code).should == "finalized\n"
+    ruby_exe(code, :args => "2>&1").should include("finalizer run\n")
   end
 
-  it "calls finalizer at exit even if it is self-referencing" do
+  it "warns if the finalizer has the object as the receiver" do
     code = <<-RUBY
-      obj = "Test"
-      handler = Proc.new { puts "finalized" }
+      class CapturesSelf
+        def initialize
+          ObjectSpace.define_finalizer(self, proc {
+            puts "finalizer run"
+          })
+        end
+      end
+      CapturesSelf.new
+      exit 0
+    RUBY
+
+    ruby_exe(code, :args => "2>&1").should include("warning: finalizer references object to be finalized\n")
+  end
+
+  it "warns if the finalizer is a method bound to the receiver" do
+    code = <<-RUBY
+      class CapturesSelf
+        def initialize
+          ObjectSpace.define_finalizer(self, method(:finalize))
+        end
+        def finalize(id)
+          puts "finalizer run"
+        end
+      end
+      CapturesSelf.new
+      exit 0
+    RUBY
+
+    ruby_exe(code, :args => "2>&1").should include("warning: finalizer references object to be finalized\n")
+  end
+
+  it "warns if the finalizer was a block in the receiver" do
+    code = <<-RUBY
+      class CapturesSelf
+        def initialize
+          ObjectSpace.define_finalizer(self) do
+            puts "finalizer run"
+          end
+        end
+      end
+      CapturesSelf.new
+      exit 0
+    RUBY
+
+    ruby_exe(code, :args => "2>&1").should include("warning: finalizer references object to be finalized\n")
+  end
+
+  it "calls a finalizer at exit even if it is self-referencing" do
+    code = <<-RUBY
+      obj = +"Test"
+      handler = Proc.new { puts "finalizer run" }
       ObjectSpace.define_finalizer(obj, handler)
       exit 0
     RUBY
 
-    ruby_exe(code).should == "finalized\n"
+    ruby_exe(code).should include("finalizer run\n")
   end
 
-  it "allows multiple finalizers with different 'callables' to be defined" do
+  it "calls a finalizer at exit even if it is indirectly self-referencing" do
+    code = <<-RUBY
+      class CapturesSelf
+        def initialize
+          ObjectSpace.define_finalizer(self, finalizer(self))
+        end
+        def finalizer(zelf)
+          proc do
+            puts "finalizer run"
+          end
+        end
+      end
+      CapturesSelf.new
+      exit 0
+    RUBY
+
+    ruby_exe(code, :args => "2>&1").should include("finalizer run\n")
+  end
+
+  it "calls a finalizer defined in a finalizer running at exit" do
     code = <<-RUBY
+      obj = +"Test"
+      handler = Proc.new do
+        obj2 = +"Test"
+        handler2 = Proc.new { puts "finalizer 2 run" }
+        ObjectSpace.define_finalizer(obj2, handler2)
+        exit 0
+      end
+      ObjectSpace.define_finalizer(obj, handler)
+      exit 0
+    RUBY
+
+    ruby_exe(code, :args => "2>&1").should include("finalizer 2 run\n")
+  end
+
+  it "allows multiple finalizers with different 'callables' to be defined" do
+    code = <<-'RUBY'
       obj = Object.new
 
       ObjectSpace.define_finalizer(obj, Proc.new { STDOUT.write "finalized1\n" })
@@ -65,4 +167,49 @@ describe "ObjectSpace.define_finalizer" do
 
     ruby_exe(code).lines.sort.should == ["finalized1\n", "finalized2\n"]
   end
+
+  it "defines same finalizer only once" do
+    code = <<~RUBY
+      obj = Object.new
+      p = proc { |id| print "ok" }
+      ObjectSpace.define_finalizer(obj, p.dup)
+      ObjectSpace.define_finalizer(obj, p.dup)
+    RUBY
+
+    ruby_exe(code).should == "ok"
+  end
+
+  it "returns the defined finalizer" do
+    obj = Object.new
+    p = proc { |id| }
+    p2 = p.dup
+
+    ret = ObjectSpace.define_finalizer(obj, p)
+    ret.should == [0, p]
+    ret[1].should.equal?(p)
+
+    ret = ObjectSpace.define_finalizer(obj, p2)
+    ret.should == [0, p]
+    ret[1].should.equal?(p)
+  end
+
+  describe "when $VERBOSE is not nil" do
+    it "warns if an exception is raised in finalizer" do
+      code = <<-RUBY
+        ObjectSpace.define_finalizer(Object.new) { raise "finalizing" }
+      RUBY
+
+      ruby_exe(code, args: "2>&1").should include("warning: Exception in finalizer", "finalizing")
+    end
+  end
+
+  describe "when $VERBOSE is nil" do
+    it "does not warn even if an exception is raised in finalizer" do
+      code = <<-RUBY
+        ObjectSpace.define_finalizer(Object.new) { raise "finalizing" }
+      RUBY
+
+      ruby_exe(code, args: "2>&1", options: "-W0").should == ""
+    end
+  end
 end
diff --git a/spec/ruby/core/objectspace/finalizers_spec.rb b/spec/ruby/core/objectspace/finalizers_spec.rb
deleted file mode 100644
index e7f20fc8a0..0000000000
--- a/spec/ruby/core/objectspace/finalizers_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ObjectSpace.finalizers" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/objectspace/garbage_collect_spec.rb b/spec/ruby/core/objectspace/garbage_collect_spec.rb
index 1aec3ea072..521eaa8785 100644
--- a/spec/ruby/core/objectspace/garbage_collect_spec.rb
+++ b/spec/ruby/core/objectspace/garbage_collect_spec.rb
@@ -6,8 +6,8 @@ describe "ObjectSpace.garbage_collect" do
     -> { ObjectSpace.garbage_collect }.should_not raise_error
   end
 
-  it "doesn't accept any arguments" do
-    -> { ObjectSpace.garbage_collect(1) }.should raise_error(ArgumentError)
+  it "accepts keyword arguments" do
+    ObjectSpace.garbage_collect(full_mark: true, immediate_sweep: true).should == nil
   end
 
   it "ignores the supplied block" do
diff --git a/spec/ruby/core/objectspace/remove_finalizer_spec.rb b/spec/ruby/core/objectspace/remove_finalizer_spec.rb
deleted file mode 100644
index 0b2b8cf16b..0000000000
--- a/spec/ruby/core/objectspace/remove_finalizer_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "ObjectSpace.remove_finalizer" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/objectspace/undefine_finalizer_spec.rb b/spec/ruby/core/objectspace/undefine_finalizer_spec.rb
index 11d43121f8..f57d5a7845 100644
--- a/spec/ruby/core/objectspace/undefine_finalizer_spec.rb
+++ b/spec/ruby/core/objectspace/undefine_finalizer_spec.rb
@@ -1,5 +1,33 @@
 require_relative '../../spec_helper'
 
 describe "ObjectSpace.undefine_finalizer" do
-  it "needs to be reviewed for spec completeness"
+  it "removes finalizers for an object" do
+    code = <<~RUBY
+      obj = Object.new
+      ObjectSpace.define_finalizer(obj, proc { |id| puts "hello" })
+      ObjectSpace.undefine_finalizer(obj)
+    RUBY
+
+    ruby_exe(code).should.empty?
+  end
+
+  it "should not remove finalizers for a frozen object" do
+    code = <<~RUBY
+      obj = Object.new
+      ObjectSpace.define_finalizer(obj, proc { |id| print "ok" })
+      obj.freeze
+      begin
+        ObjectSpace.undefine_finalizer(obj)
+      rescue
+      end
+    RUBY
+
+    ruby_exe(code).should == "ok"
+  end
+
+  it "should raise when removing finalizers for a frozen object" do
+    obj = Object.new
+    obj.freeze
+    -> { ObjectSpace.undefine_finalizer(obj) }.should raise_error(FrozenError)
+  end
 end
diff --git a/spec/ruby/core/objectspace/weakkeymap/clear_spec.rb b/spec/ruby/core/objectspace/weakkeymap/clear_spec.rb
new file mode 100644
index 0000000000..8050e2c307
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/clear_spec.rb
@@ -0,0 +1,27 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is '3.3' do
+  describe "ObjectSpace::WeakKeyMap#clear" do
+    it "removes all the entries" do
+      m = ObjectSpace::WeakKeyMap.new
+
+      key = Object.new
+      value = Object.new
+      m[key] = value
+
+      key2 = Object.new
+      value2 = Object.new
+      m[key2] = value2
+
+      m.clear
+
+      m.key?(key).should == false
+      m.key?(key2).should == false
+    end
+
+    it "returns self" do
+      m = ObjectSpace::WeakKeyMap.new
+      m.clear.should.equal?(m)
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/delete_spec.rb b/spec/ruby/core/objectspace/weakkeymap/delete_spec.rb
new file mode 100644
index 0000000000..3cd61355d6
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/delete_spec.rb
@@ -0,0 +1,51 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is '3.3' do
+  describe "ObjectSpace::WeakKeyMap#delete" do
+    it "removes the entry and returns the deleted value" do
+      m = ObjectSpace::WeakKeyMap.new
+      key = Object.new
+      value = Object.new
+      m[key] = value
+
+      m.delete(key).should == value
+      m.key?(key).should == false
+    end
+
+    it "uses equality semantic" do
+      m = ObjectSpace::WeakKeyMap.new
+      key = "foo".upcase
+      value = Object.new
+      m[key] = value
+
+      m.delete("foo".upcase).should == value
+      m.key?(key).should == false
+    end
+
+    it "calls supplied block if the key is not found" do
+      key = Object.new
+      m = ObjectSpace::WeakKeyMap.new
+      return_value = m.delete(key) do |yielded_key|
+        yielded_key.should == key
+        5
+      end
+      return_value.should == 5
+    end
+
+    it "returns nil if the key is not found when no block is given" do
+      m = ObjectSpace::WeakKeyMap.new
+      m.delete(Object.new).should == nil
+    end
+
+    it "returns nil when a key cannot be garbage collected" do
+      map = ObjectSpace::WeakKeyMap.new
+
+      map.delete(1).should == nil
+      map.delete(1.0).should == nil
+      map.delete(:a).should == nil
+      map.delete(true).should == nil
+      map.delete(false).should == nil
+      map.delete(nil).should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/element_reference_spec.rb b/spec/ruby/core/objectspace/weakkeymap/element_reference_spec.rb
new file mode 100644
index 0000000000..51368e8d3b
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/element_reference_spec.rb
@@ -0,0 +1,107 @@
+require_relative '../../../spec_helper'
+require_relative 'fixtures/classes'
+
+ruby_version_is "3.3" do
+  describe "ObjectSpace::WeakKeyMap#[]" do
+    it "is faithful to the map's content" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a b].map(&:upcase)
+      ref1, ref2 = %w[x y]
+      map[key1] = ref1
+      map[key1].should == ref1
+      map[key1] = ref1
+      map[key1].should == ref1
+      map[key2] = ref2
+      map[key1].should == ref1
+      map[key2].should == ref2
+    end
+
+    it "compares keys with #eql? semantics" do
+      map = ObjectSpace::WeakKeyMap.new
+      key = [1.0]
+      map[key] = "x"
+      map[[1]].should == nil
+      map[[1.0]].should == "x"
+      key.should == [1.0] # keep the key alive until here to keep the map entry
+
+      map = ObjectSpace::WeakKeyMap.new
+      key = [1]
+      map[key] = "x"
+      map[[1.0]].should == nil
+      map[[1]].should == "x"
+      key.should == [1] # keep the key alive until here to keep the map entry
+
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a a].map(&:upcase)
+      ref = "x"
+      map[key1] = ref
+      map[key2].should == ref
+    end
+
+    it "compares key via #hash first" do
+      x = mock('0')
+      x.should_receive(:hash).and_return(0)
+
+      map = ObjectSpace::WeakKeyMap.new
+      key = 'foo'
+      map[key] = :bar
+      map[x].should == nil
+    end
+
+    it "does not compare keys with different #hash values via #eql?" do
+      x = mock('x')
+      x.should_not_receive(:eql?)
+      x.stub!(:hash).and_return(0)
+
+      y = mock('y')
+      y.should_not_receive(:eql?)
+      y.stub!(:hash).and_return(1)
+
+      map = ObjectSpace::WeakKeyMap.new
+      map[y] = 1
+      map[x].should == nil
+    end
+
+    it "compares keys with the same #hash value via #eql?" do
+      x = mock('x')
+      x.should_receive(:eql?).and_return(true)
+      x.stub!(:hash).and_return(42)
+
+      y = mock('y')
+      y.should_not_receive(:eql?)
+      y.stub!(:hash).and_return(42)
+
+      map = ObjectSpace::WeakKeyMap.new
+      map[y] = 1
+      map[x].should == 1
+    end
+
+    it "finds a value via an identical key even when its #eql? isn't reflexive" do
+      x = mock('x')
+      x.should_receive(:hash).at_least(1).and_return(42)
+      x.stub!(:eql?).and_return(false) # Stubbed for clarity and latitude in implementation; not actually sent by MRI.
+
+      map = ObjectSpace::WeakKeyMap.new
+      map[x] = :x
+      map[x].should == :x
+    end
+
+    it "supports keys with private #hash method" do
+      key = WeakKeyMapSpecs::KeyWithPrivateHash.new
+      map = ObjectSpace::WeakKeyMap.new
+      map[key] = 42
+      map[key].should == 42
+    end
+
+    it "returns nil and does not raise error when a key cannot be garbage collected" do
+      map = ObjectSpace::WeakKeyMap.new
+
+      map[1].should == nil
+      map[1.0].should == nil
+      map[:a].should == nil
+      map[true].should == nil
+      map[false].should == nil
+      map[nil].should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/element_set_spec.rb b/spec/ruby/core/objectspace/weakkeymap/element_set_spec.rb
new file mode 100644
index 0000000000..8db8d780c7
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/element_set_spec.rb
@@ -0,0 +1,82 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "ObjectSpace::WeakKeyMap#[]=" do
+    def should_accept(map, key, value)
+      (map[key] = value).should == value
+      map.should.key?(key)
+      map[key].should == value
+    end
+
+    it "is correct" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a b].map(&:upcase)
+      ref1, ref2 = %w[x y]
+      should_accept(map, key1, ref1)
+      should_accept(map, key1, ref1)
+      should_accept(map, key2, ref2)
+      map[key1].should == ref1
+    end
+
+    it "requires the keys to implement #hash" do
+      map = ObjectSpace::WeakKeyMap.new
+      -> { map[BasicObject.new] = 1 }.should raise_error(NoMethodError, /undefined method [`']hash' for an instance of BasicObject/)
+    end
+
+    it "accepts frozen keys or values" do
+      map = ObjectSpace::WeakKeyMap.new
+      x = Object.new
+      should_accept(map, x, true)
+      should_accept(map, x, false)
+      should_accept(map, x, 42)
+      should_accept(map, x, :foo)
+
+      y = Object.new.freeze
+      should_accept(map, x, y)
+      should_accept(map, y, x)
+    end
+
+    it "does not duplicate and freeze String keys (like Hash#[]= does)" do
+      map = ObjectSpace::WeakKeyMap.new
+      key = +"a"
+      map[key] = 1
+
+      map.getkey("a").should.equal? key
+      map.getkey("a").should_not.frozen?
+
+      key.should == "a" # keep the key alive until here to keep the map entry
+    end
+
+    context "a key cannot be garbage collected" do
+      it "raises ArgumentError when Integer is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[1] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+
+      it "raises ArgumentError when Float is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[1.0] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+
+      it "raises ArgumentError when Symbol is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[:a] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+
+      it "raises ArgumentError when true is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[true] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+
+      it "raises ArgumentError when false is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[false] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+
+      it "raises ArgumentError when nil is used as a key" do
+        map = ObjectSpace::WeakKeyMap.new
+        -> { map[nil] = "x" }.should raise_error(ArgumentError, /WeakKeyMap (keys )?must be garbage collectable/)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/fixtures/classes.rb b/spec/ruby/core/objectspace/weakkeymap/fixtures/classes.rb
new file mode 100644
index 0000000000..0fd04551b5
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/fixtures/classes.rb
@@ -0,0 +1,5 @@
+module WeakKeyMapSpecs
+  class KeyWithPrivateHash
+    private :hash
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/getkey_spec.rb b/spec/ruby/core/objectspace/weakkeymap/getkey_spec.rb
new file mode 100644
index 0000000000..8a2dbf809d
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/getkey_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "ObjectSpace::WeakKeyMap#getkey" do
+    it "returns the existing equal key" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a a].map(&:upcase)
+
+      map[key1] = true
+      map.getkey(key2).should equal(key1)
+      map.getkey("X").should == nil
+
+      key1.should == "A" # keep the key alive until here to keep the map entry
+      key2.should == "A" # keep the key alive until here to keep the map entry
+    end
+
+    it "returns nil when a key cannot be garbage collected" do
+      map = ObjectSpace::WeakKeyMap.new
+
+      map.getkey(1).should == nil
+      map.getkey(1.0).should == nil
+      map.getkey(:a).should == nil
+      map.getkey(true).should == nil
+      map.getkey(false).should == nil
+      map.getkey(nil).should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/inspect_spec.rb b/spec/ruby/core/objectspace/weakkeymap/inspect_spec.rb
new file mode 100644
index 0000000000..319f050970
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/inspect_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "ObjectSpace::WeakKeyMap#inspect" do
+    it "only displays size in output" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2, key3 = "foo", "bar", "bar"
+      map.inspect.should =~ /\A\#<ObjectSpace::WeakKeyMap:0x\h+ size=0>\z/
+      map[key1] = 1
+      map.inspect.should =~ /\A\#<ObjectSpace::WeakKeyMap:0x\h+ size=1>\z/
+      map[key2] = 2
+      map.inspect.should =~ /\A\#<ObjectSpace::WeakKeyMap:0x\h+ size=2>\z/
+      map[key3] = 3
+      map.inspect.should =~ /\A\#<ObjectSpace::WeakKeyMap:0x\h+ size=2>\z/
+
+      key1.should == "foo" # keep the key alive until here to keep the map entry
+      key2.should == "bar" # keep the key alive until here to keep the map entry
+      key3.should == "bar" # keep the key alive until here to keep the map entry
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakkeymap/key_spec.rb b/spec/ruby/core/objectspace/weakkeymap/key_spec.rb
new file mode 100644
index 0000000000..a9a2e12432
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakkeymap/key_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "ObjectSpace::WeakKeyMap#key?" do
+    it "recognizes keys in use" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a b].map(&:upcase)
+      ref1, ref2 = %w[x y]
+
+      map[key1] = ref1
+      map.key?(key1).should == true
+      map[key1] = ref1
+      map.key?(key1).should == true
+      map[key2] = ref2
+      map.key?(key2).should == true
+    end
+
+    it "matches using equality semantics" do
+      map = ObjectSpace::WeakKeyMap.new
+      key1, key2 = %w[a a].map(&:upcase)
+      ref = "x"
+      map[key1] = ref
+      map.key?(key2).should == true
+    end
+
+    it "reports true if the pair exists and the value is nil" do
+      map = ObjectSpace::WeakKeyMap.new
+      key = Object.new
+      map[key] = nil
+      map.key?(key).should == true
+    end
+
+    it "returns false when a key cannot be garbage collected" do
+      map = ObjectSpace::WeakKeyMap.new
+
+      map.key?(1).should == false
+      map.key?(1.0).should == false
+      map.key?(:a).should == false
+      map.key?(true).should == false
+      map.key?(false).should == false
+      map.key?(nil).should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/delete_spec.rb b/spec/ruby/core/objectspace/weakmap/delete_spec.rb
new file mode 100644
index 0000000000..302de264fb
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/delete_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+
+ruby_version_is '3.3' do
+  describe "ObjectSpace::WeakMap#delete" do
+    it "removes the entry and returns the deleted value" do
+      m = ObjectSpace::WeakMap.new
+      key = Object.new
+      value = Object.new
+      m[key] = value
+
+      m.delete(key).should == value
+      m.key?(key).should == false
+    end
+
+    it "calls supplied block if the key is not found" do
+      key = Object.new
+      m = ObjectSpace::WeakMap.new
+      return_value = m.delete(key) do |yielded_key|
+        yielded_key.should == key
+        5
+      end
+      return_value.should == 5
+    end
+
+    it "returns nil if the key is not found when no block is given" do
+      m = ObjectSpace::WeakMap.new
+      m.delete(Object.new).should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/each_key_spec.rb b/spec/ruby/core/objectspace/weakmap/each_key_spec.rb
new file mode 100644
index 0000000000..df971deeb9
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/each_key_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+require_relative 'shared/each'
+
+describe "ObjectSpace::WeakMap#each_key" do
+  it_behaves_like :weakmap_members, -> map { a = []; map.each_key{ |k| a << k }; a }, %w[A B]
+end
+
+describe "ObjectSpace::WeakMap#each_key" do
+  it_behaves_like :weakmap_each, :each_key
+end
diff --git a/spec/ruby/core/objectspace/weakmap/each_pair_spec.rb b/spec/ruby/core/objectspace/weakmap/each_pair_spec.rb
new file mode 100644
index 0000000000..ea29edbd2f
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/each_pair_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+require_relative 'shared/each'
+
+describe "ObjectSpace::WeakMap#each_pair" do
+  it_behaves_like :weakmap_members, -> map { a = []; map.each_pair{ |k,v| a << "#{k}#{v}" }; a }, %w[Ax By]
+end
+
+describe "ObjectSpace::WeakMap#each_key" do
+  it_behaves_like :weakmap_each, :each_pair
+end
diff --git a/spec/ruby/core/objectspace/weakmap/each_spec.rb b/spec/ruby/core/objectspace/weakmap/each_spec.rb
new file mode 100644
index 0000000000..46fcb66a6f
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/each_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+require_relative 'shared/each'
+
+describe "ObjectSpace::WeakMap#each" do
+  it_behaves_like :weakmap_members, -> map { a = []; map.each{ |k,v| a << "#{k}#{v}" }; a }, %w[Ax By]
+end
+
+describe "ObjectSpace::WeakMap#each_key" do
+  it_behaves_like :weakmap_each, :each
+end
diff --git a/spec/ruby/core/objectspace/weakmap/each_value_spec.rb b/spec/ruby/core/objectspace/weakmap/each_value_spec.rb
new file mode 100644
index 0000000000..65a1a7f6fe
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/each_value_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+require_relative 'shared/each'
+
+describe "ObjectSpace::WeakMap#each_value" do
+  it_behaves_like :weakmap_members, -> map { a = []; map.each_value{ |k| a << k }; a }, %w[x y]
+end
+
+describe "ObjectSpace::WeakMap#each_key" do
+  it_behaves_like :weakmap_each, :each_value
+end
diff --git a/spec/ruby/core/objectspace/weakmap/element_reference_spec.rb b/spec/ruby/core/objectspace/weakmap/element_reference_spec.rb
new file mode 100644
index 0000000000..cb3174cbfa
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/element_reference_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+
+describe "ObjectSpace::WeakMap#[]" do
+  it "is faithful to the map's content" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a b].map(&:upcase)
+    ref1, ref2 = %w[x y]
+    map[key1] = ref1
+    map[key1].should == ref1
+    map[key1] = ref1
+    map[key1].should == ref1
+    map[key2] = ref2
+    map[key1].should == ref1
+    map[key2].should == ref2
+  end
+
+  it "matches using identity semantics" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a a].map(&:upcase)
+    ref = "x"
+    map[key1] = ref
+    map[key2].should == nil
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/element_set_spec.rb b/spec/ruby/core/objectspace/weakmap/element_set_spec.rb
new file mode 100644
index 0000000000..8588877158
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/element_set_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../../spec_helper'
+
+describe "ObjectSpace::WeakMap#[]=" do
+  def should_accept(map, key, value)
+    (map[key] = value).should == value
+    map.should.key?(key)
+    map[key].should == value
+  end
+
+  it "is correct" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a b].map(&:upcase)
+    ref1, ref2 = %w[x y]
+    should_accept(map, key1, ref1)
+    should_accept(map, key1, ref1)
+    should_accept(map, key2, ref2)
+    map[key1].should == ref1
+  end
+
+  it "accepts primitive or frozen keys or values" do
+    map = ObjectSpace::WeakMap.new
+    x = Object.new
+    should_accept(map, true, x)
+    should_accept(map, false, x)
+    should_accept(map, nil, x)
+    should_accept(map, 42, x)
+    should_accept(map, :foo, x)
+
+    should_accept(map, x, true)
+    should_accept(map, x, false)
+    should_accept(map, x, 42)
+    should_accept(map, x, :foo)
+
+    y = Object.new.freeze
+    should_accept(map, x, y)
+    should_accept(map, y, x)
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/include_spec.rb b/spec/ruby/core/objectspace/weakmap/include_spec.rb
new file mode 100644
index 0000000000..54ca6b3030
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/include_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/include'
+
+describe "ObjectSpace::WeakMap#include?" do
+  it_behaves_like :weakmap_include?, :include?
+end
diff --git a/spec/ruby/core/objectspace/weakmap/inspect_spec.rb b/spec/ruby/core/objectspace/weakmap/inspect_spec.rb
new file mode 100644
index 0000000000..f064f6e3ea
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/inspect_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+
+describe "ObjectSpace::WeakMap#inspect" do
+  it "displays object pointers in output" do
+    map = ObjectSpace::WeakMap.new
+    # important to test with BasicObject (without Kernel) here to test edge cases
+    key1, key2 = [BasicObject.new, Object.new]
+    ref1, ref2 = [BasicObject.new, Object.new]
+    map.inspect.should =~ /\A\#<ObjectSpace::WeakMap:0x\h+>\z/
+    map[key1] = ref1
+    map.inspect.should =~ /\A\#<ObjectSpace::WeakMap:0x\h+: \#<BasicObject:0x\h+> => \#<BasicObject:0x\h+>>\z/
+    map[key1] = ref1
+    map.inspect.should =~ /\A\#<ObjectSpace::WeakMap:0x\h+: \#<BasicObject:0x\h+> => \#<BasicObject:0x\h+>>\z/
+    map[key2] = ref2
+
+    regexp1 = /\A\#<ObjectSpace::WeakMap:0x\h+: \#<BasicObject:0x\h+> => \#<BasicObject:0x\h+>, \#<Object:0x\h+> => \#<Object:0x\h+>>\z/
+    regexp2 = /\A\#<ObjectSpace::WeakMap:0x\h+: \#<Object:0x\h+> => \#<Object:0x\h+>, \#<BasicObject:0x\h+> => \#<BasicObject:0x\h+>>\z/
+    str = map.inspect
+    if str =~ regexp1
+      str.should =~ regexp1
+    else
+      str.should =~ regexp2
+    end
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/key_spec.rb b/spec/ruby/core/objectspace/weakmap/key_spec.rb
new file mode 100644
index 0000000000..999685ff95
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/key_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/include'
+
+describe "ObjectSpace::WeakMap#key?" do
+  it_behaves_like :weakmap_include?, :key?
+end
diff --git a/spec/ruby/core/objectspace/weakmap/keys_spec.rb b/spec/ruby/core/objectspace/weakmap/keys_spec.rb
new file mode 100644
index 0000000000..7b1494bdd7
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/keys_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+
+describe "ObjectSpace::WeakMap#keys" do
+  it_behaves_like :weakmap_members, -> map { map.keys }, %w[A B]
+end
diff --git a/spec/ruby/core/objectspace/weakmap/length_spec.rb b/spec/ruby/core/objectspace/weakmap/length_spec.rb
new file mode 100644
index 0000000000..3a935648b1
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/length_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/size'
+
+describe "ObjectSpace::WeakMap#length" do
+  it_behaves_like :weakmap_size, :length
+end
diff --git a/spec/ruby/core/objectspace/weakmap/member_spec.rb b/spec/ruby/core/objectspace/weakmap/member_spec.rb
new file mode 100644
index 0000000000..cefb190ce7
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/member_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/include'
+
+describe "ObjectSpace::WeakMap#member?" do
+  it_behaves_like :weakmap_include?, :member?
+end
diff --git a/spec/ruby/core/objectspace/weakmap/shared/each.rb b/spec/ruby/core/objectspace/weakmap/shared/each.rb
new file mode 100644
index 0000000000..3d43a19347
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/shared/each.rb
@@ -0,0 +1,10 @@
+describe :weakmap_each, shared: true do
+  it "must take a block, except when empty" do
+    map = ObjectSpace::WeakMap.new
+    key = "a".upcase
+    ref = "x"
+    map.send(@method).should == map
+    map[key] = ref
+    -> { map.send(@method) }.should raise_error(LocalJumpError)
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/shared/include.rb b/spec/ruby/core/objectspace/weakmap/shared/include.rb
new file mode 100644
index 0000000000..1770eeac8b
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/shared/include.rb
@@ -0,0 +1,30 @@
+describe :weakmap_include?, shared: true do
+  it "recognizes keys in use" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a b].map(&:upcase)
+    ref1, ref2 = %w[x y]
+
+    map[key1] = ref1
+    map.send(@method, key1).should == true
+    map[key1] = ref1
+    map.send(@method, key1).should == true
+    map[key2] = ref2
+    map.send(@method, key2).should == true
+  end
+
+  it "matches using identity semantics" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a a].map(&:upcase)
+    ref = "x"
+    map[key1] = ref
+    map.send(@method, key2).should == false
+  end
+
+  it "reports true if the pair exists and the value is nil" do
+    map = ObjectSpace::WeakMap.new
+    key = Object.new
+    map[key] = nil
+    map.size.should == 1
+    map.send(@method, key).should == true
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/shared/members.rb b/spec/ruby/core/objectspace/weakmap/shared/members.rb
new file mode 100644
index 0000000000..57226c8d7a
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/shared/members.rb
@@ -0,0 +1,14 @@
+describe :weakmap_members, shared: true do
+  it "is correct" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a b].map(&:upcase)
+    ref1, ref2 = %w[x y]
+    @method.call(map).should == []
+    map[key1] = ref1
+    @method.call(map).should == @object[0..0]
+    map[key1] = ref1
+    @method.call(map).should == @object[0..0]
+    map[key2] = ref2
+    @method.call(map).sort.should == @object
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/shared/size.rb b/spec/ruby/core/objectspace/weakmap/shared/size.rb
new file mode 100644
index 0000000000..1064f99d1b
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/shared/size.rb
@@ -0,0 +1,14 @@
+describe :weakmap_size, shared: true do
+  it "is correct" do
+    map = ObjectSpace::WeakMap.new
+    key1, key2 = %w[a b].map(&:upcase)
+    ref1, ref2 = %w[x y]
+    map.send(@method).should == 0
+    map[key1] = ref1
+    map.send(@method).should == 1
+    map[key1] = ref1
+    map.send(@method).should == 1
+    map[key2] = ref2
+    map.send(@method).should == 2
+  end
+end
diff --git a/spec/ruby/core/objectspace/weakmap/size_spec.rb b/spec/ruby/core/objectspace/weakmap/size_spec.rb
new file mode 100644
index 0000000000..1446abaa24
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/size_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/size'
+
+describe "ObjectSpace::WeakMap#size" do
+  it_behaves_like :weakmap_size, :size
+end
diff --git a/spec/ruby/core/objectspace/weakmap/values_spec.rb b/spec/ruby/core/objectspace/weakmap/values_spec.rb
new file mode 100644
index 0000000000..6f6f90d0ba
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap/values_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/members'
+
+describe "ObjectSpace::WeakMap#values" do
+  it_behaves_like :weakmap_members, -> map { map.values }, %w[x y]
+end
diff --git a/spec/ruby/core/objectspace/weakmap_spec.rb b/spec/ruby/core/objectspace/weakmap_spec.rb
new file mode 100644
index 0000000000..2f3f93c291
--- /dev/null
+++ b/spec/ruby/core/objectspace/weakmap_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+
+describe "ObjectSpace::WeakMap" do
+
+  # Note that we can't really spec the most important aspect of this class: that entries get removed when the values
+  # become unreachable. This is because Ruby does not offer a way to reliable invoke GC (GC.start is not enough, neither
+  # on MRI or on alternative implementations).
+
+  it "includes Enumerable" do
+    ObjectSpace::WeakMap.include?(Enumerable).should == true
+  end
+end
diff --git a/spec/ruby/core/proc/arity_spec.rb b/spec/ruby/core/proc/arity_spec.rb
index f7cb5ad0f8..5c7728cb30 100644
--- a/spec/ruby/core/proc/arity_spec.rb
+++ b/spec/ruby/core/proc/arity_spec.rb
@@ -268,6 +268,14 @@ describe "Proc#arity" do
         @a.arity.should == 3
         @b.arity.should == 3
       end
+
+      # implicit rest
+      evaluate <<-ruby do
+          @a = lambda { |a, | }
+      ruby
+
+        @a.arity.should == 1
+      end
     end
 
     context "returns negative values" do
@@ -530,6 +538,14 @@ describe "Proc#arity" do
         @a.arity.should == 1
         @b.arity.should == 5
       end
+
+      # implicit rest
+      evaluate <<-ruby do
+          @a = proc { |a, | }
+      ruby
+
+        @a.arity.should == 1
+      end
     end
 
     context "returns negative values" do
diff --git a/spec/ruby/core/proc/block_pass_spec.rb b/spec/ruby/core/proc/block_pass_spec.rb
index 99255139d4..411c0bf3db 100644
--- a/spec/ruby/core/proc/block_pass_spec.rb
+++ b/spec/ruby/core/proc/block_pass_spec.rb
@@ -19,25 +19,3 @@ describe "Proc as a block pass argument" do
     p.should == p2
   end
 end
-
-ruby_version_is ""..."2.7" do
-  describe "Proc as an implicit block pass argument" do
-    def revivify
-      Proc.new
-    end
-
-    it "remains the same object if re-vivified by the target method" do
-      p = Proc.new {}
-      p2 = revivify(&p)
-      p.should equal p2
-      p.should == p2
-    end
-
-    it "remains the same object if reconstructed with Proc.new" do
-      p = Proc.new {}
-      p2 = Proc.new(&p)
-      p.should equal p2
-      p.should == p2
-    end
-  end
-end
diff --git a/spec/ruby/core/proc/clone_spec.rb b/spec/ruby/core/proc/clone_spec.rb
index a1a1292654..730dc421a8 100644
--- a/spec/ruby/core/proc/clone_spec.rb
+++ b/spec/ruby/core/proc/clone_spec.rb
@@ -1,6 +1,30 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/common'
 require_relative 'shared/dup'
 
 describe "Proc#clone" do
   it_behaves_like :proc_dup, :clone
+
+  ruby_bug "cloning a frozen proc is broken on Ruby 3.3", "3.3"..."3.4" do
+    it "preserves frozen status" do
+      proc = Proc.new { }
+      proc.freeze
+      proc.frozen?.should == true
+      proc.clone.frozen?.should == true
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "calls #initialize_clone on subclass" do
+      obj = ProcSpecs::MyProc2.new(:a, 2) { }
+      dup = obj.clone
+
+      dup.should_not equal(obj)
+      dup.class.should == ProcSpecs::MyProc2
+
+      dup.first.should == :a
+      dup.second.should == 2
+      dup.initializer.should == :clone
+    end
+  end
 end
diff --git a/spec/ruby/core/proc/compose_spec.rb b/spec/ruby/core/proc/compose_spec.rb
index 35e949a779..9e9b57e06f 100644
--- a/spec/ruby/core/proc/compose_spec.rb
+++ b/spec/ruby/core/proc/compose_spec.rb
@@ -1,110 +1,142 @@
 require_relative '../../spec_helper'
 require_relative 'shared/compose'
 
-ruby_version_is "2.6" do
-  describe "Proc#<<" do
-    it "returns a Proc that is the composition of self and the passed Proc" do
-      upcase = proc { |s| s.upcase }
-      succ = proc { |s| s.succ }
+describe "Proc#<<" do
+  it "returns a Proc that is the composition of self and the passed Proc" do
+    upcase = proc { |s| s.upcase }
+    succ = proc { |s| s.succ }
 
-      (succ << upcase).call('Ruby').should == "RUBZ"
-    end
+    (succ << upcase).call('Ruby').should == "RUBZ"
+  end
+
+  it "calls passed Proc with arguments and then calls self with result" do
+    f = proc { |x| x * x }
+    g = proc { |x| x + x }
+
+    (f << g).call(2).should == 16
+    (g << f).call(2).should == 8
+  end
+
+  it "accepts any callable object" do
+    inc = proc { |n| n + 1 }
+
+    double = Object.new
+    def double.call(n); n * 2; end
+
+    (inc << double).call(3).should == 7
+  end
 
-    it "calls passed Proc with arguments and then calls self with result" do
+  it_behaves_like :proc_compose, :<<, -> { proc { |s| s.upcase } }
+
+  describe "composition" do
+    it "is a Proc" do
       f = proc { |x| x * x }
       g = proc { |x| x + x }
 
-      (f << g).call(2).should == 16
-      (g << f).call(2).should == 8
+      (f << g).is_a?(Proc).should == true
+      (f << g).should_not.lambda?
     end
 
-    it "accepts any callable object" do
-      inc = proc { |n| n + 1 }
+    it "is a lambda when parameter is lambda" do
+      f = -> x { x * x }
+      g = proc { |x| x + x }
+      lambda_proc = -> x { x }
+
+      # lambda << proc
+      (f << g).is_a?(Proc).should == true
+      (f << g).should_not.lambda?
 
-      double = Object.new
-      def double.call(n); n * 2; end
+      # lambda << lambda
+      (f << lambda_proc).is_a?(Proc).should == true
+      (f << lambda_proc).should.lambda?
 
-      (inc << double).call(3).should == 7
+      # proc << lambda
+      (g << f).is_a?(Proc).should == true
+      (g << f).should.lambda?
     end
 
-    it_behaves_like :proc_compose, :<<, -> { proc { |s| s.upcase } }
+    it "may accept multiple arguments" do
+      inc = proc { |n| n + 1 }
+      mul = proc { |n, m| n * m }
 
-    describe "composition" do
-      it "is a Proc" do
-        f = proc { |x| x * x }
-        g = proc { |x| x + x }
+      (inc << mul).call(2, 3).should == 7
+    end
 
-        (f << g).is_a?(Proc).should == true
-        (f << g).lambda?.should == false
-      end
+    it "passes blocks to the second proc" do
+      ScratchPad.record []
+      one = proc { |&arg| arg.call :one if arg }
+      two = proc { |&arg| arg.call :two if arg }
+      (one << two).call { |x| ScratchPad << x }
+      ScratchPad.recorded.should == [:two]
+    end
+  end
+end
+
+describe "Proc#>>" do
+  it "returns a Proc that is the composition of self and the passed Proc" do
+    upcase = proc { |s| s.upcase }
+    succ = proc { |s| s.succ }
 
-      it "may accept multiple arguments" do
-        inc = proc { |n| n + 1 }
-        mul = proc { |n, m| n * m }
+    (succ >> upcase).call('Ruby').should == "RUBZ"
+  end
 
-        (inc << mul).call(2, 3).should == 7
-      end
+  it "calls passed Proc with arguments and then calls self with result" do
+    f = proc { |x| x * x }
+    g = proc { |x| x + x }
 
-      it "passes blocks to the second proc" do
-        ScratchPad.record []
-        one = proc { |&arg| arg.call :one if arg }
-        two = proc { |&arg| arg.call :two if arg }
-        (one << two).call { |x| ScratchPad << x }
-        ScratchPad.recorded.should == [:two]
-      end
-    end
+    (f >> g).call(2).should == 8
+    (g >> f).call(2).should == 16
   end
 
-  describe "Proc#>>" do
-    it "returns a Proc that is the composition of self and the passed Proc" do
-      upcase = proc { |s| s.upcase }
-      succ = proc { |s| s.succ }
+  it "accepts any callable object" do
+    inc = proc { |n| n + 1 }
 
-      (succ >> upcase).call('Ruby').should == "RUBZ"
-    end
+    double = Object.new
+    def double.call(n); n * 2; end
+
+    (inc >> double).call(3).should == 8
+  end
+
+  it_behaves_like :proc_compose, :>>, -> { proc { |s| s.upcase } }
 
-    it "calls passed Proc with arguments and then calls self with result" do
+  describe "composition" do
+    it "is a Proc" do
       f = proc { |x| x * x }
       g = proc { |x| x + x }
 
-      (f >> g).call(2).should == 8
-      (g >> f).call(2).should == 16
+      (f >> g).is_a?(Proc).should == true
+      (f >> g).should_not.lambda?
     end
 
-    it "accepts any callable object" do
-      inc = proc { |n| n + 1 }
-
-      double = Object.new
-      def double.call(n); n * 2; end
+    it "is a Proc when other is lambda" do
+      f = proc { |x| x * x }
+      g = -> x { x + x }
 
-      (inc >> double).call(3).should == 8
+      (f >> g).is_a?(Proc).should == true
+      (f >> g).should_not.lambda?
     end
 
-    it_behaves_like :proc_compose, :>>, -> { proc { |s| s.upcase } }
-
-    describe "composition" do
-      it "is a Proc" do
-        f = proc { |x| x * x }
-        g = proc { |x| x + x }
+    it "is a lambda when self is lambda" do
+      f = -> x { x * x }
+      g = proc { |x| x + x }
 
-        (f >> g).is_a?(Proc).should == true
-        (f >> g).lambda?.should == false
-      end
+      (f >> g).is_a?(Proc).should == true
+      (f >> g).should.lambda?
+    end
 
-      it "may accept multiple arguments" do
-        inc = proc { |n| n + 1 }
-        mul = proc { |n, m| n * m }
+    it "may accept multiple arguments" do
+      inc = proc { |n| n + 1 }
+      mul = proc { |n, m| n * m }
 
-        (mul >> inc).call(2, 3).should == 7
-      end
+      (mul >> inc).call(2, 3).should == 7
+    end
 
-      it "passes blocks to the first proc" do
-        ScratchPad.record []
-        one = proc { |&arg| arg.call :one if arg }
-        two = proc { |&arg| arg.call :two if arg }
-        (one >> two).call { |x| ScratchPad << x }
-        ScratchPad.recorded.should == [:one]
-      end
+    it "passes blocks to the first proc" do
+      ScratchPad.record []
+      one = proc { |&arg| arg.call :one if arg }
+      two = proc { |&arg| arg.call :two if arg }
+      (one >> two).call { |x| ScratchPad << x }
+      ScratchPad.recorded.should == [:one]
     end
   end
 end
diff --git a/spec/ruby/core/proc/curry_spec.rb b/spec/ruby/core/proc/curry_spec.rb
index 24df2a8a72..6daabe0ee1 100644
--- a/spec/ruby/core/proc/curry_spec.rb
+++ b/spec/ruby/core/proc/curry_spec.rb
@@ -159,15 +159,14 @@ describe "Proc#curry with arity argument" do
   end
 
   it "can be passed more than _arity_ arguments if created from a proc" do
-    -> { @proc_add.curry(3)[1,2,3,4].should == 6 }.should_not
-      raise_error(ArgumentError)
-    -> { @proc_add.curry(1)[1,2].curry(3)[3,4,5,6].should == 6 }.should_not
-      raise_error(ArgumentError)
+    @proc_add.curry(3)[1,2,3,4].should == 6
+
+    @proc_add.curry(3)[1,2].curry(3)[3,4,5,6].should == 6
   end
 
   it "raises an ArgumentError if passed more than _arity_ arguments when created from a lambda" do
     -> { @lambda_add.curry(3)[1,2,3,4] }.should raise_error(ArgumentError)
-    -> { @lambda_add.curry(1)[1,2].curry(3)[3,4,5,6] }.should raise_error(ArgumentError)
+    -> { @lambda_add.curry(3)[1,2].curry(3)[3,4,5,6] }.should raise_error(ArgumentError)
   end
 
   it "returns Procs with arities of -1 regardless of the value of _arity_" do
diff --git a/spec/ruby/core/proc/dup_spec.rb b/spec/ruby/core/proc/dup_spec.rb
index 6da2f3080c..716357d1f0 100644
--- a/spec/ruby/core/proc/dup_spec.rb
+++ b/spec/ruby/core/proc/dup_spec.rb
@@ -1,6 +1,28 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/common'
 require_relative 'shared/dup'
 
 describe "Proc#dup" do
   it_behaves_like :proc_dup, :dup
+
+  it "resets frozen status" do
+    proc = Proc.new { }
+    proc.freeze
+    proc.frozen?.should == true
+    proc.dup.frozen?.should == false
+  end
+
+  ruby_version_is "3.3" do
+    it "calls #initialize_dup on subclass" do
+      obj = ProcSpecs::MyProc2.new(:a, 2) { }
+      dup = obj.dup
+
+      dup.should_not equal(obj)
+      dup.class.should == ProcSpecs::MyProc2
+
+      dup.first.should == :a
+      dup.second.should == 2
+      dup.initializer.should == :dup
+    end
+  end
 end
diff --git a/spec/ruby/core/proc/element_reference_spec.rb b/spec/ruby/core/proc/element_reference_spec.rb
index 9077e44c34..81ceb91af5 100644
--- a/spec/ruby/core/proc/element_reference_spec.rb
+++ b/spec/ruby/core/proc/element_reference_spec.rb
@@ -17,7 +17,7 @@ describe "Proc#call on a Proc created with Kernel#lambda or Kernel#proc" do
   it_behaves_like :proc_call_on_proc_or_lambda, :call
 end
 
-describe "Proc#[] with frozen_string_literals" do
+describe "Proc#[] with frozen_string_literal: true/false" do
   it "doesn't duplicate frozen strings" do
     ProcArefSpecs.aref.frozen?.should be_false
     ProcArefSpecs.aref_freeze.frozen?.should be_true
diff --git a/spec/ruby/core/proc/eql_spec.rb b/spec/ruby/core/proc/eql_spec.rb
index a3c5a5658d..ad8f6749fc 100644
--- a/spec/ruby/core/proc/eql_spec.rb
+++ b/spec/ruby/core/proc/eql_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/equal'
 
 describe "Proc#eql?" do
-  it_behaves_like :proc_equal_undefined, :eql?
+  it_behaves_like :proc_equal, :eql?
 end
diff --git a/spec/ruby/core/proc/equal_value_spec.rb b/spec/ruby/core/proc/equal_value_spec.rb
index 1b6ac792cf..ec7f274732 100644
--- a/spec/ruby/core/proc/equal_value_spec.rb
+++ b/spec/ruby/core/proc/equal_value_spec.rb
@@ -2,5 +2,5 @@ require_relative '../../spec_helper'
 require_relative 'shared/equal'
 
 describe "Proc#==" do
-  it_behaves_like :proc_equal_undefined, :==
+  it_behaves_like :proc_equal, :==
 end
diff --git a/spec/ruby/core/proc/fixtures/common.rb b/spec/ruby/core/proc/fixtures/common.rb
index 6e27a2dee7..dfe67d7ba8 100644
--- a/spec/ruby/core/proc/fixtures/common.rb
+++ b/spec/ruby/core/proc/fixtures/common.rb
@@ -32,7 +32,28 @@ module ProcSpecs
       @second = b
     end
 
-    attr_reader :first, :second
+    attr_reader :first, :second, :initializer
+
+    def initialize_copy(other)
+      super
+      @initializer = :copy
+      @first = other.first
+      @second = other.second
+    end
+
+    def initialize_dup(other)
+      super
+      @initializer = :dup
+      @first = other.first
+      @second = other.second
+    end
+
+    def initialize_clone(other, **options)
+      super
+      @initializer = :clone
+      @first = other.first
+      @second = other.second
+    end
   end
 
   class Arity
diff --git a/spec/ruby/core/proc/fixtures/proc_aref.rb b/spec/ruby/core/proc/fixtures/proc_aref.rb
index a305667797..8ee355b14c 100644
--- a/spec/ruby/core/proc/fixtures/proc_aref.rb
+++ b/spec/ruby/core/proc/fixtures/proc_aref.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 module ProcArefSpecs
   def self.aref
     proc {|a| a }["sometext"]
diff --git a/spec/ruby/core/proc/fixtures/source_location.rb b/spec/ruby/core/proc/fixtures/source_location.rb
index 688dac1e22..5572094630 100644
--- a/spec/ruby/core/proc/fixtures/source_location.rb
+++ b/spec/ruby/core/proc/fixtures/source_location.rb
@@ -44,7 +44,7 @@ module ProcSpecs
 
     def self.my_detached_lambda
       body = -> { true }
-      lambda(&body)
+      suppress_warning {lambda(&body)}
     end
 
     def self.my_detached_proc_new
diff --git a/spec/ruby/core/proc/hash_spec.rb b/spec/ruby/core/proc/hash_spec.rb
index d780c1ceb0..ebe0fde1a0 100644
--- a/spec/ruby/core/proc/hash_spec.rb
+++ b/spec/ruby/core/proc/hash_spec.rb
@@ -7,7 +7,7 @@ describe "Proc#hash" do
   end
 
   it "returns an Integer" do
-    proc { 1 + 489 }.hash.should be_kind_of(Fixnum)
+    proc { 1 + 489 }.hash.should be_kind_of(Integer)
   end
 
   it "is stable" do
diff --git a/spec/ruby/core/proc/lambda_spec.rb b/spec/ruby/core/proc/lambda_spec.rb
index fe2ceb4279..5c3c38fc2a 100644
--- a/spec/ruby/core/proc/lambda_spec.rb
+++ b/spec/ruby/core/proc/lambda_spec.rb
@@ -14,9 +14,11 @@ describe "Proc#lambda?" do
     Proc.new {}.lambda?.should be_false
   end
 
-  it "is preserved when passing a Proc with & to the lambda keyword" do
-    lambda(&->{}).lambda?.should be_true
-    lambda(&proc{}).lambda?.should be_false
+  ruby_version_is ""..."3.3" do
+    it "is preserved when passing a Proc with & to the lambda keyword" do
+      suppress_warning {lambda(&->{})}.lambda?.should be_true
+      suppress_warning {lambda(&proc{})}.lambda?.should be_false
+    end
   end
 
   it "is preserved when passing a Proc with & to the proc keyword" do
diff --git a/spec/ruby/core/proc/new_spec.rb b/spec/ruby/core/proc/new_spec.rb
index cc033467e5..b2b7387756 100644
--- a/spec/ruby/core/proc/new_spec.rb
+++ b/spec/ruby/core/proc/new_spec.rb
@@ -94,20 +94,6 @@ describe "Proc.new with an associated block" do
     obj.first.should == :a
     obj.second.should == 2
   end
-
-  ruby_version_is ""..."2.7" do
-    it "returns a new Proc instance from the block passed to the containing method" do
-      prc = ProcSpecs.new_proc_in_method { "hello" }
-      prc.should be_an_instance_of(Proc)
-      prc.call.should == "hello"
-    end
-
-    it "returns a new Proc instance from the block passed to the containing method" do
-      prc = ProcSpecs.new_proc_subclass_in_method { "hello" }
-      prc.should be_an_instance_of(ProcSpecs::ProcSubclass)
-      prc.call.should == "hello"
-    end
-  end
 end
 
 describe "Proc.new with a block argument" do
@@ -180,47 +166,13 @@ describe "Proc.new without a block" do
     -> { ProcSpecs.new_proc_subclass_in_method }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.7" do
-    it "uses the implicit block from an enclosing method" do
-      def some_method
-        Proc.new
-      end
-
-      prc = some_method { "hello" }
-
-      prc.call.should == "hello"
-    end
-
-    it "uses the implicit block from an enclosing method when called inside a block" do
-      def some_method
-        proc do |&block|
-          Proc.new
-        end.call { "failing" }
-      end
-      prc = some_method { "hello" }
-
-      prc.call.should == "hello"
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "can be created if invoked from within a method with a block" do
-      -> { ProcSpecs.new_proc_in_method { "hello" } }.should complain(/Capturing the given block using Proc.new is deprecated/)
-    end
-
-    it "can be created if invoked on a subclass from within a method with a block" do
-      -> { ProcSpecs.new_proc_subclass_in_method { "hello" } }.should complain(/Capturing the given block using Proc.new is deprecated/)
+  it "raises an ArgumentError when passed no block" do
+    def some_method
+      Proc.new
     end
 
-
-    it "can be create when called with no block" do
-      def some_method
-        Proc.new
-      end
-
-      -> {
-        some_method { "hello" }
-      }.should complain(/Capturing the given block using Proc.new is deprecated/)
-    end
+    -> { ProcSpecs.new_proc_in_method { "hello" } }.should raise_error(ArgumentError, 'tried to create Proc object without a block')
+    -> { ProcSpecs.new_proc_subclass_in_method { "hello" } }.should raise_error(ArgumentError, 'tried to create Proc object without a block')
+    -> { some_method { "hello" } }.should raise_error(ArgumentError, 'tried to create Proc object without a block')
   end
 end
diff --git a/spec/ruby/core/proc/parameters_spec.rb b/spec/ruby/core/proc/parameters_spec.rb
index 2bc5f1325c..cf8a8f5b12 100644
--- a/spec/ruby/core/proc/parameters_spec.rb
+++ b/spec/ruby/core/proc/parameters_spec.rb
@@ -20,6 +20,29 @@ describe "Proc#parameters" do
     proc {|x| }.parameters.first.first.should == :opt
   end
 
+  it "sets the first element of each sub-Array to :req for required argument if lambda keyword used" do
+    proc {|x| }.parameters(lambda: true).first.first.should == :req
+    proc {|y,*x| }.parameters(lambda: true).first.first.should == :req
+  end
+
+  it "regards named parameters in procs as required if lambda keyword used" do
+    proc {|x| }.parameters(lambda: true).first.first.should == :req
+  end
+
+  it "regards named parameters in lambda as optional if lambda: false keyword used" do
+    -> x { }.parameters(lambda: false).first.first.should == :opt
+  end
+
+  it "regards named parameters in procs and lambdas as required if lambda keyword is truthy" do
+    proc {|x| }.parameters(lambda: 123).first.first.should == :req
+    -> x { }.parameters(lambda: 123).first.first.should == :req
+  end
+
+  it "ignores the lambda keyword if it is nil" do
+    proc {|x|}.parameters(lambda: nil).first.first.should == :opt
+    -> x { }.parameters(lambda: nil).first.first.should == :req
+  end
+
   it "regards optional keyword parameters in procs as optional" do
     proc {|x: :y| }.parameters.first.first.should == :key
   end
@@ -39,7 +62,7 @@ describe "Proc#parameters" do
   end
 
   it "regards keyword parameters in lambdas as required" do
-    eval("lambda {|x:| }").parameters.first.first.should == :keyreq
+    -> x: { }.parameters.first.first.should == :keyreq
   end
 
   it "sets the first element of each sub-Array to :rest for parameters prefixed with asterisks" do
@@ -57,7 +80,7 @@ describe "Proc#parameters" do
   end
 
   it "sets the first element of each sub-Array to :block for parameters prefixed with ampersands" do
-    ->&x { }.parameters.first.first.should == :block
+    -> &x { }.parameters.first.first.should == :block
     -> x, &y { }.parameters.last.first.should == :block
     proc {|&x| }.parameters.first.first.should == :block
     proc {|x,&y| }.parameters.last.first.should == :block
@@ -68,7 +91,7 @@ describe "Proc#parameters" do
     -> x=Math::PI { }.parameters.first.last.should == :x
     -> an_argument, glark, &foo { }.parameters[1].last.should == :glark
     -> *rest { }.parameters.first.last.should == :rest
-    ->&block { }.parameters.first.last.should == :block
+    -> &block { }.parameters.first.last.should == :block
     proc {|x| }.parameters.first.last.should == :x
     proc {|x=Math::PI| }.parameters.first.last.should == :x
     proc {|an_argument, glark, &foo| }.parameters[1].last.should == :glark
@@ -76,12 +99,25 @@ describe "Proc#parameters" do
     proc {|&block| }.parameters.first.last.should == :block
   end
 
-  it "ignores unnamed rest args" do
+  it "ignores unnamed rest arguments" do
     -> x {}.parameters.should == [[:req, :x]]
   end
 
-  it "adds nameless rest arg for \"star\" argument" do
-    -> x, * {}.parameters.should == [[:req, :x], [:rest]]
+  it "ignores implicit rest arguments" do
+    proc { |x, | }.parameters.should == [[:opt, :x]]
+    -> x { }.parameters.should == [[:req, :x]]
+  end
+
+  it "adds rest arg with name * for \"star\" argument" do
+    -> * {}.parameters.should == [[:rest, :*]]
+  end
+
+  it "adds keyrest arg with ** as a name for \"double star\" argument" do
+    -> ** {}.parameters.should == [[:keyrest, :**]]
+  end
+
+  it "adds block arg with name & for anonymous block argument" do
+    -> & {}.parameters.should == [[:block, :&]]
   end
 
   it "does not add locals as block options with a block and splat" do
@@ -92,4 +128,48 @@ describe "Proc#parameters" do
       local_is_not_parameter = {}
     end.parameters.should == [[:rest, :args], [:block, :blk]]
   end
+
+  it "returns all parameters defined with the name _ as _" do
+    proc = proc {|_, _, _ = 1, *_, _:, _: 2, **_, &_| }
+    proc.parameters.should == [
+      [:opt, :_],
+      [:opt, :_],
+      [:opt, :_],
+      [:rest, :_],
+      [:keyreq, :_],
+      [:key, :_],
+      [:keyrest, :_],
+      [:block, :_]
+    ]
+
+    lambda = -> _, _, _ = 1, *_, _:, _: 2, **_, &_ {}
+    lambda.parameters.should == [
+      [:req, :_],
+      [:req, :_],
+      [:opt, :_],
+      [:rest, :_],
+      [:keyreq, :_],
+      [:key, :_],
+      [:keyrest, :_],
+      [:block, :_]
+    ]
+  end
+
+  it "returns :nokey for **nil parameter" do
+    proc { |**nil| }.parameters.should == [[:nokey]]
+  end
+
+  ruby_version_is "3.4"..."4.0" do
+    it "handles the usage of `it` as a parameter" do
+      eval("proc { it }").parameters.should == [[:opt, nil]]
+      eval("lambda { it }").parameters.should == [[:req]]
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "handles the usage of `it` as a parameter" do
+      eval("proc { it }").parameters.should == [[:opt]]
+      eval("lambda { it }").parameters.should == [[:req]]
+    end
+  end
 end
diff --git a/spec/ruby/core/proc/ruby2_keywords_spec.rb b/spec/ruby/core/proc/ruby2_keywords_spec.rb
new file mode 100644
index 0000000000..d7f8f592e1
--- /dev/null
+++ b/spec/ruby/core/proc/ruby2_keywords_spec.rb
@@ -0,0 +1,66 @@
+require_relative '../../spec_helper'
+
+describe "Proc#ruby2_keywords" do
+  it "marks the final hash argument as keyword hash" do
+    f = -> *a { a.last }
+    f.ruby2_keywords
+
+    last = f.call(1, 2, a: "a")
+    Hash.ruby2_keywords_hash?(last).should == true
+  end
+
+  it "applies to the underlying method and applies across duplication" do
+    f1 = -> *a { a.last }
+    f1.ruby2_keywords
+    f2 = f1.dup
+
+    Hash.ruby2_keywords_hash?(f1.call(1, 2, a: "a")).should == true
+    Hash.ruby2_keywords_hash?(f2.call(1, 2, a: "a")).should == true
+
+    f3 = -> *a { a.last }
+    f4 = f3.dup
+    f3.ruby2_keywords
+
+    Hash.ruby2_keywords_hash?(f3.call(1, 2, a: "a")).should == true
+    Hash.ruby2_keywords_hash?(f4.call(1, 2, a: "a")).should == true
+  end
+
+  it "returns self" do
+    f = -> *a { }
+    f.ruby2_keywords.should equal f
+  end
+
+  it "prints warning when a proc does not accept argument splat" do
+    f = -> a, b, c { }
+
+    -> {
+      f.ruby2_keywords
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  it "prints warning when a proc accepts keywords" do
+    f = -> *a, b: { }
+
+    -> {
+      f.ruby2_keywords
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  it "prints warning when a proc accepts keyword splat" do
+    f = -> *a, **b { }
+
+    -> {
+      f.ruby2_keywords
+    }.should complain(/Skipping set of ruby2_keywords flag for/)
+  end
+
+  ruby_version_is "4.0" do
+    it "prints warning when a proc accepts post arguments" do
+      f = -> *a, b { }
+
+      -> {
+        f.ruby2_keywords
+      }.should complain(/Skipping set of ruby2_keywords flag for/)
+    end
+  end
+end
diff --git a/spec/ruby/core/proc/shared/call.rb b/spec/ruby/core/proc/shared/call.rb
index c30ea84b23..dbec34df4b 100644
--- a/spec/ruby/core/proc/shared/call.rb
+++ b/spec/ruby/core/proc/shared/call.rb
@@ -49,6 +49,9 @@ describe :proc_call_on_proc_or_lambda, shared: true do
 
     a = proc {|x| x}.send(@method, 1, 2, 3)
     a.should == 1
+
+    a = proc {|x:| x}.send(@method, 2, x: 1)
+    a.should == 1
   end
 
   it "will call #to_ary on argument and return self if return is nil" do
diff --git a/spec/ruby/core/proc/shared/call_arguments.rb b/spec/ruby/core/proc/shared/call_arguments.rb
index ef6ec04620..91ada3439e 100644
--- a/spec/ruby/core/proc/shared/call_arguments.rb
+++ b/spec/ruby/core/proc/shared/call_arguments.rb
@@ -1,7 +1,7 @@
 describe :proc_call_block_args, shared: true do
   it "can receive block arguments" do
     Proc.new {|&b| b.send(@method)}.send(@method) {1 + 1}.should == 2
-    ->&b { b.send(@method)}.send(@method) {1 + 1}.should == 2
+    -> &b { b.send(@method)}.send(@method) {1 + 1}.should == 2
     proc {|&b| b.send(@method)}.send(@method) {1 + 1}.should == 2
   end
 
diff --git a/spec/ruby/core/proc/shared/compose.rb b/spec/ruby/core/proc/shared/compose.rb
index 64338cada8..3d3f3b310d 100644
--- a/spec/ruby/core/proc/shared/compose.rb
+++ b/spec/ruby/core/proc/shared/compose.rb
@@ -1,47 +1,22 @@
 describe :proc_compose, shared: true do
-  ruby_version_is "2.6"..."2.7" do
-    it "raises NoMethodError when called if passed not callable object" do
-      not_callable = Object.new
-      composed = @object.call.send(@method, not_callable)
+  it "raises TypeError if passed not callable object" do
+    lhs = @object.call
+    not_callable = Object.new
 
-      -> {
-        composed.call('a')
-      }.should raise_error(NoMethodError, /undefined method `call' for/)
+    -> {
+      lhs.send(@method, not_callable)
+    }.should raise_error(TypeError, "callable object is expected")
 
-    end
-
-    it "when called does not try to coerce argument with #to_proc" do
-      succ = Object.new
-      def succ.to_proc(s); s.succ; end
-
-      composed = @object.call.send(@method, succ)
-
-      -> {
-        composed.call('a')
-      }.should raise_error(NoMethodError, /undefined method `call' for/)
-    end
   end
 
-  ruby_version_is "2.7" do # https://bugs.ruby-lang.org/issues/15428
-    it "raises TypeError if passed not callable object" do
-      lhs = @object.call
-      not_callable = Object.new
-
-      -> {
-        lhs.send(@method, not_callable)
-      }.should raise_error(TypeError, "callable object is expected")
-
-    end
-
-    it "does not try to coerce argument with #to_proc" do
-      lhs = @object.call
+  it "does not try to coerce argument with #to_proc" do
+    lhs = @object.call
 
-      succ = Object.new
-      def succ.to_proc(s); s.succ; end
+    succ = Object.new
+    def succ.to_proc(s); s.succ; end
 
-      -> {
-        lhs.send(@method, succ)
-      }.should raise_error(TypeError, "callable object is expected")
-    end
+    -> {
+      lhs.send(@method, succ)
+    }.should raise_error(TypeError, "callable object is expected")
   end
 end
diff --git a/spec/ruby/core/proc/shared/dup.rb b/spec/ruby/core/proc/shared/dup.rb
index eda1d6929d..1266337f94 100644
--- a/spec/ruby/core/proc/shared/dup.rb
+++ b/spec/ruby/core/proc/shared/dup.rb
@@ -7,4 +7,33 @@ describe :proc_dup, shared: true do
 
     a.call.should == b.call
   end
+
+  it "returns an instance of subclass" do
+    cl = Class.new(Proc)
+
+    cl.new{}.send(@method).class.should == cl
+  end
+
+  ruby_version_is "3.4" do
+    it "copies instance variables" do
+      proc = -> { "hello" }
+      proc.instance_variable_set(:@ivar, 1)
+      cl = proc.send(@method)
+      cl.instance_variables.should == [:@ivar]
+    end
+
+    it "copies the finalizer" do
+      code = <<-'RUBY'
+        obj = Proc.new { }
+
+        ObjectSpace.define_finalizer(obj, Proc.new { STDOUT.write "finalized\n" })
+
+        obj.clone
+
+        exit 0
+      RUBY
+
+      ruby_exe(code).lines.sort.should == ["finalized\n", "finalized\n"]
+    end
+  end
 end
diff --git a/spec/ruby/core/proc/shared/equal.rb b/spec/ruby/core/proc/shared/equal.rb
index 46a1894424..d0503fb064 100644
--- a/spec/ruby/core/proc/shared/equal.rb
+++ b/spec/ruby/core/proc/shared/equal.rb
@@ -36,26 +36,26 @@ describe :proc_equal, shared: true do
     a.send(@method, b).should be_false
   end
 
-  it "returns true if both procs have the same body and environment" do
+  it "returns false if procs are distinct but have the same body and environment" do
     p = proc { :foo }
     p2 = proc { :foo }
-    p.send(@method, p2).should be_true
+    p.send(@method, p2).should be_false
   end
 
-  it "returns true if both lambdas with the same body and environment" do
+  it "returns false if lambdas are distinct but have same body and environment" do
     x = -> { :foo }
     x2 = -> { :foo }
-    x.send(@method, x2).should be_true
+    x.send(@method, x2).should be_false
   end
 
-  it "returns true if both different kinds of procs with the same body and env" do
+  it "returns false if using comparing lambda to proc, even with the same body and env" do
     p = -> { :foo }
     p2 = proc { :foo }
-    p.send(@method, p2).should be_true
+    p.send(@method, p2).should be_false
 
     x = proc { :bar }
     x2 = -> { :bar }
-    x.send(@method, x2).should be_true
+    x.send(@method, x2).should be_false
   end
 
   it "returns false if other is not a Proc" do
@@ -81,20 +81,3 @@ describe :proc_equal, shared: true do
     p.send(@method, p2).should be_false
   end
 end
-
-describe :proc_equal_undefined, shared: true do
-  it "is not defined" do
-    Proc.should_not have_instance_method(@method, false)
-  end
-
-  it "returns false if other is a dup of the original" do
-    p = proc { :foo }
-    p.send(@method, p.dup).should be_false
-
-    p = Proc.new { :foo }
-    p.send(@method, p.dup).should be_false
-
-    p = -> { :foo }
-    p.send(@method, p.dup).should be_false
-  end
-end
diff --git a/spec/ruby/core/proc/shared/to_s.rb b/spec/ruby/core/proc/shared/to_s.rb
index 8b9c83927f..a52688a89f 100644
--- a/spec/ruby/core/proc/shared/to_s.rb
+++ b/spec/ruby/core/proc/shared/to_s.rb
@@ -1,9 +1,7 @@
 describe :proc_to_s, shared: true do
-  sep = ruby_version_is("2.7") ? " " : "@"
-
   describe "for a proc created with Proc.new" do
     it "returns a description including file and line number" do
-      Proc.new { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?)#{sep}#{Regexp.escape __FILE__}:#{__LINE__ }>$/
+      Proc.new { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?) #{Regexp.escape __FILE__}:#{__LINE__ }>$/
     end
 
     it "has a binary encoding" do
@@ -13,7 +11,7 @@ describe :proc_to_s, shared: true do
 
   describe "for a proc created with lambda" do
     it "returns a description including '(lambda)' and including file and line number" do
-      -> { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?)#{sep}#{Regexp.escape __FILE__}:#{__LINE__ } \(lambda\)>$/
+      -> { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?) #{Regexp.escape __FILE__}:#{__LINE__ } \(lambda\)>$/
     end
 
     it "has a binary encoding" do
@@ -23,7 +21,7 @@ describe :proc_to_s, shared: true do
 
   describe "for a proc created with proc" do
     it "returns a description including file and line number" do
-      proc { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?)#{sep}#{Regexp.escape __FILE__}:#{__LINE__ }>$/
+      proc { "hello" }.send(@method).should =~ /^#<Proc:([^ ]*?) #{Regexp.escape __FILE__}:#{__LINE__ }>$/
     end
 
     it "has a binary encoding" do
@@ -34,7 +32,12 @@ describe :proc_to_s, shared: true do
   describe "for a proc created with UnboundMethod#to_proc" do
     it "returns a description including '(lambda)' and optionally including file and line number" do
       def hello; end
-      method("hello").to_proc.send(@method).should =~ /^#<Proc:([^ ]*?)(#{sep}#{Regexp.escape __FILE__}:#{__LINE__ })? \(lambda\)>$/
+      s = method("hello").to_proc.send(@method)
+      if s.include? __FILE__
+        s.should =~ /^#<Proc:([^ ]*?) #{Regexp.escape __FILE__}:#{__LINE__ - 3} \(lambda\)>$/
+      else
+        s.should =~ /^#<Proc:([^ ]*?) \(lambda\)>$/
+      end
     end
 
     it "has a binary encoding" do
@@ -46,7 +49,7 @@ describe :proc_to_s, shared: true do
   describe "for a proc created with Symbol#to_proc" do
     it "returns a description including '(&:symbol)'" do
       proc = :foobar.to_proc
-      proc.send(@method).should =~ /^#<Proc:0x\h+\(&:foobar\)>$/
+      proc.send(@method).should.include?('(&:foobar)')
     end
 
     it "has a binary encoding" do
diff --git a/spec/ruby/core/proc/source_location_spec.rb b/spec/ruby/core/proc/source_location_spec.rb
index b5b8178df2..fd33f21a26 100644
--- a/spec/ruby/core/proc/source_location_spec.rb
+++ b/spec/ruby/core/proc/source_location_spec.rb
@@ -17,57 +17,64 @@ describe "Proc#source_location" do
   end
 
   it "sets the first value to the path of the file in which the proc was defined" do
-    file = @proc.source_location.first
+    file = @proc.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/source_location.rb', __FILE__)
+    file.should == File.realpath('fixtures/source_location.rb', __dir__)
 
-    file = @proc_new.source_location.first
+    file = @proc_new.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/source_location.rb', __FILE__)
+    file.should == File.realpath('fixtures/source_location.rb', __dir__)
 
-    file = @lambda.source_location.first
+    file = @lambda.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/source_location.rb', __FILE__)
+    file.should == File.realpath('fixtures/source_location.rb', __dir__)
 
-    file = @method.source_location.first
+    file = @method.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/source_location.rb', __FILE__)
+    file.should == File.realpath('fixtures/source_location.rb', __dir__)
   end
 
-  it "sets the last value to a Fixnum representing the line on which the proc was defined" do
-    line = @proc.source_location.last
-    line.should be_an_instance_of(Fixnum)
+  it "sets the second value to an Integer representing the line on which the proc was defined" do
+    line = @proc.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 4
 
-    line = @proc_new.source_location.last
-    line.should be_an_instance_of(Fixnum)
+    line = @proc_new.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 12
 
-    line = @lambda.source_location.last
-    line.should be_an_instance_of(Fixnum)
+    line = @lambda.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 8
 
-    line = @method.source_location.last
-    line.should be_an_instance_of(Fixnum)
+    line = @method.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 15
   end
 
   it "works even if the proc was created on the same line" do
-    proc { true }.source_location.should == [__FILE__, __LINE__]
-    Proc.new { true }.source_location.should == [__FILE__, __LINE__]
-    -> { true }.source_location.should == [__FILE__, __LINE__]
+    ruby_version_is(""..."4.1") do
+      proc { true }.source_location.should == [__FILE__, __LINE__]
+      Proc.new { true }.source_location.should == [__FILE__, __LINE__]
+      -> { true }.source_location.should == [__FILE__, __LINE__]
+    end
+    ruby_version_is("4.1") do
+      proc { true }.source_location.should == [__FILE__, __LINE__, 11, __LINE__, 19]
+      Proc.new { true }.source_location.should == [__FILE__, __LINE__, 15, __LINE__, 23]
+      -> { true }.source_location.should == [__FILE__, __LINE__, 6, __LINE__, 17]
+    end
   end
 
   it "returns the first line of a multi-line proc (i.e. the line containing 'proc do')" do
-    ProcSpecs::SourceLocation.my_multiline_proc.source_location.last.should == 20
-    ProcSpecs::SourceLocation.my_multiline_proc_new.source_location.last.should == 34
-    ProcSpecs::SourceLocation.my_multiline_lambda.source_location.last.should == 27
+    ProcSpecs::SourceLocation.my_multiline_proc.source_location[1].should == 20
+    ProcSpecs::SourceLocation.my_multiline_proc_new.source_location[1].should == 34
+    ProcSpecs::SourceLocation.my_multiline_lambda.source_location[1].should == 27
   end
 
   it "returns the location of the proc's body; not necessarily the proc itself" do
-    ProcSpecs::SourceLocation.my_detached_proc.source_location.last.should == 41
-    ProcSpecs::SourceLocation.my_detached_proc_new.source_location.last.should == 51
-    ProcSpecs::SourceLocation.my_detached_lambda.source_location.last.should == 46
+    ProcSpecs::SourceLocation.my_detached_proc.source_location[1].should == 41
+    ProcSpecs::SourceLocation.my_detached_proc_new.source_location[1].should == 51
+    ProcSpecs::SourceLocation.my_detached_lambda.source_location[1].should == 46
   end
 
   it "returns the same value for a proc-ified method as the method reports" do
@@ -83,4 +90,15 @@ describe "Proc#source_location" do
 
     proc.source_location.should == nil
   end
+
+  it "works for eval with a given line" do
+    proc = eval('-> {}', nil, "foo", 100)
+    location = proc.source_location
+    ruby_version_is(""..."4.1") do
+      location.should == ["foo", 100]
+    end
+    ruby_version_is("4.1") do
+      location.should == ["foo", 100, 0, 100, 5]
+    end
+  end
 end
diff --git a/spec/ruby/core/process/_fork_spec.rb b/spec/ruby/core/process/_fork_spec.rb
new file mode 100644
index 0000000000..e1f45e2656
--- /dev/null
+++ b/spec/ruby/core/process/_fork_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+
+describe "Process._fork" do
+  it "for #respond_to? returns the same as Process.respond_to?(:fork)" do
+    Process.respond_to?(:_fork).should == Process.respond_to?(:fork)
+  end
+
+  # Using respond_to? in a guard here is OK because the correct semantics
+  # are that _fork is implemented if and only if fork is (see above).
+  guard_not -> { Process.respond_to?(:fork) } do
+    it "raises a NotImplementedError when called" do
+      -> { Process._fork }.should raise_error(NotImplementedError)
+    end
+  end
+
+  guard -> { Process.respond_to?(:fork) } do
+    it "is called by Process#fork" do
+      Process.should_receive(:_fork).once.and_return(42)
+
+      pid = Process.fork {}
+      pid.should equal(42)
+    end
+  end
+end
diff --git a/spec/ruby/core/process/argv0_spec.rb b/spec/ruby/core/process/argv0_spec.rb
new file mode 100644
index 0000000000..f5aba719e9
--- /dev/null
+++ b/spec/ruby/core/process/argv0_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+
+describe "Process.argv0" do
+  it "returns a String" do
+    Process.argv0.should be_kind_of(String)
+  end
+
+  it "is the path given as the main script and the same as __FILE__" do
+    script = "fixtures/argv0.rb"
+
+    Dir.chdir(__dir__) do
+      ruby_exe(script).should == "#{script}\n#{script}\nOK"
+    end
+  end
+
+  ruby_bug "#19597", ""..."3.3" do
+    it "returns a frozen object" do
+      Process.argv0.should.frozen?
+    end
+  end
+
+  it "returns every time the same object" do
+    Process.argv0.should.equal?(Process.argv0)
+  end
+end
diff --git a/spec/ruby/core/process/clock_getres_spec.rb b/spec/ruby/core/process/clock_getres_spec.rb
index 7112b0520a..85aa2b25f1 100644
--- a/spec/ruby/core/process/clock_getres_spec.rb
+++ b/spec/ruby/core/process/clock_getres_spec.rb
@@ -1,37 +1,6 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/clocks'
 
 describe "Process.clock_getres" do
-  # clock_getres() seems completely buggy on FreeBSD:
-  # https://rubyci.org/logs/rubyci.s3.amazonaws.com/freebsd11zfs/ruby-trunk/log/20190428T093003Z.fail.html.gz
-  platform_is_not :freebsd, :openbsd do
-    # NOTE: Look at fixtures/clocks.rb for clock and OS-specific exclusions
-    ProcessSpecs.clock_constants_for_resolution_checks.each do |name, value|
-      it "matches the clock in practice for Process::#{name}" do
-        times = []
-        10_000.times do
-          times << Process.clock_gettime(value, :nanosecond)
-        end
-        reported = Process.clock_getres(value, :nanosecond)
-
-        # The clock should not be more accurate than reported (times should be
-        # a multiple of reported precision.)
-        times.select { |t| t % reported > 0 }.should be_empty
-
-        # We're assuming precision is a multiple of ten - it may or may not
-        # be an incompatibility if it isn't but we'd like to notice this,
-        # and the spec following these wouldn't work if it isn't.
-        reported.should > 0
-        (reported == 1 || reported % 10 == 0).should be_true
-
-        # The clock should not be less accurate than reported (times should
-        # not all be a multiple of the next precision up, assuming precisions
-        # are multiples of ten.)
-        times.select { |t| t % (reported * 10) == 0 }.size.should_not == times.size
-      end
-    end
-  end
-
   # These are documented
 
   it "with :GETTIMEOFDAY_BASED_CLOCK_REALTIME reports 1 microsecond" do
@@ -50,15 +19,15 @@ describe "Process.clock_getres" do
 
   # These are observed
 
-  platform_is_not :solaris, :aix, :openbsd do
-    it "with Process::CLOCK_REALTIME reports at least 1 microsecond" do
-      Process.clock_getres(Process::CLOCK_REALTIME, :nanosecond).should <= 1_000
+  platform_is :linux, :darwin, :windows do
+    it "with Process::CLOCK_REALTIME reports at least 10 millisecond" do
+      Process.clock_getres(Process::CLOCK_REALTIME, :nanosecond).should <= 10_000_000
     end
   end
 
-  platform_is_not :aix, :openbsd do
-    it "with Process::CLOCK_MONOTONIC reports at least 1 microsecond" do
-      Process.clock_getres(Process::CLOCK_MONOTONIC, :nanosecond).should <= 1_000
+  platform_is :linux, :darwin, :windows do
+    it "with Process::CLOCK_MONOTONIC reports at least 10 millisecond" do
+      Process.clock_getres(Process::CLOCK_MONOTONIC, :nanosecond).should <= 10_000_000
     end
   end
 end
diff --git a/spec/ruby/core/process/clock_gettime_spec.rb b/spec/ruby/core/process/clock_gettime_spec.rb
index d3f973d7ae..6c1a52f21e 100644
--- a/spec/ruby/core/process/clock_gettime_spec.rb
+++ b/spec/ruby/core/process/clock_gettime_spec.rb
@@ -41,4 +41,112 @@ describe "Process.clock_gettime" do
       t2.should be_close(t1, TIME_TOLERANCE)
     end
   end
+
+  describe "supports the platform clocks mentioned in the documentation" do
+    it "CLOCK_REALTIME" do
+      Process.clock_gettime(Process::CLOCK_REALTIME).should be_an_instance_of(Float)
+    end
+
+    it "CLOCK_MONOTONIC" do
+      Process.clock_gettime(Process::CLOCK_MONOTONIC).should be_an_instance_of(Float)
+    end
+
+    # These specs need macOS 10.12+ / darwin 16+
+    guard -> { platform_is_not(:darwin) or kernel_version_is '16' } do
+      platform_is :linux, :openbsd, :darwin do
+        it "CLOCK_PROCESS_CPUTIME_ID" do
+          Process.clock_gettime(Process::CLOCK_PROCESS_CPUTIME_ID).should be_an_instance_of(Float)
+        end
+      end
+
+      platform_is :linux, :freebsd, :openbsd, :darwin do
+        it "CLOCK_THREAD_CPUTIME_ID" do
+          Process.clock_gettime(Process::CLOCK_THREAD_CPUTIME_ID).should be_an_instance_of(Float)
+        end
+      end
+
+      platform_is :linux, :darwin do
+        it "CLOCK_MONOTONIC_RAW" do
+          Process.clock_gettime(Process::CLOCK_MONOTONIC_RAW).should be_an_instance_of(Float)
+        end
+      end
+
+      platform_is :darwin do
+        it "CLOCK_MONOTONIC_RAW_APPROX" do
+          Process.clock_gettime(Process::CLOCK_MONOTONIC_RAW_APPROX).should be_an_instance_of(Float)
+        end
+
+        it "CLOCK_UPTIME_RAW and CLOCK_UPTIME_RAW_APPROX" do
+          Process.clock_gettime(Process::CLOCK_UPTIME_RAW).should be_an_instance_of(Float)
+          Process.clock_gettime(Process::CLOCK_UPTIME_RAW_APPROX).should be_an_instance_of(Float)
+        end
+      end
+    end
+
+    platform_is :freebsd do
+      it "CLOCK_VIRTUAL" do
+        Process.clock_gettime(Process::CLOCK_VIRTUAL).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_PROF" do
+        Process.clock_gettime(Process::CLOCK_PROF).should be_an_instance_of(Float)
+      end
+    end
+
+    platform_is :freebsd, :openbsd do
+      it "CLOCK_UPTIME" do
+        Process.clock_gettime(Process::CLOCK_UPTIME).should be_an_instance_of(Float)
+      end
+    end
+
+    platform_is :freebsd do
+      it "CLOCK_REALTIME_FAST and CLOCK_REALTIME_PRECISE" do
+        Process.clock_gettime(Process::CLOCK_REALTIME_FAST).should be_an_instance_of(Float)
+        Process.clock_gettime(Process::CLOCK_REALTIME_PRECISE).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_MONOTONIC_FAST and CLOCK_MONOTONIC_PRECISE" do
+        Process.clock_gettime(Process::CLOCK_MONOTONIC_FAST).should be_an_instance_of(Float)
+        Process.clock_gettime(Process::CLOCK_MONOTONIC_PRECISE).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_UPTIME_FAST and CLOCK_UPTIME_PRECISE" do
+        Process.clock_gettime(Process::CLOCK_UPTIME_FAST).should be_an_instance_of(Float)
+        Process.clock_gettime(Process::CLOCK_UPTIME_PRECISE).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_SECOND" do
+        Process.clock_gettime(Process::CLOCK_SECOND).should be_an_instance_of(Float)
+      end
+    end
+
+    guard -> { platform_is :linux and kernel_version_is '2.6.32' } do
+      it "CLOCK_REALTIME_COARSE" do
+        Process.clock_gettime(Process::CLOCK_REALTIME_COARSE).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_MONOTONIC_COARSE" do
+        Process.clock_gettime(Process::CLOCK_MONOTONIC_COARSE).should be_an_instance_of(Float)
+      end
+    end
+
+    guard -> { platform_is :linux and kernel_version_is '2.6.39' } do
+      it "CLOCK_BOOTTIME" do
+        skip "No Process::CLOCK_BOOTTIME" unless defined?(Process::CLOCK_BOOTTIME)
+        Process.clock_gettime(Process::CLOCK_BOOTTIME).should be_an_instance_of(Float)
+      end
+    end
+
+    guard -> { platform_is "x86_64-linux" and kernel_version_is '3.0' } do
+      it "CLOCK_REALTIME_ALARM" do
+        skip "No Process::CLOCK_REALTIME_ALARM" unless defined?(Process::CLOCK_REALTIME_ALARM)
+        Process.clock_gettime(Process::CLOCK_REALTIME_ALARM).should be_an_instance_of(Float)
+      end
+
+      it "CLOCK_BOOTTIME_ALARM" do
+        skip "No Process::CLOCK_BOOTTIME_ALARM" unless defined?(Process::CLOCK_BOOTTIME_ALARM)
+        Process.clock_gettime(Process::CLOCK_BOOTTIME_ALARM).should be_an_instance_of(Float)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/process/constants_spec.rb b/spec/ruby/core/process/constants_spec.rb
index 2fa93ad8bf..57cacadef2 100644
--- a/spec/ruby/core/process/constants_spec.rb
+++ b/spec/ruby/core/process/constants_spec.rb
@@ -1,63 +1,114 @@
+require_relative '../../spec_helper'
 
 describe "Process::Constants" do
   platform_is :darwin, :netbsd, :freebsd do
-    it "has the correct constant values on BSD-like systems" do
-      Process::WNOHANG.should == 1
-      Process::WUNTRACED.should == 2
-      Process::PRIO_PROCESS.should == 0
-      Process::PRIO_PGRP.should == 1
-      Process::PRIO_USER.should == 2
-      Process::RLIM_INFINITY.should == 9223372036854775807
-      Process::RLIMIT_CPU.should == 0
-      Process::RLIMIT_FSIZE.should == 1
-      Process::RLIMIT_DATA.should == 2
-      Process::RLIMIT_STACK.should == 3
-      Process::RLIMIT_CORE.should == 4
-      Process::RLIMIT_RSS.should == 5
-      Process::RLIMIT_MEMLOCK.should == 6
-      Process::RLIMIT_NPROC.should == 7
-      Process::RLIMIT_NOFILE.should == 8
+    it "are all present on BSD-like systems" do
+      %i[
+          WNOHANG
+          WUNTRACED
+          PRIO_PROCESS
+          PRIO_PGRP
+          PRIO_USER
+          RLIM_INFINITY
+          RLIMIT_CPU
+          RLIMIT_FSIZE
+          RLIMIT_DATA
+          RLIMIT_STACK
+          RLIMIT_CORE
+          RLIMIT_RSS
+          RLIMIT_MEMLOCK
+          RLIMIT_NPROC
+          RLIMIT_NOFILE
+      ].each do |const|
+        Process.const_defined?(const).should be_true
+        Process.const_get(const).should be_an_instance_of(Integer)
+      end
     end
   end
 
   platform_is :darwin do
-    it "has the correct constant values on Darwin" do
-      Process::RLIM_SAVED_MAX.should == 9223372036854775807
-      Process::RLIM_SAVED_CUR.should == 9223372036854775807
-      Process::RLIMIT_AS.should == 5
+    it "are all present on Darwin" do
+      %i[
+        RLIM_SAVED_MAX
+        RLIM_SAVED_CUR
+        RLIMIT_AS
+      ].each do |const|
+        Process.const_defined?(const).should be_true
+        Process.const_get(const).should be_an_instance_of(Integer)
+      end
     end
   end
 
   platform_is :linux do
-    it "has the correct constant values on Linux" do
-      Process::WNOHANG.should == 1
-      Process::WUNTRACED.should == 2
-      Process::PRIO_PROCESS.should == 0
-      Process::PRIO_PGRP.should == 1
-      Process::PRIO_USER.should == 2
-      Process::RLIMIT_CPU.should == 0
-      Process::RLIMIT_FSIZE.should == 1
-      Process::RLIMIT_DATA.should == 2
-      Process::RLIMIT_STACK.should == 3
-      Process::RLIMIT_CORE.should == 4
-      Process::RLIMIT_RSS.should == 5
-      Process::RLIMIT_NPROC.should == 6
-      Process::RLIMIT_NOFILE.should == 7
-      Process::RLIMIT_MEMLOCK.should == 8
-      Process::RLIMIT_AS.should == 9
-
-      # These values appear to change according to the platform.
-      values = [4294967295, 9223372036854775807, 18446744073709551615]
-      values.include?(Process::RLIM_INFINITY).should be_true
-      values.include?(Process::RLIM_SAVED_MAX).should be_true
-      values.include?(Process::RLIM_SAVED_CUR).should be_true
+    it "are all present on Linux" do
+      %i[
+        WNOHANG
+        WUNTRACED
+        PRIO_PROCESS
+        PRIO_PGRP
+        PRIO_USER
+        RLIMIT_CPU
+        RLIMIT_FSIZE
+        RLIMIT_DATA
+        RLIMIT_STACK
+        RLIMIT_CORE
+        RLIMIT_RSS
+        RLIMIT_NPROC
+        RLIMIT_NOFILE
+        RLIMIT_MEMLOCK
+        RLIMIT_AS
+        RLIM_INFINITY
+        RLIM_SAVED_MAX
+        RLIM_SAVED_CUR
+      ].each do |const|
+        Process.const_defined?(const).should be_true
+        Process.const_get(const).should be_an_instance_of(Integer)
+      end
     end
   end
 
   platform_is :netbsd, :freebsd do
-    it "Process::RLIMIT_SBSIZE" do
-      Process::RLIMIT_SBSIZE.should == 9 # FIXME: what's it equal?
-      Process::RLIMIT_AS.should == 10
+    it "are all present on NetBSD and FreeBSD" do
+      %i[
+        RLIMIT_SBSIZE
+        RLIMIT_AS
+      ].each do |const|
+        Process.const_defined?(const).should be_true
+        Process.const_get(const).should be_an_instance_of(Integer)
+      end
+    end
+  end
+
+  platform_is :freebsd do
+    it "are all present on FreeBSD" do
+      %i[
+        RLIMIT_NPTS
+      ].each do |const|
+        Process.const_defined?(const).should be_true
+        Process.const_get(const).should be_an_instance_of(Integer)
+      end
+    end
+  end
+
+  platform_is :windows do
+    it "does not define RLIMIT constants" do
+      %i[
+          RLIMIT_CPU
+          RLIMIT_FSIZE
+          RLIMIT_DATA
+          RLIMIT_STACK
+          RLIMIT_CORE
+          RLIMIT_RSS
+          RLIMIT_NPROC
+          RLIMIT_NOFILE
+          RLIMIT_MEMLOCK
+          RLIMIT_AS
+          RLIM_INFINITY
+          RLIM_SAVED_MAX
+          RLIM_SAVED_CUR
+      ].each do |const|
+        Process.const_defined?(const).should be_false
+      end
     end
   end
 end
diff --git a/spec/ruby/core/process/daemon_spec.rb b/spec/ruby/core/process/daemon_spec.rb
index 70ffd1b320..20b0d743b9 100644
--- a/spec/ruby/core/process/daemon_spec.rb
+++ b/spec/ruby/core/process/daemon_spec.rb
@@ -2,6 +2,9 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/common'
 
 platform_is_not :windows do
+  # macOS 15 is not working this examples
+  return if /darwin/ =~ RUBY_PLATFORM && /15/ =~ `sw_vers -productVersion`
+
   describe :process_daemon_keep_stdio_open_false, shared: true do
     it "redirects stdout to /dev/null" do
       @daemon.invoke("keep_stdio_open_false_stdout", @object).should == ""
diff --git a/spec/ruby/core/process/detach_spec.rb b/spec/ruby/core/process/detach_spec.rb
index 1c27ed9c2c..f13bda1f5d 100644
--- a/spec/ruby/core/process/detach_spec.rb
+++ b/spec/ruby/core/process/detach_spec.rb
@@ -42,5 +42,40 @@ describe "Process.detach" do
 
       thr.pid.should == pid
     end
+
+    it "tolerates not existing child process pid" do
+      # Use a value that is close to the INT_MAX (pid usually is signed int).
+      # It should (at least) be greater than allowed pid limit value that depends on OS.
+      pid_not_existing = 2.pow(30)
+
+      # Check that there is no a child process with this hardcoded pid.
+      # Command `kill 0 pid`:
+      # - returns "1" if a process exists and
+      # - raises Errno::ESRCH otherwise
+      -> {  Process.kill(0, pid_not_existing) }.should raise_error(Errno::ESRCH)
+
+      thr = Process.detach(pid_not_existing)
+      thr.join
+
+      thr.should be_kind_of(Thread)
+    end
+
+    it "calls #to_int to implicitly convert non-Integer pid to Integer" do
+      pid = MockObject.new('mock-enumerable')
+      pid.should_receive(:to_int).and_return(100500)
+
+      Process.detach(pid).join
+    end
+
+    it "raises TypeError when pid argument does not have #to_int method" do
+      -> { Process.detach(Object.new) }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "raises TypeError when #to_int returns non-Integer value" do
+      pid = MockObject.new('mock-enumerable')
+      pid.should_receive(:to_int).and_return(:symbol)
+
+      -> { Process.detach(pid) }.should raise_error(TypeError, "can't convert MockObject to Integer (MockObject#to_int gives Symbol)")
+    end
   end
 end
diff --git a/spec/ruby/core/process/egid_spec.rb b/spec/ruby/core/process/egid_spec.rb
index 24dda43804..a67b623d5c 100644
--- a/spec/ruby/core/process/egid_spec.rb
+++ b/spec/ruby/core/process/egid_spec.rb
@@ -15,5 +15,44 @@ describe "Process.egid" do
 end
 
 describe "Process.egid=" do
-  it "needs to be reviewed for spec completeness"
+
+  platform_is_not :windows do
+    it "raises TypeError if not passed an Integer or String" do
+      -> { Process.egid = Object.new }.should raise_error(TypeError)
+    end
+
+    it "sets the effective group id to its own gid if given the username corresponding to its own gid" do
+      raise unless Process.gid == Process.egid
+
+      require "etc"
+      group = Etc.getgrgid(Process.gid).name
+
+      Process.egid = group
+      Process.egid.should == Process.gid
+    end
+
+    as_user do
+      it "raises Errno::ERPERM if run by a non superuser trying to set the root group id" do
+        -> { Process.egid = 0 }.should raise_error(Errno::EPERM)
+      end
+
+      platform_is :linux do
+        it "raises Errno::ERPERM if run by a non superuser trying to set the group id from group name" do
+          -> { Process.egid = "root" }.should raise_error(Errno::EPERM)
+        end
+      end
+    end
+
+    as_superuser do
+      context "when ran by a superuser" do
+        it "sets the effective group id for the current process if run by a superuser" do
+          code = <<-RUBY
+            Process.egid = 1
+            puts Process.egid
+          RUBY
+          ruby_exe(code).should == "1\n"
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/process/euid_spec.rb b/spec/ruby/core/process/euid_spec.rb
index 7bbacfadfd..c1ec4171d0 100644
--- a/spec/ruby/core/process/euid_spec.rb
+++ b/spec/ruby/core/process/euid_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Process.euid" do
   it "returns the effective user ID for this process" do
-    Process.euid.should be_kind_of(Fixnum)
+    Process.euid.should be_kind_of(Integer)
   end
 
   it "also goes by Process::UID.eid" do
@@ -21,9 +21,19 @@ describe "Process.euid=" do
       -> { Process.euid = Object.new }.should raise_error(TypeError)
     end
 
+    it "sets the effective user id to its own uid if given the username corresponding to its own uid" do
+      raise unless Process.uid == Process.euid
+
+      require "etc"
+      user = Etc.getpwuid(Process.uid).name
+
+      Process.euid = user
+      Process.euid.should == Process.uid
+    end
+
     as_user do
       it "raises Errno::ERPERM if run by a non superuser trying to set the superuser id" do
-        -> { (Process.euid = 0)}.should raise_error(Errno::EPERM)
+        -> { Process.euid = 0 }.should raise_error(Errno::EPERM)
       end
 
       it "raises Errno::ERPERM if run by a non superuser trying to set the superuser id from username" do
diff --git a/spec/ruby/core/process/exec_spec.rb b/spec/ruby/core/process/exec_spec.rb
index 848990c6dc..0f371b39c8 100644
--- a/spec/ruby/core/process/exec_spec.rb
+++ b/spec/ruby/core/process/exec_spec.rb
@@ -29,29 +29,21 @@ describe "Process.exec" do
     end
   end
 
-  platform_is_not :openbsd do
-    it "raises Errno::EACCES when passed a directory" do
-      -> { Process.exec File.dirname(__FILE__) }.should raise_error(Errno::EACCES)
-    end
-  end
-
-  platform_is :openbsd do
-    it "raises Errno::EISDIR when passed a directory" do
-      -> { Process.exec File.dirname(__FILE__) }.should raise_error(Errno::EISDIR)
-    end
+  it "raises Errno::EACCES when passed a directory" do
+    -> { Process.exec __dir__ }.should raise_error(Errno::EACCES)
   end
 
   it "runs the specified command, replacing current process" do
-    ruby_exe('Process.exec "echo hello"; puts "fail"', escape: true).should == "hello\n"
+    ruby_exe('Process.exec "echo hello"; puts "fail"').should == "hello\n"
   end
 
   it "sets the current directory when given the :chdir option" do
     tmpdir = tmp("")[0..-2]
     platform_is_not :windows do
-      ruby_exe("Process.exec(\"pwd\", chdir: #{tmpdir.inspect})", escape: true).should == "#{tmpdir}\n"
+      ruby_exe("Process.exec(\"pwd\", chdir: #{tmpdir.inspect})").should == "#{tmpdir}\n"
     end
     platform_is :windows do
-      ruby_exe("Process.exec(\"cd\", chdir: #{tmpdir.inspect})", escape: true).tr('\\', '/').should == "#{tmpdir}\n"
+      ruby_exe("Process.exec(\"cd\", chdir: #{tmpdir.inspect})").tr('\\', '/').should == "#{tmpdir}\n"
     end
   end
 
@@ -81,13 +73,13 @@ describe "Process.exec" do
     platform_is_not :windows do
       it "subjects the specified command to shell expansion" do
         result = Dir.chdir(@dir) do
-          ruby_exe('Process.exec "echo *"', escape: true)
+          ruby_exe('Process.exec "echo *"')
         end
         result.chomp.should == @name
       end
 
       it "creates an argument array with shell parsing semantics for whitespace" do
-        ruby_exe('Process.exec "echo a b  c   d"', escape: true).should == "a b c d\n"
+        ruby_exe('Process.exec "echo a b  c   d"').should == "a b c d\n"
       end
     end
 
@@ -95,13 +87,13 @@ describe "Process.exec" do
       # There is no shell expansion on Windows
       it "does not subject the specified command to shell expansion on Windows" do
         result = Dir.chdir(@dir) do
-          ruby_exe('Process.exec "echo *"', escape: true)
+          ruby_exe('Process.exec "echo *"')
         end
         result.should == "*\n"
       end
 
       it "does not create an argument array with shell parsing semantics for whitespace on Windows" do
-        ruby_exe('Process.exec "echo a b  c   d"', escape: true).should == "a b  c   d\n"
+        ruby_exe('Process.exec "echo a b  c   d"').should == "a b  c   d\n"
       end
     end
 
@@ -113,7 +105,7 @@ describe "Process.exec" do
       platform_is :windows do
         cmd = '"cmd.exe", "/C", "echo", "*"'
       end
-      ruby_exe("Process.exec #{cmd}", escape: true).should == "*\n"
+      ruby_exe("Process.exec #{cmd}").should == "*\n"
     end
   end
 
@@ -132,29 +124,29 @@ describe "Process.exec" do
     end
 
     it "sets environment variables in the child environment" do
-      ruby_exe('Process.exec({"FOO" => "BAR"}, "echo ' + var + '")', escape: true).should == "BAR\n"
+      ruby_exe('Process.exec({"FOO" => "BAR"}, "echo ' + var + '")').should == "BAR\n"
     end
 
     it "unsets environment variables whose value is nil" do
       platform_is_not :windows do
-        ruby_exe('Process.exec({"FOO" => nil}, "echo ' + var + '")', escape: true).should == "\n"
+        ruby_exe('Process.exec({"FOO" => nil}, "echo ' + var + '")').should == "\n"
       end
       platform_is :windows do
         # On Windows, echo-ing a non-existent env var is treated as echo-ing any other string of text
-        ruby_exe('Process.exec({"FOO" => nil}, "echo ' + var + '")', escape: true).should == var + "\n"
+        ruby_exe('Process.exec({"FOO" => nil}, "echo ' + var + '")').should == var + "\n"
       end
     end
 
     it "coerces environment argument using to_hash" do
-      ruby_exe('o = Object.new; def o.to_hash; {"FOO" => "BAR"}; end; Process.exec(o, "echo ' + var + '")', escape: true).should == "BAR\n"
+      ruby_exe('o = Object.new; def o.to_hash; {"FOO" => "BAR"}; end; Process.exec(o, "echo ' + var + '")').should == "BAR\n"
     end
 
     it "unsets other environment variables when given a true :unsetenv_others option" do
       platform_is_not :windows do
-        ruby_exe('Process.exec("echo ' + var + '", unsetenv_others: true)', escape: true).should == "\n"
+        ruby_exe('Process.exec("echo ' + var + '", unsetenv_others: true)').should == "\n"
       end
       platform_is :windows do
-        ruby_exe('Process.exec("' + ENV['COMSPEC'].gsub('\\', '\\\\\\') + ' /C echo ' + var + '", unsetenv_others: true)', escape: true).should == var + "\n"
+        ruby_exe('Process.exec("' + ENV['COMSPEC'].gsub('\\', '\\\\\\') + ' /C echo ' + var + '", unsetenv_others: true)').should == var + "\n"
       end
     end
   end
@@ -162,19 +154,19 @@ describe "Process.exec" do
   describe "with a command array" do
     it "uses the first element as the command name and the second as the argv[0] value" do
       platform_is_not :windows do
-        ruby_exe('Process.exec(["/bin/sh", "argv_zero"], "-c", "echo $0")', escape: true).should == "argv_zero\n"
+        ruby_exe('Process.exec(["/bin/sh", "argv_zero"], "-c", "echo $0")').should == "argv_zero\n"
       end
       platform_is :windows do
-        ruby_exe('Process.exec(["cmd.exe", "/C"], "/C", "echo", "argv_zero")', escape: true).should == "argv_zero\n"
+        ruby_exe('Process.exec(["cmd.exe", "/C"], "/C", "echo", "argv_zero")').should == "argv_zero\n"
       end
     end
 
     it "coerces the argument using to_ary" do
       platform_is_not :windows do
-        ruby_exe('o = Object.new; def o.to_ary; ["/bin/sh", "argv_zero"]; end; Process.exec(o, "-c", "echo $0")', escape: true).should == "argv_zero\n"
+        ruby_exe('o = Object.new; def o.to_ary; ["/bin/sh", "argv_zero"]; end; Process.exec(o, "-c", "echo $0")').should == "argv_zero\n"
       end
       platform_is :windows do
-        ruby_exe('o = Object.new; def o.to_ary; ["cmd.exe", "/C"]; end; Process.exec(o, "/C", "echo", "argv_zero")', escape: true).should == "argv_zero\n"
+        ruby_exe('o = Object.new; def o.to_ary; ["cmd.exe", "/C"]; end; Process.exec(o, "/C", "echo", "argv_zero")').should == "argv_zero\n"
       end
     end
 
@@ -200,18 +192,49 @@ describe "Process.exec" do
         it "maps the key to a file descriptor in the child that inherits the file descriptor from the parent specified by the value" do
           map_fd_fixture = fixture __FILE__, "map_fd.rb"
           cmd = <<-EOC
-            f = File.open("#{@name}", "w+")
-            child_fd = f.fileno + 1
-            File.open("#{@child_fd_file}", "w") { |io| io.print child_fd }
-            Process.exec "#{ruby_cmd(map_fd_fixture)} \#{child_fd}", { child_fd => f }
+            f = File.open(#{@name.inspect}, "w+")
+            File.open(#{__FILE__.inspect}, "r") do |io|
+              child_fd = io.fileno
+              File.open(#{@child_fd_file.inspect}, "w") { |io| io.print child_fd }
+              Process.exec "#{ruby_cmd(map_fd_fixture)} \#{child_fd}", { child_fd => f }
+            end
             EOC
 
-          ruby_exe(cmd, escape: true)
+          ruby_exe(cmd)
           child_fd = IO.read(@child_fd_file).to_i
           child_fd.to_i.should > STDERR.fileno
 
           File.read(@name).should == "writing to fd: #{child_fd}"
         end
+
+        it "lets the process after exec have specified file descriptor despite close_on_exec" do
+          map_fd_fixture = fixture __FILE__, "map_fd.rb"
+          cmd = <<-EOC
+            f = File.open(#{@name.inspect}, 'w+')
+            puts(f.fileno, f.close_on_exec?)
+            STDOUT.flush
+            Process.exec("#{ruby_cmd(map_fd_fixture)} \#{f.fileno}", f.fileno => f.fileno)
+            EOC
+
+          output = ruby_exe(cmd)
+          child_fd, close_on_exec = output.split
+
+          child_fd.to_i.should > STDERR.fileno
+          close_on_exec.should == 'true'
+          File.read(@name).should == "writing to fd: #{child_fd}"
+        end
+
+        it "sets close_on_exec to false on specified fd even when it fails" do
+          cmd = <<-EOC
+            f = File.open(#{__FILE__.inspect}, 'r')
+            puts(f.close_on_exec?)
+            Process.exec('/', f.fileno => f.fileno) rescue nil
+            puts(f.close_on_exec?)
+            EOC
+
+          output = ruby_exe(cmd)
+          output.split.should == ['true', 'false']
+        end
       end
     end
   end
diff --git a/spec/ruby/core/process/exit_spec.rb b/spec/ruby/core/process/exit_spec.rb
index 70d79d789d..4f7dc94407 100644
--- a/spec/ruby/core/process/exit_spec.rb
+++ b/spec/ruby/core/process/exit_spec.rb
@@ -6,5 +6,5 @@ describe "Process.exit" do
 end
 
 describe "Process.exit!" do
-  it_behaves_like :process_exit!, :exit!, Process
+  it_behaves_like :process_exit!, :exit!, "Process"
 end
diff --git a/spec/ruby/core/process/fixtures/argv0.rb b/spec/ruby/core/process/fixtures/argv0.rb
new file mode 100644
index 0000000000..847a3e903e
--- /dev/null
+++ b/spec/ruby/core/process/fixtures/argv0.rb
@@ -0,0 +1,6 @@
+puts Process.argv0
+puts __FILE__
+
+if Process.argv0 == __FILE__
+  print "OK"
+end
diff --git a/spec/ruby/core/process/fixtures/clocks.rb b/spec/ruby/core/process/fixtures/clocks.rb
index 92540ddd45..5757e280be 100644
--- a/spec/ruby/core/process/fixtures/clocks.rb
+++ b/spec/ruby/core/process/fixtures/clocks.rb
@@ -2,7 +2,7 @@ module ProcessSpecs
   def self.clock_constants
     clocks = []
 
-    platform_is_not :windows, :solaris do
+    platform_is_not :windows do
       clocks += Process.constants.select { |c| c.to_s.start_with?('CLOCK_') }
 
       # These require CAP_WAKE_ALARM and are not documented in
@@ -15,46 +15,4 @@ module ProcessSpecs
       [c, Process.const_get(c)]
     }
   end
-
-  def self.clock_constants_for_resolution_checks
-    clocks = clock_constants
-
-    # These clocks in practice on Linux do not seem to match their reported resolution.
-    platform_is :linux do
-      clocks = clocks.reject { |clock, value|
-        [:CLOCK_REALTIME_COARSE, :CLOCK_MONOTONIC_COARSE].include?(clock)
-      }
-    end
-
-    # These clocks in practice on macOS seem to be less precise than advertised by clock_getres
-    platform_is :darwin do
-      clocks = clocks.reject { |clock, value|
-        [:CLOCK_UPTIME_RAW_APPROX, :CLOCK_MONOTONIC_RAW_APPROX].include?(clock)
-      }
-    end
-
-    # These clocks in practice on ARM on Linux do not seem to match their reported resolution.
-    platform_is :armv7, :aarch64 do
-      clocks = clocks.reject { |clock, value|
-        [:CLOCK_PROCESS_CPUTIME_ID, :CLOCK_THREAD_CPUTIME_ID, :CLOCK_MONOTONIC_RAW].include?(clock)
-      }
-    end
-
-    # These clocks in practice on AIX seem to be more precise than their reported resolution.
-    platform_is :aix do
-      clocks = clocks.reject { |clock, value|
-        [:CLOCK_REALTIME, :CLOCK_MONOTONIC].include?(clock)
-      }
-    end
-
-    # On a Hyper-V Linux guest machine, these clocks in practice
-    # seem to be less precise than advertised by clock_getres
-    platform_is :linux do
-      clocks = clocks.reject { |clock, value|
-        clock == :CLOCK_MONOTONIC_RAW
-      }
-    end
-
-    clocks
-  end
 end
diff --git a/spec/ruby/core/process/fixtures/common.rb b/spec/ruby/core/process/fixtures/common.rb
index bdbf1e654b..f49513d262 100644
--- a/spec/ruby/core/process/fixtures/common.rb
+++ b/spec/ruby/core/process/fixtures/common.rb
@@ -3,11 +3,15 @@ module ProcessSpecs
     if defined?(MSpecScript::SYSTEM_RUBY)
       context.send(:before, :all) do
         @ruby = ::RUBY_EXE
-        Object.const_set(:RUBY_EXE, MSpecScript::SYSTEM_RUBY)
+        suppress_warning {
+          Object.const_set(:RUBY_EXE, MSpecScript::SYSTEM_RUBY)
+        }
       end
 
       context.send(:after, :all) do
-        Object.const_set(:RUBY_EXE, @ruby)
+        suppress_warning {
+          Object.const_set(:RUBY_EXE, @ruby)
+        }
       end
     end
   end
diff --git a/spec/ruby/core/process/fixtures/kill.rb b/spec/ruby/core/process/fixtures/kill.rb
index 0b88f8ee1f..b922a043f1 100644
--- a/spec/ruby/core/process/fixtures/kill.rb
+++ b/spec/ruby/core/process/fixtures/kill.rb
@@ -1,5 +1,3 @@
-require 'thread'
-
 pid_file = ARGV.shift
 scenario = ARGV.shift
 
diff --git a/spec/ruby/core/process/getpriority_spec.rb b/spec/ruby/core/process/getpriority_spec.rb
index 4b66e18679..a35e5956a5 100644
--- a/spec/ruby/core/process/getpriority_spec.rb
+++ b/spec/ruby/core/process/getpriority_spec.rb
@@ -5,19 +5,19 @@ describe "Process.getpriority" do
 
     it "coerces arguments to Integers" do
       ret = Process.getpriority mock_int(Process::PRIO_PROCESS), mock_int(0)
-      ret.should be_kind_of(Fixnum)
+      ret.should be_kind_of(Integer)
     end
 
     it "gets the scheduling priority for a specified process" do
-      Process.getpriority(Process::PRIO_PROCESS, 0).should be_kind_of(Fixnum)
+      Process.getpriority(Process::PRIO_PROCESS, 0).should be_kind_of(Integer)
     end
 
     it "gets the scheduling priority for a specified process group" do
-      Process.getpriority(Process::PRIO_PGRP, 0).should be_kind_of(Fixnum)
+      Process.getpriority(Process::PRIO_PGRP, 0).should be_kind_of(Integer)
     end
 
     it "gets the scheduling priority for a specified user" do
-      Process.getpriority(Process::PRIO_USER, 0).should be_kind_of(Fixnum)
+      Process.getpriority(Process::PRIO_USER, 0).should be_kind_of(Integer)
     end
   end
 end
diff --git a/spec/ruby/core/process/getrlimit_spec.rb b/spec/ruby/core/process/getrlimit_spec.rb
index f77a61a475..883b8fac48 100644
--- a/spec/ruby/core/process/getrlimit_spec.rb
+++ b/spec/ruby/core/process/getrlimit_spec.rb
@@ -11,8 +11,8 @@ platform_is :aix do
   Process.getrlimit(:DATA)
 end
 
-platform_is_not :windows do
-  describe "Process.getrlimit" do
+describe "Process.getrlimit" do
+  platform_is_not :windows do
     it "returns a two-element Array of Integers" do
       result = Process.getrlimit Process::RLIMIT_CORE
       result.size.should == 2
@@ -88,4 +88,13 @@ platform_is_not :windows do
       end
     end
   end
+
+  platform_is :windows do
+    it "is not implemented" do
+      Process.respond_to?(:getrlimit).should be_false
+      -> do
+        Process.getrlimit(nil)
+      end.should raise_error NotImplementedError
+    end
+  end
 end
diff --git a/spec/ruby/core/process/gid_spec.rb b/spec/ruby/core/process/gid_spec.rb
index 07221da420..ca935ed520 100644
--- a/spec/ruby/core/process/gid_spec.rb
+++ b/spec/ruby/core/process/gid_spec.rb
@@ -3,8 +3,8 @@ require_relative '../../spec_helper'
 describe "Process.gid" do
   platform_is_not :windows do
     it "returns the correct gid for the user executing this process" do
-       current_gid_according_to_unix = `id -gr`.to_i
-       Process.gid.should == current_gid_according_to_unix
+      current_gid_according_to_unix = `id -gr`.to_i
+      Process.gid.should == current_gid_according_to_unix
     end
   end
 
diff --git a/spec/ruby/core/process/groups_spec.rb b/spec/ruby/core/process/groups_spec.rb
index cbbe4fed25..33e0f9d7b3 100644
--- a/spec/ruby/core/process/groups_spec.rb
+++ b/spec/ruby/core/process/groups_spec.rb
@@ -4,6 +4,10 @@ describe "Process.groups" do
   platform_is_not :windows do
     it "gets an Array of the gids of groups in the supplemental group access list" do
       groups = `id -G`.scan(/\d+/).map { |i| i.to_i }
+      # Include the standard `id` command output.  On macOS, GNU
+      # coreutils `id` is limited to NGROUPS_MAX groups, because of
+      # the backward compatibility of getgroups(2).
+      (groups |= `/usr/bin/id -G`.scan(/\d+/).map { |i| i.to_i }) rescue nil
       gid = Process.gid
 
       expected = (groups.sort - [gid]).uniq.sort
diff --git a/spec/ruby/core/process/kill_spec.rb b/spec/ruby/core/process/kill_spec.rb
index 4bd64a1fe8..af9c9e6deb 100644
--- a/spec/ruby/core/process/kill_spec.rb
+++ b/spec/ruby/core/process/kill_spec.rb
@@ -16,7 +16,7 @@ describe "Process.kill" do
     -> { Process.kill("term", @pid) }.should raise_error(ArgumentError)
   end
 
-  it "raises an ArgumentError if signal is not a Fixnum or String" do
+  it "raises an ArgumentError if signal is not an Integer or String" do
     signal = mock("process kill signal")
     signal.should_not_receive(:to_int)
 
diff --git a/spec/ruby/core/process/last_status_spec.rb b/spec/ruby/core/process/last_status_spec.rb
index 3898dd6b95..2372f2aae3 100644
--- a/spec/ruby/core/process/last_status_spec.rb
+++ b/spec/ruby/core/process/last_status_spec.rb
@@ -1,20 +1,18 @@
 require_relative '../../spec_helper'
 
-ruby_version_is '2.5' do
-  describe 'Process#last_status' do
-    it 'returns the status of the last executed child process in the current thread' do
-      pid = Process.wait Process.spawn("exit 0")
-      Process.last_status.pid.should == pid
-    end
+describe 'Process#last_status' do
+  it 'returns the status of the last executed child process in the current thread' do
+    pid = Process.wait Process.spawn("exit 0")
+    Process.last_status.pid.should == pid
+  end
 
-    it 'returns nil if no child process has been ever executed in the current thread' do
-      Thread.new do
-        Process.last_status.should == nil
-      end.join
-    end
+  it 'returns nil if no child process has been ever executed in the current thread' do
+    Thread.new do
+      Process.last_status.should == nil
+    end.join
+  end
 
-    it 'raises an ArgumentError if any arguments are provided' do
-      -> { Process.last_status(1) }.should raise_error(ArgumentError)
-    end
+  it 'raises an ArgumentError if any arguments are provided' do
+    -> { Process.last_status(1) }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/core/process/maxgroups_spec.rb b/spec/ruby/core/process/maxgroups_spec.rb
index 362f788ab2..2549a7a971 100644
--- a/spec/ruby/core/process/maxgroups_spec.rb
+++ b/spec/ruby/core/process/maxgroups_spec.rb
@@ -3,7 +3,7 @@ require_relative '../../spec_helper'
 platform_is_not :windows do
   describe "Process.maxgroups" do
     it "returns the maximum number of gids allowed in the supplemental group access list" do
-      Process.maxgroups.should be_kind_of(Fixnum)
+      Process.maxgroups.should be_kind_of(Integer)
     end
 
     it "sets the maximum number of gids allowed in the supplemental group access list" do
diff --git a/spec/ruby/core/process/pid_spec.rb b/spec/ruby/core/process/pid_spec.rb
index c5947ab50d..2d008bc4b7 100644
--- a/spec/ruby/core/process/pid_spec.rb
+++ b/spec/ruby/core/process/pid_spec.rb
@@ -3,7 +3,7 @@ require_relative '../../spec_helper'
 describe "Process.pid" do
   it "returns the process id of this process" do
     pid = Process.pid
-    pid.should be_kind_of(Fixnum)
+    pid.should be_kind_of(Integer)
     Process.pid.should == pid
   end
 end
diff --git a/spec/ruby/core/process/setrlimit_spec.rb b/spec/ruby/core/process/setrlimit_spec.rb
index 8bc035a4f1..ba8d1e04ca 100644
--- a/spec/ruby/core/process/setrlimit_spec.rb
+++ b/spec/ruby/core/process/setrlimit_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
-platform_is_not :windows do
-  describe "Process.setrlimit" do
+describe "Process.setrlimit" do
+  platform_is_not :windows do
     context "when passed an Object" do
       before do
         @resource = Process::RLIMIT_CORE
@@ -73,20 +73,18 @@ platform_is_not :windows do
         Process.setrlimit(:STACK, *Process.getrlimit(Process::RLIMIT_STACK)).should be_nil
       end
 
-      platform_is_not :solaris, :aix do
+      platform_is_not :aix do
         it "coerces :MEMLOCK into RLIMIT_MEMLOCK" do
           Process.setrlimit(:MEMLOCK, *Process.getrlimit(Process::RLIMIT_MEMLOCK)).should be_nil
         end
       end
 
-      platform_is_not :solaris do
-        it "coerces :NPROC into RLIMIT_NPROC" do
-          Process.setrlimit(:NPROC, *Process.getrlimit(Process::RLIMIT_NPROC)).should be_nil
-        end
+      it "coerces :NPROC into RLIMIT_NPROC" do
+        Process.setrlimit(:NPROC, *Process.getrlimit(Process::RLIMIT_NPROC)).should be_nil
+      end
 
-        it "coerces :RSS into RLIMIT_RSS" do
-          Process.setrlimit(:RSS, *Process.getrlimit(Process::RLIMIT_RSS)).should be_nil
-        end
+      it "coerces :RSS into RLIMIT_RSS" do
+        Process.setrlimit(:RSS, *Process.getrlimit(Process::RLIMIT_RSS)).should be_nil
       end
 
       platform_is :netbsd, :freebsd do
@@ -155,20 +153,18 @@ platform_is_not :windows do
         Process.setrlimit("STACK", *Process.getrlimit(Process::RLIMIT_STACK)).should be_nil
       end
 
-      platform_is_not :solaris, :aix do
+      platform_is_not :aix do
         it "coerces 'MEMLOCK' into RLIMIT_MEMLOCK" do
           Process.setrlimit("MEMLOCK", *Process.getrlimit(Process::RLIMIT_MEMLOCK)).should be_nil
         end
       end
 
-      platform_is_not :solaris do
-        it "coerces 'NPROC' into RLIMIT_NPROC" do
-          Process.setrlimit("NPROC", *Process.getrlimit(Process::RLIMIT_NPROC)).should be_nil
-        end
+      it "coerces 'NPROC' into RLIMIT_NPROC" do
+        Process.setrlimit("NPROC", *Process.getrlimit(Process::RLIMIT_NPROC)).should be_nil
+      end
 
-        it "coerces 'RSS' into RLIMIT_RSS" do
-          Process.setrlimit("RSS", *Process.getrlimit(Process::RLIMIT_RSS)).should be_nil
-        end
+      it "coerces 'RSS' into RLIMIT_RSS" do
+        Process.setrlimit("RSS", *Process.getrlimit(Process::RLIMIT_RSS)).should be_nil
       end
 
       platform_is :netbsd, :freebsd do
@@ -229,4 +225,13 @@ platform_is_not :windows do
       end
     end
   end
+
+  platform_is :windows do
+    it "is not implemented" do
+      Process.respond_to?(:setrlimit).should be_false
+      -> do
+        Process.setrlimit(nil, nil)
+      end.should raise_error NotImplementedError
+    end
+  end
 end
diff --git a/spec/ruby/core/process/spawn_spec.rb b/spec/ruby/core/process/spawn_spec.rb
index 46faced3e4..283a7f033d 100644
--- a/spec/ruby/core/process/spawn_spec.rb
+++ b/spec/ruby/core/process/spawn_spec.rb
@@ -48,10 +48,10 @@ describe "Process.spawn" do
     -> { Process.wait Process.spawn("echo spawn") }.should output_to_fd("spawn\n")
   end
 
-  it "returns the process ID of the new process as a Fixnum" do
+  it "returns the process ID of the new process as an Integer" do
     pid = Process.spawn(*ruby_exe, "-e", "exit")
     Process.wait pid
-    pid.should be_an_instance_of(Fixnum)
+    pid.should be_an_instance_of(Integer)
   end
 
   it "returns immediately" do
@@ -207,13 +207,29 @@ describe "Process.spawn" do
 
   it "unsets environment variables whose value is nil" do
     ENV["FOO"] = "BAR"
-    Process.wait Process.spawn({"FOO" => nil}, "echo #{@var}>#{@name}")
-    expected = "\n"
-    platform_is :windows do
-      # Windows does not expand the variable if it is unset
-      expected = "#{@var}\n"
+    -> do
+      Process.wait Process.spawn({"FOO" => nil}, ruby_cmd("p ENV['FOO']"))
+    end.should output_to_fd("nil\n")
+  end
+
+  platform_is_not :windows do
+    it "uses the passed env['PATH'] to search the executable" do
+      dir = tmp("spawn_path_dir")
+      mkdir_p dir
+      begin
+        exe = 'process-spawn-executable-in-path'
+        path = "#{dir}/#{exe}"
+        File.write(path, "#!/bin/sh\necho $1")
+        File.chmod(0755, path)
+
+        env = { "PATH" => "#{dir}#{File::PATH_SEPARATOR}#{ENV['PATH']}" }
+        Process.wait Process.spawn(env, exe, 'OK', out: @name)
+        $?.should.success?
+        File.read(@name).should == "OK\n"
+      ensure
+        rm_r dir
+      end
     end
-    File.read(@name).should == expected
   end
 
   it "calls #to_hash to convert the environment" do
@@ -331,9 +347,19 @@ describe "Process.spawn" do
 
     it "joins the specified process group if pgroup: pgid" do
       pgid = Process.getpgid(Process.pid)
-      -> do
-        Process.wait Process.spawn(ruby_cmd("print Process.getpgid(Process.pid)"), pgroup: pgid)
-      end.should output_to_fd(pgid.to_s)
+      # The process group is not available on all platforms.
+      # See "man proc" - /proc/[pid]/stat - (5) pgrp
+      # In Travis aarch64 environment, the value is 0.
+      #
+      # $ cat /proc/[pid]/stat
+      # 19179 (ruby) S 19160 0 0 ...
+      unless pgid.zero?
+        -> do
+          Process.wait Process.spawn(ruby_cmd("print Process.getpgid(Process.pid)"), pgroup: pgid)
+        end.should output_to_fd(pgid.to_s)
+      else
+        skip "The process group is not available."
+      end
     end
 
     it "raises an ArgumentError if given a negative :pgroup option" do
@@ -409,7 +435,7 @@ describe "Process.spawn" do
 
       it "kills extra chdir processes" do
         pid = nil
-        Dir.chdir("/tmp") do
+        Dir.chdir("/") do
           pid = Process.spawn("sleep 10")
         end
 
@@ -451,7 +477,17 @@ describe "Process.spawn" do
 
   # redirection
 
-  it "redirects STDOUT to the given file descriptor if out: Fixnum" do
+  it 'redirects to the wrapped IO using wrapped_io.to_io if out: wrapped_io' do
+    File.open(@name, 'w') do |file|
+      -> do
+        wrapped_io = mock('wrapped IO')
+        wrapped_io.should_receive(:to_io).and_return(file)
+        Process.wait Process.spawn('echo Hello World', out: wrapped_io)
+      end.should output_to_fd("Hello World\n", file)
+    end
+  end
+
+  it "redirects STDOUT to the given file descriptor if out: Integer" do
     File.open(@name, 'w') do |file|
       -> do
         Process.wait Process.spawn("echo glark", out: file.fileno)
@@ -477,7 +513,7 @@ describe "Process.spawn" do
     File.read(@name).should == "glark\n"
   end
 
-  it "redirects STDERR to the given file descriptor if err: Fixnum" do
+  it "redirects STDERR to the given file descriptor if err: Integer" do
     File.open(@name, 'w') do |file|
       -> do
         Process.wait Process.spawn("echo glark>&2", err: file.fileno)
@@ -530,31 +566,47 @@ describe "Process.spawn" do
     File.read(@name).should == "glarkbang"
   end
 
-  # :close_others
+  platform_is_not :windows, :android do
+    it "closes STDERR in the child if :err => :close" do
+      File.open(@name, 'w') do |file|
+        -> do
+          code = "begin; STDOUT.puts 'out'; STDERR.puts 'hello'; rescue => e; puts 'rescued'; end"
+          Process.wait Process.spawn(ruby_cmd(code), :out => file, :err => :close)
+        end.should output_to_fd("out\nrescued\n", file)
+      end
+    end
+  end
 
   platform_is_not :windows do
-    context "defaults :close_others to" do
-      ruby_version_is ""..."2.6" do
-        it "true" do
-          IO.pipe do |r, w|
-            w.close_on_exec = false
-            code = "begin; IO.new(#{w.fileno}).close; rescue Errno::EBADF; puts 'not inherited'; end"
-            Process.wait Process.spawn(ruby_cmd(code), :out => @name)
-            File.read(@name).should == "not inherited\n"
-          end
-        end
+    it "redirects non-default file descriptor to itself" do
+      File.open(@name, 'w') do |file|
+        -> do
+          Process.wait Process.spawn(
+            ruby_cmd("f = IO.new(#{file.fileno}, 'w'); f.print(:bang); f.flush"), file.fileno => file.fileno)
+        end.should output_to_fd("bang", file)
       end
+    end
+  end
 
-      ruby_version_is "2.6" do
-        it "false" do
-          IO.pipe do |r, w|
-            w.close_on_exec = false
-            code = "io = IO.new(#{w.fileno}); io.puts('inherited'); io.close"
-            pid = Process.spawn(ruby_cmd(code))
-            w.close
-            Process.wait(pid)
-            r.read.should == "inherited\n"
-          end
+  it "redirects default file descriptor to itself" do
+    -> do
+      Process.wait Process.spawn(
+        ruby_cmd("f = IO.new(#{STDOUT.fileno}, 'w'); f.print(:bang); f.flush"), STDOUT.fileno => STDOUT.fileno)
+    end.should output_to_fd("bang", STDOUT)
+  end
+
+  # :close_others
+
+  platform_is_not :windows do
+    context "defaults :close_others to" do
+      it "false" do
+        IO.pipe do |r, w|
+          w.close_on_exec = false
+          code = "io = IO.new(#{w.fileno}); io.puts('inherited'); io.close"
+          pid = Process.spawn(ruby_cmd(code))
+          w.close
+          Process.wait(pid)
+          r.read.should == "inherited\n"
         end
       end
     end
@@ -662,7 +714,7 @@ describe "Process.spawn" do
   end
 
   it "raises an Errno::EACCES or Errno::EISDIR when passed a directory" do
-    -> { Process.spawn File.dirname(__FILE__) }.should raise_error(SystemCallError) { |e|
+    -> { Process.spawn __dir__ }.should raise_error(SystemCallError) { |e|
       [Errno::EACCES, Errno::EISDIR].should include(e.class)
     }
   end
@@ -689,13 +741,15 @@ describe "Process.spawn" do
       end
 
       it "maps the key to a file descriptor in the child that inherits the file descriptor from the parent specified by the value" do
-        child_fd = find_unused_fd
-        args = ruby_cmd(fixture(__FILE__, "map_fd.rb"), args: [child_fd.to_s])
-        pid = Process.spawn(*args, { child_fd => @io })
-        Process.waitpid pid
-        @io.rewind
-
-        @io.read.should == "writing to fd: #{child_fd}"
+        File.open(__FILE__, "r") do |f|
+          child_fd = f.fileno
+          args = ruby_cmd(fixture(__FILE__, "map_fd.rb"), args: [child_fd.to_s])
+          pid = Process.spawn(*args, { child_fd => @io })
+          Process.waitpid pid
+          @io.rewind
+
+          @io.read.should == "writing to fd: #{child_fd}"
+        end
       end
     end
   end
diff --git a/spec/ruby/core/process/status/bit_and_spec.rb b/spec/ruby/core/process/status/bit_and_spec.rb
index 97f768fdc1..a805364629 100644
--- a/spec/ruby/core/process/status/bit_and_spec.rb
+++ b/spec/ruby/core/process/status/bit_and_spec.rb
@@ -1,5 +1,38 @@
 require_relative '../../../spec_helper'
 
-describe "Process::Status#&" do
-  it "needs to be reviewed for spec completeness"
+ruby_version_is ""..."4.0" do
+
+  describe "Process::Status#&" do
+    it "returns a bitwise and of the integer status of an exited child" do
+      suppress_warning do
+        ruby_exe("exit(29)", exit_status: 29)
+        ($? & 0).should == 0
+        ($? & $?.to_i).should == $?.to_i
+
+        # Actual value is implementation specific
+        platform_is :linux do
+          # 29 == 0b11101
+          ($? & 0b1011100000000).should == 0b1010100000000
+        end
+      end
+    end
+
+    ruby_version_is "3.3"..."4.0" do
+      it "raises an ArgumentError if mask is negative" do
+        suppress_warning do
+          ruby_exe("exit(0)")
+          -> {
+            $? & -1
+          }.should raise_error(ArgumentError, 'negative mask value: -1')
+        end
+      end
+
+      it "shows a deprecation warning" do
+        ruby_exe("exit(0)")
+        -> {
+          $? & 0
+        }.should complain(/warning: Process::Status#& is deprecated and will be removed .*use other Process::Status predicates instead/)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/process/status/equal_value_spec.rb b/spec/ruby/core/process/status/equal_value_spec.rb
index 9e9a2d0a2b..d8a2be26b8 100644
--- a/spec/ruby/core/process/status/equal_value_spec.rb
+++ b/spec/ruby/core/process/status/equal_value_spec.rb
@@ -1,5 +1,15 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#==" do
-  it "needs to be reviewed for spec completeness"
+  it "returns true when compared to the integer status of an exited child" do
+    ruby_exe("exit(29)", exit_status: 29)
+    $?.to_i.should == $?
+    $?.should == $?.to_i
+  end
+
+  it "returns true when compared to the integer status of a terminated child" do
+    ruby_exe("Process.kill(:KILL, $$); exit(29)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
+    $?.to_i.should == $?
+    $?.should == $?.to_i
+  end
 end
diff --git a/spec/ruby/core/process/status/exited_spec.rb b/spec/ruby/core/process/status/exited_spec.rb
index 0ae3f9e7ae..a61292b146 100644
--- a/spec/ruby/core/process/status/exited_spec.rb
+++ b/spec/ruby/core/process/status/exited_spec.rb
@@ -1,9 +1,7 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#exited?" do
-
   describe "for a child that exited normally" do
-
     before :each do
       ruby_exe("exit(0)")
     end
@@ -15,9 +13,8 @@ describe "Process::Status#exited?" do
 
 
   describe "for a terminated child" do
-
     before :each do
-      ruby_exe("Process.kill(:KILL, $$); exit(42)")
+      ruby_exe("Process.kill(:KILL, $$); exit(42)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
     end
 
     platform_is_not :windows do
@@ -31,7 +28,5 @@ describe "Process::Status#exited?" do
         $?.exited?.should be_true
       end
     end
-
   end
-
 end
diff --git a/spec/ruby/core/process/status/exitstatus_spec.rb b/spec/ruby/core/process/status/exitstatus_spec.rb
index cd46b2081f..5c86c2b3c8 100644
--- a/spec/ruby/core/process/status/exitstatus_spec.rb
+++ b/spec/ruby/core/process/status/exitstatus_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 
 describe "Process::Status#exitstatus" do
   before :each do
-    ruby_exe("exit(42)")
+    ruby_exe("exit(42)", exit_status: 42)
   end
 
   it "returns the process exit code" do
@@ -11,7 +11,7 @@ describe "Process::Status#exitstatus" do
 
   describe "for a child that raised SignalException" do
     before :each do
-      ruby_exe("raise SignalException, 'SIGTERM'")
+      ruby_exe("Process.kill(:KILL, $$); exit(42)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
     end
 
     platform_is_not :windows do
diff --git a/spec/ruby/core/process/status/right_shift_spec.rb b/spec/ruby/core/process/status/right_shift_spec.rb
index e9dda437e8..355aaf4c95 100644
--- a/spec/ruby/core/process/status/right_shift_spec.rb
+++ b/spec/ruby/core/process/status/right_shift_spec.rb
@@ -1,5 +1,37 @@
 require_relative '../../../spec_helper'
 
-describe "Process::Status#>>" do
-  it "needs to be reviewed for spec completeness"
+ruby_version_is ""..."4.0" do
+
+  describe "Process::Status#>>" do
+    it "returns a right shift of the integer status of an exited child" do
+      suppress_warning do
+        ruby_exe("exit(29)", exit_status: 29)
+        ($? >> 0).should == $?.to_i
+        ($? >> 1).should == $?.to_i >> 1
+
+        # Actual value is implementation specific
+        platform_is :linux do
+          ($? >> 8).should == 29
+        end
+      end
+    end
+
+    ruby_version_is "3.3"..."4.0" do
+      it "raises an ArgumentError if shift value is negative" do
+        suppress_warning do
+          ruby_exe("exit(0)")
+          -> {
+            $? >> -1
+          }.should raise_error(ArgumentError, 'negative shift value: -1')
+        end
+      end
+
+      it "shows a deprecation warning" do
+        ruby_exe("exit(0)")
+        -> {
+          $? >> 0
+        }.should complain(/warning: Process::Status#>> is deprecated and will be removed .*use other Process::Status attributes instead/)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/process/status/signaled_spec.rb b/spec/ruby/core/process/status/signaled_spec.rb
index f23c95025f..c0de7b8006 100644
--- a/spec/ruby/core/process/status/signaled_spec.rb
+++ b/spec/ruby/core/process/status/signaled_spec.rb
@@ -1,9 +1,7 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#signaled?" do
-
   describe "for a cleanly exited child" do
-
     before :each do
       ruby_exe("exit(0)")
     end
@@ -14,9 +12,8 @@ describe "Process::Status#signaled?" do
   end
 
   describe "for a terminated child" do
-
     before :each do
-      ruby_exe("Process.kill(:KILL, $$); exit(42)")
+      ruby_exe("Process.kill(:KILL, $$); exit(42)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
     end
 
     platform_is_not :windows do
@@ -30,6 +27,5 @@ describe "Process::Status#signaled?" do
         $?.signaled?.should be_false
       end
     end
-
   end
 end
diff --git a/spec/ruby/core/process/status/success_spec.rb b/spec/ruby/core/process/status/success_spec.rb
index 28a1721800..3589cc611f 100644
--- a/spec/ruby/core/process/status/success_spec.rb
+++ b/spec/ruby/core/process/status/success_spec.rb
@@ -1,9 +1,7 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#success?" do
-
   describe "for a child that exited normally" do
-
     before :each do
       ruby_exe("exit(0)")
     end
@@ -14,9 +12,8 @@ describe "Process::Status#success?" do
   end
 
   describe "for a child that exited with a non zero status" do
-
     before :each do
-      ruby_exe("exit(42)")
+      ruby_exe("exit(42)", exit_status: 42)
     end
 
     it "returns false" do
@@ -25,27 +22,20 @@ describe "Process::Status#success?" do
   end
 
   describe "for a child that was terminated" do
-
     before :each do
-      ruby_exe("Process.kill(:KILL, $$); exit(42)")
+      ruby_exe("Process.kill(:KILL, $$); exit(42)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
     end
 
     platform_is_not :windows do
-
       it "returns nil" do
         $?.success?.should be_nil
       end
-
     end
 
     platform_is :windows do
-
       it "always returns true" do
         $?.success?.should be_true
       end
-
     end
-
   end
-
 end
diff --git a/spec/ruby/core/process/status/termsig_spec.rb b/spec/ruby/core/process/status/termsig_spec.rb
index 1482d27146..9a22dbea71 100644
--- a/spec/ruby/core/process/status/termsig_spec.rb
+++ b/spec/ruby/core/process/status/termsig_spec.rb
@@ -1,21 +1,19 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#termsig" do
-
   describe "for a child that exited normally" do
-
     before :each do
       ruby_exe("exit(0)")
     end
 
-    it "returns true" do
+    it "returns nil" do
       $?.termsig.should be_nil
     end
   end
 
   describe "for a child that raised SignalException" do
     before :each do
-      ruby_exe("raise SignalException, 'SIGTERM'")
+      ruby_exe("raise SignalException, 'SIGTERM'", exit_status: :SIGTERM)
     end
 
     platform_is_not :windows do
@@ -26,26 +24,20 @@ describe "Process::Status#termsig" do
   end
 
   describe "for a child that was sent a signal" do
-
     before :each do
-      ruby_exe("Process.kill(:KILL, $$); exit(42)")
+      ruby_exe("Process.kill(:KILL, $$); exit(42)", exit_status: platform_is(:windows) ? 0 : :SIGKILL)
     end
 
     platform_is_not :windows do
-
       it "returns the signal" do
         $?.termsig.should == Signal.list["KILL"]
       end
-
     end
 
     platform_is :windows do
-
       it "always returns nil" do
         $?.termsig.should be_nil
       end
-
     end
-
   end
 end
diff --git a/spec/ruby/core/process/status/to_i_spec.rb b/spec/ruby/core/process/status/to_i_spec.rb
index 37b7bdb1e4..39f8e2d84c 100644
--- a/spec/ruby/core/process/status/to_i_spec.rb
+++ b/spec/ruby/core/process/status/to_i_spec.rb
@@ -1,5 +1,13 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Status#to_i" do
-  it "needs to be reviewed for spec completeness"
+  it "returns an integer when the child exits" do
+    ruby_exe('exit 48', exit_status: 48)
+    $?.to_i.should be_an_instance_of(Integer)
+  end
+
+  it "returns an integer when the child is signaled" do
+    ruby_exe('raise SignalException, "TERM"', exit_status: platform_is(:windows) ? 3 : :SIGTERM)
+    $?.to_i.should be_an_instance_of(Integer)
+  end
 end
diff --git a/spec/ruby/core/process/status/wait_spec.rb b/spec/ruby/core/process/status/wait_spec.rb
new file mode 100644
index 0000000000..57d56209a9
--- /dev/null
+++ b/spec/ruby/core/process/status/wait_spec.rb
@@ -0,0 +1,100 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/common'
+
+describe "Process::Status.wait" do
+  ProcessSpecs.use_system_ruby(self)
+
+  before :all do
+    begin
+      leaked = Process.waitall
+      # Ruby-space should not see PIDs used by rjit
+      raise "subprocesses leaked before wait specs: #{leaked}" unless leaked.empty?
+    rescue NotImplementedError
+    end
+  end
+
+  it "returns a status with pid -1 if there are no child processes" do
+    Process::Status.wait.pid.should == -1
+  end
+
+  platform_is_not :windows do
+    it "returns a status with its child pid" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      status = Process::Status.wait
+      status.should be_an_instance_of(Process::Status)
+      status.pid.should == pid
+    end
+
+    it "should not set $? to the Process::Status" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      status = Process::Status.wait
+      $?.should_not equal(status)
+    end
+
+    it "should not change the value of $?" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process.wait
+      status = $?
+      Process::Status.wait
+      status.should equal($?)
+    end
+
+    it "waits for any child process if no pid is given" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process::Status.wait.pid.should == pid
+      -> { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
+    end
+
+    it "waits for a specific child if a pid is given" do
+      pid1 = Process.spawn(ruby_cmd('exit'))
+      pid2 = Process.spawn(ruby_cmd('exit'))
+      Process::Status.wait(pid2).pid.should == pid2
+      Process::Status.wait(pid1).pid.should == pid1
+      -> { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
+      -> { Process.kill(0, pid2) }.should raise_error(Errno::ESRCH)
+    end
+
+    it "coerces the pid to an Integer" do
+      pid1 = Process.spawn(ruby_cmd('exit'))
+      Process::Status.wait(mock_int(pid1)).pid.should == pid1
+      -> { Process.kill(0, pid1) }.should raise_error(Errno::ESRCH)
+    end
+
+    # This spec is probably system-dependent.
+    it "waits for a child whose process group ID is that of the calling process" do
+      pid1 = Process.spawn(ruby_cmd('exit'), pgroup: true)
+      pid2 = Process.spawn(ruby_cmd('exit'))
+
+      Process::Status.wait(0).pid.should == pid2
+      Process::Status.wait.pid.should == pid1
+    end
+
+    # This spec is probably system-dependent.
+    it "doesn't block if no child is available when WNOHANG is used" do
+      read, write = IO.pipe
+      pid = Process.fork do
+        read.close
+        Signal.trap("TERM") { Process.exit! }
+        write << 1
+        write.close
+        sleep
+      end
+
+      Process::Status.wait(pid, Process::WNOHANG).should be_nil
+
+      # wait for the child to setup its TERM handler
+      write.close
+      read.read(1)
+      read.close
+
+      Process.kill("TERM", pid)
+      Process::Status.wait.pid.should == pid
+    end
+
+    it "always accepts flags=0" do
+      pid = Process.spawn(ruby_cmd('exit'))
+      Process::Status.wait(-1, 0).pid.should == pid
+      -> { Process.kill(0, pid) }.should raise_error(Errno::ESRCH)
+    end
+  end
+end
diff --git a/spec/ruby/core/process/times_spec.rb b/spec/ruby/core/process/times_spec.rb
index 07b4fa5c9f..d3bff2cda9 100644
--- a/spec/ruby/core/process/times_spec.rb
+++ b/spec/ruby/core/process/times_spec.rb
@@ -5,23 +5,15 @@ describe "Process.times" do
     Process.times.should be_kind_of(Process::Tms)
   end
 
-  it "returns current cpu times" do
-    t = Process.times
+  # TODO: Intel C Compiler does not work this example
+  # http://rubyci.s3.amazonaws.com/icc-x64/ruby-master/log/20221013T030005Z.fail.html.gz
+  unless RbConfig::CONFIG['CC']&.include?("icx")
+    it "returns current cpu times" do
+      t = Process.times
+      user = t.utime
 
-    # Do busy work for a wall-clock interval.
-    start = Time.now
-    1 until (Time.now - start) > 0.5
-
-    # Ensure times is larger. NOTE that there is no
-    # guarantee of an upper bound since anything may be
-    # happening at the OS level, so we ONLY check that at
-    # least an interval has elapsed. Also, we are assuming
-    # there is a correlation between wall clock time and
-    # process time. In practice, there is an observed
-    # discrepancy often 10% or greater. In other words,
-    # this is a very fuzzy test.
-    t2 = Process.times
-    diff = (t2.utime + t2.stime) - (t.utime + t.stime)
-    diff.should > 0
+      1 until Process.times.utime > user
+      Process.times.utime.should > user
+    end
   end
 end
diff --git a/spec/ruby/core/process/tms/cstime_spec.rb b/spec/ruby/core/process/tms/cstime_spec.rb
index 207d4391c0..9c2d9e8632 100644
--- a/spec/ruby/core/process/tms/cstime_spec.rb
+++ b/spec/ruby/core/process/tms/cstime_spec.rb
@@ -1,9 +1,17 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Tms#cstime" do
-  it "needs to be reviewed for spec completeness"
+  it "returns cstime attribute" do
+    cstime = Object.new
+    Process::Tms.new(nil, nil, nil, cstime).cstime.should == cstime
+  end
 end
 
 describe "Process::Tms#cstime=" do
-  it "needs to be reviewed for spec completeness"
+  it "assigns a value to the cstime attribute" do
+    cstime = Object.new
+    tms = Process::Tms.new
+    tms.cstime = cstime
+    tms.cstime.should == cstime
+  end
 end
diff --git a/spec/ruby/core/process/tms/cutime_spec.rb b/spec/ruby/core/process/tms/cutime_spec.rb
index 390280f005..0ac3ff1964 100644
--- a/spec/ruby/core/process/tms/cutime_spec.rb
+++ b/spec/ruby/core/process/tms/cutime_spec.rb
@@ -1,9 +1,17 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Tms#cutime" do
-  it "needs to be reviewed for spec completeness"
+  it "returns cutime attribute" do
+    cutime = Object.new
+    Process::Tms.new(nil, nil, cutime, nil).cutime.should == cutime
+  end
 end
 
 describe "Process::Tms#cutime=" do
-  it "needs to be reviewed for spec completeness"
+  it "assigns a value to the cutime attribute" do
+    cutime = Object.new
+    tms = Process::Tms.new
+    tms.cutime = cutime
+    tms.cutime.should == cutime
+  end
 end
diff --git a/spec/ruby/core/process/tms/element_reference_spec.rb b/spec/ruby/core/process/tms/element_reference_spec.rb
deleted file mode 100644
index 84a34089ae..0000000000
--- a/spec/ruby/core/process/tms/element_reference_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../../spec_helper'
-
-describe "Process::Tms.[]" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/process/tms/members_spec.rb b/spec/ruby/core/process/tms/members_spec.rb
deleted file mode 100644
index 005a8baec1..0000000000
--- a/spec/ruby/core/process/tms/members_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../../spec_helper'
-
-describe "Process::Tms.members" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/process/tms/new_spec.rb b/spec/ruby/core/process/tms/new_spec.rb
deleted file mode 100644
index 9dd1f5a8f2..0000000000
--- a/spec/ruby/core/process/tms/new_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../../spec_helper'
-
-describe "Process::Tms.new" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/core/process/tms/stime_spec.rb b/spec/ruby/core/process/tms/stime_spec.rb
index 4104b625e2..1e8371475f 100644
--- a/spec/ruby/core/process/tms/stime_spec.rb
+++ b/spec/ruby/core/process/tms/stime_spec.rb
@@ -1,9 +1,17 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Tms#stime" do
-  it "needs to be reviewed for spec completeness"
+  it "returns stime attribute" do
+    stime = Object.new
+    Process::Tms.new(nil, stime, nil, nil).stime.should == stime
+  end
 end
 
 describe "Process::Tms#stime=" do
-  it "needs to be reviewed for spec completeness"
+  it "assigns a value to the stime attribute" do
+    stime = Object.new
+    tms = Process::Tms.new
+    tms.stime = stime
+    tms.stime.should == stime
+  end
 end
diff --git a/spec/ruby/core/process/tms/utime_spec.rb b/spec/ruby/core/process/tms/utime_spec.rb
index 28371590e9..403a31e2e6 100644
--- a/spec/ruby/core/process/tms/utime_spec.rb
+++ b/spec/ruby/core/process/tms/utime_spec.rb
@@ -1,9 +1,17 @@
 require_relative '../../../spec_helper'
 
 describe "Process::Tms#utime" do
-  it "needs to be reviewed for spec completeness"
+  it "returns utime attribute" do
+    utime = Object.new
+    Process::Tms.new(utime, nil, nil, nil).utime.should == utime
+  end
 end
 
 describe "Process::Tms#utime=" do
-  it "needs to be reviewed for spec completeness"
+  it "assigns a value to the ctime attribute" do
+    utime = Object.new
+    tms = Process::Tms.new
+    tms.utime = utime
+    tms.utime.should == utime
+  end
 end
diff --git a/spec/ruby/core/process/wait2_spec.rb b/spec/ruby/core/process/wait2_spec.rb
index 6eb7fc6d06..8ba429dc96 100644
--- a/spec/ruby/core/process/wait2_spec.rb
+++ b/spec/ruby/core/process/wait2_spec.rb
@@ -4,14 +4,14 @@ describe "Process.wait2" do
   before :all do
     # HACK: this kludge is temporarily necessary because some
     # misbehaving spec somewhere else does not clear processes
-    # Note: background processes are unavoidable with MJIT,
+    # Note: background processes are unavoidable with RJIT,
     # but we shouldn't reap them from Ruby-space
     begin
       Process.wait(-1, Process::WNOHANG)
       $stderr.puts "Leaked process before wait2 specs! Waiting for it"
       leaked = Process.waitall
       $stderr.puts "leaked before wait2 specs: #{leaked}" unless leaked.empty?
-      # Ruby-space should not see PIDs used by mjit
+      # Ruby-space should not see PIDs used by rjit
       leaked.should be_empty
     rescue Errno::ECHILD # No child processes
     rescue NotImplementedError
@@ -33,4 +33,13 @@ describe "Process.wait2" do
     -> { Process.wait2 }.should raise_error(Errno::ECHILD)
     -> { Process.wait2 }.should raise_error(StandardError)
   end
+
+  it "returns nil if the child process is still running when given the WNOHANG flag" do
+    IO.popen(ruby_cmd('STDIN.getbyte'), "w") do |io|
+      pid, status = Process.wait2(io.pid, Process::WNOHANG)
+      pid.should be_nil
+      status.should be_nil
+      io.write('a')
+    end
+  end
 end
diff --git a/spec/ruby/core/process/wait_spec.rb b/spec/ruby/core/process/wait_spec.rb
index f393a99e0f..385acc9928 100644
--- a/spec/ruby/core/process/wait_spec.rb
+++ b/spec/ruby/core/process/wait_spec.rb
@@ -7,9 +7,8 @@ describe "Process.wait" do
   before :all do
     begin
       leaked = Process.waitall
-      puts "leaked before wait specs: #{leaked}" unless leaked.empty?
-      # Ruby-space should not see PIDs used by mjit
-      leaked.should be_empty
+      # Ruby-space should not see PIDs used by rjit
+      raise "subprocesses leaked before wait specs: #{leaked}" unless leaked.empty?
     rescue NotImplementedError
     end
   end
diff --git a/spec/ruby/core/process/waitpid_spec.rb b/spec/ruby/core/process/waitpid_spec.rb
index f7cf1a45a8..a02147b663 100644
--- a/spec/ruby/core/process/waitpid_spec.rb
+++ b/spec/ruby/core/process/waitpid_spec.rb
@@ -2,7 +2,8 @@ require_relative '../../spec_helper'
 
 describe "Process.waitpid" do
   it "returns nil when the process has not yet completed and WNOHANG is specified" do
-    pid = spawn("sleep 5")
+    cmd = platform_is(:windows) ? "timeout" : "sleep"
+    pid = spawn("#{cmd} 5")
     begin
       Process.waitpid(pid, Process::WNOHANG).should == nil
       Process.kill("KILL", pid)
diff --git a/spec/ruby/core/process/warmup_spec.rb b/spec/ruby/core/process/warmup_spec.rb
new file mode 100644
index 0000000000..b562d52d22
--- /dev/null
+++ b/spec/ruby/core/process/warmup_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+
+describe "Process.warmup" do
+  ruby_version_is "3.3" do
+    # The behavior is entirely implementation specific.
+    # Other implementations are free to just make it a noop
+    it "is implemented" do
+      Process.warmup.should == true
+    end
+  end
+end
diff --git a/spec/ruby/core/queue/deq_spec.rb b/spec/ruby/core/queue/deq_spec.rb
index 9510978eac..a2784e6a63 100644
--- a/spec/ruby/core/queue/deq_spec.rb
+++ b/spec/ruby/core/queue/deq_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "Queue#deq" do
   it_behaves_like :queue_deq, :deq, -> { Queue.new }
 end
+
+describe "Queue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = Queue.new; q.push(1); q.deq(timeout: v) }
+end
diff --git a/spec/ruby/core/queue/freeze_spec.rb b/spec/ruby/core/queue/freeze_spec.rb
new file mode 100644
index 0000000000..ced2cc52dd
--- /dev/null
+++ b/spec/ruby/core/queue/freeze_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/queue/freeze'
+
+describe "Queue#freeze" do
+  it_behaves_like :queue_freeze, :freeze, -> { Queue.new }
+end
diff --git a/spec/ruby/core/queue/initialize_spec.rb b/spec/ruby/core/queue/initialize_spec.rb
new file mode 100644
index 0000000000..592fbe2487
--- /dev/null
+++ b/spec/ruby/core/queue/initialize_spec.rb
@@ -0,0 +1,60 @@
+require_relative '../../spec_helper'
+
+describe "Queue#initialize" do
+  it "can be passed no arguments for an empty Queue" do
+    q = Queue.new
+    q.size.should == 0
+    q.should.empty?
+  end
+
+  it "is a private method" do
+    Queue.private_instance_methods.include?(:initialize).should == true
+  end
+
+  it "adds all elements of the passed Enumerable to self" do
+    q = Queue.new([1, 2, 3])
+    q.size.should == 3
+    q.should_not.empty?
+    q.pop.should == 1
+    q.pop.should == 2
+    q.pop.should == 3
+    q.should.empty?
+  end
+
+  describe "converts the given argument to an Array using #to_a" do
+    it "uses #to_a on the provided Enumerable" do
+      enumerable = MockObject.new('mock-enumerable')
+      enumerable.should_receive(:to_a).and_return([1, 2, 3])
+      q = Queue.new(enumerable)
+      q.size.should == 3
+      q.should_not.empty?
+      q.pop.should == 1
+      q.pop.should == 2
+      q.pop.should == 3
+      q.should.empty?
+    end
+
+    it "raises a TypeError if the given argument can't be converted to an Array" do
+      -> { Queue.new(42) }.should raise_error(TypeError)
+      -> { Queue.new(:abc) }.should raise_error(TypeError)
+    end
+
+    it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to an Array" do
+      enumerable = MockObject.new('mock-enumerable')
+      enumerable.should_receive(:to_a).and_raise(NoMethodError)
+      -> { Queue.new(enumerable) }.should raise_error(NoMethodError)
+    end
+  end
+
+  it "raises TypeError if the provided Enumerable does not respond to #to_a" do
+    enumerable = MockObject.new('mock-enumerable')
+    -> { Queue.new(enumerable) }.should raise_error(TypeError, "can't convert MockObject into Array")
+  end
+
+  it "raises TypeError if #to_a does not return Array" do
+    enumerable = MockObject.new('mock-enumerable')
+    enumerable.should_receive(:to_a).and_return("string")
+
+    -> { Queue.new(enumerable) }.should raise_error(TypeError, "can't convert MockObject to Array (MockObject#to_a gives String)")
+  end
+end
diff --git a/spec/ruby/core/queue/pop_spec.rb b/spec/ruby/core/queue/pop_spec.rb
index 1ce9231685..3dff7db242 100644
--- a/spec/ruby/core/queue/pop_spec.rb
+++ b/spec/ruby/core/queue/pop_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "Queue#pop" do
   it_behaves_like :queue_deq, :pop, -> { Queue.new }
 end
+
+describe "Queue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = Queue.new; q.push(1); q.pop(timeout: v) }
+end
diff --git a/spec/ruby/core/queue/shift_spec.rb b/spec/ruby/core/queue/shift_spec.rb
index f84058e1df..c105da74b2 100644
--- a/spec/ruby/core/queue/shift_spec.rb
+++ b/spec/ruby/core/queue/shift_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "Queue#shift" do
   it_behaves_like :queue_deq, :shift, -> { Queue.new }
 end
+
+describe "Queue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = Queue.new; q.push(1); q.shift(timeout: v) }
+end
diff --git a/spec/ruby/core/random/bytes_spec.rb b/spec/ruby/core/random/bytes_spec.rb
index 2caf18fbd0..c9be07cd3f 100644
--- a/spec/ruby/core/random/bytes_spec.rb
+++ b/spec/ruby/core/random/bytes_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/bytes'
 
@@ -9,7 +9,6 @@ describe "Random#bytes" do
     Random.new(33).bytes(2).should == Random.new(33).bytes(2)
   end
 
-  # Should double check this is official spec
   it "returns the same numeric output for a given seed across all implementations and platforms" do
     rnd = Random.new(33)
     rnd.bytes(2).should == "\x14\\"
@@ -18,15 +17,13 @@ describe "Random#bytes" do
   end
 
   it "returns the same numeric output for a given huge seed across all implementations and platforms" do
-    rnd = Random.new(bignum_value ** 4)
+    rnd = Random.new(2 ** (63 * 4))
     rnd.bytes(2).should == "_\x91"
     rnd.bytes(1000) # skip some
     rnd.bytes(2).should == "\x17\x12"
   end
 end
 
-ruby_version_is "2.6" do
-  describe "Random.bytes" do
-    it_behaves_like :random_bytes, :bytes, Random
-  end
+describe "Random.bytes" do
+  it_behaves_like :random_bytes, :bytes, Random
 end
diff --git a/spec/ruby/core/random/default_spec.rb b/spec/ruby/core/random/default_spec.rb
index 1d8b1ce5ee..9e4845986d 100644
--- a/spec/ruby/core/random/default_spec.rb
+++ b/spec/ruby/core/random/default_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Random::DEFAULT" do
-  it "returns a Random instance" do
-    Random::DEFAULT.should be_an_instance_of(Random)
+  it "is no longer defined" do
+    Random.should_not.const_defined?(:DEFAULT)
   end
 end
diff --git a/spec/ruby/core/random/new_seed_spec.rb b/spec/ruby/core/random/new_seed_spec.rb
index 4b34e871a2..7a93da99aa 100644
--- a/spec/ruby/core/random/new_seed_spec.rb
+++ b/spec/ruby/core/random/new_seed_spec.rb
@@ -1,8 +1,8 @@
 require_relative '../../spec_helper'
 
 describe "Random.new_seed" do
-  it "returns a Bignum" do
-    Random.new_seed.should be_an_instance_of(Bignum)
+  it "returns an Integer" do
+    Random.new_seed.should be_an_instance_of(Integer)
   end
 
   it "returns an arbitrary seed value each time" do
diff --git a/spec/ruby/core/random/new_spec.rb b/spec/ruby/core/random/new_spec.rb
index 07d7b439ca..69210cef03 100644
--- a/spec/ruby/core/random/new_spec.rb
+++ b/spec/ruby/core/random/new_spec.rb
@@ -1,16 +1,17 @@
+require_relative "../../spec_helper"
 describe "Random.new" do
   it "returns a new instance of Random" do
     Random.new.should be_an_instance_of(Random)
   end
 
   it "uses a random seed value if none is supplied" do
-    Random.new.seed.should be_an_instance_of(Bignum)
+    Random.new.seed.should be_an_instance_of(Integer)
   end
 
   it "returns Random instances initialized with different seeds" do
     first = Random.new
     second = Random.new
-    (0..20).map { first.rand } .should_not == (0..20).map { second.rand }
+    (0..20).map { first.rand }.should_not == (0..20).map { second.rand }
   end
 
   it "accepts an Integer seed value as an argument" do
diff --git a/spec/ruby/core/random/rand_spec.rb b/spec/ruby/core/random/rand_spec.rb
index b585aa9737..9244177ab5 100644
--- a/spec/ruby/core/random/rand_spec.rb
+++ b/spec/ruby/core/random/rand_spec.rb
@@ -1,10 +1,10 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/rand'
 
 describe "Random.rand" do
-  it "returns a Float if no max argument is passed" do
-    Random.rand.should be_kind_of(Float)
-  end
+  it_behaves_like :random_number, :rand, Random.new
+  it_behaves_like :random_number, :rand, Random
 
   it "returns a Float >= 0 if no max argument is passed" do
     floats = 200.times.map { Random.rand }
@@ -24,10 +24,6 @@ describe "Random.rand" do
     floats_a.should == floats_b
   end
 
-  it "returns an Integer if an Integer argument is passed" do
-    Random.rand(20).should be_kind_of(Integer)
-  end
-
   it "returns an Integer >= 0 if an Integer argument is passed" do
     ints = 200.times.map { Random.rand(34) }
     ints.min.should >= 0
@@ -55,7 +51,7 @@ end
 
 describe "Random#rand with Fixnum" do
   it "returns an Integer" do
-    Random.new.rand(20).should be_an_instance_of(Fixnum)
+    Random.new.rand(20).should be_an_instance_of(Integer)
   end
 
   it "returns a Fixnum greater than or equal to 0" do
@@ -99,7 +95,7 @@ end
 describe "Random#rand with Bignum" do
   it "typically returns a Bignum" do
     rnd = Random.new(1)
-    10.times.map{ rnd.rand(bignum_value*2) }.max.should be_an_instance_of(Bignum)
+    10.times.map{ rnd.rand(bignum_value*2) }.max.should be_an_instance_of(Integer)
   end
 
   it "returns a Bignum greater than or equal to 0" do
@@ -163,7 +159,7 @@ end
 
 describe "Random#rand with Range" do
   it "returns an element from the Range" do
-    Random.new.rand(20..43).should be_an_instance_of(Fixnum)
+    Random.new.rand(20..43).should be_an_instance_of(Integer)
   end
 
   it "supports custom object types" do
@@ -209,6 +205,11 @@ describe "Random#rand with Range" do
     Random.new(42).rand(0..1.0).should be_kind_of(Float)
   end
 
+  it "returns a float within a given float range" do
+    Random.new(42).rand(0.0...100.0).should == 37.454011884736246
+    Random.new(42).rand(-100.0...0.0).should == -62.545988115263754
+  end
+
   it "raises an ArgumentError when the startpoint lacks #+ and #- methods" do
     -> do
       Random.new.rand(Object.new..67)
diff --git a/spec/ruby/core/random/random_number_spec.rb b/spec/ruby/core/random/random_number_spec.rb
new file mode 100644
index 0000000000..bad81aeff6
--- /dev/null
+++ b/spec/ruby/core/random/random_number_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'shared/rand'
+
+describe "Random.random_number" do
+  it_behaves_like :random_number, :random_number, Random.new
+
+  it_behaves_like :random_number, :random_number, Random
+end
diff --git a/spec/ruby/core/random/raw_seed_spec.rb b/spec/ruby/core/random/raw_seed_spec.rb
deleted file mode 100644
index c1a1eb1f42..0000000000
--- a/spec/ruby/core/random/raw_seed_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-# -*- encoding: binary -*-
-require_relative '../../spec_helper'
-require_relative 'shared/urandom'
-
-ruby_version_is "2.5" do
-  describe "Random.urandom" do
-    it_behaves_like :random_urandom, :urandom
-  end
-end
diff --git a/spec/ruby/core/random/shared/bytes.rb b/spec/ruby/core/random/shared/bytes.rb
index fe8cd8d683..9afad3b7f8 100644
--- a/spec/ruby/core/random/shared/bytes.rb
+++ b/spec/ruby/core/random/shared/bytes.rb
@@ -1,17 +1,17 @@
 describe :random_bytes, shared: true do
   it "returns a String" do
-    @object.bytes(1).should be_an_instance_of(String)
+    @object.send(@method, 1).should be_an_instance_of(String)
   end
 
   it "returns a String of the length given as argument" do
-    @object.bytes(15).length.should == 15
+    @object.send(@method, 15).length.should == 15
   end
 
   it "returns a binary String" do
-    @object.bytes(15).encoding.should == Encoding::BINARY
+    @object.send(@method, 15).encoding.should == Encoding::BINARY
   end
 
   it "returns a random binary String" do
-    @object.bytes(12).should_not == @object.bytes(12)
+    @object.send(@method, 12).should_not == @object.send(@method, 12)
   end
 end
diff --git a/spec/ruby/core/random/shared/rand.rb b/spec/ruby/core/random/shared/rand.rb
new file mode 100644
index 0000000000..d3b24b8851
--- /dev/null
+++ b/spec/ruby/core/random/shared/rand.rb
@@ -0,0 +1,9 @@
+describe :random_number, shared: true do
+  it "returns a Float if no max argument is passed" do
+    @object.send(@method).should be_kind_of(Float)
+  end
+
+  it "returns an Integer if an Integer argument is passed" do
+    @object.send(@method, 20).should be_kind_of(Integer)
+  end
+end
diff --git a/spec/ruby/core/random/shared/urandom.rb b/spec/ruby/core/random/shared/urandom.rb
deleted file mode 100644
index 159716075c..0000000000
--- a/spec/ruby/core/random/shared/urandom.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-describe :random_urandom, shared: true do
-  it "returns a String" do
-    Random.send(@method, 1).should be_an_instance_of(String)
-  end
-
-  it "returns a String of the length given as argument" do
-    Random.send(@method, 15).length.should == 15
-  end
-
-  it "raises an ArgumentError on a negative size" do
-    -> {
-      Random.send(@method, -1)
-    }.should raise_error(ArgumentError)
-  end
-
-  it "returns a binary String" do
-    Random.send(@method, 15).encoding.should == Encoding::BINARY
-  end
-
-  it "returns a random binary String" do
-    Random.send(@method, 12).should_not == Random.send(@method, 12)
-  end
-end
diff --git a/spec/ruby/core/random/urandom_spec.rb b/spec/ruby/core/random/urandom_spec.rb
index e27f83cdcd..6f180e54ac 100644
--- a/spec/ruby/core/random/urandom_spec.rb
+++ b/spec/ruby/core/random/urandom_spec.rb
@@ -1,9 +1,25 @@
-# -*- encoding: binary -*-
 require_relative '../../spec_helper'
-require_relative 'shared/urandom'
 
-ruby_version_is ""..."2.5" do
-  describe "Random.raw_seed" do
-    it_behaves_like :random_urandom, :raw_seed
+describe "Random.urandom" do
+  it "returns a String" do
+    Random.urandom(1).should be_an_instance_of(String)
+  end
+
+  it "returns a String of the length given as argument" do
+    Random.urandom(15).length.should == 15
+  end
+
+  it "raises an ArgumentError on a negative size" do
+    -> {
+      Random.urandom(-1)
+    }.should raise_error(ArgumentError)
+  end
+
+  it "returns a binary String" do
+    Random.urandom(15).encoding.should == Encoding::BINARY
+  end
+
+  it "returns a random binary String" do
+    Random.urandom(12).should_not == Random.urandom(12)
   end
 end
diff --git a/spec/ruby/core/range/bsearch_spec.rb b/spec/ruby/core/range/bsearch_spec.rb
index 009cafb00e..5254ab756c 100644
--- a/spec/ruby/core/range/bsearch_spec.rb
+++ b/spec/ruby/core/range/bsearch_spec.rb
@@ -9,22 +9,30 @@ describe "Range#bsearch" do
   it_behaves_like :enumeratorized_with_unknown_size, :bsearch, (1..3)
 
   it "raises a TypeError if the block returns an Object" do
-    -> { (0..1).bsearch { Object.new } }.should raise_error(TypeError)
+    -> { (0..1).bsearch { Object.new } }.should raise_error(TypeError, "wrong argument type Object (must be numeric, true, false or nil)")
   end
 
-  it "raises a TypeError if the block returns a String" do
-    -> { (0..1).bsearch { "1" } }.should raise_error(TypeError)
+  it "raises a TypeError if the block returns a String and boundaries are Integer values" do
+    -> { (0..1).bsearch { "1" } }.should raise_error(TypeError, "wrong argument type String (must be numeric, true, false or nil)")
+  end
+
+  it "raises a TypeError if the block returns a String and boundaries are Float values" do
+    -> { (0.0..1.0).bsearch { "1" } }.should raise_error(TypeError, "wrong argument type String (must be numeric, true, false or nil)")
   end
 
   it "raises a TypeError if the Range has Object values" do
     value = mock("range bsearch")
     r = Range.new value, value
 
-    -> { r.bsearch { true } }.should raise_error(TypeError)
+    -> { r.bsearch { true } }.should raise_error(TypeError, "can't do binary search for MockObject")
   end
 
   it "raises a TypeError if the Range has String values" do
-    -> { ("a".."e").bsearch { true } }.should raise_error(TypeError)
+    -> { ("a".."e").bsearch { true } }.should raise_error(TypeError, "can't do binary search for String")
+  end
+
+  it "raises TypeError when non-Numeric begin/end and block not passed" do
+    -> { ("a".."e").bsearch }.should raise_error(TypeError, "can't do binary search for String")
   end
 
   context "with Integer values" do
@@ -81,6 +89,23 @@ describe "Range#bsearch" do
         [1, 2].should include(result)
       end
     end
+
+    it "returns nil for empty ranges" do
+      (0...0).bsearch { true }.should == nil
+      (0...0).bsearch { false }.should == nil
+      (0...0).bsearch { 1 }.should == nil
+      (0...0).bsearch { 0 }.should == nil
+      (0...0).bsearch { -1 }.should == nil
+
+      (4..2).bsearch { true }.should == nil
+      (4..2).bsearch { 1 }.should == nil
+      (4..2).bsearch { 0 }.should == nil
+      (4..2).bsearch { -1 }.should == nil
+    end
+
+    it "returns enumerator when block not passed" do
+      (0...3).bsearch.kind_of?(Enumerator).should == true
+    end
   end
 
   context "with Float values" do
@@ -94,13 +119,46 @@ describe "Range#bsearch" do
       end
 
       it "returns minimum element if the block returns true for every element" do
-        (-0.2..4.8).bsearch { |x| x < 4 }.should == -0.2
+        (-0.2..4.8).bsearch { |x| x < 5 }.should == -0.2
       end
 
       it "returns the smallest element for which block returns true" do
         (0..4.2).bsearch { |x| x >= 2 }.should == 2
         (-1.2..4.3).bsearch { |x| x >= 1 }.should == 1
       end
+
+      it "returns a boundary element if appropriate" do
+        (1.0..3.0).bsearch { |x| x >= 3.0 }.should == 3.0
+        (1.0...3.0).bsearch { |x| x >= 3.0.prev_float }.should == 3.0.prev_float
+        (1.0..3.0).bsearch { |x| x >= 1.0 }.should == 1.0
+        (1.0...3.0).bsearch { |x| x >= 1.0 }.should == 1.0
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        (0..inf).bsearch { |x| x == inf }.should == inf
+        (0...inf).bsearch { |x| x == inf }.should == nil
+        (-inf..0).bsearch { |x| x != -inf }.should == -Float::MAX
+        (-inf...0).bsearch { |x| x != -inf }.should == -Float::MAX
+        (inf..inf).bsearch { |x| true }.should == inf
+        (inf...inf).bsearch { |x| true }.should == nil
+        (-inf..-inf).bsearch { |x| true }.should == -inf
+        (-inf...-inf).bsearch { |x| true }.should == nil
+        (inf..0).bsearch { true }.should == nil
+        (inf...0).bsearch { true }.should == nil
+        (0..-inf).bsearch { true }.should == nil
+        (0...-inf).bsearch { true }.should == nil
+        (inf..-inf).bsearch { true }.should == nil
+        (inf...-inf).bsearch { true }.should == nil
+        (0..inf).bsearch { |x| x >= 3 }.should == 3.0
+        (0...inf).bsearch { |x| x >= 3 }.should == 3.0
+        (-inf..0).bsearch { |x| x >= -3 }.should == -3.0
+        (-inf...0).bsearch { |x| x >= -3 }.should == -3.0
+        (-inf..inf).bsearch { |x| x >= 3 }.should == 3.0
+        (-inf...inf).bsearch { |x| x >= 3 }.should == 3.0
+        (0..inf).bsearch { |x| x >= Float::MAX }.should == Float::MAX
+        (0...inf).bsearch { |x| x >= Float::MAX }.should == Float::MAX
+      end
     end
 
     context "with a block returning negative, zero, positive numbers" do
@@ -110,7 +168,6 @@ describe "Range#bsearch" do
 
       it "returns nil if the block returns greater than zero for every element" do
         (0.3..3.0).bsearch { |x| x <=> -1 }.should be_nil
-
       end
 
       it "returns nil if the block never returns zero" do
@@ -130,8 +187,280 @@ describe "Range#bsearch" do
       it "returns an element at an index for which block returns 0" do
         result = (0.1..4.9).bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
         result.should >= 1
-        result.should <= 2
+        result.should <= 3
+      end
+
+      it "returns an element at an index for which block returns 0 (small numbers)" do
+        result = (0.1..0.3).bsearch { |x| x < 0.1 ? 1 : x > 0.3 ? -1 : 0 }
+        result.should >= 0.1
+        result.should <= 0.3
+      end
+
+      it "returns a boundary element if appropriate" do
+        (1.0..3.0).bsearch { |x| 3.0 - x }.should == 3.0
+        (1.0...3.0).bsearch { |x| 3.0.prev_float - x }.should == 3.0.prev_float
+        (1.0..3.0).bsearch { |x| 1.0 - x }.should == 1.0
+        (1.0...3.0).bsearch { |x| 1.0 - x }.should == 1.0
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        (0..inf).bsearch { |x| x == inf ? 0 : 1 }.should == inf
+        (0...inf).bsearch { |x| x == inf ? 0 : 1 }.should == nil
+        (-inf...0).bsearch { |x| x == -inf ? 0 : -1 }.should == -inf
+        (-inf..0).bsearch { |x| x == -inf ? 0 : -1 }.should == -inf
+        (inf..inf).bsearch { 0 }.should == inf
+        (inf...inf).bsearch { 0 }.should == nil
+        (-inf..-inf).bsearch { 0 }.should == -inf
+        (-inf...-inf).bsearch { 0 }.should == nil
+        (inf..0).bsearch { 0 }.should == nil
+        (inf...0).bsearch { 0 }.should == nil
+        (0..-inf).bsearch { 0 }.should == nil
+        (0...-inf).bsearch { 0 }.should == nil
+        (inf..-inf).bsearch { 0 }.should == nil
+        (inf...-inf).bsearch { 0 }.should == nil
+        (-inf..inf).bsearch { |x| 3 - x }.should == 3.0
+        (-inf...inf).bsearch { |x| 3 - x }.should == 3.0
+        (0...inf).bsearch { |x| x >= Float::MAX ? 0 : 1 }.should == Float::MAX
       end
     end
+
+    it "returns enumerator when block not passed" do
+      (0.1...2.3).bsearch.kind_of?(Enumerator).should == true
+    end
+  end
+
+  context "with endless ranges and Integer values" do
+    context "with a block returning true or false" do
+      it "returns minimum element if the block returns true for every element" do
+        eval("(-2..)").bsearch { |x| true }.should == -2
+      end
+
+      it "returns the smallest element for which block returns true" do
+        eval("(0..)").bsearch { |x| x >= 2 }.should == 2
+        eval("(-1..)").bsearch { |x| x >= 1 }.should == 1
+      end
+    end
+
+    context "with a block returning negative, zero, positive numbers" do
+      it "returns nil if the block returns less than zero for every element" do
+        eval("(0..)").bsearch { |x| -1 }.should be_nil
+      end
+
+      it "returns nil if the block never returns zero" do
+        eval("(0..)").bsearch { |x| x > 5 ? -1 : 1 }.should be_nil
+      end
+
+      it "accepts -Float::INFINITY from the block" do
+        eval("(0..)").bsearch { |x| -Float::INFINITY }.should be_nil
+      end
+
+      it "returns an element at an index for which block returns 0.0" do
+        result = eval("(0..)").bsearch { |x| x < 2 ? 1.0 : x > 2 ? -1.0 : 0.0 }
+        result.should == 2
+      end
+
+      it "returns an element at an index for which block returns 0" do
+        result = eval("(0..)").bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
+        [1, 2, 3].should include(result)
+      end
+    end
+
+    it "returns enumerator when block not passed" do
+      eval("(-2..)").bsearch.kind_of?(Enumerator).should == true
+    end
+  end
+
+  context "with endless ranges and Float values" do
+    context "with a block returning true or false" do
+      it "returns nil if the block returns false for every element" do
+        eval("(0.1..)").bsearch { |x| x < 0.0 }.should be_nil
+        eval("(0.1...)").bsearch { |x| x < 0.0 }.should be_nil
+      end
+
+      it "returns nil if the block returns nil for every element" do
+        eval("(-0.0..)").bsearch { |x| nil }.should be_nil
+        eval("(-0.0...)").bsearch { |x| nil }.should be_nil
+      end
+
+      it "returns minimum element if the block returns true for every element" do
+        eval("(-0.2..)").bsearch { |x| true }.should == -0.2
+        eval("(-0.2...)").bsearch { |x| true }.should == -0.2
+      end
+
+      it "returns the smallest element for which block returns true" do
+        eval("(0..)").bsearch { |x| x >= 2 }.should == 2
+        eval("(-1.2..)").bsearch { |x| x >= 1 }.should == 1
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        eval("(inf..)").bsearch { |x| true }.should == inf
+        eval("(inf...)").bsearch { |x| true }.should == nil
+        eval("(-inf..)").bsearch { |x| true }.should == -inf
+        eval("(-inf...)").bsearch { |x| true }.should == -inf
+      end
+    end
+
+    context "with a block returning negative, zero, positive numbers" do
+      it "returns nil if the block returns less than zero for every element" do
+        eval("(-2.0..)").bsearch { |x| -1 }.should be_nil
+        eval("(-2.0...)").bsearch { |x| -1 }.should be_nil
+      end
+
+      it "returns nil if the block returns greater than zero for every element" do
+        eval("(0.3..)").bsearch { |x| 1 }.should be_nil
+        eval("(0.3...)").bsearch { |x| 1 }.should be_nil
+      end
+
+      it "returns nil if the block never returns zero" do
+        eval("(0.2..)").bsearch { |x| x < 2 ? 1 : -1 }.should be_nil
+      end
+
+      it "accepts (+/-)Float::INFINITY from the block" do
+        eval("(0.1..)").bsearch { |x| Float::INFINITY }.should be_nil
+        eval("(-5.0..)").bsearch { |x| -Float::INFINITY }.should be_nil
+      end
+
+      it "returns an element at an index for which block returns 0.0" do
+        result = eval("(0.0..)").bsearch { |x| x < 2 ? 1.0 : x > 2 ? -1.0 : 0.0 }
+        result.should == 2
+      end
+
+      it "returns an element at an index for which block returns 0" do
+        result = eval("(0.1..)").bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
+        result.should >= 1
+        result.should <= 3
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        eval("(inf..)").bsearch { |x| 1 }.should == nil
+        eval("(inf...)").bsearch { |x| 1 }.should == nil
+        eval("(inf..)").bsearch { |x| x == inf ? 0 : 1 }.should == inf
+        eval("(inf...)").bsearch { |x| x == inf ? 0 : 1 }.should == nil
+        eval("(-inf..)").bsearch { |x| x == -inf ? 0 : -1 }.should == -inf
+        eval("(-inf...)").bsearch { |x| x == -inf ? 0 : -1 }.should == -inf
+        eval("(-inf..)").bsearch { |x| 3 - x }.should == 3
+        eval("(-inf...)").bsearch { |x| 3 - x }.should == 3
+        eval("(0.0...)").bsearch { 0 }.should != inf
+      end
+    end
+
+    it "returns enumerator when block not passed" do
+      eval("(0.1..)").bsearch.kind_of?(Enumerator).should == true
+    end
+  end
+
+  context "with beginless ranges and Integer values" do
+    context "with a block returning true or false" do
+      it "returns the smallest element for which block returns true" do
+        (..10).bsearch { |x| x >= 2 }.should == 2
+        (...-1).bsearch { |x| x >= -10 }.should == -10
+      end
+    end
+
+    context "with a block returning negative, zero, positive numbers" do
+      it "returns nil if the block returns greater than zero for every element" do
+        (..0).bsearch { |x| 1 }.should be_nil
+      end
+
+      it "returns nil if the block never returns zero" do
+        (..0).bsearch { |x| x > 5 ? -1 : 1 }.should be_nil
+      end
+
+      it "accepts Float::INFINITY from the block" do
+        (..0).bsearch { |x| Float::INFINITY }.should be_nil
+      end
+
+      it "returns an element at an index for which block returns 0.0" do
+        result = (..10).bsearch { |x| x < 2 ? 1.0 : x > 2 ? -1.0 : 0.0 }
+        result.should == 2
+      end
+
+      it "returns an element at an index for which block returns 0" do
+        result = (...10).bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
+        [1, 2, 3].should include(result)
+      end
+    end
+
+    it "returns enumerator when block not passed" do
+      (..10).bsearch.kind_of?(Enumerator).should == true
+    end
+  end
+
+  context "with beginless ranges and Float values" do
+    context "with a block returning true or false" do
+      it "returns nil if the block returns true for every element" do
+        (..-0.1).bsearch { |x| x > 0.0 }.should be_nil
+        (...-0.1).bsearch { |x| x > 0.0 }.should be_nil
+      end
+
+      it "returns nil if the block returns nil for every element" do
+        (..-0.1).bsearch { |x| nil }.should be_nil
+        (...-0.1).bsearch { |x| nil }.should be_nil
+      end
+
+      it "returns the smallest element for which block returns true" do
+        (..10).bsearch { |x| x >= 2 }.should == 2
+        (..10).bsearch { |x| x >= 1 }.should == 1
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        (..inf).bsearch { |x| true }.should == -inf
+        (...inf).bsearch { |x| true }.should == -inf
+        (..-inf).bsearch { |x| true }.should == -inf
+        (...-inf).bsearch { |x| true }.should == nil
+      end
+    end
+
+    context "with a block returning negative, zero, positive numbers" do
+      it "returns nil if the block returns less than zero for every element" do
+        (..5.0).bsearch { |x| -1 }.should be_nil
+        (...5.0).bsearch { |x| -1 }.should be_nil
+      end
+
+      it "returns nil if the block returns greater than zero for every element" do
+        (..1.1).bsearch { |x| 1 }.should be_nil
+        (...1.1).bsearch { |x| 1 }.should be_nil
+      end
+
+      it "returns nil if the block never returns zero" do
+        (..6.3).bsearch { |x| x < 2 ? 1 : -1 }.should be_nil
+      end
+
+      it "accepts (+/-)Float::INFINITY from the block" do
+        (..5.0).bsearch { |x| Float::INFINITY }.should be_nil
+        (..7.0).bsearch { |x| -Float::INFINITY }.should be_nil
+      end
+
+      it "returns an element at an index for which block returns 0.0" do
+        result = (..8.0).bsearch { |x| x < 2 ? 1.0 : x > 2 ? -1.0 : 0.0 }
+        result.should == 2
+      end
+
+      it "returns an element at an index for which block returns 0" do
+        result = (..8.0).bsearch { |x| x < 1 ? 1 : x > 3 ? -1 : 0 }
+        result.should >= 1
+        result.should <= 3
+      end
+
+      it "works with infinity bounds" do
+        inf = Float::INFINITY
+        (..-inf).bsearch { |x| 1 }.should == nil
+        (...-inf).bsearch { |x| 1 }.should == nil
+        (..inf).bsearch { |x| x == inf ? 0 : 1 }.should == inf
+        (...inf).bsearch { |x| x == inf ? 0 : 1 }.should == nil
+        (..-inf).bsearch { |x| x == -inf ? 0 : -1 }.should == -inf
+        (...-inf).bsearch { |x| x == -inf ? 0 : -1 }.should == nil
+        (..inf).bsearch { |x| 3 - x }.should == 3
+        (...inf).bsearch { |x| 3 - x }.should == 3
+      end
+    end
+
+    it "returns enumerator when block not passed" do
+      (..-0.1).bsearch.kind_of?(Enumerator).should == true
+    end
   end
 end
diff --git a/spec/ruby/core/range/case_compare_spec.rb b/spec/ruby/core/range/case_compare_spec.rb
index 0ca03f6a35..c9b253f0a5 100644
--- a/spec/ruby/core/range/case_compare_spec.rb
+++ b/spec/ruby/core/range/case_compare_spec.rb
@@ -3,26 +3,17 @@ require_relative 'shared/cover_and_include'
 require_relative 'shared/cover'
 
 describe "Range#===" do
-  ruby_version_is ""..."2.6" do
-    it "returns the result of calling #include? on self" do
-      range = 0...10
-      range.should_receive(:include?).with(2).and_return(:true)
-      (range === 2).should == :true
-    end
-
-    it "requires #succ method to be implemented" do
-      range = RangeSpecs::WithoutSucc.new(0)..RangeSpecs::WithoutSucc.new(10)
-
-      -> do
-        range === RangeSpecs::WithoutSucc.new(2)
-      end.should raise_error(TypeError, /can't iterate from/)
-    end
+  it "returns the result of calling #cover? on self" do
+    range = RangeSpecs::WithoutSucc.new(0)..RangeSpecs::WithoutSucc.new(10)
+    (range === RangeSpecs::WithoutSucc.new(2)).should == true
   end
 
-  ruby_version_is "2.6" do
-    it "returns the result of calling #cover? on self" do
-      range = RangeSpecs::WithoutSucc.new(0)..RangeSpecs::WithoutSucc.new(10)
-      (range === RangeSpecs::WithoutSucc.new(2)).should == true
+  it_behaves_like :range_cover_and_include, :===
+  it_behaves_like :range_cover, :===
+
+  ruby_bug "#19533", ""..."3.3" do
+    it "returns true on any value if begin and end are both nil" do
+      (nil..nil).should === 1
     end
   end
 end
diff --git a/spec/ruby/core/range/clone_spec.rb b/spec/ruby/core/range/clone_spec.rb
new file mode 100644
index 0000000000..cf6ce74da0
--- /dev/null
+++ b/spec/ruby/core/range/clone_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+describe "Range#clone" do
+  it "duplicates the range" do
+    original = (1..3)
+    copy = original.clone
+    copy.begin.should == 1
+    copy.end.should == 3
+    copy.should_not.exclude_end?
+    copy.should_not.equal? original
+
+    original = ("a"..."z")
+    copy = original.clone
+    copy.begin.should == "a"
+    copy.end.should == "z"
+    copy.should.exclude_end?
+    copy.should_not.equal? original
+  end
+
+  it "maintains the frozen state" do
+    (1..2).clone.frozen?.should == (1..2).frozen?
+    (1..).clone.frozen?.should == (1..).frozen?
+    Range.new(1, 2).clone.frozen?.should == Range.new(1, 2).frozen?
+    Class.new(Range).new(1, 2).clone.frozen?.should == Class.new(Range).new(1, 2).frozen?
+  end
+end
diff --git a/spec/ruby/core/range/count_spec.rb b/spec/ruby/core/range/count_spec.rb
new file mode 100644
index 0000000000..24d4a9caf3
--- /dev/null
+++ b/spec/ruby/core/range/count_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+
+describe "Range#count" do
+  it "returns Infinity for beginless ranges without arguments or blocks" do
+    inf = Float::INFINITY
+    eval("('a'...)").count.should == inf
+    eval("(7..)").count.should == inf
+    (...'a').count.should == inf
+    (...nil).count.should == inf
+    (..10.0).count.should == inf
+  end
+end
diff --git a/spec/ruby/core/range/cover_spec.rb b/spec/ruby/core/range/cover_spec.rb
index 29c0e0bfa8..c05bb50614 100644
--- a/spec/ruby/core/range/cover_spec.rb
+++ b/spec/ruby/core/range/cover_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/cover_and_include'
 require_relative 'shared/cover'
@@ -6,4 +6,9 @@ require_relative 'shared/cover'
 describe "Range#cover?" do
   it_behaves_like :range_cover_and_include, :cover?
   it_behaves_like :range_cover, :cover?
+  it_behaves_like :range_cover_subrange, :cover?
+
+  it "covers U+9995 in the range U+0999..U+9999" do
+    ("\u{999}".."\u{9999}").cover?("\u{9995}").should be_true
+  end
 end
diff --git a/spec/ruby/core/range/dup_spec.rb b/spec/ruby/core/range/dup_spec.rb
index d1c029c6b7..fab3c3f1b2 100644
--- a/spec/ruby/core/range/dup_spec.rb
+++ b/spec/ruby/core/range/dup_spec.rb
@@ -2,14 +2,22 @@ require_relative '../../spec_helper'
 
 describe "Range#dup" do
   it "duplicates the range" do
-    copy = (1..3).dup
+    original = (1..3)
+    copy = original.dup
     copy.begin.should == 1
     copy.end.should == 3
-    copy.exclude_end?.should == false
+    copy.should_not.exclude_end?
+    copy.should_not.equal?(original)
 
     copy = ("a"..."z").dup
     copy.begin.should == "a"
     copy.end.should == "z"
-    copy.exclude_end?.should == true
+    copy.should.exclude_end?
+  end
+
+  it "creates an unfrozen range" do
+    (1..2).dup.should_not.frozen?
+    (1..).dup.should_not.frozen?
+    Range.new(1, 2).dup.should_not.frozen?
   end
 end
diff --git a/spec/ruby/core/range/each_spec.rb b/spec/ruby/core/range/each_spec.rb
index 110b0602d0..f10330d61d 100644
--- a/spec/ruby/core/range/each_spec.rb
+++ b/spec/ruby/core/range/each_spec.rb
@@ -32,6 +32,36 @@ describe "Range#each" do
     a.should == [x, y]
   end
 
+  it "works for non-ASCII ranges" do
+    a = []
+    ('Σ'..'Ω').each { |i| a << i }
+    a.should == ["Σ", "Τ", "Υ", "Φ", "Χ", "Ψ", "Ω"]
+  end
+
+  it "works with endless ranges" do
+    a = []
+    (-2..).each { |x| break if x > 2; a << x }
+    a.should == [-2, -1, 0, 1, 2]
+
+    a = []
+    (-2...).each { |x| break if x > 2; a << x }
+    a.should == [-2, -1, 0, 1, 2]
+  end
+
+  it "works with String endless ranges" do
+    a = []
+    ('A'..).each { |x| break if x > "D"; a << x }
+    a.should == ["A", "B", "C", "D"]
+
+    a = []
+    ('A'...).each { |x| break if x > "D"; a << x }
+    a.should == ["A", "B", "C", "D"]
+  end
+
+  it "raises a TypeError beginless ranges" do
+    -> { (..2).each { |x| x } }.should raise_error(TypeError)
+  end
+
   it "raises a TypeError if the first element does not respond to #succ" do
     -> { (0.5..2.4).each { |i| i } }.should raise_error(TypeError)
 
@@ -52,9 +82,14 @@ describe "Range#each" do
     enum.to_a.should == [1, 2, 3]
   end
 
-  it "raises a TypeError if the first element is a Time object" do
-    t = Time.now
-    -> { (t..t+1).each { |i| i } }.should raise_error(TypeError)
+  it "supports Time objects that respond to #succ" do
+    t = Time.utc(1970)
+    def t.succ; self + 1 end
+    t_succ = t.succ
+    def t_succ.succ; self + 1; end
+
+    (t..t_succ).to_a.should == [Time.utc(1970), Time.utc(1970, nil, nil, nil, nil, 1)]
+    (t...t_succ).to_a.should == [Time.utc(1970)]
   end
 
   it "passes each Symbol element by using #succ" do
diff --git a/spec/ruby/core/range/equal_value_spec.rb b/spec/ruby/core/range/equal_value_spec.rb
index 889557fc2a..83dcf5cec8 100644
--- a/spec/ruby/core/range/equal_value_spec.rb
+++ b/spec/ruby/core/range/equal_value_spec.rb
@@ -7,4 +7,12 @@ describe "Range#==" do
   it "returns true if the endpoints are ==" do
     (0..1).should == (0..1.0)
   end
+
+  it "returns true if the endpoints are == for endless ranges" do
+    eval("(1.0..)").should == eval("(1.0..)")
+  end
+
+  it "returns true if the endpoints are == for beginless ranges" do
+    (...10).should == (...10)
+  end
 end
diff --git a/spec/ruby/core/range/exclude_end_spec.rb b/spec/ruby/core/range/exclude_end_spec.rb
index a209603d18..c4006fea78 100644
--- a/spec/ruby/core/range/exclude_end_spec.rb
+++ b/spec/ruby/core/range/exclude_end_spec.rb
@@ -2,18 +2,18 @@ require_relative '../../spec_helper'
 
 describe "Range#exclude_end?" do
   it "returns false if the range does not exclude the end value" do
-    (-2..2).exclude_end?.should == false
-    ('A'..'B').exclude_end?.should == false
-    (0.5..2.4).exclude_end?.should == false
-    (0xfffd..0xffff).exclude_end?.should == false
-    Range.new(0, 1).exclude_end?.should == false
+    (-2..2).should_not.exclude_end?
+    ('A'..'B').should_not.exclude_end?
+    (0.5..2.4).should_not.exclude_end?
+    (0xfffd..0xffff).should_not.exclude_end?
+    Range.new(0, 1).should_not.exclude_end?
   end
 
   it "returns true if the range excludes the end value" do
-    (0...5).exclude_end?.should == true
-    ('A'...'B').exclude_end?.should == true
-    (0.5...2.4).exclude_end?.should == true
-    (0xfffd...0xffff).exclude_end?.should == true
-    Range.new(0, 1, true).exclude_end?.should == true
+    (0...5).should.exclude_end?
+    ('A'...'B').should.exclude_end?
+    (0.5...2.4).should.exclude_end?
+    (0xfffd...0xffff).should.exclude_end?
+    Range.new(0, 1, true).should.exclude_end?
   end
 end
diff --git a/spec/ruby/core/range/first_spec.rb b/spec/ruby/core/range/first_spec.rb
index 5f073b48ee..2af935f439 100644
--- a/spec/ruby/core/range/first_spec.rb
+++ b/spec/ruby/core/range/first_spec.rb
@@ -46,4 +46,8 @@ describe "Range#first" do
   it "raises a TypeError when passed a String" do
     -> { (2..3).first("1") }.should raise_error(TypeError)
   end
+
+  it "raises a RangeError when called on an beginless range" do
+    -> { (..1).first }.should raise_error(RangeError)
+  end
 end
diff --git a/spec/ruby/core/range/frozen_spec.rb b/spec/ruby/core/range/frozen_spec.rb
new file mode 100644
index 0000000000..8dab5e5339
--- /dev/null
+++ b/spec/ruby/core/range/frozen_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+
+# There is no Range#frozen? method but this feels like the best place for these specs
+describe "Range#frozen?" do
+  it "is true for literal ranges" do
+    (1..2).should.frozen?
+    (1..).should.frozen?
+    (..1).should.frozen?
+  end
+
+  it "is true for Range.new" do
+    Range.new(1, 2).should.frozen?
+    Range.new(1, nil).should.frozen?
+    Range.new(nil, 1).should.frozen?
+  end
+
+  it "is false for instances of a subclass of Range" do
+    sub_range = Class.new(Range).new(1, 2)
+    sub_range.should_not.frozen?
+  end
+
+  it "is false for Range.allocate" do
+    Range.allocate.should_not.frozen?
+  end
+end
diff --git a/spec/ruby/core/range/hash_spec.rb b/spec/ruby/core/range/hash_spec.rb
index 90aeee7890..4f2681e86e 100644
--- a/spec/ruby/core/range/hash_spec.rb
+++ b/spec/ruby/core/range/hash_spec.rb
@@ -14,11 +14,11 @@ describe "Range#hash" do
     (0..10).hash.should_not == (0...10).hash
   end
 
-  it "generates a Fixnum for the hash value" do
-    (0..0).hash.should be_an_instance_of(Fixnum)
-    (0..1).hash.should be_an_instance_of(Fixnum)
-    (0...10).hash.should be_an_instance_of(Fixnum)
-    (0..10).hash.should be_an_instance_of(Fixnum)
+  it "generates an Integer for the hash value" do
+    (0..0).hash.should be_an_instance_of(Integer)
+    (0..1).hash.should be_an_instance_of(Integer)
+    (0...10).hash.should be_an_instance_of(Integer)
+    (0..10).hash.should be_an_instance_of(Integer)
   end
 
 end
diff --git a/spec/ruby/core/range/include_spec.rb b/spec/ruby/core/range/include_spec.rb
index b2c7a54545..449e18985b 100644
--- a/spec/ruby/core/range/include_spec.rb
+++ b/spec/ruby/core/range/include_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/cover_and_include'
 require_relative 'shared/include'
@@ -7,4 +7,8 @@ require_relative 'shared/cover'
 describe "Range#include?" do
   it_behaves_like :range_cover_and_include, :include?
   it_behaves_like :range_include, :include?
+
+  it "does not include U+9995 in the range U+0999..U+9999" do
+    ("\u{999}".."\u{9999}").include?("\u{9995}").should be_false
+  end
 end
diff --git a/spec/ruby/core/range/initialize_spec.rb b/spec/ruby/core/range/initialize_spec.rb
index 8caf12baa2..c653caf0c6 100644
--- a/spec/ruby/core/range/initialize_spec.rb
+++ b/spec/ruby/core/range/initialize_spec.rb
@@ -27,9 +27,9 @@ describe "Range#initialize" do
     -> { @range.send(:initialize, 1, 3, 5, 7, 9) }.should raise_error(ArgumentError)
   end
 
-  it "raises a NameError if called on an already initialized Range" do
-    -> { (0..1).send(:initialize, 1, 3) }.should raise_error(NameError)
-    -> { (0..1).send(:initialize, 1, 3, true) }.should raise_error(NameError)
+  it "raises a FrozenError if called on an already initialized Range" do
+    -> { (0..1).send(:initialize, 1, 3) }.should raise_error(FrozenError)
+    -> { (0..1).send(:initialize, 1, 3, true) }.should raise_error(FrozenError)
   end
 
   it "raises an ArgumentError if arguments don't respond to <=>" do
diff --git a/spec/ruby/core/range/inspect_spec.rb b/spec/ruby/core/range/inspect_spec.rb
index 3c130812d0..072de123b7 100644
--- a/spec/ruby/core/range/inspect_spec.rb
+++ b/spec/ruby/core/range/inspect_spec.rb
@@ -12,15 +12,18 @@ describe "Range#inspect" do
     (0.5..2.4).inspect.should == "0.5..2.4"
   end
 
-  it "returns a tainted string if either end is tainted" do
-    (("a".taint)..."c").inspect.tainted?.should be_true
-    ("a"...("c".taint)).inspect.tainted?.should be_true
-    ("a"..."c").taint.inspect.tainted?.should be_true
+  it "works for endless ranges" do
+    eval("(1..)").inspect.should ==  "1.."
+    eval("(0.1...)").inspect.should ==  "0.1..."
   end
 
-  it "returns a untrusted string if either end is untrusted" do
-    (("a".untrust)..."c").inspect.untrusted?.should be_true
-    ("a"...("c".untrust)).inspect.untrusted?.should be_true
-    ("a"..."c").untrust.inspect.untrusted?.should be_true
+  it "works for beginless ranges" do
+    (..1).inspect.should ==  "..1"
+    (...0.1).inspect.should ==  "...0.1"
+  end
+
+  it "works for nil ... nil ranges" do
+    (..nil).inspect.should ==  "nil..nil"
+    eval("(nil...)").inspect.should ==  "nil...nil"
   end
 end
diff --git a/spec/ruby/core/range/last_spec.rb b/spec/ruby/core/range/last_spec.rb
index c7e629e62c..82b3e2ff53 100644
--- a/spec/ruby/core/range/last_spec.rb
+++ b/spec/ruby/core/range/last_spec.rb
@@ -8,6 +8,10 @@ describe "Range#last" do
     (1..5).last(3).should == [3, 4, 5]
   end
 
+  it "returns the specified number if elements for single element inclusive range" do
+    (1..1).last(1).should == [1]
+  end
+
   it "returns an empty array for an empty Range" do
     (0...0).last(2).should == []
   end
@@ -46,4 +50,8 @@ describe "Range#last" do
   it "raises a TypeError when passed a String" do
     -> { (2..3).last("1") }.should raise_error(TypeError)
   end
+
+  it "raises a RangeError when called on an endless range" do
+    -> { eval("(1..)").last }.should raise_error(RangeError)
+  end
 end
diff --git a/spec/ruby/core/range/max_spec.rb b/spec/ruby/core/range/max_spec.rb
index faac0a2032..09371f5298 100644
--- a/spec/ruby/core/range/max_spec.rb
+++ b/spec/ruby/core/range/max_spec.rb
@@ -45,6 +45,35 @@ describe "Range#max" do
     time_end = Time.now + 1.0
     -> { (time_start...time_end).max  }.should raise_error(TypeError)
   end
+
+  it "raises RangeError when called on an endless range" do
+    -> { eval("(1..)").max }.should raise_error(RangeError)
+  end
+
+  it "returns the end point for beginless ranges" do
+    (..1).max.should == 1
+    (..1.0).max.should == 1.0
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "raises for an exclusive beginless Integer range" do
+      -> {
+        (...1).max
+      }.should raise_error(TypeError, 'cannot exclude end value with non Integer begin value')
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "returns the end point for exclusive beginless Integer ranges" do
+      (...1).max.should == 0
+    end
+  end
+
+  it "raises for an exclusive beginless non Integer range" do
+    -> {
+      (...1.0).max
+    }.should raise_error(TypeError, 'cannot exclude non Integer end value')
+  end
 end
 
 describe "Range#max given a block" do
@@ -79,4 +108,8 @@ describe "Range#max given a block" do
     ('z'..'l').max {|x,y| x <=> y}.should be_nil
     (5...5).max {|x,y| x <=> y}.should be_nil
   end
+
+  it "raises RangeError when called with custom comparison method on an beginless range" do
+    -> { (..1).max {|a, b| a} }.should raise_error(RangeError)
+  end
 end
diff --git a/spec/ruby/core/range/member_spec.rb b/spec/ruby/core/range/member_spec.rb
index ab61f92951..78299ae9e5 100644
--- a/spec/ruby/core/range/member_spec.rb
+++ b/spec/ruby/core/range/member_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/cover_and_include'
 require_relative 'shared/include'
diff --git a/spec/ruby/core/range/min_spec.rb b/spec/ruby/core/range/min_spec.rb
index 424bd1dc87..89310ee589 100644
--- a/spec/ruby/core/range/min_spec.rb
+++ b/spec/ruby/core/range/min_spec.rb
@@ -38,6 +38,15 @@ describe "Range#min" do
     time_end = Time.now + 1.0
     (time_start...time_end).min.should equal(time_start)
   end
+
+  it "returns the start point for endless ranges" do
+    eval("(1..)").min.should == 1
+    eval("(1.0...)").min.should == 1.0
+  end
+
+  it "raises RangeError when called on an beginless range" do
+    -> { (..1).min }.should raise_error(RangeError)
+  end
 end
 
 describe "Range#min given a block" do
@@ -72,4 +81,8 @@ describe "Range#min given a block" do
     ('z'..'l').min {|x,y| x <=> y}.should be_nil
     (7...7).min {|x,y| x <=> y}.should be_nil
   end
+
+  it "raises RangeError when called with custom comparison method on an endless range" do
+    -> { eval("(1..)").min {|a, b| a} }.should raise_error(RangeError)
+  end
 end
diff --git a/spec/ruby/core/range/minmax_spec.rb b/spec/ruby/core/range/minmax_spec.rb
new file mode 100644
index 0000000000..6651ae3726
--- /dev/null
+++ b/spec/ruby/core/range/minmax_spec.rb
@@ -0,0 +1,130 @@
+require_relative '../../spec_helper'
+
+describe 'Range#minmax' do
+  before(:each) do
+    @x = mock('x')
+    @y = mock('y')
+
+    @x.should_receive(:<=>).with(@y).any_number_of_times.and_return(-1) # x < y
+    @x.should_receive(:<=>).with(@x).any_number_of_times.and_return(0) # x == x
+    @y.should_receive(:<=>).with(@x).any_number_of_times.and_return(1) # y > x
+    @y.should_receive(:<=>).with(@y).any_number_of_times.and_return(0) # y == y
+  end
+
+  describe 'on an inclusive range' do
+    it 'should raise RangeError on an endless range without iterating the range' do
+      @x.should_not_receive(:succ)
+
+      range = (@x..)
+
+      -> { range.minmax }.should raise_error(RangeError, 'cannot get the maximum of endless range')
+    end
+
+    it 'raises RangeError or ArgumentError on a beginless range' do
+      range = (..@x)
+
+      -> { range.minmax }.should raise_error(StandardError) { |e|
+        if RangeError === e
+          # error from #min
+          -> { raise e }.should raise_error(RangeError, 'cannot get the minimum of beginless range')
+        else
+          # error from #max
+          -> { raise e }.should raise_error(ArgumentError, 'comparison of NilClass with MockObject failed')
+        end
+      }
+    end
+
+    it 'should return beginning of range if beginning and end are equal without iterating the range' do
+      @x.should_not_receive(:succ)
+
+      (@x..@x).minmax.should == [@x, @x]
+    end
+
+    it 'should return nil pair if beginning is greater than end without iterating the range' do
+      @y.should_not_receive(:succ)
+
+      (@y..@x).minmax.should == [nil, nil]
+    end
+
+    it 'should return the minimum and maximum values for a non-numeric range without iterating the range' do
+      @x.should_not_receive(:succ)
+
+      (@x..@y).minmax.should == [@x, @y]
+    end
+
+    it 'should return the minimum and maximum values for a numeric range' do
+      (1..3).minmax.should == [1, 3]
+    end
+
+    it 'should return the minimum and maximum values for a numeric range without iterating the range' do
+      # We cannot set expectations on integers,
+      # so we "prevent" iteration by picking a value that would iterate until the spec times out.
+      range_end = Float::INFINITY
+
+      (1..range_end).minmax.should == [1, range_end]
+    end
+
+    it 'should return the minimum and maximum values according to the provided block by iterating the range' do
+      @x.should_receive(:succ).once.and_return(@y)
+
+      (@x..@y).minmax { |x, y| - (x <=> y) }.should == [@y, @x]
+    end
+  end
+
+  describe 'on an exclusive range' do
+    it 'should raise RangeError on an endless range' do
+      @x.should_not_receive(:succ)
+      range = (@x...)
+
+      -> { range.minmax }.should raise_error(RangeError, 'cannot get the maximum of endless range')
+    end
+
+    it 'should raise RangeError on a beginless range' do
+      range = (...@x)
+
+      -> { range.minmax }.should raise_error(RangeError,
+        /cannot get the maximum of beginless range with custom comparison method|cannot get the minimum of beginless range/)
+    end
+
+    it 'should return nil pair if beginning and end are equal without iterating the range' do
+      @x.should_not_receive(:succ)
+
+      (@x...@x).minmax.should == [nil, nil]
+    end
+
+    it 'should return nil pair if beginning is greater than end without iterating the range' do
+      @y.should_not_receive(:succ)
+
+      (@y...@x).minmax.should == [nil, nil]
+    end
+
+    it 'should return the minimum and maximum values for a non-numeric range by iterating the range' do
+      @x.should_receive(:succ).once.and_return(@y)
+
+      (@x...@y).minmax.should == [@x, @x]
+    end
+
+    it 'should return the minimum and maximum values for a numeric range' do
+      (1...3).minmax.should == [1, 2]
+    end
+
+    it 'should return the minimum and maximum values for a numeric range without iterating the range' do
+      # We cannot set expectations on integers,
+      # so we "prevent" iteration by picking a value that would iterate until the spec times out.
+      range_end = bignum_value
+
+      (1...range_end).minmax.should == [1, range_end - 1]
+    end
+
+    it 'raises TypeError if the end value is not an integer' do
+      range = (0...Float::INFINITY)
+      -> { range.minmax }.should raise_error(TypeError, 'cannot exclude non Integer end value')
+    end
+
+    it 'should return the minimum and maximum values according to the provided block by iterating the range' do
+      @x.should_receive(:succ).once.and_return(@y)
+
+      (@x...@y).minmax { |x, y| - (x <=> y) }.should == [@x, @x]
+    end
+  end
+end
diff --git a/spec/ruby/core/range/new_spec.rb b/spec/ruby/core/range/new_spec.rb
index 9ed2b65d5a..3cab887799 100644
--- a/spec/ruby/core/range/new_spec.rb
+++ b/spec/ruby/core/range/new_spec.rb
@@ -33,55 +33,45 @@ describe "Range.new" do
     -> { Range.new(a, b) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.5" do
-    it "does not rescue exception raised in #<=> when compares the given start and end" do
-      b = mock('a')
-      a = mock('b')
-      a.should_receive(:<=>).with(b).and_raise(RangeSpecs::ComparisonError)
+  it "does not rescue exception raised in #<=> when compares the given start and end" do
+    b = mock('a')
+    a = mock('b')
+    a.should_receive(:<=>).with(b).and_raise(RangeSpecs::ComparisonError)
 
-      -> { Range.new(a, b) }.should raise_error(RangeSpecs::ComparisonError)
-    end
+    -> { Range.new(a, b) }.should raise_error(RangeSpecs::ComparisonError)
   end
 
   describe "beginless/endless range" do
-    ruby_version_is ""..."2.7" do
-      it "does not allow range without left boundary" do
-        -> { Range.new(nil, 1) }.should raise_error(ArgumentError, /bad value for range/)
-      end
+    it "allows beginless left boundary" do
+      range = Range.new(nil, 1)
+      range.begin.should == nil
     end
 
-    ruby_version_is "2.7" do
-      it "allows beginless left boundary" do
-        range = Range.new(nil, 1)
-        range.begin.should == nil
-      end
-
-      it "distinguishes ranges with included and excluded right boundary" do
-        range_exclude = Range.new(nil, 1, true)
-        range_include = Range.new(nil, 1, false)
+    it "distinguishes ranges with included and excluded right boundary" do
+      range_exclude = Range.new(nil, 1, true)
+      range_include = Range.new(nil, 1, false)
 
-        range_exclude.should_not == range_include
-      end
+      range_exclude.should_not == range_include
     end
 
-    ruby_version_is ""..."2.6" do
-      it "does not allow range without right boundary" do
-        -> { Range.new(1, nil) }.should raise_error(ArgumentError, /bad value for range/)
-      end
+    it "allows endless right boundary" do
+      range = Range.new(1, nil)
+      range.end.should == nil
     end
 
-    ruby_version_is "2.6" do
-      it "allows endless right boundary" do
-        range = Range.new(1, nil)
-        range.end.should == nil
-      end
+    it "distinguishes ranges with included and excluded right boundary" do
+      range_exclude = Range.new(1, nil, true)
+      range_include = Range.new(1, nil, false)
 
-      it "distinguishes ranges with included and excluded right boundary" do
-        range_exclude = Range.new(1, nil, true)
-        range_include = Range.new(1, nil, false)
+      range_exclude.should_not == range_include
+    end
+
+    it "creates a frozen range if the class is Range.class" do
+      Range.new(1, 2).should.frozen?
+    end
 
-        range_exclude.should_not == range_include
-      end
+    it "does not create a frozen range if the class is not Range.class" do
+      Class.new(Range).new(1, 2).should_not.frozen?
     end
   end
 end
diff --git a/spec/ruby/core/range/overlap_spec.rb b/spec/ruby/core/range/overlap_spec.rb
new file mode 100644
index 0000000000..9b6fc13493
--- /dev/null
+++ b/spec/ruby/core/range/overlap_spec.rb
@@ -0,0 +1,89 @@
+require_relative '../../spec_helper'
+
+ruby_version_is '3.3' do
+  describe "Range#overlap?" do
+    it "returns true if other Range overlaps self" do
+      (0..2).overlap?(1..3).should == true
+      (1..3).overlap?(0..2).should == true
+      (0..2).overlap?(0..2).should == true
+      (0..3).overlap?(1..2).should == true
+      (1..2).overlap?(0..3).should == true
+
+      ('a'..'c').overlap?('b'..'d').should == true
+    end
+
+    it "returns false if other Range does not overlap self" do
+      (0..2).overlap?(3..4).should == false
+      (0..2).overlap?(-4..-1).should == false
+
+      ('a'..'c').overlap?('d'..'f').should == false
+    end
+
+    it "raises TypeError when called with non-Range argument" do
+      -> {
+        (0..2).overlap?(1)
+      }.should raise_error(TypeError, "wrong argument type Integer (expected Range)")
+    end
+
+    it "returns true when beginningless and endless Ranges overlap" do
+      (0..2).overlap?(..3).should == true
+      (0..2).overlap?(..1).should == true
+      (0..2).overlap?(..0).should == true
+
+      (..3).overlap?(0..2).should == true
+      (..1).overlap?(0..2).should == true
+      (..0).overlap?(0..2).should == true
+
+      (0..2).overlap?(-1..).should == true
+      (0..2).overlap?(1..).should == true
+      (0..2).overlap?(2..).should == true
+
+      (-1..).overlap?(0..2).should == true
+      (1..).overlap?(0..2).should == true
+      (2..).overlap?(0..2).should == true
+
+      (0..).overlap?(2..).should == true
+      (..0).overlap?(..2).should == true
+    end
+
+    it "returns false when beginningless and endless Ranges do not overlap" do
+      (0..2).overlap?(..-1).should == false
+      (0..2).overlap?(3..).should == false
+
+      (..-1).overlap?(0..2).should == false
+      (3..).overlap?(0..2).should == false
+    end
+
+    it "returns false when Ranges are not compatible" do
+      (0..2).overlap?('a'..'d').should == false
+    end
+
+    it "return false when self is empty" do
+      (2..0).overlap?(1..3).should == false
+      (2...2).overlap?(1..3).should == false
+      (1...1).overlap?(1...1).should == false
+      (2..0).overlap?(2..0).should == false
+
+      ('c'..'a').overlap?('b'..'d').should == false
+      ('a'...'a').overlap?('b'..'d').should == false
+      ('b'...'b').overlap?('b'...'b').should == false
+      ('c'...'a').overlap?('c'...'a').should == false
+    end
+
+    it "return false when other Range is empty" do
+      (1..3).overlap?(2..0).should == false
+      (1..3).overlap?(2...2).should == false
+
+      ('b'..'d').overlap?('c'..'a').should == false
+      ('b'..'d').overlap?('c'...'c').should == false
+    end
+
+    it "takes into account exclusive end" do
+      (0...2).overlap?(2..4).should == false
+      (2..4).overlap?(0...2).should == false
+
+      ('a'...'c').overlap?('c'..'e').should == false
+      ('c'..'e').overlap?('a'...'c').should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/range/percent_spec.rb b/spec/ruby/core/range/percent_spec.rb
index 41badd4f72..5ec6770ddb 100644
--- a/spec/ruby/core/range/percent_spec.rb
+++ b/spec/ruby/core/range/percent_spec.rb
@@ -1,18 +1,16 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.6" do
-  describe "Range#%" do
-    it "works as a Range#step" do
-      aseq = (1..10) % 2
-      aseq.class.should == Enumerator::ArithmeticSequence
-      aseq.begin.should == 1
-      aseq.end.should == 10
-      aseq.step.should == 2
-      aseq.to_a.should == [1, 3, 5, 7, 9]
-    end
+describe "Range#%" do
+  it "works as a Range#step" do
+    aseq = (1..10) % 2
+    aseq.class.should == Enumerator::ArithmeticSequence
+    aseq.begin.should == 1
+    aseq.end.should == 10
+    aseq.step.should == 2
+    aseq.to_a.should == [1, 3, 5, 7, 9]
+  end
 
-    it "produces an arithmetic sequence with a percent sign in #inspect" do
-      ((1..10) % 2).inspect.should == "((1..10).%(2))"
-    end
+  it "produces an arithmetic sequence with a percent sign in #inspect" do
+    ((1..10) % 2).inspect.should == "((1..10).%(2))"
   end
 end
diff --git a/spec/ruby/core/range/reverse_each_spec.rb b/spec/ruby/core/range/reverse_each_spec.rb
new file mode 100644
index 0000000000..56390cc0da
--- /dev/null
+++ b/spec/ruby/core/range/reverse_each_spec.rb
@@ -0,0 +1,103 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.3" do
+  describe "Range#reverse_each" do
+    it "traverses the Range in reverse order and passes each element to block" do
+      a = []
+      (1..3).reverse_each { |i| a << i }
+      a.should == [3, 2, 1]
+
+      a = []
+      (1...3).reverse_each { |i| a << i }
+      a.should == [2, 1]
+    end
+
+    it "returns self" do
+      r = (1..3)
+      r.reverse_each { |x| }.should equal(r)
+    end
+
+    it "returns an Enumerator if no block given" do
+      enum = (1..3).reverse_each
+      enum.should be_an_instance_of(Enumerator)
+      enum.to_a.should == [3, 2, 1]
+    end
+
+    it "raises a TypeError for endless Ranges of Integers" do
+      -> {
+        (1..).reverse_each.take(3)
+      }.should raise_error(TypeError, "can't iterate from NilClass")
+    end
+
+    it "raises a TypeError for endless Ranges of non-Integers" do
+      -> {
+        ("a"..).reverse_each.take(3)
+      }.should raise_error(TypeError, "can't iterate from NilClass")
+    end
+
+    context "Integer boundaries" do
+      it "supports beginningless Ranges" do
+        (..5).reverse_each.take(3).should == [5, 4, 3]
+      end
+    end
+
+    context "non-Integer boundaries" do
+      it "uses #succ to iterate a Range of non-Integer elements" do
+        y = mock('y')
+        x = mock('x')
+
+        x.should_receive(:succ).any_number_of_times.and_return(y)
+        x.should_receive(:<=>).with(y).any_number_of_times.and_return(-1)
+        x.should_receive(:<=>).with(x).any_number_of_times.and_return(0)
+        y.should_receive(:<=>).with(x).any_number_of_times.and_return(1)
+        y.should_receive(:<=>).with(y).any_number_of_times.and_return(0)
+
+        a = []
+        (x..y).each { |i| a << i }
+        a.should == [x, y]
+      end
+
+      it "uses #succ to iterate a Range of Strings" do
+        a = []
+        ('A'..'D').reverse_each { |i| a << i }
+        a.should == ['D','C','B','A']
+      end
+
+      it "uses #succ to iterate a Range of Symbols" do
+        a = []
+        (:A..:D).reverse_each { |i| a << i }
+        a.should == [:D, :C, :B, :A]
+      end
+
+      it "raises a TypeError when `begin` value does not respond to #succ" do
+        -> { (Time.now..Time.now).reverse_each { |x| x } }.should raise_error(TypeError, /can't iterate from Time/)
+        -> { (//..//).reverse_each { |x| x } }.should raise_error(TypeError, /can't iterate from Regexp/)
+        -> { ([]..[]).reverse_each { |x| x } }.should raise_error(TypeError, /can't iterate from Array/)
+      end
+
+      it "does not support beginningless Ranges" do
+        -> {
+          (..'a').reverse_each { |x| x }
+        }.should raise_error(TypeError, /can't iterate from NilClass/)
+      end
+    end
+
+    context "when no block is given" do
+      describe "returned Enumerator size" do
+        it "returns the Range size when Range size is finite" do
+          (1..3).reverse_each.size.should == 3
+        end
+
+        ruby_bug "#20936", "3.4"..."4.0" do
+          it "returns Infinity when Range size is infinite" do
+            (..3).reverse_each.size.should == Float::INFINITY
+          end
+        end
+
+        it "returns nil when Range size is unknown" do
+          ('a'..'z').reverse_each.size.should == nil
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/range/shared/cover.rb b/spec/ruby/core/range/shared/cover.rb
index 33d416fef5..eaefb45942 100644
--- a/spec/ruby/core/range/shared/cover.rb
+++ b/spec/ruby/core/range/shared/cover.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
@@ -90,64 +90,104 @@ describe :range_cover, shared: true do
       end
     end
   end
+end
 
-  ruby_version_is "2.6" do
-    context "range argument" do
-      it "accepts range argument" do
-        (0..10).send(@method, (3..7)).should be_true
-        (0..10).send(@method, (3..15)).should be_false
-        (0..10).send(@method, (-2..7)).should be_false
-
-        (1.1..7.9).send(@method, (2.5..6.5)).should be_true
-        (1.1..7.9).send(@method, (2.5..8.5)).should be_false
-        (1.1..7.9).send(@method, (0.5..6.5)).should be_false
-
-        ('c'..'i').send(@method, ('d'..'f')).should be_true
-        ('c'..'i').send(@method, ('d'..'z')).should be_false
-        ('c'..'i').send(@method, ('a'..'f')).should be_false
-
-        range_10_100 = RangeSpecs::TenfoldSucc.new(10)..RangeSpecs::TenfoldSucc.new(100)
-        range_20_90 = RangeSpecs::TenfoldSucc.new(20)..RangeSpecs::TenfoldSucc.new(90)
-        range_20_110 = RangeSpecs::TenfoldSucc.new(20)..RangeSpecs::TenfoldSucc.new(110)
-        range_0_90 = RangeSpecs::TenfoldSucc.new(0)..RangeSpecs::TenfoldSucc.new(90)
-
-        range_10_100.send(@method, range_20_90).should be_true
-        range_10_100.send(@method, range_20_110).should be_false
-        range_10_100.send(@method, range_0_90).should be_false
-      end
+describe :range_cover_subrange, shared: true do
+  context "range argument" do
+    it "accepts range argument" do
+      (0..10).send(@method, (3..7)).should be_true
+      (0..10).send(@method, (3..15)).should be_false
+      (0..10).send(@method, (-2..7)).should be_false
+
+      (1.1..7.9).send(@method, (2.5..6.5)).should be_true
+      (1.1..7.9).send(@method, (2.5..8.5)).should be_false
+      (1.1..7.9).send(@method, (0.5..6.5)).should be_false
+
+      ('c'..'i').send(@method, ('d'..'f')).should be_true
+      ('c'..'i').send(@method, ('d'..'z')).should be_false
+      ('c'..'i').send(@method, ('a'..'f')).should be_false
+
+      range_10_100 = RangeSpecs::TenfoldSucc.new(10)..RangeSpecs::TenfoldSucc.new(100)
+      range_20_90 = RangeSpecs::TenfoldSucc.new(20)..RangeSpecs::TenfoldSucc.new(90)
+      range_20_110 = RangeSpecs::TenfoldSucc.new(20)..RangeSpecs::TenfoldSucc.new(110)
+      range_0_90 = RangeSpecs::TenfoldSucc.new(0)..RangeSpecs::TenfoldSucc.new(90)
+
+      range_10_100.send(@method, range_20_90).should be_true
+      range_10_100.send(@method, range_20_110).should be_false
+      range_10_100.send(@method, range_0_90).should be_false
+    end
 
-      it "supports boundaries of different comparable types" do
-        (0..10).send(@method, (3.1..7.9)).should be_true
-        (0..10).send(@method, (3.1..15.9)).should be_false
-        (0..10).send(@method, (-2.1..7.9)).should be_false
-      end
+    it "supports boundaries of different comparable types" do
+      (0..10).send(@method, (3.1..7.9)).should be_true
+      (0..10).send(@method, (3.1..15.9)).should be_false
+      (0..10).send(@method, (-2.1..7.9)).should be_false
+    end
 
-      it "returns false if types are not comparable" do
-        (0..10).send(@method, ('a'..'z')).should be_false
-        (0..10).send(@method, (RangeSpecs::TenfoldSucc.new(0)..RangeSpecs::TenfoldSucc.new(100))).should be_false
-      end
+    it "returns false if types are not comparable" do
+      (0..10).send(@method, ('a'..'z')).should be_false
+      (0..10).send(@method, (RangeSpecs::TenfoldSucc.new(0)..RangeSpecs::TenfoldSucc.new(100))).should be_false
+    end
 
-      it "honors exclusion of right boundary (:exclude_end option)" do
-        # Integer
-        (0..10).send(@method, (0..10)).should be_true
-        (0...10).send(@method, (0...10)).should be_true
+    it "honors exclusion of right boundary (:exclude_end option)" do
+      # Integer
+      (0..10).send(@method, (0..10)).should be_true
+      (0...10).send(@method, (0...10)).should be_true
 
-        (0..10).send(@method, (0...10)).should be_true
-        (0...10).send(@method, (0..10)).should be_false
+      (0..10).send(@method, (0...10)).should be_true
+      (0...10).send(@method, (0..10)).should be_false
 
-        (0...11).send(@method, (0..10)).should be_true
-        (0..10).send(@method, (0...11)).should be_true
+      (0...11).send(@method, (0..10)).should be_true
+      (0..10).send(@method, (0...11)).should be_true
 
-        # Float
-        (0..10.1).send(@method, (0..10.1)).should be_true
-        (0...10.1).send(@method, (0...10.1)).should be_true
+      # Float
+      (0..10.1).send(@method, (0..10.1)).should be_true
+      (0...10.1).send(@method, (0...10.1)).should be_true
 
-        (0..10.1).send(@method, (0...10.1)).should be_true
-        (0...10.1).send(@method, (0..10.1)).should be_false
+      (0..10.1).send(@method, (0...10.1)).should be_true
+      (0...10.1).send(@method, (0..10.1)).should be_false
 
-        (0...11.1).send(@method, (0..10.1)).should be_true
-        (0..10.1).send(@method, (0...11.1)).should be_false
-      end
+      (0...11.1).send(@method, (0..10.1)).should be_true
+      (0..10.1).send(@method, (0...11.1)).should be_false
     end
   end
+
+  it "allows self to be a beginless range" do
+    (...10).send(@method, (3..7)).should be_true
+    (...10).send(@method, (3..15)).should be_false
+
+    (..7.9).send(@method, (2.5..6.5)).should be_true
+    (..7.9).send(@method, (2.5..8.5)).should be_false
+
+    (..'i').send(@method, ('d'..'f')).should be_true
+    (..'i').send(@method, ('d'..'z')).should be_false
+  end
+
+  it "allows self to be a endless range" do
+    eval("(0...)").send(@method, (3..7)).should be_true
+    eval("(5...)").send(@method, (3..15)).should be_false
+
+    eval("(1.1..)").send(@method, (2.5..6.5)).should be_true
+    eval("(3.3..)").send(@method, (2.5..8.5)).should be_false
+
+    eval("('a'..)").send(@method, ('d'..'f')).should be_true
+    eval("('p'..)").send(@method, ('d'..'z')).should be_false
+  end
+
+  it "accepts beginless range argument" do
+    (..10).send(@method, (...10)).should be_true
+    (0..10).send(@method, (...10)).should be_false
+
+    (1.1..7.9).send(@method, (...10.5)).should be_false
+
+    ('c'..'i').send(@method, (..'i')).should be_false
+  end
+
+  it "accepts endless range argument" do
+    eval("(0..)").send(@method, eval("(0...)")).should be_true
+    (0..10).send(@method, eval("(0...)")).should be_false
+
+    (1.1..7.9).send(@method, eval("(0.8...)")).should be_false
+
+    ('c'..'i').send(@method, eval("('a'..)")).should be_false
+  end
 end
diff --git a/spec/ruby/core/range/shared/cover_and_include.rb b/spec/ruby/core/range/shared/cover_and_include.rb
index a19e2c6ead..13fc5e1790 100644
--- a/spec/ruby/core/range/shared/cover_and_include.rb
+++ b/spec/ruby/core/range/shared/cover_and_include.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 
 describe :range_cover_and_include, shared: true do
@@ -19,6 +19,27 @@ describe :range_cover_and_include, shared: true do
     (0.5...2.4).send(@method, 2.4).should == false
   end
 
+  it "returns true if other is an element of self for endless ranges" do
+    (1..).send(@method, 2.4).should == true
+    (0.5...).send(@method, 2.4).should == true
+  end
+
+  it "returns true if other is an element of self for beginless ranges" do
+    (..10).send(@method, 2.4).should == true
+    (...10.5).send(@method, 2.4).should == true
+  end
+
+  it "returns false if values are not comparable" do
+    (1..10).send(@method, nil).should == false
+    (1...10).send(@method, nil).should == false
+
+    (..10).send(@method, nil).should == false
+    (...10).send(@method, nil).should == false
+
+    (1..).send(@method, nil).should == false
+    (1...).send(@method, nil).should == false
+  end
+
   it "compares values using <=>" do
     rng = (1..5)
     m = mock("int")
@@ -47,7 +68,6 @@ describe :range_cover_and_include, shared: true do
   it "returns true if argument is less than the last value of the range and greater than the first value" do
     (20..30).send(@method, 28).should be_true
     ('e'..'h').send(@method, 'g').should be_true
-    ("\u{999}".."\u{9999}").send @method, "\u{9995}"
   end
 
   it "returns true if argument is sole element in the range" do
diff --git a/spec/ruby/core/range/shared/equal_value.rb b/spec/ruby/core/range/shared/equal_value.rb
index 9d8bb13351..363c6be558 100644
--- a/spec/ruby/core/range/shared/equal_value.rb
+++ b/spec/ruby/core/range/shared/equal_value.rb
@@ -42,4 +42,10 @@ describe :range_eql, shared: true do
     b = RangeSpecs::MyRange.new(RangeSpecs::Xs.new(3), RangeSpecs::Xs.new(5))
     a.send(@method, b).should == true
   end
+
+  it "works for endless Ranges" do
+    eval("(1..)").send(@method, eval("(1..)")).should == true
+    eval("(0.5...)").send(@method, eval("(0.5...)")).should == true
+    eval("(1..)").send(@method, eval("(1...)")).should == false
+  end
 end
diff --git a/spec/ruby/core/range/shared/include.rb b/spec/ruby/core/range/shared/include.rb
index c6c5c2becf..15a0e5fb9f 100644
--- a/spec/ruby/core/range/shared/include.rb
+++ b/spec/ruby/core/range/shared/include.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/core/range/size_spec.rb b/spec/ruby/core/range/size_spec.rb
index 09759940dd..1a3ddd197e 100644
--- a/spec/ruby/core/range/size_spec.rb
+++ b/spec/ruby/core/range/size_spec.rb
@@ -4,24 +4,85 @@ describe "Range#size" do
   it "returns the number of elements in the range" do
     (1..16).size.should == 16
     (1...16).size.should == 15
-
-    (1.0..16.0).size.should == 16
-    (1.0...16.0).size.should == 15
-    (1.0..15.9).size.should == 15
-    (1.1..16.0).size.should == 15
-    (1.1..15.9).size.should == 15
   end
 
   it "returns 0 if last is less than first" do
     (16..0).size.should == 0
-    (16.0..0.0).size.should == 0
-    (Float::INFINITY..0).size.should == 0
   end
 
   it 'returns Float::INFINITY for increasing, infinite ranges' do
     (0..Float::INFINITY).size.should == Float::INFINITY
-    (-Float::INFINITY..0).size.should == Float::INFINITY
-    (-Float::INFINITY..Float::INFINITY).size.should == Float::INFINITY
+  end
+
+  it 'returns Float::INFINITY for endless ranges if the start is numeric' do
+    eval("(1..)").size.should == Float::INFINITY
+  end
+
+  it 'returns nil for endless ranges if the start is not numeric' do
+    eval("('z'..)").size.should == nil
+  end
+
+  ruby_version_is ""..."3.4" do
+    it 'returns Float::INFINITY for all beginless ranges if the end is numeric' do
+      (..1).size.should == Float::INFINITY
+      (...0.5).size.should == Float::INFINITY
+    end
+
+    it 'returns nil for all beginless ranges if the end is not numeric' do
+      (...'o').size.should == nil
+    end
+
+    it 'returns nil if the start and the end is both nil' do
+      (nil..nil).size.should == nil
+    end
+  end
+
+  ruby_version_is ""..."3.4" do
+    it "returns the number of elements in the range" do
+      (1.0..16.0).size.should == 16
+      (1.0...16.0).size.should == 15
+      (1.0..15.9).size.should == 15
+      (1.1..16.0).size.should == 15
+      (1.1..15.9).size.should == 15
+    end
+
+    it "returns 0 if last is less than first" do
+      (16.0..0.0).size.should == 0
+      (Float::INFINITY..0).size.should == 0
+    end
+
+    it 'returns Float::INFINITY for increasing, infinite ranges' do
+      (-Float::INFINITY..0).size.should == Float::INFINITY
+      (-Float::INFINITY..Float::INFINITY).size.should == Float::INFINITY
+    end
+
+    it 'returns Float::INFINITY for endless ranges if the start is numeric' do
+      eval("(0.5...)").size.should == Float::INFINITY
+    end
+
+    it 'returns nil for endless ranges if the start is not numeric' do
+      eval("([]...)").size.should == nil
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it 'raises TypeError if a range is not iterable' do
+      -> { (1.0..16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.0...16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.0..15.9).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.1..16.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (1.1..15.9).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (16.0..0.0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (Float::INFINITY..0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (-Float::INFINITY..0).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (-Float::INFINITY..Float::INFINITY).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (..1).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (...0.5).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (..nil).size }.should raise_error(TypeError, /can't iterate from/)
+      -> { (...'o').size }.should raise_error(TypeError, /can't iterate from/)
+      -> { eval("(0.5...)").size }.should raise_error(TypeError, /can't iterate from/)
+      -> { eval("([]...)").size }.should raise_error(TypeError, /can't iterate from/)
+    end
   end
 
   it "returns nil if first and last are not Numeric" do
diff --git a/spec/ruby/core/range/step_spec.rb b/spec/ruby/core/range/step_spec.rb
index d564e4a5cd..0d0caf746d 100644
--- a/spec/ruby/core/range/step_spec.rb
+++ b/spec/ruby/core/range/step_spec.rb
@@ -10,44 +10,50 @@ describe "Range#step" do
     r.step { }.should equal(r)
   end
 
-  it "raises TypeError if step" do
-    obj = mock("mock")
-    -> { (1..10).step(obj) { } }.should raise_error(TypeError)
-  end
+  ruby_version_is ""..."3.4" do
+    it "calls #to_int to coerce step to an Integer" do
+      obj = mock("Range#step")
+      obj.should_receive(:to_int).and_return(1)
 
-  it "calls #to_int to coerce step to an Integer" do
-    obj = mock("Range#step")
-    obj.should_receive(:to_int).and_return(1)
+      (1..2).step(obj) { |x| ScratchPad << x }
+      ScratchPad.recorded.should eql([1, 2])
+    end
 
-    (1..2).step(obj) { |x| ScratchPad << x }
-    ScratchPad.recorded.should eql([1, 2])
-  end
+    it "raises a TypeError if step does not respond to #to_int" do
+      obj = mock("Range#step non-integer")
 
-  it "raises a TypeError if step does not respond to #to_int" do
-    obj = mock("Range#step non-integer")
+      -> { (1..2).step(obj) { } }.should raise_error(TypeError)
+    end
 
-    -> { (1..2).step(obj) { } }.should raise_error(TypeError)
-  end
+    it "raises a TypeError if #to_int does not return an Integer" do
+      obj = mock("Range#step non-integer")
+      obj.should_receive(:to_int).and_return("1")
 
-  it "raises a TypeError if #to_int does not return an Integer" do
-    obj = mock("Range#step non-integer")
-    obj.should_receive(:to_int).and_return("1")
+      -> { (1..2).step(obj) { } }.should raise_error(TypeError)
+    end
 
-    -> { (1..2).step(obj) { } }.should raise_error(TypeError)
-  end
+    it "raises a TypeError if the first element does not respond to #succ" do
+      obj = mock("Range#step non-comparable")
+      obj.should_receive(:<=>).with(obj).and_return(1)
 
-  it "coerces the argument to integer by invoking to_int" do
-    (obj = mock("2")).should_receive(:to_int).and_return(2)
-    res = []
-    (1..10).step(obj) {|x| res << x}
-    res.should == [1, 3, 5, 7, 9]
+      -> { (obj..obj).step { |x| x } }.should raise_error(TypeError)
+    end
   end
 
-  it "raises a TypeError if the first element does not respond to #succ" do
-    obj = mock("Range#step non-comparable")
-    obj.should_receive(:<=>).with(obj).and_return(1)
+  ruby_version_is "3.4" do
+    it "calls #coerce to coerce step to an Integer" do
+      obj = mock("Range#step")
+      obj.should_receive(:coerce).at_least(:once).and_return([1, 2])
+
+      (1..3).step(obj) { |x| ScratchPad << x }
+      ScratchPad.recorded.should eql([1, 3])
+    end
+
+    it "raises a TypeError if step does not respond to #coerce" do
+      obj = mock("Range#step non-coercible")
 
-    -> { (obj..obj).step { |x| x } }.should raise_error(TypeError)
+      -> { (1..2).step(obj) { } }.should raise_error(TypeError)
+    end
   end
 
   it "raises an ArgumentError if step is 0" do
@@ -58,8 +64,17 @@ describe "Range#step" do
     -> { (-1..1).step(0.0) { |x| x } }.should raise_error(ArgumentError)
   end
 
-  it "raises an ArgumentError if step is negative" do
-    -> { (-1..1).step(-2) { |x| x } }.should raise_error(ArgumentError)
+  ruby_version_is "3.4" do
+    it "does not raise an ArgumentError if step is 0 for non-numeric ranges" do
+      t = Time.utc(2023, 2, 24)
+      -> { (t..t+1).step(0) { break } }.should_not raise_error(ArgumentError)
+    end
+  end
+
+  ruby_version_is ""..."3.4" do
+    it "raises an ArgumentError if step is negative" do
+      -> { (-1..1).step(-2) { |x| x } }.should raise_error(ArgumentError)
+    end
   end
 
   describe "with inclusive end" do
@@ -78,6 +93,18 @@ describe "Range#step" do
         (-2..2).step(1.5) { |x| ScratchPad << x }
         ScratchPad.recorded.should eql([-2.0, -0.5, 1.0])
       end
+
+      ruby_version_is "3.4" do
+        it "does not iterate if step is negative for forward range" do
+          (-1..1).step(-1) { |x| ScratchPad << x }
+          ScratchPad.recorded.should eql([])
+        end
+
+        it "iterates backward if step is negative for backward range" do
+          (1..-1).step(-1) { |x| ScratchPad << x }
+          ScratchPad.recorded.should eql([1, 0, -1])
+        end
+      end
     end
 
     describe "and Float values" do
@@ -162,13 +189,96 @@ describe "Range#step" do
         -> { ("A".."G").step(2.0) { } }.should raise_error(TypeError)
       end
 
-      it "calls #succ on begin and each element returned by #succ" do
-        obj = mock("Range#step String start")
-        obj.should_receive(:<=>).exactly(3).times.and_return(-1, -1, -1, 0)
-        obj.should_receive(:succ).exactly(2).times.and_return(obj)
+      ruby_version_is ""..."3.4" do
+        it "calls #succ on begin and each element returned by #succ" do
+          obj = mock("Range#step String start")
+          obj.should_receive(:<=>).exactly(3).times.and_return(-1, -1, -1, 0)
+          obj.should_receive(:succ).exactly(2).times.and_return(obj)
 
-        (obj..obj).step { |x| ScratchPad << x }
-        ScratchPad.recorded.should == [obj, obj, obj]
+          (obj..obj).step { |x| ScratchPad << x }
+          ScratchPad.recorded.should == [obj, obj, obj]
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "yields String values adjusted by step and less than or equal to end" do
+          ("A".."AAA").step("A") { |x| ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "AA", "AAA"]
+        end
+
+        it "raises a TypeError when passed an incompatible type step" do
+          -> { ("A".."G").step([]) { } }.should raise_error(TypeError)
+        end
+
+        it "calls #+ on begin and each element returned by #+" do
+          start = mock("Range#step String start")
+          stop = mock("Range#step String stop")
+
+          mid1 = mock("Range#step String mid1")
+          mid2 = mock("Range#step String mid2")
+
+          step = mock("Range#step String step")
+
+          # Deciding on the direction of iteration
+          start.should_receive(:<=>).with(stop).at_least(:twice).and_return(-1)
+          # Deciding whether the step moves iteration in the right direction
+          start.should_receive(:<=>).with(mid1).and_return(-1)
+          # Iteration 1
+          start.should_receive(:+).at_least(:once).with(step).and_return(mid1)
+          # Iteration 2
+          mid1.should_receive(:<=>).with(stop).and_return(-1)
+          mid1.should_receive(:+).with(step).and_return(mid2)
+          # Iteration 3
+          mid2.should_receive(:<=>).with(stop).and_return(0)
+
+          (start..stop).step(step) { |x| ScratchPad << x }
+          ScratchPad.recorded.should == [start, mid1, mid2]
+        end
+
+        it "iterates backward if the step is decreasing values, and the range is backward" do
+          start = mock("Range#step String start")
+          stop = mock("Range#step String stop")
+
+          mid1 = mock("Range#step String mid1")
+          mid2 = mock("Range#step String mid2")
+
+          step = mock("Range#step String step")
+
+          # Deciding on the direction of iteration
+          start.should_receive(:<=>).with(stop).at_least(:twice).and_return(1)
+          # Deciding whether the step moves iteration in the right direction
+          start.should_receive(:<=>).with(mid1).and_return(1)
+          # Iteration 1
+          start.should_receive(:+).at_least(:once).with(step).and_return(mid1)
+          # Iteration 2
+          mid1.should_receive(:<=>).with(stop).and_return(1)
+          mid1.should_receive(:+).with(step).and_return(mid2)
+          # Iteration 3
+          mid2.should_receive(:<=>).with(stop).and_return(0)
+
+          (start..stop).step(step) { |x| ScratchPad << x }
+          ScratchPad.recorded.should == [start, mid1, mid2]
+        end
+
+        it "does no iteration of the direction of the range and of the step don't match" do
+          start = mock("Range#step String start")
+          stop = mock("Range#step String stop")
+
+          mid1 = mock("Range#step String mid1")
+          mid2 = mock("Range#step String mid2")
+
+          step = mock("Range#step String step")
+
+          # Deciding on the direction of iteration: stop > start
+          start.should_receive(:<=>).with(stop).at_least(:twice).and_return(1)
+          # Deciding whether the step moves iteration in the right direction
+          # start + step < start, the direction is opposite to the range's
+          start.should_receive(:+).with(step).and_return(mid1)
+          start.should_receive(:<=>).with(mid1).and_return(-1)
+
+          (start..stop).step(step) { |x| ScratchPad << x }
+          ScratchPad.recorded.should == []
+        end
       end
     end
   end
@@ -209,8 +319,14 @@ describe "Range#step" do
 
       it "returns Float values of 'step * n + begin < end'" do
         (1.0...6.4).step(1.8) { |x| ScratchPad << x }
+        ScratchPad.recorded.should eql([1.0, 2.8, 4.6])
+      end
+
+      it "correctly handles values near the upper limit" do # https://bugs.ruby-lang.org/issues/16612
         (1.0...55.6).step(18.2) { |x| ScratchPad << x }
-        ScratchPad.recorded.should eql([1.0, 2.8, 4.6, 1.0, 19.2, 37.4])
+        ScratchPad.recorded.should eql([1.0, 19.2, 37.4, 55.599999999999994])
+
+        (1.0...55.6).step(18.2).size.should == 4
       end
 
       it "handles infinite values at either end" do
@@ -258,60 +374,169 @@ describe "Range#step" do
     end
 
     describe "and String values" do
+      ruby_version_is ""..."3.4" do
+        it "yields String values incremented by #succ and less than or equal to end when not passed a step" do
+          ("A"..."E").step { |x| ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "B", "C", "D"]
+        end
+
+        it "yields String values incremented by #succ called Integer step times" do
+          ("A"..."G").step(2) { |x| ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "C", "E"]
+        end
+
+        it "raises a TypeError when passed a Float step" do
+          -> { ("A"..."G").step(2.0) { } }.should raise_error(TypeError)
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "yields String values adjusted by step and less than or equal to end" do
+          ("A"..."AAA").step("A") { |x| ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "AA"]
+        end
+
+        it "raises a TypeError when passed an incompatible type step" do
+          -> { ("A".."G").step([]) { } }.should raise_error(TypeError)
+        end
+      end
+    end
+  end
+
+  describe "with an endless range" do
+    describe "and Integer values" do
+      it "yield Integer values incremented by 1 when not passed a step" do
+        (-2..).step { |x| break if x > 2; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2, -1, 0, 1, 2])
+
+        ScratchPad.record []
+        (-2...).step { |x| break if x > 2; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2, -1, 0, 1, 2])
+      end
+
+      it "yields Integer values incremented by an Integer step" do
+        (-5..).step(2) { |x| break if x > 3; ScratchPad << x }
+        ScratchPad.recorded.should eql([-5, -3, -1, 1, 3])
+
+        ScratchPad.record []
+        (-5...).step(2) { |x| break if x > 3; ScratchPad << x }
+        ScratchPad.recorded.should eql([-5, -3, -1, 1, 3])
+      end
+
+      it "yields Float values incremented by a Float step" do
+        (-2..).step(1.5) { |x| break if x > 1.0; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2.0, -0.5, 1.0])
+
+        ScratchPad.record []
+        (-2..).step(1.5) { |x| break if x > 1.0; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2.0, -0.5, 1.0])
+      end
+    end
+
+    describe "and Float values" do
+      it "yields Float values incremented by 1 and less than end when not passed a step" do
+        (-2.0..).step { |x| break if x > 1.5; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2.0, -1.0, 0.0, 1.0])
+
+        ScratchPad.record []
+        (-2.0...).step { |x| break if x > 1.5; ScratchPad << x }
+        ScratchPad.recorded.should eql([-2.0, -1.0, 0.0, 1.0])
+      end
+
+      it "yields Float values incremented by an Integer step" do
+        (-5.0..).step(2) { |x| break if x > 3.5; ScratchPad << x }
+        ScratchPad.recorded.should eql([-5.0, -3.0, -1.0, 1.0, 3.0])
+
+        ScratchPad.record []
+        (-5.0...).step(2) { |x| break if x > 3.5; ScratchPad << x }
+        ScratchPad.recorded.should eql([-5.0, -3.0, -1.0, 1.0, 3.0])
+      end
+
+      it "yields Float values incremented by a Float step" do
+        (-1.0..).step(0.5) { |x| break if x > 0.6; ScratchPad << x }
+        ScratchPad.recorded.should eql([-1.0, -0.5, 0.0, 0.5])
+
+        ScratchPad.record []
+        (-1.0...).step(0.5) { |x| break if x > 0.6; ScratchPad << x }
+        ScratchPad.recorded.should eql([-1.0, -0.5, 0.0, 0.5])
+      end
+
+      it "handles infinite values at the start" do
+        (-Float::INFINITY..).step(2) { |x| ScratchPad << x; break if ScratchPad.recorded.size == 3 }
+        ScratchPad.recorded.should eql([-Float::INFINITY, -Float::INFINITY, -Float::INFINITY])
+
+        ScratchPad.record []
+        (-Float::INFINITY...).step(2) { |x| ScratchPad << x; break if ScratchPad.recorded.size == 3 }
+        ScratchPad.recorded.should eql([-Float::INFINITY, -Float::INFINITY, -Float::INFINITY])
+      end
+    end
+
+    describe "and String values" do
       it "yields String values incremented by #succ and less than or equal to end when not passed a step" do
-        ("A"..."E").step { |x| ScratchPad << x }
+        ('A'..).step { |x| break if x > "D"; ScratchPad << x }
+        ScratchPad.recorded.should == ["A", "B", "C", "D"]
+
+        ScratchPad.record []
+        ('A'...).step { |x| break if x > "D"; ScratchPad << x }
         ScratchPad.recorded.should == ["A", "B", "C", "D"]
       end
 
       it "yields String values incremented by #succ called Integer step times" do
-        ("A"..."G").step(2) { |x| ScratchPad << x }
+        ('A'..).step(2) { |x| break if x > "F"; ScratchPad << x }
+        ScratchPad.recorded.should == ["A", "C", "E"]
+
+        ScratchPad.record []
+        ('A'...).step(2) { |x| break if x > "F"; ScratchPad << x }
         ScratchPad.recorded.should == ["A", "C", "E"]
       end
 
       it "raises a TypeError when passed a Float step" do
-        -> { ("A"..."G").step(2.0) { } }.should raise_error(TypeError)
+        -> { ('A'..).step(2.0) { } }.should raise_error(TypeError)
+        -> { ('A'...).step(2.0) { } }.should raise_error(TypeError)
       end
-    end
-  end
 
-  describe "when no block is given" do
-    describe "returned Enumerator" do
-      describe "size" do
-        it "raises a TypeError if step does not respond to #to_int" do
-          obj = mock("Range#step non-integer")
-          enum = (1..2).step(obj)
-          -> { enum.size }.should raise_error(TypeError)
-        end
+      ruby_version_is "3.4" do
+        it "yields String values adjusted by step" do
+          ('A'..).step("A") { |x| break if x > "AAA"; ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "AA", "AAA"]
 
-        it "raises a TypeError if #to_int does not return an Integer" do
-          obj = mock("Range#step non-integer")
-          obj.should_receive(:to_int).and_return("1")
-          enum = (1..2).step(obj)
+          ScratchPad.record []
+          ('A'...).step("A") { |x| break if x > "AAA"; ScratchPad << x }
+          ScratchPad.recorded.should == ["A", "AA", "AAA"]
+        end
 
-          -> { enum.size }.should raise_error(TypeError)
+        it "raises a TypeError when passed an incompatible type step" do
+          -> { ('A'..).step([]) { } }.should raise_error(TypeError)
+          -> { ('A'...).step([]) { } }.should raise_error(TypeError)
         end
+      end
+    end
+  end
 
-        ruby_version_is ""..."2.6" do
-          it "raises an ArgumentError if step is 0" do
-            enum = (-1..1).step(0)
-            -> { enum.size }.should raise_error(ArgumentError)
-          end
+  describe "when no block is given" do
+    it "raises an ArgumentError if step is 0" do
+      -> { (-1..1).step(0) }.should raise_error(ArgumentError)
+    end
 
-          it "raises an ArgumentError if step is 0.0" do
-            enum = (-1..1).step(0.0)
-            -> { enum.size }.should raise_error(ArgumentError)
+    describe "returned Enumerator" do
+      describe "size" do
+        ruby_version_is ""..."3.4" do
+          it "raises a TypeError if step does not respond to #to_int" do
+            obj = mock("Range#step non-integer")
+            -> { (1..2).step(obj) }.should raise_error(TypeError)
           end
 
-          it "raises an ArgumentError if step is negative" do
-            enum = (-1..1).step(-2)
-            -> {  enum.size }.should raise_error(ArgumentError)
+          it "raises a TypeError if #to_int does not return an Integer" do
+            obj = mock("Range#step non-integer")
+            obj.should_receive(:to_int).and_return("1")
+            -> { (1..2).step(obj) }.should raise_error(TypeError)
           end
         end
 
-        ruby_version_is "2.6" do
-          it "returns Float::INFINITY for zero step" do
-            (-1..1).step(0).size.should == Float::INFINITY
-            (-1..1).step(0.0).size.should == Float::INFINITY
+        ruby_version_is "3.4" do
+          it "does not raise if step is incompatible" do
+            obj = mock("Range#step non-integer")
+            -> { (1..2).step(obj) }.should_not raise_error
           end
         end
 
@@ -328,11 +553,9 @@ describe "Range#step" do
           (-5...5).step(2).size.should == 5
         end
 
-        ruby_version_is "2.6" do
-          it "returns the ceil of range size divided by the number of steps even if step is negative" do
-            (-1..1).step(-1).size.should == 0
-            (1..-1).step(-1).size.should == 3
-          end
+        it "returns the ceil of range size divided by the number of steps even if step is negative" do
+          (-1..1).step(-1).size.should == 0
+          (1..-1).step(-1).size.should == 3
         end
 
         it "returns the correct number of steps when one of the arguments is a float" do
@@ -352,42 +575,105 @@ describe "Range#step" do
           (-2...2.0).step.size.should == 4
           (-2.0...2).step.size.should == 4
           (1.0...6.4).step(1.8).size.should == 3
-          (1.0...55.6).step(18.2).size.should == 3
         end
 
-        it "returns nil with begin and end are String" do
-          ("A".."E").step(2).size.should == nil
-          ("A"..."E").step(2).size.should == nil
-          ("A".."E").step.size.should == nil
-          ("A"..."E").step.size.should == nil
+        ruby_version_is ""..."3.4" do
+          it "returns nil with begin and end are String" do
+            ("A".."E").step(2).size.should == nil
+            ("A"..."E").step(2).size.should == nil
+            ("A".."E").step.size.should == nil
+            ("A"..."E").step.size.should == nil
+          end
+
+          it "return nil and not raises a TypeError if the first element does not respond to #succ" do
+            obj = mock("Range#step non-comparable")
+            obj.should_receive(:<=>).with(obj).and_return(1)
+            enum = (obj..obj).step
+            -> { enum.size }.should_not raise_error
+            enum.size.should == nil
+          end
         end
 
-        it "return nil and not raises a TypeError if the first element does not respond to #succ" do
-          obj = mock("Range#step non-comparable")
-          obj.should_receive(:<=>).with(obj).and_return(1)
-          enum = (obj..obj).step
-          -> { enum.size }.should_not raise_error
-          enum.size.should == nil
+        ruby_version_is "3.4" do
+          it "returns nil with begin and end are String" do
+            ("A".."E").step("A").size.should == nil
+            ("A"..."E").step("A").size.should == nil
+          end
+
+          it "return nil and not raises a TypeError if the first element is not of compatible type" do
+            obj = mock("Range#step non-comparable")
+            obj.should_receive(:<=>).with(obj).and_return(1)
+            enum = (obj..obj).step(obj)
+            -> { enum.size }.should_not raise_error
+            enum.size.should == nil
+          end
         end
       end
 
+      # We use .take below to ensure the enumerator works
+      # because that's an Enumerable method and so it uses the Enumerator behavior
+      # not just a method overridden in Enumerator::ArithmeticSequence.
       describe "type" do
-        ruby_version_is ""..."2.6" do
-          it "returns an instance of Enumerator" do
-            (1..10).step.class.should == Enumerator
+        context "when both begin and end are numerics" do
+          it "returns an instance of Enumerator::ArithmeticSequence" do
+            (1..10).step.class.should == Enumerator::ArithmeticSequence
+            (1..10).step(3).take(4).should == [1, 4, 7, 10]
+          end
+        end
+
+        context "when begin is not defined and end is numeric" do
+          it "returns an instance of Enumerator::ArithmeticSequence" do
+            (..10).step.class.should == Enumerator::ArithmeticSequence
           end
         end
 
-        ruby_version_is "2.6" do
-          context "when both begin and end are numerics" do
-            it "returns an instance of Enumerator::ArithmeticSequence" do
-              (1..10).step.class.should == Enumerator::ArithmeticSequence
+        context "when range is endless" do
+          it "returns an instance of Enumerator::ArithmeticSequence when begin is numeric" do
+            (1..).step.class.should == Enumerator::ArithmeticSequence
+            (1..).step(2).take(3).should == [1, 3, 5]
+          end
+
+          ruby_version_is ""..."3.4" do
+            it "returns an instance of Enumerator when begin is not numeric" do
+              ("a"..).step.class.should == Enumerator
+              ("a"..).step(2).take(3).should == %w[a c e]
+            end
+          end
+
+          ruby_version_is "3.4" do
+            it "returns an instance of Enumerator when begin is not numeric" do
+              ("a"..).step("a").class.should == Enumerator
+              ("a"..).step("a").take(3).should == %w[a aa aaa]
             end
           end
+        end
 
-          context "when begin and end are not numerics" do
+        context "when range is beginless and endless" do
+          ruby_version_is ""..."3.4" do
+            it "returns an instance of Enumerator" do
+              Range.new(nil, nil).step.class.should == Enumerator
+            end
+          end
+
+          ruby_version_is "3.4" do
+            it "raises an ArgumentError" do
+              -> { Range.new(nil, nil).step(1) }.should raise_error(ArgumentError)
+            end
+          end
+        end
+
+        context "when begin and end are not numerics" do
+          ruby_version_is ""..."3.4" do
             it "returns an instance of Enumerator" do
               ("a".."z").step.class.should == Enumerator
+              ("a".."z").step(3).take(4).should == %w[a d g j]
+            end
+          end
+
+          ruby_version_is "3.4" do
+            it "returns an instance of Enumerator" do
+              ("a".."z").step("a").class.should == Enumerator
+              ("a".."z").step("a").take(4).should == %w[a aa aaa aaaa]
             end
           end
         end
diff --git a/spec/ruby/core/range/to_a_spec.rb b/spec/ruby/core/range/to_a_spec.rb
index 15f0b44a9c..b1d3de32db 100644
--- a/spec/ruby/core/range/to_a_spec.rb
+++ b/spec/ruby/core/range/to_a_spec.rb
@@ -16,7 +16,24 @@ describe "Range#to_a" do
     (0xffff...0xfffd).to_a.should == []
   end
 
+  it "works with Ranges of 64-bit integers" do
+    large = 1 << 40
+    (large..large+1).to_a.should == [1099511627776, 1099511627777]
+  end
+
   it "works with Ranges of Symbols" do
     (:A..:z).to_a.size.should == 58
   end
+
+  it "works for non-ASCII ranges" do
+    ('Σ'..'Ω').to_a.should == ["Σ", "Τ", "Υ", "Φ", "Χ", "Ψ", "Ω"]
+  end
+
+  it "throws an exception for endless ranges" do
+    -> { eval("(1..)").to_a }.should raise_error(RangeError)
+  end
+
+  it "throws an exception for beginless ranges" do
+    -> { (..1).to_a }.should raise_error(TypeError)
+  end
 end
diff --git a/spec/ruby/core/range/to_s_spec.rb b/spec/ruby/core/range/to_s_spec.rb
index 4c37e81fe0..460c330912 100644
--- a/spec/ruby/core/range/to_s_spec.rb
+++ b/spec/ruby/core/range/to_s_spec.rb
@@ -11,15 +11,13 @@ describe "Range#to_s" do
     (0.5..2.4).to_s.should == "0.5..2.4"
   end
 
-  it "returns a tainted string if either end is tainted" do
-    (("a".taint)..."c").to_s.tainted?.should be_true
-    ("a"...("c".taint)).to_s.tainted?.should be_true
-    ("a"..."c").taint.to_s.tainted?.should be_true
+  it "can show endless ranges" do
+    eval("(1..)").to_s.should == "1.."
+    eval("(1.0...)").to_s.should == "1.0..."
   end
 
-  it "returns a untrusted string if either end is untrusted" do
-    (("a".untrust)..."c").to_s.untrusted?.should be_true
-    ("a"...("c".untrust)).to_s.untrusted?.should be_true
-    ("a"..."c").untrust.to_s.untrusted?.should be_true
+  it "can show beginless ranges" do
+    (..1).to_s.should == "..1"
+    (...1.0).to_s.should == "...1.0"
   end
 end
diff --git a/spec/ruby/core/range/to_set_spec.rb b/spec/ruby/core/range/to_set_spec.rb
new file mode 100644
index 0000000000..589c0e9aed
--- /dev/null
+++ b/spec/ruby/core/range/to_set_spec.rb
@@ -0,0 +1,55 @@
+require_relative '../../spec_helper'
+require_relative '../enumerable/fixtures/classes'
+
+describe "Enumerable#to_set" do
+  it "returns a new Set created from self" do
+    (1..4).to_set.should == Set[1, 2, 3, 4]
+    (1...4).to_set.should == Set[1, 2, 3]
+  end
+
+  it "passes down passed blocks" do
+    (1..3).to_set { |x| x * x }.should == Set[1, 4, 9]
+  end
+
+  ruby_version_is "4.0" do
+    it "raises a RangeError if the range is infinite" do
+      -> { (1..).to_set }.should raise_error(RangeError, "cannot convert endless range to a set")
+      -> { (1...).to_set }.should raise_error(RangeError, "cannot convert endless range to a set")
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "instantiates an object of provided as the first argument set class" do
+      set = (1..3).to_set(EnumerableSpecs::SetSubclass)
+      set.should be_kind_of(EnumerableSpecs::SetSubclass)
+      set.to_a.sort.should == [1, 2, 3]
+    end
+  end
+
+  ruby_version_is "4.0"..."4.1" do
+    it "instantiates an object of provided as the first argument set class and warns" do
+      set = nil
+      proc {
+        set = (1..3).to_set(EnumerableSpecs::SetSubclass)
+      }.should complain(/Enumerable#to_set/)
+      set.should be_kind_of(EnumerableSpecs::SetSubclass)
+      set.to_a.sort.should == [1, 2, 3]
+    end
+  end
+
+  ruby_version_is "4.1" do
+    it "does not accept any positional argument" do
+      -> {
+        (1..3).to_set(EnumerableSpecs::SetSubclass)
+      }.should raise_error(ArgumentError, 'wrong number of arguments (given 1, expected 0)')
+    end
+  end
+
+  it "does not need explicit `require 'set'`" do
+    output = ruby_exe(<<~RUBY, options: '--disable-gems', args: '2>&1')
+      puts (1..3).to_set.to_a.inspect
+    RUBY
+
+    output.chomp.should == "[1, 2, 3]"
+  end
+end
diff --git a/spec/ruby/core/rational/abs_spec.rb b/spec/ruby/core/rational/abs_spec.rb
index aed7713058..54099aa14d 100644
--- a/spec/ruby/core/rational/abs_spec.rb
+++ b/spec/ruby/core/rational/abs_spec.rb
@@ -1,4 +1,5 @@
-require_relative '../../shared/rational/abs'
+require_relative "../../spec_helper"
+require_relative 'shared/abs'
 
 describe "Rational#abs" do
   it_behaves_like :rational_abs, :abs
diff --git a/spec/ruby/core/rational/ceil_spec.rb b/spec/ruby/core/rational/ceil_spec.rb
index 5b0ca4a9d6..d5bdadf3b6 100644
--- a/spec/ruby/core/rational/ceil_spec.rb
+++ b/spec/ruby/core/rational/ceil_spec.rb
@@ -1,5 +1,45 @@
-require_relative '../../shared/rational/ceil'
+require_relative "../../spec_helper"
 
 describe "Rational#ceil" do
-  it_behaves_like :rational_ceil, :ceil
+  before do
+    @rational = Rational(2200, 7)
+  end
+
+  describe "with no arguments (precision = 0)" do
+    it "returns an Integer" do
+      @rational.ceil.should be_kind_of(Integer)
+    end
+
+    it "returns the truncated value toward positive infinity" do
+      @rational.ceil.should == 315
+      Rational(1, 2).ceil.should == 1
+      Rational(-1, 2).ceil.should == 0
+    end
+  end
+
+  describe "with a precision < 0" do
+    it "returns an Integer" do
+      @rational.ceil(-2).should be_kind_of(Integer)
+      @rational.ceil(-1).should be_kind_of(Integer)
+    end
+
+    it "moves the truncation point n decimal places left" do
+      @rational.ceil(-3).should == 1000
+      @rational.ceil(-2).should == 400
+      @rational.ceil(-1).should == 320
+    end
+  end
+
+  describe "with precision > 0" do
+    it "returns a Rational" do
+      @rational.ceil(1).should be_kind_of(Rational)
+      @rational.ceil(2).should be_kind_of(Rational)
+    end
+
+    it "moves the truncation point n decimal places right" do
+      @rational.ceil(1).should == Rational(3143, 10)
+      @rational.ceil(2).should == Rational(31429, 100)
+      @rational.ceil(3).should == Rational(157143, 500)
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/coerce_spec.rb b/spec/ruby/core/rational/coerce_spec.rb
deleted file mode 100644
index 3f78f0bcd6..0000000000
--- a/spec/ruby/core/rational/coerce_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../shared/rational/coerce'
-
-describe "Rational#coerce" do
-  it_behaves_like :rational_coerce, :coerce
-end
diff --git a/spec/ruby/core/rational/comparison_spec.rb b/spec/ruby/core/rational/comparison_spec.rb
index b2784f3e7d..c9db60d5c7 100644
--- a/spec/ruby/core/rational/comparison_spec.rb
+++ b/spec/ruby/core/rational/comparison_spec.rb
@@ -1,22 +1,93 @@
-require_relative '../../shared/rational/comparison'
+require_relative "../../spec_helper"
+require_relative 'fixtures/rational'
 
 describe "Rational#<=> when passed a Rational object" do
-  it_behaves_like :rational_cmp_rat, :<=>
+  it "returns 1 when self is greater than the passed argument" do
+    (Rational(4, 4) <=> Rational(3, 4)).should equal(1)
+    (Rational(-3, 4) <=> Rational(-4, 4)).should equal(1)
+  end
+
+  it "returns 0 when self is equal to the passed argument" do
+    (Rational(4, 4) <=> Rational(4, 4)).should equal(0)
+    (Rational(-3, 4) <=> Rational(-3, 4)).should equal(0)
+  end
+
+  it "returns -1 when self is less than the passed argument" do
+    (Rational(3, 4) <=> Rational(4, 4)).should equal(-1)
+    (Rational(-4, 4) <=> Rational(-3, 4)).should equal(-1)
+  end
 end
 
-describe "Rational#<=> when passed a Integer object" do
-  it_behaves_like :rational_cmp_int, :<=>
+describe "Rational#<=> when passed an Integer object" do
+  it "returns 1 when self is greater than the passed argument" do
+    (Rational(4, 4) <=> 0).should equal(1)
+    (Rational(4, 4) <=> -10).should equal(1)
+    (Rational(-3, 4) <=> -1).should equal(1)
+  end
+
+  it "returns 0 when self is equal to the passed argument" do
+    (Rational(4, 4) <=> 1).should equal(0)
+    (Rational(-8, 4) <=> -2).should equal(0)
+  end
+
+  it "returns -1 when self is less than the passed argument" do
+    (Rational(3, 4) <=> 1).should equal(-1)
+    (Rational(-4, 4) <=> 0).should equal(-1)
+  end
 end
 
 describe "Rational#<=> when passed a Float object" do
-  it_behaves_like :rational_cmp_float, :<=>
+  it "returns 1 when self is greater than the passed argument" do
+    (Rational(4, 4) <=> 0.5).should equal(1)
+    (Rational(4, 4) <=> -1.5).should equal(1)
+    (Rational(-3, 4) <=> -0.8).should equal(1)
+  end
+
+  it "returns 0 when self is equal to the passed argument" do
+    (Rational(4, 4) <=> 1.0).should equal(0)
+    (Rational(-6, 4) <=> -1.5).should equal(0)
+  end
+
+  it "returns -1 when self is less than the passed argument" do
+    (Rational(3, 4) <=> 1.2).should equal(-1)
+    (Rational(-4, 4) <=> 0.5).should equal(-1)
+  end
 end
 
 describe "Rational#<=> when passed an Object that responds to #coerce" do
-  it_behaves_like :rational_cmp_coerce, :<=>
-  it_behaves_like :rational_cmp_coerce_exception, :<=>
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational <=> obj
+  end
+
+  it "calls #<=> on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:<=>).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational <=> obj).should == :result
+  end
+
+  it "does not rescue exception raised in other#coerce" do
+    b = mock("numeric with failed #coerce")
+    b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
+
+    -> { Rational(3, 4) <=> b }.should raise_error(RationalSpecs::CoerceError)
+  end
 end
 
 describe "Rational#<=> when passed a non-Numeric Object that doesn't respond to #coerce" do
-  it_behaves_like :rational_cmp_other, :<=>
+  it "returns nil" do
+    (Rational <=> mock("Object")).should be_nil
+  end
 end
diff --git a/spec/ruby/core/rational/denominator_spec.rb b/spec/ruby/core/rational/denominator_spec.rb
index 6214b40587..4687244893 100644
--- a/spec/ruby/core/rational/denominator_spec.rb
+++ b/spec/ruby/core/rational/denominator_spec.rb
@@ -1,5 +1,14 @@
-require_relative '../../shared/rational/denominator'
+require_relative "../../spec_helper"
 
 describe "Rational#denominator" do
-  it_behaves_like :rational_denominator, :denominator
+  it "returns the denominator" do
+    Rational(3, 4).denominator.should equal(4)
+    Rational(3, -4).denominator.should equal(4)
+
+    Rational(1, bignum_value).denominator.should == bignum_value
+  end
+
+  it "returns 1 if no denominator was given" do
+    Rational(80).denominator.should == 1
+  end
 end
diff --git a/spec/ruby/core/rational/div_spec.rb b/spec/ruby/core/rational/div_spec.rb
index 1cd8606b90..d3adb9b536 100644
--- a/spec/ruby/core/rational/div_spec.rb
+++ b/spec/ruby/core/rational/div_spec.rb
@@ -1,17 +1,54 @@
-require_relative '../../shared/rational/div'
+require_relative "../../spec_helper"
 
 describe "Rational#div" do
-  it_behaves_like :rational_div, :div
+  it "returns an Integer" do
+    Rational(229, 21).div(82).should be_kind_of(Integer)
+  end
+
+  it "raises an ArgumentError if passed more than one argument" do
+    -> { Rational(3, 4).div(2,3) }.should raise_error(ArgumentError)
+  end
+
+  # See http://redmine.ruby-lang.org/issues/show/1648
+  it "raises a TypeError if passed a non-numeric argument" do
+    -> { Rational(3, 4).div([]) }.should raise_error(TypeError)
+  end
 end
 
 describe "Rational#div passed a Rational" do
-  it_behaves_like :rational_div_rat, :div
+  it "performs integer division and returns the result" do
+    Rational(2, 3).div(Rational(2, 3)).should == 1
+    Rational(-2, 9).div(Rational(-9, 2)).should == 0
+  end
+
+  it "raises a ZeroDivisionError when the argument has a numerator of 0" do
+    -> { Rational(3, 4).div(Rational(0, 3)) }.should raise_error(ZeroDivisionError)
+  end
+
+  it "raises a ZeroDivisionError when the argument has a numerator of 0.0" do
+    -> { Rational(3, 4).div(Rational(0.0, 3)) }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#div passed an Integer" do
-  it_behaves_like :rational_div_int, :div
+  it "performs integer division and returns the result" do
+    Rational(2, 1).div(1).should == 2
+    Rational(25, 5).div(-50).should == -1
+  end
+
+  it "raises a ZeroDivisionError when the argument is 0" do
+    -> { Rational(3, 4).div(0) }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#div passed a Float" do
-  it_behaves_like :rational_div_float, :div
+  it "performs integer division and returns the result" do
+    Rational(2, 3).div(30.333).should == 0
+    Rational(2, 9).div(Rational(-8.6)).should == -1
+    Rational(3.12).div(0.5).should == 6
+  end
+
+  it "raises a ZeroDivisionError when the argument is 0.0" do
+    -> { Rational(3, 4).div(0.0) }.should raise_error(ZeroDivisionError)
+  end
 end
diff --git a/spec/ruby/core/rational/divide_spec.rb b/spec/ruby/core/rational/divide_spec.rb
index d8e3a44dc2..8f5ca1fdec 100644
--- a/spec/ruby/core/rational/divide_spec.rb
+++ b/spec/ruby/core/rational/divide_spec.rb
@@ -1,19 +1,74 @@
-require_relative '../../shared/rational/divide'
-require_relative '../../shared/rational/arithmetic_exception_in_coerce'
+require_relative "../../spec_helper"
+require_relative 'shared/arithmetic_exception_in_coerce'
 
 describe "Rational#/" do
-  it_behaves_like :rational_divide, :/
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational / obj
+  end
+
+  it "calls #/ on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:/).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational / obj).should == :result
+  end
+
   it_behaves_like :rational_arithmetic_exception_in_coerce, :/
 end
 
 describe "Rational#/ when passed an Integer" do
-  it_behaves_like :rational_divide_int, :/
+  it "returns self divided by other as a Rational" do
+    (Rational(3, 4) / 2).should eql(Rational(3, 8))
+    (Rational(2, 4) / 2).should eql(Rational(1, 4))
+    (Rational(6, 7) / -2).should eql(Rational(-3, 7))
+  end
+
+  it "raises a ZeroDivisionError when passed 0" do
+    -> { Rational(3, 4) / 0 }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#/ when passed a Rational" do
-  it_behaves_like :rational_divide_rat, :/
+  it "returns self divided by other as a Rational" do
+    (Rational(3, 4) / Rational(3, 4)).should eql(Rational(1, 1))
+    (Rational(2, 4) / Rational(1, 4)).should eql(Rational(2, 1))
+
+    (Rational(2, 4) / 2).should == Rational(1, 4)
+    (Rational(6, 7) / -2).should == Rational(-3, 7)
+  end
+
+  it "raises a ZeroDivisionError when passed a Rational with a numerator of 0" do
+    -> { Rational(3, 4) / Rational(0, 1) }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#/ when passed a Float" do
-  it_behaves_like :rational_divide_float, :/
+  it "returns self divided by other as a Float" do
+    (Rational(3, 4) / 0.75).should eql(1.0)
+    (Rational(3, 4) / 0.25).should eql(3.0)
+    (Rational(3, 4) / 0.3).should eql(2.5)
+
+    (Rational(-3, 4) / 0.3).should eql(-2.5)
+    (Rational(3, -4) / 0.3).should eql(-2.5)
+    (Rational(3, 4) / -0.3).should eql(-2.5)
+  end
+
+  it "returns infinity when passed 0" do
+    (Rational(3, 4) / 0.0).infinite?.should eql(1)
+    (Rational(-3, -4) / 0.0).infinite?.should eql(1)
+
+    (Rational(-3, 4) / 0.0).infinite?.should eql(-1)
+    (Rational(3, -4) / 0.0).infinite?.should eql(-1)
+  end
 end
diff --git a/spec/ruby/core/rational/divmod_spec.rb b/spec/ruby/core/rational/divmod_spec.rb
index 6be1f8bd73..f0555294a3 100644
--- a/spec/ruby/core/rational/divmod_spec.rb
+++ b/spec/ruby/core/rational/divmod_spec.rb
@@ -1,13 +1,42 @@
-require_relative '../../shared/rational/divmod'
+require_relative "../../spec_helper"
 
 describe "Rational#divmod when passed a Rational" do
-  it_behaves_like :rational_divmod_rat, :divmod
+  it "returns the quotient as Integer and the remainder as Rational" do
+    Rational(7, 4).divmod(Rational(1, 2)).should eql([3, Rational(1, 4)])
+    Rational(7, 4).divmod(Rational(-1, 2)).should eql([-4, Rational(-1, 4)])
+    Rational(0, 4).divmod(Rational(4, 3)).should eql([0, Rational(0, 1)])
+
+    Rational(bignum_value, 4).divmod(Rational(4, 3)).should eql([3458764513820540928, Rational(0, 1)])
+  end
+
+  it "raises a ZeroDivisionError when passed a Rational with a numerator of 0" do
+    -> { Rational(7, 4).divmod(Rational(0, 3)) }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#divmod when passed an Integer" do
-  it_behaves_like :rational_divmod_int, :divmod
+  it "returns the quotient as Integer and the remainder as Rational" do
+    Rational(7, 4).divmod(2).should eql([0, Rational(7, 4)])
+    Rational(7, 4).divmod(-2).should eql([-1, Rational(-1, 4)])
+
+    Rational(bignum_value, 4).divmod(3).should eql([1537228672809129301, Rational(1, 1)])
+  end
+
+  it "raises a ZeroDivisionError when passed 0" do
+    -> { Rational(7, 4).divmod(0) }.should raise_error(ZeroDivisionError)
+  end
 end
 
 describe "Rational#divmod when passed a Float" do
-  it_behaves_like :rational_divmod_float, :divmod
+  it "returns the quotient as Integer and the remainder as Float" do
+    Rational(7, 4).divmod(0.5).should eql([3, 0.25])
+  end
+
+  it "returns the quotient as Integer and the remainder as Float" do
+    Rational(7, 4).divmod(-0.5).should eql([-4, -0.25])
+  end
+
+  it "raises a ZeroDivisionError when passed 0" do
+    -> { Rational(7, 4).divmod(0.0) }.should raise_error(ZeroDivisionError)
+  end
 end
diff --git a/spec/ruby/core/rational/equal_value_spec.rb b/spec/ruby/core/rational/equal_value_spec.rb
index 8e7acb1354..ba40d29c3b 100644
--- a/spec/ruby/core/rational/equal_value_spec.rb
+++ b/spec/ruby/core/rational/equal_value_spec.rb
@@ -1,17 +1,39 @@
-require_relative '../../shared/rational/equal_value'
+require_relative "../../spec_helper"
 
 describe "Rational#==" do
-  it_behaves_like :rational_equal_value, :==
+  it "returns the result of calling #== with self on the passed argument" do
+    obj = mock("Object")
+    obj.should_receive(:==).and_return(:result)
+
+    (Rational(3, 4) == obj).should_not be_false
+  end
 end
 
 describe "Rational#== when passed a Rational" do
-  it_behaves_like :rational_equal_value_rat, :==
+  it "returns true if self has the same numerator and denominator as the passed argument" do
+    (Rational(3, 4) == Rational(3, 4)).should be_true
+    (Rational(-3, -4) == Rational(3, 4)).should be_true
+    (Rational(-4, 5) == Rational(4, -5)).should be_true
+
+    (Rational(bignum_value, 3) == Rational(bignum_value, 3)).should be_true
+    (Rational(-bignum_value, 3) == Rational(bignum_value, -3)).should be_true
+  end
 end
 
 describe "Rational#== when passed a Float" do
-  it_behaves_like :rational_equal_value_float, :==
+  it "converts self to a Float and compares it with the passed argument" do
+    (Rational(3, 4) == 0.75).should be_true
+    (Rational(4, 2) == 2.0).should be_true
+    (Rational(-4, 2) == -2.0).should be_true
+    (Rational(4, -2) == -2.0).should be_true
+  end
 end
 
 describe "Rational#== when passed an Integer" do
-  it_behaves_like :rational_equal_value_int, :==
+  it "returns true if self has the passed argument as numerator and a denominator of 1" do
+    # Rational(x, y) reduces x and y automatically
+    (Rational(4, 2) == 2).should be_true
+    (Rational(-4, 2) == -2).should be_true
+    (Rational(4, -2) == -2).should be_true
+  end
 end
diff --git a/spec/ruby/core/rational/exponent_spec.rb b/spec/ruby/core/rational/exponent_spec.rb
index 622cf22782..65fbf2ed1c 100644
--- a/spec/ruby/core/rational/exponent_spec.rb
+++ b/spec/ruby/core/rational/exponent_spec.rb
@@ -1,5 +1,236 @@
-require_relative '../../shared/rational/exponent'
+require_relative "../../spec_helper"
 
 describe "Rational#**" do
-  it_behaves_like :rational_exponent, :**
+  describe "when passed Rational" do
+    # Guard against the Mathn library
+    guard -> { !defined?(Math.rsqrt) } do
+      it "returns Rational(1) if the exponent is Rational(0)" do
+        (Rational(0) ** Rational(0)).should eql(Rational(1))
+        (Rational(1) ** Rational(0)).should eql(Rational(1))
+        (Rational(3, 4) ** Rational(0)).should eql(Rational(1))
+        (Rational(-1) ** Rational(0)).should eql(Rational(1))
+        (Rational(-3, 4) ** Rational(0)).should eql(Rational(1))
+        (Rational(bignum_value) ** Rational(0)).should eql(Rational(1))
+        (Rational(-bignum_value) ** Rational(0)).should eql(Rational(1))
+      end
+
+      it "returns self raised to the argument as a Rational if the exponent's denominator is 1" do
+        (Rational(3, 4) ** Rational(1, 1)).should eql(Rational(3, 4))
+        (Rational(3, 4) ** Rational(2, 1)).should eql(Rational(9, 16))
+        (Rational(3, 4) ** Rational(-1, 1)).should eql(Rational(4, 3))
+        (Rational(3, 4) ** Rational(-2, 1)).should eql(Rational(16, 9))
+      end
+
+      it "returns self raised to the argument as a Float if the exponent's denominator is not 1" do
+        (Rational(3, 4) ** Rational(4, 3)).should be_close(0.681420222312052, TOLERANCE)
+        (Rational(3, 4) ** Rational(-4, 3)).should be_close(1.46752322173095, TOLERANCE)
+        (Rational(3, 4) ** Rational(4, -3)).should be_close(1.46752322173095, TOLERANCE)
+      end
+
+      it "returns a complex number when self is negative and the passed argument is not 0" do
+        (Rational(-3, 4) ** Rational(-4, 3)).should be_close(Complex(-0.7337616108654732, 1.2709123906625817), TOLERANCE)
+      end
+    end
+  end
+
+  describe "when passed Integer" do
+    it "returns the Rational value of self raised to the passed argument" do
+      (Rational(3, 4) ** 4).should == Rational(81, 256)
+      (Rational(3, 4) ** -4).should == Rational(256, 81)
+      (Rational(-3, 4) ** -4).should == Rational(256, 81)
+      (Rational(3, -4) ** -4).should == Rational(256, 81)
+
+      (Rational(bignum_value, 4) ** 4).should == Rational(452312848583266388373324160190187140051835877600158453279131187530910662656, 1)
+      (Rational(3, bignum_value) ** -4).should == Rational(115792089237316195423570985008687907853269984665640564039457584007913129639936, 81)
+      (Rational(-bignum_value, 4) ** -4).should == Rational(1, 452312848583266388373324160190187140051835877600158453279131187530910662656)
+      (Rational(3, -bignum_value) ** -4).should == Rational(115792089237316195423570985008687907853269984665640564039457584007913129639936, 81)
+    end
+
+    # Guard against the Mathn library
+    guard -> { !defined?(Math.rsqrt) } do
+      it "returns Rational(1, 1) when the passed argument is 0" do
+        (Rational(3, 4) ** 0).should eql(Rational(1, 1))
+        (Rational(-3, 4) ** 0).should eql(Rational(1, 1))
+        (Rational(3, -4) ** 0).should eql(Rational(1, 1))
+
+        (Rational(bignum_value, 4) ** 0).should eql(Rational(1, 1))
+        (Rational(3, -bignum_value) ** 0).should eql(Rational(1, 1))
+      end
+    end
+  end
+
+  describe "when passed Bignum" do
+    # #5713
+    it "returns Rational(0) when self is Rational(0) and the exponent is positive" do
+      (Rational(0) ** bignum_value).should eql(Rational(0))
+    end
+
+    it "raises ZeroDivisionError when self is Rational(0) and the exponent is negative" do
+      -> { Rational(0) ** -bignum_value }.should raise_error(ZeroDivisionError)
+    end
+
+    it "returns Rational(1) when self is Rational(1)" do
+      (Rational(1) **  bignum_value).should eql(Rational(1))
+      (Rational(1) ** -bignum_value).should eql(Rational(1))
+    end
+
+    it "returns Rational(1) when self is Rational(-1) and the exponent is positive and even" do
+      (Rational(-1) ** bignum_value(0)).should eql(Rational(1))
+      (Rational(-1) ** bignum_value(2)).should eql(Rational(1))
+    end
+
+    it "returns Rational(-1) when self is Rational(-1) and the exponent is positive and odd" do
+      (Rational(-1) ** bignum_value(1)).should eql(Rational(-1))
+      (Rational(-1) ** bignum_value(3)).should eql(Rational(-1))
+    end
+
+    ruby_version_is ""..."3.4" do
+      it "returns positive Infinity when self is > 1" do
+        -> {
+          (Rational(2) ** bignum_value).infinite?.should == 1
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+        -> {
+          (Rational(fixnum_max) ** bignum_value).infinite?.should == 1
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+      end
+
+      it "returns 0.0 when self is > 1 and the exponent is negative" do
+        -> {
+          (Rational(2) ** -bignum_value).should eql(0.0)
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+        -> {
+          (Rational(fixnum_max) ** -bignum_value).should eql(0.0)
+        }.should complain(/warning: in a\*\*b, b may be too big/)
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "raises an ArgumentError when self is > 1" do
+        -> {
+          (Rational(2) ** bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_max) ** bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+
+      it "raises an ArgumentError when self is > 1 and the exponent is negative" do
+        -> {
+          (Rational(2) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_max) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+
+      it "raises an ArgumentError when self is < -1" do
+        -> {
+          (Rational(-2) ** bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_min) ** bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+
+      it "raises an ArgumentError when self is < -1 and the exponent is negative" do
+        -> {
+          (Rational(-2) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+        -> {
+          (Rational(fixnum_min) ** -bignum_value)
+        }.should raise_error(ArgumentError)
+      end
+    end
+
+    # Fails on linux due to pow() bugs in glibc: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866
+    platform_is_not :linux do
+      ruby_version_is ""..."3.4" do
+        it "returns positive Infinity when self < -1" do
+          -> {
+            (Rational(-2) ** bignum_value).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(-2) ** (bignum_value + 1)).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(fixnum_min) ** bignum_value).infinite?.should == 1
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+        end
+
+        it "returns 0.0 when self is < -1 and the exponent is negative" do
+          -> {
+            (Rational(-2) ** -bignum_value).should eql(0.0)
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+          -> {
+            (Rational(fixnum_min) ** -bignum_value).should eql(0.0)
+          }.should complain(/warning: in a\*\*b, b may be too big/)
+        end
+      end
+    end
+  end
+
+  describe "when passed Float" do
+    it "returns self converted to Float and raised to the passed argument" do
+      (Rational(3, 1) ** 3.0).should eql(27.0)
+      (Rational(3, 1) ** 1.5).should be_close(5.19615242270663, TOLERANCE)
+      (Rational(3, 1) ** -1.5).should be_close(0.192450089729875, TOLERANCE)
+    end
+
+    it "returns a complex number if self is negative and the passed argument is not 0" do
+      (Rational(-3, 2) ** 1.5).should be_close(Complex(0.0, -1.8371173070873836), TOLERANCE)
+      (Rational(3, -2) ** 1.5).should be_close(Complex(0.0, -1.8371173070873836), TOLERANCE)
+      (Rational(3, -2) ** -1.5).should be_close(Complex(0.0, 0.5443310539518174), TOLERANCE)
+    end
+
+    it "returns Complex(1.0) when the passed argument is 0.0" do
+      (Rational(3, 4) ** 0.0).should == Complex(1.0)
+      (Rational(-3, 4) ** 0.0).should == Complex(1.0)
+      (Rational(-3, 4) ** 0.0).should == Complex(1.0)
+    end
+  end
+
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj      = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational ** obj
+  end
+
+  it "calls #** on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:**).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational ** obj).should == :result
+  end
+
+  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Integer" do
+    [-1, -4, -9999].each do |exponent|
+      -> { Rational(0, 1) ** exponent }.should raise_error(ZeroDivisionError, "divided by 0")
+    end
+  end
+
+  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Rational with denominator 1" do
+    [Rational(-1, 1), Rational(-3, 1)].each do |exponent|
+      -> { Rational(0, 1) ** exponent }.should raise_error(ZeroDivisionError, "divided by 0")
+    end
+  end
+
+  # #7513
+  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Rational" do
+    -> { Rational(0, 1) ** Rational(-3, 2) }.should raise_error(ZeroDivisionError, "divided by 0")
+  end
+
+  it "returns Infinity for Rational(0, 1) passed a negative Float" do
+    [-1.0, -3.0, -3.14].each do |exponent|
+      (Rational(0, 1) ** exponent).infinite?.should == 1
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/fdiv_spec.rb b/spec/ruby/core/rational/fdiv_spec.rb
index bfb321abaa..118d93dbe7 100644
--- a/spec/ruby/core/rational/fdiv_spec.rb
+++ b/spec/ruby/core/rational/fdiv_spec.rb
@@ -1,5 +1,5 @@
-require_relative '../../shared/rational/fdiv'
+require_relative "../../spec_helper"
 
 describe "Rational#fdiv" do
-  it_behaves_like :rational_fdiv, :fdiv
+  it "needs to be reviewed for spec completeness"
 end
diff --git a/spec/ruby/fixtures/rational.rb b/spec/ruby/core/rational/fixtures/rational.rb
index 844d7f9820..844d7f9820 100644
--- a/spec/ruby/fixtures/rational.rb
+++ b/spec/ruby/core/rational/fixtures/rational.rb
diff --git a/spec/ruby/core/rational/floor_spec.rb b/spec/ruby/core/rational/floor_spec.rb
index 752a2d8815..8068aaf119 100644
--- a/spec/ruby/core/rational/floor_spec.rb
+++ b/spec/ruby/core/rational/floor_spec.rb
@@ -1,5 +1,45 @@
-require_relative '../../shared/rational/floor'
+require_relative "../../spec_helper"
 
 describe "Rational#floor" do
-  it_behaves_like :rational_floor, :floor
+  before do
+    @rational = Rational(2200, 7)
+  end
+
+  describe "with no arguments (precision = 0)" do
+    it "returns an integer" do
+      @rational.floor.should be_kind_of(Integer)
+    end
+
+    it "returns the truncated value toward negative infinity" do
+      @rational.floor.should == 314
+      Rational(1, 2).floor.should == 0
+      Rational(-1, 2).floor.should == -1
+    end
+  end
+
+  describe "with a precision < 0" do
+    it "returns an integer" do
+      @rational.floor(-2).should be_kind_of(Integer)
+      @rational.floor(-1).should be_kind_of(Integer)
+    end
+
+    it "moves the truncation point n decimal places left" do
+      @rational.floor(-3).should == 0
+      @rational.floor(-2).should == 300
+      @rational.floor(-1).should == 310
+    end
+  end
+
+  describe "with a precision > 0" do
+    it "returns a Rational" do
+      @rational.floor(1).should be_kind_of(Rational)
+      @rational.floor(2).should be_kind_of(Rational)
+    end
+
+    it "moves the truncation point n decimal places right" do
+      @rational.floor(1).should == Rational(1571, 5)
+      @rational.floor(2).should == Rational(7857, 25)
+      @rational.floor(3).should == Rational(62857, 200)
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/hash_spec.rb b/spec/ruby/core/rational/hash_spec.rb
index 84cd31518a..528638056a 100644
--- a/spec/ruby/core/rational/hash_spec.rb
+++ b/spec/ruby/core/rational/hash_spec.rb
@@ -1,5 +1,9 @@
-require_relative '../../shared/rational/hash'
+require_relative "../../spec_helper"
 
 describe "Rational#hash" do
-  it_behaves_like :rational_hash, :hash
+  # BUG: Rational(2, 3).hash == Rational(3, 2).hash
+  it "is static" do
+    Rational(2, 3).hash.should == Rational(2, 3).hash
+    Rational(2, 4).hash.should_not == Rational(2, 3).hash
+  end
 end
diff --git a/spec/ruby/core/rational/inspect_spec.rb b/spec/ruby/core/rational/inspect_spec.rb
index ef337ef0ce..edc5cffee9 100644
--- a/spec/ruby/core/rational/inspect_spec.rb
+++ b/spec/ruby/core/rational/inspect_spec.rb
@@ -1,5 +1,14 @@
-require_relative '../../shared/rational/inspect'
+require_relative "../../spec_helper"
 
 describe "Rational#inspect" do
-  it_behaves_like :rational_inspect, :inspect
+  it "returns a string representation of self" do
+    Rational(3, 4).inspect.should == "(3/4)"
+    Rational(-5, 8).inspect.should == "(-5/8)"
+    Rational(-1, -2).inspect.should == "(1/2)"
+
+    # Guard against the Mathn library
+    guard -> { !defined?(Math.rsqrt) } do
+      Rational(bignum_value, 1).inspect.should == "(#{bignum_value}/1)"
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/integer_spec.rb b/spec/ruby/core/rational/integer_spec.rb
index 0f9a3bdead..be7476a9dd 100644
--- a/spec/ruby/core/rational/integer_spec.rb
+++ b/spec/ruby/core/rational/integer_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 describe "Rational#integer?" do
   # Guard against the Mathn library
   guard -> { !defined?(Math.rsqrt) } do
diff --git a/spec/ruby/core/rational/magnitude_spec.rb b/spec/ruby/core/rational/magnitude_spec.rb
index 878fc8f879..f5f667edb1 100644
--- a/spec/ruby/core/rational/magnitude_spec.rb
+++ b/spec/ruby/core/rational/magnitude_spec.rb
@@ -1,4 +1,5 @@
-require_relative '../../shared/rational/abs'
+require_relative "../../spec_helper"
+require_relative 'shared/abs'
 
 describe "Rational#abs" do
   it_behaves_like :rational_abs, :magnitude
diff --git a/spec/ruby/core/rational/minus_spec.rb b/spec/ruby/core/rational/minus_spec.rb
index 9e0f81556b..8aee85f9dd 100644
--- a/spec/ruby/core/rational/minus_spec.rb
+++ b/spec/ruby/core/rational/minus_spec.rb
@@ -1,7 +1,51 @@
-require_relative '../../shared/rational/minus'
-require_relative '../../shared/rational/arithmetic_exception_in_coerce'
+require_relative '../../spec_helper'
+require_relative 'shared/arithmetic_exception_in_coerce'
 
 describe "Rational#-" do
-  it_behaves_like :rational_minus, :-
   it_behaves_like :rational_arithmetic_exception_in_coerce, :-
+
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational - obj
+  end
+
+  it "calls #- on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:-).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational - obj).should == :result
+  end
+end
+
+describe "Rational#- passed a Rational" do
+  it "returns the result of subtracting other from self as a Rational" do
+    (Rational(3, 4) - Rational(0, 1)).should eql(Rational(3, 4))
+    (Rational(3, 4) - Rational(1, 4)).should eql(Rational(1, 2))
+
+    (Rational(3, 4) - Rational(2, 1)).should eql(Rational(-5, 4))
+  end
+end
+
+describe "Rational#- passed a Float" do
+  it "returns the result of subtracting other from self as a Float" do
+    (Rational(3, 4) - 0.2).should eql(0.55)
+    (Rational(3, 4) - 2.5).should eql(-1.75)
+  end
+end
+
+describe "Rational#- passed an Integer" do
+  it "returns the result of subtracting other from self as a Rational" do
+    (Rational(3, 4) - 1).should eql(Rational(-1, 4))
+    (Rational(3, 4) - 2).should eql(Rational(-5, 4))
+  end
 end
diff --git a/spec/ruby/core/rational/modulo_spec.rb b/spec/ruby/core/rational/modulo_spec.rb
index c43f7788e3..23ed93e118 100644
--- a/spec/ruby/core/rational/modulo_spec.rb
+++ b/spec/ruby/core/rational/modulo_spec.rb
@@ -1,5 +1,43 @@
-require_relative '../../shared/rational/modulo'
+require_relative "../../spec_helper"
 
 describe "Rational#%" do
-  it_behaves_like :rational_modulo, :%
+  it "returns the remainder when this value is divided by other" do
+    (Rational(2, 3) % Rational(2, 3)).should == Rational(0, 1)
+    (Rational(4, 3) % Rational(2, 3)).should == Rational(0, 1)
+    (Rational(2, -3) % Rational(-2, 3)).should == Rational(0, 1)
+    (Rational(0, -1) % -1).should == Rational(0, 1)
+
+    (Rational(7, 4) % Rational(1, 2)).should == Rational(1, 4)
+    (Rational(7, 4) % 1).should == Rational(3, 4)
+    (Rational(7, 4) % Rational(1, 7)).should == Rational(1, 28)
+
+    (Rational(3, 4) % -1).should == Rational(-1, 4)
+    (Rational(1, -5) % -1).should == Rational(-1, 5)
+  end
+
+  it "returns a Float value when the argument is Float" do
+    (Rational(7, 4) % 1.0).should be_kind_of(Float)
+    (Rational(7, 4) % 1.0).should == 0.75
+    (Rational(7, 4) % 0.26).should be_close(0.19, 0.0001)
+  end
+
+  it "raises ZeroDivisionError on zero denominator" do
+    -> {
+      Rational(3, 5) % Rational(0, 1)
+    }.should raise_error(ZeroDivisionError)
+
+    -> {
+      Rational(0, 1) % Rational(0, 1)
+    }.should raise_error(ZeroDivisionError)
+
+    -> {
+      Rational(3, 5) % 0
+    }.should raise_error(ZeroDivisionError)
+  end
+
+  it "raises a ZeroDivisionError when the argument is 0.0" do
+    -> {
+      Rational(3, 5) % 0.0
+    }.should raise_error(ZeroDivisionError)
+  end
 end
diff --git a/spec/ruby/core/rational/multiply_spec.rb b/spec/ruby/core/rational/multiply_spec.rb
index ea644074e9..87fb4de2b4 100644
--- a/spec/ruby/core/rational/multiply_spec.rb
+++ b/spec/ruby/core/rational/multiply_spec.rb
@@ -1,19 +1,65 @@
-require_relative '../../shared/rational/multiply'
-require_relative '../../shared/rational/arithmetic_exception_in_coerce'
+require_relative "../../spec_helper"
+require_relative 'shared/arithmetic_exception_in_coerce'
 
 describe "Rational#*" do
-  it_behaves_like :rational_multiply, :*
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational * obj
+  end
+
+  it "calls #* on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:*).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational * obj).should == :result
+  end
+
   it_behaves_like :rational_arithmetic_exception_in_coerce, :*
 end
 
 describe "Rational#* passed a Rational" do
-  it_behaves_like :rational_multiply_rat, :*
+  it "returns self divided by other as a Rational" do
+    (Rational(3, 4) * Rational(3, 4)).should eql(Rational(9, 16))
+    (Rational(2, 4) * Rational(1, 4)).should eql(Rational(1, 8))
+
+    (Rational(3, 4) * Rational(0, 1)).should eql(Rational(0, 4))
+  end
 end
 
 describe "Rational#* passed a Float" do
-  it_behaves_like :rational_multiply_float, :*
+  it "returns self divided by other as a Float" do
+    (Rational(3, 4) * 0.75).should eql(0.5625)
+    (Rational(3, 4) * 0.25).should eql(0.1875)
+    (Rational(3, 4) * 0.3).should be_close(0.225, TOLERANCE)
+
+    (Rational(-3, 4) * 0.3).should be_close(-0.225, TOLERANCE)
+    (Rational(3, -4) * 0.3).should be_close(-0.225, TOLERANCE)
+    (Rational(3, 4) * -0.3).should be_close(-0.225, TOLERANCE)
+
+    (Rational(3, 4) * 0.0).should eql(0.0)
+    (Rational(-3, -4) * 0.0).should eql(0.0)
+
+    (Rational(-3, 4) * 0.0).should eql(0.0)
+    (Rational(3, -4) * 0.0).should eql(0.0)
+  end
 end
 
 describe "Rational#* passed an Integer" do
-  it_behaves_like :rational_multiply_int, :*
+  it "returns self divided by other as a Rational" do
+    (Rational(3, 4) * 2).should eql(Rational(3, 2))
+    (Rational(2, 4) * 2).should eql(Rational(1, 1))
+    (Rational(6, 7) * -2).should eql(Rational(-12, 7))
+
+    (Rational(3, 4) * 0).should eql(Rational(0, 4))
+  end
 end
diff --git a/spec/ruby/core/rational/numerator_spec.rb b/spec/ruby/core/rational/numerator_spec.rb
index 85b2ed9e86..2b9fe2ff5c 100644
--- a/spec/ruby/core/rational/numerator_spec.rb
+++ b/spec/ruby/core/rational/numerator_spec.rb
@@ -1,5 +1,10 @@
-require_relative '../../shared/rational/numerator'
+require_relative "../../spec_helper"
 
 describe "Rational#numerator" do
-  it_behaves_like :rational_numerator, :numerator
+  it "returns the numerator" do
+    Rational(3, 4).numerator.should equal(3)
+    Rational(3, -4).numerator.should equal(-3)
+
+    Rational(bignum_value, 1).numerator.should == bignum_value
+  end
 end
diff --git a/spec/ruby/core/rational/plus_spec.rb b/spec/ruby/core/rational/plus_spec.rb
index e7ef3a8f92..01df5f6719 100644
--- a/spec/ruby/core/rational/plus_spec.rb
+++ b/spec/ruby/core/rational/plus_spec.rb
@@ -1,18 +1,50 @@
-require_relative '../../shared/rational/plus'
-require_relative '../../shared/rational/arithmetic_exception_in_coerce'
+require_relative "../../spec_helper"
+require_relative 'shared/arithmetic_exception_in_coerce'
 
 describe "Rational#+" do
-  it_behaves_like :rational_plus, :+
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational + obj
+  end
+
+  it "calls #+ on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:+).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    (rational + obj).should == :result
+  end
+
   it_behaves_like :rational_arithmetic_exception_in_coerce, :+
 end
 
 describe "Rational#+ with a Rational" do
-  it_behaves_like :rational_plus_rat, :+
+  it "returns the result of subtracting other from self as a Rational" do
+    (Rational(3, 4) + Rational(0, 1)).should eql(Rational(3, 4))
+    (Rational(3, 4) + Rational(1, 4)).should eql(Rational(1, 1))
+
+    (Rational(3, 4) + Rational(2, 1)).should eql(Rational(11, 4))
+  end
 end
 describe "Rational#+ with a Float" do
-  it_behaves_like :rational_plus_float, :+
+  it "returns the result of subtracting other from self as a Float" do
+    (Rational(3, 4) + 0.2).should eql(0.95)
+    (Rational(3, 4) + 2.5).should eql(3.25)
+  end
 end
 
 describe "Rational#+ with an Integer" do
-  it_behaves_like :rational_plus_int, :+
+  it "returns the result of subtracting other from self as a Rational" do
+    (Rational(3, 4) + 1).should eql(Rational(7, 4))
+    (Rational(3, 4) + 2).should eql(Rational(11, 4))
+  end
 end
diff --git a/spec/ruby/core/rational/quo_spec.rb b/spec/ruby/core/rational/quo_spec.rb
index 119aca1955..907898ad34 100644
--- a/spec/ruby/core/rational/quo_spec.rb
+++ b/spec/ruby/core/rational/quo_spec.rb
@@ -1,5 +1,25 @@
-require_relative '../../shared/rational/divide'
+require_relative "../../spec_helper"
 
 describe "Rational#quo" do
-  it_behaves_like :rational_divide, :quo
+  it "calls #coerce on the passed argument with self" do
+    rational = Rational(3, 4)
+    obj = mock("Object")
+    obj.should_receive(:coerce).with(rational).and_return([1, 2])
+
+    rational.quo(obj)
+  end
+
+  it "calls #/ on the coerced Rational with the coerced Object" do
+    rational = Rational(3, 4)
+
+    coerced_rational = mock("Coerced Rational")
+    coerced_rational.should_receive(:/).and_return(:result)
+
+    coerced_obj = mock("Coerced Object")
+
+    obj = mock("Object")
+    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
+
+    rational.quo(obj).should == :result
+  end
 end
diff --git a/spec/ruby/core/rational/rational_spec.rb b/spec/ruby/core/rational/rational_spec.rb
index 704e49354e..482deab38d 100644
--- a/spec/ruby/core/rational/rational_spec.rb
+++ b/spec/ruby/core/rational/rational_spec.rb
@@ -4,4 +4,8 @@ describe "Rational" do
   it "includes Comparable" do
     Rational.include?(Comparable).should == true
   end
+
+  it "does not respond to new" do
+    -> { Rational.new(1) }.should raise_error(NoMethodError)
+  end
 end
diff --git a/spec/ruby/core/rational/remainder_spec.rb b/spec/ruby/core/rational/remainder_spec.rb
index 0f9442f6f5..86ba4674e6 100644
--- a/spec/ruby/core/rational/remainder_spec.rb
+++ b/spec/ruby/core/rational/remainder_spec.rb
@@ -1,5 +1,5 @@
-require_relative '../../shared/rational/remainder'
+require_relative "../../spec_helper"
 
 describe "Rational#remainder" do
-  it_behaves_like :rational_remainder, :remainder
+  it "needs to be reviewed for spec completeness"
 end
diff --git a/spec/ruby/core/rational/round_spec.rb b/spec/ruby/core/rational/round_spec.rb
index 36614a552d..ac3dcafe7b 100644
--- a/spec/ruby/core/rational/round_spec.rb
+++ b/spec/ruby/core/rational/round_spec.rb
@@ -1,6 +1,106 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/rational/round'
 
 describe "Rational#round" do
-  it_behaves_like :rational_round, :round
+  before do
+    @rational = Rational(2200, 7)
+  end
+
+  describe "with no arguments (precision = 0)" do
+    it "returns an integer" do
+      @rational.round.should be_kind_of(Integer)
+      Rational(0, 1).round(0).should be_kind_of(Integer)
+      Rational(124, 1).round(0).should be_kind_of(Integer)
+    end
+
+    it "returns the truncated value toward the nearest integer" do
+      @rational.round.should == 314
+      Rational(0, 1).round(0).should == 0
+      Rational(2, 1).round(0).should == 2
+    end
+
+    it "returns the rounded value toward the nearest integer" do
+      Rational(1, 2).round.should == 1
+      Rational(-1, 2).round.should == -1
+      Rational(3, 2).round.should == 2
+      Rational(-3, 2).round.should == -2
+      Rational(5, 2).round.should == 3
+      Rational(-5, 2).round.should == -3
+    end
+  end
+
+  describe "with a precision < 0" do
+    it "returns an integer" do
+      @rational.round(-2).should be_kind_of(Integer)
+      @rational.round(-1).should be_kind_of(Integer)
+      Rational(0, 1).round(-1).should be_kind_of(Integer)
+      Rational(2, 1).round(-1).should be_kind_of(Integer)
+    end
+
+    it "moves the truncation point n decimal places left" do
+      @rational.round(-3).should == 0
+      @rational.round(-2).should == 300
+      @rational.round(-1).should == 310
+    end
+  end
+
+  describe "with a precision > 0" do
+    it "returns a Rational" do
+      @rational.round(1).should be_kind_of(Rational)
+      @rational.round(2).should be_kind_of(Rational)
+      # Guard against the Mathn library
+      guard -> { !defined?(Math.rsqrt) } do
+        Rational(0, 1).round(1).should be_kind_of(Rational)
+        Rational(2, 1).round(1).should be_kind_of(Rational)
+      end
+    end
+
+    it "moves the truncation point n decimal places right" do
+      @rational.round(1).should == Rational(3143, 10)
+      @rational.round(2).should == Rational(31429, 100)
+      @rational.round(3).should == Rational(157143, 500)
+      Rational(0, 1).round(1).should == Rational(0, 1)
+      Rational(2, 1).round(1).should == Rational(2, 1)
+    end
+
+    it "doesn't alter the value if the precision is too great" do
+      Rational(3, 2).round(10).should == Rational(3, 2).round(20)
+    end
+
+    # #6605
+    it "doesn't fail when rounding to an absurdly large positive precision" do
+      Rational(3, 2).round(2_097_171).should == Rational(3, 2)
+    end
+  end
+
+  describe "with half option" do
+    it "returns an Integer when precision is not passed" do
+      Rational(10, 4).round(half: nil).should == 3
+      Rational(10, 4).round(half: :up).should == 3
+      Rational(10, 4).round(half: :down).should == 2
+      Rational(10, 4).round(half: :even).should == 2
+      Rational(-10, 4).round(half: nil).should == -3
+      Rational(-10, 4).round(half: :up).should == -3
+      Rational(-10, 4).round(half: :down).should == -2
+      Rational(-10, 4).round(half: :even).should == -2
+    end
+
+    it "returns a Rational when the precision is greater than 0" do
+      Rational(25, 100).round(1, half: nil).should == Rational(3, 10)
+      Rational(25, 100).round(1, half: :up).should == Rational(3, 10)
+      Rational(25, 100).round(1, half: :down).should == Rational(1, 5)
+      Rational(25, 100).round(1, half: :even).should == Rational(1, 5)
+      Rational(35, 100).round(1, half: nil).should == Rational(2, 5)
+      Rational(35, 100).round(1, half: :up).should == Rational(2, 5)
+      Rational(35, 100).round(1, half: :down).should == Rational(3, 10)
+      Rational(35, 100).round(1, half: :even).should == Rational(2, 5)
+      Rational(-25, 100).round(1, half: nil).should == Rational(-3, 10)
+      Rational(-25, 100).round(1, half: :up).should == Rational(-3, 10)
+      Rational(-25, 100).round(1, half: :down).should == Rational(-1, 5)
+      Rational(-25, 100).round(1, half: :even).should == Rational(-1, 5)
+    end
+
+    it "raise for a non-existent round mode" do
+      -> { Rational(10, 4).round(half: :nonsense) }.should raise_error(ArgumentError, "invalid rounding mode: nonsense")
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/shared/abs.rb b/spec/ruby/core/rational/shared/abs.rb
new file mode 100644
index 0000000000..3d64bcc1a0
--- /dev/null
+++ b/spec/ruby/core/rational/shared/abs.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+
+describe :rational_abs, shared: true do
+  it "returns self's absolute value" do
+    Rational(3, 4).send(@method).should == Rational(3, 4)
+    Rational(-3, 4).send(@method).should == Rational(3, 4)
+    Rational(3, -4).send(@method).should == Rational(3, 4)
+
+    Rational(bignum_value, -bignum_value).send(@method).should == Rational(bignum_value, bignum_value)
+  end
+end
diff --git a/spec/ruby/core/rational/shared/arithmetic_exception_in_coerce.rb b/spec/ruby/core/rational/shared/arithmetic_exception_in_coerce.rb
new file mode 100644
index 0000000000..f4cf70d147
--- /dev/null
+++ b/spec/ruby/core/rational/shared/arithmetic_exception_in_coerce.rb
@@ -0,0 +1,11 @@
+require_relative '../fixtures/rational'
+
+describe :rational_arithmetic_exception_in_coerce, shared: true do
+  it "does not rescue exception raised in other#coerce" do
+    b = mock("numeric with failed #coerce")
+    b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
+
+    # e.g. Rational(3, 4) + b
+    -> { Rational(3, 4).send(@method, b) }.should raise_error(RationalSpecs::CoerceError)
+  end
+end
diff --git a/spec/ruby/core/rational/to_f_spec.rb b/spec/ruby/core/rational/to_f_spec.rb
index 15bf1e88dc..d0da49d377 100644
--- a/spec/ruby/core/rational/to_f_spec.rb
+++ b/spec/ruby/core/rational/to_f_spec.rb
@@ -1,5 +1,16 @@
-require_relative '../../shared/rational/to_f'
+require_relative "../../spec_helper"
 
 describe "Rational#to_f" do
-  it_behaves_like :rational_to_f, :to_f
+  it "returns self converted to a Float" do
+    Rational(3, 4).to_f.should eql(0.75)
+    Rational(3, -4).to_f.should eql(-0.75)
+    Rational(-1, 4).to_f.should eql(-0.25)
+    Rational(-1, -4).to_f.should eql(0.25)
+  end
+
+  it "converts to a Float for large numerator and denominator" do
+    num = 1000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146010000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146010000000000000000000000000000000000048148248609680896326399448564623182963452541226153892315137780403285956264146009
+    den = 2000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
+    Rational(num, den).to_f.should == 500.0
+  end
 end
diff --git a/spec/ruby/core/rational/to_i_spec.rb b/spec/ruby/core/rational/to_i_spec.rb
index 3deb3664e1..520a380b2a 100644
--- a/spec/ruby/core/rational/to_i_spec.rb
+++ b/spec/ruby/core/rational/to_i_spec.rb
@@ -1,5 +1,12 @@
-require_relative '../../shared/rational/to_i'
+require_relative "../../spec_helper"
 
 describe "Rational#to_i" do
-  it_behaves_like :rational_to_i, :to_i
+  it "converts self to an Integer by truncation" do
+    Rational(7, 4).to_i.should eql(1)
+    Rational(11, 4).to_i.should eql(2)
+  end
+
+  it "converts self to an Integer by truncation" do
+    Rational(-7, 4).to_i.should eql(-1)
+  end
 end
diff --git a/spec/ruby/core/rational/to_r_spec.rb b/spec/ruby/core/rational/to_r_spec.rb
index cc704c965e..34f16d7890 100644
--- a/spec/ruby/core/rational/to_r_spec.rb
+++ b/spec/ruby/core/rational/to_r_spec.rb
@@ -1,7 +1,13 @@
-require_relative '../../shared/rational/to_r'
+require_relative "../../spec_helper"
 
 describe "Rational#to_r" do
-  it_behaves_like :rational_to_r, :to_r
+  it "returns self" do
+    a = Rational(3, 4)
+    a.to_r.should equal(a)
+
+    a = Rational(bignum_value, 4)
+    a.to_r.should equal(a)
+  end
 
   it "raises TypeError trying to convert BasicObject" do
     obj = BasicObject.new
diff --git a/spec/ruby/core/rational/to_s_spec.rb b/spec/ruby/core/rational/to_s_spec.rb
index c5c419787c..24e30778e5 100644
--- a/spec/ruby/core/rational/to_s_spec.rb
+++ b/spec/ruby/core/rational/to_s_spec.rb
@@ -1,5 +1,14 @@
-require_relative '../../shared/rational/to_s'
+require_relative "../../spec_helper"
 
 describe "Rational#to_s" do
-  it_behaves_like :rational_to_s, :to_s
+  it "returns a string representation of self" do
+    # Guard against the Mathn library
+    guard -> { !defined?(Math.rsqrt) } do
+      Rational(1, 1).to_s.should == "1/1"
+      Rational(2, 1).to_s.should == "2/1"
+    end
+    Rational(1, 2).to_s.should == "1/2"
+    Rational(-1, 3).to_s.should == "-1/3"
+    Rational(1, -3).to_s.should == "-1/3"
+  end
 end
diff --git a/spec/ruby/core/rational/truncate_spec.rb b/spec/ruby/core/rational/truncate_spec.rb
index 4e72339752..728fca34ea 100644
--- a/spec/ruby/core/rational/truncate_spec.rb
+++ b/spec/ruby/core/rational/truncate_spec.rb
@@ -1,5 +1,71 @@
-require_relative '../../shared/rational/truncate'
+require_relative "../../spec_helper"
 
 describe "Rational#truncate" do
-  it_behaves_like :rational_truncate, :truncate
+  before do
+    @rational = Rational(2200, 7)
+  end
+
+  describe "with no arguments (precision = 0)" do
+    it "returns an integer" do
+      @rational.truncate.should be_kind_of(Integer)
+    end
+
+    it "returns the truncated value toward 0" do
+      @rational.truncate.should == 314
+      Rational(1, 2).truncate.should == 0
+      Rational(-1, 2).truncate.should == 0
+    end
+  end
+
+  describe "with an explicit precision = 0" do
+    it "returns an integer" do
+      @rational.truncate(0).should be_kind_of(Integer)
+    end
+
+    it "returns the truncated value toward 0" do
+      @rational.truncate(0).should == 314
+      Rational(1, 2).truncate(0).should == 0
+      Rational(-1, 2).truncate(0).should == 0
+    end
+  end
+
+  describe "with a precision < 0" do
+    it "returns an integer" do
+      @rational.truncate(-2).should be_kind_of(Integer)
+      @rational.truncate(-1).should be_kind_of(Integer)
+    end
+
+    it "moves the truncation point n decimal places left" do
+      @rational.truncate(-3).should == 0
+      @rational.truncate(-2).should == 300
+      @rational.truncate(-1).should == 310
+    end
+  end
+
+  describe "with a precision > 0" do
+    it "returns a Rational" do
+      @rational.truncate(1).should be_kind_of(Rational)
+      @rational.truncate(2).should be_kind_of(Rational)
+    end
+
+    it "moves the truncation point n decimal places right" do
+      @rational.truncate(1).should == Rational(1571, 5)
+      @rational.truncate(2).should == Rational(7857, 25)
+      @rational.truncate(3).should == Rational(62857, 200)
+    end
+  end
+
+  describe "with an invalid value for precision" do
+    it "raises a TypeError" do
+      -> { @rational.truncate(nil) }.should raise_error(TypeError, "not an integer")
+      -> { @rational.truncate(1.0) }.should raise_error(TypeError, "not an integer")
+      -> { @rational.truncate('') }.should raise_error(TypeError, "not an integer")
+    end
+
+    it "does not call to_int on the argument" do
+      object = Object.new
+      object.should_not_receive(:to_int)
+      -> { @rational.truncate(object) }.should raise_error(TypeError, "not an integer")
+    end
+  end
 end
diff --git a/spec/ruby/core/rational/zero_spec.rb b/spec/ruby/core/rational/zero_spec.rb
index e6dd751922..af7fb391ac 100644
--- a/spec/ruby/core/rational/zero_spec.rb
+++ b/spec/ruby/core/rational/zero_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 describe "Rational#zero?" do
   it "returns true if the numerator is 0" do
     Rational(0,26).zero?.should be_true
diff --git a/spec/ruby/core/refinement/append_features_spec.rb b/spec/ruby/core/refinement/append_features_spec.rb
new file mode 100644
index 0000000000..f7e5f32bc1
--- /dev/null
+++ b/spec/ruby/core/refinement/append_features_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#append_features" do
+  it "is not defined" do
+    Refinement.should_not have_private_instance_method(:append_features)
+  end
+
+  it "is not called by Module#include" do
+    c = Class.new
+    Module.new do
+      refine c do
+        called = false
+        define_method(:append_features){called = true}
+        proc{c.include(self)}.should raise_error(TypeError)
+        called.should == false
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/extend_object_spec.rb b/spec/ruby/core/refinement/extend_object_spec.rb
new file mode 100644
index 0000000000..4da8b359cc
--- /dev/null
+++ b/spec/ruby/core/refinement/extend_object_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#extend_object" do
+  it "is not defined" do
+    Refinement.should_not have_private_instance_method(:extend_object)
+  end
+
+  it "is not called by Object#extend" do
+    c = Class.new
+    Module.new do
+      refine c do
+        called = false
+        define_method(:extend_object) { called = true }
+        -> {
+          c.extend(self)
+        }.should raise_error(TypeError)
+        called.should == false
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/fixtures/classes.rb b/spec/ruby/core/refinement/fixtures/classes.rb
new file mode 100644
index 0000000000..94324db47c
--- /dev/null
+++ b/spec/ruby/core/refinement/fixtures/classes.rb
@@ -0,0 +1,10 @@
+module RefinementSpec
+
+  module ModuleWithAncestors
+    include Module.new do
+      def indent(level)
+        " " * level + self
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/import_methods_spec.rb b/spec/ruby/core/refinement/import_methods_spec.rb
new file mode 100644
index 0000000000..13c0b1004c
--- /dev/null
+++ b/spec/ruby/core/refinement/import_methods_spec.rb
@@ -0,0 +1,267 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Refinement#import_methods" do
+  context "when methods are defined in Ruby code" do
+    it "imports methods" do
+      str_utils = Module.new do
+        def indent(level)
+          " " * level + self
+        end
+      end
+
+      Module.new do
+        refine String do
+          import_methods str_utils
+          "foo".indent(3).should == "   foo"
+        end
+      end
+    end
+
+    it "throws an exception when argument is not a module" do
+      Module.new do
+        refine String do
+          -> {
+            import_methods Integer
+          }.should raise_error(TypeError, "wrong argument type Class (expected Module)")
+        end
+      end
+    end
+
+    it "imports methods from multiple modules" do
+      str_utils = Module.new do
+        def indent(level)
+          " " * level + self
+        end
+      end
+
+      str_utils_fancy = Module.new do
+        def indent_star(level)
+          "*" * level + self
+        end
+      end
+
+      Module.new do
+        refine String do
+          import_methods str_utils, str_utils_fancy
+          "foo".indent(3).should == "   foo"
+          "foo".indent_star(3).should == "***foo"
+        end
+      end
+    end
+
+    it "imports a method defined in the last module if method with same name is defined in multiple modules" do
+      str_utils = Module.new do
+        def indent(level)
+          " " * level + self
+        end
+      end
+
+      str_utils_fancy = Module.new do
+        def indent(level)
+          "*" * level + self
+        end
+      end
+
+      Module.new do
+        refine String do
+          import_methods str_utils, str_utils_fancy
+          "foo".indent(3).should == "***foo"
+        end
+      end
+    end
+
+    it "still imports methods of modules listed before a module that contains method not defined in Ruby" do
+      str_utils = Module.new do
+        def indent(level)
+          " " * level + self
+        end
+      end
+
+      string_refined = Module.new do
+        refine String do
+          -> {
+            import_methods str_utils, Kernel
+          }.should raise_error(ArgumentError)
+        end
+      end
+
+      Module.new do
+        using string_refined
+        "foo".indent(3).should == "   foo"
+      end
+    end
+  end
+
+  it "warns if a module includes/prepends some other module" do
+    module1 = Module.new do
+    end
+
+    module2 = Module.new do
+      include module1
+    end
+
+    Module.new do
+      refine String do
+        -> {
+          import_methods module2
+        }.should complain(/warning: #<Module:\w*> has ancestors, but Refinement#import_methods doesn't import their methods/)
+      end
+    end
+
+    Module.new do
+      refine String do
+        -> {
+          import_methods RefinementSpec::ModuleWithAncestors
+        }.should complain(/warning: RefinementSpec::ModuleWithAncestors has ancestors, but Refinement#import_methods doesn't import their methods/)
+      end
+    end
+  end
+
+  it "doesn't import methods from included/prepended modules" do
+    Module.new do
+      refine String do
+        suppress_warning { import_methods RefinementSpec::ModuleWithAncestors }
+      end
+
+      using self
+      -> {
+        "foo".indent(3)
+      }.should raise_error(NoMethodError, /undefined method [`']indent' for ("foo":String|an instance of String)/)
+    end
+  end
+
+  it "doesn't import any methods if one of the arguments is not a module" do
+    str_utils = Module.new do
+      def indent(level)
+        " " * level + self
+      end
+    end
+
+    string_refined = Module.new do
+      refine String do
+        -> {
+          import_methods str_utils, Integer
+        }.should raise_error(TypeError)
+      end
+    end
+
+    Module.new do
+      using string_refined
+      -> {
+        "foo".indent(3)
+      }.should raise_error(NoMethodError)
+    end
+  end
+
+  it "imports methods from multiple modules so that methods see other's module's methods" do
+    str_utils = Module.new do
+      def indent(level)
+        " " * level + self
+      end
+    end
+
+    str_utils_normal = Module.new do
+      def indent_normal(level)
+        self.indent(level)
+      end
+    end
+
+    Module.new do
+      refine String do
+        import_methods str_utils, str_utils_normal
+      end
+
+      using self
+      "foo".indent_normal(3).should == "   foo"
+    end
+  end
+
+  it "imports methods from module so that methods can see each other" do
+    str_utils = Module.new do
+      def indent(level)
+        " " * level + self
+      end
+
+      def indent_with_dot(level)
+        self.indent(level) + "."
+      end
+    end
+
+    Module.new do
+      refine String do
+        import_methods str_utils
+      end
+
+      using self
+      "foo".indent_with_dot(3).should == "   foo."
+    end
+  end
+
+  it "doesn't import module's class methods" do
+    str_utils = Module.new do
+      def self.indent(level)
+        " " * level + self
+      end
+    end
+
+    Module.new do
+      refine String do
+        import_methods str_utils
+      end
+
+      using self
+      -> {
+        String.indent(3)
+      }.should raise_error(NoMethodError, /undefined method [`']indent' for (String:Class|class String)/)
+    end
+  end
+
+  it "imports module methods with super" do
+    class_to_refine = Class.new do
+      def foo(number)
+        2 * number
+      end
+    end
+
+    extension = Module.new do
+      def foo(number)
+        super * 2
+      end
+    end
+
+    refinement = Module.new do
+      refine class_to_refine do
+        import_methods extension
+      end
+    end
+
+    Module.new do
+      using refinement
+      class_to_refine.new.foo(2).should == 8
+    end
+  end
+
+  context "when methods are not defined in Ruby code" do
+    it "raises ArgumentError" do
+      Module.new do
+        refine String do
+          -> {
+            import_methods Kernel
+          }.should raise_error(ArgumentError)
+        end
+      end
+    end
+
+    it "raises ArgumentError when importing methods from C extension" do
+      require 'zlib'
+      Module.new do
+        refine String do
+          -> {
+            import_methods Zlib
+          }.should raise_error(ArgumentError, /Can't import method which is not defined with Ruby code: Zlib#*/)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/include_spec.rb b/spec/ruby/core/refinement/include_spec.rb
new file mode 100644
index 0000000000..57451bd9bc
--- /dev/null
+++ b/spec/ruby/core/refinement/include_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#include" do
+  it "raises a TypeError" do
+    Module.new do
+      refine String do
+        -> {
+          include Module.new
+        }.should raise_error(TypeError, "Refinement#include has been removed")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/prepend_features_spec.rb b/spec/ruby/core/refinement/prepend_features_spec.rb
new file mode 100644
index 0000000000..fbc431bbd2
--- /dev/null
+++ b/spec/ruby/core/refinement/prepend_features_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#prepend_features" do
+  it "is not defined" do
+    Refinement.should_not have_private_instance_method(:prepend_features)
+  end
+
+  it "is not called by Module#prepend" do
+    c = Class.new
+    Module.new do
+      refine c do
+        called = false
+        define_method(:prepend_features){called = true}
+        proc{c.prepend(self)}.should raise_error(TypeError)
+        called.should == false
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/prepend_spec.rb b/spec/ruby/core/refinement/prepend_spec.rb
new file mode 100644
index 0000000000..64cf7cd17f
--- /dev/null
+++ b/spec/ruby/core/refinement/prepend_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Refinement#prepend" do
+  it "raises a TypeError" do
+    Module.new do
+      refine String do
+        -> {
+          prepend Module.new
+        }.should raise_error(TypeError, "Refinement#prepend has been removed")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/refined_class_spec.rb b/spec/ruby/core/refinement/refined_class_spec.rb
new file mode 100644
index 0000000000..60a58380cc
--- /dev/null
+++ b/spec/ruby/core/refinement/refined_class_spec.rb
@@ -0,0 +1,38 @@
+require_relative "../../spec_helper"
+require_relative 'shared/target'
+
+describe "Refinement#refined_class" do
+  ruby_version_is ""..."3.3" do
+    it_behaves_like :refinement_target, :refined_class
+  end
+
+  ruby_version_is "3.3"..."3.4" do
+    it "has been deprecated in favour of Refinement#target" do
+      refinement_int = nil
+
+      Module.new do
+        refine Integer do
+          refinement_int = self
+        end
+      end
+
+      -> {
+        refinement_int.refined_class
+      }.should complain(/warning: Refinement#refined_class is deprecated and will be removed in Ruby 3.4; use Refinement#target instead/)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "has been removed" do
+      refinement_int = nil
+
+      Module.new do
+        refine Integer do
+          refinement_int = self
+        end
+      end
+
+      refinement_int.should_not.respond_to?(:refined_class)
+    end
+  end
+end
diff --git a/spec/ruby/core/refinement/shared/target.rb b/spec/ruby/core/refinement/shared/target.rb
new file mode 100644
index 0000000000..79557bea0b
--- /dev/null
+++ b/spec/ruby/core/refinement/shared/target.rb
@@ -0,0 +1,13 @@
+describe :refinement_target, shared: true do
+  it "returns the class refined by the receiver" do
+    refinement_int = nil
+
+    Module.new do
+      refine Integer do
+        refinement_int = self
+      end
+    end
+
+    refinement_int.send(@method).should == Integer
+  end
+end
diff --git a/spec/ruby/core/refinement/target_spec.rb b/spec/ruby/core/refinement/target_spec.rb
new file mode 100644
index 0000000000..fee9588a96
--- /dev/null
+++ b/spec/ruby/core/refinement/target_spec.rb
@@ -0,0 +1,8 @@
+require_relative "../../spec_helper"
+require_relative 'shared/target'
+
+describe "Refinement#target" do
+  ruby_version_is "3.3" do
+    it_behaves_like :refinement_target, :target
+  end
+end
diff --git a/spec/ruby/core/regexp/case_compare_spec.rb b/spec/ruby/core/regexp/case_compare_spec.rb
index a621713f6f..5ae8b56c6a 100644
--- a/spec/ruby/core/regexp/case_compare_spec.rb
+++ b/spec/ruby/core/regexp/case_compare_spec.rb
@@ -22,4 +22,14 @@ describe "Regexp#===" do
     (/abc/ === nil).should be_false
     (/abc/ === /abc/).should be_false
   end
+
+  it "uses #to_str on string-like objects" do
+    stringlike = Class.new do
+      def to_str
+        "abc"
+      end
+    end.new
+
+    (/abc/ === stringlike).should be_true
+  end
 end
diff --git a/spec/ruby/core/regexp/casefold_spec.rb b/spec/ruby/core/regexp/casefold_spec.rb
index d84a2d63c9..d36467a989 100644
--- a/spec/ruby/core/regexp/casefold_spec.rb
+++ b/spec/ruby/core/regexp/casefold_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Regexp#casefold?" do
   it "returns the value of the case-insensitive flag" do
-    /abc/i.casefold?.should == true
-    /xyz/.casefold?.should == false
+    /abc/i.should.casefold?
+    /xyz/.should_not.casefold?
   end
 end
diff --git a/spec/ruby/core/regexp/compile_spec.rb b/spec/ruby/core/regexp/compile_spec.rb
index 329cb4f753..887c8d77dc 100644
--- a/spec/ruby/core/regexp/compile_spec.rb
+++ b/spec/ruby/core/regexp/compile_spec.rb
@@ -13,3 +13,7 @@ end
 describe "Regexp.compile given a Regexp" do
   it_behaves_like :regexp_new_regexp, :compile
 end
+
+describe "Regexp.compile given a non-String/Regexp" do
+  it_behaves_like :regexp_new_non_string_or_regexp, :compile
+end
diff --git a/spec/ruby/core/regexp/encoding_spec.rb b/spec/ruby/core/regexp/encoding_spec.rb
index 6ce6f8b3ca..dfc835b4e4 100644
--- a/spec/ruby/core/regexp/encoding_spec.rb
+++ b/spec/ruby/core/regexp/encoding_spec.rb
@@ -55,4 +55,8 @@ describe "Regexp#encoding" do
     /foo/.encoding.should_not == Encoding::EUC_JP
     Encoding.default_internal = old_internal
   end
+
+  it "allows otherwise invalid characters if NOENCODING is specified" do
+    Regexp.new('([\x00-\xFF])', Regexp::IGNORECASE | Regexp::NOENCODING).encoding.should == Encoding::BINARY
+  end
 end
diff --git a/spec/ruby/core/regexp/initialize_spec.rb b/spec/ruby/core/regexp/initialize_spec.rb
index 36fd5c7bf2..dd57292242 100644
--- a/spec/ruby/core/regexp/initialize_spec.rb
+++ b/spec/ruby/core/regexp/initialize_spec.rb
@@ -2,11 +2,11 @@ require_relative '../../spec_helper'
 
 describe "Regexp#initialize" do
   it "is a private method" do
-    Regexp.should have_private_method(:initialize)
+    Regexp.should have_private_instance_method(:initialize)
   end
 
-  it "raises a SecurityError on a Regexp literal" do
-    -> { //.send(:initialize, "") }.should raise_error(SecurityError)
+  it "raises a FrozenError on a Regexp literal" do
+    -> { //.send(:initialize, "") }.should raise_error(FrozenError)
   end
 
   it "raises a TypeError on an initialized non-literal Regexp" do
diff --git a/spec/ruby/core/regexp/last_match_spec.rb b/spec/ruby/core/regexp/last_match_spec.rb
index ed496b7941..0bfed32051 100644
--- a/spec/ruby/core/regexp/last_match_spec.rb
+++ b/spec/ruby/core/regexp/last_match_spec.rb
@@ -7,8 +7,50 @@ describe "Regexp.last_match" do
     Regexp.last_match.should be_kind_of(MatchData)
   end
 
-  it "returns the nth field in this MatchData when passed a Fixnum" do
+  it "returns the nth field in this MatchData when passed an Integer" do
     /c(.)t/ =~ 'cat'
     Regexp.last_match(1).should == 'a'
   end
+
+  it "returns nil when there is no match" do
+    /foo/ =~ "TEST123"
+    Regexp.last_match(:test).should == nil
+    Regexp.last_match(1).should == nil
+    Regexp.last_match(Object.new).should == nil
+    Regexp.last_match("test").should == nil
+  end
+
+  describe "when given a Symbol" do
+    it "returns a named capture" do
+      /(?<test>[A-Z]+.*)/ =~ "TEST123"
+      Regexp.last_match(:test).should == "TEST123"
+    end
+
+    it "raises an IndexError when given a missing name" do
+      /(?<test>[A-Z]+.*)/ =~ "TEST123"
+      -> { Regexp.last_match(:missing) }.should raise_error(IndexError)
+    end
+  end
+
+  describe "when given a String" do
+    it "returns a named capture" do
+      /(?<test>[A-Z]+.*)/ =~ "TEST123"
+      Regexp.last_match("test").should == "TEST123"
+    end
+  end
+
+  describe "when given an Object" do
+    it "coerces argument to an index using #to_int" do
+      obj = mock("converted to int")
+      obj.should_receive(:to_int).and_return(1)
+      /(?<test>[A-Z]+.*)/ =~ "TEST123"
+      Regexp.last_match(obj).should == "TEST123"
+    end
+
+    it "raises a TypeError when unable to coerce" do
+      obj = Object.new
+      /(?<test>[A-Z]+.*)/ =~ "TEST123"
+      -> { Regexp.last_match(obj) }.should raise_error(TypeError)
+    end
+  end
 end
diff --git a/spec/ruby/core/regexp/linear_time_spec.rb b/spec/ruby/core/regexp/linear_time_spec.rb
new file mode 100644
index 0000000000..cf9e73c37c
--- /dev/null
+++ b/spec/ruby/core/regexp/linear_time_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+
+describe "Regexp.linear_time?" do
+  it "returns true if matching can be done in linear time" do
+    Regexp.linear_time?(/a/).should == true
+    Regexp.linear_time?('a').should == true
+  end
+
+  it "returns true if matching can be done in linear time for a binary Regexp" do
+    Regexp.linear_time?(/[\x80-\xff]/n).should == true
+  end
+
+  it "return false if matching can't be done in linear time" do
+    Regexp.linear_time?(/(a)\1/).should == false
+    Regexp.linear_time?("(a)\\1").should == false
+  end
+
+  it "accepts flags for string argument" do
+    Regexp.linear_time?('a', Regexp::IGNORECASE).should == true
+  end
+
+  it "warns about flags being ignored for regexp arguments" do
+    -> {
+      Regexp.linear_time?(/a/, Regexp::IGNORECASE)
+    }.should complain(/warning: flags ignored/)
+  end
+
+  ruby_version_is "3.3" do
+    it "returns true for positive lookarounds" do
+      Regexp.linear_time?(/(?:(?=a*)a)*/).should == true
+    end
+  end
+end
diff --git a/spec/ruby/core/regexp/match_spec.rb b/spec/ruby/core/regexp/match_spec.rb
index a68448b39c..80dbfb4c10 100644
--- a/spec/ruby/core/regexp/match_spec.rb
+++ b/spec/ruby/core/regexp/match_spec.rb
@@ -38,6 +38,10 @@ describe "Regexp#match" do
     -> { Regexp.allocate.match('foo') }.should raise_error(TypeError)
   end
 
+  it "raises TypeError on an uninitialized Regexp" do
+    -> { Regexp.allocate.match('foo'.encode("UTF-16LE")) }.should raise_error(TypeError)
+  end
+
   describe "with [string, position]" do
     describe "when given a positive position" do
       it "matches the input at a given position" do
diff --git a/spec/ruby/core/regexp/new_spec.rb b/spec/ruby/core/regexp/new_spec.rb
index d2d867b3d3..79210e9a23 100644
--- a/spec/ruby/core/regexp/new_spec.rb
+++ b/spec/ruby/core/regexp/new_spec.rb
@@ -7,21 +7,13 @@ end
 
 describe "Regexp.new given a String" do
   it_behaves_like :regexp_new_string, :new
+  it_behaves_like :regexp_new_string_binary, :new
 end
 
 describe "Regexp.new given a Regexp" do
   it_behaves_like :regexp_new_regexp, :new
-  it_behaves_like :regexp_new_string_binary, :compile
 end
 
-describe "Regexp.new given a Fixnum" do
-  it "raises a TypeError" do
-    -> { Regexp.new(1) }.should raise_error(TypeError)
-  end
-end
-
-describe "Regexp.new given a Float" do
-  it "raises a TypeError" do
-    -> { Regexp.new(1.0) }.should raise_error(TypeError)
-  end
+describe "Regexp.new given a non-String/Regexp" do
+  it_behaves_like :regexp_new_non_string_or_regexp, :new
 end
diff --git a/spec/ruby/core/regexp/options_spec.rb b/spec/ruby/core/regexp/options_spec.rb
index fb4853a014..527b51a3b2 100644
--- a/spec/ruby/core/regexp/options_spec.rb
+++ b/spec/ruby/core/regexp/options_spec.rb
@@ -1,10 +1,10 @@
 require_relative '../../spec_helper'
 
 describe "Regexp#options" do
-  it "returns a Fixnum bitvector of regexp options for the Regexp object" do
-    /cat/.options.should be_kind_of(Fixnum)
+  it "returns an Integer bitvector of regexp options for the Regexp object" do
+    /cat/.options.should be_kind_of(Integer)
     not_supported_on :opal do
-      /cat/ix.options.should be_kind_of(Fixnum)
+      /cat/ix.options.should be_kind_of(Integer)
     end
   end
 
diff --git a/spec/ruby/core/regexp/shared/new.rb b/spec/ruby/core/regexp/shared/new.rb
index bb5df7bc2e..12c3d7c9c2 100644
--- a/spec/ruby/core/regexp/shared/new.rb
+++ b/spec/ruby/core/regexp/shared/new.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :regexp_new, shared: true do
   it "requires one argument and creates a new regular expression object" do
@@ -24,13 +24,39 @@ describe :regexp_new, shared: true do
   end
 end
 
+describe :regexp_new_non_string_or_regexp, shared: true do
+  it "calls #to_str method for non-String/Regexp argument" do
+    obj = Object.new
+    def obj.to_str() "a" end
+
+    Regexp.send(@method, obj).should == /a/
+  end
+
+  it "raises TypeError if there is no #to_str method for non-String/Regexp argument" do
+    obj = Object.new
+    -> { Regexp.send(@method, obj) }.should raise_error(TypeError, "no implicit conversion of Object into String")
+
+    -> { Regexp.send(@method, 1) }.should raise_error(TypeError, "no implicit conversion of Integer into String")
+    -> { Regexp.send(@method, 1.0) }.should raise_error(TypeError, "no implicit conversion of Float into String")
+    -> { Regexp.send(@method, :symbol) }.should raise_error(TypeError, "no implicit conversion of Symbol into String")
+    -> { Regexp.send(@method, []) }.should raise_error(TypeError, "no implicit conversion of Array into String")
+  end
+
+  it "raises TypeError if #to_str returns non-String value" do
+    obj = Object.new
+    def obj.to_str() [] end
+
+    -> { Regexp.send(@method, obj) }.should raise_error(TypeError, /can't convert Object to String/)
+  end
+end
+
 describe :regexp_new_string, shared: true do
   it "uses the String argument as an unescaped literal to construct a Regexp object" do
     Regexp.send(@method, "^hi{2,3}fo.o$").should == /^hi{2,3}fo.o$/
   end
 
   it "raises a RegexpError when passed an incorrect regexp" do
-    -> { Regexp.send(@method, "^[$", 0) }.should raise_error(RegexpError)
+    -> { Regexp.send(@method, "^[$", 0) }.should raise_error(RegexpError, Regexp.new(Regexp.escape("premature end of char-class: /^[$/")))
   end
 
   it "does not set Regexp options if only given one argument" do
@@ -58,7 +84,16 @@ describe :regexp_new_string, shared: true do
     end
   end
 
-  it "sets options from second argument if it is one of the Fixnum option constants" do
+  it "sets options from second argument if it is true" do
+    r = Regexp.send(@method, 'Hi', true)
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
+  end
+
+  it "sets options from second argument if it is one of the Integer option constants" do
     r = Regexp.send(@method, 'Hi', Regexp::IGNORECASE)
     (r.options & Regexp::IGNORECASE).should_not == 0
     (r.options & Regexp::MULTILINE).should == 0
@@ -81,15 +116,30 @@ describe :regexp_new_string, shared: true do
     end
   end
 
-  it "accepts a Fixnum of two or more options ORed together as the second argument" do
+  it "accepts an Integer of two or more options ORed together as the second argument" do
     r = Regexp.send(@method, 'Hi', Regexp::IGNORECASE | Regexp::EXTENDED)
     (r.options & Regexp::IGNORECASE).should_not == 0
     (r.options & Regexp::MULTILINE).should == 0
     (r.options & Regexp::EXTENDED).should_not == 0
   end
 
-  it "treats any non-Fixnum, non-nil, non-false second argument as IGNORECASE" do
-    r = Regexp.send(@method, 'Hi', Object.new)
+  it "does not try to convert the second argument to Integer with #to_int method call" do
+    ScratchPad.clear
+    obj = Object.new
+    def obj.to_int() ScratchPad.record(:called) end
+
+    -> {
+      Regexp.send(@method, "Hi", obj)
+    }.should complain(/expected true or false as ignorecase/, {verbose: true})
+
+    ScratchPad.recorded.should == nil
+  end
+
+  it "warns any non-Integer, non-nil, non-false second argument" do
+    r = nil
+    -> {
+      r = Regexp.send(@method, 'Hi', Object.new)
+    }.should complain(/expected true or false as ignorecase/, {verbose: true})
     (r.options & Regexp::IGNORECASE).should_not == 0
     (r.options & Regexp::MULTILINE).should == 0
     not_supported_on :opal do
@@ -97,249 +147,76 @@ describe :regexp_new_string, shared: true do
     end
   end
 
-  it "ignores the third argument if it is 'e' or 'euc' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 'e').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'euc').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'E').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'EUC').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+  it "accepts a String of supported flags as the second argument" do
+    r = Regexp.send(@method, 'Hi', 'i')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
 
-  it "ignores the third argument if it is 's' or 'sjis' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 's').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'sjis').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'S').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'SJIS').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+    r = Regexp.send(@method, 'Hi', 'imx')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should_not == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should_not == 0
+    end
 
-  it "ignores the third argument if it is 'u' or 'utf8' (case-insensitive)" do
-    -> {
-      Regexp.send(@method, 'Hi', nil, 'u').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'utf8').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'U').encoding.should == Encoding::US_ASCII
-      Regexp.send(@method, 'Hi', nil, 'UTF8').encoding.should == Encoding::US_ASCII
-    }.should complain(/encoding option is ignored/)
-  end
+    r = Regexp.send(@method, 'Hi', 'mimi')
+    (r.options & Regexp::IGNORECASE).should_not == 0
+    (r.options & Regexp::MULTILINE).should_not == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
 
-  it "uses US_ASCII encoding if third argument is 'n' or 'none' (case insensitive) and only ascii characters" do
-    Regexp.send(@method, 'Hi', nil, 'n').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'none').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'N').encoding.should == Encoding::US_ASCII
-    Regexp.send(@method, 'Hi', nil, 'NONE').encoding.should == Encoding::US_ASCII
+    r = Regexp.send(@method, 'Hi', '')
+    (r.options & Regexp::IGNORECASE).should == 0
+    (r.options & Regexp::MULTILINE).should == 0
+    not_supported_on :opal do
+      (r.options & Regexp::EXTENDED).should == 0
+    end
   end
 
-  it "uses ASCII_8BIT encoding if third argument is 'n' or 'none' (case insensitive) and non-ascii characters" do
-    a = "(?:[\x8E\xA1-\xFE])"
-    str = "\A(?:#{a}|x*)\z"
-
-    Regexp.send(@method, str, nil, 'N').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'n').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'none').encoding.should == Encoding::BINARY
-    Regexp.send(@method, str, nil, 'NONE').encoding.should == Encoding::BINARY
+  it "raises an Argument error if the second argument contains unsupported chars" do
+    -> { Regexp.send(@method, 'Hi', 'e') }.should raise_error(ArgumentError, "unknown regexp option: e")
+    -> { Regexp.send(@method, 'Hi', 'n') }.should raise_error(ArgumentError, "unknown regexp option: n")
+    -> { Regexp.send(@method, 'Hi', 's') }.should raise_error(ArgumentError, "unknown regexp option: s")
+    -> { Regexp.send(@method, 'Hi', 'u') }.should raise_error(ArgumentError, "unknown regexp option: u")
+    -> { Regexp.send(@method, 'Hi', 'j') }.should raise_error(ArgumentError, "unknown regexp option: j")
+    -> { Regexp.send(@method, 'Hi', 'mjx') }.should raise_error(ArgumentError, /unknown regexp option: mjx\b/)
   end
 
   describe "with escaped characters" do
     it "raises a Regexp error if there is a trailing backslash" do
-      -> { Regexp.send(@method, "\\") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("too short escape sequence: /\\/")))
     end
 
     it "does not raise a Regexp error if there is an escaped trailing backslash" do
       -> { Regexp.send(@method, "\\\\") }.should_not raise_error(RegexpError)
     end
 
-    it "accepts a backspace followed by a character" do
+    it "accepts a backspace followed by a non-special character" do
       Regexp.send(@method, "\\N").should == /#{"\x5c"+"N"}/
     end
 
-    it "accepts a one-digit octal value" do
-      Regexp.send(@method, "\0").should == /#{"\x00"}/
-    end
-
-    it "accepts a two-digit octal value" do
-      Regexp.send(@method, "\11").should == /#{"\x09"}/
-    end
-
-    it "accepts a one-digit hexadecimal value" do
-      Regexp.send(@method, "\x9n").should == /#{"\x09n"}/
-    end
-
-    it "accepts a two-digit hexadecimal value" do
-      Regexp.send(@method, "\x23").should == /#{"\x23"}/
-    end
-
-    it "interprets a digit following a two-digit hexadecimal value as a character" do
-      Regexp.send(@method, "\x420").should == /#{"\x420"}/
-    end
-
     it "raises a RegexpError if \\x is not followed by any hexadecimal digits" do
-      -> { Regexp.send(@method, "\\" + "xn") }.should raise_error(RegexpError)
-    end
-
-    it "accepts an escaped string interpolation" do
-      Regexp.send(@method, "\#{abc}").should == /#{"\#{abc}"}/
-    end
-
-    it "accepts '\\n'" do
-      Regexp.send(@method, "\n").should == /#{"\x0a"}/
-    end
-
-    it "accepts '\\t'" do
-      Regexp.send(@method, "\t").should == /#{"\x09"}/
-    end
-
-    it "accepts '\\r'" do
-      Regexp.send(@method, "\r").should == /#{"\x0d"}/
-    end
-
-    it "accepts '\\f'" do
-      Regexp.send(@method, "\f").should == /#{"\x0c"}/
-    end
-
-    it "accepts '\\v'" do
-      Regexp.send(@method, "\v").should == /#{"\x0b"}/
-    end
-
-    it "accepts '\\a'" do
-      Regexp.send(@method, "\a").should == /#{"\x07"}/
-    end
-
-    it "accepts '\\e'" do
-      Regexp.send(@method, "\e").should == /#{"\x1b"}/
-    end
-
-    it "accepts '\\C-\\n'" do
-      Regexp.send(@method, "\C-\n").should == /#{"\x0a"}/
-    end
-
-    it "accepts '\\C-\\t'" do
-      Regexp.send(@method, "\C-\t").should == /#{"\x09"}/
-    end
-
-    it "accepts '\\C-\\r'" do
-      Regexp.send(@method, "\C-\r").should == /#{"\x0d"}/
-    end
-
-    it "accepts '\\C-\\f'" do
-      Regexp.send(@method, "\C-\f").should == /#{"\x0c"}/
-    end
-
-    it "accepts '\\C-\\v'" do
-      Regexp.send(@method, "\C-\v").should == /#{"\x0b"}/
-    end
-
-    it "accepts '\\C-\\a'" do
-      Regexp.send(@method, "\C-\a").should == /#{"\x07"}/
-    end
-
-    it "accepts '\\C-\\e'" do
-      Regexp.send(@method, "\C-\e").should == /#{"\x1b"}/
-    end
-
-    it "accepts multiple consecutive '\\' characters" do
-      Regexp.send(@method, "\\\\\\N").should == /#{"\\\\\\"+"N"}/
-    end
-
-    it "accepts characters and escaped octal digits" do
-      Regexp.send(@method, "abc\076").should == /#{"abc\x3e"}/
-    end
-
-    it "accepts escaped octal digits and characters" do
-      Regexp.send(@method, "\076abc").should == /#{"\x3eabc"}/
-    end
-
-    it "accepts characters and escaped hexadecimal digits" do
-      Regexp.send(@method, "abc\x42").should == /#{"abc\x42"}/
-    end
-
-    it "accepts escaped hexadecimal digits and characters" do
-      Regexp.send(@method, "\x3eabc").should == /#{"\x3eabc"}/
-    end
-
-    it "accepts escaped hexadecimal and octal digits" do
-      Regexp.send(@method, "\061\x42").should == /#{"\x31\x42"}/
-    end
-
-    it "accepts \\u{H} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{f}").should == /#{"\x0f"}/
-    end
-
-    it "accepts \\u{HH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{7f}").should == /#{"\x7f"}/
-    end
-
-    it "accepts \\u{HHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{07f}").should == /#{"\x7f"}/
-    end
-
-    it "accepts \\u{HHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{0000}").should == /#{"\x00"}/
-    end
-
-    it "accepts \\u{HHHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{00001}").should == /#{"\x01"}/
-    end
-
-    it "accepts \\u{HHHHHH} for a single Unicode codepoint" do
-      Regexp.send(@method, "\u{000000}").should == /#{"\x00"}/
-    end
-
-    it "accepts characters followed by \\u{HHHH}" do
-      Regexp.send(@method, "abc\u{3042}").should == /#{"abc\u3042"}/
-    end
-
-    it "accepts \\u{HHHH} followed by characters" do
-      Regexp.send(@method, "\u{3042}abc").should == /#{"\u3042abc"}/
-    end
-
-    it "accepts escaped hexadecimal digits followed by \\u{HHHH}" do
-      Regexp.send(@method, "\x42\u{3042}").should == /#{"\x42\u3042"}/
-    end
-
-    it "accepts escaped octal digits followed by \\u{HHHH}" do
-      Regexp.send(@method, "\056\u{3042}").should == /#{"\x2e\u3042"}/
-    end
-
-    it "accepts a combination of escaped octal and hexadecimal digits and \\u{HHHH}" do
-      Regexp.send(@method, "\056\x42\u{3042}\x52\076").should == /#{"\x2e\x42\u3042\x52\x3e"}/
-    end
-
-    it "accepts \\uHHHH for a single Unicode codepoint" do
-      Regexp.send(@method, "\u3042").should == /#{"\u3042"}/
-    end
-
-    it "accepts characters followed by \\uHHHH" do
-      Regexp.send(@method, "abc\u3042").should == /#{"abc\u3042"}/
-    end
-
-    it "accepts \\uHHHH followed by characters" do
-      Regexp.send(@method, "\u3042abc").should == /#{"\u3042abc"}/
-    end
-
-    it "accepts escaped hexadecimal digits followed by \\uHHHH" do
-      Regexp.send(@method, "\x42\u3042").should == /#{"\x42\u3042"}/
-    end
-
-    it "accepts escaped octal digits followed by \\uHHHH" do
-      Regexp.send(@method, "\056\u3042").should == /#{"\x2e\u3042"}/
-    end
-
-    it "accepts a combination of escaped octal and hexadecimal digits and \\uHHHH" do
-      Regexp.send(@method, "\056\x42\u3042\x52\076").should == /#{"\x2e\x42\u3042\x52\x3e"}/
+      -> { Regexp.send(@method, "\\" + "xn") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("invalid hex escape: /\\xn/")))
     end
 
     it "raises a RegexpError if less than four digits are given for \\uHHHH" do
-      -> { Regexp.send(@method, "\\" + "u304") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u304") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("invalid Unicode escape: /\\u304/")))
     end
 
     it "raises a RegexpError if the \\u{} escape is empty" do
-      -> { Regexp.send(@method, "\\" + "u{}") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u{}") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("invalid Unicode list: /\\u{}/")))
+    end
+
+    it "raises a RegexpError if the \\u{} escape contains non hexadecimal digits" do
+      -> { Regexp.send(@method, "\\" + "u{abcX}") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("invalid Unicode list: /\\u{abcX}/")))
     end
 
     it "raises a RegexpError if more than six hexadecimal digits are given" do
-      -> { Regexp.send(@method, "\\" + "u{0ffffff}") }.should raise_error(RegexpError)
+      -> { Regexp.send(@method, "\\" + "u{0ffffff}") }.should raise_error(RegexpError, Regexp.new(Regexp.escape("invalid Unicode range: /\\u{0ffffff}/")))
     end
 
     it "returns a Regexp with US-ASCII encoding if only 7-bit ASCII characters are present regardless of the input String's encoding" do
@@ -367,12 +244,12 @@ describe :regexp_new_string, shared: true do
     end
 
     it "returns a Regexp with the input String's encoding" do
-      str = "\x82\xa0".force_encoding(Encoding::Shift_JIS)
+      str = "\x82\xa0".dup.force_encoding(Encoding::Shift_JIS)
       Regexp.send(@method, str).encoding.should == Encoding::Shift_JIS
     end
 
     it "returns a Regexp with source String having the input String's encoding" do
-      str = "\x82\xa0".force_encoding(Encoding::Shift_JIS)
+      str = "\x82\xa0".dup.force_encoding(Encoding::Shift_JIS)
       Regexp.send(@method, str).source.encoding.should == Encoding::Shift_JIS
     end
   end
@@ -380,69 +257,6 @@ end
 
 describe :regexp_new_string_binary, shared: true do
   describe "with escaped characters" do
-    it "accepts a three-digit octal value" do
-      Regexp.send(@method, "\315").should == /#{"\xcd"}/
-    end
-
-    it "interprets a digit following a three-digit octal value as a character" do
-      Regexp.send(@method, "\3762").should == /#{"\xfe2"}/
-    end
-
-    it "accepts '\\M-\\n'" do
-      Regexp.send(@method, "\M-\n").should == /#{"\x8a"}/
-    end
-
-    it "accepts '\\M-\\t'" do
-      Regexp.send(@method, "\M-\t").should == /#{"\x89"}/
-    end
-
-    it "accepts '\\M-\\r'" do
-      Regexp.send(@method, "\M-\r").should == /#{"\x8d"}/
-    end
-
-    it "accepts '\\M-\\f'" do
-      Regexp.send(@method, "\M-\f").should == /#{"\x8c"}/
-    end
-
-    it "accepts '\\M-\\v'" do
-      Regexp.send(@method, "\M-\v").should == /#{"\x8b"}/
-    end
-
-    it "accepts '\\M-\\a'" do
-      Regexp.send(@method, "\M-\a").should == /#{"\x87"}/
-    end
-
-    it "accepts '\\M-\\e'" do
-      Regexp.send(@method, "\M-\e").should == /#{"\x9b"}/
-    end
-
-    it "accepts '\\M-\\C-\\n'" do
-      Regexp.send(@method, "\M-\C-\n").should == /#{"\x8a"}/
-    end
-
-    it "accepts '\\M-\\C-\\t'" do
-      Regexp.send(@method, "\M-\C-\t").should == /#{"\x89"}/
-    end
-
-    it "accepts '\\M-\\C-\\r'" do
-      Regexp.send(@method, "\M-\C-\r").should == /#{"\x8d"}/
-    end
-
-    it "accepts '\\M-\\C-\\f'" do
-      Regexp.send(@method, "\M-\C-\f").should == /#{"\x8c"}/
-    end
-
-    it "accepts '\\M-\\C-\\v'" do
-      Regexp.send(@method, "\M-\C-\v").should == /#{"\x8b"}/
-    end
-
-    it "accepts '\\M-\\C-\\a'" do
-      Regexp.send(@method, "\M-\C-\a").should == /#{"\x87"}/
-    end
-
-    it "accepts '\\M-\\C-\\e'" do
-      Regexp.send(@method, "\M-\C-\e").should == /#{"\x9b"}/
-    end
   end
 end
 
@@ -497,9 +311,5 @@ describe :regexp_new_regexp, shared: true do
     it "sets the encoding to US-ASCII if the Regexp literal has the 'n' option and the source String is ASCII only" do
       Regexp.send(@method, /Hi/n).encoding.should == Encoding::US_ASCII
     end
-
-    it "sets the encoding to source String's encoding if the Regexp literal has the 'n' option and the source String is not ASCII only" do
-      Regexp.send(@method, Regexp.new("\\xff", nil, 'n')).encoding.should == Encoding::BINARY
-    end
   end
 end
diff --git a/spec/ruby/core/regexp/shared/quote.rb b/spec/ruby/core/regexp/shared/quote.rb
index a55adb5bf2..3f46a18b5b 100644
--- a/spec/ruby/core/regexp/shared/quote.rb
+++ b/spec/ruby/core/regexp/shared/quote.rb
@@ -1,9 +1,9 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :regexp_quote, shared: true do
   it "escapes any characters with special meaning in a regular expression" do
-    Regexp.send(@method, '\*?{}.+^[]()- ').should == '\\\\\*\?\{\}\.\+\^\[\]\(\)\-\\ '
-    Regexp.send(@method, "\*?{}.+^[]()- ").should == '\\*\\?\\{\\}\\.\\+\\^\\[\\]\\(\\)\\-\\ '
+    Regexp.send(@method, '\*?{}.+^$[]()- ').should == '\\\\\*\?\{\}\.\+\^\$\[\]\(\)\-\\ '
+    Regexp.send(@method, "\*?{}.+^$[]()- ").should == '\\*\\?\\{\\}\\.\\+\\^\\$\\[\\]\\(\\)\\-\\ '
     Regexp.send(@method, '\n\r\f\t').should == '\\\\n\\\\r\\\\f\\\\t'
     Regexp.send(@method, "\n\r\f\t").should == '\\n\\r\\f\\t'
   end
@@ -12,19 +12,29 @@ describe :regexp_quote, shared: true do
     Regexp.send(@method, :symbol).should == 'symbol'
   end
 
+  it "works with substrings" do
+    str = ".+[]()"[1...-1]
+    Regexp.send(@method, str).should == '\+\[\]\('
+  end
+
+  it "works for broken strings" do
+    Regexp.send(@method, "a.\x85b.".dup.force_encoding("US-ASCII")).should =="a\\.\x85b\\.".dup.force_encoding("US-ASCII")
+    Regexp.send(@method, "a.\x80".dup.force_encoding("UTF-8")).should == "a\\.\x80".dup.force_encoding("UTF-8")
+  end
+
   it "sets the encoding of the result to US-ASCII if there are only US-ASCII characters present in the input String" do
-    str = "abc".force_encoding("euc-jp")
+    str = "abc".dup.force_encoding("euc-jp")
     Regexp.send(@method, str).encoding.should == Encoding::US_ASCII
   end
 
   it "sets the encoding of the result to the encoding of the String if any non-US-ASCII characters are present in an input String with valid encoding" do
-    str = "ありがとう".force_encoding("utf-8")
+    str = "ありがとう".dup.force_encoding("utf-8")
     str.valid_encoding?.should be_true
     Regexp.send(@method, str).encoding.should == Encoding::UTF_8
   end
 
   it "sets the encoding of the result to BINARY if any non-US-ASCII characters are present in an input String with invalid encoding" do
-    str = "\xff".force_encoding "us-ascii"
+    str = "\xff".dup.force_encoding "us-ascii"
     str.valid_encoding?.should be_false
     Regexp.send(@method, "\xff").encoding.should == Encoding::BINARY
   end
diff --git a/spec/ruby/core/regexp/source_spec.rb b/spec/ruby/core/regexp/source_spec.rb
index 709fee49b3..5f253da9ea 100644
--- a/spec/ruby/core/regexp/source_spec.rb
+++ b/spec/ruby/core/regexp/source_spec.rb
@@ -9,8 +9,26 @@ describe "Regexp#source" do
     /x(.)xz/.source.should == "x(.)xz"
   end
 
-  it "will remove escape characters" do
-    /foo\/bar/.source.should == "foo/bar"
+  it "keeps escape sequences as is" do
+    /\x20\+/.source.should == '\x20\+'
+  end
+
+  describe "escaping" do
+    it "keeps escaping of metacharacter" do
+      /\$/.source.should == "\\$"
+    end
+
+    it "keeps escaping of metacharacter used as a terminator" do
+      %r+\++.source.should == "\\+"
+    end
+
+    it "removes escaping of non-metacharacter used as a terminator" do
+      %r@\@@.source.should == "@"
+    end
+
+    it "keeps escaping of non-metacharacter not used as a terminator" do
+      /\@/.source.should == "\\@"
+    end
   end
 
   not_supported_on :opal do
diff --git a/spec/ruby/core/regexp/timeout_spec.rb b/spec/ruby/core/regexp/timeout_spec.rb
new file mode 100644
index 0000000000..c64103c82c
--- /dev/null
+++ b/spec/ruby/core/regexp/timeout_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+
+describe "Regexp.timeout" do
+  after :each do
+    Regexp.timeout = nil
+  end
+
+  it "returns global timeout" do
+    Regexp.timeout = 3
+    Regexp.timeout.should == 3
+  end
+
+  it "raises Regexp::TimeoutError after global timeout elapsed" do
+    Regexp.timeout = 0.001
+    Regexp.timeout.should == 0.001
+
+    -> {
+      # A typical ReDoS case
+      /^(a*)*$/ =~ "a" * 1000000 + "x"
+    }.should raise_error(Regexp::TimeoutError, "regexp match timeout")
+  end
+
+  it "raises Regexp::TimeoutError after timeout keyword value elapsed" do
+    Regexp.timeout = 3 # This should be ignored
+    Regexp.timeout.should == 3
+
+    re = Regexp.new("^a*b?a*$", timeout: 0.001)
+
+    -> {
+      re =~ "a" * 1000000 + "x"
+    }.should raise_error(Regexp::TimeoutError, "regexp match timeout")
+  end
+end
diff --git a/spec/ruby/core/regexp/try_convert_spec.rb b/spec/ruby/core/regexp/try_convert_spec.rb
index be567e2130..e775dbe971 100644
--- a/spec/ruby/core/regexp/try_convert_spec.rb
+++ b/spec/ruby/core/regexp/try_convert_spec.rb
@@ -18,4 +18,10 @@ describe "Regexp.try_convert" do
     rex.should_receive(:to_regexp).and_return(/(p(a)t[e]rn)/)
     Regexp.try_convert(rex).should == /(p(a)t[e]rn)/
   end
+
+  it "raises a TypeError if the object does not return an Regexp from #to_regexp" do
+    obj = mock("regexp")
+    obj.should_receive(:to_regexp).and_return("string")
+    -> { Regexp.try_convert(obj) }.should raise_error(TypeError, "can't convert MockObject to Regexp (MockObject#to_regexp gives String)")
+  end
 end
diff --git a/spec/ruby/core/regexp/union_spec.rb b/spec/ruby/core/regexp/union_spec.rb
index 81a31d89b3..ea5a5053f7 100644
--- a/spec/ruby/core/regexp/union_spec.rb
+++ b/spec/ruby/core/regexp/union_spec.rb
@@ -43,6 +43,27 @@ describe "Regexp.union" do
     Regexp.union("\u00A9".encode("ISO-8859-1"), "a".encode("UTF-8")).encoding.should == Encoding::ISO_8859_1
   end
 
+  it "returns ASCII-8BIT if the regexp encodings are ASCII-8BIT and at least one has non-ASCII characters" do
+    us_ascii_implicit, us_ascii_explicit, binary = /abc/, /[\x00-\x7f]/n, /[\x80-\xBF]/n
+    us_ascii_implicit.encoding.should == Encoding::US_ASCII
+    us_ascii_explicit.encoding.should == Encoding::US_ASCII
+    binary.encoding.should == Encoding::BINARY
+
+    Regexp.union(us_ascii_implicit, us_ascii_explicit, binary).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_implicit, binary, us_ascii_explicit).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_explicit, us_ascii_implicit, binary).encoding.should == Encoding::BINARY
+    Regexp.union(us_ascii_explicit, binary, us_ascii_implicit).encoding.should == Encoding::BINARY
+    Regexp.union(binary, us_ascii_implicit, us_ascii_explicit).encoding.should == Encoding::BINARY
+    Regexp.union(binary, us_ascii_explicit, us_ascii_implicit).encoding.should == Encoding::BINARY
+  end
+
+  it "return US-ASCII if all patterns are ASCII-only" do
+    Regexp.union(/abc/e, /def/e).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/n, /def/n).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/s, /def/s).encoding.should == Encoding::US_ASCII
+    Regexp.union(/abc/u, /def/u).encoding.should == Encoding::US_ASCII
+  end
+
   it "returns a Regexp with UTF-8 if one part is UTF-8" do
     Regexp.union(/probl[éeè]me/i, /help/i).encoding.should == Encoding::UTF_8
   end
@@ -54,83 +75,83 @@ describe "Regexp.union" do
   it "raises ArgumentError if the arguments include conflicting ASCII-incompatible Strings" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "b".encode("UTF-16BE"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and UTF-16BE')
   end
 
   it "raises ArgumentError if the arguments include conflicting ASCII-incompatible Regexps" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")),
                    Regexp.new("b".encode("UTF-16BE")))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and UTF-16BE')
   end
 
   it "raises ArgumentError if the arguments include conflicting fixed encoding Regexps" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-8"),    Regexp::FIXEDENCODING),
                    Regexp.new("b".encode("US-ASCII"), Regexp::FIXEDENCODING))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-8 and US-ASCII')
   end
 
   it "raises ArgumentError if the arguments include a fixed encoding Regexp and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-8"), Regexp::FIXEDENCODING),
                    "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-8 and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include a String containing non-ASCII-compatible characters and a fixed encoding Regexp in a different encoding" do
     -> {
       Regexp.union("\u00A9".encode("ISO-8859-1"),
                    Regexp.new("a".encode("UTF-8"), Regexp::FIXEDENCODING))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: ISO-8859-1 and UTF-8')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and an ASCII-only String" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "b".encode("UTF-8"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and an ASCII-only String" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), "b".encode("UTF-8"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and an ASCII-only Regexp" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), Regexp.new("b".encode("UTF-8")))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and an ASCII-only Regexp" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), Regexp.new("b".encode("UTF-8")))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /ASCII incompatible encoding: UTF-16LE|incompatible encodings: UTF-16LE and US-ASCII/)
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and a String containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), "\u00A9".encode("ISO-8859-1"))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible String and a Regexp containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union("a".encode("UTF-16LE"), Regexp.new("\u00A9".encode("ISO-8859-1")))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "raises ArgumentError if the arguments include an ASCII-incompatible Regexp and a Regexp containing non-ASCII-compatible characters in a different encoding" do
     -> {
       Regexp.union(Regexp.new("a".encode("UTF-16LE")), Regexp.new("\u00A9".encode("ISO-8859-1")))
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, 'incompatible encodings: UTF-16LE and ISO-8859-1')
   end
 
   it "uses to_str to convert arguments (if not Regexp)" do
@@ -139,11 +160,23 @@ describe "Regexp.union" do
     Regexp.union(obj, "bar").should == /foo|bar/
   end
 
+  it "uses to_regexp to convert argument" do
+    obj = mock('pattern')
+    obj.should_receive(:to_regexp).and_return(/foo/)
+    Regexp.union(obj).should == /foo/
+  end
+
+  it "accepts a Symbol as argument" do
+    Regexp.union(:foo).should == /foo/
+  end
+
   it "accepts a single array of patterns as arguments" do
     Regexp.union(["skiing", "sledding"]).should == /skiing|sledding/
     not_supported_on :opal do
       Regexp.union([/dogs/, /cats/i]).should == /(?-mix:dogs)|(?i-mx:cats)/
     end
-    ->{Regexp.union(["skiing", "sledding"], [/dogs/, /cats/i])}.should raise_error(TypeError)
+    -> {
+      Regexp.union(["skiing", "sledding"], [/dogs/, /cats/i])
+    }.should raise_error(TypeError, 'no implicit conversion of Array into String')
   end
 end
diff --git a/spec/ruby/core/set/add_spec.rb b/spec/ruby/core/set/add_spec.rb
new file mode 100644
index 0000000000..0fe1a0926c
--- /dev/null
+++ b/spec/ruby/core/set/add_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+require_relative 'shared/add'
+
+describe "Set#add" do
+  it_behaves_like :set_add, :add
+end
+
+describe "Set#add?" do
+  before :each do
+    @set = Set.new
+  end
+
+  it "adds the passed Object to self" do
+    @set.add?("cat")
+    @set.should include("cat")
+  end
+
+  it "returns self when the Object has not yet been added to self" do
+    @set.add?("cat").should equal(@set)
+  end
+
+  it "returns nil when the Object has already been added to self" do
+    @set.add?("cat")
+    @set.add?("cat").should be_nil
+  end
+
+  it "raises RuntimeError when called during iteration" do
+    set = Set[:a, :b, :c, :d, :e, :f]
+    set.each do |_m|
+      -> { set << 1 }.should raise_error(RuntimeError, /iteration/)
+    end
+    set.should == Set[:a, :b, :c, :d, :e, :f]
+  end
+end
diff --git a/spec/ruby/core/set/append_spec.rb b/spec/ruby/core/set/append_spec.rb
new file mode 100644
index 0000000000..82d34d9130
--- /dev/null
+++ b/spec/ruby/core/set/append_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/add'
+
+describe "Set#<<" do
+  it_behaves_like :set_add, :<<
+end
diff --git a/spec/ruby/core/set/case_compare_spec.rb b/spec/ruby/core/set/case_compare_spec.rb
new file mode 100644
index 0000000000..3781b1b963
--- /dev/null
+++ b/spec/ruby/core/set/case_compare_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+
+describe "Set#===" do
+  it_behaves_like :set_include, :===
+
+  it "is an alias for include?" do
+    set = Set.new
+    set.method(:===).should == set.method(:include?)
+  end
+end
diff --git a/spec/ruby/core/set/case_equality_spec.rb b/spec/ruby/core/set/case_equality_spec.rb
new file mode 100644
index 0000000000..19c1fb6b9c
--- /dev/null
+++ b/spec/ruby/core/set/case_equality_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+
+describe "Set#===" do
+  it_behaves_like :set_include, :===
+end
diff --git a/spec/ruby/core/set/classify_spec.rb b/spec/ruby/core/set/classify_spec.rb
new file mode 100644
index 0000000000..d86ea2722d
--- /dev/null
+++ b/spec/ruby/core/set/classify_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+describe "Set#classify" do
+  before :each do
+    @set = Set["one", "two", "three", "four"]
+  end
+
+  it "yields each Object in self" do
+    res = []
+    @set.classify { |x| res << x }
+    res.sort.should == ["one", "two", "three", "four"].sort
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.classify
+    enum.should be_an_instance_of(Enumerator)
+
+    classified = enum.each { |x| x.length }
+    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
+  end
+
+  it "classifies the Objects in self based on the block's return value" do
+    classified = @set.classify { |x| x.length }
+    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
+  end
+end
diff --git a/spec/ruby/core/set/clear_spec.rb b/spec/ruby/core/set/clear_spec.rb
new file mode 100644
index 0000000000..ebeac211d3
--- /dev/null
+++ b/spec/ruby/core/set/clear_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+
+describe "Set#clear" do
+  before :each do
+    @set = Set["one", "two", "three", "four"]
+  end
+
+  it "removes all elements from self" do
+    @set.clear
+    @set.should be_empty
+  end
+
+  it "returns self" do
+    @set.clear.should equal(@set)
+  end
+end
diff --git a/spec/ruby/core/set/collect_spec.rb b/spec/ruby/core/set/collect_spec.rb
new file mode 100644
index 0000000000..d186f1a0d9
--- /dev/null
+++ b/spec/ruby/core/set/collect_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/collect'
+
+describe "Set#collect!" do
+  it_behaves_like :set_collect_bang, :collect!
+end
diff --git a/spec/ruby/core/set/compare_by_identity_spec.rb b/spec/ruby/core/set/compare_by_identity_spec.rb
new file mode 100644
index 0000000000..238dc117a6
--- /dev/null
+++ b/spec/ruby/core/set/compare_by_identity_spec.rb
@@ -0,0 +1,153 @@
+require_relative '../../spec_helper'
+
+describe "Set#compare_by_identity" do
+  it "compares its members by identity" do
+    a = "a"
+    b1 = "b"
+    b2 = b1.dup
+
+    set = Set.new
+    set.compare_by_identity
+    set.merge([a, a, b1, b2])
+    set.to_a.sort.should == [a, b1, b2].sort
+  end
+
+  it "causes future comparisons on the receiver to be made by identity" do
+    elt = [1]
+    set = Set.new
+    set << elt
+    set.member?(elt.dup).should be_true
+    set.compare_by_identity
+    set.member?(elt.dup).should be_false
+  end
+
+  it "rehashes internally so that old members can be looked up" do
+    set = Set.new
+    (1..10).each { |k| set << k }
+    o = Object.new
+    def o.hash; 123; end
+    set << o
+    set.compare_by_identity
+    set.member?(o).should be_true
+  end
+
+  it "returns self" do
+    set = Set.new
+    result = set.compare_by_identity
+    result.should equal(set)
+  end
+
+  it "is idempotent and has no effect on an already compare_by_identity set" do
+    set = Set.new.compare_by_identity
+    set << :foo
+    set.compare_by_identity.should equal(set)
+    set.should.compare_by_identity?
+    set.to_a.should == [:foo]
+  end
+
+  it "uses the semantics of BasicObject#equal? to determine members identity" do
+    :a.equal?(:a).should == true
+    Set.new.compare_by_identity.merge([:a, :a]).to_a.should == [:a]
+
+    ary1 = [1]
+    ary2 = [1]
+    ary1.equal?(ary2).should == false
+    Set.new.compare_by_identity.merge([ary1, ary2]).to_a.sort.should == [ary1, ary2].sort
+  end
+
+  it "uses #equal? semantics, but doesn't actually call #equal? to determine identity" do
+    set = Set.new.compare_by_identity
+    obj = mock("equal")
+    obj.should_not_receive(:equal?)
+    set << :foo
+    set << obj
+    set.to_a.should == [:foo, obj]
+  end
+
+  it "does not call #hash on members" do
+    elt = mock("element")
+    elt.should_not_receive(:hash)
+    set = Set.new.compare_by_identity
+    set << elt
+    set.member?(elt).should be_true
+  end
+
+  it "regards #dup'd objects as having different identities" do
+    a1 = "a"
+    a2 = a1.dup
+
+    set = Set.new.compare_by_identity
+    set.merge([a1, a2])
+    set.to_a.sort.should == [a1, a2].sort
+  end
+
+  it "regards #clone'd objects as having different identities" do
+    a1 = "a"
+    a2 = a1.clone
+
+    set = Set.new.compare_by_identity
+    set.merge([a1, a2])
+    set.to_a.sort.should == [a1, a2].sort
+  end
+
+  ruby_version_is "4.0" do
+    it "raises a FrozenError on frozen sets" do
+      set = Set.new.freeze
+      -> {
+        set.compare_by_identity
+      }.should raise_error(FrozenError, /can't modify frozen Set: (#<)?Set(\[|: {)[\]}]>?/)
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "raises a FrozenError on frozen sets" do
+      set = Set.new.freeze
+      -> {
+        set.compare_by_identity
+      }.should raise_error(FrozenError, /frozen Hash/)
+    end
+  end
+
+  it "persists over #dups" do
+    set = Set.new.compare_by_identity
+    set << :a
+    set_dup = set.dup
+    set_dup.should == set
+    set_dup << :a
+    set_dup.to_a.should == [:a]
+  end
+
+  it "persists over #clones" do
+    set = Set.new.compare_by_identity
+    set << :a
+    set_clone = set.clone
+    set_clone.should == set
+    set_clone << :a
+    set_clone.to_a.should == [:a]
+  end
+
+  it "is not equal to set what does not compare by identity" do
+    Set.new([1, 2]).should == Set.new([1, 2])
+    Set.new([1, 2]).should_not == Set.new([1, 2]).compare_by_identity
+  end
+end
+
+describe "Set#compare_by_identity?" do
+  it "returns false by default" do
+    Set.new.should_not.compare_by_identity?
+  end
+
+  it "returns true once #compare_by_identity has been invoked on self" do
+    set = Set.new
+    set.compare_by_identity
+    set.should.compare_by_identity?
+  end
+
+  it "returns true when called multiple times on the same set" do
+    set = Set.new
+    set.compare_by_identity
+    set.should.compare_by_identity?
+    set.should.compare_by_identity?
+    set.should.compare_by_identity?
+  end
+end
diff --git a/spec/ruby/core/set/comparison_spec.rb b/spec/ruby/core/set/comparison_spec.rb
new file mode 100644
index 0000000000..62059b70b3
--- /dev/null
+++ b/spec/ruby/core/set/comparison_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+describe "Set#<=>" do
+  it "returns 0 if the sets are equal" do
+    (Set[] <=> Set[]).should == 0
+    (Set[:a, :b, :c] <=> Set[:a, :b, :c]).should == 0
+  end
+
+  it "returns -1 if the set is a proper subset of the other set" do
+    (Set[] <=> Set[1]).should == -1
+    (Set[1, 2] <=> Set[1, 2, 3]).should == -1
+  end
+
+  it "returns +1 if the set is a proper superset of other set" do
+    (Set[1] <=> Set[]).should == +1
+    (Set[1, 2, 3] <=> Set[1, 2]).should == +1
+  end
+
+  it "returns nil if the set has unique elements" do
+    (Set[1, 2, 3] <=> Set[:a, :b, :c]).should be_nil
+  end
+
+  it "returns nil when the argument is not set-like" do
+    (Set[] <=> false).should be_nil
+  end
+end
diff --git a/spec/ruby/core/set/constructor_spec.rb b/spec/ruby/core/set/constructor_spec.rb
new file mode 100644
index 0000000000..365081ad39
--- /dev/null
+++ b/spec/ruby/core/set/constructor_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+
+describe "Set[]" do
+  it "returns a new Set populated with the passed Objects" do
+    set = Set[1, 2, 3]
+
+    set.instance_of?(Set).should be_true
+    set.size.should eql(3)
+
+    set.should include(1)
+    set.should include(2)
+    set.should include(3)
+  end
+end
diff --git a/spec/ruby/core/set/delete_if_spec.rb b/spec/ruby/core/set/delete_if_spec.rb
new file mode 100644
index 0000000000..beda73a5e5
--- /dev/null
+++ b/spec/ruby/core/set/delete_if_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+
+describe "Set#delete_if" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.delete_if { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "deletes every element from self for which the passed block returns true" do
+    @set.delete_if { |x| x.size == 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self" do
+    @set.delete_if { |x| x }.should equal(@set)
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.delete_if
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size == 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/core/set/delete_spec.rb b/spec/ruby/core/set/delete_spec.rb
new file mode 100644
index 0000000000..a2543ecbee
--- /dev/null
+++ b/spec/ruby/core/set/delete_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../spec_helper'
+
+describe "Set#delete" do
+  before :each do
+    @set = Set["a", "b", "c"]
+  end
+
+  it "deletes the passed Object from self" do
+    @set.delete("a")
+    @set.should_not include("a")
+  end
+
+  it "returns self" do
+    @set.delete("a").should equal(@set)
+    @set.delete("x").should equal(@set)
+  end
+end
+
+describe "Set#delete?" do
+  before :each do
+    @set = Set["a", "b", "c"]
+  end
+
+  it "deletes the passed Object from self" do
+    @set.delete?("a")
+    @set.should_not include("a")
+  end
+
+  it "returns self when the passed Object is in self" do
+    @set.delete?("a").should equal(@set)
+  end
+
+  it "returns nil when the passed Object is not in self" do
+    @set.delete?("x").should be_nil
+  end
+end
diff --git a/spec/ruby/core/set/difference_spec.rb b/spec/ruby/core/set/difference_spec.rb
new file mode 100644
index 0000000000..149f946592
--- /dev/null
+++ b/spec/ruby/core/set/difference_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/difference'
+
+describe "Set#difference" do
+  it_behaves_like :set_difference, :difference
+end
diff --git a/spec/ruby/core/set/disjoint_spec.rb b/spec/ruby/core/set/disjoint_spec.rb
new file mode 100644
index 0000000000..89a3c4b157
--- /dev/null
+++ b/spec/ruby/core/set/disjoint_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+
+describe "Set#disjoint?" do
+  it "returns false when two Sets have at least one element in common" do
+    Set[1, 2].disjoint?(Set[2, 3]).should == false
+  end
+
+  it "returns true when two Sets have no element in common" do
+    Set[1, 2].disjoint?(Set[3, 4]).should == true
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns false when a Set has at least one element in common with a Set-like object" do
+      Set[1, 2].disjoint?(SetSpecs::SetLike.new([2, 3])).should be_false
+    end
+
+    it "returns true when a Set has no element in common with a Set-like object" do
+      Set[1, 2].disjoint?(SetSpecs::SetLike.new([3, 4])).should be_true
+    end
+  end
+end
diff --git a/spec/ruby/core/set/divide_spec.rb b/spec/ruby/core/set/divide_spec.rb
new file mode 100644
index 0000000000..c6c6003e99
--- /dev/null
+++ b/spec/ruby/core/set/divide_spec.rb
@@ -0,0 +1,68 @@
+require_relative '../../spec_helper'
+
+describe "Set#divide" do
+  it "divides self into a set of subsets based on the blocks return values" do
+    set = Set["one", "two", "three", "four", "five"].divide { |x| x.length }
+    set.map { |x| x.to_a.sort }.sort.should == [["five", "four"], ["one", "two"], ["three"]]
+  end
+
+  it "yields each Object to the block" do
+    ret = []
+    Set["one", "two", "three", "four", "five"].divide { |x| ret << x }
+    ret.sort.should == ["five", "four", "one", "three", "two"]
+  end
+
+  it "returns an enumerator when not passed a block" do
+    ret = Set[1, 2, 3, 4].divide
+    ret.should be_kind_of(Enumerator)
+    ret.each(&:even?).should == Set[Set[1, 3], Set[2, 4]]
+  end
+end
+
+describe "Set#divide when passed a block with an arity of 2" do
+  it "divides self into a set of subsets based on the blocks return values" do
+    set = Set[1, 3, 4, 6, 9, 10, 11].divide { |x, y| (x - y).abs == 1 }
+    set.map{ |x| x.to_a.sort }.sort.should == [[1], [3, 4], [6], [9, 10, 11]]
+  end
+
+  ruby_version_is "4.0" do
+    it "yields each two Object to the block" do
+      ret = []
+      Set[1, 2].divide { |x, y| ret << [x, y] }
+      ret.sort.should == [[1, 2], [2, 1]]
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "yields each two Object to the block" do
+      ret = []
+      Set[1, 2].divide { |x, y| ret << [x, y] }
+      ret.sort.should == [[1, 1], [1, 2], [2, 1], [2, 2]]
+    end
+  end
+
+  it "returns an enumerator when not passed a block" do
+    ret = Set[1, 2, 3, 4].divide
+    ret.should be_kind_of(Enumerator)
+    ret.each { |a, b| (a + b).even? }.should == Set[Set[1, 3], Set[2, 4]]
+  end
+end
+
+describe "Set#divide when passed a block with an arity of > 2" do
+  it "only uses the first element if the arity > 2" do
+    set = Set["one", "two", "three", "four", "five"].divide do |x, y, z|
+      y.should be_nil
+      z.should be_nil
+      x.length
+    end
+    set.map { |x| x.to_a.sort }.sort.should == [["five", "four"], ["one", "two"], ["three"]]
+  end
+
+  it "only uses the first element if the arity = -1" do
+    set = Set["one", "two", "three", "four", "five"].divide do |*xs|
+      xs.size.should == 1
+      xs.first.length
+    end
+    set.map { |x| x.to_a.sort }.sort.should == [["five", "four"], ["one", "two"], ["three"]]
+  end
+end
diff --git a/spec/ruby/core/set/each_spec.rb b/spec/ruby/core/set/each_spec.rb
new file mode 100644
index 0000000000..3d9cdc2d46
--- /dev/null
+++ b/spec/ruby/core/set/each_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../spec_helper'
+
+describe "Set#each" do
+  before :each do
+    @set = Set[1, 2, 3]
+  end
+
+  it "yields each Object in self" do
+    ret = []
+    @set.each { |x| ret << x }
+    ret.sort.should == [1, 2, 3]
+  end
+
+  it "returns self" do
+    @set.each { |x| x }.should equal(@set)
+  end
+
+  it "returns an Enumerator when not passed a block" do
+    enum = @set.each
+    enum.should be_an_instance_of(Enumerator)
+
+    ret = []
+    enum.each { |x| ret << x }
+    ret.sort.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/set/empty_spec.rb b/spec/ruby/core/set/empty_spec.rb
new file mode 100644
index 0000000000..4b55658e20
--- /dev/null
+++ b/spec/ruby/core/set/empty_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+
+describe "Set#empty?" do
+  it "returns true if self is empty" do
+    Set[].empty?.should be_true
+    Set[1].empty?.should be_false
+    Set[1,2,3].empty?.should be_false
+  end
+end
diff --git a/spec/ruby/core/set/enumerable/to_set_spec.rb b/spec/ruby/core/set/enumerable/to_set_spec.rb
new file mode 100644
index 0000000000..f139e1c025
--- /dev/null
+++ b/spec/ruby/core/set/enumerable/to_set_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../../spec_helper'
+
+describe "Enumerable#to_set" do
+  it "returns a new Set created from self" do
+    [1, 2, 3].to_set.should == Set[1, 2, 3]
+    {a: 1, b: 2}.to_set.should == Set[[:b, 2], [:a, 1]]
+  end
+
+  it "passes down passed blocks" do
+    [1, 2, 3].to_set { |x| x * x }.should == Set[1, 4, 9]
+  end
+end
diff --git a/spec/ruby/core/set/eql_spec.rb b/spec/ruby/core/set/eql_spec.rb
new file mode 100644
index 0000000000..4ad5c3aa5a
--- /dev/null
+++ b/spec/ruby/core/set/eql_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+
+describe "Set#eql?" do
+  it "returns true when the passed argument is a Set and contains the same elements" do
+    Set[].should eql(Set[])
+    Set[1, 2, 3].should eql(Set[1, 2, 3])
+    Set[1, 2, 3].should eql(Set[3, 2, 1])
+    Set["a", :b, ?c].should eql(Set[?c, :b, "a"])
+
+    Set[1, 2, 3].should_not eql(Set[1.0, 2, 3])
+    Set[1, 2, 3].should_not eql(Set[2, 3])
+    Set[1, 2, 3].should_not eql(Set[])
+  end
+end
diff --git a/spec/ruby/core/set/equal_value_spec.rb b/spec/ruby/core/set/equal_value_spec.rb
new file mode 100644
index 0000000000..721a79a3f1
--- /dev/null
+++ b/spec/ruby/core/set/equal_value_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+
+describe "Set#==" do
+  it "returns true when the passed Object is a Set and self and the Object contain the same elements" do
+    Set[].should == Set[]
+    Set[1, 2, 3].should == Set[1, 2, 3]
+    Set["1", "2", "3"].should == Set["1", "2", "3"]
+
+    Set[1, 2, 3].should_not == Set[1.0, 2, 3]
+    Set[1, 2, 3].should_not == [1, 2, 3]
+  end
+
+  it "does not depend on the order of the elements" do
+    Set[1, 2, 3].should == Set[3, 2, 1]
+    Set[:a, "b", ?c].should == Set[?c, "b", :a]
+  end
+
+  it "does not depend on the order of nested Sets" do
+    Set[Set[1], Set[2], Set[3]].should == Set[Set[3], Set[2], Set[1]]
+
+    set1 = Set[Set["a", "b"], Set["c", "d"], Set["e", "f"]]
+    set2 = Set[Set["c", "d"], Set["a", "b"], Set["e", "f"]]
+    set1.should == set2
+  end
+
+  ruby_version_is ""..."4.0" do
+    context "when comparing to a Set-like object" do
+      it "returns true when a Set and a Set-like object contain the same elements" do
+        Set[1, 2, 3].should == SetSpecs::SetLike.new([1, 2, 3])
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/exclusion_spec.rb b/spec/ruby/core/set/exclusion_spec.rb
new file mode 100644
index 0000000000..bbc29afa95
--- /dev/null
+++ b/spec/ruby/core/set/exclusion_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+
+describe "Set#^" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns a new Set containing elements that are not in both self and the passed Enumerable" do
+    (@set ^ Set[3, 4, 5]).should == Set[1, 2, 5]
+    (@set ^ [3, 4, 5]).should == Set[1, 2, 5]
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { @set ^ 3 }.should raise_error(ArgumentError)
+    -> { @set ^ Object.new }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/core/set/filter_spec.rb b/spec/ruby/core/set/filter_spec.rb
new file mode 100644
index 0000000000..779254ad68
--- /dev/null
+++ b/spec/ruby/core/set/filter_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/select'
+
+describe "Set#filter!" do
+  it_behaves_like :set_select_bang, :filter!
+end
diff --git a/spec/ruby/core/set/fixtures/set_like.rb b/spec/ruby/core/set/fixtures/set_like.rb
new file mode 100644
index 0000000000..86dec2ed52
--- /dev/null
+++ b/spec/ruby/core/set/fixtures/set_like.rb
@@ -0,0 +1,30 @@
+
+module SetSpecs
+  # This class is used to test the interaction of "Set-like" objects with real Sets
+  #
+  # These "Set-like" objects reply to is_a?(Set) with true and thus real Set objects are able to transparently
+  # interoperate with them in a duck-typing manner.
+  class SetLike
+    include Enumerable
+
+    def is_a?(klass)
+      super || klass == ::Set
+    end
+
+    def initialize(entries)
+      @entries = entries
+    end
+
+    def each(&block)
+      @entries.each(&block)
+    end
+
+    def inspect
+      "#<#{self.class}: {#{map(&:inspect).join(", ")}}>"
+    end
+
+    def size
+      @entries.size
+    end
+  end
+end
diff --git a/spec/ruby/core/set/flatten_merge_spec.rb b/spec/ruby/core/set/flatten_merge_spec.rb
new file mode 100644
index 0000000000..13cedeead9
--- /dev/null
+++ b/spec/ruby/core/set/flatten_merge_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+
+describe "Set#flatten_merge" do
+  ruby_version_is ""..."4.0" do
+    it "is protected" do
+      Set.should have_protected_instance_method("flatten_merge")
+    end
+
+    it "flattens the passed Set and merges it into self" do
+      set1 = Set[1, 2]
+      set2 = Set[3, 4, Set[5, 6]]
+
+      set1.send(:flatten_merge, set2).should == Set[1, 2, 3, 4, 5, 6]
+    end
+
+    it "raises an ArgumentError when trying to flatten a recursive Set" do
+      set1 = Set[1, 2, 3]
+      set2 = Set[5, 6, 7]
+      set2 << set2
+
+      -> { set1.send(:flatten_merge, set2) }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/core/set/flatten_spec.rb b/spec/ruby/core/set/flatten_spec.rb
new file mode 100644
index 0000000000..f2cb3dfa52
--- /dev/null
+++ b/spec/ruby/core/set/flatten_spec.rb
@@ -0,0 +1,59 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+set_version = defined?(Set::VERSION) ? Set::VERSION : '1.0.0'
+
+describe "Set#flatten" do
+  it "returns a copy of self with each included Set flattened" do
+    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
+    flattened_set = set.flatten
+
+    flattened_set.should_not equal(set)
+    flattened_set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+  end
+
+  it "raises an ArgumentError when self is recursive" do
+    (set = Set[]) << set
+    -> { set.flatten }.should raise_error(ArgumentError)
+  end
+
+  ruby_version_is ""..."4.0" do
+    context "when Set contains a Set-like object" do
+      it "returns a copy of self with each included Set-like object flattened" do
+        Set[SetSpecs::SetLike.new([1])].flatten.should == Set[1]
+      end
+    end
+  end
+end
+
+describe "Set#flatten!" do
+  it "flattens self" do
+    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
+    set.flatten!
+    set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+  end
+
+  it "returns self when self was modified" do
+    set = Set[1, 2, Set[3, 4]]
+    set.flatten!.should equal(set)
+  end
+
+  it "returns nil when self was not modified" do
+    set = Set[1, 2, 3, 4]
+    set.flatten!.should be_nil
+  end
+
+  it "raises an ArgumentError when self is recursive" do
+    (set = Set[]) << set
+    -> { set.flatten! }.should raise_error(ArgumentError)
+  end
+
+  version_is(set_version, ""..."1.1.0") do #ruby_version_is ""..."3.3" do
+    ruby_version_is ""..."4.0" do
+      context "when Set contains a Set-like object" do
+        it "flattens self, including Set-like objects" do
+          Set[SetSpecs::SetLike.new([1])].flatten!.should == Set[1]
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/hash_spec.rb b/spec/ruby/core/set/hash_spec.rb
new file mode 100644
index 0000000000..63a0aa66a5
--- /dev/null
+++ b/spec/ruby/core/set/hash_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+describe "Set#hash" do
+  it "is static" do
+    Set[].hash.should == Set[].hash
+    Set[1, 2, 3].hash.should == Set[1, 2, 3].hash
+    Set[:a, "b", ?c].hash.should == Set[?c, "b", :a].hash
+
+    Set[].hash.should_not == Set[1, 2, 3].hash
+    Set[1, 2, 3].hash.should_not == Set[:a, "b", ?c].hash
+  end
+
+  ruby_version_is ""..."4.0" do
+    # see https://github.com/jruby/jruby/issues/8393
+    it "is equal to nil.hash for an uninitialized Set" do
+      Set.allocate.hash.should == nil.hash
+    end
+  end
+end
diff --git a/spec/ruby/core/set/include_spec.rb b/spec/ruby/core/set/include_spec.rb
new file mode 100644
index 0000000000..dd33bbc3bd
--- /dev/null
+++ b/spec/ruby/core/set/include_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+
+describe "Set#include?" do
+  it_behaves_like :set_include, :include?
+end
diff --git a/spec/ruby/core/set/initialize_clone_spec.rb b/spec/ruby/core/set/initialize_clone_spec.rb
new file mode 100644
index 0000000000..13abb7ee4e
--- /dev/null
+++ b/spec/ruby/core/set/initialize_clone_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+
+describe "Set#initialize_clone" do
+  # See https://bugs.ruby-lang.org/issues/14266
+  it "does not freeze the new Set when called from clone(freeze: false)" do
+    set1 = Set[1, 2]
+    set1.freeze
+    set2 = set1.clone(freeze: false)
+    set1.frozen?.should == true
+    set2.frozen?.should == false
+    set2.add 3
+    set1.should == Set[1, 2]
+    set2.should == Set[1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/set/initialize_spec.rb b/spec/ruby/core/set/initialize_spec.rb
new file mode 100644
index 0000000000..ad9e1bd8c9
--- /dev/null
+++ b/spec/ruby/core/set/initialize_spec.rb
@@ -0,0 +1,72 @@
+require_relative '../../spec_helper'
+
+describe "Set#initialize" do
+  it "is private" do
+    Set.should have_private_instance_method(:initialize)
+  end
+
+  it "adds all elements of the passed Enumerable to self" do
+    s = Set.new([1, 2, 3])
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "uses #each_entry on the provided Enumerable" do
+    enumerable = MockObject.new('mock-enumerable')
+    enumerable.should_receive(:each_entry).and_yield(1).and_yield(2).and_yield(3)
+    s = Set.new(enumerable)
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "uses #each on the provided Enumerable if it does not respond to #each_entry" do
+    enumerable = MockObject.new('mock-enumerable')
+    enumerable.should_receive(:each).and_yield(1).and_yield(2).and_yield(3)
+    s = Set.new(enumerable)
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(2)
+    s.should include(3)
+  end
+
+  it "raises if the provided Enumerable does not respond to #each_entry or #each" do
+    enumerable = MockObject.new('mock-enumerable')
+    -> { Set.new(enumerable) }.should raise_error(ArgumentError, "value must be enumerable")
+  end
+
+  it "should initialize with empty array and set" do
+    s = Set.new([])
+    s.size.should eql(0)
+
+    s = Set.new({})
+    s.size.should eql(0)
+  end
+
+  it "preprocesses all elements by a passed block before adding to self" do
+    s = Set.new([1, 2, 3]) { |x| x * x }
+    s.size.should eql(3)
+    s.should include(1)
+    s.should include(4)
+    s.should include(9)
+  end
+
+  it "should initialize with empty array and block" do
+    s = Set.new([]) { |x| x * x }
+    s.size.should eql(0)
+  end
+
+  it "should initialize with empty set and block" do
+    s = Set.new(Set.new) { |x| x * x }
+    s.size.should eql(0)
+  end
+
+  it "should initialize with just block" do
+    s = Set.new { |x| x * x }
+    s.size.should eql(0)
+    s.should eql(Set.new)
+  end
+end
diff --git a/spec/ruby/core/set/inspect_spec.rb b/spec/ruby/core/set/inspect_spec.rb
new file mode 100644
index 0000000000..0dcce83eb6
--- /dev/null
+++ b/spec/ruby/core/set/inspect_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/inspect'
+
+describe "Set#inspect" do
+  it_behaves_like :set_inspect, :inspect
+end
diff --git a/spec/ruby/core/set/intersect_spec.rb b/spec/ruby/core/set/intersect_spec.rb
new file mode 100644
index 0000000000..0736dea5fd
--- /dev/null
+++ b/spec/ruby/core/set/intersect_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+
+describe "Set#intersect?" do
+  it "returns true when two Sets have at least one element in common" do
+    Set[1, 2].intersect?(Set[2, 3]).should == true
+  end
+
+  it "returns false when two Sets have no element in common" do
+    Set[1, 2].intersect?(Set[3, 4]).should == false
+  end
+
+  context "when comparing to a Set-like object" do
+    it "returns true when a Set has at least one element in common with a Set-like object" do
+      Set[1, 2].intersect?(SetSpecs::SetLike.new([2, 3])).should be_true
+    end
+
+    it "returns false when a Set has no element in common with a Set-like object" do
+      Set[1, 2].intersect?(SetSpecs::SetLike.new([3, 4])).should be_false
+    end
+  end
+end
diff --git a/spec/ruby/core/set/intersection_spec.rb b/spec/ruby/core/set/intersection_spec.rb
new file mode 100644
index 0000000000..136b886775
--- /dev/null
+++ b/spec/ruby/core/set/intersection_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require_relative 'shared/intersection'
+
+describe "Set#intersection" do
+  it_behaves_like :set_intersection, :intersection
+end
+
+describe "Set#&" do
+  it_behaves_like :set_intersection, :&
+end
diff --git a/spec/ruby/core/set/join_spec.rb b/spec/ruby/core/set/join_spec.rb
new file mode 100644
index 0000000000..1c1e8a8af8
--- /dev/null
+++ b/spec/ruby/core/set/join_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+
+describe "Set#join" do
+  it "returns an empty string if the Set is empty" do
+    Set[].join.should == ''
+  end
+
+  it "returns a new string formed by joining elements after conversion" do
+    set = Set[:a, :b, :c]
+    set.join.should == "abc"
+  end
+
+  it "does not separate elements when the passed separator is nil" do
+    set = Set[:a, :b, :c]
+    set.join(nil).should == "abc"
+  end
+
+  it "returns a string formed by concatenating each element separated by the separator" do
+    set = Set[:a, :b, :c]
+    set.join(' | ').should == "a | b | c"
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "calls #to_a to convert the Set in to an Array" do
+      set = Set[:a, :b, :c]
+      set.should_receive(:to_a).and_return([:a, :b, :c])
+      set.join.should == "abc"
+    end
+  end
+end
diff --git a/spec/ruby/core/set/keep_if_spec.rb b/spec/ruby/core/set/keep_if_spec.rb
new file mode 100644
index 0000000000..d6abdd6adc
--- /dev/null
+++ b/spec/ruby/core/set/keep_if_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+
+describe "Set#keep_if" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.keep_if { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "keeps every element from self for which the passed block returns true" do
+    @set.keep_if { |x| x.size != 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self" do
+    @set.keep_if {}.should equal(@set)
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.keep_if
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size != 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/core/set/length_spec.rb b/spec/ruby/core/set/length_spec.rb
new file mode 100644
index 0000000000..6bb697b4ca
--- /dev/null
+++ b/spec/ruby/core/set/length_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/length'
+
+describe "Set#length" do
+  it_behaves_like :set_length, :length
+end
diff --git a/spec/ruby/core/set/map_spec.rb b/spec/ruby/core/set/map_spec.rb
new file mode 100644
index 0000000000..996191b0a8
--- /dev/null
+++ b/spec/ruby/core/set/map_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/collect'
+
+describe "Set#map!" do
+  it_behaves_like :set_collect_bang, :map!
+end
diff --git a/spec/ruby/core/set/member_spec.rb b/spec/ruby/core/set/member_spec.rb
new file mode 100644
index 0000000000..5c82e8f826
--- /dev/null
+++ b/spec/ruby/core/set/member_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/include'
+
+describe "Set#member?" do
+  it_behaves_like :set_include, :member?
+end
diff --git a/spec/ruby/core/set/merge_spec.rb b/spec/ruby/core/set/merge_spec.rb
new file mode 100644
index 0000000000..0c6ed27670
--- /dev/null
+++ b/spec/ruby/core/set/merge_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+
+describe "Set#merge" do
+  it "adds the elements of the passed Enumerable to self" do
+    Set[:a, :b].merge(Set[:b, :c, :d]).should == Set[:a, :b, :c, :d]
+    Set[1, 2].merge([3, 4]).should == Set[1, 2, 3, 4]
+  end
+
+  it "returns self" do
+    set = Set[1, 2]
+    set.merge([3, 4]).should equal(set)
+  end
+
+  it "raises an ArgumentError when passed a non-Enumerable" do
+    -> { Set[1, 2].merge(1) }.should raise_error(ArgumentError)
+    -> { Set[1, 2].merge(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  it "raises RuntimeError when called during iteration" do
+    set = Set[:a, :b]
+    set.each do |_m|
+      -> { set.merge([1, 2]) }.should raise_error(RuntimeError, /iteration/)
+    end
+  end
+
+  ruby_version_is ""..."3.3" do
+    it "accepts only a single argument" do
+      -> { Set[].merge([], []) }.should raise_error(ArgumentError, "wrong number of arguments (given 2, expected 1)")
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "accepts multiple arguments" do
+      Set[:a, :b].merge(Set[:b, :c], [:d]).should == Set[:a, :b, :c, :d]
+    end
+  end
+end
diff --git a/spec/ruby/core/set/minus_spec.rb b/spec/ruby/core/set/minus_spec.rb
new file mode 100644
index 0000000000..72f98f985e
--- /dev/null
+++ b/spec/ruby/core/set/minus_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/difference'
+
+describe "Set#-" do
+  it_behaves_like :set_difference, :-
+end
diff --git a/spec/ruby/core/set/plus_spec.rb b/spec/ruby/core/set/plus_spec.rb
new file mode 100644
index 0000000000..7e44ff0b7e
--- /dev/null
+++ b/spec/ruby/core/set/plus_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/union'
+
+describe "Set#+" do
+  it_behaves_like :set_union, :+
+end
diff --git a/spec/ruby/core/set/pretty_print_cycle_spec.rb b/spec/ruby/core/set/pretty_print_cycle_spec.rb
new file mode 100644
index 0000000000..7e6017c112
--- /dev/null
+++ b/spec/ruby/core/set/pretty_print_cycle_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+
+describe "Set#pretty_print_cycle" do
+  it "passes the 'pretty print' representation of a self-referencing Set to the pretty print writer" do
+    pp = mock("PrettyPrint")
+    ruby_version_is(""..."4.0") do
+      pp.should_receive(:text).with("#<Set: {...}>")
+    end
+    ruby_version_is("4.0") do
+      pp.should_receive(:text).with("Set[...]")
+    end
+    Set[1, 2, 3].pretty_print_cycle(pp)
+  end
+end
diff --git a/spec/ruby/core/set/proper_subset_spec.rb b/spec/ruby/core/set/proper_subset_spec.rb
new file mode 100644
index 0000000000..fb7848c001
--- /dev/null
+++ b/spec/ruby/core/set/proper_subset_spec.rb
@@ -0,0 +1,45 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+set_version = defined?(Set::VERSION) ? Set::VERSION : '1.0.0'
+
+describe "Set#proper_subset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that self is a proper subset of" do
+    Set[].proper_subset?(@set).should be_true
+    Set[].proper_subset?(Set[1, 2, 3]).should be_true
+    Set[].proper_subset?(Set["a", :b, ?c]).should be_true
+
+    Set[1, 2, 3].proper_subset?(@set).should be_true
+    Set[1, 3].proper_subset?(@set).should be_true
+    Set[1, 2].proper_subset?(@set).should be_true
+    Set[1].proper_subset?(@set).should be_true
+
+    Set[5].proper_subset?(@set).should be_false
+    Set[1, 5].proper_subset?(@set).should be_false
+    Set[nil].proper_subset?(@set).should be_false
+    Set["test"].proper_subset?(@set).should be_false
+
+    @set.proper_subset?(@set).should be_false
+    Set[].proper_subset?(Set[]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].proper_subset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].proper_subset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  version_is(set_version, ""..."1.1.0") do #ruby_version_is ""..."3.3" do
+    ruby_version_is ""..."4.0" do
+      context "when comparing to a Set-like object" do
+        it "returns true if passed a Set-like object that self is a proper subset of" do
+          Set[1, 2, 3].proper_subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/proper_superset_spec.rb b/spec/ruby/core/set/proper_superset_spec.rb
new file mode 100644
index 0000000000..dc1e87e230
--- /dev/null
+++ b/spec/ruby/core/set/proper_superset_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+
+describe "Set#proper_superset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that self is a proper superset of" do
+    @set.proper_superset?(Set[]).should be_true
+    Set[1, 2, 3].proper_superset?(Set[]).should be_true
+    Set["a", :b, ?c].proper_superset?(Set[]).should be_true
+
+    @set.proper_superset?(Set[1, 2, 3]).should be_true
+    @set.proper_superset?(Set[1, 3]).should be_true
+    @set.proper_superset?(Set[1, 2]).should be_true
+    @set.proper_superset?(Set[1]).should be_true
+
+    @set.proper_superset?(Set[5]).should be_false
+    @set.proper_superset?(Set[1, 5]).should be_false
+    @set.proper_superset?(Set[nil]).should be_false
+    @set.proper_superset?(Set["test"]).should be_false
+
+    @set.proper_superset?(@set).should be_false
+    Set[].proper_superset?(Set[]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].proper_superset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].proper_superset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  ruby_version_is ""..."4.0" do
+    context "when comparing to a Set-like object" do
+      it "returns true if passed a Set-like object that self is a proper superset of" do
+        Set[1, 2, 3, 4].proper_superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/reject_spec.rb b/spec/ruby/core/set/reject_spec.rb
new file mode 100644
index 0000000000..91d0293415
--- /dev/null
+++ b/spec/ruby/core/set/reject_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+
+describe "Set#reject!" do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.reject! { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "deletes every element from self for which the passed block returns true" do
+    @set.reject! { |x| x.size == 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self when self was modified" do
+    @set.reject! { |x| true }.should equal(@set)
+  end
+
+  it "returns nil when self was not modified" do
+    @set.reject! { |x| false }.should be_nil
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.reject!
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size == 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/core/set/replace_spec.rb b/spec/ruby/core/set/replace_spec.rb
new file mode 100644
index 0000000000..c66a2d0ec3
--- /dev/null
+++ b/spec/ruby/core/set/replace_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+
+describe "Set#replace" do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "replaces the contents with other and returns self" do
+    @set.replace(Set[1, 2, 3]).should == @set
+    @set.should == Set[1, 2, 3]
+  end
+
+  it "raises RuntimeError when called during iteration" do
+    set = Set[:a, :b, :c, :d, :e, :f]
+    set.each do |_m|
+      -> { set.replace(Set[1, 2, 3]) }.should raise_error(RuntimeError, /iteration/)
+    end
+    set.should == Set[:a, :b, :c, :d, :e, :f]
+  end
+
+  it "accepts any enumerable as other" do
+    @set.replace([1, 2, 3]).should == Set[1, 2, 3]
+  end
+end
diff --git a/spec/ruby/library/set/select_spec.rb b/spec/ruby/core/set/select_spec.rb
index b458ffacaa..b458ffacaa 100644
--- a/spec/ruby/library/set/select_spec.rb
+++ b/spec/ruby/core/set/select_spec.rb
diff --git a/spec/ruby/core/set/set_spec.rb b/spec/ruby/core/set/set_spec.rb
new file mode 100644
index 0000000000..fd1d2072e3
--- /dev/null
+++ b/spec/ruby/core/set/set_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+
+describe 'Set' do
+  it 'is available without explicit requiring' do
+    output = ruby_exe(<<~RUBY, options: '--disable-gems', args: '2>&1')
+      puts Set.new([1, 2, 3]).to_a.inspect
+    RUBY
+    output.chomp.should == "[1, 2, 3]"
+  end
+end
diff --git a/spec/ruby/library/set/shared/add.rb b/spec/ruby/core/set/shared/add.rb
index 9e797f5df9..9e797f5df9 100644
--- a/spec/ruby/library/set/shared/add.rb
+++ b/spec/ruby/core/set/shared/add.rb
diff --git a/spec/ruby/library/set/shared/collect.rb b/spec/ruby/core/set/shared/collect.rb
index bc58c231be..bc58c231be 100644
--- a/spec/ruby/library/set/shared/collect.rb
+++ b/spec/ruby/core/set/shared/collect.rb
diff --git a/spec/ruby/library/set/shared/difference.rb b/spec/ruby/core/set/shared/difference.rb
index f88987ed2a..f88987ed2a 100644
--- a/spec/ruby/library/set/shared/difference.rb
+++ b/spec/ruby/core/set/shared/difference.rb
diff --git a/spec/ruby/library/set/shared/include.rb b/spec/ruby/core/set/shared/include.rb
index b4d95cde24..b4d95cde24 100644
--- a/spec/ruby/library/set/shared/include.rb
+++ b/spec/ruby/core/set/shared/include.rb
diff --git a/spec/ruby/core/set/shared/inspect.rb b/spec/ruby/core/set/shared/inspect.rb
new file mode 100644
index 0000000000..a90af66c98
--- /dev/null
+++ b/spec/ruby/core/set/shared/inspect.rb
@@ -0,0 +1,45 @@
+describe :set_inspect, shared: true do
+  it "returns a String representation of self" do
+    Set[].send(@method).should be_kind_of(String)
+    Set[nil, false, true].send(@method).should be_kind_of(String)
+    Set[1, 2, 3].send(@method).should be_kind_of(String)
+    Set["1", "2", "3"].send(@method).should be_kind_of(String)
+    Set[:a, "b", Set[?c]].send(@method).should be_kind_of(String)
+  end
+
+  ruby_version_is "4.0" do
+    it "does include the elements of the set" do
+      Set["1"].send(@method).should == 'Set["1"]'
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "does include the elements of the set" do
+      Set["1"].send(@method).should == '#<Set: {"1"}>'
+    end
+  end
+
+  it "puts spaces between the elements" do
+    Set["1", "2"].send(@method).should include('", "')
+  end
+
+  ruby_version_is "4.0" do
+    it "correctly handles cyclic-references" do
+      set1 = Set[]
+      set2 = Set[set1]
+      set1 << set2
+      set1.send(@method).should be_kind_of(String)
+      set1.send(@method).should include("Set[...]")
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "correctly handles cyclic-references" do
+      set1 = Set[]
+      set2 = Set[set1]
+      set1 << set2
+      set1.send(@method).should be_kind_of(String)
+      set1.send(@method).should include("#<Set: {...}>")
+    end
+  end
+end
diff --git a/spec/ruby/library/set/shared/intersection.rb b/spec/ruby/core/set/shared/intersection.rb
index 5ae4199c94..5ae4199c94 100644
--- a/spec/ruby/library/set/shared/intersection.rb
+++ b/spec/ruby/core/set/shared/intersection.rb
diff --git a/spec/ruby/library/set/shared/length.rb b/spec/ruby/core/set/shared/length.rb
index a8fcee9f39..a8fcee9f39 100644
--- a/spec/ruby/library/set/shared/length.rb
+++ b/spec/ruby/core/set/shared/length.rb
diff --git a/spec/ruby/core/set/shared/select.rb b/spec/ruby/core/set/shared/select.rb
new file mode 100644
index 0000000000..467b236ed3
--- /dev/null
+++ b/spec/ruby/core/set/shared/select.rb
@@ -0,0 +1,41 @@
+require_relative '../../../spec_helper'
+
+describe :set_select_bang, shared: true do
+  before :each do
+    @set = Set["one", "two", "three"]
+  end
+
+  it "yields every element of self" do
+    ret = []
+    @set.send(@method) { |x| ret << x }
+    ret.sort.should == ["one", "two", "three"].sort
+  end
+
+  it "keeps every element from self for which the passed block returns true" do
+    @set.send(@method) { |x| x.size != 3 }
+    @set.size.should eql(1)
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+
+  it "returns self when self was modified" do
+    @set.send(@method) { false }.should equal(@set)
+  end
+
+  it "returns nil when self was not modified" do
+    @set.send(@method) { true }.should be_nil
+  end
+
+  it "returns an Enumerator when passed no block" do
+    enum = @set.send(@method)
+    enum.should be_an_instance_of(Enumerator)
+
+    enum.each { |x| x.size != 3 }
+
+    @set.should_not include("one")
+    @set.should_not include("two")
+    @set.should include("three")
+  end
+end
diff --git a/spec/ruby/library/set/shared/union.rb b/spec/ruby/core/set/shared/union.rb
index 314f0e852d..314f0e852d 100644
--- a/spec/ruby/library/set/shared/union.rb
+++ b/spec/ruby/core/set/shared/union.rb
diff --git a/spec/ruby/core/set/size_spec.rb b/spec/ruby/core/set/size_spec.rb
new file mode 100644
index 0000000000..4ae22c5f0a
--- /dev/null
+++ b/spec/ruby/core/set/size_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/length'
+
+describe "Set#size" do
+  it_behaves_like :set_length, :size
+end
diff --git a/spec/ruby/core/set/sortedset/sortedset_spec.rb b/spec/ruby/core/set/sortedset/sortedset_spec.rb
new file mode 100644
index 0000000000..f3c1ec058d
--- /dev/null
+++ b/spec/ruby/core/set/sortedset/sortedset_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+
+describe "SortedSet" do
+  ruby_version_is ""..."4.0" do
+    it "raises error including message that it has been extracted from the set stdlib" do
+      -> {
+        SortedSet
+      }.should raise_error(RuntimeError) { |e|
+        e.message.should.include?("The `SortedSet` class has been extracted from the `set` library")
+      }
+    end
+  end
+end
diff --git a/spec/ruby/core/set/subset_spec.rb b/spec/ruby/core/set/subset_spec.rb
new file mode 100644
index 0000000000..112bd9b38a
--- /dev/null
+++ b/spec/ruby/core/set/subset_spec.rb
@@ -0,0 +1,45 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+set_version = defined?(Set::VERSION) ? Set::VERSION : '1.0.0'
+
+describe "Set#subset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that is equal to self or self is a subset of" do
+    @set.subset?(@set).should be_true
+    Set[].subset?(Set[]).should be_true
+
+    Set[].subset?(@set).should be_true
+    Set[].subset?(Set[1, 2, 3]).should be_true
+    Set[].subset?(Set["a", :b, ?c]).should be_true
+
+    Set[1, 2, 3].subset?(@set).should be_true
+    Set[1, 3].subset?(@set).should be_true
+    Set[1, 2].subset?(@set).should be_true
+    Set[1].subset?(@set).should be_true
+
+    Set[5].subset?(@set).should be_false
+    Set[1, 5].subset?(@set).should be_false
+    Set[nil].subset?(@set).should be_false
+    Set["test"].subset?(@set).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].subset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].subset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].subset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].subset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  version_is(set_version, ""..."1.1.0") do #ruby_version_is ""..."3.3" do
+    ruby_version_is ""..."4.0" do
+      context "when comparing to a Set-like object" do
+        it "returns true if passed a Set-like object that self is a subset of" do
+          Set[1, 2, 3].subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/subtract_spec.rb b/spec/ruby/core/set/subtract_spec.rb
new file mode 100644
index 0000000000..ae4bc73d41
--- /dev/null
+++ b/spec/ruby/core/set/subtract_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+
+describe "Set#subtract" do
+  before :each do
+    @set = Set[:a, :b, :c]
+  end
+
+  it "deletes any elements contained in other and returns self" do
+    @set.subtract(Set[:b, :c]).should == @set
+    @set.should == Set[:a]
+  end
+
+  it "accepts any enumerable as other" do
+    @set.subtract([:c]).should == Set[:a, :b]
+  end
+end
diff --git a/spec/ruby/core/set/superset_spec.rb b/spec/ruby/core/set/superset_spec.rb
new file mode 100644
index 0000000000..9b3df2d047
--- /dev/null
+++ b/spec/ruby/core/set/superset_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/set_like'
+
+describe "Set#superset?" do
+  before :each do
+    @set = Set[1, 2, 3, 4]
+  end
+
+  it "returns true if passed a Set that equals self or self is a proper superset of" do
+    @set.superset?(@set).should be_true
+    Set[].superset?(Set[]).should be_true
+
+    @set.superset?(Set[]).should be_true
+    Set[1, 2, 3].superset?(Set[]).should be_true
+    Set["a", :b, ?c].superset?(Set[]).should be_true
+
+    @set.superset?(Set[1, 2, 3]).should be_true
+    @set.superset?(Set[1, 3]).should be_true
+    @set.superset?(Set[1, 2]).should be_true
+    @set.superset?(Set[1]).should be_true
+
+    @set.superset?(Set[5]).should be_false
+    @set.superset?(Set[1, 5]).should be_false
+    @set.superset?(Set[nil]).should be_false
+    @set.superset?(Set["test"]).should be_false
+  end
+
+  it "raises an ArgumentError when passed a non-Set" do
+    -> { Set[].superset?([]) }.should raise_error(ArgumentError)
+    -> { Set[].superset?(1) }.should raise_error(ArgumentError)
+    -> { Set[].superset?("test") }.should raise_error(ArgumentError)
+    -> { Set[].superset?(Object.new) }.should raise_error(ArgumentError)
+  end
+
+  ruby_version_is ""..."4.0" do
+    context "when comparing to a Set-like object" do
+      it "returns true if passed a Set-like object that self is a superset of" do
+        Set[1, 2, 3, 4].superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/set/to_a_spec.rb b/spec/ruby/core/set/to_a_spec.rb
new file mode 100644
index 0000000000..1e9800167a
--- /dev/null
+++ b/spec/ruby/core/set/to_a_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+
+describe "Set#to_a" do
+  it "returns an array containing elements of self" do
+    Set[1, 2, 3].to_a.sort.should == [1, 2, 3]
+  end
+end
diff --git a/spec/ruby/core/set/to_s_spec.rb b/spec/ruby/core/set/to_s_spec.rb
new file mode 100644
index 0000000000..55b8bfd9b2
--- /dev/null
+++ b/spec/ruby/core/set/to_s_spec.rb
@@ -0,0 +1,11 @@
+require_relative "../../spec_helper"
+require_relative 'shared/inspect'
+
+describe "Set#to_s" do
+  it_behaves_like :set_inspect, :to_s
+
+  it "is an alias of inspect" do
+    set = Set.new
+    set.method(:to_s).should == set.method(:inspect)
+  end
+end
diff --git a/spec/ruby/core/set/union_spec.rb b/spec/ruby/core/set/union_spec.rb
new file mode 100644
index 0000000000..3e77022d4b
--- /dev/null
+++ b/spec/ruby/core/set/union_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require_relative 'shared/union'
+
+describe "Set#union" do
+  it_behaves_like :set_union, :union
+end
+
+describe "Set#|" do
+  it_behaves_like :set_union, :|
+end
diff --git a/spec/ruby/core/signal/signame_spec.rb b/spec/ruby/core/signal/signame_spec.rb
index b66de9fc85..adfe895d97 100644
--- a/spec/ruby/core/signal/signame_spec.rb
+++ b/spec/ruby/core/signal/signame_spec.rb
@@ -9,10 +9,22 @@ describe "Signal.signame" do
     Signal.signame(-1).should == nil
   end
 
+  it "calls #to_int on an object to convert to an Integer" do
+    obj = mock('signal')
+    obj.should_receive(:to_int).and_return(0)
+    Signal.signame(obj).should == "EXIT"
+  end
+
   it "raises a TypeError when the passed argument can't be coerced to Integer" do
     -> { Signal.signame("hello") }.should raise_error(TypeError)
   end
 
+  it "raises a TypeError when the passed argument responds to #to_int but does not return an Integer" do
+    obj = mock('signal')
+    obj.should_receive(:to_int).and_return('not an int')
+    -> { Signal.signame(obj) }.should raise_error(TypeError)
+  end
+
   platform_is_not :windows do
     it "the original should take precedence over alias when looked up by number" do
       Signal.signame(Signal.list["ABRT"]).should == "ABRT"
diff --git a/spec/ruby/core/signal/trap_spec.rb b/spec/ruby/core/signal/trap_spec.rb
index 91ce1f1348..6d654a99be 100644
--- a/spec/ruby/core/signal/trap_spec.rb
+++ b/spec/ruby/core/signal/trap_spec.rb
@@ -1,11 +1,12 @@
 require_relative '../../spec_helper'
 
-platform_is_not :windows do
-  describe "Signal.trap" do
+describe "Signal.trap" do
+  platform_is_not :windows do
     before :each do
       ScratchPad.clear
       @proc = -> {}
       @saved_trap = Signal.trap(:HUP, @proc)
+      @hup_number = Signal.list["HUP"]
     end
 
     after :each do
@@ -16,10 +17,11 @@ platform_is_not :windows do
       Signal.trap(:HUP, @saved_trap).should equal(@proc)
     end
 
-    it "accepts a block in place of a proc/command argument" do
+    it "accepts a block" do
       done = false
 
-      Signal.trap(:HUP) do
+      Signal.trap(:HUP) do |signo|
+        signo.should == @hup_number
         ScratchPad.record :block_trap
         done = true
       end
@@ -30,6 +32,94 @@ platform_is_not :windows do
       ScratchPad.recorded.should == :block_trap
     end
 
+    it "accepts a proc" do
+      done = false
+
+      handler = -> signo {
+        signo.should == @hup_number
+        ScratchPad.record :proc_trap
+        done = true
+      }
+
+      Signal.trap(:HUP, handler)
+
+      Process.kill :HUP, Process.pid
+      Thread.pass until done
+
+      ScratchPad.recorded.should == :proc_trap
+    end
+
+    it "accepts a method" do
+      done = false
+
+      handler_class = Class.new
+      hup_number = @hup_number
+
+      handler_class.define_method :handler_method do |signo|
+        signo.should == hup_number
+        ScratchPad.record :method_trap
+        done = true
+      end
+
+      handler_method = handler_class.new.method(:handler_method)
+
+      Signal.trap(:HUP, handler_method)
+
+      Process.kill :HUP, Process.pid
+      Thread.pass until done
+
+      ScratchPad.recorded.should == :method_trap
+    end
+
+    it "accepts anything you can call" do
+      done = false
+
+      callable = Object.new
+      hup_number = @hup_number
+
+      callable.singleton_class.define_method :call do |signo|
+        signo.should == hup_number
+        ScratchPad.record :callable_trap
+        done = true
+      end
+
+      Signal.trap(:HUP, callable)
+
+      Process.kill :HUP, Process.pid
+      Thread.pass until done
+
+      ScratchPad.recorded.should == :callable_trap
+    end
+
+    it "raises an exception for a non-callable at the point of use" do
+      not_callable = Object.new
+      Signal.trap(:HUP, not_callable)
+      -> {
+        Process.kill :HUP, Process.pid
+        loop { Thread.pass }
+      }.should raise_error(NoMethodError)
+    end
+
+    it "accepts a non-callable that becomes callable when used" do
+      done = false
+
+      late_callable = Object.new
+      hup_number = @hup_number
+
+      Signal.trap(:HUP, late_callable)
+
+      late_callable.singleton_class.define_method :call do |signo|
+        signo.should == hup_number
+        ScratchPad.record :late_callable_trap
+        done = true
+      end
+
+      Process.kill :HUP, Process.pid
+      Thread.pass until done
+
+      ScratchPad.recorded.should == :late_callable_trap
+    end
+
     it "is possible to create a new Thread when the handler runs" do
       done = false
 
@@ -49,7 +139,21 @@ platform_is_not :windows do
 
     it "registers an handler doing nothing with :IGNORE" do
       Signal.trap :HUP, :IGNORE
+      Signal.trap(:HUP, @saved_trap).should == "IGNORE"
+    end
+
+    it "can register a new handler after :IGNORE" do
+      Signal.trap :HUP, :IGNORE
+
+      done = false
+      Signal.trap(:HUP) do
+        ScratchPad.record :block_trap
+        done = true
+      end
+
       Process.kill(:HUP, Process.pid).should == 1
+      Thread.pass until done
+      ScratchPad.recorded.should == :block_trap
     end
 
     it "ignores the signal when passed nil" do
@@ -116,14 +220,43 @@ platform_is_not :windows do
       Signal.trap :HUP, @proc
       Signal.trap(:HUP, @saved_trap).should equal(@proc)
     end
-  end
 
-  describe "Signal.trap" do
+    it "calls #to_str on an object to convert to a String" do
+      obj = mock("signal")
+      obj.should_receive(:to_str).exactly(2).times.and_return("HUP")
+      Signal.trap obj, @proc
+      Signal.trap(obj, @saved_trap).should equal(@proc)
+    end
+
+    it "accepts Integer values" do
+      hup = Signal.list["HUP"]
+      Signal.trap hup, @proc
+      Signal.trap(hup, @saved_trap).should equal(@proc)
+    end
+
+    it "does not call #to_int on an object to convert to an Integer" do
+      obj = mock("signal")
+      obj.should_not_receive(:to_int)
+      -> { Signal.trap obj, @proc }.should raise_error(ArgumentError, /bad signal type/)
+    end
+
+    it "raises ArgumentError when passed unknown signal" do
+      -> { Signal.trap(300) { } }.should raise_error(ArgumentError, "invalid signal number (300)")
+      -> { Signal.trap("USR10") { } }.should raise_error(ArgumentError, /\Aunsupported signal [`']SIGUSR10'\z/)
+      -> { Signal.trap("SIGUSR10") { } }.should raise_error(ArgumentError, /\Aunsupported signal [`']SIGUSR10'\z/)
+    end
+
+    it "raises ArgumentError when passed signal is not Integer, String or Symbol" do
+      -> { Signal.trap(nil) { } }.should raise_error(ArgumentError, "bad signal type NilClass")
+      -> { Signal.trap(100.0) { } }.should raise_error(ArgumentError, "bad signal type Float")
+      -> { Signal.trap(Rational(100)) { } }.should raise_error(ArgumentError, "bad signal type Rational")
+    end
+
     # See man 2 signal
     %w[KILL STOP].each do |signal|
       it "raises ArgumentError or Errno::EINVAL for SIG#{signal}" do
         -> {
-          trap(signal, -> {})
+          Signal.trap(signal, -> {})
         }.should raise_error(StandardError) { |e|
           [ArgumentError, Errno::EINVAL].should include(e.class)
           e.message.should =~ /Invalid argument|Signal already used by VM or OS/
@@ -131,6 +264,14 @@ platform_is_not :windows do
       end
     end
 
+    %w[SEGV BUS ILL FPE VTALRM].each do |signal|
+      it "raises ArgumentError for SIG#{signal} which is reserved by Ruby" do
+        -> {
+          Signal.trap(signal, -> {})
+        }.should raise_error(ArgumentError, "can't trap reserved signal: SIG#{signal}")
+      end
+    end
+
     it "allows to register a handler for all known signals, except reserved signals for which it raises ArgumentError" do
       out = ruby_exe(fixture(__FILE__, "trap_all.rb"), args: "2>&1")
       out.should == "OK\n"
@@ -138,7 +279,7 @@ platform_is_not :windows do
     end
 
     it "returns 'DEFAULT' for the initial SIGINT handler" do
-      ruby_exe('print trap(:INT) { abort }').should == 'DEFAULT'
+      ruby_exe("print Signal.trap(:INT) { abort }").should == 'DEFAULT'
     end
 
     it "returns SYSTEM_DEFAULT if passed DEFAULT and no handler was ever set" do
@@ -152,31 +293,28 @@ platform_is_not :windows do
         r.close
         loop { w.write("a"*1024) }
       RUBY
-      out = ruby_exe(code)
+      out = ruby_exe(code, exit_status: :SIGPIPE)
       status = $?
       out.should == "nil\n"
-      status.signaled?.should == true
-      status.termsig.should be_kind_of(Integer)
-      Signal.signame(status.termsig).should == "PIPE"
+      status.should.signaled?
     end
   end
-end
 
-describe "Signal.trap" do
   describe "the special EXIT signal code" do
     it "accepts the EXIT code" do
-      code = "trap(:EXIT, proc { print 1 })"
+      code = "Signal.trap(:EXIT, proc { print 1 })"
       ruby_exe(code).should == "1"
     end
 
     it "runs the proc before at_exit handlers" do
-      code = "at_exit {print 1}; trap(:EXIT, proc {print 2}); at_exit {print 3}"
+      code = "at_exit {print 1}; Signal.trap(:EXIT, proc {print 2}); at_exit {print 3}"
       ruby_exe(code).should == "231"
     end
 
     it "can unset the handler" do
-      code = "trap(:EXIT, proc { print 1 }); trap(:EXIT, 'DEFAULT')"
+      code = "Signal.trap(:EXIT, proc { print 1 }); Signal.trap(:EXIT, 'DEFAULT')"
       ruby_exe(code).should == ""
     end
   end
+
 end
diff --git a/spec/ruby/core/sizedqueue/append_spec.rb b/spec/ruby/core/sizedqueue/append_spec.rb
index ca79068930..c52baa3802 100644
--- a/spec/ruby/core/sizedqueue/append_spec.rb
+++ b/spec/ruby/core/sizedqueue/append_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/enque'
 require_relative '../../shared/sizedqueue/enque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#<<" do
   it_behaves_like :queue_enq, :<<, -> { SizedQueue.new(10) }
@@ -9,3 +10,7 @@ end
 describe "SizedQueue#<<" do
   it_behaves_like :sizedqueue_enq, :<<, -> n { SizedQueue.new(n) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(1); q.send(:<<, 1, timeout: v) }
+end
diff --git a/spec/ruby/core/sizedqueue/deq_spec.rb b/spec/ruby/core/sizedqueue/deq_spec.rb
index 5e1bd9f746..2aeb52f8a6 100644
--- a/spec/ruby/core/sizedqueue/deq_spec.rb
+++ b/spec/ruby/core/sizedqueue/deq_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#deq" do
   it_behaves_like :queue_deq, :deq, -> { SizedQueue.new(10) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(10); q.push(1); q.deq(timeout: v) }
+end
diff --git a/spec/ruby/core/sizedqueue/enq_spec.rb b/spec/ruby/core/sizedqueue/enq_spec.rb
index 3821afac95..b955909475 100644
--- a/spec/ruby/core/sizedqueue/enq_spec.rb
+++ b/spec/ruby/core/sizedqueue/enq_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/enque'
 require_relative '../../shared/sizedqueue/enque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#enq" do
   it_behaves_like :queue_enq, :enq, -> { SizedQueue.new(10) }
@@ -9,3 +10,7 @@ end
 describe "SizedQueue#enq" do
   it_behaves_like :sizedqueue_enq, :enq, -> n { SizedQueue.new(n) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(1); q.enq(1, timeout: v) }
+end
diff --git a/spec/ruby/core/sizedqueue/freeze_spec.rb b/spec/ruby/core/sizedqueue/freeze_spec.rb
new file mode 100644
index 0000000000..98f01cae2f
--- /dev/null
+++ b/spec/ruby/core/sizedqueue/freeze_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/queue/freeze'
+
+describe "SizedQueue#freeze" do
+  it_behaves_like :queue_freeze, :freeze, -> { SizedQueue.new(1) }
+end
diff --git a/spec/ruby/core/sizedqueue/pop_spec.rb b/spec/ruby/core/sizedqueue/pop_spec.rb
index a0cf6f509c..6338ddbaa0 100644
--- a/spec/ruby/core/sizedqueue/pop_spec.rb
+++ b/spec/ruby/core/sizedqueue/pop_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#pop" do
   it_behaves_like :queue_deq, :pop, -> { SizedQueue.new(10) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(10); q.push(1); q.pop(timeout: v) }
+end
diff --git a/spec/ruby/core/sizedqueue/push_spec.rb b/spec/ruby/core/sizedqueue/push_spec.rb
index bba9be9e3f..9eaa6beca0 100644
--- a/spec/ruby/core/sizedqueue/push_spec.rb
+++ b/spec/ruby/core/sizedqueue/push_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/enque'
 require_relative '../../shared/sizedqueue/enque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#push" do
   it_behaves_like :queue_enq, :push, -> { SizedQueue.new(10) }
@@ -9,3 +10,7 @@ end
 describe "SizedQueue#push" do
   it_behaves_like :sizedqueue_enq, :push, -> n { SizedQueue.new(n) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(1); q.push(1, timeout: v) }
+end
diff --git a/spec/ruby/core/sizedqueue/shift_spec.rb b/spec/ruby/core/sizedqueue/shift_spec.rb
index 5138e68258..52974c1d99 100644
--- a/spec/ruby/core/sizedqueue/shift_spec.rb
+++ b/spec/ruby/core/sizedqueue/shift_spec.rb
@@ -1,6 +1,11 @@
 require_relative '../../spec_helper'
 require_relative '../../shared/queue/deque'
+require_relative '../../shared/types/rb_num2dbl_fails'
 
 describe "SizedQueue#shift" do
   it_behaves_like :queue_deq, :shift, -> { SizedQueue.new(10) }
 end
+
+describe "SizedQueue operations with timeout" do
+  it_behaves_like :rb_num2dbl_fails, nil, -> v { q = SizedQueue.new(10); q.push(1); q.shift(timeout: v) }
+end
diff --git a/spec/ruby/core/string/allocate_spec.rb b/spec/ruby/core/string/allocate_spec.rb
index 5b36b4fd05..30d5f60594 100644
--- a/spec/ruby/core/string/allocate_spec.rb
+++ b/spec/ruby/core/string/allocate_spec.rb
@@ -14,6 +14,6 @@ describe "String.allocate" do
   end
 
   it "returns a binary String" do
-    String.new.encoding.should == Encoding::BINARY
+    String.allocate.encoding.should == Encoding::BINARY
   end
 end
diff --git a/spec/ruby/core/string/append_as_bytes_spec.rb b/spec/ruby/core/string/append_as_bytes_spec.rb
new file mode 100644
index 0000000000..b1703e5f89
--- /dev/null
+++ b/spec/ruby/core/string/append_as_bytes_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../spec_helper'
+
+describe "String#append_bytes" do
+  ruby_version_is "3.4" do
+    it "doesn't allow to mutate frozen strings" do
+      str = "hello".freeze
+      -> { str.append_as_bytes("\xE2\x82") }.should raise_error(FrozenError)
+    end
+
+    it "allows creating broken strings" do
+      str = +"hello"
+      str.append_as_bytes("\xE2\x82")
+      str.valid_encoding?.should == false
+
+      str.append_as_bytes("\xAC")
+      str.valid_encoding?.should == true
+
+      str = "abc".encode(Encoding::UTF_32LE)
+      str.append_as_bytes("def")
+      str.encoding.should == Encoding::UTF_32LE
+      str.valid_encoding?.should == false
+    end
+
+    it "never changes the receiver encoding" do
+      str = "".b
+      str.append_as_bytes("€")
+      str.encoding.should == Encoding::BINARY
+    end
+
+    it "accepts variadic String or Integer arguments" do
+      str = "hello".b
+      str.append_as_bytes("\xE2\x82", 12, 43, "\xAC")
+      str.encoding.should == Encoding::BINARY
+      str.should == "hello\xE2\x82\f+\xAC".b
+    end
+
+    it "truncates integers to the least significant byte" do
+      str = +""
+      str.append_as_bytes(0x131, 0x232, 0x333, bignum_value, bignum_value(1))
+      str.bytes.should == [0x31, 0x32, 0x33, 0, 1]
+    end
+
+    it "wraps negative integers" do
+      str = "".b
+      str.append_as_bytes(-1, -bignum_value, -bignum_value(1))
+      str.bytes.should == [0xFF, 0, 0xFF]
+    end
+
+    it "only accepts strings or integers, and doesn't attempt to cast with #to_str or #to_int" do
+      to_str = mock("to_str")
+      to_str.should_not_receive(:to_str)
+      to_str.should_not_receive(:to_int)
+
+      str = +"hello"
+      -> { str.append_as_bytes(to_str) }.should raise_error(TypeError, "wrong argument type MockObject (expected String or Integer)")
+    end
+  end
+end
diff --git a/spec/ruby/core/string/append_spec.rb b/spec/ruby/core/string/append_spec.rb
index 1e1667f617..8497ce8262 100644
--- a/spec/ruby/core/string/append_spec.rb
+++ b/spec/ruby/core/string/append_spec.rb
@@ -5,4 +5,10 @@ require_relative 'shared/concat'
 describe "String#<<" do
   it_behaves_like :string_concat, :<<
   it_behaves_like :string_concat_encoding, :<<
+  it_behaves_like :string_concat_type_coercion, :<<
+
+  it "raises an ArgumentError when given the incorrect number of arguments" do
+    -> { "hello".send(:<<) }.should raise_error(ArgumentError)
+    -> { "hello".send(:<<, "one", "two") }.should raise_error(ArgumentError)
+  end
 end
diff --git a/spec/ruby/core/string/ascii_only_spec.rb b/spec/ruby/core/string/ascii_only_spec.rb
index c7e02fd874..88a0559cfd 100644
--- a/spec/ruby/core/string/ascii_only_spec.rb
+++ b/spec/ruby/core/string/ascii_only_spec.rb
@@ -7,12 +7,12 @@ describe "String#ascii_only?" do
     it "returns true if the encoding is UTF-8" do
       [ ["hello",                         true],
         ["hello".encode('UTF-8'),         true],
-        ["hello".force_encoding('UTF-8'), true],
+        ["hello".dup.force_encoding('UTF-8'), true],
       ].should be_computed_by(:ascii_only?)
     end
 
     it "returns true if the encoding is US-ASCII" do
-      "hello".force_encoding(Encoding::US_ASCII).ascii_only?.should be_true
+      "hello".dup.force_encoding(Encoding::US_ASCII).ascii_only?.should be_true
       "hello".encode(Encoding::US_ASCII).ascii_only?.should be_true
     end
 
@@ -34,13 +34,13 @@ describe "String#ascii_only?" do
       [ ["\u{6666}",                          false],
         ["hello, \u{6666}",                   false],
         ["\u{6666}".encode('UTF-8'),          false],
-        ["\u{6666}".force_encoding('UTF-8'),  false],
+        ["\u{6666}".dup.force_encoding('UTF-8'),  false],
       ].should be_computed_by(:ascii_only?)
     end
 
     it "returns false if the encoding is US-ASCII" do
-      [ ["\u{6666}".force_encoding(Encoding::US_ASCII),         false],
-        ["hello, \u{6666}".force_encoding(Encoding::US_ASCII),  false],
+      [ ["\u{6666}".dup.force_encoding(Encoding::US_ASCII),         false],
+        ["hello, \u{6666}".dup.force_encoding(Encoding::US_ASCII),  false],
       ].should be_computed_by(:ascii_only?)
     end
   end
@@ -51,17 +51,16 @@ describe "String#ascii_only?" do
   end
 
   it "returns false for the empty String with a non-ASCII-compatible encoding" do
-    "".force_encoding('UTF-16LE').ascii_only?.should be_false
+    "".dup.force_encoding('UTF-16LE').ascii_only?.should be_false
     "".encode('UTF-16BE').ascii_only?.should be_false
   end
 
   it "returns false for a non-empty String with non-ASCII-compatible encoding" do
-    "\x78\x00".force_encoding("UTF-16LE").ascii_only?.should be_false
+    "\x78\x00".dup.force_encoding("UTF-16LE").ascii_only?.should be_false
   end
 
   it "returns false when interpolating non ascii strings" do
-    base = "EU currency is"
-    base.force_encoding(Encoding::US_ASCII)
+    base = "EU currency is".dup.force_encoding(Encoding::US_ASCII)
     euro = "\u20AC"
     interp = "#{base} #{euro}"
     euro.ascii_only?.should be_false
@@ -70,14 +69,14 @@ describe "String#ascii_only?" do
   end
 
   it "returns false after appending non ASCII characters to an empty String" do
-    ("" << "λ").ascii_only?.should be_false
+    ("".dup << "λ").ascii_only?.should be_false
   end
 
   it "returns false when concatenating an ASCII and non-ASCII String" do
-    "".concat("λ").ascii_only?.should be_false
+    "".dup.concat("λ").ascii_only?.should be_false
   end
 
   it "returns false when replacing an ASCII String with a non-ASCII String" do
-    "".replace("λ").ascii_only?.should be_false
+    "".dup.replace("λ").ascii_only?.should be_false
   end
 end
diff --git a/spec/ruby/core/string/b_spec.rb b/spec/ruby/core/string/b_spec.rb
index b43cb5393a..4b1fafff11 100644
--- a/spec/ruby/core/string/b_spec.rb
+++ b/spec/ruby/core/string/b_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#b" do
@@ -12,11 +13,4 @@ describe "String#b" do
     str.b.should_not equal(str)
     str.should == "こんちには"
   end
-
-  it "copies own tainted/untrusted status to the returning value" do
-    utf_8 = "こんちには".taint.untrust
-    ret = utf_8.b
-    ret.tainted?.should be_true
-    ret.untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/string/byteindex_spec.rb b/spec/ruby/core/string/byteindex_spec.rb
new file mode 100644
index 0000000000..d420f3f683
--- /dev/null
+++ b/spec/ruby/core/string/byteindex_spec.rb
@@ -0,0 +1,298 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/byte_index_common.rb'
+
+describe "String#byteindex" do
+  it "calls #to_str to convert the first argument" do
+    char = mock("string index char")
+    char.should_receive(:to_str).and_return("b")
+    "abc".byteindex(char).should == 1
+  end
+
+  it "calls #to_int to convert the second argument" do
+    offset = mock("string index offset")
+    offset.should_receive(:to_int).and_return(1)
+    "abc".byteindex("c", offset).should == 2
+  end
+
+  it "does not raise IndexError when byte offset is correct or on string boundary" do
+    "わ".byteindex("").should == 0
+    "わ".byteindex("", 0).should == 0
+    "わ".byteindex("", 3).should == 3
+  end
+
+  it_behaves_like :byte_index_common, :byteindex
+end
+
+describe "String#byteindex with String" do
+  it "behaves the same as String#byteindex(char) for one-character strings" do
+    "blablabla hello cruel world...!".split("").uniq.each do |str|
+      chr = str[0]
+      str.byteindex(str).should == str.byteindex(chr)
+
+      0.upto(str.size + 1) do |start|
+        str.byteindex(str, start).should == str.byteindex(chr, start)
+      end
+
+      (-str.size - 1).upto(-1) do |start|
+        str.byteindex(str, start).should == str.byteindex(chr, start)
+      end
+    end
+  end
+
+  it "returns the byteindex of the first occurrence of the given substring" do
+    "blablabla".byteindex("").should == 0
+    "blablabla".byteindex("b").should == 0
+    "blablabla".byteindex("bla").should == 0
+    "blablabla".byteindex("blabla").should == 0
+    "blablabla".byteindex("blablabla").should == 0
+
+    "blablabla".byteindex("l").should == 1
+    "blablabla".byteindex("la").should == 1
+    "blablabla".byteindex("labla").should == 1
+    "blablabla".byteindex("lablabla").should == 1
+
+    "blablabla".byteindex("a").should == 2
+    "blablabla".byteindex("abla").should == 2
+    "blablabla".byteindex("ablabla").should == 2
+  end
+
+  it "treats the offset as a byteindex" do
+    "aaaaa".byteindex("a", 0).should == 0
+    "aaaaa".byteindex("a", 2).should == 2
+    "aaaaa".byteindex("a", 4).should == 4
+  end
+
+  it "ignores string subclasses" do
+    "blablabla".byteindex(StringSpecs::MyString.new("bla")).should == 0
+    StringSpecs::MyString.new("blablabla").byteindex("bla").should == 0
+    StringSpecs::MyString.new("blablabla").byteindex(StringSpecs::MyString.new("bla")).should == 0
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".byteindex("bl", 0).should == 0
+    "blablabla".byteindex("bl", 1).should == 3
+    "blablabla".byteindex("bl", 2).should == 3
+    "blablabla".byteindex("bl", 3).should == 3
+
+    "blablabla".byteindex("bla", 0).should == 0
+    "blablabla".byteindex("bla", 1).should == 3
+    "blablabla".byteindex("bla", 2).should == 3
+    "blablabla".byteindex("bla", 3).should == 3
+
+    "blablabla".byteindex("blab", 0).should == 0
+    "blablabla".byteindex("blab", 1).should == 3
+    "blablabla".byteindex("blab", 2).should == 3
+    "blablabla".byteindex("blab", 3).should == 3
+
+    "blablabla".byteindex("la", 1).should == 1
+    "blablabla".byteindex("la", 2).should == 4
+    "blablabla".byteindex("la", 3).should == 4
+    "blablabla".byteindex("la", 4).should == 4
+
+    "blablabla".byteindex("lab", 1).should == 1
+    "blablabla".byteindex("lab", 2).should == 4
+    "blablabla".byteindex("lab", 3).should == 4
+    "blablabla".byteindex("lab", 4).should == 4
+
+    "blablabla".byteindex("ab", 2).should == 2
+    "blablabla".byteindex("ab", 3).should == 5
+    "blablabla".byteindex("ab", 4).should == 5
+    "blablabla".byteindex("ab", 5).should == 5
+
+    "blablabla".byteindex("", 0).should == 0
+    "blablabla".byteindex("", 1).should == 1
+    "blablabla".byteindex("", 2).should == 2
+    "blablabla".byteindex("", 7).should == 7
+    "blablabla".byteindex("", 8).should == 8
+    "blablabla".byteindex("", 9).should == 9
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.byteindex(needle, offset).should ==
+        str.byteindex(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".byteindex("B").should == nil
+    "blablabla".byteindex("z").should == nil
+    "blablabla".byteindex("BLA").should == nil
+    "blablabla".byteindex("blablablabla").should == nil
+    "blablabla".byteindex("", 10).should == nil
+
+    "hello".byteindex("he", 1).should == nil
+    "hello".byteindex("he", 2).should == nil
+    "I’ve got a multibyte character.\n".byteindex("\n\n").should == nil
+  end
+
+  it "returns the character byteindex of a multibyte character" do
+    "ありがとう".byteindex("が").should == 6
+  end
+
+  it "returns the character byteindex after offset" do
+    "われわれ".byteindex("わ", 3).should == 6
+    "ありがとうありがとう".byteindex("が", 9).should == 21
+  end
+
+  it "returns the character byteindex after a partial first match" do
+    "</</h".byteindex("</h").should == 2
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    char = "れ".encode Encoding::EUC_JP
+    -> do
+      "あれ".byteindex(char)
+    end.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.dup.force_encoding(Encoding::US_ASCII).byteindex('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.byteindex('t'.dup.force_encoding(Encoding::US_ASCII)).should == 2
+  end
+end
+
+describe "String#byteindex with Regexp" do
+  it "behaves the same as String#byteindex(string) for escaped string regexps" do
+    ["blablabla", "hello cruel world...!"].each do |str|
+      ["", "b", "bla", "lab", "o c", "d."].each do |needle|
+        regexp = Regexp.new(Regexp.escape(needle))
+        str.byteindex(regexp).should == str.byteindex(needle)
+
+        0.upto(str.size + 1) do |start|
+          str.byteindex(regexp, start).should == str.byteindex(needle, start)
+        end
+
+        (-str.size - 1).upto(-1) do |start|
+          str.byteindex(regexp, start).should == str.byteindex(needle, start)
+        end
+      end
+    end
+  end
+
+  it "returns the byteindex of the first match of regexp" do
+    "blablabla".byteindex(/bla/).should == 0
+    "blablabla".byteindex(/BLA/i).should == 0
+
+    "blablabla".byteindex(/.{0}/).should == 0
+    "blablabla".byteindex(/.{6}/).should == 0
+    "blablabla".byteindex(/.{9}/).should == 0
+
+    "blablabla".byteindex(/.*/).should == 0
+    "blablabla".byteindex(/.+/).should == 0
+
+    "blablabla".byteindex(/lab|b/).should == 0
+
+    not_supported_on :opal do
+      "blablabla".byteindex(/\A/).should == 0
+      "blablabla".byteindex(/\Z/).should == 9
+      "blablabla".byteindex(/\z/).should == 9
+      "blablabla\n".byteindex(/\Z/).should == 9
+      "blablabla\n".byteindex(/\z/).should == 10
+    end
+
+    "blablabla".byteindex(/^/).should == 0
+    "\nblablabla".byteindex(/^/).should == 0
+    "b\nablabla".byteindex(/$/).should == 1
+    "bl\nablabla".byteindex(/$/).should == 2
+
+    "blablabla".byteindex(/.l./).should == 0
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".byteindex(/.{0}/, 5).should == 5
+    "blablabla".byteindex(/.{1}/, 5).should == 5
+    "blablabla".byteindex(/.{2}/, 5).should == 5
+    "blablabla".byteindex(/.{3}/, 5).should == 5
+    "blablabla".byteindex(/.{4}/, 5).should == 5
+
+    "blablabla".byteindex(/.{0}/, 3).should == 3
+    "blablabla".byteindex(/.{1}/, 3).should == 3
+    "blablabla".byteindex(/.{2}/, 3).should == 3
+    "blablabla".byteindex(/.{5}/, 3).should == 3
+    "blablabla".byteindex(/.{6}/, 3).should == 3
+
+    "blablabla".byteindex(/.l./, 0).should == 0
+    "blablabla".byteindex(/.l./, 1).should == 3
+    "blablabla".byteindex(/.l./, 2).should == 3
+    "blablabla".byteindex(/.l./, 3).should == 3
+
+    "xblaxbla".byteindex(/x./, 0).should == 0
+    "xblaxbla".byteindex(/x./, 1).should == 4
+    "xblaxbla".byteindex(/x./, 2).should == 4
+
+    not_supported_on :opal do
+      "blablabla\n".byteindex(/\Z/, 9).should == 9
+    end
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.byteindex(needle, offset).should ==
+        str.byteindex(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".byteindex(/BLA/).should == nil
+
+    "blablabla".byteindex(/.{10}/).should == nil
+    "blaxbla".byteindex(/.x/, 3).should == nil
+    "blaxbla".byteindex(/..x/, 2).should == nil
+  end
+
+  it "returns nil if the Regexp matches the empty string and the offset is out of range" do
+    "ruby".byteindex(//, 12).should be_nil
+  end
+
+  it "supports \\G which matches at the given start offset" do
+    "helloYOU.".byteindex(/\GYOU/, 5).should == 5
+    "helloYOU.".byteindex(/\GYOU/).should == nil
+
+    re = /\G.+YOU/
+    # The # marks where \G will match.
+    [
+      ["#hi!YOUall.", 0],
+      ["h#i!YOUall.", 1],
+      ["hi#!YOUall.", 2],
+      ["hi!#YOUall.", nil]
+    ].each do |spec|
+
+      start = spec[0].byteindex("#")
+      str = spec[0].delete("#")
+
+      str.byteindex(re, start).should == spec[1]
+    end
+  end
+
+  it "converts start_offset to an integer via to_int" do
+    obj = mock('1')
+    obj.should_receive(:to_int).and_return(1)
+    "RWOARW".byteindex(/R./, obj).should == 4
+  end
+
+  it "returns the character byteindex of a multibyte character" do
+    "ありがとう".byteindex(/が/).should == 6
+  end
+
+  it "returns the character byteindex after offset" do
+    "われわれ".byteindex(/わ/, 3).should == 6
+  end
+
+  it "treats the offset as a byteindex" do
+    "われわわれ".byteindex(/わ/, 6).should == 6
+  end
+end
diff --git a/spec/ruby/core/string/byterindex_spec.rb b/spec/ruby/core/string/byterindex_spec.rb
new file mode 100644
index 0000000000..983222e35d
--- /dev/null
+++ b/spec/ruby/core/string/byterindex_spec.rb
@@ -0,0 +1,353 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/byte_index_common.rb'
+
+describe "String#byterindex with object" do
+  it "tries to convert obj to a string via to_str" do
+    obj = mock('lo')
+    def obj.to_str() "lo" end
+    "hello".byterindex(obj).should == "hello".byterindex("lo")
+
+    obj = mock('o')
+    def obj.respond_to?(arg, *) true end
+    def obj.method_missing(*args) "o" end
+    "hello".byterindex(obj).should == "hello".byterindex("o")
+  end
+
+  it "calls #to_int to convert the second argument" do
+    offset = mock("string index offset")
+    offset.should_receive(:to_int).and_return(3)
+    "abc".byterindex("c", offset).should == 2
+  end
+
+  it "does not raise IndexError when byte offset is correct or on string boundary" do
+    "わ".byterindex("", 0).should == 0
+    "わ".byterindex("", 3).should == 3
+    "わ".byterindex("").should == 3
+  end
+
+  it_behaves_like :byte_index_common, :byterindex
+end
+
+describe "String#byterindex with String" do
+  it "behaves the same as String#byterindex(char) for one-character strings" do
+    "blablabla hello cruel world...!".split("").uniq.each do |str|
+      chr = str[0]
+      str.byterindex(str).should == str.byterindex(chr)
+
+      0.upto(str.size + 1) do |start|
+        str.byterindex(str, start).should == str.byterindex(chr, start)
+      end
+
+      (-str.size - 1).upto(-1) do |start|
+        str.byterindex(str, start).should == str.byterindex(chr, start)
+      end
+    end
+  end
+
+  it "behaves the same as String#byterindex(?char) for one-character strings" do
+    "blablabla hello cruel world...!".split("").uniq.each do |str|
+      chr = str[0] =~ / / ? str[0] : eval("?#{str[0]}")
+      str.byterindex(str).should == str.byterindex(chr)
+
+      0.upto(str.size + 1) do |start|
+        str.byterindex(str, start).should == str.byterindex(chr, start)
+      end
+
+      (-str.size - 1).upto(-1) do |start|
+        str.byterindex(str, start).should == str.byterindex(chr, start)
+      end
+    end
+  end
+
+  it "returns the index of the last occurrence of the given substring" do
+    "blablabla".byterindex("").should == 9
+    "blablabla".byterindex("a").should == 8
+    "blablabla".byterindex("la").should == 7
+    "blablabla".byterindex("bla").should == 6
+    "blablabla".byterindex("abla").should == 5
+    "blablabla".byterindex("labla").should == 4
+    "blablabla".byterindex("blabla").should == 3
+    "blablabla".byterindex("ablabla").should == 2
+    "blablabla".byterindex("lablabla").should == 1
+    "blablabla".byterindex("blablabla").should == 0
+
+    "blablabla".byterindex("l").should == 7
+    "blablabla".byterindex("bl").should == 6
+    "blablabla".byterindex("abl").should == 5
+    "blablabla".byterindex("labl").should == 4
+    "blablabla".byterindex("blabl").should == 3
+    "blablabla".byterindex("ablabl").should == 2
+    "blablabla".byterindex("lablabl").should == 1
+    "blablabla".byterindex("blablabl").should == 0
+
+    "blablabla".byterindex("b").should == 6
+    "blablabla".byterindex("ab").should == 5
+    "blablabla".byterindex("lab").should == 4
+    "blablabla".byterindex("blab").should == 3
+    "blablabla".byterindex("ablab").should == 2
+    "blablabla".byterindex("lablab").should == 1
+    "blablabla".byterindex("blablab").should == 0
+  end
+
+  it "ignores string subclasses" do
+    "blablabla".byterindex(StringSpecs::MyString.new("bla")).should == 6
+    StringSpecs::MyString.new("blablabla").byterindex("bla").should == 6
+    StringSpecs::MyString.new("blablabla").byterindex(StringSpecs::MyString.new("bla")).should == 6
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".byterindex("bl", 0).should == 0
+    "blablabla".byterindex("bl", 1).should == 0
+    "blablabla".byterindex("bl", 2).should == 0
+    "blablabla".byterindex("bl", 3).should == 3
+
+    "blablabla".byterindex("bla", 0).should == 0
+    "blablabla".byterindex("bla", 1).should == 0
+    "blablabla".byterindex("bla", 2).should == 0
+    "blablabla".byterindex("bla", 3).should == 3
+
+    "blablabla".byterindex("blab", 0).should == 0
+    "blablabla".byterindex("blab", 1).should == 0
+    "blablabla".byterindex("blab", 2).should == 0
+    "blablabla".byterindex("blab", 3).should == 3
+    "blablabla".byterindex("blab", 6).should == 3
+    "blablablax".byterindex("blab", 6).should == 3
+
+    "blablabla".byterindex("la", 1).should == 1
+    "blablabla".byterindex("la", 2).should == 1
+    "blablabla".byterindex("la", 3).should == 1
+    "blablabla".byterindex("la", 4).should == 4
+
+    "blablabla".byterindex("lab", 1).should == 1
+    "blablabla".byterindex("lab", 2).should == 1
+    "blablabla".byterindex("lab", 3).should == 1
+    "blablabla".byterindex("lab", 4).should == 4
+
+    "blablabla".byterindex("ab", 2).should == 2
+    "blablabla".byterindex("ab", 3).should == 2
+    "blablabla".byterindex("ab", 4).should == 2
+    "blablabla".byterindex("ab", 5).should == 5
+
+    "blablabla".byterindex("", 0).should == 0
+    "blablabla".byterindex("", 1).should == 1
+    "blablabla".byterindex("", 2).should == 2
+    "blablabla".byterindex("", 7).should == 7
+    "blablabla".byterindex("", 8).should == 8
+    "blablabla".byterindex("", 9).should == 9
+    "blablabla".byterindex("", 10).should == 9
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.byterindex(needle, offset).should ==
+        str.byterindex(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".byterindex("B").should == nil
+    "blablabla".byterindex("z").should == nil
+    "blablabla".byterindex("BLA").should == nil
+    "blablabla".byterindex("blablablabla").should == nil
+
+    "hello".byterindex("lo", 0).should == nil
+    "hello".byterindex("lo", 1).should == nil
+    "hello".byterindex("lo", 2).should == nil
+
+    "hello".byterindex("llo", 0).should == nil
+    "hello".byterindex("llo", 1).should == nil
+
+    "hello".byterindex("el", 0).should == nil
+    "hello".byterindex("ello", 0).should == nil
+
+    "hello".byterindex("", -6).should == nil
+    "hello".byterindex("", -7).should == nil
+
+    "hello".byterindex("h", -6).should == nil
+  end
+
+  it "tries to convert start_offset to an integer via to_int" do
+    obj = mock('5')
+    def obj.to_int() 5 end
+    "str".byterindex("st", obj).should == 0
+
+    obj = mock('5')
+    def obj.respond_to?(arg, *) true end
+    def obj.method_missing(*args) 5 end
+    "str".byterindex("st", obj).should == 0
+  end
+
+  it "raises a TypeError when given offset is nil" do
+    -> { "str".byterindex("st", nil) }.should raise_error(TypeError)
+  end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.dup.force_encoding(Encoding::US_ASCII).byterindex('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.byterindex('t'.dup.force_encoding(Encoding::US_ASCII)).should == 2
+  end
+end
+
+describe "String#byterindex with Regexp" do
+  it "behaves the same as String#byterindex(string) for escaped string regexps" do
+    ["blablabla", "hello cruel world...!"].each do |str|
+      ["", "b", "bla", "lab", "o c", "d."].each do |needle|
+        regexp = Regexp.new(Regexp.escape(needle))
+        str.byterindex(regexp).should == str.byterindex(needle)
+
+        0.upto(str.size + 1) do |start|
+          str.byterindex(regexp, start).should == str.byterindex(needle, start)
+        end
+
+        (-str.size - 1).upto(-1) do |start|
+          str.byterindex(regexp, start).should == str.byterindex(needle, start)
+        end
+      end
+    end
+  end
+
+  it "returns the index of the first match from the end of string of regexp" do
+    "blablabla".byterindex(/bla/).should == 6
+    "blablabla".byterindex(/BLA/i).should == 6
+
+    "blablabla".byterindex(/.{0}/).should == 9
+    "blablabla".byterindex(/.{1}/).should == 8
+    "blablabla".byterindex(/.{2}/).should == 7
+    "blablabla".byterindex(/.{6}/).should == 3
+    "blablabla".byterindex(/.{9}/).should == 0
+
+    "blablabla".byterindex(/.*/).should == 9
+    "blablabla".byterindex(/.+/).should == 8
+
+    "blablabla".byterindex(/bla|a/).should == 8
+
+    not_supported_on :opal do
+      "blablabla".byterindex(/\A/).should == 0
+      "blablabla".byterindex(/\Z/).should == 9
+      "blablabla".byterindex(/\z/).should == 9
+      "blablabla\n".byterindex(/\Z/).should == 10
+      "blablabla\n".byterindex(/\z/).should == 10
+    end
+
+    "blablabla".byterindex(/^/).should == 0
+    not_supported_on :opal do
+      "\nblablabla".byterindex(/^/).should == 1
+      "b\nlablabla".byterindex(/^/).should == 2
+    end
+    "blablabla".byterindex(/$/).should == 9
+
+    "blablabla".byterindex(/.l./).should == 6
+  end
+
+  it "starts the search at the given offset" do
+    "blablabla".byterindex(/.{0}/, 5).should == 5
+    "blablabla".byterindex(/.{1}/, 5).should == 5
+    "blablabla".byterindex(/.{2}/, 5).should == 5
+    "blablabla".byterindex(/.{3}/, 5).should == 5
+    "blablabla".byterindex(/.{4}/, 5).should == 5
+
+    "blablabla".byterindex(/.{0}/, 3).should == 3
+    "blablabla".byterindex(/.{1}/, 3).should == 3
+    "blablabla".byterindex(/.{2}/, 3).should == 3
+    "blablabla".byterindex(/.{5}/, 3).should == 3
+    "blablabla".byterindex(/.{6}/, 3).should == 3
+
+    "blablabla".byterindex(/.l./, 0).should == 0
+    "blablabla".byterindex(/.l./, 1).should == 0
+    "blablabla".byterindex(/.l./, 2).should == 0
+    "blablabla".byterindex(/.l./, 3).should == 3
+
+    "blablablax".byterindex(/.x/, 10).should == 8
+    "blablablax".byterindex(/.x/, 9).should == 8
+    "blablablax".byterindex(/.x/, 8).should == 8
+
+    "blablablax".byterindex(/..x/, 10).should == 7
+    "blablablax".byterindex(/..x/, 9).should == 7
+    "blablablax".byterindex(/..x/, 8).should == 7
+    "blablablax".byterindex(/..x/, 7).should == 7
+
+    not_supported_on :opal do
+      "blablabla\n".byterindex(/\Z/, 9).should == 9
+    end
+  end
+
+  it "starts the search at offset + self.length if offset is negative" do
+    str = "blablabla"
+
+    ["bl", "bla", "blab", "la", "lab", "ab", ""].each do |needle|
+      (-str.length .. -1).each do |offset|
+        str.byterindex(needle, offset).should ==
+        str.byterindex(needle, offset + str.length)
+      end
+    end
+  end
+
+  it "returns nil if the substring isn't found" do
+    "blablabla".byterindex(/BLA/).should == nil
+    "blablabla".byterindex(/.{10}/).should == nil
+    "blablablax".byterindex(/.x/, 7).should == nil
+    "blablablax".byterindex(/..x/, 6).should == nil
+
+    not_supported_on :opal do
+      "blablabla".byterindex(/\Z/, 5).should == nil
+      "blablabla".byterindex(/\z/, 5).should == nil
+      "blablabla\n".byterindex(/\z/, 9).should == nil
+    end
+  end
+
+  not_supported_on :opal do
+    it "supports \\G which matches at the given start offset" do
+      "helloYOU.".byterindex(/YOU\G/, 8).should == 5
+      "helloYOU.".byterindex(/YOU\G/).should == nil
+
+      idx = "helloYOUall!".index("YOU")
+      re = /YOU.+\G.+/
+      # The # marks where \G will match.
+      [
+        ["helloYOU#all.", nil],
+        ["helloYOUa#ll.", idx],
+        ["helloYOUal#l.", idx],
+        ["helloYOUall#.", idx],
+        ["helloYOUall.#", nil]
+      ].each do |i|
+        start = i[0].index("#")
+        str = i[0].delete("#")
+
+        str.byterindex(re, start).should == i[1]
+      end
+    end
+  end
+
+  it "tries to convert start_offset to an integer" do
+    obj = mock('5')
+    def obj.to_int() 5 end
+    "str".byterindex(/../, obj).should == 1
+
+    obj = mock('5')
+    def obj.respond_to?(arg, *) true end
+    def obj.method_missing(*args); 5; end
+    "str".byterindex(/../, obj).should == 1
+  end
+
+  it "raises a TypeError when given offset is nil" do
+    -> { "str".byterindex(/../, nil) }.should raise_error(TypeError)
+  end
+
+  it "returns the reverse byte index of a multibyte character" do
+    "ありがりがとう".byterindex("が").should == 12
+    "ありがりがとう".byterindex(/が/).should == 12
+  end
+
+  it "returns the character index before the finish" do
+    "ありがりがとう".byterindex("が", 9).should == 6
+    "ありがりがとう".byterindex(/が/, 9).should == 6
+  end
+end
diff --git a/spec/ruby/core/string/bytes_spec.rb b/spec/ruby/core/string/bytes_spec.rb
index 96f1ae9cf2..02151eebbc 100644
--- a/spec/ruby/core/string/bytes_spec.rb
+++ b/spec/ruby/core/string/bytes_spec.rb
@@ -22,9 +22,9 @@ describe "String#bytes" do
     @utf8_ascii.bytes.to_a.size.should == @utf8_ascii.bytesize
   end
 
-  it "returns bytes as Fixnums" do
-    @ascii.bytes.to_a.each {|b| b.should be_an_instance_of(Fixnum)}
-    @utf8_ascii.bytes { |b| b.should be_an_instance_of(Fixnum) }
+  it "returns bytes as Integers" do
+    @ascii.bytes.to_a.each {|b| b.should be_an_instance_of(Integer)}
+    @utf8_ascii.bytes { |b| b.should be_an_instance_of(Integer) }
   end
 
   it "agrees with #unpack('C*')" do
@@ -50,6 +50,6 @@ describe "String#bytes" do
   end
 
   it "is unaffected by #force_encoding" do
-    @utf8.force_encoding('ASCII').bytes.to_a.should == @utf8.bytes.to_a
+    @utf8.dup.force_encoding('ASCII').bytes.to_a.should == @utf8.bytes.to_a
   end
 end
diff --git a/spec/ruby/core/string/bytesize_spec.rb b/spec/ruby/core/string/bytesize_spec.rb
index b8b07cfbec..2bbefc0820 100644
--- a/spec/ruby/core/string/bytesize_spec.rb
+++ b/spec/ruby/core/string/bytesize_spec.rb
@@ -2,7 +2,7 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-describe "#String#bytesize" do
+describe "String#bytesize" do
   it "returns the length of self in bytes" do
     "hello".bytesize.should == 5
     " ".bytesize.should == 1
@@ -13,21 +13,21 @@ describe "#String#bytesize" do
   end
 
   it "works with pseudo-ASCII strings containing single UTF-8 characters" do
-    "\u{6666}".force_encoding('ASCII').bytesize.should == 3
+    "\u{6666}".dup.force_encoding('ASCII').bytesize.should == 3
   end
 
   it "works with strings containing UTF-8 characters" do
-    "c \u{6666}".force_encoding('UTF-8').bytesize.should == 5
+    "c \u{6666}".dup.force_encoding('UTF-8').bytesize.should == 5
     "c \u{6666}".bytesize.should == 5
   end
 
   it "works with pseudo-ASCII strings containing UTF-8 characters" do
-    "c \u{6666}".force_encoding('ASCII').bytesize.should == 5
+    "c \u{6666}".dup.force_encoding('ASCII').bytesize.should == 5
   end
 
   it "returns 0 for the empty string" do
     "".bytesize.should == 0
-    "".force_encoding('ASCII').bytesize.should == 0
-    "".force_encoding('UTF-8').bytesize.should == 0
+    "".dup.force_encoding('ASCII').bytesize.should == 0
+    "".dup.force_encoding('UTF-8').bytesize.should == 0
   end
 end
diff --git a/spec/ruby/core/string/byteslice_spec.rb b/spec/ruby/core/string/byteslice_spec.rb
index a49da040eb..4ad9e8d8f1 100644
--- a/spec/ruby/core/string/byteslice_spec.rb
+++ b/spec/ruby/core/string/byteslice_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/slice'
@@ -17,11 +17,17 @@ describe "String#byteslice with Range" do
   it_behaves_like :string_slice_range, :byteslice
 end
 
-describe "String#byteslice on on non ASCII strings" do
+describe "String#byteslice on non ASCII strings" do
   it "returns byteslice of unicode strings" do
-    "\u3042".byteslice(1).should == "\x81".force_encoding("UTF-8")
-    "\u3042".byteslice(1, 2).should == "\x81\x82".force_encoding("UTF-8")
-    "\u3042".byteslice(1..2).should == "\x81\x82".force_encoding("UTF-8")
-    "\u3042".byteslice(-1).should == "\x82".force_encoding("UTF-8")
+    "\u3042".byteslice(1).should == "\x81".dup.force_encoding("UTF-8")
+    "\u3042".byteslice(1, 2).should == "\x81\x82".dup.force_encoding("UTF-8")
+    "\u3042".byteslice(1..2).should == "\x81\x82".dup.force_encoding("UTF-8")
+    "\u3042".byteslice(-1).should == "\x82".dup.force_encoding("UTF-8")
+  end
+
+  it "returns a String in the same encoding as self" do
+    "ruby".encode("UTF-8").slice(0).encoding.should == Encoding::UTF_8
+    "ruby".encode("US-ASCII").slice(0).encoding.should == Encoding::US_ASCII
+    "ruby".encode("Windows-1251").slice(0).encoding.should == Encoding::Windows_1251
   end
 end
diff --git a/spec/ruby/core/string/bytesplice_spec.rb b/spec/ruby/core/string/bytesplice_spec.rb
new file mode 100644
index 0000000000..2c770e340a
--- /dev/null
+++ b/spec/ruby/core/string/bytesplice_spec.rb
@@ -0,0 +1,294 @@
+# -*- encoding: utf-8 -*-
+# frozen_string_literal: false
+require_relative '../../spec_helper'
+
+describe "String#bytesplice" do
+  it "raises IndexError when index is less than -bytesize" do
+    -> { "hello".bytesplice(-6, 0, "xxx") }.should raise_error(IndexError, "index -6 out of string")
+  end
+
+  it "raises IndexError when index is greater than bytesize" do
+    -> { "hello".bytesplice(6, 0, "xxx") }.should raise_error(IndexError, "index 6 out of string")
+  end
+
+  it "raises IndexError for negative length" do
+    -> { "abc".bytesplice(0, -2, "") }.should raise_error(IndexError, "negative length -2")
+  end
+
+  it "replaces with integer indices" do
+    "hello".bytesplice(-5, 0, "xxx").should == "xxxhello"
+    "hello".bytesplice(0, 0, "xxx").should == "xxxhello"
+    "hello".bytesplice(0, 1, "xxx").should == "xxxello"
+    "hello".bytesplice(0, 5, "xxx").should == "xxx"
+    "hello".bytesplice(0, 6, "xxx").should == "xxx"
+  end
+
+  it "raises RangeError when range left boundary is less than -bytesize" do
+    -> { "hello".bytesplice(-6...-6, "xxx") }.should raise_error(RangeError, "-6...-6 out of range")
+  end
+
+  it "replaces with ranges" do
+    "hello".bytesplice(-5...-5, "xxx").should == "xxxhello"
+    "hello".bytesplice(0...0, "xxx").should == "xxxhello"
+    "hello".bytesplice(0..0, "xxx").should == "xxxello"
+    "hello".bytesplice(0...1, "xxx").should == "xxxello"
+    "hello".bytesplice(0..1, "xxx").should == "xxxllo"
+    "hello".bytesplice(0..-1, "xxx").should == "xxx"
+    "hello".bytesplice(0...5, "xxx").should == "xxx"
+    "hello".bytesplice(0...6, "xxx").should == "xxx"
+  end
+
+  it "raises TypeError when integer index is provided without length argument" do
+    -> { "hello".bytesplice(0, "xxx") }.should raise_error(TypeError, "wrong argument type Integer (expected Range)")
+  end
+
+  it "replaces on an empty string" do
+    "".bytesplice(0, 0, "").should == ""
+    "".bytesplice(0, 0, "xxx").should == "xxx"
+  end
+
+  it "mutates self" do
+    s = "hello"
+    s.bytesplice(2, 1, "xxx").should.equal?(s)
+  end
+
+  it "raises when string is frozen" do
+    s = "hello".freeze
+    -> { s.bytesplice(2, 1, "xxx") }.should raise_error(FrozenError, "can't modify frozen String: \"hello\"")
+  end
+
+  ruby_version_is "3.3" do
+    it "raises IndexError when str_index is less than -bytesize" do
+      -> { "hello".bytesplice(2, 1, "HELLO", -6, 0) }.should raise_error(IndexError, "index -6 out of string")
+    end
+
+    it "raises IndexError when str_index is greater than bytesize" do
+      -> { "hello".bytesplice(2, 1, "HELLO", 6, 0) }.should raise_error(IndexError, "index 6 out of string")
+    end
+
+    it "raises IndexError for negative str length" do
+      -> { "abc".bytesplice(0, 1, "", 0, -2) }.should raise_error(IndexError, "negative length -2")
+    end
+
+    it "replaces with integer str indices" do
+      "hello".bytesplice(1, 2, "HELLO", -5, 0).should == "hlo"
+      "hello".bytesplice(1, 2, "HELLO", 0, 0).should == "hlo"
+      "hello".bytesplice(1, 2, "HELLO", 0, 1).should == "hHlo"
+      "hello".bytesplice(1, 2, "HELLO", 0, 5).should == "hHELLOlo"
+      "hello".bytesplice(1, 2, "HELLO", 0, 6).should == "hHELLOlo"
+    end
+
+    it "raises RangeError when str range left boundary is less than -bytesize" do
+      -> { "hello".bytesplice(0..1, "HELLO", -6...-6) }.should raise_error(RangeError, "-6...-6 out of range")
+    end
+
+    it "replaces with str ranges" do
+      "hello".bytesplice(1..2, "HELLO", -5...-5).should == "hlo"
+      "hello".bytesplice(1..2, "HELLO", 0...0).should == "hlo"
+      "hello".bytesplice(1..2, "HELLO", 0..0).should == "hHlo"
+      "hello".bytesplice(1..2, "HELLO", 0...1).should == "hHlo"
+      "hello".bytesplice(1..2, "HELLO", 0..1).should == "hHElo"
+      "hello".bytesplice(1..2, "HELLO", 0..-1).should == "hHELLOlo"
+      "hello".bytesplice(1..2, "HELLO", 0...5).should == "hHELLOlo"
+      "hello".bytesplice(1..2, "HELLO", 0...6).should == "hHELLOlo"
+    end
+
+    it "raises ArgumentError when integer str index is provided without str length argument" do
+      -> { "hello".bytesplice(0, 1, "xxx", 0) }.should raise_error(ArgumentError, "wrong number of arguments (given 4, expected 2, 3, or 5)")
+    end
+
+    it "replaces on an empty string with str index/length" do
+      "".bytesplice(0, 0, "", 0, 0).should == ""
+      "".bytesplice(0, 0, "xxx", 0, 1).should == "x"
+    end
+
+    it "mutates self with substring and str index/length" do
+      s = "hello"
+      s.bytesplice(2, 1, "xxx", 1, 2).should.equal?(s)
+      s.should.eql?("hexxlo")
+    end
+
+    it "raises when string is frozen and str index/length" do
+      s = "hello".freeze
+      -> { s.bytesplice(2, 1, "xxx", 0, 1) }.should raise_error(FrozenError, "can't modify frozen String: \"hello\"")
+    end
+
+    it "replaces on an empty string with str range" do
+      "".bytesplice(0..0, "", 0..0).should == ""
+      "".bytesplice(0..0, "xyz", 0..1).should == "xy"
+    end
+
+    it "mutates self with substring and str range" do
+      s = "hello"
+      s.bytesplice(2..2, "xyz", 1..2).should.equal?(s)
+      s.should.eql?("heyzlo")
+    end
+
+    it "raises when string is frozen and str range" do
+      s = "hello".freeze
+      -> { s.bytesplice(2..2, "yzx", 0..1) }.should raise_error(FrozenError, "can't modify frozen String: \"hello\"")
+    end
+  end
+end
+
+describe "String#bytesplice with multibyte characters" do
+  it "raises IndexError when index is out of byte size boundary" do
+    -> { "こんにちは".bytesplice(-16, 0, "xxx") }.should raise_error(IndexError, "index -16 out of string")
+  end
+
+  it "raises IndexError when index is not on a codepoint boundary" do
+    -> { "こんにちは".bytesplice(1, 0, "xxx") }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+  end
+
+  it "raises IndexError when length is not matching the codepoint boundary" do
+    -> { "こんにちは".bytesplice(0, 1, "xxx") }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+    -> { "こんにちは".bytesplice(0, 2, "xxx") }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+  end
+
+  it "replaces with integer indices" do
+    "こんにちは".bytesplice(-15, 0, "xxx").should == "xxxこんにちは"
+    "こんにちは".bytesplice(0, 0, "xxx").should == "xxxこんにちは"
+    "こんにちは".bytesplice(0, 3, "xxx").should == "xxxんにちは"
+    "こんにちは".bytesplice(3, 3, "はは").should == "こははにちは"
+    "こんにちは".bytesplice(15, 0, "xxx").should == "こんにちはxxx"
+  end
+
+  it "replaces with range" do
+    "こんにちは".bytesplice(-15...-16, "xxx").should == "xxxこんにちは"
+    "こんにちは".bytesplice(0...0, "xxx").should == "xxxこんにちは"
+    "こんにちは".bytesplice(0..2, "xxx").should == "xxxんにちは"
+    "こんにちは".bytesplice(0...3, "xxx").should == "xxxんにちは"
+    "こんにちは".bytesplice(0..5, "xxx").should == "xxxにちは"
+    "こんにちは".bytesplice(0..-1, "xxx").should == "xxx"
+    "こんにちは".bytesplice(0...15, "xxx").should == "xxx"
+    "こんにちは".bytesplice(0...18, "xxx").should == "xxx"
+  end
+
+  it "treats negative length for range as 0" do
+    "こんにちは".bytesplice(0...-100, "xxx").should == "xxxこんにちは"
+    "こんにちは".bytesplice(3...-100, "xxx").should == "こxxxんにちは"
+    "こんにちは".bytesplice(-15...-100, "xxx").should == "xxxこんにちは"
+  end
+
+  it "raises when ranges not match codepoint boundaries" do
+    -> { "こんにちは".bytesplice(0..0, "x") }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+    -> { "こんにちは".bytesplice(0..1, "x") }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+    # Begin is incorrect
+    -> { "こんにちは".bytesplice(-4..-1, "x") }.should raise_error(IndexError, "offset 11 does not land on character boundary")
+    -> { "こんにちは".bytesplice(-5..-1, "x") }.should raise_error(IndexError, "offset 10 does not land on character boundary")
+    # End is incorrect
+    -> { "こんにちは".bytesplice(-3..-2, "x") }.should raise_error(IndexError, "offset 14 does not land on character boundary")
+    -> { "こんにちは".bytesplice(-3..-3, "x") }.should raise_error(IndexError, "offset 13 does not land on character boundary")
+  end
+
+  it "deals with a different encoded argument" do
+    s = "こんにちは"
+    s.encoding.should == Encoding::UTF_8
+    sub = "xxxxxx"
+    sub.force_encoding(Encoding::US_ASCII)
+
+    result = s.bytesplice(0, 3, sub)
+    result.should == "xxxxxxんにちは"
+    result.encoding.should == Encoding::UTF_8
+
+    s = "xxxxxx"
+    s.force_encoding(Encoding::US_ASCII)
+    sub = "こんにちは"
+    sub.encoding.should == Encoding::UTF_8
+
+    result = s.bytesplice(0, 3, sub)
+    result.should == "こんにちはxxx"
+    result.encoding.should == Encoding::UTF_8
+  end
+
+  ruby_version_is "3.3" do
+    it "raises IndexError when str_index is out of byte size boundary" do
+      -> { "こんにちは".bytesplice(3, 3, "こんにちは", -16, 0) }.should raise_error(IndexError, "index -16 out of string")
+    end
+
+    it "raises IndexError when str_index is not on a codepoint boundary" do
+      -> { "こんにちは".bytesplice(3, 3, "こんにちは", 1, 0) }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+    end
+
+    it "raises IndexError when str_length is not matching the codepoint boundary" do
+      -> { "こんにちは".bytesplice(3, 3, "こんにちは", 0, 1) }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+      -> { "こんにちは".bytesplice(3, 3, "こんにちは", 0, 2) }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+    end
+
+    it "replaces with integer str indices" do
+      "こんにちは".bytesplice(3, 3, "こんにちは", -15, 0).should == "こにちは"
+      "こんにちは".bytesplice(3, 3, "こんにちは", 0, 0).should == "こにちは"
+      "こんにちは".bytesplice(3, 3, "こんにちは", 0, 3).should == "ここにちは"
+      "こんにちは".bytesplice(3, 3, "はは", 3, 3).should == "こはにちは"
+      "こんにちは".bytesplice(3, 3, "こんにちは", 15, 0).should == "こにちは"
+    end
+
+    it "replaces with str range" do
+      "こんにちは".bytesplice(0..2, "こんにちは", -15...-16).should == "んにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 0...0).should == "んにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 3..5).should == "んんにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 3...6).should == "んんにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 3..8).should == "んにんにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 0..-1).should == "こんにちはんにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 0...15).should == "こんにちはんにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 0...18).should == "こんにちはんにちは"
+    end
+
+    it "treats negative length for str range as 0" do
+      "こんにちは".bytesplice(0..2, "こんにちは", 0...-100).should == "んにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", 3...-100).should == "んにちは"
+      "こんにちは".bytesplice(0..2, "こんにちは", -15...-100).should == "んにちは"
+    end
+
+    it "raises when ranges not match codepoint boundaries in str" do
+      -> { "こんにちは".bytesplice(3...3, "こ", 0..0) }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+      -> { "こんにちは".bytesplice(3...3, "こ", 0..1) }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+      # Begin is incorrect
+      -> { "こんにちは".bytesplice(3...3, "こんにちは", -4..-1) }.should raise_error(IndexError, "offset 11 does not land on character boundary")
+      -> { "こんにちは".bytesplice(3...3, "こんにちは", -5..-1) }.should raise_error(IndexError, "offset 10 does not land on character boundary")
+      # End is incorrect
+      -> { "こんにちは".bytesplice(3...3, "こんにちは", -3..-2) }.should raise_error(IndexError, "offset 14 does not land on character boundary")
+      -> { "こんにちは".bytesplice(3...3, "こんにちは", -3..-3) }.should raise_error(IndexError, "offset 13 does not land on character boundary")
+    end
+
+    it "deals with a different encoded argument with str index/length" do
+      s = "こんにちは"
+      s.encoding.should == Encoding::UTF_8
+      sub = "goodbye"
+      sub.force_encoding(Encoding::US_ASCII)
+
+      result = s.bytesplice(3, 3, sub, 0, 3)
+      result.should == "こgooにちは"
+      result.encoding.should == Encoding::UTF_8
+
+      s = "hello"
+      s.force_encoding(Encoding::US_ASCII)
+      sub = "こんにちは"
+      sub.encoding.should == Encoding::UTF_8
+
+      result = s.bytesplice(1, 2, sub, 3, 3)
+      result.should == "hんlo"
+      result.encoding.should == Encoding::UTF_8
+    end
+
+    it "deals with a different encoded argument with str range" do
+      s = "こんにちは"
+      s.encoding.should == Encoding::UTF_8
+      sub = "goodbye"
+      sub.force_encoding(Encoding::US_ASCII)
+
+      result = s.bytesplice(3..5, sub, 0..2)
+      result.should == "こgooにちは"
+      result.encoding.should == Encoding::UTF_8
+
+      s = "hello"
+      s.force_encoding(Encoding::US_ASCII)
+      sub = "こんにちは"
+      sub.encoding.should == Encoding::UTF_8
+
+      result = s.bytesplice(1..2, sub, 3..5)
+      result.should == "hんlo"
+      result.encoding.should == Encoding::UTF_8
+    end
+  end
+end
diff --git a/spec/ruby/core/string/capitalize_spec.rb b/spec/ruby/core/string/capitalize_spec.rb
index df64cdaa3b..5e59b656c5 100644
--- a/spec/ruby/core/string/capitalize_spec.rb
+++ b/spec/ruby/core/string/capitalize_spec.rb
@@ -10,11 +10,7 @@ describe "String#capitalize" do
     "hello".capitalize.should == "Hello"
     "HELLO".capitalize.should == "Hello"
     "123ABC".capitalize.should == "123abc"
-  end
-
-  it "taints resulting string when self is tainted" do
-    "".taint.capitalize.tainted?.should == true
-    "hello".taint.capitalize.tainted?.should == true
+    "abcdef"[1...-1].capitalize.should == "Bcde"
   end
 
   describe "full Unicode case mapping" do
@@ -40,6 +36,10 @@ describe "String#capitalize" do
     it "does not capitalize non-ASCII characters" do
       "ßet".capitalize(:ascii).should == "ßet"
     end
+
+    it "handles non-ASCII substrings properly" do
+      "garçon"[1...-1].capitalize(:ascii).should == "Arço"
+    end
   end
 
   describe "full Unicode case mapping adapted for Turkic languages" do
@@ -78,34 +78,50 @@ describe "String#capitalize" do
     -> { "abc".capitalize(:invalid_option) }.should raise_error(ArgumentError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("hello").capitalize.should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("Hello").capitalize.should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("hello").capitalize.should be_an_instance_of(String)
+    StringSpecs::MyString.new("Hello").capitalize.should be_an_instance_of(String)
+  end
+
+  it "returns a String in the same encoding as self" do
+    "h".encode("US-ASCII").capitalize.encoding.should == Encoding::US_ASCII
   end
 end
 
 describe "String#capitalize!" do
   it "capitalizes self in place" do
-    a = "hello"
+    a = +"hello"
     a.capitalize!.should equal(a)
     a.should == "Hello"
   end
 
+  it "modifies self in place for non-ascii-compatible encodings" do
+    a = "heLLo".encode("utf-16le")
+    a.capitalize!
+    a.should == "Hello".encode("utf-16le")
+  end
+
   describe "full Unicode case mapping" do
     it "modifies self in place for all of Unicode with no option" do
-      a = "äöÜ"
+      a = +"äöÜ"
       a.capitalize!
       a.should == "Äöü"
     end
 
     it "only capitalizes the first resulting character when upcasing a character produces a multi-character sequence" do
-      a = "ß"
+      a = +"ß"
       a.capitalize!
       a.should == "Ss"
     end
 
+    it "works for non-ascii-compatible encodings" do
+      a = "äöü".encode("utf-16le")
+      a.capitalize!
+      a.should == "Äöü".encode("utf-16le")
+    end
+
     it "updates string metadata" do
-      capitalized = "ßeT"
+      capitalized = +"ßeT"
       capitalized.capitalize!
 
       capitalized.should == "Sset"
@@ -117,21 +133,27 @@ describe "String#capitalize!" do
 
   describe "modifies self in place for ASCII-only case mapping" do
     it "does not capitalize non-ASCII characters" do
-      a = "ßet"
+      a = +"ßet"
       a.capitalize!(:ascii)
       a.should == "ßet"
     end
+
+    it "works for non-ascii-compatible encodings" do
+      a = "aBc".encode("utf-16le")
+      a.capitalize!(:ascii)
+      a.should == "Abc".encode("utf-16le")
+    end
   end
 
   describe "modifies self in place for full Unicode case mapping adapted for Turkic languages" do
     it "capitalizes ASCII characters according to Turkic semantics" do
-      a = "iSa"
+      a = +"iSa"
       a.capitalize!(:turkic)
       a.should == "İsa"
     end
 
     it "allows Lithuanian as an extra option" do
-      a = "iSa"
+      a = +"iSa"
       a.capitalize!(:turkic, :lithuanian)
       a.should == "İsa"
     end
@@ -143,13 +165,13 @@ describe "String#capitalize!" do
 
   describe "modifies self in place for full Unicode case mapping adapted for Lithuanian" do
     it "currently works the same as full Unicode case mapping" do
-      a = "iß"
+      a = +"iß"
       a.capitalize!(:lithuanian)
       a.should == "Iß"
     end
 
     it "allows Turkic as an extra option (and applies Turkic semantics)" do
-      a = "iß"
+      a = +"iß"
       a.capitalize!(:lithuanian, :turkic)
       a.should == "İß"
     end
@@ -168,18 +190,18 @@ describe "String#capitalize!" do
   end
 
   it "returns nil when no changes are made" do
-    a = "Hello"
+    a = +"Hello"
     a.capitalize!.should == nil
     a.should == "Hello"
 
-    "".capitalize!.should == nil
-    "H".capitalize!.should == nil
+    (+"").capitalize!.should == nil
+    (+"H").capitalize!.should == nil
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     ["", "Hello", "hello"].each do |a|
       a.freeze
-      -> { a.capitalize! }.should raise_error(frozen_error_class)
+      -> { a.capitalize! }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/string/casecmp_spec.rb b/spec/ruby/core/string/casecmp_spec.rb
index 01b22e8f13..81ebea557c 100644
--- a/spec/ruby/core/string/casecmp_spec.rb
+++ b/spec/ruby/core/string/casecmp_spec.rb
@@ -25,16 +25,8 @@ describe "String#casecmp independent of case" do
     "abc".casecmp(other).should == 0
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises a TypeError if other can't be converted to a string" do
-      -> { "abc".casecmp(mock('abc')) }.should raise_error(TypeError)
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns nil if other can't be converted to a string" do
-      "abc".casecmp(mock('abc')).should be_nil
-    end
+  it "returns nil if other can't be converted to a string" do
+    "abc".casecmp(mock('abc')).should be_nil
   end
 
   it "returns nil if incompatible encodings" do
@@ -125,6 +117,11 @@ describe "String#casecmp independent of case" do
       "B".casecmp(a).should == 1
     end
   end
+
+  it "returns 0 for empty strings in different encodings" do
+    ''.b.casecmp('').should == 0
+    ''.b.casecmp(''.encode("UTF-32LE")).should == 0
+  end
 end
 
 describe 'String#casecmp? independent of case' do
@@ -196,15 +193,12 @@ describe 'String#casecmp? independent of case' do
     "ß".casecmp?("ss").should be_true
   end
 
-  ruby_version_is "2.4"..."2.5" do
-    it "raises a TypeError if other can't be converted to a string" do
-      -> { "abc".casecmp?(mock('abc')) }.should raise_error(TypeError)
-    end
+  it "returns nil if other can't be converted to a string" do
+    "abc".casecmp?(mock('abc')).should be_nil
   end
 
-  ruby_version_is "2.5" do
-    it "returns nil if other can't be converted to a string" do
-      "abc".casecmp?(mock('abc')).should be_nil
-    end
+  it "returns true for empty strings in different encodings" do
+    ''.b.should.casecmp?('')
+    ''.b.should.casecmp?(''.encode("UTF-32LE"))
   end
 end
diff --git a/spec/ruby/core/string/center_spec.rb b/spec/ruby/core/string/center_spec.rb
index 27f8b7387f..1667b59327 100644
--- a/spec/ruby/core/string/center_spec.rb
+++ b/spec/ruby/core/string/center_spec.rb
@@ -47,14 +47,6 @@ describe "String#center with length, padding" do
     "radiology".center(8, '-').should == "radiology"
   end
 
-  it "taints result when self or padstr is tainted" do
-    "x".taint.center(4).tainted?.should == true
-    "x".taint.center(0).tainted?.should == true
-    "".taint.center(0).tainted?.should == true
-    "x".taint.center(4, "*").tainted?.should == true
-    "x".center(4, "*".taint).tainted?.should == true
-  end
-
   it "calls #to_int to convert length to an integer" do
     "_".center(3.8, "^").should == "^_^"
 
@@ -89,24 +81,18 @@ describe "String#center with length, padding" do
     -> { "hello".center(0, "")  }.should raise_error(ArgumentError)
   end
 
-  it "returns subclass instances when called on subclasses" do
-    StringSpecs::MyString.new("").center(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").center(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").center(10, StringSpecs::MyString.new("x")).should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on subclasses" do
+    StringSpecs::MyString.new("").center(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").center(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").center(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
 
     "".center(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
     "foo".center(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
   end
 
-  it "when padding is tainted and self is untainted returns a tainted string if and only if length is longer than self" do
-    "hello".center(4, 'X'.taint).tainted?.should be_false
-    "hello".center(5, 'X'.taint).tainted?.should be_false
-    "hello".center(6, 'X'.taint).tainted?.should be_true
-  end
-
   describe "with width" do
     it "returns a String in the same encoding as the original" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.center 6
       result.should == " abc  "
       result.encoding.should equal(Encoding::IBM437)
@@ -115,7 +101,7 @@ describe "String#center with length, padding" do
 
   describe "with width, pattern" do
     it "returns a String in the compatible encoding" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.center 6, "あ"
       result.should == "あabcああ"
       result.encoding.should equal(Encoding::UTF_8)
diff --git a/spec/ruby/core/string/chars_spec.rb b/spec/ruby/core/string/chars_spec.rb
index e4f26bc0cc..ee85430574 100644
--- a/spec/ruby/core/string/chars_spec.rb
+++ b/spec/ruby/core/string/chars_spec.rb
@@ -1,5 +1,5 @@
+require_relative "../../spec_helper"
 require_relative 'shared/chars'
-require_relative 'shared/each_char_without_block'
 
 describe "String#chars" do
   it_behaves_like :string_chars, :chars
@@ -7,4 +7,10 @@ describe "String#chars" do
   it "returns an array when no block given" do
     "hello".chars.should == ['h', 'e', 'l', 'l', 'o']
   end
+
+  it "returns Strings in the same encoding as self" do
+    "hello".encode("US-ASCII").chars.each do |c|
+      c.encoding.should == Encoding::US_ASCII
+    end
+  end
 end
diff --git a/spec/ruby/core/string/chilled_string_spec.rb b/spec/ruby/core/string/chilled_string_spec.rb
new file mode 100644
index 0000000000..73d055cbdf
--- /dev/null
+++ b/spec/ruby/core/string/chilled_string_spec.rb
@@ -0,0 +1,151 @@
+require_relative '../../spec_helper'
+
+describe "chilled String" do
+  guard -> { ruby_version_is "3.4" and !"test".equal?("test") } do
+    describe "chilled string literals" do
+
+      describe "#frozen?" do
+        it "returns false" do
+          "chilled".frozen?.should == false
+        end
+      end
+
+      describe "#-@" do
+        it "returns a different instance" do
+          input = "chilled"
+          interned = (-input)
+          interned.frozen?.should == true
+          interned.object_id.should_not == input.object_id
+        end
+      end
+
+      describe "#+@" do
+        it "returns a different instance" do
+          input = "chilled"
+          duped = (+input)
+          duped.frozen?.should == false
+          duped.object_id.should_not == input.object_id
+        end
+      end
+
+      describe "#clone" do
+        it "preserves chilled status" do
+          input = "chilled".clone
+          -> {
+            input << "-mutated"
+          }.should complain(/literal string will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+      end
+
+      describe "mutation" do
+        it "emits a warning" do
+          input = "chilled"
+          -> {
+            input << "-mutated"
+          }.should complain(/literal string will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+
+        it "emits a warning for concatenated strings" do
+          input = "still" "+chilled"
+          -> {
+            input << "-mutated"
+          }.should complain(/literal string will be frozen in the future/)
+          input.should == "still+chilled-mutated"
+        end
+
+        it "emits a warning on singleton_class creation" do
+          -> {
+            "chilled".singleton_class
+          }.should complain(/literal string will be frozen in the future/)
+        end
+
+        it "emits a warning on instance variable assignment" do
+          -> {
+            "chilled".instance_variable_set(:@ivar, 42)
+          }.should complain(/literal string will be frozen in the future/)
+        end
+
+        it "raises FrozenError after the string was explicitly frozen" do
+          input = "chilled"
+          input.freeze
+          -> {
+            -> {
+              input << "mutated"
+            }.should raise_error(FrozenError)
+          }.should_not complain(/literal string will be frozen in the future/)
+        end
+      end
+    end
+
+    describe "chilled strings returned by Symbol#to_s" do
+
+      describe "#frozen?" do
+        it "returns false" do
+          :chilled.to_s.frozen?.should == false
+        end
+      end
+
+      describe "#-@" do
+        it "returns a different instance" do
+          input = :chilled.to_s
+          interned = (-input)
+          interned.frozen?.should == true
+          interned.object_id.should_not == input.object_id
+        end
+      end
+
+      describe "#+@" do
+        it "returns a different instance" do
+          input = :chilled.to_s
+          duped = (+input)
+          duped.frozen?.should == false
+          duped.object_id.should_not == input.object_id
+        end
+      end
+
+      describe "#clone" do
+        it "preserves chilled status" do
+          input = :chilled.to_s.clone
+          -> {
+            input << "-mutated"
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+      end
+
+      describe "mutation" do
+        it "emits a warning" do
+          input = :chilled.to_s
+          -> {
+            input << "-mutated"
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+          input.should == "chilled-mutated"
+        end
+
+        it "emits a warning on singleton_class creation" do
+          -> {
+            :chilled.to_s.singleton_class
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
+
+        it "emits a warning on instance variable assignment" do
+          -> {
+            :chilled.to_s.instance_variable_set(:@ivar, 42)
+          }.should complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
+
+        it "raises FrozenError after the string was explicitly frozen" do
+          input = :chilled.to_s
+          input.freeze
+          -> {
+            -> {
+              input << "mutated"
+            }.should raise_error(FrozenError)
+          }.should_not complain(/string returned by :chilled\.to_s will be frozen in the future/)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/string/chomp_spec.rb b/spec/ruby/core/string/chomp_spec.rb
index 9db47d1dc6..d27c84c6f6 100644
--- a/spec/ruby/core/string/chomp_spec.rb
+++ b/spec/ruby/core/string/chomp_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -6,11 +7,13 @@ describe "String#chomp" do
   describe "when passed no argument" do
     before do
       # Ensure that $/ is set to the default value
+      @verbose, $VERBOSE = $VERBOSE, nil
       @dollar_slash, $/ = $/, "\n"
     end
 
     after do
       $/ = @dollar_slash
+      $VERBOSE = @verbose
     end
 
     it "does not modify a String with no trailing carriage return or newline" do
@@ -38,19 +41,23 @@ describe "String#chomp" do
       "".chomp.should == ""
     end
 
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp.tainted?.should be_true
+    it "returns a String in the same encoding as self" do
+      "abc\n\n".encode("US-ASCII").chomp.encoding.should == Encoding::US_ASCII
     end
 
-    it "returns subclass instances when called on a subclass" do
+    it "returns String instances when called on a subclass" do
       str = StringSpecs::MyString.new("hello\n").chomp
-      str.should be_an_instance_of(StringSpecs::MyString)
+      str.should be_an_instance_of(String)
     end
 
     it "removes trailing characters that match $/ when it has been assigned a value" do
       $/ = "cdef"
       "abcdef".chomp.should == "ab"
     end
+
+    it "removes one trailing newline for string with invalid encoding" do
+      "\xa0\xa1\n".chomp.should == "\xa0\xa1"
+    end
   end
 
   describe "when passed nil" do
@@ -63,10 +70,6 @@ describe "String#chomp" do
       str.chomp(nil).should_not equal(str)
     end
 
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp(nil).tainted?.should be_true
-    end
-
     it "returns an empty String when self is empty" do
       "".chomp(nil).should == ""
     end
@@ -93,13 +96,13 @@ describe "String#chomp" do
       "abc\r\n\r\n\r\n".chomp("").should == "abc"
     end
 
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp("").tainted?.should be_true
-    end
-
     it "returns an empty String when self is empty" do
       "".chomp("").should == ""
     end
+
+    it "removes one trailing newline for string with invalid encoding" do
+      "\xa0\xa1\n".chomp("").should == "\xa0\xa1"
+    end
   end
 
   describe "when passed '\\n'" do
@@ -115,10 +118,6 @@ describe "String#chomp" do
       "abc\r\n\r\n".chomp("\n").should == "abc\r\n"
     end
 
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp("\n").tainted?.should be_true
-    end
-
     it "returns an empty String when self is empty" do
       "".chomp("\n").should == ""
     end
@@ -151,14 +150,6 @@ describe "String#chomp" do
       "".chomp("abc").should == ""
     end
 
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp("abc").tainted?.should be_true
-    end
-
-    it "does not taint the result when the argument is tainted" do
-      "abc".chomp("abc".taint).tainted?.should be_false
-    end
-
     it "returns an empty String when the argument equals self" do
       "abc".chomp("abc").should == ""
     end
@@ -169,11 +160,13 @@ describe "String#chomp!" do
   describe "when passed no argument" do
     before do
       # Ensure that $/ is set to the default value
+      @verbose, $VERBOSE = $VERBOSE, nil
       @dollar_slash, $/ = $/, "\n"
     end
 
     after do
       $/ = @dollar_slash
+      $VERBOSE = @verbose
     end
 
     it "modifies self" do
@@ -201,10 +194,6 @@ describe "String#chomp!" do
       "".chomp!.should be_nil
     end
 
-    it "taints the result if self is tainted" do
-      "abc\n".taint.chomp!.tainted?.should be_true
-    end
-
     it "returns subclass instances when called on a subclass" do
       str = StringSpecs::MyString.new("hello\n").chomp!
       str.should be_an_instance_of(StringSpecs::MyString)
@@ -247,10 +236,6 @@ describe "String#chomp!" do
       "abc\r\n\r\n\r\n".chomp!("").should == "abc"
     end
 
-    it "taints the result if self is tainted" do
-      "abc\n".taint.chomp!("").tainted?.should be_true
-    end
-
     it "returns nil when self is empty" do
       "".chomp!("").should be_nil
     end
@@ -269,10 +254,6 @@ describe "String#chomp!" do
       "abc\r\n\r\n".chomp!("\n").should == "abc\r\n"
     end
 
-    it "taints the result if self is tainted" do
-      "abc\n".taint.chomp!("\n").tainted?.should be_true
-    end
-
     it "returns nil when self is empty" do
       "".chomp!("\n").should be_nil
     end
@@ -304,39 +285,33 @@ describe "String#chomp!" do
     it "returns nil when self is empty" do
       "".chomp!("abc").should be_nil
     end
-
-    it "taints the result if self is tainted" do
-      "abc".taint.chomp!("abc").tainted?.should be_true
-    end
-
-    it "does not taint the result when the argument is tainted" do
-      "abc".chomp!("abc".taint).tainted?.should be_false
-    end
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance when it is modified" do
+  it "raises a FrozenError on a frozen instance when it is modified" do
     a = "string\n\r"
     a.freeze
 
-    -> { a.chomp! }.should raise_error(frozen_error_class)
+    -> { a.chomp! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen instance when it would not be modified" do
+  it "raises a FrozenError on a frozen instance when it would not be modified" do
     a = "string\n\r"
     a.freeze
-    -> { a.chomp!(nil) }.should raise_error(frozen_error_class)
-    -> { a.chomp!("x") }.should raise_error(frozen_error_class)
+    -> { a.chomp!(nil) }.should raise_error(FrozenError)
+    -> { a.chomp!("x") }.should raise_error(FrozenError)
   end
 end
 
 describe "String#chomp" do
   before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
     @before_separator = $/
   end
 
   after :each do
     $/ = @before_separator
+    $VERBOSE = @verbose
   end
 
   it "does not modify a multi-byte character" do
@@ -361,11 +336,13 @@ end
 
 describe "String#chomp!" do
   before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
     @before_separator = $/
   end
 
   after :each do
     $/ = @before_separator
+    $VERBOSE = @verbose
   end
 
   it "returns nil when the String is not modified" do
diff --git a/spec/ruby/core/string/chop_spec.rb b/spec/ruby/core/string/chop_spec.rb
index 35a5766b2f..99c2c82190 100644
--- a/spec/ruby/core/string/chop_spec.rb
+++ b/spec/ruby/core/string/chop_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -49,18 +50,12 @@ describe "String#chop" do
     s.chop.should_not equal(s)
   end
 
-  it "taints result when self is tainted" do
-    "hello".taint.chop.tainted?.should == true
-    "".taint.chop.tainted?.should == true
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("hello\n").chop.should be_an_instance_of(String)
   end
 
-  it "untrusts result when self is untrusted" do
-    "hello".untrust.chop.untrusted?.should == true
-    "".untrust.chop.untrusted?.should == true
-  end
-
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("hello\n").chop.should be_an_instance_of(StringSpecs::MyString)
+  it "returns a String in the same encoding as self" do
+    "abc\n\n".encode("US-ASCII").chop.encoding.should == Encoding::US_ASCII
   end
 end
 
@@ -111,14 +106,14 @@ describe "String#chop!" do
     "".chop!.should be_nil
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "string\n\r".freeze.chop! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "string\n\r".freeze.chop! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
+  it "raises a FrozenError on a frozen instance that would not be modified" do
     a = ""
     a.freeze
-    -> { a.chop! }.should raise_error(frozen_error_class)
+    -> { a.chop! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/clear_spec.rb b/spec/ruby/core/string/clear_spec.rb
index 0b5b8e6998..152986fd0f 100644
--- a/spec/ruby/core/string/clear_spec.rb
+++ b/spec/ruby/core/string/clear_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#clear" do
@@ -29,9 +30,9 @@ describe "String#clear" do
     s.should == ""
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     @s.freeze
-    -> { @s.clear        }.should raise_error(frozen_error_class)
-    -> { "".freeze.clear }.should raise_error(frozen_error_class)
+    -> { @s.clear        }.should raise_error(FrozenError)
+    -> { "".freeze.clear }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/clone_spec.rb b/spec/ruby/core/string/clone_spec.rb
index f8d40423f0..a2ba2f9877 100644
--- a/spec/ruby/core/string/clone_spec.rb
+++ b/spec/ruby/core/string/clone_spec.rb
@@ -54,4 +54,8 @@ describe "String#clone" do
     orig.should == "xtring"
     clone.should == "string"
   end
+
+  it "returns a String in the same encoding as self" do
+    "a".encode("US-ASCII").clone.encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/string/codepoints_spec.rb b/spec/ruby/core/string/codepoints_spec.rb
index 0b6cde82f7..12a5bf5892 100644
--- a/spec/ruby/core/string/codepoints_spec.rb
+++ b/spec/ruby/core/string/codepoints_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/codepoints'
 require_relative 'shared/each_codepoint_without_block'
@@ -11,7 +11,7 @@ describe "String#codepoints" do
   end
 
   it "raises an ArgumentError when no block is given if self has an invalid encoding" do
-    s = "\xDF".force_encoding(Encoding::UTF_8)
+    s = "\xDF".dup.force_encoding(Encoding::UTF_8)
     s.valid_encoding?.should be_false
     -> { s.codepoints }.should raise_error(ArgumentError)
   end
diff --git a/spec/ruby/core/string/comparison_spec.rb b/spec/ruby/core/string/comparison_spec.rb
index 01199274b6..9db0cff5ee 100644
--- a/spec/ruby/core/string/comparison_spec.rb
+++ b/spec/ruby/core/string/comparison_spec.rb
@@ -61,12 +61,12 @@ describe "String#<=> with String" do
   end
 
   it "ignores encoding difference" do
-    ("ÄÖÛ".force_encoding("utf-8") <=> "ÄÖÜ".force_encoding("iso-8859-1")).should == -1
-    ("ÄÖÜ".force_encoding("utf-8") <=> "ÄÖÛ".force_encoding("iso-8859-1")).should == 1
+    ("ÄÖÛ".dup.force_encoding("utf-8") <=> "ÄÖÜ".dup.force_encoding("iso-8859-1")).should == -1
+    ("ÄÖÜ".dup.force_encoding("utf-8") <=> "ÄÖÛ".dup.force_encoding("iso-8859-1")).should == 1
   end
 
   it "returns 0 with identical ASCII-compatible bytes of different encodings" do
-    ("abc".force_encoding("utf-8") <=> "abc".force_encoding("iso-8859-1")).should == 0
+    ("abc".dup.force_encoding("utf-8") <=> "abc".dup.force_encoding("iso-8859-1")).should == 0
   end
 
   it "compares the indices of the encodings when the strings have identical non-ASCII-compatible bytes" do
@@ -75,6 +75,10 @@ describe "String#<=> with String" do
     (xff_1 <=> xff_2).should == -1
     (xff_2 <=> xff_1).should ==  1
   end
+
+  it "returns 0 when comparing 2 empty strings but one is not ASCII-compatible" do
+    ("" <=> "".dup.force_encoding('iso-2022-jp')).should == 0
+  end
 end
 
 # Note: This is inconsistent with Array#<=> which calls #to_ary instead of
diff --git a/spec/ruby/core/string/concat_spec.rb b/spec/ruby/core/string/concat_spec.rb
index 5f6daadad7..cbd7df54e2 100644
--- a/spec/ruby/core/string/concat_spec.rb
+++ b/spec/ruby/core/string/concat_spec.rb
@@ -5,21 +5,22 @@ require_relative 'shared/concat'
 describe "String#concat" do
   it_behaves_like :string_concat, :concat
   it_behaves_like :string_concat_encoding, :concat
+  it_behaves_like :string_concat_type_coercion, :concat
 
   it "takes multiple arguments" do
-    str = "hello "
+    str = +"hello "
     str.concat "wo", "", "rld"
     str.should == "hello world"
   end
 
   it "concatenates the initial value when given arguments contain 2 self" do
-    str = "hello"
+    str = +"hello"
     str.concat str, str
     str.should == "hellohellohello"
   end
 
   it "returns self when given no arguments" do
-    str = "hello"
+    str = +"hello"
     str.concat.should equal(str)
     str.should == "hello"
   end
diff --git a/spec/ruby/core/string/count_spec.rb b/spec/ruby/core/string/count_spec.rb
index 06ba5a4f0e..e614e901dd 100644
--- a/spec/ruby/core/string/count_spec.rb
+++ b/spec/ruby/core/string/count_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
diff --git a/spec/ruby/core/string/crypt_spec.rb b/spec/ruby/core/string/crypt_spec.rb
index 7a0f8835f2..06f84c70a4 100644
--- a/spec/ruby/core/string/crypt_spec.rb
+++ b/spec/ruby/core/string/crypt_spec.rb
@@ -25,19 +25,6 @@ describe "String#crypt" do
       "mypassword".crypt(obj).should == "$2a$04$0WVaz0pV3jzfZ5G5tpmHWuBQGbkjzgtSc3gJbmdy0GAGMa45MFM2."
     end
 
-    it "taints the result if either salt or self is tainted" do
-      tainted_salt = "$2a$04$0WVaz0pV3jzfZ5G5tpmHWu"
-      tainted_str = "mypassword"
-
-      tainted_salt.taint
-      tainted_str.taint
-
-      "mypassword".crypt("$2a$04$0WVaz0pV3jzfZ5G5tpmHWu").tainted?.should == false
-      tainted_str.crypt("$2a$04$0WVaz0pV3jzfZ5G5tpmHWu").tainted?.should == true
-      "mypassword".crypt(tainted_salt).tainted?.should == true
-      tainted_str.crypt(tainted_salt).tainted?.should == true
-    end
-
     it "doesn't return subclass instances" do
       StringSpecs::MyString.new("mypassword").crypt("$2a$04$0WVaz0pV3jzfZ5G5tpmHWu").should be_an_instance_of(String)
       "mypassword".crypt(StringSpecs::MyString.new("$2a$04$0WVaz0pV3jzfZ5G5tpmHWu")).should be_an_instance_of(String)
@@ -83,19 +70,6 @@ describe "String#crypt" do
       "".crypt(obj).should == "aaQSqAReePlq6"
     end
 
-    it "taints the result if either salt or self is tainted" do
-      tainted_salt = "aa"
-      tainted_str = "hello"
-
-      tainted_salt.taint
-      tainted_str.taint
-
-      "hello".crypt("aa").tainted?.should == false
-      tainted_str.crypt("aa").tainted?.should == true
-      "hello".crypt(tainted_salt).tainted?.should == true
-      tainted_str.crypt(tainted_salt).tainted?.should == true
-    end
-
     it "doesn't return subclass instances" do
       StringSpecs::MyString.new("hello").crypt("aa").should be_an_instance_of(String)
       "hello".crypt(StringSpecs::MyString.new("aa")).should be_an_instance_of(String)
diff --git a/spec/ruby/core/string/dedup_spec.rb b/spec/ruby/core/string/dedup_spec.rb
new file mode 100644
index 0000000000..2b31d80708
--- /dev/null
+++ b/spec/ruby/core/string/dedup_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/dedup'
+
+describe 'String#dedup' do
+  it_behaves_like :string_dedup, :dedup
+end
diff --git a/spec/ruby/core/string/delete_prefix_spec.rb b/spec/ruby/core/string/delete_prefix_spec.rb
index b88c503658..ee7f044905 100644
--- a/spec/ruby/core/string/delete_prefix_spec.rb
+++ b/spec/ruby/core/string/delete_prefix_spec.rb
@@ -1,81 +1,83 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is '2.5' do
-  describe "String#delete_prefix" do
-    it "returns a copy of the string, with the given prefix removed" do
-      'hello'.delete_prefix('hell').should == 'o'
-      'hello'.delete_prefix('hello').should == ''
-    end
+describe "String#delete_prefix" do
+  it "returns a copy of the string, with the given prefix removed" do
+    'hello'.delete_prefix('hell').should == 'o'
+    'hello'.delete_prefix('hello').should == ''
+  end
+
+  it "returns a copy of the string, when the prefix isn't found" do
+    s = 'hello'
+    r = s.delete_prefix('hello!')
+    r.should_not equal s
+    r.should == s
+    r = s.delete_prefix('ell')
+    r.should_not equal s
+    r.should == s
+    r = s.delete_prefix('')
+    r.should_not equal s
+    r.should == s
+  end
 
-    it "returns a copy of the string, when the prefix isn't found" do
-      s = 'hello'
-      r = s.delete_prefix('hello!')
-      r.should_not equal s
-      r.should == s
-      r = s.delete_prefix('ell')
-      r.should_not equal s
-      r.should == s
-      r = s.delete_prefix('')
-      r.should_not equal s
-      r.should == s
-    end
+  it "does not remove partial bytes, only full characters" do
+    "\xe3\x81\x82".delete_prefix("\xe3").should == "\xe3\x81\x82"
+  end
 
-    it "taints resulting strings when other is tainted" do
-      'hello'.taint.delete_prefix('hell').tainted?.should == true
-      'hello'.taint.delete_prefix('').tainted?.should == true
-    end
+  it "doesn't set $~" do
+    $~ = nil
 
-    it "doesn't set $~" do
-      $~ = nil
+    'hello'.delete_prefix('hell')
+    $~.should == nil
+  end
 
-      'hello'.delete_prefix('hell')
-      $~.should == nil
-    end
+  it "calls to_str on its argument" do
+    o = mock('x')
+    o.should_receive(:to_str).and_return 'hell'
+    'hello'.delete_prefix(o).should == 'o'
+  end
 
-    it "calls to_str on its argument" do
-      o = mock('x')
-      o.should_receive(:to_str).and_return 'hell'
-      'hello'.delete_prefix(o).should == 'o'
-    end
+  it "returns a String instance when called on a subclass instance" do
+    s = StringSpecs::MyString.new('hello')
+    s.delete_prefix('hell').should be_an_instance_of(String)
+  end
 
-    it "returns a subclass instance when called on a subclass instance" do
-      s = StringSpecs::MyString.new('hello')
-      s.delete_prefix('hell').should be_an_instance_of(StringSpecs::MyString)
-    end
+  it "returns a String in the same encoding as self" do
+    'hello'.encode("US-ASCII").delete_prefix('hell').encoding.should == Encoding::US_ASCII
   end
+end
 
-  describe "String#delete_prefix!" do
-    it "removes the found prefix" do
-      s = 'hello'
-      s.delete_prefix!('hell').should equal(s)
-      s.should == 'o'
-    end
+describe "String#delete_prefix!" do
+  it "removes the found prefix" do
+    s = 'hello'
+    s.delete_prefix!('hell').should equal(s)
+    s.should == 'o'
+  end
 
-    it "returns nil if no change is made" do
-      s = 'hello'
-      s.delete_prefix!('ell').should == nil
-      s.delete_prefix!('').should == nil
-    end
+  it "returns nil if no change is made" do
+    s = 'hello'
+    s.delete_prefix!('ell').should == nil
+    s.delete_prefix!('').should == nil
+  end
 
-    it "doesn't set $~" do
-      $~ = nil
+  it "doesn't set $~" do
+    $~ = nil
 
-      'hello'.delete_prefix!('hell')
-      $~.should == nil
-    end
+    'hello'.delete_prefix!('hell')
+    $~.should == nil
+  end
 
-    it "calls to_str on its argument" do
-      o = mock('x')
-      o.should_receive(:to_str).and_return 'hell'
-      'hello'.delete_prefix!(o).should == 'o'
-    end
+  it "calls to_str on its argument" do
+    o = mock('x')
+    o.should_receive(:to_str).and_return 'hell'
+    'hello'.delete_prefix!(o).should == 'o'
+  end
 
-    it "raises a #{frozen_error_class} when self is frozen" do
-      -> { 'hello'.freeze.delete_prefix!('hell') }.should raise_error(frozen_error_class)
-      -> { 'hello'.freeze.delete_prefix!('') }.should raise_error(frozen_error_class)
-      -> { ''.freeze.delete_prefix!('') }.should raise_error(frozen_error_class)
-    end
+  it "raises a FrozenError when self is frozen" do
+    -> { 'hello'.freeze.delete_prefix!('hell') }.should raise_error(FrozenError)
+    -> { 'hello'.freeze.delete_prefix!('') }.should raise_error(FrozenError)
+    -> { ''.freeze.delete_prefix!('') }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/delete_spec.rb b/spec/ruby/core/string/delete_spec.rb
index 6136cd54af..6d359776e4 100644
--- a/spec/ruby/core/string/delete_spec.rb
+++ b/spec/ruby/core/string/delete_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -68,13 +69,6 @@ describe "String#delete" do
     -> { "hello".delete("^h-e") }.should raise_error(ArgumentError)
   end
 
-  it "taints result when self is tainted" do
-    "hello".taint.delete("e").tainted?.should == true
-    "hello".taint.delete("a-z").tainted?.should == true
-
-    "hello".delete("e".taint).tainted?.should == false
-  end
-
   it "tries to convert each set arg to a string using to_str" do
     other_string = mock('lo')
     other_string.should_receive(:to_str).and_return("lo")
@@ -91,8 +85,12 @@ describe "String#delete" do
     -> { "hello world".delete(mock('x')) }.should raise_error(TypeError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("oh no!!!").delete("!").should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("oh no!!!").delete("!").should be_an_instance_of(String)
+  end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").delete("lo").encoding.should == Encoding::US_ASCII
   end
 end
 
@@ -109,11 +107,11 @@ describe "String#delete!" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     a = "hello"
     a.freeze
 
-    -> { a.delete!("")            }.should raise_error(frozen_error_class)
-    -> { a.delete!("aeiou", "^e") }.should raise_error(frozen_error_class)
+    -> { a.delete!("")            }.should raise_error(FrozenError)
+    -> { a.delete!("aeiou", "^e") }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/delete_suffix_spec.rb b/spec/ruby/core/string/delete_suffix_spec.rb
index 94909cf71d..1842d75aa5 100644
--- a/spec/ruby/core/string/delete_suffix_spec.rb
+++ b/spec/ruby/core/string/delete_suffix_spec.rb
@@ -1,81 +1,83 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is '2.5' do
-  describe "String#delete_suffix" do
-    it "returns a copy of the string, with the given suffix removed" do
-      'hello'.delete_suffix('ello').should == 'h'
-      'hello'.delete_suffix('hello').should == ''
-    end
+describe "String#delete_suffix" do
+  it "returns a copy of the string, with the given suffix removed" do
+    'hello'.delete_suffix('ello').should == 'h'
+    'hello'.delete_suffix('hello').should == ''
+  end
+
+  it "returns a copy of the string, when the suffix isn't found" do
+    s = 'hello'
+    r = s.delete_suffix('!hello')
+    r.should_not equal s
+    r.should == s
+    r = s.delete_suffix('ell')
+    r.should_not equal s
+    r.should == s
+    r = s.delete_suffix('')
+    r.should_not equal s
+    r.should == s
+  end
 
-    it "returns a copy of the string, when the suffix isn't found" do
-      s = 'hello'
-      r = s.delete_suffix('!hello')
-      r.should_not equal s
-      r.should == s
-      r = s.delete_suffix('ell')
-      r.should_not equal s
-      r.should == s
-      r = s.delete_suffix('')
-      r.should_not equal s
-      r.should == s
-    end
+  it "does not remove partial bytes, only full characters" do
+    "\xe3\x81\x82".delete_suffix("\x82").should == "\xe3\x81\x82"
+  end
 
-    it "taints resulting strings when other is tainted" do
-      'hello'.taint.delete_suffix('ello').tainted?.should == true
-      'hello'.taint.delete_suffix('').tainted?.should == true
-    end
+  it "doesn't set $~" do
+    $~ = nil
 
-    it "doesn't set $~" do
-      $~ = nil
+    'hello'.delete_suffix('ello')
+    $~.should == nil
+  end
 
-      'hello'.delete_suffix('ello')
-      $~.should == nil
-    end
+  it "calls to_str on its argument" do
+    o = mock('x')
+    o.should_receive(:to_str).and_return 'ello'
+    'hello'.delete_suffix(o).should == 'h'
+  end
 
-    it "calls to_str on its argument" do
-      o = mock('x')
-      o.should_receive(:to_str).and_return 'ello'
-      'hello'.delete_suffix(o).should == 'h'
-    end
+  it "returns a String instance when called on a subclass instance" do
+    s = StringSpecs::MyString.new('hello')
+    s.delete_suffix('ello').should be_an_instance_of(String)
+  end
 
-    it "returns a subclass instance when called on a subclass instance" do
-      s = StringSpecs::MyString.new('hello')
-      s.delete_suffix('ello').should be_an_instance_of(StringSpecs::MyString)
-    end
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").delete_suffix("ello").encoding.should == Encoding::US_ASCII
   end
+end
 
-  describe "String#delete_suffix!" do
-    it "removes the found prefix" do
-      s = 'hello'
-      s.delete_suffix!('ello').should equal(s)
-      s.should == 'h'
-    end
+describe "String#delete_suffix!" do
+  it "removes the found prefix" do
+    s = 'hello'
+    s.delete_suffix!('ello').should equal(s)
+    s.should == 'h'
+  end
 
-    it "returns nil if no change is made" do
-      s = 'hello'
-      s.delete_suffix!('ell').should == nil
-      s.delete_suffix!('').should == nil
-    end
+  it "returns nil if no change is made" do
+    s = 'hello'
+    s.delete_suffix!('ell').should == nil
+    s.delete_suffix!('').should == nil
+  end
 
-    it "doesn't set $~" do
-      $~ = nil
+  it "doesn't set $~" do
+    $~ = nil
 
-      'hello'.delete_suffix!('ello')
-      $~.should == nil
-    end
+    'hello'.delete_suffix!('ello')
+    $~.should == nil
+  end
 
-    it "calls to_str on its argument" do
-      o = mock('x')
-      o.should_receive(:to_str).and_return 'ello'
-      'hello'.delete_suffix!(o).should == 'h'
-    end
+  it "calls to_str on its argument" do
+    o = mock('x')
+    o.should_receive(:to_str).and_return 'ello'
+    'hello'.delete_suffix!(o).should == 'h'
+  end
 
-    it "raises a #{frozen_error_class} when self is frozen" do
-      -> { 'hello'.freeze.delete_suffix!('ello') }.should raise_error(frozen_error_class)
-      -> { 'hello'.freeze.delete_suffix!('') }.should raise_error(frozen_error_class)
-      -> { ''.freeze.delete_suffix!('') }.should raise_error(frozen_error_class)
-    end
+  it "raises a FrozenError when self is frozen" do
+    -> { 'hello'.freeze.delete_suffix!('ello') }.should raise_error(FrozenError)
+    -> { 'hello'.freeze.delete_suffix!('') }.should raise_error(FrozenError)
+    -> { ''.freeze.delete_suffix!('') }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/downcase_spec.rb b/spec/ruby/core/string/downcase_spec.rb
index 31c8f3f446..2d260f23f1 100644
--- a/spec/ruby/core/string/downcase_spec.rb
+++ b/spec/ruby/core/string/downcase_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -8,6 +9,10 @@ describe "String#downcase" do
     "hello".downcase.should == "hello"
   end
 
+  it "returns a String in the same encoding as self" do
+    "hELLO".encode("US-ASCII").downcase.encoding.should == Encoding::US_ASCII
+  end
+
   describe "full Unicode case mapping" do
     it "works for all of Unicode with no option" do
       "ÄÖÜ".downcase.should == "äöü"
@@ -27,6 +32,10 @@ describe "String#downcase" do
     it "does not downcase non-ASCII characters" do
       "CÅR".downcase(:ascii).should == "cÅr"
     end
+
+    it "works with substrings" do
+      "prefix TÉ"[-2..-1].downcase(:ascii).should == "tÉ"
+    end
   end
 
   describe "full Unicode case mapping adapted for Turkic languages" do
@@ -68,14 +77,8 @@ describe "String#downcase" do
     -> { "ABC".downcase(:invalid_option) }.should raise_error(ArgumentError)
   end
 
-  it "taints result when self is tainted" do
-    "".taint.downcase.tainted?.should == true
-    "x".taint.downcase.tainted?.should == true
-    "X".taint.downcase.tainted?.should == true
-  end
-
-  it "returns a subclass instance for subclasses" do
-    StringSpecs::MyString.new("FOObar").downcase.should be_an_instance_of(StringSpecs::MyString)
+  it "returns a String instance for subclasses" do
+    StringSpecs::MyString.new("FOObar").downcase.should be_an_instance_of(String)
   end
 end
 
@@ -86,6 +89,12 @@ describe "String#downcase!" do
     a.should == "hello"
   end
 
+  it "modifies self in place for non-ascii-compatible encodings" do
+    a = "HeLlO".encode("utf-16le")
+    a.downcase!
+    a.should == "hello".encode("utf-16le")
+  end
+
   describe "full Unicode case mapping" do
     it "modifies self in place for all of Unicode with no option" do
       a = "ÄÖÜ"
@@ -110,6 +119,12 @@ describe "String#downcase!" do
       a.downcase!(:ascii)
       a.should == "cÅr"
     end
+
+    it "works for non-ascii-compatible encodings" do
+      a = "ABC".encode("utf-16le")
+      a.downcase!(:ascii)
+      a.should == "abc".encode("utf-16le")
+    end
   end
 
   describe "full Unicode case mapping adapted for Turkic languages" do
@@ -169,9 +184,9 @@ describe "String#downcase!" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
-    -> { "HeLlo".freeze.downcase! }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.downcase! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when self is frozen" do
+    -> { "HeLlo".freeze.downcase! }.should raise_error(FrozenError)
+    -> { "hello".freeze.downcase! }.should raise_error(FrozenError)
   end
 
   it "sets the result String encoding to the source String encoding" do
diff --git a/spec/ruby/core/string/dump_spec.rb b/spec/ruby/core/string/dump_spec.rb
index aa91114893..cab8beff5a 100644
--- a/spec/ruby/core/string/dump_spec.rb
+++ b/spec/ruby/core/string/dump_spec.rb
@@ -3,22 +3,12 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "String#dump" do
-  it "taints the result if self is tainted" do
-    "foo".taint.dump.tainted?.should == true
-    "foo\n".taint.dump.tainted?.should == true
-  end
-
-  it "untrusts the result if self is untrusted" do
-    "foo".untrust.dump.untrusted?.should == true
-    "foo\n".untrust.dump.untrusted?.should == true
-  end
-
   it "does not take into account if a string is frozen" do
-    "foo".freeze.dump.frozen?.should == false
+    "foo".freeze.dump.should_not.frozen?
   end
 
-  it "returns a subclass instance" do
-    StringSpecs::MyString.new.dump.should be_an_instance_of(StringSpecs::MyString)
+  it "returns a String instance" do
+    StringSpecs::MyString.new.dump.should be_an_instance_of(String)
   end
 
   it "wraps string with \"" do
@@ -352,7 +342,7 @@ describe "String#dump" do
     ].should be_computed_by(:dump)
   end
 
-  it "returns a string with multi-byte UTF-8 characters replaced by \\u{} notation with upper-case hex digits" do
+  it "returns a string with multi-byte UTF-8 characters less than or equal 0xFFFF replaced by \\uXXXX notation with upper-case hex digits" do
     [ [0200.chr('utf-8'), '"\u0080"'],
       [0201.chr('utf-8'), '"\u0081"'],
       [0202.chr('utf-8'), '"\u0082"'],
@@ -384,15 +374,21 @@ describe "String#dump" do
       [0235.chr('utf-8'), '"\u009D"'],
       [0236.chr('utf-8'), '"\u009E"'],
       [0237.chr('utf-8'), '"\u009F"'],
+      [0177777.chr('utf-8'), '"\uFFFF"'],
     ].should be_computed_by(:dump)
   end
 
+  it "returns a string with multi-byte UTF-8 characters greater than 0xFFFF replaced by \\u{XXXXXX} notation with upper-case hex digits" do
+    0x10000.chr('utf-8').dump.should == '"\u{10000}"'
+    0x10FFFF.chr('utf-8').dump.should == '"\u{10FFFF}"'
+  end
+
   it "includes .force_encoding(name) if the encoding isn't ASCII compatible" do
-    "\u{876}".encode('utf-16be').dump.end_with?(".force_encoding(\"UTF-16BE\")").should be_true
-    "\u{876}".encode('utf-16le').dump.end_with?(".force_encoding(\"UTF-16LE\")").should be_true
+    "\u{876}".encode('utf-16be').dump.should.end_with?(".force_encoding(\"UTF-16BE\")")
+    "\u{876}".encode('utf-16le').dump.should.end_with?(".force_encoding(\"UTF-16LE\")")
   end
 
-  it "keeps origin encoding" do
+  it "returns a String in the same encoding as self" do
     "foo".encode("ISO-8859-1").dump.encoding.should == Encoding::ISO_8859_1
     "foo".encode('windows-1251').dump.encoding.should == Encoding::Windows_1251
     1.chr.dump.encoding.should == Encoding::US_ASCII
diff --git a/spec/ruby/core/string/dup_spec.rb b/spec/ruby/core/string/dup_spec.rb
index d650788210..073802d84b 100644
--- a/spec/ruby/core/string/dup_spec.rb
+++ b/spec/ruby/core/string/dup_spec.rb
@@ -49,4 +49,17 @@ describe "String#dup" do
     orig.should == "xtring"
     dup.should == "string"
   end
+
+  it "does not modify the original setbyte-mutated string when changing dupped string" do
+    orig = +"a"
+    orig.setbyte 0, "b".ord
+    copy = orig.dup
+    orig.setbyte 0, "c".ord
+    orig.should == "c"
+    copy.should == "b"
+  end
+
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").dup.encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/core/string/each_byte_spec.rb b/spec/ruby/core/string/each_byte_spec.rb
index e04dca807f..7b3db265ac 100644
--- a/spec/ruby/core/string/each_byte_spec.rb
+++ b/spec/ruby/core/string/each_byte_spec.rb
@@ -9,26 +9,26 @@ describe "String#each_byte" do
   end
 
   it "keeps iterating from the old position (to new string end) when self changes" do
-    r = ""
-    s = "hello world"
+    r = +""
+    s = +"hello world"
     s.each_byte do |c|
       r << c
       s.insert(0, "<>") if r.size < 3
     end
     r.should == "h><>hello world"
 
-    r = ""
-    s = "hello world"
+    r = +""
+    s = +"hello world"
     s.each_byte { |c| s.slice!(-1); r << c }
     r.should == "hello "
 
-    r = ""
-    s = "hello world"
+    r = +""
+    s = +"hello world"
     s.each_byte { |c| s.slice!(0); r << c }
     r.should == "hlowrd"
 
-    r = ""
-    s = "hello world"
+    r = +""
+    s = +"hello world"
     s.each_byte { |c| s.slice!(0..-1); r << c }
     r.should == "h"
   end
diff --git a/spec/ruby/core/string/each_char_spec.rb b/spec/ruby/core/string/each_char_spec.rb
index aff98c0a5c..36219f79db 100644
--- a/spec/ruby/core/string/each_char_spec.rb
+++ b/spec/ruby/core/string/each_char_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../spec_helper"
 require_relative 'shared/chars'
 require_relative 'shared/each_char_without_block'
 
diff --git a/spec/ruby/core/string/each_grapheme_cluster_spec.rb b/spec/ruby/core/string/each_grapheme_cluster_spec.rb
index 5367f84887..e1fa4ae67b 100644
--- a/spec/ruby/core/string/each_grapheme_cluster_spec.rb
+++ b/spec/ruby/core/string/each_grapheme_cluster_spec.rb
@@ -1,11 +1,16 @@
+require_relative "../../spec_helper"
 require_relative 'shared/chars'
 require_relative 'shared/grapheme_clusters'
 require_relative 'shared/each_char_without_block'
 
-ruby_version_is "2.5" do
-  describe "String#each_grapheme_cluster" do
-    it_behaves_like :string_chars, :each_grapheme_cluster
-    it_behaves_like :string_grapheme_clusters, :each_grapheme_cluster
-    it_behaves_like :string_each_char_without_block, :each_grapheme_cluster
+describe "String#each_grapheme_cluster" do
+  it_behaves_like :string_chars, :each_grapheme_cluster
+  it_behaves_like :string_grapheme_clusters, :each_grapheme_cluster
+  it_behaves_like :string_each_char_without_block, :each_grapheme_cluster
+
+  it "yields String instances for subclasses" do
+    a = []
+    StringSpecs::MyString.new("abc").each_grapheme_cluster { |s| a << s.class }
+    a.should == [String, String, String]
   end
 end
diff --git a/spec/ruby/core/string/element_set_spec.rb b/spec/ruby/core/string/element_set_spec.rb
index 34e122b055..e7599f832c 100644
--- a/spec/ruby/core/string/element_set_spec.rb
+++ b/spec/ruby/core/string/element_set_spec.rb
@@ -1,11 +1,12 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 # TODO: Add missing String#[]= specs:
 #   String#[re, idx] = obj
 
-describe "String#[]= with Fixnum index" do
+describe "String#[]= with Integer index" do
   it "replaces the char at idx with other_str" do
     a = "hello"
     a[0] = "bam"
@@ -14,16 +15,6 @@ describe "String#[]= with Fixnum index" do
     a.should == "bamelo"
   end
 
-  it "taints self if other_str is tainted" do
-    a = "hello"
-    a[0] = "".taint
-    a.tainted?.should == true
-
-    a = "hello"
-    a[0] = "x".taint
-    a.tainted?.should == true
-  end
-
   it "raises an IndexError without changing self if idx is outside of self" do
     str = "hello"
 
@@ -50,11 +41,11 @@ describe "String#[]= with Fixnum index" do
     str.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     a = "hello"
     a.freeze
 
-    -> { a[0] = "bam" }.should raise_error(frozen_error_class)
+    -> { a[0] = "bam" }.should raise_error(FrozenError)
   end
 
   it "calls to_int on index" do
@@ -83,7 +74,7 @@ describe "String#[]= with Fixnum index" do
     -> { "test"[1] = nil       }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError if passed a Fixnum replacement" do
+  it "raises a TypeError if passed an Integer replacement" do
     -> { "abc"[1] = 65 }.should raise_error(TypeError)
   end
 
@@ -100,7 +91,7 @@ describe "String#[]= with Fixnum index" do
     str.should == "あa"
   end
 
-  it "raises a TypeError if #to_int does not return an Fixnum" do
+  it "raises a TypeError if #to_int does not return an Integer" do
     index = mock("string element set")
     index.should_receive(:to_int).and_return('1')
 
@@ -139,6 +130,12 @@ describe "String#[]= with Fixnum index" do
     str.encoding.should equal(Encoding::BINARY)
   end
 
+  it "updates the string to a compatible encoding" do
+    str = "  "
+    str[1] = [0xB9].pack("C*")
+    str.encoding.should == Encoding::ASCII_8BIT
+  end
+
   it "raises an Encoding::CompatibilityError if the replacement encoding is incompatible" do
     str = "あれ"
     rep = "が".encode Encoding::EUC_JP
@@ -241,7 +238,7 @@ describe "String#[]= with a Regexp index" do
       str.should == "axc"
     end
 
-    it "raises a TypeError if #to_int does not return a Fixnum" do
+    it "raises a TypeError if #to_int does not return an Integer" do
       ref = mock("string element set regexp ref")
       ref.should_receive(:to_int).and_return(nil)
 
@@ -361,11 +358,11 @@ describe "String#[]= with a Range index" do
   end
 
   it "raises a RangeError if negative Range begin is out of range" do
-    -> { "abc"[-4..-2] = "x" }.should raise_error(RangeError)
+    -> { "abc"[-4..-2] = "x" }.should raise_error(RangeError, "-4..-2 out of range")
   end
 
   it "raises a RangeError if positive Range begin is greater than String size" do
-    -> { "abc"[4..2] = "x" }.should raise_error(RangeError)
+    -> { "abc"[4..2] = "x" }.should raise_error(RangeError, "4..2 out of range")
   end
 
   it "uses the Range end as an index rather than a count" do
@@ -436,7 +433,7 @@ describe "String#[]= with a Range index" do
   end
 end
 
-describe "String#[]= with Fixnum index, count" do
+describe "String#[]= with Integer index, count" do
   it "starts at idx and overwrites count characters before inserting the rest of other_str" do
     a = "hello"
     a[0, 2] = "xx"
@@ -485,16 +482,6 @@ describe "String#[]= with Fixnum index, count" do
     a.should == "hellobob"
   end
 
-  it "taints self if other_str is tainted" do
-    a = "hello"
-    a[0, 0] = "".taint
-    a.tainted?.should == true
-
-    a = "hello"
-    a[1, 4] = "x".taint
-    a.tainted?.should == true
-  end
-
   it "calls #to_int to convert the index and count objects" do
     index = mock("string element set index")
     index.should_receive(:to_int).and_return(-4)
diff --git a/spec/ruby/core/string/empty_spec.rb b/spec/ruby/core/string/empty_spec.rb
index fb52070723..8e53a16afc 100644
--- a/spec/ruby/core/string/empty_spec.rb
+++ b/spec/ruby/core/string/empty_spec.rb
@@ -3,10 +3,10 @@ require_relative 'fixtures/classes'
 
 describe "String#empty?" do
   it "returns true if the string has a length of zero" do
-    "hello".empty?.should == false
-    " ".empty?.should == false
-    "\x00".empty?.should == false
-    "".empty?.should == true
-    StringSpecs::MyString.new("").empty?.should == true
+    "hello".should_not.empty?
+    " ".should_not.empty?
+    "\x00".should_not.empty?
+    "".should.empty?
+    StringSpecs::MyString.new("").should.empty?
   end
 end
diff --git a/spec/ruby/core/string/encode_spec.rb b/spec/ruby/core/string/encode_spec.rb
index 1c0c939358..cd449498a3 100644
--- a/spec/ruby/core/string/encode_spec.rb
+++ b/spec/ruby/core/string/encode_spec.rb
@@ -19,19 +19,23 @@ describe "String#encode" do
     it "returns a copy when Encoding.default_internal is nil" do
       Encoding.default_internal = nil
       str = "あ"
-      str.encode.should_not equal(str)
+      encoded = str.encode
+      encoded.should_not equal(str)
+      encoded.should == str
     end
 
     it "returns a copy for a ASCII-only String when Encoding.default_internal is nil" do
       Encoding.default_internal = nil
       str = "abc"
-      str.encode.should_not equal(str)
+      encoded = str.encode
+      encoded.should_not equal(str)
+      encoded.should == str
     end
 
     it "encodes an ascii substring of a binary string to UTF-8" do
       x82 = [0x82].pack('C')
-      str =  "#{x82}foo".force_encoding("binary")[1..-1].encode("utf-8")
-      str.should == "foo".force_encoding("utf-8")
+      str =  "#{x82}foo".dup.force_encoding("binary")[1..-1].encode("utf-8")
+      str.should == "foo".dup.force_encoding("utf-8")
       str.encoding.should equal(Encoding::UTF_8)
     end
   end
@@ -39,11 +43,13 @@ describe "String#encode" do
   describe "when passed to encoding" do
     it "returns a copy when passed the same encoding as the String" do
       str = "あ"
-      str.encode(Encoding::UTF_8).should_not equal(str)
+      encoded = str.encode(Encoding::UTF_8)
+      encoded.should_not equal(str)
+      encoded.should == str
     end
 
     it "round trips a String" do
-      str = "abc def".force_encoding Encoding::US_ASCII
+      str = "abc def".dup.force_encoding Encoding::US_ASCII
       str.encode("utf-32be").encode("ascii").should == "abc def"
     end
   end
@@ -55,26 +61,84 @@ describe "String#encode" do
       str.encode(invalid: :replace).should_not equal(str)
     end
 
-    it "normalizes newlines" do
-      "\r\nfoo".encode(universal_newline: true).should == "\nfoo"
+    it "normalizes newlines with cr_newline option" do
+      "\r\nfoo".encode(cr_newline: true).should == "\r\rfoo"
+      "\rfoo".encode(cr_newline: true).should == "\rfoo"
+      "\nfoo".encode(cr_newline: true).should == "\rfoo"
+    end
 
+    it "normalizes newlines with crlf_newline option" do
+      "\r\nfoo".encode(crlf_newline: true).should == "\r\r\nfoo"
+      "\rfoo".encode(crlf_newline: true).should == "\rfoo"
+      "\nfoo".encode(crlf_newline: true).should == "\r\nfoo"
+    end
+
+    it "normalizes newlines with universal_newline option" do
+      "\r\nfoo".encode(universal_newline: true).should == "\nfoo"
       "\rfoo".encode(universal_newline: true).should == "\nfoo"
+      "\nfoo".encode(universal_newline: true).should == "\nfoo"
+    end
+
+    it "replaces invalid encoding in source with default replacement" do
+      encoded = "ち\xE3\x81\xFF".encode("UTF-16LE", invalid: :replace)
+      encoded.should == "\u3061\ufffd\ufffd".encode("UTF-16LE")
+      encoded.encode("UTF-8").should == "ち\ufffd\ufffd"
     end
 
-    it "replaces invalid encoding" do
-      encoded = "ち\xE3\x81\xFF".encode("UTF-16LE", invalid: :replace, replace: "?")
-      encoded.should == "\u3061??".encode("UTF-16LE")
-      encoded.encode("UTF-8").should == "ち??"
+    it "replaces invalid encoding in source with a specified replacement" do
+      encoded = "ち\xE3\x81\xFF".encode("UTF-16LE", invalid: :replace, replace: "foo")
+      encoded.should == "\u3061foofoo".encode("UTF-16LE")
+      encoded.encode("UTF-8").should == "ちfoofoo"
+    end
+
+    it "replace multiple invalid bytes at the end with a single replacement character" do
+      "\xE3\x81\x93\xE3\x81".encode("UTF-8", invalid: :replace).should == "\u3053\ufffd"
+    end
+
+    it "replaces invalid encoding in source using a specified replacement even when a fallback is given" do
+      encoded = "ち\xE3\x81\xFF".encode("UTF-16LE", invalid: :replace, replace: "foo", fallback: -> c { "bar" })
+      encoded.should == "\u3061foofoo".encode("UTF-16LE")
+      encoded.encode("UTF-8").should == "ちfoofoo"
+    end
+
+    it "replaces undefined encoding in destination with default replacement" do
+      encoded = "B\ufffd".encode(Encoding::US_ASCII, undef: :replace)
+      encoded.should == "B?".encode(Encoding::US_ASCII)
+      encoded.encode("UTF-8").should == "B?"
+    end
+
+    it "replaces undefined encoding in destination with a specified replacement" do
+      encoded = "B\ufffd".encode(Encoding::US_ASCII, undef: :replace, replace: "foo")
+      encoded.should == "Bfoo".encode(Encoding::US_ASCII)
+      encoded.encode("UTF-8").should == "Bfoo"
+    end
+
+    it "replaces undefined encoding in destination with a specified replacement even if a fallback is given" do
+      encoded = "B\ufffd".encode(Encoding::US_ASCII, undef: :replace, replace: "foo", fallback: proc {|x| "bar"})
+      encoded.should == "Bfoo".encode(Encoding::US_ASCII)
+      encoded.encode("UTF-8").should == "Bfoo"
+    end
+
+    it "replaces undefined encoding in destination using a fallback proc" do
+      encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: proc {|x| "bar"})
+      encoded.should == "Bbar".encode(Encoding::US_ASCII)
+      encoded.encode("UTF-8").should == "Bbar"
+    end
+
+    it "replaces invalid encoding in source using replace even when fallback is given as proc" do
+      encoded = "ち\xE3\x81\xFF".encode("UTF-16LE", invalid: :replace, replace: "foo", fallback: proc {|x| "bar"})
+      encoded.should == "\u3061foofoo".encode("UTF-16LE")
+      encoded.encode("UTF-8").should == "ちfoofoo"
     end
   end
 
   describe "when passed to, from" do
     it "returns a copy in the destination encoding when both encodings are the same" do
-      str = "あ"
-      str.force_encoding("binary")
+      str = "あ".dup.force_encoding("binary")
       encoded = str.encode("utf-8", "utf-8")
 
       encoded.should_not equal(str)
+      encoded.should == str.force_encoding("utf-8")
       encoded.encoding.should == Encoding::UTF_8
     end
 
@@ -87,14 +151,27 @@ describe "String#encode" do
   describe "when passed to, options" do
     it "returns a copy when the destination encoding is the same as the String encoding" do
       str = "あ"
-      str.encode(Encoding::UTF_8, undef: :replace).should_not equal(str)
+      encoded = str.encode(Encoding::UTF_8, undef: :replace)
+      encoded.should_not equal(str)
+      encoded.should == str
     end
   end
 
   describe "when passed to, from, options" do
     it "returns a copy when both encodings are the same" do
       str = "あ"
-      str.encode("utf-8", "utf-8", invalid: :replace).should_not equal(str)
+      encoded = str.encode("utf-8", "utf-8", invalid: :replace)
+      encoded.should_not equal(str)
+      encoded.should == str
+    end
+
+    it "returns a copy in the destination encoding when both encodings are the same" do
+      str = "あ".dup.force_encoding("binary")
+      encoded = str.encode("utf-8", "utf-8", invalid: :replace)
+
+      encoded.should_not equal(str)
+      encoded.should == str.force_encoding("utf-8")
+      encoded.encoding.should == Encoding::UTF_8
     end
   end
 end
@@ -112,25 +189,25 @@ describe "String#encode!" do
 
   it_behaves_like :string_encode, :encode!
 
-  it "raises a #{frozen_error_class} when called on a frozen String" do
-    -> { "foo".freeze.encode!("euc-jp") }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when called on a frozen String" do
+    -> { "foo".freeze.encode!("euc-jp") }.should raise_error(FrozenError)
   end
 
   # http://redmine.ruby-lang.org/issues/show/1836
-  it "raises a #{frozen_error_class} when called on a frozen String when it's a no-op" do
-    -> { "foo".freeze.encode!("utf-8") }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when called on a frozen String when it's a no-op" do
+    -> { "foo".freeze.encode!("utf-8") }.should raise_error(FrozenError)
   end
 
   describe "when passed no options" do
     it "returns self when Encoding.default_internal is nil" do
       Encoding.default_internal = nil
-      str = "あ"
+      str = +"あ"
       str.encode!.should equal(str)
     end
 
     it "returns self for a ASCII-only String when Encoding.default_internal is nil" do
       Encoding.default_internal = nil
-      str = "abc"
+      str = +"abc"
       str.encode!.should equal(str)
     end
   end
@@ -138,14 +215,14 @@ describe "String#encode!" do
   describe "when passed options" do
     it "returns self for ASCII-only String when Encoding.default_internal is nil" do
       Encoding.default_internal = nil
-      str = "abc"
+      str = +"abc"
       str.encode!(invalid: :replace).should equal(str)
     end
   end
 
   describe "when passed to encoding" do
     it "returns self" do
-      str = "abc"
+      str = +"abc"
       result = str.encode!(Encoding::BINARY)
       result.encoding.should equal(Encoding::BINARY)
       result.should equal(str)
@@ -154,7 +231,7 @@ describe "String#encode!" do
 
   describe "when passed to, from" do
     it "returns self" do
-      str = "ああ"
+      str = +"ああ"
       result = str.encode!("euc-jp", "utf-8")
       result.encoding.should equal(Encoding::EUC_JP)
       result.should equal(str)
diff --git a/spec/ruby/core/string/encoding_spec.rb b/spec/ruby/core/string/encoding_spec.rb
index 4d17a39f29..f6e8fd3470 100644
--- a/spec/ruby/core/string/encoding_spec.rb
+++ b/spec/ruby/core/string/encoding_spec.rb
@@ -10,14 +10,15 @@ describe "String#encoding" do
   it "is equal to the source encoding by default" do
     s = StringSpecs::ISO88599Encoding.new
     s.cedilla.encoding.should == s.source_encoding
+    s.cedilla.encode("utf-8").should == 350.chr(Encoding::UTF_8) # S-cedilla
   end
 
   it "returns the given encoding if #force_encoding has been called" do
-    "a".force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "a".dup.force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
   end
 
   it "returns the given encoding if #encode!has been called" do
-    "a".encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "a".dup.encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
   end
 end
 
@@ -107,13 +108,13 @@ describe "String#encoding for Strings with \\u escapes" do
   end
 
   it "returns the given encoding if #force_encoding has been called" do
-    "\u{20}".force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
-    "\u{2020}".force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "\u{20}".dup.force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "\u{2020}".dup.force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
   end
 
   it "returns the given encoding if #encode!has been called" do
-    "\u{20}".encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
-    "\u{2020}".encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "\u{20}".dup.encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "\u{2020}".dup.encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
   end
 end
 
@@ -172,16 +173,12 @@ describe "String#encoding for Strings with \\x escapes" do
   end
 
   it "returns the given encoding if #force_encoding has been called" do
-    x50 = "\x50"
-    x50.force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
-    xD4 = [212].pack('C')
-    xD4.force_encoding(Encoding::ISO_8859_9).encoding.should == Encoding::ISO_8859_9
+    "\x50".dup.force_encoding(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    [212].pack('C').force_encoding(Encoding::ISO_8859_9).encoding.should == Encoding::ISO_8859_9
   end
 
   it "returns the given encoding if #encode!has been called" do
-    x50 = "\x50"
-    x50.encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
-    x00 = "x\00"
-    x00.encode!(Encoding::UTF_8).encoding.should == Encoding::UTF_8
+    "\x50".dup.encode!(Encoding::SHIFT_JIS).encoding.should == Encoding::SHIFT_JIS
+    "x\00".dup.encode!(Encoding::UTF_8).encoding.should == Encoding::UTF_8
   end
 end
diff --git a/spec/ruby/core/string/end_with_spec.rb b/spec/ruby/core/string/end_with_spec.rb
index b7a04fdefe..ac4fff72ad 100644
--- a/spec/ruby/core/string/end_with_spec.rb
+++ b/spec/ruby/core/string/end_with_spec.rb
@@ -1,57 +1,8 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../../shared/string/end_with'
 
 describe "String#end_with?" do
-  it "returns true only if ends match" do
-    s = "hello"
-    s.end_with?('o').should be_true
-    s.end_with?('llo').should be_true
-  end
-
-  it 'returns false if the end does not match' do
-    s = 'hello'
-    s.end_with?('ll').should be_false
-  end
-
-  it "returns true if the search string is empty" do
-    "hello".end_with?("").should be_true
-    "".end_with?("").should be_true
-  end
-
-  it "returns true only if any ending match" do
-    "hello".end_with?('x', 'y', 'llo', 'z').should be_true
-  end
-
-  it "converts its argument using :to_str" do
-    s = "hello"
-    find = mock('o')
-    find.should_receive(:to_str).and_return("o")
-    s.end_with?(find).should be_true
-  end
-
-  it "ignores arguments not convertible to string" do
-    "hello".end_with?().should be_false
-    -> { "hello".end_with?(1) }.should raise_error(TypeError)
-    -> { "hello".end_with?(["o"]) }.should raise_error(TypeError)
-    -> { "hello".end_with?(1, nil, "o") }.should raise_error(TypeError)
-  end
-
-  it "uses only the needed arguments" do
-    find = mock('h')
-    find.should_not_receive(:to_str)
-    "hello".end_with?("o",find).should be_true
-  end
-
-  it "works for multibyte strings" do
-    "céréale".end_with?("réale").should be_true
-  end
-
-  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
-    pat = "ア".encode Encoding::EUC_JP
-    -> do
-      "あれ".end_with?(pat)
-    end.should raise_error(Encoding::CompatibilityError)
-  end
-
+  it_behaves_like :end_with, :to_s
 end
diff --git a/spec/ruby/core/string/fixtures/classes.rb b/spec/ruby/core/string/fixtures/classes.rb
index 1cc7600abb..26fcd51b5d 100644
--- a/spec/ruby/core/string/fixtures/classes.rb
+++ b/spec/ruby/core/string/fixtures/classes.rb
@@ -46,4 +46,15 @@ module StringSpecs
       self.replace(str)
     end
   end
+
+  class SpecialVarProcessor
+    def process(match)
+      if $~ != nil
+        str = $~[0]
+      else
+        str = "unset"
+      end
+      "<#{str}>"
+    end
+  end
 end
diff --git a/spec/ruby/core/string/fixtures/iso-8859-9-encoding.rb b/spec/ruby/core/string/fixtures/iso-8859-9-encoding.rb
index 61a691ff78..cfa91dedc3 100644
--- a/spec/ruby/core/string/fixtures/iso-8859-9-encoding.rb
+++ b/spec/ruby/core/string/fixtures/iso-8859-9-encoding.rb
@@ -4,6 +4,6 @@ module StringSpecs
     def source_encoding; __ENCODING__; end
     def x_escape; [0xDF].pack('C').force_encoding("iso-8859-9"); end
     def ascii_only; "glark"; end
-    def cedilla; "Ş"; end
+    def cedilla; "�"; end # S-cedilla
   end
 end
diff --git a/spec/ruby/core/string/fixtures/to_c.rb b/spec/ruby/core/string/fixtures/to_c.rb
new file mode 100644
index 0000000000..7776933263
--- /dev/null
+++ b/spec/ruby/core/string/fixtures/to_c.rb
@@ -0,0 +1,5 @@
+module StringSpecs
+  def self.to_c_method(string)
+    string.to_c
+  end
+end
diff --git a/spec/ruby/core/string/fixtures/utf-8-encoding.rb b/spec/ruby/core/string/fixtures/utf-8-encoding.rb
deleted file mode 100644
index fd243ec522..0000000000
--- a/spec/ruby/core/string/fixtures/utf-8-encoding.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-# -*- encoding: utf-8 -*-
-module StringSpecs
-  class UTF8Encoding
-    def self.source_encoding; __ENCODING__; end
-    def self.egrave; "é"; end
-  end
-end
diff --git a/spec/ruby/core/string/force_encoding_spec.rb b/spec/ruby/core/string/force_encoding_spec.rb
index 56d9b1e9bc..2259dcf3cf 100644
--- a/spec/ruby/core/string/force_encoding_spec.rb
+++ b/spec/ruby/core/string/force_encoding_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#force_encoding" do
@@ -60,12 +61,12 @@ describe "String#force_encoding" do
   end
 
   it "does not transcode self" do
-    str = "\u{8612}"
+    str = "é"
     str.dup.force_encoding('utf-16le').should_not == str.encode('utf-16le')
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     str = "abcd".freeze
-    -> { str.force_encoding(str.encoding) }.should raise_error(frozen_error_class)
+    -> { str.force_encoding(str.encoding) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/freeze_spec.rb b/spec/ruby/core/string/freeze_spec.rb
index 04d1e9513c..2e8e70386d 100644
--- a/spec/ruby/core/string/freeze_spec.rb
+++ b/spec/ruby/core/string/freeze_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#freeze" do
diff --git a/spec/ruby/core/string/grapheme_clusters_spec.rb b/spec/ruby/core/string/grapheme_clusters_spec.rb
index 0cba0e4216..380a245083 100644
--- a/spec/ruby/core/string/grapheme_clusters_spec.rb
+++ b/spec/ruby/core/string/grapheme_clusters_spec.rb
@@ -1,15 +1,14 @@
+require_relative "../../spec_helper"
 require_relative 'shared/chars'
 require_relative 'shared/grapheme_clusters'
 
-ruby_version_is "2.5" do
-  describe "String#grapheme_clusters" do
-    it_behaves_like :string_chars, :grapheme_clusters
-    it_behaves_like :string_grapheme_clusters, :grapheme_clusters
+describe "String#grapheme_clusters" do
+  it_behaves_like :string_chars, :grapheme_clusters
+  it_behaves_like :string_grapheme_clusters, :grapheme_clusters
 
-    it "returns an array when no block given" do
-      string = "ab\u{1f3f3}\u{fe0f}\u{200d}\u{1f308}\u{1F43E}"
-      string.grapheme_clusters.should == ['a', 'b', "\u{1f3f3}\u{fe0f}\u{200d}\u{1f308}", "\u{1F43E}"]
+  it "returns an array when no block given" do
+    string = "ab\u{1f3f3}\u{fe0f}\u{200d}\u{1f308}\u{1F43E}"
+    string.grapheme_clusters.should == ['a', 'b', "\u{1f3f3}\u{fe0f}\u{200d}\u{1f308}", "\u{1F43E}"]
 
-    end
   end
 end
diff --git a/spec/ruby/core/string/gsub_spec.rb b/spec/ruby/core/string/gsub_spec.rb
index cd66a4f875..0d9f32eca2 100644
--- a/spec/ruby/core/string/gsub_spec.rb
+++ b/spec/ruby/core/string/gsub_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -160,52 +161,12 @@ describe "String#gsub with pattern and replacement" do
 
   it_behaves_like :string_gsub_named_capture, :gsub
 
-  it "taints the result if the original string or replacement is tainted" do
-    hello = "hello"
-    hello_t = "hello"
-    a = "a"
-    a_t = "a"
-    empty = ""
-    empty_t = ""
-
-    hello_t.taint; a_t.taint; empty_t.taint
-
-    hello_t.gsub(/./, a).tainted?.should == true
-    hello_t.gsub(/./, empty).tainted?.should == true
-
-    hello.gsub(/./, a_t).tainted?.should == true
-    hello.gsub(/./, empty_t).tainted?.should == true
-    hello.gsub(//, empty_t).tainted?.should == true
-
-    hello.gsub(//.taint, "foo").tainted?.should == false
-  end
-
   it "handles pattern collapse" do
     str = "こにちわ"
     reg = %r!!
     str.gsub(reg, ".").should == ".こ.に.ち.わ."
   end
 
-  it "untrusts the result if the original string or replacement is untrusted" do
-    hello = "hello"
-    hello_t = "hello"
-    a = "a"
-    a_t = "a"
-    empty = ""
-    empty_t = ""
-
-    hello_t.untrust; a_t.untrust; empty_t.untrust
-
-    hello_t.gsub(/./, a).untrusted?.should == true
-    hello_t.gsub(/./, empty).untrusted?.should == true
-
-    hello.gsub(/./, a_t).untrusted?.should == true
-    hello.gsub(/./, empty_t).untrusted?.should == true
-    hello.gsub(//, empty_t).untrusted?.should == true
-
-    hello.gsub(//.untrust, "foo").untrusted?.should == false
-  end
-
   it "tries to convert pattern to a string using to_str" do
     pattern = mock('.')
     def pattern.to_str() "." end
@@ -232,15 +193,13 @@ describe "String#gsub with pattern and replacement" do
     -> { "hello".gsub(/[aeiou]/, nil)           }.should raise_error(TypeError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("").gsub(//, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("").gsub(/foo/, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").gsub(/foo/, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").gsub("foo", "").should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("").gsub(//, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("").gsub(/foo/, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").gsub(/foo/, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").gsub("foo", "").should be_an_instance_of(String)
   end
 
-  # Note: $~ cannot be tested because mspec messes with it
-
   it "sets $~ to MatchData of last match and nil when there's none" do
     'hello.'.gsub('hello', 'x')
     $~[0].should == 'hello'
@@ -254,6 +213,18 @@ describe "String#gsub with pattern and replacement" do
     'hello.'.gsub(/not/, 'x')
     $~.should == nil
   end
+
+  it "handles a pattern in a superset encoding" do
+    result = 'abc'.force_encoding(Encoding::US_ASCII).gsub('é', 'è')
+    result.should == 'abc'
+    result.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    result = 'été'.gsub('t'.force_encoding(Encoding::US_ASCII), 'u')
+    result.should == 'éué'
+    result.encoding.should == Encoding::UTF_8
+  end
 end
 
 describe "String#gsub with pattern and Hash" do
@@ -321,27 +292,6 @@ describe "String#gsub with pattern and Hash" do
     repl = '\& \0 \1 \` \\\' \+ \\\\ foo'
     "hello".gsub(/(.+)/, 'hello' => repl ).should == repl
   end
-
-  it "untrusts the result if the original string is untrusted" do
-    str = "Ghana".untrust
-    str.gsub(/[Aa]na/, 'ana' => '').untrusted?.should be_true
-  end
-
-  it "untrusts the result if a hash value is untrusted" do
-    str = "Ghana"
-    str.gsub(/a$/, 'a' => 'di'.untrust).untrusted?.should be_true
-  end
-
-  it "taints the result if the original string is tainted" do
-    str = "Ghana".taint
-    str.gsub(/[Aa]na/, 'ana' => '').tainted?.should be_true
-  end
-
-  it "taints the result if a hash value is tainted" do
-    str = "Ghana"
-    str.gsub(/a$/, 'a' => 'di'.taint).tainted?.should be_true
-  end
-
 end
 
 describe "String#gsub! with pattern and Hash" do
@@ -410,27 +360,6 @@ describe "String#gsub! with pattern and Hash" do
     repl = '\& \0 \1 \` \\\' \+ \\\\ foo'
     "hello".gsub!(/(.+)/, 'hello' => repl ).should == repl
   end
-
-  it "keeps untrusted state" do
-    str = "Ghana".untrust
-    str.gsub!(/[Aa]na/, 'ana' => '').untrusted?.should be_true
-  end
-
-  it "untrusts self if a hash value is untrusted" do
-    str = "Ghana"
-    str.gsub!(/a$/, 'a' => 'di'.untrust).untrusted?.should be_true
-  end
-
-  it "keeps tainted state" do
-    str = "Ghana".taint
-    str.gsub!(/[Aa]na/, 'ana' => '').tainted?.should be_true
-  end
-
-  it "taints self if a hash value is tainted" do
-    str = "Ghana"
-    str.gsub!(/a$/, 'a' => 'di'.taint).tainted?.should be_true
-  end
-
 end
 
 describe "String#gsub with pattern and block" do
@@ -458,6 +387,11 @@ describe "String#gsub with pattern and block" do
     offsets.should == [[1, 2], [4, 5]]
   end
 
+  it "does not set $~ for procs created from methods" do
+    str = "hello"
+    str.gsub("l", &StringSpecs::SpecialVarProcessor.new.method(:process)).should == "he<unset><unset>o"
+  end
+
   it "restores $~ after leaving the block" do
     [/./, "l"].each do |pattern|
       old_md = nil
@@ -504,26 +438,6 @@ describe "String#gsub with pattern and block" do
     "hello".gsub(/.+/) { obj }.should == "ok"
   end
 
-  it "untrusts the result if the original string or replacement is untrusted" do
-    hello = "hello"
-    hello_t = "hello"
-    a = "a"
-    a_t = "a"
-    empty = ""
-    empty_t = ""
-
-    hello_t.untrust; a_t.untrust; empty_t.untrust
-
-    hello_t.gsub(/./) { a }.untrusted?.should == true
-    hello_t.gsub(/./) { empty }.untrusted?.should == true
-
-    hello.gsub(/./) { a_t }.untrusted?.should == true
-    hello.gsub(/./) { empty_t }.untrusted?.should == true
-    hello.gsub(//) { empty_t }.untrusted?.should == true
-
-    hello.gsub(//.untrust) { "foo" }.untrusted?.should == false
-  end
-
   it "uses the compatible encoding if they are compatible" do
     s  = "hello"
     s2 = "#{195.chr}#{192.chr}#{195.chr}"
@@ -570,6 +484,14 @@ describe "String#gsub with pattern and without replacement and block" do
   end
 end
 
+describe "String#gsub with a string pattern" do
+  it "handles multibyte characters" do
+    "é".gsub("é", "â").should == "â"
+    "aé".gsub("é", "â").should == "aâ"
+    "éa".gsub("é", "â").should == "âa"
+  end
+end
+
 describe "String#gsub! with pattern and replacement" do
   it "modifies self in place and returns self" do
     a = "hello"
@@ -583,18 +505,6 @@ describe "String#gsub! with pattern and replacement" do
     a.should == "*¿** **é*?*"
   end
 
-  it "taints self if replacement is tainted" do
-    a = "hello"
-    a.gsub!(/./.taint, "foo").tainted?.should == false
-    a.gsub!(/./, "foo".taint).tainted?.should == true
-  end
-
-  it "untrusts self if replacement is untrusted" do
-    a = "hello"
-    a.gsub!(/./.untrust, "foo").untrusted?.should == false
-    a.gsub!(/./, "foo".untrust).untrusted?.should == true
-  end
-
   it "returns nil if no modifications were made" do
     a = "hello"
     a.gsub!(/z/, '*').should == nil
@@ -603,13 +513,34 @@ describe "String#gsub! with pattern and replacement" do
   end
 
   # See [ruby-core:23666]
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     s = "hello"
     s.freeze
 
-    -> { s.gsub!(/ROAR/, "x")    }.should raise_error(frozen_error_class)
-    -> { s.gsub!(/e/, "e")       }.should raise_error(frozen_error_class)
-    -> { s.gsub!(/[aeiou]/, '*') }.should raise_error(frozen_error_class)
+    -> { s.gsub!(/ROAR/, "x")    }.should raise_error(FrozenError)
+    -> { s.gsub!(/e/, "e")       }.should raise_error(FrozenError)
+    -> { s.gsub!(/[aeiou]/, '*') }.should raise_error(FrozenError)
+  end
+
+  it "handles a pattern in a superset encoding" do
+    string = 'abc'.force_encoding(Encoding::US_ASCII)
+
+    result = string.gsub!('é', 'è')
+
+    result.should == nil
+    string.should == 'abc'
+    string.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    string = 'été'
+    pattern = 't'.force_encoding(Encoding::US_ASCII)
+
+    result = string.gsub!(pattern, 'u')
+
+    result.should == string
+    string.should == 'éué'
+    string.encoding.should == Encoding::UTF_8
   end
 end
 
@@ -620,18 +551,6 @@ describe "String#gsub! with pattern and block" do
     a.should == "h*ll*"
   end
 
-  it "taints self if block's result is tainted" do
-    a = "hello"
-    a.gsub!(/./.taint) { "foo" }.tainted?.should == false
-    a.gsub!(/./) { "foo".taint }.tainted?.should == true
-  end
-
-  it "untrusts self if block's result is untrusted" do
-    a = "hello"
-    a.gsub!(/./.untrust) { "foo" }.untrusted?.should == false
-    a.gsub!(/./) { "foo".untrust }.untrusted?.should == true
-  end
-
   it "returns nil if no modifications were made" do
     a = "hello"
     a.gsub!(/z/) { '*' }.should == nil
@@ -640,13 +559,13 @@ describe "String#gsub! with pattern and block" do
   end
 
   # See [ruby-core:23663]
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     s = "hello"
     s.freeze
 
-    -> { s.gsub!(/ROAR/)    { "x" } }.should raise_error(frozen_error_class)
-    -> { s.gsub!(/e/)       { "e" } }.should raise_error(frozen_error_class)
-    -> { s.gsub!(/[aeiou]/) { '*' } }.should raise_error(frozen_error_class)
+    -> { s.gsub!(/ROAR/)    { "x" } }.should raise_error(FrozenError)
+    -> { s.gsub!(/e/)       { "e" } }.should raise_error(FrozenError)
+    -> { s.gsub!(/[aeiou]/) { '*' } }.should raise_error(FrozenError)
   end
 
   it "uses the compatible encoding if they are compatible" do
diff --git a/spec/ruby/core/string/include_spec.rb b/spec/ruby/core/string/include_spec.rb
index e32eb17c29..9781140a55 100644
--- a/spec/ruby/core/string/include_spec.rb
+++ b/spec/ruby/core/string/include_spec.rb
@@ -13,6 +13,20 @@ describe "String#include? with String" do
     StringSpecs::MyString.new("hello").include?(StringSpecs::MyString.new("lo")).should == true
   end
 
+  it "returns true if both strings are empty" do
+    "".should.include?("")
+    "".dup.force_encoding("EUC-JP").should.include?("")
+    "".should.include?("".dup.force_encoding("EUC-JP"))
+    "".dup.force_encoding("EUC-JP").should.include?("".dup.force_encoding("EUC-JP"))
+  end
+
+  it "returns true if the RHS is empty" do
+    "a".should.include?("")
+    "a".dup.force_encoding("EUC-JP").should.include?("")
+    "a".should.include?("".dup.force_encoding("EUC-JP"))
+    "a".dup.force_encoding("EUC-JP").should.include?("".dup.force_encoding("EUC-JP"))
+  end
+
   it "tries to convert other to string using to_str" do
     other = mock('lo')
     other.should_receive(:to_str).and_return("lo")
diff --git a/spec/ruby/core/string/index_spec.rb b/spec/ruby/core/string/index_spec.rb
index ca62911db0..835263a2cd 100644
--- a/spec/ruby/core/string/index_spec.rb
+++ b/spec/ruby/core/string/index_spec.rb
@@ -27,7 +27,7 @@ describe "String#index" do
     "abc".index("c", offset).should == 2
   end
 
-  it "raises a TypeError if passed a Fixnum" do
+  it "raises a TypeError if passed an Integer" do
     -> { "abc".index 97 }.should raise_error(TypeError)
   end
 end
@@ -146,6 +146,7 @@ describe "String#index with String" do
 
   it "returns the character index after offset" do
     "われわれ".index("わ", 1).should == 2
+    "ありがとうありがとう".index("が", 3).should == 7
   end
 
   it "returns the character index after a partial first match" do
@@ -158,6 +159,21 @@ describe "String#index with String" do
       "あれ".index char
     end.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.dup.force_encoding(Encoding::US_ASCII).index('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.index('t'.dup.force_encoding(Encoding::US_ASCII)).should == 1
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    str = 'abc'.dup.force_encoding("ISO-2022-JP")
+    pattern = 'b'.dup.force_encoding("EUC-JP")
+
+    -> { str.index(pattern) }.should raise_error(Encoding::CompatibilityError, "incompatible character encodings: ISO-2022-JP and EUC-JP")
+  end
 end
 
 describe "String#index with Regexp" do
@@ -215,6 +231,17 @@ describe "String#index with Regexp" do
     $~.should == nil
   end
 
+  ruby_bug "#20421", ""..."3.3" do
+    it "always clear $~" do
+      "a".index(/a/)
+      $~.should_not == nil
+
+      string = "blablabla"
+      string.index(/bla/, string.length + 1)
+      $~.should == nil
+    end
+  end
+
   it "starts the search at the given offset" do
     "blablabla".index(/.{0}/, 5).should == 5
     "blablabla".index(/.{1}/, 5).should == 5
@@ -303,6 +330,17 @@ describe "String#index with Regexp" do
     "われわわれ".index(/わ/, 3).should == 3
   end
 
+  ruby_bug "#19763", ""..."3.3.0" do
+    it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+      re = Regexp.new "れ".encode(Encoding::EUC_JP)
+      -> do
+        "あれ".index re
+      end.should raise_error(Encoding::CompatibilityError, "incompatible encoding regexp match (EUC-JP regexp with UTF-8 string)")
+    end
+  end
+
+  # The exception message was incorrectly "incompatible character encodings: UTF-8 and EUC-JP" before 3.3.0
+  # Still test that the right exception class is used before that.
   it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
     re = Regexp.new "れ".encode(Encoding::EUC_JP)
     -> do
diff --git a/spec/ruby/core/string/insert_spec.rb b/spec/ruby/core/string/insert_spec.rb
index 588b8ab272..483f3c9367 100644
--- a/spec/ruby/core/string/insert_spec.rb
+++ b/spec/ruby/core/string/insert_spec.rb
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -41,26 +41,16 @@ describe "String#insert with index, other" do
     "abcd".insert(-3, other).should == "abXYZcd"
   end
 
-  it "taints self if string to insert is tainted" do
-    str = "abcd"
-    str.insert(0, "T".taint).tainted?.should == true
-
-    str = "abcd"
-    other = mock('T')
-    def other.to_str() "T".taint end
-    str.insert(0, other).tainted?.should == true
-  end
-
   it "raises a TypeError if other can't be converted to string" do
     -> { "abcd".insert(-6, Object.new)}.should raise_error(TypeError)
     -> { "abcd".insert(-6, [])        }.should raise_error(TypeError)
     -> { "abcd".insert(-6, mock('x')) }.should raise_error(TypeError)
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     str = "abcd".freeze
-    -> { str.insert(4, '')  }.should raise_error(frozen_error_class)
-    -> { str.insert(4, 'X') }.should raise_error(frozen_error_class)
+    -> { str.insert(4, '')  }.should raise_error(FrozenError)
+    -> { str.insert(4, 'X') }.should raise_error(FrozenError)
   end
 
   it "inserts a character into a multibyte encoded string" do
@@ -79,4 +69,13 @@ describe "String#insert with index, other" do
       "あれ".insert 0, pat
     end.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "should not call subclassed string methods" do
+    cls = Class.new(String) do
+      def replace(arg)
+        raise "should not call replace"
+      end
+    end
+    cls.new("abcd").insert(0, 'X').should == "Xabcd"
+  end
 end
diff --git a/spec/ruby/core/string/inspect_spec.rb b/spec/ruby/core/string/inspect_spec.rb
index c1674c73c8..15db06c7f5 100644
--- a/spec/ruby/core/string/inspect_spec.rb
+++ b/spec/ruby/core/string/inspect_spec.rb
@@ -3,16 +3,6 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "String#inspect" do
-  it "taints the result if self is tainted" do
-    "foo".taint.inspect.tainted?.should == true
-    "foo\n".taint.inspect.tainted?.should == true
-  end
-
-  it "untrusts the result if self is untrusted" do
-    "foo".untrust.inspect.untrusted?.should == true
-    "foo\n".untrust.inspect.untrusted?.should == true
-  end
-
   it "does not return a subclass instance" do
     StringSpecs::MyString.new.inspect.should be_an_instance_of(String)
   end
@@ -29,6 +19,21 @@ describe "String#inspect" do
     ].should be_computed_by(:inspect)
   end
 
+  it "returns a string with special characters replaced with \\<char> notation for UTF-16" do
+    pairs = [
+      ["\a", '"\\a"'],
+      ["\b", '"\\b"'],
+      ["\t", '"\\t"'],
+      ["\n", '"\\n"'],
+      ["\v", '"\\v"'],
+      ["\f", '"\\f"'],
+      ["\r", '"\\r"'],
+      ["\e", '"\\e"']
+    ].map { |str, result| [str.encode('UTF-16LE'), result] }
+
+    pairs.should be_computed_by(:inspect)
+  end
+
   it "returns a string with \" and \\ escaped with a backslash" do
     [ ["\"", '"\\""'],
       ["\\", '"\\\\"']
@@ -317,6 +322,15 @@ describe "String#inspect" do
     0.chr.inspect.should == '"\\x00"'
   end
 
+  it "uses \\x notation for broken UTF-8 sequences" do
+    "\xF0\x9F".inspect.should == '"\\xF0\\x9F"'
+  end
+
+  it "works for broken US-ASCII strings" do
+    s = "©".dup.force_encoding("US-ASCII")
+    s.inspect.should == '"\xC2\xA9"'
+  end
+
   describe "when default external is UTF-8" do
     before :each do
       @extenc, Encoding.default_external = Encoding.default_external, Encoding::UTF_8
@@ -496,5 +510,11 @@ describe "String#inspect" do
         "\u{3042}".encode("EUC-JP").inspect.should == '"\\x{A4A2}"'
       end
     end
+
+    describe "and the string has both ASCII-compatible and ASCII-incompatible chars" do
+      it "returns a string with the non-ASCII characters replaced by \\u notation" do
+        "hello привет".encode("utf-16le").inspect.should == '"hello \\u043F\\u0440\\u0438\\u0432\\u0435\\u0442"'
+      end
+    end
   end
 end
diff --git a/spec/ruby/core/string/lines_spec.rb b/spec/ruby/core/string/lines_spec.rb
index ad4b119074..40ab5f71d8 100644
--- a/spec/ruby/core/string/lines_spec.rb
+++ b/spec/ruby/core/string/lines_spec.rb
@@ -1,7 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/each_line'
-require_relative 'shared/each_line_without_block'
 
 describe "String#lines" do
   it_behaves_like :string_each_line, :lines
diff --git a/spec/ruby/core/string/ljust_spec.rb b/spec/ruby/core/string/ljust_spec.rb
index ed4cb86859..47324c59d2 100644
--- a/spec/ruby/core/string/ljust_spec.rb
+++ b/spec/ruby/core/string/ljust_spec.rb
@@ -31,14 +31,6 @@ describe "String#ljust with length, padding" do
     "radiology".ljust(8, '-').should == "radiology"
   end
 
-  it "taints result when self or padstr is tainted" do
-    "x".taint.ljust(4).tainted?.should == true
-    "x".taint.ljust(0).tainted?.should == true
-    "".taint.ljust(0).tainted?.should == true
-    "x".taint.ljust(4, "*").tainted?.should == true
-    "x".ljust(4, "*".taint).tainted?.should == true
-  end
-
   it "tries to convert length to an integer using to_int" do
     "^".ljust(3.8, "_^").should == "^_^"
 
@@ -72,24 +64,18 @@ describe "String#ljust with length, padding" do
     -> { "hello".ljust(10, '') }.should raise_error(ArgumentError)
   end
 
-  it "returns subclass instances when called on subclasses" do
-    StringSpecs::MyString.new("").ljust(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").ljust(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").ljust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on subclasses" do
+    StringSpecs::MyString.new("").ljust(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").ljust(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").ljust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
 
     "".ljust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
     "foo".ljust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
   end
 
-  it "when padding is tainted and self is untainted returns a tainted string if and only if length is longer than self" do
-    "hello".ljust(4, 'X'.taint).tainted?.should be_false
-    "hello".ljust(5, 'X'.taint).tainted?.should be_false
-    "hello".ljust(6, 'X'.taint).tainted?.should be_true
-  end
-
   describe "with width" do
     it "returns a String in the same encoding as the original" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.ljust 5
       result.should == "abc  "
       result.encoding.should equal(Encoding::IBM437)
@@ -98,7 +84,7 @@ describe "String#ljust with length, padding" do
 
   describe "with width, pattern" do
     it "returns a String in the compatible encoding" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.ljust 5, "あ"
       result.should == "abcああ"
       result.encoding.should equal(Encoding::UTF_8)
diff --git a/spec/ruby/core/string/lstrip_spec.rb b/spec/ruby/core/string/lstrip_spec.rb
index 7f9363d398..c83650207e 100644
--- a/spec/ruby/core/string/lstrip_spec.rb
+++ b/spec/ruby/core/string/lstrip_spec.rb
@@ -1,23 +1,29 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/strip'
 
 describe "String#lstrip" do
+  it_behaves_like :string_strip, :lstrip
+
   it "returns a copy of self with leading whitespace removed" do
-   "  hello  ".lstrip.should == "hello  "
-   "  hello world  ".lstrip.should == "hello world  "
-   "\n\r\t\n\v\r hello world  ".lstrip.should == "hello world  "
-   "hello".lstrip.should == "hello"
-   "\000 \000hello\000 \000".lstrip.should == "\000 \000hello\000 \000"
+    "  hello  ".lstrip.should == "hello  "
+    "  hello world  ".lstrip.should == "hello world  "
+    "\n\r\t\n\v\r hello world  ".lstrip.should == "hello world  "
+    "hello".lstrip.should == "hello"
+    " こにちわ".lstrip.should == "こにちわ"
   end
 
-  it "does not strip leading \\0" do
-   "\x00hello".lstrip.should == "\x00hello"
+  it "works with lazy substrings" do
+    "  hello  "[1...-1].lstrip.should == "hello "
+    "  hello world  "[1...-1].lstrip.should == "hello world "
+    "\n\r\t\n\v\r hello world  "[1...-1].lstrip.should == "hello world "
+    "   こにちわ "[1...-1].lstrip.should == "こにちわ"
   end
 
-  it "taints the result when self is tainted" do
-    "".taint.lstrip.tainted?.should == true
-    "ok".taint.lstrip.tainted?.should == true
-    "   ok".taint.lstrip.tainted?.should == true
+  it "strips leading \\0" do
+    "\x00hello".lstrip.should == "hello"
+    "\000 \000hello\000 \000".lstrip.should == "hello\000 \000"
   end
 end
 
@@ -26,10 +32,6 @@ describe "String#lstrip!" do
     a = "  hello  "
     a.lstrip!.should equal(a)
     a.should == "hello  "
-
-    a = "\000 \000hello\000 \000"
-    a.lstrip!
-    a.should == "\000 \000hello\000 \000"
   end
 
   it "returns nil if no modifications were made" do
@@ -38,13 +40,35 @@ describe "String#lstrip!" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "  hello  ".freeze.lstrip! }.should raise_error(frozen_error_class)
+  it "makes a string empty if it is only whitespace" do
+    "".lstrip!.should == nil
+    " ".lstrip.should == ""
+    "  ".lstrip.should == ""
+  end
+
+  it "removes leading NULL bytes and whitespace" do
+    a = "\000 \000hello\000 \000"
+    a.lstrip!
+    a.should == "hello\000 \000"
+  end
+
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "  hello  ".freeze.lstrip! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23657]
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> { "hello".freeze.lstrip! }.should raise_error(frozen_error_class)
-    -> { "".freeze.lstrip!      }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> { "hello".freeze.lstrip! }.should raise_error(FrozenError)
+    -> { "".freeze.lstrip!      }.should raise_error(FrozenError)
+  end
+
+  it "raises an ArgumentError if the first non-space codepoint is invalid" do
+    s = "\xDFabc".force_encoding(Encoding::UTF_8)
+    s.valid_encoding?.should be_false
+    -> { s.lstrip! }.should raise_error(ArgumentError)
+
+    s = "   \xDFabc".force_encoding(Encoding::UTF_8)
+    s.valid_encoding?.should be_false
+    -> { s.lstrip! }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/core/string/match_spec.rb b/spec/ruby/core/string/match_spec.rb
index 78b94baa44..5e988f34ca 100644
--- a/spec/ruby/core/string/match_spec.rb
+++ b/spec/ruby/core/string/match_spec.rb
@@ -137,7 +137,7 @@ describe "String#match" do
   end
 
   it "calls match on the regular expression" do
-    regexp = /./
+    regexp = /./.dup
     regexp.should_receive(:match).and_return(:foo)
     'hello'.match(regexp).should == :foo
   end
diff --git a/spec/ruby/core/string/modulo_spec.rb b/spec/ruby/core/string/modulo_spec.rb
index 0ac0963403..46e0aa0f36 100644
--- a/spec/ruby/core/string/modulo_spec.rb
+++ b/spec/ruby/core/string/modulo_spec.rb
@@ -1,8 +1,22 @@
 require_relative '../../spec_helper'
+require_relative '../kernel/shared/sprintf'
+require_relative '../kernel/shared/sprintf_encoding'
 require_relative 'fixtures/classes'
 require_relative '../../shared/hash/key_error'
 
 describe "String#%" do
+  it_behaves_like :kernel_sprintf, -> format, *args {
+    format % args
+  }
+
+  it_behaves_like :kernel_sprintf_encoding, -> format, *args {
+    format % args
+  }
+end
+
+# TODO: these specs are mostly redundant with kernel/shared/sprintf.rb specs.
+# These specs should be moved there and deduplicated.
+describe "String#%" do
   context "when key is missing from passed-in hash" do
     it_behaves_like :key_error, -> obj, key { "%{#{key}}" % obj }, { a: 5 }
   end
@@ -36,47 +50,53 @@ describe "String#%" do
     end
   end
 
-  ruby_version_is ""..."2.5" do
-    it "formats single % character at the end as literal %" do
-      ("%" % []).should == "%"
-      ("foo%" % []).should == "foo%"
-    end
+  it "raises an error if single % appears at the end" do
+    -> { ("%" % []) }.should raise_error(ArgumentError)
+    -> { ("foo%" % [])}.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.5" do
-    it "raises an error if single % appears at the end" do
-      -> { ("%" % []) }.should raise_error(ArgumentError)
-      -> { ("foo%" % [])}.should raise_error(ArgumentError)
+  ruby_version_is ""..."3.4" do
+    it "formats single % character before a newline as literal %" do
+      ("%\n" % []).should == "%\n"
+      ("foo%\n" % []).should == "foo%\n"
+      ("%\n.3f" % 1.2).should == "%\n.3f"
     end
-  end
 
-  it "formats single % character before a newline as literal %" do
-    ("%\n" % []).should == "%\n"
-    ("foo%\n" % []).should == "foo%\n"
-    ("%\n.3f" % 1.2).should == "%\n.3f"
-  end
+    it "formats single % character before a NUL as literal %" do
+      ("%\0" % []).should == "%\0"
+      ("foo%\0" % []).should == "foo%\0"
+      ("%\0.3f" % 1.2).should == "%\0.3f"
+    end
 
-  it "formats single % character before a NUL as literal %" do
-    ("%\0" % []).should == "%\0"
-    ("foo%\0" % []).should == "foo%\0"
-    ("%\0.3f" % 1.2).should == "%\0.3f"
-  end
+    it "raises an error if single % appears anywhere else" do
+      -> { (" % " % []) }.should raise_error(ArgumentError)
+      -> { ("foo%quux" % []) }.should raise_error(ArgumentError)
+    end
 
-  it "raises an error if single % appears anywhere else" do
-    -> { (" % " % []) }.should raise_error(ArgumentError)
-    -> { ("foo%quux" % []) }.should raise_error(ArgumentError)
-  end
+    it "raises an error if NULL or \\n appear anywhere else in the format string" do
+      begin
+        old_debug, $DEBUG = $DEBUG, false
 
-  it "raises an error if NULL or \\n appear anywhere else in the format string" do
-    begin
-      old_debug, $DEBUG = $DEBUG, false
+        -> { "%.\n3f" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.3\nf" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.\03f" % 1.2 }.should raise_error(ArgumentError)
+        -> { "%.3\0f" % 1.2 }.should raise_error(ArgumentError)
+      ensure
+        $DEBUG = old_debug
+      end
+    end
+  end
 
+  ruby_version_is "3.4" do
+    it "raises an ArgumentError if % is not followed by a conversion specifier" do
+      -> { "%" % [] }.should raise_error(ArgumentError)
+      -> { "%\n" % [] }.should raise_error(ArgumentError)
+      -> { "%\0" % [] }.should raise_error(ArgumentError)
+      -> { " % " % [] }.should raise_error(ArgumentError)
       -> { "%.\n3f" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.3\nf" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.\03f" % 1.2 }.should raise_error(ArgumentError)
       -> { "%.3\0f" % 1.2 }.should raise_error(ArgumentError)
-    ensure
-      $DEBUG = old_debug
     end
   end
 
@@ -120,8 +140,16 @@ describe "String#%" do
     end
   end
 
-  it "replaces trailing absolute argument specifier without type with percent sign" do
-    ("hello %1$" % "foo").should == "hello %"
+  ruby_version_is ""..."3.4" do
+    it "replaces trailing absolute argument specifier without type with percent sign" do
+      ("hello %1$" % "foo").should == "hello %"
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "raises an ArgumentError if absolute argument specifier is followed by a conversion specifier" do
+      -> { "hello %1$" % "foo" }.should raise_error(ArgumentError)
+    end
   end
 
   it "raises an ArgumentError when given invalid argument specifiers" do
@@ -297,27 +325,6 @@ describe "String#%" do
     end
   end
 
-  it "always taints the result when the format string is tainted" do
-    universal = mock('0')
-    def universal.to_int() 0 end
-    def universal.to_str() "0" end
-    def universal.to_f() 0.0 end
-
-    [
-      "", "foo",
-      "%b", "%B", "%c", "%d", "%e", "%E",
-      "%f", "%g", "%G", "%i", "%o", "%p",
-      "%s", "%u", "%x", "%X"
-    ].each do |format|
-      subcls_format = StringSpecs::MyString.new(format)
-      subcls_format.taint
-      format.taint
-
-      (format % universal).tainted?.should == true
-      (subcls_format % universal).tainted?.should == true
-    end
-  end
-
   it "supports binary formats using %b for positive numbers" do
     ("%b" % 10).should == "1010"
     ("% b" % 10).should == " 1010"
@@ -384,8 +391,8 @@ describe "String#%" do
     ("%c" % 'A').should == "A"
   end
 
-  it "raises an exception for multiple character strings as argument for %c" do
-    -> { "%c" % 'AA' }.should raise_error(ArgumentError)
+  it "supports only the first character as argument for %c" do
+    ("%c" % 'AA').should == "A"
   end
 
   it "calls to_str on argument for %c formats" do
@@ -555,7 +562,7 @@ describe "String#%" do
     ("%1$p" % [10, 5]).should == "10"
     ("%-22p" % 10).should == "10                    "
     ("%*p" % [10, 10]).should == "        10"
-    ("%p" % {capture: 1}).should == "{:capture=>1}"
+    ("%p" % {capture: 1}).should == {capture: 1}.inspect
     ("%p" % "str").should == "\"str\""
   end
 
@@ -571,18 +578,6 @@ describe "String#%" do
     # ("%p" % obj).should == "obj"
   end
 
-  it "taints result for %p when argument.inspect is tainted" do
-    obj = mock('x')
-    def obj.inspect() "x".taint end
-
-    ("%p" % obj).tainted?.should == true
-
-    obj = mock('x'); obj.taint
-    def obj.inspect() "x" end
-
-    ("%p" % obj).tainted?.should == false
-  end
-
   it "supports string formats using %s" do
     ("%s" % "hello").should == "hello"
     ("%s" % "").should == ""
@@ -611,11 +606,6 @@ describe "String#%" do
     # ("%s" % obj).should == "obj"
   end
 
-  it "taints result for %s when argument is tainted" do
-    ("%s" % "x".taint).tainted?.should == true
-    ("%s" % mock('x').taint).tainted?.should == true
-  end
-
   # MRI crashes on this one.
   # See http://groups.google.com/group/ruby-core-google/t/c285c18cd94c216d
   it "raises an ArgumentError for huge precisions for %s" do
@@ -751,6 +741,11 @@ describe "String#%" do
       (format % "-10.4e-20").should == (format % -10.4e-20)
       (format % ".5").should == (format % 0.5)
       (format % "-.5").should == (format % -0.5)
+
+      ruby_version_is "3.4" do
+        (format % "10.").should == (format % 10)
+      end
+
       # Something's strange with this spec:
       # it works just fine in individual mode, but not when run as part of a group
       (format % "10_1_0.5_5_5").should == (format % 1010.555)
@@ -760,7 +755,6 @@ describe "String#%" do
       -> { format % "" }.should raise_error(ArgumentError)
       -> { format % "x" }.should raise_error(ArgumentError)
       -> { format % "." }.should raise_error(ArgumentError)
-      -> { format % "10." }.should raise_error(ArgumentError)
       -> { format % "5x" }.should raise_error(ArgumentError)
       -> { format % "0b1" }.should raise_error(ArgumentError)
       -> { format % "10e10.5" }.should raise_error(ArgumentError)
@@ -775,10 +769,6 @@ describe "String#%" do
     it "behaves as if calling Kernel#Float for #{format} arguments, when the passed argument is hexadecimal string" do
       (format % "0xA").should == (format % 0xA)
     end
-
-    it "doesn't taint the result for #{format} when argument is tainted" do
-      (format % "5".taint).tainted?.should == false
-    end
   end
 
   describe "when format string contains %{} sections" do
diff --git a/spec/ruby/core/string/ord_spec.rb b/spec/ruby/core/string/ord_spec.rb
index 0f5a3f6a37..35af3b5458 100644
--- a/spec/ruby/core/string/ord_spec.rb
+++ b/spec/ruby/core/string/ord_spec.rb
@@ -1,8 +1,8 @@
 require_relative '../../spec_helper'
 
 describe "String#ord" do
-  it "returns a Fixnum" do
-    'a'.ord.should be_an_instance_of(Fixnum)
+  it "returns an Integer" do
+    'a'.ord.should be_an_instance_of(Integer)
   end
 
   it "returns the codepoint of the first character in the String" do
@@ -25,4 +25,9 @@ describe "String#ord" do
   it "raises an ArgumentError if called on an empty String" do
     -> { ''.ord }.should raise_error(ArgumentError)
   end
+
+  it "raises ArgumentError if the character is broken" do
+    s = "©".dup.force_encoding("US-ASCII")
+    -> { s.ord }.should raise_error(ArgumentError, "invalid byte sequence in US-ASCII")
+  end
 end
diff --git a/spec/ruby/core/string/partition_spec.rb b/spec/ruby/core/string/partition_spec.rb
index 996368d6a4..d5370dcc73 100644
--- a/spec/ruby/core/string/partition_spec.rb
+++ b/spec/ruby/core/string/partition_spec.rb
@@ -1,7 +1,10 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/partition'
 
 describe "String#partition with String" do
+  it_behaves_like :string_partition, :partition
+
   it "returns an array of substrings based on splitting on the given string" do
     "hello world".partition("o").should == ["hell", "o", " world"]
   end
@@ -35,4 +38,26 @@ describe "String#partition with String" do
   it "takes precedence over a given block" do
     "hello world".partition("o") { true }.should == ["hell", "o", " world"]
   end
+
+  it "handles a pattern in a superset encoding" do
+    string = "hello".dup.force_encoding(Encoding::US_ASCII)
+
+    result = string.partition("é")
+
+    result.should == ["hello", "", ""]
+    result[0].encoding.should == Encoding::US_ASCII
+    result[1].encoding.should == Encoding::US_ASCII
+    result[2].encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    pattern = "o".dup.force_encoding(Encoding::US_ASCII)
+
+    result = "héllo world".partition(pattern)
+
+    result.should == ["héll", "o", " world"]
+    result[0].encoding.should == Encoding::UTF_8
+    result[1].encoding.should == Encoding::US_ASCII
+    result[2].encoding.should == Encoding::UTF_8
+  end
 end
diff --git a/spec/ruby/core/string/percent_spec.rb b/spec/ruby/core/string/percent_spec.rb
deleted file mode 100644
index e3460522b1..0000000000
--- a/spec/ruby/core/string/percent_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../kernel/shared/sprintf'
-require_relative '../kernel/shared/sprintf_encoding'
-
-describe "String#%" do
-  it_behaves_like :kernel_sprintf, -> format, *args {
-    format % args
-  }
-
-  it_behaves_like :kernel_sprintf_encoding, -> format, *args {
-    format % args
-  }
-end
diff --git a/spec/ruby/core/string/plus_spec.rb b/spec/ruby/core/string/plus_spec.rb
index b8e3bf0a4b..9da17451c6 100644
--- a/spec/ruby/core/string/plus_spec.rb
+++ b/spec/ruby/core/string/plus_spec.rb
@@ -3,6 +3,9 @@ require_relative 'fixtures/classes'
 require_relative 'shared/concat'
 
 describe "String#+" do
+  it_behaves_like :string_concat_encoding, :+
+  it_behaves_like :string_concat_type_coercion, :+
+
   it "returns a new string containing the given string concatenated to self" do
     ("" + "").should == ""
     ("" + "Hello").should == "Hello"
@@ -31,17 +34,4 @@ describe "String#+" do
     ("hello" + StringSpecs::MyString.new("foo")).should be_an_instance_of(String)
     ("hello" + StringSpecs::MyString.new("")).should be_an_instance_of(String)
   end
-
-  it "taints the result when self or other is tainted" do
-    strs = ["", "OK", StringSpecs::MyString.new(""), StringSpecs::MyString.new("OK")]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      strs.each do |other|
-        (str + other).tainted?.should == (str.tainted? | other.tainted?)
-      end
-    end
-  end
-
-  it_behaves_like :string_concat_encoding, :+
 end
diff --git a/spec/ruby/core/string/prepend_spec.rb b/spec/ruby/core/string/prepend_spec.rb
index 485c578e2d..5248ea8056 100644
--- a/spec/ruby/core/string/prepend_spec.rb
+++ b/spec/ruby/core/string/prepend_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -20,12 +21,12 @@ describe "String#prepend" do
     -> { 'hello '.prepend mock('x') }.should raise_error(TypeError)
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     a = "hello"
     a.freeze
 
-    -> { a.prepend "" }.should raise_error(frozen_error_class)
-    -> { a.prepend "test" }.should raise_error(frozen_error_class)
+    -> { a.prepend "" }.should raise_error(FrozenError)
+    -> { a.prepend "test" }.should raise_error(FrozenError)
   end
 
   it "works when given a subclass instance" do
@@ -34,14 +35,6 @@ describe "String#prepend" do
     a.should == "hello world"
   end
 
-  it "taints self if other is tainted" do
-    x = "x"
-    x.prepend("".taint).tainted?.should be_true
-
-    x = "x"
-    x.prepend("y".taint).tainted?.should be_true
-  end
-
   it "takes multiple arguments" do
     str = " world"
     str.prepend "he", "", "llo"
diff --git a/spec/ruby/core/string/reverse_spec.rb b/spec/ruby/core/string/reverse_spec.rb
index 3941ea0521..aa6abe6036 100644
--- a/spec/ruby/core/string/reverse_spec.rb
+++ b/spec/ruby/core/string/reverse_spec.rb
@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: false
 
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
@@ -10,15 +11,27 @@ describe "String#reverse" do
     "".reverse.should == ""
   end
 
-  it "taints the result if self is tainted" do
-    "".taint.reverse.tainted?.should == true
-    "m".taint.reverse.tainted?.should == true
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("stressed").reverse.should be_an_instance_of(String)
+    StringSpecs::MyString.new("m").reverse.should be_an_instance_of(String)
+    StringSpecs::MyString.new("").reverse.should be_an_instance_of(String)
   end
 
   it "reverses a string with multi byte characters" do
     "微軟正黑體".reverse.should == "體黑正軟微"
   end
 
+  it "works with a broken string" do
+    str = "微軟\xDF\xDE正黑體".force_encoding(Encoding::UTF_8)
+
+    str.valid_encoding?.should be_false
+
+    str.reverse.should == "體黑正\xDE\xDF軟微"
+  end
+
+  it "returns a String in the same encoding as self" do
+    "stressed".encode("US-ASCII").reverse.encoding.should == Encoding::US_ASCII
+  end
 end
 
 describe "String#reverse!" do
@@ -30,14 +43,14 @@ describe "String#reverse!" do
     "".reverse!.should == ""
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "anna".freeze.reverse!  }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.reverse! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "anna".freeze.reverse!  }.should raise_error(FrozenError)
+    -> { "hello".freeze.reverse! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> { "".freeze.reverse! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> { "".freeze.reverse! }.should raise_error(FrozenError)
   end
 
   it "reverses a string with multi byte characters" do
@@ -45,4 +58,13 @@ describe "String#reverse!" do
     str.reverse!
     str.should == "體黑正軟微"
   end
+
+  it "works with a broken string" do
+    str = "微軟\xDF\xDE正黑體".force_encoding(Encoding::UTF_8)
+
+    str.valid_encoding?.should be_false
+    str.reverse!
+
+    str.should == "體黑正\xDE\xDF軟微"
+  end
 end
diff --git a/spec/ruby/core/string/rindex_spec.rb b/spec/ruby/core/string/rindex_spec.rb
index e021486bc2..0863a9c3be 100644
--- a/spec/ruby/core/string/rindex_spec.rb
+++ b/spec/ruby/core/string/rindex_spec.rb
@@ -1,16 +1,19 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
-require_relative 'fixtures/utf-8-encoding'
 
 describe "String#rindex with object" do
-  it "raises a TypeError if obj isn't a String, Fixnum or Regexp" do
+  it "raises a TypeError if obj isn't a String or Regexp" do
     not_supported_on :opal do
       -> { "hello".rindex(:sym) }.should raise_error(TypeError)
     end
     -> { "hello".rindex(mock('x')) }.should raise_error(TypeError)
   end
 
+  it "raises a TypeError if obj is an Integer" do
+    -> { "hello".rindex(42) }.should raise_error(TypeError)
+  end
+
   it "doesn't try to convert obj to an integer via to_int" do
     obj = mock('x')
     obj.should_not_receive(:to_int)
@@ -192,6 +195,21 @@ describe "String#rindex with String" do
   it "raises a TypeError when given offset is nil" do
     -> { "str".rindex("st", nil) }.should raise_error(TypeError)
   end
+
+  it "handles a substring in a superset encoding" do
+    'abc'.dup.force_encoding(Encoding::US_ASCII).rindex('é').should == nil
+  end
+
+  it "handles a substring in a subset encoding" do
+    'été'.rindex('t'.dup.force_encoding(Encoding::US_ASCII)).should == 1
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    str = 'abc'.dup.force_encoding("ISO-2022-JP")
+    pattern = 'b'.dup.force_encoding("EUC-JP")
+
+    -> { str.rindex(pattern) }.should raise_error(Encoding::CompatibilityError, "incompatible character encodings: ISO-2022-JP and EUC-JP")
+  end
 end
 
 describe "String#rindex with Regexp" do
@@ -353,14 +371,14 @@ describe "String#rindex with Regexp" do
   end
 
   it "returns the character index before the finish" do
-     "ありがりがとう".rindex("が", 3).should == 2
-     "ありがりがとう".rindex(/が/, 3).should == 2
+    "ありがりがとう".rindex("が", 3).should == 2
+    "ありがりがとう".rindex(/が/, 3).should == 2
   end
 
   it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
     re = Regexp.new "れ".encode(Encoding::EUC_JP)
     -> do
       "あれ".rindex re
-    end.should raise_error(Encoding::CompatibilityError)
+    end.should raise_error(Encoding::CompatibilityError, "incompatible encoding regexp match (EUC-JP regexp with UTF-8 string)")
   end
 end
diff --git a/spec/ruby/core/string/rjust_spec.rb b/spec/ruby/core/string/rjust_spec.rb
index 1ba298e8f3..4ad3e54aea 100644
--- a/spec/ruby/core/string/rjust_spec.rb
+++ b/spec/ruby/core/string/rjust_spec.rb
@@ -31,14 +31,6 @@ describe "String#rjust with length, padding" do
     "radiology".rjust(8, '-').should == "radiology"
   end
 
-  it "taints result when self or padstr is tainted" do
-    "x".taint.rjust(4).tainted?.should == true
-    "x".taint.rjust(0).tainted?.should == true
-    "".taint.rjust(0).tainted?.should == true
-    "x".taint.rjust(4, "*").tainted?.should == true
-    "x".rjust(4, "*".taint).tainted?.should == true
-  end
-
   it "tries to convert length to an integer using to_int" do
     "^".rjust(3.8, "^_").should == "^_^"
 
@@ -72,24 +64,18 @@ describe "String#rjust with length, padding" do
     -> { "hello".rjust(10, '') }.should raise_error(ArgumentError)
   end
 
-  it "returns subclass instances when called on subclasses" do
-    StringSpecs::MyString.new("").rjust(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").rjust(10).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").rjust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on subclasses" do
+    StringSpecs::MyString.new("").rjust(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").rjust(10).should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").rjust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
 
     "".rjust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
     "foo".rjust(10, StringSpecs::MyString.new("x")).should be_an_instance_of(String)
   end
 
-  it "when padding is tainted and self is untainted returns a tainted string if and only if length is longer than self" do
-    "hello".rjust(4, 'X'.taint).tainted?.should be_false
-    "hello".rjust(5, 'X'.taint).tainted?.should be_false
-    "hello".rjust(6, 'X'.taint).tainted?.should be_true
-  end
-
   describe "with width" do
     it "returns a String in the same encoding as the original" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.rjust 5
       result.should == "  abc"
       result.encoding.should equal(Encoding::IBM437)
@@ -98,7 +84,7 @@ describe "String#rjust with length, padding" do
 
   describe "with width, pattern" do
     it "returns a String in the compatible encoding" do
-      str = "abc".force_encoding Encoding::IBM437
+      str = "abc".dup.force_encoding Encoding::IBM437
       result = str.rjust 5, "あ"
       result.should == "ああabc"
       result.encoding.should equal(Encoding::UTF_8)
diff --git a/spec/ruby/core/string/rpartition_spec.rb b/spec/ruby/core/string/rpartition_spec.rb
index c6428636f6..cef0384c73 100644
--- a/spec/ruby/core/string/rpartition_spec.rb
+++ b/spec/ruby/core/string/rpartition_spec.rb
@@ -1,7 +1,10 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/partition'
 
 describe "String#rpartition with String" do
+  it_behaves_like :string_partition, :rpartition
+
   it "returns an array of substrings based on splitting on the given string" do
     "hello world".rpartition("o").should == ["hello w", "o", "rld"]
   end
@@ -11,6 +14,19 @@ describe "String#rpartition with String" do
     "hello".rpartition("hello").should == ["", "hello", ""]
   end
 
+  it "returns original string if regexp doesn't match" do
+    "hello".rpartition("/x/").should == ["", "", "hello"]
+  end
+
+  it "returns new object if doesn't match" do
+    str = "hello"
+    str.rpartition("/no_match/").last.should_not.equal?(str)
+  end
+
+  it "handles multibyte string correctly" do
+    "ユーザ@ドメイン".rpartition(/@/).should == ["ユーザ", "@", "ドメイン"]
+  end
+
   it "accepts regexp" do
     "hello!".rpartition(/l./).should == ["hel", "lo", "!"]
   end
@@ -30,4 +46,26 @@ describe "String#rpartition with String" do
     ->{ "hello".rpartition(5) }.should raise_error(TypeError)
     ->{ "hello".rpartition(nil) }.should raise_error(TypeError)
   end
+
+  it "handles a pattern in a superset encoding" do
+    string = "hello".dup.force_encoding(Encoding::US_ASCII)
+
+    result = string.rpartition("é")
+
+    result.should == ["", "", "hello"]
+    result[0].encoding.should == Encoding::US_ASCII
+    result[1].encoding.should == Encoding::US_ASCII
+    result[2].encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    pattern = "o".dup.force_encoding(Encoding::US_ASCII)
+
+    result = "héllo world".rpartition(pattern)
+
+    result.should == ["héllo w", "o", "rld"]
+    result[0].encoding.should == Encoding::UTF_8
+    result[1].encoding.should == Encoding::US_ASCII
+    result[2].encoding.should == Encoding::UTF_8
+  end
 end
diff --git a/spec/ruby/core/string/rstrip_spec.rb b/spec/ruby/core/string/rstrip_spec.rb
index 2f32836e54..55773f5238 100644
--- a/spec/ruby/core/string/rstrip_spec.rb
+++ b/spec/ruby/core/string/rstrip_spec.rb
@@ -1,23 +1,29 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/strip'
 
 describe "String#rstrip" do
+  it_behaves_like :string_strip, :rstrip
+
   it "returns a copy of self with trailing whitespace removed" do
     "  hello  ".rstrip.should == "  hello"
     "  hello world  ".rstrip.should == "  hello world"
     "  hello world \n\r\t\n\v\r".rstrip.should == "  hello world"
     "hello".rstrip.should == "hello"
     "hello\x00".rstrip.should == "hello"
+    "こにちわ ".rstrip.should == "こにちわ"
   end
 
-  it "returns a copy of self with all trailing whitespace and NULL bytes removed" do
-    "\x00 \x00hello\x00 \x00".rstrip.should == "\x00 \x00hello"
+  it "works with lazy substrings" do
+    "  hello  "[1...-1].rstrip.should == " hello"
+    "  hello world  "[1...-1].rstrip.should == " hello world"
+    "  hello world \n\r\t\n\v\r"[1...-1].rstrip.should == " hello world"
+    " こにちわ  "[1...-1].rstrip.should == "こにちわ"
   end
 
-  it "taints the result when self is tainted" do
-    "".taint.rstrip.tainted?.should == true
-    "ok".taint.rstrip.tainted?.should == true
-    "ok    ".taint.rstrip.tainted?.should == true
+  it "returns a copy of self with all trailing whitespace and NULL bytes removed" do
+    "\x00 \x00hello\x00 \x00".rstrip.should == "\x00 \x00hello"
   end
 end
 
@@ -40,13 +46,35 @@ describe "String#rstrip!" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "  hello  ".freeze.rstrip! }.should raise_error(frozen_error_class)
+  it "makes a string empty if it is only whitespace" do
+    "".rstrip!.should == nil
+    " ".rstrip.should == ""
+    "  ".rstrip.should == ""
+  end
+
+  it "removes trailing NULL bytes and whitespace" do
+    a = "\000 goodbye \000"
+    a.rstrip!
+    a.should == "\000 goodbye"
+  end
+
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "  hello  ".freeze.rstrip! }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> { "hello".freeze.rstrip! }.should raise_error(frozen_error_class)
-    -> { "".freeze.rstrip!      }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> { "hello".freeze.rstrip! }.should raise_error(FrozenError)
+    -> { "".freeze.rstrip!      }.should raise_error(FrozenError)
+  end
+
+  it "raises an Encoding::CompatibilityError if the last non-space codepoint is invalid" do
+    s = "abc\xDF".force_encoding(Encoding::UTF_8)
+    s.valid_encoding?.should be_false
+    -> { s.rstrip! }.should raise_error(Encoding::CompatibilityError)
+
+    s = "abc\xDF   ".force_encoding(Encoding::UTF_8)
+    s.valid_encoding?.should be_false
+    -> { s.rstrip! }.should raise_error(Encoding::CompatibilityError)
   end
 end
diff --git a/spec/ruby/core/string/scan_spec.rb b/spec/ruby/core/string/scan_spec.rb
index 06400fc745..bbe843b591 100644
--- a/spec/ruby/core/string/scan_spec.rb
+++ b/spec/ruby/core/string/scan_spec.rb
@@ -65,30 +65,16 @@ describe "String#scan" do
     -> { "cruel world".scan(mock('x')) }.should raise_error(TypeError)
   end
 
-  it "taints the results if the String argument is tainted" do
-    a = "hello hello hello".scan("hello".taint)
-    a.each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results when passed a String argument if self is tainted" do
-    a = "hello hello hello".taint.scan("hello")
-    a.each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results if the Regexp argument is tainted" do
-    a = "hello".scan(/./.taint)
-    a.each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results when passed a Regexp argument if self is tainted" do
-    a = "hello".taint.scan(/./)
-    a.each { |m| m.tainted?.should be_true }
-  end
-
   # jruby/jruby#5513
   it "does not raise any errors when passed a multi-byte string" do
     "あああaaaあああ".scan("あああ").should == ["あああ", "あああ"]
   end
+
+  it "returns Strings in the same encoding as self" do
+    "cruel world".encode("US-ASCII").scan(/\w+/).each do |s|
+      s.encoding.should == Encoding::US_ASCII
+    end
+  end
 end
 
 describe "String#scan with pattern and block" do
@@ -117,11 +103,11 @@ describe "String#scan with pattern and block" do
     offsets = []
 
     str.scan(/([aeiou])/) do
-       md = $~
-       md.string.should == str
-       matches << md.to_a
-       offsets << md.offset(0)
-       str
+      md = $~
+      md.string.should == str
+      matches << md.to_a
+      offsets << md.offset(0)
+      str
     end
 
     matches.should == [["e", "e"], ["o", "o"]]
@@ -131,11 +117,11 @@ describe "String#scan with pattern and block" do
     offsets = []
 
     str.scan("l") do
-       md = $~
-       md.string.should == str
-       matches << md.to_a
-       offsets << md.offset(0)
-       str
+      md = $~
+      md.string.should == str
+      matches << md.to_a
+      offsets << md.offset(0)
+      str
     end
 
     matches.should == [["l"], ["l"]]
@@ -171,22 +157,6 @@ describe "String#scan with pattern and block" do
     $~.should == nil
   end
 
-  it "taints the results if the String argument is tainted" do
-    "hello hello hello".scan("hello".taint).each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results when passed a String argument if self is tainted" do
-    "hello hello hello".taint.scan("hello").each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results if the Regexp argument is tainted" do
-    "hello".scan(/./.taint).each { |m| m.tainted?.should be_true }
-  end
-
-  it "taints the results when passed a Regexp argument if self is tainted" do
-    "hello".taint.scan(/./).each { |m| m.tainted?.should be_true }
-  end
-
   it "passes block arguments as individual arguments when blocks are provided" do
     "a b c\na b c\na b c".scan(/(\w*) (\w*) (\w*)/) do |first,second,third|
       first.should == 'a';
@@ -194,4 +164,10 @@ describe "String#scan with pattern and block" do
       third.should == 'c';
     end
   end
+
+  it "yields String instances for subclasses" do
+    a = []
+    StringSpecs::MyString.new("abc").scan(/./) { |s| a << s.class }
+    a.should == [String, String, String]
+  end
 end
diff --git a/spec/ruby/core/string/scrub_spec.rb b/spec/ruby/core/string/scrub_spec.rb
index 390035ef30..b9ef0f1a16 100644
--- a/spec/ruby/core/string/scrub_spec.rb
+++ b/spec/ruby/core/string/scrub_spec.rb
@@ -1,5 +1,7 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe "String#scrub with a default replacement" do
   it "returns self for valid strings" do
@@ -13,18 +15,33 @@ describe "String#scrub with a default replacement" do
     "abc\u3042#{x81}".scrub.should == "abc\u3042\uFFFD"
   end
 
+  it "replaces invalid byte sequences in lazy substrings" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    "abc\u3042#{x81}def"[1...-1].scrub.should == "bc\u3042\uFFFDde"
+  end
+
   it "returns a copy of self when the input encoding is BINARY" do
     input = "foo".encode('BINARY')
 
     input.scrub.should == "foo"
   end
 
-
   it "replaces invalid byte sequences when using ASCII as the input encoding" do
     xE3x80 = [0xE3, 0x80].pack('CC').force_encoding 'utf-8'
     input = "abc\u3042#{xE3x80}".force_encoding('ASCII')
     input.scrub.should == "abc?????"
   end
+
+  it "returns a String in the same encoding as self" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    "abc\u3042#{x81}".scrub.encoding.should == Encoding::UTF_8
+  end
+
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("foo").scrub.should be_an_instance_of(String)
+    input = [0x81].pack('C').force_encoding('utf-8')
+    StringSpecs::MyString.new(input).scrub.should be_an_instance_of(String)
+  end
 end
 
 describe "String#scrub with a custom replacement" do
@@ -39,6 +56,15 @@ describe "String#scrub with a custom replacement" do
     "abc\u3042#{x81}".scrub("*").should == "abc\u3042*"
   end
 
+  it "replaces invalid byte sequences in frozen strings" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    (-"abc\u3042#{x81}").scrub("*").should == "abc\u3042*"
+
+    leading_surrogate = [0x00, 0xD8]
+    utf16_str = ("abc".encode('UTF-16LE').bytes + leading_surrogate).pack('c*').force_encoding('UTF-16LE')
+    (-(utf16_str)).scrub("*".encode('UTF-16LE')).should == "abc*".encode('UTF-16LE')
+  end
+
   it "replaces an incomplete character at the end with a single replacement" do
     xE3x80 = [0xE3, 0x80].pack('CC').force_encoding 'utf-8'
     xE3x80.scrub("*").should == "*"
@@ -52,12 +78,23 @@ describe "String#scrub with a custom replacement" do
     block.should raise_error(ArgumentError)
   end
 
+  it "returns a String in the same encoding as self" do
+    x81 = [0x81].pack('C').force_encoding('utf-8')
+    "abc\u3042#{x81}".scrub("*").encoding.should == Encoding::UTF_8
+  end
+
   it "raises TypeError when a non String replacement is given" do
     x81 = [0x81].pack('C').force_encoding('utf-8')
     block = -> { "foo#{x81}".scrub(1) }
 
     block.should raise_error(TypeError)
   end
+
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("foo").scrub("*").should be_an_instance_of(String)
+    input = [0x81].pack('C').force_encoding('utf-8')
+    StringSpecs::MyString.new(input).scrub("*").should be_an_instance_of(String)
+  end
 end
 
 describe "String#scrub with a block" do
@@ -82,6 +119,12 @@ describe "String#scrub with a block" do
 
     replaced.should == "€€"
   end
+
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("foo").scrub { |b| "*" }.should be_an_instance_of(String)
+    input = [0x81].pack('C').force_encoding('utf-8')
+    StringSpecs::MyString.new(input).scrub { |b| "<#{b.unpack("H*")[0]}>" }.should be_an_instance_of(String)
+  end
 end
 
 describe "String#scrub!" do
@@ -98,4 +141,24 @@ describe "String#scrub!" do
     input.scrub! { |b| "<?>" }
     input.should == "a<?>"
   end
+
+  it "maintains the state of frozen strings that are already valid" do
+    input = "a"
+    input.freeze
+    input.scrub!
+    input.frozen?.should be_true
+  end
+
+  it "preserves the instance variables of already valid strings" do
+    input = "a"
+    input.instance_variable_set(:@a, 'b')
+    input.scrub!
+    input.instance_variable_get(:@a).should == 'b'
+  end
+
+  it "accepts a frozen string as a replacement" do
+    input = "a\xE2"
+    input.scrub!('.'.freeze)
+    input.should == 'a.'
+  end
 end
diff --git a/spec/ruby/core/string/setbyte_spec.rb b/spec/ruby/core/string/setbyte_spec.rb
index 6912b1b66f..85403ca62c 100644
--- a/spec/ruby/core/string/setbyte_spec.rb
+++ b/spec/ruby/core/string/setbyte_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#setbyte" do
@@ -36,6 +37,12 @@ describe "String#setbyte" do
     str.valid_encoding?.should be_true
     str.setbyte(2,253)
     str.valid_encoding?.should be_false
+
+    str = "ABC"
+    str.setbyte(0, 0x20) # ' '
+    str.should.valid_encoding?
+    str.setbyte(0, 0xE3)
+    str.should_not.valid_encoding?
   end
 
   it "regards a negative index as counting from the end of the String" do
@@ -75,10 +82,10 @@ describe "String#setbyte" do
     str1.should_not == "ledgehog"
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     str = "cold".freeze
     str.frozen?.should be_true
-    -> { str.setbyte(3,96) }.should raise_error(frozen_error_class)
+    -> { str.setbyte(3,96) }.should raise_error(FrozenError)
   end
 
   it "raises a TypeError unless the second argument is an Integer" do
diff --git a/spec/ruby/core/string/shared/byte_index_common.rb b/spec/ruby/core/string/shared/byte_index_common.rb
new file mode 100644
index 0000000000..3de1453f4f
--- /dev/null
+++ b/spec/ruby/core/string/shared/byte_index_common.rb
@@ -0,0 +1,63 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../../spec_helper'
+
+describe :byte_index_common, shared: true do
+  describe "raises on type errors" do
+    it "raises a TypeError if passed nil" do
+      -> { "abc".send(@method, nil) }.should raise_error(TypeError, "no implicit conversion of nil into String")
+    end
+
+    it "raises a TypeError if passed a boolean" do
+      -> { "abc".send(@method, true) }.should raise_error(TypeError, "no implicit conversion of true into String")
+    end
+
+    it "raises a TypeError if passed a Symbol" do
+      not_supported_on :opal do
+        -> { "abc".send(@method, :a) }.should raise_error(TypeError, "no implicit conversion of Symbol into String")
+      end
+    end
+
+    it "raises a TypeError if passed a Symbol" do
+      obj = mock('x')
+      obj.should_not_receive(:to_int)
+      -> { "hello".send(@method, obj) }.should raise_error(TypeError, "no implicit conversion of MockObject into String")
+    end
+
+    it "raises a TypeError if passed an Integer" do
+      -> { "abc".send(@method, 97) }.should raise_error(TypeError, "no implicit conversion of Integer into String")
+    end
+  end
+
+  describe "with multibyte codepoints" do
+    it "raises an IndexError when byte offset lands in the middle of a multibyte character" do
+      -> { "わ".send(@method, "", 1) }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+      -> { "わ".send(@method, "", 2) }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+      -> { "わ".send(@method, "", -1) }.should raise_error(IndexError, "offset 2 does not land on character boundary")
+      -> { "わ".send(@method, "", -2) }.should raise_error(IndexError, "offset 1 does not land on character boundary")
+    end
+
+    it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+      re = Regexp.new "れ".encode(Encoding::EUC_JP)
+      -> do
+        "あれ".send(@method, re)
+      end.should raise_error(Encoding::CompatibilityError, "incompatible encoding regexp match (EUC-JP regexp with UTF-8 string)")
+    end
+  end
+
+  describe "with global variables" do
+    it "doesn't set $~ for non regex search" do
+      $~ = nil
+
+      'hello.'.send(@method, 'll')
+      $~.should == nil
+    end
+
+    it "sets $~ to MatchData of match and nil when there's none" do
+      'hello.'.send(@method, /.e./)
+      $~[0].should == 'hel'
+
+      'hello.'.send(@method, /not/)
+      $~.should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/string/shared/chars.rb b/spec/ruby/core/string/shared/chars.rb
index c8716521bd..c730643cf4 100644
--- a/spec/ruby/core/string/shared/chars.rb
+++ b/spec/ruby/core/string/shared/chars.rb
@@ -21,12 +21,12 @@ describe :string_chars, shared: true do
   end
 
   it "returns characters in the same encoding as self" do
-    "&%".force_encoding('Shift_JIS').send(@method).to_a.all? {|c| c.encoding.name.should == 'Shift_JIS'}
+    "&%".dup.force_encoding('Shift_JIS').send(@method).to_a.all? {|c| c.encoding.name.should == 'Shift_JIS'}
     "&%".encode('BINARY').send(@method).to_a.all? {|c| c.encoding.should == Encoding::BINARY }
   end
 
   it "works with multibyte characters" do
-    s = "\u{8987}".force_encoding("UTF-8")
+    s = "\u{8987}".dup.force_encoding("UTF-8")
     s.bytesize.should == 3
     s.send(@method).to_a.should == [s]
   end
@@ -39,14 +39,14 @@ describe :string_chars, shared: true do
   end
 
   it "returns a different character if the String is transcoded" do
-    s = "\u{20AC}".force_encoding('UTF-8')
-    s.encode('UTF-8').send(@method).to_a.should == ["\u{20AC}".force_encoding('UTF-8')]
+    s = "\u{20AC}".dup.force_encoding('UTF-8')
+    s.encode('UTF-8').send(@method).to_a.should == ["\u{20AC}".dup.force_encoding('UTF-8')]
     s.encode('iso-8859-15').send(@method).to_a.should == [[0xA4].pack('C').force_encoding('iso-8859-15')]
-    s.encode('iso-8859-15').encode('UTF-8').send(@method).to_a.should == ["\u{20AC}".force_encoding('UTF-8')]
+    s.encode('iso-8859-15').encode('UTF-8').send(@method).to_a.should == ["\u{20AC}".dup.force_encoding('UTF-8')]
   end
 
   it "uses the String's encoding to determine what characters it contains" do
-    s = "\u{24B62}"
+    s = +"\u{24B62}"
 
     s.force_encoding('UTF-8').send(@method).to_a.should == [
       s.force_encoding('UTF-8')
@@ -63,16 +63,4 @@ describe :string_chars, shared: true do
       [0xA2].pack('C').force_encoding('SJIS')
     ]
   end
-
-  it "taints resulting strings when self is tainted" do
-    str = "hello"
-
-    str.send(@method) do |x|
-      x.tainted?.should == false
-    end
-
-    str.dup.taint.send(@method) do |x|
-      x.tainted?.should == true
-    end
-  end
 end
diff --git a/spec/ruby/core/string/shared/codepoints.rb b/spec/ruby/core/string/shared/codepoints.rb
index e94a57f48e..1c28ba3d5e 100644
--- a/spec/ruby/core/string/shared/codepoints.rb
+++ b/spec/ruby/core/string/shared/codepoints.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :string_codepoints, shared: true do
   it "returns self" do
     s = "foo"
@@ -7,7 +7,7 @@ describe :string_codepoints, shared: true do
   end
 
   it "raises an ArgumentError when self has an invalid encoding and a method is called on the returned Enumerator" do
-    s = "\xDF".force_encoding(Encoding::UTF_8)
+    s = "\xDF".dup.force_encoding(Encoding::UTF_8)
     s.valid_encoding?.should be_false
     -> { s.send(@method).to_a }.should raise_error(ArgumentError)
   end
@@ -21,14 +21,14 @@ describe :string_codepoints, shared: true do
   end
 
   it "raises an ArgumentError if self's encoding is invalid and a block is given" do
-    s = "\xDF".force_encoding(Encoding::UTF_8)
+    s = "\xDF".dup.force_encoding(Encoding::UTF_8)
     s.valid_encoding?.should be_false
     -> { s.send(@method) { } }.should raise_error(ArgumentError)
   end
 
-  it "yields codepoints as Fixnums" do
+  it "yields codepoints as Integers" do
     "glark\u{20}".send(@method).to_a.each do |codepoint|
-      codepoint.should be_an_instance_of(Fixnum)
+      codepoint.should be_an_instance_of(Integer)
     end
   end
 
@@ -49,7 +49,7 @@ describe :string_codepoints, shared: true do
 
   it "round-trips to the original String using Integer#chr" do
     s = "\u{13}\u{7711}\u{1010}"
-    s2 = ""
+    s2 = +""
     s.send(@method) {|n| s2 << n.chr(Encoding::UTF_8)}
     s.should == s2
   end
diff --git a/spec/ruby/core/string/shared/concat.rb b/spec/ruby/core/string/shared/concat.rb
index 53a8bc23fb..dded9a69e7 100644
--- a/spec/ruby/core/string/shared/concat.rb
+++ b/spec/ruby/core/string/shared/concat.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 describe :string_concat, shared: true do
   it "concatenates the given argument to self and returns self" do
     str = 'hello '
@@ -5,24 +6,12 @@ describe :string_concat, shared: true do
     str.should == "hello world"
   end
 
-  it "converts the given argument to a String using to_str" do
-    obj = mock('world!')
-    obj.should_receive(:to_str).and_return("world!")
-    a = 'hello '.send(@method, obj)
-    a.should == 'hello world!'
-  end
-
-  it "raises a TypeError if the given argument can't be converted to a String" do
-    -> { 'hello '.send(@method, [])        }.should raise_error(TypeError)
-    -> { 'hello '.send(@method, mock('x')) }.should raise_error(TypeError)
-  end
-
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     a = "hello"
     a.freeze
 
-    -> { a.send(@method, "")     }.should raise_error(frozen_error_class)
-    -> { a.send(@method, "test") }.should raise_error(frozen_error_class)
+    -> { a.send(@method, "")     }.should raise_error(FrozenError)
+    -> { a.send(@method, "test") }.should raise_error(FrozenError)
   end
 
   it "returns a String when given a subclass instance" do
@@ -39,16 +28,6 @@ describe :string_concat, shared: true do
     str.should be_an_instance_of(StringSpecs::MyString)
   end
 
-  it "taints self if other is tainted" do
-    "x".send(@method, "".taint).tainted?.should == true
-    "x".send(@method, "y".taint).tainted?.should == true
-  end
-
-  it "untrusts self if other is untrusted" do
-    "x".send(@method, "".untrust).untrusted?.should == true
-    "x".send(@method, "y".untrust).untrusted?.should == true
-  end
-
   describe "with Integer" do
     it "concatenates the argument interpreted as a codepoint" do
       b = "".send(@method, 33)
@@ -87,12 +66,12 @@ describe :string_concat, shared: true do
       -> { "".send(@method, x) }.should raise_error(TypeError)
     end
 
-    it "raises a #{frozen_error_class} when self is frozen" do
+    it "raises a FrozenError when self is frozen" do
       a = "hello"
       a.freeze
 
-      -> { a.send(@method, 0)  }.should raise_error(frozen_error_class)
-      -> { a.send(@method, 33) }.should raise_error(frozen_error_class)
+      -> { a.send(@method, 0)  }.should raise_error(FrozenError)
+      -> { a.send(@method, 33) }.should raise_error(FrozenError)
     end
   end
 end
@@ -158,3 +137,23 @@ describe :string_concat_encoding, shared: true do
     end
   end
 end
+
+describe :string_concat_type_coercion, shared: true do
+  it "converts the given argument to a String using to_str" do
+    obj = mock('world!')
+    obj.should_receive(:to_str).and_return("world!")
+    a = 'hello '.send(@method, obj)
+    a.should == 'hello world!'
+  end
+
+  it "raises a TypeError if the given argument can't be converted to a String" do
+    -> { 'hello '.send(@method, [])        }.should raise_error(TypeError)
+    -> { 'hello '.send(@method, mock('x')) }.should raise_error(TypeError)
+  end
+
+  it "raises a NoMethodError if the given argument raises a NoMethodError during type coercion to a String" do
+    obj = mock('world!')
+    obj.should_receive(:to_str).and_raise(NoMethodError)
+    -> { 'hello '.send(@method, obj) }.should raise_error(NoMethodError)
+  end
+end
diff --git a/spec/ruby/core/string/shared/dedup.rb b/spec/ruby/core/string/shared/dedup.rb
new file mode 100644
index 0000000000..1ffd6aa0fd
--- /dev/null
+++ b/spec/ruby/core/string/shared/dedup.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: false
+describe :string_dedup, shared: true do
+  it 'returns self if the String is frozen' do
+    input  = 'foo'.freeze
+    output = input.send(@method)
+
+    output.should equal(input)
+    output.should.frozen?
+  end
+
+  it 'returns a frozen copy if the String is not frozen' do
+    input  = 'foo'
+    output = input.send(@method)
+
+    output.should.frozen?
+    output.should_not equal(input)
+    output.should == 'foo'
+  end
+
+  it "returns the same object for equal unfrozen strings" do
+    origin = "this is a string"
+    dynamic = %w(this is a string).join(' ')
+
+    origin.should_not equal(dynamic)
+    origin.send(@method).should equal(dynamic.send(@method))
+  end
+
+  it "returns the same object when it's called on the same String literal" do
+    "unfrozen string".send(@method).should equal("unfrozen string".send(@method))
+    "unfrozen string".send(@method).should_not equal("another unfrozen string".send(@method))
+  end
+
+  it "deduplicates frozen strings" do
+    dynamic = %w(this string is frozen).join(' ').freeze
+
+    dynamic.should_not equal("this string is frozen".freeze)
+
+    dynamic.send(@method).should equal("this string is frozen".freeze)
+    dynamic.send(@method).should equal("this string is frozen".send(@method).freeze)
+  end
+
+  it "does not deduplicate a frozen string when it has instance variables" do
+    dynamic = %w(this string is frozen).join(' ')
+    dynamic.instance_variable_set(:@a, 1)
+    dynamic.freeze
+
+    dynamic.send(@method).should_not equal("this string is frozen".freeze)
+    dynamic.send(@method).should_not equal("this string is frozen".send(@method).freeze)
+    dynamic.send(@method).should equal(dynamic)
+  end
+end
diff --git a/spec/ruby/core/string/shared/each_codepoint_without_block.rb b/spec/ruby/core/string/shared/each_codepoint_without_block.rb
index 92b7f76032..c88e5c54c7 100644
--- a/spec/ruby/core/string/shared/each_codepoint_without_block.rb
+++ b/spec/ruby/core/string/shared/each_codepoint_without_block.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :string_each_codepoint_without_block, shared: true do
   describe "when no block is given" do
     it "returns an Enumerator" do
@@ -6,7 +6,7 @@ describe :string_each_codepoint_without_block, shared: true do
     end
 
     it "returns an Enumerator even when self has an invalid encoding" do
-      s = "\xDF".force_encoding(Encoding::UTF_8)
+      s = "\xDF".dup.force_encoding(Encoding::UTF_8)
       s.valid_encoding?.should be_false
       s.send(@method).should be_an_instance_of(Enumerator)
     end
@@ -23,7 +23,7 @@ describe :string_each_codepoint_without_block, shared: true do
         end
 
         it "should return the size of the string even when the string has an invalid encoding" do
-          s = "\xDF".force_encoding(Encoding::UTF_8)
+          s = "\xDF".dup.force_encoding(Encoding::UTF_8)
           s.valid_encoding?.should be_false
           s.send(@method).size.should == 1
         end
diff --git a/spec/ruby/core/string/shared/each_line.rb b/spec/ruby/core/string/shared/each_line.rb
index 241a90eee3..231a6d9d4f 100644
--- a/spec/ruby/core/string/shared/each_line.rb
+++ b/spec/ruby/core/string/shared/each_line.rb
@@ -40,40 +40,20 @@ describe :string_each_line, shared: true do
     b.should == ["foo\n", "🤡🤡🤡🤡🤡🤡🤡\n", "bar\n", "baz\n"]
   end
 
-  it "taints substrings that are passed to the block if self is tainted" do
-    "one\ntwo\r\nthree".taint.send(@method) { |s| s.tainted?.should == true }
-
-    "x.y.".send(@method, ".".taint) { |s| s.tainted?.should == false }
-  end
-
   it "passes self as a whole to the block if the separator is nil" do
     a = []
     "one\ntwo\r\nthree".send(@method, nil) { |s| a << s }
     a.should == ["one\ntwo\r\nthree"]
   end
 
-  ruby_version_is ''...'2.5' do
-    it "yields paragraphs (broken by 2 or more successive newlines) when passed ''" do
-      a = []
-      "hello\nworld\n\n\nand\nuniverse\n\n\n\n\n".send(@method, '') { |s| a << s }
-      a.should == ["hello\nworld\n\n\n", "and\nuniverse\n\n\n\n\n"]
-
-      a = []
-      "hello\nworld\n\n\nand\nuniverse\n\n\n\n\ndog".send(@method, '') { |s| a << s }
-      a.should == ["hello\nworld\n\n\n", "and\nuniverse\n\n\n\n\n", "dog"]
-    end
-  end
-
-  ruby_version_is '2.5' do
-    it "yields paragraphs (broken by 2 or more successive newlines) when passed '' and replaces multiple newlines with only two ones" do
-      a = []
-      "hello\nworld\n\n\nand\nuniverse\n\n\n\n\n".send(@method, '') { |s| a << s }
-      a.should == ["hello\nworld\n\n", "and\nuniverse\n\n"]
+  it "yields paragraphs (broken by 2 or more successive newlines) when passed '' and replaces multiple newlines with only two ones" do
+    a = []
+    "hello\nworld\n\n\nand\nuniverse\n\n\n\n\n".send(@method, '') { |s| a << s }
+    a.should == ["hello\nworld\n\n", "and\nuniverse\n\n"]
 
-      a = []
-      "hello\nworld\n\n\nand\nuniverse\n\n\n\n\ndog".send(@method, '') { |s| a << s }
-      a.should == ["hello\nworld\n\n", "and\nuniverse\n\n", "dog"]
-    end
+    a = []
+    "hello\nworld\n\n\nand\nuniverse\n\n\n\n\ndog".send(@method, '') { |s| a << s }
+    a.should == ["hello\nworld\n\n", "and\nuniverse\n\n", "dog"]
   end
 
   describe "uses $/" do
@@ -82,7 +62,7 @@ describe :string_each_line, shared: true do
     end
 
     after :each do
-      $/ = @before_separator
+      suppress_warning {$/ = @before_separator}
     end
 
     it "as the separator when none is given" do
@@ -94,10 +74,10 @@ describe :string_each_line, shared: true do
           expected = []
           str.send(@method, sep) { |x| expected << x }
 
-          $/ = sep
+          suppress_warning {$/ = sep}
 
           actual = []
-          str.send(@method) { |x| actual << x }
+          suppress_warning {str.send(@method) { |x| actual << x }}
 
           actual.should == expected
         end
@@ -105,10 +85,10 @@ describe :string_each_line, shared: true do
     end
   end
 
-  it "yields subclass instances for subclasses" do
+  it "yields String instances for subclasses" do
     a = []
     StringSpecs::MyString.new("hello\nworld").send(@method) { |s| a << s.class }
-    a.should == [StringSpecs::MyString, StringSpecs::MyString]
+    a.should == [String, String]
   end
 
   it "returns self" do
@@ -126,12 +106,18 @@ describe :string_each_line, shared: true do
   end
 
   it "does not care if the string is modified while substituting" do
-    str = "hello\nworld."
+    str = +"hello\nworld."
     out = []
     str.send(@method){|x| out << x; str[-1] = '!' }.should == "hello\nworld!"
     out.should == ["hello\n", "world."]
   end
 
+  it "returns Strings in the same encoding as self" do
+    "one\ntwo\r\nthree".encode("US-ASCII").send(@method) do |s|
+      s.encoding.should == Encoding::US_ASCII
+    end
+  end
+
   it "raises a TypeError when the separator can't be converted to a string" do
     -> { "hello world".send(@method, false) {}     }.should raise_error(TypeError)
     -> { "hello world".send(@method, mock('x')) {} }.should raise_error(TypeError)
diff --git a/spec/ruby/core/string/shared/encode.rb b/spec/ruby/core/string/shared/encode.rb
index b5a8bf9b72..9466308886 100644
--- a/spec/ruby/core/string/shared/encode.rb
+++ b/spec/ruby/core/string/shared/encode.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 describe :string_encode, shared: true do
   describe "when passed no options" do
     it "transcodes to Encoding.default_internal when set" do
@@ -83,7 +84,7 @@ describe :string_encode, shared: true do
       options = mock("string encode options")
       options.should_receive(:to_hash).and_return({ undef: :replace })
 
-      result = "あ\ufffdあ".send(@method, options)
+      result = "あ\ufffdあ".send(@method, **options)
       result.should == "あ\ufffdあ"
     end
 
@@ -145,7 +146,7 @@ describe :string_encode, shared: true do
       options = mock("string encode options")
       options.should_receive(:to_hash).and_return({ undef: :replace })
 
-      result = "あ?あ".send(@method, Encoding::EUC_JP, options)
+      result = "あ?あ".send(@method, Encoding::EUC_JP, **options)
       xA4xA2 = [0xA4, 0xA2].pack('CC').force_encoding('utf-8')
       result.should == "#{xA4xA2}?#{xA4xA2}".force_encoding("euc-jp")
     end
@@ -189,7 +190,191 @@ describe :string_encode, shared: true do
 
       xFF = [0xFF].pack('C').force_encoding('utf-8')
       str = "ab#{xFF}c".force_encoding Encoding::BINARY
-      str.send(@method, "iso-8859-1", "utf-8", options).should == "ab?c"
+      str.send(@method, "iso-8859-1", "utf-8", **options).should == "ab?c"
+    end
+  end
+
+  describe "given the fallback option" do
+    context "given a hash" do
+      it "looks up the replacement value from the hash" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: { "\ufffd" => "bar" })
+        encoded.should == "Bbar"
+      end
+
+      it "calls to_str on the returned value" do
+        obj = Object.new
+        obj.should_receive(:to_str).and_return("bar")
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: { "\ufffd" => obj })
+        encoded.should == "Bbar"
+      end
+
+      it "does not call to_s on the returned value" do
+        obj = Object.new
+        obj.should_not_receive(:to_s)
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: { "\ufffd" => obj })
+        }.should raise_error(TypeError, "no implicit conversion of Object into String")
+      end
+
+      it "raises an error if the key is not present in the hash" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: { "foo" => "bar" })
+        }.should raise_error(Encoding::UndefinedConversionError, "U+FFFD from UTF-8 to US-ASCII")
+      end
+
+      it "raises an error if the value is itself invalid" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: { "\ufffd" => "\uffee" })
+        }.should raise_error(ArgumentError, "too big fallback string")
+      end
+
+      it "uses the hash's default value if set" do
+        hash = {}
+        hash.default = "bar"
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: hash)
+        encoded.should == "Bbar"
+      end
+
+      it "uses the result of calling default_proc if set" do
+        hash = {}
+        hash.default_proc = -> _, _ { "bar" }
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: hash)
+        encoded.should == "Bbar"
+      end
+    end
+
+    context "given an object inheriting from Hash" do
+      before do
+        klass = Class.new(Hash)
+        @hash_like = klass.new
+        @hash_like["\ufffd"] = "bar"
+      end
+
+      it "looks up the replacement value from the object" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: @hash_like)
+        encoded.should == "Bbar"
+      end
+    end
+
+    context "given an object responding to []" do
+      before do
+        klass = Class.new do
+          def [](c) = c.bytes.inspect
+        end
+        @hash_like = klass.new
+      end
+
+      it "calls [] on the object, passing the invalid character" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: @hash_like)
+        encoded.should == "B[239, 191, 189]"
+      end
+    end
+
+    context "given an object not responding to []" do
+      before do
+        @non_hash_like = Object.new
+      end
+
+      it "raises an error" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: @non_hash_like)
+        }.should raise_error(Encoding::UndefinedConversionError, "U+FFFD from UTF-8 to US-ASCII")
+      end
+    end
+
+    context "given a proc" do
+      it "calls the proc to get the replacement value, passing in the invalid character" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: proc { |c| c.bytes.inspect })
+        encoded.should == "B[239, 191, 189]"
+      end
+
+      it "calls to_str on the returned value" do
+        obj = Object.new
+        obj.should_receive(:to_str).and_return("bar")
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: proc { |c| obj })
+        encoded.should == "Bbar"
+      end
+
+      it "does not call to_s on the returned value" do
+        obj = Object.new
+        obj.should_not_receive(:to_s)
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: proc { |c| obj })
+        }.should raise_error(TypeError, "no implicit conversion of Object into String")
+      end
+
+      it "raises an error if the returned value is itself invalid" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: -> c { "\uffee" })
+        }.should raise_error(ArgumentError, "too big fallback string")
+      end
+    end
+
+    context "given a lambda" do
+      it "calls the lambda to get the replacement value, passing in the invalid character" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: -> c { c.bytes.inspect })
+        encoded.should == "B[239, 191, 189]"
+      end
+
+      it "calls to_str on the returned value" do
+        obj = Object.new
+        obj.should_receive(:to_str).and_return("bar")
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: -> c { obj })
+        encoded.should == "Bbar"
+      end
+
+      it "does not call to_s on the returned value" do
+        obj = Object.new
+        obj.should_not_receive(:to_s)
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: -> c { obj })
+        }.should raise_error(TypeError, "no implicit conversion of Object into String")
+      end
+
+      it "raises an error if the returned value is itself invalid" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: -> c { "\uffee" })
+        }.should raise_error(ArgumentError, "too big fallback string")
+      end
+    end
+
+    context "given a method" do
+      def replace(c) = c.bytes.inspect
+      def replace_bad(c) = "\uffee"
+
+      def replace_to_str(c)
+        obj = Object.new
+        obj.should_receive(:to_str).and_return("bar")
+        obj
+      end
+
+      def replace_to_s(c)
+        obj = Object.new
+        obj.should_not_receive(:to_s)
+        obj
+      end
+
+      it "calls the method to get the replacement value, passing in the invalid character" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: method(:replace))
+        encoded.should == "B[239, 191, 189]"
+      end
+
+      it "calls to_str on the returned value" do
+        encoded = "B\ufffd".encode(Encoding::US_ASCII, fallback: method(:replace_to_str))
+        encoded.should == "Bbar"
+      end
+
+      it "does not call to_s on the returned value" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: method(:replace_to_s))
+        }.should raise_error(TypeError, "no implicit conversion of Object into String")
+      end
+
+      it "raises an error if the returned value is itself invalid" do
+        -> {
+          "B\ufffd".encode(Encoding::US_ASCII, fallback: method(:replace_bad))
+        }.should raise_error(ArgumentError, "too big fallback string")
+      end
     end
   end
 
diff --git a/spec/ruby/core/string/shared/eql.rb b/spec/ruby/core/string/shared/eql.rb
index 85b861f4f1..d5af337d53 100644
--- a/spec/ruby/core/string/shared/eql.rb
+++ b/spec/ruby/core/string/shared/eql.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
@@ -13,15 +13,15 @@ describe :string_eql_value, shared: true do
   end
 
   it "ignores encoding difference of compatible string" do
-    "hello".force_encoding("utf-8").send(@method, "hello".force_encoding("iso-8859-1")).should be_true
+    "hello".dup.force_encoding("utf-8").send(@method, "hello".dup.force_encoding("iso-8859-1")).should be_true
   end
 
   it "considers encoding difference of incompatible string" do
-    "\xff".force_encoding("utf-8").send(@method, "\xff".force_encoding("iso-8859-1")).should be_false
+    "\xff".dup.force_encoding("utf-8").send(@method, "\xff".dup.force_encoding("iso-8859-1")).should be_false
   end
 
   it "considers encoding compatibility" do
-    "hello".force_encoding("utf-8").send(@method, "hello".force_encoding("utf-32le")).should be_false
+    "abcd".dup.force_encoding("utf-8").send(@method, "abcd".dup.force_encoding("utf-32le")).should be_false
   end
 
   it "ignores subclass differences" do
@@ -31,4 +31,8 @@ describe :string_eql_value, shared: true do
     a.send(@method, b).should be_true
     b.send(@method, a).should be_true
   end
+
+  it "returns true when comparing 2 empty strings but one is not ASCII-compatible" do
+    "".send(@method, "".dup.force_encoding('iso-2022-jp')).should == true
+  end
 end
diff --git a/spec/ruby/core/string/shared/length.rb b/spec/ruby/core/string/shared/length.rb
index f387fb251c..ae572ba755 100644
--- a/spec/ruby/core/string/shared/length.rb
+++ b/spec/ruby/core/string/shared/length.rb
@@ -12,15 +12,44 @@ describe :string_length, shared: true do
 
   it "returns the length of a string in different encodings" do
     utf8_str = 'こにちわ' * 100
-    utf8_str.size.should == 400
-    utf8_str.encode(Encoding::UTF_32BE).size.should == 400
-    utf8_str.encode(Encoding::SHIFT_JIS).size.should == 400
+    utf8_str.send(@method).should == 400
+    utf8_str.encode(Encoding::UTF_32BE).send(@method).should == 400
+    utf8_str.encode(Encoding::SHIFT_JIS).send(@method).should == 400
   end
 
   it "returns the length of the new self after encoding is changed" do
-    str = 'こにちわ'
+    str = +'こにちわ'
     str.send(@method)
 
     str.force_encoding('BINARY').send(@method).should == 12
   end
+
+  it "returns the correct length after force_encoding(BINARY)" do
+    utf8 = "あ"
+    ascii = "a"
+    concat = utf8 + ascii
+
+    concat.encoding.should == Encoding::UTF_8
+    concat.bytesize.should == 4
+
+    concat.send(@method).should == 2
+    concat.force_encoding(Encoding::ASCII_8BIT)
+    concat.send(@method).should == 4
+  end
+
+  it "adds 1 for every invalid byte in UTF-8" do
+    "\xF4\x90\x80\x80".send(@method).should == 4
+    "a\xF4\x90\x80\x80b".send(@method).should == 6
+    "é\xF4\x90\x80\x80è".send(@method).should == 6
+  end
+
+  it "adds 1 (and not 2) for a incomplete surrogate in UTF-16" do
+    "\x00\xd8".dup.force_encoding("UTF-16LE").send(@method).should == 1
+    "\xd8\x00".dup.force_encoding("UTF-16BE").send(@method).should == 1
+  end
+
+  it "adds 1 for a broken sequence in UTF-32" do
+    "\x04\x03\x02\x01".dup.force_encoding("UTF-32LE").send(@method).should == 1
+    "\x01\x02\x03\x04".dup.force_encoding("UTF-32BE").send(@method).should == 1
+  end
 end
diff --git a/spec/ruby/core/string/shared/partition.rb b/spec/ruby/core/string/shared/partition.rb
new file mode 100644
index 0000000000..4cac149ce5
--- /dev/null
+++ b/spec/ruby/core/string/shared/partition.rb
@@ -0,0 +1,33 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe :string_partition, shared: true do
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("hello").send(@method, "l").each do |item|
+      item.should be_an_instance_of(String)
+    end
+
+    StringSpecs::MyString.new("hello").send(@method, "x").each do |item|
+      item.should be_an_instance_of(String)
+    end
+
+    StringSpecs::MyString.new("hello").send(@method, /l./).each do |item|
+      item.should be_an_instance_of(String)
+    end
+  end
+
+  it "returns before- and after- parts in the same encoding as self" do
+    strings = "hello".encode("US-ASCII").send(@method, "ello")
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[2].encoding.should == Encoding::US_ASCII
+
+    strings = "hello".encode("US-ASCII").send(@method, /ello/)
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[2].encoding.should == Encoding::US_ASCII
+  end
+
+  it "returns the matching part in the separator's encoding" do
+    strings = "hello".encode("US-ASCII").send(@method, "ello")
+    strings[1].encoding.should == Encoding::UTF_8
+  end
+end
diff --git a/spec/ruby/core/string/shared/replace.rb b/spec/ruby/core/string/shared/replace.rb
index f13afb3f95..24dac0eb27 100644
--- a/spec/ruby/core/string/shared/replace.rb
+++ b/spec/ruby/core/string/shared/replace.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 describe :string_replace, shared: true do
   it "returns self" do
     a = "a"
@@ -10,34 +11,6 @@ describe :string_replace, shared: true do
     a.should == "another string"
   end
 
-  it "taints self if other is tainted" do
-    a = ""
-    b = "".taint
-    a.send(@method, b)
-    a.tainted?.should == true
-  end
-
-  it "does not untaint self if other is untainted" do
-    a = "".taint
-    b = ""
-    a.send(@method, b)
-    a.tainted?.should == true
-  end
-
-  it "untrusts self if other is untrusted" do
-    a = ""
-    b = "".untrust
-    a.send(@method, b)
-    a.untrusted?.should == true
-  end
-
-  it "does not trust self if other is trusted" do
-    a = "".untrust
-    b = ""
-    a.send(@method, b)
-    a.untrusted?.should == true
-  end
-
   it "replaces the encoding of self with that of other" do
     a = "".encode("UTF-16LE")
     b = "".encode("UTF-8")
@@ -62,14 +35,14 @@ describe :string_replace, shared: true do
     -> { "hello".send(@method, mock('x')) }.should raise_error(TypeError)
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
+  it "raises a FrozenError on a frozen instance that is modified" do
     a = "hello".freeze
-    -> { a.send(@method, "world") }.should raise_error(frozen_error_class)
+    -> { a.send(@method, "world") }.should raise_error(FrozenError)
   end
 
   # see [ruby-core:23666]
-  it "raises a #{frozen_error_class} on a frozen instance when self-replacing" do
+  it "raises a FrozenError on a frozen instance when self-replacing" do
     a = "hello".freeze
-    -> { a.send(@method, a) }.should raise_error(frozen_error_class)
+    -> { a.send(@method, a) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/shared/slice.rb b/spec/ruby/core/string/shared/slice.rb
index ef7a8787ce..7b9b9f6a14 100644
--- a/spec/ruby/core/string/shared/slice.rb
+++ b/spec/ruby/core/string/shared/slice.rb
@@ -80,21 +80,12 @@ describe :string_slice_index_length, shared: true do
     "hello there".send(@method, -3,2).should == "er"
   end
 
-  it "always taints resulting strings when self is tainted" do
-    str = "hello world"
-    str.taint
-
-    str.send(@method, 0,0).tainted?.should == true
-    str.send(@method, 0,1).tainted?.should == true
-    str.send(@method, 2,1).tainted?.should == true
-  end
-
-  it "returns a string with the same encoding" do
+  it "returns a string with the same encoding as self" do
     s = "hello there"
     s.send(@method, 1, 9).encoding.should == s.encoding
 
-    a = "hello".force_encoding("binary")
-    b = " there".force_encoding("ISO-8859-1")
+    a = "hello".dup.force_encoding("binary")
+    b = " there".dup.force_encoding("ISO-8859-1")
     c = (a + b).force_encoding(Encoding::US_ASCII)
 
     c.send(@method, 0, 5).encoding.should == Encoding::US_ASCII
@@ -119,6 +110,8 @@ describe :string_slice_index_length, shared: true do
 
     "x".send(@method, -2,0).should == nil
     "x".send(@method, -2,1).should == nil
+
+    "x".send(@method, fixnum_max, 1).should == nil
   end
 
   it "returns nil if the length is negative" do
@@ -126,6 +119,18 @@ describe :string_slice_index_length, shared: true do
     "hello there".send(@method, -4,-3).should == nil
   end
 
+  platform_is pointer_size: 64 do
+    it "returns nil if the length is negative big value" do
+      "hello there".send(@method, 4, -(1 << 31)).should == nil
+
+      # by some reason length < -(1 << 31) on CI on Windows leads to
+      # 'RangeError: bignum too big to convert into `long'' error
+      platform_is_not :windows do
+        "hello there".send(@method, 4, -(1 << 63)).should == nil
+      end
+    end
+  end
+
   it "calls to_int on the given index and the given length" do
     "hello".send(@method, 0.5, 1).should == "h"
     "hello".send(@method, 0.5, 2.5).should == "he"
@@ -159,11 +164,16 @@ describe :string_slice_index_length, shared: true do
     -> { "hello".send(@method, 0, bignum_value) }.should raise_error(RangeError)
   end
 
-  it "returns subclass instances" do
+  it "raises a RangeError if the index or length is too small" do
+    -> { "hello".send(@method, -bignum_value, 1) }.should raise_error(RangeError)
+    -> { "hello".send(@method, 0, -bignum_value) }.should raise_error(RangeError)
+  end
+
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.send(@method, 0,0).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, 0,4).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, 1,4).should be_an_instance_of(StringSpecs::MyString)
+    s.send(@method, 0,0).should be_an_instance_of(String)
+    s.send(@method, 0,4).should be_an_instance_of(String)
+    s.send(@method, 1,4).should be_an_instance_of(String)
   end
 
   it "handles repeated application" do
@@ -202,6 +212,10 @@ describe :string_slice_range, shared: true do
     "x".send(@method, 1..-1).should == ""
   end
 
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, 1..1).encoding.should == Encoding::US_ASCII
+  end
+
   it "returns nil if the beginning of the range falls outside of self" do
     "hello there".send(@method, 12..-1).should == nil
     "hello there".send(@method, 20..25).should == nil
@@ -234,23 +248,11 @@ describe :string_slice_range, shared: true do
     "x".send(@method, 1...-1).should == ""
   end
 
-  it "always taints resulting strings when self is tainted" do
-    str = "hello world"
-    str.taint
-
-    str.send(@method, 0..0).tainted?.should == true
-    str.send(@method, 0...0).tainted?.should == true
-    str.send(@method, 0..1).tainted?.should == true
-    str.send(@method, 0...1).tainted?.should == true
-    str.send(@method, 2..3).tainted?.should == true
-    str.send(@method, 2..0).tainted?.should == true
-  end
-
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.send(@method, 0...0).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, 0..4).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, 1..4).should be_an_instance_of(StringSpecs::MyString)
+    s.send(@method, 0...0).should be_an_instance_of(String)
+    s.send(@method, 0..4).should be_an_instance_of(String)
+    s.send(@method, 1..4).should be_an_instance_of(String)
   end
 
   it "calls to_int on range arguments" do
@@ -289,6 +291,30 @@ describe :string_slice_range, shared: true do
     "hello world".send(@method, 6..5).send(@method, -1..-1).should == nil
     "hello world".send(@method, 6..5).send(@method, 1..1).should == nil
   end
+
+  it "raises a type error if a range is passed with a length" do
+    ->{ "hello".send(@method, 1..2, 1) }.should raise_error(TypeError)
+  end
+
+  it "raises a RangeError if one of the bound is too big" do
+    -> { "hello".send(@method, bignum_value..(bignum_value + 1)) }.should raise_error(RangeError)
+    -> { "hello".send(@method, 0..bignum_value) }.should raise_error(RangeError)
+  end
+
+  it "works with endless ranges" do
+    "hello there".send(@method, eval("(2..)")).should == "llo there"
+    "hello there".send(@method, eval("(2...)")).should == "llo there"
+    "hello there".send(@method, eval("(-4..)")).should == "here"
+    "hello there".send(@method, eval("(-4...)")).should == "here"
+  end
+
+  it "works with beginless ranges" do
+    "hello there".send(@method, (..5)).should == "hello "
+    "hello there".send(@method, (...5)).should == "hello"
+    "hello there".send(@method, (..-4)).should == "hello th"
+    "hello there".send(@method, (...-4)).should == "hello t"
+    "hello there".send(@method, (...nil)).should == "hello there"
+  end
 end
 
 describe :string_slice_regexp, shared: true do
@@ -301,31 +327,14 @@ describe :string_slice_regexp, shared: true do
     "hello there".send(@method, /xyz/).should == nil
   end
 
-  not_supported_on :opal do
-    it "always taints resulting strings when self or regexp is tainted" do
-      strs = ["hello world"]
-      strs += strs.map { |s| s.dup.taint }
-
-      strs.each do |str|
-        str.send(@method, //).tainted?.should == str.tainted?
-        str.send(@method, /hello/).tainted?.should == str.tainted?
-
-        tainted_re = /./
-        tainted_re.taint
-
-        str.send(@method, tainted_re).tainted?.should == true
-      end
-    end
-
-    it "returns an untrusted string if the regexp is untrusted" do
-      "hello".send(@method, /./.untrust).untrusted?.should be_true
-    end
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, /[aeiou](.)\1/).encoding.should == Encoding::US_ASCII
   end
 
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.send(@method, //).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, /../).should be_an_instance_of(StringSpecs::MyString)
+    s.send(@method, //).should be_an_instance_of(String)
+    s.send(@method, /../).should be_an_instance_of(String)
   end
 
   it "sets $~ to MatchData when there is a match and nil when there's none" do
@@ -352,42 +361,28 @@ describe :string_slice_regexp_index, shared: true do
     "har".send(@method, /(.)(.)(.)/, -3).should == "h"
   end
 
-  it "always taints resulting strings when self or regexp is tainted" do
-    strs = ["hello world"]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      str.send(@method, //, 0).tainted?.should == str.tainted?
-      str.send(@method, /hello/, 0).tainted?.should == str.tainted?
-
-      str.send(@method, /(.)(.)(.)/, 0).tainted?.should == str.tainted?
-      str.send(@method, /(.)(.)(.)/, 1).tainted?.should == str.tainted?
-      str.send(@method, /(.)(.)(.)/, -1).tainted?.should == str.tainted?
-      str.send(@method, /(.)(.)(.)/, -2).tainted?.should == str.tainted?
-
-      tainted_re = /(.)(.)(.)/
-      tainted_re.taint
+  it "returns nil if there is no match" do
+    "hello there".send(@method, /(what?)/, 1).should == nil
+  end
 
-      str.send(@method, tainted_re, 0).tainted?.should == true
-      str.send(@method, tainted_re, 1).tainted?.should == true
-      str.send(@method, tainted_re, -1).tainted?.should == true
-    end
+  it "returns nil if the index is larger than the number of captures" do
+    "hello there".send(@method, /hello (.)/, 2).should == nil
+    # You can't refer to 0 using negative indices
+    "hello there".send(@method, /hello (.)/, -2).should == nil
   end
 
-  not_supported_on :opal do
-    it "returns an untrusted string if the regexp is untrusted" do
-      "hello".send(@method, /(.)/.untrust, 1).untrusted?.should be_true
-    end
+  it "returns nil if there is no capture for the given index" do
+    "hello there".send(@method, /[aeiou](.)\1/, 2).should == nil
   end
 
-  it "returns nil if there is no match" do
-    "hello there".send(@method, /(what?)/, 1).should == nil
+  it "returns nil if the given capture group was not matched but still sets $~" do
+    "test".send(@method, /te(z)?/, 1).should == nil
+    $~[0].should == "te"
+    $~[1].should == nil
   end
 
-  it "returns nil if there is no capture for the given index" do
-    "hello there".send(@method, /[aeiou](.)\1/, 2).should == nil
-    # You can't refer to 0 using negative indices
-    "hello there".send(@method, /[aeiou](.)\1/, -2).should == nil
+  it "returns a String in the same encoding as self" do
+    "hello there".encode("US-ASCII").send(@method, /[aeiou](.)\1/, 0).encoding.should == Encoding::US_ASCII
   end
 
   it "calls to_int on the given index" do
@@ -408,10 +403,10 @@ describe :string_slice_regexp_index, shared: true do
     -> { "hello".send(@method, /(.)(.)(.)/, nil) }.should raise_error(TypeError)
   end
 
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.send(@method, /(.)(.)/, 0).should be_an_instance_of(StringSpecs::MyString)
-    s.send(@method, /(.)(.)/, 1).should be_an_instance_of(StringSpecs::MyString)
+    s.send(@method, /(.)(.)/, 0).should be_an_instance_of(String)
+    s.send(@method, /(.)(.)/, 1).should be_an_instance_of(String)
   end
 
   it "sets $~ to MatchData when there is a match and nil when there's none" do
@@ -432,19 +427,6 @@ describe :string_slice_string, shared: true do
     "hello there".send(@method, s).should == s
   end
 
-  it "taints resulting strings when other is tainted" do
-    strs = ["", "hello world", "hello"]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      strs.each do |other|
-        r = str.send(@method, other)
-
-        r.tainted?.should == !r.nil? & other.tainted?
-      end
-    end
-  end
-
   it "doesn't set $~" do
     $~ = nil
 
@@ -463,11 +445,11 @@ describe :string_slice_string, shared: true do
     -> { "hello".send(@method, o) }.should raise_error(TypeError)
   end
 
-  it "returns a subclass instance when given a subclass instance" do
+  it "returns a String instance when given a subclass instance" do
     s = StringSpecs::MyString.new("el")
     r = "hello".send(@method, s)
     r.should == "el"
-    r.should be_an_instance_of(StringSpecs::MyString)
+    r.should be_an_instance_of(String)
   end
 end
 
@@ -493,28 +475,6 @@ describe :string_slice_regexp_group, shared: true do
       "hello there".send(@method, /(?<g>h(?<g>.))/, 'g').should == "e"
     end
 
-    it "always taints resulting strings when self or regexp is tainted" do
-      strs = ["hello world"]
-      strs += strs.map { |s| s.dup.taint }
-
-      strs.each do |str|
-        str.send(@method, /(?<hi>hello)/, 'hi').tainted?.should == str.tainted?
-
-        str.send(@method, /(?<g>(.)(.)(.))/, 'g').tainted?.should == str.tainted?
-        str.send(@method, /(?<h>.)(.)(.)/, 'h').tainted?.should == str.tainted?
-        str.send(@method, /(.)(?<a>.)(.)/, 'a').tainted?.should == str.tainted?
-        str.send(@method, /(.)(.)(?<r>.)/, 'r').tainted?.should == str.tainted?
-        str.send(@method, /(?<h>.)(?<a>.)(?<r>.)/, 'r').tainted?.should == str.tainted?
-
-        tainted_re = /(?<a>.)(?<b>.)(?<c>.)/
-        tainted_re.taint
-
-        str.send(@method, tainted_re, 'a').tainted?.should be_true
-        str.send(@method, tainted_re, 'b').tainted?.should be_true
-        str.send(@method, tainted_re, 'c').tainted?.should be_true
-      end
-    end
-
     it "returns nil if there is no match" do
       "hello there".send(@method, /(?<whut>what?)/, 'whut').should be_nil
     end
@@ -535,9 +495,9 @@ describe :string_slice_regexp_group, shared: true do
       -> { "hello".send(@method, /(?<q>)/, '') }.should raise_error(IndexError)
     end
 
-    it "returns subclass instances" do
+    it "returns String instances" do
       s = StringSpecs::MyString.new("hello")
-      s.send(@method, /(?<q>.)/, 'q').should be_an_instance_of(StringSpecs::MyString)
+      s.send(@method, /(?<q>.)/, 'q').should be_an_instance_of(String)
     end
 
     it "sets $~ to MatchData when there is a match and nil when there's none" do
diff --git a/spec/ruby/core/string/shared/strip.rb b/spec/ruby/core/string/shared/strip.rb
new file mode 100644
index 0000000000..3af77b50fe
--- /dev/null
+++ b/spec/ruby/core/string/shared/strip.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe :string_strip, shared: true do
+  it "returns a String in the same encoding as self" do
+    " hello ".encode("US-ASCII").send(@method).encoding.should == Encoding::US_ASCII
+  end
+
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new(" hello ").send(@method).should be_an_instance_of(String)
+    StringSpecs::MyString.new(" ").send(@method).should be_an_instance_of(String)
+    StringSpecs::MyString.new("").send(@method).should be_an_instance_of(String)
+  end
+end
diff --git a/spec/ruby/core/string/shared/succ.rb b/spec/ruby/core/string/shared/succ.rb
index 31b4a8b5dd..7c68345f10 100644
--- a/spec/ruby/core/string/shared/succ.rb
+++ b/spec/ruby/core/string/shared/succ.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :string_succ, shared: true do
   it "returns an empty string for empty strings" do
     "".send(@method).should == ""
@@ -59,30 +59,29 @@ describe :string_succ, shared: true do
     "\xFF\xFF".send(@method).should == "\x01\x00\x00"
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("").send(@method).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("a").send(@method).should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("z").send(@method).should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("").send(@method).should be_an_instance_of(String)
+    StringSpecs::MyString.new("a").send(@method).should be_an_instance_of(String)
+    StringSpecs::MyString.new("z").send(@method).should be_an_instance_of(String)
   end
 
-  it "taints the result if self is tainted" do
-    ["", "a", "z", "Z", "9", "\xFF", "\xFF\xFF"].each do |s|
-      s.taint.send(@method).tainted?.should == true
-    end
+  it "returns a String in the same encoding as self" do
+    "z".encode("US-ASCII").send(@method).encoding.should == Encoding::US_ASCII
   end
 end
 
 describe :string_succ_bang, shared: true do
   it "is equivalent to succ, but modifies self in place (still returns self)" do
     ["", "abcd", "THX1138"].each do |s|
+      s = +s
       r = s.dup.send(@method)
       s.send(@method).should equal(s)
       s.should == r
     end
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { "".freeze.send(@method)     }.should raise_error(frozen_error_class)
-    -> { "abcd".freeze.send(@method) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { "".freeze.send(@method)     }.should raise_error(FrozenError)
+    -> { "abcd".freeze.send(@method) }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/shared/to_a.rb b/spec/ruby/core/string/shared/to_a.rb
deleted file mode 100644
index bad3ea6584..0000000000
--- a/spec/ruby/core/string/shared/to_a.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-describe :string_to_a, shared: true do
-  it "returns an empty array for empty strings" do
-    "".send(@method).should == []
-  end
-
-  it "returns an array containing the string for non-empty strings" do
-    "hello".send(@method).should == ["hello"]
-  end
-end
diff --git a/spec/ruby/core/string/shared/to_s.rb b/spec/ruby/core/string/shared/to_s.rb
index a5a13e4f26..4b87a6cbe1 100644
--- a/spec/ruby/core/string/shared/to_s.rb
+++ b/spec/ruby/core/string/shared/to_s.rb
@@ -10,9 +10,4 @@ describe :string_to_s, shared: true do
     s.should == "a string"
     s.should be_an_instance_of(String)
   end
-
-  it "taints the result when self is tainted" do
-    "x".taint.send(@method).tainted?.should == true
-    StringSpecs::MyString.new("x").taint.send(@method).tainted?.should == true
-  end
 end
diff --git a/spec/ruby/core/string/shared/to_sym.rb b/spec/ruby/core/string/shared/to_sym.rb
index 1180d64712..833eae100e 100644
--- a/spec/ruby/core/string/shared/to_sym.rb
+++ b/spec/ruby/core/string/shared/to_sym.rb
@@ -53,11 +53,20 @@ describe :string_to_sym, shared: true do
     sym.to_s.should == binary_string
   end
 
+  it "ignores existing symbols with different encoding" do
+    source = "fée"
+
+    iso_symbol = source.dup.force_encoding(Encoding::ISO_8859_1).send(@method)
+    iso_symbol.encoding.should == Encoding::ISO_8859_1
+    binary_symbol = source.dup.force_encoding(Encoding::BINARY).send(@method)
+    binary_symbol.encoding.should == Encoding::BINARY
+  end
+
   it "raises an EncodingError for UTF-8 String containing invalid bytes" do
     invalid_utf8 = "\xC3"
-    invalid_utf8.valid_encoding?.should == false
+    invalid_utf8.should_not.valid_encoding?
     -> {
       invalid_utf8.send(@method)
-    }.should raise_error(EncodingError, /invalid/)
+    }.should raise_error(EncodingError, 'invalid symbol in encoding UTF-8 :"\xC3"')
   end
 end
diff --git a/spec/ruby/core/string/slice_spec.rb b/spec/ruby/core/string/slice_spec.rb
index 2af663117c..5aba2d3be0 100644
--- a/spec/ruby/core/string/slice_spec.rb
+++ b/spec/ruby/core/string/slice_spec.rb
@@ -1,5 +1,5 @@
 # -*- encoding: utf-8 -*-
-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 require_relative 'shared/slice'
@@ -53,10 +53,10 @@ describe "String#slice! with index" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { "hello".freeze.slice!(1)  }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(10) }.should raise_error(frozen_error_class)
-    -> { "".freeze.slice!(0)       }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { "hello".freeze.slice!(1)  }.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(10) }.should raise_error(FrozenError)
+    -> { "".freeze.slice!(0)       }.should raise_error(FrozenError)
   end
 
   it "calls to_int on index" do
@@ -94,14 +94,6 @@ describe "String#slice! with index, length" do
     a.should == "h"
   end
 
-  it "always taints resulting strings when self is tainted" do
-    str = "hello world"
-    str.taint
-
-    str.slice!(0, 0).tainted?.should == true
-    str.slice!(2, 1).tainted?.should == true
-  end
-
   it "returns nil if the given position is out of self" do
     a = "hello"
     a.slice(10, 3).should == nil
@@ -117,14 +109,14 @@ describe "String#slice! with index, length" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { "hello".freeze.slice!(1, 2)  }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(10, 3) }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(-10, 3)}.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(4, -3) }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(10, 3) }.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(-10, 3)}.should raise_error(frozen_error_class)
-    -> { "hello".freeze.slice!(4, -3) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { "hello".freeze.slice!(1, 2)  }.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(10, 3) }.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(-10, 3)}.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(4, -3) }.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(10, 3) }.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(-10, 3)}.should raise_error(FrozenError)
+    -> { "hello".freeze.slice!(4, -3) }.should raise_error(FrozenError)
   end
 
   it "calls to_int on idx and length" do
@@ -140,13 +132,12 @@ describe "String#slice! with index, length" do
     "hello".slice!(obj, obj).should == "ll"
   end
 
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.slice!(0, 0).should be_an_instance_of(StringSpecs::MyString)
-    s.slice!(0, 4).should be_an_instance_of(StringSpecs::MyString)
+    s.slice!(0, 0).should be_an_instance_of(String)
+    s.slice!(0, 4).should be_an_instance_of(String)
   end
 
-
   it "returns the substring given by the character offsets" do
     "hellö there".slice!(1,0).should == ""
     "hellö there".slice!(1,3).should == "ell"
@@ -184,18 +175,10 @@ describe "String#slice! Range" do
     b.should == "hello"
   end
 
-  it "always taints resulting strings when self is tainted" do
-    str = "hello world"
-    str.taint
-
-    str.slice!(0..0).tainted?.should == true
-    str.slice!(2..3).tainted?.should == true
-  end
-
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.slice!(0...0).should be_an_instance_of(StringSpecs::MyString)
-    s.slice!(0..4).should be_an_instance_of(StringSpecs::MyString)
+    s.slice!(0...0).should be_an_instance_of(String)
+    s.slice!(0..4).should be_an_instance_of(String)
   end
 
   it "calls to_int on range arguments" do
@@ -244,13 +227,13 @@ describe "String#slice! Range" do
   end
 
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "hello".freeze.slice!(1..3)  }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "hello".freeze.slice!(1..3)  }.should raise_error(FrozenError)
   end
 
   # see redmine #1551
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> { "hello".freeze.slice!(10..20)}.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> { "hello".freeze.slice!(10..20)}.should raise_error(FrozenError)
   end
 end
 
@@ -271,32 +254,10 @@ describe "String#slice! with Regexp" do
     s.should == "this is a string"
   end
 
-  it "always taints resulting strings when self or regexp is tainted" do
-    strs = ["hello world"]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      str = str.dup
-      str.slice!(//).tainted?.should == str.tainted?
-      str.slice!(/hello/).tainted?.should == str.tainted?
-
-      tainted_re = /./
-      tainted_re.taint
-
-      str.slice!(tainted_re).tainted?.should == true
-    end
-  end
-
-  it "doesn't taint self when regexp is tainted" do
-    s = "hello"
-    s.slice!(/./.taint)
-    s.tainted?.should == false
-  end
-
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.slice!(//).should be_an_instance_of(StringSpecs::MyString)
-    s.slice!(/../).should be_an_instance_of(StringSpecs::MyString)
+    s.slice!(//).should be_an_instance_of(String)
+    s.slice!(/../).should be_an_instance_of(String)
   end
 
   it "returns the matching portion of self with a multi byte character" do
@@ -312,12 +273,12 @@ describe "String#slice! with Regexp" do
     $~.should == nil
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "this is a string".freeze.slice!(/s.*t/) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "this is a string".freeze.slice!(/s.*t/) }.should raise_error(FrozenError)
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> { "this is a string".freeze.slice!(/zzz/)  }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> { "this is a string".freeze.slice!(/zzz/)  }.should raise_error(FrozenError)
   end
 end
 
@@ -330,28 +291,6 @@ describe "String#slice! with Regexp, index" do
     str.should == "ho here"
   end
 
-  it "always taints resulting strings when self or regexp is tainted" do
-    strs = ["hello world"]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      str = str.dup
-      str.slice!(//, 0).tainted?.should == str.tainted?
-      str.slice!(/hello/, 0).tainted?.should == str.tainted?
-
-      tainted_re = /(.)(.)(.)/
-      tainted_re.taint
-
-      str.slice!(tainted_re, 1).tainted?.should == true
-    end
-  end
-
-  it "doesn't taint self when regexp is tainted" do
-    s = "hello"
-    s.slice!(/(.)(.)/.taint, 1)
-    s.tainted?.should == false
-  end
-
   it "returns nil if there was no match" do
     s = "this is a string"
     s.slice!(/x(zzz)/, 1).should == nil
@@ -375,10 +314,10 @@ describe "String#slice! with Regexp, index" do
     "har".slice!(/(.)(.)(.)/, obj).should == "a"
   end
 
-  it "returns subclass instances" do
+  it "returns String instances" do
     s = StringSpecs::MyString.new("hello")
-    s.slice!(/(.)(.)/, 0).should be_an_instance_of(StringSpecs::MyString)
-    s.slice!(/(.)(.)/, 1).should be_an_instance_of(StringSpecs::MyString)
+    s.slice!(/(.)(.)/, 0).should be_an_instance_of(String)
+    s.slice!(/(.)(.)/, 1).should be_an_instance_of(String)
   end
 
   it "returns the encoding aware capture for the given index" do
@@ -402,10 +341,10 @@ describe "String#slice! with Regexp, index" do
     $~.should == nil
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { "this is a string".freeze.slice!(/s.*t/)  }.should raise_error(frozen_error_class)
-    -> { "this is a string".freeze.slice!(/zzz/, 0)}.should raise_error(frozen_error_class)
-    -> { "this is a string".freeze.slice!(/(.)/, 2)}.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { "this is a string".freeze.slice!(/s.*t/)  }.should raise_error(FrozenError)
+    -> { "this is a string".freeze.slice!(/zzz/, 0)}.should raise_error(FrozenError)
+    -> { "this is a string".freeze.slice!(/(.)/, 2)}.should raise_error(FrozenError)
   end
 end
 
@@ -416,21 +355,6 @@ describe "String#slice! with String" do
     c.should == "he hello"
   end
 
-  it "taints resulting strings when other is tainted" do
-    strs = ["", "hello world", "hello"]
-    strs += strs.map { |s| s.dup.taint }
-
-    strs.each do |str|
-      str = str.dup
-      strs.each do |other|
-        other = other.dup
-        r = str.slice!(other)
-
-        r.tainted?.should == !r.nil? & other.tainted?
-      end
-    end
-  end
-
   it "doesn't set $~" do
     $~ = nil
 
@@ -455,12 +379,12 @@ describe "String#slice! with String" do
     s = StringSpecs::MyString.new("el")
     r = "hello".slice!(s)
     r.should == "el"
-    r.should be_an_instance_of(StringSpecs::MyString)
+    r.should be_an_instance_of(String)
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
-    -> { "hello hello".freeze.slice!('llo')     }.should raise_error(frozen_error_class)
-    -> { "this is a string".freeze.slice!('zzz')}.should raise_error(frozen_error_class)
-    -> { "this is a string".freeze.slice!('zzz')}.should raise_error(frozen_error_class)
+  it "raises a FrozenError if self is frozen" do
+    -> { "hello hello".freeze.slice!('llo')     }.should raise_error(FrozenError)
+    -> { "this is a string".freeze.slice!('zzz')}.should raise_error(FrozenError)
+    -> { "this is a string".freeze.slice!('zzz')}.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/split_spec.rb b/spec/ruby/core/string/split_spec.rb
index 655f0dae76..3c6d1864d1 100644
--- a/spec/ruby/core/string/split_spec.rb
+++ b/spec/ruby/core/string/split_spec.rb
@@ -3,12 +3,17 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "String#split with String" do
+  it "throws an ArgumentError if the string  is not a valid" do
+    s = "\xDF".dup.force_encoding(Encoding::UTF_8)
+
+    -> { s.split }.should raise_error(ArgumentError)
+    -> { s.split(':') }.should raise_error(ArgumentError)
+  end
+
   it "throws an ArgumentError if the pattern is not a valid string" do
     str = 'проверка'
-    broken_str = 'проверка'
-    broken_str.force_encoding('binary')
-    broken_str.chop!
-    broken_str.force_encoding('utf-8')
+    broken_str = "\xDF".dup.force_encoding(Encoding::UTF_8)
+
     -> { str.split(broken_str) }.should raise_error(ArgumentError)
   end
 
@@ -24,9 +29,35 @@ describe "String#split with String" do
     "1,2,,3,4,,".split(',').should == ["1", "2", "", "3", "4"]
     "1,2,,3,4,,".split(',', 0).should == ["1", "2", "", "3", "4"]
     "  a  b  c\nd  ".split("  ").should == ["", "a", "b", "c\nd"]
+    "  a  あ  c\nd  ".split("  ").should == ["", "a", "あ", "c\nd"]
     "hai".split("hai").should == []
     ",".split(",").should == []
     ",".split(",", 0).should == []
+    "あ".split("あ").should == []
+    "あ".split("あ", 0).should == []
+  end
+
+  it "does not suppress trailing empty fields when a positive limit is given" do
+    " 1 2 ".split(" ", 2).should == ["1", "2 "]
+    " 1 2 ".split(" ", 3).should == ["1", "2", ""]
+    " 1 2 ".split(" ", 4).should == ["1", "2", ""]
+    " 1 あ ".split(" ", 2).should == ["1", "あ "]
+    " 1 あ ".split(" ", 3).should == ["1", "あ", ""]
+    " 1 あ ".split(" ", 4).should == ["1", "あ", ""]
+
+    "1,2,".split(',', 2).should == ["1", "2,"]
+    "1,2,".split(',', 3).should == ["1", "2", ""]
+    "1,2,".split(',', 4).should == ["1", "2", ""]
+    "1,あ,".split(',', 2).should == ["1", "あ,"]
+    "1,あ,".split(',', 3).should == ["1", "あ", ""]
+    "1,あ,".split(',', 4).should == ["1", "あ", ""]
+
+    "1 2 ".split(/ /, 2).should == ["1", "2 "]
+    "1 2 ".split(/ /, 3).should == ["1", "2", ""]
+    "1 2 ".split(/ /, 4).should == ["1", "2", ""]
+    "1 あ ".split(/ /, 2).should == ["1", "あ "]
+    "1 あ ".split(/ /, 3).should == ["1", "あ", ""]
+    "1 あ ".split(/ /, 4).should == ["1", "あ", ""]
   end
 
   it "returns an array with one entry if limit is 1: the original string" do
@@ -62,6 +93,10 @@ describe "String#split with String" do
     ",".split(",", -1).should == ["", ""]
   end
 
+  it "raises a RangeError when the limit is larger than int" do
+    -> { "a,b".split(" ", 2147483649) }.should raise_error(RangeError)
+  end
+
   it "defaults to $; when string isn't given or nil" do
     suppress_warning do
       old_fs = $;
@@ -84,6 +119,22 @@ describe "String#split with String" do
         $; = old_fs
       end
     end
+
+    context "when $; is not nil" do
+      before do
+        suppress_warning do
+          @old_value, $; = $;, 'foobar'
+        end
+      end
+
+      after do
+        $; = @old_value
+      end
+
+      it "warns" do
+        -> { "".split }.should complain(/warning: \$; is set to non-nil value/)
+      end
+    end
   end
 
   it "ignores leading and continuous whitespace when string is a single space" do
@@ -141,12 +192,12 @@ describe "String#split with String" do
     "foo".split("bar", 3).should == ["foo"]
   end
 
-  it "returns subclass instances based on self" do
+  it "returns String instances based on self" do
     ["", "x.y.z.", "  x  y  "].each do |str|
       ["", ".", " "].each do |pat|
         [-1, 0, 1, 2].each do |limit|
           StringSpecs::MyString.new(str).split(pat, limit).each do |x|
-            x.should be_an_instance_of(StringSpecs::MyString)
+            x.should be_an_instance_of(String)
           end
 
           str.split(StringSpecs::MyString.new(pat), limit).each do |x|
@@ -157,32 +208,32 @@ describe "String#split with String" do
     end
   end
 
-  it "does not call constructor on created subclass instances" do
-    # can't call should_not_receive on an object that doesn't yet exist
-    # so failure here is signalled by exception, not expectation failure
+  it "returns an empty array when whitespace is split on whitespace" do
+    " ".split(" ").should == []
+    " \n ".split(" ").should == []
+    "  ".split(" ").should == []
+    " \t ".split(" ").should == []
+  end
 
-    s = StringSpecs::StringWithRaisingConstructor.new('silly:string')
-    s.split(':').first.should == 'silly'
+  it "doesn't split on non-ascii whitespace" do
+    "a\u{2008}b".split(" ").should == ["a\u{2008}b"]
   end
 
-  it "taints the resulting strings if self is tainted" do
-    ["", "x.y.z.", "  x  y  "].each do |str|
-      ["", ".", " "].each do |pat|
-        [-1, 0, 1, 2].each do |limit|
-          str.dup.taint.split(pat).each do |x|
-            x.tainted?.should == true
-          end
+  it "returns Strings in the same encoding as self" do
+    strings = "hello world".encode("US-ASCII").split(" ")
 
-          str.split(pat.dup.taint).each do |x|
-            x.tainted?.should == false
-          end
-        end
-      end
-    end
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[1].encoding.should == Encoding::US_ASCII
   end
 end
 
 describe "String#split with Regexp" do
+  it "throws an ArgumentError if the string  is not a valid" do
+    s = "\xDF".dup.force_encoding(Encoding::UTF_8)
+
+    -> { s.split(/./) }.should raise_error(ArgumentError)
+  end
+
   it "divides self on regexp matches" do
     " now's  the time".split(/ /).should == ["", "now's", "", "the", "time"]
     " x\ny ".split(/ /).should == ["", "x\ny"]
@@ -335,95 +386,161 @@ describe "String#split with Regexp" do
     "foo".split(/bar/, 3).should == ["foo"]
   end
 
-  it "returns subclass instances based on self" do
+  it "returns String instances based on self" do
     ["", "x:y:z:", "  x  y  "].each do |str|
       [//, /:/, /\s+/].each do |pat|
         [-1, 0, 1, 2].each do |limit|
           StringSpecs::MyString.new(str).split(pat, limit).each do |x|
-            x.should be_an_instance_of(StringSpecs::MyString)
-          end
-        end
-      end
-    end
-  end
-
-  it "does not call constructor on created subclass instances" do
-    # can't call should_not_receive on an object that doesn't yet exist
-    # so failure here is signalled by exception, not expectation failure
-
-    s = StringSpecs::StringWithRaisingConstructor.new('silly:string')
-    s.split(/:/).first.should == 'silly'
-  end
-
-  it "taints the resulting strings if self is tainted" do
-    ["", "x:y:z:", "  x  y  "].each do |str|
-      [//, /:/, /\s+/].each do |pat|
-        [-1, 0, 1, 2].each do |limit|
-          str.dup.taint.split(pat, limit).each do |x|
-            # See the spec below for why the conditional is here
-            x.tainted?.should be_true unless x.empty?
-          end
-        end
-      end
-    end
-  end
-
-  it "taints an empty string if self is tainted" do
-    ":".taint.split(//, -1).last.tainted?.should be_true
-  end
-
-  it "doesn't taints the resulting strings if the Regexp is tainted" do
-    ["", "x:y:z:", "  x  y  "].each do |str|
-      [//, /:/, /\s+/].each do |pat|
-        [-1, 0, 1, 2].each do |limit|
-          str.split(pat.dup.taint, limit).each do |x|
-            x.tainted?.should be_false
+            x.should be_an_instance_of(String)
           end
         end
       end
     end
   end
 
-  it "retains the encoding of the source string" do
+  it "returns Strings in the same encoding as self" do
     ary = "а б в".split
     encodings = ary.map { |s| s.encoding }
     encodings.should == [Encoding::UTF_8, Encoding::UTF_8, Encoding::UTF_8]
   end
 
-
   it "splits a string on each character for a multibyte encoding and empty split" do
     "That's why efficiency could not be helped".split("").size.should == 39
   end
 
   it "returns an ArgumentError if an invalid UTF-8 string is supplied" do
-    broken_str = 'проверка' # in russian, means "test"
+    broken_str = +'проверка' # in russian, means "test"
     broken_str.force_encoding('binary')
     broken_str.chop!
     broken_str.force_encoding('utf-8')
     ->{ broken_str.split(/\r\n|\r|\n/) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.6" do
-    it "yields each split substrings if a block is given" do
+  # See https://bugs.ruby-lang.org/issues/12689 and https://github.com/jruby/jruby/issues/4868
+  it "allows concurrent Regexp calls in a shared context" do
+    str = 'a,b,c,d,e'
+
+    p = proc { str.split(/,/) }
+    results = 10.times.map { Thread.new { x = nil; 100.times { x = p.call }; x } }.map(&:value)
+
+    results.should == [%w[a b c d e]] * 10
+  end
+
+  context "when a block is given" do
+    it "yields each split substring with default pattern" do
       a = []
-      returned_object = "chunky bacon".split(" ") { |str| a << str.capitalize }
+      returned_object = "chunky bacon".split { |str| a << str.capitalize }
 
       returned_object.should == "chunky bacon"
       a.should == ["Chunky", "Bacon"]
     end
 
-    describe "for a String subclass" do
-      it "yields instances of the same subclass" do
-        a = []
-        StringSpecs::MyString.new("a|b").split("|") { |str| a << str }
-        first, last = a
+    it "yields each split substring with default pattern for a lazy substring" do
+      a = []
+      returned_object = "chunky bacon"[1...-1].split { |str| a << str.capitalize }
 
-        first.should be_an_instance_of(StringSpecs::MyString)
-        first.should == "a"
+      returned_object.should == "hunky baco"
+      a.should == ["Hunky", "Baco"]
+    end
 
-        last.should be_an_instance_of(StringSpecs::MyString)
-        last.should == "b"
-      end
+    it "yields each split substring with default pattern for a non-ASCII string" do
+      a = []
+      returned_object = "l'été arrive bientôt".split { |str| a << str }
+
+      returned_object.should == "l'été arrive bientôt"
+      a.should == ["l'été", "arrive", "bientôt"]
+    end
+
+    it "yields each split substring with default pattern for a non-ASCII lazy substring" do
+      a = []
+      returned_object = "l'été arrive bientôt"[1...-1].split { |str| a << str }
+
+      returned_object.should == "'été arrive bientô"
+      a.should == ["'été", "arrive", "bientô"]
+    end
+
+    it "yields the string when limit is 1" do
+      a = []
+      returned_object = "chunky bacon".split("", 1) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky bacon"
+      a.should == ["Chunky bacon"]
+    end
+
+    it "yields each split letter" do
+      a = []
+      returned_object = "chunky".split("", 0) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky"
+      a.should == %w(C H U N K Y)
+    end
+
+    it "yields each split substring with a pattern" do
+      a = []
+      returned_object = "chunky-bacon".split("-", 0) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky-bacon"
+      a.should == ["Chunky", "Bacon"]
     end
+
+    it "yields each split substring with empty regexp pattern" do
+      a = []
+      returned_object = "chunky".split(//) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky"
+      a.should == %w(C H U N K Y)
+    end
+
+    it "yields each split substring with empty regexp pattern and limit" do
+      a = []
+      returned_object = "chunky".split(//, 3) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky"
+      a.should == %w(C H Unky)
+    end
+
+    it "yields each split substring with a regexp pattern" do
+      a = []
+      returned_object = "chunky:bacon".split(/:/) { |str| a << str.capitalize }
+
+      returned_object.should == "chunky:bacon"
+      a.should == ["Chunky", "Bacon"]
+    end
+
+    it "returns a string as is (and doesn't call block) if it is empty" do
+      a = []
+      returned_object = "".split { |str| a << str.capitalize }
+
+      returned_object.should == ""
+      a.should == []
+    end
+  end
+
+  describe "for a String subclass" do
+    it "yields instances of String" do
+      a = []
+      StringSpecs::MyString.new("a|b").split("|") { |str| a << str }
+      first, last = a
+
+      first.should be_an_instance_of(String)
+      first.should == "a"
+
+      last.should be_an_instance_of(String)
+      last.should == "b"
+    end
+  end
+
+  it "raises a TypeError when not called with nil, String, or Regexp" do
+    -> { "hello".split(42) }.should raise_error(TypeError)
+    -> { "hello".split(:ll) }.should raise_error(TypeError)
+    -> { "hello".split(false) }.should raise_error(TypeError)
+    -> { "hello".split(Object.new) }.should raise_error(TypeError)
+  end
+
+  it "returns Strings in the same encoding as self" do
+    strings = "hello world".encode("US-ASCII").split(/ /)
+
+    strings[0].encoding.should == Encoding::US_ASCII
+    strings[1].encoding.should == Encoding::US_ASCII
   end
 end
diff --git a/spec/ruby/core/string/squeeze_spec.rb b/spec/ruby/core/string/squeeze_spec.rb
index bcc320bb5b..981d480684 100644
--- a/spec/ruby/core/string/squeeze_spec.rb
+++ b/spec/ruby/core/string/squeeze_spec.rb
@@ -1,4 +1,5 @@
-# -*- encoding: binary -*-
+# encoding: binary
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -54,14 +55,6 @@ describe "String#squeeze" do
     -> { s.squeeze("^e-b") }.should raise_error(ArgumentError)
   end
 
-  it "taints the result when self is tainted" do
-    "hello".taint.squeeze("e").tainted?.should == true
-    "hello".taint.squeeze("a-z").tainted?.should == true
-
-    "hello".squeeze("e".taint).tainted?.should == false
-    "hello".squeeze("l".taint).tainted?.should == false
-  end
-
   it "tries to convert each set arg to a string using to_str" do
     other_string = mock('lo')
     other_string.should_receive(:to_str).and_return("lo")
@@ -72,14 +65,19 @@ describe "String#squeeze" do
     "hello room".squeeze(other_string, other_string2).should == "hello rom"
   end
 
+  it "returns a String in the same encoding as self" do
+    "yellow moon".encode("US-ASCII").squeeze.encoding.should == Encoding::US_ASCII
+    "yellow moon".encode("US-ASCII").squeeze("a").encoding.should == Encoding::US_ASCII
+  end
+
   it "raises a TypeError when one set arg can't be converted to a string" do
     -> { "hello world".squeeze([])        }.should raise_error(TypeError)
     -> { "hello world".squeeze(Object.new)}.should raise_error(TypeError)
     -> { "hello world".squeeze(mock('x')) }.should raise_error(TypeError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("oh no!!!").squeeze("!").should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("oh no!!!").squeeze("!").should be_an_instance_of(String)
   end
 end
 
@@ -103,11 +101,11 @@ describe "String#squeeze!" do
     -> { s.squeeze!("^e-b") }.should raise_error(ArgumentError)
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     a = "yellow moon"
     a.freeze
 
-    -> { a.squeeze!("") }.should raise_error(frozen_error_class)
-    -> { a.squeeze!     }.should raise_error(frozen_error_class)
+    -> { a.squeeze!("") }.should raise_error(FrozenError)
+    -> { a.squeeze!     }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/start_with_spec.rb b/spec/ruby/core/string/start_with_spec.rb
index f66ec55266..35e33b46a6 100644
--- a/spec/ruby/core/string/start_with_spec.rb
+++ b/spec/ruby/core/string/start_with_spec.rb
@@ -1,76 +1,27 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../../shared/string/start_with'
 
 describe "String#start_with?" do
-  it "returns true only if beginning match" do
-    s = "hello"
-    s.start_with?('h').should be_true
-    s.start_with?('hel').should be_true
-    s.start_with?('el').should be_false
-  end
-
-  it "returns true only if any beginning match" do
-    "hello".start_with?('x', 'y', 'he', 'z').should be_true
-  end
-
-  it "returns true if the search string is empty" do
-    "hello".start_with?("").should be_true
-    "".start_with?("").should be_true
-  end
-
-  it "converts its argument using :to_str" do
-    s = "hello"
-    find = mock('h')
-    find.should_receive(:to_str).and_return("h")
-    s.start_with?(find).should be_true
-  end
+  it_behaves_like :start_with, :to_s
 
-  it "ignores arguments not convertible to string" do
-    "hello".start_with?().should be_false
-    -> { "hello".start_with?(1) }.should raise_error(TypeError)
-    -> { "hello".start_with?(["h"]) }.should raise_error(TypeError)
-    -> { "hello".start_with?(1, nil, "h") }.should raise_error(TypeError)
+  # Here and not in the shared examples because this is invalid as a Symbol
+  it "matches part of a character with the same part" do
+    "\xA9".should.start_with?("\xA9") # A9 is not a character head for UTF-8
   end
 
-  it "uses only the needed arguments" do
-    find = mock('h')
-    find.should_not_receive(:to_str)
-    "hello".start_with?("h",find).should be_true
-  end
-
-  it "works for multibyte strings" do
-    "céréale".start_with?("cér").should be_true
-  end
-
-  ruby_version_is "2.5" do
-    it "supports regexps" do
-      regexp = /[h1]/
-      "hello".start_with?(regexp).should be_true
-      "1337".start_with?(regexp).should be_true
-      "foxes are 1337".start_with?(regexp).should be_false
-      "chunky\n12bacon".start_with?(/12/).should be_false
+  ruby_version_is ""..."3.3" do
+    it "does not check we are matching only part of a character" do
+      "\xe3\x81\x82".size.should == 1
+      "\xe3\x81\x82".should.start_with?("\xe3")
     end
+  end
 
-    it "supports regexps with ^ and $ modifiers" do
-      regexp1 = /^\d{2}/
-      regexp2 = /\d{2}$/
-      "12test".start_with?(regexp1).should be_true
-      "test12".start_with?(regexp1).should be_false
-      "12test".start_with?(regexp2).should be_false
-      "test12".start_with?(regexp2).should be_false
-    end
-
-    it "sets Regexp.last_match if it returns true" do
-      regexp = /test-(\d+)/
-      "test-1337".start_with?(regexp).should be_true
-      Regexp.last_match.should_not be_nil
-      Regexp.last_match[1].should == "1337"
-      $1.should == "1337"
-
-      "test-asdf".start_with?(regexp).should be_false
-      Regexp.last_match.should be_nil
-      $1.should be_nil
+  ruby_version_is "3.3" do # #19784
+    it "checks we are matching only part of a character" do
+      "\xe3\x81\x82".size.should == 1
+      "\xe3\x81\x82".should_not.start_with?("\xe3")
     end
   end
 end
diff --git a/spec/ruby/core/string/strip_spec.rb b/spec/ruby/core/string/strip_spec.rb
index c205746483..edb6ea3b44 100644
--- a/spec/ruby/core/string/strip_spec.rb
+++ b/spec/ruby/core/string/strip_spec.rb
@@ -1,22 +1,19 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/strip'
 
 describe "String#strip" do
+  it_behaves_like :string_strip, :strip
+
   it "returns a new string with leading and trailing whitespace removed" do
     "   hello   ".strip.should == "hello"
     "   hello world   ".strip.should == "hello world"
     "\tgoodbye\r\v\n".strip.should == "goodbye"
-    "\x00 goodbye \x00".strip.should == "\x00 goodbye"
-  end
-
-  it "returns a copy of self with trailing NULL bytes and whitespace" do
-    " \x00 goodbye \x00 ".strip.should == "\x00 goodbye"
   end
 
-  it "taints the result when self is tainted" do
-    "".taint.strip.tainted?.should == true
-    "ok".taint.strip.tainted?.should == true
-    "  ok  ".taint.strip.tainted?.should == true
+  it "returns a copy of self without leading and trailing NULL bytes and whitespace" do
+    " \x00 goodbye \x00 ".strip.should == "goodbye"
   end
 end
 
@@ -29,11 +26,6 @@ describe "String#strip!" do
     a = "\tgoodbye\r\v\n"
     a.strip!
     a.should == "goodbye"
-
-    a = "\000 goodbye \000"
-    a.strip!
-    a.should == "\000 goodbye"
-
   end
 
   it "returns nil if no modifications where made" do
@@ -42,19 +34,25 @@ describe "String#strip!" do
     a.should == "hello"
   end
 
-  it "modifies self removing trailing NULL bytes and whitespace" do
-    a = " \x00 goodbye \x00 "
+  it "makes a string empty if it is only whitespace" do
+    "".strip!.should == nil
+    " ".strip.should == ""
+    "  ".strip.should == ""
+  end
+
+  it "removes leading and trailing NULL bytes and whitespace" do
+    a = "\000 goodbye \000"
     a.strip!
-    a.should == "\x00 goodbye"
+    a.should == "goodbye"
   end
 
-  it "raises a #{frozen_error_class} on a frozen instance that is modified" do
-    -> { "  hello  ".freeze.strip! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that is modified" do
+    -> { "  hello  ".freeze.strip! }.should raise_error(FrozenError)
   end
 
   # see #1552
-  it "raises a #{frozen_error_class} on a frozen instance that would not be modified" do
-    -> {"hello".freeze.strip! }.should raise_error(frozen_error_class)
-    -> {"".freeze.strip!      }.should raise_error(frozen_error_class)
+  it "raises a FrozenError on a frozen instance that would not be modified" do
+    -> {"hello".freeze.strip! }.should raise_error(FrozenError)
+    -> {"".freeze.strip!      }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/sub_spec.rb b/spec/ruby/core/string/sub_spec.rb
index 630f0d6b70..6ff28ec851 100644
--- a/spec/ruby/core/string/sub_spec.rb
+++ b/spec/ruby/core/string/sub_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -137,26 +138,6 @@ describe "String#sub with pattern, replacement" do
     "hello".sub(/./, 'hah\\').should == 'hah\\ello'
   end
 
-  it "taints the result if the original string or replacement is tainted" do
-    hello = "hello"
-    hello_t = "hello"
-    a = "a"
-    a_t = "a"
-    empty = ""
-    empty_t = ""
-
-    hello_t.taint; a_t.taint; empty_t.taint
-
-    hello_t.sub(/./, a).tainted?.should == true
-    hello_t.sub(/./, empty).tainted?.should == true
-
-    hello.sub(/./, a_t).tainted?.should == true
-    hello.sub(/./, empty_t).tainted?.should == true
-    hello.sub(//, empty_t).tainted?.should == true
-
-    hello.sub(//.taint, "foo").tainted?.should == false
-  end
-
   it "tries to convert pattern to a string using to_str" do
     pattern = mock('.')
     pattern.should_receive(:to_str).and_return(".")
@@ -190,11 +171,11 @@ describe "String#sub with pattern, replacement" do
     -> { "hello".sub(/[aeiou]/, 99) }.should raise_error(TypeError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("").sub(//, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("").sub(/foo/, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").sub(/foo/, "").should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("foo").sub("foo", "").should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("").sub(//, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("").sub(/foo/, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").sub(/foo/, "").should be_an_instance_of(String)
+    StringSpecs::MyString.new("foo").sub("foo", "").should be_an_instance_of(String)
   end
 
   it "sets $~ to MatchData of match and nil when there's none" do
@@ -223,6 +204,17 @@ describe "String#sub with pattern, replacement" do
     "ababa".sub(/(b)/, '\\\\\1').should == "a\\baba"
   end
 
+  it "handles a pattern in a superset encoding" do
+    result = 'abc'.force_encoding(Encoding::US_ASCII).sub('é', 'è')
+    result.should == 'abc'
+    result.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    result = 'été'.sub('t'.force_encoding(Encoding::US_ASCII), 'u')
+    result.should == 'éué'
+    result.encoding.should == Encoding::UTF_8
+  end
 end
 
 describe "String#sub with pattern and block" do
@@ -240,10 +232,10 @@ describe "String#sub with pattern and block" do
     offsets = []
 
     str.sub(/([aeiou])/) do
-       md = $~
-       md.string.should == str
-       offsets << md.offset(0)
-       str
+      md = $~
+      md.string.should == str
+      offsets << md.offset(0)
+      str
     end.should == "hhellollo"
 
     offsets.should == [[1, 2]]
@@ -284,26 +276,6 @@ describe "String#sub with pattern and block" do
     obj.should_receive(:to_s).and_return("ok")
     "hello".sub(/.+/) { obj }.should == "ok"
   end
-
-  it "taints the result if the original string or replacement is tainted" do
-    hello = "hello"
-    hello_t = "hello"
-    a = "a"
-    a_t = "a"
-    empty = ""
-    empty_t = ""
-
-    hello_t.taint; a_t.taint; empty_t.taint
-
-    hello_t.sub(/./) { a }.tainted?.should == true
-    hello_t.sub(/./) { empty }.tainted?.should == true
-
-    hello.sub(/./) { a_t }.tainted?.should == true
-    hello.sub(/./) { empty_t }.tainted?.should == true
-    hello.sub(//) { empty_t }.tainted?.should == true
-
-    hello.sub(//.taint) { "foo" }.tainted?.should == false
-  end
 end
 
 describe "String#sub! with pattern, replacement" do
@@ -313,12 +285,6 @@ describe "String#sub! with pattern, replacement" do
     a.should == "h*llo"
   end
 
-  it "taints self if replacement is tainted" do
-    a = "hello"
-    a.sub!(/./.taint, "foo").tainted?.should == false
-    a.sub!(/./, "foo".taint).tainted?.should == true
-  end
-
   it "returns nil if no modifications were made" do
     a = "hello"
     a.sub!(/z/, '*').should == nil
@@ -326,13 +292,34 @@ describe "String#sub! with pattern, replacement" do
     a.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     s = "hello"
     s.freeze
 
-    -> { s.sub!(/ROAR/, "x")    }.should raise_error(frozen_error_class)
-    -> { s.sub!(/e/, "e")       }.should raise_error(frozen_error_class)
-    -> { s.sub!(/[aeiou]/, '*') }.should raise_error(frozen_error_class)
+    -> { s.sub!(/ROAR/, "x")    }.should raise_error(FrozenError)
+    -> { s.sub!(/e/, "e")       }.should raise_error(FrozenError)
+    -> { s.sub!(/[aeiou]/, '*') }.should raise_error(FrozenError)
+  end
+
+  it "handles a pattern in a superset encoding" do
+    string = 'abc'.force_encoding(Encoding::US_ASCII)
+
+    result = string.sub!('é', 'è')
+
+    result.should == nil
+    string.should == 'abc'
+    string.encoding.should == Encoding::US_ASCII
+  end
+
+  it "handles a pattern in a subset encoding" do
+    string = 'été'
+    pattern = 't'.force_encoding(Encoding::US_ASCII)
+
+    result = string.sub!(pattern, 'u')
+
+    result.should == string
+    string.should == 'éué'
+    string.encoding.should == Encoding::UTF_8
   end
 end
 
@@ -352,21 +339,15 @@ describe "String#sub! with pattern and block" do
     offsets = []
 
     str.dup.sub!(/([aeiou])/) do
-       md = $~
-       md.string.should == str
-       offsets << md.offset(0)
-       str
+      md = $~
+      md.string.should == str
+      offsets << md.offset(0)
+      str
     end.should == "hhellollo"
 
     offsets.should == [[1, 2]]
   end
 
-  it "taints self if block's result is tainted" do
-    a = "hello"
-    a.sub!(/./.taint) { "foo" }.tainted?.should == false
-    a.sub!(/./) { "foo".taint }.tainted?.should == true
-  end
-
   it "returns nil if no modifications were made" do
     a = "hello"
     a.sub!(/z/) { '*' }.should == nil
@@ -379,13 +360,13 @@ describe "String#sub! with pattern and block" do
     -> { str.sub!(//) { str << 'x' } }.should raise_error(RuntimeError)
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     s = "hello"
     s.freeze
 
-    -> { s.sub!(/ROAR/) { "x" }    }.should raise_error(frozen_error_class)
-    -> { s.sub!(/e/) { "e" }       }.should raise_error(frozen_error_class)
-    -> { s.sub!(/[aeiou]/) { '*' } }.should raise_error(frozen_error_class)
+    -> { s.sub!(/ROAR/) { "x" }    }.should raise_error(FrozenError)
+    -> { s.sub!(/e/) { "e" }       }.should raise_error(FrozenError)
+    -> { s.sub!(/[aeiou]/) { '*' } }.should raise_error(FrozenError)
   end
 end
 
@@ -452,26 +433,6 @@ describe "String#sub with pattern and Hash" do
     "hello".sub(/(.+)/, 'hello' => repl ).should == repl
   end
 
-  it "untrusts the result if the original string is untrusted" do
-    str = "Ghana".untrust
-    str.sub(/[Aa]na/, 'ana' => '').untrusted?.should be_true
-  end
-
-  it "untrusts the result if a hash value is untrusted" do
-    str = "Ghana"
-    str.sub(/a$/, 'a' => 'di'.untrust).untrusted?.should be_true
-  end
-
-  it "taints the result if the original string is tainted" do
-    str = "Ghana".taint
-    str.sub(/[Aa]na/, 'ana' => '').tainted?.should be_true
-  end
-
-  it "taints the result if a hash value is tainted" do
-    str = "Ghana"
-    str.sub(/a$/, 'a' => 'di'.taint).tainted?.should be_true
-  end
-
 end
 
 describe "String#sub! with pattern and Hash" do
@@ -536,26 +497,6 @@ describe "String#sub! with pattern and Hash" do
     repl = '\& \0 \1 \` \\\' \+ \\\\ foo'
     "hello".sub!(/(.+)/, 'hello' => repl ).should == repl
   end
-
-  it "keeps untrusted state" do
-    str = "Ghana".untrust
-    str.sub!(/[Aa]na/, 'ana' => '').untrusted?.should be_true
-  end
-
-  it "untrusts self if a hash value is untrusted" do
-    str = "Ghana"
-    str.sub!(/a$/, 'a' => 'di'.untrust).untrusted?.should be_true
-  end
-
-  it "keeps tainted state" do
-    str = "Ghana".taint
-    str.sub!(/[Aa]na/, 'ana' => '').tainted?.should be_true
-  end
-
-  it "taints self if a hash value is tainted" do
-    str = "Ghana"
-    str.sub!(/a$/, 'a' => 'di'.taint).tainted?.should be_true
-  end
 end
 
 describe "String#sub with pattern and without replacement and block" do
diff --git a/spec/ruby/core/string/swapcase_spec.rb b/spec/ruby/core/string/swapcase_spec.rb
index 95edcec7d1..011a213501 100644
--- a/spec/ruby/core/string/swapcase_spec.rb
+++ b/spec/ruby/core/string/swapcase_spec.rb
@@ -1,17 +1,17 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe "String#swapcase" do
   it "returns a new string with all uppercase chars from self converted to lowercase and vice versa" do
-   "Hello".swapcase.should == "hELLO"
-   "cYbEr_PuNk11".swapcase.should == "CyBeR_pUnK11"
-   "+++---111222???".swapcase.should == "+++---111222???"
+    "Hello".swapcase.should == "hELLO"
+    "cYbEr_PuNk11".swapcase.should == "CyBeR_pUnK11"
+    "+++---111222???".swapcase.should == "+++---111222???"
   end
 
-  it "taints resulting string when self is tainted" do
-    "".taint.swapcase.tainted?.should == true
-    "hello".taint.swapcase.tainted?.should == true
+  it "returns a String in the same encoding as self" do
+    "Hello".encode("US-ASCII").swapcase.encoding.should == Encoding::US_ASCII
   end
 
   describe "full Unicode case mapping" do
@@ -33,6 +33,10 @@ describe "String#swapcase" do
     it "does not swapcase non-ASCII characters" do
       "aßet".swapcase(:ascii).should == "AßET"
     end
+
+    it "works with substrings" do
+      "prefix aTé"[-3..-1].swapcase(:ascii).should == "Até"
+    end
   end
 
   describe "full Unicode case mapping adapted for Turkic languages" do
@@ -71,9 +75,9 @@ describe "String#swapcase" do
     -> { "abc".swapcase(:invalid_option) }.should raise_error(ArgumentError)
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("").swapcase.should be_an_instance_of(StringSpecs::MyString)
-    StringSpecs::MyString.new("hello").swapcase.should be_an_instance_of(StringSpecs::MyString)
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("").swapcase.should be_an_instance_of(String)
+    StringSpecs::MyString.new("hello").swapcase.should be_an_instance_of(String)
   end
 end
 
@@ -84,6 +88,12 @@ describe "String#swapcase!" do
     a.should == "CyBeR_pUnK11"
   end
 
+  it "modifies self in place for non-ascii-compatible encodings" do
+    a = "cYbEr_PuNk11".encode("utf-16le")
+    a.swapcase!
+    a.should == "CyBeR_pUnK11".encode("utf-16le")
+  end
+
   describe "full Unicode case mapping" do
     it "modifies self in place for all of Unicode with no option" do
       a = "äÖü"
@@ -91,6 +101,12 @@ describe "String#swapcase!" do
       a.should == "ÄöÜ"
     end
 
+    it "works for non-ascii-compatible encodings" do
+      a = "äÖü".encode("utf-16le")
+      a.swapcase!
+      a.should == "ÄöÜ".encode("utf-16le")
+    end
+
     it "updates string metadata" do
       swapcased = "Aßet"
       swapcased.swapcase!
@@ -108,6 +124,12 @@ describe "String#swapcase!" do
       a.swapcase!(:ascii)
       a.should == "AßET"
     end
+
+    it "works for non-ascii-compatible encodings" do
+      a = "aBc".encode("utf-16le")
+      a.swapcase!(:ascii)
+      a.should == "AbC".encode("utf-16le")
+    end
   end
 
   describe "modifies self in place for full Unicode case mapping adapted for Turkic languages" do
@@ -162,10 +184,10 @@ describe "String#swapcase!" do
     "".swapcase!.should == nil
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
+  it "raises a FrozenError when self is frozen" do
     ["", "hello"].each do |a|
       a.freeze
-      -> { a.swapcase! }.should raise_error(frozen_error_class)
+      -> { a.swapcase! }.should raise_error(FrozenError)
     end
   end
 end
diff --git a/spec/ruby/core/string/to_c_spec.rb b/spec/ruby/core/string/to_c_spec.rb
index 9c84b14f4d..1813890e72 100644
--- a/spec/ruby/core/string/to_c_spec.rb
+++ b/spec/ruby/core/string/to_c_spec.rb
@@ -1,99 +1,53 @@
 require_relative '../../spec_helper'
+require_relative '../../shared/kernel/complex'
+require_relative 'fixtures/to_c'
 
 describe "String#to_c" do
-  it "returns a Complex object" do
-    '9'.to_c.should be_an_instance_of(Complex)
-  end
-
-  it "understands integers" do
-    '20'.to_c.should == Complex(20)
-  end
-
-  it "understands negative integers" do
-    '-3'.to_c.should == Complex(-3)
-  end
-
-  it "understands fractions (numerator/denominator) for the real part" do
-    '2/3'.to_c.should == Complex(Rational(2, 3))
-  end
-
-  it "understands fractions (numerator/denominator) for the imaginary part" do
-    '4+2/3i'.to_c.should == Complex(4, Rational(2, 3))
-  end
-
-  it "understands negative fractions (-numerator/denominator) for the real part" do
-    '-2/3'.to_c.should == Complex(Rational(-2, 3))
-  end
-
-  it "understands negative fractions (-numerator/denominator) for the imaginary part" do
-    '7-2/3i'.to_c.should == Complex(7, Rational(-2, 3))
-  end
-
-  it "understands floats (a.b) for the real part" do
-    '2.3'.to_c.should == Complex(2.3)
-  end
-
-  it "understands floats (a.b) for the imaginary part" do
-    '4+2.3i'.to_c.should == Complex(4, 2.3)
-  end
-
-  it "understands negative floats (-a.b) for the real part" do
-    '-2.33'.to_c.should == Complex(-2.33)
-  end
-
-  it "understands negative floats (-a.b) for the imaginary part" do
-    '7-28.771i'.to_c.should == Complex(7, -28.771)
-  end
-
-  it "understands an integer followed by 'i' to mean that integer is the imaginary part" do
-    '35i'.to_c.should == Complex(0,35)
-  end
-
-  it "understands a negative integer followed by 'i' to mean that negative integer is the imaginary part" do
-    '-29i'.to_c.should == Complex(0,-29)
-  end
-
-  it "understands an 'i' by itself as denoting a complex number with an imaginary part of 1" do
-    'i'.to_c.should == Complex(0,1)
-  end
-
-  it "understands a '-i' by itself as denoting a complex number with an imaginary part of -1" do
-    '-i'.to_c.should == Complex(0,-1)
-  end
-
-  it "understands 'a+bi' to mean a complex number with 'a' as the real part, 'b' as the imaginary" do
-    '79+4i'.to_c.should == Complex(79,4)
-  end
+  it_behaves_like :kernel_complex, :to_c_method, StringSpecs
+end
 
-  it "understands 'a-bi' to mean a complex number with 'a' as the real part, '-b' as the imaginary" do
-    '79-4i'.to_c.should == Complex(79,-4)
+describe "String#to_c" do
+  it "returns a complex number with 0 as the real part, 0 as the imaginary part for unrecognised Strings" do
+    'ruby'.to_c.should == Complex(0, 0)
   end
 
-  it "understands scientific notation for the real part" do
-    '2e3+4i'.to_c.should == Complex(2e3,4)
+  it "ignores trailing garbage" do
+    '79+4iruby'.to_c.should == Complex(79, 4)
+    '7__9+4__0i'.to_c.should == Complex(7, 0)
   end
 
-  it "understands negative scientific notation for the real part" do
-    '-2e3+4i'.to_c.should == Complex(-2e3,4)
-  end
+  context "it treats special float value strings as characters" do
+    it "parses any string that starts with 'I' as 1i" do
+      'Infinity'.to_c.should == Complex(0, 1)
+      '-Infinity'.to_c.should == Complex(0, -1)
+      'Insecure'.to_c.should == Complex(0, 1)
+      '-Insecure'.to_c.should == Complex(0, -1)
+    end
 
-  it "understands scientific notation for the imaginary part" do
-    '4+2e3i'.to_c.should == Complex(4, 2e3)
+    it "does not parse any numeric information in 'NaN'" do
+      'NaN'.to_c.should == Complex(0, 0)
+    end
   end
 
-  it "understands negative scientific notation for the imaginary part" do
-    '4-2e3i'.to_c.should == Complex(4, -2e3)
+  it "allows null-byte" do
+    "1-2i\0".to_c.should == Complex(1, -2)
+    "1\0-2i".to_c.should == Complex(1, 0)
+    "\01-2i".to_c.should == Complex(0, 0)
   end
 
-  it "understands scientific notation for the real and imaginary part in the same String" do
-    '2e3+2e4i'.to_c.should == Complex(2e3,2e4)
+  it "raises Encoding::CompatibilityError if String is in not ASCII-compatible encoding" do
+    -> {
+      '79+4i'.encode("UTF-16").to_c
+    }.should raise_error(Encoding::CompatibilityError, "ASCII incompatible encoding: UTF-16")
   end
 
-  it "understands negative scientific notation for the real and imaginary part in the same String" do
-    '-2e3-2e4i'.to_c.should == Complex(-2e3,-2e4)
-  end
+  it "treats a sequence of underscores as an end of Complex string" do
+    "5+3_1i".to_c.should == Complex(5, 31)
+    "5+3__1i".to_c.should == Complex(5)
+    "5+3___1i".to_c.should == Complex(5)
 
-  it "returns a complex number with 0 as the real part, 0 as the imaginary part for unrecognised Strings" do
-  'ruby'.to_c.should == Complex(0,0)
+    "12_3".to_c.should == Complex(123)
+    "12__3".to_c.should == Complex(12)
+    "12___3".to_c.should == Complex(12)
   end
 end
diff --git a/spec/ruby/core/string/to_f_spec.rb b/spec/ruby/core/string/to_f_spec.rb
index cf64ecfc5d..abfd2517b6 100644
--- a/spec/ruby/core/string/to_f_spec.rb
+++ b/spec/ruby/core/string/to_f_spec.rb
@@ -5,16 +5,15 @@ require_relative 'fixtures/classes'
 
 describe "String#to_f" do
   it "treats leading characters of self as a floating point number" do
-   "123.45e1".to_f.should == 1234.5
-   "45.67 degrees".to_f.should == 45.67
-   "0".to_f.should == 0.0
-   "123.45e1".to_f.should == 1234.5
+    "123.45e1".to_f.should == 1234.5
+    "45.67 degrees".to_f.should == 45.67
+    "0".to_f.should == 0.0
 
-   ".5".to_f.should == 0.5
-   ".5e1".to_f.should == 5.0
-   "5.".to_f.should == 5.0
-   "5e".to_f.should == 5.0
-   "5E".to_f.should == 5.0
+    ".5".to_f.should == 0.5
+    ".5e1".to_f.should == 5.0
+    "5.".to_f.should == 5.0
+    "5e".to_f.should == 5.0
+    "5E".to_f.should == 5.0
   end
 
   it "treats special float value strings as characters" do
@@ -43,18 +42,39 @@ describe "String#to_f" do
     "1_234_567.890_1".to_f.should == 1_234_567.890_1
   end
 
-  it "returns 0 for strings with any non-digit in them" do
-    "blah".to_f.should == 0
-    "0b5".to_f.should == 0
-    "0d5".to_f.should == 0
-    "0o5".to_f.should == 0
-    "0xx5".to_f.should == 0
-  end
-
   it "returns 0 for strings with leading underscores" do
     "_9".to_f.should == 0
   end
 
+  it "stops if the underscore is not followed or preceded by a number" do
+    "1__2".to_f.should == 1.0
+    "1_.2".to_f.should == 1.0
+    "1._2".to_f.should == 1.0
+    "1.2_e2".to_f.should == 1.2
+    "1.2e_2".to_f.should == 1.2
+    "1_x2".to_f.should == 1.0
+    "1x_2".to_f.should == 1.0
+    "+_1".to_f.should == 0.0
+    "-_1".to_f.should == 0.0
+  end
+
+  it "does not allow prefixes to autodetect the base" do
+    "0b10".to_f.should == 0
+    "010".to_f.should == 10
+    "0o10".to_f.should == 0
+    "0d10".to_f.should == 0
+    "0x10".to_f.should == 0
+  end
+
+  it "treats any non-numeric character other than '.', 'e' and '_' as terminals" do
+    "blah".to_f.should == 0
+    "1b5".to_f.should == 1
+    "1d5".to_f.should == 1
+    "1o5".to_f.should == 1
+    "1xx5".to_f.should == 1
+    "x5".to_f.should == 0
+  end
+
   it "takes an optional sign" do
     "-45.67 degrees".to_f.should == -45.67
     "+45.67 degrees".to_f.should == 45.67
@@ -63,8 +83,60 @@ describe "String#to_f" do
     (1.0 / "-0".to_f).to_s.should == "-Infinity"
   end
 
+  it "treats a second 'e' as terminal" do
+    "1.234e1e2".to_f.should == 1.234e1
+  end
+
+  it "treats a second '.' as terminal" do
+    "1.2.3".to_f.should == 1.2
+  end
+
+  it "treats a '.' after an 'e' as terminal" do
+    "1.234e1.9".to_f.should == 1.234e1
+  end
+
   it "returns 0.0 if the conversion fails" do
     "bad".to_f.should == 0.0
     "thx1138".to_f.should == 0.0
   end
+
+  it "ignores leading and trailing whitespace" do
+    "  1.2".to_f.should == 1.2
+    "1.2  ".to_f.should == 1.2
+    " 1.2 ".to_f.should == 1.2
+    "\t1.2".to_f.should == 1.2
+    "\n1.2".to_f.should == 1.2
+    "\v1.2".to_f.should == 1.2
+    "\f1.2".to_f.should == 1.2
+    "\r1.2".to_f.should == 1.2
+  end
+
+  it "treats non-printable ASCII characters as terminals" do
+    "\0001.2".to_f.should == 0
+    "\0011.2".to_f.should == 0
+    "\0371.2".to_f.should == 0
+    "\1771.2".to_f.should == 0
+    "\2001.2".b.to_f.should == 0
+    "\3771.2".b.to_f.should == 0
+  end
+
+  ruby_version_is "3.2.3" do
+    it "raises Encoding::CompatibilityError if String is in not ASCII-compatible encoding" do
+      -> {
+        '1.2'.encode("UTF-16").to_f
+      }.should raise_error(Encoding::CompatibilityError, "ASCII incompatible encoding: UTF-16")
+    end
+  end
+
+  it "allows String representation without a fractional part" do
+    "1.".to_f.should == 1.0
+    "+1.".to_f.should == 1.0
+    "-1.".to_f.should == -1.0
+    "1.e+0".to_f.should == 1.0
+    "1.e+0".to_f.should == 1.0
+
+    ruby_bug "#20705", ""..."3.4" do
+      "1.e-2".to_f.should be_close(0.01, TOLERANCE)
+    end
+  end
 end
diff --git a/spec/ruby/core/string/to_i_spec.rb b/spec/ruby/core/string/to_i_spec.rb
index a37be47778..39f69acda3 100644
--- a/spec/ruby/core/string/to_i_spec.rb
+++ b/spec/ruby/core/string/to_i_spec.rb
@@ -10,6 +10,18 @@ describe "String#to_i" do
     "1_2_3asdf".to_i.should == 123
   end
 
+  it "ignores multiple non-consecutive underscores when the first digit is 0" do
+    (2..16).each do |base|
+      "0_0_010".to_i(base).should == base;
+    end
+  end
+
+  it "bails out at the first double underscore if the first digit is 0" do
+    (2..16).each do |base|
+      "010__1".to_i(base).should == base;
+    end
+  end
+
   it "ignores leading whitespaces" do
     [ " 123", "     123", "\r\n\r\n123", "\t\t123",
       "\r\n\t\n123", " \t\n\r\t 123"].each do |str|
@@ -131,29 +143,29 @@ describe "String#to_i" do
     -> { "".to_i(37) }.should raise_error(ArgumentError)
   end
 
-  it "returns a Fixnum for long strings with trailing spaces" do
+  it "returns an Integer for long strings with trailing spaces" do
     "0                             ".to_i.should == 0
-    "0                             ".to_i.should be_an_instance_of(Fixnum)
+    "0                             ".to_i.should be_an_instance_of(Integer)
 
     "10                             ".to_i.should == 10
-    "10                             ".to_i.should be_an_instance_of(Fixnum)
+    "10                             ".to_i.should be_an_instance_of(Integer)
 
     "-10                            ".to_i.should == -10
-    "-10                            ".to_i.should be_an_instance_of(Fixnum)
+    "-10                            ".to_i.should be_an_instance_of(Integer)
   end
 
-  it "returns a Fixnum for long strings with leading spaces" do
+  it "returns an Integer for long strings with leading spaces" do
     "                             0".to_i.should == 0
-    "                             0".to_i.should be_an_instance_of(Fixnum)
+    "                             0".to_i.should be_an_instance_of(Integer)
 
     "                             10".to_i.should == 10
-    "                             10".to_i.should be_an_instance_of(Fixnum)
+    "                             10".to_i.should be_an_instance_of(Integer)
 
     "                            -10".to_i.should == -10
-    "                            -10".to_i.should be_an_instance_of(Fixnum)
+    "                            -10".to_i.should be_an_instance_of(Integer)
   end
 
-  it "returns the correct Bignum for long strings" do
+  it "returns the correct Integer for long strings" do
     "245789127594125924165923648312749312749327482".to_i.should == 245789127594125924165923648312749312749327482
     "-245789127594125924165923648312749312749327482".to_i.should == -245789127594125924165923648312749312749327482
   end
diff --git a/spec/ruby/core/string/to_r_spec.rb b/spec/ruby/core/string/to_r_spec.rb
index 7e1d635d3b..4ffbb10d98 100644
--- a/spec/ruby/core/string/to_r_spec.rb
+++ b/spec/ruby/core/string/to_r_spec.rb
@@ -33,6 +33,10 @@ describe "String#to_r" do
     "-20".to_r.should == Rational(-20, 1)
   end
 
+  it "accepts leading plus signs" do
+    "+20".to_r.should == Rational(20, 1)
+  end
+
   it "does not treat a leading period without a numeric prefix as a decimal point" do
     ".9".to_r.should_not == Rational(8106479329266893, 9007199254740992)
   end
diff --git a/spec/ruby/core/string/tr_s_spec.rb b/spec/ruby/core/string/tr_s_spec.rb
index 4380f2d548..dd72da440c 100644
--- a/spec/ruby/core/string/tr_s_spec.rb
+++ b/spec/ruby/core/string/tr_s_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -17,6 +18,15 @@ describe "String#tr_s" do
     "hello ^--^".tr_s("---", "_").should == "hello ^_^"
   end
 
+  ruby_bug "#19769", ""..."3.3" do
+    it "accepts c1-c1 notation to denote range of one character" do
+      "hello".tr_s('e-e', 'x').should == "hxllo"
+      "123456789".tr_s("2-23","xy").should == "1xy456789"
+      "hello ^-^".tr_s("e-", "a-a_").should == "hallo ^_^"
+      "hello ^-^".tr_s("---o", "_a").should == "hella ^_^"
+    end
+  end
+
   it "pads to_str with its last char if it is shorter than from_string" do
     "this".tr_s("this", "x").should == "x"
   end
@@ -45,19 +55,8 @@ describe "String#tr_s" do
     "bla".tr_s(from_str, to_str).should == "BlA"
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("hello").tr_s("e", "a").should be_an_instance_of(StringSpecs::MyString)
-  end
-
-  it "taints the result when self is tainted" do
-    ["h", "hello"].each do |str|
-      tainted_str = str.dup.taint
-
-      tainted_str.tr_s("e", "a").tainted?.should == true
-
-      str.tr_s("e".taint, "a").tainted?.should == false
-      str.tr_s("e", "a".taint).tainted?.should == false
-    end
+  it "returns String instances when called on a subclass" do
+    StringSpecs::MyString.new("hello").tr_s("e", "a").should be_an_instance_of(String)
   end
 
   # http://redmine.ruby-lang.org/issues/show/1839
@@ -125,10 +124,10 @@ describe "String#tr_s!" do
     s.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     s = "hello".freeze
-    -> { s.tr_s!("el", "ar") }.should raise_error(frozen_error_class)
-    -> { s.tr_s!("l", "r")   }.should raise_error(frozen_error_class)
-    -> { s.tr_s!("", "")     }.should raise_error(frozen_error_class)
+    -> { s.tr_s!("el", "ar") }.should raise_error(FrozenError)
+    -> { s.tr_s!("l", "r")   }.should raise_error(FrozenError)
+    -> { s.tr_s!("", "")     }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/tr_spec.rb b/spec/ruby/core/string/tr_spec.rb
index 721ebab51c..75841a974f 100644
--- a/spec/ruby/core/string/tr_spec.rb
+++ b/spec/ruby/core/string/tr_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -16,6 +17,15 @@ describe "String#tr" do
     "hello ^-^".tr("---", "_").should == "hello ^_^"
   end
 
+  ruby_bug "#19769", ""..."3.3" do
+    it "accepts c1-c1 notation to denote range of one character" do
+      "hello".tr('e-e', 'x').should == "hxllo"
+      "123456789".tr("2-23","xy").should == "1xy456789"
+      "hello ^-^".tr("e-", "a-a_").should == "hallo ^_^"
+      "hello ^-^".tr("---o", "_a").should == "hella ^_^"
+    end
+  end
+
   it "pads to_str with its last char if it is shorter than from_string" do
     "this".tr("this", "x").should == "xxxx"
     "hello".tr("a-z", "A-H.").should == "HE..."
@@ -57,19 +67,8 @@ describe "String#tr" do
     "bla".tr(from_str, to_str).should == "BlA"
   end
 
-  it "returns subclass instances when called on a subclass" do
-    StringSpecs::MyString.new("hello").tr("e", "a").should be_an_instance_of(StringSpecs::MyString)
-  end
-
-  it "taints the result when self is tainted" do
-    ["h", "hello"].each do |str|
-      tainted_str = str.dup.taint
-
-      tainted_str.tr("e", "a").tainted?.should == true
-
-      str.tr("e".taint, "a").tainted?.should == false
-      str.tr("e", "a".taint).tainted?.should == false
-    end
+  it "returns Stringinstances when called on a subclass" do
+    StringSpecs::MyString.new("hello").tr("e", "a").should be_an_instance_of(String)
   end
 
   # http://redmine.ruby-lang.org/issues/show/1839
@@ -120,10 +119,10 @@ describe "String#tr!" do
     s.should == "hello"
   end
 
-  it "raises a #{frozen_error_class} if self is frozen" do
+  it "raises a FrozenError if self is frozen" do
     s = "abcdefghijklmnopqR".freeze
-    -> { s.tr!("cdefg", "12") }.should raise_error(frozen_error_class)
-    -> { s.tr!("R", "S")      }.should raise_error(frozen_error_class)
-    -> { s.tr!("", "")        }.should raise_error(frozen_error_class)
+    -> { s.tr!("cdefg", "12") }.should raise_error(FrozenError)
+    -> { s.tr!("R", "S")      }.should raise_error(FrozenError)
+    -> { s.tr!("", "")        }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/try_convert_spec.rb b/spec/ruby/core/string/try_convert_spec.rb
index 84415c4a75..72ce5dd8b2 100644
--- a/spec/ruby/core/string/try_convert_spec.rb
+++ b/spec/ruby/core/string/try_convert_spec.rb
@@ -39,7 +39,7 @@ describe "String.try_convert" do
   it "sends #to_str to the argument and raises TypeError if it's not a kind of String" do
     obj = mock("to_str")
     obj.should_receive(:to_str).and_return(Object.new)
-    -> { String.try_convert obj }.should raise_error(TypeError)
+    -> { String.try_convert obj }.should raise_error(TypeError, "can't convert MockObject to String (MockObject#to_str gives Object)")
   end
 
   it "does not rescue exceptions raised by #to_str" do
diff --git a/spec/ruby/core/string/uminus_spec.rb b/spec/ruby/core/string/uminus_spec.rb
index dace04846c..46d88f6704 100644
--- a/spec/ruby/core/string/uminus_spec.rb
+++ b/spec/ruby/core/string/uminus_spec.rb
@@ -1,74 +1,6 @@
 require_relative '../../spec_helper'
+require_relative 'shared/dedup'
 
 describe 'String#-@' do
-  it 'returns self if the String is frozen' do
-    input  = 'foo'.freeze
-    output = -input
-
-    output.should equal(input)
-    output.frozen?.should == true
-  end
-
-  it 'returns a frozen copy if the String is not frozen' do
-    input  = 'foo'
-    output = -input
-
-    output.frozen?.should == true
-    output.should_not equal(input)
-    output.should == 'foo'
-  end
-
-  ruby_version_is "2.5" do
-    it "returns the same object for equal unfrozen strings" do
-      origin = "this is a string"
-      dynamic = %w(this is a string).join(' ')
-
-      origin.should_not equal(dynamic)
-      (-origin).should equal(-dynamic)
-    end
-
-    it "returns the same object when it's called on the same String literal" do
-      (-"unfrozen string").should equal(-"unfrozen string")
-      (-"unfrozen string").should_not equal(-"another unfrozen string")
-    end
-  end
-
-  ruby_version_is "2.5"..."2.6" do
-    it "does not deduplicate already frozen strings" do
-      dynamic = %w(this string is frozen).join(' ').freeze
-
-      dynamic.should_not equal("this string is frozen".freeze)
-
-      (-dynamic).should_not equal("this string is frozen".freeze)
-      (-dynamic).should_not equal(-"this string is frozen".freeze)
-      (-dynamic).should == "this string is frozen"
-    end
-
-    it "does not deduplicate tainted strings" do
-      dynamic = %w(this string is frozen).join(' ')
-      dynamic.taint
-      (-dynamic).should_not equal("this string is frozen".freeze)
-      (-dynamic).should_not equal(-"this string is frozen".freeze)
-      (-dynamic).should == "this string is frozen"
-    end
-
-    it "does not deduplicate strings with additional instance variables" do
-      dynamic = %w(this string is frozen).join(' ')
-      dynamic.instance_variable_set(:@foo, :bar)
-      (-dynamic).should_not equal("this string is frozen".freeze)
-      (-dynamic).should_not equal(-"this string is frozen".freeze)
-      (-dynamic).should == "this string is frozen"
-    end
-  end
-
-  ruby_version_is "2.6" do
-    it "deduplicates frozen strings" do
-      dynamic = %w(this string is frozen).join(' ').freeze
-
-      dynamic.should_not equal("this string is frozen".freeze)
-
-      (-dynamic).should equal("this string is frozen".freeze)
-      (-dynamic).should equal(-"this string is frozen".freeze)
-    end
-  end
+  it_behaves_like :string_dedup, :-@
 end
diff --git a/spec/ruby/core/string/undump_spec.rb b/spec/ruby/core/string/undump_spec.rb
index 315d27cad4..6ff220161c 100644
--- a/spec/ruby/core/string/undump_spec.rb
+++ b/spec/ruby/core/string/undump_spec.rb
@@ -2,450 +2,440 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is '2.5' do
-  describe "String#undump" do
-    it "taints the result if self is tainted" do
-      '"foo"'.taint.undump.tainted?.should == true
-    end
+describe "String#undump" do
+  it "does not take into account if a string is frozen" do
+    '"foo"'.freeze.undump.should_not.frozen?
+  end
 
-    it "untrusts the result if self is untrusted" do
-      '"foo"'.untrust.undump.untrusted?.should == true
-    end
+  it "always returns String instance" do
+    StringSpecs::MyString.new('"foo"').undump.should be_an_instance_of(String)
+  end
 
-    it "does not take into account if a string is frozen" do
-      '"foo"'.freeze.undump.frozen?.should == false
-    end
+  it "strips outer \"" do
+    '"foo"'.undump.should == 'foo'
+  end
 
-    it "always returns String instance" do
-      StringSpecs::MyString.new('"foo"').undump.should be_an_instance_of(String)
-    end
+  it "returns a string with special characters in \\<char> notation replaced with the characters" do
+    [ ['"\\a"', "\a"],
+      ['"\\b"', "\b"],
+      ['"\\t"', "\t"],
+      ['"\\n"', "\n"],
+      ['"\\v"', "\v"],
+      ['"\\f"', "\f"],
+      ['"\\r"', "\r"],
+      ['"\\e"', "\e"]
+    ].should be_computed_by(:undump)
+  end
 
-    it "strips outer \"" do
-      '"foo"'.undump.should == 'foo'
-    end
+  it "returns a string with unescaped sequences \" and \\" do
+    [ ['"\\""' , "\""],
+      ['"\\\\"', "\\"]
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with special characters in \\<char> notation replaced with the characters" do
-      [ ['"\\a"', "\a"],
-        ['"\\b"', "\b"],
-        ['"\\t"', "\t"],
-        ['"\\n"', "\n"],
-        ['"\\v"', "\v"],
-        ['"\\f"', "\f"],
-        ['"\\r"', "\r"],
-        ['"\\e"', "\e"]
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with unescaped sequences \\#<char> when # is followed by $, @, {" do
+    [ ['"\\#$PATH"', "\#$PATH"],
+      ['"\\#@a"',    "\#@a"],
+      ['"\\#@@a"',   "\#@@a"],
+      ['"\\#{a}"',   "\#{a}"]
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with unescaped sequencies \" and \\" do
-      [ ['"\\""' , "\""],
-        ['"\\\\"', "\\"]
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with # not escaped when followed by any other character" do
+    [ ['"#"', '#'],
+      ['"#1"', '#1']
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with unescaped sequences \\#<char> when # is followed by $, @, {" do
-      [ ['"\\#$PATH"', "\#$PATH"],
-        ['"\\#@a"',    "\#@a"],
-        ['"\\#@@a"',   "\#@@a"],
-        ['"\\#{a}"',   "\#{a}"]
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with printable non-alphanumeric characters" do
+    [ ['" "', ' '],
+      ['"!"', '!'],
+      ['"$"', '$'],
+      ['"%"', '%'],
+      ['"&"', '&'],
+      ['"\'"', '\''],
+      ['"("', '('],
+      ['")"', ')'],
+      ['"*"', '*'],
+      ['"+"', '+'],
+      ['","', ','],
+      ['"-"', '-'],
+      ['"."', '.'],
+      ['"/"', '/'],
+      ['":"', ':'],
+      ['";"', ';'],
+      ['"<"', '<'],
+      ['"="', '='],
+      ['">"', '>'],
+      ['"?"', '?'],
+      ['"@"', '@'],
+      ['"["', '['],
+      ['"]"', ']'],
+      ['"^"', '^'],
+      ['"_"', '_'],
+      ['"`"', '`'],
+      ['"{"', '{'],
+      ['"|"', '|'],
+      ['"}"', '}'],
+      ['"~"', '~']
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with # not escaped when followed by any other character" do
-      [ ['"#"', '#'],
-        ['"#1"', '#1']
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with numeric characters unescaped" do
+    [ ['"0"', "0"],
+      ['"1"', "1"],
+      ['"2"', "2"],
+      ['"3"', "3"],
+      ['"4"', "4"],
+      ['"5"', "5"],
+      ['"6"', "6"],
+      ['"7"', "7"],
+      ['"8"', "8"],
+      ['"9"', "9"],
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with printable non-alphanumeric characters" do
-      [ ['" "', ' '],
-        ['"!"', '!'],
-        ['"$"', '$'],
-        ['"%"', '%'],
-        ['"&"', '&'],
-        ['"\'"', '\''],
-        ['"("', '('],
-        ['")"', ')'],
-        ['"*"', '*'],
-        ['"+"', '+'],
-        ['","', ','],
-        ['"-"', '-'],
-        ['"."', '.'],
-        ['"/"', '/'],
-        ['":"', ':'],
-        ['";"', ';'],
-        ['"<"', '<'],
-        ['"="', '='],
-        ['">"', '>'],
-        ['"?"', '?'],
-        ['"@"', '@'],
-        ['"["', '['],
-        ['"]"', ']'],
-        ['"^"', '^'],
-        ['"_"', '_'],
-        ['"`"', '`'],
-        ['"{"', '{'],
-        ['"|"', '|'],
-        ['"}"', '}'],
-        ['"~"', '~']
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with upper-case alpha characters unescaped" do
+    [ ['"A"', 'A'],
+      ['"B"', 'B'],
+      ['"C"', 'C'],
+      ['"D"', 'D'],
+      ['"E"', 'E'],
+      ['"F"', 'F'],
+      ['"G"', 'G'],
+      ['"H"', 'H'],
+      ['"I"', 'I'],
+      ['"J"', 'J'],
+      ['"K"', 'K'],
+      ['"L"', 'L'],
+      ['"M"', 'M'],
+      ['"N"', 'N'],
+      ['"O"', 'O'],
+      ['"P"', 'P'],
+      ['"Q"', 'Q'],
+      ['"R"', 'R'],
+      ['"S"', 'S'],
+      ['"T"', 'T'],
+      ['"U"', 'U'],
+      ['"V"', 'V'],
+      ['"W"', 'W'],
+      ['"X"', 'X'],
+      ['"Y"', 'Y'],
+      ['"Z"', 'Z']
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with numeric characters unescaped" do
-      [ ['"0"', "0"],
-        ['"1"', "1"],
-        ['"2"', "2"],
-        ['"3"', "3"],
-        ['"4"', "4"],
-        ['"5"', "5"],
-        ['"6"', "6"],
-        ['"7"', "7"],
-        ['"8"', "8"],
-        ['"9"', "9"],
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with lower-case alpha characters unescaped" do
+    [ ['"a"', 'a'],
+      ['"b"', 'b'],
+      ['"c"', 'c'],
+      ['"d"', 'd'],
+      ['"e"', 'e'],
+      ['"f"', 'f'],
+      ['"g"', 'g'],
+      ['"h"', 'h'],
+      ['"i"', 'i'],
+      ['"j"', 'j'],
+      ['"k"', 'k'],
+      ['"l"', 'l'],
+      ['"m"', 'm'],
+      ['"n"', 'n'],
+      ['"o"', 'o'],
+      ['"p"', 'p'],
+      ['"q"', 'q'],
+      ['"r"', 'r'],
+      ['"s"', 's'],
+      ['"t"', 't'],
+      ['"u"', 'u'],
+      ['"v"', 'v'],
+      ['"w"', 'w'],
+      ['"x"', 'x'],
+      ['"y"', 'y'],
+      ['"z"', 'z']
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with upper-case alpha characters unescaped" do
-      [ ['"A"', 'A'],
-        ['"B"', 'B'],
-        ['"C"', 'C'],
-        ['"D"', 'D'],
-        ['"E"', 'E'],
-        ['"F"', 'F'],
-        ['"G"', 'G'],
-        ['"H"', 'H'],
-        ['"I"', 'I'],
-        ['"J"', 'J'],
-        ['"K"', 'K'],
-        ['"L"', 'L'],
-        ['"M"', 'M'],
-        ['"N"', 'N'],
-        ['"O"', 'O'],
-        ['"P"', 'P'],
-        ['"Q"', 'Q'],
-        ['"R"', 'R'],
-        ['"S"', 'S'],
-        ['"T"', 'T'],
-        ['"U"', 'U'],
-        ['"V"', 'V'],
-        ['"W"', 'W'],
-        ['"X"', 'X'],
-        ['"Y"', 'Y'],
-        ['"Z"', 'Z']
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with \\x notation replaced with non-printing ASCII character" do
+    [ ['"\\x00"', 0000.chr.force_encoding('utf-8')],
+      ['"\\x01"', 0001.chr.force_encoding('utf-8')],
+      ['"\\x02"', 0002.chr.force_encoding('utf-8')],
+      ['"\\x03"', 0003.chr.force_encoding('utf-8')],
+      ['"\\x04"', 0004.chr.force_encoding('utf-8')],
+      ['"\\x05"', 0005.chr.force_encoding('utf-8')],
+      ['"\\x06"', 0006.chr.force_encoding('utf-8')],
+      ['"\\x0E"', 0016.chr.force_encoding('utf-8')],
+      ['"\\x0F"', 0017.chr.force_encoding('utf-8')],
+      ['"\\x10"', 0020.chr.force_encoding('utf-8')],
+      ['"\\x11"', 0021.chr.force_encoding('utf-8')],
+      ['"\\x12"', 0022.chr.force_encoding('utf-8')],
+      ['"\\x13"', 0023.chr.force_encoding('utf-8')],
+      ['"\\x14"', 0024.chr.force_encoding('utf-8')],
+      ['"\\x15"', 0025.chr.force_encoding('utf-8')],
+      ['"\\x16"', 0026.chr.force_encoding('utf-8')],
+      ['"\\x17"', 0027.chr.force_encoding('utf-8')],
+      ['"\\x18"', 0030.chr.force_encoding('utf-8')],
+      ['"\\x19"', 0031.chr.force_encoding('utf-8')],
+      ['"\\x1A"', 0032.chr.force_encoding('utf-8')],
+      ['"\\x1C"', 0034.chr.force_encoding('utf-8')],
+      ['"\\x1D"', 0035.chr.force_encoding('utf-8')],
+      ['"\\x1E"', 0036.chr.force_encoding('utf-8')],
+      ['"\\x1F"', 0037.chr.force_encoding('utf-8')],
+      ['"\\x7F"', 0177.chr.force_encoding('utf-8')],
+      ['"\\x80"', 0200.chr.force_encoding('utf-8')],
+      ['"\\x81"', 0201.chr.force_encoding('utf-8')],
+      ['"\\x82"', 0202.chr.force_encoding('utf-8')],
+      ['"\\x83"', 0203.chr.force_encoding('utf-8')],
+      ['"\\x84"', 0204.chr.force_encoding('utf-8')],
+      ['"\\x85"', 0205.chr.force_encoding('utf-8')],
+      ['"\\x86"', 0206.chr.force_encoding('utf-8')],
+      ['"\\x87"', 0207.chr.force_encoding('utf-8')],
+      ['"\\x88"', 0210.chr.force_encoding('utf-8')],
+      ['"\\x89"', 0211.chr.force_encoding('utf-8')],
+      ['"\\x8A"', 0212.chr.force_encoding('utf-8')],
+      ['"\\x8B"', 0213.chr.force_encoding('utf-8')],
+      ['"\\x8C"', 0214.chr.force_encoding('utf-8')],
+      ['"\\x8D"', 0215.chr.force_encoding('utf-8')],
+      ['"\\x8E"', 0216.chr.force_encoding('utf-8')],
+      ['"\\x8F"', 0217.chr.force_encoding('utf-8')],
+      ['"\\x90"', 0220.chr.force_encoding('utf-8')],
+      ['"\\x91"', 0221.chr.force_encoding('utf-8')],
+      ['"\\x92"', 0222.chr.force_encoding('utf-8')],
+      ['"\\x93"', 0223.chr.force_encoding('utf-8')],
+      ['"\\x94"', 0224.chr.force_encoding('utf-8')],
+      ['"\\x95"', 0225.chr.force_encoding('utf-8')],
+      ['"\\x96"', 0226.chr.force_encoding('utf-8')],
+      ['"\\x97"', 0227.chr.force_encoding('utf-8')],
+      ['"\\x98"', 0230.chr.force_encoding('utf-8')],
+      ['"\\x99"', 0231.chr.force_encoding('utf-8')],
+      ['"\\x9A"', 0232.chr.force_encoding('utf-8')],
+      ['"\\x9B"', 0233.chr.force_encoding('utf-8')],
+      ['"\\x9C"', 0234.chr.force_encoding('utf-8')],
+      ['"\\x9D"', 0235.chr.force_encoding('utf-8')],
+      ['"\\x9E"', 0236.chr.force_encoding('utf-8')],
+      ['"\\x9F"', 0237.chr.force_encoding('utf-8')],
+      ['"\\xA0"', 0240.chr.force_encoding('utf-8')],
+      ['"\\xA1"', 0241.chr.force_encoding('utf-8')],
+      ['"\\xA2"', 0242.chr.force_encoding('utf-8')],
+      ['"\\xA3"', 0243.chr.force_encoding('utf-8')],
+      ['"\\xA4"', 0244.chr.force_encoding('utf-8')],
+      ['"\\xA5"', 0245.chr.force_encoding('utf-8')],
+      ['"\\xA6"', 0246.chr.force_encoding('utf-8')],
+      ['"\\xA7"', 0247.chr.force_encoding('utf-8')],
+      ['"\\xA8"', 0250.chr.force_encoding('utf-8')],
+      ['"\\xA9"', 0251.chr.force_encoding('utf-8')],
+      ['"\\xAA"', 0252.chr.force_encoding('utf-8')],
+      ['"\\xAB"', 0253.chr.force_encoding('utf-8')],
+      ['"\\xAC"', 0254.chr.force_encoding('utf-8')],
+      ['"\\xAD"', 0255.chr.force_encoding('utf-8')],
+      ['"\\xAE"', 0256.chr.force_encoding('utf-8')],
+      ['"\\xAF"', 0257.chr.force_encoding('utf-8')],
+      ['"\\xB0"', 0260.chr.force_encoding('utf-8')],
+      ['"\\xB1"', 0261.chr.force_encoding('utf-8')],
+      ['"\\xB2"', 0262.chr.force_encoding('utf-8')],
+      ['"\\xB3"', 0263.chr.force_encoding('utf-8')],
+      ['"\\xB4"', 0264.chr.force_encoding('utf-8')],
+      ['"\\xB5"', 0265.chr.force_encoding('utf-8')],
+      ['"\\xB6"', 0266.chr.force_encoding('utf-8')],
+      ['"\\xB7"', 0267.chr.force_encoding('utf-8')],
+      ['"\\xB8"', 0270.chr.force_encoding('utf-8')],
+      ['"\\xB9"', 0271.chr.force_encoding('utf-8')],
+      ['"\\xBA"', 0272.chr.force_encoding('utf-8')],
+      ['"\\xBB"', 0273.chr.force_encoding('utf-8')],
+      ['"\\xBC"', 0274.chr.force_encoding('utf-8')],
+      ['"\\xBD"', 0275.chr.force_encoding('utf-8')],
+      ['"\\xBE"', 0276.chr.force_encoding('utf-8')],
+      ['"\\xBF"', 0277.chr.force_encoding('utf-8')],
+      ['"\\xC0"', 0300.chr.force_encoding('utf-8')],
+      ['"\\xC1"', 0301.chr.force_encoding('utf-8')],
+      ['"\\xC2"', 0302.chr.force_encoding('utf-8')],
+      ['"\\xC3"', 0303.chr.force_encoding('utf-8')],
+      ['"\\xC4"', 0304.chr.force_encoding('utf-8')],
+      ['"\\xC5"', 0305.chr.force_encoding('utf-8')],
+      ['"\\xC6"', 0306.chr.force_encoding('utf-8')],
+      ['"\\xC7"', 0307.chr.force_encoding('utf-8')],
+      ['"\\xC8"', 0310.chr.force_encoding('utf-8')],
+      ['"\\xC9"', 0311.chr.force_encoding('utf-8')],
+      ['"\\xCA"', 0312.chr.force_encoding('utf-8')],
+      ['"\\xCB"', 0313.chr.force_encoding('utf-8')],
+      ['"\\xCC"', 0314.chr.force_encoding('utf-8')],
+      ['"\\xCD"', 0315.chr.force_encoding('utf-8')],
+      ['"\\xCE"', 0316.chr.force_encoding('utf-8')],
+      ['"\\xCF"', 0317.chr.force_encoding('utf-8')],
+      ['"\\xD0"', 0320.chr.force_encoding('utf-8')],
+      ['"\\xD1"', 0321.chr.force_encoding('utf-8')],
+      ['"\\xD2"', 0322.chr.force_encoding('utf-8')],
+      ['"\\xD3"', 0323.chr.force_encoding('utf-8')],
+      ['"\\xD4"', 0324.chr.force_encoding('utf-8')],
+      ['"\\xD5"', 0325.chr.force_encoding('utf-8')],
+      ['"\\xD6"', 0326.chr.force_encoding('utf-8')],
+      ['"\\xD7"', 0327.chr.force_encoding('utf-8')],
+      ['"\\xD8"', 0330.chr.force_encoding('utf-8')],
+      ['"\\xD9"', 0331.chr.force_encoding('utf-8')],
+      ['"\\xDA"', 0332.chr.force_encoding('utf-8')],
+      ['"\\xDB"', 0333.chr.force_encoding('utf-8')],
+      ['"\\xDC"', 0334.chr.force_encoding('utf-8')],
+      ['"\\xDD"', 0335.chr.force_encoding('utf-8')],
+      ['"\\xDE"', 0336.chr.force_encoding('utf-8')],
+      ['"\\xDF"', 0337.chr.force_encoding('utf-8')],
+      ['"\\xE0"', 0340.chr.force_encoding('utf-8')],
+      ['"\\xE1"', 0341.chr.force_encoding('utf-8')],
+      ['"\\xE2"', 0342.chr.force_encoding('utf-8')],
+      ['"\\xE3"', 0343.chr.force_encoding('utf-8')],
+      ['"\\xE4"', 0344.chr.force_encoding('utf-8')],
+      ['"\\xE5"', 0345.chr.force_encoding('utf-8')],
+      ['"\\xE6"', 0346.chr.force_encoding('utf-8')],
+      ['"\\xE7"', 0347.chr.force_encoding('utf-8')],
+      ['"\\xE8"', 0350.chr.force_encoding('utf-8')],
+      ['"\\xE9"', 0351.chr.force_encoding('utf-8')],
+      ['"\\xEA"', 0352.chr.force_encoding('utf-8')],
+      ['"\\xEB"', 0353.chr.force_encoding('utf-8')],
+      ['"\\xEC"', 0354.chr.force_encoding('utf-8')],
+      ['"\\xED"', 0355.chr.force_encoding('utf-8')],
+      ['"\\xEE"', 0356.chr.force_encoding('utf-8')],
+      ['"\\xEF"', 0357.chr.force_encoding('utf-8')],
+      ['"\\xF0"', 0360.chr.force_encoding('utf-8')],
+      ['"\\xF1"', 0361.chr.force_encoding('utf-8')],
+      ['"\\xF2"', 0362.chr.force_encoding('utf-8')],
+      ['"\\xF3"', 0363.chr.force_encoding('utf-8')],
+      ['"\\xF4"', 0364.chr.force_encoding('utf-8')],
+      ['"\\xF5"', 0365.chr.force_encoding('utf-8')],
+      ['"\\xF6"', 0366.chr.force_encoding('utf-8')],
+      ['"\\xF7"', 0367.chr.force_encoding('utf-8')],
+      ['"\\xF8"', 0370.chr.force_encoding('utf-8')],
+      ['"\\xF9"', 0371.chr.force_encoding('utf-8')],
+      ['"\\xFA"', 0372.chr.force_encoding('utf-8')],
+      ['"\\xFB"', 0373.chr.force_encoding('utf-8')],
+      ['"\\xFC"', 0374.chr.force_encoding('utf-8')],
+      ['"\\xFD"', 0375.chr.force_encoding('utf-8')],
+      ['"\\xFE"', 0376.chr.force_encoding('utf-8')],
+      ['"\\xFF"', 0377.chr.force_encoding('utf-8')]
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with lower-case alpha characters unescaped" do
-      [ ['"a"', 'a'],
-        ['"b"', 'b'],
-        ['"c"', 'c'],
-        ['"d"', 'd'],
-        ['"e"', 'e'],
-        ['"f"', 'f'],
-        ['"g"', 'g'],
-        ['"h"', 'h'],
-        ['"i"', 'i'],
-        ['"j"', 'j'],
-        ['"k"', 'k'],
-        ['"l"', 'l'],
-        ['"m"', 'm'],
-        ['"n"', 'n'],
-        ['"o"', 'o'],
-        ['"p"', 'p'],
-        ['"q"', 'q'],
-        ['"r"', 'r'],
-        ['"s"', 's'],
-        ['"t"', 't'],
-        ['"u"', 'u'],
-        ['"v"', 'v'],
-        ['"w"', 'w'],
-        ['"x"', 'x'],
-        ['"y"', 'y'],
-        ['"z"', 'z']
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with \\u{} notation replaced with multi-byte UTF-8 characters" do
+    [ ['"\u{80}"', 0200.chr('utf-8')],
+      ['"\u{81}"', 0201.chr('utf-8')],
+      ['"\u{82}"', 0202.chr('utf-8')],
+      ['"\u{83}"', 0203.chr('utf-8')],
+      ['"\u{84}"', 0204.chr('utf-8')],
+      ['"\u{86}"', 0206.chr('utf-8')],
+      ['"\u{87}"', 0207.chr('utf-8')],
+      ['"\u{88}"', 0210.chr('utf-8')],
+      ['"\u{89}"', 0211.chr('utf-8')],
+      ['"\u{8a}"', 0212.chr('utf-8')],
+      ['"\u{8b}"', 0213.chr('utf-8')],
+      ['"\u{8c}"', 0214.chr('utf-8')],
+      ['"\u{8d}"', 0215.chr('utf-8')],
+      ['"\u{8e}"', 0216.chr('utf-8')],
+      ['"\u{8f}"', 0217.chr('utf-8')],
+      ['"\u{90}"', 0220.chr('utf-8')],
+      ['"\u{91}"', 0221.chr('utf-8')],
+      ['"\u{92}"', 0222.chr('utf-8')],
+      ['"\u{93}"', 0223.chr('utf-8')],
+      ['"\u{94}"', 0224.chr('utf-8')],
+      ['"\u{95}"', 0225.chr('utf-8')],
+      ['"\u{96}"', 0226.chr('utf-8')],
+      ['"\u{97}"', 0227.chr('utf-8')],
+      ['"\u{98}"', 0230.chr('utf-8')],
+      ['"\u{99}"', 0231.chr('utf-8')],
+      ['"\u{9a}"', 0232.chr('utf-8')],
+      ['"\u{9b}"', 0233.chr('utf-8')],
+      ['"\u{9c}"', 0234.chr('utf-8')],
+      ['"\u{9d}"', 0235.chr('utf-8')],
+      ['"\u{9e}"', 0236.chr('utf-8')],
+      ['"\u{9f}"', 0237.chr('utf-8')],
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with \\x notation replaced with non-printing ASCII character" do
-      [ ['"\\x00"', 0000.chr.force_encoding('utf-8')],
-        ['"\\x01"', 0001.chr.force_encoding('utf-8')],
-        ['"\\x02"', 0002.chr.force_encoding('utf-8')],
-        ['"\\x03"', 0003.chr.force_encoding('utf-8')],
-        ['"\\x04"', 0004.chr.force_encoding('utf-8')],
-        ['"\\x05"', 0005.chr.force_encoding('utf-8')],
-        ['"\\x06"', 0006.chr.force_encoding('utf-8')],
-        ['"\\x0E"', 0016.chr.force_encoding('utf-8')],
-        ['"\\x0F"', 0017.chr.force_encoding('utf-8')],
-        ['"\\x10"', 0020.chr.force_encoding('utf-8')],
-        ['"\\x11"', 0021.chr.force_encoding('utf-8')],
-        ['"\\x12"', 0022.chr.force_encoding('utf-8')],
-        ['"\\x13"', 0023.chr.force_encoding('utf-8')],
-        ['"\\x14"', 0024.chr.force_encoding('utf-8')],
-        ['"\\x15"', 0025.chr.force_encoding('utf-8')],
-        ['"\\x16"', 0026.chr.force_encoding('utf-8')],
-        ['"\\x17"', 0027.chr.force_encoding('utf-8')],
-        ['"\\x18"', 0030.chr.force_encoding('utf-8')],
-        ['"\\x19"', 0031.chr.force_encoding('utf-8')],
-        ['"\\x1A"', 0032.chr.force_encoding('utf-8')],
-        ['"\\x1C"', 0034.chr.force_encoding('utf-8')],
-        ['"\\x1D"', 0035.chr.force_encoding('utf-8')],
-        ['"\\x1E"', 0036.chr.force_encoding('utf-8')],
-        ['"\\x1F"', 0037.chr.force_encoding('utf-8')],
-        ['"\\x7F"', 0177.chr.force_encoding('utf-8')],
-        ['"\\x80"', 0200.chr.force_encoding('utf-8')],
-        ['"\\x81"', 0201.chr.force_encoding('utf-8')],
-        ['"\\x82"', 0202.chr.force_encoding('utf-8')],
-        ['"\\x83"', 0203.chr.force_encoding('utf-8')],
-        ['"\\x84"', 0204.chr.force_encoding('utf-8')],
-        ['"\\x85"', 0205.chr.force_encoding('utf-8')],
-        ['"\\x86"', 0206.chr.force_encoding('utf-8')],
-        ['"\\x87"', 0207.chr.force_encoding('utf-8')],
-        ['"\\x88"', 0210.chr.force_encoding('utf-8')],
-        ['"\\x89"', 0211.chr.force_encoding('utf-8')],
-        ['"\\x8A"', 0212.chr.force_encoding('utf-8')],
-        ['"\\x8B"', 0213.chr.force_encoding('utf-8')],
-        ['"\\x8C"', 0214.chr.force_encoding('utf-8')],
-        ['"\\x8D"', 0215.chr.force_encoding('utf-8')],
-        ['"\\x8E"', 0216.chr.force_encoding('utf-8')],
-        ['"\\x8F"', 0217.chr.force_encoding('utf-8')],
-        ['"\\x90"', 0220.chr.force_encoding('utf-8')],
-        ['"\\x91"', 0221.chr.force_encoding('utf-8')],
-        ['"\\x92"', 0222.chr.force_encoding('utf-8')],
-        ['"\\x93"', 0223.chr.force_encoding('utf-8')],
-        ['"\\x94"', 0224.chr.force_encoding('utf-8')],
-        ['"\\x95"', 0225.chr.force_encoding('utf-8')],
-        ['"\\x96"', 0226.chr.force_encoding('utf-8')],
-        ['"\\x97"', 0227.chr.force_encoding('utf-8')],
-        ['"\\x98"', 0230.chr.force_encoding('utf-8')],
-        ['"\\x99"', 0231.chr.force_encoding('utf-8')],
-        ['"\\x9A"', 0232.chr.force_encoding('utf-8')],
-        ['"\\x9B"', 0233.chr.force_encoding('utf-8')],
-        ['"\\x9C"', 0234.chr.force_encoding('utf-8')],
-        ['"\\x9D"', 0235.chr.force_encoding('utf-8')],
-        ['"\\x9E"', 0236.chr.force_encoding('utf-8')],
-        ['"\\x9F"', 0237.chr.force_encoding('utf-8')],
-        ['"\\xA0"', 0240.chr.force_encoding('utf-8')],
-        ['"\\xA1"', 0241.chr.force_encoding('utf-8')],
-        ['"\\xA2"', 0242.chr.force_encoding('utf-8')],
-        ['"\\xA3"', 0243.chr.force_encoding('utf-8')],
-        ['"\\xA4"', 0244.chr.force_encoding('utf-8')],
-        ['"\\xA5"', 0245.chr.force_encoding('utf-8')],
-        ['"\\xA6"', 0246.chr.force_encoding('utf-8')],
-        ['"\\xA7"', 0247.chr.force_encoding('utf-8')],
-        ['"\\xA8"', 0250.chr.force_encoding('utf-8')],
-        ['"\\xA9"', 0251.chr.force_encoding('utf-8')],
-        ['"\\xAA"', 0252.chr.force_encoding('utf-8')],
-        ['"\\xAB"', 0253.chr.force_encoding('utf-8')],
-        ['"\\xAC"', 0254.chr.force_encoding('utf-8')],
-        ['"\\xAD"', 0255.chr.force_encoding('utf-8')],
-        ['"\\xAE"', 0256.chr.force_encoding('utf-8')],
-        ['"\\xAF"', 0257.chr.force_encoding('utf-8')],
-        ['"\\xB0"', 0260.chr.force_encoding('utf-8')],
-        ['"\\xB1"', 0261.chr.force_encoding('utf-8')],
-        ['"\\xB2"', 0262.chr.force_encoding('utf-8')],
-        ['"\\xB3"', 0263.chr.force_encoding('utf-8')],
-        ['"\\xB4"', 0264.chr.force_encoding('utf-8')],
-        ['"\\xB5"', 0265.chr.force_encoding('utf-8')],
-        ['"\\xB6"', 0266.chr.force_encoding('utf-8')],
-        ['"\\xB7"', 0267.chr.force_encoding('utf-8')],
-        ['"\\xB8"', 0270.chr.force_encoding('utf-8')],
-        ['"\\xB9"', 0271.chr.force_encoding('utf-8')],
-        ['"\\xBA"', 0272.chr.force_encoding('utf-8')],
-        ['"\\xBB"', 0273.chr.force_encoding('utf-8')],
-        ['"\\xBC"', 0274.chr.force_encoding('utf-8')],
-        ['"\\xBD"', 0275.chr.force_encoding('utf-8')],
-        ['"\\xBE"', 0276.chr.force_encoding('utf-8')],
-        ['"\\xBF"', 0277.chr.force_encoding('utf-8')],
-        ['"\\xC0"', 0300.chr.force_encoding('utf-8')],
-        ['"\\xC1"', 0301.chr.force_encoding('utf-8')],
-        ['"\\xC2"', 0302.chr.force_encoding('utf-8')],
-        ['"\\xC3"', 0303.chr.force_encoding('utf-8')],
-        ['"\\xC4"', 0304.chr.force_encoding('utf-8')],
-        ['"\\xC5"', 0305.chr.force_encoding('utf-8')],
-        ['"\\xC6"', 0306.chr.force_encoding('utf-8')],
-        ['"\\xC7"', 0307.chr.force_encoding('utf-8')],
-        ['"\\xC8"', 0310.chr.force_encoding('utf-8')],
-        ['"\\xC9"', 0311.chr.force_encoding('utf-8')],
-        ['"\\xCA"', 0312.chr.force_encoding('utf-8')],
-        ['"\\xCB"', 0313.chr.force_encoding('utf-8')],
-        ['"\\xCC"', 0314.chr.force_encoding('utf-8')],
-        ['"\\xCD"', 0315.chr.force_encoding('utf-8')],
-        ['"\\xCE"', 0316.chr.force_encoding('utf-8')],
-        ['"\\xCF"', 0317.chr.force_encoding('utf-8')],
-        ['"\\xD0"', 0320.chr.force_encoding('utf-8')],
-        ['"\\xD1"', 0321.chr.force_encoding('utf-8')],
-        ['"\\xD2"', 0322.chr.force_encoding('utf-8')],
-        ['"\\xD3"', 0323.chr.force_encoding('utf-8')],
-        ['"\\xD4"', 0324.chr.force_encoding('utf-8')],
-        ['"\\xD5"', 0325.chr.force_encoding('utf-8')],
-        ['"\\xD6"', 0326.chr.force_encoding('utf-8')],
-        ['"\\xD7"', 0327.chr.force_encoding('utf-8')],
-        ['"\\xD8"', 0330.chr.force_encoding('utf-8')],
-        ['"\\xD9"', 0331.chr.force_encoding('utf-8')],
-        ['"\\xDA"', 0332.chr.force_encoding('utf-8')],
-        ['"\\xDB"', 0333.chr.force_encoding('utf-8')],
-        ['"\\xDC"', 0334.chr.force_encoding('utf-8')],
-        ['"\\xDD"', 0335.chr.force_encoding('utf-8')],
-        ['"\\xDE"', 0336.chr.force_encoding('utf-8')],
-        ['"\\xDF"', 0337.chr.force_encoding('utf-8')],
-        ['"\\xE0"', 0340.chr.force_encoding('utf-8')],
-        ['"\\xE1"', 0341.chr.force_encoding('utf-8')],
-        ['"\\xE2"', 0342.chr.force_encoding('utf-8')],
-        ['"\\xE3"', 0343.chr.force_encoding('utf-8')],
-        ['"\\xE4"', 0344.chr.force_encoding('utf-8')],
-        ['"\\xE5"', 0345.chr.force_encoding('utf-8')],
-        ['"\\xE6"', 0346.chr.force_encoding('utf-8')],
-        ['"\\xE7"', 0347.chr.force_encoding('utf-8')],
-        ['"\\xE8"', 0350.chr.force_encoding('utf-8')],
-        ['"\\xE9"', 0351.chr.force_encoding('utf-8')],
-        ['"\\xEA"', 0352.chr.force_encoding('utf-8')],
-        ['"\\xEB"', 0353.chr.force_encoding('utf-8')],
-        ['"\\xEC"', 0354.chr.force_encoding('utf-8')],
-        ['"\\xED"', 0355.chr.force_encoding('utf-8')],
-        ['"\\xEE"', 0356.chr.force_encoding('utf-8')],
-        ['"\\xEF"', 0357.chr.force_encoding('utf-8')],
-        ['"\\xF0"', 0360.chr.force_encoding('utf-8')],
-        ['"\\xF1"', 0361.chr.force_encoding('utf-8')],
-        ['"\\xF2"', 0362.chr.force_encoding('utf-8')],
-        ['"\\xF3"', 0363.chr.force_encoding('utf-8')],
-        ['"\\xF4"', 0364.chr.force_encoding('utf-8')],
-        ['"\\xF5"', 0365.chr.force_encoding('utf-8')],
-        ['"\\xF6"', 0366.chr.force_encoding('utf-8')],
-        ['"\\xF7"', 0367.chr.force_encoding('utf-8')],
-        ['"\\xF8"', 0370.chr.force_encoding('utf-8')],
-        ['"\\xF9"', 0371.chr.force_encoding('utf-8')],
-        ['"\\xFA"', 0372.chr.force_encoding('utf-8')],
-        ['"\\xFB"', 0373.chr.force_encoding('utf-8')],
-        ['"\\xFC"', 0374.chr.force_encoding('utf-8')],
-        ['"\\xFD"', 0375.chr.force_encoding('utf-8')],
-        ['"\\xFE"', 0376.chr.force_encoding('utf-8')],
-        ['"\\xFF"', 0377.chr.force_encoding('utf-8')]
-      ].should be_computed_by(:undump)
-    end
+  it "returns a string with \\uXXXX notation replaced with multi-byte UTF-8 characters" do
+    [ ['"\u0080"', 0200.chr('utf-8')],
+      ['"\u0081"', 0201.chr('utf-8')],
+      ['"\u0082"', 0202.chr('utf-8')],
+      ['"\u0083"', 0203.chr('utf-8')],
+      ['"\u0084"', 0204.chr('utf-8')],
+      ['"\u0086"', 0206.chr('utf-8')],
+      ['"\u0087"', 0207.chr('utf-8')],
+      ['"\u0088"', 0210.chr('utf-8')],
+      ['"\u0089"', 0211.chr('utf-8')],
+      ['"\u008a"', 0212.chr('utf-8')],
+      ['"\u008b"', 0213.chr('utf-8')],
+      ['"\u008c"', 0214.chr('utf-8')],
+      ['"\u008d"', 0215.chr('utf-8')],
+      ['"\u008e"', 0216.chr('utf-8')],
+      ['"\u008f"', 0217.chr('utf-8')],
+      ['"\u0090"', 0220.chr('utf-8')],
+      ['"\u0091"', 0221.chr('utf-8')],
+      ['"\u0092"', 0222.chr('utf-8')],
+      ['"\u0093"', 0223.chr('utf-8')],
+      ['"\u0094"', 0224.chr('utf-8')],
+      ['"\u0095"', 0225.chr('utf-8')],
+      ['"\u0096"', 0226.chr('utf-8')],
+      ['"\u0097"', 0227.chr('utf-8')],
+      ['"\u0098"', 0230.chr('utf-8')],
+      ['"\u0099"', 0231.chr('utf-8')],
+      ['"\u009a"', 0232.chr('utf-8')],
+      ['"\u009b"', 0233.chr('utf-8')],
+      ['"\u009c"', 0234.chr('utf-8')],
+      ['"\u009d"', 0235.chr('utf-8')],
+      ['"\u009e"', 0236.chr('utf-8')],
+      ['"\u009f"', 0237.chr('utf-8')],
+    ].should be_computed_by(:undump)
+  end
 
-    it "returns a string with \\u{} notation replaced with multi-byte UTF-8 characters" do
-      [ ['"\u{80}"', 0200.chr('utf-8')],
-        ['"\u{81}"', 0201.chr('utf-8')],
-        ['"\u{82}"', 0202.chr('utf-8')],
-        ['"\u{83}"', 0203.chr('utf-8')],
-        ['"\u{84}"', 0204.chr('utf-8')],
-        ['"\u{86}"', 0206.chr('utf-8')],
-        ['"\u{87}"', 0207.chr('utf-8')],
-        ['"\u{88}"', 0210.chr('utf-8')],
-        ['"\u{89}"', 0211.chr('utf-8')],
-        ['"\u{8a}"', 0212.chr('utf-8')],
-        ['"\u{8b}"', 0213.chr('utf-8')],
-        ['"\u{8c}"', 0214.chr('utf-8')],
-        ['"\u{8d}"', 0215.chr('utf-8')],
-        ['"\u{8e}"', 0216.chr('utf-8')],
-        ['"\u{8f}"', 0217.chr('utf-8')],
-        ['"\u{90}"', 0220.chr('utf-8')],
-        ['"\u{91}"', 0221.chr('utf-8')],
-        ['"\u{92}"', 0222.chr('utf-8')],
-        ['"\u{93}"', 0223.chr('utf-8')],
-        ['"\u{94}"', 0224.chr('utf-8')],
-        ['"\u{95}"', 0225.chr('utf-8')],
-        ['"\u{96}"', 0226.chr('utf-8')],
-        ['"\u{97}"', 0227.chr('utf-8')],
-        ['"\u{98}"', 0230.chr('utf-8')],
-        ['"\u{99}"', 0231.chr('utf-8')],
-        ['"\u{9a}"', 0232.chr('utf-8')],
-        ['"\u{9b}"', 0233.chr('utf-8')],
-        ['"\u{9c}"', 0234.chr('utf-8')],
-        ['"\u{9d}"', 0235.chr('utf-8')],
-        ['"\u{9e}"', 0236.chr('utf-8')],
-        ['"\u{9f}"', 0237.chr('utf-8')],
-      ].should be_computed_by(:undump)
-    end
+  it "undumps correctly string produced from non ASCII-compatible one" do
+    s = "\u{876}".encode('utf-16be')
+    s.dump.undump.should == s
 
-    it "returns a string with \\uXXXX notation replaced with multi-byte UTF-8 characters" do
-      [ ['"\u0080"', 0200.chr('utf-8')],
-        ['"\u0081"', 0201.chr('utf-8')],
-        ['"\u0082"', 0202.chr('utf-8')],
-        ['"\u0083"', 0203.chr('utf-8')],
-        ['"\u0084"', 0204.chr('utf-8')],
-        ['"\u0086"', 0206.chr('utf-8')],
-        ['"\u0087"', 0207.chr('utf-8')],
-        ['"\u0088"', 0210.chr('utf-8')],
-        ['"\u0089"', 0211.chr('utf-8')],
-        ['"\u008a"', 0212.chr('utf-8')],
-        ['"\u008b"', 0213.chr('utf-8')],
-        ['"\u008c"', 0214.chr('utf-8')],
-        ['"\u008d"', 0215.chr('utf-8')],
-        ['"\u008e"', 0216.chr('utf-8')],
-        ['"\u008f"', 0217.chr('utf-8')],
-        ['"\u0090"', 0220.chr('utf-8')],
-        ['"\u0091"', 0221.chr('utf-8')],
-        ['"\u0092"', 0222.chr('utf-8')],
-        ['"\u0093"', 0223.chr('utf-8')],
-        ['"\u0094"', 0224.chr('utf-8')],
-        ['"\u0095"', 0225.chr('utf-8')],
-        ['"\u0096"', 0226.chr('utf-8')],
-        ['"\u0097"', 0227.chr('utf-8')],
-        ['"\u0098"', 0230.chr('utf-8')],
-        ['"\u0099"', 0231.chr('utf-8')],
-        ['"\u009a"', 0232.chr('utf-8')],
-        ['"\u009b"', 0233.chr('utf-8')],
-        ['"\u009c"', 0234.chr('utf-8')],
-        ['"\u009d"', 0235.chr('utf-8')],
-        ['"\u009e"', 0236.chr('utf-8')],
-        ['"\u009f"', 0237.chr('utf-8')],
-      ].should be_computed_by(:undump)
-    end
+    '"\\bv".force_encoding("UTF-16BE")'.undump.should == "\u0876".encode('utf-16be')
+  end
 
-    it "undumps correctly string produced from non ASCII-compatible one" do
-      s = "\u{876}".encode('utf-16be')
-      s.dump.undump.should == s
+  it "returns a String in the same encoding as self" do
+    '"foo"'.encode("ISO-8859-1").undump.encoding.should == Encoding::ISO_8859_1
+    '"foo"'.encode('windows-1251').undump.encoding.should == Encoding::Windows_1251
+  end
 
-      '"\\bv".force_encoding("UTF-16BE")'.undump.should == "\u0876".encode('utf-16be')
+  describe "Limitations" do
+    it "cannot undump non ASCII-compatible string" do
+      -> { '"foo"'.encode('utf-16le').undump }.should raise_error(Encoding::CompatibilityError)
     end
+  end
 
-    it "keeps origin encoding" do
-      '"foo"'.encode("ISO-8859-1").undump.encoding.should == Encoding::ISO_8859_1
-      '"foo"'.encode('windows-1251').undump.encoding.should == Encoding::Windows_1251
+  describe "invalid dump" do
+    it "raises RuntimeError exception if wrapping \" are missing" do
+      -> { 'foo'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
+      -> { '"foo'.undump }.should raise_error(RuntimeError, /unterminated dumped string/)
+      -> { 'foo"'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
+      -> { "'foo'".undump }.should raise_error(RuntimeError, /invalid dumped string/)
     end
 
-    describe "Limitations" do
-      it "cannot undump non ASCII-compatible string" do
-        -> { '"foo"'.encode('utf-16le').undump }.should raise_error(Encoding::CompatibilityError)
-      end
+    it "raises RuntimeError if there is incorrect \\x sequence" do
+      -> { '"\x"'.undump }.should raise_error(RuntimeError, /invalid hex escape/)
+      -> { '"\\x3y"'.undump }.should raise_error(RuntimeError, /invalid hex escape/)
     end
 
-    describe "invalid dump" do
-      it "raises RuntimeError exception if wrapping \" are missing" do
-        -> { 'foo'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
-        -> { '"foo'.undump }.should raise_error(RuntimeError, /unterminated dumped string/)
-        -> { 'foo"'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
-        -> { "'foo'".undump }.should raise_error(RuntimeError, /invalid dumped string/)
-      end
-
-      it "raises RuntimeError if there is incorrect \\x sequence" do
-        -> { '"\x"'.undump }.should raise_error(RuntimeError, /invalid hex escape/)
-        -> { '"\\x3y"'.undump }.should raise_error(RuntimeError, /invalid hex escape/)
-      end
-
-      it "raises RuntimeError in there is incorrect \\u sequence" do
-        -> { '"\\u"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
-        -> { '"\\u{"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
-        -> { '"\\u{3042"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
-        -> { '"\\u"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
-      end
+    it "raises RuntimeError in there is incorrect \\u sequence" do
+      -> { '"\\u"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
+      -> { '"\\u{"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
+      -> { '"\\u{3042"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
+      -> { '"\\u"'.undump }.should raise_error(RuntimeError, /invalid Unicode escape/)
+    end
 
-      it "raises RuntimeError if there is malformed dump of non ASCII-compatible string" do
-        -> { '"".force_encoding("BINARY"'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
-        -> { '"".force_encoding("Unknown")'.undump }.should raise_error(RuntimeError, /dumped string has unknown encoding name/)
-        -> { '"".force_encoding()'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
-      end
+    it "raises RuntimeError if there is malformed dump of non ASCII-compatible string" do
+      -> { '"".force_encoding("BINARY"'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
+      -> { '"".force_encoding("Unknown")'.undump }.should raise_error(RuntimeError, /dumped string has unknown encoding name/)
+      -> { '"".force_encoding()'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
+    end
 
-      it "raises RuntimeError if string contains \0 character" do
-        -> { "\"foo\0\"".undump }.should raise_error(RuntimeError, /string contains null byte/)
-      end
+    it "raises RuntimeError if string contains \0 character" do
+      -> { "\"foo\0\"".undump }.should raise_error(RuntimeError, /string contains null byte/)
+    end
 
-      it "raises RuntimeError if string contains non ASCII character" do
-        -> { "\"\u3042\"".undump }.should raise_error(RuntimeError, /non-ASCII character detected/)
-      end
+    it "raises RuntimeError if string contains non ASCII character" do
+      -> { "\"\u3042\"".undump }.should raise_error(RuntimeError, /non-ASCII character detected/)
+    end
 
-      it "raises RuntimeError if there are some excessive \"" do
-        -> { '" "" "'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
-      end
+    it "raises RuntimeError if there are some excessive \"" do
+      -> { '" "" "'.undump }.should raise_error(RuntimeError, /invalid dumped string/)
     end
   end
 end
diff --git a/spec/ruby/core/string/unicode_normalize_spec.rb b/spec/ruby/core/string/unicode_normalize_spec.rb
index 6de7533fc7..2e7d22394a 100644
--- a/spec/ruby/core/string/unicode_normalize_spec.rb
+++ b/spec/ruby/core/string/unicode_normalize_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 # Examples taken from http://www.unicode.org/reports/tr15/#Norm_Forms
diff --git a/spec/ruby/core/string/unicode_normalized_spec.rb b/spec/ruby/core/string/unicode_normalized_spec.rb
index 25c810a98f..91cf2086b2 100644
--- a/spec/ruby/core/string/unicode_normalized_spec.rb
+++ b/spec/ruby/core/string/unicode_normalized_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe "String#unicode_normalized?" do
@@ -24,16 +25,16 @@ describe "String#unicode_normalized?" do
   end
 
   it "defaults to the nfc normalization form if no forms are specified" do
-    @nfc_normalized_str.unicode_normalized?.should == true
-    @nfd_normalized_str.unicode_normalized?.should == false
+    @nfc_normalized_str.should.unicode_normalized?
+    @nfd_normalized_str.should_not.unicode_normalized?
   end
 
   it "returns true if string is empty" do
-    "".unicode_normalized?.should == true
+    "".should.unicode_normalized?
   end
 
   it "returns true if string does not contain any unicode codepoints" do
-    "abc".unicode_normalized?.should == true
+    "abc".should.unicode_normalized?
   end
 
   it "raises an Encoding::CompatibilityError if the string is not in an unicode encoding" do
diff --git a/spec/ruby/core/string/unpack/a_spec.rb b/spec/ruby/core/string/unpack/a_spec.rb
index 2d83b4c824..a68e842e15 100644
--- a/spec/ruby/core/string/unpack/a_spec.rb
+++ b/spec/ruby/core/string/unpack/a_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -31,7 +31,7 @@ describe "String#unpack with format 'A'" do
   end
 
   it "decodes into raw (ascii) string values" do
-    str = "str".force_encoding('UTF-8').unpack("A*")[0]
+    str = "str".dup.force_encoding('UTF-8').unpack("A*")[0]
     str.encoding.should == Encoding::BINARY
   end
 
diff --git a/spec/ruby/core/string/unpack/at_spec.rb b/spec/ruby/core/string/unpack/at_spec.rb
index 70b2389d69..d4133c23ee 100644
--- a/spec/ruby/core/string/unpack/at_spec.rb
+++ b/spec/ruby/core/string/unpack/at_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
diff --git a/spec/ruby/core/string/unpack/b_spec.rb b/spec/ruby/core/string/unpack/b_spec.rb
index 1a838d6c7c..b088f901fc 100644
--- a/spec/ruby/core/string/unpack/b_spec.rb
+++ b/spec/ruby/core/string/unpack/b_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -86,13 +86,30 @@ describe "String#unpack with format 'B'" do
     ].should be_computed_by(:unpack, "BBB")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x80\x00".unpack("B\x00B").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x80\x00".unpack("B\x00B").should == ["1", "0"]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x80\x00".unpack("B\x00B")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
     "\x80\x00".unpack("B B").should == ["1", "0"]
   end
+
+  it "decodes into US-ASCII string values" do
+    str = "s".dup.force_encoding('UTF-8').unpack("B*")[0]
+    str.encoding.name.should == 'US-ASCII'
+  end
 end
 
 describe "String#unpack with format 'b'" do
@@ -177,8 +194,20 @@ describe "String#unpack with format 'b'" do
     ].should be_computed_by(:unpack, "bbb")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x00".unpack("b\x00b").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x01\x00".unpack("b\x00b").should == ["1", "0"]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x00".unpack("b\x00b")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -186,8 +215,7 @@ describe "String#unpack with format 'b'" do
   end
 
   it "decodes into US-ASCII string values" do
-    str = "s".force_encoding('UTF-8').unpack("b*")[0]
+    str = "s".dup.force_encoding('UTF-8').unpack("b*")[0]
     str.encoding.name.should == 'US-ASCII'
   end
-
 end
diff --git a/spec/ruby/core/string/unpack/c_spec.rb b/spec/ruby/core/string/unpack/c_spec.rb
index ed8caa4895..1e9548fb82 100644
--- a/spec/ruby/core/string/unpack/c_spec.rb
+++ b/spec/ruby/core/string/unpack/c_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -35,8 +35,20 @@ describe :string_unpack_8bit, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abc".unpack(unpack_format("\000", 2)).should == [97, 98]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "abc".unpack(unpack_format("\000", 2)).should == [97, 98]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/comment_spec.rb b/spec/ruby/core/string/unpack/comment_spec.rb
index e18a53df3c..050d2b7fc0 100644
--- a/spec/ruby/core/string/unpack/comment_spec.rb
+++ b/spec/ruby/core/string/unpack/comment_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/core/string/unpack/h_spec.rb b/spec/ruby/core/string/unpack/h_spec.rb
index f2f5dcf396..535836087d 100644
--- a/spec/ruby/core/string/unpack/h_spec.rb
+++ b/spec/ruby/core/string/unpack/h_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -56,8 +56,20 @@ describe "String#unpack with format 'H'" do
     ].should be_computed_by(:unpack, "HHH")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x10".unpack("H\x00H").should == ["0", "1"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x01\x10".unpack("H\x00H").should == ["0", "1"]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x10".unpack("H\x00H")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -121,8 +133,20 @@ describe "String#unpack with format 'h'" do
     ].should be_computed_by(:unpack, "hhh")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x10".unpack("h\x00h").should == ["1", "0"]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x01\x10".unpack("h\x00h").should == ["1", "0"]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x10".unpack("h\x00h")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/l_spec.rb b/spec/ruby/core/string/unpack/l_spec.rb
index 18bb68b8d0..0adb567eca 100644
--- a/spec/ruby/core/string/unpack/l_spec.rb
+++ b/spec/ruby/core/string/unpack/l_spec.rb
@@ -14,7 +14,7 @@ describe "String#unpack with format 'L'" do
     it_behaves_like :string_unpack_32bit_be_unsigned, 'L>'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :string_unpack_32bit_le, 'L<_'
       it_behaves_like :string_unpack_32bit_le, 'L_<'
@@ -44,7 +44,7 @@ describe "String#unpack with format 'L'" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :string_unpack_64bit_le, 'L<_'
       it_behaves_like :string_unpack_64bit_le, 'L_<'
@@ -86,7 +86,7 @@ describe "String#unpack with format 'l'" do
     it_behaves_like :string_unpack_32bit_be_signed, 'l>'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :string_unpack_32bit_le, 'l<_'
       it_behaves_like :string_unpack_32bit_le, 'l_<'
@@ -116,7 +116,7 @@ describe "String#unpack with format 'l'" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "with modifier '<' and '_'" do
       it_behaves_like :string_unpack_64bit_le, 'l<_'
       it_behaves_like :string_unpack_64bit_le, 'l_<'
@@ -160,7 +160,7 @@ little_endian do
     it_behaves_like :string_unpack_32bit_le_signed, 'l'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "String#unpack with format 'L' with modifier '_'" do
       it_behaves_like :string_unpack_32bit_le, 'L_'
       it_behaves_like :string_unpack_32bit_le_unsigned, 'L_'
@@ -182,7 +182,7 @@ little_endian do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "String#unpack with format 'L' with modifier '_'" do
       it_behaves_like :string_unpack_64bit_le, 'L_'
       it_behaves_like :string_unpack_64bit_le_unsigned, 'L_'
@@ -218,7 +218,7 @@ big_endian do
     it_behaves_like :string_unpack_32bit_be_signed, 'l'
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     describe "String#unpack with format 'L' with modifier '_'" do
       it_behaves_like :string_unpack_32bit_be, 'L_'
       it_behaves_like :string_unpack_32bit_be_unsigned, 'L_'
@@ -240,7 +240,7 @@ big_endian do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "String#unpack with format 'L' with modifier '_'" do
       it_behaves_like :string_unpack_64bit_be, 'L_'
       it_behaves_like :string_unpack_64bit_be_unsigned, 'L_'
diff --git a/spec/ruby/core/string/unpack/m_spec.rb b/spec/ruby/core/string/unpack/m_spec.rb
index 96841f24cb..357987a053 100644
--- a/spec/ruby/core/string/unpack/m_spec.rb
+++ b/spec/ruby/core/string/unpack/m_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -97,6 +97,11 @@ describe "String#unpack with format 'M'" do
       ["=FF=\n",                      ["\xff"]]
     ].should be_computed_by(:unpack, "M")
   end
+
+  it "unpacks incomplete escape sequences as literal characters" do
+    "foo=".unpack("M").should == ["foo="]
+    "foo=4".unpack("M").should == ["foo=4"]
+  end
 end
 
 describe "String#unpack with format 'm'" do
@@ -170,4 +175,18 @@ describe "String#unpack with format 'm'" do
     "".unpack("m").first.encoding.should == Encoding::BINARY
     "Ojs8PT4/QA==\n".unpack("m").first.encoding.should == Encoding::BINARY
   end
+
+  it "does not raise an error for an invalid base64 character" do
+    "dGV%zdA==".unpack("m").should == ["test"]
+  end
+
+  describe "when given count 0" do
+    it "decodes base64" do
+      "dGVzdA==".unpack("m0").should == ["test"]
+    end
+
+    it "raises an ArgumentError for an invalid base64 character" do
+      -> { "dGV%zdA==".unpack("m0") }.should raise_error(ArgumentError)
+    end
+  end
 end
diff --git a/spec/ruby/core/string/unpack/p_spec.rb b/spec/ruby/core/string/unpack/p_spec.rb
index a544bc29c1..cd48c0523d 100644
--- a/spec/ruby/core/string/unpack/p_spec.rb
+++ b/spec/ruby/core/string/unpack/p_spec.rb
@@ -18,10 +18,6 @@ describe "String#unpack with format 'P'" do
     -> { packed.to_sym.to_s.unpack("P5") }.should raise_error(ArgumentError, /no associated pointer/)
   end
 
-  it "taints the unpacked string" do
-    ["hello"].pack("P").unpack("P5").first.tainted?.should be_true
-  end
-
   it "reads as many characters as specified" do
     ["hello"].pack("P").unpack("P1").should == ["h"]
   end
@@ -45,8 +41,4 @@ describe "String#unpack with format 'p'" do
     packed.dup.unpack("p").should == ["hello"]
     -> { packed.to_sym.to_s.unpack("p") }.should raise_error(ArgumentError, /no associated pointer/)
   end
-
-  it "taints the unpacked string" do
-    ["hello"].pack("p").unpack("p").first.tainted?.should be_true
-  end
 end
diff --git a/spec/ruby/core/string/unpack/shared/basic.rb b/spec/ruby/core/string/unpack/shared/basic.rb
index 332e39d8d1..734630bda0 100644
--- a/spec/ruby/core/string/unpack/shared/basic.rb
+++ b/spec/ruby/core/string/unpack/shared/basic.rb
@@ -9,12 +9,20 @@ describe :string_unpack_basic, shared: true do
     "abc".unpack(d).should be_an_instance_of(Array)
   end
 
-  it "raises a TypeError when passed nil" do
-    -> { "abc".unpack(nil) }.should raise_error(TypeError)
+  ruby_version_is ""..."3.3" do
+    it "warns about using an unknown directive" do
+      -> { "abcdefgh".unpack("a R" + unpack_format) }.should complain(/unknown unpack directive 'R' in 'a R#{unpack_format}'/)
+      -> { "abcdefgh".unpack("a 0" + unpack_format) }.should complain(/unknown unpack directive '0' in 'a 0#{unpack_format}'/)
+      -> { "abcdefgh".unpack("a :" + unpack_format) }.should complain(/unknown unpack directive ':' in 'a :#{unpack_format}'/)
+    end
   end
 
-  it "raises a TypeError when passed an Integer" do
-    -> { "abc".unpack(1) }.should raise_error(TypeError)
+  ruby_version_is "3.3" do
+    it "raises ArgumentError when a directive is unknown" do
+      -> { "abcdefgh".unpack("a K" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive 'K' in 'a K#{unpack_format}'")
+      -> { "abcdefgh".unpack("a 0" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive '0' in 'a 0#{unpack_format}'")
+      -> { "abcdefgh".unpack("a :" + unpack_format) }.should raise_error(ArgumentError, "unknown unpack directive ':' in 'a :#{unpack_format}'")
+    end
   end
 end
 
diff --git a/spec/ruby/core/string/unpack/shared/float.rb b/spec/ruby/core/string/unpack/shared/float.rb
index 99bd8a3401..b31c2c8bdc 100644
--- a/spec/ruby/core/string/unpack/shared/float.rb
+++ b/spec/ruby/core/string/unpack/shared/float.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :string_unpack_float_le, shared: true do
   it "decodes one float for a single format character" do
@@ -56,9 +56,21 @@ describe :string_unpack_float_le, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
-    array.should == [2.9000000953674316, 1.399999976158142]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        array = "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
+        array.should == [2.9000000953674316, 1.399999976158142]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x9a\x999@33\xb3?".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -123,9 +135,21 @@ describe :string_unpack_float_be, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
-    array.should == [2.9000000953674316, 1.399999976158142]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        array = "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
+        array.should == [2.9000000953674316, 1.399999976158142]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "@9\x99\x9a?\xb333".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -193,8 +217,20 @@ describe :string_unpack_double_le, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "333333\x07@ffffff\xf6?".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -261,8 +297,20 @@ describe :string_unpack_double_be, shared: true do
     [nan_value].pack(unpack_format).unpack(unpack_format).first.nan?.should be_true
   end
 
-  it "ignores NULL bytes between directives" do
-    "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2)).should == [2.9, 1.4]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "@\x07333333?\xf6ffffff".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/shared/integer.rb b/spec/ruby/core/string/unpack/shared/integer.rb
index cbaa743683..d3934753ba 100644
--- a/spec/ruby/core/string/unpack/shared/integer.rb
+++ b/spec/ruby/core/string/unpack/shared/integer.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 describe :string_unpack_16bit_le, shared: true do
   it "decodes one short for a single format character" do
@@ -32,8 +32,20 @@ describe :string_unpack_16bit_le, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abcd".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "abcd".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abcd".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -85,8 +97,20 @@ describe :string_unpack_16bit_be, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "badc".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "badc".unpack(unpack_format("\000", 2)).should == [25185, 25699]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "badc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -139,8 +163,20 @@ describe :string_unpack_32bit_le, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "abcdefgh".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "abcdefgh".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "abcdefgh".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -193,8 +229,20 @@ describe :string_unpack_32bit_be, shared: true do
     ].should be_computed_by(:unpack, unpack_format(3))
   end
 
-  it "ignores NULL bytes between directives" do
-    "dcbahgfe".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "dcbahgfe".unpack(unpack_format("\000", 2)).should == [1684234849, 1751606885]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "dcbahgfe".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -243,9 +291,21 @@ describe :string_unpack_64bit_le, shared: true do
     "abc".unpack(unpack_format('*')).should == []
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "abcdefghabghefcd".unpack(unpack_format("\000", 2))
-    array.should == [7523094288207667809, 7233738012216484449]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        array = "abcdefghabghefcd".unpack(unpack_format("\000", 2))
+        array.should == [7523094288207667809, 7233738012216484449]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "badc".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
@@ -305,9 +365,21 @@ describe :string_unpack_64bit_be, shared: true do
     "abc".unpack(unpack_format('*')).should == []
   end
 
-  it "ignores NULL bytes between directives" do
-    array = "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
-    array.should == [7523094288207667809, 7233738012216484449]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        array = "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
+        array.should == [7523094288207667809, 7233738012216484449]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "hgfedcbadcfehgba".unpack(unpack_format("\000", 2))
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/shared/taint.rb b/spec/ruby/core/string/unpack/shared/taint.rb
index 391338192a..79c7251f01 100644
--- a/spec/ruby/core/string/unpack/shared/taint.rb
+++ b/spec/ruby/core/string/unpack/shared/taint.rb
@@ -1,81 +1,2 @@
 describe :string_unpack_taint, shared: true do
-  it "does not taint returned arrays if given an untainted format string" do
-    "".unpack(unpack_format(2)).tainted?.should be_false
-  end
-
-  it "does not taint returned arrays if given a tainted format string" do
-    format_string = unpack_format(2).dup
-    format_string.taint
-    "".unpack(format_string).tainted?.should be_false
-  end
-
-  it "does not taint returned strings if given an untainted format string" do
-    "".unpack(unpack_format(2)).any?(&:tainted?).should be_false
-  end
-
-  it "does not taint returned strings if given a tainted format string" do
-    format_string = unpack_format(2).dup
-    format_string.taint
-    "".unpack(format_string).any?(&:tainted?).should be_false
-  end
-
-  it "does not taint returned arrays if given an untainted packed string" do
-    "".unpack(unpack_format(2)).tainted?.should be_false
-  end
-
-  it "does not taint returned arrays if given a tainted packed string" do
-    packed_string = ""
-    packed_string.taint
-    packed_string.unpack(unpack_format(2)).tainted?.should be_false
-  end
-
-  it "does not taint returned strings if given an untainted packed string" do
-    "".unpack(unpack_format(2)).any?(&:tainted?).should be_false
-  end
-
-  it "taints returned strings if given a tainted packed string" do
-    packed_string = ""
-    packed_string.taint
-    packed_string.unpack(unpack_format(2)).all?(&:tainted?).should be_true
-  end
-
-  it "does not untrust returned arrays if given an untrusted format string" do
-    "".unpack(unpack_format(2)).untrusted?.should be_false
-  end
-
-  it "does not untrust returned arrays if given a untrusted format string" do
-    format_string = unpack_format(2).dup
-    format_string.untrust
-    "".unpack(format_string).untrusted?.should be_false
-  end
-
-  it "does not untrust returned strings if given an untainted format string" do
-    "".unpack(unpack_format(2)).any?(&:untrusted?).should be_false
-  end
-
-  it "does not untrust returned strings if given a untrusted format string" do
-    format_string = unpack_format(2).dup
-    format_string.untrust
-    "".unpack(format_string).any?(&:untrusted?).should be_false
-  end
-
-  it "does not untrust returned arrays if given an trusted packed string" do
-    "".unpack(unpack_format(2)).untrusted?.should be_false
-  end
-
-  it "does not untrust returned arrays if given a untrusted packed string" do
-    packed_string = ""
-    packed_string.untrust
-    packed_string.unpack(unpack_format(2)).untrusted?.should be_false
-  end
-
-  it "does not untrust returned strings if given an trusted packed string" do
-    "".unpack(unpack_format(2)).any?(&:untrusted?).should be_false
-  end
-
-  it "untrusts returned strings if given a untrusted packed string" do
-    packed_string = ""
-    packed_string.untrust
-    packed_string.unpack(unpack_format(2)).all?(&:untrusted?).should be_true
-  end
 end
diff --git a/spec/ruby/core/string/unpack/shared/unicode.rb b/spec/ruby/core/string/unpack/shared/unicode.rb
index a2b4e142b2..9fe07f53ae 100644
--- a/spec/ruby/core/string/unpack/shared/unicode.rb
+++ b/spec/ruby/core/string/unpack/shared/unicode.rb
@@ -50,8 +50,20 @@ describe :string_unpack_unicode, shared: true do
     "\xc2\x80".unpack("UUUU").should == [0x80]
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x02".unpack("U\x00U").should == [1, 2]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x01\x02".unpack("U\x00U").should == [1, 2]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x02".unpack("U\x00U")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
diff --git a/spec/ruby/core/string/unpack/u_spec.rb b/spec/ruby/core/string/unpack/u_spec.rb
index 7845e6d5f2..68c8f6f11c 100644
--- a/spec/ruby/core/string/unpack/u_spec.rb
+++ b/spec/ruby/core/string/unpack/u_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -33,7 +33,7 @@ describe "String#unpack with format 'u'" do
     str = "".unpack("u")[0]
     str.encoding.should == Encoding::BINARY
 
-    str = "1".force_encoding('UTF-8').unpack("u")[0]
+    str = "1".dup.force_encoding('UTF-8').unpack("u")[0]
     str.encoding.should == Encoding::BINARY
   end
 
diff --git a/spec/ruby/core/string/unpack/w_spec.rb b/spec/ruby/core/string/unpack/w_spec.rb
index 166ae58869..7d3533ccae 100644
--- a/spec/ruby/core/string/unpack/w_spec.rb
+++ b/spec/ruby/core/string/unpack/w_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -15,11 +15,33 @@ describe "String#unpack with directive 'w'" do
     ].should be_computed_by(:unpack, "w")
   end
 
-  it "ignores NULL bytes between directives" do
-    "\x01\x02\x03".unpack("w\x00w").should == [1, 2]
+  ruby_version_is ""..."3.3" do
+    it "ignores NULL bytes between directives" do
+      suppress_warning do
+        "\x01\x02\x03".unpack("w\x00w").should == [1, 2]
+      end
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raise ArgumentError for NULL bytes between directives" do
+      -> {
+        "\x01\x02\x03".unpack("w\x00w")
+      }.should raise_error(ArgumentError, /unknown unpack directive/)
+    end
   end
 
   it "ignores spaces between directives" do
     "\x01\x02\x03".unpack("w w").should == [1, 2]
   end
 end
+
+describe "String#unpack with directive 'w*'" do
+
+  it "decodes BER-compressed integers" do
+    "\x01\x02\x03\x04".unpack("w*").should == [1, 2, 3, 4]
+    "\x00\xCE\x0F\x84\x80\x80\x80\x80\x80\x80\x80\x80\x00\x01\x00".unpack("w*").should == [0, 9999, 2**65, 1, 0]
+    "\x81\x80\x80\x80\x80\x80\x80\x80\x80\x00\x90\x80\x80\x80\x80\x80\x80\x80\x03\x01\x02".unpack("w*").should == [2**63, (2**60 + 3), 1, 2]
+  end
+
+end
diff --git a/spec/ruby/core/string/unpack/x_spec.rb b/spec/ruby/core/string/unpack/x_spec.rb
index 5e248de77e..2926ebbe0f 100644
--- a/spec/ruby/core/string/unpack/x_spec.rb
+++ b/spec/ruby/core/string/unpack/x_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
diff --git a/spec/ruby/core/string/unpack/z_spec.rb b/spec/ruby/core/string/unpack/z_spec.rb
index 552851ce04..1030390550 100644
--- a/spec/ruby/core/string/unpack/z_spec.rb
+++ b/spec/ruby/core/string/unpack/z_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 require_relative 'shared/basic'
@@ -20,4 +20,9 @@ describe "String#unpack with format 'Z'" do
       ["\x00a\x00 bc \x00",  ["", "c"]]
     ].should be_computed_by(:unpack, "Z5Z")
   end
+
+  it "does not advance past the null byte when given a 'Z' format specifier" do
+    "a\x00\x0f".unpack('Zxc').should == ['a', 15]
+    "a\x00\x0f".unpack('Zcc').should == ['a', 0, 15]
+  end
 end
diff --git a/spec/ruby/core/string/unpack1_spec.rb b/spec/ruby/core/string/unpack1_spec.rb
index 5fe81733fb..cfb47fe695 100644
--- a/spec/ruby/core/string/unpack1_spec.rb
+++ b/spec/ruby/core/string/unpack1_spec.rb
@@ -7,4 +7,41 @@ describe "String#unpack1" do
     "aG9nZWZ1Z2E=".unpack1("m").should == "hogefuga"
     "A".unpack1("B*").should == "01000001"
   end
+
+  it "starts unpacking from the given offset" do
+    "ZZABCD".unpack1('x3C', offset: 2).should == "ABCD".unpack('x3C')[0]
+    "ZZZZaG9nZWZ1Z2E=".unpack1("m", offset: 4).should == "hogefuga"
+    "ZA".unpack1("B*", offset: 1).should == "01000001"
+  end
+
+  it "traits offset as a bytes offset" do
+    "؈".unpack("CC").should == [216, 136]
+    "؈".unpack1("C").should == 216
+    "؈".unpack1("C", offset: 1).should == 136
+  end
+
+  it "raises an ArgumentError when the offset is negative" do
+    -> { "a".unpack1("C", offset: -1) }.should raise_error(ArgumentError, "offset can't be negative")
+  end
+
+  it "returns nil if the offset is at the end of the string" do
+    "a".unpack1("C", offset: 1).should == nil
+  end
+
+  it "raises an ArgumentError when the offset is larger than the string bytesize" do
+    -> { "a".unpack1("C", offset: 2) }.should raise_error(ArgumentError, "offset outside of string")
+  end
+
+  context "with format 'm0'" do
+    # unpack1("m0") takes a special code path that calls Pack.unpackBase46Strict instead of Pack.unpack_m,
+    # which is why we repeat the tests for unpack("m0") here.
+
+    it "decodes base64" do
+      "dGVzdA==".unpack1("m0").should == "test"
+    end
+
+    it "raises an ArgumentError for an invalid base64 character" do
+      -> { "dGV%zdA==".unpack1("m0") }.should raise_error(ArgumentError)
+    end
+  end
 end
diff --git a/spec/ruby/core/string/unpack_spec.rb b/spec/ruby/core/string/unpack_spec.rb
new file mode 100644
index 0000000000..a0abf8fa99
--- /dev/null
+++ b/spec/ruby/core/string/unpack_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../spec_helper'
+
+describe "String#unpack" do
+  it "raises a TypeError when passed nil" do
+    -> { "abc".unpack(nil) }.should raise_error(TypeError)
+  end
+
+  it "raises a TypeError when passed an Integer" do
+    -> { "abc".unpack(1) }.should raise_error(TypeError)
+  end
+
+  it "starts unpacking from the given offset" do
+    "abc".unpack("CC", offset: 1).should == [98, 99]
+  end
+
+  it "traits offset as a bytes offset" do
+    "؈".unpack("CC").should == [216, 136]
+    "؈".unpack("CC", offset: 1).should == [136, nil]
+  end
+
+  it "raises an ArgumentError when the offset is negative" do
+    -> { "a".unpack("C", offset: -1) }.should raise_error(ArgumentError, "offset can't be negative")
+  end
+
+  it "returns nil if the offset is at the end of the string" do
+    "a".unpack("C", offset: 1).should == [nil]
+  end
+
+  it "raises an ArgumentError when the offset is larger than the string" do
+    -> { "a".unpack("C", offset: 2) }.should raise_error(ArgumentError, "offset outside of string")
+  end
+end
diff --git a/spec/ruby/core/string/upcase_spec.rb b/spec/ruby/core/string/upcase_spec.rb
index 72aacd88a9..652de5c2ef 100644
--- a/spec/ruby/core/string/upcase_spec.rb
+++ b/spec/ruby/core/string/upcase_spec.rb
@@ -1,4 +1,5 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
@@ -8,6 +9,10 @@ describe "String#upcase" do
     "hello".upcase.should == "HELLO"
   end
 
+  it "returns a String in the same encoding as self" do
+    "hello".encode("US-ASCII").upcase.encoding.should == Encoding::US_ASCII
+  end
+
   describe "full Unicode case mapping" do
     it "works for all of Unicode with no option" do
       "äöü".upcase.should == "ÄÖÜ"
@@ -27,6 +32,10 @@ describe "String#upcase" do
     it "does not upcase non-ASCII characters" do
       "aßet".upcase(:ascii).should == "AßET"
     end
+
+    it "works with substrings" do
+      "prefix té"[-2..-1].upcase(:ascii).should == "Té"
+    end
   end
 
   describe "full Unicode case mapping adapted for Turkic languages" do
@@ -65,14 +74,8 @@ describe "String#upcase" do
     -> { "abc".upcase(:invalid_option) }.should raise_error(ArgumentError)
   end
 
-  it "taints result when self is tainted" do
-    "".taint.upcase.tainted?.should == true
-    "X".taint.upcase.tainted?.should == true
-    "x".taint.upcase.tainted?.should == true
-  end
-
-  it "returns a subclass instance for subclasses" do
-    StringSpecs::MyString.new("fooBAR").upcase.should be_an_instance_of(StringSpecs::MyString)
+  it "returns a String instance for subclasses" do
+    StringSpecs::MyString.new("fooBAR").upcase.should be_an_instance_of(String)
   end
 end
 
@@ -83,6 +86,12 @@ describe "String#upcase!" do
     a.should == "HELLO"
   end
 
+  it "modifies self in place for non-ascii-compatible encodings" do
+    a = "HeLlO".encode("utf-16le")
+    a.upcase!
+    a.should == "HELLO".encode("utf-16le")
+  end
+
   describe "full Unicode case mapping" do
     it "modifies self in place for all of Unicode with no option" do
       a = "äöü"
@@ -90,6 +99,12 @@ describe "String#upcase!" do
       a.should == "ÄÖÜ"
     end
 
+    it "works for non-ascii-compatible encodings" do
+      a = "äöü".encode("utf-16le")
+      a.upcase!
+      a.should == "ÄÖÜ".encode("utf-16le")
+    end
+
     it "updates string metadata for self" do
       upcased = "aßet"
       upcased.upcase!
@@ -107,6 +122,12 @@ describe "String#upcase!" do
       a.upcase!(:ascii)
       a.should == "AßET"
     end
+
+    it "works for non-ascii-compatible encodings" do
+      a = "abc".encode("utf-16le")
+      a.upcase!(:ascii)
+      a.should == "ABC".encode("utf-16le")
+    end
   end
 
   describe "modifies self in place for full Unicode case mapping adapted for Turkic languages" do
@@ -159,8 +180,8 @@ describe "String#upcase!" do
     a.should == "HELLO"
   end
 
-  it "raises a #{frozen_error_class} when self is frozen" do
-    -> { "HeLlo".freeze.upcase! }.should raise_error(frozen_error_class)
-    -> { "HELLO".freeze.upcase! }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when self is frozen" do
+    -> { "HeLlo".freeze.upcase! }.should raise_error(FrozenError)
+    -> { "HELLO".freeze.upcase! }.should raise_error(FrozenError)
   end
 end
diff --git a/spec/ruby/core/string/uplus_spec.rb b/spec/ruby/core/string/uplus_spec.rb
index a7402b4549..20767bcc01 100644
--- a/spec/ruby/core/string/uplus_spec.rb
+++ b/spec/ruby/core/string/uplus_spec.rb
@@ -1,3 +1,4 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 
 describe 'String#+@' do
@@ -5,18 +6,55 @@ describe 'String#+@' do
     input  = 'foo'.freeze
     output = +input
 
-    output.frozen?.should == false
+    output.should_not.frozen?
     output.should == 'foo'
+
+    output << 'bar'
+    output.should == 'foobar'
   end
 
-  it 'returns self if the String is not frozen' do
-    input  = 'foo'
+  it 'returns a mutable String itself' do
+    input = String.new("foo")
     output = +input
 
-    output.equal?(input).should == true
+    output.should.equal?(input)
+
+    input << "bar"
+    output.should == "foobar"
+  end
+
+  context 'if file has "frozen_string_literal: true" magic comment' do
+    it 'returns mutable copy of a literal' do
+      ruby_exe(fixture(__FILE__, "freeze_magic_comment.rb")).should == 'mutable'
+    end
   end
 
-  it 'returns mutable copy despite freeze-magic-comment in file' do
-    ruby_exe(fixture(__FILE__, "freeze_magic_comment.rb")).should == 'mutable'
+  context 'if file has "frozen_string_literal: false" magic comment' do
+    it 'returns literal string itself' do
+      input  = 'foo'
+      output = +input
+
+      output.equal?(input).should == true
+    end
+  end
+
+  context 'if file has no frozen_string_literal magic comment' do
+    ruby_version_is ''...'3.4' do
+      it 'returns literal string itself' do
+        eval(<<~RUBY).should == true
+          s = "foo"
+          s.equal?(+s)
+        RUBY
+      end
+    end
+
+    ruby_version_is '3.4' do
+      it 'returns mutable copy of a literal' do
+        eval(<<~RUBY).should == false
+          s = "foo"
+          s.equal?(+s)
+        RUBY
+      end
+    end
   end
 end
diff --git a/spec/ruby/core/string/upto_spec.rb b/spec/ruby/core/string/upto_spec.rb
index b988613a80..8bc847d5ac 100644
--- a/spec/ruby/core/string/upto_spec.rb
+++ b/spec/ruby/core/string/upto_spec.rb
@@ -74,6 +74,18 @@ describe "String#upto" do
     a.should == ["a", "b", "c"]
   end
 
+  it "works with non-ASCII ranges" do
+    a = []
+    'Σ'.upto('Ω') { |s| a << s }
+    a.should == ["Σ", "Τ", "Υ", "Φ", "Χ", "Ψ", "Ω"]
+  end
+
+  it "raises Encoding::CompatibilityError when incompatible characters are given" do
+    char1 = 'a'.dup.force_encoding("EUC-JP")
+    char2 = 'b'.dup.force_encoding("ISO-2022-JP")
+    -> { char1.upto(char2) {} }.should raise_error(Encoding::CompatibilityError, "incompatible character encodings: EUC-JP and ISO-2022-JP")
+  end
+
   describe "on sequence of numbers" do
     it "calls the block as Integer#upto"  do
       "8".upto("11").to_a.should == 8.upto(11).map(&:to_s)
diff --git a/spec/ruby/core/string/valid_encoding/utf_8_spec.rb b/spec/ruby/core/string/valid_encoding/utf_8_spec.rb
new file mode 100644
index 0000000000..a14c3af830
--- /dev/null
+++ b/spec/ruby/core/string/valid_encoding/utf_8_spec.rb
@@ -0,0 +1,214 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../../spec_helper'
+
+describe "String#valid_encoding? and UTF-8" do
+  def utf8(bytes)
+    bytes.pack("C*").force_encoding("UTF-8")
+  end
+
+  describe "1-byte character" do
+    it "is valid if is in format 0xxxxxxx" do
+      utf8([0b00000000]).valid_encoding?.should == true
+      utf8([0b01111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if is not in format 0xxxxxxx" do
+      utf8([0b10000000]).valid_encoding?.should == false
+      utf8([0b11111111]).valid_encoding?.should == false
+    end
+  end
+
+  describe "2-bytes character" do
+    it "is valid if in format [110xxxxx 10xxxxx]" do
+      utf8([0b11000010, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11000010, 0b10111111]).valid_encoding?.should == true
+
+      utf8([0b11011111, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11011111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 110xxxxx" do
+      utf8([0b00000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10100010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11100010, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11000010, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11000010, 0b11000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxxxx10 xx000000] (codepoints < U+007F, that are encoded with the 1-byte format)" do
+      utf8([0b11000000, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11000001, 0b10111111]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11000010, 0b10000000]
+      utf8(bytes[1..1]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11000010, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+
+  describe "3-bytes character" do
+    it "is valid if in format [1110xxxx 10xxxxxx 10xxxxxx]" do
+      utf8([0b11100000, 0b10100000, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11100000, 0b10100000, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11100000, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11101111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 1110xxxx" do
+      utf8([0b00000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b00110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10100000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11000000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11010000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10100000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11100000, 0b00100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b01100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b11100000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the third byte is not in format 10xxxxxx" do
+      utf8([0b11100000, 0b10100000, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10100000, 0b01000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxx0000 xx100000 xx000000] (codepoints < U+07FF that are encoded with the 2-byte format)" do
+      utf8([0b11100000, 0b10010000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10001000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000100, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000010, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000001, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11100000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if in range [xxxx1101 xx100000 xx000000] - [xxxx1101 xx111111 xx111111] (codepoints U+D800 - U+DFFF)" do
+      utf8([0b11101101, 0b10100000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11101101, 0b10100000, 0b10000001]).valid_encoding?.should == false
+      utf8([0b11101101, 0b10111111, 0b10111111]).valid_encoding?.should == false
+
+      utf8([0b11101101, 0b10011111, 0b10111111]).valid_encoding?.should == true # lower boundary - 1
+      utf8([0b11101110, 0b10000000, 0b10000000]).valid_encoding?.should == true # upper boundary + 1
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8(bytes[2..3]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8([bytes[0], bytes[2]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second and the third bytes are missing" do
+      bytes = [0b11100000, 0b10100000, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+
+  describe "4-bytes character" do
+    it "is valid if in format [11110xxx 10xxxxxx 10xxxxxx 10xxxxxx]" do
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10010000, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110000, 0b10111111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+      utf8([0b11110100, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == true
+    end
+
+    it "is not valid if the first byte is not in format 11110xxx" do
+      utf8([0b11100000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11010000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b10110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b01110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b00010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b01010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b11010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the third byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b10010000, 0b00000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b01000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10010000, 0b11000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the forth byte is not in format 10xxxxxx" do
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b00000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b01000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == true # correct bytes
+      utf8([0b11110000, 0b10010000, 0b10000000, 0b11000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is smaller than [xxxxx000 xx001000 xx000000 xx000000] (codepoint < U+10000)" do
+      utf8([0b11110000, 0b10000111, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000110, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000101, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000100, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000011, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000010, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000001, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110000, 0b10000000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+    end
+
+    it "is not valid if is greater than [xxxxx100 xx001111 xx111111 xx111111] (codepoint > U+10FFFF)" do
+      utf8([0b11110100, 0b10010000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110100, 0b10100000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+      utf8([0b11110100, 0b10110000, 0b10000000, 0b10000000]).valid_encoding?.should == false
+
+      utf8([0b11110101, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11110110, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+      utf8([0b11110111, 0b10001111, 0b10111111, 0b10111111]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the first byte is missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8(bytes[1..3]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second byte is missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8([bytes[0], bytes[2], bytes[3]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second and the third bytes are missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8([bytes[0], bytes[3]]).valid_encoding?.should == false
+    end
+
+    it "is not valid if the second, the third and the fourth bytes are missing" do
+      bytes = [0b11110000, 0b10010000, 0b10000000, 0b10000000]
+      utf8(bytes[0..0]).valid_encoding?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/string/valid_encoding_spec.rb b/spec/ruby/core/string/valid_encoding_spec.rb
index 09916df079..375035cd94 100644
--- a/spec/ruby/core/string/valid_encoding_spec.rb
+++ b/spec/ruby/core/string/valid_encoding_spec.rb
@@ -7,13 +7,13 @@ describe "String#valid_encoding?" do
   end
 
   it "returns true if self is valid in the current encoding and other encodings" do
-    str = "\x77"
+    str = +"\x77"
     str.force_encoding('utf-8').valid_encoding?.should be_true
     str.force_encoding('binary').valid_encoding?.should be_true
   end
 
   it "returns true for all encodings self is valid in" do
-    str = "\u{6754}"
+    str = +"\xE6\x9D\x94"
     str.force_encoding('BINARY').valid_encoding?.should be_true
     str.force_encoding('UTF-8').valid_encoding?.should be_true
     str.force_encoding('US-ASCII').valid_encoding?.should be_false
@@ -43,10 +43,10 @@ describe "String#valid_encoding?" do
     str.force_encoding('KOI8-R').valid_encoding?.should be_true
     str.force_encoding('KOI8-U').valid_encoding?.should be_true
     str.force_encoding('Shift_JIS').valid_encoding?.should be_false
-    str.force_encoding('UTF-16BE').valid_encoding?.should be_false
-    str.force_encoding('UTF-16LE').valid_encoding?.should be_false
-    str.force_encoding('UTF-32BE').valid_encoding?.should be_false
-    str.force_encoding('UTF-32LE').valid_encoding?.should be_false
+    "\xD8\x00".dup.force_encoding('UTF-16BE').valid_encoding?.should be_false
+    "\x00\xD8".dup.force_encoding('UTF-16LE').valid_encoding?.should be_false
+    "\x04\x03\x02\x01".dup.force_encoding('UTF-32BE').valid_encoding?.should be_false
+    "\x01\x02\x03\x04".dup.force_encoding('UTF-32LE').valid_encoding?.should be_false
     str.force_encoding('Windows-1251').valid_encoding?.should be_true
     str.force_encoding('IBM437').valid_encoding?.should be_true
     str.force_encoding('IBM737').valid_encoding?.should be_true
@@ -100,19 +100,25 @@ describe "String#valid_encoding?" do
     str.force_encoding('UTF8-MAC').valid_encoding?.should be_true
   end
 
+  it "returns true for IBM720 encoding self is valid in" do
+    str = +"\xE6\x9D\x94"
+    str.force_encoding('IBM720').valid_encoding?.should be_true
+    str.force_encoding('CP720').valid_encoding?.should be_true
+  end
+
   it "returns false if self is valid in one encoding, but invalid in the one it's tagged with" do
-    str = "\u{8765}"
+    str = +"\u{8765}"
     str.valid_encoding?.should be_true
-    str = str.force_encoding('ascii')
+    str.force_encoding('ascii')
     str.valid_encoding?.should be_false
   end
 
   it "returns false if self contains a character invalid in the associated encoding" do
-    "abc#{[0x80].pack('C')}".force_encoding('ascii').valid_encoding?.should be_false
+    "abc#{[0x80].pack('C')}".dup.force_encoding('ascii').valid_encoding?.should be_false
   end
 
   it "returns false if a valid String had an invalid character appended to it" do
-    str = "a"
+    str = +"a"
     str.valid_encoding?.should be_true
     str << [0xDD].pack('C').force_encoding('utf-8')
     str.valid_encoding?.should be_false
diff --git a/spec/ruby/core/struct/clone_spec.rb b/spec/ruby/core/struct/clone_spec.rb
new file mode 100644
index 0000000000..40c4d52d57
--- /dev/null
+++ b/spec/ruby/core/struct/clone_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative 'shared/dup'
+
+describe "Struct-based class#clone" do
+  it_behaves_like :struct_dup, :clone
+end
diff --git a/spec/ruby/core/struct/constants_spec.rb b/spec/ruby/core/struct/constants_spec.rb
new file mode 100644
index 0000000000..7e8af1a211
--- /dev/null
+++ b/spec/ruby/core/struct/constants_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "Struct::Group" do
+  it "is no longer defined" do
+    Struct.should_not.const_defined?(:Group)
+  end
+end
+
+describe "Struct::Passwd" do
+  it "is no longer defined" do
+    Struct.should_not.const_defined?(:Passwd)
+  end
+end
diff --git a/spec/ruby/core/struct/deconstruct_keys_spec.rb b/spec/ruby/core/struct/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..e16b50f930
--- /dev/null
+++ b/spec/ruby/core/struct/deconstruct_keys_spec.rb
@@ -0,0 +1,130 @@
+require_relative '../../spec_helper'
+
+describe "Struct#deconstruct_keys" do
+  it "returns a hash of attributes" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys([:x, :y]).should == {x: 1, y: 2}
+  end
+
+  it "requires one argument" do
+    struct = Struct.new(:x)
+    obj = struct.new(1)
+
+    -> {
+      obj.deconstruct_keys
+    }.should raise_error(ArgumentError, /wrong number of arguments \(given 0, expected 1\)/)
+  end
+
+  it "returns only specified keys" do
+    struct = Struct.new(:x, :y, :z)
+    s = struct.new(1, 2, 3)
+
+    s.deconstruct_keys([:x, :y]).should == {x: 1, y: 2}
+    s.deconstruct_keys([:x]    ).should == {x: 1}
+    s.deconstruct_keys([]      ).should == {}
+  end
+
+  it "accepts string attribute names" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys(['x', 'y']).should == {'x' => 1, 'y' => 2}
+  end
+
+  it "accepts argument position number as well but returns them as keys" do
+    struct = Struct.new(:x, :y, :z)
+    s = struct.new(10, 20, 30)
+
+    s.deconstruct_keys([0, 1, 2]).should == {0 => 10, 1 => 20, 2 => 30}
+    s.deconstruct_keys([0, 1]   ).should == {0 => 10, 1 => 20}
+    s.deconstruct_keys([0]      ).should == {0 => 10}
+    s.deconstruct_keys([-1]     ).should == {-1 => 30}
+  end
+
+  it "ignores incorrect position numbers" do
+    struct = Struct.new(:x, :y, :z)
+    s = struct.new(10, 20, 30)
+
+    s.deconstruct_keys([0, 3]).should == {0 => 10}
+  end
+
+  it "support mixing attribute names and argument position numbers" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys([0, :x]).should == {0 => 1, :x => 1}
+  end
+
+  it "returns an empty hash when there are more keys than attributes" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys([:x, :y, :a]).should == {}
+  end
+
+  it "returns at first not existing attribute name" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys([:a, :x]).should == {}
+    s.deconstruct_keys([:x, :a]).should == {x: 1}
+  end
+
+  it "returns at first not existing argument position number" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct_keys([3, 0]).should == {}
+    s.deconstruct_keys([0, 3]).should == {0 => 1}
+  end
+
+  it "accepts nil argument and return all the attributes" do
+    struct = Struct.new(:x, :y)
+    obj = struct.new(1, 2)
+
+    obj.deconstruct_keys(nil).should == {x: 1, y: 2}
+  end
+
+  it "tries to convert a key with #to_int if index is not a String nor a Symbol, but responds to #to_int" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    key = mock("to_int")
+    key.should_receive(:to_int).and_return(1)
+
+    s.deconstruct_keys([key]).should == { key => 2 }
+  end
+
+  it "raises a TypeError if the conversion with #to_int does not return an Integer" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    key = mock("to_int")
+    key.should_receive(:to_int).and_return("not an Integer")
+
+    -> {
+      s.deconstruct_keys([key])
+    }.should raise_error(TypeError, /can't convert MockObject to Integer/)
+  end
+
+  it "raises TypeError if index is not a String, a Symbol and not convertible to Integer" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    -> {
+      s.deconstruct_keys([0, []])
+    }.should raise_error(TypeError, "no implicit conversion of Array into Integer")
+  end
+
+  it "raise TypeError if passed anything except nil or array" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    -> { s.deconstruct_keys('x') }.should raise_error(TypeError, /expected Array or nil/)
+    -> { s.deconstruct_keys(1)   }.should raise_error(TypeError, /expected Array or nil/)
+    -> { s.deconstruct_keys(:x)  }.should raise_error(TypeError, /expected Array or nil/)
+    -> { s.deconstruct_keys({})  }.should raise_error(TypeError, /expected Array or nil/)
+  end
+end
diff --git a/spec/ruby/core/struct/deconstruct_spec.rb b/spec/ruby/core/struct/deconstruct_spec.rb
new file mode 100644
index 0000000000..32d4f6bac4
--- /dev/null
+++ b/spec/ruby/core/struct/deconstruct_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+
+describe "Struct#deconstruct" do
+  it "returns an array of attribute values" do
+    struct = Struct.new(:x, :y)
+    s = struct.new(1, 2)
+
+    s.deconstruct.should == [1, 2]
+  end
+end
diff --git a/spec/ruby/core/struct/dig_spec.rb b/spec/ruby/core/struct/dig_spec.rb
index 4e39e5a4ef..93a52dbbe1 100644
--- a/spec/ruby/core/struct/dig_spec.rb
+++ b/spec/ruby/core/struct/dig_spec.rb
@@ -10,6 +10,16 @@ describe "Struct#dig" do
     @instance.dig(:a, :a).should == { b: [1, 2, 3] }
   end
 
+  it "accepts String keys" do
+    @instance.dig('a', 'a').should == { b: [1, 2, 3] }
+  end
+
+  it "returns the value by the index" do
+    instance = Struct.new(:a, :b).new(:one, :two)
+    instance.dig(0).should == :one
+    instance.dig(1).should == :two
+  end
+
   it "returns the nested value specified if the sequence includes an index" do
     @instance.dig(:a, :a, :b, 0).should == 1
   end
diff --git a/spec/ruby/core/struct/dup_spec.rb b/spec/ruby/core/struct/dup_spec.rb
index cb54b7ceee..8b50c39014 100644
--- a/spec/ruby/core/struct/dup_spec.rb
+++ b/spec/ruby/core/struct/dup_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative 'shared/dup'
 
 describe "Struct-based class#dup" do
 
+  it_behaves_like :struct_dup, :dup
+
   # From https://github.com/jruby/jruby/issues/3686
   it "retains an included module in the ancestor chain for the struct's singleton class" do
     klass = Struct.new(:foo)
diff --git a/spec/ruby/core/struct/element_set_spec.rb b/spec/ruby/core/struct/element_set_spec.rb
index 6ba7b081a9..0a0e34a5ee 100644
--- a/spec/ruby/core/struct/element_set_spec.rb
+++ b/spec/ruby/core/struct/element_set_spec.rb
@@ -26,4 +26,11 @@ describe "Struct#[]=" do
     -> { car[-4] = true         }.should raise_error(IndexError)
     -> { car[Object.new] = true }.should raise_error(TypeError)
   end
+
+  it "raises a FrozenError on a frozen struct" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.freeze
+
+    -> { car[:model] = 'Escape' }.should raise_error(FrozenError)
+  end
 end
diff --git a/spec/ruby/core/struct/filter_spec.rb b/spec/ruby/core/struct/filter_spec.rb
index 1105ed064a..0ccd8ad6b2 100644
--- a/spec/ruby/core/struct/filter_spec.rb
+++ b/spec/ruby/core/struct/filter_spec.rb
@@ -3,10 +3,8 @@ require_relative 'shared/select'
 require_relative 'shared/accessor'
 require_relative '../enumerable/shared/enumeratorized'
 
-ruby_version_is "2.6" do
-  describe "Struct#filter" do
-    it_behaves_like :struct_select, :filter
-    it_behaves_like :struct_accessor, :filter
-    it_behaves_like :enumeratorized_with_origin_size, :filter, Struct.new(:foo).new
-  end
+describe "Struct#filter" do
+  it_behaves_like :struct_select, :filter
+  it_behaves_like :struct_accessor, :filter
+  it_behaves_like :enumeratorized_with_origin_size, :filter, Struct.new(:foo).new
 end
diff --git a/spec/ruby/core/struct/fixtures/classes.rb b/spec/ruby/core/struct/fixtures/classes.rb
index 6d620f9060..7b80b814ef 100644
--- a/spec/ruby/core/struct/fixtures/classes.rb
+++ b/spec/ruby/core/struct/fixtures/classes.rb
@@ -13,6 +13,12 @@ module StructClasses
     end
   end
 
+  class StructWithOverriddenName < Struct.new(:a)
+    def self.name
+      "A"
+    end
+  end
+
   class SubclassX < Struct
   end
 
@@ -23,4 +29,6 @@ module StructClasses
       super
     end
   end
+
+  class StructSubclass < Struct; end
 end
diff --git a/spec/ruby/core/struct/hash_spec.rb b/spec/ruby/core/struct/hash_spec.rb
index 71e8ccbd3a..53361eb7a9 100644
--- a/spec/ruby/core/struct/hash_spec.rb
+++ b/spec/ruby/core/struct/hash_spec.rb
@@ -4,11 +4,11 @@ require_relative 'shared/accessor'
 
 describe "Struct#hash" do
 
-  it "returns the same fixnum for structs with the same content" do
+  it "returns the same integer for structs with the same content" do
     [StructClasses::Ruby.new("1.8.6", "PPC"),
      StructClasses::Car.new("Hugo", "Foo", "1972")].each do |stc|
       stc.hash.should == stc.dup.hash
-      stc.hash.should be_kind_of(Fixnum)
+      stc.hash.should be_kind_of(Integer)
     end
   end
 
@@ -19,6 +19,20 @@ describe "Struct#hash" do
     car.hash.should == similar_car.hash
   end
 
+  it "returns different hashes for structs with different values" do
+    s1 = StructClasses::Ruby.new('2.7.0', 'linux')
+    s2 = StructClasses::Ruby.new('2.7.0', 'macos')
+    s1.hash.should_not == s2.hash
+  end
+
+  it "returns different hashes for structs with different values when using keyword_init: true" do
+    key = :"1 non symbol member"
+    struct_class = Struct.new(key, keyword_init: true)
+    t1 = struct_class.new(key => 1)
+    t2 = struct_class.new(key => 2)
+    t1.hash.should_not == t2.hash
+  end
+
   it "allows for overriding methods in an included module" do
     mod = Module.new do
       def hash
@@ -42,5 +56,9 @@ describe "Struct#hash" do
     # See the Struct#eql? specs
   end
 
+  it "returns different hashes for different struct classes" do
+    Struct.new(:x).new(1).hash.should != Struct.new(:y).new(1).hash
+  end
+
   it_behaves_like :struct_accessor, :hash
 end
diff --git a/spec/ruby/core/struct/initialize_spec.rb b/spec/ruby/core/struct/initialize_spec.rb
index e82289071a..06055594d5 100644
--- a/spec/ruby/core/struct/initialize_spec.rb
+++ b/spec/ruby/core/struct/initialize_spec.rb
@@ -40,4 +40,12 @@ describe "Struct#initialize" do
   it "can be overridden" do
     StructClasses::SubclassX.new(:y).new.key.should == :value
   end
+
+  it "can be initialized with keyword arguments" do
+    positional_args = StructClasses::Ruby.new("3.2", "OS")
+    keyword_args = StructClasses::Ruby.new(version: "3.2", platform: "OS")
+
+    positional_args.version.should == keyword_args.version
+    positional_args.platform.should == keyword_args.platform
+  end
 end
diff --git a/spec/ruby/core/struct/inspect_spec.rb b/spec/ruby/core/struct/inspect_spec.rb
index 83e13597ba..657b06abc1 100644
--- a/spec/ruby/core/struct/inspect_spec.rb
+++ b/spec/ruby/core/struct/inspect_spec.rb
@@ -3,10 +3,5 @@ require_relative 'fixtures/classes'
 require_relative 'shared/inspect'
 
 describe "Struct#inspect" do
-  it "returns a string representation showing members and values" do
-    car = StructClasses::Car.new('Ford', 'Ranger')
-    car.inspect.should == '#<struct StructClasses::Car make="Ford", model="Ranger", year=nil>'
-  end
-
   it_behaves_like :struct_inspect, :inspect
 end
diff --git a/spec/ruby/core/struct/instance_variable_get_spec.rb b/spec/ruby/core/struct/instance_variable_get_spec.rb
new file mode 100644
index 0000000000..e4a3ea87dc
--- /dev/null
+++ b/spec/ruby/core/struct/instance_variable_get_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Struct#instance_variable_get" do
+  it "returns nil for attributes" do
+    car = StructClasses::Car.new("Hugo", "Foo", "1972")
+    car.instance_variable_get(:@make).should be_nil
+  end
+
+  it "returns a user value for variables with the same name as attributes" do
+    car = StructClasses::Car.new("Hugo", "Foo", "1972")
+    car.instance_variable_set :@make, "explicit"
+    car.instance_variable_get(:@make).should == "explicit"
+    car.make.should == "Hugo"
+  end
+end
diff --git a/spec/ruby/core/struct/keyword_init_spec.rb b/spec/ruby/core/struct/keyword_init_spec.rb
new file mode 100644
index 0000000000..536b82041a
--- /dev/null
+++ b/spec/ruby/core/struct/keyword_init_spec.rb
@@ -0,0 +1,45 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+# See https://bugs.ruby-lang.org/issues/18008
+describe "StructClass#keyword_init?" do
+  it "returns true for a struct that accepts keyword arguments to initialize" do
+    struct = Struct.new(:arg, keyword_init: true)
+    struct.keyword_init?.should be_true
+  end
+
+  it "returns false for a struct that does not accept keyword arguments to initialize" do
+    struct = Struct.new(:arg, keyword_init: false)
+    struct.keyword_init?.should be_false
+  end
+
+  it "returns nil for a struct that did not explicitly specify keyword_init" do
+    struct = Struct.new(:arg)
+    struct.keyword_init?.should be_nil
+  end
+
+  it "returns nil for a struct that does specify keyword_init to be nil" do
+    struct = Struct.new(:arg, keyword_init: nil)
+    struct.keyword_init?.should be_nil
+  end
+
+  it "returns true for any truthy value, not just for true" do
+    struct = Struct.new(:arg, keyword_init: 1)
+    struct.keyword_init?.should be_true
+
+    struct = Struct.new(:arg, keyword_init: "")
+    struct.keyword_init?.should be_true
+
+    struct = Struct.new(:arg, keyword_init: [])
+    struct.keyword_init?.should be_true
+
+    struct = Struct.new(:arg, keyword_init: {})
+    struct.keyword_init?.should be_true
+  end
+
+  context "class inheriting Struct" do
+    it "isn't available in a subclass" do
+      StructClasses::StructSubclass.should_not.respond_to?(:keyword_init?)
+    end
+  end
+end
diff --git a/spec/ruby/core/struct/members_spec.rb b/spec/ruby/core/struct/members_spec.rb
index 1f2ff950d9..1ff7b9387a 100644
--- a/spec/ruby/core/struct/members_spec.rb
+++ b/spec/ruby/core/struct/members_spec.rb
@@ -11,3 +11,15 @@ describe "Struct#members" do
 
   it_behaves_like :struct_accessor, :members
 end
+
+describe "StructClass#members" do
+  it "returns an array of attribute names" do
+    StructClasses::Car.members.should == [:make, :model, :year]
+  end
+
+  context "class inheriting Struct" do
+    it "isn't available in a subclass" do
+      StructClasses::StructSubclass.should_not.respond_to?(:members)
+    end
+  end
+end
diff --git a/spec/ruby/core/struct/new_spec.rb b/spec/ruby/core/struct/new_spec.rb
index f888106950..1d35de7b87 100644
--- a/spec/ruby/core/struct/new_spec.rb
+++ b/spec/ruby/core/struct/new_spec.rb
@@ -6,6 +6,8 @@ describe "Struct.new" do
     struct = Struct.new('Animal', :name, :legs, :eyeballs)
     struct.should == Struct::Animal
     struct.name.should == "Struct::Animal"
+  ensure
+    Struct.send(:remove_const, :Animal)
   end
 
   it "overwrites previously defined constants with string as first argument" do
@@ -15,10 +17,12 @@ describe "Struct.new" do
     second = nil
     -> {
       second = Struct.new('Person', :hair, :sex)
-    }.should complain(/redefining constant/)
+    }.should complain(/constant/)
     second.should == Struct::Person
 
     first.members.should_not == second.members
+  ensure
+    Struct.send(:remove_const, :Person)
   end
 
   it "calls to_str on its first argument (constant name)" do
@@ -27,6 +31,8 @@ describe "Struct.new" do
     struct = Struct.new(obj)
     struct.should == Struct::Foo
     struct.name.should == "Struct::Foo"
+  ensure
+    Struct.send(:remove_const, :Foo)
   end
 
   it "creates a new anonymous class with nil first argument" do
@@ -47,6 +53,11 @@ describe "Struct.new" do
     Struct.const_defined?("Animal2").should be_false
   end
 
+  it "allows non-ASCII member name" do
+    name = "r\xe9sum\xe9".dup.force_encoding(Encoding::ISO_8859_1).to_sym
+    struct = Struct.new(name)
+    struct.new("foo").send(name).should == "foo"
+  end
 
   it "fails with invalid constant name as first argument" do
     -> { Struct.new('animal', :name, :legs, :eyeballs) }.should raise_error(NameError)
@@ -62,18 +73,28 @@ describe "Struct.new" do
     -> { Struct.new(:animal, ['chris', 'evan'])    }.should raise_error(TypeError)
   end
 
-  ruby_version_is ""..."2.5" do
-    it "raises a TypeError if an argument is a Hash" do
-      -> { Struct.new(:animal, { name: 'chris' }) }.should raise_error(TypeError)
+  it "raises a TypeError if passed a Hash with an unknown key" do
+    -> { Struct.new(:animal, { name: 'chris' }) }.should raise_error(TypeError)
+  end
+
+  ruby_version_is ""..."3.3" do
+    it "raises ArgumentError if not provided any arguments" do
+      -> { Struct.new }.should raise_error(ArgumentError)
     end
   end
 
-  ruby_version_is "2.5" do
-    it "raises a ArgumentError if passed a Hash with an unknown key" do
-      -> { Struct.new(:animal, { name: 'chris' }) }.should raise_error(ArgumentError)
+  ruby_version_is "3.3" do
+    it "works when not provided any arguments" do
+      c = Struct.new
+      c.should be_kind_of(Class)
+      c.superclass.should == Struct
     end
   end
 
+  it "raises ArgumentError when there is a duplicate member" do
+    -> { Struct.new(:foo, :foo) }.should raise_error(ArgumentError, "duplicate member: foo")
+  end
+
   it "raises a TypeError if object is not a Symbol" do
     obj = mock(':ruby')
     def obj.to_sym() :ruby end
@@ -111,6 +132,8 @@ describe "Struct.new" do
     it "creates a constant in subclass' namespace" do
       struct = StructClasses::Apple.new('Computer', :size)
       struct.should == StructClasses::Apple::Computer
+    ensure
+      StructClasses::Apple.send(:remove_const, :Computer)
     end
 
     it "creates an instance" do
@@ -131,64 +154,110 @@ describe "Struct.new" do
       -> { StructClasses::Ruby.new('2.0', 'i686', true) }.should raise_error(ArgumentError)
     end
 
-    it "passes a hash as a normal argument" do
+    it "accepts keyword arguments to initialize" do
       type = Struct.new(:args)
 
-      obj = type.new(keyword: :arg)
-      obj2 = type.new(*[{keyword: :arg}])
+      obj = type.new(args: 42)
+      obj2 = type.new(42)
 
       obj.should == obj2
-      obj.args.should == {keyword: :arg}
-      obj2.args.should == {keyword: :arg}
+      obj.args.should == 42
+      obj2.args.should == 42
     end
-  end
 
-  ruby_version_is "2.5" do
-    context "keyword_init: true option" do
-      before :all do
-        @struct_with_kwa = Struct.new(:name, :legs, keyword_init: true)
-        @struct_without_kwa = Struct.new(:name, :legs, keyword_init: false)
+    context "given positional and keyword arguments" do
+      it "treats keyword arguments as a positional parameter" do
+        type = Struct.new(:a, :b)
+        s = type.new("a", b: "b")
+        s.a.should == "a"
+        s.b.should == {b: "b"}
+
+        type = Struct.new(:a, :b, :c)
+        s = type.new("a", b: "b", c: "c")
+        s.a.should == "a"
+        s.b.should == {b: "b", c: "c"}
+        s.c.should == nil
       end
 
-      it "creates a class that accepts keyword arguments to initialize" do
-        obj = @struct_with_kwa.new(name: "elefant", legs: 4)
-        obj.name.should == "elefant"
-        obj.legs.should == 4
+      it "ignores empty keyword arguments" do
+        type = Struct.new(:a, :b)
+        h = {}
+        s = type.new("a", **h)
+
+        s.a.should == "a"
+        s.b.should == nil
       end
 
-      describe "new class instantiation" do
-        it "accepts arguments as hash as well" do
-          obj = @struct_with_kwa.new({name: "elefant", legs: 4})
-          obj.name.should == "elefant"
-          obj.legs.should == 4
-        end
+      it "raises ArgumentError when all struct attribute values are specified" do
+        type = Struct.new(:a, :b)
+        -> { type.new("a", "b", c: "c") }.should raise_error(ArgumentError, "struct size differs")
+      end
+    end
+  end
 
-        it "raises ArgumentError when passed not declared keyword argument" do
-          -> {
-            @struct_with_kwa.new(name: "elefant", legs: 4, foo: "bar")
-          }.should raise_error(ArgumentError, /unknown keywords: foo/)
-        end
+  context "keyword_init: true option" do
+    before :all do
+      @struct_with_kwa = Struct.new(:name, :legs, keyword_init: true)
+    end
 
-        it "raises ArgumentError when passed a list of arguments" do
-          -> {
-            @struct_with_kwa.new("elefant", 4)
-          }.should raise_error(ArgumentError, /wrong number of arguments/)
-        end
+    it "creates a class that accepts keyword arguments to initialize" do
+      obj = @struct_with_kwa.new(name: "elefant", legs: 4)
+      obj.name.should == "elefant"
+      obj.legs.should == 4
+    end
 
-        it "raises ArgumentError when passed a single non-hash argument" do
-          -> {
-            @struct_with_kwa.new("elefant")
-          }.should raise_error(ArgumentError, /wrong number of arguments/)
-        end
-      end
+    it "raises when there is a duplicate member" do
+      -> { Struct.new(:foo, :foo, keyword_init: true) }.should raise_error(ArgumentError, "duplicate member: foo")
     end
 
-    context "keyword_init: false option" do
-      it "behaves like it does without :keyword_init option" do
-        obj = @struct_without_kwa.new("elefant", 4)
+    describe "new class instantiation" do
+      it "accepts arguments as hash as well" do
+        obj = @struct_with_kwa.new({name: "elefant", legs: 4})
         obj.name.should == "elefant"
         obj.legs.should == 4
       end
+
+      it "allows missing arguments" do
+        obj = @struct_with_kwa.new(name: "elefant")
+        obj.name.should == "elefant"
+        obj.legs.should be_nil
+      end
+
+      it "allows no arguments" do
+        obj = @struct_with_kwa.new
+        obj.name.should be_nil
+        obj.legs.should be_nil
+      end
+
+      it "raises ArgumentError when passed not declared keyword argument" do
+        -> {
+          @struct_with_kwa.new(name: "elefant", legs: 4, foo: "bar")
+        }.should raise_error(ArgumentError, /unknown keywords: foo/)
+      end
+
+      it "raises ArgumentError when passed a list of arguments" do
+        -> {
+          @struct_with_kwa.new("elefant", 4)
+        }.should raise_error(ArgumentError, /wrong number of arguments/)
+      end
+
+      it "raises ArgumentError when passed a single non-hash argument" do
+        -> {
+          @struct_with_kwa.new("elefant")
+        }.should raise_error(ArgumentError, /wrong number of arguments/)
+      end
+    end
+  end
+
+  context "keyword_init: false option" do
+    before :all do
+      @struct_without_kwa = Struct.new(:name, :legs, keyword_init: false)
+    end
+
+    it "behaves like it does without :keyword_init option" do
+      obj = @struct_without_kwa.new("elefant", 4)
+      obj.name.should == "elefant"
+      obj.legs.should == 4
     end
   end
 end
diff --git a/spec/ruby/core/struct/shared/dup.rb b/spec/ruby/core/struct/shared/dup.rb
new file mode 100644
index 0000000000..994f3f443e
--- /dev/null
+++ b/spec/ruby/core/struct/shared/dup.rb
@@ -0,0 +1,9 @@
+describe :struct_dup, shared: true do
+  it "duplicates members" do
+    klass = Struct.new(:foo, :bar)
+    instance = klass.new(14, 2)
+    duped = instance.send(@method)
+    duped.foo.should == 14
+    duped.bar.should == 2
+  end
+end
diff --git a/spec/ruby/core/struct/shared/inspect.rb b/spec/ruby/core/struct/shared/inspect.rb
index 90594a5452..1a0fb6a6b2 100644
--- a/spec/ruby/core/struct/shared/inspect.rb
+++ b/spec/ruby/core/struct/shared/inspect.rb
@@ -1,5 +1,40 @@
 describe :struct_inspect, shared: true do
+  it "returns a string representation showing members and values" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.send(@method).should == '#<struct StructClasses::Car make="Ford", model="Ranger", year=nil>'
+  end
+
   it "returns a string representation without the class name for anonymous structs" do
     Struct.new(:a).new("").send(@method).should == '#<struct a="">'
   end
+
+  it "returns a string representation without the class name for structs nested in anonymous classes" do
+    c = Class.new
+    c.class_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    c::Foo.new("").send(@method).should == '#<struct a="">'
+  end
+
+  it "returns a string representation without the class name for structs nested in anonymous modules" do
+    m = Module.new
+    m.module_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    m::Foo.new("").send(@method).should == '#<struct a="">'
+  end
+
+  it "does not call #name method" do
+    struct = StructClasses::StructWithOverriddenName.new("")
+    struct.send(@method).should == '#<struct StructClasses::StructWithOverriddenName a="">'
+  end
+
+  it "does not call #name method when struct is anonymous" do
+    struct = Struct.new(:a)
+    def struct.name; "A"; end
+
+    struct.new("").send(@method).should == '#<struct a="">'
+  end
 end
diff --git a/spec/ruby/core/struct/struct_spec.rb b/spec/ruby/core/struct/struct_spec.rb
index 8817dc1a58..1b6a4488ce 100644
--- a/spec/ruby/core/struct/struct_spec.rb
+++ b/spec/ruby/core/struct/struct_spec.rb
@@ -33,6 +33,13 @@ describe "Struct anonymous class instance methods" do
     car['model'].should == 'F150'
     car[1].should == 'F150'
   end
+
+  it "writer methods raise a FrozenError on a frozen struct" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.freeze
+
+    -> { car.model = 'Escape' }.should raise_error(FrozenError)
+  end
 end
 
 describe "Struct subclasses" do
diff --git a/spec/ruby/core/struct/to_h_spec.rb b/spec/ruby/core/struct/to_h_spec.rb
index b5f4e40701..861ce3f49d 100644
--- a/spec/ruby/core/struct/to_h_spec.rb
+++ b/spec/ruby/core/struct/to_h_spec.rb
@@ -13,46 +13,56 @@ describe "Struct#to_h" do
     car.make.should == 'Ford'
   end
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      it "converts [key, value] pairs returned by the block to a hash" do
-        car = StructClasses::Car.new('Ford', 'Ranger')
-
-        h = car.to_h { |k, v| [k.to_s, "#{v}".downcase] }
-        h.should == { "make" => "ford", "model" => "ranger", "year" => "" }
-      end
-
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          StructClasses::Car.new.to_h { |k, v| [k.to_s, "#{v}".downcase, 1] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-
-        -> do
-          StructClasses::Car.new.to_h { |k, v| [k] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-      end
-
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          StructClasses::Car.new.to_h { |k, v| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String/)
-      end
-
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
-
-        StructClasses::Car.new.to_h { |k| x }.should == { :b => 'b' }
-      end
-
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
-
-        -> do
-          StructClasses::Car.new.to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject/)
-      end
+  context "with block" do
+    it "converts [key, value] pairs returned by the block to a hash" do
+      car = StructClasses::Car.new('Ford', 'Ranger')
+
+      h = car.to_h { |k, v| [k.to_s, "#{v}".downcase] }
+      h.should == { "make" => "ford", "model" => "ranger", "year" => "" }
+    end
+
+    it "passes to a block each pair's key and value as separate arguments" do
+      s = StructClasses::Ruby.new('3.2.4', 'macos')
+
+      ScratchPad.record []
+      s.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+      ScratchPad.recorded.sort.should == [[:platform, 'macos'], [:version, '3.2.4']]
+
+      ScratchPad.record []
+      s.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[:platform, 'macos'], [:version, '3.2.4']]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        StructClasses::Car.new.to_h { |k, v| [k.to_s, "#{v}".downcase, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+
+      -> do
+        StructClasses::Car.new.to_h { |k, v| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        StructClasses::Car.new.to_h { |k, v| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      StructClasses::Car.new.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        StructClasses::Car.new.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
     end
   end
 end
diff --git a/spec/ruby/core/struct/values_at_spec.rb b/spec/ruby/core/struct/values_at_spec.rb
index 7e517cdb4b..5e5a496600 100644
--- a/spec/ruby/core/struct/values_at_spec.rb
+++ b/spec/ruby/core/struct/values_at_spec.rb
@@ -1,16 +1,59 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
+# Should be synchronized with core/array/values_at_spec.rb
 describe "Struct#values_at" do
-  it "returns an array of values" do
+  before do
     clazz = Struct.new(:name, :director, :year)
-    movie = clazz.new('Sympathy for Mr. Vengence', 'Chan-wook Park', 2002)
-    movie.values_at(0, 1).should == ['Sympathy for Mr. Vengence', 'Chan-wook Park']
-    movie.values_at(0..2).should == ['Sympathy for Mr. Vengence', 'Chan-wook Park', 2002]
+    @movie = clazz.new('Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002)
+  end
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      @movie.values_at(0, 1).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park']
+    end
+
+    it "raises IndexError if any of integers is out of range" do
+      -> { @movie.values_at(3) }.should raise_error(IndexError, "offset 3 too large for struct(size:3)")
+      -> { @movie.values_at(-4) }.should raise_error(IndexError, "offset -4 too small for struct(size:3)")
+    end
+  end
+
+  context "when passed an integer Range" do
+    it "returns an array containing each value given by the elements of the range" do
+      @movie.values_at(0..2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002]
+    end
+
+    it "fills with nil values for range elements larger than the structure" do
+      @movie.values_at(0..3).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, nil]
+    end
+
+    it "raises RangeError if any element of the range is negative and out of range" do
+      -> { @movie.values_at(-4..3) }.should raise_error(RangeError, "-4..3 out of range")
+    end
+
+    it "supports endless Range" do
+      @movie.values_at(0..).should == ["Sympathy for Mr. Vengeance", "Chan-wook Park", 2002]
+    end
+
+    it "supports beginningless Range" do
+      @movie.values_at(..2).should == ["Sympathy for Mr. Vengeance", "Chan-wook Park", 2002]
+    end
+  end
+
+  it "supports multiple integer Ranges" do
+    @movie.values_at(0..2, 1..2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, 'Chan-wook Park', 2002]
+  end
+
+  it "supports mixing integer Ranges and Integers" do
+    @movie.values_at(0..2, 2).should == ['Sympathy for Mr. Vengeance', 'Chan-wook Park', 2002, 2002]
+  end
+
+  it "returns a new empty Array if no arguments given" do
+    @movie.values_at().should == []
   end
 
   it "fails when passed unsupported types" do
-    car = StructClasses::Car.new('Ford', 'Ranger')
-    -> { car.values_at('make') }.should raise_error(TypeError)
+    -> { @movie.values_at('make') }.should raise_error(TypeError, "no implicit conversion of String into Integer")
   end
 end
diff --git a/spec/ruby/core/symbol/all_symbols_spec.rb b/spec/ruby/core/symbol/all_symbols_spec.rb
index ef2b4f85e6..1e21809093 100644
--- a/spec/ruby/core/symbol/all_symbols_spec.rb
+++ b/spec/ruby/core/symbol/all_symbols_spec.rb
@@ -1,14 +1,19 @@
 require_relative '../../spec_helper'
 
 describe "Symbol.all_symbols" do
-  it "returns an array containing all the Symbols in the symbol table" do
+  it "returns an array of Symbols" do
     all_symbols = Symbol.all_symbols
     all_symbols.should be_an_instance_of(Array)
-    all_symbols.all? { |s| s.is_a?(Symbol) ? true : (p s; false) }.should == true
+    all_symbols.each { |s| s.should be_an_instance_of(Symbol) }
   end
 
-  it "returns an Array containing Symbols that have been created" do
+  it "includes symbols that are strongly referenced" do
     symbol = "symbol_specs_#{rand(5_000_000)}".to_sym
     Symbol.all_symbols.should include(symbol)
   end
+
+  it "includes symbols that are referenced in source code but not yet executed" do
+    Symbol.all_symbols.any? { |s| s.to_s == 'symbol_specs_referenced_in_source_code' }.should be_true
+    :symbol_specs_referenced_in_source_code
+  end
 end
diff --git a/spec/ruby/core/symbol/casecmp_spec.rb b/spec/ruby/core/symbol/casecmp_spec.rb
index b485101d63..662a29a284 100644
--- a/spec/ruby/core/symbol/casecmp_spec.rb
+++ b/spec/ruby/core/symbol/casecmp_spec.rb
@@ -56,6 +56,10 @@ describe "Symbol#casecmp with Symbol" do
     lower_a_tilde.casecmp(upper_a_tilde).should == 1
     lower_a_umlaut.casecmp(upper_a_umlaut).should == 1
   end
+
+  it "returns 0 for empty strings in different encodings" do
+    ''.to_sym.casecmp(''.encode("UTF-32LE").to_sym).should == 0
+  end
 end
 
 describe "Symbol#casecmp" do
@@ -63,7 +67,7 @@ describe "Symbol#casecmp" do
     :abc.casecmp("abc").should be_nil
   end
 
-  it "returns nil if other is a Fixnum" do
+  it "returns nil if other is an Integer" do
     :abc.casecmp(1).should be_nil
   end
 
@@ -141,4 +145,8 @@ describe 'Symbol#casecmp?' do
     upper_a_tilde.casecmp?(lower_a_tilde).should == nil
     lower_a_tilde.casecmp?(upper_a_tilde).should == nil
   end
+
+  it "returns true for empty symbols in different encodings" do
+    ''.to_sym.should.casecmp?(''.encode("UTF-32LE").to_sym)
+  end
 end
diff --git a/spec/ruby/core/symbol/comparison_spec.rb b/spec/ruby/core/symbol/comparison_spec.rb
index 173a7da625..613177be05 100644
--- a/spec/ruby/core/symbol/comparison_spec.rb
+++ b/spec/ruby/core/symbol/comparison_spec.rb
@@ -40,7 +40,7 @@ describe "Symbol#<=>" do
     (:abc <=> "abc").should be_nil
   end
 
-  it "returns nil if other is a Fixnum" do
+  it "returns nil if other is an Integer" do
     (:abc <=> 1).should be_nil
   end
 
diff --git a/spec/ruby/core/symbol/end_with_spec.rb b/spec/ruby/core/symbol/end_with_spec.rb
new file mode 100644
index 0000000000..4b9f5a4996
--- /dev/null
+++ b/spec/ruby/core/symbol/end_with_spec.rb
@@ -0,0 +1,8 @@
+# -*- encoding: utf-8 -*-
+
+require_relative '../../spec_helper'
+require_relative '../../shared/string/end_with'
+
+describe "Symbol#end_with?" do
+  it_behaves_like :end_with, :to_sym
+end
diff --git a/spec/ruby/core/symbol/inspect_spec.rb b/spec/ruby/core/symbol/inspect_spec.rb
index 58402ab261..df4566c48e 100644
--- a/spec/ruby/core/symbol/inspect_spec.rb
+++ b/spec/ruby/core/symbol/inspect_spec.rb
@@ -5,6 +5,8 @@ describe "Symbol#inspect" do
     fred:         ":fred",
     :fred?     => ":fred?",
     :fred!     => ":fred!",
+    :BAD!      => ":BAD!",
+    :_BAD!     => ":_BAD!",
     :$ruby     => ":$ruby",
     :@ruby     => ":@ruby",
     :@@ruby    => ":@@ruby",
@@ -64,9 +66,9 @@ describe "Symbol#inspect" do
     :~         => ":~",
     :|         => ":|",
 
-    :"!"       => [":\"!\"",  ":!" ],
-    :"!="      => [":\"!=\"", ":!="],
-    :"!~"      => [":\"!~\"", ":!~"],
+    :"!"       => ":!",
+    :"!="      => ":!=",
+    :"!~"      => ":!~",
     :"\$"      => ":\"$\"", # for justice!
     :"&&"      => ":\"&&\"",
     :"'"       => ":\"\'\"",
@@ -94,10 +96,15 @@ describe "Symbol#inspect" do
     :"foo "    => ":\"foo \"",
     :" foo"    => ":\" foo\"",
     :" "       => ":\" \"",
+
+    :"ê"       => [":ê", ":\"\\u00EA\""],
+    :"测"      => [":测", ":\"\\u6D4B\""],
+    :"🦊"      => [":🦊", ":\"\\u{1F98A}\""],
   }
 
+  expected_by_encoding = Encoding::default_external == Encoding::UTF_8 ? 0 : 1
   symbols.each do |input, expected|
-    expected = expected[1] if expected.is_a?(Array)
+    expected = expected[expected_by_encoding] if expected.is_a?(Array)
     it "returns self as a symbol literal for #{expected}" do
       input.inspect.should == expected
     end
diff --git a/spec/ruby/core/symbol/match_spec.rb b/spec/ruby/core/symbol/match_spec.rb
index d37155537b..41e058f977 100644
--- a/spec/ruby/core/symbol/match_spec.rb
+++ b/spec/ruby/core/symbol/match_spec.rb
@@ -34,6 +34,23 @@ describe "Symbol#match" do
     :a.match(/(.)/)[0].should == 'a'
     $1.should == "a"
   end
+
+  describe "when passed a block" do
+    it "yields the MatchData" do
+      :abc.match(/./) {|m| ScratchPad.record m }
+      ScratchPad.recorded.should be_kind_of(MatchData)
+    end
+
+    it "returns the block result" do
+      :abc.match(/./) { :result }.should == :result
+    end
+
+    it "does not yield if there is no match" do
+      ScratchPad.record []
+      :b.match(/a/) {|m| ScratchPad << m }
+      ScratchPad.recorded.should == []
+    end
+  end
 end
 
 describe "Symbol#match?" do
diff --git a/spec/ruby/core/symbol/name_spec.rb b/spec/ruby/core/symbol/name_spec.rb
new file mode 100644
index 0000000000..f9b631266c
--- /dev/null
+++ b/spec/ruby/core/symbol/name_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+
+describe "Symbol#name" do
+  it "returns string" do
+    :ruby.name.should == "ruby"
+    :ルビー.name.should == "ルビー"
+  end
+
+  it "returns same string instance" do
+    :"ruby_3".name.should.equal?(:ruby_3.name)
+    :"ruby_#{1+2}".name.should.equal?(:ruby_3.name)
+  end
+
+  it "returns frozen string" do
+    :symbol.name.should.frozen?
+  end
+end
diff --git a/spec/ruby/core/symbol/shared/id2name.rb b/spec/ruby/core/symbol/shared/id2name.rb
index 47f97bd332..00a9c7d7dc 100644
--- a/spec/ruby/core/symbol/shared/id2name.rb
+++ b/spec/ruby/core/symbol/shared/id2name.rb
@@ -6,4 +6,25 @@ describe :symbol_id2name, shared: true do
     :@ruby.send(@method).should == "@ruby"
     :@@ruby.send(@method).should == "@@ruby"
   end
+
+  it "returns a String in the same encoding as self" do
+    string = "ruby".encode("US-ASCII")
+    symbol = string.to_sym
+
+    symbol.send(@method).encoding.should == Encoding::US_ASCII
+  end
+
+  ruby_version_is "3.4" do
+    it "warns about mutating returned string" do
+      -> { :bad!.send(@method).upcase! }.should complain(/warning: string returned by :bad!.to_s will be frozen in the future/)
+    end
+
+    it "does not warn about mutation when Warning[:deprecated] is false" do
+      deprecated = Warning[:deprecated]
+      Warning[:deprecated] = false
+      -> { :bad!.send(@method).upcase! }.should_not complain
+    ensure
+      Warning[:deprecated] = deprecated
+    end
+  end
 end
diff --git a/spec/ruby/core/symbol/shared/slice.rb b/spec/ruby/core/symbol/shared/slice.rb
index 478e0d80ae..d3d4aad617 100644
--- a/spec/ruby/core/symbol/shared/slice.rb
+++ b/spec/ruby/core/symbol/shared/slice.rb
@@ -7,7 +7,7 @@ describe :symbol_slice, shared: true do
     end
 
     it "returns nil if the index starts from the end and is greater than the length" do
-        :symbol.send(@method, -10).should be_nil
+      :symbol.send(@method, -10).should be_nil
     end
 
     it "returns nil if the index is greater than the length" do
@@ -190,14 +190,6 @@ describe :symbol_slice, shared: true do
         :symbol.send(@method, /[0-9]+/)
         $~.should be_nil
       end
-
-      it "returns a tainted string if the regexp is tainted" do
-        :symbol.send(@method, /./.taint).tainted?.should be_true
-      end
-
-      it "returns an untrusted string if the regexp is untrusted" do
-        :symbol.send(@method, /./.untrust).untrusted?.should be_true
-      end
     end
 
     describe "with a capture index" do
@@ -219,14 +211,6 @@ describe :symbol_slice, shared: true do
         :symbol.send(@method, /(sy)(mb)(ol)/, 1.5).should == "sy"
       end
 
-      it "returns a tainted string if the regexp is tainted" do
-        :symbol.send(@method, /(.)/.taint, 1).tainted?.should be_true
-      end
-
-      it "returns an untrusted string if the regexp is untrusted" do
-        :symbol.send(@method, /(.)/.untrust, 1).untrusted?.should be_true
-      end
-
       describe "and an index that cannot be converted to an Integer" do
         it "raises a TypeError when given an Hash" do
           -> { :symbol.send(@method, /(sy)(mb)(ol)/, Hash.new) }.should raise_error(TypeError)
diff --git a/spec/ruby/core/symbol/start_with_spec.rb b/spec/ruby/core/symbol/start_with_spec.rb
new file mode 100644
index 0000000000..cd43279003
--- /dev/null
+++ b/spec/ruby/core/symbol/start_with_spec.rb
@@ -0,0 +1,8 @@
+# -*- encoding: utf-8 -*-
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+require_relative '../../shared/string/start_with'
+
+describe "Symbol#start_with?" do
+  it_behaves_like :start_with, :to_sym
+end
diff --git a/spec/ruby/core/symbol/to_proc_spec.rb b/spec/ruby/core/symbol/to_proc_spec.rb
index 60e33d7cb8..def5d6d344 100644
--- a/spec/ruby/core/symbol/to_proc_spec.rb
+++ b/spec/ruby/core/symbol/to_proc_spec.rb
@@ -12,18 +12,50 @@ describe "Symbol#to_proc" do
     :to_s.to_proc.call(obj).should == "Received #to_s"
   end
 
-  it "produces a proc with arity -1" do
+  it "returns a Proc with #lambda? true" do
     pr = :to_s.to_proc
-    pr.arity.should == -1
+    pr.should.lambda?
   end
 
-  it "raises an ArgumentError when calling #call on the Proc without receiver" do
-    -> { :object_id.to_proc.call }.should raise_error(ArgumentError, "no receiver given")
+  it "produces a Proc with arity -2" do
+    pr = :to_s.to_proc
+    pr.arity.should == -2
   end
 
-  it "produces a proc that always returns [[:rest]] for #parameters" do
+  it "produces a Proc that always returns [[:req], [:rest]] for #parameters" do
     pr = :to_s.to_proc
-    pr.parameters.should == [[:rest]]
+    pr.parameters.should == [[:req], [:rest]]
+  end
+
+  it "only calls public methods" do
+    body = proc do
+      public def pub; @a << :pub end
+      protected def pro; @a << :pro end
+      private def pri; @a << :pri end
+      attr_reader :a
+    end
+
+    @a = []
+    singleton_class.class_eval(&body)
+    tap(&:pub)
+    proc{tap(&:pro)}.should raise_error(NoMethodError, /protected method [`']pro' called/)
+    proc{tap(&:pri)}.should raise_error(NoMethodError, /private method [`']pri' called/)
+    @a.should == [:pub]
+
+    @a = []
+    c = Class.new(&body)
+    o = c.new
+    o.instance_variable_set(:@a, [])
+    o.tap(&:pub)
+    proc{tap(&:pro)}.should raise_error(NoMethodError, /protected method [`']pro' called/)
+    proc{o.tap(&:pri)}.should raise_error(NoMethodError, /private method [`']pri' called/)
+    o.a.should == [:pub]
+  end
+
+  it "raises an ArgumentError when calling #call on the Proc without receiver" do
+    -> {
+      :object_id.to_proc.call
+    }.should raise_error(ArgumentError, /no receiver given|wrong number of arguments \(given 0, expected 1\+\)/)
   end
 
   it "passes along the block passed to Proc#call" do
@@ -38,4 +70,9 @@ describe "Symbol#to_proc" do
     end
     klass.new.to_proc.should == :value
   end
+
+  it "produces a proc with source location nil" do
+    pr = :to_s.to_proc
+    pr.source_location.should == nil
+  end
 end
diff --git a/spec/ruby/core/systemexit/success_spec.rb b/spec/ruby/core/systemexit/success_spec.rb
index 6d36509c80..ba2fd22ded 100644
--- a/spec/ruby/core/systemexit/success_spec.rb
+++ b/spec/ruby/core/systemexit/success_spec.rb
@@ -3,11 +3,11 @@ require_relative '../../spec_helper'
 describe "SystemExit#success?" do
   it "returns true when the status is 0" do
     s = SystemExit.new 0
-    s.success?.should == true
+    s.should.success?
   end
 
   it "returns false when the status is not 0" do
     s = SystemExit.new 1
-    s.success?.should == false
+    s.should_not.success?
   end
 end
diff --git a/spec/ruby/core/thread/abort_on_exception_spec.rb b/spec/ruby/core/thread/abort_on_exception_spec.rb
index 34b648ca0f..49be84ea9f 100644
--- a/spec/ruby/core/thread/abort_on_exception_spec.rb
+++ b/spec/ruby/core/thread/abort_on_exception_spec.rb
@@ -72,7 +72,7 @@ describe "Thread.abort_on_exception" do
   end
 
   after do
-     Thread.abort_on_exception = @abort_on_exception
+    Thread.abort_on_exception = @abort_on_exception
   end
 
   it "is false by default" do
diff --git a/spec/ruby/core/thread/alive_spec.rb b/spec/ruby/core/thread/alive_spec.rb
index d4ba149d87..c2f5f5371d 100644
--- a/spec/ruby/core/thread/alive_spec.rb
+++ b/spec/ruby/core/thread/alive_spec.rb
@@ -3,39 +3,39 @@ require_relative 'fixtures/classes'
 
 describe "Thread#alive?" do
   it "can check it's own status" do
-    ThreadSpecs.status_of_current_thread.alive?.should == true
+    ThreadSpecs.status_of_current_thread.should.alive?
   end
 
   it "describes a running thread" do
-    ThreadSpecs.status_of_running_thread.alive?.should == true
+    ThreadSpecs.status_of_running_thread.should.alive?
   end
 
   it "describes a sleeping thread" do
-    ThreadSpecs.status_of_sleeping_thread.alive?.should == true
+    ThreadSpecs.status_of_sleeping_thread.should.alive?
   end
 
   it "describes a blocked thread" do
-    ThreadSpecs.status_of_blocked_thread.alive?.should == true
+    ThreadSpecs.status_of_blocked_thread.should.alive?
   end
 
   it "describes a completed thread" do
-    ThreadSpecs.status_of_completed_thread.alive?.should == false
+    ThreadSpecs.status_of_completed_thread.should_not.alive?
   end
 
   it "describes a killed thread" do
-    ThreadSpecs.status_of_killed_thread.alive?.should == false
+    ThreadSpecs.status_of_killed_thread.should_not.alive?
   end
 
   it "describes a thread with an uncaught exception" do
-    ThreadSpecs.status_of_thread_with_uncaught_exception.alive?.should == false
+    ThreadSpecs.status_of_thread_with_uncaught_exception.should_not.alive?
   end
 
   it "describes a dying running thread" do
-    ThreadSpecs.status_of_dying_running_thread.alive?.should == true
+    ThreadSpecs.status_of_dying_running_thread.should.alive?
   end
 
   it "describes a dying sleeping thread" do
-    ThreadSpecs.status_of_dying_sleeping_thread.alive?.should == true
+    ThreadSpecs.status_of_dying_sleeping_thread.should.alive?
   end
 
   it "returns true for a killed but still running thread" do
@@ -51,7 +51,7 @@ describe "Thread#alive?" do
     ThreadSpecs.spin_until_sleeping(t)
 
     t.kill
-    t.alive?.should == true
+    t.should.alive?
     exit = true
     t.join
   end
diff --git a/spec/ruby/core/thread/backtrace/limit_spec.rb b/spec/ruby/core/thread/backtrace/limit_spec.rb
new file mode 100644
index 0000000000..b55ca67ea0
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/limit_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+
+describe "Thread::Backtrace.limit" do
+  it "returns maximum backtrace length set by --backtrace-limit command-line option" do
+    out = ruby_exe("print Thread::Backtrace.limit", options: "--backtrace-limit=2")
+    out.should == "2"
+  end
+
+  it "returns -1 when --backtrace-limit command-line option is not set" do
+    out = ruby_exe("print Thread::Backtrace.limit")
+    out.should == "-1"
+  end
+end
diff --git a/spec/ruby/core/thread/backtrace/location/absolute_path_spec.rb b/spec/ruby/core/thread/backtrace/location/absolute_path_spec.rb
index d38659c257..68a69049d9 100644
--- a/spec/ruby/core/thread/backtrace/location/absolute_path_spec.rb
+++ b/spec/ruby/core/thread/backtrace/location/absolute_path_spec.rb
@@ -10,11 +10,28 @@ describe 'Thread::Backtrace::Location#absolute_path' do
     @frame.absolute_path.should == File.realpath(__FILE__)
   end
 
+  it 'returns an absolute path when using a relative main script path' do
+    script = fixture(__FILE__, 'absolute_path_main.rb')
+    Dir.chdir(File.dirname(script)) do
+      ruby_exe('absolute_path_main.rb').should == "absolute_path_main.rb\n#{script}\n"
+    end
+  end
+
+  it 'returns the correct absolute path when using a relative main script path and changing CWD' do
+    script = fixture(__FILE__, 'subdir/absolute_path_main_chdir.rb')
+    sibling = fixture(__FILE__, 'subdir/sibling.rb')
+    subdir = File.dirname script
+    Dir.chdir(fixture(__FILE__)) do
+      ruby_exe('subdir/absolute_path_main_chdir.rb').should == "subdir/absolute_path_main_chdir.rb\n#{subdir}\n#{subdir}\n#{script}\n#{sibling}\n"
+    end
+  end
+
   context "when used in eval with a given filename" do
-    it "returns filename" do
+    it "returns nil with absolute_path" do
       code = "caller_locations(0)[0].absolute_path"
-      eval(code, nil, "foo.rb").should == "foo.rb"
-      eval(code, nil, "foo/bar.rb").should == "foo/bar.rb"
+
+      eval(code, nil, "foo.rb").should == nil
+      eval(code, nil, "foo/bar.rb").should == nil
     end
   end
 
@@ -29,33 +46,48 @@ describe 'Thread::Backtrace::Location#absolute_path' do
     end
   end
 
-  platform_is_not :windows do
-    before :each do
-      @file = fixture(__FILE__, "absolute_path.rb")
-      @symlink = tmp("symlink.rb")
-      File.symlink(@file, @symlink)
-      ScratchPad.record []
+  context "when used in a core method" do
+    it "returns nil" do
+      location = nil
+      tap { location = caller_locations(1, 1)[0] }
+      location.label.should =~ /\A(?:Kernel#)?tap\z/
+      if location.path.start_with?("<internal:")
+        location.absolute_path.should == nil
+      else
+        location.absolute_path.should == File.realpath(__FILE__)
+      end
     end
+  end
 
-    after :each do
-      rm_r @symlink
-    end
+  context "canonicalization" do
+    platform_is_not :windows do
+      before :each do
+        @file = fixture(__FILE__, "absolute_path.rb")
+        @symlink = tmp("symlink.rb")
+        File.symlink(@file, @symlink)
+        ScratchPad.record []
+      end
 
-    it "returns a canonical path without symlinks, even when __FILE__ does not" do
-      realpath = File.realpath(@symlink)
-      realpath.should_not == @symlink
+      after :each do
+        rm_r @symlink
+      end
 
-      load @symlink
-      ScratchPad.recorded.should == [@symlink, realpath]
-    end
+      it "returns a canonical path without symlinks, even when __FILE__ does not" do
+        realpath = File.realpath(@symlink)
+        realpath.should_not == @symlink
+
+        load @symlink
+        ScratchPad.recorded.should == [@symlink, realpath]
+      end
 
-    it "returns a canonical path without symlinks, even when __FILE__ is removed" do
-      realpath = File.realpath(@symlink)
-      realpath.should_not == @symlink
+      it "returns a canonical path without symlinks, even when __FILE__ is removed" do
+        realpath = File.realpath(@symlink)
+        realpath.should_not == @symlink
 
-      ScratchPad << -> { rm_r(@symlink) }
-      load @symlink
-      ScratchPad.recorded.should == [@symlink, realpath]
+        ScratchPad << -> { rm_r(@symlink) }
+        load @symlink
+        ScratchPad.recorded.should == [@symlink, realpath]
+      end
     end
   end
 end
diff --git a/spec/ruby/core/thread/backtrace/location/base_label_spec.rb b/spec/ruby/core/thread/backtrace/location/base_label_spec.rb
index 139a68e2c8..739f62f42f 100644
--- a/spec/ruby/core/thread/backtrace/location/base_label_spec.rb
+++ b/spec/ruby/core/thread/backtrace/location/base_label_spec.rb
@@ -19,4 +19,31 @@ describe 'Thread::Backtrace::Location#base_label' do
       @frame.base_label.should == 'block_location'
     end
   end
+
+  it "is <module:A> for a module body" do
+    module ThreadBacktraceLocationSpecs
+      module ModuleLabel
+        ScratchPad.record caller_locations(0, 1)[0].base_label
+      end
+    end
+    ScratchPad.recorded.should == '<module:ModuleLabel>'
+  end
+
+  it "is <class:A> for a class body" do
+    module ThreadBacktraceLocationSpecs
+      class ClassLabel
+        ScratchPad.record caller_locations(0, 1)[0].base_label
+      end
+    end
+    ScratchPad.recorded.should == '<class:ClassLabel>'
+  end
+
+  it "is 'singleton class' for a singleton class body" do
+    module ThreadBacktraceLocationSpecs
+      class << Object.new
+        ScratchPad.record caller_locations(0, 1)[0].base_label
+      end
+    end
+    ScratchPad.recorded.should =~ /\A(singleton class|<singleton class>)\z/
+  end
 end
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/absolute_path_main.rb b/spec/ruby/core/thread/backtrace/location/fixtures/absolute_path_main.rb
new file mode 100644
index 0000000000..d2b23393d4
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/absolute_path_main.rb
@@ -0,0 +1,2 @@
+puts __FILE__
+puts caller_locations(0)[0].absolute_path
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/classes.rb b/spec/ruby/core/thread/backtrace/location/fixtures/classes.rb
index 3e42d8cf81..e903c3e450 100644
--- a/spec/ruby/core/thread/backtrace/location/fixtures/classes.rb
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/classes.rb
@@ -14,4 +14,22 @@ module ThreadBacktraceLocationSpecs
       return caller_locations(0)
     end
   end
+
+  def self.locations_inside_nested_blocks
+    first_level_location = nil
+    second_level_location = nil
+    third_level_location = nil
+
+    1.times do
+      first_level_location = locations[0]
+      1.times do
+        second_level_location = locations[0]
+        1.times do
+          third_level_location = locations[0]
+        end
+      end
+    end
+
+    [first_level_location, second_level_location, third_level_location]
+  end
 end
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_main.rb b/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_main.rb
new file mode 100644
index 0000000000..b124c8161c
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_main.rb
@@ -0,0 +1,5 @@
+1.times do
+  puts Thread.current.backtrace_locations(1..1)[0].label
+end
+
+require_relative 'locations_in_required'
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_required.rb b/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_required.rb
new file mode 100644
index 0000000000..5f5ed89e98
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/locations_in_required.rb
@@ -0,0 +1,3 @@
+1.times do
+  puts Thread.current.backtrace_locations(1..1)[0].label
+end
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/path.rb b/spec/ruby/core/thread/backtrace/location/fixtures/path.rb
new file mode 100644
index 0000000000..fba34cb0bc
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/path.rb
@@ -0,0 +1,2 @@
+ScratchPad << __FILE__
+ScratchPad << caller_locations(0)[0].path
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/subdir/absolute_path_main_chdir.rb b/spec/ruby/core/thread/backtrace/location/fixtures/subdir/absolute_path_main_chdir.rb
new file mode 100644
index 0000000000..33c8fb36ef
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/subdir/absolute_path_main_chdir.rb
@@ -0,0 +1,11 @@
+puts __FILE__
+puts __dir__
+Dir.chdir __dir__
+
+# Check __dir__ is still correct after chdir
+puts __dir__
+
+puts caller_locations(0)[0].absolute_path
+
+# require_relative also needs to know the absolute path of the current file so we test it here too
+require_relative 'sibling'
diff --git a/spec/ruby/core/thread/backtrace/location/fixtures/subdir/sibling.rb b/spec/ruby/core/thread/backtrace/location/fixtures/subdir/sibling.rb
new file mode 100644
index 0000000000..2a854ddccd
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace/location/fixtures/subdir/sibling.rb
@@ -0,0 +1 @@
+puts __FILE__
diff --git a/spec/ruby/core/thread/backtrace/location/label_spec.rb b/spec/ruby/core/thread/backtrace/location/label_spec.rb
index be8da5646f..85ddccc8e3 100644
--- a/spec/ruby/core/thread/backtrace/location/label_spec.rb
+++ b/spec/ruby/core/thread/backtrace/location/label_spec.rb
@@ -7,14 +7,31 @@ describe 'Thread::Backtrace::Location#label' do
   end
 
   it 'returns the method name for a method location' do
-    ThreadBacktraceLocationSpecs.method_location[0].label.should == "method_location"
+    ThreadBacktraceLocationSpecs.method_location[0].label.should =~ /\A(?:ThreadBacktraceLocationSpecs\.)?method_location\z/
   end
 
   it 'returns the block name for a block location' do
-    ThreadBacktraceLocationSpecs.block_location[0].label.should == "block in block_location"
+    ThreadBacktraceLocationSpecs.block_location[0].label.should =~ /\Ablock in (?:ThreadBacktraceLocationSpecs\.)?block_location\z/
   end
 
   it 'returns the module name for a module location' do
     ThreadBacktraceLocationSpecs::MODULE_LOCATION[0].label.should include "ThreadBacktraceLocationSpecs"
   end
+
+  it 'includes the nesting level of a block as part of the location label' do
+    first_level_location, second_level_location, third_level_location =
+      ThreadBacktraceLocationSpecs.locations_inside_nested_blocks
+
+    first_level_location.label.should =~ /\Ablock in (?:ThreadBacktraceLocationSpecs\.)?locations_inside_nested_blocks\z/
+    second_level_location.label.should =~ /\Ablock \(2 levels\) in (?:ThreadBacktraceLocationSpecs\.)?locations_inside_nested_blocks\z/
+    third_level_location.label.should =~ /\Ablock \(3 levels\) in (?:ThreadBacktraceLocationSpecs\.)?locations_inside_nested_blocks\z/
+  end
+
+  it 'sets the location label for a top-level block differently depending on it being in the main file or a required file' do
+    path = fixture(__FILE__, "locations_in_main.rb")
+    main_label, required_label = ruby_exe(path).lines
+
+    main_label.should == "block in <main>\n"
+    required_label.should == "block in <top (required)>\n"
+  end
 end
diff --git a/spec/ruby/core/thread/backtrace/location/lineno_spec.rb b/spec/ruby/core/thread/backtrace/location/lineno_spec.rb
index dc93d32d75..10457f80f0 100644
--- a/spec/ruby/core/thread/backtrace/location/lineno_spec.rb
+++ b/spec/ruby/core/thread/backtrace/location/lineno_spec.rb
@@ -7,7 +7,17 @@ describe 'Thread::Backtrace::Location#lineno' do
     @line  = __LINE__ - 1
   end
 
-  it 'returns the absolute path of the call frame' do
+  it 'returns the line number of the call frame' do
     @frame.lineno.should == @line
   end
+
+  it 'should be the same line number as in #to_s, including for core methods' do
+    # Get the caller_locations from a call made into a core library method
+    locations = [:non_empty].map { caller_locations }[0]
+
+    locations.each do |location|
+      line_number = location.to_s[/:(\d+):/, 1]
+      location.lineno.should == Integer(line_number)
+    end
+  end
 end
diff --git a/spec/ruby/core/thread/backtrace/location/path_spec.rb b/spec/ruby/core/thread/backtrace/location/path_spec.rb
index b1a3439747..75f76833a9 100644
--- a/spec/ruby/core/thread/backtrace/location/path_spec.rb
+++ b/spec/ruby/core/thread/backtrace/location/path_spec.rb
@@ -41,7 +41,7 @@ describe 'Thread::Backtrace::Location#path' do
       context 'when using a relative script path' do
         it 'returns a path relative to the working directory' do
           path      = 'fixtures/main.rb'
-          directory = File.dirname(__FILE__)
+          directory = __dir__
           Dir.chdir(directory) {
             ruby_exe(path)
           }.should == path
@@ -86,4 +86,39 @@ describe 'Thread::Backtrace::Location#path' do
       end
     end
   end
+
+  it 'should be the same path as in #to_s, including for core methods' do
+    # Get the caller_locations from a call made into a core library method
+    locations = [:non_empty].map { caller_locations }[0]
+
+    locations.each do |location|
+      filename = location.to_s[/^(.+):\d+:/, 1]
+      path = location.path
+
+      path.should == filename
+    end
+  end
+
+  context "canonicalization" do
+    platform_is_not :windows do
+      before :each do
+        @file = fixture(__FILE__, "path.rb")
+        @symlink = tmp("symlink.rb")
+        File.symlink(@file, @symlink)
+        ScratchPad.record []
+      end
+
+      after :each do
+        rm_r @symlink
+      end
+
+      it "returns a non-canonical path with symlinks, the same as __FILE__" do
+        realpath = File.realpath(@symlink)
+        realpath.should_not == @symlink
+
+        load @symlink
+        ScratchPad.recorded.should == [@symlink, @symlink]
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/thread/backtrace_locations_spec.rb b/spec/ruby/core/thread/backtrace_locations_spec.rb
new file mode 100644
index 0000000000..09fe622e0d
--- /dev/null
+++ b/spec/ruby/core/thread/backtrace_locations_spec.rb
@@ -0,0 +1,79 @@
+require_relative '../../spec_helper'
+
+describe "Thread#backtrace_locations" do
+  it "returns an Array" do
+    locations = Thread.current.backtrace_locations
+    locations.should be_an_instance_of(Array)
+    locations.should_not be_empty
+  end
+
+  it "sets each element to a Thread::Backtrace::Location" do
+    locations = Thread.current.backtrace_locations
+    locations.each { |loc| loc.should be_an_instance_of(Thread::Backtrace::Location) }
+  end
+
+  it "can be called on any Thread" do
+    locations = Thread.new { Thread.current.backtrace_locations }.value
+    locations.should be_an_instance_of(Array)
+    locations.should_not be_empty
+    locations.each { |loc| loc.should be_an_instance_of(Thread::Backtrace::Location) }
+  end
+
+  it "can be called with a number of locations to omit" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2)
+    locations2.length.should == locations1[2..-1].length
+    locations2.map(&:to_s).should == locations1[2..-1].map(&:to_s)
+  end
+
+  it "can be called with a maximum number of locations to return as second parameter" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2, 3)
+    locations2.map(&:to_s).should == locations1[2..4].map(&:to_s)
+  end
+
+  it "can be called with a range" do
+    locations1 = Thread.current.backtrace_locations
+    locations2 = Thread.current.backtrace_locations(2..4)
+    locations2.map(&:to_s).should == locations1[2..4].map(&:to_s)
+  end
+
+  it "can be called with a range whose end is negative" do
+    Thread.current.backtrace_locations(2..-1).map(&:to_s).should == Thread.current.backtrace_locations[2..-1].map(&:to_s)
+    Thread.current.backtrace_locations(2..-2).map(&:to_s).should == Thread.current.backtrace_locations[2..-2].map(&:to_s)
+  end
+
+  it "can be called with an endless range" do
+    locations1 = Thread.current.backtrace_locations(0)
+    locations2 = Thread.current.backtrace_locations(eval("(2..)"))
+    locations2.map(&:to_s).should == locations1[2..-1].map(&:to_s)
+  end
+
+  it "can be called with an beginless range" do
+    locations1 = Thread.current.backtrace_locations(0)
+    locations2 = Thread.current.backtrace_locations((..5))
+    locations2.map(&:to_s)[eval("(2..)")].should == locations1[(..5)].map(&:to_s)[eval("(2..)")]
+  end
+
+  it "returns nil if omitting more locations than available" do
+    Thread.current.backtrace_locations(100).should == nil
+    Thread.current.backtrace_locations(100..-1).should == nil
+  end
+
+  it "returns [] if omitting exactly the number of locations available" do
+    omit = Thread.current.backtrace_locations.length
+    Thread.current.backtrace_locations(omit).should == []
+  end
+
+  it "without argument is the same as showing all locations with 0..-1" do
+    Thread.current.backtrace_locations.map(&:to_s).should == Thread.current.backtrace_locations(0..-1).map(&:to_s)
+  end
+
+  it "the first location reports the call to #backtrace_locations" do
+    Thread.current.backtrace_locations(0..0)[0].to_s.should =~ /\A#{__FILE__ }:#{__LINE__ }:in [`'](?:Thread#)?backtrace_locations'\z/
+  end
+
+  it "[1..-1] is the same as #caller_locations(0..-1) for Thread.current" do
+    Thread.current.backtrace_locations(1..-1).map(&:to_s).should == caller_locations(0..-1).map(&:to_s)
+  end
+end
diff --git a/spec/ruby/core/thread/backtrace_spec.rb b/spec/ruby/core/thread/backtrace_spec.rb
index 84ed574d5c..15bb29a349 100644
--- a/spec/ruby/core/thread/backtrace_spec.rb
+++ b/spec/ruby/core/thread/backtrace_spec.rb
@@ -13,7 +13,7 @@ describe "Thread#backtrace" do
 
     backtrace = t.backtrace
     backtrace.should be_kind_of(Array)
-    backtrace.first.should =~ /`sleep'/
+    backtrace.first.should =~ /[`'](?:Kernel#)?sleep'/
 
     t.raise 'finish the thread'
     t.join
@@ -32,4 +32,38 @@ describe "Thread#backtrace" do
     t.join
     backtrace.should be_kind_of(Array)
   end
+
+  it "can be called with a number of locations to omit" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2)
+    locations1[2..-1].length.should == locations2.length
+    locations1[2..-1].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a maximum number of locations to return as second parameter" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2, 3)
+    locations1[2..4].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a range" do
+    locations1 = Thread.current.backtrace
+    locations2 = Thread.current.backtrace(2..4)
+    locations1[2..4].map(&:to_s).should == locations2.map(&:to_s)
+  end
+
+  it "can be called with a range whose end is negative" do
+    Thread.current.backtrace(2..-1).should == Thread.current.backtrace[2..-1]
+    Thread.current.backtrace(2..-2).should == Thread.current.backtrace[2..-2]
+  end
+
+  it "returns nil if omitting more locations than available" do
+    Thread.current.backtrace(100).should == nil
+    Thread.current.backtrace(100..-1).should == nil
+  end
+
+  it "returns [] if omitting exactly the number of locations available" do
+    omit = Thread.current.backtrace.length
+    Thread.current.backtrace(omit).should == []
+  end
 end
diff --git a/spec/ruby/core/thread/each_caller_location_spec.rb b/spec/ruby/core/thread/each_caller_location_spec.rb
new file mode 100644
index 0000000000..aa7423675b
--- /dev/null
+++ b/spec/ruby/core/thread/each_caller_location_spec.rb
@@ -0,0 +1,47 @@
+require_relative '../../spec_helper'
+
+describe "Thread.each_caller_location" do
+  it "iterates through the current execution stack and matches caller_locations content and type" do
+    ScratchPad.record []
+    Thread.each_caller_location { |l| ScratchPad << l; }
+
+    ScratchPad.recorded.map(&:to_s).should == caller_locations.map(&:to_s)
+    ScratchPad.recorded[0].should be_kind_of(Thread::Backtrace::Location)
+  end
+
+  it "returns subset of 'Thread.to_enum(:each_caller_location)' locations" do
+    ar = []
+    ecl = Thread.each_caller_location { |x| ar << x }
+
+    (ar.map(&:to_s) - Thread.to_enum(:each_caller_location).to_a.map(&:to_s)).should.empty?
+  end
+
+  it "stops the backtrace iteration if 'break' occurs" do
+    i = 0
+    ar = []
+    ecl = Thread.each_caller_location do |x|
+      ar << x
+      i += 1
+      break x if i == 2
+    end
+
+    ar.map(&:to_s).should == caller_locations(1, 2).map(&:to_s)
+    ecl.should be_kind_of(Thread::Backtrace::Location)
+  end
+
+  it "returns nil" do
+    Thread.each_caller_location {}.should == nil
+  end
+
+  it "raises LocalJumpError when called without a block" do
+    -> {
+      Thread.each_caller_location
+    }.should raise_error(LocalJumpError, "no block given")
+  end
+
+  it "doesn't accept keyword arguments" do
+    -> {
+      Thread.each_caller_location(12, foo: 10) {}
+    }.should raise_error(ArgumentError);
+  end
+end
diff --git a/spec/ruby/core/thread/element_reference_spec.rb b/spec/ruby/core/thread/element_reference_spec.rb
index 85280cb287..fde9d1f440 100644
--- a/spec/ruby/core/thread/element_reference_spec.rb
+++ b/spec/ruby/core/thread/element_reference_spec.rb
@@ -37,6 +37,17 @@ describe "Thread#[]" do
     t2["value"].should == 2
   end
 
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('value')
+    key.should_receive(:to_str).and_return('value')
+
+    th = Thread.new do
+      Thread.current[:value] = 1
+    end.join
+
+    th[key].should == 1
+  end
+
   it "raises exceptions on the wrong type of keys" do
     -> { Thread.current[nil] }.should raise_error(TypeError)
     -> { Thread.current[5] }.should raise_error(TypeError)
diff --git a/spec/ruby/core/thread/element_set_spec.rb b/spec/ruby/core/thread/element_set_spec.rb
index d974b5e1c7..f205177304 100644
--- a/spec/ruby/core/thread/element_set_spec.rb
+++ b/spec/ruby/core/thread/element_set_spec.rb
@@ -6,16 +6,39 @@ describe "Thread#[]=" do
     Thread.current[:value] = nil
   end
 
-  it "raises a #{frozen_error_class} if the thread is frozen" do
+  it "raises a FrozenError if the thread is frozen" do
     Thread.new do
       th = Thread.current
       th.freeze
       -> {
         th[:foo] = "bar"
-      }.should raise_error(frozen_error_class, /frozen/)
+      }.should raise_error(FrozenError, "can't modify frozen thread locals")
     end.join
   end
 
+  it "accepts Strings and Symbols" do
+    t1 = Thread.new do
+      Thread.current[:value] = 1
+    end.join
+    t2 = Thread.new do
+      Thread.current["value"] = 2
+    end.join
+
+    t1[:value].should == 1
+    t2[:value].should == 2
+  end
+
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('value')
+    key.should_receive(:to_str).and_return('value')
+
+    th = Thread.new do
+      Thread.current[key] = 1
+    end.join
+
+    th[:value].should == 1
+  end
+
   it "raises exceptions on the wrong type of keys" do
     -> { Thread.current[nil] = true }.should raise_error(TypeError)
     -> { Thread.current[5] = true }.should raise_error(TypeError)
diff --git a/spec/ruby/core/thread/exclusive_spec.rb b/spec/ruby/core/thread/exclusive_spec.rb
deleted file mode 100644
index a96ebe749d..0000000000
--- a/spec/ruby/core/thread/exclusive_spec.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Thread.exclusive" do
-  before :each do
-    ScratchPad.clear
-  end
-
-  it "yields to the block" do
-    Thread.exclusive { ScratchPad.record true }
-    ScratchPad.recorded.should == true
-  end
-
-  it "returns the result of yielding" do
-    Thread.exclusive { :result }.should == :result
-  end
-
-  it "blocks the caller if another thread is also in an exclusive block" do
-    m = Mutex.new
-    q1 = Queue.new
-    q2 = Queue.new
-
-    t = Thread.new {
-      Thread.exclusive {
-        q1.push :ready
-        q2.pop
-      }
-    }
-
-    q1.pop.should == :ready
-
-    -> { Thread.exclusive { } }.should block_caller
-
-    q2.push :done
-    t.join
-  end
-
-  it "is not recursive" do
-    Thread.exclusive do
-      -> { Thread.exclusive { } }.should raise_error(ThreadError)
-    end
-  end
-end
diff --git a/spec/ruby/core/thread/fetch_spec.rb b/spec/ruby/core/thread/fetch_spec.rb
index d71c938880..85ffb71874 100644
--- a/spec/ruby/core/thread/fetch_spec.rb
+++ b/spec/ruby/core/thread/fetch_spec.rb
@@ -1,38 +1,66 @@
 require_relative '../../spec_helper'
 
-ruby_version_is '2.5' do
-  describe 'Thread#fetch' do
-    describe 'with 2 arguments' do
-      it 'returns the value of the fiber-local variable if value has been assigned' do
-        th = Thread.new { Thread.current[:cat] = 'meow' }
-        th.join
-        th.fetch(:cat, true).should == 'meow'
-      end
-
-      it "returns the default value if fiber-local variable hasn't been assigned" do
-        th = Thread.new {}
-        th.join
-        th.fetch(:cat, true).should == true
-      end
-    end
-
-    describe 'with 1 argument' do
-      it 'raises a KeyError when the Thread does not have a fiber-local variable of the same name' do
-        th = Thread.new {}
-        th.join
-        -> { th.fetch(:cat) }.should raise_error(KeyError)
-      end
-
-      it 'returns the value of the fiber-local variable if value has been assigned' do
-        th = Thread.new { Thread.current[:cat] = 'meow' }
-        th.join
-        th.fetch(:cat).should == 'meow'
-      end
-    end
-
-    it 'raises an ArgumentError when not passed one or two arguments' do
-      -> { Thread.current.fetch() }.should raise_error(ArgumentError)
-      -> { Thread.current.fetch(1, 2, 3) }.should raise_error(ArgumentError)
+describe 'Thread#fetch' do
+  describe 'with 2 arguments' do
+    it 'returns the value of the fiber-local variable if value has been assigned' do
+      th = Thread.new { Thread.current[:cat] = 'meow' }
+      th.join
+      th.fetch(:cat, true).should == 'meow'
     end
+
+    it "returns the default value if fiber-local variable hasn't been assigned" do
+      th = Thread.new {}
+      th.join
+      th.fetch(:cat, true).should == true
+    end
+  end
+
+  describe 'with 1 argument' do
+    it 'raises a KeyError when the Thread does not have a fiber-local variable of the same name' do
+      th = Thread.new {}
+      th.join
+      -> { th.fetch(:cat) }.should raise_error(KeyError)
+    end
+
+    it 'returns the value of the fiber-local variable if value has been assigned' do
+      th = Thread.new { Thread.current[:cat] = 'meow' }
+      th.join
+      th.fetch(:cat).should == 'meow'
+    end
+  end
+
+  describe 'with a block' do
+    it 'returns the value of the fiber-local variable if value has been assigned' do
+      th = Thread.new { Thread.current[:cat] = 'meow' }
+      th.join
+      th.fetch(:cat) { true }.should == 'meow'
+    end
+
+    it "returns the block value if fiber-local variable hasn't been assigned" do
+      th = Thread.new {}
+      th.join
+      th.fetch(:cat) { true }.should == true
+    end
+
+    it "does not call the block if value has been assigned" do
+      th = Thread.new { Thread.current[:cat] = 'meow' }
+      th.join
+      var = :not_updated
+      th.fetch(:cat) { var = :updated }.should == 'meow'
+      var.should == :not_updated
+    end
+
+    it "uses the block if a default is given and warns about it" do
+      th = Thread.new {}
+      th.join
+      -> {
+        th.fetch(:cat, false) { true }.should == true
+      }.should complain(/warning: block supersedes default value argument/)
+    end
+  end
+
+  it 'raises an ArgumentError when not passed one or two arguments' do
+    -> { Thread.current.fetch() }.should raise_error(ArgumentError)
+    -> { Thread.current.fetch(1, 2, 3) }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/core/thread/fixtures/classes.rb b/spec/ruby/core/thread/fixtures/classes.rb
index c1f15935ee..7c485660a8 100644
--- a/spec/ruby/core/thread/fixtures/classes.rb
+++ b/spec/ruby/core/thread/fixtures/classes.rb
@@ -6,12 +6,38 @@ module ThreadSpecs
     end
   end
 
+  class NewThreadToRaise
+    def self.raise(*args, **kwargs, &block)
+      thread = Thread.new do
+        Thread.current.report_on_exception = false
+
+        if block_given?
+          block.call do
+            sleep
+          end
+        else
+          sleep
+        end
+      end
+
+      Thread.pass until thread.stop?
+
+      thread.raise(*args, **kwargs)
+
+      thread.join
+    ensure
+      thread.kill if thread.alive?
+      Thread.pass while thread.alive? # Thread#kill may not terminate a thread immediately so it may be detected as a leaked one
+    end
+  end
+
   class Status
-    attr_reader :thread, :inspect, :status
+    attr_reader :thread, :inspect, :status, :to_s
     def initialize(thread)
       @thread = thread
       @alive = thread.alive?
       @inspect = thread.inspect
+      @to_s = thread.to_s
       @status = thread.status
       @stop = thread.stop?
     end
diff --git a/spec/ruby/core/thread/group_spec.rb b/spec/ruby/core/thread/group_spec.rb
index 59f5ac37c8..d0d4704b66 100644
--- a/spec/ruby/core/thread/group_spec.rb
+++ b/spec/ruby/core/thread/group_spec.rb
@@ -1,5 +1,16 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
+
 describe "Thread#group" do
-  it "needs to be reviewed for spec completeness"
+  it "returns the default thread group for the main thread" do
+    Thread.main.group.should == ThreadGroup::Default
+  end
+
+  it "returns the thread group explicitly set for this thread" do
+    thread = Thread.new { nil }
+    thread_group = ThreadGroup.new
+    thread_group.add(thread)
+    thread.group.should == thread_group
+  ensure
+    thread.join if thread
+  end
 end
diff --git a/spec/ruby/core/thread/handle_interrupt_spec.rb b/spec/ruby/core/thread/handle_interrupt_spec.rb
new file mode 100644
index 0000000000..ea7e81cb98
--- /dev/null
+++ b/spec/ruby/core/thread/handle_interrupt_spec.rb
@@ -0,0 +1,125 @@
+require_relative '../../spec_helper'
+
+describe "Thread.handle_interrupt" do
+  def make_handle_interrupt_thread(interrupt_config, blocking = true)
+    interrupt_class = Class.new(RuntimeError)
+
+    ScratchPad.record []
+
+    in_handle_interrupt = Queue.new
+    can_continue = Queue.new
+
+    thread = Thread.new do
+      begin
+        Thread.handle_interrupt(interrupt_config) do
+          begin
+            in_handle_interrupt << true
+            if blocking
+              Thread.pass # Make it clearer the other thread needs to wait for this one to be in #pop
+              can_continue.pop
+            else
+              begin
+                can_continue.pop(true)
+              rescue ThreadError
+                Thread.pass
+                retry
+              end
+            end
+          rescue interrupt_class
+            ScratchPad << :interrupted
+          end
+        end
+      rescue interrupt_class
+        ScratchPad << :deferred
+      end
+    end
+
+    in_handle_interrupt.pop
+    if blocking
+      # Ensure the thread is inside Thread#pop, as if thread.raise is done before it would be deferred
+      Thread.pass until thread.stop?
+    end
+    thread.raise interrupt_class, "interrupt"
+    can_continue << true
+    thread.join
+
+    ScratchPad.recorded
+  end
+
+  before :each do
+    Thread.pending_interrupt?.should == false # sanity check
+  end
+
+  it "with :never defers interrupts until exiting the handle_interrupt block" do
+    make_handle_interrupt_thread(RuntimeError => :never).should == [:deferred]
+  end
+
+  it "with :on_blocking defers interrupts until the next blocking call" do
+    make_handle_interrupt_thread(RuntimeError => :on_blocking).should == [:interrupted]
+    make_handle_interrupt_thread({ RuntimeError => :on_blocking }, false).should == [:deferred]
+  end
+
+  it "with :immediate handles interrupts immediately" do
+    make_handle_interrupt_thread(RuntimeError => :immediate).should == [:interrupted]
+  end
+
+  it "with :immediate immediately runs pending interrupts, before the block" do
+    Thread.handle_interrupt(RuntimeError => :never) do
+      current = Thread.current
+      Thread.new {
+        current.raise "interrupt immediate"
+      }.join
+
+      Thread.pending_interrupt?.should == true
+      -> {
+        Thread.handle_interrupt(RuntimeError => :immediate) {
+          flunk "not reached"
+        }
+      }.should raise_error(RuntimeError, "interrupt immediate")
+      Thread.pending_interrupt?.should == false
+    end
+  end
+
+  it "also works with suspended Fibers and does not duplicate interrupts" do
+    fiber = Fiber.new { Fiber.yield }
+    fiber.resume
+
+    Thread.handle_interrupt(RuntimeError => :never) do
+      current = Thread.current
+      Thread.new {
+        current.raise "interrupt with fibers"
+      }.join
+
+      Thread.pending_interrupt?.should == true
+      -> {
+        Thread.handle_interrupt(RuntimeError => :immediate) {
+          flunk "not reached"
+        }
+      }.should raise_error(RuntimeError, "interrupt with fibers")
+      Thread.pending_interrupt?.should == false
+    end
+
+    fiber.resume
+  end
+
+  it "runs pending interrupts at the end of the block, even if there was an exception raised in the block" do
+    executed = false
+    -> {
+      Thread.handle_interrupt(RuntimeError => :never) do
+        current = Thread.current
+        Thread.new {
+          current.raise "interrupt exception"
+        }.join
+
+        Thread.pending_interrupt?.should == true
+        executed = true
+        raise "regular exception"
+      end
+    }.should raise_error(RuntimeError, "interrupt exception")
+    executed.should == true
+  end
+
+  it "supports multiple pairs in the Hash" do
+    make_handle_interrupt_thread(ArgumentError => :never, RuntimeError => :never).should == [:deferred]
+  end
+end
diff --git a/spec/ruby/core/thread/ignore_deadlock_spec.rb b/spec/ruby/core/thread/ignore_deadlock_spec.rb
new file mode 100644
index 0000000000..b48bc9f9b0
--- /dev/null
+++ b/spec/ruby/core/thread/ignore_deadlock_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+describe "Thread.ignore_deadlock" do
+  it "returns false by default" do
+    Thread.ignore_deadlock.should == false
+  end
+end
+
+describe "Thread.ignore_deadlock=" do
+  it "changes the value of Thread.ignore_deadlock" do
+    ignore_deadlock = Thread.ignore_deadlock
+    Thread.ignore_deadlock = true
+    begin
+      Thread.ignore_deadlock.should == true
+    ensure
+      Thread.ignore_deadlock = ignore_deadlock
+    end
+  end
+end
diff --git a/spec/ruby/core/thread/inspect_spec.rb b/spec/ruby/core/thread/inspect_spec.rb
index 4c635b7aaa..bd6e0c31fc 100644
--- a/spec/ruby/core/thread/inspect_spec.rb
+++ b/spec/ruby/core/thread/inspect_spec.rb
@@ -1,44 +1,6 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
+require_relative 'shared/to_s'
 
 describe "Thread#inspect" do
-  it "can check it's own status" do
-    ThreadSpecs.status_of_current_thread.inspect.should include('run')
-  end
-
-  it "describes a running thread" do
-    ThreadSpecs.status_of_running_thread.inspect.should include('run')
-  end
-
-  it "describes a sleeping thread" do
-    ThreadSpecs.status_of_sleeping_thread.inspect.should include('sleep')
-  end
-
-  it "describes a blocked thread" do
-    ThreadSpecs.status_of_blocked_thread.inspect.should include('sleep')
-  end
-
-  it "describes a completed thread" do
-    ThreadSpecs.status_of_completed_thread.inspect.should include('dead')
-  end
-
-  it "describes a killed thread" do
-    ThreadSpecs.status_of_killed_thread.inspect.should include('dead')
-  end
-
-  it "describes a thread with an uncaught exception" do
-    ThreadSpecs.status_of_thread_with_uncaught_exception.inspect.should include('dead')
-  end
-
-  it "describes a dying sleeping thread" do
-    ThreadSpecs.status_of_dying_sleeping_thread.inspect.should include('sleep')
-  end
-
-  it "reports aborting on a killed thread" do
-    ThreadSpecs.status_of_dying_running_thread.inspect.should include('aborting')
-  end
-
-  it "reports aborting on a killed thread after sleep" do
-    ThreadSpecs.status_of_dying_thread_after_sleep.inspect.should include('aborting')
-  end
+  it_behaves_like :thread_to_s, :inspect
 end
diff --git a/spec/ruby/core/thread/join_spec.rb b/spec/ruby/core/thread/join_spec.rb
index f3c5cdc1ed..213fe2e505 100644
--- a/spec/ruby/core/thread/join_spec.rb
+++ b/spec/ruby/core/thread/join_spec.rb
@@ -19,6 +19,11 @@ describe "Thread#join" do
     t.join(0).should equal(t)
     t.join(0.0).should equal(t)
     t.join(nil).should equal(t)
+  end
+
+  it "raises TypeError if the argument is not a valid timeout" do
+    t = Thread.new { }
+    t.join
     -> { t.join(:foo) }.should raise_error TypeError
     -> { t.join("bar") }.should raise_error TypeError
   end
diff --git a/spec/ruby/core/thread/key_spec.rb b/spec/ruby/core/thread/key_spec.rb
index 6940cf5f28..339fa98f53 100644
--- a/spec/ruby/core/thread/key_spec.rb
+++ b/spec/ruby/core/thread/key_spec.rb
@@ -16,6 +16,13 @@ describe "Thread#key?" do
     @th.key?(:stanley.to_s).should == false
   end
 
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('key')
+    key.should_receive(:to_str).and_return('oliver')
+
+    @th.key?(key).should == true
+  end
+
   it "raises exceptions on the wrong type of keys" do
     -> { Thread.current.key? nil }.should raise_error(TypeError)
     -> { Thread.current.key? 5 }.should raise_error(TypeError)
diff --git a/spec/ruby/core/thread/kill_spec.rb b/spec/ruby/core/thread/kill_spec.rb
index f932bf5232..4b62c686c7 100644
--- a/spec/ruby/core/thread/kill_spec.rb
+++ b/spec/ruby/core/thread/kill_spec.rb
@@ -9,10 +9,6 @@ platform_is_not :mingw do
     it_behaves_like :thread_exit, :kill
   end
 
-  describe "Thread#kill!" do
-    it "needs to be reviewed for spec completeness"
-  end
-
   describe "Thread.kill" do
     it "causes the given thread to exit" do
       thread = Thread.new { sleep }
diff --git a/spec/ruby/core/thread/list_spec.rb b/spec/ruby/core/thread/list_spec.rb
index a0bf831856..3c6f70c13e 100644
--- a/spec/ruby/core/thread/list_spec.rb
+++ b/spec/ruby/core/thread/list_spec.rb
@@ -43,11 +43,11 @@ describe "Thread.list" do
       end
     end
 
-    while spawner.alive?
+    begin
       Thread.list.each { |th|
         th.should be_kind_of(Thread)
       }
-    end
+    end while spawner.alive?
 
     threads = spawner.value
     threads.each(&:join)
diff --git a/spec/ruby/core/thread/native_thread_id_spec.rb b/spec/ruby/core/thread/native_thread_id_spec.rb
new file mode 100644
index 0000000000..374cc59279
--- /dev/null
+++ b/spec/ruby/core/thread/native_thread_id_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../spec_helper'
+
+platform_is :linux, :darwin, :windows, :freebsd do
+  describe "Thread#native_thread_id" do
+    it "returns an integer when the thread is alive" do
+      Thread.current.native_thread_id.should be_kind_of(Integer)
+    end
+
+    it "returns nil when the thread is not running" do
+      t = Thread.new {}
+      t.join
+      t.native_thread_id.should == nil
+    end
+
+    it "each thread has different native thread id" do
+      t = Thread.new { sleep }
+      Thread.pass until t.stop?
+      main_thread_id = Thread.current.native_thread_id
+      t_thread_id = t.native_thread_id
+
+      if ruby_version_is "3.3"
+        # native_thread_id can be nil on a M:N scheduler
+        t_thread_id.should be_kind_of(Integer) if t_thread_id != nil
+      else
+        t_thread_id.should be_kind_of(Integer)
+      end
+
+      main_thread_id.should_not == t_thread_id
+
+      t.run
+      t.join
+      t.native_thread_id.should == nil
+    end
+  end
+end
diff --git a/spec/ruby/core/thread/new_spec.rb b/spec/ruby/core/thread/new_spec.rb
index 3a57149381..47a836201c 100644
--- a/spec/ruby/core/thread/new_spec.rb
+++ b/spec/ruby/core/thread/new_spec.rb
@@ -58,13 +58,13 @@ describe "Thread.new" do
     m2 = Mutex.new
     t = Thread.new {
       m1.lock
-      m1.locked?.should == true
+      m1.should.locked?
       m2.lock
-      m2.locked?.should == true
+      m2.should.locked?
     }
     t.join
-    m1.locked?.should == false
-    m2.locked?.should == false
+    m1.should_not.locked?
+    m2.should_not.locked?
   end
 
   it "releases Mutexes held by the Thread when the Thread finishes, also with Mutex#synchronize" do
@@ -75,9 +75,9 @@ describe "Thread.new" do
         m.lock
       }
       m.lock
-      m.locked?.should == true
+      m.should.locked?
     }
     t.join
-    m.locked?.should == false
+    m.should_not.locked?
   end
 end
diff --git a/spec/ruby/core/thread/pending_interrupt_spec.rb b/spec/ruby/core/thread/pending_interrupt_spec.rb
new file mode 100644
index 0000000000..cd565d92a4
--- /dev/null
+++ b/spec/ruby/core/thread/pending_interrupt_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../spec_helper'
+
+describe "Thread.pending_interrupt?" do
+  it "returns false if there are no pending interrupts, e.g., outside any Thread.handle_interrupt block" do
+    Thread.pending_interrupt?.should == false
+  end
+
+  it "returns true if there are pending interrupts, e.g., Thread#raise inside Thread.handle_interrupt" do
+    executed = false
+    -> {
+      Thread.handle_interrupt(RuntimeError => :never) do
+        Thread.pending_interrupt?.should == false
+
+        current = Thread.current
+        Thread.new {
+          current.raise "interrupt"
+        }.join
+
+        Thread.pending_interrupt?.should == true
+        executed = true
+      end
+    }.should raise_error(RuntimeError, "interrupt")
+    executed.should == true
+    Thread.pending_interrupt?.should == false
+  end
+end
+
+describe "Thread#pending_interrupt?" do
+  it "returns whether the given threads has pending interrupts" do
+    Thread.current.pending_interrupt?.should == false
+  end
+end
diff --git a/spec/ruby/core/thread/raise_spec.rb b/spec/ruby/core/thread/raise_spec.rb
index 38571854ef..b473eabd42 100644
--- a/spec/ruby/core/thread/raise_spec.rb
+++ b/spec/ruby/core/thread/raise_spec.rb
@@ -3,6 +3,9 @@ require_relative 'fixtures/classes'
 require_relative '../../shared/kernel/raise'
 
 describe "Thread#raise" do
+  it_behaves_like :kernel_raise, :raise, ThreadSpecs::NewThreadToRaise
+  it_behaves_like :kernel_raise_across_contexts, :raise, ThreadSpecs::NewThreadToRaise
+
   it "ignores dead threads and returns nil" do
     t = Thread.new { :dead }
     Thread.pass while t.alive?
@@ -102,6 +105,30 @@ describe "Thread#raise on a sleeping thread" do
       raised_again.backtrace.first.should_not include("#{__FILE__}:#{raise_again_line}:")
     end
   end
+
+  it "calls #exception in both the caller and in the target thread" do
+    cls = Class.new(Exception) do
+      attr_accessor :log
+      def initialize(*args)
+        @log = [] # This is shared because the super #exception uses a shallow clone
+        super
+      end
+
+      def exception(*args)
+        @log << [self, Thread.current, args]
+        super
+      end
+    end
+    exc = cls.new
+
+    @thr.raise exc, "Thread#raise #exception spec"
+    @thr.join
+    ScratchPad.recorded.should.is_a?(cls)
+    exc.log.should == [
+      [exc, Thread.current, ["Thread#raise #exception spec"]],
+      [ScratchPad.recorded, @thr, []]
+    ]
+  end
 end
 
 describe "Thread#raise on a running thread" do
@@ -138,11 +165,14 @@ describe "Thread#raise on a running thread" do
   end
 
   it "can go unhandled" do
+    q = Queue.new
     t = Thread.new do
       Thread.current.report_on_exception = false
+      q << true
       loop { Thread.pass }
     end
 
+    q.pop # wait for `report_on_exception = false`.
     t.raise
     -> { t.value }.should raise_error(RuntimeError)
   end
@@ -200,6 +230,6 @@ describe "Thread#raise on same thread" do
         Thread.current.raise
       end
     end
-    -> { t.value }.should raise_error(RuntimeError)
+    -> { t.value }.should raise_error(RuntimeError, '')
   end
 end
diff --git a/spec/ruby/core/thread/report_on_exception_spec.rb b/spec/ruby/core/thread/report_on_exception_spec.rb
index a6042ba759..d9daa041cd 100644
--- a/spec/ruby/core/thread/report_on_exception_spec.rb
+++ b/spec/ruby/core/thread/report_on_exception_spec.rb
@@ -1,16 +1,8 @@
 require_relative '../../spec_helper'
 
 describe "Thread.report_on_exception" do
-  ruby_version_is "2.4"..."2.5" do
-    it "defaults to false" do
-      ruby_exe("p Thread.report_on_exception").should == "false\n"
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "defaults to true" do
-      ruby_exe("p Thread.report_on_exception").should == "true\n"
-    end
+  it "defaults to true" do
+    ruby_exe("p Thread.report_on_exception").should == "true\n"
   end
 end
 
@@ -33,14 +25,12 @@ describe "Thread.report_on_exception=" do
 end
 
 describe "Thread#report_on_exception" do
-  ruby_version_is "2.5" do
-    it "returns true for the main Thread" do
-      Thread.current.report_on_exception.should == true
-    end
+  it "returns true for the main Thread" do
+    Thread.current.report_on_exception.should == true
+  end
 
-    it "returns true for new Threads" do
-      Thread.new { Thread.current.report_on_exception }.value.should == true
-    end
+  it "returns true for new Threads" do
+    Thread.new { Thread.current.report_on_exception }.value.should == true
   end
 
   it "returns whether the Thread will print a backtrace if it exits with an exception" do
@@ -70,6 +60,55 @@ describe "Thread#report_on_exception=" do
         t.join
       }.should raise_error(RuntimeError, "Thread#report_on_exception specs")
     end
+
+    it "prints a backtrace on $stderr in the regular backtrace order" do
+      line_raise = __LINE__ + 2
+      def foo
+        raise RuntimeError, "Thread#report_on_exception specs backtrace order"
+      end
+
+      line_call_foo = __LINE__ + 5
+      go = false
+      t = Thread.new {
+        Thread.current.report_on_exception = true
+        Thread.pass until go
+        foo
+      }
+
+      -> {
+        go = true
+        Thread.pass while t.alive?
+      }.should output("", /\A
+#{Regexp.quote(t.inspect)}\sterminated\swith\sexception\s\(report_on_exception\sis\strue\):\n
+#{Regexp.quote(__FILE__)}:#{line_raise}:in\s[`']foo':\sThread\#report_on_exception\sspecs\sbacktrace\sorder\s\(RuntimeError\)\n
+\tfrom\s#{Regexp.quote(__FILE__)}:#{line_call_foo}:in\s[`']block\s\(4\slevels\)\sin\s<top\s\(required\)>'\n
+\z/x)
+
+      -> {
+        t.join
+      }.should raise_error(RuntimeError, "Thread#report_on_exception specs backtrace order")
+    end
+
+    it "prints the backtrace even if the thread was killed just after Thread#raise" do
+      t = nil
+      ready = false
+      -> {
+        t = Thread.new {
+          Thread.current.report_on_exception = true
+          ready = true
+          sleep
+        }
+
+        Thread.pass until ready and t.stop?
+        t.raise RuntimeError, "Thread#report_on_exception before kill spec"
+        t.kill
+        Thread.pass while t.alive?
+      }.should output("", /Thread.+terminated with exception.+Thread#report_on_exception before kill spec/m)
+
+      -> {
+        t.join
+      }.should raise_error(RuntimeError, "Thread#report_on_exception before kill spec")
+    end
   end
 
   describe "when set to false" do
diff --git a/spec/ruby/core/thread/shared/exit.rb b/spec/ruby/core/thread/shared/exit.rb
index 40dc478947..13e8832684 100644
--- a/spec/ruby/core/thread/shared/exit.rb
+++ b/spec/ruby/core/thread/shared/exit.rb
@@ -66,6 +66,26 @@ describe :thread_exit, shared: true do
     ScratchPad.recorded.should == nil
   end
 
+  it "does not reset $!" do
+    ScratchPad.record []
+
+    exc = RuntimeError.new("foo")
+    thread = Thread.new do
+      begin
+        raise exc
+      ensure
+        ScratchPad << $!
+        begin
+          Thread.current.send(@method)
+        ensure
+          ScratchPad << $!
+        end
+      end
+    end
+    thread.join
+    ScratchPad.recorded.should == [exc, exc]
+  end
+
   it "cannot be rescued" do
     thread = Thread.new do
       begin
@@ -73,7 +93,7 @@ describe :thread_exit, shared: true do
       rescue Exception
         ScratchPad.record :in_rescue
       end
-     ScratchPad.record :end_of_thread_block
+      ScratchPad.record :end_of_thread_block
     end
 
     thread.join
@@ -93,6 +113,25 @@ describe :thread_exit, shared: true do
     ScratchPad.recorded.should == nil
   end
 
+  it "kills other fibers of that thread without running their ensure clauses" do
+    t = Thread.new do
+      f = Fiber.new do
+        ScratchPad.record :fiber_resumed
+        begin
+          Fiber.yield
+        ensure
+          ScratchPad.record :fiber_ensure
+        end
+      end
+      f.resume
+      sleep
+    end
+    Thread.pass until t.stop?
+    t.send(@method)
+    t.join
+    ScratchPad.recorded.should == :fiber_resumed
+  end
+
   # This spec is a mess. It fails randomly, it hangs on MRI, it needs to be removed
   quarantine! do
   it "killing dying running does nothing" do
diff --git a/spec/ruby/core/thread/shared/to_s.rb b/spec/ruby/core/thread/shared/to_s.rb
new file mode 100644
index 0000000000..43640deb33
--- /dev/null
+++ b/spec/ruby/core/thread/shared/to_s.rb
@@ -0,0 +1,53 @@
+require_relative '../fixtures/classes'
+
+describe :thread_to_s, shared: true do
+  it "returns a description including file and line number" do
+    thread, line = Thread.new { "hello" }, __LINE__
+    thread.join
+    thread.send(@method).should =~ /^#<Thread:([^ ]*?) #{Regexp.escape __FILE__}:#{line} \w+>$/
+  end
+
+  it "has a binary encoding" do
+    ThreadSpecs.status_of_current_thread.send(@method).encoding.should == Encoding::BINARY
+  end
+
+  it "can check it's own status" do
+    ThreadSpecs.status_of_current_thread.send(@method).should include('run')
+  end
+
+  it "describes a running thread" do
+    ThreadSpecs.status_of_running_thread.send(@method).should include('run')
+  end
+
+  it "describes a sleeping thread" do
+    ThreadSpecs.status_of_sleeping_thread.send(@method).should include('sleep')
+  end
+
+  it "describes a blocked thread" do
+    ThreadSpecs.status_of_blocked_thread.send(@method).should include('sleep')
+  end
+
+  it "describes a completed thread" do
+    ThreadSpecs.status_of_completed_thread.send(@method).should include('dead')
+  end
+
+  it "describes a killed thread" do
+    ThreadSpecs.status_of_killed_thread.send(@method).should include('dead')
+  end
+
+  it "describes a thread with an uncaught exception" do
+    ThreadSpecs.status_of_thread_with_uncaught_exception.send(@method).should include('dead')
+  end
+
+  it "describes a dying sleeping thread" do
+    ThreadSpecs.status_of_dying_sleeping_thread.send(@method).should include('sleep')
+  end
+
+  it "reports aborting on a killed thread" do
+    ThreadSpecs.status_of_dying_running_thread.send(@method).should include('aborting')
+  end
+
+  it "reports aborting on a killed thread after sleep" do
+    ThreadSpecs.status_of_dying_thread_after_sleep.send(@method).should include('aborting')
+  end
+end
diff --git a/spec/ruby/core/thread/shared/wakeup.rb b/spec/ruby/core/thread/shared/wakeup.rb
index f111edf0fd..6f010fea25 100644
--- a/spec/ruby/core/thread/shared/wakeup.rb
+++ b/spec/ruby/core/thread/shared/wakeup.rb
@@ -36,7 +36,7 @@ describe :thread_wakeup, shared: true do
 
   it "does not result in a deadlock" do
     t = Thread.new do
-      100.times { Thread.stop }
+      10.times { Thread.stop }
     end
 
     while t.status
@@ -47,6 +47,7 @@ describe :thread_wakeup, shared: true do
         t.status.should == false
       end
       Thread.pass
+      sleep 0.001
     end
 
     t.status.should == false
diff --git a/spec/ruby/core/thread/stop_spec.rb b/spec/ruby/core/thread/stop_spec.rb
index 33cf8f7b5c..084ab46ef6 100644
--- a/spec/ruby/core/thread/stop_spec.rb
+++ b/spec/ruby/core/thread/stop_spec.rb
@@ -13,42 +13,42 @@ end
 
 describe "Thread#stop?" do
   it "can check it's own status" do
-    ThreadSpecs.status_of_current_thread.stop?.should == false
+    ThreadSpecs.status_of_current_thread.should_not.stop?
   end
 
   it "describes a running thread" do
-    ThreadSpecs.status_of_running_thread.stop?.should == false
+    ThreadSpecs.status_of_running_thread.should_not.stop?
   end
 
   it "describes a sleeping thread" do
-    ThreadSpecs.status_of_sleeping_thread.stop?.should == true
+    ThreadSpecs.status_of_sleeping_thread.should.stop?
   end
 
   it "describes a blocked thread" do
-    ThreadSpecs.status_of_blocked_thread.stop?.should == true
+    ThreadSpecs.status_of_blocked_thread.should.stop?
   end
 
   it "describes a completed thread" do
-    ThreadSpecs.status_of_completed_thread.stop?.should == true
+    ThreadSpecs.status_of_completed_thread.should.stop?
   end
 
   it "describes a killed thread" do
-    ThreadSpecs.status_of_killed_thread.stop?.should == true
+    ThreadSpecs.status_of_killed_thread.should.stop?
   end
 
   it "describes a thread with an uncaught exception" do
-    ThreadSpecs.status_of_thread_with_uncaught_exception.stop?.should == true
+    ThreadSpecs.status_of_thread_with_uncaught_exception.should.stop?
   end
 
   it "describes a dying running thread" do
-    ThreadSpecs.status_of_dying_running_thread.stop?.should == false
+    ThreadSpecs.status_of_dying_running_thread.should_not.stop?
   end
 
   it "describes a dying sleeping thread" do
-    ThreadSpecs.status_of_dying_sleeping_thread.stop?.should == true
+    ThreadSpecs.status_of_dying_sleeping_thread.should.stop?
   end
 
   it "describes a dying thread after sleep" do
-    ThreadSpecs.status_of_dying_thread_after_sleep.stop?.should == false
+    ThreadSpecs.status_of_dying_thread_after_sleep.should_not.stop?
   end
 end
diff --git a/spec/ruby/core/thread/thread_variable_get_spec.rb b/spec/ruby/core/thread/thread_variable_get_spec.rb
index 38f90d5830..1ea34cf2b3 100644
--- a/spec/ruby/core/thread/thread_variable_get_spec.rb
+++ b/spec/ruby/core/thread/thread_variable_get_spec.rb
@@ -13,13 +13,48 @@ describe "Thread#thread_variable_get" do
     @t.thread_variable_get(:a).should be_nil
   end
 
-  it "returns the value previously set by #[]=" do
-    @t.thread_variable_set :a, 49
+  it "returns the value previously set by #thread_variable_set" do
+    @t.thread_variable_set(:a, 49)
     @t.thread_variable_get(:a).should == 49
   end
 
   it "returns a value private to self" do
-    @t.thread_variable_set :thread_variable_get_spec, 82
+    @t.thread_variable_set(:thread_variable_get_spec, 82)
     Thread.current.thread_variable_get(:thread_variable_get_spec).should be_nil
   end
+
+  it "accepts String and Symbol keys interchangeably" do
+    @t.thread_variable_set("a", 49)
+    @t.thread_variable_get("a").should == 49
+    @t.thread_variable_get(:a).should == 49
+  end
+
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('key')
+    key.should_receive(:to_str).and_return('a')
+    @t.thread_variable_set(:a, 49)
+    @t.thread_variable_get(key).should == 49
+  end
+
+  it "does not raise FrozenError if the thread is frozen" do
+    @t.freeze
+    @t.thread_variable_get(:a).should be_nil
+  end
+
+  it "raises a TypeError if the key is neither Symbol nor String when thread variables are already set" do
+    @t.thread_variable_set(:a, 49)
+    -> { @t.thread_variable_get(123) }.should raise_error(TypeError, /123 is not a symbol/)
+  end
+
+  ruby_version_is '3.4' do
+    it "raises a TypeError if the key is neither Symbol nor String when no thread variables are set" do
+      -> { @t.thread_variable_get(123) }.should raise_error(TypeError, /123 is not a symbol/)
+    end
+
+    it "raises a TypeError if the key is neither Symbol nor String without calling #to_sym" do
+      key = mock('key')
+      key.should_not_receive(:to_sym)
+      -> { @t.thread_variable_get(key) }.should raise_error(TypeError, /#{Regexp.escape(key.inspect)} is not a symbol/)
+    end
+  end
 end
diff --git a/spec/ruby/core/thread/thread_variable_set_spec.rb b/spec/ruby/core/thread/thread_variable_set_spec.rb
index 1338c306c7..eadee76afb 100644
--- a/spec/ruby/core/thread/thread_variable_set_spec.rb
+++ b/spec/ruby/core/thread/thread_variable_set_spec.rb
@@ -10,17 +10,53 @@ describe "Thread#thread_variable_set" do
   end
 
   it "returns the value set" do
-    (@t.thread_variable_set :a, 2).should == 2
+    @t.thread_variable_set(:a, 2).should == 2
   end
 
   it "sets a value that will be returned by #thread_variable_get" do
-    @t.thread_variable_set :a, 49
+    @t.thread_variable_set(:a, 49)
     @t.thread_variable_get(:a).should == 49
   end
 
   it "sets a value private to self" do
-    @t.thread_variable_set :thread_variable_get_spec, 82
+    @t.thread_variable_set(:thread_variable_get_spec, 82)
     @t.thread_variable_get(:thread_variable_get_spec).should == 82
     Thread.current.thread_variable_get(:thread_variable_get_spec).should be_nil
   end
+
+  it "accepts String and Symbol keys interchangeably" do
+    @t.thread_variable_set('a', 49)
+    @t.thread_variable_get('a').should == 49
+
+    @t.thread_variable_set(:a, 50)
+    @t.thread_variable_get('a').should == 50
+  end
+
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('key')
+    key.should_receive(:to_str).and_return('a')
+    @t.thread_variable_set(key, 49)
+    @t.thread_variable_get(:a).should == 49
+  end
+
+  it "removes a key if the value is nil" do
+    @t.thread_variable_set(:a, 52)
+    @t.thread_variable_set(:a, nil)
+    @t.thread_variable?(:a).should be_false
+  end
+
+  it "raises a FrozenError if the thread is frozen" do
+    @t.freeze
+    -> { @t.thread_variable_set(:a, 1) }.should raise_error(FrozenError, "can't modify frozen thread locals")
+  end
+
+  it "raises a TypeError if the key is neither Symbol nor String, nor responds to #to_str" do
+    -> { @t.thread_variable_set(123, 1) }.should raise_error(TypeError, /123 is not a symbol/)
+  end
+
+  it "does not try to convert the key with #to_sym" do
+    key = mock('key')
+    key.should_not_receive(:to_sym)
+    -> { @t.thread_variable_set(key, 42) }.should raise_error(TypeError, /#{Regexp.quote(key.inspect)} is not a symbol/)
+  end
 end
diff --git a/spec/ruby/core/thread/thread_variable_spec.rb b/spec/ruby/core/thread/thread_variable_spec.rb
index 6bd1950c04..1b021e9404 100644
--- a/spec/ruby/core/thread/thread_variable_spec.rb
+++ b/spec/ruby/core/thread/thread_variable_spec.rb
@@ -10,12 +10,51 @@ describe "Thread#thread_variable?" do
   end
 
   it "returns false if the thread variables do not contain 'key'" do
-    @t.thread_variable_set :a, 2
+    @t.thread_variable_set(:a, 2)
     @t.thread_variable?(:b).should be_false
   end
 
   it "returns true if the thread variables contain 'key'" do
-    @t.thread_variable_set :a, 2
+    @t.thread_variable_set(:a, 2)
     @t.thread_variable?(:a).should be_true
   end
+
+  it "accepts String and Symbol keys interchangeably" do
+    @t.thread_variable?('a').should be_false
+    @t.thread_variable?(:a).should be_false
+
+    @t.thread_variable_set(:a, 49)
+
+    @t.thread_variable?('a').should be_true
+    @t.thread_variable?(:a).should be_true
+  end
+
+  it "converts a key that is neither String nor Symbol with #to_str" do
+    key = mock('key')
+    key.should_receive(:to_str).and_return('a')
+    @t.thread_variable_set(:a, 49)
+    @t.thread_variable?(key).should be_true
+  end
+
+  it "does not raise FrozenError if the thread is frozen" do
+    @t.freeze
+    @t.thread_variable?(:a).should be_false
+  end
+
+  it "raises a TypeError if the key is neither Symbol nor String when thread variables are already set" do
+    @t.thread_variable_set(:a, 49)
+    -> { @t.thread_variable?(123) }.should raise_error(TypeError, /123 is not a symbol/)
+  end
+
+  ruby_version_is '3.4' do
+    it "raises a TypeError if the key is neither Symbol nor String when no thread variables are set" do
+      -> { @t.thread_variable?(123) }.should raise_error(TypeError, /123 is not a symbol/)
+    end
+
+    it "raises a TypeError if the key is neither Symbol nor String without calling #to_sym" do
+      key = mock('key')
+      key.should_not_receive(:to_sym)
+      -> { @t.thread_variable?(key) }.should raise_error(TypeError, /#{Regexp.escape(key.inspect)} is not a symbol/)
+    end
+  end
 end
diff --git a/spec/ruby/core/thread/thread_variables_spec.rb b/spec/ruby/core/thread/thread_variables_spec.rb
index 1bd68b17f1..51ceef3376 100644
--- a/spec/ruby/core/thread/thread_variables_spec.rb
+++ b/spec/ruby/core/thread/thread_variables_spec.rb
@@ -10,15 +10,15 @@ describe "Thread#thread_variables" do
   end
 
   it "returns the keys of all the values set" do
-    @t.thread_variable_set :a, 2
-    @t.thread_variable_set :b, 4
-    @t.thread_variable_set :c, 6
+    @t.thread_variable_set(:a, 2)
+    @t.thread_variable_set(:b, 4)
+    @t.thread_variable_set(:c, 6)
     @t.thread_variables.sort.should == [:a, :b, :c]
   end
 
-  it "sets a value private to self" do
-    @t.thread_variable_set :a, 82
-    @t.thread_variable_set :b, 82
+  it "returns the keys private to self" do
+    @t.thread_variable_set(:a, 82)
+    @t.thread_variable_set(:b, 82)
     Thread.current.thread_variables.should_not include(:a, :b)
   end
 
@@ -26,4 +26,14 @@ describe "Thread#thread_variables" do
     Thread.current.thread_variables.should == []
     @t.thread_variables.should == []
   end
+
+  it "returns keys as Symbols" do
+    key = mock('key')
+    key.should_receive(:to_str).and_return('a')
+
+    @t.thread_variable_set(key, 49)
+    @t.thread_variable_set('b', 50)
+    @t.thread_variable_set(:c, 51)
+    @t.thread_variables.sort.should == [:a, :b, :c]
+  end
 end
diff --git a/spec/ruby/core/thread/to_s_spec.rb b/spec/ruby/core/thread/to_s_spec.rb
new file mode 100644
index 0000000000..cb182a017f
--- /dev/null
+++ b/spec/ruby/core/thread/to_s_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/to_s'
+
+describe "Thread#to_s" do
+  it_behaves_like :thread_to_s, :to_s
+end
diff --git a/spec/ruby/core/time/_dump_spec.rb b/spec/ruby/core/time/_dump_spec.rb
index 6941a1531f..852f9a07ab 100644
--- a/spec/ruby/core/time/_dump_spec.rb
+++ b/spec/ruby/core/time/_dump_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 
 describe "Time#_dump" do
@@ -15,11 +15,11 @@ describe "Time#_dump" do
 
   # http://redmine.ruby-lang.org/issues/show/627
   it "preserves the GMT flag" do
-    @t.gmt?.should == true
+    @t.should.gmt?
     dump = @t.send(:_dump).unpack("VV").first
     ((dump >> 30) & 0x1).should == 1
 
-    @local.gmt?.should == false
+    @local.should_not.gmt?
     dump = @local.send(:_dump).unpack("VV").first
     ((dump >> 30) & 0x1).should == 0
   end
diff --git a/spec/ruby/core/time/_load_spec.rb b/spec/ruby/core/time/_load_spec.rb
index 152934370f..30899de262 100644
--- a/spec/ruby/core/time/_load_spec.rb
+++ b/spec/ruby/core/time/_load_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 
 describe "Time._load" do
@@ -44,8 +44,7 @@ describe "Time._load" do
   end
 
   it "treats the data as binary data" do
-    data = "\x04\bu:\tTime\r\fM\x1C\xC0\x00\x00\xD0\xBE"
-    data.force_encoding Encoding::UTF_8
+    data = "\x04\bu:\tTime\r\fM\x1C\xC0\x00\x00\xD0\xBE".dup.force_encoding Encoding::UTF_8
     t = Marshal.load(data)
     t.to_s.should == "2013-04-08 12:47:45 UTC"
   end
diff --git a/spec/ruby/core/time/at_spec.rb b/spec/ruby/core/time/at_spec.rb
index 8434e8dd16..97906b8c8c 100644
--- a/spec/ruby/core/time/at_spec.rb
+++ b/spec/ruby/core/time/at_spec.rb
@@ -14,7 +14,7 @@ describe "Time.at" do
     end
 
     it "returns a non-UTC Time" do
-      Time.at(1184027924).utc?.should == false
+      Time.at(1184027924).should_not.utc?
     end
 
     it "returns a subclass instance on a Time subclass" do
@@ -32,10 +32,17 @@ describe "Time.at" do
       t2.nsec.should == t.nsec
     end
 
-    describe "passed BigDecimal" do
-      it "doesn't round input value" do
-        require 'bigdecimal'
-        Time.at(BigDecimal('1.1')).to_f.should == 1.1
+    describe "passed Rational" do
+      it "returns Time with correct microseconds" do
+        t = Time.at(Rational(1_486_570_508_539_759, 1_000_000))
+        t.usec.should == 539_759
+        t.nsec.should == 539_759_000
+      end
+
+      it "returns Time with correct nanoseconds" do
+        t = Time.at(Rational(1_486_570_508_539_759_123, 1_000_000_000))
+        t.usec.should == 539_759
+        t.nsec.should == 539_759_123
       end
     end
   end
@@ -54,12 +61,12 @@ describe "Time.at" do
 
     it "returns a UTC time if the argument is UTC" do
       t = Time.now.getgm
-      Time.at(t).utc?.should == true
+      Time.at(t).should.utc?
     end
 
     it "returns a non-UTC time if the argument is non-UTC" do
       t = Time.now
-      Time.at(t).utc?.should == false
+      Time.at(t).should_not.utc?
     end
 
     it "returns a subclass instance" do
@@ -92,6 +99,12 @@ describe "Time.at" do
         o.should_receive(:to_r).and_return(Rational(5, 2))
         Time.at(o).should == Time.at(Rational(5, 2))
       end
+
+      it "needs for the argument to respond to #to_int too" do
+        o = mock('rational-but-no-to_int')
+        def o.to_r; Rational(5, 2) end
+        -> { Time.at(o) }.should raise_error(TypeError, "can't convert MockObject into an exact number")
+      end
     end
   end
 
@@ -144,110 +157,159 @@ describe "Time.at" do
     end
   end
 
-  ruby_version_is "2.5" do
-    describe "passed [Time, Numeric, format]" do
-      context ":nanosecond format" do
-        it "traits second argument as nanoseconds" do
-          Time.at(0, 123456789, :nanosecond).nsec.should == 123456789
-        end
+  describe "passed [Time, Numeric, format]" do
+    context ":nanosecond format" do
+      it "treats second argument as nanoseconds" do
+        Time.at(0, 123456789, :nanosecond).nsec.should == 123456789
       end
+    end
 
-      context ":nsec format" do
-        it "traits second argument as nanoseconds" do
-          Time.at(0, 123456789, :nsec).nsec.should == 123456789
-        end
+    context ":nsec format" do
+      it "treats second argument as nanoseconds" do
+        Time.at(0, 123456789, :nsec).nsec.should == 123456789
       end
+    end
 
-      context ":microsecond format" do
-        it "traits second argument as microseconds" do
-          Time.at(0, 123456, :microsecond).nsec.should == 123456000
-        end
+    context ":microsecond format" do
+      it "treats second argument as microseconds" do
+        Time.at(0, 123456, :microsecond).nsec.should == 123456000
       end
+    end
 
-      context ":usec format" do
-        it "traits second argument as microseconds" do
-          Time.at(0, 123456, :usec).nsec.should == 123456000
-        end
+    context ":usec format" do
+      it "treats second argument as microseconds" do
+        Time.at(0, 123456, :usec).nsec.should == 123456000
       end
+    end
 
-      context ":millisecond format" do
-        it "traits second argument as milliseconds" do
-          Time.at(0, 123, :millisecond).nsec.should == 123000000
-        end
+    context ":millisecond format" do
+      it "treats second argument as milliseconds" do
+        Time.at(0, 123, :millisecond).nsec.should == 123000000
       end
+    end
 
-      context "not supported format" do
-        it "raises ArgumentError" do
-          -> { Time.at(0, 123456, 2) }.should raise_error(ArgumentError)
-          -> { Time.at(0, 123456, nil) }.should raise_error(ArgumentError)
-          -> { Time.at(0, 123456, :invalid) }.should raise_error(ArgumentError)
-        end
-
-        it "does not try to convert format to Symbol with #to_sym" do
-          format = "usec"
-          format.should_not_receive(:to_sym)
-          -> { Time.at(0, 123456, format) }.should raise_error(ArgumentError)
-        end
+    context "not supported format" do
+      it "raises ArgumentError" do
+        -> { Time.at(0, 123456, 2) }.should raise_error(ArgumentError)
+        -> { Time.at(0, 123456, nil) }.should raise_error(ArgumentError)
+        -> { Time.at(0, 123456, :invalid) }.should raise_error(ArgumentError)
       end
 
-      it "supports Float second argument" do
-        Time.at(0, 123456789.500, :nanosecond).nsec.should == 123456789
-        Time.at(0, 123456789.500, :nsec).nsec.should == 123456789
-        Time.at(0, 123456.500, :microsecond).nsec.should == 123456500
-        Time.at(0, 123456.500, :usec).nsec.should == 123456500
-        Time.at(0, 123.500, :millisecond).nsec.should == 123500000
+      it "does not try to convert format to Symbol with #to_sym" do
+        format = +"usec"
+        format.should_not_receive(:to_sym)
+        -> { Time.at(0, 123456, format) }.should raise_error(ArgumentError)
       end
     end
+
+    it "supports Float second argument" do
+      Time.at(0, 123456789.500, :nanosecond).nsec.should == 123456789
+      Time.at(0, 123456789.500, :nsec).nsec.should == 123456789
+      Time.at(0, 123456.500, :microsecond).nsec.should == 123456500
+      Time.at(0, 123456.500, :usec).nsec.should == 123456500
+      Time.at(0, 123.500, :millisecond).nsec.should == 123500000
+    end
   end
 
-  ruby_version_is "2.6" do
-    describe ":in keyword argument" do
-      before do
-        @epoch_time = Time.now.to_i
-      end
+  describe ":in keyword argument" do
+    before do
+      @epoch_time = Time.now.to_i
+    end
 
-      it "could be UTC offset as a String in '+HH:MM or '-HH:MM' format" do
-        time = Time.at(@epoch_time, in: "+05:00")
+    it "could be UTC offset as a String in '+HH:MM or '-HH:MM' format" do
+      time = Time.at(@epoch_time, in: "+05:00")
 
-        time.utc_offset.should == 5*60*60
-        time.zone.should == nil
-        time.to_i.should == @epoch_time
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
 
-        time = Time.at(@epoch_time, in: "-09:00")
+      time = Time.at(@epoch_time, in: "-09:00")
 
-        time.utc_offset.should == -9*60*60
-        time.zone.should == nil
-        time.to_i.should == @epoch_time
-      end
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
 
-      it "could be UTC offset as a number of seconds" do
-        time = Time.at(@epoch_time, in: 5*60*60)
+      time = Time.at(@epoch_time, in: "-09:00:01")
 
-        time.utc_offset.should == 5*60*60
-        time.zone.should == nil
-        time.to_i.should == @epoch_time
+      time.utc_offset.should == -(9*60*60 + 1)
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
+    end
 
-        time = Time.at(@epoch_time, in: -9*60*60)
+    it "could be UTC offset as a number of seconds" do
+      time = Time.at(@epoch_time, in: 5*60*60)
 
-        time.utc_offset.should == -9*60*60
-        time.zone.should == nil
-        time.to_i.should == @epoch_time
-      end
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
+
+      time = Time.at(@epoch_time, in: -9*60*60)
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
+    end
+
+    it "could be UTC offset as a 'UTC' String" do
+      time = Time.at(@epoch_time, in: "UTC")
+
+      time.utc_offset.should == 0
+      time.zone.should == "UTC"
+      time.to_i.should == @epoch_time
+    end
+
+    it "could be UTC offset as a military zone A-Z" do
+      time = Time.at(@epoch_time, in: "B")
+
+      time.utc_offset.should == 3600 * 2
+      time.zone.should == nil
+      time.to_i.should == @epoch_time
+    end
+
+    it "could be a timezone object" do
+      zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
+      time = Time.at(@epoch_time, in: zone)
+
+      time.utc_offset.should == 5*3600+30*60
+      time.zone.should == zone
+      time.to_i.should == @epoch_time
 
-      it "could be a timezone object" do
-        zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
-        time = Time.at(@epoch_time, in: zone)
+      zone = TimeSpecs::TimezoneWithName.new(name: "PST")
+      time = Time.at(@epoch_time, in: zone)
 
-        time.utc_offset.should == 5*3600+30*60
-        time.zone.should == zone
-        time.to_i.should == @epoch_time
+      time.utc_offset.should == -9*60*60
+      time.zone.should == zone
+      time.to_i.should == @epoch_time
+    end
+
+    it "raises ArgumentError if format is invalid" do
+      -> { Time.at(@epoch_time, in: "+09:99") }.should raise_error(ArgumentError)
+      -> { Time.at(@epoch_time, in: "ABC") }.should raise_error(ArgumentError)
+    end
+
+    it "raises ArgumentError if hours greater than 23" do # TODO
+      -> { Time.at(@epoch_time, in: "+24:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.at(@epoch_time, in: "+2400") }.should raise_error(ArgumentError, "utc_offset out of range")
+
+      -> { Time.at(@epoch_time, in: "+99:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.at(@epoch_time, in: "+9900") }.should raise_error(ArgumentError, "utc_offset out of range")
+    end
+
+    it "raises ArgumentError if minutes greater than 59" do # TODO
+      -> { Time.at(@epoch_time, in: "+00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:60')
+      -> { Time.at(@epoch_time, in: "+0060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0060')
+
+      -> { Time.at(@epoch_time, in: "+00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:99')
+      -> { Time.at(@epoch_time, in: "+0099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0099')
+    end
 
-        zone = TimeSpecs::TimezoneWithName.new(name: "PST")
-        time = Time.at(@epoch_time, in: zone)
+    ruby_bug '#20797', ''...'3.4' do
+      it "raises ArgumentError if seconds greater than 59" do
+        -> { Time.at(@epoch_time, in: "+00:00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:60')
+        -> { Time.at(@epoch_time, in: "+000060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000060')
 
-        time.utc_offset.should == -9*60*60
-        time.zone.should == zone
-        time.to_i.should == @epoch_time
+        -> { Time.at(@epoch_time, in: "+00:00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:99')
+        -> { Time.at(@epoch_time, in: "+000099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000099')
       end
     end
   end
diff --git a/spec/ruby/core/time/ceil_spec.rb b/spec/ruby/core/time/ceil_spec.rb
index 29dcec5d72..9d624a1ed0 100644
--- a/spec/ruby/core/time/ceil_spec.rb
+++ b/spec/ruby/core/time/ceil_spec.rb
@@ -1,45 +1,44 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.7" do
-  describe "Time#ceil" do
-    before do
-      @time = Time.utc(2010, 3, 30, 5, 43, "25.0123456789".to_r)
-    end
+describe "Time#ceil" do
+  before do
+    @time = Time.utc(2010, 3, 30, 5, 43, "25.0123456789".to_r)
+  end
 
-    it "defaults to ceiling to 0 places" do
-      @time.ceil.should == Time.utc(2010, 3, 30, 5, 43, 26.to_r)
-    end
+  it "defaults to ceiling to 0 places" do
+    @time.ceil.should == Time.utc(2010, 3, 30, 5, 43, 26.to_r)
+  end
 
-    it "ceils to 0 decimal places with an explicit argument" do
-      @time.ceil(0).should == Time.utc(2010, 3, 30, 5, 43, 26.to_r)
-    end
+  it "ceils to 0 decimal places with an explicit argument" do
+    @time.ceil(0).should == Time.utc(2010, 3, 30, 5, 43, 26.to_r)
+  end
 
-    it "ceils to 2 decimal places with an explicit argument" do
-      @time.ceil(2).should == Time.utc(2010, 3, 30, 5, 43, "25.02".to_r)
-    end
+  it "ceils to 2 decimal places with an explicit argument" do
+    @time.ceil(2).should == Time.utc(2010, 3, 30, 5, 43, "25.02".to_r)
+  end
 
-    it "ceils to 4 decimal places with an explicit argument" do
-      @time.ceil(4).should == Time.utc(2010, 3, 30, 5, 43, "25.0124".to_r)
-    end
+  it "ceils to 4 decimal places with an explicit argument" do
+    @time.ceil(4).should == Time.utc(2010, 3, 30, 5, 43, "25.0124".to_r)
+  end
 
-    it "ceils to 7 decimal places with an explicit argument" do
-      @time.ceil(7).should == Time.utc(2010, 3, 30, 5, 43, "25.0123457".to_r)
-    end
+  it "ceils to 7 decimal places with an explicit argument" do
+    @time.ceil(7).should == Time.utc(2010, 3, 30, 5, 43, "25.0123457".to_r)
+  end
 
-    it "returns an instance of Time, even if #ceil is called on a subclass" do
-      subclass = Class.new(Time)
-      instance = subclass.at(0)
-      instance.class.should equal subclass
-      instance.ceil.should be_an_instance_of(Time)
-    end
+  it "returns an instance of Time, even if #ceil is called on a subclass" do
+    subclass = Class.new(Time)
+    instance = subclass.at(0)
+    instance.class.should equal subclass
+    instance.ceil.should be_an_instance_of(Time)
+  end
 
-    it "copies own timezone to the returning value" do
-      @time.zone.should == @time.ceil.zone
+  it "copies own timezone to the returning value" do
+    @time.zone.should == @time.ceil.zone
 
-      with_timezone "JST-9" do
-        time = Time.at 0, 1
-        time.zone.should == time.ceil.zone
-      end
+    time = with_timezone "JST-9" do
+      Time.at 0, 1
     end
+
+    time.zone.should == time.ceil.zone
   end
 end
diff --git a/spec/ruby/core/time/comparison_spec.rb b/spec/ruby/core/time/comparison_spec.rb
index 5b53c9fb50..866fbea72e 100644
--- a/spec/ruby/core/time/comparison_spec.rb
+++ b/spec/ruby/core/time/comparison_spec.rb
@@ -55,6 +55,32 @@ describe "Time#<=>" do
     }.should_not complain
   end
 
+  context "given different timezones" do
+    it "returns 0 if time is the same as other" do
+      # three timezones, all at the same timestamp
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_cet = Time.new(2000, 1, 1, 1, 0, 0, '+01:00')
+      time_brt = Time.new(1999, 12, 31, 21, 0, 0, '-03:00')
+      (time_utc <=> time_cet).should == 0
+      (time_utc <=> time_brt).should == 0
+      (time_cet <=> time_brt).should == 0
+    end
+
+    it "returns -1 if the first argument is before the second argument" do
+      # time_brt is later, even though the date is earlier
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_brt = Time.new(1999, 12, 31, 23, 0, 0, '-03:00')
+      (time_utc <=> time_brt).should == -1
+    end
+
+    it "returns 1 if the first argument is before the second argument" do
+      # time_brt is later, even though the date is earlier
+      time_utc = Time.new(2000, 1, 1, 0, 0, 0, 0)
+      time_brt = Time.new(1999, 12, 31, 23, 0, 0, '-03:00')
+      (time_brt <=> time_utc).should == 1
+    end
+  end
+
   describe "given a non-Time argument" do
     it "returns nil if argument <=> self returns nil" do
       t = Time.now
diff --git a/spec/ruby/core/time/deconstruct_keys_spec.rb b/spec/ruby/core/time/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..b5cfdaa93f
--- /dev/null
+++ b/spec/ruby/core/time/deconstruct_keys_spec.rb
@@ -0,0 +1,43 @@
+require_relative '../../spec_helper'
+
+describe "Time#deconstruct_keys" do
+  it "returns whole hash for nil as an argument" do
+    d = Time.utc(2022, 10, 5, 13, 30)
+    res = { year: 2022, month: 10, day: 5, yday: 278, wday: 3, hour: 13,
+            min: 30, sec: 0, subsec: 0, dst: false, zone: "UTC" }
+    d.deconstruct_keys(nil).should == res
+  end
+
+  it "returns only specified keys" do
+    d = Time.utc(2022, 10, 5, 13, 39)
+    d.deconstruct_keys([:zone, :subsec]).should == { zone: "UTC", subsec: 0 }
+  end
+
+  it "requires one argument" do
+    -> {
+      Time.new(2022, 10, 5, 13, 30).deconstruct_keys
+    }.should raise_error(ArgumentError)
+  end
+
+  it "it raises error when argument is neither nil nor array" do
+    d = Time.new(2022, 10, 5, 13, 30)
+
+    -> { d.deconstruct_keys(1) }.should raise_error(TypeError, "wrong argument type Integer (expected Array or nil)")
+    -> { d.deconstruct_keys("asd") }.should raise_error(TypeError, "wrong argument type String (expected Array or nil)")
+    -> { d.deconstruct_keys(:x) }.should raise_error(TypeError, "wrong argument type Symbol (expected Array or nil)")
+    -> { d.deconstruct_keys({}) }.should raise_error(TypeError, "wrong argument type Hash (expected Array or nil)")
+  end
+
+  it "returns {} when passed []" do
+    Time.new(2022, 10, 5, 13, 30).deconstruct_keys([]).should == {}
+  end
+
+  it "ignores non-Symbol keys" do
+    Time.new(2022, 10, 5, 13, 30).deconstruct_keys(['year', []]).should == {}
+  end
+
+  it "ignores not existing Symbol keys and processes keys after the first non-existing one" do
+    d = Time.utc(2022, 10, 5, 13, 30)
+    d.deconstruct_keys([:year, :a, :month, :b, :day]).should == { year: 2022, month: 10, day: 5 }
+  end
+end
diff --git a/spec/ruby/core/time/dup_spec.rb b/spec/ruby/core/time/dup_spec.rb
index ee2ff7dbba..5d6621beaa 100644
--- a/spec/ruby/core/time/dup_spec.rb
+++ b/spec/ruby/core/time/dup_spec.rb
@@ -7,7 +7,7 @@ describe "Time#dup" do
   end
 
   it "copies the gmt state flag" do
-    Time.now.gmtime.dup.gmt?.should == true
+    Time.now.gmtime.dup.should.gmt?
   end
 
   it "returns an independent Time object" do
@@ -15,7 +15,7 @@ describe "Time#dup" do
     t2 = t.dup
     t.gmtime
 
-    t2.gmt?.should == false
+    t2.should_not.gmt?
   end
 
   it "returns a subclass instance" do
diff --git a/spec/ruby/core/time/fixtures/classes.rb b/spec/ruby/core/time/fixtures/classes.rb
index 1a9511b261..21c4e1effb 100644
--- a/spec/ruby/core/time/fixtures/classes.rb
+++ b/spec/ruby/core/time/fixtures/classes.rb
@@ -59,7 +59,6 @@ module TimeSpecs
   Zone = Struct.new(:std, :dst, :dst_range)
   Zones = {
     "Asia/Colombo" => Zone[Z[5*3600+30*60, "MMT"], nil, nil],
-    "Europe/Kiev" => Zone[Z[2*3600, "EET"], Z[3*3600, "EEST"], 4..10],
     "PST" => Zone[Z[(-9*60*60), "PST"], nil, nil],
   }
 
diff --git a/spec/ruby/core/time/floor_spec.rb b/spec/ruby/core/time/floor_spec.rb
index 763ed1ba51..b0003469c9 100644
--- a/spec/ruby/core/time/floor_spec.rb
+++ b/spec/ruby/core/time/floor_spec.rb
@@ -1,37 +1,36 @@
 require_relative '../../spec_helper'
 
-ruby_version_is "2.7" do
-  describe "Time#floor" do
-    before do
-      @time = Time.utc(2010, 3, 30, 5, 43, "25.123456789".to_r)
-    end
+describe "Time#floor" do
+  before do
+    @time = Time.utc(2010, 3, 30, 5, 43, "25.123456789".to_r)
+  end
 
-    it "defaults to flooring to 0 places" do
-      @time.floor.should == Time.utc(2010, 3, 30, 5, 43, 25.to_r)
-    end
+  it "defaults to flooring to 0 places" do
+    @time.floor.should == Time.utc(2010, 3, 30, 5, 43, 25.to_r)
+  end
 
-    it "floors to 0 decimal places with an explicit argument" do
-      @time.floor(0).should == Time.utc(2010, 3, 30, 5, 43, 25.to_r)
-    end
+  it "floors to 0 decimal places with an explicit argument" do
+    @time.floor(0).should == Time.utc(2010, 3, 30, 5, 43, 25.to_r)
+  end
 
-    it "floors to 7 decimal places with an explicit argument" do
-      @time.floor(7).should == Time.utc(2010, 3, 30, 5, 43, "25.1234567".to_r)
-    end
+  it "floors to 7 decimal places with an explicit argument" do
+    @time.floor(7).should == Time.utc(2010, 3, 30, 5, 43, "25.1234567".to_r)
+  end
 
-    it "returns an instance of Time, even if #floor is called on a subclass" do
-      subclass = Class.new(Time)
-      instance = subclass.at(0)
-      instance.class.should equal subclass
-      instance.floor.should be_an_instance_of(Time)
-    end
+  it "returns an instance of Time, even if #floor is called on a subclass" do
+    subclass = Class.new(Time)
+    instance = subclass.at(0)
+    instance.class.should equal subclass
+    instance.floor.should be_an_instance_of(Time)
+  end
 
-    it "copies own timezone to the returning value" do
-      @time.zone.should == @time.floor.zone
+  it "copies own timezone to the returning value" do
+    @time.zone.should == @time.floor.zone
 
-      with_timezone "JST-9" do
-        time = Time.at 0, 1
-        time.zone.should == time.floor.zone
-      end
+    time = with_timezone "JST-9" do
+      Time.at 0, 1
     end
+
+    time.zone.should == time.floor.zone
   end
 end
diff --git a/spec/ruby/core/time/friday_spec.rb b/spec/ruby/core/time/friday_spec.rb
index 27f9e1dbe5..8bee7f7558 100644
--- a/spec/ruby/core/time/friday_spec.rb
+++ b/spec/ruby/core/time/friday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#friday?" do
   it "returns true if time represents Friday" do
-    Time.local(2000, 1, 7).friday?.should == true
+    Time.local(2000, 1, 7).should.friday?
   end
 
   it "returns false if time doesn't represent Friday" do
-    Time.local(2000, 1, 1).friday?.should == false
+    Time.local(2000, 1, 1).should_not.friday?
   end
 end
diff --git a/spec/ruby/core/time/getlocal_spec.rb b/spec/ruby/core/time/getlocal_spec.rb
index 7196577dab..398596f400 100644
--- a/spec/ruby/core/time/getlocal_spec.rb
+++ b/spec/ruby/core/time/getlocal_spec.rb
@@ -14,6 +14,7 @@ describe "Time#getlocal" do
     t = Time.gm(2007, 1, 9, 12, 0, 0).getlocal(3630)
     t.should == Time.new(2007, 1, 9, 13, 0, 30, 3630)
     t.utc_offset.should == 3630
+    t.zone.should be_nil
   end
 
   platform_is_not :windows do
@@ -59,12 +60,24 @@ describe "Time#getlocal" do
     t.utc_offset.should == 3600
   end
 
+  it "returns a Time with a UTC offset specified as +HH:MM:SS" do
+    t = Time.gm(2007, 1, 9, 12, 0, 0).getlocal("+01:00:01")
+    t.should == Time.new(2007, 1, 9, 13, 0, 1, 3601)
+    t.utc_offset.should == 3601
+  end
+
   it "returns a Time with a UTC offset specified as -HH:MM" do
     t = Time.gm(2007, 1, 9, 12, 0, 0).getlocal("-01:00")
     t.should == Time.new(2007, 1, 9, 11, 0, 0, -3600)
     t.utc_offset.should == -3600
   end
 
+  it "returns a Time with a UTC offset specified as -HH:MM:SS" do
+    t = Time.gm(2007, 1, 9, 12, 0, 0).getlocal("-01:00:01")
+    t.should == Time.new(2007, 1, 9, 10, 59, 59, -3601)
+    t.utc_offset.should == -3601
+  end
+
   describe "with an argument that responds to #to_str" do
     it "coerces using #to_str" do
       o = mock('string')
@@ -97,71 +110,95 @@ describe "Time#getlocal" do
     -> { t.getlocal(86400) }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is "2.6" do
-    describe "with a timezone argument" do
-      it "returns a Time in the timezone" do
-        zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-        time = Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone)
+  it "raises ArgumentError if String argument and hours greater than 23" do
+    -> { Time.now.getlocal("+24:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+    -> { Time.now.getlocal("+2400") }.should raise_error(ArgumentError, "utc_offset out of range")
 
-        time.zone.should == zone
-        time.utc_offset.should == 5*3600+30*60
-      end
+    -> { Time.now.getlocal("+99:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+    -> { Time.now.getlocal("+9900") }.should raise_error(ArgumentError, "utc_offset out of range")
+  end
 
-      it "accepts timezone argument that must have #local_to_utc and #utc_to_local methods" do
-        zone = Object.new
-        def zone.utc_to_local(time)
-          time
-        end
-        def zone.local_to_utc(time)
-          time
-        end
+  it "raises ArgumentError if String argument and minutes greater than 59" do
+    -> { Time.now.getlocal("+00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:60')
+    -> { Time.now.getlocal("+0060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0060')
+
+    -> { Time.now.getlocal("+00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:99')
+    -> { Time.now.getlocal("+0099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0099')
+  end
+
+  ruby_bug '#20797', ''...'3.4' do
+    it "raises ArgumentError if String argument and seconds greater than 59" do
+      -> { Time.now.getlocal("+00:00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:60')
+      -> { Time.now.getlocal("+000060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000060')
+
+      -> { Time.now.getlocal("+00:00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:99')
+      -> { Time.now.getlocal("+000099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000099')
+    end
+  end
+
+  describe "with a timezone argument" do
+    it "returns a Time in the timezone" do
+      zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
+      time = Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone)
+
+      time.zone.should == zone
+      time.utc_offset.should == 5*3600+30*60
+    end
 
-        -> {
-          Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone).should be_kind_of(Time)
-        }.should_not raise_error
+    it "accepts timezone argument that must have #local_to_utc and #utc_to_local methods" do
+      zone = Object.new
+      def zone.utc_to_local(time)
+        time
+      end
+      def zone.local_to_utc(time)
+        time
       end
 
-      it "raises TypeError if timezone does not implement #utc_to_local method" do
-        zone = Object.new
-        def zone.local_to_utc(time)
-          time
-        end
+      -> {
+        Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone).should be_kind_of(Time)
+      }.should_not raise_error
+    end
 
-        -> {
-          Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone)
-        }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
+    it "raises TypeError if timezone does not implement #utc_to_local method" do
+      zone = Object.new
+      def zone.local_to_utc(time)
+        time
       end
 
-      it "does not raise exception if timezone does not implement #local_to_utc method" do
-        zone = Object.new
-        def zone.utc_to_local(time)
-          time
-        end
+      -> {
+        Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone)
+      }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
+    end
 
-        -> {
-          Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone).should be_kind_of(Time)
-        }.should_not raise_error
+    it "does not raise exception if timezone does not implement #local_to_utc method" do
+      zone = Object.new
+      def zone.utc_to_local(time)
+        time
       end
 
-      context "subject's class implements .find_timezone method" do
-        it "calls .find_timezone to build a time object if passed zone name as a timezone argument" do
-          time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0).getlocal("Asia/Colombo")
-          time.zone.should be_kind_of TimeSpecs::TimezoneWithName
-          time.zone.name.should == "Asia/Colombo"
+      -> {
+        Time.utc(2000, 1, 1, 12, 0, 0).getlocal(zone).should be_kind_of(Time)
+      }.should_not raise_error
+    end
+
+    context "subject's class implements .find_timezone method" do
+      it "calls .find_timezone to build a time object if passed zone name as a timezone argument" do
+        time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0).getlocal("Asia/Colombo")
+        time.zone.should be_kind_of TimeSpecs::TimezoneWithName
+        time.zone.name.should == "Asia/Colombo"
 
-          time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0).getlocal("some invalid zone name")
-          time.zone.should be_kind_of TimeSpecs::TimezoneWithName
-          time.zone.name.should == "some invalid zone name"
-        end
+        time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0).getlocal("some invalid zone name")
+        time.zone.should be_kind_of TimeSpecs::TimezoneWithName
+        time.zone.name.should == "some invalid zone name"
+      end
 
-        it "does not call .find_timezone if passed any not string/numeric/timezone timezone argument" do
-          [Object.new, [], {}, :"some zone"].each do |zone|
-            time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0)
+      it "does not call .find_timezone if passed any not string/numeric/timezone timezone argument" do
+        [Object.new, [], {}, :"some zone"].each do |zone|
+          time = TimeSpecs::TimeWithFindTimezone.utc(2000, 1, 1, 12, 0, 0)
 
-            -> {
-              time.getlocal(zone)
-            }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
-          end
+          -> {
+            time.getlocal(zone)
+          }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
         end
       end
     end
diff --git a/spec/ruby/core/time/gmt_spec.rb b/spec/ruby/core/time/gmt_spec.rb
index 7e85749d5b..840f59e0e8 100644
--- a/spec/ruby/core/time/gmt_spec.rb
+++ b/spec/ruby/core/time/gmt_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 
 describe "Time#gmt?" do
   it "returns true if time represents a time in UTC (GMT)" do
-    Time.now.gmt?.should == false
-    Time.now.gmtime.gmt?.should == true
+    Time.now.should_not.gmt?
+    Time.now.gmtime.should.gmt?
   end
 end
diff --git a/spec/ruby/core/time/hash_spec.rb b/spec/ruby/core/time/hash_spec.rb
index 577aaf9b0a..4f4d11a2cd 100644
--- a/spec/ruby/core/time/hash_spec.rb
+++ b/spec/ruby/core/time/hash_spec.rb
@@ -1,8 +1,8 @@
 require_relative '../../spec_helper'
 
 describe "Time#hash" do
-  it "returns a Fixnum" do
-    Time.at(100).hash.should be_an_instance_of(Fixnum)
+  it "returns an Integer" do
+    Time.at(100).hash.should be_an_instance_of(Integer)
   end
 
   it "is stable" do
diff --git a/spec/ruby/core/time/inspect_spec.rb b/spec/ruby/core/time/inspect_spec.rb
index 01e1dfdaa6..c3a4519a24 100644
--- a/spec/ruby/core/time/inspect_spec.rb
+++ b/spec/ruby/core/time/inspect_spec.rb
@@ -3,4 +3,31 @@ require_relative 'shared/inspect'
 
 describe "Time#inspect" do
   it_behaves_like :inspect, :inspect
+
+  it "preserves microseconds" do
+    t = Time.utc(2007, 11, 1, 15, 25, 0, 123456)
+    t.inspect.should == "2007-11-01 15:25:00.123456 UTC"
+  end
+
+  it "omits trailing zeros from microseconds" do
+    t = Time.utc(2007, 11, 1, 15, 25, 0, 100000)
+    t.inspect.should == "2007-11-01 15:25:00.1 UTC"
+  end
+
+  it "uses the correct time zone without microseconds" do
+    t = Time.utc(2000, 1, 1)
+    t = t.localtime(9*3600)
+    t.inspect.should == "2000-01-01 09:00:00 +0900"
+  end
+
+  it "uses the correct time zone with microseconds" do
+    t = Time.utc(2000, 1, 1, 0, 0, 0, 123456)
+    t = t.localtime(9*3600)
+    t.inspect.should == "2000-01-01 09:00:00.123456 +0900"
+  end
+
+  it "preserves nanoseconds" do
+    t = Time.utc(2007, 11, 1, 15, 25, 0, 123456.789r)
+    t.inspect.should == "2007-11-01 15:25:00.123456789 UTC"
+  end
 end
diff --git a/spec/ruby/core/time/iso8601_spec.rb b/spec/ruby/core/time/iso8601_spec.rb
new file mode 100644
index 0000000000..ad60c3bb32
--- /dev/null
+++ b/spec/ruby/core/time/iso8601_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/xmlschema'
+
+describe "Time#iso8601" do
+  it_behaves_like :time_xmlschema, :iso8601
+end
diff --git a/spec/ruby/core/time/localtime_spec.rb b/spec/ruby/core/time/localtime_spec.rb
index 2975e112d0..71c0dfebde 100644
--- a/spec/ruby/core/time/localtime_spec.rb
+++ b/spec/ruby/core/time/localtime_spec.rb
@@ -29,10 +29,10 @@ describe "Time#localtime" do
       time.localtime.should equal(time)
     end
 
-    it "raises a RuntimeError if the time has a different time zone" do
+    it "raises a FrozenError if the time has a different time zone" do
       time = Time.gm(2007, 1, 9, 12, 0, 0)
       time.freeze
-      -> { time.localtime }.should raise_error(RuntimeError)
+      -> { time.localtime }.should raise_error(FrozenError)
     end
   end
 
@@ -72,6 +72,13 @@ describe "Time#localtime" do
     t.utc_offset.should == 3600
   end
 
+  it "returns a Time with a UTC offset specified as +HH:MM:SS" do
+    t = Time.gm(2007, 1, 9, 12, 0, 0)
+    t.localtime("+01:00:01")
+    t.should == Time.new(2007, 1, 9, 13, 0, 1, 3601)
+    t.utc_offset.should == 3601
+  end
+
   it "returns a Time with a UTC offset specified as -HH:MM" do
     t = Time.gm(2007, 1, 9, 12, 0, 0)
     t.localtime("-01:00")
@@ -79,6 +86,51 @@ describe "Time#localtime" do
     t.utc_offset.should == -3600
   end
 
+  it "returns a Time with a UTC offset specified as -HH:MM:SS" do
+    t = Time.gm(2007, 1, 9, 12, 0, 0)
+    t.localtime("-01:00:01")
+    t.should == Time.new(2007, 1, 9, 10, 59, 59, -3601)
+    t.utc_offset.should == -3601
+  end
+
+  it "returns a Time with a UTC offset specified as UTC" do
+    t = Time.new(2007, 1, 9, 12, 0, 0, 3600)
+    t.localtime("UTC")
+    t.utc_offset.should == 0
+  end
+
+  it "returns a Time with a UTC offset specified as A-Z military zone" do
+    t = Time.new(2007, 1, 9, 12, 0, 0, 3600)
+    t.localtime("B")
+    t.utc_offset.should == 3600 * 2
+  end
+
+  it "raises ArgumentError if String argument and hours greater than 23" do
+    -> { Time.now.localtime("+24:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+    -> { Time.now.localtime("+2400") }.should raise_error(ArgumentError, "utc_offset out of range")
+
+    -> { Time.now.localtime("+99:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+    -> { Time.now.localtime("+9900") }.should raise_error(ArgumentError, "utc_offset out of range")
+  end
+
+  it "raises ArgumentError if String argument and minutes greater than 59" do
+    -> { Time.now.localtime("+00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:60')
+    -> { Time.now.localtime("+0060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0060')
+
+    -> { Time.now.localtime("+00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:99')
+    -> { Time.now.localtime("+0099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0099')
+  end
+
+  ruby_bug '#20797', ''...'3.4' do
+    it "raises ArgumentError if String argument and seconds greater than 59" do
+      -> { Time.now.localtime("+00:00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:60')
+      -> { Time.now.localtime("+000060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000060')
+
+      -> { Time.now.localtime("+00:00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:99')
+      -> { Time.now.localtime("+000099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000099')
+    end
+  end
+
   platform_is_not :windows do
     it "changes the timezone according to the set one" do
       t = Time.new(2005, 2, 27, 22, 50, 0, -3600)
@@ -116,6 +168,17 @@ describe "Time#localtime" do
     end
   end
 
+  describe "with an argument that responds to #utc_to_local" do
+    it "coerces using #utc_to_local" do
+      o = mock('string')
+      o.should_receive(:utc_to_local).and_return(Time.new(2007, 1, 9, 13, 0, 0, 3600))
+      t = Time.gm(2007, 1, 9, 12, 0, 0)
+      t.localtime(o)
+      t.should == Time.new(2007, 1, 9, 13, 0, 0, 3600)
+      t.utc_offset.should == 3600
+    end
+  end
+
   it "raises ArgumentError if the String argument is not of the form (+|-)HH:MM" do
     t = Time.now
     -> { t.localtime("3600") }.should raise_error(ArgumentError)
diff --git a/spec/ruby/core/time/minus_spec.rb b/spec/ruby/core/time/minus_spec.rb
index e0fbf94cb0..9182d99652 100644
--- a/spec/ruby/core/time/minus_spec.rb
+++ b/spec/ruby/core/time/minus_spec.rb
@@ -79,11 +79,11 @@ describe "Time#-" do
   end
 
   it "returns a UTC time if self is UTC" do
-    (Time.utc(2012) - 10).utc?.should == true
+    (Time.utc(2012) - 10).should.utc?
   end
 
   it "returns a non-UTC time if self is non-UTC" do
-    (Time.local(2012) - 10).utc?.should == false
+    (Time.local(2012) - 10).should_not.utc?
   end
 
   it "returns a time with the same fixed offset as self" do
@@ -92,26 +92,24 @@ describe "Time#-" do
 
   it "preserves time zone" do
     time_with_zone = Time.now.utc
-    time_with_zone.zone.should == (time_with_zone - 60*60).zone
+    time_with_zone.zone.should == (time_with_zone - 1).zone
 
     time_with_zone = Time.now
-    time_with_zone.zone.should == (time_with_zone - 60*60).zone
+    time_with_zone.zone.should == (time_with_zone - 1).zone
   end
 
-  ruby_version_is "2.6" do
-    context "zone is a timezone object" do
-      it "preserves time zone" do
-        zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-        time = Time.new(2012, 1, 1, 12, 0, 0, zone) - 60*60
+  context "zone is a timezone object" do
+    it "preserves time zone" do
+      zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
+      time = Time.new(2012, 1, 1, 12, 0, 0, zone) - 1
 
-        time.zone.should == zone
-      end
+      time.zone.should == zone
     end
   end
 
   it "does not return a subclass instance" do
     c = Class.new(Time)
-    x = c.now + 1
+    x = c.now - 1
     x.should be_an_instance_of(Time)
   end
 
diff --git a/spec/ruby/core/time/monday_spec.rb b/spec/ruby/core/time/monday_spec.rb
index c5c43a5c3e..47ecaeb1db 100644
--- a/spec/ruby/core/time/monday_spec.rb
+++ b/spec/ruby/core/time/monday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#monday?" do
   it "returns true if time represents Monday" do
-    Time.local(2000, 1, 3).monday?.should == true
+    Time.local(2000, 1, 3).should.monday?
   end
 
   it "returns false if time doesn't represent Monday" do
-    Time.local(2000, 1, 1).monday?.should == false
+    Time.local(2000, 1, 1).should_not.monday?
   end
 end
diff --git a/spec/ruby/core/time/new_spec.rb b/spec/ruby/core/time/new_spec.rb
index dcdd83a085..dc3ccbdc00 100644
--- a/spec/ruby/core/time/new_spec.rb
+++ b/spec/ruby/core/time/new_spec.rb
@@ -15,7 +15,7 @@ end
 
 describe "Time.new with a utc_offset argument" do
   it "returns a non-UTC time" do
-    Time.new(2000, 1, 1, 0, 0, 0, 0).utc?.should == false
+    Time.new(2000, 1, 1, 0, 0, 0, 0).should_not.utc?
   end
 
   it "returns a Time with a UTC offset of the specified number of Integer seconds" do
@@ -58,6 +58,30 @@ describe "Time.new with a utc_offset argument" do
     Time.new(2000, 1, 1, 0, 0, 0, "-04:10:43").utc_offset.should == -15043
   end
 
+  it "returns a Time with a UTC offset specified as +HH" do
+    Time.new(2000, 1, 1, 0, 0, 0, "+05").utc_offset.should == 3600 * 5
+  end
+
+  it "returns a Time with a UTC offset specified as -HH" do
+    Time.new(2000, 1, 1, 0, 0, 0, "-05").utc_offset.should == -3600 * 5
+  end
+
+  it "returns a Time with a UTC offset specified as +HHMM" do
+    Time.new(2000, 1, 1, 0, 0, 0, "+0530").utc_offset.should == 19800
+  end
+
+  it "returns a Time with a UTC offset specified as -HHMM" do
+    Time.new(2000, 1, 1, 0, 0, 0, "-0530").utc_offset.should == -19800
+  end
+
+  it "returns a Time with a UTC offset specified as +HHMMSS" do
+    Time.new(2000, 1, 1, 0, 0, 0, "+053037").utc_offset.should == 19837
+  end
+
+  it "returns a Time with a UTC offset specified as -HHMMSS" do
+    Time.new(2000, 1, 1, 0, 0, 0, "-053037").utc_offset.should == -19837
+  end
+
   describe "with an argument that responds to #to_str" do
     it "coerces using #to_str" do
       o = mock('string')
@@ -66,6 +90,48 @@ describe "Time.new with a utc_offset argument" do
     end
   end
 
+  it "returns a Time with UTC offset specified as UTC" do
+    Time.new(2000, 1, 1, 0, 0, 0, "UTC").utc_offset.should == 0
+  end
+
+  it "returns a Time with UTC offset specified as a single letter military timezone" do
+    [
+      ["A", 3600],
+      ["B", 3600 * 2],
+      ["C", 3600 * 3],
+      ["D", 3600 * 4],
+      ["E", 3600 * 5],
+      ["F", 3600 * 6],
+      ["G", 3600 * 7],
+      ["H", 3600 * 8],
+      ["I", 3600 * 9],
+      # J is not supported
+      ["K", 3600 * 10],
+      ["L", 3600 * 11],
+      ["M", 3600 * 12],
+      ["N", 3600 * -1],
+      ["O", 3600 * -2],
+      ["P", 3600 * -3],
+      ["Q", 3600 * -4],
+      ["R", 3600 * -5],
+      ["S", 3600 * -6],
+      ["T", 3600 * -7],
+      ["U", 3600 * -8],
+      ["V", 3600 * -9],
+      ["W", 3600 * -10],
+      ["X", 3600 * -11],
+      ["Y", 3600 * -12],
+      ["Z", 0]
+    ].each do |letter, offset|
+      Time.new(2000, 1, 1, 0, 0, 0, letter).utc_offset.should == offset
+    end
+  end
+
+  it "raises ArgumentError if the string argument is J" do
+    message = '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: J'
+    -> { Time.new(2000, 1, 1, 0, 0, 0, "J") }.should raise_error(ArgumentError, message)
+  end
+
   it "returns a local Time if the argument is nil" do
     with_timezone("PST", -8) do
       t = Time.new(2000, 1, 1, 0, 0, 0, nil)
@@ -93,7 +159,12 @@ describe "Time.new with a utc_offset argument" do
   end
 
   it "raises ArgumentError if the String argument is not in an ASCII-compatible encoding" do
-    -> { Time.new(2000, 1, 1, 0, 0, 0, "-04:10".encode("UTF-16LE")) }.should raise_error(ArgumentError)
+    # Don't check exception message - it was changed in previous CRuby versions:
+    # - "string contains null byte"
+    # - '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset'
+    -> {
+      Time.new(2000, 1, 1, 0, 0, 0, "-04:10".encode("UTF-16LE"))
+    }.should raise_error(ArgumentError)
   end
 
   it "raises ArgumentError if the argument represents a value less than or equal to -86400 seconds" do
@@ -106,221 +177,576 @@ describe "Time.new with a utc_offset argument" do
     -> { Time.new(2000, 1, 1, 0, 0, 0, 86400) }.should raise_error(ArgumentError)
   end
 
-  it "raises ArgumentError if the seconds argument is negative" do
-    -> { Time.new(2000, 1, 1, 0, 0, -1) }.should raise_error(ArgumentError)
-  end
-
   it "raises ArgumentError if the utc_offset argument is greater than or equal to 10e9" do
     -> { Time.new(2000, 1, 1, 0, 0, 0, 1000000000) }.should raise_error(ArgumentError)
   end
 end
 
-ruby_version_is "2.6" do
-  describe "Time.new with a timezone argument" do
-    it "returns a Time in the timezone" do
-      zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-      time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+# The method #local_to_utc is tested only here because Time.new is the only method that calls #local_to_utc.
+describe "Time.new with a timezone argument" do
+  it "returns a Time in the timezone" do
+    zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
+    time = Time.new(2000, 1, 1, 12, 0, 0, zone)
 
-      time.zone.should == zone
-      time.utc_offset.should == 5*3600+30*60
+    time.zone.should == zone
+    time.utc_offset.should == 5*3600+30*60
+    time.wday.should == 6
+    time.yday.should == 1
+  end
+
+  it "accepts timezone argument that must have #local_to_utc and #utc_to_local methods" do
+    zone = Object.new
+    def zone.utc_to_local(time)
+      time
+    end
+    def zone.local_to_utc(time)
+      time
+    end
+
+    Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
+  end
+
+  it "raises TypeError if timezone does not implement #local_to_utc method" do
+    zone = Object.new
+    def zone.utc_to_local(time)
+      time
     end
 
-    it "accepts timezone argument that must have #local_to_utc and #utc_to_local methods" do
+    -> {
+      Time.new(2000, 1, 1, 12, 0, 0, zone)
+    }.should raise_error(TypeError, /can't convert Object into an exact number/)
+  end
+
+  it "does not raise exception if timezone does not implement #utc_to_local method" do
+    zone = Object.new
+    def zone.local_to_utc(time)
+      time
+    end
+
+    Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
+  end
+
+  # The result also should be a Time or Time-like object (not necessary to be the same class)
+  # or respond to #to_int method. The zone of the result is just ignored.
+  describe "returned value by #utc_to_local and #local_to_utc methods" do
+    it "could be Time instance" do
       zone = Object.new
-      def zone.utc_to_local(time)
-        time
+      def zone.local_to_utc(t)
+        time = Time.utc(t.year, t.mon, t.day, t.hour, t.min, t.sec)
+        time - 60 * 60 # - 1 hour
       end
-      def zone.local_to_utc(time)
-        time
+
+      Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
+    end
+
+    it "could be Time subclass instance" do
+      zone = Object.new
+      def zone.local_to_utc(t)
+        time = Time.utc(t.year, t.mon, t.day, t.hour, t.min, t.sec)
+        time -= 60 * 60 # - 1 hour
+        Class.new(Time).utc(time.year, time.mon, time.day, time.hour, t.min, t.sec)
       end
 
-      -> {
-        Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
-      }.should_not raise_error
+      Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
     end
 
-    it "raises TypeError if timezone does not implement #local_to_utc method" do
+    it "could be any object with #to_i method" do
       zone = Object.new
-      def zone.utc_to_local(time)
-        time
+      def zone.local_to_utc(time)
+        obj = Object.new
+        obj.singleton_class.define_method(:to_i) { time.to_i - 60*60 }
+        obj
       end
 
-      -> {
-        Time.new(2000, 1, 1, 12, 0, 0, zone)
-      }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
+      Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
     end
 
-    it "does not raise exception if timezone does not implement #utc_to_local method" do
+    it "could have any #zone and #utc_offset because they are ignored if it isn't an instance of Time" do
+      zone = Object.new
+      def zone.local_to_utc(time)
+        Struct.new(:to_i, :zone, :utc_offset).new(time.to_i, 'America/New_York', -5*60*60)
+      end
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 0
+
       zone = Object.new
       def zone.local_to_utc(time)
-        time
+        Struct.new(:to_i, :zone, :utc_offset).new(time.to_i, 'Asia/Tokyo', 9*60*60)
+      end
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 0
+    end
+
+    it "cannot have arbitrary #utc_offset if it is an instance of Time" do
+      zone = Object.new
+      def zone.local_to_utc(t)
+        Time.new(t.year, t.mon, t.mday, t.hour, t.min, t.sec, 9*60*60)
+      end
+      Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 9*60*60
+    end
+
+    it "raises ArgumentError if difference between argument and result is too large" do
+      zone = Object.new
+      def zone.local_to_utc(t)
+        Time.utc(t.year, t.mon, t.day + 1, t.hour, t.min, t.sec)
       end
 
       -> {
-        Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
-      }.should_not raise_error
+        Time.new(2000, 1, 1, 12, 0, 0, zone)
+      }.should raise_error(ArgumentError, "utc_offset out of range")
     end
+  end
 
-    # The result also should be a Time or Time-like object (not necessary to be the same class)
-    # The zone of the result is just ignored
-    describe "returned value by #utc_to_local and #local_to_utc methods" do
-      it "could be Time instance" do
-        zone = Object.new
-        def zone.local_to_utc(t)
-          Time.utc(t.year, t.mon, t.day, t.hour - 1, t.min, t.sec)
-        end
+  # https://github.com/ruby/ruby/blob/v2_6_0/time.c#L5330
+  #
+  # Time-like argument to these methods is similar to a Time object in UTC without sub-second;
+  # it has attribute readers for the parts, e.g. year, month, and so on, and epoch time readers, to_i
+  #
+  # The sub-second attributes are fixed as 0, and utc_offset, zone, isdst, and their aliases are same as a Time object in UTC
+  describe "Time-like argument of #utc_to_local and #local_to_utc methods" do
+    before do
+      @obj = TimeSpecs::TimeLikeArgumentRecorder.result
+      @obj.should_not == nil
+    end
 
-        -> {
-          Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
-          Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
-        }.should_not raise_error
+    it "implements subset of Time methods" do
+      # List only methods that are explicitly documented.
+      [
+        :year, :mon, :mday, :hour, :min, :sec, :to_i, :isdst
+      ].each do |name|
+        @obj.respond_to?(name).should == true
       end
+    end
+
+    it "has attribute values the same as a Time object in UTC" do
+      @obj.usec.should == 0
+      @obj.nsec.should == 0
+      @obj.subsec.should == 0
+      @obj.tv_usec.should == 0
+      @obj.tv_nsec.should == 0
+
+      @obj.utc_offset.should == 0
+      @obj.zone.should == "UTC"
+      @obj.isdst.should == Time.new.utc.isdst
+    end
+  end
+
+  context "#name method" do
+    it "uses the optional #name method for marshaling" do
+      zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
+      time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+      time_loaded = Marshal.load(Marshal.dump(time))
+
+      time_loaded.zone.should == "Asia/Colombo"
+      time_loaded.utc_offset.should == 5*3600+30*60
+    end
+
+    it "cannot marshal Time if #name method isn't implemented" do
+      zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
+      time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+
+      -> {
+        Marshal.dump(time)
+      }.should raise_error(NoMethodError, /undefined method [`']name' for/)
+    end
+  end
+
+  it "the #abbr method is used by '%Z' in #strftime" do
+    zone = TimeSpecs::TimezoneWithAbbr.new(name: "Asia/Colombo")
+    time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+
+    time.strftime("%Z").should == "MMT"
+  end
+
+  # At loading marshaled data, a timezone name will be converted to a timezone object
+  # by find_timezone class method, if the method is defined.
+  # Similarly, that class method will be called when a timezone argument does not have
+  # the necessary methods mentioned above.
+  context "subject's class implements .find_timezone method" do
+    it "calls .find_timezone to build a time object at loading marshaled data" do
+      zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
+      time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, zone)
+      time_loaded = Marshal.load(Marshal.dump(time))
+
+      time_loaded.zone.should be_kind_of TimeSpecs::TimezoneWithName
+      time_loaded.zone.name.should == "Asia/Colombo"
+      time_loaded.utc_offset.should == 5*3600+30*60
+    end
+
+    it "calls .find_timezone to build a time object if passed zone name as a timezone argument" do
+      time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, "Asia/Colombo")
+      time.zone.should be_kind_of TimeSpecs::TimezoneWithName
+      time.zone.name.should == "Asia/Colombo"
 
-      it "could be Time subclass instance" do
-        zone = Object.new
-        def zone.local_to_utc(t)
-          Class.new(Time).utc(t.year, t.mon, t.day, t.hour - 1, t.min, t.sec)
-        end
+      time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, "some invalid zone name")
+      time.zone.should be_kind_of TimeSpecs::TimezoneWithName
+      time.zone.name.should == "some invalid zone name"
+    end
 
+    it "does not call .find_timezone if passed any not string/numeric/timezone timezone argument" do
+      [Object.new, [], {}, :"some zone"].each do |zone|
         -> {
-          Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
-          Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
-        }.should_not raise_error
+          TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, zone)
+        }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
       end
+    end
+  end
+
+  describe ":in keyword argument" do
+    it "could be UTC offset as a String in '+HH:MM or '-HH:MM' format" do
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: "+05:00")
+
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: "-09:00")
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: "-09:00:01")
+
+      time.utc_offset.should == -(9*60*60 + 1)
+      time.zone.should == nil
+    end
+
+    it "could be UTC offset as a number of seconds" do
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: 5*60*60)
+
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: -9*60*60)
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+    end
+
+    it "returns a Time with UTC offset specified as a single letter military timezone" do
+      Time.new(2000, 1, 1, 0, 0, 0, in: "W").utc_offset.should == 3600 * -10
+    end
+
+    it "could be a timezone object" do
+      zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: zone)
+
+      time.utc_offset.should == 5*3600+30*60
+      time.zone.should == zone
+
+      zone = TimeSpecs::TimezoneWithName.new(name: "PST")
+      time = Time.new(2000, 1, 1, 12, 0, 0, in: zone)
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == zone
+    end
+
+    it "allows omitting minor arguments" do
+      Time.new(2000, 1, 1, 12, 1, 1, in: "+05:00").should == Time.new(2000, 1, 1, 12, 1, 1, "+05:00")
+      Time.new(2000, 1, 1, 12, 1, in: "+05:00").should == Time.new(2000, 1, 1, 12, 1, 0, "+05:00")
+      Time.new(2000, 1, 1, 12, in: "+05:00").should == Time.new(2000, 1, 1, 12, 0, 0, "+05:00")
+      Time.new(2000, 1, 1, in: "+05:00").should == Time.new(2000, 1, 1, 0, 0, 0, "+05:00")
+      Time.new(2000, 1, in: "+05:00").should == Time.new(2000, 1, 1, 0, 0, 0, "+05:00")
+      Time.new(2000, in: "+05:00").should == Time.new(2000, 1, 1, 0, 0, 0, "+05:00")
+      Time.new(in: "+05:00").should be_close(Time.now.getlocal("+05:00"), TIME_TOLERANCE)
+    end
+
+    it "converts to a provided timezone if all the positional arguments are omitted" do
+      Time.new(in: "+05:00").utc_offset.should == 5*3600
+    end
+
+    it "raises ArgumentError if format is invalid" do
+      -> { Time.new(2000, 1, 1, 12, 0, 0, in: "+09:99") }.should raise_error(ArgumentError)
+      -> { Time.new(2000, 1, 1, 12, 0, 0, in: "ABC") }.should raise_error(ArgumentError)
+    end
+
+    it "raises ArgumentError if two offset arguments are given" do
+      -> {
+        Time.new(2000, 1, 1, 12, 0, 0, "+05:00", in: "+05:00")
+      }.should raise_error(ArgumentError, "timezone argument given as positional and keyword arguments")
+    end
+  end
+
+  describe "Time.new with a String argument" do
+    it "parses an ISO-8601 like format" do
+      t = Time.utc(2020, 12, 24, 15, 56, 17)
+
+      Time.new("2020-12-24T15:56:17Z").should == t
+      Time.new("2020-12-25 00:56:17 +09:00").should == t
+      Time.new("2020-12-25 00:57:47 +09:01:30").should == t
+      Time.new("2020-12-25 00:56:17 +0900").should == t
+      Time.new("2020-12-25 00:57:47 +090130").should == t
+      Time.new("2020-12-25T00:56:17+09:00").should == t
+
+      Time.new("2020-12-25T00:56:17.123456+09:00").should == Time.utc(2020, 12, 24, 15, 56, 17, 123456)
+    end
+
+    it "accepts precision keyword argument and truncates specified digits of sub-second part" do
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00").subsec.should == 0.123456789r
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: nil).subsec.should == 0.123456789876r
+      Time.new("2021-12-25 00:00:00 +09:00", precision: 0).subsec.should == 0
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: -1).subsec.should == 0.123456789876r
+    end
+
+    it "returns Time in local timezone if not provided in the String argument" do
+      Time.new("2021-12-25 00:00:00").zone.should == Time.new(2021, 12, 25).zone
+      Time.new("2021-12-25 00:00:00").utc_offset.should == Time.new(2021, 12, 25).utc_offset
+    end
+
+    it "returns Time in timezone specified in the String argument" do
+      Time.new("2021-12-25 00:00:00 +05:00").to_s.should == "2021-12-25 00:00:00 +0500"
+    end
+
+    it "returns Time in timezone specified in the String argument even if the in keyword argument provided" do
+      Time.new("2021-12-25 00:00:00 +09:00", in: "-01:00").to_s.should == "2021-12-25 00:00:00 +0900"
+    end
 
-      it "could be any object with #to_i method" do
-        zone = Object.new
-        def zone.local_to_utc(time)
-          Struct.new(:to_i).new(time.to_i - 60*60)
-        end
+    it "returns Time in timezone specified with in keyword argument if timezone isn't provided in the String argument" do
+      Time.new("2021-12-25 00:00:00", in: "-01:00").to_s.should == "2021-12-25 00:00:00 -0100"
+    end
+
+    it "returns Time of Jan 1 for string with just year" do
+      Time.new("2021").should == Time.new(2021, 1, 1)
+      Time.new("2021").zone.should == Time.new(2021, 1, 1).zone
+      Time.new("2021").utc_offset.should == Time.new(2021, 1, 1).utc_offset
+    end
+
+    it "returns Time of Jan 1 for string with just year in timezone specified with in keyword argument" do
+      Time.new("2021", in: "+17:00").to_s.should == "2021-01-01 00:00:00 +1700"
+    end
+
+    it "converts precision keyword argument into Integer if is not nil" do
+      obj = Object.new
+      def obj.to_int; 3; end
+
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: 1.2).subsec.should == 0.1r
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: obj).subsec.should == 0.123r
+      Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: 3r).subsec.should == 0.123r
+    end
+
+    it "returns Time with correct subseconds when given seconds fraction is shorted than 6 digits" do
+      Time.new("2020-12-25T00:56:17.123 +09:00").nsec.should == 123000000
+      Time.new("2020-12-25T00:56:17.123 +09:00").usec.should == 123000
+      Time.new("2020-12-25T00:56:17.123 +09:00").subsec.should == 0.123
+    end
+
+    it "returns Time with correct subseconds when given seconds fraction is milliseconds" do
+      Time.new("2020-12-25T00:56:17.123456 +09:00").nsec.should == 123456000
+      Time.new("2020-12-25T00:56:17.123456 +09:00").usec.should == 123456
+      Time.new("2020-12-25T00:56:17.123456 +09:00").subsec.should == 0.123456
+    end
+
+    it "returns Time with correct subseconds when given seconds fraction is longer that 6 digits but shorted than 9 digits" do
+      Time.new("2020-12-25T00:56:17.12345678 +09:00").nsec.should == 123456780
+      Time.new("2020-12-25T00:56:17.12345678 +09:00").usec.should == 123456
+      Time.new("2020-12-25T00:56:17.12345678 +09:00").subsec.should == 0.12345678
+    end
 
+    it "returns Time with correct subseconds when given seconds fraction is nanoseconds" do
+      Time.new("2020-12-25T00:56:17.123456789 +09:00").nsec.should == 123456789
+      Time.new("2020-12-25T00:56:17.123456789 +09:00").usec.should == 123456
+      Time.new("2020-12-25T00:56:17.123456789 +09:00").subsec.should == 0.123456789
+    end
+
+    it "returns Time with correct subseconds when given seconds fraction is longer than 9 digits" do
+      Time.new("2020-12-25T00:56:17.123456789876 +09:00").nsec.should == 123456789
+      Time.new("2020-12-25T00:56:17.123456789876 +09:00").usec.should == 123456
+      Time.new("2020-12-25T00:56:17.123456789876 +09:00").subsec.should == 0.123456789
+    end
+
+    ruby_version_is ""..."3.3" do
+      it "raise TypeError is can't convert precision keyword argument into Integer" do
         -> {
-          Time.new(2000, 1, 1, 12, 0, 0, zone).should be_kind_of(Time)
-          Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 60*60
-        }.should_not raise_error
+          Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: "")
+        }.should raise_error(TypeError, "no implicit conversion from string")
       end
+    end
 
-      it "could have any #zone and #utc_offset because they are ignored" do
-        zone = Object.new
-        def zone.local_to_utc(time)
-          Struct.new(:to_i, :zone, :utc_offset).new(time.to_i, 'America/New_York', -5*60*60)
-        end
-        Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 0
-
-        zone = Object.new
-        def zone.local_to_utc(time)
-          Struct.new(:to_i, :zone, :utc_offset).new(time.to_i, 'Asia/Tokyo', 9*60*60)
-        end
-        Time.new(2000, 1, 1, 12, 0, 0, zone).utc_offset.should == 0
+    ruby_version_is "3.3" do
+      it "raise TypeError is can't convert precision keyword argument into Integer" do
+        -> {
+          Time.new("2021-12-25 00:00:00.123456789876 +09:00", precision: "")
+        }.should raise_error(TypeError, "no implicit conversion of String into Integer")
       end
+    end
 
-      it "leads to raising Argument error if difference between argument and result is too large" do
-        zone = Object.new
-        def zone.local_to_utc(t)
-          Time.utc(t.year, t.mon, t.day + 1, t.hour, t.min, t.sec)
-        end
+    it "raises ArgumentError if part of time string is missing" do
+      -> {
+        Time.new("2020-12-25 00:56 +09:00")
+      }.should raise_error(ArgumentError, /missing sec part: 00:56 |can't parse:/)
 
-        -> {
-          Time.new(2000, 1, 1, 12, 0, 0, zone)
-        }.should raise_error(ArgumentError, "utc_offset out of range")
-      end
+      -> {
+        Time.new("2020-12-25 00 +09:00")
+      }.should raise_error(ArgumentError, /missing min part: 00 |can't parse:/)
     end
 
-    # https://github.com/ruby/ruby/blob/v2_6_0/time.c#L5330
-    #
-    # Time-like argument to these methods is similar to a Time object in UTC without sub-second;
-    # it has attribute readers for the parts, e.g. year, month, and so on, and epoch time readers, to_i
-    #
-    # The sub-second attributes are fixed as 0, and utc_offset, zone, isdst, and their aliases are same as a Time object in UTC
-    describe "Time-like argument of #utc_to_local and #local_to_utc methods" do
-      before do
-        @obj = TimeSpecs::TimeLikeArgumentRecorder.result
-        @obj.should_not == nil
+    ruby_version_is "3.2.3" do
+      it "raises ArgumentError if the time part is missing" do
+        -> {
+          Time.new("2020-12-25")
+        }.should raise_error(ArgumentError, /no time information|can't parse:/)
       end
 
-      it "implements subset of Time methods" do
-        [
-          :year, :mon, :month, :mday, :hour, :min, :sec,
-          :tv_sec, :tv_usec, :usec, :tv_nsec, :nsec, :subsec,
-          :to_i, :to_f, :to_r, :+, :-,
-          :isdst, :dst?, :zone, :gmtoff, :gmt_offset, :utc_offset, :utc?, :gmt?,
-          :to_s, :inspect, :to_a, :to_time,
-        ].each do |name|
-          @obj.respond_to?(name).should == true
-        end
+      it "raises ArgumentError if day is missing" do
+        -> {
+          Time.new("2020-12")
+        }.should raise_error(ArgumentError, /no time information|can't parse:/)
       end
+    end
 
-      it "has attribute values the same as a Time object in UTC" do
-        @obj.usec.should == 0
-        @obj.nsec.should == 0
-        @obj.subsec.should == 0
-        @obj.tv_usec.should == 0
-        @obj.tv_nsec.should == 0
+    it "raises ArgumentError if subsecond is missing after dot" do
+      -> {
+        Time.new("2020-12-25 00:56:17. +0900")
+      }.should raise_error(ArgumentError, /subsecond expected after dot: 00:56:17. |can't parse:/)
+    end
 
-        @obj.utc_offset.should == 0
-        @obj.zone.should == "UTC"
-        @obj.isdst.should == Time.new.utc.isdst
-      end
+    it "raises ArgumentError if String argument is not in the supported format" do
+      -> {
+        Time.new("021-12-25 00:00:00.123456 +09:00")
+      }.should raise_error(ArgumentError, /year must be 4 or more digits: 021|can't parse:/)
+
+      -> {
+        Time.new("2020-012-25 00:56:17 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits mon is expected after [`']-': -012-25 00:\z|can't parse:/)
+
+      -> {
+        Time.new("2020-2-25 00:56:17 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits mon is expected after [`']-': -2-25 00:56\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-215 00:56:17 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits mday is expected after [`']-': -215 00:56:\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 000:56:17 +0900")
+      }.should raise_error(ArgumentError, /two digits hour is expected:  000:56:17 |can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 0:56:17 +0900")
+      }.should raise_error(ArgumentError, /two digits hour is expected:  0:56:17 \+0|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00:516:17 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits min is expected after [`']:': :516:17 \+09\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00:6:17 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits min is expected after [`']:': :6:17 \+0900\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00:56:137 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits sec is expected after [`']:': :137 \+0900\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00:56:7 +0900")
+      }.should raise_error(ArgumentError, /\Atwo digits sec is expected after [`']:': :7 \+0900\z|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00:56. +0900")
+      }.should raise_error(ArgumentError, /fraction min is not supported: 00:56\.|can't parse:/)
+
+      -> {
+        Time.new("2020-12-25 00. +0900")
+      }.should raise_error(ArgumentError, /fraction hour is not supported: 00\.|can't parse:/)
     end
 
-    context "#name method" do
-      it "uses the optional #name method for marshaling" do
-        zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
-        time = Time.new(2000, 1, 1, 12, 0, 0, zone)
-        time_loaded = Marshal.load(Marshal.dump(time))
+    it "raises ArgumentError if date/time parts values are not valid" do
+      -> {
+        Time.new("2020-13-25 00:56:17 +09:00")
+      }.should raise_error(ArgumentError, /(mon|argument) out of range/)
 
-        time_loaded.zone.should == "Asia/Colombo"
-        time_loaded.utc_offset.should == 5*3600+30*60
-      end
+      -> {
+        Time.new("2020-12-32 00:56:17 +09:00")
+      }.should raise_error(ArgumentError, /(mday|argument) out of range/)
+
+      -> {
+        Time.new("2020-12-25 25:56:17 +09:00")
+      }.should raise_error(ArgumentError, /(hour|argument) out of range/)
+
+      -> {
+        Time.new("2020-12-25 00:61:17 +09:00")
+      }.should raise_error(ArgumentError, /(min|argument) out of range/)
 
-      it "cannot marshal Time if #name method isn't implemented" do
-        zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-        time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+      -> {
+        Time.new("2020-12-25 00:56:61 +09:00")
+      }.should raise_error(ArgumentError, /(sec|argument) out of range/)
+
+      -> {
+        Time.new("2020-12-25 00:56:17 +23:59:60")
+      }.should raise_error(ArgumentError, /utc_offset|argument out of range/)
+
+      -> {
+        Time.new("2020-12-25 00:56:17 +24:00")
+      }.should raise_error(ArgumentError, /(utc_offset|argument) out of range/)
+
+      -> {
+        Time.new("2020-12-25 00:56:17 +23:61")
+      }.should raise_error(ArgumentError, /utc_offset/)
 
+      ruby_bug '#20797', ''...'3.4' do
         -> {
-          Marshal.dump(time)
-        }.should raise_error(NoMethodError, /undefined method `name' for/)
+          Time.new("2020-12-25 00:56:17 +00:23:61")
+        }.should raise_error(ArgumentError, /utc_offset/)
       end
     end
 
-    it "the #abbr method is used by '%Z' in #strftime" do
-      zone = TimeSpecs::TimezoneWithAbbr.new(name: "Asia/Colombo")
-      time = Time.new(2000, 1, 1, 12, 0, 0, zone)
+    it "raises ArgumentError if utc offset parts are not valid" do
+      -> { Time.new("2020-12-25 00:56:17 +24:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.new("2020-12-25 00:56:17 +2400") }.should raise_error(ArgumentError, "utc_offset out of range")
 
-      time.strftime("%Z").should == "MMT"
-    end
+      -> { Time.new("2020-12-25 00:56:17 +99:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.new("2020-12-25 00:56:17 +9900") }.should raise_error(ArgumentError, "utc_offset out of range")
+
+      -> { Time.new("2020-12-25 00:56:17 +00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:60')
+      -> { Time.new("2020-12-25 00:56:17 +0060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0060')
+
+      -> { Time.new("2020-12-25 00:56:17 +00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:99')
+      -> { Time.new("2020-12-25 00:56:17 +0099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0099')
 
-    # At loading marshaled data, a timezone name will be converted to a timezone object
-    # by find_timezone class method, if the method is defined.
-    # Similary, that class method will be called when a timezone argument does not have
-    # the necessary methods mentioned above.
-    context "subject's class implements .find_timezone method" do
-      it "calls .find_timezone to build a time object at loading marshaled data" do
-        zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
-        time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, zone)
-        time_loaded = Marshal.load(Marshal.dump(time))
+      ruby_bug '#20797', ''...'3.4' do
+        -> { Time.new("2020-12-25 00:56:17 +00:00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:60')
+        -> { Time.new("2020-12-25 00:56:17 +000060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000060')
 
-        time_loaded.zone.should be_kind_of TimeSpecs::TimezoneWithName
-        time_loaded.zone.name.should == "Asia/Colombo"
-        time_loaded.utc_offset.should == 5*3600+30*60
+        -> { Time.new("2020-12-25 00:56:17 +00:00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:99')
+        -> { Time.new("2020-12-25 00:56:17 +000099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000099')
       end
+    end
 
-      it "calls .find_timezone to build a time object if passed zone name as a timezone argument" do
-        time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, "Asia/Colombo")
-        time.zone.should be_kind_of TimeSpecs::TimezoneWithName
-        time.zone.name.should == "Asia/Colombo"
+    it "raises ArgumentError if string has not ascii-compatible encoding" do
+      -> {
+        Time.new("2021-11-31 00:00:60 +09:00".encode("utf-32le"))
+      }.should raise_error(ArgumentError, "time string should have ASCII compatible encoding")
+    end
+
+    it "raises ArgumentError if string doesn't start with year" do
+      -> {
+        Time.new("a\nb")
+      }.should raise_error(ArgumentError, "can't parse: \"a\\nb\"")
+    end
+
+    it "raises ArgumentError if string has extra characters after offset" do
+      -> {
+        Time.new("2021-11-31 00:00:59 +09:00 abc")
+      }.should raise_error(ArgumentError, /can't parse.+ abc/)
+    end
 
-        time = TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, "some invalid zone name")
-        time.zone.should be_kind_of TimeSpecs::TimezoneWithName
-        time.zone.name.should == "some invalid zone name"
+    ruby_version_is "3.2.3" do
+      it "raises ArgumentError when there are leading space characters" do
+        -> { Time.new(" 2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("\t2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("\n2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("\v2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("\f2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("\r2020-12-02 00:00:00") }.should raise_error(ArgumentError, /can't parse/)
       end
 
-      it "does not call .find_timezone if passed any not string/numeric/timezone timezone argument" do
-        [Object.new, [], {}, :"some zone"].each do |zone|
-          -> {
-            TimeSpecs::TimeWithFindTimezone.new(2000, 1, 1, 12, 0, 0, zone)
-          }.should raise_error(TypeError, /can't convert \w+ into an exact number/)
-        end
+      it "raises ArgumentError when there are trailing whitespaces" do
+        -> { Time.new("2020-12-02 00:00:00 ") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("2020-12-02 00:00:00\t") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("2020-12-02 00:00:00\n") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("2020-12-02 00:00:00\v") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("2020-12-02 00:00:00\f") }.should raise_error(ArgumentError, /can't parse/)
+        -> { Time.new("2020-12-02 00:00:00\r") }.should raise_error(ArgumentError, /can't parse/)
       end
     end
   end
diff --git a/spec/ruby/core/time/now_spec.rb b/spec/ruby/core/time/now_spec.rb
index 7dc7951996..e3fe6edad6 100644
--- a/spec/ruby/core/time/now_spec.rb
+++ b/spec/ruby/core/time/now_spec.rb
@@ -3,4 +3,179 @@ require_relative 'shared/now'
 
 describe "Time.now" do
   it_behaves_like :time_now, :now
+
+  describe ":in keyword argument" do
+    it "could be UTC offset as a String in '+HH:MM or '-HH:MM' format" do
+      time = Time.now(in: "+05:00")
+
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+
+      time = Time.now(in: "-09:00")
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+
+      time = Time.now(in: "-09:00:01")
+
+      time.utc_offset.should == -(9*60*60 + 1)
+      time.zone.should == nil
+    end
+
+    it "could be UTC offset as a number of seconds" do
+      time = Time.now(in: 5*60*60)
+
+      time.utc_offset.should == 5*60*60
+      time.zone.should == nil
+
+      time = Time.now(in: -9*60*60)
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == nil
+    end
+
+    it "returns a Time with UTC offset specified as a single letter military timezone" do
+      Time.now(in: "W").utc_offset.should == 3600 * -10
+    end
+
+    it "could be a timezone object" do
+      zone = TimeSpecs::TimezoneWithName.new(name: "Asia/Colombo")
+      time = Time.now(in: zone)
+
+      time.utc_offset.should == 5*3600+30*60
+      time.zone.should == zone
+
+      zone = TimeSpecs::TimezoneWithName.new(name: "PST")
+      time = Time.now(in: zone)
+
+      time.utc_offset.should == -9*60*60
+      time.zone.should == zone
+    end
+
+    it "raises ArgumentError if format is invalid" do
+      -> { Time.now(in: "+09:99") }.should raise_error(ArgumentError)
+      -> { Time.now(in: "ABC") }.should raise_error(ArgumentError)
+    end
+
+    it "raises ArgumentError if String argument and hours greater than 23" do
+      -> { Time.now(in: "+24:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.now(in: "+2400") }.should raise_error(ArgumentError, "utc_offset out of range")
+
+      -> { Time.now(in: "+99:00") }.should raise_error(ArgumentError, "utc_offset out of range")
+      -> { Time.now(in: "+9900") }.should raise_error(ArgumentError, "utc_offset out of range")
+    end
+
+    it "raises ArgumentError if String argument and minutes greater than 59" do
+      -> { Time.now(in: "+00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:60')
+      -> { Time.now(in: "+0060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0060')
+
+      -> { Time.now(in: "+00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:99')
+      -> { Time.now(in: "+0099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +0099')
+    end
+
+    ruby_bug '#20797', ''...'3.4' do
+      it "raises ArgumentError if String argument and seconds greater than 59" do
+        -> { Time.now(in: "+00:00:60") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:60')
+        -> { Time.now(in: "+000060") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000060')
+
+        -> { Time.now(in: "+00:00:99") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +00:00:99')
+        -> { Time.now(in: "+000099") }.should raise_error(ArgumentError, '"+HH:MM", "-HH:MM", "UTC" or "A".."I","K".."Z" expected for utc_offset: +000099')
+      end
+    end
+  end
+
+  describe "Timezone object" do # https://bugs.ruby-lang.org/issues/17485
+    it "raises TypeError if timezone does not implement #utc_to_local method" do
+      zone = Object.new
+      def zone.local_to_utc(time)
+        time
+      end
+
+      -> {
+        Time.now(in: zone)
+      }.should raise_error(TypeError, /can't convert Object into an exact number/)
+    end
+
+    it "does not raise exception if timezone does not implement #local_to_utc method" do
+      zone = Object.new
+      def zone.utc_to_local(time)
+        time
+      end
+
+      Time.now(in: zone).should be_kind_of(Time)
+    end
+
+    # The result also should be a Time or Time-like object (not necessary to be the same class)
+    # or Integer. The zone of the result is just ignored.
+    describe "returned value by #utc_to_local and #local_to_utc methods" do
+      it "could be Time instance" do
+        zone = Object.new
+        def zone.utc_to_local(t)
+          time = Time.new(t.year, t.mon, t.day, t.hour, t.min, t.sec, t.utc_offset)
+          time + 60 * 60 # + 1 hour
+        end
+
+        Time.now(in: zone).should be_kind_of(Time)
+        Time.now(in: zone).utc_offset.should == 3600
+      end
+
+      it "could be Time subclass instance" do
+        zone = Object.new
+        def zone.utc_to_local(t)
+          time = Time.new(t.year, t.mon, t.day, t.hour, t.min, t.sec, t.utc_offset)
+          time += 60 * 60 # + 1 hour
+
+          Class.new(Time).new(time.year, time.mon, time.day, time.hour, time.min, time.sec, time.utc_offset)
+        end
+
+        Time.now(in: zone).should be_kind_of(Time)
+        Time.now(in: zone).utc_offset.should == 3600
+      end
+
+      it "could be Integer" do
+        zone = Object.new
+        def zone.utc_to_local(time)
+          time.to_i + 60*60
+        end
+
+        Time.now(in: zone).should be_kind_of(Time)
+        Time.now(in: zone).utc_offset.should == 60*60
+      end
+
+      it "could have any #zone and #utc_offset because they are ignored" do
+        zone = Object.new
+        def zone.utc_to_local(t)
+          Struct.new(:year, :mon, :mday, :hour, :min, :sec, :isdst, :to_i, :zone, :utc_offset) # rubocop:disable Lint/StructNewOverride
+                .new(t.year, t.mon, t.mday, t.hour, t.min, t.sec, t.isdst, t.to_i, 'America/New_York', -5*60*60)
+        end
+        Time.now(in: zone).utc_offset.should == 0
+
+        zone = Object.new
+        def zone.utc_to_local(t)
+          Struct.new(:year, :mon, :mday, :hour, :min, :sec, :isdst, :to_i, :zone, :utc_offset) # rubocop:disable Lint/StructNewOverride
+                .new(t.year, t.mon, t.mday, t.hour, t.min, t.sec, t.isdst, t.to_i, 'Asia/Tokyo', 9*60*60)
+        end
+        Time.now(in: zone).utc_offset.should == 0
+
+        zone = Object.new
+        def zone.utc_to_local(t)
+          Time.new(t.year, t.mon, t.mday, t.hour, t.min, t.sec, 9*60*60)
+        end
+        Time.now(in: zone).utc_offset.should == 0
+      end
+
+      it "raises ArgumentError if difference between argument and result is too large" do
+        zone = Object.new
+        def zone.utc_to_local(t)
+          time = Time.utc(t.year, t.mon, t.day, t.hour, t.min, t.sec, t.utc_offset)
+          time -= 24 * 60 * 60 # - 1 day
+          Time.utc(time.year, time.mon, time.day, time.hour, time.min, time.sec, time.utc_offset)
+        end
+
+        -> {
+          Time.now(in: zone)
+        }.should raise_error(ArgumentError, "utc_offset out of range")
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/time/plus_spec.rb b/spec/ruby/core/time/plus_spec.rb
index 0a9984f180..642393b615 100644
--- a/spec/ruby/core/time/plus_spec.rb
+++ b/spec/ruby/core/time/plus_spec.rb
@@ -37,11 +37,11 @@ describe "Time#+" do
   end
 
   it "returns a UTC time if self is UTC" do
-    (Time.utc(2012) + 10).utc?.should == true
+    (Time.utc(2012) + 10).should.utc?
   end
 
   it "returns a non-UTC time if self is non-UTC" do
-    (Time.local(2012) + 10).utc?.should == false
+    (Time.local(2012) + 10).should_not.utc?
   end
 
   it "returns a time with the same fixed offset as self" do
@@ -50,20 +50,18 @@ describe "Time#+" do
 
   it "preserves time zone" do
     time_with_zone = Time.now.utc
-    time_with_zone.zone.should == (time_with_zone + 60*60).zone
+    time_with_zone.zone.should == (time_with_zone + 1).zone
 
     time_with_zone = Time.now
-    time_with_zone.zone.should == (time_with_zone + 60*60).zone
+    time_with_zone.zone.should == (time_with_zone + 1).zone
   end
 
-  ruby_version_is "2.6" do
-    context "zone is a timezone object" do
-      it "preserves time zone" do
-        zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-        time = Time.new(2012, 1, 1, 12, 0, 0, zone) + 60*60
+  context "zone is a timezone object" do
+    it "preserves time zone" do
+      zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
+      time = Time.new(2012, 1, 1, 12, 0, 0, zone) + 1
 
-        time.zone.should == zone
-      end
+      time.zone.should == zone
     end
   end
 
diff --git a/spec/ruby/core/time/saturday_spec.rb b/spec/ruby/core/time/saturday_spec.rb
index 60ffea4198..0e51407366 100644
--- a/spec/ruby/core/time/saturday_spec.rb
+++ b/spec/ruby/core/time/saturday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#saturday?" do
   it "returns true if time represents Saturday" do
-    Time.local(2000, 1, 1).saturday?.should == true
+    Time.local(2000, 1, 1).should.saturday?
   end
 
   it "returns false if time doesn't represent Saturday" do
-    Time.local(2000, 1, 2).saturday?.should == false
+    Time.local(2000, 1, 2).should_not.saturday?
   end
 end
diff --git a/spec/ruby/core/time/shared/gmtime.rb b/spec/ruby/core/time/shared/gmtime.rb
index 5ed64c2ab6..7b4f65f0b7 100644
--- a/spec/ruby/core/time/shared/gmtime.rb
+++ b/spec/ruby/core/time/shared/gmtime.rb
@@ -4,7 +4,14 @@ describe :time_gmtime, shared: true do
     with_timezone("CST", -6) do
       t = Time.local(2007, 1, 9, 6, 0, 0)
       t.send(@method)
-      t.should == Time.gm(2007, 1, 9, 12, 0, 0)
+      # Time#== compensates for time zones, so check all parts separately
+      t.year.should == 2007
+      t.month.should == 1
+      t.mday.should == 9
+      t.hour.should == 12
+      t.min.should == 0
+      t.sec.should == 0
+      t.zone.should == "UTC"
     end
   end
 
@@ -22,11 +29,11 @@ describe :time_gmtime, shared: true do
       time.send(@method).should equal(time)
     end
 
-    it "raises a RuntimeError if the time is not UTC" do
+    it "raises a FrozenError if the time is not UTC" do
       with_timezone("CST", -6) do
         time = Time.now
         time.freeze
-        -> { time.send(@method) }.should raise_error(RuntimeError)
+        -> { time.send(@method) }.should raise_error(FrozenError)
       end
     end
   end
diff --git a/spec/ruby/core/time/shared/local.rb b/spec/ruby/core/time/shared/local.rb
index 43f331c4c1..068e314999 100644
--- a/spec/ruby/core/time/shared/local.rb
+++ b/spec/ruby/core/time/shared/local.rb
@@ -7,12 +7,10 @@ describe :time_local, shared: true do
   end
 
   platform_is_not :windows do
-    describe "timezone changes" do
-      it "correctly adjusts the timezone change to 'CEST' on 'Europe/Amsterdam'" do
-        with_timezone("Europe/Amsterdam") do
-          Time.send(@method, 1940, 5, 16).to_a.should ==
-            [0, 40, 1, 16, 5, 1940, 4, 137, true, "CEST"]
-        end
+    it "uses the 'CET' timezone with TZ=Europe/Amsterdam in 1970" do
+      with_timezone("Europe/Amsterdam") do
+        Time.send(@method, 1970, 5, 16).to_a.should ==
+          [0, 0, 0, 16, 5, 1970, 6, 136, false, "CET"]
       end
     end
   end
@@ -41,5 +39,4 @@ describe :time_local_10_arg, shared: true do
       end
     end
   end
-
 end
diff --git a/spec/ruby/core/time/shared/now.rb b/spec/ruby/core/time/shared/now.rb
index d8e5ac9d50..f4018d72f4 100644
--- a/spec/ruby/core/time/shared/now.rb
+++ b/spec/ruby/core/time/shared/now.rb
@@ -18,18 +18,16 @@ describe :time_now, shared: true do
     end
   end
 
-  guard_not -> { platform_is :windows and ruby_version_is ""..."2.5" } do
-    it "has at least microsecond precision" do
-      times = []
-      10_000.times do
-        times << Time.now.nsec
-      end
-
-      # The clock should not be less accurate than expected (times should
-      # not all be a multiple of the next precision up, assuming precisions
-      # are multiples of ten.)
-      expected = 1_000
-      times.select { |t| t % (expected * 10) == 0  }.size.should_not == times.size
+  it "has at least microsecond precision" do
+    # The clock should not be less accurate than expected (times should
+    # not all be a multiple of the next precision up, assuming precisions
+    # are multiples of ten.)
+    expected = 1_000
+    t = 0
+    10_000.times.find do
+      t = Time.now.nsec
+      t % (expected * 10) != 0
     end
+    (t % (expected * 10)).should != 0
   end
 end
diff --git a/spec/ruby/core/time/shared/time_params.rb b/spec/ruby/core/time/shared/time_params.rb
index 63d0dbc120..9832fd17fe 100644
--- a/spec/ruby/core/time/shared/time_params.rb
+++ b/spec/ruby/core/time/shared/time_params.rb
@@ -145,9 +145,10 @@ describe :time_params, shared: true do
   end
 
   it "raises an ArgumentError for out of range month" do
+    # For some reason MRI uses a different message for month in 13-15 and month>=16
     -> {
-      Time.send(@method, 2008, 13, 31, 23, 59, 59)
-    }.should raise_error(ArgumentError)
+      Time.send(@method, 2008, 16, 31, 23, 59, 59)
+    }.should raise_error(ArgumentError, /(mon|argument) out of range/)
   end
 
   it "raises an ArgumentError for out of range day" do
@@ -169,9 +170,17 @@ describe :time_params, shared: true do
   end
 
   it "raises an ArgumentError for out of range second" do
+    # For some reason MRI uses different messages for seconds 61-63 and seconds >= 64
     -> {
       Time.send(@method, 2008, 12, 31, 23, 59, 61)
-    }.should raise_error(ArgumentError)
+    }.should raise_error(ArgumentError, /(sec|argument) out of range/)
+    -> {
+      Time.send(@method, 2008, 12, 31, 23, 59, -1)
+    }.should raise_error(ArgumentError, "argument out of range")
+  end
+
+  it "raises ArgumentError when given 8 arguments" do
+    -> { Time.send(@method, *[0]*8) }.should raise_error(ArgumentError)
   end
 
   it "raises ArgumentError when given 9 arguments" do
diff --git a/spec/ruby/core/time/shared/to_i.rb b/spec/ruby/core/time/shared/to_i.rb
index 03497c700b..06c966b708 100644
--- a/spec/ruby/core/time/shared/to_i.rb
+++ b/spec/ruby/core/time/shared/to_i.rb
@@ -6,4 +6,11 @@ describe :time_to_i, shared: true do
   it "doesn't return an actual number of seconds in time" do
     Time.at(65.5).send(@method).should == 65
   end
+
+  it "rounds fractional seconds toward zero" do
+    t = Time.utc(1960, 1, 1, 0, 0, 0, 999_999)
+
+    t.to_f.to_i.should == -315619199
+    t.to_i.should == -315619200
+  end
 end
diff --git a/spec/ruby/core/time/shared/xmlschema.rb b/spec/ruby/core/time/shared/xmlschema.rb
new file mode 100644
index 0000000000..d68c18df36
--- /dev/null
+++ b/spec/ruby/core/time/shared/xmlschema.rb
@@ -0,0 +1,31 @@
+describe :time_xmlschema, shared: true do
+  ruby_version_is "3.4" do
+    it "generates ISO-8601 strings in Z for UTC times" do
+      t = Time.utc(1985, 4, 12, 23, 20, 50, 521245)
+      t.send(@method).should == "1985-04-12T23:20:50Z"
+      t.send(@method, 2).should == "1985-04-12T23:20:50.52Z"
+      t.send(@method, 9).should == "1985-04-12T23:20:50.521245000Z"
+    end
+
+    it "generates ISO-8601 string with timeone offset for non-UTC times" do
+      t = Time.new(1985, 4, 12, 23, 20, 50, "+02:00")
+      t.send(@method).should == "1985-04-12T23:20:50+02:00"
+      t.send(@method, 2).should == "1985-04-12T23:20:50.00+02:00"
+    end
+
+    it "year is always at least 4 digits" do
+      t = Time.utc(12, 4, 12)
+      t.send(@method).should ==  "0012-04-12T00:00:00Z"
+    end
+
+    it "year can be more than 4 digits" do
+      t = Time.utc(40_000, 4, 12)
+      t.send(@method).should ==  "40000-04-12T00:00:00Z"
+    end
+
+    it "year can be negative" do
+      t = Time.utc(-2000, 4, 12)
+      t.send(@method).should ==  "-2000-04-12T00:00:00Z"
+    end
+  end
+end
diff --git a/spec/ruby/core/time/strftime_spec.rb b/spec/ruby/core/time/strftime_spec.rb
index 1bd24b0538..fd233f3577 100644
--- a/spec/ruby/core/time/strftime_spec.rb
+++ b/spec/ruby/core/time/strftime_spec.rb
@@ -49,4 +49,43 @@ describe "Time#strftime" do
     time = @new_time_with_offset[2012, 1, 1, 0, 0, 0, Rational(36645, 10)]
     time.strftime("%::z").should == "+01:01:05"
   end
+
+  it "supports RFC 3339 UTC for unknown offset local time, -0000, as %-z" do
+    time = Time.gm(2022)
+
+    time.strftime("%z").should == "+0000"
+    time.strftime("%-z").should == "-0000"
+    time.strftime("%-:z").should == "-00:00"
+    time.strftime("%-::z").should == "-00:00:00"
+  end
+
+  it "applies '-' flag to UTC time" do
+    time = Time.utc(2022)
+    time.strftime("%-z").should == "-0000"
+
+    time = Time.gm(2022)
+    time.strftime("%-z").should == "-0000"
+
+    time = Time.new(2022, 1, 1, 0, 0, 0, "Z")
+    time.strftime("%-z").should == "-0000"
+
+    time = Time.new(2022, 1, 1, 0, 0, 0, "-00:00")
+    time.strftime("%-z").should == "-0000"
+
+    time = Time.new(2022, 1, 1, 0, 0, 0, "+03:00").utc
+    time.strftime("%-z").should == "-0000"
+  end
+
+  it "ignores '-' flag for non-UTC time" do
+    time = Time.new(2022, 1, 1, 0, 0, 0, "+03:00")
+    time.strftime("%-z").should == "+0300"
+  end
+
+  it "works correctly with width, _ and 0 flags, and :" do
+    Time.now.utc.strftime("%-_10z").should == "      -000"
+    Time.now.utc.strftime("%-10z").should == "-000000000"
+    Time.now.utc.strftime("%-010:z").should == "-000000:00"
+    Time.now.utc.strftime("%-_10:z").should == "     -0:00"
+    Time.now.utc.strftime("%-_10::z").should == "  -0:00:00"
+  end
 end
diff --git a/spec/ruby/core/time/subsec_spec.rb b/spec/ruby/core/time/subsec_spec.rb
index 583a26412b..0f2c4eb856 100644
--- a/spec/ruby/core/time/subsec_spec.rb
+++ b/spec/ruby/core/time/subsec_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "Time#subsec" do
-  it "returns 0 as a Fixnum for a Time with a whole number of seconds" do
+  it "returns 0 as an Integer for a Time with a whole number of seconds" do
     Time.at(100).subsec.should eql(0)
   end
 
diff --git a/spec/ruby/core/time/succ_spec.rb b/spec/ruby/core/time/succ_spec.rb
deleted file mode 100644
index e68e64b0cc..0000000000
--- a/spec/ruby/core/time/succ_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-
-describe "Time#succ" do
-  it "returns a new time one second later than time" do
-    suppress_warning {
-      @result = Time.at(100).succ
-    }
-
-    @result.should == Time.at(101)
-  end
-
-  it "returns a new instance" do
-    time = Time.at(100)
-
-    suppress_warning {
-      @result = time.succ
-    }
-
-    @result.should_not equal time
-  end
-
-  it "is obsolete" do
-    -> {
-      Time.at(100).succ
-    }.should complain(/Time#succ is obsolete/)
-  end
-
-  ruby_version_is "2.6" do
-    context "zone is a timezone object" do
-      it "preserves time zone" do
-        zone = TimeSpecs::Timezone.new(offset: (5*3600+30*60))
-        time = Time.new(2012, 1, 1, 12, 0, 0, zone) - 60*60
-
-        time.zone.should == zone
-      end
-    end
-  end
-end
diff --git a/spec/ruby/core/time/sunday_spec.rb b/spec/ruby/core/time/sunday_spec.rb
index 2285583579..0d46421132 100644
--- a/spec/ruby/core/time/sunday_spec.rb
+++ b/spec/ruby/core/time/sunday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#sunday?" do
   it "returns true if time represents Sunday" do
-    Time.local(2000, 1, 2).sunday?.should == true
+    Time.local(2000, 1, 2).should.sunday?
   end
 
   it "returns false if time doesn't represent Sunday" do
-    Time.local(2000, 1, 1).sunday?.should == false
+    Time.local(2000, 1, 1).should_not.sunday?
   end
 end
diff --git a/spec/ruby/core/time/thursday_spec.rb b/spec/ruby/core/time/thursday_spec.rb
index c82d517519..c11e79d2fa 100644
--- a/spec/ruby/core/time/thursday_spec.rb
+++ b/spec/ruby/core/time/thursday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#thursday?" do
   it "returns true if time represents Thursday" do
-    Time.local(2000, 1, 6).thursday?.should == true
+    Time.local(2000, 1, 6).should.thursday?
   end
 
   it "returns false if time doesn't represent Thursday" do
-    Time.local(2000, 1, 1).thursday?.should == false
+    Time.local(2000, 1, 1).should_not.thursday?
   end
 end
diff --git a/spec/ruby/core/time/tuesday_spec.rb b/spec/ruby/core/time/tuesday_spec.rb
index 7abbdc92c0..0e7b9e7506 100644
--- a/spec/ruby/core/time/tuesday_spec.rb
+++ b/spec/ruby/core/time/tuesday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#tuesday?" do
   it "returns true if time represents Tuesday" do
-    Time.local(2000, 1, 4).tuesday?.should == true
+    Time.local(2000, 1, 4).should.tuesday?
   end
 
   it "returns false if time doesn't represent Tuesday" do
-    Time.local(2000, 1, 1).tuesday?.should == false
+    Time.local(2000, 1, 1).should_not.tuesday?
   end
 end
diff --git a/spec/ruby/core/time/utc_spec.rb b/spec/ruby/core/time/utc_spec.rb
index 5074c8d54d..ab3c0df657 100644
--- a/spec/ruby/core/time/utc_spec.rb
+++ b/spec/ruby/core/time/utc_spec.rb
@@ -4,8 +4,53 @@ require_relative 'shared/gmtime'
 require_relative 'shared/time_params'
 
 describe "Time#utc?" do
-  it "returns true if time represents a time in UTC (GMT)" do
+  it "returns true only if time represents a time in UTC (GMT)" do
     Time.now.utc?.should == false
+    Time.now.utc.utc?.should == true
+  end
+
+  it "treats time as UTC what was created in different ways" do
+    Time.now.utc.utc?.should == true
+    Time.now.gmtime.utc?.should == true
+    Time.now.getgm.utc?.should == true
+    Time.now.getutc.utc?.should == true
+    Time.utc(2022).utc?.should == true
+  end
+
+  it "does treat time with 'UTC' offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "UTC").utc?.should == true
+    Time.now.localtime("UTC").utc?.should == true
+    Time.at(Time.now, in: 'UTC').utc?.should == true
+
+    Time.new(2022, 1, 1, 0, 0, 0, in: "UTC").utc?.should == true
+    Time.now(in: "UTC").utc?.should == true
+  end
+
+  it "does treat time with Z offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "Z").utc?.should == true
+    Time.now.localtime("Z").utc?.should == true
+    Time.at(Time.now, in: 'Z').utc?.should == true
+
+    Time.new(2022, 1, 1, 0, 0, 0, in: "Z").utc?.should == true
+    Time.now(in: "Z").utc?.should == true
+  end
+
+  it "does treat time with -00:00 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "-00:00").utc?.should == true
+    Time.now.localtime("-00:00").utc?.should == true
+    Time.at(Time.now, in: '-00:00').utc?.should == true
+  end
+
+  it "does not treat time with +00:00 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, "+00:00").utc?.should == false
+    Time.now.localtime("+00:00").utc?.should == false
+    Time.at(Time.now, in: "+00:00").utc?.should == false
+  end
+
+  it "does not treat time with 0 offset as UTC" do
+    Time.new(2022, 1, 1, 0, 0, 0, 0).utc?.should == false
+    Time.now.localtime(0).utc?.should == false
+    Time.at(Time.now, in: 0).utc?.should == false
   end
 end
 
diff --git a/spec/ruby/core/time/wednesday_spec.rb b/spec/ruby/core/time/wednesday_spec.rb
index 6a52c3577b..cc686681d7 100644
--- a/spec/ruby/core/time/wednesday_spec.rb
+++ b/spec/ruby/core/time/wednesday_spec.rb
@@ -2,10 +2,10 @@ require_relative '../../spec_helper'
 
 describe "Time#wednesday?" do
   it "returns true if time represents Wednesday" do
-    Time.local(2000, 1, 5).wednesday?.should == true
+    Time.local(2000, 1, 5).should.wednesday?
   end
 
   it "returns false if time doesn't represent Wednesday" do
-    Time.local(2000, 1, 1).wednesday?.should == false
+    Time.local(2000, 1, 1).should_not.wednesday?
   end
 end
diff --git a/spec/ruby/core/time/xmlschema_spec.rb b/spec/ruby/core/time/xmlschema_spec.rb
new file mode 100644
index 0000000000..bdf1dc7923
--- /dev/null
+++ b/spec/ruby/core/time/xmlschema_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/xmlschema'
+
+describe "Time#xmlschema" do
+  it_behaves_like :time_xmlschema, :xmlschema
+end
diff --git a/spec/ruby/core/time/yday_spec.rb b/spec/ruby/core/time/yday_spec.rb
index 6ea5ff8f1b..e920c2e28d 100644
--- a/spec/ruby/core/time/yday_spec.rb
+++ b/spec/ruby/core/time/yday_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative '../../shared/time/yday'
 
 describe "Time#yday" do
   it "returns an integer representing the day of the year, 1..366" do
@@ -7,15 +8,5 @@ describe "Time#yday" do
     end
   end
 
-  it 'returns the correct value for each day of each month' do
-    mdays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
-
-    yday = 1
-    mdays.each_with_index do |days, month|
-      days.times do |day|
-        Time.new(2014, month+1, day+1).yday.should == yday
-        yday += 1
-      end
-    end
-  end
+  it_behaves_like :time_yday, -> year, month, day { Time.new(year, month, day).yday }
 end
diff --git a/spec/ruby/core/time/zone_spec.rb b/spec/ruby/core/time/zone_spec.rb
index 907ccf9f4b..9a15bd569b 100644
--- a/spec/ruby/core/time/zone_spec.rb
+++ b/spec/ruby/core/time/zone_spec.rb
@@ -52,14 +52,35 @@ describe "Time#zone" do
     end
 
     it "doesn't raise errors for a Time with a fixed offset" do
-      -> {
-        Time.new(2001, 1, 1, 0, 0, 0, "+05:00").zone
-      }.should_not raise_error
+      Time.new(2001, 1, 1, 0, 0, 0, "+05:00").zone.should == nil
     end
   end
 
   it "returns UTC when called on a UTC time" do
     Time.now.utc.zone.should == "UTC"
+    Time.now.gmtime.zone.should == "UTC"
+    Time.now.getgm.zone.should == "UTC"
+    Time.now.getutc.zone.should == "UTC"
+    Time.utc(2022).zone.should == "UTC"
+    Time.new(2022, 1, 1, 0, 0, 0, "UTC").zone.should == "UTC"
+    Time.new(2022, 1, 1, 0, 0, 0, "Z").zone.should == "UTC"
+    Time.now.localtime("UTC").zone.should == "UTC"
+    Time.now.localtime("Z").zone.should == "UTC"
+    Time.at(Time.now, in: 'UTC').zone.should == "UTC"
+    Time.at(Time.now, in: 'Z').zone.should == "UTC"
+
+    Time.new(2022, 1, 1, 0, 0, 0, "-00:00").zone.should == "UTC"
+    Time.now.localtime("-00:00").zone.should == "UTC"
+    Time.at(Time.now, in: '-00:00').zone.should == "UTC"
+
+    Time.new(2022, 1, 1, 0, 0, 0, in: "UTC").zone.should == "UTC"
+    Time.new(2022, 1, 1, 0, 0, 0, in: "Z").zone.should == "UTC"
+
+    Time.now(in: 'UTC').zone.should == "UTC"
+    Time.now(in: 'Z').zone.should == "UTC"
+
+    Time.at(Time.now, in: 'UTC').zone.should == "UTC"
+    Time.at(Time.now, in: 'Z').zone.should == "UTC"
   end
 
   platform_is_not :aix, :windows do
diff --git a/spec/ruby/core/tracepoint/allow_reentry_spec.rb b/spec/ruby/core/tracepoint/allow_reentry_spec.rb
new file mode 100644
index 0000000000..75e9e859a9
--- /dev/null
+++ b/spec/ruby/core/tracepoint/allow_reentry_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe 'TracePoint.allow_reentry' do
+  it 'allows the reentrance in a given block' do
+    event_lines = []
+    l1 = l2 = l3 = l4 = nil
+    TracePoint.new(:line) do |tp|
+      next unless TracePointSpec.target_thread?
+
+      event_lines << tp.lineno
+      next if (__LINE__ + 2 .. __LINE__ + 4).cover?(tp.lineno)
+      TracePoint.allow_reentry do
+        a = 1; l3 = __LINE__
+        b = 2; l4 = __LINE__
+      end
+    end.enable do
+      c = 3; l1 = __LINE__
+      d = 4; l2 = __LINE__
+    end
+
+    event_lines.should == [l1, l3, l4, l2, l3, l4]
+  end
+
+  it 'raises RuntimeError when not called inside a TracePoint' do
+    -> {
+      TracePoint.allow_reentry{}
+    }.should raise_error(RuntimeError)
+  end
+end
diff --git a/spec/ruby/core/tracepoint/binding_spec.rb b/spec/ruby/core/tracepoint/binding_spec.rb
index f37753602e..6a7ef5f85a 100644
--- a/spec/ruby/core/tracepoint/binding_spec.rb
+++ b/spec/ruby/core/tracepoint/binding_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#binding' do
   def test
@@ -8,6 +9,7 @@ describe 'TracePoint#binding' do
   it 'return the generated binding object from event' do
     bindings = []
     TracePoint.new(:return) { |tp|
+      next unless TracePointSpec.target_thread?
       bindings << tp.binding
     }.enable {
       test
diff --git a/spec/ruby/core/tracepoint/callee_id_spec.rb b/spec/ruby/core/tracepoint/callee_id_spec.rb
index d340290d8b..cc08a45504 100644
--- a/spec/ruby/core/tracepoint/callee_id_spec.rb
+++ b/spec/ruby/core/tracepoint/callee_id_spec.rb
@@ -7,6 +7,7 @@ describe "TracePoint#callee_id" do
     obj = TracePointSpec::ClassWithMethodAlias.new
 
     TracePoint.new(:call) do |tp|
+      next unless TracePointSpec.target_thread?
       a << tp.callee_id
     end.enable do
       obj.m_alias
diff --git a/spec/ruby/core/tracepoint/defined_class_spec.rb b/spec/ruby/core/tracepoint/defined_class_spec.rb
index 72536e6a56..4593db6d1f 100644
--- a/spec/ruby/core/tracepoint/defined_class_spec.rb
+++ b/spec/ruby/core/tracepoint/defined_class_spec.rb
@@ -5,6 +5,7 @@ describe 'TracePoint#defined_class' do
   it 'returns class or module of the method being called' do
     last_class_name = nil
     TracePoint.new(:call) do |tp|
+      next unless TracePointSpec.target_thread?
       last_class_name = tp.defined_class
     end.enable do
       TracePointSpec::B.new.foo
diff --git a/spec/ruby/core/tracepoint/disable_spec.rb b/spec/ruby/core/tracepoint/disable_spec.rb
index 612ca3c25a..73a31b3b81 100644
--- a/spec/ruby/core/tracepoint/disable_spec.rb
+++ b/spec/ruby/core/tracepoint/disable_spec.rb
@@ -1,9 +1,11 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#disable' do
   it 'returns true if trace was enabled' do
     called = false
     trace = TracePoint.new(:line) do |tp|
+      next unless TracePointSpec.target_thread?
       called = true
     end
 
@@ -25,6 +27,7 @@ describe 'TracePoint#disable' do
   it 'returns false if trace was disabled' do
     called = false
     trace = TracePoint.new(:line) do |tp|
+      next unless TracePointSpec.target_thread?
       called = true
     end
 
@@ -41,7 +44,7 @@ describe 'TracePoint#disable' do
     begin
       trace.disable { enabled = trace.enabled? }
       enabled.should == false
-      trace.enabled?.should == true
+      trace.should.enabled?
     ensure
       trace.disable
     end
@@ -52,7 +55,7 @@ describe 'TracePoint#disable' do
     trace.enable
     begin
       trace.disable { 42 }.should == 42
-      trace.enabled?.should == true
+      trace.should.enabled?
     ensure
       trace.disable
     end
@@ -65,7 +68,7 @@ describe 'TracePoint#disable' do
       trace.disable do |*args|
         args.should == []
       end
-      trace.enabled?.should == true
+      trace.should.enabled?
     ensure
       trace.disable
     end
diff --git a/spec/ruby/core/tracepoint/enable_spec.rb b/spec/ruby/core/tracepoint/enable_spec.rb
index b0fe38c559..93a6b281e3 100644
--- a/spec/ruby/core/tracepoint/enable_spec.rb
+++ b/spec/ruby/core/tracepoint/enable_spec.rb
@@ -1,20 +1,21 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#enable' do
-  # def test; end
-
   describe 'without a block' do
-    it 'returns true if trace was enabled' do
+    it 'returns false if trace was disabled' do
       called = false
       trace = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
         called = true
       end
 
       line_event = true
       called.should == false
 
-      trace.enable
+      ret = trace.enable
       begin
+        ret.should == false
         line_event = true
         called.should == true
       ensure
@@ -22,30 +23,27 @@ describe 'TracePoint#enable' do
       end
     end
 
-    it 'returns false if trace was disabled' do
+    it 'returns true if trace was already enabled' do
       called = false
       trace = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
         called = true
       end
 
-      trace.enable.should == false
-      begin
-        line_event = true
-        called.should == true
-      ensure
-        trace.disable
-      end
-
-      called = false
       line_event = true
       called.should == false
 
-      trace.enable.should == false
+      ret = trace.enable
       begin
+        ret.should == false
+
+        trace.enable.should == true
+
         line_event = true
         called.should == true
       ensure
         trace.disable
+        trace.should_not.enabled?
       end
     end
   end
@@ -54,18 +52,43 @@ describe 'TracePoint#enable' do
     it 'enables the trace object within a block' do
       event_name = nil
       TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
         event_name = tp.event
       end.enable { event_name.should equal(:line) }
     end
 
+    it 'enables the trace object only for the current thread' do
+      threads = []
+      trace = TracePoint.new(:line) do |tp|
+        # Runs on purpose on any Thread
+        threads << Thread.current
+      end
+
+      thread = nil
+      trace.enable do
+        line_event = true
+        thread = Thread.new do
+          event_in_other_thread = true
+        end
+        thread.join
+      end
+
+      threads = threads.uniq
+      threads.should.include?(Thread.current)
+      threads.should_not.include?(thread)
+    end
+
     it 'can accept arguments within a block but it should not yield arguments' do
       event_name = nil
-      trace = TracePoint.new(:line) { |tp| event_name = tp.event }
+      trace = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
+        event_name = tp.event
+      end
       trace.enable do |*args|
         event_name.should equal(:line)
         args.should == []
       end
-      trace.enabled?.should == false
+      trace.should_not.enabled?
     end
 
     it 'enables trace object on calling with a block if it was already enabled' do
@@ -87,394 +110,434 @@ describe 'TracePoint#enable' do
 
     it 'disables the trace object outside the block' do
       called = false
-      trace = TracePoint.new(:line) { called = true }
+      trace = TracePoint.new(:line) do
+        next unless TracePointSpec.target_thread?
+        called = true
+      end
       trace.enable {
         line_event = true
       }
       called.should == true
-      trace.enabled?.should == false
+      trace.should_not.enabled?
     end
   end
 
-  ruby_version_is "2.6" do
-    describe 'target: option' do
-      before :each do
-        ScratchPad.record []
+  describe "when nested" do
+    before do
+      @path_prefix = ' '
+    end
+
+    it "enables both TracePoints but only calls the respective callbacks" do
+      called = false
+      first = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
+        called = true
       end
 
-      it 'enables trace point for specific location' do
-        trace = TracePoint.new(:call) do |tp|
-          ScratchPad << tp.method_id
+      all = []
+      inspects = []
+      second = TracePoint.new(:line) { |tp|
+        next unless TracePointSpec.target_thread?
+        all << tp
+        inspects << tp.inspect
+      }
+
+      line = nil
+      first.enable do
+        second.enable do
+          line = __LINE__
         end
+      end
 
-        obj = Object.new
-        def obj.foo; end
-        def obj.bar; end
+      all.uniq.should == [second]
+      inspects.uniq.should == ["#<TracePoint:line#{@path_prefix}#{__FILE__}:#{line}>"]
+      called.should == true
+    end
+  end
 
-        trace.enable(target: obj.method(:foo)) do
-          obj.foo
-          obj.bar
-        end
+  describe 'target: option' do
+    before :each do
+      ScratchPad.record []
+    end
 
-        ScratchPad.recorded.should == [:foo]
+    it 'enables trace point for specific location' do
+      trace = TracePoint.new(:call) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.method_id
       end
 
-      it 'traces all the events triggered in specified location' do
-        trace = TracePoint.new(:line, :call, :return, :b_call, :b_return) do |tp|
-          ScratchPad << tp.event
-        end
+      obj = Object.new
+      def obj.foo; end
+      def obj.bar; end
 
-        obj = Object.new
-        def obj.foo
-          bar
-          -> {}.call
-        end
-        def obj.bar; end
+      trace.enable(target: obj.method(:foo)) do
+        obj.foo
+        obj.bar
+      end
 
-        trace.enable(target: obj.method(:foo)) do
-          obj.foo
-        end
+      ScratchPad.recorded.should == [:foo]
+    end
 
-        ScratchPad.recorded.uniq.sort.should == [:call, :return, :b_call, :b_return, :line].sort
+    it 'traces all the events triggered in specified location' do
+      trace = TracePoint.new(:line, :call, :return, :b_call, :b_return) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.event
       end
 
-      it 'does not trace events in nested locations' do
-        trace = TracePoint.new(:call) do |tp|
-          ScratchPad << tp.method_id
-        end
+      obj = Object.new
+      def obj.foo
+        bar
+        -> {}.call
+      end
+      def obj.bar; end
 
-        obj = Object.new
-        def obj.foo
-          bar
-        end
-        def obj.bar
-          baz
-        end
-        def obj.baz
-        end
+      trace.enable(target: obj.method(:foo)) do
+        obj.foo
+      end
 
-        trace.enable(target: obj.method(:foo)) do
-          obj.foo
-        end
+      ScratchPad.recorded.uniq.sort.should == [:call, :return, :b_call, :b_return, :line].sort
+    end
 
-        ScratchPad.recorded.should == [:foo]
+    it 'does not trace events in nested locations' do
+      trace = TracePoint.new(:call) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.method_id
       end
 
-      it "traces some events in nested blocks" do
-        klass = Class.new do
-          def foo
+      obj = Object.new
+      def obj.foo
+        bar
+      end
+      def obj.bar
+        baz
+      end
+      def obj.baz
+      end
+
+      trace.enable(target: obj.method(:foo)) do
+        obj.foo
+      end
+
+      ScratchPad.recorded.should == [:foo]
+    end
+
+    it "traces some events in nested blocks" do
+      klass = Class.new do
+        def foo
+          1.times do
             1.times do
-              1.times do
-                bar do
-                end
+              bar do
               end
             end
           end
+        end
 
-          def bar(&blk)
-            blk.call
-          end
+        def bar(&blk)
+          blk.call
         end
+      end
 
-        trace = TracePoint.new(:b_call) do |tp|
-          ScratchPad << tp.lineno
+      trace = TracePoint.new(:b_call) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.lineno
+      end
+
+      obj = klass.new
+      _, lineno = obj.method(:foo).source_location
+
+      trace.enable(target: obj.method(:foo)) do
+        obj.foo
+      end
+
+      ScratchPad.recorded.should == (lineno+1..lineno+3).to_a
+    end
+
+    describe 'option value' do
+      it 'accepts Method' do
+        trace = TracePoint.new(:call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << tp.method_id
         end
 
-        obj = klass.new
-        _, lineno = obj.method(:foo).source_location
+        obj = Object.new
+        def obj.foo; end
 
         trace.enable(target: obj.method(:foo)) do
           obj.foo
         end
 
-        ScratchPad.recorded.should == (lineno+1..lineno+3).to_a
+        ScratchPad.recorded.should == [:foo]
       end
 
-      describe 'option value' do
-        it 'accepts Method' do
-          trace = TracePoint.new(:call) do |tp|
-            ScratchPad << tp.method_id
-          end
-
-          obj = Object.new
-          def obj.foo; end
+      it 'accepts UnboundMethod' do
+        trace = TracePoint.new(:call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << tp.method_id
+        end
 
-          trace.enable(target: obj.method(:foo)) do
-            obj.foo
-          end
+        klass = Class.new do
+          def foo; end
+        end
 
-          ScratchPad.recorded.should == [:foo]
+        unbound_method = klass.instance_method(:foo)
+        trace.enable(target: unbound_method) do
+          klass.new.foo
         end
 
-        it 'accepts UnboundMethod' do
-          trace = TracePoint.new(:call) do |tp|
-            ScratchPad << tp.method_id
-          end
+        ScratchPad.recorded.should == [:foo]
+      end
 
-          klass = Class.new do
-            def foo; end
-          end
+      it 'accepts Proc' do
+        trace = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << tp.lineno
+        end
 
-          unbound_method = klass.instance_method(:foo)
-          trace.enable(target: unbound_method) do
-            klass.new.foo
-          end
+        block = proc {}
+        _, lineno = block.source_location
 
-          ScratchPad.recorded.should == [:foo]
+        trace.enable(target: block) do
+          block.call
         end
 
-        it 'accepts Proc' do
-          trace = TracePoint.new(:b_call) do |tp|
-            ScratchPad << tp.lineno
-          end
+        ScratchPad.recorded.should == [lineno]
+        lineno.should be_kind_of(Integer)
+      end
+    end
 
-          block = proc {}
-          _, lineno = block.source_location
+    it "raises ArgumentError if target object cannot trigger specified event" do
+      trace = TracePoint.new(:call) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.method_id
+      end
 
-          trace.enable(target: block) do
-            block.call
-          end
+      block = proc {}
 
-          ScratchPad.recorded.should == [lineno]
-          lineno.should be_kind_of(Integer)
+      -> {
+        trace.enable(target: block) do
+          block.call # triggers :b_call and :b_return events
         end
-      end
+      }.should raise_error(ArgumentError, /can not enable any hooks/)
+    end
 
-      it "raises ArgumentError if target object cannot trigger specified event" do
-        trace = TracePoint.new(:call) do |tp|
-          ScratchPad << tp.method_id
+    it "raises ArgumentError if passed not Method/UnboundMethod/Proc" do
+      trace = TracePoint.new(:call) {}
+
+      -> {
+        trace.enable(target: Object.new) do
         end
+      }.should raise_error(ArgumentError, /specified target is not supported/)
+    end
 
-        block = proc {}
+    context "nested enabling and disabling" do
+      it "raises ArgumentError if trace point already enabled with target is re-enabled with target" do
+        trace = TracePoint.new(:b_call) {}
 
         -> {
-          trace.enable(target: block) do
-            block.call # triggers :b_call and :b_return events
+          trace.enable(target: -> {}) do
+            trace.enable(target: -> {}) do
+            end
           end
-        }.should raise_error(ArgumentError, /can not enable any hooks/)
+        }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
       end
 
-      it "raises ArgumentError if passed not Method/UnboundMethod/Proc" do
-        trace = TracePoint.new(:call) do |tp|
-        end
+      it "raises ArgumentError if trace point already enabled without target is re-enabled with target" do
+        trace = TracePoint.new(:b_call) {}
 
         -> {
-          trace.enable(target: Object.new) do
+          trace.enable do
+            trace.enable(target: -> {}) do
+            end
           end
-        }.should raise_error(ArgumentError, /specified target is not supported/)
+        }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
       end
 
-      context "nested enabling and disabling" do
-        it "raises ArgumentError if trace point already enabled with target is re-enabled with target" do
-          trace = TracePoint.new(:b_call) do
-          end
+      it "raises ArgumentError if trace point already enabled with target is re-enabled without target" do
+        trace = TracePoint.new(:b_call) {}
 
-          -> {
-            trace.enable(target: -> {}) do
-              trace.enable(target: -> {}) do
-              end
+        -> {
+          trace.enable(target: -> {}) do
+            trace.enable do
             end
-          }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
-        end
-
-        it "raises ArgumentError if trace point already enabled without target is re-enabled with target" do
-          trace = TracePoint.new(:b_call) do
           end
+        }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
+      end
 
-          -> {
-            trace.enable do
-              trace.enable(target: -> {}) do
-              end
-            end
-          }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
-        end
+      it "raises ArgumentError if trace point already enabled with target is disabled with block" do
+        trace = TracePoint.new(:b_call) {}
 
-        it "raises ArgumentError if trace point already enabled with target is re-enabled without target" do
-          trace = TracePoint.new(:b_call) do
+        -> {
+          trace.enable(target: -> {}) do
+            trace.disable do
+            end
           end
+        }.should raise_error(ArgumentError, /can't disable a targett?ing TracePoint in a block/)
+      end
 
-          -> {
-            trace.enable(target: -> {}) do
-              trace.enable do
-              end
-            end
-          }.should raise_error(ArgumentError, /can't nest-enable a targett?ing TracePoint/)
+      it "traces events when trace point with target is enabled in another trace point enabled without target" do
+        trace_outer = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :outer
         end
 
-        it "raises ArgumentError if trace point already enabled with target is disabled with block" do
-          trace = TracePoint.new(:b_call) do
-          end
-
-          -> {
-            trace.enable(target: -> {}) do
-              trace.disable do
-              end
-            end
-          }.should raise_error(ArgumentError, /can't disable a targett?ing TracePoint in a block/)
+        trace_inner = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :inner
         end
 
-        it "traces events when trace point with target is enabled in another trace point enabled without target" do
-          trace_outer = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :outer
-          end
+        target = -> {}
 
-          trace_inner = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :inner
+        trace_outer.enable do
+          trace_inner.enable(target: target) do
+            target.call
           end
+        end
 
-          target = -> {}
+        ScratchPad.recorded.should == [:outer, :outer, :outer, :inner]
+      end
 
-          trace_outer.enable do
-            trace_inner.enable(target: target) do
-              target.call
-            end
-          end
+      it "traces events when trace point with target is enabled in another trace point enabled with target" do
+        trace_outer = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :outer
+        end
 
-          ScratchPad.recorded.should == [:outer, :outer, :outer, :inner]
+        trace_inner = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :inner
         end
 
-        it "traces events when trace point with target is enabled in another trace point enabled with target" do
-          trace_outer = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :outer
-          end
+        target = -> {}
 
-          trace_inner = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :inner
+        trace_outer.enable(target: target) do
+          trace_inner.enable(target: target) do
+            target.call
           end
+        end
 
-          target = -> {}
-
-          trace_outer.enable(target: target) do
-            trace_inner.enable(target: target) do
-              target.call
-            end
-          end
+        ScratchPad.recorded.should == [:inner, :outer]
+      end
 
-          ScratchPad.recorded.should == [:inner, :outer]
+      it "traces events when trace point without target is enabled in another trace point enabled with target" do
+        trace_outer = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :outer
         end
 
-        it "traces events when trace point without target is enabled in another trace point enabled with target" do
-          trace_outer = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :outer
-          end
-
-          trace_inner = TracePoint.new(:b_call) do |tp|
-            ScratchPad << :inner
-          end
+        trace_inner = TracePoint.new(:b_call) do |tp|
+          next unless TracePointSpec.target_thread?
+          ScratchPad << :inner
+        end
 
-          target = -> {}
+        target = -> {}
 
-          trace_outer.enable(target: target) do
-            trace_inner.enable do
-              target.call
-            end
+        trace_outer.enable(target: target) do
+          trace_inner.enable do
+            target.call
           end
-
-          ScratchPad.recorded.should == [:inner, :inner, :outer]
         end
-      end
-    end
 
-    describe 'target_line: option' do
-      before :each do
-        ScratchPad.record []
+        ScratchPad.recorded.should == [:inner, :inner, :outer]
       end
+    end
+  end
 
-      it "traces :line events only on specified line of code" do
-        trace = TracePoint.new(:line) do |tp|
-          ScratchPad << tp.lineno
-        end
+  describe 'target_line: option' do
+    before :each do
+      ScratchPad.record []
+    end
 
-        target = -> {
-          x = 1
-          y = 2      # <= this line is target
-          z = x + y
-        }
-        _, lineno = target.source_location
-        target_line = lineno + 2
+    it "traces :line events only on specified line of code" do
+      trace = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.lineno
+      end
 
-        trace.enable(target_line: target_line, target: target) do
-          target.call
-        end
+      target = -> {
+        x = 1
+        y = 2      # <= this line is target
+        z = x + y
+      }
+      _, lineno = target.source_location
+      target_line = lineno + 2
 
-        ScratchPad.recorded.should == [target_line]
+      trace.enable(target_line: target_line, target: target) do
+        target.call
       end
 
-      it "raises ArgumentError if :target option isn't specified" do
-        trace = TracePoint.new(:line) do |tp|
-        end
+      ScratchPad.recorded.should == [target_line]
+    end
 
-        -> {
-          trace.enable(target_line: 67) do
-          end
-        }.should raise_error(ArgumentError, /only target_line is specified/)
-      end
+    it "raises ArgumentError if :target option isn't specified" do
+      trace = TracePoint.new(:line) {}
 
-      it "raises ArgumentError if :line event isn't registered" do
-        trace = TracePoint.new(:call) do |tp|
+      -> {
+        trace.enable(target_line: 67) do
         end
+      }.should raise_error(ArgumentError, /only target_line is specified/)
+    end
 
-        target = -> {
-          x = 1
-          y = 2     # <= this line is target
-          z = x + y
-        }
-        _, lineno = target.source_location
-        target_line = lineno + 2
+    it "raises ArgumentError if :line event isn't registered" do
+      trace = TracePoint.new(:call) {}
 
-        -> {
-          trace.enable(target_line: target_line, target: target) do
-          end
-        }.should raise_error(ArgumentError, /target_line is specified, but line event is not specified/)
-      end
+      target = -> {
+        x = 1
+        y = 2     # <= this line is target
+        z = x + y
+      }
+      _, lineno = target.source_location
+      target_line = lineno + 2
 
-      it "raises ArgumentError if :target_line value is out of target code lines range" do
-        trace = TracePoint.new(:line) do |tp|
+      -> {
+        trace.enable(target_line: target_line, target: target) do
         end
+      }.should raise_error(ArgumentError, /target_line is specified, but line event is not specified/)
+    end
 
-        -> {
-          trace.enable(target_line: 1, target: -> { }) do
-          end
-        }.should raise_error(ArgumentError, /can not enable any hooks/)
-      end
+    it "raises ArgumentError if :target_line value is out of target code lines range" do
+      trace = TracePoint.new(:line) {}
 
-      it "raises TypeError if :target_line value couldn't be coerced to Integer" do
-        trace = TracePoint.new(:line) do |tp|
+      -> {
+        trace.enable(target_line: 1, target: -> { }) do
         end
+      }.should raise_error(ArgumentError, /can not enable any hooks/)
+    end
 
-        -> {
-          trace.enable(target_line: Object.new, target: -> { }) do
-          end
-        }.should raise_error(TypeError, /no implicit conversion of \w+? into Integer/)
-      end
+    it "raises TypeError if :target_line value couldn't be coerced to Integer" do
+      trace = TracePoint.new(:line) {}
 
-      it "raises ArgumentError if :target_line value is negative" do
-        trace = TracePoint.new(:line) do |tp|
+      -> {
+        trace.enable(target_line: Object.new, target: -> { }) do
         end
+      }.should raise_error(TypeError, /no implicit conversion of \w+? into Integer/)
+    end
 
-        -> {
-          trace.enable(target_line: -2, target: -> { }) do
-          end
-        }.should raise_error(ArgumentError, /can not enable any hooks/)
-      end
+    it "raises ArgumentError if :target_line value is negative" do
+      trace = TracePoint.new(:line) {}
 
-      it "accepts value that could be coerced to Integer" do
-        trace = TracePoint.new(:line) do |tp|
-          ScratchPad << tp.lineno
+      -> {
+        trace.enable(target_line: -2, target: -> { }) do
         end
+      }.should raise_error(ArgumentError, /can not enable any hooks/)
+    end
 
-        target = -> {
-          x = 1         #  <= this line is target
-        }
-        _, lineno = target.source_location
-        target_line = lineno + 1
+    it "accepts value that could be coerced to Integer" do
+      trace = TracePoint.new(:line) do |tp|
+        next unless TracePointSpec.target_thread?
+        ScratchPad << tp.lineno
+      end
 
-        trace.enable(target_line: target_line.to_r, target: target) do
-          target.call
-        end
+      target = -> {
+        x = 1         #  <= this line is target
+      }
+      _, lineno = target.source_location
+      target_line = lineno + 1
 
-        ScratchPad.recorded.should == [target_line]
+      trace.enable(target_line: target_line.to_r, target: target) do
+        target.call
       end
+
+      ScratchPad.recorded.should == [target_line]
     end
   end
 end
diff --git a/spec/ruby/core/tracepoint/enabled_spec.rb b/spec/ruby/core/tracepoint/enabled_spec.rb
index 0167d32fb0..0e9566a02c 100644
--- a/spec/ruby/core/tracepoint/enabled_spec.rb
+++ b/spec/ruby/core/tracepoint/enabled_spec.rb
@@ -1,14 +1,15 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#enabled?' do
   it 'returns true when current status of the trace is enable' do
     trace = TracePoint.new(:line) {}
     trace.enable do
-      trace.enabled?.should == true
+      trace.should.enabled?
     end
   end
 
   it 'returns false when current status of the trace is disabled' do
-    TracePoint.new(:line) {}.enabled?.should == false
+    TracePoint.new(:line) {}.should_not.enabled?
   end
 end
diff --git a/spec/ruby/core/tracepoint/eval_script_spec.rb b/spec/ruby/core/tracepoint/eval_script_spec.rb
index 1d8e425a9a..7ec53e7094 100644
--- a/spec/ruby/core/tracepoint/eval_script_spec.rb
+++ b/spec/ruby/core/tracepoint/eval_script_spec.rb
@@ -1,24 +1,23 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is "2.6" do
-  describe "TracePoint#eval_script" do
-    it "is the evald source code" do
-      ScratchPad.record []
+describe "TracePoint#eval_script" do
+  it "is the evald source code" do
+    ScratchPad.record []
 
-      script = <<-CODE
-        def foo
-          p :hello
-        end
-      CODE
-
-      TracePoint.new(:script_compiled) do |e|
-        ScratchPad << e.eval_script
-      end.enable do
-        eval script
+    script = <<-CODE
+      def foo
+        p :hello
       end
+    CODE
 
-      ScratchPad.recorded.should == [script]
+    TracePoint.new(:script_compiled) do |e|
+      next unless TracePointSpec.target_thread?
+      ScratchPad << e.eval_script
+    end.enable do
+      eval script
     end
+
+    ScratchPad.recorded.should == [script]
   end
 end
diff --git a/spec/ruby/core/tracepoint/event_spec.rb b/spec/ruby/core/tracepoint/event_spec.rb
index 019d0c3253..9dea24d125 100644
--- a/spec/ruby/core/tracepoint/event_spec.rb
+++ b/spec/ruby/core/tracepoint/event_spec.rb
@@ -5,6 +5,7 @@ describe 'TracePoint#event' do
   it 'returns the type of event' do
     event_name = nil
     TracePoint.new(:end, :call) do |tp|
+      next unless TracePointSpec.target_thread?
       event_name = tp.event
     end.enable do
       TracePointSpec.test
diff --git a/spec/ruby/core/tracepoint/fixtures/classes.rb b/spec/ruby/core/tracepoint/fixtures/classes.rb
index 49c70e1915..3ab1b00b16 100644
--- a/spec/ruby/core/tracepoint/fixtures/classes.rb
+++ b/spec/ruby/core/tracepoint/fixtures/classes.rb
@@ -1,4 +1,10 @@
 module TracePointSpec
+  @thread = Thread.current
+
+  def self.target_thread?
+    Thread.current == @thread
+  end
+
   class ClassWithMethodAlias
     def m
     end
diff --git a/spec/ruby/core/tracepoint/inspect_spec.rb b/spec/ruby/core/tracepoint/inspect_spec.rb
index 9ff1653ae8..6cc2ebe243 100644
--- a/spec/ruby/core/tracepoint/inspect_spec.rb
+++ b/spec/ruby/core/tracepoint/inspect_spec.rb
@@ -2,27 +2,140 @@ require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
 describe 'TracePoint#inspect' do
+  before do
+    @path_prefix = ' '
+  end
+
   it 'returns a string containing a human-readable TracePoint status' do
-    TracePoint.new(:line) {}.inspect.should ==
-      '#<TracePoint:disabled>'
+    TracePoint.new(:line) {}.inspect.should == '#<TracePoint:disabled>'
+  end
+
+  it "shows only whether it's enabled when outside the TracePoint handler" do
+    trace = TracePoint.new(:line) {}
+    trace.enable
+
+    trace.inspect.should == '#<TracePoint:enabled>'
+
+    trace.disable
   end
 
   it 'returns a String showing the event, path and line' do
     inspect = nil
-    line = __LINE__
-    TracePoint.new(:line) { |tp| inspect = tp.inspect }.enable do
-      inspect.should == "#<TracePoint:line@#{__FILE__}:#{line+2}>"
+    line = nil
+    TracePoint.new(:line) { |tp|
+      next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
+      inspect ||= tp.inspect
+    }.enable do
+      line = __LINE__
+    end
+
+    inspect.should == "#<TracePoint:line#{@path_prefix}#{__FILE__}:#{line}>"
+  end
+
+  it 'returns a String showing the event, method, path and line for a :call event' do
+    inspect = nil
+    line = nil
+    TracePoint.new(:call) { |tp|
+      next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
+      inspect ||= tp.inspect
+    }.enable do
+      line = __LINE__ + 1
+      def trace_point_spec_test_call; end
+      trace_point_spec_test_call
+    end
+
+    inspect.should =~ /\A#<TracePoint:call [`']trace_point_spec_test_call'#{@path_prefix}#{__FILE__}:#{line}>\z/
+  end
+
+  it 'returns a String showing the event, method, path and line for a :return event' do
+    inspect = nil
+    line = nil
+    TracePoint.new(:return) { |tp|
+      next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
+      inspect ||= tp.inspect
+    }.enable do
+      line = __LINE__ + 4
+      def trace_point_spec_test_return
+        a = 1
+        return a
+      end
+      trace_point_spec_test_return
+    end
+    ruby_version_is("3.4") { line -= 1 }
+
+    inspect.should =~ /\A#<TracePoint:return [`']trace_point_spec_test_return'#{@path_prefix}#{__FILE__}:#{line}>\z/
+  end
+
+  it 'returns a String showing the event, method, path and line for a :c_call event' do
+    inspect = nil
+    tracepoint = TracePoint.new(:c_call) { |tp|
+      next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
+      inspect ||= tp.inspect
+    }
+    line = __LINE__ + 2
+    tracepoint.enable do
+      [0, 1].max
     end
+
+    inspect.should =~ /\A#<TracePoint:c_call [`']max'#{@path_prefix}#{__FILE__}:#{line}>\z/
   end
 
   it 'returns a String showing the event, path and line for a :class event' do
     inspect = nil
-    line = __LINE__
-    TracePoint.new(:class) { |tp| inspect = tp.inspect }.enable do
+    line = nil
+    TracePoint.new(:class) { |tp|
+      next unless TracePointSpec.target_thread?
+      next unless tp.path == __FILE__
+
+      inspect ||= tp.inspect
+    }.enable do
+      line = __LINE__ + 1
       class TracePointSpec::C
       end
     end
 
-    inspect.should == "#<TracePoint:class@#{__FILE__}:#{line+2}>"
+    inspect.should == "#<TracePoint:class#{@path_prefix}#{__FILE__}:#{line}>"
+  end
+
+  it 'returns a String showing the event and thread for :thread_begin event' do
+    inspect = nil
+    thread = nil
+    thread_inspection = nil
+    TracePoint.new(:thread_begin) { |tp|
+      next unless Thread.current == thread
+
+      inspect ||= tp.inspect
+    }.enable(target_thread: nil) do
+      thread = Thread.new {}
+      thread_inspection = thread.inspect
+      thread.join
+    end
+
+    inspect.should == "#<TracePoint:thread_begin #{thread_inspection}>"
+  end
+
+  it 'returns a String showing the event and thread for :thread_end event' do
+    inspect = nil
+    thread = nil
+    thread_inspection = nil
+    TracePoint.new(:thread_end) { |tp|
+      next unless Thread.current == thread
+
+      inspect ||= tp.inspect
+    }.enable(target_thread: nil) do
+      thread = Thread.new {}
+      thread_inspection = thread.inspect
+      thread.join
+    end
+
+    inspect.should == "#<TracePoint:thread_end #{thread_inspection}>"
   end
 end
diff --git a/spec/ruby/core/tracepoint/lineno_spec.rb b/spec/ruby/core/tracepoint/lineno_spec.rb
index a4d7e77e8d..77b3ac8b54 100644
--- a/spec/ruby/core/tracepoint/lineno_spec.rb
+++ b/spec/ruby/core/tracepoint/lineno_spec.rb
@@ -1,10 +1,20 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#lineno' do
   it 'returns the line number of the event' do
     lineno = nil
-    TracePoint.new(:line) { |tp| lineno = tp.lineno }.enable do
-      lineno.should == 7
+    TracePoint.new(:line) { |tp|
+      next unless TracePointSpec.target_thread?
+      lineno = tp.lineno
+    }.enable do
+      line_event = true
     end
+    lineno.should == __LINE__ - 2
+  end
+
+  it 'raises RuntimeError if accessed from outside' do
+    tp = TracePoint.new(:line) {}
+    -> { tp.lineno }.should raise_error(RuntimeError, 'access from outside')
   end
 end
diff --git a/spec/ruby/core/tracepoint/method_id_spec.rb b/spec/ruby/core/tracepoint/method_id_spec.rb
index 82254d1299..43e23248b7 100644
--- a/spec/ruby/core/tracepoint/method_id_spec.rb
+++ b/spec/ruby/core/tracepoint/method_id_spec.rb
@@ -1,12 +1,14 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#method_id' do
-  def test; end
-
   it 'returns the name at the definition of the method being called' do
     method_name = nil
-    TracePoint.new(:call) { |tp| method_name = tp.method_id}.enable do
-      test
+    TracePoint.new(:call) { |tp|
+      next unless TracePointSpec.target_thread?
+      method_name = tp.method_id
+    }.enable do
+      TracePointSpec.test
       method_name.should equal(:test)
     end
   end
diff --git a/spec/ruby/core/tracepoint/new_spec.rb b/spec/ruby/core/tracepoint/new_spec.rb
index 916d826fdf..e53c2b04a2 100644
--- a/spec/ruby/core/tracepoint/new_spec.rb
+++ b/spec/ruby/core/tracepoint/new_spec.rb
@@ -8,7 +8,10 @@ describe 'TracePoint.new' do
 
   it 'includes :line event when event is not specified' do
     event_name = nil
-    TracePoint.new() { |tp| event_name = tp.event }.enable do
+    TracePoint.new { |tp|
+      next unless TracePointSpec.target_thread?
+      event_name = tp.event
+    }.enable do
       event_name.should equal(:line)
 
       event_name = nil
@@ -25,7 +28,10 @@ describe 'TracePoint.new' do
     event_name = nil
     (o = mock('line')).should_receive(:to_sym).and_return(:line)
 
-    TracePoint.new(o) { |tp| event_name = tp.event }.enable do
+    TracePoint.new(o) { |tp|
+      next unless TracePointSpec.target_thread?
+      event_name = tp.event
+    }.enable do
       line_event = true
       event_name.should == :line
     end
@@ -34,6 +40,7 @@ describe 'TracePoint.new' do
   it 'includes multiple events when multiple event names are passed as params' do
     event_name = nil
     TracePoint.new(:end, :call) do |tp|
+      next unless TracePointSpec.target_thread?
       event_name = tp.event
     end.enable do
       TracePointSpec.test
@@ -49,16 +56,14 @@ describe 'TracePoint.new' do
 
   it 'raises a TypeError when the given object is not a string/symbol' do
     o = mock('123')
-    -> { TracePoint.new(o) {}}.should raise_error(TypeError)
+    -> { TracePoint.new(o) {} }.should raise_error(TypeError)
 
     o.should_receive(:to_sym).and_return(123)
-    -> { TracePoint.new(o) {}}.should raise_error(TypeError)
+    -> { TracePoint.new(o) {} }.should raise_error(TypeError)
   end
 
-  ruby_version_is "2.5" do
-    it 'expects to be called with a block' do
-      -> { TracePoint.new(:line) }.should raise_error(ArgumentError, "must be called with a block")
-    end
+  it 'expects to be called with a block' do
+    -> { TracePoint.new(:line) }.should raise_error(ArgumentError, "must be called with a block")
   end
 
   it "raises a Argument error when the given argument doesn't match an event name" do
diff --git a/spec/ruby/core/tracepoint/parameters_spec.rb b/spec/ruby/core/tracepoint/parameters_spec.rb
index f901c184f4..82aee3caa4 100644
--- a/spec/ruby/core/tracepoint/parameters_spec.rb
+++ b/spec/ruby/core/tracepoint/parameters_spec.rb
@@ -1,23 +1,28 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
-ruby_version_is "2.6" do
-  describe 'TracePoint#parameters' do
-    it 'returns the parameters of block' do
-      f = proc {|x, y, z| }
-      parameters = nil
-      TracePoint.new(:b_call) {|tp| parameters = tp.parameters }.enable do
-        f.call
-        parameters.should == [[:opt, :x], [:opt, :y], [:opt, :z]]
-      end
+describe 'TracePoint#parameters' do
+  it 'returns the parameters of block' do
+    f = proc {|x, y, z| }
+    parameters = nil
+    TracePoint.new(:b_call) { |tp|
+      next unless TracePointSpec.target_thread?
+      parameters = tp.parameters
+    }.enable do
+      f.call
+      parameters.should == [[:opt, :x], [:opt, :y], [:opt, :z]]
     end
+  end
 
-    it 'returns the parameters of lambda block' do
-      f = -> x, y, z { }
-      parameters = nil
-      TracePoint.new(:b_call) {|tp| parameters = tp.parameters }.enable do
-        f.call(1, 2, 3)
-        parameters.should == [[:req, :x], [:req, :y], [:req, :z]]
-      end
+  it 'returns the parameters of lambda block' do
+    f = -> x, y, z { }
+    parameters = nil
+    TracePoint.new(:b_call) { |tp|
+      next unless TracePointSpec.target_thread?
+      parameters = tp.parameters
+    }.enable do
+      f.call(1, 2, 3)
+      parameters.should == [[:req, :x], [:req, :y], [:req, :z]]
     end
   end
 end
diff --git a/spec/ruby/core/tracepoint/path_spec.rb b/spec/ruby/core/tracepoint/path_spec.rb
index 1e31c1bb68..dc2ca840b8 100644
--- a/spec/ruby/core/tracepoint/path_spec.rb
+++ b/spec/ruby/core/tracepoint/path_spec.rb
@@ -1,18 +1,41 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#path' do
   it 'returns the path of the file being run' do
     path = nil
-    TracePoint.new(:line) { |tp| path = tp.path }.enable do
-      path.should == "#{__FILE__}"
+    TracePoint.new(:line) { |tp|
+      next unless TracePointSpec.target_thread?
+      path = tp.path
+    }.enable do
+      line_event = true
     end
+    path.should == "#{__FILE__}"
   end
 
-  it 'equals (eval) inside an eval for :end event' do
-    path = nil
-    TracePoint.new(:end) { |tp| path = tp.path }.enable do
-      eval("module TracePointSpec; end")
+  ruby_version_is ""..."3.3" do
+    it 'equals (eval) inside an eval for :end event' do
+      path = nil
+      TracePoint.new(:end) { |tp|
+        next unless TracePointSpec.target_thread?
+        path = tp.path
+      }.enable do
+        eval("module TracePointSpec; end")
+      end
       path.should == '(eval)'
     end
   end
+
+  ruby_version_is "3.3" do
+    it 'equals "(eval at __FILE__:__LINE__)" inside an eval for :end event' do
+      path = nil
+      TracePoint.new(:end) { |tp|
+        next unless TracePointSpec.target_thread?
+        path = tp.path
+      }.enable do
+        eval("module TracePointSpec; end")
+      end
+      path.should == "(eval at #{__FILE__}:#{__LINE__ - 2})"
+    end
+  end
 end
diff --git a/spec/ruby/core/tracepoint/raised_exception_spec.rb b/spec/ruby/core/tracepoint/raised_exception_spec.rb
index 450717b958..5ac8531840 100644
--- a/spec/ruby/core/tracepoint/raised_exception_spec.rb
+++ b/spec/ruby/core/tracepoint/raised_exception_spec.rb
@@ -1,9 +1,13 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#raised_exception' do
   it 'returns value from exception raised on the :raise event' do
     raised_exception, error_result = nil
-    trace = TracePoint.new(:raise) { |tp| raised_exception = tp.raised_exception }
+    trace = TracePoint.new(:raise) { |tp|
+      next unless TracePointSpec.target_thread?
+      raised_exception = tp.raised_exception
+    }
     trace.enable do
       begin
         raise StandardError
@@ -13,4 +17,22 @@ describe 'TracePoint#raised_exception' do
       raised_exception.should equal(error_result)
     end
   end
+
+  ruby_version_is "3.3" do
+    it 'returns value from exception rescued on the :rescue event' do
+      raised_exception, error_result = nil
+      trace = TracePoint.new(:rescue) { |tp|
+        next unless TracePointSpec.target_thread?
+        raised_exception = tp.raised_exception
+      }
+      trace.enable do
+        begin
+          raise StandardError
+        rescue => e
+          error_result = e
+        end
+        raised_exception.should equal(error_result)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/core/tracepoint/return_value_spec.rb b/spec/ruby/core/tracepoint/return_value_spec.rb
index f0ed86bd00..e84c7dd762 100644
--- a/spec/ruby/core/tracepoint/return_value_spec.rb
+++ b/spec/ruby/core/tracepoint/return_value_spec.rb
@@ -1,11 +1,15 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint#return_value' do
   def test; 'test' end
 
   it 'returns value from :return event' do
     trace_value = nil
-    TracePoint.new(:return) { |tp| trace_value = tp.return_value}.enable do
+    TracePoint.new(:return) { |tp|
+      next unless TracePointSpec.target_thread?
+      trace_value = tp.return_value
+    }.enable do
       test
       trace_value.should == 'test'
     end
diff --git a/spec/ruby/core/tracepoint/self_spec.rb b/spec/ruby/core/tracepoint/self_spec.rb
index 8bfd09301e..2098860e59 100644
--- a/spec/ruby/core/tracepoint/self_spec.rb
+++ b/spec/ruby/core/tracepoint/self_spec.rb
@@ -4,14 +4,20 @@ require_relative 'fixtures/classes'
 describe 'TracePoint#self' do
   it 'return the trace object from event' do
     trace = nil
-    TracePoint.new(:line) { |tp| trace = tp.self }.enable do
+    TracePoint.new(:line) { |tp|
+      next unless TracePointSpec.target_thread?
+      trace = tp.self
+    }.enable do
       trace.equal?(self).should be_true
     end
   end
 
   it 'return the class object from a class event' do
     trace = nil
-    TracePoint.new(:class) { |tp| trace = tp.self }.enable do
+    TracePoint.new(:class) { |tp|
+      next unless TracePointSpec.target_thread?
+      trace = tp.self
+    }.enable do
       class TracePointSpec::C
       end
     end
diff --git a/spec/ruby/core/tracepoint/trace_spec.rb b/spec/ruby/core/tracepoint/trace_spec.rb
index ea6c85bcc5..167f594bb9 100644
--- a/spec/ruby/core/tracepoint/trace_spec.rb
+++ b/spec/ruby/core/tracepoint/trace_spec.rb
@@ -1,9 +1,10 @@
 require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
 
 describe 'TracePoint.trace' do
   it 'activates the trace automatically' do
     trace = TracePoint.trace(:line) {}
-    trace.enabled?.should == true
+    trace.should.enabled?
     trace.disable
   end
 end
diff --git a/spec/ruby/core/true/case_compare_spec.rb b/spec/ruby/core/true/case_compare_spec.rb
new file mode 100644
index 0000000000..dee6dd0227
--- /dev/null
+++ b/spec/ruby/core/true/case_compare_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe "TrueClass#===" do
+  it "returns true for true" do
+    (true === true).should == true
+  end
+
+  it "returns false for non-true object" do
+    (true === 1).should == false
+    (true === "").should == false
+    (true === Object).should == false
+  end
+end
diff --git a/spec/ruby/core/true/singleton_method_spec.rb b/spec/ruby/core/true/singleton_method_spec.rb
new file mode 100644
index 0000000000..c06793850f
--- /dev/null
+++ b/spec/ruby/core/true/singleton_method_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+
+describe "TrueClass#singleton_method" do
+  ruby_version_is '3.3' do
+    it "raises regardless of whether TrueClass defines the method" do
+      -> { true.singleton_method(:foo) }.should raise_error(NameError)
+      begin
+        def (true).foo; end
+        -> { true.singleton_method(:foo) }.should raise_error(NameError)
+      ensure
+        TrueClass.send(:remove_method, :foo)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/true/to_s_spec.rb b/spec/ruby/core/true/to_s_spec.rb
index 30ca354b0c..fa1b53a580 100644
--- a/spec/ruby/core/true/to_s_spec.rb
+++ b/spec/ruby/core/true/to_s_spec.rb
@@ -4,4 +4,12 @@ describe "TrueClass#to_s" do
   it "returns the string 'true'" do
     true.to_s.should == "true"
   end
+
+  it "returns a frozen string" do
+    true.to_s.should.frozen?
+  end
+
+  it "always returns the same string" do
+    true.to_s.should equal(true.to_s)
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/bind_call_spec.rb b/spec/ruby/core/unboundmethod/bind_call_spec.rb
index c5d392156c..80b2095d86 100644
--- a/spec/ruby/core/unboundmethod/bind_call_spec.rb
+++ b/spec/ruby/core/unboundmethod/bind_call_spec.rb
@@ -1,52 +1,58 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
 
-ruby_version_is '2.7' do
-  describe "UnboundMethod#bind_call" do
-    before :each do
-      @normal_um = UnboundMethodSpecs::Methods.new.method(:foo).unbind
-      @parent_um = UnboundMethodSpecs::Parent.new.method(:foo).unbind
-      @child1_um = UnboundMethodSpecs::Child1.new.method(:foo).unbind
-      @child2_um = UnboundMethodSpecs::Child2.new.method(:foo).unbind
-    end
+describe "UnboundMethod#bind_call" do
+  before :each do
+    @normal_um = UnboundMethodSpecs::Methods.new.method(:foo).unbind
+    @parent_um = UnboundMethodSpecs::Parent.new.method(:foo).unbind
+    @child1_um = UnboundMethodSpecs::Child1.new.method(:foo).unbind
+    @child2_um = UnboundMethodSpecs::Child2.new.method(:foo).unbind
+    @normal_um_super = UnboundMethodSpecs::Mod.instance_method(:foo_super)
+    @parent_um_super = UnboundMethodSpecs::Parent.new.method(:foo_super).unbind
+  end
 
-    it "raises TypeError if object is not kind_of? the Module the method defined in" do
-      -> { @normal_um.bind_call(UnboundMethodSpecs::B.new) }.should raise_error(TypeError)
-    end
+  it "raises TypeError if object is not kind_of? the Module the method defined in" do
+    -> { @normal_um.bind_call(UnboundMethodSpecs::B.new) }.should raise_error(TypeError)
+  end
 
-    it "binds and calls the method if object is kind_of the Module the method defined in" do
-      @normal_um.bind_call(UnboundMethodSpecs::Methods.new).should == true
-    end
+  it "binds and calls the method if object is kind_of the Module the method defined in" do
+    @normal_um.bind_call(UnboundMethodSpecs::Methods.new).should == true
+  end
 
-    it "binds and calls the method on any object when UnboundMethod is unbound from a module" do
-      UnboundMethodSpecs::Mod.instance_method(:from_mod).bind_call(Object.new).should == nil
-    end
+  it "binds and calls the method on any object when UnboundMethod is unbound from a module" do
+    UnboundMethodSpecs::Mod.instance_method(:from_mod).bind_call(Object.new).should == nil
+  end
 
-    it "binds and calls the method for any object kind_of? the Module the method is defined in" do
-      @parent_um.bind_call(UnboundMethodSpecs::Child1.new).should == nil
-      @child1_um.bind_call(UnboundMethodSpecs::Parent.new).should == nil
-      @child2_um.bind_call(UnboundMethodSpecs::Child1.new).should == nil
-    end
+  it "binds and calls the method for any object kind_of? the Module the method is defined in" do
+    @parent_um.bind_call(UnboundMethodSpecs::Child1.new).should == nil
+    @child1_um.bind_call(UnboundMethodSpecs::Parent.new).should == nil
+    @child2_um.bind_call(UnboundMethodSpecs::Child1.new).should == nil
+  end
 
-    it "binds and calls a Kernel method retrieved from Object on BasicObject" do
-      Object.instance_method(:instance_of?).bind_call(BasicObject.new, BasicObject).should == true
-    end
+  it "binds and calls a Kernel method retrieved from Object on BasicObject" do
+    Object.instance_method(:instance_of?).bind_call(BasicObject.new, BasicObject).should == true
+  end
 
-    it "binds and calls a Parent's class method to any Child's class methods" do
-      um = UnboundMethodSpecs::Parent.method(:class_method).unbind
-      um.bind_call(UnboundMethodSpecs::Child1).should == "I am UnboundMethodSpecs::Child1"
-    end
+  it "binds and calls a Parent's class method to any Child's class methods" do
+    um = UnboundMethodSpecs::Parent.method(:class_method).unbind
+    um.bind_call(UnboundMethodSpecs::Child1).should == "I am UnboundMethodSpecs::Child1"
+  end
 
-    it "will raise when binding a an object singleton's method to another object" do
-      other = UnboundMethodSpecs::Parent.new
-      p = UnboundMethodSpecs::Parent.new
-      class << p
-        def singleton_method
-          :single
-        end
+  it "will raise when binding a an object singleton's method to another object" do
+    other = UnboundMethodSpecs::Parent.new
+    p = UnboundMethodSpecs::Parent.new
+    class << p
+      def singleton_method
+        :single
       end
-      um = p.method(:singleton_method).unbind
-      ->{ um.bind_call(other) }.should raise_error(TypeError)
     end
+    um = p.method(:singleton_method).unbind
+    ->{ um.bind_call(other) }.should raise_error(TypeError)
+  end
+
+  it "allows calling super for module methods bound to hierarchies that do not already have that module" do
+    p = UnboundMethodSpecs::Parent.new
+
+    @normal_um_super.bind_call(p).should == true
   end
 end
diff --git a/spec/ruby/core/unboundmethod/bind_spec.rb b/spec/ruby/core/unboundmethod/bind_spec.rb
index 03aaa22e74..7658b664e5 100644
--- a/spec/ruby/core/unboundmethod/bind_spec.rb
+++ b/spec/ruby/core/unboundmethod/bind_spec.rb
@@ -7,6 +7,8 @@ describe "UnboundMethod#bind" do
     @parent_um = UnboundMethodSpecs::Parent.new.method(:foo).unbind
     @child1_um = UnboundMethodSpecs::Child1.new.method(:foo).unbind
     @child2_um = UnboundMethodSpecs::Child2.new.method(:foo).unbind
+    @normal_um_super = UnboundMethodSpecs::Mod.instance_method(:foo_super)
+    @parent_um_super = UnboundMethodSpecs::Parent.new.method(:foo_super).unbind
   end
 
   it "raises TypeError if object is not kind_of? the Module the method defined in" do
@@ -58,4 +60,10 @@ describe "UnboundMethod#bind" do
     um = p.method(:singleton_method).unbind
     ->{ um.bind(other) }.should raise_error(TypeError)
   end
+
+  it "allows calling super for module methods bound to hierarchies that do not already have that module" do
+    p = UnboundMethodSpecs::Parent.new
+
+    @normal_um_super.bind(p).call.should == true
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/clone_spec.rb b/spec/ruby/core/unboundmethod/clone_spec.rb
index 098ee61476..1e7fb18744 100644
--- a/spec/ruby/core/unboundmethod/clone_spec.rb
+++ b/spec/ruby/core/unboundmethod/clone_spec.rb
@@ -1,12 +1,13 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
+require_relative 'shared/dup'
 
 describe "UnboundMethod#clone" do
-  it "returns a copy of the UnboundMethod" do
-    um1 = UnboundMethodSpecs::Methods.instance_method(:foo)
-    um2 = um1.clone
+  it_behaves_like :unboundmethod_dup, :clone
 
-    (um1 == um2).should == true
-    um1.bind(UnboundMethodSpecs::Methods.new).call.should == um2.bind(UnboundMethodSpecs::Methods.new).call
+  it "preserves frozen status" do
+    method = Class.instance_method(:instance_method)
+    method.freeze
+    method.frozen?.should == true
+    method.clone.frozen?.should == true
   end
 end
diff --git a/spec/ruby/core/unboundmethod/dup_spec.rb b/spec/ruby/core/unboundmethod/dup_spec.rb
new file mode 100644
index 0000000000..5a78dd8e36
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/dup_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+require_relative 'shared/dup'
+
+describe "UnboundMethod#dup" do
+  ruby_version_is "3.4" do
+    it_behaves_like :unboundmethod_dup, :dup
+
+    it "resets frozen status" do
+      method = Class.instance_method(:instance_method)
+      method.freeze
+      method.frozen?.should == true
+      method.dup.frozen?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/equal_value_spec.rb b/spec/ruby/core/unboundmethod/equal_value_spec.rb
index 6242b04884..b2d78c50af 100644
--- a/spec/ruby/core/unboundmethod/equal_value_spec.rb
+++ b/spec/ruby/core/unboundmethod/equal_value_spec.rb
@@ -76,19 +76,19 @@ describe "UnboundMethod#==" do
     (@identical_body == @original_body).should == false
   end
 
-  it "returns false if same method but one extracted from a subclass" do
-    (@parent == @child1).should == false
-    (@child1 == @parent).should == false
+  it "returns true if same method but one extracted from a subclass" do
+    (@parent == @child1).should == true
+    (@child1 == @parent).should == true
   end
 
-  it "returns false if same method but extracted from two different subclasses" do
-    (@child2 == @child1).should == false
-    (@child1 == @child2).should == false
+  it "returns true if same method but extracted from two different subclasses" do
+    (@child2 == @child1).should == true
+    (@child1 == @child2).should == true
   end
 
-  it "returns false if methods are the same but added from an included Module" do
-    (@includee == @includer).should == false
-    (@includer == @includee).should == false
+  it "returns true if methods are the same but added from an included Module" do
+    (@includee == @includer).should == true
+    (@includer == @includee).should == true
   end
 
   it "returns false if both have same Module, same name, identical body but not the same" do
@@ -98,4 +98,41 @@ describe "UnboundMethod#==" do
 
     (@discard_1 == UnboundMethodSpecs::Methods.instance_method(:discard_1)).should == false
   end
+
+  it "considers methods through aliasing equal" do
+    c = Class.new do
+      class << self
+        alias_method :n, :new
+      end
+    end
+
+    c.method(:new).should == c.method(:n)
+    c.method(:n).should == Class.instance_method(:new).bind(c)
+  end
+
+  # On CRuby < 3.2, the 2 specs below pass due to method/instance_method skipping zsuper methods.
+  # We are interested in the general pattern working, i.e. the combination of method/instance_method
+  # and #== exposes the wanted behavior.
+  it "considers methods through visibility change equal" do
+    c = Class.new do
+      class << self
+        private :new
+      end
+    end
+
+    c.method(:new).should == Class.instance_method(:new).bind(c)
+  end
+
+  it "considers methods through aliasing and visibility change equal" do
+    c = Class.new do
+      class << self
+        alias_method :n, :new
+        private :new
+      end
+    end
+
+    c.method(:new).should == c.method(:n)
+    c.method(:n).should == Class.instance_method(:new).bind(c)
+    c.method(:new).should == Class.instance_method(:new).bind(c)
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/fixtures/classes.rb b/spec/ruby/core/unboundmethod/fixtures/classes.rb
index 43e21916bf..28d8e0a965 100644
--- a/spec/ruby/core/unboundmethod/fixtures/classes.rb
+++ b/spec/ruby/core/unboundmethod/fixtures/classes.rb
@@ -22,6 +22,7 @@ module UnboundMethodSpecs
 
   module Mod
     def from_mod; end
+    def foo_super; super; end
   end
 
   class Methods
@@ -34,6 +35,7 @@ module UnboundMethodSpecs
     def with_block(&block); end
 
     alias bar foo
+    alias baz bar
     alias alias_1 foo
     alias alias_2 foo
 
@@ -52,10 +54,19 @@ module UnboundMethodSpecs
 
     def discard_1(); :discard; end
     def discard_2(); :discard; end
+
+    def my_public_method; end
+    def my_protected_method; end
+    def my_private_method; end
+    protected :my_protected_method
+    private :my_private_method
   end
 
   class Parent
     def foo; end
+    def foo_super
+      true
+    end
     def self.class_method
       "I am #{name}"
     end
@@ -83,4 +94,14 @@ module UnboundMethodSpecs
   class C < B
     def overridden; end
   end
+
+  module HashSpecs
+    class SuperClass
+      def foo
+      end
+    end
+
+    class SubClass < SuperClass
+    end
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/hash_spec.rb b/spec/ruby/core/unboundmethod/hash_spec.rb
index 12dce0020f..6888675bc1 100644
--- a/spec/ruby/core/unboundmethod/hash_spec.rb
+++ b/spec/ruby/core/unboundmethod/hash_spec.rb
@@ -12,4 +12,11 @@ describe "UnboundMethod#hash" do
     to_s, inspect = Array.instance_method(:to_s), Array.instance_method(:inspect)
     to_s.hash.should == inspect.hash
   end
+
+  it "equals a hash of the same method in the superclass" do
+    foo_in_superclass = UnboundMethodSpecs::HashSpecs::SuperClass.instance_method(:foo)
+    foo = UnboundMethodSpecs::HashSpecs::SubClass.instance_method(:foo)
+
+    foo.hash.should == foo_in_superclass.hash
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/original_name_spec.rb b/spec/ruby/core/unboundmethod/original_name_spec.rb
new file mode 100644
index 0000000000..7280dcb2b4
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/original_name_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "UnboundMethod#original_name" do
+  it "returns the name of the method" do
+    String.instance_method(:upcase).original_name.should == :upcase
+  end
+
+  it "returns the original name" do
+    obj = UnboundMethodSpecs::Methods.new
+    obj.method(:foo).unbind.original_name.should == :foo
+    obj.method(:bar).unbind.original_name.should == :foo
+    UnboundMethodSpecs::Methods.instance_method(:bar).original_name.should == :foo
+  end
+
+  it "returns the original name even when aliased twice" do
+    obj = UnboundMethodSpecs::Methods.new
+    obj.method(:foo).unbind.original_name.should == :foo
+    obj.method(:baz).unbind.original_name.should == :foo
+    UnboundMethodSpecs::Methods.instance_method(:baz).original_name.should == :foo
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/owner_spec.rb b/spec/ruby/core/unboundmethod/owner_spec.rb
index 5f1f4646b3..b099c56de1 100644
--- a/spec/ruby/core/unboundmethod/owner_spec.rb
+++ b/spec/ruby/core/unboundmethod/owner_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../method/fixtures/classes'
 
 describe "UnboundMethod#owner" do
   it "returns the owner of the method" do
@@ -23,4 +24,8 @@ describe "UnboundMethod#owner" do
     child_singleton_class.instance_method(:class_method).owner.should == parent_singleton_class
     child_singleton_class.instance_method(:another_class_method).owner.should == child_singleton_class
   end
+
+  it "returns the class on which public was called for a private method in ancestor" do
+    MethodSpecs::InheritedMethods::C.instance_method(:derp).owner.should == MethodSpecs::InheritedMethods::C
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/private_spec.rb b/spec/ruby/core/unboundmethod/private_spec.rb
new file mode 100644
index 0000000000..5a563939d1
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/private_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "UnboundMethod#private?" do
+  it "has been removed" do
+    obj = UnboundMethodSpecs::Methods.new
+    obj.method(:my_private_method).unbind.should_not.respond_to?(:private?)
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/protected_spec.rb b/spec/ruby/core/unboundmethod/protected_spec.rb
new file mode 100644
index 0000000000..70622d658d
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/protected_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "UnboundMethod#protected?" do
+  it "has been removed" do
+    obj = UnboundMethodSpecs::Methods.new
+    obj.method(:my_protected_method).unbind.should_not.respond_to?(:protected?)
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/public_spec.rb b/spec/ruby/core/unboundmethod/public_spec.rb
new file mode 100644
index 0000000000..ae75e2601c
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/public_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "UnboundMethod#public?" do
+  it "has been removed" do
+    obj = UnboundMethodSpecs::Methods.new
+    obj.method(:my_public_method).unbind.should_not.respond_to?(:public?)
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/shared/dup.rb b/spec/ruby/core/unboundmethod/shared/dup.rb
new file mode 100644
index 0000000000..194e2cc1a1
--- /dev/null
+++ b/spec/ruby/core/unboundmethod/shared/dup.rb
@@ -0,0 +1,32 @@
+describe :unboundmethod_dup, shared: true do
+  it "returns a copy of self" do
+    a = Class.instance_method(:instance_method)
+    b = a.send(@method)
+
+    a.should == b
+    a.should_not equal(b)
+  end
+
+  ruby_version_is "3.4" do
+    it "copies instance variables" do
+      method = Class.instance_method(:instance_method)
+      method.instance_variable_set(:@ivar, 1)
+      cl = method.send(@method)
+      cl.instance_variables.should == [:@ivar]
+    end
+
+    it "copies the finalizer" do
+      code = <<-'RUBY'
+        obj = Class.instance_method(:instance_method)
+
+        ObjectSpace.define_finalizer(obj, Proc.new { STDOUT.write "finalized\n" })
+
+        obj.clone
+
+        exit 0
+      RUBY
+
+      ruby_exe(code).lines.sort.should == ["finalized\n", "finalized\n"]
+    end
+  end
+end
diff --git a/spec/ruby/core/unboundmethod/shared/to_s.rb b/spec/ruby/core/unboundmethod/shared/to_s.rb
index 3987611d3f..6b2c9c3e79 100644
--- a/spec/ruby/core/unboundmethod/shared/to_s.rb
+++ b/spec/ruby/core/unboundmethod/shared/to_s.rb
@@ -20,6 +20,14 @@ describe :unboundmethod_to_s, shared: true do
   it "the String shows the method name, Module defined in and Module extracted from" do
     @from_module.send(@method).should =~ /\bfrom_mod\b/
     @from_module.send(@method).should =~ /\bUnboundMethodSpecs::Mod\b/
-    @from_method.send(@method).should =~ /\bUnboundMethodSpecs::Methods\b/
+  end
+
+  it "returns a String including all details" do
+    @from_module.send(@method).should.start_with? "#<UnboundMethod: UnboundMethodSpecs::Mod#from_mod"
+    @from_method.send(@method).should.start_with? "#<UnboundMethod: UnboundMethodSpecs::Mod#from_mod"
+  end
+
+  it "does not show the defining module if it is the same as the origin" do
+    UnboundMethodSpecs::A.instance_method(:baz).send(@method).should.start_with? "#<UnboundMethod: UnboundMethodSpecs::A#baz"
   end
 end
diff --git a/spec/ruby/core/unboundmethod/source_location_spec.rb b/spec/ruby/core/unboundmethod/source_location_spec.rb
index b5e6413816..9cc2198017 100644
--- a/spec/ruby/core/unboundmethod/source_location_spec.rb
+++ b/spec/ruby/core/unboundmethod/source_location_spec.rb
@@ -7,23 +7,23 @@ describe "UnboundMethod#source_location" do
   end
 
   it "sets the first value to the path of the file in which the method was defined" do
-    file = @method.source_location.first
+    file = @method.source_location[0]
     file.should be_an_instance_of(String)
-    file.should == File.realpath('../fixtures/classes.rb', __FILE__)
+    file.should == File.realpath('fixtures/classes.rb', __dir__)
   end
 
-  it "sets the last value to a Fixnum representing the line on which the method was defined" do
-    line = @method.source_location.last
-    line.should be_an_instance_of(Fixnum)
+  it "sets the second value to an Integer representing the line on which the method was defined" do
+    line = @method.source_location[1]
+    line.should be_an_instance_of(Integer)
     line.should == 5
   end
 
   it "returns the last place the method was defined" do
-    UnboundMethodSpecs::SourceLocation.method(:redefined).unbind.source_location.last.should == 13
+    UnboundMethodSpecs::SourceLocation.method(:redefined).unbind.source_location[1].should == 13
   end
 
   it "returns the location of the original method even if it was aliased" do
-    UnboundMethodSpecs::SourceLocation.instance_method(:aka).source_location.last.should == 17
+    UnboundMethodSpecs::SourceLocation.instance_method(:aka).source_location[1].should == 17
   end
 
   it "works for define_method methods" do
@@ -49,4 +49,17 @@ describe "UnboundMethod#source_location" do
     method.source_location[0].should =~ /#{__FILE__}/
     method.source_location[1].should == line
   end
+
+  it "works for eval with a given line" do
+    c = Class.new do
+      eval('def m; end', nil, "foo", 100)
+    end
+    location = c.instance_method(:m).source_location
+    ruby_version_is(""..."4.1") do
+      location.should == ["foo", 100]
+    end
+    ruby_version_is("4.1") do
+      location.should == ["foo", 100, 0, 100, 10]
+    end
+  end
 end
diff --git a/spec/ruby/core/unboundmethod/super_method_spec.rb b/spec/ruby/core/unboundmethod/super_method_spec.rb
index c9fa1ec533..aa7c129377 100644
--- a/spec/ruby/core/unboundmethod/super_method_spec.rb
+++ b/spec/ruby/core/unboundmethod/super_method_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/classes'
+require_relative '../method/fixtures/classes'
 
 describe "UnboundMethod#super_method" do
   it "returns the method that would be called by super in the method" do
@@ -25,4 +26,24 @@ describe "UnboundMethod#super_method" do
 
     method.super_method.should == nil
   end
+
+  # https://github.com/jruby/jruby/issues/7240
+  context "after changing an inherited methods visibility" do
+    it "calls the proper super method" do
+      method = MethodSpecs::InheritedMethods::C.instance_method(:derp)
+      method.bind(MethodSpecs::InheritedMethods::C.new).call.should == 'BA'
+    end
+
+    it "returns the expected super_method" do
+      method = MethodSpecs::InheritedMethods::C.instance_method(:derp)
+      method.super_method.owner.should == MethodSpecs::InheritedMethods::A
+    end
+  end
+
+  context "after aliasing an inherited method" do
+    it "returns the expected super_method" do
+      method = MethodSpecs::InheritedMethods::C.instance_method(:meow)
+      method.super_method.owner.should == MethodSpecs::InheritedMethods::A
+    end
+  end
 end
diff --git a/spec/ruby/core/warning/categories_spec.rb b/spec/ruby/core/warning/categories_spec.rb
new file mode 100644
index 0000000000..1e310ef38b
--- /dev/null
+++ b/spec/ruby/core/warning/categories_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "Warning.categories" do
+    # There might be more, but these are standard across Ruby implementations
+    it "returns the list of possible warning categories" do
+      Warning.categories.should.include? :deprecated
+      Warning.categories.should.include? :experimental
+      Warning.categories.should.include? :performance
+    end
+  end
+end
diff --git a/spec/ruby/core/warning/element_reference_spec.rb b/spec/ruby/core/warning/element_reference_spec.rb
new file mode 100644
index 0000000000..c0ed37ef13
--- /dev/null
+++ b/spec/ruby/core/warning/element_reference_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../spec_helper'
+
+describe "Warning.[]" do
+  it "returns default values for categories :deprecated and :experimental" do
+    # If any warning options were set on the Ruby that will be executed, then
+    # it's possible this test will fail. In this case we will skip this test.
+    skip if ruby_exe.any? { |opt| opt.start_with?("-W") }
+
+    ruby_exe('p [Warning[:deprecated], Warning[:experimental]]').chomp.should == "[false, true]"
+    ruby_exe('p [Warning[:deprecated], Warning[:experimental]]', options: "-w").chomp.should == "[true, true]"
+  end
+
+  ruby_version_is '3.3' do
+    it "returns default values for :performance category" do
+      ruby_exe('p Warning[:performance]').chomp.should == "false"
+      ruby_exe('p Warning[:performance]', options: "-w").chomp.should == "false"
+    end
+  end
+
+  it "raises for unknown category" do
+    -> { Warning[:noop] }.should raise_error(ArgumentError, /unknown category: noop/)
+  end
+
+  it "raises for non-Symbol category" do
+    -> { Warning[42] }.should raise_error(TypeError)
+    -> { Warning[false] }.should raise_error(TypeError)
+    -> { Warning["noop"] }.should raise_error(TypeError)
+  end
+end
diff --git a/spec/ruby/core/warning/element_set_spec.rb b/spec/ruby/core/warning/element_set_spec.rb
new file mode 100644
index 0000000000..d59a7d4c9e
--- /dev/null
+++ b/spec/ruby/core/warning/element_set_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+
+describe "Warning.[]=" do
+  it "emits and suppresses warnings for :deprecated" do
+    ruby_exe('Warning[:deprecated] = true; $; = ""', args: "2>&1").should =~ /is deprecated/
+    ruby_exe('Warning[:deprecated] = false; $; = ""', args: "2>&1").should == ""
+  end
+
+  describe ":experimental" do
+    before do
+      @src = 'warn "This is experimental warning.", category: :experimental'
+    end
+
+    it "emits and suppresses warnings for :experimental" do
+      ruby_exe("Warning[:experimental] = true; eval('#{@src}')", args: "2>&1").should =~ /is experimental/
+      ruby_exe("Warning[:experimental] = false; eval('#{@src}')", args: "2>&1").should == ""
+    end
+  end
+
+  ruby_version_is '3.3' do
+    it "enables or disables performance warnings" do
+      original = Warning[:performance]
+      begin
+        Warning[:performance] = !original
+        Warning[:performance].should == !original
+      ensure
+        Warning[:performance] = original
+      end
+    end
+  end
+
+  it "raises for unknown category" do
+    -> { Warning[:noop] = false }.should raise_error(ArgumentError, /unknown category: noop/)
+  end
+
+  it "raises for non-Symbol category" do
+    -> { Warning[42] = false }.should raise_error(TypeError)
+    -> { Warning[false] = false }.should raise_error(TypeError)
+    -> { Warning["noop"] = false }.should raise_error(TypeError)
+  end
+end
diff --git a/spec/ruby/core/warning/performance_warning_spec.rb b/spec/ruby/core/warning/performance_warning_spec.rb
new file mode 100644
index 0000000000..ab0badcd3d
--- /dev/null
+++ b/spec/ruby/core/warning/performance_warning_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../spec_helper'
+
+
+describe "Performance warnings" do
+  guard -> { ruby_version_is("3.4") || RUBY_ENGINE == "truffleruby" } do
+    # Optimising Integer, Float or Symbol methods is kind of implementation detail
+    # but multiple implementations do so. So it seems reasonable to have a test case
+    # for at least one such common method.
+    # See https://bugs.ruby-lang.org/issues/20429
+    context "when redefined optimised methods" do
+      it "emits performance warning for redefining Integer#+" do
+        code = <<~CODE
+          Warning[:performance] = true
+
+          class Integer
+            ORIG_METHOD = instance_method(:+)
+
+            def +(...)
+              ORIG_METHOD.bind(self).call(...)
+            end
+          end
+        CODE
+
+        ruby_exe(code, args: "2>&1").should.include?("warning: Redefining 'Integer#+' disables interpreter and JIT optimizations")
+      end
+    end
+  end
+end
diff --git a/spec/ruby/core/warning/warn_spec.rb b/spec/ruby/core/warning/warn_spec.rb
index 7daf6323c3..2e4a822e02 100644
--- a/spec/ruby/core/warning/warn_spec.rb
+++ b/spec/ruby/core/warning/warn_spec.rb
@@ -51,16 +51,137 @@ describe "Warning.warn" do
     end
   end
 
-  ruby_version_is "2.5" do
-    it "is called by Kernel.warn" do
-      Warning.should_receive(:warn).with("Chunky bacon!\n")
-      verbose = $VERBOSE
-      $VERBOSE = false
+  it "is called by Kernel.warn with nil category keyword" do
+    Warning.should_receive(:warn).with("Chunky bacon!\n", category: nil)
+    verbose = $VERBOSE
+    $VERBOSE = false
+    begin
+      Kernel.warn("Chunky bacon!")
+    ensure
+      $VERBOSE = verbose
+    end
+  end
+
+  it "is called by Kernel.warn with given category keyword converted to a symbol" do
+    Warning.should_receive(:warn).with("Chunky bacon!\n", category: :deprecated)
+    verbose = $VERBOSE
+    $VERBOSE = false
+    begin
+      Kernel.warn("Chunky bacon!", category: "deprecated")
+    ensure
+      $VERBOSE = verbose
+    end
+  end
+
+  it "warns when category is :deprecated and Warning[:deprecated] is true" do
+    warn_deprecated = Warning[:deprecated]
+    Warning[:deprecated] = true
+    begin
+      -> {
+        Warning.warn("foo", category: :deprecated)
+      }.should complain("foo")
+    ensure
+      Warning[:deprecated] = warn_deprecated
+    end
+  end
+
+  it "warns when category is :experimental and Warning[:experimental] is true" do
+    warn_experimental = Warning[:experimental]
+    Warning[:experimental] = true
+    begin
+      -> {
+        Warning.warn("foo", category: :experimental)
+      }.should complain("foo")
+    ensure
+      Warning[:experimental] = warn_experimental
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "warns when category is :strict_unused_block but Warning[:strict_unused_block] is false" do
+      warn_strict_unused_block = Warning[:strict_unused_block]
+      Warning[:strict_unused_block] = true
       begin
-        Kernel.warn("Chunky bacon!")
+        -> {
+          Warning.warn("foo", category: :strict_unused_block)
+        }.should complain("foo")
       ensure
-        $VERBOSE = verbose
+        Warning[:strict_unused_block] = warn_strict_unused_block
       end
     end
   end
+
+  it "doesn't print message when category is :deprecated but Warning[:deprecated] is false" do
+    warn_deprecated = Warning[:deprecated]
+    Warning[:deprecated] = false
+    begin
+      -> {
+        Warning.warn("foo", category: :deprecated)
+      }.should_not complain
+    ensure
+      Warning[:deprecated] = warn_deprecated
+    end
+  end
+
+  it "doesn't print message when category is :experimental but Warning[:experimental] is false" do
+    warn_experimental = Warning[:experimental]
+    Warning[:experimental] = false
+    begin
+      -> {
+        Warning.warn("foo", category: :experimental)
+      }.should_not complain
+    ensure
+      Warning[:experimental] = warn_experimental
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "doesn't print message when category is :strict_unused_block but Warning[:strict_unused_block] is false" do
+      warn_strict_unused_block = Warning[:strict_unused_block]
+      Warning[:strict_unused_block] = false
+      begin
+        -> {
+          Warning.warn("foo", category: :strict_unused_block)
+        }.should_not complain
+      ensure
+        Warning[:strict_unused_block] = warn_strict_unused_block
+      end
+    end
+  end
+
+  ruby_bug '#20573', ''...'3.4' do
+    it "isn't called by Kernel.warn when category is :deprecated but Warning[:deprecated] is false" do
+      warn_deprecated = Warning[:deprecated]
+      begin
+        Warning[:deprecated] = false
+        Warning.should_not_receive(:warn)
+        Kernel.warn("foo", category: :deprecated)
+      ensure
+        Warning[:deprecated] = warn_deprecated
+      end
+    end
+
+    it "isn't called by Kernel.warn when category is :experimental but Warning[:experimental] is false" do
+      warn_experimental = Warning[:experimental]
+      begin
+        Warning[:experimental] = false
+        Warning.should_not_receive(:warn)
+        Kernel.warn("foo", category: :experimental)
+      ensure
+        Warning[:experimental] = warn_experimental
+      end
+    end
+  end
+
+  it "prints the message when VERBOSE is false" do
+    -> { Warning.warn("foo") }.should complain("foo")
+  end
+
+  it "prints the message when VERBOSE is nil" do
+    -> { Warning.warn("foo") }.should complain("foo", verbose: nil)
+  end
+
+  it "prints the message when VERBOSE is true" do
+    -> { Warning.warn("foo") }.should complain("foo", verbose: true)
+  end
 end
diff --git a/spec/ruby/default.mspec b/spec/ruby/default.mspec
index 6fd6d2bf9c..c8b1215f56 100644
--- a/spec/ruby/default.mspec
+++ b/spec/ruby/default.mspec
@@ -1,3 +1,4 @@
+# -*- ruby -*-
 # Configuration file for Ruby >= 2.0 implementations.
 
 class MSpecScript
@@ -19,8 +20,11 @@ class MSpecScript
   # C extension API specs
   set :capi, [ 'optional/capi' ]
 
+  # Thread safety specs
+  set :thread_safety, [ 'optional/thread_safety' ]
+
   # A list of _all_ optional specs
-  set :optional, get(:capi)
+  set :optional, get(:capi) + get(:thread_safety)
 
   # An ordered list of the directories containing specs to run
   set :files, get(:command_line) + get(:language) + get(:core) + get(:library) + get(:security) + get(:optional)
@@ -45,5 +49,6 @@ class MSpecScript
   set :toplevel_constants_excludes, [
     /\wSpecs?$/,
     /^CS_CONST/,
+    /^CSL_CONST/,
   ]
 end
diff --git a/spec/ruby/fixtures/class.rb b/spec/ruby/fixtures/class.rb
index 68fbca7ba7..98cb6c82a2 100644
--- a/spec/ruby/fixtures/class.rb
+++ b/spec/ruby/fixtures/class.rb
@@ -122,6 +122,10 @@ module ClassSpecs
       end
     end
   end
+
+  DEFINE_CLASS = -> do
+    class ::A; end
+  end
 end
 
 class Class
diff --git a/spec/ruby/fixtures/code/a/load_fixture.dylib b/spec/ruby/fixtures/code/a/load_fixture.dylib
new file mode 100644
index 0000000000..31f4b1a7bb
--- /dev/null
+++ b/spec/ruby/fixtures/code/a/load_fixture.dylib
@@ -0,0 +1 @@
+ScratchPad << :ext_dylib
diff --git a/spec/ruby/fixtures/code/c/load_fixture.rb b/spec/ruby/fixtures/code/c/load_fixture.rb
new file mode 100644
index 0000000000..4a6e9c9601
--- /dev/null
+++ b/spec/ruby/fixtures/code/c/load_fixture.rb
@@ -0,0 +1 @@
+ScratchPad << :loaded
diff --git a/spec/ruby/fixtures/code/concurrent.rb b/spec/ruby/fixtures/code/concurrent.rb
index 054b8fc055..b3602a3db4 100644
--- a/spec/ruby/fixtures/code/concurrent.rb
+++ b/spec/ruby/fixtures/code/concurrent.rb
@@ -2,7 +2,7 @@ ScratchPad.recorded << :con_pre
 Thread.current[:in_concurrent_rb] = true
 
 if t = Thread.current[:wait_for]
-  Thread.pass until t.backtrace && t.backtrace.any? { |call| call.include? 'require' }
+  Thread.pass until t.backtrace && t.backtrace.any? { |call| call.include? 'require' } && t.stop?
 end
 
 if Thread.current[:con_raise]
diff --git a/spec/ruby/fixtures/code/concurrent_require_fixture.rb b/spec/ruby/fixtures/code/concurrent_require_fixture.rb
new file mode 100644
index 0000000000..d4ce734183
--- /dev/null
+++ b/spec/ruby/fixtures/code/concurrent_require_fixture.rb
@@ -0,0 +1,4 @@
+object = ScratchPad.recorded
+thread = Thread.new { object.require(__FILE__) }
+Thread.pass until thread.stop?
+ScratchPad.record(thread)
diff --git a/spec/ruby/fixtures/code/d/load_fixture.rb.rb b/spec/ruby/fixtures/code/d/load_fixture.rb.rb
new file mode 100644
index 0000000000..7e9217729a
--- /dev/null
+++ b/spec/ruby/fixtures/code/d/load_fixture.rb.rb
@@ -0,0 +1 @@
+ScratchPad << :rbrb
diff --git a/spec/ruby/fixtures/code/load_fixture.dylib b/spec/ruby/fixtures/code/load_fixture.dylib
new file mode 100644
index 0000000000..31f4b1a7bb
--- /dev/null
+++ b/spec/ruby/fixtures/code/load_fixture.dylib
@@ -0,0 +1 @@
+ScratchPad << :ext_dylib
diff --git a/spec/ruby/fixtures/code/load_fixture.ext.dylib b/spec/ruby/fixtures/code/load_fixture.ext.dylib
new file mode 100644
index 0000000000..31f4b1a7bb
--- /dev/null
+++ b/spec/ruby/fixtures/code/load_fixture.ext.dylib
@@ -0,0 +1 @@
+ScratchPad << :ext_dylib
diff --git a/spec/ruby/fixtures/code/load_wrap_fixture.rb b/spec/ruby/fixtures/code/load_wrap_fixture.rb
new file mode 100644
index 0000000000..526bbf8c82
--- /dev/null
+++ b/spec/ruby/fixtures/code/load_wrap_fixture.rb
@@ -0,0 +1,12 @@
+class LoadSpecWrap
+  ScratchPad << String
+end
+
+LOAD_WRAP_SPECS_TOP_LEVEL_CONSTANT = 1
+
+def load_wrap_specs_top_level_method
+  :load_wrap_specs_top_level_method
+end
+ScratchPad << method(:load_wrap_specs_top_level_method).owner
+
+ScratchPad << self
diff --git a/spec/ruby/fixtures/code/wrap_fixture.rb b/spec/ruby/fixtures/code/wrap_fixture.rb
deleted file mode 100644
index b83a8970d7..0000000000
--- a/spec/ruby/fixtures/code/wrap_fixture.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-class LoadSpecWrap
-  ScratchPad << self
-end
diff --git a/spec/ruby/fixtures/code_loading.rb b/spec/ruby/fixtures/code_loading.rb
index d6cf0edb47..decd56a358 100644
--- a/spec/ruby/fixtures/code_loading.rb
+++ b/spec/ruby/fixtures/code_loading.rb
@@ -12,7 +12,22 @@ module CodeLoadingSpecs
     end
   end
 
+  def self.preload_rubygems
+    # Require RubyGems eagerly, to ensure #require is already the RubyGems
+    # version and RubyGems is only loaded once, before starting #require/#autoload specs
+    # which snapshot $LOADED_FEATURES and could cause RubyGems to load twice.
+    # #require specs also snapshot #require, and could end up redefining #require as the original core Kernel#require.
+    @rubygems ||= begin
+      require "rubygems"
+      true
+    rescue LoadError
+      true
+    end
+  end
+
   def self.spec_setup
+    preload_rubygems
+
     @saved_loaded_features = $LOADED_FEATURES.clone
     @saved_load_path = $LOAD_PATH.clone
     ScratchPad.record []
diff --git a/spec/ruby/fixtures/constants.rb b/spec/ruby/fixtures/constants.rb
index e5b20596ef..7f0b88daab 100644
--- a/spec/ruby/fixtures/constants.rb
+++ b/spec/ruby/fixtures/constants.rb
@@ -1,7 +1,7 @@
 # Contains all static code examples of all constants behavior in language and
 # library specs. The specs include language/constants_spec.rb and the specs
-# for Module#const_defined?, Module#const_get, Module#const_set,
-# Module#remove_const, Module#const_missing and Module#constants.
+# for Module#const_defined?, Module#const_get, Module#const_set, Module#remove_const,
+# Module#const_source_location, Module#const_missing and Module#constants.
 #
 # Rather than defining a class structure for each example, a canonical set of
 # classes is used along with numerous constants, in most cases, a unique
@@ -10,7 +10,7 @@
 # variety in class and module configurations, including hierarchy,
 # containment, inclusion, singletons and toplevel.
 #
-# Constants are numbered for for uniqueness. The CS_ prefix is uniformly used
+# Constants are numbered for uniqueness. The CS_ prefix is uniformly used
 # and is to minimize clashes with other toplevel constants (see e.g. ModuleA
 # which is included in Object). Constant values are symbols. A numbered suffix
 # is used to distinguish constants with the same name defined in different
@@ -28,28 +28,34 @@
 # for completeness. No other constant of this name should be defined in the
 # specs.
 CS_CONST1 = :const1   # only defined here
+CS_CONST1_LINE = __LINE__ - 1
 
 module ConstantSpecs
 
   # Included at toplevel
   module ModuleA
     CS_CONST10 = :const10_1
+    CS_CONST10_LINE = __LINE__ - 1
     CS_CONST12 = :const12_2
     CS_CONST13 = :const13
+    CS_CONST13_LINE = __LINE__ - 1
     CS_CONST21 = :const21_2
   end
 
   # Included in ParentA
   module ModuleB
+    LINE = __LINE__ - 1
     CS_CONST10 = :const10_9
     CS_CONST11 = :const11_2
     CS_CONST12 = :const12_1
+    CS_CONST12_LINE = __LINE__ - 1
   end
 
   # Included in ChildA
   module ModuleC
     CS_CONST10 = :const10_4
     CS_CONST15 = :const15_1
+    CS_CONST15_LINE = __LINE__ - 1
   end
 
   # Included in ChildA metaclass
@@ -70,12 +76,21 @@ module ConstantSpecs
     CS_CONST10 = :const10_8
   end
 
+  # Included in ContainerA
+  module ModuleIncludePrepended
+    prepend ModuleD
+
+    CS_CONST11 = :const11_8
+  end
+
   # The following classes/modules have all the constants set "statically".
   # Contrast with the classes below where the constants are set as the specs
   # are run.
 
   class ClassA
+    LINE = __LINE__ - 1
     CS_CONST10 = :const10_10
+    CS_CONST10_LINE = __LINE__ - 1
     CS_CONST16 = :const16
     CS_CONST17 = :const17_2
     CS_CONST22 = :const22_1
@@ -97,10 +112,14 @@ module ConstantSpecs
     include ModuleB
 
     CS_CONST4 = :const4
+    CS_CONST4_LINE = __LINE__ - 1
     CS_CONST10 = :const10_5
+    CS_CONST10_LINE = __LINE__ - 1
     CS_CONST11 = :const11_1
+    CS_CONST11_LINE = __LINE__ - 1
     CS_CONST15 = :const15_2
     CS_CONST20 = :const20_2
+    CS_CONST20_LINE = __LINE__ - 1
     CS_CONST21 = :const21_1
     CS_CONST22 = :const22_2
 
@@ -118,6 +137,7 @@ module ConstantSpecs
 
     CS_CONST5 = :const5
     CS_CONST10 = :const10_2
+    CS_CONST10_LINE = __LINE__ - 1
     CS_CONST23 = :const23
 
     class ChildA < ParentA
@@ -135,6 +155,7 @@ module ConstantSpecs
 
       CS_CONST6 = :const6
       CS_CONST10 = :const10_3
+      CS_CONST10_LINE = __LINE__ - 1
       CS_CONST19 = :const19_2
 
       def self.const10; CS_CONST10; end
@@ -156,6 +177,10 @@ module ConstantSpecs
     def const10; CS_CONST10; end
   end
 
+  class ContainerPrepend
+    include ModuleIncludePrepended
+  end
+
   class ContainerA::ChildA
     def self.const23; CS_CONST23; end
   end
@@ -282,7 +307,18 @@ module ConstantSpecs
   end
 
   CS_PRIVATE = :cs_private
+  CS_PRIVATE_LINE = __LINE__ - 1
   private_constant :CS_PRIVATE
 end
 
+module ConstantSpecsThree
+  module ConstantSpecsTwo
+    Foo = :cs_three_foo
+  end
+end
+
+module ConstantSpecsTwo
+  Foo = :cs_two_foo
+end
+
 include ConstantSpecs::ModuleA
diff --git a/spec/ruby/fixtures/io.rb b/spec/ruby/fixtures/io.rb
new file mode 100644
index 0000000000..87ebbbb2bd
--- /dev/null
+++ b/spec/ruby/fixtures/io.rb
@@ -0,0 +1,12 @@
+module IOSpec
+  def self.exhaust_write_buffer(io)
+    written = 0
+    buf = " " * 4096
+
+    while true
+      written += io.write_nonblock(buf)
+    end
+  rescue Errno::EAGAIN, Errno::EWOULDBLOCK
+    written
+  end
+end
diff --git a/spec/ruby/language/BEGIN_spec.rb b/spec/ruby/language/BEGIN_spec.rb
index 58cc2bebfb..5aef5a1d7c 100644
--- a/spec/ruby/language/BEGIN_spec.rb
+++ b/spec/ruby/language/BEGIN_spec.rb
@@ -18,6 +18,11 @@ describe "The BEGIN keyword" do
     -> { eval "1.times { BEGIN { 1 } }" }.should raise_error(SyntaxError)
   end
 
+  it "uses top-level for self" do
+    eval("BEGIN { ScratchPad << self.to_s }", TOPLEVEL_BINDING)
+    ScratchPad.recorded.should == ['main']
+  end
+
   it "runs first in a given code unit" do
     eval "ScratchPad << 'foo'; BEGIN { ScratchPad << 'bar' }"
 
diff --git a/spec/ruby/language/END_spec.rb b/spec/ruby/language/END_spec.rb
new file mode 100644
index 0000000000..c84f0cc9ac
--- /dev/null
+++ b/spec/ruby/language/END_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../spec_helper'
+require_relative '../shared/kernel/at_exit'
+
+describe "The END keyword" do
+  it_behaves_like :kernel_at_exit, :END
+
+  it "runs only once for multiple calls" do
+    ruby_exe("10.times { END { puts 'foo' }; } ").should == "foo\n"
+  end
+
+  it "is affected by the toplevel assignment" do
+    ruby_exe("foo = 'foo'; END { puts foo }").should == "foo\n"
+  end
+
+  it "warns when END is used in a method" do
+    ruby_exe(<<~ruby, args: "2>&1").should =~ /warning: END in method; use at_exit/
+      def foo
+        END { }
+      end
+    ruby
+  end
+
+  context "END blocks and at_exit callbacks are mixed" do
+    it "runs them all in reverse order of registration" do
+      ruby_exe(<<~ruby).should == "at_exit#2\nEND#2\nat_exit#1\nEND#1\n"
+        END { puts 'END#1' }
+        at_exit { puts 'at_exit#1' }
+        END { puts 'END#2' }
+        at_exit { puts 'at_exit#2' }
+      ruby
+    end
+  end
+end
diff --git a/spec/ruby/language/README b/spec/ruby/language/README
index 74eaf58709..ae08e17fb1 100644
--- a/spec/ruby/language/README
+++ b/spec/ruby/language/README
@@ -4,7 +4,7 @@ words. These words significantly describe major elements of the language,
 including flow control constructs like 'for' and 'while', conditional
 execution like 'if' and 'unless', exceptional execution control like 'rescue',
 etc. There are also literals for the basic "types" like String, Regexp, Array
-and Fixnum.
+and Integer.
 
 Behavioral specifications describe the behavior of concrete entities. Rather
 than using concepts of computation to organize these spec files, we use
diff --git a/spec/ruby/language/alias_spec.rb b/spec/ruby/language/alias_spec.rb
index 79348f70c3..61fddb0184 100644
--- a/spec/ruby/language/alias_spec.rb
+++ b/spec/ruby/language/alias_spec.rb
@@ -52,6 +52,15 @@ describe "The alias keyword" do
     @obj.a.should == 5
   end
 
+  it "works with an interpolated symbol with non-literal embedded expression on the left-hand side" do
+    @meta.class_eval do
+      eval %Q{
+        alias :"#{'a' + ''.to_s}" value
+      }
+    end
+    @obj.a.should == 5
+  end
+
   it "works with a simple symbol on the right-hand side" do
     @meta.class_eval do
       alias a :value
@@ -80,6 +89,15 @@ describe "The alias keyword" do
     @obj.a.should == 5
   end
 
+  it "works with an interpolated symbol with non-literal embedded expression on the right-hand side" do
+    @meta.class_eval do
+      eval %Q{
+        alias a :"#{'value' + ''.to_s}"
+      }
+    end
+    @obj.a.should == 5
+  end
+
   it "adds the new method to the list of methods" do
     original_methods = @obj.methods
     @meta.class_eval do
@@ -218,7 +236,7 @@ describe "The alias keyword" do
     subclass.new.test("testing").should == 4
   end
 
-  it "is not allowed against Fixnum or String instances" do
+  it "is not allowed against Integer or String instances" do
     -> do
       1.instance_eval do
         alias :foo :to_s
@@ -234,7 +252,7 @@ describe "The alias keyword" do
 
   it "on top level defines the alias on Object" do
     # because it defines on the default definee / current module
-    ruby_exe("def foo; end; alias bla foo; print method(:bla).owner", escape: true).should == "Object"
+    ruby_exe("def foo; end; alias bla foo; print method(:bla).owner").should == "Object"
   end
 
   it "raises a NameError when passed a missing name" do
@@ -243,6 +261,19 @@ describe "The alias keyword" do
       e.class.should == NameError
     }
   end
+
+  it "defines the method on the aliased class when the original method is from a parent class" do
+    parent = Class.new do
+      def parent_method
+      end
+    end
+    child = Class.new(parent) do
+      alias parent_method_alias parent_method
+    end
+
+    child.instance_method(:parent_method_alias).owner.should == child
+    child.instance_methods(false).should include(:parent_method_alias)
+  end
 end
 
 describe "The alias keyword" do
@@ -255,4 +286,9 @@ describe "The alias keyword" do
     code = '$a = 1; $b = 2; alias $b $a; p [$a, $b]; $b = 3; p [$a, $b]'
     ruby_exe(code).should == "[1, 1]\n[3, 3]\n"
   end
+
+  it "supports aliasing twice the same global variables" do
+    code = '$a = 1; alias $b $a; alias $b $a; p [$a, $b]'
+    ruby_exe(code).should == "[1, 1]\n"
+  end
 end
diff --git a/spec/ruby/language/assignments_spec.rb b/spec/ruby/language/assignments_spec.rb
new file mode 100644
index 0000000000..c4adf73c1c
--- /dev/null
+++ b/spec/ruby/language/assignments_spec.rb
@@ -0,0 +1,590 @@
+require_relative '../spec_helper'
+
+# Should be synchronized with spec/ruby/language/optional_assignments_spec.rb
+# Some specs for assignments are located in language/variables_spec.rb
+describe 'Assignments' do
+  describe 'using =' do
+    describe 'evaluation order' do
+      it 'evaluates expressions left to right when assignment with an accessor' do
+        object = Object.new
+        def object.a=(value) end
+        ScratchPad.record []
+
+        (ScratchPad << :receiver; object).a = (ScratchPad << :rhs; :value)
+        ScratchPad.recorded.should == [:receiver, :rhs]
+      end
+
+      it 'evaluates expressions left to right when assignment with a #[]=' do
+        object = Object.new
+        def object.[]=(_, _) end
+        ScratchPad.record []
+
+        (ScratchPad << :receiver; object)[(ScratchPad << :argument; :a)] = (ScratchPad << :rhs; :value)
+        ScratchPad.recorded.should == [:receiver, :argument, :rhs]
+      end
+
+      it 'evaluates expressions left to right when assignment with compounded constant' do
+        m = Module.new
+        ScratchPad.record []
+
+        (ScratchPad << :module; m)::A = (ScratchPad << :rhs; :value)
+        ScratchPad.recorded.should == [:module, :rhs]
+      end
+
+      it 'raises TypeError after evaluation of right-hand-side when compounded constant module is not a module' do
+        ScratchPad.record []
+
+        -> {
+          (:not_a_module)::A = (ScratchPad << :rhs; :value)
+        }.should raise_error(TypeError)
+
+        ScratchPad.recorded.should == [:rhs]
+      end
+    end
+
+    context "given block argument" do
+      before do
+        @klass = Class.new do
+          def initialize(h) @h = h end
+          def [](k, &block) @h[k]; end
+          def []=(k, v, &block) @h[k] = v; end
+        end
+      end
+
+      ruby_version_is ""..."3.4" do
+        it "accepts block argument" do
+          obj = @klass.new(a: 1)
+          block = proc {}
+
+          eval "obj[:a, &block] = 2"
+          eval("obj[:a, &block]").should == 2
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "raises SyntaxError" do
+          obj = @klass.new(a: 1)
+          block = proc {}
+
+          -> {
+            eval "obj[:a, &block] = 2"
+          }.should raise_error(SyntaxError, /unexpected block arg given in index assignment|block arg given in index assignment/)
+        end
+      end
+    end
+
+    context "given keyword arguments" do
+      before do
+        @klass = Class.new do
+          attr_reader :x
+
+          def []=(*args, **kw)
+            @x = [args, kw]
+          end
+        end
+      end
+
+      ruby_version_is ""..."3.4" do
+        it "supports keyword arguments in index assignments" do
+          a = @klass.new
+          eval "a[1, 2, 3, b: 4] = 5"
+          a.x.should == [[1, 2, 3, {b: 4}, 5], {}]
+        end
+      end
+
+      ruby_version_is "3.4" do
+        it "raises SyntaxError when given keyword arguments in index assignments" do
+          a = @klass.new
+          -> { eval "a[1, 2, 3, b: 4] = 5" }.should raise_error(SyntaxError,
+            /keywords are not allowed in index assignment expressions|keyword arg given in index assignment/) # prism|parse.y
+        end
+      end
+    end
+  end
+
+  describe 'using +=' do
+    describe 'using an accessor' do
+      before do
+        klass = Class.new { attr_accessor :b }
+        @a    = klass.new
+      end
+
+      it 'does evaluate receiver only once when assigns' do
+        ScratchPad.record []
+        @a.b = 1
+
+        (ScratchPad << :evaluated; @a).b += 2
+
+        ScratchPad.recorded.should == [:evaluated]
+        @a.b.should == 3
+      end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(n) @a = n end
+          def public_method(n); self.a += n end
+          private
+          def a; @a end
+          def a=(n) @a = n; 42 end
+        end
+
+        a = klass_with_private_methods.new(0)
+        a.public_method(2).should == 2
+      end
+    end
+
+    describe 'using a #[]' do
+      before do
+        klass = Class.new do
+          def [](k)
+            @hash ||= {}
+            @hash[k]
+          end
+
+          def []=(k, v)
+            @hash ||= {}
+            @hash[k] = v
+            7
+          end
+        end
+        @b = klass.new
+      end
+
+      it 'evaluates receiver only once when assigns' do
+        ScratchPad.record []
+        a = {k: 1}
+
+        (ScratchPad << :evaluated; a)[:k] += 2
+
+        ScratchPad.recorded.should == [:evaluated]
+        a[:k].should == 3
+      end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(h) @a = h end
+          def public_method(k, n); self[k] += n end
+          private
+          def [](k) @a[k] end
+          def []=(k, v) @a[k] = v; 42 end
+        end
+
+        a = klass_with_private_methods.new(k: 0)
+        a.public_method(:k, 2).should == 2
+      end
+
+      context "given block argument" do
+        before do
+          @klass = Class.new do
+            def initialize(h) @h = h end
+            def [](k, &block) @h[k]; end
+            def []=(k, v, &block) @h[k] = v; end
+          end
+        end
+
+        ruby_version_is ""..."3.4" do
+          it "accepts block argument" do
+            obj = @klass.new(a: 1)
+            block = proc {}
+
+            eval "obj[:a, &block] += 2"
+            eval("obj[:a, &block]").should == 3
+          end
+        end
+
+        ruby_version_is "3.4" do
+          it "raises SyntaxError" do
+            obj = @klass.new(a: 1)
+            block = proc {}
+
+            -> {
+              eval "obj[:a, &block] += 2"
+            }.should raise_error(SyntaxError, /unexpected block arg given in index assignment|block arg given in index assignment/)
+          end
+        end
+      end
+
+      context "given keyword arguments" do
+        before do
+          @klass = Class.new do
+            attr_reader :x
+
+            def [](*args)
+              100
+            end
+
+            def []=(*args, **kw)
+              @x = [args, kw]
+            end
+          end
+        end
+
+        ruby_version_is ""..."3.3" do
+          it "supports keyword arguments in index assignments" do
+            a = @klass.new
+            eval "a[1, 2, 3, b: 4] += 5"
+            a.x.should == [[1, 2, 3, {b: 4}, 105], {}]
+          end
+        end
+
+        ruby_version_is "3.3"..."3.4" do
+          it "supports keyword arguments in index assignments" do
+            a = @klass.new
+            eval "a[1, 2, 3, b: 4] += 5"
+            a.x.should == [[1, 2, 3, 105], {b: 4}]
+          end
+        end
+
+        ruby_version_is "3.4" do
+          it "raises SyntaxError when given keyword arguments in index assignments" do
+            a = @klass.new
+            -> { eval "a[1, 2, 3, b: 4] += 5" }.should raise_error(SyntaxError,
+              /keywords are not allowed in index assignment expressions|keyword arg given in index assignment/) # prism|parse.y
+          end
+        end
+      end
+
+      context 'splatted argument' do
+        it 'correctly handles it' do
+          @b[:m] = 10
+          (@b[*[:m]] += 10).should == 20
+          @b[:m].should == 20
+
+          @b[:n] = 10
+          (@b[*(1; [:n])] += 10).should == 20
+          @b[:n].should == 20
+
+          @b[:k] = 10
+          (@b[*begin 1; [:k] end] += 10).should == 20
+          @b[:k].should == 20
+        end
+
+        it 'calls #to_a only once' do
+          k = Object.new
+          def k.to_a
+            ScratchPad << :to_a
+            [:k]
+          end
+
+          ScratchPad.record []
+          @b[:k] = 10
+          (@b[*k] += 10).should == 20
+          @b[:k].should == 20
+          ScratchPad.recorded.should == [:to_a]
+        end
+
+        it 'correctly handles a nested splatted argument' do
+          @b[:k] = 10
+          (@b[*[*[:k]]] += 10).should == 20
+          @b[:k].should == 20
+        end
+
+        it 'correctly handles multiple nested splatted arguments' do
+          klass_with_multiple_parameters = Class.new do
+            def [](k1, k2, k3)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"]
+            end
+
+            def []=(k1, k2, k3, v)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"] = v
+              7
+            end
+          end
+          a = klass_with_multiple_parameters.new
+
+          a[:a, :b, :c] = 10
+          (a[*[:a], *[:b], *[:c]] += 10).should == 20
+          a[:a, :b, :c].should == 20
+        end
+      end
+    end
+
+    describe 'using compounded constants' do
+      it 'causes side-effects of the module part to be applied only once (when assigns)' do
+        module ConstantSpecs
+          OpAssignTrue = 1
+        end
+
+        suppress_warning do # already initialized constant
+          x = 0
+          (x += 1; ConstantSpecs)::OpAssignTrue += 2
+          x.should == 1
+          ConstantSpecs::OpAssignTrue.should == 3
+        end
+
+        ConstantSpecs.send :remove_const, :OpAssignTrue
+      end
+    end
+  end
+end
+
+# generic cases
+describe 'Multiple assignments' do
+  it 'assigns multiple targets when assignment with an accessor' do
+    object = Object.new
+    class << object
+      attr_accessor :a, :b
+    end
+
+    object.a, object.b = :a, :b
+
+    object.a.should == :a
+    object.b.should == :b
+  end
+
+  it 'assigns multiple targets when assignment with a nested accessor' do
+    object = Object.new
+    class << object
+      attr_accessor :a, :b
+    end
+
+    (object.a, object.b), c = [:a, :b], nil
+
+    object.a.should == :a
+    object.b.should == :b
+  end
+
+  it 'assigns multiple targets when assignment with a #[]=' do
+    object = Object.new
+    class << object
+      def []=(k, v) (@h ||= {})[k] = v; end
+      def [](k) (@h ||= {})[k]; end
+    end
+
+    object[:a], object[:b] = :a, :b
+
+    object[:a].should == :a
+    object[:b].should == :b
+  end
+
+  it 'assigns multiple targets when assignment with a nested #[]=' do
+    object = Object.new
+    class << object
+      def []=(k, v) (@h ||= {})[k] = v; end
+      def [](k) (@h ||= {})[k]; end
+    end
+
+    (object[:a], object[:b]), c = [:v1, :v2], nil
+
+    object[:a].should == :v1
+    object[:b].should == :v2
+  end
+
+  it 'assigns multiple targets when assignment with compounded constant' do
+    m = Module.new
+
+    m::A, m::B = :a, :b
+
+    m::A.should == :a
+    m::B.should == :b
+  end
+
+  it 'assigns multiple targets when assignment with a nested compounded constant' do
+    m = Module.new
+
+    (m::A, m::B), c = [:a, :b], nil
+
+    m::A.should == :a
+    m::B.should == :b
+  end
+end
+
+describe 'Multiple assignments' do
+  describe 'evaluation order' do
+    it 'evaluates expressions left to right when assignment with an accessor' do
+      object = Object.new
+      def object.a=(value) end
+      ScratchPad.record []
+
+      (ScratchPad << :a; object).a, (ScratchPad << :b; object).a = (ScratchPad << :c; :c), (ScratchPad << :d; :d)
+      ScratchPad.recorded.should == [:a, :b, :c, :d]
+    end
+
+    it 'evaluates expressions left to right when assignment with a nested accessor' do
+      object = Object.new
+      def object.a=(value) end
+      ScratchPad.record []
+
+      ((ScratchPad << :a; object).a, foo), bar = [(ScratchPad << :b; :b)]
+      ScratchPad.recorded.should == [:a, :b]
+    end
+
+    it 'evaluates expressions left to right when assignment with a deeply nested accessor' do
+      o = Object.new
+      def o.a=(value) end
+      def o.b=(value) end
+      def o.c=(value) end
+      def o.d=(value) end
+      def o.e=(value) end
+      def o.f=(value) end
+      ScratchPad.record []
+
+      (ScratchPad << :a; o).a,
+        ((ScratchPad << :b; o).b,
+        ((ScratchPad << :c; o).c, (ScratchPad << :d; o).d),
+        (ScratchPad << :e; o).e),
+      (ScratchPad << :f; o).f = (ScratchPad << :value; :value)
+
+      ScratchPad.recorded.should == [:a, :b, :c, :d, :e, :f, :value]
+    end
+
+    it 'evaluates expressions left to right when assignment with a #[]=' do
+      object = Object.new
+      def object.[]=(_, _) end
+      ScratchPad.record []
+
+      (ScratchPad << :a; object)[(ScratchPad << :b; :b)], (ScratchPad << :c; object)[(ScratchPad << :d; :d)] = (ScratchPad << :e; :e), (ScratchPad << :f; :f)
+      ScratchPad.recorded.should == [:a, :b, :c, :d, :e, :f]
+    end
+
+    it 'evaluates expressions left to right when assignment with a nested #[]=' do
+      object = Object.new
+      def object.[]=(_, _) end
+      ScratchPad.record []
+
+      ((ScratchPad << :a; object)[(ScratchPad << :b; :b)], foo), bar = [(ScratchPad << :c; :c)]
+      ScratchPad.recorded.should == [:a, :b, :c]
+    end
+
+    it 'evaluates expressions left to right when assignment with a deeply nested #[]=' do
+      o = Object.new
+      def o.[]=(_, _) end
+      ScratchPad.record []
+
+      (ScratchPad << :ra; o)[(ScratchPad << :aa; :aa)],
+        ((ScratchPad << :rb; o)[(ScratchPad << :ab; :ab)],
+        ((ScratchPad << :rc; o)[(ScratchPad << :ac; :ac)], (ScratchPad << :rd; o)[(ScratchPad << :ad; :ad)]),
+        (ScratchPad << :re; o)[(ScratchPad << :ae; :ae)]),
+      (ScratchPad << :rf; o)[(ScratchPad << :af; :af)] = (ScratchPad << :value; :value)
+
+      ScratchPad.recorded.should == [:ra, :aa, :rb, :ab, :rc, :ac, :rd, :ad, :re, :ae, :rf, :af, :value]
+    end
+
+    it 'evaluates expressions left to right when assignment with compounded constant' do
+      m = Module.new
+      ScratchPad.record []
+
+      (ScratchPad << :a; m)::A, (ScratchPad << :b; m)::B = (ScratchPad << :c; :c), (ScratchPad << :d; :d)
+      ScratchPad.recorded.should == [:a, :b, :c, :d]
+    end
+
+    it 'evaluates expressions left to right when assignment with a nested compounded constant' do
+      m = Module.new
+      ScratchPad.record []
+
+      ((ScratchPad << :a; m)::A, foo), bar = [(ScratchPad << :b; :b)]
+      ScratchPad.recorded.should == [:a, :b]
+    end
+
+    it 'evaluates expressions left to right when assignment with deeply nested compounded constants' do
+      m = Module.new
+      ScratchPad.record []
+
+      (ScratchPad << :a; m)::A,
+        ((ScratchPad << :b; m)::B,
+        ((ScratchPad << :c; m)::C, (ScratchPad << :d; m)::D),
+        (ScratchPad << :e; m)::E),
+      (ScratchPad << :f; m)::F = (ScratchPad << :value; :value)
+
+      ScratchPad.recorded.should == [:a, :b, :c, :d, :e, :f, :value]
+    end
+  end
+
+  context 'when assignment with method call and receiver is self' do
+    it 'assigns values correctly when assignment with accessor' do
+      object = Object.new
+      class << object
+        attr_accessor :a, :b
+
+        def assign(v1, v2)
+          self.a, self.b = v1, v2
+        end
+      end
+
+      object.assign :v1, :v2
+      object.a.should == :v1
+      object.b.should == :v2
+    end
+
+    it 'evaluates expressions right to left when assignment with a nested accessor' do
+      object = Object.new
+      class << object
+        attr_accessor :a, :b
+
+        def assign(v1, v2)
+          (self.a, self.b), c = [v1, v2], nil
+        end
+      end
+
+      object.assign :v1, :v2
+      object.a.should == :v1
+      object.b.should == :v2
+    end
+
+    it 'assigns values correctly when assignment with a #[]=' do
+      object = Object.new
+      class << object
+        def []=(key, v)
+          @h ||= {}
+          @h[key] = v
+        end
+
+        def [](key)
+          (@h || {})[key]
+        end
+
+        def assign(k1, v1, k2, v2)
+          self[k1], self[k2] = v1, v2
+        end
+      end
+
+      object.assign :k1, :v1, :k2, :v2
+      object[:k1].should == :v1
+      object[:k2].should == :v2
+    end
+
+    it 'assigns values correctly when assignment with a nested #[]=' do
+      object = Object.new
+      class << object
+        def []=(key, v)
+          @h ||= {}
+          @h[key] = v
+        end
+
+        def [](key)
+          (@h || {})[key]
+        end
+
+        def assign(k1, v1, k2, v2)
+          (self[k1], self[k2]), c = [v1, v2], nil
+        end
+      end
+
+      object.assign :k1, :v1, :k2, :v2
+      object[:k1].should == :v1
+      object[:k2].should == :v2
+    end
+
+    it 'assigns values correctly when assignment with compounded constant' do
+      m = Module.new
+      m.module_exec do
+        self::A, self::B = :v1, :v2
+      end
+
+      m::A.should == :v1
+      m::B.should == :v2
+    end
+
+    it 'assigns values correctly when assignment with a nested compounded constant' do
+      m = Module.new
+      m.module_exec do
+        (self::A, self::B), c = [:v1, :v2], nil
+      end
+
+      m::A.should == :v1
+      m::B.should == :v2
+    end
+  end
+end
diff --git a/spec/ruby/language/block_spec.rb b/spec/ruby/language/block_spec.rb
index f8bfc8d9ed..cc003b8946 100644
--- a/spec/ruby/language/block_spec.rb
+++ b/spec/ruby/language/block_spec.rb
@@ -6,14 +6,6 @@ describe "A block yielded a single" do
     def m(a) yield a end
   end
 
-  def supress_keyword_warning(&block)
-    if RUBY_VERSION > '2.7'
-      suppress_warning(&block)
-    else
-      yield
-    end
-  end
-
   context "Array" do
     it "assigns the Array to a single argument" do
       m([1, 2]) { |a| a }.should == [1, 2]
@@ -48,111 +40,98 @@ describe "A block yielded a single" do
       m([1, 2]) { |a=5, b, c, d| [a, b, c, d] }.should == [5, 1, 2, nil]
     end
 
-    it "assigns elements to required arguments when a keyword rest argument is present" do
-      m([1, 2]) { |a, **k| [a, k] }.should == [1, {}]
+    it "assigns elements to pre arguments" do
+      m([1, 2]) { |a, b, c, d=5| [a, b, c, d] }.should == [1, 2, nil, 5]
     end
 
-    it "assigns elements to mixed argument types" do
-      supress_keyword_warning do
-        result = m([1, 2, 3, {x: 9}]) { |a, b=5, *c, d, e: 2, **k| [a, b, c, d, e, k] }
-        result.should == [1, 2, [], 3, 2, {x: 9}]
-      end
+    it "assigns elements to pre and post arguments" do
+      m([1               ]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 5, 6, nil, nil]
+      m([1, 2            ]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 5, 6, 2, nil]
+      m([1, 2, 3         ]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 5, 6, 2, 3]
+      m([1, 2, 3, 4      ]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 2, 6, 3, 4]
+      m([1, 2, 3, 4, 5   ]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 2, 3, 4, 5]
+      m([1, 2, 3, 4, 5, 6]) { |a, b=5, c=6, d, e| [a, b, c, d, e] }.should == [1, 2, 3, 4, 5]
     end
 
-    it "assigns symbol keys from a Hash to keyword arguments" do
-      supress_keyword_warning do
-        result = m(["a" => 1, a: 10]) { |a=nil, **b| [a, b] }
-        result.should == [{"a" => 1}, a: 10]
-      end
+    it "assigns elements to pre and post arguments when *rest is present" do
+      m([1               ]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 5, 6, [], nil, nil]
+      m([1, 2            ]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 5, 6, [], 2, nil]
+      m([1, 2, 3         ]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 5, 6, [], 2, 3]
+      m([1, 2, 3, 4      ]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 2, 6, [], 3, 4]
+      m([1, 2, 3, 4, 5   ]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 2, 3, [], 4, 5]
+      m([1, 2, 3, 4, 5, 6]) { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.should == [1, 2, 3, [4], 5, 6]
     end
 
-    it "assigns symbol keys from a Hash returned by #to_hash to keyword arguments" do
-      supress_keyword_warning do
-        obj = mock("coerce block keyword arguments")
-        obj.should_receive(:to_hash).and_return({"a" => 1, b: 2})
+    it "does not autosplat single argument to required arguments when a keyword rest argument is present" do
+      m([1, 2]) { |a, **k| [a, k] }.should == [[1, 2], {}]
+    end
 
-        result = m([obj]) { |a=nil, **b| [a, b] }
-        result.should == [{"a" => 1}, b: 2]
-      end
+    it "does not autosplat single argument to required arguments when keyword arguments are present" do
+      m([1, 2]) { |a, b: :b, c: :c| [a, b, c] }.should == [[1, 2], :b, :c]
     end
 
-    ruby_version_is "0"..."2.7" do
-      it "calls #to_hash on the argument and uses resulting hash as first argument when optional argument and keyword argument accepted" do
-        obj = mock("coerce block keyword arguments")
-        obj.should_receive(:to_hash).and_return({"a" => 1, "b" => 2})
+    it "raises error when required keyword arguments are present" do
+      -> {
+        m([1, 2]) { |a, b:, c:| [a, b, c] }
+      }.should raise_error(ArgumentError, "missing keywords: :b, :c")
+    end
 
-        result = m([obj]) { |a=nil, **b| [a, b] }
-        result.should == [{"a" => 1, "b" => 2}, {}]
-      end
+    it "assigns elements to mixed argument types" do
+      result = m([1, 2, 3, {x: 9}]) { |a, b=5, *c, d, e: 2, **k| [a, b, c, d, e, k] }
+      result.should == [1, 2, [3], {x: 9}, 2, {}]
+    end
+
+    it "does not treat final Hash as keyword arguments and does not autosplat" do
+      result = m(["a" => 1, a: 10]) { |a=nil, **b| [a, b] }
+      result.should == [[{"a" => 1, a: 10}], {}]
     end
 
-    ruby_version_is "2.7" do
-      it "calls #to_hash on the argument but ignores result when optional argument and keyword argument accepted" do
+    it "does not call #to_hash on final argument to get keyword arguments and does not autosplat" do
+      suppress_keyword_warning do
         obj = mock("coerce block keyword arguments")
-        obj.should_receive(:to_hash).and_return({"a" => 1, "b" => 2})
+        obj.should_not_receive(:to_hash)
 
         result = m([obj]) { |a=nil, **b| [a, b] }
-        result.should == [obj, {}]
+        result.should == [[obj], {}]
       end
     end
 
+    it "does not call #to_hash on the argument when optional argument and keyword argument accepted and does not autosplat" do
+      obj = mock("coerce block keyword arguments")
+      obj.should_not_receive(:to_hash)
+
+      result = m([obj]) { |a=nil, **b| [a, b] }
+      result.should == [[obj], {}]
+    end
+
     describe "when non-symbol keys are in a keyword arguments Hash" do
-      it "separates non-symbol keys and symbol keys" do
-        supress_keyword_warning do
+      it "does not separate non-symbol keys and symbol keys and does not autosplat" do
+        suppress_keyword_warning do
           result = m(["a" => 10, b: 2]) { |a=nil, **b| [a, b] }
-          result.should == [{"a" => 10}, {b: 2}]
+          result.should == [[{"a" => 10, b: 2}], {}]
         end
       end
     end
 
-    it "does not treat hashes with string keys as keyword arguments" do
+    it "does not treat hashes with string keys as keyword arguments and does not autosplat" do
       result = m(["a" => 10]) { |a = nil, **b| [a, b] }
-      result.should == [{"a" => 10}, {}]
-    end
-
-    it "calls #to_hash on the last element if keyword arguments are present" do
-      supress_keyword_warning do
-        obj = mock("destructure block keyword arguments")
-        obj.should_receive(:to_hash).and_return({x: 9})
-
-        result = m([1, 2, 3, obj]) { |a, *b, c, **k| [a, b, c, k] }
-        result.should == [1, [2], 3, {x: 9}]
-      end
-    end
-
-    it "assigns the last element to a non-keyword argument if #to_hash returns nil" do
-      supress_keyword_warning do
-        obj = mock("destructure block keyword arguments")
-        obj.should_receive(:to_hash).and_return(nil)
-
-        result = m([1, 2, 3, obj]) { |a, *b, c, **k| [a, b, c, k] }
-        result.should == [1, [2, 3], obj, {}]
-      end
-    end
-
-    it "calls #to_hash on the last element when there are more arguments than parameters" do
-      supress_keyword_warning do
-        x = mock("destructure matching block keyword argument")
-        x.should_receive(:to_hash).and_return({x: 9})
-
-        result = m([1, 2, 3, {y: 9}, 4, 5, x]) { |a, b=5, c, **k| [a, b, c, k] }
-        result.should == [1, 2, 3, {x: 9}]
-      end
+      result.should == [[{"a" => 10}], {}]
     end
 
-    it "raises a TypeError if #to_hash does not return a Hash" do
+    it "does not call #to_hash on the last element if keyword arguments are present" do
       obj = mock("destructure block keyword arguments")
-      obj.should_receive(:to_hash).and_return(1)
+      obj.should_not_receive(:to_hash)
 
-      -> { m([1, 2, 3, obj]) { |a, *b, c, **k| } }.should raise_error(TypeError)
+      result = m([1, 2, 3, obj]) { |a, *b, c, **k| [a, b, c, k] }
+      result.should == [1, [2, 3], obj, {}]
     end
 
-    it "raises the error raised inside #to_hash" do
-      obj = mock("destructure block keyword arguments")
-      error = RuntimeError.new("error while converting to a hash")
-      obj.should_receive(:to_hash).and_raise(error)
+    it "does not call #to_hash on the last element when there are more arguments than parameters" do
+      x = mock("destructure matching block keyword argument")
+      x.should_not_receive(:to_hash)
 
-      -> { m([1, 2, 3, obj]) { |a, *b, c, **k| } }.should raise_error(error)
+      result = m([1, 2, 3, {y: 9}, 4, 5, x]) { |a, b=5, c, **k| [a, b, c, k] }
+      result.should == [1, 2, 3, {}]
     end
 
     it "does not call #to_ary on the Array" do
@@ -199,12 +178,55 @@ describe "A block yielded a single" do
       m(obj) { |a, b, c| [a, b, c] }.should == [obj, nil, nil]
     end
 
+    it "receives the object if it does not respond to #to_ary" do
+      obj = Object.new
+
+      m(obj) { |a, b, c| [a, b, c] }.should == [obj, nil, nil]
+    end
+
+    it "calls #respond_to? to check if object has method #to_ary" do
+      obj = mock("destructure block arguments")
+      obj.should_receive(:respond_to?).with(:to_ary, true).and_return(true)
+      obj.should_receive(:to_ary).and_return([1, 2])
+
+      m(obj) { |a, b, c| [a, b, c] }.should == [1, 2, nil]
+    end
+
+    it "receives the object if it does not respond to #respond_to?" do
+      obj = BasicObject.new
+
+      m(obj) { |a, b, c| [a, b, c] }.should == [obj, nil, nil]
+    end
+
+    it "calls #to_ary on the object when it is defined dynamically" do
+      obj = Object.new
+      def obj.method_missing(name, *args, &block)
+        if name == :to_ary
+          [1, 2]
+        else
+          super
+        end
+      end
+      def obj.respond_to_missing?(name, include_private)
+        name == :to_ary
+      end
+
+      m(obj) { |a, b, c| [a, b, c] }.should == [1, 2, nil]
+    end
+
     it "raises a TypeError if #to_ary does not return an Array" do
       obj = mock("destructure block arguments")
       obj.should_receive(:to_ary).and_return(1)
 
       -> { m(obj) { |a, b| } }.should raise_error(TypeError)
     end
+
+    it "raises error transparently if #to_ary raises error on its own" do
+      obj = Object.new
+      def obj.to_ary; raise "Exception raised in #to_ary" end
+
+      -> { m(obj) { |a, b| } }.should raise_error(RuntimeError, "Exception raised in #to_ary")
+    end
   end
 end
 
@@ -252,10 +274,8 @@ describe "A block" do
       @y.s(0) { 1 }.should == 1
     end
 
-    ruby_version_is "2.5" do
-      it "may include a rescue clause" do
-        eval("@y.z do raise ArgumentError; rescue ArgumentError; 7; end").should == 7
-      end
+    it "may include a rescue clause" do
+      @y.z do raise ArgumentError; rescue ArgumentError; 7; end.should == 7
     end
   end
 
@@ -268,10 +288,8 @@ describe "A block" do
       @y.s(0) { || 1 }.should == 1
     end
 
-    ruby_version_is "2.5" do
-      it "may include a rescue clause" do
-        eval('@y.z do || raise ArgumentError; rescue ArgumentError; 7; end').should == 7
-      end
+    it "may include a rescue clause" do
+      @y.z do || raise ArgumentError; rescue ArgumentError; 7; end.should == 7
     end
   end
 
@@ -299,10 +317,8 @@ describe "A block" do
       @y.s([1, 2]) { |a| a }.should == [1, 2]
     end
 
-    ruby_version_is "2.5" do
-      it "may include a rescue clause" do
-        eval('@y.s(1) do |x| raise ArgumentError; rescue ArgumentError; 7; end').should == 7
-      end
+    it "may include a rescue clause" do
+      @y.s(1) do |x| raise ArgumentError; rescue ArgumentError; 7; end.should == 7
     end
   end
 
@@ -375,7 +391,6 @@ describe "A block" do
 
       -> { @y.s(obj) { |a, b| } }.should raise_error(ZeroDivisionError)
     end
-
   end
 
   describe "taking |a, *b| arguments" do
@@ -703,9 +718,45 @@ describe "A block" do
     end
 
     it "accepts unnamed arguments" do
-      eval("lambda { |_,_| }").should be_an_instance_of(Proc)
-      eval("->(_,_) {}").should be_an_instance_of(Proc)
-      eval("Proc.new { |_,_| }").should be_an_instance_of(Proc)
+      lambda { |_,_| }.should be_an_instance_of(Proc) # rubocop:disable Style/Lambda
+      -> _,_ {}.should be_an_instance_of(Proc)
+      Proc.new { |_,_| }.should be_an_instance_of(Proc)
+    end
+  end
+
+  describe 'pre and post parameters' do
+    it "assigns nil to unassigned required arguments" do
+      proc { |a, *b, c, d| [a, b, c, d] }.call(1, 2).should == [1, [], 2, nil]
+    end
+
+    it "assigns elements to optional arguments" do
+      proc { |a=5, b=4, c=3| [a, b, c] }.call(1, 2).should == [1, 2, 3]
+    end
+
+    it "assigns elements to post arguments" do
+      proc { |a=5, b, c, d| [a, b, c, d] }.call(1, 2).should == [5, 1, 2, nil]
+    end
+
+    it "assigns elements to pre arguments" do
+      proc { |a, b, c, d=5| [a, b, c, d] }.call(1, 2).should == [1, 2, nil, 5]
+    end
+
+    it "assigns elements to pre and post arguments" do
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1               ).should == [1, 5, 6, nil, nil]
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1, 2            ).should == [1, 5, 6, 2, nil]
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1, 2, 3         ).should == [1, 5, 6, 2, 3]
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1, 2, 3, 4      ).should == [1, 2, 6, 3, 4]
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1, 2, 3, 4, 5   ).should == [1, 2, 3, 4, 5]
+      proc { |a, b=5, c=6, d, e| [a, b, c, d, e] }.call(1, 2, 3, 4, 5, 6).should == [1, 2, 3, 4, 5]
+    end
+
+    it "assigns elements to pre and post arguments when *rest is present" do
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1               ).should == [1, 5, 6, [], nil, nil]
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1, 2            ).should == [1, 5, 6, [], 2, nil]
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1, 2, 3         ).should == [1, 5, 6, [], 2, 3]
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1, 2, 3, 4      ).should == [1, 2, 6, [], 3, 4]
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1, 2, 3, 4, 5   ).should == [1, 2, 3, [], 4, 5]
+      proc { |a, b=5, c=6, *d, e, f| [a, b, c, d, e, f] }.call(1, 2, 3, 4, 5, 6).should == [1, 2, 3, [4], 5, 6]
     end
   end
 end
@@ -814,7 +865,7 @@ describe "Post-args" do
     end.call(1, 2, 3).should == [[], 1, 2, 3]
   end
 
-  it "are required" do
+  it "are required for a lambda" do
     -> {
       -> *a, b do
         [a, b]
@@ -822,6 +873,12 @@ describe "Post-args" do
     }.should raise_error(ArgumentError)
   end
 
+  it "are assigned to nil when not enough arguments are given to a proc" do
+    proc do |a, *b, c|
+      [a, b, c]
+    end.call.should == [nil, [], nil]
+  end
+
   describe "with required args" do
 
     it "gathers remaining args in the splat" do
@@ -884,26 +941,27 @@ describe "Post-args" do
     end
 
     describe "with a circular argument reference" do
-      it "shadows an existing local with the same name as the argument" do
-        a = 1
-        -> {
-          @proc = eval "proc { |a=a| a }"
-        }.should complain(/circular argument reference/)
-        @proc.call.should == nil
+      ruby_version_is ""..."3.4" do
+        it "raises a SyntaxError if using the argument in its default value" do
+          a = 1
+          -> {
+            eval "proc { |a=a| a }"
+          }.should raise_error(SyntaxError)
+        end
       end
 
-      it "shadows an existing method with the same name as the argument" do
-        def a; 1; end
-        -> {
-          @proc = eval "proc { |a=a| a }"
-        }.should complain(/circular argument reference/)
-        @proc.call.should == nil
+      ruby_version_is "3.4" do
+        it "is nil if using the argument in its default value" do
+          -> {
+            eval "proc { |a=a| a }.call"
+          }.call.should == nil
+        end
       end
+    end
 
-      it "calls an existing method with the same name as the argument if explicitly using ()" do
-        def a; 1; end
-        proc { |a=a()| a }.call.should == 1
-      end
+    it "calls an existing method with the same name as the argument if explicitly using ()" do
+      def a; 1; end
+      proc { |a=a()| a }.call.should == 1
     end
   end
 
@@ -921,3 +979,160 @@ describe "Post-args" do
     end
   end
 end
+
+# tested more thoroughly in language/delegation_spec.rb
+describe "Anonymous block forwarding" do
+  it "forwards blocks to other method that formally declares anonymous block" do
+    def b(&); c(&) end
+    def c(&); yield :non_null end
+
+    b { |c| c }.should == :non_null
+  end
+
+  it "requires the anonymous block parameter to be declared if directly passing a block" do
+    -> { eval "def a; b(&); end; def b; end" }.should raise_error(SyntaxError)
+  end
+
+  it "works when it's the only declared parameter" do
+    def inner; yield end
+    def block_only(&); inner(&) end
+
+    block_only { 1 }.should == 1
+  end
+
+  it "works alongside positional parameters" do
+    def inner; yield end
+    def pos(arg1, &); inner(&) end
+
+    pos(:a) { 1 }.should == 1
+  end
+
+  it "works alongside positional arguments and splatted keyword arguments" do
+    def inner; yield end
+    def pos_kwrest(arg1, **kw, &); inner(&) end
+
+    pos_kwrest(:a, arg: 3) { 1 }.should == 1
+  end
+
+  it "works alongside positional arguments and disallowed keyword arguments" do
+    def inner; yield end
+    def no_kw(arg1, **nil, &); inner(&) end
+
+    no_kw(:a) { 1 }.should == 1
+  end
+
+  it "works alongside explicit keyword arguments" do
+    eval <<-EOF
+        def inner; yield end
+        def rest_kw(*a, kwarg: 1, &); inner(&) end
+        def kw(kwarg: 1, &); inner(&) end
+        def pos_kw_kwrest(arg1, kwarg: 1, **kw, &); inner(&) end
+        def pos_rkw(arg1, kwarg1:, &); inner(&) end
+        def all(arg1, arg2, *rest, post1, post2, kw1: 1, kw2: 2, okw1:, okw2:, &); inner(&) end
+        def all_kwrest(arg1, arg2, *rest, post1, post2, kw1: 1, kw2: 2, okw1:, okw2:, **kw, &); inner(&) end
+    EOF
+
+    rest_kw { 1 }.should == 1
+    kw { 1 }.should == 1
+    pos_kw_kwrest(:a) { 1 }.should == 1
+    pos_rkw(:a, kwarg1: 3) { 1 }.should == 1
+    all(:a, :b, :c, :d, :e, okw1: 'x', okw2: 'y') { 1 }.should == 1
+    all_kwrest(:a, :b, :c, :d, :e, okw1: 'x', okw2: 'y') { 1 }.should == 1
+  end
+end
+
+describe "`it` calls without arguments in a block with no ordinary parameters" do
+  ruby_version_is "3.3"..."3.4" do
+    it "emits a deprecation warning" do
+      -> {
+        eval "proc { it }"
+      }.should complain(/warning: `it` calls without arguments will refer to the first block param in Ruby 3.4; use it\(\) or self.it/)
+    end
+
+    it "emits a deprecation warning if numbered parameters are used" do
+      -> {
+        eval "proc { it; _1 }"
+      }.should complain(/warning: `it` calls without arguments will refer to the first block param in Ruby 3.4; use it\(\) or self.it/)
+    end
+
+    it "does not emit a deprecation warning when a block has parameters" do
+      -> { eval "proc { |a, b| it }" }.should_not complain
+      -> { eval "proc { |*rest| it }" }.should_not complain
+      -> { eval "proc { |*| it }" }.should_not complain
+      -> { eval "proc { |a:, b:| it }" }.should_not complain
+      -> { eval "proc { |**kw| it }" }.should_not complain
+      -> { eval "proc { |**| it }" }.should_not complain
+      -> { eval "proc { |&block| it }" }.should_not complain
+      -> { eval "proc { |&| it }" }.should_not complain
+      -> { eval "proc { || it }" }.should_not complain
+    end
+
+    it "does not emit a deprecation warning when `it` calls with arguments" do
+      -> { eval "proc { it(42) }" }.should_not complain
+      -> { eval "proc { it 42 }" }.should_not complain
+    end
+
+    it "does not emit a deprecation warning when `it` calls with a block" do
+      -> { eval "proc { it {} }" }.should_not complain
+    end
+
+    it "does not emit a deprecation warning when a local variable inside the block named `it` exists" do
+      -> { eval "proc { it = 42; it }" }.should_not complain
+    end
+
+    it "does not emit a deprecation warning when `it` calls with explicit empty arguments list" do
+      -> { eval "proc { it() }" }.should_not complain
+    end
+
+    it "calls the method `it` if defined" do
+      o = Object.new
+      def o.it
+        21
+      end
+      suppress_warning do
+        o.instance_eval("proc { it * 2 }").call(1).should == 42
+      end
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "does not emit a deprecation warning" do
+      -> {
+        eval "proc { it }"
+      }.should_not complain
+    end
+
+    it "acts as the first argument if no local variables exist" do
+      eval("proc { it * 2 }").call(5).should == 10
+    end
+
+    it "can be reassigned to act as a local variable" do
+      eval("proc { tmp = it; it = tmp * 2; it }").call(21).should == 42
+    end
+
+    it "can be used in nested calls" do
+      eval("proc { it.map { it * 2 } }").call([1, 2, 3]).should == [2, 4, 6]
+    end
+
+    it "cannot be mixed with numbered parameters" do
+      -> {
+        eval "proc { it + _1 }"
+      }.should raise_error(SyntaxError, /numbered parameters are not allowed when 'it' is already used|'it' is already used in/)
+
+      -> {
+        eval "proc { _1 + it }"
+      }.should raise_error(SyntaxError, /numbered parameter is already used in|'it' is not allowed when a numbered parameter is already used/)
+    end
+  end
+end
+
+describe "if `it` is defined as a variable" do
+  it "treats `it` as a captured variable if defined outside of a block" do
+    it = 5
+    proc { it }.call(0).should == 5
+  end
+
+  it "treats `it` as a local variable if defined inside of a block" do
+    proc { it = 5; it }.call(0).should == 5
+  end
+end
diff --git a/spec/ruby/language/break_spec.rb b/spec/ruby/language/break_spec.rb
index 754d5d3c49..7e5b6fb328 100644
--- a/spec/ruby/language/break_spec.rb
+++ b/spec/ruby/language/break_spec.rb
@@ -252,6 +252,25 @@ describe "Break inside a while loop" do
   end
 end
 
+describe "The break statement in a method" do
+  it "is invalid and raises a SyntaxError" do
+    -> {
+      eval("def m; break; end")
+    }.should raise_error(SyntaxError)
+  end
+end
+
+describe "The break statement in a module literal" do
+  it "is invalid and raises a SyntaxError" do
+    code = <<~RUBY
+      module BreakSpecs:ModuleWithBreak
+        break
+      end
+    RUBY
+
+    -> { eval(code) }.should raise_error(SyntaxError)
+  end
+end
 
 # TODO: Rewrite all the specs from here to the end of the file in the style
 # above.
@@ -362,4 +381,22 @@ describe "Executing break from within a block" do
     bt2.three
     ScratchPad.recorded.should == [:two_ensure, :three_post, :three_ensure]
   end
+
+  it "works when passing through a super call" do
+    cls1 = Class.new { def foo; yield; end }
+    cls2 = Class.new(cls1) { def foo; super { break 1 }; end }
+
+    -> do
+      cls2.new.foo.should == 1
+    end.should_not raise_error
+  end
+
+  it "raises LocalJumpError when converted into a proc during a super call" do
+    cls1 = Class.new { def foo(&b); b; end }
+    cls2 = Class.new(cls1) { def foo; super { break 1 }.call; end }
+
+    -> do
+      cls2.new.foo
+    end.should raise_error(LocalJumpError)
+  end
 end
diff --git a/spec/ruby/language/case_spec.rb b/spec/ruby/language/case_spec.rb
index 1475e20f75..464d06e46a 100644
--- a/spec/ruby/language/case_spec.rb
+++ b/spec/ruby/language/case_spec.rb
@@ -103,7 +103,7 @@ describe "The 'case'-construct" do
     $1.should == "42"
   end
 
-  it "tests with a regexp interpolated within another regexp" do
+  it "tests with a string interpolated in a regexp" do
     digits = '\d+'
     case "foo44"
     when /oo(#{digits})/
@@ -116,7 +116,7 @@ describe "The 'case'-construct" do
     $1.should == "44"
   end
 
-  it "tests with a string interpolated in a regexp" do
+  it "tests with a regexp interpolated within another regexp" do
     digits_regexp = /\d+/
     case "foo43"
     when /oo(#{digits_regexp})/
@@ -156,6 +156,15 @@ describe "The 'case'-construct" do
     end.should == "foo"
   end
 
+  it "tests an empty array" do
+    case []
+    when []
+      'foo'
+    else
+      'bar'
+    end.should == 'foo'
+  end
+
   it "expands arrays to lists of values" do
     case 'z'
     when *['a', 'b', 'c', 'd']
@@ -320,49 +329,6 @@ describe "The 'case'-construct" do
       100
     end.should == 100
   end
-end
-
-describe "The 'case'-construct with no target expression" do
-  it "evaluates the body of the first clause when at least one of its condition expressions is true" do
-    case
-    when true, false; 'foo'
-    end.should == 'foo'
-  end
-
-  it "evaluates the body of the first when clause that is not false/nil" do
-    case
-    when false; 'foo'
-    when 2; 'bar'
-    when 1 == 1; 'baz'
-    end.should == 'bar'
-
-    case
-    when false; 'foo'
-    when nil; 'foo'
-    when 1 == 1; 'bar'
-    end.should == 'bar'
-  end
-
-  it "evaluates the body of the else clause if all when clauses are false/nil" do
-    case
-    when false; 'foo'
-    when nil; 'foo'
-    when 1 == 2; 'bar'
-    else 'baz'
-    end.should == 'baz'
-  end
-
-  it "evaluates multiple conditional expressions as a boolean disjunction" do
-    case
-    when true, false; 'foo'
-    else 'bar'
-    end.should == 'foo'
-
-    case
-    when false, true; 'foo'
-    else 'bar'
-    end.should == 'foo'
-  end
 
   it "evaluates true as only 'true' when true is the first clause" do
     case 1
@@ -424,4 +390,120 @@ describe "The 'case'-construct with no target expression" do
       :called
     end.should == :called
   end
+
+  it "only matches last value in complex expressions within ()" do
+    case 'a'
+    when ('a'; 'b')
+      :wrong_called
+    when ('b'; 'a')
+      :called
+    end.should == :called
+  end
+
+  it "supports declaring variables in the case target expression" do
+    def test(v)
+      case new_variable_in_expression = v
+      when true
+        # This extra block is a test that `new_variable_in_expression` is declared outside of it and not inside
+        self.then { new_variable_in_expression }
+      else
+        # Same
+        self.then { new_variable_in_expression.casecmp?("foo") }
+      end
+    end
+
+    self.test("bar").should == false
+    self.test(true).should == true
+  end
+
+  ruby_version_is ""..."3.4" do
+    it "warns if there are identical when clauses" do
+      -> {
+        eval <<~RUBY
+          case 1
+          when 2
+            :foo
+          when 2
+            :bar
+          end
+        RUBY
+      }.should complain(/warning: (duplicated .when' clause with line \d+ is ignored|'when' clause on line \d+ duplicates 'when' clause on line \d+ and is ignored)/, verbose: true)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "warns if there are identical when clauses" do
+      -> {
+        eval <<~RUBY
+          case 1
+          when 2
+            :foo
+          when 2
+            :bar
+          end
+        RUBY
+      }.should complain(/warning: 'when' clause on line \d+ duplicates 'when' clause on line \d+ and is ignored/, verbose: true)
+    end
+  end
+end
+
+describe "The 'case'-construct with no target expression" do
+  it "evaluates the body of the first clause when at least one of its condition expressions is true" do
+    case
+    when true, false; 'foo'
+    end.should == 'foo'
+  end
+
+  it "evaluates the body of the first when clause that is not false/nil" do
+    case
+    when false; 'foo'
+    when 2; 'bar'
+    when 1 == 1; 'baz'
+    end.should == 'bar'
+
+    case
+    when false; 'foo'
+    when nil; 'foo'
+    when 1 == 1; 'bar'
+    end.should == 'bar'
+  end
+
+  it "evaluates the body of the else clause if all when clauses are false/nil" do
+    case
+    when false; 'foo'
+    when nil; 'foo'
+    when 1 == 2; 'bar'
+    else 'baz'
+    end.should == 'baz'
+  end
+
+  it "evaluates multiple conditional expressions as a boolean disjunction" do
+    case
+    when true, false; 'foo'
+    else 'bar'
+    end.should == 'foo'
+
+    case
+    when false, true; 'foo'
+    else 'bar'
+    end.should == 'foo'
+  end
+
+  # Homogeneous cases are often optimized to avoid === using a jump table, and should be tested separately.
+  # See https://github.com/jruby/jruby/issues/6440
+  it "handles homogeneous cases" do
+    case
+    when 1; 'foo'
+    when 2; 'bar'
+    end.should == 'foo'
+  end
+
+  it "expands arrays to lists of values" do
+    case
+    when *[false]
+      "foo"
+    when *[true]
+      "bar"
+    end.should == "bar"
+  end
 end
diff --git a/spec/ruby/language/class_spec.rb b/spec/ruby/language/class_spec.rb
index 88b7a6a74f..6fb785fd56 100644
--- a/spec/ruby/language/class_spec.rb
+++ b/spec/ruby/language/class_spec.rb
@@ -17,6 +17,19 @@ describe "The class keyword" do
     eval "class ClassSpecsKeywordWithoutSemicolon end"
     ClassSpecsKeywordWithoutSemicolon.should be_an_instance_of(Class)
   end
+
+  it "can redefine a class when called from a block" do
+    ClassSpecs::DEFINE_CLASS.call
+    A.should be_an_instance_of(Class)
+
+    Object.send(:remove_const, :A)
+    defined?(A).should be_nil
+
+    ClassSpecs::DEFINE_CLASS.call
+    A.should be_an_instance_of(Class)
+  ensure
+    Object.send(:remove_const, :A) if defined?(::A)
+  end
 end
 
 describe "A class definition" do
@@ -33,7 +46,14 @@ describe "A class definition" do
     -> {
       class ClassSpecsNumber
       end
-    }.should raise_error(TypeError)
+    }.should raise_error(TypeError, /\AClassSpecsNumber is not a class/)
+  end
+
+  it "raises TypeError if constant given as class name exists and is a Module but not a Class" do
+    -> {
+      class ClassSpecs
+      end
+    }.should raise_error(TypeError, /\AClassSpecs is not a class/)
   end
 
   # test case known to be detecting bugs (JRuby, MRI)
@@ -258,6 +278,8 @@ describe "A class definition" do
 
       AnonWithConstant.name.should == 'AnonWithConstant'
       klass.get_class_name.should == 'AnonWithConstant'
+    ensure
+      Object.send(:remove_const, :AnonWithConstant)
     end
   end
 end
@@ -285,12 +307,20 @@ describe "A class definition extending an object (sclass)" do
     }.should raise_error(TypeError)
   end
 
-  ruby_version_is ""..."3.0" do
-    it "allows accessing the block of the original scope" do
-      suppress_warning do
-        ClassSpecs.sclass_with_block { 123 }.should == 123
-      end
-    end
+  it "raises a TypeError when trying to extend non-Class" do
+    error_msg = /superclass must be a.* Class/
+    -> { class TestClass < "";              end }.should raise_error(TypeError, error_msg)
+    -> { class TestClass < 1;               end }.should raise_error(TypeError, error_msg)
+    -> { class TestClass < :symbol;         end }.should raise_error(TypeError, error_msg)
+    -> { class TestClass < mock('o');       end }.should raise_error(TypeError, error_msg)
+    -> { class TestClass < Module.new;      end }.should raise_error(TypeError, error_msg)
+    -> { class TestClass < BasicObject.new; end }.should raise_error(TypeError, error_msg)
+  end
+
+  it "does not allow accessing the block of the original scope" do
+    -> {
+      ClassSpecs.sclass_with_block { 123 }
+    }.should raise_error(SyntaxError)
   end
 
   it "can use return to cause the enclosing method to return" do
@@ -323,6 +353,39 @@ describe "Reopening a class" do
     ClassSpecs::M.m.should == 1
     ClassSpecs::L.singleton_class.send(:remove_method, :m)
   end
+
+  it "does not reopen a class included in Object" do
+    ruby_exe(<<~RUBY).should == "false"
+      module IncludedInObject
+        class IncludedClass
+        end
+      end
+      class Object
+        include IncludedInObject
+      end
+      class IncludedClass
+      end
+      print IncludedInObject::IncludedClass == Object::IncludedClass
+    RUBY
+  end
+
+  it "does not reopen a class included in non-Object modules" do
+    ruby_exe(<<~RUBY).should == "false/false"
+      module Included
+        module IncludedClass; end
+      end
+      module M
+        include Included
+        module IncludedClass; end
+      end
+      class C
+        include Included
+        module IncludedClass; end
+      end
+      print Included::IncludedClass == M::IncludedClass, "/",
+            Included::IncludedClass == C::IncludedClass
+    RUBY
+  end
 end
 
 describe "class provides hooks" do
diff --git a/spec/ruby/language/class_variable_spec.rb b/spec/ruby/language/class_variable_spec.rb
index dffab47a6b..a26a3fb8de 100644
--- a/spec/ruby/language/class_variable_spec.rb
+++ b/spec/ruby/language/class_variable_spec.rb
@@ -82,3 +82,33 @@ describe 'A class variable definition' do
     c.class_variable_get(:@@cv).should == :next
   end
 end
+
+describe 'Accessing a class variable' do
+  it "raises a RuntimeError when accessed from the toplevel scope (not in some module or class)" do
+    -> {
+      eval "@@cvar_toplevel1"
+    }.should raise_error(RuntimeError, 'class variable access from toplevel')
+    -> {
+      eval "@@cvar_toplevel2 = 2"
+    }.should raise_error(RuntimeError, 'class variable access from toplevel')
+  end
+
+  it "does not raise an error when checking if defined from the toplevel scope" do
+    -> {
+      eval "defined?(@@cvar_toplevel1)"
+    }.should_not raise_error
+  end
+
+  it "raises a RuntimeError when a class variable is overtaken in an ancestor class" do
+    parent = Class.new()
+    subclass = Class.new(parent)
+    subclass.class_variable_set(:@@cvar_overtaken, :subclass)
+    parent.class_variable_set(:@@cvar_overtaken, :parent)
+
+    -> {
+      subclass.class_variable_get(:@@cvar_overtaken)
+    }.should raise_error(RuntimeError, /class variable @@cvar_overtaken of .+ is overtaken by .+/)
+
+    parent.class_variable_get(:@@cvar_overtaken).should == :parent
+  end
+end
diff --git a/spec/ruby/language/comment_spec.rb b/spec/ruby/language/comment_spec.rb
new file mode 100644
index 0000000000..dd788e681c
--- /dev/null
+++ b/spec/ruby/language/comment_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../spec_helper'
+
+describe "The comment" do
+  it "can be placed between fluent dot now" do
+    code = <<~CODE
+      10
+        # some comment
+        .to_s
+      CODE
+
+    eval(code).should == '10'
+  end
+end
diff --git a/spec/ruby/language/constants_spec.rb b/spec/ruby/language/constants_spec.rb
index c4cf940cba..063c52c422 100644
--- a/spec/ruby/language/constants_spec.rb
+++ b/spec/ruby/language/constants_spec.rb
@@ -72,39 +72,60 @@ describe "Literal (A::X) constant resolution" do
 
       ConstantSpecs::ModuleA::CS_CONST101 = :const101_5
       ConstantSpecs::ModuleA::CS_CONST101.should == :const101_5
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST101)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST101)
+      ConstantSpecs::ContainerB.send(:remove_const, :CS_CONST101)
+      ConstantSpecs::ContainerB::ChildB.send(:remove_const, :CS_CONST101)
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST101)
     end
 
     it "searches a module included in the immediate class before the superclass" do
       ConstantSpecs::ParentB::CS_CONST102 = :const102_1
       ConstantSpecs::ModuleF::CS_CONST102 = :const102_2
       ConstantSpecs::ContainerB::ChildB::CS_CONST102.should == :const102_2
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST102)
+      ConstantSpecs::ModuleF.send(:remove_const, :CS_CONST102)
     end
 
     it "searches the superclass before a module included in the superclass" do
       ConstantSpecs::ModuleE::CS_CONST103 = :const103_1
       ConstantSpecs::ParentB::CS_CONST103 = :const103_2
       ConstantSpecs::ContainerB::ChildB::CS_CONST103.should == :const103_2
+    ensure
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST103)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST103)
     end
 
     it "searches a module included in the superclass" do
       ConstantSpecs::ModuleA::CS_CONST104 = :const104_1
       ConstantSpecs::ModuleE::CS_CONST104 = :const104_2
       ConstantSpecs::ContainerB::ChildB::CS_CONST104.should == :const104_2
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST104)
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST104)
     end
 
     it "searches the superclass chain" do
       ConstantSpecs::ModuleA::CS_CONST105 = :const105
       ConstantSpecs::ContainerB::ChildB::CS_CONST105.should == :const105
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST105)
     end
 
     it "searches Object if no class or module qualifier is given" do
       CS_CONST106 = :const106
       CS_CONST106.should == :const106
+    ensure
+      Object.send(:remove_const, :CS_CONST106)
     end
 
     it "searches Object if a toplevel qualifier (::X) is given" do
       ::CS_CONST107 = :const107
       ::CS_CONST107.should == :const107
+    ensure
+      Object.send(:remove_const, :CS_CONST107)
     end
 
     it "does not search the singleton class of the class or module" do
@@ -123,6 +144,9 @@ describe "Literal (A::X) constant resolution" do
       end
 
       -> { ConstantSpecs::CS_CONST108 }.should raise_error(NameError)
+    ensure
+      ConstantSpecs::ContainerB::ChildB.singleton_class.send(:remove_const, :CS_CONST108)
+      ConstantSpecs.singleton_class.send(:remove_const, :CS_CONST108)
     end
 
     it "returns the updated value when a constant is reassigned" do
@@ -133,20 +157,20 @@ describe "Literal (A::X) constant resolution" do
         ConstantSpecs::ClassB::CS_CONST109 = :const109_2
       }.should complain(/already initialized constant/)
       ConstantSpecs::ClassB::CS_CONST109.should == :const109_2
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST109)
     end
 
-    it "evaluates the right hand side before evaluating a constant path" do
+    it "evaluates left-to-right" do
       mod = Module.new
 
       mod.module_eval <<-EOC
-        ConstantSpecsRHS::B = begin
-          module ConstantSpecsRHS; end
-
-          "hello"
-        end
+        order = []
+        ConstantSpecsRHS = Module.new
+        (order << :lhs; ConstantSpecsRHS)::B = (order << :rhs)
       EOC
 
-      mod::ConstantSpecsRHS::B.should == 'hello'
+      mod::ConstantSpecsRHS::B.should == [:lhs, :rhs]
     end
   end
 
@@ -154,6 +178,34 @@ describe "Literal (A::X) constant resolution" do
     -> { ConstantSpecs::ParentA::CS_CONSTX }.should raise_error(NameError)
   end
 
+  it "uses the module or class #name to craft the error message" do
+    mod = Module.new do
+      def self.name
+        "ModuleName"
+      end
+
+      def self.inspect
+        "<unusable info>"
+      end
+    end
+
+    -> { mod::DOES_NOT_EXIST }.should raise_error(NameError, /uninitialized constant ModuleName::DOES_NOT_EXIST/)
+  end
+
+  it "uses the module or class #inspect to craft the error message if they are anonymous" do
+    mod = Module.new do
+      def self.name
+        nil
+      end
+
+      def self.inspect
+        "<unusable info>"
+      end
+    end
+
+    -> { mod::DOES_NOT_EXIST }.should raise_error(NameError, /uninitialized constant <unusable info>::DOES_NOT_EXIST/)
+  end
+
   it "sends #const_missing to the original class or module scope" do
     ConstantSpecs::ClassA::CS_CONSTX.should == :CS_CONSTX
   end
@@ -248,6 +300,12 @@ describe "Constant resolution within methods" do
       ConstantSpecs::ClassB.new.const201.should == :const201_2
       ConstantSpecs::ParentB.new.const201.should == :const201_3
       ConstantSpecs::ContainerB::ChildB.new.const201.should == :const201_5
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST201)
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST201)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST201)
+      ConstantSpecs::ContainerB.send(:remove_const, :CS_CONST201)
+      ConstantSpecs::ContainerB::ChildB.send(:remove_const, :CS_CONST201)
     end
 
     it "searches a module included in the immediate class before the superclass" do
@@ -256,6 +314,9 @@ describe "Constant resolution within methods" do
 
       ConstantSpecs::ContainerB::ChildB.const202.should == :const202_1
       ConstantSpecs::ContainerB::ChildB.new.const202.should == :const202_1
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST202)
+      ConstantSpecs::ContainerB::ChildB.send(:remove_const, :CS_CONST202)
     end
 
     it "searches the superclass before a module included in the superclass" do
@@ -264,6 +325,9 @@ describe "Constant resolution within methods" do
 
       ConstantSpecs::ContainerB::ChildB.const203.should == :const203_1
       ConstantSpecs::ContainerB::ChildB.new.const203.should == :const203_1
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST203)
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST203)
     end
 
     it "searches a module included in the superclass" do
@@ -272,6 +336,9 @@ describe "Constant resolution within methods" do
 
       ConstantSpecs::ContainerB::ChildB.const204.should == :const204_1
       ConstantSpecs::ContainerB::ChildB.new.const204.should == :const204_1
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST204)
+      ConstantSpecs::ModuleE.send(:remove_const, :CS_CONST204)
     end
 
     it "searches the superclass chain" do
@@ -279,6 +346,8 @@ describe "Constant resolution within methods" do
 
       ConstantSpecs::ContainerB::ChildB.const205.should == :const205
       ConstantSpecs::ContainerB::ChildB.new.const205.should == :const205
+    ensure
+      ConstantSpecs::ModuleA.send(:remove_const, :CS_CONST205)
     end
 
     it "searches the lexical scope of the method not the receiver's immediate class" do
@@ -290,6 +359,9 @@ describe "Constant resolution within methods" do
       end
 
       ConstantSpecs::ContainerB::ChildB.const206.should == :const206_1
+    ensure
+      ConstantSpecs::ContainerB::ChildB.send(:remove_const, :CS_CONST206)
+      ConstantSpecs::ContainerB::ChildB.singleton_class.send(:remove_const, :CS_CONST206)
     end
 
     it "searches the lexical scope of a singleton method" do
@@ -297,12 +369,17 @@ describe "Constant resolution within methods" do
       ConstantSpecs::ClassB::CS_CONST207 = :const207_2
 
       ConstantSpecs::CS_CONST208.const207.should == :const207_1
+    ensure
+      ConstantSpecs.send(:remove_const, :CS_CONST207)
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST207)
     end
 
     it "does not search the lexical scope of the caller" do
       ConstantSpecs::ClassB::CS_CONST209 = :const209
 
       -> { ConstantSpecs::ClassB.const209 }.should raise_error(NameError)
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST209)
     end
 
     it "searches the lexical scope of a block" do
@@ -310,6 +387,9 @@ describe "Constant resolution within methods" do
       ConstantSpecs::ParentB::CS_CONST210 = :const210_2
 
       ConstantSpecs::ClassB.const210.should == :const210_1
+    ensure
+      ConstantSpecs::ClassB.send(:remove_const, :CS_CONST210)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST210)
     end
 
     it "searches Object as a lexical scope only if Object is explicitly opened" do
@@ -320,6 +400,11 @@ describe "Constant resolution within methods" do
       Object::CS_CONST212 = :const212_2
       ConstantSpecs::ParentB::CS_CONST212 = :const212_1
       ConstantSpecs::ContainerB::ChildB.const212.should == :const212_1
+    ensure
+      Object.send(:remove_const, :CS_CONST211)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST211)
+      Object.send(:remove_const, :CS_CONST212)
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST212)
     end
 
     it "returns the updated value when a constant is reassigned" do
@@ -332,6 +417,8 @@ describe "Constant resolution within methods" do
       }.should complain(/already initialized constant/)
       ConstantSpecs::ContainerB::ChildB.const213.should == :const213_2
       ConstantSpecs::ContainerB::ChildB.new.const213.should == :const213_2
+    ensure
+      ConstantSpecs::ParentB.send(:remove_const, :CS_CONST213)
     end
 
     it "does not search the lexical scope of qualifying modules" do
@@ -340,6 +427,8 @@ describe "Constant resolution within methods" do
       -> do
         ConstantSpecs::ContainerB::ChildB.const214
       end.should raise_error(NameError)
+    ensure
+      ConstantSpecs::ContainerB.send(:remove_const, :CS_CONST214)
     end
   end
 
@@ -351,52 +440,6 @@ describe "Constant resolution within methods" do
     ConstantSpecs::ClassA.constx.should == :CS_CONSTX
     ConstantSpecs::ClassA.new.constx.should == :CS_CONSTX
   end
-
-  describe "with ||=" do
-    it "assigns a scoped constant if previously undefined" do
-      ConstantSpecs.should_not have_constant(:OpAssignUndefined)
-      module ConstantSpecs
-        OpAssignUndefined ||= 42
-      end
-      ConstantSpecs::OpAssignUndefined.should == 42
-      ConstantSpecs::OpAssignUndefinedOutside ||= 42
-      ConstantSpecs::OpAssignUndefinedOutside.should == 42
-      ConstantSpecs.send(:remove_const, :OpAssignUndefined)
-      ConstantSpecs.send(:remove_const, :OpAssignUndefinedOutside)
-    end
-
-    it "assigns a global constant if previously undefined" do
-      OpAssignGlobalUndefined ||= 42
-      ::OpAssignGlobalUndefinedExplicitScope ||= 42
-      OpAssignGlobalUndefined.should == 42
-      ::OpAssignGlobalUndefinedExplicitScope.should == 42
-      Object.send :remove_const, :OpAssignGlobalUndefined
-      Object.send :remove_const, :OpAssignGlobalUndefinedExplicitScope
-    end
-
-  end
-
-  describe "with &&=" do
-    it "re-assigns a scoped constant if already true" do
-      module ConstantSpecs
-        OpAssignTrue = true
-      end
-      suppress_warning do
-        ConstantSpecs::OpAssignTrue &&= 1
-      end
-      ConstantSpecs::OpAssignTrue.should == 1
-      ConstantSpecs.send :remove_const, :OpAssignTrue
-    end
-
-    it "leaves scoped constant if not true" do
-      module ConstantSpecs
-        OpAssignFalse = false
-      end
-      ConstantSpecs::OpAssignFalse &&= 1
-      ConstantSpecs::OpAssignFalse.should == false
-      ConstantSpecs.send :remove_const, :OpAssignFalse
-    end
-  end
 end
 
 describe "Constant resolution within a singleton class (class << obj)" do
@@ -425,18 +468,8 @@ end
 
 describe "top-level constant lookup" do
   context "on a class" do
-    ruby_version_is "" ... "2.5" do
-      it "searches Object successfully after searching other scopes" do
-        -> {
-          String::Hash.should == Hash
-        }.should complain(/toplevel constant Hash referenced by/)
-      end
-    end
-
-    ruby_version_is "2.5" do
-      it "does not search Object after searching other scopes" do
-        -> { String::Hash }.should raise_error(NameError)
-      end
+    it "does not search Object after searching other scopes" do
+      -> { String::Hash }.should raise_error(NameError)
     end
   end
 
@@ -458,17 +491,15 @@ describe "Module#private_constant marked constants" do
     -> {mod::Foo}.should raise_error(NameError)
   end
 
-  ruby_version_is "2.6" do
-    it "sends #const_missing to the original class or module" do
-      mod = Module.new
-      mod.const_set :Foo, true
-      mod.send :private_constant, :Foo
-      def mod.const_missing(name)
-        name == :Foo ? name : super
-      end
-
-      mod::Foo.should == :Foo
+  it "sends #const_missing to the original class or module" do
+    mod = Module.new
+    mod.const_set :Foo, true
+    mod.send :private_constant, :Foo
+    def mod.const_missing(name)
+      name == :Foo ? name : super
     end
+
+    mod::Foo.should == :Foo
   end
 
   describe "in a module" do
@@ -498,6 +529,10 @@ describe "Module#private_constant marked constants" do
 
         PrivateModule::X.should == 1
       end
+    ensure
+      module ::ConstantVisibility::ModuleContainer
+        PrivateModule.send(:remove_const, :X)
+      end
     end
 
     it "can be reopened as a class where constant is not private" do
@@ -508,6 +543,10 @@ describe "Module#private_constant marked constants" do
 
         PrivateClass::X.should == 1
       end
+    ensure
+      module ::ConstantVisibility::ModuleContainer
+        PrivateClass.send(:remove_const, :X)
+      end
     end
 
     it "is not defined? with A::B form" do
@@ -531,11 +570,24 @@ describe "Module#private_constant marked constants" do
     end
 
     it "can be accessed from classes that include the module" do
-      ConstantVisibility::PrivConstModuleChild.new.private_constant_from_include.should be_true
+      ConstantVisibility::ClassIncludingPrivConstModule.new.private_constant_from_include.should be_true
+    end
+
+    it "can be accessed from modules that include the module" do
+      ConstantVisibility::ModuleIncludingPrivConstModule.private_constant_from_include.should be_true
+    end
+
+    it "raises a NameError when accessed directly from modules that include the module" do
+      -> do
+        ConstantVisibility::ModuleIncludingPrivConstModule.private_constant_self_from_include
+      end.should raise_error(NameError)
+      -> do
+        ConstantVisibility::ModuleIncludingPrivConstModule.private_constant_named_from_include
+      end.should raise_error(NameError)
     end
 
     it "is defined? from classes that include the module" do
-      ConstantVisibility::PrivConstModuleChild.new.defined_from_include.should == "constant"
+      ConstantVisibility::ClassIncludingPrivConstModule.new.defined_from_include.should == "constant"
     end
   end
 
@@ -566,6 +618,10 @@ describe "Module#private_constant marked constants" do
 
         PrivateModule::X.should == 1
       end
+    ensure
+      class ::ConstantVisibility::ClassContainer
+        PrivateModule.send(:remove_const, :X)
+      end
     end
 
     it "can be reopened as a class where constant is not private" do
@@ -576,6 +632,10 @@ describe "Module#private_constant marked constants" do
 
         PrivateClass::X.should == 1
       end
+    ensure
+      class ::ConstantVisibility::ClassContainer
+        PrivateClass.send(:remove_const, :X)
+      end
     end
 
     it "is not defined? with A::B form" do
@@ -653,7 +713,7 @@ describe "Module#private_constant marked constants" do
       }
 
       -> do
-        ConstantVisibility::PrivConstModuleChild::PRIVATE_CONSTANT_MODULE
+        ConstantVisibility::ClassIncludingPrivConstModule::PRIVATE_CONSTANT_MODULE
       end.should raise_error(NameError) {|e|
         e.receiver.should == ConstantVisibility::PrivConstModule
         e.name.should == :PRIVATE_CONSTANT_MODULE
@@ -726,20 +786,24 @@ describe 'Allowed characters' do
     end.should raise_error(NameError, /wrong constant name/)
   end
 
-  ruby_version_is ""..."2.6" do
-    it 'does not allow not ASCII upcased characters at the beginning' do
-      -> do
-        Module.new.const_set("ἍBB", 1)
-      end.should raise_error(NameError, /wrong constant name/)
-    end
-  end
+  it 'allows not ASCII upcased characters at the beginning' do
+    mod = Module.new
+    mod.const_set("ἍBB", 1)
 
-  ruby_version_is "2.6" do
-    it 'allows not ASCII upcased characters at the beginning' do
-      mod = Module.new
-      mod.const_set("ἍBB", 1)
+    eval("mod::ἍBB").should == 1
+  end
+end
 
-      eval("mod::ἍBB").should == 1
+describe 'Assignment' do
+  context 'dynamic assignment' do
+    it 'raises SyntaxError' do
+      -> do
+        eval <<-CODE
+          def test
+            B = 1
+          end
+        CODE
+      end.should raise_error(SyntaxError, /dynamic constant assignment/)
     end
   end
 end
diff --git a/spec/ruby/language/def_spec.rb b/spec/ruby/language/def_spec.rb
index 82813bd36c..0cf1790791 100644
--- a/spec/ruby/language/def_spec.rb
+++ b/spec/ruby/language/def_spec.rb
@@ -89,6 +89,28 @@ describe "An instance method" do
     def foo(a); end
     -> { foo 1, 2 }.should raise_error(ArgumentError, 'wrong number of arguments (given 2, expected 1)')
   end
+
+  it "raises FrozenError with the correct class name" do
+    -> {
+      Module.new do
+        self.freeze
+        def foo; end
+      end
+    }.should raise_error(FrozenError) { |e|
+      msg_class = ruby_version_is("4.0") ? "Module" : "module"
+      e.message.should == "can't modify frozen #{msg_class}: #{e.receiver}"
+    }
+
+    -> {
+      Class.new do
+        self.freeze
+        def foo; end
+      end
+    }.should raise_error(FrozenError){ |e|
+      msg_class = ruby_version_is("4.0") ? "Class" : "class"
+      e.message.should == "can't modify frozen #{msg_class}: #{e.receiver}"
+    }
+  end
 end
 
 describe "An instance method definition with a splat" do
@@ -177,17 +199,25 @@ describe "An instance method with a default argument" do
     foo(2,3,3).should == [2,3,[3]]
   end
 
-  it "shadows an existing method with the same name as the local" do
-    def bar
-      1
+  ruby_version_is ""..."3.4" do
+    it "raises a SyntaxError if using the argument in its default value" do
+      -> {
+        eval "def foo(bar = bar)
+          bar
+        end"
+      }.should raise_error(SyntaxError)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "is nil if using the argument in its default value" do
+      -> {
+        eval "def foo(bar = bar)
+          bar
+        end
+        foo"
+      }.call.should == nil
     end
-    -> {
-      eval "def foo(bar = bar)
-        bar
-      end"
-    }.should complain(/circular argument reference/)
-    foo.should == nil
-    foo(2).should == 2
   end
 
   it "calls a method with the same name as the local when explicitly using ()" do
@@ -220,7 +250,7 @@ describe "A singleton method definition" do
   end
 
   it "can be declared for a global variable" do
-    $__a__ = "hi"
+    $__a__ = +"hi"
     def $__a__.foo
       7
     end
@@ -246,10 +276,30 @@ describe "A singleton method definition" do
     (obj==2).should == 2
   end
 
-  it "raises #{frozen_error_class} if frozen" do
+  it "raises FrozenError if frozen" do
+    obj = Object.new
+    obj.freeze
+    -> { def obj.foo; end }.should raise_error(FrozenError)
+  end
+
+  it "raises FrozenError with the correct class name" do
     obj = Object.new
     obj.freeze
-    -> { def obj.foo; end }.should raise_error(frozen_error_class)
+    msg_class = ruby_version_is("4.0") ? "Object" : "object"
+    -> { def obj.foo; end }.should raise_error(FrozenError, "can't modify frozen #{msg_class}: #{obj}")
+
+    obj = Object.new
+    c = obj.singleton_class
+    c.singleton_class.freeze
+    -> { def c.foo; end }.should raise_error(FrozenError, "can't modify frozen Class: #{c}")
+
+    c = Class.new
+    c.freeze
+    -> { def c.foo; end }.should raise_error(FrozenError, "can't modify frozen Class: #{c}")
+
+    m = Module.new
+    m.freeze
+    -> { def m.foo; end }.should raise_error(FrozenError, "can't modify frozen Module: #{m}")
   end
 end
 
@@ -397,12 +447,12 @@ describe "A method definition inside a metaclass scope" do
     -> { Object.new.a_singleton_method }.should raise_error(NoMethodError)
   end
 
-  it "raises #{frozen_error_class} if frozen" do
+  it "raises FrozenError if frozen" do
     obj = Object.new
     obj.freeze
 
     class << obj
-      -> { def foo; end }.should raise_error(frozen_error_class)
+      -> { def foo; end }.should raise_error(FrozenError)
     end
   end
 end
@@ -477,6 +527,8 @@ describe "A nested method definition" do
 
     obj = DefSpecNested.new
     obj.inherited_method.should == obj
+  ensure
+    DefSpecNested.send(:remove_const, :TARGET)
   end
 
   # See http://yugui.jp/articles/846#label-3
@@ -498,6 +550,8 @@ describe "A nested method definition" do
 
     DefSpecNested.should_not have_instance_method :arg_method
     DefSpecNested.should_not have_instance_method :body_method
+  ensure
+    DefSpecNested.send(:remove_const, :OBJ)
   end
 
   it "creates an instance method inside Class.new" do
diff --git a/spec/ruby/language/defined_spec.rb b/spec/ruby/language/defined_spec.rb
index 02c69d27b8..80ad1818b1 100644
--- a/spec/ruby/language/defined_spec.rb
+++ b/spec/ruby/language/defined_spec.rb
@@ -5,21 +5,25 @@ describe "The defined? keyword for literals" do
   it "returns 'self' for self" do
     ret = defined?(self)
     ret.should == "self"
+    ret.frozen?.should == true
   end
 
   it "returns 'nil' for nil" do
     ret = defined?(nil)
     ret.should == "nil"
+    ret.frozen?.should == true
   end
 
   it "returns 'true' for true" do
     ret = defined?(true)
     ret.should == "true"
+    ret.frozen?.should == true
   end
 
   it "returns 'false' for false" do
     ret = defined?(false)
     ret.should == "false"
+    ret.frozen?.should == true
   end
 
   describe "for a literal Array" do
@@ -27,6 +31,7 @@ describe "The defined? keyword for literals" do
     it "returns 'expression' if each element is defined" do
       ret = defined?([Object, Array])
       ret.should == "expression"
+      ret.frozen?.should == true
     end
 
     it "returns nil if one element is not defined" do
@@ -43,9 +48,25 @@ describe "The defined? keyword for literals" do
 end
 
 describe "The defined? keyword when called with a method name" do
+  before :each do
+    ScratchPad.clear
+  end
+
+  it "does not call the method" do
+    defined?(DefinedSpecs.side_effects).should == "method"
+    ScratchPad.recorded.should != :defined_specs_side_effects
+  end
+
+  it "does not execute the arguments" do
+    defined?(DefinedSpecs.any_args(DefinedSpecs.side_effects)).should == "method"
+    ScratchPad.recorded.should != :defined_specs_side_effects
+  end
+
   describe "without a receiver" do
     it "returns 'method' if the method is defined" do
-      defined?(puts).should == "method"
+      ret = defined?(puts)
+      ret.should == "method"
+      ret.frozen?.should == true
     end
 
     it "returns nil if the method is not defined" do
@@ -95,6 +116,11 @@ describe "The defined? keyword when called with a method name" do
       defined?(obj.a_defined_method).should == "method"
     end
 
+    it "returns 'method' for []=" do
+      a = []
+      defined?(a[0] = 1).should == "method"
+    end
+
     it "returns nil if the method is not defined" do
       obj = DefinedSpecs::Basic.new
       defined?(obj.an_undefined_method).should be_nil
@@ -159,6 +185,32 @@ describe "The defined? keyword when called with a method name" do
       ScratchPad.recorded.should == :defined_specs_fixnum_method
     end
   end
+
+  describe "having a throw in the receiver" do
+    it "escapes defined? and performs the throw semantics as normal" do
+      defined_returned = false
+      catch(:out) {
+        # NOTE: defined? behaves differently if it is called in a void context, see below
+        defined?(throw(:out, 42).foo).should == :unreachable
+        defined_returned = true
+      }.should == 42
+      defined_returned.should == false
+    end
+  end
+
+  describe "in a void context" do
+    it "does not execute the receiver" do
+      ScratchPad.record :not_executed
+      defined?(DefinedSpecs.side_effects / 2)
+      ScratchPad.recorded.should == :not_executed
+    end
+
+    it "warns about the void context when parsing it" do
+      -> {
+        eval "defined?(DefinedSpecs.side_effects / 2); 42"
+      }.should complain(/warning: possibly useless use of defined\? in void context/, verbose: true)
+    end
+  end
 end
 
 describe "The defined? keyword for an expression" do
@@ -167,7 +219,9 @@ describe "The defined? keyword for an expression" do
   end
 
   it "returns 'assignment' for assigning a local variable" do
-    defined?(x = 2).should == "assignment"
+    ret = defined?(x = 2)
+    ret.should == "assignment"
+    ret.frozen?.should == true
   end
 
   it "returns 'assignment' for assigning an instance variable" do
@@ -182,6 +236,14 @@ describe "The defined? keyword for an expression" do
     defined?(@@defined_specs_x = 2).should == "assignment"
   end
 
+  it "returns 'assignment' for assigning a constant" do
+    defined?(A = 2).should == "assignment"
+  end
+
+  it "returns 'assignment' for assigning a fully qualified constant" do
+    defined?(Object::A = 2).should == "assignment"
+  end
+
   it "returns 'assignment' for assigning multiple variables" do
     defined?((a, b = 1, 2)).should == "assignment"
   end
@@ -199,7 +261,27 @@ describe "The defined? keyword for an expression" do
   end
 
   it "returns 'assignment' for an expression with '+='" do
-    defined?(x += 2).should == "assignment"
+    defined?(a += 1).should == "assignment"
+    defined?(@a += 1).should == "assignment"
+    defined?(@@a += 1).should == "assignment"
+    defined?($a += 1).should == "assignment"
+    defined?(A += 1).should == "assignment"
+    # fully qualified constant check is moved out into a separate test case
+    defined?(a.b += 1).should == "assignment"
+    defined?(a[:b] += 1).should == "assignment"
+  end
+
+  # https://bugs.ruby-lang.org/issues/20111
+  ruby_version_is ""..."3.4" do
+    it "returns 'expression' for an assigning a fully qualified constant with '+='" do
+      defined?(Object::A += 1).should == "expression"
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "returns 'assignment' for an assigning a fully qualified constant with '+='" do
+      defined?(Object::A += 1).should == "assignment"
+    end
   end
 
   it "returns 'assignment' for an expression with '*='" do
@@ -230,12 +312,90 @@ describe "The defined? keyword for an expression" do
     defined?(x >>= 2).should == "assignment"
   end
 
-  it "returns 'assignment' for an expression with '||='" do
-    defined?(x ||= 2).should == "assignment"
+  context "||=" do
+    it "returns 'assignment' for assigning a local variable with '||='" do
+      defined?(a ||= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning an instance variable with '||='" do
+      defined?(@a ||= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a class variable with '||='" do
+      defined?(@@a ||= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a global variable with '||='" do
+      defined?($a ||= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a constant with '||='" do
+      defined?(A ||= true).should == "assignment"
+    end
+
+    # https://bugs.ruby-lang.org/issues/20111
+    ruby_version_is ""..."3.4" do
+      it "returns 'expression' for assigning a fully qualified constant with '||='" do
+        defined?(Object::A ||= true).should == "expression"
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "returns 'assignment' for assigning a fully qualified constant with '||='" do
+        defined?(Object::A ||= true).should == "assignment"
+      end
+    end
+
+    it "returns 'assignment' for assigning an attribute with '||='" do
+      defined?(a.b ||= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a referenced element with '||='" do
+      defined?(a[:b] ||= true).should == "assignment"
+    end
   end
 
-  it "returns 'assignment' for an expression with '&&='" do
-    defined?(x &&= 2).should == "assignment"
+  context "&&=" do
+    it "returns 'assignment' for assigning a local variable with '&&='" do
+      defined?(a &&= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning an instance variable with '&&='" do
+      defined?(@a &&= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a class variable with '&&='" do
+      defined?(@@a &&= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a global variable with '&&='" do
+      defined?($a &&= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a constant with '&&='" do
+      defined?(A &&= true).should == "assignment"
+    end
+
+    # https://bugs.ruby-lang.org/issues/20111
+    ruby_version_is ""..."3.4" do
+      it "returns 'expression' for assigning a fully qualified constant with '&&='" do
+        defined?(Object::A &&= true).should == "expression"
+      end
+    end
+
+    ruby_version_is "3.4" do
+      it "returns 'assignment' for assigning a fully qualified constant with '&&='" do
+        defined?(Object::A &&= true).should == "assignment"
+      end
+    end
+
+    it "returns 'assignment' for assigning an attribute with '&&='" do
+      defined?(a.b &&= true).should == "assignment"
+    end
+
+    it "returns 'assignment' for assigning a referenced element with '&&='" do
+      defined?(a[:b] &&= true).should == "assignment"
+    end
   end
 
   it "returns 'assignment' for an expression with '**='" do
@@ -275,9 +435,7 @@ describe "The defined? keyword for an expression" do
     end
 
     it "returns nil for an expression with '!' and an unset class variable" do
-      -> {
-        @result = defined?(!@@defined_specs_undefined_class_variable)
-      }.should complain(/class variable access from toplevel/)
+      @result = eval("class singleton_class::A; defined?(!@@doesnt_exist) end", binding, __FILE__, __LINE__)
       @result.should be_nil
     end
 
@@ -286,9 +444,7 @@ describe "The defined? keyword for an expression" do
     end
 
     it "returns nil for an expression with 'not' and an unset class variable" do
-      -> {
-        @result = defined?(not @@defined_specs_undefined_class_variable)
-      }.should complain(/class variable access from toplevel/)
+      @result = eval("class singleton_class::A; defined?(not @@doesnt_exist) end", binding, __FILE__, __LINE__)
       @result.should be_nil
     end
 
@@ -474,7 +630,9 @@ end
 
 describe "The defined? keyword for variables" do
   it "returns 'local-variable' when called with the name of a local variable" do
-    DefinedSpecs::Basic.new.local_variable_defined.should == "local-variable"
+    ret = DefinedSpecs::Basic.new.local_variable_defined
+    ret.should == "local-variable"
+    ret.frozen?.should == true
   end
 
   it "returns 'local-variable' when called with the name of a local variable assigned to nil" do
@@ -490,7 +648,9 @@ describe "The defined? keyword for variables" do
   end
 
   it "returns 'instance-variable' for an instance variable that has been assigned" do
-    DefinedSpecs::Basic.new.instance_variable_defined.should == "instance-variable"
+    ret = DefinedSpecs::Basic.new.instance_variable_defined
+    ret.should == "instance-variable"
+    ret.frozen?.should == true
   end
 
   it "returns 'instance-variable' for an instance variable that has been assigned to nil" do
@@ -506,7 +666,9 @@ describe "The defined? keyword for variables" do
   end
 
   it "returns 'global-variable' for a global variable that has been assigned nil" do
-    DefinedSpecs::Basic.new.global_variable_defined_as_nil.should == "global-variable"
+    ret = DefinedSpecs::Basic.new.global_variable_defined_as_nil
+    ret.should == "global-variable"
+    ret.frozen?.should == true
   end
 
   # MRI appears to special case defined? for $! and $~ in that it returns
@@ -678,7 +840,9 @@ describe "The defined? keyword for variables" do
   # get to the defined? call so it really has nothing to do with 'defined?'.
 
   it "returns 'class variable' when called with the name of a class variable" do
-    DefinedSpecs::Basic.new.class_variable_defined.should == "class variable"
+    ret = DefinedSpecs::Basic.new.class_variable_defined
+    ret.should == "class variable"
+    ret.frozen?.should == true
   end
 
   it "returns 'local-variable' when called with the name of a block local" do
@@ -689,7 +853,9 @@ end
 
 describe "The defined? keyword for a simple constant" do
   it "returns 'constant' when the constant is defined" do
-    defined?(DefinedSpecs).should == "constant"
+    ret = defined?(DefinedSpecs)
+    ret.should == "constant"
+    ret.frozen?.should == true
   end
 
   it "returns nil when the constant is not defined" do
@@ -734,6 +900,10 @@ describe "The defined? keyword for a scoped constant" do
     defined?(DefinedSpecs::Undefined).should be_nil
   end
 
+  it "returns nil when the constant is not defined and the outer module implements .const_missing" do
+    defined?(DefinedSpecs::ModuleWithConstMissing::Undefined).should be_nil
+  end
+
   it "does not call .const_missing if the constant is not defined" do
     DefinedSpecs.should_not_receive(:const_missing)
     defined?(DefinedSpecs::UnknownChild).should be_nil
@@ -756,16 +926,8 @@ describe "The defined? keyword for a scoped constant" do
     defined?(DefinedSpecs::String).should be_nil
   end
 
-  ruby_version_is ""..."2.5" do
-    it "returns 'constant' when a constant is defined on top-level but not on the class" do
-      defined?(DefinedSpecs::Basic::String).should == 'constant'
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns nil when a constant is defined on top-level but not on the class" do
-      defined?(DefinedSpecs::Basic::String).should be_nil
-    end
+  it "returns nil when a constant is defined on top-level but not on the class" do
+    defined?(DefinedSpecs::Basic::String).should be_nil
   end
 
   it "returns 'constant' if the scoped-scoped constant is defined" do
@@ -905,17 +1067,21 @@ describe "The defined? keyword for a variable scoped constant" do
   end
 
   it "returns nil if the class scoped constant is not defined" do
-    -> {
-      @@defined_specs_obj = DefinedSpecs::Basic
-      defined?(@@defined_specs_obj::Undefined).should be_nil
-    }.should complain(/class variable access from toplevel/)
+    eval(<<-END, binding, __FILE__, __LINE__)
+      class singleton_class::A
+        @@defined_specs_obj = DefinedSpecs::Basic
+        defined?(@@defined_specs_obj::Undefined).should be_nil
+      end
+    END
   end
 
   it "returns 'constant' if the constant is defined in the scope of the class variable" do
-    -> {
-      @@defined_specs_obj = DefinedSpecs::Basic
-      defined?(@@defined_specs_obj::A).should == "constant"
-    }.should complain(/class variable access from toplevel/)
+    eval(<<-END, binding, __FILE__, __LINE__)
+      class singleton_class::A
+        @@defined_specs_obj = DefinedSpecs::Basic
+        defined?(@@defined_specs_obj::A).should == "constant"
+      end
+    END
   end
 
   it "returns nil if the local scoped constant is not defined" do
@@ -949,12 +1115,26 @@ describe "The defined? keyword for yield" do
   end
 
   it "returns 'yield' if a block is passed to a method not taking a block parameter" do
-    DefinedSpecs::Basic.new.yield_block.should == "yield"
+    ret = DefinedSpecs::Basic.new.yield_block
+    ret.should == "yield"
+    ret.frozen?.should == true
   end
 
   it "returns 'yield' if a block is passed to a method taking a block parameter" do
     DefinedSpecs::Basic.new.yield_block_parameter.should == "yield"
   end
+
+  it "returns 'yield' when called within a block" do
+    def yielder
+      yield
+    end
+
+    def call_defined
+      yielder { defined?(yield) }
+    end
+
+    call_defined() { }.should == "yield"
+  end
 end
 
 describe "The defined? keyword for super" do
@@ -980,7 +1160,9 @@ describe "The defined? keyword for super" do
     end
 
     it "returns 'super' when a superclass method exists" do
-      DefinedSpecs::Super.new.method_no_args.should == "super"
+      ret = DefinedSpecs::Super.new.method_no_args
+      ret.should == "super"
+      ret.frozen?.should == true
     end
 
     it "returns 'super' from a block when a superclass method exists" do
diff --git a/spec/ruby/language/delegation_spec.rb b/spec/ruby/language/delegation_spec.rb
new file mode 100644
index 0000000000..c711a536c2
--- /dev/null
+++ b/spec/ruby/language/delegation_spec.rb
@@ -0,0 +1,158 @@
+require_relative '../spec_helper'
+require_relative 'fixtures/delegation'
+
+# Forwarding anonymous parameters
+describe "delegation with def(...)" do
+  it "delegates rest and kwargs" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(...)
+        target(...)
+      end
+    RUBY
+
+    a.new.delegate(1, b: 2).should == [[1], {b: 2}, nil]
+  end
+
+  it "delegates a block literal" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate_block(...)
+        target_block(...)
+      end
+    RUBY
+
+    a.new.delegate_block(1, b: 2) { |x| x }.should == [{b: 2}, [1]]
+  end
+
+  it "delegates a block argument" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(...)
+        target(...)
+      end
+    RUBY
+
+    block = proc {}
+    a.new.delegate(1, b: 2, &block).should == [[1], {b: 2}, block]
+  end
+
+  it "parses as open endless Range when brackets are omitted" do
+    a = Class.new(DelegationSpecs::Target)
+    suppress_warning do
+      a.class_eval(<<-RUBY)
+        def delegate(...)
+          target ...
+        end
+      RUBY
+    end
+
+    a.new.delegate(1, b: 2).should == Range.new([[], {}, nil], nil, true)
+  end
+end
+
+describe "delegation with def(x, ...)" do
+  it "delegates rest and kwargs" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(x, ...)
+        target(...)
+      end
+    RUBY
+
+    a.new.delegate(0, 1, b: 2).should == [[1], {b: 2}, nil]
+  end
+
+  it "delegates a block literal" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate_block(x, ...)
+        target_block(...)
+      end
+    RUBY
+
+    a.new.delegate_block(0, 1, b: 2) { |x| x }.should == [{b: 2}, [1]]
+  end
+
+  it "delegates a block argument" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+      def delegate(...)
+        target(...)
+      end
+    RUBY
+
+    block = proc {}
+    a.new.delegate(1, b: 2, &block).should == [[1], {b: 2}, block]
+  end
+end
+
+describe "delegation with def(*)" do
+  it "delegates rest" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+    def delegate(*)
+      target(*)
+    end
+    RUBY
+
+    a.new.delegate(0, 1).should == [[0, 1], {}, nil]
+  end
+
+  ruby_version_is "3.3" do
+    context "within a block that accepts anonymous rest within a method that accepts anonymous rest" do
+      it "does not allow delegating rest" do
+        -> {
+          eval "def m(*); proc { |*| n(*) } end"
+        }.should raise_error(SyntaxError, /anonymous rest parameter is also used within block/)
+      end
+    end
+  end
+end
+
+describe "delegation with def(**)" do
+  it "delegates kwargs" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+    def delegate(**)
+      target(**)
+    end
+    RUBY
+
+    a.new.delegate(a: 1) { |x| x }.should == [[], {a: 1}, nil]
+  end
+
+  ruby_version_is "3.3" do
+    context "within a block that accepts anonymous kwargs within a method that accepts anonymous kwargs" do
+      it "does not allow delegating kwargs" do
+        -> {
+          eval "def m(**); proc { |**| n(**) } end"
+        }.should raise_error(SyntaxError, /anonymous keyword rest parameter is also used within block/)
+      end
+    end
+  end
+end
+
+describe "delegation with def(&)" do
+  it "delegates an anonymous block parameter" do
+    a = Class.new(DelegationSpecs::Target)
+    a.class_eval(<<-RUBY)
+    def delegate(&)
+      target(&)
+    end
+    RUBY
+
+    block = proc {}
+    a.new.delegate(&block).should == [[], {}, block]
+  end
+
+  ruby_version_is "3.3" do
+    context "within a block that accepts anonymous block within a method that accepts anonymous block" do
+      it "does not allow delegating a block" do
+        -> {
+          eval "def m(&); proc { |&| n(&) } end"
+        }.should raise_error(SyntaxError, /anonymous block parameter is also used within block/)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/language/encoding_spec.rb b/spec/ruby/language/encoding_spec.rb
index 5430c9cb98..e761a53cb6 100644
--- a/spec/ruby/language/encoding_spec.rb
+++ b/spec/ruby/language/encoding_spec.rb
@@ -13,15 +13,15 @@ describe "The __ENCODING__ pseudo-variable" do
   end
 
   it "is the evaluated strings's one inside an eval" do
-    eval("__ENCODING__".force_encoding("US-ASCII")).should == Encoding::US_ASCII
-    eval("__ENCODING__".force_encoding("BINARY")).should == Encoding::BINARY
+    eval("__ENCODING__".dup.force_encoding("US-ASCII")).should == Encoding::US_ASCII
+    eval("__ENCODING__".dup.force_encoding("BINARY")).should == Encoding::BINARY
   end
 
   it "is the encoding specified by a magic comment inside an eval" do
-    code = "# encoding: BINARY\n__ENCODING__".force_encoding("US-ASCII")
+    code = "# encoding: BINARY\n__ENCODING__".dup.force_encoding("US-ASCII")
     eval(code).should == Encoding::BINARY
 
-    code = "# encoding: us-ascii\n__ENCODING__".force_encoding("BINARY")
+    code = "# encoding: us-ascii\n__ENCODING__".dup.force_encoding("BINARY")
     eval(code).should == Encoding::US_ASCII
   end
 
diff --git a/spec/ruby/language/ensure_spec.rb b/spec/ruby/language/ensure_spec.rb
index a930bda36b..b76292c007 100644
--- a/spec/ruby/language/ensure_spec.rb
+++ b/spec/ruby/language/ensure_spec.rb
@@ -74,9 +74,9 @@ describe "An ensure block inside a begin block" do
       ensure
         raise "from ensure"
       end
-    }.should raise_error(RuntimeError, "from ensure") do |e|
+    }.should raise_error(RuntimeError, "from ensure") { |e|
       e.cause.message.should == "from block"
-    end
+    }
   end
 end
 
@@ -251,83 +251,96 @@ describe "An ensure block inside {} block" do
   end
 end
 
-ruby_version_is "2.5" do
-  describe "An ensure block inside 'do end' block" do
-    before :each do
-      ScratchPad.record []
-    end
-
-    it "is executed when an exception is raised in it's corresponding begin block" do
-      -> {
-        eval(<<-ruby).call
-          lambda do
-            ScratchPad << :begin
-            raise EnsureSpec::Error
-          ensure
-            ScratchPad << :ensure
-          end
-        ruby
-      }.should raise_error(EnsureSpec::Error)
-
-      ScratchPad.recorded.should == [:begin, :ensure]
-    end
+describe "An ensure block inside 'do end' block" do
+  before :each do
+    ScratchPad.record []
+  end
 
-    it "is executed when an exception is raised and rescued in it's corresponding begin block" do
+  it "is executed when an exception is raised in it's corresponding begin block" do
+    -> {
       eval(<<-ruby).call
         lambda do
           ScratchPad << :begin
-          raise "An exception occurred!"
-        rescue
-          ScratchPad << :rescue
+          raise EnsureSpec::Error
         ensure
           ScratchPad << :ensure
         end
       ruby
+    }.should raise_error(EnsureSpec::Error)
 
-      ScratchPad.recorded.should == [:begin, :rescue, :ensure]
-    end
+    ScratchPad.recorded.should == [:begin, :ensure]
+  end
 
-    it "is executed even when a symbol is thrown in it's corresponding begin block" do
-      catch(:symbol) do
-        eval(<<-ruby).call
-          lambda do
-            ScratchPad << :begin
-            throw(:symbol)
-          rescue
-            ScratchPad << :rescue
-          ensure
-            ScratchPad << :ensure
-          end
-        ruby
+  it "is executed when an exception is raised and rescued in it's corresponding begin block" do
+    eval(<<-ruby).call
+      lambda do
+        ScratchPad << :begin
+        raise "An exception occurred!"
+      rescue
+        ScratchPad << :rescue
+      ensure
+        ScratchPad << :ensure
       end
+    ruby
 
-      ScratchPad.recorded.should == [:begin, :ensure]
-    end
+    ScratchPad.recorded.should == [:begin, :rescue, :ensure]
+  end
 
-    it "is executed when nothing is raised or thrown in it's corresponding begin block" do
+  it "is executed even when a symbol is thrown in it's corresponding begin block" do
+    catch(:symbol) do
       eval(<<-ruby).call
         lambda do
           ScratchPad << :begin
+          throw(:symbol)
         rescue
           ScratchPad << :rescue
         ensure
           ScratchPad << :ensure
         end
       ruby
-
-      ScratchPad.recorded.should == [:begin, :ensure]
     end
 
-    it "has no return value" do
-      result = eval(<<-ruby).call
-        lambda do
-          :begin
+    ScratchPad.recorded.should == [:begin, :ensure]
+  end
+
+  it "is executed when nothing is raised or thrown in it's corresponding begin block" do
+    eval(<<-ruby).call
+      lambda do
+        ScratchPad << :begin
+      rescue
+        ScratchPad << :rescue
+      ensure
+        ScratchPad << :ensure
+      end
+    ruby
+
+    ScratchPad.recorded.should == [:begin, :ensure]
+  end
+
+  it "has no return value" do
+    result = eval(<<-ruby).call
+      lambda do
+        :begin
+      ensure
+        :ensure
+      end
+    ruby
+
+    result.should == :begin
+  end
+
+  ruby_version_is "3.4" do
+    it "does not introduce extra backtrace entries" do
+      def foo
+        begin
+          raise "oops"
         ensure
-          :ensure
+          return caller(0, 2) # rubocop:disable Lint/EnsureReturn
         end
-      ruby
-
-      result.should == :begin
+      end
+      line = __LINE__
+      foo[0].should =~ /#{__FILE__}:#{line-3}:in 'foo'/
+      foo[1].should =~ /#{__FILE__}:#{line+2}:in 'block/
     end
   end
 end
diff --git a/spec/ruby/language/execution_spec.rb b/spec/ruby/language/execution_spec.rb
index 4e0310946d..51bcde62e8 100644
--- a/spec/ruby/language/execution_spec.rb
+++ b/spec/ruby/language/execution_spec.rb
@@ -5,6 +5,45 @@ describe "``" do
     ip = 'world'
     `echo disc #{ip}`.should == "disc world\n"
   end
+
+  it "can be redefined and receive a frozen string as argument" do
+    called = false
+    runner = Object.new
+
+    runner.singleton_class.define_method(:`) do |str|
+      called = true
+
+      str.should == "test command"
+      str.frozen?.should == true
+    end
+
+    runner.instance_exec do
+      `test command`
+    end
+
+    called.should == true
+  end
+
+  it "the argument isn't frozen if it contains interpolation" do
+    called = false
+    runner = Object.new
+
+    runner.singleton_class.define_method(:`) do |str|
+      called = true
+
+      str.should == "test command"
+      str.frozen?.should == false
+      str << "mutated"
+    end
+
+    2.times do
+      runner.instance_exec do
+        `test #{:command}` # rubocop:disable Lint/LiteralInInterpolation
+      end
+    end
+
+    called.should == true
+  end
 end
 
 describe "%x" do
@@ -12,4 +51,43 @@ describe "%x" do
     ip = 'world'
     %x(echo disc #{ip}).should == "disc world\n"
   end
+
+  it "can be redefined and receive a frozen string as argument" do
+    called = false
+    runner = Object.new
+
+    runner.singleton_class.define_method(:`) do |str|
+      called = true
+
+      str.should == "test command"
+      str.frozen?.should == true
+    end
+
+    runner.instance_exec do
+      %x{test command}
+    end
+
+    called.should == true
+  end
+
+  it "the argument isn't frozen if it contains interpolation" do
+    called = false
+    runner = Object.new
+
+    runner.singleton_class.define_method(:`) do |str|
+      called = true
+
+      str.should == "test command"
+      str.frozen?.should == false
+      str << "mutated"
+    end
+
+    2.times do
+      runner.instance_exec do
+        %x{test #{:command}} # rubocop:disable Lint/LiteralInInterpolation
+      end
+    end
+
+    called.should == true
+  end
 end
diff --git a/spec/ruby/language/file_spec.rb b/spec/ruby/language/file_spec.rb
index 729dee1008..59563d9642 100644
--- a/spec/ruby/language/file_spec.rb
+++ b/spec/ruby/language/file_spec.rb
@@ -7,23 +7,23 @@ describe "The __FILE__ pseudo-variable" do
     -> { eval("__FILE__ = 1") }.should raise_error(SyntaxError)
   end
 
-  it "equals (eval) inside an eval" do
-    eval("__FILE__").should == "(eval)"
+  ruby_version_is ""..."3.3" do
+    it "equals (eval) inside an eval" do
+      eval("__FILE__").should == "(eval)"
+    end
   end
-end
 
-describe "The __FILE__ pseudo-variable" do
-  it_behaves_like :language___FILE__, :require, CodeLoadingSpecs::Method.new
+  ruby_version_is "3.3" do
+    it "equals (eval at __FILE__:__LINE__) inside an eval" do
+      eval("__FILE__").should == "(eval at #{__FILE__}:#{__LINE__})"
+    end
+  end
 end
 
-describe "The __FILE__ pseudo-variable" do
+describe "The __FILE__ pseudo-variable with require" do
   it_behaves_like :language___FILE__, :require, Kernel
 end
 
-describe "The __FILE__ pseudo-variable" do
-  it_behaves_like :language___FILE__, :load, CodeLoadingSpecs::Method.new
-end
-
-describe "The __FILE__ pseudo-variable" do
+describe "The __FILE__ pseudo-variable with load" do
   it_behaves_like :language___FILE__, :load, Kernel
 end
diff --git a/spec/ruby/language/fixtures/class_with_class_variable.rb b/spec/ruby/language/fixtures/class_with_class_variable.rb
new file mode 100644
index 0000000000..0b07f16d30
--- /dev/null
+++ b/spec/ruby/language/fixtures/class_with_class_variable.rb
@@ -0,0 +1,9 @@
+module StringSpecs
+  class ClassWithClassVariable
+    @@a = "xxx"
+
+    def foo
+      "#@@a"
+    end
+  end
+end
diff --git a/spec/ruby/language/fixtures/constant_visibility.rb b/spec/ruby/language/fixtures/constant_visibility.rb
index 022554430e..af38b2d8f2 100644
--- a/spec/ruby/language/fixtures/constant_visibility.rb
+++ b/spec/ruby/language/fixtures/constant_visibility.rb
@@ -65,7 +65,7 @@ module ConstantVisibility
     end
   end
 
-  class PrivConstModuleChild
+  class ClassIncludingPrivConstModule
     include PrivConstModule
 
     def private_constant_from_include
@@ -77,6 +77,22 @@ module ConstantVisibility
     end
   end
 
+  module ModuleIncludingPrivConstModule
+    include PrivConstModule
+
+    def self.private_constant_from_include
+      PRIVATE_CONSTANT_MODULE
+    end
+
+    def self.private_constant_self_from_include
+      self::PRIVATE_CONSTANT_MODULE
+    end
+
+    def self.private_constant_named_from_include
+      PrivConstModule::PRIVATE_CONSTANT_MODULE
+    end
+  end
+
   class PrivConstClassChild < PrivConstClass
     def private_constant_from_subclass
       PRIVATE_CONSTANT_CLASS
diff --git a/spec/ruby/language/fixtures/defined.rb b/spec/ruby/language/fixtures/defined.rb
index 8b6004c19f..3761cfa5bd 100644
--- a/spec/ruby/language/fixtures/defined.rb
+++ b/spec/ruby/language/fixtures/defined.rb
@@ -19,6 +19,9 @@ module DefinedSpecs
     DefinedSpecs
   end
 
+  def self.any_args(*)
+  end
+
   class Basic
     A = 42
 
@@ -282,6 +285,12 @@ module DefinedSpecs
     end
   end
 
+  module ModuleWithConstMissing
+    def self.const_missing(const)
+      const
+    end
+  end
+
   class SuperWithIntermediateModules
     include IntermediateModule1
     include IntermediateModule2
diff --git a/spec/ruby/language/fixtures/delegation.rb b/spec/ruby/language/fixtures/delegation.rb
new file mode 100644
index 0000000000..da2b024791
--- /dev/null
+++ b/spec/ruby/language/fixtures/delegation.rb
@@ -0,0 +1,11 @@
+module DelegationSpecs
+  class Target
+    def target(*args, **kwargs, &block)
+      [args, kwargs, block]
+    end
+
+    def target_block(*args, **kwargs)
+      yield [kwargs, args]
+    end
+  end
+end
diff --git a/spec/ruby/language/fixtures/freeze_magic_comment_required_diff_enc.rb b/spec/ruby/language/fixtures/freeze_magic_comment_required_diff_enc.rb
index d0558a2251..f72a32e879 100644
--- a/spec/ruby/language/fixtures/freeze_magic_comment_required_diff_enc.rb
+++ b/spec/ruby/language/fixtures/freeze_magic_comment_required_diff_enc.rb
diff --git a/spec/ruby/language/fixtures/freeze_magic_comment_two_literals.rb b/spec/ruby/language/fixtures/freeze_magic_comment_two_literals.rb
index a4d655ad02..cccc5969bd 100644
--- a/spec/ruby/language/fixtures/freeze_magic_comment_two_literals.rb
+++ b/spec/ruby/language/fixtures/freeze_magic_comment_two_literals.rb
@@ -1,3 +1,3 @@
 # frozen_string_literal: true
 
-p "abc".object_id == "abc".object_id
+p "abc".equal?("abc")
diff --git a/spec/ruby/language/fixtures/module.rb b/spec/ruby/language/fixtures/module.rb
index 33d323846e..75eee77791 100644
--- a/spec/ruby/language/fixtures/module.rb
+++ b/spec/ruby/language/fixtures/module.rb
@@ -12,13 +12,4 @@ module ModuleSpecs
 
   module Anonymous
   end
-
-  module IncludedInObject
-    module IncludedModuleSpecs
-    end
-  end
-end
-
-class Object
-  include ModuleSpecs::IncludedInObject
 end
diff --git a/spec/ruby/language/fixtures/private.rb b/spec/ruby/language/fixtures/private.rb
index 96f73cea3f..da3e0a97f9 100644
--- a/spec/ruby/language/fixtures/private.rb
+++ b/spec/ruby/language/fixtures/private.rb
@@ -43,17 +43,17 @@ module Private
     end
   end
 
-   class E
-     include D
-   end
-
-   class G
-     def foo
-       "foo"
-     end
-   end
-
-   class H < A
-     private :foo
-   end
+  class E
+    include D
+  end
+
+  class G
+    def foo
+      "foo"
+    end
+  end
+
+  class H < A
+    private :foo
+  end
 end
diff --git a/spec/ruby/language/fixtures/rescue/top_level.rb b/spec/ruby/language/fixtures/rescue/top_level.rb
new file mode 100644
index 0000000000..59e78ef1d6
--- /dev/null
+++ b/spec/ruby/language/fixtures/rescue/top_level.rb
@@ -0,0 +1,7 @@
+# capturing in local variable at top-level
+
+begin
+  raise "message"
+rescue => e
+  ScratchPad << e.message
+end
diff --git a/spec/ruby/language/fixtures/rescue_captures.rb b/spec/ruby/language/fixtures/rescue_captures.rb
new file mode 100644
index 0000000000..69f9b83904
--- /dev/null
+++ b/spec/ruby/language/fixtures/rescue_captures.rb
@@ -0,0 +1,107 @@
+module RescueSpecs
+  class Captor
+    attr_accessor :captured_error
+
+    def self.should_capture_exception
+      captor = new
+      captor.capture('some text').should == :caught # Ensure rescue body still runs
+      captor.captured_error.message.should == 'some text'
+    end
+  end
+
+  class ClassVariableCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => @@captured_error
+      :caught
+    end
+
+    def captured_error
+      self.class.remove_class_variable(:@@captured_error)
+    end
+  end
+
+  class ConstantCaptor < Captor
+    # Using lambda gets around the dynamic constant assignment warning
+    CAPTURE = -> msg {
+      begin
+        raise msg
+      rescue => CapturedError
+        :caught
+      end
+    }
+
+    def capture(msg)
+      CAPTURE.call(msg)
+    end
+
+    def captured_error
+      self.class.send(:remove_const, :CapturedError)
+    end
+  end
+
+  class GlobalVariableCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => $captured_error
+      :caught
+    end
+
+    def captured_error
+      $captured_error.tap do
+        $captured_error = nil # Can't remove globals, only nil them out
+      end
+    end
+  end
+
+  class InstanceVariableCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => @captured_error
+      :caught
+    end
+  end
+
+  class LocalVariableCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => captured_error
+      @captured_error = captured_error
+      :caught
+    end
+  end
+
+  class SafeNavigationSetterCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => self&.captured_error
+      :caught
+    end
+  end
+
+  class SetterCaptor < Captor
+    def capture(msg)
+      raise msg
+    rescue => self.captured_error
+      :caught
+    end
+  end
+
+  class SquareBracketsCaptor < Captor
+    def capture(msg)
+      @hash = {}
+
+      raise msg
+    rescue => self[:error]
+      :caught
+    end
+
+    def []=(key, value)
+      @hash[key] = value
+    end
+
+    def captured_error
+      @hash[:error]
+    end
+  end
+end
diff --git a/spec/ruby/language/fixtures/return.rb b/spec/ruby/language/fixtures/return.rb
index 0414c356e8..f6b143f3fa 100644
--- a/spec/ruby/language/fixtures/return.rb
+++ b/spec/ruby/language/fixtures/return.rb
@@ -101,18 +101,14 @@ module ReturnSpecs
       # return value will go into val before we run the ensure.
       #
       # If lamb's return keeps unwinding incorrectly, val will still
-      # have it's old value.
+      # have its old value.
       #
       # We can therefore use val to figure out what happened.
       begin
         val = foo()
       ensure
-        if val != :good
-          return :bad
-        end
+        return val
       end
-
-      return val
     end
   end
 
diff --git a/spec/ruby/language/fixtures/send.rb b/spec/ruby/language/fixtures/send.rb
index c3013616b2..4787abee5c 100644
--- a/spec/ruby/language/fixtures/send.rb
+++ b/spec/ruby/language/fixtures/send.rb
@@ -43,9 +43,9 @@ module LangSendSpecs
     attr_writer :foo
     private :foo=
 
-      def call_self_foo_equals(value)
-        self.foo = value
-      end
+    def call_self_foo_equals(value)
+      self.foo = value
+    end
 
     def call_self_foo_equals_masgn(value)
       a, self.foo = 1, value
@@ -53,8 +53,9 @@ module LangSendSpecs
   end
 
   class PrivateGetter
-    attr_reader :foo
+    attr_accessor :foo
     private :foo
+    private :foo=
 
     def call_self_foo
       self.foo
@@ -80,6 +81,16 @@ module LangSendSpecs
     end
   end
 
+  class RawToProc
+    def initialize(to_proc)
+      @to_proc = to_proc
+    end
+
+    def to_proc
+      @to_proc
+    end
+  end
+
   class ToAry
     def initialize(obj)
       @obj = obj
diff --git a/spec/ruby/language/fixtures/squiggly_heredoc.rb b/spec/ruby/language/fixtures/squiggly_heredoc.rb
index afc87514c7..984a629e5b 100644
--- a/spec/ruby/language/fixtures/squiggly_heredoc.rb
+++ b/spec/ruby/language/fixtures/squiggly_heredoc.rb
@@ -29,6 +29,22 @@ module SquigglyHeredocSpecs
     HERE
   end
 
+  def self.backslash
+    <<~HERE
+      a
+      b\
+      c
+    HERE
+  end
+
+  def self.least_indented_on_the_first_line
+    <<~HERE
+      a
+        b
+          c
+    HERE
+  end
+
   def self.least_indented_on_the_last_line
     <<~HERE
           a
@@ -36,4 +52,20 @@ module SquigglyHeredocSpecs
       c
     HERE
   end
+
+  def self.least_indented_on_the_first_line_single
+    <<~'HERE'
+      a
+        b
+          c
+    HERE
+  end
+
+  def self.least_indented_on_the_last_line_single
+    <<~'HERE'
+          a
+        b
+      c
+    HERE
+  end
 end
diff --git a/spec/ruby/language/fixtures/super.rb b/spec/ruby/language/fixtures/super.rb
index 6a024cae23..c5bdcf0e40 100644
--- a/spec/ruby/language/fixtures/super.rb
+++ b/spec/ruby/language/fixtures/super.rb
@@ -455,6 +455,52 @@ module SuperSpecs
     end
   end
 
+  module ZSuperWithRestAndPost
+    class A
+      def m(*args, a, b)
+        args
+      end
+
+      def m_modified(*args, a, b)
+        args
+      end
+    end
+
+    class B < A
+      def m(*args, a, b)
+        super
+      end
+
+      def m_modified(*args, a, b)
+        args[1] = 14
+        super
+      end
+    end
+  end
+
+  module ZSuperWithRestOthersAndPost
+    class A
+      def m(a, *args, b)
+        args
+      end
+
+      def m_modified(a, *args, b)
+        args
+      end
+    end
+
+    class B < A
+      def m(a, *args, b)
+        super
+      end
+
+      def m_modified(a, *args, b)
+        args[1] = 14
+        super
+      end
+    end
+  end
+
   module ZSuperWithRestReassigned
     class A
       def a(*args)
@@ -493,6 +539,30 @@ module SuperSpecs
         args
       end
 
+      def m3(*args)
+        args
+      end
+
+      def m4(*args)
+        args
+      end
+
+      def m_default(*args)
+        args
+      end
+
+      def m_rest(*args)
+        args
+      end
+
+      def m_pre_default_rest_post(*args)
+        args
+      end
+
+      def m_kwrest(**kw)
+        kw
+      end
+
       def m_modified(*args)
         args
       end
@@ -503,6 +573,30 @@ module SuperSpecs
         super
       end
 
+      def m3(_, _, _)
+        super
+      end
+
+      def m4(_, _, _, _)
+        super
+      end
+
+      def m_default(_ = 0)
+        super
+      end
+
+      def m_rest(*_)
+        super
+      end
+
+      def m_pre_default_rest_post(_, _, _=:a, _=:b, *_, _, _)
+        super
+      end
+
+      def m_kwrest(**_)
+        super
+      end
+
       def m_modified(_, _)
         _ = 14
         super
@@ -510,6 +604,20 @@ module SuperSpecs
     end
   end
 
+  module ZSuperInBlock
+    class A
+      def m(arg:)
+        arg
+      end
+    end
+
+    class B < A
+      def m(arg:)
+        proc { super }.call
+      end
+    end
+  end
+
   module Keywords
     class Arguments
       def foo(**args)
diff --git a/spec/ruby/language/fixtures/variables.rb b/spec/ruby/language/fixtures/variables.rb
index 07265dbb2b..527caa7a78 100644
--- a/spec/ruby/language/fixtures/variables.rb
+++ b/spec/ruby/language/fixtures/variables.rb
@@ -82,4 +82,76 @@ module VariablesSpecs
   def self.false
     false
   end
+
+  class EvalOrder
+    attr_reader :order
+
+    def initialize
+      @order = []
+    end
+
+    def reset
+      @order = []
+    end
+
+    def foo
+      self << "foo"
+      FooClass.new(self)
+    end
+
+    def bar
+      self << "bar"
+      BarClass.new(self)
+    end
+
+    def a
+      self << "a"
+    end
+
+    def b
+      self << "b"
+    end
+
+    def node
+      self << "node"
+
+      node = Node.new
+      node.left = Node.new
+      node.left.right = Node.new
+
+      node
+    end
+
+    def <<(value)
+      order << value
+    end
+
+    class FooClass
+      attr_reader :evaluator
+
+      def initialize(evaluator)
+        @evaluator = evaluator
+      end
+
+      def []=(_index, _value)
+        evaluator << "foo[]="
+      end
+    end
+
+    class BarClass
+      attr_reader :evaluator
+
+      def initialize(evaluator)
+        @evaluator = evaluator
+      end
+
+      def baz=(_value)
+        evaluator << "bar.baz="
+      end
+    end
+
+    class Node
+      attr_accessor :left, :right
+    end
+  end
 end
diff --git a/spec/ruby/language/for_spec.rb b/spec/ruby/language/for_spec.rb
index 0ad5ea88af..b8ddfe5f0d 100644
--- a/spec/ruby/language/for_spec.rb
+++ b/spec/ruby/language/for_spec.rb
@@ -19,6 +19,27 @@ describe "The for expression" do
     end
   end
 
+  it "iterates over a list of arrays and destructures with an empty splat" do
+    for i, * in [[1,2]]
+      i.should == 1
+    end
+  end
+
+  it "iterates over a list of arrays and destructures with a splat" do
+    for i, *j in [[1,2]]
+      i.should == 1
+      j.should == [2]
+    end
+  end
+
+  it "iterates over a list of arrays and destructures with a splat and additional targets" do
+    for i, *j, k in [[1,2,3,4]]
+      i.should == 1
+      j.should == [2,3]
+      k.should == 4
+    end
+  end
+
   it "iterates over an Hash passing each key-value pair to the block" do
     k = 0
     l = 0
@@ -81,6 +102,88 @@ describe "The for expression" do
     end
   end
 
+  it "allows a global variable as an iterator name" do
+    old_global_var = $var
+    m = [1,2,3]
+    n = 0
+    for $var in m
+      n += 1
+    end
+    $var.should == 3
+    n.should == 3
+    $var = old_global_var
+  end
+
+  it "allows an attribute as an iterator name" do
+    class OFor
+      attr_accessor :target
+    end
+
+    ofor = OFor.new
+    m = [1,2,3]
+    n = 0
+    for ofor.target in m
+      n += 1
+    end
+    ofor.target.should == 3
+    n.should == 3
+  end
+
+  # Segfault in MRI 3.3 and lower: https://bugs.ruby-lang.org/issues/20468
+  ruby_bug "#20468", ""..."3.4" do
+    it "allows an attribute with safe navigation as an iterator name" do
+      class OFor
+        attr_accessor :target
+      end
+
+      ofor = OFor.new
+      m = [1,2,3]
+      n = 0
+      eval <<~RUBY
+        for ofor&.target in m
+          n += 1
+        end
+      RUBY
+      ofor.target.should == 3
+      n.should == 3
+    end
+
+    it "allows an attribute with safe navigation on a nil base as an iterator name" do
+      ofor = nil
+      m = [1,2,3]
+      n = 0
+      eval <<~RUBY
+        for ofor&.target in m
+          n += 1
+        end
+      RUBY
+      ofor.should be_nil
+      n.should == 3
+    end
+  end
+
+  it "allows an array index writer as an iterator name" do
+    arr = [:a, :b, :c]
+    m = [1,2,3]
+    n = 0
+    for arr[1] in m
+      n += 1
+    end
+    arr.should == [:a, 3, :c]
+    n.should == 3
+  end
+
+  it "allows a hash index writer as an iterator name" do
+    hash = { a: 10, b: 20, c: 30 }
+    m = [1,2,3]
+    n = 0
+    for hash[:b] in m
+      n += 1
+    end
+    hash.should == { a: 10, b: 3, c: 30 }
+    n.should == 3
+  end
+
   # 1.9 behaviour verified by nobu in
   # http://redmine.ruby-lang.org/issues/show/2053
   it "yields only as many values as there are arguments" do
diff --git a/spec/ruby/language/hash_spec.rb b/spec/ruby/language/hash_spec.rb
index 79131e9da6..668716e2e3 100644
--- a/spec/ruby/language/hash_spec.rb
+++ b/spec/ruby/language/hash_spec.rb
@@ -33,12 +33,12 @@ describe "Hash literal" do
   end
 
   it "freezes string keys on initialization" do
-    key = "foo"
+    key = +"foo"
     h = {key => "bar"}
     key.reverse!
     h["foo"].should == "bar"
     h.keys.first.should == "foo"
-    h.keys.first.frozen?.should == true
+    h.keys.first.should.frozen?
     key.should == "oof"
   end
 
@@ -48,6 +48,24 @@ describe "Hash literal" do
     }.should complain(/key :foo is duplicated|duplicated key/)
     @h.keys.size.should == 1
     @h.should == {foo: :foo}
+    -> {
+      @h = eval "{%q{a} => :bar, %q{a} => :foo}"
+    }.should complain(/key "a" is duplicated|duplicated key/)
+    @h.keys.size.should == 1
+    @h.should == {%q{a} => :foo}
+    -> {
+      @h = eval "{1000 => :bar, 1000 => :foo}"
+    }.should complain(/key 1000 is duplicated|duplicated key/)
+    @h.keys.size.should == 1
+    @h.should == {1000 => :foo}
+  end
+
+  it "checks duplicated float keys on initialization" do
+    -> {
+      @h = eval "{1.0 => :bar, 1.0 => :foo}"
+    }.should complain(/key 1.0 is duplicated|duplicated key/)
+    @h.keys.size.should == 1
+    @h.should == {1.0 => :foo}
   end
 
   it "accepts a hanging comma" do
@@ -57,15 +75,39 @@ describe "Hash literal" do
   end
 
   it "recognizes '=' at the end of the key" do
-    eval("{:a==>1}").should == {:"a=" => 1}
-    eval("{:a= =>1}").should == {:"a=" => 1}
-    eval("{:a= => 1}").should == {:"a=" => 1}
+    {:a==>1}.should == {:"a=" => 1}
+    {:a= =>1}.should == {:"a=" => 1}
+    {:a= => 1}.should == {:"a=" => 1}
   end
 
   it "with '==>' in the middle raises SyntaxError" do
     -> { eval("{:a ==> 1}") }.should raise_error(SyntaxError)
   end
 
+  it "recognizes '!' at the end of the key" do
+    {:a! =>1}.should == {:"a!" => 1}
+    {:a! => 1}.should == {:"a!" => 1}
+
+    {a!:1}.should == {:"a!" => 1}
+    {a!: 1}.should == {:"a!" => 1}
+  end
+
+  it "raises a SyntaxError if there is no space between `!` and `=>`" do
+    -> { eval("{:a!=> 1}") }.should raise_error(SyntaxError)
+  end
+
+  it "recognizes '?' at the end of the key" do
+    {:a? =>1}.should == {:"a?" => 1}
+    {:a? => 1}.should == {:"a?" => 1}
+
+    {a?:1}.should == {:"a?" => 1}
+    {a?: 1}.should == {:"a?" => 1}
+  end
+
+  it "raises a SyntaxError if there is no space between `?` and `=>`" do
+    -> { eval("{:a?=> 1}") }.should raise_error(SyntaxError)
+  end
+
   it "constructs a new hash with the given elements" do
     {foo: 123}.should == {foo: 123}
     h = {rbx: :cool, specs: 'fail_sometimes'}
@@ -85,7 +127,7 @@ describe "Hash literal" do
 
   it "accepts mixed 'key: value', 'key => value' and '\"key\"': value' syntax" do
     h = {:a => 1, :b => 2, "c" => 3, :d => 4}
-    eval('{a: 1, :b => 2, "c" => 3, "d": 4}').should == h
+    {a: 1, :b => 2, "c" => 3, "d": 4}.should == h
   end
 
   it "expands an '**{}' element into the containing Hash literal initialization" do
@@ -107,11 +149,44 @@ describe "Hash literal" do
     {a: 1, **h, c: 4}.should == {a: 1, b: 2, c: 4}
   end
 
-  it "expands an '**{}' element with the last key/value pair taking precedence" do
+  ruby_version_is ""..."3.4" do
+    it "does not expand nil using ** into {} and raises TypeError" do
+      h = nil
+      -> { {a: 1, **h} }.should raise_error(TypeError, "no implicit conversion of nil into Hash")
+
+      -> { {a: 1, **nil} }.should raise_error(TypeError, "no implicit conversion of nil into Hash")
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "expands nil using ** into {}" do
+      h = nil
+      {**h}.should == {}
+      {a: 1, **h}.should == {a: 1}
+
+      {**nil}.should == {}
+      {a: 1, **nil}.should == {a: 1}
+    end
+  end
+
+  it "expands an '**{}' or '**obj' element with the last key/value pair taking precedence" do
     -> {
       @h = eval "{a: 1, **{a: 2, b: 3, c: 1}, c: 3}"
     }.should complain(/key :a is duplicated|duplicated key/)
     @h.should == {a: 2, b: 3, c: 3}
+
+    -> {
+      h = {a: 2, b: 3, c: 1}
+      @h = eval "{a: 1, **h, c: 3}"
+    }.should_not complain
+    @h.should == {a: 2, b: 3, c: 3}
+  end
+
+  it "expands an '**{}' and warns when finding an additional duplicate key afterwards" do
+    -> {
+      @h = eval "{d: 1, **{a: 2, b: 3, c: 1}, c: 3}"
+    }.should complain(/key :c is duplicated|duplicated key/)
+    @h.should == {a: 2, b: 3, c: 3, d: 1}
   end
 
   it "merges multiple nested '**obj' in Hash literals" do
@@ -128,18 +203,9 @@ describe "Hash literal" do
     {a: 1, **obj, c: 3}.should == {a:1, b: 2, c: 3, d: 4}
   end
 
-  ruby_version_is "0"..."2.7" do
-    it "raises a TypeError if any splatted elements keys are not symbols" do
-      h = {1 => 2, b: 3}
-      -> { {a: 1, **h} }.should raise_error(TypeError)
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "allows splatted elements keys that are not symbols" do
-      h = {1 => 2, b: 3}
-      {a: 1, **h}.should == {a: 1, 1 => 2, b: 3}
-    end
+  it "allows splatted elements keys that are not symbols" do
+    h = {1 => 2, b: 3}
+    {a: 1, **h}.should == {a: 1, 1 => 2, b: 3}
   end
 
   it "raises a TypeError if #to_hash does not return a Hash" do
@@ -149,6 +215,12 @@ describe "Hash literal" do
     -> { {**obj} }.should raise_error(TypeError)
   end
 
+  it "raises a TypeError if the object does not respond to #to_hash" do
+    obj = 42
+    -> { {**obj} }.should raise_error(TypeError)
+    -> { {a: 1, **obj} }.should raise_error(TypeError)
+  end
+
   it "does not change encoding of literal string keys during creation" do
     binary_hash = HashStringsBinary.literal_hash
     utf8_hash = HashStringsUTF8.literal_hash
@@ -160,4 +232,93 @@ describe "Hash literal" do
     utf8_hash.keys.first.should == usascii_hash.keys.first
     usascii_hash.keys.first.encoding.should == Encoding::US_ASCII
   end
+
+  ruby_bug "#20280", ""..."3.4" do
+    it "raises a SyntaxError at parse time when Symbol key with invalid bytes" do
+      ScratchPad.record []
+      -> {
+        eval 'ScratchPad << 1; {:"\xC3" => 1}'
+      }.should raise_error(SyntaxError, /invalid symbol/)
+      ScratchPad.recorded.should == []
+    end
+
+    it "raises a SyntaxError at parse time when Symbol key with invalid bytes and 'key: value' syntax used" do
+      ScratchPad.record []
+      -> {
+        eval 'ScratchPad << 1; {"\xC3": 1}'
+      }.should raise_error(SyntaxError, /invalid symbol/)
+      ScratchPad.recorded.should == []
+    end
+  end
+end
+
+describe "The ** operator" do
+  it "makes a copy when calling a method taking a keyword rest argument" do
+    def m(**h)
+      h.delete(:one); h
+    end
+
+    h = { one: 1, two: 2 }
+    m(**h).should == { two: 2 }
+    m(**h).should_not.equal?(h)
+    h.should == { one: 1, two: 2 }
+  end
+
+  ruby_bug "#20012", ""..."3.3" do
+    it "makes a copy when calling a method taking a positional Hash" do
+      def m(h)
+        h.delete(:one); h
+      end
+
+      h = { one: 1, two: 2 }
+      m(**h).should == { two: 2 }
+      m(**h).should_not.equal?(h)
+      h.should == { one: 1, two: 2 }
+    end
+  end
+
+  describe "hash with omitted value" do
+    it "accepts short notation 'key' for 'key: value' syntax" do
+      a, b, c = 1, 2, 3
+      h = {a:}
+      {a: 1}.should == h
+      h = {a:, b:, c:}
+      {a: 1, b: 2, c: 3}.should == h
+    end
+
+    it "ignores hanging comma on short notation" do
+      a, b, c = 1, 2, 3
+      h = {a:, b:, c:,}
+      {a: 1, b: 2, c: 3}.should == h
+    end
+
+    it "accepts mixed syntax" do
+      a, e = 1, 5
+      h = {a:, b: 2, "c" => 3, :d => 4, e:}
+      {a: 1, :b => 2, "c" => 3, "d": 4, e: 5}.should == h
+    end
+
+    it "works with methods and local vars" do
+      a = Class.new
+      a.class_eval(<<-RUBY)
+        def bar
+          "baz"
+        end
+
+        def foo(val)
+          {bar:, val:}
+        end
+      RUBY
+
+      a.new.foo(1).should == {bar: "baz", val: 1}
+    end
+
+    it "raises a SyntaxError when the hash key ends with `!`" do
+      -> { eval("{a!:}") }.should raise_error(SyntaxError, /identifier a! is not valid to get/)
+    end
+
+    it "raises a SyntaxError when the hash key ends with `?`" do
+      -> { eval("{a?:}") }.should raise_error(SyntaxError, /identifier a\? is not valid to get/)
+    end
+  end
 end
diff --git a/spec/ruby/language/heredoc_spec.rb b/spec/ruby/language/heredoc_spec.rb
index e7655a9216..47ee9c2c51 100644
--- a/spec/ruby/language/heredoc_spec.rb
+++ b/spec/ruby/language/heredoc_spec.rb
@@ -59,6 +59,12 @@ HERE
     s.encoding.should == Encoding::US_ASCII
   end
 
+  it 'raises SyntaxError if quoted HEREDOC identifier is ending not on same line' do
+    -> {
+      eval %{<<"HERE\n"\nraises syntax error\nHERE}
+    }.should raise_error(SyntaxError)
+  end
+
   it "allows HEREDOC with <<~'identifier', allowing to indent identifier and content" do
     require_relative 'fixtures/squiggly_heredoc'
     SquigglyHeredocSpecs.message.should == "character density, n.:\n  The number of very weird people in the office.\n"
@@ -84,8 +90,30 @@ HERE
     SquigglyHeredocSpecs.singlequoted.should == "singlequoted \#{\"interpolated\"}\n"
   end
 
+  it "allows HEREDOC with <<~'identifier', no interpolation, with backslash" do
+    require_relative 'fixtures/squiggly_heredoc'
+    SquigglyHeredocSpecs.backslash.should == "a\nbc\n"
+  end
+
   it "selects the least-indented line and removes its indentation from all the lines" do
     require_relative 'fixtures/squiggly_heredoc'
+    SquigglyHeredocSpecs.least_indented_on_the_first_line.should == "a\n  b\n    c\n"
     SquigglyHeredocSpecs.least_indented_on_the_last_line.should == "    a\n  b\nc\n"
   end
+
+  it "selects the least-indented line and removes its indentation from all the lines for <<~'identifier'" do
+    require_relative 'fixtures/squiggly_heredoc'
+    SquigglyHeredocSpecs.least_indented_on_the_first_line_single.should == "a\n  b\n    c\n"
+    SquigglyHeredocSpecs.least_indented_on_the_last_line_single.should == "    a\n  b\nc\n"
+  end
+
+  it "reports line numbers inside HEREDOC with method call" do
+    -> {
+      <<-HERE.chomp
+        a
+        b
+        #{c}
+      HERE
+    }.should raise_error(NameError) { |e| e.backtrace[0].should.start_with?("#{__FILE__}:#{__LINE__ - 2}") }
+  end
 end
diff --git a/spec/ruby/language/if_spec.rb b/spec/ruby/language/if_spec.rb
index d1d95c1607..2d1a89f081 100644
--- a/spec/ruby/language/if_spec.rb
+++ b/spec/ruby/language/if_spec.rb
@@ -305,6 +305,59 @@ describe "The if expression" do
       6.times(&b)
       ScratchPad.recorded.should == [4, 5, 4, 5]
     end
+
+    it "warns when Integer literals are used instead of predicates" do
+      -> {
+        eval <<~RUBY
+          $. = 0
+          10.times { |i| ScratchPad << i if 4..5 }
+        RUBY
+      }.should complain(/warning: integer literal in flip-flop/, verbose: true)
+      ScratchPad.recorded.should == []
+    end
+  end
+
+  describe "when a branch syntactically does not return a value" do
+    it "raises SyntaxError if both do not return a value" do
+      -> {
+        eval <<~RUBY
+        def m
+          a = if rand
+            return
+          else
+            return
+          end
+          a
+        end
+        RUBY
+      }.should raise_error(SyntaxError, /void value expression/)
+    end
+
+    it "does not raise SyntaxError if one branch returns a value" do
+      eval(<<~RUBY).should == 1
+      def m
+        a = if false # using false to make it clear that's not checked for
+          42
+        else
+          return 1
+        end
+        a
+      end
+      m
+      RUBY
+
+      eval(<<~RUBY).should == 1
+      def m
+        a = if true # using true to make it clear that's not checked for
+          return 1
+        else
+          42
+        end
+        a
+      end
+      m
+      RUBY
+    end
   end
 end
 
diff --git a/spec/ruby/language/it_parameter_spec.rb b/spec/ruby/language/it_parameter_spec.rb
new file mode 100644
index 0000000000..72023180d9
--- /dev/null
+++ b/spec/ruby/language/it_parameter_spec.rb
@@ -0,0 +1,66 @@
+require_relative '../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "The `it` parameter" do
+    it "provides it in a block" do
+      -> { it }.call("a").should == "a"
+      proc { it }.call("a").should == "a"
+      lambda { it }.call("a").should == "a"
+      ["a"].map { it }.should == ["a"]
+    end
+
+    it "assigns nil to not passed parameters" do
+      proc { it }.call().should == nil
+    end
+
+    it "can be used in both outer and nested blocks at the same time" do
+      -> { it + -> { it * it }.call(2) }.call(3).should == 7
+    end
+
+    it "is a regular local variable if there is already a 'it' local variable" do
+        it = 0
+        proc { it }.call("a").should == 0
+    end
+
+    it "raises SyntaxError when block parameters are specified explicitly" do
+      -> { eval("-> () { it }")         }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("-> (x) { it }")        }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("proc { || it }")       }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("proc { |x| it }")      }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("lambda { || it }")     }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("lambda { |x| it }")    }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("['a'].map { || it }")  }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("['a'].map { |x| it }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    end
+
+    it "affects block arity" do
+      -> {}.arity.should == 0
+      -> { it }.arity.should == 1
+    end
+
+    it "affects block parameters" do
+      -> { it }.parameters.should == [[:req]]
+
+      ruby_version_is ""..."4.0" do
+        proc { it }.parameters.should == [[:opt, nil]]
+      end
+      ruby_version_is "4.0" do
+        proc { it }.parameters.should == [[:opt]]
+      end
+    end
+
+    it "does not affect binding local variables" do
+      -> { it; binding.local_variables }.call("a").should == []
+    end
+
+    it "does not work in methods" do
+      obj = Object.new
+      def obj.foo; it; end
+
+      -> { obj.foo("a") }.should raise_error(ArgumentError, /wrong number of arguments/)
+    end
+  end
+end
diff --git a/spec/ruby/language/keyword_arguments_spec.rb b/spec/ruby/language/keyword_arguments_spec.rb
new file mode 100644
index 0000000000..4f6370d419
--- /dev/null
+++ b/spec/ruby/language/keyword_arguments_spec.rb
@@ -0,0 +1,386 @@
+require_relative '../spec_helper'
+
+describe "Keyword arguments" do
+  def target(*args, **kwargs)
+    [args, kwargs]
+  end
+
+  it "are separated from positional arguments" do
+    def m(*args, **kwargs)
+      [args, kwargs]
+    end
+
+    empty = {}
+    m(**empty).should == [[], {}]
+    m(empty).should == [[{}], {}]
+
+    m(a: 1).should == [[], {a: 1}]
+    m({a: 1}).should == [[{a: 1}], {}]
+  end
+
+  it "when the receiving method has not keyword parameters it treats kwargs as positional" do
+    def m(*a)
+      a
+    end
+
+    m(a: 1).should == [{a: 1}]
+    m({a: 1}).should == [{a: 1}]
+  end
+
+  context "empty kwargs are treated as if they were not passed" do
+    it "when calling a method" do
+      def m(*a)
+        a
+      end
+
+      empty = {}
+      m(**empty).should == []
+      m(empty).should == [{}]
+    end
+
+    it "when yielding to a block" do
+      def y(*args, **kwargs)
+        yield(*args, **kwargs)
+      end
+
+      empty = {}
+      y(**empty) { |*a| a }.should == []
+      y(empty) { |*a| a }.should == [{}]
+    end
+  end
+
+  it "extra keywords are not allowed without **kwrest" do
+    def m(*a, kw:)
+      a
+    end
+
+    m(kw: 1).should == []
+    -> { m(kw: 1, kw2: 2) }.should raise_error(ArgumentError, 'unknown keyword: :kw2')
+    -> { m(kw: 1, true => false) }.should raise_error(ArgumentError, 'unknown keyword: true')
+    -> { m(kw: 1, a: 1, b: 2, c: 3) }.should raise_error(ArgumentError, 'unknown keywords: :a, :b, :c')
+  end
+
+  it "raises ArgumentError exception when required keyword argument is not passed" do
+    def m(a:, b:, c:)
+      [a, b, c]
+    end
+
+    -> { m(a: 1, b: 2) }.should raise_error(ArgumentError, /missing keyword: :c/)
+    -> { m() }.should raise_error(ArgumentError, /missing keywords: :a, :b, :c/)
+  end
+
+  it "raises ArgumentError for missing keyword arguments even if there are extra ones" do
+    def m(a:)
+      a
+    end
+
+    -> { m(b: 1) }.should raise_error(ArgumentError, /missing keyword: :a/)
+  end
+
+  it "handle * and ** at the same call site" do
+    def m(*a)
+      a
+    end
+
+    m(*[], **{}).should == []
+    m(*[], 42, **{}).should == [42]
+  end
+
+  context "**" do
+    ruby_version_is "3.3" do
+      it "copies a non-empty Hash for a method taking (*args)" do
+        def m(*args)
+          args[0]
+        end
+
+        h = {a: 1}
+        m(**h).should_not.equal?(h)
+        h.should == {a: 1}
+      end
+    end
+
+    it "copies the given Hash for a method taking (**kwargs)" do
+      def m(**kw)
+        kw
+      end
+
+      empty = {}
+      m(**empty).should == empty
+      m(**empty).should_not.equal?(empty)
+
+      h = {a: 1}
+      m(**h).should == h
+      m(**h).should_not.equal?(h)
+    end
+  end
+
+  context "delegation" do
+    it "works with (*args, **kwargs)" do
+      def m(*args, **kwargs)
+        target(*args, **kwargs)
+      end
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      m(empty).should == [[{}], {}]
+
+      m(a: 1).should == [[], {a: 1}]
+      m({a: 1}).should == [[{a: 1}], {}]
+    end
+
+    it "works with proc { |*args, **kwargs| }" do
+      m = proc do |*args, **kwargs|
+        target(*args, **kwargs)
+      end
+
+      empty = {}
+      m.(**empty).should == [[], {}]
+      m.(empty).should == [[{}], {}]
+
+      m.(a: 1).should == [[], {a: 1}]
+      m.({a: 1}).should == [[{a: 1}], {}]
+
+      # no autosplatting for |*args, **kwargs|
+      m.([1, 2]).should == [[[1, 2]], {}]
+    end
+
+    it "works with -> (*args, **kwargs) {}" do
+      m = -> *args, **kwargs do
+        target(*args, **kwargs)
+      end
+
+      empty = {}
+      m.(**empty).should == [[], {}]
+      m.(empty).should == [[{}], {}]
+
+      m.(a: 1).should == [[], {a: 1}]
+      m.({a: 1}).should == [[{a: 1}], {}]
+    end
+
+    it "works with (...)" do
+      instance_eval <<~DEF
+      def m(...)
+        target(...)
+      end
+      DEF
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      m(empty).should == [[{}], {}]
+
+      m(a: 1).should == [[], {a: 1}]
+      m({a: 1}).should == [[{a: 1}], {}]
+    end
+
+    it "works with call(*ruby2_keyword_args)" do
+      class << self
+        ruby2_keywords def m(*args)
+          target(*args)
+        end
+      end
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+      m(empty).should == [[{}], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+
+      m(a: 1).should == [[], {a: 1}]
+      m({a: 1}).should == [[{a: 1}], {}]
+
+      kw = {a: 1}
+
+      m(**kw).should == [[], {a: 1}]
+      m(**kw)[1].should == kw
+      m(**kw)[1].should_not.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+      Hash.ruby2_keywords_hash?(m(**kw)[1]).should == false
+
+      m(kw).should == [[{a: 1}], {}]
+      m(kw)[0][0].should.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+    end
+
+    it "works with super(*ruby2_keyword_args)" do
+      parent = Class.new do
+        def m(*args, **kwargs)
+          [args, kwargs]
+        end
+      end
+
+      child = Class.new(parent) do
+        ruby2_keywords def m(*args)
+          super(*args)
+        end
+      end
+
+      obj = child.new
+
+      empty = {}
+      obj.m(**empty).should == [[], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+      obj.m(empty).should == [[{}], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+
+      obj.m(a: 1).should == [[], {a: 1}]
+      obj.m({a: 1}).should == [[{a: 1}], {}]
+
+      kw = {a: 1}
+
+      obj.m(**kw).should == [[], {a: 1}]
+      obj.m(**kw)[1].should == kw
+      obj.m(**kw)[1].should_not.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+      Hash.ruby2_keywords_hash?(obj.m(**kw)[1]).should == false
+
+      obj.m(kw).should == [[{a: 1}], {}]
+      obj.m(kw)[0][0].should.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+    end
+
+    it "works with zsuper" do
+      parent = Class.new do
+        def m(*args, **kwargs)
+          [args, kwargs]
+        end
+      end
+
+      child = Class.new(parent) do
+        ruby2_keywords def m(*args)
+          super
+        end
+      end
+
+      obj = child.new
+
+      empty = {}
+      obj.m(**empty).should == [[], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+      obj.m(empty).should == [[{}], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+
+      obj.m(a: 1).should == [[], {a: 1}]
+      obj.m({a: 1}).should == [[{a: 1}], {}]
+
+      kw = {a: 1}
+
+      obj.m(**kw).should == [[], {a: 1}]
+      obj.m(**kw)[1].should == kw
+      obj.m(**kw)[1].should_not.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+      Hash.ruby2_keywords_hash?(obj.m(**kw)[1]).should == false
+
+      obj.m(kw).should == [[{a: 1}], {}]
+      obj.m(kw)[0][0].should.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+    end
+
+    it "works with yield(*ruby2_keyword_args)" do
+      class << self
+        def y(args)
+          yield(*args)
+        end
+
+        ruby2_keywords def m(*outer_args)
+          y(outer_args, &-> *args, **kwargs { target(*args, **kwargs) })
+        end
+      end
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+      m(empty).should == [[{}], {}]
+      Hash.ruby2_keywords_hash?(empty).should == false
+
+      m(a: 1).should == [[], {a: 1}]
+      m({a: 1}).should == [[{a: 1}], {}]
+
+      kw = {a: 1}
+
+      m(**kw).should == [[], {a: 1}]
+      m(**kw)[1].should == kw
+      m(**kw)[1].should_not.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+      Hash.ruby2_keywords_hash?(m(**kw)[1]).should == false
+
+      m(kw).should == [[{a: 1}], {}]
+      m(kw)[0][0].should.equal?(kw)
+      Hash.ruby2_keywords_hash?(kw).should == false
+    end
+
+    it "does not work with (*args)" do
+      class << self
+        def m(*args)
+          target(*args)
+        end
+      end
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      m(empty).should == [[{}], {}]
+
+      m(a: 1).should == [[{a: 1}], {}]
+      m({a: 1}).should == [[{a: 1}], {}]
+    end
+
+    describe "omitted values" do
+      it "accepts short notation 'key' for 'key: value' syntax" do
+        def m(a:, b:)
+          [a, b]
+        end
+
+        a = 1
+        b = 2
+
+        m(a:, b:).should == [1, 2]
+      end
+    end
+
+    it "does not work with call(*ruby2_keyword_args) with missing ruby2_keywords in between" do
+      class << self
+        def n(*args) # Note the missing ruby2_keywords here
+          target(*args)
+        end
+
+        ruby2_keywords def m(*args)
+          n(*args)
+        end
+      end
+
+      empty = {}
+      m(**empty).should == [[], {}]
+      m(empty).should == [[{}], {}]
+
+      m(a: 1).should == [[{a: 1}], {}]
+      m({a: 1}).should == [[{a: 1}], {}]
+    end
+  end
+
+  context "in define_method(name, &proc)" do
+    # This tests that a free-standing proc used in define_method and converted to ruby2_keywords adopts that logic.
+    # See jruby/jruby#8119 for a case where aggressive JIT optimization broke later ruby2_keywords changes.
+    it "works with ruby2_keywords" do
+      m = Class.new do
+        def bar(a, foo: nil)
+          [a, foo]
+        end
+
+        # define_method and ruby2_keywords using send to avoid peephole optimizations
+        def self.setup
+          pr = make_proc
+          send :define_method, :foo, &pr
+          send :ruby2_keywords, :foo
+        end
+
+        # create proc in isolated method to force jit compilation on some implementations
+        def self.make_proc
+          proc { |a, *args| bar(a, *args) }
+        end
+      end
+
+      m.setup
+
+      m.new.foo(1, foo:2).should == [1, 2]
+    end
+  end
+end
diff --git a/spec/ruby/language/lambda_spec.rb b/spec/ruby/language/lambda_spec.rb
index 3b06a0d595..ed5a1c69e8 100644
--- a/spec/ruby/language/lambda_spec.rb
+++ b/spec/ruby/language/lambda_spec.rb
@@ -22,14 +22,12 @@ describe "A lambda literal -> () { }" do
     -> { }.lambda?.should be_true
   end
 
-  ruby_version_is "2.6" do
-    it "may include a rescue clause" do
-      eval('-> do raise ArgumentError; rescue ArgumentError; 7; end').should be_an_instance_of(Proc)
-    end
+  it "may include a rescue clause" do
+    eval('-> do raise ArgumentError; rescue ArgumentError; 7; end').should be_an_instance_of(Proc)
+  end
 
-    it "may include a ensure clause" do
-      eval('-> do 1; ensure; 2; end').should be_an_instance_of(Proc)
-    end
+  it "may include a ensure clause" do
+    eval('-> do 1; ensure; 2; end').should be_an_instance_of(Proc)
   end
 
   it "has its own scope for local variables" do
@@ -186,19 +184,9 @@ describe "A lambda literal -> () { }" do
       @a.().should == {}
       @a.(1, 2, 3, a: 4, b: 5).should == {a: 4, b: 5}
 
-      def self.suppress_keyword_warning(&block)
-        if RUBY_VERSION > '2.7'
-          suppress_warning(&block)
-        else
-          yield
-        end
-      end
-
-      suppress_keyword_warning do
-        h = mock("keyword splat")
-        h.should_receive(:to_hash).and_return({a: 1})
-        @a.(h).should == {a: 1}
-      end
+      h = mock("keyword splat")
+      h.should_not_receive(:to_hash)
+      @a.(h).should == {}
     end
 
     evaluate <<-ruby do
@@ -275,20 +263,21 @@ describe "A lambda literal -> () { }" do
     end
 
     describe "with circular optional argument reference" do
-      it "shadows an existing local with the same name as the argument" do
-        a = 1
-        -> {
-          @proc = eval "-> (a=a) { a }"
-        }.should complain(/circular argument reference/)
-        @proc.call.should == nil
+      ruby_version_is ""..."3.4" do
+        it "raises a SyntaxError if using the argument in its default value" do
+          a = 1
+          -> {
+            eval "-> (a=a) { a }"
+          }.should raise_error(SyntaxError)
+        end
       end
 
-      it "shadows an existing method with the same name as the argument" do
-        def a; 1; end
-        -> {
-          @proc = eval "-> (a=a) { a }"
-        }.should complain(/circular argument reference/)
-        @proc.call.should == nil
+      ruby_version_is "3.4" do
+        it "is nil if using the argument in its default value" do
+          -> {
+            eval "-> (a=a) { a }.call"
+          }.call.should == nil
+        end
       end
 
       it "calls an existing method with the same name as the argument if explicitly using ()" do
@@ -322,36 +311,23 @@ describe "A lambda expression 'lambda { ... }'" do
   end
 
   it "requires a block" do
-    lambda { lambda }.should raise_error(ArgumentError)
-  end
-
-  ruby_version_is "2.5" do
-    it "may include a rescue clause" do
-      eval('lambda do raise ArgumentError; rescue ArgumentError; 7; end').should be_an_instance_of(Proc)
+    suppress_warning do
+      lambda { lambda }.should raise_error(ArgumentError)
     end
   end
 
+  it "may include a rescue clause" do
+    eval('lambda do raise ArgumentError; rescue ArgumentError; 7; end').should be_an_instance_of(Proc)
+  end
 
   context "with an implicit block" do
     before do
       def meth; lambda; end
     end
 
-    ruby_version_is ""..."2.7" do
-      it "can be created" do
-        implicit_lambda = nil
-        -> {
-          implicit_lambda = meth { 1 }
-        }.should complain(/tried to create Proc object without a block/)
-
-        implicit_lambda.lambda?.should be_true
-        implicit_lambda.call.should == 1
-      end
-    end
-
-    ruby_version_is "2.7" do
-      it "raises ArgumentError" do
-        implicit_lambda = nil
+    it "raises ArgumentError" do
+      implicit_lambda = nil
+      suppress_warning do
         -> {
           meth { 1 }
         }.should raise_error(ArgumentError, /tried to create Proc object without a block/)
@@ -530,19 +506,9 @@ describe "A lambda expression 'lambda { ... }'" do
       @a.().should == {}
       @a.(1, 2, 3, a: 4, b: 5).should == {a: 4, b: 5}
 
-      def self.suppress_keyword_warning(&block)
-        if RUBY_VERSION > '2.7'
-          suppress_warning(&block)
-        else
-          yield
-        end
-      end
-
-      suppress_keyword_warning do
-        h = mock("keyword splat")
-        h.should_receive(:to_hash).and_return({a: 1})
-        @a.(h).should == {a: 1}
-      end
+      h = mock("keyword splat")
+      h.should_not_receive(:to_hash)
+      @a.(h).should == {}
     end
 
     evaluate <<-ruby do
diff --git a/spec/ruby/language/magic_comment_spec.rb b/spec/ruby/language/magic_comment_spec.rb
index f2bf3a08e5..af9c9dbfd0 100644
--- a/spec/ruby/language/magic_comment_spec.rb
+++ b/spec/ruby/language/magic_comment_spec.rb
@@ -45,7 +45,8 @@ end
 
 describe "Magic comments" do
   describe "in stdin" do
-    it_behaves_like :magic_comments, :locale, -> file {
+    default = (platform_is :windows and ruby_version_is "4.0") ? :UTF8 : :locale
+    it_behaves_like :magic_comments, default, -> file {
       print_at_exit = fixture(__FILE__, "print_magic_comment_result_at_exit.rb")
       ruby_exe(nil, args: "< #{fixture(__FILE__, file)}", options: "-r#{print_at_exit}")
     }
diff --git a/spec/ruby/language/match_spec.rb b/spec/ruby/language/match_spec.rb
index 36d347bd57..ebf677cabc 100644
--- a/spec/ruby/language/match_spec.rb
+++ b/spec/ruby/language/match_spec.rb
@@ -48,6 +48,13 @@ describe "The =~ operator with named captures" do
     end
   end
 
+  describe "on syntax of 'string_literal' =~ /regexp/" do
+    it "does not set local variables" do
+      'string literal' =~ /(?<matched>str)(?<unmatched>lit)?/
+      local_variables.should == []
+    end
+  end
+
   describe "on syntax of string_variable =~ /regexp/" do
     it "does not set local variables" do
       @string =~ /(?<matched>foo)(?<unmatched>bar)?/
diff --git a/spec/ruby/language/method_spec.rb b/spec/ruby/language/method_spec.rb
index 410dba99e2..8f72bd45ed 100644
--- a/spec/ruby/language/method_spec.rb
+++ b/spec/ruby/language/method_spec.rb
@@ -156,6 +156,26 @@ describe "A method send" do
       -> { m(1, 2, *x) }.should raise_error(TypeError)
     end
   end
+
+  context "with a block argument" do
+    before :all do
+      def m(x)
+        if block_given?
+          [true, yield(x + 'b')]
+        else
+          [false]
+        end
+      end
+    end
+
+    it "that refers to a proc passes the proc as the block" do
+      m('a', &-> y { y + 'c'}).should == [true, 'abc']
+    end
+
+    it "that is nil passes no block" do
+      m('a', &nil).should == [false]
+    end
+  end
 end
 
 describe "An element assignment method send" do
@@ -480,15 +500,6 @@ describe "A method" do
   end
 
   context "assigns local variables from method parameters" do
-
-    suppress_keyword_warning = ->(&block) do
-      if RUBY_VERSION >= '2.7'
-        suppress_warning(&block)
-      else
-        block.call
-      end
-    end
-
     evaluate <<-ruby do
         def m(a) a end
       ruby
@@ -555,12 +566,19 @@ describe "A method" do
 
       -> { m() }.should raise_error(ArgumentError)
       m(a: 1).should == 1
-      suppress_keyword_warning.call do
+      suppress_keyword_warning do
         -> { m("a" => 1, a: 1) }.should raise_error(ArgumentError)
       end
     end
 
     evaluate <<-ruby do
+        def m(a:, **kw) [a, kw] end
+      ruby
+
+      -> { m(b: 1) }.should raise_error(ArgumentError)
+    end
+
+    evaluate <<-ruby do
         def m(a: 1) a end
       ruby
 
@@ -585,11 +603,20 @@ describe "A method" do
       m(a: 1, b: 2).should == { a: 1, b: 2 }
       m(*[]).should == {}
       m(**{}).should == {}
-      m(**{a: 1, b: 2}, **{a: 4, c: 7}).should == { a: 4, b: 2, c: 7 }
+      suppress_warning {
+        eval "m(**{a: 1, b: 2}, **{a: 4, c: 7})"
+      }.should == { a: 4, b: 2, c: 7 }
       -> { m(2) }.should raise_error(ArgumentError)
     end
 
     evaluate <<-ruby do
+      def m(**k); k end;
+      ruby
+
+      m("a" => 1).should == { "a" => 1 }
+    end
+
+    evaluate <<-ruby do
         def m(&b) b end
       ruby
 
@@ -717,7 +744,7 @@ describe "A method" do
       ruby
 
       m(1, b: 2).should == [1, 2]
-      suppress_keyword_warning.call do
+      suppress_keyword_warning do
         -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
       end
     end
@@ -728,9 +755,7 @@ describe "A method" do
 
       m(2).should == [2, 1]
       m(1, b: 2).should == [1, 2]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [{"a" => 1, b: 2}, 1]
-      end
+      -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
     end
 
     evaluate <<-ruby do
@@ -739,9 +764,7 @@ describe "A method" do
 
       m(1).should == 1
       m(1, a: 2, b: 3).should == 1
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == {"a" => 1, b: 2}
-      end
+      -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
     end
 
     evaluate <<-ruby do
@@ -750,9 +773,7 @@ describe "A method" do
 
       m(1).should == [1, {}]
       m(1, a: 2, b: 3).should == [1, {a: 2, b: 3}]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [{"a" => 1, b: 2}, {}]
-      end
+      -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
     end
 
     evaluate <<-ruby do
@@ -869,9 +890,7 @@ describe "A method" do
 
       m(b: 2).should == [1, 2]
       m(2, b: 1).should == [2, 1]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [{"a" => 1}, 2]
-      end
+      -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
     end
 
     evaluate <<-ruby do
@@ -881,31 +900,16 @@ describe "A method" do
       m().should == [1, 2]
       m(2).should == [2, 2]
       m(b: 3).should == [1, 3]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [{"a" => 1}, 2]
-      end
-    end
-
-    ruby_version_is "0"..."2.7" do
-      evaluate <<-ruby do
-          def m(a=1, **) a end
-        ruby
-
-        m().should == 1
-        m(2, a: 1, b: 0).should == 2
-        m("a" => 1, a: 2).should == {"a" => 1}
-      end
+      -> { m("a" => 1, b: 2) }.should raise_error(ArgumentError)
     end
 
-    ruby_version_is "2.7" do
-      evaluate <<-ruby do
-          def m(a=1, **) a end
-        ruby
+    evaluate <<-ruby do
+        def m(a=1, **) a end
+      ruby
 
-        m().should == 1
-        m(2, a: 1, b: 0).should == 2
-        m("a" => 1, a: 2).should == 1
-      end
+      m().should == 1
+      m(2, a: 1, b: 0).should == 2
+      m("a" => 1, a: 2).should == 1
     end
 
     evaluate <<-ruby do
@@ -946,256 +950,6 @@ describe "A method" do
     end
 
     evaluate <<-ruby do
-        def m(*, a:) a end
-      ruby
-
-      m(a: 1).should == 1
-      m(1, 2, a: 3).should == 3
-      suppress_keyword_warning.call do
-        m("a" => 1, a: 2).should == 2
-      end
-    end
-
-    evaluate <<-ruby do
-        def m(*a, b:) [a, b] end
-      ruby
-
-      m(b: 1).should == [[], 1]
-      m(1, 2, b: 3).should == [[1, 2], 3]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [[{"a" => 1}], 2]
-      end
-    end
-
-    evaluate <<-ruby do
-        def m(*, a: 1) a end
-      ruby
-
-      m().should == 1
-      m(1, 2).should == 1
-      m(a: 2).should == 2
-      m(1, a: 2).should == 2
-      suppress_keyword_warning.call do
-        m("a" => 1, a: 2).should == 2
-      end
-    end
-
-    evaluate <<-ruby do
-        def m(*a, b: 1) [a, b] end
-      ruby
-
-      m().should == [[], 1]
-      m(1, 2, 3, b: 4).should == [[1, 2, 3], 4]
-      suppress_keyword_warning.call do
-        m("a" => 1, b: 2).should == [[{"a" => 1}], 2]
-      end
-
-      a = mock("splat")
-      a.should_not_receive(:to_ary)
-      m(*a).should == [[a], 1]
-    end
-
-    evaluate <<-ruby do
-        def m(*, **) end
-      ruby
-
-      m().should be_nil
-      m(a: 1, b: 2).should be_nil
-      m(1, 2, 3, a: 4, b: 5).should be_nil
-
-      h = mock("keyword splat")
-      h.should_receive(:to_hash).and_return({a: 1})
-      suppress_keyword_warning.call do
-        m(h).should be_nil
-      end
-
-      h = mock("keyword splat")
-      error = RuntimeError.new("error while converting to a hash")
-      h.should_receive(:to_hash).and_raise(error)
-      -> { m(h) }.should raise_error(error)
-    end
-
-    ruby_version_is "0"..."2.7" do
-      evaluate <<-ruby do
-          def m(*a, **) a end
-        ruby
-
-        m().should == []
-        m(1, 2, 3, a: 4, b: 5).should == [1, 2, 3]
-        m("a" => 1, a: 1).should == [{"a" => 1}]
-        m(1, **{a: 2}).should == [1]
-
-        h = mock("keyword splat")
-        h.should_receive(:to_hash)
-        -> { m(**h) }.should raise_error(TypeError)
-      end
-
-      evaluate <<-ruby do
-          def m(*, **k) k end
-        ruby
-
-        m().should == {}
-        m(1, 2, 3, a: 4, b: 5).should == {a: 4, b: 5}
-        m("a" => 1, a: 1).should == {a: 1}
-
-        h = mock("keyword splat")
-        h.should_receive(:to_hash).and_return({a: 1})
-        m(h).should == {a: 1}
-      end
-
-      evaluate <<-ruby do
-          def m(a = nil, **k) [a, k] end
-        ruby
-
-        m().should == [nil, {}]
-        m("a" => 1).should == [{"a" => 1}, {}]
-        m(a: 1).should == [nil, {a: 1}]
-        m("a" => 1, a: 1).should == [{"a" => 1}, {a: 1}]
-        m({ "a" => 1 }, a: 1).should == [{"a" => 1}, {a: 1}]
-        m({a: 1}, {}).should == [{a: 1}, {}]
-
-        h = {"a" => 1, b: 2}
-        m(h).should == [{"a" => 1}, {b: 2}]
-        h.should == {"a" => 1, b: 2}
-
-        h = {"a" => 1}
-        m(h).first.should == h
-
-        h = {}
-        r = m(h)
-        r.first.should be_nil
-        r.last.should == {}
-
-        hh = {}
-        h = mock("keyword splat empty hash")
-        h.should_receive(:to_hash).and_return(hh)
-        r = m(h)
-        r.first.should be_nil
-        r.last.should == {}
-
-        h = mock("keyword splat")
-        h.should_receive(:to_hash).and_return({"a" => 1, a: 2})
-        m(h).should == [{"a" => 1}, {a: 2}]
-      end
-
-      evaluate <<-ruby do
-          def m(*a, **k) [a, k] end
-        ruby
-
-        m().should == [[], {}]
-        m(1).should == [[1], {}]
-        m(a: 1, b: 2).should == [[], {a: 1, b: 2}]
-        m(1, 2, 3, a: 2).should == [[1, 2, 3], {a: 2}]
-
-        m("a" => 1).should == [[{"a" => 1}], {}]
-        m(a: 1).should == [[], {a: 1}]
-        m("a" => 1, a: 1).should == [[{"a" => 1}], {a: 1}]
-        m({ "a" => 1 }, a: 1).should == [[{"a" => 1}], {a: 1}]
-        m({a: 1}, {}).should == [[{a: 1}], {}]
-        m({a: 1}, {"a" => 1}).should == [[{a: 1}, {"a" => 1}], {}]
-
-        bo = BasicObject.new
-        def bo.to_a; [1, 2, 3]; end
-        def bo.to_hash; {:b => 2, :c => 3}; end
-
-        m(*bo, **bo).should == [[1, 2, 3], {:b => 2, :c => 3}]
-      end
-    end
-
-    ruby_version_is "2.7" do
-      evaluate <<-ruby do
-          def m(*a, **) a end
-        ruby
-
-        m().should == []
-        m(1, 2, 3, a: 4, b: 5).should == [1, 2, 3]
-        m("a" => 1, a: 1).should == []
-        m(1, **{a: 2}).should == [1]
-
-        h = mock("keyword splat")
-        h.should_receive(:to_hash)
-        -> { m(**h) }.should raise_error(TypeError)
-      end
-
-      evaluate <<-ruby do
-          def m(*, **k) k end
-        ruby
-
-        m().should == {}
-        m(1, 2, 3, a: 4, b: 5).should == {a: 4, b: 5}
-        m("a" => 1, a: 1).should == {"a" => 1, a: 1}
-
-        h = mock("keyword splat")
-        h.should_receive(:to_hash).and_return({a: 1})
-        suppress_warning do
-          m(h).should == {a: 1}
-        end
-      end
-
-      evaluate <<-ruby do
-          def m(a = nil, **k) [a, k] end
-        ruby
-
-        m().should == [nil, {}]
-        m("a" => 1).should == [nil, {"a" => 1}]
-        m(a: 1).should == [nil, {a: 1}]
-        m("a" => 1, a: 1).should == [nil, {"a" => 1, a: 1}]
-        m({ "a" => 1 }, a: 1).should == [{"a" => 1}, {a: 1}]
-        suppress_warning do
-          m({a: 1}, {}).should == [{a: 1}, {}]
-
-          h = {"a" => 1, b: 2}
-          m(h).should == [{"a" => 1}, {b: 2}]
-          h.should == {"a" => 1, b: 2}
-
-          h = {"a" => 1}
-          m(h).first.should == h
-
-          h = {}
-          r = m(h)
-          r.first.should be_nil
-          r.last.should == {}
-
-          hh = {}
-          h = mock("keyword splat empty hash")
-          h.should_receive(:to_hash).and_return(hh)
-          r = m(h)
-          r.first.should be_nil
-          r.last.should == {}
-
-          h = mock("keyword splat")
-          h.should_receive(:to_hash).and_return({"a" => 1, a: 2})
-          m(h).should == [{"a" => 1}, {a: 2}]
-        end
-      end
-
-      evaluate <<-ruby do
-          def m(*a, **k) [a, k] end
-        ruby
-
-        m().should == [[], {}]
-        m(1).should == [[1], {}]
-        m(a: 1, b: 2).should == [[], {a: 1, b: 2}]
-        m(1, 2, 3, a: 2).should == [[1, 2, 3], {a: 2}]
-
-        m("a" => 1).should == [[], {"a" => 1}]
-        m(a: 1).should == [[], {a: 1}]
-        m("a" => 1, a: 1).should == [[], {"a" => 1, a: 1}]
-        m({ "a" => 1 }, a: 1).should == [[{"a" => 1}], {a: 1}]
-        suppress_warning do
-          m({a: 1}, {}).should == [[{a: 1}], {}]
-        end
-        m({a: 1}, {"a" => 1}).should == [[{a: 1}, {"a" => 1}], {}]
-
-        bo = BasicObject.new
-        def bo.to_a; [1, 2, 3]; end
-        def bo.to_hash; {:b => 2, :c => 3}; end
-
-        m(*bo, **bo).should == [[1, 2, 3], {:b => 2, :c => 3}]
-      end
-    end
-
-    evaluate <<-ruby do
         def m(*, &b) b end
       ruby
 
@@ -1218,7 +972,7 @@ describe "A method" do
       ruby
 
       m(a: 1, b: 2).should == [1, 2]
-      suppress_keyword_warning.call do
+      suppress_keyword_warning do
         -> { m("a" => 1, a: 1, b: 2) }.should raise_error(ArgumentError)
       end
     end
@@ -1229,51 +983,27 @@ describe "A method" do
 
       m(a: 1).should == [1, 1]
       m(a: 1, b: 2).should == [1, 2]
-      suppress_keyword_warning.call do
+      suppress_keyword_warning do
         -> { m("a" => 1, a: 1, b: 2) }.should raise_error(ArgumentError)
       end
     end
 
-    ruby_version_is '0'...'2.7' do
-      evaluate <<-ruby do
-          def m(a:, **) a end
-        ruby
-
-        m(a: 1).should == 1
-        m(a: 1, b: 2).should == 1
-        -> { m("a" => 1, a: 1, b: 2) }.should raise_error(ArgumentError)
-      end
-
-      evaluate <<-ruby do
-          def m(a:, **k) [a, k] end
-        ruby
+    evaluate <<-ruby do
+        def m(a:, **) a end
+      ruby
 
-        m(a: 1).should == [1, {}]
-        m(a: 1, b: 2, c: 3).should == [1, {b: 2, c: 3}]
-        -> { m("a" => 1, a: 1, b: 2) }.should raise_error(ArgumentError)
-      end
+      m(a: 1).should == 1
+      m(a: 1, b: 2).should == 1
+      m("a" => 1, a: 1, b: 2).should == 1
     end
 
-    ruby_version_is '2.7' do
-      evaluate <<-ruby do
-          def m(a:, **) a end
-        ruby
-
-        m(a: 1).should == 1
-        m(a: 1, b: 2).should == 1
-        m("a" => 1, a: 1, b: 2).should == 1
-      end
-
-      evaluate <<-ruby do
-          def m(a:, **k) [a, k] end
-        ruby
+    evaluate <<-ruby do
+        def m(a:, **k) [a, k] end
+      ruby
 
-        m(a: 1).should == [1, {}]
-        m(a: 1, b: 2, c: 3).should == [1, {b: 2, c: 3}]
-        suppress_warning do
-          m("a" => 1, a: 1, b: 2).should == [1, {"a" => 1, b: 2}]
-        end
-      end
+      m(a: 1).should == [1, {}]
+      m(a: 1, b: 2, c: 3).should == [1, {b: 2, c: 3}]
+      m("a" => 1, a: 1, b: 2).should == [1, {"a" => 1, b: 2}]
     end
 
     evaluate <<-ruby do
@@ -1371,6 +1101,18 @@ describe "A method" do
     end
 
     evaluate <<-ruby do
+      def m(a, **nil); a end;
+      ruby
+
+      m({a: 1}).should == {a: 1}
+      m({"a" => 1}).should == {"a" => 1}
+
+      -> { m(a: 1) }.should raise_error(ArgumentError, 'no keywords accepted')
+      -> { m(**{a: 1}) }.should raise_error(ArgumentError, 'no keywords accepted')
+      -> { m("a" => 1) }.should raise_error(ArgumentError, 'no keywords accepted')
+    end
+
+    evaluate <<-ruby do
         def m(a, b = nil, c = nil, d, e: nil, **f)
           [a, b, c, d, e, f]
         end
@@ -1379,28 +1121,81 @@ describe "A method" do
       result = m(1, 2)
       result.should == [1, nil, nil, 2, nil, {}]
 
-      suppress_warning do
-        result = m(1, 2, {foo: :bar})
-        result.should == [1, nil, nil, 2, nil, {foo: :bar}]
-      end
+      result = m(1, 2, {foo: :bar})
+      result.should == [1, 2, nil, {foo: :bar}, nil, {}]
 
       result = m(1, {foo: :bar})
       result.should == [1, nil, nil, {foo: :bar}, nil, {}]
     end
   end
 
-  context "assigns keyword arguments from a passed Hash without modifying it" do
+  context 'when passing an empty keyword splat to a method that does not accept keywords' do
+    evaluate <<-ruby do
+        def m(*a); a; end
+      ruby
+
+      h = {}
+      m(**h).should == []
+    end
+  end
+
+  context 'when passing an empty keyword splat to a method that does not accept keywords' do
+    evaluate <<-ruby do
+        def m(a); a; end
+      ruby
+      h = {}
+
+      -> do
+        m(**h).should == {}
+      end.should raise_error(ArgumentError)
+    end
+  end
+
+  context "raises ArgumentError if passing hash as keyword arguments" do
     evaluate <<-ruby do
         def m(a: nil); a; end
       ruby
 
       options = {a: 1}.freeze
       -> do
-        suppress_warning do
-          m(options).should == 1
-        end
-      end.should_not raise_error
-      options.should == {a: 1}
+        m(options)
+      end.should raise_error(ArgumentError)
+    end
+  end
+
+  it "assigns the last Hash to the last optional argument if the Hash contains non-Symbol keys and is not passed as keywords" do
+    def m(a = nil, b = {}, v: false)
+      [a, b, v]
+    end
+
+    h = { "key" => "value" }
+    m(:a, h).should == [:a, h, false]
+    m(:a, h, v: true).should == [:a, h, true]
+    m(v: true).should == [nil, {}, true]
+  end
+end
+
+context "when passing **nil into a method that accepts keyword arguments" do
+  ruby_version_is ""..."3.4" do
+    it "raises TypeError" do
+      def m(**kw) kw; end
+
+      h = nil
+      -> { m(a: 1, **h) }.should raise_error(TypeError, "no implicit conversion of nil into Hash")
+      -> { m(a: 1, **nil) }.should raise_error(TypeError, "no implicit conversion of nil into Hash")
+    end
+  end
+
+  ruby_version_is "3.4" do
+    it "expands nil using ** into {}" do
+      def m(**kw) kw; end
+
+      h = nil
+      m(**h).should == {}
+      m(a: 1, **h).should == {a: 1}
+
+      m(**nil).should == {}
+      m(a: 1, **nil).should == {a: 1}
     end
   end
 end
@@ -1423,14 +1218,42 @@ describe "A method call with a space between method name and parentheses" do
     end
   end
 
-  context "when a single argument provided" do
-    it "assigns it" do
+  context "when a single argument is provided" do
+    it "assigns a simple expression" do
+      args = m (1)
+      args.should == [1]
+    end
+
+    it "assigns an expression consisting of multiple statements" do
+      args = m ((0; 1))
+      args.should == [1]
+    end
+
+    it "assigns one single statement, without the need of parentheses" do
       args = m (1 == 1 ? true : false)
       args.should == [true]
     end
+
+    ruby_version_is "3.3" do
+      it "supports multiple statements" do
+        eval("m (1; 2)").should == [2]
+      end
+    end
   end
 
-  context "when 2+ arguments provided" do
+  context "when multiple arguments are provided" do
+    it "assigns simple expressions" do
+      args = m (1), (2)
+      args.should == [1, 2]
+    end
+
+    it "assigns expressions consisting of multiple statements" do
+      args = m ((0; 1)), ((2; 3))
+      args.should == [1, 3]
+    end
+  end
+
+  context "when the argument looks like an argument list" do
     it "raises a syntax error" do
       -> {
         eval("m (1, 2)")
@@ -1494,3 +1317,333 @@ describe "An array-dereference method ([])" do
     end
   end
 end
+
+describe "An endless method definition" do
+  context "without arguments" do
+    evaluate <<-ruby do
+        def m() = 42
+      ruby
+
+      m.should == 42
+    end
+
+    context "without parenthesis" do
+      evaluate <<-ruby do
+        def m = 42
+      ruby
+
+        m.should == 42
+      end
+    end
+  end
+
+  context "with arguments" do
+    evaluate <<-ruby do
+        def m(a, b) = a + b
+      ruby
+
+      m(1, 4).should == 5
+    end
+  end
+
+  context "with multiline body" do
+    evaluate <<-ruby do
+        def m(n) =
+          if n > 2
+            m(n - 2) + m(n - 1)
+          else
+            1
+          end
+      ruby
+
+      m(6).should == 8
+    end
+  end
+
+  # tested more thoroughly in language/delegation_spec.rb
+  context "with args forwarding" do
+    evaluate <<-ruby do
+        def mm(word, num:)
+          word * num
+        end
+
+        def m(...) = mm(...) + mm(...)
+      ruby
+
+      m("meow", num: 2).should == "meow" * 4
+    end
+  end
+end
+
+describe "Keyword arguments are now separated from positional arguments" do
+  context "when the method has only positional parameters" do
+    it "treats incoming keyword arguments as positional for compatibility" do
+      def foo(a, b, c, hsh)
+        hsh[:key]
+      end
+
+      foo(1, 2, 3, key: 42).should == 42
+    end
+  end
+
+  context "when the method takes a ** parameter" do
+    it "captures the passed literal keyword arguments" do
+      def foo(a, b, c, **hsh)
+        hsh[:key]
+      end
+
+      foo(1, 2, 3, key: 42).should == 42
+    end
+
+    it "captures the passed ** keyword arguments" do
+      def foo(a, b, c, **hsh)
+        hsh[:key]
+      end
+
+      h = { key: 42 }
+      foo(1, 2, 3, **h).should == 42
+    end
+
+    it "does not convert a positional Hash to keyword arguments" do
+      def foo(a, b, c, **hsh)
+        hsh[:key]
+      end
+
+      -> {
+        foo(1, 2, 3, { key: 42 })
+      }.should raise_error(ArgumentError, 'wrong number of arguments (given 4, expected 3)')
+    end
+  end
+
+  context "when the method takes a key: parameter" do
+    context "when it's called with a positional Hash and no **" do
+      it "raises ArgumentError" do
+        def foo(a, b, c, key: 1)
+          key
+        end
+
+        -> {
+          foo(1, 2, 3, { key: 42 })
+        }.should raise_error(ArgumentError, 'wrong number of arguments (given 4, expected 3)')
+      end
+    end
+
+    context "when it's called with **" do
+      it "captures the passed keyword arguments" do
+        def foo(a, b, c, key: 1)
+          key
+        end
+
+        h = { key: 42 }
+        foo(1, 2, 3, **h).should == 42
+      end
+    end
+  end
+end
+
+describe "kwarg with omitted value in a method call" do
+  context "accepts short notation 'kwarg' in method call" do
+    evaluate <<-ruby do
+        def call(*args, **kwargs) = [args, kwargs]
+      ruby
+
+      a, b, c = 1, 2, 3
+      arr, h = call(a:)
+      h.should == {a: 1}
+      arr.should == []
+
+      arr, h = call(a:, b:, c:)
+      h.should == {a: 1, b: 2, c: 3}
+      arr.should == []
+
+      arr, h = call(a:, b: 10, c:)
+      h.should == {a: 1, b: 10, c: 3}
+      arr.should == []
+    end
+  end
+
+  context "with methods and local variables" do
+    evaluate <<-ruby do
+        def call(*args, **kwargs) = [args, kwargs]
+
+        def bar
+          "baz"
+        end
+
+        def foo(val)
+          call bar:, val:
+        end
+      ruby
+
+      foo(1).should == [[], {bar: "baz", val: 1}]
+    end
+  end
+end
+
+describe "Inside 'endless' method definitions" do
+  it "allows method calls without parenthesis" do
+    def greet(person) = "Hi, ".dup.concat person
+
+    greet("Homer").should == "Hi, Homer"
+  end
+end
+
+describe "warning about not used block argument" do
+  ruby_version_is "3.4" do
+    it "warns when passing a block argument to a method that never uses it" do
+      def m_that_does_not_use_block
+        42
+      end
+
+      -> {
+        m_that_does_not_use_block { }
+      }.should complain(
+        /#{__FILE__}:#{__LINE__ - 2}: warning: the block passed to 'm_that_does_not_use_block' defined at #{__FILE__}:#{__LINE__ - 7} may be ignored/,
+        verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that declares a block parameter" do
+      def m_with_block_parameter(&block)
+        42
+      end
+
+      -> { m_with_block_parameter { } }.should_not complain(verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that declares an anonymous block parameter" do
+      def m_with_anonymous_block_parameter(&)
+        42
+      end
+
+      -> { m_with_anonymous_block_parameter { } }.should_not complain(verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that yields an implicit block parameter" do
+      def m_with_yield
+        yield 42
+      end
+
+      -> { m_with_yield { } }.should_not complain(verbose: true)
+    end
+
+    it "warns when passing a block argument to a method that calls #block_given?" do
+      def m_with_block_given
+        block_given?
+      end
+
+      -> {
+        m_with_block_given { }
+      }.should complain(
+        /#{__FILE__}:#{__LINE__ - 2}: warning: the block passed to 'm_with_block_given' defined at #{__FILE__}:#{__LINE__ - 7} may be ignored/,
+        verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that calls super" do
+      parent = Class.new do
+        def m
+        end
+      end
+
+      child = Class.new(parent) do
+        def m
+          super
+        end
+      end
+
+      obj = child.new
+      -> { obj.m { } }.should_not complain(verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that calls super(...)" do
+      parent = Class.new do
+        def m(a)
+        end
+      end
+
+      child = Class.new(parent) do
+        def m(...)
+          super(...)
+        end
+      end
+
+      obj = child.new
+      -> { obj.m(42) { } }.should_not complain(verbose: true)
+    end
+
+    it "does not warn when called #initialize()" do
+      klass = Class.new do
+        def initialize
+        end
+      end
+
+      -> { klass.new {} }.should_not complain(verbose: true)
+    end
+
+    it "does not warn when passing a block argument to a method that calls super()" do
+      parent = Class.new do
+        def m
+        end
+      end
+
+      child = Class.new(parent) do
+        def m
+          super()
+        end
+      end
+
+      obj = child.new
+      -> { obj.m { } }.should_not complain(verbose: true)
+    end
+
+    it "warns only once per call site" do
+      def m_that_does_not_use_block
+        42
+      end
+
+      def call_m_that_does_not_use_block
+        m_that_does_not_use_block {}
+      end
+
+      -> {
+        m_that_does_not_use_block { }
+      }.should complain(/the block passed to 'm_that_does_not_use_block' defined at .+ may be ignored/, verbose: true)
+
+      -> {
+        m_that_does_not_use_block { }
+      }.should_not complain(verbose: true)
+    end
+
+    it "can be disabled with :strict_unused_block warning category" do
+      def m_that_does_not_use_block
+        42
+      end
+
+      # ensure that warning is emitted
+      -> { m_that_does_not_use_block { } }.should complain(verbose: true)
+
+      warn_strict_unused_block = Warning[:strict_unused_block]
+      Warning[:strict_unused_block] = false
+      begin
+        -> { m_that_does_not_use_block { } }.should_not complain(verbose: true)
+      ensure
+        Warning[:strict_unused_block] = warn_strict_unused_block
+      end
+    end
+
+    it "can be enabled with :strict_unused_block = true warning category in not verbose mode" do
+      def m_that_does_not_use_block
+        42
+      end
+
+      warn_strict_unused_block = Warning[:strict_unused_block]
+      Warning[:strict_unused_block] = true
+      begin
+        -> {
+          m_that_does_not_use_block { }
+      }.should complain(/the block passed to 'm_that_does_not_use_block' defined at .+ may be ignored/)
+      ensure
+        Warning[:strict_unused_block] = warn_strict_unused_block
+      end
+    end
+  end
+end
diff --git a/spec/ruby/language/module_spec.rb b/spec/ruby/language/module_spec.rb
index 1b41e184bb..fba4aa8c6e 100644
--- a/spec/ruby/language/module_spec.rb
+++ b/spec/ruby/language/module_spec.rb
@@ -26,11 +26,39 @@ describe "The module keyword" do
   it "reopens an existing module" do
     module ModuleSpecs; Reopened = true; end
     ModuleSpecs::Reopened.should be_true
+  ensure
+    ModuleSpecs.send(:remove_const, :Reopened)
   end
 
-  it "reopens a module included in Object" do
-    module IncludedModuleSpecs; Reopened = true; end
-    ModuleSpecs::IncludedInObject::IncludedModuleSpecs::Reopened.should be_true
+  it "does not reopen a module included in Object" do
+    ruby_exe(<<~RUBY).should == "false"
+      module IncludedInObject
+        module IncludedModule; end
+      end
+      class Object
+        include IncludedInObject
+      end
+      module IncludedModule; end
+      print IncludedInObject::IncludedModule == Object::IncludedModule
+    RUBY
+  end
+
+  it "does not reopen a module included in non-Object modules" do
+    ruby_exe(<<~RUBY).should == "false/false"
+      module Included
+        module IncludedModule; end
+      end
+      module M
+        include Included
+        module IncludedModule; end
+      end
+      class C
+        include Included
+        module IncludedModule; end
+      end
+      print Included::IncludedModule == M::IncludedModule, "/",
+            Included::IncludedModule == C::IncludedModule
+    RUBY
   end
 
   it "raises a TypeError if the constant is a Class" do
@@ -43,7 +71,7 @@ describe "The module keyword" do
     -> { module ModuleSpecs::Modules::A; end }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError if the constant is a Fixnum" do
+  it "raises a TypeError if the constant is an Integer" do
     -> { module ModuleSpecs::Modules::B; end }.should raise_error(TypeError)
   end
 
@@ -67,12 +95,14 @@ describe "Assigning an anonymous module to a constant" do
 
     ::ModuleSpecs_CS1 = mod
     mod.name.should == "ModuleSpecs_CS1"
+  ensure
+    Object.send(:remove_const, :ModuleSpecs_CS1)
   end
 
-  it "does not set the name of a module scoped by an anonymous module" do
+  it "sets the name of a module scoped by an anonymous module" do
     a, b = Module.new, Module.new
     a::B = b
-    b.name.should be_nil
+    b.name.should.end_with? '::B'
   end
 
   it "sets the name of contained modules when assigning a toplevel anonymous module" do
@@ -87,5 +117,7 @@ describe "Assigning an anonymous module to a constant" do
     b.name.should == "ModuleSpecs_CS2::B"
     c.name.should == "ModuleSpecs_CS2::B::C"
     d.name.should == "ModuleSpecs_CS2::D"
+  ensure
+    Object.send(:remove_const, :ModuleSpecs_CS2)
   end
 end
diff --git a/spec/ruby/language/numbered_parameters_spec.rb b/spec/ruby/language/numbered_parameters_spec.rb
new file mode 100644
index 0000000000..de532c326d
--- /dev/null
+++ b/spec/ruby/language/numbered_parameters_spec.rb
@@ -0,0 +1,113 @@
+require_relative '../spec_helper'
+
+describe "Numbered parameters" do
+  it "provides default parameters _1, _2, ... in a block" do
+    -> { _1 }.call("a").should == "a"
+    proc { _1 }.call("a").should == "a"
+    lambda { _1 }.call("a").should == "a"
+    ["a"].map { _1 }.should == ["a"]
+  end
+
+  it "assigns nil to not passed parameters" do
+    proc { [_1, _2] }.call("a").should == ["a", nil]
+    proc { [_1, _2] }.call("a", "b").should == ["a", "b"]
+  end
+
+  it "supports variables _1-_9 only for the first 9 passed parameters" do
+    block = proc { [_1, _2, _3, _4, _5, _6, _7, _8, _9] }
+    result = block.call(1, 2, 3, 4, 5, 6, 7, 8, 9)
+    result.should == [1, 2, 3, 4, 5, 6, 7, 8, 9]
+  end
+
+  it "does not support more than 9 parameters" do
+    -> {
+      proc { [_10] }.call(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+    }.should raise_error(NameError, /undefined local variable or method [`']_10'/)
+  end
+
+  it "can not be used in both outer and nested blocks at the same time" do
+    -> {
+      eval("-> { _1; -> { _2 } }")
+    }.should raise_error(SyntaxError, /numbered parameter is already used in/m)
+  end
+
+  it "cannot be overwritten with local variable" do
+    -> {
+      eval <<~CODE
+        _1 = 0
+        proc { _1 }.call("a").should == 0
+      CODE
+    }.should raise_error(SyntaxError, /_1 is reserved for numbered parameter/)
+  end
+
+  it "errors when numbered parameter is overwritten with local variable" do
+    -> {
+      eval("_1 = 0")
+    }.should raise_error(SyntaxError, /_1 is reserved for numbered parameter/)
+  end
+
+  it "raises SyntaxError when block parameters are specified explicitly" do
+    -> { eval("-> () { _1 }")         }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("-> (x) { _1 }")        }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("proc { || _1 }")       }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("proc { |x| _1 }")      }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("lambda { || _1 }")     }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("lambda { |x| _1 }")    }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("['a'].map { || _1 }")  }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("['a'].map { |x| _1 }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+  end
+
+  describe "assigning to a numbered parameter" do
+    it "raises SyntaxError" do
+      -> { eval("proc { _1 = 0 }") }.should raise_error(SyntaxError, /_1 is reserved for numbered parameter/)
+    end
+  end
+
+  it "affects block arity" do
+    -> { _1 }.arity.should == 1
+    -> { _2 }.arity.should == 2
+    -> { _3 }.arity.should == 3
+    -> { _4 }.arity.should == 4
+    -> { _5 }.arity.should == 5
+    -> { _6 }.arity.should == 6
+    -> { _7 }.arity.should == 7
+    -> { _8 }.arity.should == 8
+    -> { _9 }.arity.should == 9
+
+    ->     { _9 }.arity.should == 9
+    proc   { _9 }.arity.should == 9
+    lambda { _9 }.arity.should == 9
+  end
+
+  it "affects block parameters" do
+    -> { _1 }.parameters.should == [[:req, :_1]]
+    -> { _2 }.parameters.should == [[:req, :_1], [:req, :_2]]
+
+    proc { _1 }.parameters.should == [[:opt, :_1]]
+    proc { _2 }.parameters.should == [[:opt, :_1], [:opt, :_2]]
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "affects binding local variables" do
+      -> { _1; binding.local_variables }.call("a").should == [:_1]
+      -> { _2; binding.local_variables }.call("a", "b").should == [:_1, :_2]
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "does not affect binding local variables" do
+      -> { _1; binding.local_variables }.call("a").should == []
+      -> { _2; binding.local_variables }.call("a", "b").should == []
+    end
+  end
+
+  it "does not work in methods" do
+    obj = Object.new
+    def obj.foo; _1 end
+
+    -> { obj.foo("a") }.should raise_error(ArgumentError, /wrong number of arguments/)
+  end
+end
diff --git a/spec/ruby/language/numbers_spec.rb b/spec/ruby/language/numbers_spec.rb
index c82a630632..a8e023efb6 100644
--- a/spec/ruby/language/numbers_spec.rb
+++ b/spec/ruby/language/numbers_spec.rb
@@ -45,7 +45,15 @@ describe "A number literal" do
     eval('-3r').should == Rational(-3, 1)
   end
 
-  it "can be an bignum literal with trailing 'r' to represent a Rational" do
+  it "can be an float literal with trailing 'r' to represent a Rational in a canonical form" do
+    eval('1.0r').should == Rational(1, 1)
+  end
+
+  it "can be a float literal with trailing 'r' to represent a Rational" do
+    eval('0.0174532925199432957r').should == Rational(174532925199432957, 10000000000000000000)
+  end
+
+  it "can be a bignum literal with trailing 'r' to represent a Rational" do
     eval('1111111111111111111111111111111111111111111111r').should == Rational(1111111111111111111111111111111111111111111111, 1)
     eval('-1111111111111111111111111111111111111111111111r').should == Rational(-1111111111111111111111111111111111111111111111, 1)
   end
diff --git a/spec/ruby/language/optional_assignments_spec.rb b/spec/ruby/language/optional_assignments_spec.rb
index 04abc2496b..5fe3e3671b 100644
--- a/spec/ruby/language/optional_assignments_spec.rb
+++ b/spec/ruby/language/optional_assignments_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../spec_helper'
+require_relative '../fixtures/constants'
 
 describe 'Optional variable assignments' do
   describe 'using ||=' do
@@ -42,9 +43,21 @@ describe 'Optional variable assignments' do
 
         a.should == 10
       end
+
+      it 'returns the new value if set to false' do
+        a = false
+
+        (a ||= 20).should == 20
+      end
+
+      it 'returns the original value if truthy' do
+        a = 10
+
+        (a ||= 20).should == 10
+      end
     end
 
-    describe 'using a accessor' do
+    describe 'using an accessor' do
       before do
         klass = Class.new { attr_accessor :b }
         @a    = klass.new
@@ -89,6 +102,178 @@ describe 'Optional variable assignments' do
 
         @a.b.should == 10
       end
+
+      it 'does evaluate receiver only once when assigns' do
+        ScratchPad.record []
+        @a.b = nil
+
+        (ScratchPad << :evaluated; @a).b ||= 10
+
+        ScratchPad.recorded.should == [:evaluated]
+        @a.b.should == 10
+      end
+
+      it 'returns the new value if set to false' do
+        def @a.b=(x)
+          :v
+        end
+
+        @a.b = false
+        (@a.b ||= 20).should == 20
+      end
+
+      it 'returns the original value if truthy' do
+        def @a.b=(x)
+          @b = x
+          :v
+        end
+
+        @a.b = 10
+        (@a.b ||= 20).should == 10
+      end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(v) @a = v end
+          def public_method(v); self.a ||= v end
+          private
+          def a; @a end
+          def a=(v) @a = v; 42 end
+        end
+
+        a = klass_with_private_methods.new(false)
+        a.public_method(10).should == 10
+      end
+    end
+
+    describe 'using a #[]' do
+      before do
+        @a = {}
+        klass = Class.new do
+          def [](k)
+            @hash ||= {}
+            @hash[k]
+          end
+
+          def []=(k, v)
+            @hash ||= {}
+            @hash[k] = v
+            7
+          end
+        end
+        @b = klass.new
+      end
+
+      it 'returns the assigned value, not the result of the []= method with ||=' do
+        (@b[:k] ||= 12).should == 12
+      end
+
+      it "evaluates the index precisely once" do
+        ary = [:x, :y]
+        @a[:x] = 15
+        @a[ary.pop] ||= 25
+        ary.should == [:x]
+        @a.should == { x: 15, y: 25 }
+      end
+
+      it "evaluates the index arguments in the correct order" do
+        ary = Class.new(Array) do
+          def [](x, y)
+            super(x + 3 * y)
+          end
+
+          def []=(x, y, value)
+            super(x + 3 * y, value)
+          end
+        end.new
+        ary[0, 0] = 1
+        ary[1, 0] = 1
+        ary[2, 0] = nil
+        ary[3, 0] = 1
+        ary[4, 0] = 1
+        ary[5, 0] = 1
+        ary[6, 0] = nil
+
+        foo = [0, 2]
+
+        ary[foo.pop, foo.pop] ||= 2 # expected `ary[2, 0] ||= 2`
+
+        ary[2, 0].should == 2
+        ary[6, 0].should == nil # returns the same element as `ary[0, 2]`
+      end
+
+      it 'evaluates receiver only once when assigns' do
+        ScratchPad.record []
+        @a[:k] = nil
+
+        (ScratchPad << :evaluated; @a)[:k] ||= 2
+
+        ScratchPad.recorded.should == [:evaluated]
+        @a[:k].should == 2
+      end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(h) @a = h end
+          def public_method(k, v); self[k] ||= v end
+          private
+          def [](k) @a[k] end
+          def []=(k, v) @a[k] = v; 42 end
+        end
+
+        a = klass_with_private_methods.new(k: false)
+        a.public_method(:k, 10).should == 10
+      end
+
+      context 'splatted argument' do
+        it 'correctly handles it' do
+          (@b[*[:m]] ||= 10).should == 10
+          @b[:m].should == 10
+
+          (@b[*(1; [:n])] ||= 10).should == 10
+          @b[:n].should == 10
+
+          (@b[*begin 1; [:k] end] ||= 10).should == 10
+          @b[:k].should == 10
+        end
+
+        it 'calls #to_a only once' do
+          k = Object.new
+          def k.to_a
+            ScratchPad << :to_a
+            [:k]
+          end
+
+          ScratchPad.record []
+          (@b[*k] ||= 20).should == 20
+          @b[:k].should == 20
+          ScratchPad.recorded.should == [:to_a]
+        end
+
+        it 'correctly handles a nested splatted argument' do
+          (@b[*[*[:k]]] ||= 20).should == 20
+          @b[:k].should == 20
+        end
+
+        it 'correctly handles multiple nested splatted arguments' do
+          klass_with_multiple_parameters = Class.new do
+            def [](k1, k2, k3)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"]
+            end
+
+            def []=(k1, k2, k3, v)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"] = v
+              7
+            end
+          end
+          a = klass_with_multiple_parameters.new
+
+          (a[*[:a], *[:b], *[:c]] ||= 20).should == 20
+          a[:a, :b, :c].should == 20
+        end
+      end
     end
   end
 
@@ -135,7 +320,7 @@ describe 'Optional variable assignments' do
       end
     end
 
-    describe 'using a single variable' do
+    describe 'using an accessor' do
       before do
         klass = Class.new { attr_accessor :b }
         @a    = klass.new
@@ -180,6 +365,29 @@ describe 'Optional variable assignments' do
 
         @a.b.should == 20
       end
+
+      it 'does evaluate receiver only once when assigns' do
+        ScratchPad.record []
+        @a.b = 10
+
+        (ScratchPad << :evaluated; @a).b &&= 20
+
+        ScratchPad.recorded.should == [:evaluated]
+        @a.b.should == 20
+      end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(v) @a = v end
+          def public_method(v); self.a &&= v end
+          private
+          def a; @a end
+          def a=(v) @a = v; 42 end
+        end
+
+        a = klass_with_private_methods.new(true)
+        a.public_method(10).should == 10
+      end
     end
 
     describe 'using a #[]' do
@@ -241,13 +449,128 @@ describe 'Optional variable assignments' do
       end
 
       it 'returns the assigned value, not the result of the []= method with ||=' do
-        (@b[:k] ||= 12).should == 12
+        @b[:k] = 10
+        (@b[:k] &&= 12).should == 12
+      end
+
+      it "evaluates the index precisely once" do
+        ary = [:x, :y]
+        @a[:x] = 15
+        @a[:y] = 20
+        @a[ary.pop] &&= 25
+        ary.should == [:x]
+        @a.should == { x: 15, y: 25 }
+      end
+
+      it "evaluates the index arguments in the correct order" do
+        ary = Class.new(Array) do
+          def [](x, y)
+            super(x + 3 * y)
+          end
+
+          def []=(x, y, value)
+            super(x + 3 * y, value)
+          end
+        end.new
+        ary[0, 0] = 1
+        ary[1, 0] = 1
+        ary[2, 0] = 1
+        ary[3, 0] = 1
+        ary[4, 0] = 1
+        ary[5, 0] = 1
+        ary[6, 0] = 1
+
+        foo = [0, 2]
+
+        ary[foo.pop, foo.pop] &&= 2 # expected `ary[2, 0] &&= 2`
+
+        ary[2, 0].should == 2
+        ary[6, 0].should == 1 # returns the same element as `ary[0, 2]`
+      end
+
+      it 'evaluates receiver only once when assigns' do
+        ScratchPad.record []
+        @a[:k] = 1
+
+        (ScratchPad << :evaluated; @a)[:k] &&= 2
+
+        ScratchPad.recorded.should == [:evaluated]
+        @a[:k].should == 2
       end
 
       it 'returns the assigned value, not the result of the []= method with +=' do
         @b[:k] = 17
         (@b[:k] += 12).should == 29
       end
+
+      it 'ignores method visibility when receiver is self' do
+        klass_with_private_methods = Class.new do
+          def initialize(h) @a = h end
+          def public_method(k, v); self[k] &&= v end
+          private
+          def [](k) @a[k] end
+          def []=(k, v) @a[k] = v; 42 end
+        end
+
+        a = klass_with_private_methods.new(k: true)
+        a.public_method(:k, 10).should == 10
+      end
+
+      context 'splatted argument' do
+        it 'correctly handles it' do
+          @b[:m] = 0
+          (@b[*[:m]] &&= 10).should == 10
+          @b[:m].should == 10
+
+          @b[:n] = 0
+          (@b[*(1; [:n])] &&= 10).should == 10
+          @b[:n].should == 10
+
+          @b[:k] = 0
+          (@b[*begin 1; [:k] end] &&= 10).should == 10
+          @b[:k].should == 10
+        end
+
+        it 'calls #to_a only once' do
+          k = Object.new
+          def k.to_a
+            ScratchPad << :to_a
+            [:k]
+          end
+
+          ScratchPad.record []
+          @b[:k] = 10
+          (@b[*k] &&= 20).should == 20
+          @b[:k].should == 20
+          ScratchPad.recorded.should == [:to_a]
+        end
+
+        it 'correctly handles a nested splatted argument' do
+          @b[:k] = 10
+          (@b[*[*[:k]]] &&= 20).should == 20
+          @b[:k].should == 20
+        end
+
+        it 'correctly handles multiple nested splatted arguments' do
+          klass_with_multiple_parameters = Class.new do
+            def [](k1, k2, k3)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"]
+            end
+
+            def []=(k1, k2, k3, v)
+              @hash ||= {}
+              @hash[:"#{k1}#{k2}#{k3}"] = v
+              7
+            end
+          end
+          a = klass_with_multiple_parameters.new
+
+          a[:a, :b, :c] = 10
+          (a[*[:a], *[:b], *[:c]] &&= 20).should == 20
+          a[:a, :b, :c].should == 20
+        end
+      end
     end
   end
 
@@ -296,3 +619,124 @@ describe 'Optional variable assignments' do
     end
   end
 end
+
+describe 'Optional constant assignment' do
+  describe 'with ||=' do
+    it "assigns a scoped constant if previously undefined" do
+      ConstantSpecs.should_not have_constant(:OpAssignUndefined)
+      module ConstantSpecs
+        OpAssignUndefined ||= 42
+      end
+      ConstantSpecs::OpAssignUndefined.should == 42
+      ConstantSpecs::OpAssignUndefinedOutside ||= 42
+      ConstantSpecs::OpAssignUndefinedOutside.should == 42
+      ConstantSpecs.send(:remove_const, :OpAssignUndefined)
+      ConstantSpecs.send(:remove_const, :OpAssignUndefinedOutside)
+    end
+
+    it "assigns a global constant if previously undefined" do
+      OpAssignGlobalUndefined ||= 42
+      ::OpAssignGlobalUndefinedExplicitScope ||= 42
+      OpAssignGlobalUndefined.should == 42
+      ::OpAssignGlobalUndefinedExplicitScope.should == 42
+      Object.send :remove_const, :OpAssignGlobalUndefined
+      Object.send :remove_const, :OpAssignGlobalUndefinedExplicitScope
+    end
+
+    it 'correctly defines non-existing constants' do
+      ConstantSpecs::ClassA::OR_ASSIGNED_CONSTANT1 ||= :assigned
+      ConstantSpecs::ClassA::OR_ASSIGNED_CONSTANT1.should == :assigned
+    end
+
+    it 'correctly overwrites nil constants' do
+      suppress_warning do # already initialized constant
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT1 = nil
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT1 ||= :assigned
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT1.should == :assigned
+      end
+    end
+
+    it 'causes side-effects of the module part to be applied only once (for undefined constant)' do
+      x = 0
+      (x += 1; ConstantSpecs::ClassA)::OR_ASSIGNED_CONSTANT2 ||= :assigned
+      x.should == 1
+      ConstantSpecs::ClassA::OR_ASSIGNED_CONSTANT2.should == :assigned
+    end
+
+    it 'causes side-effects of the module part to be applied only once (for nil constant)' do
+      suppress_warning do # already initialized constant
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT2 = nil
+      x = 0
+      (x += 1; ConstantSpecs::ClassA)::NIL_OR_ASSIGNED_CONSTANT2 ||= :assigned
+      x.should == 1
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT2.should == :assigned
+      end
+    end
+
+    it 'does not evaluate the right-hand side if the module part raises an exception (for undefined constant)' do
+      x = 0
+      y = 0
+
+      -> {
+        (x += 1; raise Exception; ConstantSpecs::ClassA)::OR_ASSIGNED_CONSTANT3 ||= (y += 1; :assigned)
+      }.should raise_error(Exception)
+
+      x.should == 1
+      y.should == 0
+      defined?(ConstantSpecs::ClassA::OR_ASSIGNED_CONSTANT3).should == nil
+    end
+
+    it 'does not evaluate the right-hand side if the module part raises an exception (for nil constant)' do
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT3 = nil
+      x = 0
+      y = 0
+
+      -> {
+        (x += 1; raise Exception; ConstantSpecs::ClassA)::NIL_OR_ASSIGNED_CONSTANT3 ||= (y += 1; :assigned)
+      }.should raise_error(Exception)
+
+      x.should == 1
+      y.should == 0
+      ConstantSpecs::ClassA::NIL_OR_ASSIGNED_CONSTANT3.should == nil
+    ensure
+      ConstantSpecs::ClassA.send(:remove_const, :NIL_OR_ASSIGNED_CONSTANT3)
+    end
+  end
+
+  describe "with &&=" do
+    it "re-assigns a scoped constant if already true" do
+      module ConstantSpecs
+        OpAssignTrue = true
+      end
+      suppress_warning do
+        ConstantSpecs::OpAssignTrue &&= 1
+      end
+      ConstantSpecs::OpAssignTrue.should == 1
+      ConstantSpecs.send :remove_const, :OpAssignTrue
+    end
+
+    it "leaves scoped constant if not true" do
+      module ConstantSpecs
+        OpAssignFalse = false
+      end
+      ConstantSpecs::OpAssignFalse &&= 1
+      ConstantSpecs::OpAssignFalse.should == false
+      ConstantSpecs.send :remove_const, :OpAssignFalse
+    end
+
+    it 'causes side-effects of the module part to be applied only once (when assigns)' do
+      module ConstantSpecs
+        OpAssignTrue = true
+      end
+
+      suppress_warning do # already initialized constant
+        x = 0
+        (x += 1; ConstantSpecs)::OpAssignTrue &&= :assigned
+        x.should == 1
+        ConstantSpecs::OpAssignTrue.should == :assigned
+      end
+
+      ConstantSpecs.send :remove_const, :OpAssignTrue
+    end
+  end
+end
diff --git a/spec/ruby/language/pattern_matching_spec.rb b/spec/ruby/language/pattern_matching_spec.rb
new file mode 100644
index 0000000000..c1a6f0e4d6
--- /dev/null
+++ b/spec/ruby/language/pattern_matching_spec.rb
@@ -0,0 +1,1310 @@
+require_relative '../spec_helper'
+
+describe "Pattern matching" do
+  before :each do
+    ScratchPad.record []
+  end
+
+  describe "Rightward assignment (`=>`) that can be standalone assoc operator that" do
+    it "deconstructs value" do
+      suppress_warning do
+        [0, 1] => [a, b]
+        [a, b].should == [0, 1]
+      end
+    end
+
+    it "deconstructs value and properly scopes variables" do
+      suppress_warning do
+        a = nil
+        1.times {
+          [0, 1] => [a, b]
+        }
+        [a, defined?(b)].should == [0, nil]
+      end
+    end
+
+    it "can work with keywords" do
+      { a: 0, b: 1 } => { a:, b: }
+      [a, b].should == [0, 1]
+    end
+  end
+
+  describe "One-line pattern matching" do
+    it "can be used to check if a pattern matches for Array-like entities" do
+      ([0, 1] in [a, b]).should == true
+      ([0, 1] in [a, b, c]).should == false
+    end
+
+    it "can be used to check if a pattern matches for Hash-like entities" do
+      ({ a: 0, b: 1 } in { a:, b: }).should == true
+      ({ a: 0, b: 1 } in { a:, b:, c: }).should == false
+    end
+  end
+
+  describe "find pattern" do
+    it "captures preceding elements to the pattern" do
+      case [0, 1, 2, 3]
+      in [*pre, 2, 3]
+        pre
+      else
+        false
+      end.should == [0, 1]
+    end
+
+    it "captures following elements to the pattern" do
+      case [0, 1, 2, 3]
+      in [0, 1, *post]
+        post
+      else
+        false
+      end.should == [2, 3]
+    end
+
+    it "captures both preceding and following elements to the pattern" do
+      case [0, 1, 2, 3, 4]
+      in [*pre, 2, *post]
+        [pre, post]
+      else
+        false
+      end.should == [[0, 1], [3, 4]]
+    end
+
+    it "can capture the entirety of the pattern" do
+      case [0, 1, 2, 3, 4]
+      in [*everything]
+        everything
+      else
+        false
+      end.should == [0, 1, 2, 3, 4]
+    end
+
+    it "will match an empty Array-like structure" do
+      case []
+      in [*everything]
+        everything
+      else
+        false
+      end.should == []
+    end
+
+    it "can be nested" do
+      case [0, [2, 4, 6], [3, 9, 27], [4, 16, 64]]
+      in [*pre, [*, 9, a], *post]
+        [pre, post, a]
+      else
+        false
+      end.should == [[0, [2, 4, 6]], [[4, 16, 64]], 27]
+    end
+
+    it "can be nested with an array pattern" do
+      case [0, [2, 4, 6], [3, 9, 27], [4, 16, 64]]
+      in [_, _, [*, 9, *], *post]
+        post
+      else
+        false
+      end.should == [[4, 16, 64]]
+    end
+
+    it "can be nested within a hash pattern" do
+      case {a: [3, 9, 27]}
+      in {a: [*, 9, *post]}
+        post
+      else
+        false
+      end.should == [27]
+    end
+
+    it "can nest hash and array patterns" do
+      case [0, {a: 42, b: [0, 1]}, {a: 42, b: [1, 2]}]
+      in [*, {a:, b: [1, c]}, *]
+        [a, c]
+      else
+        false
+      end.should == [42, 2]
+    end
+  end
+
+  it "extends case expression with case/in construction" do
+    case [0, 1]
+    in [0]
+      :foo
+    in [0, 1]
+      :bar
+    end.should == :bar
+  end
+
+  it "allows using then operator" do
+    case [0, 1]
+    in [0] then :foo
+    in [0, 1] then :bar
+    end.should == :bar
+  end
+
+  describe "warning" do
+    before :each do
+      @experimental, Warning[:experimental] = Warning[:experimental], true
+    end
+
+    after :each do
+      Warning[:experimental] = @experimental
+    end
+
+    context 'when regular form' do
+      before :each do
+        @src = 'case [0, 1]; in [a, b]; end'
+      end
+
+      it "does not warn about pattern matching is experimental feature" do
+        -> { eval @src }.should_not complain
+      end
+    end
+
+    context 'when one-line form' do
+      before :each do
+        @src = '[0, 1] => [a, b]'
+      end
+
+      it "does not warn about pattern matching is experimental feature" do
+        -> { eval @src }.should_not complain
+      end
+    end
+  end
+
+  it "binds variables" do
+    case [0, 1]
+    in [0, a]
+      a
+    end.should == 1
+  end
+
+  it "cannot mix in and when operators" do
+    -> {
+      eval <<~RUBY
+        case []
+        when 1 == 1
+        in []
+        end
+      RUBY
+    }.should raise_error(SyntaxError, /syntax error, unexpected `in'|\(eval\):3: syntax error, unexpected keyword_in|unexpected 'in'/)
+
+    -> {
+      eval <<~RUBY
+        case []
+        in []
+        when 1 == 1
+        end
+      RUBY
+    }.should raise_error(SyntaxError, /syntax error, unexpected `when'|\(eval\):3: syntax error, unexpected keyword_when|unexpected 'when'/)
+  end
+
+  it "checks patterns until the first matching" do
+    case [0, 1]
+    in [0]
+      :foo
+    in [0, 1]
+      :bar
+    in [0, 1]
+      :baz
+    end.should == :bar
+  end
+
+  it "executes else clause if no pattern matches" do
+    case [0, 1]
+    in [0]
+      true
+    else
+      false
+    end.should == false
+  end
+
+  it "raises NoMatchingPatternError if no pattern matches and no else clause" do
+    -> {
+      case [0, 1]
+      in [0]
+      end
+    }.should raise_error(NoMatchingPatternError, /\[0, 1\]/)
+
+    error_pattern = ruby_version_is("3.4") ? /\{a: 0, b: 1\}/ : /\{:a=>0, :b=>1\}/
+    -> {
+      case {a: 0, b: 1}
+      in a: 1, b: 1
+      end
+    }.should raise_error(NoMatchingPatternError, error_pattern)
+  end
+
+  it "raises NoMatchingPatternError if no pattern matches and evaluates the expression only once" do
+    evals = 0
+    -> {
+      case (evals += 1; [0, 1])
+      in [0]
+      end
+    }.should raise_error(NoMatchingPatternError, /\[0, 1\]/)
+    evals.should == 1
+  end
+
+  it "does not allow calculation or method calls in a pattern" do
+    -> {
+      eval <<~RUBY
+        case 0
+        in 1 + 1
+          true
+        end
+      RUBY
+    }.should raise_error(SyntaxError, /unexpected|expected a delimiter after the patterns of an `in` clause/)
+  end
+
+  it "evaluates the case expression once for multiple patterns, caching the result" do
+    case (ScratchPad << :foo; 1)
+    in 0
+      false
+    in 1
+      true
+    end.should == true
+
+    ScratchPad.recorded.should == [:foo]
+  end
+
+  describe "guards" do
+    it "supports if guard" do
+      case 0
+      in 0 if false
+        true
+      else
+        false
+      end.should == false
+
+      case 0
+      in 0 if true
+        true
+      else
+        false
+      end.should == true
+    end
+
+    it "supports unless guard" do
+      case 0
+      in 0 unless true
+        true
+      else
+        false
+      end.should == false
+
+      case 0
+      in 0 unless false
+        true
+      else
+        false
+      end.should == true
+    end
+
+    it "makes bound variables visible in guard" do
+      case [0, 1]
+      in [a, 1] if a >= 0
+        true
+      end.should == true
+    end
+
+    it "does not evaluate guard if pattern does not match" do
+      case 0
+      in 1 if (ScratchPad << :foo) || true
+      else
+      end
+
+      ScratchPad.recorded.should == []
+    end
+
+    it "takes guards into account when there are several matching patterns" do
+      case 0
+      in 0 if false
+        :foo
+      in 0 if true
+        :bar
+      end.should == :bar
+    end
+
+    it "executes else clause if no guarded pattern matches" do
+      case 0
+      in 0 if false
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "raises NoMatchingPatternError if no guarded pattern matches and no else clause" do
+      -> {
+        case [0, 1]
+        in [0, 1] if false
+        end
+      }.should raise_error(NoMatchingPatternError, /\[0, 1\]/)
+    end
+  end
+
+  describe "value pattern" do
+    it "matches an object such that pattern === object" do
+      case 0
+      in 0
+        true
+      end.should == true
+
+      case 0
+      in (
+        -1..1)
+        true
+      end.should == true
+
+      case 0
+      in Integer
+        true
+      end.should == true
+
+      case "0"
+      in /0/
+        true
+      end.should == true
+
+      case "0"
+      in -> s { s == "0" }
+        true
+      end.should == true
+    end
+
+    it "allows string literal with interpolation" do
+      x = "x"
+
+      case "x"
+      in "#{x + ""}"
+        true
+      end.should == true
+    end
+  end
+
+  describe "variable pattern" do
+    it "matches a value and binds variable name to this value" do
+      case 0
+      in a
+        a
+      end.should == 0
+    end
+
+    it "makes bounded variable visible outside a case statement scope" do
+      case 0
+      in a
+      end
+
+      a.should == 0
+    end
+
+    it "create local variables even if a pattern doesn't match" do
+      case 0
+      in a
+      in b
+      in c
+      end
+
+      [a, b, c].should == [0, nil, nil]
+    end
+
+    it "allow using _ name to drop values" do
+      case [0, 1]
+      in [a, _]
+        a
+      end.should == 0
+    end
+
+    it "supports using _ in a pattern several times" do
+      case [0, 1, 2]
+      in [0, _, _]
+        true
+      end.should == true
+    end
+
+    it "supports using any name with _ at the beginning in a pattern several times" do
+      case [0, 1, 2]
+      in [0, _x, _x]
+        true
+      end.should == true
+
+      case {a: 0, b: 1, c: 2}
+      in {a: 0, b: _x, c: _x}
+        true
+      end.should == true
+    end
+
+    it "does not support using variable name (except _) several times" do
+      -> {
+        eval <<~RUBY
+          case [0]
+          in [a, a]
+          end
+        RUBY
+      }.should raise_error(SyntaxError, /duplicated variable name/)
+    end
+
+    it "supports existing variables in a pattern specified with ^ operator" do
+      a = 0
+
+      case 0
+      in ^a
+        true
+      end.should == true
+    end
+
+    it "allows applying ^ operator to bound variables" do
+      case [1, 1]
+      in [n, ^n]
+        n
+      end.should == 1
+
+      case [1, 2]
+      in [n, ^n]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "requires bound variable to be specified in a pattern before ^ operator when it relies on a bound variable" do
+      -> {
+        eval <<~RUBY
+          case [1, 2]
+          in [^n, n]
+            true
+          else
+            false
+          end
+        RUBY
+      }.should raise_error(SyntaxError, /n: no such local variable/)
+    end
+  end
+
+  describe "alternative pattern" do
+    it "matches if any of patterns matches" do
+      case 0
+      in 0 | 1 | 2
+        true
+      end.should == true
+    end
+
+    it "does not support variable binding" do
+      -> {
+        eval <<~RUBY
+          case [0, 1]
+          in [0, 0] | [0, a]
+          end
+        RUBY
+      }.should raise_error(SyntaxError)
+    end
+
+    it "support underscore prefixed variables in alternation" do
+      case [0, 1]
+      in [1, _]
+        false
+      in [0, 0] | [0, _a]
+        true
+      end.should == true
+    end
+
+    it "can be used as a nested pattern" do
+      case [[1], ["2"]]
+      in [[0] | nil, _]
+        false
+      in [[1], [1]]
+        false
+      in [[1], [2 | "2"]]
+        true
+      end.should == true
+
+      case [1, 2]
+      in [0, _] | {a: 0}
+        false
+      in {a: 1, b: 2} | [1, 2]
+        true
+      end.should == true
+    end
+  end
+
+  describe "AS pattern" do
+    it "binds a variable to a value if pattern matches" do
+      case 0
+      in Integer => n
+        n
+      end.should == 0
+    end
+
+    it "can be used as a nested pattern" do
+      case [1, [2, 3]]
+      in [1, Array => ary]
+        ary
+      end.should == [2, 3]
+    end
+  end
+
+  describe "Array pattern" do
+    it "supports form Constant(pat, pat, ...)" do
+      case [0, 1, 2]
+      in Array(0, 1, 2)
+        true
+      end.should == true
+    end
+
+    it "supports form Constant[pat, pat, ...]" do
+      case [0, 1, 2]
+      in Array[0, 1, 2]
+        true
+      end.should == true
+    end
+
+    it "supports form [pat, pat, ...]" do
+      case [0, 1, 2]
+      in [0, 1, 2]
+        true
+      end.should == true
+    end
+
+    it "supports form pat, pat, ..." do
+      case [0, 1, 2]
+      in 0, 1, 2
+        true
+      end.should == true
+
+      case [0, 1, 2]
+      in 0, a, 2
+        a
+      end.should == 1
+
+      case [0, 1, 2]
+      in 0, *rest
+        rest
+      end.should == [1, 2]
+    end
+
+    it "matches an object with #deconstruct method which returns an array and each element in array matches element in pattern" do
+      obj = Object.new
+
+      def obj.deconstruct
+        [0, 1]
+      end
+
+      case obj
+      in [Integer, Integer]
+        true
+      end.should == true
+    end
+
+    it "calls #deconstruct once for multiple patterns, caching the result" do
+      obj = Object.new
+
+      def obj.deconstruct
+        ScratchPad << :deconstruct
+        [0, 1]
+      end
+
+      case obj
+      in [1, 2]
+        false
+      in [0, 1]
+        true
+      end.should == true
+
+      ScratchPad.recorded.should == [:deconstruct]
+    end
+
+    it "calls #deconstruct even on objects that are already an array" do
+      obj = [1, 2]
+
+      def obj.deconstruct
+        ScratchPad << :deconstruct
+        [3, 4]
+      end
+
+      case obj
+      in [3, 4]
+        true
+      else
+        false
+      end.should == true
+
+      ScratchPad.recorded.should == [:deconstruct]
+    end
+
+    it "does not match object if Constant === object returns false" do
+      case [0, 1, 2]
+      in String[0, 1, 2]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "checks Constant === object before calling #deconstruct" do
+      c1 = Class.new
+      obj = c1.new
+      obj.should_not_receive(:deconstruct)
+
+      case obj
+      in String[1]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "does not match object without #deconstruct method" do
+      obj = Object.new
+      obj.should_receive(:respond_to?).with(:deconstruct)
+
+      case obj
+      in Object[]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "raises TypeError if #deconstruct method does not return array" do
+      obj = Object.new
+
+      def obj.deconstruct
+        ""
+      end
+
+      -> {
+        case obj
+        in Object[]
+        else
+        end
+      }.should raise_error(TypeError, /deconstruct must return Array/)
+    end
+
+    it "accepts a subclass of Array from #deconstruct" do
+      obj = Object.new
+
+      def obj.deconstruct
+        Class.new(Array).new([0, 1])
+      end
+
+      case obj
+      in [1, 2]
+        false
+      in [0, 1]
+        true
+      end.should == true
+    end
+
+    it "does not match object if elements of array returned by #deconstruct method does not match elements in pattern" do
+      obj = Object.new
+
+      def obj.deconstruct
+        [1]
+      end
+
+      case obj
+      in Object[0]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "binds variables" do
+      case [0, 1, 2]
+      in [a, b, c]
+        [a, b, c]
+      end.should == [0, 1, 2]
+    end
+
+    it "supports splat operator *rest" do
+      case [0, 1, 2]
+      in [0, *rest]
+        rest
+      end.should == [1, 2]
+    end
+
+    it "does not match partially by default" do
+      case [0, 1, 2, 3]
+      in [1, 2]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "does match partially from the array beginning if list + , syntax used" do
+      case [0, 1, 2, 3]
+      in [0, 1, ]
+        true
+      end.should == true
+
+      case [0, 1, 2, 3]
+      in 0, 1,;
+        true
+      end.should == true
+    end
+
+    it "matches [] with []" do
+      case []
+      in []
+        true
+      end.should == true
+    end
+
+    it "matches anything with *" do
+      case [0, 1]
+      in *;
+        true
+      end.should == true
+    end
+
+    it "can be used as a nested pattern" do
+      case [[1], ["2"]]
+      in [[0] | nil, _]
+        false
+      in [[1], [1]]
+        false
+      in [[1], [2 | "2"]]
+        true
+      end.should == true
+
+      case [1, 2]
+      in [0, _] | {a: 0}
+        false
+      in {a: 1, b: 2} | [1, 2]
+        true
+      end.should == true
+    end
+  end
+
+  describe "Hash pattern" do
+    it "supports form Constant(id: pat, id: pat, ...)" do
+      case {a: 0, b: 1}
+      in Hash(a: 0, b: 1)
+        true
+      end.should == true
+    end
+
+    it "supports form Constant[id: pat, id: pat, ...]" do
+      case {a: 0, b: 1}
+      in Hash[a: 0, b: 1]
+        true
+      end.should == true
+    end
+
+    it "supports form {id: pat, id: pat, ...}" do
+      case {a: 0, b: 1}
+      in {a: 0, b: 1}
+        true
+      end.should == true
+    end
+
+    it "supports form id: pat, id: pat, ..." do
+      case {a: 0, b: 1}
+      in a: 0, b: 1
+        true
+      end.should == true
+
+      case {a: 0, b: 1}
+      in a: a, b: b
+        [a, b]
+      end.should == [0, 1]
+
+      case {a: 0, b: 1, c: 2}
+      in a: 0, **rest
+        rest
+      end.should == {b: 1, c: 2}
+    end
+
+    it "supports a: which means a: a" do
+      case {a: 0, b: 1}
+      in Hash(a:, b:)
+        [a, b]
+      end.should == [0, 1]
+
+      a = b = nil
+
+      case {a: 0, b: 1}
+      in Hash[a:, b:]
+        [a, b]
+      end.should == [0, 1]
+
+      a = b = nil
+
+      case {a: 0, b: 1}
+      in {a:, b:}
+        [a, b]
+      end.should == [0, 1]
+
+      a = nil
+
+      case {a: 0, b: 1, c: 2}
+      in {a:, **rest}
+        [a, rest]
+      end.should == [0, {b: 1, c: 2}]
+
+      a = b = nil
+
+      case {a: 0, b: 1}
+      in a:, b:
+        [a, b]
+      end.should == [0, 1]
+    end
+
+    it "can mix key (a:) and key-value (a: b) declarations" do
+      case {a: 0, b: 1}
+      in Hash(a:, b: x)
+        [a, x]
+      end.should == [0, 1]
+    end
+
+    it "supports 'string': key literal" do
+      case {a: 0}
+      in {"a": 0}
+        true
+      end.should == true
+    end
+
+    it "does not support non-symbol keys" do
+      -> {
+        eval <<~RUBY
+          case {a: 1}
+          in {"a" => 1}
+          end
+        RUBY
+      }.should raise_error(SyntaxError, /unexpected|expected a label as the key in the hash pattern/)
+    end
+
+    it "does not support string interpolation in keys" do
+      -> {
+        eval <<~'RUBY'
+          case {a: 1}
+          in {"#{x}": 1}
+          end
+        RUBY
+      }.should raise_error(SyntaxError, /symbol literal with interpolation is not allowed|expected a label as the key in the hash pattern/)
+    end
+
+    it "raise SyntaxError when keys duplicate in pattern" do
+      -> {
+        eval <<~RUBY
+          case {a: 1}
+          in {a: 1, b: 2, a: 3}
+          end
+        RUBY
+      }.should raise_error(SyntaxError, /duplicated key name/)
+    end
+
+    it "matches an object with #deconstruct_keys method which returns a Hash with equal keys and each value in Hash matches value in pattern" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*)
+        {a: 1}
+      end
+
+      case obj
+      in {a: 1}
+        true
+      end.should == true
+    end
+
+    it "calls #deconstruct_keys per pattern" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*)
+        ScratchPad << :deconstruct_keys
+        {a: 1}
+      end
+
+      case obj
+      in {b: 1}
+        false
+      in {a: 1}
+        true
+      end.should == true
+
+      ScratchPad.recorded.should == [:deconstruct_keys, :deconstruct_keys]
+    end
+
+    it "does not match object if Constant === object returns false" do
+      case {a: 1}
+      in String[a: 1]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "checks Constant === object before calling #deconstruct_keys" do
+      c1 = Class.new
+      obj = c1.new
+      obj.should_not_receive(:deconstruct_keys)
+
+      case obj
+      in String(a: 1)
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "does not match object without #deconstruct_keys method" do
+      obj = Object.new
+      obj.should_receive(:respond_to?).with(:deconstruct_keys)
+
+      case obj
+      in Object[a: 1]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "does not match object if #deconstruct_keys method does not return Hash" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*)
+        ""
+      end
+
+      -> {
+        case obj
+        in Object[a: 1]
+        end
+      }.should raise_error(TypeError, /deconstruct_keys must return Hash/)
+    end
+
+    it "does not match object if #deconstruct_keys method returns Hash with non-symbol keys" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*)
+        {"a" => 1}
+      end
+
+      case obj
+      in Object[a: 1]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "does not match object if elements of Hash returned by #deconstruct_keys method does not match values in pattern" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*)
+        {a: 1}
+      end
+
+      case obj
+      in Object[a: 2]
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "passes keys specified in pattern as arguments to #deconstruct_keys method" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*args)
+        ScratchPad << args
+        {a: 1, b: 2, c: 3}
+      end
+
+      case obj
+      in Object[a: 1, b: 2, c: 3]
+      end
+
+      ScratchPad.recorded.sort.should == [[[:a, :b, :c]]]
+    end
+
+    it "passes keys specified in pattern to #deconstruct_keys method if pattern contains double splat operator **" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*args)
+        ScratchPad << args
+        {a: 1, b: 2, c: 3}
+      end
+
+      case obj
+      in Object[a: 1, b: 2, **]
+      end
+
+      ScratchPad.recorded.sort.should == [[[:a, :b]]]
+    end
+
+    it "passes nil to #deconstruct_keys method if pattern contains double splat operator **rest" do
+      obj = Object.new
+
+      def obj.deconstruct_keys(*args)
+        ScratchPad << args
+        {a: 1, b: 2}
+      end
+
+      case obj
+      in Object[a: 1, **rest]
+      end
+
+      ScratchPad.recorded.should == [[nil]]
+    end
+
+    it "binds variables" do
+      case {a: 0, b: 1, c: 2}
+      in {a: x, b: y, c: z}
+        [x, y, z]
+      end.should == [0, 1, 2]
+    end
+
+    it "supports double splat operator **rest" do
+      case {a: 0, b: 1, c: 2}
+      in {a: 0, **rest}
+        rest
+      end.should == {b: 1, c: 2}
+    end
+
+    it "treats **nil like there should not be any other keys in a matched Hash" do
+      case {a: 1, b: 2}
+      in {a: 1, b: 2, **nil}
+        true
+      end.should == true
+
+      case {a: 1, b: 2}
+      in {a: 1, **nil}
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "can match partially" do
+      case {a: 1, b: 2}
+      in {a: 1}
+        true
+      end.should == true
+    end
+
+    it "matches {} with {}" do
+      case {}
+      in {}
+        true
+      end.should == true
+    end
+
+    it "in {} only matches empty hashes" do
+      case {a: 1}
+      in {}
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "in {**nil} only matches empty hashes" do
+      case {}
+      in {**nil}
+        true
+      else
+        false
+      end.should == true
+
+      case {a: 1}
+      in {**nil}
+        true
+      else
+        false
+      end.should == false
+    end
+
+    it "matches anything with **" do
+      case {a: 1}
+      in **;
+        true
+      end.should == true
+    end
+
+    it "can be used as a nested pattern" do
+      case {a: {a: 1, b: 1}, b: {a: 1, b: 2}}
+      in {a: {a: 0}}
+        false
+      in {a: {a: 1}, b: {b: 1}}
+        false
+      in {a: {a: 1}, b: {b: 2} }
+        true
+      end.should == true
+
+      case [{a: 1, b: [1]}, {a: 1, c: ["2"]}]
+      in [{a:, c:}, ]
+        false
+      in [{a: 1, b:}, {a: 1, c: [Integer]}]
+        false
+      in [_, {a: 1, c: [String]}]
+        true
+      end.should == true
+    end
+  end
+
+  describe "refinements" do
+    it "are used for #deconstruct" do
+      refinery = Module.new do
+        refine Array do
+          def deconstruct
+            [0]
+          end
+        end
+      end
+
+      result = nil
+      Module.new do
+        using refinery
+
+        result =
+          case []
+          in [0]
+            true
+          end
+      end
+
+      result.should == true
+    end
+
+    it "are used for #deconstruct_keys" do
+      refinery = Module.new do
+        refine Hash do
+          def deconstruct_keys(_)
+            {a: 0}
+          end
+        end
+      end
+
+      result = nil
+      Module.new do
+        using refinery
+
+        result =
+          case {}
+          in a: 0
+            true
+          end
+      end
+
+      result.should == true
+    end
+
+    it "are used for #=== in constant pattern" do
+      refinery = Module.new do
+        refine Array.singleton_class do
+          def ===(obj)
+            obj.is_a?(Hash)
+          end
+        end
+      end
+
+      result = nil
+      Module.new do
+        using refinery
+
+        result =
+          case {}
+          in Array
+            true
+          end
+      end
+
+      result.should == true
+    end
+  end
+
+  describe "Ruby 3.1 improvements" do
+    it "can omit parentheses in one line pattern matching" do
+      [1, 2] => a, b
+      [a, b].should == [1, 2]
+
+      {a: 1} => a:
+      a.should == 1
+    end
+
+    it "supports pinning instance variables" do
+      @a = /a/
+      case 'abc'
+      in ^@a
+        true
+      end.should == true
+    end
+
+    it "supports pinning class variables" do
+      result = nil
+      Module.new do
+        # avoid "class variable access from toplevel" runtime error with #module_eval
+        result = module_eval(<<~RUBY)
+          @@a = 0..10
+
+          case 2
+          in ^@@a
+            true
+          end
+        RUBY
+      end
+
+      result.should == true
+    end
+
+    it "supports pinning global variables" do
+      $a = /a/
+      case 'abc'
+      in ^$a
+        true
+      end.should == true
+    end
+
+    it "supports pinning expressions" do
+      case 'abc'
+      in ^(/a/)
+        true
+      end.should == true
+
+      case 0
+      in ^(0 + 0)
+        true
+      end.should == true
+    end
+
+    it "supports pinning expressions in array pattern" do
+      case [3]
+      in [^(1 + 2)]
+        true
+      end.should == true
+    end
+
+    it "supports pinning expressions in hash pattern" do
+      case {name: '2.6', released_at: Time.new(2018, 12, 25)}
+      in {released_at: ^(Time.new(2010)..Time.new(2020))}
+        true
+      end.should == true
+    end
+  end
+
+  describe "value in pattern" do
+    it "returns true if the pattern matches" do
+      (1 in 1).should == true
+
+      (1 in Integer).should == true
+
+      e = nil
+      ([1, 2] in [1, e]).should == true
+      e.should == 2
+
+      k = nil
+      ({k: 1} in {k:}).should == true
+      k.should == 1
+    end
+
+    it "returns false if the pattern does not match" do
+      (1 in 2).should == false
+
+      (1 in Float).should == false
+
+      ([1, 2] in [2, e]).should == false
+
+      ({k: 1} in {k: 2}).should == false
+    end
+  end
+end
diff --git a/spec/ruby/language/precedence_spec.rb b/spec/ruby/language/precedence_spec.rb
index 5a3c2861ce..5e606c16d8 100644
--- a/spec/ruby/language/precedence_spec.rb
+++ b/spec/ruby/language/precedence_spec.rb
@@ -14,46 +14,44 @@ require_relative 'fixtures/precedence'
 # the level below (as well as showing associativity within
 # the precedence level).
 
-=begin
-Excerpted from 'Programming Ruby: The Pragmatic Programmer's Guide'
-Second Edition by Dave Thomas, Chad Fowler, and Andy Hunt, page 324
-
-Table 22.4. Ruby operators (high to low precedence)
-Method   Operator                  Description
------------------------------------------------------------------------
-         :: .
- x*      [ ] [ ]=                  Element reference, element set
- x       **                        Exponentiation
- x       ! ~ + -                   Not, complement, unary plus and minus
-                                   (method names for the last two are +@ and -@)
- x       * / %                     Multiply, divide, and modulo
- x       + -                       Plus and minus
- x       >> <<                     Right and left shift
- x       &                         “And” (bitwise for integers)
- x       ^ |                       Exclusive “or” and regular “or” (bitwise for integers)
- x       <= < > >=                 Comparison operators
- x       <=> == === != =~ !~       Equality and pattern match operators (!=
-                                   and !~ may not be defined as methods)
-         &&                        Logical “and”
-         ||                        Logical “or”
-         .. ...                    Range (inclusive and exclusive)
-         ? :                       Ternary if-then-else
-         = %= /= -= += |= &=       Assignment
-         >>= <<= *= &&= ||= **=
-         defined?                  Check if symbol defined
-         not                       Logical negation
-         or and                    Logical composition
-         if unless while until     Expression modifiers
-         begin/end                 Block expression
------------------------------------------------------------------------
-
-* Operators marked with 'x' in the Method column are implemented as methods
-and can be overridden (except != and !~ as noted). (But see the specs
-below for implementations that define != and !~ as methods.)
-
-** These are not included in the excerpted table but are shown here for
-completeness.
-=end
+# Excerpted from 'Programming Ruby: The Pragmatic Programmer's Guide'
+# Second Edition by Dave Thomas, Chad Fowler, and Andy Hunt, page 324
+#
+# Table 22.4. Ruby operators (high to low precedence)
+# Method   Operator                  Description
+# -----------------------------------------------------------------------
+#          :: .
+#  x*      [ ] [ ]=                  Element reference, element set
+#  x       **                        Exponentiation
+#  x       ! ~ + -                   Not, complement, unary plus and minus
+#                                    (method names for the last two are +@ and -@)
+#  x       * / %                     Multiply, divide, and modulo
+#  x       + -                       Plus and minus
+#  x       >> <<                     Right and left shift
+#  x       &                         “And” (bitwise for integers)
+#  x       ^ |                       Exclusive “or” and regular “or” (bitwise for integers)
+#  x       <= < > >=                 Comparison operators
+#  x       <=> == === != =~ !~       Equality and pattern match operators (!=
+#                                    and !~ may not be defined as methods)
+#          &&                        Logical “and”
+#          ||                        Logical “or”
+#          .. ...                    Range (inclusive and exclusive)
+#          ? :                       Ternary if-then-else
+#          = %= /= -= += |= &=       Assignment
+#          >>= <<= *= &&= ||= **=
+#          defined?                  Check if symbol defined
+#          not                       Logical negation
+#          or and                    Logical composition
+#          if unless while until     Expression modifiers
+#          begin/end                 Block expression
+# -----------------------------------------------------------------------
+#
+# * Operators marked with 'x' in the Method column are implemented as methods
+# and can be overridden (except != and !~ as noted). (But see the specs
+# below for implementations that define != and !~ as methods.)
+#
+# ** These are not included in the excerpted table but are shown here for
+# completeness.
 
 # -----------------------------------------------------------------------
 # It seems that this table is not correct anymore
@@ -296,14 +294,14 @@ describe "Operators" do
     -> { eval("1...2...3")  }.should raise_error(SyntaxError)
   end
 
- it ".. ... have higher precedence than ? :" do
-   # Use variables to avoid warnings
-   from = 1
-   to = 2
-   # These are flip-flop, not Range instances
-   (from..to ? 3 : 4).should == 3
-   (from...to ? 3 : 4).should == 3
- end
+  it ".. ... have higher precedence than ? :" do
+    # Use variables to avoid warnings
+    from = 1
+    to = 2
+    # These are flip-flop, not Range instances
+    (from..to ? 3 : 4).should == 3
+    (from...to ? 3 : 4).should == 3
+  end
 
   it "? : is right-associative" do
     (true ? 2 : 3 ? 4 : 5).should == 2
diff --git a/spec/ruby/language/predefined_spec.rb b/spec/ruby/language/predefined_spec.rb
index 90ea8c6bb1..fc1667a38f 100644
--- a/spec/ruby/language/predefined_spec.rb
+++ b/spec/ruby/language/predefined_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../spec_helper'
+require_relative '../core/exception/shared/set_backtrace'
 require 'stringio'
 
 # The following tables are excerpted from Programming Ruby: The Pragmatic Programmer's Guide'
@@ -7,37 +8,33 @@ require 'stringio'
 # Entries marked [r/o] are read-only and an error will be raised of the program attempts to
 # modify them. Entries marked [thread] are thread local.
 
-=begin
-Exception Information
----------------------------------------------------------------------------------------------------
-
-$!               Exception       The exception object passed to raise. [thread]
-$@               Array           The stack backtrace generated by the last exception. [thread]
-=end
-
-=begin
-Pattern Matching Variables
----------------------------------------------------------------------------------------------------
-
-These variables are set to nil after an unsuccessful pattern match.
-
-$&               String          The string matched (following a successful pattern match). This variable is
-                                 local to the current scope. [r/o, thread]
-$+               String          The contents of the highest-numbered group matched following a successful
-                                 pattern match. Thus, in "cat" =~/(c|a)(t|z)/, $+ will be set to “t”. This
-                                 variable is local to the current scope. [r/o, thread]
-$`               String          The string preceding the match in a successful pattern match. This variable
-                                 is local to the current scope. [r/o, thread]
-$'               String          The string following the match in a successful pattern match. This variable
-                                 is local to the current scope. [r/o, thread]
-$1 to $<N>       String          The contents of successive groups matched in a successful pattern match. In
-                                 "cat" =~/(c|a)(t|z)/, $1 will be set to “a” and $2 to “t”. This variable
-                                 is local to the current scope. [r/o, thread]
-$~               MatchData       An object that encapsulates the results of a successful pattern match. The
-                                 variables $&, $`, $', and $1 to $<N> are all derived from $~. Assigning to $~
-                                 changes the values of these derived variables. This variable is local to the
-                                 current scope. [thread]
-=end
+# Exception Information
+# ---------------------------------------------------------------------------------------------------
+#
+# $!               Exception       The exception object passed to raise. [thread]
+# $@               Array           The stack backtrace generated by the last exception. [thread]
+
+# Pattern Matching Variables
+# ---------------------------------------------------------------------------------------------------
+#
+# These variables are set to nil after an unsuccessful pattern match.
+#
+# $&               String          The string matched (following a successful pattern match). This variable is
+#                                  local to the current scope. [r/o, thread]
+# $+               String          The contents of the highest-numbered group matched following a successful
+#                                  pattern match. Thus, in "cat" =~/(c|a)(t|z)/, $+ will be set to “t”. This
+#                                  variable is local to the current scope. [r/o, thread]
+# $`               String          The string preceding the match in a successful pattern match. This variable
+#                                  is local to the current scope. [r/o, thread]
+# $'               String          The string following the match in a successful pattern match. This variable
+#                                  is local to the current scope. [r/o, thread]
+# $1 to $<N>       String          The contents of successive groups matched in a successful pattern match. In
+#                                  "cat" =~/(c|a)(t|z)/, $1 will be set to “a” and $2 to “t”. This variable
+#                                  is local to the current scope. [r/o, thread]
+# $~               MatchData       An object that encapsulates the results of a successful pattern match. The
+#                                  variables $&, $`, $', and $1 to $<N> are all derived from $~. Assigning to $~
+#                                  changes the values of these derived variables. This variable is local to the
+#                                  current scope. [thread]
 
 
 describe "Predefined global $~" do
@@ -53,10 +50,10 @@ describe "Predefined global $~" do
 
   it "is set to nil if the last match was unsuccessful" do
     /foo/ =~ 'foo'
-    $~.nil?.should == false
+    $~.should_not.nil?
 
     /foo/ =~ 'bar'
-    $~.nil?.should == true
+    $~.should.nil?
   end
 
   it "is set at the method-scoped level rather than block-scoped" do
@@ -75,7 +72,7 @@ describe "Predefined global $~" do
     match2.should_not == nil
     $~.should == match2
 
-    eval 'match3 = /baz/.match("baz")'
+    match3 = /baz/.match("baz")
 
     match3.should_not == nil
     $~.should == match3
@@ -92,8 +89,8 @@ describe "Predefined global $~" do
     $~ = /foo/.match("foo")
     $~.should be_an_instance_of(MatchData)
 
-    -> { $~ = Object.new }.should raise_error(TypeError)
-    -> { $~ = 1 }.should raise_error(TypeError)
+    -> { $~ = Object.new }.should raise_error(TypeError, 'wrong argument type Object (expected MatchData)')
+    -> { $~ = 1 }.should raise_error(TypeError, 'wrong argument type Integer (expected MatchData)')
   end
 
   it "changes the value of derived capture globals when assigned" do
@@ -137,9 +134,22 @@ describe "Predefined global $&" do
   end
 
   it "sets the encoding to the encoding of the source String" do
-    "abc".force_encoding(Encoding::EUC_JP) =~ /b/
+    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
     $&.encoding.should equal(Encoding::EUC_JP)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$& = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$&/)
+  end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_ampersand $&
+    -> {
+      $predefined_spec_ampersand = ""
+    }.should raise_error(NameError, '$predefined_spec_ampersand is a read-only variable')
+  end
 end
 
 describe "Predefined global $`" do
@@ -150,14 +160,27 @@ describe "Predefined global $`" do
   end
 
   it "sets the encoding to the encoding of the source String" do
-    "abc".force_encoding(Encoding::EUC_JP) =~ /b/
+    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
     $`.encoding.should equal(Encoding::EUC_JP)
   end
 
   it "sets an empty result to the encoding of the source String" do
-    "abc".force_encoding(Encoding::ISO_8859_1) =~ /a/
+    "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /a/
     $`.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$` = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$`/)
+  end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_backquote $`
+    -> {
+      $predefined_spec_backquote = ""
+    }.should raise_error(NameError, '$predefined_spec_backquote is a read-only variable')
+  end
 end
 
 describe "Predefined global $'" do
@@ -168,14 +191,27 @@ describe "Predefined global $'" do
   end
 
   it "sets the encoding to the encoding of the source String" do
-    "abc".force_encoding(Encoding::EUC_JP) =~ /b/
+    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /b/
     $'.encoding.should equal(Encoding::EUC_JP)
   end
 
   it "sets an empty result to the encoding of the source String" do
-    "abc".force_encoding(Encoding::ISO_8859_1) =~ /c/
+    "abc".dup.force_encoding(Encoding::ISO_8859_1) =~ /c/
     $'.encoding.should equal(Encoding::ISO_8859_1)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$' = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$'/)
+  end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_single_quote $'
+    -> {
+      $predefined_spec_single_quote = ""
+    }.should raise_error(NameError, '$predefined_spec_single_quote is a read-only variable')
+  end
 end
 
 describe "Predefined global $+" do
@@ -191,9 +227,22 @@ describe "Predefined global $+" do
   end
 
   it "sets the encoding to the encoding of the source String" do
-    "abc".force_encoding(Encoding::EUC_JP) =~ /(b)/
+    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /(b)/
     $+.encoding.should equal(Encoding::EUC_JP)
   end
+
+  it "is read-only" do
+    -> {
+      eval %q{$+ = ""}
+    }.should raise_error(SyntaxError, /Can't set variable \$\+/)
+  end
+
+  it "is read-only when aliased" do
+    alias $predefined_spec_plus $+
+    -> {
+      $predefined_spec_plus = ""
+    }.should raise_error(NameError, '$predefined_spec_plus is a read-only variable')
+  end
 end
 
 describe "Predefined globals $1..N" do
@@ -218,7 +267,7 @@ describe "Predefined globals $1..N" do
   end
 
   it "sets the encoding to the encoding of the source String" do
-    "abc".force_encoding(Encoding::EUC_JP) =~ /(b)/
+    "abc".dup.force_encoding(Encoding::EUC_JP) =~ /(b)/
     $1.encoding.should equal(Encoding::EUC_JP)
   end
 end
@@ -233,7 +282,7 @@ describe "Predefined global $stdout" do
   end
 
   it "raises TypeError error if assigned to nil" do
-    -> { $stdout = nil }.should raise_error(TypeError)
+    -> { $stdout = nil }.should raise_error(TypeError, '$stdout must have write method, NilClass given')
   end
 
   it "raises TypeError error if assigned to object that doesn't respond to #write" do
@@ -247,6 +296,22 @@ describe "Predefined global $stdout" do
 end
 
 describe "Predefined global $!" do
+  it "is Fiber-local" do
+    Fiber.new do
+      raise "hi"
+    rescue
+      Fiber.yield
+    end.resume
+
+    $!.should == nil
+  end
+
+  it "is read-only" do
+    -> {
+      $! = []
+    }.should raise_error(NameError, '$! is a read-only variable')
+  end
+
   # See http://jira.codehaus.org/browse/JRUBY-5550
   it "remains nil after a failed core class \"checked\" coercion against a class that defines method_missing" do
     $!.should == nil
@@ -398,6 +463,22 @@ describe "Predefined global $!" do
       $!.should == nil
     end
 
+    it "should be cleared when an exception is rescued even when a non-local return from block" do
+      def foo
+        [ 1 ].each do
+          begin
+            raise StandardError.new('err')
+          rescue => e
+            $!.should == e
+            return
+          end
+        end
+      end
+
+      foo
+      $!.should == nil
+    end
+
     it "should not be cleared when an exception is not rescued" do
       e = StandardError.new
       begin
@@ -490,44 +571,112 @@ describe "Predefined global $!" do
   end
 end
 
-=begin
-Input/Output Variables
----------------------------------------------------------------------------------------------------
-
-$/               String          The input record separator (newline by default). This is the value that rou-
-                                 tines such as Kernel#gets use to determine record boundaries. If set to
-                                 nil, gets will read the entire file.
-$-0              String          Synonym for $/.
-$\               String          The string appended to the output of every call to methods such as
-                                 Kernel#print and IO#write. The default value is nil.
-$,               String          The separator string output between the parameters to methods such as
-                                 Kernel#print and Array#join. Defaults to nil, which adds no text.
-$.               Fixnum          The number of the last line read from the current input file.
-$;               String          The default separator pattern used by String#split. May be set from the
-                                 command line using the -F flag.
-$<               Object          An object that provides access to the concatenation of the contents of all
-                                 the files given as command-line arguments or $stdin (in the case where
-                                 there are no arguments). $< supports methods similar to a File object:
-                                 binmode, close, closed?, each, each_byte, each_line, eof, eof?,
-                                 file, filename, fileno, getc, gets, lineno, lineno=, path, pos, pos=,
-                                 read, readchar, readline, readlines, rewind, seek, skip, tell, to_a,
-                                 to_i, to_io, to_s, along with the methods in Enumerable. The method
-                                 file returns a File object for the file currently being read. This may change
-                                 as $< reads through the files on the command line. [r/o]
-$>               IO              The destination of output for Kernel#print and Kernel#printf. The
-                                 default value is $stdout.
-$_               String          The last line read by Kernel#gets or Kernel#readline. Many string-
-                                 related functions in the Kernel module operate on $_ by default. The vari-
-                                 able is local to the current scope. [thread]
-$-F              String          Synonym for $;.
-$stderr          IO              The current standard error output.
-$stdin           IO              The current standard input.
-$stdout          IO              The current standard output. Assignment to $stdout is deprecated: use
-                                 $stdout.reopen instead.
-=end
+describe "Predefined global $@" do
+  it "is Fiber-local" do
+    Fiber.new do
+      raise "hi"
+    rescue
+      Fiber.yield
+    end.resume
+
+    $@.should == nil
+  end
+
+  it "is set to a backtrace of a rescued exception" do
+    begin
+      raise
+    rescue
+      $@.should be_an_instance_of(Array)
+      $@.should == $!.backtrace
+    end
+  end
+
+  it "is cleared when an exception is rescued" do
+    begin
+      raise
+    rescue
+    end
+
+    $@.should == nil
+  end
+
+  it "is not set when there is no current exception" do
+    $@.should == nil
+  end
+
+  it "is set to a backtrace of a rescued exception" do
+    begin
+      raise
+    rescue
+      $@.should be_an_instance_of(Array)
+      $@.should == $!.backtrace
+    end
+  end
+
+  it "is not read-only" do
+    begin
+      raise
+    rescue
+      $@ = []
+      $@.should == []
+    end
+  end
+
+  it_behaves_like :exception_set_backtrace, -> backtrace {
+    exception = nil
+    begin
+      raise
+    rescue
+      $@ = backtrace
+      exception = $!
+    end
+    exception
+  }
+
+  it "cannot be assigned when there is no a rescued exception" do
+    -> {
+      $@ = []
+    }.should raise_error(ArgumentError, '$! not set')
+  end
+end
+
+# Input/Output Variables
+# ---------------------------------------------------------------------------------------------------
+#
+# $/               String          The input record separator (newline by default). This is the value that rou-
+#                                  tines such as Kernel#gets use to determine record boundaries. If set to
+#                                  nil, gets will read the entire file.
+# $-0              String          Synonym for $/.
+# $\               String          The string appended to the output of every call to methods such as
+#                                  Kernel#print and IO#write. The default value is nil.
+# $,               String          The separator string output between the parameters to methods such as
+#                                  Kernel#print and Array#join. Defaults to nil, which adds no text.
+# $.               Integer          The number of the last line read from the current input file.
+# $;               String          The default separator pattern used by String#split. May be set from the
+#                                  command line using the -F flag.
+# $<               Object          An object that provides access to the concatenation of the contents of all
+#                                  the files given as command-line arguments or $stdin (in the case where
+#                                  there are no arguments). $< supports methods similar to a File object:
+#                                  binmode, close, closed?, each, each_byte, each_line, eof, eof?,
+#                                  file, filename, fileno, getc, gets, lineno, lineno=, path, pos, pos=,
+#                                  read, readchar, readline, readlines, rewind, seek, skip, tell, to_a,
+#                                  to_i, to_io, to_s, along with the methods in Enumerable. The method
+#                                  file returns a File object for the file currently being read. This may change
+#                                  as $< reads through the files on the command line. [r/o]
+# $>               IO              The destination of output for Kernel#print and Kernel#printf. The
+#                                  default value is $stdout.
+# $_               String          The last line read by Kernel#gets or Kernel#readline. Many string-
+#                                  related functions in the Kernel module operate on $_ by default. The vari-
+#                                  able is local to the current scope. [thread]
+# $-F              String          Synonym for $;.
+# $stderr          IO              The current standard error output.
+# $stdin           IO              The current standard input.
+# $stdout          IO              The current standard output. Assignment to $stdout is deprecated: use
+#                                  $stdout.reopen instead.
 
 describe "Predefined global $/" do
   before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
     @dollar_slash = $/
     @dollar_dash_zero = $-0
   end
@@ -535,14 +684,42 @@ describe "Predefined global $/" do
   after :each do
     $/ = @dollar_slash
     $-0 = @dollar_dash_zero
+    $VERBOSE = @verbose
   end
 
-  it "can be assigned a String" do
-    str = "abc"
-    $/ = str
-    $/.should equal(str)
+  ruby_version_is ""..."4.0" do
+    it "can be assigned a String" do
+      str = +"abc"
+      $/ = str
+      $/.should equal(str)
+    end
   end
 
+  ruby_version_is "4.0" do
+    it "makes a new frozen String from the assigned String" do
+      string_subclass = Class.new(String)
+      str = string_subclass.new("abc")
+      str.instance_variable_set(:@ivar, 1)
+      $/ = str
+      $/.should.frozen?
+      $/.should be_an_instance_of(String)
+      $/.should_not.instance_variable_defined?(:@ivar)
+      $/.should == str
+    end
+
+    it "makes a new frozen String if it's not frozen" do
+      str = +"abc"
+      $/ = str
+      $/.should.frozen?
+      $/.should == str
+    end
+
+    it "assigns the given String if it's frozen and has no instance variables" do
+      str = "abc".freeze
+      $/ = str
+      $/.should equal(str)
+    end
+  end
   it "can be assigned nil" do
     $/ = nil
     $/.should be_nil
@@ -552,7 +729,6 @@ describe "Predefined global $/" do
     ($/ = "xyz").should == "xyz"
   end
 
-
   it "changes $-0" do
     $/ = "xyz"
     $-0.should equal($/)
@@ -562,20 +738,25 @@ describe "Predefined global $/" do
     obj = mock("$/ value")
     obj.should_not_receive(:to_str)
 
-    -> { $/ = obj }.should raise_error(TypeError)
+    -> { $/ = obj }.should raise_error(TypeError, 'value of $/ must be String')
   end
 
-  it "raises a TypeError if assigned a Fixnum" do
-    -> { $/ = 1 }.should raise_error(TypeError)
+  it "raises a TypeError if assigned an Integer" do
+    -> { $/ = 1 }.should raise_error(TypeError, 'value of $/ must be String')
   end
 
   it "raises a TypeError if assigned a boolean" do
-    -> { $/ = true }.should raise_error(TypeError)
+    -> { $/ = true }.should raise_error(TypeError, 'value of $/ must be String')
+  end
+
+  it "warns if assigned non-nil" do
+    -> { $/ = "_" }.should complain(/warning: (?:non-nil )?[`']\$\/' is deprecated/)
   end
 end
 
 describe "Predefined global $-0" do
   before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
     @dollar_slash = $/
     @dollar_dash_zero = $-0
   end
@@ -583,12 +764,41 @@ describe "Predefined global $-0" do
   after :each do
     $/ = @dollar_slash
     $-0 = @dollar_dash_zero
+    $VERBOSE = @verbose
   end
 
-  it "can be assigned a String" do
-    str = "abc"
-    $-0 = str
-    $-0.should equal(str)
+  ruby_version_is ""..."4.0" do
+    it "can be assigned a String" do
+      str = +"abc"
+      $-0 = str
+      $-0.should equal(str)
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "makes a new frozen String from the assigned String" do
+      string_subclass = Class.new(String)
+      str = string_subclass.new("abc")
+      str.instance_variable_set(:@ivar, 1)
+      $-0 = str
+      $-0.should.frozen?
+      $-0.should be_an_instance_of(String)
+      $-0.should_not.instance_variable_defined?(:@ivar)
+      $-0.should == str
+    end
+
+    it "makes a new frozen String if it's not frozen" do
+      str = +"abc"
+      $-0 = str
+      $-0.should.frozen?
+      $-0.should == str
+    end
+
+    it "assigns the given String if it's frozen and has no instance variables" do
+      str = "abc".freeze
+      $-0 = str
+      $-0.should equal(str)
+    end
   end
 
   it "can be assigned nil" do
@@ -609,15 +819,62 @@ describe "Predefined global $-0" do
     obj = mock("$-0 value")
     obj.should_not_receive(:to_str)
 
-    -> { $-0 = obj }.should raise_error(TypeError)
+    -> { $-0 = obj }.should raise_error(TypeError, 'value of $-0 must be String')
   end
 
-  it "raises a TypeError if assigned a Fixnum" do
-    -> { $-0 = 1 }.should raise_error(TypeError)
+  it "raises a TypeError if assigned an Integer" do
+    -> { $-0 = 1 }.should raise_error(TypeError, 'value of $-0 must be String')
   end
 
   it "raises a TypeError if assigned a boolean" do
-    -> { $-0 = true }.should raise_error(TypeError)
+    -> { $-0 = true }.should raise_error(TypeError, 'value of $-0 must be String')
+  end
+
+  it "warns if assigned non-nil" do
+    -> { $-0 = "_" }.should complain(/warning: (?:non-nil )?[`']\$-0' is deprecated/)
+  end
+end
+
+describe "Predefined global $\\" do
+  before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
+    @dollar_backslash = $\
+  end
+
+  after :each do
+    $\ = @dollar_backslash
+    $VERBOSE = @verbose
+  end
+
+  it "can be assigned a String" do
+    str = "abc"
+    $\ = str
+    $\.should equal(str)
+  end
+
+  it "can be assigned nil" do
+    $\ = nil
+    $\.should be_nil
+  end
+
+  it "returns the value assigned" do
+    ($\ = "xyz").should == "xyz"
+  end
+
+  it "does not call #to_str to convert the object to a String" do
+    obj = mock("$\\ value")
+    obj.should_not_receive(:to_str)
+
+    -> { $\ = obj }.should raise_error(TypeError, 'value of $\ must be String')
+  end
+
+  it "raises a TypeError if assigned not String" do
+    -> { $\ = 1 }.should raise_error(TypeError, 'value of $\ must be String')
+    -> { $\ = true }.should raise_error(TypeError, 'value of $\ must be String')
+  end
+
+  it "warns if assigned non-nil" do
+    -> { $\ = "_" }.should complain(/warning: (?:non-nil )?[`']\$\\' is deprecated/)
   end
 end
 
@@ -631,7 +888,11 @@ describe "Predefined global $," do
   end
 
   it "raises TypeError if assigned a non-String" do
-    -> { $, = Object.new }.should raise_error(TypeError)
+    -> { $, = Object.new }.should raise_error(TypeError, 'value of $, must be String')
+  end
+
+  it "warns if assigned non-nil" do
+    -> { $, = "_" }.should complain(/warning: (?:non-nil )?[`']\$,' is deprecated/)
   end
 end
 
@@ -662,6 +923,16 @@ describe "Predefined global $." do
   end
 end
 
+describe "Predefined global $;" do
+  after :each do
+    $; = nil
+  end
+
+  it "warns if assigned non-nil" do
+    -> { $; = "_" }.should complain(/warning: (?:non-nil )?[`']\$;' is deprecated/)
+  end
+end
+
 describe "Predefined global $_" do
   it "is set to the last line read by e.g. StringIO#gets" do
     stdin = StringIO.new("foo\nbar\n", "r")
@@ -692,7 +963,7 @@ describe "Predefined global $_" do
     match.should == "bar\n"
     $_.should == match
 
-    eval 'match = stdin.gets'
+    match = stdin.gets
 
     match.should == "baz\n"
     $_.should == match
@@ -731,56 +1002,52 @@ describe "Predefined global $_" do
   end
 end
 
-=begin
-Execution Environment Variables
----------------------------------------------------------------------------------------------------
-
-$0               String          The name of the top-level Ruby program being executed. Typically this will
-                                 be the program’s filename. On some operating systems, assigning to this
-                                 variable will change the name of the process reported (for example) by the
-                                 ps(1) command.
-$*               Array           An array of strings containing the command-line options from the invoca-
-                                 tion of the program. Options used by the Ruby interpreter will have been
-                                 removed. [r/o]
-$"               Array           An array containing the filenames of modules loaded by require. [r/o]
-$$               Fixnum          The process number of the program being executed. [r/o]
-$?               Process::Status The exit status of the last child process to terminate. [r/o, thread]
-$:               Array           An array of strings, where each string specifies a directory to be searched for
-                                 Ruby scripts and binary extensions used by the load and require methods.
-                                 The initial value is the value of the arguments passed via the -I command-
-                                 line option, followed by an installation-defined standard library location, fol-
-                                 lowed by the current directory (“.”). This variable may be set from within a
-                                 program to alter the default search path; typically, programs use $: << dir
-                                 to append dir to the path. [r/o]
-$-a              Object          True if the -a option is specified on the command line. [r/o]
-$-d              Object          Synonym for $DEBUG.
-$DEBUG           Object          Set to true if the -d command-line option is specified.
-__FILE__         String          The name of the current source file. [r/o]
-$F               Array           The array that receives the split input line if the -a command-line option is
-                                 used.
-$FILENAME        String          The name of the current input file. Equivalent to $<.filename. [r/o]
-$-i              String          If in-place edit mode is enabled (perhaps using the -i command-line
-                                 option), $-i holds the extension used when creating the backup file. If you
-                                 set a value into $-i, enables in-place edit mode.
-$-I              Array           Synonym for $:. [r/o]
-$-K              String          Sets the multibyte coding system for strings and regular expressions. Equiv-
-                                 alent to the -K command-line option.
-$-l              Object          Set to true if the -l option (which enables line-end processing) is present
-                                 on the command line. [r/o]
-__LINE__         String          The current line number in the source file. [r/o]
-$LOAD_PATH       Array           A synonym for $:. [r/o]
-$-p              Object          Set to true if the -p option (which puts an implicit while gets . . . end
-                                 loop around your program) is present on the command line. [r/o]
-$SAFE            Fixnum          The current safe level. This variable’s value may never be
-                                 reduced by assignment. [thread] (Not implemented in Rubinius)
-$VERBOSE         Object          Set to true if the -v, --version, -W, or -w option is specified on the com-
-                                 mand line. Set to false if no option, or -W1 is given. Set to nil if -W0
-                                 was specified. Setting this option to true causes the interpreter and some
-                                 library routines to report additional information. Setting to nil suppresses
-                                 all warnings (including the output of Kernel.warn).
-$-v              Object          Synonym for $VERBOSE.
-$-w              Object          Synonym for $VERBOSE.
-=end
+# Execution Environment Variables
+# ---------------------------------------------------------------------------------------------------
+#
+# $0               String          The name of the top-level Ruby program being executed. Typically this will
+#                                  be the program’s filename. On some operating systems, assigning to this
+#                                  variable will change the name of the process reported (for example) by the
+#                                  ps(1) command.
+# $*               Array           An array of strings containing the command-line options from the invoca-
+#                                  tion of the program. Options used by the Ruby interpreter will have been
+#                                  removed. [r/o]
+# $"               Array           An array containing the filenames of modules loaded by require. [r/o]
+# $$               Integer          The process number of the program being executed. [r/o]
+# $?               Process::Status The exit status of the last child process to terminate. [r/o, thread]
+# $:               Array           An array of strings, where each string specifies a directory to be searched for
+#                                  Ruby scripts and binary extensions used by the load and require methods.
+#                                  The initial value is the value of the arguments passed via the -I command-
+#                                  line option, followed by an installation-defined standard library location, fol-
+#                                  lowed by the current directory (“.”). This variable may be set from within a
+#                                  program to alter the default search path; typically, programs use $: << dir
+#                                  to append dir to the path. [r/o]
+# $-a              Object          True if the -a option is specified on the command line. [r/o]
+# $-d              Object          Synonym for $DEBUG.
+# $DEBUG           Object          Set to true if the -d command-line option is specified.
+# __FILE__         String          The name of the current source file. [r/o]
+# $F               Array           The array that receives the split input line if the -a command-line option is
+#                                  used.
+# $FILENAME        String          The name of the current input file. Equivalent to $<.filename. [r/o]
+# $-i              String          If in-place edit mode is enabled (perhaps using the -i command-line
+#                                  option), $-i holds the extension used when creating the backup file. If you
+#                                  set a value into $-i, enables in-place edit mode.
+# $-I              Array           Synonym for $:. [r/o]
+# $-K              String          Sets the multibyte coding system for strings and regular expressions. Equiv-
+#                                  alent to the -K command-line option.
+# $-l              Object          Set to true if the -l option (which enables line-end processing) is present
+#                                  on the command line. [r/o]
+# __LINE__         String          The current line number in the source file. [r/o]
+# $LOAD_PATH       Array           A synonym for $:. [r/o]
+# $-p              Object          Set to true if the -p option (which puts an implicit while gets . . . end
+#                                  loop around your program) is present on the command line. [r/o]
+# $VERBOSE         Object          Set to true if the -v, --version, -W, or -w option is specified on the com-
+#                                  mand line. Set to false if no option, or -W1 is given. Set to nil if -W0
+#                                  was specified. Setting this option to true causes the interpreter and some
+#                                  library routines to report additional information. Setting to nil suppresses
+#                                  all warnings (including the output of Kernel.warn).
+# $-v              Object          Synonym for $VERBOSE.
+# $-w              Object          Synonym for $VERBOSE.
 describe "Execution variable $:" do
   it "is initialized to an array of strings" do
     $:.is_a?(Array).should == true
@@ -799,20 +1066,38 @@ describe "Execution variable $:" do
   it "can be changed via <<" do
     $: << "foo"
     $:.should include("foo")
+  ensure
+    $:.delete("foo")
   end
 
   it "is read-only" do
     -> {
       $: = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$: is a read-only variable')
 
     -> {
       $LOAD_PATH = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$LOAD_PATH is a read-only variable')
 
     -> {
       $-I = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$-I is a read-only variable')
+  end
+
+  it "default $LOAD_PATH entries until sitelibdir included have @gem_prelude_index set" do
+    skip "no sense in ruby itself" if MSpecScript.instance_variable_defined?(:@testing_ruby)
+
+    if platform_is :windows
+      # See https://github.com/ruby/setup-ruby/pull/762#issuecomment-2917460440
+      $:.should.find { |e| File.realdirpath(e) == RbConfig::CONFIG['sitelibdir'] }
+      idx = $:.index { |e| File.realdirpath(e) == RbConfig::CONFIG['sitelibdir'] }
+    else
+      $:.should.include?(RbConfig::CONFIG['sitelibdir'])
+      idx = $:.index(RbConfig::CONFIG['sitelibdir'])
+    end
+
+    $:[idx..-1].all? { |p| p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
+    $:[0...idx].all? { |p| !p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
   end
 end
 
@@ -824,11 +1109,11 @@ describe "Global variable $\"" do
   it "is read-only" do
     -> {
       $" = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$" is a read-only variable')
 
     -> {
       $LOADED_FEATURES = []
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$LOADED_FEATURES is a read-only variable')
   end
 end
 
@@ -836,7 +1121,7 @@ describe "Global variable $<" do
   it "is read-only" do
     -> {
       $< = nil
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$< is a read-only variable')
   end
 end
 
@@ -844,7 +1129,7 @@ describe "Global variable $FILENAME" do
   it "is read-only" do
     -> {
       $FILENAME = "-"
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$FILENAME is a read-only variable')
   end
 end
 
@@ -852,7 +1137,7 @@ describe "Global variable $?" do
   it "is read-only" do
     -> {
       $? = nil
-    }.should raise_error(NameError)
+    }.should raise_error(NameError, '$? is a read-only variable')
   end
 
   it "is thread-local" do
@@ -863,19 +1148,19 @@ end
 
 describe "Global variable $-a" do
   it "is read-only" do
-    -> { $-a = true }.should raise_error(NameError)
+    -> { $-a = true }.should raise_error(NameError, '$-a is a read-only variable')
   end
 end
 
 describe "Global variable $-l" do
   it "is read-only" do
-    -> { $-l = true }.should raise_error(NameError)
+    -> { $-l = true }.should raise_error(NameError, '$-l is a read-only variable')
   end
 end
 
 describe "Global variable $-p" do
   it "is read-only" do
-    -> { $-p = true }.should raise_error(NameError)
+    -> { $-p = true }.should raise_error(NameError, '$-p is a read-only variable')
   end
 end
 
@@ -897,6 +1182,18 @@ describe "Global variable $-d" do
 end
 
 describe "Global variable $VERBOSE" do
+  before :each do
+    @verbose = $VERBOSE
+  end
+
+  after :each do
+    $VERBOSE = @verbose
+  end
+
+  it "is false by default" do
+    $VERBOSE.should be_false
+  end
+
   it "converts truthy values to true" do
     [true, 1, 0, [], ""].each do |true_value|
       $VERBOSE = true_value
@@ -951,7 +1248,7 @@ describe "Global variable $0" do
 
   it "is the path given as the main script and the same as __FILE__" do
     script = "fixtures/dollar_zero.rb"
-    Dir.chdir(File.dirname(__FILE__)) do
+    Dir.chdir(__dir__) do
       ruby_exe(script).should == "#{script}\n#{script}\nOK"
     end
   end
@@ -978,22 +1275,20 @@ describe "Global variable $0" do
   end
 end
 
-=begin
-Standard Objects
----------------------------------------------------------------------------------------------------
-
-ARGF             Object          A synonym for $<.
-ARGV             Array           A synonym for $*.
-ENV              Object          A hash-like object containing the program’s environment variables. An
-                                 instance of class Object, ENV implements the full set of Hash methods. Used
-                                 to query and set the value of an environment variable, as in ENV["PATH"]
-                                 and ENV["term"]="ansi".
-false            FalseClass      Singleton instance of class FalseClass. [r/o]
-nil              NilClass        The singleton instance of class NilClass. The value of uninitialized
-                                 instance and global variables. [r/o]
-self             Object          The receiver (object) of the current method. [r/o]
-true             TrueClass       Singleton instance of class TrueClass. [r/o]
-=end
+# Standard Objects
+# ---------------------------------------------------------------------------------------------------
+#
+# ARGF             Object          A synonym for $<.
+# ARGV             Array           A synonym for $*.
+# ENV              Object          A hash-like object containing the program’s environment variables. An
+#                                  instance of class Object, ENV implements the full set of Hash methods. Used
+#                                  to query and set the value of an environment variable, as in ENV["PATH"]
+#                                  and ENV["term"]="ansi".
+# false            FalseClass      Singleton instance of class FalseClass. [r/o]
+# nil              NilClass        The singleton instance of class NilClass. The value of uninitialized
+#                                  instance and global variables. [r/o]
+# self             Object          The receiver (object) of the current method. [r/o]
+# true             TrueClass       Singleton instance of class TrueClass. [r/o]
 
 describe "The predefined standard objects" do
   it "includes ARGF" do
@@ -1016,7 +1311,7 @@ describe "The predefined standard object nil" do
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("nil = true") }.should raise_error(SyntaxError)
+    -> { eval("nil = true") }.should raise_error(SyntaxError, /Can't assign to nil/)
   end
 end
 
@@ -1026,7 +1321,7 @@ describe "The predefined standard object true" do
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("true = false") }.should raise_error(SyntaxError)
+    -> { eval("true = false") }.should raise_error(SyntaxError, /Can't assign to true/)
   end
 end
 
@@ -1036,67 +1331,62 @@ describe "The predefined standard object false" do
   end
 
   it "raises a SyntaxError if assigned to" do
-    -> { eval("false = nil") }.should raise_error(SyntaxError)
+    -> { eval("false = nil") }.should raise_error(SyntaxError, /Can't assign to false/)
   end
 end
 
 describe "The self pseudo-variable" do
   it "raises a SyntaxError if assigned to" do
-    -> { eval("self = 1") }.should raise_error(SyntaxError)
+    -> { eval("self = 1") }.should raise_error(SyntaxError, /Can't change the value of self/)
   end
 end
 
-=begin
-Global Constants
----------------------------------------------------------------------------------------------------
-
-The following constants are defined by the Ruby interpreter.
-
-DATA                 IO          If the main program file contains the directive __END__, then
-                                 the constant DATA will be initialized so that reading from it will
-                                 return lines following __END__ from the source file.
-FALSE                FalseClass  Synonym for false.
-NIL                  NilClass    Synonym for nil.
-RUBY_PLATFORM        String      The identifier of the platform running this program. This string
-                                 is in the same form as the platform identifier used by the GNU
-                                 configure utility (which is not a coincidence).
-RUBY_RELEASE_DATE    String      The date of this release.
-RUBY_VERSION         String      The version number of the interpreter.
-STDERR               IO          The actual standard error stream for the program. The initial
-                                 value of $stderr.
-STDIN                IO          The actual standard input stream for the program. The initial
-                                 value of $stdin.
-STDOUT               IO          The actual standard output stream for the program. The initial
-                                 value of $stdout.
-SCRIPT_LINES__       Hash        If a constant SCRIPT_LINES__ is defined and references a Hash,
-                                 Ruby will store an entry containing the contents of each file it
-                                 parses, with the file’s name as the key and an array of strings as
-                                 the value.
-TOPLEVEL_BINDING     Binding     A Binding object representing the binding at Ruby’s top level—
-                                 the level where programs are initially executed.
-TRUE                 TrueClass   Synonym for true.
-=end
+# Global Constants
+# ---------------------------------------------------------------------------------------------------
+#
+# The following constants are defined by the Ruby interpreter.
+#
+# DATA                 IO          If the main program file contains the directive __END__, then
+#                                  the constant DATA will be initialized so that reading from it will
+#                                  return lines following __END__ from the source file.
+# FALSE                FalseClass  Synonym for false (deprecated, removed in Ruby 3).
+# NIL                  NilClass    Synonym for nil (deprecated, removed in Ruby 3).
+# RUBY_PLATFORM        String      The identifier of the platform running this program. This string
+#                                  is in the same form as the platform identifier used by the GNU
+#                                  configure utility (which is not a coincidence).
+# RUBY_RELEASE_DATE    String      The date of this release.
+# RUBY_VERSION         String      The version number of the interpreter.
+# STDERR               IO          The actual standard error stream for the program. The initial
+#                                  value of $stderr.
+# STDIN                IO          The actual standard input stream for the program. The initial
+#                                  value of $stdin.
+# STDOUT               IO          The actual standard output stream for the program. The initial
+#                                  value of $stdout.
+# SCRIPT_LINES__       Hash        If a constant SCRIPT_LINES__ is defined and references a Hash,
+#                                  Ruby will store an entry containing the contents of each file it
+#                                  parses, with the file’s name as the key and an array of strings as
+#                                  the value.
+# TOPLEVEL_BINDING     Binding     A Binding object representing the binding at Ruby’s top level—
+#                                  the level where programs are initially executed.
+# TRUE                 TrueClass   Synonym for true (deprecated, removed in Ruby 3).
 
 describe "The predefined global constants" do
-  it "includes TRUE" do
-    Object.const_defined?(:TRUE).should == true
-    -> {
-      TRUE.should equal(true)
-    }.should complain(/constant ::TRUE is deprecated/)
+  describe "TRUE" do
+    it "is no longer defined" do
+      Object.const_defined?(:TRUE).should == false
+    end
   end
 
-  it "includes FALSE" do
-    Object.const_defined?(:FALSE).should == true
-    -> {
-      FALSE.should equal(false)
-    }.should complain(/constant ::FALSE is deprecated/)
+  describe "FALSE" do
+    it "is no longer defined" do
+      Object.const_defined?(:FALSE).should == false
+    end
   end
 
-  it "includes NIL" do
-    Object.const_defined?(:NIL).should == true
-    -> {
-      NIL.should equal(nil)
-    }.should complain(/constant ::NIL is deprecated/)
+  describe "NIL" do
+    it "is no longer defined" do
+      Object.const_defined?(:NIL).should == false
+    end
   end
 
   it "includes STDIN" do
@@ -1126,7 +1416,6 @@ describe "The predefined global constants" do
   it "includes TOPLEVEL_BINDING" do
     Object.const_defined?(:TOPLEVEL_BINDING).should == true
   end
-
 end
 
 describe "The predefined global constant" do
@@ -1141,13 +1430,24 @@ describe "The predefined global constant" do
   end
 
   describe "STDIN" do
-    it "has the same external encoding as Encoding.default_external" do
-      STDIN.external_encoding.should equal(Encoding.default_external)
-    end
+    platform_is_not :windows do
+      it "has the same external encoding as Encoding.default_external" do
+        STDIN.external_encoding.should equal(Encoding.default_external)
+      end
+
+      it "has the same external encoding as Encoding.default_external when that encoding is changed" do
+        Encoding.default_external = Encoding::ISO_8859_16
+        STDIN.external_encoding.should equal(Encoding::ISO_8859_16)
+      end
+
+      it "has nil for the internal encoding" do
+        STDIN.internal_encoding.should be_nil
+      end
 
-    it "has the same external encoding as Encoding.default_external when that encoding is changed" do
-      Encoding.default_external = Encoding::ISO_8859_16
-      STDIN.external_encoding.should equal(Encoding::ISO_8859_16)
+      it "has nil for the internal encoding despite Encoding.default_internal being changed" do
+        Encoding.default_internal = Encoding::IBM437
+        STDIN.internal_encoding.should be_nil
+      end
     end
 
     it "has the encodings set by #set_encoding" do
@@ -1162,15 +1462,6 @@ describe "The predefined global constant" do
              "p [STDIN.external_encoding.name, STDIN.internal_encoding.name]"
       ruby_exe(code).chomp.should == %{["IBM775", "IBM866"]}
     end
-
-    it "has nil for the internal encoding" do
-      STDIN.internal_encoding.should be_nil
-    end
-
-    it "has nil for the internal encoding despite Encoding.default_internal being changed" do
-      Encoding.default_internal = Encoding::IBM437
-      STDIN.internal_encoding.should be_nil
-    end
   end
 
   describe "STDOUT" do
@@ -1234,3 +1525,50 @@ describe "The predefined global constant" do
     end
   end
 end
+
+describe "$LOAD_PATH.resolve_feature_path" do
+  it "returns what will be loaded without actual loading, .rb file" do
+    extension, path = $LOAD_PATH.resolve_feature_path('pp')
+    extension.should == :rb
+    path.should.end_with?('/pp.rb')
+  end
+
+  it "returns what will be loaded without actual loading, .so file" do
+    require 'rbconfig'
+    skip "no dynamically loadable standard extension" if RbConfig::CONFIG["EXTSTATIC"] == "static"
+
+    extension, path = $LOAD_PATH.resolve_feature_path('etc')
+    extension.should == :so
+    path.should.end_with?("/etc.#{RbConfig::CONFIG['DLEXT']}")
+  end
+
+  it "return nil if feature cannot be found" do
+    $LOAD_PATH.resolve_feature_path('noop').should be_nil
+  end
+end
+
+# Some other pre-defined global variables
+
+describe "Predefined global $=" do
+  before :each do
+    @verbose, $VERBOSE = $VERBOSE, nil
+    @dollar_assign = $=
+  end
+
+  after :each do
+    $= = @dollar_assign
+    $VERBOSE = @verbose
+  end
+
+  it "warns when accessed" do
+    -> { a = $= }.should complain(/is no longer effective/)
+  end
+
+  it "warns when assigned" do
+    -> { $= = "_" }.should complain(/is no longer effective/)
+  end
+
+  it "returns the value assigned" do
+    ($= = "xyz").should == "xyz"
+  end
+end
diff --git a/spec/ruby/language/private_spec.rb b/spec/ruby/language/private_spec.rb
index ddf185e6d2..b04aa25c9e 100644
--- a/spec/ruby/language/private_spec.rb
+++ b/spec/ruby/language/private_spec.rb
@@ -34,7 +34,7 @@ describe "The private keyword" do
   it "changes visibility of previously called method" do
     klass = Class.new do
       def foo
-       "foo"
+        "foo"
       end
     end
     f = klass.new
diff --git a/spec/ruby/language/proc_spec.rb b/spec/ruby/language/proc_spec.rb
index c44e711d2b..ca9a13aa61 100644
--- a/spec/ruby/language/proc_spec.rb
+++ b/spec/ruby/language/proc_spec.rb
@@ -104,7 +104,7 @@ describe "A Proc" do
     end
 
     it "assigns all passed values after the first to the rest argument" do
-        @l.call(1, 2, 3).should == [1, [2, 3]]
+      @l.call(1, 2, 3).should == [1, [2, 3]]
     end
 
     it "does not call #to_ary to convert a single passed object to an Array" do
@@ -161,6 +161,18 @@ describe "A Proc" do
     end
   end
 
+  describe "taking |*a, b| arguments" do
+    it "assigns [] to the argument when passed no values" do
+      proc { |*a, b| [a, b] }.call.should == [[], nil]
+    end
+  end
+
+  describe "taking |a, *b, c| arguments" do
+    it "assigns [] to the argument when passed no values" do
+      proc { |a, *b, c| [a, b, c] }.call.should == [nil, [], nil]
+    end
+  end
+
   describe "taking |a, | arguments" do
     before :each do
       @l = lambda { |a, | a }
@@ -217,4 +229,21 @@ describe "A Proc" do
       lambda { @l.call(obj) }.should raise_error(TypeError)
     end
   end
+
+  describe "taking |*a, **kw| arguments" do
+    before :each do
+      @p = proc { |*a, **kw| [a, kw] }
+    end
+
+    it 'does not autosplat keyword arguments' do
+      @p.call([1, {a: 1}]).should == [[[1, {a: 1}]], {}]
+    end
+  end
+
+  describe "taking |required keyword arguments, **kw| arguments" do
+    it "raises ArgumentError for missing required argument" do
+      p = proc { |a:, **kw| [a, kw] }
+      -> { p.call() }.should raise_error(ArgumentError)
+    end
+  end
 end
diff --git a/spec/ruby/language/range_spec.rb b/spec/ruby/language/range_spec.rb
index c720c5b98e..ccc9f55537 100644
--- a/spec/ruby/language/range_spec.rb
+++ b/spec/ruby/language/range_spec.rb
@@ -10,10 +10,21 @@ describe "Literal Ranges" do
     (1...10).should == Range.new(1, 10, true)
   end
 
-  ruby_version_is "2.6" do
-    it "creates endless ranges" do
-      eval("(1..)").should == Range.new(1, nil)
-      eval("(1...)").should == Range.new(1, nil, true)
+  it "creates a simple range as an object literal" do
+    ary = []
+    2.times do
+      ary.push(1..3)
     end
+    ary[0].should.equal?(ary[1])
+  end
+
+  it "creates endless ranges" do
+    (1..).should == Range.new(1, nil)
+    (1...).should == Range.new(1, nil, true)
+  end
+
+  it "creates beginless ranges" do
+    (..1).should == Range.new(nil, 1)
+    (...1).should == Range.new(nil, 1, true)
   end
 end
diff --git a/spec/ruby/language/regexp/anchors_spec.rb b/spec/ruby/language/regexp/anchors_spec.rb
index 0129e255da..cdc06c0b4d 100644
--- a/spec/ruby/language/regexp/anchors_spec.rb
+++ b/spec/ruby/language/regexp/anchors_spec.rb
@@ -124,10 +124,10 @@ describe "Regexps with anchors" do
     /foo\b/.match("foo").to_a.should == ["foo"]
     /foo\b/.match("foo\n").to_a.should == ["foo"]
     LanguageSpecs.white_spaces.scan(/./).each do |c|
-    /foo\b/.match("foo" + c).to_a.should == ["foo"]
+      /foo\b/.match("foo" + c).to_a.should == ["foo"]
     end
     LanguageSpecs.non_alphanum_non_space.scan(/./).each do |c|
-    /foo\b/.match("foo" + c).to_a.should == ["foo"]
+      /foo\b/.match("foo" + c).to_a.should == ["foo"]
     end
     /foo\b/.match("foo\0").to_a.should == ["foo"]
     # Basic non-matching
@@ -145,10 +145,10 @@ describe "Regexps with anchors" do
     /foo\B/.match("foo").should be_nil
     /foo\B/.match("foo\n").should be_nil
     LanguageSpecs.white_spaces.scan(/./).each do |c|
-    /foo\B/.match("foo" + c).should be_nil
+      /foo\B/.match("foo" + c).should be_nil
     end
     LanguageSpecs.non_alphanum_non_space.scan(/./).each do |c|
-    /foo\B/.match("foo" + c).should be_nil
+      /foo\B/.match("foo" + c).should be_nil
     end
     /foo\B/.match("foo\0").should be_nil
   end
diff --git a/spec/ruby/language/regexp/back-references_spec.rb b/spec/ruby/language/regexp/back-references_spec.rb
index 81015ac21e..627c8daace 100644
--- a/spec/ruby/language/regexp/back-references_spec.rb
+++ b/spec/ruby/language/regexp/back-references_spec.rb
@@ -22,6 +22,15 @@ describe "Regexps with back-references" do
     $10.should == "0"
   end
 
+  it "returns nil for numbered variable with too large index" do
+    -> {
+      eval(<<~CODE).should == nil
+        "a" =~ /(.)/
+        eval('$4294967296')
+      CODE
+    }.should complain(/warning: ('|`)\$4294967296' is too big for a number variable, always nil/)
+  end
+
   it "will not clobber capture variables across threads" do
     cap1, cap2, cap3 = nil
     "foo" =~ /(o+)/
@@ -47,7 +56,94 @@ describe "Regexps with back-references" do
     /(a\1?){2}/.match("aaaa").to_a.should == ["aa", "a"]
   end
 
+  it "does not reset enclosed capture groups" do
+    /((a)|(b))+/.match("ab").captures.should == [ "b", "a", "b" ]
+  end
+
   it "can match an optional quote, followed by content, followed by a matching quote, as the whole string" do
     /^("|)(.*)\1$/.match('x').to_a.should == ["x", "", "x"]
   end
+
+  it "allows forward references" do
+    /(?:(\2)|(.))+/.match("aa").to_a.should == [ "aa", "a", "a" ]
+  end
+
+  it "disallows forward references >= 10" do
+    (/\10()()()()()()()()()()/ =~ "\x08").should == 0
+  end
+
+  it "fails when trying to match a backreference to an unmatched capture group" do
+    /\1()/.match("").should == nil
+    /(?:(a)|b)\1/.match("b").should == nil
+  end
+
+  it "ignores backreferences > 1000" do
+    /\99999/.match("99999")[0].should == "99999"
+  end
+
+  it "0 is not a valid backreference" do
+    -> { Regexp.new("\\k<0>") }.should raise_error(RegexpError)
+  end
+
+  it "allows numeric conditional backreferences" do
+    /(a)(?(1)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?(<1>)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?('1')a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+
+  it "allows either <> or '' in named conditional backreferences" do
+    -> { Regexp.new("(?<a>a)(?(a)a|b)") }.should raise_error(RegexpError)
+    /(?<a>a)(?(<a>)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a>a)(?('a')a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+
+  it "allows negative numeric backreferences" do
+    /(a)\k<-1>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)\g<-1>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?(<-1>)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?('-1')a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+
+  it "delimited numeric backreferences can start with 0" do
+    /(a)\k<01>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)\g<01>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?(01)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?(<01>)a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+    /(a)(?('01')a|b)/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+
+  it "regular numeric backreferences cannot start with 0" do
+    /(a)\01/.match("aa").should == nil
+    /(a)\01/.match("a\x01").to_a.should == [ "a\x01", "a" ]
+  end
+
+  it "named capture groups invalidate numeric backreferences" do
+    -> { Regexp.new("(?<a>a)\\1") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a>a)\\k<1>") }.should raise_error(RegexpError)
+    -> { Regexp.new("(a)(?<a>a)\\1") }.should raise_error(RegexpError)
+    -> { Regexp.new("(a)(?<a>a)\\k<1>") }.should raise_error(RegexpError)
+  end
+
+  it "treats + or - as the beginning of a level specifier in \\k<> backreferences and (?(...)...|...) conditional backreferences" do
+    -> { Regexp.new("(?<a+>a)\\k<a+>") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+b>a)\\k<a+b>") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+1>a)\\k<a+1>") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a->a)\\k<a->") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-b>a)\\k<a-b>") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-1>a)\\k<a-1>") }.should raise_error(RegexpError)
+
+    -> { Regexp.new("(?<a+>a)(?(<a+>)a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+b>a)(?(<a+b>)a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+1>a)(?(<a+1>)a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a->a)(?(<a->)a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-b>a)(?(<a-b>)a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-1>a)(?(<a-1>)a|b)") }.should raise_error(RegexpError)
+
+    -> { Regexp.new("(?<a+>a)(?('a+')a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+b>a)(?('a+b')a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a+1>a)(?('a+1')a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a->a)(?('a-')a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-b>a)(?('a-b')a|b)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<a-1>a)(?('a-1')a|b)") }.should raise_error(RegexpError)
+  end
 end
diff --git a/spec/ruby/language/regexp/character_classes_spec.rb b/spec/ruby/language/regexp/character_classes_spec.rb
index 5f4221e213..018757db41 100644
--- a/spec/ruby/language/regexp/character_classes_spec.rb
+++ b/spec/ruby/language/regexp/character_classes_spec.rb
@@ -113,7 +113,7 @@ describe "Regexp with character classes" do
   end
 
   it "doesn't matches Unicode marks with [[:alnum:]]" do
-    "\u{36F}".match(/[[:alnum:]]/).should be_nil
+    "\u{3099}".match(/[[:alnum:]]/).should be_nil
   end
 
   it "doesn't match Unicode control characters with [[:alnum:]]" do
@@ -133,7 +133,7 @@ describe "Regexp with character classes" do
   end
 
   it "doesn't matches Unicode marks with [[:alpha:]]" do
-    "\u{36F}".match(/[[:alpha:]]/).should be_nil
+    "\u{3099}".match(/[[:alpha:]]/).should be_nil
   end
 
   it "doesn't match Unicode control characters with [[:alpha:]]" do
@@ -226,7 +226,7 @@ describe "Regexp with character classes" do
   end
 
   it "matches Unicode letter characters with [[:graph:]]" do
-      "à".match(/[[:graph:]]/).to_a.should == ["à"]
+    "à".match(/[[:graph:]]/).to_a.should == ["à"]
   end
 
   it "matches Unicode digits with [[:graph:]]" do
@@ -562,6 +562,13 @@ describe "Regexp with character classes" do
     "\u{16EE}".match(/[[:word:]]/).to_a.should == ["\u{16EE}"]
   end
 
+  ruby_bug "#19417", ""..."3.4.6" do
+    it "matches Unicode join control characters with [[:word:]]" do
+      "\u{200C}".match(/[[:word:]]/).to_a.should == ["\u{200C}"]
+      "\u{200D}".match(/[[:word:]]/).to_a.should == ["\u{200D}"]
+    end
+  end
+
   it "doesn't match Unicode No characters with [[:word:]]" do
     "\u{17F0}".match(/[[:word:]]/).should be_nil
   end
@@ -609,6 +616,15 @@ describe "Regexp with character classes" do
     "루비(Ruby)".match(/\p{Hangul}+/u).to_a.should == ["루비"]
   end
 
+  it "supports negated property condition" do
+    "a".match(eval("/\P{L}/")).should be_nil
+    "1".match(eval("/\P{N}/")).should be_nil
+  end
+
+  it "raises a RegexpError for an unterminated unicode property" do
+    -> { Regexp.new('\p{') }.should raise_error(RegexpError)
+  end
+
   it "supports \\X (unicode 9.0 with UTR #51 workarounds)" do
     # simple emoji without any fancy modifier or ZWJ
     /\X/.match("\u{1F98A}").to_a.should == ["🦊"]
diff --git a/spec/ruby/language/regexp/empty_checks_spec.rb b/spec/ruby/language/regexp/empty_checks_spec.rb
new file mode 100644
index 0000000000..391e65b003
--- /dev/null
+++ b/spec/ruby/language/regexp/empty_checks_spec.rb
@@ -0,0 +1,135 @@
+require_relative '../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "empty checks in Regexps" do
+
+  it "allow extra empty iterations" do
+    /()?/.match("").to_a.should == ["", ""]
+    /(a*)?/.match("").to_a.should == ["", ""]
+    /(a*)*/.match("").to_a.should == ["", ""]
+    # The bounds are high to avoid DFA-based matchers in implementations
+    # and to check backtracking behavior.
+    /(?:a|()){500,1000}/.match("a" * 500).to_a.should == ["a" * 500, ""]
+
+    # Variations with non-greedy loops.
+    /()??/.match("").to_a.should == ["", nil]
+    /(a*?)?/.match("").to_a.should == ["", ""]
+    /(a*)??/.match("").to_a.should == ["", nil]
+    /(a*?)??/.match("").to_a.should == ["", nil]
+    /(a*?)*/.match("").to_a.should == ["", ""]
+    /(a*)*?/.match("").to_a.should == ["", nil]
+    /(a*?)*?/.match("").to_a.should == ["", nil]
+  end
+
+  it "allow empty iterations in the middle of a loop" do
+    # One empty iteration between a's and b's.
+    /(a|\2b|())*/.match("aaabbb").to_a.should == ["aaabbb", "", ""]
+    /(a|\2b|()){2,4}/.match("aaabbb").to_a.should == ["aaa", "", ""]
+
+    # Two empty iterations between a's and b's.
+    /(a|\2b|\3()|())*/.match("aaabbb").to_a.should == ["aaabbb", "", "", ""]
+    /(a|\2b|\3()|()){2,4}/.match("aaabbb").to_a.should == ["aaa", "", nil, ""]
+
+    # Check that the empty iteration correctly updates the loop counter.
+    /(a|\2b|()){20,24}/.match("a" * 20 + "b" * 5).to_a.should == ["a" * 20 + "b" * 3, "b", ""]
+
+    # Variations with non-greedy loops.
+    /(a|\2b|())*?/.match("aaabbb").to_a.should == ["", nil, nil]
+    /(a|\2b|()){2,4}/.match("aaabbb").to_a.should == ["aaa", "", ""]
+    /(a|\2b|\3()|())*?/.match("aaabbb").to_a.should == ["", nil, nil, nil]
+    /(a|\2b|\3()|()){2,4}/.match("aaabbb").to_a.should == ["aaa", "", nil, ""]
+    /(a|\2b|()){20,24}/.match("a" * 20 + "b" * 5).to_a.should == ["a" * 20 + "b" * 3, "b", ""]
+  end
+
+  it "make the Regexp proceed past the quantified expression on failure" do
+    # If the contents of the ()* quantified group are empty (i.e., they fail
+    # the empty check), the loop will abort. It will not try to backtrack
+    # and try other alternatives (e.g. matching the "a") like in other Regexp
+    # dialects such as ECMAScript.
+    /(?:|a)*/.match("aaa").to_a.should == [""]
+    /(?:()|a)*/.match("aaa").to_a.should == ["", ""]
+    /(|a)*/.match("aaa").to_a.should == ["", ""]
+    /(()|a)*/.match("aaa").to_a.should == ["", "", ""]
+
+    # Same expressions, but with backreferences, to force the use of non-DFA-based
+    # engines.
+    /()\1(?:|a)*/.match("aaa").to_a.should == ["", ""]
+    /()\1(?:()|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()\1(|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()\1(()|a)*/.match("aaa").to_a.should == ["", "", "", ""]
+
+    # Variations with other zero-width contents of the quantified
+    # group: backreferences, capture groups, lookarounds
+    /()(?:\1|a)*/.match("aaa").to_a.should == ["", ""]
+    /()(?:()\1|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()(?:(\1)|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()(?:\1()|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()(\1|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()(()\1|a)*/.match("aaa").to_a.should == ["", "", "", ""]
+    /()((\1)|a)*/.match("aaa").to_a.should == ["", "", "", ""]
+    /()(\1()|a)*/.match("aaa").to_a.should == ["", "", "", ""]
+
+    /(?:(?=a)|a)*/.match("aaa").to_a.should == [""]
+    /(?:(?=a)()|a)*/.match("aaa").to_a.should == ["", ""]
+    /(?:()(?=a)|a)*/.match("aaa").to_a.should == ["", ""]
+    /(?:((?=a))|a)*/.match("aaa").to_a.should == ["", ""]
+    /()\1(?:(?=a)|a)*/.match("aaa").to_a.should == ["", ""]
+    /()\1(?:(?=a)()|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()\1(?:()(?=a)|a)*/.match("aaa").to_a.should == ["", "", ""]
+    /()\1(?:((?=a))|a)*/.match("aaa").to_a.should == ["", "", ""]
+
+    # Variations with non-greedy loops.
+    /(?:|a)*?/.match("aaa").to_a.should == [""]
+    /(?:()|a)*?/.match("aaa").to_a.should == ["", nil]
+    /(|a)*?/.match("aaa").to_a.should == ["", nil]
+    /(()|a)*?/.match("aaa").to_a.should == ["", nil, nil]
+
+    /()\1(?:|a)*?/.match("aaa").to_a.should == ["", ""]
+    /()\1(?:()|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()\1(|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()\1(()|a)*?/.match("aaa").to_a.should == ["", "", nil, nil]
+
+    /()(?:\1|a)*?/.match("aaa").to_a.should == ["", ""]
+    /()(?:()\1|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()(?:(\1)|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()(?:\1()|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()(\1|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()(()\1|a)*?/.match("aaa").to_a.should == ["", "", nil, nil]
+    /()((\1)|a)*?/.match("aaa").to_a.should == ["", "", nil, nil]
+    /()(\1()|a)*?/.match("aaa").to_a.should == ["", "", nil, nil]
+
+    /(?:(?=a)|a)*?/.match("aaa").to_a.should == [""]
+    /(?:(?=a)()|a)*?/.match("aaa").to_a.should == ["", nil]
+    /(?:()(?=a)|a)*?/.match("aaa").to_a.should == ["", nil]
+    /(?:((?=a))|a)*?/.match("aaa").to_a.should == ["", nil]
+    /()\1(?:(?=a)|a)*?/.match("aaa").to_a.should == ["", ""]
+    /()\1(?:(?=a)()|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()\1(?:()(?=a)|a)*?/.match("aaa").to_a.should == ["", "", nil]
+    /()\1(?:((?=a))|a)*?/.match("aaa").to_a.should == ["", "", nil]
+  end
+
+  it "shouldn't cause the Regexp parser to get stuck in a loop" do
+    /(|a|\2b|())*/.match("aaabbb").to_a.should == ["", "", nil]
+    /(a||\2b|())*/.match("aaabbb").to_a.should == ["aaa", "", nil]
+    /(a|\2b||())*/.match("aaabbb").to_a.should == ["aaa", "", nil]
+    /(a|\2b|()|)*/.match("aaabbb").to_a.should == ["aaabbb", "", ""]
+    /(()|a|\3b|())*/.match("aaabbb").to_a.should == ["", "", "", nil]
+    /(a|()|\3b|())*/.match("aaabbb").to_a.should == ["aaa", "", "", nil]
+    /(a|\2b|()|())*/.match("aaabbb").to_a.should == ["aaabbb", "", "", nil]
+    /(a|\3b|()|())*/.match("aaabbb").to_a.should == ["aaa", "", "", nil]
+    /(a|()|())*/.match("aaa").to_a.should == ["aaa", "", "", nil]
+    /^(()|a|())*$/.match("aaa").to_a.should == ["aaa", "", "", nil]
+
+    # Variations with non-greedy loops.
+    /(|a|\2b|())*?/.match("aaabbb").to_a.should == ["", nil, nil]
+    /(a||\2b|())*?/.match("aaabbb").to_a.should == ["", nil, nil]
+    /(a|\2b||())*?/.match("aaabbb").to_a.should == ["", nil, nil]
+    /(a|\2b|()|)*?/.match("aaabbb").to_a.should == ["", nil, nil]
+    /(()|a|\3b|())*?/.match("aaabbb").to_a.should == ["", nil, nil, nil]
+    /(a|()|\3b|())*?/.match("aaabbb").to_a.should == ["", nil, nil, nil]
+    /(a|\2b|()|())*?/.match("aaabbb").to_a.should == ["", nil, nil, nil]
+    /(a|\3b|()|())*?/.match("aaabbb").to_a.should == ["", nil, nil, nil]
+    /(a|()|())*?/.match("aaa").to_a.should == ["", nil, nil, nil]
+    /^(()|a|())*?$/.match("aaa").to_a.should == ["aaa", "a", "", nil]
+  end
+end
diff --git a/spec/ruby/language/regexp/encoding_spec.rb b/spec/ruby/language/regexp/encoding_spec.rb
index dce64a4753..ceb9cf823a 100644
--- a/spec/ruby/language/regexp/encoding_spec.rb
+++ b/spec/ruby/language/regexp/encoding_spec.rb
@@ -1,21 +1,21 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "Regexps with encoding modifiers" do
   it "supports /e (EUC encoding)" do
-    match = /./e.match("\303\251".force_encoding(Encoding::EUC_JP))
-    match.to_a.should == ["\303\251".force_encoding(Encoding::EUC_JP)]
+    match = /./e.match("\303\251".dup.force_encoding(Encoding::EUC_JP))
+    match.to_a.should == ["\303\251".dup.force_encoding(Encoding::EUC_JP)]
   end
 
   it "supports /e (EUC encoding) with interpolation" do
-    match = /#{/./}/e.match("\303\251".force_encoding(Encoding::EUC_JP))
-    match.to_a.should == ["\303\251".force_encoding(Encoding::EUC_JP)]
+    match = /#{/./}/e.match("\303\251".dup.force_encoding(Encoding::EUC_JP))
+    match.to_a.should == ["\303\251".dup.force_encoding(Encoding::EUC_JP)]
   end
 
   it "supports /e (EUC encoding) with interpolation /o" do
-    match = /#{/./}/e.match("\303\251".force_encoding(Encoding::EUC_JP))
-    match.to_a.should == ["\303\251".force_encoding(Encoding::EUC_JP)]
+    match = /#{/./}/e.match("\303\251".dup.force_encoding(Encoding::EUC_JP))
+    match.to_a.should == ["\303\251".dup.force_encoding(Encoding::EUC_JP)]
   end
 
   it 'uses EUC-JP as /e encoding' do
@@ -38,10 +38,22 @@ describe "Regexps with encoding modifiers" do
     /#{/./}/n.match("\303\251").to_a.should == ["\303"]
   end
 
+  it "warns when using /n with a match string with non-ASCII characters and an encoding other than ASCII-8BIT" do
+    -> {
+      eval <<~RUBY
+      /./n.match("\303\251".dup.force_encoding('utf-8'))
+      RUBY
+    }.should complain(%r{historical binary regexp match /.../n against UTF-8 string})
+  end
+
   it 'uses US-ASCII as /n encoding if all chars are 7-bit' do
     /./n.encoding.should == Encoding::US_ASCII
   end
 
+  it 'uses BINARY when is not initialized' do
+    Regexp.allocate.encoding.should == Encoding::BINARY
+  end
+
   it 'uses BINARY as /n encoding if not all chars are 7-bit' do
     /\xFF/n.encoding.should == Encoding::BINARY
   end
@@ -55,18 +67,18 @@ describe "Regexps with encoding modifiers" do
   end
 
   it "supports /s (Windows_31J encoding)" do
-    match = /./s.match("\303\251".force_encoding(Encoding::Windows_31J))
-    match.to_a.should == ["\303".force_encoding(Encoding::Windows_31J)]
+    match = /./s.match("\303\251".dup.force_encoding(Encoding::Windows_31J))
+    match.to_a.should == ["\303".dup.force_encoding(Encoding::Windows_31J)]
   end
 
   it "supports /s (Windows_31J encoding) with interpolation" do
-    match = /#{/./}/s.match("\303\251".force_encoding(Encoding::Windows_31J))
-    match.to_a.should == ["\303".force_encoding(Encoding::Windows_31J)]
+    match = /#{/./}/s.match("\303\251".dup.force_encoding(Encoding::Windows_31J))
+    match.to_a.should == ["\303".dup.force_encoding(Encoding::Windows_31J)]
   end
 
   it "supports /s (Windows_31J encoding) with interpolation and /o" do
-    match = /#{/./}/s.match("\303\251".force_encoding(Encoding::Windows_31J))
-    match.to_a.should == ["\303".force_encoding(Encoding::Windows_31J)]
+    match = /#{/./}/s.match("\303\251".dup.force_encoding(Encoding::Windows_31J))
+    match.to_a.should == ["\303".dup.force_encoding(Encoding::Windows_31J)]
   end
 
   it 'uses Windows-31J as /s encoding' do
@@ -78,15 +90,15 @@ describe "Regexps with encoding modifiers" do
   end
 
   it "supports /u (UTF8 encoding)" do
-    /./u.match("\303\251".force_encoding('utf-8')).to_a.should == ["\u{e9}"]
+    /./u.match("\303\251".dup.force_encoding('utf-8')).to_a.should == ["\u{e9}"]
   end
 
   it "supports /u (UTF8 encoding) with interpolation" do
-    /#{/./}/u.match("\303\251".force_encoding('utf-8')).to_a.should == ["\u{e9}"]
+    /#{/./}/u.match("\303\251".dup.force_encoding('utf-8')).to_a.should == ["\u{e9}"]
   end
 
   it "supports /u (UTF8 encoding) with interpolation and /o" do
-    /#{/./}/u.match("\303\251".force_encoding('utf-8')).to_a.should == ["\u{e9}"]
+    /#{/./}/u.match("\303\251".dup.force_encoding('utf-8')).to_a.should == ["\u{e9}"]
   end
 
   it 'uses UTF-8 as /u encoding' do
@@ -100,4 +112,41 @@ describe "Regexps with encoding modifiers" do
   it "selects last of multiple encoding specifiers" do
     /foo/ensuensuens.should == /foo/s
   end
+
+  it "raises Encoding::CompatibilityError when trying match against different encodings" do
+    -> { /\A[[:space:]]*\z/.match(" ".encode("UTF-16LE")) }.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "raises Encoding::CompatibilityError when trying match? against different encodings" do
+    -> { /\A[[:space:]]*\z/.match?(" ".encode("UTF-16LE")) }.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "raises Encoding::CompatibilityError when trying =~ against different encodings" do
+    -> { /\A[[:space:]]*\z/ =~ " ".encode("UTF-16LE") }.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "raises Encoding::CompatibilityError when the regexp has a fixed, non-ASCII-compatible encoding" do
+    -> { Regexp.new("".dup.force_encoding("UTF-16LE"), Regexp::FIXEDENCODING) =~ " ".encode("UTF-8") }.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "raises Encoding::CompatibilityError when the regexp has a fixed encoding and the match string has non-ASCII characters" do
+    -> { Regexp.new("".dup.force_encoding("US-ASCII"), Regexp::FIXEDENCODING) =~ "\303\251".dup.force_encoding('UTF-8') }.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "raises ArgumentError when trying to match a broken String" do
+    s = "\x80".dup.force_encoding('UTF-8')
+    -> { s =~ /./ }.should raise_error(ArgumentError, "invalid byte sequence in UTF-8")
+  end
+
+  it "computes the Regexp Encoding for each interpolated Regexp instance" do
+    make_regexp = -> str { /#{str}/ }
+
+    r = make_regexp.call("été".dup.force_encoding(Encoding::UTF_8))
+    r.should.fixed_encoding?
+    r.encoding.should == Encoding::UTF_8
+
+    r = make_regexp.call("abc".dup.force_encoding(Encoding::UTF_8))
+    r.should_not.fixed_encoding?
+    r.encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/language/regexp/escapes_spec.rb b/spec/ruby/language/regexp/escapes_spec.rb
index 14e1424d47..541998b937 100644
--- a/spec/ruby/language/regexp/escapes_spec.rb
+++ b/spec/ruby/language/regexp/escapes_spec.rb
@@ -1,9 +1,11 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative '../fixtures/classes'
 
+# TODO: synchronize with spec/core/regexp/new_spec.rb -
+#       escaping is also tested there
 describe "Regexps with escape characters" do
-  it "they're supported" do
+  it "supports escape sequences" do
     /\t/.match("\t").to_a.should == ["\t"] # horizontal tab
     /\v/.match("\v").to_a.should == ["\v"] # vertical tab
     /\n/.match("\n").to_a.should == ["\n"] # newline
@@ -15,9 +17,7 @@ describe "Regexps with escape characters" do
     # \nnn         octal char            (encoded byte value)
   end
 
-  it "support quoting meta-characters via escape sequence" do
-    /\\/.match("\\").to_a.should == ["\\"]
-    /\//.match("/").to_a.should == ["/"]
+  it "supports quoting meta-characters via escape sequence" do
     # parenthesis, etc
     /\(/.match("(").to_a.should == ["("]
     /\)/.match(")").to_a.should == [")"]
@@ -25,6 +25,8 @@ describe "Regexps with escape characters" do
     /\]/.match("]").to_a.should == ["]"]
     /\{/.match("{").to_a.should == ["{"]
     /\}/.match("}").to_a.should == ["}"]
+    /\</.match("<").to_a.should == ["<"]
+    /\>/.match(">").to_a.should == [">"]
     # alternation separator
     /\|/.match("|").to_a.should == ["|"]
     # quantifiers
@@ -37,11 +39,81 @@ describe "Regexps with escape characters" do
     /\$/.match("$").to_a.should == ["$"]
   end
 
+  it "supports quoting meta-characters via escape sequence when used as a terminator" do
+    # parenthesis, etc
+    # %r[[, %r((, etc literals - are forbidden
+    %r(\().match("(").to_a.should == ["("]
+    %r(\)).match(")").to_a.should == [")"]
+    %r)\().match("(").to_a.should == ["("]
+    %r)\)).match(")").to_a.should == [")"]
+
+    %r[\[].match("[").to_a.should == ["["]
+    %r[\]].match("]").to_a.should == ["]"]
+    %r]\[].match("[").to_a.should == ["["]
+    %r]\]].match("]").to_a.should == ["]"]
+
+    %r{\{}.match("{").to_a.should == ["{"]
+    %r{\}}.match("}").to_a.should == ["}"]
+    %r}\{}.match("{").to_a.should == ["{"]
+    %r}\}}.match("}").to_a.should == ["}"]
+
+    %r<\<>.match("<").to_a.should == ["<"]
+    %r<\>>.match(">").to_a.should == [">"]
+    %r>\<>.match("<").to_a.should == ["<"]
+    %r>\>>.match(">").to_a.should == [">"]
+
+    # alternation separator
+    %r|\||.match("|").to_a.should == ["|"]
+    # quantifiers
+    %r?\??.match("?").to_a.should == ["?"]
+    %r.\...match(".").to_a.should == ["."]
+    %r*\**.match("*").to_a.should == ["*"]
+    %r+\++.match("+").to_a.should == ["+"]
+    # line anchors
+    %r^\^^.match("^").to_a.should == ["^"]
+    %r$\$$.match("$").to_a.should == ["$"]
+  end
+
+  it "supports quoting non-meta-characters via escape sequence when used as a terminator" do
+    non_meta_character_terminators = [
+      '!', '"', '#', '%', '&', "'", ',', '-', ':', ';', '@', '_', '`', '/', '=', '~'
+    ]
+
+    non_meta_character_terminators.each do |c|
+      pattern = eval("%r" + c + "\\" + c + c)
+      pattern.match(c).to_a.should == [c]
+    end
+  end
+
+  it "does not change semantics of escaped non-meta-character when used as a terminator" do
+    all_terminators = [*("!".."/"), *(":".."@"), *("[".."`"), *("{".."~")]
+    meta_character_terminators = ["$", "^", "*", "+", ".", "?", "|", "}", ")", ">", "]"]
+    special_cases = ['(', '{', '[', '<', '\\']
+
+    # it should be equivalent to
+    #   [ '!', '"', '#', '%', '&', "'", ',', '-', ':', ';', '@', '_', '`', '/', '=', '~' ]
+    non_meta_character_terminators = all_terminators - meta_character_terminators - special_cases
+
+    non_meta_character_terminators.each do |c|
+      pattern = eval("%r" + c + "\\" + c + c)
+      pattern.should == /#{c}/
+    end
+  end
+
+  it "does not change semantics of escaped meta-character when used as a terminator" do
+    meta_character_terminators = ["$", "^", "*", "+", ".", "?", "|", "}", ")", ">", "]"]
+
+    meta_character_terminators.each do |c|
+      pattern = eval("%r" + c + "\\" + c + c)
+      pattern.should == eval("/\\#{c}/")
+    end
+  end
+
   it "allows any character to be escaped" do
     /\y/.match("y").to_a.should == ["y"]
   end
 
-  it "support \\x (hex characters)" do
+  it "supports \\x (hex characters)" do
     /\xA/.match("\nxyz").to_a.should == ["\n"]
     /\x0A/.match("\n").to_a.should == ["\n"]
     /\xAA/.match("\nA").should be_nil
@@ -53,7 +125,7 @@ describe "Regexps with escape characters" do
     # \x{7HHHHHHH} wide hexadecimal char (character code point value)
   end
 
-  it "support \\c (control characters)" do
+  it "supports \\c (control characters)" do
     #/\c \c@\c`/.match("\00\00\00").to_a.should == ["\00\00\00"]
     /\c#\cc\cC/.match("\03\03\03").to_a.should == ["\03\03\03"]
     /\c'\cG\cg/.match("\a\a\a").to_a.should == ["\a\a\a"]
@@ -78,4 +150,20 @@ describe "Regexps with escape characters" do
     # \M-x         meta  (x|0x80)        (character code point value)
     # \M-\C-x      meta control char     (character code point value)
   end
+
+  it "handles three digit octal escapes starting with 0" do
+    /[\000-\b]/.match("\x00")[0].should == "\x00"
+  end
+
+  it "handles control escapes with \\C-x syntax" do
+    /\C-*\C-J\C-j/.match("\n\n\n")[0].should == "\n\n\n"
+  end
+
+  it "supports the \\K keep operator" do
+    /a\Kb/.match("ab")[0].should == "b"
+  end
+
+  it "supports the \\R line break escape" do
+    /\R/.match("\n")[0].should == "\n"
+  end
 end
diff --git a/spec/ruby/language/regexp/grouping_spec.rb b/spec/ruby/language/regexp/grouping_spec.rb
index 8806d06746..313858f714 100644
--- a/spec/ruby/language/regexp/grouping_spec.rb
+++ b/spec/ruby/language/regexp/grouping_spec.rb
@@ -12,7 +12,7 @@ describe "Regexps with grouping" do
   end
 
   it "raises a SyntaxError when parentheses aren't balanced" do
-   -> { eval "/(hay(st)ack/" }.should raise_error(SyntaxError)
+    -> { eval "/(hay(st)ack/" }.should raise_error(SyntaxError)
   end
 
   it "supports (?: ) (non-capturing group)" do
@@ -20,4 +20,44 @@ describe "Regexps with grouping" do
     # Parsing precedence
     /(?:xdigit:)/.match("xdigit:").to_a.should == ["xdigit:"]
   end
+
+  it "group names cannot start with digits or minus" do
+    -> { Regexp.new("(?<1a>a)") }.should raise_error(RegexpError)
+    -> { Regexp.new("(?<-a>a)") }.should raise_error(RegexpError)
+  end
+
+  it "ignore capture groups in line comments" do
+    /^
+     (a) # there is a capture group on this line
+     b   # there is no capture group on this line (not even here)
+     $/x.match("ab").to_a.should == [ "ab", "a" ]
+  end
+
+  it "does not consider # inside a character class as a comment" do
+    # From https://github.com/rubocop/rubocop/blob/39fcf1c568/lib/rubocop/cop/utils/format_string.rb#L18
+    regexp = /
+        % (?<type>%) # line comment
+      | % (?<flags>(?-mix:[ #0+-]|(?-mix:(\d+)\$))*) (?#group comment)
+        (?:
+          (?: (?-mix:(?<width>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:\.(?<precision>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:<(?<name>\w+)>)?
+            | (?-mix:(?<width>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:<(?<name>\w+)>) (?-mix:\.(?<precision>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))?
+            | (?-mix:<(?<name>\w+)>) (?<more_flags>(?-mix:[ #0+-]|(?-mix:(\d+)\$))*) (?-mix:(?<width>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:\.(?<precision>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))?
+          ) (?-mix:(?<type>[bBdiouxXeEfgGaAcps]))
+          | (?-mix:(?<width>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:\.(?<precision>(?-mix:\d+|(?-mix:\*(?-mix:(\d+)\$)?))))? (?-mix:\{(?<name>\w+)\})
+        )
+    /x
+    regexp.named_captures.should == {
+      "type" => [1, 13],
+      "flags" => [2],
+      "width" => [3, 6, 11, 14],
+      "precision" => [4, 8, 12, 15],
+      "name" => [5, 7, 9, 16],
+      "more_flags" => [10]
+    }
+    match = regexp.match("%6.3f")
+    match[:width].should == '6'
+    match[:precision].should == '3'
+    match[:type].should == 'f'
+    match.to_a.should == [ "%6.3f", nil, "", "6", "3"] + [nil] * 8 + ["f"] + [nil] * 3
+  end
 end
diff --git a/spec/ruby/language/regexp/interpolation_spec.rb b/spec/ruby/language/regexp/interpolation_spec.rb
index ed0b724763..6951fd38ca 100644
--- a/spec/ruby/language/regexp/interpolation_spec.rb
+++ b/spec/ruby/language/regexp/interpolation_spec.rb
@@ -36,7 +36,7 @@ describe "Regexps with interpolation" do
 
   it "gives precedence to escape sequences over substitution" do
     str = "J"
-    /\c#{str}/.to_s.should == '(?-mix:\c#' + '{str})'
+    /\c#{str}/.to_s.should include('{str}')
   end
 
   it "throws RegexpError for malformed interpolation" do
diff --git a/spec/ruby/language/regexp/modifiers_spec.rb b/spec/ruby/language/regexp/modifiers_spec.rb
index 9f3cf8acf8..2f5522bc8a 100644
--- a/spec/ruby/language/regexp/modifiers_spec.rb
+++ b/spec/ruby/language/regexp/modifiers_spec.rb
@@ -104,7 +104,7 @@ describe "Regexps with modifiers" do
     /./m.match("\n").to_a.should == ["\n"]
   end
 
-  it "supports ASII/Unicode modifiers" do
+  it "supports ASCII/Unicode modifiers" do
     eval('/(?a)[[:alpha:]]+/').match("a\u3042").to_a.should == ["a"]
     eval('/(?d)[[:alpha:]]+/').match("a\u3042").to_a.should == ["a\u3042"]
     eval('/(?u)[[:alpha:]]+/').match("a\u3042").to_a.should == ["a\u3042"]
diff --git a/spec/ruby/language/regexp/repetition_spec.rb b/spec/ruby/language/regexp/repetition_spec.rb
index 7bb767ccaf..d76619688f 100644
--- a/spec/ruby/language/regexp/repetition_spec.rb
+++ b/spec/ruby/language/regexp/repetition_spec.rb
@@ -45,4 +45,94 @@ describe "Regexps with repetition" do
     /a?/.match("aaa").to_a.should == ["a"]
     /a?/.match("bbb").to_a.should == [""]
   end
+
+  it "handles incomplete range quantifiers" do
+    /a{}/.match("a{}")[0].should == "a{}"
+    /a{,}/.match("a{,}")[0].should == "a{,}"
+    /a{1/.match("a{1")[0].should == "a{1"
+    /a{1,2/.match("a{1,2")[0].should == "a{1,2"
+    /a{,5}/.match("aaa")[0].should == "aaa"
+  end
+
+  it "lets us use quantifiers on assertions" do
+    /a^?b/.match("ab")[0].should == "ab"
+    /a$?b/.match("ab")[0].should == "ab"
+    /a\A?b/.match("ab")[0].should == "ab"
+    /a\Z?b/.match("ab")[0].should == "ab"
+    /a\z?b/.match("ab")[0].should == "ab"
+    /a\G?b/.match("ab")[0].should == "ab"
+    /a\b?b/.match("ab")[0].should == "ab"
+    /a\B?b/.match("ab")[0].should == "ab"
+    /a(?=c)?b/.match("ab")[0].should == "ab"
+    /a(?!=b)?b/.match("ab")[0].should == "ab"
+    /a(?<=c)?b/.match("ab")[0].should == "ab"
+    /a(?<!a)?b/.match("ab")[0].should == "ab"
+  end
+
+  it "does not delete optional assertions" do
+    /(?=(a))?/.match("a").to_a.should == [ "", "a" ]
+  end
+
+  it "supports nested quantifiers" do
+    suppress_warning do
+      eval <<-RUBY
+      /a***/.match("aaa")[0].should == "aaa"
+
+      # a+?* should not be reduced, it should be equivalent to (a+?)*
+      # NB: the capture group prevents regex engines from reducing the two quantifiers
+      # https://bugs.ruby-lang.org/issues/17341
+      /a+?*/.match("")[0].should == ""
+      /(a+?)*/.match("")[0].should == ""
+
+      /a+?*/.match("a")[0].should == "a"
+      /(a+?)*/.match("a")[0].should == "a"
+
+      /a+?*/.match("aa")[0].should == "aa"
+      /(a+?)*/.match("aa")[0].should == "aa"
+
+      # a+?+ should not be reduced, it should be equivalent to (a+?)+
+      # https://bugs.ruby-lang.org/issues/17341
+      /a+?+/.match("").should == nil
+      /(a+?)+/.match("").should == nil
+
+      /a+?+/.match("a")[0].should == "a"
+      /(a+?)+/.match("a")[0].should == "a"
+
+      /a+?+/.match("aa")[0].should == "aa"
+      /(a+?)+/.match("aa")[0].should == "aa"
+
+      # both a**? and a+*? should be equivalent to (a+)??
+      # this quantifier would rather match nothing, but if that's not possible,
+      # it will greedily take everything
+      /a**?/.match("")[0].should == ""
+      /(a*)*?/.match("")[0].should == ""
+      /a+*?/.match("")[0].should == ""
+      /(a+)*?/.match("")[0].should == ""
+      /(a+)??/.match("")[0].should == ""
+
+      /a**?/.match("aaa")[0].should == ""
+      /(a*)*?/.match("aaa")[0].should == ""
+      /a+*?/.match("aaa")[0].should == ""
+      /(a+)*?/.match("aaa")[0].should == ""
+      /(a+)??/.match("aaa")[0].should == ""
+
+      /b.**?b/.match("baaabaaab")[0].should == "baaabaaab"
+      /b(.*)*?b/.match("baaabaaab")[0].should == "baaabaaab"
+      /b.+*?b/.match("baaabaaab")[0].should == "baaabaaab"
+      /b(.+)*?b/.match("baaabaaab")[0].should == "baaabaaab"
+      /b(.+)??b/.match("baaabaaab")[0].should == "baaabaaab"
+      RUBY
+    end
+  end
+
+  it "treats ? after {n} quantifier as another quantifier, not as non-greedy marker" do
+    /a{2}?/.match("").to_a.should == [""]
+  end
+
+  it "matches zero-width capture groups in optional iterations of loops" do
+    /()?/.match("").to_a.should == ["", ""]
+    /(a*)?/.match("").to_a.should == ["", ""]
+    /(a*)*/.match("").to_a.should == ["", ""]
+    /(?:a|()){500,1000}/.match("a" * 500).to_a.should == ["a" * 500, ""]
+  end
 end
diff --git a/spec/ruby/language/regexp/subexpression_call_spec.rb b/spec/ruby/language/regexp/subexpression_call_spec.rb
new file mode 100644
index 0000000000..16b64cb327
--- /dev/null
+++ b/spec/ruby/language/regexp/subexpression_call_spec.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "Regexps with subexpression calls" do
+  it "allows numeric subexpression calls" do
+    /(a)\g<1>/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+
+  it "treats subexpression calls as distinct from simple back-references" do
+    # Back-references only match a string which is equal to the original captured string.
+    /(?<three_digits>[0-9]{3})-\k<three_digits>/.match("123-123")[0].should == "123-123"
+    /(?<three_digits>[0-9]{3})-\k<three_digits>/.match("123-456").should == nil
+    # However, subexpression calls reuse the previous expression and can match a different
+    # string.
+    /(?<three_digits>[0-9]{3})-\g<three_digits>/.match("123-456")[0].should == "123-456"
+  end
+
+  it "allows recursive subexpression calls" do
+    # This pattern matches well-nested parenthesized expression.
+    parens = /^ (?<parens>  (?: \( \g<parens> \) | [^()] )*  ) $/x
+    parens.match("((a)(b))c(d)")[0].should == "((a)(b))c(d)"
+    parens.match("((a)(b)c(d)").should == nil
+  end
+
+  it "allows access to back-references from the current level" do
+    # Using \\k<first_char-0> accesses the last value captured in first_char
+    # on the current stack level.
+    mirror = /^ (?<mirror> (?: (?<first_char>.) \g<mirror> \k<first_char-0> )? ) $/x
+    mirror.match("abccba")[0].should == "abccba"
+    mirror.match("abccbd").should == nil
+
+    # OTOH, using \\k<first_char> accesses the last value captured in first_char,
+    # regardless of the stack level. Therefore, it can't be used to implement
+    # the mirror language.
+    broken_mirror = /^ (?<mirror> (?: (?<first_char>.) \g<mirror> \k<first_char> )? ) $/x
+    broken_mirror.match("abccba").should == nil
+    # This matches because the 'c' is captured in first_char and that value is
+    # then used for all subsequent back-references, regardless of nesting.
+    broken_mirror.match("abcccc")[0].should == "abcccc"
+  end
+
+  it "allows + and - in group names and referential constructs that don't use levels, i.e. subexpression calls" do
+    /(?<a+>a)\g<a+>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a+b>a)\g<a+b>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a+1>a)\g<a+1>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a->a)\g<a->/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a-b>a)\g<a-b>/.match("aa").to_a.should == [ "aa", "a" ]
+    /(?<a-1>a)\g<a-1>/.match("aa").to_a.should == [ "aa", "a" ]
+  end
+end
diff --git a/spec/ruby/language/regexp_spec.rb b/spec/ruby/language/regexp_spec.rb
index 67c7c034e9..ce344b5b05 100644
--- a/spec/ruby/language/regexp_spec.rb
+++ b/spec/ruby/language/regexp_spec.rb
@@ -18,6 +18,10 @@ describe "Literal Regexps" do
     /Hello/.should be_kind_of(Regexp)
   end
 
+  it "is frozen" do
+    /Hello/.should.frozen?
+  end
+
   it "caches the Regexp object" do
     rs = []
     2.times do |i|
@@ -58,7 +62,7 @@ describe "Literal Regexps" do
     end
   end
 
-  it "supports non-paired delimiters delimiters with %r" do
+  it "supports non-paired delimiters with %r" do
     LanguageSpecs.non_paired_delimiters.each do |c|
       eval("%r#{c} foo #{c}").should == / foo /
     end
@@ -90,7 +94,6 @@ describe "Literal Regexps" do
     /./.match("\0").to_a.should == ["\0"]
   end
 
-
   it "supports | (alternations)" do
     /a|b/.match("a").to_a.should == ["a"]
   end
@@ -109,6 +112,13 @@ describe "Literal Regexps" do
     /foo.(?<=\d)/.match("fooA foo1").to_a.should == ["foo1"]
   end
 
+  ruby_bug "#13671", ""..."4.0" do # https://bugs.ruby-lang.org/issues/13671
+    it "handles a lookbehind with ss characters" do
+      r =  Regexp.new("(?<!dss)", Regexp::IGNORECASE)
+      r.should =~ "✨"
+    end
+  end
+
   it "supports (?<! ) (negative lookbehind)" do
     /foo.(?<!\d)/.match("foo1 fooA").to_a.should == ["fooA"]
   end
@@ -148,26 +158,6 @@ describe "Literal Regexps" do
     pattern.should_not =~ 'T'
   end
 
-  escapable_terminators =  ['!', '"', '#', '%', '&', "'", ',', '-', ':', ';', '@', '_', '`']
-
-  it "supports escaping characters when used as a terminator" do
-    escapable_terminators.each do |c|
-      ref = "(?-mix:#{c})"
-      pattern = eval("%r" + c + "\\" + c + c)
-      pattern.to_s.should == ref
-    end
-  end
-
-  it "treats an escaped non-escapable character normally when used as a terminator" do
-    all_terminators = [*("!".."/"), *(":".."@"), *("[".."`"), *("{".."~")]
-    special_cases = ['(', '{', '[', '<', '\\', '=', '~']
-    (all_terminators - special_cases - escapable_terminators).each do |c|
-      ref = "(?-mix:\\#{c})"
-      pattern = eval("%r" + c + "\\" + c + c)
-      pattern.to_s.should == ref
-    end
-  end
-
   it "support handling unicode 9.0 characters with POSIX bracket expressions" do
     char_lowercase = "\u{104D8}" # OSAGE SMALL LETTER A
     /[[:lower:]]/.match(char_lowercase).to_s.should == char_lowercase
diff --git a/spec/ruby/language/rescue_spec.rb b/spec/ruby/language/rescue_spec.rb
index a912e17431..6be3bfd023 100644
--- a/spec/ruby/language/rescue_spec.rb
+++ b/spec/ruby/language/rescue_spec.rb
@@ -23,11 +23,127 @@ describe "The rescue keyword" do
     end.should == :caught
   end
 
-  it "can capture the raised exception in a local variable" do
-    begin
-      raise SpecificExampleException, "some text"
-    rescue SpecificExampleException => e
-      e.message.should == "some text"
+  describe 'can capture the raised exception' do
+    before :all do
+      require_relative 'fixtures/rescue_captures'
+    end
+
+    it 'in a local variable' do
+      RescueSpecs::LocalVariableCaptor.should_capture_exception
+    end
+
+    it 'in a class variable' do
+      RescueSpecs::ClassVariableCaptor.should_capture_exception
+    end
+
+    it 'in a constant' do
+      RescueSpecs::ConstantCaptor.should_capture_exception
+    end
+
+    it 'in a global variable' do
+      RescueSpecs::GlobalVariableCaptor.should_capture_exception
+    end
+
+    it 'in an instance variable' do
+      RescueSpecs::InstanceVariableCaptor.should_capture_exception
+    end
+
+    it 'using a safely navigated setter method' do
+      RescueSpecs::SafeNavigationSetterCaptor.should_capture_exception
+    end
+
+    it 'using a safely navigated setter method on a nil target' do
+      target = nil
+      begin
+        raise SpecificExampleException, "Raising this to be handled below"
+      rescue SpecificExampleException => target&.captured_error
+        :caught
+      end.should == :caught
+      target.should be_nil
+    end
+
+    it 'using a setter method' do
+      RescueSpecs::SetterCaptor.should_capture_exception
+    end
+
+    it 'using a square brackets setter' do
+      RescueSpecs::SquareBracketsCaptor.should_capture_exception
+    end
+  end
+
+  describe 'capturing in a local variable (that defines it)' do
+    it 'captures successfully in a method' do
+      ScratchPad.record []
+
+      def a
+        raise "message"
+      rescue => e
+        ScratchPad << e.message
+      end
+
+      a
+      ScratchPad.recorded.should == ["message"]
+    end
+
+    it 'captures successfully in a block' do
+      ScratchPad.record []
+
+      p = proc do
+        raise "message"
+      rescue => e
+        ScratchPad << e.message
+      end
+
+      p.call
+      ScratchPad.recorded.should == ["message"]
+    end
+
+    it 'captures successfully in a class' do
+      ScratchPad.record []
+
+      class RescueSpecs::C
+        raise "message"
+      rescue => e
+        ScratchPad << e.message
+      end
+
+      ScratchPad.recorded.should == ["message"]
+    end
+
+    it 'captures successfully in a module' do
+      ScratchPad.record []
+
+      module RescueSpecs::M
+        raise "message"
+      rescue => e
+        ScratchPad << e.message
+      end
+
+      ScratchPad.recorded.should == ["message"]
+    end
+
+    it 'captures sucpcessfully in a singleton class' do
+      ScratchPad.record []
+
+      class << Object.new
+        raise "message"
+      rescue => e
+        ScratchPad << e.message
+      end
+
+      ScratchPad.recorded.should == ["message"]
+    end
+
+    it 'captures successfully at the top-level' do
+      ScratchPad.record []
+      loaded_features = $".dup
+      begin
+        require_relative 'fixtures/rescue/top_level'
+
+        ScratchPad.recorded.should == ["message"]
+      ensure
+        $".replace loaded_features
+      end
     end
   end
 
@@ -85,6 +201,18 @@ describe "The rescue keyword" do
     end
   end
 
+  it "converts the splatted list of exceptions using #to_a" do
+    exceptions = mock("to_a")
+    exceptions.should_receive(:to_a).and_return(exception_list)
+    caught_it = false
+    begin
+      raise SpecificExampleException, "not important"
+    rescue *exceptions
+      caught_it = true
+    end
+    caught_it.should be_true
+  end
+
   it "can combine a splatted list of exceptions with a literal list of exceptions" do
     caught_it = false
     begin
@@ -149,7 +277,7 @@ describe "The rescue keyword" do
       rescue ArgumentError
       end
     rescue StandardError => e
-      e.backtrace.first.should include ":in `raise_standard_error'"
+      e.backtrace.first.should =~ /:in [`'](?:RescueSpecs\.)?raise_standard_error'/
     else
       fail("exception wasn't handled by the correct rescue block")
     end
@@ -208,34 +336,16 @@ describe "The rescue keyword" do
     ScratchPad.recorded.should == [:one, :else_ran, :ensure_ran, :outside_begin]
   end
 
-  ruby_version_is ''...'2.6' do
-    it "will execute an else block even without rescue and ensure" do
-      -> {
-        eval <<-ruby
-          begin
-            ScratchPad << :begin
-          else
-            ScratchPad << :else
-          end
-        ruby
-      }.should complain(/else without rescue is useless/)
-
-      ScratchPad.recorded.should == [:begin, :else]
-    end
-  end
-
-  ruby_version_is '2.6' do
-    it "raises SyntaxError when else is used without rescue and ensure" do
-      -> {
-        eval <<-ruby
-          begin
-            ScratchPad << :begin
-          else
-            ScratchPad << :else
-          end
-        ruby
-      }.should raise_error(SyntaxError, /else without rescue is useless/)
-    end
+  it "raises SyntaxError when else is used without rescue and ensure" do
+    -> {
+      eval <<-ruby
+        begin
+          ScratchPad << :begin
+        else
+          ScratchPad << :else
+        end
+      ruby
+    }.should raise_error(SyntaxError, /else without rescue is useless/)
   end
 
   it "will not execute an else block if an exception was raised" do
@@ -398,9 +508,9 @@ describe "The rescue keyword" do
         raise "from block"
       rescue (raise "from rescue expression")
       end
-    }.should raise_error(RuntimeError, "from rescue expression") do |e|
+    }.should raise_error(RuntimeError, "from rescue expression") { |e|
       e.cause.message.should == "from block"
-    end
+    }
   end
 
   it "should splat the handling Error classes" do
@@ -435,18 +545,16 @@ describe "The rescue keyword" do
     }.should raise_error(SyntaxError)
   end
 
-  ruby_version_is "2.5" do
-    it "allows rescue in 'do end' block" do
-      lambda = eval <<-ruby
-        lambda do
-          raise SpecificExampleException
-        rescue SpecificExampleException
-          ScratchPad << :caught
-        end.call
-      ruby
+  it "allows rescue in 'do end' block" do
+    lambda = eval <<-ruby
+      lambda do
+        raise SpecificExampleException
+      rescue SpecificExampleException
+        ScratchPad << :caught
+      end.call
+    ruby
 
-      ScratchPad.recorded.should == [:caught]
-    end
+    ScratchPad.recorded.should == [:caught]
   end
 
   it "allows 'rescue' in method arguments" do
@@ -459,6 +567,21 @@ describe "The rescue keyword" do
     eval('1.+((1 rescue 1))').should == 2
   end
 
+  ruby_version_is "3.4" do
+    it "does not introduce extra backtrace entries" do
+      def foo
+        begin
+          raise "oops"
+        rescue
+          return caller(0, 2)
+        end
+      end
+      line = __LINE__
+      foo[0].should =~ /#{__FILE__}:#{line-3}:in 'foo'/
+      foo[1].should =~ /#{__FILE__}:#{line+2}:in 'block/
+    end
+  end
+
   describe "inline form" do
     it "can be inlined" do
       a = 1/0 rescue 1
@@ -481,5 +604,13 @@ describe "The rescue keyword" do
         a = raise(Exception) rescue 1
       }.should raise_error(Exception)
     end
+
+    it "rescues with multiple assignment" do
+
+      a, b = raise rescue [1, 2]
+
+      a.should == 1
+      b.should == 2
+    end
   end
 end
diff --git a/spec/ruby/language/reserved_keywords.rb b/spec/ruby/language/reserved_keywords.rb
new file mode 100644
index 0000000000..6c40e34ccc
--- /dev/null
+++ b/spec/ruby/language/reserved_keywords.rb
@@ -0,0 +1,149 @@
+require_relative '../spec_helper'
+
+describe "Ruby's reserved keywords" do
+  # Copied from https://github.com/ruby/ruby/blob/master/defs/keywords
+  keywords = %w[
+    alias
+    and
+    begin
+    BEGIN
+    break
+    case
+    class
+    def
+    defined?
+    do
+    else
+    elsif
+    end
+    END
+    ensure
+    false
+    for
+    if
+    in
+    module
+    next
+    nil
+    not
+    or
+    redo
+    rescue
+    retry
+    return
+    self
+    super
+    then
+    true
+    undef
+    unless
+    until
+    when
+    while
+    yield
+    __ENCODING__
+    __FILE__
+    __LINE__
+  ]
+
+  keywords.each do |name|
+    describe "keyword '#{name}'" do
+      it "can't be used as local variable name" do
+        -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            #{name} = :local_variable
+        RUBY
+      end
+
+      if name == "defined?"
+        it "can't be used as an instance variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            @#{name} = :instance_variable
+          RUBY
+        end
+
+        it "can't be used as a class variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            class C
+              @@#{name} = :class_variable
+            end
+          RUBY
+        end
+
+        it "can't be used as a global variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            $#{name} = :global_variable
+          RUBY
+        end
+      else
+        it "can be used as an instance variable name" do
+          result = eval <<~RUBY
+            @#{name} = :instance_variable
+            @#{name}
+          RUBY
+
+          result.should == :instance_variable
+        end
+
+        it "can be used as a class variable name" do
+          result = eval <<~RUBY
+            class C
+              @@#{name} = :class_variable
+              @@#{name}
+            end
+          RUBY
+
+          result.should == :class_variable
+        end
+
+        it "can be used as a global variable name" do
+          result = eval <<~RUBY
+            $#{name} = :global_variable
+            $#{name}
+          RUBY
+
+          result.should == :global_variable
+        end
+      end
+
+      it "can't be used as a positional parameter name" do
+        -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+          def x(#{name}); end
+        RUBY
+      end
+
+      invalid_kw_param_names = ["BEGIN","END","defined?"]
+
+      if invalid_kw_param_names.include?(name)
+        it "can't be used a keyword parameter name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            def m(#{name}:); end
+          RUBY
+        end
+      else
+        it "can be used a keyword parameter name" do
+          result = instance_eval <<~RUBY
+            def m(#{name}:)
+              binding.local_variable_get(:#{name})
+            end
+
+            m(#{name}: :argument)
+          RUBY
+
+          result.should == :argument
+        end
+      end
+
+      it "can be used as a method name" do
+        result = instance_eval <<~RUBY
+          def #{name}
+            :method_return_value
+          end
+
+          send(:#{name})
+        RUBY
+
+        result.should == :method_return_value
+      end
+    end
+  end
+end
diff --git a/spec/ruby/language/retry_spec.rb b/spec/ruby/language/retry_spec.rb
index ee5377946f..669d5f0ff5 100644
--- a/spec/ruby/language/retry_spec.rb
+++ b/spec/ruby/language/retry_spec.rb
@@ -31,8 +31,11 @@ describe "The retry statement" do
     results.should == [1, 2, 3, 1, 2, 4, 5, 6, 4, 5]
   end
 
-  it "raises a SyntaxError when used outside of a begin statement" do
+  it "raises a SyntaxError when used outside of a rescue statement" do
     -> { eval 'retry' }.should raise_error(SyntaxError)
+    -> { eval 'begin; retry; end' }.should raise_error(SyntaxError)
+    -> { eval 'def m; retry; end' }.should raise_error(SyntaxError)
+    -> { eval 'module RetrySpecs; retry; end' }.should raise_error(SyntaxError)
   end
 end
 
diff --git a/spec/ruby/language/return_spec.rb b/spec/ruby/language/return_spec.rb
index 27729750f1..a62ed1242d 100644
--- a/spec/ruby/language/return_spec.rb
+++ b/spec/ruby/language/return_spec.rb
@@ -250,261 +250,240 @@ describe "The return keyword" do
     end
   end
 
-  ruby_version_is '2.4.2' do
-    describe "at top level" do
-      before :each do
-        @filename = tmp("top_return.rb")
-        ScratchPad.record []
-      end
+  describe "at top level" do
+    before :each do
+      @filename = tmp("top_return.rb")
+      ScratchPad.record []
+    end
 
-      after do
-        rm_r @filename
-      end
+    after do
+      rm_r @filename
+    end
 
-      it "stops file execution" do
-        ruby_exe(<<-END_OF_CODE).should == "before return\n"
-          puts "before return"
-          return
+    it "stops file execution" do
+      ruby_exe(<<-END_OF_CODE).should == "before return\n"
+        puts "before return"
+        return
 
-          puts "after return"
+        puts "after return"
+      END_OF_CODE
+
+      $?.exitstatus.should == 0
+    end
+
+    describe "within if" do
+      it "is allowed" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before if"
+          if true
+            return
+          end
+
+          ScratchPad << "after if"
         END_OF_CODE
 
-        $?.exitstatus.should == 0
+        load @filename
+        ScratchPad.recorded.should == ["before if"]
       end
+    end
 
-      describe "within if" do
-        it "is allowed" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before if"
-            if true
-              return
-            end
+    describe "within while loop" do
+      it "is allowed" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before while"
+          while true
+            return
+          end
 
-            ScratchPad << "after if"
-          END_OF_CODE
+          ScratchPad << "after while"
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before if"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before while"]
       end
+    end
 
-      describe "within while loop" do
-        it "is allowed" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before while"
-            while true
-              return
-            end
+    describe "within a begin" do
+      it "is allowed in begin block" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before begin"
+          begin
+            return
+          end
 
-            ScratchPad << "after while"
-          END_OF_CODE
+          ScratchPad << "after begin"
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before while"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before begin"]
       end
 
-      describe "within a begin" do
-        it "is allowed in begin block" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before begin"
-            begin
-              return
-            end
+      it "is allowed in ensure block" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before begin"
+          begin
+          ensure
+            return
+          end
 
-            ScratchPad << "after begin"
-          END_OF_CODE
+          ScratchPad << "after begin"
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before begin"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before begin"]
+      end
 
-        it "is allowed in ensure block" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before begin"
-            begin
-            ensure
-              return
-            end
+      it "is allowed in rescue block" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before begin"
+          begin
+            raise
+          rescue RuntimeError
+            return
+          end
 
-            ScratchPad << "after begin"
-          END_OF_CODE
+          ScratchPad << "after begin"
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before begin"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before begin"]
+      end
 
-        it "is allowed in rescue block" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before begin"
-            begin
-              raise
-            rescue RuntimeError
-              return
-            end
+      it "fires ensure block before returning" do
+        ruby_exe(<<-END_OF_CODE).should == "within ensure\n"
+          begin
+            return
+          ensure
+            puts "within ensure"
+          end
 
-            ScratchPad << "after begin"
-          END_OF_CODE
+          puts "after begin"
+        END_OF_CODE
+      end
 
-          load @filename
-          ScratchPad.recorded.should == ["before begin"]
-        end
+      it "fires ensure block before returning while loads file" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before begin"
+          begin
+            return
+          ensure
+            ScratchPad << "within ensure"
+          end
 
-        it "fires ensure block before returning" do
-          ruby_exe(<<-END_OF_CODE).should == "within ensure\n"
-            begin
-              return
-            ensure
-              puts "within ensure"
-            end
+          ScratchPad << "after begin"
+        END_OF_CODE
 
-            puts "after begin"
-          END_OF_CODE
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before begin", "within ensure"]
+      end
 
-        ruby_bug "#14061", "2.4"..."2.5" do
-          it "fires ensure block before returning while loads file" do
-            File.write(@filename, <<-END_OF_CODE)
-              ScratchPad << "before begin"
-              begin
-                return
-              ensure
-                ScratchPad << "within ensure"
-              end
-
-              ScratchPad << "after begin"
-            END_OF_CODE
-
-            load @filename
-            ScratchPad.recorded.should == ["before begin", "within ensure"]
+      it "swallows exception if returns in ensure block" do
+        File.write(@filename, <<-END_OF_CODE)
+          begin
+            raise
+          ensure
+            ScratchPad << "before return"
+            return
           end
-        end
+        END_OF_CODE
 
-        it "swallows exception if returns in ensure block" do
-          File.write(@filename, <<-END_OF_CODE)
-            begin
-              raise
-            ensure
-              ScratchPad << "before return"
-              return
-            end
-          END_OF_CODE
-
-          load @filename
-          ScratchPad.recorded.should == ["before return"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before return"]
       end
+    end
 
-      describe "within a block" do
-        it "is allowed" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before call"
-            proc { return }.call
+    describe "within a block" do
+      it "is allowed" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before call"
+          proc { return }.call
 
-            ScratchPad << "after call"
-          END_OF_CODE
+          ScratchPad << "after call"
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before call"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before call"]
       end
+    end
 
-      describe "within a class" do
-        ruby_version_is ""..."2.5" do
-          it "is allowed" do
-            File.write(@filename, <<-END_OF_CODE)
-              class ReturnSpecs::A
-                ScratchPad << "before return"
-                return
-
-                ScratchPad << "after return"
-              end
-            END_OF_CODE
+    describe "within a class" do
+      it "raises a SyntaxError" do
+        File.write(@filename, <<-END_OF_CODE)
+          class ReturnSpecs::A
+            ScratchPad << "before return"
+            return
 
-            load @filename
-            ScratchPad.recorded.should == ["before return"]
+            ScratchPad << "after return"
           end
-        end
-
-        ruby_version_is "2.5" do
-          it "raises a SyntaxError" do
-            File.write(@filename, <<-END_OF_CODE)
-              class ReturnSpecs::A
-                ScratchPad << "before return"
-                return
+        END_OF_CODE
 
-                ScratchPad << "after return"
-              end
-            END_OF_CODE
+        -> { load @filename }.should raise_error(SyntaxError)
+      end
+    end
 
-            -> { load @filename }.should raise_error(SyntaxError)
+    describe "within a block within a class" do
+      it "is not allowed" do
+        File.write(@filename, <<-END_OF_CODE)
+          class ReturnSpecs::A
+            ScratchPad << "before return"
+            1.times { return }
+            ScratchPad << "after return"
           end
-        end
-      end
+        END_OF_CODE
 
-      describe "within a block within a class" do
-        it "is allowed" do
-          File.write(@filename, <<-END_OF_CODE)
-            class ReturnSpecs::A
-              ScratchPad << "before return"
-              1.times { return }
-              ScratchPad << "after return"
-            end
-          END_OF_CODE
-
-          load @filename
-          ScratchPad.recorded.should == ["before return"]
-        end
+        -> { load @filename }.should raise_error(LocalJumpError)
       end
+    end
 
-      describe "file loading" do
-        it "stops file loading and execution" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before return"
+    describe "within BEGIN" do
+      it "is allowed" do
+        File.write(@filename, <<-END_OF_CODE)
+          BEGIN {
+            ScratchPad << "before call"
             return
-            ScratchPad << "after return"
-          END_OF_CODE
+            ScratchPad << "after call"
+          }
+        END_OF_CODE
 
-          load @filename
-          ScratchPad.recorded.should == ["before return"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before call"]
       end
+    end
 
-      describe "file requiring" do
-        it "stops file loading and execution" do
-          File.write(@filename, <<-END_OF_CODE)
-            ScratchPad << "before return"
-            return
-            ScratchPad << "after return"
-          END_OF_CODE
+    describe "file loading" do
+      it "stops file loading and execution" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before return"
+          return
+          ScratchPad << "after return"
+        END_OF_CODE
 
-          require @filename
-          ScratchPad.recorded.should == ["before return"]
-        end
+        load @filename
+        ScratchPad.recorded.should == ["before return"]
       end
+    end
 
-      describe "return with argument" do
-        ruby_version_is ""..."2.7" do
-          it "does not affect exit status" do
-            ruby_exe(<<-END_OF_CODE).should == ""
-              return 10
-            END_OF_CODE
+    describe "file requiring" do
+      it "stops file loading and execution" do
+        File.write(@filename, <<-END_OF_CODE)
+          ScratchPad << "before return"
+          return
+          ScratchPad << "after return"
+        END_OF_CODE
 
-            $?.exitstatus.should == 0
-          end
-        end
+        require @filename
+        ScratchPad.recorded.should == ["before return"]
+      end
+    end
 
-        ruby_version_is "2.7" do
-          it "warns but does not affect exit status" do
-            ruby_exe(<<-END_OF_CODE).should == "-e: warning: argument of top-level return is ignored\n"
-              $stderr.reopen($stdout)
-              system(ENV['RUBY_EXE'], '-e', 'return 10')
-              exit($?.exitstatus)
-            END_OF_CODE
+    describe "return with argument" do
+      it "warns but does not affect exit status" do
+        err = ruby_exe(<<-END_OF_CODE, args: "2>&1")
+          return 10
+        END_OF_CODE
+        $?.exitstatus.should == 0
 
-            $?.exitstatus.should == 0
-          end
-        end
+        err.should =~ /warning: argument of top-level return is ignored/
       end
     end
   end
diff --git a/spec/ruby/language/safe_navigator_spec.rb b/spec/ruby/language/safe_navigator_spec.rb
index c3aecff2dd..b1e28c3963 100644
--- a/spec/ruby/language/safe_navigator_spec.rb
+++ b/spec/ruby/language/safe_navigator_spec.rb
@@ -7,43 +7,43 @@ describe "Safe navigator" do
 
   context "when context is nil" do
     it "always returns nil" do
-      eval("nil&.unknown").should == nil
-      eval("[][10]&.unknown").should == nil
+      nil&.unknown.should == nil
+      [][10]&.unknown.should == nil
     end
 
     it "can be chained" do
-      eval("nil&.one&.two&.three").should == nil
+      nil&.one&.two&.three.should == nil
     end
 
     it "doesn't evaluate arguments" do
       obj = Object.new
       obj.should_not_receive(:m)
-      eval("nil&.unknown(obj.m) { obj.m }")
+      nil&.unknown(obj.m) { obj.m }
     end
   end
 
   context "when context is false" do
     it "calls the method" do
-      eval("false&.to_s").should == "false"
+      false&.to_s.should == "false"
 
-      -> { eval("false&.unknown") }.should raise_error(NoMethodError)
+      -> { false&.unknown }.should raise_error(NoMethodError)
     end
   end
 
   context "when context is truthy" do
     it "calls the method" do
-      eval("1&.to_s").should == "1"
+      1&.to_s.should == "1"
 
-      -> { eval("1&.unknown") }.should raise_error(NoMethodError)
+      -> { 1&.unknown }.should raise_error(NoMethodError)
     end
   end
 
   it "takes a list of arguments" do
-    eval("[1,2,3]&.first(2)").should == [1,2]
+    [1,2,3]&.first(2).should == [1,2]
   end
 
   it "takes a block" do
-    eval("[1,2]&.map { |i| i * 2 }").should == [2, 4]
+    [1,2]&.map { |i| i * 2 }.should == [2, 4]
   end
 
   it "allows assignment methods" do
@@ -56,29 +56,77 @@ describe "Safe navigator" do
     end
     obj = klass.new
 
-    eval("obj&.foo = 3").should == 3
+    (obj&.foo = 3).should == 3
     obj.foo.should == 3
 
     obj = nil
-    eval("obj&.foo = 3").should == nil
+    (obj&.foo = 3).should == nil
   end
 
   it "allows assignment operators" do
     klass = Class.new do
-      attr_accessor :m
+      attr_reader :m
 
       def initialize
         @m = 0
       end
+
+      def m=(v)
+        @m = v
+        42
+      end
     end
 
     obj = klass.new
 
-    eval("obj&.m += 3")
+    obj&.m += 3
     obj.m.should == 3
 
     obj = nil
-    eval("obj&.m += 3").should == nil
+    (obj&.m += 3).should == nil
+  end
+
+  it "allows ||= operator" do
+    klass = Class.new do
+      attr_reader :m
+
+      def initialize
+        @m = false
+      end
+
+      def m=(v)
+        @m = v
+        42
+      end
+    end
+
+    obj = klass.new
+
+    (obj&.m ||= true).should == true
+    obj.m.should == true
+
+    obj = nil
+    (obj&.m ||= true).should == nil
+    obj.should == nil
+  end
+
+  it "allows &&= operator" do
+    klass = Class.new do
+      attr_accessor :m
+
+      def initialize
+        @m = true
+      end
+    end
+
+    obj = klass.new
+
+    (obj&.m &&= false).should == false
+    obj.m.should == false
+
+    obj = nil
+    (obj&.m &&= false).should == nil
+    obj.should == nil
   end
 
   it "does not call the operator method lazily with an assignment operator" do
@@ -91,7 +139,7 @@ describe "Safe navigator" do
     obj = klass.new
 
     -> {
-      eval("obj&.foo += 3")
+      obj&.foo += 3
     }.should raise_error(NoMethodError) { |e|
       e.name.should == :+
     }
diff --git a/spec/ruby/language/safe_spec.rb b/spec/ruby/language/safe_spec.rb
index be150df9d1..03ae96148e 100644
--- a/spec/ruby/language/safe_spec.rb
+++ b/spec/ruby/language/safe_spec.rb
@@ -1,137 +1,11 @@
 require_relative '../spec_helper'
 
 describe "The $SAFE variable" do
-
-  ruby_version_is "2.6" do
-    after :each do
-      $SAFE = 0
-    end
-  end
-
-  it "is 0 by default" do
-    $SAFE.should == 0
-    proc {
-      $SAFE.should == 0
-    }.call
-  end
-
-  it "can be set to 0" do
-    proc {
-      $SAFE = 0
-      $SAFE.should == 0
-    }.call
-  end
-
-  it "can be set to 1" do
-    proc {
-      $SAFE = 1
-      $SAFE.should == 1
-    }.call
-  end
-
-  [2, 3, 4].each do |n|
-    it "cannot be set to #{n}" do
-      -> {
-        proc {
-          $SAFE = n
-        }.call
-      }.should raise_error(ArgumentError, /\$SAFE=2 to 4 are obsolete/)
-    end
-  end
-
-  ruby_version_is ""..."2.6" do
-    it "cannot be set to values below 0" do
-      -> {
-        proc {
-          $SAFE = -100
-        }.call
-      }.should raise_error(SecurityError, /tried to downgrade safe level from 0 to -100/)
-    end
-  end
-
-  ruby_version_is "2.6" do
-    it "raises ArgumentError when set to values below 0" do
-      -> {
-        proc {
-          $SAFE = -100
-        }.call
-      }.should raise_error(ArgumentError, "$SAFE should be >= 0")
-    end
-  end
-
-  it "cannot be set to values above 4" do
-    -> {
-      proc {
-        $SAFE = 100
-      }.call
-    }.should raise_error(ArgumentError, /\$SAFE=2 to 4 are obsolete/)
-  end
-
-  ruby_version_is ""..."2.6" do
-    it "cannot be manually lowered" do
-      proc {
-        $SAFE = 1
-        -> {
-          $SAFE = 0
-        }.should raise_error(SecurityError, /tried to downgrade safe level from 1 to 0/)
-      }.call
-    end
-
-    it "is automatically lowered when leaving a proc" do
-      $SAFE.should == 0
-      proc {
-        $SAFE = 1
-      }.call
-      $SAFE.should == 0
-    end
-
-    it "is automatically lowered when leaving a lambda" do
-      $SAFE.should == 0
-      -> {
-        $SAFE = 1
-      }.call
-      $SAFE.should == 0
-    end
-  end
-
-  ruby_version_is "2.6" do
-    it "can be manually lowered" do
-      $SAFE = 1
-      $SAFE = 0
-      $SAFE.should == 0
-    end
-
-    it "is not Proc local" do
-      $SAFE.should == 0
-      proc {
-        $SAFE = 1
-      }.call
-      $SAFE.should == 1
-    end
-
-    it "is not lambda local" do
-      $SAFE.should == 0
-      -> {
-        $SAFE = 1
-      }.call
-      $SAFE.should == 1
-    end
-
-    it "is global like regular global variables" do
-      Thread.new { $SAFE }.value.should == 0
-      $SAFE = 1
-      Thread.new { $SAFE }.value.should == 1
-    end
-  end
-
-  it "can be read when default from Thread#safe_level" do
-    Thread.current.safe_level.should == 0
-  end
-
-  it "can be read when modified from Thread#safe_level" do
-    proc {
-      $SAFE = 1
-      Thread.current.safe_level.should == 1
-    }.call
+  it "$SAFE is a regular global variable" do
+    $SAFE.should == nil
+    $SAFE = 42
+    $SAFE.should == 42
+  ensure
+    $SAFE = nil
   end
 end
diff --git a/spec/ruby/language/send_spec.rb b/spec/ruby/language/send_spec.rb
index 4ba3dcc9c2..5d6340ffc5 100644
--- a/spec/ruby/language/send_spec.rb
+++ b/spec/ruby/language/send_spec.rb
@@ -43,7 +43,7 @@ describe "Invoking a method" do
   end
 
   describe "with optional arguments" do
-    it "uses the optional argument if none is is passed" do
+    it "uses the optional argument if none is passed" do
       specs.fooM0O1.should == [1]
     end
 
@@ -106,6 +106,24 @@ describe "Invoking a method" do
     specs.yield_now(&o).should == :from_to_proc
   end
 
+  ruby_version_is "4.0" do
+    it "raises TypeError if 'to_proc' doesn't return a Proc" do
+      o = LangSendSpecs::RawToProc.new(42)
+
+      -> {
+        specs.makeproc(&o)
+      }.should raise_error(TypeError, "can't convert LangSendSpecs::RawToProc to Proc (LangSendSpecs::RawToProc#to_proc gives Integer)")
+    end
+
+    it "raises TypeError if block object isn't a Proc and doesn't respond to `to_proc`" do
+      o = Object.new
+
+      -> {
+        specs.makeproc(&o)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Proc")
+    end
+  end
+
   it "raises a SyntaxError with both a literal block and an object as block" do
     -> {
       eval "specs.oneb(10, &l){ 42 }"
@@ -258,10 +276,10 @@ describe "Invoking a private setter method" do
 end
 
 describe "Invoking a private getter method" do
-  it "does not permit self as a receiver" do
+  it "permits self as a receiver" do
     receiver = LangSendSpecs::PrivateGetter.new
-    -> { receiver.call_self_foo }.should raise_error(NoMethodError)
-    -> { receiver.call_self_foo_or_equals(6) }.should raise_error(NoMethodError)
+    receiver.call_self_foo_or_equals(6)
+    receiver.call_self_foo.should == 6
   end
 end
 
@@ -411,17 +429,17 @@ describe "Invoking a method" do
     specs.rest_len(0,*a,4,*5,6,7,*c,-1).should == 11
   end
 
-  it "expands the Array elements from the splat after executing the arguments and block if no other arguments follow the splat" do
+  it "expands the Array elements from the splat before applying block argument operations" do
     def self.m(*args, &block)
       [args, block]
     end
 
     args = [1, nil]
-    m(*args, &args.pop).should == [[1], nil]
+    m(*args, &args.pop).should == [[1, nil], nil]
 
     args = [1, nil]
     order = []
-    m(*(order << :args; args), &(order << :block; args.pop)).should == [[1], nil]
+    m(*(order << :args; args), &(order << :block; args.pop)).should == [[1, nil], nil]
     order.should == [:args, :block]
   end
 
diff --git a/spec/ruby/language/singleton_class_spec.rb b/spec/ruby/language/singleton_class_spec.rb
index df735018af..45e1f7f3ad 100644
--- a/spec/ruby/language/singleton_class_spec.rb
+++ b/spec/ruby/language/singleton_class_spec.rb
@@ -14,7 +14,7 @@ describe "A singleton class" do
     nil.singleton_class.should == NilClass
   end
 
-  it "raises a TypeError for Fixnum's" do
+  it "raises a TypeError for Integer's" do
     -> { 1.singleton_class }.should raise_error(TypeError)
   end
 
@@ -70,11 +70,11 @@ describe "A singleton class" do
   end
 
   it "has class String as the superclass of a String instance" do
-    "blah".singleton_class.superclass.should == String
+    "blah".dup.singleton_class.superclass.should == String
   end
 
   it "doesn't have singleton class" do
-    -> { bignum_value.singleton_class.superclass.should == Bignum }.should raise_error(TypeError)
+    -> { bignum_value.singleton_class }.should raise_error(TypeError)
   end
 end
 
@@ -291,3 +291,27 @@ describe "Instantiating a singleton class" do
     }.should raise_error(TypeError)
   end
 end
+
+describe "Frozen properties" do
+  it "is frozen if the object it is created from is frozen" do
+    o = Object.new
+    o.freeze
+    klass = o.singleton_class
+    klass.frozen?.should == true
+  end
+
+  it "will be frozen if the object it is created from becomes frozen" do
+    o = Object.new
+    klass = o.singleton_class
+    klass.frozen?.should == false
+    o.freeze
+    klass.frozen?.should == true
+  end
+
+  it "will be unfrozen if the frozen object is cloned with freeze set to false" do
+    o = Object.new
+    o.freeze
+    o2 = o.clone(freeze: false)
+    o2.singleton_class.frozen?.should == false
+  end
+end
diff --git a/spec/ruby/language/source_encoding_spec.rb b/spec/ruby/language/source_encoding_spec.rb
index a0a29f63de..7135bc0a70 100644
--- a/spec/ruby/language/source_encoding_spec.rb
+++ b/spec/ruby/language/source_encoding_spec.rb
@@ -15,7 +15,7 @@ describe "Source files" do
   end
 
   describe "encoded in UTF-16 LE without a BOM" do
-    it "are parsed because empty as they contain a NUL byte before the encoding comment" do
+    it "are parsed as empty because they contain a NUL byte before the encoding comment" do
       ruby_exe(fixture(__FILE__, "utf16-le-nobom.rb"), args: "2>&1").should == ""
     end
   end
@@ -29,7 +29,7 @@ describe "Source files" do
 
       touch(path, "wb") { |f| f.write source }
       begin
-        ruby_exe(path, args: "2>&1").should =~ /invalid multibyte char/
+        ruby_exe(path, args: "2>&1", exit_status: 1).should =~ /invalid multibyte char/
       ensure
         rm_r path
       end
@@ -51,7 +51,7 @@ describe "Source files" do
 
       touch(path, "wb") { |f| f.write source }
       begin
-        ruby_exe(path, args: "2>&1").should =~ /invalid multibyte char/
+        ruby_exe(path, args: "2>&1", exit_status: 1).should =~ /invalid multibyte char/
       ensure
         rm_r path
       end
diff --git a/spec/ruby/language/string_spec.rb b/spec/ruby/language/string_spec.rb
index a7ca00ef03..f287731bed 100644
--- a/spec/ruby/language/string_spec.rb
+++ b/spec/ruby/language/string_spec.rb
@@ -1,6 +1,7 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require_relative '../spec_helper'
+require_relative 'fixtures/class_with_class_variable'
 
 # TODO: rewrite these horrid specs. it "are..." seriously?!
 
@@ -27,11 +28,21 @@ describe "Ruby character strings" do
     "#$ip".should == 'xxx'
   end
 
+  it "interpolate class variables just with the # character" do
+    object = StringSpecs::ClassWithClassVariable.new
+    object.foo.should == 'xxx'
+  end
+
   it "allows underscore as part of a variable name in a simple interpolation" do
     @my_ip = 'xxx'
     "#@my_ip".should == 'xxx'
   end
 
+  it "does not interpolate invalid variable names" do
+    "#@".should == '#@'
+    "#$%".should == '#$%'
+  end
+
   it "has characters [.(=?!# end simple # interpolation" do
     "#@ip[".should == 'xxx['
     "#@ip.".should == 'xxx.'
@@ -51,26 +62,6 @@ describe "Ruby character strings" do
     "#\$".should == '#$'
   end
 
-  it "taints the result of interpolation when an interpolated value is tainted" do
-    "#{"".taint}".tainted?.should be_true
-
-    @ip.taint
-    "#@ip".tainted?.should be_true
-
-    $ip.taint
-    "#$ip".tainted?.should be_true
-  end
-
-  it "untrusts the result of interpolation when an interpolated value is untrusted" do
-    "#{"".untrust}".untrusted?.should be_true
-
-    @ip.untrust
-    "#@ip".untrusted?.should be_true
-
-    $ip.untrust
-    "#$ip".untrusted?.should be_true
-  end
-
   it "allows using non-alnum characters as string delimiters" do
     %(hey #{@ip}).should == "hey xxx"
     %[hey #{@ip}].should == "hey xxx"
@@ -246,8 +237,16 @@ describe "Ruby String literals" do
       ruby_exe(fixture(__FILE__, "freeze_magic_comment_across_files.rb")).chomp.should == "true"
     end
 
-    it "produce different objects for literals with the same content in different files if the other file doesn't have the comment" do
-      ruby_exe(fixture(__FILE__, "freeze_magic_comment_across_files_no_comment.rb")).chomp.should == "true"
+    guard -> { !(eval("'test'").frozen? && "test".equal?("test")) } do
+      it "produces different objects for literals with the same content in different files if the other file doesn't have the comment and String literals aren't frozen by default" do
+        ruby_exe(fixture(__FILE__, "freeze_magic_comment_across_files_no_comment.rb")).chomp.should == "true"
+      end
+    end
+
+    guard -> { eval("'test'").frozen? && "test".equal?("test") } do
+      it "produces the same objects for literals with the same content in different files if the other file doesn't have the comment and String literals are frozen by default" do
+        ruby_exe(fixture(__FILE__, "freeze_magic_comment_across_files_no_comment.rb")).chomp.should == "false"
+      end
     end
 
     it "produce different objects for literals with the same content in different files if they have different encodings" do
@@ -258,30 +257,45 @@ describe "Ruby String literals" do
 end
 
 describe "Ruby String interpolation" do
-  it "creates a String having an Encoding compatible with all components" do
-    a = "\u3042"
-    b = "abc".encode("binary")
-
-    str = "#{a} x #{b}"
+  it "permits an empty expression" do
+    s = "#{}" # rubocop:disable Lint/EmptyInterpolation
+    s.should.empty?
+    s.should_not.frozen?
+  end
 
-    str.should == "\xe3\x81\x82\x20\x78\x20\x61\x62\x63".force_encoding("utf-8")
-    str.encoding.should == Encoding::UTF_8
+  it "returns a string with the source encoding by default" do
+    "a#{"b"}c".encoding.should == Encoding::BINARY
+    eval('"a#{"b"}c"'.dup.force_encoding("us-ascii")).encoding.should == Encoding::US_ASCII
+    eval("# coding: US-ASCII \n 'a#{"b"}c'").encoding.should == Encoding::US_ASCII
   end
 
-  it "creates a String having the Encoding of the components when all are the same Encoding" do
-    a = "abc".force_encoding("euc-jp")
-    b = "def".force_encoding("euc-jp")
-    str = '"#{a} x #{b}"'.force_encoding("euc-jp")
+  it "returns a string with the source encoding, even if the components have another encoding" do
+    a = "abc".dup.force_encoding("euc-jp")
+    "#{a}".encoding.should == Encoding::BINARY
 
-    result = eval(str)
-    result.should == "\x61\x62\x63\x20\x78\x20\x64\x65\x66".force_encoding("euc-jp")
-    result.encoding.should == Encoding::EUC_JP
+    b = "abc".encode("utf-8")
+    "#{b}".encoding.should == Encoding::BINARY
   end
 
   it "raises an Encoding::CompatibilityError if the Encodings are not compatible" do
     a = "\u3042"
-    b = "\xff".force_encoding "binary"
+    b = "\xff".dup.force_encoding "binary"
 
     -> { "#{a} #{b}" }.should raise_error(Encoding::CompatibilityError)
   end
+
+  it "creates a non-frozen String" do
+    code = <<~'RUBY'
+      "a#{6*7}c"
+    RUBY
+    eval(code).should_not.frozen?
+  end
+
+  it "creates a non-frozen String when # frozen-string-literal: true is used" do
+    code = <<~'RUBY'
+      # frozen-string-literal: true
+      "a#{6*7}c"
+    RUBY
+    eval(code).should_not.frozen?
+  end
 end
diff --git a/spec/ruby/language/super_spec.rb b/spec/ruby/language/super_spec.rb
index 66a1ec7592..7d9e896d8b 100644
--- a/spec/ruby/language/super_spec.rb
+++ b/spec/ruby/language/super_spec.rb
@@ -70,7 +70,7 @@ describe "The super keyword" do
     SuperSpecs::S4::B.new.foo([],"test").should == ["B#foo(a,test)", "A#foo"]
   end
 
-  it "raises an error error when super method does not exist" do
+  it "raises an error when super method does not exist" do
     sup = Class.new
     sub_normal = Class.new(sup) do
       def foo
@@ -102,6 +102,37 @@ describe "The super keyword" do
     c2.new.m(:dump) { :value }.should == :value
   end
 
+  it "can pass an explicit block" do
+    c1 = Class.new do
+      def m(v)
+        yield(v)
+      end
+    end
+    c2 = Class.new(c1) do
+      def m(v)
+        block = -> w { yield(w + 'b') }
+        super(v, &block)
+      end
+    end
+
+    c2.new.m('a') { |x| x + 'c' }.should == 'abc'
+  end
+
+  it "can pass no block using &nil" do
+    c1 = Class.new do
+      def m(v)
+        block_given?
+      end
+    end
+    c2 = Class.new(c1) do
+      def m(v)
+        super(v, &nil)
+      end
+    end
+
+    c2.new.m('a') { raise }.should be_false
+  end
+
   it "uses block argument given to method when used in a block" do
     c1 = Class.new do
       def m
@@ -172,6 +203,25 @@ describe "The super keyword" do
     -> { klass.new.a(:a_called) }.should raise_error(RuntimeError)
   end
 
+  it "is able to navigate to super, when a method is defined dynamically on the singleton class" do
+    foo_class = Class.new do
+      def bar
+        "bar"
+      end
+    end
+
+    mixin_module = Module.new do
+      def bar
+        "super_" + super
+      end
+    end
+
+    foo = foo_class.new
+    foo.singleton_class.define_method(:bar, mixin_module.instance_method(:bar))
+
+    foo.bar.should == "super_bar"
+  end
+
   # Rubinius ticket github#157
   it "calls method_missing when a superclass method is not found" do
     SuperSpecs::MM_B.new.is_a?(Hash).should == false
@@ -262,6 +312,21 @@ describe "The super keyword" do
 
   it "without explicit arguments passes arguments and rest arguments" do
     SuperSpecs::ZSuperWithRestAndOthers::B.new.m(1, 2, 3, 4, 5).should == [3, 4, 5]
+    SuperSpecs::ZSuperWithRestAndOthers::B.new.m(1, 2).should == []
+  end
+
+  it "without explicit arguments passes arguments, rest arguments, and post arguments" do
+    SuperSpecs::ZSuperWithRestAndPost::B.new.m(1, 2, 3, 4, 5).should == [1, 2, 3]
+    SuperSpecs::ZSuperWithRestOthersAndPost::B.new.m(1, 2, 3, 4, 5).should == [2, 3, 4]
+    SuperSpecs::ZSuperWithRestAndPost::B.new.m(1, 2).should == []
+    SuperSpecs::ZSuperWithRestOthersAndPost::B.new.m(1, 2).should == []
+  end
+
+  it "without explicit arguments passes arguments, rest arguments including modifications, and post arguments" do
+    SuperSpecs::ZSuperWithRestAndPost::B.new.m_modified(1, 2, 3, 4, 5).should == [1, 14, 3]
+    SuperSpecs::ZSuperWithRestOthersAndPost::B.new.m_modified(1, 2, 3, 4, 5).should == [2, 14, 4]
+    SuperSpecs::ZSuperWithRestAndPost::B.new.m_modified(1, 2).should == [nil, 14]
+    SuperSpecs::ZSuperWithRestOthersAndPost::B.new.m_modified(1, 2).should == [nil, 14]
   end
 
   it "without explicit arguments passes arguments and rest arguments including any modifications" do
@@ -270,12 +335,23 @@ describe "The super keyword" do
 
   it "without explicit arguments that are '_'" do
     SuperSpecs::ZSuperWithUnderscores::B.new.m(1, 2).should == [1, 2]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m3(1, 2, 3).should == [1, 2, 3]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m4(1, 2, 3, 4).should == [1, 2, 3, 4]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m_default(1).should == [1]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m_default.should == [0]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m_pre_default_rest_post(1, 2, 3, 4, 5, 6, 7).should == [1, 2, 3, 4, 5, 6, 7]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m_rest(1, 2).should == [1, 2]
+    SuperSpecs::ZSuperWithUnderscores::B.new.m_kwrest(a: 1).should == {a: 1}
   end
 
   it "without explicit arguments that are '_' including any modifications" do
     SuperSpecs::ZSuperWithUnderscores::B.new.m_modified(1, 2).should == [14, 2]
   end
 
+  it "should pass method arguments when called within a closure" do
+    SuperSpecs::ZSuperInBlock::B.new.m(arg: 1).should == 1
+  end
+
   describe 'when using keyword arguments' do
     before :each do
       @req  = SuperSpecs::Keywords::RequiredArguments.new
diff --git a/spec/ruby/language/symbol_spec.rb b/spec/ruby/language/symbol_spec.rb
index d6a41d3059..0801d3223e 100644
--- a/spec/ruby/language/symbol_spec.rb
+++ b/spec/ruby/language/symbol_spec.rb
@@ -96,11 +96,13 @@ describe "A Symbol literal" do
     %I{a b #{"c"}}.should == [:a, :b, :c]
   end
 
-  it "with invalid bytes raises an EncodingError at parse time" do
-    ScratchPad.record []
-    -> {
-      eval 'ScratchPad << 1; :"\xC3"'
-    }.should raise_error(EncodingError, /invalid/)
-    ScratchPad.recorded.should == []
+  ruby_bug "#20280", ""..."3.4" do
+    it "raises an SyntaxError at parse time when Symbol with invalid bytes" do
+      ScratchPad.record []
+      -> {
+        eval 'ScratchPad << 1; :"\xC3"'
+      }.should raise_error(SyntaxError, /invalid symbol/)
+      ScratchPad.recorded.should == []
+    end
   end
 end
diff --git a/spec/ruby/language/undef_spec.rb b/spec/ruby/language/undef_spec.rb
index 4e473b803f..268c0b84c3 100644
--- a/spec/ruby/language/undef_spec.rb
+++ b/spec/ruby/language/undef_spec.rb
@@ -38,12 +38,19 @@ describe "The undef keyword" do
       -> { @obj.meth(5) }.should raise_error(NoMethodError)
     end
 
-    it "with a interpolated symbol" do
+    it "with an interpolated symbol" do
       @undef_class.class_eval do
         undef :"#{'meth'}"
       end
       -> { @obj.meth(5) }.should raise_error(NoMethodError)
     end
+
+    it "with an interpolated symbol when interpolated expression is not a String literal" do
+      @undef_class.class_eval do
+        undef :"#{'meth'.to_sym}"
+      end
+      -> { @obj.meth(5) }.should raise_error(NoMethodError)
+    end
   end
 
   it "allows undefining multiple methods at a time" do
@@ -62,7 +69,7 @@ describe "The undef keyword" do
   it "raises a NameError when passed a missing name" do
     Class.new do
       -> {
-         undef not_exist
+        undef not_exist
       }.should raise_error(NameError) { |e|
         # a NameError and not a NoMethodError
         e.class.should == NameError
diff --git a/spec/ruby/language/variables_spec.rb b/spec/ruby/language/variables_spec.rb
index 868603eb88..e134271939 100644
--- a/spec/ruby/language/variables_spec.rb
+++ b/spec/ruby/language/variables_spec.rb
@@ -1,6 +1,51 @@
 require_relative '../spec_helper'
 require_relative 'fixtures/variables'
 
+describe "Evaluation order during assignment" do
+  context "with single assignment" do
+    it "evaluates from left to right" do
+      obj = VariablesSpecs::EvalOrder.new
+      obj.instance_eval do
+        foo[0] = a
+      end
+
+      obj.order.should == ["foo", "a", "foo[]="]
+    end
+  end
+
+  context "with multiple assignment" do
+    it "evaluates from left to right, receivers first then methods" do
+      obj = VariablesSpecs::EvalOrder.new
+      obj.instance_eval do
+        foo[0], bar.baz = a, b
+      end
+
+      obj.order.should == ["foo", "bar", "a", "b", "foo[]=", "bar.baz="]
+    end
+
+    it "can be used to swap variables with nested method calls" do
+      node = VariablesSpecs::EvalOrder.new.node
+
+      original_node = node
+      original_node_left = node.left
+      original_node_left_right = node.left.right
+
+      node.left, node.left.right, node = node.left.right, node, node.left
+      # Should evaluate in the order of:
+      # LHS: node, node.left(original_node_left)
+      # RHS: original_node_left_right, original_node, original_node_left
+      # Ops:
+      # * node(original_node), original_node.left = original_node_left_right
+      # * original_node_left.right = original_node
+      # * node = original_node_left
+
+      node.should == original_node_left
+      node.right.should == original_node
+      node.right.left.should == original_node_left_right
+    end
+  end
+end
+
 describe "Multiple assignment" do
   context "with a single RHS value" do
     it "assigns a simple MLHS" do
@@ -287,8 +332,13 @@ describe "Multiple assignment" do
 
     it "assigns indexed elements" do
       a = []
-      a[1], a[2] = 1
-      a.should == [nil, 1, nil]
+      a[1], a[2] = 1, 2
+      a.should == [nil, 1, 2]
+
+      # with splatted argument
+      a = []
+      a[*[1]], a[*[2]] = 1, 2
+      a.should == [nil, 1, 2]
     end
 
     it "assigns constants" do
@@ -296,6 +346,9 @@ describe "Multiple assignment" do
         SINGLE_RHS_1, SINGLE_RHS_2 = 1
         [SINGLE_RHS_1, SINGLE_RHS_2].should == [1, nil]
       end
+    ensure
+      VariableSpecs.send(:remove_const, :SINGLE_RHS_1)
+      VariableSpecs.send(:remove_const, :SINGLE_RHS_2)
     end
   end
 
@@ -310,11 +363,22 @@ describe "Multiple assignment" do
       a.should == []
     end
 
-    it "calls #to_a to convert nil to an empty Array" do
-      nil.should_receive(:to_a).and_return([])
+    ruby_version_is "4.0" do
+      it "converts nil to empty array without calling a method" do
+        nil.should_not_receive(:to_a)
 
-      (*a = *nil).should == []
-      a.should == []
+        (*a = *nil).should == []
+        a.should == []
+      end
+    end
+
+    ruby_version_is ""..."4.0"  do
+      it "calls #to_a to convert nil to an empty Array" do
+        nil.should_receive(:to_a).and_return([])
+
+        (*a = *nil).should == []
+        a.should == []
+      end
     end
 
     it "does not call #to_a on an Array" do
@@ -354,6 +418,16 @@ describe "Multiple assignment" do
       a.should be_an_instance_of(Array)
     end
 
+    it "unfreezes the array returned from calling 'to_a' on the splatted value" do
+      obj = Object.new
+      def obj.to_a
+        [1,2].freeze
+      end
+      res = *obj
+      res.should == [1,2]
+      res.should_not.frozen?
+    end
+
     it "consumes values for an anonymous splat" do
       a = 1
       (* = *a).should == [1]
@@ -524,6 +598,8 @@ describe "Multiple assignment" do
         (*SINGLE_SPLATTED_RHS) = *1
         SINGLE_SPLATTED_RHS.should == [1]
       end
+    ensure
+      VariableSpecs.send(:remove_const, :SINGLE_SPLATTED_RHS)
     end
   end
 
@@ -705,12 +781,27 @@ describe "Multiple assignment" do
       x.should == [1, 2, 3, 4, 5]
     end
 
+    it "can be used to swap array elements" do
+      a = [1, 2]
+      a[0], a[1] = a[1], a[0]
+      a.should == [2, 1]
+    end
+
+    it "can be used to swap range of array elements" do
+      a = [1, 2, 3, 4]
+      a[0, 2], a[2, 2] = a[2, 2], a[0, 2]
+      a.should == [3, 4, 1, 2]
+    end
+
     it "assigns RHS values to LHS constants" do
       module VariableSpecs
         MRHS_VALUES_1, MRHS_VALUES_2 = 1, 2
         MRHS_VALUES_1.should == 1
         MRHS_VALUES_2.should == 2
       end
+    ensure
+      VariableSpecs.send(:remove_const, :MRHS_VALUES_1)
+      VariableSpecs.send(:remove_const, :MRHS_VALUES_2)
     end
 
     it "assigns all RHS values as an array to a single LHS constant" do
@@ -718,6 +809,8 @@ describe "Multiple assignment" do
         MRHS_VALUES = 1, 2, 3
         MRHS_VALUES.should == [1, 2, 3]
       end
+    ensure
+      VariableSpecs.send(:remove_const, :MRHS_VALUES)
     end
   end
 
@@ -760,29 +853,78 @@ describe "A local variable assigned only within a conditional block" do
 end
 
 describe 'Local variable shadowing' do
-  ruby_version_is ""..."2.6" do
-    it "leads to warning in verbose mode" do
-      -> do
-        eval <<-CODE
-          a = [1, 2, 3]
-          a.each { |a| a = 3 }
-        CODE
-      end.should complain(/shadowing outer local variable/, verbose: true)
+  it "does not warn in verbose mode" do
+    result = nil
+
+    -> do
+      eval <<-CODE
+        a = [1, 2, 3]
+        result = a.map { |a| a = 3 }
+      CODE
+    end.should_not complain(verbose: true)
+
+    result.should == [3, 3, 3]
+  end
+end
+
+describe 'Allowed characters' do
+  it 'allows non-ASCII lowercased characters at the beginning' do
+    result = nil
+
+    eval <<-CODE
+      def test
+        μ = 1
+      end
+
+      result = test
+    CODE
+
+    result.should == 1
+  end
+
+  it 'parses a non-ASCII upcased character as a constant identifier' do
+    -> do
+      eval <<-CODE
+        def test
+          ἍBB = 1
+        end
+      CODE
+    end.should raise_error(SyntaxError, /dynamic constant assignment/)
+  end
+end
+
+describe "Instance variables" do
+  context "when instance variable is uninitialized" do
+    it "doesn't warn about accessing uninitialized instance variable" do
+      obj = Object.new
+      def obj.foobar; a = @a; end
+
+      -> { obj.foobar }.should_not complain(verbose: true)
+    end
+
+    it "doesn't warn at lazy initialization" do
+      obj = Object.new
+      def obj.foobar; @a ||= 42; end
+
+      -> { obj.foobar }.should_not complain(verbose: true)
     end
   end
 
-  ruby_version_is "2.6" do
-    it "does not warn in verbose mode" do
-      result = nil
+  describe "global variable" do
+    context "when global variable is uninitialized" do
+      it "warns about accessing uninitialized global variable in verbose mode" do
+        obj = Object.new
+        def obj.foobar; a = $specs_uninitialized_global_variable; end
 
-      -> do
-        eval <<-CODE
-          a = [1, 2, 3]
-          result = a.map { |a| a = 3 }
-        CODE
-      end.should_not complain(verbose: true)
+        -> { obj.foobar }.should complain(/warning: global variable [`']\$specs_uninitialized_global_variable' not initialized/, verbose: true)
+      end
+
+      it "doesn't warn at lazy initialization" do
+        obj = Object.new
+        def obj.foobar; $specs_uninitialized_global_variable_lazy ||= 42; end
 
-      result.should == [3, 3, 3]
+        -> { obj.foobar }.should_not complain(verbose: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/language/yield_spec.rb b/spec/ruby/language/yield_spec.rb
index 5fad7cb176..e125cf8e73 100644
--- a/spec/ruby/language/yield_spec.rb
+++ b/spec/ruby/language/yield_spec.rb
@@ -183,5 +183,38 @@ describe "The yield call" do
   it "uses captured block of a block used in define_method" do
     @y.deep(2).should == 4
   end
+end
+
+describe "Using yield in a singleton class literal" do
+  it 'raises a SyntaxError' do
+    code = <<~RUBY
+      class << Object.new
+        yield
+      end
+    RUBY
+
+    -> { eval(code) }.should raise_error(SyntaxError, /Invalid yield/)
+  end
+end
+
+describe "Using yield in non-lambda block" do
+  it 'raises a SyntaxError' do
+    code = <<~RUBY
+        1.times { yield }
+      RUBY
 
+    -> { eval(code) }.should raise_error(SyntaxError, /Invalid yield/)
+  end
+end
+
+describe "Using yield in a module literal" do
+  it 'raises a SyntaxError' do
+    code = <<~RUBY
+      module YieldSpecs::ModuleWithYield
+        yield
+      end
+    RUBY
+
+    -> { eval(code) }.should raise_error(SyntaxError, /Invalid yield/)
+  end
 end
diff --git a/spec/ruby/library/English/English_spec.rb b/spec/ruby/library/English/English_spec.rb
index f6153ec7c9..4d615d1e25 100644
--- a/spec/ruby/library/English/English_spec.rb
+++ b/spec/ruby/library/English/English_spec.rb
@@ -67,18 +67,18 @@ describe "English" do
 
   it "aliases $ORS to $\\" do
     original = $\
-    $\ = "\t"
+    suppress_warning {$\ = "\t"}
     $ORS.should_not be_nil
     $ORS.should == $\
-    $\ = original
+    suppress_warning {$\ = original}
   end
 
   it "aliases $OUTPUT_RECORD_SEPARATOR to $\\" do
     original = $\
-    $\ = "\t"
+    suppress_warning {$\ = "\t"}
     $OUTPUT_RECORD_SEPARATOR.should_not be_nil
     $OUTPUT_RECORD_SEPARATOR.should == $\
-    $\ = original
+    suppress_warning {$\ = original}
   end
 
   it "aliases $INPUT_LINE_NUMBER to $." do
@@ -130,13 +130,15 @@ describe "English" do
     $LAST_MATCH_INFO.should == $~
   end
 
-  it "aliases $IGNORECASE to $=" do
-    $VERBOSE, verbose = nil, $VERBOSE
-    begin
-      $IGNORECASE.should_not be_nil
-      $IGNORECASE.should == $=
-    ensure
-      $VERBOSE = verbose
+  ruby_version_is ""..."3.3" do
+    it "aliases $IGNORECASE to $=" do
+      $VERBOSE, verbose = nil, $VERBOSE
+      begin
+        $IGNORECASE.should_not be_nil
+        $IGNORECASE.should == $=
+      ensure
+        $VERBOSE = verbose
+      end
     end
   end
 
diff --git a/spec/ruby/library/English/alias_spec.rb b/spec/ruby/library/English/alias_spec.rb
new file mode 100644
index 0000000000..78ccfb4398
--- /dev/null
+++ b/spec/ruby/library/English/alias_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+require 'English'
+
+describe "English" do
+  it "aliases $! to $ERROR_INFO and $ERROR_INFO still returns an Exception with a backtrace" do
+    exception = (1 / 0 rescue $ERROR_INFO)
+    exception.should be_kind_of(Exception)
+    exception.backtrace.should be_kind_of(Array)
+  end
+
+  it "aliases $@ to $ERROR_POSITION and $ERROR_POSITION still returns a backtrace" do
+    (1 / 0 rescue $ERROR_POSITION).should be_kind_of(Array)
+  end
+end
diff --git a/spec/ruby/library/base64/decode64_spec.rb b/spec/ruby/library/base64/decode64_spec.rb
index 3b81203588..6dd33dddfe 100644
--- a/spec/ruby/library/base64/decode64_spec.rb
+++ b/spec/ruby/library/base64/decode64_spec.rb
@@ -6,4 +6,24 @@ describe "Base64#decode64" do
   it "returns the Base64-decoded version of the given string" do
     Base64.decode64("U2VuZCByZWluZm9yY2VtZW50cw==\n").should == "Send reinforcements"
   end
+
+  it "returns the Base64-decoded version of the given shared string" do
+    Base64.decode64("base64: U2VuZCByZWluZm9yY2VtZW50cw==\n".split(" ").last).should == "Send reinforcements"
+  end
+
+  it "returns the Base64-decoded version of the given string with wrong padding" do
+    Base64.decode64("XU2VuZCByZWluZm9yY2VtZW50cw===").should == "]M\x95\xB9\x90\x81\xC9\x95\xA5\xB9\x99\xBD\xC9\x8D\x95\xB5\x95\xB9\xD1\xCC".b
+  end
+
+  it "returns the Base64-decoded version of the given string that contains an invalid character" do
+    Base64.decode64("%3D").should == "\xDC".b
+  end
+
+  it "returns a binary encoded string" do
+    Base64.decode64("SEk=").encoding.should == Encoding::BINARY
+  end
+
+  it "decodes without padding suffix ==" do
+    Base64.decode64("eyJrZXkiOnsibiI6InR0dCJ9fQ").should == "{\"key\":{\"n\":\"ttt\"}}"
+  end
 end
diff --git a/spec/ruby/library/base64/encode64_spec.rb b/spec/ruby/library/base64/encode64_spec.rb
index 91ac41bed0..64de6257bc 100644
--- a/spec/ruby/library/base64/encode64_spec.rb
+++ b/spec/ruby/library/base64/encode64_spec.rb
@@ -11,4 +11,13 @@ describe "Base64#encode64" do
   it "returns the Base64-encoded version of the given string" do
     Base64.encode64('Send reinforcements').should == "U2VuZCByZWluZm9yY2VtZW50cw==\n"
   end
+
+  it "returns the Base64-encoded version of the given shared string" do
+    Base64.encode64("Now is the time for all good coders\nto learn Ruby".split("\n").last).should ==
+      "dG8gbGVhcm4gUnVieQ==\n"
+  end
+
+  it "returns a US_ASCII encoded string" do
+    Base64.encode64("HI").encoding.should == Encoding::US_ASCII
+  end
 end
diff --git a/spec/ruby/library/base64/strict_decode64_spec.rb b/spec/ruby/library/base64/strict_decode64_spec.rb
new file mode 100644
index 0000000000..d258223c82
--- /dev/null
+++ b/spec/ruby/library/base64/strict_decode64_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+
+require 'base64'
+
+describe "Base64#strict_decode64" do
+  it "returns the Base64-decoded version of the given string" do
+    Base64.strict_decode64("U2VuZCByZWluZm9yY2VtZW50cw==").should == "Send reinforcements"
+  end
+
+  it "returns the Base64-decoded version of the given shared string" do
+    Base64.strict_decode64("base64: U2VuZCByZWluZm9yY2VtZW50cw==".split(" ").last).should == "Send reinforcements"
+  end
+
+  it "raises ArgumentError when the given string contains CR" do
+    -> do
+      Base64.strict_decode64("U2VuZCByZWluZm9yY2VtZW50cw==\r")
+    end.should raise_error(ArgumentError)
+  end
+
+  it "raises ArgumentError when the given string contains LF" do
+    -> do
+      Base64.strict_decode64("U2VuZCByZWluZm9yY2VtZW50cw==\n")
+    end.should raise_error(ArgumentError)
+  end
+
+  it "raises ArgumentError when the given string has wrong padding" do
+    -> do
+      Base64.strict_decode64("=U2VuZCByZWluZm9yY2VtZW50cw==")
+    end.should raise_error(ArgumentError)
+  end
+
+  it "raises ArgumentError when the given string contains an invalid character" do
+    -> do
+      Base64.strict_decode64("%3D")
+    end.should raise_error(ArgumentError)
+  end
+
+  it "returns a binary encoded string" do
+    Base64.strict_decode64("SEk=").encoding.should == Encoding::BINARY
+  end
+end
diff --git a/spec/ruby/library/base64/strict_encode64_spec.rb b/spec/ruby/library/base64/strict_encode64_spec.rb
new file mode 100644
index 0000000000..7cabcf190c
--- /dev/null
+++ b/spec/ruby/library/base64/strict_encode64_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+
+require 'base64'
+
+describe "Base64#strict_encode64" do
+  it "returns the Base64-encoded version of the given string" do
+    Base64.strict_encode64("Now is the time for all good coders\nto learn Ruby").should ==
+      "Tm93IGlzIHRoZSB0aW1lIGZvciBhbGwgZ29vZCBjb2RlcnMKdG8gbGVhcm4gUnVieQ=="
+  end
+
+  it "returns the Base64-encoded version of the given shared string" do
+    Base64.strict_encode64("Now is the time for all good coders\nto learn Ruby".split("\n").last).should ==
+      "dG8gbGVhcm4gUnVieQ=="
+  end
+
+  it "returns a US_ASCII encoded string" do
+    Base64.strict_encode64("HI").encoding.should == Encoding::US_ASCII
+  end
+end
diff --git a/spec/ruby/library/bigdecimal/BigDecimal_spec.rb b/spec/ruby/library/bigdecimal/BigDecimal_spec.rb
index e1e6fe9fb1..8596356abd 100644
--- a/spec/ruby/library/bigdecimal/BigDecimal_spec.rb
+++ b/spec/ruby/library/bigdecimal/BigDecimal_spec.rb
@@ -24,38 +24,39 @@ describe "Kernel#BigDecimal" do
     }
   end
 
+  it "BigDecimal(Rational) with bigger-than-double numerator" do
+    rational = 99999999999999999999/100r
+    rational.numerator.should > 2**64
+    BigDecimal(rational, 100).to_s.should == "0.99999999999999999999e18"
+  end
+
   it "accepts significant digits >= given precision" do
-    BigDecimal("3.1415923", 10).precs[1].should >= 10
+    BigDecimal("3.1415923", 10).should == BigDecimal("3.1415923")
   end
 
   it "determines precision from initial value" do
     pi_string = "3.14159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593014782083152134043"
-    BigDecimal(pi_string).precs[1].should >= pi_string.size-1
+    BigDecimal(pi_string).precision.should == pi_string.size-1
   end
 
-  it "ignores leading whitespace" do
-    BigDecimal("  \t\n \r1234").should == BigDecimal("1234")
-    BigDecimal("  \t\n \rNaN   \n").nan?.should == true
+  it "ignores leading and trailing whitespace" do
+    BigDecimal("  \t\n \r1234\t\r\n ").should == BigDecimal("1234")
+    BigDecimal("  \t\n \rNaN   \n").should.nan?
     BigDecimal("  \t\n \rInfinity   \n").infinite?.should == 1
     BigDecimal("  \t\n \r-Infinity   \n").infinite?.should == -1
   end
 
-  ruby_version_is ""..."2.6" do
-    it "ignores trailing garbage" do
-      BigDecimal("123E45ruby").should == BigDecimal("123E45")
-      BigDecimal("123x45").should == BigDecimal("123")
-      BigDecimal("123.4%E5").should == BigDecimal("123.4")
-      BigDecimal("1E2E3E4E5E").should == BigDecimal("100")
-    end
+  it "coerces the value argument with #to_str" do
+    initial = mock("value")
+    initial.should_receive(:to_str).and_return("123")
+    BigDecimal(initial).should == BigDecimal("123")
   end
 
-  ruby_version_is "2.6" do
-    it "does not ignores trailing garbage" do
-      -> { BigDecimal("123E45ruby") }.should raise_error(ArgumentError)
-      -> { BigDecimal("123x45") }.should raise_error(ArgumentError)
-      -> { BigDecimal("123.4%E5") }.should raise_error(ArgumentError)
-      -> { BigDecimal("1E2E3E4E5E") }.should raise_error(ArgumentError)
-    end
+  it "does not ignores trailing garbage" do
+    -> { BigDecimal("123E45ruby") }.should raise_error(ArgumentError)
+    -> { BigDecimal("123x45") }.should raise_error(ArgumentError)
+    -> { BigDecimal("123.4%E5") }.should raise_error(ArgumentError)
+    -> { BigDecimal("1E2E3E4E5E") }.should raise_error(ArgumentError)
   end
 
   it "raises ArgumentError for invalid strings" do
@@ -67,63 +68,64 @@ describe "Kernel#BigDecimal" do
     BigDecimal(".123").should == BigDecimal("0.123")
   end
 
-  ruby_version_is ""..."2.6" do
-    it "allows for underscores in all parts" do
-      reference = BigDecimal("12345.67E89")
-
-      BigDecimal("12_345.67E89").should == reference
-      BigDecimal("1_2_3_4_5_._6____7_E89").should == reference
-      BigDecimal("12345_.67E_8__9_").should == reference
-    end
-  end
-
-  ruby_version_is "2.6" do
-    it "process underscores as Float()" do
-      reference = BigDecimal("12345.67E89")
+  it "process underscores as Float()" do
+    reference = BigDecimal("12345.67E89")
 
-      BigDecimal("12_345.67E89").should == reference
-      -> { BigDecimal("1_2_3_4_5_._6____7_E89") }.should raise_error(ArgumentError)
-      -> { BigDecimal("12345_.67E_8__9_") }.should raise_error(ArgumentError)
-    end
+    BigDecimal("12_345.67E89").should == reference
+    -> { BigDecimal("1_2_3_4_5_._6____7_E89") }.should raise_error(ArgumentError)
+    -> { BigDecimal("12345_.67E_8__9_") }.should raise_error(ArgumentError)
   end
 
   it "accepts NaN and [+-]Infinity" do
-    BigDecimal("NaN").nan?.should == true
+    BigDecimal("NaN").should.nan?
 
     pos_inf = BigDecimal("Infinity")
-    pos_inf.finite?.should == false
+    pos_inf.should_not.finite?
     pos_inf.should > 0
     pos_inf.should == BigDecimal("+Infinity")
 
     neg_inf = BigDecimal("-Infinity")
-    neg_inf.finite?.should == false
+    neg_inf.should_not.finite?
     neg_inf.should < 0
   end
 
+  describe "with exception: false" do
+    it "returns nil for invalid strings" do
+      BigDecimal("invalid", exception: false).should be_nil
+      BigDecimal("0invalid", exception: false).should be_nil
+      BigDecimal("invalid0", exception: false).should be_nil
+      if BigDecimal::VERSION >= "3.1.9"
+        BigDecimal("0.", exception: false).to_i.should == 0
+      else
+        BigDecimal("0.", exception: false).should be_nil
+      end
+    end
+  end
+
   describe "accepts NaN and [+-]Infinity as Float values" do
     it "works without an explicit precision" do
-      BigDecimal(Float::NAN).nan?.should == true
+      BigDecimal(Float::NAN).should.nan?
 
       pos_inf = BigDecimal(Float::INFINITY)
-      pos_inf.finite?.should == false
+      pos_inf.should_not.finite?
       pos_inf.should > 0
       pos_inf.should == BigDecimal("+Infinity")
 
       neg_inf = BigDecimal(-Float::INFINITY)
-      neg_inf.finite?.should == false
+      neg_inf.should_not.finite?
       neg_inf.should < 0
     end
 
     it "works with an explicit precision" do
-      BigDecimal(Float::NAN, Float::DIG).nan?.should == true
+      BigDecimal(Float::NAN, Float::DIG).should.nan?
 
       pos_inf = BigDecimal(Float::INFINITY, Float::DIG)
-      pos_inf.finite?.should == false
+      pos_inf.should_not.finite?
       pos_inf.should > 0
       pos_inf.should == BigDecimal("+Infinity")
 
       neg_inf = BigDecimal(-Float::INFINITY, Float::DIG)
-      neg_inf.finite?.should == false
+      neg_inf.should_not.finite?
       neg_inf.should < 0
     end
   end
@@ -150,8 +152,10 @@ describe "Kernel#BigDecimal" do
     BigDecimal("-12345.6E-1").should == -reference
   end
 
-  it "raises ArgumentError when Float is used without precision" do
-    -> { BigDecimal(1.0) }.should raise_error(ArgumentError)
+  version_is BigDecimal::VERSION, "3.3.0" do
+    it "allows Float without precision" do
+      BigDecimal(1.2).should == BigDecimal("1.2")
+    end
   end
 
   it "returns appropriate BigDecimal zero for signed zero" do
@@ -159,4 +163,77 @@ describe "Kernel#BigDecimal" do
     BigDecimal(0.0, Float::DIG).sign.should == 1
   end
 
+  it "pre-coerces long integers" do
+    BigDecimal(3).add(1 << 50, 3).should == BigDecimal('0.113e16')
+  end
+
+  it "does not call to_s when calling inspect" do
+    value = BigDecimal('44.44')
+    value.to_s.should == '0.4444e2'
+    value.inspect.should == '0.4444e2'
+
+    ruby_exe( <<-'EOF').should == "cheese 0.4444e2"
+      require 'bigdecimal'
+      module BigDecimalOverride
+        def to_s; "cheese"; end
+      end
+      BigDecimal.prepend BigDecimalOverride
+      value = BigDecimal('44.44')
+      print "#{value.to_s} #{value.inspect}"
+    EOF
+  end
+
+  describe "when interacting with Rational" do
+    before :each do
+      @a = BigDecimal('166.666666666')
+      @b = Rational(500, 3)
+      @c = @a - @b
+    end
+
+    # Check the input is as we understand it
+
+    it "has the LHS print as expected" do
+      @a.to_s.should == "0.166666666666e3"
+      @a.to_f.to_s.should == "166.666666666"
+      Float(@a).to_s.should == "166.666666666"
+    end
+
+    it "has the RHS print as expected" do
+      @b.to_s.should == "500/3"
+      @b.to_f.to_s.should == "166.66666666666666"
+      Float(@b).to_s.should == "166.66666666666666"
+    end
+
+    it "produces the expected result when done via Float" do
+      (Float(@a) - Float(@b)).to_s.should == "-6.666596163995564e-10"
+    end
+
+    it "produces the expected result when done via to_f" do
+      (@a.to_f - @b.to_f).to_s.should == "-6.666596163995564e-10"
+    end
+
+    # Check underlying methods work as we understand
+
+    it "BigDecimal(Rational, 18) produces the result we expect" do
+      BigDecimal(@b, 18).to_s.should == "0.166666666666666667e3"
+    end
+
+    # Check the top-level expression works as we expect
+
+    it "produces a BigDecimal" do
+      @c.class.should == BigDecimal
+    end
+
+    it "produces the expected result" do
+      @c.round(15).should == BigDecimal("-0.666667e-9")
+      @c.round(15).to_s.should == "-0.666667e-9"
+    end
+
+    it "produces the correct class for other arithmetic operators" do
+      (@a + @b).class.should == BigDecimal
+      (@a * @b).class.should == BigDecimal
+      (@a / @b).class.should == BigDecimal
+      (@a % @b).class.should == BigDecimal
+    end
+  end
 end
diff --git a/spec/ruby/library/bigdecimal/abs_spec.rb b/spec/ruby/library/bigdecimal/abs_spec.rb
index ddd2bae9a9..95dc45a905 100644
--- a/spec/ruby/library/bigdecimal/abs_spec.rb
+++ b/spec/ruby/library/bigdecimal/abs_spec.rb
@@ -38,7 +38,7 @@ describe "BigDecimal#abs" do
   it "properly handles special values" do
     @infinity.abs.should == @infinity
     @infinity_minus.abs.should == @infinity
-    @nan.abs.nan?.should == true # have to do it this way, since == doesn't work on NaN
+    @nan.abs.should.nan? # have to do it this way, since == doesn't work on NaN
     @zero.abs.should == 0
     @zero.abs.sign.should == BigDecimal::SIGN_POSITIVE_ZERO
     @zero_pos.abs.should == 0
diff --git a/spec/ruby/library/bigdecimal/add_spec.rb b/spec/ruby/library/bigdecimal/add_spec.rb
index 5b874687fe..9cdab7d910 100644
--- a/spec/ruby/library/bigdecimal/add_spec.rb
+++ b/spec/ruby/library/bigdecimal/add_spec.rb
@@ -24,7 +24,7 @@ describe "BigDecimal#add" do
   end
 
   it "returns a + b with given precision" do
-    # documentation states, that precision ist optional, but it ain't,
+    # documentation states that precision is optional, but it ain't,
     @two.add(@one, 1).should == @three
     @one .add(@two, 1).should == @three
     @one.add(@one_minus, 1).should == @zero
@@ -60,7 +60,7 @@ describe "BigDecimal#add" do
   end
 
 #  TODO:
-#  http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-core/17374
+#  https://blade.ruby-lang.org/ruby-core/17374
 #
 #  This doesn't work on MRI and looks like a bug to me:
 #  one can use BigDecimal + Float, but not Bigdecimal.add(Float)
@@ -73,14 +73,6 @@ describe "BigDecimal#add" do
 #    BigDecimal("0.88").add(0.0, 1).should == BigDecimal("0.9")
 #  end
 
-  describe "with Object" do
-    it "tries to coerce the other operand to self" do
-      object = mock("Object")
-      object.should_receive(:coerce).with(@frac_3).and_return([@frac_3, @frac_4])
-      @frac_3.add(object, 1).should == BigDecimal("0.1E16")
-    end
-  end
-
   describe "with Rational" do
     it "produces a BigDecimal" do
       (@three + Rational(500, 2)).should == BigDecimal("0.253e3")
@@ -136,8 +128,8 @@ describe "BigDecimal#add" do
   end
 
   it "returns NaN if NaN is involved" do
-    @one.add(@nan, 10000).nan?.should == true
-    @nan.add(@one, 1).nan?.should == true
+    @one.add(@nan, 10000).should.nan?
+    @nan.add(@one, 1).should.nan?
   end
 
   it "returns Infinity or -Infinity if these are involved" do
@@ -166,8 +158,8 @@ describe "BigDecimal#add" do
   end
 
   it "returns NaN if Infinity + (- Infinity)" do
-    @infinity.add(@infinity_minus, 10000).nan?.should == true
-    @infinity_minus.add(@infinity, 10000).nan?.should == true
+    @infinity.add(@infinity_minus, 10000).should.nan?
+    @infinity_minus.add(@infinity, 10000).should.nan?
   end
 
   it "raises TypeError when adds nil" do
diff --git a/spec/ruby/library/bigdecimal/comparison_spec.rb b/spec/ruby/library/bigdecimal/comparison_spec.rb
index a1e09b601f..c53187b727 100644
--- a/spec/ruby/library/bigdecimal/comparison_spec.rb
+++ b/spec/ruby/library/bigdecimal/comparison_spec.rb
@@ -18,7 +18,7 @@ describe "BigDecimal#<=>" do
       def coerce(other)
         return [other, BigDecimal('123')]
       end
-      def >= (other)
+      def >=(other)
         BigDecimal('123') >= other
       end
     end
diff --git a/spec/ruby/library/bigdecimal/constants_spec.rb b/spec/ruby/library/bigdecimal/constants_spec.rb
index 1eb24d85cb..8d879c036a 100644
--- a/spec/ruby/library/bigdecimal/constants_spec.rb
+++ b/spec/ruby/library/bigdecimal/constants_spec.rb
@@ -2,10 +2,8 @@ require_relative '../../spec_helper'
 require 'bigdecimal'
 
 describe "BigDecimal constants" do
-  ruby_version_is "2.5" do
-    it "defines a VERSION value" do
-      BigDecimal.const_defined?(:VERSION).should be_true
-    end
+  it "defines a VERSION value" do
+    BigDecimal.const_defined?(:VERSION).should be_true
   end
 
   it "has a BASE value" do
diff --git a/spec/ruby/library/bigdecimal/core_spec.rb b/spec/ruby/library/bigdecimal/core_spec.rb
new file mode 100644
index 0000000000..5097d70865
--- /dev/null
+++ b/spec/ruby/library/bigdecimal/core_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../spec_helper'
+require 'bigdecimal'
+
+describe "Core extension by bigdecimal" do
+  context "Integer#coerce" do
+    it "produces Floats" do
+      x, y = 3.coerce(BigDecimal("3.4"))
+      x.class.should == Float
+      x.should == 3.4
+      y.class.should == Float
+      y.should == 3.0
+    end
+  end
+
+  describe "Time.at passed BigDecimal" do
+    it "doesn't round input value" do
+      Time.at(BigDecimal('1.1')).to_f.should == 1.1
+    end
+  end
+
+  describe "BigDecimal#log" do
+    it "handles high-precision Rational arguments" do
+      # log(BigDecimal(r, 50), 50)
+      result1 = BigDecimal('0.22314354220170971436137296411949880462556361100856e0')
+      # log(BigDecimal(r, 1000), 50)
+      result2 = BigDecimal('0.22314354220170971436137296411949880462556361100853e0')
+      r = Rational(1_234_567_890, 987_654_321)
+      [result1, result2].should include(BigMath.log(r, 50).mult(1, 50))
+    end
+  end
+
+  describe "Rational#coerce" do
+    it "returns the passed argument, self as Float, when given a Float" do
+      result = Rational(3, 4).coerce(1.0)
+      result.should == [1.0, 0.75]
+      result.first.is_a?(Float).should be_true
+      result.last.is_a?(Float).should be_true
+    end
+
+    it "returns the passed argument, self as Rational, when given an Integer" do
+      result = Rational(3, 4).coerce(10)
+      result.should == [Rational(10, 1), Rational(3, 4)]
+      result.first.is_a?(Rational).should be_true
+      result.last.is_a?(Rational).should be_true
+    end
+
+    it "coerces to Rational, when given a Complex" do
+      Rational(3, 4).coerce(Complex(5)).should == [Rational(5, 1), Rational(3, 4)]
+      Rational(12, 4).coerce(Complex(5, 1)).should == [Complex(5, 1), Complex(3)]
+    end
+
+    it "returns [argument, self] when given a Rational" do
+      Rational(3, 7).coerce(Rational(9, 2)).should == [Rational(9, 2), Rational(3, 7)]
+    end
+
+    it "raises an error when passed a BigDecimal" do
+      -> {
+        Rational(500, 3).coerce(BigDecimal('166.666666666'))
+      }.should raise_error(TypeError, /BigDecimal can't be coerced into Rational/)
+    end
+  end
+end
diff --git a/spec/ruby/library/bigdecimal/div_spec.rb b/spec/ruby/library/bigdecimal/div_spec.rb
index 0c9eb2ddec..53ad6d0418 100644
--- a/spec/ruby/library/bigdecimal/div_spec.rb
+++ b/spec/ruby/library/bigdecimal/div_spec.rb
@@ -80,13 +80,13 @@ describe "BigDecimal#div" do
   end
 
   it "returns NaN if zero is divided by zero" do
-    @zero.div(@zero, 0).nan?.should == true
-    @zero_minus.div(@zero_plus, 0).nan?.should == true
-    @zero_plus.div(@zero_minus, 0).nan?.should == true
+    @zero.div(@zero, 0).should.nan?
+    @zero_minus.div(@zero_plus, 0).should.nan?
+    @zero_plus.div(@zero_minus, 0).should.nan?
 
-    @zero.div(@zero, 10).nan?.should == true
-    @zero_minus.div(@zero_plus, 10).nan?.should == true
-    @zero_plus.div(@zero_minus, 10).nan?.should == true
+    @zero.div(@zero, 10).should.nan?
+    @zero_minus.div(@zero_plus, 10).should.nan?
+    @zero_plus.div(@zero_minus, 10).should.nan?
   end
 
   it "raises FloatDomainError if (+|-) Infinity divided by 1 and no precision given" do
@@ -102,8 +102,8 @@ describe "BigDecimal#div" do
   end
 
   it "returns NaN if Infinity / ((+|-) Infinity)" do
-    @infinity.div(@infinity_minus, 100000).nan?.should == true
-    @infinity_minus.div(@infinity, 1).nan?.should == true
+    @infinity.div(@infinity_minus, 100000).should.nan?
+    @infinity_minus.div(@infinity, 1).should.nan?
   end
 
 
diff --git a/spec/ruby/library/bigdecimal/divmod_spec.rb b/spec/ruby/library/bigdecimal/divmod_spec.rb
index ae8b84983a..85c014bb8c 100644
--- a/spec/ruby/library/bigdecimal/divmod_spec.rb
+++ b/spec/ruby/library/bigdecimal/divmod_spec.rb
@@ -5,8 +5,8 @@ require 'bigdecimal'
 module DivmodSpecs
   def self.check_both_nan(array)
     array.length.should == 2
-    array[0].nan?.should == true
-    array[1].nan?.should == true
+    array[0].should.nan?
+    array[1].should.nan?
   end
   def self.check_both_bigdecimal(array)
     array.length.should == 2
@@ -33,14 +33,16 @@ describe "BigDecimal#mod_part_of_divmod" do
     end
   end
 
-  it_behaves_like :bigdecimal_modulo, :mod_part_of_divmod
+  version_is BigDecimal::VERSION, ""..."4.0.0" do
+    it_behaves_like :bigdecimal_modulo, :mod_part_of_divmod
+  end
 
   it "raises ZeroDivisionError if other is zero" do
     bd5667 = BigDecimal("5667.19")
-
+    zero = BigDecimal("0")
     -> { bd5667.mod_part_of_divmod(0) }.should raise_error(ZeroDivisionError)
     -> { bd5667.mod_part_of_divmod(BigDecimal("0")) }.should raise_error(ZeroDivisionError)
-    -> { @zero.mod_part_of_divmod(@zero) }.should raise_error(ZeroDivisionError)
+    -> { zero.mod_part_of_divmod(zero) }.should raise_error(ZeroDivisionError)
   end
 end
 
@@ -73,14 +75,25 @@ describe "BigDecimal#divmod" do
     @zeroes = [@zero, @zero_pos, @zero_neg]
   end
 
-  it "divides value, returns an array" do
-    res = @a.divmod(5)
-    res.kind_of?(Array).should == true
+  version_is BigDecimal::VERSION, ""..."4.0.0" do
+    it "divides value, returns [BigDecimal, BigDecimal]" do
+      res = @a.divmod(5)
+      res.kind_of?(Array).should == true
+      DivmodSpecs.check_both_bigdecimal(res)
+    end
+  end
+
+  version_is BigDecimal::VERSION, "4.0.0" do
+    it "divides value, returns [Integer, BigDecimal]" do
+      res = @a.divmod(5)
+      res.kind_of?(Array).should == true
+      res[0].kind_of?(Integer).should == true
+      res[1].kind_of?(BigDecimal).should == true
+    end
   end
 
   it "array contains quotient and modulus as BigDecimal" do
     res = @a.divmod(5)
-    DivmodSpecs.check_both_bigdecimal(res)
     res[0].should == BigDecimal('0.8E1')
     res[1].should == BigDecimal('2.00000000000000000001')
 
@@ -123,17 +136,27 @@ describe "BigDecimal#divmod" do
     values_and_zeroes.each do |val1|
       values.each do |val2|
         res = val1.divmod(val2)
-        DivmodSpecs.check_both_bigdecimal(res)
         res[0].should == ((val1/val2).floor)
         res[1].should == (val1 - res[0] * val2)
       end
     end
   end
 
-  it "returns an array of two NaNs if NaN is involved" do
-    (@special_vals + @regular_vals + @zeroes).each do |val|
-      DivmodSpecs.check_both_nan(val.divmod(@nan))
-      DivmodSpecs.check_both_nan(@nan.divmod(val))
+  version_is BigDecimal::VERSION, "4.0.0" do
+    it "raise FloatDomainError error if NaN is involved" do
+      (@special_vals + @regular_vals + @zeroes).each do |val|
+        -> { val.divmod(@nan) }.should raise_error(FloatDomainError)
+        -> { @nan.divmod(val) }.should raise_error(FloatDomainError)
+      end
+    end
+  end
+
+  version_is BigDecimal::VERSION, ""..."4.0.0" do
+    it "returns an array of two NaNs if NaN is involved" do
+      (@special_vals + @regular_vals + @zeroes).each do |val|
+        DivmodSpecs.check_both_nan(val.divmod(@nan))
+        DivmodSpecs.check_both_nan(@nan.divmod(val))
+      end
     end
   end
 
@@ -145,21 +168,30 @@ describe "BigDecimal#divmod" do
     end
   end
 
-  it "returns an array of Infinity and NaN if the dividend is Infinity" do
-    @regular_vals.each do |val|
-      array = @infinity.divmod(val)
-      array.length.should == 2
-      array[0].infinite?.should == (val > 0 ? 1 : -1)
-      array[1].nan?.should == true
+  version_is BigDecimal::VERSION, ""..."4.0.0" do
+    it "returns an array of Infinity and NaN if the dividend is Infinity" do
+      @regular_vals.each do |val|
+        array = @infinity.divmod(val)
+        array.length.should == 2
+        array[0].infinite?.should == (val > 0 ? 1 : -1)
+        array[1].should.nan?
+      end
     end
   end
 
-  it "returns an array of zero and the dividend if the divisor is Infinity" do
-    @regular_vals.each do |val|
-      array = val.divmod(@infinity)
-      array.length.should == 2
-      array[0].should == @zero
-      array[1].should == val
+  version_is BigDecimal::VERSION, "3.3.0" do
+    it "returns an array of zero and the dividend or minus one and Infinity if the divisor is Infinity" do
+      @regular_vals.each do |val|
+        array = val.divmod(@infinity)
+        array.length.should == 2
+        if val >= 0
+          array[0].should == @zero
+          array[1].should == val
+        else
+          array[0].should == @one_minus
+          array[1].should == @infinity
+        end
+      end
     end
   end
 
diff --git a/spec/ruby/library/bigdecimal/exponent_spec.rb b/spec/ruby/library/bigdecimal/exponent_spec.rb
index a349ac093f..8877147955 100644
--- a/spec/ruby/library/bigdecimal/exponent_spec.rb
+++ b/spec/ruby/library/bigdecimal/exponent_spec.rb
@@ -18,17 +18,6 @@ describe "BigDecimal#exponent" do
     BigDecimal("1234567E10").exponent.should == 17
   end
 
-# commenting this spec out after discussion with Defiler, since it seems to be an MRI bug, not a real feature
-=begin
-  platform_is wordsize: 32 do
-    # TODO: write specs for both 32 and 64 bit
-    it "returns 0 if exponent can't be represented as Fixnum" do
-      BigDecimal("2E1000000000000000").exponent.should == 0
-      BigDecimal("-5E-999999999999999").exponent.should == 0
-    end
-  end
-=end
-
   it "returns 0 if self is 0" do
     BigDecimal("0").exponent.should == 0
     BigDecimal("+0").exponent.should == 0
diff --git a/spec/ruby/library/bigdecimal/finite_spec.rb b/spec/ruby/library/bigdecimal/finite_spec.rb
index 6685d589b6..8fc06029bb 100644
--- a/spec/ruby/library/bigdecimal/finite_spec.rb
+++ b/spec/ruby/library/bigdecimal/finite_spec.rb
@@ -21,14 +21,14 @@ describe "BigDecimal#finite?" do
   end
 
   it "is false if Infinity or NaN" do
-    @infinity.finite?.should == false
-    @infinity_minus.finite?.should == false
-    @nan.finite?.should == false
+    @infinity.should_not.finite?
+    @infinity_minus.should_not.finite?
+    @nan.should_not.finite?
   end
 
   it "returns true for finite values" do
     @finite_vals.each do |val|
-      val.finite?.should == true
+      val.should.finite?
     end
   end
 end
diff --git a/spec/ruby/library/bigdecimal/fix_spec.rb b/spec/ruby/library/bigdecimal/fix_spec.rb
index 53b30cbf8b..2c6276899e 100644
--- a/spec/ruby/library/bigdecimal/fix_spec.rb
+++ b/spec/ruby/library/bigdecimal/fix_spec.rb
@@ -2,20 +2,20 @@ require_relative '../../spec_helper'
 require 'bigdecimal'
 
 describe "BigDecimal#fix" do
-    before :each do
-      @zero = BigDecimal("0")
-      @mixed = BigDecimal("1.23456789")
-      @pos_int = BigDecimal("2E5555")
-      @neg_int = BigDecimal("-2E5555")
-      @pos_frac = BigDecimal("2E-9999")
-      @neg_frac = BigDecimal("-2E-9999")
-
-      @infinity = BigDecimal("Infinity")
-      @infinity_neg = BigDecimal("-Infinity")
-      @nan = BigDecimal("NaN")
-      @zero_pos = BigDecimal("+0")
-      @zero_neg = BigDecimal("-0")
-    end
+  before :each do
+    @zero = BigDecimal("0")
+    @mixed = BigDecimal("1.23456789")
+    @pos_int = BigDecimal("2E5555")
+    @neg_int = BigDecimal("-2E5555")
+    @pos_frac = BigDecimal("2E-9999")
+    @neg_frac = BigDecimal("-2E-9999")
+
+    @infinity = BigDecimal("Infinity")
+    @infinity_neg = BigDecimal("-Infinity")
+    @nan = BigDecimal("NaN")
+    @zero_pos = BigDecimal("+0")
+    @zero_neg = BigDecimal("-0")
+  end
 
   it "returns a BigDecimal" do
     BigDecimal("2E100000000").fix.kind_of?(BigDecimal).should == true
@@ -34,7 +34,7 @@ describe "BigDecimal#fix" do
   it "correctly handles special values" do
     @infinity.fix.should == @infinity
     @infinity_neg.fix.should == @infinity_neg
-    @nan.fix.nan?.should == true
+    @nan.fix.should.nan?
   end
 
   it "returns 0 if the absolute value is < 1" do
diff --git a/spec/ruby/library/bigdecimal/frac_spec.rb b/spec/ruby/library/bigdecimal/frac_spec.rb
index 4a023b4ff6..11ccf03c2f 100644
--- a/spec/ruby/library/bigdecimal/frac_spec.rb
+++ b/spec/ruby/library/bigdecimal/frac_spec.rb
@@ -42,7 +42,7 @@ describe "BigDecimal#frac" do
   it "correctly handles special values" do
     @infinity.frac.should == @infinity
     @infinity_neg.frac.should == @infinity_neg
-    @nan.frac.nan?.should == true
+    @nan.frac.should.nan?
   end
 
 end
diff --git a/spec/ruby/library/bigdecimal/gt_spec.rb b/spec/ruby/library/bigdecimal/gt_spec.rb
index 4717cfdd9d..78547fb85f 100644
--- a/spec/ruby/library/bigdecimal/gt_spec.rb
+++ b/spec/ruby/library/bigdecimal/gt_spec.rb
@@ -17,7 +17,7 @@ describe "BigDecimal#>" do
       def coerce(other)
         return [other, BigDecimal('123')]
       end
-      def > (other)
+      def >(other)
         BigDecimal('123') > other
       end
     end
diff --git a/spec/ruby/library/bigdecimal/gte_spec.rb b/spec/ruby/library/bigdecimal/gte_spec.rb
index 8dc81707f0..2a5cc025ba 100644
--- a/spec/ruby/library/bigdecimal/gte_spec.rb
+++ b/spec/ruby/library/bigdecimal/gte_spec.rb
@@ -17,7 +17,7 @@ describe "BigDecimal#>=" do
       def coerce(other)
         return [other, BigDecimal('123')]
       end
-      def >= (other)
+      def >=(other)
         BigDecimal('123') >= other
       end
     end
diff --git a/spec/ruby/library/bigdecimal/lt_spec.rb b/spec/ruby/library/bigdecimal/lt_spec.rb
index 61f4f19912..02390e76e3 100644
--- a/spec/ruby/library/bigdecimal/lt_spec.rb
+++ b/spec/ruby/library/bigdecimal/lt_spec.rb
@@ -17,7 +17,7 @@ describe "BigDecimal#<" do
       def coerce(other)
         return [other, BigDecimal('123')]
       end
-      def < (other)
+      def <(other)
         BigDecimal('123') < other
       end
     end
diff --git a/spec/ruby/library/bigdecimal/lte_spec.rb b/spec/ruby/library/bigdecimal/lte_spec.rb
index fc632315f8..b92be04123 100644
--- a/spec/ruby/library/bigdecimal/lte_spec.rb
+++ b/spec/ruby/library/bigdecimal/lte_spec.rb
@@ -17,7 +17,7 @@ describe "BigDecimal#<=" do
       def coerce(other)
         return [other, BigDecimal('123')]
       end
-      def <= (other)
+      def <=(other)
         BigDecimal('123') <= other
       end
     end
diff --git a/spec/ruby/library/bigdecimal/minus_spec.rb b/spec/ruby/library/bigdecimal/minus_spec.rb
index 267a0f7eab..bd3c19584b 100644
--- a/spec/ruby/library/bigdecimal/minus_spec.rb
+++ b/spec/ruby/library/bigdecimal/minus_spec.rb
@@ -26,18 +26,18 @@ describe "BigDecimal#-" do
   end
 
   it "returns NaN if NaN is involved" do
-    (@one - @nan).nan?.should == true
-    (@nan - @one).nan?.should == true
-    (@nan - @nan).nan?.should == true
-    (@nan - @infinity).nan?.should == true
-    (@nan - @infinity_minus).nan?.should == true
-    (@infinity - @nan).nan?.should == true
-    (@infinity_minus - @nan).nan?.should == true
+    (@one - @nan).should.nan?
+    (@nan - @one).should.nan?
+    (@nan - @nan).should.nan?
+    (@nan - @infinity).should.nan?
+    (@nan - @infinity_minus).should.nan?
+    (@infinity - @nan).should.nan?
+    (@infinity_minus - @nan).should.nan?
   end
 
   it "returns NaN both operands are infinite with the same sign" do
-    (@infinity - @infinity).nan?.should == true
-    (@infinity_minus - @infinity_minus).nan?.should == true
+    (@infinity - @infinity).should.nan?
+    (@infinity_minus - @infinity_minus).should.nan?
   end
 
   it "returns Infinity or -Infinity if these are involved" do
diff --git a/spec/ruby/library/bigdecimal/mode_spec.rb b/spec/ruby/library/bigdecimal/mode_spec.rb
index f57028ae5d..73fa1a118e 100644
--- a/spec/ruby/library/bigdecimal/mode_spec.rb
+++ b/spec/ruby/library/bigdecimal/mode_spec.rb
@@ -12,7 +12,7 @@ describe "BigDecimal.mode" do
   end
 
   it "returns the appropriate value and continue the computation if the flag is false" do
-    BigDecimal("NaN").add(BigDecimal("1"),0).nan?.should == true
+    BigDecimal("NaN").add(BigDecimal("1"),0).should.nan?
     BigDecimal("0").add(BigDecimal("Infinity"),0).should == BigDecimal("Infinity")
     BigDecimal("1").quo(BigDecimal("0")).should == BigDecimal("Infinity")
   end
diff --git a/spec/ruby/library/bigdecimal/mult_spec.rb b/spec/ruby/library/bigdecimal/mult_spec.rb
index b7f8044b0b..2353df9cb8 100644
--- a/spec/ruby/library/bigdecimal/mult_spec.rb
+++ b/spec/ruby/library/bigdecimal/mult_spec.rb
@@ -21,12 +21,4 @@ describe "BigDecimal#mult" do
     @e.mult(@one, 1).should be_close(@one, @tolerance)
     @e3_minus.mult(@one, 1).should be_close(0, @tolerance2)
   end
-
-  describe "with Object" do
-    it "tries to coerce the other operand to self" do
-      object = mock("Object")
-      object.should_receive(:coerce).with(@e3_minus).and_return([@e3_minus, @e3_plus])
-      @e3_minus.mult(object, 1).should == BigDecimal("9")
-    end
-  end
 end
diff --git a/spec/ruby/library/bigdecimal/nan_spec.rb b/spec/ruby/library/bigdecimal/nan_spec.rb
index 705492614b..9eaf69b610 100644
--- a/spec/ruby/library/bigdecimal/nan_spec.rb
+++ b/spec/ruby/library/bigdecimal/nan_spec.rb
@@ -4,20 +4,20 @@ require 'bigdecimal'
 describe "BigDecimal#nan?" do
 
   it "returns true if self is not a number" do
-    BigDecimal("NaN").nan?.should == true
+    BigDecimal("NaN").should.nan?
   end
 
   it "returns false if self is not a NaN" do
-    BigDecimal("Infinity").nan?.should == false
-    BigDecimal("-Infinity").nan?.should == false
-    BigDecimal("0").nan?.should == false
-    BigDecimal("+0").nan?.should == false
-    BigDecimal("-0").nan?.should == false
-    BigDecimal("2E40001").nan?.should == false
-    BigDecimal("3E-20001").nan?.should == false
-    BigDecimal("0E-200000000").nan?.should == false
-    BigDecimal("0E200000000000").nan?.should == false
-    BigDecimal("0.000000000000000000000000").nan?.should == false
+    BigDecimal("Infinity").should_not.nan?
+    BigDecimal("-Infinity").should_not.nan?
+    BigDecimal("0").should_not.nan?
+    BigDecimal("+0").should_not.nan?
+    BigDecimal("-0").should_not.nan?
+    BigDecimal("2E40001").should_not.nan?
+    BigDecimal("3E-20001").should_not.nan?
+    BigDecimal("0E-200000000").should_not.nan?
+    BigDecimal("0E200000000000").should_not.nan?
+    BigDecimal("0.000000000000000000000000").should_not.nan?
   end
 
 end
diff --git a/spec/ruby/library/bigdecimal/plus_spec.rb b/spec/ruby/library/bigdecimal/plus_spec.rb
index cefc43aeaa..d1934841c8 100644
--- a/spec/ruby/library/bigdecimal/plus_spec.rb
+++ b/spec/ruby/library/bigdecimal/plus_spec.rb
@@ -30,8 +30,8 @@ describe "BigDecimal#+" do
   end
 
   it "returns NaN if NaN is involved" do
-    (@one + @nan).nan?.should == true
-    (@nan + @one).nan?.should == true
+    (@one + @nan).should.nan?
+    (@nan + @one).should.nan?
   end
 
   it "returns Infinity or -Infinity if these are involved" do
@@ -41,7 +41,7 @@ describe "BigDecimal#+" do
   end
 
   it "returns NaN if Infinity + (- Infinity)" do
-    (@infinity + @infinity_minus).nan?.should == true
+    (@infinity + @infinity_minus).should.nan?
   end
 
   describe "with Object" do
diff --git a/spec/ruby/library/bigdecimal/precs_spec.rb b/spec/ruby/library/bigdecimal/precs_spec.rb
deleted file mode 100644
index f9320f2b9e..0000000000
--- a/spec/ruby/library/bigdecimal/precs_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../spec_helper'
-require 'bigdecimal'
-
-describe "BigDecimal#precs" do
-
-  before :each do
-    @infinity = BigDecimal("Infinity")
-    @infinity_neg = BigDecimal("-Infinity")
-    @nan = BigDecimal("NaN")
-    @zero = BigDecimal("0")
-    @zero_neg = BigDecimal("-0")
-
-    @arr = [BigDecimal("2E40001"), BigDecimal("3E-20001"),\
-            @infinity, @infinity_neg, @nan, @zero, @zero_neg]
-    @precision = BigDecimal::BASE.to_s.length - 1
-  end
-
-  it "returns array of two values" do
-    @arr.each do |x|
-      x.precs.kind_of?(Array).should == true
-      x.precs.size.should == 2
-    end
-  end
-
-  it "returns Integers as array values" do
-    @arr.each do |x|
-      x.precs[0].kind_of?(Integer).should == true
-      x.precs[1].kind_of?(Integer).should == true
-    end
-  end
-
-  it "returns the current value of significant digits as the first value" do
-    BigDecimal("3.14159").precs[0].should >= 6
-    BigDecimal('1').precs[0].should == BigDecimal('1' + '0' * 100).precs[0]
-    [@infinity, @infinity_neg, @nan, @zero, @zero_neg].each do |value|
-      value.precs[0].should <= @precision
-    end
-  end
-
-  it "returns the maximum number of significant digits as the second value" do
-    BigDecimal("3.14159").precs[1].should >= 6
-    BigDecimal('1').precs[1].should >= 1
-    BigDecimal('1' + '0' * 100).precs[1] >= 101
-    [@infinity, @infinity_neg, @nan, @zero, @zero_neg].each do |value|
-      value.precs[1].should >= 1
-    end
-  end
-end
diff --git a/spec/ruby/library/bigdecimal/quo_spec.rb b/spec/ruby/library/bigdecimal/quo_spec.rb
index a5c5651778..65a4330303 100644
--- a/spec/ruby/library/bigdecimal/quo_spec.rb
+++ b/spec/ruby/library/bigdecimal/quo_spec.rb
@@ -6,7 +6,7 @@ describe "BigDecimal#quo" do
   it_behaves_like :bigdecimal_quo, :quo, []
 
   it "returns NaN if NaN is involved" do
-    BigDecimal("1").quo(BigDecimal("NaN")).nan?.should == true
-    BigDecimal("NaN").quo(BigDecimal("1")).nan?.should == true
+    BigDecimal("1").quo(BigDecimal("NaN")).should.nan?
+    BigDecimal("NaN").quo(BigDecimal("1")).should.nan?
   end
 end
diff --git a/spec/ruby/library/bigdecimal/remainder_spec.rb b/spec/ruby/library/bigdecimal/remainder_spec.rb
index 04233edece..0eb06f7ef1 100644
--- a/spec/ruby/library/bigdecimal/remainder_spec.rb
+++ b/spec/ruby/library/bigdecimal/remainder_spec.rb
@@ -37,9 +37,11 @@ describe "BigDecimal#remainder" do
     @neg_int.remainder(@pos_frac).should == @neg_int - @pos_frac * (@neg_int / @pos_frac).truncate
   end
 
-  it "returns NaN used with zero" do
-    @mixed.remainder(@zero).nan?.should == true
-    @zero.remainder(@zero).nan?.should == true
+  version_is BigDecimal::VERSION, "3.3.0" do
+    it "raises ZeroDivisionError used with zero" do
+      -> { @mixed.remainder(@zero) }.should raise_error(ZeroDivisionError)
+      -> { @zero.remainder(@zero) }.should raise_error(ZeroDivisionError)
+    end
   end
 
   it "returns zero if used on zero" do
@@ -47,28 +49,30 @@ describe "BigDecimal#remainder" do
   end
 
   it "returns NaN if NaN is involved" do
-    @nan.remainder(@nan).nan?.should == true
-    @nan.remainder(@one).nan?.should == true
-    @one.remainder(@nan).nan?.should == true
-    @infinity.remainder(@nan).nan?.should == true
-    @nan.remainder(@infinity).nan?.should == true
+    @nan.remainder(@nan).should.nan?
+    @nan.remainder(@one).should.nan?
+    @one.remainder(@nan).should.nan?
+    @infinity.remainder(@nan).should.nan?
+    @nan.remainder(@infinity).should.nan?
   end
 
-  it "returns NaN if Infinity is involved" do
-    @infinity.remainder(@infinity).nan?.should == true
-    @infinity.remainder(@one).nan?.should == true
-    @infinity.remainder(@mixed).nan?.should == true
-    @infinity.remainder(@one_minus).nan?.should == true
-    @infinity.remainder(@frac_1).nan?.should == true
-    @one.remainder(@infinity).nan?.should == true
+  version_is BigDecimal::VERSION, ""..."3.1.4" do #ruby_version_is ""..."3.3" do
+    it "returns NaN if Infinity is involved" do
+      @infinity.remainder(@infinity).should.nan?
+      @infinity.remainder(@one).should.nan?
+      @infinity.remainder(@mixed).should.nan?
+      @infinity.remainder(@one_minus).should.nan?
+      @infinity.remainder(@frac_1).should.nan?
+      @one.remainder(@infinity).should.nan?
 
-    @infinity_minus.remainder(@infinity_minus).nan?.should == true
-    @infinity_minus.remainder(@one).nan?.should == true
-    @one.remainder(@infinity_minus).nan?.should == true
-    @frac_2.remainder(@infinity_minus).nan?.should == true
+      @infinity_minus.remainder(@infinity_minus).should.nan?
+      @infinity_minus.remainder(@one).should.nan?
+      @one.remainder(@infinity_minus).should.nan?
+      @frac_2.remainder(@infinity_minus).should.nan?
 
-    @infinity.remainder(@infinity_minus).nan?.should == true
-    @infinity_minus.remainder(@infinity).nan?.should == true
+      @infinity.remainder(@infinity_minus).should.nan?
+      @infinity_minus.remainder(@infinity).should.nan?
+    end
   end
 
   it "coerces arguments to BigDecimal if possible" do
diff --git a/spec/ruby/library/bigdecimal/round_spec.rb b/spec/ruby/library/bigdecimal/round_spec.rb
index 501a1a7342..6a4d220417 100644
--- a/spec/ruby/library/bigdecimal/round_spec.rb
+++ b/spec/ruby/library/bigdecimal/round_spec.rb
@@ -228,7 +228,7 @@ describe "BigDecimal#round" do
     -> { BigDecimal('-Infinity').round(2) }.should_not raise_error(FloatDomainError)
   end
 
-  it "raise for a non-existent round mode" do
-    -> { @p1_50.round(0, :nonsense) }.should raise_error(ArgumentError, "invalid rounding mode")
+  it 'raise for a non-existent round mode' do
+    -> { @p1_50.round(0, :nonsense) }.should raise_error(ArgumentError, "invalid rounding mode (nonsense)")
   end
 end
diff --git a/spec/ruby/library/bigdecimal/shared/clone.rb b/spec/ruby/library/bigdecimal/shared/clone.rb
index e58df3a94b..935ef76e7e 100644
--- a/spec/ruby/library/bigdecimal/shared/clone.rb
+++ b/spec/ruby/library/bigdecimal/shared/clone.rb
@@ -5,20 +5,9 @@ describe :bigdecimal_clone, shared: true do
     @obj = BigDecimal("1.2345")
   end
 
-  ruby_version_is "" ... "2.5" do
-    it "copies the BigDecimal's value to a newly allocated object" do
-      copy = @obj.public_send(@method)
+  it "returns self" do
+    copy = @obj.public_send(@method)
 
-      copy.should_not equal(@obj)
-      copy.should == @obj
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns self" do
-      copy = @obj.public_send(@method)
-
-      copy.should equal(@obj)
-    end
+    copy.should equal(@obj)
   end
 end
diff --git a/spec/ruby/library/bigdecimal/shared/modulo.rb b/spec/ruby/library/bigdecimal/shared/modulo.rb
index 67c0ecf2fc..eeb030fd23 100644
--- a/spec/ruby/library/bigdecimal/shared/modulo.rb
+++ b/spec/ruby/library/bigdecimal/shared/modulo.rb
@@ -80,31 +80,37 @@ describe :bigdecimal_modulo, shared: true do
   end
 
   it "returns NaN if NaN is involved" do
-    @nan.send(@method, @nan).nan?.should == true
-    @nan.send(@method, @one).nan?.should == true
-    @one.send(@method, @nan).nan?.should == true
-    @infinity.send(@method, @nan).nan?.should == true
-    @nan.send(@method, @infinity).nan?.should == true
+    @nan.send(@method, @nan).should.nan?
+    @nan.send(@method, @one).should.nan?
+    @one.send(@method, @nan).should.nan?
+    @infinity.send(@method, @nan).should.nan?
+    @nan.send(@method, @infinity).should.nan?
   end
 
   it "returns NaN if the dividend is Infinity" do
-    @infinity.send(@method, @infinity).nan?.should == true
-    @infinity.send(@method, @one).nan?.should == true
-    @infinity.send(@method, @mixed).nan?.should == true
-    @infinity.send(@method, @one_minus).nan?.should == true
-    @infinity.send(@method, @frac_1).nan?.should == true
+    @infinity.send(@method, @infinity).should.nan?
+    @infinity.send(@method, @one).should.nan?
+    @infinity.send(@method, @mixed).should.nan?
+    @infinity.send(@method, @one_minus).should.nan?
+    @infinity.send(@method, @frac_1).should.nan?
 
-    @infinity_minus.send(@method, @infinity_minus).nan?.should == true
-    @infinity_minus.send(@method, @one).nan?.should == true
+    @infinity_minus.send(@method, @infinity_minus).should.nan?
+    @infinity_minus.send(@method, @one).should.nan?
 
-    @infinity.send(@method, @infinity_minus).nan?.should == true
-    @infinity_minus.send(@method, @infinity).nan?.should == true
+    @infinity.send(@method, @infinity_minus).should.nan?
+    @infinity_minus.send(@method, @infinity).should.nan?
   end
 
-  it "returns the dividend if the divisor is Infinity" do
-    @one.send(@method, @infinity).should == @one
-    @one.send(@method, @infinity_minus).should == @one
-    @frac_2.send(@method, @infinity_minus).should == @frac_2
+  version_is BigDecimal::VERSION, "3.3.0" do
+    it "returns the dividend if the divisor is Infinity and signs are same" do
+      @one.send(@method, @infinity).should == @one
+      (-@frac_2).send(@method, @infinity_minus).should == -@frac_2
+    end
+
+    it "returns the divisor if the divisor is Infinity and signs are different" do
+      (-@one).send(@method, @infinity).should == @infinity
+      @frac_2.send(@method, @infinity_minus).should == @infinity_minus
+    end
   end
 
   it "raises TypeError if the argument cannot be coerced to BigDecimal" do
diff --git a/spec/ruby/library/bigdecimal/shared/mult.rb b/spec/ruby/library/bigdecimal/shared/mult.rb
index b94c9385de..c613df04c4 100644
--- a/spec/ruby/library/bigdecimal/shared/mult.rb
+++ b/spec/ruby/library/bigdecimal/shared/mult.rb
@@ -51,8 +51,8 @@ describe :bigdecimal_mult, shared: true do
     values = @regular_vals + @zeroes
 
     values.each do |val|
-      @nan.send(@method, val, *@object).nan?.should == true
-      val.send(@method, @nan, *@object).nan?.should == true
+      @nan.send(@method, val, *@object).should.nan?
+      val.send(@method, @nan, *@object).should.nan?
     end
   end
 
@@ -62,9 +62,9 @@ describe :bigdecimal_mult, shared: true do
     values.each do |val|
       @zeroes.each do |zero|
         zero.send(@method, val, *@object).should == 0
-        zero.send(@method, val, *@object).zero?.should == true
+        zero.send(@method, val, *@object).should.zero?
         val.send(@method, zero, *@object).should == 0
-        val.send(@method, zero, *@object).zero?.should == true
+        val.send(@method, zero, *@object).should.zero?
       end
     end
   end
@@ -75,8 +75,8 @@ describe :bigdecimal_mult, shared: true do
 
     values.each do |val|
       infs.each do |inf|
-        inf.send(@method, val, *@object).finite?.should == false
-        val.send(@method, inf, *@object).finite?.should == false
+        inf.send(@method, val, *@object).should_not.finite?
+        val.send(@method, inf, *@object).should_not.finite?
       end
     end
 
@@ -89,9 +89,9 @@ describe :bigdecimal_mult, shared: true do
   end
 
   it "returns NaN if the result is undefined" do
-    @zero.send(@method, @infinity, *@object).nan?.should == true
-    @zero.send(@method, @infinity_minus, *@object).nan?.should == true
-    @infinity.send(@method, @zero, *@object).nan?.should == true
-    @infinity_minus.send(@method, @zero, *@object).nan?.should == true
+    @zero.send(@method, @infinity, *@object).should.nan?
+    @zero.send(@method, @infinity_minus, *@object).should.nan?
+    @infinity.send(@method, @zero, *@object).should.nan?
+    @infinity_minus.send(@method, @zero, *@object).should.nan?
   end
 end
diff --git a/spec/ruby/library/bigdecimal/shared/power.rb b/spec/ruby/library/bigdecimal/shared/power.rb
index a4848fb2e2..6dafb638e2 100644
--- a/spec/ruby/library/bigdecimal/shared/power.rb
+++ b/spec/ruby/library/bigdecimal/shared/power.rb
@@ -10,8 +10,8 @@ describe :bigdecimal_power, shared: true do
     e = BigDecimal("1.00000000000000000000123456789")
     one = BigDecimal("1")
     ten = BigDecimal("10")
-    # The tolerance is dependent upon the size of BASE_FIG
-    tolerance = BigDecimal("1E-70")
+    # Accuracy is at least ndigits(== 30) + DOUBLE_FIG(== 16)
+    tolerance = BigDecimal("1E-46")
     ten_powers = BigDecimal("1E10000")
     pi = BigDecimal("3.14159265358979")
     e3_minus.send(@method, 2).should == e3_minus_power_2
@@ -53,8 +53,8 @@ describe :bigdecimal_power, shared: true do
   end
 
   it "returns NaN if self is NaN" do
-    BigDecimal("NaN").send(@method, -5).nan?.should == true
-    BigDecimal("NaN").send(@method, 5).nan?.should == true
+    BigDecimal("NaN").send(@method, -5).should.nan?
+    BigDecimal("NaN").send(@method, 5).should.nan?
   end
 
   it "returns 0.0 if self is infinite and argument is negative" do
diff --git a/spec/ruby/library/bigdecimal/shared/quo.rb b/spec/ruby/library/bigdecimal/shared/quo.rb
index 4d6d64b787..18ff2fe9a5 100644
--- a/spec/ruby/library/bigdecimal/shared/quo.rb
+++ b/spec/ruby/library/bigdecimal/shared/quo.rb
@@ -31,6 +31,7 @@ describe :bigdecimal_quo, shared: true do
 
   describe "with Object" do
     it "tries to coerce the other operand to self" do
+      skip if @method == :div
       object = mock("Object")
       object.should_receive(:coerce).with(@one).and_return([@one, @two])
       @one.send(@method, object, *@object).should == BigDecimal("0.5")
@@ -49,8 +50,8 @@ describe :bigdecimal_quo, shared: true do
   end
 
   it "returns NaN if Infinity / ((+|-) Infinity)" do
-    @infinity.send(@method, @infinity_minus, *@object).nan?.should == true
-    @infinity_minus.send(@method, @infinity, *@object).nan?.should == true
+    @infinity.send(@method, @infinity_minus, *@object).should.nan?
+    @infinity_minus.send(@method, @infinity, *@object).should.nan?
   end
 
   it "returns (+|-) Infinity if divided by zero" do
@@ -60,8 +61,8 @@ describe :bigdecimal_quo, shared: true do
   end
 
   it "returns NaN if zero is divided by zero" do
-    @zero.send(@method, @zero, *@object).nan?.should == true
-    @zero_minus.send(@method, @zero_plus, *@object).nan?.should == true
-    @zero_plus.send(@method, @zero_minus, *@object).nan?.should == true
+    @zero.send(@method, @zero, *@object).should.nan?
+    @zero_minus.send(@method, @zero_plus, *@object).should.nan?
+    @zero_plus.send(@method, @zero_minus, *@object).should.nan?
   end
 end
diff --git a/spec/ruby/library/bigdecimal/shared/to_int.rb b/spec/ruby/library/bigdecimal/shared/to_int.rb
index 02f6092f23..44b6a3c7b2 100644
--- a/spec/ruby/library/bigdecimal/shared/to_int.rb
+++ b/spec/ruby/library/bigdecimal/shared/to_int.rb
@@ -1,12 +1,12 @@
 require 'bigdecimal'
 
-describe :bigdecimal_to_int , shared: true do
+describe :bigdecimal_to_int, shared: true do
   it "raises FloatDomainError if BigDecimal is infinity or NaN" do
     -> { BigDecimal("Infinity").send(@method) }.should raise_error(FloatDomainError)
     -> { BigDecimal("NaN").send(@method) }.should raise_error(FloatDomainError)
   end
 
-  it "returns Integer or Bignum otherwise" do
+  it "returns Integer otherwise" do
     BigDecimal("3E-20001").send(@method).should == 0
     BigDecimal("2E4000").send(@method).should == 2 * 10 ** 4000
     BigDecimal("2").send(@method).should == 2
diff --git a/spec/ruby/library/bigdecimal/split_spec.rb b/spec/ruby/library/bigdecimal/split_spec.rb
index f9b4bab5f7..53b1f649d9 100644
--- a/spec/ruby/library/bigdecimal/split_spec.rb
+++ b/spec/ruby/library/bigdecimal/split_spec.rb
@@ -58,16 +58,16 @@ describe "BigDecimal#split" do
   end
 
   it "third value: the base (currently always ten)" do
-   @arr[2].should == 10
-   @arr_neg[2].should == 10
-   @arr_big[2].should == 10
-   @arr_big_neg[2].should == 10
-   @huge[2].should == 10
-   @infinity.split[2].should == 10
-   @nan.split[2].should == 10
-   @infinity_neg.split[2].should == 10
-   @zero.split[2].should == 10
-   @zero_neg.split[2].should == 10
+    @arr[2].should == 10
+    @arr_neg[2].should == 10
+    @arr_big[2].should == 10
+    @arr_big_neg[2].should == 10
+    @huge[2].should == 10
+    @infinity.split[2].should == 10
+    @nan.split[2].should == 10
+    @infinity_neg.split[2].should == 10
+    @zero.split[2].should == 10
+    @zero_neg.split[2].should == 10
   end
 
   it "fourth value: the exponent" do
diff --git a/spec/ruby/library/bigdecimal/sqrt_spec.rb b/spec/ruby/library/bigdecimal/sqrt_spec.rb
index d149003b9f..42cf4545cb 100644
--- a/spec/ruby/library/bigdecimal/sqrt_spec.rb
+++ b/spec/ruby/library/bigdecimal/sqrt_spec.rb
@@ -36,8 +36,10 @@ describe "BigDecimal#sqrt" do
     BigDecimal('121').sqrt(5).should be_close(11, 0.00001)
   end
 
-  it "returns square root of 0.9E-99999 with desired precision" do
-    @frac_2.sqrt(1).to_s.should =~ /\A0\.3E-49999\z/i
+  platform_is_not c_long_size: 32 do # fails on i686
+    it "returns square root of 0.9E-99999 with desired precision" do
+      @frac_2.sqrt(1).to_s.should =~ /\A0\.3E-49999\z/i
+    end
   end
 
   it "raises ArgumentError when no argument is given" do
diff --git a/spec/ruby/library/bigdecimal/sub_spec.rb b/spec/ruby/library/bigdecimal/sub_spec.rb
index 29ec851193..3b62a0c794 100644
--- a/spec/ruby/library/bigdecimal/sub_spec.rb
+++ b/spec/ruby/library/bigdecimal/sub_spec.rb
@@ -35,14 +35,6 @@ describe "BigDecimal#sub" do
     @frac_1.sub(@frac_1, 1000000).should == @zero
   end
 
-  describe "with Object" do
-    it "tries to coerce the other operand to self" do
-      object = mock("Object")
-      object.should_receive(:coerce).with(@frac_3).and_return([@frac_3, @frac_4])
-      @frac_3.sub(object, 1).should == BigDecimal("-0.9E15")
-    end
-  end
-
   describe "with Rational" do
     it "produces a BigDecimal" do
       (@three - Rational(500, 2)).should == BigDecimal('-0.247e3')
@@ -50,13 +42,13 @@ describe "BigDecimal#sub" do
   end
 
   it "returns NaN if NaN is involved" do
-    @one.sub(@nan, 1).nan?.should == true
-    @nan.sub(@one, 1).nan?.should == true
+    @one.sub(@nan, 1).should.nan?
+    @nan.sub(@one, 1).should.nan?
   end
 
   it "returns NaN if both values are infinite with the same signs" do
-    @infinity.sub(@infinity, 1).nan?.should == true
-    @infinity_minus.sub(@infinity_minus, 1).nan?.should == true
+    @infinity.sub(@infinity, 1).should.nan?
+    @infinity_minus.sub(@infinity_minus, 1).should.nan?
   end
 
   it "returns Infinity or -Infinity if these are involved" do
diff --git a/spec/ruby/library/bigdecimal/to_f_spec.rb b/spec/ruby/library/bigdecimal/to_f_spec.rb
index 1cc25d5c40..84d4d49de2 100644
--- a/spec/ruby/library/bigdecimal/to_f_spec.rb
+++ b/spec/ruby/library/bigdecimal/to_f_spec.rb
@@ -41,7 +41,7 @@ describe "BigDecimal#to_f" do
     @zero.to_f.should == 0
     @zero.to_f.to_s.should == "0.0"
 
-    @nan.to_f.nan?.should == true
+    @nan.to_f.should.nan?
 
     @infinity.to_f.infinite?.should == 1
     @infinity_minus.to_f.infinite?.should == -1
diff --git a/spec/ruby/library/bigdecimal/to_i_spec.rb b/spec/ruby/library/bigdecimal/to_i_spec.rb
index 09481fce15..e5e65c562e 100644
--- a/spec/ruby/library/bigdecimal/to_i_spec.rb
+++ b/spec/ruby/library/bigdecimal/to_i_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/to_int'
 require 'bigdecimal'
 
 describe "BigDecimal#to_i" do
-    it_behaves_like :bigdecimal_to_int, :to_i
+  it_behaves_like :bigdecimal_to_int, :to_i
 end
diff --git a/spec/ruby/library/bigdecimal/to_r_spec.rb b/spec/ruby/library/bigdecimal/to_r_spec.rb
index 91d2b33993..c350beff08 100644
--- a/spec/ruby/library/bigdecimal/to_r_spec.rb
+++ b/spec/ruby/library/bigdecimal/to_r_spec.rb
@@ -13,4 +13,16 @@ describe "BigDecimal#to_r" do
     r.denominator.should eql(1000000000000000000000000)
   end
 
+  it "returns a Rational from a BigDecimal with an exponent" do
+    r = BigDecimal("1E2").to_r
+    r.numerator.should eql(100)
+    r.denominator.should eql(1)
+  end
+
+  it "returns a Rational from a negative BigDecimal with an exponent" do
+    r = BigDecimal("-1E2").to_r
+    r.numerator.should eql(-100)
+    r.denominator.should eql(1)
+  end
+
 end
diff --git a/spec/ruby/library/bigdecimal/to_s_spec.rb b/spec/ruby/library/bigdecimal/to_s_spec.rb
index b6154c680d..ba9f960eb3 100644
--- a/spec/ruby/library/bigdecimal/to_s_spec.rb
+++ b/spec/ruby/library/bigdecimal/to_s_spec.rb
@@ -8,6 +8,11 @@ describe "BigDecimal#to_s" do
     @bigneg_str = "-3.1415926535897932384626433832795028841971693993"
     @bigdec = BigDecimal(@bigdec_str)
     @bigneg = BigDecimal(@bigneg_str)
+    @internal = Encoding.default_internal
+  end
+
+  after :each do
+    Encoding.default_internal = @internal
   end
 
   it "return type is of class String" do
@@ -34,9 +39,9 @@ describe "BigDecimal#to_s" do
     @bigneg.to_s("+").should_not =~ /^\+.*/
   end
 
-  it "inserts a space every n chars, if integer n is supplied" do
+  it "inserts a space every n chars to fraction part, if integer n is supplied" do
     re =\
-      /\A0\.314 159 265 358 979 323 846 264 338 327 950 288 419 716 939 937E1\z/i
+    /\A0\.314 159 265 358 979 323 846 264 338 327 950 288 419 716 939 937E1\z/i
     @bigdec.to_s(3).should =~ re
 
     str1 = '-123.45678 90123 45678 9'
@@ -47,6 +52,12 @@ describe "BigDecimal#to_s" do
     BigDecimal("1.2345").to_s('0F').should == "1.2345"
   end
 
+  version_is BigDecimal::VERSION, "3.1.5" do #ruby_version_is '3.3' do
+    it "inserts a space every n chars to integer part, if integer n is supplied" do
+      BigDecimal('1000010').to_s('5F').should == "10 00010.0"
+    end
+  end
+
   it "can return a leading space for values > 0" do
     @bigdec.to_s(" F").should =~ /\ .*/
     @bigneg.to_s(" F").should_not =~ /\ .*/
@@ -77,4 +88,13 @@ describe "BigDecimal#to_s" do
     end
   end
 
+  it "returns a String in US-ASCII encoding when Encoding.default_internal is nil" do
+    Encoding.default_internal = nil
+    BigDecimal('1.23').to_s.encoding.should equal(Encoding::US_ASCII)
+  end
+
+  it "returns a String in US-ASCII encoding when Encoding.default_internal is not nil" do
+    Encoding.default_internal = Encoding::IBM437
+    BigDecimal('1.23').to_s.encoding.should equal(Encoding::US_ASCII)
+  end
 end
diff --git a/spec/ruby/library/bigdecimal/truncate_spec.rb b/spec/ruby/library/bigdecimal/truncate_spec.rb
index d3a15f62c7..0ae0421b30 100644
--- a/spec/ruby/library/bigdecimal/truncate_spec.rb
+++ b/spec/ruby/library/bigdecimal/truncate_spec.rb
@@ -4,11 +4,11 @@ require 'bigdecimal'
 describe "BigDecimal#truncate" do
 
   before :each do
-      @arr = ['3.14159', '8.7', "0.314159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593014782083152134043E1"]
-      @big = BigDecimal("123456.789")
-      @nan = BigDecimal('NaN')
-      @infinity = BigDecimal('Infinity')
-      @infinity_negative = BigDecimal('-Infinity')
+    @arr = ['3.14159', '8.7', "0.314159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745028410270193852110555964462294895493038196442881097566593014782083152134043E1"]
+    @big = BigDecimal("123456.789")
+    @nan = BigDecimal('NaN')
+    @infinity = BigDecimal('Infinity')
+    @infinity_negative = BigDecimal('-Infinity')
   end
 
   it "returns value of type Integer." do
@@ -58,9 +58,9 @@ describe "BigDecimal#truncate" do
   end
 
   it "returns NaN if self is NaN" do
-    @nan.truncate(-1).nan?.should == true
-    @nan.truncate(+1).nan?.should == true
-    @nan.truncate(0).nan?.should == true
+    @nan.truncate(-1).should.nan?
+    @nan.truncate(+1).should.nan?
+    @nan.truncate(0).should.nan?
   end
 
   it "returns Infinity if self is infinite" do
diff --git a/spec/ruby/library/bigdecimal/uminus_spec.rb b/spec/ruby/library/bigdecimal/uminus_spec.rb
index 5e2a786c4c..c780cdfac5 100644
--- a/spec/ruby/library/bigdecimal/uminus_spec.rb
+++ b/spec/ruby/library/bigdecimal/uminus_spec.rb
@@ -53,6 +53,6 @@ describe "BigDecimal#-@" do
     @zero_neg.send(:-@).should == @zero
     @zero_neg.send(:-@).sign.should == 1
 
-    @nan.send(:-@).nan?.should == true
+    @nan.send(:-@).should.nan?
   end
 end
diff --git a/spec/ruby/library/bigdecimal/util_spec.rb b/spec/ruby/library/bigdecimal/util_spec.rb
index f41e131144..fc67fcf200 100644
--- a/spec/ruby/library/bigdecimal/util_spec.rb
+++ b/spec/ruby/library/bigdecimal/util_spec.rb
@@ -27,10 +27,8 @@ describe "BigDecimal's util method definitions" do
       Rational(22, 7).to_d(3).should == BigDecimal(3.14, 3)
     end
 
-    ruby_version_is "2.6" do
-      it "should define #to_d on nil" do
-        nil.to_d.should == BigDecimal(0)
-      end
+    it "should define #to_d on nil" do
+      nil.to_d.should == BigDecimal(0)
     end
   end
 
diff --git a/spec/ruby/library/bigdecimal/zero_spec.rb b/spec/ruby/library/bigdecimal/zero_spec.rb
index c5d3acb8c3..2563210939 100644
--- a/spec/ruby/library/bigdecimal/zero_spec.rb
+++ b/spec/ruby/library/bigdecimal/zero_spec.rb
@@ -6,22 +6,22 @@ describe "BigDecimal#zero?" do
   it "returns true if self does equal zero" do
     really_small_zero = BigDecimal("0E-200000000")
     really_big_zero = BigDecimal("0E200000000000")
-    really_small_zero.zero?.should == true
-    really_big_zero.zero?.should == true
-    BigDecimal("0.000000000000000000000000").zero?.should == true
-    BigDecimal("0").zero?.should == true
-    BigDecimal("0E0").zero?.should == true
-    BigDecimal("+0").zero?.should == true
-    BigDecimal("-0").zero?.should == true
+    really_small_zero.should.zero?
+    really_big_zero.should.zero?
+    BigDecimal("0.000000000000000000000000").should.zero?
+    BigDecimal("0").should.zero?
+    BigDecimal("0E0").should.zero?
+    BigDecimal("+0").should.zero?
+    BigDecimal("-0").should.zero?
   end
 
   it "returns false otherwise" do
-    BigDecimal("0000000001").zero?.should == false
-    BigDecimal("2E40001").zero?.should == false
-    BigDecimal("3E-20001").zero?.should == false
-    BigDecimal("Infinity").zero?.should == false
-    BigDecimal("-Infinity").zero?.should == false
-    BigDecimal("NaN").zero?.should == false
+    BigDecimal("0000000001").should_not.zero?
+    BigDecimal("2E40001").should_not.zero?
+    BigDecimal("3E-20001").should_not.zero?
+    BigDecimal("Infinity").should_not.zero?
+    BigDecimal("-Infinity").should_not.zero?
+    BigDecimal("NaN").should_not.zero?
   end
 
 end
diff --git a/spec/ruby/library/bigmath/log_spec.rb b/spec/ruby/library/bigmath/log_spec.rb
deleted file mode 100644
index 2ffbf8b6b9..0000000000
--- a/spec/ruby/library/bigmath/log_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-require 'bigdecimal'
-
-describe "BigDecimal#log" do
-  it "handles high-precision Rational arguments" do
-    result = BigDecimal('0.22314354220170971436137296411949880462556361100856391620766259404746040597133837784E0')
-    r = Rational(1_234_567_890, 987_654_321)
-    BigMath.log(r, 50).should == result
-  end
-end
diff --git a/spec/ruby/library/cgi/cookie/domain_spec.rb b/spec/ruby/library/cgi/cookie/domain_spec.rb
index 962609ebaf..0ed56d6d61 100644
--- a/spec/ruby/library/cgi/cookie/domain_spec.rb
+++ b/spec/ruby/library/cgi/cookie/domain_spec.rb
@@ -1,23 +1,26 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#domain" do
-  it "returns self's domain" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.domain.should be_nil
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("name" => "test-cookie", "domain" => "example.com")
-    cookie.domain.should == "example.com"
+  describe "CGI::Cookie#domain" do
+    it "returns self's domain" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.domain.should be_nil
+
+      cookie = CGI::Cookie.new("name" => "test-cookie", "domain" => "example.com")
+      cookie.domain.should == "example.com"
+    end
   end
-end
 
-describe "CGI::Cookie#domain=" do
-  it "sets self's domain" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.domain = "test.com"
-    cookie.domain.should == "test.com"
+  describe "CGI::Cookie#domain=" do
+    it "sets self's domain" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.domain = "test.com"
+      cookie.domain.should == "test.com"
 
-    cookie.domain = "example.com"
-    cookie.domain.should == "example.com"
+      cookie.domain = "example.com"
+      cookie.domain.should == "example.com"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/expires_spec.rb b/spec/ruby/library/cgi/cookie/expires_spec.rb
index c8f26d01cd..c5b2c4faf9 100644
--- a/spec/ruby/library/cgi/cookie/expires_spec.rb
+++ b/spec/ruby/library/cgi/cookie/expires_spec.rb
@@ -1,23 +1,26 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#expires" do
-  it "returns self's expiration date" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.expires.should be_nil
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("name" => "test-cookie", "expires" => Time.at(1196524602))
-    cookie.expires.should == Time.at(1196524602)
+  describe "CGI::Cookie#expires" do
+    it "returns self's expiration date" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.expires.should be_nil
+
+      cookie = CGI::Cookie.new("name" => "test-cookie", "expires" => Time.at(1196524602))
+      cookie.expires.should == Time.at(1196524602)
+    end
   end
-end
 
-describe "CGI::Cookie#expires=" do
-  it "sets self's expiration date" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.expires = Time.at(1196524602)
-    cookie.expires.should == Time.at(1196524602)
+  describe "CGI::Cookie#expires=" do
+    it "sets self's expiration date" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.expires = Time.at(1196524602)
+      cookie.expires.should == Time.at(1196524602)
 
-    cookie.expires = Time.at(1196525000)
-    cookie.expires.should == Time.at(1196525000)
+      cookie.expires = Time.at(1196525000)
+      cookie.expires.should == Time.at(1196525000)
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/initialize_spec.rb b/spec/ruby/library/cgi/cookie/initialize_spec.rb
index 4b6e104b10..248f35e78b 100644
--- a/spec/ruby/library/cgi/cookie/initialize_spec.rb
+++ b/spec/ruby/library/cgi/cookie/initialize_spec.rb
@@ -1,147 +1,150 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#initialize when passed String" do
-  before :each do
-    @cookie = CGI::Cookie.allocate
-  end
-
-  it "sets the self's name to the passed String" do
-    @cookie.send(:initialize, "test-cookie")
-    @cookie.name.should == "test-cookie"
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  it "sets the self's value to an empty Array" do
-    @cookie.send(:initialize, "test-cookie")
-    @cookie.value.should == []
-  end
-
-  it "sets self to a non-secure cookie" do
-    @cookie.send(:initialize, "test")
-    @cookie.secure.should be_false
-  end
-
-  it "does set self's path to an empty String when ENV[\"SCRIPT_NAME\"] is not set" do
-    @cookie.send(:initialize, "test-cookie")
-    @cookie.path.should == ""
-  end
-
-  it "does set self's path based on ENV[\"SCRIPT_NAME\"] when ENV[\"SCRIPT_NAME\"] is set" do
-    old_script_name = ENV["SCRIPT_NAME"]
+  describe "CGI::Cookie#initialize when passed String" do
+    before :each do
+      @cookie = CGI::Cookie.allocate
+    end
 
-    begin
-      ENV["SCRIPT_NAME"] = "some/path/script.rb"
+    it "sets the self's name to the passed String" do
       @cookie.send(:initialize, "test-cookie")
-      @cookie.path.should == "some/path/"
+      @cookie.name.should == "test-cookie"
+    end
 
-      ENV["SCRIPT_NAME"] = "script.rb"
+    it "sets the self's value to an empty Array" do
       @cookie.send(:initialize, "test-cookie")
-      @cookie.path.should == ""
+      @cookie.value.should == []
+    end
 
-      ENV["SCRIPT_NAME"] = nil
+    it "sets self to a non-secure cookie" do
+      @cookie.send(:initialize, "test")
+      @cookie.secure.should be_false
+    end
+
+    it "does set self's path to an empty String when ENV[\"SCRIPT_NAME\"] is not set" do
       @cookie.send(:initialize, "test-cookie")
       @cookie.path.should == ""
-    ensure
-      ENV["SCRIPT_NAME"] = old_script_name
     end
-  end
 
-  it "does not set self's expiration date" do
-    @cookie.expires.should be_nil
-  end
+    it "does set self's path based on ENV[\"SCRIPT_NAME\"] when ENV[\"SCRIPT_NAME\"] is set" do
+      old_script_name = ENV["SCRIPT_NAME"]
 
-  it "does not set self's domain" do
-    @cookie.domain.should be_nil
-  end
-end
+      begin
+        ENV["SCRIPT_NAME"] = "some/path/script.rb"
+        @cookie.send(:initialize, "test-cookie")
+        @cookie.path.should == "some/path/"
 
-describe "CGI::Cookie#initialize when passed Hash" do
-  before :each do
-    @cookie = CGI::Cookie.allocate
-  end
+        ENV["SCRIPT_NAME"] = "script.rb"
+        @cookie.send(:initialize, "test-cookie")
+        @cookie.path.should == ""
+
+        ENV["SCRIPT_NAME"] = nil
+        @cookie.send(:initialize, "test-cookie")
+        @cookie.path.should == ""
+      ensure
+        ENV["SCRIPT_NAME"] = old_script_name
+      end
+    end
+
+    it "does not set self's expiration date" do
+      @cookie.expires.should be_nil
+    end
 
-  it "sets self's contents based on the passed Hash" do
-    @cookie.send(:initialize,
-      'name'    => 'test-cookie',
-      'value'   => ["one", "two", "three"],
-      'path'    => 'some/path/',
-      'domain'  => 'example.com',
-      'expires' => Time.at(1196524602),
-      'secure'  => true)
-
-    @cookie.name.should == "test-cookie"
-    @cookie.value.should == ["one", "two", "three"]
-    @cookie.path.should == "some/path/"
-    @cookie.domain.should == "example.com"
-    @cookie.expires.should == Time.at(1196524602)
-    @cookie.secure.should be_true
+    it "does not set self's domain" do
+      @cookie.domain.should be_nil
+    end
   end
 
-  it "does set self's path based on ENV[\"SCRIPT_NAME\"] when the Hash has no 'path' entry" do
-    old_script_name = ENV["SCRIPT_NAME"]
+  describe "CGI::Cookie#initialize when passed Hash" do
+    before :each do
+      @cookie = CGI::Cookie.allocate
+    end
 
-    begin
-      ENV["SCRIPT_NAME"] = "some/path/script.rb"
-      @cookie.send(:initialize, 'name' => 'test-cookie')
+    it "sets self's contents based on the passed Hash" do
+      @cookie.send(:initialize,
+        'name'    => 'test-cookie',
+        'value'   => ["one", "two", "three"],
+        'path'    => 'some/path/',
+        'domain'  => 'example.com',
+        'expires' => Time.at(1196524602),
+        'secure'  => true)
+
+      @cookie.name.should == "test-cookie"
+      @cookie.value.should == ["one", "two", "three"]
       @cookie.path.should == "some/path/"
+      @cookie.domain.should == "example.com"
+      @cookie.expires.should == Time.at(1196524602)
+      @cookie.secure.should be_true
+    end
 
-      ENV["SCRIPT_NAME"] = "script.rb"
-      @cookie.send(:initialize, 'name' => 'test-cookie')
-      @cookie.path.should == ""
+    it "does set self's path based on ENV[\"SCRIPT_NAME\"] when the Hash has no 'path' entry" do
+      old_script_name = ENV["SCRIPT_NAME"]
 
-      ENV["SCRIPT_NAME"] = nil
-      @cookie.send(:initialize, 'name' => 'test-cookie')
-      @cookie.path.should == ""
-    ensure
-      ENV["SCRIPT_NAME"] = old_script_name
+      begin
+        ENV["SCRIPT_NAME"] = "some/path/script.rb"
+        @cookie.send(:initialize, 'name' => 'test-cookie')
+        @cookie.path.should == "some/path/"
+
+        ENV["SCRIPT_NAME"] = "script.rb"
+        @cookie.send(:initialize, 'name' => 'test-cookie')
+        @cookie.path.should == ""
+
+        ENV["SCRIPT_NAME"] = nil
+        @cookie.send(:initialize, 'name' => 'test-cookie')
+        @cookie.path.should == ""
+      ensure
+        ENV["SCRIPT_NAME"] = old_script_name
+      end
     end
-  end
 
-  it "tries to convert the Hash's 'value' to an Array using #Array" do
-    obj = mock("Converted To Array")
-    obj.should_receive(:to_ary).and_return(["1", "2", "3"])
-    @cookie.send(:initialize,
-      'name'  => 'test-cookie',
-      'value' => obj)
-    @cookie.value.should == [ "1", "2", "3" ]
-
-    obj = mock("Converted To Array")
-    obj.should_receive(:to_a).and_return(["one", "two", "three"])
-    @cookie.send(:initialize,
-      'name'  => 'test-cookie',
-      'value' => obj)
-    @cookie.value.should == [ "one", "two", "three" ]
-
-    obj = mock("Put into an Array")
-    @cookie.send(:initialize,
-      'name'  => 'test-cookie',
-      'value' => obj)
-    @cookie.value.should == [ obj ]
-  end
+    it "tries to convert the Hash's 'value' to an Array using #Array" do
+      obj = mock("Converted To Array")
+      obj.should_receive(:to_ary).and_return(["1", "2", "3"])
+      @cookie.send(:initialize,
+        'name'  => 'test-cookie',
+        'value' => obj)
+      @cookie.value.should == [ "1", "2", "3" ]
+
+      obj = mock("Converted To Array")
+      obj.should_receive(:to_a).and_return(["one", "two", "three"])
+      @cookie.send(:initialize,
+        'name'  => 'test-cookie',
+        'value' => obj)
+      @cookie.value.should == [ "one", "two", "three" ]
+
+      obj = mock("Put into an Array")
+      @cookie.send(:initialize,
+        'name'  => 'test-cookie',
+        'value' => obj)
+      @cookie.value.should == [ obj ]
+    end
 
-  it "raises a ArgumentError when the passed Hash has no 'name' entry" do
-    -> { @cookie.send(:initialize, {}) }.should raise_error(ArgumentError)
-    -> { @cookie.send(:initialize, "value" => "test") }.should raise_error(ArgumentError)
+    it "raises a ArgumentError when the passed Hash has no 'name' entry" do
+      -> { @cookie.send(:initialize, {}) }.should raise_error(ArgumentError)
+      -> { @cookie.send(:initialize, "value" => "test") }.should raise_error(ArgumentError)
+    end
   end
-end
 
-describe "CGI::Cookie#initialize when passed String, values ..." do
-  before :each do
-    @cookie = CGI::Cookie.allocate
-  end
+  describe "CGI::Cookie#initialize when passed String, values ..." do
+    before :each do
+      @cookie = CGI::Cookie.allocate
+    end
 
-  it "sets the self's name to the passed String" do
-    @cookie.send(:initialize, "test-cookie", "one", "two", "three")
-    @cookie.name.should == "test-cookie"
-  end
+    it "sets the self's name to the passed String" do
+      @cookie.send(:initialize, "test-cookie", "one", "two", "three")
+      @cookie.name.should == "test-cookie"
+    end
 
-  it "sets the self's value to an Array containing all passed values" do
-    @cookie.send(:initialize, "test-cookie", "one", "two", "three")
-    @cookie.value.should == ["one", "two", "three"]
-  end
+    it "sets the self's value to an Array containing all passed values" do
+      @cookie.send(:initialize, "test-cookie", "one", "two", "three")
+      @cookie.value.should == ["one", "two", "three"]
+    end
 
-  it "sets self to a non-secure cookie" do
-    @cookie.send(:initialize, "test", "one", "two", "three")
-    @cookie.secure.should be_false
+    it "sets self to a non-secure cookie" do
+      @cookie.send(:initialize, "test", "one", "two", "three")
+      @cookie.secure.should be_false
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/name_spec.rb b/spec/ruby/library/cgi/cookie/name_spec.rb
index 14226824c8..4908204e8a 100644
--- a/spec/ruby/library/cgi/cookie/name_spec.rb
+++ b/spec/ruby/library/cgi/cookie/name_spec.rb
@@ -1,23 +1,26 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#name" do
-  it "returns self's name" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.name.should == "test-cookie"
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("name" => "another cookie")
-    cookie.name.should == "another cookie"
+  describe "CGI::Cookie#name" do
+    it "returns self's name" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.name.should == "test-cookie"
+
+      cookie = CGI::Cookie.new("name" => "another-cookie")
+      cookie.name.should == "another-cookie"
+    end
   end
-end
 
-describe "CGI::Cookie#name=" do
-  it "sets self's expiration date" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.name = "another name"
-    cookie.name.should == "another name"
+  describe "CGI::Cookie#name=" do
+    it "sets self's expiration date" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.name = "another-name"
+      cookie.name.should == "another-name"
 
-    cookie.name = "and one more"
-    cookie.name.should == "and one more"
+      cookie.name = "and-one-more"
+      cookie.name.should == "and-one-more"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/parse_spec.rb b/spec/ruby/library/cgi/cookie/parse_spec.rb
index 90d2c3d148..bc505c37ba 100644
--- a/spec/ruby/library/cgi/cookie/parse_spec.rb
+++ b/spec/ruby/library/cgi/cookie/parse_spec.rb
@@ -1,26 +1,29 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie.parse" do
-  it "parses a raw cookie string into a hash of Cookies" do
-    expected = { "test-cookie" => ["one", "two", "three"] }
-    CGI::Cookie.parse("test-cookie=one&two&three").should == expected
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    expected = { "second cookie" => ["three", "four"], "first cookie" => ["one", "two"] }
-    CGI::Cookie.parse("first cookie=one&two;second cookie=three&four").should == expected
-  end
+  describe "CGI::Cookie.parse" do
+    it "parses a raw cookie string into a hash of Cookies" do
+      expected = { "test-cookie" => ["one", "two", "three"] }
+      CGI::Cookie.parse("test-cookie=one&two&three").should == expected
 
-  it "does not use , for cookie separators" do
-    expected = {
-      "first cookie" => ["one", "two"],
-      "second cookie" => ["three", "four,third_cookie=five", "six"]
-    }
-    CGI::Cookie.parse("first cookie=one&two;second cookie=three&four,third_cookie=five&six").should == expected
-  end
+      expected = { "second-cookie" => ["three", "four"], "first-cookie" => ["one", "two"] }
+      CGI::Cookie.parse("first-cookie=one&two;second-cookie=three&four").should == expected
+    end
+
+    it "does not use , for cookie separators" do
+      expected = {
+        "first-cookie" => ["one", "two"],
+        "second-cookie" => ["three", "four,third_cookie=five", "six"]
+      }
+      CGI::Cookie.parse("first-cookie=one&two;second-cookie=three&four,third_cookie=five&six").should == expected
+    end
 
-  it "unescapes the Cookie values" do
-    cookie = "test-cookie=+%21%22%23%24%25%26%27%28%29%2A%2B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWXYZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D%7E"
-    expected = { "test-cookie" => [ " !\"\#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~" ] }
-    CGI::Cookie.parse(cookie).should == expected
+    it "unescapes the Cookie values" do
+      cookie = "test-cookie=+%21%22%23%24%25%26%27%28%29%2A%2B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWXYZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D%7E"
+      expected = { "test-cookie" => [ " !\"\#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~" ] }
+      CGI::Cookie.parse(cookie).should == expected
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/path_spec.rb b/spec/ruby/library/cgi/cookie/path_spec.rb
index 8a2f05aa50..13ee5d726b 100644
--- a/spec/ruby/library/cgi/cookie/path_spec.rb
+++ b/spec/ruby/library/cgi/cookie/path_spec.rb
@@ -1,23 +1,26 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#path" do
-  it "returns self's path" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.path.should == ""
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("name" => "test-cookie", "path" => "/some/path/")
-    cookie.path.should == "/some/path/"
+  describe "CGI::Cookie#path" do
+    it "returns self's path" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.path.should == ""
+
+      cookie = CGI::Cookie.new("name" => "test-cookie", "path" => "/some/path/")
+      cookie.path.should == "/some/path/"
+    end
   end
-end
 
-describe "CGI::Cookie#path=" do
-  it "sets self's path" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.path = "/some/path/"
-    cookie.path.should == "/some/path/"
+  describe "CGI::Cookie#path=" do
+    it "sets self's path" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.path = "/some/path/"
+      cookie.path.should == "/some/path/"
 
-    cookie.path = "/another/path/"
-    cookie.path.should == "/another/path/"
+      cookie.path = "/another/path/"
+      cookie.path.should == "/another/path/"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/secure_spec.rb b/spec/ruby/library/cgi/cookie/secure_spec.rb
index 694bc2eeed..cb38c8c2e0 100644
--- a/spec/ruby/library/cgi/cookie/secure_spec.rb
+++ b/spec/ruby/library/cgi/cookie/secure_spec.rb
@@ -1,70 +1,73 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#secure" do
-  before :each do
-    @cookie = CGI::Cookie.new("test-cookie")
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  it "returns whether self is a secure cookie or not" do
-    @cookie.secure = true
-    @cookie.secure.should be_true
+  describe "CGI::Cookie#secure" do
+    before :each do
+      @cookie = CGI::Cookie.new("test-cookie")
+    end
 
-    @cookie.secure = false
-    @cookie.secure.should be_false
-  end
-end
+    it "returns whether self is a secure cookie or not" do
+      @cookie.secure = true
+      @cookie.secure.should be_true
 
-describe "CGI::Cookie#secure= when passed true" do
-  before :each do
-    @cookie = CGI::Cookie.new("test-cookie")
+      @cookie.secure = false
+      @cookie.secure.should be_false
+    end
   end
 
-  it "returns true" do
-    (@cookie.secure = true).should be_true
-  end
+  describe "CGI::Cookie#secure= when passed true" do
+    before :each do
+      @cookie = CGI::Cookie.new("test-cookie")
+    end
 
-  it "sets self to a secure cookie" do
-    @cookie.secure = true
-    @cookie.secure.should be_true
-  end
-end
+    it "returns true" do
+      (@cookie.secure = true).should be_true
+    end
 
-describe "CGI::Cookie#secure= when passed false" do
-  before :each do
-    @cookie = CGI::Cookie.new("test-cookie")
+    it "sets self to a secure cookie" do
+      @cookie.secure = true
+      @cookie.secure.should be_true
+    end
   end
 
-  it "returns false" do
-    (@cookie.secure = false).should be_false
-  end
+  describe "CGI::Cookie#secure= when passed false" do
+    before :each do
+      @cookie = CGI::Cookie.new("test-cookie")
+    end
 
-  it "sets self to a non-secure cookie" do
-    @cookie.secure = false
-    @cookie.secure.should be_false
-  end
-end
+    it "returns false" do
+      (@cookie.secure = false).should be_false
+    end
 
-describe "CGI::Cookie#secure= when passed Object" do
-  before :each do
-    @cookie = CGI::Cookie.new("test-cookie")
+    it "sets self to a non-secure cookie" do
+      @cookie.secure = false
+      @cookie.secure.should be_false
+    end
   end
 
-  it "does not change self's secure value" do
-    @cookie.secure = false
+  describe "CGI::Cookie#secure= when passed Object" do
+    before :each do
+      @cookie = CGI::Cookie.new("test-cookie")
+    end
+
+    it "does not change self's secure value" do
+      @cookie.secure = false
 
-    @cookie.secure = Object.new
-    @cookie.secure.should be_false
+      @cookie.secure = Object.new
+      @cookie.secure.should be_false
 
-    @cookie.secure = "Test"
-    @cookie.secure.should be_false
+      @cookie.secure = "Test"
+      @cookie.secure.should be_false
 
-    @cookie.secure = true
+      @cookie.secure = true
 
-    @cookie.secure = Object.new
-    @cookie.secure.should be_true
+      @cookie.secure = Object.new
+      @cookie.secure.should be_true
 
-    @cookie.secure = "Test"
-    @cookie.secure.should be_true
+      @cookie.secure = "Test"
+      @cookie.secure.should be_true
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/cookie/to_s_spec.rb b/spec/ruby/library/cgi/cookie/to_s_spec.rb
index 978c2d33eb..20d2579f8d 100644
--- a/spec/ruby/library/cgi/cookie/to_s_spec.rb
+++ b/spec/ruby/library/cgi/cookie/to_s_spec.rb
@@ -1,42 +1,36 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#to_s" do
-  it "returns a String representation of self" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.to_s.should == "test-cookie=; path="
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("test-cookie", "value")
-    cookie.to_s.should == "test-cookie=value; path="
+  describe "CGI::Cookie#to_s" do
+    it "returns a String representation of self" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.to_s.should == "test-cookie=; path="
 
-    cookie = CGI::Cookie.new("test-cookie", "one", "two", "three")
-    cookie.to_s.should == "test-cookie=one&two&three; path="
+      cookie = CGI::Cookie.new("test-cookie", "value")
+      cookie.to_s.should == "test-cookie=value; path="
 
-    cookie = CGI::Cookie.new(
-      'name'    => 'test-cookie',
-      'value'   => ["one", "two", "three"],
-      'path'    => 'some/path/',
-      'domain'  => 'example.com',
-      'expires' => Time.at(1196524602),
-      'secure'  => true)
-    cookie.to_s.should == "test-cookie=one&two&three; domain=example.com; path=some/path/; expires=Sat, 01 Dec 2007 15:56:42 GMT; secure"
-  end
+      cookie = CGI::Cookie.new("test-cookie", "one", "two", "three")
+      cookie.to_s.should == "test-cookie=one&two&three; path="
 
-  it "escapes the self's values" do
-    cookie = CGI::Cookie.new("test-cookie", " !\"\#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}")
-    cookie.to_s.should == "test-cookie=+%21%22%23%24%25%26%27%28%29%2A%2B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWXYZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D; path="
-  end
+      cookie = CGI::Cookie.new(
+        'name'    => 'test-cookie',
+        'value'   => ["one", "two", "three"],
+        'path'    => 'some/path/',
+        'domain'  => 'example.com',
+        'expires' => Time.at(1196524602),
+        'secure'  => true)
+      cookie.to_s.should == "test-cookie=one&two&three; domain=example.com; path=some/path/; expires=Sat, 01 Dec 2007 15:56:42 GMT; secure"
+    end
 
-  ruby_version_is ""..."2.5" do
-    it "escapes tilde" do
-      cookie = CGI::Cookie.new("test-cookie", "~").to_s.should == "test-cookie=%7E; path="
+    it "escapes the self's values" do
+      cookie = CGI::Cookie.new("test-cookie", " !\"\#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}")
+      cookie.to_s.should == "test-cookie=+%21%22%23%24%25%26%27%28%29%2A%2B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWXYZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D; path="
     end
-  end
 
-  ruby_version_is "2.5" do
     it "does not escape tilde" do
       cookie = CGI::Cookie.new("test-cookie", "~").to_s.should == "test-cookie=~; path="
     end
   end
-
 end
diff --git a/spec/ruby/library/cgi/cookie/value_spec.rb b/spec/ruby/library/cgi/cookie/value_spec.rb
index 1d5da3a3ac..672653d7f4 100644
--- a/spec/ruby/library/cgi/cookie/value_spec.rb
+++ b/spec/ruby/library/cgi/cookie/value_spec.rb
@@ -1,76 +1,79 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::Cookie#value" do
-  it "returns self's value" do
-    cookie = CGI::Cookie.new("test-cookie")
-    cookie.value.should == []
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    cookie = CGI::Cookie.new("test-cookie", "one")
-    cookie.value.should == ["one"]
+  describe "CGI::Cookie#value" do
+    it "returns self's value" do
+      cookie = CGI::Cookie.new("test-cookie")
+      cookie.value.should == []
 
-    cookie = CGI::Cookie.new("test-cookie", "one", "two", "three")
-    cookie.value.should == ["one", "two", "three"]
+      cookie = CGI::Cookie.new("test-cookie", "one")
+      cookie.value.should == ["one"]
 
-    cookie = CGI::Cookie.new("name" => "test-cookie", "value" => ["one", "two", "three"])
-    cookie.value.should == ["one", "two", "three"]
-  end
+      cookie = CGI::Cookie.new("test-cookie", "one", "two", "three")
+      cookie.value.should == ["one", "two", "three"]
 
-  it "is in synch with self" do
-    fail = []
-    [
-      :pop,
-      :shift,
-      [:<<, "Hello"],
-      [:push, "Hello"],
-      [:unshift, "World"],
-      [:replace, ["A", "B"]],
-      [:[]=, 1, "Set"],
-      [:delete, "first"],
-      [:delete_at, 0],
-    ].each do |method, *args|
-      cookie1 = CGI::Cookie.new("test-cookie", "first", "second")
-      cookie2 = CGI::Cookie.new("test-cookie", "first", "second")
-      cookie1.send(method, *args)
-      cookie2.value.send(method, *args)
-      fail << method unless cookie1.value == cookie2.value
+      cookie = CGI::Cookie.new("name" => "test-cookie", "value" => ["one", "two", "three"])
+      cookie.value.should == ["one", "two", "three"]
     end
-    fail.should be_empty
-  end
-end
 
-describe "CGI::Cookie#value=" do
-  before :each do
-    @cookie = CGI::Cookie.new("test-cookie")
+    it "is in synch with self" do
+      fail = []
+      [
+        :pop,
+        :shift,
+        [:<<, "Hello"],
+        [:push, "Hello"],
+        [:unshift, "World"],
+        [:replace, ["A", "B"]],
+        [:[]=, 1, "Set"],
+        [:delete, "first"],
+        [:delete_at, 0],
+      ].each do |method, *args|
+        cookie1 = CGI::Cookie.new("test-cookie", "first", "second")
+        cookie2 = CGI::Cookie.new("test-cookie", "first", "second")
+        cookie1.send(method, *args)
+        cookie2.value.send(method, *args)
+        fail << method unless cookie1.value == cookie2.value
+      end
+      fail.should be_empty
+    end
   end
 
-  it "sets self's value" do
-    @cookie.value = ["one"]
-    @cookie.value.should == ["one"]
+  describe "CGI::Cookie#value=" do
+    before :each do
+      @cookie = CGI::Cookie.new("test-cookie")
+    end
 
-    @cookie.value = ["one", "two", "three"]
-    @cookie.value.should == ["one", "two", "three"]
-  end
+    it "sets self's value" do
+      @cookie.value = ["one"]
+      @cookie.value.should == ["one"]
 
-  it "automatically converts the passed Object to an Array using #Array" do
-    @cookie.value = "test"
-    @cookie.value.should == ["test"]
+      @cookie.value = ["one", "two", "three"]
+      @cookie.value.should == ["one", "two", "three"]
+    end
 
-    obj = mock("to_a")
-    obj.should_receive(:to_a).and_return(["1", "2"])
-    @cookie.value = obj
-    @cookie.value.should == ["1", "2"]
+    it "automatically converts the passed Object to an Array using #Array" do
+      @cookie.value = "test"
+      @cookie.value.should == ["test"]
 
-    obj = mock("to_ary")
-    obj.should_receive(:to_ary).and_return(["1", "2"])
-    @cookie.value = obj
-    @cookie.value.should == ["1", "2"]
-  end
+      obj = mock("to_a")
+      obj.should_receive(:to_a).and_return(["1", "2"])
+      @cookie.value = obj
+      @cookie.value.should == ["1", "2"]
 
-  it "does keep self and the values in sync" do
-    @cookie.value = ["one", "two", "three"]
-    @cookie[0].should == "one"
-    @cookie[1].should == "two"
-    @cookie[2].should == "three"
+      obj = mock("to_ary")
+      obj.should_receive(:to_ary).and_return(["1", "2"])
+      @cookie.value = obj
+      @cookie.value.should == ["1", "2"]
+    end
+
+    it "does keep self and the values in sync" do
+      @cookie.value = ["one", "two", "three"]
+      @cookie[0].should == "one"
+      @cookie[1].should == "two"
+      @cookie[2].should == "three"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/escapeElement_spec.rb b/spec/ruby/library/cgi/escapeElement_spec.rb
index 148926c453..72c38d6028 100644
--- a/spec/ruby/library/cgi/escapeElement_spec.rb
+++ b/spec/ruby/library/cgi/escapeElement_spec.rb
@@ -1,5 +1,11 @@
 require_relative '../../spec_helper'
-require 'cgi'
+
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+end
+ruby_version_is "4.0" do
+  require 'cgi/escape'
+end
 
 describe "CGI.escapeElement when passed String, elements, ..." do
   it "escapes only the tags of the passed elements in the passed String" do
diff --git a/spec/ruby/library/cgi/escapeHTML_spec.rb b/spec/ruby/library/cgi/escapeHTML_spec.rb
index dcbfebe720..6e70e87ed7 100644
--- a/spec/ruby/library/cgi/escapeHTML_spec.rb
+++ b/spec/ruby/library/cgi/escapeHTML_spec.rb
@@ -1,11 +1,19 @@
 require_relative '../../spec_helper'
-require 'cgi'
+begin
+  require 'cgi/escape'
+rescue LoadError
+  require 'cgi'
+end
 
 describe "CGI.escapeHTML" do
   it "escapes special HTML characters (&\"<>') in the passed argument" do
     CGI.escapeHTML(%[& < > " ']).should == '&amp; &lt; &gt; &quot; &#39;'
   end
 
+  it "escapes invalid encoding" do
+    CGI.escapeHTML(%[<\xA4??>]).should == "&lt;\xA4??&gt;"
+  end
+
   it "does not escape any other characters" do
     chars = " !\#$%()*+,-./0123456789:;=?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
     CGI.escapeHTML(chars).should == chars
diff --git a/spec/ruby/library/cgi/escapeURIComponent_spec.rb b/spec/ruby/library/cgi/escapeURIComponent_spec.rb
new file mode 100644
index 0000000000..1cea2b786a
--- /dev/null
+++ b/spec/ruby/library/cgi/escapeURIComponent_spec.rb
@@ -0,0 +1,78 @@
+require_relative '../../spec_helper'
+begin
+  require 'cgi/escape'
+rescue LoadError
+  require 'cgi'
+end
+
+describe "CGI.escapeURIComponent" do
+  it "percent-encodes characters reserved according to RFC 3986" do
+    # https://www.rfc-editor.org/rfc/rfc3986#section-2.2
+    string = ":/?#[]@!$&'()*+,;="
+    CGI.escapeURIComponent(string).should == "%3A%2F%3F%23%5B%5D%40%21%24%26%27%28%29%2A%2B%2C%3B%3D"
+  end
+
+  it "does not percent-encode unreserved characters according to RFC 3986" do
+    string = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+    CGI.escapeURIComponent(string).should == "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+  end
+
+  it "encodes % character as %25" do
+    CGI.escapeURIComponent("%").should == "%25"
+  end
+
+  # Compare to .escape which uses "+".
+  it "percent-encodes single whitespace" do
+    CGI.escapeURIComponent(" ").should == "%20"
+  end
+
+  it "percent-encodes all non-reserved and non-unreserved ASCII characters" do
+    special_set = ":/?#[]@!$&'()*+,;=ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-._~"
+    all_other = (0x00..0x7F).filter_map { |i| i.chr unless special_set.include?(i.chr) }.join
+    encoded = CGI.escapeURIComponent(all_other)
+    encoded.should.match?(/\A(?:%[0-9A-F]{2}){#{all_other.length}}\z/)
+  end
+
+  it "percent-encodes non-ASCII bytes" do
+    bytes = (0x80..0xFF).map(&:chr).join
+    encoded = CGI.escapeURIComponent(bytes)
+    encoded.should.match?(/\A(?:%[0-9A-F]{2}){#{bytes.length}}\z/)
+  end
+
+  it "processes multi-byte characters as separate bytes, percent-encoding each one" do
+    CGI.escapeURIComponent("β").should == "%CE%B2" # "β" bytes representation is CE B2
+  end
+
+  it "produces a copy of an empty string" do
+    string = "".encode(Encoding::BINARY)
+    encoded = CGI.escapeURIComponent(string)
+    encoded.should == ""
+    encoded.encoding.should == Encoding::BINARY
+    string.should_not.equal?(encoded)
+  end
+
+  it "preserves string's encoding" do
+    string = "whatever".encode("ASCII-8BIT")
+    CGI.escapeURIComponent(string).encoding.should == Encoding::ASCII_8BIT
+  end
+
+  it "processes even strings with invalid encoding, percent-encoding octets as-is" do
+    string = "\xC0<<".dup.force_encoding("UTF-8")
+    CGI.escapeURIComponent(string).should == "%C0%3C%3C"
+  end
+
+  it "raises a TypeError with nil" do
+    -> {
+      CGI.escapeURIComponent(nil)
+    }.should raise_error(TypeError, "no implicit conversion of nil into String")
+  end
+
+  it "uses implicit type conversion to String" do
+    object = Object.new
+    def object.to_str
+      "a b"
+    end
+
+    CGI.escapeURIComponent(object).should == "a%20b"
+  end
+end
diff --git a/spec/ruby/library/cgi/escape_spec.rb b/spec/ruby/library/cgi/escape_spec.rb
index 351bfe1070..55eb0b66c2 100644
--- a/spec/ruby/library/cgi/escape_spec.rb
+++ b/spec/ruby/library/cgi/escape_spec.rb
@@ -1,5 +1,9 @@
 require_relative '../../spec_helper'
-require 'cgi'
+begin
+  require 'cgi/escape'
+rescue LoadError
+  require 'cgi'
+end
 
 describe "CGI.escape" do
   it "url-encodes the passed argument" do
@@ -7,20 +11,12 @@ describe "CGI.escape" do
     expected = "+%21%22%23%24%25%26%27%28%29%2A%2B%2C-.%2F0123456789%3A%3B%3C%3D%3E%3F%40ABCDEFGHIJKLMNOPQRSTUVWXYZ%5B%5C%5D%5E_%60abcdefghijklmnopqrstuvwxyz%7B%7C%7D"
     CGI.escape(input).should == expected
 
-    input = "http://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
-    expected = 'http%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
+    input = "https://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
+    expected = 'https%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
     CGI.escape(input).should == expected
   end
 
-  ruby_version_is ""..."2.5" do
-    it "escapes tilde" do
-      CGI.escape("~").should == "%7E"
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not escape tilde" do
-      CGI.escape("~").should == "~"
-    end
+  it "does not escape tilde" do
+    CGI.escape("~").should == "~"
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/a_spec.rb b/spec/ruby/library/cgi/htmlextension/a_spec.rb
index 05b4c2d14c..78d3dec8fa 100644
--- a/spec/ruby/library/cgi/htmlextension/a_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/a_spec.rb
@@ -1,49 +1,52 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#a" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed a String" do
-    it "returns an 'a'-element, using the passed String as the 'href'-attribute" do
-      output = @html.a("http://www.example.com")
-      output.should equal_element("A", "HREF" => "http://www.example.com")
+  describe "CGI::HtmlExtension#a" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "includes the passed block's return value when passed a block" do
-      output = @html.a("http://www.example.com") { "Example" }
-      output.should equal_element("A", { "HREF" => "http://www.example.com" }, "Example")
-    end
-  end
+    describe "when passed a String" do
+      it "returns an 'a'-element, using the passed String as the 'href'-attribute" do
+        output = @html.a("http://www.example.com")
+        output.should equal_element("A", "HREF" => "http://www.example.com")
+      end
 
-  describe "when passed a Hash" do
-    it "returns an 'a'-element, using the passed Hash for attributes" do
-      attributes = {"HREF" => "http://www.example.com", "TARGET" => "_top"}
-      @html.a(attributes).should equal_element("A", attributes)
+      it "includes the passed block's return value when passed a block" do
+        output = @html.a("http://www.example.com") { "Example" }
+        output.should equal_element("A", { "HREF" => "http://www.example.com" }, "Example")
+      end
     end
 
-    it "includes the passed block's return value when passed a block" do
-      attributes = {"HREF" => "http://www.example.com", "TARGET" => "_top"}
-      @html.a(attributes) { "Example" }.should equal_element("A", attributes, "Example")
-    end
-  end
+    describe "when passed a Hash" do
+      it "returns an 'a'-element, using the passed Hash for attributes" do
+        attributes = {"HREF" => "http://www.example.com", "TARGET" => "_top"}
+        @html.a(attributes).should equal_element("A", attributes)
+      end
 
-  describe "when each HTML generation" do
-    it "returns the doctype declaration for HTML3" do
-      CGISpecs.cgi_new("html3").a.should == %(<A HREF=""></A>)
-      CGISpecs.cgi_new("html3").a { "link text" }.should == %(<A HREF="">link text</A>)
+      it "includes the passed block's return value when passed a block" do
+        attributes = {"HREF" => "http://www.example.com", "TARGET" => "_top"}
+        @html.a(attributes) { "Example" }.should equal_element("A", attributes, "Example")
+      end
     end
 
-    it "returns the doctype declaration for HTML4" do
-      CGISpecs.cgi_new("html4").a.should == %(<A HREF=""></A>)
-      CGISpecs.cgi_new("html4").a { "link text" }.should == %(<A HREF="">link text</A>)
-    end
-    it "returns the doctype declaration for the Transitional version of HTML4" do
-      CGISpecs.cgi_new("html4Tr").a.should == %(<A HREF=""></A>)
-      CGISpecs.cgi_new("html4Tr").a { "link text" }.should == %(<A HREF="">link text</A>)
+    describe "when each HTML generation" do
+      it "returns the doctype declaration for HTML3" do
+        CGISpecs.cgi_new("html3").a.should == %(<A HREF=""></A>)
+        CGISpecs.cgi_new("html3").a { "link text" }.should == %(<A HREF="">link text</A>)
+      end
+
+      it "returns the doctype declaration for HTML4" do
+        CGISpecs.cgi_new("html4").a.should == %(<A HREF=""></A>)
+        CGISpecs.cgi_new("html4").a { "link text" }.should == %(<A HREF="">link text</A>)
+      end
+      it "returns the doctype declaration for the Transitional version of HTML4" do
+        CGISpecs.cgi_new("html4Tr").a.should == %(<A HREF=""></A>)
+        CGISpecs.cgi_new("html4Tr").a { "link text" }.should == %(<A HREF="">link text</A>)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/base_spec.rb b/spec/ruby/library/cgi/htmlextension/base_spec.rb
index 877ac321cd..1eedfdea54 100644
--- a/spec/ruby/library/cgi/htmlextension/base_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/base_spec.rb
@@ -1,33 +1,36 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#base" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when bassed a String" do
-    it "returns a 'base'-element, using the passed String as the 'href'-attribute" do
-      output = @html.base("http://www.example.com")
-      output.should equal_element("BASE", {"HREF" => "http://www.example.com"}, nil, not_closed: true)
+  describe "CGI::HtmlExtension#base" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.base("http://www.example.com") { "Example" }
-      output.should equal_element("BASE", {"HREF" => "http://www.example.com"}, nil, not_closed: true)
-    end
-  end
+    describe "when bassed a String" do
+      it "returns a 'base'-element, using the passed String as the 'href'-attribute" do
+        output = @html.base("http://www.example.com")
+        output.should equal_element("BASE", {"HREF" => "http://www.example.com"}, nil, not_closed: true)
+      end
 
-  describe "when passed a Hash" do
-    it "returns a 'base'-element, using the passed Hash for attributes" do
-      output = @html.base("HREF" => "http://www.example.com", "ID" => "test")
-      output.should equal_element("BASE", {"HREF" => "http://www.example.com", "ID" => "test"}, nil, not_closed: true)
+      it "ignores a passed block" do
+        output = @html.base("http://www.example.com") { "Example" }
+        output.should equal_element("BASE", {"HREF" => "http://www.example.com"}, nil, not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.base("HREF" => "http://www.example.com", "ID" => "test") { "Example" }
-      output.should equal_element("BASE", {"HREF" => "http://www.example.com", "ID" => "test"}, nil, not_closed: true)
+    describe "when passed a Hash" do
+      it "returns a 'base'-element, using the passed Hash for attributes" do
+        output = @html.base("HREF" => "http://www.example.com", "ID" => "test")
+        output.should equal_element("BASE", {"HREF" => "http://www.example.com", "ID" => "test"}, nil, not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.base("HREF" => "http://www.example.com", "ID" => "test") { "Example" }
+        output.should equal_element("BASE", {"HREF" => "http://www.example.com", "ID" => "test"}, nil, not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/blockquote_spec.rb b/spec/ruby/library/cgi/htmlextension/blockquote_spec.rb
index a7b833b1c5..883e36f78b 100644
--- a/spec/ruby/library/cgi/htmlextension/blockquote_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/blockquote_spec.rb
@@ -1,33 +1,36 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#blockquote" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed a String" do
-    it "returns a 'blockquote'-element, using the passed String for the 'cite'-attribute" do
-      output = @html.blockquote("http://www.example.com/quotes/foo.html")
-      output.should equal_element("BLOCKQUOTE", "CITE" => "http://www.example.com/quotes/foo.html")
+  describe "CGI::HtmlExtension#blockquote" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "includes the passed block's return value when passed a block" do
-      output = @html.blockquote("http://www.example.com/quotes/foo.html") { "Foo!" }
-      output.should equal_element("BLOCKQUOTE", { "CITE" => "http://www.example.com/quotes/foo.html" }, "Foo!")
-    end
-  end
+    describe "when passed a String" do
+      it "returns a 'blockquote'-element, using the passed String for the 'cite'-attribute" do
+        output = @html.blockquote("http://www.example.com/quotes/foo.html")
+        output.should equal_element("BLOCKQUOTE", "CITE" => "http://www.example.com/quotes/foo.html")
+      end
 
-  describe "when passed a Hash" do
-    it "returns a 'blockquote'-element, using the passed Hash for attributes" do
-      output = @html.blockquote("CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test")
-      output.should equal_element("BLOCKQUOTE", "CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test")
+      it "includes the passed block's return value when passed a block" do
+        output = @html.blockquote("http://www.example.com/quotes/foo.html") { "Foo!" }
+        output.should equal_element("BLOCKQUOTE", { "CITE" => "http://www.example.com/quotes/foo.html" }, "Foo!")
+      end
     end
 
-    it "includes the passed block's return value when passed a block" do
-      output = @html.blockquote("CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test") { "Foo!" }
-      output.should equal_element("BLOCKQUOTE", {"CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test"}, "Foo!")
+    describe "when passed a Hash" do
+      it "returns a 'blockquote'-element, using the passed Hash for attributes" do
+        output = @html.blockquote("CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test")
+        output.should equal_element("BLOCKQUOTE", "CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test")
+      end
+
+      it "includes the passed block's return value when passed a block" do
+        output = @html.blockquote("CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test") { "Foo!" }
+        output.should equal_element("BLOCKQUOTE", {"CITE" => "http://www.example.com/quotes/foo.html", "ID" => "test"}, "Foo!")
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/br_spec.rb b/spec/ruby/library/cgi/htmlextension/br_spec.rb
index dfca121884..23c2cb4a48 100644
--- a/spec/ruby/library/cgi/htmlextension/br_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/br_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#br" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when each HTML generation" do
-    it "returns the doctype declaration for HTML3" do
-      CGISpecs.cgi_new("html3").br.should == "<BR>"
+  describe "CGI::HtmlExtension#br" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "returns the doctype declaration for HTML4" do
-      CGISpecs.cgi_new("html4").br.should == "<BR>"
-    end
-    it "returns the doctype declaration for the Transitional version of HTML4" do
-      CGISpecs.cgi_new("html4Tr").br.should == "<BR>"
+    describe "when each HTML generation" do
+      it "returns the doctype declaration for HTML3" do
+        CGISpecs.cgi_new("html3").br.should == "<BR>"
+      end
+
+      it "returns the doctype declaration for HTML4" do
+        CGISpecs.cgi_new("html4").br.should == "<BR>"
+      end
+      it "returns the doctype declaration for the Transitional version of HTML4" do
+        CGISpecs.cgi_new("html4Tr").br.should == "<BR>"
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/caption_spec.rb b/spec/ruby/library/cgi/htmlextension/caption_spec.rb
index 16615028b8..3d3e21ecaa 100644
--- a/spec/ruby/library/cgi/htmlextension/caption_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/caption_spec.rb
@@ -1,33 +1,36 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#caption" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed a String" do
-    it "returns a 'caption'-element, using the passed String for the 'align'-attribute" do
-      output = @html.caption("left")
-      output.should equal_element("CAPTION", "ALIGN" => "left")
+  describe "CGI::HtmlExtension#caption" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "includes the passed block's return value when passed a block" do
-      output = @html.caption("left") { "Capital Cities" }
-      output.should equal_element("CAPTION", {"ALIGN" => "left"}, "Capital Cities")
-    end
-  end
+    describe "when passed a String" do
+      it "returns a 'caption'-element, using the passed String for the 'align'-attribute" do
+        output = @html.caption("left")
+        output.should equal_element("CAPTION", "ALIGN" => "left")
+      end
 
-  describe "when passed a Hash" do
-    it "returns a 'caption'-element, using the passed Hash for attributes" do
-      output = @html.caption("ALIGN" => "left", "ID" => "test")
-      output.should equal_element("CAPTION", "ALIGN" => "left", "ID" => "test")
+      it "includes the passed block's return value when passed a block" do
+        output = @html.caption("left") { "Capital Cities" }
+        output.should equal_element("CAPTION", {"ALIGN" => "left"}, "Capital Cities")
+      end
     end
 
-    it "includes the passed block's return value when passed a block" do
-      output = @html.caption("ALIGN" => "left", "ID" => "test") { "Capital Cities" }
-      output.should equal_element("CAPTION", {"ALIGN" => "left", "ID" => "test"}, "Capital Cities")
+    describe "when passed a Hash" do
+      it "returns a 'caption'-element, using the passed Hash for attributes" do
+        output = @html.caption("ALIGN" => "left", "ID" => "test")
+        output.should equal_element("CAPTION", "ALIGN" => "left", "ID" => "test")
+      end
+
+      it "includes the passed block's return value when passed a block" do
+        output = @html.caption("ALIGN" => "left", "ID" => "test") { "Capital Cities" }
+        output.should equal_element("CAPTION", {"ALIGN" => "left", "ID" => "test"}, "Capital Cities")
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/checkbox_group_spec.rb b/spec/ruby/library/cgi/htmlextension/checkbox_group_spec.rb
index 64f852cc52..07163c010e 100644
--- a/spec/ruby/library/cgi/htmlextension/checkbox_group_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/checkbox_group_spec.rb
@@ -1,76 +1,79 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#checkbox_group" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed name, values ..." do
-    it "returns a sequence of 'checkbox'-elements with the passed name and the passed values" do
-      output = CGISpecs.split(@html.checkbox_group("test", "foo", "bar", "baz"))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+  describe "CGI::HtmlExtension#checkbox_group" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "allows passing a value inside an Array" do
-      output = CGISpecs.split(@html.checkbox_group("test", ["foo"], "bar", ["baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
-    end
+    describe "when passed name, values ..." do
+      it "returns a sequence of 'checkbox'-elements with the passed name and the passed values" do
+        output = CGISpecs.split(@html.checkbox_group("test", "foo", "bar", "baz"))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
 
-    it "allows passing a value as an Array containing the value and the checked state or a label" do
-      output = CGISpecs.split(@html.checkbox_group("test", ["foo"], ["bar", true], ["baz", "label for baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "label for baz", not_closed: true)
-    end
+      it "allows passing a value inside an Array" do
+        output = CGISpecs.split(@html.checkbox_group("test", ["foo"], "bar", ["baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
 
-    it "allows passing a value as an Array containing the value, a label and the checked state" do
-      output = CGISpecs.split(@html.checkbox_group("test", ["foo", "label for foo", true], ["bar", "label for bar", false], ["baz", "label for baz", true]))
-      output[0].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "label for foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "label for bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "label for baz", not_closed: true)
-    end
+      it "allows passing a value as an Array containing the value and the checked state or a label" do
+        output = CGISpecs.split(@html.checkbox_group("test", ["foo"], ["bar", true], ["baz", "label for baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "label for baz", not_closed: true)
+      end
 
-    it "returns an empty String when passed no values" do
-      @html.checkbox_group("test").should == ""
-    end
+      it "allows passing a value as an Array containing the value, a label and the checked state" do
+        output = CGISpecs.split(@html.checkbox_group("test", ["foo", "label for foo", true], ["bar", "label for bar", false], ["baz", "label for baz", true]))
+        output[0].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "label for foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "label for bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "label for baz", not_closed: true)
+      end
+
+      it "returns an empty String when passed no values" do
+        @html.checkbox_group("test").should == ""
+      end
 
-    it "ignores a passed block" do
-      output = CGISpecs.split(@html.checkbox_group("test", "foo", "bar", "baz") { "test" })
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      it "ignores a passed block" do
+        output = CGISpecs.split(@html.checkbox_group("test", "foo", "bar", "baz") { "test" })
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "uses the passed Hash to generate the checkbox sequence" do
-      output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+    describe "when passed Hash" do
+      it "uses the passed Hash to generate the checkbox sequence" do
+        output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
 
-      output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => [["foo"], ["bar", true], "baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+        output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => [["foo"], ["bar", true], "baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
 
-      output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => [["1", "Foo"], ["2", "Bar", true], "Baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "1"}, "Foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "checkbox", "VALUE" => "2"}, "Bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "Baz"}, "Baz", not_closed: true)
-    end
+        output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => [["1", "Foo"], ["2", "Bar", true], "Baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "1"}, "Foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "checkbox", "VALUE" => "2"}, "Bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "Baz"}, "Baz", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]) { "test" })
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      it "ignores a passed block" do
+        output = CGISpecs.split(@html.checkbox_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]) { "test" })
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "checkbox", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/checkbox_spec.rb b/spec/ruby/library/cgi/htmlextension/checkbox_spec.rb
index af76fa1da9..ad87b78061 100644
--- a/spec/ruby/library/cgi/htmlextension/checkbox_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/checkbox_spec.rb
@@ -1,77 +1,80 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#checkbox" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a checkbox-'input'-element without a name" do
-      output = @html.checkbox
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "checkbox"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#checkbox" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.checkbox { "test" }
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "checkbox"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a checkbox-'input'-element without a name" do
+        output = @html.checkbox
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "checkbox"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns a checkbox-'input'-element with the passed name" do
-      output = @html.checkbox("test")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.checkbox { "test" }
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "checkbox"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.checkbox("test") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns a checkbox-'input'-element with the passed name" do
+        output = @html.checkbox("test")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox"}, "", not_closed: true)
+      end
 
-  describe "CGI::HtmlExtension#checkbox when passed name, value" do
-    it "returns a checkbox-'input'-element with the passed name and value" do
-      output = @html.checkbox("test", "test-value")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.checkbox("test") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.checkbox("test", "test-value") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+    describe "CGI::HtmlExtension#checkbox when passed name, value" do
+      it "returns a checkbox-'input'-element with the passed name and value" do
+        output = @html.checkbox("test", "test-value")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.checkbox("test", "test-value") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed name, value, checked" do
-    it "returns a checked checkbox-'input'-element with the passed name and value when checked is true" do
-      output = @html.checkbox("test", "test-value", true)
-      output.should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+    describe "when passed name, value, checked" do
+      it "returns a checked checkbox-'input'-element with the passed name and value when checked is true" do
+        output = @html.checkbox("test", "test-value", true)
+        output.should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
 
-      output = @html.checkbox("test", "test-value", false)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+        output = @html.checkbox("test", "test-value", false)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
 
-      output = @html.checkbox("test", "test-value", nil)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
-    end
+        output = @html.checkbox("test", "test-value", nil)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = @html.checkbox("test", "test-value", nil) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.checkbox("test", "test-value", nil) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "checkbox", "VALUE" => "test-value"}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "returns a checkbox-'input'-element using the passed Hash for attributes" do
-      attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
-      output = @html.checkbox(attributes)
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
-    end
+    describe "when passed Hash" do
+      it "returns a checkbox-'input'-element using the passed Hash for attributes" do
+        attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
+        output = @html.checkbox(attributes)
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
-      output = @html.checkbox(attributes) { "test" }
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
+      it "ignores a passed block" do
+        attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
+        output = @html.checkbox(attributes) { "test" }
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/doctype_spec.rb b/spec/ruby/library/cgi/htmlextension/doctype_spec.rb
index 9a28a8883b..02af831855 100644
--- a/spec/ruby/library/cgi/htmlextension/doctype_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/doctype_spec.rb
@@ -1,27 +1,30 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#doctype" do
-  describe "when each HTML generation" do
-    it "returns the doctype declaration for HTML3" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">'
-      CGISpecs.cgi_new("html3").doctype.should == expect
-    end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-    it "returns the doctype declaration for HTML4" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">'
-      CGISpecs.cgi_new("html4").doctype.should == expect
-    end
+  describe "CGI::HtmlExtension#doctype" do
+    describe "when each HTML generation" do
+      it "returns the doctype declaration for HTML3" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">'
+        CGISpecs.cgi_new("html3").doctype.should == expect
+      end
 
-    it "returns the doctype declaration for the Frameset version of HTML4" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">'
-      CGISpecs.cgi_new("html4Fr").doctype.should == expect
-    end
+      it "returns the doctype declaration for HTML4" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">'
+        CGISpecs.cgi_new("html4").doctype.should == expect
+      end
+
+      it "returns the doctype declaration for the Frameset version of HTML4" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">'
+        CGISpecs.cgi_new("html4Fr").doctype.should == expect
+      end
 
-    it "returns the doctype declaration for the Transitional version of HTML4" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">'
-      CGISpecs.cgi_new("html4Tr").doctype.should == expect
+      it "returns the doctype declaration for the Transitional version of HTML4" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">'
+        CGISpecs.cgi_new("html4Tr").doctype.should == expect
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/file_field_spec.rb b/spec/ruby/library/cgi/htmlextension/file_field_spec.rb
index 2a0632fd58..eff077b9a2 100644
--- a/spec/ruby/library/cgi/htmlextension/file_field_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/file_field_spec.rb
@@ -1,72 +1,75 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#file_field" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a file-'input'-element without a name and a size of 20" do
-      output = @html.file_field
-      output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "", "TYPE" => "file"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#file_field" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.file_field { "test" }
-      output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "", "TYPE" => "file"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a file-'input'-element without a name and a size of 20" do
+        output = @html.file_field
+        output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "", "TYPE" => "file"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns a checkbox-'input'-element with the passed name" do
-      output = @html.file_field("Example")
-      output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.file_field { "test" }
+        output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "", "TYPE" => "file"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.file_field("Example") { "test" }
-      output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns a checkbox-'input'-element with the passed name" do
+        output = @html.file_field("Example")
+        output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      end
 
-  describe "when passed name, size" do
-    it "returns a checkbox-'input'-element with the passed name and size" do
-      output = @html.file_field("Example", 40)
-      output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.file_field("Example") { "test" }
+        output.should equal_element("INPUT", {"SIZE" => 20, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.file_field("Example", 40) { "test" }
-      output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, size" do
+      it "returns a checkbox-'input'-element with the passed name and size" do
+        output = @html.file_field("Example", 40)
+        output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      end
 
-  describe "when passed name, size, maxlength" do
-    it "returns a checkbox-'input'-element with the passed name, size and maxlength" do
-      output = @html.file_field("Example", 40, 100)
-      output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file", "MAXLENGTH" => 100}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.file_field("Example", 40) { "test" }
+        output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.file_field("Example", 40, 100) { "test" }
-      output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file", "MAXLENGTH" => 100}, "", not_closed: true)
+    describe "when passed name, size, maxlength" do
+      it "returns a checkbox-'input'-element with the passed name, size and maxlength" do
+        output = @html.file_field("Example", 40, 100)
+        output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file", "MAXLENGTH" => 100}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.file_field("Example", 40, 100) { "test" }
+        output.should equal_element("INPUT", {"SIZE" => 40, "NAME" => "Example", "TYPE" => "file", "MAXLENGTH" => 100}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed a Hash" do
-    it "returns a file-'input'-element using the passed Hash for attributes" do
-      output = @html.file_field("NAME" => "test", "SIZE" => 40)
-      output.should equal_element("INPUT", {"NAME" => "test", "SIZE" => 40}, "", not_closed: true)
+    describe "when passed a Hash" do
+      it "returns a file-'input'-element using the passed Hash for attributes" do
+        output = @html.file_field("NAME" => "test", "SIZE" => 40)
+        output.should equal_element("INPUT", {"NAME" => "test", "SIZE" => 40}, "", not_closed: true)
 
-      output = @html.file_field("NAME" => "test", "MAXLENGTH" => 100)
-      output.should equal_element("INPUT", {"NAME" => "test", "MAXLENGTH" => 100}, "", not_closed: true)
-    end
+        output = @html.file_field("NAME" => "test", "MAXLENGTH" => 100)
+        output.should equal_element("INPUT", {"NAME" => "test", "MAXLENGTH" => 100}, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = @html.file_field("NAME" => "test", "SIZE" => 40) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "SIZE" => 40}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.file_field("NAME" => "test", "SIZE" => 40) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "SIZE" => 40}, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/form_spec.rb b/spec/ruby/library/cgi/htmlextension/form_spec.rb
index 8c0ac97735..55ac63152b 100644
--- a/spec/ruby/library/cgi/htmlextension/form_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/form_spec.rb
@@ -1,58 +1,61 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#form" do
-  before :each do
-    @html = CGISpecs.cgi_new
-    @html.stub!(:script_name).and_return("/path/to/some/script")
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a 'form'-element" do
-      output = @html.form
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/path/to/some/script"}, "")
+  describe "CGI::HtmlExtension#form" do
+    before :each do
+      @html = CGISpecs.cgi_new
+      @html.stub!(:script_name).and_return("/path/to/some/script")
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.form { "test" }
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/path/to/some/script"}, "test")
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a 'form'-element" do
+        output = @html.form
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/path/to/some/script"}, "")
+      end
 
-  describe "when passed method" do
-    it "returns a 'form'-element with the passed method" do
-      output = @html.form("get")
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/path/to/some/script"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.form { "test" }
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/path/to/some/script"}, "test")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.form("get") { "test" }
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/path/to/some/script"}, "test")
-    end
-  end
+    describe "when passed method" do
+      it "returns a 'form'-element with the passed method" do
+        output = @html.form("get")
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/path/to/some/script"}, "")
+      end
 
-  describe "when passed method, action" do
-    it "returns a 'form'-element with the passed method and the passed action" do
-      output = @html.form("get", "/some/other/script")
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/some/other/script"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.form("get") { "test" }
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/path/to/some/script"}, "test")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.form("get", "/some/other/script") { "test" }
-      output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/some/other/script"}, "test")
-    end
-  end
+    describe "when passed method, action" do
+      it "returns a 'form'-element with the passed method and the passed action" do
+        output = @html.form("get", "/some/other/script")
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/some/other/script"}, "")
+      end
 
-  describe "when passed method, action, enctype" do
-    it "returns a 'form'-element with the passed method, action and enctype" do
-      output = @html.form("get", "/some/other/script", "multipart/form-data")
-      output.should equal_element("FORM", {"ENCTYPE" => "multipart/form-data", "METHOD" => "get", "ACTION" => "/some/other/script"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.form("get", "/some/other/script") { "test" }
+        output.should equal_element("FORM", {"ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ACTION" => "/some/other/script"}, "test")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.form("get", "/some/other/script", "multipart/form-data") { "test" }
-      output.should equal_element("FORM", {"ENCTYPE" => "multipart/form-data", "METHOD" => "get", "ACTION" => "/some/other/script"}, "test")
+    describe "when passed method, action, enctype" do
+      it "returns a 'form'-element with the passed method, action and enctype" do
+        output = @html.form("get", "/some/other/script", "multipart/form-data")
+        output.should equal_element("FORM", {"ENCTYPE" => "multipart/form-data", "METHOD" => "get", "ACTION" => "/some/other/script"}, "")
+      end
+
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.form("get", "/some/other/script", "multipart/form-data") { "test" }
+        output.should equal_element("FORM", {"ENCTYPE" => "multipart/form-data", "METHOD" => "get", "ACTION" => "/some/other/script"}, "test")
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/frame_spec.rb b/spec/ruby/library/cgi/htmlextension/frame_spec.rb
index 2ddd4e1ef0..fef40849eb 100644
--- a/spec/ruby/library/cgi/htmlextension/frame_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/frame_spec.rb
@@ -1,14 +1,17 @@
 require_relative '../../../spec_helper'
-require_relative 'fixtures/common'
-require 'cgi'
 
-describe "CGI::HtmlExtension#frame" do
-  before :each do
-    @html = CGISpecs.cgi_new("html4Fr")
-  end
+ruby_version_is ""..."4.0" do
+  require_relative 'fixtures/common'
+  require 'cgi'
+
+  describe "CGI::HtmlExtension#frame" do
+    before :each do
+      @html = CGISpecs.cgi_new("html4Fr")
+    end
 
-  it "initializes the HTML Generation methods for the Frameset version of HTML4" do
-    @html.frameset.should == "<FRAMESET></FRAMESET>"
-    @html.frameset { "link text" }.should == "<FRAMESET>link text</FRAMESET>"
+    it "initializes the HTML Generation methods for the Frameset version of HTML4" do
+      @html.frameset.should == "<FRAMESET></FRAMESET>"
+      @html.frameset { "link text" }.should == "<FRAMESET>link text</FRAMESET>"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/frameset_spec.rb b/spec/ruby/library/cgi/htmlextension/frameset_spec.rb
index baeb446593..3ad0a9c4d2 100644
--- a/spec/ruby/library/cgi/htmlextension/frameset_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/frameset_spec.rb
@@ -1,14 +1,17 @@
 require_relative '../../../spec_helper'
-require_relative 'fixtures/common'
-require 'cgi'
 
-describe "CGI::HtmlExtension#frameset" do
-  before :each do
-    @html = CGISpecs.cgi_new("html4Fr")
-  end
+ruby_version_is ""..."4.0" do
+  require_relative 'fixtures/common'
+  require 'cgi'
+
+  describe "CGI::HtmlExtension#frameset" do
+    before :each do
+      @html = CGISpecs.cgi_new("html4Fr")
+    end
 
-  it "initializes the HTML Generation methods for the Frameset version of HTML4" do
-    @html.frameset.should == "<FRAMESET></FRAMESET>"
-    @html.frameset { "link text" }.should == "<FRAMESET>link text</FRAMESET>"
+    it "initializes the HTML Generation methods for the Frameset version of HTML4" do
+      @html.frameset.should == "<FRAMESET></FRAMESET>"
+      @html.frameset { "link text" }.should == "<FRAMESET>link text</FRAMESET>"
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/hidden_spec.rb b/spec/ruby/library/cgi/htmlextension/hidden_spec.rb
index 52ebd8c261..b2323775f6 100644
--- a/spec/ruby/library/cgi/htmlextension/hidden_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/hidden_spec.rb
@@ -1,59 +1,62 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#hidden" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an hidden-'input'-element without a name" do
-      output = @html.hidden
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "hidden"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#hidden" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.hidden { "test" }
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "hidden"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an hidden-'input'-element without a name" do
+        output = @html.hidden
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "hidden"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns an hidden-'input'-element with the passed name" do
-      output = @html.hidden("test")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.hidden { "test" }
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "hidden"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.hidden("test") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns an hidden-'input'-element with the passed name" do
+        output = @html.hidden("test")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value" do
-    it "returns an hidden-'input'-element with the passed name and value" do
-      output = @html.hidden("test", "some value")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden", "VALUE" => "some value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.hidden("test") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.hidden("test", "some value") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden", "VALUE" => "some value"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, value" do
+      it "returns an hidden-'input'-element with the passed name and value" do
+        output = @html.hidden("test", "some value")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden", "VALUE" => "some value"}, "", not_closed: true)
+      end
 
-  describe "when passed Hash" do
-    it "returns a checkbox-'input'-element using the passed Hash for attributes" do
-      attributes = { "NAME" => "test", "VALUE" => "some value" }
-      output = @html.hidden("test", "some value")
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.hidden("test", "some value") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "hidden", "VALUE" => "some value"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      attributes = { "NAME" => "test", "VALUE" => "some value" }
-      output = @html.hidden("test", "some value") { "test" }
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a checkbox-'input'-element using the passed Hash for attributes" do
+        attributes = { "NAME" => "test", "VALUE" => "some value" }
+        output = @html.hidden("test", "some value")
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        attributes = { "NAME" => "test", "VALUE" => "some value" }
+        output = @html.hidden("test", "some value") { "test" }
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/html_spec.rb b/spec/ruby/library/cgi/htmlextension/html_spec.rb
index 5d89c82086..60a10fb6b4 100644
--- a/spec/ruby/library/cgi/htmlextension/html_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/html_spec.rb
@@ -1,66 +1,69 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#html" do
-  before :each do
-    @html = CGISpecs.cgi_new
-    @html.stub!(:doctype).and_return("<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>")
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a self's doctype and an 'html'-element" do
-      expected = '<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE><HTML>'
-      @html.html.should == expected
+  describe "CGI::HtmlExtension#html" do
+    before :each do
+      @html = CGISpecs.cgi_new
+      @html.stub!(:doctype).and_return("<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>")
     end
 
-    it "includes the passed block when passed a block" do
-      expected = '<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE><HTML>test</HTML>'
-      @html.html { "test" }.should == expected
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a self's doctype and an 'html'-element" do
+        expected = '<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE><HTML>'
+        @html.html.should == expected
+      end
 
-  describe "when passed 'PRETTY'" do
-    it "returns pretty output when the passed String is 'PRETTY" do
-      expected = "<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>\n<HTML>\n"
-      @html.html("PRETTY").should == expected
+      it "includes the passed block when passed a block" do
+        expected = '<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE><HTML>test</HTML>'
+        @html.html { "test" }.should == expected
+      end
     end
 
-    it "includes the passed block when passed a block" do
-      expected = "<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>\n<HTML>\n  test\n</HTML>\n"
-      @html.html("PRETTY") { "test" }.should == expected
-    end
-  end
+    describe "when passed 'PRETTY'" do
+      it "returns pretty output when the passed String is 'PRETTY" do
+        expected = "<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>\n<HTML>\n"
+        @html.html("PRETTY").should == expected
+      end
 
-  describe "when passed a Hash" do
-    it "returns an 'html'-element using the passed Hash for attributes" do
-      expected = '<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"><HTML BLA="TEST">'
-      @html.html("DOCTYPE" => '<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">', "BLA" => "TEST").should == expected
+      it "includes the passed block when passed a block" do
+        expected = "<!DOCTYPE SUPA-FUNKAY-RUBYSPEC-DOCTYPE>\n<HTML>\n  test\n</HTML>\n"
+        @html.html("PRETTY") { "test" }.should == expected
+      end
     end
 
-    it "omits the doctype when the Hash contains a 'DOCTYPE' entry that's false or nil" do
-      @html.html("DOCTYPE" => false).should == "<HTML>"
-      @html.html("DOCTYPE" => nil).should == "<HTML>"
-    end
-  end
+    describe "when passed a Hash" do
+      it "returns an 'html'-element using the passed Hash for attributes" do
+        expected = '<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"><HTML BLA="TEST">'
+        @html.html("DOCTYPE" => '<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN">', "BLA" => "TEST").should == expected
+      end
 
-  describe "when each HTML generation" do
-    it "returns the doctype declaration for HTML3" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">'
-      CGISpecs.cgi_new("html3").html.should == expect + "<HTML>"
-      CGISpecs.cgi_new("html3").html { "html body" }.should == expect + "<HTML>html body</HTML>"
+      it "omits the doctype when the Hash contains a 'DOCTYPE' entry that's false or nil" do
+        @html.html("DOCTYPE" => false).should == "<HTML>"
+        @html.html("DOCTYPE" => nil).should == "<HTML>"
+      end
     end
 
-    it "returns the doctype declaration for HTML4" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">'
-      CGISpecs.cgi_new("html4").html.should == expect + "<HTML>"
-      CGISpecs.cgi_new("html4").html { "html body" }.should == expect + "<HTML>html body</HTML>"
-    end
+    describe "when each HTML generation" do
+      it "returns the doctype declaration for HTML3" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">'
+        CGISpecs.cgi_new("html3").html.should == expect + "<HTML>"
+        CGISpecs.cgi_new("html3").html { "html body" }.should == expect + "<HTML>html body</HTML>"
+      end
+
+      it "returns the doctype declaration for HTML4" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">'
+        CGISpecs.cgi_new("html4").html.should == expect + "<HTML>"
+        CGISpecs.cgi_new("html4").html { "html body" }.should == expect + "<HTML>html body</HTML>"
+      end
 
-    it "returns the doctype declaration for the Transitional version of HTML4" do
-      expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">'
-      CGISpecs.cgi_new("html4Tr").html.should == expect + "<HTML>"
-      CGISpecs.cgi_new("html4Tr").html { "html body" }.should == expect + "<HTML>html body</HTML>"
+      it "returns the doctype declaration for the Transitional version of HTML4" do
+        expect = '<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">'
+        CGISpecs.cgi_new("html4Tr").html.should == expect + "<HTML>"
+        CGISpecs.cgi_new("html4Tr").html { "html body" }.should == expect + "<HTML>html body</HTML>"
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/image_button_spec.rb b/spec/ruby/library/cgi/htmlextension/image_button_spec.rb
index d14bec9ca3..f8770119d4 100644
--- a/spec/ruby/library/cgi/htmlextension/image_button_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/image_button_spec.rb
@@ -1,69 +1,72 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#image_button" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an image-'input'-element without a source image" do
-      output = @html.image_button
-      output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#image_button" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.image_button { "test" }
-      output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an image-'input'-element without a source image" do
+        output = @html.image_button
+        output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image"}, "", not_closed: true)
+      end
 
-  describe "when passed src" do
-    it "returns an image-'input'-element with the passed src" do
-      output = @html.image_button("/path/to/image.png")
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.image_button { "test" }
+        output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.image_button("/path/to/image.png") { "test" }
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image"}, "", not_closed: true)
-    end
-  end
+    describe "when passed src" do
+      it "returns an image-'input'-element with the passed src" do
+        output = @html.image_button("/path/to/image.png")
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image"}, "", not_closed: true)
+      end
 
-  describe "when passed src, name" do
-    it "returns an image-'input'-element with the passed src and name" do
-      output = @html.image_button("/path/to/image.png", "test")
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.image_button("/path/to/image.png") { "test" }
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.image_button("/path/to/image.png", "test") { "test" }
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test"}, "", not_closed: true)
-    end
-  end
+    describe "when passed src, name" do
+      it "returns an image-'input'-element with the passed src and name" do
+        output = @html.image_button("/path/to/image.png", "test")
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test"}, "", not_closed: true)
+      end
 
-  describe "when passed src, name, alt" do
-    it "returns an image-'input'-element with the passed src, name and alt" do
-      output = @html.image_button("/path/to/image.png", "test", "alternative")
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test", "ALT" => "alternative"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.image_button("/path/to/image.png", "test") { "test" }
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.image_button("/path/to/image.png", "test", "alternative") { "test" }
-      output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test", "ALT" => "alternative"}, "", not_closed: true)
-    end
-  end
+    describe "when passed src, name, alt" do
+      it "returns an image-'input'-element with the passed src, name and alt" do
+        output = @html.image_button("/path/to/image.png", "test", "alternative")
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test", "ALT" => "alternative"}, "", not_closed: true)
+      end
 
-  describe "when passed Hash" do
-    it "returns a image-'input'-element using the passed Hash for attributes" do
-      output = @html.image_button("NAME" => "test", "VALUE" => "test-value")
-      output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image", "NAME" => "test", "VALUE" => "test-value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.image_button("/path/to/image.png", "test", "alternative") { "test" }
+        output.should equal_element("INPUT", {"SRC" => "/path/to/image.png", "TYPE" => "image", "NAME" => "test", "ALT" => "alternative"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.image_button("NAME" => "test", "VALUE" => "test-value") { "test" }
-      output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image", "NAME" => "test", "VALUE" => "test-value"}, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a image-'input'-element using the passed Hash for attributes" do
+        output = @html.image_button("NAME" => "test", "VALUE" => "test-value")
+        output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image", "NAME" => "test", "VALUE" => "test-value"}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.image_button("NAME" => "test", "VALUE" => "test-value") { "test" }
+        output.should equal_element("INPUT", {"SRC" => "", "TYPE" => "image", "NAME" => "test", "VALUE" => "test-value"}, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/img_spec.rb b/spec/ruby/library/cgi/htmlextension/img_spec.rb
index 994ae7fedf..a05cfdea48 100644
--- a/spec/ruby/library/cgi/htmlextension/img_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/img_spec.rb
@@ -1,83 +1,86 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#img" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an 'img'-element without an src-url or alt-text" do
-      output = @html.img
-      output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
+  describe "CGI::HtmlExtension#img" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.img { "test" }
-      output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an 'img'-element without an src-url or alt-text" do
+        output = @html.img
+        output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
+      end
 
-  describe "when passed src" do
-    it "returns an 'img'-element with the passed src-url" do
-      output = @html.img("/path/to/some/image.png")
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.img { "test" }
+        output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.img("/path/to/some/image.png")
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "" }, "", not_closed: true)
-    end
-  end
+    describe "when passed src" do
+      it "returns an 'img'-element with the passed src-url" do
+        output = @html.img("/path/to/some/image.png")
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "" }, "", not_closed: true)
+      end
 
-  describe "when passed src, alt" do
-    it "returns an 'img'-element with the passed src-url and the passed alt-text" do
-      output = @html.img("/path/to/some/image.png", "Alternative")
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.img("/path/to/some/image.png")
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "" }, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.img("/path/to/some/image.png", "Alternative") { "test" }
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative" }, "", not_closed: true)
-    end
-  end
+    describe "when passed src, alt" do
+      it "returns an 'img'-element with the passed src-url and the passed alt-text" do
+        output = @html.img("/path/to/some/image.png", "Alternative")
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative" }, "", not_closed: true)
+      end
 
-  describe "when passed src, alt, width" do
-    it "returns an 'img'-element with the passed src-url, the passed alt-text and the passed width" do
-      output = @html.img("/path/to/some/image.png", "Alternative", 40)
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.img("/path/to/some/image.png", "Alternative") { "test" }
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative" }, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.img("/path/to/some/image.png", "Alternative", 40) { "test" }
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40" }, "", not_closed: true)
-    end
-  end
+    describe "when passed src, alt, width" do
+      it "returns an 'img'-element with the passed src-url, the passed alt-text and the passed width" do
+        output = @html.img("/path/to/some/image.png", "Alternative", 40)
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40" }, "", not_closed: true)
+      end
 
-  describe "when passed src, alt, width, height" do
-    it "returns an 'img'-element with the passed src-url, the passed alt-text, the passed width and the passed height" do
-      output = @html.img("/path/to/some/image.png", "Alternative", 40, 60)
-      output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40", "HEIGHT" => "60" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.img("/path/to/some/image.png", "Alternative", 40) { "test" }
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40" }, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.img { "test" }
-      output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
-    end
-  end
+    describe "when passed src, alt, width, height" do
+      it "returns an 'img'-element with the passed src-url, the passed alt-text, the passed width and the passed height" do
+        output = @html.img("/path/to/some/image.png", "Alternative", 40, 60)
+        output.should equal_element("IMG", { "SRC" => "/path/to/some/image.png", "ALT" => "Alternative", "WIDTH" => "40", "HEIGHT" => "60" }, "", not_closed: true)
+      end
 
-  describe "when passed Hash" do
-    it "returns an 'img'-element with the passed Hash as attributes" do
-      attributes = { "SRC" => "src", "ALT" => "alt", "WIDTH" => 100, "HEIGHT" => 50 }
-      output = @html.img(attributes)
-      output.should equal_element("IMG", attributes, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.img { "test" }
+        output.should equal_element("IMG", { "SRC" => "", "ALT" => "" }, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      attributes = { "SRC" => "src", "ALT" => "alt", "WIDTH" => 100, "HEIGHT" => 50 }
-      output = @html.img(attributes) { "test" }
-      output.should equal_element("IMG", attributes, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns an 'img'-element with the passed Hash as attributes" do
+        attributes = { "SRC" => "src", "ALT" => "alt", "WIDTH" => 100, "HEIGHT" => 50 }
+        output = @html.img(attributes)
+        output.should equal_element("IMG", attributes, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        attributes = { "SRC" => "src", "ALT" => "alt", "WIDTH" => 100, "HEIGHT" => 50 }
+        output = @html.img(attributes) { "test" }
+        output.should equal_element("IMG", attributes, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/multipart_form_spec.rb b/spec/ruby/library/cgi/htmlextension/multipart_form_spec.rb
index 0bf2042a33..ee1c45b84e 100644
--- a/spec/ruby/library/cgi/htmlextension/multipart_form_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/multipart_form_spec.rb
@@ -1,64 +1,67 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#multipart_form" do
-  before :each do
-    @html = CGISpecs.cgi_new
-    @html.stub!(:script_name).and_return("/path/to/some/script.rb")
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a 'form'-element with it's enctype set to multipart" do
-      output = @html.multipart_form
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post" }, "")
+  describe "CGI::HtmlExtension#multipart_form" do
+    before :each do
+      @html = CGISpecs.cgi_new
+      @html.stub!(:script_name).and_return("/path/to/some/script.rb")
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.multipart_form { "test" }
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post" }, "test")
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a 'form'-element with it's enctype set to multipart" do
+        output = @html.multipart_form
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post" }, "")
+      end
 
-  describe "when passed action" do
-    it "returns a 'form'-element with the passed action" do
-      output = @html.multipart_form("/some/other/script.rb")
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.multipart_form { "test" }
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post" }, "test")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.multipart_form("/some/other/script.rb") { "test" }
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "test")
-    end
-  end
+    describe "when passed action" do
+      it "returns a 'form'-element with the passed action" do
+        output = @html.multipart_form("/some/other/script.rb")
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "")
+      end
 
-  describe "when passed action, enctype" do
-    it "returns a 'form'-element with the passed action and enctype" do
-      output = @html.multipart_form("/some/other/script.rb", "application/x-www-form-urlencoded")
-      output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.multipart_form("/some/other/script.rb") { "test" }
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "test")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.multipart_form("/some/other/script.rb", "application/x-www-form-urlencoded") { "test" }
-      output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "test")
+    describe "when passed action, enctype" do
+      it "returns a 'form'-element with the passed action and enctype" do
+        output = @html.multipart_form("/some/other/script.rb", "application/x-www-form-urlencoded")
+        output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "")
+      end
+
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.multipart_form("/some/other/script.rb", "application/x-www-form-urlencoded") { "test" }
+        output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "post", "ACTION" => "/some/other/script.rb" }, "test")
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "returns a 'form'-element with the passed Hash as attributes" do
-      output = @html.multipart_form("ID" => "test")
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ID" => "test" }, "")
+    describe "when passed Hash" do
+      it "returns a 'form'-element with the passed Hash as attributes" do
+        output = @html.multipart_form("ID" => "test")
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ID" => "test" }, "")
 
-      output = @html.multipart_form("ID" => "test", "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get")
-      output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ID" => "test" }, "")
-    end
+        output = @html.multipart_form("ID" => "test", "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get")
+        output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ID" => "test" }, "")
+      end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.multipart_form("ID" => "test") { "test" }
-      output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ID" => "test" }, "test")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.multipart_form("ID" => "test") { "test" }
+        output.should equal_element("FORM", { "ENCTYPE" => "multipart/form-data", "METHOD" => "post", "ID" => "test" }, "test")
 
-      output = @html.multipart_form("ID" => "test", "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get") { "test" }
-      output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ID" => "test" }, "test")
+        output = @html.multipart_form("ID" => "test", "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get") { "test" }
+        output.should equal_element("FORM", { "ENCTYPE" => "application/x-www-form-urlencoded", "METHOD" => "get", "ID" => "test" }, "test")
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/password_field_spec.rb b/spec/ruby/library/cgi/htmlextension/password_field_spec.rb
index 683bc428ba..0fefdd5c45 100644
--- a/spec/ruby/library/cgi/htmlextension/password_field_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/password_field_spec.rb
@@ -1,84 +1,87 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#password_field" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an password-'input'-element without a name" do
-      output = @html.password_field
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#password_field" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.password_field { "test" }
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an password-'input'-element without a name" do
+        output = @html.password_field
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns an password-'input'-element with the passed name" do
-      output = @html.password_field("test")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.password_field { "test" }
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.password_field("test") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns an password-'input'-element with the passed name" do
+        output = @html.password_field("test")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value" do
-    it "returns an password-'input'-element with the passed name and value" do
-      output = @html.password_field("test", "some value")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.password_field("test") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.password_field("test", "some value") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, value" do
+      it "returns an password-'input'-element with the passed name and value" do
+        output = @html.password_field("test", "some value")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value, size" do
-    it "returns an password-'input'-element with the passed name, value and size" do
-      output = @html.password_field("test", "some value", 60)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.password_field("test", "some value") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.password_field("test", "some value", 60) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, value, size" do
+      it "returns an password-'input'-element with the passed name, value and size" do
+        output = @html.password_field("test", "some value", 60)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value, size, maxlength" do
-    it "returns an password-'input'-element with the passed name, value, size and maxlength" do
-      output = @html.password_field("test", "some value", 60, 12)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.password_field("test", "some value", 60) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.password_field("test", "some value", 60, 12) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+    describe "when passed name, value, size, maxlength" do
+      it "returns an password-'input'-element with the passed name, value, size and maxlength" do
+        output = @html.password_field("test", "some value", 60, 12)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.password_field("test", "some value", 60, 12) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "password", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "returns a checkbox-'input'-element using the passed Hash for attributes" do
-      output = @html.password_field("NAME" => "test", "VALUE" => "some value")
-      output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "password" }, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a checkbox-'input'-element using the passed Hash for attributes" do
+        output = @html.password_field("NAME" => "test", "VALUE" => "some value")
+        output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "password" }, "", not_closed: true)
 
-      output = @html.password_field("TYPE" => "hidden")
-      output.should equal_element("INPUT", {"TYPE" => "password"}, "", not_closed: true)
-    end
+        output = @html.password_field("TYPE" => "hidden")
+        output.should equal_element("INPUT", {"TYPE" => "password"}, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = @html.password_field("NAME" => "test", "VALUE" => "some value") { "test" }
-      output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "password" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.password_field("NAME" => "test", "VALUE" => "some value") { "test" }
+        output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "password" }, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/popup_menu_spec.rb b/spec/ruby/library/cgi/htmlextension/popup_menu_spec.rb
index 3462be09b0..7452d15317 100644
--- a/spec/ruby/library/cgi/htmlextension/popup_menu_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/popup_menu_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
-require_relative 'shared/popup_menu'
 
-describe "CGI::HtmlExtension#popup_menu" do
-  it_behaves_like :cgi_htmlextension_popup_menu, :popup_menu
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
+  require_relative 'shared/popup_menu'
+
+  describe "CGI::HtmlExtension#popup_menu" do
+    it_behaves_like :cgi_htmlextension_popup_menu, :popup_menu
+  end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/radio_button_spec.rb b/spec/ruby/library/cgi/htmlextension/radio_button_spec.rb
index 3dc3c879b5..8458685cdc 100644
--- a/spec/ruby/library/cgi/htmlextension/radio_button_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/radio_button_spec.rb
@@ -1,77 +1,80 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#radio_button" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a radio-'input'-element without a name" do
-      output = @html.radio_button
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "radio"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#radio_button" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.radio_button { "test" }
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "radio"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a radio-'input'-element without a name" do
+        output = @html.radio_button
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "radio"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns a radio-'input'-element with the passed name" do
-      output = @html.radio_button("test")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.radio_button { "test" }
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "radio"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.radio_button("test") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns a radio-'input'-element with the passed name" do
+        output = @html.radio_button("test")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio"}, "", not_closed: true)
+      end
 
-  describe "CGI::HtmlExtension#checkbox when passed name, value" do
-    it "returns a radio-'input'-element with the passed name and value" do
-      output = @html.radio_button("test", "test-value")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.radio_button("test") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.radio_button("test", "test-value") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+    describe "CGI::HtmlExtension#checkbox when passed name, value" do
+      it "returns a radio-'input'-element with the passed name and value" do
+        output = @html.radio_button("test", "test-value")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.radio_button("test", "test-value") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed name, value, checked" do
-    it "returns a checked radio-'input'-element with the passed name and value when checked is true" do
-      output = @html.radio_button("test", "test-value", true)
-      output.should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+    describe "when passed name, value, checked" do
+      it "returns a checked radio-'input'-element with the passed name and value when checked is true" do
+        output = @html.radio_button("test", "test-value", true)
+        output.should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
 
-      output = @html.radio_button("test", "test-value", false)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+        output = @html.radio_button("test", "test-value", false)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
 
-      output = @html.radio_button("test", "test-value", nil)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
-    end
+        output = @html.radio_button("test", "test-value", nil)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = @html.radio_button("test", "test-value", nil) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.radio_button("test", "test-value", nil) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "test-value"}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "returns a radio-'input'-element using the passed Hash for attributes" do
-      attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
-      output = @html.radio_button(attributes)
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
-    end
+    describe "when passed Hash" do
+      it "returns a radio-'input'-element using the passed Hash for attributes" do
+        attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
+        output = @html.radio_button(attributes)
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
-      output = @html.radio_button(attributes) { "test" }
-      output.should equal_element("INPUT", attributes, "", not_closed: true)
+      it "ignores a passed block" do
+        attributes = {"NAME" => "test", "VALUE" => "test-value", "CHECKED" => true}
+        output = @html.radio_button(attributes) { "test" }
+        output.should equal_element("INPUT", attributes, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/radio_group_spec.rb b/spec/ruby/library/cgi/htmlextension/radio_group_spec.rb
index 1bfd43449d..fd925a5165 100644
--- a/spec/ruby/library/cgi/htmlextension/radio_group_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/radio_group_spec.rb
@@ -1,77 +1,80 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#radio_group" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed name, values ..." do
-    it "returns a sequence of 'radio'-elements with the passed name and the passed values" do
-      output = CGISpecs.split(@html.radio_group("test", "foo", "bar", "baz"))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+  describe "CGI::HtmlExtension#radio_group" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "allows passing a value inside an Array" do
-      output = CGISpecs.split(@html.radio_group("test", ["foo"], "bar", ["baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
-    end
+    describe "when passed name, values ..." do
+      it "returns a sequence of 'radio'-elements with the passed name and the passed values" do
+        output = CGISpecs.split(@html.radio_group("test", "foo", "bar", "baz"))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
 
-    it "allows passing a value as an Array containing the value and the checked state or a label" do
-      output = CGISpecs.split(@html.radio_group("test", ["foo"], ["bar", true], ["baz", "label for baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "label for baz", not_closed: true)
-    end
+      it "allows passing a value inside an Array" do
+        output = CGISpecs.split(@html.radio_group("test", ["foo"], "bar", ["baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
 
-    # TODO: CGI does not like passing false instead of true.
-    it "allows passing a value as an Array containing the value, a label and the checked state" do
-      output = CGISpecs.split(@html.radio_group("test", ["foo", "label for foo", true], ["bar", "label for bar", false], ["baz", "label for baz", true]))
-      output[0].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "label for foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "label for bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "label for baz", not_closed: true)
-    end
+      it "allows passing a value as an Array containing the value and the checked state or a label" do
+        output = CGISpecs.split(@html.radio_group("test", ["foo"], ["bar", true], ["baz", "label for baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "label for baz", not_closed: true)
+      end
 
-    it "returns an empty String when passed no values" do
-      @html.radio_group("test").should == ""
-    end
+      # TODO: CGI does not like passing false instead of true.
+      it "allows passing a value as an Array containing the value, a label and the checked state" do
+        output = CGISpecs.split(@html.radio_group("test", ["foo", "label for foo", true], ["bar", "label for bar", false], ["baz", "label for baz", true]))
+        output[0].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "label for foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "label for bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "label for baz", not_closed: true)
+      end
+
+      it "returns an empty String when passed no values" do
+        @html.radio_group("test").should == ""
+      end
 
-    it "ignores a passed block" do
-      output = CGISpecs.split(@html.radio_group("test", "foo", "bar", "baz") { "test" })
-      output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      it "ignores a passed block" do
+        output = CGISpecs.split(@html.radio_group("test", "foo", "bar", "baz") { "test" })
+        output[0].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "test", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "uses the passed Hash to generate the radio sequence" do
-      output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+    describe "when passed Hash" do
+      it "uses the passed Hash to generate the radio sequence" do
+        output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
 
-      output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => [["foo"], ["bar", true], "baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+        output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => [["foo"], ["bar", true], "baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
 
-      output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => [["1", "Foo"], ["2", "Bar", true], "Baz"]))
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "1"}, "Foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "radio", "VALUE" => "2"}, "Bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "Baz"}, "Baz", not_closed: true)
-    end
+        output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => [["1", "Foo"], ["2", "Bar", true], "Baz"]))
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "1"}, "Foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"CHECKED" => true, "NAME" => "name", "TYPE" => "radio", "VALUE" => "2"}, "Bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "Baz"}, "Baz", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]) { "test" })
-      output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
-      output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
-      output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      it "ignores a passed block" do
+        output = CGISpecs.split(@html.radio_group("NAME" => "name", "VALUES" => ["foo", "bar", "baz"]) { "test" })
+        output[0].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "foo"}, "foo", not_closed: true)
+        output[1].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "bar"}, "bar", not_closed: true)
+        output[2].should equal_element("INPUT", {"NAME" => "name", "TYPE" => "radio", "VALUE" => "baz"}, "baz", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/reset_spec.rb b/spec/ruby/library/cgi/htmlextension/reset_spec.rb
index 86fa25fc8a..80e4441b16 100644
--- a/spec/ruby/library/cgi/htmlextension/reset_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/reset_spec.rb
@@ -1,57 +1,60 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#reset" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a reset-'input'-element" do
-      output = @html.reset
-      output.should equal_element("INPUT", {"TYPE" => "reset"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#reset" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.reset { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "reset"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a reset-'input'-element" do
+        output = @html.reset
+        output.should equal_element("INPUT", {"TYPE" => "reset"}, "", not_closed: true)
+      end
 
-  describe "when passed value" do
-    it "returns a reset-'input'-element with the passed value" do
-      output = @html.reset("Example")
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.reset { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "reset"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.reset("Example") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
-    end
-  end
+    describe "when passed value" do
+      it "returns a reset-'input'-element with the passed value" do
+        output = @html.reset("Example")
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      end
 
-  describe "when passed value, name" do
-    it "returns a reset-'input'-element with the passed value and the passed name" do
-      output = @html.reset("Example", "test-name")
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.reset("Example") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.reset("Example", "test-name") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
-    end
-  end
+    describe "when passed value, name" do
+      it "returns a reset-'input'-element with the passed value and the passed name" do
+        output = @html.reset("Example", "test-name")
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      end
 
-  describe "when passed Hash" do
-    it "returns a reset-'input'-element with the passed value" do
-      output = @html.reset("Example")
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.reset("Example", "test-name") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.reset("Example") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a reset-'input'-element with the passed value" do
+        output = @html.reset("Example")
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.reset("Example") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "reset", "VALUE" => "Example"}, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/scrolling_list_spec.rb b/spec/ruby/library/cgi/htmlextension/scrolling_list_spec.rb
index 4eb0c86c1a..b565444679 100644
--- a/spec/ruby/library/cgi/htmlextension/scrolling_list_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/scrolling_list_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../../spec_helper'
-require_relative 'fixtures/common'
-require 'cgi'
-require_relative 'shared/popup_menu'
 
-describe "CGI::HtmlExtension#scrolling_list" do
-  it_behaves_like :cgi_htmlextension_popup_menu, :scrolling_list
+ruby_version_is ""..."4.0" do
+  require_relative 'fixtures/common'
+  require 'cgi'
+  require_relative 'shared/popup_menu'
+
+  describe "CGI::HtmlExtension#scrolling_list" do
+    it_behaves_like :cgi_htmlextension_popup_menu, :scrolling_list
+  end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/submit_spec.rb b/spec/ruby/library/cgi/htmlextension/submit_spec.rb
index 063891b959..bb6e079c4e 100644
--- a/spec/ruby/library/cgi/htmlextension/submit_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/submit_spec.rb
@@ -1,57 +1,60 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#submit" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns a submit-'input'-element" do
-      output = @html.submit
-      output.should equal_element("INPUT", {"TYPE" => "submit"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#submit" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.submit { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "submit"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns a submit-'input'-element" do
+        output = @html.submit
+        output.should equal_element("INPUT", {"TYPE" => "submit"}, "", not_closed: true)
+      end
 
-  describe "when passed value" do
-    it "returns a submit-'input'-element with the passed value" do
-      output = @html.submit("Example")
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.submit { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "submit"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.submit("Example") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
-    end
-  end
+    describe "when passed value" do
+      it "returns a submit-'input'-element with the passed value" do
+        output = @html.submit("Example")
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      end
 
-  describe "when passed value, name" do
-    it "returns a submit-'input'-element with the passed value and the passed name" do
-      output = @html.submit("Example", "test-name")
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.submit("Example") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.submit("Example", "test-name") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
-    end
-  end
+    describe "when passed value, name" do
+      it "returns a submit-'input'-element with the passed value and the passed name" do
+        output = @html.submit("Example", "test-name")
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      end
 
-  describe "when passed Hash" do
-    it "returns a submit-'input'-element with the passed value" do
-      output = @html.submit("Example")
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.submit("Example", "test-name") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example", "NAME" => "test-name"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.submit("Example") { "test" }
-      output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a submit-'input'-element with the passed value" do
+        output = @html.submit("Example")
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.submit("Example") { "test" }
+        output.should equal_element("INPUT", {"TYPE" => "submit", "VALUE" => "Example"}, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/text_field_spec.rb b/spec/ruby/library/cgi/htmlextension/text_field_spec.rb
index 44b5a5e69f..37e13e3746 100644
--- a/spec/ruby/library/cgi/htmlextension/text_field_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/text_field_spec.rb
@@ -1,84 +1,87 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#text_field" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an text-'input'-element without a name" do
-      output = @html.text_field
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+  describe "CGI::HtmlExtension#text_field" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "ignores a passed block" do
-      output = @html.text_field { "test" }
-      output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an text-'input'-element without a name" do
+        output = @html.text_field
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name" do
-    it "returns an text-'input'-element with the passed name" do
-      output = @html.text_field("test")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.text_field { "test" }
+        output.should equal_element("INPUT", {"NAME" => "", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.text_field("test") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name" do
+      it "returns an text-'input'-element with the passed name" do
+        output = @html.text_field("test")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value" do
-    it "returns an text-'input'-element with the passed name and value" do
-      output = @html.text_field("test", "some value")
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.text_field("test") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.text_field("test", "some value") { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, value" do
+      it "returns an text-'input'-element with the passed name and value" do
+        output = @html.text_field("test", "some value")
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value, size" do
-    it "returns an text-'input'-element with the passed name, value and size" do
-      output = @html.text_field("test", "some value", 60)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.text_field("test", "some value") { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "40"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.text_field("test", "some value", 60) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
-    end
-  end
+    describe "when passed name, value, size" do
+      it "returns an text-'input'-element with the passed name, value and size" do
+        output = @html.text_field("test", "some value", 60)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      end
 
-  describe "when passed name, value, size, maxlength" do
-    it "returns an text-'input'-element with the passed name, value, size and maxlength" do
-      output = @html.text_field("test", "some value", 60, 12)
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.text_field("test", "some value", 60) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60"}, "", not_closed: true)
+      end
     end
 
-    it "ignores a passed block" do
-      output = @html.text_field("test", "some value", 60, 12) { "test" }
-      output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+    describe "when passed name, value, size, maxlength" do
+      it "returns an text-'input'-element with the passed name, value, size and maxlength" do
+        output = @html.text_field("test", "some value", 60, 12)
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      end
+
+      it "ignores a passed block" do
+        output = @html.text_field("test", "some value", 60, 12) { "test" }
+        output.should equal_element("INPUT", {"NAME" => "test", "TYPE" => "text", "VALUE" => "some value", "SIZE" => "60", "MAXLENGTH" => 12}, "", not_closed: true)
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "returns a checkbox-'input'-element using the passed Hash for attributes" do
-      output = @html.text_field("NAME" => "test", "VALUE" => "some value")
-      output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "text" }, "", not_closed: true)
+    describe "when passed Hash" do
+      it "returns a checkbox-'input'-element using the passed Hash for attributes" do
+        output = @html.text_field("NAME" => "test", "VALUE" => "some value")
+        output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "text" }, "", not_closed: true)
 
-      output = @html.text_field("TYPE" => "hidden")
-      output.should equal_element("INPUT", {"TYPE" => "text"}, "", not_closed: true)
-    end
+        output = @html.text_field("TYPE" => "hidden")
+        output.should equal_element("INPUT", {"TYPE" => "text"}, "", not_closed: true)
+      end
 
-    it "ignores a passed block" do
-      output = @html.text_field("NAME" => "test", "VALUE" => "some value") { "test" }
-      output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "text" }, "", not_closed: true)
+      it "ignores a passed block" do
+        output = @html.text_field("NAME" => "test", "VALUE" => "some value") { "test" }
+        output.should equal_element("INPUT", { "NAME" => "test", "VALUE" => "some value", "TYPE" => "text" }, "", not_closed: true)
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/htmlextension/textarea_spec.rb b/spec/ruby/library/cgi/htmlextension/textarea_spec.rb
index db84a973d2..99c6d3dd2d 100644
--- a/spec/ruby/library/cgi/htmlextension/textarea_spec.rb
+++ b/spec/ruby/library/cgi/htmlextension/textarea_spec.rb
@@ -1,73 +1,76 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'fixtures/common'
 
-describe "CGI::HtmlExtension#textarea" do
-  before :each do
-    @html = CGISpecs.cgi_new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'fixtures/common'
 
-  describe "when passed no arguments" do
-    it "returns an 'textarea'-element without a name" do
-      output = @html.textarea
-      output.should equal_element("TEXTAREA", {"NAME" => "", "COLS" => "70", "ROWS" => "10"}, "")
+  describe "CGI::HtmlExtension#textarea" do
+    before :each do
+      @html = CGISpecs.cgi_new
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.textarea { "Example" }
-      output.should equal_element("TEXTAREA", {"NAME" => "", "COLS" => "70", "ROWS" => "10"}, "Example")
-    end
-  end
+    describe "when passed no arguments" do
+      it "returns an 'textarea'-element without a name" do
+        output = @html.textarea
+        output.should equal_element("TEXTAREA", {"NAME" => "", "COLS" => "70", "ROWS" => "10"}, "")
+      end
 
-  describe "when passed name" do
-    it "returns an 'textarea'-element with the passed name" do
-      output = @html.textarea("test")
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "70", "ROWS" => "10"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.textarea { "Example" }
+        output.should equal_element("TEXTAREA", {"NAME" => "", "COLS" => "70", "ROWS" => "10"}, "Example")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.textarea("test") { "Example" }
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "70", "ROWS" => "10"}, "Example")
-    end
-  end
+    describe "when passed name" do
+      it "returns an 'textarea'-element with the passed name" do
+        output = @html.textarea("test")
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "70", "ROWS" => "10"}, "")
+      end
 
-  describe "when passed name, cols" do
-    it "returns an 'textarea'-element with the passed name and the passed amount of columns" do
-      output = @html.textarea("test", 40)
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "10"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.textarea("test") { "Example" }
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "70", "ROWS" => "10"}, "Example")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.textarea("test", 40) { "Example" }
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "10"}, "Example")
-    end
-  end
+    describe "when passed name, cols" do
+      it "returns an 'textarea'-element with the passed name and the passed amount of columns" do
+        output = @html.textarea("test", 40)
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "10"}, "")
+      end
 
-  describe "when passed name, cols, rows" do
-    it "returns an 'textarea'-element with the passed name, the passed amount of columns and the passed number of rows" do
-      output = @html.textarea("test", 40, 5)
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "5"}, "")
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.textarea("test", 40) { "Example" }
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "10"}, "Example")
+      end
     end
 
-    it "includes the return value of the passed block when passed a block" do
-      output = @html.textarea("test", 40, 5) { "Example" }
-      output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "5"}, "Example")
+    describe "when passed name, cols, rows" do
+      it "returns an 'textarea'-element with the passed name, the passed amount of columns and the passed number of rows" do
+        output = @html.textarea("test", 40, 5)
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "5"}, "")
+      end
+
+      it "includes the return value of the passed block when passed a block" do
+        output = @html.textarea("test", 40, 5) { "Example" }
+        output.should equal_element("TEXTAREA", {"NAME" => "test", "COLS" => "40", "ROWS" => "5"}, "Example")
+      end
     end
-  end
 
-  describe "when passed Hash" do
-    it "uses the passed Hash as attributes" do
-      @html.textarea("ID" => "test").should == '<TEXTAREA ID="test"></TEXTAREA>'
+    describe "when passed Hash" do
+      it "uses the passed Hash as attributes" do
+        @html.textarea("ID" => "test").should == '<TEXTAREA ID="test"></TEXTAREA>'
 
-      attributes = {"ID" => "test-id", "NAME" => "test-name"}
-      output = @html.textarea(attributes)
-      output.should equal_element("TEXTAREA", attributes, "")
-    end
+        attributes = {"ID" => "test-id", "NAME" => "test-name"}
+        output = @html.textarea(attributes)
+        output.should equal_element("TEXTAREA", attributes, "")
+      end
 
-    it "includes the return value of the passed block when passed a block" do
-      attributes = {"ID" => "test-id", "NAME" => "test-name"}
-      output = @html.textarea(attributes) { "test" }
-      output.should equal_element("TEXTAREA", attributes, "test")
+      it "includes the return value of the passed block when passed a block" do
+        attributes = {"ID" => "test-id", "NAME" => "test-name"}
+        output = @html.textarea(attributes) { "test" }
+        output.should equal_element("TEXTAREA", attributes, "test")
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/http_header_spec.rb b/spec/ruby/library/cgi/http_header_spec.rb
index 4094bebed3..8d9f3fe9b8 100644
--- a/spec/ruby/library/cgi/http_header_spec.rb
+++ b/spec/ruby/library/cgi/http_header_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-require_relative 'shared/http_header'
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-describe "CGI#http_header" do
-  it_behaves_like :cgi_http_header, :http_header
+  require_relative 'shared/http_header'
+
+  describe "CGI#http_header" do
+    it_behaves_like :cgi_http_header, :http_header
+  end
 end
diff --git a/spec/ruby/library/cgi/initialize_spec.rb b/spec/ruby/library/cgi/initialize_spec.rb
index f794f157f0..b8ecf5cac2 100644
--- a/spec/ruby/library/cgi/initialize_spec.rb
+++ b/spec/ruby/library/cgi/initialize_spec.rb
@@ -1,133 +1,136 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI#initialize" do
-  it "is private" do
-    CGI.should have_private_instance_method(:initialize)
-  end
-end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-describe "CGI#initialize when passed no arguments" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.allocate
-  end
-
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
-
-  it "extends self with CGI::QueryExtension" do
-    @cgi.send(:initialize)
-    @cgi.should be_kind_of(CGI::QueryExtension)
+  describe "CGI#initialize" do
+    it "is private" do
+      CGI.should have_private_instance_method(:initialize)
+    end
   end
 
-  it "does not extend self with CGI::HtmlExtension" do
-    @cgi.send(:initialize)
-    @cgi.should_not be_kind_of(CGI::HtmlExtension)
-  end
+  describe "CGI#initialize when passed no arguments" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.allocate
+    end
 
-  it "does not extend self with any of the other HTML modules" do
-    @cgi.send(:initialize)
-    @cgi.should_not be_kind_of(CGI::Html3)
-    @cgi.should_not be_kind_of(CGI::HtmlExtension)
-    @cgi.should_not be_kind_of(CGI::Html4)
-    @cgi.should_not be_kind_of(CGI::Html4Tr)
-    @cgi.should_not be_kind_of(CGI::Html4Fr)
-  end
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "sets #cookies based on ENV['HTTP_COOKIE']" do
-    begin
-      old_env, ENV["HTTP_COOKIE"] = ENV["HTTP_COOKIE"], "test=test yay"
+    it "extends self with CGI::QueryExtension" do
       @cgi.send(:initialize)
-      @cgi.cookies.should == { "test"=>[ "test yay" ] }
-    ensure
-      ENV["HTTP_COOKIE"] = old_env
+      @cgi.should be_kind_of(CGI::QueryExtension)
     end
-  end
 
-  it "sets #params based on ENV['QUERY_STRING'] when ENV['REQUEST_METHOD'] is GET" do
-    begin
-      old_env_query, ENV["QUERY_STRING"] = ENV["QUERY_STRING"], "?test=a&test2=b"
-      old_env_method, ENV["REQUEST_METHOD"] = ENV["REQUEST_METHOD"], "GET"
+    it "does not extend self with CGI::HtmlExtension" do
       @cgi.send(:initialize)
-      @cgi.params.should == { "test2" => ["b"], "?test" => ["a"] }
-    ensure
-      ENV["QUERY_STRING"] = old_env_query
-      ENV["REQUEST_METHOD"] = old_env_method
+      @cgi.should_not be_kind_of(CGI::HtmlExtension)
     end
-  end
 
-  it "sets #params based on ENV['QUERY_STRING'] when ENV['REQUEST_METHOD'] is HEAD" do
-    begin
-      old_env_query, ENV["QUERY_STRING"] = ENV["QUERY_STRING"], "?test=a&test2=b"
-      old_env_method, ENV["REQUEST_METHOD"] = ENV["REQUEST_METHOD"], "HEAD"
+    it "does not extend self with any of the other HTML modules" do
       @cgi.send(:initialize)
-      @cgi.params.should == { "test2" => ["b"], "?test" => ["a"] }
-    ensure
-      ENV["QUERY_STRING"] = old_env_query
-      ENV["REQUEST_METHOD"] = old_env_method
+      @cgi.should_not be_kind_of(CGI::HtmlExtension)
+      @cgi.should_not be_kind_of(CGI::Html3)
+      @cgi.should_not be_kind_of(CGI::Html4)
+      @cgi.should_not be_kind_of(CGI::Html4Tr)
+      @cgi.should_not be_kind_of(CGI::Html4Fr)
     end
-  end
-end
 
-describe "CGI#initialize when passed type" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.allocate
-  end
+    it "sets #cookies based on ENV['HTTP_COOKIE']" do
+      begin
+        old_env, ENV["HTTP_COOKIE"] = ENV["HTTP_COOKIE"], "test=test yay"
+        @cgi.send(:initialize)
+        @cgi.cookies.should == { "test"=>[ "test yay" ] }
+      ensure
+        ENV["HTTP_COOKIE"] = old_env
+      end
+    end
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
+    it "sets #params based on ENV['QUERY_STRING'] when ENV['REQUEST_METHOD'] is GET" do
+      begin
+        old_env_query, ENV["QUERY_STRING"] = ENV["QUERY_STRING"], "?test=a&test2=b"
+        old_env_method, ENV["REQUEST_METHOD"] = ENV["REQUEST_METHOD"], "GET"
+        @cgi.send(:initialize)
+        @cgi.params.should == { "test2" => ["b"], "?test" => ["a"] }
+      ensure
+        ENV["QUERY_STRING"] = old_env_query
+        ENV["REQUEST_METHOD"] = old_env_method
+      end
+    end
+
+    it "sets #params based on ENV['QUERY_STRING'] when ENV['REQUEST_METHOD'] is HEAD" do
+      begin
+        old_env_query, ENV["QUERY_STRING"] = ENV["QUERY_STRING"], "?test=a&test2=b"
+        old_env_method, ENV["REQUEST_METHOD"] = ENV["REQUEST_METHOD"], "HEAD"
+        @cgi.send(:initialize)
+        @cgi.params.should == { "test2" => ["b"], "?test" => ["a"] }
+      ensure
+        ENV["QUERY_STRING"] = old_env_query
+        ENV["REQUEST_METHOD"] = old_env_method
+      end
+    end
   end
 
+  describe "CGI#initialize when passed type" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.allocate
+    end
 
-  it "extends self with CGI::QueryExtension" do
-    @cgi.send(:initialize, "test")
-    @cgi.should be_kind_of(CGI::QueryExtension)
-  end
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "extends self with CGI::QueryExtension, CGI::Html3 and CGI::HtmlExtension when the passed type is 'html3'" do
-    @cgi.send(:initialize, "html3")
-    @cgi.should be_kind_of(CGI::Html3)
-    @cgi.should be_kind_of(CGI::HtmlExtension)
-    @cgi.should be_kind_of(CGI::QueryExtension)
 
-    @cgi.should_not be_kind_of(CGI::Html4)
-    @cgi.should_not be_kind_of(CGI::Html4Tr)
-    @cgi.should_not be_kind_of(CGI::Html4Fr)
-  end
+    it "extends self with CGI::QueryExtension" do
+      @cgi.send(:initialize, "test")
+      @cgi.should be_kind_of(CGI::QueryExtension)
+    end
 
-  it "extends self with CGI::QueryExtension, CGI::Html4 and CGI::HtmlExtension when the passed type is 'html4'" do
-    @cgi.send(:initialize, "html4")
-    @cgi.should be_kind_of(CGI::Html4)
-    @cgi.should be_kind_of(CGI::HtmlExtension)
-    @cgi.should be_kind_of(CGI::QueryExtension)
+    it "extends self with CGI::QueryExtension, CGI::Html3 and CGI::HtmlExtension when the passed type is 'html3'" do
+      @cgi.send(:initialize, "html3")
+      @cgi.should be_kind_of(CGI::Html3)
+      @cgi.should be_kind_of(CGI::HtmlExtension)
+      @cgi.should be_kind_of(CGI::QueryExtension)
 
-    @cgi.should_not be_kind_of(CGI::Html3)
-    @cgi.should_not be_kind_of(CGI::Html4Tr)
-    @cgi.should_not be_kind_of(CGI::Html4Fr)
-  end
+      @cgi.should_not be_kind_of(CGI::Html4)
+      @cgi.should_not be_kind_of(CGI::Html4Tr)
+      @cgi.should_not be_kind_of(CGI::Html4Fr)
+    end
 
-  it "extends self with CGI::QueryExtension, CGI::Html4Tr and CGI::HtmlExtension when the passed type is 'html4Tr'" do
-    @cgi.send(:initialize, "html4Tr")
-    @cgi.should be_kind_of(CGI::Html4Tr)
-    @cgi.should be_kind_of(CGI::HtmlExtension)
-    @cgi.should be_kind_of(CGI::QueryExtension)
+    it "extends self with CGI::QueryExtension, CGI::Html4 and CGI::HtmlExtension when the passed type is 'html4'" do
+      @cgi.send(:initialize, "html4")
+      @cgi.should be_kind_of(CGI::Html4)
+      @cgi.should be_kind_of(CGI::HtmlExtension)
+      @cgi.should be_kind_of(CGI::QueryExtension)
 
-    @cgi.should_not be_kind_of(CGI::Html3)
-    @cgi.should_not be_kind_of(CGI::Html4)
-    @cgi.should_not be_kind_of(CGI::Html4Fr)
-  end
+      @cgi.should_not be_kind_of(CGI::Html3)
+      @cgi.should_not be_kind_of(CGI::Html4Tr)
+      @cgi.should_not be_kind_of(CGI::Html4Fr)
+    end
 
-  it "extends self with CGI::QueryExtension, CGI::Html4Tr, CGI::Html4Fr and CGI::HtmlExtension when the passed type is 'html4Fr'" do
-    @cgi.send(:initialize, "html4Fr")
-    @cgi.should be_kind_of(CGI::Html4Tr)
-    @cgi.should be_kind_of(CGI::Html4Fr)
-    @cgi.should be_kind_of(CGI::HtmlExtension)
-    @cgi.should be_kind_of(CGI::QueryExtension)
+    it "extends self with CGI::QueryExtension, CGI::Html4Tr and CGI::HtmlExtension when the passed type is 'html4Tr'" do
+      @cgi.send(:initialize, "html4Tr")
+      @cgi.should be_kind_of(CGI::Html4Tr)
+      @cgi.should be_kind_of(CGI::HtmlExtension)
+      @cgi.should be_kind_of(CGI::QueryExtension)
 
-    @cgi.should_not be_kind_of(CGI::Html3)
-    @cgi.should_not be_kind_of(CGI::Html4)
+      @cgi.should_not be_kind_of(CGI::Html3)
+      @cgi.should_not be_kind_of(CGI::Html4)
+      @cgi.should_not be_kind_of(CGI::Html4Fr)
+    end
+
+    it "extends self with CGI::QueryExtension, CGI::Html4Tr, CGI::Html4Fr and CGI::HtmlExtension when the passed type is 'html4Fr'" do
+      @cgi.send(:initialize, "html4Fr")
+      @cgi.should be_kind_of(CGI::Html4Tr)
+      @cgi.should be_kind_of(CGI::Html4Fr)
+      @cgi.should be_kind_of(CGI::HtmlExtension)
+      @cgi.should be_kind_of(CGI::QueryExtension)
+
+      @cgi.should_not be_kind_of(CGI::Html3)
+      @cgi.should_not be_kind_of(CGI::Html4)
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/out_spec.rb b/spec/ruby/library/cgi/out_spec.rb
index bc09f5bcbb..733e656ea1 100644
--- a/spec/ruby/library/cgi/out_spec.rb
+++ b/spec/ruby/library/cgi/out_spec.rb
@@ -1,51 +1,54 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI#out" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-    $stdout, @old_stdout = IOStub.new, $stdout
-  end
-
-  after :each do
-    $stdout = @old_stdout
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
-
-  it "it writes a HTMl header based on the passed argument to $stdout" do
-    @cgi.out { "" }
-    $stdout.should == "Content-Type: text/html\r\nContent-Length: 0\r\n\r\n"
-  end
-
-  it "appends the block's return value to the HTML header" do
-    @cgi.out { "test!" }
-    $stdout.should == "Content-Type: text/html\r\nContent-Length: 5\r\n\r\ntest!"
-  end
-
-  it "automatically sets the Content-Length Header based on the block's return value" do
-    @cgi.out { "0123456789" }
-    $stdout.should == "Content-Type: text/html\r\nContent-Length: 10\r\n\r\n0123456789"
-  end
-
-  it "includes Cookies in the @output_cookies field" do
-    @cgi.instance_variable_set(:@output_cookies, ["multiple", "cookies"])
-    @cgi.out { "" }
-    $stdout.should == "Content-Type: text/html\r\nContent-Length: 0\r\nSet-Cookie: multiple\r\nSet-Cookie: cookies\r\n\r\n"
-  end
-end
-
-describe "CGI#out when passed no block" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
-
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
-
-  it "raises a LocalJumpError" do
-    -> { @cgi.out }.should raise_error(LocalJumpError)
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+
+  describe "CGI#out" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+      $stdout, @old_stdout = IOStub.new, $stdout
+    end
+
+    after :each do
+      $stdout = @old_stdout
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
+
+    it "it writes a HTMl header based on the passed argument to $stdout" do
+      @cgi.out { "" }
+      $stdout.should == "Content-Type: text/html\r\nContent-Length: 0\r\n\r\n"
+    end
+
+    it "appends the block's return value to the HTML header" do
+      @cgi.out { "test!" }
+      $stdout.should == "Content-Type: text/html\r\nContent-Length: 5\r\n\r\ntest!"
+    end
+
+    it "automatically sets the Content-Length Header based on the block's return value" do
+      @cgi.out { "0123456789" }
+      $stdout.should == "Content-Type: text/html\r\nContent-Length: 10\r\n\r\n0123456789"
+    end
+
+    it "includes Cookies in the @output_cookies field" do
+      @cgi.instance_variable_set(:@output_cookies, ["multiple", "cookies"])
+      @cgi.out { "" }
+      $stdout.should == "Content-Type: text/html\r\nContent-Length: 0\r\nSet-Cookie: multiple\r\nSet-Cookie: cookies\r\n\r\n"
+    end
+  end
+
+  describe "CGI#out when passed no block" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
+
+    it "raises a LocalJumpError" do
+      -> { @cgi.out }.should raise_error(LocalJumpError)
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/parse_spec.rb b/spec/ruby/library/cgi/parse_spec.rb
index 04539b1226..f09270c195 100644
--- a/spec/ruby/library/cgi/parse_spec.rb
+++ b/spec/ruby/library/cgi/parse_spec.rb
@@ -1,24 +1,27 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI.parse when passed String" do
-  it "parses a HTTP Query String into a Hash" do
-    CGI.parse("test=test&a=b").should == { "a" => ["b"], "test" => ["test"] }
-    CGI.parse("test=1,2,3").should == { "test" => ["1,2,3"] }
-    CGI.parse("test=a&a=&b=").should == { "test" => ["a"], "a" => [""], "b" => [""] }
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  it "parses query strings with semicolons in place of ampersands" do
-    CGI.parse("test=test;a=b").should == { "a" => ["b"], "test" => ["test"] }
-    CGI.parse("test=a;a=;b=").should == { "test" => ["a"], "a" => [""], "b" => [""] }
-  end
+  describe "CGI.parse when passed String" do
+    it "parses a HTTP Query String into a Hash" do
+      CGI.parse("test=test&a=b").should == { "a" => ["b"], "test" => ["test"] }
+      CGI.parse("test=1,2,3").should == { "test" => ["1,2,3"] }
+      CGI.parse("test=a&a=&b=").should == { "test" => ["a"], "a" => [""], "b" => [""] }
+    end
 
-  it "allows passing multiple values for one key" do
-    CGI.parse("test=1&test=2&test=3").should == { "test" => ["1", "2", "3"] }
-    CGI.parse("test[]=1&test[]=2&test[]=3").should == { "test[]" => [ "1", "2", "3" ] }
-  end
+    it "parses query strings with semicolons in place of ampersands" do
+      CGI.parse("test=test;a=b").should == { "a" => ["b"], "test" => ["test"] }
+      CGI.parse("test=a;a=;b=").should == { "test" => ["a"], "a" => [""], "b" => [""] }
+    end
+
+    it "allows passing multiple values for one key" do
+      CGI.parse("test=1&test=2&test=3").should == { "test" => ["1", "2", "3"] }
+      CGI.parse("test[]=1&test[]=2&test[]=3").should == { "test[]" => [ "1", "2", "3" ] }
+    end
 
-  it "unescapes keys and values" do
-    CGI.parse("hello%3F=hello%21").should == { "hello?" => ["hello!"] }
+    it "unescapes keys and values" do
+      CGI.parse("hello%3F=hello%21").should == { "hello?" => ["hello!"] }
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/pretty_spec.rb b/spec/ruby/library/cgi/pretty_spec.rb
index a7b7505c15..9df1611037 100644
--- a/spec/ruby/library/cgi/pretty_spec.rb
+++ b/spec/ruby/library/cgi/pretty_spec.rb
@@ -1,24 +1,27 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI.pretty when passed html" do
-  it "indents the passed html String with two spaces" do
-    CGI.pretty("<HTML><BODY></BODY></HTML>").should == <<-EOS
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+
+  describe "CGI.pretty when passed html" do
+    it "indents the passed html String with two spaces" do
+      CGI.pretty("<HTML><BODY></BODY></HTML>").should == <<-EOS
 <HTML>
   <BODY>
   </BODY>
 </HTML>
 EOS
+    end
   end
-end
 
-describe "CGI.pretty when passed html, indentation_unit" do
-  it "indents the passed html String with the passed indentation_unit" do
-    CGI.pretty("<HTML><BODY></BODY></HTML>", "\t").should == <<-EOS
+  describe "CGI.pretty when passed html, indentation_unit" do
+    it "indents the passed html String with the passed indentation_unit" do
+      CGI.pretty("<HTML><BODY></BODY></HTML>", "\t").should == <<-EOS
 <HTML>
 \t<BODY>
 \t</BODY>
 </HTML>
 EOS
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/print_spec.rb b/spec/ruby/library/cgi/print_spec.rb
index 18ab8d673b..f4f461c5c0 100644
--- a/spec/ruby/library/cgi/print_spec.rb
+++ b/spec/ruby/library/cgi/print_spec.rb
@@ -1,26 +1,29 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI#print" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI#print" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
 
-  it "passes all arguments to $stdout.print" do
-    $stdout.should_receive(:print).with("test")
-    @cgi.print("test")
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-    $stdout.should_receive(:print).with("one", "two", "three", ["four", "five"])
-    @cgi.print("one", "two", "three", ["four", "five"])
-  end
+    it "passes all arguments to $stdout.print" do
+      $stdout.should_receive(:print).with("test")
+      @cgi.print("test")
+
+      $stdout.should_receive(:print).with("one", "two", "three", ["four", "five"])
+      @cgi.print("one", "two", "three", ["four", "five"])
+    end
 
-  it "returns the result of calling $stdout.print" do
-    $stdout.should_receive(:print).with("test").and_return(:expected)
-    @cgi.print("test").should == :expected
+    it "returns the result of calling $stdout.print" do
+      $stdout.should_receive(:print).with("test").and_return(:expected)
+      @cgi.print("test").should == :expected
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/accept_charset_spec.rb b/spec/ruby/library/cgi/queryextension/accept_charset_spec.rb
index 0487569b9c..be05f0c175 100644
--- a/spec/ruby/library/cgi/queryextension/accept_charset_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/accept_charset_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#accept_charset" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#accept_charset" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_ACCEPT_CHARSET']" do
-    old_value, ENV['HTTP_ACCEPT_CHARSET'] = ENV['HTTP_ACCEPT_CHARSET'], "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
-    begin
-      @cgi.accept_charset.should == "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
-    ensure
-      ENV['HTTP_ACCEPT_CHARSET'] = old_value
+    it "returns ENV['HTTP_ACCEPT_CHARSET']" do
+      old_value, ENV['HTTP_ACCEPT_CHARSET'] = ENV['HTTP_ACCEPT_CHARSET'], "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
+      begin
+        @cgi.accept_charset.should == "ISO-8859-1,utf-8;q=0.7,*;q=0.7"
+      ensure
+        ENV['HTTP_ACCEPT_CHARSET'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/accept_encoding_spec.rb b/spec/ruby/library/cgi/queryextension/accept_encoding_spec.rb
index 35ff3c2b30..42eb4a49b5 100644
--- a/spec/ruby/library/cgi/queryextension/accept_encoding_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/accept_encoding_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#accept_encoding" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#accept_encoding" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_ACCEPT_ENCODING']" do
-    old_value, ENV['HTTP_ACCEPT_ENCODING'] = ENV['HTTP_ACCEPT_ENCODING'], "gzip,deflate"
-    begin
-      @cgi.accept_encoding.should == "gzip,deflate"
-    ensure
-      ENV['HTTP_ACCEPT_ENCODING'] = old_value
+    it "returns ENV['HTTP_ACCEPT_ENCODING']" do
+      old_value, ENV['HTTP_ACCEPT_ENCODING'] = ENV['HTTP_ACCEPT_ENCODING'], "gzip,deflate"
+      begin
+        @cgi.accept_encoding.should == "gzip,deflate"
+      ensure
+        ENV['HTTP_ACCEPT_ENCODING'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/accept_language_spec.rb b/spec/ruby/library/cgi/queryextension/accept_language_spec.rb
index 4a15d58914..19f29c6345 100644
--- a/spec/ruby/library/cgi/queryextension/accept_language_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/accept_language_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#accept_language" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#accept_language" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_ACCEPT_LANGUAGE']" do
-    old_value, ENV['HTTP_ACCEPT_LANGUAGE'] = ENV['HTTP_ACCEPT_LANGUAGE'], "en-us,en;q=0.5"
-    begin
-      @cgi.accept_language.should == "en-us,en;q=0.5"
-    ensure
-      ENV['HTTP_ACCEPT_LANGUAGE'] = old_value
+    it "returns ENV['HTTP_ACCEPT_LANGUAGE']" do
+      old_value, ENV['HTTP_ACCEPT_LANGUAGE'] = ENV['HTTP_ACCEPT_LANGUAGE'], "en-us,en;q=0.5"
+      begin
+        @cgi.accept_language.should == "en-us,en;q=0.5"
+      ensure
+        ENV['HTTP_ACCEPT_LANGUAGE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/accept_spec.rb b/spec/ruby/library/cgi/queryextension/accept_spec.rb
index af5209ffbe..dcae39a736 100644
--- a/spec/ruby/library/cgi/queryextension/accept_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/accept_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#accept" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#accept" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_ACCEPT']" do
-    old_value, ENV['HTTP_ACCEPT'] = ENV['HTTP_ACCEPT'], "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
-    begin
-      @cgi.accept.should == "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
-    ensure
-      ENV['HTTP_ACCEPT'] = old_value
+    it "returns ENV['HTTP_ACCEPT']" do
+      old_value, ENV['HTTP_ACCEPT'] = ENV['HTTP_ACCEPT'], "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
+      begin
+        @cgi.accept.should == "text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5"
+      ensure
+        ENV['HTTP_ACCEPT'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/auth_type_spec.rb b/spec/ruby/library/cgi/queryextension/auth_type_spec.rb
index 25318269b1..75e9cdb27a 100644
--- a/spec/ruby/library/cgi/queryextension/auth_type_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/auth_type_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#auth_type" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#auth_type" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['AUTH_TYPE']" do
-    old_value, ENV['AUTH_TYPE'] = ENV['AUTH_TYPE'], "Basic"
-    begin
-      @cgi.auth_type.should == "Basic"
-    ensure
-      ENV['AUTH_TYPE'] = old_value
+    it "returns ENV['AUTH_TYPE']" do
+      old_value, ENV['AUTH_TYPE'] = ENV['AUTH_TYPE'], "Basic"
+      begin
+        @cgi.auth_type.should == "Basic"
+      ensure
+        ENV['AUTH_TYPE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/cache_control_spec.rb b/spec/ruby/library/cgi/queryextension/cache_control_spec.rb
index 0471307c22..c4b727e671 100644
--- a/spec/ruby/library/cgi/queryextension/cache_control_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/cache_control_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#cache_control" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#cache_control" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_CACHE_CONTROL']" do
-    old_value, ENV['HTTP_CACHE_CONTROL'] = ENV['HTTP_CACHE_CONTROL'], "no-cache"
-    begin
-      @cgi.cache_control.should == "no-cache"
-    ensure
-      ENV['HTTP_CACHE_CONTROL'] = old_value
+    it "returns ENV['HTTP_CACHE_CONTROL']" do
+      old_value, ENV['HTTP_CACHE_CONTROL'] = ENV['HTTP_CACHE_CONTROL'], "no-cache"
+      begin
+        @cgi.cache_control.should == "no-cache"
+      ensure
+        ENV['HTTP_CACHE_CONTROL'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/content_length_spec.rb b/spec/ruby/library/cgi/queryextension/content_length_spec.rb
index de823f7119..a8b87e148c 100644
--- a/spec/ruby/library/cgi/queryextension/content_length_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/content_length_spec.rb
@@ -1,26 +1,29 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#content_length" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#content_length" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['CONTENT_LENGTH'] as Integer" do
-    old_value = ENV['CONTENT_LENGTH']
-    begin
-      ENV['CONTENT_LENGTH'] = nil
-      @cgi.content_length.should be_nil
+    it "returns ENV['CONTENT_LENGTH'] as Integer" do
+      old_value = ENV['CONTENT_LENGTH']
+      begin
+        ENV['CONTENT_LENGTH'] = nil
+        @cgi.content_length.should be_nil
 
-      ENV['CONTENT_LENGTH'] = "100"
-      @cgi.content_length.should eql(100)
-    ensure
-      ENV['CONTENT_LENGTH'] = old_value
+        ENV['CONTENT_LENGTH'] = "100"
+        @cgi.content_length.should eql(100)
+      ensure
+        ENV['CONTENT_LENGTH'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/content_type_spec.rb b/spec/ruby/library/cgi/queryextension/content_type_spec.rb
index 49b8389c87..d3cbdf0b14 100644
--- a/spec/ruby/library/cgi/queryextension/content_type_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/content_type_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#content_type" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#content_type" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['CONTENT_TYPE']" do
-    old_value, ENV['CONTENT_TYPE'] = ENV['CONTENT_TYPE'], "text/html"
-    begin
-      @cgi.content_type.should == "text/html"
-    ensure
-      ENV['CONTENT_TYPE'] = old_value
+    it "returns ENV['CONTENT_TYPE']" do
+      old_value, ENV['CONTENT_TYPE'] = ENV['CONTENT_TYPE'], "text/html"
+      begin
+        @cgi.content_type.should == "text/html"
+      ensure
+        ENV['CONTENT_TYPE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/cookies_spec.rb b/spec/ruby/library/cgi/queryextension/cookies_spec.rb
index 4befd61ab7..266fe0c721 100644
--- a/spec/ruby/library/cgi/queryextension/cookies_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/cookies_spec.rb
@@ -1,10 +1,13 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#cookies" do
-  it "needs to be reviewed for spec completeness"
-end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+
+  describe "CGI::QueryExtension#cookies" do
+    it "needs to be reviewed for spec completeness"
+  end
 
-describe "CGI::QueryExtension#cookies=" do
-  it "needs to be reviewed for spec completeness"
+  describe "CGI::QueryExtension#cookies=" do
+    it "needs to be reviewed for spec completeness"
+  end
 end
diff --git a/spec/ruby/library/cgi/queryextension/element_reference_spec.rb b/spec/ruby/library/cgi/queryextension/element_reference_spec.rb
index 6ac5b46407..0b57387efc 100644
--- a/spec/ruby/library/cgi/queryextension/element_reference_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/element_reference_spec.rb
@@ -1,27 +1,30 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#[]" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    ENV['QUERY_STRING'], @old_query_string = "one=a&two=b&two=c", ENV['QUERY_STRING']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-    ENV['QUERY_STRING']   = @old_query_string
-  end
+  describe "CGI::QueryExtension#[]" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      ENV['QUERY_STRING'], @old_query_string = "one=a&two=b&two=c", ENV['QUERY_STRING']
+      @cgi = CGI.new
+    end
 
-  it "it returns the value for the parameter with the given key" do
-    @cgi["one"].should == "a"
-  end
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+      ENV['QUERY_STRING']   = @old_query_string
+    end
 
-  it "only returns the first value for parameters with multiple values" do
-    @cgi["two"].should == "b"
-  end
+    it "it returns the value for the parameter with the given key" do
+      @cgi["one"].should == "a"
+    end
+
+    it "only returns the first value for parameters with multiple values" do
+      @cgi["two"].should == "b"
+    end
 
-  it "returns a String" do
-    @cgi["one"].should be_kind_of(String)
+    it "returns a String" do
+      @cgi["one"].should be_kind_of(String)
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/from_spec.rb b/spec/ruby/library/cgi/queryextension/from_spec.rb
index 04a992cfc7..b341e0be10 100644
--- a/spec/ruby/library/cgi/queryextension/from_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/from_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#from" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#from" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_FROM']" do
-    old_value, ENV['HTTP_FROM'] = ENV['HTTP_FROM'], "googlebot(at)googlebot.com"
-    begin
-      @cgi.from.should == "googlebot(at)googlebot.com"
-    ensure
-      ENV['HTTP_FROM'] = old_value
+    it "returns ENV['HTTP_FROM']" do
+      old_value, ENV['HTTP_FROM'] = ENV['HTTP_FROM'], "googlebot(at)googlebot.com"
+      begin
+        @cgi.from.should == "googlebot(at)googlebot.com"
+      ensure
+        ENV['HTTP_FROM'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/gateway_interface_spec.rb b/spec/ruby/library/cgi/queryextension/gateway_interface_spec.rb
index 3ead5bd8bf..c82522326b 100644
--- a/spec/ruby/library/cgi/queryextension/gateway_interface_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/gateway_interface_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#gateway_interface" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#gateway_interface" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['GATEWAY_INTERFACE']" do
-    old_value, ENV['GATEWAY_INTERFACE'] = ENV['GATEWAY_INTERFACE'], "CGI/1.1"
-    begin
-      @cgi.gateway_interface.should == "CGI/1.1"
-    ensure
-      ENV['GATEWAY_INTERFACE'] = old_value
+    it "returns ENV['GATEWAY_INTERFACE']" do
+      old_value, ENV['GATEWAY_INTERFACE'] = ENV['GATEWAY_INTERFACE'], "CGI/1.1"
+      begin
+        @cgi.gateway_interface.should == "CGI/1.1"
+      ensure
+        ENV['GATEWAY_INTERFACE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/has_key_spec.rb b/spec/ruby/library/cgi/queryextension/has_key_spec.rb
index 525b45b507..43f7aae1b2 100644
--- a/spec/ruby/library/cgi/queryextension/has_key_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/has_key_spec.rb
@@ -1,7 +1,10 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'shared/has_key'
 
-describe "CGI::QueryExtension#has_key?" do
-  it_behaves_like :cgi_query_extension_has_key_p, :has_key?
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'shared/has_key'
+
+  describe "CGI::QueryExtension#has_key?" do
+    it_behaves_like :cgi_query_extension_has_key_p, :has_key?
+  end
 end
diff --git a/spec/ruby/library/cgi/queryextension/host_spec.rb b/spec/ruby/library/cgi/queryextension/host_spec.rb
index e820e0afc3..e1047c942b 100644
--- a/spec/ruby/library/cgi/queryextension/host_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/host_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#host" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#host" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_HOST']" do
-    old_value, ENV['HTTP_HOST'] = ENV['HTTP_HOST'], "localhost"
-    begin
-      @cgi.host.should == "localhost"
-    ensure
-      ENV['HTTP_HOST'] = old_value
+    it "returns ENV['HTTP_HOST']" do
+      old_value, ENV['HTTP_HOST'] = ENV['HTTP_HOST'], "localhost"
+      begin
+        @cgi.host.should == "localhost"
+      ensure
+        ENV['HTTP_HOST'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/include_spec.rb b/spec/ruby/library/cgi/queryextension/include_spec.rb
index 12365ea284..7275c309f9 100644
--- a/spec/ruby/library/cgi/queryextension/include_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/include_spec.rb
@@ -1,7 +1,10 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'shared/has_key'
 
-describe "CGI::QueryExtension#include?" do
-  it_behaves_like :cgi_query_extension_has_key_p, :include?
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'shared/has_key'
+
+  describe "CGI::QueryExtension#include?" do
+    it_behaves_like :cgi_query_extension_has_key_p, :include?
+  end
 end
diff --git a/spec/ruby/library/cgi/queryextension/key_spec.rb b/spec/ruby/library/cgi/queryextension/key_spec.rb
index d0f1e4cee2..dc2f52fbe0 100644
--- a/spec/ruby/library/cgi/queryextension/key_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/key_spec.rb
@@ -1,7 +1,10 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require_relative 'shared/has_key'
 
-describe "CGI::QueryExtension#key?" do
-  it_behaves_like :cgi_query_extension_has_key_p, :key?
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require_relative 'shared/has_key'
+
+  describe "CGI::QueryExtension#key?" do
+    it_behaves_like :cgi_query_extension_has_key_p, :key?
+  end
 end
diff --git a/spec/ruby/library/cgi/queryextension/keys_spec.rb b/spec/ruby/library/cgi/queryextension/keys_spec.rb
index 14d77180fa..bb16914065 100644
--- a/spec/ruby/library/cgi/queryextension/keys_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/keys_spec.rb
@@ -1,20 +1,23 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#keys" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    ENV['QUERY_STRING'], @old_query_string = "one=a&two=b", ENV['QUERY_STRING']
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-    @cgi = CGI.new
-  end
+  describe "CGI::QueryExtension#keys" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      ENV['QUERY_STRING'], @old_query_string = "one=a&two=b", ENV['QUERY_STRING']
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-    ENV['QUERY_STRING']   = @old_query_string
-  end
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+      ENV['QUERY_STRING']   = @old_query_string
+    end
 
-  it "returns all parameter keys as an Array" do
-    @cgi.keys.sort.should == ["one", "two"]
+    it "returns all parameter keys as an Array" do
+      @cgi.keys.sort.should == ["one", "two"]
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/multipart_spec.rb b/spec/ruby/library/cgi/queryextension/multipart_spec.rb
index ced4cb05a1..281791892c 100644
--- a/spec/ruby/library/cgi/queryextension/multipart_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/multipart_spec.rb
@@ -1,20 +1,22 @@
 require_relative '../../../spec_helper'
-require 'cgi'
-require "stringio"
 
-describe "CGI::QueryExtension#multipart?" do
-  before :each do
-    @old_stdin = $stdin
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+  require "stringio"
 
-    @old_request_method = ENV['REQUEST_METHOD']
-    @old_content_type = ENV['CONTENT_TYPE']
-    @old_content_length = ENV['CONTENT_LENGTH']
+  describe "CGI::QueryExtension#multipart?" do
+    before :each do
+      @old_stdin = $stdin
 
-    ENV['REQUEST_METHOD'] = "POST"
-    ENV["CONTENT_TYPE"] = "multipart/form-data; boundary=---------------------------1137522503144128232716531729"
-    ENV["CONTENT_LENGTH"] = "222"
+      @old_request_method = ENV['REQUEST_METHOD']
+      @old_content_type = ENV['CONTENT_TYPE']
+      @old_content_length = ENV['CONTENT_LENGTH']
 
-    $stdin = StringIO.new <<-EOS
+      ENV['REQUEST_METHOD'] = "POST"
+      ENV["CONTENT_TYPE"] = "multipart/form-data; boundary=---------------------------1137522503144128232716531729"
+      ENV["CONTENT_LENGTH"] = "222"
+
+      $stdin = StringIO.new <<-EOS
 -----------------------------1137522503144128232716531729\r
 Content-Disposition: form-data; name="file"; filename=""\r
 Content-Type: application/octet-stream\r
@@ -23,18 +25,19 @@ Content-Type: application/octet-stream\r
 -----------------------------1137522503144128232716531729--\r
 EOS
 
-    @cgi = CGI.new
-  end
+      @cgi = CGI.new
+    end
 
-  after :each do
-    $stdin = @old_stdin
+    after :each do
+      $stdin = @old_stdin
 
-    ENV['REQUEST_METHOD'] = @old_request_method
-    ENV['CONTENT_TYPE'] = @old_content_type
-    ENV['CONTENT_LENGTH'] = @old_content_length
-  end
+      ENV['REQUEST_METHOD'] = @old_request_method
+      ENV['CONTENT_TYPE'] = @old_content_type
+      ENV['CONTENT_LENGTH'] = @old_content_length
+    end
 
-  it "returns true if the current Request is a multipart request" do
-    @cgi.multipart?.should be_true
+    it "returns true if the current Request is a multipart request" do
+      @cgi.multipart?.should be_true
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/negotiate_spec.rb b/spec/ruby/library/cgi/queryextension/negotiate_spec.rb
index b6fe036042..4083e6a8cd 100644
--- a/spec/ruby/library/cgi/queryextension/negotiate_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/negotiate_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#negotiate" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#negotiate" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_NEGOTIATE']" do
-    old_value, ENV['HTTP_NEGOTIATE'] = ENV['HTTP_NEGOTIATE'], "trans"
-    begin
-      @cgi.negotiate.should == "trans"
-    ensure
-      ENV['HTTP_NEGOTIATE'] = old_value
+    it "returns ENV['HTTP_NEGOTIATE']" do
+      old_value, ENV['HTTP_NEGOTIATE'] = ENV['HTTP_NEGOTIATE'], "trans"
+      begin
+        @cgi.negotiate.should == "trans"
+      ensure
+        ENV['HTTP_NEGOTIATE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/params_spec.rb b/spec/ruby/library/cgi/queryextension/params_spec.rb
index f4449e3c8a..938028ea14 100644
--- a/spec/ruby/library/cgi/queryextension/params_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/params_spec.rb
@@ -1,37 +1,40 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#params" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    ENV['QUERY_STRING'], @old_query_string = "one=a&two=b&two=c&three", ENV['QUERY_STRING']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['QUERY_STRING'] = @old_query_string
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#params" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      ENV['QUERY_STRING'], @old_query_string = "one=a&two=b&two=c&three", ENV['QUERY_STRING']
+      @cgi = CGI.new
+    end
 
-  it "returns the parsed HTTP Query Params" do
-    @cgi.params.should == {"three"=>[], "two"=>["b", "c"], "one"=>["a"]}
-  end
-end
+    after :each do
+      ENV['QUERY_STRING'] = @old_query_string
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-describe "CGI::QueryExtension#params=" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
+    it "returns the parsed HTTP Query Params" do
+      @cgi.params.should == {"three"=>[], "two"=>["b", "c"], "one"=>["a"]}
+    end
   end
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#params=" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "sets the HTTP Query Params to the passed argument" do
-    @cgi.params.should == {}
+    it "sets the HTTP Query Params to the passed argument" do
+      @cgi.params.should == {}
 
-    @cgi.params = {"one"=>["a"], "two"=>["b", "c"]}
-    @cgi.params.should == {"one"=>["a"], "two"=>["b", "c"]}
+      @cgi.params = {"one"=>["a"], "two"=>["b", "c"]}
+      @cgi.params.should == {"one"=>["a"], "two"=>["b", "c"]}
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/path_info_spec.rb b/spec/ruby/library/cgi/queryextension/path_info_spec.rb
index 9785df85f1..9b7834c514 100644
--- a/spec/ruby/library/cgi/queryextension/path_info_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/path_info_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#path_info" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#path_info" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['PATH_INFO']" do
-    old_value, ENV['PATH_INFO'] = ENV['PATH_INFO'], "/test/path"
-    begin
-      @cgi.path_info.should == "/test/path"
-    ensure
-      ENV['PATH_INFO'] = old_value
+    it "returns ENV['PATH_INFO']" do
+      old_value, ENV['PATH_INFO'] = ENV['PATH_INFO'], "/test/path"
+      begin
+        @cgi.path_info.should == "/test/path"
+      ensure
+        ENV['PATH_INFO'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/path_translated_spec.rb b/spec/ruby/library/cgi/queryextension/path_translated_spec.rb
index 417a749341..a773aaafdb 100644
--- a/spec/ruby/library/cgi/queryextension/path_translated_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/path_translated_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#path_translated" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#path_translated" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['PATH_TRANSLATED']" do
-    old_value, ENV['PATH_TRANSLATED'] = ENV['PATH_TRANSLATED'], "/full/path/to/dir"
-    begin
-      @cgi.path_translated.should == "/full/path/to/dir"
-    ensure
-      ENV['PATH_TRANSLATED'] = old_value
+    it "returns ENV['PATH_TRANSLATED']" do
+      old_value, ENV['PATH_TRANSLATED'] = ENV['PATH_TRANSLATED'], "/full/path/to/dir"
+      begin
+        @cgi.path_translated.should == "/full/path/to/dir"
+      ensure
+        ENV['PATH_TRANSLATED'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/pragma_spec.rb b/spec/ruby/library/cgi/queryextension/pragma_spec.rb
index 02d5c91221..be384182a5 100644
--- a/spec/ruby/library/cgi/queryextension/pragma_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/pragma_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#pragma" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#pragma" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_PRAGMA']" do
-    old_value, ENV['HTTP_PRAGMA'] = ENV['HTTP_PRAGMA'], "no-cache"
-    begin
-      @cgi.pragma.should == "no-cache"
-    ensure
-      ENV['HTTP_PRAGMA'] = old_value
+    it "returns ENV['HTTP_PRAGMA']" do
+      old_value, ENV['HTTP_PRAGMA'] = ENV['HTTP_PRAGMA'], "no-cache"
+      begin
+        @cgi.pragma.should == "no-cache"
+      ensure
+        ENV['HTTP_PRAGMA'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/query_string_spec.rb b/spec/ruby/library/cgi/queryextension/query_string_spec.rb
index a6b454a7eb..64fbeaea10 100644
--- a/spec/ruby/library/cgi/queryextension/query_string_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/query_string_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#query_string" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#query_string" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['QUERY_STRING']" do
-    old_value, ENV['QUERY_STRING'] = ENV['QUERY_STRING'], "one=a&two=b"
-    begin
-      @cgi.query_string.should == "one=a&two=b"
-    ensure
-      ENV['QUERY_STRING'] = old_value
+    it "returns ENV['QUERY_STRING']" do
+      old_value, ENV['QUERY_STRING'] = ENV['QUERY_STRING'], "one=a&two=b"
+      begin
+        @cgi.query_string.should == "one=a&two=b"
+      ensure
+        ENV['QUERY_STRING'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/raw_cookie2_spec.rb b/spec/ruby/library/cgi/queryextension/raw_cookie2_spec.rb
index 3d7072e346..30d314aca1 100644
--- a/spec/ruby/library/cgi/queryextension/raw_cookie2_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/raw_cookie2_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#raw_cookie2" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#raw_cookie2" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_COOKIE2']" do
-    old_value, ENV['HTTP_COOKIE2'] = ENV['HTTP_COOKIE2'], "some_cookie=data"
-    begin
-      @cgi.raw_cookie2.should == "some_cookie=data"
-    ensure
-      ENV['HTTP_COOKIE2'] = old_value
+    it "returns ENV['HTTP_COOKIE2']" do
+      old_value, ENV['HTTP_COOKIE2'] = ENV['HTTP_COOKIE2'], "some_cookie=data"
+      begin
+        @cgi.raw_cookie2.should == "some_cookie=data"
+      ensure
+        ENV['HTTP_COOKIE2'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/raw_cookie_spec.rb b/spec/ruby/library/cgi/queryextension/raw_cookie_spec.rb
index ede7b9ff87..affa504b39 100644
--- a/spec/ruby/library/cgi/queryextension/raw_cookie_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/raw_cookie_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#raw_cookie" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#raw_cookie" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_COOKIE']" do
-    old_value, ENV['HTTP_COOKIE'] = ENV['HTTP_COOKIE'], "some_cookie=data"
-    begin
-      @cgi.raw_cookie.should == "some_cookie=data"
-    ensure
-      ENV['HTTP_COOKIE'] = old_value
+    it "returns ENV['HTTP_COOKIE']" do
+      old_value, ENV['HTTP_COOKIE'] = ENV['HTTP_COOKIE'], "some_cookie=data"
+      begin
+        @cgi.raw_cookie.should == "some_cookie=data"
+      ensure
+        ENV['HTTP_COOKIE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/referer_spec.rb b/spec/ruby/library/cgi/queryextension/referer_spec.rb
index 6cd5dc96f8..53fc19ddd0 100644
--- a/spec/ruby/library/cgi/queryextension/referer_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/referer_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#referer" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#referer" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_REFERER']" do
-    old_value, ENV['HTTP_REFERER'] = ENV['HTTP_REFERER'], "example.com"
-    begin
-      @cgi.referer.should == "example.com"
-    ensure
-      ENV['HTTP_REFERER'] = old_value
+    it "returns ENV['HTTP_REFERER']" do
+      old_value, ENV['HTTP_REFERER'] = ENV['HTTP_REFERER'], "example.com"
+      begin
+        @cgi.referer.should == "example.com"
+      ensure
+        ENV['HTTP_REFERER'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/remote_addr_spec.rb b/spec/ruby/library/cgi/queryextension/remote_addr_spec.rb
index 0259402b23..7b5addc2d5 100644
--- a/spec/ruby/library/cgi/queryextension/remote_addr_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/remote_addr_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#remote_addr" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#remote_addr" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['REMOTE_ADDR']" do
-    old_value, ENV['REMOTE_ADDR'] = ENV['REMOTE_ADDR'], "127.0.0.1"
-    begin
-      @cgi.remote_addr.should == "127.0.0.1"
-    ensure
-      ENV['REMOTE_ADDR'] = old_value
+    it "returns ENV['REMOTE_ADDR']" do
+      old_value, ENV['REMOTE_ADDR'] = ENV['REMOTE_ADDR'], "127.0.0.1"
+      begin
+        @cgi.remote_addr.should == "127.0.0.1"
+      ensure
+        ENV['REMOTE_ADDR'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/remote_host_spec.rb b/spec/ruby/library/cgi/queryextension/remote_host_spec.rb
index cf77e0031b..2dfe59ca38 100644
--- a/spec/ruby/library/cgi/queryextension/remote_host_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/remote_host_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#remote_host" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#remote_host" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['REMOTE_HOST']" do
-    old_value, ENV['REMOTE_HOST'] = ENV['REMOTE_HOST'], "test.host"
-    begin
-      @cgi.remote_host.should == "test.host"
-    ensure
-      ENV['REMOTE_HOST'] = old_value
+    it "returns ENV['REMOTE_HOST']" do
+      old_value, ENV['REMOTE_HOST'] = ENV['REMOTE_HOST'], "test.host"
+      begin
+        @cgi.remote_host.should == "test.host"
+      ensure
+        ENV['REMOTE_HOST'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/remote_ident_spec.rb b/spec/ruby/library/cgi/queryextension/remote_ident_spec.rb
index 5b51d6b8ee..bb05fc7942 100644
--- a/spec/ruby/library/cgi/queryextension/remote_ident_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/remote_ident_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#remote_ident" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#remote_ident" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['REMOTE_IDENT']" do
-    old_value, ENV['REMOTE_IDENT'] = ENV['REMOTE_IDENT'], "no-idea-what-this-is-for"
-    begin
-      @cgi.remote_ident.should == "no-idea-what-this-is-for"
-    ensure
-      ENV['REMOTE_IDENT'] = old_value
+    it "returns ENV['REMOTE_IDENT']" do
+      old_value, ENV['REMOTE_IDENT'] = ENV['REMOTE_IDENT'], "no-idea-what-this-is-for"
+      begin
+        @cgi.remote_ident.should == "no-idea-what-this-is-for"
+      ensure
+        ENV['REMOTE_IDENT'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/remote_user_spec.rb b/spec/ruby/library/cgi/queryextension/remote_user_spec.rb
index 1a93bb6561..29856302ab 100644
--- a/spec/ruby/library/cgi/queryextension/remote_user_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/remote_user_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#remote_user" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#remote_user" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['REMOTE_USER']" do
-    old_value, ENV['REMOTE_USER'] = ENV['REMOTE_USER'], "username"
-    begin
-      @cgi.remote_user.should == "username"
-    ensure
-      ENV['REMOTE_USER'] = old_value
+    it "returns ENV['REMOTE_USER']" do
+      old_value, ENV['REMOTE_USER'] = ENV['REMOTE_USER'], "username"
+      begin
+        @cgi.remote_user.should == "username"
+      ensure
+        ENV['REMOTE_USER'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/request_method_spec.rb b/spec/ruby/library/cgi/queryextension/request_method_spec.rb
index eabdd6998b..7331b134d2 100644
--- a/spec/ruby/library/cgi/queryextension/request_method_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/request_method_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#request_method" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#request_method" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['REQUEST_METHOD']" do
-    old_value, ENV['REQUEST_METHOD'] = ENV['REQUEST_METHOD'], "GET"
-    begin
-      @cgi.request_method.should == "GET"
-    ensure
-      ENV['REQUEST_METHOD'] = old_value
+    it "returns ENV['REQUEST_METHOD']" do
+      old_value, ENV['REQUEST_METHOD'] = ENV['REQUEST_METHOD'], "GET"
+      begin
+        @cgi.request_method.should == "GET"
+      ensure
+        ENV['REQUEST_METHOD'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/script_name_spec.rb b/spec/ruby/library/cgi/queryextension/script_name_spec.rb
index 341b7b6fea..4b359a545f 100644
--- a/spec/ruby/library/cgi/queryextension/script_name_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/script_name_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#script_name" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#script_name" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['SCRIPT_NAME']" do
-    old_value, ENV['SCRIPT_NAME'] = ENV['SCRIPT_NAME'], "/path/to/script.rb"
-    begin
-      @cgi.script_name.should == "/path/to/script.rb"
-    ensure
-      ENV['SCRIPT_NAME'] = old_value
+    it "returns ENV['SCRIPT_NAME']" do
+      old_value, ENV['SCRIPT_NAME'] = ENV['SCRIPT_NAME'], "/path/to/script.rb"
+      begin
+        @cgi.script_name.should == "/path/to/script.rb"
+      ensure
+        ENV['SCRIPT_NAME'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/server_name_spec.rb b/spec/ruby/library/cgi/queryextension/server_name_spec.rb
index b12aaf8c5c..c1f7fb4c54 100644
--- a/spec/ruby/library/cgi/queryextension/server_name_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/server_name_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#server_name" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#server_name" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['SERVER_NAME']" do
-    old_value, ENV['SERVER_NAME'] = ENV['SERVER_NAME'], "localhost"
-    begin
-      @cgi.server_name.should == "localhost"
-    ensure
-      ENV['SERVER_NAME'] = old_value
+    it "returns ENV['SERVER_NAME']" do
+      old_value, ENV['SERVER_NAME'] = ENV['SERVER_NAME'], "localhost"
+      begin
+        @cgi.server_name.should == "localhost"
+      ensure
+        ENV['SERVER_NAME'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/server_port_spec.rb b/spec/ruby/library/cgi/queryextension/server_port_spec.rb
index 0e688a99bf..60c03ea639 100644
--- a/spec/ruby/library/cgi/queryextension/server_port_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/server_port_spec.rb
@@ -1,26 +1,29 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#server_port" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#server_port" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['SERVER_PORT'] as Integer" do
-    old_value = ENV['SERVER_PORT']
-    begin
-      ENV['SERVER_PORT'] = nil
-      @cgi.server_port.should be_nil
+    it "returns ENV['SERVER_PORT'] as Integer" do
+      old_value = ENV['SERVER_PORT']
+      begin
+        ENV['SERVER_PORT'] = nil
+        @cgi.server_port.should be_nil
 
-      ENV['SERVER_PORT'] = "3000"
-      @cgi.server_port.should eql(3000)
-    ensure
-      ENV['SERVER_PORT'] = old_value
+        ENV['SERVER_PORT'] = "3000"
+        @cgi.server_port.should eql(3000)
+      ensure
+        ENV['SERVER_PORT'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/server_protocol_spec.rb b/spec/ruby/library/cgi/queryextension/server_protocol_spec.rb
index f9dcf3c5b8..fdbcc2108f 100644
--- a/spec/ruby/library/cgi/queryextension/server_protocol_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/server_protocol_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#server_protocol" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#server_protocol" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['SERVER_PROTOCOL']" do
-    old_value, ENV['SERVER_PROTOCOL'] = ENV['SERVER_PROTOCOL'], "HTTP/1.1"
-    begin
-      @cgi.server_protocol.should == "HTTP/1.1"
-    ensure
-      ENV['SERVER_PROTOCOL'] = old_value
+    it "returns ENV['SERVER_PROTOCOL']" do
+      old_value, ENV['SERVER_PROTOCOL'] = ENV['SERVER_PROTOCOL'], "HTTP/1.1"
+      begin
+        @cgi.server_protocol.should == "HTTP/1.1"
+      ensure
+        ENV['SERVER_PROTOCOL'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/server_software_spec.rb b/spec/ruby/library/cgi/queryextension/server_software_spec.rb
index df349cdf2e..c5811a2268 100644
--- a/spec/ruby/library/cgi/queryextension/server_software_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/server_software_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#server_software" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#server_software" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['SERVER_SOFTWARE']" do
-    old_value, ENV['SERVER_SOFTWARE'] = ENV['SERVER_SOFTWARE'], "Server/1.0.0"
-    begin
-      @cgi.server_software.should == "Server/1.0.0"
-    ensure
-      ENV['SERVER_SOFTWARE'] = old_value
+    it "returns ENV['SERVER_SOFTWARE']" do
+      old_value, ENV['SERVER_SOFTWARE'] = ENV['SERVER_SOFTWARE'], "Server/1.0.0"
+      begin
+        @cgi.server_software.should == "Server/1.0.0"
+      ensure
+        ENV['SERVER_SOFTWARE'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/queryextension/user_agent_spec.rb b/spec/ruby/library/cgi/queryextension/user_agent_spec.rb
index ec5ef187dd..3240352ef6 100644
--- a/spec/ruby/library/cgi/queryextension/user_agent_spec.rb
+++ b/spec/ruby/library/cgi/queryextension/user_agent_spec.rb
@@ -1,22 +1,25 @@
 require_relative '../../../spec_helper'
-require 'cgi'
 
-describe "CGI::QueryExtension#user_agent" do
-  before :each do
-    ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
-    @cgi = CGI.new
-  end
+ruby_version_is ""..."4.0" do
+  require 'cgi'
 
-  after :each do
-    ENV['REQUEST_METHOD'] = @old_request_method
-  end
+  describe "CGI::QueryExtension#user_agent" do
+    before :each do
+      ENV['REQUEST_METHOD'], @old_request_method = "GET", ENV['REQUEST_METHOD']
+      @cgi = CGI.new
+    end
+
+    after :each do
+      ENV['REQUEST_METHOD'] = @old_request_method
+    end
 
-  it "returns ENV['HTTP_USER_AGENT']" do
-    old_value, ENV['HTTP_USER_AGENT'] = ENV['HTTP_USER_AGENT'], "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_2; de-de) AppleWebKit/527+ (KHTML, like Gecko) Version/3.1 Safari/525.13"
-    begin
-      @cgi.user_agent.should == "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_2; de-de) AppleWebKit/527+ (KHTML, like Gecko) Version/3.1 Safari/525.13"
-    ensure
-      ENV['HTTP_USER_AGENT'] = old_value
+    it "returns ENV['HTTP_USER_AGENT']" do
+      old_value, ENV['HTTP_USER_AGENT'] = ENV['HTTP_USER_AGENT'], "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_2; de-de) AppleWebKit/527+ (KHTML, like Gecko) Version/3.1 Safari/525.13"
+      begin
+        @cgi.user_agent.should == "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_2; de-de) AppleWebKit/527+ (KHTML, like Gecko) Version/3.1 Safari/525.13"
+      ensure
+        ENV['HTTP_USER_AGENT'] = old_value
+      end
     end
   end
 end
diff --git a/spec/ruby/library/cgi/rfc1123_date_spec.rb b/spec/ruby/library/cgi/rfc1123_date_spec.rb
index 6904eeabaa..636185f22c 100644
--- a/spec/ruby/library/cgi/rfc1123_date_spec.rb
+++ b/spec/ruby/library/cgi/rfc1123_date_spec.rb
@@ -1,10 +1,13 @@
 require_relative '../../spec_helper'
-require 'cgi'
 
-describe "CGI.rfc1123_date when passed Time" do
-  it "returns the passed Time formatted in RFC1123 ('Sat, 01 Dec 2007 15:56:42 GMT')" do
-    input = Time.at(1196524602)
-    expected = 'Sat, 01 Dec 2007 15:56:42 GMT'
-    CGI.rfc1123_date(input).should == expected
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+
+  describe "CGI.rfc1123_date when passed Time" do
+    it "returns the passed Time formatted in RFC1123 ('Sat, 01 Dec 2007 15:56:42 GMT')" do
+      input = Time.at(1196524602)
+      expected = 'Sat, 01 Dec 2007 15:56:42 GMT'
+      CGI.rfc1123_date(input).should == expected
+    end
   end
 end
diff --git a/spec/ruby/library/cgi/unescapeElement_spec.rb b/spec/ruby/library/cgi/unescapeElement_spec.rb
index ae4d50b076..db83f0d2fb 100644
--- a/spec/ruby/library/cgi/unescapeElement_spec.rb
+++ b/spec/ruby/library/cgi/unescapeElement_spec.rb
@@ -1,5 +1,11 @@
 require_relative '../../spec_helper'
-require 'cgi'
+
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+end
+ruby_version_is "4.0" do
+  require 'cgi/escape'
+end
 
 describe "CGI.unescapeElement when passed String, elements, ..." do
   it "unescapes only the tags of the passed elements in the passed String" do
diff --git a/spec/ruby/library/cgi/unescapeHTML_spec.rb b/spec/ruby/library/cgi/unescapeHTML_spec.rb
index 46387d4f01..e43dcc83e5 100644
--- a/spec/ruby/library/cgi/unescapeHTML_spec.rb
+++ b/spec/ruby/library/cgi/unescapeHTML_spec.rb
@@ -1,5 +1,9 @@
 require_relative '../../spec_helper'
-require 'cgi'
+begin
+  require 'cgi/escape'
+rescue LoadError
+  require 'cgi'
+end
 
 describe "CGI.unescapeHTML" do
   it "unescapes '&amp; &lt; &gt; &quot;' to '& < > \"'" do
@@ -36,4 +40,9 @@ describe "CGI.unescapeHTML" do
     input = "fooooooo&#"
     CGI.unescapeHTML(input).should == input
   end
+
+  it "unescapes invalid encoding" do
+    input = "\xFF&"
+    CGI.unescapeHTML(input).should == input
+  end
 end
diff --git a/spec/ruby/library/cgi/unescapeURIComponent_spec.rb b/spec/ruby/library/cgi/unescapeURIComponent_spec.rb
new file mode 100644
index 0000000000..f80eb1626b
--- /dev/null
+++ b/spec/ruby/library/cgi/unescapeURIComponent_spec.rb
@@ -0,0 +1,128 @@
+require_relative '../../spec_helper'
+
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+end
+ruby_version_is "4.0" do
+  require 'cgi/escape'
+end
+
+describe "CGI.unescapeURIComponent" do
+  it "decodes any percent-encoded octets to their corresponding bytes according to RFC 3986" do
+    string = (0x00..0xff).map { |i| "%%%02x" % i }.join
+    expected = (0x00..0xff).map { |i| i.chr }.join.force_encoding(Encoding::UTF_8)
+    CGI.unescapeURIComponent(string).should == expected
+  end
+
+  it "disregards case of characters in a percent-encoding triplet" do
+    CGI.unescapeURIComponent("%CE%B2abc").should == "βabc"
+    CGI.unescapeURIComponent("%ce%b2ABC").should == "βABC"
+  end
+
+  it "leaves any non-percent-encoded characters as-is" do
+    string = "ABCDEFGHIJKLMNOPQRSTUVWXYZ:/?#[]@!$&'()*+,;=\t\x0D\xFFβᛉ▒90%"
+    decoded = CGI.unescapeURIComponent(string)
+    decoded.should == string
+    string.should_not.equal?(decoded)
+  end
+
+  it "leaves sequences which can't be a percent-encoded octet as-is" do
+    string = "%AZ%B"
+    decoded = CGI.unescapeURIComponent(string)
+    decoded.should == string
+    string.should_not.equal?(decoded)
+  end
+
+  it "creates a String with the specified target Encoding" do
+    string = CGI.unescapeURIComponent("%D2%3C%3CABC", Encoding::ISO_8859_1)
+    string.encoding.should == Encoding::ISO_8859_1
+    string.should == "Ò<<ABC".encode("ISO-8859-1")
+  end
+
+  it "accepts a string name of an Encoding" do
+    CGI.unescapeURIComponent("%D2%3C%3CABC", "ISO-8859-1").should == "Ò<<ABC".encode("ISO-8859-1")
+  end
+
+  it "raises ArgumentError if specified encoding is unknown" do
+    -> { CGI.unescapeURIComponent("ABC", "ISO-JOKE-1") }.should raise_error(ArgumentError, "unknown encoding name - ISO-JOKE-1")
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "uses CGI.accept_charset as the default target encoding" do
+      original_charset = CGI.accept_charset
+      CGI.accept_charset = "ISO-8859-1"
+      decoded = CGI.unescapeURIComponent("%D2%3C%3CABC")
+      decoded.should == "Ò<<ABC".encode("ISO-8859-1")
+      decoded.encoding.should == Encoding::ISO_8859_1
+    ensure
+      CGI.accept_charset = original_charset
+    end
+
+    it "has CGI.accept_charset as UTF-8 by default" do
+      decoded = CGI.unescapeURIComponent("%CE%B2ABC")
+      decoded.should == "βABC"
+      decoded.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  ruby_version_is "4.0" do
+    # "cgi/escape" does not have methods to access @@accept_charset.
+    # Full "cgi" gem provides them, allowing to possibly change it.
+    it "uses CGI's @@accept_charset as the default target encoding" do
+      original_charset = CGI.class_variable_get(:@@accept_charset)
+      CGI.class_variable_set(:@@accept_charset, "ISO-8859-1")
+      decoded = CGI.unescapeURIComponent("%D2%3C%3CABC")
+      decoded.should == "Ò<<ABC".encode("ISO-8859-1")
+      decoded.encoding.should == Encoding::ISO_8859_1
+    ensure
+      CGI.class_variable_set(:@@accept_charset, original_charset)
+    end
+
+    it "has CGI's @@accept_charset as UTF-8 by default" do
+      decoded = CGI.unescapeURIComponent("%CE%B2ABC")
+      decoded.should == "βABC"
+      decoded.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  context "when source string specifies octets invalid in target encoding" do
+    it "uses source string's encoding" do
+      string = "%A2%A6%A3".encode(Encoding::SHIFT_JIS)
+      decoded = CGI.unescapeURIComponent(string, Encoding::US_ASCII)
+      decoded.encoding.should == Encoding::SHIFT_JIS
+      decoded.should == "｢ｦ｣".encode(Encoding::SHIFT_JIS)
+      decoded.valid_encoding?.should be_true
+    end
+
+    it "uses source string's encoding even if it's also invalid" do
+      string = "%FF".encode(Encoding::US_ASCII)
+      decoded = CGI.unescapeURIComponent(string, Encoding::SHIFT_JIS)
+      decoded.encoding.should == Encoding::US_ASCII
+      decoded.should == "\xFF".dup.force_encoding(Encoding::US_ASCII)
+      decoded.valid_encoding?.should be_false
+    end
+  end
+
+  it "decodes an empty string as an empty string with target encoding" do
+    string = "".encode(Encoding::BINARY)
+    decoded = CGI.unescapeURIComponent(string, "UTF-8")
+    decoded.should == ""
+    decoded.encoding.should == Encoding::UTF_8
+    string.should_not.equal?(decoded)
+  end
+
+  it "raises a TypeError with nil" do
+    -> {
+      CGI.unescapeURIComponent(nil)
+    }.should raise_error(TypeError, "no implicit conversion of nil into String")
+  end
+
+  it "uses implicit type conversion to String" do
+    object = Object.new
+    def object.to_str
+      "a%20b"
+    end
+
+    CGI.unescapeURIComponent(object).should == "a b"
+  end
+end
diff --git a/spec/ruby/library/cgi/unescape_spec.rb b/spec/ruby/library/cgi/unescape_spec.rb
index db4834e7e8..aa731b9367 100644
--- a/spec/ruby/library/cgi/unescape_spec.rb
+++ b/spec/ruby/library/cgi/unescape_spec.rb
@@ -1,6 +1,12 @@
 # -*- encoding: utf-8 -*-
 require_relative '../../spec_helper'
-require 'cgi'
+
+ruby_version_is ""..."4.0" do
+  require 'cgi'
+end
+ruby_version_is "4.0" do
+  require 'cgi/escape'
+end
 
 describe "CGI.unescape" do
   it "url-decodes the passed argument" do
@@ -8,8 +14,8 @@ describe "CGI.unescape" do
     expected = " !\"\#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz{|}~"
     CGI.unescape(input).should == expected
 
-    input    = 'http%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
-    expected = "http://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
+    input    = 'https%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
+    expected = "https://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
     CGI.unescape(input).should == expected
   end
 end
diff --git a/spec/ruby/library/complex/math/acos_spec.rb b/spec/ruby/library/complex/math/acos_spec.rb
deleted file mode 100644
index c7b2362a2c..0000000000
--- a/spec/ruby/library/complex/math/acos_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/acos'
-
-describe "Math#acos" do
-  it_behaves_like :complex_math_acos, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:acos)
-  end
-end
-
-describe "Math.acos" do
-  it_behaves_like :complex_math_acos, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/acosh_spec.rb b/spec/ruby/library/complex/math/acosh_spec.rb
deleted file mode 100644
index 33adb73b64..0000000000
--- a/spec/ruby/library/complex/math/acosh_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/acosh'
-
-describe "Math#acosh" do
-  it_behaves_like :complex_math_acosh, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:acosh)
-  end
-end
-
-describe "Math.acosh" do
-  it_behaves_like :complex_math_acosh, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/asin_spec.rb b/spec/ruby/library/complex/math/asin_spec.rb
deleted file mode 100644
index f0647bbc14..0000000000
--- a/spec/ruby/library/complex/math/asin_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/asin'
-
-describe "Math#asin" do
-  it_behaves_like :complex_math_asin, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:asin)
-  end
-end
-
-describe "Math.asin" do
-  it_behaves_like :complex_math_asin, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/asinh_spec.rb b/spec/ruby/library/complex/math/asinh_spec.rb
deleted file mode 100644
index ef93a9dc22..0000000000
--- a/spec/ruby/library/complex/math/asinh_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/asinh'
-
-describe "Math#asinh" do
-  it_behaves_like :complex_math_asinh, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:asinh)
-  end
-end
-
-describe "Math.asinh" do
-  it_behaves_like :complex_math_asinh, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/atan2_spec.rb b/spec/ruby/library/complex/math/atan2_spec.rb
deleted file mode 100644
index 46874f89e4..0000000000
--- a/spec/ruby/library/complex/math/atan2_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/atan2'
-
-describe "Math#atan2" do
-  it_behaves_like :complex_math_atan2, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:atan2)
-  end
-end
-
-describe "Math.atan2" do
-  it_behaves_like :complex_math_atan2, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/atan_spec.rb b/spec/ruby/library/complex/math/atan_spec.rb
deleted file mode 100644
index e60c088b5e..0000000000
--- a/spec/ruby/library/complex/math/atan_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/atan'
-
-describe "Math#atan" do
-  it_behaves_like :complex_math_atan, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:atan)
-  end
-end
-
-describe "Math.atan" do
-  it_behaves_like :complex_math_atan, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/atanh_spec.rb b/spec/ruby/library/complex/math/atanh_spec.rb
deleted file mode 100644
index b8eaec3a09..0000000000
--- a/spec/ruby/library/complex/math/atanh_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require 'complex'
-require_relative '../../../spec_helper'
-require_relative '../../../fixtures/math/common'
-require_relative '../../../shared/math/atanh'
-require_relative 'shared/atanh'
-
-describe "Math#atanh" do
-  it_behaves_like :math_atanh_base, :atanh, IncludesMath.new
-  it_behaves_like :complex_math_atanh_complex, :atanh, IncludesMath.new
-
-  it_behaves_like :math_atanh_private, :atanh, IncludesMath.new
-end
-
-describe "Math.atanh" do
-  it_behaves_like :math_atanh_base, :atanh, CMath
-  it_behaves_like :complex_math_atanh_complex, :atanh, CMath
-end
diff --git a/spec/ruby/library/complex/math/cos_spec.rb b/spec/ruby/library/complex/math/cos_spec.rb
deleted file mode 100644
index 847acb7fa2..0000000000
--- a/spec/ruby/library/complex/math/cos_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/cos'
-
-describe "Math#cos" do
-  it_behaves_like :complex_math_cos, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:cos)
-  end
-end
-
-describe "Math.cos" do
-  it_behaves_like :complex_math_cos, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/cosh_spec.rb b/spec/ruby/library/complex/math/cosh_spec.rb
deleted file mode 100644
index c0a87d4865..0000000000
--- a/spec/ruby/library/complex/math/cosh_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/cosh'
-
-describe "Math#cosh" do
-  it_behaves_like :complex_math_cosh, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:cosh)
-  end
-end
-
-describe "Math.cosh" do
-  it_behaves_like :complex_math_cosh, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/exp_spec.rb b/spec/ruby/library/complex/math/exp_spec.rb
deleted file mode 100644
index e1e51f7948..0000000000
--- a/spec/ruby/library/complex/math/exp_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/exp'
-
-describe "Math#exp" do
-  it_behaves_like :complex_math_exp, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:exp)
-  end
-end
-
-describe "Math.exp" do
-  it_behaves_like :complex_math_exp, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/fixtures/classes.rb b/spec/ruby/library/complex/math/fixtures/classes.rb
deleted file mode 100644
index 443c1a9ace..0000000000
--- a/spec/ruby/library/complex/math/fixtures/classes.rb
+++ /dev/null
@@ -1,4 +0,0 @@
-require 'cmath'
-class IncludesMath
-  include CMath
-end
diff --git a/spec/ruby/library/complex/math/log10_spec.rb b/spec/ruby/library/complex/math/log10_spec.rb
deleted file mode 100644
index 295189ae53..0000000000
--- a/spec/ruby/library/complex/math/log10_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/log10'
-
-describe "Math#log10" do
-  it_behaves_like :complex_math_log10, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:log10)
-  end
-end
-
-describe "Math.log10" do
-  it_behaves_like :complex_math_log10, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/log_spec.rb b/spec/ruby/library/complex/math/log_spec.rb
deleted file mode 100644
index 6d80d045c9..0000000000
--- a/spec/ruby/library/complex/math/log_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/log'
-
-describe "Math#log" do
-  it_behaves_like :complex_math_log, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:log)
-  end
-end
-
-describe "Math.log" do
-  it_behaves_like :complex_math_log, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/shared/acos.rb b/spec/ruby/library/complex/math/shared/acos.rb
deleted file mode 100644
index 65637fa838..0000000000
--- a/spec/ruby/library/complex/math/shared/acos.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_acos, shared: true do
-  it "returns the arccosine of the passed argument" do
-    @object.send(:acos, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:acos, 0).should be_close(1.5707963267949, TOLERANCE)
-    @object.send(:acos, -1).should be_close(Math::PI,TOLERANCE)
-  end
-
-  it "returns the arccosine for Complex numbers" do
-    @object.send(:acos, Complex(3, 4)).should be_close(Complex(0.93681246115572, -2.30550903124348), TOLERANCE)
-  end
-
-  it "returns the arccosine for numbers greater than 1.0 as a Complex number" do
-    @object.send(:acos, 1.0001).should be_close(Complex(0.0, 0.0141420177752494), TOLERANCE)
-  end
-
-  it "returns the arccosine for numbers less than -1.0 as a Complex number" do
-    @object.send(:acos, -1.0001).should be_close(Complex(3.14159265358979, -0.0141420177752495), TOLERANCE)
-  end
-end
-
-describe :complex_math_acos_bang, shared: true do
-  it "returns the arccosine of the argument" do
-    @object.send(:acos!, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:acos!, 0).should be_close(1.5707963267949, TOLERANCE)
-    @object.send(:acos!, -1).should be_close(Math::PI,TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:acos!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-
-  it "raises an Errno::EDOM for numbers greater than 1.0" do
-    -> { @object.send(:acos!, 1.0001) }.should raise_error(Errno::EDOM)
-  end
-
-  it "raises an Errno::EDOM for numbers less than -1.0" do
-    -> { @object.send(:acos!, -1.0001) }.should raise_error(Errno::EDOM)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/acosh.rb b/spec/ruby/library/complex/math/shared/acosh.rb
deleted file mode 100644
index 285b0b823f..0000000000
--- a/spec/ruby/library/complex/math/shared/acosh.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_acosh, shared: true do
-  it "returns the principle value of the inverse hyperbolic cosine of the argument" do
-    @object.send(:acosh, 14.2).should be_close(3.345146999647, TOLERANCE)
-    @object.send(:acosh, 1.0).should be_close(0.0, TOLERANCE)
-  end
-
-  it "returns the principle value of the inverse hyperbolic cosine for numbers less than 1.0 as a Complex number" do
-    @object.send(:acosh, 1.0 - TOLERANCE).should be_close(Complex(0.0, 0.00774598605746135), TOLERANCE)
-    @object.send(:acosh, 0).should be_close(Complex(0.0, 1.5707963267949), TOLERANCE)
-    @object.send(:acosh, -1.0).should be_close(Complex(0.0, 3.14159265358979), TOLERANCE)
-  end
-
-  it "returns the principle value of the inverse hyperbolic cosine for Complex numbers" do
-    @object.send(:acosh, Complex(3, 4))
-    @object.send(:acosh, Complex(3, 4)).imaginary.should be_close(0.93681246115572, TOLERANCE)
-    @object.send(:acosh, Complex(3, 4)).real.should be_close(2.305509031243477, TOLERANCE)
-  end
-end
-
-describe :complex_math_acosh_bang, shared: true do
-  it "returns the principle value of the inverse hyperbolic cosine of the argument" do
-    @object.send(:acosh!, 14.2).should be_close(3.345146999647, TOLERANCE)
-    @object.send(:acosh!, 1.0).should be_close(0.0, TOLERANCE)
-  end
-
-  it "raises Errno::EDOM for numbers less than 1.0" do
-    -> { @object.send(:acosh!, 1.0 - TOLERANCE) }.should raise_error(Errno::EDOM)
-    -> { @object.send(:acosh!, 0) }.should raise_error(Errno::EDOM)
-    -> { @object.send(:acosh!, -1.0) }.should raise_error(Errno::EDOM)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:acosh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/asin.rb b/spec/ruby/library/complex/math/shared/asin.rb
deleted file mode 100644
index 91fed7aa06..0000000000
--- a/spec/ruby/library/complex/math/shared/asin.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_asin, shared: true do
-  it "returns the arcsine of the argument" do
-    @object.send(:asin, 1).should be_close(Math::PI/2, TOLERANCE)
-    @object.send(:asin, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:asin, -1).should be_close(-Math::PI/2, TOLERANCE)
-    @object.send(:asin, 0.25).should be_close(0.252680255142079, TOLERANCE)
-    @object.send(:asin, 0.50).should be_close(0.523598775598299, TOLERANCE)
-    @object.send(:asin, 0.75).should be_close(0.8480620789814816,TOLERANCE)
-  end
-
-  it "returns the arcsine for Complex numbers" do
-    @object.send(:asin, Complex(3, 4)).should be_close(Complex(0.633983865639174, 2.30550903124347), TOLERANCE)
-  end
-
-  it "returns a Complex number when the argument is greater than 1.0" do
-    @object.send(:asin, 1.0001).should be_close(Complex(1.5707963267949, -0.0141420177752494), TOLERANCE)
-  end
-
-  it "returns a Complex number when the argument is less than -1.0" do
-    @object.send(:asin, -1.0001).should be_close(Complex(-1.5707963267949, 0.0141420177752494), TOLERANCE)
-  end
-end
-
-describe :complex_math_asin_bang, shared: true do
-  it "returns the arcsine of the argument" do
-    @object.send(:asin!, 1).should be_close(Math::PI/2, TOLERANCE)
-    @object.send(:asin!, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:asin!, -1).should be_close(-Math::PI/2, TOLERANCE)
-    @object.send(:asin!, 0.25).should be_close(0.252680255142079, TOLERANCE)
-    @object.send(:asin!, 0.50).should be_close(0.523598775598299, TOLERANCE)
-    @object.send(:asin!, 0.75).should be_close(0.8480620789814816,TOLERANCE)
-  end
-
-  it "raises an Errno::EDOM if the argument is greater than 1.0" do
-    -> { @object.send(:asin!, 1.0001) }.should raise_error( Errno::EDOM)
-  end
-
-  it "raises an Errno::EDOM if the argument is less than -1.0" do
-    -> { @object.send(:asin!, -1.0001) }.should raise_error( Errno::EDOM)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:asin!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/asinh.rb b/spec/ruby/library/complex/math/shared/asinh.rb
deleted file mode 100644
index b4ddd3a22e..0000000000
--- a/spec/ruby/library/complex/math/shared/asinh.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_asinh, shared: true do
-  it "returns the inverse hyperbolic sin of the argument" do
-    @object.send(:asinh, 1.5).should be_close(1.19476321728711, TOLERANCE)
-    @object.send(:asinh, -2.97).should be_close(-1.8089166921397, TOLERANCE)
-    @object.send(:asinh, 0.0).should == 0.0
-    @object.send(:asinh, -0.0).should == -0.0
-    @object.send(:asinh, 1.05367e-08).should be_close(1.05367e-08, TOLERANCE)
-    @object.send(:asinh, -1.05367e-08).should be_close(-1.05367e-08, TOLERANCE)
-  end
-
-  it "returns the inverse hyperbolic sin for Complex numbers" do
-    @object.send(:asinh, Complex(3, 4)).should be_close(Complex(2.29991404087927, 0.917616853351479), TOLERANCE)
-    @object.send(:asinh, Complex(3.5, -4)).should be_close(Complex(2.36263337274419, -0.843166327537659), TOLERANCE)
-  end
-end
-
-describe :complex_math_asinh_bang, shared: true do
-  it "returns the inverse hyperbolic sin of the argument" do
-    @object.send(:asinh!, 1.5).should be_close(1.19476321728711, TOLERANCE)
-    @object.send(:asinh!, -2.97).should be_close(-1.8089166921397, TOLERANCE)
-    @object.send(:asinh!, 0.0).should == 0.0
-    @object.send(:asinh!, -0.0).should == -0.0
-    @object.send(:asinh!, 1.05367e-08).should be_close(1.05367e-08, TOLERANCE)
-    @object.send(:asinh!, -1.05367e-08).should be_close(-1.05367e-08, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:asinh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/atan.rb b/spec/ruby/library/complex/math/shared/atan.rb
deleted file mode 100644
index 63a496e841..0000000000
--- a/spec/ruby/library/complex/math/shared/atan.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_atan, shared: true do
-  it "returns the arctangent of the argument" do
-    @object.send(:atan, 1).should be_close(Math::PI/4, TOLERANCE)
-    @object.send(:atan, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:atan, -1).should be_close(-Math::PI/4, TOLERANCE)
-    @object.send(:atan, 0.25).should be_close(0.244978663126864, TOLERANCE)
-    @object.send(:atan, 0.50).should be_close(0.463647609000806, TOLERANCE)
-    @object.send(:atan, 0.75).should be_close(0.643501108793284, TOLERANCE)
-  end
-
-  it "returns the arctangent for Complex numbers" do
-    @object.send(:atan, Complex(3, 4)).should be_close(Complex(1.44830699523146, 0.158997191679999), TOLERANCE)
-    @object.send(:atan, Complex(3.5, -4)).should be_close(Complex(1.44507428165589, -0.140323762363786), TOLERANCE)
-  end
-end
-
-describe :complex_math_atan_bang, shared: true do
-  it "returns the arctangent of the argument" do
-    @object.send(:atan!, 1).should be_close(Math::PI/4, TOLERANCE)
-    @object.send(:atan!, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:atan!, -1).should be_close(-Math::PI/4, TOLERANCE)
-    @object.send(:atan!, 0.25).should be_close(0.244978663126864, TOLERANCE)
-    @object.send(:atan!, 0.50).should be_close(0.463647609000806, TOLERANCE)
-    @object.send(:atan!, 0.75).should be_close(0.643501108793284, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:atan!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/atan2.rb b/spec/ruby/library/complex/math/shared/atan2.rb
deleted file mode 100644
index 6d89423924..0000000000
--- a/spec/ruby/library/complex/math/shared/atan2.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_atan2, shared: true do
-  it "returns the arc tangent of the passed arguments" do
-    @object.send(:atan2, 4.2, 0.3).should be_close(1.49948886200961, TOLERANCE)
-    @object.send(:atan2, 0.0, 1.0).should be_close(0.0, TOLERANCE)
-    @object.send(:atan2, -9.1, 3.2).should be_close(-1.23265379809025, TOLERANCE)
-    @object.send(:atan2, 7.22, -3.3).should be_close(1.99950888779256, TOLERANCE)
-  end
-
-  it "returns the arc tangent for two Complex numbers" do
-    CMath.atan2(Complex(3, 4), Complex(3.5, -4)).should be_close(Complex(-0.641757436698881, 1.10829873031207), TOLERANCE)
-  end
-
-  it "returns the arc tangent for Complex and real numbers" do
-    CMath.atan2(Complex(3, 4), -7).should be_close(Complex(2.61576754731561, -0.494290673139855), TOLERANCE)
-    CMath.atan2(5, Complex(3.5, -4)).should be_close(Complex(0.739102348493673, 0.487821626522923), TOLERANCE)
-  end
-end
-
-describe :complex_math_atan2_bang, shared: true do
-  it "returns the arc tangent of the passed arguments" do
-    @object.send(:atan2!, 4.2, 0.3).should be_close(1.49948886200961, TOLERANCE)
-    @object.send(:atan2!, 0.0, 1.0).should be_close(0.0, TOLERANCE)
-    @object.send(:atan2!, -9.1, 3.2).should be_close(-1.23265379809025, TOLERANCE)
-    @object.send(:atan2!, 7.22, -3.3).should be_close(1.99950888779256, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:atan2!, Complex(4, 5), Complex(4, 5)) }.should raise_error(TypeError)
-    -> { @object.send(:atan2!, 4, Complex(4, 5)) }.should raise_error(TypeError)
-    -> { @object.send(:atan2!, Complex(4, 5), 5) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/atanh.rb b/spec/ruby/library/complex/math/shared/atanh.rb
deleted file mode 100644
index ae80e61bec..0000000000
--- a/spec/ruby/library/complex/math/shared/atanh.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_atanh_complex, shared: true do
-  it "returns the inverse hyperbolic tangent as a Complex number for arguments greater than 1.0" do
-    value = Complex(18.36840028483855, 1.5707963267948966)
-    @object.send(@method, 1.0 + Float::EPSILON).should be_close(value, TOLERANCE)
-
-    value = Complex(0.100335347731076, 1.5707963267949)
-    @object.send(@method, 10).should be_close(value, TOLERANCE)
-  end
-
-  it "returns the inverse hyperbolic tangent as a Complex number for arguments greater than 1.0" do
-    value = Complex(-18.36840028483855, 1.5707963267948966)
-    @object.send(@method, -1.0 - Float::EPSILON).should be_close(value, TOLERANCE)
-
-    value = Complex(0.100335347731076, 1.5707963267949)
-    @object.send(@method, 10).should be_close(value, TOLERANCE)
-  end
-
-  it "returns the inverse hyperbolic tangent for Complex numbers" do
-    value = Complex(0.117500907311434, 1.40992104959658)
-    @object.send(@method, Complex(3, 4)).should be_close(value, TOLERANCE)
-  end
-end
-
-describe :complex_math_atanh_no_complex, shared: true do
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:atanh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/cos.rb b/spec/ruby/library/complex/math/shared/cos.rb
deleted file mode 100644
index 31cb5ab1e5..0000000000
--- a/spec/ruby/library/complex/math/shared/cos.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_cos, shared: true do
-  it "returns the cosine of the argument expressed in radians" do
-    @object.send(:cos, CMath::PI).should be_close(-1.0, TOLERANCE)
-    @object.send(:cos, 0).should be_close(1.0, TOLERANCE)
-    @object.send(:cos, CMath::PI/2).should be_close(0.0, TOLERANCE)
-    @object.send(:cos, 3*Math::PI/2).should be_close(0.0, TOLERANCE)
-    @object.send(:cos, 2*Math::PI).should be_close(1.0, TOLERANCE)
-  end
-
-  it "returns the cosine for Complex numbers" do
-    @object.send(:cos, Complex(0, CMath::PI)).should be_close(Complex(11.5919532755215, 0.0), TOLERANCE)
-    @object.send(:cos, Complex(3, 4)).should be_close(Complex(-27.0349456030742, -3.85115333481178), TOLERANCE)
-  end
-end
-
-describe :complex_math_cos_bang, shared: true do
-  it "returns the cosine of the argument expressed in radians" do
-    @object.send(:cos!, CMath::PI).should be_close(-1.0, TOLERANCE)
-    @object.send(:cos!, 0).should be_close(1.0, TOLERANCE)
-    @object.send(:cos!, CMath::PI/2).should be_close(0.0, TOLERANCE)
-    @object.send(:cos!, 3*Math::PI/2).should be_close(0.0, TOLERANCE)
-    @object.send(:cos!, 2*Math::PI).should be_close(1.0, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:cos!, Complex(3, 4)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/cosh.rb b/spec/ruby/library/complex/math/shared/cosh.rb
deleted file mode 100644
index 7cf561c985..0000000000
--- a/spec/ruby/library/complex/math/shared/cosh.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_cosh, shared: true do
-  it "returns the hyperbolic cosine of the passed argument" do
-    @object.send(:cosh, 0.0).should == 1.0
-    @object.send(:cosh, -0.0).should == 1.0
-    @object.send(:cosh, 1.5).should be_close(2.35240961524325, TOLERANCE)
-    @object.send(:cosh, -2.99).should be_close(9.96798496414416, TOLERANCE)
-  end
-
-  it "returns the hyperbolic cosine for Complex numbers" do
-    @object.send(:cosh, Complex(0, CMath::PI)).should be_close(Complex(-1.0, 0.0), TOLERANCE)
-    @object.send(:cosh, Complex(3, 4)).should be_close(Complex(-6.58066304055116, -7.58155274274654), TOLERANCE)
-  end
-end
-
-describe :complex_math_cosh_bang, shared: true do
-  it "returns the hyperbolic cosine of the passed argument" do
-    @object.send(:cosh!, 0.0).should == 1.0
-    @object.send(:cosh!, -0.0).should == 1.0
-    @object.send(:cosh!, 1.5).should be_close(2.35240961524325, TOLERANCE)
-    @object.send(:cosh!, -2.99).should be_close(9.96798496414416, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:cosh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/exp.rb b/spec/ruby/library/complex/math/shared/exp.rb
deleted file mode 100644
index 6715ac63d3..0000000000
--- a/spec/ruby/library/complex/math/shared/exp.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_exp, shared: true do
-  it "returns the base-e exponential of the passed argument" do
-    @object.send(:exp, 0.0).should == 1.0
-    @object.send(:exp, -0.0).should == 1.0
-    @object.send(:exp, -1.8).should be_close(0.165298888221587, TOLERANCE)
-    @object.send(:exp, 1.25).should be_close(3.49034295746184, TOLERANCE)
-  end
-
-  it "returns the base-e exponential for Complex numbers" do
-    @object.send(:exp, Complex(0, 0)).should == Complex(1.0, 0.0)
-    @object.send(:exp, Complex(1, 3)).should be_close(Complex(-2.69107861381979, 0.383603953541131), TOLERANCE)
-  end
-end
-
-describe :complex_math_exp_bang, shared: true do
-  it "returns the base-e exponential of the passed argument" do
-    @object.send(:exp!, 0.0).should == 1.0
-    @object.send(:exp!, -0.0).should == 1.0
-    @object.send(:exp!, -1.8).should be_close(0.165298888221587, TOLERANCE)
-    @object.send(:exp!, 1.25).should be_close(3.49034295746184, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:exp!, Complex(1, 3)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/log.rb b/spec/ruby/library/complex/math/shared/log.rb
deleted file mode 100644
index 4b23e8c5f2..0000000000
--- a/spec/ruby/library/complex/math/shared/log.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_log, shared: true do
-  it "returns the natural logarithm of the passed argument" do
-    @object.send(:log, 0.0001).should be_close(-9.21034037197618, TOLERANCE)
-    @object.send(:log, 0.000000000001e-15).should be_close(-62.1697975108392, TOLERANCE)
-    @object.send(:log, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:log, 10).should be_close( 2.30258509299405, TOLERANCE)
-    @object.send(:log, 10e15).should be_close(36.8413614879047, TOLERANCE)
-  end
-
-  it "returns the natural logarithm for Complex numbers" do
-    @object.send(:log, Complex(3, 4)).should be_close(Complex(1.6094379124341, 0.927295218001612), TOLERANCE)
-    @object.send(:log, Complex(-3, 4)).should be_close(Complex(1.6094379124341, 2.21429743558818), TOLERANCE)
-  end
-
-  it "returns the natural logarithm for negative numbers as a Complex number" do
-    @object.send(:log, -10).should be_close(Complex(2.30258509299405, 3.14159265358979), TOLERANCE)
-    @object.send(:log, -20).should be_close(Complex(2.99573227355399, 3.14159265358979), TOLERANCE)
-  end
-end
-
-describe :complex_math_log_bang, shared: true do
-  it "returns the natural logarithm of the argument" do
-    @object.send(:log!, 0.0001).should be_close(-9.21034037197618, TOLERANCE)
-    @object.send(:log!, 0.000000000001e-15).should be_close(-62.1697975108392, TOLERANCE)
-    @object.send(:log!, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:log!, 10).should be_close( 2.30258509299405, TOLERANCE)
-    @object.send(:log!, 10e15).should be_close(36.8413614879047, TOLERANCE)
-  end
-
-  it "raises an Errno::EDOM if the argument is less than 0" do
-    -> { @object.send(:log!, -10) }.should raise_error(Errno::EDOM)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:log!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/log10.rb b/spec/ruby/library/complex/math/shared/log10.rb
deleted file mode 100644
index f49934d958..0000000000
--- a/spec/ruby/library/complex/math/shared/log10.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_log10, shared: true do
-  it "returns the base-10 logarithm of the passed argument" do
-    @object.send(:log10, 0.0001).should be_close(-4.0, TOLERANCE)
-    @object.send(:log10, 0.000000000001e-15).should be_close(-27.0, TOLERANCE)
-    @object.send(:log10, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:log10, 10).should be_close(1.0, TOLERANCE)
-    @object.send(:log10, 10e15).should be_close(16.0, TOLERANCE)
-  end
-
-  it "returns the base-10 logarithm for Complex numbers" do
-    @object.send(:log10, Complex(3, 4)).should be_close(Complex(0.698970004336019, 0.402719196273373), TOLERANCE)
-    @object.send(:log10, Complex(-3, 4)).should be_close(Complex(0.698970004336019, 0.961657157568468), TOLERANCE)
-  end
-
-  # BUG: does not work correctly, because Math#log10
-  # does not check for negative values
-  #it "returns the base-10 logarithm for negative numbers as a Complex number" do
-  #  @object.send(:log10, -10).should be_close(Complex(2.30258509299405, 3.14159265358979), TOLERANCE)
-  #  @object.send(:log10, -20).should be_close(Complex(2.99573227355399, 3.14159265358979), TOLERANCE)
-  #end
-end
-
-describe :complex_math_log10_bang, shared: true do
-  it "returns the base-10 logarithm of the argument" do
-    @object.send(:log10!, 0.0001).should be_close(-4.0, TOLERANCE)
-    @object.send(:log10!, 0.000000000001e-15).should be_close(-27.0, TOLERANCE)
-    @object.send(:log10!, 1).should be_close(0.0, TOLERANCE)
-    @object.send(:log10!, 10).should be_close(1.0, TOLERANCE)
-    @object.send(:log10!, 10e15).should be_close(16.0, TOLERANCE)
-  end
-
-  it "raises an Errno::EDOM when the passed argument is negative" do
-    -> { @object.send(:log10!, -10) }.should raise_error(Errno::EDOM)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:log10!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/sin.rb b/spec/ruby/library/complex/math/shared/sin.rb
deleted file mode 100644
index 1cb1b29cda..0000000000
--- a/spec/ruby/library/complex/math/shared/sin.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_sin, shared: true do
-  it "returns the sine of the passed argument expressed in radians" do
-    @object.send(:sin, CMath::PI).should be_close(0.0, TOLERANCE)
-    @object.send(:sin, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:sin, CMath::PI/2).should be_close(1.0, TOLERANCE)
-    @object.send(:sin, 3*Math::PI/2).should be_close(-1.0, TOLERANCE)
-    @object.send(:sin, 2*Math::PI).should be_close(0.0, TOLERANCE)
-  end
-
-  it "returns the sine for Complex numbers" do
-    @object.send(:sin, Complex(0, CMath::PI)).should be_close(Complex(0.0, 11.5487393572577), TOLERANCE)
-    @object.send(:sin, Complex(3, 4)).should be_close(Complex(3.85373803791938, -27.0168132580039), TOLERANCE)
-  end
-end
-
-describe :complex_math_sin_bang, shared: true do
-  it "returns the sine of the passed argument expressed in radians" do
-    @object.send(:sin!, CMath::PI).should be_close(0.0, TOLERANCE)
-    @object.send(:sin!, 0).should be_close(0.0, TOLERANCE)
-    @object.send(:sin!, CMath::PI/2).should be_close(1.0, TOLERANCE)
-    @object.send(:sin!, 3*Math::PI/2).should be_close(-1.0, TOLERANCE)
-    @object.send(:sin!, 2*Math::PI).should be_close(0.0, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:sin!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/sinh.rb b/spec/ruby/library/complex/math/shared/sinh.rb
deleted file mode 100644
index de80a376da..0000000000
--- a/spec/ruby/library/complex/math/shared/sinh.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_sinh, shared: true do
-  it "returns the hyperbolic sin of the argument" do
-    @object.send(:sinh, 0.0).should == 0.0
-    @object.send(:sinh, -0.0).should == 0.0
-    @object.send(:sinh, 1.5).should be_close(2.12927945509482, TOLERANCE)
-    @object.send(:sinh, -2.8).should be_close(-8.19191835423591, TOLERANCE)
-  end
-
-  it "returns the hyperbolic sin for Complex numbers" do
-    @object.send(:sinh, Complex(0, CMath::PI)).should be_close(Complex(-0.0, 1.22464679914735e-16), TOLERANCE)
-    @object.send(:sinh, Complex(3, 4)).should be_close(Complex(-6.548120040911, -7.61923172032141), TOLERANCE)
-  end
-end
-
-describe :complex_math_sinh_bang, shared: true do
-  it "returns the hyperbolic sin of the argument" do
-    @object.send(:sinh!, 0.0).should == 0.0
-    @object.send(:sinh!, -0.0).should == 0.0
-    @object.send(:sinh!, 1.5).should be_close(2.12927945509482, TOLERANCE)
-    @object.send(:sinh!, -2.8).should be_close(-8.19191835423591, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:sinh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/sqrt.rb b/spec/ruby/library/complex/math/shared/sqrt.rb
deleted file mode 100644
index 23b1ba48ff..0000000000
--- a/spec/ruby/library/complex/math/shared/sqrt.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_sqrt, shared: true do
-  it "returns the square root for positive numbers" do
-    @object.send(:sqrt, 4).should == 2
-    @object.send(:sqrt, 19.36).should == 4.4
-  end
-
-  it "returns the square root for negative numbers" do
-    @object.send(:sqrt, -4).should == Complex(0, 2.0)
-    @object.send(:sqrt, -19.36).should == Complex(0, 4.4)
-  end
-
-  it "returns the square root for Complex numbers" do
-    @object.send(:sqrt, Complex(4, 5)).should be_close(Complex(2.2806933416653, 1.09615788950152), TOLERANCE)
-    @object.send(:sqrt, Complex(4, -5)).should be_close(Complex(2.2806933416653, -1.09615788950152), TOLERANCE)
-  end
-end
-
-describe :complex_math_sqrt_bang, shared: true do
-  it "returns the square root for positive numbers" do
-    @object.send(:sqrt!, 4).should == 2
-    @object.send(:sqrt!, 19.36).should == 4.4
-  end
-
-  it "raises Errno::EDOM when the passed argument is negative" do
-    -> { @object.send(:sqrt!, -4) }.should raise_error(Errno::EDOM)
-    -> { @object.send(:sqrt!, -19.36) }.should raise_error(Errno::EDOM)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:sqrt!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/tan.rb b/spec/ruby/library/complex/math/shared/tan.rb
deleted file mode 100644
index 9022c84fc9..0000000000
--- a/spec/ruby/library/complex/math/shared/tan.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_tan, shared: true do
-  it "returns the tangent of the argument" do
-    @object.send(:tan, 0.0).should == 0.0
-    @object.send(:tan, -0.0).should == -0.0
-    @object.send(:tan, 4.22).should be_close(1.86406937682395, TOLERANCE)
-    @object.send(:tan, -9.65).should be_close(-0.229109052606441, TOLERANCE)
-  end
-
-  it "returns the tangent for Complex numbers" do
-    @object.send(:tan, Complex(0, CMath::PI)).should be_close(Complex(0.0, 0.99627207622075), TOLERANCE)
-    @object.send(:tan, Complex(3, 4)).should be_close(Complex(-0.000187346204629452, 0.999355987381473), TOLERANCE)
-  end
-end
-
-describe :complex_math_tan_bang, shared: true do
-  it "returns the tangent of the argument" do
-    @object.send(:tan!, 0.0).should == 0.0
-    @object.send(:tan!, -0.0).should == -0.0
-    @object.send(:tan!, 4.22).should be_close(1.86406937682395, TOLERANCE)
-    @object.send(:tan!, -9.65).should be_close(-0.229109052606441, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:tan!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/shared/tanh.rb b/spec/ruby/library/complex/math/shared/tanh.rb
deleted file mode 100644
index f2c9a5abb1..0000000000
--- a/spec/ruby/library/complex/math/shared/tanh.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../fixtures/classes'
-
-describe :complex_math_tanh, shared: true do
-  it "returns the hyperbolic tangent of the argument" do
-    @object.send(:tanh, 0.0).should == 0.0
-    @object.send(:tanh, -0.0).should == -0.0
-    @object.send(:tanh, infinity_value).should == 1.0
-    @object.send(:tanh, -infinity_value).should == -1.0
-    @object.send(:tanh, 2.5).should be_close(0.98661429815143, TOLERANCE)
-    @object.send(:tanh, -4.892).should be_close(-0.999887314427707, TOLERANCE)
-  end
-
-  it "returns the hyperbolic tangent for Complex numbers" do
-    @object.send(:tanh, Complex(0, CMath::PI)).should be_close(Complex(0.0, -1.22464679914735e-16), TOLERANCE)
-    @object.send(:tanh, Complex(3, 4)).should be_close(Complex(1.00070953606723, 0.00490825806749599), TOLERANCE)
-  end
-end
-
-describe :complex_math_tanh_bang, shared: true do
-  it "returns the hyperbolic tangent of the argument" do
-    @object.send(:tanh!, 0.0).should == 0.0
-    @object.send(:tanh!, -0.0).should == -0.0
-    @object.send(:tanh!, infinity_value).should == 1.0
-    @object.send(:tanh!, -infinity_value).should == -1.0
-    @object.send(:tanh!, 2.5).should be_close(0.98661429815143, TOLERANCE)
-    @object.send(:tanh!, -4.892).should be_close(-0.999887314427707, TOLERANCE)
-  end
-
-  it "raises a TypeError when passed a Complex number" do
-    -> { @object.send(:tanh!, Complex(4, 5)) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/complex/math/sin_spec.rb b/spec/ruby/library/complex/math/sin_spec.rb
deleted file mode 100644
index 6046cd29c3..0000000000
--- a/spec/ruby/library/complex/math/sin_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/sin'
-
-describe "Math#sin" do
-  it_behaves_like :complex_math_sin, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:sin)
-  end
-end
-
-describe "Math.sin" do
-  it_behaves_like :complex_math_sin, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/sinh_spec.rb b/spec/ruby/library/complex/math/sinh_spec.rb
deleted file mode 100644
index f5f98778b2..0000000000
--- a/spec/ruby/library/complex/math/sinh_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/sinh'
-
-describe "Math#sinh" do
-  it_behaves_like :complex_math_sinh, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:sinh)
-  end
-end
-
-describe "Math.sinh" do
-  it_behaves_like :complex_math_sinh, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/sqrt_spec.rb b/spec/ruby/library/complex/math/sqrt_spec.rb
deleted file mode 100644
index 8b7050c108..0000000000
--- a/spec/ruby/library/complex/math/sqrt_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/sqrt'
-
-describe "Math#sqrt" do
-  it_behaves_like :complex_math_sqrt, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:sqrt)
-  end
-end
-
-describe "Math.sqrt" do
-  it_behaves_like :complex_math_sqrt, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/tan_spec.rb b/spec/ruby/library/complex/math/tan_spec.rb
deleted file mode 100644
index b0f18bb515..0000000000
--- a/spec/ruby/library/complex/math/tan_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/tan'
-
-describe "Math#tan" do
-  it_behaves_like :complex_math_tan, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:tan)
-  end
-end
-
-describe "Math.tan" do
-  it_behaves_like :complex_math_tan, :_, CMath
-end
diff --git a/spec/ruby/library/complex/math/tanh_spec.rb b/spec/ruby/library/complex/math/tanh_spec.rb
deleted file mode 100644
index 469bba7554..0000000000
--- a/spec/ruby/library/complex/math/tanh_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'complex'
-require_relative 'shared/tanh'
-
-describe "Math#tanh" do
-  it_behaves_like :complex_math_tanh, :_, IncludesMath.new
-
-  it "is a private instance method" do
-    IncludesMath.should have_private_instance_method(:tanh)
-  end
-end
-
-describe "Math.tanh" do
-  it_behaves_like :complex_math_tanh, :_, CMath
-end
diff --git a/spec/ruby/library/complex/numeric/im_spec.rb b/spec/ruby/library/complex/numeric/im_spec.rb
deleted file mode 100644
index 17f4a0476b..0000000000
--- a/spec/ruby/library/complex/numeric/im_spec.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-require_relative '../../../spec_helper'
-
-require 'complex'
diff --git a/spec/ruby/library/conditionvariable/broadcast_spec.rb b/spec/ruby/library/conditionvariable/broadcast_spec.rb
deleted file mode 100644
index a31a0443bd..0000000000
--- a/spec/ruby/library/conditionvariable/broadcast_spec.rb
+++ /dev/null
@@ -1,67 +0,0 @@
-require_relative '../../spec_helper'
-require 'thread'
-
-describe "ConditionVariable#broadcast" do
-  it "returns self if nothing to broadcast to" do
-    cv = ConditionVariable.new
-    cv.broadcast.should == cv
-  end
-
-  it "returns self if something is waiting for a broadcast" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    in_synchronize = false
-
-    th = Thread.new do
-      m.synchronize do
-        in_synchronize = true
-        cv.wait(m)
-      end
-    end
-
-    # wait for m to acquire the mutex
-    Thread.pass until in_synchronize
-    # wait until th is sleeping (ie waiting)
-    Thread.pass while th.status and th.status != "sleep"
-
-    m.synchronize { cv.broadcast }.should == cv
-
-    th.join
-  end
-
-  it "releases all threads waiting in line for this resource" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    threads = []
-    r1 = []
-    r2 = []
-
-    # large number to attempt to cause race conditions
-    100.times do |i|
-      threads << Thread.new(i) do |tid|
-        m.synchronize do
-          r1 << tid
-          cv.wait(m)
-          r2 << tid
-        end
-      end
-    end
-
-    # wait for all threads to acquire the mutex the first time
-    Thread.pass until m.synchronize { r1.size == threads.size }
-    # wait until all threads are sleeping (ie waiting)
-    Thread.pass until threads.all? {|th| th.status == "sleep" }
-
-    r2.should be_empty
-    m.synchronize do
-      cv.broadcast
-    end
-
-    threads.each {|t| t.join }
-
-    # ensure that all threads that enter cv.wait are released
-    r2.sort.should == r1.sort
-    # note that order is not specified as broadcast results in a race
-    # condition on regaining the lock m
-  end
-end
diff --git a/spec/ruby/library/conditionvariable/marshal_dump_spec.rb b/spec/ruby/library/conditionvariable/marshal_dump_spec.rb
deleted file mode 100644
index f951a13e28..0000000000
--- a/spec/ruby/library/conditionvariable/marshal_dump_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-require 'thread'
-
-describe "ConditionVariable#marshal_dump" do
-  it "raises a TypeError" do
-    cv = ConditionVariable.new
-    -> { cv.marshal_dump }.should raise_error(TypeError, /can't dump/)
-  end
-end
diff --git a/spec/ruby/library/conditionvariable/signal_spec.rb b/spec/ruby/library/conditionvariable/signal_spec.rb
deleted file mode 100644
index 0dafe8527f..0000000000
--- a/spec/ruby/library/conditionvariable/signal_spec.rb
+++ /dev/null
@@ -1,69 +0,0 @@
-require_relative '../../spec_helper'
-require 'thread'
-
-describe "ConditionVariable#signal" do
-  it "returns self if nothing to signal" do
-    cv = ConditionVariable.new
-    cv.signal.should == cv
-  end
-
-  it "returns self if something is waiting for a signal" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    in_synchronize = false
-
-    th = Thread.new do
-      m.synchronize do
-        in_synchronize = true
-        cv.wait(m)
-      end
-    end
-
-    # wait for m to acquire the mutex
-    Thread.pass until in_synchronize
-    # wait until th is sleeping (ie waiting)
-    Thread.pass while th.status and th.status != "sleep"
-
-    m.synchronize { cv.signal }.should == cv
-
-    th.join
-  end
-
-  it "releases the first thread waiting in line for this resource" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    threads = []
-    r1 = []
-    r2 = []
-
-    # large number to attempt to cause race conditions
-    100.times do |i|
-      threads << Thread.new(i) do |tid|
-        m.synchronize do
-          r1 << tid
-          cv.wait(m)
-          r2 << tid
-        end
-      end
-    end
-
-    # wait for all threads to acquire the mutex the first time
-    Thread.pass until m.synchronize { r1.size == threads.size }
-    # wait until all threads are sleeping (ie waiting)
-    Thread.pass until threads.all? {|th| th.status == "sleep" }
-
-    r2.should be_empty
-    100.times do |i|
-      m.synchronize do
-        cv.signal
-      end
-      Thread.pass until r2.size == i+1
-    end
-
-    threads.each {|t| t.join }
-
-    # ensure that all the threads that went into the cv.wait are
-    # released in the same order
-    r2.should == r1
-  end
-end
diff --git a/spec/ruby/library/conditionvariable/wait_spec.rb b/spec/ruby/library/conditionvariable/wait_spec.rb
deleted file mode 100644
index f57ab4c778..0000000000
--- a/spec/ruby/library/conditionvariable/wait_spec.rb
+++ /dev/null
@@ -1,132 +0,0 @@
-require_relative '../../spec_helper'
-require 'thread'
-
-describe "ConditionVariable#wait" do
-  it "calls #sleep on the given object" do
-    o = Object.new
-    o.should_receive(:sleep).with(1234)
-
-    cv = ConditionVariable.new
-
-    cv.wait(o, 1234)
-  end
-
-  it "returns self" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    in_synchronize = false
-
-    th = Thread.new do
-      m.synchronize do
-        in_synchronize = true
-        cv.wait(m).should == cv
-      end
-    end
-
-    # wait for m to acquire the mutex
-    Thread.pass until in_synchronize
-    # wait until th is sleeping (ie waiting)
-    Thread.pass while th.status and th.status != "sleep"
-
-    m.synchronize { cv.signal }
-    th.join
-  end
-
-  it "reacquires the lock even if the thread is killed" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    in_synchronize = false
-    owned = nil
-
-    th = Thread.new do
-      m.synchronize do
-        in_synchronize = true
-        begin
-          cv.wait(m)
-        ensure
-          owned = m.owned?
-          $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
-        end
-      end
-    end
-
-    # wait for m to acquire the mutex
-    Thread.pass until in_synchronize
-    # wait until th is sleeping (ie waiting)
-    Thread.pass while th.status and th.status != "sleep"
-
-    th.kill
-    th.join
-
-    owned.should == true
-  end
-
-  ruby_bug '#14999', ''...'2.5' do
-    it "reacquires the lock even if the thread is killed after being signaled" do
-      m = Mutex.new
-      cv = ConditionVariable.new
-      in_synchronize = false
-      owned = nil
-
-      th = Thread.new do
-        m.synchronize do
-          in_synchronize = true
-          begin
-            cv.wait(m)
-          ensure
-            owned = m.owned?
-            $stderr.puts "\nThe Thread doesn't own the Mutex!" unless owned
-          end
-        end
-      end
-
-      # wait for m to acquire the mutex
-      Thread.pass until in_synchronize
-      # wait until th is sleeping (ie waiting)
-      Thread.pass while th.status and th.status != "sleep"
-
-      m.synchronize {
-        cv.signal
-        # Wait that the thread is blocked on acquiring the Mutex
-        sleep 0.001
-        # Kill the thread, yet the thread should first acquire the Mutex before going on
-        th.kill
-      }
-
-      th.join
-      owned.should == true
-    end
-  end
-
-  it "supports multiple Threads waiting on the same ConditionVariable and Mutex" do
-    m = Mutex.new
-    cv = ConditionVariable.new
-    n_threads = 4
-    events = []
-
-    threads = n_threads.times.map {
-      Thread.new {
-        m.synchronize {
-          events << :t_in_synchronize
-          cv.wait(m)
-        }
-      }
-    }
-
-    Thread.pass until m.synchronize { events.size } == n_threads
-    Thread.pass while threads.any? { |th| th.status and th.status != "sleep" }
-    m.synchronize do
-      threads.each { |t|
-        # Cause interactions with the waiting threads.
-        # On TruffleRuby, this causes a safepoint which has interesting
-        # interactions with the ConditionVariable.
-        bt = t.backtrace
-        bt.should be_kind_of(Array)
-        bt.size.should >= 2
-      }
-    end
-
-    cv.broadcast
-    threads.each(&:join)
-  end
-end
diff --git a/spec/ruby/library/coverage/fixtures/code_with_begin.rb b/spec/ruby/library/coverage/fixtures/code_with_begin.rb
new file mode 100644
index 0000000000..9a6384e337
--- /dev/null
+++ b/spec/ruby/library/coverage/fixtures/code_with_begin.rb
@@ -0,0 +1,3 @@
+begin
+  'coverage with begin'
+end
diff --git a/spec/ruby/library/coverage/fixtures/eval_code.rb b/spec/ruby/library/coverage/fixtures/eval_code.rb
new file mode 100644
index 0000000000..8ab82218f3
--- /dev/null
+++ b/spec/ruby/library/coverage/fixtures/eval_code.rb
@@ -0,0 +1,11 @@
+5 + 5
+
+module CoverageSpecs
+
+  class_eval <<-RUBY, __FILE__, __LINE__ + 1
+    attr_reader :ok
+  RUBY
+
+end
+
+4 + 4
diff --git a/spec/ruby/library/coverage/result_spec.rb b/spec/ruby/library/coverage/result_spec.rb
index ebfa5538b4..0101eb6a64 100644
--- a/spec/ruby/library/coverage/result_spec.rb
+++ b/spec/ruby/library/coverage/result_spec.rb
@@ -5,11 +5,21 @@ describe 'Coverage.result' do
   before :all do
     @class_file = fixture __FILE__, 'some_class.rb'
     @config_file = fixture __FILE__, 'start_coverage.rb'
+    @eval_code_file = fixture __FILE__, 'eval_code.rb'
+    @with_begin_file = fixture __FILE__, 'code_with_begin.rb'
+  end
+
+  before :each do
+    Coverage.running?.should == false
   end
 
   after :each do
     $LOADED_FEATURES.delete(@class_file)
     $LOADED_FEATURES.delete(@config_file)
+    $LOADED_FEATURES.delete(@eval_code_file)
+    $LOADED_FEATURES.delete(@with_begin_file)
+
+    Coverage.result if Coverage.running?
   end
 
   it 'gives the covered files as a hash with arrays of count or nil' do
@@ -24,6 +34,39 @@ describe 'Coverage.result' do
     }
   end
 
+  it 'returns results for each mode separately when enabled :all modes' do
+    Coverage.start(:all)
+    require @class_file.chomp('.rb')
+    result = Coverage.result
+
+    result.should == {
+      @class_file => {
+        lines: [
+          nil, nil, 1, nil, nil, 1, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+        ],
+        branches: {},
+        methods: {
+          [SomeClass, :some_method, 6, 2, 11, 5] => 0
+        }
+      }
+    }
+  end
+
+  it 'returns results for each mode separately when enabled any mode explicitly' do
+    Coverage.start(lines: true)
+    require @class_file.chomp('.rb')
+    result = Coverage.result
+
+    result.should == {
+      @class_file =>
+        {
+          lines: [
+            nil, nil, 1, nil, nil, 1, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+          ]
+        }
+    }
+  end
+
   it 'no requires/loads should give empty hash' do
     Coverage.start
     result = Coverage.result
@@ -35,8 +78,9 @@ describe 'Coverage.result' do
     Coverage.start
     require @class_file.chomp('.rb')
     Coverage.result
-    -> { Coverage.result }
-      .should raise_error(RuntimeError, 'coverage measurement is not enabled')
+    -> {
+      Coverage.result
+    }.should raise_error(RuntimeError, 'coverage measurement is not enabled')
   end
 
   it 'second run should give same result' do
@@ -62,16 +106,238 @@ describe 'Coverage.result' do
     result.should == {}
   end
 
-  it 'second Coverage.start does nothing' do
-    Coverage.start
+  it 'does not include the file starting coverage since it is not tracked' do
     require @config_file.chomp('.rb')
+    Coverage.result.should_not include(@config_file)
+  end
+
+  it 'returns the correct results when eval coverage is enabled' do
+    Coverage.supported?(:eval).should == true
+
+    Coverage.start(lines: true, eval: true)
+    require @eval_code_file.chomp('.rb')
     result = Coverage.result
 
-    result.should == { @config_file => [1, 1, 1] }
+    result.should == {
+      @eval_code_file => {
+        lines: [1, nil, 1, nil, 1, 1, nil, nil, nil, nil, 1]
+      }
+    }
   end
 
-  it 'does not include the file starting coverage since it is not tracked' do
-    require @config_file.chomp('.rb')
-    Coverage.result.should_not include(@config_file)
+  it 'returns the correct results when eval coverage is disabled' do
+    Coverage.supported?(:eval).should == true
+
+    Coverage.start(lines: true, eval: false)
+    require @eval_code_file.chomp('.rb')
+    result = Coverage.result
+
+    result.should == {
+      @eval_code_file => {
+        lines: [1, nil, 1, nil, 1, nil, nil, nil, nil, nil, 1]
+      }
+    }
+  end
+
+  it "disables coverage measurement when stop option is not specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result
+    Coverage.running?.should == false
+  end
+
+  it "disables coverage measurement when stop: true option is specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    -> {
+      Coverage.result(stop: true)
+    }.should complain(/warning: stop implies clear/)
+
+    Coverage.running?.should == false
+  end
+
+  it "does not disable coverage measurement when stop: false option is specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: false)
+    Coverage.running?.should == true
+  end
+
+  it "does not disable coverage measurement when stop option is not specified but clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(clear: true)
+    Coverage.running?.should == true
+  end
+
+  it "does not disable coverage measurement when stop option is not specified but clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(clear: false)
+    Coverage.running?.should == true
+  end
+
+  it "disables coverage measurement when stop: true and clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: true, clear: true)
+    Coverage.running?.should == false
+  end
+
+  it "disables coverage measurement when stop: true and clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    -> {
+      Coverage.result(stop: true, clear: false)
+    }.should complain(/warning: stop implies clear/)
+
+    Coverage.running?.should == false
+  end
+
+  it "does not disable coverage measurement when stop: false and clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: false, clear: true)
+    Coverage.running?.should == true
+  end
+
+  it "does not disable coverage measurement when stop: false and clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: false, clear: false)
+    Coverage.running?.should == true
+  end
+
+  it "resets counters (remove them) when stop: true specified but clear option is not specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    -> {
+      Coverage.result(stop: true) # clears counters
+    }.should complain(/warning: stop implies clear/)
+
+    Coverage.start
+    Coverage.peek_result.should == {}
+  end
+
+  it "resets counters (remove them) when stop: true and clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: true, clear: true) # clears counters
+
+    Coverage.start
+    Coverage.peek_result.should == {}
+  end
+
+  it "resets counters (remove them) when stop: true and clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    -> {
+      Coverage.result(stop: true, clear: false) # clears counters
+    }.should complain(/warning: stop implies clear/)
+
+    Coverage.start
+    Coverage.peek_result.should == {}
+  end
+
+  it "resets counters (remove them) when both stop and clear options are not specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result # clears counters
+
+    Coverage.start
+    Coverage.peek_result.should == {}
+  end
+
+  it "clears counters (sets 0 values) when stop is not specified but clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(clear: true) # clears counters
+
+    Coverage.peek_result.should == {
+      @class_file => [
+        nil, nil, 0, nil, nil, 0, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+      ]
+    }
+  end
+
+  it "does not clear counters when stop is not specified but clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    result = Coverage.result(clear: false) # doesn't clear counters
+    result.should == {
+      @class_file => [
+        nil, nil, 1, nil, nil, 1, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+      ]
+    }
+
+    Coverage.peek_result.should == result
+  end
+
+  it "does not clear counters when stop: false and clear is not specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    result = Coverage.result(stop: false) # doesn't clear counters
+    result.should == {
+      @class_file => [
+        nil, nil, 1, nil, nil, 1, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+      ]
+    }
+
+    Coverage.peek_result.should == result
+  end
+
+  it "clears counters (sets 0 values) when stop: false and clear: true specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    Coverage.result(stop: false, clear: true) # clears counters
+
+    Coverage.peek_result.should == {
+      @class_file => [
+        nil, nil, 0, nil, nil, 0, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+      ]
+    }
+  end
+
+  it "does not clear counters when stop: false and clear: false specified" do
+    Coverage.start
+    require @class_file.chomp('.rb')
+
+    result = Coverage.result(stop: false, clear: false) # doesn't clear counters
+    result.should == {
+      @class_file => [
+        nil, nil, 1, nil, nil, 1, nil, nil, 0, nil, nil, nil, nil, nil, nil, nil
+      ]
+    }
+
+    Coverage.peek_result.should == result
+  end
+
+  it 'covers 100% lines with begin' do
+    Coverage.start
+    require @with_begin_file.chomp('.rb')
+    result = Coverage.result
+
+    result.should == {
+      @with_begin_file => [
+        nil, 1, nil
+      ]
+    }
   end
 end
diff --git a/spec/ruby/library/coverage/running_spec.rb b/spec/ruby/library/coverage/running_spec.rb
new file mode 100644
index 0000000000..e9cc7ada5a
--- /dev/null
+++ b/spec/ruby/library/coverage/running_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../spec_helper'
+require 'coverage'
+
+describe 'Coverage.running?' do
+  it "returns false if coverage is not started" do
+    Coverage.running?.should == false
+  end
+
+  it "returns true if coverage is started" do
+    Coverage.start
+    Coverage.running?.should == true
+    Coverage.result
+  end
+
+  it "returns false if coverage was started and stopped" do
+    Coverage.start
+    Coverage.result
+    Coverage.running?.should == false
+  end
+end
diff --git a/spec/ruby/library/coverage/start_spec.rb b/spec/ruby/library/coverage/start_spec.rb
index ddfad8b47c..c921b85401 100644
--- a/spec/ruby/library/coverage/start_spec.rb
+++ b/spec/ruby/library/coverage/start_spec.rb
@@ -2,5 +2,86 @@ require_relative '../../spec_helper'
 require 'coverage'
 
 describe 'Coverage.start' do
-  it 'needs to be reviewed for spec completeness'
+  before :each do
+    Coverage.should_not.running?
+  end
+
+  after :each do
+    Coverage.result(stop: true, clear: true) if Coverage.running?
+  end
+
+  it "enables the coverage measurement" do
+    Coverage.start
+    Coverage.should.running?
+  end
+
+  it "returns nil" do
+    Coverage.start.should == nil
+  end
+
+  it 'raises error when repeated Coverage.start call happens' do
+    Coverage.start
+
+    -> {
+      Coverage.start
+    }.should raise_error(RuntimeError, 'coverage measurement is already setup')
+  end
+
+  it "accepts :all optional argument" do
+    Coverage.start(:all)
+    Coverage.should.running?
+  end
+
+  it "accepts lines: optional keyword argument" do
+    Coverage.start(lines: true)
+    Coverage.should.running?
+  end
+
+  it "accepts branches: optional keyword argument" do
+    Coverage.start(branches: true)
+    Coverage.should.running?
+  end
+
+  it "accepts methods: optional keyword argument" do
+    Coverage.start(methods: true)
+    Coverage.should.running?
+  end
+
+  it "accepts eval: optional keyword argument" do
+    Coverage.start(eval: true)
+    Coverage.should.running?
+  end
+
+  it "accepts oneshot_lines: optional keyword argument" do
+    Coverage.start(oneshot_lines: true)
+    Coverage.should.running?
+  end
+
+  it "ignores unknown keyword arguments" do
+    Coverage.start(foo: true)
+    Coverage.should.running?
+  end
+
+  it "expects a Hash if not passed :all" do
+    -> {
+      Coverage.start(42)
+    }.should raise_error(TypeError, "no implicit conversion of Integer into Hash")
+  end
+
+  it "does not accept both lines: and oneshot_lines: keyword arguments" do
+    -> {
+      Coverage.start(lines: true, oneshot_lines: true)
+    }.should raise_error(RuntimeError, "cannot enable lines and oneshot_lines simultaneously")
+  end
+
+  it "enables the coverage measurement if passed options with `false` value" do
+    Coverage.start(lines: false, branches: false, methods: false, eval: false, oneshot_lines: false)
+    Coverage.should.running?
+  end
+
+  it "measures coverage within eval" do
+    Coverage.start(lines: true, eval: true)
+    eval("Object.new\n"*3, binding, "test.rb", 1)
+    Coverage.result["test.rb"].should == {lines: [1, 1, 1]}
+  end
 end
diff --git a/spec/ruby/library/coverage/supported_spec.rb b/spec/ruby/library/coverage/supported_spec.rb
new file mode 100644
index 0000000000..9226548c1f
--- /dev/null
+++ b/spec/ruby/library/coverage/supported_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require 'coverage'
+
+describe "Coverage.supported?" do
+  it "returns true or false if coverage measurement is supported for the given mode" do
+    [true, false].should.include?(Coverage.supported?(:lines))
+    [true, false].should.include?(Coverage.supported?(:branches))
+    [true, false].should.include?(Coverage.supported?(:methods))
+    [true, false].should.include?(Coverage.supported?(:eval))
+  end
+
+  it "returns false for not existing modes" do
+    Coverage.supported?(:foo).should == false
+    Coverage.supported?(:bar).should == false
+  end
+
+  it "raise TypeError if argument is not Symbol" do
+    -> {
+      Coverage.supported?("lines")
+    }.should raise_error(TypeError, "wrong argument type String (expected Symbol)")
+
+    -> {
+      Coverage.supported?([])
+    }.should raise_error(TypeError, "wrong argument type Array (expected Symbol)")
+
+    -> {
+      Coverage.supported?(1)
+    }.should raise_error(TypeError, "wrong argument type Integer (expected Symbol)")
+  end
+end
diff --git a/spec/ruby/library/csv/generate_spec.rb b/spec/ruby/library/csv/generate_spec.rb
index 0a1e3d9604..b45e2eb95b 100644
--- a/spec/ruby/library/csv/generate_spec.rb
+++ b/spec/ruby/library/csv/generate_spec.rb
@@ -21,7 +21,7 @@ describe "CSV.generate" do
   end
 
   it "appends and returns the argument itself" do
-    str = ""
+    str = +""
     csv_str = CSV.generate(str) do |csv|
       csv.add_row [1, 2, 3]
       csv << [4, 5, 6]
diff --git a/spec/ruby/library/csv/liberal_parsing_spec.rb b/spec/ruby/library/csv/liberal_parsing_spec.rb
index 2929d6e2aa..9878658027 100644
--- a/spec/ruby/library/csv/liberal_parsing_spec.rb
+++ b/spec/ruby/library/csv/liberal_parsing_spec.rb
@@ -4,16 +4,16 @@ require 'csv'
 describe "CSV#liberal_parsing?" do
   it "returns true if illegal input is handled" do
     csv = CSV.new("", liberal_parsing: true)
-    csv.liberal_parsing?.should == true
+    csv.should.liberal_parsing?
   end
 
   it "returns false if illegal input is not handled" do
     csv = CSV.new("", liberal_parsing: false)
-    csv.liberal_parsing?.should == false
+    csv.should_not.liberal_parsing?
   end
 
   it "returns false by default" do
     csv = CSV.new("")
-    csv.liberal_parsing?.should == false
+    csv.should_not.liberal_parsing?
   end
 end
diff --git a/spec/ruby/library/date/accessor_spec.rb b/spec/ruby/library/date/accessor_spec.rb
index 68a2d9f3de..74ed0e9c21 100644
--- a/spec/ruby/library/date/accessor_spec.rb
+++ b/spec/ruby/library/date/accessor_spec.rb
@@ -38,7 +38,7 @@ describe "Date#year" do
 end
 
 describe "Date#yday" do
-  it "determines the year" do
+  it "determines the day of the year" do
     Date.civil(2007,  1, 17).yday.should == 17
     Date.civil(2008, 10, 28).yday.should == 302
   end
diff --git a/spec/ruby/library/date/civil_spec.rb b/spec/ruby/library/date/civil_spec.rb
index f3537c2f84..1c780fce56 100644
--- a/spec/ruby/library/date/civil_spec.rb
+++ b/spec/ruby/library/date/civil_spec.rb
@@ -2,11 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'shared/civil'
 require 'date'
 
-describe "Date#civil" do
-  it_behaves_like :date_civil, :civil
-end
-
-
 describe "Date.civil" do
-  it "needs to be reviewed for spec completeness"
+  it_behaves_like :date_civil, :civil
 end
diff --git a/spec/ruby/library/date/constants_spec.rb b/spec/ruby/library/date/constants_spec.rb
index fc1dba4999..1d18dd1b0c 100644
--- a/spec/ruby/library/date/constants_spec.rb
+++ b/spec/ruby/library/date/constants_spec.rb
@@ -36,11 +36,11 @@ describe "Date constants" do
     [Date::MONTHNAMES, Date::DAYNAMES, Date::ABBR_MONTHNAMES, Date::ABBR_DAYNAMES].each do |ary|
       -> {
         ary << "Unknown"
-      }.should raise_error(frozen_error_class, /frozen/)
+      }.should raise_error(FrozenError, /frozen/)
       ary.compact.each do |name|
         -> {
           name << "modified"
-        }.should raise_error(frozen_error_class, /frozen/)
+        }.should raise_error(FrozenError, /frozen/)
       end
     end
   end
diff --git a/spec/ruby/library/date/deconstruct_keys_spec.rb b/spec/ruby/library/date/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..b9dd6b8816
--- /dev/null
+++ b/spec/ruby/library/date/deconstruct_keys_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require 'date'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
+
+describe "Date#deconstruct_keys" do
+  it "returns whole hash for nil as an argument" do
+    d = Date.new(2022, 10, 5)
+    d.deconstruct_keys(nil).should == { year: 2022, month: 10, day: 5, yday: 278, wday: 3 }
+  end
+
+  it "returns only specified keys" do
+    d = Date.new(2022, 10, 5)
+    d.deconstruct_keys([:year, :month]).should == { year: 2022, month: 10 }
+  end
+
+  it "requires one argument" do
+    -> {
+      Date.new(2022, 10, 5).deconstruct_keys
+    }.should raise_error(ArgumentError)
+  end
+
+  it "it raises error when argument is neither nil nor array" do
+    d = Date.new(2022, 10, 5)
+
+    -> { d.deconstruct_keys(1) }.should raise_error(TypeError, "wrong argument type Integer (expected Array or nil)")
+    -> { d.deconstruct_keys("asd") }.should raise_error(TypeError, "wrong argument type String (expected Array or nil)")
+    -> { d.deconstruct_keys(:x) }.should raise_error(TypeError, "wrong argument type Symbol (expected Array or nil)")
+    -> { d.deconstruct_keys({}) }.should raise_error(TypeError, "wrong argument type Hash (expected Array or nil)")
+  end
+
+  it "returns {} when passed []" do
+    Date.new(2022, 10, 5).deconstruct_keys([]).should == {}
+  end
+
+  it "ignores non-Symbol keys" do
+    Date.new(2022, 10, 5).deconstruct_keys(['year', []]).should == {}
+  end
+
+  it "ignores not existing Symbol keys" do
+    Date.new(2022, 10, 5).deconstruct_keys([:year, :a]).should == { year: 2022 }
+  end
+end
diff --git a/spec/ruby/library/date/gregorian_spec.rb b/spec/ruby/library/date/gregorian_spec.rb
index 8b7033fe75..ea7ece2ade 100644
--- a/spec/ruby/library/date/gregorian_spec.rb
+++ b/spec/ruby/library/date/gregorian_spec.rb
@@ -9,7 +9,7 @@ describe "Date#gregorian?" do
   end
 
   it "marks a day after the calendar reform as Julian" do
-    Date.civil(2007, 2, 27).gregorian?.should == true
+    Date.civil(2007, 2, 27).should.gregorian?
     Date.civil(1607, 2, 27, Date.civil(1582, 1, 1).jd).gregorian?.should be_true
   end
 
diff --git a/spec/ruby/library/date/infinity_spec.rb b/spec/ruby/library/date/infinity_spec.rb
index 81d67ae249..721fd76066 100644
--- a/spec/ruby/library/date/infinity_spec.rb
+++ b/spec/ruby/library/date/infinity_spec.rb
@@ -5,16 +5,16 @@ describe "Date::Infinity" do
 
   it "should be able to check whether Infinity is zero" do
     i = Date::Infinity.new
-    i.zero?.should == false
+    i.should_not.zero?
   end
 
   it "should be able to check whether Infinity is finite" do
     i1 = Date::Infinity.new
-    i1.finite?.should == false
+    i1.should_not.finite?
     i2 = Date::Infinity.new(-1)
-    i2.finite?.should == false
+    i2.should_not.finite?
     i3 = Date::Infinity.new(0)
-    i3.finite?.should == false
+    i3.should_not.finite?
   end
 
   it "should be able to check whether Infinity is infinite" do
@@ -28,11 +28,11 @@ describe "Date::Infinity" do
 
   it "should be able to check whether Infinity is not a number" do
     i1 = Date::Infinity.new
-    i1.nan?.should == false
+    i1.should_not.nan?
     i2 = Date::Infinity.new(-1)
-    i2.nan?.should == false
+    i2.should_not.nan?
     i3 = Date::Infinity.new(0)
-    i3.nan?.should == true
+    i3.should.nan?
   end
 
   it "should be able to compare Infinity objects" do
diff --git a/spec/ruby/library/date/iso8601_spec.rb b/spec/ruby/library/date/iso8601_spec.rb
index 21b0a4cedd..af66845a6b 100644
--- a/spec/ruby/library/date/iso8601_spec.rb
+++ b/spec/ruby/library/date/iso8601_spec.rb
@@ -17,21 +17,40 @@ describe "Date.iso8601" do
     d.should == Date.civil(-4712, 1, 1)
   end
 
-  it "parses a Symbol into a Date object" do
-    d = Date.iso8601(:'2015-10-15')
-    d.should == Date.civil(2015, 10, 15)
-  end
-
   it "parses a StringSubclass into a Date object" do
     d = Date.iso8601(Class.new(String).new("-4712-01-01"))
     d.should == Date.civil(-4712, 1, 1)
   end
 
-  it "raises an ArgumentError when passed a Symbol without a valid Date" do
-    -> { Date.iso8601(:test) }.should raise_error(ArgumentError)
+  it "raises a Date::Error if the argument is a invalid Date" do
+    -> {
+      Date.iso8601('invalid')
+    }.should raise_error(Date::Error, "invalid date")
+  end
+
+  it "raises a Date::Error when passed a nil" do
+    -> {
+      Date.iso8601(nil)
+    }.should raise_error(Date::Error, "invalid date")
   end
 
   it "raises a TypeError when passed an Object" do
     -> { Date.iso8601(Object.new) }.should raise_error(TypeError)
   end
 end
+
+describe "Date._iso8601" do
+  it "returns an empty hash if the argument is a invalid Date" do
+    h = Date._iso8601('invalid')
+    h.should == {}
+  end
+
+  it "returns an empty hash if the argument is nil" do
+    h = Date._iso8601(nil)
+    h.should == {}
+  end
+
+  it "raises a TypeError when passed an Object" do
+    -> { Date._iso8601(Object.new) }.should raise_error(TypeError)
+  end
+end
diff --git a/spec/ruby/library/date/julian_spec.rb b/spec/ruby/library/date/julian_spec.rb
index 637a4739e5..db2629d1e7 100644
--- a/spec/ruby/library/date/julian_spec.rb
+++ b/spec/ruby/library/date/julian_spec.rb
@@ -4,12 +4,12 @@ require_relative '../../spec_helper'
 describe "Date#julian?" do
 
   it "marks a day before the calendar reform as Julian" do
-    Date.civil(1007, 2, 27).julian?.should == true
+    Date.civil(1007, 2, 27).should.julian?
     Date.civil(1907, 2, 27, Date.civil(1930, 1, 1).jd).julian?.should be_true
   end
 
   it "marks a day after the calendar reform as Julian" do
-    Date.civil(2007, 2, 27).julian?.should == false
+    Date.civil(2007, 2, 27).should_not.julian?
     Date.civil(1607, 2, 27, Date.civil(1582, 1, 1).jd).julian?.should be_false
   end
 
diff --git a/spec/ruby/library/date/mon_spec.rb b/spec/ruby/library/date/mon_spec.rb
index 724e7d6564..616d72cf88 100644
--- a/spec/ruby/library/date/mon_spec.rb
+++ b/spec/ruby/library/date/mon_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
+require_relative 'shared/month'
 require 'date'
 
 describe "Date#mon" do
-  it "needs to be reviewed for spec completeness"
+  it_behaves_like :date_month, :mon
 end
diff --git a/spec/ruby/library/date/month_spec.rb b/spec/ruby/library/date/month_spec.rb
index e040f9a94c..f493ec8119 100644
--- a/spec/ruby/library/date/month_spec.rb
+++ b/spec/ruby/library/date/month_spec.rb
@@ -1,9 +1,7 @@
 require_relative '../../spec_helper'
+require_relative 'shared/month'
 require 'date'
 
 describe "Date#month" do
-  it "returns the month" do
-    m = Date.new(2000, 7, 1).month
-    m.should == 7
-  end
+  it_behaves_like :date_month, :month
 end
diff --git a/spec/ruby/library/date/new_spec.rb b/spec/ruby/library/date/new_spec.rb
index 18120118c0..cb64cabce6 100644
--- a/spec/ruby/library/date/new_spec.rb
+++ b/spec/ruby/library/date/new_spec.rb
@@ -1,7 +1,6 @@
 require 'date'
 require_relative '../../spec_helper'
 require_relative 'shared/civil'
-require_relative 'shared/new_bang'
 
 describe "Date.new" do
   it_behaves_like :date_civil, :new
diff --git a/spec/ruby/library/date/parse_spec.rb b/spec/ruby/library/date/parse_spec.rb
index 379847a6fd..5ef4f6e9b5 100644
--- a/spec/ruby/library/date/parse_spec.rb
+++ b/spec/ruby/library/date/parse_spec.rb
@@ -67,7 +67,24 @@ describe "Date#parse" do
 
   it "raises a TypeError trying to parse non-String-like object" do
     -> { Date.parse(1) }.should raise_error(TypeError)
-    -> { Date.parse(:invalid) }.should raise_error(TypeError)
+    -> { Date.parse([]) }.should raise_error(TypeError)
+  end
+
+  it "coerces using to_str" do
+    c = Class.new do
+      attr_accessor :string
+      def to_str
+        @string
+      end
+    end
+    o = c.new
+    o.string = "19101101"
+
+    d = Date.parse(o)
+    d.should == Date.civil(1910, 11, 1)
+
+    # parse should not modify string value
+    o.to_str.should == "19101101"
   end
 end
 
@@ -76,7 +93,7 @@ describe "Date#parse with '.' separator" do
     @sep = '.'
   end
 
-  it_should_behave_like "date_parse"
+  it_should_behave_like :date_parse
 end
 
 describe "Date#parse with '/' separator" do
@@ -84,7 +101,7 @@ describe "Date#parse with '/' separator" do
     @sep = '/'
   end
 
-  it_should_behave_like "date_parse"
+  it_should_behave_like :date_parse
 end
 
 describe "Date#parse with ' ' separator" do
@@ -92,7 +109,7 @@ describe "Date#parse with ' ' separator" do
     @sep = ' '
   end
 
-  it_should_behave_like "date_parse"
+  it_should_behave_like :date_parse
 end
 
 describe "Date#parse with '/' separator US-style" do
@@ -100,7 +117,7 @@ describe "Date#parse with '/' separator US-style" do
     @sep = '/'
   end
 
-  it_should_behave_like "date_parse_us"
+  it_should_behave_like :date_parse_us
 end
 
 describe "Date#parse with '-' separator EU-style" do
@@ -108,7 +125,7 @@ describe "Date#parse with '-' separator EU-style" do
     @sep = '-'
   end
 
-  it_should_behave_like "date_parse_eu"
+  it_should_behave_like :date_parse_eu
 end
 
 describe "Date#parse(.)" do
diff --git a/spec/ruby/library/date/rfc3339_spec.rb b/spec/ruby/library/date/rfc3339_spec.rb
new file mode 100644
index 0000000000..a8711d47b2
--- /dev/null
+++ b/spec/ruby/library/date/rfc3339_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require 'date'
+
+describe "Date.rfc3339" do
+  it "needs to be reviewed for spec completeness"
+end
+
+describe "Date._rfc3339" do
+  it "returns an empty hash if the argument is a invalid Date" do
+    h = Date._rfc3339('invalid')
+    h.should == {}
+  end
+end
diff --git a/spec/ruby/library/date/shared/civil.rb b/spec/ruby/library/date/shared/civil.rb
index 4c8ba23622..bbed4a8866 100644
--- a/spec/ruby/library/date/shared/civil.rb
+++ b/spec/ruby/library/date/shared/civil.rb
@@ -5,7 +5,7 @@ describe :date_civil, shared: true do
     d.year.should == -4712
     d.month.should == 1
     d.day.should == 1
-    d.julian?.should == true
+    d.should.julian?
     d.jd.should == 0
   end
 
@@ -14,7 +14,7 @@ describe :date_civil, shared: true do
     d.year.should == 2000
     d.month.should == 3
     d.day.should == 5
-    d.julian?.should == false
+    d.should_not.julian?
     d.jd.should == 2451609
 
     # Should also work with years far in the past and future
@@ -23,14 +23,14 @@ describe :date_civil, shared: true do
     d.year.should == -9000
     d.month.should == 7
     d.day.should == 5
-    d.julian?.should == true
+    d.should.julian?
     d.jd.should == -1566006
 
     d = Date.send(@method, 9000, 10, 14)
     d.year.should == 9000
     d.month.should == 10
     d.day.should == 14
-    d.julian?.should == false
+    d.should_not.julian?
     d.jd.should == 5008529
 
   end
diff --git a/spec/ruby/library/date/shared/month.rb b/spec/ruby/library/date/shared/month.rb
new file mode 100644
index 0000000000..5fcb2cbeb0
--- /dev/null
+++ b/spec/ruby/library/date/shared/month.rb
@@ -0,0 +1,6 @@
+describe :date_month, shared: true do
+  it "returns the month" do
+    m = Date.new(2000, 7, 1).send(@method)
+    m.should == 7
+  end
+end
diff --git a/spec/ruby/library/date/shared/new_bang.rb b/spec/ruby/library/date/shared/new_bang.rb
deleted file mode 100644
index 90f1b432f0..0000000000
--- a/spec/ruby/library/date/shared/new_bang.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-describe :date_new_bang, shared: true do
-
-  it "returns a new Date object set to Astronomical Julian Day 0 if no arguments passed" do
-    d = Date.send(@method)
-    d.ajd.should == 0
-  end
-
-  it "accepts astronomical julian day number, offset as a fraction of a day and returns a new Date object" do
-    d = Date.send(@method, 10, 0.5)
-    d.ajd.should == 10
-    d.jd.should == 11
-  end
-
-end
diff --git a/spec/ruby/library/date/shared/parse.rb b/spec/ruby/library/date/shared/parse.rb
index 1015285e04..40af908386 100644
--- a/spec/ruby/library/date/shared/parse.rb
+++ b/spec/ruby/library/date/shared/parse.rb
@@ -13,7 +13,7 @@ describe :date_parse, shared: true do
     d.day.should == 23
   end
 
-  it "can parse a 'mmm DD YYYY' string into a Date object" do
+  it "can parse a 'DD mmm YYYY' string into a Date object" do
     d = Date.parse("23#{@sep}feb#{@sep}2008")
     d.year.should == 2008
     d.month.should == 2
@@ -42,7 +42,7 @@ describe :date_parse, shared: true do
     d.should == Date.civil(2005, 11, 5)
   end
 
-  it "can parse a year, day and month name into a Date object" do
+  it "can parse a day, month name and year into a Date object" do
     d = Date.parse("5th#{@sep}november#{@sep}2005")
     d.should == Date.civil(2005, 11, 5)
   end
diff --git a/spec/ruby/library/date/shared/parse_eu.rb b/spec/ruby/library/date/shared/parse_eu.rb
index ecb15e3c0e..3819524a57 100644
--- a/spec/ruby/library/date/shared/parse_eu.rb
+++ b/spec/ruby/library/date/shared/parse_eu.rb
@@ -7,28 +7,28 @@ describe :date_parse_eu, shared: true do
     d.day.should == 1
   end
 
-  it "can parse a MM-DD-YYYY string into a Date object" do
+  it "can parse a DD-MM-YYYY string into a Date object" do
     d = Date.parse("10#{@sep}01#{@sep}2007")
     d.year.should == 2007
     d.month.should == 1
     d.day.should == 10
   end
 
-  it "can parse a MM-DD-YY string into a Date object" do
+  it "can parse a YY-MM-DD string into a Date object" do
     d = Date.parse("10#{@sep}01#{@sep}07")
     d.year.should == 2010
     d.month.should == 1
     d.day.should == 7
   end
 
-  it "can parse a MM-DD-YY string into a Date object NOT using the year digits as 20XX" do
+  it "can parse a YY-MM-DD string into a Date object NOT using the year digits as 20XX" do
     d = Date.parse("10#{@sep}01#{@sep}07", false)
     d.year.should == 10
     d.month.should == 1
     d.day.should == 7
   end
 
-  it "can parse a MM-DD-YY string into a Date object using the year digits as 20XX" do
+  it "can parse a YY-MM-DD string into a Date object using the year digits as 20XX" do
     d = Date.parse("10#{@sep}01#{@sep}07", true)
     d.year.should == 2010
     d.month.should == 1
diff --git a/spec/ruby/library/date/shared/parse_us.rb b/spec/ruby/library/date/shared/parse_us.rb
index 7be62b1af1..17e2fc96c1 100644
--- a/spec/ruby/library/date/shared/parse_us.rb
+++ b/spec/ruby/library/date/shared/parse_us.rb
@@ -6,28 +6,28 @@ describe :date_parse_us, shared: true do
     d.day.should == 1
   end
 
-  it "parses a MM#{@sep}DD#{@sep}YYYY string into a Date object" do
+  it "parses a DD#{@sep}MM#{@sep}YYYY string into a Date object" do
     d = Date.parse("10#{@sep}01#{@sep}2007")
     d.year.should == 2007
     d.month.should == 1
     d.day.should == 10
   end
 
-  it "parses a MM#{@sep}DD#{@sep}YY string into a Date object" do
+  it "parses a YY#{@sep}MM#{@sep}DD string into a Date object" do
     d = Date.parse("10#{@sep}01#{@sep}07")
     d.year.should == 2010
     d.month.should == 1
     d.day.should == 7
   end
 
-  it "parses a MM#{@sep}DD#{@sep}YY string into a Date object NOT using the year digits as 20XX" do
+  it "parses a YY#{@sep}MM#{@sep}DD string into a Date object NOT using the year digits as 20XX" do
     d = Date.parse("10#{@sep}01#{@sep}07", false)
     d.year.should == 10
     d.month.should == 1
     d.day.should == 7
   end
 
-  it "parses a MM#{@sep}DD#{@sep}YY string into a Date object using the year digits as 20XX" do
+  it "parses a YY#{@sep}MM#{@sep}DD string into a Date object using the year digits as 20XX" do
     d = Date.parse("10#{@sep}01#{@sep}07", true)
     d.year.should == 2010
     d.month.should == 1
diff --git a/spec/ruby/library/date/shared/valid_jd.rb b/spec/ruby/library/date/shared/valid_jd.rb
index bd71f5abba..e474dfb450 100644
--- a/spec/ruby/library/date/shared/valid_jd.rb
+++ b/spec/ruby/library/date/shared/valid_jd.rb
@@ -1,7 +1,8 @@
 describe :date_valid_jd?, shared: true do
-  it "returns true if passed any value other than nil" do
+  it "returns true if passed a number value" do
     Date.send(@method, -100).should be_true
-    Date.send(@method, :number).should be_true
+    Date.send(@method, 100.0).should be_true
+    Date.send(@method, 2**100).should be_true
     Date.send(@method, Rational(1,2)).should be_true
   end
 
@@ -9,7 +10,11 @@ describe :date_valid_jd?, shared: true do
     Date.send(@method, nil).should be_false
   end
 
-  it "returns true if passed false" do
-    Date.send(@method, false).should be_true
+  it "returns false if passed symbol" do
+    Date.send(@method, :number).should be_false
+  end
+
+  it "returns false if passed false" do
+    Date.send(@method, false).should be_false
   end
 end
diff --git a/spec/ruby/library/date/strftime_spec.rb b/spec/ruby/library/date/strftime_spec.rb
index 9d298e42e6..1b93a8d1b2 100644
--- a/spec/ruby/library/date/strftime_spec.rb
+++ b/spec/ruby/library/date/strftime_spec.rb
@@ -1,5 +1,7 @@
+require_relative "../../spec_helper"
 require 'date'
 require_relative '../../shared/time/strftime_for_date'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
 
 describe "Date#strftime" do
   before :all do
@@ -21,10 +23,9 @@ describe "Date#strftime" do
     @date.strftime("%Z").should == "+00:00"
   end
 
-  # %v is %e-%b-%Y for Date/DateTime
   it "should be able to show the commercial week" do
-    @date.strftime("%v").should == " 9-Apr-2000"
-    @date.strftime("%v").should == @date.strftime('%e-%b-%Y')
+    @date.strftime("%v").should == " 9-APR-2000"
+    @date.strftime("%v").should != @date.strftime('%e-%b-%Y')
   end
 
   # additional conversion specifiers only in Date/DateTime
diff --git a/spec/ruby/library/date/time/to_date_spec.rb b/spec/ruby/library/date/time/to_date_spec.rb
new file mode 100644
index 0000000000..f9132da289
--- /dev/null
+++ b/spec/ruby/library/date/time/to_date_spec.rb
@@ -0,0 +1,42 @@
+
+require_relative '../../../spec_helper'
+require 'time'
+
+describe "Time#to_date" do
+  it "yields accurate julian date for ambiguous pre-Gregorian reform value" do
+    Time.utc(1582, 10, 4).to_date.jd.should == Date::ITALY - 11 # 2299150j
+  end
+
+  it "yields accurate julian date for Julian-Gregorian gap value" do
+    Time.utc(1582, 10, 14).to_date.jd.should == Date::ITALY - 1 # 2299160j
+  end
+
+  it "yields accurate julian date for post-Gregorian reform value" do
+    Time.utc(1582, 10, 15).to_date.jd.should == Date::ITALY # 2299161j
+  end
+
+  it "yields same julian day regardless of UTC time value" do
+    Time.utc(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
+    Time.utc(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
+  end
+
+  it "yields same julian day regardless of local time or zone" do
+
+    with_timezone("Pacific/Pago_Pago", -11) do
+      Time.local(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
+      Time.local(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
+    end
+
+    with_timezone("Asia/Kamchatka", +12) do
+      Time.local(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
+      Time.local(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
+    end
+
+  end
+
+  it "yields date with default Calendar reform day" do
+    Time.utc(1582, 10,  4).to_date.start.should == Date::ITALY
+    Time.utc(1582, 10, 14).to_date.start.should == Date::ITALY
+    Time.utc(1582, 10, 15).to_date.start.should == Date::ITALY
+  end
+end
diff --git a/spec/ruby/library/date/yday_spec.rb b/spec/ruby/library/date/yday_spec.rb
index cfb174a4c2..7dd42e52a5 100644
--- a/spec/ruby/library/date/yday_spec.rb
+++ b/spec/ruby/library/date/yday_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
+require_relative '../../shared/time/yday'
 require 'date'
 
 describe "Date#yday" do
-  it "needs to be reviewed for spec completeness"
+  it_behaves_like :time_yday, -> year, month, day { Date.new(year, month, day).yday }
 end
diff --git a/spec/ruby/library/datetime/deconstruct_keys_spec.rb b/spec/ruby/library/datetime/deconstruct_keys_spec.rb
new file mode 100644
index 0000000000..154c024a23
--- /dev/null
+++ b/spec/ruby/library/datetime/deconstruct_keys_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../spec_helper'
+require 'date'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
+
+describe "DateTime#deconstruct_keys" do
+  it "returns whole hash for nil as an argument" do
+    d = DateTime.new(2022, 10, 5, 13, 30)
+    res = { year: 2022, month: 10, day: 5, yday: 278, wday: 3, hour: 13,
+            min: 30, sec: 0, sec_fraction: (0/1), zone: "+00:00" }
+    d.deconstruct_keys(nil).should == res
+  end
+
+  it "returns only specified keys" do
+    d = DateTime.new(2022, 10, 5, 13, 39)
+    d.deconstruct_keys([:zone, :hour]).should == { zone: "+00:00", hour: 13 }
+  end
+
+  it "requires one argument" do
+    -> {
+      DateTime.new(2022, 10, 5, 13, 30).deconstruct_keys
+    }.should raise_error(ArgumentError)
+  end
+
+  it "it raises error when argument is neither nil nor array" do
+    d = DateTime.new(2022, 10, 5, 13, 30)
+
+    -> { d.deconstruct_keys(1) }.should raise_error(TypeError, "wrong argument type Integer (expected Array or nil)")
+    -> { d.deconstruct_keys("asd") }.should raise_error(TypeError, "wrong argument type String (expected Array or nil)")
+    -> { d.deconstruct_keys(:x) }.should raise_error(TypeError, "wrong argument type Symbol (expected Array or nil)")
+    -> { d.deconstruct_keys({}) }.should raise_error(TypeError, "wrong argument type Hash (expected Array or nil)")
+  end
+
+  it "returns {} when passed []" do
+    DateTime.new(2022, 10, 5, 13, 30).deconstruct_keys([]).should == {}
+  end
+
+  it "ignores non-Symbol keys" do
+    DateTime.new(2022, 10, 5, 13, 30).deconstruct_keys(['year', []]).should == {}
+  end
+
+  it "ignores not existing Symbol keys" do
+    DateTime.new(2022, 10, 5, 13, 30).deconstruct_keys([:year, :a]).should == { year: 2022 }
+  end
+end
diff --git a/spec/ruby/library/datetime/rfc2822_spec.rb b/spec/ruby/library/datetime/rfc2822_spec.rb
index 70bfca60b4..83f7fa8d5b 100644
--- a/spec/ruby/library/datetime/rfc2822_spec.rb
+++ b/spec/ruby/library/datetime/rfc2822_spec.rb
@@ -3,4 +3,8 @@ require 'date'
 
 describe "DateTime.rfc2822" do
   it "needs to be reviewed for spec completeness"
+
+  it "raises DateError if passed nil" do
+    -> { DateTime.rfc2822(nil) }.should raise_error(Date::Error, "invalid date")
+  end
 end
diff --git a/spec/ruby/library/datetime/strftime_spec.rb b/spec/ruby/library/datetime/strftime_spec.rb
index 1c925f92eb..a07cc9c1aa 100644
--- a/spec/ruby/library/datetime/strftime_spec.rb
+++ b/spec/ruby/library/datetime/strftime_spec.rb
@@ -1,6 +1,8 @@
+require_relative '../../spec_helper'
 require 'date'
 require_relative '../../shared/time/strftime_for_date'
 require_relative '../../shared/time/strftime_for_time'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
 
 describe "DateTime#strftime" do
   before :all do
@@ -31,10 +33,9 @@ describe "DateTime#strftime" do
     @time.strftime("%Z").should == "+00:00"
   end
 
-  # %v is %e-%b-%Y for Date/DateTime
   it "should be able to show the commercial week" do
-    @time.strftime("%v").should == " 3-Feb-2001"
-    @time.strftime("%v").should == @time.strftime('%e-%b-%Y')
+    @time.strftime("%v").should == " 3-FEB-2001"
+    @time.strftime("%v").should != @time.strftime('%e-%b-%Y')
   end
 
   # additional conversion specifiers only in Date/DateTime
diff --git a/spec/ruby/library/datetime/time/to_datetime_spec.rb b/spec/ruby/library/datetime/time/to_datetime_spec.rb
new file mode 100644
index 0000000000..5589725238
--- /dev/null
+++ b/spec/ruby/library/datetime/time/to_datetime_spec.rb
@@ -0,0 +1,40 @@
+require_relative '../../../spec_helper'
+require 'time'
+require 'date'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
+
+describe "Time#to_datetime" do
+  it "returns a DateTime representing the same instant" do
+    time = Time.utc(2012, 12, 31, 23, 58, 59)
+    datetime = time.to_datetime
+    datetime.year.should == 2012
+    datetime.month.should == 12
+    datetime.day.should == 31
+    datetime.hour.should == 23
+    datetime.min.should == 58
+    datetime.sec.should == 59
+  end
+
+  it "returns a DateTime representing the same instant before Gregorian" do
+    time = Time.utc(1582, 10, 14, 23, 58, 59)
+    datetime = time.to_datetime
+    datetime.year.should == 1582
+    datetime.month.should == 10
+    datetime.day.should == 4
+    datetime.hour.should == 23
+    datetime.min.should == 58
+    datetime.sec.should == 59
+  end
+
+  it "roundtrips" do
+    time = Time.utc(3, 12, 31, 23, 58, 59)
+    datetime = time.to_datetime
+    datetime.to_time.utc.should == time
+  end
+
+  it "yields a DateTime with the default Calendar reform day" do
+    Time.utc(1582, 10,  4, 1, 2, 3).to_datetime.start.should == Date::ITALY
+    Time.utc(1582, 10, 14, 1, 2, 3).to_datetime.start.should == Date::ITALY
+    Time.utc(1582, 10, 15, 1, 2, 3).to_datetime.start.should == Date::ITALY
+  end
+end
diff --git a/spec/ruby/library/datetime/to_time_spec.rb b/spec/ruby/library/datetime/to_time_spec.rb
index a11b6e30e1..58bb363653 100644
--- a/spec/ruby/library/datetime/to_time_spec.rb
+++ b/spec/ruby/library/datetime/to_time_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
 require 'date'
+date_version = defined?(Date::VERSION) ? Date::VERSION : '3.1.0'
 
 describe "DateTime#to_time" do
   it "yields a new Time object" do
@@ -7,10 +8,10 @@ describe "DateTime#to_time" do
   end
 
   it "returns a Time representing the same instant" do
-    datetime = DateTime.civil(3, 12, 31, 23, 58, 59)
+    datetime = DateTime.civil(2012, 12, 31, 23, 58, 59)
     time = datetime.to_time.utc
 
-    time.year.should == 3
+    time.year.should == 2012
     time.month.should == 12
     time.day.should == 31
     time.hour.should == 23
@@ -18,6 +19,17 @@ describe "DateTime#to_time" do
     time.sec.should == 59
   end
 
+  it "returns a Time representing the same instant before Gregorian" do
+    datetime = DateTime.civil(1582, 10, 4, 23, 58, 59)
+    time = datetime.to_time.utc
+    time.year.should == 1582
+    time.month.should == 10
+    time.day.should == 14
+    time.hour.should == 23
+    time.min.should == 58
+    time.sec.should == 59
+  end
+
   it "preserves the same time regardless of local time or zone" do
     date = DateTime.new(2012, 12, 24, 12, 23, 00, '+03:00')
 
diff --git a/spec/ruby/library/datetime/yday_spec.rb b/spec/ruby/library/datetime/yday_spec.rb
new file mode 100644
index 0000000000..08a72c6480
--- /dev/null
+++ b/spec/ruby/library/datetime/yday_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/time/yday'
+require 'date'
+
+describe "DateTime#yday" do
+  it_behaves_like :time_yday, -> year, month, day { DateTime.new(year, month, day).yday }
+end
diff --git a/spec/ruby/library/delegate/delegate_class/respond_to_missing_spec.rb b/spec/ruby/library/delegate/delegate_class/respond_to_missing_spec.rb
index 729cfc96c6..3975e5208b 100644
--- a/spec/ruby/library/delegate/delegate_class/respond_to_missing_spec.rb
+++ b/spec/ruby/library/delegate/delegate_class/respond_to_missing_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require 'delegate'
 
 describe "DelegateClass#respond_to_missing?" do
diff --git a/spec/ruby/library/delegate/delegator/eql_spec.rb b/spec/ruby/library/delegate/delegator/eql_spec.rb
index 3170d5727a..34f56f44c9 100644
--- a/spec/ruby/library/delegate/delegator/eql_spec.rb
+++ b/spec/ruby/library/delegate/delegator/eql_spec.rb
@@ -2,45 +2,34 @@ require_relative '../../../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "Delegator#eql?" do
-  ruby_version_is ""..."2.5" do
-    it "is delegated" do
-      base = mock('base')
-      delegator = DelegateSpecs::Delegator.new(base)
-      base.should_receive(:eql?).with(42).and_return(:foo)
-      delegator.eql?(42).should == :foo
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "returns true when compared with same delegator" do
-      base = mock('base')
-      delegator = DelegateSpecs::Delegator.new(base)
+  it "returns true when compared with same delegator" do
+    base = mock('base')
+    delegator = DelegateSpecs::Delegator.new(base)
 
-      delegator.eql?(delegator).should be_true
-    end
+    delegator.eql?(delegator).should be_true
+  end
 
-    it "returns true when compared with the inner object" do
-      base = mock('base')
-      delegator = DelegateSpecs::Delegator.new(base)
+  it "returns true when compared with the inner object" do
+    base = mock('base')
+    delegator = DelegateSpecs::Delegator.new(base)
 
-      delegator.eql?(base).should be_true
-    end
+    delegator.eql?(base).should be_true
+  end
 
-    it "returns false when compared with the delegator with other object" do
-      base = mock('base')
-      other = mock('other')
-      delegator0 = DelegateSpecs::Delegator.new(base)
-      delegator1 = DelegateSpecs::Delegator.new(other)
+  it "returns false when compared with the delegator with other object" do
+    base = mock('base')
+    other = mock('other')
+    delegator0 = DelegateSpecs::Delegator.new(base)
+    delegator1 = DelegateSpecs::Delegator.new(other)
 
-      delegator0.eql?(delegator1).should be_false
-    end
+    delegator0.eql?(delegator1).should be_false
+  end
 
-    it "returns false when compared with the other object" do
-      base = mock('base')
-      other = mock('other')
-      delegator = DelegateSpecs::Delegator.new(base)
+  it "returns false when compared with the other object" do
+    base = mock('base')
+    other = mock('other')
+    delegator = DelegateSpecs::Delegator.new(base)
 
-      delegator.eql?(other).should be_false
-    end
+    delegator.eql?(other).should be_false
   end
 end
diff --git a/spec/ruby/library/delegate/delegator/taint_spec.rb b/spec/ruby/library/delegate/delegator/taint_spec.rb
index 2dd0493b53..6bf13bb73d 100644
--- a/spec/ruby/library/delegate/delegator/taint_spec.rb
+++ b/spec/ruby/library/delegate/delegator/taint_spec.rb
@@ -5,19 +5,4 @@ describe "Delegator#taint" do
   before :each do
     @delegate = DelegateSpecs::Delegator.new("")
   end
-
-  it "returns self" do
-    @delegate.taint.equal?(@delegate).should be_true
-  end
-
-  it "taints the delegator" do
-    @delegate.__setobj__(nil)
-    @delegate.taint
-    @delegate.tainted?.should be_true
-  end
-
-  it "taints the delegated object" do
-    @delegate.taint
-    @delegate.__getobj__.tainted?.should be_true
-  end
 end
diff --git a/spec/ruby/library/delegate/delegator/trust_spec.rb b/spec/ruby/library/delegate/delegator/trust_spec.rb
index ba57b3ea18..f1b81814c5 100644
--- a/spec/ruby/library/delegate/delegator/trust_spec.rb
+++ b/spec/ruby/library/delegate/delegator/trust_spec.rb
@@ -5,18 +5,4 @@ describe "Delegator#trust" do
   before :each do
     @delegate = DelegateSpecs::Delegator.new([])
   end
-
-  it "returns self" do
-    @delegate.trust.equal?(@delegate).should be_true
-  end
-
-  it "trusts the delegator" do
-    @delegate.trust
-    @delegate.untrusted?.should be_false
-  end
-
-  it "trusts the delegated object" do
-    @delegate.trust
-    @delegate.__getobj__.untrusted?.should be_false
-  end
 end
diff --git a/spec/ruby/library/delegate/delegator/untaint_spec.rb b/spec/ruby/library/delegate/delegator/untaint_spec.rb
index ddcf854a43..4051fd2629 100644
--- a/spec/ruby/library/delegate/delegator/untaint_spec.rb
+++ b/spec/ruby/library/delegate/delegator/untaint_spec.rb
@@ -5,20 +5,4 @@ describe "Delegator#untaint" do
   before :each do
     @delegate = -> { DelegateSpecs::Delegator.new("") }.call
   end
-
-  it "returns self" do
-    @delegate.untaint.equal?(@delegate).should be_true
-  end
-
-  it "untaints the delegator" do
-    @delegate.untaint
-    @delegate.tainted?.should be_false
-    # No additional meaningful test; that it does or not taint
-    # "for real" the delegator has no consequence
-  end
-
-  it "untaints the delegated object" do
-    @delegate.untaint
-    @delegate.__getobj__.tainted?.should be_false
-  end
 end
diff --git a/spec/ruby/library/delegate/delegator/untrust_spec.rb b/spec/ruby/library/delegate/delegator/untrust_spec.rb
index b7f4bc823e..4f7fa1e582 100644
--- a/spec/ruby/library/delegate/delegator/untrust_spec.rb
+++ b/spec/ruby/library/delegate/delegator/untrust_spec.rb
@@ -5,19 +5,4 @@ describe "Delegator#untrust" do
   before :each do
     @delegate = DelegateSpecs::Delegator.new("")
   end
-
-  it "returns self" do
-    @delegate.untrust.equal?(@delegate).should be_true
-  end
-
-  it "untrusts the delegator" do
-    @delegate.__setobj__(nil)
-    @delegate.untrust
-    @delegate.untrusted?.should be_true
-  end
-
-  it "untrusts the delegated object" do
-    @delegate.untrust
-    @delegate.__getobj__.untrusted?.should be_true
-  end
 end
diff --git a/spec/ruby/library/digest/bubblebabble_spec.rb b/spec/ruby/library/digest/bubblebabble_spec.rb
index e651671108..bbc11ceec5 100644
--- a/spec/ruby/library/digest/bubblebabble_spec.rb
+++ b/spec/ruby/library/digest/bubblebabble_spec.rb
@@ -23,7 +23,7 @@ describe "Digest.bubblebabble" do
     -> { Digest.bubblebabble(nil) }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError when passed a Fixnum" do
+  it "raises a TypeError when passed an Integer" do
     -> { Digest.bubblebabble(9001) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/library/digest/hexencode_spec.rb b/spec/ruby/library/digest/hexencode_spec.rb
index fcbbf4846a..4b6db6eaff 100644
--- a/spec/ruby/library/digest/hexencode_spec.rb
+++ b/spec/ruby/library/digest/hexencode_spec.rb
@@ -25,7 +25,7 @@ describe "Digest.hexencode" do
     -> { Digest.hexencode(nil) }.should raise_error(TypeError)
   end
 
-  it "raises a TypeError when passed a Fixnum" do
+  it "raises a TypeError when passed an Integer" do
     -> { Digest.hexencode(9001) }.should raise_error(TypeError)
   end
 end
diff --git a/spec/ruby/library/digest/instance/append_spec.rb b/spec/ruby/library/digest/instance/append_spec.rb
new file mode 100644
index 0000000000..2499579298
--- /dev/null
+++ b/spec/ruby/library/digest/instance/append_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'digest'
+require_relative 'shared/update'
+
+describe "Digest::Instance#<<" do
+  it_behaves_like :digest_instance_update, :<<
+end
diff --git a/spec/ruby/library/digest/instance/new_spec.rb b/spec/ruby/library/digest/instance/new_spec.rb
new file mode 100644
index 0000000000..3f7939844b
--- /dev/null
+++ b/spec/ruby/library/digest/instance/new_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../../spec_helper'
+require 'digest'
+require_relative '../md5/shared/constants'
+
+describe "Digest::Instance#new" do
+  it "returns a copy of the digest instance" do
+    digest = Digest::MD5.new
+    copy = digest.new
+    copy.should_not.equal?(digest)
+  end
+
+  it "calls reset" do
+    digest = Digest::MD5.new
+    digest << "test"
+    digest.hexdigest.should != MD5Constants::BlankHexdigest
+    copy = digest.new
+    copy.hexdigest.should == MD5Constants::BlankHexdigest
+  end
+end
diff --git a/spec/ruby/library/digest/instance/shared/update.rb b/spec/ruby/library/digest/instance/shared/update.rb
new file mode 100644
index 0000000000..17779e54a4
--- /dev/null
+++ b/spec/ruby/library/digest/instance/shared/update.rb
@@ -0,0 +1,8 @@
+describe :digest_instance_update, shared: true do
+  it "raises a RuntimeError if called" do
+    c = Class.new do
+      include Digest::Instance
+    end
+    -> { c.new.send(@method, "test") }.should raise_error(RuntimeError)
+  end
+end
diff --git a/spec/ruby/library/digest/instance/update_spec.rb b/spec/ruby/library/digest/instance/update_spec.rb
new file mode 100644
index 0000000000..3bb4dd7f1b
--- /dev/null
+++ b/spec/ruby/library/digest/instance/update_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'digest'
+require_relative 'shared/update'
+
+describe "Digest::Instance#update" do
+  it_behaves_like :digest_instance_update, :update
+end
diff --git a/spec/ruby/library/digest/md5/append_spec.rb b/spec/ruby/library/digest/md5/append_spec.rb
index a7f841c883..0abdc074a1 100644
--- a/spec/ruby/library/digest/md5/append_spec.rb
+++ b/spec/ruby/library/digest/md5/append_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/constants'
 require_relative 'shared/update'
 
 describe "Digest::MD5#<<" do
- it_behaves_like :md5_update, :<<
+  it_behaves_like :md5_update, :<<
 end
diff --git a/spec/ruby/library/digest/md5/shared/constants.rb b/spec/ruby/library/digest/md5/shared/constants.rb
index fdfae56d63..664dd18e9c 100644
--- a/spec/ruby/library/digest/md5/shared/constants.rb
+++ b/spec/ruby/library/digest/md5/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require 'digest/md5'
 
 module MD5Constants
@@ -12,5 +12,6 @@ module MD5Constants
   Digest         = "\2473\267qw\276\364\343\345\320\304\350\313\314\217n"
   BlankHexdigest = "d41d8cd98f00b204e9800998ecf8427e"
   Hexdigest      = "a733b77177bef4e3e5d0c4e8cbcc8f6e"
+  Base64digest   = "pzO3cXe+9OPl0MToy8yPbg=="
 
 end
diff --git a/spec/ruby/library/digest/md5/shared/sample.rb b/spec/ruby/library/digest/md5/shared/sample.rb
deleted file mode 100644
index 2bb4f658b1..0000000000
--- a/spec/ruby/library/digest/md5/shared/sample.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-# -*- encoding: binary -*-
-
-require 'digest/md5'
-
-module MD5Constants
-
-  Contents = "Ipsum is simply dummy text of the printing and typesetting industry. \nLorem Ipsum has been the industrys standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. \nIt has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. \nIt was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum."
-
-  Klass          = ::Digest::MD5
-  BlockLength    = 64
-  DigestLength   = 16
-  BlankDigest    = "\324\035\214\331\217\000\262\004\351\200\t\230\354\370B~"
-  Digest         = "\2473\267qw\276\364\343\345\320\304\350\313\314\217n"
-  BlankHexdigest = "d41d8cd98f00b204e9800998ecf8427e"
-  Hexdigest      = "a733b77177bef4e3e5d0c4e8cbcc8f6e"
-
-end
diff --git a/spec/ruby/library/digest/sha1/shared/constants.rb b/spec/ruby/library/digest/sha1/shared/constants.rb
index add86b1dd3..d77c05a968 100644
--- a/spec/ruby/library/digest/sha1/shared/constants.rb
+++ b/spec/ruby/library/digest/sha1/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require 'digest/sha1'
 
@@ -12,6 +12,7 @@ module SHA1Constants
   BlankDigest    = "\3329\243\356^kK\r2U\277\357\225`\030\220\257\330\a\t"
   Digest         = "X!\255b\323\035\352\314a|q\344+\376\317\361V9\324\343"
   BlankHexdigest = "da39a3ee5e6b4b0d3255bfef95601890afd80709"
-  Hexdigest      = "e907d2ba21c6c74bc0efd76e44d11fb9bbb7a75e"
+  Hexdigest      = "5821ad62d31deacc617c71e42bfecff15639d4e3"
+  Base64digest   = "WCGtYtMd6sxhfHHkK/7P8VY51OM="
 
 end
diff --git a/spec/ruby/library/digest/sha2/hexdigest_spec.rb b/spec/ruby/library/digest/sha2/hexdigest_spec.rb
new file mode 100644
index 0000000000..79beca5788
--- /dev/null
+++ b/spec/ruby/library/digest/sha2/hexdigest_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../../spec_helper'
+require_relative '../sha256/shared/constants'
+
+describe "Digest::SHA2#hexdigest" do
+
+  it "returns a SHA256 hexdigest by default" do
+    cur_digest = Digest::SHA2.new
+    cur_digest.hexdigest.should == SHA256Constants::BlankHexdigest
+
+    # add something to check that the state is reset later
+    cur_digest << "test"
+
+    cur_digest.hexdigest(SHA256Constants::Contents).should == SHA256Constants::Hexdigest
+    # second invocation is intentional, to make sure there are no side-effects
+    cur_digest.hexdigest(SHA256Constants::Contents).should == SHA256Constants::Hexdigest
+
+    # after all is done, verify that the digest is in the original, blank state
+    cur_digest.hexdigest.should == SHA256Constants::BlankHexdigest
+  end
+
+end
+
+describe "Digest::SHA2.hexdigest" do
+
+  it "returns a SHA256 hexdigest by default" do
+    Digest::SHA2.hexdigest(SHA256Constants::Contents).should == SHA256Constants::Hexdigest
+    # second invocation is intentional, to make sure there are no side-effects
+    Digest::SHA2.hexdigest(SHA256Constants::Contents).should == SHA256Constants::Hexdigest
+    Digest::SHA2.hexdigest("").should == SHA256Constants::BlankHexdigest
+  end
+
+end
diff --git a/spec/ruby/library/digest/sha256/append_spec.rb b/spec/ruby/library/digest/sha256/append_spec.rb
index 9ca3496afc..ab594c105f 100644
--- a/spec/ruby/library/digest/sha256/append_spec.rb
+++ b/spec/ruby/library/digest/sha256/append_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/constants'
 require_relative 'shared/update'
 
 describe "Digest::SHA256#<<" do
- it_behaves_like :sha256_update, :<<
+  it_behaves_like :sha256_update, :<<
 end
diff --git a/spec/ruby/library/digest/sha256/file_spec.rb b/spec/ruby/library/digest/sha256/file_spec.rb
index 6103971b5a..8cbc5a2755 100644
--- a/spec/ruby/library/digest/sha256/file_spec.rb
+++ b/spec/ruby/library/digest/sha256/file_spec.rb
@@ -22,6 +22,10 @@ describe "Digest::SHA256.file" do
       Digest::SHA256.file(@file).digest.should == SHA256Constants::Digest
     end
 
+    it "can be used with frozen-string-literal" do
+      ruby_exe("require 'digest'; puts Digest::SHA256.file(#{@file.inspect}).digest.inspect", options: "--enable=frozen-string-literal").chomp.should == SHA256Constants::Digest.inspect
+    end
+
     it "calls #to_str on an object and returns the Digest::SHA256 with the result" do
       obj = mock("to_str")
       obj.should_receive(:to_str).and_return(@file)
diff --git a/spec/ruby/library/digest/sha256/shared/constants.rb b/spec/ruby/library/digest/sha256/shared/constants.rb
index dd5b48dca9..afe8f11426 100644
--- a/spec/ruby/library/digest/sha256/shared/constants.rb
+++ b/spec/ruby/library/digest/sha256/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require 'digest/sha2'
 
@@ -13,5 +13,6 @@ module SHA256Constants
   Digest         = "\230b\265\344_\337\357\337\242\004\314\311A\211jb\350\373\254\370\365M\230B\002\372\020j\as\270\376"
   BlankHexdigest = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
   Hexdigest      = "9862b5e45fdfefdfa204ccc941896a62e8fbacf8f54d984202fa106a0773b8fe"
+  Base64digest   = "mGK15F/f79+iBMzJQYlqYuj7rPj1TZhCAvoQagdzuP4="
 
 end
diff --git a/spec/ruby/library/digest/sha384/append_spec.rb b/spec/ruby/library/digest/sha384/append_spec.rb
index 2bc0c5b90b..94c036cc3f 100644
--- a/spec/ruby/library/digest/sha384/append_spec.rb
+++ b/spec/ruby/library/digest/sha384/append_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/constants'
 require_relative 'shared/update'
 
 describe "Digest::SHA384#<<" do
- it_behaves_like :sha384_update, :<<
+  it_behaves_like :sha384_update, :<<
 end
diff --git a/spec/ruby/library/digest/sha384/shared/constants.rb b/spec/ruby/library/digest/sha384/shared/constants.rb
index 3697384fc3..a78d571d26 100644
--- a/spec/ruby/library/digest/sha384/shared/constants.rb
+++ b/spec/ruby/library/digest/sha384/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require 'digest/sha2'
 
@@ -14,5 +14,6 @@ module SHA384Constants
   Digest         = "B&\266:\314\216z\361!TD\001{`\355\323\320MW%\270\272\0034n\034\026g\a\217\"\333s\202\275\002Y*\217]\207u\f\034\244\231\266f"
   BlankHexdigest = "38b060a751ac96384cd9327eb1b1e36a21fdb71114be07434c0cc7bf63f6e1da274edebfe76f65fbd51ad2f14898b95b"
   Hexdigest      = "4226b63acc8e7af1215444017b60edd3d04d5725b8ba03346e1c1667078f22db7382bd02592a8f5d87750c1ca499b666"
+  Base64digest   = "Qia2OsyOevEhVEQBe2Dt09BNVyW4ugM0bhwWZwePIttzgr0CWSqPXYd1DBykmbZm"
 
 end
diff --git a/spec/ruby/library/digest/sha512/append_spec.rb b/spec/ruby/library/digest/sha512/append_spec.rb
index e5f84b56f4..9106e9685d 100644
--- a/spec/ruby/library/digest/sha512/append_spec.rb
+++ b/spec/ruby/library/digest/sha512/append_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/constants'
 require_relative 'shared/update'
 
 describe "Digest::SHA512#<<" do
- it_behaves_like :sha512_update, :<<
+  it_behaves_like :sha512_update, :<<
 end
diff --git a/spec/ruby/library/digest/sha512/shared/constants.rb b/spec/ruby/library/digest/sha512/shared/constants.rb
index 80f5b7bc1d..91787381ee 100644
--- a/spec/ruby/library/digest/sha512/shared/constants.rb
+++ b/spec/ruby/library/digest/sha512/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 
 require 'digest/sha2'
 
@@ -13,5 +13,6 @@ module SHA512Constants
   Digest         = "\241\231\232\365\002z\241\331\242\310=\367F\272\004\326\331g\315n\251Q\222\250\374E\257\254=\325\225\003SM\350\244\234\220\233=\031\230A;\000\203\233\340\323t\333\271\222w\266\307\2678\344\255j\003\216\300"
   BlankHexdigest = "cf83e1357eefb8bdf1542850d66d8007d620e4050b5715dc83f4a921d36ce9ce47d0d13c5d85f2b0ff8318d2877eec2f63b931bd47417a81a538327af927da3e"
   Hexdigest      = "a1999af5027aa1d9a2c83df746ba04d6d967cd6ea95192a8fc45afac3dd59503534de8a49c909b3d1998413b00839be0d374dbb99277b6c7b738e4ad6a038ec0"
+  Base64digest   = "oZma9QJ6odmiyD33RroE1tlnzW6pUZKo/EWvrD3VlQNTTeiknJCbPRmYQTsAg5vg03TbuZJ3tse3OOStagOOwA=="
 
 end
diff --git a/spec/ruby/library/drb/start_service_spec.rb b/spec/ruby/library/drb/start_service_spec.rb
index 016c8b2cff..57a8cf6e15 100644
--- a/spec/ruby/library/drb/start_service_spec.rb
+++ b/spec/ruby/library/drb/start_service_spec.rb
@@ -1,28 +1,33 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/test_server'
-require 'drb'
 
-describe "DRb.start_service" do
-  before :each do
-    @server = DRb.start_service("druby://localhost:0", TestServer.new)
-  end
+# This does not work yet when run in CRuby via make test-spec:
+# Gem::MissingSpecError: Could not find 'ruby2_keywords' (>= 0) among 28 total gem(s)
+guard_not -> { MSpecScript.instance_variable_defined?(:@testing_ruby) } do
+  require_relative 'fixtures/test_server'
+  require 'drb'
 
-  after :each do
-    DRb.stop_service if @server
-  end
+  describe "DRb.start_service" do
+    before :each do
+      @server = DRb.start_service("druby://localhost:0", TestServer.new)
+    end
 
-  it "runs a basic remote call" do
-    DRb.current_server.should == @server
-    obj = DRbObject.new(nil, @server.uri)
-    obj.add(1,2,3).should == 6
-  end
+    after :each do
+      DRb.stop_service if @server
+    end
+
+    it "runs a basic remote call" do
+      DRb.current_server.should == @server
+      obj = DRbObject.new(nil, @server.uri)
+      obj.add(1,2,3).should == 6
+    end
 
-  it "runs a basic remote call passing a block" do
-    DRb.current_server.should == @server
-    obj = DRbObject.new(nil, @server.uri)
-    obj.add_yield(2) do |i|
-      i.should == 2
-      i+1
-    end.should == 4
+    it "runs a basic remote call passing a block" do
+      DRb.current_server.should == @server
+      obj = DRbObject.new(nil, @server.uri)
+      obj.add_yield(2) do |i|
+        i.should == 2
+        i+1
+      end.should == 4
+    end
   end
 end
diff --git a/spec/ruby/library/erb/def_class_spec.rb b/spec/ruby/library/erb/def_class_spec.rb
index 88bd385f4c..fb687531e0 100644
--- a/spec/ruby/library/erb/def_class_spec.rb
+++ b/spec/ruby/library/erb/def_class_spec.rb
@@ -24,6 +24,8 @@ END
     MyClass1ForErb = erb.def_class(MyClass1ForErb_, 'render()')
     MyClass1ForErb.method_defined?(:render).should == true
     MyClass1ForErb.new('foo', 123).render().should == expected
+  ensure
+    Object.send(:remove_const, :MyClass1ForErb)
   end
 
 end
diff --git a/spec/ruby/library/erb/def_module_spec.rb b/spec/ruby/library/erb/def_module_spec.rb
index 806e564ef0..5f67aeb2b9 100644
--- a/spec/ruby/library/erb/def_module_spec.rb
+++ b/spec/ruby/library/erb/def_module_spec.rb
@@ -22,6 +22,9 @@ END
       include MyModule2ForErb
     end
     MyClass2ForErb.new.render('foo', 123).should == expected
+  ensure
+    Object.send(:remove_const, :MyClass2ForErb)
+    Object.send(:remove_const, :MyModule2ForErb)
   end
 
 end
diff --git a/spec/ruby/library/erb/defmethod/def_erb_method_spec.rb b/spec/ruby/library/erb/defmethod/def_erb_method_spec.rb
index dc1e044d9c..1cd7582936 100644
--- a/spec/ruby/library/erb/defmethod/def_erb_method_spec.rb
+++ b/spec/ruby/library/erb/defmethod/def_erb_method_spec.rb
@@ -58,6 +58,8 @@ END
       end
     end
     MyClass4ForErb.new([10,20,30]).render().should == expected
+  ensure
+    Object.send(:remove_const, :MY_INPUT4_FOR_ERB)
   end
 
 
diff --git a/spec/ruby/library/erb/fixtures/classes.rb b/spec/ruby/library/erb/fixtures/classes.rb
index 03da889941..e07a6ed68d 100644
--- a/spec/ruby/library/erb/fixtures/classes.rb
+++ b/spec/ruby/library/erb/fixtures/classes.rb
@@ -1,9 +1,5 @@
 module ERBSpecs
   def self.new_erb(input, trim_mode: nil)
-    if ruby_version_is "2.6"
-      ERB.new(input, trim_mode: trim_mode)
-    else
-      ERB.new(input, nil, trim_mode)
-    end
+    ERB.new(input, trim_mode: trim_mode)
   end
 end
diff --git a/spec/ruby/library/erb/new_spec.rb b/spec/ruby/library/erb/new_spec.rb
index 3bb870dd3f..f8192bff99 100644
--- a/spec/ruby/library/erb/new_spec.rb
+++ b/spec/ruby/library/erb/new_spec.rb
@@ -36,12 +36,10 @@ END
     end
   end
 
-  ruby_version_is "2.6" do
-    it "warns invalid trim_mode" do
-      -> do
-        ERBSpecs.new_erb(@eruby_str, trim_mode: '')
-      end.should complain(/Invalid ERB trim mode/)
-    end
+  it "warns invalid trim_mode" do
+    -> do
+      ERBSpecs.new_erb(@eruby_str, trim_mode: '')
+    end.should complain(/Invalid ERB trim mode/)
   end
 
   it "removes '\n' when trim_mode is 1 or '>'" do
@@ -120,13 +118,8 @@ END
 
   it "changes '_erbout' variable name in the produced source" do
     input = @eruby_str
-    if RUBY_VERSION >= '2.6'
-      match_erbout = ERB.new(input, trim_mode: nil).src
-      match_buf = ERB.new(input, trim_mode: nil, eoutvar: 'buf').src
-    else
-      match_erbout = ERB.new(input, nil, nil).src
-      match_buf = ERB.new(input, nil, nil, 'buf').src
-    end
+    match_erbout = ERB.new(input, trim_mode: nil).src
+    match_buf = ERB.new(input, trim_mode: nil, eoutvar: 'buf').src
     match_erbout.gsub("_erbout", "buf").should == match_buf
   end
 
@@ -137,7 +130,7 @@ END
 <b><%#= item %></b>
 <%# end %>
 END
-  ERBSpecs.new_erb(input).result.should == "\n<b></b>\n\n"
+    ERBSpecs.new_erb(input).result.should == "\n<b></b>\n\n"
     ERBSpecs.new_erb(input, trim_mode: '<>').result.should == "<b></b>\n"
   end
 
@@ -145,4 +138,20 @@ END
     ERB.new(@eruby_str).result
     ->{ ERB.new("<%= list %>").result }.should raise_error(NameError)
   end
+
+  version_is ERB.const_get(:VERSION, false), ""..."6.0.0" do
+    describe "warning about arguments" do
+      it "warns when passed safe_level and later arguments" do
+        -> {
+          ERB.new(@eruby_str, nil, '%')
+        }.should complain(/warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments./)
+      end
+
+      it "does not warn when passed arguments as keyword argument" do
+        -> {
+          ERB.new(@eruby_str, trim_mode: '%')
+        }.should_not complain(/warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments./)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/erb/run_spec.rb b/spec/ruby/library/erb/run_spec.rb
index 8c07442d8f..602e53ab38 100644
--- a/spec/ruby/library/erb/run_spec.rb
+++ b/spec/ruby/library/erb/run_spec.rb
@@ -6,7 +6,7 @@ describe "ERB#run" do
   # lambda { ... }.should output
   def _steal_stdout
     orig = $stdout
-    s = ''
+    s = +''
     def s.write(arg); self << arg.to_s; end
     $stdout = s
     begin
diff --git a/spec/ruby/library/erb/util/shared/url_encode.rb b/spec/ruby/library/erb/util/shared/url_encode.rb
index 5ac6215523..34009c4903 100644
--- a/spec/ruby/library/erb/util/shared/url_encode.rb
+++ b/spec/ruby/library/erb/util/shared/url_encode.rb
@@ -6,21 +6,13 @@ describe :erb_util_url_encode, shared: true do
     ERB::Util.__send__(@method, input).should == expected
   end
 
-  ruby_version_is ""..."2.5" do
-    it "escapes tilde" do
-      ERB::Util.__send__(@method, "~").should == "%7E"
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not escape tilde" do
-      ERB::Util.__send__(@method, "~").should == "~"
-    end
+  it "does not escape tilde" do
+    ERB::Util.__send__(@method, "~").should == "~"
   end
 
   it "encode unicode string" do
-    input = "http://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
-    expected = 'http%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
+    input = "https://ja.wikipedia.org/wiki/\343\203\255\343\203\240\343\202\271\343\202\253\343\203\273\343\203\221\343\203\255\343\203\273\343\202\246\343\203\253\343\203\273\343\203\251\343\203\224\343\203\245\343\202\277"
+    expected = 'https%3A%2F%2Fja.wikipedia.org%2Fwiki%2F%E3%83%AD%E3%83%A0%E3%82%B9%E3%82%AB%E3%83%BB%E3%83%91%E3%83%AD%E3%83%BB%E3%82%A6%E3%83%AB%E3%83%BB%E3%83%A9%E3%83%94%E3%83%A5%E3%82%BF'
     ERB::Util.__send__(@method, input).should == expected
   end
 
diff --git a/spec/ruby/library/etc/confstr_spec.rb b/spec/ruby/library/etc/confstr_spec.rb
index 0c922a3a77..5b43461150 100644
--- a/spec/ruby/library/etc/confstr_spec.rb
+++ b/spec/ruby/library/etc/confstr_spec.rb
@@ -1,7 +1,7 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+require_relative '../../spec_helper'
 require 'etc'
 
-platform_is_not :windows do
+platform_is_not :windows, :android do
   describe "Etc.confstr" do
     it "returns a String for Etc::CS_PATH" do
       Etc.confstr(Etc::CS_PATH).should be_an_instance_of(String)
diff --git a/spec/ruby/library/etc/getgrgid_spec.rb b/spec/ruby/library/etc/getgrgid_spec.rb
index c7bd55b20e..14da5e041d 100644
--- a/spec/ruby/library/etc/getgrgid_spec.rb
+++ b/spec/ruby/library/etc/getgrgid_spec.rb
@@ -46,13 +46,6 @@ platform_is_not :windows do
         gr.name.should == @name
       end
 
-      it "returns the Group for a given gid if it exists" do
-        grp = Etc.getgrgid(@gid)
-        grp.should be_kind_of(Struct::Group)
-        grp.gid.should == @gid
-        grp.name.should == @name
-      end
-
       it "raises if the group does not exist" do
         -> { Etc.getgrgid(9876)}.should raise_error(ArgumentError)
       end
diff --git a/spec/ruby/library/etc/getgrnam_spec.rb b/spec/ruby/library/etc/getgrnam_spec.rb
index a7c624efbf..fa49f15349 100644
--- a/spec/ruby/library/etc/getgrnam_spec.rb
+++ b/spec/ruby/library/etc/getgrnam_spec.rb
@@ -11,7 +11,7 @@ platform_is :windows do
   end
 end
 
-platform_is_not :windows do
+platform_is_not :windows, :android do
   describe "Etc.getgrnam" do
     it "returns a Etc::Group struct instance for the given group" do
       gr_name = Etc.getgrent.name
diff --git a/spec/ruby/library/etc/group_spec.rb b/spec/ruby/library/etc/group_spec.rb
index fdd39bda16..fda808eec9 100644
--- a/spec/ruby/library/etc/group_spec.rb
+++ b/spec/ruby/library/etc/group_spec.rb
@@ -5,7 +5,7 @@ require 'etc'
 describe "Etc.group" do
   it_behaves_like :etc_on_windows, :group
 
-  platform_is_not :windows do
+  platform_is_not :windows, :android do
     it "returns a Etc::Group struct" do
       group = Etc.group
       begin
diff --git a/spec/ruby/library/etc/passwd_spec.rb b/spec/ruby/library/etc/passwd_spec.rb
index d61dada451..7157fd3f2e 100644
--- a/spec/ruby/library/etc/passwd_spec.rb
+++ b/spec/ruby/library/etc/passwd_spec.rb
@@ -1,4 +1,4 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+require_relative '../../spec_helper'
 require 'etc'
 
 platform_is_not :windows do
diff --git a/spec/ruby/library/etc/struct_group_spec.rb b/spec/ruby/library/etc/struct_group_spec.rb
index 0b50ff578f..b2147e306d 100644
--- a/spec/ruby/library/etc/struct_group_spec.rb
+++ b/spec/ruby/library/etc/struct_group_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require 'etc'
 
-describe "Struct::Group" do
+describe "Etc::Group" do
   platform_is_not :windows do
     grpname = IO.popen(%w'id -gn', err: IO::NULL, &:read)
     next unless $?.success?
diff --git a/spec/ruby/library/etc/struct_passwd_spec.rb b/spec/ruby/library/etc/struct_passwd_spec.rb
index 93ad9dfa2a..dc37c17e7d 100644
--- a/spec/ruby/library/etc/struct_passwd_spec.rb
+++ b/spec/ruby/library/etc/struct_passwd_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require 'etc'
 
-describe "Struct::Passwd" do
+describe "Etc::Passwd" do
   platform_is_not :windows do
     before :all do
       @pw = Etc.getpwuid(`id -u`.strip.to_i)
diff --git a/spec/ruby/library/etc/sysconf_spec.rb b/spec/ruby/library/etc/sysconf_spec.rb
index e7d59d1b22..1f2c7a770f 100644
--- a/spec/ruby/library/etc/sysconf_spec.rb
+++ b/spec/ruby/library/etc/sysconf_spec.rb
@@ -1,4 +1,4 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+require_relative '../../spec_helper'
 require 'etc'
 
 platform_is_not :windows do
diff --git a/spec/ruby/library/etc/sysconfdir_spec.rb b/spec/ruby/library/etc/sysconfdir_spec.rb
index d54299c513..8538faa65b 100644
--- a/spec/ruby/library/etc/sysconfdir_spec.rb
+++ b/spec/ruby/library/etc/sysconfdir_spec.rb
@@ -1,4 +1,4 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+require_relative '../../spec_helper'
 require 'etc'
 
 describe "Etc.sysconfdir" do
diff --git a/spec/ruby/library/etc/systmpdir_spec.rb b/spec/ruby/library/etc/systmpdir_spec.rb
index 99c82903f8..5b007aa9f9 100644
--- a/spec/ruby/library/etc/systmpdir_spec.rb
+++ b/spec/ruby/library/etc/systmpdir_spec.rb
@@ -1,4 +1,4 @@
-require File.expand_path('../../../spec_helper', __FILE__)
+require_relative '../../spec_helper'
 require 'etc'
 
 describe "Etc.systmpdir" do
diff --git a/spec/ruby/library/etc/uname_spec.rb b/spec/ruby/library/etc/uname_spec.rb
new file mode 100644
index 0000000000..a42558f593
--- /dev/null
+++ b/spec/ruby/library/etc/uname_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+require 'etc'
+
+describe "Etc.uname" do
+  it "returns a Hash with the documented keys" do
+    uname = Etc.uname
+    uname.should be_kind_of(Hash)
+    uname.should.key?(:sysname)
+    uname.should.key?(:nodename)
+    uname.should.key?(:release)
+    uname.should.key?(:version)
+    uname.should.key?(:machine)
+  end
+end
diff --git a/spec/ruby/library/expect/expect_spec.rb b/spec/ruby/library/expect/expect_spec.rb
index a7041d42ee..76ea3d5451 100644
--- a/spec/ruby/library/expect/expect_spec.rb
+++ b/spec/ruby/library/expect/expect_spec.rb
@@ -1,5 +1,6 @@
+require_relative '../../spec_helper'
+
 platform_is_not :windows do
-  require_relative '../../spec_helper'
   require 'expect'
 
   describe "IO#expect" do
diff --git a/spec/ruby/library/fiber/alive_spec.rb b/spec/ruby/library/fiber/alive_spec.rb
deleted file mode 100644
index 47149d5279..0000000000
--- a/spec/ruby/library/fiber/alive_spec.rb
+++ /dev/null
@@ -1,46 +0,0 @@
-require_relative '../../spec_helper'
-
-require 'fiber'
-
-describe "Fiber#alive?" do
-  it "returns true for a Fiber that hasn't had #resume called" do
-    fiber = Fiber.new { true }
-    fiber.alive?.should be_true
-  end
-
-  # FIXME: Better description?
-  it "returns true for a Fiber that's yielded to the caller" do
-    fiber = Fiber.new { Fiber.yield }
-    fiber.resume
-    fiber.alive?.should be_true
-  end
-
-  it "returns true when called from its Fiber" do
-    fiber = Fiber.new { fiber.alive?.should be_true }
-    fiber.resume
-  end
-
-  it "doesn't invoke the block associated with the Fiber" do
-    offthehook = mock('do not call')
-    offthehook.should_not_receive(:ring)
-    fiber = Fiber.new { offthehook.ring }
-    fiber.alive?
-  end
-
-  it "returns false for a Fiber that's dead" do
-    fiber = Fiber.new { true }
-    fiber.resume
-    -> { fiber.resume }.should raise_error(FiberError)
-    fiber.alive?.should be_false
-  end
-
-  it "always returns false for a dead Fiber" do
-    fiber = Fiber.new { true }
-    fiber.resume
-    -> { fiber.resume }.should raise_error(FiberError)
-    fiber.alive?.should be_false
-    -> { fiber.resume }.should raise_error(FiberError)
-    fiber.alive?.should be_false
-    fiber.alive?.should be_false
-  end
-end
diff --git a/spec/ruby/library/fiber/current_spec.rb b/spec/ruby/library/fiber/current_spec.rb
deleted file mode 100644
index 52dff3dea1..0000000000
--- a/spec/ruby/library/fiber/current_spec.rb
+++ /dev/null
@@ -1,51 +0,0 @@
-require_relative '../../spec_helper'
-
-require 'fiber'
-
-describe "Fiber.current" do
-  it "returns the root Fiber when called outside of a Fiber" do
-    root = Fiber.current
-    root.should be_an_instance_of(Fiber)
-    # We can always transfer to the root Fiber; it will never die
-    5.times do
-      root.transfer.should be_nil
-      root.alive?.should be_true
-    end
-  end
-
-  it "returns the current Fiber when called from a Fiber" do
-    fiber = Fiber.new do
-      this = Fiber.current
-      this.should be_an_instance_of(Fiber)
-      this.should == fiber
-      this.alive?.should be_true
-    end
-    fiber.resume
-  end
-
-  it "returns the current Fiber when called from a Fiber that transferred to another" do
-    states = []
-    fiber = Fiber.new do
-      states << :fiber
-      this = Fiber.current
-      this.should be_an_instance_of(Fiber)
-      this.should == fiber
-      this.alive?.should be_true
-    end
-
-    fiber2 = Fiber.new do
-      states << :fiber2
-      fiber.transfer
-      flunk
-    end
-
-    fiber3 = Fiber.new do
-      states << :fiber3
-      fiber2.transfer
-      flunk
-    end
-
-    fiber3.resume
-    states.should == [:fiber3, :fiber2, :fiber]
-  end
-end
diff --git a/spec/ruby/library/fiber/resume_spec.rb b/spec/ruby/library/fiber/resume_spec.rb
deleted file mode 100644
index dae717c8a1..0000000000
--- a/spec/ruby/library/fiber/resume_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../spec_helper'
-
-require 'fiber'
-
-describe "Fiber#resume" do
-  it "raises a FiberError if the Fiber has transferred control to another Fiber" do
-    fiber1 = Fiber.new { true }
-    fiber2 = Fiber.new { fiber1.transfer; Fiber.yield }
-    fiber2.resume
-    -> { fiber2.resume }.should raise_error(FiberError)
-  end
-end
diff --git a/spec/ruby/library/fiber/transfer_spec.rb b/spec/ruby/library/fiber/transfer_spec.rb
deleted file mode 100644
index d13053666c..0000000000
--- a/spec/ruby/library/fiber/transfer_spec.rb
+++ /dev/null
@@ -1,86 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../../shared/fiber/resume'
-
-require 'fiber'
-
-describe "Fiber#transfer" do
-  it_behaves_like :fiber_resume, :transfer
-end
-
-describe "Fiber#transfer" do
-  it "transfers control from one Fiber to another when called from a Fiber" do
-    fiber1 = Fiber.new { :fiber1 }
-    fiber2 = Fiber.new { fiber1.transfer; :fiber2 }
-    fiber2.resume.should == :fiber1
-  end
-
-  it "returns to the root Fiber when finished" do
-    f1 = Fiber.new { :fiber_1 }
-    f2 = Fiber.new { f1.transfer; :fiber_2 }
-
-    f2.transfer.should == :fiber_1
-    f2.transfer.should == :fiber_2
-  end
-
-  it "can be invoked from the same Fiber it transfers control to" do
-    states = []
-    fiber = Fiber.new { states << :start; fiber.transfer; states << :end }
-    fiber.transfer
-    states.should == [:start, :end]
-
-    states = []
-    fiber = Fiber.new { states << :start; fiber.transfer; states << :end }
-    fiber.resume
-    states.should == [:start, :end]
-  end
-
-  it "can transfer control to a Fiber that has transferred to another Fiber" do
-    states = []
-    fiber1 = Fiber.new { states << :fiber1 }
-    fiber2 = Fiber.new { states << :fiber2_start; fiber1.transfer; states << :fiber2_end}
-    fiber2.resume.should == [:fiber2_start, :fiber1]
-    fiber2.transfer.should == [:fiber2_start, :fiber1, :fiber2_end]
-  end
-
-  it "raises a FiberError when transferring to a Fiber which resumes itself" do
-    fiber = Fiber.new { fiber.resume }
-    -> { fiber.transfer }.should raise_error(FiberError)
-  end
-
-  it "works if Fibers in different Threads each transfer to a Fiber in the same Thread" do
-    # This catches a bug where Fibers are running on a thread-pool
-    # and Fibers from a different Ruby Thread reuse the same native thread.
-    # Caching the Ruby Thread based on the native thread is not correct in that case,
-    # and the check for "fiber called across threads" in Fiber#transfer
-    # might be incorrect based on that.
-    2.times do
-      Thread.new do
-        io_fiber = Fiber.new do |calling_fiber|
-          calling_fiber.transfer
-        end
-        io_fiber.transfer(Fiber.current)
-        value = Object.new
-        io_fiber.transfer(value).should equal value
-      end.join
-    end
-  end
-
-  it "transfers control between a non-main thread's root fiber to a child fiber and back again" do
-    states = []
-    thread = Thread.new do
-      f1 = Fiber.new do |f0|
-        states << 0
-        value2 = f0.transfer(1)
-        states << value2
-        3
-      end
-
-      value1 = f1.transfer(Fiber.current)
-      states << value1
-      value3 = f1.transfer(2)
-      states << value3
-    end
-    thread.join
-    states.should == [0, 1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/fiddle/handle/initialize_spec.rb b/spec/ruby/library/fiddle/handle/initialize_spec.rb
new file mode 100644
index 0000000000..51c2470efd
--- /dev/null
+++ b/spec/ruby/library/fiddle/handle/initialize_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+require 'fiddle'
+
+describe "Fiddle::Handle#initialize" do
+  it "raises Fiddle::DLError if the library cannot be found" do
+    -> {
+      Fiddle::Handle.new("doesnotexist.doesnotexist")
+    }.should raise_error(Fiddle::DLError)
+  end
+end
diff --git a/spec/ruby/library/find/fixtures/common.rb b/spec/ruby/library/find/fixtures/common.rb
index 14a7edb09a..99f3bbb45a 100644
--- a/spec/ruby/library/find/fixtures/common.rb
+++ b/spec/ruby/library/find/fixtures/common.rb
@@ -71,13 +71,17 @@ module FindDirSpecs
   end
 
   def self.create_mock_dirs
+    tmp('') # make sure there is an tmpdir
     umask = File.umask 0
-    mock_dir_files.each do |name|
-      file = File.join mock_dir, name
-      mkdir_p File.dirname(file)
-      touch file
+    begin
+      mock_dir_files.each do |name|
+        file = File.join mock_dir, name
+        mkdir_p File.dirname(file)
+        touch file
+      end
+    ensure
+      File.umask umask
     end
-    File.umask umask
   end
 
   def self.delete_mock_dirs
diff --git a/spec/ruby/library/getoptlong/shared/get.rb b/spec/ruby/library/getoptlong/shared/get.rb
index 772a7f6773..f44cf583d2 100644
--- a/spec/ruby/library/getoptlong/shared/get.rb
+++ b/spec/ruby/library/getoptlong/shared/get.rb
@@ -53,12 +53,10 @@ describe :getoptlong_get, shared: true do
     end
   end
 
-  ruby_version_is "2.5" do
-    # https://bugs.ruby-lang.org/issues/13858
-    it "returns multiline argument" do
-      argv [ "--size=\n10k\n" ] do
-        @opts.send(@method).should == [ "--size", "\n10k\n" ]
-      end
+  # https://bugs.ruby-lang.org/issues/13858
+  it "returns multiline argument" do
+    argv [ "--size=\n10k\n" ] do
+      @opts.send(@method).should == [ "--size", "\n10k\n" ]
     end
   end
 end
diff --git a/spec/ruby/library/getoptlong/terminated_spec.rb b/spec/ruby/library/getoptlong/terminated_spec.rb
index 01a8feddea..6108a7f6e9 100644
--- a/spec/ruby/library/getoptlong/terminated_spec.rb
+++ b/spec/ruby/library/getoptlong/terminated_spec.rb
@@ -5,13 +5,13 @@ describe "GetoptLong#terminated?" do
   it "returns true if option processing has terminated" do
     argv [ "--size", "10k" ] do
       opts = GetoptLong.new(["--size", GetoptLong::REQUIRED_ARGUMENT])
-      opts.terminated?.should == false
+      opts.should_not.terminated?
 
       opts.get.should == ["--size", "10k"]
-      opts.terminated?.should == false
+      opts.should_not.terminated?
 
       opts.get.should == nil
-      opts.terminated?.should == true
+      opts.should.terminated?
     end
   end
 end
diff --git a/spec/ruby/library/io-wait/wait_readable_spec.rb b/spec/ruby/library/io-wait/wait_readable_spec.rb
new file mode 100644
index 0000000000..d7473f029f
--- /dev/null
+++ b/spec/ruby/library/io-wait/wait_readable_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+
+describe "IO#wait_readable" do
+  before :each do
+    @io = File.new(__FILE__ )
+  end
+
+  after :each do
+    @io.close
+  end
+
+  it "waits for the IO to become readable with no timeout" do
+    @io.wait_readable.should == @io
+  end
+
+  it "waits for the IO to become readable with the given timeout" do
+    @io.wait_readable(1).should == @io
+  end
+
+  it "waits for the IO to become readable with the given large timeout" do
+    @io.wait_readable(365 * 24 * 60 * 60).should == @io
+  end
+
+  it "can be interrupted" do
+    rd, wr = IO.pipe
+    start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+    t = Thread.new do
+      rd.wait_readable(10)
+    end
+
+    Thread.pass until t.stop?
+    t.kill
+    t.join
+
+    finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    (finish - start).should < 9
+  ensure
+    rd.close
+    wr.close
+  end
+end
diff --git a/spec/ruby/library/io-wait/wait_spec.rb b/spec/ruby/library/io-wait/wait_spec.rb
new file mode 100644
index 0000000000..6a3890a401
--- /dev/null
+++ b/spec/ruby/library/io-wait/wait_spec.rb
@@ -0,0 +1,162 @@
+require_relative '../../spec_helper'
+require_relative '../../fixtures/io'
+
+describe "IO#wait" do
+  before :each do
+    @io = File.new(__FILE__ )
+
+    if /mswin|mingw/ =~ RUBY_PLATFORM
+      require 'socket'
+      @r, @w = Socket.pair(Socket::AF_INET, Socket::SOCK_STREAM, 0)
+    else
+      @r, @w = IO.pipe
+    end
+  end
+
+  after :each do
+    @io.close unless @io.closed?
+
+    @r.close unless @r.closed?
+    @w.close unless @w.closed?
+  end
+
+  context "[events, timeout] passed" do
+    it "returns events mask when the READABLE event is ready during the timeout" do
+      @w.write('data to read')
+      @r.wait(IO::READABLE, 2).should == IO::READABLE
+    end
+
+    it "returns events mask when the WRITABLE event is ready during the timeout" do
+      @w.wait(IO::WRITABLE, 0).should == IO::WRITABLE
+    end
+
+    it "waits for the READABLE event to be ready" do
+      @r.wait(IO::READABLE, 0).should == nil
+
+      @w.write('data to read')
+      @r.wait(IO::READABLE, 0).should_not == nil
+    end
+
+    it "waits for the WRITABLE event to be ready" do
+      written_bytes = IOSpec.exhaust_write_buffer(@w)
+      @w.wait(IO::WRITABLE, 0).should == nil
+
+      @r.read(written_bytes)
+      @w.wait(IO::WRITABLE, 0).should_not == nil
+    end
+
+    it "returns nil when the READABLE event is not ready during the timeout" do
+      @w.wait(IO::READABLE, 0).should == nil
+    end
+
+    it "returns nil when the WRITABLE event is not ready during the timeout" do
+      IOSpec.exhaust_write_buffer(@w)
+      @w.wait(IO::WRITABLE, 0).should == nil
+    end
+
+    it "raises IOError when io is closed (closed stream (IOError))" do
+      @io.close
+      -> { @io.wait(IO::READABLE, 0) }.should raise_error(IOError, "closed stream")
+    end
+
+    it "raises ArgumentError when events is not positive" do
+      -> { @w.wait(0, 0) }.should raise_error(ArgumentError, "Events must be positive integer!")
+      -> { @w.wait(-1, 0) }.should raise_error(ArgumentError, "Events must be positive integer!")
+    end
+
+    it "changes thread status to 'sleep' when waits for READABLE event" do
+      t = Thread.new { @r.wait(IO::READABLE, 10) }
+      sleep 1
+      t.status.should == 'sleep'
+      t.kill
+      t.join # Thread#kill doesn't wait for the thread to end
+    end
+
+    # https://github.com/ruby/ruby/actions/runs/11948300522/job/33305664284?pr=12139
+    platform_is_not :windows do
+      it "changes thread status to 'sleep' when waits for WRITABLE event" do
+        IOSpec.exhaust_write_buffer(@w)
+
+        t = Thread.new { @w.wait(IO::WRITABLE, 10) }
+        sleep 1
+        t.status.should == 'sleep'
+        t.kill
+        t.join # Thread#kill doesn't wait for the thread to end
+      end
+    end
+
+    it "can be interrupted when waiting for READABLE event" do
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+      t = Thread.new do
+        @r.wait(IO::READABLE, 10)
+      end
+
+      Thread.pass until t.stop?
+      t.kill
+      t.join # Thread#kill doesn't wait for the thread to end
+
+      finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (finish - start).should < 9
+    end
+
+    it "can be interrupted when waiting for WRITABLE event" do
+      IOSpec.exhaust_write_buffer(@w)
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+      t = Thread.new do
+        @w.wait(IO::WRITABLE, 10)
+      end
+
+      Thread.pass until t.stop?
+      t.kill
+      t.join # Thread#kill doesn't wait for the thread to end
+
+      finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (finish - start).should < 9
+    end
+  end
+
+  context "[timeout, mode] passed" do
+    it "accepts :r, :read, :readable mode to check READABLE event" do
+      @io.wait(0, :r).should == @io
+      @io.wait(0, :read).should == @io
+      @io.wait(0, :readable).should == @io
+    end
+
+    it "accepts :w, :write, :writable mode to check WRITABLE event" do
+      @io.wait(0, :w).should == @io
+      @io.wait(0, :write).should == @io
+      @io.wait(0, :writable).should == @io
+    end
+
+    it "accepts :rw, :read_write, :readable_writable mode to check READABLE and WRITABLE events" do
+      @io.wait(0, :rw).should == @io
+      @io.wait(0, :read_write).should == @io
+      @io.wait(0, :readable_writable).should == @io
+    end
+
+    it "accepts a list of modes" do
+      @io.wait(0, :r, :w, :rw).should == @io
+    end
+
+    it "accepts timeout and mode in any order" do
+      @io.wait(0, :r).should == @io
+      @io.wait(:r, 0).should == @io
+      @io.wait(:r, 0, :w).should == @io
+    end
+
+    it "raises ArgumentError when passed wrong Symbol value as mode argument" do
+      -> { @io.wait(0, :wrong) }.should raise_error(ArgumentError, "unsupported mode: wrong")
+    end
+
+    it "raises ArgumentError when several Integer arguments passed" do
+      -> { @w.wait(0, 10, :r) }.should raise_error(ArgumentError, "timeout given more than once")
+    end
+
+    it "raises IOError when io is closed (closed stream (IOError))" do
+      @io.close
+      -> { @io.wait(0, :r) }.should raise_error(IOError, "closed stream")
+    end
+  end
+end
diff --git a/spec/ruby/library/io-wait/wait_writable_spec.rb b/spec/ruby/library/io-wait/wait_writable_spec.rb
new file mode 100644
index 0000000000..2017817caa
--- /dev/null
+++ b/spec/ruby/library/io-wait/wait_writable_spec.rb
@@ -0,0 +1,37 @@
+require_relative '../../spec_helper'
+require_relative '../../fixtures/io'
+
+describe "IO#wait_writable" do
+  it "waits for the IO to become writable with no timeout" do
+    STDOUT.wait_writable.should == STDOUT
+  end
+
+  it "waits for the IO to become writable with the given timeout" do
+    STDOUT.wait_writable(1).should == STDOUT
+  end
+
+  it "waits for the IO to become writable with the given large timeout" do
+    # Represents one year and is larger than a 32-bit int
+    STDOUT.wait_writable(365 * 24 * 60 * 60).should == STDOUT
+  end
+
+  it "can be interrupted" do
+    rd, wr = IO.pipe
+    IOSpec.exhaust_write_buffer(wr)
+    start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+    t = Thread.new do
+      wr.wait_writable(10)
+    end
+
+    Thread.pass until t.stop?
+    t.kill
+    t.join
+
+    finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    (finish - start).should < 9
+  ensure
+    rd.close unless rd.closed?
+    wr.close unless wr.closed?
+  end
+end
diff --git a/spec/ruby/library/ipaddr/ipv4_conversion_spec.rb b/spec/ruby/library/ipaddr/ipv4_conversion_spec.rb
index 9d45055d76..1128c16dd2 100644
--- a/spec/ruby/library/ipaddr/ipv4_conversion_spec.rb
+++ b/spec/ruby/library/ipaddr/ipv4_conversion_spec.rb
@@ -8,11 +8,11 @@ describe "IPAddr#ipv4_compat" do
     a.to_s.should == "::192.168.1.2"
     a.to_string.should == "0000:0000:0000:0000:0000:0000:c0a8:0102"
     a.family.should == Socket::AF_INET6
-    a.ipv4_compat?.should == true
+    a.should.ipv4_compat?
     b = a.native
     b.to_s.should == "192.168.1.2"
     b.family.should == Socket::AF_INET
-    b.ipv4_compat?.should == false
+    b.should_not.ipv4_compat?
 
     a = IPAddr.new("192.168.1.2")
     b = a.ipv4_compat
@@ -29,11 +29,11 @@ describe "IPAddr#ipv4_mapped" do
     a.to_s.should == "::ffff:192.168.1.2"
     a.to_string.should == "0000:0000:0000:0000:0000:ffff:c0a8:0102"
     a.family.should == Socket::AF_INET6
-    a.ipv4_mapped?.should == true
+    a.should.ipv4_mapped?
     b = a.native
     b.to_s.should == "192.168.1.2"
     b.family.should == Socket::AF_INET
-    b.ipv4_mapped?.should == false
+    b.should_not.ipv4_mapped?
 
     a = IPAddr.new("192.168.1.2")
     b = a.ipv4_mapped
diff --git a/spec/ruby/library/ipaddr/new_spec.rb b/spec/ruby/library/ipaddr/new_spec.rb
index c8c8bc80b3..2c0f44acf2 100644
--- a/spec/ruby/library/ipaddr/new_spec.rb
+++ b/spec/ruby/library/ipaddr/new_spec.rb
@@ -27,8 +27,8 @@ describe "IPAddr#new" do
     a.to_s.should == "3ffe:505:2::"
     a.to_string.should == "3ffe:0505:0002:0000:0000:0000:0000:0000"
     a.family.should == Socket::AF_INET6
-    a.ipv4?.should == false
-    a.ipv6?.should == true
+    a.should_not.ipv4?
+    a.should.ipv6?
     a.inspect.should == "#<IPAddr: IPv6:3ffe:0505:0002:0000:0000:0000:0000:0000/ffff:ffff:ffff:0000:0000:0000:0000:0000>"
   end
 
@@ -51,8 +51,8 @@ describe "IPAddr#new" do
     a.to_s.should == "192.168.1.2"
     a.to_string.should == "192.168.1.2"
     a.family.should == Socket::AF_INET
-    a.ipv4?.should == true
-    a.ipv6?.should == false
+    a.should.ipv4?
+    a.should_not.ipv6?
   end
 
   it "initializes IPAddr ipv4 address with / subnet notation" do
@@ -79,7 +79,6 @@ describe "IPAddr#new" do
 
   it "raises on incorrect IPAddr strings" do
     [
-      ["fe80::1%fxp0"],
       ["::1/255.255.255.0"],
       [IPAddr.new("::1").to_i],
       ["::ffff:192.168.1.2/120", Socket::AF_INET],
diff --git a/spec/ruby/library/irb/fixtures/irb.rb b/spec/ruby/library/irb/fixtures/irb.rb
new file mode 100644
index 0000000000..8d386dfda1
--- /dev/null
+++ b/spec/ruby/library/irb/fixtures/irb.rb
@@ -0,0 +1,3 @@
+a = 10
+
+binding.irb # rubocop:disable Lint/Debugger
diff --git a/spec/ruby/library/irb/irb_spec.rb b/spec/ruby/library/irb/irb_spec.rb
new file mode 100644
index 0000000000..2607c7ef33
--- /dev/null
+++ b/spec/ruby/library/irb/irb_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require 'tmpdir'
+
+describe "Binding#irb" do
+  it "creates an IRB session with the binding in scope" do
+    irb_fixture = fixture __FILE__, "irb.rb"
+    envs = %w[IRBRC HOME XDG_CONFIG_HOME].to_h {|e| [e, nil]}
+
+    out = Dir.mktmpdir do |dir|
+      IO.popen([envs, *ruby_exe, irb_fixture, chdir: dir], "r+") do |pipe|
+        pipe.puts "a ** 2"
+        pipe.puts "exit"
+        pipe.readlines.map(&:chomp).reject(&:empty?)
+      end
+    end
+
+    out.last(3).should == ["a ** 2", "100", "exit"]
+  end
+end
diff --git a/spec/ruby/library/logger/device/close_spec.rb b/spec/ruby/library/logger/device/close_spec.rb
index d7d107fcce..1db5d582a7 100644
--- a/spec/ruby/library/logger/device/close_spec.rb
+++ b/spec/ruby/library/logger/device/close_spec.rb
@@ -15,17 +15,8 @@ describe "Logger::LogDevice#close" do
     rm_r @file_path
   end
 
-  ruby_version_is ""..."2.7" do
-    it "closes the LogDevice's stream" do
-      @device.close
-      -> { @device.write("Test") }.should complain(/\Alog writing failed\./)
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "closes the LogDevice's stream" do
-      @device.close
-      -> { @device.write("Test") }.should complain(/\Alog shifting failed\./)
-    end
+  it "closes the LogDevice's stream" do
+    @device.close
+    -> { @device.write("Test") }.should complain(/\Alog shifting failed\./)
   end
 end
diff --git a/spec/ruby/library/logger/device/new_spec.rb b/spec/ruby/library/logger/device/new_spec.rb
index c77376d078..26a38c2b8c 100644
--- a/spec/ruby/library/logger/device/new_spec.rb
+++ b/spec/ruby/library/logger/device/new_spec.rb
@@ -31,7 +31,7 @@ describe "Logger::LogDevice#new" do
     l.write("Test message")
     l.close
 
-    File.exist?(path).should be_true
+    File.should.exist?(path)
     File.open(path) do |f|
       f.readlines.should_not be_empty
     end
@@ -40,8 +40,8 @@ describe "Logger::LogDevice#new" do
   end
 
   it "receives options via a hash as second argument" do
-    -> { Logger::LogDevice.new(STDERR,
-                               shift_age: 8, shift_size: 10
-                              )}.should_not raise_error
+    -> {
+      Logger::LogDevice.new(STDERR, shift_age: 8, shift_size: 10)
+    }.should_not raise_error
   end
 end
diff --git a/spec/ruby/library/logger/device/write_spec.rb b/spec/ruby/library/logger/device/write_spec.rb
index 5506bb2c38..87ecf2ad6a 100644
--- a/spec/ruby/library/logger/device/write_spec.rb
+++ b/spec/ruby/library/logger/device/write_spec.rb
@@ -35,17 +35,8 @@ describe "Logger::LogDevice#write" do
     rm_r path
   end
 
-  ruby_version_is ""..."2.7" do
-    it "fails if the device is already closed" do
-      @device.close
-      -> { @device.write "foo" }.should complain(/\Alog writing failed\./)
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "fails if the device is already closed" do
-      @device.close
-      -> { @device.write "foo" }.should complain(/\Alog shifting failed\./)
-    end
+  it "fails if the device is already closed" do
+    @device.close
+    -> { @device.write "foo" }.should complain(/\Alog shifting failed\./)
   end
 end
diff --git a/spec/ruby/library/logger/logger/debug_spec.rb b/spec/ruby/library/logger/logger/debug_spec.rb
index d92c339232..9375ab0cc6 100644
--- a/spec/ruby/library/logger/logger/debug_spec.rb
+++ b/spec/ruby/library/logger/logger/debug_spec.rb
@@ -16,12 +16,12 @@ describe "Logger#debug?" do
 
   it "returns true if severity level allows debug messages" do
     @logger.level = Logger::DEBUG
-    @logger.debug?.should == true
+    @logger.should.debug?
   end
 
   it "returns false if severity level does not allow debug messages" do
     @logger.level = Logger::WARN
-    @logger.debug?.should == false
+    @logger.should_not.debug?
   end
 end
 
diff --git a/spec/ruby/library/logger/logger/error_spec.rb b/spec/ruby/library/logger/logger/error_spec.rb
index d5d0bd2d2f..42f1dbd883 100644
--- a/spec/ruby/library/logger/logger/error_spec.rb
+++ b/spec/ruby/library/logger/logger/error_spec.rb
@@ -16,12 +16,12 @@ describe "Logger#error?" do
 
   it "returns true if severity level allows printing errors" do
     @logger.level = Logger::INFO
-    @logger.error?.should == true
+    @logger.should.error?
   end
 
   it "returns false if severity level does not allow errors" do
     @logger.level = Logger::FATAL
-    @logger.error?.should == false
+    @logger.should_not.error?
   end
 end
 
diff --git a/spec/ruby/library/logger/logger/fatal_spec.rb b/spec/ruby/library/logger/logger/fatal_spec.rb
index 42d4341319..f12fa3a89f 100644
--- a/spec/ruby/library/logger/logger/fatal_spec.rb
+++ b/spec/ruby/library/logger/logger/fatal_spec.rb
@@ -16,12 +16,12 @@ describe "Logger#fatal?" do
 
   it "returns true if severity level allows fatal messages" do
     @logger.level = Logger::FATAL
-    @logger.fatal?.should == true
+    @logger.should.fatal?
   end
 
   it "returns false if severity level does not allow fatal messages" do
     @logger.level = Logger::UNKNOWN
-    @logger.fatal?.should == false
+    @logger.should_not.fatal?
   end
 end
 
diff --git a/spec/ruby/library/logger/logger/info_spec.rb b/spec/ruby/library/logger/logger/info_spec.rb
index 21eacbbb31..eb5dca48dd 100644
--- a/spec/ruby/library/logger/logger/info_spec.rb
+++ b/spec/ruby/library/logger/logger/info_spec.rb
@@ -16,12 +16,12 @@ describe "Logger#info?" do
 
   it "returns true if severity level allows info messages" do
     @logger.level = Logger::INFO
-    @logger.info?.should == true
+    @logger.should.info?
   end
 
   it "returns false if severity level does not allow info messages" do
     @logger.level = Logger::FATAL
-    @logger.info?.should == false
+    @logger.should_not.info?
   end
 end
 
diff --git a/spec/ruby/library/logger/logger/new_spec.rb b/spec/ruby/library/logger/logger/new_spec.rb
index f70e1904f3..3db20e7432 100644
--- a/spec/ruby/library/logger/logger/new_spec.rb
+++ b/spec/ruby/library/logger/logger/new_spec.rb
@@ -13,24 +13,24 @@ describe "Logger#new" do
     rm_r @file_path
   end
 
-   it "creates a new logger object" do
-     l = Logger.new(STDERR)
-     -> { l.add(Logger::WARN, "Foo") }.should output_to_fd(/Foo/, STDERR)
-   end
+  it "creates a new logger object" do
+    l = Logger.new(STDERR)
+    -> { l.add(Logger::WARN, "Foo") }.should output_to_fd(/Foo/, STDERR)
+  end
 
-   it "receives a logging device as first argument" do
-     l = Logger.new(@log_file)
-     l.add(Logger::WARN, "Test message")
+  it "receives a logging device as first argument" do
+    l = Logger.new(@log_file)
+    l.add(Logger::WARN, "Test message")
 
-     @log_file.rewind
-     LoggerSpecs.strip_date(@log_file.readline).should == "WARN -- : Test message\n"
-     l.close
-   end
+    @log_file.rewind
+    LoggerSpecs.strip_date(@log_file.readline).should == "WARN -- : Test message\n"
+    l.close
+  end
 
   it "receives a frequency rotation as second argument" do
-     -> { Logger.new(@log_file, "daily") }.should_not raise_error
-     -> { Logger.new(@log_file, "weekly") }.should_not raise_error
-     -> { Logger.new(@log_file, "monthly") }.should_not raise_error
+    -> { Logger.new(@log_file, "daily") }.should_not raise_error
+    -> { Logger.new(@log_file, "weekly") }.should_not raise_error
+    -> { Logger.new(@log_file, "monthly") }.should_not raise_error
   end
 
   it "also receives a number of log files to keep as second argument" do
@@ -46,8 +46,8 @@ describe "Logger#new" do
     l.add Logger::WARN, "foo"
     l.add Logger::WARN, "bar"
 
-    File.exist?(path).should be_true
-    File.exist?(path + ".0").should be_true
+    File.should.exist?(path)
+    File.should.exist?(path + ".0")
 
     # first line will be a comment so we'll have to skip it.
     f = File.open(path)
@@ -108,7 +108,7 @@ describe "Logger#new" do
 
     shifted_path = "#{path}.#{now.strftime(shift_period_suffix)}"
 
-    File.exist?(shifted_path).should == true
+    File.should.exist?(shifted_path)
 
     logger.close
 
diff --git a/spec/ruby/library/logger/logger/warn_spec.rb b/spec/ruby/library/logger/logger/warn_spec.rb
index 6617b2b41a..0bca34824a 100644
--- a/spec/ruby/library/logger/logger/warn_spec.rb
+++ b/spec/ruby/library/logger/logger/warn_spec.rb
@@ -16,12 +16,12 @@ describe "Logger#warn?" do
 
   it "returns true if severity level allows printing warn messages" do
     @logger.level = Logger::WARN
-    @logger.warn?.should == true
+    @logger.should.warn?
   end
 
   it "returns false if severity level does not allow printing warn messages" do
     @logger.level = Logger::FATAL
-    @logger.warn?.should == false
+    @logger.should_not.warn?
   end
 end
 
diff --git a/spec/ruby/library/mathn/bignum/exponent_spec.rb b/spec/ruby/library/mathn/bignum/exponent_spec.rb
deleted file mode 100644
index ddd19ffdb4..0000000000
--- a/spec/ruby/library/mathn/bignum/exponent_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Bignum#**" do
-    before :each do
-      @bignum = bignum_value(47)
-    end
-
-    it "returns self raised to other (positive) power" do
-      (@bignum ** 4).should == 7237005577332262361485077344629993318496048279512298547155833600056910050625
-      (@bignum ** 1.2).should be_close(57262152889751597425762.57804, TOLERANCE)
-    end
-
-    it "returns a complex number when negative and raised to a fractional power" do
-      ((-@bignum) ** (1/3)).should be_close(Complex(1048576,1816186.907597341), TOLERANCE)
-      ((-@bignum) ** (1.0/3)).should be_close(Complex(1048576,1816186.907597341), TOLERANCE)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/complex/Complex_spec.rb b/spec/ruby/library/mathn/complex/Complex_spec.rb
deleted file mode 100644
index 105902ed5d..0000000000
--- a/spec/ruby/library/mathn/complex/Complex_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Kernel#Complex" do
-    it "returns an Integer if imaginary part is 0" do
-      Complex(42,0).should == 42
-      Complex(42,0).should be_kind_of(Fixnum)
-      Complex(bignum_value,0).should == bignum_value
-      Complex(bignum_value,0).should be_kind_of(Bignum)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/fixnum/exponent_spec.rb b/spec/ruby/library/mathn/fixnum/exponent_spec.rb
deleted file mode 100644
index 160bf7f115..0000000000
--- a/spec/ruby/library/mathn/fixnum/exponent_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Fixnum#**" do
-    it "returns self raised to other (positive) power" do
-      (2 ** 4).should == 16
-      (2 ** 1.2).should be_close(2.2973967, TOLERANCE)
-    end
-
-    it "returns a complex number when negative and raised to a fractional power" do
-      ((-8) ** (1/3)).should be_close(Complex(1, 1.73205), TOLERANCE)
-      ((-8) ** (1.0/3)).should be_close(Complex(1, 1.73205), TOLERANCE)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/float/exponent_spec.rb b/spec/ruby/library/mathn/float/exponent_spec.rb
deleted file mode 100644
index 312119db00..0000000000
--- a/spec/ruby/library/mathn/float/exponent_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Float#**" do
-    it "returns self raised to other (positive) power" do
-      (2.0 ** 4).should == 16.0
-      (2.0 ** 1.2).should be_close(2.2973967, TOLERANCE)
-    end
-
-    it "returns a complex number when negative and raised to a fractional power" do
-      ((-8.0) ** (1/3)).should be_close(Complex(1, 1.73205), TOLERANCE)
-      ((-8.0) ** (1.0/3)).should be_close(Complex(1, 1.73205), TOLERANCE)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/integer/from_prime_division_spec.rb b/spec/ruby/library/mathn/integer/from_prime_division_spec.rb
deleted file mode 100644
index df2db6d8c1..0000000000
--- a/spec/ruby/library/mathn/integer/from_prime_division_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Integer.from_prime_division" do
-    it "reverses a prime factorization of an integer" do
-      Integer.from_prime_division([[2, 1], [3, 2], [7, 1]]).should == 126
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/integer/prime_division_spec.rb b/spec/ruby/library/mathn/integer/prime_division_spec.rb
deleted file mode 100644
index fb4a1c3fea..0000000000
--- a/spec/ruby/library/mathn/integer/prime_division_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Integer#prime_division" do
-    it "performs a prime factorization of a positive integer" do
-      100.prime_division.should == [[2, 2], [5, 2]]
-    end
-
-    # Proper handling of negative integers has been added to MRI trunk
-    # in revision 24091. Prior to that, all versions of MRI returned nonsense.
-    it "performs a prime factorization of a negative integer" do
-      -26.prime_division.should == [[-1, 1], [2, 1], [13, 1]]
-    end
-
-    it "raises a ZeroDivisionError when is called on zero" do
-      -> { 0.prime_division }.should raise_error(ZeroDivisionError)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/math/fixtures/classes.rb b/spec/ruby/library/mathn/math/fixtures/classes.rb
deleted file mode 100644
index 024732fa7a..0000000000
--- a/spec/ruby/library/mathn/math/fixtures/classes.rb
+++ /dev/null
@@ -1,3 +0,0 @@
-class IncludesMath
-  include Math
-end
diff --git a/spec/ruby/library/mathn/math/rsqrt_spec.rb b/spec/ruby/library/mathn/math/rsqrt_spec.rb
deleted file mode 100644
index 6cb7595afe..0000000000
--- a/spec/ruby/library/mathn/math/rsqrt_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require_relative 'shared/rsqrt'
-
-  describe "Math#rsqrt" do
-    it_behaves_like :mathn_math_rsqrt, :_, IncludesMath.new
-
-    it "is a private instance method" do
-      IncludesMath.should have_private_instance_method(:rsqrt)
-    end
-  end
-
-  describe "Math.rsqrt" do
-    it_behaves_like :mathn_math_rsqrt, :_, Math
-  end
-end
diff --git a/spec/ruby/library/mathn/math/shared/rsqrt.rb b/spec/ruby/library/mathn/math/shared/rsqrt.rb
deleted file mode 100644
index ea3d1b0cfc..0000000000
--- a/spec/ruby/library/mathn/math/shared/rsqrt.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require 'mathn'
-require_relative '../fixtures/classes'
-
-describe :mathn_math_rsqrt, shared: true do
-  it "returns the square root for Rational numbers" do
-    @object.send(:rsqrt, Rational(9, 25)).should == Rational(3, 5)
-    @object.send(:rsqrt, 16/64).should == Rational(1, 2)
-  end
-
-  it "returns the square root for positive numbers" do
-    @object.send(:rsqrt, 1).should == 1
-    @object.send(:rsqrt, 4.0).should == 2.0
-    @object.send(:rsqrt, 12.34).should == Math.sqrt!(12.34)
-  end
-
-  it "raises an Math::DomainError if the argument is a negative number" do
-    -> { @object.send(:rsqrt, -1) }.should raise_error(Math::DomainError)
-    -> { @object.send(:rsqrt, -4.0) }.should raise_error(Math::DomainError)
-    -> { @object.send(:rsqrt, -16/64) }.should raise_error(Math::DomainError)
-  end
-end
diff --git a/spec/ruby/library/mathn/math/shared/sqrt.rb b/spec/ruby/library/mathn/math/shared/sqrt.rb
deleted file mode 100644
index 5e6dae1d4f..0000000000
--- a/spec/ruby/library/mathn/math/shared/sqrt.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require 'mathn'
-require_relative '../fixtures/classes'
-
-describe :mathn_math_sqrt, shared: true do
-  it "returns the square root for Rational numbers" do
-    @object.send(:sqrt, Rational(9, 25)).should == Rational(3, 5)
-    @object.send(:sqrt, 16/64).should == Rational(1, 2)
-  end
-
-  it "returns the square root for Complex numbers" do
-    @object.send(:sqrt, Complex(1, 0)).should == 1
-  end
-
-  it "returns the square root for positive numbers" do
-    @object.send(:sqrt, 1).should == 1
-    @object.send(:sqrt, 4.0).should == 2.0
-    @object.send(:sqrt, 12.34).should == Math.sqrt!(12.34)
-  end
-
-  it "returns the square root for negative numbers" do
-    @object.send(:sqrt, -9).should == Complex(0, 3)
-    @object.send(:sqrt, -5.29).should == Complex(0, 2.3)
-    @object.send(:sqrt, -16/64).should == Complex(0, 1/2)
-  end
-end
diff --git a/spec/ruby/library/mathn/math/sqrt_spec.rb b/spec/ruby/library/mathn/math/sqrt_spec.rb
deleted file mode 100644
index 49cfe3600e..0000000000
--- a/spec/ruby/library/mathn/math/sqrt_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require_relative 'shared/sqrt'
-
-  describe "Math#rsqrt" do
-    it_behaves_like :mathn_math_sqrt, :_, IncludesMath.new
-
-    it "is a private instance method" do
-      IncludesMath.should have_private_instance_method(:sqrt)
-    end
-  end
-
-  describe "Math.rsqrt" do
-    it_behaves_like :mathn_math_sqrt, :_, Math
-  end
-end
diff --git a/spec/ruby/library/mathn/mathn_spec.rb b/spec/ruby/library/mathn/mathn_spec.rb
deleted file mode 100644
index 129c8f3288..0000000000
--- a/spec/ruby/library/mathn/mathn_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "mathn" do
-  ruby_version_is "2.5" do
-    it "is no longer part of the standard library" do
-      -> {
-        require "mathn"
-      }.should raise_error(LoadError) { |e|
-        e.path.should == 'mathn'
-      }
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/rational/Rational_spec.rb b/spec/ruby/library/mathn/rational/Rational_spec.rb
deleted file mode 100644
index 9a34c99751..0000000000
--- a/spec/ruby/library/mathn/rational/Rational_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Kernel#Rational" do
-    it "returns an Integer if denominator divides numerator evenly" do
-      Rational(42,6).should == 7
-      Rational(42,6).should be_kind_of(Fixnum)
-      Rational(bignum_value,1).should == bignum_value
-      Rational(bignum_value,1).should be_kind_of(Bignum)
-    end
-  end
-end
diff --git a/spec/ruby/library/mathn/rational/inspect_spec.rb b/spec/ruby/library/mathn/rational/inspect_spec.rb
deleted file mode 100644
index cbf67ec0f3..0000000000
--- a/spec/ruby/library/mathn/rational/inspect_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-
-ruby_version_is ''...'2.5' do
-  require 'mathn'
-
-  describe "Rational#inspect" do
-    it "returns a string representation of self" do
-      Rational(3, 4).inspect.should == "(3/4)"
-      Rational(-5, 8).inspect.should == "(-5/8)"
-      Rational(-1, -2).inspect.should == "(1/2)"
-      Rational(0, 2).inspect.should == "0"
-      Rational(bignum_value, 1).inspect.should == "#{bignum_value}"
-    end
-  end
-end
diff --git a/spec/ruby/library/matrix/antisymmetric_spec.rb b/spec/ruby/library/matrix/antisymmetric_spec.rb
index 3eb0f8b726..200df703cb 100644
--- a/spec/ruby/library/matrix/antisymmetric_spec.rb
+++ b/spec/ruby/library/matrix/antisymmetric_spec.rb
@@ -1,37 +1,36 @@
 require_relative '../../spec_helper'
+
 require 'matrix'
 
-ruby_version_is "2.6" do
-  describe "Matrix#antisymmetric?" do
-    it "returns true for an antisymmetric Matrix" do
-      Matrix[[0, -2, Complex(1, 3)], [2, 0, 5], [-Complex(1, 3), -5, 0]].antisymmetric?.should be_true
-    end
+describe "Matrix#antisymmetric?" do
+  it "returns true for an antisymmetric Matrix" do
+    Matrix[[0, -2, Complex(1, 3)], [2, 0, 5], [-Complex(1, 3), -5, 0]].antisymmetric?.should be_true
+  end
 
-    it "returns true for a 0x0 empty matrix" do
-      Matrix.empty.antisymmetric?.should be_true
-    end
+  it "returns true for a 0x0 empty matrix" do
+    Matrix.empty.antisymmetric?.should be_true
+  end
 
-    it "returns false for non-antisymmetric matrices" do
-      [
-        Matrix[[1, 2, 3], [4, 5, 6], [7, 8, 9]],
-        Matrix[[1, -2, 3], [2, 0, 6], [-3, -6, 0]],  # wrong diagonal element
-        Matrix[[0, 2, -3], [2, 0, 6], [-3, 6, 0]]    # only signs wrong
-      ].each do |matrix|
-        matrix.antisymmetric?.should be_false
-      end
+  it "returns false for non-antisymmetric matrices" do
+    [
+      Matrix[[1, 2, 3], [4, 5, 6], [7, 8, 9]],
+      Matrix[[1, -2, 3], [2, 0, 6], [-3, -6, 0]],  # wrong diagonal element
+      Matrix[[0, 2, -3], [2, 0, 6], [-3, 6, 0]]    # only signs wrong
+    ].each do |matrix|
+      matrix.antisymmetric?.should be_false
     end
+  end
 
-    it "raises an error for rectangular matrices" do
-      [
-        Matrix[[0], [0]],
-        Matrix[[0, 0]],
-        Matrix.empty(0, 2),
-        Matrix.empty(2, 0),
-      ].each do |rectangular_matrix|
-        -> {
-          rectangular_matrix.antisymmetric?
-        }.should raise_error(Matrix::ErrDimensionMismatch)
-      end
+  it "raises an error for rectangular matrices" do
+    [
+      Matrix[[0], [0]],
+      Matrix[[0, 0]],
+      Matrix.empty(0, 2),
+      Matrix.empty(2, 0),
+    ].each do |rectangular_matrix|
+      -> {
+        rectangular_matrix.antisymmetric?
+      }.should raise_error(Matrix::ErrDimensionMismatch)
     end
   end
 end
diff --git a/spec/ruby/library/matrix/coerce_spec.rb b/spec/ruby/library/matrix/coerce_spec.rb
index 280243d372..4022f00236 100644
--- a/spec/ruby/library/matrix/coerce_spec.rb
+++ b/spec/ruby/library/matrix/coerce_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 require 'matrix'
 
 describe "Matrix#coerce" do
-  it "allows the division of fixnum by a Matrix " do
+  it "allows the division of integer by a Matrix " do
     (1/Matrix[[0,1],[-1,0]]).should == Matrix[[0,-1],[1,0]]
   end
 end
diff --git a/spec/ruby/library/matrix/exponent_spec.rb b/spec/ruby/library/matrix/exponent_spec.rb
index 447c962967..38cdfa9276 100644
--- a/spec/ruby/library/matrix/exponent_spec.rb
+++ b/spec/ruby/library/matrix/exponent_spec.rb
@@ -21,17 +21,28 @@ describe "Matrix#**" do
       -> { m ** 0 }.should raise_error(Matrix::ErrDimensionMismatch)
     end
 
-    describe "that is <= 0" do
+    describe "that is < 0" do
       it "returns the inverse of **(-n)" do
         m = Matrix[ [1, 1], [1, 2] ]
         (m ** -2).should == Matrix[ [5, -3], [-3, 2]]
         (m ** -4).should == (m.inverse ** 4)
       end
 
-      it "raises a ErrDimensionMismatch for irregular matrices" do
+      it "raises a ErrNotRegular for irregular matrices" do
         m = Matrix[ [1, 1], [1, 1] ]
         -> { m ** -2 }.should raise_error(Matrix::ErrNotRegular)
-        -> { m ** 0 }.should raise_error(Matrix::ErrNotRegular)
+      end
+    end
+
+    describe "that is 0" do
+      it "returns the identity for square matrices" do
+        m = Matrix[ [1, 1], [1, 1] ]
+        (m ** 0).should == Matrix.identity(2)
+      end
+
+      it "raises an ErrDimensionMismatch for non-square matrices" do
+        m = Matrix[ [1, 1] ]
+        -> { m ** 0 }.should raise_error(Matrix::ErrDimensionMismatch)
       end
     end
   end
diff --git a/spec/ruby/library/matrix/hash_spec.rb b/spec/ruby/library/matrix/hash_spec.rb
index fac9a06527..7dabcd3737 100644
--- a/spec/ruby/library/matrix/hash_spec.rb
+++ b/spec/ruby/library/matrix/hash_spec.rb
@@ -3,8 +3,8 @@ require 'matrix'
 
 describe "Matrix#hash" do
 
-  it "returns a Fixnum" do
-    Matrix[ [1,2] ].hash.should be_an_instance_of(Fixnum)
+  it "returns an Integer" do
+    Matrix[ [1,2] ].hash.should be_an_instance_of(Integer)
   end
 
   it "returns the same value for the same matrix" do
diff --git a/spec/ruby/library/matrix/multiply_spec.rb b/spec/ruby/library/matrix/multiply_spec.rb
index 585f268931..206868af92 100644
--- a/spec/ruby/library/matrix/multiply_spec.rb
+++ b/spec/ruby/library/matrix/multiply_spec.rb
@@ -1,4 +1,5 @@
 require_relative '../../spec_helper'
+
 require_relative 'fixtures/classes'
 require 'matrix'
 
@@ -22,8 +23,8 @@ describe "Matrix#*" do
 
   it "returns the result of multiplying the elements of self and a Bignum" do
     (@a * bignum_value).should == Matrix[
-      [9223372036854775808, 18446744073709551616],
-      [27670116110564327424, 36893488147419103232]
+      [18446744073709551616, 36893488147419103232],
+      [55340232221128654848, 73786976294838206464]
     ]
   end
 
diff --git a/spec/ruby/library/matrix/normal_spec.rb b/spec/ruby/library/matrix/normal_spec.rb
index ebd73aaf40..a9e6c645fa 100644
--- a/spec/ruby/library/matrix/normal_spec.rb
+++ b/spec/ruby/library/matrix/normal_spec.rb
@@ -3,12 +3,12 @@ require 'matrix'
 
 describe "Matrix.normal?" do
   # it "returns false for non normal matrices" do
-  #   Matrix[[0, 1], [1, 2]].normal?.should == false
+  #   Matrix[[0, 1], [1, 2]].should_not.normal?
   # end
 
   it "returns true for normal matrices" do
-    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].normal?.should == true
-    Matrix[[0, Complex(0, 2)], [Complex(0, -2), 0]].normal?.should == true
+    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].should.normal?
+    Matrix[[0, Complex(0, 2)], [Complex(0, -2), 0]].should.normal?
   end
 
   it "raises an error for rectangular matrices" do
diff --git a/spec/ruby/library/matrix/orthogonal_spec.rb b/spec/ruby/library/matrix/orthogonal_spec.rb
index 07b098a58d..26afe89ff0 100644
--- a/spec/ruby/library/matrix/orthogonal_spec.rb
+++ b/spec/ruby/library/matrix/orthogonal_spec.rb
@@ -3,12 +3,12 @@ require 'matrix'
 
 describe "Matrix.orthogonal?" do
   it "returns false for non orthogonal matrices" do
-    Matrix[[0, 1], [1, 2]].orthogonal?.should == false
-    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].orthogonal?.should == false
+    Matrix[[0, 1], [1, 2]].should_not.orthogonal?
+    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].should_not.orthogonal?
   end
 
   it "returns true for orthogonal matrices" do
-    Matrix[[0, 1], [1, 0]].orthogonal?.should == true
+    Matrix[[0, 1], [1, 0]].should.orthogonal?
   end
 
   it "raises an error for rectangular matrices" do
diff --git a/spec/ruby/library/matrix/unitary_spec.rb b/spec/ruby/library/matrix/unitary_spec.rb
index 9c2a106ea5..c214ee9b2f 100644
--- a/spec/ruby/library/matrix/unitary_spec.rb
+++ b/spec/ruby/library/matrix/unitary_spec.rb
@@ -1,16 +1,20 @@
 require_relative '../../spec_helper'
+
 require 'matrix'
 
 describe "Matrix.unitary?" do
   it "returns false for non unitary matrices" do
-    Matrix[[0, 1], [1, 2]].unitary?.should == false
-    Matrix[[0, Complex(0, 2)], [Complex(0, 2), 0]].unitary?.should == false
-    Matrix[[0, Complex(0, 1)], [Complex(0, -1), 0]].unitary?.should == false
-    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].unitary?.should == false
+    Matrix[[0, 1], [1, 2]].should_not.unitary?
+    Matrix[[0, Complex(0, 2)], [Complex(0, 2), 0]].should_not.unitary?
+    Matrix[[1, 1, 0], [0, 1, 1], [1, 0, 1]].should_not.unitary?
   end
 
   it "returns true for unitary matrices" do
-    Matrix[[0, Complex(0, 1)], [Complex(0, 1), 0]].unitary?.should == true
+    Matrix[[0, Complex(0, 1)], [Complex(0, 1), 0]].should.unitary?
+  end
+
+  it "returns true for unitary matrices with a Complex and a negative #imag" do
+    Matrix[[0, Complex(0, 1)], [Complex(0, -1), 0]].should.unitary?
   end
 
   it "raises an error for rectangular matrices" do
diff --git a/spec/ruby/library/matrix/zero_spec.rb b/spec/ruby/library/matrix/zero_spec.rb
index 643c57acba..68e8567c26 100644
--- a/spec/ruby/library/matrix/zero_spec.rb
+++ b/spec/ruby/library/matrix/zero_spec.rb
@@ -37,16 +37,16 @@ end
 
 describe "Matrix.zero?" do
   it "returns true for empty matrices" do
-    Matrix.empty.zero?.should == true
-    Matrix.empty(3,0).zero?.should == true
-    Matrix.empty(0,3).zero?.should == true
+    Matrix.empty.should.zero?
+    Matrix.empty(3,0).should.zero?
+    Matrix.empty(0,3).should.zero?
   end
 
   it "returns true for matrices with zero entries" do
-    Matrix.zero(2,3).zero?.should == true
+    Matrix.zero(2,3).should.zero?
   end
 
   it "returns false for matrices with non zero entries" do
-    Matrix[[1]].zero?.should == false
+    Matrix[[1]].should_not.zero?
   end
 end
diff --git a/spec/ruby/library/mkmf/mkmf_spec.rb b/spec/ruby/library/mkmf/mkmf_spec.rb
new file mode 100644
index 0000000000..18b090e703
--- /dev/null
+++ b/spec/ruby/library/mkmf/mkmf_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+
+describe 'mkmf' do
+  it 'can be required with --enable-frozen-string-literal' do
+    ruby_exe('p MakeMakefile', options: '-rmkmf --enable-frozen-string-literal').should == "MakeMakefile\n"
+  end
+end
diff --git a/spec/ruby/library/monitor/enter_spec.rb b/spec/ruby/library/monitor/enter_spec.rb
new file mode 100644
index 0000000000..f523c42087
--- /dev/null
+++ b/spec/ruby/library/monitor/enter_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../spec_helper'
+require 'monitor'
+
+describe "Monitor#enter" do
+  it "acquires the monitor" do
+    monitor = Monitor.new
+    10.times do
+      wait_q = Queue.new
+      continue_q = Queue.new
+
+      thread = Thread.new do
+        begin
+          monitor.enter
+          wait_q << true
+          continue_q.pop
+        ensure
+          monitor.exit
+        end
+      end
+
+      wait_q.pop
+      monitor.mon_locked?.should == true
+      continue_q << true
+      thread.join
+      monitor.mon_locked?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/library/monitor/exit_spec.rb b/spec/ruby/library/monitor/exit_spec.rb
new file mode 100644
index 0000000000..952ad9525d
--- /dev/null
+++ b/spec/ruby/library/monitor/exit_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require 'monitor'
+
+describe "Monitor#exit" do
+  it "raises ThreadError when monitor is not entered" do
+    m = Monitor.new
+
+    -> { m.exit }.should raise_error(ThreadError)
+  end
+end
diff --git a/spec/ruby/library/monitor/new_cond_spec.rb b/spec/ruby/library/monitor/new_cond_spec.rb
new file mode 100644
index 0000000000..ec25d3f8a2
--- /dev/null
+++ b/spec/ruby/library/monitor/new_cond_spec.rb
@@ -0,0 +1,88 @@
+require_relative '../../spec_helper'
+require 'monitor'
+
+describe "Monitor#new_cond" do
+  it "creates a MonitorMixin::ConditionVariable" do
+    m = Monitor.new
+    c = m.new_cond
+    c.class.should == MonitorMixin::ConditionVariable
+  end
+
+  it 'returns a condition variable which can be waited on by a thread holding the monitor' do
+    m = Monitor.new
+    c = m.new_cond
+
+    10.times do
+
+      wait_q = Queue.new
+      thread = Thread.new do
+        m.synchronize do
+          wait_q << true
+          c.wait
+        end
+        :done
+      end
+
+      wait_q.pop
+
+      # Synchronize can't happen until the other thread is waiting.
+      m.synchronize { c.signal }
+
+      thread.join
+      thread.value.should == :done
+    end
+  end
+
+  it 'returns a condition variable which can be waited on by a thread holding the monitor inside multiple synchronize blocks' do
+    m = Monitor.new
+    c = m.new_cond
+
+    10.times do
+
+      wait_q = Queue.new
+      thread = Thread.new do
+        m.synchronize do
+          m.synchronize do
+            wait_q << true
+            c.wait
+          end
+        end
+        :done
+      end
+
+      wait_q.pop
+
+      #No need to wait here as we cannot synchronize until the other thread is waiting.
+      m.synchronize { c.signal }
+
+      thread.join
+      thread.value.should == :done
+    end
+  end
+
+  it 'returns a condition variable which can be signalled by a thread holding the monitor inside multiple synchronize blocks' do
+    m = Monitor.new
+    c = m.new_cond
+
+    10.times do
+
+      wait_q = Queue.new
+      thread = Thread.new do
+        m.synchronize do
+          wait_q << true
+          c.wait
+        end
+        :done
+      end
+
+      wait_q.pop
+
+      # Synchronize can't happen until the other thread is waiting.
+      m.synchronize { m.synchronize { c.signal } }
+
+      thread.join
+      thread.value.should == :done
+    end
+  end
+
+end
diff --git a/spec/ruby/library/monitor/synchronize_spec.rb b/spec/ruby/library/monitor/synchronize_spec.rb
new file mode 100644
index 0000000000..d78393eb3a
--- /dev/null
+++ b/spec/ruby/library/monitor/synchronize_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../spec_helper'
+require 'monitor'
+
+describe "Monitor#synchronize" do
+  it "unlocks after return, even if it was interrupted by Thread#raise" do
+    exc_class = Class.new(RuntimeError)
+
+    monitor = Monitor.new
+    10.times do
+      wait_q = Queue.new
+      continue_q = Queue.new
+
+      thread = Thread.new do
+        begin
+          monitor.synchronize do
+            wait_q << true
+            # Do not wait here, we are trying to interrupt the ensure part of #synchronize
+          end
+          continue_q.pop
+        rescue exc_class
+          monitor.should_not.mon_locked?
+          :ok
+        end
+      end
+
+      wait_q.pop
+      thread.raise exc_class, "interrupt"
+      continue_q << true
+      thread.value.should == :ok
+    end
+  end
+
+  it "raises a LocalJumpError if not passed a block" do
+    -> { Monitor.new.synchronize }.should raise_error(LocalJumpError)
+  end
+
+  it "raises a thread error if the monitor is not owned on exiting the block" do
+    monitor = Monitor.new
+    -> { monitor.synchronize { monitor.exit } }.should raise_error(ThreadError)
+  end
+end
diff --git a/spec/ruby/library/monitor/try_enter_spec.rb b/spec/ruby/library/monitor/try_enter_spec.rb
new file mode 100644
index 0000000000..04b878f720
--- /dev/null
+++ b/spec/ruby/library/monitor/try_enter_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../spec_helper'
+require 'monitor'
+
+describe "Monitor#try_enter" do
+  it "will acquire a monitor not held by another thread" do
+    monitor = Monitor.new
+    10.times do
+
+      thread = Thread.new do
+        val = monitor.try_enter
+        monitor.exit if val
+        val
+      end
+
+      thread.join
+      thread.value.should == true
+    end
+  end
+
+  it "will not acquire a monitor already held by another thread" do
+    monitor = Monitor.new
+    10.times do
+      monitor.enter
+      begin
+        thread = Thread.new do
+          val = monitor.try_enter
+          monitor.exit if val
+          val
+        end
+
+        thread.join
+        thread.value.should == false
+      ensure
+        monitor.exit
+      end
+      monitor.mon_locked?.should == false
+    end
+  end
+end
diff --git a/spec/ruby/library/net/FTPError_spec.rb b/spec/ruby/library/net-ftp/FTPError_spec.rb
index 0c31b65dcc..0c31b65dcc 100644
--- a/spec/ruby/library/net/FTPError_spec.rb
+++ b/spec/ruby/library/net-ftp/FTPError_spec.rb
diff --git a/spec/ruby/library/net/FTPPermError_spec.rb b/spec/ruby/library/net-ftp/FTPPermError_spec.rb
index b43e12c503..b43e12c503 100644
--- a/spec/ruby/library/net/FTPPermError_spec.rb
+++ b/spec/ruby/library/net-ftp/FTPPermError_spec.rb
diff --git a/spec/ruby/library/net/FTPProtoError_spec.rb b/spec/ruby/library/net-ftp/FTPProtoError_spec.rb
index e7abbc0dd8..e7abbc0dd8 100644
--- a/spec/ruby/library/net/FTPProtoError_spec.rb
+++ b/spec/ruby/library/net-ftp/FTPProtoError_spec.rb
diff --git a/spec/ruby/library/net/FTPReplyError_spec.rb b/spec/ruby/library/net-ftp/FTPReplyError_spec.rb
index fcc7501fc1..fcc7501fc1 100644
--- a/spec/ruby/library/net/FTPReplyError_spec.rb
+++ b/spec/ruby/library/net-ftp/FTPReplyError_spec.rb
diff --git a/spec/ruby/library/net/FTPTempError_spec.rb b/spec/ruby/library/net-ftp/FTPTempError_spec.rb
index f4b045dfb5..f4b045dfb5 100644
--- a/spec/ruby/library/net/FTPTempError_spec.rb
+++ b/spec/ruby/library/net-ftp/FTPTempError_spec.rb
diff --git a/spec/ruby/library/net-ftp/abort_spec.rb b/spec/ruby/library/net-ftp/abort_spec.rb
new file mode 100644
index 0000000000..335d056512
--- /dev/null
+++ b/spec/ruby/library/net-ftp/abort_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#abort" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the ABOR command to the server" do
+    -> { @ftp.abort }.should_not raise_error
+  end
+
+  it "ignores the response" do
+    @ftp.abort
+    @ftp.last_response.should == "220 Dummy FTP Server ready!\n"
+  end
+
+  it "returns the full response" do
+    @ftp.abort.should == "226 Closing data connection. (ABOR)\n"
+  end
+
+  it "does not raise any error when the response code is 225" do
+    @server.should_receive(:abor).and_respond("225 Data connection open; no transfer in progress.")
+    -> { @ftp.abort }.should_not raise_error
+  end
+
+  it "does not raise any error when the response code is 226" do
+    @server.should_receive(:abor).and_respond("226 Closing data connection.")
+    -> { @ftp.abort }.should_not raise_error
+  end
+
+  it "raises a Net::FTPProtoError when the response code is 500" do
+    @server.should_receive(:abor).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
+  end
+
+  it "raises a Net::FTPProtoError when the response code is 501" do
+    @server.should_receive(:abor).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
+  end
+
+  it "raises a Net::FTPProtoError when the response code is 502" do
+    @server.should_receive(:abor).and_respond("502 Command not implemented.")
+    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
+  end
+
+  it "raises a Net::FTPProtoError when the response code is 421" do
+    @server.should_receive(:abor).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/acct_spec.rb b/spec/ruby/library/net-ftp/acct_spec.rb
new file mode 100644
index 0000000000..ab093448a2
--- /dev/null
+++ b/spec/ruby/library/net-ftp/acct_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#acct" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "writes the ACCT command to the server" do
+    @ftp.acct("my_account")
+    @ftp.last_response.should == "230 User 'my_account' logged in, proceed. (ACCT)\n"
+  end
+
+  it "returns nil" do
+    @ftp.acct("my_account").should == nil
+  end
+
+  it "does not raise any error when the response code is 230" do
+    @server.should_receive(:acct).and_respond("230 User logged in, proceed.")
+    -> { @ftp.acct("my_account") }.should_not raise_error
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:acct).and_respond("530 Not logged in.")
+    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:acct).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:acct).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 503" do
+    @server.should_receive(:acct).and_respond("503 Bad sequence of commands.")
+    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:acct).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/binary_spec.rb b/spec/ruby/library/net-ftp/binary_spec.rb
new file mode 100644
index 0000000000..1e0585b795
--- /dev/null
+++ b/spec/ruby/library/net-ftp/binary_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#binary" do
+  it "returns true when self is in binary mode" do
+    ftp = Net::FTP.new
+    ftp.binary.should be_true
+
+    ftp.binary = false
+    ftp.binary.should be_false
+  end
+end
+
+describe "Net::FTP#binary=" do
+  it "sets self to binary mode when passed true" do
+    ftp = Net::FTP.new
+
+    ftp.binary = true
+    ftp.binary.should be_true
+
+    ftp.binary = false
+    ftp.binary.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-ftp/chdir_spec.rb b/spec/ruby/library/net-ftp/chdir_spec.rb
new file mode 100644
index 0000000000..cc129b5e42
--- /dev/null
+++ b/spec/ruby/library/net-ftp/chdir_spec.rb
@@ -0,0 +1,99 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#chdir" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  describe "when switching to the parent directory" do
+    it "sends the 'CDUP' command to the server" do
+      @ftp.chdir("..")
+      @ftp.last_response.should == "200 Command okay. (CDUP)\n"
+    end
+
+    it "returns nil" do
+      @ftp.chdir("..").should be_nil
+    end
+
+    it "does not raise a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:cdup).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.chdir("..") }.should_not raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:cdup).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:cdup).and_respond("502 Command not implemented.")
+      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:cdup).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.chdir("..") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:cdup).and_respond("530 Not logged in.")
+      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 550" do
+      @server.should_receive(:cdup).and_respond("550 Requested action not taken.")
+      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  it "writes the 'CWD' command with the passed directory to the socket" do
+    @ftp.chdir("test")
+    @ftp.last_response.should == "200 Command okay. (CWD test)\n"
+  end
+
+  it "returns nil" do
+    @ftp.chdir("test").should be_nil
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:cwd).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:cwd).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:cwd).and_respond("502 Command not implemented.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:cwd).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:cwd).and_respond("530 Not logged in.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:cwd).and_respond("550 Requested action not taken.")
+    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/close_spec.rb b/spec/ruby/library/net-ftp/close_spec.rb
new file mode 100644
index 0000000000..183f14a84b
--- /dev/null
+++ b/spec/ruby/library/net-ftp/close_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#close" do
+  before :each do
+    @socket = mock("Socket")
+    @socket.stub!(:closed?).and_return(false)
+    @socket.stub!(:read_timeout).and_return(60)
+    @socket.stub!(:read_timeout=).and_return(3)
+
+    @ftp = Net::FTP.new
+    @ftp.instance_variable_set(:@sock, @socket)
+  end
+
+  it "closes the socket" do
+    @socket.should_receive(:close)
+    @ftp.close.should be_nil
+  end
+
+  it "does not try to close the socket if it has already been closed" do
+    @socket.should_receive(:closed?).and_return(true)
+    @socket.should_not_receive(:close)
+    @ftp.close.should be_nil
+  end
+
+  it "does not try to close the socket if it is nil" do
+    @ftp.instance_variable_set(:@sock, nil)
+    @ftp.close.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-ftp/closed_spec.rb b/spec/ruby/library/net-ftp/closed_spec.rb
new file mode 100644
index 0000000000..84001cdc0f
--- /dev/null
+++ b/spec/ruby/library/net-ftp/closed_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#closed?" do
+  before :each do
+    @socket = mock("Socket")
+
+    @ftp = Net::FTP.new
+    @ftp.instance_variable_set(:@sock, @socket)
+  end
+
+  it "returns true when the socket is closed" do
+    @socket.should_receive(:closed?).and_return(true)
+    @ftp.closed?.should be_true
+  end
+
+  it "returns true when the socket is nil" do
+    @ftp.instance_variable_set(:@sock, nil)
+    @ftp.closed?.should be_true
+  end
+end
diff --git a/spec/ruby/library/net-ftp/connect_spec.rb b/spec/ruby/library/net-ftp/connect_spec.rb
new file mode 100644
index 0000000000..e606b11e2a
--- /dev/null
+++ b/spec/ruby/library/net-ftp/connect_spec.rb
@@ -0,0 +1,43 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+# TODO: Add specs for using the SOCKSSocket
+describe "Net::FTP#connect" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+  end
+
+  after :each do
+    @server.connect_message = nil
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "tries to connect to the FTP Server on the given host and port" do
+    -> { @ftp.connect(@server.hostname, @server.server_port) }.should_not raise_error
+  end
+
+  it "returns nil" do
+    @ftp.connect(@server.hostname, @server.server_port).should be_nil
+  end
+
+  it "does not raise any error when the response code is 220" do
+    @server.connect_message = "220 Dummy FTP Server ready!"
+    -> { @ftp.connect(@server.hostname, @server.server_port) }.should_not raise_error
+  end
+
+  it "raises a Net::FTPReplyError when the response code is 120" do
+    @server.connect_message = "120 Service ready in nnn minutes."
+    -> { @ftp.connect(@server.hostname, @server.server_port) }.should raise_error(Net::FTPReplyError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.connect_message = "421 Service not available, closing control connection."
+    -> { @ftp.connect(@server.hostname, @server.server_port) }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/debug_mode_spec.rb b/spec/ruby/library/net-ftp/debug_mode_spec.rb
new file mode 100644
index 0000000000..f2ef53c089
--- /dev/null
+++ b/spec/ruby/library/net-ftp/debug_mode_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#debug_mode" do
+  it "returns true when self is in debug mode" do
+    ftp = Net::FTP.new
+    ftp.debug_mode.should be_false
+
+    ftp.debug_mode = true
+    ftp.debug_mode.should be_true
+  end
+end
+
+describe "Net::FTP#debug_mode=" do
+  it "sets self into debug mode when passed true" do
+    ftp = Net::FTP.new
+    ftp.debug_mode = true
+    ftp.debug_mode.should be_true
+
+    ftp.debug_mode = false
+    ftp.debug_mode.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-ftp/default_passive_spec.rb b/spec/ruby/library/net-ftp/default_passive_spec.rb
new file mode 100644
index 0000000000..3f14f6187e
--- /dev/null
+++ b/spec/ruby/library/net-ftp/default_passive_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#default_passive" do
+  it "is true by default" do
+    ruby_exe(fixture(__FILE__, "default_passive.rb")).should == "true\ntrue\n"
+  end
+end
diff --git a/spec/ruby/library/net-ftp/delete_spec.rb b/spec/ruby/library/net-ftp/delete_spec.rb
new file mode 100644
index 0000000000..bfb7da1ffe
--- /dev/null
+++ b/spec/ruby/library/net-ftp/delete_spec.rb
@@ -0,0 +1,59 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#delete" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the DELE command with the passed filename to the server" do
+    @ftp.delete("test.file")
+    @ftp.last_response.should == "250 Requested file action okay, completed. (DELE test.file)\n"
+  end
+
+  it "raises a Net::FTPTempError when the response code is 450" do
+    @server.should_receive(:dele).and_respond("450 Requested file action not taken.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:dele).and_respond("550 Requested action not taken.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:dele).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:dele).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:dele).and_respond("502 Command not implemented.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:dele).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:dele).and_respond("530 Not logged in.")
+    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/dir_spec.rb b/spec/ruby/library/net-ftp/dir_spec.rb
new file mode 100644
index 0000000000..894f03dd7b
--- /dev/null
+++ b/spec/ruby/library/net-ftp/dir_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/list'
+
+describe "Net::FTP#dir" do
+  it_behaves_like :net_ftp_list, :dir
+end
diff --git a/spec/ruby/library/net/ftp/fixtures/default_passive.rb b/spec/ruby/library/net-ftp/fixtures/default_passive.rb
index b6995d6f34..b6995d6f34 100644
--- a/spec/ruby/library/net/ftp/fixtures/default_passive.rb
+++ b/spec/ruby/library/net-ftp/fixtures/default_passive.rb
diff --git a/spec/ruby/library/net/ftp/fixtures/passive.rb b/spec/ruby/library/net-ftp/fixtures/passive.rb
index 6b5cde82df..6b5cde82df 100644
--- a/spec/ruby/library/net/ftp/fixtures/passive.rb
+++ b/spec/ruby/library/net-ftp/fixtures/passive.rb
diff --git a/spec/ruby/library/net/ftp/fixtures/putbinaryfile b/spec/ruby/library/net-ftp/fixtures/putbinaryfile
index f3130c6e43..f3130c6e43 100644
--- a/spec/ruby/library/net/ftp/fixtures/putbinaryfile
+++ b/spec/ruby/library/net-ftp/fixtures/putbinaryfile
diff --git a/spec/ruby/library/net/ftp/fixtures/puttextfile b/spec/ruby/library/net-ftp/fixtures/puttextfile
index b4f3b2b62d..b4f3b2b62d 100644
--- a/spec/ruby/library/net/ftp/fixtures/puttextfile
+++ b/spec/ruby/library/net-ftp/fixtures/puttextfile
diff --git a/spec/ruby/library/net-ftp/fixtures/server.rb b/spec/ruby/library/net-ftp/fixtures/server.rb
new file mode 100644
index 0000000000..8b34d3f8bd
--- /dev/null
+++ b/spec/ruby/library/net-ftp/fixtures/server.rb
@@ -0,0 +1,277 @@
+module NetFTPSpecs
+  class DummyFTP
+    attr_accessor :connect_message
+    attr_reader :login_user, :login_pass, :login_acct
+
+    # hostname or IP address
+    attr_reader :hostname
+    # port number
+    attr_reader :server_port
+
+    def initialize
+      @hostname = "127.0.0.1"
+      @server = TCPServer.new(@hostname, 0)
+      @server_port = @server.addr[1]
+
+      @handlers = {}
+      @commands = []
+      @connect_message = nil
+    end
+
+    def serve_once
+      @thread = Thread.new do
+        @socket = @server.accept
+        @socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_OOBINLINE, 1)
+        begin
+          handle_request
+        ensure
+          @socket.close
+        end
+      end
+    end
+
+    def handle_request
+      # Send out the welcome message.
+      response @connect_message || "220 Dummy FTP Server ready!"
+
+      begin
+        while command = @socket.gets
+          command, argument = command.chomp.split(" ", 2)
+
+          if command == "QUIT"
+            self.response("221 OK, bye")
+            break
+          elsif proc_handler = @handlers[command.downcase.to_sym]
+            if argument.nil?
+              proc_handler.call(self)
+            else
+              proc_handler.call(self, argument)
+            end
+          else
+            if argument.nil?
+              self.send(command.downcase.to_sym)
+            else
+              self.send(command.downcase.to_sym, argument)
+            end
+          end
+        end
+      rescue => e
+        self.error_response("Exception: #{e} #{e.backtrace.inspect}")
+      end
+    end
+
+    def error_response(text)
+      self.response("451 #{text}")
+    end
+
+    def response(text)
+      @socket.puts(text) unless @socket.closed?
+    end
+
+    def stop
+      @datasocket.close unless @datasocket.nil? || @datasocket.closed?
+      @server.close
+      @thread.join
+    end
+
+
+    ##
+    def handle(sym, &block)
+      @handlers[sym] = block
+    end
+
+    def should_receive(method)
+      @handler_for = method
+      self
+    end
+
+    def and_respond(text)
+      @handlers[@handler_for] = -> s, *args { s.response(text) }
+    end
+
+    ##
+    # FTP methods
+    ##
+
+    def abor
+      self.response("226 Closing data connection. (ABOR)")
+    end
+
+    def acct(account)
+      @login_acct = account
+      self.response("230 User '#{account}' logged in, proceed. (ACCT)")
+    end
+
+    def cdup
+      self.response("200 Command okay. (CDUP)")
+    end
+
+    def cwd(dir)
+      self.response("200 Command okay. (CWD #{dir})")
+    end
+
+    def dele(file)
+      self.response("250 Requested file action okay, completed. (DELE #{file})")
+    end
+
+    def eprt(arg)
+      _, _, host, port = arg.split("|")
+
+      @datasocket = TCPSocket.new(host, port)
+      self.response("200 port opened")
+    end
+
+    def help(param = :default)
+      if param == :default
+        self.response("211 System status, or system help reply. (HELP)")
+      else
+        self.response("211 System status, or system help reply. (HELP #{param})")
+      end
+    end
+
+    def list(folder)
+      self.response("150 opening ASCII connection for file list")
+      @datasocket.puts("-rw-r--r--  1 spec  staff  507 17 Jul 18:41 last_response_code.rb")
+      @datasocket.puts("-rw-r--r--  1 spec  staff   50 17 Jul 18:41 list.rb")
+      @datasocket.puts("-rw-r--r--  1 spec  staff   48 17 Jul 18:41 pwd.rb")
+      @datasocket.close()
+      self.response("226 transfer complete (LIST #{folder})")
+    end
+
+    def mdtm(filename)
+      self.response("213 19980705132316")
+    end
+
+    def mkd(foldername)
+      self.response(%Q{257 "#{foldername.gsub('"', '""')}" created.})
+    end
+
+    def nlst(folder = nil)
+      self.response("150 opening ASCII connection for file list")
+      @datasocket.puts("last_response_code.rb")
+      @datasocket.puts("list.rb")
+      @datasocket.puts("pwd.rb")
+      @datasocket.close()
+      self.response("226 transfer complete (NLST#{folder ? " #{folder}" : ""})")
+    end
+
+    def noop
+      self.response("200 Command okay. (NOOP)")
+    end
+
+    def pass(password)
+      @login_pass = password
+      self.response("230 User logged in, proceed. (PASS #{password})")
+    end
+
+    def port(arg)
+      nums = arg.split(",")
+
+      if nums[0] == "::1"
+        # IPv6
+        port = nums[1].to_i * 256 + nums[2].to_i
+        host = nums[0]
+      else
+        # IPv4
+        port = nums[4].to_i * 256 + nums[5].to_i
+        host = nums[0..3].join(".")
+      end
+
+      @datasocket = TCPSocket.new(host, port)
+      self.response("200 port opened")
+    end
+
+    def pwd
+      self.response('257 "/some/dir/" - current directory')
+    end
+
+    def retr(file)
+      self.response("125 Data transfer starting")
+      if @restart_at && @restart_at == 20
+        @datasocket.puts("of the file named '#{file}'.")
+        @restart_at = nil
+      else
+        @datasocket.puts("This is the content")
+        @datasocket.puts("of the file named '#{file}'.")
+      end
+      @datasocket.close()
+      self.response("226 Closing data connection. (RETR #{file})")
+    end
+
+    def rest(at_bytes)
+      @restart_at = at_bytes.to_i
+      self.response("350 Requested file action pending further information. (REST)")
+    end
+
+    def rmd(folder)
+      self.response("250 Requested file action okay, completed. (RMD #{folder})")
+    end
+
+    def rnfr(from)
+      @rename_from = from
+      self.response("350 Requested file action pending further information.")
+    end
+
+    def rnto(to)
+      self.response("250 Requested file action okay, completed. (Renamed #{@rename_from} to #{to})")
+      @rename_from = nil
+    end
+
+    def site(param)
+      self.response("200 Command okay. (SITE #{param})")
+    end
+
+    def size(filename)
+      if filename == "binary"
+        self.response("213 24")
+      else
+        self.response("213 1024")
+      end
+    end
+
+    def stat(param = :default)
+      if param == :default
+        self.response("211 System status, or system help reply. (STAT)")
+      else
+        self.response("211 System status, or system help reply. (STAT #{param})")
+      end
+    end
+
+    def stor(file)
+      tmp_file = tmp("#{file}file", false)
+
+      self.response("125 Data transfer starting.")
+
+      mode = @restart_at ? "a" : "w"
+
+      File.open(tmp_file, mode + "b") do |f|
+        loop do
+          data = @datasocket.recv(1024)
+          break if !data || data.empty?
+          f << data
+        end
+      end
+
+      @datasocket.close()
+      self.response("200 OK, Data received. (STOR #{file})")
+    end
+
+    def appe(file)
+      @restart_at = true
+      stor(file)
+    end
+
+    def syst
+      self.response("215 FTP Dummy Server (SYST)")
+    end
+
+    def type(type)
+      self.response("200 TYPE switched to #{type}")
+    end
+
+    def user(name)
+      @login_user = name
+      self.response("230 User logged in, proceed. (USER #{name})")
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/get_spec.rb b/spec/ruby/library/net-ftp/get_spec.rb
new file mode 100644
index 0000000000..1bc1bd744b
--- /dev/null
+++ b/spec/ruby/library/net-ftp/get_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/gettextfile'
+require_relative 'shared/getbinaryfile'
+
+describe "Net::FTP#get (binary mode)" do
+  before :each do
+    @binary_mode = true
+  end
+
+  it_behaves_like :net_ftp_getbinaryfile, :get
+end
+
+describe "Net::FTP#get (text mode)" do
+  before :each do
+    @binary_mode = false
+  end
+
+  it_behaves_like :net_ftp_gettextfile, :get
+end
diff --git a/spec/ruby/library/net-ftp/getbinaryfile_spec.rb b/spec/ruby/library/net-ftp/getbinaryfile_spec.rb
new file mode 100644
index 0000000000..e9898fccc7
--- /dev/null
+++ b/spec/ruby/library/net-ftp/getbinaryfile_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/getbinaryfile'
+
+describe "Net::FTP#getbinaryfile" do
+  it_behaves_like :net_ftp_getbinaryfile, :getbinaryfile
+end
diff --git a/spec/ruby/library/net-ftp/getdir_spec.rb b/spec/ruby/library/net-ftp/getdir_spec.rb
new file mode 100644
index 0000000000..756d6a23af
--- /dev/null
+++ b/spec/ruby/library/net-ftp/getdir_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'shared/pwd'
+
+describe "Net::FTP#getdir" do
+  it_behaves_like :net_ftp_pwd, :getdir
+end
diff --git a/spec/ruby/library/net-ftp/gettextfile_spec.rb b/spec/ruby/library/net-ftp/gettextfile_spec.rb
new file mode 100644
index 0000000000..cdd1b4c797
--- /dev/null
+++ b/spec/ruby/library/net-ftp/gettextfile_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/gettextfile'
+
+describe "Net::FTP#gettextfile" do
+  it_behaves_like :net_ftp_gettextfile, :gettextfile
+end
diff --git a/spec/ruby/library/net-ftp/help_spec.rb b/spec/ruby/library/net-ftp/help_spec.rb
new file mode 100644
index 0000000000..c562be50b2
--- /dev/null
+++ b/spec/ruby/library/net-ftp/help_spec.rb
@@ -0,0 +1,66 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#help" do
+  def with_connection
+    yield
+  end
+
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "writes the HELP command to the server" do
+    @ftp.help
+    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
+  end
+
+  it "returns the server's response" do
+    @ftp.help.should == "211 System status, or system help reply. (HELP)\n"
+  end
+
+  it "writes the HELP command with an optional parameter to the socket" do
+    @ftp.help("some parameter").should == "211 System status, or system help reply. (HELP some parameter)\n"
+  end
+
+  it "does not raise any error when the response code is 211" do
+    @server.should_receive(:help).and_respond("211 System status, or system help reply.")
+    -> { @ftp.help }.should_not raise_error
+  end
+
+  it "does not raise any error when the response code is 214" do
+    @server.should_receive(:help).and_respond("214 Help message.")
+    -> { @ftp.help }.should_not raise_error
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:help).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.help }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:help).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.help }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:help).and_respond("502 Command not implemented.")
+    -> { @ftp.help }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:help).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.help }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/initialize_spec.rb b/spec/ruby/library/net-ftp/initialize_spec.rb
new file mode 100644
index 0000000000..4d775e8dc1
--- /dev/null
+++ b/spec/ruby/library/net-ftp/initialize_spec.rb
@@ -0,0 +1,405 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#initialize" do
+  before :each do
+    @ftp = Net::FTP.allocate
+    @ftp.stub!(:connect)
+    @port_args = []
+    @port_args << 21
+  end
+
+  it "is private" do
+    Net::FTP.should have_private_instance_method(:initialize)
+  end
+
+  it "sets self into binary mode" do
+    @ftp.binary.should be_nil
+    @ftp.send(:initialize)
+    @ftp.binary.should be_true
+  end
+
+  it "sets self into active mode" do
+    @ftp.passive.should be_nil
+    @ftp.send(:initialize)
+    @ftp.passive.should be_false
+  end
+
+  it "sets self into non-debug mode" do
+    @ftp.debug_mode.should be_nil
+    @ftp.send(:initialize)
+    @ftp.debug_mode.should be_false
+  end
+
+  it "sets self to not resume file uploads/downloads" do
+    @ftp.resume.should be_nil
+    @ftp.send(:initialize)
+    @ftp.resume.should be_false
+  end
+
+  describe "when passed no arguments" do
+    it "does not try to connect" do
+      @ftp.should_not_receive(:connect)
+      @ftp.send(:initialize)
+    end
+  end
+
+  describe "when passed host" do
+    it "tries to connect to the passed host" do
+      @ftp.should_receive(:connect).with("localhost", *@port_args)
+      @ftp.send(:initialize, "localhost")
+    end
+  end
+
+  describe "when passed host, user" do
+    it "tries to connect to the passed host" do
+      @ftp.should_receive(:connect).with("localhost", *@port_args)
+      @ftp.send(:initialize, "localhost")
+    end
+
+    it "tries to login with the passed username" do
+      @ftp.should_receive(:login).with("rubyspec", nil, nil)
+      @ftp.send(:initialize, "localhost", "rubyspec")
+    end
+  end
+
+  describe "when passed host, user, password" do
+    it "tries to connect to the passed host" do
+      @ftp.should_receive(:connect).with("localhost", *@port_args)
+      @ftp.send(:initialize, "localhost")
+    end
+
+    it "tries to login with the passed username and password" do
+      @ftp.should_receive(:login).with("rubyspec", "rocks", nil)
+      @ftp.send(:initialize, "localhost", "rubyspec", "rocks")
+    end
+  end
+
+  describe "when passed host, user" do
+    it "tries to connect to the passed host" do
+      @ftp.should_receive(:connect).with("localhost", *@port_args)
+      @ftp.send(:initialize, "localhost")
+    end
+
+    it "tries to login with the passed username, password and account" do
+      @ftp.should_receive(:login).with("rubyspec", "rocks", "account")
+      @ftp.send(:initialize, "localhost", "rubyspec", "rocks", "account")
+    end
+  end
+
+  before :each do
+    @ftp.stub!(:login)
+  end
+
+  describe 'when the host' do
+    describe 'is set' do
+      describe 'and port option' do
+        describe 'is set' do
+          it 'tries to connect to the host on the specified port' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({ port: 8080 })
+            @ftp.should_receive(:connect).with('localhost', 8080)
+
+            @ftp.send(:initialize, 'localhost', options)
+          end
+        end
+
+        describe 'is not set' do
+          it 'tries to connect to the host without a port' do
+            @ftp.should_receive(:connect).with("localhost", *@port_args)
+
+            @ftp.send(:initialize, 'localhost')
+          end
+        end
+      end
+
+      describe 'when the username option' do
+        describe 'is set' do
+          describe 'and the password option' do
+            describe 'is set' do
+              describe 'and the account option' do
+                describe 'is set' do
+                  it 'tries to log in with the supplied parameters' do
+                    options = mock('ftp initialize options')
+                    options.should_receive(:to_hash).and_return({ username: 'a', password: 'topsecret', account: 'b' })
+                    @ftp.should_receive(:login).with('a', 'topsecret', 'b')
+
+                    @ftp.send(:initialize, 'localhost', options)
+                  end
+                end
+
+                describe 'is unset' do
+                  it 'tries to log in with the supplied parameters' do
+                    options = mock('ftp initialize options')
+                    options.should_receive(:to_hash).and_return({ username: 'a', password: 'topsecret' })
+                    @ftp.should_receive(:login).with('a', 'topsecret', nil)
+
+                    @ftp.send(:initialize, 'localhost', options)
+                  end
+                end
+              end
+            end
+
+            describe 'is unset' do
+              describe 'and the account option' do
+                describe 'is set' do
+                  it 'tries to log in with the supplied parameters' do
+                    options = mock('ftp initialize options')
+                    options.should_receive(:to_hash).and_return({ username: 'a', account: 'b' })
+                    @ftp.should_receive(:login).with('a', nil, 'b')
+
+                    @ftp.send(:initialize, 'localhost', options)
+                  end
+                end
+
+                describe 'is unset' do
+                  it 'tries to log in with the supplied parameters' do
+                    options = mock('ftp initialize options')
+                    options.should_receive(:to_hash).and_return({ username: 'a'})
+                    @ftp.should_receive(:login).with('a', nil, nil)
+
+                    @ftp.send(:initialize, 'localhost', options)
+                  end
+                end
+              end
+            end
+          end
+        end
+
+        describe 'is not set' do
+          it 'does not try to log in' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({})
+            @ftp.should_not_receive(:login)
+
+            @ftp.send(:initialize, 'localhost', options)
+          end
+        end
+      end
+    end
+
+    describe 'is unset' do
+      it 'does not try to connect' do
+        @ftp.should_not_receive(:connect)
+
+        @ftp.send(:initialize)
+      end
+
+      it 'does not try to log in' do
+        @ftp.should_not_receive(:login)
+
+        @ftp.send(:initialize)
+      end
+    end
+  end
+
+  describe 'when the passive option' do
+    describe 'is set' do
+      describe 'to true' do
+        it 'sets passive to true' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ passive: true })
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.passive.should == true
+        end
+      end
+
+      describe 'to false' do
+        it 'sets passive to false' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ passive: false })
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.passive.should == false
+        end
+      end
+    end
+
+    describe 'is unset' do
+      it 'sets passive to false' do
+        @ftp.send(:initialize)
+        @ftp.passive.should == false
+      end
+    end
+  end
+
+  describe 'when the debug_mode option' do
+    describe 'is set' do
+      describe 'to true' do
+        it 'sets debug_mode to true' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ debug_mode: true })
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.debug_mode.should == true
+        end
+      end
+
+      describe 'to false' do
+        it 'sets debug_mode to false' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ debug_mode: false })
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.debug_mode.should == false
+        end
+      end
+    end
+
+    describe 'is unset' do
+      it 'sets debug_mode to false' do
+        @ftp.send(:initialize)
+        @ftp.debug_mode.should == false
+      end
+    end
+  end
+
+  describe 'when the open_timeout option' do
+    describe 'is set' do
+      it 'sets open_timeout to the specified value' do
+        options = mock('ftp initialize options')
+        options.should_receive(:to_hash).and_return({ open_timeout: 42 })
+
+        @ftp.send(:initialize, nil, options)
+        @ftp.open_timeout.should == 42
+      end
+    end
+
+    describe 'is not set' do
+      it 'sets open_timeout to nil' do
+        @ftp.send(:initialize)
+        @ftp.open_timeout.should == nil
+      end
+    end
+  end
+
+  describe 'when the read_timeout option' do
+    describe 'is set' do
+      it 'sets read_timeout to the specified value' do
+        options = mock('ftp initialize options')
+        options.should_receive(:to_hash).and_return({ read_timeout: 100 })
+
+        @ftp.send(:initialize, nil, options)
+        @ftp.read_timeout.should == 100
+      end
+    end
+
+    describe 'is not set' do
+      it 'sets read_timeout to the default value' do
+        @ftp.send(:initialize)
+        @ftp.read_timeout.should == 60
+      end
+    end
+  end
+
+  describe 'when the ssl_handshake_timeout option' do
+    describe 'is set' do
+      it 'sets ssl_handshake_timeout to the specified value' do
+        options = mock('ftp initialize options')
+        options.should_receive(:to_hash).and_return({ ssl_handshake_timeout: 23 })
+
+        @ftp.send(:initialize, nil, options)
+        @ftp.ssl_handshake_timeout.should == 23
+      end
+    end
+
+    describe 'is not set' do
+      it 'sets ssl_handshake_timeout to nil' do
+        @ftp.send(:initialize)
+        @ftp.ssl_handshake_timeout.should == nil
+      end
+    end
+  end
+
+  describe 'when the ssl option' do
+    describe 'is set' do
+      describe "and the ssl option's value is true" do
+        it 'initializes ssl_context to a blank SSLContext object' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ ssl: true })
+
+          ssl_context = OpenSSL::SSL::SSLContext.allocate
+          ssl_context.stub!(:set_params)
+
+          OpenSSL::SSL::SSLContext.should_receive(:new).and_return(ssl_context)
+          ssl_context.should_receive(:set_params).with({})
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.instance_variable_get(:@ssl_context).should == ssl_context
+        end
+      end
+
+      describe "and the ssl option's value is a hash" do
+        it 'initializes ssl_context to a configured SSLContext object' do
+          options = mock('ftp initialize options')
+          options.should_receive(:to_hash).and_return({ ssl: {key: 'value'} })
+
+          ssl_context = OpenSSL::SSL::SSLContext.allocate
+          ssl_context.stub!(:set_params)
+
+          OpenSSL::SSL::SSLContext.should_receive(:new).and_return(ssl_context)
+          ssl_context.should_receive(:set_params).with({key: 'value'})
+
+          @ftp.send(:initialize, nil, options)
+          @ftp.instance_variable_get(:@ssl_context).should == ssl_context
+        end
+      end
+
+      describe 'and private_data_connection' do
+        describe 'is set' do
+          it 'sets private_data_connection to that value' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({ ssl: true, private_data_connection: 'true' })
+
+            @ftp.send(:initialize, nil, options)
+            @ftp.instance_variable_get(:@private_data_connection).should == 'true'
+          end
+        end
+
+        describe 'is not set' do
+          it 'sets private_data_connection to nil' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({ ssl: true })
+
+            @ftp.send(:initialize, nil, options)
+            @ftp.instance_variable_get(:@private_data_connection).should == true
+          end
+        end
+      end
+    end
+
+    describe 'is not set' do
+      it 'sets ssl_context to nil' do
+        options = mock('ftp initialize options')
+        options.should_receive(:to_hash).and_return({})
+
+        @ftp.send(:initialize, nil, options)
+        @ftp.instance_variable_get(:@ssl_context).should == nil
+      end
+
+      describe 'private_data_connection' do
+        describe 'is set' do
+          it 'raises an ArgumentError' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({ private_data_connection: true })
+
+            -> {
+              @ftp.send(:initialize, nil, options)
+            }.should raise_error(ArgumentError, /private_data_connection can be set to true only when ssl is enabled/)
+          end
+        end
+
+        describe 'is not set' do
+          it 'sets private_data_connection to false' do
+            options = mock('ftp initialize options')
+            options.should_receive(:to_hash).and_return({})
+
+            @ftp.send(:initialize, nil, options)
+            @ftp.instance_variable_get(:@private_data_connection).should == false
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/last_response_code_spec.rb b/spec/ruby/library/net-ftp/last_response_code_spec.rb
new file mode 100644
index 0000000000..c17c28f0f8
--- /dev/null
+++ b/spec/ruby/library/net-ftp/last_response_code_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'shared/last_response_code'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#last_response_code" do
+  it_behaves_like :net_ftp_last_response_code, :last_response_code
+end
diff --git a/spec/ruby/library/net-ftp/last_response_spec.rb b/spec/ruby/library/net-ftp/last_response_spec.rb
new file mode 100644
index 0000000000..c9d9d70f35
--- /dev/null
+++ b/spec/ruby/library/net-ftp/last_response_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#last_response" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "returns the last response" do
+    @ftp.last_response.should == "220 Dummy FTP Server ready!\n"
+    @ftp.help
+    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
+  end
+end
diff --git a/spec/ruby/library/net-ftp/lastresp_spec.rb b/spec/ruby/library/net-ftp/lastresp_spec.rb
new file mode 100644
index 0000000000..e0c1b862a0
--- /dev/null
+++ b/spec/ruby/library/net-ftp/lastresp_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'shared/last_response_code'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#lastresp" do
+  it_behaves_like :net_ftp_last_response_code, :lastresp
+end
diff --git a/spec/ruby/library/net-ftp/list_spec.rb b/spec/ruby/library/net-ftp/list_spec.rb
new file mode 100644
index 0000000000..6cb1bbc4b8
--- /dev/null
+++ b/spec/ruby/library/net-ftp/list_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/list'
+
+describe "Net::FTP#list" do
+  it_behaves_like :net_ftp_list, :list
+end
diff --git a/spec/ruby/library/net-ftp/login_spec.rb b/spec/ruby/library/net-ftp/login_spec.rb
new file mode 100644
index 0000000000..0de2f5cc63
--- /dev/null
+++ b/spec/ruby/library/net-ftp/login_spec.rb
@@ -0,0 +1,195 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#login" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  describe "when passed no arguments" do
+    it "sends the USER command with 'anonymous' as name to the server" do
+      @ftp.login
+      @server.login_user.should == "anonymous"
+    end
+
+    it "sends 'anonymous@' as a password when required" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @ftp.login
+      @server.login_pass.should == "anonymous@"
+    end
+
+    it "raises a Net::FTPReplyError when the server requests an account" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @server.should_receive(:pass).and_respond("332 Need account for login.")
+      -> { @ftp.login }.should raise_error(Net::FTPReplyError)
+    end
+  end
+
+  describe "when passed name" do
+    it "sends the USER command with the passed name to the server" do
+      @ftp.login("rubyspec")
+      @server.login_user.should == "rubyspec"
+    end
+
+    it "raises a Net::FTPReplyError when the server requests a password, but none was given" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      -> { @ftp.login("rubyspec") }.should raise_error(Net::FTPReplyError)
+    end
+
+    it "raises a Net::FTPReplyError when the server requests an account, but none was given" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @server.should_receive(:pass).and_respond("332 Need account for login.")
+      -> { @ftp.login("rubyspec") }.should raise_error(Net::FTPReplyError)
+    end
+  end
+
+  describe "when passed name, password" do
+    it "sends the USER command with the passed name to the server" do
+      @ftp.login("rubyspec", "rocks")
+      @server.login_user.should == "rubyspec"
+    end
+
+    it "sends the passed password when required" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @ftp.login("rubyspec", "rocks")
+      @server.login_pass.should == "rocks"
+    end
+
+    it "raises a Net::FTPReplyError when the server requests an account" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @server.should_receive(:pass).and_respond("332 Need account for login.")
+      -> { @ftp.login("rubyspec", "rocks") }.should raise_error(Net::FTPReplyError)
+    end
+  end
+
+  describe "when passed name, password, account" do
+    it "sends the USER command with the passed name to the server" do
+      @ftp.login("rubyspec", "rocks", "account")
+      @server.login_user.should == "rubyspec"
+    end
+
+    it "sends the passed password when required" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @ftp.login("rubyspec", "rocks", "account")
+      @server.login_pass.should == "rocks"
+    end
+
+    it "sends the passed account when required" do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @server.should_receive(:pass).and_respond("332 Need account for login.")
+      @ftp.login("rubyspec", "rocks", "account")
+      @server.login_acct.should == "account"
+    end
+  end
+
+  describe "when the USER command fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:user).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:user).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:user).and_respond("502 Command not implemented.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:user).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:user).and_respond("530 Not logged in.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when the PASS command fails" do
+    before :each do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+    end
+
+    it "does not raise an Error when the response code is 202" do
+      @server.should_receive(:pass).and_respond("202 Command not implemented, superfluous at this site.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should_not raise_error
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:pass).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:pass).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:pass).and_respond("502 Command not implemented.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:pass).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:pass).and_respond("530 Not logged in.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when the ACCT command fails" do
+    before :each do
+      @server.should_receive(:user).and_respond("331 User name okay, need password.")
+      @server.should_receive(:pass).and_respond("332 Need account for login.")
+    end
+
+    it "does not raise an Error when the response code is 202" do
+      @server.should_receive(:acct).and_respond("202 Command not implemented, superfluous at this site.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should_not raise_error
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:acct).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:acct).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:acct).and_respond("502 Command not implemented.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:acct).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:acct).and_respond("530 Not logged in.")
+      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/ls_spec.rb b/spec/ruby/library/net-ftp/ls_spec.rb
new file mode 100644
index 0000000000..acd7e9e523
--- /dev/null
+++ b/spec/ruby/library/net-ftp/ls_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/list'
+
+describe "Net::FTP#ls" do
+  it_behaves_like :net_ftp_list, :ls
+end
diff --git a/spec/ruby/library/net-ftp/mdtm_spec.rb b/spec/ruby/library/net-ftp/mdtm_spec.rb
new file mode 100644
index 0000000000..a504507c84
--- /dev/null
+++ b/spec/ruby/library/net-ftp/mdtm_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#mdtm" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the MDTM with the passed filename command to the server" do
+    @ftp.mdtm("test.file")
+    @ftp.last_response.should == "213 19980705132316\n"
+  end
+
+  it "returns the last modification time of the passed file" do
+    @ftp.mdtm("test.file").should == "19980705132316"
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:mdtm).and_respond("550 Requested action not taken.")
+    -> { @ftp.mdtm("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:mdtm).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.mdtm("test.file") }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/mkdir_spec.rb b/spec/ruby/library/net-ftp/mkdir_spec.rb
new file mode 100644
index 0000000000..8cc6ae785e
--- /dev/null
+++ b/spec/ruby/library/net-ftp/mkdir_spec.rb
@@ -0,0 +1,61 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#mkdir" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the MKD command with the passed pathname to the server" do
+    @ftp.mkdir("test.folder")
+    @ftp.last_response.should == %{257 "test.folder" created.\n}
+  end
+
+  it "returns the path to the newly created directory" do
+    @ftp.mkdir("test.folder").should == "test.folder"
+    @ftp.mkdir("/absolute/path/to/test.folder").should == "/absolute/path/to/test.folder"
+    @ftp.mkdir("relative/path/to/test.folder").should == "relative/path/to/test.folder"
+    @ftp.mkdir('/usr/dm/foo"bar').should == '/usr/dm/foo"bar'
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:mkd).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:mkd).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:mkd).and_respond("502 Command not implemented.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:mkd).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:mkd).and_respond("530 Not logged in.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:mkd).and_respond("550 Requested action not taken.")
+    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/mtime_spec.rb b/spec/ruby/library/net-ftp/mtime_spec.rb
new file mode 100644
index 0000000000..9dde1278a8
--- /dev/null
+++ b/spec/ruby/library/net-ftp/mtime_spec.rb
@@ -0,0 +1,50 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#mtime" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the MDTM with the passed filename command to the server" do
+    @ftp.mtime("test.file")
+    @ftp.last_response.should == "213 19980705132316\n"
+  end
+
+  describe "when passed filename" do
+    it "returns the last modification time of the passed file as a Time object in the local time" do
+      @ftp.mtime("test.file").should == Time.gm("1998", "07", "05", "13", "23", "16")
+    end
+  end
+
+  describe "when passed filename, local_time" do
+    it "returns the last modification time as a Time object in UTC when local_time is true" do
+      @ftp.mtime("test.file", true).should == Time.local("1998", "07", "05", "13", "23", "16")
+    end
+
+    it "returns the last modification time as a Time object in the local time when local_time is false" do
+      @ftp.mtime("test.file", false).should == Time.gm("1998", "07", "05", "13", "23", "16")
+    end
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:mdtm).and_respond("550 Requested action not taken.")
+    -> { @ftp.mtime("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:mdtm).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.mtime("test.file") }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/nlst_spec.rb b/spec/ruby/library/net-ftp/nlst_spec.rb
new file mode 100644
index 0000000000..2f22543af6
--- /dev/null
+++ b/spec/ruby/library/net-ftp/nlst_spec.rb
@@ -0,0 +1,92 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#nlst" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.passive = false
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  describe "when passed no arguments" do
+    it "returns an Array containing a list of files in the current dir" do
+      @ftp.nlst.should == ["last_response_code.rb", "list.rb", "pwd.rb"]
+      @ftp.last_response.should == "226 transfer complete (NLST)\n"
+    end
+  end
+
+  describe "when passed dir" do
+    it "returns an Array containing a list of files in the passed dir" do
+      @ftp.nlst("test.folder").should == ["last_response_code.rb", "list.rb", "pwd.rb"]
+      @ftp.last_response.should == "226 transfer complete (NLST test.folder)\n"
+    end
+  end
+
+  describe "when the NLST command fails" do
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:nlst).and_respond("450 Requested file action not taken..")
+      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:nlst).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:nlst).and_respond("501 Syntax error, command unrecognized.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:nlst).and_respond("502 Command not implemented.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:nlst).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:nlst).and_respond("530 Not logged in.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when opening the data port fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
+      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
+      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
+      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:eprt).and_respond("530 Not logged in.")
+      @server.should_receive(:port).and_respond("530 Not logged in.")
+      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/noop_spec.rb b/spec/ruby/library/net-ftp/noop_spec.rb
new file mode 100644
index 0000000000..4743a39ef6
--- /dev/null
+++ b/spec/ruby/library/net-ftp/noop_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#noop" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the NOOP command to the server" do
+    @ftp.noop
+    @ftp.last_response.should == "200 Command okay. (NOOP)\n"
+  end
+
+  it "returns nil" do
+    @ftp.noop.should be_nil
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:noop).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.noop }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:noop).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.noop }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/open_spec.rb b/spec/ruby/library/net-ftp/open_spec.rb
new file mode 100644
index 0000000000..e59496dc3c
--- /dev/null
+++ b/spec/ruby/library/net-ftp/open_spec.rb
@@ -0,0 +1,55 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP.open" do
+  before :each do
+    @ftp = mock("Net::FTP instance")
+    Net::FTP.stub!(:new).and_return(@ftp)
+  end
+
+  describe "when passed no block" do
+    it "returns a new Net::FTP instance" do
+      Net::FTP.open("localhost").should equal(@ftp)
+    end
+
+    it "passes the passed arguments down to Net::FTP.new" do
+      Net::FTP.should_receive(:new).with("localhost", "user", "password", "account")
+      Net::FTP.open("localhost", "user", "password", "account")
+    end
+  end
+
+  describe "when passed a block" do
+    before :each do
+      @ftp.stub!(:close)
+    end
+
+    it "yields a new Net::FTP instance to the passed block" do
+      yielded = false
+      Net::FTP.open("localhost") do |ftp|
+        yielded = true
+        ftp.should equal(@ftp)
+      end
+      yielded.should be_true
+    end
+
+    it "closes the Net::FTP instance after yielding" do
+      Net::FTP.open("localhost") do |ftp|
+        ftp.should_receive(:close)
+      end
+    end
+
+    it "closes the Net::FTP instance even if an exception is raised while yielding" do
+      begin
+        Net::FTP.open("localhost") do |ftp|
+          ftp.should_receive(:close)
+          raise ArgumentError, "some exception"
+        end
+      rescue ArgumentError
+      end
+    end
+
+    it "returns the block's return value" do
+      Net::FTP.open("localhost") { :test }.should == :test
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/passive_spec.rb b/spec/ruby/library/net-ftp/passive_spec.rb
new file mode 100644
index 0000000000..97659f1b68
--- /dev/null
+++ b/spec/ruby/library/net-ftp/passive_spec.rb
@@ -0,0 +1,28 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#passive" do
+  it "returns true when self is in passive mode" do
+    ftp = Net::FTP.new
+    ftp.passive.should be_false
+
+    ftp.passive = true
+    ftp.passive.should be_true
+  end
+
+  it "is the value of Net::FTP.default_value by default" do
+    ruby_exe(fixture(__FILE__, "passive.rb")).should == "true"
+  end
+end
+
+describe "Net::FTP#passive=" do
+  it "sets self to passive mode when passed true" do
+    ftp = Net::FTP.new
+
+    ftp.passive = true
+    ftp.passive.should be_true
+
+    ftp.passive = false
+    ftp.passive.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-ftp/put_spec.rb b/spec/ruby/library/net-ftp/put_spec.rb
new file mode 100644
index 0000000000..6d40d3d5b9
--- /dev/null
+++ b/spec/ruby/library/net-ftp/put_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/puttextfile'
+require_relative 'shared/putbinaryfile'
+
+describe "Net::FTP#put (binary mode)" do
+  before :each do
+    @binary_mode = true
+  end
+
+  it_behaves_like :net_ftp_putbinaryfile, :put
+end
+
+describe "Net::FTP#put (text mode)" do
+  before :each do
+    @binary_mode = false
+  end
+
+  it_behaves_like :net_ftp_puttextfile, :put
+end
diff --git a/spec/ruby/library/net-ftp/putbinaryfile_spec.rb b/spec/ruby/library/net-ftp/putbinaryfile_spec.rb
new file mode 100644
index 0000000000..d0398229e5
--- /dev/null
+++ b/spec/ruby/library/net-ftp/putbinaryfile_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/putbinaryfile'
+
+describe "Net::FTP#putbinaryfile" do
+  it_behaves_like :net_ftp_putbinaryfile, :putbinaryfile
+end
diff --git a/spec/ruby/library/net-ftp/puttextfile_spec.rb b/spec/ruby/library/net-ftp/puttextfile_spec.rb
new file mode 100644
index 0000000000..b8bcac33df
--- /dev/null
+++ b/spec/ruby/library/net-ftp/puttextfile_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+require_relative 'shared/puttextfile'
+
+describe "Net::FTP#puttextfile" do
+  it_behaves_like :net_ftp_puttextfile, :puttextfile
+end
diff --git a/spec/ruby/library/net-ftp/pwd_spec.rb b/spec/ruby/library/net-ftp/pwd_spec.rb
new file mode 100644
index 0000000000..992e2c4ed2
--- /dev/null
+++ b/spec/ruby/library/net-ftp/pwd_spec.rb
@@ -0,0 +1,53 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#pwd" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the PWD command to the server" do
+    @ftp.pwd
+    @ftp.last_response.should == "257 \"/some/dir/\" - current directory\n"
+  end
+
+  it "returns the current directory" do
+    @ftp.pwd.should == "/some/dir/"
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:pwd).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:pwd).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:pwd).and_respond("502 Command not implemented.")
+    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:pwd).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.pwd }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:pwd).and_respond("550 Requested action not taken.")
+    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/quit_spec.rb b/spec/ruby/library/net-ftp/quit_spec.rb
new file mode 100644
index 0000000000..c5352ceada
--- /dev/null
+++ b/spec/ruby/library/net-ftp/quit_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#quit" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the QUIT command to the server" do
+    @ftp.quit
+    @ftp.last_response.should == "221 OK, bye\n"
+  end
+
+  it "does not close the socket automatically" do
+    @ftp.quit
+    @ftp.closed?.should be_false
+  end
+
+  it "returns nil" do
+    @ftp.quit.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-ftp/rename_spec.rb b/spec/ruby/library/net-ftp/rename_spec.rb
new file mode 100644
index 0000000000..48f81b7deb
--- /dev/null
+++ b/spec/ruby/library/net-ftp/rename_spec.rb
@@ -0,0 +1,94 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#rename" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  describe "when passed from_name, to_name" do
+    it "sends the RNFR command with the passed from_name and the RNTO command with the passed to_name to the server" do
+      @ftp.rename("from.file", "to.file")
+      @ftp.last_response.should == "250 Requested file action okay, completed. (Renamed from.file to to.file)\n"
+    end
+
+    it "returns something" do
+      @ftp.rename("from.file", "to.file").should be_nil
+    end
+  end
+
+  describe "when the RNFR command fails" do
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:rnfr).and_respond("450 Requested file action not taken.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 550" do
+      @server.should_receive(:rnfr).and_respond("550 Requested action not taken.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:rnfr).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:rnfr).and_respond("502 Command not implemented.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:rnfr).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:rnfr).and_respond("530 Not logged in.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when the RNTO command fails" do
+    it "raises a Net::FTPPermError when the response code is 532" do
+      @server.should_receive(:rnfr).and_respond("532 Need account for storing files.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 553" do
+      @server.should_receive(:rnto).and_respond("553 Requested action not taken.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:rnto).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 502" do
+      @server.should_receive(:rnto).and_respond("502 Command not implemented.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:rnto).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:rnto).and_respond("530 Not logged in.")
+      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/resume_spec.rb b/spec/ruby/library/net-ftp/resume_spec.rb
new file mode 100644
index 0000000000..6592fc5bb0
--- /dev/null
+++ b/spec/ruby/library/net-ftp/resume_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#resume" do
+  it "returns true when self is set to resume uploads/downloads" do
+    ftp = Net::FTP.new
+    ftp.resume.should be_false
+
+    ftp.resume = true
+    ftp.resume.should be_true
+  end
+end
+
+describe "Net::FTP#resume=" do
+  it "sets self to resume uploads/downloads when set to true" do
+    ftp = Net::FTP.new
+    ftp.resume = true
+    ftp.resume.should be_true
+
+    ftp.resume = false
+    ftp.resume.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-ftp/retrbinary_spec.rb b/spec/ruby/library/net-ftp/retrbinary_spec.rb
new file mode 100644
index 0000000000..de024208aa
--- /dev/null
+++ b/spec/ruby/library/net-ftp/retrbinary_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#retrbinary" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the passed command to the server" do
+    @ftp.retrbinary("RETR test", 4096) {}
+    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
+  end
+
+  it "yields the received content as binary blocks of the passed size" do
+    res = []
+    @ftp.retrbinary("RETR test", 10) { |bin| res << bin }
+    res.should == [ "This is th", "e content\n", "of the fil", "e named 't", "est'.\n" ]
+  end
+end
diff --git a/spec/ruby/library/net-ftp/retrlines_spec.rb b/spec/ruby/library/net-ftp/retrlines_spec.rb
new file mode 100644
index 0000000000..866ecb5f40
--- /dev/null
+++ b/spec/ruby/library/net-ftp/retrlines_spec.rb
@@ -0,0 +1,34 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#retrlines" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the passed command over the socket" do
+    @ftp.retrlines("LIST test.dir") {}
+    @ftp.last_response.should == "226 transfer complete (LIST test.dir)\n"
+  end
+
+  it "yields each received line to the passed block" do
+    res = []
+    @ftp.retrlines("LIST test.dir") { |x| res << x }
+    res.should == [
+      "-rw-r--r--  1 spec  staff  507 17 Jul 18:41 last_response_code.rb",
+      "-rw-r--r--  1 spec  staff   50 17 Jul 18:41 list.rb",
+      "-rw-r--r--  1 spec  staff   48 17 Jul 18:41 pwd.rb"
+    ]
+  end
+end
diff --git a/spec/ruby/library/net-ftp/return_code_spec.rb b/spec/ruby/library/net-ftp/return_code_spec.rb
new file mode 100644
index 0000000000..35a6232f7e
--- /dev/null
+++ b/spec/ruby/library/net-ftp/return_code_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#return_code" do
+  before :each do
+    @ftp = Net::FTP.new
+  end
+
+  it "outputs a warning and returns a newline" do
+    -> do
+      @ftp.return_code.should == "\n"
+    end.should complain(/warning: Net::FTP#return_code is obsolete and do nothing/)
+  end
+end
+
+describe "Net::FTP#return_code=" do
+  before :each do
+    @ftp = Net::FTP.new
+  end
+
+  it "outputs a warning" do
+    -> { @ftp.return_code = 123 }.should complain(/warning: Net::FTP#return_code= is obsolete and do nothing/)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/rmdir_spec.rb b/spec/ruby/library/net-ftp/rmdir_spec.rb
new file mode 100644
index 0000000000..400874d60d
--- /dev/null
+++ b/spec/ruby/library/net-ftp/rmdir_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#rmdir" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the RMD command with the passed pathname to the server" do
+    @ftp.rmdir("test.folder")
+    @ftp.last_response.should == "250 Requested file action okay, completed. (RMD test.folder)\n"
+  end
+
+  it "returns nil" do
+    @ftp.rmdir("test.folder").should be_nil
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:rmd).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:rmd).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:rmd).and_respond("502 Command not implemented.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:rmd).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:rmd).and_respond("530 Not logged in.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:rmd).and_respond("550 Requested action not taken.")
+    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/sendcmd_spec.rb b/spec/ruby/library/net-ftp/sendcmd_spec.rb
new file mode 100644
index 0000000000..c50b373869
--- /dev/null
+++ b/spec/ruby/library/net-ftp/sendcmd_spec.rb
@@ -0,0 +1,54 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#sendcmd" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the passed command to the server" do
+    @ftp.sendcmd("HELP")
+    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
+  end
+
+  it "returns the server's response" do
+    @ftp.sendcmd("HELP").should == "211 System status, or system help reply. (HELP)\n"
+  end
+
+  it "raises no error when the response code is 1xx, 2xx or 3xx" do
+    @server.should_receive(:help).and_respond("120 Service ready in nnn minutes.")
+    -> { @ftp.sendcmd("HELP") }.should_not raise_error
+
+    @server.should_receive(:help).and_respond("200 Command okay.")
+    -> { @ftp.sendcmd("HELP") }.should_not raise_error
+
+    @server.should_receive(:help).and_respond("350 Requested file action pending further information.")
+    -> { @ftp.sendcmd("HELP") }.should_not raise_error
+  end
+
+  it "raises a Net::FTPTempError when the response code is 4xx" do
+    @server.should_receive(:help).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 5xx" do
+    @server.should_receive(:help).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPProtoError when the response code is not between 1xx-5xx" do
+    @server.should_receive(:help).and_respond("999 Invalid response.")
+    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPProtoError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/set_socket_spec.rb b/spec/ruby/library/net-ftp/set_socket_spec.rb
new file mode 100644
index 0000000000..8182dd8b33
--- /dev/null
+++ b/spec/ruby/library/net-ftp/set_socket_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+
+describe "Net::FTP#set_socket" do
+  # TODO: I won't spec this method, as it is not used
+  #       anywhere and it should be private anyway.
+  it "needs to be reviewed for spec completeness"
+end
diff --git a/spec/ruby/library/net-ftp/shared/getbinaryfile.rb b/spec/ruby/library/net-ftp/shared/getbinaryfile.rb
new file mode 100644
index 0000000000..ceec8e7cd5
--- /dev/null
+++ b/spec/ruby/library/net-ftp/shared/getbinaryfile.rb
@@ -0,0 +1,150 @@
+describe :net_ftp_getbinaryfile, shared: true do
+  before :each do
+    @fixture_file = __dir__ + "/../fixtures/getbinaryfile"
+    @tmp_file = tmp("getbinaryfile")
+
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+    @ftp.binary = @binary_mode
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @tmp_file
+  end
+
+  it "sends the RETR command to the server" do
+    @ftp.send(@method, "test", @tmp_file)
+    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
+  end
+
+  it "returns nil" do
+    @ftp.send(@method, "test", @tmp_file).should be_nil
+  end
+
+  it "saves the contents of the passed remote file to the passed local file" do
+    @ftp.send(@method, "test", @tmp_file)
+    File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
+  end
+
+  describe "when passed a block" do
+    it "yields the received content as binary blocks of the passed size" do
+      res = []
+      @ftp.send(@method, "test", @tmp_file, 10) { |bin| res << bin }
+      res.should == [ "This is th", "e content\n", "of the fil", "e named 't", "est'.\n" ]
+    end
+  end
+
+  describe "when resuming an existing file" do
+    before :each do
+      @tmp_file = tmp("getbinaryfile_resume")
+
+      File.open(@tmp_file, "wb") do |f|
+        f << "This is the content\n"
+      end
+
+      @ftp.resume = true
+    end
+
+    it "saves the remaining content of the passed remote file to the passed local file" do
+      @ftp.send(@method, "test", @tmp_file)
+      File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
+    end
+
+    describe "and the REST command fails" do
+      it "raises a Net::FTPProtoError when the response code is 550" do
+        @server.should_receive(:rest).and_respond("Requested action not taken.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 500" do
+        @server.should_receive(:rest).and_respond("500 Syntax error, command unrecognized.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 501" do
+        @server.should_receive(:rest).and_respond("501 Syntax error, command unrecognized.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 502" do
+        @server.should_receive(:rest).and_respond("502 Command not implemented.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPTempError when the response code is 421" do
+        @server.should_receive(:rest).and_respond("421 Service not available, closing control connection.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 530" do
+        @server.should_receive(:rest).and_respond("530 Not logged in.")
+        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+      end
+    end
+  end
+
+  describe "when the RETR command fails" do
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:retr).and_respond("450 Requested file action not taken.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPProtoError when the response code is 550" do
+      @server.should_receive(:retr).and_respond("Requested action not taken.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:retr).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:retr).and_respond("501 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:retr).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:retr).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when opening the data port fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
+      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
+      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
+      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:eprt).and_respond("530 Not logged in.")
+      @server.should_receive(:port).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/shared/gettextfile.rb b/spec/ruby/library/net-ftp/shared/gettextfile.rb
new file mode 100644
index 0000000000..7fe14f7dfb
--- /dev/null
+++ b/spec/ruby/library/net-ftp/shared/gettextfile.rb
@@ -0,0 +1,100 @@
+describe :net_ftp_gettextfile, shared: true do
+  before :each do
+    @tmp_file = tmp("gettextfile")
+
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+    @ftp.binary = @binary_mode
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @tmp_file
+  end
+
+  it "sends the RETR command to the server" do
+    @ftp.send(@method, "test", @tmp_file)
+    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
+  end
+
+  it "returns nil" do
+    @ftp.send(@method, "test", @tmp_file).should be_nil
+  end
+
+  it "saves the contents of the passed remote file to the passed local file" do
+    @ftp.send(@method, "test", @tmp_file)
+    File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
+  end
+
+  describe "when passed a block" do
+    it "yields each line of the retrieved file to the passed block" do
+      res = []
+      @ftp.send(@method, "test", @tmp_file) { |line| res << line }
+      res.should == [ "This is the content", "of the file named 'test'."]
+    end
+  end
+
+  describe "when the RETR command fails" do
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:retr).and_respond("450 Requested file action not taken.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPProtoError when the response code is 550" do
+      @server.should_receive(:retr).and_respond("Requested action not taken.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:retr).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:retr).and_respond("501 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:retr).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:retr).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when opening the data port fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
+      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
+      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
+      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:eprt).and_respond("530 Not logged in.")
+      @server.should_receive(:port).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net/ftp/shared/last_response_code.rb b/spec/ruby/library/net-ftp/shared/last_response_code.rb
index 4fe53677db..4fe53677db 100644
--- a/spec/ruby/library/net/ftp/shared/last_response_code.rb
+++ b/spec/ruby/library/net-ftp/shared/last_response_code.rb
diff --git a/spec/ruby/library/net/ftp/shared/list.rb b/spec/ruby/library/net-ftp/shared/list.rb
index adc3fa59c1..adc3fa59c1 100644
--- a/spec/ruby/library/net/ftp/shared/list.rb
+++ b/spec/ruby/library/net-ftp/shared/list.rb
diff --git a/spec/ruby/library/net-ftp/shared/putbinaryfile.rb b/spec/ruby/library/net-ftp/shared/putbinaryfile.rb
new file mode 100644
index 0000000000..45f53adc2a
--- /dev/null
+++ b/spec/ruby/library/net-ftp/shared/putbinaryfile.rb
@@ -0,0 +1,167 @@
+describe :net_ftp_putbinaryfile, shared: true do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @local_fixture_file  = __dir__ + "/../fixtures/putbinaryfile"
+    @remote_tmp_file = tmp("binaryfile", false)
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+    @ftp.binary = @binary_mode
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @remote_tmp_file
+  end
+
+  it "sends the STOR command to the server" do
+    @ftp.send(@method, @local_fixture_file, "binary")
+    @ftp.last_response.should == "200 OK, Data received. (STOR binary)\n"
+  end
+
+  it "sends the contents of the passed local_file, without modifications" do
+    @ftp.send(@method, @local_fixture_file, "binary")
+
+    remote_lines = File.readlines(@remote_tmp_file)
+    local_lines  = File.readlines(@local_fixture_file)
+
+    remote_lines.should == local_lines
+  end
+
+  it "returns nil" do
+    @ftp.send(@method, @local_fixture_file, "binary").should be_nil
+  end
+
+  describe "when passed a block" do
+    it "yields the transmitted content as binary blocks of the passed size" do
+      res = []
+      @ftp.send(@method, @local_fixture_file, "binary", 10) { |x| res << x }
+      res.should == [
+        "This is an", " example f",
+        "ile\nwhich ", "is going t",
+        "o be trans", "mitted\nusi",
+        "ng #putbin", "aryfile.\n"
+      ]
+    end
+  end
+
+  describe "when resuming an existing file" do
+    before :each do
+      File.open(@remote_tmp_file, "w") do |f|
+        f << "This is an example file\n"
+      end
+
+      @ftp.resume = true
+    end
+
+    it "sends the remaining content of the passed local_file to the passed remote_file" do
+      @ftp.send(@method, @local_fixture_file, "binary")
+      File.read(@remote_tmp_file).should == File.read(@local_fixture_file)
+    end
+
+    describe "and the APPE command fails" do
+      it "raises a Net::FTPProtoError when the response code is 550" do
+        @server.should_receive(:appe).and_respond("Requested action not taken.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPProtoError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 500" do
+        @server.should_receive(:appe).and_respond("500 Syntax error, command unrecognized.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 501" do
+        @server.should_receive(:appe).and_respond("501 Syntax error, command unrecognized.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 502" do
+        @server.should_receive(:appe).and_respond("502 Command not implemented.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+      end
+
+      it "raises a Net::FTPTempError when the response code is 421" do
+        @server.should_receive(:appe).and_respond("421 Service not available, closing control connection.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
+      end
+
+      it "raises a Net::FTPPermError when the response code is 530" do
+        @server.should_receive(:appe).and_respond("530 Not logged in.")
+        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+      end
+    end
+  end
+
+  describe "when the STOR command fails" do
+    it "raises a Net::FTPPermError when the response code is 532" do
+      @server.should_receive(:stor).and_respond("532 Need account for storing files.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:stor).and_respond("450 Requested file action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 452" do
+      @server.should_receive(:stor).and_respond("452 Requested action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 553" do
+      @server.should_receive(:stor).and_respond("553 Requested action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:stor).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:stor).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:stor).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:stor).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when opening the data port fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
+      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
+      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
+      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:eprt).and_respond("530 Not logged in.")
+      @server.should_receive(:port).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/shared/puttextfile.rb b/spec/ruby/library/net-ftp/shared/puttextfile.rb
new file mode 100644
index 0000000000..e2c0453352
--- /dev/null
+++ b/spec/ruby/library/net-ftp/shared/puttextfile.rb
@@ -0,0 +1,128 @@
+describe :net_ftp_puttextfile, shared: true do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @local_fixture_file  = __dir__ + "/../fixtures/puttextfile"
+    @remote_tmp_file = tmp("textfile", false)
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+    @ftp.binary = @binary_mode
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @remote_tmp_file
+  end
+
+  it "sends the STOR command to the server" do
+    @ftp.send(@method, @local_fixture_file, "text")
+    @ftp.last_response.should == "200 OK, Data received. (STOR text)\n"
+  end
+
+  it "sends the contents of the passed local_file, using \\r\\n as the newline separator" do
+    @ftp.send(@method, @local_fixture_file, "text")
+
+    remote_lines = File.binread(@remote_tmp_file)
+    local_lines  = File.binread(@local_fixture_file)
+
+    remote_lines.should_not == local_lines
+    remote_lines.should == local_lines.gsub("\n", "\r\n")
+  end
+
+  guard -> { Net::FTP::VERSION < '0.3.6' } do
+    it "returns nil" do
+      @ftp.send(@method, @local_fixture_file, "text").should be_nil
+    end
+  end
+
+  guard -> { Net::FTP::VERSION >= '0.3.6' } do
+    it "returns the response" do
+      @ftp.send(@method, @local_fixture_file, "text").should == @ftp.last_response
+    end
+  end
+
+  describe "when passed a block" do
+    it "yields each transmitted line" do
+      res = []
+      @ftp.send(@method, @local_fixture_file, "text") { |x| res << x }
+      res.should == [
+        "This is an example file\r\n",
+        "which is going to be transmitted\r\n",
+        "using #puttextfile.\r\n"
+      ]
+    end
+  end
+
+  describe "when the STOR command fails" do
+    it "raises a Net::FTPPermError when the response code is 532" do
+      @server.should_receive(:stor).and_respond("532 Need account for storing files.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 450" do
+      @server.should_receive(:stor).and_respond("450 Requested file action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 452" do
+      @server.should_receive(:stor).and_respond("452 Requested action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 553" do
+      @server.should_receive(:stor).and_respond("553 Requested action not taken.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:stor).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:stor).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:stor).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:stor).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+  end
+
+  describe "when opening the data port fails" do
+    it "raises a Net::FTPPermError when the response code is 500" do
+      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
+      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 501" do
+      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
+      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+
+    it "raises a Net::FTPTempError when the response code is 421" do
+      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
+      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
+    end
+
+    it "raises a Net::FTPPermError when the response code is 530" do
+      @server.should_receive(:eprt).and_respond("530 Not logged in.")
+      @server.should_receive(:port).and_respond("530 Not logged in.")
+      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net/ftp/shared/pwd.rb b/spec/ruby/library/net-ftp/shared/pwd.rb
index 951d020f2d..951d020f2d 100644
--- a/spec/ruby/library/net/ftp/shared/pwd.rb
+++ b/spec/ruby/library/net-ftp/shared/pwd.rb
diff --git a/spec/ruby/library/net-ftp/site_spec.rb b/spec/ruby/library/net-ftp/site_spec.rb
new file mode 100644
index 0000000000..c3e589a920
--- /dev/null
+++ b/spec/ruby/library/net-ftp/site_spec.rb
@@ -0,0 +1,53 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#site" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the SITE command with the passed argument to the server" do
+    @ftp.site("param")
+    @ftp.last_response.should == "200 Command okay. (SITE param)\n"
+  end
+
+  it "returns nil" do
+    @ftp.site("param").should be_nil
+  end
+
+  it "does not raise an error when the response code is 202" do
+    @server.should_receive(:site).and_respond("202 Command not implemented, superfluous at this site.")
+    -> { @ftp.site("param") }.should_not raise_error
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:site).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:site).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:site).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.site("param") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:site).and_respond("530 Requested action not taken.")
+    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/size_spec.rb b/spec/ruby/library/net-ftp/size_spec.rb
new file mode 100644
index 0000000000..0cf2e24477
--- /dev/null
+++ b/spec/ruby/library/net-ftp/size_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#size" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the SIZE command to the server" do
+    @ftp.size("test.file")
+    @ftp.last_response.should == "213 1024\n"
+  end
+
+  it "returns the size of the passed file as Integer" do
+    @ftp.size("test.file").should eql(1024)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:size).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:size).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:size).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.size("test.file") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 550" do
+    @server.should_receive(:size).and_respond("550 Requested action not taken.")
+    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net/ftp/spec_helper.rb b/spec/ruby/library/net-ftp/spec_helper.rb
index c87d16218b..c87d16218b 100644
--- a/spec/ruby/library/net/ftp/spec_helper.rb
+++ b/spec/ruby/library/net-ftp/spec_helper.rb
diff --git a/spec/ruby/library/net-ftp/status_spec.rb b/spec/ruby/library/net-ftp/status_spec.rb
new file mode 100644
index 0000000000..9d9f86c381
--- /dev/null
+++ b/spec/ruby/library/net-ftp/status_spec.rb
@@ -0,0 +1,67 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#status" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the STAT command to the server" do
+    @ftp.status
+    @ftp.last_response.should == "211 System status, or system help reply. (STAT)\n"
+  end
+
+  it "sends the STAT command with an optional parameter to the server" do
+    @ftp.status("/pub").should == "211 System status, or system help reply. (STAT /pub)\n"
+  end
+
+  it "returns the received information" do
+    @ftp.status.should == "211 System status, or system help reply. (STAT)\n"
+  end
+
+  it "does not raise an error when the response code is 212" do
+    @server.should_receive(:stat).and_respond("212 Directory status.")
+    -> { @ftp.status }.should_not raise_error
+  end
+
+  it "does not raise an error when the response code is 213" do
+    @server.should_receive(:stat).and_respond("213 File status.")
+    -> { @ftp.status }.should_not raise_error
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:stat).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.status }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:stat).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.status }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:stat).and_respond("502 Command not implemented.")
+    -> { @ftp.status }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:stat).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.status }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 530" do
+    @server.should_receive(:stat).and_respond("530 Requested action not taken.")
+    -> { @ftp.status }.should raise_error(Net::FTPPermError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/storbinary_spec.rb b/spec/ruby/library/net-ftp/storbinary_spec.rb
new file mode 100644
index 0000000000..aa4c51f2e8
--- /dev/null
+++ b/spec/ruby/library/net-ftp/storbinary_spec.rb
@@ -0,0 +1,49 @@
+require_relative '../../spec_helper'
+
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#storbinary" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @local_fixture_file  = __dir__ + "/fixtures/putbinaryfile"
+    @tmp_file = tmp("binaryfile", false)
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @tmp_file
+  end
+
+  it "sends the passed command and the passed File object's content to the server" do
+    File.open(@local_fixture_file) do |f|
+      f.binmode
+
+      @ftp.storbinary("STOR binary", f, 4096) {}
+      @ftp.last_response.should == "200 OK, Data received. (STOR binary)\n"
+    end
+  end
+
+  it "yields the transmitted content as binary blocks of the passed size" do
+    File.open(@local_fixture_file) do |f|
+      f.binmode
+
+      res = []
+      @ftp.storbinary("STOR binary", f, 10) { |x| res << x }
+      res.should == [
+        "This is an", " example f",
+        "ile\nwhich ", "is going t",
+        "o be trans", "mitted\nusi",
+        "ng #putbin", "aryfile.\n"
+      ]
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/storlines_spec.rb b/spec/ruby/library/net-ftp/storlines_spec.rb
new file mode 100644
index 0000000000..dc6830da7b
--- /dev/null
+++ b/spec/ruby/library/net-ftp/storlines_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../spec_helper'
+
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#storlines" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @local_fixture_file  = __dir__ + "/fixtures/puttextfile"
+    @tmp_file = tmp("textfile", false)
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+
+    rm_r @tmp_file
+  end
+
+  it "sends the passed command and the passed File object's content to the server" do
+    File.open(@local_fixture_file) do |f|
+      @ftp.storlines("STOR text", f) {}
+      @ftp.last_response.should == "200 OK, Data received. (STOR text)\n"
+    end
+  end
+
+  it "yields each line of the transmitted content" do
+    File.open(@local_fixture_file) do |f|
+      res = []
+      @ftp.storlines("STOR text", f) { |x| res << x }
+      res.should == [
+        "This is an example file\r\n",
+        "which is going to be transmitted\r\n",
+        "using #puttextfile.\r\n"
+      ]
+    end
+  end
+end
diff --git a/spec/ruby/library/net-ftp/system_spec.rb b/spec/ruby/library/net-ftp/system_spec.rb
new file mode 100644
index 0000000000..2b7f0d2560
--- /dev/null
+++ b/spec/ruby/library/net-ftp/system_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#system" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the SYST command to the server" do
+    @ftp.system
+    @ftp.last_response.should =~ /\A215 FTP Dummy Server \(SYST\)\Z/
+  end
+
+  it "returns the received information" do
+    @ftp.system.should =~ /\AFTP Dummy Server \(SYST\)\Z/
+  end
+
+  it "raises a Net::FTPPermError when the response code is 500" do
+    @server.should_receive(:syst).and_respond("500 Syntax error, command unrecognized.")
+    -> { @ftp.system }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 501" do
+    @server.should_receive(:syst).and_respond("501 Syntax error in parameters or arguments.")
+    -> { @ftp.system }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 502" do
+    @server.should_receive(:syst).and_respond("502 Command not implemented.")
+    -> { @ftp.system }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 421" do
+    @server.should_receive(:syst).and_respond("421 Service not available, closing control connection.")
+    -> { @ftp.system }.should raise_error(Net::FTPTempError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/voidcmd_spec.rb b/spec/ruby/library/net-ftp/voidcmd_spec.rb
new file mode 100644
index 0000000000..f2536fe697
--- /dev/null
+++ b/spec/ruby/library/net-ftp/voidcmd_spec.rb
@@ -0,0 +1,54 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#voidcmd" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "sends the passed command to the server" do
+    @server.should_receive(:help).and_respond("2xx Does not raise.")
+    -> { @ftp.voidcmd("HELP") }.should_not raise_error
+  end
+
+  it "returns nil" do
+    @server.should_receive(:help).and_respond("2xx Does not raise.")
+    @ftp.voidcmd("HELP").should be_nil
+  end
+
+  it "raises a Net::FTPReplyError when the response code is 1xx" do
+    @server.should_receive(:help).and_respond("1xx Does raise a Net::FTPReplyError.")
+    -> { @ftp.voidcmd("HELP")  }.should raise_error(Net::FTPReplyError)
+  end
+
+  it "raises a Net::FTPReplyError when the response code is 3xx" do
+    @server.should_receive(:help).and_respond("3xx Does raise a Net::FTPReplyError.")
+    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPReplyError)
+  end
+
+  it "raises a Net::FTPTempError when the response code is 4xx" do
+    @server.should_receive(:help).and_respond("4xx Does raise a Net::FTPTempError.")
+    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPTempError)
+  end
+
+  it "raises a Net::FTPPermError when the response code is 5xx" do
+    @server.should_receive(:help).and_respond("5xx Does raise a Net::FTPPermError.")
+    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPPermError)
+  end
+
+  it "raises a Net::FTPProtoError when the response code is not valid" do
+    @server.should_receive(:help).and_respond("999 Does raise a Net::FTPProtoError.")
+    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPProtoError)
+  end
+end
diff --git a/spec/ruby/library/net-ftp/welcome_spec.rb b/spec/ruby/library/net-ftp/welcome_spec.rb
new file mode 100644
index 0000000000..4279127ce3
--- /dev/null
+++ b/spec/ruby/library/net-ftp/welcome_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../spec_helper'
+require_relative 'spec_helper'
+require_relative 'fixtures/server'
+
+describe "Net::FTP#welcome" do
+  before :each do
+    @server = NetFTPSpecs::DummyFTP.new
+    @server.serve_once
+
+    @ftp = Net::FTP.new
+    @ftp.connect(@server.hostname, @server.server_port)
+  end
+
+  after :each do
+    @ftp.quit rescue nil
+    @ftp.close
+    @server.stop
+  end
+
+  it "returns the server's welcome message" do
+    @ftp.welcome.should be_nil
+    @ftp.login
+    @ftp.welcome.should == "230 User logged in, proceed. (USER anonymous)\n"
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPBadResponse_spec.rb b/spec/ruby/library/net-http/HTTPBadResponse_spec.rb
new file mode 100644
index 0000000000..8f2e8ccfaf
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPBadResponse_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPBadResponse" do
+  it "is a subclass of StandardError" do
+    Net::HTTPBadResponse.should < StandardError
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPClientExcepton_spec.rb b/spec/ruby/library/net-http/HTTPClientExcepton_spec.rb
new file mode 100644
index 0000000000..2992e6596f
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPClientExcepton_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPClientException" do
+  it "is a subclass of Net::ProtoServerError" do
+    Net::HTTPClientException.should < Net::ProtoServerError
+  end
+
+  it "includes the Net::HTTPExceptions module" do
+    Net::HTTPClientException.should < Net::HTTPExceptions
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPError_spec.rb b/spec/ruby/library/net-http/HTTPError_spec.rb
new file mode 100644
index 0000000000..7f79eef8cf
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPError_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPError" do
+  it "is a subclass of Net::ProtocolError" do
+    Net::HTTPError.should < Net::ProtocolError
+  end
+
+  it "includes the Net::HTTPExceptions module" do
+    Net::HTTPError.should < Net::HTTPExceptions
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPFatalError_spec.rb b/spec/ruby/library/net-http/HTTPFatalError_spec.rb
new file mode 100644
index 0000000000..0113b9da2d
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPFatalError_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPFatalError" do
+  it "is a subclass of Net::ProtoFatalError" do
+    Net::HTTPFatalError.should < Net::ProtoFatalError
+  end
+
+  it "includes the Net::HTTPExceptions module" do
+    Net::HTTPFatalError.should < Net::HTTPExceptions
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPHeaderSyntaxError_spec.rb b/spec/ruby/library/net-http/HTTPHeaderSyntaxError_spec.rb
new file mode 100644
index 0000000000..b3b73ff46f
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPHeaderSyntaxError_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPHeaderSyntaxError" do
+  it "is a subclass of StandardError" do
+    Net::HTTPHeaderSyntaxError.should < StandardError
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPRetriableError_spec.rb b/spec/ruby/library/net-http/HTTPRetriableError_spec.rb
new file mode 100644
index 0000000000..677731fb68
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPRetriableError_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPRetriableError" do
+  it "is a subclass of Net::ProtoRetriableError" do
+    Net::HTTPRetriableError.should < Net::ProtoRetriableError
+  end
+
+  it "includes the Net::HTTPExceptions module" do
+    Net::HTTPRetriableError.should < Net::HTTPExceptions
+  end
+end
diff --git a/spec/ruby/library/net-http/HTTPServerException_spec.rb b/spec/ruby/library/net-http/HTTPServerException_spec.rb
new file mode 100644
index 0000000000..020d3cce85
--- /dev/null
+++ b/spec/ruby/library/net-http/HTTPServerException_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPServerException" do
+  it "is a subclass of Net::ProtoServerError and is warned as deprecated" do
+    -> { eval("Net::HTTPServerException").should < Net::ProtoServerError }.should complain(/warning: constant Net::HTTPServerException is deprecated/)
+  end
+
+  it "includes the Net::HTTPExceptions module and is warned as deprecated" do
+    -> { eval("Net::HTTPServerException").should < Net::HTTPExceptions }.should complain(/warning: constant Net::HTTPServerException is deprecated/)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/Proxy_spec.rb b/spec/ruby/library/net-http/http/Proxy_spec.rb
new file mode 100644
index 0000000000..a1a04fa00b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/Proxy_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.Proxy" do
+  it "returns a new subclass of Net::HTTP" do
+    Net::HTTP.Proxy("localhost").should < Net::HTTP
+  end
+
+  it "returns Net::HTTP when the passed address is nil" do
+    Net::HTTP.Proxy(nil).should == Net::HTTP
+  end
+
+  it "sets the returned subclasses' proxy options based on the passed arguments" do
+    http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+    http_with_proxy.proxy_address.should == "localhost"
+    http_with_proxy.proxy_port.should eql(1234)
+    http_with_proxy.proxy_user.should == "rspec"
+    http_with_proxy.proxy_pass.should == "rocks"
+  end
+end
+
+describe "Net::HTTP#proxy?" do
+  describe "when self is no proxy class instance" do
+    it "returns false" do
+      Net::HTTP.new("localhost", 3333).proxy?.should be_false
+    end
+  end
+
+  describe "when self is a proxy class instance" do
+    it "returns false" do
+      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+      http_with_proxy.new("localhost", 3333).proxy?.should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/active_spec.rb b/spec/ruby/library/net-http/http/active_spec.rb
new file mode 100644
index 0000000000..c260274594
--- /dev/null
+++ b/spec/ruby/library/net-http/http/active_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/started'
+
+describe "Net::HTTP#active?" do
+  it_behaves_like :net_http_started_p, :active?
+end
diff --git a/spec/ruby/library/net-http/http/address_spec.rb b/spec/ruby/library/net-http/http/address_spec.rb
new file mode 100644
index 0000000000..7c5b82a8f9
--- /dev/null
+++ b/spec/ruby/library/net-http/http/address_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#address" do
+  it "returns the current host name" do
+    net = Net::HTTP.new("localhost")
+    net.address.should == "localhost"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/close_on_empty_response_spec.rb b/spec/ruby/library/net-http/http/close_on_empty_response_spec.rb
new file mode 100644
index 0000000000..9cc756befb
--- /dev/null
+++ b/spec/ruby/library/net-http/http/close_on_empty_response_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#close_on_empty_response" do
+  it "needs to be reviewed for spec completeness"
+end
+
+describe "Net::HTTP#close_on_empty_response=" do
+  it "needs to be reviewed for spec completeness"
+end
diff --git a/spec/ruby/library/net-http/http/copy_spec.rb b/spec/ruby/library/net-http/http/copy_spec.rb
new file mode 100644
index 0000000000..fba96c0f11
--- /dev/null
+++ b/spec/ruby/library/net-http/http/copy_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#copy" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a COPY request to the passed path and returns the response" do
+    response = @http.copy("/request")
+    response.should be_kind_of(Net::HTTPResponse)
+    response.body.should == "Request type: COPY"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/default_port_spec.rb b/spec/ruby/library/net-http/http/default_port_spec.rb
new file mode 100644
index 0000000000..95b7316a0c
--- /dev/null
+++ b/spec/ruby/library/net-http/http/default_port_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.default_port" do
+  it "returns 80" do
+    Net::HTTP.http_default_port.should eql(80)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/delete_spec.rb b/spec/ruby/library/net-http/http/delete_spec.rb
new file mode 100644
index 0000000000..d73aa5b375
--- /dev/null
+++ b/spec/ruby/library/net-http/http/delete_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#delete" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a DELETE request to the passed path and returns the response" do
+    response = @http.delete("/request")
+    response.should be_kind_of(Net::HTTPResponse)
+    response.body.should == "Request type: DELETE"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/finish_spec.rb b/spec/ruby/library/net-http/http/finish_spec.rb
new file mode 100644
index 0000000000..d4aa00dffe
--- /dev/null
+++ b/spec/ruby/library/net-http/http/finish_spec.rb
@@ -0,0 +1,29 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#finish" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when self has been started" do
+    it "closes the tcp connection" do
+      @http.start
+      @http.finish
+      @http.started?.should be_false
+    end
+  end
+
+  describe "when self has not been started yet" do
+    it "raises an IOError" do
+      -> { @http.finish }.should raise_error(IOError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/fixtures/http_server.rb b/spec/ruby/library/net-http/http/fixtures/http_server.rb
new file mode 100644
index 0000000000..c1cedbfa76
--- /dev/null
+++ b/spec/ruby/library/net-http/http/fixtures/http_server.rb
@@ -0,0 +1,123 @@
+require 'socket'
+
+module NetHTTPSpecs
+  class NullWriter
+    def <<(s) end
+    def puts(*args) end
+    def print(*args) end
+    def printf(*args) end
+  end
+
+  class SmallHTTPServer
+    def initialize(bind_address)
+      @server = TCPServer.new(bind_address, 0)
+      @thread = Thread.new {
+        Thread.current.abort_on_exception = true
+        listen
+      }
+    end
+
+    def ip
+      @server.addr[3]
+    end
+
+    def port
+      @server.addr[1]
+    end
+
+    def listen
+      until @server.closed?
+        client = @server.accept
+        handle_client(client)
+      end
+    end
+
+    def handle_client(client)
+      begin
+        until client.closed?
+          request = client.gets("\r\n\r\n")
+          break unless request
+          if request == "CLOSE"
+            @server.close
+            break
+          end
+          handle_request(client, request)
+        end
+      ensure
+        client.close
+      end
+    end
+
+    def parse_request(request)
+      request, *headers = request.chomp.lines.map { |line| line.chomp }
+      request_method, request_uri, _http_version = request.split
+      headers = headers.map { |line| line.split(': ', 2) }.to_h
+      [request_method, request_uri, headers]
+    end
+
+    def handle_request(client, request)
+      request_method, request_uri, headers = parse_request(request)
+
+      if headers.include? 'Content-Length'
+        request_body_size = Integer(headers['Content-Length'])
+        request_body = client.read(request_body_size)
+      end
+
+      case request_uri
+      when '/'
+        raise request_method unless request_method == 'GET'
+        reply(client, "This is the index page.", request_method)
+      when '/request'
+        reply(client, "Request type: #{request_method}", request_method)
+      when '/request/body'
+        reply(client, request_body, request_method)
+      when '/request/header'
+        reply(client, headers.inspect, request_method)
+      when '/request/basic_auth'
+        reply(client, "username: \npassword: ", request_method)
+      else
+        raise request_uri
+      end
+    end
+
+    def reply(client, body, request_method)
+      client.print "HTTP/1.1 200 OK\r\n"
+      if request_method == 'HEAD'
+        client.close
+      else
+        client.print "Content-Type: text/plain\r\n"
+        client.print "Content-Length: #{body.bytesize}\r\n"
+        client.print "\r\n"
+        client.print body
+      end
+    end
+
+    def close
+      TCPSocket.open(ip, port) do |socket|
+        socket.write "CLOSE"
+      end
+      @thread.join
+    end
+  end
+
+  @server = nil
+
+  class << self
+    def port
+      raise "server not started" unless @server
+      @server.port
+    end
+
+    def start_server
+      bind_address = platform_is(:windows) ? "localhost" : "127.0.0.1"
+      @server = SmallHTTPServer.new(bind_address)
+    end
+
+    def stop_server
+      if @server
+        @server.close
+        @server = nil
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/get2_spec.rb b/spec/ruby/library/net-http/http/get2_spec.rb
new file mode 100644
index 0000000000..57c05ec64b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/get2_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_get'
+
+describe "Net::HTTP#get2" do
+  it_behaves_like :net_http_request_get, :get2
+end
diff --git a/spec/ruby/library/net-http/http/get_print_spec.rb b/spec/ruby/library/net-http/http/get_print_spec.rb
new file mode 100644
index 0000000000..3c24ce44ea
--- /dev/null
+++ b/spec/ruby/library/net-http/http/get_print_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.get_print" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed URI" do
+    it "it prints the body of the specified uri to $stdout" do
+      -> do
+        Net::HTTP.get_print URI.parse("http://localhost:#{@port}/")
+      end.should output(/This is the index page\./)
+    end
+  end
+
+  describe "when passed host, path, port" do
+    it "it prints the body of the specified uri to $stdout" do
+      -> do
+        Net::HTTP.get_print 'localhost', "/", @port
+      end.should output(/This is the index page\./)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/get_response_spec.rb b/spec/ruby/library/net-http/http/get_response_spec.rb
new file mode 100644
index 0000000000..7133ef8101
--- /dev/null
+++ b/spec/ruby/library/net-http/http/get_response_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.get_response" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed URI" do
+    it "returns the response for the specified uri" do
+      res = Net::HTTP.get_response(URI.parse("http://localhost:#{@port}/"))
+      res.content_type.should == "text/plain"
+      res.body.should == "This is the index page."
+    end
+  end
+
+  describe "when passed host, path, port" do
+    it "returns the response for the specified host-path-combination" do
+      res = Net::HTTP.get_response('localhost', "/", @port)
+      res.content_type.should == "text/plain"
+      res.body.should == "This is the index page."
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/get_spec.rb b/spec/ruby/library/net-http/http/get_spec.rb
new file mode 100644
index 0000000000..e64a61c52c
--- /dev/null
+++ b/spec/ruby/library/net-http/http/get_spec.rb
@@ -0,0 +1,94 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.get" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed URI" do
+    it "returns the body of the specified uri" do
+      Net::HTTP.get(URI.parse("http://localhost:#{@port}/")).should == "This is the index page."
+    end
+  end
+
+  describe "when passed host, path, port" do
+    it "returns the body of the specified host-path-combination" do
+      Net::HTTP.get('localhost', "/", @port).should == "This is the index page."
+    end
+  end
+end
+
+quarantine! do # These specs fail frequently with CHECK_LEAKS=true
+describe "Net::HTTP.get" do
+  describe "when reading gzipped contents" do
+    def start_threads
+      require 'zlib'
+      require 'stringio'
+
+      server = nil
+      server_thread = Thread.new do
+        server = TCPServer.new("127.0.0.1", 0)
+        begin
+          c = server.accept
+        ensure
+          server.close
+        end
+        c.print "HTTP/1.1 200\r\n"
+        c.print "Content-Type: text/plain\r\n"
+        c.print "Content-Encoding: gzip\r\n"
+        s = StringIO.new
+        z = Zlib::GzipWriter.new(s)
+        begin
+          z.write 'Hello World!'
+        ensure
+          z.close
+        end
+        c.print "Content-Length: #{s.length}\r\n\r\n"
+        # Write partial gzip content
+        c.write s.string.byteslice(0..-2)
+        c.flush
+        c
+      end
+      Thread.pass until server && server_thread.stop?
+
+      client_thread = Thread.new do
+        Thread.current.report_on_exception = false
+        Net::HTTP.get("127.0.0.1", '/', server.connect_address.ip_port)
+      end
+
+      socket = server_thread.value
+      Thread.pass until client_thread.stop?
+
+      [socket, client_thread]
+    end
+
+    it "propagates exceptions interrupting the thread and does not replace it with Zlib::BufError" do
+      my_exception = Class.new(RuntimeError)
+      socket, client_thread = start_threads
+      begin
+        client_thread.raise my_exception, "my exception"
+        -> { client_thread.value }.should raise_error(my_exception)
+      ensure
+        socket.close
+      end
+    end
+
+    it "lets the kill Thread exception goes through and does not replace it with Zlib::BufError" do
+      socket, client_thread = start_threads
+      begin
+        client_thread.kill
+        client_thread.value.should == nil
+      ensure
+        socket.close
+      end
+    end
+  end
+end
+end
diff --git a/spec/ruby/library/net-http/http/head2_spec.rb b/spec/ruby/library/net-http/http/head2_spec.rb
new file mode 100644
index 0000000000..84cfff33d7
--- /dev/null
+++ b/spec/ruby/library/net-http/http/head2_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_head'
+
+describe "Net::HTTP#head2" do
+  it_behaves_like :net_http_request_head, :head2
+end
diff --git a/spec/ruby/library/net-http/http/head_spec.rb b/spec/ruby/library/net-http/http/head_spec.rb
new file mode 100644
index 0000000000..64621fa87b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/head_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#head" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a HEAD request to the passed path and returns the response" do
+    response = @http.head("/request")
+    # HEAD requests have no responses
+    response.body.should be_nil
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.head("/request").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/http_default_port_spec.rb b/spec/ruby/library/net-http/http/http_default_port_spec.rb
new file mode 100644
index 0000000000..3b17bcd0a5
--- /dev/null
+++ b/spec/ruby/library/net-http/http/http_default_port_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.http_default_port" do
+  it "returns 80" do
+    Net::HTTP.http_default_port.should eql(80)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/https_default_port_spec.rb b/spec/ruby/library/net-http/http/https_default_port_spec.rb
new file mode 100644
index 0000000000..8c24e1d97c
--- /dev/null
+++ b/spec/ruby/library/net-http/http/https_default_port_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.https_default_port" do
+  it "returns 443" do
+    Net::HTTP.https_default_port.should eql(443)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/initialize_spec.rb b/spec/ruby/library/net-http/http/initialize_spec.rb
new file mode 100644
index 0000000000..78aa01e1aa
--- /dev/null
+++ b/spec/ruby/library/net-http/http/initialize_spec.rb
@@ -0,0 +1,46 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#initialize" do
+  it "is private" do
+    Net::HTTP.should have_private_instance_method(:initialize)
+  end
+
+  describe "when passed address" do
+    before :each do
+      @net = Net::HTTP.allocate
+      @net.send(:initialize, "localhost")
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @net.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the default HTTP port" do
+      @net.port.should eql(Net::HTTP.default_port)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @net.started?.should be_false
+    end
+  end
+
+  describe "when passed address, port" do
+    before :each do
+      @net = Net::HTTP.allocate
+      @net.send(:initialize, "localhost", 3333)
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @net.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the passed port" do
+      @net.port.should eql(3333)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @net.started?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/inspect_spec.rb b/spec/ruby/library/net-http/http/inspect_spec.rb
new file mode 100644
index 0000000000..b8f650809e
--- /dev/null
+++ b/spec/ruby/library/net-http/http/inspect_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#inspect" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+    @http = Net::HTTP.new("localhost", @port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "returns a String representation of self" do
+    @http.inspect.should be_kind_of(String)
+    @http.inspect.should == "#<Net::HTTP localhost:#{@port} open=false>"
+
+    @http.start
+    @http.inspect.should == "#<Net::HTTP localhost:#{@port} open=true>"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/is_version_1_1_spec.rb b/spec/ruby/library/net-http/http/is_version_1_1_spec.rb
new file mode 100644
index 0000000000..bdb343f9e0
--- /dev/null
+++ b/spec/ruby/library/net-http/http/is_version_1_1_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/version_1_1'
+
+describe "Net::HTTP.is_version_1_1?" do
+  it_behaves_like :net_http_version_1_1_p, :is_version_1_1?
+end
diff --git a/spec/ruby/library/net-http/http/is_version_1_2_spec.rb b/spec/ruby/library/net-http/http/is_version_1_2_spec.rb
new file mode 100644
index 0000000000..555bb205dd
--- /dev/null
+++ b/spec/ruby/library/net-http/http/is_version_1_2_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/version_1_2'
+
+describe "Net::HTTP.is_version_1_2?" do
+  it_behaves_like :net_http_version_1_2_p, :is_version_1_2?
+end
diff --git a/spec/ruby/library/net-http/http/lock_spec.rb b/spec/ruby/library/net-http/http/lock_spec.rb
new file mode 100644
index 0000000000..aa1f944196
--- /dev/null
+++ b/spec/ruby/library/net-http/http/lock_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#lock" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a LOCK request to the passed path and returns the response" do
+    response = @http.lock("/request", "test=test")
+    response.should be_kind_of(Net::HTTPResponse)
+    response.body.should == "Request type: LOCK"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/mkcol_spec.rb b/spec/ruby/library/net-http/http/mkcol_spec.rb
new file mode 100644
index 0000000000..f8009f9059
--- /dev/null
+++ b/spec/ruby/library/net-http/http/mkcol_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#mkcol" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a MKCOL request to the passed path and returns the response" do
+    response = @http.mkcol("/request")
+    response.should be_kind_of(Net::HTTPResponse)
+    response.body.should == "Request type: MKCOL"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/move_spec.rb b/spec/ruby/library/net-http/http/move_spec.rb
new file mode 100644
index 0000000000..ae43016a2c
--- /dev/null
+++ b/spec/ruby/library/net-http/http/move_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#head" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a MOVE request to the passed path and returns the response" do
+    response = @http.move("/request")
+    # HEAD requests have no responses
+    response.body.should == "Request type: MOVE"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.move("/request").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/new_spec.rb b/spec/ruby/library/net-http/http/new_spec.rb
new file mode 100644
index 0000000000..1ec6bbd0c0
--- /dev/null
+++ b/spec/ruby/library/net-http/http/new_spec.rb
@@ -0,0 +1,86 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.new" do
+  describe "when passed address" do
+    before :each do
+      @http = Net::HTTP.new("localhost")
+    end
+
+    it "returns a Net::HTTP instance" do
+      @http.proxy?.should be_false
+      @http.instance_of?(Net::HTTP).should be_true
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @http.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the default HTTP port" do
+      @http.port.should eql(Net::HTTP.default_port)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @http.started?.should be_false
+    end
+  end
+
+  describe "when passed address, port" do
+    before :each do
+      @http = Net::HTTP.new("localhost", 3333)
+    end
+
+    it "returns a Net::HTTP instance" do
+      @http.proxy?.should be_false
+      @http.instance_of?(Net::HTTP).should be_true
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @http.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the passed port" do
+      @http.port.should eql(3333)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @http.started?.should be_false
+    end
+  end
+
+  describe "when passed address, port, *proxy_options" do
+    it "returns a Net::HTTP instance" do
+      http = Net::HTTP.new("localhost", 3333, "localhost")
+      http.proxy?.should be_true
+      http.instance_of?(Net::HTTP).should be_true
+      http.should be_kind_of(Net::HTTP)
+    end
+
+    it "correctly sets the passed Proxy options" do
+      http = Net::HTTP.new("localhost", 3333, "localhost")
+      http.proxy_address.should == "localhost"
+      http.proxy_port.should eql(80)
+      http.proxy_user.should be_nil
+      http.proxy_pass.should be_nil
+
+      http = Net::HTTP.new("localhost", 3333, "localhost", 1234)
+      http.proxy_address.should == "localhost"
+      http.proxy_port.should eql(1234)
+      http.proxy_user.should be_nil
+      http.proxy_pass.should be_nil
+
+      http = Net::HTTP.new("localhost", 3333, "localhost", 1234, "rubyspec")
+      http.proxy_address.should == "localhost"
+      http.proxy_port.should eql(1234)
+      http.proxy_user.should == "rubyspec"
+      http.proxy_pass.should be_nil
+
+      http = Net::HTTP.new("localhost", 3333, "localhost", 1234, "rubyspec", "rocks")
+      http.proxy_address.should == "localhost"
+      http.proxy_port.should eql(1234)
+      http.proxy_user.should == "rubyspec"
+      http.proxy_pass.should == "rocks"
+    end
+  end
+
+end
diff --git a/spec/ruby/library/net-http/http/newobj_spec.rb b/spec/ruby/library/net-http/http/newobj_spec.rb
new file mode 100644
index 0000000000..e19b30fca9
--- /dev/null
+++ b/spec/ruby/library/net-http/http/newobj_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.newobj" do
+  before :each do
+    @net = Net::HTTP.newobj("localhost")
+  end
+
+  describe "when passed address" do
+    it "returns a new Net::HTTP instance" do
+      @net.should be_kind_of(Net::HTTP)
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @net.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the default HTTP port" do
+      @net.port.should eql(Net::HTTP.default_port)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @net.started?.should be_false
+    end
+  end
+
+  describe "when passed address, port" do
+    before :each do
+      @net = Net::HTTP.newobj("localhost", 3333)
+    end
+
+    it "returns a new Net::HTTP instance" do
+      @net.should be_kind_of(Net::HTTP)
+    end
+
+    it "sets the new Net::HTTP instance's address to the passed address" do
+      @net.address.should == "localhost"
+    end
+
+    it "sets the new Net::HTTP instance's port to the passed port" do
+      @net.port.should eql(3333)
+    end
+
+    it "does not start the new Net::HTTP instance" do
+      @net.started?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/open_timeout_spec.rb b/spec/ruby/library/net-http/http/open_timeout_spec.rb
new file mode 100644
index 0000000000..0d93752271
--- /dev/null
+++ b/spec/ruby/library/net-http/http/open_timeout_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#open_timeout" do
+  it "returns the seconds to wait till the connection is open" do
+    net = Net::HTTP.new("localhost")
+    net.open_timeout.should eql(60)
+    net.open_timeout = 10
+    net.open_timeout.should eql(10)
+  end
+end
+
+describe "Net::HTTP#open_timeout=" do
+  it "sets the seconds to wait till the connection is open" do
+    net = Net::HTTP.new("localhost")
+    net.open_timeout = 10
+    net.open_timeout.should eql(10)
+  end
+
+  it "returns the newly set value" do
+    net = Net::HTTP.new("localhost")
+    (net.open_timeout = 10).should eql(10)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/options_spec.rb b/spec/ruby/library/net-http/http/options_spec.rb
new file mode 100644
index 0000000000..3d9887a557
--- /dev/null
+++ b/spec/ruby/library/net-http/http/options_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#options" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an options request to the passed path and returns the response" do
+    response = @http.options("/request")
+
+    response.body.should == "Request type: OPTIONS"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.options("/request").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/port_spec.rb b/spec/ruby/library/net-http/http/port_spec.rb
new file mode 100644
index 0000000000..0984d5e6ce
--- /dev/null
+++ b/spec/ruby/library/net-http/http/port_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#port" do
+  it "returns the current port number" do
+    net = Net::HTTP.new("localhost", 3333)
+    net.port.should eql(3333)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/post2_spec.rb b/spec/ruby/library/net-http/http/post2_spec.rb
new file mode 100644
index 0000000000..abc998709f
--- /dev/null
+++ b/spec/ruby/library/net-http/http/post2_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_post'
+
+describe "Net::HTTP#post2" do
+  it_behaves_like :net_http_request_post, :post2
+end
diff --git a/spec/ruby/library/net-http/http/post_form_spec.rb b/spec/ruby/library/net-http/http/post_form_spec.rb
new file mode 100644
index 0000000000..de64a25bae
--- /dev/null
+++ b/spec/ruby/library/net-http/http/post_form_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.post_form when passed URI" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  it "POSTs the passed form data to the given uri" do
+    uri = URI.parse("http://localhost:#{@port}/request/body")
+    data = { test: :data }
+
+    res = Net::HTTP.post_form(uri, data)
+    res.body.should == "test=data"
+  end
+end
diff --git a/spec/ruby/library/net-http/http/post_spec.rb b/spec/ruby/library/net-http/http/post_spec.rb
new file mode 100644
index 0000000000..b8b8d16ad1
--- /dev/null
+++ b/spec/ruby/library/net-http/http/post_spec.rb
@@ -0,0 +1,76 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require 'uri'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.post" do
+  before :each do
+    NetHTTPSpecs.start_server
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends post request to the specified URI and returns response" do
+    response = Net::HTTP.post(
+      URI("http://localhost:#{NetHTTPSpecs.port}/request"),
+      '{ "q": "ruby", "max": "50" }',
+      "Content-Type" => "application/json")
+    response.body.should == "Request type: POST"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    response = Net::HTTP.post(URI("http://localhost:#{NetHTTPSpecs.port}/request"), "test=test")
+    response.should be_kind_of(Net::HTTPResponse)
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "sends Content-Type: application/x-www-form-urlencoded by default" do
+      response = Net::HTTP.post(URI("http://localhost:#{NetHTTPSpecs.port}/request/header"), "test=test")
+      response.body.should include({ "Content-Type" => "application/x-www-form-urlencoded" }.inspect.delete("{}"))
+    end
+  end
+
+  it "does not support HTTP Basic Auth" do
+    response = Net::HTTP.post(
+      URI("http://john:qwerty@localhost:#{NetHTTPSpecs.port}/request/basic_auth"),
+      "test=test")
+    response.body.should == "username: \npassword: "
+  end
+end
+
+describe "Net::HTTP#post" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an post request to the passed path and returns the response" do
+    response = @http.post("/request", "test=test")
+    response.body.should == "Request type: POST"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.post("/request", "test=test").should be_kind_of(Net::HTTPResponse)
+  end
+
+  describe "when passed a block" do
+    it "yields fragments of the response body to the passed block" do
+      str = +""
+      @http.post("/request", "test=test") do |res|
+        str << res
+      end
+      str.should == "Request type: POST"
+    end
+
+    it "returns a Net::HTTPResponse" do
+      @http.post("/request", "test=test") {}.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/propfind_spec.rb b/spec/ruby/library/net-http/http/propfind_spec.rb
new file mode 100644
index 0000000000..f3742d1b1a
--- /dev/null
+++ b/spec/ruby/library/net-http/http/propfind_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#propfind" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an propfind request to the passed path and returns the response" do
+    response = @http.propfind("/request", "test=test")
+    response.body.should == "Request type: PROPFIND"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.propfind("/request", "test=test").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proppatch_spec.rb b/spec/ruby/library/net-http/http/proppatch_spec.rb
new file mode 100644
index 0000000000..0163d24d46
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proppatch_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#proppatch" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an proppatch request to the passed path and returns the response" do
+    response = @http.proppatch("/request", "test=test")
+    response.body.should == "Request type: PROPPATCH"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.proppatch("/request", "test=test").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proxy_address_spec.rb b/spec/ruby/library/net-http/http/proxy_address_spec.rb
new file mode 100644
index 0000000000..5b5efb7ac0
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proxy_address_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.proxy_address" do
+  describe "when self is no proxy class" do
+    it "returns nil" do
+      Net::HTTP.proxy_address.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class" do
+    it "returns the address for self's proxy connection" do
+      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_address.should == "localhost"
+    end
+  end
+end
+
+describe "Net::HTTP#proxy_address" do
+  describe "when self is no proxy class instance" do
+    it "returns nil" do
+      Net::HTTP.new("localhost", 3333).proxy_address.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class instance" do
+    it "returns the password for self's proxy connection" do
+      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+      http_with_proxy.new("localhost", 3333).proxy_address.should == "localhost"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proxy_class_spec.rb b/spec/ruby/library/net-http/http/proxy_class_spec.rb
new file mode 100644
index 0000000000..00975aef4e
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proxy_class_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.proxy_class?" do
+  it "returns true if self is a class created with Net::HTTP.Proxy" do
+    Net::HTTP.proxy_class?.should be_false
+    Net::HTTP.Proxy("localhost").proxy_class?.should be_true
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proxy_pass_spec.rb b/spec/ruby/library/net-http/http/proxy_pass_spec.rb
new file mode 100644
index 0000000000..4e393a53ff
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proxy_pass_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.proxy_pass" do
+  describe "when self is no proxy class" do
+    it "returns nil" do
+      Net::HTTP.proxy_pass.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class" do
+    it "returns nil if no password was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").proxy_pass.should be_nil
+    end
+
+    it "returns the password for self's proxy connection" do
+      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_pass.should == "rocks"
+    end
+  end
+end
+
+describe "Net::HTTP#proxy_pass" do
+  describe "when self is no proxy class instance" do
+    it "returns nil" do
+      Net::HTTP.new("localhost", 3333).proxy_pass.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class instance" do
+    it "returns nil if no password was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_pass.should be_nil
+    end
+
+    it "returns the password for self's proxy connection" do
+      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+      http_with_proxy.new("localhost", 3333).proxy_pass.should == "rocks"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proxy_port_spec.rb b/spec/ruby/library/net-http/http/proxy_port_spec.rb
new file mode 100644
index 0000000000..d7d37f3927
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proxy_port_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.proxy_port" do
+  describe "when self is no proxy class" do
+    it "returns nil" do
+      Net::HTTP.proxy_port.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class" do
+    it "returns 80 if no port was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").proxy_port.should eql(80)
+    end
+
+    it "returns the port for self's proxy connection" do
+      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_port.should eql(1234)
+    end
+  end
+end
+
+describe "Net::HTTP#proxy_port" do
+  describe "when self is no proxy class instance" do
+    it "returns nil" do
+      Net::HTTP.new("localhost", 3333).proxy_port.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class instance" do
+    it "returns 80 if no port was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_port.should eql(80)
+    end
+
+    it "returns the port for self's proxy connection" do
+      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+      http_with_proxy.new("localhost", 3333).proxy_port.should eql(1234)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/proxy_user_spec.rb b/spec/ruby/library/net-http/http/proxy_user_spec.rb
new file mode 100644
index 0000000000..ef7654425d
--- /dev/null
+++ b/spec/ruby/library/net-http/http/proxy_user_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.proxy_user" do
+  describe "when self is no proxy class" do
+    it "returns nil" do
+      Net::HTTP.proxy_user.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class" do
+    it "returns nil if no username was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").proxy_user.should be_nil
+    end
+
+    it "returns the username for self's proxy connection" do
+      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_user.should == "rspec"
+    end
+  end
+end
+
+describe "Net::HTTP#proxy_user" do
+  describe "when self is no proxy class instance" do
+    it "returns nil" do
+      Net::HTTP.new("localhost", 3333).proxy_user.should be_nil
+    end
+  end
+
+  describe "when self is a proxy class instance" do
+    it "returns nil if no username was set for self's proxy connection" do
+      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_user.should be_nil
+    end
+
+    it "returns the username for self's proxy connection" do
+      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
+      http_with_proxy.new("localhost", 3333).proxy_user.should == "rspec"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/put2_spec.rb b/spec/ruby/library/net-http/http/put2_spec.rb
new file mode 100644
index 0000000000..7b03a39d0b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/put2_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_put'
+
+describe "Net::HTTP#put2" do
+  it_behaves_like :net_http_request_put, :put2
+end
diff --git a/spec/ruby/library/net-http/http/put_spec.rb b/spec/ruby/library/net-http/http/put_spec.rb
new file mode 100644
index 0000000000..75f3c243d4
--- /dev/null
+++ b/spec/ruby/library/net-http/http/put_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#put" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an put request to the passed path and returns the response" do
+    response = @http.put("/request", "test=test")
+    response.body.should == "Request type: PUT"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.put("/request", "test=test").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/read_timeout_spec.rb b/spec/ruby/library/net-http/http/read_timeout_spec.rb
new file mode 100644
index 0000000000..7a0d2f1d72
--- /dev/null
+++ b/spec/ruby/library/net-http/http/read_timeout_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#read_timeout" do
+  it "returns the seconds to wait until reading one block" do
+    net = Net::HTTP.new("localhost")
+    net.read_timeout.should eql(60)
+    net.read_timeout = 10
+    net.read_timeout.should eql(10)
+  end
+end
+
+describe "Net::HTTP#read_timeout=" do
+  it "sets the seconds to wait till the connection is open" do
+    net = Net::HTTP.new("localhost")
+    net.read_timeout = 10
+    net.read_timeout.should eql(10)
+  end
+
+  it "returns the newly set value" do
+    net = Net::HTTP.new("localhost")
+    (net.read_timeout = 10).should eql(10)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/request_get_spec.rb b/spec/ruby/library/net-http/http/request_get_spec.rb
new file mode 100644
index 0000000000..98025a14a1
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_get_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_get'
+
+describe "Net::HTTP#request_get" do
+  it_behaves_like :net_http_request_get, :get2
+end
diff --git a/spec/ruby/library/net-http/http/request_head_spec.rb b/spec/ruby/library/net-http/http/request_head_spec.rb
new file mode 100644
index 0000000000..8f514d4eee
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_head_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_head'
+
+describe "Net::HTTP#request_head" do
+  it_behaves_like :net_http_request_head, :request_head
+end
diff --git a/spec/ruby/library/net-http/http/request_post_spec.rb b/spec/ruby/library/net-http/http/request_post_spec.rb
new file mode 100644
index 0000000000..719bd5a7ee
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_post_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_post'
+
+describe "Net::HTTP#request_post" do
+  it_behaves_like :net_http_request_post, :request_post
+end
diff --git a/spec/ruby/library/net-http/http/request_put_spec.rb b/spec/ruby/library/net-http/http/request_put_spec.rb
new file mode 100644
index 0000000000..9fcf3a98d6
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_put_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/request_put'
+
+describe "Net::HTTP#request_put" do
+  it_behaves_like :net_http_request_put, :request_put
+end
diff --git a/spec/ruby/library/net-http/http/request_spec.rb b/spec/ruby/library/net-http/http/request_spec.rb
new file mode 100644
index 0000000000..356e605b3b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_spec.rb
@@ -0,0 +1,109 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#request" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed request_object" do
+    it "makes a HTTP Request based on the passed request_object" do
+      response = @http.request(Net::HTTP::Get.new("/request"), "test=test")
+      response.body.should == "Request type: GET"
+
+      response = @http.request(Net::HTTP::Head.new("/request"), "test=test")
+      response.body.should be_nil
+
+      response = @http.request(Net::HTTP::Post.new("/request"), "test=test")
+      response.body.should == "Request type: POST"
+
+      response = @http.request(Net::HTTP::Put.new("/request"), "test=test")
+      response.body.should == "Request type: PUT"
+
+      response = @http.request(Net::HTTP::Proppatch.new("/request"), "test=test")
+      response.body.should == "Request type: PROPPATCH"
+
+      response = @http.request(Net::HTTP::Lock.new("/request"), "test=test")
+      response.body.should == "Request type: LOCK"
+
+      response = @http.request(Net::HTTP::Unlock.new("/request"), "test=test")
+      response.body.should == "Request type: UNLOCK"
+
+      # TODO: Does not work?
+      #response = @http.request(Net::HTTP::Options.new("/request"), "test=test")
+      #response.body.should be_nil
+
+      response = @http.request(Net::HTTP::Propfind.new("/request"), "test=test")
+      response.body.should == "Request type: PROPFIND"
+
+      response = @http.request(Net::HTTP::Delete.new("/request"), "test=test")
+      response.body.should == "Request type: DELETE"
+
+      response = @http.request(Net::HTTP::Move.new("/request"), "test=test")
+      response.body.should == "Request type: MOVE"
+
+      response = @http.request(Net::HTTP::Copy.new("/request"), "test=test")
+      response.body.should == "Request type: COPY"
+
+      response = @http.request(Net::HTTP::Mkcol.new("/request"), "test=test")
+      response.body.should == "Request type: MKCOL"
+
+      response = @http.request(Net::HTTP::Trace.new("/request"), "test=test")
+      response.body.should == "Request type: TRACE"
+    end
+  end
+
+  describe "when passed request_object and request_body" do
+    it "sends the passed request_body when making the HTTP Request" do
+      response = @http.request(Net::HTTP::Get.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Head.new("/request/body"), "test=test")
+      response.body.should be_nil
+
+      response = @http.request(Net::HTTP::Post.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Put.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Proppatch.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Lock.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Unlock.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      # TODO: Does not work?
+      #response = @http.request(Net::HTTP::Options.new("/request/body"), "test=test")
+      #response.body.should be_nil
+
+      response = @http.request(Net::HTTP::Propfind.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Delete.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Move.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Copy.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Mkcol.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+
+      response = @http.request(Net::HTTP::Trace.new("/request/body"), "test=test")
+      response.body.should == "test=test"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/request_types_spec.rb b/spec/ruby/library/net-http/http/request_types_spec.rb
new file mode 100644
index 0000000000..53aef1ee58
--- /dev/null
+++ b/spec/ruby/library/net-http/http/request_types_spec.rb
@@ -0,0 +1,254 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP::Get" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Get.should < Net::HTTPRequest
+  end
+
+  it "represents the 'GET'-Request-Method" do
+    Net::HTTP::Get::METHOD.should == "GET"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Get::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Get::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Head" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Head.should < Net::HTTPRequest
+  end
+
+  it "represents the 'HEAD'-Request-Method" do
+    Net::HTTP::Head::METHOD.should == "HEAD"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Head::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has no Response Body" do
+    Net::HTTP::Head::RESPONSE_HAS_BODY.should be_false
+  end
+end
+
+describe "Net::HTTP::Post" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Post.should < Net::HTTPRequest
+  end
+
+  it "represents the 'POST'-Request-Method" do
+    Net::HTTP::Post::METHOD.should == "POST"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Post::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Post::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Put" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Put.should < Net::HTTPRequest
+  end
+
+  it "represents the 'PUT'-Request-Method" do
+    Net::HTTP::Put::METHOD.should == "PUT"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Put::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Put::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Delete" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Delete.should < Net::HTTPRequest
+  end
+
+  it "represents the 'DELETE'-Request-Method" do
+    Net::HTTP::Delete::METHOD.should == "DELETE"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Delete::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Delete::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Options" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Options.should < Net::HTTPRequest
+  end
+
+  it "represents the 'OPTIONS'-Request-Method" do
+    Net::HTTP::Options::METHOD.should == "OPTIONS"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Options::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has no Response Body" do
+    Net::HTTP::Options::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Trace" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Trace.should < Net::HTTPRequest
+  end
+
+  it "represents the 'TRACE'-Request-Method" do
+    Net::HTTP::Trace::METHOD.should == "TRACE"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Trace::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Trace::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Propfind" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Propfind.should < Net::HTTPRequest
+  end
+
+  it "represents the 'PROPFIND'-Request-Method" do
+    Net::HTTP::Propfind::METHOD.should == "PROPFIND"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Propfind::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Propfind::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Proppatch" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Proppatch.should < Net::HTTPRequest
+  end
+
+  it "represents the 'PROPPATCH'-Request-Method" do
+    Net::HTTP::Proppatch::METHOD.should == "PROPPATCH"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Proppatch::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Proppatch::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Mkcol" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Mkcol.should < Net::HTTPRequest
+  end
+
+  it "represents the 'MKCOL'-Request-Method" do
+    Net::HTTP::Mkcol::METHOD.should == "MKCOL"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Mkcol::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Mkcol::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Copy" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Copy.should < Net::HTTPRequest
+  end
+
+  it "represents the 'COPY'-Request-Method" do
+    Net::HTTP::Copy::METHOD.should == "COPY"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Copy::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Copy::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Move" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Move.should < Net::HTTPRequest
+  end
+
+  it "represents the 'MOVE'-Request-Method" do
+    Net::HTTP::Move::METHOD.should == "MOVE"
+  end
+
+  it "has no Request Body" do
+    Net::HTTP::Move::REQUEST_HAS_BODY.should be_false
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Move::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Lock" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Lock.should < Net::HTTPRequest
+  end
+
+  it "represents the 'LOCK'-Request-Method" do
+    Net::HTTP::Lock::METHOD.should == "LOCK"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Lock::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Lock::RESPONSE_HAS_BODY.should be_true
+  end
+end
+
+describe "Net::HTTP::Unlock" do
+  it "is a subclass of Net::HTTPRequest" do
+    Net::HTTP::Unlock.should < Net::HTTPRequest
+  end
+
+  it "represents the 'UNLOCK'-Request-Method" do
+    Net::HTTP::Unlock::METHOD.should == "UNLOCK"
+  end
+
+  it "has a Request Body" do
+    Net::HTTP::Unlock::REQUEST_HAS_BODY.should be_true
+  end
+
+  it "has a Response Body" do
+    Net::HTTP::Unlock::RESPONSE_HAS_BODY.should be_true
+  end
+end
diff --git a/spec/ruby/library/net-http/http/send_request_spec.rb b/spec/ruby/library/net-http/http/send_request_spec.rb
new file mode 100644
index 0000000000..af35c068ce
--- /dev/null
+++ b/spec/ruby/library/net-http/http/send_request_spec.rb
@@ -0,0 +1,61 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#send_request" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+
+    # HEAD is special so handled separately
+    @methods = %w[
+      GET POST PUT DELETE
+      OPTIONS
+      PROPFIND PROPPATCH LOCK UNLOCK
+    ]
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  # TODO: Does only work with GET and POST requests
+  describe "when passed type, path" do
+    it "sends a HTTP Request of the passed type to the passed path" do
+      response = @http.send_request("HEAD", "/request")
+      response.body.should be_nil
+
+      (@methods - %w[POST PUT]).each do |method|
+        response = @http.send_request(method, "/request")
+        response.body.should == "Request type: #{method}"
+      end
+    end
+  end
+
+  describe "when passed type, path, body" do
+    it "sends a HTTP Request with the passed body" do
+      response = @http.send_request("HEAD", "/request/body", "test=test")
+      response.body.should be_nil
+
+      @methods.each do |method|
+        response = @http.send_request(method, "/request/body", "test=test")
+        response.body.should == "test=test"
+      end
+    end
+  end
+
+  describe "when passed type, path, body, headers" do
+    it "sends a HTTP Request with the passed headers" do
+      referer = 'https://www.ruby-lang.org/'.freeze
+
+      response = @http.send_request("HEAD", "/request/header", "test=test", "referer" => referer)
+      response.body.should be_nil
+
+      @methods.each do |method|
+        response = @http.send_request(method, "/request/header", "test=test", "referer" => referer)
+        response.body.should include({ "Referer" => referer }.inspect.delete("{}"))
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/set_debug_output_spec.rb b/spec/ruby/library/net-http/http/set_debug_output_spec.rb
new file mode 100644
index 0000000000..5ceecb39fb
--- /dev/null
+++ b/spec/ruby/library/net-http/http/set_debug_output_spec.rb
@@ -0,0 +1,33 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#set_debug_output when passed io" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sets the passed io as output stream for debugging" do
+    io = StringIO.new
+
+    @http.set_debug_output(io)
+    @http.start
+    io.string.should_not be_empty
+    size = io.string.size
+
+    @http.get("/")
+    io.string.size.should > size
+  end
+
+  it "outputs a warning when the connection has already been started" do
+    @http.start
+    -> { @http.set_debug_output(StringIO.new) }.should complain(/Net::HTTP#set_debug_output called after HTTP started/)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/shared/request_get.rb b/spec/ruby/library/net-http/http/shared/request_get.rb
new file mode 100644
index 0000000000..d25f32049b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/shared/request_get.rb
@@ -0,0 +1,41 @@
+describe :net_http_request_get, shared: true do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed no block" do
+    it "sends a GET request to the passed path and returns the response" do
+      response = @http.send(@method, "/request")
+      response.body.should == "Request type: GET"
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request")
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+
+  describe "when passed a block" do
+    it "sends a GET request to the passed path and returns the response" do
+      response = @http.send(@method, "/request") {}
+      response.body.should == "Request type: GET"
+    end
+
+    it "yields the response to the passed block" do
+      @http.send(@method, "/request") do |response|
+        response.body.should == "Request type: GET"
+      end
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request") {}
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/shared/request_head.rb b/spec/ruby/library/net-http/http/shared/request_head.rb
new file mode 100644
index 0000000000..78b555884b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/shared/request_head.rb
@@ -0,0 +1,41 @@
+describe :net_http_request_head, shared: true do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed no block" do
+    it "sends a head request to the passed path and returns the response" do
+      response = @http.send(@method, "/request")
+      response.body.should be_nil
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request")
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+
+  describe "when passed a block" do
+    it "sends a head request to the passed path and returns the response" do
+      response = @http.send(@method, "/request") {}
+      response.body.should be_nil
+    end
+
+    it "yields the response to the passed block" do
+      @http.send(@method, "/request") do |response|
+        response.body.should be_nil
+      end
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request") {}
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/shared/request_post.rb b/spec/ruby/library/net-http/http/shared/request_post.rb
new file mode 100644
index 0000000000..e832411c48
--- /dev/null
+++ b/spec/ruby/library/net-http/http/shared/request_post.rb
@@ -0,0 +1,41 @@
+describe :net_http_request_post, shared: true do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed no block" do
+    it "sends a post request to the passed path and returns the response" do
+      response = @http.send(@method, "/request", "test=test")
+      response.body.should == "Request type: POST"
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request", "test=test")
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+
+  describe "when passed a block" do
+    it "sends a post request to the passed path and returns the response" do
+      response = @http.send(@method, "/request", "test=test") {}
+      response.body.should == "Request type: POST"
+    end
+
+    it "yields the response to the passed block" do
+      @http.send(@method, "/request", "test=test") do |response|
+        response.body.should == "Request type: POST"
+      end
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request", "test=test") {}
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/shared/request_put.rb b/spec/ruby/library/net-http/http/shared/request_put.rb
new file mode 100644
index 0000000000..3b902f4957
--- /dev/null
+++ b/spec/ruby/library/net-http/http/shared/request_put.rb
@@ -0,0 +1,41 @@
+describe :net_http_request_put, shared: true do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when passed no block" do
+    it "sends a put request to the passed path and returns the response" do
+      response = @http.send(@method, "/request", "test=test")
+      response.body.should == "Request type: PUT"
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request", "test=test")
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+
+  describe "when passed a block" do
+    it "sends a put request to the passed path and returns the response" do
+      response = @http.send(@method, "/request", "test=test") {}
+      response.body.should == "Request type: PUT"
+    end
+
+    it "yields the response to the passed block" do
+      @http.send(@method, "/request", "test=test") do |response|
+        response.body.should == "Request type: PUT"
+      end
+    end
+
+    it "returns a Net::HTTPResponse object" do
+      response = @http.send(@method, "/request", "test=test") {}
+      response.should be_kind_of(Net::HTTPResponse)
+    end
+  end
+end
diff --git a/spec/ruby/library/net/http/http/shared/started.rb b/spec/ruby/library/net-http/http/shared/started.rb
index 9ff6272c31..9ff6272c31 100644
--- a/spec/ruby/library/net/http/http/shared/started.rb
+++ b/spec/ruby/library/net-http/http/shared/started.rb
diff --git a/spec/ruby/library/net/http/http/shared/version_1_1.rb b/spec/ruby/library/net-http/http/shared/version_1_1.rb
index db3d6a986d..db3d6a986d 100644
--- a/spec/ruby/library/net/http/http/shared/version_1_1.rb
+++ b/spec/ruby/library/net-http/http/shared/version_1_1.rb
diff --git a/spec/ruby/library/net/http/http/shared/version_1_2.rb b/spec/ruby/library/net-http/http/shared/version_1_2.rb
index b044182c60..b044182c60 100644
--- a/spec/ruby/library/net/http/http/shared/version_1_2.rb
+++ b/spec/ruby/library/net-http/http/shared/version_1_2.rb
diff --git a/spec/ruby/library/net-http/http/socket_type_spec.rb b/spec/ruby/library/net-http/http/socket_type_spec.rb
new file mode 100644
index 0000000000..f6826777b0
--- /dev/null
+++ b/spec/ruby/library/net-http/http/socket_type_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP.socket_type" do
+  it "returns BufferedIO" do
+    Net::HTTP.socket_type.should == Net::BufferedIO
+  end
+end
diff --git a/spec/ruby/library/net-http/http/start_spec.rb b/spec/ruby/library/net-http/http/start_spec.rb
new file mode 100644
index 0000000000..0ce3e79269
--- /dev/null
+++ b/spec/ruby/library/net-http/http/start_spec.rb
@@ -0,0 +1,111 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP.start" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @port = NetHTTPSpecs.port
+  end
+
+  after :each do
+    NetHTTPSpecs.stop_server
+  end
+
+  describe "when not passed a block" do
+    before :each do
+      @http = Net::HTTP.start("localhost", @port)
+    end
+
+    after :each do
+      @http.finish if @http.started?
+    end
+
+    it "returns a new Net::HTTP object for the passed address and port" do
+      @http.should be_kind_of(Net::HTTP)
+      @http.address.should == "localhost"
+      @http.port.should == @port
+    end
+
+    it "opens the tcp connection" do
+      @http.started?.should be_true
+    end
+  end
+
+  describe "when passed a block" do
+    it "returns the blocks return value" do
+      Net::HTTP.start("localhost", @port) { :test }.should == :test
+    end
+
+    it "yields the new Net::HTTP object to the block" do
+      yielded = false
+      Net::HTTP.start("localhost", @port) do |net|
+        yielded = true
+        net.should be_kind_of(Net::HTTP)
+      end
+      yielded.should be_true
+    end
+
+    it "opens the tcp connection before yielding" do
+      Net::HTTP.start("localhost", @port) { |http| http.started?.should be_true }
+    end
+
+    it "closes the tcp connection after yielding" do
+      net = nil
+      Net::HTTP.start("localhost", @port) { |x| net = x }
+      net.started?.should be_false
+    end
+  end
+end
+
+describe "Net::HTTP#start" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "returns self" do
+    @http.start.should equal(@http)
+  end
+
+  it "opens the tcp connection" do
+    @http.start
+    @http.started?.should be_true
+  end
+
+  describe "when self has already been started" do
+    it "raises an IOError" do
+      @http.start
+      -> { @http.start }.should raise_error(IOError)
+    end
+  end
+
+  describe "when passed a block" do
+    it "returns the blocks return value" do
+      @http.start { :test }.should == :test
+    end
+
+    it "yields the new Net::HTTP object to the block" do
+      yielded = false
+      @http.start do |http|
+        yielded = true
+        http.should equal(@http)
+      end
+      yielded.should be_true
+    end
+
+    it "opens the tcp connection before yielding" do
+      @http.start { |http| http.started?.should be_true }
+    end
+
+    it "closes the tcp connection after yielding" do
+      @http.start { }
+      @http.started?.should be_false
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/http/started_spec.rb b/spec/ruby/library/net-http/http/started_spec.rb
new file mode 100644
index 0000000000..cbb82ceefa
--- /dev/null
+++ b/spec/ruby/library/net-http/http/started_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+require_relative 'shared/started'
+
+describe "Net::HTTP#started?" do
+  it_behaves_like :net_http_started_p, :started?
+end
diff --git a/spec/ruby/library/net-http/http/trace_spec.rb b/spec/ruby/library/net-http/http/trace_spec.rb
new file mode 100644
index 0000000000..9809d537c5
--- /dev/null
+++ b/spec/ruby/library/net-http/http/trace_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#trace" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends a TRACE request to the passed path and returns the response" do
+    response = @http.trace("/request")
+    response.body.should == "Request type: TRACE"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.trace("/request").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/unlock_spec.rb b/spec/ruby/library/net-http/http/unlock_spec.rb
new file mode 100644
index 0000000000..adf0b49f65
--- /dev/null
+++ b/spec/ruby/library/net-http/http/unlock_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/http_server'
+
+describe "Net::HTTP#unlock" do
+  before :each do
+    NetHTTPSpecs.start_server
+    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
+  end
+
+  after :each do
+    @http.finish if @http.started?
+    NetHTTPSpecs.stop_server
+  end
+
+  it "sends an UNLOCK request to the passed path and returns the response" do
+    response = @http.unlock("/request", "test=test")
+    response.body.should == "Request type: UNLOCK"
+  end
+
+  it "returns a Net::HTTPResponse" do
+    @http.unlock("/request", "test=test").should be_kind_of(Net::HTTPResponse)
+  end
+end
diff --git a/spec/ruby/library/net-http/http/use_ssl_spec.rb b/spec/ruby/library/net-http/http/use_ssl_spec.rb
new file mode 100644
index 0000000000..912a62a8ba
--- /dev/null
+++ b/spec/ruby/library/net-http/http/use_ssl_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTP#use_ssl?" do
+  it "returns false" do
+    http = Net::HTTP.new("localhost")
+    http.use_ssl?.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-http/http/version_1_1_spec.rb b/spec/ruby/library/net-http/http/version_1_1_spec.rb
new file mode 100644
index 0000000000..34a4ac8a6b
--- /dev/null
+++ b/spec/ruby/library/net-http/http/version_1_1_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/version_1_1'
+
+describe "Net::HTTP.version_1_1?" do
+  it_behaves_like :net_http_version_1_1_p, :version_1_1?
+end
diff --git a/spec/ruby/library/net-http/http/version_1_2_spec.rb b/spec/ruby/library/net-http/http/version_1_2_spec.rb
new file mode 100644
index 0000000000..e994511aea
--- /dev/null
+++ b/spec/ruby/library/net-http/http/version_1_2_spec.rb
@@ -0,0 +1,20 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/version_1_2'
+
+describe "Net::HTTP.version_1_2" do
+  it "turns on net/http 1.2 features" do
+    Net::HTTP.version_1_2
+
+    Net::HTTP.version_1_2?.should be_true
+    Net::HTTP.version_1_1?.should be_false
+  end
+
+  it "returns true" do
+    Net::HTTP.version_1_2.should be_true
+  end
+end
+
+describe "Net::HTTP.version_1_2?" do
+  it_behaves_like :net_http_version_1_2_p, :version_1_2?
+end
diff --git a/spec/ruby/library/net/http/httpexceptions/fixtures/classes.rb b/spec/ruby/library/net-http/httpexceptions/fixtures/classes.rb
index abe8855eff..abe8855eff 100644
--- a/spec/ruby/library/net/http/httpexceptions/fixtures/classes.rb
+++ b/spec/ruby/library/net-http/httpexceptions/fixtures/classes.rb
diff --git a/spec/ruby/library/net-http/httpexceptions/initialize_spec.rb b/spec/ruby/library/net-http/httpexceptions/initialize_spec.rb
new file mode 100644
index 0000000000..5316cca69d
--- /dev/null
+++ b/spec/ruby/library/net-http/httpexceptions/initialize_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPExceptions#initialize when passed message, response" do
+  before :each do
+    @exception = NetHTTPExceptionsSpecs::Simple.new("error message", "a http response")
+  end
+
+  it "calls super with the passed message" do
+    @exception.message.should == "error message"
+  end
+
+  it "sets self's response to the passed response" do
+    @exception.response.should == "a http response"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpexceptions/response_spec.rb b/spec/ruby/library/net-http/httpexceptions/response_spec.rb
new file mode 100644
index 0000000000..d718b1ae21
--- /dev/null
+++ b/spec/ruby/library/net-http/httpexceptions/response_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPExceptions#response" do
+  it "returns self's response" do
+    exception = NetHTTPExceptionsSpecs::Simple.new("error message", "a http response")
+    exception.response.should == "a http response"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/body_exist_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/body_exist_spec.rb
new file mode 100644
index 0000000000..6c886499ca
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/body_exist_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#body_exist?" do
+  it "returns true when the response is expected to have a body" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.body_exist?.should be_true
+
+    request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
+    request.body_exist?.should be_false
+  end
+
+  describe "when $VERBOSE is true" do
+    it "emits a warning" do
+      request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
+      -> {
+        request.body_exist?
+      }.should complain(/body_exist\? is obsolete/, verbose: true)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/body_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/body_spec.rb
new file mode 100644
index 0000000000..5f7315f303
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/body_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+
+describe "Net::HTTPGenericRequest#body" do
+  it "returns self's request body" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.body.should be_nil
+
+    request.body = "Some Content"
+    request.body.should == "Some Content"
+  end
+end
+
+describe "Net::HTTPGenericRequest#body=" do
+  before :each do
+    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+  end
+
+  it "sets self's body content to the passed String" do
+    @request.body = "Some Content"
+    @request.body.should == "Some Content"
+  end
+
+  it "sets self's body stream to nil" do
+    @request.body_stream = StringIO.new("")
+    @request.body = "Some Content"
+    @request.body_stream.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/body_stream_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/body_stream_spec.rb
new file mode 100644
index 0000000000..dea1c8c883
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/body_stream_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+
+describe "Net::HTTPGenericRequest#body_stream" do
+  it "returns self's body stream Object" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.body_stream.should be_nil
+
+    stream = StringIO.new("test")
+    request.body_stream = stream
+    request.body_stream.should equal(stream)
+  end
+end
+
+describe "Net::HTTPGenericRequest#body_stream=" do
+  before :each do
+    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    @stream = StringIO.new("test")
+  end
+
+  it "sets self's body stream to the passed Object" do
+    @request.body_stream = @stream
+    @request.body_stream.should equal(@stream)
+  end
+
+  it "sets self's body to nil" do
+    @request.body = "Some Content"
+    @request.body_stream = @stream
+    @request.body.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/exec_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/exec_spec.rb
new file mode 100644
index 0000000000..a09f9d5bec
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/exec_spec.rb
@@ -0,0 +1,135 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+
+describe "Net::HTTPGenericRequest#exec when passed socket, version, path" do
+  before :each do
+    @socket = StringIO.new(+"")
+    @buffered_socket = Net::BufferedIO.new(@socket)
+  end
+
+  it "executes the request over the socket to the path using the HTTP version" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+
+    request.exec(@buffered_socket, "1.1", "/some/path")
+    str = @socket.string
+
+    str.should =~ %r[POST /some/path HTTP/1.1\r\n]
+    str.should =~ %r[Accept: \*/\*\r\n]
+    str[-4..-1].should == "\r\n\r\n"
+
+    request = Net::HTTPGenericRequest.new("GET", true, true, "/some/path",
+                                          "Content-Type" => "text/html")
+
+    request.exec(@buffered_socket, "1.0", "/some/other/path")
+    str = @socket.string
+
+    str.should =~ %r[GET /some/other/path HTTP/1.0\r\n]
+    str.should =~ %r[Accept: \*/\*\r\n]
+    str.should =~ %r[Content-Type: text/html\r\n]
+    str[-4..-1].should == "\r\n\r\n"
+  end
+
+  describe "when a request body is set" do
+    ruby_version_is ""..."4.0" do
+      it "sets the 'Content-Type' header to 'application/x-www-form-urlencoded' unless the 'Content-Type' header is supplied" do
+        request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+        request.body = "Some Content"
+
+        request.exec(@buffered_socket, "1.1", "/some/other/path")
+        str = @socket.string
+
+        str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
+        str.should =~ %r[Accept: \*/\*\r\n]
+        str.should =~ %r[Content-Type: application/x-www-form-urlencoded\r\n]
+        str.should =~ %r[Content-Length: 12\r\n]
+        str[-16..-1].should == "\r\n\r\nSome Content"
+      end
+    end
+
+    it "correctly sets the 'Content-Length' header and includes the body" do
+      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
+                                            "Content-Type" => "text/html")
+      request.body = "Some Content"
+
+      request.exec(@buffered_socket, "1.1", "/some/other/path")
+      str = @socket.string
+
+      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
+      str.should =~ %r[Accept: \*/\*\r\n]
+      str.should =~ %r[Content-Type: text/html\r\n]
+      str.should =~ %r[Content-Length: 12\r\n]
+      str[-16..-1].should == "\r\n\r\nSome Content"
+    end
+  end
+
+  describe "when a body stream is set" do
+    ruby_version_is ""..."4.0" do
+      it "sets the 'Content-Type' header to 'application/x-www-form-urlencoded' unless the 'Content-Type' header is supplied" do
+        request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
+                                              "Content-Length" => "10")
+        request.body_stream = StringIO.new("a" * 20)
+
+        request.exec(@buffered_socket, "1.1", "/some/other/path")
+        str = @socket.string
+
+        str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
+        str.should =~ %r[Accept: \*/\*\r\n]
+        str.should =~ %r[Content-Type: application/x-www-form-urlencoded\r\n]
+        str.should =~ %r[Content-Length: 10\r\n]
+        str[-24..-1].should == "\r\n\r\naaaaaaaaaaaaaaaaaaaa"
+      end
+    end
+
+    it "sends the whole stream, regardless of the 'Content-Length' header" do
+      request = Net::HTTPGenericRequest.new("POST", true, true,"/some/path",
+                                            "Content-Type" => "text/html",
+                                            "Content-Length" => "10")
+      request.body_stream = StringIO.new("a" * 20)
+
+      request.exec(@buffered_socket, "1.1", "/some/other/path")
+      str = @socket.string
+
+      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
+      str.should =~ %r[Accept: \*/\*\r\n]
+      str.should =~ %r[Content-Type: text/html\r\n]
+      str.should =~ %r[Content-Length: 10\r\n]
+      str[-24..-1].should == "\r\n\r\naaaaaaaaaaaaaaaaaaaa"
+    end
+
+    it "sends the request in chunks when 'Transfer-Encoding' is set to 'chunked'" do
+      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
+                                            "Content-Type" => "text/html",
+                                            "Transfer-Encoding" => "chunked")
+      datasize = 1024 * 10
+      request.body_stream = StringIO.new("a" * datasize)
+
+      request.exec(@buffered_socket, "1.1", "/some/other/path")
+      str = @socket.string
+
+      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
+      str.should =~ %r[Accept: \*/\*\r\n]
+      str.should =~ %r[Content-Type: text/html\r\n]
+      str.should =~ %r[Transfer-Encoding: chunked\r\n]
+      str =~ %r[\r\n\r\n]
+      str = $'
+      while datasize > 0
+        chunk_size_line, str = str.split(/\r\n/, 2)
+        chunk_size = chunk_size_line[/\A[0-9A-Fa-f]+/].to_i(16)
+        str.slice!(0, chunk_size).should == 'a' * chunk_size
+        datasize -= chunk_size
+        str.slice!(0, 2).should == "\r\n"
+      end
+      datasize.should == 0
+      str.should == %"0\r\n\r\n"
+    end
+
+    it "raises an ArgumentError when the 'Content-Length' is not set or 'Transfer-Encoding' is not set to 'chunked'" do
+      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
+                                            "Content-Type" => "text/html")
+      request.body_stream = StringIO.new("Some Content")
+
+      -> { request.exec(@buffered_socket, "1.1", "/some/other/path") }.should raise_error(ArgumentError)
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/inspect_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/inspect_spec.rb
new file mode 100644
index 0000000000..d03b6e6953
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/inspect_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#inspect" do
+  it "returns a String representation of self" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.inspect.should == "#<Net::HTTPGenericRequest POST>"
+
+    request = Net::HTTPGenericRequest.new("GET", false, true, "/some/path")
+    request.inspect.should == "#<Net::HTTPGenericRequest GET>"
+
+    request = Net::HTTPGenericRequest.new("BLA", true, true, "/some/path")
+    request.inspect.should == "#<Net::HTTPGenericRequest BLA>"
+
+    # Subclasses
+    request = Net::HTTP::Get.new("/some/path")
+    request.inspect.should == "#<Net::HTTP::Get GET>"
+
+    request = Net::HTTP::Post.new("/some/path")
+    request.inspect.should == "#<Net::HTTP::Post POST>"
+
+    request = Net::HTTP::Trace.new("/some/path")
+    request.inspect.should == "#<Net::HTTP::Trace TRACE>"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/method_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/method_spec.rb
new file mode 100644
index 0000000000..794bd328cd
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/method_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#method" do
+  it "returns self's request method" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.method.should == "POST"
+
+    request = Net::HTTPGenericRequest.new("GET", false, true, "/some/path")
+    request.method.should == "GET"
+
+    request = Net::HTTPGenericRequest.new("BLA", true, true, "/some/path")
+    request.method.should == "BLA"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/path_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/path_spec.rb
new file mode 100644
index 0000000000..a9fac3f67e
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/path_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#path" do
+  it "returns self's request path" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.path.should == "/some/path"
+
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/other/path")
+    request.path.should == "/some/other/path"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/request_body_permitted_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/request_body_permitted_spec.rb
new file mode 100644
index 0000000000..1713b59baf
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/request_body_permitted_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#request_body_permitted?" do
+  it "returns true when the request is expected to have a body" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.request_body_permitted?.should be_true
+
+    request = Net::HTTPGenericRequest.new("POST", false, true, "/some/path")
+    request.request_body_permitted?.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/response_body_permitted_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/response_body_permitted_spec.rb
new file mode 100644
index 0000000000..2f0751c344
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/response_body_permitted_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#response_body_permitted?" do
+  it "returns true when the response is expected to have a body" do
+    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+    request.response_body_permitted?.should be_true
+
+    request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
+    request.response_body_permitted?.should be_false
+  end
+end
diff --git a/spec/ruby/library/net-http/httpgenericrequest/set_body_internal_spec.rb b/spec/ruby/library/net-http/httpgenericrequest/set_body_internal_spec.rb
new file mode 100644
index 0000000000..358aa6cde3
--- /dev/null
+++ b/spec/ruby/library/net-http/httpgenericrequest/set_body_internal_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPGenericRequest#set_body_internal when passed string" do
+  before :each do
+    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
+  end
+
+  it "sets self's body to the passed string" do
+    @request.set_body_internal("Some Content")
+    @request.body.should == "Some Content"
+  end
+
+  it "raises an ArgumentError when the body or body_stream of self have already been set" do
+    @request.body = "Some Content"
+    -> { @request.set_body_internal("Some other Content") }.should raise_error(ArgumentError)
+
+    @request.body_stream = "Some Content"
+    -> { @request.set_body_internal("Some other Content") }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/add_field_spec.rb b/spec/ruby/library/net-http/httpheader/add_field_spec.rb
new file mode 100644
index 0000000000..8cd3d33517
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/add_field_spec.rb
@@ -0,0 +1,31 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#add_field when passed key, value" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "adds the passed value to the header entry with the passed key" do
+    @headers.add_field("My-Header", "a")
+    @headers.get_fields("My-Header").should == ["a"]
+
+    @headers.add_field("My-Header", "b")
+    @headers.get_fields("My-Header").should == ["a", "b"]
+
+    @headers.add_field("My-Header", "c")
+    @headers.get_fields("My-Header").should == ["a", "b", "c"]
+  end
+
+  it "is case-insensitive" do
+    @headers.add_field("My-Header", "a")
+    @headers.get_fields("My-Header").should == ["a"]
+
+    @headers.add_field("my-header", "b")
+    @headers.get_fields("My-Header").should == ["a", "b"]
+
+    @headers.add_field("MY-HEADER", "c")
+    @headers.get_fields("My-Header").should == ["a", "b", "c"]
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/basic_auth_spec.rb b/spec/ruby/library/net-http/httpheader/basic_auth_spec.rb
new file mode 100644
index 0000000000..db7ca84d13
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/basic_auth_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#basic_auth when passed account, password" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "sets the 'Authorization' Header entry for basic authorization" do
+    @headers.basic_auth("rubyspec", "rocks")
+    @headers["Authorization"].should == "Basic cnVieXNwZWM6cm9ja3M="
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/canonical_each_spec.rb b/spec/ruby/library/net-http/httpheader/canonical_each_spec.rb
new file mode 100644
index 0000000000..64a5cae89e
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/canonical_each_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_capitalized'
+
+describe "Net::HTTPHeader#canonical_each" do
+  it_behaves_like :net_httpheader_each_capitalized, :canonical_each
+end
diff --git a/spec/ruby/library/net-http/httpheader/chunked_spec.rb b/spec/ruby/library/net-http/httpheader/chunked_spec.rb
new file mode 100644
index 0000000000..b32a0aab38
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/chunked_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#chunked?" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns true if the 'Transfer-Encoding' header entry is set to chunked" do
+    @headers.chunked?.should be_false
+
+    @headers["Transfer-Encoding"] = "bla"
+    @headers.chunked?.should be_false
+
+    @headers["Transfer-Encoding"] = "blachunkedbla"
+    @headers.chunked?.should be_false
+
+    @headers["Transfer-Encoding"] = "chunked"
+    @headers.chunked?.should be_true
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/content_length_spec.rb b/spec/ruby/library/net-http/httpheader/content_length_spec.rb
new file mode 100644
index 0000000000..f05c5f8d8b
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/content_length_spec.rb
@@ -0,0 +1,54 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#content_length" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns nil if no 'Content-Length' header entry is set" do
+    @headers.content_length.should be_nil
+  end
+
+  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Length' header entry has an invalid format" do
+    @headers["Content-Length"] = "invalid"
+    -> { @headers.content_length }.should raise_error(Net::HTTPHeaderSyntaxError)
+  end
+
+  it "returns the value of the 'Content-Length' header entry as an Integer" do
+    @headers["Content-Length"] = "123"
+    @headers.content_length.should eql(123)
+
+    @headers["Content-Length"] = "123valid"
+    @headers.content_length.should eql(123)
+
+    @headers["Content-Length"] = "valid123"
+    @headers.content_length.should eql(123)
+  end
+end
+
+describe "Net::HTTPHeader#content_length=" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "removes the 'Content-Length' entry if passed false or nil" do
+    @headers["Content-Length"] = "123"
+    @headers.content_length = nil
+    @headers["Content-Length"].should be_nil
+  end
+
+  it "sets the 'Content-Length' entry to the passed value" do
+    @headers.content_length = "123"
+    @headers["Content-Length"].should == "123"
+
+    @headers.content_length = "123valid"
+    @headers["Content-Length"].should == "123"
+  end
+
+  it "sets the 'Content-Length' entry to 0 if the passed value is not valid" do
+    @headers.content_length = "invalid123"
+    @headers["Content-Length"].should == "0"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/content_range_spec.rb b/spec/ruby/library/net-http/httpheader/content_range_spec.rb
new file mode 100644
index 0000000000..09737141a5
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/content_range_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#content_range" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns a Range object that represents the 'Content-Range' header entry" do
+    @headers["Content-Range"] = "bytes 0-499/1234"
+    @headers.content_range.should == (0..499)
+
+    @headers["Content-Range"] = "bytes 500-1233/1234"
+    @headers.content_range.should == (500..1233)
+  end
+
+  it "returns nil when there is no 'Content-Range' header entry" do
+    @headers.content_range.should be_nil
+  end
+
+  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Range' has an invalid format" do
+    @headers["Content-Range"] = "invalid"
+    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Content-Range"] = "bytes 123-abc"
+    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Content-Range"] = "bytes abc-123"
+    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/content_type_spec.rb b/spec/ruby/library/net-http/httpheader/content_type_spec.rb
new file mode 100644
index 0000000000..a6e1ae1093
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/content_type_spec.rb
@@ -0,0 +1,26 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_content_type'
+
+describe "Net::HTTPHeader#content_type" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns the content type string, as per 'Content-Type' header entry" do
+    @headers["Content-Type"] = "text/html"
+    @headers.content_type.should == "text/html"
+
+    @headers["Content-Type"] = "text/html;charset=utf-8"
+    @headers.content_type.should == "text/html"
+  end
+
+  it "returns nil if the 'Content-Type' header entry does not exist" do
+    @headers.content_type.should be_nil
+  end
+end
+
+describe "Net::HTTPHeader#content_type=" do
+  it_behaves_like :net_httpheader_set_content_type, :content_type=
+end
diff --git a/spec/ruby/library/net-http/httpheader/delete_spec.rb b/spec/ruby/library/net-http/httpheader/delete_spec.rb
new file mode 100644
index 0000000000..8d929dbd86
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/delete_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#delete when passed key" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "removes the header entry with the passed key" do
+    @headers["My-Header"] = "test"
+    @headers.delete("My-Header")
+
+    @headers["My-Header"].should be_nil
+    @headers.size.should eql(0)
+  end
+
+  it "returns the removed values" do
+    @headers["My-Header"] = "test"
+    @headers.delete("My-Header").should == ["test"]
+  end
+
+  it "is case-insensitive" do
+    @headers["My-Header"] = "test"
+    @headers.delete("my-header")
+
+    @headers["My-Header"].should be_nil
+    @headers.size.should eql(0)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_capitalized_name_spec.rb b/spec/ruby/library/net-http/httpheader/each_capitalized_name_spec.rb
new file mode 100644
index 0000000000..27713577f9
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_capitalized_name_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#each_capitalized_name" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+    @headers["My-Header"] = "test"
+    @headers.add_field("My-Other-Header", "a")
+    @headers.add_field("My-Other-Header", "b")
+  end
+
+  describe "when passed a block" do
+    it "yields each header key to the passed block (keys capitalized)" do
+      res = []
+      @headers.each_capitalized_name do |key|
+        res << key
+      end
+      res.sort.should == ["My-Header", "My-Other-Header"]
+    end
+  end
+
+  describe "when passed no block" do
+    it "returns an Enumerator" do
+      enumerator = @headers.each_capitalized_name
+      enumerator.should be_an_instance_of(Enumerator)
+
+      res = []
+      enumerator.each do |key|
+        res << key
+      end
+      res.sort.should == ["My-Header", "My-Other-Header"]
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_capitalized_spec.rb b/spec/ruby/library/net-http/httpheader/each_capitalized_spec.rb
new file mode 100644
index 0000000000..1e853995ea
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_capitalized_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_capitalized'
+
+describe "Net::HTTPHeader#each_capitalized" do
+  it_behaves_like :net_httpheader_each_capitalized, :each_capitalized
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_header_spec.rb b/spec/ruby/library/net-http/httpheader/each_header_spec.rb
new file mode 100644
index 0000000000..869feebacf
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_header_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_header'
+
+describe "Net::HTTPHeader#each_header" do
+  it_behaves_like :net_httpheader_each_header, :each_header
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_key_spec.rb b/spec/ruby/library/net-http/httpheader/each_key_spec.rb
new file mode 100644
index 0000000000..1ad145629f
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_key_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_name'
+
+describe "Net::HTTPHeader#each_key" do
+  it_behaves_like :net_httpheader_each_name, :each_key
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_name_spec.rb b/spec/ruby/library/net-http/httpheader/each_name_spec.rb
new file mode 100644
index 0000000000..f819bd989d
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_name_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_name'
+
+describe "Net::HTTPHeader#each_name" do
+  it_behaves_like :net_httpheader_each_name, :each_name
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_spec.rb b/spec/ruby/library/net-http/httpheader/each_spec.rb
new file mode 100644
index 0000000000..ff37249d0a
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/each_header'
+
+describe "Net::HTTPHeader#each" do
+  it_behaves_like :net_httpheader_each_header, :each
+end
diff --git a/spec/ruby/library/net-http/httpheader/each_value_spec.rb b/spec/ruby/library/net-http/httpheader/each_value_spec.rb
new file mode 100644
index 0000000000..b71df58c65
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/each_value_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#each_value" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+    @headers["My-Header"] = "test"
+    @headers.add_field("My-Other-Header", "a")
+    @headers.add_field("My-Other-Header", "b")
+  end
+
+  describe "when passed a block" do
+    it "yields each header entry's joined values" do
+      res = []
+      @headers.each_value do |value|
+        res << value
+      end
+      res.sort.should == ["a, b", "test"]
+    end
+  end
+
+  describe "when passed no block" do
+    it "returns an Enumerator" do
+      enumerator = @headers.each_value
+      enumerator.should be_an_instance_of(Enumerator)
+
+      res = []
+      enumerator.each do |key|
+        res << key
+      end
+      res.sort.should == ["a, b", "test"]
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/element_reference_spec.rb b/spec/ruby/library/net-http/httpheader/element_reference_spec.rb
new file mode 100644
index 0000000000..1003c41af9
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/element_reference_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#[] when passed key" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns the value of the header entry with the passed key" do
+    @headers["My-Header"] = "test"
+    @headers["My-Header"].should == "test"
+    @headers["My-Other-Header"] = "another test"
+    @headers["My-Other-Header"].should == "another test"
+  end
+
+  it "is case-insensitive" do
+    @headers["My-Header"] = "test"
+
+    @headers['My-Header'].should == "test"
+    @headers['my-Header'].should == "test"
+    @headers['My-header'].should == "test"
+    @headers['my-header'].should == "test"
+    @headers['MY-HEADER'].should == "test"
+  end
+
+  it "returns multi-element values joined together" do
+    @headers["My-Header"] = "test"
+    @headers.add_field("My-Header", "another test")
+    @headers.add_field("My-Header", "and one more")
+
+    @headers["My-Header"].should == "test, another test, and one more"
+  end
+
+  it "returns nil for non-existing entries" do
+    @headers["My-Header"].should be_nil
+    @headers["My-Other-Header"].should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/element_set_spec.rb b/spec/ruby/library/net-http/httpheader/element_set_spec.rb
new file mode 100644
index 0000000000..376df2f977
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/element_set_spec.rb
@@ -0,0 +1,41 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#[]= when passed key, value" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "sets the header entry with the passed key to the passed value" do
+    @headers["My-Header"] = "test"
+    @headers["My-Header"].should == "test"
+
+    @headers["My-Header"] = "overwritten"
+    @headers["My-Header"].should == "overwritten"
+
+    @headers["My-Other-Header"] = "another test"
+    @headers["My-Other-Header"].should == "another test"
+  end
+
+  it "is case-insensitive" do
+    @headers['My-Header'] = "test"
+    @headers['my-Header'] = "another test"
+    @headers['My-header'] = "and one more test"
+    @headers['my-header'] = "and another one"
+    @headers['MY-HEADER'] = "last one"
+
+    @headers["My-Header"].should == "last one"
+    @headers.size.should eql(1)
+  end
+
+  it "removes the header entry with the passed key when the value is false or nil" do
+    @headers['My-Header'] = "test"
+    @headers['My-Header'] = nil
+    @headers['My-Header'].should be_nil
+
+    @headers['My-Header'] = "test"
+    @headers['My-Header'] = false
+    @headers['My-Header'].should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/fetch_spec.rb b/spec/ruby/library/net-http/httpheader/fetch_spec.rb
new file mode 100644
index 0000000000..58c69c0377
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/fetch_spec.rb
@@ -0,0 +1,68 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#fetch" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  describe "when passed key" do
+    it "returns the header entry for the passed key" do
+      @headers["My-Header"] = "test"
+      @headers.fetch("My-Header").should == "test"
+
+      @headers.add_field("My-Other-Header", "a")
+      @headers.add_field("My-Other-Header", "b")
+      @headers.add_field("My-Other-Header", "c")
+      @headers.fetch("My-Other-Header").should == "a, b, c"
+    end
+
+    it "is case-insensitive" do
+      @headers["My-Header"] = "test"
+      @headers.fetch("my-header").should == "test"
+      @headers.fetch("MY-HEADER").should == "test"
+    end
+
+    it "returns nil when there is no entry for the passed key" do
+      -> { @headers.fetch("my-header") }.should raise_error(IndexError)
+    end
+  end
+
+  describe "when passed key, default" do
+    it "returns the header entry for the passed key" do
+      @headers["My-Header"] = "test"
+      @headers.fetch("My-Header", "bla").should == "test"
+
+      @headers.add_field("My-Other-Header", "a")
+      @headers.add_field("My-Other-Header", "b")
+      @headers.add_field("My-Other-Header", "c")
+      @headers.fetch("My-Other-Header", "bla").should == "a, b, c"
+    end
+
+    # TODO: This raises a NoMethodError: undefined method `join' for "bla":String
+    it "returns the default value when there is no entry for the passed key" do
+      @headers.fetch("My-Header", "bla").should == "bla"
+    end
+  end
+
+  describe "when passed key and block" do
+    it "returns the header entry for the passed key" do
+      @headers["My-Header"] = "test"
+      @headers.fetch("My-Header") {}.should == "test"
+
+      @headers.add_field("My-Other-Header", "a")
+      @headers.add_field("My-Other-Header", "b")
+      @headers.add_field("My-Other-Header", "c")
+      -> {
+        @result = @headers.fetch("My-Other-Header", "bla") {}
+      }.should complain(/block supersedes default value argument/)
+      @result.should == "a, b, c"
+    end
+
+    # TODO: This raises a NoMethodError: undefined method `join' for "redaeh-ym":String
+    it "yieldsand returns the block's return value when there is no entry for the passed key" do
+      @headers.fetch("My-Header") { |key| key.reverse }.should == "redaeh-ym"
+    end
+  end
+end
diff --git a/spec/ruby/library/net/http/httpheader/fixtures/classes.rb b/spec/ruby/library/net-http/httpheader/fixtures/classes.rb
index b5ec6abd75..b5ec6abd75 100644
--- a/spec/ruby/library/net/http/httpheader/fixtures/classes.rb
+++ b/spec/ruby/library/net-http/httpheader/fixtures/classes.rb
diff --git a/spec/ruby/library/net-http/httpheader/form_data_spec.rb b/spec/ruby/library/net-http/httpheader/form_data_spec.rb
new file mode 100644
index 0000000000..acd913f53a
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/form_data_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_form_data'
+
+describe "Net::HTTPHeader#form_data=" do
+  it_behaves_like :net_httpheader_set_form_data, :form_data=
+end
diff --git a/spec/ruby/library/net-http/httpheader/get_fields_spec.rb b/spec/ruby/library/net-http/httpheader/get_fields_spec.rb
new file mode 100644
index 0000000000..0278bcede2
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/get_fields_spec.rb
@@ -0,0 +1,39 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#get_fields when passed key" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns an Array containing the values of the header entry with the passed key" do
+    @headers["My-Header"] = "a"
+    @headers.get_fields("My-Header").should == ["a"]
+
+    @headers.add_field("My-Header", "b")
+    @headers.get_fields("My-Header").should == ["a", "b"]
+  end
+
+  it "returns a copy of the header entry values" do
+    @headers["My-Header"] = "a"
+
+    @headers.get_fields("My-Header").clear
+    @headers.get_fields("My-Header").should == ["a"]
+
+    @headers.get_fields("My-Header") << "b"
+    @headers.get_fields("My-Header").should == ["a"]
+  end
+
+  it "returns nil for non-existing header entries" do
+    @headers.get_fields("My-Header").should be_nil
+    @headers.get_fields("My-Other-header").should be_nil
+  end
+
+  it "is case-insensitive" do
+    @headers["My-Header"] = "test"
+    @headers.get_fields("My-Header").should == ["test"]
+    @headers.get_fields("my-header").should == ["test"]
+    @headers.get_fields("MY-HEADER").should == ["test"]
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/initialize_http_header_spec.rb b/spec/ruby/library/net-http/httpheader/initialize_http_header_spec.rb
new file mode 100644
index 0000000000..f9e6d208e5
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/initialize_http_header_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#initialize_http_header when passed Hash" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.allocate
+  end
+
+  it "initializes the HTTP Header using the passed Hash" do
+    @headers.initialize_http_header("My-Header" => "test", "My-Other-Header" => "another test")
+    @headers["My-Header"].should == "test"
+    @headers["My-Other-Header"].should == "another test"
+  end
+
+  it "complains about duplicate keys when in verbose mode" do
+    -> do
+      @headers.initialize_http_header("My-Header" => "test", "my-header" => "another test")
+    end.should complain(/duplicated HTTP header/, verbose: true)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/key_spec.rb b/spec/ruby/library/net-http/httpheader/key_spec.rb
new file mode 100644
index 0000000000..2b7aeb9c2a
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/key_spec.rb
@@ -0,0 +1,21 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#key? when passed key" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns true if the header entry with the passed key exists" do
+    @headers.key?("My-Header").should be_false
+    @headers["My-Header"] = "test"
+    @headers.key?("My-Header").should be_true
+  end
+
+  it "is case-insensitive" do
+    @headers["My-Header"] = "test"
+    @headers.key?("my-header").should be_true
+    @headers.key?("MY-HEADER").should be_true
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/length_spec.rb b/spec/ruby/library/net-http/httpheader/length_spec.rb
new file mode 100644
index 0000000000..57e32742e4
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/length_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/size'
+
+describe "Net::HTTPHeader#length" do
+  it_behaves_like :net_httpheader_size, :length
+end
diff --git a/spec/ruby/library/net-http/httpheader/main_type_spec.rb b/spec/ruby/library/net-http/httpheader/main_type_spec.rb
new file mode 100644
index 0000000000..4dd551d8f4
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/main_type_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#main_type" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns the 'main-content-type', as per 'Content-Type' header entry" do
+    @headers["Content-Type"] = "text/html"
+    @headers.main_type.should == "text"
+
+    @headers["Content-Type"] = "application/pdf"
+    @headers.main_type.should == "application"
+
+    @headers["Content-Type"] = "text/html;charset=utf-8"
+    @headers.main_type.should == "text"
+  end
+
+  it "returns nil if the 'Content-Type' header entry does not exist" do
+    @headers.main_type.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/proxy_basic_auth_spec.rb b/spec/ruby/library/net-http/httpheader/proxy_basic_auth_spec.rb
new file mode 100644
index 0000000000..d9f6afc5a7
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/proxy_basic_auth_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#proxy_basic_auth when passed account, password" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "sets the 'Proxy-Authorization' Header entry for basic authorization" do
+    @headers.proxy_basic_auth("rubyspec", "rocks")
+    @headers["Proxy-Authorization"].should == "Basic cnVieXNwZWM6cm9ja3M="
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/range_length_spec.rb b/spec/ruby/library/net-http/httpheader/range_length_spec.rb
new file mode 100644
index 0000000000..77323ac872
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/range_length_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#range_length" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns the length of the Range represented by the 'Content-Range' header entry" do
+    @headers["Content-Range"] = "bytes 0-499/1234"
+    @headers.range_length.should eql(500)
+
+    @headers["Content-Range"] = "bytes 500-1233/1234"
+    @headers.range_length.should eql(734)
+  end
+
+  it "returns nil when there is no 'Content-Range' header entry" do
+    @headers.range_length.should be_nil
+  end
+
+  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Range' has an invalid format" do
+    @headers["Content-Range"] = "invalid"
+    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Content-Range"] = "bytes 123-abc"
+    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Content-Range"] = "bytes abc-123"
+    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/range_spec.rb b/spec/ruby/library/net-http/httpheader/range_spec.rb
new file mode 100644
index 0000000000..2de80a825e
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/range_spec.rb
@@ -0,0 +1,48 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_range'
+
+describe "Net::HTTPHeader#range" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns a Range object that represents the 'Range' header entry" do
+    @headers["Range"] = "bytes=0-499"
+    @headers.range.should == [0..499]
+
+    @headers["Range"] = "bytes=500-1233"
+    @headers.range.should == [500..1233]
+
+    @headers["Range"] = "bytes=10-"
+    @headers.range.should == [10..-1]
+
+    @headers["Range"] = "bytes=-10"
+    @headers.range.should == [-10..-1]
+  end
+
+  it "returns nil when there is no 'Range' header entry" do
+    @headers.range.should be_nil
+  end
+
+  it "raises a Net::HTTPHeaderSyntaxError when the 'Range' has an invalid format" do
+    @headers["Range"] = "invalid"
+    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Range"] = "bytes 123-abc"
+    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
+
+    @headers["Range"] = "bytes abc-123"
+    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
+  end
+
+  it "raises a Net::HTTPHeaderSyntaxError when the 'Range' was not specified" do
+    @headers["Range"] = "bytes=-"
+    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
+  end
+end
+
+describe "Net::HTTPHeader#range=" do
+  it_behaves_like :net_httpheader_set_range, :range=
+end
diff --git a/spec/ruby/library/net-http/httpheader/set_content_type_spec.rb b/spec/ruby/library/net-http/httpheader/set_content_type_spec.rb
new file mode 100644
index 0000000000..7ec4f90b8e
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/set_content_type_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_content_type'
+
+describe "Net::HTTPHeader#set_content_type" do
+  it_behaves_like :net_httpheader_set_content_type, :set_content_type
+end
diff --git a/spec/ruby/library/net-http/httpheader/set_form_data_spec.rb b/spec/ruby/library/net-http/httpheader/set_form_data_spec.rb
new file mode 100644
index 0000000000..7aac19f045
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/set_form_data_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_form_data'
+
+describe "Net::HTTPHeader#set_form_data" do
+  it_behaves_like :net_httpheader_set_form_data, :set_form_data
+end
diff --git a/spec/ruby/library/net-http/httpheader/set_range_spec.rb b/spec/ruby/library/net-http/httpheader/set_range_spec.rb
new file mode 100644
index 0000000000..0f98de55e6
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/set_range_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/set_range'
+
+describe "Net::HTTPHeader#set_range" do
+  it_behaves_like :net_httpheader_set_range, :set_range
+end
diff --git a/spec/ruby/library/net/http/httpheader/shared/each_capitalized.rb b/spec/ruby/library/net-http/httpheader/shared/each_capitalized.rb
index 3bac409876..3bac409876 100644
--- a/spec/ruby/library/net/http/httpheader/shared/each_capitalized.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/each_capitalized.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/each_header.rb b/spec/ruby/library/net-http/httpheader/shared/each_header.rb
index 6bf3a6ddfe..6bf3a6ddfe 100644
--- a/spec/ruby/library/net/http/httpheader/shared/each_header.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/each_header.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/each_name.rb b/spec/ruby/library/net-http/httpheader/shared/each_name.rb
index efc6a09dfd..efc6a09dfd 100644
--- a/spec/ruby/library/net/http/httpheader/shared/each_name.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/each_name.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/set_content_type.rb b/spec/ruby/library/net-http/httpheader/shared/set_content_type.rb
index b7359bdca6..b7359bdca6 100644
--- a/spec/ruby/library/net/http/httpheader/shared/set_content_type.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/set_content_type.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/set_form_data.rb b/spec/ruby/library/net-http/httpheader/shared/set_form_data.rb
index db20b18803..db20b18803 100644
--- a/spec/ruby/library/net/http/httpheader/shared/set_form_data.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/set_form_data.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/set_range.rb b/spec/ruby/library/net-http/httpheader/shared/set_range.rb
index 87f51d46f3..87f51d46f3 100644
--- a/spec/ruby/library/net/http/httpheader/shared/set_range.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/set_range.rb
diff --git a/spec/ruby/library/net/http/httpheader/shared/size.rb b/spec/ruby/library/net-http/httpheader/shared/size.rb
index e2b1e4c22b..e2b1e4c22b 100644
--- a/spec/ruby/library/net/http/httpheader/shared/size.rb
+++ b/spec/ruby/library/net-http/httpheader/shared/size.rb
diff --git a/spec/ruby/library/net-http/httpheader/size_spec.rb b/spec/ruby/library/net-http/httpheader/size_spec.rb
new file mode 100644
index 0000000000..210060ce21
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/size_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+require_relative 'shared/size'
+
+describe "Net::HTTPHeader#size" do
+  it_behaves_like :net_httpheader_size, :size
+end
diff --git a/spec/ruby/library/net-http/httpheader/sub_type_spec.rb b/spec/ruby/library/net-http/httpheader/sub_type_spec.rb
new file mode 100644
index 0000000000..b39b57fe8d
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/sub_type_spec.rb
@@ -0,0 +1,32 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#sub_type" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns the 'sub-content-type', as per 'Content-Type' header entry" do
+    @headers["Content-Type"] = "text/html"
+    @headers.sub_type.should == "html"
+
+    @headers["Content-Type"] = "application/pdf"
+    @headers.sub_type.should == "pdf"
+
+    @headers["Content-Type"] = "text/html;charset=utf-8"
+    @headers.sub_type.should == "html"
+  end
+
+  it "returns nil if no 'sub-content-type' is set" do
+    @headers["Content-Type"] = "text"
+    @headers.sub_type.should be_nil
+
+    @headers["Content-Type"] = "text;charset=utf-8"
+    @headers.sub_type.should be_nil
+  end
+
+  it "returns nil if the 'Content-Type' header entry does not exist" do
+    @headers.sub_type.should be_nil
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/to_hash_spec.rb b/spec/ruby/library/net-http/httpheader/to_hash_spec.rb
new file mode 100644
index 0000000000..3cebc519a6
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/to_hash_spec.rb
@@ -0,0 +1,25 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#to_hash" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns a Hash representing all Header entries (keys in lower case, values as arrays)" do
+    @headers.to_hash.should == {}
+
+    @headers["My-Header"] = "test"
+    @headers.to_hash.should == { "my-header" => ["test"] }
+
+    @headers.add_field("My-Header", "another test")
+    @headers.to_hash.should == { "my-header" => ["test", "another test"] }
+  end
+
+  it "does not allow modifying the headers from the returned hash" do
+    @headers.to_hash["my-header"] = ["test"]
+    @headers.to_hash.should == {}
+    @headers.key?("my-header").should be_false
+  end
+end
diff --git a/spec/ruby/library/net-http/httpheader/type_params_spec.rb b/spec/ruby/library/net-http/httpheader/type_params_spec.rb
new file mode 100644
index 0000000000..ac97e2b48c
--- /dev/null
+++ b/spec/ruby/library/net-http/httpheader/type_params_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'fixtures/classes'
+
+describe "Net::HTTPHeader#type_params" do
+  before :each do
+    @headers = NetHTTPHeaderSpecs::Example.new
+  end
+
+  it "returns additional 'Content-Type' information as a Hash" do
+    @headers["Content-Type"] = "text/html;charset=utf-8"
+    @headers.type_params.should == {"charset" => "utf-8"}
+
+    @headers["Content-Type"] = "text/html; charset=utf-8; rubyspec=rocks"
+    @headers.type_params.should == {"charset" => "utf-8", "rubyspec" => "rocks"}
+  end
+
+  it "returns an empty Hash when no additional 'Content-Type' information is set" do
+    @headers.type_params.should == {}
+
+    @headers["Content-Type"] = "text/html"
+    @headers.type_params.should == {}
+  end
+end
diff --git a/spec/ruby/library/net-http/httprequest/initialize_spec.rb b/spec/ruby/library/net-http/httprequest/initialize_spec.rb
new file mode 100644
index 0000000000..d009a00ed2
--- /dev/null
+++ b/spec/ruby/library/net-http/httprequest/initialize_spec.rb
@@ -0,0 +1,45 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+module NetHTTPRequestSpecs
+  class TestRequest < Net::HTTPRequest
+    METHOD = "TEST"
+    REQUEST_HAS_BODY  = false
+    RESPONSE_HAS_BODY = true
+  end
+end
+
+describe "Net::HTTPRequest#initialize" do
+  before :each do
+    @req = NetHTTPRequestSpecs::TestRequest.allocate
+  end
+
+  it "uses the METHOD constants to set the request method" do
+    @req.send(:initialize, "/some/path")
+    @req.method.should == "TEST"
+  end
+
+  it "uses the REQUEST_HAS_BODY to set whether the Request has a body or not" do
+    @req.send(:initialize, "/some/path")
+    @req.request_body_permitted?.should be_false
+  end
+
+  it "uses the RESPONSE_HAS_BODY to set whether the Response can have a body or not" do
+    @req.send(:initialize, "/some/path")
+    @req.response_body_permitted?.should be_true
+  end
+
+  describe "when passed path" do
+    it "sets self's path to the passed path" do
+      @req.send(:initialize, "/some/path")
+      @req.path.should == "/some/path"
+    end
+  end
+
+  describe "when passed path, headers" do
+    it "uses the passed headers Hash to initialize self's header entries" do
+      @req.send(:initialize, "/some/path", "Content-Type" => "text/html")
+      @req["Content-Type"].should == "text/html"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/body_permitted_spec.rb b/spec/ruby/library/net-http/httpresponse/body_permitted_spec.rb
new file mode 100644
index 0000000000..68965de4a1
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/body_permitted_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse.body_permitted?" do
+  it "returns true if this response type can have a response body" do
+    Net::HTTPUnknownResponse.should.body_permitted?
+    Net::HTTPInformation.should_not.body_permitted?
+    Net::HTTPSuccess.should.body_permitted?
+    Net::HTTPRedirection.should.body_permitted?
+    Net::HTTPClientError.should.body_permitted?
+    Net::HTTPServerError.should.body_permitted?
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/body_spec.rb b/spec/ruby/library/net-http/httpresponse/body_spec.rb
new file mode 100644
index 0000000000..ddfcd834c4
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/body_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/body'
+
+describe "Net::HTTPResponse#body" do
+  it_behaves_like :net_httpresponse_body, :body
+end
diff --git a/spec/ruby/library/net-http/httpresponse/code_spec.rb b/spec/ruby/library/net-http/httpresponse/code_spec.rb
new file mode 100644
index 0000000000..699062ad97
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/code_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#code" do
+  it "returns the result code string" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.code.should == "???"
+
+    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
+    res.code.should == "1xx"
+
+    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
+    res.code.should == "2xx"
+
+    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
+    res.code.should == "3xx"
+
+    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
+    res.code.should == "4xx"
+
+    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
+    res.code.should == "5xx"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/code_type_spec.rb b/spec/ruby/library/net-http/httpresponse/code_type_spec.rb
new file mode 100644
index 0000000000..beb661cbbe
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/code_type_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#code_type" do
+  it "returns self's class" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.code_type.should == Net::HTTPUnknownResponse
+
+    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
+    res.code_type.should == Net::HTTPInformation
+
+    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
+    res.code_type.should == Net::HTTPSuccess
+
+    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
+    res.code_type.should == Net::HTTPRedirection
+
+    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
+    res.code_type.should == Net::HTTPClientError
+
+    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
+    res.code_type.should == Net::HTTPServerError
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/entity_spec.rb b/spec/ruby/library/net-http/httpresponse/entity_spec.rb
new file mode 100644
index 0000000000..ca8c4b29c0
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/entity_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require_relative 'shared/body'
+
+describe "Net::HTTPResponse#entity" do
+  it_behaves_like :net_httpresponse_body, :entity
+end
diff --git a/spec/ruby/library/net-http/httpresponse/error_spec.rb b/spec/ruby/library/net-http/httpresponse/error_spec.rb
new file mode 100644
index 0000000000..6ced90fa23
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/error_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#error!" do
+  it "raises self's class 'EXCEPTION_TYPE' Exception" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPError)
+
+    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPError)
+
+    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPError)
+
+    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPRetriableError)
+
+    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPClientException)
+
+    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
+    -> { res.error! }.should raise_error(Net::HTTPFatalError)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/error_type_spec.rb b/spec/ruby/library/net-http/httpresponse/error_type_spec.rb
new file mode 100644
index 0000000000..3969621a5e
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/error_type_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#error_type" do
+  it "returns self's class 'EXCEPTION_TYPE' constant" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.error_type.should == Net::HTTPError
+
+    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
+    res.error_type.should == Net::HTTPError
+
+    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
+    res.error_type.should == Net::HTTPError
+
+    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
+    res.error_type.should == Net::HTTPRetriableError
+
+    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
+    res.error_type.should == Net::HTTPClientException
+
+    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
+    res.error_type.should == Net::HTTPFatalError
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/exception_type_spec.rb b/spec/ruby/library/net-http/httpresponse/exception_type_spec.rb
new file mode 100644
index 0000000000..dd2761a744
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/exception_type_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse.exception_type" do
+  it "returns self's 'EXCEPTION_TYPE' constant" do
+    Net::HTTPUnknownResponse.exception_type.should == Net::HTTPError
+    Net::HTTPInformation.exception_type.should == Net::HTTPError
+    Net::HTTPSuccess.exception_type.should == Net::HTTPError
+    Net::HTTPRedirection.exception_type.should == Net::HTTPRetriableError
+    Net::HTTPClientError.exception_type.should == Net::HTTPClientException
+    Net::HTTPServerError.exception_type.should == Net::HTTPFatalError
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/header_spec.rb b/spec/ruby/library/net-http/httpresponse/header_spec.rb
new file mode 100644
index 0000000000..a403dbd2c3
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/header_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#header" do
+  it "returns self" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.response.should equal(res)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/http_version_spec.rb b/spec/ruby/library/net-http/httpresponse/http_version_spec.rb
new file mode 100644
index 0000000000..a3e413a360
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/http_version_spec.rb
@@ -0,0 +1,12 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#http_version" do
+  it "returns self's http version" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.http_version.should == "1.0"
+
+    res = Net::HTTPUnknownResponse.new("1.1", "???", "test response")
+    res.http_version.should == "1.1"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/initialize_spec.rb b/spec/ruby/library/net-http/httpresponse/initialize_spec.rb
new file mode 100644
index 0000000000..673c11a245
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/initialize_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#initialize when passed http_version, response_code, response_message" do
+  it "sets self http_version, response_code and response_message to the passed values" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.http_version.should == "1.0"
+    res.code.should == "???"
+    res.message.should == "test response"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/inspect_spec.rb b/spec/ruby/library/net-http/httpresponse/inspect_spec.rb
new file mode 100644
index 0000000000..43071ec8cd
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/inspect_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+
+describe "Net::HTTPResponse#inspect" do
+  it "returns a String representation of self" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=false>"
+
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    socket = Net::BufferedIO.new(StringIO.new("test body"))
+    res.reading_body(socket, true) {}
+    res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=true>"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/message_spec.rb b/spec/ruby/library/net-http/httpresponse/message_spec.rb
new file mode 100644
index 0000000000..5ba73bb449
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/message_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#message" do
+  it "returns self's response message" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.message.should == "test response"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/msg_spec.rb b/spec/ruby/library/net-http/httpresponse/msg_spec.rb
new file mode 100644
index 0000000000..04f5836d7a
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/msg_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#msg" do
+  it "returns self's response message" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.message.should == "test response"
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/read_body_spec.rb b/spec/ruby/library/net-http/httpresponse/read_body_spec.rb
new file mode 100644
index 0000000000..4530a26bfc
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/read_body_spec.rb
@@ -0,0 +1,86 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require 'stringio'
+
+describe "Net::HTTPResponse#read_body" do
+  before :each do
+    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    @socket = Net::BufferedIO.new(StringIO.new("test body"))
+  end
+
+  describe "when passed no arguments" do
+    it "returns the read body" do
+      @res.reading_body(@socket, true) do
+        @res.read_body.should == "test body"
+      end
+    end
+
+    it "returns the previously read body if called a second time" do
+      @res.reading_body(@socket, true) do
+        @res.read_body.should equal(@res.read_body)
+      end
+    end
+  end
+
+  describe "when passed a buffer" do
+    it "reads the body to the passed buffer" do
+      @res.reading_body(@socket, true) do
+        buffer = +""
+        @res.read_body(buffer)
+        buffer.should == "test body"
+      end
+    end
+
+    it "returns the passed buffer" do
+      @res.reading_body(@socket, true) do
+        buffer = +""
+        @res.read_body(buffer).should equal(buffer)
+      end
+    end
+
+    it "raises an IOError if called a second time" do
+      @res.reading_body(@socket, true) do
+        @res.read_body(+"")
+        -> { @res.read_body(+"") }.should raise_error(IOError)
+      end
+    end
+  end
+
+  describe "when passed a block" do
+    it "reads the body and yields it to the passed block (in chunks)" do
+      @res.reading_body(@socket, true) do
+        yielded = false
+
+        buffer = +""
+        @res.read_body do |body|
+          yielded = true
+          buffer << body
+        end
+
+        yielded.should be_true
+        buffer.should == "test body"
+      end
+    end
+
+    it "returns the ReadAdapter" do
+      @res.reading_body(@socket, true) do
+        @res.read_body { nil }.should be_kind_of(Net::ReadAdapter)
+      end
+    end
+
+    it "raises an IOError if called a second time" do
+      @res.reading_body(@socket, true) do
+        @res.read_body {}
+        -> { @res.read_body {} }.should raise_error(IOError)
+      end
+    end
+  end
+
+  describe "when passed buffer and block" do
+    it "raises an ArgumentError" do
+      @res.reading_body(@socket, true) do
+        -> { @res.read_body(+"") {} }.should raise_error(ArgumentError)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/read_header_spec.rb b/spec/ruby/library/net-http/httpresponse/read_header_spec.rb
new file mode 100644
index 0000000000..3ea4ee834b
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/read_header_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#read_header" do
+  it "returns self" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.response.should equal(res)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/read_new_spec.rb b/spec/ruby/library/net-http/httpresponse/read_new_spec.rb
new file mode 100644
index 0000000000..82f7a47ce8
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/read_new_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require 'stringio'
+
+describe "Net::HTTPResponse.read_new" do
+  it "creates a HTTPResponse object based on the response read from the passed socket" do
+    socket = Net::BufferedIO.new(StringIO.new(<<EOS))
+HTTP/1.1 200 OK
+Content-Type: text/html; charset=utf-8
+
+test-body
+EOS
+    response = Net::HTTPResponse.read_new(socket)
+
+    response.should be_kind_of(Net::HTTPOK)
+    response.code.should == "200"
+    response["Content-Type"].should == "text/html; charset=utf-8"
+
+    response.reading_body(socket, true) do
+      response.body.should == "test-body\n"
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/reading_body_spec.rb b/spec/ruby/library/net-http/httpresponse/reading_body_spec.rb
new file mode 100644
index 0000000000..637a2806f8
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/reading_body_spec.rb
@@ -0,0 +1,58 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+require "stringio"
+
+describe "Net::HTTPResponse#reading_body" do
+  before :each do
+    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    @socket = Net::BufferedIO.new(StringIO.new("test body"))
+  end
+
+  describe "when body_allowed is true" do
+    it "reads and returns the response body for self from the passed socket" do
+      @res.reading_body(@socket, true) {}.should == "test body"
+      @res.body.should == "test body"
+    end
+
+    it "yields the passed block before reading the body" do
+      yielded = false
+
+      @res.reading_body(@socket, true) do
+        @res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=false>"
+        yielded = true
+      end
+
+      yielded.should be_true
+    end
+
+    describe "but the response type is not allowed to have a body" do
+      before :each do
+        @res = Net::HTTPInformation.new("1.0", "???", "test response")
+      end
+
+      it "returns nil" do
+        @res.reading_body(@socket, false) {}.should be_nil
+        @res.body.should be_nil
+      end
+
+      it "yields the passed block" do
+        yielded = false
+        @res.reading_body(@socket, true) { yielded = true }
+        yielded.should be_true
+      end
+    end
+  end
+
+  describe "when body_allowed is false" do
+    it "returns nil" do
+      @res.reading_body(@socket, false) {}.should be_nil
+      @res.body.should be_nil
+    end
+
+    it "yields the passed block" do
+      yielded = false
+      @res.reading_body(@socket, true) { yielded = true }
+      yielded.should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/response_spec.rb b/spec/ruby/library/net-http/httpresponse/response_spec.rb
new file mode 100644
index 0000000000..caa0ca2d19
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/response_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#response" do
+  it "returns self" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    res.response.should equal(res)
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/shared/body.rb b/spec/ruby/library/net-http/httpresponse/shared/body.rb
new file mode 100644
index 0000000000..618e3936fb
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/shared/body.rb
@@ -0,0 +1,20 @@
+require 'stringio'
+
+describe :net_httpresponse_body, shared: true do
+  before :each do
+    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    @socket = Net::BufferedIO.new(StringIO.new("test body"))
+  end
+
+  it "returns the read body" do
+    @res.reading_body(@socket, true) do
+      @res.send(@method).should == "test body"
+    end
+  end
+
+  it "returns the previously read body if called a second time" do
+    @res.reading_body(@socket, true) do
+      @res.send(@method).should equal(@res.send(@method))
+    end
+  end
+end
diff --git a/spec/ruby/library/net-http/httpresponse/value_spec.rb b/spec/ruby/library/net-http/httpresponse/value_spec.rb
new file mode 100644
index 0000000000..2df8beaa10
--- /dev/null
+++ b/spec/ruby/library/net-http/httpresponse/value_spec.rb
@@ -0,0 +1,24 @@
+require_relative '../../../spec_helper'
+require 'net/http'
+
+describe "Net::HTTPResponse#value" do
+  it "raises an HTTP error for non 2xx HTTP Responses" do
+    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
+    -> { res.value }.should raise_error(Net::HTTPError)
+
+    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
+    -> { res.value }.should raise_error(Net::HTTPError)
+
+    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
+    -> { res.value }.should_not raise_error(Net::HTTPError)
+
+    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
+    -> { res.value }.should raise_error(Net::HTTPRetriableError)
+
+    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
+    -> { res.value }.should raise_error(Net::HTTPClientException)
+
+    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
+    -> { res.value }.should raise_error(Net::HTTPFatalError)
+  end
+end
diff --git a/spec/ruby/library/net/ftp/abort_spec.rb b/spec/ruby/library/net/ftp/abort_spec.rb
deleted file mode 100644
index 57651468d8..0000000000
--- a/spec/ruby/library/net/ftp/abort_spec.rb
+++ /dev/null
@@ -1,62 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#abort" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the ABOR command to the server" do
-    -> { @ftp.abort }.should_not raise_error
-  end
-
-  it "ignores the response" do
-    @ftp.abort
-    @ftp.last_response.should == "220 Dummy FTP Server ready!\n"
-  end
-
-  it "returns the full response" do
-    @ftp.abort.should == "226 Closing data connection. (ABOR)\n"
-  end
-
-  it "does not raise any error when the response code is 225" do
-    @server.should_receive(:abor).and_respond("225 Data connection open; no transfer in progress.")
-    -> { @ftp.abort }.should_not raise_error
-  end
-
-  it "does not raise any error when the response code is 226" do
-    @server.should_receive(:abor).and_respond("226 Closing data connection.")
-    -> { @ftp.abort }.should_not raise_error
-  end
-
-  it "raises a Net::FTPProtoError when the response code is 500" do
-    @server.should_receive(:abor).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
-  end
-
-  it "raises a Net::FTPProtoError when the response code is 501" do
-    @server.should_receive(:abor).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
-  end
-
-  it "raises a Net::FTPProtoError when the response code is 502" do
-    @server.should_receive(:abor).and_respond("502 Command not implemented.")
-    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
-  end
-
-  it "raises a Net::FTPProtoError when the response code is 421" do
-    @server.should_receive(:abor).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.abort }.should raise_error(Net::FTPProtoError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/acct_spec.rb b/spec/ruby/library/net/ftp/acct_spec.rb
deleted file mode 100644
index d8068dc81e..0000000000
--- a/spec/ruby/library/net/ftp/acct_spec.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#acct" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "writes the ACCT command to the server" do
-    @ftp.acct("my_account")
-    @ftp.last_response.should == "230 User 'my_account' logged in, proceed. (ACCT)\n"
-  end
-
-  it "returns nil" do
-    @ftp.acct("my_account").should == nil
-  end
-
-  it "does not raise any error when the response code is 230" do
-    @server.should_receive(:acct).and_respond("230 User logged in, proceed.")
-    -> { @ftp.acct("my_account") }.should_not raise_error
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:acct).and_respond("530 Not logged in.")
-    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:acct).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:acct).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 503" do
-    @server.should_receive(:acct).and_respond("503 Bad sequence of commands.")
-    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:acct).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.acct("my_account") }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/binary_spec.rb b/spec/ruby/library/net/ftp/binary_spec.rb
deleted file mode 100644
index 60e312a673..0000000000
--- a/spec/ruby/library/net/ftp/binary_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#binary" do
-  it "returns true when self is in binary mode" do
-    ftp = Net::FTP.new
-    ftp.binary.should be_true
-
-    ftp.binary = false
-    ftp.binary.should be_false
-  end
-end
-
-describe "Net::FTP#binary=" do
-  it "sets self to binary mode when passed true" do
-    ftp = Net::FTP.new
-
-    ftp.binary = true
-    ftp.binary.should be_true
-
-    ftp.binary = false
-    ftp.binary.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/ftp/chdir_spec.rb b/spec/ruby/library/net/ftp/chdir_spec.rb
deleted file mode 100644
index 4c10fa78b4..0000000000
--- a/spec/ruby/library/net/ftp/chdir_spec.rb
+++ /dev/null
@@ -1,99 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#chdir" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  describe "when switching to the parent directory" do
-    it "sends the 'CDUP' command to the server" do
-      @ftp.chdir("..")
-      @ftp.last_response.should == "200 Command okay. (CDUP)\n"
-    end
-
-    it "returns nil" do
-      @ftp.chdir("..").should be_nil
-    end
-
-    it "does not raise a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:cdup).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.chdir("..") }.should_not raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:cdup).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:cdup).and_respond("502 Command not implemented.")
-      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:cdup).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.chdir("..") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:cdup).and_respond("530 Not logged in.")
-      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 550" do
-      @server.should_receive(:cdup).and_respond("550 Requested action not taken.")
-      -> { @ftp.chdir("..") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  it "writes the 'CWD' command with the passed directory to the socket" do
-    @ftp.chdir("test")
-    @ftp.last_response.should == "200 Command okay. (CWD test)\n"
-  end
-
-  it "returns nil" do
-    @ftp.chdir("test").should be_nil
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:cwd).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:cwd).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:cwd).and_respond("502 Command not implemented.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:cwd).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:cwd).and_respond("530 Not logged in.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:cwd).and_respond("550 Requested action not taken.")
-    -> { @ftp.chdir("test") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/close_spec.rb b/spec/ruby/library/net/ftp/close_spec.rb
deleted file mode 100644
index 95c72b29ed..0000000000
--- a/spec/ruby/library/net/ftp/close_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#close" do
-  before :each do
-    @socket = mock("Socket")
-    @socket.stub!(:closed?).and_return(false)
-    @socket.stub!(:read_timeout).and_return(60)
-    @socket.stub!(:read_timeout=).and_return(3)
-
-    @ftp = Net::FTP.new
-    @ftp.instance_variable_set(:@sock, @socket)
-  end
-
-  it "closes the socket" do
-    @socket.should_receive(:close)
-    @ftp.close.should be_nil
-  end
-
-  it "does not try to close the socket if it has already been closed" do
-    @socket.should_receive(:closed?).and_return(true)
-    @socket.should_not_receive(:close)
-    @ftp.close.should be_nil
-  end
-
-  it "does not try to close the socket if it is nil" do
-    @ftp.instance_variable_set(:@sock, nil)
-    @ftp.close.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/ftp/closed_spec.rb b/spec/ruby/library/net/ftp/closed_spec.rb
deleted file mode 100644
index 1f3e69b0c1..0000000000
--- a/spec/ruby/library/net/ftp/closed_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#closed?" do
-  before :each do
-    @socket = mock("Socket")
-
-    @ftp = Net::FTP.new
-    @ftp.instance_variable_set(:@sock, @socket)
-  end
-
-  it "returns true when the socket is closed" do
-    @socket.should_receive(:closed?).and_return(true)
-    @ftp.closed?.should be_true
-  end
-
-  it "returns true when the socket is nil" do
-    @ftp.instance_variable_set(:@sock, nil)
-    @ftp.closed?.should be_true
-  end
-end
diff --git a/spec/ruby/library/net/ftp/connect_spec.rb b/spec/ruby/library/net/ftp/connect_spec.rb
deleted file mode 100644
index 9ee9bcd2c6..0000000000
--- a/spec/ruby/library/net/ftp/connect_spec.rb
+++ /dev/null
@@ -1,49 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-# TODO: Add specs for using the SOCKSSocket
-describe "Net::FTP#connect" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-  end
-
-  after :each do
-    @server.connect_message = nil
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "tries to connect to the FTP Server on the given host and port" do
-    -> { @ftp.connect(@server.hostname, @server.server_port) }.should_not raise_error
-  end
-
-  it "returns nil" do
-    @ftp.connect(@server.hostname, @server.server_port).should be_nil
-  end
-
-  it "prints a small debug line when in debug mode" do
-    @ftp.debug_mode = true
-    -> { @ftp.connect(@server.hostname, @server.server_port) }.should output(/#{"connect: "}#{@server.hostname}#{", "}#{@server.server_port}#{"\\nget: 220 Dummy FTP Server ready!"}/)
-    @ftp.debug_mode = false
-  end
-
-  it "does not raise any error when the response code is 220" do
-    @server.connect_message = "220 Dummy FTP Server ready!"
-    -> { @ftp.connect(@server.hostname, @server.server_port) }.should_not raise_error
-  end
-
-  it "raises a Net::FTPReplyError when the response code is 120" do
-    @server.connect_message = "120 Service ready in nnn minutes."
-    -> { @ftp.connect(@server.hostname, @server.server_port) }.should raise_error(Net::FTPReplyError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.connect_message = "421 Service not available, closing control connection."
-    -> { @ftp.connect(@server.hostname, @server.server_port) }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/debug_mode_spec.rb b/spec/ruby/library/net/ftp/debug_mode_spec.rb
deleted file mode 100644
index f49da55ed1..0000000000
--- a/spec/ruby/library/net/ftp/debug_mode_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#debug_mode" do
-  it "returns true when self is in debug mode" do
-    ftp = Net::FTP.new
-    ftp.debug_mode.should be_false
-
-    ftp.debug_mode = true
-    ftp.debug_mode.should be_true
-  end
-end
-
-describe "Net::FTP#debug_mode=" do
-  it "sets self into debug mode when passed true" do
-    ftp = Net::FTP.new
-    ftp.debug_mode = true
-    ftp.debug_mode.should be_true
-
-    ftp.debug_mode = false
-    ftp.debug_mode.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/ftp/default_passive_spec.rb b/spec/ruby/library/net/ftp/default_passive_spec.rb
deleted file mode 100644
index 30eb8f9da2..0000000000
--- a/spec/ruby/library/net/ftp/default_passive_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#default_passive" do
-  it "is true by default" do
-    ruby_exe(fixture(__FILE__, "default_passive.rb")).should == "true\ntrue\n"
-  end
-end
diff --git a/spec/ruby/library/net/ftp/delete_spec.rb b/spec/ruby/library/net/ftp/delete_spec.rb
deleted file mode 100644
index cf8f9332e2..0000000000
--- a/spec/ruby/library/net/ftp/delete_spec.rb
+++ /dev/null
@@ -1,59 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#delete" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the DELE command with the passed filename to the server" do
-    @ftp.delete("test.file")
-    @ftp.last_response.should == "250 Requested file action okay, completed. (DELE test.file)\n"
-  end
-
-  it "raises a Net::FTPTempError when the response code is 450" do
-    @server.should_receive(:dele).and_respond("450 Requested file action not taken.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:dele).and_respond("550 Requested action not taken.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:dele).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:dele).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:dele).and_respond("502 Command not implemented.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:dele).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:dele).and_respond("530 Not logged in.")
-    -> { @ftp.delete("test.file") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/dir_spec.rb b/spec/ruby/library/net/ftp/dir_spec.rb
deleted file mode 100644
index 47ac7b8d9b..0000000000
--- a/spec/ruby/library/net/ftp/dir_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/list'
-
-describe "Net::FTP#dir" do
-  it_behaves_like :net_ftp_list, :dir
-end
diff --git a/spec/ruby/library/net/ftp/fixtures/server.rb b/spec/ruby/library/net/ftp/fixtures/server.rb
deleted file mode 100644
index d4795a5c58..0000000000
--- a/spec/ruby/library/net/ftp/fixtures/server.rb
+++ /dev/null
@@ -1,277 +0,0 @@
-module NetFTPSpecs
-  class DummyFTP
-    attr_accessor :connect_message
-    attr_reader :login_user, :login_pass, :login_acct
-
-    # hostname or IP address
-    attr_reader :hostname
-    # port number
-    attr_reader :server_port
-
-    def initialize
-      @hostname = "localhost"
-      @server = TCPServer.new(@hostname, 0)
-      @server_port = @server.addr[1]
-
-      @handlers = {}
-      @commands = []
-      @connect_message = nil
-    end
-
-    def serve_once
-      @thread = Thread.new do
-        @socket = @server.accept
-        @socket.setsockopt(Socket::SOL_SOCKET, Socket::SO_OOBINLINE, 1)
-        begin
-          handle_request
-        ensure
-          @socket.close
-        end
-      end
-    end
-
-    def handle_request
-      # Send out the welcome message.
-      response @connect_message || "220 Dummy FTP Server ready!"
-
-      begin
-        while command = @socket.gets
-          command, argument = command.chomp.split(" ", 2)
-
-          if command == "QUIT"
-            self.response("221 OK, bye")
-            break
-          elsif proc_handler = @handlers[command.downcase.to_sym]
-            if argument.nil?
-              proc_handler.call(self)
-            else
-              proc_handler.call(self, argument)
-            end
-          else
-            if argument.nil?
-              self.send(command.downcase.to_sym)
-            else
-              self.send(command.downcase.to_sym, argument)
-            end
-          end
-        end
-      rescue => e
-        self.error_response("Exception: #{e} #{e.backtrace.inspect}")
-      end
-    end
-
-    def error_response(text)
-      self.response("451 #{text}")
-    end
-
-    def response(text)
-      @socket.puts(text) unless @socket.closed?
-    end
-
-    def stop
-      @datasocket.close unless @datasocket.nil? || @datasocket.closed?
-      @server.close
-      @thread.join
-    end
-
-
-    ##
-    def handle(sym, &block)
-      @handlers[sym] = block
-    end
-
-    def should_receive(method)
-      @handler_for = method
-      self
-    end
-
-    def and_respond(text)
-      @handlers[@handler_for] = -> s, *args { s.response(text) }
-    end
-
-    ##
-    # FTP methods
-    ##
-
-    def abor
-      self.response("226 Closing data connection. (ABOR)")
-    end
-
-    def acct(account)
-      @login_acct = account
-      self.response("230 User '#{account}' logged in, proceed. (ACCT)")
-    end
-
-    def cdup
-      self.response("200 Command okay. (CDUP)")
-    end
-
-    def cwd(dir)
-      self.response("200 Command okay. (CWD #{dir})")
-    end
-
-    def dele(file)
-      self.response("250 Requested file action okay, completed. (DELE #{file})")
-    end
-
-    def eprt(arg)
-      _, _, host, port = arg.split("|")
-
-      @datasocket = TCPSocket.new(host, port)
-      self.response("200 port opened")
-    end
-
-    def help(param = :default)
-      if param == :default
-        self.response("211 System status, or system help reply. (HELP)")
-      else
-        self.response("211 System status, or system help reply. (HELP #{param})")
-      end
-    end
-
-    def list(folder)
-      self.response("150 opening ASCII connection for file list")
-      @datasocket.puts("-rw-r--r--  1 spec  staff  507 17 Jul 18:41 last_response_code.rb")
-      @datasocket.puts("-rw-r--r--  1 spec  staff   50 17 Jul 18:41 list.rb")
-      @datasocket.puts("-rw-r--r--  1 spec  staff   48 17 Jul 18:41 pwd.rb")
-      @datasocket.close()
-      self.response("226 transfer complete (LIST #{folder})")
-    end
-
-    def mdtm(filename)
-      self.response("213 19980705132316")
-    end
-
-    def mkd(foldername)
-      self.response(%Q{257 "#{foldername.gsub('"', '""')}" created.})
-    end
-
-    def nlst(folder = nil)
-      self.response("150 opening ASCII connection for file list")
-      @datasocket.puts("last_response_code.rb")
-      @datasocket.puts("list.rb")
-      @datasocket.puts("pwd.rb")
-      @datasocket.close()
-      self.response("226 transfer complete (NLST#{folder ? " #{folder}" : ""})")
-    end
-
-    def noop
-      self.response("200 Command okay. (NOOP)")
-    end
-
-    def pass(password)
-      @login_pass = password
-      self.response("230 User logged in, proceed. (PASS #{password})")
-    end
-
-    def port(arg)
-      nums = arg.split(",")
-
-      if nums[0] == "::1"
-        # IPv6
-        port = nums[1].to_i * 256 + nums[2].to_i
-        host = nums[0]
-      else
-        # IPv4
-        port = nums[4].to_i * 256 + nums[5].to_i
-        host = nums[0..3].join(".")
-      end
-
-      @datasocket = TCPSocket.new(host, port)
-      self.response("200 port opened")
-    end
-
-    def pwd
-      self.response('257 "/some/dir/" - current directory')
-    end
-
-    def retr(file)
-      self.response("125 Data transfer starting")
-      if @restart_at && @restart_at == 20
-        @datasocket.puts("of the file named '#{file}'.")
-        @restart_at = nil
-      else
-        @datasocket.puts("This is the content")
-        @datasocket.puts("of the file named '#{file}'.")
-      end
-      @datasocket.close()
-      self.response("226 Closing data connection. (RETR #{file})")
-    end
-
-    def rest(at_bytes)
-      @restart_at = at_bytes.to_i
-      self.response("350 Requested file action pending further information. (REST)")
-    end
-
-    def rmd(folder)
-      self.response("250 Requested file action okay, completed. (RMD #{folder})")
-    end
-
-    def rnfr(from)
-      @rename_from = from
-      self.response("350 Requested file action pending further information.")
-    end
-
-    def rnto(to)
-      self.response("250 Requested file action okay, completed. (Renamed #{@rename_from} to #{to})")
-      @rename_from = nil
-    end
-
-    def site(param)
-      self.response("200 Command okay. (SITE #{param})")
-    end
-
-    def size(filename)
-      if filename == "binary"
-        self.response("213 24")
-      else
-        self.response("213 1024")
-      end
-    end
-
-    def stat(param = :default)
-      if param == :default
-        self.response("211 System status, or system help reply. (STAT)")
-      else
-        self.response("211 System status, or system help reply. (STAT #{param})")
-      end
-    end
-
-    def stor(file)
-      tmp_file = tmp("#{file}file", false)
-
-      self.response("125 Data transfer starting.")
-
-      mode = @restart_at ? "a" : "w"
-
-      File.open(tmp_file, mode + "b") do |f|
-        loop do
-          data = @datasocket.recv(1024)
-          break if !data || data.empty?
-          f << data
-        end
-      end
-
-      #@datasocket.close()
-      self.response("200 OK, Data received. (STOR #{file})")
-    end
-
-    def appe(file)
-      @restart_at = true
-      stor(file)
-    end
-
-    def syst
-      self.response("215 FTP Dummy Server (SYST)")
-    end
-
-    def type(type)
-      self.response("200 TYPE switched to #{type}")
-    end
-
-    def user(name)
-      @login_user = name
-      self.response("230 User logged in, proceed. (USER #{name})")
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/get_spec.rb b/spec/ruby/library/net/ftp/get_spec.rb
deleted file mode 100644
index c4672b55a5..0000000000
--- a/spec/ruby/library/net/ftp/get_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/gettextfile'
-require_relative 'shared/getbinaryfile'
-
-describe "Net::FTP#get (binary mode)" do
-  before :each do
-    @binary_mode = true
-  end
-
-  it_behaves_like :net_ftp_getbinaryfile, :get
-end
-
-describe "Net::FTP#get (text mode)" do
-  before :each do
-    @binary_mode = false
-  end
-
-  it_behaves_like :net_ftp_gettextfile, :get
-end
diff --git a/spec/ruby/library/net/ftp/getbinaryfile_spec.rb b/spec/ruby/library/net/ftp/getbinaryfile_spec.rb
deleted file mode 100644
index 155851b53c..0000000000
--- a/spec/ruby/library/net/ftp/getbinaryfile_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/getbinaryfile'
-
-describe "Net::FTP#getbinaryfile" do
-  it_behaves_like :net_ftp_getbinaryfile, :getbinaryfile
-end
diff --git a/spec/ruby/library/net/ftp/getdir_spec.rb b/spec/ruby/library/net/ftp/getdir_spec.rb
deleted file mode 100644
index eea35ac130..0000000000
--- a/spec/ruby/library/net/ftp/getdir_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'shared/pwd'
-
-describe "Net::FTP#getdir" do
-  it_behaves_like :net_ftp_pwd, :getdir
-end
diff --git a/spec/ruby/library/net/ftp/gettextfile_spec.rb b/spec/ruby/library/net/ftp/gettextfile_spec.rb
deleted file mode 100644
index 79395ae009..0000000000
--- a/spec/ruby/library/net/ftp/gettextfile_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/gettextfile'
-
-describe "Net::FTP#gettextfile" do
-  it_behaves_like :net_ftp_gettextfile, :gettextfile
-end
diff --git a/spec/ruby/library/net/ftp/help_spec.rb b/spec/ruby/library/net/ftp/help_spec.rb
deleted file mode 100644
index d2e9fe7ee8..0000000000
--- a/spec/ruby/library/net/ftp/help_spec.rb
+++ /dev/null
@@ -1,66 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#help" do
-  def with_connection
-    yield
-  end
-
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "writes the HELP command to the server" do
-    @ftp.help
-    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
-  end
-
-  it "returns the server's response" do
-    @ftp.help.should == "211 System status, or system help reply. (HELP)\n"
-  end
-
-  it "writes the HELP command with an optional parameter to the socket" do
-    @ftp.help("some parameter").should == "211 System status, or system help reply. (HELP some parameter)\n"
-  end
-
-  it "does not raise any error when the response code is 211" do
-    @server.should_receive(:help).and_respond("211 System status, or system help reply.")
-    -> { @ftp.help }.should_not raise_error
-  end
-
-  it "does not raise any error when the response code is 214" do
-    @server.should_receive(:help).and_respond("214 Help message.")
-    -> { @ftp.help }.should_not raise_error
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:help).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.help }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:help).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.help }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:help).and_respond("502 Command not implemented.")
-    -> { @ftp.help }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:help).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.help }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/initialize_spec.rb b/spec/ruby/library/net/ftp/initialize_spec.rb
deleted file mode 100644
index 507320e494..0000000000
--- a/spec/ruby/library/net/ftp/initialize_spec.rb
+++ /dev/null
@@ -1,407 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#initialize" do
-  before :each do
-    @ftp = Net::FTP.allocate
-    @ftp.stub!(:connect)
-    @port_args = []
-    ruby_version_is "2.5" do
-      @port_args << 21
-    end
-  end
-
-  it "is private" do
-    Net::FTP.should have_private_instance_method(:initialize)
-  end
-
-  it "sets self into binary mode" do
-    @ftp.binary.should be_nil
-    @ftp.send(:initialize)
-    @ftp.binary.should be_true
-  end
-
-  it "sets self into active mode" do
-    @ftp.passive.should be_nil
-    @ftp.send(:initialize)
-    @ftp.passive.should be_false
-  end
-
-  it "sets self into non-debug mode" do
-    @ftp.debug_mode.should be_nil
-    @ftp.send(:initialize)
-    @ftp.debug_mode.should be_false
-  end
-
-  it "sets self to not resume file uploads/downloads" do
-    @ftp.resume.should be_nil
-    @ftp.send(:initialize)
-    @ftp.resume.should be_false
-  end
-
-  describe "when passed no arguments" do
-    it "does not try to connect" do
-      @ftp.should_not_receive(:connect)
-      @ftp.send(:initialize)
-    end
-  end
-
-  describe "when passed host" do
-    it "tries to connect to the passed host" do
-      @ftp.should_receive(:connect).with("localhost", *@port_args)
-      @ftp.send(:initialize, "localhost")
-    end
-  end
-
-  describe "when passed host, user" do
-    it "tries to connect to the passed host" do
-      @ftp.should_receive(:connect).with("localhost", *@port_args)
-      @ftp.send(:initialize, "localhost")
-    end
-
-    it "tries to login with the passed username" do
-      @ftp.should_receive(:login).with("rubyspec", nil, nil)
-      @ftp.send(:initialize, "localhost", "rubyspec")
-    end
-  end
-
-  describe "when passed host, user, password" do
-    it "tries to connect to the passed host" do
-      @ftp.should_receive(:connect).with("localhost", *@port_args)
-      @ftp.send(:initialize, "localhost")
-    end
-
-    it "tries to login with the passed username and password" do
-      @ftp.should_receive(:login).with("rubyspec", "rocks", nil)
-      @ftp.send(:initialize, "localhost", "rubyspec", "rocks")
-    end
-  end
-
-  describe "when passed host, user" do
-    it "tries to connect to the passed host" do
-      @ftp.should_receive(:connect).with("localhost", *@port_args)
-      @ftp.send(:initialize, "localhost")
-    end
-
-    it "tries to login with the passed username, password and account" do
-      @ftp.should_receive(:login).with("rubyspec", "rocks", "account")
-      @ftp.send(:initialize, "localhost", "rubyspec", "rocks", "account")
-    end
-  end
-
-  before :each do
-    @ftp.stub!(:login)
-  end
-
-  describe 'when the host' do
-    describe 'is set' do
-      describe 'and port option' do
-        describe 'is set' do
-          it 'tries to connect to the host on the specified port' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({ port: 8080 })
-            @ftp.should_receive(:connect).with('localhost', 8080)
-
-            @ftp.send(:initialize, 'localhost', options)
-          end
-        end
-
-        describe 'is not set' do
-          it 'tries to connect to the host without a port' do
-            @ftp.should_receive(:connect).with("localhost", *@port_args)
-
-            @ftp.send(:initialize, 'localhost')
-          end
-        end
-      end
-
-      describe 'when the username option' do
-        describe 'is set' do
-          describe 'and the password option' do
-            describe 'is set' do
-              describe 'and the account option' do
-                describe 'is set' do
-                  it 'tries to log in with the supplied parameters' do
-                    options = mock('ftp initialize options')
-                    options.should_receive(:to_hash).and_return({ username: 'a', password: 'topsecret', account: 'b' })
-                    @ftp.should_receive(:login).with('a', 'topsecret', 'b')
-
-                    @ftp.send(:initialize, 'localhost', options)
-                  end
-                end
-
-                describe 'is unset' do
-                  it 'tries to log in with the supplied parameters' do
-                    options = mock('ftp initialize options')
-                    options.should_receive(:to_hash).and_return({ username: 'a', password: 'topsecret' })
-                    @ftp.should_receive(:login).with('a', 'topsecret', nil)
-
-                    @ftp.send(:initialize, 'localhost', options)
-                  end
-                end
-              end
-            end
-
-            describe 'is unset' do
-              describe 'and the account option' do
-                describe 'is set' do
-                  it 'tries to log in with the supplied parameters' do
-                    options = mock('ftp initialize options')
-                    options.should_receive(:to_hash).and_return({ username: 'a', account: 'b' })
-                    @ftp.should_receive(:login).with('a', nil, 'b')
-
-                    @ftp.send(:initialize, 'localhost', options)
-                  end
-                end
-
-                describe 'is unset' do
-                  it 'tries to log in with the supplied parameters' do
-                    options = mock('ftp initialize options')
-                    options.should_receive(:to_hash).and_return({ username: 'a'})
-                    @ftp.should_receive(:login).with('a', nil, nil)
-
-                    @ftp.send(:initialize, 'localhost', options)
-                  end
-                end
-              end
-            end
-          end
-        end
-
-        describe 'is not set' do
-          it 'does not try to log in' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({})
-            @ftp.should_not_receive(:login)
-
-            @ftp.send(:initialize, 'localhost', options)
-          end
-        end
-      end
-    end
-
-    describe 'is unset' do
-      it 'does not try to connect' do
-        @ftp.should_not_receive(:connect)
-
-        @ftp.send(:initialize)
-      end
-
-      it 'does not try to log in' do
-        @ftp.should_not_receive(:login)
-
-        @ftp.send(:initialize)
-      end
-    end
-  end
-
-  describe 'when the passive option' do
-    describe 'is set' do
-      describe 'to true' do
-        it 'sets passive to true' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ passive: true })
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.passive.should == true
-        end
-      end
-
-      describe 'to false' do
-        it 'sets passive to false' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ passive: false })
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.passive.should == false
-        end
-      end
-    end
-
-    describe 'is unset' do
-      it 'sets passive to false' do
-        @ftp.send(:initialize)
-        @ftp.passive.should == false
-      end
-    end
-  end
-
-  describe 'when the debug_mode option' do
-    describe 'is set' do
-      describe 'to true' do
-        it 'sets debug_mode to true' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ debug_mode: true })
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.debug_mode.should == true
-        end
-      end
-
-      describe 'to false' do
-        it 'sets debug_mode to false' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ debug_mode: false })
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.debug_mode.should == false
-        end
-      end
-    end
-
-    describe 'is unset' do
-      it 'sets debug_mode to false' do
-        @ftp.send(:initialize)
-        @ftp.debug_mode.should == false
-      end
-    end
-  end
-
-  describe 'when the open_timeout option' do
-    describe 'is set' do
-      it 'sets open_timeout to the specified value' do
-        options = mock('ftp initialize options')
-        options.should_receive(:to_hash).and_return({ open_timeout: 42 })
-
-        @ftp.send(:initialize, nil, options)
-        @ftp.open_timeout.should == 42
-      end
-    end
-
-    describe 'is not set' do
-      it 'sets open_timeout to nil' do
-        @ftp.send(:initialize)
-        @ftp.open_timeout.should == nil
-      end
-    end
-  end
-
-  describe 'when the read_timeout option' do
-    describe 'is set' do
-      it 'sets read_timeout to the specified value' do
-        options = mock('ftp initialize options')
-        options.should_receive(:to_hash).and_return({ read_timeout: 100 })
-
-        @ftp.send(:initialize, nil, options)
-        @ftp.read_timeout.should == 100
-      end
-    end
-
-    describe 'is not set' do
-      it 'sets read_timeout to the default value' do
-        @ftp.send(:initialize)
-        @ftp.read_timeout.should == 60
-      end
-    end
-  end
-
-  describe 'when the ssl_handshake_timeout option' do
-    describe 'is set' do
-      it 'sets ssl_handshake_timeout to the specified value' do
-        options = mock('ftp initialize options')
-        options.should_receive(:to_hash).and_return({ ssl_handshake_timeout: 23 })
-
-        @ftp.send(:initialize, nil, options)
-        @ftp.ssl_handshake_timeout.should == 23
-      end
-    end
-
-    describe 'is not set' do
-      it 'sets ssl_handshake_timeout to nil' do
-        @ftp.send(:initialize)
-        @ftp.ssl_handshake_timeout.should == nil
-      end
-    end
-  end
-
-  describe 'when the ssl option' do
-    describe 'is set' do
-      describe "and the ssl option's value is true" do
-        it 'initializes ssl_context to a blank SSLContext object' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ ssl: true })
-
-          ssl_context = OpenSSL::SSL::SSLContext.allocate
-          ssl_context.stub!(:set_params)
-
-          OpenSSL::SSL::SSLContext.should_receive(:new).and_return(ssl_context)
-          ssl_context.should_receive(:set_params).with({})
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.instance_variable_get(:@ssl_context).should == ssl_context
-        end
-      end
-
-      describe "and the ssl option's value is a hash" do
-        it 'initializes ssl_context to a configured SSLContext object' do
-          options = mock('ftp initialize options')
-          options.should_receive(:to_hash).and_return({ ssl: {key: 'value'} })
-
-          ssl_context = OpenSSL::SSL::SSLContext.allocate
-          ssl_context.stub!(:set_params)
-
-          OpenSSL::SSL::SSLContext.should_receive(:new).and_return(ssl_context)
-          ssl_context.should_receive(:set_params).with({key: 'value'})
-
-          @ftp.send(:initialize, nil, options)
-          @ftp.instance_variable_get(:@ssl_context).should == ssl_context
-        end
-      end
-
-      describe 'and private_data_connection' do
-        describe 'is set' do
-          it 'sets private_data_connection to that value' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({ ssl: true, private_data_connection: 'true' })
-
-            @ftp.send(:initialize, nil, options)
-            @ftp.instance_variable_get(:@private_data_connection).should == 'true'
-          end
-        end
-
-        describe 'is not set' do
-          it 'sets private_data_connection to nil' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({ ssl: true })
-
-            @ftp.send(:initialize, nil, options)
-            @ftp.instance_variable_get(:@private_data_connection).should == true
-          end
-        end
-      end
-    end
-
-    describe 'is not set' do
-      it 'sets ssl_context to nil' do
-        options = mock('ftp initialize options')
-        options.should_receive(:to_hash).and_return({})
-
-        @ftp.send(:initialize, nil, options)
-        @ftp.instance_variable_get(:@ssl_context).should == nil
-      end
-
-      describe 'private_data_connection' do
-        describe 'is set' do
-          it 'raises an ArgumentError' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({ private_data_connection: true })
-
-            -> {
-              @ftp.send(:initialize, nil, options)
-            }.should raise_error(ArgumentError, /private_data_connection can be set to true only when ssl is enabled/)
-          end
-        end
-
-        describe 'is not set' do
-          it 'sets private_data_connection to false' do
-            options = mock('ftp initialize options')
-            options.should_receive(:to_hash).and_return({})
-
-            @ftp.send(:initialize, nil, options)
-            @ftp.instance_variable_get(:@private_data_connection).should == false
-          end
-        end
-      end
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/last_response_code_spec.rb b/spec/ruby/library/net/ftp/last_response_code_spec.rb
deleted file mode 100644
index 3eb20f7ad8..0000000000
--- a/spec/ruby/library/net/ftp/last_response_code_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'shared/last_response_code'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#last_response_code" do
-  it_behaves_like :net_ftp_last_response_code, :last_response_code
-end
diff --git a/spec/ruby/library/net/ftp/last_response_spec.rb b/spec/ruby/library/net/ftp/last_response_spec.rb
deleted file mode 100644
index ada665d59c..0000000000
--- a/spec/ruby/library/net/ftp/last_response_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#last_response" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "returns the last response" do
-    @ftp.last_response.should == "220 Dummy FTP Server ready!\n"
-    @ftp.help
-    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
-  end
-end
diff --git a/spec/ruby/library/net/ftp/lastresp_spec.rb b/spec/ruby/library/net/ftp/lastresp_spec.rb
deleted file mode 100644
index 273e216e8b..0000000000
--- a/spec/ruby/library/net/ftp/lastresp_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'shared/last_response_code'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#lastresp" do
-  it_behaves_like :net_ftp_last_response_code, :lastresp
-end
diff --git a/spec/ruby/library/net/ftp/list_spec.rb b/spec/ruby/library/net/ftp/list_spec.rb
deleted file mode 100644
index 6175172923..0000000000
--- a/spec/ruby/library/net/ftp/list_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/list'
-
-describe "Net::FTP#list" do
-  it_behaves_like :net_ftp_list, :list
-end
diff --git a/spec/ruby/library/net/ftp/login_spec.rb b/spec/ruby/library/net/ftp/login_spec.rb
deleted file mode 100644
index 46736851ee..0000000000
--- a/spec/ruby/library/net/ftp/login_spec.rb
+++ /dev/null
@@ -1,195 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#login" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  describe "when passed no arguments" do
-    it "sends the USER command with 'anonymous' as name to the server" do
-      @ftp.login
-      @server.login_user.should == "anonymous"
-    end
-
-    it "sends 'anonymous@' as a password when required" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @ftp.login
-      @server.login_pass.should == "anonymous@"
-    end
-
-    it "raises a Net::FTPReplyError when the server requests an account" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @server.should_receive(:pass).and_respond("332 Need account for login.")
-      -> { @ftp.login }.should raise_error(Net::FTPReplyError)
-    end
-  end
-
-  describe "when passed name" do
-    it "sends the USER command with the passed name to the server" do
-      @ftp.login("rubyspec")
-      @server.login_user.should == "rubyspec"
-    end
-
-    it "raises a Net::FTPReplyError when the server requests a password, but none was given" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      -> { @ftp.login("rubyspec") }.should raise_error(Net::FTPReplyError)
-    end
-
-    it "raises a Net::FTPReplyError when the server requests an account, but none was given" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @server.should_receive(:pass).and_respond("332 Need account for login.")
-      -> { @ftp.login("rubyspec") }.should raise_error(Net::FTPReplyError)
-    end
-  end
-
-  describe "when passed name, password" do
-    it "sends the USER command with the passed name to the server" do
-      @ftp.login("rubyspec", "rocks")
-      @server.login_user.should == "rubyspec"
-    end
-
-    it "sends the passed password when required" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @ftp.login("rubyspec", "rocks")
-      @server.login_pass.should == "rocks"
-    end
-
-    it "raises a Net::FTPReplyError when the server requests an account" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @server.should_receive(:pass).and_respond("332 Need account for login.")
-      -> { @ftp.login("rubyspec", "rocks") }.should raise_error(Net::FTPReplyError)
-    end
-  end
-
-  describe "when passed name, password, account" do
-    it "sends the USER command with the passed name to the server" do
-      @ftp.login("rubyspec", "rocks", "account")
-      @server.login_user.should == "rubyspec"
-    end
-
-    it "sends the passed password when required" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @ftp.login("rubyspec", "rocks", "account")
-      @server.login_pass.should == "rocks"
-    end
-
-    it "sends the passed account when required" do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @server.should_receive(:pass).and_respond("332 Need account for login.")
-      @ftp.login("rubyspec", "rocks", "account")
-      @server.login_acct.should == "account"
-    end
-  end
-
-  describe "when the USER command fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:user).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:user).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:user).and_respond("502 Command not implemented.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:user).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:user).and_respond("530 Not logged in.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when the PASS command fails" do
-    before :each do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-    end
-
-    it "does not raise an Error when the response code is 202" do
-      @server.should_receive(:pass).and_respond("202 Command not implemented, superfluous at this site.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should_not raise_error
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:pass).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:pass).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:pass).and_respond("502 Command not implemented.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:pass).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:pass).and_respond("530 Not logged in.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when the ACCT command fails" do
-    before :each do
-      @server.should_receive(:user).and_respond("331 User name okay, need password.")
-      @server.should_receive(:pass).and_respond("332 Need account for login.")
-    end
-
-    it "does not raise an Error when the response code is 202" do
-      @server.should_receive(:acct).and_respond("202 Command not implemented, superfluous at this site.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should_not raise_error
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:acct).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:acct).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:acct).and_respond("502 Command not implemented.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:acct).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:acct).and_respond("530 Not logged in.")
-      -> { @ftp.login("rubyspec", "rocks", "account") }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/ls_spec.rb b/spec/ruby/library/net/ftp/ls_spec.rb
deleted file mode 100644
index e729eb9481..0000000000
--- a/spec/ruby/library/net/ftp/ls_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/list'
-
-describe "Net::FTP#ls" do
-  it_behaves_like :net_ftp_list, :ls
-end
diff --git a/spec/ruby/library/net/ftp/mdtm_spec.rb b/spec/ruby/library/net/ftp/mdtm_spec.rb
deleted file mode 100644
index b74cf8d3c7..0000000000
--- a/spec/ruby/library/net/ftp/mdtm_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#mdtm" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the MDTM with the passed filename command to the server" do
-    @ftp.mdtm("test.file")
-    @ftp.last_response.should == "213 19980705132316\n"
-  end
-
-  it "returns the last modification time of the passed file" do
-    @ftp.mdtm("test.file").should == "19980705132316"
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:mdtm).and_respond("550 Requested action not taken.")
-    -> { @ftp.mdtm("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:mdtm).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.mdtm("test.file") }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/mkdir_spec.rb b/spec/ruby/library/net/ftp/mkdir_spec.rb
deleted file mode 100644
index 7dc45b5711..0000000000
--- a/spec/ruby/library/net/ftp/mkdir_spec.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#mkdir" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the MKD command with the passed pathname to the server" do
-    @ftp.mkdir("test.folder")
-    @ftp.last_response.should == %{257 "test.folder" created.\n}
-  end
-
-  it "returns the path to the newly created directory" do
-    @ftp.mkdir("test.folder").should == "test.folder"
-    @ftp.mkdir("/absolute/path/to/test.folder").should == "/absolute/path/to/test.folder"
-    @ftp.mkdir("relative/path/to/test.folder").should == "relative/path/to/test.folder"
-    @ftp.mkdir('/usr/dm/foo"bar').should == '/usr/dm/foo"bar'
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:mkd).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:mkd).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:mkd).and_respond("502 Command not implemented.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:mkd).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:mkd).and_respond("530 Not logged in.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:mkd).and_respond("550 Requested action not taken.")
-    -> { @ftp.mkdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/mtime_spec.rb b/spec/ruby/library/net/ftp/mtime_spec.rb
deleted file mode 100644
index 0f6cc1ba20..0000000000
--- a/spec/ruby/library/net/ftp/mtime_spec.rb
+++ /dev/null
@@ -1,50 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#mtime" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the MDTM with the passed filename command to the server" do
-    @ftp.mtime("test.file")
-    @ftp.last_response.should == "213 19980705132316\n"
-  end
-
-  describe "when passed filename" do
-    it "returns the last modification time of the passed file as a Time object in the local time" do
-      @ftp.mtime("test.file").should == Time.gm("1998", "07", "05", "13", "23", "16")
-    end
-  end
-
-  describe "when passed filename, local_time" do
-    it "returns the last modification time as a Time object in UTC when local_time is true" do
-      @ftp.mtime("test.file", true).should == Time.local("1998", "07", "05", "13", "23", "16")
-    end
-
-    it "returns the last modification time as a Time object in the local time when local_time is false" do
-      @ftp.mtime("test.file", false).should == Time.gm("1998", "07", "05", "13", "23", "16")
-    end
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:mdtm).and_respond("550 Requested action not taken.")
-    -> { @ftp.mtime("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:mdtm).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.mtime("test.file") }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/nlst_spec.rb b/spec/ruby/library/net/ftp/nlst_spec.rb
deleted file mode 100644
index 34384fb8c4..0000000000
--- a/spec/ruby/library/net/ftp/nlst_spec.rb
+++ /dev/null
@@ -1,92 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#nlst" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.passive = false
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  describe "when passed no arguments" do
-    it "returns an Array containing a list of files in the current dir" do
-      @ftp.nlst.should == ["last_response_code.rb", "list.rb", "pwd.rb"]
-      @ftp.last_response.should == "226 transfer complete (NLST)\n"
-    end
-  end
-
-  describe "when passed dir" do
-    it "returns an Array containing a list of files in the passed dir" do
-      @ftp.nlst("test.folder").should == ["last_response_code.rb", "list.rb", "pwd.rb"]
-      @ftp.last_response.should == "226 transfer complete (NLST test.folder)\n"
-    end
-  end
-
-  describe "when the NLST command fails" do
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:nlst).and_respond("450 Requested file action not taken..")
-      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:nlst).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:nlst).and_respond("501 Syntax error, command unrecognized.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:nlst).and_respond("502 Command not implemented.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:nlst).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:nlst).and_respond("530 Not logged in.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when opening the data port fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
-      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
-      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
-      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:eprt).and_respond("530 Not logged in.")
-      @server.should_receive(:port).and_respond("530 Not logged in.")
-      -> { @ftp.nlst }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/noop_spec.rb b/spec/ruby/library/net/ftp/noop_spec.rb
deleted file mode 100644
index 070750ced7..0000000000
--- a/spec/ruby/library/net/ftp/noop_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#noop" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the NOOP command to the server" do
-    @ftp.noop
-    @ftp.last_response.should == "200 Command okay. (NOOP)\n"
-  end
-
-  it "returns nil" do
-    @ftp.noop.should be_nil
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:noop).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.noop }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:noop).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.noop }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/open_spec.rb b/spec/ruby/library/net/ftp/open_spec.rb
deleted file mode 100644
index 7be02ff373..0000000000
--- a/spec/ruby/library/net/ftp/open_spec.rb
+++ /dev/null
@@ -1,55 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP.open" do
-  before :each do
-    @ftp = mock("Net::FTP instance")
-    Net::FTP.stub!(:new).and_return(@ftp)
-  end
-
-  describe "when passed no block" do
-    it "returns a new Net::FTP instance" do
-      Net::FTP.open("localhost").should equal(@ftp)
-    end
-
-    it "passes the passed arguments down to Net::FTP.new" do
-      Net::FTP.should_receive(:new).with("localhost", "user", "password", "account")
-      Net::FTP.open("localhost", "user", "password", "account")
-    end
-  end
-
-  describe "when passed a block" do
-    before :each do
-      @ftp.stub!(:close)
-    end
-
-    it "yields a new Net::FTP instance to the passed block" do
-      yielded = false
-      Net::FTP.open("localhost") do |ftp|
-        yielded = true
-        ftp.should equal(@ftp)
-      end
-      yielded.should be_true
-    end
-
-    it "closes the Net::FTP instance after yielding" do
-      Net::FTP.open("localhost") do |ftp|
-        ftp.should_receive(:close)
-      end
-    end
-
-    it "closes the Net::FTP instance even if an exception is raised while yielding" do
-      begin
-        Net::FTP.open("localhost") do |ftp|
-          ftp.should_receive(:close)
-          raise ArgumentError, "some exception"
-        end
-      rescue ArgumentError
-      end
-    end
-
-    it "returns the block's return value" do
-      Net::FTP.open("localhost") { :test }.should == :test
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/passive_spec.rb b/spec/ruby/library/net/ftp/passive_spec.rb
deleted file mode 100644
index e8db030cbd..0000000000
--- a/spec/ruby/library/net/ftp/passive_spec.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#passive" do
-  it "returns true when self is in passive mode" do
-    ftp = Net::FTP.new
-    ftp.passive.should be_false
-
-    ftp.passive = true
-    ftp.passive.should be_true
-  end
-
-  it "is the value of Net::FTP.default_value by default" do
-    ruby_exe(fixture(__FILE__, "passive.rb")).should == "true"
-  end
-end
-
-describe "Net::FTP#passive=" do
-  it "sets self to passive mode when passed true" do
-    ftp = Net::FTP.new
-
-    ftp.passive = true
-    ftp.passive.should be_true
-
-    ftp.passive = false
-    ftp.passive.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/ftp/put_spec.rb b/spec/ruby/library/net/ftp/put_spec.rb
deleted file mode 100644
index f1f85b5d05..0000000000
--- a/spec/ruby/library/net/ftp/put_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/puttextfile'
-require_relative 'shared/putbinaryfile'
-
-describe "Net::FTP#put (binary mode)" do
-  before :each do
-    @binary_mode = true
-  end
-
-  it_behaves_like :net_ftp_putbinaryfile, :put
-end
-
-describe "Net::FTP#put (text mode)" do
-  before :each do
-    @binary_mode = false
-  end
-
-  it_behaves_like :net_ftp_puttextfile, :put
-end
diff --git a/spec/ruby/library/net/ftp/putbinaryfile_spec.rb b/spec/ruby/library/net/ftp/putbinaryfile_spec.rb
deleted file mode 100644
index cb1c7bef5a..0000000000
--- a/spec/ruby/library/net/ftp/putbinaryfile_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/putbinaryfile'
-
-describe "Net::FTP#putbinaryfile" do
-  it_behaves_like :net_ftp_putbinaryfile, :putbinaryfile
-end
diff --git a/spec/ruby/library/net/ftp/puttextfile_spec.rb b/spec/ruby/library/net/ftp/puttextfile_spec.rb
deleted file mode 100644
index 00a930afd7..0000000000
--- a/spec/ruby/library/net/ftp/puttextfile_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-require_relative 'shared/puttextfile'
-
-describe "Net::FTP#puttextfile" do
-  it_behaves_like :net_ftp_puttextfile, :puttextfile
-end
diff --git a/spec/ruby/library/net/ftp/pwd_spec.rb b/spec/ruby/library/net/ftp/pwd_spec.rb
deleted file mode 100644
index a3998cc730..0000000000
--- a/spec/ruby/library/net/ftp/pwd_spec.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#pwd" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the PWD command to the server" do
-    @ftp.pwd
-    @ftp.last_response.should == "257 \"/some/dir/\" - current directory\n"
-  end
-
-  it "returns the current directory" do
-    @ftp.pwd.should == "/some/dir/"
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:pwd).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:pwd).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:pwd).and_respond("502 Command not implemented.")
-    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:pwd).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.pwd }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:pwd).and_respond("550 Requested action not taken.")
-    -> { @ftp.pwd }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/quit_spec.rb b/spec/ruby/library/net/ftp/quit_spec.rb
deleted file mode 100644
index 8e3cb28b90..0000000000
--- a/spec/ruby/library/net/ftp/quit_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#quit" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the QUIT command to the server" do
-    @ftp.quit
-    @ftp.last_response.should == "221 OK, bye\n"
-  end
-
-  it "does not close the socket automatically" do
-    @ftp.quit
-    @ftp.closed?.should be_false
-  end
-
-  it "returns nil" do
-    @ftp.quit.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/ftp/rename_spec.rb b/spec/ruby/library/net/ftp/rename_spec.rb
deleted file mode 100644
index 376b203ac9..0000000000
--- a/spec/ruby/library/net/ftp/rename_spec.rb
+++ /dev/null
@@ -1,94 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#rename" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  describe "when passed from_name, to_name" do
-    it "sends the RNFR command with the passed from_name and the RNTO command with the passed to_name to the server" do
-      @ftp.rename("from.file", "to.file")
-      @ftp.last_response.should == "250 Requested file action okay, completed. (Renamed from.file to to.file)\n"
-    end
-
-    it "returns something" do
-      @ftp.rename("from.file", "to.file").should be_nil
-    end
-  end
-
-  describe "when the RNFR command fails" do
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:rnfr).and_respond("450 Requested file action not taken.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 550" do
-      @server.should_receive(:rnfr).and_respond("550 Requested action not taken.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:rnfr).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:rnfr).and_respond("502 Command not implemented.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:rnfr).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:rnfr).and_respond("530 Not logged in.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when the RNTO command fails" do
-    it "raises a Net::FTPPermError when the response code is 532" do
-      @server.should_receive(:rnfr).and_respond("532 Need account for storing files.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 553" do
-      @server.should_receive(:rnto).and_respond("553 Requested action not taken.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:rnto).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 502" do
-      @server.should_receive(:rnto).and_respond("502 Command not implemented.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:rnto).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:rnto).and_respond("530 Not logged in.")
-      -> { @ftp.rename("from.file", "to.file") }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/resume_spec.rb b/spec/ruby/library/net/ftp/resume_spec.rb
deleted file mode 100644
index 51b1cff2a4..0000000000
--- a/spec/ruby/library/net/ftp/resume_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#resume" do
-  it "returns true when self is set to resume uploads/downloads" do
-    ftp = Net::FTP.new
-    ftp.resume.should be_false
-
-    ftp.resume = true
-    ftp.resume.should be_true
-  end
-end
-
-describe "Net::FTP#resume=" do
-  it "sets self to resume uploads/downloads when set to true" do
-    ftp = Net::FTP.new
-    ftp.resume = true
-    ftp.resume.should be_true
-
-    ftp.resume = false
-    ftp.resume.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/ftp/retrbinary_spec.rb b/spec/ruby/library/net/ftp/retrbinary_spec.rb
deleted file mode 100644
index 30e2484af5..0000000000
--- a/spec/ruby/library/net/ftp/retrbinary_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#retrbinary" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the passed command to the server" do
-    @ftp.retrbinary("RETR test", 4096) {}
-    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
-  end
-
-  it "yields the received content as binary blocks of the passed size" do
-    res = []
-    @ftp.retrbinary("RETR test", 10) { |bin| res << bin }
-    res.should == [ "This is th", "e content\n", "of the fil", "e named 't", "est'.\n" ]
-  end
-end
diff --git a/spec/ruby/library/net/ftp/retrlines_spec.rb b/spec/ruby/library/net/ftp/retrlines_spec.rb
deleted file mode 100644
index 546df3844e..0000000000
--- a/spec/ruby/library/net/ftp/retrlines_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#retrlines" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the passed command over the socket" do
-    @ftp.retrlines("LIST test.dir") {}
-    @ftp.last_response.should == "226 transfer complete (LIST test.dir)\n"
-  end
-
-  it "yields each received line to the passed block" do
-    res = []
-    @ftp.retrlines("LIST test.dir") { |x| res << x }
-    res.should == [
-      "-rw-r--r--  1 spec  staff  507 17 Jul 18:41 last_response_code.rb",
-      "-rw-r--r--  1 spec  staff   50 17 Jul 18:41 list.rb",
-      "-rw-r--r--  1 spec  staff   48 17 Jul 18:41 pwd.rb"
-    ]
-  end
-end
diff --git a/spec/ruby/library/net/ftp/return_code_spec.rb b/spec/ruby/library/net/ftp/return_code_spec.rb
deleted file mode 100644
index e4b98c8031..0000000000
--- a/spec/ruby/library/net/ftp/return_code_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#return_code" do
-  before :each do
-    @ftp = Net::FTP.new
-  end
-
-  it "outputs a warning and returns a newline" do
-    -> do
-      @ftp.return_code.should == "\n"
-    end.should complain(/warning: Net::FTP#return_code is obsolete and do nothing/)
-  end
-end
-
-describe "Net::FTP#return_code=" do
-  before :each do
-    @ftp = Net::FTP.new
-  end
-
-  it "outputs a warning" do
-    -> { @ftp.return_code = 123 }.should complain(/warning: Net::FTP#return_code= is obsolete and do nothing/)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/rmdir_spec.rb b/spec/ruby/library/net/ftp/rmdir_spec.rb
deleted file mode 100644
index 0515897998..0000000000
--- a/spec/ruby/library/net/ftp/rmdir_spec.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#rmdir" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the RMD command with the passed pathname to the server" do
-    @ftp.rmdir("test.folder")
-    @ftp.last_response.should == "250 Requested file action okay, completed. (RMD test.folder)\n"
-  end
-
-  it "returns nil" do
-    @ftp.rmdir("test.folder").should be_nil
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:rmd).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:rmd).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:rmd).and_respond("502 Command not implemented.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:rmd).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:rmd).and_respond("530 Not logged in.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:rmd).and_respond("550 Requested action not taken.")
-    -> { @ftp.rmdir("test.folder") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/sendcmd_spec.rb b/spec/ruby/library/net/ftp/sendcmd_spec.rb
deleted file mode 100644
index dafa36e032..0000000000
--- a/spec/ruby/library/net/ftp/sendcmd_spec.rb
+++ /dev/null
@@ -1,54 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#sendcmd" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the passed command to the server" do
-    @ftp.sendcmd("HELP")
-    @ftp.last_response.should == "211 System status, or system help reply. (HELP)\n"
-  end
-
-  it "returns the server's response" do
-    @ftp.sendcmd("HELP").should == "211 System status, or system help reply. (HELP)\n"
-  end
-
-  it "raises no error when the response code is 1xx, 2xx or 3xx" do
-    @server.should_receive(:help).and_respond("120 Service ready in nnn minutes.")
-    -> { @ftp.sendcmd("HELP") }.should_not raise_error
-
-    @server.should_receive(:help).and_respond("200 Command okay.")
-    -> { @ftp.sendcmd("HELP") }.should_not raise_error
-
-    @server.should_receive(:help).and_respond("350 Requested file action pending further information.")
-    -> { @ftp.sendcmd("HELP") }.should_not raise_error
-  end
-
-  it "raises a Net::FTPTempError when the response code is 4xx" do
-    @server.should_receive(:help).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 5xx" do
-    @server.should_receive(:help).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPProtoError when the response code is not between 1xx-5xx" do
-    @server.should_receive(:help).and_respond("999 Invalid response.")
-    -> { @ftp.sendcmd("HELP") }.should raise_error(Net::FTPProtoError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/set_socket_spec.rb b/spec/ruby/library/net/ftp/set_socket_spec.rb
deleted file mode 100644
index 7ca3bbbe27..0000000000
--- a/spec/ruby/library/net/ftp/set_socket_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-
-describe "Net::FTP#set_socket" do
-  # TODO: I won't spec this method, as it is not used
-  #       anywhere and it should be private anyway.
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/library/net/ftp/shared/getbinaryfile.rb b/spec/ruby/library/net/ftp/shared/getbinaryfile.rb
deleted file mode 100644
index f324f5b85d..0000000000
--- a/spec/ruby/library/net/ftp/shared/getbinaryfile.rb
+++ /dev/null
@@ -1,150 +0,0 @@
-describe :net_ftp_getbinaryfile, shared: :true do
-  before :each do
-    @fixture_file = File.dirname(__FILE__) + "/../fixtures/getbinaryfile"
-    @tmp_file = tmp("getbinaryfile")
-
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-    @ftp.binary = @binary_mode
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @tmp_file
-  end
-
-  it "sends the RETR command to the server" do
-    @ftp.send(@method, "test", @tmp_file)
-    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
-  end
-
-  it "returns nil" do
-    @ftp.send(@method, "test", @tmp_file).should be_nil
-  end
-
-  it "saves the contents of the passed remote file to the passed local file" do
-    @ftp.send(@method, "test", @tmp_file)
-    File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
-  end
-
-  describe "when passed a block" do
-    it "yields the received content as binary blocks of the passed size" do
-      res = []
-      @ftp.send(@method, "test", @tmp_file, 10) { |bin| res << bin }
-      res.should == [ "This is th", "e content\n", "of the fil", "e named 't", "est'.\n" ]
-    end
-  end
-
-  describe "when resuming an existing file" do
-    before :each do
-      @tmp_file = tmp("getbinaryfile_resume")
-
-      File.open(@tmp_file, "wb") do |f|
-        f << "This is the content\n"
-      end
-
-      @ftp.resume = true
-    end
-
-    it "saves the remaining content of the passed remote file to the passed local file" do
-      @ftp.send(@method, "test", @tmp_file)
-      File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
-    end
-
-    describe "and the REST command fails" do
-      it "raises a Net::FTPProtoError when the response code is 550" do
-        @server.should_receive(:rest).and_respond("Requested action not taken.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 500" do
-        @server.should_receive(:rest).and_respond("500 Syntax error, command unrecognized.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 501" do
-        @server.should_receive(:rest).and_respond("501 Syntax error, command unrecognized.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 502" do
-        @server.should_receive(:rest).and_respond("502 Command not implemented.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPTempError when the response code is 421" do
-        @server.should_receive(:rest).and_respond("421 Service not available, closing control connection.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 530" do
-        @server.should_receive(:rest).and_respond("530 Not logged in.")
-        -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-      end
-    end
-  end
-
-  describe "when the RETR command fails" do
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:retr).and_respond("450 Requested file action not taken.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPProtoError when the response code is 550" do
-      @server.should_receive(:retr).and_respond("Requested action not taken.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:retr).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:retr).and_respond("501 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:retr).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:retr).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when opening the data port fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
-      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
-      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
-      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:eprt).and_respond("530 Not logged in.")
-      @server.should_receive(:port).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/shared/gettextfile.rb b/spec/ruby/library/net/ftp/shared/gettextfile.rb
deleted file mode 100644
index 82bec2a4a7..0000000000
--- a/spec/ruby/library/net/ftp/shared/gettextfile.rb
+++ /dev/null
@@ -1,100 +0,0 @@
-describe :net_ftp_gettextfile, shared: :true do
-  before :each do
-    @tmp_file = tmp("gettextfile")
-
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-    @ftp.binary = @binary_mode
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @tmp_file
-  end
-
-  it "sends the RETR command to the server" do
-    @ftp.send(@method, "test", @tmp_file)
-    @ftp.last_response.should == "226 Closing data connection. (RETR test)\n"
-  end
-
-  it "returns nil" do
-    @ftp.send(@method, "test", @tmp_file).should be_nil
-  end
-
-  it "saves the contents of the passed remote file to the passed local file" do
-    @ftp.send(@method, "test", @tmp_file)
-    File.read(@tmp_file).should == "This is the content\nof the file named 'test'.\n"
-  end
-
-  describe "when passed a block" do
-    it "yields each line of the retrieved file to the passed block" do
-      res = []
-      @ftp.send(@method, "test", @tmp_file) { |line| res << line }
-      res.should == [ "This is the content", "of the file named 'test'."]
-    end
-  end
-
-  describe "when the RETR command fails" do
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:retr).and_respond("450 Requested file action not taken.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPProtoError when the response code is 550" do
-      @server.should_receive(:retr).and_respond("Requested action not taken.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPProtoError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:retr).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:retr).and_respond("501 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:retr).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:retr).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when opening the data port fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
-      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
-      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
-      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:eprt).and_respond("530 Not logged in.")
-      @server.should_receive(:port).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, "test", @tmp_file) }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/shared/putbinaryfile.rb b/spec/ruby/library/net/ftp/shared/putbinaryfile.rb
deleted file mode 100644
index 1163a1cfea..0000000000
--- a/spec/ruby/library/net/ftp/shared/putbinaryfile.rb
+++ /dev/null
@@ -1,167 +0,0 @@
-describe :net_ftp_putbinaryfile, shared: :true do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @local_fixture_file  = File.dirname(__FILE__) + "/../fixtures/putbinaryfile"
-    @remote_tmp_file = tmp("binaryfile", false)
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-    @ftp.binary = @binary_mode
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @remote_tmp_file
-  end
-
-  it "sends the STOR command to the server" do
-    @ftp.send(@method, @local_fixture_file, "binary")
-    @ftp.last_response.should == "200 OK, Data received. (STOR binary)\n"
-  end
-
-  it "sends the contents of the passed local_file, without modifications" do
-    @ftp.send(@method, @local_fixture_file, "binary")
-
-    remote_lines = File.readlines(@remote_tmp_file)
-    local_lines  = File.readlines(@local_fixture_file)
-
-    remote_lines.should == local_lines
-  end
-
-  it "returns nil" do
-    @ftp.send(@method, @local_fixture_file, "binary").should be_nil
-  end
-
-  describe "when passed a block" do
-    it "yields the transmitted content as binary blocks of the passed size" do
-      res = []
-      @ftp.send(@method, @local_fixture_file, "binary", 10) { |x| res << x }
-      res.should == [
-        "This is an", " example f",
-        "ile\nwhich ", "is going t",
-        "o be trans", "mitted\nusi",
-        "ng #putbin", "aryfile.\n"
-      ]
-    end
-  end
-
-  describe "when resuming an existing file" do
-    before :each do
-      File.open(@remote_tmp_file, "w") do |f|
-        f << "This is an example file\n"
-      end
-
-      @ftp.resume = true
-    end
-
-    it "sends the remaining content of the passed local_file to the passed remote_file" do
-      @ftp.send(@method, @local_fixture_file, "binary")
-      File.read(@remote_tmp_file).should == File.read(@local_fixture_file)
-    end
-
-    describe "and the APPE command fails" do
-      it "raises a Net::FTPProtoError when the response code is 550" do
-        @server.should_receive(:appe).and_respond("Requested action not taken.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPProtoError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 500" do
-        @server.should_receive(:appe).and_respond("500 Syntax error, command unrecognized.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 501" do
-        @server.should_receive(:appe).and_respond("501 Syntax error, command unrecognized.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 502" do
-        @server.should_receive(:appe).and_respond("502 Command not implemented.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-      end
-
-      it "raises a Net::FTPTempError when the response code is 421" do
-        @server.should_receive(:appe).and_respond("421 Service not available, closing control connection.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
-      end
-
-      it "raises a Net::FTPPermError when the response code is 530" do
-        @server.should_receive(:appe).and_respond("530 Not logged in.")
-        -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-      end
-    end
-  end
-
-  describe "when the STOR command fails" do
-    it "raises a Net::FTPPermError when the response code is 532" do
-      @server.should_receive(:stor).and_respond("532 Need account for storing files.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:stor).and_respond("450 Requested file action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 452" do
-      @server.should_receive(:stor).and_respond("452 Requested action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 553" do
-      @server.should_receive(:stor).and_respond("553 Requested action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:stor).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:stor).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:stor).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:stor).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when opening the data port fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
-      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
-      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
-      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:eprt).and_respond("530 Not logged in.")
-      @server.should_receive(:port).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, @local_fixture_file, "binary") }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/shared/puttextfile.rb b/spec/ruby/library/net/ftp/shared/puttextfile.rb
deleted file mode 100644
index 50e8de28e6..0000000000
--- a/spec/ruby/library/net/ftp/shared/puttextfile.rb
+++ /dev/null
@@ -1,120 +0,0 @@
-describe :net_ftp_puttextfile, shared: true do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @local_fixture_file  = File.dirname(__FILE__) + "/../fixtures/puttextfile"
-    @remote_tmp_file = tmp("textfile", false)
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-    @ftp.binary = @binary_mode
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @remote_tmp_file
-  end
-
-  it "sends the STOR command to the server" do
-    @ftp.send(@method, @local_fixture_file, "text")
-    @ftp.last_response.should == "200 OK, Data received. (STOR text)\n"
-  end
-
-  it "sends the contents of the passed local_file, using \\r\\n as the newline separator" do
-    @ftp.send(@method, @local_fixture_file, "text")
-
-    remote_lines = open(@remote_tmp_file,    "rb") {|f| f.read }
-    local_lines  = open(@local_fixture_file, "rb") {|f| f.read }
-
-    remote_lines.should_not == local_lines
-    remote_lines.should == local_lines.gsub("\n", "\r\n")
-  end
-
-  it "returns nil" do
-    @ftp.send(@method, @local_fixture_file, "text").should be_nil
-  end
-
-  describe "when passed a block" do
-    it "yields each transmitted line" do
-      res = []
-      @ftp.send(@method, @local_fixture_file, "text") { |x| res << x }
-      res.should == [
-        "This is an example file\r\n",
-        "which is going to be transmitted\r\n",
-        "using #puttextfile.\r\n"
-      ]
-    end
-  end
-
-  describe "when the STOR command fails" do
-    it "raises a Net::FTPPermError when the response code is 532" do
-      @server.should_receive(:stor).and_respond("532 Need account for storing files.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 450" do
-      @server.should_receive(:stor).and_respond("450 Requested file action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 452" do
-      @server.should_receive(:stor).and_respond("452 Requested action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 553" do
-      @server.should_receive(:stor).and_respond("553 Requested action not taken.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:stor).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:stor).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:stor).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:stor).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-  end
-
-  describe "when opening the data port fails" do
-    it "raises a Net::FTPPermError when the response code is 500" do
-      @server.should_receive(:eprt).and_respond("500 Syntax error, command unrecognized.")
-      @server.should_receive(:port).and_respond("500 Syntax error, command unrecognized.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 501" do
-      @server.should_receive(:eprt).and_respond("501 Syntax error in parameters or arguments.")
-      @server.should_receive(:port).and_respond("501 Syntax error in parameters or arguments.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-
-    it "raises a Net::FTPTempError when the response code is 421" do
-      @server.should_receive(:eprt).and_respond("421 Service not available, closing control connection.")
-      @server.should_receive(:port).and_respond("421 Service not available, closing control connection.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPTempError)
-    end
-
-    it "raises a Net::FTPPermError when the response code is 530" do
-      @server.should_receive(:eprt).and_respond("530 Not logged in.")
-      @server.should_receive(:port).and_respond("530 Not logged in.")
-      -> { @ftp.send(@method, @local_fixture_file, "text") }.should raise_error(Net::FTPPermError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/site_spec.rb b/spec/ruby/library/net/ftp/site_spec.rb
deleted file mode 100644
index 4d6a9b4a0c..0000000000
--- a/spec/ruby/library/net/ftp/site_spec.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#site" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the SITE command with the passed argument to the server" do
-    @ftp.site("param")
-    @ftp.last_response.should == "200 Command okay. (SITE param)\n"
-  end
-
-  it "returns nil" do
-    @ftp.site("param").should be_nil
-  end
-
-  it "does not raise an error when the response code is 202" do
-    @server.should_receive(:site).and_respond("202 Command not implemented, superfluous at this site.")
-    -> { @ftp.site("param") }.should_not raise_error
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:site).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:site).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:site).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.site("param") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:site).and_respond("530 Requested action not taken.")
-    -> { @ftp.site("param") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/size_spec.rb b/spec/ruby/library/net/ftp/size_spec.rb
deleted file mode 100644
index 17615079e9..0000000000
--- a/spec/ruby/library/net/ftp/size_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#size" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the SIZE command to the server" do
-    @ftp.size("test.file")
-    @ftp.last_response.should == "213 1024\n"
-  end
-
-  it "returns the size of the passed file as Integer" do
-    @ftp.size("test.file").should eql(1024)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:size).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:size).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:size).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.size("test.file") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 550" do
-    @server.should_receive(:size).and_respond("550 Requested action not taken.")
-    -> { @ftp.size("test.file") }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/status_spec.rb b/spec/ruby/library/net/ftp/status_spec.rb
deleted file mode 100644
index 6e3840bf93..0000000000
--- a/spec/ruby/library/net/ftp/status_spec.rb
+++ /dev/null
@@ -1,67 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#status" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the STAT command to the server" do
-    @ftp.status
-    @ftp.last_response.should == "211 System status, or system help reply. (STAT)\n"
-  end
-
-  it "sends the STAT command with an optional parameter to the server" do
-    @ftp.status("/pub").should == "211 System status, or system help reply. (STAT /pub)\n"
-  end
-
-  it "returns the received information" do
-    @ftp.status.should == "211 System status, or system help reply. (STAT)\n"
-  end
-
-  it "does not raise an error when the response code is 212" do
-    @server.should_receive(:stat).and_respond("212 Directory status.")
-    -> { @ftp.status }.should_not raise_error
-  end
-
-  it "does not raise an error when the response code is 213" do
-    @server.should_receive(:stat).and_respond("213 File status.")
-    -> { @ftp.status }.should_not raise_error
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:stat).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.status }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:stat).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.status }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:stat).and_respond("502 Command not implemented.")
-    -> { @ftp.status }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:stat).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.status }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 530" do
-    @server.should_receive(:stat).and_respond("530 Requested action not taken.")
-    -> { @ftp.status }.should raise_error(Net::FTPPermError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/storbinary_spec.rb b/spec/ruby/library/net/ftp/storbinary_spec.rb
deleted file mode 100644
index eb65db1e8d..0000000000
--- a/spec/ruby/library/net/ftp/storbinary_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#storbinary" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @local_fixture_file  = File.dirname(__FILE__) + "/fixtures/putbinaryfile"
-    @tmp_file = tmp("binaryfile", false)
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @tmp_file
-  end
-
-  it "sends the passed command and the passed File object's content to the server" do
-    File.open(@local_fixture_file) do |f|
-      f.binmode
-
-      @ftp.storbinary("STOR binary", f, 4096) {}
-      @ftp.last_response.should == "200 OK, Data received. (STOR binary)\n"
-    end
-  end
-
-  it "yields the transmitted content as binary blocks of the passed size" do
-    File.open(@local_fixture_file) do |f|
-      f.binmode
-
-      res = []
-      @ftp.storbinary("STOR binary", f, 10) { |x| res << x }
-      res.should == [
-        "This is an", " example f",
-        "ile\nwhich ", "is going t",
-        "o be trans", "mitted\nusi",
-        "ng #putbin", "aryfile.\n"
-      ]
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/storlines_spec.rb b/spec/ruby/library/net/ftp/storlines_spec.rb
deleted file mode 100644
index 4affa37eee..0000000000
--- a/spec/ruby/library/net/ftp/storlines_spec.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#storlines" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @local_fixture_file  = File.dirname(__FILE__) + "/fixtures/puttextfile"
-    @tmp_file = tmp("textfile", false)
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-
-    rm_r @tmp_file
-  end
-
-  it "sends the passed command and the passed File object's content to the server" do
-    File.open(@local_fixture_file) do |f|
-      @ftp.storlines("STOR text", f) {}
-      @ftp.last_response.should == "200 OK, Data received. (STOR text)\n"
-    end
-  end
-
-  it "yields each line of the transmitted content" do
-    File.open(@local_fixture_file) do |f|
-      res = []
-      @ftp.storlines("STOR text", f) { |x| res << x }
-      res.should == [
-        "This is an example file\r\n",
-        "which is going to be transmitted\r\n",
-        "using #puttextfile.\r\n"
-      ]
-    end
-  end
-end
diff --git a/spec/ruby/library/net/ftp/system_spec.rb b/spec/ruby/library/net/ftp/system_spec.rb
deleted file mode 100644
index 749258622d..0000000000
--- a/spec/ruby/library/net/ftp/system_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#system" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the SYST command to the server" do
-    @ftp.system
-    @ftp.last_response.should =~ /\A215 FTP Dummy Server \(SYST\)\Z/
-  end
-
-  it "returns the received information" do
-    @ftp.system.should =~ /\AFTP Dummy Server \(SYST\)\Z/
-  end
-
-  it "raises a Net::FTPPermError when the response code is 500" do
-    @server.should_receive(:syst).and_respond("500 Syntax error, command unrecognized.")
-    -> { @ftp.system }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 501" do
-    @server.should_receive(:syst).and_respond("501 Syntax error in parameters or arguments.")
-    -> { @ftp.system }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 502" do
-    @server.should_receive(:syst).and_respond("502 Command not implemented.")
-    -> { @ftp.system }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 421" do
-    @server.should_receive(:syst).and_respond("421 Service not available, closing control connection.")
-    -> { @ftp.system }.should raise_error(Net::FTPTempError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/voidcmd_spec.rb b/spec/ruby/library/net/ftp/voidcmd_spec.rb
deleted file mode 100644
index 3673c7fd5b..0000000000
--- a/spec/ruby/library/net/ftp/voidcmd_spec.rb
+++ /dev/null
@@ -1,54 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#voidcmd" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "sends the passed command to the server" do
-    @server.should_receive(:help).and_respond("2xx Does not raise.")
-    -> { @ftp.voidcmd("HELP") }.should_not raise_error
-  end
-
-  it "returns nil" do
-    @server.should_receive(:help).and_respond("2xx Does not raise.")
-    @ftp.voidcmd("HELP").should be_nil
-  end
-
-  it "raises a Net::FTPReplyError when the response code is 1xx" do
-    @server.should_receive(:help).and_respond("1xx Does raise a Net::FTPReplyError.")
-    -> { @ftp.voidcmd("HELP")  }.should raise_error(Net::FTPReplyError)
-  end
-
-  it "raises a Net::FTPReplyError when the response code is 3xx" do
-    @server.should_receive(:help).and_respond("3xx Does raise a Net::FTPReplyError.")
-    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPReplyError)
-  end
-
-  it "raises a Net::FTPTempError when the response code is 4xx" do
-    @server.should_receive(:help).and_respond("4xx Does raise a Net::FTPTempError.")
-    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPTempError)
-  end
-
-  it "raises a Net::FTPPermError when the response code is 5xx" do
-    @server.should_receive(:help).and_respond("5xx Does raise a Net::FTPPermError.")
-    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPPermError)
-  end
-
-  it "raises a Net::FTPProtoError when the response code is not valid" do
-    @server.should_receive(:help).and_respond("999 Does raise a Net::FTPProtoError.")
-    -> { @ftp.voidcmd("HELP") }.should raise_error(Net::FTPProtoError)
-  end
-end
diff --git a/spec/ruby/library/net/ftp/welcome_spec.rb b/spec/ruby/library/net/ftp/welcome_spec.rb
deleted file mode 100644
index a0d7483949..0000000000
--- a/spec/ruby/library/net/ftp/welcome_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'spec_helper'
-require_relative 'fixtures/server'
-
-describe "Net::FTP#welcome" do
-  before :each do
-    @server = NetFTPSpecs::DummyFTP.new
-    @server.serve_once
-
-    @ftp = Net::FTP.new
-    @ftp.connect(@server.hostname, @server.server_port)
-  end
-
-  after :each do
-    @ftp.quit rescue nil
-    @ftp.close
-    @server.stop
-  end
-
-  it "returns the server's welcome message" do
-    @ftp.welcome.should be_nil
-    @ftp.login
-    @ftp.welcome.should == "230 User logged in, proceed. (USER anonymous)\n"
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPBadResponse_spec.rb b/spec/ruby/library/net/http/HTTPBadResponse_spec.rb
deleted file mode 100644
index be644968f5..0000000000
--- a/spec/ruby/library/net/http/HTTPBadResponse_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPBadResponse" do
-  it "is a subclass of StandardError" do
-    Net::HTTPBadResponse.should < StandardError
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPClientExcepton_spec.rb b/spec/ruby/library/net/http/HTTPClientExcepton_spec.rb
deleted file mode 100644
index 08347464ec..0000000000
--- a/spec/ruby/library/net/http/HTTPClientExcepton_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-ruby_version_is "2.6" do
-  describe "Net::HTTPClientException" do
-    it "is a subclass of Net::ProtoServerError" do
-      Net::HTTPClientException.should < Net::ProtoServerError
-    end
-
-    it "includes the Net::HTTPExceptions module" do
-      Net::HTTPClientException.should < Net::HTTPExceptions
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPError_spec.rb b/spec/ruby/library/net/http/HTTPError_spec.rb
deleted file mode 100644
index ab5f491bb7..0000000000
--- a/spec/ruby/library/net/http/HTTPError_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPError" do
-  it "is a subclass of Net::ProtocolError" do
-    Net::HTTPError.should < Net::ProtocolError
-  end
-
-  it "includes the Net::HTTPExceptions module" do
-    Net::HTTPError.should < Net::HTTPExceptions
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPFatalError_spec.rb b/spec/ruby/library/net/http/HTTPFatalError_spec.rb
deleted file mode 100644
index 6ab36bff6c..0000000000
--- a/spec/ruby/library/net/http/HTTPFatalError_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPFatalError" do
-  it "is a subclass of Net::ProtoFatalError" do
-    Net::HTTPFatalError.should < Net::ProtoFatalError
-  end
-
-  it "includes the Net::HTTPExceptions module" do
-    Net::HTTPFatalError.should < Net::HTTPExceptions
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPHeaderSyntaxError_spec.rb b/spec/ruby/library/net/http/HTTPHeaderSyntaxError_spec.rb
deleted file mode 100644
index 38e9454f99..0000000000
--- a/spec/ruby/library/net/http/HTTPHeaderSyntaxError_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPHeaderSyntaxError" do
-  it "is a subclass of StandardError" do
-    Net::HTTPHeaderSyntaxError.should < StandardError
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPRetriableError_spec.rb b/spec/ruby/library/net/http/HTTPRetriableError_spec.rb
deleted file mode 100644
index 3a4bb9146c..0000000000
--- a/spec/ruby/library/net/http/HTTPRetriableError_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPRetriableError" do
-  it "is a subclass of Net::ProtoRetriableError" do
-    Net::HTTPRetriableError.should < Net::ProtoRetriableError
-  end
-
-  it "includes the Net::HTTPExceptions module" do
-    Net::HTTPRetriableError.should < Net::HTTPExceptions
-  end
-end
diff --git a/spec/ruby/library/net/http/HTTPServerException_spec.rb b/spec/ruby/library/net/http/HTTPServerException_spec.rb
deleted file mode 100644
index 87841ab499..0000000000
--- a/spec/ruby/library/net/http/HTTPServerException_spec.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require_relative '../../../spec_helper'
-require 'net/http'
-
-ruby_version_is ""..."2.6" do
-  describe "Net::HTTPServerException" do
-    it "is a subclass of Net::ProtoServerError" do
-      Net::HTTPServerException.should < Net::ProtoServerError
-    end
-
-    it "includes the Net::HTTPExceptions module" do
-      Net::HTTPServerException.should < Net::HTTPExceptions
-    end
-  end
-end
-
-ruby_version_is "2.6" do
-  describe "Net::HTTPServerException" do
-    it "is a subclass of Net::ProtoServerError and is warned as deprecated" do
-      -> { Net::HTTPServerException.should < Net::ProtoServerError }.should complain(/warning: constant Net::HTTPServerException is deprecated/)
-    end
-
-    it "includes the Net::HTTPExceptions module and is warned as deprecated" do
-      -> { Net::HTTPServerException.should < Net::HTTPExceptions }.should complain(/warning: constant Net::HTTPServerException is deprecated/)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/Proxy_spec.rb b/spec/ruby/library/net/http/http/Proxy_spec.rb
deleted file mode 100644
index f85ccc0ee9..0000000000
--- a/spec/ruby/library/net/http/http/Proxy_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.Proxy" do
-  it "returns a new subclass of Net::HTTP" do
-    Net::HTTP.Proxy("localhost").should < Net::HTTP
-  end
-
-  it "returns Net::HTTP when the passed address is nil" do
-    Net::HTTP.Proxy(nil).should == Net::HTTP
-  end
-
-  it "sets the returned subclasses' proxy options based on the passed arguments" do
-    http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-    http_with_proxy.proxy_address.should == "localhost"
-    http_with_proxy.proxy_port.should eql(1234)
-    http_with_proxy.proxy_user.should == "rspec"
-    http_with_proxy.proxy_pass.should == "rocks"
-  end
-end
-
-describe "Net::HTTP#proxy?" do
-  describe "when self is no proxy class instance" do
-    it "returns false" do
-      Net::HTTP.new("localhost", 3333).proxy?.should be_false
-    end
-  end
-
-  describe "when self is a proxy class instance" do
-    it "returns false" do
-      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-      http_with_proxy.new("localhost", 3333).proxy?.should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/active_spec.rb b/spec/ruby/library/net/http/http/active_spec.rb
deleted file mode 100644
index ef657243ba..0000000000
--- a/spec/ruby/library/net/http/http/active_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/started'
-
-describe "Net::HTTP#active?" do
-  it_behaves_like :net_http_started_p, :active?
-end
diff --git a/spec/ruby/library/net/http/http/address_spec.rb b/spec/ruby/library/net/http/http/address_spec.rb
deleted file mode 100644
index 5fce76d767..0000000000
--- a/spec/ruby/library/net/http/http/address_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#address" do
-  it "returns the current host name" do
-    net = Net::HTTP.new("localhost")
-    net.address.should == "localhost"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/close_on_empty_response_spec.rb b/spec/ruby/library/net/http/http/close_on_empty_response_spec.rb
deleted file mode 100644
index a97b7b6c43..0000000000
--- a/spec/ruby/library/net/http/http/close_on_empty_response_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#close_on_empty_response" do
-  it "needs to be reviewed for spec completeness"
-end
-
-describe "Net::HTTP#close_on_empty_response=" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/library/net/http/http/copy_spec.rb b/spec/ruby/library/net/http/http/copy_spec.rb
deleted file mode 100644
index 5ebfdc334e..0000000000
--- a/spec/ruby/library/net/http/http/copy_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#copy" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a COPY request to the passed path and returns the response" do
-    response = @http.copy("/request")
-    response.should be_kind_of(Net::HTTPResponse)
-    response.body.should == "Request type: COPY"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/default_port_spec.rb b/spec/ruby/library/net/http/http/default_port_spec.rb
deleted file mode 100644
index 30db18efae..0000000000
--- a/spec/ruby/library/net/http/http/default_port_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.default_port" do
-  it "returns 80" do
-    Net::HTTP.http_default_port.should eql(80)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/delete_spec.rb b/spec/ruby/library/net/http/http/delete_spec.rb
deleted file mode 100644
index 160c653115..0000000000
--- a/spec/ruby/library/net/http/http/delete_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#delete" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a DELETE request to the passed path and returns the response" do
-    response = @http.delete("/request")
-    response.should be_kind_of(Net::HTTPResponse)
-    response.body.should == "Request type: DELETE"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/finish_spec.rb b/spec/ruby/library/net/http/http/finish_spec.rb
deleted file mode 100644
index f98bc7be13..0000000000
--- a/spec/ruby/library/net/http/http/finish_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#finish" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when self has been started" do
-    it "closes the tcp connection" do
-      @http.start
-      @http.finish
-      @http.started?.should be_false
-    end
-  end
-
-  describe "when self has not been started yet" do
-    it "raises an IOError" do
-      -> { @http.finish }.should raise_error(IOError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/fixtures/http_server.rb b/spec/ruby/library/net/http/http/fixtures/http_server.rb
deleted file mode 100644
index 49e8f437cc..0000000000
--- a/spec/ruby/library/net/http/http/fixtures/http_server.rb
+++ /dev/null
@@ -1,105 +0,0 @@
-require 'webrick'
-require 'webrick/httpservlet/abstract'
-
-module NetHTTPSpecs
-  class NullWriter
-    def <<(s) end
-    def puts(*args) end
-    def print(*args) end
-    def printf(*args) end
-  end
-
-  class SpecServlet < WEBrick::HTTPServlet::AbstractServlet
-    def handle(req, res)
-      reply(req, res)
-    end
-
-    %w{ do_GET do_HEAD do_POST do_PUT do_PROPPATCH do_LOCK do_UNLOCK
-        do_OPTIONS do_PROPFIND do_DELETE do_MOVE do_COPY
-        do_MKCOL do_TRACE }.each do |method|
-      alias_method method.to_sym, :handle
-    end
-  end
-
-  class RequestServlet < SpecServlet
-    def reply(req, res)
-      res.content_type = "text/plain"
-      res.body = "Request type: #{req.request_method}"
-    end
-  end
-
-  class RequestBodyServlet < SpecServlet
-    def reply(req, res)
-      res.content_type = "text/plain"
-      res.body = req.body
-    end
-  end
-
-  class RequestHeaderServlet < SpecServlet
-    def reply(req, res)
-      res.content_type = "text/plain"
-      res.body = req.header.inspect
-    end
-  end
-
-  class RequestBasicAuthServlet < SpecServlet
-    def reply(req, res)
-      res.content_type = "text/plain"
-
-      WEBrick::HTTPAuth.basic_auth(req, res, "realm") do |user, pass|
-        res.body = "username: #{user}\npassword: #{pass}"
-        true
-      end
-    end
-  end
-
-  class << self
-    @server = nil
-    @server_thread = nil
-
-    def port
-      raise "server not started" unless @server
-      @server.config[:Port]
-    end
-
-    def start_server
-      server_config = {
-        BindAddress: "127.0.0.1",
-        Port: 0,
-        Logger: WEBrick::Log.new(NullWriter.new),
-        AccessLog: [],
-        ServerType: Thread
-      }
-
-      @server = WEBrick::HTTPServer.new(server_config)
-
-      @server.mount_proc('/') do |req, res|
-        res.content_type = "text/plain"
-        res.body = "This is the index page."
-      end
-      @server.mount('/request', RequestServlet)
-      @server.mount("/request/body", RequestBodyServlet)
-      @server.mount("/request/header", RequestHeaderServlet)
-      @server.mount("/request/basic_auth", RequestBasicAuthServlet)
-
-      @server_thread = @server.start
-    end
-
-    def stop_server
-      if @server
-        begin
-          @server.shutdown
-        rescue Errno::EPIPE
-          # Because WEBrick is not thread-safe and only catches IOError
-        end
-        @server = nil
-      end
-      if @server_thread
-        @server_thread.join
-        @server_thread = nil
-      end
-      timeout = WEBrick::Utils::TimeoutHandler
-      timeout.terminate if timeout.respond_to?(:terminate)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/get2_spec.rb b/spec/ruby/library/net/http/http/get2_spec.rb
deleted file mode 100644
index 71dfc3d39b..0000000000
--- a/spec/ruby/library/net/http/http/get2_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_get'
-
-describe "Net::HTTP#get2" do
-  it_behaves_like :net_ftp_request_get, :get2
-end
diff --git a/spec/ruby/library/net/http/http/get_print_spec.rb b/spec/ruby/library/net/http/http/get_print_spec.rb
deleted file mode 100644
index f59dd68c81..0000000000
--- a/spec/ruby/library/net/http/http/get_print_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.get_print" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed URI" do
-    it "it prints the body of the specified uri to $stdout" do
-      -> do
-        Net::HTTP.get_print URI.parse("http://localhost:#{@port}/")
-      end.should output(/This is the index page\./)
-    end
-  end
-
-  describe "when passed host, path, port" do
-    it "it prints the body of the specified uri to $stdout" do
-      -> do
-        Net::HTTP.get_print 'localhost', "/", @port
-      end.should output(/This is the index page\./)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/get_response_spec.rb b/spec/ruby/library/net/http/http/get_response_spec.rb
deleted file mode 100644
index 941b35e773..0000000000
--- a/spec/ruby/library/net/http/http/get_response_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.get_response" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed URI" do
-    it "returns the response for the specified uri" do
-      res = Net::HTTP.get_response(URI.parse("http://localhost:#{@port}/"))
-      res.content_type.should == "text/plain"
-      res.body.should == "This is the index page."
-    end
-  end
-
-  describe "when passed host, path, port" do
-    it "returns the response for the specified host-path-combination" do
-      res = Net::HTTP.get_response('localhost', "/", @port)
-      res.content_type.should == "text/plain"
-      res.body.should == "This is the index page."
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/get_spec.rb b/spec/ruby/library/net/http/http/get_spec.rb
deleted file mode 100644
index 4b8af5950a..0000000000
--- a/spec/ruby/library/net/http/http/get_spec.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.get when passed URI" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed URI" do
-    it "returns the body of the specified uri" do
-      Net::HTTP.get(URI.parse("http://localhost:#{@port}/")).should == "This is the index page."
-    end
-  end
-
-  describe "when passed host, path, port" do
-    it "returns the body of the specified host-path-combination" do
-      Net::HTTP.get('localhost', "/", @port).should == "This is the index page."
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/head2_spec.rb b/spec/ruby/library/net/http/http/head2_spec.rb
deleted file mode 100644
index 606798e4af..0000000000
--- a/spec/ruby/library/net/http/http/head2_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_head'
-
-describe "Net::HTTP#head2" do
-  it_behaves_like :net_ftp_request_head, :head2
-end
diff --git a/spec/ruby/library/net/http/http/head_spec.rb b/spec/ruby/library/net/http/http/head_spec.rb
deleted file mode 100644
index 925a8e6043..0000000000
--- a/spec/ruby/library/net/http/http/head_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#head" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a HEAD request to the passed path and returns the response" do
-    response = @http.head("/request")
-    # HEAD requests have no responses
-    response.body.should be_nil
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.head("/request").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/http_default_port_spec.rb b/spec/ruby/library/net/http/http/http_default_port_spec.rb
deleted file mode 100644
index cf7f73e630..0000000000
--- a/spec/ruby/library/net/http/http/http_default_port_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.http_default_port" do
-  it "returns 80" do
-    Net::HTTP.http_default_port.should eql(80)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/https_default_port_spec.rb b/spec/ruby/library/net/http/http/https_default_port_spec.rb
deleted file mode 100644
index fbf0bd1abc..0000000000
--- a/spec/ruby/library/net/http/http/https_default_port_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.https_default_port" do
-  it "returns 443" do
-    Net::HTTP.https_default_port.should eql(443)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/initialize_spec.rb b/spec/ruby/library/net/http/http/initialize_spec.rb
deleted file mode 100644
index 7683713a0e..0000000000
--- a/spec/ruby/library/net/http/http/initialize_spec.rb
+++ /dev/null
@@ -1,46 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#initialize" do
-  it "is private" do
-    Net::HTTP.should have_private_instance_method(:initialize)
-  end
-
-  describe "when passed address" do
-    before :each do
-      @net = Net::HTTP.allocate
-      @net.send(:initialize, "localhost")
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @net.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the default HTTP port" do
-      @net.port.should eql(Net::HTTP.default_port)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @net.started?.should be_false
-    end
-  end
-
-  describe "when passed address, port" do
-    before :each do
-      @net = Net::HTTP.allocate
-      @net.send(:initialize, "localhost", 3333)
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @net.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the passed port" do
-      @net.port.should eql(3333)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @net.started?.should be_false
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/inspect_spec.rb b/spec/ruby/library/net/http/http/inspect_spec.rb
deleted file mode 100644
index b1e799ca34..0000000000
--- a/spec/ruby/library/net/http/http/inspect_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#inspect" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-    @http = Net::HTTP.new("localhost", @port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "returns a String representation of self" do
-    @http.inspect.should be_kind_of(String)
-    @http.inspect.should == "#<Net::HTTP localhost:#{@port} open=false>"
-
-    @http.start
-    @http.inspect.should == "#<Net::HTTP localhost:#{@port} open=true>"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/is_version_1_1_spec.rb b/spec/ruby/library/net/http/http/is_version_1_1_spec.rb
deleted file mode 100644
index f37695b777..0000000000
--- a/spec/ruby/library/net/http/http/is_version_1_1_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/version_1_1'
-
-describe "Net::HTTP.is_version_1_1?" do
-  it_behaves_like :net_http_version_1_1_p, :is_version_1_1?
-end
diff --git a/spec/ruby/library/net/http/http/is_version_1_2_spec.rb b/spec/ruby/library/net/http/http/is_version_1_2_spec.rb
deleted file mode 100644
index 82dbdc87aa..0000000000
--- a/spec/ruby/library/net/http/http/is_version_1_2_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/version_1_2'
-
-describe "Net::HTTP.is_version_1_2?" do
-  it_behaves_like :net_http_version_1_2_p, :is_version_1_2?
-end
diff --git a/spec/ruby/library/net/http/http/lock_spec.rb b/spec/ruby/library/net/http/http/lock_spec.rb
deleted file mode 100644
index bb76607a8b..0000000000
--- a/spec/ruby/library/net/http/http/lock_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#lock" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a LOCK request to the passed path and returns the response" do
-    response = @http.lock("/request", "test=test")
-    response.should be_kind_of(Net::HTTPResponse)
-    response.body.should == "Request type: LOCK"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/mkcol_spec.rb b/spec/ruby/library/net/http/http/mkcol_spec.rb
deleted file mode 100644
index 33017625e2..0000000000
--- a/spec/ruby/library/net/http/http/mkcol_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#mkcol" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a MKCOL request to the passed path and returns the response" do
-    response = @http.mkcol("/request")
-    response.should be_kind_of(Net::HTTPResponse)
-    response.body.should == "Request type: MKCOL"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/move_spec.rb b/spec/ruby/library/net/http/http/move_spec.rb
deleted file mode 100644
index 4d6b828150..0000000000
--- a/spec/ruby/library/net/http/http/move_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#head" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a MOVE request to the passed path and returns the response" do
-    response = @http.move("/request")
-    # HEAD requests have no responses
-    response.body.should == "Request type: MOVE"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.move("/request").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/new_spec.rb b/spec/ruby/library/net/http/http/new_spec.rb
deleted file mode 100644
index 491d1d01fd..0000000000
--- a/spec/ruby/library/net/http/http/new_spec.rb
+++ /dev/null
@@ -1,86 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.new" do
-  describe "when passed address" do
-    before :each do
-      @http = Net::HTTP.new("localhost")
-    end
-
-    it "returns a Net::HTTP instance" do
-      @http.proxy?.should be_false
-      @http.instance_of?(Net::HTTP).should be_true
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @http.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the default HTTP port" do
-      @http.port.should eql(Net::HTTP.default_port)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @http.started?.should be_false
-    end
-  end
-
-  describe "when passed address, port" do
-    before :each do
-      @http = Net::HTTP.new("localhost", 3333)
-    end
-
-    it "returns a Net::HTTP instance" do
-      @http.proxy?.should be_false
-      @http.instance_of?(Net::HTTP).should be_true
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @http.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the passed port" do
-      @http.port.should eql(3333)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @http.started?.should be_false
-    end
-  end
-
-  describe "when passed address, port, *proxy_options" do
-    it "returns a Net::HTTP instance" do
-      http = Net::HTTP.new("localhost", 3333, "localhost")
-      http.proxy?.should be_true
-      http.instance_of?(Net::HTTP).should be_true
-      http.should be_kind_of(Net::HTTP)
-    end
-
-    it "correctly sets the passed Proxy options" do
-      http = Net::HTTP.new("localhost", 3333, "localhost")
-      http.proxy_address.should == "localhost"
-      http.proxy_port.should eql(80)
-      http.proxy_user.should be_nil
-      http.proxy_pass.should be_nil
-
-      http = Net::HTTP.new("localhost", 3333, "localhost", 1234)
-      http.proxy_address.should == "localhost"
-      http.proxy_port.should eql(1234)
-      http.proxy_user.should be_nil
-      http.proxy_pass.should be_nil
-
-      http = Net::HTTP.new("localhost", 3333, "localhost", 1234, "rubyspec")
-      http.proxy_address.should == "localhost"
-      http.proxy_port.should eql(1234)
-      http.proxy_user.should == "rubyspec"
-      http.proxy_pass.should be_nil
-
-      http = Net::HTTP.new("localhost", 3333, "localhost", 1234, "rubyspec", "rocks")
-      http.proxy_address.should == "localhost"
-      http.proxy_port.should eql(1234)
-      http.proxy_user.should == "rubyspec"
-      http.proxy_pass.should == "rocks"
-    end
-  end
-
-end
diff --git a/spec/ruby/library/net/http/http/newobj_spec.rb b/spec/ruby/library/net/http/http/newobj_spec.rb
deleted file mode 100644
index b261dcc5db..0000000000
--- a/spec/ruby/library/net/http/http/newobj_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.newobj" do
-  before :each do
-    @net = Net::HTTP.newobj("localhost")
-  end
-
-  describe "when passed address" do
-    it "returns a new Net::HTTP instance" do
-      @net.should be_kind_of(Net::HTTP)
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @net.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the default HTTP port" do
-      @net.port.should eql(Net::HTTP.default_port)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @net.started?.should be_false
-    end
-  end
-
-  describe "when passed address, port" do
-    before :each do
-      @net = Net::HTTP.newobj("localhost", 3333)
-    end
-
-    it "returns a new Net::HTTP instance" do
-      @net.should be_kind_of(Net::HTTP)
-    end
-
-    it "sets the new Net::HTTP instance's address to the passed address" do
-      @net.address.should == "localhost"
-    end
-
-    it "sets the new Net::HTTP instance's port to the passed port" do
-      @net.port.should eql(3333)
-    end
-
-    it "does not start the new Net::HTTP instance" do
-      @net.started?.should be_false
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/open_timeout_spec.rb b/spec/ruby/library/net/http/http/open_timeout_spec.rb
deleted file mode 100644
index 44b33615e6..0000000000
--- a/spec/ruby/library/net/http/http/open_timeout_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#open_timeout" do
-  it "returns the seconds to wait till the connection is open" do
-    net = Net::HTTP.new("localhost")
-    net.open_timeout.should eql(60)
-    net.open_timeout = 10
-    net.open_timeout.should eql(10)
-  end
-end
-
-describe "Net::HTTP#open_timeout=" do
-  it "sets the seconds to wait till the connection is open" do
-    net = Net::HTTP.new("localhost")
-    net.open_timeout = 10
-    net.open_timeout.should eql(10)
-  end
-
-  it "returns the newly set value" do
-    net = Net::HTTP.new("localhost")
-    (net.open_timeout = 10).should eql(10)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/options_spec.rb b/spec/ruby/library/net/http/http/options_spec.rb
deleted file mode 100644
index d798e69197..0000000000
--- a/spec/ruby/library/net/http/http/options_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#options" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an options request to the passed path and returns the response" do
-    response = @http.options("/request")
-
-    response.body.should == "Request type: OPTIONS"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.options("/request").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/port_spec.rb b/spec/ruby/library/net/http/http/port_spec.rb
deleted file mode 100644
index 7de295ca75..0000000000
--- a/spec/ruby/library/net/http/http/port_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#port" do
-  it "returns the current port number" do
-    net = Net::HTTP.new("localhost", 3333)
-    net.port.should eql(3333)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/post2_spec.rb b/spec/ruby/library/net/http/http/post2_spec.rb
deleted file mode 100644
index eab9a6a1d2..0000000000
--- a/spec/ruby/library/net/http/http/post2_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_post'
-
-describe "Net::HTTP#post2" do
-  it_behaves_like :net_ftp_request_post, :post2
-end
diff --git a/spec/ruby/library/net/http/http/post_form_spec.rb b/spec/ruby/library/net/http/http/post_form_spec.rb
deleted file mode 100644
index 891e05e7af..0000000000
--- a/spec/ruby/library/net/http/http/post_form_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.post_form when passed URI" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  it "POSTs the passed form data to the given uri" do
-    uri = URI.parse("http://localhost:#{@port}/request/body")
-    data = { test: :data }
-
-    res = Net::HTTP.post_form(uri, data)
-    res.body.should == "test=data"
-  end
-end
diff --git a/spec/ruby/library/net/http/http/post_spec.rb b/spec/ruby/library/net/http/http/post_spec.rb
deleted file mode 100644
index 9f20a03c85..0000000000
--- a/spec/ruby/library/net/http/http/post_spec.rb
+++ /dev/null
@@ -1,74 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require 'uri'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.post" do
-  before :each do
-    NetHTTPSpecs.start_server
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends post request to the specified URI and returns response" do
-    response = Net::HTTP.post(
-      URI("http://localhost:#{NetHTTPSpecs.port}/request"),
-      '{ "q": "ruby", "max": "50" }',
-      "Content-Type" => "application/json")
-    response.body.should == "Request type: POST"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    response = Net::HTTP.post(URI("http://localhost:#{NetHTTPSpecs.port}/request"), "test=test")
-    response.should be_kind_of(Net::HTTPResponse)
-  end
-
-  it "sends Content-Type: application/x-www-form-urlencoded by default" do
-    response = Net::HTTP.post(URI("http://localhost:#{NetHTTPSpecs.port}/request/header"), "test=test")
-    response.body.should include('"content-type"=>["application/x-www-form-urlencoded"]')
-  end
-
-  it "does not support HTTP Basic Auth" do
-    response = Net::HTTP.post(
-      URI("http://john:qwerty@localhost:#{NetHTTPSpecs.port}/request/basic_auth"),
-      "test=test")
-    response.body.should == "username: \npassword: "
-  end
-end
-
-describe "Net::HTTP#post" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an post request to the passed path and returns the response" do
-    response = @http.post("/request", "test=test")
-    response.body.should == "Request type: POST"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.post("/request", "test=test").should be_kind_of(Net::HTTPResponse)
-  end
-
-  describe "when passed a block" do
-    it "yields fragments of the response body to the passed block" do
-      str = ""
-      @http.post("/request", "test=test") do |res|
-        str << res
-      end
-      str.should == "Request type: POST"
-    end
-
-    it "returns a Net::HTTPResponse" do
-      @http.post("/request", "test=test") {}.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/propfind_spec.rb b/spec/ruby/library/net/http/http/propfind_spec.rb
deleted file mode 100644
index 5240171618..0000000000
--- a/spec/ruby/library/net/http/http/propfind_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#propfind" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an propfind request to the passed path and returns the response" do
-    response = @http.propfind("/request", "test=test")
-    response.body.should == "Request type: PROPFIND"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.propfind("/request", "test=test").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proppatch_spec.rb b/spec/ruby/library/net/http/http/proppatch_spec.rb
deleted file mode 100644
index 7a761a9f23..0000000000
--- a/spec/ruby/library/net/http/http/proppatch_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#proppatch" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an proppatch request to the passed path and returns the response" do
-    response = @http.proppatch("/request", "test=test")
-    response.body.should == "Request type: PROPPATCH"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.proppatch("/request", "test=test").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proxy_address_spec.rb b/spec/ruby/library/net/http/http/proxy_address_spec.rb
deleted file mode 100644
index 8d152b8d44..0000000000
--- a/spec/ruby/library/net/http/http/proxy_address_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.proxy_address" do
-  describe "when self is no proxy class" do
-    it "returns nil" do
-      Net::HTTP.proxy_address.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class" do
-    it "returns the address for self's proxy connection" do
-      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_address.should == "localhost"
-    end
-  end
-end
-
-describe "Net::HTTP#proxy_address" do
-  describe "when self is no proxy class instance" do
-    it "returns nil" do
-      Net::HTTP.new("localhost", 3333).proxy_address.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class instance" do
-    it "returns the password for self's proxy connection" do
-      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-      http_with_proxy.new("localhost", 3333).proxy_address.should == "localhost"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proxy_class_spec.rb b/spec/ruby/library/net/http/http/proxy_class_spec.rb
deleted file mode 100644
index 2d32a39f01..0000000000
--- a/spec/ruby/library/net/http/http/proxy_class_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.proxy_class?" do
-  it "returns true if self is a class created with Net::HTTP.Proxy" do
-    Net::HTTP.proxy_class?.should be_false
-    Net::HTTP.Proxy("localhost").proxy_class?.should be_true
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proxy_pass_spec.rb b/spec/ruby/library/net/http/http/proxy_pass_spec.rb
deleted file mode 100644
index 94a0034544..0000000000
--- a/spec/ruby/library/net/http/http/proxy_pass_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.proxy_pass" do
-  describe "when self is no proxy class" do
-    it "returns nil" do
-      Net::HTTP.proxy_pass.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class" do
-    it "returns nil if no password was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").proxy_pass.should be_nil
-    end
-
-    it "returns the password for self's proxy connection" do
-      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_pass.should == "rocks"
-    end
-  end
-end
-
-describe "Net::HTTP#proxy_pass" do
-  describe "when self is no proxy class instance" do
-    it "returns nil" do
-      Net::HTTP.new("localhost", 3333).proxy_pass.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class instance" do
-    it "returns nil if no password was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_pass.should be_nil
-    end
-
-    it "returns the password for self's proxy connection" do
-      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-      http_with_proxy.new("localhost", 3333).proxy_pass.should == "rocks"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proxy_port_spec.rb b/spec/ruby/library/net/http/http/proxy_port_spec.rb
deleted file mode 100644
index 339f7ee850..0000000000
--- a/spec/ruby/library/net/http/http/proxy_port_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.proxy_port" do
-  describe "when self is no proxy class" do
-    it "returns nil" do
-      Net::HTTP.proxy_port.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class" do
-    it "returns 80 if no port was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").proxy_port.should eql(80)
-    end
-
-    it "returns the port for self's proxy connection" do
-      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_port.should eql(1234)
-    end
-  end
-end
-
-describe "Net::HTTP#proxy_port" do
-  describe "when self is no proxy class instance" do
-    it "returns nil" do
-      Net::HTTP.new("localhost", 3333).proxy_port.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class instance" do
-    it "returns 80 if no port was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_port.should eql(80)
-    end
-
-    it "returns the port for self's proxy connection" do
-      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-      http_with_proxy.new("localhost", 3333).proxy_port.should eql(1234)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/proxy_user_spec.rb b/spec/ruby/library/net/http/http/proxy_user_spec.rb
deleted file mode 100644
index 01fda400e9..0000000000
--- a/spec/ruby/library/net/http/http/proxy_user_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.proxy_user" do
-  describe "when self is no proxy class" do
-    it "returns nil" do
-      Net::HTTP.proxy_user.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class" do
-    it "returns nil if no username was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").proxy_user.should be_nil
-    end
-
-    it "returns the username for self's proxy connection" do
-      Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks").proxy_user.should == "rspec"
-    end
-  end
-end
-
-describe "Net::HTTP#proxy_user" do
-  describe "when self is no proxy class instance" do
-    it "returns nil" do
-      Net::HTTP.new("localhost", 3333).proxy_user.should be_nil
-    end
-  end
-
-  describe "when self is a proxy class instance" do
-    it "returns nil if no username was set for self's proxy connection" do
-      Net::HTTP.Proxy("localhost").new("localhost", 3333).proxy_user.should be_nil
-    end
-
-    it "returns the username for self's proxy connection" do
-      http_with_proxy = Net::HTTP.Proxy("localhost", 1234, "rspec", "rocks")
-      http_with_proxy.new("localhost", 3333).proxy_user.should == "rspec"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/put2_spec.rb b/spec/ruby/library/net/http/http/put2_spec.rb
deleted file mode 100644
index 0ee3590639..0000000000
--- a/spec/ruby/library/net/http/http/put2_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_put'
-
-describe "Net::HTTP#put2" do
-  it_behaves_like :net_ftp_request_put, :put2
-end
diff --git a/spec/ruby/library/net/http/http/put_spec.rb b/spec/ruby/library/net/http/http/put_spec.rb
deleted file mode 100644
index 3ca0d0963e..0000000000
--- a/spec/ruby/library/net/http/http/put_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#put" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an put request to the passed path and returns the response" do
-    response = @http.put("/request", "test=test")
-    response.body.should == "Request type: PUT"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.put("/request", "test=test").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/read_timeout_spec.rb b/spec/ruby/library/net/http/http/read_timeout_spec.rb
deleted file mode 100644
index e23ee76025..0000000000
--- a/spec/ruby/library/net/http/http/read_timeout_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#read_timeout" do
-  it "returns the seconds to wait until reading one block" do
-    net = Net::HTTP.new("localhost")
-    net.read_timeout.should eql(60)
-    net.read_timeout = 10
-    net.read_timeout.should eql(10)
-  end
-end
-
-describe "Net::HTTP#read_timeout=" do
-  it "sets the seconds to wait till the connection is open" do
-    net = Net::HTTP.new("localhost")
-    net.read_timeout = 10
-    net.read_timeout.should eql(10)
-  end
-
-  it "returns the newly set value" do
-    net = Net::HTTP.new("localhost")
-    (net.read_timeout = 10).should eql(10)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/request_get_spec.rb b/spec/ruby/library/net/http/http/request_get_spec.rb
deleted file mode 100644
index f53a2e9d65..0000000000
--- a/spec/ruby/library/net/http/http/request_get_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_get'
-
-describe "Net::HTTP#request_get" do
-  it_behaves_like :net_ftp_request_get, :get2
-end
diff --git a/spec/ruby/library/net/http/http/request_head_spec.rb b/spec/ruby/library/net/http/http/request_head_spec.rb
deleted file mode 100644
index dc47557b9d..0000000000
--- a/spec/ruby/library/net/http/http/request_head_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_head'
-
-describe "Net::HTTP#request_head" do
-  it_behaves_like :net_ftp_request_head, :request_head
-end
diff --git a/spec/ruby/library/net/http/http/request_post_spec.rb b/spec/ruby/library/net/http/http/request_post_spec.rb
deleted file mode 100644
index 0b408fa84d..0000000000
--- a/spec/ruby/library/net/http/http/request_post_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_post'
-
-describe "Net::HTTP#request_post" do
-  it_behaves_like :net_ftp_request_post, :request_post
-end
diff --git a/spec/ruby/library/net/http/http/request_put_spec.rb b/spec/ruby/library/net/http/http/request_put_spec.rb
deleted file mode 100644
index 987b52ceb0..0000000000
--- a/spec/ruby/library/net/http/http/request_put_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/request_put'
-
-describe "Net::HTTP#request_put" do
-  it_behaves_like :net_ftp_request_put, :request_put
-end
diff --git a/spec/ruby/library/net/http/http/request_spec.rb b/spec/ruby/library/net/http/http/request_spec.rb
deleted file mode 100644
index e63dde9c8d..0000000000
--- a/spec/ruby/library/net/http/http/request_spec.rb
+++ /dev/null
@@ -1,109 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#request" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed request_object" do
-    it "makes a HTTP Request based on the passed request_object" do
-      response = @http.request(Net::HTTP::Get.new("/request"), "test=test")
-      response.body.should == "Request type: GET"
-
-      response = @http.request(Net::HTTP::Head.new("/request"), "test=test")
-      response.body.should be_nil
-
-      response = @http.request(Net::HTTP::Post.new("/request"), "test=test")
-      response.body.should == "Request type: POST"
-
-      response = @http.request(Net::HTTP::Put.new("/request"), "test=test")
-      response.body.should == "Request type: PUT"
-
-      response = @http.request(Net::HTTP::Proppatch.new("/request"), "test=test")
-      response.body.should == "Request type: PROPPATCH"
-
-      response = @http.request(Net::HTTP::Lock.new("/request"), "test=test")
-      response.body.should == "Request type: LOCK"
-
-      response = @http.request(Net::HTTP::Unlock.new("/request"), "test=test")
-      response.body.should == "Request type: UNLOCK"
-
-      # TODO: Does not work?
-      #response = @http.request(Net::HTTP::Options.new("/request"), "test=test")
-      #response.body.should be_nil
-
-      response = @http.request(Net::HTTP::Propfind.new("/request"), "test=test")
-      response.body.should == "Request type: PROPFIND"
-
-      response = @http.request(Net::HTTP::Delete.new("/request"), "test=test")
-      response.body.should == "Request type: DELETE"
-
-      response = @http.request(Net::HTTP::Move.new("/request"), "test=test")
-      response.body.should == "Request type: MOVE"
-
-      response = @http.request(Net::HTTP::Copy.new("/request"), "test=test")
-      response.body.should == "Request type: COPY"
-
-      response = @http.request(Net::HTTP::Mkcol.new("/request"), "test=test")
-      response.body.should == "Request type: MKCOL"
-
-      response = @http.request(Net::HTTP::Trace.new("/request"), "test=test")
-      response.body.should == "Request type: TRACE"
-    end
-  end
-
-  describe "when passed request_object and request_body" do
-    it "sends the passed request_body when making the HTTP Request" do
-      response = @http.request(Net::HTTP::Get.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Head.new("/request/body"), "test=test")
-      response.body.should be_nil
-
-      response = @http.request(Net::HTTP::Post.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Put.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Proppatch.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Lock.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Unlock.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      # TODO: Does not work?
-      #response = @http.request(Net::HTTP::Options.new("/request/body"), "test=test")
-      #response.body.should be_nil
-
-      response = @http.request(Net::HTTP::Propfind.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Delete.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Move.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Copy.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Mkcol.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-
-      response = @http.request(Net::HTTP::Trace.new("/request/body"), "test=test")
-      response.body.should == "test=test"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/request_types_spec.rb b/spec/ruby/library/net/http/http/request_types_spec.rb
deleted file mode 100644
index 99d754d3d1..0000000000
--- a/spec/ruby/library/net/http/http/request_types_spec.rb
+++ /dev/null
@@ -1,254 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP::Get" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Get.should < Net::HTTPRequest
-  end
-
-  it "represents the 'GET'-Request-Method" do
-    Net::HTTP::Get::METHOD.should == "GET"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Get::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Get::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Head" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Head.should < Net::HTTPRequest
-  end
-
-  it "represents the 'HEAD'-Request-Method" do
-    Net::HTTP::Head::METHOD.should == "HEAD"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Head::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has no Response Body" do
-    Net::HTTP::Head::RESPONSE_HAS_BODY.should be_false
-  end
-end
-
-describe "Net::HTTP::Post" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Post.should < Net::HTTPRequest
-  end
-
-  it "represents the 'POST'-Request-Method" do
-    Net::HTTP::Post::METHOD.should == "POST"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Post::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Post::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Put" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Put.should < Net::HTTPRequest
-  end
-
-  it "represents the 'PUT'-Request-Method" do
-    Net::HTTP::Put::METHOD.should == "PUT"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Put::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Put::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Delete" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Delete.should < Net::HTTPRequest
-  end
-
-  it "represents the 'DELETE'-Request-Method" do
-    Net::HTTP::Delete::METHOD.should == "DELETE"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Delete::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Delete::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Options" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Options.should < Net::HTTPRequest
-  end
-
-  it "represents the 'OPTIONS'-Request-Method" do
-    Net::HTTP::Options::METHOD.should == "OPTIONS"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Options::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has no Response Body" do
-    Net::HTTP::Options::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Trace" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Trace.should < Net::HTTPRequest
-  end
-
-  it "represents the 'TRACE'-Request-Method" do
-    Net::HTTP::Trace::METHOD.should == "TRACE"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Trace::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Trace::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Propfind" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Propfind.should < Net::HTTPRequest
-  end
-
-  it "represents the 'PROPFIND'-Request-Method" do
-    Net::HTTP::Propfind::METHOD.should == "PROPFIND"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Propfind::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Propfind::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Proppatch" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Proppatch.should < Net::HTTPRequest
-  end
-
-  it "represents the 'PROPPATCH'-Request-Method" do
-    Net::HTTP::Proppatch::METHOD.should == "PROPPATCH"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Proppatch::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Proppatch::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Mkcol" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Mkcol.should < Net::HTTPRequest
-  end
-
-  it "represents the 'MKCOL'-Request-Method" do
-    Net::HTTP::Mkcol::METHOD.should == "MKCOL"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Mkcol::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Mkcol::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Copy" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Copy.should < Net::HTTPRequest
-  end
-
-  it "represents the 'COPY'-Request-Method" do
-    Net::HTTP::Copy::METHOD.should == "COPY"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Copy::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Copy::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Move" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Move.should < Net::HTTPRequest
-  end
-
-  it "represents the 'MOVE'-Request-Method" do
-    Net::HTTP::Move::METHOD.should == "MOVE"
-  end
-
-  it "has no Request Body" do
-    Net::HTTP::Move::REQUEST_HAS_BODY.should be_false
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Move::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Lock" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Lock.should < Net::HTTPRequest
-  end
-
-  it "represents the 'LOCK'-Request-Method" do
-    Net::HTTP::Lock::METHOD.should == "LOCK"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Lock::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Lock::RESPONSE_HAS_BODY.should be_true
-  end
-end
-
-describe "Net::HTTP::Unlock" do
-  it "is a subclass of Net::HTTPRequest" do
-    Net::HTTP::Unlock.should < Net::HTTPRequest
-  end
-
-  it "represents the 'UNLOCK'-Request-Method" do
-    Net::HTTP::Unlock::METHOD.should == "UNLOCK"
-  end
-
-  it "has a Request Body" do
-    Net::HTTP::Unlock::REQUEST_HAS_BODY.should be_true
-  end
-
-  it "has a Response Body" do
-    Net::HTTP::Unlock::RESPONSE_HAS_BODY.should be_true
-  end
-end
diff --git a/spec/ruby/library/net/http/http/send_request_spec.rb b/spec/ruby/library/net/http/http/send_request_spec.rb
deleted file mode 100644
index 03fd32e470..0000000000
--- a/spec/ruby/library/net/http/http/send_request_spec.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#send_request" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-
-    # HEAD is special so handled separately
-    @methods = %w[
-      GET POST PUT DELETE
-      OPTIONS
-      PROPFIND PROPPATCH LOCK UNLOCK
-    ]
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  # TODO: Does only work with GET and POST requests
-  describe "when passed type, path" do
-    it "sends a HTTP Request of the passed type to the passed path" do
-      response = @http.send_request("HEAD", "/request")
-      response.body.should be_nil
-
-      @methods.each do |method|
-        response = @http.send_request(method, "/request")
-        response.body.should == "Request type: #{method}"
-      end
-    end
-  end
-
-  describe "when passed type, path, body" do
-    it "sends a HTTP Request with the passed body" do
-      response = @http.send_request("HEAD", "/request/body", "test=test")
-      response.body.should be_nil
-
-      @methods.each do |method|
-        response = @http.send_request(method, "/request/body", "test=test")
-        response.body.should == "test=test"
-      end
-    end
-  end
-
-  describe "when passed type, path, body, headers" do
-    it "sends a HTTP Request with the passed headers" do
-      referer = 'https://www.ruby-lang.org/'.freeze
-
-      response = @http.send_request("HEAD", "/request/header", "test=test", "referer" => referer)
-      response.body.should be_nil
-
-      @methods.each do |method|
-        response = @http.send_request(method, "/request/header", "test=test", "referer" => referer)
-        response.body.should include('"referer"=>["' + referer + '"]')
-      end
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/set_debug_output_spec.rb b/spec/ruby/library/net/http/http/set_debug_output_spec.rb
deleted file mode 100644
index 94b6f4499d..0000000000
--- a/spec/ruby/library/net/http/http/set_debug_output_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#set_debug_output when passed io" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sets the passed io as output stream for debugging" do
-    io = StringIO.new
-
-    @http.set_debug_output(io)
-    @http.start
-    io.string.should_not be_empty
-    size = io.string.size
-
-    @http.get("/")
-    io.string.size.should > size
-  end
-
-  it "outputs a warning when the connection has already been started" do
-    @http.start
-    -> { @http.set_debug_output(StringIO.new) }.should complain(/Net::HTTP#set_debug_output called after HTTP started/)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/shared/request_get.rb b/spec/ruby/library/net/http/http/shared/request_get.rb
deleted file mode 100644
index b0eca665d6..0000000000
--- a/spec/ruby/library/net/http/http/shared/request_get.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-describe :net_ftp_request_get, shared: true do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed no block" do
-    it "sends a GET request to the passed path and returns the response" do
-      response = @http.send(@method, "/request")
-      response.body.should == "Request type: GET"
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request")
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-
-  describe "when passed a block" do
-    it "sends a GET request to the passed path and returns the response" do
-      response = @http.send(@method, "/request") {}
-      response.body.should == "Request type: GET"
-    end
-
-    it "yields the response to the passed block" do
-      @http.send(@method, "/request") do |response|
-        response.body.should == "Request type: GET"
-      end
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request") {}
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/shared/request_head.rb b/spec/ruby/library/net/http/http/shared/request_head.rb
deleted file mode 100644
index 0e669de9ac..0000000000
--- a/spec/ruby/library/net/http/http/shared/request_head.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-describe :net_ftp_request_head, shared: true do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed no block" do
-    it "sends a head request to the passed path and returns the response" do
-      response = @http.send(@method, "/request")
-      response.body.should be_nil
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request")
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-
-  describe "when passed a block" do
-    it "sends a head request to the passed path and returns the response" do
-      response = @http.send(@method, "/request") {}
-      response.body.should be_nil
-    end
-
-    it "yields the response to the passed block" do
-      @http.send(@method, "/request") do |response|
-        response.body.should be_nil
-      end
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request") {}
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/shared/request_post.rb b/spec/ruby/library/net/http/http/shared/request_post.rb
deleted file mode 100644
index 06c5e139f9..0000000000
--- a/spec/ruby/library/net/http/http/shared/request_post.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-describe :net_ftp_request_post, shared: true do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed no block" do
-    it "sends a post request to the passed path and returns the response" do
-      response = @http.send(@method, "/request", "test=test")
-      response.body.should == "Request type: POST"
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request", "test=test")
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-
-  describe "when passed a block" do
-    it "sends a post request to the passed path and returns the response" do
-      response = @http.send(@method, "/request", "test=test") {}
-      response.body.should == "Request type: POST"
-    end
-
-    it "yields the response to the passed block" do
-      @http.send(@method, "/request", "test=test") do |response|
-        response.body.should == "Request type: POST"
-      end
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request", "test=test") {}
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/shared/request_put.rb b/spec/ruby/library/net/http/http/shared/request_put.rb
deleted file mode 100644
index 6ae791d7e7..0000000000
--- a/spec/ruby/library/net/http/http/shared/request_put.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-describe :net_ftp_request_put, shared: true do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when passed no block" do
-    it "sends a put request to the passed path and returns the response" do
-      response = @http.send(@method, "/request", "test=test")
-      response.body.should == "Request type: PUT"
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request", "test=test")
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-
-  describe "when passed a block" do
-    it "sends a put request to the passed path and returns the response" do
-      response = @http.send(@method, "/request", "test=test") {}
-      response.body.should == "Request type: PUT"
-    end
-
-    it "yields the response to the passed block" do
-      @http.send(@method, "/request", "test=test") do |response|
-        response.body.should == "Request type: PUT"
-      end
-    end
-
-    it "returns a Net::HTTPResponse object" do
-      response = @http.send(@method, "/request", "test=test") {}
-      response.should be_kind_of(Net::HTTPResponse)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/socket_type_spec.rb b/spec/ruby/library/net/http/http/socket_type_spec.rb
deleted file mode 100644
index 5c844ddf94..0000000000
--- a/spec/ruby/library/net/http/http/socket_type_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP.socket_type" do
-  it "returns BufferedIO" do
-    Net::HTTP.socket_type.should == Net::BufferedIO
-  end
-end
diff --git a/spec/ruby/library/net/http/http/start_spec.rb b/spec/ruby/library/net/http/http/start_spec.rb
deleted file mode 100644
index a2768eed18..0000000000
--- a/spec/ruby/library/net/http/http/start_spec.rb
+++ /dev/null
@@ -1,111 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP.start" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @port = NetHTTPSpecs.port
-  end
-
-  after :each do
-    NetHTTPSpecs.stop_server
-  end
-
-  describe "when not passed a block" do
-    before :each do
-      @http = Net::HTTP.start("localhost", @port)
-    end
-
-    after :each do
-      @http.finish if @http.started?
-    end
-
-    it "returns a new Net::HTTP object for the passed address and port" do
-      @http.should be_kind_of(Net::HTTP)
-      @http.address.should == "localhost"
-      @http.port.should == @port
-    end
-
-    it "opens the tcp connection" do
-      @http.started?.should be_true
-    end
-  end
-
-  describe "when passed a block" do
-    it "returns the blocks return value" do
-      Net::HTTP.start("localhost", @port) { :test }.should == :test
-    end
-
-    it "yields the new Net::HTTP object to the block" do
-      yielded = false
-      Net::HTTP.start("localhost", @port) do |net|
-        yielded = true
-        net.should be_kind_of(Net::HTTP)
-      end
-      yielded.should be_true
-    end
-
-    it "opens the tcp connection before yielding" do
-      Net::HTTP.start("localhost", @port) { |http| http.started?.should be_true }
-    end
-
-    it "closes the tcp connection after yielding" do
-      net = nil
-      Net::HTTP.start("localhost", @port) { |x| net = x }
-      net.started?.should be_false
-    end
-  end
-end
-
-describe "Net::HTTP#start" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.new("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "returns self" do
-    @http.start.should equal(@http)
-  end
-
-  it "opens the tcp connection" do
-    @http.start
-    @http.started?.should be_true
-  end
-
-  describe "when self has already been started" do
-    it "raises an IOError" do
-      @http.start
-      -> { @http.start }.should raise_error(IOError)
-    end
-  end
-
-  describe "when passed a block" do
-    it "returns the blocks return value" do
-      @http.start { :test }.should == :test
-    end
-
-    it "yields the new Net::HTTP object to the block" do
-      yielded = false
-      @http.start do |http|
-        yielded = true
-        http.should equal(@http)
-      end
-      yielded.should be_true
-    end
-
-    it "opens the tcp connection before yielding" do
-      @http.start { |http| http.started?.should be_true }
-    end
-
-    it "closes the tcp connection after yielding" do
-      @http.start { }
-      @http.started?.should be_false
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/http/started_spec.rb b/spec/ruby/library/net/http/http/started_spec.rb
deleted file mode 100644
index ea441ed16a..0000000000
--- a/spec/ruby/library/net/http/http/started_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-require_relative 'shared/started'
-
-describe "Net::HTTP#started?" do
-  it_behaves_like :net_http_started_p, :started?
-end
diff --git a/spec/ruby/library/net/http/http/trace_spec.rb b/spec/ruby/library/net/http/http/trace_spec.rb
deleted file mode 100644
index 94a1bf6655..0000000000
--- a/spec/ruby/library/net/http/http/trace_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#trace" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends a TRACE request to the passed path and returns the response" do
-    response = @http.trace("/request")
-    response.body.should == "Request type: TRACE"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.trace("/request").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/unlock_spec.rb b/spec/ruby/library/net/http/http/unlock_spec.rb
deleted file mode 100644
index a4f1b7a1d1..0000000000
--- a/spec/ruby/library/net/http/http/unlock_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/http_server'
-
-describe "Net::HTTP#unlock" do
-  before :each do
-    NetHTTPSpecs.start_server
-    @http = Net::HTTP.start("localhost", NetHTTPSpecs.port)
-  end
-
-  after :each do
-    @http.finish if @http.started?
-    NetHTTPSpecs.stop_server
-  end
-
-  it "sends an UNLOCK request to the passed path and returns the response" do
-    response = @http.unlock("/request", "test=test")
-    response.body.should == "Request type: UNLOCK"
-  end
-
-  it "returns a Net::HTTPResponse" do
-    @http.unlock("/request", "test=test").should be_kind_of(Net::HTTPResponse)
-  end
-end
diff --git a/spec/ruby/library/net/http/http/use_ssl_spec.rb b/spec/ruby/library/net/http/http/use_ssl_spec.rb
deleted file mode 100644
index be1ec7fa25..0000000000
--- a/spec/ruby/library/net/http/http/use_ssl_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTP#use_ssl?" do
-  it "returns false" do
-    http = Net::HTTP.new("localhost")
-    http.use_ssl?.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/http/http/version_1_1_spec.rb b/spec/ruby/library/net/http/http/version_1_1_spec.rb
deleted file mode 100644
index 1c069e9ea6..0000000000
--- a/spec/ruby/library/net/http/http/version_1_1_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/version_1_1'
-
-describe "Net::HTTP.version_1_1?" do
-  it_behaves_like :net_http_version_1_1_p, :version_1_1?
-end
diff --git a/spec/ruby/library/net/http/http/version_1_2_spec.rb b/spec/ruby/library/net/http/http/version_1_2_spec.rb
deleted file mode 100644
index 4e601462c9..0000000000
--- a/spec/ruby/library/net/http/http/version_1_2_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/version_1_2'
-
-describe "Net::HTTP.version_1_2" do
-  it "turns on net/http 1.2 features" do
-    Net::HTTP.version_1_2
-
-    Net::HTTP.version_1_2?.should be_true
-    Net::HTTP.version_1_1?.should be_false
-  end
-
-  it "returns true" do
-    Net::HTTP.version_1_2.should be_true
-  end
-end
-
-describe "Net::HTTP.version_1_2?" do
-  it_behaves_like :net_http_version_1_2_p, :version_1_2?
-end
diff --git a/spec/ruby/library/net/http/httpexceptions/initialize_spec.rb b/spec/ruby/library/net/http/httpexceptions/initialize_spec.rb
deleted file mode 100644
index 8e3fd8cc02..0000000000
--- a/spec/ruby/library/net/http/httpexceptions/initialize_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPExceptions#initialize when passed message, response" do
-  before :each do
-    @exception = NetHTTPExceptionsSpecs::Simple.new("error message", "a http response")
-  end
-
-  it "calls super with the passed message" do
-    @exception.message.should == "error message"
-  end
-
-  it "sets self's response to the passed response" do
-    @exception.response.should == "a http response"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpexceptions/response_spec.rb b/spec/ruby/library/net/http/httpexceptions/response_spec.rb
deleted file mode 100644
index 205b2bc212..0000000000
--- a/spec/ruby/library/net/http/httpexceptions/response_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPExceptions#response" do
-  it "returns self's response" do
-    exception = NetHTTPExceptionsSpecs::Simple.new("error message", "a http response")
-    exception.response.should == "a http response"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/body_exist_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/body_exist_spec.rb
deleted file mode 100644
index 7d081939b8..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/body_exist_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#body_exist?" do
-  it "returns true when the response is expected to have a body" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.body_exist?.should be_true
-
-    request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
-    request.body_exist?.should be_false
-  end
-
-  describe "when $VERBOSE is true" do
-    it "emits a warning" do
-      request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
-      -> {
-        request.body_exist?
-      }.should complain(/body_exist\? is obsolete/, verbose: true)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/body_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/body_spec.rb
deleted file mode 100644
index a215895b57..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/body_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-
-describe "Net::HTTPGenericRequest#body" do
-  it "returns self's request body" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.body.should be_nil
-
-    request.body = "Some Content"
-    request.body.should == "Some Content"
-  end
-end
-
-describe "Net::HTTPGenericRequest#body=" do
-  before :each do
-    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-  end
-
-  it "sets self's body content to the passed String" do
-    @request.body = "Some Content"
-    @request.body.should == "Some Content"
-  end
-
-  it "sets self's body stream to nil" do
-    @request.body_stream = StringIO.new("")
-    @request.body = "Some Content"
-    @request.body_stream.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/body_stream_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/body_stream_spec.rb
deleted file mode 100644
index c2a60e6836..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/body_stream_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-
-describe "Net::HTTPGenericRequest#body_stream" do
-  it "returns self's body stream Object" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.body_stream.should be_nil
-
-    stream = StringIO.new("test")
-    request.body_stream = stream
-    request.body_stream.should equal(stream)
-  end
-end
-
-describe "Net::HTTPGenericRequest#body_stream=" do
-  before :each do
-    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    @stream = StringIO.new("test")
-  end
-
-  it "sets self's body stream to the passed Object" do
-    @request.body_stream = @stream
-    @request.body_stream.should equal(@stream)
-  end
-
-  it "sets self's body to nil" do
-    @request.body = "Some Content"
-    @request.body_stream = @stream
-    @request.body.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/exec_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/exec_spec.rb
deleted file mode 100644
index da5b1a63be..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/exec_spec.rb
+++ /dev/null
@@ -1,131 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-
-describe "Net::HTTPGenericRequest#exec when passed socket, version, path" do
-  before :each do
-    @socket = StringIO.new("")
-    @buffered_socket = Net::BufferedIO.new(@socket)
-  end
-
-  it "executes the request over the socket to the path using the HTTP version" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-
-    request.exec(@buffered_socket, "1.1", "/some/path")
-    str = @socket.string
-
-    str.should =~ %r[POST /some/path HTTP/1.1\r\n]
-    str.should =~ %r[Accept: \*/\*\r\n]
-    str[-4..-1].should == "\r\n\r\n"
-
-    request = Net::HTTPGenericRequest.new("GET", true, true, "/some/path",
-                                          "Content-Type" => "text/html")
-
-    request.exec(@buffered_socket, "1.0", "/some/other/path")
-    str = @socket.string
-
-    str.should =~ %r[GET /some/other/path HTTP/1.0\r\n]
-    str.should =~ %r[Accept: \*/\*\r\n]
-    str.should =~ %r[Content-Type: text/html\r\n]
-    str[-4..-1].should == "\r\n\r\n"
-  end
-
-  describe "when a request body is set" do
-    it "sets the 'Content-Type' header to 'application/x-www-form-urlencoded' unless the 'Content-Type' header is supplied" do
-      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-      request.body = "Some Content"
-
-      request.exec(@buffered_socket, "1.1", "/some/other/path")
-      str = @socket.string
-
-      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
-      str.should =~ %r[Accept: \*/\*\r\n]
-      str.should =~ %r[Content-Type: application/x-www-form-urlencoded\r\n]
-      str.should =~ %r[Content-Length: 12\r\n]
-      str[-16..-1].should == "\r\n\r\nSome Content"
-    end
-
-    it "correctly sets the 'Content-Length' header and includes the body" do
-      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
-                                            "Content-Type" => "text/html")
-      request.body = "Some Content"
-
-      request.exec(@buffered_socket, "1.1", "/some/other/path")
-      str = @socket.string
-
-      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
-      str.should =~ %r[Accept: \*/\*\r\n]
-      str.should =~ %r[Content-Type: text/html\r\n]
-      str.should =~ %r[Content-Length: 12\r\n]
-      str[-16..-1].should == "\r\n\r\nSome Content"
-    end
-  end
-
-  describe "when a body stream is set" do
-    it "sets the 'Content-Type' header to 'application/x-www-form-urlencoded' unless the 'Content-Type' header is supplied" do
-      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
-                                            "Content-Length" => "10")
-      request.body_stream = StringIO.new("a" * 20)
-
-      request.exec(@buffered_socket, "1.1", "/some/other/path")
-      str = @socket.string
-
-      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
-      str.should =~ %r[Accept: \*/\*\r\n]
-      str.should =~ %r[Content-Type: application/x-www-form-urlencoded\r\n]
-      str.should =~ %r[Content-Length: 10\r\n]
-      str[-24..-1].should == "\r\n\r\naaaaaaaaaaaaaaaaaaaa"
-    end
-
-    it "sends the whole stream, regardless of the 'Content-Length' header" do
-      request = Net::HTTPGenericRequest.new("POST", true, true,"/some/path",
-                                            "Content-Type" => "text/html",
-                                            "Content-Length" => "10")
-      request.body_stream = StringIO.new("a" * 20)
-
-      request.exec(@buffered_socket, "1.1", "/some/other/path")
-      str = @socket.string
-
-      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
-      str.should =~ %r[Accept: \*/\*\r\n]
-      str.should =~ %r[Content-Type: text/html\r\n]
-      str.should =~ %r[Content-Length: 10\r\n]
-      str[-24..-1].should == "\r\n\r\naaaaaaaaaaaaaaaaaaaa"
-    end
-
-    it "sends the request in chunks when 'Transfer-Encoding' is set to 'chunked'" do
-      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
-                                            "Content-Type" => "text/html",
-                                            "Transfer-Encoding" => "chunked")
-      datasize = 1024 * 10
-      request.body_stream = StringIO.new("a" * datasize)
-
-      request.exec(@buffered_socket, "1.1", "/some/other/path")
-      str = @socket.string
-
-      str.should =~ %r[POST /some/other/path HTTP/1.1\r\n]
-      str.should =~ %r[Accept: \*/\*\r\n]
-      str.should =~ %r[Content-Type: text/html\r\n]
-      str.should =~ %r[Transfer-Encoding: chunked\r\n]
-      str =~ %r[\r\n\r\n]
-      str = $'
-      while datasize > 0
-        chunk_size_line, str = str.split(/\r\n/, 2)
-        chunk_size = chunk_size_line[/\A[0-9A-Fa-f]+/].to_i(16)
-        str.slice!(0, chunk_size).should == 'a' * chunk_size
-        datasize -= chunk_size
-        str.slice!(0, 2).should == "\r\n"
-      end
-      datasize.should == 0
-      str.should == %"0\r\n\r\n"
-    end
-
-    it "raises an ArgumentError when the 'Content-Length' is not set or 'Transfer-Encoding' is not set to 'chunked'" do
-      request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path",
-                                            "Content-Type" => "text/html")
-      request.body_stream = StringIO.new("Some Content")
-
-      -> { request.exec(@buffered_socket, "1.1", "/some/other/path") }.should raise_error(ArgumentError)
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/inspect_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/inspect_spec.rb
deleted file mode 100644
index 36240949c3..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/inspect_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#inspect" do
-  it "returns a String representation of self" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.inspect.should == "#<Net::HTTPGenericRequest POST>"
-
-    request = Net::HTTPGenericRequest.new("GET", false, true, "/some/path")
-    request.inspect.should == "#<Net::HTTPGenericRequest GET>"
-
-    request = Net::HTTPGenericRequest.new("BLA", true, true, "/some/path")
-    request.inspect.should == "#<Net::HTTPGenericRequest BLA>"
-
-    # Subclasses
-    request = Net::HTTP::Get.new("/some/path")
-    request.inspect.should == "#<Net::HTTP::Get GET>"
-
-    request = Net::HTTP::Post.new("/some/path")
-    request.inspect.should == "#<Net::HTTP::Post POST>"
-
-    request = Net::HTTP::Trace.new("/some/path")
-    request.inspect.should == "#<Net::HTTP::Trace TRACE>"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/method_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/method_spec.rb
deleted file mode 100644
index 3f7c2cbf2b..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/method_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#method" do
-  it "returns self's request method" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.method.should == "POST"
-
-    request = Net::HTTPGenericRequest.new("GET", false, true, "/some/path")
-    request.method.should == "GET"
-
-    request = Net::HTTPGenericRequest.new("BLA", true, true, "/some/path")
-    request.method.should == "BLA"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/path_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/path_spec.rb
deleted file mode 100644
index fc4cf9af53..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/path_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#path" do
-  it "returns self's request path" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.path.should == "/some/path"
-
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/other/path")
-    request.path.should == "/some/other/path"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/request_body_permitted_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/request_body_permitted_spec.rb
deleted file mode 100644
index 50cd1ff637..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/request_body_permitted_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#request_body_permitted?" do
-  it "returns true when the request is expected to have a body" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.request_body_permitted?.should be_true
-
-    request = Net::HTTPGenericRequest.new("POST", false, true, "/some/path")
-    request.request_body_permitted?.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/response_body_permitted_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/response_body_permitted_spec.rb
deleted file mode 100644
index 0c4165d0ab..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/response_body_permitted_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#response_body_permitted?" do
-  it "returns true when the response is expected to have a body" do
-    request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-    request.response_body_permitted?.should be_true
-
-    request = Net::HTTPGenericRequest.new("POST", true, false, "/some/path")
-    request.response_body_permitted?.should be_false
-  end
-end
diff --git a/spec/ruby/library/net/http/httpgenericrequest/set_body_internal_spec.rb b/spec/ruby/library/net/http/httpgenericrequest/set_body_internal_spec.rb
deleted file mode 100644
index 7494c69173..0000000000
--- a/spec/ruby/library/net/http/httpgenericrequest/set_body_internal_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPGenericRequest#set_body_internal when passed string" do
-  before :each do
-    @request = Net::HTTPGenericRequest.new("POST", true, true, "/some/path")
-  end
-
-  it "sets self's body to the passed string" do
-    @request.set_body_internal("Some Content")
-    @request.body.should == "Some Content"
-  end
-
-  it "raises an ArgumentError when the body or body_stream of self have already been set" do
-    @request.body = "Some Content"
-    -> { @request.set_body_internal("Some other Content") }.should raise_error(ArgumentError)
-
-    @request.body_stream = "Some Content"
-    -> { @request.set_body_internal("Some other Content") }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/add_field_spec.rb b/spec/ruby/library/net/http/httpheader/add_field_spec.rb
deleted file mode 100644
index 882d5ac5bb..0000000000
--- a/spec/ruby/library/net/http/httpheader/add_field_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#add_field when passed key, value" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "adds the passed value to the header entry with the passed key" do
-    @headers.add_field("My-Header", "a")
-    @headers.get_fields("My-Header").should == ["a"]
-
-    @headers.add_field("My-Header", "b")
-    @headers.get_fields("My-Header").should == ["a", "b"]
-
-    @headers.add_field("My-Header", "c")
-    @headers.get_fields("My-Header").should == ["a", "b", "c"]
-  end
-
-  it "is case-insensitive" do
-    @headers.add_field("My-Header", "a")
-    @headers.get_fields("My-Header").should == ["a"]
-
-    @headers.add_field("my-header", "b")
-    @headers.get_fields("My-Header").should == ["a", "b"]
-
-    @headers.add_field("MY-HEADER", "c")
-    @headers.get_fields("My-Header").should == ["a", "b", "c"]
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/basic_auth_spec.rb b/spec/ruby/library/net/http/httpheader/basic_auth_spec.rb
deleted file mode 100644
index fa2a710fe1..0000000000
--- a/spec/ruby/library/net/http/httpheader/basic_auth_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#basic_auth when passed account, password" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "sets the 'Authorization' Header entry for basic authorization" do
-    @headers.basic_auth("rubyspec", "rocks")
-    @headers["Authorization"].should == "Basic cnVieXNwZWM6cm9ja3M="
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/canonical_each_spec.rb b/spec/ruby/library/net/http/httpheader/canonical_each_spec.rb
deleted file mode 100644
index 0dddd3049b..0000000000
--- a/spec/ruby/library/net/http/httpheader/canonical_each_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_capitalized'
-
-describe "Net::HTTPHeader#canonical_each" do
-  it_behaves_like :net_httpheader_each_capitalized, :canonical_each
-end
diff --git a/spec/ruby/library/net/http/httpheader/chunked_spec.rb b/spec/ruby/library/net/http/httpheader/chunked_spec.rb
deleted file mode 100644
index 96b758981b..0000000000
--- a/spec/ruby/library/net/http/httpheader/chunked_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#chunked?" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns true if the 'Transfer-Encoding' header entry is set to chunked" do
-    @headers.chunked?.should be_false
-
-    @headers["Transfer-Encoding"] = "bla"
-    @headers.chunked?.should be_false
-
-    @headers["Transfer-Encoding"] = "blachunkedbla"
-    @headers.chunked?.should be_false
-
-    @headers["Transfer-Encoding"] = "chunked"
-    @headers.chunked?.should be_true
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/content_length_spec.rb b/spec/ruby/library/net/http/httpheader/content_length_spec.rb
deleted file mode 100644
index e344817e82..0000000000
--- a/spec/ruby/library/net/http/httpheader/content_length_spec.rb
+++ /dev/null
@@ -1,54 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#content_length" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns nil if no 'Content-Length' header entry is set" do
-    @headers.content_length.should be_nil
-  end
-
-  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Length' header entry has an invalid format" do
-    @headers["Content-Length"] = "invalid"
-    -> { @headers.content_length }.should raise_error(Net::HTTPHeaderSyntaxError)
-  end
-
-  it "returns the value of the 'Content-Length' header entry as an Integer" do
-    @headers["Content-Length"] = "123"
-    @headers.content_length.should eql(123)
-
-    @headers["Content-Length"] = "123valid"
-    @headers.content_length.should eql(123)
-
-    @headers["Content-Length"] = "valid123"
-    @headers.content_length.should eql(123)
-  end
-end
-
-describe "Net::HTTPHeader#content_length=" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "removes the 'Content-Length' entry if passed false or nil" do
-    @headers["Content-Length"] = "123"
-    @headers.content_length = nil
-    @headers["Content-Length"].should be_nil
-  end
-
-  it "sets the 'Content-Length' entry to the passed value" do
-    @headers.content_length = "123"
-    @headers["Content-Length"].should == "123"
-
-    @headers.content_length = "123valid"
-    @headers["Content-Length"].should == "123"
-  end
-
-  it "sets the 'Content-Length' entry to 0 if the passed value is not valid" do
-    @headers.content_length = "invalid123"
-    @headers["Content-Length"].should == "0"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/content_range_spec.rb b/spec/ruby/library/net/http/httpheader/content_range_spec.rb
deleted file mode 100644
index ba75f9a9a1..0000000000
--- a/spec/ruby/library/net/http/httpheader/content_range_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#content_range" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns a Range object that represents the 'Content-Range' header entry" do
-    @headers["Content-Range"] = "bytes 0-499/1234"
-    @headers.content_range.should == (0..499)
-
-    @headers["Content-Range"] = "bytes 500-1233/1234"
-    @headers.content_range.should == (500..1233)
-  end
-
-  it "returns nil when there is no 'Content-Range' header entry" do
-    @headers.content_range.should be_nil
-  end
-
-  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Range' has an invalid format" do
-    @headers["Content-Range"] = "invalid"
-    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Content-Range"] = "bytes 123-abc"
-    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Content-Range"] = "bytes abc-123"
-    -> { @headers.content_range }.should raise_error(Net::HTTPHeaderSyntaxError)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/content_type_spec.rb b/spec/ruby/library/net/http/httpheader/content_type_spec.rb
deleted file mode 100644
index 1f8b4ba326..0000000000
--- a/spec/ruby/library/net/http/httpheader/content_type_spec.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_content_type'
-
-describe "Net::HTTPHeader#content_type" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns the content type string, as per 'Content-Type' header entry" do
-    @headers["Content-Type"] = "text/html"
-    @headers.content_type.should == "text/html"
-
-    @headers["Content-Type"] = "text/html;charset=utf-8"
-    @headers.content_type.should == "text/html"
-  end
-
-  it "returns nil if the 'Content-Type' header entry does not exist" do
-    @headers.content_type.should be_nil
-  end
-end
-
-describe "Net::HTTPHeader#content_type=" do
-  it_behaves_like :net_httpheader_set_content_type, :content_type=
-end
diff --git a/spec/ruby/library/net/http/httpheader/delete_spec.rb b/spec/ruby/library/net/http/httpheader/delete_spec.rb
deleted file mode 100644
index 603ae198de..0000000000
--- a/spec/ruby/library/net/http/httpheader/delete_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#delete when passed key" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "removes the header entry with the passed key" do
-    @headers["My-Header"] = "test"
-    @headers.delete("My-Header")
-
-    @headers["My-Header"].should be_nil
-    @headers.size.should eql(0)
-  end
-
-  it "returns the removed values" do
-    @headers["My-Header"] = "test"
-    @headers.delete("My-Header").should == ["test"]
-  end
-
-  it "is case-insensitive" do
-    @headers["My-Header"] = "test"
-    @headers.delete("my-header")
-
-    @headers["My-Header"].should be_nil
-    @headers.size.should eql(0)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_capitalized_name_spec.rb b/spec/ruby/library/net/http/httpheader/each_capitalized_name_spec.rb
deleted file mode 100644
index 1af2c6939c..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_capitalized_name_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#each_capitalized_name" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-    @headers["My-Header"] = "test"
-    @headers.add_field("My-Other-Header", "a")
-    @headers.add_field("My-Other-Header", "b")
-  end
-
-  describe "when passed a block" do
-    it "yields each header key to the passed block (keys capitalized)" do
-      res = []
-      @headers.each_capitalized_name do |key|
-        res << key
-      end
-      res.sort.should == ["My-Header", "My-Other-Header"]
-    end
-  end
-
-  describe "when passed no block" do
-    it "returns an Enumerator" do
-      enumerator = @headers.each_capitalized_name
-      enumerator.should be_an_instance_of(Enumerator)
-
-      res = []
-      enumerator.each do |key|
-        res << key
-      end
-      res.sort.should == ["My-Header", "My-Other-Header"]
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_capitalized_spec.rb b/spec/ruby/library/net/http/httpheader/each_capitalized_spec.rb
deleted file mode 100644
index 961a2d051f..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_capitalized_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_capitalized'
-
-describe "Net::HTTPHeader#each_capitalized" do
-  it_behaves_like :net_httpheader_each_capitalized, :each_capitalized
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_header_spec.rb b/spec/ruby/library/net/http/httpheader/each_header_spec.rb
deleted file mode 100644
index 19634a001b..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_header_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_header'
-
-describe "Net::HTTPHeader#each_header" do
-  it_behaves_like :net_httpheader_each_header, :each_header
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_key_spec.rb b/spec/ruby/library/net/http/httpheader/each_key_spec.rb
deleted file mode 100644
index ebb17d2eac..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_key_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_name'
-
-describe "Net::HTTPHeader#each_key" do
-  it_behaves_like :net_httpheader_each_name, :each_key
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_name_spec.rb b/spec/ruby/library/net/http/httpheader/each_name_spec.rb
deleted file mode 100644
index f4533ebcfb..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_name_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_name'
-
-describe "Net::HTTPHeader#each_name" do
-  it_behaves_like :net_httpheader_each_name, :each_name
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_spec.rb b/spec/ruby/library/net/http/httpheader/each_spec.rb
deleted file mode 100644
index 7ba8434f75..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/each_header'
-
-describe "Net::HTTPHeader#each" do
-  it_behaves_like :net_httpheader_each_header, :each
-end
diff --git a/spec/ruby/library/net/http/httpheader/each_value_spec.rb b/spec/ruby/library/net/http/httpheader/each_value_spec.rb
deleted file mode 100644
index 3224de7703..0000000000
--- a/spec/ruby/library/net/http/httpheader/each_value_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#each_value" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-    @headers["My-Header"] = "test"
-    @headers.add_field("My-Other-Header", "a")
-    @headers.add_field("My-Other-Header", "b")
-  end
-
-  describe "when passed a block" do
-    it "yields each header entry's joined values" do
-      res = []
-      @headers.each_value do |value|
-        res << value
-      end
-      res.sort.should == ["a, b", "test"]
-    end
-  end
-
-  describe "when passed no block" do
-    it "returns an Enumerator" do
-      enumerator = @headers.each_value
-      enumerator.should be_an_instance_of(Enumerator)
-
-      res = []
-      enumerator.each do |key|
-        res << key
-      end
-      res.sort.should == ["a, b", "test"]
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/element_reference_spec.rb b/spec/ruby/library/net/http/httpheader/element_reference_spec.rb
deleted file mode 100644
index 4a35e20d20..0000000000
--- a/spec/ruby/library/net/http/httpheader/element_reference_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#[] when passed key" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns the value of the header entry with the passed key" do
-    @headers["My-Header"] = "test"
-    @headers["My-Header"].should == "test"
-    @headers["My-Other-Header"] = "another test"
-    @headers["My-Other-Header"].should == "another test"
-  end
-
-  it "is case-insensitive" do
-    @headers["My-Header"] = "test"
-
-    @headers['My-Header'].should == "test"
-    @headers['my-Header'].should == "test"
-    @headers['My-header'].should == "test"
-    @headers['my-header'].should == "test"
-    @headers['MY-HEADER'].should == "test"
-  end
-
-  it "returns multi-element values joined together" do
-    @headers["My-Header"] = "test"
-    @headers.add_field("My-Header", "another test")
-    @headers.add_field("My-Header", "and one more")
-
-    @headers["My-Header"].should == "test, another test, and one more"
-  end
-
-  it "returns nil for non-existing entries" do
-    @headers["My-Header"].should be_nil
-    @headers["My-Other-Header"].should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/element_set_spec.rb b/spec/ruby/library/net/http/httpheader/element_set_spec.rb
deleted file mode 100644
index e9ad64fafc..0000000000
--- a/spec/ruby/library/net/http/httpheader/element_set_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#[]= when passed key, value" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "sets the header entry with the passed key to the passed value" do
-    @headers["My-Header"] = "test"
-    @headers["My-Header"].should == "test"
-
-    @headers["My-Header"] = "overwritten"
-    @headers["My-Header"].should == "overwritten"
-
-    @headers["My-Other-Header"] = "another test"
-    @headers["My-Other-Header"].should == "another test"
-  end
-
-  it "is case-insensitive" do
-    @headers['My-Header'] = "test"
-    @headers['my-Header'] = "another test"
-    @headers['My-header'] = "and one more test"
-    @headers['my-header'] = "and another one"
-    @headers['MY-HEADER'] = "last one"
-
-    @headers["My-Header"].should == "last one"
-    @headers.size.should eql(1)
-  end
-
-  it "removes the header entry with the passed key when the value is false or nil" do
-    @headers['My-Header'] = "test"
-    @headers['My-Header'] = nil
-    @headers['My-Header'].should be_nil
-
-    @headers['My-Header'] = "test"
-    @headers['My-Header'] = false
-    @headers['My-Header'].should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/fetch_spec.rb b/spec/ruby/library/net/http/httpheader/fetch_spec.rb
deleted file mode 100644
index ea15679acb..0000000000
--- a/spec/ruby/library/net/http/httpheader/fetch_spec.rb
+++ /dev/null
@@ -1,68 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#fetch" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  describe "when passed key" do
-    it "returns the header entry for the passed key" do
-      @headers["My-Header"] = "test"
-      @headers.fetch("My-Header").should == "test"
-
-      @headers.add_field("My-Other-Header", "a")
-      @headers.add_field("My-Other-Header", "b")
-      @headers.add_field("My-Other-Header", "c")
-      @headers.fetch("My-Other-Header").should == "a, b, c"
-    end
-
-    it "is case-insensitive" do
-      @headers["My-Header"] = "test"
-      @headers.fetch("my-header").should == "test"
-      @headers.fetch("MY-HEADER").should == "test"
-    end
-
-    it "returns nil when there is no entry for the passed key" do
-      -> { @headers.fetch("my-header") }.should raise_error(IndexError)
-    end
-  end
-
-  describe "when passed key, default" do
-    it "returns the header entry for the passed key" do
-      @headers["My-Header"] = "test"
-      @headers.fetch("My-Header", "bla").should == "test"
-
-      @headers.add_field("My-Other-Header", "a")
-      @headers.add_field("My-Other-Header", "b")
-      @headers.add_field("My-Other-Header", "c")
-      @headers.fetch("My-Other-Header", "bla").should == "a, b, c"
-    end
-
-    # TODO: This raises a NoMethodError: undefined method `join' for "bla":String
-    it "returns the default value when there is no entry for the passed key" do
-      @headers.fetch("My-Header", "bla").should == "bla"
-    end
-  end
-
-  describe "when passed key and block" do
-    it "returns the header entry for the passed key" do
-      @headers["My-Header"] = "test"
-      @headers.fetch("My-Header") {}.should == "test"
-
-      @headers.add_field("My-Other-Header", "a")
-      @headers.add_field("My-Other-Header", "b")
-      @headers.add_field("My-Other-Header", "c")
-      -> {
-        @result = @headers.fetch("My-Other-Header", "bla") {}
-      }.should complain(/block supersedes default value argument/)
-      @result.should == "a, b, c"
-    end
-
-    # TODO: This raises a NoMethodError: undefined method `join' for "redaeh-ym":String
-    it "yieldsand returns the block's return value when there is no entry for the passed key" do
-      @headers.fetch("My-Header") { |key| key.reverse }.should == "redaeh-ym"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/form_data_spec.rb b/spec/ruby/library/net/http/httpheader/form_data_spec.rb
deleted file mode 100644
index 9b29a03159..0000000000
--- a/spec/ruby/library/net/http/httpheader/form_data_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_form_data'
-
-describe "Net::HTTPHeader#form_data=" do
-  it_behaves_like :net_httpheader_set_form_data, :form_data=
-end
diff --git a/spec/ruby/library/net/http/httpheader/get_fields_spec.rb b/spec/ruby/library/net/http/httpheader/get_fields_spec.rb
deleted file mode 100644
index 1b623bf2a3..0000000000
--- a/spec/ruby/library/net/http/httpheader/get_fields_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#get_fields when passed key" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns an Array containing the values of the header entry with the passed key" do
-    @headers["My-Header"] = "a"
-    @headers.get_fields("My-Header").should == ["a"]
-
-    @headers.add_field("My-Header", "b")
-    @headers.get_fields("My-Header").should == ["a", "b"]
-  end
-
-  it "returns a copy of the header entry values" do
-    @headers["My-Header"] = "a"
-
-    @headers.get_fields("My-Header").clear
-    @headers.get_fields("My-Header").should == ["a"]
-
-    @headers.get_fields("My-Header") << "b"
-    @headers.get_fields("My-Header").should == ["a"]
-  end
-
-  it "returns nil for non-existing header entries" do
-    @headers.get_fields("My-Header").should be_nil
-    @headers.get_fields("My-Other-header").should be_nil
-  end
-
-  it "is case-insensitive" do
-    @headers["My-Header"] = "test"
-    @headers.get_fields("My-Header").should == ["test"]
-    @headers.get_fields("my-header").should == ["test"]
-    @headers.get_fields("MY-HEADER").should == ["test"]
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/initialize_http_header_spec.rb b/spec/ruby/library/net/http/httpheader/initialize_http_header_spec.rb
deleted file mode 100644
index efc5e7d0b2..0000000000
--- a/spec/ruby/library/net/http/httpheader/initialize_http_header_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#initialize_http_header when passed Hash" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.allocate
-  end
-
-  it "initializes the HTTP Header using the passed Hash" do
-    @headers.initialize_http_header("My-Header" => "test", "My-Other-Header" => "another test")
-    @headers["My-Header"].should == "test"
-    @headers["My-Other-Header"].should == "another test"
-  end
-
-  it "complains about duplicate keys when in verbose mode" do
-    -> do
-      @headers.initialize_http_header("My-Header" => "test", "my-header" => "another test")
-    end.should complain(/duplicated HTTP header/, verbose: true)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/key_spec.rb b/spec/ruby/library/net/http/httpheader/key_spec.rb
deleted file mode 100644
index 9099024229..0000000000
--- a/spec/ruby/library/net/http/httpheader/key_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#key? when passed key" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns true if the header entry with the passed key exists" do
-    @headers.key?("My-Header").should be_false
-    @headers["My-Header"] = "test"
-    @headers.key?("My-Header").should be_true
-  end
-
-  it "is case-insensitive" do
-    @headers["My-Header"] = "test"
-    @headers.key?("my-header").should be_true
-    @headers.key?("MY-HEADER").should be_true
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/length_spec.rb b/spec/ruby/library/net/http/httpheader/length_spec.rb
deleted file mode 100644
index 0d1da149f4..0000000000
--- a/spec/ruby/library/net/http/httpheader/length_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/size'
-
-describe "Net::HTTPHeader#length" do
-  it_behaves_like :net_httpheader_size, :length
-end
diff --git a/spec/ruby/library/net/http/httpheader/main_type_spec.rb b/spec/ruby/library/net/http/httpheader/main_type_spec.rb
deleted file mode 100644
index 3e18de6b5b..0000000000
--- a/spec/ruby/library/net/http/httpheader/main_type_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#main_type" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns the 'main-content-type', as per 'Content-Type' header entry" do
-    @headers["Content-Type"] = "text/html"
-    @headers.main_type.should == "text"
-
-    @headers["Content-Type"] = "application/pdf"
-    @headers.main_type.should == "application"
-
-    @headers["Content-Type"] = "text/html;charset=utf-8"
-    @headers.main_type.should == "text"
-  end
-
-  it "returns nil if the 'Content-Type' header entry does not exist" do
-    @headers.main_type.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/proxy_basic_auth_spec.rb b/spec/ruby/library/net/http/httpheader/proxy_basic_auth_spec.rb
deleted file mode 100644
index 8b576ee164..0000000000
--- a/spec/ruby/library/net/http/httpheader/proxy_basic_auth_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#proxy_basic_auth when passed account, password" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "sets the 'Proxy-Authorization' Header entry for basic authorization" do
-    @headers.proxy_basic_auth("rubyspec", "rocks")
-    @headers["Proxy-Authorization"].should == "Basic cnVieXNwZWM6cm9ja3M="
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/range_length_spec.rb b/spec/ruby/library/net/http/httpheader/range_length_spec.rb
deleted file mode 100644
index b8fce4f690..0000000000
--- a/spec/ruby/library/net/http/httpheader/range_length_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#range_length" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns the length of the Range represented by the 'Content-Range' header entry" do
-    @headers["Content-Range"] = "bytes 0-499/1234"
-    @headers.range_length.should eql(500)
-
-    @headers["Content-Range"] = "bytes 500-1233/1234"
-    @headers.range_length.should eql(734)
-  end
-
-  it "returns nil when there is no 'Content-Range' header entry" do
-    @headers.range_length.should be_nil
-  end
-
-  it "raises a Net::HTTPHeaderSyntaxError when the 'Content-Range' has an invalid format" do
-    @headers["Content-Range"] = "invalid"
-    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Content-Range"] = "bytes 123-abc"
-    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Content-Range"] = "bytes abc-123"
-    -> { @headers.range_length }.should raise_error(Net::HTTPHeaderSyntaxError)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/range_spec.rb b/spec/ruby/library/net/http/httpheader/range_spec.rb
deleted file mode 100644
index 005177f6be..0000000000
--- a/spec/ruby/library/net/http/httpheader/range_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_range'
-
-describe "Net::HTTPHeader#range" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns a Range object that represents the 'Range' header entry" do
-    @headers["Range"] = "bytes=0-499"
-    @headers.range.should == [0..499]
-
-    @headers["Range"] = "bytes=500-1233"
-    @headers.range.should == [500..1233]
-
-    @headers["Range"] = "bytes=10-"
-    @headers.range.should == [10..-1]
-
-    @headers["Range"] = "bytes=-10"
-    @headers.range.should == [-10..-1]
-  end
-
-  it "returns nil when there is no 'Range' header entry" do
-    @headers.range.should be_nil
-  end
-
-  it "raises a Net::HTTPHeaderSyntaxError when the 'Range' has an invalid format" do
-    @headers["Range"] = "invalid"
-    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Range"] = "bytes 123-abc"
-    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
-
-    @headers["Range"] = "bytes abc-123"
-    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
-  end
-
-  it "raises a Net::HTTPHeaderSyntaxError when the 'Range' was not specified" do
-    @headers["Range"] = "bytes=-"
-    -> { @headers.range }.should raise_error(Net::HTTPHeaderSyntaxError)
-  end
-end
-
-describe "Net::HTTPHeader#range=" do
-  it_behaves_like :net_httpheader_set_range, :range=
-end
diff --git a/spec/ruby/library/net/http/httpheader/set_content_type_spec.rb b/spec/ruby/library/net/http/httpheader/set_content_type_spec.rb
deleted file mode 100644
index 125f7a7e0d..0000000000
--- a/spec/ruby/library/net/http/httpheader/set_content_type_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_content_type'
-
-describe "Net::HTTPHeader#set_content_type" do
-  it_behaves_like :net_httpheader_set_content_type, :set_content_type
-end
diff --git a/spec/ruby/library/net/http/httpheader/set_form_data_spec.rb b/spec/ruby/library/net/http/httpheader/set_form_data_spec.rb
deleted file mode 100644
index 14c66ae01c..0000000000
--- a/spec/ruby/library/net/http/httpheader/set_form_data_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_form_data'
-
-describe "Net::HTTPHeader#set_form_data" do
-  it_behaves_like :net_httpheader_set_form_data, :set_form_data
-end
diff --git a/spec/ruby/library/net/http/httpheader/set_range_spec.rb b/spec/ruby/library/net/http/httpheader/set_range_spec.rb
deleted file mode 100644
index 85b9c50422..0000000000
--- a/spec/ruby/library/net/http/httpheader/set_range_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/set_range'
-
-describe "Net::HTTPHeader#set_range" do
-  it_behaves_like :net_httpheader_set_range, :set_range
-end
diff --git a/spec/ruby/library/net/http/httpheader/size_spec.rb b/spec/ruby/library/net/http/httpheader/size_spec.rb
deleted file mode 100644
index a7d78f96e0..0000000000
--- a/spec/ruby/library/net/http/httpheader/size_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-require_relative 'shared/size'
-
-describe "Net::HTTPHeader#size" do
-  it_behaves_like :net_httpheader_size, :size
-end
diff --git a/spec/ruby/library/net/http/httpheader/sub_type_spec.rb b/spec/ruby/library/net/http/httpheader/sub_type_spec.rb
deleted file mode 100644
index 3c73ca0027..0000000000
--- a/spec/ruby/library/net/http/httpheader/sub_type_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#sub_type" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns the 'sub-content-type', as per 'Content-Type' header entry" do
-    @headers["Content-Type"] = "text/html"
-    @headers.sub_type.should == "html"
-
-    @headers["Content-Type"] = "application/pdf"
-    @headers.sub_type.should == "pdf"
-
-    @headers["Content-Type"] = "text/html;charset=utf-8"
-    @headers.sub_type.should == "html"
-  end
-
-  it "returns nil if no 'sub-content-type' is set" do
-    @headers["Content-Type"] = "text"
-    @headers.sub_type.should be_nil
-
-    @headers["Content-Type"] = "text;charset=utf-8"
-    @headers.sub_type.should be_nil
-  end
-
-  it "returns nil if the 'Content-Type' header entry does not exist" do
-    @headers.sub_type.should be_nil
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/to_hash_spec.rb b/spec/ruby/library/net/http/httpheader/to_hash_spec.rb
deleted file mode 100644
index 8c1d36c30a..0000000000
--- a/spec/ruby/library/net/http/httpheader/to_hash_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#to_hash" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns a Hash representing all Header entries (keys in lower case, values as arrays)" do
-    @headers.to_hash.should == {}
-
-    @headers["My-Header"] = "test"
-    @headers.to_hash.should == { "my-header" => ["test"] }
-
-    @headers.add_field("My-Header", "another test")
-    @headers.to_hash.should == { "my-header" => ["test", "another test"] }
-  end
-
-  it "does not allow modifying the headers from the returned hash" do
-    @headers.to_hash["my-header"] = ["test"]
-    @headers.to_hash.should == {}
-    @headers.key?("my-header").should be_false
-  end
-end
diff --git a/spec/ruby/library/net/http/httpheader/type_params_spec.rb b/spec/ruby/library/net/http/httpheader/type_params_spec.rb
deleted file mode 100644
index e77be7ea85..0000000000
--- a/spec/ruby/library/net/http/httpheader/type_params_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'fixtures/classes'
-
-describe "Net::HTTPHeader#type_params" do
-  before :each do
-    @headers = NetHTTPHeaderSpecs::Example.new
-  end
-
-  it "returns additional 'Content-Type' information as a Hash" do
-    @headers["Content-Type"] = "text/html;charset=utf-8"
-    @headers.type_params.should == {"charset" => "utf-8"}
-
-    @headers["Content-Type"] = "text/html; charset=utf-8; rubyspec=rocks"
-    @headers.type_params.should == {"charset" => "utf-8", "rubyspec" => "rocks"}
-  end
-
-  it "returns an empty Hash when no additional 'Content-Type' information is set" do
-    @headers.type_params.should == {}
-
-    @headers["Content-Type"] = "text/html"
-    @headers.type_params.should == {}
-  end
-end
diff --git a/spec/ruby/library/net/http/httprequest/initialize_spec.rb b/spec/ruby/library/net/http/httprequest/initialize_spec.rb
deleted file mode 100644
index 88e9fb1c77..0000000000
--- a/spec/ruby/library/net/http/httprequest/initialize_spec.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-module NetHTTPRequestSpecs
-  class TestRequest < Net::HTTPRequest
-    METHOD = "TEST"
-    REQUEST_HAS_BODY  = false
-    RESPONSE_HAS_BODY = true
-  end
-end
-
-describe "Net::HTTPRequest#initialize" do
-  before :each do
-    @req = NetHTTPRequestSpecs::TestRequest.allocate
-  end
-
-  it "uses the METHOD constants to set the request method" do
-    @req.send(:initialize, "/some/path")
-    @req.method.should == "TEST"
-  end
-
-  it "uses the REQUEST_HAS_BODY to set whether the Request has a body or not" do
-    @req.send(:initialize, "/some/path")
-    @req.request_body_permitted?.should be_false
-  end
-
-  it "uses the RESPONSE_HAS_BODY to set whether the Response can have a body or not" do
-    @req.send(:initialize, "/some/path")
-    @req.response_body_permitted?.should be_true
-  end
-
-  describe "when passed path" do
-    it "sets self's path to the passed path" do
-      @req.send(:initialize, "/some/path")
-      @req.path.should == "/some/path"
-    end
-  end
-
-  describe "when passed path, headers" do
-    it "uses the passed headers Hash to initialize self's header entries" do
-      @req.send(:initialize, "/some/path", "Content-Type" => "text/html")
-      @req["Content-Type"].should == "text/html"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/body_permitted_spec.rb b/spec/ruby/library/net/http/httpresponse/body_permitted_spec.rb
deleted file mode 100644
index 68a0454f79..0000000000
--- a/spec/ruby/library/net/http/httpresponse/body_permitted_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse.body_permitted?" do
-  it "returns true if this response type can have a response body" do
-    Net::HTTPUnknownResponse.body_permitted?.should == true
-    Net::HTTPInformation.body_permitted?.should == false
-    Net::HTTPSuccess.body_permitted?.should == true
-    Net::HTTPRedirection.body_permitted?.should == true
-    Net::HTTPClientError.body_permitted?.should == true
-    Net::HTTPServerError.body_permitted?.should == true
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/body_spec.rb b/spec/ruby/library/net/http/httpresponse/body_spec.rb
deleted file mode 100644
index 79569441f1..0000000000
--- a/spec/ruby/library/net/http/httpresponse/body_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/body'
-
-describe "Net::HTTPResponse#body" do
-  it_behaves_like :net_httpresponse_body, :body
-end
diff --git a/spec/ruby/library/net/http/httpresponse/code_spec.rb b/spec/ruby/library/net/http/httpresponse/code_spec.rb
deleted file mode 100644
index 114277cb43..0000000000
--- a/spec/ruby/library/net/http/httpresponse/code_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#code" do
-  it "returns the result code string" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.code.should == "???"
-
-    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
-    res.code.should == "1xx"
-
-    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
-    res.code.should == "2xx"
-
-    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
-    res.code.should == "3xx"
-
-    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
-    res.code.should == "4xx"
-
-    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
-    res.code.should == "5xx"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/code_type_spec.rb b/spec/ruby/library/net/http/httpresponse/code_type_spec.rb
deleted file mode 100644
index fa2d572e9a..0000000000
--- a/spec/ruby/library/net/http/httpresponse/code_type_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#code_type" do
-  it "returns self's class" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.code_type.should == Net::HTTPUnknownResponse
-
-    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
-    res.code_type.should == Net::HTTPInformation
-
-    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
-    res.code_type.should == Net::HTTPSuccess
-
-    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
-    res.code_type.should == Net::HTTPRedirection
-
-    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
-    res.code_type.should == Net::HTTPClientError
-
-    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
-    res.code_type.should == Net::HTTPServerError
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/entity_spec.rb b/spec/ruby/library/net/http/httpresponse/entity_spec.rb
deleted file mode 100644
index f1639042c1..0000000000
--- a/spec/ruby/library/net/http/httpresponse/entity_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require_relative 'shared/body'
-
-describe "Net::HTTPResponse#entity" do
-  it_behaves_like :net_httpresponse_body, :entity
-end
diff --git a/spec/ruby/library/net/http/httpresponse/error_spec.rb b/spec/ruby/library/net/http/httpresponse/error_spec.rb
deleted file mode 100644
index d2b2f53d89..0000000000
--- a/spec/ruby/library/net/http/httpresponse/error_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#error!" do
-  it "raises self's class 'EXCEPTION_TYPE' Exception" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    -> { res.error! }.should raise_error(Net::HTTPError)
-
-    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
-    -> { res.error! }.should raise_error(Net::HTTPError)
-
-    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
-    -> { res.error! }.should raise_error(Net::HTTPError)
-
-    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
-    -> { res.error! }.should raise_error(Net::HTTPRetriableError)
-
-    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
-    ruby_version_is ""..."2.6" do
-      -> { res.error! }.should raise_error(Net::HTTPServerException)
-    end
-    ruby_version_is "2.6" do
-      -> { res.error! }.should raise_error(Net::HTTPClientException)
-    end
-
-    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
-    -> { res.error! }.should raise_error(Net::HTTPFatalError)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/error_type_spec.rb b/spec/ruby/library/net/http/httpresponse/error_type_spec.rb
deleted file mode 100644
index 6705f8b1aa..0000000000
--- a/spec/ruby/library/net/http/httpresponse/error_type_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#error_type" do
-  it "returns self's class 'EXCEPTION_TYPE' constant" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.error_type.should == Net::HTTPError
-
-    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
-    res.error_type.should == Net::HTTPError
-
-    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
-    res.error_type.should == Net::HTTPError
-
-    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
-    res.error_type.should == Net::HTTPRetriableError
-
-    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
-    ruby_version_is ""..."2.6" do
-      res.error_type.should == Net::HTTPServerException
-    end
-    ruby_version_is "2.6" do
-      res.error_type.should == Net::HTTPClientException
-    end
-
-    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
-    res.error_type.should == Net::HTTPFatalError
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/exception_type_spec.rb b/spec/ruby/library/net/http/httpresponse/exception_type_spec.rb
deleted file mode 100644
index c0812cd322..0000000000
--- a/spec/ruby/library/net/http/httpresponse/exception_type_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse.exception_type" do
-  it "returns self's 'EXCEPTION_TYPE' constant" do
-    Net::HTTPUnknownResponse.exception_type.should == Net::HTTPError
-    Net::HTTPInformation.exception_type.should == Net::HTTPError
-    Net::HTTPSuccess.exception_type.should == Net::HTTPError
-    Net::HTTPRedirection.exception_type.should == Net::HTTPRetriableError
-    ruby_version_is ""..."2.6" do
-      Net::HTTPClientError.exception_type.should == Net::HTTPServerException
-    end
-    ruby_version_is "2.6" do
-      Net::HTTPClientError.exception_type.should == Net::HTTPClientException
-    end
-    Net::HTTPServerError.exception_type.should == Net::HTTPFatalError
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/header_spec.rb b/spec/ruby/library/net/http/httpresponse/header_spec.rb
deleted file mode 100644
index a9615feda8..0000000000
--- a/spec/ruby/library/net/http/httpresponse/header_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#header" do
-  it "returns self" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.response.should equal(res)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/http_version_spec.rb b/spec/ruby/library/net/http/httpresponse/http_version_spec.rb
deleted file mode 100644
index db85696d77..0000000000
--- a/spec/ruby/library/net/http/httpresponse/http_version_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#http_version" do
-  it "returns self's http version" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.http_version.should == "1.0"
-
-    res = Net::HTTPUnknownResponse.new("1.1", "???", "test response")
-    res.http_version.should == "1.1"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/initialize_spec.rb b/spec/ruby/library/net/http/httpresponse/initialize_spec.rb
deleted file mode 100644
index eb77e2e277..0000000000
--- a/spec/ruby/library/net/http/httpresponse/initialize_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#initialize when passed http_version, response_code, response_message" do
-  it "sets self http_version, response_code and response_message to the passed values" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.http_version.should == "1.0"
-    res.code.should == "???"
-    res.message.should == "test response"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/inspect_spec.rb b/spec/ruby/library/net/http/httpresponse/inspect_spec.rb
deleted file mode 100644
index 1e1a2c7cc7..0000000000
--- a/spec/ruby/library/net/http/httpresponse/inspect_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-
-describe "Net::HTTPResponse#inspect" do
-  it "returns a String representation of self" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=false>"
-
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    socket = Net::BufferedIO.new(StringIO.new("test body"))
-    res.reading_body(socket, true) {}
-    res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=true>"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/message_spec.rb b/spec/ruby/library/net/http/httpresponse/message_spec.rb
deleted file mode 100644
index ae8e3678a1..0000000000
--- a/spec/ruby/library/net/http/httpresponse/message_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#message" do
-  it "returns self's response message" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.message.should == "test response"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/msg_spec.rb b/spec/ruby/library/net/http/httpresponse/msg_spec.rb
deleted file mode 100644
index 0e5e7eb4aa..0000000000
--- a/spec/ruby/library/net/http/httpresponse/msg_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#msg" do
-  it "returns self's response message" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.message.should == "test response"
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/read_body_spec.rb b/spec/ruby/library/net/http/httpresponse/read_body_spec.rb
deleted file mode 100644
index 99d8e5fa88..0000000000
--- a/spec/ruby/library/net/http/httpresponse/read_body_spec.rb
+++ /dev/null
@@ -1,85 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#read_body" do
-  before :each do
-    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    @socket = Net::BufferedIO.new(StringIO.new("test body"))
-  end
-
-  describe "when passed no arguments" do
-    it "returns the read body" do
-      @res.reading_body(@socket, true) do
-        @res.read_body.should == "test body"
-      end
-    end
-
-    it "returns the previously read body if called a second time" do
-      @res.reading_body(@socket, true) do
-        @res.read_body.should equal(@res.read_body)
-      end
-    end
-  end
-
-  describe "when passed a buffer" do
-    it "reads the body to the passed buffer" do
-      @res.reading_body(@socket, true) do
-        buffer = ""
-        @res.read_body(buffer)
-        buffer.should == "test body"
-      end
-    end
-
-    it "returns the passed buffer" do
-      @res.reading_body(@socket, true) do
-        buffer = ""
-        @res.read_body(buffer).should equal(buffer)
-      end
-    end
-
-    it "raises an IOError if called a second time" do
-      @res.reading_body(@socket, true) do
-        @res.read_body("")
-        -> { @res.read_body("") }.should raise_error(IOError)
-      end
-    end
-  end
-
-  describe "when passed a block" do
-    it "reads the body and yields it to the passed block (in chunks)" do
-      @res.reading_body(@socket, true) do
-        yielded = false
-
-        buffer = ""
-        @res.read_body do |body|
-          yielded = true
-          buffer << body
-        end
-
-        yielded.should be_true
-        buffer.should == "test body"
-      end
-    end
-
-    it "returns the ReadAdapter" do
-      @res.reading_body(@socket, true) do
-        @res.read_body { nil }.should be_kind_of(Net::ReadAdapter)
-      end
-    end
-
-    it "raises an IOError if called a second time" do
-      @res.reading_body(@socket, true) do
-        @res.read_body {}
-        -> { @res.read_body {} }.should raise_error(IOError)
-      end
-    end
-  end
-
-  describe "when passed buffer and block" do
-    it "raises an ArgumentError" do
-      @res.reading_body(@socket, true) do
-        -> { @res.read_body("") {} }.should raise_error(ArgumentError)
-      end
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/read_header_spec.rb b/spec/ruby/library/net/http/httpresponse/read_header_spec.rb
deleted file mode 100644
index 6af8c6bd6a..0000000000
--- a/spec/ruby/library/net/http/httpresponse/read_header_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#read_header" do
-  it "returns self" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.response.should equal(res)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/read_new_spec.rb b/spec/ruby/library/net/http/httpresponse/read_new_spec.rb
deleted file mode 100644
index 73c7ddc100..0000000000
--- a/spec/ruby/library/net/http/httpresponse/read_new_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse.read_new" do
-  it "creates a HTTPResponse object based on the response read from the passed socket" do
-    socket = Net::BufferedIO.new(StringIO.new(<<EOS))
-HTTP/1.1 200 OK
-Content-Type: text/html; charset=utf-8
-
-test-body
-EOS
-    response = Net::HTTPResponse.read_new(socket)
-
-    response.should be_kind_of(Net::HTTPOK)
-    response.code.should == "200"
-    response["Content-Type"].should == "text/html; charset=utf-8"
-
-    response.reading_body(socket, true) do
-      response.body.should == "test-body\n"
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/reading_body_spec.rb b/spec/ruby/library/net/http/httpresponse/reading_body_spec.rb
deleted file mode 100644
index ebdab891e1..0000000000
--- a/spec/ruby/library/net/http/httpresponse/reading_body_spec.rb
+++ /dev/null
@@ -1,58 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-require "stringio"
-
-describe "Net::HTTPResponse#reading_body" do
-  before :each do
-    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    @socket = Net::BufferedIO.new(StringIO.new("test body"))
-  end
-
-  describe "when body_allowed is true" do
-    it "reads and returns the response body for self from the passed socket" do
-      @res.reading_body(@socket, true) {}.should == "test body"
-      @res.body.should == "test body"
-    end
-
-    it "yields the passed block before reading the body" do
-      yielded = false
-
-      @res.reading_body(@socket, true) do
-        @res.inspect.should == "#<Net::HTTPUnknownResponse ??? test response readbody=false>"
-        yielded = true
-      end
-
-      yielded.should be_true
-    end
-
-    describe "but the response type is not allowed to have a body" do
-      before :each do
-        @res = Net::HTTPInformation.new("1.0", "???", "test response")
-      end
-
-      it "returns nil" do
-        @res.reading_body(@socket, false) {}.should be_nil
-        @res.body.should be_nil
-      end
-
-      it "yields the passed block" do
-        yielded = false
-        @res.reading_body(@socket, true) { yielded = true }
-        yielded.should be_true
-      end
-    end
-  end
-
-  describe "when body_allowed is false" do
-    it "returns nil" do
-      @res.reading_body(@socket, false) {}.should be_nil
-      @res.body.should be_nil
-    end
-
-    it "yields the passed block" do
-      yielded = false
-      @res.reading_body(@socket, true) { yielded = true }
-      yielded.should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/response_spec.rb b/spec/ruby/library/net/http/httpresponse/response_spec.rb
deleted file mode 100644
index f6035f3695..0000000000
--- a/spec/ruby/library/net/http/httpresponse/response_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#response" do
-  it "returns self" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    res.response.should equal(res)
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/shared/body.rb b/spec/ruby/library/net/http/httpresponse/shared/body.rb
deleted file mode 100644
index 91d5fe6375..0000000000
--- a/spec/ruby/library/net/http/httpresponse/shared/body.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-describe :net_httpresponse_body, shared: true do
-  before :each do
-    @res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    @socket = Net::BufferedIO.new(StringIO.new("test body"))
-  end
-
-  it "returns the read body" do
-    @res.reading_body(@socket, true) do
-      @res.send(@method).should == "test body"
-    end
-  end
-
-  it "returns the previously read body if called a second time" do
-    @res.reading_body(@socket, true) do
-      @res.send(@method).should equal(@res.send(@method))
-    end
-  end
-end
diff --git a/spec/ruby/library/net/http/httpresponse/value_spec.rb b/spec/ruby/library/net/http/httpresponse/value_spec.rb
deleted file mode 100644
index 4a5930d4e5..0000000000
--- a/spec/ruby/library/net/http/httpresponse/value_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'net/http'
-
-describe "Net::HTTPResponse#value" do
-  it "raises an HTTP error for non 2xx HTTP Responses" do
-    res = Net::HTTPUnknownResponse.new("1.0", "???", "test response")
-    -> { res.value }.should raise_error(Net::HTTPError)
-
-    res = Net::HTTPInformation.new("1.0", "1xx", "test response")
-    -> { res.value }.should raise_error(Net::HTTPError)
-
-    res = Net::HTTPSuccess.new("1.0", "2xx", "test response")
-    -> { res.value }.should_not raise_error(Net::HTTPError)
-
-    res = Net::HTTPRedirection.new("1.0", "3xx", "test response")
-    -> { res.value }.should raise_error(Net::HTTPRetriableError)
-
-    res = Net::HTTPClientError.new("1.0", "4xx", "test response")
-    ruby_version_is ""..."2.6" do
-      -> { res.value }.should raise_error(Net::HTTPServerException)
-    end
-    ruby_version_is "2.6" do
-      -> { res.value }.should raise_error(Net::HTTPClientException)
-    end
-
-    res = Net::HTTPServerError.new("1.0", "5xx", "test response")
-    -> { res.value }.should raise_error(Net::HTTPFatalError)
-  end
-end
diff --git a/spec/ruby/library/objectspace/dump_all_spec.rb b/spec/ruby/library/objectspace/dump_all_spec.rb
new file mode 100644
index 0000000000..e9b449a905
--- /dev/null
+++ b/spec/ruby/library/objectspace/dump_all_spec.rb
@@ -0,0 +1,112 @@
+require_relative '../../spec_helper'
+require 'objspace'
+
+describe "ObjectSpace.dump_all" do
+  it "dumps Ruby heap to string when passed output: :string" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace")
+      string = "abc"
+      dump = ObjectSpace.dump_all(output: :string)
+      puts dump.class
+      puts dump.include?('"value":"abc"')
+    RUBY
+
+    stdout.should == "String\ntrue\n"
+  end
+
+  it "dumps Ruby heap to a temporary file when passed output: :file" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace")
+      string = "abc"
+      file = ObjectSpace.dump_all(output: :file)
+
+      begin
+        file.flush
+        file.rewind
+        content = file.read
+
+        puts file.class
+        puts content.include?('"value":"abc"')
+      ensure
+        file.close
+        File.unlink file.path
+      end
+    RUBY
+
+    stdout.should == "File\ntrue\n"
+  end
+
+  it "dumps Ruby heap to a temporary file when :output not specified" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace")
+      string = "abc"
+      file = ObjectSpace.dump_all
+
+      begin
+        file.flush
+        file.rewind
+        content = file.read
+
+        puts file.class
+        puts content.include?('"value":"abc"')
+      ensure
+        file.close
+        File.unlink file.path
+      end
+    RUBY
+
+    stdout.should == "File\ntrue\n"
+  end
+
+  it "dumps Ruby heap to a temporary file when passed output: :nil" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace")
+    string = "abc"
+    file = ObjectSpace.dump_all(output: nil)
+
+    begin
+      file.flush
+      file.rewind
+      content = file.read
+
+      puts file.class
+      puts content.include?('"value":"abc"')
+    ensure
+      file.close
+      File.unlink file.path
+    end
+    RUBY
+
+    stdout.should == "File\ntrue\n"
+  end
+
+  it "dumps Ruby heap to stdout when passed output: :stdout" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace")
+      string = "abc"
+      ObjectSpace.dump_all(output: :stdout)
+    RUBY
+
+    stdout.should include('"value":"abc"')
+  end
+
+  it "dumps Ruby heap to provided IO when passed output: IO" do
+    stdout = ruby_exe(<<~RUBY, options: "-robjspace -rtempfile")
+      string = "abc"
+      io = Tempfile.create("object_space_dump_all")
+
+      begin
+        result = ObjectSpace.dump_all(output: io)
+        io.rewind
+        content = io.read
+
+        puts result.equal?(io)
+        puts content.include?('"value":"abc"')
+      ensure
+        io.close
+        File.unlink io.path
+      end
+    RUBY
+
+    stdout.should == "true\ntrue\n"
+  end
+
+  it "raises ArgumentError when passed not supported :output value" do
+    -> { ObjectSpace.dump_all(output: Object.new) }.should raise_error(ArgumentError, /wrong output option/)
+  end
+end
diff --git a/spec/ruby/library/objectspace/dump_spec.rb b/spec/ruby/library/objectspace/dump_spec.rb
new file mode 100644
index 0000000000..e22ee3df1e
--- /dev/null
+++ b/spec/ruby/library/objectspace/dump_spec.rb
@@ -0,0 +1,70 @@
+require_relative '../../spec_helper'
+require 'objspace'
+
+describe "ObjectSpace.dump" do
+  it "dumps the content of object as JSON" do
+    require 'json'
+    string = ObjectSpace.dump("abc")
+    dump = JSON.parse(string)
+
+    dump['type'].should == "STRING"
+    dump['value'].should == "abc"
+  end
+
+  it "dumps to string when passed output: :string" do
+    string = ObjectSpace.dump("abc", output: :string)
+    string.should be_kind_of(String)
+    string.should include('"value":"abc"')
+  end
+
+  it "dumps to string when :output not specified" do
+    string = ObjectSpace.dump("abc")
+    string.should be_kind_of(String)
+    string.should include('"value":"abc"')
+  end
+
+  it "dumps to a temporary file when passed output: :file" do
+    file = ObjectSpace.dump("abc", output: :file)
+    file.should be_kind_of(File)
+
+    file.rewind
+    content = file.read
+    content.should include('"value":"abc"')
+  ensure
+    file.close
+    File.unlink file.path
+  end
+
+  it "dumps to a temporary file when passed output: :nil" do
+    file = ObjectSpace.dump("abc", output: nil)
+    file.should be_kind_of(File)
+
+    file.rewind
+    file.read.should include('"value":"abc"')
+  ensure
+    file.close
+    File.unlink file.path
+  end
+
+  it "dumps to stdout when passed output: :stdout" do
+    stdout = ruby_exe('ObjectSpace.dump("abc", output: :stdout)', options: "-robjspace").chomp
+    stdout.should include('"value":"abc"')
+  end
+
+  it "dumps to provided IO when passed output: IO" do
+    filename = tmp("io_read.txt")
+    io = File.open(filename, "w+")
+    result = ObjectSpace.dump("abc", output: io)
+    result.should.equal? io
+
+    io.rewind
+    io.read.should include('"value":"abc"')
+  ensure
+    io.close
+    rm_r filename
+  end
+
+  it "raises ArgumentError when passed not supported :output value" do
+    -> { ObjectSpace.dump("abc", output: Object.new) }.should raise_error(ArgumentError, /wrong output option/)
+  end
+end
diff --git a/spec/ruby/library/objectspace/fixtures/trace.rb b/spec/ruby/library/objectspace/fixtures/trace.rb
new file mode 100644
index 0000000000..e53a7a0cac
--- /dev/null
+++ b/spec/ruby/library/objectspace/fixtures/trace.rb
@@ -0,0 +1,6 @@
+# frozen_string_literal: false
+require "objspace/trace"
+a = "foo"
+b = "b" + "a" + "r"
+c = 42
+p a, b, c
diff --git a/spec/ruby/library/objectspace/memsize_of_all_spec.rb b/spec/ruby/library/objectspace/memsize_of_all_spec.rb
new file mode 100644
index 0000000000..c5a48165ce
--- /dev/null
+++ b/spec/ruby/library/objectspace/memsize_of_all_spec.rb
@@ -0,0 +1,22 @@
+require_relative '../../spec_helper'
+require 'objspace'
+
+describe "ObjectSpace.memsize_of_all" do
+  it "returns a non-zero Integer for all objects" do
+    ObjectSpace.memsize_of_all.should be_kind_of(Integer)
+    ObjectSpace.memsize_of_all.should > 0
+  end
+
+  it "returns a non-zero Integer for Class" do
+    ObjectSpace.memsize_of_all(Class).should be_kind_of(Integer)
+    ObjectSpace.memsize_of_all(Class).should > 0
+  end
+
+  it "increases when a new object is allocated" do
+    c = Class.new
+    before = ObjectSpace.memsize_of_all(c)
+    o = c.new
+    after = ObjectSpace.memsize_of_all(c)
+    after.should > before
+  end
+end
diff --git a/spec/ruby/library/objectspace/memsize_of_spec.rb b/spec/ruby/library/objectspace/memsize_of_spec.rb
index 06a80d9f9c..cbb5a07d54 100644
--- a/spec/ruby/library/objectspace/memsize_of_spec.rb
+++ b/spec/ruby/library/objectspace/memsize_of_spec.rb
@@ -12,7 +12,11 @@ describe "ObjectSpace.memsize_of" do
     ObjectSpace.memsize_of(42).should == 0
   end
 
-  it "returns an Integer for an Object" do
+  it "returns 0 for literal Symbols" do
+    ObjectSpace.memsize_of(:object_space_memsize_spec_static_sym).should == 0
+  end
+
+  it "returns a positive Integer for an Object" do
     obj = Object.new
     ObjectSpace.memsize_of(obj).should be_kind_of(Integer)
     ObjectSpace.memsize_of(obj).should > 0
diff --git a/spec/ruby/library/objectspace/reachable_objects_from_spec.rb b/spec/ruby/library/objectspace/reachable_objects_from_spec.rb
index 7e70bc8569..dee5961663 100644
--- a/spec/ruby/library/objectspace/reachable_objects_from_spec.rb
+++ b/spec/ruby/library/objectspace/reachable_objects_from_spec.rb
@@ -38,7 +38,6 @@ describe "ObjectSpace.reachable_objects_from" do
   end
 
   it "finds an object stored in a Queue" do
-    require 'thread'
     o = Object.new
     q = Queue.new
     q << o
@@ -49,7 +48,6 @@ describe "ObjectSpace.reachable_objects_from" do
   end
 
   it "finds an object stored in a SizedQueue" do
-    require 'thread'
     o = Object.new
     q = SizedQueue.new(3)
     q << o
diff --git a/spec/ruby/library/objectspace/trace_object_allocations_spec.rb b/spec/ruby/library/objectspace/trace_object_allocations_spec.rb
new file mode 100644
index 0000000000..0f1e2aa8b9
--- /dev/null
+++ b/spec/ruby/library/objectspace/trace_object_allocations_spec.rb
@@ -0,0 +1,163 @@
+require_relative '../../spec_helper'
+require 'objspace'
+
+describe "ObjectSpace.trace_object_allocations" do
+  def has_class_frame?
+    Class.new {
+      attr_reader :c
+
+      def initialize
+        @c = caller_locations.first.label =~ /new/
+      end
+    }.new.c
+  end
+
+  def obj_class_path
+    has_class_frame? ? "Class" : nil
+  end
+
+  it "runs a block" do
+    ScratchPad.clear
+    ObjectSpace.trace_object_allocations do
+      ScratchPad.record :a
+    end
+    ScratchPad.recorded.should == :a
+  end
+
+  it "records info for allocation_class_path" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_class_path(o).should == obj_class_path
+      a = [1, 2, 3]
+      ObjectSpace.allocation_class_path(a).should == nil
+    end
+  end
+
+  it "records info for allocation_generation" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_generation(o).should.kind_of?(Integer)
+      a = [1, 2, 3]
+      ObjectSpace.allocation_generation(a).should.kind_of?(Integer)
+    end
+  end
+
+  it "records info for allocation_method_id" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_method_id(o).should == (has_class_frame? ? :new : nil)
+      a = [1, 2, 3]
+      ObjectSpace.allocation_method_id(a).should == nil
+    end
+  end
+
+  it "records info for allocation_sourcefile" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_sourcefile(o).should == __FILE__
+      a = [1, 2, 3]
+      ObjectSpace.allocation_sourcefile(a).should == __FILE__
+    end
+  end
+
+  it "records info for allocation_sourceline" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_sourceline(o).should == __LINE__ - 1
+      a = [1, 2, 3]
+      ObjectSpace.allocation_sourceline(a).should == __LINE__ - 1
+    end
+  end
+
+  it "can be cleared using trace_object_allocations_clear" do
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+      ObjectSpace.allocation_class_path(o).should == obj_class_path
+      ObjectSpace.trace_object_allocations_clear
+      ObjectSpace.allocation_class_path(o).should be_nil
+    end
+  end
+
+  it "does not clears allocation data after returning" do
+    o = nil
+    ObjectSpace.trace_object_allocations do
+      o = Object.new
+    end
+    ObjectSpace.allocation_class_path(o).should == obj_class_path
+  end
+
+  it "can be used without a block using trace_object_allocations_start and _stop" do
+    ObjectSpace.trace_object_allocations_start
+    begin
+      o = Object.new
+      ObjectSpace.allocation_class_path(o).should == obj_class_path
+      a = [1, 2, 3]
+      ObjectSpace.allocation_class_path(a).should == nil
+    ensure
+      ObjectSpace.trace_object_allocations_stop
+    end
+  end
+
+  it "does not clears allocation data after trace_object_allocations_stop" do
+    ObjectSpace.trace_object_allocations_start
+    begin
+      o = Object.new
+    ensure
+      ObjectSpace.trace_object_allocations_stop
+    end
+    ObjectSpace.allocation_class_path(o).should == obj_class_path
+  end
+
+  it "can be nested" do
+    ObjectSpace.trace_object_allocations do
+      ObjectSpace.trace_object_allocations do
+        o = Object.new
+        ObjectSpace.allocation_class_path(o).should == obj_class_path
+      end
+    end
+  end
+
+  it "can be nested without a block using trace_object_allocations_start and _stop" do
+    ObjectSpace.trace_object_allocations_start
+    begin
+      ObjectSpace.trace_object_allocations_start
+      begin
+        o = Object.new
+        ObjectSpace.allocation_class_path(o).should == obj_class_path
+      ensure
+        ObjectSpace.trace_object_allocations_stop
+      end
+    ensure
+      ObjectSpace.trace_object_allocations_stop
+    end
+  end
+
+  it "can be nested with more _stop than _start" do
+    ObjectSpace.trace_object_allocations_start
+    begin
+      o = Object.new
+      ObjectSpace.allocation_class_path(o).should == obj_class_path
+      ObjectSpace.trace_object_allocations_stop
+    ensure
+      ObjectSpace.trace_object_allocations_stop
+    end
+  end
+
+  it "returns nil for class_path, generation, method_id, sourcefile, and sourceline for immutable objects" do
+    ObjectSpace.trace_object_allocations_start
+    begin
+      one = nil
+      two = 42
+      three = :foo
+      [one, two, three].each do |i|
+        ObjectSpace.allocation_class_path(i).should == nil
+        ObjectSpace.allocation_generation(i).should == nil
+        ObjectSpace.allocation_method_id(i).should == nil
+        ObjectSpace.allocation_sourcefile(i).should == nil
+        ObjectSpace.allocation_sourceline(i).should == nil
+      end
+    ensure
+      ObjectSpace.trace_object_allocations_stop
+    end
+  end
+end
diff --git a/spec/ruby/library/objectspace/trace_spec.rb b/spec/ruby/library/objectspace/trace_spec.rb
new file mode 100644
index 0000000000..3957dc930d
--- /dev/null
+++ b/spec/ruby/library/objectspace/trace_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+
+describe 'require "objspace/trace"' do
+  it "shows object allocation sites" do
+    file = fixture(__FILE__ , "trace.rb")
+    ruby_exe(file, args: "2>&1").lines(chomp: true).should == [
+      "objspace/trace is enabled",
+      "\"foo\" @ #{file}:3",
+      "\"bar\" @ #{file}:4",
+      "42"
+    ]
+  end
+end
diff --git a/spec/ruby/library/openssl/config/freeze_spec.rb b/spec/ruby/library/openssl/config/freeze_spec.rb
deleted file mode 100644
index 1876095d9f..0000000000
--- a/spec/ruby/library/openssl/config/freeze_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative '../shared/constants'
-
-require 'openssl'
-
-describe "OpenSSL::Config#freeze" do
-  it "needs to be reviewed for completeness"
-
-  it "freezes" do
-    c = OpenSSL::Config.new
-    -> {
-      c['foo'] = [ ['key', 'value'] ]
-    }.should_not raise_error
-    c.freeze
-    c.frozen?.should be_true
-    -> {
-      c['foo'] = [ ['key', 'value'] ]
-    }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/library/openssl/digest/append_spec.rb b/spec/ruby/library/openssl/digest/append_spec.rb
new file mode 100644
index 0000000000..08802b7253
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/append_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/update'
+
+describe "OpenSSL::Digest#<<" do
+  it_behaves_like :openssl_digest_update, :<<
+end
diff --git a/spec/ruby/library/openssl/digest/block_length_spec.rb b/spec/ruby/library/openssl/digest/block_length_spec.rb
new file mode 100644
index 0000000000..444ed9d20d
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/block_length_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../../spec_helper'
+require_relative '../../../library/digest/sha1/shared/constants'
+require_relative '../../../library/digest/sha256/shared/constants'
+require_relative '../../../library/digest/sha384/shared/constants'
+require_relative '../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe "OpenSSL::Digest#block_length" do
+  context "when the digest object is created via a name argument" do
+    it "returns a SHA1 block length" do
+      OpenSSL::Digest.new('sha1').block_length.should == SHA1Constants::BlockLength
+    end
+
+    it "returns a SHA256 block length" do
+      OpenSSL::Digest.new('sha256').block_length.should == SHA256Constants::BlockLength
+    end
+
+    it "returns a SHA384 block length" do
+      OpenSSL::Digest.new('sha384').block_length.should == SHA384Constants::BlockLength
+    end
+
+    it "returns a SHA512 block length" do
+      OpenSSL::Digest.new('sha512').block_length.should == SHA512Constants::BlockLength
+    end
+  end
+
+  context "when the digest object is created via a subclass" do
+    it "returns a SHA1 block length" do
+      OpenSSL::Digest::SHA1.new.block_length.should == SHA1Constants::BlockLength
+    end
+
+    it "returns a SHA256 block length" do
+      OpenSSL::Digest::SHA256.new.block_length.should == SHA256Constants::BlockLength
+    end
+
+    it "returns a SHA384 block length" do
+      OpenSSL::Digest::SHA384.new.block_length.should == SHA384Constants::BlockLength
+    end
+
+    it "returns a SHA512 block length" do
+      OpenSSL::Digest::SHA512.new.block_length.should == SHA512Constants::BlockLength
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/digest_length_spec.rb b/spec/ruby/library/openssl/digest/digest_length_spec.rb
new file mode 100644
index 0000000000..37d1cba9a7
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/digest_length_spec.rb
@@ -0,0 +1,44 @@
+require_relative '../../../spec_helper'
+require_relative '../../../library/digest/sha1/shared/constants'
+require_relative '../../../library/digest/sha256/shared/constants'
+require_relative '../../../library/digest/sha384/shared/constants'
+require_relative '../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe "OpenSSL::Digest#digest_length" do
+  context "when the digest object is created via a name argument" do
+    it "returns a SHA1 digest length" do
+      OpenSSL::Digest.new('sha1').digest_length.should == SHA1Constants::DigestLength
+    end
+
+    it "returns a SHA256 digest length" do
+      OpenSSL::Digest.new('sha256').digest_length.should == SHA256Constants::DigestLength
+    end
+
+    it "returns a SHA384 digest length" do
+      OpenSSL::Digest.new('sha384').digest_length.should == SHA384Constants::DigestLength
+    end
+
+    it "returns a SHA512 digest length" do
+      OpenSSL::Digest.new('sha512').digest_length.should == SHA512Constants::DigestLength
+    end
+  end
+
+  context "when the digest object is created via a subclass" do
+    it "returns a SHA1 digest length" do
+      OpenSSL::Digest::SHA1.new.digest_length.should == SHA1Constants::DigestLength
+    end
+
+    it "returns a SHA256 digest length" do
+      OpenSSL::Digest::SHA256.new.digest_length.should == SHA256Constants::DigestLength
+    end
+
+    it "returns a SHA384 digest length" do
+      OpenSSL::Digest::SHA384.new.digest_length.should == SHA384Constants::DigestLength
+    end
+
+    it "returns a SHA512 digest length" do
+      OpenSSL::Digest::SHA512.new.digest_length.should == SHA512Constants::DigestLength
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/digest_spec.rb b/spec/ruby/library/openssl/digest/digest_spec.rb
new file mode 100644
index 0000000000..cf27d01b6d
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/digest_spec.rb
@@ -0,0 +1,62 @@
+require_relative '../../../spec_helper'
+require_relative '../../../library/digest/sha1/shared/constants'
+require_relative '../../../library/digest/sha256/shared/constants'
+require_relative '../../../library/digest/sha384/shared/constants'
+require_relative '../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe "OpenSSL::Digest class methods" do
+  describe ".digest" do
+    it "returns a SHA1 digest" do
+      OpenSSL::Digest.digest('sha1', SHA1Constants::Contents).should == SHA1Constants::Digest
+    end
+
+    it "returns a SHA256 digest" do
+      OpenSSL::Digest.digest('sha256', SHA256Constants::Contents).should == SHA256Constants::Digest
+    end
+
+    it "returns a SHA384 digest" do
+      OpenSSL::Digest.digest('sha384', SHA384Constants::Contents).should == SHA384Constants::Digest
+    end
+
+    it "returns a SHA512 digest" do
+      OpenSSL::Digest.digest('sha512', SHA512Constants::Contents).should == SHA512Constants::Digest
+    end
+  end
+
+  describe ".hexdigest" do
+    it "returns a SHA1 hexdigest" do
+      OpenSSL::Digest.hexdigest('sha1', SHA1Constants::Contents).should == SHA1Constants::Hexdigest
+    end
+
+    it "returns a SHA256 hexdigest" do
+      OpenSSL::Digest.hexdigest('sha256', SHA256Constants::Contents).should == SHA256Constants::Hexdigest
+    end
+
+    it "returns a SHA384 hexdigest" do
+      OpenSSL::Digest.hexdigest('sha384', SHA384Constants::Contents).should == SHA384Constants::Hexdigest
+    end
+
+    it "returns a SHA512 hexdigest" do
+      OpenSSL::Digest.hexdigest('sha512', SHA512Constants::Contents).should == SHA512Constants::Hexdigest
+    end
+  end
+
+  describe ".base64digest" do
+    it "returns a SHA1 base64digest" do
+      OpenSSL::Digest.base64digest('sha1', SHA1Constants::Contents).should == SHA1Constants::Base64digest
+    end
+
+    it "returns a SHA256 base64digest" do
+      OpenSSL::Digest.base64digest('sha256', SHA256Constants::Contents).should == SHA256Constants::Base64digest
+    end
+
+    it "returns a SHA384 base64digest" do
+      OpenSSL::Digest.base64digest('sha384', SHA384Constants::Contents).should == SHA384Constants::Base64digest
+    end
+
+    it "returns a SHA512 base64digest" do
+      OpenSSL::Digest.base64digest('sha512', SHA512Constants::Contents).should == SHA512Constants::Base64digest
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/initialize_spec.rb b/spec/ruby/library/openssl/digest/initialize_spec.rb
new file mode 100644
index 0000000000..b5911716ca
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/initialize_spec.rb
@@ -0,0 +1,137 @@
+require_relative '../../../spec_helper'
+require_relative '../../../library/digest/sha1/shared/constants'
+require_relative '../../../library/digest/sha256/shared/constants'
+require_relative '../../../library/digest/sha384/shared/constants'
+require_relative '../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe "OpenSSL::Digest#initialize" do
+  describe "can be called with a digest name" do
+    it "returns a SHA1 object" do
+      OpenSSL::Digest.new("sha1").name.should == "SHA1"
+    end
+
+    it "returns a SHA256 object" do
+      OpenSSL::Digest.new("sha256").name.should == "SHA256"
+    end
+
+    it "returns a SHA384 object" do
+      OpenSSL::Digest.new("sha384").name.should == "SHA384"
+    end
+
+    it "returns a SHA512 object" do
+      OpenSSL::Digest.new("sha512").name.should ==  "SHA512"
+    end
+
+    version_is OpenSSL::VERSION, "4.0.0" do
+      it "throws an error when called with an unknown digest" do
+        -> { OpenSSL::Digest.new("wd40") }.should raise_error(OpenSSL::Digest::DigestError, /wd40/)
+      end
+    end
+
+    it "cannot be called with a symbol" do
+      -> { OpenSSL::Digest.new(:SHA1) }.should raise_error(TypeError)
+    end
+  end
+
+  describe "can be called with a digest object" do
+    it "returns a SHA1 object" do
+      OpenSSL::Digest.new(OpenSSL::Digest::SHA1.new).name.should == "SHA1"
+    end
+
+    it "returns a SHA256 object" do
+      OpenSSL::Digest.new(OpenSSL::Digest::SHA256.new).name.should == "SHA256"
+    end
+
+    it "returns a SHA384 object" do
+      OpenSSL::Digest.new(OpenSSL::Digest::SHA384.new).name.should == "SHA384"
+    end
+
+    it "returns a SHA512 object" do
+      OpenSSL::Digest.new(OpenSSL::Digest::SHA512.new).name.should ==  "SHA512"
+    end
+
+    it "ignores the state of the digest object" do
+      sha1 = OpenSSL::Digest.new('sha1', SHA1Constants::Contents)
+      OpenSSL::Digest.new(sha1).digest.should == SHA1Constants::BlankDigest
+    end
+  end
+
+  it "cannot be called with a digest class" do
+    -> { OpenSSL::Digest.new(OpenSSL::Digest::SHA1) }.should raise_error(TypeError)
+  end
+
+  context "when called without an initial String argument" do
+    it "returns a SHA1 digest" do
+      OpenSSL::Digest.new("sha1").digest.should == SHA1Constants::BlankDigest
+    end
+
+    it "returns a SHA256 digest" do
+      OpenSSL::Digest.new("sha256").digest.should == SHA256Constants::BlankDigest
+    end
+
+    it "returns a SHA384 digest" do
+      OpenSSL::Digest.new("sha384").digest.should == SHA384Constants::BlankDigest
+    end
+
+    it "returns a SHA512 digest" do
+      OpenSSL::Digest.new("sha512").digest.should == SHA512Constants::BlankDigest
+    end
+  end
+
+  context "when called with an initial String argument" do
+    it "returns a SHA1 digest of that argument" do
+      OpenSSL::Digest.new("sha1", SHA1Constants::Contents).digest.should == SHA1Constants::Digest
+    end
+
+    it "returns a SHA256 digest of that argument" do
+      OpenSSL::Digest.new("sha256", SHA256Constants::Contents).digest.should == SHA256Constants::Digest
+    end
+
+    it "returns a SHA384 digest of that argument" do
+      OpenSSL::Digest.new("sha384", SHA384Constants::Contents).digest.should == SHA384Constants::Digest
+    end
+
+    it "returns a SHA512 digest of that argument" do
+      OpenSSL::Digest.new("sha512", SHA512Constants::Contents).digest.should == SHA512Constants::Digest
+    end
+  end
+
+  context "can be called on subclasses" do
+    describe "can be called without an initial String argument on subclasses" do
+      it "returns a SHA1 digest" do
+        OpenSSL::Digest::SHA1.new.digest.should == SHA1Constants::BlankDigest
+      end
+
+      it "returns a SHA256 digest" do
+        OpenSSL::Digest::SHA256.new.digest.should == SHA256Constants::BlankDigest
+      end
+
+      it "returns a SHA384 digest" do
+        OpenSSL::Digest::SHA384.new.digest.should == SHA384Constants::BlankDigest
+      end
+
+      it "returns a SHA512 digest" do
+        OpenSSL::Digest::SHA512.new.digest.should == SHA512Constants::BlankDigest
+      end
+    end
+
+    describe "can be called with an initial String argument on subclasses" do
+      it "returns a SHA1 digest" do
+        OpenSSL::Digest::SHA1.new(SHA1Constants::Contents).digest.should == SHA1Constants::Digest
+      end
+
+      it "returns a SHA256 digest" do
+        OpenSSL::Digest::SHA256.new(SHA256Constants::Contents).digest.should == SHA256Constants::Digest
+      end
+
+      it "returns a SHA384 digest" do
+        OpenSSL::Digest::SHA384.new(SHA384Constants::Contents).digest.should == SHA384Constants::Digest
+      end
+
+      it "returns a SHA512 digest" do
+        OpenSSL::Digest::SHA512.new(SHA512Constants::Contents).digest.should == SHA512Constants::Digest
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/name_spec.rb b/spec/ruby/library/openssl/digest/name_spec.rb
new file mode 100644
index 0000000000..b379f35c1c
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/name_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../../spec_helper'
+require 'openssl'
+
+describe "OpenSSL::Digest#name" do
+  it "returns the name of digest" do
+    OpenSSL::Digest.new('SHA1').name.should == 'SHA1'
+  end
+
+  it "converts the name to the internal representation of OpenSSL" do
+    OpenSSL::Digest.new('sha1').name.should == 'SHA1'
+  end
+
+  it "works on subclasses too" do
+    OpenSSL::Digest::SHA1.new.name.should == 'SHA1'
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/reset_spec.rb b/spec/ruby/library/openssl/digest/reset_spec.rb
new file mode 100644
index 0000000000..c19bf46633
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/reset_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../../spec_helper'
+require_relative '../../../library/digest/sha1/shared/constants'
+require_relative '../../../library/digest/sha256/shared/constants'
+require_relative '../../../library/digest/sha384/shared/constants'
+require_relative '../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe "OpenSSL::Digest#reset" do
+  it "works for a SHA1 digest" do
+    digest = OpenSSL::Digest.new('sha1', SHA1Constants::Contents)
+    digest.reset
+    digest.update(SHA1Constants::Contents)
+    digest.digest.should == SHA1Constants::Digest
+  end
+
+  it "works for a SHA256 digest" do
+    digest = OpenSSL::Digest.new('sha256', SHA256Constants::Contents)
+    digest.reset
+    digest.update(SHA256Constants::Contents)
+    digest.digest.should == SHA256Constants::Digest
+  end
+
+  it "works for a SHA384 digest" do
+    digest = OpenSSL::Digest.new('sha384', SHA384Constants::Contents)
+    digest.reset
+    digest.update(SHA384Constants::Contents)
+    digest.digest.should == SHA384Constants::Digest
+  end
+
+  it "works for a SHA512 digest" do
+    digest = OpenSSL::Digest.new('sha512', SHA512Constants::Contents)
+    digest.reset
+    digest.update(SHA512Constants::Contents)
+    digest.digest.should == SHA512Constants::Digest
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/shared/update.rb b/spec/ruby/library/openssl/digest/shared/update.rb
new file mode 100644
index 0000000000..e5ff9dcb16
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/shared/update.rb
@@ -0,0 +1,123 @@
+require_relative '../../../../library/digest/sha1/shared/constants'
+require_relative '../../../../library/digest/sha256/shared/constants'
+require_relative '../../../../library/digest/sha384/shared/constants'
+require_relative '../../../../library/digest/sha512/shared/constants'
+require 'openssl'
+
+describe :openssl_digest_update, shared: true do
+  context "when given input as a single string" do
+    it "returns a SHA1 digest" do
+      digest = OpenSSL::Digest.new('sha1')
+      digest.send(@method, SHA1Constants::Contents)
+      digest.digest.should == SHA1Constants::Digest
+    end
+
+    it "returns a SHA256 digest" do
+      digest = OpenSSL::Digest.new('sha256')
+      digest.send(@method, SHA256Constants::Contents)
+      digest.digest.should == SHA256Constants::Digest
+    end
+
+    it "returns a SHA384 digest" do
+      digest = OpenSSL::Digest.new('sha384')
+      digest.send(@method, SHA384Constants::Contents)
+      digest.digest.should == SHA384Constants::Digest
+    end
+
+    it "returns a SHA512 digest" do
+      digest = OpenSSL::Digest.new('sha512')
+      digest.send(@method, SHA512Constants::Contents)
+      digest.digest.should == SHA512Constants::Digest
+    end
+  end
+
+  context "when given input as multiple smaller substrings" do
+    it "returns a SHA1 digest" do
+      digest = OpenSSL::Digest.new('sha1')
+      SHA1Constants::Contents.each_char { |b| digest.send(@method, b) }
+      digest.digest.should == SHA1Constants::Digest
+    end
+
+    it "returns a SHA256 digest" do
+      digest = OpenSSL::Digest.new('sha256')
+      SHA256Constants::Contents.each_char { |b| digest.send(@method, b) }
+      digest.digest.should == SHA256Constants::Digest
+    end
+
+    it "returns a SHA384 digest" do
+      digest = OpenSSL::Digest.new('sha384')
+      SHA384Constants::Contents.each_char { |b| digest.send(@method, b) }
+      digest.digest.should == SHA384Constants::Digest
+    end
+
+    it "returns a SHA512 digest" do
+      digest = OpenSSL::Digest.new('sha512')
+      SHA512Constants::Contents.each_char { |b| digest.send(@method, b) }
+      digest.digest.should == SHA512Constants::Digest
+    end
+  end
+
+  context "when input is not a String and responds to #to_str" do
+    it "returns a SHA1 digest" do
+      str = mock('str')
+      str.should_receive(:to_str).and_return(SHA1Constants::Contents)
+      digest = OpenSSL::Digest.new('sha1')
+      digest.send(@method, str)
+      digest.digest.should == SHA1Constants::Digest
+    end
+
+    it "returns a SHA256 digest" do
+      str = mock('str')
+      str.should_receive(:to_str).and_return(SHA256Constants::Contents)
+      digest = OpenSSL::Digest.new('sha256')
+      digest.send(@method, str)
+      digest.digest.should == SHA256Constants::Digest
+    end
+
+    it "returns a SHA384 digest" do
+      str = mock('str')
+      str.should_receive(:to_str).and_return(SHA384Constants::Contents)
+      digest = OpenSSL::Digest.new('sha384')
+      digest.send(@method, str)
+      digest.digest.should == SHA384Constants::Digest
+    end
+
+    it "returns a SHA512 digest" do
+      str = mock('str')
+      str.should_receive(:to_str).and_return(SHA512Constants::Contents)
+      digest = OpenSSL::Digest.new('sha512')
+      digest.send(@method, str)
+      digest.digest.should == SHA512Constants::Digest
+    end
+  end
+
+  context "when input is not a String and does not respond to #to_str" do
+    it "raises a TypeError with SHA1" do
+      digest = OpenSSL::Digest.new('sha1')
+      -> {
+        digest.send(@method, Object.new)
+      }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+    end
+
+    it "raises a TypeError with SHA256" do
+      digest = OpenSSL::Digest.new('sha256')
+      -> {
+        digest.send(@method, Object.new)
+      }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+    end
+
+    it "raises a TypeError with SHA384" do
+      digest = OpenSSL::Digest.new('sha384')
+      -> {
+        digest.send(@method, Object.new)
+      }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+    end
+
+    it "raises a TypeError with SHA512" do
+      digest = OpenSSL::Digest.new('sha512')
+      -> {
+        digest.send(@method, Object.new)
+      }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/digest/update_spec.rb b/spec/ruby/library/openssl/digest/update_spec.rb
new file mode 100644
index 0000000000..3a90b06c6b
--- /dev/null
+++ b/spec/ruby/library/openssl/digest/update_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../../spec_helper'
+require_relative 'shared/update'
+
+describe "OpenSSL::Digest#update" do
+  it_behaves_like :openssl_digest_update, :update
+end
diff --git a/spec/ruby/library/openssl/fixed_length_secure_compare_spec.rb b/spec/ruby/library/openssl/fixed_length_secure_compare_spec.rb
new file mode 100644
index 0000000000..5a2ca168b5
--- /dev/null
+++ b/spec/ruby/library/openssl/fixed_length_secure_compare_spec.rb
@@ -0,0 +1,42 @@
+require_relative '../../spec_helper'
+require 'openssl'
+
+describe "OpenSSL.fixed_length_secure_compare" do
+  it "returns true for two strings with the same content" do
+    input1 = "the quick brown fox jumps over the lazy dog"
+    input2 = "the quick brown fox jumps over the lazy dog"
+    OpenSSL.fixed_length_secure_compare(input1, input2).should be_true
+  end
+
+  it "returns false for two strings of equal size with different content" do
+    input1 = "the quick brown fox jumps over the lazy dog"
+    input2 = "the lazy dog jumps over the quick brown fox"
+    OpenSSL.fixed_length_secure_compare(input1, input2).should be_false
+  end
+
+  it "converts both arguments to strings using #to_str" do
+    input1 = mock("input1")
+    input1.should_receive(:to_str).and_return("the quick brown fox jumps over the lazy dog")
+    input2 = mock("input2")
+    input2.should_receive(:to_str).and_return("the quick brown fox jumps over the lazy dog")
+    OpenSSL.fixed_length_secure_compare(input1, input2).should be_true
+  end
+
+  it "does not accept arguments that are not string and cannot be coerced into strings" do
+    -> {
+      OpenSSL.fixed_length_secure_compare("input1", :input2)
+    }.should raise_error(TypeError, 'no implicit conversion of Symbol into String')
+
+    -> {
+      OpenSSL.fixed_length_secure_compare(Object.new, "input2")
+    }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+  end
+
+  it "raises an ArgumentError for two strings of different size" do
+    input1 = "the quick brown fox jumps over the lazy dog"
+    input2 = "the quick brown fox"
+    -> {
+      OpenSSL.fixed_length_secure_compare(input1, input2)
+    }.should raise_error(ArgumentError, 'inputs must be of equal length')
+  end
+end
diff --git a/spec/ruby/library/openssl/hmac/digest_spec.rb b/spec/ruby/library/openssl/hmac/digest_spec.rb
index 22bc7023bc..03ed136e64 100644
--- a/spec/ruby/library/openssl/hmac/digest_spec.rb
+++ b/spec/ruby/library/openssl/hmac/digest_spec.rb
@@ -4,7 +4,7 @@ require 'openssl'
 
 describe "OpenSSL::HMAC.digest" do
   it "returns an SHA1 digest" do
-    cur_digest = OpenSSL::Digest::SHA1.new
+    cur_digest = OpenSSL::Digest.new("SHA1")
     cur_digest.digest.should == HMACConstants::BlankSHA1Digest
     digest = OpenSSL::HMAC.digest(cur_digest,
                                         HMACConstants::Key,
diff --git a/spec/ruby/library/openssl/hmac/hexdigest_spec.rb b/spec/ruby/library/openssl/hmac/hexdigest_spec.rb
index 7f73b2db09..3508c1bbd7 100644
--- a/spec/ruby/library/openssl/hmac/hexdigest_spec.rb
+++ b/spec/ruby/library/openssl/hmac/hexdigest_spec.rb
@@ -4,7 +4,7 @@ require 'openssl'
 
 describe "OpenSSL::HMAC.hexdigest" do
   it "returns an SHA1 hex digest" do
-    cur_digest = OpenSSL::Digest::SHA1.new
+    cur_digest = OpenSSL::Digest.new("SHA1")
     cur_digest.hexdigest.should == HMACConstants::BlankSHA1HexDigest
     hexdigest = OpenSSL::HMAC.hexdigest(cur_digest,
                                         HMACConstants::Key,
diff --git a/spec/ruby/library/openssl/kdf/pbkdf2_hmac_spec.rb b/spec/ruby/library/openssl/kdf/pbkdf2_hmac_spec.rb
new file mode 100644
index 0000000000..1112972060
--- /dev/null
+++ b/spec/ruby/library/openssl/kdf/pbkdf2_hmac_spec.rb
@@ -0,0 +1,162 @@
+require_relative '../../../spec_helper'
+require 'openssl'
+
+describe "OpenSSL::KDF.pbkdf2_hmac" do
+  before :each do
+    @defaults = {
+      salt: "\x00".b * 16,
+      iterations: 20_000,
+      length: 16,
+      hash: "sha1"
+    }
+  end
+
+  it "creates the same value with the same input" do
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "supports nullbytes embedded in the password" do
+    key = OpenSSL::KDF.pbkdf2_hmac("sec\x00ret".b, **@defaults)
+    key.should == "\xB9\x7F\xB0\xC2\th\xC8<\x86\xF3\x94Ij7\xEF\xF1".b
+  end
+
+  it "coerces the password into a String using #to_str" do
+    pass = mock("pass")
+    pass.should_receive(:to_str).and_return("secret")
+    key = OpenSSL::KDF.pbkdf2_hmac(pass, **@defaults)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "coerces the salt into a String using #to_str" do
+    salt = mock("salt")
+    salt.should_receive(:to_str).and_return("\x00".b * 16)
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, salt: salt)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "coerces the iterations into an Integer using #to_int" do
+    iterations = mock("iterations")
+    iterations.should_receive(:to_int).and_return(20_000)
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, iterations: iterations)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "coerces the length into an Integer using #to_int" do
+    length = mock("length")
+    length.should_receive(:to_int).and_return(16)
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, length: length)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "accepts a OpenSSL::Digest object as hash" do
+    hash = OpenSSL::Digest.new("sha1")
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, hash: hash)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0".b
+  end
+
+  it "accepts an empty password" do
+    key = OpenSSL::KDF.pbkdf2_hmac("", **@defaults)
+    key.should == "k\x9F-\xB1\xF7\x9A\v\xA1(C\xF9\x85!P\xEF\x8C".b
+  end
+
+  it "accepts an empty salt" do
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, salt: "")
+    key.should == "\xD5f\xE5\xEA\xF91\x1D\xD3evD\xED\xDB\xE80\x80".b
+  end
+
+  it "accepts an empty length" do
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, length: 0)
+    key.should.empty?
+  end
+
+  it "accepts an arbitrary length" do
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, length: 19)
+    key.should == "!\x99+\xF0^\xD0\x8BM\x158\xC4\xAC\x9C\xF1\xF0\xE0\xCF\xBB\x7F".b
+  end
+
+  it "accepts any hash function known to OpenSSL" do
+    key = OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, hash: "sha512")
+    key.should == "N\x12}D\xCE\x99\xDBC\x8E\xEC\xAAr\xEA1\xDF\xFF".b
+  end
+
+  it "raises a TypeError when password is not a String and does not respond to #to_str" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac(Object.new, **@defaults)
+    }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
+
+  it "raises a TypeError when salt is not a String and does not respond to #to_str" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, salt: Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into String")
+  end
+
+  it "raises a TypeError when iterations is not an Integer and does not respond to #to_int" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, iterations: Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+  end
+
+  it "raises a TypeError when length is not an Integer and does not respond to #to_int" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, length: Object.new)
+    }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+  end
+
+  it "raises a TypeError when hash is neither a String nor an OpenSSL::Digest" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, hash: Object.new)
+    }.should raise_error(TypeError)
+  end
+
+  version_is OpenSSL::VERSION, "4.0.0" do
+    it "raises a OpenSSL::Digest::DigestError for unknown digest algorithms" do
+      -> {
+        OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, hash: "wd40")
+      }.should raise_error(OpenSSL::Digest::DigestError, /wd40/)
+    end
+  end
+
+  it "treats salt as a required keyword" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults.except(:salt))
+    }.should raise_error(ArgumentError, 'missing keyword: :salt')
+  end
+
+  it "treats iterations as a required keyword" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults.except(:iterations))
+    }.should raise_error(ArgumentError, 'missing keyword: :iterations')
+  end
+
+  it "treats length as a required keyword" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults.except(:length))
+    }.should raise_error(ArgumentError, 'missing keyword: :length')
+  end
+
+  it "treats hash as a required keyword" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults.except(:hash))
+    }.should raise_error(ArgumentError, 'missing keyword: :hash')
+  end
+
+  it "treats all keywords as required" do
+    -> {
+      OpenSSL::KDF.pbkdf2_hmac("secret")
+    }.should raise_error(ArgumentError, 'missing keywords: :salt, :iterations, :length, :hash')
+  end
+
+  guard -> { OpenSSL::OPENSSL_VERSION_NUMBER >= 0x30000000 } do
+    it "raises an OpenSSL::KDF::KDFError for 0 or less iterations" do
+      -> {
+        OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, iterations: 0)
+      }.should raise_error(OpenSSL::KDF::KDFError, "PKCS5_PBKDF2_HMAC: invalid iteration count")
+
+      -> {
+        OpenSSL::KDF.pbkdf2_hmac("secret", **@defaults, iterations: -1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /PKCS5_PBKDF2_HMAC/)
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/kdf/scrypt_spec.rb b/spec/ruby/library/openssl/kdf/scrypt_spec.rb
new file mode 100644
index 0000000000..e01b8bca8a
--- /dev/null
+++ b/spec/ruby/library/openssl/kdf/scrypt_spec.rb
@@ -0,0 +1,210 @@
+require_relative '../../../spec_helper'
+require 'openssl'
+
+# LibreSSL seems not to support scrypt
+guard -> { OpenSSL::OPENSSL_VERSION.start_with?('OpenSSL') and OpenSSL::OPENSSL_VERSION_NUMBER >= 0x10100000 } do
+  describe "OpenSSL::KDF.scrypt" do
+    before :each do
+      @defaults = {
+        salt: "\x00".b * 16,
+        N: 2**14,
+        r: 8,
+        p: 1,
+        length: 32
+      }
+    end
+
+    it "creates the same value with the same input" do
+      key = OpenSSL::KDF.scrypt("secret", **@defaults)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "supports nullbytes embedded into the password" do
+      key = OpenSSL::KDF.scrypt("sec\x00ret".b, **@defaults)
+      key.should == "\xF9\xA4\xA0\xF1p\xF4\xF0\xCAT\xB4v\xEB\r7\x88N\xF7\x15]Ns\xFCwt4a\xC9\xC6\xA7\x13\x81&".b
+    end
+
+    it "coerces the password into a String using #to_str" do
+      pass = mock("pass")
+      pass.should_receive(:to_str).and_return("secret")
+      key = OpenSSL::KDF.scrypt(pass, **@defaults)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "coerces the salt into a String using #to_str" do
+      salt = mock("salt")
+      salt.should_receive(:to_str).and_return("\x00".b * 16)
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, salt: salt)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "coerces the N into an Integer using #to_int" do
+      n = mock("N")
+      n.should_receive(:to_int).and_return(2**14)
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, N: n)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "coerces the r into an Integer using #to_int" do
+      r = mock("r")
+      r.should_receive(:to_int).and_return(8)
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, r: r)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "coerces the p into an Integer using #to_int" do
+      p = mock("p")
+      p.should_receive(:to_int).and_return(1)
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, p: p)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "coerces the length into an Integer using #to_int" do
+      length = mock("length")
+      length.should_receive(:to_int).and_return(32)
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, length: length)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D\x17}\xF2\x84T\xD4)\xC2>\xFE\x93\xE3\xF4".b
+    end
+
+    it "accepts an empty password" do
+      key = OpenSSL::KDF.scrypt("", **@defaults)
+      key.should == "\xAA\xFC\xF5^E\x94v\xFFk\xE6\xF0vR\xE7\x13\xA7\xF5\x15'\x9A\xE4C\x9Dn\x18F_E\xD2\v\e\xB3".b
+    end
+
+    it "accepts an empty salt" do
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, salt: "")
+      key.should == "\x96\xACDl\xCB3/aN\xB0F\x8A#\xD7\x92\xD2O\x1E\v\xBB\xCE\xC0\xAA\xB9\x0F]\xB09\xEA8\xDD\e".b
+    end
+
+    it "accepts a zero length" do
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, length: 0)
+      key.should.empty?
+    end
+
+    it "accepts an arbitrary length" do
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, length: 19)
+      key.should == "h\xB2k\xDF]\xDA\xE1.-(\xCF\xAC\x91D\x8F\xC2a\x9C\x9D".b
+    end
+
+    it "raises a TypeError when password is not a String and does not respond to #to_str" do
+      -> {
+        OpenSSL::KDF.scrypt(Object.new, **@defaults)
+      }.should raise_error(TypeError, "no implicit conversion of Object into String")
+    end
+
+    it "raises a TypeError when salt is not a String and does not respond to #to_str" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, salt: Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into String")
+    end
+
+    it "raises a TypeError when N is not an Integer and does not respond to #to_int" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, N: Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "raises a TypeError when r is not an Integer and does not respond to #to_int" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, r: Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "raises a TypeError when p is not an Integer and does not respond to #to_int" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, p: Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "raises a TypeError when length is not an Integer and does not respond to #to_int" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, length: Object.new)
+      }.should raise_error(TypeError, "no implicit conversion of Object into Integer")
+    end
+
+    it "treats salt as a required keyword" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults.except(:salt))
+      }.should raise_error(ArgumentError, 'missing keyword: :salt')
+    end
+
+    it "treats N as a required keyword" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults.except(:N))
+      }.should raise_error(ArgumentError, 'missing keyword: :N')
+    end
+
+    it "treats r as a required keyword" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults.except(:r))
+      }.should raise_error(ArgumentError, 'missing keyword: :r')
+    end
+
+    it "treats p as a required keyword" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults.except(:p))
+      }.should raise_error(ArgumentError, 'missing keyword: :p')
+    end
+
+    it "treats length as a required keyword" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults.except(:length))
+      }.should raise_error(ArgumentError, 'missing keyword: :length')
+    end
+
+    it "treats all keywords as required" do
+      -> {
+        OpenSSL::KDF.scrypt("secret")
+      }.should raise_error(ArgumentError, 'missing keywords: :salt, :N, :r, :p, :length')
+    end
+
+    it "requires N to be a power of 2" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, N: 2**14 - 1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+    end
+
+    it "requires N to be at least 2" do
+      key = OpenSSL::KDF.scrypt("secret", **@defaults, N: 2)
+      key.should == "\x06A$a\xA9!\xBE\x01\x85\xA7\x18\xBCEa\x82\xC5\xFEl\x93\xAB\xBD\xF7\x8B\x84\v\xFC\eN\xEBQ\xE6\xD2".b
+
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, N: 1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, N: 0)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, N: -1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+    end
+
+    it "requires r to be positive" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, r: 0)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, r: -1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+    end
+
+    it "requires p to be positive" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, p: 0)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, p: -1)
+      }.should raise_error(OpenSSL::KDF::KDFError, /EVP_PBE_scrypt/)
+    end
+
+    it "requires length to be not negative" do
+      -> {
+        OpenSSL::KDF.scrypt("secret", **@defaults, length: -1)
+      }.should raise_error(ArgumentError, "negative string size (or size too big)")
+    end
+  end
+end
diff --git a/spec/ruby/library/openssl/random/shared/random_bytes.rb b/spec/ruby/library/openssl/random/shared/random_bytes.rb
index 037f10d409..f97ccd9974 100644
--- a/spec/ruby/library/openssl/random/shared/random_bytes.rb
+++ b/spec/ruby/library/openssl/random/shared/random_bytes.rb
@@ -1,7 +1,7 @@
 require_relative '../../../../spec_helper'
 require 'openssl'
 
-describe :openssl_random_bytes, shared: true do |cmd|
+describe :openssl_random_bytes, shared: true do
   it "generates a random binary string of specified length" do
     (1..64).each do |idx|
       bytes = OpenSSL::Random.send(@method, idx)
diff --git a/spec/ruby/library/openssl/secure_compare_spec.rb b/spec/ruby/library/openssl/secure_compare_spec.rb
new file mode 100644
index 0000000000..cec48e01e7
--- /dev/null
+++ b/spec/ruby/library/openssl/secure_compare_spec.rb
@@ -0,0 +1,38 @@
+require_relative '../../spec_helper'
+require 'openssl'
+
+describe "OpenSSL.secure_compare" do
+  it "returns true for two strings with the same content" do
+    input1 = "the quick brown fox jumps over the lazy dog"
+    input2 = "the quick brown fox jumps over the lazy dog"
+    OpenSSL.secure_compare(input1, input2).should be_true
+  end
+
+  it "returns false for two strings with different content" do
+    input1 = "the quick brown fox jumps over the lazy dog"
+    input2 = "the lazy dog jumps over the quick brown fox"
+    OpenSSL.secure_compare(input1, input2).should be_false
+  end
+
+  it "converts both arguments to strings using #to_str, but adds equality check for the original objects" do
+    input1 = mock("input1")
+    input1.should_receive(:to_str).and_return("the quick brown fox jumps over the lazy dog")
+    input2 = mock("input2")
+    input2.should_receive(:to_str).and_return("the quick brown fox jumps over the lazy dog")
+    OpenSSL.secure_compare(input1, input2).should be_false
+
+    input = mock("input")
+    input.should_receive(:to_str).twice.and_return("the quick brown fox jumps over the lazy dog")
+    OpenSSL.secure_compare(input, input).should be_true
+  end
+
+  it "does not accept arguments that are not string and cannot be coerced into strings" do
+    -> {
+      OpenSSL.secure_compare("input1", :input2)
+    }.should raise_error(TypeError, 'no implicit conversion of Symbol into String')
+
+    -> {
+      OpenSSL.secure_compare(Object.new, "input2")
+    }.should raise_error(TypeError, 'no implicit conversion of Object into String')
+  end
+end
diff --git a/spec/ruby/library/openssl/shared/constants.rb b/spec/ruby/library/openssl/shared/constants.rb
index 0bed4156a1..836f75011b 100644
--- a/spec/ruby/library/openssl/shared/constants.rb
+++ b/spec/ruby/library/openssl/shared/constants.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 module HMACConstants
 
   Contents = "Ipsum is simply dummy text of the printing and typesetting industry. \nLorem Ipsum has been the industrys standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. \nIt has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. \nIt was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum."
diff --git a/spec/ruby/library/openssl/x509/store/verify_spec.rb b/spec/ruby/library/openssl/x509/store/verify_spec.rb
new file mode 100644
index 0000000000..6a6a53d992
--- /dev/null
+++ b/spec/ruby/library/openssl/x509/store/verify_spec.rb
@@ -0,0 +1,78 @@
+require_relative '../../../../spec_helper'
+require 'openssl'
+
+describe "OpenSSL::X509::Store#verify" do
+  it "returns true for valid certificate" do
+    key = OpenSSL::PKey::RSA.new 2048
+    cert = OpenSSL::X509::Certificate.new
+    cert.version = 2
+    cert.serial = 1
+    cert.subject = OpenSSL::X509::Name.parse "/DC=org/DC=truffleruby/CN=TruffleRuby CA"
+    cert.issuer = cert.subject
+    cert.public_key = key.public_key
+    cert.not_before = Time.now - 10
+    cert.not_after = cert.not_before + 365 * 24 * 60 * 60
+    cert.sign key, OpenSSL::Digest.new('SHA256')
+    store = OpenSSL::X509::Store.new
+    store.add_cert(cert)
+    [store.verify(cert), store.error, store.error_string].should == [true, 0, "ok"]
+  end
+
+  it "returns false for an expired certificate" do
+    key = OpenSSL::PKey::RSA.new 2048
+    cert = OpenSSL::X509::Certificate.new
+    cert.version = 2
+    cert.serial = 1
+    cert.subject = OpenSSL::X509::Name.parse "/DC=org/DC=truffleruby/CN=TruffleRuby CA"
+    cert.issuer = cert.subject
+    cert.public_key = key.public_key
+    cert.not_before = Time.now - 10
+    cert.not_after = Time.now - 5
+    cert.sign key, OpenSSL::Digest.new('SHA256')
+    store = OpenSSL::X509::Store.new
+    store.add_cert(cert)
+    store.verify(cert).should == false
+  end
+
+  it "returns false for an expired root certificate" do
+    root_key = OpenSSL::PKey::RSA.new 2048
+    root_cert = OpenSSL::X509::Certificate.new
+    root_cert.version = 2
+    root_cert.serial = 1
+    root_cert.subject = OpenSSL::X509::Name.parse "/DC=org/DC=truffleruby/CN=TruffleRuby CA"
+    root_cert.issuer = root_cert.subject
+    root_cert.public_key = root_key.public_key
+    root_cert.not_before = Time.now - 10
+    root_cert.not_after = Time.now - 5
+    ef = OpenSSL::X509::ExtensionFactory.new
+    ef.subject_certificate = root_cert
+    ef.issuer_certificate = root_cert
+    root_cert.add_extension(ef.create_extension("basicConstraints","CA:TRUE",true))
+    root_cert.add_extension(ef.create_extension("keyUsage","keyCertSign, cRLSign", true))
+    root_cert.add_extension(ef.create_extension("subjectKeyIdentifier","hash",false))
+    root_cert.add_extension(ef.create_extension("authorityKeyIdentifier","keyid:always",false))
+    root_cert.sign(root_key, OpenSSL::Digest.new('SHA256'))
+
+
+    key = OpenSSL::PKey::RSA.new 2048
+    cert = OpenSSL::X509::Certificate.new
+    cert.version = 2
+    cert.serial = 2
+    cert.subject = OpenSSL::X509::Name.parse "/DC=org/DC=truffleruby/CN=TruffleRuby certificate"
+    cert.issuer = root_cert.subject
+    cert.public_key = key.public_key
+    cert.not_before = Time.now
+    cert.not_after = cert.not_before + 1 * 365 * 24 * 60 * 60
+    ef = OpenSSL::X509::ExtensionFactory.new
+    ef.subject_certificate = cert
+    ef.issuer_certificate = root_cert
+    cert.add_extension(ef.create_extension("keyUsage","digitalSignature", true))
+    cert.add_extension(ef.create_extension("subjectKeyIdentifier","hash",false))
+    cert.sign(root_key, OpenSSL::Digest.new('SHA256'))
+
+    store = OpenSSL::X509::Store.new
+    store.add_cert(root_cert)
+    store.add_cert(cert)
+    store.verify(cert).should == false
+  end
+end
diff --git a/spec/ruby/library/openstruct/frozen_spec.rb b/spec/ruby/library/openstruct/frozen_spec.rb
index 63767bb54d..c14a4bac55 100644
--- a/spec/ruby/library/openstruct/frozen_spec.rb
+++ b/spec/ruby/library/openstruct/frozen_spec.rb
@@ -24,6 +24,7 @@ describe "OpenStruct.new when frozen" do
 
   it "creates a frozen clone" do
     f = @os.clone
+    f.frozen?.should == true
     f.age.should == 70
     ->{ f.age = 0 }.should raise_error( RuntimeError )
     ->{ f.state = :newer }.should raise_error( RuntimeError )
@@ -31,6 +32,7 @@ describe "OpenStruct.new when frozen" do
 
   it "creates an unfrozen dup" do
     d = @os.dup
+    d.frozen?.should == false
     d.age.should == 70
     d.age = 42
     d.age.should == 42
diff --git a/spec/ruby/library/openstruct/marshal_load_spec.rb b/spec/ruby/library/openstruct/marshal_load_spec.rb
index e07c4cef05..342e5e68cd 100644
--- a/spec/ruby/library/openstruct/marshal_load_spec.rb
+++ b/spec/ruby/library/openstruct/marshal_load_spec.rb
@@ -4,7 +4,7 @@ require "ostruct"
 describe "OpenStruct#marshal_load when passed [Hash]" do
   it "defines methods based on the passed Hash" do
     os = OpenStruct.new
-    os.marshal_load(age: 20, name: "John")
+    os.send :marshal_load, age: 20, name: "John"
 
     os.age.should eql(20)
     os.name.should == "John"
diff --git a/spec/ruby/library/openstruct/method_missing_spec.rb b/spec/ruby/library/openstruct/method_missing_spec.rb
index 1992b7255c..89f83d07b3 100644
--- a/spec/ruby/library/openstruct/method_missing_spec.rb
+++ b/spec/ruby/library/openstruct/method_missing_spec.rb
@@ -7,43 +7,18 @@ describe "OpenStruct#method_missing when called with a method name ending in '='
   end
 
   it "raises an ArgumentError when not passed any additional arguments" do
-    -> { @os.method_missing(:test=) }.should raise_error(ArgumentError)
-  end
-
-  it "raises a TypeError when self is frozen" do
-    @os.freeze
-    -> { @os.method_missing(:test=, "test") }.should raise_error(RuntimeError)
-  end
-
-  it "creates accessor methods" do
-    @os.method_missing(:test=, "test")
-    @os.respond_to?(:test=).should be_true
-    @os.respond_to?(:test).should be_true
-
-    @os.test.should == "test"
-    @os.test = "changed"
-    @os.test.should == "changed"
+    -> { @os.send(:test=) }.should raise_error(ArgumentError)
   end
 end
 
 describe "OpenStruct#method_missing when passed additional arguments" do
   it "raises a NoMethodError when the key does not exist" do
     os = OpenStruct.new
-    -> { os.method_missing(:test, 1, 2, 3) }.should raise_error(NoMethodError)
-  end
-
-  ruby_version_is "2.7" do
-    it "raises an ArgumentError when the key exists" do
-      os = OpenStruct.new(test: 20)
-      -> { os.method_missing(:test, 1, 2, 3) }.should raise_error(ArgumentError)
-    end
+    -> { os.test(1, 2, 3) }.should raise_error(NoMethodError)
   end
-end
 
-describe "OpenStruct#method_missing when not passed any additional arguments" do
-  it "returns the value for the passed method from the method/value table" do
-    os = OpenStruct.new(age: 20)
-    os.method_missing(:age).should eql(20)
-    os.method_missing(:name).should be_nil
+  it "raises an ArgumentError when the key exists" do
+    os = OpenStruct.new(test: 20)
+    -> { os.test(1, 2, 3) }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/library/openstruct/to_h_spec.rb b/spec/ruby/library/openstruct/to_h_spec.rb
index ebdec16174..6c272bcc71 100644
--- a/spec/ruby/library/openstruct/to_h_spec.rb
+++ b/spec/ruby/library/openstruct/to_h_spec.rb
@@ -27,44 +27,42 @@ describe "OpenStruct#to_h" do
     @os.age.should == 70
   end
 
-  ruby_version_is "2.6" do
-    context "with block" do
-      it "converts [key, value] pairs returned by the block to a hash" do
-        h = @os.to_h { |k, v| [k.to_s, v*2] }
-        h.should == { "name" => "John SmithJohn Smith", "age" => 140, "pension" => 600 }
-      end
+  context "with block" do
+    it "converts [key, value] pairs returned by the block to a hash" do
+      h = @os.to_h { |k, v| [k.to_s, v*2] }
+      h.should == { "name" => "John SmithJohn Smith", "age" => 140, "pension" => 600 }
+    end
 
-      it "raises ArgumentError if block returns longer or shorter array" do
-        -> do
-          @os.to_h { |k, v| [k.to_s, v*2, 1] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        @os.to_h { |k, v| [k.to_s, v*2, 1] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
 
-        -> do
-          @os.to_h { |k, v| [k] }
-        end.should raise_error(ArgumentError, /element has wrong array length/)
-      end
+      -> do
+        @os.to_h { |k, v| [k] }
+      end.should raise_error(ArgumentError, /element has wrong array length/)
+    end
 
-      it "raises TypeError if block returns something other than Array" do
-        -> do
-          @os.to_h { |k, v| "not-array" }
-        end.should raise_error(TypeError, /wrong element type String/)
-      end
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        @os.to_h { |k, v| "not-array" }
+      end.should raise_error(TypeError, /wrong element type String/)
+    end
 
-      it "coerces returned pair to Array with #to_ary" do
-        x = mock('x')
-        x.stub!(:to_ary).and_return([:b, 'b'])
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
 
-        @os.to_h { |k| x }.should == { :b => 'b' }
-      end
+      @os.to_h { |k| x }.should == { :b => 'b' }
+    end
 
-      it "does not coerce returned pair to Array with #to_a" do
-        x = mock('x')
-        x.stub!(:to_a).and_return([:b, 'b'])
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
 
-        -> do
-          @os.to_h { |k| x }
-        end.should raise_error(TypeError, /wrong element type MockObject/)
-      end
+      -> do
+        @os.to_h { |k| x }
+      end.should raise_error(TypeError, /wrong element type MockObject/)
     end
   end
 end
diff --git a/spec/ruby/library/pathname/absolute_spec.rb b/spec/ruby/library/pathname/absolute_spec.rb
index dce3ae72ee..109abb8ee9 100644
--- a/spec/ruby/library/pathname/absolute_spec.rb
+++ b/spec/ruby/library/pathname/absolute_spec.rb
@@ -4,19 +4,19 @@ require 'pathname'
 describe "Pathname#absolute?" do
 
   it "returns true for the root directory" do
-    Pathname.new('/').absolute?.should == true
+    Pathname.new('/').should.absolute?
   end
 
   it "returns true for a dir starting with a slash" do
-    Pathname.new('/usr/local/bin').absolute?.should == true
+    Pathname.new('/usr/local/bin').should.absolute?
   end
 
   it "returns false for a dir not starting with a slash" do
-    Pathname.new('fish').absolute?.should == false
+    Pathname.new('fish').should_not.absolute?
   end
 
   it "returns false for a dir not starting with a slash" do
-    Pathname.new('fish/dog/cow').absolute?.should == false
+    Pathname.new('fish/dog/cow').should_not.absolute?
   end
 
 end
diff --git a/spec/ruby/library/pathname/birthtime_spec.rb b/spec/ruby/library/pathname/birthtime_spec.rb
new file mode 100644
index 0000000000..109c112303
--- /dev/null
+++ b/spec/ruby/library/pathname/birthtime_spec.rb
@@ -0,0 +1,16 @@
+require_relative '../../spec_helper'
+require 'pathname'
+
+describe "Pathname#birthtime" do
+  platform_is :windows, :darwin, :freebsd, :netbsd do
+    it "returns the birth time for self" do
+      Pathname.new(__FILE__).birthtime.should be_kind_of(Time)
+    end
+  end
+
+  platform_is :openbsd do
+    it "raises an NotImplementedError" do
+      -> { Pathname.new(__FILE__).birthtime }.should raise_error(NotImplementedError)
+    end
+  end
+end
diff --git a/spec/ruby/library/pathname/divide_spec.rb b/spec/ruby/library/pathname/divide_spec.rb
new file mode 100644
index 0000000000..8af79d0c8f
--- /dev/null
+++ b/spec/ruby/library/pathname/divide_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/plus'
+
+describe "Pathname#/" do
+  it_behaves_like :pathname_plus, :/
+end
diff --git a/spec/ruby/library/pathname/glob_spec.rb b/spec/ruby/library/pathname/glob_spec.rb
new file mode 100644
index 0000000000..de322bab47
--- /dev/null
+++ b/spec/ruby/library/pathname/glob_spec.rb
@@ -0,0 +1,92 @@
+require_relative '../../spec_helper'
+require 'pathname'
+
+describe 'Pathname.glob' do
+  before :all  do
+    @dir = tmp('pathname_glob') + '/'
+    @file_1 = @dir + 'lib/ipaddr.rb'
+    @file_2 = @dir + 'lib/irb.rb'
+    @file_3 = @dir + 'lib/.hidden.rb'
+
+    touch @file_1
+    touch @file_2
+    touch @file_3
+  end
+
+  after :all do
+    rm_r @dir[0...-1]
+  end
+
+  it 'returns [] for no match' do
+    Pathname.glob(@dir + 'lib/*.js').should == []
+  end
+
+  it 'returns [] when the pathname does not exist' do
+    Pathname.glob('i_dont_exist/lib/*.js').should == []
+  end
+
+  it 'returns matching file paths' do
+    Pathname.glob(@dir + 'lib/*i*.rb').sort.should == [Pathname.new(@file_1), Pathname.new(@file_2)].sort
+  end
+
+  it 'returns matching file paths when a flag is provided' do
+    expected = [Pathname.new(@file_1), Pathname.new(@file_2), Pathname.new(@file_3)].sort
+    Pathname.glob(@dir + 'lib/*i*.rb', File::FNM_DOTMATCH).sort.should == expected
+  end
+
+  it 'returns matching file paths when supplied :base keyword argument' do
+    Pathname.glob('*i*.rb', base: @dir + 'lib').sort.should == [Pathname.new('ipaddr.rb'), Pathname.new('irb.rb')].sort
+  end
+
+  it "raises an ArgumentError when supplied a keyword argument other than :base" do
+    -> {
+      Pathname.glob('*i*.rb', foo: @dir + 'lib')
+    }.should raise_error(ArgumentError, /unknown keyword: :?foo/)
+  end
+
+  it "does not raise an ArgumentError when supplied a flag and :base keyword argument" do
+    expected = [Pathname.new('ipaddr.rb'), Pathname.new('irb.rb'), Pathname.new('.hidden.rb')].sort
+    Pathname.glob('*i*.rb', File::FNM_DOTMATCH, base: @dir + 'lib').sort.should == expected
+  end
+end
+
+
+describe 'Pathname#glob' do
+  before :all  do
+    @dir = tmp('pathname_glob') + '/'
+    @file_1 = @dir + 'lib/ipaddr.rb'
+    @file_2 = @dir + 'lib/irb.rb'
+    @file_3 = @dir + 'lib/.hidden.rb'
+
+    touch @file_1
+    touch @file_2
+    touch @file_3
+  end
+
+  after :all do
+    rm_r @dir[0...-1]
+  end
+
+  it 'returns [] for no match' do
+    Pathname.new(@dir).glob('lib/*.js').should == []
+  end
+
+  it 'returns [] when the pathname does not exist' do
+    Pathname.new('./i_dont_exist').glob('lib/*.js').should == []
+  end
+
+  it 'returns matching file paths' do
+    Pathname.new(@dir).glob('lib/*i*.rb').sort.should == [Pathname.new(@file_1), Pathname.new(@file_2)].sort
+  end
+
+  it 'yields matching file paths to block' do
+    ary = []
+    Pathname.new(@dir).glob('lib/*i*.rb') { |p| ary << p }.should be_nil
+    ary.sort.should == [Pathname.new(@file_1), Pathname.new(@file_2)].sort
+  end
+
+  it 'returns matching file paths when a flag is provided' do
+    expected = [Pathname.new(@file_1), Pathname.new(@file_2), Pathname.new(@file_3)].sort
+    Pathname.new(@dir).glob('lib/*i*.rb', File::FNM_DOTMATCH).sort.should == expected
+  end
+end
diff --git a/spec/ruby/library/pathname/inspect_spec.rb b/spec/ruby/library/pathname/inspect_spec.rb
new file mode 100644
index 0000000000..304746fbe5
--- /dev/null
+++ b/spec/ruby/library/pathname/inspect_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require 'pathname'
+
+describe "Pathname#inspect" do
+  it "returns a consistent String" do
+    result = Pathname.new('/tmp').inspect
+    result.should be_an_instance_of(String)
+    result.should == "#<Pathname:/tmp>"
+  end
+end
diff --git a/spec/ruby/library/pathname/new_spec.rb b/spec/ruby/library/pathname/new_spec.rb
index f400444887..36226ed515 100644
--- a/spec/ruby/library/pathname/new_spec.rb
+++ b/spec/ruby/library/pathname/new_spec.rb
@@ -10,11 +10,6 @@ describe "Pathname.new" do
     -> { Pathname.new("\0")}.should raise_error(ArgumentError)
   end
 
-  it "is tainted if path is tainted" do
-    path = '/usr/local/bin'.taint
-    Pathname.new(path).tainted?.should == true
-  end
-
   it "raises a TypeError if not passed a String type" do
     -> { Pathname.new(nil)   }.should raise_error(TypeError)
     -> { Pathname.new(0)     }.should raise_error(TypeError)
diff --git a/spec/ruby/library/pathname/pathname_spec.rb b/spec/ruby/library/pathname/pathname_spec.rb
new file mode 100644
index 0000000000..0fb2881468
--- /dev/null
+++ b/spec/ruby/library/pathname/pathname_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require 'pathname'
+
+describe "Kernel#Pathname" do
+  it "is a private instance method" do
+    Kernel.should have_private_instance_method(:Pathname)
+  end
+
+  it "is also a public method" do
+    Kernel.should have_method(:Pathname)
+  end
+
+  it "returns same argument when called with a pathname argument" do
+    path = Pathname('foo')
+    new_path = Pathname(path)
+
+    path.should.equal?(new_path)
+  end
+end
diff --git a/spec/ruby/library/pathname/plus_spec.rb b/spec/ruby/library/pathname/plus_spec.rb
new file mode 100644
index 0000000000..57e472c266
--- /dev/null
+++ b/spec/ruby/library/pathname/plus_spec.rb
@@ -0,0 +1,6 @@
+require_relative '../../spec_helper'
+require_relative 'shared/plus'
+
+describe "Pathname#+" do
+  it_behaves_like :pathname_plus, :+
+end
diff --git a/spec/ruby/library/pathname/relative_path_from_spec.rb b/spec/ruby/library/pathname/relative_path_from_spec.rb
index abe9c80a45..133a149849 100644
--- a/spec/ruby/library/pathname/relative_path_from_spec.rb
+++ b/spec/ruby/library/pathname/relative_path_from_spec.rb
@@ -48,4 +48,8 @@ describe "Pathname#relative_path_from" do
     relative_path_str('..', '..').should == '.'
     relative_path_str('..', '.').should == '..'
   end
+
+  it 'converts string argument to Pathname' do
+    Pathname.new('/usr/bin/ls').relative_path_from('/usr').to_s.should == 'bin/ls'
+  end
 end
diff --git a/spec/ruby/library/pathname/relative_spec.rb b/spec/ruby/library/pathname/relative_spec.rb
index 1a08891e6c..0fab9a7b9f 100644
--- a/spec/ruby/library/pathname/relative_spec.rb
+++ b/spec/ruby/library/pathname/relative_spec.rb
@@ -4,19 +4,19 @@ require 'pathname'
 describe "Pathname#relative?" do
 
   it "returns false for the root directory" do
-    Pathname.new('/').relative?.should == false
+    Pathname.new('/').should_not.relative?
   end
 
   it "returns false for a dir starting with a slash" do
-    Pathname.new('/usr/local/bin').relative?.should == false
+    Pathname.new('/usr/local/bin').should_not.relative?
   end
 
   it "returns true for a dir not starting with a slash" do
-    Pathname.new('fish').relative?.should == true
+    Pathname.new('fish').should.relative?
   end
 
   it "returns true for a dir not starting with a slash" do
-    Pathname.new('fish/dog/cow').relative?.should == true
+    Pathname.new('fish/dog/cow').should.relative?
   end
 
 end
diff --git a/spec/ruby/library/pathname/root_spec.rb b/spec/ruby/library/pathname/root_spec.rb
index 5fec0ee956..cd2be24516 100644
--- a/spec/ruby/library/pathname/root_spec.rb
+++ b/spec/ruby/library/pathname/root_spec.rb
@@ -4,23 +4,23 @@ require 'pathname'
 describe "Pathname#root?" do
 
   it "returns true for root directories" do
-    Pathname.new('/').root?.should == true
+    Pathname.new('/').should.root?
   end
 
   it "returns false for empty string" do
-    Pathname.new('').root?.should == false
+    Pathname.new('').should_not.root?
   end
 
   it "returns false for a top level directory" do
-    Pathname.new('/usr').root?.should == false
+    Pathname.new('/usr').should_not.root?
   end
 
   it "returns false for a top level with .. appended directory" do
-    Pathname.new('/usr/..').root?.should == false
+    Pathname.new('/usr/..').should_not.root?
   end
 
   it "returns false for a directory below top level" do
-    Pathname.new('/usr/local/bin/').root?.should == false
+    Pathname.new('/usr/local/bin/').should_not.root?
   end
 
 end
diff --git a/spec/ruby/library/pathname/shared/plus.rb b/spec/ruby/library/pathname/shared/plus.rb
new file mode 100644
index 0000000000..b3b896ea43
--- /dev/null
+++ b/spec/ruby/library/pathname/shared/plus.rb
@@ -0,0 +1,8 @@
+require 'pathname'
+
+describe :pathname_plus, shared: true do
+  it "appends a pathname to self" do
+    p = Pathname.new("/usr")
+    p.send(@method, "bin/ruby").should == Pathname.new("/usr/bin/ruby")
+  end
+end
diff --git a/spec/ruby/library/pp/pp_spec.rb b/spec/ruby/library/pp/pp_spec.rb
index 06b22601d8..e45a6bb94f 100644
--- a/spec/ruby/library/pp/pp_spec.rb
+++ b/spec/ruby/library/pp/pp_spec.rb
@@ -20,4 +20,11 @@ describe "PP.pp" do
 
     other_out.to_s.should == "[1, 2, 3]\n"
   end
+
+  it 'correctly prints a Hash' do
+    hash = { 'key' => 42 }
+    -> {
+      PP.pp hash
+    }.should output("#{hash.inspect}\n")
+  end
 end
diff --git a/spec/ruby/library/random/formatter/alphanumeric_spec.rb b/spec/ruby/library/random/formatter/alphanumeric_spec.rb
new file mode 100644
index 0000000000..9bd325e1d0
--- /dev/null
+++ b/spec/ruby/library/random/formatter/alphanumeric_spec.rb
@@ -0,0 +1,56 @@
+require_relative '../../../spec_helper'
+
+require 'random/formatter'
+
+describe "Random::Formatter#alphanumeric" do
+  before :each do
+    @object = Object.new
+    @object.extend(Random::Formatter)
+    @object.define_singleton_method(:bytes) do |n|
+      "\x00".b * n
+    end
+  end
+
+  it "generates a random alphanumeric string" do
+    @object.alphanumeric.should =~ /\A[A-Za-z0-9]+\z/
+  end
+
+  it "has a default size of 16 characters" do
+    @object.alphanumeric.size.should == 16
+  end
+
+  it "accepts a 'size' argument" do
+    @object.alphanumeric(10).size.should == 10
+  end
+
+  it "uses the default size if 'nil' is given as size argument" do
+    @object.alphanumeric(nil).size.should == 16
+  end
+
+  it "raises an ArgumentError if the size is not numeric" do
+    -> {
+      @object.alphanumeric("10")
+    }.should raise_error(ArgumentError)
+  end
+
+  it "does not coerce the size argument with #to_int" do
+    size = mock("size")
+    size.should_not_receive(:to_int)
+    -> {
+      @object.alphanumeric(size)
+    }.should raise_error(ArgumentError)
+  end
+
+  ruby_version_is "3.3" do
+    it "accepts a 'chars' argument with the output alphabet" do
+      @object.alphanumeric(chars: ['a', 'b']).should =~ /\A[ab]+\z/
+    end
+
+    it "converts the elements of chars using #to_s" do
+      to_s = mock("to_s")
+      to_s.should_receive(:to_s).and_return("[mock to_s]")
+      # Using 1 value in chars results in an infinite loop
+      @object.alphanumeric(1, chars: [to_s, to_s]).should == "[mock to_s]"
+    end
+  end
+end
diff --git a/spec/ruby/library/rbconfig/rbconfig_spec.rb b/spec/ruby/library/rbconfig/rbconfig_spec.rb
index 6725de8289..b9a4588bf0 100644
--- a/spec/ruby/library/rbconfig/rbconfig_spec.rb
+++ b/spec/ruby/library/rbconfig/rbconfig_spec.rb
@@ -9,18 +9,114 @@ describe 'RbConfig::CONFIG' do
     end
   end
 
+  it 'has MAJOR, MINOR, TEENY, and PATCHLEVEL matching RUBY_VERSION and RUBY_PATCHLEVEL' do
+    major, minor, teeny = RUBY_VERSION.split('.')
+    RbConfig::CONFIG.values_at("MAJOR", "MINOR", "TEENY", "PATCHLEVEL").should == [
+      major, minor, teeny, RUBY_PATCHLEVEL.to_s
+    ]
+  end
+
   # These directories have no meanings before the installation.
   guard -> { RbConfig::TOPDIR } do
     it "['rubylibdir'] returns the directory containing Ruby standard libraries" do
       rubylibdir = RbConfig::CONFIG['rubylibdir']
       File.directory?(rubylibdir).should == true
-      File.exist?("#{rubylibdir}/fileutils.rb").should == true
+      File.should.exist?("#{rubylibdir}/fileutils.rb")
     end
 
     it "['archdir'] returns the directory containing standard libraries C extensions" do
       archdir = RbConfig::CONFIG['archdir']
       File.directory?(archdir).should == true
-      File.exist?("#{archdir}/etc.#{RbConfig::CONFIG['DLEXT']}").should == true
+      File.should.exist?("#{archdir}/etc.#{RbConfig::CONFIG['DLEXT']}")
+    end
+
+    it "['sitelibdir'] is set and is part of $LOAD_PATH" do
+      sitelibdir = RbConfig::CONFIG['sitelibdir']
+      sitelibdir.should be_kind_of String
+      $LOAD_PATH.map{|path| File.realpath(path) rescue path }.should.include? sitelibdir
+    end
+  end
+
+  it "contains no frozen strings even with --enable-frozen-string-literal" do
+    ruby_exe(<<-RUBY, options: '--enable-frozen-string-literal').should == "Done\n"
+      require 'rbconfig'
+      RbConfig::CONFIG.each do |k, v|
+        if v.frozen?
+          puts "\#{k} Failure"
+        end
+      end
+      puts 'Done'
+    RUBY
+  end
+
+  platform_is_not :windows do
+    it "['LIBRUBY'] is the same as LIBRUBY_SO if and only if ENABLE_SHARED" do
+      case RbConfig::CONFIG['ENABLE_SHARED']
+      when 'yes'
+        RbConfig::CONFIG['LIBRUBY'].should == RbConfig::CONFIG['LIBRUBY_SO']
+      when 'no'
+        RbConfig::CONFIG['LIBRUBY'].should_not == RbConfig::CONFIG['LIBRUBY_SO']
+      end
+    end
+  end
+
+  guard -> { RbConfig::TOPDIR } do
+    it "libdir/LIBRUBY_SO is the path to libruby and it exists if and only if ENABLE_SHARED" do
+      libdirname = RbConfig::CONFIG['LIBPATHENV'] == 'PATH' ? 'bindir' :
+                     RbConfig::CONFIG['libdirname']
+      libdir = RbConfig::CONFIG[libdirname]
+      libruby_so = "#{libdir}/#{RbConfig::CONFIG['LIBRUBY_SO']}"
+      case RbConfig::CONFIG['ENABLE_SHARED']
+      when 'yes'
+        File.should.exist?(libruby_so)
+      when 'no'
+        File.should_not.exist?(libruby_so)
+      end
+    end
+  end
+
+  platform_is :linux do
+    it "['AR'] exists and can be executed" do
+      ar = RbConfig::CONFIG.fetch('AR')
+      out = `#{ar} --version`
+      $?.should.success?
+      out.should_not be_empty
+    end
+
+    it "['STRIP'] exists and can be executed" do
+      strip = RbConfig::CONFIG.fetch('STRIP')
+      copy = tmp("sh")
+      cp '/bin/sh', copy
+      begin
+        out = `#{strip} #{copy}`
+        $?.should.success?
+      ensure
+        rm_r copy
+      end
+    end
+  end
+
+  guard -> { %w[aarch64 arm64].include? RbConfig::CONFIG['host_cpu'] } do
+    it "['host_cpu'] returns CPU architecture properly for AArch64" do
+      platform_is :darwin do
+        RbConfig::CONFIG['host_cpu'].should == 'arm64'
+      end
+
+      platform_is_not :darwin do
+        RbConfig::CONFIG['host_cpu'].should == 'aarch64'
+      end
+    end
+  end
+
+  guard -> { platform_is(:linux) || platform_is(:darwin) } do
+    it "['host_os'] returns a proper OS name or platform" do
+      platform_is :darwin do
+        RbConfig::CONFIG['host_os'].should.match?(/darwin/)
+      end
+
+      platform_is :linux do
+        RbConfig::CONFIG['host_os'].should.match?(/linux/)
+      end
     end
   end
 end
@@ -34,3 +130,34 @@ describe "RbConfig::TOPDIR" do
     end
   end
 end
+
+describe "RUBY_PLATFORM" do
+  it "RUBY_PLATFORM contains a proper CPU architecture" do
+    RUBY_PLATFORM.should.include? RbConfig::CONFIG['host_cpu']
+  end
+
+  guard -> { platform_is(:linux) || platform_is(:darwin) } do
+    it "RUBY_PLATFORM contains OS name" do
+      # don't use RbConfig::CONFIG['host_os'] as far as it could be slightly different, e.g. linux-gnu
+      platform_is(:linux) do
+        RUBY_PLATFORM.should.include? 'linux'
+      end
+
+      platform_is(:darwin) do
+        RUBY_PLATFORM.should.include? 'darwin'
+      end
+    end
+  end
+end
+
+describe "RUBY_DESCRIPTION" do
+  guard_not -> { RUBY_ENGINE == "ruby" && !RbConfig::TOPDIR } do
+    it "contains version" do
+      RUBY_DESCRIPTION.should.include? RUBY_VERSION
+    end
+
+    it "contains RUBY_PLATFORM" do
+      RUBY_DESCRIPTION.should.include? RUBY_PLATFORM
+    end
+  end
+end
diff --git a/spec/ruby/library/rbconfig/sizeof/limits_spec.rb b/spec/ruby/library/rbconfig/sizeof/limits_spec.rb
new file mode 100644
index 0000000000..776099da27
--- /dev/null
+++ b/spec/ruby/library/rbconfig/sizeof/limits_spec.rb
@@ -0,0 +1,40 @@
+require_relative '../../../spec_helper'
+require 'rbconfig/sizeof'
+
+describe "RbConfig::LIMITS" do
+  it "is a Hash" do
+    RbConfig::LIMITS.should be_kind_of(Hash)
+  end
+
+  it "has string keys and numeric values" do
+    RbConfig::LIMITS.each do |key, value|
+      key.should be_kind_of String
+      value.should be_kind_of Numeric
+    end
+  end
+
+  it "contains FIXNUM_MIN and FIXNUM_MAX" do
+    RbConfig::LIMITS["FIXNUM_MIN"].should < 0
+    RbConfig::LIMITS["FIXNUM_MAX"].should > 0
+  end
+
+  it "contains CHAR_MIN and CHAR_MAX" do
+    RbConfig::LIMITS["CHAR_MIN"].should <= 0
+    RbConfig::LIMITS["CHAR_MAX"].should > 0
+  end
+
+  it "contains SHRT_MIN and SHRT_MAX" do
+    RbConfig::LIMITS["SHRT_MIN"].should == -32768
+    RbConfig::LIMITS["SHRT_MAX"].should == 32767
+  end
+
+  it "contains INT_MIN and INT_MAX" do
+    RbConfig::LIMITS["INT_MIN"].should < 0
+    RbConfig::LIMITS["INT_MAX"].should > 0
+  end
+
+  it "contains LONG_MIN and LONG_MAX" do
+    RbConfig::LIMITS["LONG_MIN"].should < 0
+    RbConfig::LIMITS["LONG_MAX"].should > 0
+  end
+end
diff --git a/spec/ruby/library/rbconfig/unicode_emoji_version_spec.rb b/spec/ruby/library/rbconfig/unicode_emoji_version_spec.rb
new file mode 100644
index 0000000000..521a750bf7
--- /dev/null
+++ b/spec/ruby/library/rbconfig/unicode_emoji_version_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'rbconfig'
+
+describe "RbConfig::CONFIG['UNICODE_EMOJI_VERSION']" do
+  ruby_version_is ""..."3.4" do
+    it "is 15.0" do
+      RbConfig::CONFIG['UNICODE_EMOJI_VERSION'].should == "15.0"
+    end
+  end
+
+  # Caution: ruby_version_is means is_or_later
+  ruby_version_is "4.0" do
+    it "is 17.0" do
+      RbConfig::CONFIG['UNICODE_EMOJI_VERSION'].should == "17.0"
+    end
+  end
+end
diff --git a/spec/ruby/library/rbconfig/unicode_version_spec.rb b/spec/ruby/library/rbconfig/unicode_version_spec.rb
new file mode 100644
index 0000000000..5cdde74f79
--- /dev/null
+++ b/spec/ruby/library/rbconfig/unicode_version_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'rbconfig'
+
+describe "RbConfig::CONFIG['UNICODE_VERSION']" do
+  ruby_version_is ""..."3.4" do
+    it "is 15.0.0" do
+      RbConfig::CONFIG['UNICODE_VERSION'].should == "15.0.0"
+    end
+  end
+
+  # Caution: ruby_version_is means is_or_later
+  ruby_version_is "4.0" do
+    it "is 17.0.0" do
+      RbConfig::CONFIG['UNICODE_VERSION'].should == "17.0.0"
+    end
+  end
+end
diff --git a/spec/ruby/library/readline/history/delete_at_spec.rb b/spec/ruby/library/readline/history/delete_at_spec.rb
index 8dcce259bb..3bd577e75c 100644
--- a/spec/ruby/library/readline/history/delete_at_spec.rb
+++ b/spec/ruby/library/readline/history/delete_at_spec.rb
@@ -34,12 +34,5 @@ with_feature :readline do
       -> { Readline::HISTORY.delete_at(10) }.should raise_error(IndexError)
       -> { Readline::HISTORY.delete_at(-10) }.should raise_error(IndexError)
     end
-
-    it "taints the returned strings" do
-      Readline::HISTORY.push("1", "2", "3")
-      Readline::HISTORY.delete_at(0).tainted?.should be_true
-      Readline::HISTORY.delete_at(0).tainted?.should be_true
-      Readline::HISTORY.delete_at(0).tainted?.should be_true
-    end
   end
 end
diff --git a/spec/ruby/library/readline/history/each_spec.rb b/spec/ruby/library/readline/history/each_spec.rb
index 4b87df7640..aa48dd46df 100644
--- a/spec/ruby/library/readline/history/each_spec.rb
+++ b/spec/ruby/library/readline/history/each_spec.rb
@@ -19,11 +19,5 @@ with_feature :readline do
       end
       result.should == ["1", "2", "3"]
     end
-
-    it "yields tainted Objects" do
-      Readline::HISTORY.each do |x|
-        x.tainted?.should be_true
-      end
-    end
   end
 end
diff --git a/spec/ruby/library/readline/history/element_reference_spec.rb b/spec/ruby/library/readline/history/element_reference_spec.rb
index 09cac5e28f..0a74f3d62d 100644
--- a/spec/ruby/library/readline/history/element_reference_spec.rb
+++ b/spec/ruby/library/readline/history/element_reference_spec.rb
@@ -12,11 +12,6 @@ with_feature :readline do
       Readline::HISTORY.pop
     end
 
-    it "returns tainted objects" do
-      Readline::HISTORY[0].tainted?.should be_true
-      Readline::HISTORY[1].tainted?.should be_true
-    end
-
     it "returns the history item at the passed index" do
       Readline::HISTORY[0].should == "1"
       Readline::HISTORY[1].should == "2"
diff --git a/spec/ruby/library/readline/history/pop_spec.rb b/spec/ruby/library/readline/history/pop_spec.rb
index 3a4c3579d0..156a8a06f8 100644
--- a/spec/ruby/library/readline/history/pop_spec.rb
+++ b/spec/ruby/library/readline/history/pop_spec.rb
@@ -19,12 +19,5 @@ with_feature :readline do
       Readline::HISTORY.pop.should == "1"
       Readline::HISTORY.size.should == 0
     end
-
-    it "taints the returned strings" do
-      Readline::HISTORY.push("1", "2", "3")
-      Readline::HISTORY.pop.tainted?.should be_true
-      Readline::HISTORY.pop.tainted?.should be_true
-      Readline::HISTORY.pop.tainted?.should be_true
-    end
   end
 end
diff --git a/spec/ruby/library/readline/history/shift_spec.rb b/spec/ruby/library/readline/history/shift_spec.rb
index fdc637fc35..9aad7d5399 100644
--- a/spec/ruby/library/readline/history/shift_spec.rb
+++ b/spec/ruby/library/readline/history/shift_spec.rb
@@ -19,12 +19,5 @@ with_feature :readline do
       Readline::HISTORY.shift.should == "3"
       Readline::HISTORY.size.should == 0
     end
-
-    it "taints the returned strings" do
-      Readline::HISTORY.push("1", "2", "3")
-      Readline::HISTORY.shift.tainted?.should be_true
-      Readline::HISTORY.shift.tainted?.should be_true
-      Readline::HISTORY.shift.tainted?.should be_true
-    end
   end
 end
diff --git a/spec/ruby/library/readline/readline_spec.rb b/spec/ruby/library/readline/readline_spec.rb
index f716d7b2df..6e349ad543 100644
--- a/spec/ruby/library/readline/readline_spec.rb
+++ b/spec/ruby/library/readline/readline_spec.rb
@@ -21,11 +21,6 @@ with_feature :readline do
         ruby_exe('File.write ARGV[0], Readline.readline', @options)
         File.read(@out).should == "test"
       end
-
-      it "taints the returned strings" do
-        ruby_exe('File.write ARGV[0], Readline.readline.tainted?', @options)
-        File.read(@out).should == "true"
-      end
     end
   end
 end
diff --git a/spec/ruby/library/rexml/attribute/clone_spec.rb b/spec/ruby/library/rexml/attribute/clone_spec.rb
deleted file mode 100644
index 9a4a4079e1..0000000000
--- a/spec/ruby/library/rexml/attribute/clone_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#clone" do
-  it "returns a copy of this Attribute" do
-    orig = REXML::Attribute.new("name", "value&&")
-    orig.should == orig.clone
-    orig.clone.to_s.should == orig.to_s
-    orig.clone.to_string.should == orig.to_string
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/element_spec.rb b/spec/ruby/library/rexml/attribute/element_spec.rb
deleted file mode 100644
index 832e7e9a41..0000000000
--- a/spec/ruby/library/rexml/attribute/element_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#element" do
-  it "returns the parent element" do
-    e = REXML::Element.new "root"
-
-    REXML::Attribute.new("name", "value", e).element.should == e
-    REXML::Attribute.new("name", "default_constructor").element.should == nil
-  end
-end
-
-describe "REXML::Attribute#element=" do
-  it "sets the parent element" do
-    e = REXML::Element.new "root"
-    f = REXML::Element.new "temp"
-    a = REXML::Attribute.new("name", "value", e)
-    a.element.should == e
-
-    a.element = f
-    a.element.should == f
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/equal_value_spec.rb b/spec/ruby/library/rexml/attribute/equal_value_spec.rb
deleted file mode 100644
index 8bf2c0a3a1..0000000000
--- a/spec/ruby/library/rexml/attribute/equal_value_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#==" do
-  it "returns true if other has equal name and value" do
-    a1 = REXML::Attribute.new("foo", "bar")
-    a1.should == a1.clone
-
-    a2 = REXML::Attribute.new("foo", "bar")
-    a1.should == a2
-
-    a3 = REXML::Attribute.new("foo", "bla")
-    a1.should_not == a3
-
-    a4 = REXML::Attribute.new("baz", "bar")
-    a1.should_not == a4
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/hash_spec.rb b/spec/ruby/library/rexml/attribute/hash_spec.rb
deleted file mode 100644
index dd71b28108..0000000000
--- a/spec/ruby/library/rexml/attribute/hash_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#hash" do
-  # These are not really complete, any idea on how to make them more
-  # "testable" will be appreciated.
-  it "returns a hashcode made of the name and value of self" do
-    a = REXML::Attribute.new("name", "value")
-    a.hash.should be_kind_of(Numeric)
-    b = REXML::Attribute.new(a)
-    a.hash.should == b.hash
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/initialize_spec.rb b/spec/ruby/library/rexml/attribute/initialize_spec.rb
deleted file mode 100644
index 9f5e30c517..0000000000
--- a/spec/ruby/library/rexml/attribute/initialize_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#initialize" do
-  before :each do
-    @e = REXML::Element.new "root"
-    @name = REXML::Attribute.new("name", "Nicko")
-    @e.add_attribute @name
-  end
-
-  it "receives two strings for name and value" do
-    @e.attributes["name"].should == "Nicko"
-    @e.add_attribute REXML::Attribute.new("last_name", nil)
-    @e.attributes["last_name"].should == ""
-  end
-
-  it "receives an Attribute and clones it" do
-    copy = REXML::Attribute.new(@name)
-    copy.should == @name
-  end
-
-  it "receives a parent node" do
-    last_name = REXML::Attribute.new("last_name", "McBrain", @e)
-    last_name.element.should == @e
-
-    last_name = REXML::Attribute.new(@name, @e)
-    last_name.element.should == @e
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/inspect_spec.rb b/spec/ruby/library/rexml/attribute/inspect_spec.rb
deleted file mode 100644
index 632b477cca..0000000000
--- a/spec/ruby/library/rexml/attribute/inspect_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#inspect" do
-  it "returns the name and value as a string" do
-    a = REXML::Attribute.new("my_name", "my_value")
-    a.inspect.should == "my_name='my_value'"
-  end
-
-  it "accepts attributes with no value" do
-    a = REXML::Attribute.new("my_name")
-    a.inspect.should == "my_name=''"
-  end
-
-  it "does not escape text" do
-    a = REXML::Attribute.new("name", "<>")
-    a.inspect.should == "name='<>'"
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/namespace_spec.rb b/spec/ruby/library/rexml/attribute/namespace_spec.rb
deleted file mode 100644
index 9d50770735..0000000000
--- a/spec/ruby/library/rexml/attribute/namespace_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#namespace" do
-  it "returns the namespace url" do
-    e = REXML::Element.new("root")
-    e.add_attribute REXML::Attribute.new("xmlns:ns", "http://some_uri")
-    e.namespace("ns").should == "http://some_uri"
-  end
-
-  it "returns nil if namespace is not defined" do
-    e = REXML::Element.new("root")
-    e.add_attribute REXML::Attribute.new("test", "value")
-    e.namespace("test").should == nil
-    e.namespace("ns").should == nil
-  end
-
-  it "defaults arg to nil" do
-    e = REXML::Element.new("root")
-    e.add_attribute REXML::Attribute.new("xmlns:ns", "http://some_uri")
-    e.namespace.should == ""
-    e.namespace("ns").should == "http://some_uri"
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/node_type_spec.rb b/spec/ruby/library/rexml/attribute/node_type_spec.rb
deleted file mode 100644
index 664d7cfa03..0000000000
--- a/spec/ruby/library/rexml/attribute/node_type_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#node_type" do
-  it "always returns :attribute" do
-    attr = REXML::Attribute.new("foo", "bar")
-    attr.node_type.should == :attribute
-    REXML::Attribute.new(attr).node_type.should == :attribute
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/prefix_spec.rb b/spec/ruby/library/rexml/attribute/prefix_spec.rb
deleted file mode 100644
index 2a47f74ad1..0000000000
--- a/spec/ruby/library/rexml/attribute/prefix_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#prefix" do
-  it "returns the namespace of the Attribute" do
-    ans = REXML::Attribute.new("ns:someattr", "some_value")
-    out = REXML::Attribute.new("out:something", "some_other_value")
-
-    ans.prefix.should == "ns"
-    out.prefix.should == "out"
-  end
-
-  it "returns an empty string for Attributes with no prefixes" do
-    attr = REXML::Attribute.new("foo", "bar")
-
-    attr.prefix.should == ""
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/remove_spec.rb b/spec/ruby/library/rexml/attribute/remove_spec.rb
deleted file mode 100644
index 08d22cb6ba..0000000000
--- a/spec/ruby/library/rexml/attribute/remove_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#remove" do
-  before :each do
-    @e = REXML::Element.new "Root"
-    @attr = REXML::Attribute.new("foo", "bar")
-  end
-
-  it "deletes this Attribute from parent" do
-    @e.add_attribute(@attr)
-    @e.attributes["foo"].should_not == nil
-    @attr.remove
-    @e.attributes["foo"].should == nil
-  end
-
-  it "does not anything if element has no parent" do
-    -> {@attr.remove}.should_not raise_error(Exception)
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/to_s_spec.rb b/spec/ruby/library/rexml/attribute/to_s_spec.rb
deleted file mode 100644
index e1ce48ec33..0000000000
--- a/spec/ruby/library/rexml/attribute/to_s_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#to_s" do
-  it "returns the value of the Attribute" do
-    REXML::Attribute.new("name", "some_value").to_s.should == "some_value"
-  end
-
-  it "returns the escaped value if it was created from Attribute" do
-    orig = REXML::Attribute.new("name", "<&>")
-    copy =  REXML::Attribute.new(orig)
-    copy.to_s.should == "&lt;&amp;&gt;"
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/to_string_spec.rb b/spec/ruby/library/rexml/attribute/to_string_spec.rb
deleted file mode 100644
index 420913afeb..0000000000
--- a/spec/ruby/library/rexml/attribute/to_string_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#to_string" do
-  it "returns the attribute as XML" do
-    attr = REXML::Attribute.new("name", "value")
-    attr_empty = REXML::Attribute.new("name")
-    attr_ns = REXML::Attribute.new("xmlns:ns", "http://uri")
-
-    attr.to_string.should == "name='value'"
-    attr_empty.to_string.should == "name=''"
-    attr_ns.to_string.should == "xmlns:ns='http://uri'"
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/value_spec.rb b/spec/ruby/library/rexml/attribute/value_spec.rb
deleted file mode 100644
index 7763976881..0000000000
--- a/spec/ruby/library/rexml/attribute/value_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#value" do
-  it "returns the value of the Attribute unnormalized" do
-    attr = REXML::Attribute.new("name", "value")
-    attr_ents = REXML::Attribute.new("name", "<&>")
-    attr_empty = REXML::Attribute.new("name")
-
-    attr.value.should == "value"
-    attr_ents.value.should == "<&>"
-    attr_empty.value.should == ""
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/write_spec.rb b/spec/ruby/library/rexml/attribute/write_spec.rb
deleted file mode 100644
index 7ada7460f9..0000000000
--- a/spec/ruby/library/rexml/attribute/write_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#write" do
-  before :each do
-    @attr = REXML::Attribute.new("name", "Charlotte")
-    @s = ""
-  end
-
-  it "writes the name and value to output" do
-    @attr.write(@s)
-    @s.should == "name='Charlotte'"
-  end
-
-  it "currently ignores the second argument" do
-    @attr.write(@s, 3)
-    @s.should == "name='Charlotte'"
-
-    @s = ""
-    @attr.write(@s, "foo")
-    @s.should == "name='Charlotte'"
-  end
-end
diff --git a/spec/ruby/library/rexml/attribute/xpath_spec.rb b/spec/ruby/library/rexml/attribute/xpath_spec.rb
deleted file mode 100644
index 8335e0a8ef..0000000000
--- a/spec/ruby/library/rexml/attribute/xpath_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attribute#xpath" do
-
-  before :each do
-    @e = REXML::Element.new "root"
-    @attr = REXML::Attribute.new("year", "1989")
-  end
-
-  it "returns the path for Attribute" do
-    @e.add_attribute @attr
-    @attr.xpath.should == "root/@year"
-  end
-
-  it "raises an error if attribute has no parent" do
-    -> { @attr.xpath }.should raise_error(Exception)
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/add_spec.rb b/spec/ruby/library/rexml/attributes/add_spec.rb
deleted file mode 100644
index 32a927e10b..0000000000
--- a/spec/ruby/library/rexml/attributes/add_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/add'
-require 'rexml/document'
-
-describe "REXML::Attributes#add" do
- it_behaves_like :rexml_attribute_add, :add
-end
diff --git a/spec/ruby/library/rexml/attributes/append_spec.rb b/spec/ruby/library/rexml/attributes/append_spec.rb
deleted file mode 100644
index f1b08f7d6a..0000000000
--- a/spec/ruby/library/rexml/attributes/append_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/add'
-require 'rexml/document'
-
-describe "REXML::Attributes#<<" do
- it_behaves_like :rexml_attribute_add, :<<
-end
diff --git a/spec/ruby/library/rexml/attributes/delete_all_spec.rb b/spec/ruby/library/rexml/attributes/delete_all_spec.rb
deleted file mode 100644
index 9340b5693b..0000000000
--- a/spec/ruby/library/rexml/attributes/delete_all_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#delete_all" do
-  before :each do
-    @e = REXML::Element.new("root")
-  end
-
-  it "deletes all attributes that match name" do
-    uri = REXML::Attribute.new("uri", "http://something")
-    @e.attributes << uri
-    @e.attributes.delete_all("uri")
-    @e.attributes.should be_empty
-    @e.attributes["uri"].should == nil
-  end
-
-  it "deletes all attributes that match name with a namespace" do
-    ns_uri = REXML::Attribute.new("xmlns:uri", "http://something_here_too")
-    @e.attributes << ns_uri
-    @e.attributes.delete_all("xmlns:uri")
-    @e.attributes.should be_empty
-    @e.attributes["xmlns:uri"].should == nil
-  end
-
-  it "returns the removed attribute" do
-    uri = REXML::Attribute.new("uri", "http://something_here_too")
-    @e.attributes << uri
-    attrs = @e.attributes.delete_all("uri")
-    attrs.first.should == uri
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/delete_spec.rb b/spec/ruby/library/rexml/attributes/delete_spec.rb
deleted file mode 100644
index 495e4085ef..0000000000
--- a/spec/ruby/library/rexml/attributes/delete_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#delete" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @name = REXML::Attribute.new("name", "Pepe")
-  end
-
-  it "takes an attribute name and deletes the attribute" do
-    @e.attributes.delete("name")
-    @e.attributes["name"].should be_nil
-    @e.attributes.should be_empty
-  end
-
-  it "takes an Attribute and deletes it" do
-    @e.attributes.delete(@name)
-    @e.attributes["name"].should be_nil
-    @e.attributes.should be_empty
-  end
-
-  it "returns the element with the attribute removed" do
-    ret_val = @e.attributes.delete(@name)
-    ret_val.should == @e
-    ret_val.attributes.should be_empty
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/each_attribute_spec.rb b/spec/ruby/library/rexml/attributes/each_attribute_spec.rb
deleted file mode 100644
index e84c8dbf51..0000000000
--- a/spec/ruby/library/rexml/attributes/each_attribute_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#each_attribute" do
-  it "iterates over the attributes yielding actual Attribute objects" do
-    e = REXML::Element.new("root")
-    name = REXML::Attribute.new("name", "Joe")
-    ns_uri = REXML::Attribute.new("xmlns:ns", "http://some_uri")
-    e.add_attribute name
-    e.add_attribute ns_uri
-
-    attributes = []
-
-    e.attributes.each_attribute do |attr|
-      attributes << attr
-    end
-
-    attributes = attributes.sort_by {|a| a.name }
-    attributes.first.should == name
-    attributes.last.should == ns_uri
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/each_spec.rb b/spec/ruby/library/rexml/attributes/each_spec.rb
deleted file mode 100644
index ed60634b90..0000000000
--- a/spec/ruby/library/rexml/attributes/each_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#each" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @name = REXML::Attribute.new("name", "Joe")
-    @ns_uri = REXML::Attribute.new("xmlns:ns", "http://some_uri")
-    @e.add_attribute @name
-    @e.add_attribute @ns_uri
-  end
-
-  it "iterates over the attributes yielding expanded-name/value" do
-    attributes = []
-    @e.attributes.each do |attr|
-      attr.should be_kind_of(Array)
-      attributes << attr
-    end
-    attributes = attributes.sort_by {|a| a.first }
-    attributes.first.should == ["name", "Joe"]
-    attributes.last.should == ["xmlns:ns", "http://some_uri"]
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/element_reference_spec.rb b/spec/ruby/library/rexml/attributes/element_reference_spec.rb
deleted file mode 100644
index dac7952669..0000000000
--- a/spec/ruby/library/rexml/attributes/element_reference_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#[]" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @lang = REXML::Attribute.new("language", "english")
-    @e.attributes << @lang
-  end
-
-  it "returns the value of an attribute" do
-    @e.attributes["language"].should == "english"
-  end
-
-  it "returns nil if the attribute does not exist" do
-    @e.attributes["chunky bacon"].should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/element_set_spec.rb b/spec/ruby/library/rexml/attributes/element_set_spec.rb
deleted file mode 100644
index 1ed94dd2a1..0000000000
--- a/spec/ruby/library/rexml/attributes/element_set_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#[]=" do
-  before :each do
-    @e = REXML::Element.new("song")
-    @name = REXML::Attribute.new("name", "Holy Smoke!")
-    @e.attributes << @name
-  end
-
-  it "sets an attribute" do
-    @e.attributes["author"] = "_why's foxes"
-    @e.attributes["author"].should == "_why's foxes"
-  end
-
-  it "overwrites an existing attribute" do
-    @e.attributes["name"] = "Chunky Bacon"
-    @e.attributes["name"].should == "Chunky Bacon"
-  end
-
-  it "deletes an attribute is value is nil" do
-    @e.attributes["name"] = nil
-    @e.attributes.length.should == 0
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/get_attribute_ns_spec.rb b/spec/ruby/library/rexml/attributes/get_attribute_ns_spec.rb
deleted file mode 100644
index 1664d6e42a..0000000000
--- a/spec/ruby/library/rexml/attributes/get_attribute_ns_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#get_attribute_ns" do
-  it "returns an attribute by name and namespace" do
-    e = REXML::Element.new("root")
-    attr = REXML::Attribute.new("xmlns:ns", "http://some_url")
-    e.attributes << attr
-    attr.prefix.should == "xmlns"
-    # This might be a bug in Attribute, commenting until those specs
-    # are ready
-    # e.attributes.get_attribute_ns(attr.prefix, "name").should == "http://some_url"
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/get_attribute_spec.rb b/spec/ruby/library/rexml/attributes/get_attribute_spec.rb
deleted file mode 100644
index cfe58c1b9e..0000000000
--- a/spec/ruby/library/rexml/attributes/get_attribute_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#get_attribute" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @name = REXML::Attribute.new("name", "Dave")
-    @e.attributes << @name
-  end
-
-  it "fetches an attributes" do
-    @e.attributes.get_attribute("name").should == @name
-  end
-
-  it "fetches an namespaced attribute" do
-    ns_name = REXML::Attribute.new("im:name", "Murray")
-    @e.attributes << ns_name
-    @e.attributes.get_attribute("name").should == @name
-    @e.attributes.get_attribute("im:name").should == ns_name
-  end
-
-  it "returns an Attribute" do
-    @e.attributes.get_attribute("name").should be_kind_of(REXML::Attribute)
-  end
-
-  it "returns nil if it attribute does not exist" do
-    @e.attributes.get_attribute("fake").should be_nil
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/initialize_spec.rb b/spec/ruby/library/rexml/attributes/initialize_spec.rb
deleted file mode 100644
index f18bd20c69..0000000000
--- a/spec/ruby/library/rexml/attributes/initialize_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#initialize" do
-  it "is auto initialized by Element" do
-    e = REXML::Element.new "root"
-    e.attributes.should be_kind_of(REXML::Attributes)
-
-    e.attributes << REXML::Attribute.new("name", "Paul")
-    e.attributes["name"].should == "Paul"
-  end
-
-  it "receives a parent node" do
-    e = REXML::Element.new "root"
-    e.attributes << REXML::Attribute.new("name", "Vic")
-    e.attributes["name"].should == "Vic"
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/length_spec.rb b/spec/ruby/library/rexml/attributes/length_spec.rb
deleted file mode 100644
index 3a8361b8d7..0000000000
--- a/spec/ruby/library/rexml/attributes/length_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/length'
-require 'rexml/document'
-
-describe "REXML::Attributes#length" do
- it_behaves_like :rexml_attribute_length, :length
-end
diff --git a/spec/ruby/library/rexml/attributes/namespaces_spec.rb b/spec/ruby/library/rexml/attributes/namespaces_spec.rb
deleted file mode 100644
index 9e329fef6f..0000000000
--- a/spec/ruby/library/rexml/attributes/namespaces_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#namespaces" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/library/rexml/attributes/prefixes_spec.rb b/spec/ruby/library/rexml/attributes/prefixes_spec.rb
deleted file mode 100644
index 4675095aad..0000000000
--- a/spec/ruby/library/rexml/attributes/prefixes_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#prefixes" do
-  before :each do
-    @e = REXML::Element.new("root")
-    a1 = REXML::Attribute.new("xmlns:a", "bar")
-    a2 = REXML::Attribute.new("xmlns:b", "bla")
-    a3 = REXML::Attribute.new("xmlns:c", "baz")
-    @e.attributes << a1
-    @e.attributes << a2
-    @e.attributes << a3
-
-    @e.attributes << REXML::Attribute.new("xmlns", "foo")
-  end
-
-  it "returns an array with the prefixes of each attribute" do
-    @e.attributes.prefixes.sort.should == ["a", "b", "c"]
-  end
-
-  it "does not include the default namespace" do
-    @e.attributes.prefixes.include?("xmlns").should == false
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/shared/add.rb b/spec/ruby/library/rexml/attributes/shared/add.rb
deleted file mode 100644
index 872f149f45..0000000000
--- a/spec/ruby/library/rexml/attributes/shared/add.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-describe :rexml_attribute_add, shared: true do
-  before :each do
-    @e = REXML::Element.new("root")
-    @attr = REXML::Attributes.new(@e)
-    @name = REXML::Attribute.new("name", "Joe")
-  end
-
-  it "adds an attribute" do
-    @attr.send(@method, @name)
-    @attr["name"].should == "Joe"
-  end
-
-  it "replaces an existing attribute" do
-    @attr.send(@method, REXML::Attribute.new("name", "Bruce"))
-    @attr["name"].should == "Bruce"
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/shared/length.rb b/spec/ruby/library/rexml/attributes/shared/length.rb
deleted file mode 100644
index 7848f9bf33..0000000000
--- a/spec/ruby/library/rexml/attributes/shared/length.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'rexml/document'
-
-describe :rexml_attribute_length, shared: true do
-  it "returns the number of attributes" do
-    e = REXML::Element.new("root")
-    e.attributes.send(@method).should == 0
-
-    e.attributes << REXML::Attribute.new("name", "John")
-    e.attributes << REXML::Attribute.new("another_name", "Leo")
-    e.attributes.send(@method).should == 2
-  end
-end
diff --git a/spec/ruby/library/rexml/attributes/size_spec.rb b/spec/ruby/library/rexml/attributes/size_spec.rb
deleted file mode 100644
index 3b1df9510d..0000000000
--- a/spec/ruby/library/rexml/attributes/size_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/length'
-require 'rexml/document'
-
-describe "REXML::Attributes#size" do
- it_behaves_like :rexml_attribute_length, :size
-end
diff --git a/spec/ruby/library/rexml/attributes/to_a_spec.rb b/spec/ruby/library/rexml/attributes/to_a_spec.rb
deleted file mode 100644
index 1fbf71b683..0000000000
--- a/spec/ruby/library/rexml/attributes/to_a_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Attributes#to_a" do
-  it "returns an array with the attributes" do
-    e = REXML::Element.new("root")
-    name = REXML::Attribute.new("name", "Dave")
-    last = REXML::Attribute.new("last_name", "Murray")
-
-    e.attributes << name
-    e.attributes << last
-
-    e.attributes.to_a.sort{|a,b|a.to_s<=>b.to_s}.should == [name, last]
-  end
-
-  it "returns an empty array if it has no attributes" do
-    REXML::Element.new("root").attributes.to_a.should == []
-  end
-end
diff --git a/spec/ruby/library/rexml/cdata/clone_spec.rb b/spec/ruby/library/rexml/cdata/clone_spec.rb
deleted file mode 100644
index 7d3cfda902..0000000000
--- a/spec/ruby/library/rexml/cdata/clone_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::CData#clone" do
-  it "makes a copy of itself" do
-    c = REXML::CData.new("some text")
-    c.clone.to_s.should == c.to_s
-    c.clone.should == c
-  end
-end
diff --git a/spec/ruby/library/rexml/cdata/initialize_spec.rb b/spec/ruby/library/rexml/cdata/initialize_spec.rb
deleted file mode 100644
index 0184440d87..0000000000
--- a/spec/ruby/library/rexml/cdata/initialize_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::CData#initialize" do
-  it "creates a new CData object" do
-    c = REXML::CData.new("some    text")
-    c.should be_kind_of(REXML::CData)
-    c.should be_kind_of(REXML::Text)
-  end
-
-  it "respects whitespace if whitespace is true" do
-    c = REXML::CData.new("whitespace     test", true)
-    c1 = REXML::CData.new("whitespace     test", false)
-
-    c.to_s.should == "whitespace     test"
-    c1.to_s.should == "whitespace test"
-  end
-
-  it "receives parent as third argument" do
-    e = REXML::Element.new("root")
-    REXML::CData.new("test", true, e)
-    e.to_s.should == "<root><![CDATA[test]]></root>"
-  end
-end
diff --git a/spec/ruby/library/rexml/cdata/shared/to_s.rb b/spec/ruby/library/rexml/cdata/shared/to_s.rb
deleted file mode 100644
index f8c4951c95..0000000000
--- a/spec/ruby/library/rexml/cdata/shared/to_s.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-describe :rexml_cdata_to_s, shared: true do
-  it "returns the contents of the CData" do
-    c = REXML::CData.new("some text")
-    c.send(@method).should == "some text"
-  end
-
-  it "does not escape text" do
-    c1 = REXML::CData.new("some& text\n")
-    c1.send(@method).should == "some& text\n"
-  end
-end
diff --git a/spec/ruby/library/rexml/cdata/to_s_spec.rb b/spec/ruby/library/rexml/cdata/to_s_spec.rb
deleted file mode 100644
index ff3076e55e..0000000000
--- a/spec/ruby/library/rexml/cdata/to_s_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/to_s'
-require 'rexml/document'
-
-describe "REXML::CData#to_s" do
-  it_behaves_like :rexml_cdata_to_s, :to_s
-end
diff --git a/spec/ruby/library/rexml/cdata/value_spec.rb b/spec/ruby/library/rexml/cdata/value_spec.rb
deleted file mode 100644
index 6e8f8587a1..0000000000
--- a/spec/ruby/library/rexml/cdata/value_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/to_s'
-require 'rexml/document'
-
-describe "REXML::CData#value" do
-  it_behaves_like :rexml_cdata_to_s, :value
-end
diff --git a/spec/ruby/library/rexml/document/add_element_spec.rb b/spec/ruby/library/rexml/document/add_element_spec.rb
deleted file mode 100644
index 42981d6465..0000000000
--- a/spec/ruby/library/rexml/document/add_element_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#add_element" do
-  it "adds arg1 with attributes arg2 as root node" do
-    d = REXML::Document.new
-    e = REXML::Element.new("root")
-    d.add_element e
-    d.root.should == e
-  end
-
-  it "sets arg2 as arg1's attributes" do
-    d = REXML::Document.new
-    e = REXML::Element.new("root")
-    attr = {"foo" => "bar"}
-    d.add_element(e,attr)
-    d.root.attributes["foo"].should == attr["foo"]
-  end
-
-  it "accepts a node name as arg1 and adds it as root" do
-    d = REXML::Document.new
-    d.add_element "foo"
-    d.root.name.should == "foo"
-  end
-
-  it "sets arg1's context to the root's context" do
-    d = REXML::Document.new("", {"foo" => "bar"})
-    d.add_element "foo"
-    d.root.context.should == d.context
-  end
-end
diff --git a/spec/ruby/library/rexml/document/add_spec.rb b/spec/ruby/library/rexml/document/add_spec.rb
deleted file mode 100644
index db95114e7e..0000000000
--- a/spec/ruby/library/rexml/document/add_spec.rb
+++ /dev/null
@@ -1,57 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-# This spec defines Document#add and Document#<<
-
-describe :rexml_document_add, shared: true do
-  before :each do
-    @doc  = REXML::Document.new("<root/>")
-    @decl = REXML::XMLDecl.new("1.0")
-  end
-
-  it "sets document's XML declaration" do
-    @doc.send(@method, @decl)
-    @doc.xml_decl.should == @decl
-  end
-
-  it "inserts XML declaration as first node" do
-    @doc.send(@method, @decl)
-    @doc.children[0].version.should == "1.0"
-  end
-
-  it "overwrites existing XML declaration" do
-    @doc.send(@method, @decl)
-    @doc.send(@method, REXML::XMLDecl.new("2.0"))
-    @doc.xml_decl.version.should == "2.0"
-  end
-
-  it "sets document DocType" do
-    @doc.send(@method, REXML::DocType.new("transitional"))
-    @doc.doctype.name.should == "transitional"
-  end
-
-  it "overwrites existing DocType" do
-    @doc.send(@method, REXML::DocType.new("transitional"))
-    @doc.send(@method, REXML::DocType.new("strict"))
-    @doc.doctype.name.should == "strict"
-  end
-
-  it "adds root node unless it exists" do
-    d = REXML::Document.new("")
-    elem = REXML::Element.new "root"
-    d.send(@method, elem)
-    d.root.should == elem
-  end
-
-  it "refuses to add second root" do
-    -> { @doc.send(@method, REXML::Element.new("foo")) }.should raise_error(RuntimeError)
-  end
-end
-
-describe "REXML::Document#add" do
-  it_behaves_like :rexml_document_add, :add
-end
-
-describe "REXML::Document#<<" do
-  it_behaves_like :rexml_document_add, :<<
-end
diff --git a/spec/ruby/library/rexml/document/clone_spec.rb b/spec/ruby/library/rexml/document/clone_spec.rb
deleted file mode 100644
index 4aebb6f156..0000000000
--- a/spec/ruby/library/rexml/document/clone_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-# According to the MRI documentation (http://www.ruby-doc.org/stdlib/libdoc/rexml/rdoc/index.html),
-# clone's behavior "should be obvious". Apparently "obvious" means cloning
-# only the attributes and the context of the document, not its children.
-describe "REXML::Document#clone" do
-  it "clones document attributes" do
-    d = REXML::Document.new("foo")
-    d.attributes["foo"] = "bar"
-    e = d.clone
-    e.attributes.should == d.attributes
-  end
-
-  it "clones document context" do
-    d = REXML::Document.new("foo", {"foo" => "bar"})
-    e = d.clone
-    e.context.should == d.context
-  end
-end
diff --git a/spec/ruby/library/rexml/document/doctype_spec.rb b/spec/ruby/library/rexml/document/doctype_spec.rb
deleted file mode 100644
index b919b071e1..0000000000
--- a/spec/ruby/library/rexml/document/doctype_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#doctype" do
-  it "returns the doctype" do
-    d = REXML::Document.new
-    dt = REXML::DocType.new("foo")
-    d.add dt
-    d.doctype.should == dt
-  end
-
-  it "returns nil if there's no doctype" do
-    REXML::Document.new.doctype.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/document/encoding_spec.rb b/spec/ruby/library/rexml/document/encoding_spec.rb
deleted file mode 100644
index 343e0ee45f..0000000000
--- a/spec/ruby/library/rexml/document/encoding_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#encoding" do
-  before :each do
-    @doc = REXML::Document.new
-  end
-
-  it "returns encoding from XML declaration" do
-    @doc.add REXML::XMLDecl.new(nil, "UTF-16", nil)
-    @doc.encoding.should == "UTF-16"
-  end
-
-  it "returns encoding from XML declaration (for UTF-16 as well)" do
-    @doc.add REXML::XMLDecl.new("1.0", "UTF-8", nil)
-    @doc.encoding.should == "UTF-8"
-  end
-
-  it "uses UTF-8 as default encoding" do
-    @doc.encoding.should == "UTF-8"
-  end
-end
diff --git a/spec/ruby/library/rexml/document/expanded_name_spec.rb b/spec/ruby/library/rexml/document/expanded_name_spec.rb
deleted file mode 100644
index 1225d13fb0..0000000000
--- a/spec/ruby/library/rexml/document/expanded_name_spec.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe :document_expanded_name, shared: true do
-  it "returns an empty string for root" do # root nodes have no expanded name
-    REXML::Document.new.send(@method).should == ""
-  end
-end
-
-describe "REXML::Document#expanded_name" do
-  it_behaves_like :document_expanded_name, :expanded_name
-end
-
-describe "REXML::Document#name" do
-  it_behaves_like :document_expanded_name, :name
-end
diff --git a/spec/ruby/library/rexml/document/new_spec.rb b/spec/ruby/library/rexml/document/new_spec.rb
deleted file mode 100644
index 3ff5e99b25..0000000000
--- a/spec/ruby/library/rexml/document/new_spec.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Document#new" do
-
-  it "initializes context of {} unless specified" do
-    d = REXML::Document.new("<foo />")
-    d.context.should == {}
-  end
-
-  it "has empty attributes if source is nil" do
-    d = REXML::Document.new(nil)
-    d.elements.should be_empty
-  end
-
-  it "can use other document context" do
-    s = REXML::Document.new("")
-    d = REXML::Document.new(s)
-    d.context.should == s.context
-  end
-
-  it "clones source attributes" do
-    s = REXML::Document.new("<root />")
-    s.attributes["some_attr"] = "some_val"
-    d = REXML::Document.new(s)
-    d.attributes.should == s.attributes
-  end
-
-  it "raises an error if source is not a Document, String or IO" do
-    -> {REXML::Document.new(3)}.should raise_error(RuntimeError)
-  end
-
-  it "does not perform XML validation" do
-    REXML::Document.new("Invalid document").should be_kind_of(REXML::Document)
-  end
-end
diff --git a/spec/ruby/library/rexml/document/node_type_spec.rb b/spec/ruby/library/rexml/document/node_type_spec.rb
deleted file mode 100644
index 85a4d507aa..0000000000
--- a/spec/ruby/library/rexml/document/node_type_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#node_type" do
-  it "returns :document" do
-    REXML::Document.new.node_type.should == :document
-  end
-end
diff --git a/spec/ruby/library/rexml/document/root_spec.rb b/spec/ruby/library/rexml/document/root_spec.rb
deleted file mode 100644
index 3c24e79b2d..0000000000
--- a/spec/ruby/library/rexml/document/root_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#root" do
-  it "returns document root tag name" do
-    REXML::Document.new("<foo/>").root.name.should == "foo"
-  end
-
-  it "returns nil if there is not root" do
-    REXML::Document.new.root.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/document/stand_alone_spec.rb b/spec/ruby/library/rexml/document/stand_alone_spec.rb
deleted file mode 100644
index 4ac24329d6..0000000000
--- a/spec/ruby/library/rexml/document/stand_alone_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#stand_alone?" do
-  it "returns the XMLDecl standalone value" do
-    d = REXML::Document.new
-    decl = REXML::XMLDecl.new("1.0", "UTF-8", "yes")
-    d.add decl
-    d.stand_alone?.should == "yes"
-  end
-
-  # According to the docs this should return the default XMLDecl but that
-  # will carry some more problems when printing the document. Currently, it
-  # returns nil. See http://www.ruby-forum.com/topic/146812#650061
-  it "returns the default value when no XML declaration present" do
-    REXML::Document.new.stand_alone?.should == nil
-  end
-
-end
diff --git a/spec/ruby/library/rexml/document/version_spec.rb b/spec/ruby/library/rexml/document/version_spec.rb
deleted file mode 100644
index 983b4b9af0..0000000000
--- a/spec/ruby/library/rexml/document/version_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#version" do
-  it "returns XML version from declaration" do
-    d = REXML::Document.new
-    d.add REXML::XMLDecl.new("1.1")
-    d.version.should == "1.1"
-  end
-
-  it "returns the default version when declaration is not present" do
-    REXML::Document.new.version.should == REXML::XMLDecl::DEFAULT_VERSION
-  end
-end
diff --git a/spec/ruby/library/rexml/document/write_spec.rb b/spec/ruby/library/rexml/document/write_spec.rb
deleted file mode 100644
index efa94b7117..0000000000
--- a/spec/ruby/library/rexml/document/write_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require 'rexml/document'
-require 'rexml/formatters/transitive'
-require_relative '../../../spec_helper'
-
-# Maybe this can be cleaned
-describe "REXML::Document#write" do
-  before :each do
-    @d      = REXML::Document.new
-    city    = REXML::Element.new "Springfield"
-    street  = REXML::Element.new "EvergreenTerrace"
-    address = REXML::Element.new "House742"
-    @d << city << street << address
-    @str = ""
-  end
-
-  it "returns document source as string" do
-    @d.write(@str)
-    @str.should == "<Springfield><EvergreenTerrace><House742/></EvergreenTerrace></Springfield>"
-  end
-
-  it "returns document indented" do
-    @d.write(@str, 2)
-    @str.should =~ /\s*<Springfield>\s*<EvergreenTerrace>\s*<House742\/>\s*<\/EvergreenTerrace>\s*<\/Springfield>/
-  end
-
-  it "returns document with transitive support" do
-    @d.write(@str, 2, true)
-    @str.should =~ /\s*<Springfield\s*><EvergreenTerrace\s*><House742\s*\/><\/EvergreenTerrace\s*><\/Springfield\s*>/
-  end
-
-  it "returns document with support for IE" do
-    @d.write(@str, -1, false, true)
-    @str.should ==  "<Springfield><EvergreenTerrace><House742 /></EvergreenTerrace></Springfield>"
-  end
-end
diff --git a/spec/ruby/library/rexml/document/xml_decl_spec.rb b/spec/ruby/library/rexml/document/xml_decl_spec.rb
deleted file mode 100644
index 30288a150b..0000000000
--- a/spec/ruby/library/rexml/document/xml_decl_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Document#xml_decl" do
-  it "returns XML declaration of the document" do
-    d = REXML::Document.new
-    decl = REXML::XMLDecl.new("1.0", "UTF-16", "yes")
-    d.add decl
-    d.xml_decl.should == decl
-  end
-
-  it "returns default XML declaration unless present" do
-    REXML::Document.new.xml_decl.should == REXML::XMLDecl.new
-  end
-end
diff --git a/spec/ruby/library/rexml/element/add_attribute_spec.rb b/spec/ruby/library/rexml/element/add_attribute_spec.rb
deleted file mode 100644
index d15fb81ef1..0000000000
--- a/spec/ruby/library/rexml/element/add_attribute_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#add_attribute" do
-  before :each do
-    @person = REXML::Element.new "person"
-    @person.attributes["name"] = "Bill"
-  end
-
-  it "adds a new attribute" do
-    @person.add_attribute("age", "17")
-    @person.attributes["age"].should == "17"
-  end
-
-  it "overwrites an existing attribute" do
-    @person.add_attribute("name", "Bill")
-    @person.attributes["name"].should == "Bill"
-  end
-
-  it "accepts a pair of strings" do
-    @person.add_attribute("male", "true")
-    @person.attributes["male"].should == "true"
-  end
-
-  it "accepts an Attribute for key" do
-    attr = REXML::Attribute.new("male", "true")
-    @person.add_attribute attr
-    @person.attributes["male"].should == "true"
-  end
-
-  it "ignores value if key is an Attribute" do
-    attr = REXML::Attribute.new("male", "true")
-    @person.add_attribute(attr, "false")
-    @person.attributes["male"].should == "true"
-  end
-
-  it "returns the attribute added" do
-    attr = REXML::Attribute.new("name", "Tony")
-    @person.add_attribute(attr).should == attr
-  end
-end
diff --git a/spec/ruby/library/rexml/element/add_attributes_spec.rb b/spec/ruby/library/rexml/element/add_attributes_spec.rb
deleted file mode 100644
index b462fdf5fe..0000000000
--- a/spec/ruby/library/rexml/element/add_attributes_spec.rb
+++ /dev/null
@@ -1,22 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#add_attributes" do
-  before :each do
-    @person = REXML::Element.new "person"
-    @person.attributes["name"] = "Bill"
-  end
-
-  it "adds multiple attributes from a hash" do
-    @person.add_attributes({"name" => "Joe", "age" => "27"})
-    @person.attributes["name"].should == "Joe"
-    @person.attributes["age"].should == "27"
-  end
-
-  it "adds multiple attributes from an array" do
-    attrs =  { "name" => "Joe", "age" => "27"}
-    @person.add_attributes attrs.to_a
-    @person.attributes["name"].should == "Joe"
-    @person.attributes["age"].should == "27"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/add_element_spec.rb b/spec/ruby/library/rexml/element/add_element_spec.rb
deleted file mode 100644
index 8e2ffe3148..0000000000
--- a/spec/ruby/library/rexml/element/add_element_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-
-describe "REXML::Element#add_element" do
-  before :each do
-    @root = REXML::Element.new("root")
-  end
-
-  it "adds a child without attributes" do
-    name = REXML::Element.new("name")
-    @root.add_element name
-    @root.elements["name"].name.should == name.name
-    @root.elements["name"].attributes.should == name.attributes
-    @root.elements["name"].context.should == name.context
-  end
-
-  it "adds a child with attributes" do
-    person = REXML::Element.new("person")
-    @root.add_element(person, {"name" => "Madonna"})
-    @root.elements["person"].name.should == person.name
-    @root.elements["person"].attributes.should == person.attributes
-    @root.elements["person"].context.should == person.context
-  end
-
-  it "adds a child with name" do
-    @root.add_element "name"
-    @root.elements["name"].name.should == "name"
-    @root.elements["name"].attributes.should == {}
-    @root.elements["name"].context.should == nil
-  end
-
-  it "returns the added child" do
-    name = @root.add_element "name"
-    @root.elements["name"].name.should == name.name
-    @root.elements["name"].attributes.should == name.attributes
-    @root.elements["name"].context.should == name.context
-  end
-end
diff --git a/spec/ruby/library/rexml/element/add_namespace_spec.rb b/spec/ruby/library/rexml/element/add_namespace_spec.rb
deleted file mode 100644
index 77c00eec46..0000000000
--- a/spec/ruby/library/rexml/element/add_namespace_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#add_namespace" do
-  before :each do
-    @elem = REXML::Element.new("person")
-  end
-
-  it "adds a namespace to element" do
-    @elem.add_namespace("foo", "bar")
-    @elem.namespace("foo").should == "bar"
-  end
-
-  it "accepts a prefix string as prefix" do
-    @elem.add_namespace("xmlns:foo", "bar")
-    @elem.namespace("foo").should == "bar"
-  end
-
-  it "uses prefix as URI if uri is nil" do
-    @elem.add_namespace("some_uri", nil)
-    @elem.namespace.should == "some_uri"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/add_text_spec.rb b/spec/ruby/library/rexml/element/add_text_spec.rb
deleted file mode 100644
index 54e127bf4b..0000000000
--- a/spec/ruby/library/rexml/element/add_text_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#add_text" do
-  before :each do
-    @name = REXML::Element.new "Name"
-  end
-
-  it "adds text to an element" do
-    @name.add_text "Ringo"
-    @name.to_s.should == "<Name>Ringo</Name>"
-  end
-
-  it "accepts a Text" do
-    @name.add_text(REXML::Text.new("Ringo"))
-    @name.to_s.should == "<Name>Ringo</Name>"
-  end
-
-  it "joins the new text with the old one" do
-    @name.add_text "Ringo"
-    @name.add_text " Starr"
-    @name.to_s.should == "<Name>Ringo Starr</Name>"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/attribute_spec.rb b/spec/ruby/library/rexml/element/attribute_spec.rb
deleted file mode 100644
index e40d612ef3..0000000000
--- a/spec/ruby/library/rexml/element/attribute_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#attribute" do
-  it "returns an attribute by name" do
-    person = REXML::Element.new "Person"
-    attribute = REXML::Attribute.new("drink", "coffee")
-    person.add_attribute(attribute)
-    person.attribute("drink").should == attribute
-  end
-
-  it "supports attributes inside namespaces" do
-    e = REXML::Element.new("element")
-    e.add_attributes({"xmlns:ns" => "http://some_uri"})
-    e.attribute("ns", "ns").to_s.should == "http://some_uri"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/attributes_spec.rb b/spec/ruby/library/rexml/element/attributes_spec.rb
deleted file mode 100644
index 8959b769a8..0000000000
--- a/spec/ruby/library/rexml/element/attributes_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#attributes" do
-  it "returns element's Attributes" do
-    p = REXML::Element.new "Person"
-
-    name = REXML::Attribute.new("name", "John")
-    attrs = REXML::Attributes.new(p)
-    attrs.add name
-
-    p.add_attribute name
-    p.attributes.should == attrs
-  end
-
-  it "returns an empty hash if element has no attributes" do
-    REXML::Element.new("Person").attributes.should == {}
-  end
-end
diff --git a/spec/ruby/library/rexml/element/cdatas_spec.rb b/spec/ruby/library/rexml/element/cdatas_spec.rb
deleted file mode 100644
index a371a5734b..0000000000
--- a/spec/ruby/library/rexml/element/cdatas_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#cdatas" do
-  before :each do
-    @e = REXML::Element.new("Root")
-  end
-
-  it "returns the array of children cdatas" do
-    c = REXML::CData.new("Primary")
-    d = REXML::CData.new("Secondary")
-    @e << c
-    @e << d
-    @e.cdatas.should == [c, d]
-  end
-
-  it "freezes the returned array" do
-    @e.cdatas.frozen?.should == true
-  end
-
-  it "returns an empty array if element has no cdata" do
-    @e.cdatas.should == []
-  end
-end
diff --git a/spec/ruby/library/rexml/element/clone_spec.rb b/spec/ruby/library/rexml/element/clone_spec.rb
deleted file mode 100644
index d26392db41..0000000000
--- a/spec/ruby/library/rexml/element/clone_spec.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#clone" do
-  before :each do
-    @e = REXML::Element.new "a"
-  end
-  it "creates a copy of element" do
-    @e.clone.to_s.should == @e.to_s
-  end
-
-  it "copies the attributes" do
-    @e.add_attribute("foo", "bar")
-    @e.clone.to_s.should == @e.to_s
-  end
-
-  it "does not copy the text" do
-    @e.add_text "some text..."
-    @e.clone.to_s.should_not == @e
-    @e.clone.to_s.should == "<a/>"
-  end
-
-  it "does not copy the child elements" do
-    b = REXML::Element.new "b"
-    @e << b
-    @e.clone.should_not == @e
-    @e.clone.to_s.should == "<a/>"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/comments_spec.rb b/spec/ruby/library/rexml/element/comments_spec.rb
deleted file mode 100644
index 9dac2cc5b8..0000000000
--- a/spec/ruby/library/rexml/element/comments_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#comments" do
-  before :each do
-    @e = REXML::Element.new "root"
-    @c1 = REXML::Comment.new "this is a comment"
-    @c2 = REXML::Comment.new "this is another comment"
-    @e << @c1
-    @e << @c2
-  end
-
-  it "returns the array of comments" do
-    @e.comments.should == [@c1, @c2]
-  end
-
-  it "returns a frozen object" do
-    @e.comments.frozen?.should == true
-  end
-end
diff --git a/spec/ruby/library/rexml/element/delete_attribute_spec.rb b/spec/ruby/library/rexml/element/delete_attribute_spec.rb
deleted file mode 100644
index 5c55c5efda..0000000000
--- a/spec/ruby/library/rexml/element/delete_attribute_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#delete_attribute" do
-  before :each do
-    @e = REXML::Element.new("Person")
-    @attr = REXML::Attribute.new("name", "Sean")
-    @e.add_attribute(@attr)
-  end
-
-  it "deletes an attribute from the element" do
-    @e.delete_attribute("name")
-    @e.attributes["name"].should be_nil
-  end
-
-#  Bug was filled with a patch in Ruby's tracker #20298
-  quarantine! do
-    it "receives an Attribute" do
-      @e.add_attribute(@attr)
-      @e.delete_attribute(@attr)
-      @e.attributes["name"].should be_nil
-    end
-  end
-
-  # Docs say that it returns the removed attribute but then examples
-  # show it returns the element with the attribute removed.
-  # Also fixed in #20298
-  it "returns the element with the attribute removed" do
-    elem = @e.delete_attribute("name")
-    elem.attributes.should be_empty
-    elem.to_s.should eql("<Person/>")
-  end
-
-  it "returns nil if the attribute does not exist" do
-    @e.delete_attribute("name")
-    at = @e.delete_attribute("name")
-    at.should be_nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/delete_element_spec.rb b/spec/ruby/library/rexml/element/delete_element_spec.rb
deleted file mode 100644
index 9417229bd4..0000000000
--- a/spec/ruby/library/rexml/element/delete_element_spec.rb
+++ /dev/null
@@ -1,49 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#delete_element" do
-  before :each do
-    @root = REXML::Element.new("root")
-  end
-
-  it "deletes the child element" do
-    node = REXML::Element.new("some_node")
-    @root.add_element node
-    @root.delete_element node
-    @root.elements.size.should == 0
-  end
-
-  it "deletes a child via XPath" do
-    @root.add_element "some_node"
-    @root.delete_element "some_node"
-    @root.elements.size.should == 0
-  end
-
-  it "deletes the child at index" do
-    @root.add_element "some_node"
-    @root.delete_element 1
-    @root.elements.size.should == 0
-  end
-
-  # According to the docs this should return the deleted element
-  # but it won't if it's an Element.
-  it "deletes Element and returns it" do
-    node = REXML::Element.new("some_node")
-    @root.add_element node
-    del_node = @root.delete_element node
-    del_node.should == node
-  end
-
-  # Note how passing the string will return the removed element
-  # but passing the Element as above won't.
-  it "deletes an element and returns it" do
-    node = REXML::Element.new("some_node")
-    @root.add_element node
-    del_node = @root.delete_element "some_node"
-    del_node.should == node
-  end
-
-  it "returns nil unless element exists" do
-    @root.delete_element("something").should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/delete_namespace_spec.rb b/spec/ruby/library/rexml/element/delete_namespace_spec.rb
deleted file mode 100644
index 8683a40cab..0000000000
--- a/spec/ruby/library/rexml/element/delete_namespace_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#delete_namespace" do
-
-  before :each do
-    @doc = REXML::Document.new "<a xmlns:foo='bar' xmlns='twiddle'/>"
-  end
-
-  it "deletes a namespace from the element" do
-    @doc.root.delete_namespace 'foo'
-    @doc.root.namespace("foo").should be_nil
-    @doc.root.to_s.should == "<a xmlns='twiddle'/>"
-  end
-
-  it "deletes default namespace when called with no args" do
-    @doc.root.delete_namespace
-    @doc.root.namespace.should be_empty
-    @doc.root.to_s.should == "<a xmlns:foo='bar'/>"
-  end
-
-  it "returns the element" do
-    @doc.root.delete_namespace.should == @doc.root
-  end
-end
diff --git a/spec/ruby/library/rexml/element/document_spec.rb b/spec/ruby/library/rexml/element/document_spec.rb
deleted file mode 100644
index 24773580f2..0000000000
--- a/spec/ruby/library/rexml/element/document_spec.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#document" do
-
-  it "returns the element's document" do
-    d = REXML::Document.new("<root><elem/></root>")
-    d << REXML::XMLDecl.new
-    d.root.document.should == d
-    d.root.document.to_s.should == d.to_s
-  end
-
-  it "returns nil if it belongs to no document" do
-    REXML::Element.new("standalone").document.should be_nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/each_element_with_attribute_spec.rb b/spec/ruby/library/rexml/element/each_element_with_attribute_spec.rb
deleted file mode 100644
index 3c5da3f015..0000000000
--- a/spec/ruby/library/rexml/element/each_element_with_attribute_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#each_element_with_attributes" do
-  before :each do
-    @document = REXML::Element.new("people")
-    @father = REXML::Element.new("Person")
-    @father.attributes["name"] = "Joe"
-    @son = REXML::Element.new("Child")
-    @son.attributes["name"] = "Fred"
-    @document.root << @father
-    @document.root << @son
-    @childs = []
-  end
-
-  it "returns childs with attribute" do
-    @document.each_element_with_attribute("name") { |elem| @childs << elem }
-    @childs[0].should == @father
-    @childs[1].should == @son
-  end
-
-  it "takes attribute value as second argument" do
-    @document.each_element_with_attribute("name", "Fred"){ |elem| elem.should == @son }
-  end
-
-  it "takes max number of childs as third argument" do
-    @document.each_element_with_attribute("name", nil, 1) { |elem| @childs << elem }
-    @childs.size.should == 1
-    @childs[0].should == @father
-  end
-
-  it "takes XPath filter as fourth argument" do
-    @document.each_element_with_attribute("name", nil, 0, "Child"){ |elem| elem.should == @son}
-  end
-end
diff --git a/spec/ruby/library/rexml/element/each_element_with_text_spec.rb b/spec/ruby/library/rexml/element/each_element_with_text_spec.rb
deleted file mode 100644
index 5f9e5b85dc..0000000000
--- a/spec/ruby/library/rexml/element/each_element_with_text_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#each_element_with_text" do
-  before :each do
-    @document = REXML::Element.new("people")
-
-    @joe = REXML::Element.new("Person")
-    @joe.text = "Joe"
-    @fred = REXML::Element.new("Person")
-    @fred.text = "Fred"
-    @another = REXML::Element.new("AnotherPerson")
-    @another.text = "Fred"
-    @document.root << @joe
-    @document.root << @fred
-    @document.root << @another
-    @childs = []
-  end
-
-  it "returns childs with text" do
-    @document.each_element_with_text("Joe"){|c| c.should == @joe}
-  end
-
-  it "takes max as second argument" do
-    @document.each_element_with_text("Fred", 1){ |c| c.should == @fred}
-  end
-
-  it "takes XPath filter as third argument" do
-    @document.each_element_with_text("Fred", 0, "Person"){ |c| c.should == @fred}
-  end
-end
diff --git a/spec/ruby/library/rexml/element/element_reference_spec.rb b/spec/ruby/library/rexml/element/element_reference_spec.rb
deleted file mode 100644
index 9660ff7507..0000000000
--- a/spec/ruby/library/rexml/element/element_reference_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#[]" do
-
-  before :each do
-    @doc = REXML::Document.new("<root foo='bar'></root>")
-    @child = REXML::Element.new("child")
-    @doc.root.add_element @child
-  end
-
-  it "return attribute value if argument is string or symbol" do
-    @doc.root[:foo].should == 'bar'
-    @doc.root['foo'].should == 'bar'
-  end
-
-  it "return nth element if argument is int" do
-    @doc.root[0].should == @child
-  end
-end
diff --git a/spec/ruby/library/rexml/element/get_text_spec.rb b/spec/ruby/library/rexml/element/get_text_spec.rb
deleted file mode 100644
index 8ee9ea0824..0000000000
--- a/spec/ruby/library/rexml/element/get_text_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#get_text" do
-  before :each do
-    @doc = REXML::Document.new "<p>some text<b>this is bold!</b> more text</p>"
-  end
-
-  it "returns the first text child node" do
-    @doc.root.get_text.value.should == "some text"
-    @doc.root.get_text.should be_kind_of(REXML::Text)
-  end
-
-  it "returns text from an element matching path" do
-    @doc.root.get_text("b").value.should == "this is bold!"
-    @doc.root.get_text("b").should be_kind_of(REXML::Text)
-  end
-end
diff --git a/spec/ruby/library/rexml/element/has_attributes_spec.rb b/spec/ruby/library/rexml/element/has_attributes_spec.rb
deleted file mode 100644
index f89ec675f5..0000000000
--- a/spec/ruby/library/rexml/element/has_attributes_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#has_attributes?" do
-  before :each do
-    @e = REXML::Element.new("test_elem")
-  end
-
-  it "returns true when element has any attributes" do
-    @e.add_attribute("name", "Joe")
-    @e.has_attributes?.should be_true
-  end
-
-  it "returns false if element has no attributes" do
-    @e.has_attributes?.should be_false
-  end
-end
diff --git a/spec/ruby/library/rexml/element/has_elements_spec.rb b/spec/ruby/library/rexml/element/has_elements_spec.rb
deleted file mode 100644
index dc5fc9c25b..0000000000
--- a/spec/ruby/library/rexml/element/has_elements_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#has_elements?" do
-  before :each do
-    @e = REXML::Element.new("root")
-  end
-
-  it "returns true if element has child elements" do
-    child = REXML::Element.new("child")
-    @e << child
-    @e.has_elements?.should be_true
-  end
-
-  it "returns false if element doesn't have child elements" do
-    @e.has_elements?.should be_false
-  end
-end
diff --git a/spec/ruby/library/rexml/element/has_text_spec.rb b/spec/ruby/library/rexml/element/has_text_spec.rb
deleted file mode 100644
index e9d5a176cb..0000000000
--- a/spec/ruby/library/rexml/element/has_text_spec.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#has_text?" do
-
-  it "returns true if element has a Text child" do
-    e = REXML::Element.new("Person")
-    e.text = "My text"
-    e.has_text?.should be_true
-  end
-
-  it "returns false if it has no Text childs" do
-    e = REXML::Element.new("Person")
-    e.has_text?.should be_false
-  end
-end
diff --git a/spec/ruby/library/rexml/element/inspect_spec.rb b/spec/ruby/library/rexml/element/inspect_spec.rb
deleted file mode 100644
index f45edd0b1f..0000000000
--- a/spec/ruby/library/rexml/element/inspect_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#inspect" do
-
-  before :each do
-    @name = REXML::Element.new "name"
-  end
-
-  it "returns the node as a string" do
-    @name.inspect.should == "<name/>"
-  end
-
-  it "inserts '...' if the node has children" do
-    e = REXML::Element.new "last_name"
-    @name << e
-    @name.inspect.should == "<name> ... </>"
-    # This might make more sense but differs from MRI's default behavior
-    # @name.inspect.should == "<name> ... </name>"
-  end
-
-  it "inserts the attributes in the string" do
-    @name.add_attribute "language"
-    @name.attributes["language"] = "english"
-    @name.inspect.should == "<name language='english'/>"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/instructions_spec.rb b/spec/ruby/library/rexml/element/instructions_spec.rb
deleted file mode 100644
index aa2d192e7c..0000000000
--- a/spec/ruby/library/rexml/element/instructions_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#instructions" do
-  before :each do
-    @elem = REXML::Element.new("root")
-  end
-  it "returns the Instruction children nodes" do
-    inst = REXML::Instruction.new("xml-stylesheet", "href='headlines.css'")
-    @elem << inst
-    @elem.instructions.first.should == inst
-  end
-
-  it "returns an empty array if it has no Instruction children" do
-    @elem.instructions.should be_empty
-  end
-
-  it "freezes the returned array" do
-    @elem.instructions.frozen?.should be_true
-  end
-end
diff --git a/spec/ruby/library/rexml/element/namespace_spec.rb b/spec/ruby/library/rexml/element/namespace_spec.rb
deleted file mode 100644
index 89662f3599..0000000000
--- a/spec/ruby/library/rexml/element/namespace_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#namespace" do
-  before :each do
-    @doc = REXML::Document.new("<a xmlns='1' xmlns:y='2'><b/><c xmlns:z='3'/></a>")
-    @elem = @doc.elements["//b"]
-  end
-
-  it "returns the default namespace" do
-    @elem.namespace.should == "1"
-  end
-
-  it "accepts a namespace prefix" do
-    @elem.namespace("y").should == "2"
-    @doc.elements["//c"].namespace("z").should == "3"
-  end
-
-  it "returns an empty String if default namespace is not defined" do
-    e = REXML::Document.new("<a/>")
-    e.root.namespace.should be_empty
-  end
-
-  it "returns nil if namespace is not defined" do
-    @elem.namespace("z").should be_nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/namespaces_spec.rb b/spec/ruby/library/rexml/element/namespaces_spec.rb
deleted file mode 100644
index a84c1d1dab..0000000000
--- a/spec/ruby/library/rexml/element/namespaces_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#namespaces" do
-  before :each do
-    doc = REXML::Document.new("<a xmlns='1' xmlns:y='2'><b/><c xmlns:z='3'/></a>")
-    @elem = doc.elements["//c"]
-  end
-
-  it "returns a hash of the namespaces" do
-    ns = {"y"=>"2", "z"=>"3", "xmlns"=>"1"}
-    @elem.namespaces.keys.sort.should == ns.keys.sort
-    @elem.namespaces.values.sort.should == ns.values.sort
-  end
-
-  it "returns an empty hash if no namespaces exist" do
-    e = REXML::Element.new "element"
-    e.namespaces.kind_of?(Hash).should == true
-    e.namespaces.should be_empty
-  end
-
-  it "uses namespace prefixes as keys" do
-    prefixes = ["y", "z", "xmlns"]
-    @elem.namespaces.keys.sort.should == prefixes.sort
-  end
-
-  it "uses namespace values as the hash values" do
-    values = ["2", "3", "1"]
-    @elem.namespaces.values.sort.should == values.sort
-  end
-
-end
diff --git a/spec/ruby/library/rexml/element/new_spec.rb b/spec/ruby/library/rexml/element/new_spec.rb
deleted file mode 100644
index 4ffdf4dabe..0000000000
--- a/spec/ruby/library/rexml/element/new_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#new" do
-
-  it "creates element from tag name" do
-    REXML::Element.new("foo").name.should == "foo"
-  end
-
-  it "creates element with default attributes" do
-    e = REXML::Element.new
-    e.name.should == REXML::Element::UNDEFINED
-    e.context.should == nil
-    e.parent.should == nil
-  end
-
-  it "creates element from another element" do
-    e = REXML::Element.new "foo"
-    f = REXML::Element.new e
-    e.name.should == f.name
-    e.context.should == f.context
-    e.parent.should == f.parent
-  end
-
-  it "takes parent as second argument" do
-    parent = REXML::Element.new "foo"
-    child = REXML::Element.new "bar", parent
-    child.parent.should == parent
-  end
-
-  it "takes context as third argument" do
-    context = {"some_key" => "some_value"}
-    REXML::Element.new("foo", nil, context).context.should == context
-  end
-end
diff --git a/spec/ruby/library/rexml/element/next_element_spec.rb b/spec/ruby/library/rexml/element/next_element_spec.rb
deleted file mode 100644
index 5b6d6cad9b..0000000000
--- a/spec/ruby/library/rexml/element/next_element_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#next_element" do
-  before :each do
-    @a = REXML::Element.new "a"
-    @b = REXML::Element.new "b"
-    @c = REXML::Element.new "c"
-    @a.root << @b
-    @a.root << @c
-  end
-  it "returns next existing element" do
-    @a.elements["b"].next_element.should == @c
-  end
-
-  it "returns nil on last element" do
-    @a.elements["c"].next_element.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/node_type_spec.rb b/spec/ruby/library/rexml/element/node_type_spec.rb
deleted file mode 100644
index bcab9e126d..0000000000
--- a/spec/ruby/library/rexml/element/node_type_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#node_type" do
-  it "returns :element" do
-    REXML::Element.new("MyElem").node_type.should == :element
-  end
-end
diff --git a/spec/ruby/library/rexml/element/prefixes_spec.rb b/spec/ruby/library/rexml/element/prefixes_spec.rb
deleted file mode 100644
index b6edf9a847..0000000000
--- a/spec/ruby/library/rexml/element/prefixes_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#prefixes" do
-  before :each do
-    doc = REXML::Document.new("<a xmlns='1' xmlns:y='2'><b/><c xmlns:z='3'/></a>")
-    @elem = doc.elements["//c"]
-  end
-
-  it "returns an array of the prefixes of the namespaces" do
-    @elem.prefixes.should == ["y", "z"]
-  end
-
-  it "does not include the default namespace" do
-    @elem.prefixes.include?("xmlns").should == false
-  end
-
-  it "returns an empty array if no namespace was defined" do
-    doc = REXML::Document.new "<root><something/></root>"
-    root = doc.elements["//root"]
-    root.prefixes.should == []
-  end
-end
diff --git a/spec/ruby/library/rexml/element/previous_element_spec.rb b/spec/ruby/library/rexml/element/previous_element_spec.rb
deleted file mode 100644
index 2fe79d955f..0000000000
--- a/spec/ruby/library/rexml/element/previous_element_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#previous_element" do
-  before :each do
-    @a = REXML::Element.new "a"
-    @b = REXML::Element.new "b"
-    @c = REXML::Element.new "c"
-    @a.root << @b
-    @a.root << @c
-  end
-
-  it "returns previous element" do
-    @a.elements["c"].previous_element.should == @b
-  end
-
-  it "returns nil on first element" do
-    @a.elements["b"].previous_element.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/raw_spec.rb b/spec/ruby/library/rexml/element/raw_spec.rb
deleted file mode 100644
index 404ccce5f4..0000000000
--- a/spec/ruby/library/rexml/element/raw_spec.rb
+++ /dev/null
@@ -1,24 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#raw" do
-  it "returns true if raw mode is set to all" do
-    REXML::Element.new("MyElem", nil, {raw: :all}).raw.should == true
-  end
-
-  it "returns true if raw mode is set to expanded_name" do
-    REXML::Element.new("MyElem", nil, {raw: "MyElem"}).raw.should == true
-  end
-
-  it "returns false if raw mode is not set" do
-    REXML::Element.new("MyElem", nil, {raw: ""}).raw.should == false
-  end
-
-  it "returns false if raw is not :all or expanded_name" do
-    REXML::Element.new("MyElem", nil, {raw: "Something"}).raw.should == false
-  end
-
-  it "returns nil if context is not set" do
-    REXML::Element.new("MyElem").raw.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/element/root_spec.rb b/spec/ruby/library/rexml/element/root_spec.rb
deleted file mode 100644
index 1e0669033e..0000000000
--- a/spec/ruby/library/rexml/element/root_spec.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Element#root" do
-  before :each do
-    @doc  = REXML::Document.new
-    @root = REXML::Element.new "root"
-    @node = REXML::Element.new "node"
-    @doc << @root << @node
-  end
-
-  it "returns first child on documents" do
-    @doc.root.should == @root
-  end
-
-  it "returns self on root nodes" do
-    @root.root.should == @root
-  end
-
-  it "returns parent's root on child nodes" do
-    @node.root.should == @root
-  end
-
-  it "returns self on standalone nodes" do
-    e = REXML::Element.new "Elem"         # Note that it doesn't have a parent node
-    e.root.should == e
-  end
-end
diff --git a/spec/ruby/library/rexml/element/text_spec.rb b/spec/ruby/library/rexml/element/text_spec.rb
deleted file mode 100644
index 7c290c4cda..0000000000
--- a/spec/ruby/library/rexml/element/text_spec.rb
+++ /dev/null
@@ -1,46 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#text" do
-  before :each do
-    @e = REXML::Element.new "name"
-    @e.text = "John"
-  end
-
-  it "returns the text node of element" do
-    @e.text.should == "John"
-  end
-
-  it "returns the text node value" do
-    t = REXML::Text.new "Joe"
-    @e.text = t
-    @e.text.should == "Joe"
-    @e.text.should_not == t
-  end
-
-  it "returns nil if no text is attached" do
-    elem = REXML::Element.new "name"
-    elem.text.should == nil
-  end
-end
-
-describe "REXML::Element#text=" do
-  before :each do
-    @e = REXML::Element.new "name"
-    @e.text = "John"
-  end
-
-  it "sets the text node" do
-    @e.to_s.should == "<name>John</name>"
-  end
-
-  it "replaces existing text" do
-    @e.text = "Joe"
-    @e.to_s.should == "<name>Joe</name>"
-  end
-
-  it "receives nil as an argument" do
-    @e.text = nil
-    @e.to_s.should == "<name/>"
-  end
-end
diff --git a/spec/ruby/library/rexml/element/texts_spec.rb b/spec/ruby/library/rexml/element/texts_spec.rb
deleted file mode 100644
index 7975833c89..0000000000
--- a/spec/ruby/library/rexml/element/texts_spec.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#texts" do
-
-  it "returns an array of the Text children" do
-    e = REXML::Element.new("root")
-    e.add_text "First"
-    e.add_text "Second"
-    e.texts.should == ["FirstSecond"]
-  end
-
-  it "returns an empty array if it has no Text children" do
-    REXML::Element.new("root").texts.should == []
-  end
-end
diff --git a/spec/ruby/library/rexml/element/whitespace_spec.rb b/spec/ruby/library/rexml/element/whitespace_spec.rb
deleted file mode 100644
index dc785ae5ce..0000000000
--- a/spec/ruby/library/rexml/element/whitespace_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe "REXML::Element#whitespace" do
-  it "returns true if whitespace is respected in the element" do
-    e = REXML::Element.new("root")
-    e.whitespace.should be_true
-
-    e = REXML::Element.new("root", nil, respect_whitespace: :all)
-    e.whitespace.should be_true
-
-    e = REXML::Element.new("root", nil, respect_whitespace: ["root"])
-    e.whitespace.should be_true
-  end
-
-  it "returns false if whitespace is ignored inside element" do
-    e = REXML::Element.new("root", nil, compress_whitespace: :all)
-    e.whitespace.should be_false
-
-    e = REXML::Element.new("root", nil, compress_whitespace: ["root"])
-    e.whitespace.should be_false
-  end
-end
diff --git a/spec/ruby/library/rexml/node/each_recursive_spec.rb b/spec/ruby/library/rexml/node/each_recursive_spec.rb
deleted file mode 100644
index dd4aa9a2f2..0000000000
--- a/spec/ruby/library/rexml/node/each_recursive_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#each_recursive" do
-  before :each do
-    @doc = REXML::Document.new
-    @doc << REXML::XMLDecl.new
-    @root = REXML::Element.new "root"
-    @child1 = REXML::Element.new "child1"
-    @child2 = REXML::Element.new "child2"
-    @root << @child1
-    @root << @child2
-    @doc << @root
-  end
-
-  it "visits all subnodes of self" do
-    nodes = []
-    @doc.each_recursive { |node| nodes << node}
-    nodes.should == [@root, @child1, @child2]
-  end
-end
diff --git a/spec/ruby/library/rexml/node/find_first_recursive_spec.rb b/spec/ruby/library/rexml/node/find_first_recursive_spec.rb
deleted file mode 100644
index ba46f2ca35..0000000000
--- a/spec/ruby/library/rexml/node/find_first_recursive_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#find_first_recursive" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @node1 = REXML::Element.new("node")
-    @node2 = REXML::Element.new("another node")
-    @subnode = REXML::Element.new("another node")
-    @node1 << @subnode
-    @e << @node1
-    @e << @node2
-  end
-
-  it "finds the first element that matches block" do
-    found = @e.find_first_recursive { |n| n.to_s == "<node><another node/></node>"}
-    found.should == @node1
-  end
-
-  it "visits the nodes in preorder" do
-    found = @e.find_first_recursive { |n| n.to_s == "<another node/>"}
-    found.should == @subnode
-    found.should_not == @node2
-  end
-end
diff --git a/spec/ruby/library/rexml/node/index_in_parent_spec.rb b/spec/ruby/library/rexml/node/index_in_parent_spec.rb
deleted file mode 100644
index 092851e3e7..0000000000
--- a/spec/ruby/library/rexml/node/index_in_parent_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#index_in_parent" do
-  it "returns the index (starting from 1) of self in parent" do
-    e = REXML::Element.new("root")
-    node1 = REXML::Element.new("node")
-    node2 = REXML::Element.new("another node")
-    e << node1
-    e << node2
-
-    node1.index_in_parent.should == 1
-    node2.index_in_parent.should == 2
-  end
-end
diff --git a/spec/ruby/library/rexml/node/next_sibling_node_spec.rb b/spec/ruby/library/rexml/node/next_sibling_node_spec.rb
deleted file mode 100644
index 2e8601627d..0000000000
--- a/spec/ruby/library/rexml/node/next_sibling_node_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#next_sibling_node" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @node1 = REXML::Element.new("node")
-    @node2 = REXML::Element.new("another node")
-    @e << @node1
-    @e << @node2
-  end
-
-  it "returns the next child node in parent" do
-    @node1.next_sibling_node.should == @node2
-  end
-
-  it "returns nil if there are no more child nodes next" do
-    @node2.next_sibling_node.should == nil
-    @e.next_sibling_node.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/node/parent_spec.rb b/spec/ruby/library/rexml/node/parent_spec.rb
deleted file mode 100644
index d88ba69657..0000000000
--- a/spec/ruby/library/rexml/node/parent_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#parent?" do
-  it "returns true for Elements" do
-    e = REXML::Element.new("foo")
-    e.parent?.should == true
-  end
-
-  it "returns true for Documents" do
-    e = REXML::Document.new
-    e.parent?.should == true
-  end
-
-  # This includes attributes, CDatas and declarations.
-  it "returns false for Texts" do
-    e = REXML::Text.new("foo")
-    e.parent?.should == false
-  end
-end
diff --git a/spec/ruby/library/rexml/node/previous_sibling_node_spec.rb b/spec/ruby/library/rexml/node/previous_sibling_node_spec.rb
deleted file mode 100644
index 8b96f1565a..0000000000
--- a/spec/ruby/library/rexml/node/previous_sibling_node_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Node#previous_sibling_node" do
-  before :each do
-    @e = REXML::Element.new("root")
-    @node1 = REXML::Element.new("node")
-    @node2 = REXML::Element.new("another node")
-    @e << @node1
-    @e << @node2
-  end
-
-  it "returns the previous child node in parent" do
-    @node2.previous_sibling_node.should == @node1
-  end
-
-  it "returns nil if there are no more child nodes before" do
-    @node1.previous_sibling_node.should == nil
-    @e.previous_sibling_node.should == nil
-  end
-end
diff --git a/spec/ruby/library/rexml/shared/each_element.rb b/spec/ruby/library/rexml/shared/each_element.rb
deleted file mode 100644
index 2e0871161d..0000000000
--- a/spec/ruby/library/rexml/shared/each_element.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe :rexml_each_element, shared: true do
-  before :each do
-    @e = REXML::Element.new "root"
-    s1 = REXML::Element.new "node1"
-    s2 = REXML::Element.new "node2"
-    s3 = REXML::Element.new "node3"
-    s4 = REXML::Element.new "sub_node"
-    @e << s1
-    @e << s2
-    @e << s3
-    @e << s4
-  end
-
-  it "iterates through element" do
-    str = ""
-      @e.send(@method) { |elem| str << elem.name << " " }
-    str.should == "node1 node2 node3 sub_node "
-  end
-
-  it "iterates through element filtering with XPath" do
-    str = ""
-     @e.send(@method, "/*"){ |e| str << e.name << " "}
-     str.should == "node1 node2 node3 sub_node "
-  end
-end
-
-describe "REXML::Element#each_element" do
- it_behaves_like :rexml_each_element, :each_element
-end
-
-describe "REXML::Elements#each" do
-  it_behaves_like :rexml_each_element, :each
-end
diff --git a/spec/ruby/library/rexml/shared/elements_to_a.rb b/spec/ruby/library/rexml/shared/elements_to_a.rb
deleted file mode 100644
index 388250d8b3..0000000000
--- a/spec/ruby/library/rexml/shared/elements_to_a.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require 'rexml/document'
-require_relative '../../../spec_helper'
-
-describe :rexml_elements_to_a, shared: true do
-  before :each do
-    @e = REXML::Element.new "root"
-    @first = REXML::Element.new("FirstChild")
-    @second = REXML::Element.new("SecondChild")
-    @e << @first
-    @e << @second
-  end
-
-  it "returns elements that match xpath" do
-    @e.elements.send(@method, "FirstChild").first.should == @first
-  end
-
-  # According to the docs REXML::Element#get_elements is an alias for
-  # REXML::Elements.to_a. Implementation wise there's a difference, get_elements
-  # always needs the first param (even if it's nil).
-  # A patch was submitted:
-  # http://rubyforge.org/tracker/index.php?func=detail&aid=19354&group_id=426&atid=1698
-  it "returns all childs if xpath is nil" do
-    @e.elements.send(@method).should == [@first, @second]
-  end
-
-end
-
-describe "REXML::REXML::Elements#to_a" do
-  it_behaves_like :rexml_elements_to_a, :to_a
-end
-
-describe "REXML::REXML::Element#get_elements" do
-  it_behaves_like :rexml_elements_to_a, :get_elements
-end
diff --git a/spec/ruby/library/rexml/text/append_spec.rb b/spec/ruby/library/rexml/text/append_spec.rb
deleted file mode 100644
index de281fb0b0..0000000000
--- a/spec/ruby/library/rexml/text/append_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#<<" do
-  it "appends a string to this text node" do
-    text = REXML::Text.new("foo")
-    text << "bar"
-    text.should == "foobar"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/clone_spec.rb b/spec/ruby/library/rexml/text/clone_spec.rb
deleted file mode 100644
index 8031e140c7..0000000000
--- a/spec/ruby/library/rexml/text/clone_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#clone" do
-  it "creates a copy of this node" do
-    text = REXML::Text.new("foo")
-    text.clone.should == "foo"
-    text.clone.should == text
-  end
-end
diff --git a/spec/ruby/library/rexml/text/comparison_spec.rb b/spec/ruby/library/rexml/text/comparison_spec.rb
deleted file mode 100644
index 8bc5d66a03..0000000000
--- a/spec/ruby/library/rexml/text/comparison_spec.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#<=>" do
-  before :each do
-    @first = REXML::Text.new("abc")
-    @last = REXML::Text.new("def")
-  end
-
-  it "returns -1 if lvalue is less than rvalue" do
-    val = @first <=> @last
-    val.should == -1
-  end
-
-  it "returns -1 if lvalue is greater than rvalue" do
-    val = @last <=> @first
-    val.should == 1
-  end
-
-  it "returns 0 if both values are equal" do
-    tmp = REXML::Text.new("tmp")
-    val = tmp <=> tmp
-    val.should == 0
-  end
-end
diff --git a/spec/ruby/library/rexml/text/empty_spec.rb b/spec/ruby/library/rexml/text/empty_spec.rb
deleted file mode 100644
index d0b66b7a2a..0000000000
--- a/spec/ruby/library/rexml/text/empty_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#empty?" do
-  it "returns true if the text is empty" do
-    REXML::Text.new("").empty?.should == true
-  end
-
-  it "returns false if the text is not empty" do
-    REXML::Text.new("some_text").empty?.should == false
-  end
-end
diff --git a/spec/ruby/library/rexml/text/indent_text_spec.rb b/spec/ruby/library/rexml/text/indent_text_spec.rb
deleted file mode 100644
index 1b0ee5ab16..0000000000
--- a/spec/ruby/library/rexml/text/indent_text_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#indent_text" do
-  before :each do
-    @t = REXML::Text.new("")
-  end
-  it "indents a string with default parameters" do
-    @t.indent_text("foo").should == "\tfoo"
-  end
-
-  it "accepts a custom indentation level as second argument" do
-    @t.indent_text("foo", 2, "\t", true).should == "\t\tfoo"
-  end
-
-  it "accepts a custom separator as third argument" do
-    @t.indent_text("foo", 1, "\n", true).should == "\nfoo"
-  end
-
-  it "accepts a fourth parameter to skip the first line" do
-    @t.indent_text("foo", 1, "\t", false).should == "foo"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/inspect_spec.rb b/spec/ruby/library/rexml/text/inspect_spec.rb
deleted file mode 100644
index 0d66088a64..0000000000
--- a/spec/ruby/library/rexml/text/inspect_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#inspect" do
-  it "inspects the string attribute as a string" do
-    REXML::Text.new("a text").inspect.should == "a text".inspect
-  end
-end
diff --git a/spec/ruby/library/rexml/text/new_spec.rb b/spec/ruby/library/rexml/text/new_spec.rb
deleted file mode 100644
index 3c081dec30..0000000000
--- a/spec/ruby/library/rexml/text/new_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text.new" do
-
-  it "creates a Text child node with no parent" do
-    t = REXML::Text.new("test")
-    t.should be_kind_of(REXML::Child)
-    t.should == "test"
-    t.parent.should == nil
-  end
-
-  it "respects whitespace if second argument is true" do
-    t = REXML::Text.new("testing   whitespace", true)
-    t.should == "testing   whitespace"
-    t = REXML::Text.new("   ", true)
-    t.should == "   "
-  end
-
-  it "receives a parent as third argument" do
-    e = REXML::Element.new("root")
-    t = REXML::Text.new("test", false, e)
-    t.parent.should == e
-    e.to_s.should == "<root>test</root>"
-  end
-
-  it "expects escaped text if raw is true" do
-    t = REXML::Text.new("&lt;&amp;&gt;", false, nil, true)
-    t.should == "&lt;&amp;&gt;"
-
-    ->{ REXML::Text.new("<&>", false, nil, true)}.should raise_error(Exception)
-  end
-
-  it "uses raw value of the parent if raw is nil" do
-    e1 = REXML::Element.new("root", nil, { raw: :all})
-    -> {REXML::Text.new("<&>", false, e1)}.should raise_error(Exception)
-
-    e2 = REXML::Element.new("root", nil, { raw: []})
-    e2.raw.should be_false
-    t1 = REXML::Text.new("<&>", false, e2)
-    t1.should == "&lt;&amp;&gt;"
-  end
-
-  it "escapes the values if raw is false" do
-    t = REXML::Text.new("<&>", false, nil, false)
-    t.should == "&lt;&amp;&gt;"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/node_type_spec.rb b/spec/ruby/library/rexml/text/node_type_spec.rb
deleted file mode 100644
index 1c25a74dad..0000000000
--- a/spec/ruby/library/rexml/text/node_type_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#node_type" do
-  it "returns :text" do
-    REXML::Text.new("test").node_type.should == :text
-  end
-end
diff --git a/spec/ruby/library/rexml/text/normalize_spec.rb b/spec/ruby/library/rexml/text/normalize_spec.rb
deleted file mode 100644
index ce3b2b3b5f..0000000000
--- a/spec/ruby/library/rexml/text/normalize_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text.normalize" do
-  it "escapes a string with <, >, &, ' and \" " do
-    REXML::Text.normalize("< > & \" '").should == "&lt; &gt; &amp; &quot; &apos;"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/read_with_substitution_spec.rb b/spec/ruby/library/rexml/text/read_with_substitution_spec.rb
deleted file mode 100644
index 83b42f6d6b..0000000000
--- a/spec/ruby/library/rexml/text/read_with_substitution_spec.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text.read_with_substitution" do
-  it "reads a text and escapes entities" do
-    REXML::Text.read_with_substitution("&lt; &gt; &amp; &quot; &apos;").should == "< > & \" '"
-  end
-
-  it "accepts an regex for invalid expressions and raises an error if text matches" do
-    -> {REXML::Text.read_with_substitution("this is illegal", /illegal/)}.should raise_error(Exception)
-  end
-end
diff --git a/spec/ruby/library/rexml/text/to_s_spec.rb b/spec/ruby/library/rexml/text/to_s_spec.rb
deleted file mode 100644
index 14d7399a60..0000000000
--- a/spec/ruby/library/rexml/text/to_s_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#to_s" do
-  it "returns the string of this Text node" do
-    u = REXML::Text.new("sean russell", false, nil, true)
-    u.to_s.should == "sean russell"
-
-    t = REXML::Text.new("some test text")
-    t.to_s.should == "some test text"
-  end
-
-  it "escapes the text" do
-    t = REXML::Text.new("& < >")
-    t.to_s.should == "&amp; &lt; &gt;"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/unnormalize_spec.rb b/spec/ruby/library/rexml/text/unnormalize_spec.rb
deleted file mode 100644
index 3072809c13..0000000000
--- a/spec/ruby/library/rexml/text/unnormalize_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text.unnormalize" do
-  it "unescapes a string with the values defined in SETUTITSBUS" do
-    REXML::Text.unnormalize("&lt; &gt; &amp; &quot; &apos;").should == "< > & \" '"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/value_spec.rb b/spec/ruby/library/rexml/text/value_spec.rb
deleted file mode 100644
index b0545b3cbd..0000000000
--- a/spec/ruby/library/rexml/text/value_spec.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#value" do
-  it "returns the text value of this node" do
-    REXML::Text.new("test").value.should == "test"
-  end
-
-  it "does not escape entities" do
-    REXML::Text.new("& \"").value.should == "& \""
-  end
-
-  it "follows the respect_whitespace attribute" do
-    REXML::Text.new("test     bar", false).value.should == "test bar"
-    REXML::Text.new("test     bar", true).value.should == "test     bar"
-  end
-
-  it "ignores the raw attribute" do
-    REXML::Text.new("sean russell", false, nil, true).value.should == "sean russell"
-  end
-end
-
-describe "REXML::Text#value=" do
-  before :each do
-    @t = REXML::Text.new("new")
-  end
-
-  it "sets the text of the node" do
-    @t.value = "another text"
-    @t.to_s.should == "another text"
-  end
-
-  it "escapes entities" do
-    @t.value = "<a>"
-    @t.to_s.should == "&lt;a&gt;"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/wrap_spec.rb b/spec/ruby/library/rexml/text/wrap_spec.rb
deleted file mode 100644
index 0b60fd4151..0000000000
--- a/spec/ruby/library/rexml/text/wrap_spec.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#wrap" do
-  before :each do
-    @t = REXML::Text.new("abc def")
-  end
-
-  it "wraps the text at width" do
-    @t.wrap("abc def", 3, false).should == "abc\ndef"
-  end
-
-  it "returns the string if width is greater than the size of the string" do
-    @t.wrap("abc def", 10, false).should == "abc def"
-  end
-
-  it "takes a newline at the beginning option as the third parameter" do
-    @t.wrap("abc def", 3, true).should == "\nabc\ndef"
-  end
-end
diff --git a/spec/ruby/library/rexml/text/write_with_substitution_spec.rb b/spec/ruby/library/rexml/text/write_with_substitution_spec.rb
deleted file mode 100644
index ee79489d86..0000000000
--- a/spec/ruby/library/rexml/text/write_with_substitution_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require 'rexml/document'
-
-describe "REXML::Text#write_with_substitution" do
-  before :each do
-    @t = REXML::Text.new("test")
-    @f = tmp("rexml_spec")
-    @file = File.open(@f, "w+")
-  end
-
-  after :each do
-    @file.close
-    rm_r @f
-  end
-
-  it "writes out the input to a String" do
-    s = ""
-    @t.write_with_substitution(s, "some text")
-    s.should == "some text"
-  end
-
-  it "writes out the input to an IO" do
-    @t.write_with_substitution(@file, "some text")
-    @file.rewind
-    @file.gets.should == "some text"
-  end
-
-  it "escapes characters" do
-    @t.write_with_substitution(@file, "& < >")
-    @file.rewind
-    @file.gets.should == "&amp; &lt; &gt;"
-  end
-end
diff --git a/spec/ruby/library/ripper/lex_spec.rb b/spec/ruby/library/ripper/lex_spec.rb
new file mode 100644
index 0000000000..97cfb06904
--- /dev/null
+++ b/spec/ruby/library/ripper/lex_spec.rb
@@ -0,0 +1,23 @@
+require_relative '../../spec_helper'
+require 'ripper'
+
+describe "Ripper.lex" do
+  it "lexes a simple method declaration" do
+    expected = [
+        [[1, 0], :on_kw, "def", 'FNAME'],
+        [[1, 3], :on_sp, " ", 'FNAME'],
+        [[1, 4], :on_ident, "m", 'ENDFN'],
+        [[1, 5], :on_lparen, "(", 'BEG|LABEL'],
+        [[1, 6], :on_ident, "a", 'ARG'],
+        [[1, 7], :on_rparen, ")", 'ENDFN'],
+        [[1, 8], :on_sp, " ", 'BEG'],
+        [[1, 9], :on_kw, "nil", 'END'],
+        [[1, 12], :on_sp, " ", 'END'],
+        [[1, 13], :on_kw, "end", 'END']
+    ]
+    lexed = Ripper.lex("def m(a) nil end")
+    lexed.map { |e|
+      e[0...-1] + [e[-1].to_s.split('|').map { |s| s.sub(/^EXPR_/, '') }.join('|')]
+    }.should == expected
+  end
+end
diff --git a/spec/ruby/library/ripper/sexp_spec.rb b/spec/ruby/library/ripper/sexp_spec.rb
new file mode 100644
index 0000000000..6c69624c65
--- /dev/null
+++ b/spec/ruby/library/ripper/sexp_spec.rb
@@ -0,0 +1,13 @@
+require_relative '../../spec_helper'
+require 'ripper'
+
+describe "Ripper.sexp" do
+  it "returns an s-expression for a method declaration" do
+    expected = [:program,
+                [[:def,
+                  [:@ident, "hello", [1, 4]],
+                  [:params, nil, nil, nil, nil, nil, nil, nil],
+                  [:bodystmt, [[:@int, "42", [1, 11]]], nil, nil, nil]]]]
+    Ripper.sexp("def hello; 42; end").should == expected
+  end
+end
diff --git a/spec/ruby/library/rubygems/gem/bin_path_spec.rb b/spec/ruby/library/rubygems/gem/bin_path_spec.rb
new file mode 100644
index 0000000000..0b8c4db08b
--- /dev/null
+++ b/spec/ruby/library/rubygems/gem/bin_path_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../../spec_helper'
+require 'rubygems'
+
+describe "Gem.bin_path" do
+  before :each do
+    @bundle_gemfile = ENV['BUNDLE_GEMFILE']
+    ENV['BUNDLE_GEMFILE'] = tmp("no-gemfile")
+  end
+
+  after :each do
+    ENV['BUNDLE_GEMFILE'] = @bundle_gemfile
+  end
+
+  platform_is_not :windows do
+    it "finds executables of default gems, which are the only files shipped for default gems" do
+      # For instance, Gem.bin_path("bundler", "bundle") is used by rails new
+
+      if Gem.respond_to? :default_specifications_dir
+        default_specifications_dir = Gem.default_specifications_dir
+      else
+        default_specifications_dir = Gem::Specification.default_specifications_dir
+      end
+
+      skip "Could not find the default gemspecs" unless Dir.exist?(default_specifications_dir)
+      skip "default_specifications_dir mismatch with GEM_HOME" if ENV["GEM_HOME"] && !default_specifications_dir.start_with?(ENV['GEM_HOME'])
+
+      Gem::Specification.each_spec([default_specifications_dir]) do |spec|
+        spec.executables.each do |exe|
+          path = Gem.bin_path(spec.name, exe)
+          File.should.exist?(path)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/rubygems/gem/load_path_insert_index_spec.rb b/spec/ruby/library/rubygems/gem/load_path_insert_index_spec.rb
new file mode 100644
index 0000000000..9b37eaa43c
--- /dev/null
+++ b/spec/ruby/library/rubygems/gem/load_path_insert_index_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../../spec_helper'
+require 'rubygems'
+
+describe "Gem.load_path_insert_index" do
+  guard -> { RbConfig::TOPDIR } do
+    it "is set for an installed Ruby" do
+      Gem.load_path_insert_index.should be_kind_of Integer
+    end
+  end
+end
diff --git a/spec/ruby/library/scanf/io/block_scanf_spec.rb b/spec/ruby/library/scanf/io/block_scanf_spec.rb
deleted file mode 100644
index 2c1e242cf6..0000000000
--- a/spec/ruby/library/scanf/io/block_scanf_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/block_scanf'
-require 'scanf'
-
-describe "IO#block_scanf" do
-  it_behaves_like :scanf_io_block_scanf, :block_scanf
-end
diff --git a/spec/ruby/library/scanf/io/fixtures/date.txt b/spec/ruby/library/scanf/io/fixtures/date.txt
deleted file mode 100644
index a1bd635c0c..0000000000
--- a/spec/ruby/library/scanf/io/fixtures/date.txt
+++ /dev/null
@@ -1,4 +0,0 @@
-Beethoven  1770
-Bach       1685
-Handel     1685
-
diff --git a/spec/ruby/library/scanf/io/fixtures/helloworld.txt b/spec/ruby/library/scanf/io/fixtures/helloworld.txt
deleted file mode 100644
index 3b18e512db..0000000000
--- a/spec/ruby/library/scanf/io/fixtures/helloworld.txt
+++ /dev/null
@@ -1 +0,0 @@
-hello world
diff --git a/spec/ruby/library/scanf/io/scanf_spec.rb b/spec/ruby/library/scanf/io/scanf_spec.rb
deleted file mode 100644
index 94e999335e..0000000000
--- a/spec/ruby/library/scanf/io/scanf_spec.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/block_scanf'
-require 'scanf'
-
-describe "IO#scanf" do
-  before :each do
-    @hw = File.open(File.dirname(__FILE__) + '/fixtures/helloworld.txt', 'r')
-    @data = File.open(File.dirname(__FILE__) + '/fixtures/date.txt', 'r')
-  end
-
-  after :each do
-    @hw.close unless @hw.closed?
-    @data.close unless @data.closed?
-  end
-
-  it "returns an array containing the input converted in the specified type" do
-    @hw.scanf("%s%s").should == ["hello", "world"]
-    @data.scanf("%s%d").should == ["Beethoven", 1770]
-  end
-
-  it "returns an array containing the input converted in the specified type with given maximum field width" do
-    @hw.scanf("%2s").should == ["he"]
-    @data.scanf("%2c").should == ["Be"]
-  end
-
-  it "returns an empty array when a wrong specifier is passed" do
-    @hw.scanf("%a").should == []
-    @hw.scanf("%1").should == []
-    @data.scanf("abc").should == []
-  end
-end
-
-describe "IO#scanf with block" do
-  it_behaves_like :scanf_io_block_scanf, :scanf
-end
diff --git a/spec/ruby/library/scanf/io/shared/block_scanf.rb b/spec/ruby/library/scanf/io/shared/block_scanf.rb
deleted file mode 100644
index 8c5bffb93b..0000000000
--- a/spec/ruby/library/scanf/io/shared/block_scanf.rb
+++ /dev/null
@@ -1,28 +0,0 @@
-require 'scanf'
-
-describe :scanf_io_block_scanf, shared: true do
-  before :each do
-    @data= File.open(File.dirname(__FILE__) + '/../fixtures/date.txt', 'r')
-  end
-
-  after :each do
-    @data.close unless @data.closed?
-  end
-
-  it "passes each match to the block as an array" do
-    res = @data.send(@method, "%s%d") { |name, year| "#{name} was born in #{year}." }
-    res.should == ["Beethoven was born in 1770.", "Bach was born in 1685.", "Handel was born in 1685."]
-  end
-
-  it "keeps scanning the input and cycling back to the beginning of the input string" do
-    a = []
-    @data.send(@method, "%s"){|w| a << w}
-    a.should == [["Beethoven"], ["1770"], ["Bach"], ["1685"], ["Handel"], ["1685"]]
-  end
-
-  it "returns an empty array when a wrong specifier is passed" do
-    a = []
-    @data.send(@method, "%z"){|w| a << w}
-    a.empty?.should be_true
-  end
-end
diff --git a/spec/ruby/library/scanf/string/block_scanf_spec.rb b/spec/ruby/library/scanf/string/block_scanf_spec.rb
deleted file mode 100644
index d5c42cb395..0000000000
--- a/spec/ruby/library/scanf/string/block_scanf_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/block_scanf'
-require 'scanf'
-
-describe "String#block_scanf" do
-  it_behaves_like :scanf_string_block_scanf, :block_scanf
-end
diff --git a/spec/ruby/library/scanf/string/scanf_spec.rb b/spec/ruby/library/scanf/string/scanf_spec.rb
deleted file mode 100644
index fbe2590476..0000000000
--- a/spec/ruby/library/scanf/string/scanf_spec.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/block_scanf'
-require 'scanf'
-
-describe "String#scanf" do
-  it "returns an array containing the input converted in the specified type" do
-    "hello world".scanf("%s").should == ["hello"]
-    "hello world".scanf("%s%d").should == ["hello"]
-    "hello world".scanf("%s%c").should == ["hello", " "]
-    "hello world".scanf("%c%s").should == ["h", "ello"]
-    "hello world".scanf("%s%s").should == ["hello", "world"]
-    "hello world".scanf("%c").should == ["h"]
-    "123".scanf("%s").should == ["123"]
-    "123".scanf("%c").should == ["1"]
-    "123".scanf("%d").should == [123]
-    "123".scanf("%u").should == [123]
-    "123".scanf("%o").should == [83]
-    "123".scanf("%x").should == [291]
-    "123".scanf("%i").should == [123]
-    "0123".scanf("%i").should == [83]
-    "123".scanf("%f").should == [123.0]
-    "0X123".scanf("%i").should == [291]
-    "0x123".scanf("%i").should == [291]
-  end
-
-  it "returns an array containing the input converted in the specified type with given maximum field width" do
-    "hello world".scanf("%2s").should == ["he"]
-    "hello world".scanf("%2c").should == ["he"]
-    "123".scanf("%2s").should == ["12"]
-    "123".scanf("%2c").should == ["12"]
-    "123".scanf("%2d").should == [12]
-    "123".scanf("%2u").should == [12]
-    "123".scanf("%2o").should == [10]
-    "123".scanf("%2x").should == [18]
-    "123".scanf("%2i").should == [12]
-    "0123".scanf("%2i").should == [1]
-    "123".scanf("%2f").should == [12.0]
-    "0X123".scanf("%2i").should == [0]
-    "0X123".scanf("%3i").should == [1]
-    "0X123".scanf("%4i").should == [18]
-  end
-
-  it "returns an empty array when a wrong specifier is passed" do
-    "hello world".scanf("%a").should == []
-    "123".scanf("%1").should == []
-    "123".scanf("abc").should == []
-    "123".scanf(:d).should == []
-  end
-end
-
-describe "String#scanf with block" do
-  it_behaves_like :scanf_string_block_scanf, :scanf
-end
diff --git a/spec/ruby/library/scanf/string/shared/block_scanf.rb b/spec/ruby/library/scanf/string/shared/block_scanf.rb
deleted file mode 100644
index 25ab3f442a..0000000000
--- a/spec/ruby/library/scanf/string/shared/block_scanf.rb
+++ /dev/null
@@ -1,25 +0,0 @@
-require 'scanf'
-
-describe :scanf_string_block_scanf, shared: true do
-  it "passes each match to the block as an array" do
-    a = []
-    "hello world".send(@method, "%s%s"){|w| a << w}
-    a.should == [["hello", "world"]]
-  end
-
-  it "keeps scanning the input and cycling back to the beginning of the input string" do
-    a = []
-    "hello world".send(@method, "%s"){|w| a << w}
-    a.should == [["hello"], ["world"]]
-
-    string = "123 abc 456 def 789 ghi"
-    s = string.send(@method, "%d%s"){|num,str| [num * 2, str.upcase]}
-    s.should == [[246, "ABC"], [912, "DEF"], [1578, "GHI"]]
-  end
-
-  it "returns an empty array when a wrong specifier is passed" do
-    a = []
-    "hello world".send(@method, "%z"){|w| a << w}
-    a.empty?.should be_true
-  end
-end
diff --git a/spec/ruby/library/securerandom/bytes_spec.rb b/spec/ruby/library/securerandom/bytes_spec.rb
new file mode 100644
index 0000000000..a1ab836d16
--- /dev/null
+++ b/spec/ruby/library/securerandom/bytes_spec.rb
@@ -0,0 +1,8 @@
+require_relative '../../spec_helper'
+require_relative '../../core/random/shared/bytes'
+
+require 'securerandom'
+
+describe "SecureRandom.bytes" do
+  it_behaves_like :random_bytes, :bytes, SecureRandom
+end
diff --git a/spec/ruby/library/securerandom/random_bytes_spec.rb b/spec/ruby/library/securerandom/random_bytes_spec.rb
index 275a897315..ed3a02255c 100644
--- a/spec/ruby/library/securerandom/random_bytes_spec.rb
+++ b/spec/ruby/library/securerandom/random_bytes_spec.rb
@@ -1,8 +1,11 @@
 require_relative '../../spec_helper'
+require_relative '../../core/random/shared/bytes'
 
 require 'securerandom'
 
 describe "SecureRandom.random_bytes" do
+  it_behaves_like :random_bytes, :random_bytes, SecureRandom
+
   it "generates a random binary string of length 16 if no argument is provided" do
     bytes = SecureRandom.random_bytes
     bytes.should be_kind_of(String)
diff --git a/spec/ruby/library/securerandom/random_number_spec.rb b/spec/ruby/library/securerandom/random_number_spec.rb
index 3c86f55bf5..bb25bc496e 100644
--- a/spec/ruby/library/securerandom/random_number_spec.rb
+++ b/spec/ruby/library/securerandom/random_number_spec.rb
@@ -1,14 +1,18 @@
 require_relative '../../spec_helper'
+require_relative '../../core/random/shared/rand'
 
 require 'securerandom'
 
 describe "SecureRandom.random_number" do
+  it_behaves_like :random_number, :rand, SecureRandom
+  it_behaves_like :random_number, :random_number, SecureRandom
+
   it "generates a random positive number smaller then the positive integer argument" do
     (1..64).each do |idx|
       num = SecureRandom.random_number(idx)
-      num.should be_kind_of(Fixnum)
-      (0 <= num).should == true
-      (num < idx).should == true
+      num.should be_kind_of(Integer)
+      0.should <= num
+      num.should < idx
     end
   end
 
@@ -17,8 +21,8 @@ describe "SecureRandom.random_number" do
     11.times do
       num = SecureRandom.random_number max
       num.should be_kind_of(Integer)
-      (0 <= num).should == true
-      (num < max).should == true
+      0.should <= num
+      num.should < max
     end
   end
 
@@ -26,8 +30,8 @@ describe "SecureRandom.random_number" do
     64.times do
       num = SecureRandom.random_number
       num.should be_kind_of(Float)
-      (0.0 <= num).should == true
-      (num < 1.0).should == true
+      0.0.should <= num
+      num.should < 1.0
     end
   end
 
@@ -35,8 +39,8 @@ describe "SecureRandom.random_number" do
     64.times do
       num = SecureRandom.random_number 11...13
       num.should be_kind_of(Integer)
-      (11 <= num).should == true
-      (num < 13).should == true
+      11.should <= num
+      num.should < 13
     end
   end
 
@@ -46,8 +50,8 @@ describe "SecureRandom.random_number" do
     32.times do
       num = SecureRandom.random_number lower..upper
       num.should be_kind_of(Integer)
-      (lower <= num).should == true
-      (num <= upper).should == true
+      lower.should <= num
+      num.should <= upper
     end
   end
 
@@ -55,23 +59,23 @@ describe "SecureRandom.random_number" do
     64.times do
       num = SecureRandom.random_number 0.6..0.9
       num.should be_kind_of(Float)
-      (0.6 <= num).should == true
-      (num <= 0.9).should == true
+      0.6.should <= num
+      num.should <= 0.9
     end
   end
 
   it "generates a random float number between 0.0 and 1.0 if argument is negative" do
     num = SecureRandom.random_number(-10)
     num.should be_kind_of(Float)
-    (0.0 <= num).should == true
-    (num < 1.0).should == true
+    0.0.should <= num
+    num.should < 1.0
   end
 
   it "generates a random float number between 0.0 and 1.0 if argument is negative float" do
     num = SecureRandom.random_number(-11.1)
     num.should be_kind_of(Float)
-    (0.0 <= num).should == true
-    (num < 1.0).should == true
+    0.0.should <= num
+    num.should < 1.0
   end
 
   it "generates different float numbers with subsequent invocations" do
@@ -80,7 +84,7 @@ describe "SecureRandom.random_number" do
     256.times do
       val = SecureRandom.random_number
       # make sure the random values are not repeating
-      values.include?(val).should == false
+      values.should_not include(val)
       values << val
     end
   end
diff --git a/spec/ruby/library/set/add_spec.rb b/spec/ruby/library/set/add_spec.rb
deleted file mode 100644
index 68356cc111..0000000000
--- a/spec/ruby/library/set/add_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/add'
-
-describe "Set#add" do
-  it_behaves_like :set_add, :add
-end
-
-describe "Set#add?" do
-  before :each do
-    @set = Set.new
-  end
-
-  it "adds the passed Object to self" do
-    @set.add?("cat")
-    @set.should include("cat")
-  end
-
-  it "returns self when the Object has not yet been added to self" do
-    @set.add?("cat").should equal(@set)
-  end
-
-  it "returns nil when the Object has already been added to self" do
-    @set.add?("cat")
-    @set.add?("cat").should be_nil
-  end
-end
diff --git a/spec/ruby/library/set/append_spec.rb b/spec/ruby/library/set/append_spec.rb
deleted file mode 100644
index 8b3498b779..0000000000
--- a/spec/ruby/library/set/append_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/add'
-
-describe "Set#<<" do
-  it_behaves_like :set_add, :<<
-end
diff --git a/spec/ruby/library/set/case_compare_spec.rb b/spec/ruby/library/set/case_compare_spec.rb
deleted file mode 100644
index 193006dbda..0000000000
--- a/spec/ruby/library/set/case_compare_spec.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-ruby_version_is "2.5" do
-  describe "Set#===" do
-    it_behaves_like :set_include, :===
-
-    it "is an alias for include?" do
-      set = Set.new
-      set.method(:===).should == set.method(:include?)
-    end
-  end
-end
diff --git a/spec/ruby/library/set/case_equality_spec.rb b/spec/ruby/library/set/case_equality_spec.rb
deleted file mode 100644
index 875630612e..0000000000
--- a/spec/ruby/library/set/case_equality_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-ruby_version_is "2.5" do
-  describe "Set#===" do
-    it_behaves_like :set_include, :===
-  end
-end
diff --git a/spec/ruby/library/set/classify_spec.rb b/spec/ruby/library/set/classify_spec.rb
deleted file mode 100644
index ec600c91d6..0000000000
--- a/spec/ruby/library/set/classify_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#classify" do
-  before :each do
-    @set = Set["one", "two", "three", "four"]
-  end
-
-  it "yields each Object in self" do
-    res = []
-    @set.classify { |x| res << x }
-    res.sort.should == ["one", "two", "three", "four"].sort
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.classify
-    enum.should be_an_instance_of(Enumerator)
-
-    classified = enum.each { |x| x.length }
-    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
-  end
-
-  it "classifies the Objects in self based on the block's return value" do
-    classified = @set.classify { |x| x.length }
-    classified.should == { 3 => Set["one", "two"], 4 => Set["four"], 5 => Set["three"] }
-  end
-end
diff --git a/spec/ruby/library/set/clear_spec.rb b/spec/ruby/library/set/clear_spec.rb
deleted file mode 100644
index 2b1c9c5b5a..0000000000
--- a/spec/ruby/library/set/clear_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#clear" do
-  before :each do
-    @set = Set["one", "two", "three", "four"]
-  end
-
-  it "removes all elements from self" do
-    @set.clear
-    @set.should be_empty
-  end
-
-  it "returns self" do
-    @set.clear.should equal(@set)
-  end
-end
diff --git a/spec/ruby/library/set/collect_spec.rb b/spec/ruby/library/set/collect_spec.rb
deleted file mode 100644
index f8813a9331..0000000000
--- a/spec/ruby/library/set/collect_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/collect'
-
-describe "Set#collect!" do
-  it_behaves_like :set_collect_bang, :collect!
-end
diff --git a/spec/ruby/library/set/compare_by_identity_spec.rb b/spec/ruby/library/set/compare_by_identity_spec.rb
deleted file mode 100644
index a6ad794ad3..0000000000
--- a/spec/ruby/library/set/compare_by_identity_spec.rb
+++ /dev/null
@@ -1,143 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#compare_by_identity" do
-  it "compares its members by identity" do
-    a = "a"
-    b1 = "b"
-    b2 = "b"
-
-    set = Set.new
-    set.compare_by_identity
-    set.merge([a, a, b1, b2])
-    set.to_a.sort.should == [a, b1, b2].sort
-  end
-
-  it "causes future comparisons on the receiver to be made by identity" do
-    elt = [1]
-    set = Set.new
-    set << elt
-    set.member?(elt.dup).should be_true
-    set.compare_by_identity
-    set.member?(elt.dup).should be_false
-  end
-
-  it "rehashes internally so that old members can be looked up" do
-    set = Set.new
-    (1..10).each { |k| set << k }
-    o = Object.new
-    def o.hash; 123; end
-    set << o
-    set.compare_by_identity
-    set.member?(o).should be_true
-  end
-
-  it "returns self" do
-    set = Set.new
-    result = set.compare_by_identity
-    result.should equal(set)
-  end
-
-  it "is idempotent and has no effect on an already compare_by_identity set" do
-    set = Set.new.compare_by_identity
-    set << :foo
-    set.compare_by_identity.should equal(set)
-    set.compare_by_identity?.should == true
-    set.to_a.should == [:foo]
-  end
-
-  it "uses the semantics of BasicObject#equal? to determine members identity" do
-    :a.equal?(:a).should == true
-    Set.new.compare_by_identity.merge([:a, :a]).to_a.should == [:a]
-
-    ary1 = [1]
-    ary2 = [1]
-    ary1.equal?(ary2).should == false
-    Set.new.compare_by_identity.merge([ary1, ary2]).to_a.sort.should == [ary1, ary2].sort
-  end
-
-  it "uses #equal? semantics, but doesn't actually call #equal? to determine identity" do
-    set = Set.new.compare_by_identity
-    obj = mock("equal")
-    obj.should_not_receive(:equal?)
-    set << :foo
-    set << obj
-    set.to_a.should == [:foo, obj]
-  end
-
-  it "does not call #hash on members" do
-    elt = mock("element")
-    elt.should_not_receive(:hash)
-    set = Set.new.compare_by_identity
-    set << elt
-    set.member?(elt).should be_true
-  end
-
-  it "regards #dup'd objects as having different identities" do
-    a1 = "a"
-    a2 = a1.dup
-
-    set = Set.new.compare_by_identity
-    set.merge([a1, a2])
-    set.to_a.sort.should == [a1, a2].sort
-  end
-
-  it "regards #clone'd objects as having different identities" do
-    a1 = "a"
-    a2 = a1.clone
-
-    set = Set.new.compare_by_identity
-    set.merge([a1, a2])
-    set.to_a.sort.should == [a1, a2].sort
-  end
-
-  it "raises a #{frozen_error_class} on frozen sets" do
-    set = Set.new.freeze
-    -> {
-      set.compare_by_identity
-    }.should raise_error(frozen_error_class, /frozen Hash/)
-  end
-
-  it "persists over #dups" do
-    set = Set.new.compare_by_identity
-    set << :a
-    set_dup = set.dup
-    set_dup.should == set
-    set_dup << :a
-    set_dup.to_a.should == [:a]
-  end
-
-  it "persists over #clones" do
-    set = Set.new.compare_by_identity
-    set << :a
-    set_clone = set.clone
-    set_clone.should == set
-    set_clone << :a
-    set_clone.to_a.should == [:a]
-  end
-
-  it "is not equal to set what does not compare by identity" do
-    Set.new([1, 2]).should == Set.new([1, 2])
-    Set.new([1, 2]).should_not == Set.new([1, 2]).compare_by_identity
-  end
-end
-
-describe "Set#compare_by_identity?" do
-  it "returns false by default" do
-    Set.new.compare_by_identity?.should == false
-  end
-
-  it "returns true once #compare_by_identity has been invoked on self" do
-    set = Set.new
-    set.compare_by_identity
-    set.compare_by_identity?.should == true
-  end
-
-  it "returns true when called multiple times on the same set" do
-    set = Set.new
-    set.compare_by_identity
-    set.compare_by_identity?.should == true
-    set.compare_by_identity?.should == true
-    set.compare_by_identity?.should == true
-  end
-end
diff --git a/spec/ruby/library/set/constructor_spec.rb b/spec/ruby/library/set/constructor_spec.rb
deleted file mode 100644
index bb84861514..0000000000
--- a/spec/ruby/library/set/constructor_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set[]" do
-  it "returns a new Set populated with the passed Objects" do
-    set = Set[1, 2, 3]
-
-    set.instance_of?(Set).should be_true
-    set.size.should eql(3)
-
-    set.should include(1)
-    set.should include(2)
-    set.should include(3)
-  end
-end
diff --git a/spec/ruby/library/set/delete_if_spec.rb b/spec/ruby/library/set/delete_if_spec.rb
deleted file mode 100644
index 33caeeaab7..0000000000
--- a/spec/ruby/library/set/delete_if_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#delete_if" do
-  before :each do
-    @set = Set["one", "two", "three"]
-  end
-
-  it "yields every element of self" do
-    ret = []
-    @set.delete_if { |x| ret << x }
-    ret.sort.should == ["one", "two", "three"].sort
-  end
-
-  it "deletes every element from self for which the passed block returns true" do
-    @set.delete_if { |x| x.size == 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self" do
-    @set.delete_if { |x| x }.should equal(@set)
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.delete_if
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size == 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/delete_spec.rb b/spec/ruby/library/set/delete_spec.rb
deleted file mode 100644
index b12524384a..0000000000
--- a/spec/ruby/library/set/delete_spec.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#delete" do
-  before :each do
-    @set = Set["a", "b", "c"]
-  end
-
-  it "deletes the passed Object from self" do
-    @set.delete("a")
-    @set.should_not include("a")
-  end
-
-  it "returns self" do
-    @set.delete("a").should equal(@set)
-    @set.delete("x").should equal(@set)
-  end
-end
-
-describe "Set#delete?" do
-  before :each do
-    @set = Set["a", "b", "c"]
-  end
-
-  it "deletes the passed Object from self" do
-    @set.delete?("a")
-    @set.should_not include("a")
-  end
-
-  it "returns self when the passed Object is in self" do
-    @set.delete?("a").should equal(@set)
-  end
-
-  it "returns nil when the passed Object is not in self" do
-    @set.delete?("x").should be_nil
-  end
-end
diff --git a/spec/ruby/library/set/difference_spec.rb b/spec/ruby/library/set/difference_spec.rb
deleted file mode 100644
index 422f2ed3c7..0000000000
--- a/spec/ruby/library/set/difference_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/difference'
-
-describe "Set#difference" do
-  it_behaves_like :set_difference, :difference
-end
diff --git a/spec/ruby/library/set/disjoint_spec.rb b/spec/ruby/library/set/disjoint_spec.rb
deleted file mode 100644
index ea3b141455..0000000000
--- a/spec/ruby/library/set/disjoint_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#disjoint?" do
-  it "returns false when two Sets have at least one element in common" do
-    Set[1, 2].disjoint?(Set[2, 3]).should == false
-  end
-
-  it "returns true when two Sets have no element in common" do
-    Set[1, 2].disjoint?(Set[3, 4]).should == true
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns false when a Set has at least one element in common with a Set-like object" do
-      Set[1, 2].disjoint?(SetSpecs::SetLike.new([2, 3])).should be_false
-    end
-
-    it "returns true when a Set has no element in common with a Set-like object" do
-      Set[1, 2].disjoint?(SetSpecs::SetLike.new([3, 4])).should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/set/divide_spec.rb b/spec/ruby/library/set/divide_spec.rb
deleted file mode 100644
index fdd8cd9622..0000000000
--- a/spec/ruby/library/set/divide_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#divide" do
-  it "divides self into a set of subsets based on the blocks return values" do
-    set = Set["one", "two", "three", "four", "five"].divide { |x| x.length }
-    set.map { |x| x.to_a.sort }.sort.should == [["five", "four"], ["one", "two"], ["three"]]
-  end
-
-  it "yields each Object to the block" do
-    ret = []
-    Set["one", "two", "three", "four", "five"].divide { |x| ret << x }
-    ret.sort.should == ["five", "four", "one", "three", "two"]
-  end
-
-  # BUG: Does not raise a LocalJumpError, but a NoMethodError
-  #
-  # it "raises a LocalJumpError when not passed a block" do
-  #   lambda { Set[1].divide }.should raise_error(LocalJumpError)
-  # end
-end
-
-describe "Set#divide when passed a block with an arity of 2" do
-  it "divides self into a set of subsets based on the blocks return values" do
-    set = Set[1, 3, 4, 6, 9, 10, 11].divide { |x, y| (x - y).abs == 1 }
-    set.map{ |x| x.to_a.sort }.sort.should == [[1], [3, 4], [6], [9, 10, 11]]
-  end
-
-  it "yields each two Object to the block" do
-    ret = []
-    Set[1, 2].divide { |x, y| ret << [x, y] }
-    ret.sort.should == [[1, 1], [1, 2], [2, 1], [2, 2]]
-  end
-end
diff --git a/spec/ruby/library/set/each_spec.rb b/spec/ruby/library/set/each_spec.rb
deleted file mode 100644
index 9bb5ead03a..0000000000
--- a/spec/ruby/library/set/each_spec.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#each" do
-  before :each do
-    @set = Set[1, 2, 3]
-  end
-
-  it "yields each Object in self" do
-    ret = []
-    @set.each { |x| ret << x }
-    ret.sort.should == [1, 2, 3]
-  end
-
-  it "returns self" do
-    @set.each { |x| x }.should equal(@set)
-  end
-
-  it "returns an Enumerator when not passed a block" do
-    enum = @set.each
-
-    ret = []
-    enum.each { |x| ret << x }
-    ret.sort.should == [1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/empty_spec.rb b/spec/ruby/library/set/empty_spec.rb
deleted file mode 100644
index 1789a664c7..0000000000
--- a/spec/ruby/library/set/empty_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#empty?" do
-  it "returns true if self is empty" do
-    Set[].empty?.should be_true
-    Set[1].empty?.should be_false
-    Set[1,2,3].empty?.should be_false
-  end
-end
diff --git a/spec/ruby/library/set/enumerable/to_set_spec.rb b/spec/ruby/library/set/enumerable/to_set_spec.rb
deleted file mode 100644
index 0f5504fef2..0000000000
--- a/spec/ruby/library/set/enumerable/to_set_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "Enumerable#to_set" do
-  it "returns a new Set created from self" do
-    [1, 2, 3].to_set.should == Set[1, 2, 3]
-    {a: 1, b: 2}.to_set.should == Set[[:b, 2], [:a, 1]]
-  end
-
-  it "allows passing an alternate class for Set" do
-    sorted_set = [1, 2, 3].to_set(SortedSet)
-    sorted_set.should == SortedSet[1, 2, 3]
-    sorted_set.instance_of?(SortedSet).should == true
-  end
-
-  it "passes down passed blocks" do
-    [1, 2, 3].to_set { |x| x * x }.should == Set[1, 4, 9]
-  end
-end
diff --git a/spec/ruby/library/set/eql_spec.rb b/spec/ruby/library/set/eql_spec.rb
deleted file mode 100644
index dd8e633775..0000000000
--- a/spec/ruby/library/set/eql_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#eql?" do
-  it "returns true when the passed argument is a Set and contains the same elements" do
-    Set[].should eql(Set[])
-    Set[1, 2, 3].should eql(Set[1, 2, 3])
-    Set[1, 2, 3].should eql(Set[3, 2, 1])
-    Set["a", :b, ?c].should eql(Set[?c, :b, "a"])
-
-    Set[1, 2, 3].should_not eql(Set[1.0, 2, 3])
-    Set[1, 2, 3].should_not eql(Set[2, 3])
-    Set[1, 2, 3].should_not eql(Set[])
-  end
-end
diff --git a/spec/ruby/library/set/equal_value_spec.rb b/spec/ruby/library/set/equal_value_spec.rb
deleted file mode 100644
index f5b5f790c0..0000000000
--- a/spec/ruby/library/set/equal_value_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#==" do
-  it "returns true when the passed Object is a Set and self and the Object contain the same elements" do
-    Set[].should == Set[]
-    Set[1, 2, 3].should == Set[1, 2, 3]
-    Set["1", "2", "3"].should == Set["1", "2", "3"]
-
-    Set[1, 2, 3].should_not == Set[1.0, 2, 3]
-    Set[1, 2, 3].should_not == [1, 2, 3]
-  end
-
-  it "does not depend on the order of the elements" do
-    Set[1, 2, 3].should == Set[3, 2, 1]
-    Set[:a, "b", ?c].should == Set[?c, "b", :a]
-  end
-
-  it "does not depend on the order of nested Sets" do
-    Set[Set[1], Set[2], Set[3]].should == Set[Set[3], Set[2], Set[1]]
-
-    set1 = Set[Set["a", "b"], Set["c", "d"], Set["e", "f"]]
-    set2 = Set[Set["c", "d"], Set["a", "b"], Set["e", "f"]]
-    set1.should == set2
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true when a Set and a Set-like object contain the same elements" do
-      Set[1, 2, 3].should == SetSpecs::SetLike.new([1, 2, 3])
-    end
-  end
-end
diff --git a/spec/ruby/library/set/exclusion_spec.rb b/spec/ruby/library/set/exclusion_spec.rb
deleted file mode 100644
index 5bc4b5a2bf..0000000000
--- a/spec/ruby/library/set/exclusion_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#^" do
-  before :each do
-    @set = Set[1, 2, 3, 4]
-  end
-
-  it "returns a new Set containing elements that are not in both self and the passed Enumerable" do
-    (@set ^ Set[3, 4, 5]).should == Set[1, 2, 5]
-    (@set ^ [3, 4, 5]).should == Set[1, 2, 5]
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { @set ^ 3 }.should raise_error(ArgumentError)
-    -> { @set ^ Object.new }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/filter_spec.rb b/spec/ruby/library/set/filter_spec.rb
deleted file mode 100644
index a4dfe70d52..0000000000
--- a/spec/ruby/library/set/filter_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/select'
-
-ruby_version_is "2.6" do
-  describe "Set#filter!" do
-    it_behaves_like :set_select_bang, :filter!
-  end
-end
diff --git a/spec/ruby/library/set/fixtures/set_like.rb b/spec/ruby/library/set/fixtures/set_like.rb
deleted file mode 100644
index 46f61a451e..0000000000
--- a/spec/ruby/library/set/fixtures/set_like.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require 'set'
-
-module SetSpecs
-  # This class is used to test the interaction of "Set-like" objects with real Sets
-  #
-  # These "Set-like" objects reply to is_a?(Set) with true and thus real Set objects are able to transparently
-  # interoperate with them in a duck-typing manner.
-  class SetLike
-    include Enumerable
-
-    def is_a?(klass)
-      super || klass == ::Set
-    end
-
-    def initialize(entries)
-      @entries = entries
-    end
-
-    def each(&block)
-      @entries.each(&block)
-    end
-
-    def inspect
-      "#<#{self.class}: {#{map(&:inspect).join(", ")}}>"
-    end
-
-    def size
-      @entries.size
-    end
-  end
-end
diff --git a/spec/ruby/library/set/flatten_merge_spec.rb b/spec/ruby/library/set/flatten_merge_spec.rb
deleted file mode 100644
index f2c99a9481..0000000000
--- a/spec/ruby/library/set/flatten_merge_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#flatten_merge" do
-  it "is protected" do
-    Set.should have_protected_instance_method("flatten_merge")
-  end
-
-  it "flattens the passed Set and merges it into self" do
-    set1 = Set[1, 2]
-    set2 = Set[3, 4, Set[5, 6]]
-
-    set1.send(:flatten_merge, set2).should == Set[1, 2, 3, 4, 5, 6]
-  end
-
-  it "raises an ArgumentError when trying to flatten a recursive Set" do
-    set1 = Set[1, 2, 3]
-    set2 = Set[5, 6, 7]
-    set2 << set2
-
-    -> { set1.send(:flatten_merge, set2) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/flatten_spec.rb b/spec/ruby/library/set/flatten_spec.rb
deleted file mode 100644
index 4ac83ea825..0000000000
--- a/spec/ruby/library/set/flatten_spec.rb
+++ /dev/null
@@ -1,53 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#flatten" do
-  it "returns a copy of self with each included Set flattened" do
-    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
-    flattened_set = set.flatten
-
-    flattened_set.should_not equal(set)
-    flattened_set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
-  end
-
-  it "raises an ArgumentError when self is recursive" do
-    (set = Set[]) << set
-    -> { set.flatten }.should raise_error(ArgumentError)
-  end
-
-  context "when Set contains a Set-like object" do
-    it "returns a copy of self with each included Set-like object flattened" do
-      Set[SetSpecs::SetLike.new([1])].flatten.should == Set[1]
-    end
-  end
-end
-
-describe "Set#flatten!" do
-  it "flattens self" do
-    set = Set[1, 2, Set[3, 4, Set[5, 6, Set[7, 8]]], 9, 10]
-    set.flatten!
-    set.should == Set[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
-  end
-
-  it "returns self when self was modified" do
-    set = Set[1, 2, Set[3, 4]]
-    set.flatten!.should equal(set)
-  end
-
-  it "returns nil when self was not modified" do
-    set = Set[1, 2, 3, 4]
-    set.flatten!.should be_nil
-  end
-
-  it "raises an ArgumentError when self is recursive" do
-    (set = Set[]) << set
-    -> { set.flatten! }.should raise_error(ArgumentError)
-  end
-
-  context "when Set contains a Set-like object" do
-    it "flattens self, including Set-like objects" do
-      Set[SetSpecs::SetLike.new([1])].flatten!.should == Set[1]
-    end
-  end
-end
diff --git a/spec/ruby/library/set/hash_spec.rb b/spec/ruby/library/set/hash_spec.rb
deleted file mode 100644
index 47c43c05f1..0000000000
--- a/spec/ruby/library/set/hash_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#hash" do
-  it "is static" do
-    Set[].hash.should == Set[].hash
-    Set[1, 2, 3].hash.should == Set[1, 2, 3].hash
-    Set[:a, "b", ?c].hash.should == Set[?c, "b", :a].hash
-
-    Set[].hash.should_not == Set[1, 2, 3].hash
-    Set[1, 2, 3].hash.should_not == Set[:a, "b", ?c].hash
-  end
-end
diff --git a/spec/ruby/library/set/include_spec.rb b/spec/ruby/library/set/include_spec.rb
deleted file mode 100644
index 68532d9a04..0000000000
--- a/spec/ruby/library/set/include_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-describe "Set#include?" do
-  it_behaves_like :set_include, :include?
-end
diff --git a/spec/ruby/library/set/initialize_spec.rb b/spec/ruby/library/set/initialize_spec.rb
deleted file mode 100644
index 887cae45fc..0000000000
--- a/spec/ruby/library/set/initialize_spec.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#initialize" do
-  it "is private" do
-    Set.should have_private_instance_method(:initialize)
-  end
-
-  it "adds all elements of the passed Enumerable to self" do
-    s = Set.new([1, 2, 3])
-    s.size.should eql(3)
-    s.should include(1)
-    s.should include(2)
-    s.should include(3)
-  end
-
-  it "should initialize with empty array and set" do
-    s = Set.new([])
-    s.size.should eql(0)
-
-    s = Set.new({})
-    s.size.should eql(0)
-  end
-
-  it "preprocesses all elements by a passed block before adding to self" do
-    s = Set.new([1, 2, 3]) { |x| x * x }
-    s.size.should eql(3)
-    s.should include(1)
-    s.should include(4)
-    s.should include(9)
-  end
-
-  it "should initialize with empty array and block" do
-    s = Set.new([]) { |x| x * x }
-    s.size.should eql(0)
-  end
-
-  it "should initialize with empty set and block" do
-    s = Set.new(Set.new) { |x| x * x }
-    s.size.should eql(0)
-  end
-
-  it "should initialize with just block" do
-    s = Set.new { |x| x * x }
-    s.size.should eql(0)
-    s.should eql(Set.new)
-  end
-end
diff --git a/spec/ruby/library/set/inspect_spec.rb b/spec/ruby/library/set/inspect_spec.rb
deleted file mode 100644
index 4060c63b95..0000000000
--- a/spec/ruby/library/set/inspect_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/inspect'
-require 'set'
-
-describe "Set#inspect" do
-  it_behaves_like :set_inspect, :inspect
-end
diff --git a/spec/ruby/library/set/intersect_spec.rb b/spec/ruby/library/set/intersect_spec.rb
deleted file mode 100644
index e60f06db94..0000000000
--- a/spec/ruby/library/set/intersect_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#intersect?" do
-  it "returns true when two Sets have at least one element in common" do
-    Set[1, 2].intersect?(Set[2, 3]).should == true
-  end
-
-  it "returns false when two Sets have no element in common" do
-    Set[1, 2].intersect?(Set[3, 4]).should == false
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true when a Set has at least one element in common with a Set-like object" do
-      Set[1, 2].intersect?(SetSpecs::SetLike.new([2, 3])).should be_true
-    end
-
-    it "returns false when a Set has no element in common with a Set-like object" do
-      Set[1, 2].intersect?(SetSpecs::SetLike.new([3, 4])).should be_false
-    end
-  end
-end
diff --git a/spec/ruby/library/set/intersection_spec.rb b/spec/ruby/library/set/intersection_spec.rb
deleted file mode 100644
index 792c2d8f07..0000000000
--- a/spec/ruby/library/set/intersection_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/intersection'
-require 'set'
-
-describe "Set#intersection" do
-  it_behaves_like :set_intersection, :intersection
-end
-
-describe "Set#&" do
-  it_behaves_like :set_intersection, :&
-end
diff --git a/spec/ruby/library/set/keep_if_spec.rb b/spec/ruby/library/set/keep_if_spec.rb
deleted file mode 100644
index 7edc80769f..0000000000
--- a/spec/ruby/library/set/keep_if_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#keep_if" do
-  before :each do
-    @set = Set["one", "two", "three"]
-  end
-
-  it "yields every element of self" do
-    ret = []
-    @set.keep_if { |x| ret << x }
-    ret.sort.should == ["one", "two", "three"].sort
-  end
-
-  it "keeps every element from self for which the passed block returns true" do
-    @set.keep_if { |x| x.size != 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self" do
-    @set.keep_if {}.should equal(@set)
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.keep_if
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size != 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/length_spec.rb b/spec/ruby/library/set/length_spec.rb
deleted file mode 100644
index fef63d25a7..0000000000
--- a/spec/ruby/library/set/length_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/length'
-require 'set'
-
-describe "Set#length" do
-  it_behaves_like :set_length, :length
-end
diff --git a/spec/ruby/library/set/map_spec.rb b/spec/ruby/library/set/map_spec.rb
deleted file mode 100644
index e60e98b179..0000000000
--- a/spec/ruby/library/set/map_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/collect'
-
-describe "Set#map!" do
-  it_behaves_like :set_collect_bang, :map!
-end
diff --git a/spec/ruby/library/set/member_spec.rb b/spec/ruby/library/set/member_spec.rb
deleted file mode 100644
index 5b56a38ab9..0000000000
--- a/spec/ruby/library/set/member_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-describe "Set#member?" do
-  it_behaves_like :set_include, :member?
-end
diff --git a/spec/ruby/library/set/merge_spec.rb b/spec/ruby/library/set/merge_spec.rb
deleted file mode 100644
index a8e3ffc870..0000000000
--- a/spec/ruby/library/set/merge_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#merge" do
-  it "adds the elements of the passed Enumerable to self" do
-    Set[:a, :b].merge(Set[:b, :c, :d]).should == Set[:a, :b, :c, :d]
-    Set[1, 2].merge([3, 4]).should == Set[1, 2, 3, 4]
-  end
-
-  it "returns self" do
-    set = Set[1, 2]
-    set.merge([3, 4]).should equal(set)
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { Set[1, 2].merge(1) }.should raise_error(ArgumentError)
-    -> { Set[1, 2].merge(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/minus_spec.rb b/spec/ruby/library/set/minus_spec.rb
deleted file mode 100644
index 3fe0b6a2cc..0000000000
--- a/spec/ruby/library/set/minus_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-require_relative 'shared/difference'
-
-describe "Set#-" do
-  it_behaves_like :set_difference, :-
-end
diff --git a/spec/ruby/library/set/plus_spec.rb b/spec/ruby/library/set/plus_spec.rb
deleted file mode 100644
index 3e70d3269d..0000000000
--- a/spec/ruby/library/set/plus_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/union'
-require 'set'
-
-describe "Set#+" do
-  it_behaves_like :set_union, :+
-end
diff --git a/spec/ruby/library/set/pretty_print_cycle_spec.rb b/spec/ruby/library/set/pretty_print_cycle_spec.rb
deleted file mode 100644
index 4f440353e5..0000000000
--- a/spec/ruby/library/set/pretty_print_cycle_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#pretty_print_cycle" do
-  it "passes the 'pretty print' representation of a self-referencing Set to the pretty print writer" do
-    pp = mock("PrettyPrint")
-    pp.should_receive(:text).with("#<Set: {...}>")
-    Set[1, 2, 3].pretty_print_cycle(pp)
-  end
-end
diff --git a/spec/ruby/library/set/pretty_print_spec.rb b/spec/ruby/library/set/pretty_print_spec.rb
deleted file mode 100644
index f2392e6968..0000000000
--- a/spec/ruby/library/set/pretty_print_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#pretty_print" do
-  it "passes the 'pretty print' representation of self to the pretty print writer" do
-    pp = mock("PrettyPrint")
-    set = Set[1, 2, 3]
-
-    pp.should_receive(:text).with("#<Set: {")
-    pp.should_receive(:text).with("}>")
-
-    pp.should_receive(:nest).with(1).and_yield
-    pp.should_receive(:seplist).with(set)
-
-    set.pretty_print(pp)
-  end
-end
diff --git a/spec/ruby/library/set/proper_subset_spec.rb b/spec/ruby/library/set/proper_subset_spec.rb
deleted file mode 100644
index 1f496a6199..0000000000
--- a/spec/ruby/library/set/proper_subset_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#proper_subset?" do
-  before :each do
-    @set = Set[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a Set that self is a proper subset of" do
-    Set[].proper_subset?(@set).should be_true
-    Set[].proper_subset?(Set[1, 2, 3]).should be_true
-    Set[].proper_subset?(Set["a", :b, ?c]).should be_true
-
-    Set[1, 2, 3].proper_subset?(@set).should be_true
-    Set[1, 3].proper_subset?(@set).should be_true
-    Set[1, 2].proper_subset?(@set).should be_true
-    Set[1].proper_subset?(@set).should be_true
-
-    Set[5].proper_subset?(@set).should be_false
-    Set[1, 5].proper_subset?(@set).should be_false
-    Set[nil].proper_subset?(@set).should be_false
-    Set["test"].proper_subset?(@set).should be_false
-
-    @set.proper_subset?(@set).should be_false
-    Set[].proper_subset?(Set[]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-Set" do
-    -> { Set[].proper_subset?([]) }.should raise_error(ArgumentError)
-    -> { Set[].proper_subset?(1) }.should raise_error(ArgumentError)
-    -> { Set[].proper_subset?("test") }.should raise_error(ArgumentError)
-    -> { Set[].proper_subset?(Object.new) }.should raise_error(ArgumentError)
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true if passed a Set-like object that self is a proper subset of" do
-      Set[1, 2, 3].proper_subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/set/proper_superset_spec.rb b/spec/ruby/library/set/proper_superset_spec.rb
deleted file mode 100644
index a386c8c097..0000000000
--- a/spec/ruby/library/set/proper_superset_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#proper_superset?" do
-  before :each do
-    @set = Set[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a Set that self is a proper superset of" do
-    @set.proper_superset?(Set[]).should be_true
-    Set[1, 2, 3].proper_superset?(Set[]).should be_true
-    Set["a", :b, ?c].proper_superset?(Set[]).should be_true
-
-    @set.proper_superset?(Set[1, 2, 3]).should be_true
-    @set.proper_superset?(Set[1, 3]).should be_true
-    @set.proper_superset?(Set[1, 2]).should be_true
-    @set.proper_superset?(Set[1]).should be_true
-
-    @set.proper_superset?(Set[5]).should be_false
-    @set.proper_superset?(Set[1, 5]).should be_false
-    @set.proper_superset?(Set[nil]).should be_false
-    @set.proper_superset?(Set["test"]).should be_false
-
-    @set.proper_superset?(@set).should be_false
-    Set[].proper_superset?(Set[]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-Set" do
-    -> { Set[].proper_superset?([]) }.should raise_error(ArgumentError)
-    -> { Set[].proper_superset?(1) }.should raise_error(ArgumentError)
-    -> { Set[].proper_superset?("test") }.should raise_error(ArgumentError)
-    -> { Set[].proper_superset?(Object.new) }.should raise_error(ArgumentError)
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true if passed a Set-like object that self is a proper superset of" do
-      Set[1, 2, 3, 4].proper_superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/set/reject_spec.rb b/spec/ruby/library/set/reject_spec.rb
deleted file mode 100644
index 9131f960ad..0000000000
--- a/spec/ruby/library/set/reject_spec.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#reject!" do
-  before :each do
-    @set = Set["one", "two", "three"]
-  end
-
-  it "yields every element of self" do
-    ret = []
-    @set.reject! { |x| ret << x }
-    ret.sort.should == ["one", "two", "three"].sort
-  end
-
-  it "deletes every element from self for which the passed block returns true" do
-    @set.reject! { |x| x.size == 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self when self was modified" do
-    @set.reject! { |x| true }.should equal(@set)
-  end
-
-  it "returns nil when self was not modified" do
-    @set.reject! { |x| false }.should be_nil
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.reject!
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size == 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/replace_spec.rb b/spec/ruby/library/set/replace_spec.rb
deleted file mode 100644
index 7511066c9c..0000000000
--- a/spec/ruby/library/set/replace_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#replace" do
-  before :each do
-    @set = Set[:a, :b, :c]
-  end
-
-  it "replaces the contents with other and returns self" do
-    @set.replace(Set[1, 2, 3]).should == @set
-    @set.should == Set[1, 2, 3]
-  end
-
-  it "accepts any enumerable as other" do
-    @set.replace([1, 2, 3]).should == Set[1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/shared/inspect.rb b/spec/ruby/library/set/shared/inspect.rb
deleted file mode 100644
index 69fbdd12f6..0000000000
--- a/spec/ruby/library/set/shared/inspect.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-describe "set_inspect", shared: true do
-  it "returns a String representation of self" do
-    Set[].send(@method).should be_kind_of(String)
-    Set[nil, false, true].send(@method).should be_kind_of(String)
-    Set[1, 2, 3].send(@method).should be_kind_of(String)
-    Set["1", "2", "3"].send(@method).should be_kind_of(String)
-    Set[:a, "b", Set[?c]].send(@method).should be_kind_of(String)
-  end
-
-  it "correctly handles self-references" do
-    (set = Set[]) << set
-    set.send(@method).should be_kind_of(String)
-    set.send(@method).should include("#<Set: {...}>")
-  end
-end
diff --git a/spec/ruby/library/set/shared/select.rb b/spec/ruby/library/set/shared/select.rb
deleted file mode 100644
index 2108d398b4..0000000000
--- a/spec/ruby/library/set/shared/select.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe :set_select_bang, shared: true do
-  before :each do
-    @set = Set["one", "two", "three"]
-  end
-
-  it "yields every element of self" do
-    ret = []
-    @set.send(@method) { |x| ret << x }
-    ret.sort.should == ["one", "two", "three"].sort
-  end
-
-  it "keeps every element from self for which the passed block returns true" do
-    @set.send(@method) { |x| x.size != 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self when self was modified" do
-    @set.send(@method) { false }.should equal(@set)
-  end
-
-  it "returns nil when self was not modified" do
-    @set.send(@method) { true }.should be_nil
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.send(@method)
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size != 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/size_spec.rb b/spec/ruby/library/set/size_spec.rb
deleted file mode 100644
index 3c8cb38517..0000000000
--- a/spec/ruby/library/set/size_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/length'
-require 'set'
-
-describe "Set#size" do
-  it_behaves_like :set_length, :size
-end
diff --git a/spec/ruby/library/set/sortedset/add_spec.rb b/spec/ruby/library/set/sortedset/add_spec.rb
deleted file mode 100644
index 5f8bde02f5..0000000000
--- a/spec/ruby/library/set/sortedset/add_spec.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/add'
-
-describe "SortedSet#add" do
-  it_behaves_like :sorted_set_add, :add
-
-  it "takes only values which responds <=>" do
-    obj = mock('no_comparison_operator')
-    obj.stub!(:respond_to?).with(:<=>).and_return(false)
-    -> { SortedSet["hello"].add(obj) }.should raise_error(ArgumentError)
-  end
-
-  it "raises on incompatible <=> comparison" do
-    # Use #to_a here as elements are sorted only when needed.
-    # Therefore the <=> incompatibility is only noticed on sorting.
-    -> { SortedSet['1', '2'].add(3).to_a }.should raise_error(ArgumentError)
-  end
-end
-
-describe "SortedSet#add?" do
-  before :each do
-    @set = SortedSet.new
-  end
-
-  it "adds the passed Object to self" do
-    @set.add?("cat")
-    @set.should include("cat")
-  end
-
-  it "returns self when the Object has not yet been added to self" do
-    @set.add?("cat").should equal(@set)
-  end
-
-  it "returns nil when the Object has already been added to self" do
-    @set.add?("cat")
-    @set.add?("cat").should be_nil
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/append_spec.rb b/spec/ruby/library/set/sortedset/append_spec.rb
deleted file mode 100644
index ebcceba962..0000000000
--- a/spec/ruby/library/set/sortedset/append_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/add'
-
-describe "SortedSet#<<" do
-  it_behaves_like :sorted_set_add, :<<
-end
diff --git a/spec/ruby/library/set/sortedset/case_equality_spec.rb b/spec/ruby/library/set/sortedset/case_equality_spec.rb
deleted file mode 100644
index 5627917677..0000000000
--- a/spec/ruby/library/set/sortedset/case_equality_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-ruby_version_is "2.5" do
-  describe "SortedSet#===" do
-    it_behaves_like :sorted_set_include, :===
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/classify_spec.rb b/spec/ruby/library/set/sortedset/classify_spec.rb
deleted file mode 100644
index 62b26d5d28..0000000000
--- a/spec/ruby/library/set/sortedset/classify_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#classify" do
-  before :each do
-    @set = SortedSet["one", "two", "three", "four"]
-  end
-
-  it "yields each Object in self in sorted order" do
-    res = []
-    @set.classify { |x| res << x }
-    res.should == ["one", "two", "three", "four"].sort
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.classify
-    enum.should be_an_instance_of(Enumerator)
-
-    classified = enum.each { |x| x.length }
-    classified.should == { 3 => SortedSet["one", "two"], 4 => SortedSet["four"], 5 => SortedSet["three"] }
-  end
-
-  it "classifies the Objects in self based on the block's return value" do
-    classified = @set.classify { |x| x.length }
-    classified.should == { 3 => SortedSet["one", "two"], 4 => SortedSet["four"], 5 => SortedSet["three"] }
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/clear_spec.rb b/spec/ruby/library/set/sortedset/clear_spec.rb
deleted file mode 100644
index 11b5db2095..0000000000
--- a/spec/ruby/library/set/sortedset/clear_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#clear" do
-  before :each do
-    @set = SortedSet["one", "two", "three", "four"]
-  end
-
-  it "removes all elements from self" do
-    @set.clear
-    @set.should be_empty
-  end
-
-  it "returns self" do
-    @set.clear.should equal(@set)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/collect_spec.rb b/spec/ruby/library/set/sortedset/collect_spec.rb
deleted file mode 100644
index 21ead4fe55..0000000000
--- a/spec/ruby/library/set/sortedset/collect_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/collect'
-
-describe "SortedSet#collect!" do
-  it_behaves_like :sorted_set_collect_bang, :collect!
-end
diff --git a/spec/ruby/library/set/sortedset/constructor_spec.rb b/spec/ruby/library/set/sortedset/constructor_spec.rb
deleted file mode 100644
index 953144dbdb..0000000000
--- a/spec/ruby/library/set/sortedset/constructor_spec.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet[]" do
-  it "returns a new SortedSet populated with the passed Objects" do
-    set = SortedSet[1, 2, 3]
-
-    set.instance_of?(SortedSet).should be_true
-    set.size.should eql(3)
-
-    set.should include(1)
-    set.should include(2)
-    set.should include(3)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/delete_if_spec.rb b/spec/ruby/library/set/sortedset/delete_if_spec.rb
deleted file mode 100644
index 1ff689376a..0000000000
--- a/spec/ruby/library/set/sortedset/delete_if_spec.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#delete_if" do
-  before :each do
-    @set = SortedSet["one", "two", "three"]
-  end
-
-  it "yields each Object in self in sorted order" do
-    ret = []
-    @set.delete_if { |x| ret << x }
-    ret.should == ["one", "two", "three"].sort
-  end
-
-  it "deletes every element from self for which the passed block returns true" do
-    @set.delete_if { |x| x.size == 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self" do
-    @set.delete_if { |x| x }.should equal(@set)
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.delete_if
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size == 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/delete_spec.rb b/spec/ruby/library/set/sortedset/delete_spec.rb
deleted file mode 100644
index 71583c7f13..0000000000
--- a/spec/ruby/library/set/sortedset/delete_spec.rb
+++ /dev/null
@@ -1,37 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#delete" do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "deletes the passed Object from self" do
-    @set.delete("a")
-    @set.should_not include("a")
-  end
-
-  it "returns self" do
-    @set.delete("a").should equal(@set)
-    @set.delete("x").should equal(@set)
-  end
-end
-
-describe "SortedSet#delete?" do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "deletes the passed Object from self" do
-    @set.delete?("a")
-    @set.should_not include("a")
-  end
-
-  it "returns self when the passed Object is in self" do
-    @set.delete?("a").should equal(@set)
-  end
-
-  it "returns nil when the passed Object is not in self" do
-    @set.delete?("x").should be_nil
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/difference_spec.rb b/spec/ruby/library/set/sortedset/difference_spec.rb
deleted file mode 100644
index c3d679aff8..0000000000
--- a/spec/ruby/library/set/sortedset/difference_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/difference'
-
-describe "SortedSet#difference" do
-  it_behaves_like :sorted_set_difference, :difference
-end
diff --git a/spec/ruby/library/set/sortedset/divide_spec.rb b/spec/ruby/library/set/sortedset/divide_spec.rb
deleted file mode 100644
index 4b2135a8c9..0000000000
--- a/spec/ruby/library/set/sortedset/divide_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#divide" do
-  it "divides self into a set of subsets based on the blocks return values" do
-    set = SortedSet["one", "two", "three", "four", "five"].divide { |x| x.length }
-    set.map { |x| x.to_a }.to_a.sort.should == [["five", "four"], ["one", "two"], ["three"]]
-  end
-
-  it "yields each Object in self in sorted order" do
-    ret = []
-    SortedSet["one", "two", "three", "four", "five"].divide { |x| ret << x }
-    ret.should == ["one", "two", "three", "four", "five"].sort
-  end
-
-  # BUG: Does not raise a LocalJumpError, but a NoMethodError
-  #
-  # it "raises a LocalJumpError when not passed a block" do
-  #   lambda { SortedSet[1].divide }.should raise_error(LocalJumpError)
-  # end
-end
-
-describe "SortedSet#divide when passed a block with an arity of 2" do
-  it "divides self into a set of subsets based on the blocks return values" do
-    set = SortedSet[1, 3, 4, 6, 9, 10, 11].divide { |x, y| (x - y).abs == 1 }
-    set.map { |x| x.to_a }.to_a.sort.should == [[1], [3, 4], [6], [9, 10, 11]]
-  end
-
-  it "yields each two Objects to the block" do
-    ret = []
-    SortedSet[1, 2].divide { |x, y| ret << [x, y] }
-    ret.should == [[1, 1], [1, 2], [2, 1], [2, 2]]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/each_spec.rb b/spec/ruby/library/set/sortedset/each_spec.rb
deleted file mode 100644
index bcf0d74d1f..0000000000
--- a/spec/ruby/library/set/sortedset/each_spec.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#each" do
-  before :each do
-    @set = SortedSet[1, 2, 3]
-  end
-
-  it "yields each Object in self in sorted order" do
-    ret = []
-    SortedSet["one", "two", "three"].each { |x| ret << x }
-    ret.should == ["one", "two", "three"].sort
-  end
-
-  it "returns self" do
-    @set.each { |x| x }.should equal(@set)
-  end
-
-  it "returns an Enumerator when not passed a block" do
-    enum = @set.each
-
-    ret = []
-    enum.each { |x| ret << x }
-    ret.sort.should == [1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/empty_spec.rb b/spec/ruby/library/set/sortedset/empty_spec.rb
deleted file mode 100644
index deb3b567fb..0000000000
--- a/spec/ruby/library/set/sortedset/empty_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#empty?" do
-  it "returns true if self is empty" do
-    SortedSet[].empty?.should be_true
-    SortedSet[1].empty?.should be_false
-    SortedSet[1,2,3].empty?.should be_false
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/eql_spec.rb b/spec/ruby/library/set/sortedset/eql_spec.rb
deleted file mode 100644
index b22858a362..0000000000
--- a/spec/ruby/library/set/sortedset/eql_spec.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#eql?" do
-  it "returns true when the passed argument is a SortedSet and contains the same elements" do
-    SortedSet[].should eql(SortedSet[])
-    SortedSet[1, 2, 3].should eql(SortedSet[1, 2, 3])
-    SortedSet[1, 2, 3].should eql(SortedSet[3, 2, 1])
-
-#    SortedSet["a", :b, ?c].should eql(SortedSet[?c, :b, "a"])
-
-    SortedSet[1, 2, 3].should_not eql(SortedSet[1.0, 2, 3])
-    SortedSet[1, 2, 3].should_not eql(SortedSet[2, 3])
-    SortedSet[1, 2, 3].should_not eql(SortedSet[])
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/equal_value_spec.rb b/spec/ruby/library/set/sortedset/equal_value_spec.rb
deleted file mode 100644
index cb1b7c9443..0000000000
--- a/spec/ruby/library/set/sortedset/equal_value_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#==" do
-  it "returns true when the passed Object is a SortedSet and self and the Object contain the same elements" do
-    SortedSet[].should == SortedSet[]
-    SortedSet[1, 2, 3].should == SortedSet[1, 2, 3]
-    SortedSet["1", "2", "3"].should == SortedSet["1", "2", "3"]
-
-    SortedSet[1, 2, 3].should_not == SortedSet[1.0, 2, 3]
-    SortedSet[1, 2, 3].should_not == [1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/exclusion_spec.rb b/spec/ruby/library/set/sortedset/exclusion_spec.rb
deleted file mode 100644
index d0f1ab95cb..0000000000
--- a/spec/ruby/library/set/sortedset/exclusion_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#^" do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns a new SortedSet containing elements that are not in both self and the passed Enumerable" do
-    (@set ^ SortedSet[3, 4, 5]).should == SortedSet[1, 2, 5]
-    (@set ^ [3, 4, 5]).should == SortedSet[1, 2, 5]
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { @set ^ 3 }.should raise_error(ArgumentError)
-    -> { @set ^ Object.new }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/filter_spec.rb b/spec/ruby/library/set/sortedset/filter_spec.rb
deleted file mode 100644
index cfaa8b2729..0000000000
--- a/spec/ruby/library/set/sortedset/filter_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/select'
-require 'set'
-
-ruby_version_is "2.6" do
-  describe "SortedSet#filter!" do
-    it_behaves_like :sorted_set_select_bang, :filter!
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/flatten_merge_spec.rb b/spec/ruby/library/set/sortedset/flatten_merge_spec.rb
deleted file mode 100644
index 9a8ed13f00..0000000000
--- a/spec/ruby/library/set/sortedset/flatten_merge_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#flatten_merge" do
-  it "is protected" do
-    SortedSet.should have_protected_instance_method("flatten_merge")
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/flatten_spec.rb b/spec/ruby/library/set/sortedset/flatten_spec.rb
deleted file mode 100644
index ca4e4637e6..0000000000
--- a/spec/ruby/library/set/sortedset/flatten_spec.rb
+++ /dev/null
@@ -1,44 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-# Note: Flatten make little sens on sorted sets, because SortedSets are not (by default)
-# comparable. For a SortedSet to be both valid and nested, we need to define a comparison operator:
-module SortedSet_FlattenSpecs
-  class ComparableSortedSet < SortedSet
-    def <=>(other)
-      return puts "#{other} vs #{self}" unless other.is_a?(ComparableSortedSet)
-      to_a <=> other.to_a
-    end
-  end
-end
-
-describe "SortedSet#flatten" do
-  it "returns a copy of self with each included SortedSet flattened" do
-    klass = SortedSet_FlattenSpecs::ComparableSortedSet
-    set = klass[klass[1,2], klass[3,4], klass[5,6,7], klass[8]]
-    flattened_set = set.flatten
-
-    flattened_set.should_not equal(set)
-    flattened_set.should == klass[1, 2, 3, 4, 5, 6, 7, 8]
-  end
-end
-
-describe "SortedSet#flatten!" do
-  it "flattens self" do
-    klass = SortedSet_FlattenSpecs::ComparableSortedSet
-    set = klass[klass[1,2], klass[3,4], klass[5,6,7], klass[8]]
-    set.flatten!
-    set.should == klass[1, 2, 3, 4, 5, 6, 7, 8]
-  end
-
-  it "returns self when self was modified" do
-    klass = SortedSet_FlattenSpecs::ComparableSortedSet
-    set = klass[klass[1,2], klass[3,4]]
-    set.flatten!.should equal(set)
-  end
-
-  it "returns nil when self was not modified" do
-    set = SortedSet[1, 2, 3, 4]
-    set.flatten!.should be_nil
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/hash_spec.rb b/spec/ruby/library/set/sortedset/hash_spec.rb
deleted file mode 100644
index 7833c68a10..0000000000
--- a/spec/ruby/library/set/sortedset/hash_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#hash" do
-  it "is static" do
-    SortedSet[].hash.should == SortedSet[].hash
-    SortedSet[1, 2, 3].hash.should == SortedSet[1, 2, 3].hash
-    SortedSet["a", "b", "c"].hash.should == SortedSet["c", "b", "a"].hash
-
-    SortedSet[].hash.should_not == SortedSet[1, 2, 3].hash
-    SortedSet[1, 2, 3].hash.should_not == SortedSet["a", "b", "c"].hash
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/include_spec.rb b/spec/ruby/library/set/sortedset/include_spec.rb
deleted file mode 100644
index 030a9e146a..0000000000
--- a/spec/ruby/library/set/sortedset/include_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-describe "SortedSet#include?" do
-  it_behaves_like :sorted_set_include, :include?
-end
diff --git a/spec/ruby/library/set/sortedset/initialize_spec.rb b/spec/ruby/library/set/sortedset/initialize_spec.rb
deleted file mode 100644
index 1238f4efc4..0000000000
--- a/spec/ruby/library/set/sortedset/initialize_spec.rb
+++ /dev/null
@@ -1,30 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#initialize" do
-  it "is private" do
-    SortedSet.should have_private_instance_method("initialize")
-  end
-
-  it "adds all elements of the passed Enumerable to self" do
-    s = SortedSet.new([1, 2, 3])
-    s.size.should eql(3)
-    s.should include(1)
-    s.should include(2)
-    s.should include(3)
-  end
-
-  it "preprocesses all elements by a passed block before adding to self" do
-    s = SortedSet.new([1, 2, 3]) { |x| x * x }
-    s.size.should eql(3)
-    s.should include(1)
-    s.should include(4)
-    s.should include(9)
-  end
-
-  it "raises on incompatible <=> comparison" do
-    # Use #to_a here as elements are sorted only when needed.
-    # Therefore the <=> incompatibility is only noticed on sorting.
-    -> { SortedSet.new(['00', nil]).to_a }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/inspect_spec.rb b/spec/ruby/library/set/sortedset/inspect_spec.rb
deleted file mode 100644
index 7103bee3f5..0000000000
--- a/spec/ruby/library/set/sortedset/inspect_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#inspect" do
-  it "returns a String representation of self" do
-    SortedSet[].inspect.should be_kind_of(String)
-    SortedSet[1, 2, 3].inspect.should be_kind_of(String)
-    SortedSet["1", "2", "3"].inspect.should be_kind_of(String)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/intersection_spec.rb b/spec/ruby/library/set/sortedset/intersection_spec.rb
deleted file mode 100644
index 6ff9c80ce1..0000000000
--- a/spec/ruby/library/set/sortedset/intersection_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/intersection'
-require 'set'
-
-describe "SortedSet#intersection" do
-  it_behaves_like :sorted_set_intersection, :intersection
-end
-
-describe "SortedSet#&" do
-  it_behaves_like :sorted_set_intersection, :&
-end
diff --git a/spec/ruby/library/set/sortedset/keep_if_spec.rb b/spec/ruby/library/set/sortedset/keep_if_spec.rb
deleted file mode 100644
index 2235eb3766..0000000000
--- a/spec/ruby/library/set/sortedset/keep_if_spec.rb
+++ /dev/null
@@ -1,31 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#keep_if" do
-  before :each do
-    @set = SortedSet["one", "two", "three"]
-  end
-
-  it "yields each Object in self in sorted order" do
-    ret = []
-    @set.keep_if { |x| ret << x }
-    ret.should == ["one", "two", "three"].sort
-  end
-
-  it "keeps every element from self for which the passed block returns true" do
-    @set.keep_if { |x| x.size != 3 }
-    @set.to_a.should == ["three"]
-  end
-
-  it "returns self" do
-    @set.keep_if {}.should equal(@set)
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.keep_if
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size != 3 }
-    @set.to_a.should == ["three"]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/length_spec.rb b/spec/ruby/library/set/sortedset/length_spec.rb
deleted file mode 100644
index 5f138dd6f7..0000000000
--- a/spec/ruby/library/set/sortedset/length_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/length'
-require 'set'
-
-describe "SortedSet#length" do
-  it_behaves_like :sorted_set_length, :length
-end
diff --git a/spec/ruby/library/set/sortedset/map_spec.rb b/spec/ruby/library/set/sortedset/map_spec.rb
deleted file mode 100644
index 1d7b5954e5..0000000000
--- a/spec/ruby/library/set/sortedset/map_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/collect'
-
-describe "SortedSet#map!" do
-  it_behaves_like :sorted_set_collect_bang, :map!
-end
diff --git a/spec/ruby/library/set/sortedset/member_spec.rb b/spec/ruby/library/set/sortedset/member_spec.rb
deleted file mode 100644
index d6005557ab..0000000000
--- a/spec/ruby/library/set/sortedset/member_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/include'
-require 'set'
-
-describe "SortedSet#member?" do
-  it_behaves_like :sorted_set_include, :member?
-end
diff --git a/spec/ruby/library/set/sortedset/merge_spec.rb b/spec/ruby/library/set/sortedset/merge_spec.rb
deleted file mode 100644
index 31570ad4db..0000000000
--- a/spec/ruby/library/set/sortedset/merge_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#merge" do
-  it "adds the elements of the passed Enumerable to self" do
-    SortedSet["a", "b"].merge(SortedSet["b", "c", "d"]).should == SortedSet["a", "b", "c", "d"]
-    SortedSet[1, 2].merge([3, 4]).should == SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns self" do
-    set = SortedSet[1, 2]
-    set.merge([3, 4]).should equal(set)
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { SortedSet[1, 2].merge(1) }.should raise_error(ArgumentError)
-    -> { SortedSet[1, 2].merge(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/minus_spec.rb b/spec/ruby/library/set/sortedset/minus_spec.rb
deleted file mode 100644
index ffb8ee85d1..0000000000
--- a/spec/ruby/library/set/sortedset/minus_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-require_relative 'shared/difference'
-
-describe "SortedSet#-" do
-  it_behaves_like :sorted_set_difference, :-
-end
diff --git a/spec/ruby/library/set/sortedset/plus_spec.rb b/spec/ruby/library/set/sortedset/plus_spec.rb
deleted file mode 100644
index 355c775d7e..0000000000
--- a/spec/ruby/library/set/sortedset/plus_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/union'
-require 'set'
-
-describe "SortedSet#+" do
-  it_behaves_like :sorted_set_union, :+
-end
diff --git a/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb b/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb
deleted file mode 100644
index fe15f1bf7d..0000000000
--- a/spec/ruby/library/set/sortedset/pretty_print_cycle_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#pretty_print_cycle" do
-  it "passes the 'pretty print' representation of a self-referencing SortedSet to the pretty print writer" do
-    pp = mock("PrettyPrint")
-    pp.should_receive(:text).with("#<SortedSet: {...}>")
-    SortedSet[1, 2, 3].pretty_print_cycle(pp)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/pretty_print_spec.rb b/spec/ruby/library/set/sortedset/pretty_print_spec.rb
deleted file mode 100644
index 601ff4d182..0000000000
--- a/spec/ruby/library/set/sortedset/pretty_print_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#pretty_print" do
-  it "passes the 'pretty print' representation of self to the pretty print writer" do
-    pp = mock("PrettyPrint")
-    set = SortedSet[1, 2, 3]
-
-    pp.should_receive(:text).with("#<SortedSet: {")
-    pp.should_receive(:text).with("}>")
-
-    pp.should_receive(:nest).with(1).and_yield
-    pp.should_receive(:seplist).with(set)
-
-    set.pretty_print(pp)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/proper_subset_spec.rb b/spec/ruby/library/set/sortedset/proper_subset_spec.rb
deleted file mode 100644
index 818173a7f9..0000000000
--- a/spec/ruby/library/set/sortedset/proper_subset_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#proper_subset?" do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a SortedSet that self is a proper subset of" do
-    SortedSet[].proper_subset?(@set).should be_true
-    SortedSet[].proper_subset?(SortedSet[1, 2, 3]).should be_true
-    SortedSet[].proper_subset?(SortedSet["a", "b", "c"]).should be_true
-
-    SortedSet[1, 2, 3].proper_subset?(@set).should be_true
-    SortedSet[1, 3].proper_subset?(@set).should be_true
-    SortedSet[1, 2].proper_subset?(@set).should be_true
-    SortedSet[1].proper_subset?(@set).should be_true
-
-    SortedSet[5].proper_subset?(@set).should be_false
-    SortedSet[1, 5].proper_subset?(@set).should be_false
-    SortedSet["test"].proper_subset?(@set).should be_false
-
-    @set.proper_subset?(@set).should be_false
-    SortedSet[].proper_subset?(SortedSet[]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-SortedSet" do
-    -> { SortedSet[].proper_subset?([]) }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_subset?(1) }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_subset?("test") }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_subset?(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/proper_superset_spec.rb b/spec/ruby/library/set/sortedset/proper_superset_spec.rb
deleted file mode 100644
index 2699290f0e..0000000000
--- a/spec/ruby/library/set/sortedset/proper_superset_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#proper_superset?" do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a SortedSet that self is a proper superset of" do
-    @set.proper_superset?(SortedSet[]).should be_true
-    SortedSet[1, 2, 3].proper_superset?(SortedSet[]).should be_true
-    SortedSet["a", "b", "c"].proper_superset?(SortedSet[]).should be_true
-
-    @set.proper_superset?(SortedSet[1, 2, 3]).should be_true
-    @set.proper_superset?(SortedSet[1, 3]).should be_true
-    @set.proper_superset?(SortedSet[1, 2]).should be_true
-    @set.proper_superset?(SortedSet[1]).should be_true
-
-    @set.proper_superset?(SortedSet[5]).should be_false
-    @set.proper_superset?(SortedSet[1, 5]).should be_false
-    @set.proper_superset?(SortedSet["test"]).should be_false
-
-    @set.proper_superset?(@set).should be_false
-    SortedSet[].proper_superset?(SortedSet[]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-SortedSet" do
-    -> { SortedSet[].proper_superset?([]) }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_superset?(1) }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_superset?("test") }.should raise_error(ArgumentError)
-    -> { SortedSet[].proper_superset?(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/reject_spec.rb b/spec/ruby/library/set/sortedset/reject_spec.rb
deleted file mode 100644
index da2a76e7a7..0000000000
--- a/spec/ruby/library/set/sortedset/reject_spec.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#reject!" do
-  before :each do
-    @set = SortedSet["one", "two", "three"]
-  end
-
-  it "yields each Object in self in sorted order" do
-    res = []
-    @set.reject! { |x| res << x }
-    res.should == ["one", "two", "three"].sort
-  end
-
-  it "deletes every element from self for which the passed block returns true" do
-    @set.reject! { |x| x.size == 3 }
-    @set.size.should eql(1)
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-
-  it "returns self when self was modified" do
-    @set.reject! { |x| true }.should equal(@set)
-  end
-
-  it "returns nil when self was not modified" do
-    @set.reject! { |x| false }.should be_nil
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.reject!
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size == 3 }
-
-    @set.should_not include("one")
-    @set.should_not include("two")
-    @set.should include("three")
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/replace_spec.rb b/spec/ruby/library/set/sortedset/replace_spec.rb
deleted file mode 100644
index 2a7fa73efb..0000000000
--- a/spec/ruby/library/set/sortedset/replace_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#replace" do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "replaces the contents with other and returns self" do
-    @set.replace(SortedSet[1, 2, 3]).should == @set
-    @set.should == SortedSet[1, 2, 3]
-  end
-
-  it "accepts any enumerable as other" do
-    @set.replace([1, 2, 3]).should == SortedSet[1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/select_spec.rb b/spec/ruby/library/set/sortedset/select_spec.rb
deleted file mode 100644
index 68326cd02c..0000000000
--- a/spec/ruby/library/set/sortedset/select_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/select'
-require 'set'
-
-describe "SortedSet#select!" do
-  it_behaves_like :sorted_set_select_bang, :select!
-end
diff --git a/spec/ruby/library/set/sortedset/shared/add.rb b/spec/ruby/library/set/sortedset/shared/add.rb
deleted file mode 100644
index 95ef1b090e..0000000000
--- a/spec/ruby/library/set/sortedset/shared/add.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-describe :sorted_set_add, shared: true do
-  before :each do
-    @set = SortedSet.new
-  end
-
-  it "adds the passed Object to self" do
-    @set.send(@method, "dog")
-    @set.should include("dog")
-  end
-
-  it "returns self" do
-    @set.send(@method, "dog").should equal(@set)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/collect.rb b/spec/ruby/library/set/sortedset/shared/collect.rb
deleted file mode 100644
index e53304d427..0000000000
--- a/spec/ruby/library/set/sortedset/shared/collect.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-describe :sorted_set_collect_bang, shared: true do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4, 5]
-  end
-
-  it "yields each Object in self in sorted order" do
-    res = []
-    SortedSet["one", "two", "three"].send(@method) { |x| res << x; x }
-    res.should == ["one", "two", "three"].sort
-  end
-
-  it "returns self" do
-    @set.send(@method) { |x| x }.should equal(@set)
-  end
-
-  it "replaces self with the return values of the block" do
-    @set.send(@method) { |x| x * 2 }
-    @set.should == SortedSet[2, 4, 6, 8, 10]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/difference.rb b/spec/ruby/library/set/sortedset/shared/difference.rb
deleted file mode 100644
index 688e23a7a7..0000000000
--- a/spec/ruby/library/set/sortedset/shared/difference.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-describe :sorted_set_difference, shared: true do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "returns a new SortedSet containing self's elements excluding the elements in the passed Enumerable" do
-    @set.send(@method, SortedSet["a", "b"]).should == SortedSet["c"]
-    @set.send(@method, ["b", "c"]).should == SortedSet["a"]
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
-    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/include.rb b/spec/ruby/library/set/sortedset/shared/include.rb
deleted file mode 100644
index cd1758819d..0000000000
--- a/spec/ruby/library/set/sortedset/shared/include.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-describe :sorted_set_include, shared: true do
-  it "returns true when self contains the passed Object" do
-    set = SortedSet["a", "b", "c"]
-    set.send(@method, "a").should be_true
-    set.send(@method, "e").should be_false
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/intersection.rb b/spec/ruby/library/set/sortedset/shared/intersection.rb
deleted file mode 100644
index 045716ad05..0000000000
--- a/spec/ruby/library/set/sortedset/shared/intersection.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-describe :sorted_set_intersection, shared: true do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "returns a new SortedSet containing only elements shared by self and the passed Enumerable" do
-    @set.send(@method, SortedSet["b", "c", "d", "e"]).should == SortedSet["b", "c"]
-    @set.send(@method, ["b", "c", "d"]).should == SortedSet["b", "c"]
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
-    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/length.rb b/spec/ruby/library/set/sortedset/shared/length.rb
deleted file mode 100644
index d1dfee1cff..0000000000
--- a/spec/ruby/library/set/sortedset/shared/length.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-describe :sorted_set_length, shared: true do
-  it "returns the number of elements in the set" do
-    set = SortedSet["a", "b", "c"]
-    set.send(@method).should == 3
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/select.rb b/spec/ruby/library/set/sortedset/shared/select.rb
deleted file mode 100644
index e13311eda5..0000000000
--- a/spec/ruby/library/set/sortedset/shared/select.rb
+++ /dev/null
@@ -1,35 +0,0 @@
-require_relative '../../../../spec_helper'
-require 'set'
-
-describe :sorted_set_select_bang, shared: true do
-  before :each do
-    @set = SortedSet["one", "two", "three"]
-  end
-
-  it "yields each Object in self in sorted order" do
-    res = []
-    @set.send(@method) { |x| res << x }
-    res.should == ["one", "two", "three"].sort
-  end
-
-  it "keeps every element from self for which the passed block returns true" do
-    @set.send(@method) { |x| x.size != 3 }
-    @set.to_a.should == ["three"]
-  end
-
-  it "returns self when self was modified" do
-    @set.send(@method) { false }.should equal(@set)
-  end
-
-  it "returns nil when self was not modified" do
-    @set.send(@method) { true }.should be_nil
-  end
-
-  it "returns an Enumerator when passed no block" do
-    enum = @set.send(@method)
-    enum.should be_an_instance_of(Enumerator)
-
-    enum.each { |x| x.size != 3 }
-    @set.to_a.should == ["three"]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/shared/union.rb b/spec/ruby/library/set/sortedset/shared/union.rb
deleted file mode 100644
index 9015bdc8e3..0000000000
--- a/spec/ruby/library/set/sortedset/shared/union.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-describe :sorted_set_union, shared: true do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "returns a new SortedSet containing all elements of self and the passed Enumerable" do
-    @set.send(@method, SortedSet["b", "d", "e"]).should == SortedSet["a", "b", "c", "d", "e"]
-    @set.send(@method, ["b", "e"]).should == SortedSet["a", "b", "c", "e"]
-  end
-
-  it "raises an ArgumentError when passed a non-Enumerable" do
-    -> { @set.send(@method, 1) }.should raise_error(ArgumentError)
-    -> { @set.send(@method, Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/size_spec.rb b/spec/ruby/library/set/sortedset/size_spec.rb
deleted file mode 100644
index 13e5085b0c..0000000000
--- a/spec/ruby/library/set/sortedset/size_spec.rb
+++ /dev/null
@@ -1,7 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/length'
-require 'set'
-
-describe "SortedSet#size" do
-  it_behaves_like :sorted_set_length, :size
-end
diff --git a/spec/ruby/library/set/sortedset/subset_spec.rb b/spec/ruby/library/set/sortedset/subset_spec.rb
deleted file mode 100644
index 7768692df6..0000000000
--- a/spec/ruby/library/set/sortedset/subset_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#subset?" do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a SortedSet that is equal to self or self is a subset of" do
-    @set.subset?(@set).should be_true
-    SortedSet[].subset?(SortedSet[]).should be_true
-
-    SortedSet[].subset?(@set).should be_true
-    SortedSet[].subset?(SortedSet[1, 2, 3]).should be_true
-    SortedSet[].subset?(SortedSet["a", "b", "c"]).should be_true
-
-    SortedSet[1, 2, 3].subset?(@set).should be_true
-    SortedSet[1, 3].subset?(@set).should be_true
-    SortedSet[1, 2].subset?(@set).should be_true
-    SortedSet[1].subset?(@set).should be_true
-
-    SortedSet[5].subset?(@set).should be_false
-    SortedSet[1, 5].subset?(@set).should be_false
-    SortedSet["test"].subset?(@set).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-SortedSet" do
-    -> { SortedSet[].subset?([]) }.should raise_error(ArgumentError)
-    -> { SortedSet[].subset?(1) }.should raise_error(ArgumentError)
-    -> { SortedSet[].subset?("test") }.should raise_error(ArgumentError)
-    -> { SortedSet[].subset?(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/subtract_spec.rb b/spec/ruby/library/set/sortedset/subtract_spec.rb
deleted file mode 100644
index 64d66c3688..0000000000
--- a/spec/ruby/library/set/sortedset/subtract_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#subtract" do
-  before :each do
-    @set = SortedSet["a", "b", "c"]
-  end
-
-  it "deletes any elements contained in other and returns self" do
-    @set.subtract(SortedSet["b", "c"]).should == @set
-    @set.should == SortedSet["a"]
-  end
-
-  it "accepts any enumerable as other" do
-    @set.subtract(["c"]).should == SortedSet["a", "b"]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/superset_spec.rb b/spec/ruby/library/set/sortedset/superset_spec.rb
deleted file mode 100644
index 823781b860..0000000000
--- a/spec/ruby/library/set/sortedset/superset_spec.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#superset?" do
-  before :each do
-    @set = SortedSet[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a SortedSet that equals self or self is a proper superset of" do
-    @set.superset?(@set).should be_true
-    SortedSet[].superset?(SortedSet[]).should be_true
-
-    @set.superset?(SortedSet[]).should be_true
-    SortedSet[1, 2, 3].superset?(SortedSet[]).should be_true
-    SortedSet["a", "b", "c"].superset?(SortedSet[]).should be_true
-
-    @set.superset?(SortedSet[1, 2, 3]).should be_true
-    @set.superset?(SortedSet[1, 3]).should be_true
-    @set.superset?(SortedSet[1, 2]).should be_true
-    @set.superset?(SortedSet[1]).should be_true
-
-    @set.superset?(SortedSet[5]).should be_false
-    @set.superset?(SortedSet[1, 5]).should be_false
-    @set.superset?(SortedSet["test"]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-SortedSet" do
-    -> { SortedSet[].superset?([]) }.should raise_error(ArgumentError)
-    -> { SortedSet[].superset?(1) }.should raise_error(ArgumentError)
-    -> { SortedSet[].superset?("test") }.should raise_error(ArgumentError)
-    -> { SortedSet[].superset?(Object.new) }.should raise_error(ArgumentError)
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/to_a_spec.rb b/spec/ruby/library/set/sortedset/to_a_spec.rb
deleted file mode 100644
index ba37d18cdb..0000000000
--- a/spec/ruby/library/set/sortedset/to_a_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../../spec_helper'
-require 'set'
-
-describe "SortedSet#to_a" do
-  it "returns an array containing elements" do
-    set = SortedSet.new [1, 2, 3]
-    set.to_a.should == [1, 2, 3]
-  end
-
-  it "returns a sorted array containing elements" do
-    set = SortedSet[2, 3, 1]
-    set.to_a.should == [1, 2, 3]
-
-    set = SortedSet.new [5, 6, 4, 4]
-    set.to_a.should == [4, 5, 6]
-  end
-end
diff --git a/spec/ruby/library/set/sortedset/union_spec.rb b/spec/ruby/library/set/sortedset/union_spec.rb
deleted file mode 100644
index eb77600fee..0000000000
--- a/spec/ruby/library/set/sortedset/union_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../../spec_helper'
-require_relative 'shared/union'
-require 'set'
-
-describe "SortedSet#union" do
-  it_behaves_like :sorted_set_union, :union
-end
-
-describe "SortedSet#|" do
-  it_behaves_like :sorted_set_union, :|
-end
diff --git a/spec/ruby/library/set/subset_spec.rb b/spec/ruby/library/set/subset_spec.rb
deleted file mode 100644
index f375efa6df..0000000000
--- a/spec/ruby/library/set/subset_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#subset?" do
-  before :each do
-    @set = Set[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a Set that is equal to self or self is a subset of" do
-    @set.subset?(@set).should be_true
-    Set[].subset?(Set[]).should be_true
-
-    Set[].subset?(@set).should be_true
-    Set[].subset?(Set[1, 2, 3]).should be_true
-    Set[].subset?(Set["a", :b, ?c]).should be_true
-
-    Set[1, 2, 3].subset?(@set).should be_true
-    Set[1, 3].subset?(@set).should be_true
-    Set[1, 2].subset?(@set).should be_true
-    Set[1].subset?(@set).should be_true
-
-    Set[5].subset?(@set).should be_false
-    Set[1, 5].subset?(@set).should be_false
-    Set[nil].subset?(@set).should be_false
-    Set["test"].subset?(@set).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-Set" do
-    -> { Set[].subset?([]) }.should raise_error(ArgumentError)
-    -> { Set[].subset?(1) }.should raise_error(ArgumentError)
-    -> { Set[].subset?("test") }.should raise_error(ArgumentError)
-    -> { Set[].subset?(Object.new) }.should raise_error(ArgumentError)
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true if passed a Set-like object that self is a subset of" do
-      Set[1, 2, 3].subset?(SetSpecs::SetLike.new([1, 2, 3, 4])).should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/set/subtract_spec.rb b/spec/ruby/library/set/subtract_spec.rb
deleted file mode 100644
index 56713de8b3..0000000000
--- a/spec/ruby/library/set/subtract_spec.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#subtract" do
-  before :each do
-    @set = Set[:a, :b, :c]
-  end
-
-  it "deletes any elements contained in other and returns self" do
-    @set.subtract(Set[:b, :c]).should == @set
-    @set.should == Set[:a]
-  end
-
-  it "accepts any enumerable as other" do
-    @set.subtract([:c]).should == Set[:a, :b]
-  end
-end
diff --git a/spec/ruby/library/set/superset_spec.rb b/spec/ruby/library/set/superset_spec.rb
deleted file mode 100644
index bd9d2f3eee..0000000000
--- a/spec/ruby/library/set/superset_spec.rb
+++ /dev/null
@@ -1,41 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/set_like'
-require 'set'
-
-describe "Set#superset?" do
-  before :each do
-    @set = Set[1, 2, 3, 4]
-  end
-
-  it "returns true if passed a Set that equals self or self is a proper superset of" do
-    @set.superset?(@set).should be_true
-    Set[].superset?(Set[]).should be_true
-
-    @set.superset?(Set[]).should be_true
-    Set[1, 2, 3].superset?(Set[]).should be_true
-    Set["a", :b, ?c].superset?(Set[]).should be_true
-
-    @set.superset?(Set[1, 2, 3]).should be_true
-    @set.superset?(Set[1, 3]).should be_true
-    @set.superset?(Set[1, 2]).should be_true
-    @set.superset?(Set[1]).should be_true
-
-    @set.superset?(Set[5]).should be_false
-    @set.superset?(Set[1, 5]).should be_false
-    @set.superset?(Set[nil]).should be_false
-    @set.superset?(Set["test"]).should be_false
-  end
-
-  it "raises an ArgumentError when passed a non-Set" do
-    -> { Set[].superset?([]) }.should raise_error(ArgumentError)
-    -> { Set[].superset?(1) }.should raise_error(ArgumentError)
-    -> { Set[].superset?("test") }.should raise_error(ArgumentError)
-    -> { Set[].superset?(Object.new) }.should raise_error(ArgumentError)
-  end
-
-  context "when comparing to a Set-like object" do
-    it "returns true if passed a Set-like object that self is a superset of" do
-      Set[1, 2, 3, 4].superset?(SetSpecs::SetLike.new([1, 2, 3])).should be_true
-    end
-  end
-end
diff --git a/spec/ruby/library/set/to_a_spec.rb b/spec/ruby/library/set/to_a_spec.rb
deleted file mode 100644
index 689e44f38a..0000000000
--- a/spec/ruby/library/set/to_a_spec.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-require_relative '../../spec_helper'
-require 'set'
-
-describe "Set#to_a" do
-  it "returns an array containing elements of self" do
-    Set[1, 2, 3].to_a.sort.should == [1, 2, 3]
-  end
-end
diff --git a/spec/ruby/library/set/to_s_spec.rb b/spec/ruby/library/set/to_s_spec.rb
deleted file mode 100644
index ca2806d669..0000000000
--- a/spec/ruby/library/set/to_s_spec.rb
+++ /dev/null
@@ -1,13 +0,0 @@
-require_relative 'shared/inspect'
-require 'set'
-
-ruby_version_is "2.5" do
-  describe "Set#to_s" do
-    it_behaves_like :set_inspect, :to_s
-
-    it "is an alias of inspect" do
-      set = Set.new
-      set.method(:to_s).should == set.method(:inspect)
-    end
-  end
-end
diff --git a/spec/ruby/library/set/union_spec.rb b/spec/ruby/library/set/union_spec.rb
deleted file mode 100644
index 20fe0ddca3..0000000000
--- a/spec/ruby/library/set/union_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/union'
-require 'set'
-
-describe "Set#union" do
-  it_behaves_like :set_union, :union
-end
-
-describe "Set#|" do
-  it_behaves_like :set_union, :|
-end
diff --git a/spec/ruby/library/shellwords/shellwords_spec.rb b/spec/ruby/library/shellwords/shellwords_spec.rb
index 2975fd9974..fe86b6faab 100644
--- a/spec/ruby/library/shellwords/shellwords_spec.rb
+++ b/spec/ruby/library/shellwords/shellwords_spec.rb
@@ -1,34 +1,33 @@
 require_relative '../../spec_helper'
 require 'shellwords'
-include Shellwords
 
 describe "Shellwords#shellwords" do
   it "honors quoted strings" do
-    shellwords('a "b b" a').should == ['a', 'b b', 'a']
+    Shellwords.shellwords('a "b b" a').should == ['a', 'b b', 'a']
   end
 
   it "honors escaped double quotes" do
-    shellwords('a "\"b\" c" d').should == ['a', '"b" c', 'd']
+    Shellwords.shellwords('a "\"b\" c" d').should == ['a', '"b" c', 'd']
   end
 
   it "honors escaped single quotes" do
-    shellwords("a \"'b' c\" d").should == ['a', "'b' c", 'd']
+    Shellwords.shellwords("a \"'b' c\" d").should == ['a', "'b' c", 'd']
   end
 
   it "honors escaped spaces" do
-    shellwords('a b\ c d').should == ['a', 'b c', 'd']
+    Shellwords.shellwords('a b\ c d').should == ['a', 'b c', 'd']
   end
 
   it "raises ArgumentError when double quoted strings are misquoted" do
-    -> { shellwords('a "b c d e') }.should raise_error(ArgumentError)
+    -> { Shellwords.shellwords('a "b c d e') }.should raise_error(ArgumentError)
   end
 
   it "raises ArgumentError when single quoted strings are misquoted" do
-    -> { shellwords("a 'b c d e") }.should raise_error(ArgumentError)
+    -> { Shellwords.shellwords("a 'b c d e") }.should raise_error(ArgumentError)
   end
 
   # https://bugs.ruby-lang.org/issues/10055
   it "matches POSIX sh behavior for backslashes within double quoted strings" do
-    shellsplit('printf "%s\n"').should == ['printf', '%s\n']
+    Shellwords.shellsplit('printf "%s\n"').should == ['printf', '%s\n']
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/afamily_spec.rb b/spec/ruby/library/socket/addrinfo/afamily_spec.rb
index 7229dab9de..5d075be057 100644
--- a/spec/ruby/library/socket/addrinfo/afamily_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/afamily_spec.rb
@@ -23,15 +23,13 @@ describe "Addrinfo#afamily" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
-
-      it "returns Socket::AF_UNIX" do
-        @addrinfo.afamily.should == Socket::AF_UNIX
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
+
+    it "returns Socket::AF_UNIX" do
+      @addrinfo.afamily.should == Socket::AF_UNIX
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/family_addrinfo_spec.rb b/spec/ruby/library/socket/addrinfo/family_addrinfo_spec.rb
index 2bc3b6a2e3..3c2f9f73d8 100644
--- a/spec/ruby/library/socket/addrinfo/family_addrinfo_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/family_addrinfo_spec.rb
@@ -50,38 +50,36 @@ describe 'Addrinfo#family_addrinfo' do
       end
     end
 
-    with_feature :unix_socket do
-      describe 'with a UNIX Addrinfo' do
-        before do
-          @source = Addrinfo.unix('cats')
-        end
+    describe 'with a UNIX Addrinfo' do
+      before do
+        @source = Addrinfo.unix('cats')
+      end
 
-        it 'raises ArgumentError if more than 1 argument is given' do
-          -> { @source.family_addrinfo('foo', 'bar') }.should raise_error(ArgumentError)
-        end
+      it 'raises ArgumentError if more than 1 argument is given' do
+        -> { @source.family_addrinfo('foo', 'bar') }.should raise_error(ArgumentError)
+      end
 
-        it 'returns an Addrinfo when a UNIX socket path is given' do
-          addr = @source.family_addrinfo('dogs')
+      it 'returns an Addrinfo when a UNIX socket path is given' do
+        addr = @source.family_addrinfo('dogs')
 
-          addr.should be_an_instance_of(Addrinfo)
-        end
+        addr.should be_an_instance_of(Addrinfo)
+      end
 
-        describe 'the returned Addrinfo' do
-          before do
-            @addr = @source.family_addrinfo('dogs')
-          end
+      describe 'the returned Addrinfo' do
+        before do
+          @addr = @source.family_addrinfo('dogs')
+        end
 
-          it 'uses AF_UNIX as the address family' do
-            @addr.afamily.should == Socket::AF_UNIX
-          end
+        it 'uses AF_UNIX as the address family' do
+          @addr.afamily.should == Socket::AF_UNIX
+        end
 
-          it 'uses PF_UNIX as the protocol family' do
-            @addr.pfamily.should == Socket::PF_UNIX
-          end
+        it 'uses PF_UNIX as the protocol family' do
+          @addr.pfamily.should == Socket::PF_UNIX
+        end
 
-          it 'uses the given socket path' do
-            @addr.unix_path.should == 'dogs'
-          end
+        it 'uses the given socket path' do
+          @addr.unix_path.should == 'dogs'
         end
       end
     end
diff --git a/spec/ruby/library/socket/addrinfo/getaddrinfo_spec.rb b/spec/ruby/library/socket/addrinfo/getaddrinfo_spec.rb
index 67fad73815..e05fe9967a 100644
--- a/spec/ruby/library/socket/addrinfo/getaddrinfo_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/getaddrinfo_spec.rb
@@ -73,19 +73,15 @@ describe 'Addrinfo.getaddrinfo' do
     end
   end
 
-  platform_is_not :'solaris2.10' do # i386-solaris
-    it 'sets a custom socket protocol of the Addrinfo instances' do
-      array = Addrinfo.getaddrinfo('127.0.0.1', 80, nil, nil, Socket::IPPROTO_UDP)
+  it 'sets a custom socket protocol of the Addrinfo instances' do
+    array = Addrinfo.getaddrinfo('127.0.0.1', 80, nil, nil, Socket::IPPROTO_UDP)
 
-      array[0].protocol.should == Socket::IPPROTO_UDP
-    end
+    array[0].protocol.should == Socket::IPPROTO_UDP
   end
 
-  platform_is_not :solaris do
-    it 'sets the canonical name when AI_CANONNAME is given as a flag' do
-      array = Addrinfo.getaddrinfo('localhost', 80, nil, nil, nil, Socket::AI_CANONNAME)
+  it 'sets the canonical name when AI_CANONNAME is given as a flag' do
+    array = Addrinfo.getaddrinfo('localhost', 80, nil, nil, nil, Socket::AI_CANONNAME)
 
-      array[0].canonname.should be_an_instance_of(String)
-    end
+    array[0].canonname.should be_an_instance_of(String)
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/getnameinfo_spec.rb b/spec/ruby/library/socket/addrinfo/getnameinfo_spec.rb
index c5284f1c0f..43b5a2000a 100644
--- a/spec/ruby/library/socket/addrinfo/getnameinfo_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/getnameinfo_spec.rb
@@ -21,7 +21,7 @@ describe 'Addrinfo#getnameinfo' do
   end
 
   platform_is :linux do
-    with_feature :unix_socket do
+    platform_is_not :android do
       describe 'using a UNIX Addrinfo' do
         before do
           @addr = Addrinfo.unix('cats')
diff --git a/spec/ruby/library/socket/addrinfo/initialize_spec.rb b/spec/ruby/library/socket/addrinfo/initialize_spec.rb
index 8354553f61..1f16531aaa 100644
--- a/spec/ruby/library/socket/addrinfo/initialize_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/initialize_spec.rb
@@ -17,7 +17,7 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 25
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the UNSPEC pfamily" do
         @addrinfo.pfamily.should == Socket::PF_UNSPEC
       end
 
@@ -53,7 +53,7 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 25
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET6 pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET6
       end
 
@@ -83,7 +83,7 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 25
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET6 pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET6
       end
 
@@ -91,7 +91,7 @@ describe "Addrinfo#initialize" do
         @addrinfo.afamily.should == Socket::AF_INET6
       end
 
-      it "returns the 0 socket type" do
+      it "returns the specified socket type" do
         @addrinfo.socktype.should == Socket::SOCK_STREAM
       end
 
@@ -113,7 +113,7 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 25
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET6 pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET6
       end
 
@@ -147,11 +147,11 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 46102
       end
 
-      it "returns the Socket::PF_INET pfamily" do
+      it "returns the INET pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET
       end
 
-      it "returns the INET6 afamily" do
+      it "returns the INET afamily" do
         @addrinfo.afamily.should == Socket::AF_INET
       end
 
@@ -217,11 +217,11 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 46102
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET
       end
 
-      it "returns the INET6 afamily" do
+      it "returns the INET afamily" do
         @addrinfo.afamily.should == Socket::AF_INET
       end
 
@@ -247,11 +247,11 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 46102
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET
       end
 
-      it "returns the INET6 afamily" do
+      it "returns the INET afamily" do
         @addrinfo.afamily.should == Socket::AF_INET
       end
 
@@ -274,15 +274,17 @@ describe "Addrinfo#initialize" do
         end
       end
 
-      with_feature :sock_packet do
-        [:SOCK_SEQPACKET].each do |type|
-          it "overwrites the socket type #{type}" do
-            sockaddr = ['AF_INET', 80, 'hostname', '127.0.0.1']
+      platform_is_not :android do
+        with_feature :sock_packet do
+          [:SOCK_SEQPACKET].each do |type|
+            it "overwrites the socket type #{type}" do
+              sockaddr = ['AF_INET', 80, 'hostname', '127.0.0.1']
 
-            value = Socket.const_get(type)
-            addr  = Addrinfo.new(sockaddr, nil, value)
+              value = Socket.const_get(type)
+              addr  = Addrinfo.new(sockaddr, nil, value)
 
-            addr.socktype.should == value
+              addr.socktype.should == value
+            end
           end
         end
       end
@@ -309,11 +311,11 @@ describe "Addrinfo#initialize" do
         @addrinfo.ip_port.should == 46102
       end
 
-      it "returns the Socket::UNSPEC pfamily" do
+      it "returns the INET pfamily" do
         @addrinfo.pfamily.should == Socket::PF_INET
       end
 
-      it "returns the INET6 afamily" do
+      it "returns the INET afamily" do
         @addrinfo.afamily.should == Socket::AF_INET
       end
 
@@ -333,7 +335,7 @@ describe "Addrinfo#initialize" do
         @sockaddr = ['AF_INET6', 80, 'hostname', '127.0.0.1']
       end
 
-      it "raises SocketError when using any Socket constant except except AF_INET(6)/PF_INET(6)" do
+      it "raises SocketError when using any Socket constant except AF_INET(6)/PF_INET(6)" do
         Socket.constants.grep(/(^AF_|^PF_)(?!INET)/).each do |constant|
           value = Socket.const_get(constant)
           -> {
@@ -360,7 +362,7 @@ describe "Addrinfo#initialize" do
           end
         end
 
-        platform_is_not :windows, :aix, :solaris do
+        platform_is_not :windows, :aix do
           (Socket.constants.grep(/^IPPROTO/) - valid).each do |type|
             it "raises SocketError when using #{type}" do
               value = Socket.const_get(type)
@@ -388,7 +390,7 @@ describe "Addrinfo#initialize" do
           end
         end
 
-        platform_is_not :windows, :aix, :solaris do
+        platform_is_not :windows, :aix do
           (Socket.constants.grep(/^IPPROTO/) - valid).each do |type|
             it "raises SocketError when using #{type}" do
               value = Socket.const_get(type)
@@ -448,28 +450,30 @@ describe "Addrinfo#initialize" do
       end
 
       platform_is :linux do
-        describe 'and the socket type is set to SOCK_SEQPACKET' do
-          before do
-            @socktype = Socket::SOCK_SEQPACKET
-          end
+        platform_is_not :android do
+          describe 'and the socket type is set to SOCK_SEQPACKET' do
+            before do
+              @socktype = Socket::SOCK_SEQPACKET
+            end
 
-          valid = [:IPPROTO_IP, :IPPROTO_HOPOPTS]
+            valid = [:IPPROTO_IP, :IPPROTO_HOPOPTS]
 
-          valid.each do |type|
-            it "overwrites the protocol when using #{type}" do
-              value = Socket.const_get(type)
-              addr  = Addrinfo.new(@sockaddr, nil, @socktype, value)
+            valid.each do |type|
+              it "overwrites the protocol when using #{type}" do
+                value = Socket.const_get(type)
+                addr  = Addrinfo.new(@sockaddr, nil, @socktype, value)
 
-              addr.protocol.should == value
+                addr.protocol.should == value
+              end
             end
-          end
 
-          (Socket.constants.grep(/^IPPROTO/) - valid).each do |type|
-            it "raises SocketError when using #{type}" do
-              value = Socket.const_get(type)
-              block = -> { Addrinfo.new(@sockaddr, nil, @socktype, value) }
+            (Socket.constants.grep(/^IPPROTO/) - valid).each do |type|
+              it "raises SocketError when using #{type}" do
+                value = Socket.const_get(type)
+                block = -> { Addrinfo.new(@sockaddr, nil, @socktype, value) }
 
-              block.should raise_error(SocketError)
+                block.should raise_error(SocketError)
+              end
             end
           end
         end
@@ -491,7 +495,7 @@ describe "Addrinfo#initialize" do
           end
         end
 
-        platform_is_not :windows, :aix, :solaris do
+        platform_is_not :windows, :aix do
           (Socket.constants.grep(/^IPPROTO/) - valid).each do |type|
             it "raises SocketError when using #{type}" do
               value = Socket.const_get(type)
@@ -510,13 +514,13 @@ describe "Addrinfo#initialize" do
       @sockaddr = Socket.sockaddr_in(80, '127.0.0.1')
     end
 
-    it 'returns an Addrinfo with :PF_INET  family' do
+    it 'returns an Addrinfo with :PF_INET family' do
       addr = Addrinfo.new(@sockaddr, :PF_INET)
 
       addr.pfamily.should == Socket::PF_INET
     end
 
-    it 'returns an Addrinfo with :INET  family' do
+    it 'returns an Addrinfo with :INET family' do
       addr = Addrinfo.new(@sockaddr, :INET)
 
       addr.pfamily.should == Socket::PF_INET
@@ -540,13 +544,13 @@ describe "Addrinfo#initialize" do
       @sockaddr = Socket.sockaddr_in(80, '127.0.0.1')
     end
 
-    it 'returns an Addrinfo with "PF_INET"  family' do
+    it 'returns an Addrinfo with "PF_INET" family' do
       addr = Addrinfo.new(@sockaddr, 'PF_INET')
 
       addr.pfamily.should == Socket::PF_INET
     end
 
-    it 'returns an Addrinfo with "INET"  family' do
+    it 'returns an Addrinfo with "INET" family' do
       addr = Addrinfo.new(@sockaddr, 'INET')
 
       addr.pfamily.should == Socket::PF_INET
@@ -565,23 +569,21 @@ describe "Addrinfo#initialize" do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using separate arguments for a Unix socket' do
-      before do
-        @sockaddr = Socket.pack_sockaddr_un('socket')
-      end
+  describe 'using separate arguments for a Unix socket' do
+    before do
+      @sockaddr = Socket.pack_sockaddr_un('socket')
+    end
 
-      it 'returns an Addrinfo with the correct unix path' do
-        Addrinfo.new(@sockaddr).unix_path.should == 'socket'
-      end
+    it 'returns an Addrinfo with the correct unix path' do
+      Addrinfo.new(@sockaddr).unix_path.should == 'socket'
+    end
 
-      it 'returns an Addrinfo with the correct protocol family' do
-        Addrinfo.new(@sockaddr).pfamily.should == Socket::PF_UNSPEC
-      end
+    it 'returns an Addrinfo with the correct protocol family' do
+      Addrinfo.new(@sockaddr).pfamily.should == Socket::PF_UNSPEC
+    end
 
-      it 'returns an Addrinfo with the correct address family' do
-        Addrinfo.new(@sockaddr).afamily.should == Socket::AF_UNIX
-      end
+    it 'returns an Addrinfo with the correct address family' do
+      Addrinfo.new(@sockaddr).afamily.should == Socket::AF_UNIX
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/inspect_sockaddr_spec.rb b/spec/ruby/library/socket/addrinfo/inspect_sockaddr_spec.rb
index 70ca4dd4d7..6b18c79469 100644
--- a/spec/ruby/library/socket/addrinfo/inspect_sockaddr_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/inspect_sockaddr_spec.rb
@@ -32,19 +32,17 @@ describe 'Addrinfo#inspect_sockaddr' do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using a UNIX path' do
-      it 'returns a String containing the UNIX path' do
-        addr = Addrinfo.unix('/foo/bar')
+  describe 'using a UNIX path' do
+    it 'returns a String containing the UNIX path' do
+      addr = Addrinfo.unix('/foo/bar')
 
-        addr.inspect_sockaddr.should == '/foo/bar'
-      end
+      addr.inspect_sockaddr.should == '/foo/bar'
+    end
 
-      it 'returns a String containing the UNIX path when using a relative path' do
-        addr = Addrinfo.unix('foo')
+    it 'returns a String containing the UNIX path when using a relative path' do
+      addr = Addrinfo.unix('foo')
 
-        addr.inspect_sockaddr.should == 'UNIX foo'
-      end
+      addr.inspect_sockaddr.should == 'UNIX foo'
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/inspect_spec.rb b/spec/ruby/library/socket/addrinfo/inspect_spec.rb
index 98e1e83ffa..1442af6162 100644
--- a/spec/ruby/library/socket/addrinfo/inspect_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/inspect_spec.rb
@@ -41,25 +41,23 @@ describe 'Addrinfo#inspect' do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using a UNIX Addrinfo' do
-      it 'returns a String' do
-        addr = Addrinfo.unix('/foo')
+  describe 'using a UNIX Addrinfo' do
+    it 'returns a String' do
+      addr = Addrinfo.unix('/foo')
 
-        addr.inspect.should == '#<Addrinfo: /foo SOCK_STREAM>'
-      end
+      addr.inspect.should == '#<Addrinfo: /foo SOCK_STREAM>'
+    end
 
-      it 'returns a String when using a relative UNIX path' do
-        addr = Addrinfo.unix('foo')
+    it 'returns a String when using a relative UNIX path' do
+      addr = Addrinfo.unix('foo')
 
-        addr.inspect.should == '#<Addrinfo: UNIX foo SOCK_STREAM>'
-      end
+      addr.inspect.should == '#<Addrinfo: UNIX foo SOCK_STREAM>'
+    end
 
-      it 'returns a String when using a DGRAM socket' do
-        addr = Addrinfo.unix('/foo', Socket::SOCK_DGRAM)
+    it 'returns a String when using a DGRAM socket' do
+      addr = Addrinfo.unix('/foo', Socket::SOCK_DGRAM)
 
-        addr.inspect.should == '#<Addrinfo: /foo SOCK_DGRAM>'
-      end
+      addr.inspect.should == '#<Addrinfo: /foo SOCK_DGRAM>'
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ip_address_spec.rb b/spec/ruby/library/socket/addrinfo/ip_address_spec.rb
index 4522cf5cfd..193432e861 100644
--- a/spec/ruby/library/socket/addrinfo/ip_address_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ip_address_spec.rb
@@ -21,15 +21,13 @@ describe "Addrinfo#ip_address" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "raises an exception" do
-        -> { @addrinfo.ip_address }.should raise_error(SocketError)
-      end
+    it "raises an exception" do
+      -> { @addrinfo.ip_address }.should raise_error(SocketError)
     end
   end
 
diff --git a/spec/ruby/library/socket/addrinfo/ip_port_spec.rb b/spec/ruby/library/socket/addrinfo/ip_port_spec.rb
index 4118607db0..f10ce35143 100644
--- a/spec/ruby/library/socket/addrinfo/ip_port_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ip_port_spec.rb
@@ -21,15 +21,13 @@ describe "Addrinfo#ip_port" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "raises an exception" do
-        -> { @addrinfo.ip_port }.should raise_error(SocketError)
-      end
+    it "raises an exception" do
+      -> { @addrinfo.ip_port }.should raise_error(SocketError)
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ip_spec.rb b/spec/ruby/library/socket/addrinfo/ip_spec.rb
index 80e7a62df7..09b9341605 100644
--- a/spec/ruby/library/socket/addrinfo/ip_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ip_spec.rb
@@ -22,15 +22,13 @@ describe "Addrinfo#ip?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ip?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ip?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ip_unpack_spec.rb b/spec/ruby/library/socket/addrinfo/ip_unpack_spec.rb
index 6c81c48d1c..58260c4557 100644
--- a/spec/ruby/library/socket/addrinfo/ip_unpack_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ip_unpack_spec.rb
@@ -21,15 +21,13 @@ describe "Addrinfo#ip_unpack" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "raises an exception" do
-        -> { @addrinfo.ip_unpack }.should raise_error(SocketError)
-      end
+    it "raises an exception" do
+      -> { @addrinfo.ip_unpack }.should raise_error(SocketError)
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv4_loopback_spec.rb b/spec/ruby/library/socket/addrinfo/ipv4_loopback_spec.rb
index f5bab711db..3a584d4f52 100644
--- a/spec/ruby/library/socket/addrinfo/ipv4_loopback_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv4_loopback_spec.rb
@@ -3,10 +3,10 @@ require_relative '../spec_helper'
 describe "Addrinfo#ipv4_loopback?" do
   describe "for an ipv4 socket" do
     it "returns true for the loopback address" do
-      Addrinfo.ip('127.0.0.1').ipv4_loopback?.should == true
-      Addrinfo.ip('127.0.0.2').ipv4_loopback?.should == true
-      Addrinfo.ip('127.255.0.1').ipv4_loopback?.should == true
-      Addrinfo.ip('127.255.255.255').ipv4_loopback?.should == true
+      Addrinfo.ip('127.0.0.1').should.ipv4_loopback?
+      Addrinfo.ip('127.0.0.2').should.ipv4_loopback?
+      Addrinfo.ip('127.255.0.1').should.ipv4_loopback?
+      Addrinfo.ip('127.255.255.255').should.ipv4_loopback?
     end
 
     it "returns false for another address" do
@@ -29,15 +29,13 @@ describe "Addrinfo#ipv4_loopback?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv4_loopback?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv4_loopback?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv4_multicast_spec.rb b/spec/ruby/library/socket/addrinfo/ipv4_multicast_spec.rb
index bdd14c1b00..e4b4cfcc84 100644
--- a/spec/ruby/library/socket/addrinfo/ipv4_multicast_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv4_multicast_spec.rb
@@ -2,28 +2,26 @@ require_relative '../spec_helper'
 
 describe "Addrinfo#ipv4_multicast?" do
   it 'returns true for a multicast address' do
-    Addrinfo.ip('224.0.0.0').ipv4_multicast?.should == true
-    Addrinfo.ip('224.0.0.9').ipv4_multicast?.should == true
-    Addrinfo.ip('239.255.255.250').ipv4_multicast?.should == true
+    Addrinfo.ip('224.0.0.0').should.ipv4_multicast?
+    Addrinfo.ip('224.0.0.9').should.ipv4_multicast?
+    Addrinfo.ip('239.255.255.250').should.ipv4_multicast?
   end
 
   it 'returns false for a regular address' do
-    Addrinfo.ip('8.8.8.8').ipv4_multicast?.should == false
+    Addrinfo.ip('8.8.8.8').should_not.ipv4_multicast?
   end
 
   it 'returns false for an IPv6 address' do
-    Addrinfo.ip('::1').ipv4_multicast?.should == false
+    Addrinfo.ip('::1').should_not.ipv4_multicast?
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv4_multicast?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv4_multicast?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv4_private_spec.rb b/spec/ruby/library/socket/addrinfo/ipv4_private_spec.rb
index 733577609e..97218b5ba3 100644
--- a/spec/ruby/library/socket/addrinfo/ipv4_private_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv4_private_spec.rb
@@ -8,14 +8,14 @@ describe "Addrinfo#ipv4_private?" do
     end
 
     it "returns true for a private address" do
-      Addrinfo.ip('10.0.0.0').ipv4_private?.should == true
-      Addrinfo.ip('10.0.0.5').ipv4_private?.should == true
+      Addrinfo.ip('10.0.0.0').should.ipv4_private?
+      Addrinfo.ip('10.0.0.5').should.ipv4_private?
 
-      Addrinfo.ip('172.16.0.0').ipv4_private?.should == true
-      Addrinfo.ip('172.16.0.5').ipv4_private?.should == true
+      Addrinfo.ip('172.16.0.0').should.ipv4_private?
+      Addrinfo.ip('172.16.0.5').should.ipv4_private?
 
-      Addrinfo.ip('192.168.0.0').ipv4_private?.should == true
-      Addrinfo.ip('192.168.0.5').ipv4_private?.should == true
+      Addrinfo.ip('192.168.0.0').should.ipv4_private?
+      Addrinfo.ip('192.168.0.5').should.ipv4_private?
     end
 
     it "returns false for a public address" do
@@ -33,15 +33,13 @@ describe "Addrinfo#ipv4_private?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv4_private?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv4_private?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv4_spec.rb b/spec/ruby/library/socket/addrinfo/ipv4_spec.rb
index 7cba8209b6..61f7759b10 100644
--- a/spec/ruby/library/socket/addrinfo/ipv4_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv4_spec.rb
@@ -21,15 +21,13 @@ describe "Addrinfo#ipv4?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv4?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv4?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_linklocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_linklocal_spec.rb
index 291b4d7d6b..bfef396381 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_linklocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_linklocal_spec.rb
@@ -5,19 +5,19 @@ guard -> { SocketSpecs.ipv6_available? } do
   describe 'Addrinfo#ipv6_linklocal?' do
     platform_is_not :aix do
       it 'returns true for a link-local address' do
-        Addrinfo.ip('fe80::').ipv6_linklocal?.should == true
-        Addrinfo.ip('fe81::').ipv6_linklocal?.should == true
-        Addrinfo.ip('fe8f::').ipv6_linklocal?.should == true
-        Addrinfo.ip('fe80::1').ipv6_linklocal?.should == true
+        Addrinfo.ip('fe80::').should.ipv6_linklocal?
+        Addrinfo.ip('fe81::').should.ipv6_linklocal?
+        Addrinfo.ip('fe8f::').should.ipv6_linklocal?
+        Addrinfo.ip('fe80::1').should.ipv6_linklocal?
       end
     end
 
     it 'returns false for a regular address' do
-      Addrinfo.ip('::1').ipv6_linklocal?.should == false
+      Addrinfo.ip('::1').should_not.ipv6_linklocal?
     end
 
     it 'returns false for an IPv4 address' do
-      Addrinfo.ip('127.0.0.1').ipv6_linklocal?.should == false
+      Addrinfo.ip('127.0.0.1').should_not.ipv6_linklocal?
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_loopback_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_loopback_spec.rb
index 9ff8f107bf..ffc75185ea 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_loopback_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_loopback_spec.rb
@@ -31,15 +31,13 @@ describe "Addrinfo#ipv6_loopback?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
-
-      it "returns false" do
-        @addrinfo.ipv6_loopback?.should be_false
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
+
+    it "returns false" do
+      @addrinfo.ipv6_loopback?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_mc_global_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_mc_global_spec.rb
index 9c8e4dccb4..01fa0992ba 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_mc_global_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_mc_global_spec.rb
@@ -2,19 +2,19 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_mc_global?' do
   it 'returns true for a multi-cast address in the global scope' do
-    Addrinfo.ip('ff1e::').ipv6_mc_global?.should == true
-    Addrinfo.ip('fffe::').ipv6_mc_global?.should == true
-    Addrinfo.ip('ff0e::').ipv6_mc_global?.should == true
-    Addrinfo.ip('ff1e::1').ipv6_mc_global?.should == true
+    Addrinfo.ip('ff1e::').should.ipv6_mc_global?
+    Addrinfo.ip('fffe::').should.ipv6_mc_global?
+    Addrinfo.ip('ff0e::').should.ipv6_mc_global?
+    Addrinfo.ip('ff1e::1').should.ipv6_mc_global?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_mc_global?.should == false
-    Addrinfo.ip('ff1a::').ipv6_mc_global?.should == false
-    Addrinfo.ip('ff1f::1').ipv6_mc_global?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_mc_global?
+    Addrinfo.ip('ff1a::').should_not.ipv6_mc_global?
+    Addrinfo.ip('ff1f::1').should_not.ipv6_mc_global?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_mc_global?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_mc_global?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_mc_linklocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_mc_linklocal_spec.rb
index dd52a9ad8b..a1298919eb 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_mc_linklocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_mc_linklocal_spec.rb
@@ -2,18 +2,18 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_mc_linklocal?' do
   it 'returns true for a multi-cast link-local address' do
-    Addrinfo.ip('ff12::').ipv6_mc_linklocal?.should == true
-    Addrinfo.ip('ff02::').ipv6_mc_linklocal?.should == true
-    Addrinfo.ip('fff2::').ipv6_mc_linklocal?.should == true
-    Addrinfo.ip('ff12::1').ipv6_mc_linklocal?.should == true
+    Addrinfo.ip('ff12::').should.ipv6_mc_linklocal?
+    Addrinfo.ip('ff02::').should.ipv6_mc_linklocal?
+    Addrinfo.ip('fff2::').should.ipv6_mc_linklocal?
+    Addrinfo.ip('ff12::1').should.ipv6_mc_linklocal?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_mc_linklocal?.should == false
-    Addrinfo.ip('fff1::').ipv6_mc_linklocal?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_mc_linklocal?
+    Addrinfo.ip('fff1::').should_not.ipv6_mc_linklocal?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_mc_linklocal?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_mc_linklocal?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_mc_nodelocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_mc_nodelocal_spec.rb
index b3cf5ffbab..0aee952d88 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_mc_nodelocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_mc_nodelocal_spec.rb
@@ -2,17 +2,17 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_mc_nodelocal?' do
   it 'returns true for a multi-cast node-local address' do
-    Addrinfo.ip('ff11::').ipv6_mc_nodelocal?.should == true
-    Addrinfo.ip('ff01::').ipv6_mc_nodelocal?.should == true
-    Addrinfo.ip('fff1::').ipv6_mc_nodelocal?.should == true
-    Addrinfo.ip('ff11::1').ipv6_mc_nodelocal?.should == true
+    Addrinfo.ip('ff11::').should.ipv6_mc_nodelocal?
+    Addrinfo.ip('ff01::').should.ipv6_mc_nodelocal?
+    Addrinfo.ip('fff1::').should.ipv6_mc_nodelocal?
+    Addrinfo.ip('ff11::1').should.ipv6_mc_nodelocal?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_mc_nodelocal?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_mc_nodelocal?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_mc_nodelocal?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_mc_nodelocal?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_mc_orglocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_mc_orglocal_spec.rb
index 90653dd49c..2977a98d30 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_mc_orglocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_mc_orglocal_spec.rb
@@ -2,17 +2,17 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_mc_orglocal?' do
   it 'returns true for a multi-cast org-local address' do
-    Addrinfo.ip('ff18::').ipv6_mc_orglocal?.should == true
-    Addrinfo.ip('ff08::').ipv6_mc_orglocal?.should == true
-    Addrinfo.ip('fff8::').ipv6_mc_orglocal?.should == true
-    Addrinfo.ip('ff18::1').ipv6_mc_orglocal?.should == true
+    Addrinfo.ip('ff18::').should.ipv6_mc_orglocal?
+    Addrinfo.ip('ff08::').should.ipv6_mc_orglocal?
+    Addrinfo.ip('fff8::').should.ipv6_mc_orglocal?
+    Addrinfo.ip('ff18::1').should.ipv6_mc_orglocal?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_mc_orglocal?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_mc_orglocal?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_mc_orglocal?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_mc_orglocal?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_mc_sitelocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_mc_sitelocal_spec.rb
index 686b625e0d..58e5976a40 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_mc_sitelocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_mc_sitelocal_spec.rb
@@ -2,17 +2,17 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_mc_sitelocal?' do
   it 'returns true for a multi-cast site-local address' do
-    Addrinfo.ip('ff15::').ipv6_mc_sitelocal?.should == true
-    Addrinfo.ip('ff05::').ipv6_mc_sitelocal?.should == true
-    Addrinfo.ip('fff5::').ipv6_mc_sitelocal?.should == true
-    Addrinfo.ip('ff15::1').ipv6_mc_sitelocal?.should == true
+    Addrinfo.ip('ff15::').should.ipv6_mc_sitelocal?
+    Addrinfo.ip('ff05::').should.ipv6_mc_sitelocal?
+    Addrinfo.ip('fff5::').should.ipv6_mc_sitelocal?
+    Addrinfo.ip('ff15::1').should.ipv6_mc_sitelocal?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_mc_sitelocal?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_mc_sitelocal?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_mc_sitelocal?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_mc_sitelocal?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_multicast_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_multicast_spec.rb
index c25322869c..99d4e8cf4d 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_multicast_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_multicast_spec.rb
@@ -18,31 +18,29 @@ describe "Addrinfo#ipv6_multicast?" do
 
   describe "for an ipv6 socket" do
     it "returns true for a multicast address" do
-      Addrinfo.ip('ff00::').ipv6_multicast?.should == true
-      Addrinfo.ip('ff00::1').ipv6_multicast?.should == true
-      Addrinfo.ip('ff08::1').ipv6_multicast?.should == true
-      Addrinfo.ip('fff8::1').ipv6_multicast?.should == true
-
-      Addrinfo.ip('ff02::').ipv6_multicast?.should == true
-      Addrinfo.ip('ff02::1').ipv6_multicast?.should == true
-      Addrinfo.ip('ff0f::').ipv6_multicast?.should == true
+      Addrinfo.ip('ff00::').should.ipv6_multicast?
+      Addrinfo.ip('ff00::1').should.ipv6_multicast?
+      Addrinfo.ip('ff08::1').should.ipv6_multicast?
+      Addrinfo.ip('fff8::1').should.ipv6_multicast?
+
+      Addrinfo.ip('ff02::').should.ipv6_multicast?
+      Addrinfo.ip('ff02::1').should.ipv6_multicast?
+      Addrinfo.ip('ff0f::').should.ipv6_multicast?
     end
 
     it "returns false for another address" do
-      Addrinfo.ip('::1').ipv6_multicast?.should == false
-      Addrinfo.ip('fe80::').ipv6_multicast?.should == false
+      Addrinfo.ip('::1').should_not.ipv6_multicast?
+      Addrinfo.ip('fe80::').should_not.ipv6_multicast?
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv6_multicast?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv6_multicast?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_sitelocal_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_sitelocal_spec.rb
index dd202a1749..9158eb5809 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_sitelocal_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_sitelocal_spec.rb
@@ -5,19 +5,19 @@ guard -> { SocketSpecs.ipv6_available? } do
   describe 'Addrinfo#ipv6_sitelocal?' do
     platform_is_not :aix do
       it 'returns true for a site-local address' do
-        Addrinfo.ip('feef::').ipv6_sitelocal?.should == true
-        Addrinfo.ip('fee0::').ipv6_sitelocal?.should == true
-        Addrinfo.ip('fee2::').ipv6_sitelocal?.should == true
-        Addrinfo.ip('feef::1').ipv6_sitelocal?.should == true
+        Addrinfo.ip('feef::').should.ipv6_sitelocal?
+        Addrinfo.ip('fee0::').should.ipv6_sitelocal?
+        Addrinfo.ip('fee2::').should.ipv6_sitelocal?
+        Addrinfo.ip('feef::1').should.ipv6_sitelocal?
       end
     end
 
     it 'returns false for a regular IPv6 address' do
-      Addrinfo.ip('::1').ipv6_sitelocal?.should == false
+      Addrinfo.ip('::1').should_not.ipv6_sitelocal?
     end
 
     it 'returns false for an IPv4 address' do
-      Addrinfo.ip('127.0.0.1').ipv6_sitelocal?.should == false
+      Addrinfo.ip('127.0.0.1').should_not.ipv6_sitelocal?
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_spec.rb
index 131e38849c..436d5e930b 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_spec.rb
@@ -21,15 +21,13 @@ describe "Addrinfo#ipv6?" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns false" do
-        @addrinfo.ipv6?.should be_false
-      end
+    it "returns false" do
+      @addrinfo.ipv6?.should be_false
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_to_ipv4_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_to_ipv4_spec.rb
index 6dfaf531ae..29050bec20 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_to_ipv4_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_to_ipv4_spec.rb
@@ -62,7 +62,7 @@ guard -> { SocketSpecs.ipv6_available? } do
       Addrinfo.ip('192.168.1.1').ipv6_to_ipv4.should be_nil
     end
 
-    with_feature :unix_socket do
+    describe 'for a unix socket' do
       it 'returns nil for a UNIX Addrinfo' do
         Addrinfo.unix('foo').ipv6_to_ipv4.should be_nil
       end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_unique_local_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_unique_local_spec.rb
index b80a15fcb0..22f0fa3b75 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_unique_local_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_unique_local_spec.rb
@@ -2,17 +2,17 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_unique_local?' do
   it 'returns true for an unique local IPv6 address' do
-    Addrinfo.ip('fc00::').ipv6_unique_local?.should == true
-    Addrinfo.ip('fd00::').ipv6_unique_local?.should == true
-    Addrinfo.ip('fcff::').ipv6_unique_local?.should == true
+    Addrinfo.ip('fc00::').should.ipv6_unique_local?
+    Addrinfo.ip('fd00::').should.ipv6_unique_local?
+    Addrinfo.ip('fcff::').should.ipv6_unique_local?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_unique_local?.should == false
-    Addrinfo.ip('fe00::').ipv6_unique_local?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_unique_local?
+    Addrinfo.ip('fe00::').should_not.ipv6_unique_local?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_unique_local?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_unique_local?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_unspecified_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_unspecified_spec.rb
index dd79d57503..d63979ceda 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_unspecified_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_unspecified_spec.rb
@@ -2,14 +2,14 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_unspecified?' do
   it 'returns true for an unspecified IPv6 address' do
-    Addrinfo.ip('::').ipv6_unspecified?.should == true
+    Addrinfo.ip('::').should.ipv6_unspecified?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_unspecified?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_unspecified?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_unspecified?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_unspecified?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_v4compat_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_v4compat_spec.rb
index ab8388a21b..21ca85af99 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_v4compat_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_v4compat_spec.rb
@@ -2,19 +2,19 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_v4compat?' do
   it 'returns true for an IPv4 compatible address' do
-    Addrinfo.ip('::127.0.0.1').ipv6_v4compat?.should == true
-    Addrinfo.ip('::192.168.1.1').ipv6_v4compat?.should == true
+    Addrinfo.ip('::127.0.0.1').should.ipv6_v4compat?
+    Addrinfo.ip('::192.168.1.1').should.ipv6_v4compat?
   end
 
   it 'returns false for an IPv4 mapped address' do
-    Addrinfo.ip('::ffff:192.168.1.1').ipv6_v4compat?.should == false
+    Addrinfo.ip('::ffff:192.168.1.1').should_not.ipv6_v4compat?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_v4compat?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_v4compat?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_v4compat?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_v4compat?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/ipv6_v4mapped_spec.rb b/spec/ruby/library/socket/addrinfo/ipv6_v4mapped_spec.rb
index 82b272c165..7dac0e75db 100644
--- a/spec/ruby/library/socket/addrinfo/ipv6_v4mapped_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/ipv6_v4mapped_spec.rb
@@ -2,19 +2,19 @@ require_relative '../spec_helper'
 
 describe 'Addrinfo#ipv6_v4mapped?' do
   it 'returns true for an IPv4 compatible address' do
-    Addrinfo.ip('::ffff:192.168.1.1').ipv6_v4mapped?.should == true
+    Addrinfo.ip('::ffff:192.168.1.1').should.ipv6_v4mapped?
   end
 
   it 'returns false for an IPv4 compatible address' do
-    Addrinfo.ip('::192.168.1.1').ipv6_v4mapped?.should == false
-    Addrinfo.ip('::127.0.0.1').ipv6_v4mapped?.should == false
+    Addrinfo.ip('::192.168.1.1').should_not.ipv6_v4mapped?
+    Addrinfo.ip('::127.0.0.1').should_not.ipv6_v4mapped?
   end
 
   it 'returns false for a regular IPv6 address' do
-    Addrinfo.ip('::1').ipv6_v4mapped?.should == false
+    Addrinfo.ip('::1').should_not.ipv6_v4mapped?
   end
 
   it 'returns false for an IPv4 address' do
-    Addrinfo.ip('127.0.0.1').ipv6_v4mapped?.should == false
+    Addrinfo.ip('127.0.0.1').should_not.ipv6_v4mapped?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/listen_spec.rb b/spec/ruby/library/socket/addrinfo/listen_spec.rb
index 714a96ed6c..931093f732 100644
--- a/spec/ruby/library/socket/addrinfo/listen_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/listen_spec.rb
@@ -29,6 +29,6 @@ describe 'Addrinfo#listen' do
       socket = sock
     end
 
-    socket.closed?.should == true
+    socket.should.closed?
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/marshal_dump_spec.rb b/spec/ruby/library/socket/addrinfo/marshal_dump_spec.rb
index c4220a6f3e..e2c3497f7f 100644
--- a/spec/ruby/library/socket/addrinfo/marshal_dump_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/marshal_dump_spec.rb
@@ -32,10 +32,8 @@ describe 'Addrinfo#marshal_dump' do
         @array[3].should == 'SOCK_STREAM'
       end
 
-      platform_is_not :'solaris2.10' do # i386-solaris
-        it 'includes the protocol as the 5th value' do
-          @array[4].should == 'IPPROTO_TCP'
-        end
+      it 'includes the protocol as the 5th value' do
+        @array[4].should == 'IPPROTO_TCP'
       end
 
       it 'includes the canonical name as the 6th value' do
@@ -44,40 +42,38 @@ describe 'Addrinfo#marshal_dump' do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using a UNIX Addrinfo' do
+  describe 'using a UNIX Addrinfo' do
+    before do
+      @addr = Addrinfo.unix('foo')
+    end
+
+    it 'returns an Array' do
+      @addr.marshal_dump.should be_an_instance_of(Array)
+    end
+
+    describe 'the returned Array' do
       before do
-        @addr = Addrinfo.unix('foo')
+        @array = @addr.marshal_dump
       end
 
-      it 'returns an Array' do
-        @addr.marshal_dump.should be_an_instance_of(Array)
+      it 'includes the address family as the 1st value' do
+        @array[0].should == 'AF_UNIX'
       end
 
-      describe 'the returned Array' do
-        before do
-          @array = @addr.marshal_dump
-        end
-
-        it 'includes the address family as the 1st value' do
-          @array[0].should == 'AF_UNIX'
-        end
-
-        it 'includes the UNIX path as the 2nd value' do
-          @array[1].should == @addr.unix_path
-        end
+      it 'includes the UNIX path as the 2nd value' do
+        @array[1].should == @addr.unix_path
+      end
 
-        it 'includes the protocol family as the 3rd value' do
-          @array[2].should == 'PF_UNIX'
-        end
+      it 'includes the protocol family as the 3rd value' do
+        @array[2].should == 'PF_UNIX'
+      end
 
-        it 'includes the socket type as the 4th value' do
-          @array[3].should == 'SOCK_STREAM'
-        end
+      it 'includes the socket type as the 4th value' do
+        @array[3].should == 'SOCK_STREAM'
+      end
 
-        it 'includes the protocol as the 5th value' do
-          @array[4].should == 0
-        end
+      it 'includes the protocol as the 5th value' do
+        @array[4].should == 0
       end
     end
   end
diff --git a/spec/ruby/library/socket/addrinfo/marshal_load_spec.rb b/spec/ruby/library/socket/addrinfo/marshal_load_spec.rb
index aa20865224..02cef90115 100644
--- a/spec/ruby/library/socket/addrinfo/marshal_load_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/marshal_load_spec.rb
@@ -18,18 +18,16 @@ describe 'Addrinfo#marshal_load' do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using a UNIX socket' do
-      it 'returns a new Addrinfo' do
-        source = Addrinfo.unix('foo')
-        addr   = Marshal.load(Marshal.dump(source))
+  describe 'using a UNIX socket' do
+    it 'returns a new Addrinfo' do
+      source = Addrinfo.unix('foo')
+      addr   = Marshal.load(Marshal.dump(source))
 
-        addr.afamily.should   == source.afamily
-        addr.pfamily.should   == source.pfamily
-        addr.socktype.should  == source.socktype
-        addr.protocol.should  == source.protocol
-        addr.unix_path.should == source.unix_path
-      end
+      addr.afamily.should   == source.afamily
+      addr.pfamily.should   == source.pfamily
+      addr.socktype.should  == source.socktype
+      addr.protocol.should  == source.protocol
+      addr.unix_path.should == source.unix_path
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/pfamily_spec.rb b/spec/ruby/library/socket/addrinfo/pfamily_spec.rb
index 984744a964..da530b7fdc 100644
--- a/spec/ruby/library/socket/addrinfo/pfamily_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/pfamily_spec.rb
@@ -29,15 +29,13 @@ describe "Addrinfo#pfamily" do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
-
-      it "returns Socket::PF_UNIX" do
-        @addrinfo.pfamily.should == Socket::PF_UNIX
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
+
+    it "returns Socket::PF_UNIX" do
+      @addrinfo.pfamily.should == Socket::PF_UNIX
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/protocol_spec.rb b/spec/ruby/library/socket/addrinfo/protocol_spec.rb
index ea143fc4a8..f6ffc9acf9 100644
--- a/spec/ruby/library/socket/addrinfo/protocol_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/protocol_spec.rb
@@ -10,15 +10,13 @@ describe "Addrinfo#protocol" do
     Addrinfo.tcp('::1', 80).protocol.should == Socket::IPPROTO_TCP
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns 0" do
-        @addrinfo.protocol.should == 0
-      end
+    it "returns 0" do
+      @addrinfo.protocol.should == 0
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/shared/to_sockaddr.rb b/spec/ruby/library/socket/addrinfo/shared/to_sockaddr.rb
index c32da5986d..70d6bfbbfe 100644
--- a/spec/ruby/library/socket/addrinfo/shared/to_sockaddr.rb
+++ b/spec/ruby/library/socket/addrinfo/shared/to_sockaddr.rb
@@ -1,5 +1,4 @@
-describe :socket_addrinfo_to_sockaddr, :shared => true do
-
+describe :socket_addrinfo_to_sockaddr, shared: true do
   describe "for an ipv4 socket" do
     before :each do
       @addrinfo = Addrinfo.tcp("127.0.0.1", 80)
@@ -20,15 +19,13 @@ describe :socket_addrinfo_to_sockaddr, :shared => true do
     end
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns a sockaddr packed structure" do
-        @addrinfo.send(@method).should == Socket.sockaddr_un('/tmp/sock')
-      end
+    it "returns a sockaddr packed structure" do
+      @addrinfo.send(@method).should == Socket.sockaddr_un('/tmp/sock')
     end
   end
 
@@ -47,5 +44,4 @@ describe :socket_addrinfo_to_sockaddr, :shared => true do
       addr.send(@method).should == Socket.sockaddr_in(0, '')
     end
   end
-
 end
diff --git a/spec/ruby/library/socket/addrinfo/socktype_spec.rb b/spec/ruby/library/socket/addrinfo/socktype_spec.rb
index b994bea140..e5f02cd759 100644
--- a/spec/ruby/library/socket/addrinfo/socktype_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/socktype_spec.rb
@@ -9,15 +9,13 @@ describe "Addrinfo#socktype" do
     Addrinfo.tcp('127.0.0.1', 80).socktype.should == Socket::SOCK_STREAM
   end
 
-  with_feature :unix_socket do
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns Socket::SOCK_STREAM" do
-        @addrinfo.socktype.should == Socket::SOCK_STREAM
-      end
+    it "returns Socket::SOCK_STREAM" do
+      @addrinfo.socktype.should == Socket::SOCK_STREAM
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/udp_spec.rb b/spec/ruby/library/socket/addrinfo/udp_spec.rb
index b05cbf9b0b..ac02e76ef5 100644
--- a/spec/ruby/library/socket/addrinfo/udp_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/udp_spec.rb
@@ -27,10 +27,8 @@ describe 'Addrinfo.udp' do
       Addrinfo.udp(ip_address, 80).socktype.should == Socket::SOCK_DGRAM
     end
 
-    platform_is_not :solaris do
-      it 'sets the socket protocol' do
-        Addrinfo.udp(ip_address, 80).protocol.should == Socket::IPPROTO_UDP
-      end
+    it 'sets the socket protocol' do
+      Addrinfo.udp(ip_address, 80).protocol.should == Socket::IPPROTO_UDP
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/unix_path_spec.rb b/spec/ruby/library/socket/addrinfo/unix_path_spec.rb
index 6bfb56a4ac..2a9076a354 100644
--- a/spec/ruby/library/socket/addrinfo/unix_path_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/unix_path_spec.rb
@@ -1,37 +1,35 @@
 require_relative '../spec_helper'
 
-with_feature :unix_socket do
-  describe "Addrinfo#unix_path" do
-    describe "for an ipv4 socket" do
+describe "Addrinfo#unix_path" do
+  describe "for an ipv4 socket" do
 
-      before :each do
-        @addrinfo = Addrinfo.tcp("127.0.0.1", 80)
-      end
-
-      it "raises an exception" do
-        -> { @addrinfo.unix_path }.should raise_error(SocketError)
-      end
+    before :each do
+      @addrinfo = Addrinfo.tcp("127.0.0.1", 80)
+    end
 
+    it "raises an exception" do
+      -> { @addrinfo.unix_path }.should raise_error(SocketError)
     end
 
-    describe "for an ipv6 socket" do
-      before :each do
-        @addrinfo = Addrinfo.tcp("::1", 80)
-      end
+  end
 
-      it "raises an exception" do
-        -> { @addrinfo.unix_path }.should raise_error(SocketError)
-      end
+  describe "for an ipv6 socket" do
+    before :each do
+      @addrinfo = Addrinfo.tcp("::1", 80)
     end
 
-    describe "for a unix socket" do
-      before :each do
-        @addrinfo = Addrinfo.unix("/tmp/sock")
-      end
+    it "raises an exception" do
+      -> { @addrinfo.unix_path }.should raise_error(SocketError)
+    end
+  end
+
+  describe "for a unix socket" do
+    before :each do
+      @addrinfo = Addrinfo.unix("/tmp/sock")
+    end
 
-      it "returns the socket path" do
-        @addrinfo.unix_path.should == "/tmp/sock"
-      end
+    it "returns the socket path" do
+      @addrinfo.unix_path.should == "/tmp/sock"
     end
   end
 end
diff --git a/spec/ruby/library/socket/addrinfo/unix_spec.rb b/spec/ruby/library/socket/addrinfo/unix_spec.rb
index 4596ece17e..7597533a76 100644
--- a/spec/ruby/library/socket/addrinfo/unix_spec.rb
+++ b/spec/ruby/library/socket/addrinfo/unix_spec.rb
@@ -1,36 +1,34 @@
 require_relative '../spec_helper'
 
-with_feature :unix_socket do
-  describe 'Addrinfo.unix' do
-    it 'returns an Addrinfo instance' do
-      Addrinfo.unix('socket').should be_an_instance_of(Addrinfo)
-    end
+describe 'Addrinfo.unix' do
+  it 'returns an Addrinfo instance' do
+    Addrinfo.unix('socket').should be_an_instance_of(Addrinfo)
+  end
 
-    it 'sets the IP address' do
-      Addrinfo.unix('socket').unix_path.should == 'socket'
-    end
+  it 'sets the IP address' do
+    Addrinfo.unix('socket').unix_path.should == 'socket'
+  end
 
-    it 'sets the address family' do
-      Addrinfo.unix('socket').afamily.should == Socket::AF_UNIX
-    end
+  it 'sets the address family' do
+    Addrinfo.unix('socket').afamily.should == Socket::AF_UNIX
+  end
 
-    it 'sets the protocol family' do
-      Addrinfo.unix('socket').pfamily.should == Socket::PF_UNIX
-    end
+  it 'sets the protocol family' do
+    Addrinfo.unix('socket').pfamily.should == Socket::PF_UNIX
+  end
 
-    it 'sets the socket type' do
-      Addrinfo.unix('socket').socktype.should == Socket::SOCK_STREAM
-    end
+  it 'sets the socket type' do
+    Addrinfo.unix('socket').socktype.should == Socket::SOCK_STREAM
+  end
 
-    it 'sets a custom socket type' do
-      addr = Addrinfo.unix('socket', Socket::SOCK_DGRAM)
+  it 'sets a custom socket type' do
+    addr = Addrinfo.unix('socket', Socket::SOCK_DGRAM)
 
-      addr.socktype.should == Socket::SOCK_DGRAM
-    end
+    addr.socktype.should == Socket::SOCK_DGRAM
+  end
 
-    it 'sets the socket protocol to 0' do
-      Addrinfo.unix('socket').protocol.should == 0
-    end
+  it 'sets the socket protocol to 0' do
+    Addrinfo.unix('socket').protocol.should == 0
   end
 end
 
diff --git a/spec/ruby/library/socket/ancillarydata/initialize_spec.rb b/spec/ruby/library/socket/ancillarydata/initialize_spec.rb
index 344d1485c5..eca45599d7 100644
--- a/spec/ruby/library/socket/ancillarydata/initialize_spec.rb
+++ b/spec/ruby/library/socket/ancillarydata/initialize_spec.rb
@@ -106,7 +106,7 @@ with_feature :ancillary_data do
         Socket::AncillaryData.new(:INET, :SOCKET, :RIGHTS, '').type.should == Socket::SCM_RIGHTS
       end
 
-      platform_is_not :"solaris2.10", :aix do
+      platform_is_not :aix do
         it 'sets the type to SCM_TIMESTAMP when using :TIMESTAMP as the type argument' do
           Socket::AncillaryData.new(:INET, :SOCKET, :TIMESTAMP, '').type.should == Socket::SCM_TIMESTAMP
         end
diff --git a/spec/ruby/library/socket/ancillarydata/unix_rights_spec.rb b/spec/ruby/library/socket/ancillarydata/unix_rights_spec.rb
index 65ffcb01af..95052fd91c 100644
--- a/spec/ruby/library/socket/ancillarydata/unix_rights_spec.rb
+++ b/spec/ruby/library/socket/ancillarydata/unix_rights_spec.rb
@@ -50,7 +50,7 @@ with_feature :ancillary_data do
       -> { data.unix_rights }.should raise_error(TypeError)
     end
 
-    platform_is_not :"solaris2.10", :aix do
+    platform_is_not :aix do
       it 'raises TypeError when the type is not SCM_RIGHTS' do
         data = Socket::AncillaryData.new(:INET, :SOCKET, :TIMESTAMP, '')
 
diff --git a/spec/ruby/library/socket/basicsocket/connect_address_spec.rb b/spec/ruby/library/socket/basicsocket/connect_address_spec.rb
index 1a1c9982d9..2e318fcb85 100644
--- a/spec/ruby/library/socket/basicsocket/connect_address_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/connect_address_spec.rb
@@ -94,61 +94,59 @@ describe 'Socket#connect_address' do
     end
   end
 
-  with_feature :unix_socket do
-    platform_is_not :aix do
-      describe 'using an unbound UNIX socket' do
-        before do
-          @path = SocketSpecs.socket_path
-          @server = UNIXServer.new(@path)
-          @client = UNIXSocket.new(@path)
-        end
-
-        after do
-          @client.close
-          @server.close
-          rm_r(@path)
-        end
-
-        it 'raises SocketError' do
-          -> { @client.connect_address }.should raise_error(SocketError)
-        end
-      end
-    end
-
-    describe 'using a bound UNIX socket' do
+  platform_is_not :aix do
+    describe 'using an unbound UNIX socket' do
       before do
         @path = SocketSpecs.socket_path
-        @sock = UNIXServer.new(@path)
+        @server = UNIXServer.new(@path)
+        @client = UNIXSocket.new(@path)
       end
 
       after do
-        @sock.close
+        @client.close
+        @server.close
         rm_r(@path)
       end
 
-      it 'returns an Addrinfo' do
-        @sock.connect_address.should be_an_instance_of(Addrinfo)
+      it 'raises SocketError' do
+        -> { @client.connect_address }.should raise_error(SocketError)
       end
+    end
+  end
 
-      it 'uses the correct socket path' do
-        @sock.connect_address.unix_path.should == @path
-      end
+  describe 'using a bound UNIX socket' do
+    before do
+      @path = SocketSpecs.socket_path
+      @sock = UNIXServer.new(@path)
+    end
 
-      it 'uses AF_UNIX as the address family' do
-        @sock.connect_address.afamily.should == Socket::AF_UNIX
-      end
+    after do
+      @sock.close
+      rm_r(@path)
+    end
 
-      it 'uses PF_UNIX as the protocol family' do
-        @sock.connect_address.pfamily.should == Socket::PF_UNIX
-      end
+    it 'returns an Addrinfo' do
+      @sock.connect_address.should be_an_instance_of(Addrinfo)
+    end
 
-      it 'uses SOCK_STREAM as the socket type' do
-        @sock.connect_address.socktype.should == Socket::SOCK_STREAM
-      end
+    it 'uses the correct socket path' do
+      @sock.connect_address.unix_path.should == @path
+    end
 
-      it 'uses 0 as the protocol' do
-        @sock.connect_address.protocol.should == 0
-      end
+    it 'uses AF_UNIX as the address family' do
+      @sock.connect_address.afamily.should == Socket::AF_UNIX
+    end
+
+    it 'uses PF_UNIX as the protocol family' do
+      @sock.connect_address.pfamily.should == Socket::PF_UNIX
+    end
+
+    it 'uses SOCK_STREAM as the socket type' do
+      @sock.connect_address.socktype.should == Socket::SOCK_STREAM
+    end
+
+    it 'uses 0 as the protocol' do
+      @sock.connect_address.protocol.should == 0
     end
   end
 end
diff --git a/spec/ruby/library/socket/basicsocket/getpeereid_spec.rb b/spec/ruby/library/socket/basicsocket/getpeereid_spec.rb
index 6179211d96..2e03cd3684 100644
--- a/spec/ruby/library/socket/basicsocket/getpeereid_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/getpeereid_spec.rb
@@ -2,7 +2,7 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe 'BasicSocket#getpeereid' do
-  with_feature :unix_socket do
+  platform_is_not :windows do
     describe 'using a UNIXSocket' do
       before do
         @path = SocketSpecs.socket_path
diff --git a/spec/ruby/library/socket/basicsocket/local_address_spec.rb b/spec/ruby/library/socket/basicsocket/local_address_spec.rb
new file mode 100644
index 0000000000..0bd60a44cd
--- /dev/null
+++ b/spec/ruby/library/socket/basicsocket/local_address_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../spec_helper'
+require_relative '../shared/address'
+
+describe 'BasicSocket#local_address' do
+  it_behaves_like :socket_local_remote_address, :local_address, -> socket {
+    a2 = BasicSocket.for_fd(socket.fileno)
+    a2.autoclose = false
+    a2.local_address
+  }
+end
diff --git a/spec/ruby/library/socket/basicsocket/read_nonblock_spec.rb b/spec/ruby/library/socket/basicsocket/read_nonblock_spec.rb
new file mode 100644
index 0000000000..ea5e65da5c
--- /dev/null
+++ b/spec/ruby/library/socket/basicsocket/read_nonblock_spec.rb
@@ -0,0 +1,74 @@
+require_relative '../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "BasicSocket#read_nonblock" do
+  SocketSpecs.each_ip_protocol do |family, ip_address|
+    before :each do
+      @r = Socket.new(family, :DGRAM)
+      @w = Socket.new(family, :DGRAM)
+
+      @r.bind(Socket.pack_sockaddr_in(0, ip_address))
+      @w.send("aaa", 0, @r.getsockname)
+    end
+
+    after :each do
+      @r.close unless @r.closed?
+      @w.close unless @w.closed?
+    end
+
+    it "receives data after it's ready" do
+      IO.select([@r], nil, nil, 2)
+      @r.read_nonblock(5).should == "aaa"
+    end
+
+    platform_is_not :windows do
+      it 'returned data is binary encoded regardless of the external encoding' do
+        IO.select([@r], nil, nil, 2)
+        @r.read_nonblock(1).encoding.should == Encoding::BINARY
+
+        @w.send("bbb", 0, @r.getsockname)
+        @r.set_encoding(Encoding::ISO_8859_1)
+        IO.select([@r], nil, nil, 2)
+        buffer = @r.read_nonblock(3)
+        buffer.should == "bbb"
+        buffer.encoding.should == Encoding::BINARY
+      end
+    end
+
+    it 'replaces the content of the provided buffer without changing its encoding' do
+      buffer = "initial data".dup.force_encoding(Encoding::UTF_8)
+
+      IO.select([@r], nil, nil, 2)
+      @r.read_nonblock(3, buffer)
+      buffer.should == "aaa"
+      buffer.encoding.should == Encoding::UTF_8
+
+      @w.send("bbb", 0, @r.getsockname)
+      @r.set_encoding(Encoding::ISO_8859_1)
+      IO.select([@r], nil, nil, 2)
+      @r.read_nonblock(3, buffer)
+      buffer.should == "bbb"
+      buffer.encoding.should == Encoding::UTF_8
+    end
+
+    platform_is :linux do
+      it 'does not set the IO in nonblock mode' do
+        require 'io/nonblock'
+        @r.nonblock = false
+        IO.select([@r], nil, nil, 2)
+        @r.read_nonblock(3).should == "aaa"
+        @r.should_not.nonblock?
+      end
+    end
+
+    platform_is_not :linux, :windows do
+      it 'sets the IO in nonblock mode' do
+        require 'io/nonblock'
+        @r.nonblock = false
+        IO.select([@r], nil, nil, 2)
+        @r.read_nonblock(3).should == "aaa"
+        @r.should.nonblock?
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/basicsocket/read_spec.rb b/spec/ruby/library/socket/basicsocket/read_spec.rb
new file mode 100644
index 0000000000..ba9de7d5cf
--- /dev/null
+++ b/spec/ruby/library/socket/basicsocket/read_spec.rb
@@ -0,0 +1,47 @@
+require_relative '../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "BasicSocket#read" do
+  SocketSpecs.each_ip_protocol do |family, ip_address|
+    before :each do
+      @r = Socket.new(family, :DGRAM)
+      @w = Socket.new(family, :DGRAM)
+
+      @r.bind(Socket.pack_sockaddr_in(0, ip_address))
+      @w.send("aaa", 0, @r.getsockname)
+    end
+
+    after :each do
+      @r.close unless @r.closed?
+      @w.close unless @w.closed?
+    end
+
+    it "receives data after it's ready" do
+      @r.read(3).should == "aaa"
+    end
+
+    it 'returned data is binary encoded regardless of the external encoding' do
+      @r.read(3).encoding.should == Encoding::BINARY
+
+      @w.send("bbb", 0, @r.getsockname)
+      @r.set_encoding(Encoding::UTF_8)
+      buffer = @r.read(3)
+      buffer.should == "bbb"
+      buffer.encoding.should == Encoding::BINARY
+    end
+
+    it 'replaces the content of the provided buffer without changing its encoding' do
+      buffer = "initial data".dup.force_encoding(Encoding::UTF_8)
+
+      @r.read(3, buffer)
+      buffer.should == "aaa"
+      buffer.encoding.should == Encoding::UTF_8
+
+      @w.send("bbb", 0, @r.getsockname)
+      @r.set_encoding(Encoding::ISO_8859_1)
+      @r.read(3, buffer)
+      buffer.should == "bbb"
+      buffer.encoding.should == Encoding::UTF_8
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/basicsocket/recv_nonblock_spec.rb b/spec/ruby/library/socket/basicsocket/recv_nonblock_spec.rb
index 0363f2f8de..f2a6682f12 100644
--- a/spec/ruby/library/socket/basicsocket/recv_nonblock_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/recv_nonblock_spec.rb
@@ -52,9 +52,19 @@ describe "Socket::BasicSocket#recv_nonblock" do
       @s2.send("data", 0, @s1.getsockname)
       IO.select([@s1], nil, nil, 2)
 
-      buf = "foo"
-      @s1.recv_nonblock(5, 0, buf)
-      buf.should == "data"
+      buffer = +"foo"
+      @s1.recv_nonblock(5, 0, buffer).should.equal?(buffer)
+      buffer.should == "data"
+    end
+
+    it "preserves the encoding of the given buffer" do
+      @s1.bind(Socket.pack_sockaddr_in(0, ip_address))
+      @s2.send("data", 0, @s1.getsockname)
+      IO.select([@s1], nil, nil, 2)
+
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @s1.recv_nonblock(5, 0, buffer)
+      buffer.encoding.should == Encoding::ISO_8859_1
     end
 
     it "does not block if there's no data available" do
@@ -67,4 +77,96 @@ describe "Socket::BasicSocket#recv_nonblock" do
       }.should raise_error(IO::WaitReadable)
     end
   end
+
+  SocketSpecs.each_ip_protocol do |family, ip_address|
+    describe 'using a connected but not bound socket' do
+      before do
+        @server = Socket.new(family, :STREAM)
+      end
+
+      after do
+        @server.close
+      end
+
+      it "raises Errno::ENOTCONN" do
+        -> { @server.recv_nonblock(1) }.should raise_error { |e|
+          [Errno::ENOTCONN, Errno::EINVAL].should.include?(e.class)
+        }
+        -> { @server.recv_nonblock(1, exception: false) }.should raise_error { |e|
+          [Errno::ENOTCONN, Errno::EINVAL].should.include?(e.class)
+        }
+      end
+    end
+  end
+end
+
+describe "Socket::BasicSocket#recv_nonblock" do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = TCPServer.new('127.0.0.1', 0)
+        @port = @server.addr[1]
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        it "returns an empty String on a closed stream socket" do
+          ready = false
+
+          t = Thread.new do
+            client = @server.accept
+
+            Thread.pass while !ready
+            begin
+              client.recv_nonblock(10)
+            rescue IO::EAGAINWaitReadable
+              retry
+            end
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          socket = TCPSocket.new('127.0.0.1', @port)
+          socket.close
+          ready = true
+
+          t.value.should == ""
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "returns nil on a closed stream socket" do
+          ready = false
+
+          t = Thread.new do
+            client = @server.accept
+
+            Thread.pass while !ready
+            begin
+              client.recv_nonblock(10)
+            rescue IO::EAGAINWaitReadable
+              retry
+            end
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          socket = TCPSocket.new('127.0.0.1', @port)
+          socket.close
+          ready = true
+
+          t.value.should be_nil
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/socket/basicsocket/recv_spec.rb b/spec/ruby/library/socket/basicsocket/recv_spec.rb
index b6ccda5d00..a51920f52a 100644
--- a/spec/ruby/library/socket/basicsocket/recv_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/recv_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
@@ -32,28 +32,26 @@ describe "BasicSocket#recv" do
     ScratchPad.recorded.should == 'hello'
   end
 
-  platform_is_not :solaris do
-    it "accepts flags to specify unusual receiving behaviour" do
-      t = Thread.new do
-        client = @server.accept
+  it "accepts flags to specify unusual receiving behaviour" do
+    t = Thread.new do
+      client = @server.accept
 
-        # in-band data (TCP), doesn't receive the flag.
-        ScratchPad.record client.recv(10)
+      # in-band data (TCP), doesn't receive the flag.
+      ScratchPad.record client.recv(10)
 
-        # this recv is important (TODO: explain)
-        client.recv(10)
-        client.close
-      end
-      Thread.pass while t.status and t.status != "sleep"
-      t.status.should_not be_nil
-
-      socket = TCPSocket.new('127.0.0.1', @port)
-      socket.send('helloU', Socket::MSG_OOB)
-      socket.shutdown(1)
-      t.join
-      socket.close
-      ScratchPad.recorded.should == 'hello'
+      # this recv is important (TODO: explain)
+      client.recv(10)
+      client.close
     end
+    Thread.pass while t.status and t.status != "sleep"
+    t.status.should_not be_nil
+
+    socket = TCPSocket.new('127.0.0.1', @port)
+    socket.send('helloU', Socket::MSG_OOB)
+    socket.shutdown(1)
+    t.join
+    socket.close
+    ScratchPad.recorded.should == 'hello'
   end
 
   it "gets lines delimited with a custom separator"  do
@@ -81,13 +79,29 @@ describe "BasicSocket#recv" do
     socket.write("data")
 
     client = @server.accept
-    buf = "foo"
+    buffer = +"foo"
     begin
-      client.recv(4, 0, buf)
+      client.recv(4, 0, buffer).should.equal?(buffer)
     ensure
       client.close
     end
-    buf.should == "data"
+    buffer.should == "data"
+
+    socket.close
+  end
+
+  it "preserves the encoding of the given buffer" do
+    socket = TCPSocket.new('127.0.0.1', @port)
+    socket.write("data")
+
+    client = @server.accept
+    buffer = ''.encode(Encoding::ISO_8859_1)
+    begin
+      client.recv(4, 0, buffer)
+    ensure
+      client.close
+    end
+    buffer.encoding.should == Encoding::ISO_8859_1
 
     socket.close
   end
@@ -157,3 +171,80 @@ describe 'BasicSocket#recv' do
     end
   end
 end
+
+describe "BasicSocket#recv" do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = TCPServer.new('127.0.0.1', 0)
+        @port = @server.addr[1]
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        it "returns an empty String on a closed stream socket" do
+          t = Thread.new do
+            client = @server.accept
+            client.recv(10)
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          socket = TCPSocket.new('127.0.0.1', @port)
+          socket.close
+
+          t.value.should == ""
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "returns nil on a closed stream socket" do
+          t = Thread.new do
+            client = @server.accept
+            client.recv(10)
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          socket = TCPSocket.new('127.0.0.1', @port)
+          socket.close
+
+          t.value.should be_nil
+        end
+      end
+    end
+
+    describe "datagram socket" do
+      SocketSpecs.each_ip_protocol do |family, ip_address|
+        before :each do
+          @server = UDPSocket.new(family)
+          @client = UDPSocket.new(family)
+        end
+
+        after :each do
+          @server.close unless @server.closed?
+          @client.close unless @client.closed?
+        end
+
+        it "returns empty String" do
+          @server.bind(ip_address, 0)
+          addr = @server.connect_address
+          @client.connect(addr.ip_address, addr.ip_port)
+
+          @client.send('', 0)
+
+          @server.recv(1).should == ""
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/basicsocket/recvmsg_nonblock_spec.rb b/spec/ruby/library/socket/basicsocket/recvmsg_nonblock_spec.rb
index 8e6c232c59..b5fdd7c93b 100644
--- a/spec/ruby/library/socket/basicsocket/recvmsg_nonblock_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/recvmsg_nonblock_spec.rb
@@ -114,6 +114,21 @@ describe 'BasicSocket#recvmsg_nonblock' do
     end
 
     platform_is_not :windows do
+      describe 'using a connected but not bound socket' do
+        before do
+          @server = Socket.new(family, :STREAM)
+        end
+
+        after do
+          @server.close
+        end
+
+        it "raises Errno::ENOTCONN" do
+          -> { @server.recvmsg_nonblock }.should raise_error(Errno::ENOTCONN)
+          -> { @server.recvmsg_nonblock(exception: false) }.should raise_error(Errno::ENOTCONN)
+        end
+      end
+
       describe 'using a connected socket' do
         before do
           @client = Socket.new(family, :STREAM)
@@ -207,3 +222,79 @@ describe 'BasicSocket#recvmsg_nonblock' do
     end
   end
 end
+
+describe 'BasicSocket#recvmsg_nonblock' do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = TCPServer.new('127.0.0.1', 0)
+        @port = @server.addr[1]
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        platform_is_not :windows do # #recvmsg_nonblock() raises 'Errno::EINVAL: Invalid argument - recvmsg(2)'
+          it "returns an empty String as received data on a closed stream socket" do
+            ready = false
+
+            t = Thread.new do
+              client = @server.accept
+
+              Thread.pass while !ready
+              begin
+                client.recvmsg_nonblock(10)
+              rescue IO::EAGAINWaitReadable
+                retry
+              end
+            ensure
+              client.close if client
+            end
+
+            Thread.pass while t.status and t.status != "sleep"
+            t.status.should_not be_nil
+
+            socket = TCPSocket.new('127.0.0.1', @port)
+            socket.close
+            ready = true
+
+            t.value.should.is_a? Array
+            t.value[0].should == ""
+          end
+        end
+      end
+
+      ruby_version_is "3.3" do
+        platform_is_not :windows do
+          it "returns nil on a closed stream socket" do
+            ready = false
+
+            t = Thread.new do
+              client = @server.accept
+
+              Thread.pass while !ready
+              begin
+                client.recvmsg_nonblock(10)
+              rescue IO::EAGAINWaitReadable
+                retry
+              end
+            ensure
+              client.close if client
+            end
+
+            Thread.pass while t.status and t.status != "sleep"
+            t.status.should_not be_nil
+
+            socket = TCPSocket.new('127.0.0.1', @port)
+            socket.close
+            ready = true
+
+            t.value.should be_nil
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/basicsocket/recvmsg_spec.rb b/spec/ruby/library/socket/basicsocket/recvmsg_spec.rb
index 8063723701..04ba1d74c7 100644
--- a/spec/ruby/library/socket/basicsocket/recvmsg_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/recvmsg_spec.rb
@@ -195,3 +195,87 @@ describe 'BasicSocket#recvmsg' do
     end
   end
 end
+
+describe 'BasicSocket#recvmsg' do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = TCPServer.new('127.0.0.1', 0)
+        @port = @server.addr[1]
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        platform_is_not :windows do
+          it "returns an empty String as received data on a closed stream socket" do
+            t = Thread.new do
+              client = @server.accept
+              client.recvmsg(10)
+            ensure
+              client.close if client
+            end
+
+            Thread.pass while t.status and t.status != "sleep"
+            t.status.should_not be_nil
+
+            socket = TCPSocket.new('127.0.0.1', @port)
+            socket.close
+
+            t.value.should.is_a? Array
+            t.value[0].should == ""
+          end
+        end
+      end
+
+      ruby_version_is "3.3" do
+        platform_is_not :windows do
+          it "returns nil on a closed stream socket" do
+            t = Thread.new do
+              client = @server.accept
+              client.recvmsg(10)
+            ensure
+              client.close if client
+            end
+
+            Thread.pass while t.status and t.status != "sleep"
+            t.status.should_not be_nil
+
+            socket = TCPSocket.new('127.0.0.1', @port)
+            socket.close
+
+            t.value.should be_nil
+          end
+        end
+      end
+    end
+
+    describe "datagram socket" do
+      SocketSpecs.each_ip_protocol do |family, ip_address|
+        before :each do
+          @server = UDPSocket.new(family)
+          @client = UDPSocket.new(family)
+        end
+
+        after :each do
+          @server.close unless @server.closed?
+          @client.close unless @client.closed?
+        end
+
+        it "returns an empty String as received data" do
+          @server.bind(ip_address, 0)
+          addr = @server.connect_address
+          @client.connect(addr.ip_address, addr.ip_port)
+
+          @client.send('', 0)
+          message = @server.recvmsg(1)
+
+          message.should.is_a? Array
+          message[0].should == ""
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/basicsocket/remote_address_spec.rb b/spec/ruby/library/socket/basicsocket/remote_address_spec.rb
new file mode 100644
index 0000000000..439bf31592
--- /dev/null
+++ b/spec/ruby/library/socket/basicsocket/remote_address_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../spec_helper'
+require_relative '../shared/address'
+
+describe 'BasicSocket#remote_address' do
+  it_behaves_like :socket_local_remote_address, :remote_address, -> socket {
+    a2 = BasicSocket.for_fd(socket.fileno)
+    a2.autoclose = false
+    a2.remote_address
+  }
+end
diff --git a/spec/ruby/library/socket/basicsocket/send_spec.rb b/spec/ruby/library/socket/basicsocket/send_spec.rb
index 041ee46998..25ba3f5655 100644
--- a/spec/ruby/library/socket/basicsocket/send_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/send_spec.rb
@@ -16,29 +16,29 @@ describe "BasicSocket#send" do
     @socket.close
   end
 
-   it "sends a message to another socket and returns the number of bytes sent" do
-     data = ""
-     t = Thread.new do
-       client = @server.accept
-       loop do
-         got = client.recv(5)
-         break if got.empty?
-         data << got
-       end
-       client.close
-     end
-     Thread.pass while t.status and t.status != "sleep"
-     t.status.should_not be_nil
-
-     @socket.send('hello', 0).should == 5
-     @socket.shutdown(1) # indicate, that we are done sending
-     @socket.recv(10)
-
-     t.join
-     data.should == 'hello'
-   end
-
-  platform_is_not :solaris, :windows do
+  it "sends a message to another socket and returns the number of bytes sent" do
+    data = +""
+    t = Thread.new do
+      client = @server.accept
+      loop do
+        got = client.recv(5)
+        break if got.nil? || got.empty?
+        data << got
+      end
+      client.close
+    end
+    Thread.pass while t.status and t.status != "sleep"
+    t.status.should_not be_nil
+
+    @socket.send('hello', 0).should == 5
+    @socket.shutdown(1) # indicate, that we are done sending
+    @socket.recv(10)
+
+    t.join
+    data.should == 'hello'
+  end
+
+  platform_is_not :windows do
     it "accepts flags to specify unusual sending behaviour" do
       data = nil
       peek_data = nil
@@ -62,25 +62,25 @@ describe "BasicSocket#send" do
   end
 
   it "accepts a sockaddr as recipient address" do
-     data = ""
-     t = Thread.new do
-       client = @server.accept
-       loop do
-         got = client.recv(5)
-         break if got.empty?
-         data << got
-       end
-       client.close
-     end
-     Thread.pass while t.status and t.status != "sleep"
-     t.status.should_not be_nil
-
-     sockaddr = Socket.pack_sockaddr_in(@port, "127.0.0.1")
-     @socket.send('hello', 0, sockaddr).should == 5
-     @socket.shutdown # indicate, that we are done sending
-
-     t.join
-     data.should == 'hello'
+    data = +""
+    t = Thread.new do
+      client = @server.accept
+      loop do
+        got = client.recv(5)
+        break if got.nil? || got.empty?
+        data << got
+      end
+      client.close
+    end
+    Thread.pass while t.status and t.status != "sleep"
+    t.status.should_not be_nil
+
+    sockaddr = Socket.pack_sockaddr_in(@port, "127.0.0.1")
+    @socket.send('hello', 0, sockaddr).should == 5
+    @socket.shutdown # indicate, that we are done sending
+
+    t.join
+    data.should == 'hello'
   end
 end
 
@@ -99,6 +99,14 @@ describe 'BasicSocket#send' do
         @server.close
       end
 
+      describe 'with an object implementing #to_str' do
+        it 'returns the amount of sent bytes' do
+          data = mock('message')
+          data.should_receive(:to_str).and_return('hello')
+          @client.send(data, 0, @server.getsockname).should == 5
+        end
+      end
+
       describe 'without a destination address' do
         it "raises #{SocketSpecs.dest_addr_req_error}" do
           -> { @client.send('hello', 0) }.should raise_error(SocketSpecs.dest_addr_req_error)
diff --git a/spec/ruby/library/socket/basicsocket/sendmsg_nonblock_spec.rb b/spec/ruby/library/socket/basicsocket/sendmsg_nonblock_spec.rb
index c112f2ab4a..7acfc659bd 100644
--- a/spec/ruby/library/socket/basicsocket/sendmsg_nonblock_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/sendmsg_nonblock_spec.rb
@@ -18,7 +18,12 @@ describe 'BasicSocket#sendmsg_nonblock' do
 
       describe 'without a destination address' do
         it "raises #{SocketSpecs.dest_addr_req_error}" do
-          -> { @client.sendmsg_nonblock('hello') }.should raise_error(SocketSpecs.dest_addr_req_error)
+          -> {
+            @client.sendmsg_nonblock('hello')
+          }.should raise_error(SocketSpecs.dest_addr_req_error)
+          -> {
+            @client.sendmsg_nonblock('hello', exception: false)
+          }.should raise_error(SocketSpecs.dest_addr_req_error)
         end
       end
 
diff --git a/spec/ruby/library/socket/basicsocket/setsockopt_spec.rb b/spec/ruby/library/socket/basicsocket/setsockopt_spec.rb
index 1e8d84e1c9..f686e67326 100644
--- a/spec/ruby/library/socket/basicsocket/setsockopt_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/setsockopt_spec.rb
@@ -315,22 +315,20 @@ describe 'BasicSocket#setsockopt' do
     end
   end
 
-  with_feature :unix_socket do
-    describe 'using a UNIX socket' do
-      before do
-        @path = SocketSpecs.socket_path
-        @server = UNIXServer.new(@path)
-      end
+  describe 'using a UNIX socket' do
+    before do
+      @path = SocketSpecs.socket_path
+      @server = UNIXServer.new(@path)
+    end
 
-      after do
-        @server.close
-        rm_r @path
-      end
+    after do
+      @server.close
+      rm_r @path
+    end
 
-      it 'sets a boolean option' do
-        @server.setsockopt(:SOCKET, :REUSEADDR, true)
-        @server.getsockopt(:SOCKET, :REUSEADDR).bool.should == true
-      end
+    it 'sets a boolean option' do
+      @server.setsockopt(:SOCKET, :REUSEADDR, true)
+      @server.getsockopt(:SOCKET, :REUSEADDR).bool.should == true
     end
   end
 end
diff --git a/spec/ruby/library/socket/basicsocket/shutdown_spec.rb b/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
index 41d9581bde..c78b32de38 100644
--- a/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
+++ b/spec/ruby/library/socket/basicsocket/shutdown_spec.rb
@@ -23,7 +23,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading' do
           @client.shutdown(Socket::SHUT_RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing' do
@@ -35,7 +35,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading and writing' do
           @client.shutdown(Socket::SHUT_RDWR)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
@@ -49,13 +49,13 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading using :RD' do
           @client.shutdown(:RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using :SHUT_RD' do
           @client.shutdown(:SHUT_RD)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing using :WR' do
@@ -73,7 +73,7 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading and writing' do
           @client.shutdown(:RDWR)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
@@ -87,13 +87,13 @@ platform_is_not :windows do # hangs
         it 'shuts down a socket for reading using "RD"' do
           @client.shutdown('RD')
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using "SHUT_RD"' do
           @client.shutdown('SHUT_RD')
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for writing using "WR"' do
@@ -123,7 +123,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading using "SHUT_RD"' do
@@ -131,7 +131,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
         end
 
         it 'shuts down a socket for reading and writing' do
@@ -139,7 +139,7 @@ platform_is_not :windows do # hangs
 
           @client.shutdown(@dummy)
 
-          @client.recv(1).should be_empty
+          @client.recv(1).to_s.should be_empty
 
           -> { @client.write('hello') }.should raise_error(Errno::EPIPE)
         end
diff --git a/spec/ruby/library/socket/basicsocket/write_nonblock_spec.rb b/spec/ruby/library/socket/basicsocket/write_nonblock_spec.rb
new file mode 100644
index 0000000000..523e732959
--- /dev/null
+++ b/spec/ruby/library/socket/basicsocket/write_nonblock_spec.rb
@@ -0,0 +1,43 @@
+require_relative '../spec_helper'
+require_relative '../fixtures/classes'
+
+describe "BasicSocket#write_nonblock" do
+  SocketSpecs.each_ip_protocol do |family, ip_address|
+    before :each do
+      @r = Socket.new(family, :DGRAM)
+      @w = Socket.new(family, :DGRAM)
+
+      @r.bind(Socket.pack_sockaddr_in(0, ip_address))
+      @w.connect(@r.getsockname)
+    end
+
+    after :each do
+      @r.close unless @r.closed?
+      @w.close unless @w.closed?
+    end
+
+    it "sends data" do
+      @w.write_nonblock("aaa").should == 3
+      IO.select([@r], nil, nil, 2)
+      @r.recv_nonblock(5).should == "aaa"
+    end
+
+    platform_is :linux do
+      it 'does not set the IO in nonblock mode' do
+        require 'io/nonblock'
+        @w.nonblock = false
+        @w.write_nonblock("aaa").should == 3
+        @w.should_not.nonblock?
+      end
+    end
+
+    platform_is_not :linux, :windows do
+      it 'sets the IO in nonblock mode' do
+        require 'io/nonblock'
+        @w.nonblock = false
+        @w.write_nonblock("aaa").should == 3
+        @w.should.nonblock?
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/constants/constants_spec.rb b/spec/ruby/library/socket/constants/constants_spec.rb
index 710af12828..b9a9d42725 100644
--- a/spec/ruby/library/socket/constants/constants_spec.rb
+++ b/spec/ruby/library/socket/constants/constants_spec.rb
@@ -68,7 +68,7 @@ describe "Socket::Constants" do
     end
   end
 
-  platform_is_not :solaris, :windows, :aix do
+  platform_is_not :windows, :aix, :android do
     it "defines multicast options" do
       consts = ["IP_MAX_MEMBERSHIPS"]
       consts.each do |c|
diff --git a/spec/ruby/library/socket/fixtures/classes.rb b/spec/ruby/library/socket/fixtures/classes.rb
index 4a590502ca..786629d2ef 100644
--- a/spec/ruby/library/socket/fixtures/classes.rb
+++ b/spec/ruby/library/socket/fixtures/classes.rb
@@ -37,7 +37,9 @@ module SocketSpecs
     # Check for too long unix socket path (max 104 bytes on macOS)
     # Note that Linux accepts not null-terminated paths but the man page advises against it.
     if path.bytesize > 104
-      path = "/tmp/unix_server_spec.socket"
+      # rm_r in spec/mspec/lib/mspec/helpers/fs.rb fails against
+      # "/tmp/unix_server_spec.socket"
+      skip "too long unix socket path: #{path}"
     end
     rm_socket(path)
     path
@@ -111,7 +113,7 @@ module SocketSpecs
       begin
         data = socket.recv(1024)
 
-        return if data.empty?
+        return if data.nil? || data.empty?
         log "SpecTCPServer received: #{data.inspect}"
 
         return if data == "QUIT"
diff --git a/spec/ruby/library/socket/ipsocket/getaddress_spec.rb b/spec/ruby/library/socket/ipsocket/getaddress_spec.rb
index 746d2ab86b..329f8267d3 100644
--- a/spec/ruby/library/socket/ipsocket/getaddress_spec.rb
+++ b/spec/ruby/library/socket/ipsocket/getaddress_spec.rb
@@ -2,7 +2,6 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "Socket::IPSocket#getaddress" do
-
   it "returns the IP address of hostname" do
     addr_local = IPSocket.getaddress(SocketSpecs.hostname)
     ["127.0.0.1", "::1"].include?(addr_local).should == true
@@ -14,12 +13,16 @@ describe "Socket::IPSocket#getaddress" do
     IPSocket.getaddress('::1').should == '::1'
   end
 
+  it 'returns IPv4 compatible IPv6 addresses' do
+    IPSocket.getaddress('::ffff:192.168.1.1').should == '::ffff:192.168.1.1'
+  end
+
   # There is no way to make this fail-proof on all machines, because
   # DNS servers like opendns return A records for ANY host, including
   # traditionally invalidly named ones.
   it "raises an error on unknown hostnames" do
     -> {
-      IPSocket.getaddress("rubyspecdoesntexist.fallingsnow.net")
+      IPSocket.getaddress("rubyspecdoesntexist.ruby-lang.org")
     }.should raise_error(SocketError)
   end
 end
diff --git a/spec/ruby/library/socket/ipsocket/recvfrom_spec.rb b/spec/ruby/library/socket/ipsocket/recvfrom_spec.rb
index 3bcb7b8f02..b58903df23 100644
--- a/spec/ruby/library/socket/ipsocket/recvfrom_spec.rb
+++ b/spec/ruby/library/socket/ipsocket/recvfrom_spec.rb
@@ -64,11 +64,93 @@ describe "Socket::IPSocket#recvfrom" do
 
     data.size.should == 2
     data.first.should == "hel"
-    # This does not apply to every platform, dependant on recvfrom(2)
+    # This does not apply to every platform, dependent on recvfrom(2)
     # data.last.should == nil
   end
 end
 
+describe "Socket::IPSocket#recvfrom" do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = TCPServer.new("127.0.0.1", 0)
+        port = @server.addr[1]
+        @client = TCPSocket.new("127.0.0.1", port)
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+        @client.close unless @client.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        it "returns an empty String as received data on a closed stream socket" do
+          t = Thread.new do
+            client = @server.accept
+            message = client.recvfrom(10)
+            message
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.close
+
+          t.value.should.is_a? Array
+          t.value[0].should == ""
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "returns nil on a closed stream socket" do
+          t = Thread.new do
+            client = @server.accept
+            message = client.recvfrom(10)
+            message
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.close
+
+          t.value.should be_nil
+        end
+      end
+    end
+
+    describe "datagram socket" do
+      SocketSpecs.each_ip_protocol do |family, ip_address|
+        before :each do
+          @server = UDPSocket.new(family)
+          @client = UDPSocket.new(family)
+        end
+
+        after :each do
+          @server.close unless @server.closed?
+          @client.close unless @client.closed?
+        end
+
+        it "returns an empty String as received data" do
+          @server.bind(ip_address, 0)
+          addr = @server.connect_address
+          @client.connect(addr.ip_address, addr.ip_port)
+
+          @client.send('', 0)
+          message = @server.recvfrom(1)
+
+          message.should.is_a? Array
+          message[0].should == ""
+        end
+      end
+    end
+  end
+end
+
 describe 'Socket::IPSocket#recvfrom' do
   SocketSpecs.each_ip_protocol do |family, ip_address, family_name|
     before do
diff --git a/spec/ruby/library/socket/shared/address.rb b/spec/ruby/library/socket/shared/address.rb
new file mode 100644
index 0000000000..49ba17c400
--- /dev/null
+++ b/spec/ruby/library/socket/shared/address.rb
@@ -0,0 +1,259 @@
+require_relative '../fixtures/classes'
+
+describe :socket_local_remote_address, shared: true do
+  describe 'using TCPSocket' do
+    before :each do
+      @s = TCPServer.new('127.0.0.1', 0)
+      @a = TCPSocket.new('127.0.0.1', @s.addr[1])
+      @b = @s.accept
+      @addr = @object.call(@a)
+    end
+
+    after :each do
+      [@b, @a, @s].each(&:close)
+    end
+
+    it 'uses AF_INET as the address family' do
+      @addr.afamily.should == Socket::AF_INET
+    end
+
+    it 'uses PF_INET as the protocol family' do
+      @addr.pfamily.should == Socket::PF_INET
+    end
+
+    it 'uses SOCK_STREAM as the socket type' do
+      @addr.socktype.should == Socket::SOCK_STREAM
+    end
+
+    it 'uses the correct IP address' do
+      @addr.ip_address.should == '127.0.0.1'
+    end
+
+    it 'uses the correct port' do
+      if @method == :local_address
+        @addr.ip_port.should != @s.addr[1]
+      else
+        @addr.ip_port.should == @s.addr[1]
+      end
+    end
+
+    it 'equals address of peer socket' do
+      if @method == :local_address
+        @addr.to_s.should == @b.remote_address.to_s
+      else
+        @addr.to_s.should == @b.local_address.to_s
+      end
+    end
+
+    it 'returns an Addrinfo' do
+      @addr.should be_an_instance_of(Addrinfo)
+    end
+
+    it 'uses 0 as the protocol' do
+      @addr.protocol.should == 0
+    end
+
+    it 'can be used to connect to the server' do
+      skip if @method == :local_address
+      b = @addr.connect
+      begin
+        b.remote_address.to_s.should == @addr.to_s
+      ensure
+        b.close
+      end
+    end
+  end
+
+  guard -> { SocketSpecs.ipv6_available? } do
+    describe 'using IPv6' do
+      before :each do
+        @s = TCPServer.new('::1', 0)
+        @a = TCPSocket.new('::1', @s.addr[1])
+        @b = @s.accept
+        @addr = @object.call(@a)
+      end
+
+      after :each do
+        [@b, @a, @s].each(&:close)
+      end
+
+      it 'uses AF_INET6 as the address family' do
+        @addr.afamily.should == Socket::AF_INET6
+      end
+
+      it 'uses PF_INET6 as the protocol family' do
+        @addr.pfamily.should == Socket::PF_INET6
+      end
+
+      it 'uses SOCK_STREAM as the socket type' do
+        @addr.socktype.should == Socket::SOCK_STREAM
+      end
+
+      it 'uses the correct IP address' do
+        @addr.ip_address.should == '::1'
+      end
+
+      it 'uses the correct port' do
+        if @method == :local_address
+          @addr.ip_port.should != @s.addr[1]
+        else
+          @addr.ip_port.should == @s.addr[1]
+        end
+      end
+
+      it 'equals address of peer socket' do
+        if @method == :local_address
+          @addr.to_s.should == @b.remote_address.to_s
+        else
+          @addr.to_s.should == @b.local_address.to_s
+        end
+      end
+
+      it 'returns an Addrinfo' do
+        @addr.should be_an_instance_of(Addrinfo)
+      end
+
+      it 'uses 0 as the protocol' do
+        @addr.protocol.should == 0
+      end
+
+      it 'can be used to connect to the server' do
+        skip if @method == :local_address
+        b = @addr.connect
+        begin
+          b.remote_address.to_s.should == @addr.to_s
+        ensure
+          b.close
+        end
+      end
+    end
+  end
+
+  describe 'using UNIXSocket' do
+    before :each do
+      @path = SocketSpecs.socket_path
+      @s = UNIXServer.new(@path)
+      @a = UNIXSocket.new(@path)
+      @b = @s.accept
+      @addr = @object.call(@a)
+    end
+
+    after :each do
+      [@b, @a, @s].each(&:close)
+      rm_r(@path)
+    end
+
+    it 'uses AF_UNIX as the address family' do
+      @addr.afamily.should == Socket::AF_UNIX
+    end
+
+    it 'uses PF_UNIX as the protocol family' do
+      @addr.pfamily.should == Socket::PF_UNIX
+    end
+
+    it 'uses SOCK_STREAM as the socket type' do
+      @addr.socktype.should == Socket::SOCK_STREAM
+    end
+
+    it 'uses the correct socket path' do
+      if @method == :local_address
+        @addr.unix_path.should == ""
+      else
+        @addr.unix_path.should == @path
+      end
+    end
+
+    platform_is_not :windows do
+      it 'equals address of peer socket' do
+        if @method == :local_address
+          @addr.to_s.should == @b.remote_address.to_s
+        else
+          @addr.to_s.should == @b.local_address.to_s
+        end
+      end
+    end
+
+    guard -> { platform_is :windows and ruby_bug "#21702", ""..."4.2" } do
+      it 'equals address of peer socket' do
+        if @method == :local_address
+          @addr.to_s.should == @b.remote_address.to_s
+        else
+          @addr.to_s.should == @b.local_address.to_s
+        end
+      end
+    end
+
+    it 'returns an Addrinfo' do
+      @addr.should be_an_instance_of(Addrinfo)
+    end
+
+    it 'uses 0 as the protocol' do
+      @addr.protocol.should == 0
+    end
+
+    it 'can be used to connect to the server' do
+      skip if @method == :local_address
+      b = @addr.connect
+      begin
+        b.remote_address.to_s.should == @addr.to_s
+      ensure
+        b.close
+      end
+    end
+  end
+
+  describe 'using UDPSocket' do
+    before :each do
+      @s = UDPSocket.new
+      @s.bind("127.0.0.1", 0)
+      @a = UDPSocket.new
+      @a.connect("127.0.0.1", @s.addr[1])
+      @addr = @object.call(@a)
+    end
+
+    after :each do
+      [@a, @s].each(&:close)
+    end
+
+    it 'uses the correct address family' do
+      @addr.afamily.should == Socket::AF_INET
+    end
+
+    it 'uses the correct protocol family' do
+      @addr.pfamily.should == Socket::PF_INET
+    end
+
+    it 'uses SOCK_DGRAM as the socket type' do
+      @addr.socktype.should == Socket::SOCK_DGRAM
+    end
+
+    it 'uses the correct IP address' do
+      @addr.ip_address.should == '127.0.0.1'
+    end
+
+    it 'uses the correct port' do
+      if @method == :local_address
+        @addr.ip_port.should != @s.addr[1]
+      else
+        @addr.ip_port.should == @s.addr[1]
+      end
+    end
+
+    it 'returns an Addrinfo' do
+      @addr.should be_an_instance_of(Addrinfo)
+    end
+
+    it 'uses 0 as the protocol' do
+      @addr.protocol.should == 0
+    end
+
+    it 'can be used to connect to the peer' do
+      b = @addr.connect
+      begin
+        b.remote_address.to_s.should == @addr.to_s
+      ensure
+        b.close
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/shared/pack_sockaddr.rb b/spec/ruby/library/socket/shared/pack_sockaddr.rb
index 2df09027c9..4bfcf4edb9 100644
--- a/spec/ruby/library/socket/shared/pack_sockaddr.rb
+++ b/spec/ruby/library/socket/shared/pack_sockaddr.rb
@@ -17,6 +17,14 @@ describe :socket_pack_sockaddr_in, shared: true do
 
     sockaddr_in = Socket.public_send(@method, nil, '127.0.0.1')
     Socket.unpack_sockaddr_in(sockaddr_in).should == [0, '127.0.0.1']
+
+    sockaddr_in = Socket.public_send(@method, 80, Socket::INADDR_ANY)
+    Socket.unpack_sockaddr_in(sockaddr_in).should == [80, '0.0.0.0']
+  end
+
+  it 'resolves the service name to a port' do
+    sockaddr_in = Socket.public_send(@method, 'http', '127.0.0.1')
+    Socket.unpack_sockaddr_in(sockaddr_in).should == [80, '127.0.0.1']
   end
 
   describe 'using an IPv4 address' do
@@ -28,47 +36,32 @@ describe :socket_pack_sockaddr_in, shared: true do
     end
   end
 
-  platform_is_not :solaris do
-    describe 'using an IPv6 address' do
-      it 'returns a String of 28 bytes' do
-        str = Socket.public_send(@method, 80, '::1')
-
-        str.should be_an_instance_of(String)
-        str.bytesize.should == 28
-      end
-    end
-  end
-
-  platform_is :solaris do
-    describe 'using an IPv6 address' do
-      it 'returns a String of 32 bytes' do
-        str = Socket.public_send(@method, 80, '::1')
+  describe 'using an IPv6 address' do
+    it 'returns a String of 28 bytes' do
+      str = Socket.public_send(@method, 80, '::1')
 
-        str.should be_an_instance_of(String)
-        str.bytesize.should == 32
-      end
+      str.should be_an_instance_of(String)
+      str.bytesize.should == 28
     end
   end
 end
 
 describe :socket_pack_sockaddr_un, shared: true do
-  with_feature :unix_socket do
-    it 'should be idempotent' do
-      bytes = Socket.public_send(@method, '/tmp/foo').bytes
-      bytes[2..9].should == [47, 116, 109, 112, 47, 102, 111, 111]
-      bytes[10..-1].all?(&:zero?).should == true
-    end
+  it 'should be idempotent' do
+    bytes = Socket.public_send(@method, '/tmp/foo').bytes
+    bytes[2..9].should == [47, 116, 109, 112, 47, 102, 111, 111]
+    bytes[10..-1].all?(&:zero?).should == true
+  end
 
-    it "packs and unpacks" do
-      sockaddr_un = Socket.public_send(@method, '/tmp/s')
-      Socket.unpack_sockaddr_un(sockaddr_un).should == '/tmp/s'
-    end
+  it "packs and unpacks" do
+    sockaddr_un = Socket.public_send(@method, '/tmp/s')
+    Socket.unpack_sockaddr_un(sockaddr_un).should == '/tmp/s'
+  end
 
-    it "handles correctly paths with multibyte chars" do
-      sockaddr_un = Socket.public_send(@method, '/home/вася/sock')
-      path = Socket.unpack_sockaddr_un(sockaddr_un).encode('UTF-8', 'UTF-8')
-      path.should == '/home/вася/sock'
-    end
+  it "handles correctly paths with multibyte chars" do
+    sockaddr_un = Socket.public_send(@method, '/home/вася/sock')
+    path = Socket.unpack_sockaddr_un(sockaddr_un).encode('UTF-8', 'UTF-8')
+    path.should == '/home/вася/sock'
   end
 
   platform_is :linux do
@@ -89,7 +82,7 @@ describe :socket_pack_sockaddr_un, shared: true do
     end
   end
 
-  platform_is_not :windows, :aix do
+  platform_is_not :aix do
     it "raises ArgumentError for paths that are too long" do
       # AIX doesn't raise error
       long_path = 'a' * 110
diff --git a/spec/ruby/library/socket/shared/partially_closable_sockets.rb b/spec/ruby/library/socket/shared/partially_closable_sockets.rb
index 1bdff08bf6..b1c2ebabe1 100644
--- a/spec/ruby/library/socket/shared/partially_closable_sockets.rb
+++ b/spec/ruby/library/socket/shared/partially_closable_sockets.rb
@@ -1,4 +1,4 @@
-describe "partially closable sockets", shared: true do
+describe :partially_closable_sockets, shared: true do
   it "if the write end is closed then the other side can read past EOF without blocking" do
     @s1.write("foo")
     @s1.close_write
diff --git a/spec/ruby/library/socket/socket/accept_nonblock_spec.rb b/spec/ruby/library/socket/socket/accept_nonblock_spec.rb
index 3221f0b128..011622988c 100644
--- a/spec/ruby/library/socket/socket/accept_nonblock_spec.rb
+++ b/spec/ruby/library/socket/socket/accept_nonblock_spec.rb
@@ -46,6 +46,7 @@ describe 'Socket#accept_nonblock' do
     describe 'using an unbound socket' do
       it 'raises Errno::EINVAL' do
         -> { @server.accept_nonblock }.should raise_error(Errno::EINVAL)
+        -> { @server.accept_nonblock(exception: false) }.should raise_error(Errno::EINVAL)
       end
     end
 
@@ -56,6 +57,7 @@ describe 'Socket#accept_nonblock' do
 
       it 'raises Errno::EINVAL' do
         -> { @server.accept_nonblock }.should raise_error(Errno::EINVAL)
+        -> { @server.accept_nonblock(exception: false) }.should raise_error(Errno::EINVAL)
       end
     end
 
@@ -64,6 +66,7 @@ describe 'Socket#accept_nonblock' do
         @server.close
 
         -> { @server.accept_nonblock }.should raise_error(IOError)
+        -> { @server.accept_nonblock(exception: false) }.should raise_error(IOError)
       end
     end
 
diff --git a/spec/ruby/library/socket/socket/bind_spec.rb b/spec/ruby/library/socket/socket/bind_spec.rb
index 0349df84a6..e76336eafa 100644
--- a/spec/ruby/library/socket/socket/bind_spec.rb
+++ b/spec/ruby/library/socket/socket/bind_spec.rb
@@ -33,6 +33,7 @@ describe "Socket#bind on SOCK_DGRAM socket" do
 
   platform_is_not :windows, :cygwin do
     as_user do
+      break if File.read('/proc/sys/net/ipv4/ip_unprivileged_port_start').to_i <= 1 rescue nil
       it "raises Errno::EACCES when the current user does not have permission to bind" do
         sockaddr1 = Socket.pack_sockaddr_in(1, "127.0.0.1")
         -> { @sock.bind(sockaddr1) }.should raise_error(Errno::EACCES)
@@ -74,6 +75,7 @@ describe "Socket#bind on SOCK_STREAM socket" do
 
   platform_is_not :windows, :cygwin do
     as_user do
+      break if File.read('/proc/sys/net/ipv4/ip_unprivileged_port_start').to_i <= 1 rescue nil
       it "raises Errno::EACCES when the current user does not have permission to bind" do
         sockaddr1 = Socket.pack_sockaddr_in(1, "127.0.0.1")
         -> { @sock.bind(sockaddr1) }.should raise_error(Errno::EACCES)
@@ -113,12 +115,14 @@ describe 'Socket#bind' do
 
       platform_is_not :windows do
         as_user do
+          break if File.read('/proc/sys/net/ipv4/ip_unprivileged_port_start').to_i <= 1 rescue nil
+
           it 'raises Errno::EACCES when the user is not allowed to bind to the port' do
             sockaddr1 = Socket.pack_sockaddr_in(1, ip_address)
 
             -> { @socket.bind(sockaddr1) }.should raise_error(Errno::EACCES)
           end
-       end
+        end
       end
     end
 
diff --git a/spec/ruby/library/socket/socket/connect_nonblock_spec.rb b/spec/ruby/library/socket/socket/connect_nonblock_spec.rb
index 3cf667fc4a..359b8719fb 100644
--- a/spec/ruby/library/socket/socket/connect_nonblock_spec.rb
+++ b/spec/ruby/library/socket/socket/connect_nonblock_spec.rb
@@ -16,42 +16,40 @@ describe "Socket#connect_nonblock" do
     @thread.join if @thread
   end
 
-  platform_is_not :solaris do
-    it "connects the socket to the remote side" do
-      port = nil
-      accept = false
-      @thread = Thread.new do
-        server = TCPServer.new(@hostname, 0)
-        port = server.addr[1]
-        Thread.pass until accept
-        conn = server.accept
-        conn << "hello!"
-        conn.close
-        server.close
-      end
-
-      Thread.pass until port
+  it "connects the socket to the remote side" do
+    port = nil
+    accept = false
+    @thread = Thread.new do
+      server = TCPServer.new(@hostname, 0)
+      port = server.addr[1]
+      Thread.pass until accept
+      conn = server.accept
+      conn << "hello!"
+      conn.close
+      server.close
+    end
 
-      addr = Socket.sockaddr_in(port, @hostname)
-      begin
-        @socket.connect_nonblock(addr)
-      rescue Errno::EINPROGRESS
-      end
+    Thread.pass until port
 
-      accept = true
-      IO.select nil, [@socket]
+    addr = Socket.sockaddr_in(port, @hostname)
+    begin
+      @socket.connect_nonblock(addr)
+    rescue Errno::EINPROGRESS
+    end
 
-      begin
-        @socket.connect_nonblock(addr)
-      rescue Errno::EISCONN
-        # Not all OS's use this errno, so we trap and ignore it
-      end
+    accept = true
+    IO.select nil, [@socket]
 
-      @socket.read(6).should == "hello!"
+    begin
+      @socket.connect_nonblock(addr)
+    rescue Errno::EISCONN
+      # Not all OS's use this errno, so we trap and ignore it
     end
+
+    @socket.read(6).should == "hello!"
   end
 
-  platform_is_not :freebsd, :solaris, :aix do
+  platform_is_not :freebsd, :aix do
     it "raises Errno::EINPROGRESS when the connect would block" do
       -> do
         @socket.connect_nonblock(@addr)
@@ -135,7 +133,7 @@ describe 'Socket#connect_nonblock' do
         end
       end
 
-      platform_is_not :freebsd, :solaris do
+      platform_is_not :freebsd do
         it 'raises IO:EINPROGRESSWaitWritable when the connection would block' do
           @server.bind(@sockaddr)
 
diff --git a/spec/ruby/library/socket/socket/connect_spec.rb b/spec/ruby/library/socket/socket/connect_spec.rb
index 8653fba552..130379ce2b 100644
--- a/spec/ruby/library/socket/socket/connect_spec.rb
+++ b/spec/ruby/library/socket/socket/connect_spec.rb
@@ -53,4 +53,26 @@ describe 'Socket#connect' do
       end
     end
   end
+
+  ruby_version_is "3.4" do
+    it "fails with timeout" do
+      # TEST-NET-1 IP address are reserved for documentation and example purposes.
+      address = Socket.pack_sockaddr_in(1, "192.0.2.1")
+
+      client = Socket.new(Socket::AF_INET, Socket::SOCK_STREAM)
+      client.timeout = 0
+
+      -> {
+        begin
+          client.connect(address)
+        rescue Errno::ECONNREFUSED
+          skip "Outgoing packets may be filtered"
+        rescue Errno::ENETUNREACH
+          skip "Off line"
+        end
+      }.should raise_error(IO::TimeoutError)
+    ensure
+      client.close
+    end
+  end
 end
diff --git a/spec/ruby/library/socket/socket/getaddrinfo_spec.rb b/spec/ruby/library/socket/socket/getaddrinfo_spec.rb
index e0eff3cef4..6576af52ee 100644
--- a/spec/ruby/library/socket/socket/getaddrinfo_spec.rb
+++ b/spec/ruby/library/socket/socket/getaddrinfo_spec.rb
@@ -11,7 +11,7 @@ describe "Socket.getaddrinfo" do
     BasicSocket.do_not_reverse_lookup = @do_not_reverse_lookup
   end
 
-  platform_is_not :solaris, :windows do
+  platform_is_not :windows do
     it "gets the address information" do
       expected = []
       # The check for AP_INET6's class is needed because ipaddr.rb adds
@@ -106,6 +106,24 @@ describe "Socket.getaddrinfo" do
       ]
       res.each { |a| expected.should include(a) }
     end
+
+    ruby_version_is ""..."3.3" do
+      it "raises SocketError when fails to resolve address" do
+        -> {
+          Socket.getaddrinfo("www.kame.net", 80, "AF_UNIX")
+        }.should raise_error(SocketError)
+      end
+    end
+
+    ruby_version_is "3.3" do
+      it "raises ResolutionError when fails to resolve address" do
+        -> {
+          Socket.getaddrinfo("www.kame.net", 80, "AF_UNIX")
+        }.should raise_error(Socket::ResolutionError) { |e|
+          [Socket::EAI_FAMILY, Socket::EAI_FAIL].should.include?(e.error_code)
+        }
+      end
+    end
   end
 end
 
diff --git a/spec/ruby/library/socket/socket/gethostbyaddr_spec.rb b/spec/ruby/library/socket/socket/gethostbyaddr_spec.rb
index 5d97341103..5d936046f5 100644
--- a/spec/ruby/library/socket/socket/gethostbyaddr_spec.rb
+++ b/spec/ruby/library/socket/socket/gethostbyaddr_spec.rb
@@ -10,19 +10,16 @@ describe 'Socket.gethostbyaddr' do
 
     describe 'without an explicit address family' do
       it 'returns an Array' do
-        Socket.gethostbyaddr(@addr).should be_an_instance_of(Array)
+        suppress_warning { Socket.gethostbyaddr(@addr) }.should be_an_instance_of(Array)
       end
 
       describe 'the returned Array' do
         before do
-          @array = Socket.gethostbyaddr(@addr)
+          @array = suppress_warning { Socket.gethostbyaddr(@addr) }
         end
 
-        # RubyCI Solaris 11x defines 127.0.0.1 as unstable11x
-        platform_is_not :"solaris2.11" do
-          it 'includes the hostname as the first value' do
-            @array[0].should == SocketSpecs.hostname_reverse_lookup
-          end
+        it 'includes the hostname as the first value' do
+          @array[0].should == SocketSpecs.hostname_reverse_lookup
         end
 
         it 'includes the aliases as the 2nd value' do
@@ -49,15 +46,15 @@ describe 'Socket.gethostbyaddr' do
 
     describe 'with an explicit address family' do
       it 'returns an Array when using an Integer as the address family' do
-        Socket.gethostbyaddr(@addr, Socket::AF_INET).should be_an_instance_of(Array)
+        suppress_warning { Socket.gethostbyaddr(@addr, Socket::AF_INET) }.should be_an_instance_of(Array)
       end
 
       it 'returns an Array when using a Symbol as the address family' do
-        Socket.gethostbyaddr(@addr, :INET).should be_an_instance_of(Array)
+        suppress_warning { Socket.gethostbyaddr(@addr, :INET) }.should be_an_instance_of(Array)
       end
 
       it 'raises SocketError when the address is not supported by the family' do
-        -> { Socket.gethostbyaddr(@addr, :INET6) }.should raise_error(SocketError)
+        -> { suppress_warning { Socket.gethostbyaddr(@addr, :INET6) } }.should raise_error(SocketError)
       end
     end
   end
@@ -70,12 +67,12 @@ describe 'Socket.gethostbyaddr' do
 
       describe 'without an explicit address family' do
         it 'returns an Array' do
-          Socket.gethostbyaddr(@addr).should be_an_instance_of(Array)
+          suppress_warning { Socket.gethostbyaddr(@addr) }.should be_an_instance_of(Array)
         end
 
         describe 'the returned Array' do
           before do
-            @array = Socket.gethostbyaddr(@addr)
+            @array = suppress_warning { Socket.gethostbyaddr(@addr) }
           end
 
           it 'includes the hostname as the first value' do
@@ -106,16 +103,16 @@ describe 'Socket.gethostbyaddr' do
 
       describe 'with an explicit address family' do
         it 'returns an Array when using an Integer as the address family' do
-          Socket.gethostbyaddr(@addr, Socket::AF_INET6).should be_an_instance_of(Array)
+          suppress_warning { Socket.gethostbyaddr(@addr, Socket::AF_INET6) }.should be_an_instance_of(Array)
         end
 
         it 'returns an Array when using a Symbol as the address family' do
-          Socket.gethostbyaddr(@addr, :INET6).should be_an_instance_of(Array)
+          suppress_warning { Socket.gethostbyaddr(@addr, :INET6) }.should be_an_instance_of(Array)
         end
 
-        platform_is_not :windows do
+        platform_is_not :windows, :wsl do
           it 'raises SocketError when the address is not supported by the family' do
-            -> { Socket.gethostbyaddr(@addr, :INET) }.should raise_error(SocketError)
+            -> { suppress_warning { Socket.gethostbyaddr(@addr, :INET) } }.should raise_error(SocketError)
           end
         end
       end
diff --git a/spec/ruby/library/socket/socket/gethostbyname_spec.rb b/spec/ruby/library/socket/socket/gethostbyname_spec.rb
index 2696f44566..618ef85387 100644
--- a/spec/ruby/library/socket/socket/gethostbyname_spec.rb
+++ b/spec/ruby/library/socket/socket/gethostbyname_spec.rb
@@ -1,27 +1,27 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "Socket.gethostbyname" do
   it "returns broadcast address info for '<broadcast>'" do
-    addr = Socket.gethostbyname('<broadcast>');
+    addr = suppress_warning { Socket.gethostbyname('<broadcast>') }
     addr.should == ["255.255.255.255", [], 2, "\xFF\xFF\xFF\xFF"]
   end
 
   it "returns broadcast address info for '<any>'" do
-    addr = Socket.gethostbyname('<any>');
+    addr = suppress_warning { Socket.gethostbyname('<any>') }
     addr.should == ["0.0.0.0", [], 2, "\x00\x00\x00\x00"]
   end
 end
 
 describe 'Socket.gethostbyname' do
   it 'returns an Array' do
-    Socket.gethostbyname('127.0.0.1').should be_an_instance_of(Array)
+    suppress_warning { Socket.gethostbyname('127.0.0.1') }.should be_an_instance_of(Array)
   end
 
   describe 'the returned Array' do
     before do
-      @array = Socket.gethostbyname('127.0.0.1')
+      @array = suppress_warning { Socket.gethostbyname('127.0.0.1') }
     end
 
     it 'includes the hostname as the first value' do
@@ -54,7 +54,7 @@ describe 'Socket.gethostbyname' do
   describe 'using <broadcast> as the input address' do
     describe 'the returned Array' do
       before do
-        @addr = Socket.gethostbyname('<broadcast>')
+        @addr = suppress_warning { Socket.gethostbyname('<broadcast>') }
       end
 
       it 'includes the broadcast address as the first value' do
@@ -74,7 +74,7 @@ describe 'Socket.gethostbyname' do
   describe 'using <any> as the input address' do
     describe 'the returned Array' do
       before do
-        @addr = Socket.gethostbyname('<any>')
+        @addr = suppress_warning { Socket.gethostbyname('<any>') }
       end
 
       it 'includes the wildcard address as the first value' do
@@ -94,7 +94,7 @@ describe 'Socket.gethostbyname' do
   describe 'using an IPv4 address' do
     describe 'the returned Array' do
       before do
-        @addr = Socket.gethostbyname('127.0.0.1')
+        @addr = suppress_warning { Socket.gethostbyname('127.0.0.1') }
       end
 
       it 'includes the IP address as the first value' do
@@ -115,7 +115,7 @@ describe 'Socket.gethostbyname' do
     describe 'using an IPv6 address' do
       describe 'the returned Array' do
         before do
-          @addr = Socket.gethostbyname('::1')
+          @addr = suppress_warning { Socket.gethostbyname('::1') }
         end
 
         it 'includes the IP address as the first value' do
diff --git a/spec/ruby/library/socket/socket/gethostname_spec.rb b/spec/ruby/library/socket/socket/gethostname_spec.rb
index 4b79747b27..dfca7cf5cd 100644
--- a/spec/ruby/library/socket/socket/gethostname_spec.rb
+++ b/spec/ruby/library/socket/socket/gethostname_spec.rb
@@ -2,7 +2,17 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "Socket.gethostname" do
+  def system_hostname
+    if platform_is_not :windows
+      # `uname -n` is the most portable way to get the hostname, as it is a POSIX standard:
+      `uname -n`.strip
+    else
+      # Windows does not have uname, so we use hostname instead:
+      `hostname`.strip
+    end
+  end
+
   it "returns the host name" do
-    Socket.gethostname.should == `hostname`.strip
+    Socket.gethostname.should == system_hostname
   end
 end
diff --git a/spec/ruby/library/socket/socket/getifaddrs_spec.rb b/spec/ruby/library/socket/socket/getifaddrs_spec.rb
index 7df542abe6..839854ea27 100644
--- a/spec/ruby/library/socket/socket/getifaddrs_spec.rb
+++ b/spec/ruby/library/socket/socket/getifaddrs_spec.rb
@@ -1,6 +1,6 @@
 require_relative '../spec_helper'
 
-platform_is_not :aix, :"solaris2.10" do
+platform_is_not :aix do
 describe 'Socket.getifaddrs' do
   before do
     @ifaddrs = Socket.getifaddrs
diff --git a/spec/ruby/library/socket/socket/getnameinfo_spec.rb b/spec/ruby/library/socket/socket/getnameinfo_spec.rb
index b406348aa8..af4a10c9c2 100644
--- a/spec/ruby/library/socket/socket/getnameinfo_spec.rb
+++ b/spec/ruby/library/socket/socket/getnameinfo_spec.rb
@@ -60,6 +60,24 @@ describe "Socket.getnameinfo" do
     name_info = Socket.getnameinfo ["AF_INET", 9, 'foo', '127.0.0.1']
     name_info[1].should == 'discard'
   end
+
+  ruby_version_is ""..."3.3" do
+    it "raises SocketError when fails to resolve address" do
+      -> {
+        Socket.getnameinfo(["AF_UNIX", 80, "0.0.0.0"])
+      }.should raise_error(SocketError)
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises ResolutionError when fails to resolve address" do
+      -> {
+        Socket.getnameinfo(["AF_UNIX", 80, "0.0.0.0"])
+      }.should raise_error(Socket::ResolutionError) { |e|
+        [Socket::EAI_FAMILY, Socket::EAI_FAIL].should.include?(e.error_code)
+      }
+    end
+  end
 end
 
 describe 'Socket.getnameinfo' do
@@ -70,7 +88,7 @@ describe 'Socket.getnameinfo' do
 
     it 'raises SocketError or TypeError when using an invalid String' do
       -> { Socket.getnameinfo('cats') }.should raise_error(Exception) { |e|
-        [SocketError, TypeError].should include(e.class)
+        (e.is_a?(SocketError) || e.is_a?(TypeError)).should == true
       }
     end
 
diff --git a/spec/ruby/library/socket/socket/listen_spec.rb b/spec/ruby/library/socket/socket/listen_spec.rb
index 5de70d6db0..4d2aedab19 100644
--- a/spec/ruby/library/socket/socket/listen_spec.rb
+++ b/spec/ruby/library/socket/socket/listen_spec.rb
@@ -34,8 +34,10 @@ describe 'Socket#listen' do
         @server.close
       end
 
-      it 'raises Errno::EOPNOTSUPP' do
-        -> { @server.listen(1) }.should raise_error(Errno::EOPNOTSUPP)
+      it 'raises Errno::EOPNOTSUPP or Errno::EACCES' do
+        -> { @server.listen(1) }.should raise_error { |e|
+          [Errno::EOPNOTSUPP, Errno::EACCES].should.include?(e.class)
+        }
       end
     end
 
diff --git a/spec/ruby/library/socket/socket/new_spec.rb b/spec/ruby/library/socket/socket/new_spec.rb
deleted file mode 100644
index b2ec607f6a..0000000000
--- a/spec/ruby/library/socket/socket/new_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../spec_helper'
-require_relative '../fixtures/classes'
diff --git a/spec/ruby/library/socket/socket/pack_sockaddr_in_spec.rb b/spec/ruby/library/socket/socket/pack_sockaddr_in_spec.rb
index 63d4724453..ef2a2d4ba9 100644
--- a/spec/ruby/library/socket/socket/pack_sockaddr_in_spec.rb
+++ b/spec/ruby/library/socket/socket/pack_sockaddr_in_spec.rb
@@ -2,6 +2,6 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/pack_sockaddr'
 
-describe "Socket#pack_sockaddr_in" do
+describe "Socket.pack_sockaddr_in" do
   it_behaves_like :socket_pack_sockaddr_in, :pack_sockaddr_in
 end
diff --git a/spec/ruby/library/socket/socket/pair_spec.rb b/spec/ruby/library/socket/socket/pair_spec.rb
index 292eacd38d..8dd470a95e 100644
--- a/spec/ruby/library/socket/socket/pair_spec.rb
+++ b/spec/ruby/library/socket/socket/pair_spec.rb
@@ -2,6 +2,6 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/socketpair'
 
-describe "Socket#pair" do
+describe "Socket.pair" do
   it_behaves_like :socket_socketpair, :pair
 end
diff --git a/spec/ruby/library/socket/socket/recvfrom_nonblock_spec.rb b/spec/ruby/library/socket/socket/recvfrom_nonblock_spec.rb
index 94f58ac49f..01b42bcc52 100644
--- a/spec/ruby/library/socket/socket/recvfrom_nonblock_spec.rb
+++ b/spec/ruby/library/socket/socket/recvfrom_nonblock_spec.rb
@@ -52,6 +52,27 @@ describe 'Socket#recvfrom_nonblock' do
           end
         end
 
+        it "allows an output buffer as third argument" do
+          @client.write('hello')
+
+          IO.select([@server])
+          buffer = +''
+          message, = @server.recvfrom_nonblock(5, 0, buffer)
+
+          message.should.equal?(buffer)
+          buffer.should == 'hello'
+        end
+
+        it "preserves the encoding of the given buffer" do
+          @client.write('hello')
+
+          IO.select([@server])
+          buffer = ''.encode(Encoding::ISO_8859_1)
+          @server.recvfrom_nonblock(5, 0, buffer)
+
+          buffer.encoding.should == Encoding::ISO_8859_1
+        end
+
         describe 'the returned data' do
           it 'is the same as the sent data' do
             5.times do
@@ -116,3 +137,83 @@ describe 'Socket#recvfrom_nonblock' do
     end
   end
 end
+
+describe 'Socket#recvfrom_nonblock' do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = Socket.new Socket::AF_INET, :STREAM, 0
+        @sockaddr = Socket.sockaddr_in(0, "127.0.0.1")
+        @server.bind(@sockaddr)
+        @server.listen(1)
+
+        server_ip    = @server.local_address.ip_port
+        @server_addr = Socket.sockaddr_in(server_ip, "127.0.0.1")
+
+        @client = Socket.new(Socket::AF_INET, :STREAM, 0)
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+        @client.close unless @client.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        it "returns an empty String as received data on a closed stream socket" do
+          ready = false
+
+          t = Thread.new do
+            client, _ = @server.accept
+
+            Thread.pass while !ready
+            begin
+              client.recvfrom_nonblock(10)
+            rescue IO::EAGAINWaitReadable
+              retry
+            end
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.connect(@server_addr)
+          @client.close
+          ready = true
+
+          t.value.should.is_a? Array
+          t.value[0].should == ""
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "returns nil on a closed stream socket" do
+          ready = false
+
+          t = Thread.new do
+            client, _ = @server.accept
+
+            Thread.pass while !ready
+            begin
+              client.recvfrom_nonblock(10)
+            rescue IO::EAGAINWaitReadable
+              retry
+            end
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.connect(@server_addr)
+          @client.close
+          ready = true
+
+          t.value.should be_nil
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/socket/recvfrom_spec.rb b/spec/ruby/library/socket/socket/recvfrom_spec.rb
index faf161e4a5..6ba39ffcaf 100644
--- a/spec/ruby/library/socket/socket/recvfrom_spec.rb
+++ b/spec/ruby/library/socket/socket/recvfrom_spec.rb
@@ -90,3 +90,90 @@ describe 'Socket#recvfrom' do
     end
   end
 end
+
+describe 'Socket#recvfrom' do
+  context "when recvfrom(2) returns 0 (if no messages are available to be received and the peer has performed an orderly shutdown)" do
+    describe "stream socket" do
+      before :each do
+        @server = Socket.new Socket::AF_INET, :STREAM, 0
+        sockaddr = Socket.sockaddr_in(0, "127.0.0.1")
+        @server.bind(sockaddr)
+        @server.listen(1)
+
+        server_ip    = @server.local_address.ip_port
+        @server_addr = Socket.sockaddr_in(server_ip, "127.0.0.1")
+
+        @client = Socket.new(Socket::AF_INET, :STREAM, 0)
+      end
+
+      after :each do
+        @server.close unless @server.closed?
+        @client.close unless @client.closed?
+      end
+
+      ruby_version_is ""..."3.3" do
+        it "returns an empty String as received data on a closed stream socket" do
+          t = Thread.new do
+            client, _ = @server.accept
+            client.recvfrom(10)
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.connect(@server_addr)
+          @client.close
+
+          t.value.should.is_a? Array
+          t.value[0].should == ""
+        end
+      end
+
+      ruby_version_is "3.3" do
+        it "returns nil on a closed stream socket" do
+          t = Thread.new do
+            client, _ = @server.accept
+            client.recvfrom(10)
+          ensure
+            client.close if client
+          end
+
+          Thread.pass while t.status and t.status != "sleep"
+          t.status.should_not be_nil
+
+          @client.connect(@server_addr)
+          @client.close
+
+          t.value.should be_nil
+        end
+      end
+    end
+
+    describe "datagram socket" do
+      SocketSpecs.each_ip_protocol do |family, ip_address|
+        before :each do
+          @server = Socket.new(family, :DGRAM)
+          @client = Socket.new(family, :DGRAM)
+        end
+
+        after :each do
+          @server.close unless @server.closed?
+          @client.close unless @client.closed?
+        end
+
+        it "returns an empty String as received data" do
+          @server.bind(Socket.sockaddr_in(0, ip_address))
+          @client.connect(@server.getsockname)
+
+          @client.send('', 0)
+          message = @server.recvfrom(1)
+
+          message.should.is_a? Array
+          message[0].should == ""
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/socket/socketpair_spec.rb b/spec/ruby/library/socket/socket/socketpair_spec.rb
index 5b8311124e..551c376d49 100644
--- a/spec/ruby/library/socket/socket/socketpair_spec.rb
+++ b/spec/ruby/library/socket/socket/socketpair_spec.rb
@@ -2,6 +2,6 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/socketpair'
 
-describe "Socket#socketpair" do
+describe "Socket.socketpair" do
   it_behaves_like :socket_socketpair, :socketpair
 end
diff --git a/spec/ruby/library/socket/socket/tcp_server_sockets_spec.rb b/spec/ruby/library/socket/socket/tcp_server_sockets_spec.rb
index 10c030a8ce..bd496d3015 100644
--- a/spec/ruby/library/socket/socket/tcp_server_sockets_spec.rb
+++ b/spec/ruby/library/socket/socket/tcp_server_sockets_spec.rb
@@ -32,7 +32,7 @@ describe 'Socket.tcp_server_sockets' do
       Socket.tcp_server_sockets(0) { |socks| sockets = socks }
 
       sockets.each do |socket|
-        socket.closed?.should == true
+        socket.should.closed?
       end
     end
   end
diff --git a/spec/ruby/library/socket/socket/tcp_spec.rb b/spec/ruby/library/socket/socket/tcp_spec.rb
index d36e3e6adb..faf020b1ea 100644
--- a/spec/ruby/library/socket/socket/tcp_spec.rb
+++ b/spec/ruby/library/socket/socket/tcp_spec.rb
@@ -36,7 +36,7 @@ describe 'Socket.tcp' do
       @socket = socket
     end
 
-    @socket.closed?.should == true
+    @socket.should.closed?
   end
 
   it 'binds to a local address and port when specified' do
diff --git a/spec/ruby/library/socket/socket/udp_server_loop_spec.rb b/spec/ruby/library/socket/socket/udp_server_loop_spec.rb
index 66563bc742..cd22ea56cf 100644
--- a/spec/ruby/library/socket/socket/udp_server_loop_spec.rb
+++ b/spec/ruby/library/socket/socket/udp_server_loop_spec.rb
@@ -21,7 +21,7 @@ describe 'Socket.udp_server_loop' do
     it 'yields the message and a Socket::UDPSource' do
       msg, src = nil
 
-      Thread.new do
+      thread = Thread.new do
         SocketSpecs::ServerLoopPortFinder.udp_server_loop('127.0.0.1', 0) do |message, source|
           msg = message
           src = source
@@ -50,6 +50,8 @@ describe 'Socket.udp_server_loop' do
         end
       end
 
+      thread.join
+
       msg.should == 'hello'
       src.should be_an_instance_of(Socket::UDPSource)
     end
diff --git a/spec/ruby/library/socket/socket/udp_server_sockets_spec.rb b/spec/ruby/library/socket/socket/udp_server_sockets_spec.rb
index 3aeb472dda..f8be672612 100644
--- a/spec/ruby/library/socket/socket/udp_server_sockets_spec.rb
+++ b/spec/ruby/library/socket/socket/udp_server_sockets_spec.rb
@@ -32,7 +32,7 @@ describe 'Socket.udp_server_sockets' do
       Socket.udp_server_sockets(0) { |socks| sockets = socks }
 
       sockets.each do |socket|
-        socket.closed?.should == true
+        socket.should.closed?
       end
     end
   end
diff --git a/spec/ruby/library/socket/socket/unix_server_loop_spec.rb b/spec/ruby/library/socket/socket/unix_server_loop_spec.rb
index 0f34d4a50b..6192bc8bf6 100644
--- a/spec/ruby/library/socket/socket/unix_server_loop_spec.rb
+++ b/spec/ruby/library/socket/socket/unix_server_loop_spec.rb
@@ -1,58 +1,56 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'Socket.unix_server_loop' do
-    before do
-      @path = SocketSpecs.socket_path
-    end
+describe 'Socket.unix_server_loop' do
+  before do
+    @path = SocketSpecs.socket_path
+  end
 
-    after do
-      rm_r(@path) if File.file?(@path)
-    end
+  after do
+    rm_r(@path) if File.file?(@path)
+  end
 
-    describe 'when no connections are available' do
-      it 'blocks the caller' do
-        -> { Socket.unix_server_loop(@path) }.should block_caller
-      end
+  describe 'when no connections are available' do
+    it 'blocks the caller' do
+      -> { Socket.unix_server_loop(@path) }.should block_caller
     end
+  end
 
-    describe 'when a connection is available' do
-      before do
-        @client = nil
-      end
+  describe 'when a connection is available' do
+    before do
+      @client = nil
+    end
 
-      after do
-        @sock.close if @sock
-        @client.close if @client
-      end
+    after do
+      @sock.close if @sock
+      @client.close if @client
+    end
 
-      it 'yields a Socket and an Addrinfo' do
-        @sock, addr = nil
+    it 'yields a Socket and an Addrinfo' do
+      @sock, addr = nil
 
-        thread = Thread.new do
-          Socket.unix_server_loop(@path) do |socket, addrinfo|
-            @sock = socket
-            addr = addrinfo
+      thread = Thread.new do
+        Socket.unix_server_loop(@path) do |socket, addrinfo|
+          @sock = socket
+          addr = addrinfo
 
-            break
-          end
+          break
         end
+      end
 
-        SocketSpecs.loop_with_timeout do
-          begin
-            @client = Socket.unix(@path)
-          rescue SystemCallError
-            sleep 0.01
-            :retry
-          end
+      SocketSpecs.loop_with_timeout do
+        begin
+          @client = Socket.unix(@path)
+        rescue SystemCallError
+          sleep 0.01
+          :retry
         end
+      end
 
-        thread.join
+      thread.join
 
-        @sock.should be_an_instance_of(Socket)
-        addr.should be_an_instance_of(Addrinfo)
-      end
+      @sock.should be_an_instance_of(Socket)
+      addr.should be_an_instance_of(Addrinfo)
     end
   end
 end
diff --git a/spec/ruby/library/socket/socket/unix_server_socket_spec.rb b/spec/ruby/library/socket/socket/unix_server_socket_spec.rb
index fc357740fa..34c3b96d07 100644
--- a/spec/ruby/library/socket/socket/unix_server_socket_spec.rb
+++ b/spec/ruby/library/socket/socket/unix_server_socket_spec.rb
@@ -1,48 +1,46 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'Socket.unix_server_socket' do
+describe 'Socket.unix_server_socket' do
+  before do
+    @path = SocketSpecs.socket_path
+  end
+
+  after do
+    rm_r(@path)
+  end
+
+  describe 'when no block is given' do
     before do
-      @path = SocketSpecs.socket_path
+      @socket = nil
     end
 
     after do
-      rm_r(@path)
+      @socket.close
     end
 
-    describe 'when no block is given' do
-      before do
-        @socket = nil
-      end
-
-      after do
-        @socket.close
-      end
+    it 'returns a Socket' do
+      @socket = Socket.unix_server_socket(@path)
 
-      it 'returns a Socket' do
-        @socket = Socket.unix_server_socket(@path)
-
-        @socket.should be_an_instance_of(Socket)
-      end
+      @socket.should be_an_instance_of(Socket)
     end
+  end
 
-    describe 'when a block is given' do
-      it 'yields a Socket' do
-        Socket.unix_server_socket(@path) do |sock|
-          sock.should be_an_instance_of(Socket)
-        end
+  describe 'when a block is given' do
+    it 'yields a Socket' do
+      Socket.unix_server_socket(@path) do |sock|
+        sock.should be_an_instance_of(Socket)
       end
+    end
 
-      it 'closes the Socket when the block returns' do
-        socket = nil
-
-        Socket.unix_server_socket(@path) do |sock|
-          socket = sock
-        end
+    it 'closes the Socket when the block returns' do
+      socket = nil
 
-        socket.should be_an_instance_of(Socket)
+      Socket.unix_server_socket(@path) do |sock|
+        socket = sock
       end
+
+      socket.should be_an_instance_of(Socket)
     end
   end
 end
diff --git a/spec/ruby/library/socket/socket/unix_spec.rb b/spec/ruby/library/socket/socket/unix_spec.rb
index add54a097d..2a5d77f96f 100644
--- a/spec/ruby/library/socket/socket/unix_spec.rb
+++ b/spec/ruby/library/socket/socket/unix_spec.rb
@@ -1,45 +1,43 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'Socket.unix' do
-    before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
-      @socket = nil
-    end
+describe 'Socket.unix' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+    @socket = nil
+  end
 
-    after do
-      @server.close
-      @socket.close if @socket
+  after do
+    @server.close
+    @socket.close if @socket
 
-      rm_r(@path)
-    end
+    rm_r(@path)
+  end
 
-    describe 'when no block is given' do
-      it 'returns a Socket' do
-        @socket = Socket.unix(@path)
+  describe 'when no block is given' do
+    it 'returns a Socket' do
+      @socket = Socket.unix(@path)
 
-        @socket.should be_an_instance_of(Socket)
-      end
+      @socket.should be_an_instance_of(Socket)
     end
+  end
 
-    describe 'when a block is given' do
-      it 'yields a Socket' do
-        Socket.unix(@path) do |sock|
-          sock.should be_an_instance_of(Socket)
-        end
+  describe 'when a block is given' do
+    it 'yields a Socket' do
+      Socket.unix(@path) do |sock|
+        sock.should be_an_instance_of(Socket)
       end
+    end
 
-      it 'closes the Socket when the block returns' do
-        socket = nil
-
-        Socket.unix(@path) do |sock|
-          socket = sock
-        end
+    it 'closes the Socket when the block returns' do
+      socket = nil
 
-        socket.closed?.should == true
+      Socket.unix(@path) do |sock|
+        socket = sock
       end
+
+      socket.should.closed?
     end
   end
 end
diff --git a/spec/ruby/library/socket/socket/unpack_sockaddr_in_spec.rb b/spec/ruby/library/socket/socket/unpack_sockaddr_in_spec.rb
index 79ec68cd18..935b5cb543 100644
--- a/spec/ruby/library/socket/socket/unpack_sockaddr_in_spec.rb
+++ b/spec/ruby/library/socket/socket/unpack_sockaddr_in_spec.rb
@@ -32,15 +32,13 @@ describe "Socket.unpack_sockaddr_in" do
     end
   end
 
-  with_feature :unix_socket do
-    it "raises an ArgumentError when the sin_family is not AF_INET" do
-      sockaddr = Socket.sockaddr_un '/tmp/x'
-      -> { Socket.unpack_sockaddr_in sockaddr }.should raise_error(ArgumentError)
-    end
+  it "raises an ArgumentError when the sin_family is not AF_INET" do
+    sockaddr = Socket.sockaddr_un '/tmp/x'
+    -> { Socket.unpack_sockaddr_in sockaddr }.should raise_error(ArgumentError)
+  end
 
-    it "raises an ArgumentError when passed addrinfo is not AF_INET/AF_INET6" do
-      addrinfo = Addrinfo.unix('/tmp/sock')
-      -> { Socket.unpack_sockaddr_in(addrinfo) }.should raise_error(ArgumentError)
-    end
+  it "raises an ArgumentError when passed addrinfo is not AF_INET/AF_INET6" do
+    addrinfo = Addrinfo.unix('/tmp/sock')
+    -> { Socket.unpack_sockaddr_in(addrinfo) }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/library/socket/socket/unpack_sockaddr_un_spec.rb b/spec/ruby/library/socket/socket/unpack_sockaddr_un_spec.rb
index bd95f1db08..6e0f11de3d 100644
--- a/spec/ruby/library/socket/socket/unpack_sockaddr_un_spec.rb
+++ b/spec/ruby/library/socket/socket/unpack_sockaddr_un_spec.rb
@@ -1,26 +1,24 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'Socket.unpack_sockaddr_un' do
-    it 'decodes sockaddr to unix path' do
-      sockaddr = Socket.sockaddr_un('/tmp/sock')
-      Socket.unpack_sockaddr_un(sockaddr).should == '/tmp/sock'
-    end
+describe 'Socket.unpack_sockaddr_un' do
+  it 'decodes sockaddr to unix path' do
+    sockaddr = Socket.sockaddr_un('/tmp/sock')
+    Socket.unpack_sockaddr_un(sockaddr).should == '/tmp/sock'
+  end
 
-    it 'returns unix path from a passed Addrinfo' do
-      addrinfo = Addrinfo.unix('/tmp/sock')
-      Socket.unpack_sockaddr_un(addrinfo).should == '/tmp/sock'
-    end
+  it 'returns unix path from a passed Addrinfo' do
+    addrinfo = Addrinfo.unix('/tmp/sock')
+    Socket.unpack_sockaddr_un(addrinfo).should == '/tmp/sock'
+  end
 
-    it 'raises an ArgumentError when the sin_family is not AF_UNIX' do
-      sockaddr = Socket.sockaddr_in(0, '127.0.0.1')
-      -> { Socket.unpack_sockaddr_un(sockaddr) }.should raise_error(ArgumentError)
-    end
+  it 'raises an ArgumentError when the sa_family is not AF_UNIX' do
+    sockaddr = Socket.sockaddr_in(0, '127.0.0.1')
+    -> { Socket.unpack_sockaddr_un(sockaddr) }.should raise_error(ArgumentError)
+  end
 
-    it 'raises an ArgumentError when passed addrinfo is not AF_UNIX' do
-      addrinfo = Addrinfo.tcp('127.0.0.1', 0)
-      -> { Socket.unpack_sockaddr_un(addrinfo) }.should raise_error(ArgumentError)
-    end
+  it 'raises an ArgumentError when passed addrinfo is not AF_UNIX' do
+    addrinfo = Addrinfo.tcp('127.0.0.1', 0)
+    -> { Socket.unpack_sockaddr_un(addrinfo) }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/library/socket/spec_helper.rb b/spec/ruby/library/socket/spec_helper.rb
index 1121542dd5..b33663e02d 100644
--- a/spec/ruby/library/socket/spec_helper.rb
+++ b/spec/ruby/library/socket/spec_helper.rb
@@ -2,7 +2,6 @@ require_relative '../../spec_helper'
 require 'socket'
 
 MSpec.enable_feature :sock_packet if Socket.const_defined?(:SOCK_PACKET)
-MSpec.enable_feature :unix_socket unless PlatformGuard.windows?
 MSpec.enable_feature :udp_cork if Socket.const_defined?(:UDP_CORK)
 MSpec.enable_feature :tcp_cork if Socket.const_defined?(:TCP_CORK)
 MSpec.enable_feature :pktinfo if Socket.const_defined?(:IP_PKTINFO)
diff --git a/spec/ruby/library/socket/tcpserver/accept_spec.rb b/spec/ruby/library/socket/tcpserver/accept_spec.rb
index 0da4e2218b..d8892cd5f0 100644
--- a/spec/ruby/library/socket/tcpserver/accept_spec.rb
+++ b/spec/ruby/library/socket/tcpserver/accept_spec.rb
@@ -58,6 +58,26 @@ describe "TCPServer#accept" do
     t.join
   end
 
+  it "is automatically retried when interrupted by SIGVTALRM" do
+    t = Thread.new do
+      client = @server.accept
+      value = client.read(2)
+      client.close
+      value
+    end
+
+    Thread.pass while t.status and t.status != "sleep"
+    # Thread#backtrace uses SIGVTALRM on TruffleRuby and potentially other implementations.
+    # Sending a signal to a thread is not possible with Ruby APIs.
+    t.backtrace.join("\n").should =~ /in [`'](?:TCPServer#)?accept'/
+
+    socket = TCPSocket.new('127.0.0.1', @port)
+    socket.write("OK")
+    socket.close
+
+    t.value.should == "OK"
+  end
+
   it "raises an IOError if the socket is closed" do
     @server.close
     -> { @server.accept }.should raise_error(IOError)
@@ -94,6 +114,19 @@ describe 'TCPServer#accept' do
         @socket = @server.accept
         @socket.should be_an_instance_of(TCPSocket)
       end
+
+      platform_is_not :windows do
+        it "returns a TCPSocket which is set to nonblocking" do
+          require 'io/nonblock'
+          @socket = @server.accept
+          @socket.should.nonblock?
+        end
+      end
+
+      it "returns a TCPSocket which is set to close on exec" do
+        @socket = @server.accept
+        @socket.should.close_on_exec?
+      end
     end
   end
 end
diff --git a/spec/ruby/library/socket/tcpserver/new_spec.rb b/spec/ruby/library/socket/tcpserver/new_spec.rb
index 94e5744995..dd1ba676bd 100644
--- a/spec/ruby/library/socket/tcpserver/new_spec.rb
+++ b/spec/ruby/library/socket/tcpserver/new_spec.rb
@@ -40,7 +40,25 @@ describe "TCPServer.new" do
   end
 
   it "binds to INADDR_ANY if the hostname is empty and the port is a string" do
-    @server = TCPServer.new('', 0)
+    @server = TCPServer.new('', '0')
+    addr = @server.addr
+    addr[0].should == 'AF_INET'
+    addr[1].should be_kind_of(Integer)
+    addr[2].should == '0.0.0.0'
+    addr[3].should == '0.0.0.0'
+  end
+
+  it "binds to a port if the port is explicitly nil" do
+    @server = TCPServer.new('', nil)
+    addr = @server.addr
+    addr[0].should == 'AF_INET'
+    addr[1].should be_kind_of(Integer)
+    addr[2].should == '0.0.0.0'
+    addr[3].should == '0.0.0.0'
+  end
+
+  it "binds to a port if the port is an empty string" do
+    @server = TCPServer.new('', '')
     addr = @server.addr
     addr[0].should == 'AF_INET'
     addr[1].should be_kind_of(Integer)
@@ -62,6 +80,29 @@ describe "TCPServer.new" do
     # pick such a service port that will be able to reliably bind...
   end
 
+  it "has a single argument form and treats it as a port number" do
+    @server = TCPServer.new(0)
+    addr = @server.addr
+    addr[1].should be_kind_of(Integer)
+  end
+
+  it "coerces port to a string when it is the only argument" do
+    -> { TCPServer.new(Object.new) }.should raise_error(TypeError)
+
+    port = Object.new
+    port.should_receive(:to_str).and_return("0")
+
+    @server = TCPServer.new(port)
+    addr = @server.addr
+    addr[1].should be_kind_of(Integer)
+  end
+
+  it "does not use the given block and warns to use TCPServer::open" do
+    -> {
+      @server = TCPServer.new(0) { raise }
+    }.should complain(/warning: TCPServer::new\(\) does not take block; use TCPServer::open\(\) instead/)
+  end
+
   it "raises Errno::EADDRNOTAVAIL when the address is unknown" do
     -> { TCPServer.new("1.2.3.4", 0) }.should raise_error(Errno::EADDRNOTAVAIL)
   end
diff --git a/spec/ruby/library/socket/tcpsocket/gethostbyname_spec.rb b/spec/ruby/library/socket/tcpsocket/gethostbyname_spec.rb
index 703abff81c..5a2c704f35 100644
--- a/spec/ruby/library/socket/tcpsocket/gethostbyname_spec.rb
+++ b/spec/ruby/library/socket/tcpsocket/gethostbyname_spec.rb
@@ -2,9 +2,11 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 # TODO: verify these for windows
-describe "TCPSocket#gethostbyname" do
+describe "TCPSocket.gethostbyname" do
   before :each do
-    @host_info = TCPSocket.gethostbyname(SocketSpecs.hostname)
+    suppress_warning do
+      @host_info = TCPSocket.gethostbyname(SocketSpecs.hostname)
+    end
   end
 
   it "returns an array elements of information on the hostname" do
@@ -50,15 +52,19 @@ describe "TCPSocket#gethostbyname" do
   end
 end
 
-describe 'TCPSocket#gethostbyname' do
+describe 'TCPSocket.gethostbyname' do
   it 'returns an Array' do
-    TCPSocket.gethostbyname('127.0.0.1').should be_an_instance_of(Array)
+    suppress_warning do
+      TCPSocket.gethostbyname('127.0.0.1').should be_an_instance_of(Array)
+    end
   end
 
   describe 'using a hostname' do
     describe 'the returned Array' do
       before do
-        @array = TCPSocket.gethostbyname('127.0.0.1')
+        suppress_warning do
+          @array = TCPSocket.gethostbyname('127.0.0.1')
+        end
       end
 
       it 'includes the canonical name as the 1st value' do
@@ -88,7 +94,9 @@ describe 'TCPSocket#gethostbyname' do
   SocketSpecs.each_ip_protocol do |family, ip_address|
     describe 'the returned Array' do
       before do
-        @array = TCPSocket.gethostbyname(ip_address)
+        suppress_warning do
+          @array = TCPSocket.gethostbyname(ip_address)
+        end
       end
 
       it 'includes the IP address as the 1st value' do
diff --git a/spec/ruby/library/socket/tcpsocket/initialize_spec.rb b/spec/ruby/library/socket/tcpsocket/initialize_spec.rb
index a3cee05412..d7feb9751b 100644
--- a/spec/ruby/library/socket/tcpsocket/initialize_spec.rb
+++ b/spec/ruby/library/socket/tcpsocket/initialize_spec.rb
@@ -1,5 +1,31 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
+require_relative 'shared/new'
+
+describe 'TCPSocket#initialize' do
+  it_behaves_like :tcpsocket_new, :new
+
+  describe "with a running server" do
+    before :each do
+      @server = SocketSpecs::SpecTCPServer.new
+      @hostname = @server.hostname
+    end
+
+    after :each do
+      if @socket
+        @socket.write "QUIT"
+        @socket.close
+      end
+      @server.shutdown
+    end
+
+    it "does not use the given block and warns to use TCPSocket::open" do
+      -> {
+        @socket = TCPSocket.new(@hostname, @server.port, nil) { raise }
+      }.should complain(/warning: TCPSocket::new\(\) does not take block; use TCPSocket::open\(\) instead/)
+    end
+  end
+end
 
 describe 'TCPSocket#initialize' do
   SocketSpecs.each_ip_protocol do |family, ip_address|
@@ -46,6 +72,19 @@ describe 'TCPSocket#initialize' do
         @client.remote_address.ip_port.should    == @server.local_address.ip_port
       end
 
+      platform_is_not :windows do
+        it "creates a socket which is set to nonblocking" do
+          require 'io/nonblock'
+          @client = TCPSocket.new(ip_address, @port)
+          @client.should.nonblock?
+        end
+      end
+
+      it "creates a socket which is set to close on exec" do
+        @client = TCPSocket.new(ip_address, @port)
+        @client.should.close_on_exec?
+      end
+
       describe 'using a local address and service' do
         it 'binds the client socket to the local address and service' do
           @client = TCPSocket.new(ip_address, @port, ip_address, 0)
diff --git a/spec/ruby/library/socket/tcpsocket/new_spec.rb b/spec/ruby/library/socket/tcpsocket/new_spec.rb
deleted file mode 100644
index 4924468be7..0000000000
--- a/spec/ruby/library/socket/tcpsocket/new_spec.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative 'shared/new'
-
-describe "TCPSocket.new" do
-  it_behaves_like :tcpsocket_new, :new
-end
diff --git a/spec/ruby/library/socket/tcpsocket/open_spec.rb b/spec/ruby/library/socket/tcpsocket/open_spec.rb
index 31b630a23b..0c0b579064 100644
--- a/spec/ruby/library/socket/tcpsocket/open_spec.rb
+++ b/spec/ruby/library/socket/tcpsocket/open_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/new'
 
 describe "TCPSocket.open" do
diff --git a/spec/ruby/library/socket/tcpsocket/partially_closable_spec.rb b/spec/ruby/library/socket/tcpsocket/partially_closable_spec.rb
index a381627a39..d365ecd335 100644
--- a/spec/ruby/library/socket/tcpsocket/partially_closable_spec.rb
+++ b/spec/ruby/library/socket/tcpsocket/partially_closable_spec.rb
@@ -16,6 +16,6 @@ describe "TCPSocket partial closability" do
     @s2.close
   end
 
-  it_should_behave_like "partially closable sockets"
+  it_should_behave_like :partially_closable_sockets
 
 end
diff --git a/spec/ruby/library/socket/tcpsocket/recv_nonblock_spec.rb b/spec/ruby/library/socket/tcpsocket/recv_nonblock_spec.rb
index bfd815c658..6ce5a41b58 100644
--- a/spec/ruby/library/socket/tcpsocket/recv_nonblock_spec.rb
+++ b/spec/ruby/library/socket/tcpsocket/recv_nonblock_spec.rb
@@ -27,6 +27,20 @@ describe "TCPSocket#recv_nonblock" do
     @socket.recv_nonblock(50).should == "TCPSocket#recv_nonblock"
   end
 
+  it 'writes the read to a buffer from the socket' do
+    @socket = TCPSocket.new @hostname, @server.port
+    @socket.write "TCPSocket#recv_nonblock"
+
+    # Wait for the server to echo. This spec is testing the return
+    # value, not the non-blocking behavior.
+    #
+    # TODO: Figure out a good way to test non-blocking.
+    IO.select([@socket])
+    buffer = "".b
+    @socket.recv_nonblock(50, 0, buffer)
+    buffer.should == 'TCPSocket#recv_nonblock'
+  end
+
   it 'returns :wait_readable in exceptionless mode' do
     @socket = TCPSocket.new @hostname, @server.port
     @socket.recv_nonblock(50, exception: false).should == :wait_readable
diff --git a/spec/ruby/library/socket/tcpsocket/shared/new.rb b/spec/ruby/library/socket/tcpsocket/shared/new.rb
index 5ca3a0e6cc..0e405253c8 100644
--- a/spec/ruby/library/socket/tcpsocket/shared/new.rb
+++ b/spec/ruby/library/socket/tcpsocket/shared/new.rb
@@ -14,6 +14,15 @@ describe :tcpsocket_new, shared: true do
     }
   end
 
+  it 'raises IO::TimeoutError with :connect_timeout when no server is listening on the given address' do
+    -> {
+      TCPSocket.send(@method, "192.0.2.1", 80, connect_timeout: 0)
+    }.should raise_error(IO::TimeoutError)
+  rescue Errno::ENETUNREACH
+    # In the case all network interfaces down.
+    # raise_error cannot deal with multiple expected exceptions
+  end
+
   describe "with a running server" do
     before :each do
       @server = SocketSpecs::SpecTCPServer.new
@@ -44,14 +53,23 @@ describe :tcpsocket_new, shared: true do
     end
 
     it "connects to a server when passed local_host and local_port arguments" do
-      server = TCPServer.new(SocketSpecs.hostname, 0)
+      retries = 0
+      max_retries = 3
+
       begin
-        available_port = server.addr[1]
-      ensure
-        server.close
+        retries += 1
+        server = TCPServer.new(SocketSpecs.hostname, 0)
+        begin
+          available_port = server.addr[1]
+        ensure
+          server.close
+        end
+        @socket = TCPSocket.send(@method, @hostname, @server.port,
+                                 @hostname, available_port)
+      rescue Errno::EADDRINUSE
+        raise if retries >= max_retries
+        retry
       end
-      @socket = TCPSocket.send(@method, @hostname, @server.port,
-                               @hostname, available_port)
       @socket.should be_an_instance_of(TCPSocket)
     end
 
@@ -75,5 +93,10 @@ describe :tcpsocket_new, shared: true do
       @socket.addr[1].should be_kind_of(Integer)
       @socket.addr[2].should =~ /^#{@hostname}/
     end
+
+    it "connects to a server when passed connect_timeout argument" do
+      @socket = TCPSocket.send(@method, @hostname, @server.port, connect_timeout: 1)
+      @socket.should be_an_instance_of(TCPSocket)
+    end
   end
 end
diff --git a/spec/ruby/library/socket/udpsocket/initialize_spec.rb b/spec/ruby/library/socket/udpsocket/initialize_spec.rb
index 1d635149f7..ecf0043c10 100644
--- a/spec/ruby/library/socket/udpsocket/initialize_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/initialize_spec.rb
@@ -30,6 +30,19 @@ describe 'UDPSocket#initialize' do
     @socket.binmode?.should be_true
   end
 
+  platform_is_not :windows do
+    it 'sets the socket to nonblock' do
+      require 'io/nonblock'
+      @socket = UDPSocket.new(:INET)
+      @socket.should.nonblock?
+    end
+  end
+
+  it 'sets the socket to close on exec' do
+    @socket = UDPSocket.new(:INET)
+    @socket.should.close_on_exec?
+  end
+
   it 'raises Errno::EAFNOSUPPORT or Errno::EPROTONOSUPPORT when given an invalid address family' do
     -> {
       UDPSocket.new(666)
diff --git a/spec/ruby/library/socket/udpsocket/inspect_spec.rb b/spec/ruby/library/socket/udpsocket/inspect_spec.rb
index 201e8b3fc6..e212120b14 100644
--- a/spec/ruby/library/socket/udpsocket/inspect_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/inspect_spec.rb
@@ -10,16 +10,8 @@ describe 'UDPSocket#inspect' do
     @socket.close
   end
 
-  ruby_version_is ""..."2.5" do
-    it 'returns a String with the fd' do
-      @socket.inspect.should == "#<UDPSocket:fd #{@socket.fileno}>"
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it 'returns a String with the fd, family, address and port' do
-      port = @socket.addr[1]
-      @socket.inspect.should == "#<UDPSocket:fd #{@socket.fileno}, AF_INET, 127.0.0.1, #{port}>"
-    end
+  it 'returns a String with the fd, family, address and port' do
+    port = @socket.addr[1]
+    @socket.inspect.should == "#<UDPSocket:fd #{@socket.fileno}, AF_INET, 127.0.0.1, #{port}>"
   end
 end
diff --git a/spec/ruby/library/socket/udpsocket/new_spec.rb b/spec/ruby/library/socket/udpsocket/new_spec.rb
index 6cc0cadbcb..79bfcb624d 100644
--- a/spec/ruby/library/socket/udpsocket/new_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/new_spec.rb
@@ -26,6 +26,12 @@ describe 'UDPSocket.new' do
     @socket.should be_an_instance_of(UDPSocket)
   end
 
+  it "does not use the given block and warns to use UDPSocket::open" do
+    -> {
+      @socket = UDPSocket.new { raise }
+    }.should complain(/warning: UDPSocket::new\(\) does not take block; use UDPSocket::open\(\) instead/)
+  end
+
   it 'raises Errno::EAFNOSUPPORT or Errno::EPROTONOSUPPORT if unsupported family passed' do
     -> { UDPSocket.new(-1) }.should raise_error(SystemCallError) { |e|
       [Errno::EAFNOSUPPORT, Errno::EPROTONOSUPPORT].should include(e.class)
diff --git a/spec/ruby/library/socket/udpsocket/recvfrom_nonblock_spec.rb b/spec/ruby/library/socket/udpsocket/recvfrom_nonblock_spec.rb
index c66d1df84d..b804099589 100644
--- a/spec/ruby/library/socket/udpsocket/recvfrom_nonblock_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/recvfrom_nonblock_spec.rb
@@ -51,6 +51,22 @@ describe 'UDPSocket#recvfrom_nonblock' do
             @server.recvfrom_nonblock(1).should be_an_instance_of(Array)
           end
 
+          it 'writes the data to the buffer when one is present' do
+            buffer = "".b
+            IO.select([@server])
+            @server.recvfrom_nonblock(1, 0, buffer)
+            buffer.should == 'h'
+          end
+
+          it "preserves the encoding of the given buffer" do
+            buffer = ''.encode(Encoding::ISO_8859_1)
+            IO.select([@server])
+            message, = @server.recvfrom_nonblock(1, 0, buffer)
+
+            message.should.equal?(buffer)
+            buffer.encoding.should == Encoding::ISO_8859_1
+          end
+
           describe 'the returned Array' do
             before do
               IO.select([@server])
diff --git a/spec/ruby/library/socket/udpsocket/send_spec.rb b/spec/ruby/library/socket/udpsocket/send_spec.rb
index 5d5de684af..6dd5f67bea 100644
--- a/spec/ruby/library/socket/udpsocket/send_spec.rb
+++ b/spec/ruby/library/socket/udpsocket/send_spec.rb
@@ -63,7 +63,7 @@ describe "UDPSocket#send" do
     @msg[1][3].should == "127.0.0.1"
   end
 
-  it "raises EMSGSIZE if data is too too big" do
+  it "raises EMSGSIZE if data is too big" do
     @socket = UDPSocket.open
     begin
       -> do
diff --git a/spec/ruby/library/socket/unixserver/accept_nonblock_spec.rb b/spec/ruby/library/socket/unixserver/accept_nonblock_spec.rb
index 30688b46b6..f67941b296 100644
--- a/spec/ruby/library/socket/unixserver/accept_nonblock_spec.rb
+++ b/spec/ruby/library/socket/unixserver/accept_nonblock_spec.rb
@@ -2,89 +2,84 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXServer#accept_nonblock" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @client = UNIXSocket.open(@path)
 
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @client = UNIXSocket.open(@path)
+    @socket = @server.accept_nonblock
+    @client.send("foobar", 0)
+  end
 
-      @socket = @server.accept_nonblock
-      @client.send("foobar", 0)
-    end
+  after :each do
+    @socket.close
+    @client.close
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    after :each do
-      @socket.close
-      @client.close
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
+  it "accepts a connection in a non-blocking way" do
+    data = @socket.recvfrom(6).first
+    data.should == "foobar"
+  end
 
-    it "accepts a connection in a non-blocking way" do
-      data = @socket.recvfrom(6).first
-      data.should == "foobar"
-    end
+  it "returns a UNIXSocket" do
+    @socket.should be_kind_of(UNIXSocket)
+  end
 
-    it "returns a UNIXSocket" do
-      @socket.should be_kind_of(UNIXSocket)
-    end
+  it 'returns :wait_readable in exceptionless mode' do
+    @server.accept_nonblock(exception: false).should == :wait_readable
+  end
+end
+
+describe 'UNIXServer#accept_nonblock' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+  end
 
-    it 'returns :wait_readable in exceptionless mode' do
-      @server.accept_nonblock(exception: false).should == :wait_readable
+  after do
+    @server.close
+    rm_r(@path)
+  end
+
+  describe 'without a client' do
+    it 'raises IO::WaitReadable' do
+      -> { @server.accept_nonblock }.should raise_error(IO::WaitReadable)
     end
   end
-end
 
-with_feature :unix_socket do
-  describe 'UNIXServer#accept_nonblock' do
+  describe 'with a client' do
     before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
+      @client = UNIXSocket.new(@path)
     end
 
     after do
-      @server.close
-      rm_r(@path)
+      @client.close
+      @socket.close if @socket
     end
 
-    describe 'without a client' do
-      it 'raises IO::WaitReadable' do
-        -> { @server.accept_nonblock }.should raise_error(IO::WaitReadable)
+    describe 'without any data' do
+      it 'returns a UNIXSocket' do
+        @socket = @server.accept_nonblock
+        @socket.should be_an_instance_of(UNIXSocket)
       end
     end
 
-    describe 'with a client' do
+    describe 'with data available' do
       before do
-        @client = UNIXSocket.new(@path)
-      end
-
-      after do
-        @client.close
-        @socket.close if @socket
+        @client.write('hello')
       end
 
-      describe 'without any data' do
-        it 'returns a UNIXSocket' do
-          @socket = @server.accept_nonblock
-          @socket.should be_an_instance_of(UNIXSocket)
-        end
+      it 'returns a UNIXSocket' do
+        @socket = @server.accept_nonblock
+        @socket.should be_an_instance_of(UNIXSocket)
       end
 
-      describe 'with data available' do
-        before do
-          @client.write('hello')
-        end
-
-        it 'returns a UNIXSocket' do
+      describe 'the returned UNIXSocket' do
+        it 'can read the data written' do
           @socket = @server.accept_nonblock
-          @socket.should be_an_instance_of(UNIXSocket)
-        end
-
-        describe 'the returned UNIXSocket' do
-          it 'can read the data written' do
-            @socket = @server.accept_nonblock
-            @socket.recv(5).should == 'hello'
-          end
+          @socket.recv(5).should == 'hello'
         end
       end
     end
diff --git a/spec/ruby/library/socket/unixserver/accept_spec.rb b/spec/ruby/library/socket/unixserver/accept_spec.rb
index c05fbe7f22..cc2c922b6f 100644
--- a/spec/ruby/library/socket/unixserver/accept_spec.rb
+++ b/spec/ruby/library/socket/unixserver/accept_spec.rb
@@ -1,115 +1,124 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-platform_is_not :windows do
-  describe "UNIXServer#accept" do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-    end
+describe "UNIXServer#accept" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+  end
 
-    after :each do
-      @server.close if @server
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @server.close if @server
+    SocketSpecs.rm_socket @path
+  end
 
-    it "accepts what is written by the client" do
-      client = UNIXSocket.open(@path)
+  it "accepts what is written by the client" do
+    client = UNIXSocket.open(@path)
 
-      client.send('hello', 0)
+    client.send('hello', 0)
 
-      sock = @server.accept
-      begin
-        data, info = sock.recvfrom(5)
+    sock = @server.accept
+    begin
+      data, info = sock.recvfrom(5)
 
-        data.should == 'hello'
-        info.should_not be_empty
-      ensure
-        sock.close
-        client.close
-      end
+      data.should == 'hello'
+      info.should_not be_empty
+    ensure
+      sock.close
+      client.close
     end
+  end
 
-    it "can be interrupted by Thread#kill" do
-      t = Thread.new {
-        @server.accept
-      }
-      Thread.pass while t.status and t.status != "sleep"
-
-      # kill thread, ensure it dies in a reasonable amount of time
-      t.kill
-      a = 0
-      while t.alive? and a < 5000
-        sleep 0.001
-        a += 1
-      end
-      a.should < 5000
+  it "can be interrupted by Thread#kill" do
+    t = Thread.new {
+      @server.accept
+    }
+    Thread.pass while t.status and t.status != "sleep"
+
+    # kill thread, ensure it dies in a reasonable amount of time
+    t.kill
+    a = 0
+    while t.alive? and a < 5000
+      sleep 0.001
+      a += 1
     end
+    a.should < 5000
+  end
 
-    it "can be interrupted by Thread#raise" do
-      t = Thread.new {
-        -> {
-          @server.accept
-        }.should raise_error(Exception, "interrupted")
-      }
+  it "can be interrupted by Thread#raise" do
+    t = Thread.new {
+      -> {
+        @server.accept
+      }.should raise_error(Exception, "interrupted")
+    }
 
-      Thread.pass while t.status and t.status != "sleep"
-      t.raise Exception, "interrupted"
-      t.join
-    end
+    Thread.pass while t.status and t.status != "sleep"
+    t.raise Exception, "interrupted"
+    t.join
   end
 end
 
-with_feature :unix_socket do
-  describe 'UNIXServer#accept' do
+describe 'UNIXServer#accept' do
+  before do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+  end
+
+  after do
+    @server.close
+    rm_r(@path)
+  end
+
+  describe 'without a client' do
+    it 'blocks the calling thread' do
+      -> { @server.accept }.should block_caller
+    end
+  end
+
+  describe 'with a client' do
     before do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
+      @client = UNIXSocket.new(@path)
     end
 
     after do
-      @server.close
-      rm_r(@path)
+      @client.close
+      @socket.close if @socket
     end
 
-    describe 'without a client' do
-      it 'blocks the calling thread' do
-        -> { @server.accept }.should block_caller
+    describe 'without any data' do
+      it 'returns a UNIXSocket' do
+        @socket = @server.accept
+        @socket.should be_an_instance_of(UNIXSocket)
       end
     end
 
-    describe 'with a client' do
+    describe 'with data available' do
       before do
-        @client = UNIXSocket.new(@path)
+        @client.write('hello')
       end
 
-      after do
-        @client.close
-        @socket.close if @socket
+      it 'returns a UNIXSocket' do
+        @socket = @server.accept
+        @socket.should be_an_instance_of(UNIXSocket)
       end
 
-      describe 'without any data' do
-        it 'returns a UNIXSocket' do
+      describe 'the returned UNIXSocket' do
+        it 'can read the data written' do
           @socket = @server.accept
-          @socket.should be_an_instance_of(UNIXSocket)
+          @socket.recv(5).should == 'hello'
         end
-      end
 
-      describe 'with data available' do
-        before do
-          @client.write('hello')
+        platform_is_not :windows do
+          it "is set to nonblocking" do
+            require 'io/nonblock'
+            @socket = @server.accept
+            @socket.should.nonblock?
+          end
         end
 
-        it 'returns a UNIXSocket' do
+        it "is set to close on exec" do
           @socket = @server.accept
-          @socket.should be_an_instance_of(UNIXSocket)
-        end
-
-        describe 'the returned UNIXSocket' do
-          it 'can read the data written' do
-            @socket = @server.accept
-            @socket.recv(5).should == 'hello'
-          end
+          @socket.should.close_on_exec?
         end
       end
     end
diff --git a/spec/ruby/library/socket/unixserver/for_fd_spec.rb b/spec/ruby/library/socket/unixserver/for_fd_spec.rb
index 4f3816ad37..be1c2df4d7 100644
--- a/spec/ruby/library/socket/unixserver/for_fd_spec.rb
+++ b/spec/ruby/library/socket/unixserver/for_fd_spec.rb
@@ -1,23 +1,21 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-platform_is_not :windows do
-  describe "UNIXServer#for_fd" do
-    before :each do
-      @unix_path = SocketSpecs.socket_path
-      @unix = UNIXServer.new(@unix_path)
-    end
+describe "UNIXServer.for_fd" do
+  before :each do
+    @unix_path = SocketSpecs.socket_path
+    @unix = UNIXServer.new(@unix_path)
+  end
 
-    after :each do
-      @unix.close if @unix
-      SocketSpecs.rm_socket @unix_path
-    end
+  after :each do
+    @unix.close if @unix
+    SocketSpecs.rm_socket @unix_path
+  end
 
-    it "can calculate the path" do
-      b = UNIXServer.for_fd(@unix.fileno)
-      b.autoclose = false
+  it "can calculate the path" do
+    b = UNIXServer.for_fd(@unix.fileno)
+    b.autoclose = false
 
-      b.path.should == @unix_path
-    end
+    b.path.should == @unix_path
   end
 end
diff --git a/spec/ruby/library/socket/unixserver/initialize_spec.rb b/spec/ruby/library/socket/unixserver/initialize_spec.rb
index 0cc49ef1eb..3728a307b0 100644
--- a/spec/ruby/library/socket/unixserver/initialize_spec.rb
+++ b/spec/ruby/library/socket/unixserver/initialize_spec.rb
@@ -1,28 +1,26 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXServer#initialize' do
-    before do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
-    end
+describe 'UNIXServer#initialize' do
+  before do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+  end
 
-    after do
-      @server.close if @server
-      rm_r @path
-    end
+  after do
+    @server.close if @server
+    rm_r @path
+  end
 
-    it 'returns a new UNIXServer' do
-      @server.should be_an_instance_of(UNIXServer)
-    end
+  it 'returns a new UNIXServer' do
+    @server.should be_an_instance_of(UNIXServer)
+  end
 
-    it 'sets the socket to binmode' do
-      @server.binmode?.should be_true
-    end
+  it 'sets the socket to binmode' do
+    @server.binmode?.should be_true
+  end
 
-    it 'raises Errno::EADDRINUSE when the socket is already in use' do
-      -> { UNIXServer.new(@path) }.should raise_error(Errno::EADDRINUSE)
-    end
+  it 'raises Errno::EADDRINUSE when the socket is already in use' do
+    -> { UNIXServer.new(@path) }.should raise_error(Errno::EADDRINUSE)
   end
 end
diff --git a/spec/ruby/library/socket/unixserver/listen_spec.rb b/spec/ruby/library/socket/unixserver/listen_spec.rb
index b90b3bbb09..7938d648c4 100644
--- a/spec/ruby/library/socket/unixserver/listen_spec.rb
+++ b/spec/ruby/library/socket/unixserver/listen_spec.rb
@@ -1,21 +1,19 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXServer#listen' do
-    before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
-    end
+describe 'UNIXServer#listen' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+  end
 
-    after do
-      @server.close
+  after do
+    @server.close
 
-      rm_r(@path)
-    end
+    rm_r(@path)
+  end
 
-    it 'returns 0' do
-      @server.listen(1).should == 0
-    end
+  it 'returns 0' do
+    @server.listen(1).should == 0
   end
 end
diff --git a/spec/ruby/library/socket/unixserver/new_spec.rb b/spec/ruby/library/socket/unixserver/new_spec.rb
index f831f40bc6..7d0c7bf76e 100644
--- a/spec/ruby/library/socket/unixserver/new_spec.rb
+++ b/spec/ruby/library/socket/unixserver/new_spec.rb
@@ -3,4 +3,10 @@ require_relative 'shared/new'
 
 describe "UNIXServer.new" do
   it_behaves_like :unixserver_new, :new
+
+  it "does not use the given block and warns to use UNIXServer::open" do
+    -> {
+      @server = UNIXServer.new(@path) { raise }
+    }.should complain(/warning: UNIXServer::new\(\) does not take block; use UNIXServer::open\(\) instead/)
+  end
 end
diff --git a/spec/ruby/library/socket/unixserver/open_spec.rb b/spec/ruby/library/socket/unixserver/open_spec.rb
index f2506d9f6f..c49df802d0 100644
--- a/spec/ruby/library/socket/unixserver/open_spec.rb
+++ b/spec/ruby/library/socket/unixserver/open_spec.rb
@@ -5,22 +5,20 @@ require_relative 'shared/new'
 describe "UNIXServer.open" do
   it_behaves_like :unixserver_new, :open
 
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-    end
+  before :each do
+    @path = SocketSpecs.socket_path
+  end
 
-    after :each do
-      @server.close if @server
-      @server = nil
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @server.close if @server
+    @server = nil
+    SocketSpecs.rm_socket @path
+  end
 
-    it "yields the new UNIXServer object to the block, if given" do
-      UNIXServer.open(@path) do |unix|
-        unix.path.should == @path
-        unix.addr.should == ["AF_UNIX", @path]
-      end
+  it "yields the new UNIXServer object to the block, if given" do
+    UNIXServer.open(@path) do |unix|
+      unix.path.should == @path
+      unix.addr.should == ["AF_UNIX", @path]
     end
   end
 end
diff --git a/spec/ruby/library/socket/unixserver/shared/new.rb b/spec/ruby/library/socket/unixserver/shared/new.rb
index 35395826c9..b537f2a871 100644
--- a/spec/ruby/library/socket/unixserver/shared/new.rb
+++ b/spec/ruby/library/socket/unixserver/shared/new.rb
@@ -2,21 +2,19 @@ require_relative '../../spec_helper'
 require_relative '../../fixtures/classes'
 
 describe :unixserver_new, shared: true do
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-    end
+  before :each do
+    @path = SocketSpecs.socket_path
+  end
 
-    after :each do
-      @server.close if @server
-      @server = nil
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @server.close if @server
+    @server = nil
+    SocketSpecs.rm_socket @path
+  end
 
-    it "creates a new UNIXServer" do
-      @server = UNIXServer.send(@method, @path)
-      @server.path.should == @path
-      @server.addr.should == ["AF_UNIX", @path]
-    end
+  it "creates a new UNIXServer" do
+    @server = UNIXServer.send(@method, @path)
+    @server.path.should == @path
+    @server.addr.should == ["AF_UNIX", @path]
   end
 end
diff --git a/spec/ruby/library/socket/unixserver/sysaccept_spec.rb b/spec/ruby/library/socket/unixserver/sysaccept_spec.rb
index e59731878a..c4a4ecc824 100644
--- a/spec/ruby/library/socket/unixserver/sysaccept_spec.rb
+++ b/spec/ruby/library/socket/unixserver/sysaccept_spec.rb
@@ -1,51 +1,49 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXServer#sysaccept' do
+describe 'UNIXServer#sysaccept' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+  end
+
+  after do
+    @server.close
+
+    rm_r(@path)
+  end
+
+  describe 'without a client' do
+    it 'blocks the calling thread' do
+      -> { @server.sysaccept }.should block_caller
+    end
+  end
+
+  describe 'with a client' do
     before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
+      @client = UNIXSocket.new(@path)
     end
 
     after do
-      @server.close
-
-      rm_r(@path)
+      Socket.for_fd(@fd).close if @fd
+      @client.close
     end
 
-    describe 'without a client' do
-      it 'blocks the calling thread' do
-        -> { @server.sysaccept }.should block_caller
+    describe 'without any data' do
+      it 'returns an Integer' do
+        @fd = @server.sysaccept
+        @fd.should be_kind_of(Integer)
       end
     end
 
-    describe 'with a client' do
+    describe 'with data available' do
       before do
-        @client = UNIXSocket.new(@path)
-      end
-
-      after do
-        Socket.for_fd(@fd).close if @fd
-        @client.close
+        @client.write('hello')
       end
 
-      describe 'without any data' do
-        it 'returns an Integer' do
-          @fd = @server.sysaccept
-          @fd.should be_kind_of(Integer)
-        end
-      end
-
-      describe 'with data available' do
-        before do
-          @client.write('hello')
-        end
-
-        it 'returns an Integer' do
-          @fd = @server.sysaccept
-          @fd.should be_kind_of(Integer)
-        end
+      it 'returns an Integer' do
+        @fd = @server.sysaccept
+        @fd.should be_kind_of(Integer)
       end
     end
   end
diff --git a/spec/ruby/library/socket/unixsocket/addr_spec.rb b/spec/ruby/library/socket/unixsocket/addr_spec.rb
index e8431bea16..1afe9b12dc 100644
--- a/spec/ruby/library/socket/unixsocket/addr_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/addr_spec.rb
@@ -2,35 +2,32 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXSocket#addr" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @client = UNIXSocket.open(@path)
+  end
 
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @client = UNIXSocket.open(@path)
-    end
-
-    after :each do
-      @client.close
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @client.close
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    it "returns an array" do
-      @client.addr.should be_kind_of(Array)
-    end
+  it "returns an array" do
+    @client.addr.should be_kind_of(Array)
+  end
 
-    it "returns the address family of this socket in an array" do
-      @client.addr[0].should == "AF_UNIX"
-      @server.addr[0].should == "AF_UNIX"
-    end
+  it "returns the address family of this socket in an array" do
+    @client.addr[0].should == "AF_UNIX"
+    @server.addr[0].should == "AF_UNIX"
+  end
 
-    it "returns the path of the socket in an array if it's a server" do
-      @server.addr[1].should == @path
-    end
+  it "returns the path of the socket in an array if it's a server" do
+    @server.addr[1].should == @path
+  end
 
-    it "returns an empty string for path if it's a client" do
-      @client.addr[1].should == ""
-    end
+  it "returns an empty string for path if it's a client" do
+    @client.addr[1].should == ""
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/initialize_spec.rb b/spec/ruby/library/socket/unixsocket/initialize_spec.rb
index 13b6972f03..5dccfcc745 100644
--- a/spec/ruby/library/socket/unixsocket/initialize_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/initialize_spec.rb
@@ -1,38 +1,56 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXSocket#initialize' do
-    describe 'using a non existing path' do
+describe 'UNIXSocket#initialize' do
+  describe 'using a non existing path' do
+    platform_is_not :windows do
       it 'raises Errno::ENOENT' do
         -> { UNIXSocket.new(SocketSpecs.socket_path) }.should raise_error(Errno::ENOENT)
       end
     end
 
-    describe 'using an existing socket path' do
-      before do
-        @path = SocketSpecs.socket_path
-        @server = UNIXServer.new(@path)
-        @socket = UNIXSocket.new(@path)
+    platform_is :windows do
+      # Why, Windows, why?
+      it 'raises Errno::ECONNREFUSED' do
+        -> { UNIXSocket.new(SocketSpecs.socket_path) }.should raise_error(Errno::ECONNREFUSED)
       end
+    end
+  end
 
-      after do
-        @socket.close
-        @server.close
-        rm_r(@path)
-      end
+  describe 'using an existing socket path' do
+    before do
+      @path = SocketSpecs.socket_path
+      @server = UNIXServer.new(@path)
+      @socket = UNIXSocket.new(@path)
+    end
 
-      it 'returns a new UNIXSocket' do
-        @socket.should be_an_instance_of(UNIXSocket)
-      end
+    after do
+      @socket.close
+      @server.close
+      rm_r(@path)
+    end
 
-      it 'sets the socket path to an empty String' do
-        @socket.path.should == ''
-      end
+    it 'returns a new UNIXSocket' do
+      @socket.should be_an_instance_of(UNIXSocket)
+    end
+
+    it 'sets the socket path to an empty String' do
+      @socket.path.should == ''
+    end
 
-      it 'sets the socket to binmode' do
-        @socket.binmode?.should be_true
+    it 'sets the socket to binmode' do
+      @socket.binmode?.should be_true
+    end
+
+    platform_is_not :windows do
+      it 'sets the socket to nonblock' do
+        require 'io/nonblock'
+        @socket.should.nonblock?
       end
     end
+
+    it 'sets the socket to close on exec' do
+      @socket.should.close_on_exec?
+    end
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/inspect_spec.rb b/spec/ruby/library/socket/unixsocket/inspect_spec.rb
index d2e3cabbd3..77bb521069 100644
--- a/spec/ruby/library/socket/unixsocket/inspect_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/inspect_spec.rb
@@ -2,16 +2,14 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXSocket#inspect" do
-  platform_is_not :windows do
-    it "returns sockets fd for unnamed sockets" do
-      begin
-        s1, s2 = UNIXSocket.socketpair
-        s1.inspect.should == "#<UNIXSocket:fd #{s1.fileno}>"
-        s2.inspect.should == "#<UNIXSocket:fd #{s2.fileno}>"
-      ensure
-        s1.close
-        s2.close
-      end
+  it "returns sockets fd for unnamed sockets" do
+    begin
+      s1, s2 = UNIXSocket.socketpair
+      s1.inspect.should == "#<UNIXSocket:fd #{s1.fileno}>"
+      s2.inspect.should == "#<UNIXSocket:fd #{s2.fileno}>"
+    ensure
+      s1.close
+      s2.close
     end
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/local_address_spec.rb b/spec/ruby/library/socket/unixsocket/local_address_spec.rb
index cbf315f9f4..0fdec38293 100644
--- a/spec/ruby/library/socket/unixsocket/local_address_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/local_address_spec.rb
@@ -1,96 +1,92 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXSocket#local_address' do
-    before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
-      @client = UNIXSocket.new(@path)
-    end
+describe 'UNIXSocket#local_address' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+    @client = UNIXSocket.new(@path)
+  end
 
-    after do
-      @client.close
-      @server.close
+  after do
+    @client.close
+    @server.close
 
-      rm_r(@path)
-    end
-
-    it 'returns an Addrinfo' do
-      @client.local_address.should be_an_instance_of(Addrinfo)
-    end
+    rm_r(@path)
+  end
 
-    describe 'the returned Addrinfo' do
-      platform_is_not :aix do
-        it 'uses AF_UNIX as the address family' do
-          @client.local_address.afamily.should == Socket::AF_UNIX
-        end
+  it 'returns an Addrinfo' do
+    @client.local_address.should be_an_instance_of(Addrinfo)
+  end
 
-        it 'uses PF_UNIX as the protocol family' do
-          @client.local_address.pfamily.should == Socket::PF_UNIX
-        end
+  describe 'the returned Addrinfo' do
+    platform_is_not :aix do
+      it 'uses AF_UNIX as the address family' do
+        @client.local_address.afamily.should == Socket::AF_UNIX
       end
 
-      it 'uses SOCK_STREAM as the socket type' do
-        @client.local_address.socktype.should == Socket::SOCK_STREAM
+      it 'uses PF_UNIX as the protocol family' do
+        @client.local_address.pfamily.should == Socket::PF_UNIX
       end
+    end
 
-      platform_is_not :aix do
-        it 'uses an empty socket path' do
-          @client.local_address.unix_path.should == ''
-        end
-      end
+    it 'uses SOCK_STREAM as the socket type' do
+      @client.local_address.socktype.should == Socket::SOCK_STREAM
+    end
 
-      it 'uses 0 as the protocol' do
-        @client.local_address.protocol.should == 0
+    platform_is_not :aix do
+      it 'uses an empty socket path' do
+        @client.local_address.unix_path.should == ''
       end
     end
+
+    it 'uses 0 as the protocol' do
+      @client.local_address.protocol.should == 0
+    end
   end
 end
 
-with_feature :unix_socket do
-  describe 'UNIXSocket#local_address with a UNIX socket pair' do
-    before :each do
-      @sock, @sock2 = Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM)
-    end
+describe 'UNIXSocket#local_address with a UNIX socket pair' do
+  before :each do
+    @sock, @sock2 = Socket.pair(Socket::AF_UNIX, Socket::SOCK_STREAM)
+  end
 
-    after :each do
-      @sock.close
-      @sock2.close
-    end
+  after :each do
+    @sock.close
+    @sock2.close
+  end
 
-    it 'returns an Addrinfo' do
-      @sock.local_address.should be_an_instance_of(Addrinfo)
-    end
+  it 'returns an Addrinfo' do
+    @sock.local_address.should be_an_instance_of(Addrinfo)
+  end
 
-    describe 'the returned Addrinfo' do
-      it 'uses AF_UNIX as the address family' do
-        @sock.local_address.afamily.should == Socket::AF_UNIX
-      end
+  describe 'the returned Addrinfo' do
+    it 'uses AF_UNIX as the address family' do
+      @sock.local_address.afamily.should == Socket::AF_UNIX
+    end
 
-      it 'uses PF_UNIX as the protocol family' do
-        @sock.local_address.pfamily.should == Socket::PF_UNIX
-      end
+    it 'uses PF_UNIX as the protocol family' do
+      @sock.local_address.pfamily.should == Socket::PF_UNIX
+    end
 
-      it 'uses SOCK_STREAM as the socket type' do
-        @sock.local_address.socktype.should == Socket::SOCK_STREAM
-      end
+    it 'uses SOCK_STREAM as the socket type' do
+      @sock.local_address.socktype.should == Socket::SOCK_STREAM
+    end
 
-      it 'raises SocketError for #ip_address' do
-        -> {
-          @sock.local_address.ip_address
-        }.should raise_error(SocketError, "need IPv4 or IPv6 address")
-      end
+    it 'raises SocketError for #ip_address' do
+      -> {
+        @sock.local_address.ip_address
+      }.should raise_error(SocketError, "need IPv4 or IPv6 address")
+    end
 
-      it 'raises SocketError for #ip_port' do
-        -> {
-          @sock.local_address.ip_port
-        }.should raise_error(SocketError, "need IPv4 or IPv6 address")
-      end
+    it 'raises SocketError for #ip_port' do
+      -> {
+        @sock.local_address.ip_port
+      }.should raise_error(SocketError, "need IPv4 or IPv6 address")
+    end
 
-      it 'uses 0 as the protocol' do
-        @sock.local_address.protocol.should == 0
-      end
+    it 'uses 0 as the protocol' do
+      @sock.local_address.protocol.should == 0
     end
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/new_spec.rb b/spec/ruby/library/socket/unixsocket/new_spec.rb
index 05a6b3eda2..fea2c1e2b7 100644
--- a/spec/ruby/library/socket/unixsocket/new_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/new_spec.rb
@@ -3,4 +3,10 @@ require_relative 'shared/new'
 
 describe "UNIXSocket.new" do
   it_behaves_like :unixsocket_new, :new
+
+  it "does not use the given block and warns to use UNIXSocket::open" do
+    -> {
+      @client = UNIXSocket.new(@path) { raise }
+    }.should complain(/warning: UNIXSocket::new\(\) does not take block; use UNIXSocket::open\(\) instead/)
+  end
 end
diff --git a/spec/ruby/library/socket/unixsocket/open_spec.rb b/spec/ruby/library/socket/unixsocket/open_spec.rb
index ad5048fedd..b5e8c6c23a 100644
--- a/spec/ruby/library/socket/unixsocket/open_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/open_spec.rb
@@ -7,22 +7,20 @@ describe "UNIXSocket.open" do
 end
 
 describe "UNIXSocket.open" do
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-    end
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+  end
 
-    after :each do
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    it "opens a unix socket on the specified file and yields it to the block" do
-      UNIXSocket.open(@path) do |client|
-        client.addr[0].should == "AF_UNIX"
-        client.closed?.should == false
-      end
+  it "opens a unix socket on the specified file and yields it to the block" do
+    UNIXSocket.open(@path) do |client|
+      client.addr[0].should == "AF_UNIX"
+      client.should_not.closed?
     end
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/pair_spec.rb b/spec/ruby/library/socket/unixsocket/pair_spec.rb
index 845ff76ecc..9690142668 100644
--- a/spec/ruby/library/socket/unixsocket/pair_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/pair_spec.rb
@@ -1,39 +1,18 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/partially_closable_sockets'
+require_relative 'shared/pair'
 
-describe "UNIXSocket#pair" do
-  platform_is_not :windows do
+describe "UNIXSocket.pair" do
+  it_should_behave_like :unixsocket_pair
+  it_should_behave_like :partially_closable_sockets
 
-    it_should_behave_like "partially closable sockets"
-
-    before :each do
-      @s1, @s2 = UNIXSocket.pair
-    end
-
-    after :each do
-      @s1.close
-      @s2.close
-    end
-
-    it "returns a pair of connected sockets" do
-      @s1.puts "foo"
-      @s2.gets.should == "foo\n"
-    end
-
-    it "returns sockets with no name" do
-      @s1.path.should == @s2.path
-      @s1.path.should == ""
-    end
-
-    it "returns sockets with no address" do
-      @s1.addr.should == ["AF_UNIX", ""]
-      @s2.addr.should == ["AF_UNIX", ""]
-    end
+  before :each do
+    @s1, @s2 = UNIXSocket.pair
+  end
 
-    it "returns sockets with no peeraddr" do
-      @s1.peeraddr.should == ["AF_UNIX", ""]
-      @s2.peeraddr.should == ["AF_UNIX", ""]
-    end
+  after :each do
+    @s1.close
+    @s2.close
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/partially_closable_spec.rb b/spec/ruby/library/socket/unixsocket/partially_closable_spec.rb
index 78a64fe6be..108a6c3063 100644
--- a/spec/ruby/library/socket/unixsocket/partially_closable_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/partially_closable_spec.rb
@@ -2,24 +2,20 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 require_relative '../shared/partially_closable_sockets'
 
-platform_is_not :windows do
-  describe "UNIXSocket partial closability" do
-
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @s1 = UNIXSocket.new(@path)
-      @s2 = @server.accept
-    end
-
-    after :each do
-      @server.close
-      @s1.close
-      @s2.close
-      SocketSpecs.rm_socket @path
-    end
-
-    it_should_behave_like "partially closable sockets"
+describe "UNIXSocket partial closability" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @s1 = UNIXSocket.new(@path)
+    @s2 = @server.accept
+  end
 
+  after :each do
+    @server.close
+    @s1.close
+    @s2.close
+    SocketSpecs.rm_socket @path
   end
+
+  it_should_behave_like :partially_closable_sockets
 end
diff --git a/spec/ruby/library/socket/unixsocket/path_spec.rb b/spec/ruby/library/socket/unixsocket/path_spec.rb
index 317ffc0975..ffe7e4bea2 100644
--- a/spec/ruby/library/socket/unixsocket/path_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/path_spec.rb
@@ -2,27 +2,23 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXSocket#path" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @client = UNIXSocket.open(@path)
+  end
 
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @client = UNIXSocket.open(@path)
-    end
-
-    after :each do
-      @client.close
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
-
-    it "returns the path of the socket if it's a server" do
-      @server.path.should == @path
-    end
+  after :each do
+    @client.close
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    it "returns an empty string for path if it's a client" do
-      @client.path.should == ""
-    end
+  it "returns the path of the socket if it's a server" do
+    @server.path.should == @path
   end
 
+  it "returns an empty string for path if it's a client" do
+    @client.path.should == ""
+  end
 end
diff --git a/spec/ruby/library/socket/unixsocket/peeraddr_spec.rb b/spec/ruby/library/socket/unixsocket/peeraddr_spec.rb
index 0b6b1ccf04..10cab13b42 100644
--- a/spec/ruby/library/socket/unixsocket/peeraddr_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/peeraddr_spec.rb
@@ -2,29 +2,25 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXSocket#peeraddr" do
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @client = UNIXSocket.open(@path)
+  end
 
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @client = UNIXSocket.open(@path)
-    end
-
-    after :each do
-      @client.close
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
-
-    it "returns the address family and path of the server end of the connection" do
-      @client.peeraddr.should == ["AF_UNIX", @path]
-    end
+  after :each do
+    @client.close
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    it "raises an error in server sockets" do
-      -> {
-        @server.peeraddr
-      }.should raise_error(Errno::ENOTCONN)
-    end
+  it "returns the address family and path of the server end of the connection" do
+    @client.peeraddr.should == ["AF_UNIX", @path]
   end
 
+  it "raises an error in server sockets" do
+    -> {
+      @server.peeraddr
+    }.should raise_error(Errno::ENOTCONN)
+  end
 end
diff --git a/spec/ruby/library/socket/unixsocket/recv_io_spec.rb b/spec/ruby/library/socket/unixsocket/recv_io_spec.rb
index 533f02a0fa..f0b408f309 100644
--- a/spec/ruby/library/socket/unixsocket/recv_io_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/recv_io_spec.rb
@@ -1,9 +1,8 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-describe "UNIXSocket#recv_io" do
-
-  platform_is_not :windows do
+platform_is_not :windows do
+  describe "UNIXSocket#recv_io" do
     before :each do
       @path = SocketSpecs.socket_path
       @server = UNIXServer.open(@path)
@@ -41,9 +40,7 @@ describe "UNIXSocket#recv_io" do
       @io.should be_an_instance_of(File)
     end
   end
-end
 
-with_feature :unix_socket do
   describe 'UNIXSocket#recv_io' do
     before do
       @file = File.open('/dev/null', 'w')
diff --git a/spec/ruby/library/socket/unixsocket/recvfrom_spec.rb b/spec/ruby/library/socket/unixsocket/recvfrom_spec.rb
index c0e1cf670b..9ae3777961 100644
--- a/spec/ruby/library/socket/unixsocket/recvfrom_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/recvfrom_spec.rb
@@ -2,35 +2,104 @@ require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
 describe "UNIXSocket#recvfrom" do
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-      @client = UNIXSocket.open(@path)
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+    @client = UNIXSocket.open(@path)
+  end
+
+  after :each do
+    @client.close
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
+
+  it "receives len bytes from sock, returning an array containing sent data as first element" do
+    @client.send("foobar", 0)
+    sock = @server.accept
+    sock.recvfrom(6).first.should == "foobar"
+    sock.close
+  end
+
+  context "when called on a server's socket" do
+    platform_is_not :windows do
+      it "returns an array containing basic information on the client as second element" do
+        @client.send("foobar", 0)
+        sock = @server.accept
+        data = sock.recvfrom(6)
+        data.last.should == ["AF_UNIX", ""]
+        sock.close
+      end
     end
 
-    after :each do
-      @client.close
-      @server.close
-      SocketSpecs.rm_socket @path
+    guard -> { platform_is :windows and ruby_bug "#21702", ""..."4.2" } do
+      it "returns an array containing basic information on the client as second element" do
+        @client.send("foobar", 0)
+        sock = @server.accept
+        data = sock.recvfrom(6)
+        data.last.should == ["AF_UNIX", ""]
+        sock.close
+      end
     end
+  end
 
-    it "receives len bytes from sock" do
-      @client.send("foobar", 0)
-      sock = @server.accept
-      sock.recvfrom(6).first.should == "foobar"
-      sock.close
+  context "when called on a client's socket" do
+    platform_is :linux do
+      it "returns an array containing server's address as second element" do
+        @client.send("", 0)
+        sock = @server.accept
+        sock.send("barfoo", 0)
+        @client.recvfrom(6).last.should == ["AF_UNIX", @server.local_address.unix_path]
+        sock.close
+      end
     end
 
-    it "returns an array with data and information on the sender" do
-      @client.send("foobar", 0)
-      sock = @server.accept
-      data = sock.recvfrom(6)
-      data.first.should == "foobar"
-      data.last.should == ["AF_UNIX", ""]
-      sock.close
+    guard -> { platform_is :windows and ruby_bug "#21702", ""..."4.2" } do
+      it "returns an array containing server's address as second element" do
+        @client.send("", 0)
+        sock = @server.accept
+        sock.send("barfoo", 0)
+        # This may not be correct, depends on what underlying recvfrom actually returns.
+        @client.recvfrom(6).last.should == ["AF_UNIX", @server.local_address.unix_path]
+        sock.close
+      end
     end
 
+    platform_is :darwin do
+      it "returns an array containing basic information on the server as second element" do
+        @client.send("", 0)
+        sock = @server.accept
+        sock.send("barfoo", 0)
+        @client.recvfrom(6).last.should == ["AF_UNIX", ""]
+        sock.close
+      end
+    end
+  end
+
+  it "allows an output buffer as third argument" do
+    buffer = +''
+
+    @client.send("foobar", 0)
+    sock = @server.accept
+    message, = sock.recvfrom(6, 0, buffer)
+    sock.close
+
+    message.should.equal?(buffer)
+    buffer.should == "foobar"
+  end
+
+  it "preserves the encoding of the given buffer" do
+    buffer = ''.encode(Encoding::ISO_8859_1)
+
+    @client.send("foobar", 0)
+    sock = @server.accept
+    sock.recvfrom(6, 0, buffer)
+    sock.close
+
+    buffer.encoding.should == Encoding::ISO_8859_1
+  end
+
+  platform_is_not :windows do
     it "uses different message options" do
       @client.send("foobar", Socket::MSG_PEEK)
       sock = @server.accept
@@ -44,25 +113,32 @@ describe "UNIXSocket#recvfrom" do
   end
 end
 
+describe 'UNIXSocket#recvfrom' do
+  describe 'using a socket pair' do
+    before do
+      @client, @server = UNIXSocket.socketpair
+      @client.write('hello')
+    end
 
-with_feature :unix_socket do
-  describe 'UNIXSocket#recvfrom' do
-    describe 'using a socket pair' do
-      before do
-        @client, @server = UNIXSocket.socketpair
-        @client.write('hello')
-      end
+    after do
+      @client.close
+      @server.close
+    end
 
-      after do
-        @client.close
-        @server.close
+    platform_is_not :windows do
+      it 'returns an Array containing the data and address information' do
+        @server.recvfrom(5).should == ['hello', ['AF_UNIX', '']]
       end
+    end
 
+    guard -> { platform_is :windows and ruby_bug "#21702", ""..."4.2" } do
       it 'returns an Array containing the data and address information' do
         @server.recvfrom(5).should == ['hello', ['AF_UNIX', '']]
       end
     end
+  end
 
+  platform_is_not :windows do
     # These specs are taken from the rdoc examples on UNIXSocket#recvfrom.
     describe 'using a UNIX socket constructed using UNIXSocket.for_fd' do
       before do
diff --git a/spec/ruby/library/socket/unixsocket/remote_address_spec.rb b/spec/ruby/library/socket/unixsocket/remote_address_spec.rb
index 0b416254d0..84bdff0a6a 100644
--- a/spec/ruby/library/socket/unixsocket/remote_address_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/remote_address_spec.rb
@@ -1,45 +1,43 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-with_feature :unix_socket do
-  describe 'UNIXSocket#remote_address' do
-    before do
-      @path   = SocketSpecs.socket_path
-      @server = UNIXServer.new(@path)
-      @client = UNIXSocket.new(@path)
-    end
+describe 'UNIXSocket#remote_address' do
+  before do
+    @path   = SocketSpecs.socket_path
+    @server = UNIXServer.new(@path)
+    @client = UNIXSocket.new(@path)
+  end
 
-    after do
-      @client.close
-      @server.close
+  after do
+    @client.close
+    @server.close
 
-      rm_r(@path)
-    end
+    rm_r(@path)
+  end
 
-    it 'returns an Addrinfo' do
-      @client.remote_address.should be_an_instance_of(Addrinfo)
-    end
+  it 'returns an Addrinfo' do
+    @client.remote_address.should be_an_instance_of(Addrinfo)
+  end
 
-    describe 'the returned Addrinfo' do
-      it 'uses AF_UNIX as the address family' do
-        @client.remote_address.afamily.should == Socket::AF_UNIX
-      end
+  describe 'the returned Addrinfo' do
+    it 'uses AF_UNIX as the address family' do
+      @client.remote_address.afamily.should == Socket::AF_UNIX
+    end
 
-      it 'uses PF_UNIX as the protocol family' do
-        @client.remote_address.pfamily.should == Socket::PF_UNIX
-      end
+    it 'uses PF_UNIX as the protocol family' do
+      @client.remote_address.pfamily.should == Socket::PF_UNIX
+    end
 
-      it 'uses SOCK_STREAM as the socket type' do
-        @client.remote_address.socktype.should == Socket::SOCK_STREAM
-      end
+    it 'uses SOCK_STREAM as the socket type' do
+      @client.remote_address.socktype.should == Socket::SOCK_STREAM
+    end
 
-      it 'uses the correct socket path' do
-        @client.remote_address.unix_path.should == @path
-      end
+    it 'uses the correct socket path' do
+      @client.remote_address.unix_path.should == @path
+    end
 
-      it 'uses 0 as the protocol' do
-        @client.remote_address.protocol.should == 0
-      end
+    it 'uses 0 as the protocol' do
+      @client.remote_address.protocol.should == 0
     end
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/send_io_spec.rb b/spec/ruby/library/socket/unixsocket/send_io_spec.rb
index a2a7d26539..52186ec3cf 100644
--- a/spec/ruby/library/socket/unixsocket/send_io_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/send_io_spec.rb
@@ -1,9 +1,8 @@
 require_relative '../spec_helper'
 require_relative '../fixtures/classes'
 
-describe "UNIXSocket#send_io" do
-
-  platform_is_not :windows do
+platform_is_not :windows do
+  describe "UNIXSocket#send_io" do
     before :each do
       @path = SocketSpecs.socket_path
       @server = UNIXServer.open(@path)
@@ -32,9 +31,7 @@ describe "UNIXSocket#send_io" do
       @io.read.should == File.read(@send_io_path)
     end
   end
-end
 
-with_feature :unix_socket do
   describe 'UNIXSocket#send_io' do
     before do
       @file = File.open('/dev/null', 'w')
diff --git a/spec/ruby/library/socket/unixsocket/shared/new.rb b/spec/ruby/library/socket/unixsocket/shared/new.rb
index 76a4e1701e..f075b03c5e 100644
--- a/spec/ruby/library/socket/unixsocket/shared/new.rb
+++ b/spec/ruby/library/socket/unixsocket/shared/new.rb
@@ -2,23 +2,21 @@ require_relative '../../spec_helper'
 require_relative '../../fixtures/classes'
 
 describe :unixsocket_new, shared: true do
-  platform_is_not :windows do
-    before :each do
-      @path = SocketSpecs.socket_path
-      @server = UNIXServer.open(@path)
-    end
+  before :each do
+    @path = SocketSpecs.socket_path
+    @server = UNIXServer.open(@path)
+  end
 
-    after :each do
-      @client.close if @client
-      @server.close
-      SocketSpecs.rm_socket @path
-    end
+  after :each do
+    @client.close if @client
+    @server.close
+    SocketSpecs.rm_socket @path
+  end
 
-    it "opens a unix socket on the specified file" do
-      @client = UNIXSocket.send(@method, @path)
+  it "opens a unix socket on the specified file" do
+    @client = UNIXSocket.send(@method, @path)
 
-      @client.addr[0].should == "AF_UNIX"
-      @client.closed?.should == false
-    end
+    @client.addr[0].should == "AF_UNIX"
+    @client.should_not.closed?
   end
 end
diff --git a/spec/ruby/library/socket/unixsocket/shared/pair.rb b/spec/ruby/library/socket/unixsocket/shared/pair.rb
new file mode 100644
index 0000000000..d68ee466bf
--- /dev/null
+++ b/spec/ruby/library/socket/unixsocket/shared/pair.rb
@@ -0,0 +1,47 @@
+require_relative '../../spec_helper'
+require_relative '../../fixtures/classes'
+
+describe :unixsocket_pair, shared: true do
+  it "returns two UNIXSockets" do
+    @s1.should be_an_instance_of(UNIXSocket)
+    @s2.should be_an_instance_of(UNIXSocket)
+  end
+
+  it "returns a pair of connected sockets" do
+    @s1.puts "foo"
+    @s2.gets.should == "foo\n"
+  end
+
+  platform_is_not :windows do
+    it "sets the socket paths to empty Strings" do
+      @s1.path.should == ""
+      @s2.path.should == ""
+    end
+
+    it "sets the socket addresses to empty Strings" do
+      @s1.addr.should == ["AF_UNIX", ""]
+      @s2.addr.should == ["AF_UNIX", ""]
+    end
+
+    it "sets the socket peer addresses to empty Strings" do
+      @s1.peeraddr.should == ["AF_UNIX", ""]
+      @s2.peeraddr.should == ["AF_UNIX", ""]
+    end
+  end
+
+  platform_is :windows do
+    it "emulates unnamed sockets with a temporary file with a path" do
+      @s1.addr.should == ["AF_UNIX", @s1.path]
+      @s2.peeraddr.should == ["AF_UNIX", @s1.path]
+    end
+
+    it "sets the peer address of first socket to an empty string" do
+      @s1.peeraddr.should == ["AF_UNIX", ""]
+    end
+
+    it "sets the address and path of second socket to an empty string" do
+      @s2.addr.should == ["AF_UNIX", ""]
+      @s2.path.should == ""
+    end
+  end
+end
diff --git a/spec/ruby/library/socket/unixsocket/socketpair_spec.rb b/spec/ruby/library/socket/unixsocket/socketpair_spec.rb
index 3e9646f76b..c61fc00be4 100644
--- a/spec/ruby/library/socket/unixsocket/socketpair_spec.rb
+++ b/spec/ruby/library/socket/unixsocket/socketpair_spec.rb
@@ -1,40 +1,18 @@
 require_relative '../spec_helper'
+require_relative '../fixtures/classes'
+require_relative '../shared/partially_closable_sockets'
+require_relative 'shared/pair'
 
-with_feature :unix_socket do
-  describe 'UNIXSocket.socketpair' do
-    before do
-      @s1, @s2 = UNIXSocket.socketpair
-    end
+describe "UNIXSocket.socketpair" do
+  it_should_behave_like :unixsocket_pair
+  it_should_behave_like :partially_closable_sockets
 
-    after do
-      @s1.close
-      @s2.close
-    end
-
-    it 'returns two UNIXSockets' do
-      @s1.should be_an_instance_of(UNIXSocket)
-      @s2.should be_an_instance_of(UNIXSocket)
-    end
-
-    it 'connects the sockets to each other' do
-      @s1.write('hello')
-
-      @s2.recv(5).should == 'hello'
-    end
-
-    it 'sets the socket paths to empty Strings' do
-      @s1.path.should == ''
-      @s2.path.should == ''
-    end
-
-    it 'sets the socket addresses to empty Strings' do
-      @s1.addr.should == ['AF_UNIX', '']
-      @s2.addr.should == ['AF_UNIX', '']
-    end
+  before :each do
+    @s1, @s2 = UNIXSocket.socketpair
+  end
 
-    it 'sets the socket peer addresses to empty Strings' do
-      @s1.peeraddr.should == ['AF_UNIX', '']
-      @s2.peeraddr.should == ['AF_UNIX', '']
-    end
+  after :each do
+    @s1.close
+    @s2.close
   end
 end
diff --git a/spec/ruby/library/stringio/append_spec.rb b/spec/ruby/library/stringio/append_spec.rb
index a8bc6aabdb..cb50d73d1b 100644
--- a/spec/ruby/library/stringio/append_spec.rb
+++ b/spec/ruby/library/stringio/append_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#<< when passed [Object]" do
   before :each do
-    @io = StringIO.new("example")
+    @io = StringIO.new(+"example")
   end
 
   it "returns self" do
@@ -29,16 +29,6 @@ describe "StringIO#<< when passed [Object]" do
     @io.string.should == "example\000\000\000\000\000\000\000\000just testing"
   end
 
-  it "taints self's String when the passed argument is tainted" do
-    (@io << "test".taint)
-    @io.string.tainted?.should be_true
-  end
-
-  it "does not taint self when the passed argument is tainted" do
-    (@io << "test".taint)
-    @io.tainted?.should be_false
-  end
-
   it "updates self's position" do
     @io << "test"
     @io.pos.should eql(4)
@@ -54,10 +44,10 @@ end
 
 describe "StringIO#<< when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io << "test" }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io << "test" }.should raise_error(IOError)
   end
@@ -65,7 +55,7 @@ end
 
 describe "StringIO#<< when in append mode" do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self, ignoring current position" do
diff --git a/spec/ruby/library/stringio/binmode_spec.rb b/spec/ruby/library/stringio/binmode_spec.rb
index 5d9a8c41df..9e92c63814 100644
--- a/spec/ruby/library/stringio/binmode_spec.rb
+++ b/spec/ruby/library/stringio/binmode_spec.rb
@@ -3,7 +3,21 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#binmode" do
   it "returns self" do
-    io = StringIO.new("example")
+    io = StringIO.new(+"example")
     io.binmode.should equal(io)
   end
+
+  it "changes external encoding to BINARY" do
+    io = StringIO.new
+    io.external_encoding.should == Encoding.find('external')
+    io.binmode
+    io.external_encoding.should == Encoding::BINARY
+  end
+
+  it "does not set internal encoding" do
+    io = StringIO.new
+    io.internal_encoding.should == nil
+    io.binmode
+    io.internal_encoding.should == nil
+  end
 end
diff --git a/spec/ruby/library/stringio/bytes_spec.rb b/spec/ruby/library/stringio/bytes_spec.rb
deleted file mode 100644
index 692fba997f..0000000000
--- a/spec/ruby/library/stringio/bytes_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-require 'stringio'
-require_relative 'shared/each_byte'
-
-describe "StringIO#bytes" do
-  it_behaves_like :stringio_each_byte, :bytes
-end
-
-describe "StringIO#bytes when self is not readable" do
-  it_behaves_like :stringio_each_byte_not_readable, :bytes
-end
diff --git a/spec/ruby/library/stringio/chars_spec.rb b/spec/ruby/library/stringio/chars_spec.rb
deleted file mode 100644
index 7dc55d4b37..0000000000
--- a/spec/ruby/library/stringio/chars_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-require 'stringio'
-require_relative 'shared/each_char'
-
-describe "StringIO#chars" do
-  it_behaves_like :stringio_each_char, :chars
-end
-
-describe "StringIO#chars when self is not readable" do
-  it_behaves_like :stringio_each_char_not_readable, :chars
-end
diff --git a/spec/ruby/library/stringio/close_read_spec.rb b/spec/ruby/library/stringio/close_read_spec.rb
index 80bd547e85..0f08e1ff2e 100644
--- a/spec/ruby/library/stringio/close_read_spec.rb
+++ b/spec/ruby/library/stringio/close_read_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#close_read" do
   before :each do
-    @io = StringIO.new("example")
+    @io = StringIO.new(+"example")
   end
 
   it "returns nil" do
@@ -21,7 +21,7 @@ describe "StringIO#close_read" do
   end
 
   it "raises an IOError when in write-only mode" do
-    io = StringIO.new("example", "w")
+    io = StringIO.new(+"example", "w")
     -> { io.close_read }.should raise_error(IOError)
 
     io = StringIO.new("example")
diff --git a/spec/ruby/library/stringio/close_write_spec.rb b/spec/ruby/library/stringio/close_write_spec.rb
index 1a4cfa113e..c86c3f9826 100644
--- a/spec/ruby/library/stringio/close_write_spec.rb
+++ b/spec/ruby/library/stringio/close_write_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#close_write" do
   before :each do
-    @io = StringIO.new("example")
+    @io = StringIO.new(+"example")
   end
 
   it "returns nil" do
@@ -21,10 +21,10 @@ describe "StringIO#close_write" do
   end
 
   it "raises an IOError when in read-only mode" do
-    io = StringIO.new("example", "r")
+    io = StringIO.new(+"example", "r")
     -> { io.close_write }.should raise_error(IOError)
 
-    io = StringIO.new("example")
+    io = StringIO.new(+"example")
     io.close_write
     io.close_write.should == nil
   end
diff --git a/spec/ruby/library/stringio/closed_read_spec.rb b/spec/ruby/library/stringio/closed_read_spec.rb
index cb4267ac98..b4dcadc3a4 100644
--- a/spec/ruby/library/stringio/closed_read_spec.rb
+++ b/spec/ruby/library/stringio/closed_read_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#closed_read?" do
   it "returns true if self is not readable" do
-    io = StringIO.new("example", "r+")
+    io = StringIO.new(+"example", "r+")
     io.close_write
     io.closed_read?.should be_false
     io.close_read
diff --git a/spec/ruby/library/stringio/closed_spec.rb b/spec/ruby/library/stringio/closed_spec.rb
index ca8a2232a8..bf7ba63184 100644
--- a/spec/ruby/library/stringio/closed_spec.rb
+++ b/spec/ruby/library/stringio/closed_spec.rb
@@ -3,13 +3,13 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#closed?" do
   it "returns true if self is completely closed" do
-    io = StringIO.new("example", "r+")
+    io = StringIO.new(+"example", "r+")
     io.close_read
     io.closed?.should be_false
     io.close_write
     io.closed?.should be_true
 
-    io = StringIO.new("example", "r+")
+    io = StringIO.new(+"example", "r+")
     io.close
     io.closed?.should be_true
   end
diff --git a/spec/ruby/library/stringio/closed_write_spec.rb b/spec/ruby/library/stringio/closed_write_spec.rb
index 5c111affd8..2bd3e6fa8b 100644
--- a/spec/ruby/library/stringio/closed_write_spec.rb
+++ b/spec/ruby/library/stringio/closed_write_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#closed_write?" do
   it "returns true if self is not writable" do
-    io = StringIO.new("example", "r+")
+    io = StringIO.new(+"example", "r+")
     io.close_read
     io.closed_write?.should be_false
     io.close_write
diff --git a/spec/ruby/library/stringio/codepoints_spec.rb b/spec/ruby/library/stringio/codepoints_spec.rb
deleted file mode 100644
index cc2e5d1b5d..0000000000
--- a/spec/ruby/library/stringio/codepoints_spec.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-# -*- encoding: utf-8 -*-
-require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-require_relative 'shared/codepoints'
-
-# See redmine #1667
-describe "StringIO#codepoints" do
-  it_behaves_like :stringio_codepoints, :codepoints
-end
diff --git a/spec/ruby/library/stringio/each_char_spec.rb b/spec/ruby/library/stringio/each_char_spec.rb
index 7305162ee6..14b2f09a17 100644
--- a/spec/ruby/library/stringio/each_char_spec.rb
+++ b/spec/ruby/library/stringio/each_char_spec.rb
@@ -7,5 +7,5 @@ describe "StringIO#each_char" do
 end
 
 describe "StringIO#each_char when self is not readable" do
-  it_behaves_like :stringio_each_char_not_readable, :chars
+  it_behaves_like :stringio_each_char_not_readable, :each_char
 end
diff --git a/spec/ruby/library/stringio/each_codepoint_spec.rb b/spec/ruby/library/stringio/each_codepoint_spec.rb
index 85aa34d9d8..f18de22aad 100644
--- a/spec/ruby/library/stringio/each_codepoint_spec.rb
+++ b/spec/ruby/library/stringio/each_codepoint_spec.rb
@@ -5,5 +5,5 @@ require_relative 'shared/codepoints'
 
 # See redmine #1667
 describe "StringIO#each_codepoint" do
-  it_behaves_like :stringio_codepoints, :codepoints
+  it_behaves_like :stringio_codepoints, :each_codepoint
 end
diff --git a/spec/ruby/library/stringio/each_line_spec.rb b/spec/ruby/library/stringio/each_line_spec.rb
index 1389408399..4ac0db7c45 100644
--- a/spec/ruby/library/stringio/each_line_spec.rb
+++ b/spec/ruby/library/stringio/each_line_spec.rb
@@ -17,3 +17,11 @@ end
 describe "StringIO#each_line when passed chomp" do
   it_behaves_like :stringio_each_chomp, :each_line
 end
+
+describe "StringIO#each_line when passed limit" do
+  it_behaves_like :stringio_each_limit, :each_line
+end
+
+describe "StringIO#each when passed separator and limit" do
+  it_behaves_like :stringio_each_separator_and_limit, :each_line
+end
diff --git a/spec/ruby/library/stringio/each_spec.rb b/spec/ruby/library/stringio/each_spec.rb
index a76460049b..7eb322f3ff 100644
--- a/spec/ruby/library/stringio/each_spec.rb
+++ b/spec/ruby/library/stringio/each_spec.rb
@@ -17,3 +17,15 @@ end
 describe "StringIO#each when passed chomp" do
   it_behaves_like :stringio_each_chomp, :each
 end
+
+describe "StringIO#each when passed chomp" do
+  it_behaves_like :stringio_each_separator_and_chomp, :each
+end
+
+describe "StringIO#each when passed limit" do
+  it_behaves_like :stringio_each_limit, :each
+end
+
+describe "StringIO#each when passed separator and limit" do
+  it_behaves_like :stringio_each_separator_and_limit, :each
+end
diff --git a/spec/ruby/library/stringio/fileno_spec.rb b/spec/ruby/library/stringio/fileno_spec.rb
index eea03a5af3..5a9f440a0f 100644
--- a/spec/ruby/library/stringio/fileno_spec.rb
+++ b/spec/ruby/library/stringio/fileno_spec.rb
@@ -1,6 +1,5 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/classes'
-require_relative 'shared/each'
+require 'stringio'
 
 describe "StringIO#fileno" do
   it "returns nil" do
diff --git a/spec/ruby/library/stringio/fixtures/classes.rb b/spec/ruby/library/stringio/fixtures/classes.rb
index bb8dc354cc..832c5457d7 100644
--- a/spec/ruby/library/stringio/fixtures/classes.rb
+++ b/spec/ruby/library/stringio/fixtures/classes.rb
@@ -4,12 +4,12 @@ class StringSubclass < String; end
 
 module StringIOSpecs
   def self.build
-  str = <<-EOS
+    str = <<-EOS
     each
     peach
     pear
     plum
-  EOS
+    EOS
     StringIO.new(str)
   end
 end
diff --git a/spec/ruby/library/stringio/flush_spec.rb b/spec/ruby/library/stringio/flush_spec.rb
index 17a16dfdd5..4dc58b1d48 100644
--- a/spec/ruby/library/stringio/flush_spec.rb
+++ b/spec/ruby/library/stringio/flush_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#flush" do
   it "returns self" do
-    io = StringIO.new("flush")
+    io = StringIO.new(+"flush")
     io.flush.should equal(io)
   end
 end
diff --git a/spec/ruby/library/stringio/fsync_spec.rb b/spec/ruby/library/stringio/fsync_spec.rb
index 8fb2b59a24..85053cb2e5 100644
--- a/spec/ruby/library/stringio/fsync_spec.rb
+++ b/spec/ruby/library/stringio/fsync_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#fsync" do
   it "returns zero" do
-    io = StringIO.new("fsync")
+    io = StringIO.new(+"fsync")
     io.fsync.should eql(0)
   end
 end
diff --git a/spec/ruby/library/stringio/getpass_spec.rb b/spec/ruby/library/stringio/getpass_spec.rb
new file mode 100644
index 0000000000..60fc64f0c5
--- /dev/null
+++ b/spec/ruby/library/stringio/getpass_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../spec_helper'
+require 'stringio'
+
+# This method is added by io/console on require.
+describe "StringIO#getpass" do
+  require 'io/console'
+
+  it "is defined by io/console" do
+    StringIO.new("example").should.respond_to?(:getpass)
+  end
+end
diff --git a/spec/ruby/library/stringio/gets_spec.rb b/spec/ruby/library/stringio/gets_spec.rb
index 69880672a3..ac876f0b4f 100644
--- a/spec/ruby/library/stringio/gets_spec.rb
+++ b/spec/ruby/library/stringio/gets_spec.rb
@@ -1,245 +1,61 @@
 require_relative '../../spec_helper'
 require "stringio"
+require_relative "shared/gets"
 
-describe "StringIO#gets when passed [separator]" do
-  before :each do
-    @io = StringIO.new("this>is>an>example")
-  end
-
-  it "returns the data read till the next occurrence of the passed separator" do
-    @io.gets(">").should == "this>"
-    @io.gets(">").should == "is>"
-    @io.gets(">").should == "an>"
-    @io.gets(">").should == "example"
-  end
-
-  it "sets $_ to the read content" do
-    @io.gets(">")
-    $_.should == "this>"
-    @io.gets(">")
-    $_.should == "is>"
-    @io.gets(">")
-    $_.should == "an>"
-    @io.gets(">")
-    $_.should == "example"
-    @io.gets(">")
-    $_.should be_nil
-  end
-
-  it "accepts string as separator" do
-    @io.gets("is>")
-    $_.should == "this>"
-    @io.gets("an>")
-    $_.should == "is>an>"
-    @io.gets("example")
-    $_.should == "example"
-    @io.gets("ple")
-    $_.should be_nil
-  end
-
-  it "updates self's lineno by one" do
-    @io.gets(">")
-    @io.lineno.should eql(1)
+describe "StringIO#gets" do
+  describe "when passed [separator]" do
+    it_behaves_like :stringio_gets_separator, :gets
 
-    @io.gets(">")
-    @io.lineno.should eql(2)
+    it "returns nil if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-    @io.gets(">")
-    @io.lineno.should eql(3)
-  end
-
-  it "returns the next paragraph when the passed separator is an empty String" do
-    io = StringIO.new("this is\n\nan example")
-    io.gets("").should == "this is\n\n"
-    io.gets("").should == "an example"
-  end
-
-  it "returns the remaining content starting at the current position when passed nil" do
-    io = StringIO.new("this is\n\nan example")
-    io.pos = 5
-    io.gets(nil).should == "is\n\nan example"
-  end
-
-  it "tries to convert the passed separator to a String using #to_str" do
-    obj = mock('to_str')
-    obj.should_receive(:to_str).and_return(">")
-    @io.gets(obj).should == "this>"
-  end
-end
-
-describe "StringIO#gets when passed no argument" do
-  before :each do
-    @io = StringIO.new("this is\nan example\nfor StringIO#gets")
-  end
-
-  it "returns the data read till the next occurrence of $/ or till eof" do
-    @io.gets.should == "this is\n"
-
-    begin
-      old_sep, $/ = $/, " "
-      @io.gets.should == "an "
-      @io.gets.should == "example\nfor "
-      @io.gets.should == "StringIO#gets"
-    ensure
-      $/ = old_sep
+      @io.pos = 36
+      @io.gets(">").should be_nil
+      @io.gets(">").should be_nil
     end
   end
 
-  it "sets $_ to the read content" do
-    @io.gets
-    $_.should == "this is\n"
-    @io.gets
-    $_.should == "an example\n"
-    @io.gets
-    $_.should == "for StringIO#gets"
-    @io.gets
-    $_.should be_nil
-  end
-
-  it "updates self's position" do
-    @io.gets
-    @io.pos.should eql(8)
-
-    @io.gets
-    @io.pos.should eql(19)
-
-    @io.gets
-    @io.pos.should eql(36)
-  end
-
-  it "updates self's lineno" do
-    @io.gets
-    @io.lineno.should eql(1)
-
-    @io.gets
-    @io.lineno.should eql(2)
-
-    @io.gets
-    @io.lineno.should eql(3)
-  end
-
-  it "returns nil if self is at the end" do
-    @io.pos = 36
-    @io.gets.should be_nil
-    @io.gets.should be_nil
-  end
-end
-
-describe "StringIO#gets when passed [limit]" do
-  before :each do
-    @io = StringIO.new("this>is>an>example")
-  end
-
-  it "returns the data read until the limit is met" do
-    @io.gets(4).should == "this"
-    @io.gets(3).should == ">is"
-    @io.gets(5).should == ">an>e"
-    @io.gets(6).should == "xample"
-  end
+  describe "when passed [limit]" do
+    it_behaves_like :stringio_gets_limit, :gets
 
-  it "sets $_ to the read content" do
-    @io.gets(4)
-    $_.should == "this"
-    @io.gets(3)
-    $_.should == ">is"
-    @io.gets(5)
-    $_.should == ">an>e"
-    @io.gets(6)
-    $_.should == "xample"
-    @io.gets(3)
-    $_.should be_nil
-  end
+    it "returns nil if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-  it "updates self's lineno by one" do
-    @io.gets(3)
-    @io.lineno.should eql(1)
-
-    @io.gets(3)
-    @io.lineno.should eql(2)
-
-    @io.gets(3)
-    @io.lineno.should eql(3)
-  end
-
-  it "tries to convert the passed limit to an Integer using #to_int" do
-    obj = mock('to_int')
-    obj.should_receive(:to_int).and_return(4)
-    @io.gets(obj).should == "this"
-  end
-
-  it "returns a blank string when passed a limit of 0" do
-    @io.gets(0).should == ""
-  end
-end
-
-describe "StringIO#gets when passed [separator] and [limit]" do
-  before :each do
-    @io = StringIO.new("this>is>an>example")
-  end
-
-  it "returns the data read until the limit is consumed or the separator is met" do
-    @io.gets('>', 8).should == "this>"
-    @io.gets('>', 2).should == "is"
-    @io.gets('>', 10).should == ">"
-    @io.gets('>', 6).should == "an>"
-    @io.gets('>', 5).should == "examp"
-  end
-
-  it "sets $_ to the read content" do
-    @io.gets('>', 8)
-    $_.should == "this>"
-    @io.gets('>', 2)
-    $_.should == "is"
-    @io.gets('>', 10)
-    $_.should == ">"
-    @io.gets('>', 6)
-    $_.should == "an>"
-    @io.gets('>', 5)
-    $_.should == "examp"
+      @io.pos = 36
+      @io.gets(3).should be_nil
+      @io.gets(3).should be_nil
+    end
   end
 
-  it "updates self's lineno by one" do
-    @io.gets('>', 3)
-    @io.lineno.should eql(1)
+  describe "when passed [separator] and [limit]" do
+    it_behaves_like :stringio_gets_separator_and_limit, :gets
 
-    @io.gets('>', 3)
-    @io.lineno.should eql(2)
+    it "returns nil if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-    @io.gets('>', 3)
-    @io.lineno.should eql(3)
+      @io.pos = 36
+      @io.gets(">", 3).should be_nil
+      @io.gets(">", 3).should be_nil
+    end
   end
 
-  it "tries to convert the passed separator to a String using #to_str" do
-    obj = mock('to_str')
-    obj.should_receive(:to_str).and_return('>')
-    @io.gets(obj, 5).should == "this>"
-  end
+  describe "when passed no argument" do
+    it_behaves_like :stringio_gets_no_argument, :gets
 
-  it "does not raise TypeError if passed separator is nil" do
-    @io.gets(nil, 5).should == "this>"
-  end
+    it "returns nil if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-  it "tries to convert the passed limit to an Integer using #to_int" do
-    obj = mock('to_int')
-    obj.should_receive(:to_int).and_return(5)
-    @io.gets('>', obj).should == "this>"
+      @io.pos = 36
+      @io.gets.should be_nil
+      @io.gets.should be_nil
+    end
   end
-end
-
-describe "StringIO#gets when in write-only mode" do
-  it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
-    -> { io.gets }.should raise_error(IOError)
 
-    io = StringIO.new("xyz")
-    io.close_read
-    -> { io.gets }.should raise_error(IOError)
+  describe "when passed [chomp]" do
+    it_behaves_like :stringio_gets_chomp, :gets
   end
-end
 
-describe "StringIO#gets when passed [chomp]" do
-  it "returns the data read without a trailing newline character" do
-    io = StringIO.new("this>is>an>example\n")
-    io.gets(chomp: true).should == "this>is>an>example"
+  describe "when in write-only mode" do
+    it_behaves_like :stringio_gets_write_only, :gets
   end
 end
diff --git a/spec/ruby/library/stringio/initialize_spec.rb b/spec/ruby/library/stringio/initialize_spec.rb
index cc4f4c9254..6f4d2e456c 100644
--- a/spec/ruby/library/stringio/initialize_spec.rb
+++ b/spec/ruby/library/stringio/initialize_spec.rb
@@ -13,112 +13,112 @@ describe "StringIO#initialize when passed [Object, mode]" do
 
   it "sets the mode based on the passed mode" do
     io = StringIO.allocate
-    io.send(:initialize, "example", "r")
+    io.send(:initialize, +"example", "r")
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "rb")
+    io.send(:initialize, +"example", "rb")
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "r+")
+    io.send(:initialize, +"example", "r+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "rb+")
+    io.send(:initialize, +"example", "rb+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "w")
+    io.send(:initialize, +"example", "w")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "wb")
+    io.send(:initialize, +"example", "wb")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "w+")
+    io.send(:initialize, +"example", "w+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "wb+")
+    io.send(:initialize, +"example", "wb+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "a")
+    io.send(:initialize, +"example", "a")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "ab")
+    io.send(:initialize, +"example", "ab")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "a+")
+    io.send(:initialize, +"example", "a+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", "ab+")
+    io.send(:initialize, +"example", "ab+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
   end
 
   it "allows passing the mode as an Integer" do
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::RDONLY)
+    io.send(:initialize, +"example", IO::RDONLY)
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::RDWR)
+    io.send(:initialize, +"example", IO::RDWR)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::WRONLY)
+    io.send(:initialize, +"example", IO::WRONLY)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::WRONLY | IO::TRUNC)
+    io.send(:initialize, +"example", IO::WRONLY | IO::TRUNC)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::RDWR | IO::TRUNC)
+    io.send(:initialize, +"example", IO::RDWR | IO::TRUNC)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::WRONLY | IO::APPEND)
+    io.send(:initialize, +"example", IO::WRONLY | IO::APPEND)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
     io = StringIO.allocate
-    io.send(:initialize, "example", IO::RDWR | IO::APPEND)
+    io.send(:initialize, +"example", IO::RDWR | IO::APPEND)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
   end
 
-  it "raises a #{frozen_error_class} when passed a frozen String in truncate mode as StringIO backend" do
+  it "raises a FrozenError when passed a frozen String in truncate mode as StringIO backend" do
     io = StringIO.allocate
-    -> { io.send(:initialize, "example".freeze, IO::TRUNC) }.should raise_error(frozen_error_class)
+    -> { io.send(:initialize, "example".freeze, IO::TRUNC) }.should raise_error(FrozenError)
   end
 
   it "tries to convert the passed mode to a String using #to_str" do
     obj = mock('to_str')
     obj.should_receive(:to_str).and_return("r")
-    @io.send(:initialize, "example", obj)
+    @io.send(:initialize, +"example", obj)
 
     @io.closed_read?.should be_false
     @io.closed_write?.should be_true
@@ -130,6 +130,26 @@ describe "StringIO#initialize when passed [Object, mode]" do
     -> { @io.send(:initialize, str, "w") }.should raise_error(Errno::EACCES)
     -> { @io.send(:initialize, str, "a") }.should raise_error(Errno::EACCES)
   end
+
+  it "truncates all the content if passed w mode" do
+    io = StringIO.allocate
+    source = +"example".encode(Encoding::ISO_8859_1);
+
+    io.send(:initialize, source, "w")
+
+    io.string.should.empty?
+    io.string.encoding.should == Encoding::ISO_8859_1
+  end
+
+  it "truncates all the content if passed IO::TRUNC mode" do
+    io = StringIO.allocate
+    source = +"example".encode(Encoding::ISO_8859_1);
+
+    io.send(:initialize, source, IO::TRUNC)
+
+    io.string.should.empty?
+    io.string.encoding.should == Encoding::ISO_8859_1
+  end
 end
 
 describe "StringIO#initialize when passed [Object]" do
@@ -142,12 +162,18 @@ describe "StringIO#initialize when passed [Object]" do
     @io.string.should equal(str)
   end
 
-  it "sets the mode to read-write" do
-    @io.send(:initialize, "example")
+  it "sets the mode to read-write if the string is mutable" do
+    @io.send(:initialize, +"example")
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
   end
 
+  it "sets the mode to read if the string is frozen" do
+    @io.send(:initialize, -"example")
+    @io.closed_read?.should be_false
+    @io.closed_write?.should be_true
+  end
+
   it "tries to convert the passed Object to a String using #to_str" do
     obj = mock('to_str')
     obj.should_receive(:to_str).and_return("example")
@@ -163,6 +189,91 @@ describe "StringIO#initialize when passed [Object]" do
   end
 end
 
+# NOTE: Synchronise with core/io/new_spec.rb (core/io/shared/new.rb)
+describe "StringIO#initialize when passed keyword arguments" do
+  it "sets the mode based on the passed :mode option" do
+    io = StringIO.new("example", mode: "r")
+    io.closed_read?.should be_false
+    io.closed_write?.should be_true
+  end
+
+  it "accepts a mode argument set to nil with a valid :mode option" do
+    @io = StringIO.new(+'', nil, mode: "w")
+    @io.write("foo").should == 3
+  end
+
+  it "accepts a mode argument with a :mode option set to nil" do
+    @io = StringIO.new(+'', "w", mode: nil)
+    @io.write("foo").should == 3
+  end
+
+  it "sets binmode from :binmode option" do
+    @io = StringIO.new(+'', 'w', binmode: true)
+    @io.external_encoding.to_s.should == "ASCII-8BIT" # #binmode? isn't implemented in StringIO
+  end
+
+  it "does not set binmode from false :binmode" do
+    @io = StringIO.new(+'', 'w', binmode: false)
+    @io.external_encoding.to_s.should == "UTF-8" # #binmode? isn't implemented in StringIO
+  end
+end
+
+# NOTE: Synchronise with core/io/new_spec.rb (core/io/shared/new.rb)
+describe "StringIO#initialize when passed keyword arguments and error happens" do
+  it "raises an error if passed encodings two ways" do
+    -> {
+      @io = StringIO.new(+'', 'w:ISO-8859-1', encoding: 'ISO-8859-1')
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', 'w:ISO-8859-1', external_encoding: 'ISO-8859-1')
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', 'w:ISO-8859-1:UTF-8', internal_encoding: 'ISO-8859-1')
+    }.should raise_error(ArgumentError)
+  end
+
+  it "raises an error if passed matching binary/text mode two ways" do
+    -> {
+      @io = StringIO.new(+'', "wb", binmode: true)
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', "wt", textmode: true)
+    }.should raise_error(ArgumentError)
+
+    -> {
+      @io = StringIO.new(+'', "wb", textmode: false)
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', "wt", binmode: false)
+    }.should raise_error(ArgumentError)
+  end
+
+  it "raises an error if passed conflicting binary/text mode two ways" do
+    -> {
+      @io = StringIO.new(+'', "wb", binmode: false)
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', "wt", textmode: false)
+    }.should raise_error(ArgumentError)
+
+    -> {
+      @io = StringIO.new(+'', "wb", textmode: true)
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', "wt", binmode: true)
+    }.should raise_error(ArgumentError)
+  end
+
+  it "raises an error when trying to set both binmode and textmode" do
+    -> {
+      @io = StringIO.new(+'', "w", textmode: true, binmode: true)
+    }.should raise_error(ArgumentError)
+    -> {
+      @io = StringIO.new(+'', File::Constants::WRONLY, textmode: true, binmode: true)
+    }.should raise_error(ArgumentError)
+  end
+end
+
 describe "StringIO#initialize when passed no arguments" do
   before :each do
     @io = StringIO.allocate
@@ -173,7 +284,7 @@ describe "StringIO#initialize when passed no arguments" do
   end
 
   it "sets the mode to read-write" do
-    @io.send(:initialize, "example")
+    @io.send(:initialize)
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
   end
@@ -184,26 +295,34 @@ describe "StringIO#initialize when passed no arguments" do
   end
 end
 
-describe "StringIO#initialize sets the encoding to" do
+describe "StringIO#initialize sets" do
   before :each do
     @external = Encoding.default_external
+    @internal = Encoding.default_internal
     Encoding.default_external = Encoding::ISO_8859_2
+    Encoding.default_internal = Encoding::ISO_8859_2
   end
 
   after :each do
     Encoding.default_external = @external
+    Encoding.default_internal = @internal
   end
 
-  it "Encoding.default_external when passed no arguments" do
+  it "the encoding to Encoding.default_external when passed no arguments" do
     io = StringIO.new
     io.external_encoding.should == Encoding::ISO_8859_2
     io.string.encoding.should == Encoding::ISO_8859_2
   end
 
-  it "the same as the encoding of the String when passed a String" do
-    s = ''.force_encoding(Encoding::EUC_JP)
+  it "the encoding to the encoding of the String when passed a String" do
+    s = ''.dup.force_encoding(Encoding::EUC_JP)
     io = StringIO.new(s)
-    io.external_encoding.should == Encoding::EUC_JP
     io.string.encoding.should == Encoding::EUC_JP
   end
+
+  it "the #external_encoding to the encoding of the String when passed a String" do
+    s = ''.dup.force_encoding(Encoding::EUC_JP)
+    io = StringIO.new(s)
+    io.external_encoding.should == Encoding::EUC_JP
+  end
 end
diff --git a/spec/ruby/library/stringio/inspect_spec.rb b/spec/ruby/library/stringio/inspect_spec.rb
new file mode 100644
index 0000000000..7c02f8d360
--- /dev/null
+++ b/spec/ruby/library/stringio/inspect_spec.rb
@@ -0,0 +1,19 @@
+require_relative '../../spec_helper'
+require "stringio"
+
+describe "StringIO#inspect" do
+  it "returns the same as #to_s" do
+    io = StringIO.new("example")
+    io.inspect.should == io.to_s
+  end
+
+  it "does not include the contents" do
+    io = StringIO.new("contents")
+    io.inspect.should_not include("contents")
+  end
+
+  it "uses the regular Object#inspect without any instance variable" do
+    io = StringIO.new("example")
+    io.inspect.should =~ /\A#<StringIO:0x\h+>\z/
+  end
+end
diff --git a/spec/ruby/library/stringio/lines_spec.rb b/spec/ruby/library/stringio/lines_spec.rb
deleted file mode 100644
index d9dd26c2e2..0000000000
--- a/spec/ruby/library/stringio/lines_spec.rb
+++ /dev/null
@@ -1,19 +0,0 @@
-require_relative '../../spec_helper'
-require 'stringio'
-require_relative 'shared/each'
-
-describe "StringIO#lines when passed a separator" do
-  it_behaves_like :stringio_each_separator, :lines
-end
-
-describe "StringIO#lines when passed no arguments" do
-  it_behaves_like :stringio_each_no_arguments, :lines
-end
-
-describe "StringIO#lines when self is not readable" do
-  it_behaves_like :stringio_each_not_readable, :lines
-end
-
-describe "StringIO#lines when passed chomp" do
-  it_behaves_like :stringio_each_chomp, :lines
-end
diff --git a/spec/ruby/library/stringio/new_spec.rb b/spec/ruby/library/stringio/new_spec.rb
new file mode 100644
index 0000000000..ec4b32aa11
--- /dev/null
+++ b/spec/ruby/library/stringio/new_spec.rb
@@ -0,0 +1,10 @@
+require_relative '../../spec_helper'
+require 'stringio'
+
+describe "StringIO.new" do
+  it "does not use the given block and warns to use StringIO::open" do
+    -> {
+      StringIO.new { raise }
+    }.should complain(/warning: StringIO::new\(\) does not take block; use StringIO::open\(\) instead/)
+  end
+end
diff --git a/spec/ruby/library/stringio/open_spec.rb b/spec/ruby/library/stringio/open_spec.rb
index adb784c890..b7c90661f9 100644
--- a/spec/ruby/library/stringio/open_spec.rb
+++ b/spec/ruby/library/stringio/open_spec.rb
@@ -8,26 +8,26 @@ describe "StringIO.open when passed [Object, mode]" do
   end
 
   it "returns the blocks return value when yielding" do
-    ret = StringIO.open("example", "r") { :test }
+    ret = StringIO.open(+"example", "r") { :test }
     ret.should equal(:test)
   end
 
   it "yields self to the passed block" do
     io = nil
-    StringIO.open("example", "r") { |strio| io = strio }
+    StringIO.open(+"example", "r") { |strio| io = strio }
     io.should be_kind_of(StringIO)
   end
 
   it "closes self after yielding" do
     io = nil
-    StringIO.open("example", "r") { |strio| io = strio }
+    StringIO.open(+"example", "r") { |strio| io = strio }
     io.closed?.should be_true
   end
 
   it "even closes self when an exception is raised while yielding" do
     io = nil
     begin
-      StringIO.open("example", "r") do |strio|
+      StringIO.open(+"example", "r") do |strio|
         io = strio
         raise "Error"
       end
@@ -38,14 +38,14 @@ describe "StringIO.open when passed [Object, mode]" do
 
   it "sets self's string to nil after yielding" do
     io = nil
-    StringIO.open("example", "r") { |strio| io = strio }
+    StringIO.open(+"example", "r") { |strio| io = strio }
     io.string.should be_nil
   end
 
   it "even sets self's string to nil when an exception is raised while yielding" do
     io = nil
     begin
-      StringIO.open("example", "r") do |strio|
+      StringIO.open(+"example", "r") do |strio|
         io = strio
         raise "Error"
       end
@@ -55,93 +55,93 @@ describe "StringIO.open when passed [Object, mode]" do
   end
 
   it "sets the mode based on the passed mode" do
-    io = StringIO.open("example", "r")
+    io = StringIO.open(+"example", "r")
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
-    io = StringIO.open("example", "rb")
+    io = StringIO.open(+"example", "rb")
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
-    io = StringIO.open("example", "r+")
+    io = StringIO.open(+"example", "r+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "rb+")
+    io = StringIO.open(+"example", "rb+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "w")
+    io = StringIO.open(+"example", "w")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "wb")
+    io = StringIO.open(+"example", "wb")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "w+")
+    io = StringIO.open(+"example", "w+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "wb+")
+    io = StringIO.open(+"example", "wb+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "a")
+    io = StringIO.open(+"example", "a")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "ab")
+    io = StringIO.open(+"example", "ab")
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "a+")
+    io = StringIO.open(+"example", "a+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", "ab+")
+    io = StringIO.open(+"example", "ab+")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
   end
 
   it "allows passing the mode as an Integer" do
-    io = StringIO.open("example", IO::RDONLY)
+    io = StringIO.open(+"example", IO::RDONLY)
     io.closed_read?.should be_false
     io.closed_write?.should be_true
 
-    io = StringIO.open("example", IO::RDWR)
+    io = StringIO.open(+"example", IO::RDWR)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", IO::WRONLY)
+    io = StringIO.open(+"example", IO::WRONLY)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", IO::WRONLY | IO::TRUNC)
+    io = StringIO.open(+"example", IO::WRONLY | IO::TRUNC)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", IO::RDWR | IO::TRUNC)
+    io = StringIO.open(+"example", IO::RDWR | IO::TRUNC)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", IO::WRONLY | IO::APPEND)
+    io = StringIO.open(+"example", IO::WRONLY | IO::APPEND)
     io.closed_read?.should be_true
     io.closed_write?.should be_false
 
-    io = StringIO.open("example", IO::RDWR | IO::APPEND)
+    io = StringIO.open(+"example", IO::RDWR | IO::APPEND)
     io.closed_read?.should be_false
     io.closed_write?.should be_false
   end
 
-  it "raises a #{frozen_error_class} when passed a frozen String in truncate mode as StringIO backend" do
-    -> { StringIO.open("example".freeze, IO::TRUNC) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when passed a frozen String in truncate mode as StringIO backend" do
+    -> { StringIO.open("example".freeze, IO::TRUNC) }.should raise_error(FrozenError)
   end
 
   it "tries to convert the passed mode to a String using #to_str" do
     obj = mock('to_str')
     obj.should_receive(:to_str).and_return("r")
-    io = StringIO.open("example", obj)
+    io = StringIO.open(+"example", obj)
 
     io.closed_read?.should be_false
     io.closed_write?.should be_true
@@ -163,14 +163,18 @@ describe "StringIO.open when passed [Object]" do
 
   it "yields self to the passed block" do
     io = nil
-    ret = StringIO.open("example") { |strio| io = strio }
+    ret = StringIO.open(+"example") { |strio| io = strio }
     io.should equal(ret)
   end
 
-  it "sets the mode to read-write" do
-    io = StringIO.open("example")
+  it "sets the mode to read-write (r+)" do
+    io = StringIO.open(+"example")
     io.closed_read?.should be_false
     io.closed_write?.should be_false
+
+    io = StringIO.new(+"example")
+    io.printf("%d", 123)
+    io.string.should == "123mple"
   end
 
   it "tries to convert the passed Object to a String using #to_str" do
@@ -195,10 +199,14 @@ describe "StringIO.open when passed no arguments" do
     io.should equal(ret)
   end
 
-  it "sets the mode to read-write" do
+  it "sets the mode to read-write (r+)" do
     io = StringIO.open
     io.closed_read?.should be_false
     io.closed_write?.should be_false
+
+    io = StringIO.new(+"example")
+    io.printf("%d", 123)
+    io.string.should == "123mple"
   end
 
   it "uses an empty String as the StringIO backend" do
diff --git a/spec/ruby/library/stringio/print_spec.rb b/spec/ruby/library/stringio/print_spec.rb
index d0f07d1e50..00c33367dc 100644
--- a/spec/ruby/library/stringio/print_spec.rb
+++ b/spec/ruby/library/stringio/print_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#print" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new(+'example')
   end
 
   it "prints $_ when passed no arguments" do
@@ -39,13 +39,14 @@ describe "StringIO#print" do
   end
 
   it "honors the output record separator global" do
-    old_rs, $\ = $\, 'x'
+    old_rs = $\
+    suppress_warning {$\ = 'x'}
 
     begin
       @io.print(5, 6, 7, 8)
       @io.string.should == '5678xle'
     ensure
-      $\ = old_rs
+      suppress_warning {$\ = old_rs}
     end
   end
 
@@ -58,20 +59,21 @@ describe "StringIO#print" do
   end
 
   it "correctly updates the current position when honoring the output record separator global" do
-    old_rs, $\ = $\, 'x'
+    old_rs = $\
+    suppress_warning {$\ = 'x'}
 
     begin
       @io.print(5, 6, 7, 8)
       @io.pos.should eql(5)
     ensure
-      $\ = old_rs
+      suppress_warning {$\ = old_rs}
     end
   end
 end
 
 describe "StringIO#print when in append mode" do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self" do
@@ -90,10 +92,10 @@ end
 
 describe "StringIO#print when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.print("test") }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.print("test") }.should raise_error(IOError)
   end
diff --git a/spec/ruby/library/stringio/printf_spec.rb b/spec/ruby/library/stringio/printf_spec.rb
index f88ca1eb20..ca82e84757 100644
--- a/spec/ruby/library/stringio/printf_spec.rb
+++ b/spec/ruby/library/stringio/printf_spec.rb
@@ -4,7 +4,7 @@ require_relative '../../core/kernel/shared/sprintf'
 
 describe "StringIO#printf" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new()
   end
 
   it "returns nil" do
@@ -12,9 +12,9 @@ describe "StringIO#printf" do
   end
 
   it "pads self with \\000 when the current position is after the end" do
-    @io.pos = 10
+    @io.pos = 3
     @io.printf("%d", 123)
-    @io.string.should == "example\000\000\000123"
+    @io.string.should == "\000\000\000123"
   end
 
   it "performs format conversion" do
@@ -32,16 +32,37 @@ describe "StringIO#printf" do
 
   describe "formatting" do
     it_behaves_like :kernel_sprintf, -> format, *args {
-      io = StringIO.new
+      io = StringIO.new(+"")
       io.printf(format, *args)
       io.string
     }
   end
 end
 
+describe "StringIO#printf when in read-write mode" do
+  before :each do
+    @io = StringIO.new(+"example", "r+")
+  end
+
+  it "starts from the beginning" do
+    @io.printf("%s", "abcdefghijk")
+    @io.string.should == "abcdefghijk"
+  end
+
+  it "does not truncate existing string" do
+    @io.printf("%s", "abc")
+    @io.string.should == "abcmple"
+  end
+
+  it "correctly updates self's position" do
+    @io.printf("%s", "abc")
+    @io.pos.should eql(3)
+  end
+end
+
 describe "StringIO#printf when in append mode" do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self" do
@@ -60,10 +81,10 @@ end
 
 describe "StringIO#printf when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.printf("test") }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.printf("test") }.should raise_error(IOError)
   end
diff --git a/spec/ruby/library/stringio/putc_spec.rb b/spec/ruby/library/stringio/putc_spec.rb
index 223b3523e5..9f1ac8ffb2 100644
--- a/spec/ruby/library/stringio/putc_spec.rb
+++ b/spec/ruby/library/stringio/putc_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#putc when passed [String]" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new(+'example')
   end
 
   it "overwrites the character at the current position" do
@@ -35,11 +35,26 @@ describe "StringIO#putc when passed [String]" do
     @io.putc("t")
     @io.pos.should == 3
   end
+
+  it "handles concurrent writes correctly" do
+    @io = StringIO.new
+    n = 8
+    go = false
+    threads = n.times.map { |i|
+      Thread.new {
+        Thread.pass until go
+        @io.putc i.to_s
+      }
+    }
+    go = true
+    threads.each(&:join)
+    @io.string.size.should == n
+  end
 end
 
 describe "StringIO#putc when passed [Object]" do
   before :each do
-    @io = StringIO.new('example')
+    @io = StringIO.new(+'example')
   end
 
   it "it writes the passed Integer % 256 to self" do
@@ -70,7 +85,7 @@ end
 
 describe "StringIO#putc when in append mode" do
   it "appends to the end of self" do
-    io = StringIO.new("test", "a")
+    io = StringIO.new(+"test", "a")
     io.putc(?t)
     io.string.should == "testt"
   end
@@ -78,10 +93,10 @@ end
 
 describe "StringIO#putc when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.putc(?a) }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.putc("t") }.should raise_error(IOError)
   end
diff --git a/spec/ruby/library/stringio/puts_spec.rb b/spec/ruby/library/stringio/puts_spec.rb
index 2d3db25c5f..054ec8227f 100644
--- a/spec/ruby/library/stringio/puts_spec.rb
+++ b/spec/ruby/library/stringio/puts_spec.rb
@@ -30,11 +30,12 @@ describe "StringIO#puts when passed an Array" do
 
   it "does not honor the global output record separator $\\" do
     begin
-      old_rs, $\ = $\, "test"
+      old_rs = $\
+      suppress_warning {$\ = "test"}
       @io.puts([1, 2, 3, 4])
       @io.string.should == "1\n2\n3\n4\n"
     ensure
-      $\ = old_rs
+      suppress_warning {$\ = old_rs}
     end
   end
 
@@ -68,11 +69,12 @@ describe "StringIO#puts when passed 1 or more objects" do
 
   it "does not honor the global output record separator $\\" do
     begin
-      old_rs, $\ = $\, "test"
+      old_rs = $\
+      suppress_warning {$\ = "test"}
       @io.puts(1, 2, 3, 4)
       @io.string.should == "1\n2\n3\n4\n"
     ensure
-      $\ = old_rs
+      suppress_warning {$\ = old_rs}
     end
   end
 
@@ -99,6 +101,20 @@ describe "StringIO#puts when passed 1 or more objects" do
     @io.puts ''
     @io.string.should == "\n"
   end
+
+  it "handles concurrent writes correctly" do
+    n = 8
+    go = false
+    threads = n.times.map { |i|
+      Thread.new {
+        Thread.pass until go
+        @io.puts i
+      }
+    }
+    go = true
+    threads.each(&:join)
+    @io.string.size.should == n.times.map { |i| "#{i}\n" }.join.size
+  end
 end
 
 describe "StringIO#puts when passed no arguments" do
@@ -117,18 +133,19 @@ describe "StringIO#puts when passed no arguments" do
 
   it "does not honor the global output record separator $\\" do
     begin
-      old_rs, $\ = $\, "test"
+      old_rs = $\
+      suppress_warning {$\ = "test"}
       @io.puts
       @io.string.should == "\n"
     ensure
-      $\ = old_rs
+      suppress_warning {$\ = old_rs}
     end
   end
 end
 
 describe "StringIO#puts when in append mode" do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self" do
@@ -147,10 +164,10 @@ end
 
 describe "StringIO#puts when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.puts }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.puts }.should raise_error(IOError)
   end
@@ -158,7 +175,7 @@ end
 
 describe "StringIO#puts when passed an encoded string" do
   it "stores the bytes unmodified" do
-    io = StringIO.new("")
+    io = StringIO.new(+"")
     io.puts "\x00\x01\x02"
     io.puts "æåø"
 
diff --git a/spec/ruby/library/stringio/read_nonblock_spec.rb b/spec/ruby/library/stringio/read_nonblock_spec.rb
index 2a8f926bd0..74736f7792 100644
--- a/spec/ruby/library/stringio/read_nonblock_spec.rb
+++ b/spec/ruby/library/stringio/read_nonblock_spec.rb
@@ -5,10 +5,21 @@ require_relative 'shared/sysread'
 
 describe "StringIO#read_nonblock when passed length, buffer" do
   it_behaves_like :stringio_read, :read_nonblock
+
+  it "accepts :exception option" do
+    io = StringIO.new("example")
+    io.read_nonblock(3, buffer = +"", exception: true)
+    buffer.should == "exa"
+  end
 end
 
 describe "StringIO#read_nonblock when passed length" do
   it_behaves_like :stringio_read_length, :read_nonblock
+
+  it "accepts :exception option" do
+    io = StringIO.new("example")
+    io.read_nonblock(3, exception: true).should == "exa"
+  end
 end
 
 describe "StringIO#read_nonblock when passed nil" do
@@ -29,7 +40,7 @@ describe "StringIO#read_nonblock" do
   context "when exception option is set to false" do
     context "when the end is reached" do
       it "returns nil" do
-        stringio = StringIO.new('')
+        stringio = StringIO.new(+'')
         stringio << "hello"
         stringio.rewind
 
diff --git a/spec/ruby/library/stringio/read_spec.rb b/spec/ruby/library/stringio/read_spec.rb
index 52ab3dcf47..e49f262127 100644
--- a/spec/ruby/library/stringio/read_spec.rb
+++ b/spec/ruby/library/stringio/read_spec.rb
@@ -53,7 +53,7 @@ describe "StringIO#read when passed length and a buffer" do
   end
 
   it "reads [length] characters into the buffer" do
-    buf = "foo"
+    buf = +"foo"
     result = @io.read(10, buf)
 
     buf.should == "abcdefghij"
diff --git a/spec/ruby/library/stringio/readline_spec.rb b/spec/ruby/library/stringio/readline_spec.rb
index 9af633472e..085360707f 100644
--- a/spec/ruby/library/stringio/readline_spec.rb
+++ b/spec/ruby/library/stringio/readline_spec.rb
@@ -1,129 +1,58 @@
 require_relative '../../spec_helper'
+require "stringio"
 require_relative 'fixtures/classes'
+require_relative "shared/gets"
 
+describe "StringIO#readline" do
+  describe "when passed [separator]" do
+    it_behaves_like :stringio_gets_separator, :readline
 
-describe "StringIO#readline when passed [separator]" do
-  before :each do
-    @io = StringIO.new("this>is>an>example")
-  end
-
-  it "returns the data read till the next occurrence of the passed separator" do
-    @io.readline(">").should == "this>"
-    @io.readline(">").should == "is>"
-    @io.readline(">").should == "an>"
-    @io.readline(">").should == "example"
-  end
-
-  it "sets $_ to the read content" do
-    @io.readline(">")
-    $_.should == "this>"
-    @io.readline(">")
-    $_.should == "is>"
-    @io.readline(">")
-    $_.should == "an>"
-    @io.readline(">")
-    $_.should == "example"
-  end
-
-  it "updates self's lineno by one" do
-    @io.readline(">")
-    @io.lineno.should eql(1)
-
-    @io.readline(">")
-    @io.lineno.should eql(2)
-
-    @io.readline(">")
-    @io.lineno.should eql(3)
-  end
-
-  it "returns the next paragraph when the passed separator is an empty String" do
-    io = StringIO.new("this is\n\nan example")
-    io.readline("").should == "this is\n\n"
-    io.readline("").should == "an example"
-  end
-
-  it "returns the remaining content starting at the current position when passed nil" do
-    io = StringIO.new("this is\n\nan example")
-    io.pos = 5
-    io.readline(nil).should == "is\n\nan example"
-  end
+    it "raises an IOError if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-  it "tries to convert the passed separator to a String using #to_str" do
-    obj = mock('to_str')
-    obj.should_receive(:to_str).and_return(">")
-    @io.readline(obj).should == "this>"
+      @io.pos = 36
+      -> { @io.readline(">") }.should raise_error(IOError)
+    end
   end
-end
 
-describe "StringIO#readline when passed no argument" do
-  before :each do
-    @io = StringIO.new("this is\nan example\nfor StringIO#readline")
-  end
+  describe "when passed [limit]" do
+    it_behaves_like :stringio_gets_limit, :readline
 
-  it "returns the data read till the next occurrence of $/ or till eof" do
-    @io.readline.should == "this is\n"
+    it "raises an IOError if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-    begin
-      old_sep, $/ = $/, " "
-      @io.readline.should == "an "
-      @io.readline.should == "example\nfor "
-      @io.readline.should == "StringIO#readline"
-    ensure
-      $/ = old_sep
+      @io.pos = 36
+      -> { @io.readline(3) }.should raise_error(IOError)
     end
   end
 
-  it "sets $_ to the read content" do
-    @io.readline
-    $_.should == "this is\n"
-    @io.readline
-    $_.should == "an example\n"
-    @io.readline
-    $_.should == "for StringIO#readline"
-  end
-
-  it "updates self's position" do
-    @io.readline
-    @io.pos.should eql(8)
+  describe "when passed [separator] and [limit]" do
+    it_behaves_like :stringio_gets_separator_and_limit, :readline
 
-    @io.readline
-    @io.pos.should eql(19)
+    it "raises an IOError if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-    @io.readline
-    @io.pos.should eql(40)
+      @io.pos = 36
+      -> { @io.readline(">", 3) }.should raise_error(IOError)
+    end
   end
 
-  it "updates self's lineno" do
-    @io.readline
-    @io.lineno.should eql(1)
+  describe "when passed no argument" do
+    it_behaves_like :stringio_gets_no_argument, :readline
 
-    @io.readline
-    @io.lineno.should eql(2)
+    it "raises an IOError if self is at the end" do
+      @io = StringIO.new("this>is>an>example")
 
-    @io.readline
-    @io.lineno.should eql(3)
-  end
-
-  it "raises an IOError if self is at the end" do
-    @io.pos = 40
-    -> { @io.readline }.should raise_error(IOError)
+      @io.pos = 36
+      -> { @io.readline }.should raise_error(IOError)
+    end
   end
-end
-
-describe "StringIO#readline when in write-only mode" do
-  it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
-    -> { io.readline }.should raise_error(IOError)
 
-    io = StringIO.new("xyz")
-    io.close_read
-    -> { io.readline }.should raise_error(IOError)
+  describe "when passed [chomp]" do
+    it_behaves_like :stringio_gets_chomp, :readline
   end
-end
 
-describe "StringIO#readline when passed [chomp]" do
-  it "returns the data read without a trailing newline character" do
-    io = StringIO.new("this>is>an>example\n")
-    io.readline(chomp: true).should == "this>is>an>example"
+  describe "when in write-only mode" do
+    it_behaves_like :stringio_gets_write_only, :readline
   end
 end
diff --git a/spec/ruby/library/stringio/readlines_spec.rb b/spec/ruby/library/stringio/readlines_spec.rb
index 7f9f9f5846..ed7cc22b3d 100644
--- a/spec/ruby/library/stringio/readlines_spec.rb
+++ b/spec/ruby/library/stringio/readlines_spec.rb
@@ -51,10 +51,11 @@ describe "StringIO#readlines when passed no argument" do
 
   it "returns an Array containing lines based on $/" do
     begin
-      old_sep, $/ = $/, " "
+      old_sep = $/;
+      suppress_warning {$/ = " "}
       @io.readlines.should == ["this ", "is\nan ", "example\nfor ", "StringIO#readlines"]
     ensure
-      $/ = old_sep
+      suppress_warning {$/ = old_sep}
     end
   end
 
@@ -82,7 +83,7 @@ end
 
 describe "StringIO#readlines when in write-only mode" do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
+    io = StringIO.new(+"xyz", "w")
     -> { io.readlines }.should raise_error(IOError)
 
     io = StringIO.new("xyz")
@@ -97,3 +98,21 @@ describe "StringIO#readlines when passed [chomp]" do
     io.readlines(chomp: true).should == ["this>is", "an>example"]
   end
 end
+
+describe "StringIO#readlines when passed [limit]" do
+  before :each do
+    @io = StringIO.new("a b c d e\n1 2 3 4 5")
+  end
+
+  it "returns the data read until the limit is met" do
+    @io.readlines(4).should == ["a b ", "c d ", "e\n", "1 2 ", "3 4 ", "5"]
+  end
+
+  it "raises ArgumentError when limit is 0" do
+    -> { @io.readlines(0) }.should raise_error(ArgumentError)
+  end
+
+  it "ignores it when the limit is negative" do
+    @io.readlines(-4).should == ["a b c d e\n", "1 2 3 4 5"]
+  end
+end
diff --git a/spec/ruby/library/stringio/readpartial_spec.rb b/spec/ruby/library/stringio/readpartial_spec.rb
index 2601fe8c42..dadefb7837 100644
--- a/spec/ruby/library/stringio/readpartial_spec.rb
+++ b/spec/ruby/library/stringio/readpartial_spec.rb
@@ -3,20 +3,14 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#readpartial" do
   before :each do
-    @string = StringIO.new('Stop, look, listen')
+    @string = StringIO.new(+'Stop, look, listen')
   end
 
   after :each do
     @string.close unless @string.closed?
   end
 
-  it "raises IOError on closed stream" do
-    @string.close
-    -> { @string.readpartial(10) }.should raise_error(IOError)
-  end
-
   it "reads at most the specified number of bytes" do
-
     # buffered read
     @string.read(1).should == 'S'
     # return only specified number, not the whole buffer
@@ -30,6 +24,14 @@ describe "StringIO#readpartial" do
     @string.readpartial(3).should == ", l"
   end
 
+  it "reads after ungetc with multibyte characters in the buffer" do
+    @string = StringIO.new(+"∂φ/∂x = gaîté")
+    c = @string.getc
+    @string.ungetc(c)
+    @string.readpartial(3).should == "\xE2\x88\x82".b
+    @string.readpartial(3).should == "\xCF\x86/".b
+  end
+
   it "reads after ungetc without data in the buffer" do
     @string = StringIO.new
     @string.write("f").should == 1
@@ -48,7 +50,7 @@ describe "StringIO#readpartial" do
   end
 
   it "discards the existing buffer content upon successful read" do
-    buffer = "existing"
+    buffer = +"existing"
     @string.readpartial(11, buffer)
     buffer.should == "Stop, look,"
   end
@@ -59,7 +61,7 @@ describe "StringIO#readpartial" do
   end
 
   it "discards the existing buffer content upon error" do
-    buffer = 'hello'
+    buffer = +'hello'
     @string.readpartial(100)
     -> { @string.readpartial(1, buffer) }.should raise_error(EOFError)
     buffer.should be_empty
@@ -67,14 +69,34 @@ describe "StringIO#readpartial" do
 
   it "raises IOError if the stream is closed" do
     @string.close
-    -> { @string.readpartial(1) }.should raise_error(IOError)
+    -> { @string.readpartial(1) }.should raise_error(IOError, "not opened for reading")
   end
 
   it "raises ArgumentError if the negative argument is provided" do
-    -> { @string.readpartial(-1) }.should raise_error(ArgumentError)
+    -> { @string.readpartial(-1) }.should raise_error(ArgumentError, "negative length -1 given")
   end
 
   it "immediately returns an empty string if the length argument is 0" do
     @string.readpartial(0).should == ""
   end
+
+  it "raises IOError if the stream is closed and the length argument is 0" do
+    @string.close
+    -> { @string.readpartial(0) }.should raise_error(IOError, "not opened for reading")
+  end
+
+  it "clears and returns the given buffer if the length argument is 0" do
+    buffer = +"existing content"
+    @string.readpartial(0, buffer).should == buffer
+    buffer.should == ""
+  end
+
+  version_is StringIO::VERSION, "3.1.2" do # ruby_version_is "3.4"
+    it "preserves the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @string.readpartial(10, buffer)
+
+      buffer.encoding.should == Encoding::ISO_8859_1
+    end
+  end
 end
diff --git a/spec/ruby/library/stringio/reopen_spec.rb b/spec/ruby/library/stringio/reopen_spec.rb
index 6b5bdb57a1..7021ff17e5 100644
--- a/spec/ruby/library/stringio/reopen_spec.rb
+++ b/spec/ruby/library/stringio/reopen_spec.rb
@@ -12,29 +12,20 @@ describe "StringIO#reopen when passed [Object, Integer]" do
     @io.closed_write?.should be_true
     @io.string.should == "reopened"
 
-    @io.reopen("reopened, twice", IO::WRONLY)
+    @io.reopen(+"reopened, twice", IO::WRONLY)
     @io.closed_read?.should be_true
     @io.closed_write?.should be_false
     @io.string.should == "reopened, twice"
 
-    @io.reopen("reopened, another time", IO::RDWR)
+    @io.reopen(+"reopened, another time", IO::RDWR)
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
     @io.string.should == "reopened, another time"
   end
 
-  # NOTE: WEIRD!
-  it "does not taint self when the passed Object was tainted" do
-    @io.reopen("reopened".taint, IO::RDONLY)
-    @io.tainted?.should be_false
-
-    @io.reopen("reopened".taint, IO::WRONLY)
-    @io.tainted?.should be_false
-  end
-
   it "tries to convert the passed Object to a String using #to_str" do
     obj = mock("to_str")
-    obj.should_receive(:to_str).and_return("to_str")
+    obj.should_receive(:to_str).and_return(+"to_str")
     @io.reopen(obj, IO::RDWR)
     @io.string.should == "to_str"
   end
@@ -48,8 +39,8 @@ describe "StringIO#reopen when passed [Object, Integer]" do
     -> { @io.reopen("burn".freeze, IO::WRONLY | IO::APPEND) }.should raise_error(Errno::EACCES)
   end
 
-  it "raises a #{frozen_error_class} when trying to reopen self with a frozen String in truncate-mode" do
-    -> { @io.reopen("burn".freeze, IO::RDONLY | IO::TRUNC) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError when trying to reopen self with a frozen String in truncate-mode" do
+    -> { @io.reopen("burn".freeze, IO::RDONLY | IO::TRUNC) }.should raise_error(FrozenError)
   end
 
   it "does not raise IOError when passed a frozen String in read-mode" do
@@ -69,36 +60,27 @@ describe "StringIO#reopen when passed [Object, Object]" do
     @io.closed_write?.should be_true
     @io.string.should == "reopened"
 
-    @io.reopen("reopened, twice", "r+")
+    @io.reopen(+"reopened, twice", "r+")
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
     @io.string.should == "reopened, twice"
 
-    @io.reopen("reopened, another", "w+")
+    @io.reopen(+"reopened, another", "w+")
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
     @io.string.should == ""
 
-    @io.reopen("reopened, another time", "r+")
+    @io.reopen(+"reopened, another time", "r+")
     @io.closed_read?.should be_false
     @io.closed_write?.should be_false
     @io.string.should == "reopened, another time"
   end
 
   it "truncates the passed String when opened in truncate mode" do
-    @io.reopen(str = "reopened", "w")
+    @io.reopen(str = +"reopened", "w")
     str.should == ""
   end
 
-  # NOTE: WEIRD!
-  it "does not taint self when the passed Object was tainted" do
-    @io.reopen("reopened".taint, "r")
-    @io.tainted?.should be_false
-
-    @io.reopen("reopened".taint, "w")
-    @io.tainted?.should be_false
-  end
-
   it "tries to convert the passed Object to a String using #to_str" do
     obj = mock("to_str")
     obj.should_receive(:to_str).and_return("to_str")
@@ -112,13 +94,13 @@ describe "StringIO#reopen when passed [Object, Object]" do
 
   it "resets self's position to 0" do
     @io.read(5)
-    @io.reopen("reopened")
+    @io.reopen(+"reopened")
     @io.pos.should eql(0)
   end
 
   it "resets self's line number to 0" do
     @io.gets
-    @io.reopen("reopened")
+    @io.reopen(+"reopened")
     @io.lineno.should eql(0)
   end
 
@@ -152,7 +134,7 @@ describe "StringIO#reopen when passed [String]" do
   it "reopens self with the passed String in read-write mode" do
     @io.close
 
-    @io.reopen("reopened")
+    @io.reopen(+"reopened")
 
     @io.closed_write?.should be_false
     @io.closed_read?.should be_false
@@ -160,21 +142,15 @@ describe "StringIO#reopen when passed [String]" do
     @io.string.should == "reopened"
   end
 
-  # NOTE: WEIRD!
-  it "does not taint self when the passed Object was tainted" do
-    @io.reopen("reopened".taint)
-    @io.tainted?.should be_false
-  end
-
   it "resets self's position to 0" do
     @io.read(5)
-    @io.reopen("reopened")
+    @io.reopen(+"reopened")
     @io.pos.should eql(0)
   end
 
   it "resets self's line number to 0" do
     @io.gets
-    @io.reopen("reopened")
+    @io.reopen(+"reopened")
     @io.lineno.should eql(0)
   end
 end
@@ -196,16 +172,10 @@ describe "StringIO#reopen when passed [Object]" do
 
   it "tries to convert the passed Object to a StringIO using #to_strio" do
     obj = mock("to_strio")
-    obj.should_receive(:to_strio).and_return(StringIO.new("to_strio"))
+    obj.should_receive(:to_strio).and_return(StringIO.new(+"to_strio"))
     @io.reopen(obj)
     @io.string.should == "to_strio"
   end
-
-  # NOTE: WEIRD!
-  it "taints self when the passed Object was tainted" do
-    @io.reopen(StringIO.new("reopened").taint)
-    @io.tainted?.should be_true
-  end
 end
 
 describe "StringIO#reopen when passed no arguments" do
@@ -238,47 +208,40 @@ end
 # for details.
 describe "StringIO#reopen" do
   before :each do
-    @io = StringIO.new('hello','a')
+    @io = StringIO.new(+'hello', 'a')
   end
 
   # TODO: find out if this is really a bug
   it "reopens a stream when given a String argument" do
-    @io.reopen('goodbye').should == @io
+    @io.reopen(+'goodbye').should == @io
     @io.string.should == 'goodbye'
     @io << 'x'
     @io.string.should == 'xoodbye'
   end
 
   it "reopens a stream in append mode when flagged as such" do
-    @io.reopen('goodbye', 'a').should == @io
+    @io.reopen(+'goodbye', 'a').should == @io
     @io.string.should == 'goodbye'
     @io << 'x'
     @io.string.should == 'goodbyex'
   end
 
   it "reopens and truncate when reopened in write mode" do
-    @io.reopen('goodbye', 'wb').should == @io
+    @io.reopen(+'goodbye', 'wb').should == @io
     @io.string.should == ''
     @io << 'x'
     @io.string.should == 'x'
   end
 
   it "truncates the given string, not a copy" do
-    str = 'goodbye'
+    str = +'goodbye'
     @io.reopen(str, 'w')
     @io.string.should == ''
     str.should == ''
   end
 
-  it "taints self if the provided StringIO argument is tainted" do
-    new_io = StringIO.new("tainted")
-    new_io.taint
-    @io.reopen(new_io)
-    @io.tainted?.should == true
-  end
-
   it "does not truncate the content even when the StringIO argument is in the truncate mode" do
-    orig_io = StringIO.new("Original StringIO", IO::RDWR|IO::TRUNC)
+    orig_io = StringIO.new(+"Original StringIO", IO::RDWR|IO::TRUNC)
     orig_io.write("BLAH") # make sure the content is not empty
 
     @io.reopen(orig_io)
diff --git a/spec/ruby/library/stringio/set_encoding_by_bom_spec.rb b/spec/ruby/library/stringio/set_encoding_by_bom_spec.rb
new file mode 100644
index 0000000000..1030aad042
--- /dev/null
+++ b/spec/ruby/library/stringio/set_encoding_by_bom_spec.rb
@@ -0,0 +1,237 @@
+require 'stringio'
+require_relative '../../spec_helper'
+
+# Should be synced with specs for IO#set_encoding_by_bom
+describe "StringIO#set_encoding_by_bom" do
+  it "returns nil if not readable" do
+    io = StringIO.new("".b, "wb")
+
+    io.set_encoding_by_bom.should be_nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+  end
+
+  it "returns the result encoding if found BOM UTF-8 sequence" do
+    io = StringIO.new("\u{FEFF}".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_8
+    io.external_encoding.should == Encoding::UTF_8
+    io.read.b.should == "".b
+
+    io = StringIO.new("\u{FEFF}abc".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_8
+    io.external_encoding.should == Encoding::UTF_8
+    io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16LE sequence" do
+    io = StringIO.new("\xFF\xFE".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    io.external_encoding.should == Encoding::UTF_16LE
+    io.read.b.should == "".b
+
+    io = StringIO.new("\xFF\xFEabc".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    io.external_encoding.should == Encoding::UTF_16LE
+    io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_16BE sequence" do
+    io = StringIO.new("\xFE\xFF".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    io.external_encoding.should == Encoding::UTF_16BE
+    io.read.b.should == "".b
+
+    io = StringIO.new("\xFE\xFFabc".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16BE
+    io.external_encoding.should == Encoding::UTF_16BE
+    io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32LE sequence" do
+    io = StringIO.new("\xFF\xFE\x00\x00".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    io.external_encoding.should == Encoding::UTF_32LE
+    io.read.b.should == "".b
+
+    io = StringIO.new("\xFF\xFE\x00\x00abc".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_32LE
+    io.external_encoding.should == Encoding::UTF_32LE
+    io.read.b.should == "abc".b
+  end
+
+  it "returns the result encoding if found BOM UTF_32BE sequence" do
+    io = StringIO.new("\x00\x00\xFE\xFF".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    io.external_encoding.should == Encoding::UTF_32BE
+    io.read.b.should == "".b
+
+    io = StringIO.new("\x00\x00\xFE\xFFabc".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_32BE
+    io.external_encoding.should == Encoding::UTF_32BE
+    io.read.b.should == "abc".b
+  end
+
+  it "returns nil if io is empty" do
+    io = StringIO.new("".b, "rb")
+    io.set_encoding_by_bom.should be_nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+  end
+
+  it "returns nil if UTF-8 BOM sequence is incomplete" do
+    io = StringIO.new("\xEF".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xEF".b
+
+    io = StringIO.new("\xEFa".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xEFa".b
+
+    io = StringIO.new("\xEF\xBB".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xEF\xBB".b
+
+    io = StringIO.new("\xEF\xBBa".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xEF\xBBa".b
+  end
+
+  it "returns nil if UTF-16BE BOM sequence is incomplete" do
+    io = StringIO.new("\xFE".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xFE".b
+
+    io = StringIO.new("\xFEa".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xFEa".b
+  end
+
+  it "returns nil if UTF-16LE/UTF-32LE BOM sequence is incomplete" do
+    io = StringIO.new("\xFF".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xFF".b
+
+    io = StringIO.new("\xFFa".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\xFFa".b
+  end
+
+  it "returns UTF-16LE if UTF-32LE BOM sequence is incomplete" do
+    io = StringIO.new("\xFF\xFE".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    io.external_encoding.should == Encoding::UTF_16LE
+    io.read.b.should == "".b
+
+    io = StringIO.new("\xFF\xFE\x00".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    io.external_encoding.should == Encoding::UTF_16LE
+    io.read.b.should == "\x00".b
+
+    io = StringIO.new("\xFF\xFE\x00a".b, "rb")
+
+    io.set_encoding_by_bom.should == Encoding::UTF_16LE
+    io.external_encoding.should == Encoding::UTF_16LE
+    io.read.b.should == "\x00a".b
+  end
+
+  it "returns nil if UTF-32BE BOM sequence is incomplete" do
+    io = StringIO.new("\x00".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00".b
+
+    io = StringIO.new("\x00a".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00a".b
+
+    io = StringIO.new("\x00\x00".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00\x00".b
+
+    io = StringIO.new("\x00\x00a".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00\x00a".b
+
+    io = StringIO.new("\x00\x00\xFE".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00\x00\xFE".b
+
+    io = StringIO.new("\x00\x00\xFEa".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read.b.should == "\x00\x00\xFEa".b
+  end
+
+  it "returns nil if found BOM sequence not provided" do
+    io = StringIO.new("abc".b, "rb")
+
+    io.set_encoding_by_bom.should == nil
+    io.external_encoding.should == Encoding::ASCII_8BIT
+    io.read(3).should == "abc".b
+  end
+
+  it "does not raise exception if io not in binary mode" do
+    io = StringIO.new("", 'r')
+    io.set_encoding_by_bom.should == nil
+  end
+
+  it "does not raise exception if encoding already set" do
+    io = StringIO.new("".b, "rb")
+    io.set_encoding("utf-8")
+    io.set_encoding_by_bom.should == nil
+  end
+
+  it "does not raise exception if encoding conversion is already set" do
+    io = StringIO.new("".b, "rb")
+    io.set_encoding(Encoding::UTF_8, Encoding::UTF_16BE)
+
+    io.set_encoding_by_bom.should == nil
+  end
+
+  it "raises FrozenError when io is frozen" do
+    io = StringIO.new()
+    io.freeze
+    -> { io.set_encoding_by_bom }.should raise_error(FrozenError)
+  end
+
+  it "does not raise FrozenError when initial string is frozen" do
+    io = StringIO.new("".freeze)
+    io.set_encoding_by_bom.should == nil
+  end
+end
diff --git a/spec/ruby/library/stringio/set_encoding_spec.rb b/spec/ruby/library/stringio/set_encoding_spec.rb
index 21d45750f3..19ca0875bf 100644
--- a/spec/ruby/library/stringio/set_encoding_spec.rb
+++ b/spec/ruby/library/stringio/set_encoding_spec.rb
@@ -17,4 +17,12 @@ describe "StringIO#set_encoding" do
     io.set_encoding Encoding::UTF_8
     io.string.encoding.should == Encoding::US_ASCII
   end
+
+  it "accepts a String" do
+    str = "".encode(Encoding::US_ASCII)
+    io = StringIO.new(str)
+    io.set_encoding("ASCII-8BIT")
+    io.external_encoding.should == Encoding::BINARY
+    str.encoding.should == Encoding::BINARY
+  end
 end
diff --git a/spec/ruby/library/stringio/shared/codepoints.rb b/spec/ruby/library/stringio/shared/codepoints.rb
index 9d84aa4919..25333bb0fd 100644
--- a/spec/ruby/library/stringio/shared/codepoints.rb
+++ b/spec/ruby/library/stringio/shared/codepoints.rb
@@ -27,7 +27,7 @@ describe :stringio_codepoints, shared: true do
     @io.close_read
     -> { @enum.to_a }.should raise_error(IOError)
 
-    io = StringIO.new("xyz", "w")
+    io = StringIO.new(+"xyz", "w")
     -> { io.send(@method).to_a }.should raise_error(IOError)
   end
 
diff --git a/spec/ruby/library/stringio/shared/each.rb b/spec/ruby/library/stringio/shared/each.rb
index c08d40344c..626b41a4d3 100644
--- a/spec/ruby/library/stringio/shared/each.rb
+++ b/spec/ruby/library/stringio/shared/each.rb
@@ -36,11 +36,11 @@ describe :stringio_each_separator, shared: true do
     seen.should == ["2 1 2 1 2"]
   end
 
-  it "yields each paragraph when passed an empty String as separator" do
+  it "yields each paragraph with all separation characters when passed an empty String as separator" do
     seen = []
     io = StringIO.new("para1\n\npara2\n\n\npara3")
     io.send(@method, "") {|s| seen << s}
-    seen.should == ["para1\n\n", "para2\n\n", "para3"]
+    seen.should == ["para1\n\n", "para2\n\n\n", "para3"]
   end
 end
 
@@ -71,11 +71,12 @@ describe :stringio_each_no_arguments, shared: true do
   it "uses $/ as the default line separator" do
     seen = []
     begin
-      old_rs, $/ = $/, " "
+      old_rs = $/
+      suppress_warning {$/ = " "}
       @io.send(@method) {|s| seen << s }
       seen.should eql(["a ", "b ", "c ", "d ", "e\n1 ", "2 ", "3 ", "4 ", "5"])
     ensure
-      $/ = old_rs
+      suppress_warning {$/ = old_rs}
     end
   end
 
@@ -95,7 +96,7 @@ end
 
 describe :stringio_each_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("a b c d e", "w")
+    io = StringIO.new(+"a b c d e", "w")
     -> { io.send(@method) { |b| b } }.should raise_error(IOError)
 
     io = StringIO.new("a b c d e")
@@ -111,4 +112,98 @@ describe :stringio_each_chomp, shared: true do
     io.send(@method, chomp: true) {|s| seen << s }
     seen.should == ["a b \rc d e", "1 2 3 4 5", "the end"]
   end
+
+  it "returns each line with removed newline characters when called without block" do
+    seen = []
+    io = StringIO.new("a b \rc d e\n1 2 3 4 5\r\nthe end")
+    enum = io.send(@method, chomp: true)
+    enum.each {|s| seen << s }
+    seen.should == ["a b \rc d e", "1 2 3 4 5", "the end"]
+  end
+end
+
+describe :stringio_each_separator_and_chomp, shared: true do
+  it "yields each line with removed separator to the passed block" do
+    seen = []
+    io = StringIO.new("a b \nc d e|1 2 3 4 5\n|the end")
+    io.send(@method, "|", chomp: true) {|s| seen << s }
+    seen.should == ["a b \nc d e", "1 2 3 4 5\n", "the end"]
+  end
+
+  it "returns each line with removed separator when called without block" do
+    seen = []
+    io = StringIO.new("a b \nc d e|1 2 3 4 5\n|the end")
+    enum = io.send(@method, "|", chomp: true)
+    enum.each {|s| seen << s }
+    seen.should == ["a b \nc d e", "1 2 3 4 5\n", "the end"]
+  end
+end
+
+describe :stringio_each_limit, shared: true do
+  before :each do
+    @io = StringIO.new("a b c d e\n1 2 3 4 5")
+  end
+
+  it "returns the data read until the limit is met" do
+    seen = []
+    @io.send(@method, 4) { |s| seen << s }
+    seen.should == ["a b ", "c d ", "e\n", "1 2 ", "3 4 ", "5"]
+  end
+end
+
+describe :stringio_each_separator_and_limit, shared: true do
+  before :each do
+    @io = StringIO.new("this>is>an>example")
+  end
+
+  it "returns the data read until the limit is consumed or the separator is met" do
+    @io.send(@method, '>', 8) { |s| break s }.should == "this>"
+    @io.send(@method, '>', 2) { |s| break s }.should == "is"
+    @io.send(@method, '>', 10) { |s| break s }.should == ">"
+    @io.send(@method, '>', 6) { |s| break s }.should == "an>"
+    @io.send(@method, '>', 5) { |s| break s }.should == "examp"
+  end
+
+  it "truncates the multi-character separator at the end to meet the limit" do
+    @io.send(@method, "is>an", 7) { |s| break s }.should == "this>is"
+  end
+
+  it "does not change $_" do
+    $_ = "test"
+    @io.send(@method, '>', 8) { |s| s }
+    $_.should == "test"
+  end
+
+  it "updates self's lineno by one" do
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should eql(1)
+
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should eql(2)
+
+    @io.send(@method, '>', 3) { |s| break s }
+    @io.lineno.should eql(3)
+  end
+
+  it "tries to convert the passed separator to a String using #to_str" do # TODO
+    obj = mock('to_str')
+    obj.should_receive(:to_str).and_return('>')
+
+    seen = []
+    @io.send(@method, obj, 5) { |s| seen << s }
+    seen.should == ["this>", "is>", "an>", "examp", "le"]
+  end
+
+  it "does not raise TypeError if passed separator is nil" do
+    @io.send(@method, nil, 5) { |s| break s }.should == "this>"
+  end
+
+  it "tries to convert the passed limit to an Integer using #to_int" do # TODO
+    obj = mock('to_int')
+    obj.should_receive(:to_int).and_return(5)
+
+    seen = []
+    @io.send(@method, '>', obj) { |s| seen << s }
+    seen.should == ["this>", "is>", "an>", "examp", "le"]
+  end
 end
diff --git a/spec/ruby/library/stringio/shared/each_byte.rb b/spec/ruby/library/stringio/shared/each_byte.rb
index 56734ff99d..b51fa38f2f 100644
--- a/spec/ruby/library/stringio/shared/each_byte.rb
+++ b/spec/ruby/library/stringio/shared/each_byte.rb
@@ -38,7 +38,7 @@ end
 
 describe :stringio_each_byte_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
+    io = StringIO.new(+"xyz", "w")
     -> { io.send(@method) { |b| b } }.should raise_error(IOError)
 
     io = StringIO.new("xyz")
diff --git a/spec/ruby/library/stringio/shared/each_char.rb b/spec/ruby/library/stringio/shared/each_char.rb
index bcdac53282..197237c1c8 100644
--- a/spec/ruby/library/stringio/shared/each_char.rb
+++ b/spec/ruby/library/stringio/shared/each_char.rb
@@ -26,7 +26,7 @@ end
 
 describe :stringio_each_char_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
+    io = StringIO.new(+"xyz", "w")
     -> { io.send(@method) { |b| b } }.should raise_error(IOError)
 
     io = StringIO.new("xyz")
diff --git a/spec/ruby/library/stringio/shared/getc.rb b/spec/ruby/library/stringio/shared/getc.rb
index 6318bcc30f..ba65040bce 100644
--- a/spec/ruby/library/stringio/shared/getc.rb
+++ b/spec/ruby/library/stringio/shared/getc.rb
@@ -33,7 +33,7 @@ end
 
 describe :stringio_getc_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("xyz", "w")
+    io = StringIO.new(+"xyz", "w")
     -> { io.send(@method) }.should raise_error(IOError)
 
     io = StringIO.new("xyz")
diff --git a/spec/ruby/library/stringio/shared/gets.rb b/spec/ruby/library/stringio/shared/gets.rb
new file mode 100644
index 0000000000..8396b161f1
--- /dev/null
+++ b/spec/ruby/library/stringio/shared/gets.rb
@@ -0,0 +1,249 @@
+describe :stringio_gets_separator, shared: true do
+  describe "when passed [separator]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read till the next occurrence of the passed separator" do
+      @io.send(@method, ">").should == "this>"
+      @io.send(@method, ">").should == "is>"
+      @io.send(@method, ">").should == "an>"
+      @io.send(@method, ">").should == "example"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, ">")
+      $_.should == "this>"
+      @io.send(@method, ">")
+      $_.should == "is>"
+      @io.send(@method, ">")
+      $_.should == "an>"
+      @io.send(@method, ">")
+      $_.should == "example"
+    end
+
+    it "accepts string as separator" do
+      @io.send(@method, "is>")
+      $_.should == "this>"
+      @io.send(@method, "an>")
+      $_.should == "is>an>"
+      @io.send(@method, "example")
+      $_.should == "example"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, ">")
+      @io.lineno.should eql(1)
+
+      @io.send(@method, ">")
+      @io.lineno.should eql(2)
+
+      @io.send(@method, ">")
+      @io.lineno.should eql(3)
+    end
+
+    it "returns the next paragraph when the passed separator is an empty String" do
+      io = StringIO.new("this is\n\nan example")
+      io.send(@method, "").should == "this is\n\n"
+      io.send(@method, "").should == "an example"
+    end
+
+    it "returns the remaining content starting at the current position when passed nil" do
+      io = StringIO.new("this is\n\nan example")
+      io.pos = 5
+      io.send(@method, nil).should == "is\n\nan example"
+    end
+
+    it "tries to convert the passed separator to a String using #to_str" do
+      obj = mock('to_str')
+      obj.should_receive(:to_str).and_return(">")
+      @io.send(@method, obj).should == "this>"
+    end
+  end
+end
+
+describe :stringio_gets_limit, shared: true do
+  describe "when passed [limit]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read until the limit is met" do
+      @io.send(@method, 4).should == "this"
+      @io.send(@method, 3).should == ">is"
+      @io.send(@method, 5).should == ">an>e"
+      @io.send(@method, 6).should == "xample"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, 4)
+      $_.should == "this"
+      @io.send(@method, 3)
+      $_.should == ">is"
+      @io.send(@method, 5)
+      $_.should == ">an>e"
+      @io.send(@method, 6)
+      $_.should == "xample"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, 3)
+      @io.lineno.should eql(1)
+
+      @io.send(@method, 3)
+      @io.lineno.should eql(2)
+
+      @io.send(@method, 3)
+      @io.lineno.should eql(3)
+    end
+
+    it "tries to convert the passed limit to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(4)
+      @io.send(@method, obj).should == "this"
+    end
+
+    it "returns a blank string when passed a limit of 0" do
+      @io.send(@method, 0).should == ""
+    end
+
+    it "ignores it when passed a negative limit" do
+      @io.send(@method, -4).should == "this>is>an>example"
+    end
+  end
+end
+
+describe :stringio_gets_separator_and_limit, shared: true do
+  describe "when passed [separator] and [limit]" do
+    before :each do
+      @io = StringIO.new("this>is>an>example")
+    end
+
+    it "returns the data read until the limit is consumed or the separator is met" do
+      @io.send(@method, '>', 8).should == "this>"
+      @io.send(@method, '>', 2).should == "is"
+      @io.send(@method, '>', 10).should == ">"
+      @io.send(@method, '>', 6).should == "an>"
+      @io.send(@method, '>', 5).should == "examp"
+    end
+
+    it "truncates the multi-character separator at the end to meet the limit" do
+      @io.send(@method, "is>an", 7).should == "this>is"
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method, '>', 8)
+      $_.should == "this>"
+      @io.send(@method, '>', 2)
+      $_.should == "is"
+      @io.send(@method, '>', 10)
+      $_.should == ">"
+      @io.send(@method, '>', 6)
+      $_.should == "an>"
+      @io.send(@method, '>', 5)
+      $_.should == "examp"
+    end
+
+    it "updates self's lineno by one" do
+      @io.send(@method, '>', 3)
+      @io.lineno.should eql(1)
+
+      @io.send(@method, '>', 3)
+      @io.lineno.should eql(2)
+
+      @io.send(@method, '>', 3)
+      @io.lineno.should eql(3)
+    end
+
+    it "tries to convert the passed separator to a String using #to_str" do
+      obj = mock('to_str')
+      obj.should_receive(:to_str).and_return('>')
+      @io.send(@method, obj, 5).should == "this>"
+    end
+
+    it "does not raise TypeError if passed separator is nil" do
+      @io.send(@method, nil, 5).should == "this>"
+    end
+
+    it "tries to convert the passed limit to an Integer using #to_int" do
+      obj = mock('to_int')
+      obj.should_receive(:to_int).and_return(5)
+      @io.send(@method, '>', obj).should == "this>"
+    end
+  end
+end
+
+describe :stringio_gets_no_argument, shared: true do
+  describe "when passed no argument" do
+    before :each do
+      @io = StringIO.new("this is\nan example\nfor StringIO#gets")
+    end
+
+    it "returns the data read till the next occurrence of $/ or till eof" do
+      @io.send(@method).should == "this is\n"
+
+      begin
+        old_sep = $/
+        suppress_warning {$/ = " "}
+        @io.send(@method).should == "an "
+        @io.send(@method).should == "example\nfor "
+        @io.send(@method).should == "StringIO#gets"
+      ensure
+        suppress_warning {$/ = old_sep}
+      end
+    end
+
+    it "sets $_ to the read content" do
+      @io.send(@method)
+      $_.should == "this is\n"
+      @io.send(@method)
+      $_.should == "an example\n"
+      @io.send(@method)
+      $_.should == "for StringIO#gets"
+    end
+
+    it "updates self's position" do
+      @io.send(@method)
+      @io.pos.should eql(8)
+
+      @io.send(@method)
+      @io.pos.should eql(19)
+
+      @io.send(@method)
+      @io.pos.should eql(36)
+    end
+
+    it "updates self's lineno" do
+      @io.send(@method)
+      @io.lineno.should eql(1)
+
+      @io.send(@method)
+      @io.lineno.should eql(2)
+
+      @io.send(@method)
+      @io.lineno.should eql(3)
+    end
+  end
+end
+
+describe :stringio_gets_chomp, shared: true do
+  describe "when passed [chomp]" do
+    it "returns the data read without a trailing newline character" do
+      io = StringIO.new("this>is>an>example\n")
+      io.send(@method, chomp: true).should == "this>is>an>example"
+    end
+  end
+end
+
+describe :stringio_gets_write_only, shared: true do
+  describe "when in write-only mode" do
+    it "raises an IOError" do
+      io = StringIO.new(+"xyz", "w")
+      -> { io.send(@method) }.should raise_error(IOError)
+
+      io = StringIO.new("xyz")
+      io.close_read
+      -> { io.send(@method) }.should raise_error(IOError)
+    end
+  end
+end
diff --git a/spec/ruby/library/stringio/shared/isatty.rb b/spec/ruby/library/stringio/shared/isatty.rb
index 3da5999953..c9e7ee7321 100644
--- a/spec/ruby/library/stringio/shared/isatty.rb
+++ b/spec/ruby/library/stringio/shared/isatty.rb
@@ -1,5 +1,5 @@
 describe :stringio_isatty, shared: true do
   it "returns false" do
-    StringIO.new('tty').send(@method).should be_false
+    StringIO.new("tty").send(@method).should be_false
   end
 end
diff --git a/spec/ruby/library/stringio/shared/read.rb b/spec/ruby/library/stringio/shared/read.rb
index 15ce58ae6a..22f76b0fb0 100644
--- a/spec/ruby/library/stringio/shared/read.rb
+++ b/spec/ruby/library/stringio/shared/read.rb
@@ -5,19 +5,37 @@ describe :stringio_read, shared: true do
 
   it "returns the passed buffer String" do
     # Note: Rubinius bug:
-    # @io.send(@method, 7, buffer = "").should equal(buffer)
-    ret = @io.send(@method, 7, buffer = "")
+    # @io.send(@method, 7, buffer = +"").should equal(buffer)
+    ret = @io.send(@method, 7, buffer = +"")
     ret.should equal(buffer)
   end
 
   it "reads length bytes and writes them to the buffer String" do
-    @io.send(@method, 7, buffer = "")
+    @io.send(@method, 7, buffer = +"").should.equal?(buffer)
     buffer.should == "example"
   end
 
+  guard -> { StringIO::VERSION < "3.1.2" } do
+    it "does not preserve the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @io.send(@method, 7, buffer)
+
+      buffer.encoding.should_not == Encoding::ISO_8859_1
+    end
+  end
+
+  guard -> { StringIO::VERSION >= "3.1.2" } do
+    it "preserves the encoding of the given buffer" do
+      buffer = ''.encode(Encoding::ISO_8859_1)
+      @io.send(@method, 7, buffer)
+
+      buffer.encoding.should == Encoding::ISO_8859_1
+    end
+  end
+
   it "tries to convert the passed buffer Object to a String using #to_str" do
     obj = mock("to_str")
-    obj.should_receive(:to_str).and_return(buffer = "")
+    obj.should_receive(:to_str).and_return(buffer = +"")
 
     @io.send(@method, 7, obj)
     buffer.should == "example"
@@ -27,8 +45,8 @@ describe :stringio_read, shared: true do
     -> { @io.send(@method, 7, Object.new) }.should raise_error(TypeError)
   end
 
-  it "raises a #{frozen_error_class} error when passed a frozen String as buffer" do
-    -> { @io.send(@method, 7, "".freeze) }.should raise_error(frozen_error_class)
+  it "raises a FrozenError error when passed a frozen String as buffer" do
+    -> { @io.send(@method, 7, "".freeze) }.should raise_error(FrozenError)
   end
 end
 
@@ -75,7 +93,7 @@ end
 
 describe :stringio_read_no_arguments, shared: true do
   before :each do
-    @io = StringIO.new("example")
+    @io = StringIO.new(+"example")
   end
 
   it "reads the whole content starting from the current position" do
@@ -89,6 +107,12 @@ describe :stringio_read_no_arguments, shared: true do
     @io.send(@method)
     @io.pos.should eql(7)
   end
+
+  it "correctly update the current position in bytes when multi-byte characters are used" do
+    @io.print("example\u03A3") # Overwrite the original string with 8 characters containing 9 bytes.
+    @io.send(@method)
+    @io.pos.should eql(9)
+  end
 end
 
 describe :stringio_read_nil, shared: true do
@@ -111,7 +135,7 @@ end
 
 describe :stringio_read_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("test", "w")
+    io = StringIO.new(+"test", "w")
     -> { io.send(@method) }.should raise_error(IOError)
 
     io = StringIO.new("test")
diff --git a/spec/ruby/library/stringio/shared/readchar.rb b/spec/ruby/library/stringio/shared/readchar.rb
index 4248e75420..72d7446c36 100644
--- a/spec/ruby/library/stringio/shared/readchar.rb
+++ b/spec/ruby/library/stringio/shared/readchar.rb
@@ -19,7 +19,7 @@ end
 
 describe :stringio_readchar_not_readable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("a b c d e", "w")
+    io = StringIO.new(+"a b c d e", "w")
     -> { io.send(@method) }.should raise_error(IOError)
 
     io = StringIO.new("a b c d e")
diff --git a/spec/ruby/library/stringio/shared/sysread.rb b/spec/ruby/library/stringio/shared/sysread.rb
index 3376bd9907..3e23fbc233 100644
--- a/spec/ruby/library/stringio/shared/sysread.rb
+++ b/spec/ruby/library/stringio/shared/sysread.rb
@@ -1,4 +1,4 @@
-describe :stringio_sysread_length, :shared => true do
+describe :stringio_sysread_length, shared: true do
   before :each do
     @io = StringIO.new("example")
   end
@@ -10,6 +10,6 @@ describe :stringio_sysread_length, :shared => true do
 
   it "raises an EOFError when passed length > 0 and no data remains" do
     @io.read.should == "example"
-    -> { @io.sysread(1) }.should raise_error(EOFError)
+    -> { @io.send(@method, 1) }.should raise_error(EOFError)
   end
 end
diff --git a/spec/ruby/library/stringio/shared/write.rb b/spec/ruby/library/stringio/shared/write.rb
index df4822cc16..4661658baf 100644
--- a/spec/ruby/library/stringio/shared/write.rb
+++ b/spec/ruby/library/stringio/shared/write.rb
@@ -1,6 +1,6 @@
 describe :stringio_write, shared: true do
   before :each do
-    @io = StringIO.new('12345')
+    @io = StringIO.new(+'12345')
   end
 
   it "tries to convert the passed Object to a String using #to_s" do
@@ -13,7 +13,7 @@ end
 
 describe :stringio_write_string, shared: true do
   before :each do
-    @io = StringIO.new('12345')
+    @io = StringIO.new(+'12345')
   end
 
   # TODO: RDoc says that #write appends at the current position.
@@ -45,23 +45,71 @@ describe :stringio_write_string, shared: true do
     @io.pos.should eql(4)
   end
 
-  it "taints self's String when the passed argument is tainted" do
-    @io.send(@method, "test".taint)
-    @io.string.tainted?.should be_true
+  it "handles concurrent writes correctly" do
+    @io = StringIO.new
+    n = 8
+    go = false
+    threads = n.times.map { |i|
+      Thread.new {
+        Thread.pass until go
+        @io.write i.to_s
+      }
+    }
+    go = true
+    threads.each(&:join)
+    @io.string.size.should == n.times.map(&:to_s).join.size
   end
 
-  it "does not taint self when the passed argument is tainted" do
-    @io.send(@method, "test".taint)
-    @io.tainted?.should be_false
+  it "handles writing non-ASCII UTF-8 after seek" do
+    @io.binmode
+    @io << "\x80"
+    @io.pos = 0
+    @io << "\x81"
+    @io.string.should == "\x812345".b
+  end
+
+  it "handles writing with position < buffer size" do
+    @io.pos = 2
+    @io.write "abc"
+    @io.string.should == "12abc"
+
+    @io.pos = 2
+    @io.write "de"
+    @io.string.should == "12dec"
+
+    @io.pos = 2
+    @io.write "fghi"
+    @io.string.should == "12fghi"
+  end
+
+  it "transcodes the given string when the external encoding is set and neither is BINARY" do
+    utf8_str = "hello"
+    io = StringIO.new.set_encoding(Encoding::UTF_16BE)
+    io.external_encoding.should == Encoding::UTF_16BE
+
+    io.send(@method, utf8_str)
+
+    expected = [0, 104, 0, 101, 0, 108, 0, 108, 0, 111] # UTF-16BE bytes for "hello"
+    io.string.bytes.should == expected
+  end
+
+  it "does not transcode the given string when the external encoding is set and the string encoding is BINARY" do
+    str = "été_".b
+    io = StringIO.new.set_encoding(Encoding::UTF_16BE)
+    io.external_encoding.should == Encoding::UTF_16BE
+
+    io.send(@method, str)
+
+    io.string.bytes.should == str.bytes
   end
 end
 
 describe :stringio_write_not_writable, shared: true do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.send(@method, "test") }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.send(@method, "test") }.should raise_error(IOError)
   end
@@ -69,7 +117,7 @@ end
 
 describe :stringio_write_append, shared: true do
   before :each do
-    @io = StringIO.new("example", "a")
+    @io = StringIO.new(+"example", "a")
   end
 
   it "appends the passed argument to the end of self" do
diff --git a/spec/ruby/library/stringio/sysread_spec.rb b/spec/ruby/library/stringio/sysread_spec.rb
index 8f78073f42..fabb06dd9a 100644
--- a/spec/ruby/library/stringio/sysread_spec.rb
+++ b/spec/ruby/library/stringio/sysread_spec.rb
@@ -1,6 +1,7 @@
 require_relative '../../spec_helper'
 require "stringio"
 require_relative 'shared/read'
+require_relative 'shared/sysread'
 
 describe "StringIO#sysread when passed length, buffer" do
   it_behaves_like :stringio_read, :sysread
@@ -32,6 +33,10 @@ describe "StringIO#sysread when passed nil" do
   end
 end
 
+describe "StringIO#sysread when passed length" do
+  it_behaves_like :stringio_sysread_length, :sysread
+end
+
 describe "StringIO#sysread when passed [length]" do
   before :each do
     @io = StringIO.new("example")
diff --git a/spec/ruby/library/stringio/truncate_spec.rb b/spec/ruby/library/stringio/truncate_spec.rb
index ba910ee98c..592ca5a6e1 100644
--- a/spec/ruby/library/stringio/truncate_spec.rb
+++ b/spec/ruby/library/stringio/truncate_spec.rb
@@ -3,13 +3,11 @@ require "stringio"
 
 describe "StringIO#truncate when passed [length]" do
   before :each do
-    @io = StringIO.new('123456789')
+    @io = StringIO.new(+'123456789')
   end
 
-  # TODO: Report to Ruby-Core: The RDoc says it always returns 0
-  it "returns the passed length" do
-    @io.truncate(4).should eql(4)
-    @io.truncate(10).should eql(10)
+  it "returns an Integer" do
+    @io.truncate(4).should be_kind_of(Integer)
   end
 
   it "truncated the underlying string down to the passed length" do
@@ -18,7 +16,7 @@ describe "StringIO#truncate when passed [length]" do
   end
 
   it "does not create a copy of the underlying string" do
-    io = StringIO.new(str = "123456789")
+    io = StringIO.new(str = +"123456789")
     io.truncate(4)
     io.string.should equal(str)
   end
@@ -47,12 +45,6 @@ describe "StringIO#truncate when passed [length]" do
     @io.string.should == "1234"
   end
 
-  it "returns the passed length Object, NOT the result of #to_int" do
-    obj = mock("to_int")
-    obj.should_receive(:to_int).and_return(4)
-    @io.truncate(obj).should equal(obj)
-  end
-
   it "raises a TypeError when the passed length can't be converted to an Integer" do
     -> { @io.truncate(Object.new) }.should raise_error(TypeError)
   end
@@ -60,10 +52,10 @@ end
 
 describe "StringIO#truncate when self is not writable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "r")
+    io = StringIO.new(+"test", "r")
     -> { io.truncate(2) }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.close_write
     -> { io.truncate(2) }.should raise_error(IOError)
   end
diff --git a/spec/ruby/library/stringio/ungetbyte_spec.rb b/spec/ruby/library/stringio/ungetbyte_spec.rb
index 701463e621..87b27b837e 100644
--- a/spec/ruby/library/stringio/ungetbyte_spec.rb
+++ b/spec/ruby/library/stringio/ungetbyte_spec.rb
@@ -1,6 +1,42 @@
+# frozen_string_literal: false
 require_relative '../../spec_helper'
 require 'stringio'
 
 describe "StringIO#ungetbyte" do
-  it "needs to be reviewed for spec completeness"
+  it "ungets a single byte from a string starting with a single byte character" do
+    str = 'This is a simple string.'
+    io = StringIO.new("#{str}")
+    c = io.getc
+    c.should == 'T'
+    io.ungetbyte(83)
+    io.string.should == 'Shis is a simple string.'
+  end
+
+  it "ungets a single byte from a string in the middle of a multibyte character" do
+    str = "\u01a9"
+    io = StringIO.new(str)
+    b = io.getbyte
+    b.should == 0xc6 # First byte of UTF-8 encoding of \u01a9
+    io.ungetbyte(0xce) # First byte of UTF-8 encoding of \u03a9
+    io.string.should == "\u03a9"
+  end
+
+  it "constrains the value of a numeric argument to a single byte" do
+    str = 'This is a simple string.'
+    io = StringIO.new("#{str}")
+    c = io.getc
+    c.should == 'T'
+    io.ungetbyte(83 | 0xff00)
+    io.string.should == 'Shis is a simple string.'
+  end
+
+  it "ungets the bytes of a string if given a string as an argument" do
+    str = "\u01a9"
+    io = StringIO.new(str)
+    b = io.getbyte
+    b.should == 0xc6 # First byte of UTF-8 encoding of \u01a9
+    io.ungetbyte("\u01a9")
+    io.string.bytes.should == [198, 169, 169]
+  end
+
 end
diff --git a/spec/ruby/library/stringio/ungetc_spec.rb b/spec/ruby/library/stringio/ungetc_spec.rb
index 91ef2100a1..bceafa79ff 100644
--- a/spec/ruby/library/stringio/ungetc_spec.rb
+++ b/spec/ruby/library/stringio/ungetc_spec.rb
@@ -3,7 +3,7 @@ require_relative 'fixtures/classes'
 
 describe "StringIO#ungetc when passed [char]" do
   before :each do
-    @io = StringIO.new('1234')
+    @io = StringIO.new(+'1234')
   end
 
   it "writes the passed char before the current position" do
@@ -45,11 +45,11 @@ end
 
 describe "StringIO#ungetc when self is not readable" do
   it "raises an IOError" do
-    io = StringIO.new("test", "w")
+    io = StringIO.new(+"test", "w")
     io.pos = 1
     -> { io.ungetc(?A) }.should raise_error(IOError)
 
-    io = StringIO.new("test")
+    io = StringIO.new(+"test")
     io.pos = 1
     io.close_read
     -> { io.ungetc(?A) }.should raise_error(IOError)
@@ -60,11 +60,11 @@ end
 #
 # describe "StringIO#ungetc when self is not writable" do
 #   it "raises an IOError" do
-#     io = StringIO.new("test", "r")
+#     io = StringIO.new(+"test", "r")
 #     io.pos = 1
 #     lambda { io.ungetc(?A) }.should raise_error(IOError)
 #
-#     io = StringIO.new("test")
+#     io = StringIO.new(+"test")
 #     io.pos = 1
 #     io.close_write
 #     lambda { io.ungetc(?A) }.should raise_error(IOError)
diff --git a/spec/ruby/library/stringio/write_nonblock_spec.rb b/spec/ruby/library/stringio/write_nonblock_spec.rb
index 4f4c5039fe..b48ef6698a 100644
--- a/spec/ruby/library/stringio/write_nonblock_spec.rb
+++ b/spec/ruby/library/stringio/write_nonblock_spec.rb
@@ -8,6 +8,12 @@ end
 
 describe "StringIO#write_nonblock when passed [String]" do
   it_behaves_like :stringio_write_string, :write_nonblock
+
+  it "accepts :exception option" do
+    io = StringIO.new(+"12345", "a")
+    io.write_nonblock("67890", exception: true)
+    io.string.should == "1234567890"
+  end
 end
 
 describe "StringIO#write_nonblock when self is not writable" do
diff --git a/spec/ruby/library/stringscanner/append_spec.rb b/spec/ruby/library/stringscanner/append_spec.rb
index 378c62e2b1..fef5dcf2bd 100644
--- a/spec/ruby/library/stringscanner/append_spec.rb
+++ b/spec/ruby/library/stringscanner/append_spec.rb
@@ -6,6 +6,6 @@ describe "StringScanner#<<" do
   it_behaves_like :strscan_concat, :<<
 end
 
-describe "StringScanner#<< when passed a Fixnum" do
+describe "StringScanner#<< when passed an Integer" do
   it_behaves_like :strscan_concat_fixnum, :<<
 end
diff --git a/spec/ruby/library/stringscanner/captures_spec.rb b/spec/ruby/library/stringscanner/captures_spec.rb
new file mode 100644
index 0000000000..bdfb0e0cc5
--- /dev/null
+++ b/spec/ruby/library/stringscanner/captures_spec.rb
@@ -0,0 +1,36 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#captures" do
+  before do
+    @s = StringScanner.new('Fri Dec 12 1975 14:39')
+  end
+
+  it "returns the array of captured values of the most recent matching" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+    @s.captures.should == ["Fri", "Dec", "12"]
+  end
+
+  it "returns nil if the last match fails" do
+    @s.scan(/nope/)
+    @s.captures.should == nil
+  end
+
+  it "returns nil if there is no any match done" do
+    @s.captures.should == nil
+  end
+
+  version_is StringScanner::Version, ""..."3.0.8" do # ruby_version_is ""..."3.3.3"
+    it "returns '' for an optional capturing group if it doesn't match" do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\s+)?/)
+      @s.captures.should == ["Fri", "Dec", ""]
+    end
+  end
+
+  version_is StringScanner::Version, "3.0.8" do # ruby_version_is "3.3.3"
+    it "returns nil for an optional capturing group if it doesn't match" do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\s+)?/)
+      @s.captures.should == ["Fri", "Dec", nil]
+    end
+  end
+end
diff --git a/spec/ruby/library/stringscanner/charpos_spec.rb b/spec/ruby/library/stringscanner/charpos_spec.rb
new file mode 100644
index 0000000000..9aa5b00dd9
--- /dev/null
+++ b/spec/ruby/library/stringscanner/charpos_spec.rb
@@ -0,0 +1,18 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#charpos" do
+  it "returns character index corresponding to the current position" do
+    s = StringScanner.new("abc")
+
+    s.scan_until(/b/)
+    s.charpos.should == 2
+  end
+
+  it "is multi-byte character sensitive" do
+    s = StringScanner.new("abcädeföghi")
+
+    s.scan_until(/ö/)
+    s.charpos.should == 8
+  end
+end
diff --git a/spec/ruby/library/stringscanner/check_spec.rb b/spec/ruby/library/stringscanner/check_spec.rb
index c7f788f0b3..5e855e154a 100644
--- a/spec/ruby/library/stringscanner/check_spec.rb
+++ b/spec/ruby/library/stringscanner/check_spec.rb
@@ -13,4 +13,81 @@ describe "StringScanner#check" do
     @s.check(/is/).should == nil
     @s.matched.should == nil
   end
+
+  it "treats String as the pattern itself" do
+    @s.check("This").should == "This"
+    @s.matched.should == "This"
+    @s.pos.should == 0
+    @s.check(/is/).should == nil
+    @s.matched.should == nil
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #check was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.check(/(?<a>This)/)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.check(/(?<a>2008)/)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    context "when #check was called with a String pattern" do
+      # https://github.com/ruby/strscan/issues/139
+      version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "returns nil when matching succeeded" do
+          @s.check("This")
+          @s.should.matched?
+          @s[:a].should be_nil
+        end
+      end
+      version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+        it "raises IndexError when matching succeeded" do
+          @s.check("This")
+          @s.should.matched?
+          -> { @s[:a] }.should raise_error(IndexError)
+        end
+      end
+
+      it "returns nil when matching failed" do
+        @s.check("2008")
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+
+      it "returns a matching substring when given Integer index" do
+        @s.check("This")
+        @s[0].should == "This"
+      end
+
+      # https://github.com/ruby/strscan/issues/135
+      version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "ignores the previous matching with Regexp" do
+          @s.exist?(/(?<a>This)/)
+          @s.should.matched?
+          @s[:a].should == "This"
+
+          @s.check("This")
+          @s.should.matched?
+          @s[:a].should be_nil
+        end
+      end
+      version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "ignores the previous matching with Regexp" do
+          @s.exist?(/(?<a>This)/)
+          @s.should.matched?
+          @s[:a].should == "This"
+
+          @s.check("This")
+          @s.should.matched?
+          -> { @s[:a] }.should raise_error(IndexError)
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/check_until_spec.rb b/spec/ruby/library/stringscanner/check_until_spec.rb
index e92ae5a2e9..582da66b37 100644
--- a/spec/ruby/library/stringscanner/check_until_spec.rb
+++ b/spec/ruby/library/stringscanner/check_until_spec.rb
@@ -2,14 +2,128 @@ require_relative '../../spec_helper'
 require 'strscan'
 
 describe "StringScanner#check_until" do
-  before :each do
+  before do
     @s = StringScanner.new("This is a test")
   end
 
-  it "returns the same value of scan_until, but don't advances the scan pointer" do
+  it "returns the same value of #scan_until, but don't advances the scan pointer" do
     @s.check_until(/a/).should == "This is a"
     @s.pos.should == 0
-    @s.matched.should == "a"
     @s.check_until(/test/).should == "This is a test"
   end
+
+  it "sets the last match result" do
+    @s.check_until(/a/)
+
+    @s.pre_match.should == "This is "
+    @s.matched.should == "a"
+    @s.post_match.should == " test"
+  end
+
+  version_is StringScanner::Version, ""..."3.1.1" do # ruby_version_is ""..."3.4"
+    it "raises TypeError if given a String" do
+      -> {
+        @s.check_until('T')
+      }.should raise_error(TypeError, 'wrong argument type String (expected Regexp)')
+    end
+  end
+
+  version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+    it "searches a substring in the rest part of a string if given a String" do
+      @s.check_until("a").should == "This is a"
+      @s.pos.should == 0
+    end
+
+    # https://github.com/ruby/strscan/issues/131
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.1"
+      it "sets the last match result if given a String" do
+        @s.check_until("a")
+
+        @s.pre_match.should == ""
+        @s.matched.should == "This is a"
+        @s.post_match.should == " test"
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "sets the last match result if given a String" do
+        @s.check_until("a")
+
+        @s.pre_match.should == "This is "
+        @s.matched.should == "a"
+        @s.post_match.should == " test"
+      end
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #check_until was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.check_until(/(?<a>This)/)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.check_until(/(?<a>2008)/)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+      context "when #check_until was called with a String pattern" do
+        # https://github.com/ruby/strscan/issues/139
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "returns nil when matching succeeded" do
+            @s.check_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+          it "raises IndexError when matching succeeded" do
+            @s.check_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+
+        it "returns nil when matching failed" do
+          @s.check_until("2008")
+          @s.should_not.matched?
+          @s[:a].should be_nil
+        end
+
+        it "returns a matching substring when given Integer index" do
+          @s.check_until("This")
+          @s[0].should == "This"
+        end
+
+        # https://github.com/ruby/strscan/issues/135
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.check_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.check_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/clear_spec.rb b/spec/ruby/library/stringscanner/clear_spec.rb
deleted file mode 100644
index 7ae089704a..0000000000
--- a/spec/ruby/library/stringscanner/clear_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/terminate'
-require 'strscan'
-
-describe "StringScanner#clear" do
-  it_behaves_like :strscan_terminate, :clear
-
-  it "warns in verbose mode that the method is obsolete" do
-    s = StringScanner.new("abc")
-    -> {
-      s.clear
-    }.should complain(/clear.*obsolete.*terminate/, verbose: true)
-
-    -> {
-      s.clear
-    }.should_not complain(verbose: false)
-  end
-end
diff --git a/spec/ruby/library/stringscanner/concat_spec.rb b/spec/ruby/library/stringscanner/concat_spec.rb
index 17a699dd2e..4f790e2505 100644
--- a/spec/ruby/library/stringscanner/concat_spec.rb
+++ b/spec/ruby/library/stringscanner/concat_spec.rb
@@ -6,6 +6,6 @@ describe "StringScanner#concat" do
   it_behaves_like :strscan_concat, :concat
 end
 
-describe "StringScanner#concat when passed a Fixnum" do
+describe "StringScanner#concat when passed an Integer" do
   it_behaves_like :strscan_concat_fixnum, :concat
 end
diff --git a/spec/ruby/library/stringscanner/dup_spec.rb b/spec/ruby/library/stringscanner/dup_spec.rb
index 3b426f138e..0fc52a1477 100644
--- a/spec/ruby/library/stringscanner/dup_spec.rb
+++ b/spec/ruby/library/stringscanner/dup_spec.rb
@@ -12,7 +12,7 @@ describe "StringScanner#dup" do
     s.string.should == @string
   end
 
-  it "copies the passed StringSCanner's position to self" do
+  it "copies the passed StringScanner's position to self" do
     @orig_s.pos = 5
     s = @orig_s.dup
     s.pos.should eql(5)
diff --git a/spec/ruby/library/stringscanner/element_reference_spec.rb b/spec/ruby/library/stringscanner/element_reference_spec.rb
index 60fe15d807..91b6d86dc7 100644
--- a/spec/ruby/library/stringscanner/element_reference_spec.rb
+++ b/spec/ruby/library/stringscanner/element_reference_spec.rb
@@ -8,6 +8,7 @@ describe "StringScanner#[]" do
 
   it "returns nil if there is no current match" do
     @s[0].should be_nil
+    @s[:wday].should be_nil
   end
 
   it "returns the n-th subgroup in the most recent match" do
@@ -42,12 +43,18 @@ describe "StringScanner#[]" do
     -> { @s[0..2]}.should raise_error(TypeError)
   end
 
-  it "raises a IndexError when there's no named capture" do
+  it "raises a IndexError when there's no any named capture group in the regexp" do
     @s.scan(/(\w+) (\w+) (\d+) /)
     -> { @s["wday"]}.should raise_error(IndexError)
     -> { @s[:wday]}.should raise_error(IndexError)
   end
 
+  it "raises a IndexError when given a not existing capture group name" do
+    @s.scan(/(?<a>\w+) (?<b>\w+) (?<c>\d+) /)
+    -> { @s["wday"]}.should raise_error(IndexError)
+    -> { @s[:wday]}.should raise_error(IndexError)
+  end
+
   it "returns named capture" do
     @s.scan(/(?<wday>\w+) (?<month>\w+) (?<day>\d+) /)
     @s["wday"].should == "Fri"
diff --git a/spec/ruby/library/stringscanner/empty_spec.rb b/spec/ruby/library/stringscanner/empty_spec.rb
deleted file mode 100644
index d9449bea6e..0000000000
--- a/spec/ruby/library/stringscanner/empty_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/eos'
-require 'strscan'
-
-describe "StringScanner#empty?" do
-  it_behaves_like :strscan_eos, :empty?
-
-  it "warns in verbose mode that the method is obsolete" do
-    s = StringScanner.new("abc")
-    -> {
-      s.empty?
-    }.should complain(/empty?.*obsolete.*eos?/, verbose: true)
-
-    -> {
-      s.empty?
-    }.should_not complain(verbose: false)
-  end
-end
diff --git a/spec/ruby/library/stringscanner/eos_spec.rb b/spec/ruby/library/stringscanner/eos_spec.rb
index b58ee1e473..03c2804e5b 100644
--- a/spec/ruby/library/stringscanner/eos_spec.rb
+++ b/spec/ruby/library/stringscanner/eos_spec.rb
@@ -1,7 +1,20 @@
 require_relative '../../spec_helper'
-require_relative 'shared/eos'
 require 'strscan'
 
 describe "StringScanner#eos?" do
-  it_behaves_like :strscan_eos, :eos?
+  before :each do
+    @s = StringScanner.new("This is a test")
+  end
+
+  it "returns true if the scan pointer is at the end of the string" do
+    @s.terminate
+    @s.should.eos?
+
+    s = StringScanner.new('')
+    s.should.eos?
+  end
+
+  it "returns false if the scan pointer is not at the end of the string" do
+    @s.should_not.eos?
+  end
 end
diff --git a/spec/ruby/library/stringscanner/exist_spec.rb b/spec/ruby/library/stringscanner/exist_spec.rb
index beafadc07b..a408fd0b8d 100644
--- a/spec/ruby/library/stringscanner/exist_spec.rb
+++ b/spec/ruby/library/stringscanner/exist_spec.rb
@@ -2,11 +2,11 @@ require_relative '../../spec_helper'
 require 'strscan'
 
 describe "StringScanner#exist?" do
-  before :each do
+  before do
     @s = StringScanner.new("This is a test")
   end
 
-  it "returns the index of the first occurrence of the given pattern" do
+  it "returns distance in bytes between the current position and the end of the matched substring" do
     @s.exist?(/s/).should == 4
     @s.scan(/This is/)
     @s.exist?(/s/).should == 6
@@ -21,4 +21,99 @@ describe "StringScanner#exist?" do
     @s.scan(/This is/)
     @s.exist?(/i/).should == nil
   end
+
+  it "does not modify the current position" do
+    @s.pos.should == 0
+    @s.exist?(/s/).should == 4
+    @s.pos.should == 0
+  end
+
+  version_is StringScanner::Version, ""..."3.1.1" do # ruby_version_is ""..."3.4"
+    it "raises TypeError if given a String" do
+      -> {
+        @s.exist?('T')
+      }.should raise_error(TypeError, 'wrong argument type String (expected Regexp)')
+    end
+  end
+
+  version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+    it "searches a substring in the rest part of a string if given a String" do
+      @s.exist?('a').should == 9
+    end
+
+    it "returns nil if the pattern isn't found in the string" do
+      @s.exist?("S").should == nil
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #exist? was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.exist?(/(?<a>This)/)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.exist?(/(?<a>2008)/)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+      context "when #exist? was called with a String pattern" do
+        # https://github.com/ruby/strscan/issues/139
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "returns nil when matching succeeded" do
+            @s.exist?("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+          it "raises IndexError when matching succeeded" do
+            @s.exist?("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+
+        it "returns nil when matching failed" do
+          @s.exist?("2008")
+          @s.should_not.matched?
+          @s[:a].should be_nil
+        end
+
+        it "returns a matching substring when given Integer index" do
+          @s.exist?("This")
+          @s[0].should == "This"
+        end
+
+        # https://github.com/ruby/strscan/issues/135
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.exist?("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.exist?("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/fixed_anchor_spec.rb b/spec/ruby/library/stringscanner/fixed_anchor_spec.rb
new file mode 100644
index 0000000000..ce0b714fa8
--- /dev/null
+++ b/spec/ruby/library/stringscanner/fixed_anchor_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#fixed_anchor?" do
+  it "returns whether the fixed-anchor property is set" do
+    s = StringScanner.new("foo", fixed_anchor: true)
+    s.should.fixed_anchor?
+
+    s = StringScanner.new("foo", fixed_anchor: false)
+    s.should_not.fixed_anchor?
+  end
+
+  it "is set to false by default" do
+    s = StringScanner.new("foo")
+    s.should_not.fixed_anchor?
+  end
+end
diff --git a/spec/ruby/library/stringscanner/get_byte_spec.rb b/spec/ruby/library/stringscanner/get_byte_spec.rb
index 29e2f557de..144859abc9 100644
--- a/spec/ruby/library/stringscanner/get_byte_spec.rb
+++ b/spec/ruby/library/stringscanner/get_byte_spec.rb
@@ -1,7 +1,84 @@
+# encoding: binary
 require_relative '../../spec_helper'
-require_relative 'shared/get_byte'
 require 'strscan'
 
 describe "StringScanner#get_byte" do
-  it_behaves_like :strscan_get_byte, :get_byte
+  it "scans one byte and returns it" do
+    s = StringScanner.new('abc5.')
+    s.get_byte.should == 'a'
+    s.get_byte.should == 'b'
+    s.get_byte.should == 'c'
+    s.get_byte.should == '5'
+    s.get_byte.should == '.'
+  end
+
+  it "is not multi-byte character sensitive" do
+    s = StringScanner.new("\244\242")
+    s.get_byte.should == "\244"
+    s.get_byte.should == "\242"
+  end
+
+  it "returns nil at the end of the string" do
+    # empty string case
+    s = StringScanner.new('')
+    s.get_byte.should == nil
+    s.get_byte.should == nil
+
+    # non-empty string case
+    s = StringScanner.new('a')
+    s.get_byte # skip one
+    s.get_byte.should == nil
+  end
+
+  describe "#[] successive call with a capture group name" do
+    # https://github.com/ruby/strscan/issues/139
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "returns nil" do
+        s = StringScanner.new("This is a test")
+        s.get_byte
+        s.should.matched?
+        s[:a].should be_nil
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+      it "raises IndexError" do
+        s = StringScanner.new("This is a test")
+        s.get_byte
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+
+    it "returns a matching character when given Integer index" do
+      s = StringScanner.new("This is a test")
+      s.get_byte
+      s[0].should == "T"
+    end
+
+    # https://github.com/ruby/strscan/issues/135
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "ignores the previous matching with Regexp" do
+        s = StringScanner.new("This is a test")
+        s.exist?(/(?<a>This)/)
+        s.should.matched?
+        s[:a].should == "This"
+
+        s.get_byte
+        s.should.matched?
+        s[:a].should be_nil
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+      it "ignores the previous matching with Regexp" do
+        s = StringScanner.new("This is a test")
+        s.exist?(/(?<a>This)/)
+        s.should.matched?
+        s[:a].should == "This"
+
+        s.get_byte
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/getbyte_spec.rb b/spec/ruby/library/stringscanner/getbyte_spec.rb
deleted file mode 100644
index e0659a5829..0000000000
--- a/spec/ruby/library/stringscanner/getbyte_spec.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/get_byte'
-require_relative 'shared/extract_range'
-require 'strscan'
-
-describe "StringScanner#getbyte" do
-  it_behaves_like :strscan_get_byte, :getbyte
-
-  it "warns in verbose mode that the method is obsolete" do
-    s = StringScanner.new("abc")
-    -> {
-      s.getbyte
-    }.should complain(/getbyte.*obsolete.*get_byte/, verbose: true)
-
-    -> {
-      s.getbyte
-    }.should_not complain(verbose: false)
-  end
-
-  it_behaves_like :extract_range, :getbyte
-end
diff --git a/spec/ruby/library/stringscanner/getch_spec.rb b/spec/ruby/library/stringscanner/getch_spec.rb
index a6be0d4221..d369391b14 100644
--- a/spec/ruby/library/stringscanner/getch_spec.rb
+++ b/spec/ruby/library/stringscanner/getch_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../spec_helper'
 require_relative 'shared/extract_range'
 require 'strscan'
@@ -13,7 +13,7 @@ describe "StringScanner#getch" do
 
   it "is multi-byte character sensitive" do
     # Japanese hiragana "A" in EUC-JP
-    src = "\244\242".force_encoding("euc-jp")
+    src = "\244\242".dup.force_encoding("euc-jp")
 
     s = StringScanner.new(src)
     s.getch.should == src
@@ -31,5 +31,59 @@ describe "StringScanner#getch" do
     s.getch.should == nil
   end
 
+  describe "#[] successive call with a capture group name" do
+    # https://github.com/ruby/strscan/issues/139
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "returns nil" do
+        s = StringScanner.new("This is a test")
+        s.getch
+        s.should.matched?
+        s[:a].should be_nil
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+      it "raises IndexError" do
+        s = StringScanner.new("This is a test")
+        s.getch
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+
+    it "returns a matching character when given Integer index" do
+      s = StringScanner.new("This is a test")
+      s.getch
+      s[0].should == "T"
+    end
+
+    # https://github.com/ruby/strscan/issues/135
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "ignores the previous matching with Regexp" do
+        s = StringScanner.new("This is a test")
+
+        s.exist?(/(?<a>This)/)
+        s.should.matched?
+        s[:a].should == "This"
+
+        s.getch
+        s.should.matched?
+        s[:a].should be_nil
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "ignores the previous matching with Regexp" do
+        s = StringScanner.new("This is a test")
+
+        s.exist?(/(?<a>This)/)
+        s.should.matched?
+        s[:a].should == "This"
+
+        s.getch
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+  end
+
   it_behaves_like :extract_range, :getch
 end
diff --git a/spec/ruby/library/stringscanner/initialize_spec.rb b/spec/ruby/library/stringscanner/initialize_spec.rb
index 07f71572ce..77f6084c1b 100644
--- a/spec/ruby/library/stringscanner/initialize_spec.rb
+++ b/spec/ruby/library/stringscanner/initialize_spec.rb
@@ -12,7 +12,6 @@ describe "StringScanner#initialize" do
 
   it "returns an instance of StringScanner" do
     @s.should be_kind_of(StringScanner)
-    @s.tainted?.should be_false
     @s.eos?.should be_false
   end
 
@@ -25,4 +24,9 @@ describe "StringScanner#initialize" do
     scan = StringScanner.new(m)
     scan.string.should == s
   end
+
+  it "accepts a fixed_anchor keyword argument" do
+    s = StringScanner.new("foo", fixed_anchor: true)
+    s.should.fixed_anchor?
+  end
 end
diff --git a/spec/ruby/library/stringscanner/match_spec.rb b/spec/ruby/library/stringscanner/match_spec.rb
index ec59680914..a27bb51d72 100644
--- a/spec/ruby/library/stringscanner/match_spec.rb
+++ b/spec/ruby/library/stringscanner/match_spec.rb
@@ -17,6 +17,15 @@ describe "StringScanner#match?" do
     @s.match?(/\s+/).should == nil
   end
 
+  it "sets the last match result" do
+    @s.pos = 8
+    @s.match?(/a/)
+
+    @s.pre_match.should == "This is "
+    @s.matched.should == "a"
+    @s.post_match.should == " test"
+  end
+
   it "effects pre_match" do
     @s.scan(/\w+/)
     @s.scan(/\s/)
@@ -25,4 +34,18 @@ describe "StringScanner#match?" do
     @s.match?(/\w+/)
     @s.pre_match.should == "This "
   end
+
+  describe "#[] successive call with a capture group name" do
+    it "returns matched substring when matching succeeded" do
+      @s.match?(/(?<a>This)/)
+      @s.should.matched?
+      @s[:a].should == "This"
+    end
+
+    it "returns nil when matching failed" do
+      @s.match?(/(?<a>2008)/)
+      @s.should_not.matched?
+      @s[:a].should be_nil
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/matched_size_spec.rb b/spec/ruby/library/stringscanner/matched_size_spec.rb
index a36bd3aafe..d9c338a07e 100644
--- a/spec/ruby/library/stringscanner/matched_size_spec.rb
+++ b/spec/ruby/library/stringscanner/matched_size_spec.rb
@@ -1,7 +1,24 @@
 require_relative '../../spec_helper'
-require_relative 'shared/matched_size'
 require 'strscan'
 
 describe "StringScanner#matched_size" do
-  it_behaves_like :strscan_matched_size, :matched_size
+  before :each do
+    @s = StringScanner.new("This is a test")
+  end
+
+  it "returns the size of the most recent match" do
+    @s.check(/This/)
+    @s.matched_size.should == 4
+    @s.matched_size.should == 4
+    @s.scan(//)
+    @s.matched_size.should == 0
+  end
+
+  it "returns nil if there was no recent match" do
+    @s.matched_size.should == nil
+    @s.check(/\d+/)
+    @s.matched_size.should == nil
+    @s.terminate
+    @s.matched_size.should == nil
+  end
 end
diff --git a/spec/ruby/library/stringscanner/must_C_version_spec.rb b/spec/ruby/library/stringscanner/must_C_version_spec.rb
index fcc5b596f6..9d6edfe7b6 100644
--- a/spec/ruby/library/stringscanner/must_C_version_spec.rb
+++ b/spec/ruby/library/stringscanner/must_C_version_spec.rb
@@ -3,6 +3,6 @@ require 'strscan'
 
 describe "StringScanner.must_C_version" do
   it "returns self" do
-     StringScanner.must_C_version.should == StringScanner
+    StringScanner.must_C_version.should == StringScanner
   end
 end
diff --git a/spec/ruby/library/stringscanner/named_captures_spec.rb b/spec/ruby/library/stringscanner/named_captures_spec.rb
new file mode 100644
index 0000000000..a68d66c216
--- /dev/null
+++ b/spec/ruby/library/stringscanner/named_captures_spec.rb
@@ -0,0 +1,30 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#named_captures" do
+  before do
+    @s = StringScanner.new('Fri Dec 12 1975 14:39')
+  end
+
+  it "returns a hash of names and matched substrings for named capturing groups in a regular expression of the most recent matching" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+    @s.named_captures.should == {"wday" => "Fri", "month" => "Dec", "day" => "12"}
+  end
+
+  it "returns {} if there are no named capturing groups" do
+    @s.exist?(/(\w+) (\w+) (\d+)/)
+    @s.named_captures.should == {}
+  end
+
+  # https://github.com/ruby/strscan/issues/132
+  ruby_bug "", ""..."3.3" do # fixed in strscan v3.0.7
+    it "returns {} if there is no any matching done" do
+      @s.named_captures.should == {}
+    end
+  end
+
+  it "returns nil for an optional named capturing group if it doesn't match" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\s+)?/)
+    @s.named_captures.should == {"wday" => "Fri", "month" => "Dec", "day" => nil}
+  end
+end
diff --git a/spec/ruby/library/stringscanner/peek_byte_spec.rb b/spec/ruby/library/stringscanner/peek_byte_spec.rb
new file mode 100644
index 0000000000..88ef4a2b7c
--- /dev/null
+++ b/spec/ruby/library/stringscanner/peek_byte_spec.rb
@@ -0,0 +1,35 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+  describe "StringScanner#peek_byte" do
+    it "returns a byte at the current position as an Integer" do
+      s = StringScanner.new('This is a test')
+      s.peek_byte.should == 84
+    end
+
+    it "returns nil at the end of the string" do
+      s = StringScanner.new('a')
+      s.getch # skip one
+      s.pos.should == 1
+      s.peek_byte.should == nil
+    end
+
+    it "is not multi-byte character sensitive" do
+      s = StringScanner.new("∂") # "∂".bytes => [226, 136, 130]
+      s.peek_byte.should == 226
+      s.pos = 1
+      s.peek_byte.should == 136
+      s.pos = 2
+      s.peek_byte.should == 130
+    end
+
+    it "doesn't change current position" do
+      s = StringScanner.new('This is a test')
+
+      s.pos.should == 0
+      s.peek_byte.should == 84
+      s.pos.should == 0
+    end
+  end
+end
diff --git a/spec/ruby/library/stringscanner/peek_spec.rb b/spec/ruby/library/stringscanner/peek_spec.rb
index cbb5630ff9..d490abecf9 100644
--- a/spec/ruby/library/stringscanner/peek_spec.rb
+++ b/spec/ruby/library/stringscanner/peek_spec.rb
@@ -1,7 +1,42 @@
 require_relative '../../spec_helper'
-require_relative 'shared/peek'
 require 'strscan'
 
 describe "StringScanner#peek" do
-  it_behaves_like :strscan_peek, :peek
+  before :each do
+    @s = StringScanner.new('This is a test')
+  end
+
+  it "returns at most the specified number of bytes from the current position" do
+    @s.peek(4).should == "This"
+    @s.pos.should == 0
+    @s.pos = 5
+    @s.peek(2).should == "is"
+    @s.peek(1000).should == "is a test"
+
+    s = StringScanner.new("été")
+    s.peek(2).should == "é"
+  end
+
+  it "returns an empty string when the passed argument is zero" do
+    @s.peek(0).should == ""
+  end
+
+  it "raises a ArgumentError when the passed argument is negative" do
+    -> { @s.peek(-2) }.should raise_error(ArgumentError)
+  end
+
+  it "raises a RangeError when the passed argument is a Bignum" do
+    -> { @s.peek(bignum_value) }.should raise_error(RangeError)
+  end
+
+  it "returns an instance of String when passed a String subclass" do
+    cls = Class.new(String)
+    sub = cls.new("abc")
+
+    s = StringScanner.new(sub)
+
+    ch = s.peek(1)
+    ch.should_not be_kind_of(cls)
+    ch.should be_an_instance_of(String)
+  end
 end
diff --git a/spec/ruby/library/stringscanner/peep_spec.rb b/spec/ruby/library/stringscanner/peep_spec.rb
deleted file mode 100644
index bf6d579325..0000000000
--- a/spec/ruby/library/stringscanner/peep_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/peek'
-require 'strscan'
-
-describe "StringScanner#peep" do
-  it_behaves_like :strscan_peek, :peep
-
-  it "warns in verbose mode that the method is obsolete" do
-    s = StringScanner.new("abc")
-    -> {
-      s.peep(1)
-    }.should complain(/peep.*obsolete.*peek/, verbose: true)
-
-    -> {
-      s.peep(1)
-    }.should_not complain(verbose: false)
-  end
-end
diff --git a/spec/ruby/library/stringscanner/rest_size_spec.rb b/spec/ruby/library/stringscanner/rest_size_spec.rb
index e62e3a8f8c..a5e971631a 100644
--- a/spec/ruby/library/stringscanner/rest_size_spec.rb
+++ b/spec/ruby/library/stringscanner/rest_size_spec.rb
@@ -1,7 +1,21 @@
 require_relative '../../spec_helper'
-require_relative 'shared/rest_size'
 require 'strscan'
 
 describe "StringScanner#rest_size" do
-  it_behaves_like :strscan_rest_size, :rest_size
+  before :each do
+    @s = StringScanner.new('This is a test')
+  end
+
+  it "returns the length of the rest of the string" do
+    @s.rest_size.should == 14
+    @s.scan(/This/)
+    @s.rest_size.should == 10
+    @s.terminate
+    @s.rest_size.should == 0
+  end
+
+  it "is equivalent to rest.size" do
+    @s.scan(/This/)
+    @s.rest_size.should == @s.rest.size
+  end
 end
diff --git a/spec/ruby/library/stringscanner/restsize_spec.rb b/spec/ruby/library/stringscanner/restsize_spec.rb
deleted file mode 100644
index 710520afae..0000000000
--- a/spec/ruby/library/stringscanner/restsize_spec.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'shared/rest_size'
-require 'strscan'
-
-describe "StringScanner#restsize" do
-  it_behaves_like :strscan_rest_size, :restsize
-
-  it "warns in verbose mode that the method is obsolete" do
-    s = StringScanner.new("abc")
-    -> {
-      s.restsize
-    }.should complain(/restsize.*obsolete.*rest_size/, verbose: true)
-
-    -> {
-      s.restsize
-    }.should_not complain(verbose: false)
-  end
-end
diff --git a/spec/ruby/library/stringscanner/scan_byte_spec.rb b/spec/ruby/library/stringscanner/scan_byte_spec.rb
new file mode 100644
index 0000000000..aa2decc8f7
--- /dev/null
+++ b/spec/ruby/library/stringscanner/scan_byte_spec.rb
@@ -0,0 +1,98 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+  describe "StringScanner#scan_byte" do
+    it "scans one byte and returns it as on Integer" do
+      s = StringScanner.new('abc') # "abc".bytes => [97, 98, 99]
+      s.scan_byte.should == 97
+      s.scan_byte.should == 98
+      s.scan_byte.should == 99
+    end
+
+    it "is not multi-byte character sensitive" do
+      s = StringScanner.new("あ") # "あ".bytes => [227, 129, 130]
+      s.scan_byte.should == 227
+      s.scan_byte.should == 129
+      s.scan_byte.should == 130
+    end
+
+    it "returns nil at the end of the string" do
+      s = StringScanner.new('a')
+      s.scan_byte # skip one
+      s.scan_byte.should == nil
+      s.pos.should == 1
+    end
+
+    it "changes current position" do
+      s = StringScanner.new('abc')
+      s.pos.should == 0
+      s.scan_byte
+      s.pos.should == 1
+    end
+
+    it "sets the last match result" do
+      s = StringScanner.new('abc')
+      s.pos = 1
+      s.scan_byte
+
+      s.pre_match.should == "a"
+      s.matched.should == "b"
+      s.post_match.should == "c"
+    end
+
+    describe "#[] successive call with a capture group name" do
+      # https://github.com/ruby/strscan/issues/139
+      version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "returns nil" do
+          s = StringScanner.new("abc")
+          s.scan_byte
+          s.should.matched?
+          s[:a].should be_nil
+        end
+      end
+      version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+        it "raises IndexError" do
+          s = StringScanner.new("abc")
+          s.scan_byte
+          s.should.matched?
+          -> { s[:a] }.should raise_error(IndexError)
+        end
+      end
+
+      it "returns a matching character when given Integer index" do
+        s = StringScanner.new("This is a test")
+        s.scan_byte
+        s[0].should == "T"
+      end
+
+      # https://github.com/ruby/strscan/issues/135
+      version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "ignores the previous matching with Regexp" do
+          s = StringScanner.new("abc")
+
+          s.exist?(/(?<a>a)/)
+          s.should.matched?
+          s[:a].should == "a"
+
+          s.scan_byte
+          s.should.matched?
+          s[:a].should == nil
+        end
+      end
+      version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "ignores the previous matching with Regexp" do
+          s = StringScanner.new("abc")
+
+          s.exist?(/(?<a>a)/)
+          s.should.matched?
+          s[:a].should == "a"
+
+          s.scan_byte
+          s.should.matched?
+          -> { s[:a] }.should raise_error(IndexError)
+        end
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/stringscanner/scan_full_spec.rb b/spec/ruby/library/stringscanner/scan_full_spec.rb
index ed34d7d3f6..967313f5ca 100644
--- a/spec/ruby/library/stringscanner/scan_full_spec.rb
+++ b/spec/ruby/library/stringscanner/scan_full_spec.rb
@@ -27,4 +27,18 @@ describe "StringScanner#scan_full" do
     @s.scan_full(/This/, true, true).should == "This"
     @s.pos.should == 4
   end
+
+  describe "#[] successive call with a capture group name" do
+    it "returns matched substring when matching succeeded" do
+      @s.scan_full(/(?<a>This)/, false, false)
+      @s.should.matched?
+      @s[:a].should == "This"
+    end
+
+    it "returns nil when matching failed" do
+      @s.scan_full(/(?<a>2008)/, false, false)
+      @s.should_not.matched?
+      @s[:a].should be_nil
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/scan_integer_spec.rb b/spec/ruby/library/stringscanner/scan_integer_spec.rb
new file mode 100644
index 0000000000..fe0d26f404
--- /dev/null
+++ b/spec/ruby/library/stringscanner/scan_integer_spec.rb
@@ -0,0 +1,157 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+  describe "StringScanner#scan_integer" do
+    it "returns the matched Integer literal starting from the current position" do
+      s = StringScanner.new("42")
+      s.scan_integer.should == 42
+    end
+
+    it "returns nil when no Integer literal matched starting from the current position" do
+      s = StringScanner.new("a42")
+      s.scan_integer.should == nil
+    end
+
+    it "supports a sign +/-" do
+      StringScanner.new("+42").scan_integer.should == 42
+      StringScanner.new("-42").scan_integer.should == -42
+    end
+
+    it "changes the current position" do
+      s = StringScanner.new("42abc")
+      s.scan_integer
+      s.pos.should == 2
+    end
+
+    # https://github.com/ruby/strscan/issues/130
+    ruby_bug "", "3.4"..."4.0" do # introduced in strscan v3.1.1
+      it "sets the last match result" do
+        s = StringScanner.new("42abc")
+        s.scan_integer
+
+        s.should.matched?
+        s.matched.should == "42"
+        s.pre_match.should == ""
+        s.post_match.should == "abc"
+        s.matched_size.should == 2
+      end
+    end
+
+    it "raises Encoding::CompatibilityError when a scanned string not is ASCII-compatible encoding" do
+      string = "42".encode(Encoding::UTF_16BE)
+      s = StringScanner.new(string)
+
+      -> {
+        s.scan_integer
+      }.should raise_error(Encoding::CompatibilityError, 'ASCII incompatible encoding: UTF-16BE')
+    end
+
+    context "given base" do
+      it "supports base: 10" do
+        s = StringScanner.new("42")
+        s.scan_integer(base: 10).should == 42
+      end
+
+      it "supports base: 16" do
+        StringScanner.new("0xff").scan_integer(base: 16).should == 0xff
+        StringScanner.new("-0xff").scan_integer(base: 16).should == -0xff
+        StringScanner.new("0xFF").scan_integer(base: 16).should == 0xff
+        StringScanner.new("-0xFF").scan_integer(base: 16).should == -0xff
+        StringScanner.new("ff").scan_integer(base: 16).should == 0xff
+        StringScanner.new("-ff").scan_integer(base: 16).should == -0xff
+      end
+
+      it "raises ArgumentError when passed not supported base" do
+        -> {
+          StringScanner.new("42").scan_integer(base: 5)
+        }.should raise_error(ArgumentError, "Unsupported integer base: 5, expected 10 or 16")
+      end
+
+      version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+        it "does not match '0x' prefix on its own" do
+          StringScanner.new("0x").scan_integer(base: 16).should == nil
+          StringScanner.new("-0x").scan_integer(base: 16).should == nil
+          StringScanner.new("+0x").scan_integer(base: 16).should == nil
+        end
+      end
+
+      version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+        it "matches '0' in a '0x' that is followed by non-hex characters" do
+          StringScanner.new("0x!@#").scan_integer(base: 16).should == 0
+          StringScanner.new("-0x!@#").scan_integer(base: 16).should == 0
+          StringScanner.new("+0x!@#").scan_integer(base: 16).should == 0
+        end
+
+        it "matches '0' in a '0x' located in the end of a string" do
+          StringScanner.new("0x").scan_integer(base: 16).should == 0
+          StringScanner.new("-0x").scan_integer(base: 16).should == 0
+          StringScanner.new("+0x").scan_integer(base: 16).should == 0
+        end
+      end
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    # https://github.com/ruby/strscan/issues/139
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "returns nil substring when matching succeeded" do
+        s = StringScanner.new("42")
+        s.scan_integer
+        s.should.matched?
+        s[:a].should == nil
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+      it "raises IndexError when matching succeeded" do
+        s = StringScanner.new("42")
+        s.scan_integer
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+
+    it "returns nil when matching failed" do
+      s = StringScanner.new("a42")
+      s.scan_integer
+      s.should_not.matched?
+      s[:a].should be_nil
+    end
+
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "returns a matching substring when given Integer index" do
+        s = StringScanner.new("42")
+        s.scan_integer
+        s[0].should == "42"
+      end
+    end
+
+    # https://github.com/ruby/strscan/issues/135
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+      it "does not ignore the previous matching with Regexp" do
+        s = StringScanner.new("42")
+
+        s.exist?(/(?<a>42)/)
+        s.should.matched?
+        s[:a].should == "42"
+
+        s.scan_integer
+        s.should.matched?
+        s[:a].should == "42"
+      end
+    end
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "ignores the previous matching with Regexp" do
+        s = StringScanner.new("42")
+
+        s.exist?(/(?<a>42)/)
+        s.should.matched?
+        s[:a].should == "42"
+
+        s.scan_integer
+        s.should.matched?
+        -> { s[:a] }.should raise_error(IndexError)
+      end
+    end
+  end
+end
diff --git a/spec/ruby/library/stringscanner/scan_spec.rb b/spec/ruby/library/stringscanner/scan_spec.rb
index 8b9960e6e6..088c3419fb 100644
--- a/spec/ruby/library/stringscanner/scan_spec.rb
+++ b/spec/ruby/library/stringscanner/scan_spec.rb
@@ -50,10 +50,52 @@ describe "StringScanner#scan" do
     @s.scan(/./).should be_nil
   end
 
-  it "raises a TypeError if pattern isn't a Regexp" do
-    -> { @s.scan("aoeu")    }.should raise_error(TypeError)
+  it "treats String as the pattern itself" do
+    @s.scan("this").should be_nil
+    @s.scan("This").should == "This"
+  end
+
+  it "raises a TypeError if pattern isn't a Regexp nor String" do
     -> { @s.scan(5)         }.should raise_error(TypeError)
     -> { @s.scan(:test)     }.should raise_error(TypeError)
     -> { @s.scan(mock('x')) }.should raise_error(TypeError)
   end
+
+  describe "#[] successive call with a capture group name" do
+    it "returns matched substring when matching succeeded" do
+      @s.scan(/(?<a>This)/)
+      @s.should.matched?
+      @s[:a].should == "This"
+    end
+
+    it "returns nil when matching failed" do
+      @s.scan(/(?<a>2008)/)
+      @s.should_not.matched?
+      @s[:a].should be_nil
+    end
+  end
+end
+
+describe "StringScanner#scan with fixed_anchor: true" do
+  before :each do
+    @s = StringScanner.new("This\nis\na\ntest", fixed_anchor: true)
+  end
+
+  it "returns the matched string" do
+    @s.scan(/\w+/).should == "This"
+    @s.scan(/.../m).should == "\nis"
+    @s.scan(//).should == ""
+    @s.scan(/\s+/).should == "\n"
+  end
+
+  it "treats ^ as matching from the beginning of line" do
+    @s.scan(/\w+\n/).should == "This\n"
+    @s.scan(/^\w/).should == "i"
+    @s.scan(/^\w/).should be_nil
+  end
+
+  it "treats \\A as matching from the beginning of string" do
+    @s.scan(/\A\w/).should == "T"
+    @s.scan(/\A\w/).should be_nil
+  end
 end
diff --git a/spec/ruby/library/stringscanner/scan_until_spec.rb b/spec/ruby/library/stringscanner/scan_until_spec.rb
index 94239db50e..610060d6f1 100644
--- a/spec/ruby/library/stringscanner/scan_until_spec.rb
+++ b/spec/ruby/library/stringscanner/scan_until_spec.rb
@@ -2,14 +2,20 @@ require_relative '../../spec_helper'
 require 'strscan'
 
 describe "StringScanner#scan_until" do
-  before :each do
+  before do
     @s = StringScanner.new("This is a test")
   end
 
   it "returns the substring up to and including the end of the match" do
-   @s.scan_until(/a/).should == "This is a"
-   @s.pre_match.should == "This is "
-   @s.post_match.should == " test"
+    @s.scan_until(/a/).should == "This is a"
+  end
+
+  it "sets the last match result" do
+    @s.scan_until(/a/)
+
+    @s.pre_match.should == "This is "
+    @s.matched.should == "a"
+    @s.post_match.should == " test"
   end
 
   it "returns nil if there's no match" do
@@ -20,4 +26,110 @@ describe "StringScanner#scan_until" do
     @s.scan(/T/)
     @s.scan_until(/^h/).should == "h"
   end
+
+  version_is StringScanner::Version, ""..."3.1.1" do # ruby_version_is ""..."3.4"
+    it "raises TypeError if given a String" do
+      -> {
+        @s.scan_until('T')
+      }.should raise_error(TypeError, 'wrong argument type String (expected Regexp)')
+    end
+  end
+
+  version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+    it "searches a substring in the rest part of a string if given a String" do
+      @s.scan_until("a").should == "This is a"
+    end
+
+    # https://github.com/ruby/strscan/issues/131
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.1"
+      it "sets the last match result if given a String" do
+        @s.scan_until("a")
+
+        @s.pre_match.should == ""
+        @s.matched.should == "This is a"
+        @s.post_match.should == " test"
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "sets the last match result if given a String" do
+        @s.scan_until("a")
+
+        @s.pre_match.should == "This is "
+        @s.matched.should == "a"
+        @s.post_match.should == " test"
+      end
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #scan_until was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.scan_until(/(?<a>This)/)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.scan_until(/(?<a>2008)/)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+      context "when #scan_until was called with a String pattern" do
+        # https://github.com/ruby/strscan/issues/139
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "returns nil when matching succeeded" do
+            @s.scan_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+          it "raises IndexError when matching succeeded" do
+            @s.scan_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+
+        it "returns nil when matching failed" do
+          @s.scan_until("2008")
+          @s.should_not.matched?
+          @s[:a].should be_nil
+        end
+
+        it "returns a matching substring when given Integer index" do
+          @s.scan_until("This")
+          @s[0].should == "This"
+        end
+
+        # https://github.com/ruby/strscan/issues/135
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.scan_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.scan_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/search_full_spec.rb b/spec/ruby/library/stringscanner/search_full_spec.rb
index da9067e012..197adfda4d 100644
--- a/spec/ruby/library/stringscanner/search_full_spec.rb
+++ b/spec/ruby/library/stringscanner/search_full_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../spec_helper'
 require 'strscan'
 
 describe "StringScanner#search_full" do
-  before :each do
+  before do
     @s = StringScanner.new("This is a test")
   end
 
@@ -27,4 +27,107 @@ describe "StringScanner#search_full" do
     @s.search_full(/This/, true, true).should == "This"
     @s.pos.should == 4
   end
+
+  it "sets the last match result" do
+    @s.search_full(/is a/, false, false)
+
+    @s.pre_match.should == "This "
+    @s.matched.should == "is a"
+    @s.post_match.should == " test"
+  end
+
+  version_is StringScanner::Version, ""..."3.1.1" do # ruby_version_is ""..."3.4"
+    it "raises TypeError if given a String" do
+      -> {
+        @s.search_full('T', true, true)
+      }.should raise_error(TypeError, 'wrong argument type String (expected Regexp)')
+    end
+  end
+
+  version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+    it "searches a substring in the rest part of a string if given a String" do
+      @s.search_full("is a", false, false).should == 9
+    end
+
+    # https://github.com/ruby/strscan/issues/131
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.1"
+      it "sets the last match result if given a String" do
+        @s.search_full("is a", false, false)
+
+        @s.pre_match.should == ""
+        @s.matched.should == "This is a"
+        @s.post_match.should == " test"
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "sets the last match result if given a String" do
+        @s.search_full("is a", false, false)
+
+        @s.pre_match.should == "This "
+        @s.matched.should == "is a"
+        @s.post_match.should == " test"
+      end
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #search_full was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.search_full(/(?<a>This)/, false, false)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.search_full(/(?<a>2008)/, false, false)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+      context "when #search_full was called with a String pattern" do
+        # https://github.com/ruby/strscan/issues/139
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "returns nil when matching succeeded" do
+            @s.search_full("This", false, false)
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+          it "raises IndexError when matching succeeded" do
+            @s.search_full("This", false, false)
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+
+        it "returns nil when matching failed" do
+          @s.search_full("2008", false, false)
+          @s.should_not.matched?
+          @s[:a].should be_nil
+        end
+
+        it "returns a matching substring when given Integer index" do
+          @s.search_full("This", false, false)
+          @s[0].should == "This"
+        end
+
+        # https://github.com/ruby/strscan/issues/135
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.search_full("This", false, false)
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/shared/concat.rb b/spec/ruby/library/stringscanner/shared/concat.rb
index cb884a5c01..1dbae11f7c 100644
--- a/spec/ruby/library/stringscanner/shared/concat.rb
+++ b/spec/ruby/library/stringscanner/shared/concat.rb
@@ -1,6 +1,6 @@
 describe :strscan_concat, shared: true do
   it "concatenates the given argument to self and returns self" do
-    s = StringScanner.new("hello ")
+    s = StringScanner.new(+"hello ")
     s.send(@method, 'world').should == s
     s.string.should == "hello world"
     s.eos?.should be_false
diff --git a/spec/ruby/library/stringscanner/shared/eos.rb b/spec/ruby/library/stringscanner/shared/eos.rb
deleted file mode 100644
index ea04c764a2..0000000000
--- a/spec/ruby/library/stringscanner/shared/eos.rb
+++ /dev/null
@@ -1,17 +0,0 @@
-describe :strscan_eos, shared: true do
-  before :each do
-    @s = StringScanner.new("This is a test")
-  end
-
-  it "returns true if the scan pointer is at the end of the string" do
-    @s.terminate
-    @s.send(@method).should be_true
-
-    s = StringScanner.new('')
-    s.send(@method).should be_true
-  end
-
-  it "returns false if the scan pointer is not at the end of the string" do
-    @s.send(@method).should be_false
-  end
-end
diff --git a/spec/ruby/library/stringscanner/shared/extract_range.rb b/spec/ruby/library/stringscanner/shared/extract_range.rb
index 7e98540b1a..e7404fd0cb 100644
--- a/spec/ruby/library/stringscanner/shared/extract_range.rb
+++ b/spec/ruby/library/stringscanner/shared/extract_range.rb
@@ -8,15 +8,4 @@ describe :extract_range, shared: true do
     ch.should_not be_kind_of(cls)
     ch.should be_an_instance_of(String)
   end
-
-  it "taints the returned String if the input was tainted" do
-    str = 'abc'
-    str.taint
-
-    s = StringScanner.new(str)
-
-    s.send(@method).tainted?.should be_true
-    s.send(@method).tainted?.should be_true
-    s.send(@method).tainted?.should be_true
-  end
 end
diff --git a/spec/ruby/library/stringscanner/shared/extract_range_matched.rb b/spec/ruby/library/stringscanner/shared/extract_range_matched.rb
index fe695e8ac1..070a132812 100644
--- a/spec/ruby/library/stringscanner/shared/extract_range_matched.rb
+++ b/spec/ruby/library/stringscanner/shared/extract_range_matched.rb
@@ -10,13 +10,4 @@ describe :extract_range_matched, shared: true do
     ch.should_not be_kind_of(cls)
     ch.should be_an_instance_of(String)
   end
-
-  it "taints the returned String if the input was tainted" do
-    str = 'abc'
-    str.taint
-
-    s = StringScanner.new(str)
-    s.scan(/\w{1}/)
-    s.send(@method).tainted?.should be_true
-  end
 end
diff --git a/spec/ruby/library/stringscanner/shared/get_byte.rb b/spec/ruby/library/stringscanner/shared/get_byte.rb
deleted file mode 100644
index 763ab6f4a4..0000000000
--- a/spec/ruby/library/stringscanner/shared/get_byte.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-# -*- encoding: binary -*-
-describe :strscan_get_byte, shared: true do
-  it "scans one byte and returns it" do
-    s = StringScanner.new('abc5.')
-    s.send(@method).should == 'a'
-    s.send(@method).should == 'b'
-    s.send(@method).should == 'c'
-    s.send(@method).should == '5'
-    s.send(@method).should == '.'
-  end
-
-  it "is not multi-byte character sensitive" do
-    s = StringScanner.new("\244\242")
-    s.send(@method).should == "\244"
-    s.send(@method).should == "\242"
-  end
-
-  it "returns nil at the end of the string" do
-    # empty string case
-    s = StringScanner.new('')
-    s.send(@method).should == nil
-    s.send(@method).should == nil
-
-    # non-empty string case
-    s = StringScanner.new('a')
-    s.send(@method) # skip one
-    s.send(@method).should == nil
-  end
-end
diff --git a/spec/ruby/library/stringscanner/shared/matched_size.rb b/spec/ruby/library/stringscanner/shared/matched_size.rb
deleted file mode 100644
index 92174733f7..0000000000
--- a/spec/ruby/library/stringscanner/shared/matched_size.rb
+++ /dev/null
@@ -1,21 +0,0 @@
-describe :strscan_matched_size, shared: true do
-  before :each do
-    @s = StringScanner.new("This is a test")
-  end
-
-  it "returns the size of the most recent match" do
-    @s.check(/This/)
-    @s.send(@method).should == 4
-    @s.send(@method).should == 4
-    @s.scan(//)
-    @s.send(@method).should == 0
-  end
-
-  it "returns nil if there was no recent match" do
-    @s.send(@method).should == nil
-    @s.check(/\d+/)
-    @s.send(@method).should == nil
-    @s.terminate
-    @s.send(@method).should == nil
-  end
-end
diff --git a/spec/ruby/library/stringscanner/shared/peek.rb b/spec/ruby/library/stringscanner/shared/peek.rb
deleted file mode 100644
index a59afdc6c0..0000000000
--- a/spec/ruby/library/stringscanner/shared/peek.rb
+++ /dev/null
@@ -1,47 +0,0 @@
-describe :strscan_peek, shared: true do
-  before :each do
-    @s = StringScanner.new('This is a test')
-  end
-
-  it "returns at most the specified number of bytes from the current position" do
-    @s.send(@method, 4).should == "This"
-    @s.pos.should == 0
-    @s.pos = 5
-    @s.send(@method, 2).should == "is"
-    @s.send(@method, 1000).should == "is a test"
-
-    s = StringScanner.new("été")
-    s.send(@method, 2).should == "é"
-  end
-
-  it "returns an empty string when the passed argument is zero" do
-    @s.send(@method, 0).should == ""
-  end
-
-  it "raises a ArgumentError when the passed argument is negative" do
-    -> { @s.send(@method, -2) }.should raise_error(ArgumentError)
-  end
-
-  it "raises a RangeError when the passed argument is a Bignum" do
-    -> { @s.send(@method, bignum_value) }.should raise_error(RangeError)
-  end
-
-  it "returns an instance of String when passed a String subclass" do
-    cls = Class.new(String)
-    sub = cls.new("abc")
-
-    s = StringScanner.new(sub)
-
-    ch = s.send(@method, 1)
-    ch.should_not be_kind_of(cls)
-    ch.should be_an_instance_of(String)
-  end
-
-  it "taints the returned String if the input was tainted" do
-    str = 'abc'
-    str.taint
-
-    s = StringScanner.new(str)
-    s.send(@method, 1).tainted?.should be_true
-  end
-end
diff --git a/spec/ruby/library/stringscanner/shared/pos.rb b/spec/ruby/library/stringscanner/shared/pos.rb
index 6d540881f2..eea7ead6b5 100644
--- a/spec/ruby/library/stringscanner/shared/pos.rb
+++ b/spec/ruby/library/stringscanner/shared/pos.rb
@@ -22,6 +22,13 @@ describe :strscan_pos, shared: true do
     @s.terminate
     @s.send(@method).should == @s.string.length
   end
+
+  it "is not multi-byte character sensitive" do
+    s = StringScanner.new("abcädeföghi")
+
+    s.scan_until(/ö/)
+    s.pos.should == 10
+  end
 end
 
 describe :strscan_pos_set, shared: true do
diff --git a/spec/ruby/library/stringscanner/shared/rest_size.rb b/spec/ruby/library/stringscanner/shared/rest_size.rb
deleted file mode 100644
index 4c4f49e45c..0000000000
--- a/spec/ruby/library/stringscanner/shared/rest_size.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-describe :strscan_rest_size, shared: true do
-  before :each do
-    @s = StringScanner.new('This is a test')
-  end
-
-  it "returns the length of the rest of the string" do
-    @s.send(@method).should == 14
-    @s.scan(/This/)
-    @s.send(@method).should == 10
-    @s.terminate
-    @s.send(@method).should == 0
-  end
-
-  it "is equivalent to rest.size" do
-    @s.scan(/This/)
-    @s.send(@method).should == @s.rest.size
-  end
-end
diff --git a/spec/ruby/library/stringscanner/shared/terminate.rb b/spec/ruby/library/stringscanner/shared/terminate.rb
deleted file mode 100644
index bf41d097e2..0000000000
--- a/spec/ruby/library/stringscanner/shared/terminate.rb
+++ /dev/null
@@ -1,8 +0,0 @@
-describe :strscan_terminate, shared: true do
-  it "set the scan pointer to the end of the string and clear matching data." do
-    s = StringScanner.new('This is a test')
-    s.send(@method)
-    s.bol?.should be_false
-    s.eos?.should be_true
-  end
-end
diff --git a/spec/ruby/library/stringscanner/size_spec.rb b/spec/ruby/library/stringscanner/size_spec.rb
new file mode 100644
index 0000000000..3e475489e3
--- /dev/null
+++ b/spec/ruby/library/stringscanner/size_spec.rb
@@ -0,0 +1,17 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#size" do
+  before :each do
+    @s = StringScanner.new("This is a test")
+  end
+
+  it "returns the number of captures groups of the last match" do
+    @s.scan(/(.)(.)(.)/)
+    @s.size.should == 4
+  end
+
+  it "returns nil if there is no last match" do
+    @s.size.should == nil
+  end
+end
diff --git a/spec/ruby/library/stringscanner/skip_spec.rb b/spec/ruby/library/stringscanner/skip_spec.rb
index 473361782c..12f5b7781c 100644
--- a/spec/ruby/library/stringscanner/skip_spec.rb
+++ b/spec/ruby/library/stringscanner/skip_spec.rb
@@ -15,4 +15,18 @@ describe "StringScanner#skip" do
     @s.skip(/\s+/).should == nil
     @s.skip(/\d+/).should == nil
   end
+
+  describe "#[] successive call with a capture group name" do
+    it "returns matched substring when matching succeeded" do
+      @s.skip(/(?<a>This)/)
+      @s.should.matched?
+      @s[:a].should == "This"
+    end
+
+    it "returns nil when matching failed" do
+      @s.skip(/(?<a>2008)/)
+      @s.should_not.matched?
+      @s[:a].should be_nil
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/skip_until_spec.rb b/spec/ruby/library/stringscanner/skip_until_spec.rb
index 73eb91b8ad..5d73d8f0b9 100644
--- a/spec/ruby/library/stringscanner/skip_until_spec.rb
+++ b/spec/ruby/library/stringscanner/skip_until_spec.rb
@@ -2,17 +2,131 @@ require_relative '../../spec_helper'
 require 'strscan'
 
 describe "StringScanner#skip_until" do
-  before :each do
+  before do
     @s = StringScanner.new("This is a test")
   end
 
   it "returns the number of bytes advanced and advances the scan pointer until pattern is matched and consumed" do
     @s.skip_until(/a/).should == 9
     @s.pos.should == 9
+  end
+
+  it "sets the last match result" do
+    @s.skip_until(/a/)
+
+    @s.pre_match.should == "This is "
     @s.matched.should == "a"
+    @s.post_match.should == " test"
   end
 
   it "returns nil if no match was found" do
     @s.skip_until(/d+/).should == nil
   end
+
+  version_is StringScanner::Version, ""..."3.1.1" do # ruby_version_is ""..."3.4"
+    it "raises TypeError if given a String" do
+      -> {
+        @s.skip_until('T')
+      }.should raise_error(TypeError, 'wrong argument type String (expected Regexp)')
+    end
+  end
+
+  version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+    it "searches a substring in the rest part of a string if given a String" do
+      @s.skip_until("a").should == 9
+      @s.pos.should == 9
+    end
+
+    # https://github.com/ruby/strscan/issues/131
+    version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.1"
+      it "sets the last match result if given a String" do
+        @s.skip_until("a")
+
+        @s.pre_match.should == ""
+        @s.matched.should == "This is a"
+        @s.post_match.should == " test"
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+      it "sets the last match result if given a String" do
+        @s.skip_until("a")
+
+        @s.pre_match.should == "This is "
+        @s.matched.should == "a"
+        @s.post_match.should == " test"
+      end
+    end
+  end
+
+  describe "#[] successive call with a capture group name" do
+    context "when #scan_until was called with a Regexp pattern" do
+      it "returns matched substring when matching succeeded" do
+        @s.skip_until(/(?<a>This)/)
+        @s.should.matched?
+        @s[:a].should == "This"
+      end
+
+      it "returns nil when matching failed" do
+        @s.skip_until(/(?<a>2008)/)
+        @s.should_not.matched?
+        @s[:a].should be_nil
+      end
+    end
+
+    version_is StringScanner::Version, "3.1.1" do # ruby_version_is "3.4"
+      context "when #skip_until was called with a String pattern" do
+        # https://github.com/ruby/strscan/issues/139
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "returns nil when matching succeeded" do
+            @s.skip_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4.3"
+          it "raises IndexError when matching succeeded" do
+            @s.skip_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+
+        it "returns nil when matching failed" do
+          @s.skip_until("2008")
+          @s.should_not.matched?
+          @s[:a].should be_nil
+        end
+
+        it "returns a matching substring when given Integer index" do
+          @s.skip_until("This")
+          @s[0].should == "This"
+        end
+
+        # https://github.com/ruby/strscan/issues/135
+        version_is StringScanner::Version, "3.1.1"..."3.1.3" do # ruby_version_is "3.4.0"..."3.4.3"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.skip_until("This")
+            @s.should.matched?
+            @s[:a].should be_nil
+          end
+        end
+        version_is StringScanner::Version, "3.1.3" do # ruby_version_is "3.4"
+          it "ignores the previous matching with Regexp" do
+            @s.exist?(/(?<a>This)/)
+            @s.should.matched?
+            @s[:a].should == "This"
+
+            @s.skip_until("This")
+            @s.should.matched?
+            -> { @s[:a] }.should raise_error(IndexError)
+          end
+        end
+      end
+    end
+  end
 end
diff --git a/spec/ruby/library/stringscanner/string_spec.rb b/spec/ruby/library/stringscanner/string_spec.rb
index 28e2f0ed37..cba6bd51dd 100644
--- a/spec/ruby/library/stringscanner/string_spec.rb
+++ b/spec/ruby/library/stringscanner/string_spec.rb
@@ -3,7 +3,7 @@ require 'strscan'
 
 describe "StringScanner#string" do
   before :each do
-    @string = "This is a test"
+    @string = +"This is a test"
     @s = StringScanner.new(@string)
   end
 
diff --git a/spec/ruby/library/stringscanner/terminate_spec.rb b/spec/ruby/library/stringscanner/terminate_spec.rb
index 249023f1ab..3cff5c010c 100644
--- a/spec/ruby/library/stringscanner/terminate_spec.rb
+++ b/spec/ruby/library/stringscanner/terminate_spec.rb
@@ -1,7 +1,11 @@
 require_relative '../../spec_helper'
-require_relative 'shared/terminate'
 require 'strscan'
 
 describe "StringScanner#terminate" do
-    it_behaves_like :strscan_terminate, :terminate
+  it "set the scan pointer to the end of the string and clear matching data." do
+    s = StringScanner.new('This is a test')
+    s.terminate
+    s.should_not.bol?
+    s.should.eos?
+  end
 end
diff --git a/spec/ruby/library/stringscanner/unscan_spec.rb b/spec/ruby/library/stringscanner/unscan_spec.rb
index df0ea43367..b7b4876b8a 100644
--- a/spec/ruby/library/stringscanner/unscan_spec.rb
+++ b/spec/ruby/library/stringscanner/unscan_spec.rb
@@ -21,8 +21,8 @@ describe "StringScanner#unscan" do
     @s.pos.should == pos
   end
 
-  it "raises a ScanError when the previous match had failed" do
-    -> { @s.unscan }.should raise_error(ScanError)
-    -> { @s.scan(/\d/); @s.unscan }.should raise_error(ScanError)
+  it "raises a StringScanner::Error when the previous match had failed" do
+    -> { @s.unscan }.should raise_error(StringScanner::Error)
+    -> { @s.scan(/\d/); @s.unscan }.should raise_error(StringScanner::Error)
   end
 end
diff --git a/spec/ruby/library/stringscanner/values_at_spec.rb b/spec/ruby/library/stringscanner/values_at_spec.rb
new file mode 100644
index 0000000000..14d4a5f6a7
--- /dev/null
+++ b/spec/ruby/library/stringscanner/values_at_spec.rb
@@ -0,0 +1,68 @@
+require_relative '../../spec_helper'
+require 'strscan'
+
+describe "StringScanner#captures" do
+  before do
+    @s = StringScanner.new('Fri Dec 12 1975 14:39')
+  end
+
+  context "when passed a list of Integers" do
+    it "returns an array containing each value given by one of integers" do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+      @s.values_at(0, 1, 2, 3).should == ["Fri Dec 12", "Fri", "Dec", "12"]
+    end
+
+    it "returns nil value for any integer that is out of range" do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+      @s.values_at(4).should == [nil]
+      @s.values_at(-5).should == [nil]
+    end
+  end
+
+  context "when passed names" do
+    it 'slices captures with the given names' do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+      @s.values_at(:wday, :month, :day).should == ["Fri", "Dec", "12"]
+    end
+
+    it 'slices captures with the given String names' do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+      @s.values_at("wday", "month", "day").should == ["Fri", "Dec", "12"]
+    end
+
+    it "raises IndexError when given unknown name" do
+      @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+
+      -> {
+        @s.values_at("foo")
+      }.should raise_error(IndexError, "undefined group name reference: foo")
+    end
+  end
+
+  it 'supports mixing of names and indices' do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+    @s.values_at(1, "wday", 2, "month", 3, "day").should == ["Fri", "Fri", "Dec", "Dec", "12", "12"]
+  end
+
+  it "returns a new empty Array if no arguments given" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+    @s.values_at().should == []
+  end
+
+  it "fails when passed arguments of unsupported types" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\d+)/)
+
+    -> {
+      @s.values_at([])
+    }.should raise_error(TypeError, "no implicit conversion of Array into Integer")
+  end
+
+  it "returns nil if the most recent matching fails" do
+    @s.exist?(/(?<wday>\w+) (?<month>\w+) (?<day>\s+)/)
+    @s.values_at(1, 2, 3).should == nil
+  end
+
+  it "returns nil if there is no any matching done" do
+    @s.values_at(1, 2, 3).should == nil
+  end
+end
diff --git a/spec/ruby/library/syslog/close_spec.rb b/spec/ruby/library/syslog/close_spec.rb
index 8186ecf125..8c3b67c05b 100644
--- a/spec/ruby/library/syslog/close_spec.rb
+++ b/spec/ruby/library/syslog/close_spec.rb
@@ -30,7 +30,7 @@ platform_is_not :windows do
         -> {
           Syslog.open { |s| s.close }
         }.should raise_error(RuntimeError)
-        Syslog.opened?.should == false
+        Syslog.should_not.opened?
       end
 
       it "sets the identity to nil" do
diff --git a/spec/ruby/library/syslog/constants_spec.rb b/spec/ruby/library/syslog/constants_spec.rb
index 2b9524c53d..fc9db47dd8 100644
--- a/spec/ruby/library/syslog/constants_spec.rb
+++ b/spec/ruby/library/syslog/constants_spec.rb
@@ -4,7 +4,7 @@ platform_is_not :windows do
   require 'syslog'
 
   describe "Syslog::Constants" do
-    platform_is_not :windows, :solaris, :aix do
+    platform_is_not :windows, :aix do
       before :all do
         @constants = %w(LOG_AUTHPRIV LOG_USER LOG_LOCAL2 LOG_NOTICE LOG_NDELAY
                       LOG_SYSLOG LOG_ALERT LOG_FTP LOG_LOCAL5 LOG_ERR LOG_AUTH
diff --git a/spec/ruby/library/syslog/ident_spec.rb b/spec/ruby/library/syslog/ident_spec.rb
index e8345ebb49..3b08327140 100644
--- a/spec/ruby/library/syslog/ident_spec.rb
+++ b/spec/ruby/library/syslog/ident_spec.rb
@@ -21,7 +21,7 @@ platform_is_not :windows do
       end
 
       it "returns nil if the log is closed" do
-        Syslog.opened?.should == false
+        Syslog.should_not.opened?
         Syslog.ident.should == nil
       end
 
diff --git a/spec/ruby/library/syslog/log_spec.rb b/spec/ruby/library/syslog/log_spec.rb
index ee62d484ac..0c855b8257 100644
--- a/spec/ruby/library/syslog/log_spec.rb
+++ b/spec/ruby/library/syslog/log_spec.rb
@@ -4,7 +4,7 @@ platform_is_not :windows do
   require 'syslog'
 
   describe "Syslog.log" do
-    platform_is_not :windows, :darwin, :solaris, :aix do
+    platform_is_not :windows, :darwin, :aix, :android do
 
       before :each do
         Syslog.opened?.should be_false
@@ -20,7 +20,7 @@ platform_is_not :windows do
             s.log(Syslog::LOG_ALERT, "Hello")
             s.log(Syslog::LOG_CRIT, "World")
           end
-        }.should output_to_fd("rubyspec: Hello\nrubyspec: World\n", $stderr)
+        }.should output_to_fd(/\Arubyspec(?::| \d+ - -) Hello\nrubyspec(?::| \d+ - -) World\n\z/, $stderr)
       end
 
       it "accepts undefined priorities" do
@@ -29,7 +29,7 @@ platform_is_not :windows do
             s.log(1337, "Hello")
           end
           # use a regex since it'll output unknown facility/priority messages
-        }.should output_to_fd(/rubyspec: Hello/, $stderr)
+        }.should output_to_fd(/rubyspec(?::| \d+ - -) Hello\n\z/, $stderr)
       end
 
       it "fails with TypeError on nil log messages" do
@@ -49,7 +49,7 @@ platform_is_not :windows do
           Syslog.open("rubyspec", Syslog::LOG_PERROR) do |s|
             s.log(Syslog::LOG_ALERT, "%s x %d", "chunky bacon", 2)
           end
-        }.should output_to_fd("rubyspec: chunky bacon x 2\n", $stderr)
+        }.should output_to_fd(/rubyspec(?::| \d+ - -) chunky bacon x 2\n\z/, $stderr)
       end
     end
   end
diff --git a/spec/ruby/library/syslog/mask_spec.rb b/spec/ruby/library/syslog/mask_spec.rb
index 6581f6a756..b3f1250b24 100644
--- a/spec/ruby/library/syslog/mask_spec.rb
+++ b/spec/ruby/library/syslog/mask_spec.rb
@@ -32,7 +32,7 @@ platform_is_not :windows do
       end
 
       it "returns nil if the log is closed" do
-        Syslog.opened?.should == false
+        Syslog.should_not.opened?
         Syslog.mask.should == nil
       end
 
diff --git a/spec/ruby/library/syslog/shared/log.rb b/spec/ruby/library/syslog/shared/log.rb
index b19c2eae0d..9f9302b214 100644
--- a/spec/ruby/library/syslog/shared/log.rb
+++ b/spec/ruby/library/syslog/shared/log.rb
@@ -1,5 +1,5 @@
 describe :syslog_log, shared: true do
-  platform_is_not :windows, :darwin, :solaris, :aix do
+  platform_is_not :windows, :darwin, :aix, :android do
     before :each do
       Syslog.opened?.should be_false
     end
@@ -13,7 +13,7 @@ describe :syslog_log, shared: true do
         Syslog.open("rubyspec", Syslog::LOG_PERROR) do
           Syslog.send(@method, "Hello")
         end
-      }.should output_to_fd("rubyspec: Hello\n", $stderr)
+      }.should output_to_fd(/\Arubyspec(?::| \d+ - -) Hello\n\z/, $stderr)
     end
 
     it "accepts sprintf arguments" do
@@ -22,19 +22,18 @@ describe :syslog_log, shared: true do
           Syslog.send(@method, "Hello %s", "world")
           Syslog.send(@method, "%d dogs", 2)
         end
-      }.should output_to_fd("rubyspec: Hello world\nrubyspec: 2 dogs\n", $stderr)
+      }.should output_to_fd(/\Arubyspec(?::| \d+ - -) Hello world\nrubyspec(?::| \d+ - -) 2 dogs\n\z/, $stderr)
     end
 
     it "works as an alias for Syslog.log" do
       level = Syslog.const_get "LOG_#{@method.to_s.upcase}"
-      response = "rubyspec: Hello\n"
       -> {
         Syslog.open("rubyspec", Syslog::LOG_PERROR) do
           Syslog.send(@method, "Hello")
           Syslog.log(level, "Hello")
         end
         # make sure the same thing is written to $stderr.
-      }.should output_to_fd(response * 2, $stderr)
+      }.should output_to_fd(/\A(?:rubyspec(?::| \d+ - -) Hello\n){2}\z/, $stderr)
     end
   end
 end
diff --git a/spec/ruby/library/tempfile/callback_spec.rb b/spec/ruby/library/tempfile/callback_spec.rb
deleted file mode 100644
index c0b1518326..0000000000
--- a/spec/ruby/library/tempfile/callback_spec.rb
+++ /dev/null
@@ -1,6 +0,0 @@
-require_relative '../../spec_helper'
-require 'tempfile'
-
-describe "Tempfile.callback" do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/library/tempfile/close_spec.rb b/spec/ruby/library/tempfile/close_spec.rb
index 6cd55beecf..db0eae3fa5 100644
--- a/spec/ruby/library/tempfile/close_spec.rb
+++ b/spec/ruby/library/tempfile/close_spec.rb
@@ -18,7 +18,7 @@ describe "Tempfile#close when passed no argument or [false]" do
   it "does not unlink self" do
     path = @tempfile.path
     @tempfile.close
-    File.exist?(path).should be_true
+    File.should.exist?(path)
   end
 end
 
@@ -35,7 +35,7 @@ describe "Tempfile#close when passed [true]" do
   it "unlinks self" do
     path = @tempfile.path
     @tempfile.close(true)
-    File.exist?(path).should be_false
+    File.should_not.exist?(path)
   end
 end
 
@@ -52,6 +52,6 @@ describe "Tempfile#close!" do
   it "unlinks self" do
     path =  @tempfile.path
     @tempfile.close!
-    File.exist?(path).should be_false
+    File.should_not.exist?(path)
   end
 end
diff --git a/spec/ruby/library/tempfile/create_spec.rb b/spec/ruby/library/tempfile/create_spec.rb
new file mode 100644
index 0000000000..74c48bf32a
--- /dev/null
+++ b/spec/ruby/library/tempfile/create_spec.rb
@@ -0,0 +1,176 @@
+require_relative '../../spec_helper'
+require 'tempfile'
+
+describe "Tempfile.create" do
+  after :each do
+    if @tempfile
+      @tempfile.close
+      File.unlink(@tempfile.path) if File.file?(@tempfile.path)
+    end
+  end
+
+  it "returns a new, open regular File instance placed in tmpdir" do
+    @tempfile = Tempfile.create
+    # Unlike Tempfile.open this returns a true File,
+    # but `.should be_an_instance_of(File)` would be true either way.
+    @tempfile.instance_of?(File).should be_true
+
+    @tempfile.should_not.closed?
+    File.file?(@tempfile.path).should be_true
+
+    @tempfile.path.should.start_with?(Dir.tmpdir)
+    @tempfile.path.should_not == "#{Dir.tmpdir}/"
+  end
+
+  it "returns file in w+ mode" do
+    @tempfile = Tempfile.create
+    @tempfile << "Test!\nMore test!"
+    @tempfile.rewind
+    @tempfile.read.should == "Test!\nMore test!"
+
+    # Not "a+" mode, which would write at the end of the file.
+    @tempfile.rewind
+    @tempfile.print "Trust"
+    @tempfile.rewind
+    @tempfile.read.should == "Trust\nMore test!"
+  end
+
+  platform_is_not :windows do
+    it "returns a private, readable and writable file" do
+      @tempfile = Tempfile.create
+      stat = @tempfile.stat
+      stat.should.readable?
+      stat.should.writable?
+      stat.should_not.executable?
+      stat.should_not.world_readable?
+      stat.should_not.world_writable?
+    end
+  end
+
+  platform_is :windows do
+    it "returns a public, readable and writable file" do
+      @tempfile = Tempfile.create
+      stat = @tempfile.stat
+      stat.should.readable?
+      stat.should.writable?
+      stat.should_not.executable?
+      stat.should.world_readable?
+      stat.should.world_writable?
+    end
+  end
+
+  context "when called with a block" do
+    it "returns the value of the block" do
+      value = Tempfile.create do |tempfile|
+        tempfile << "Test!"
+        "return"
+      end
+      value.should == "return"
+    end
+
+    it "closes and unlinks file after block execution" do
+      Tempfile.create do |tempfile|
+        @tempfile = tempfile
+        @tempfile.should_not.closed?
+        File.exist?(@tempfile.path).should be_true
+      end
+
+      @tempfile.should.closed?
+      File.exist?(@tempfile.path).should be_false
+    end
+  end
+
+  context "when called with a single positional argument" do
+    it "uses a String as a prefix for the filename" do
+      @tempfile = Tempfile.create("create_spec")
+      @tempfile.path.should.start_with?("#{Dir.tmpdir}/create_spec")
+      @tempfile.path.should_not == "#{Dir.tmpdir}/create_spec"
+    end
+
+    it "uses an array of one String as a prefix for the filename" do
+      @tempfile = Tempfile.create(["create_spec"])
+      @tempfile.path.should.start_with?("#{Dir.tmpdir}/create_spec")
+      @tempfile.path.should_not == "#{Dir.tmpdir}/create_spec"
+    end
+
+    it "uses an array of two Strings as a prefix and suffix for the filename" do
+      @tempfile = Tempfile.create(["create_spec", ".temp"])
+      @tempfile.path.should.start_with?("#{Dir.tmpdir}/create_spec")
+      @tempfile.path.should.end_with?(".temp")
+    end
+
+    it "ignores excessive array elements after the first two" do
+      @tempfile = Tempfile.create(["create_spec", ".temp", :".txt"])
+      @tempfile.path.should.start_with?("#{Dir.tmpdir}/create_spec")
+      @tempfile.path.should.end_with?(".temp")
+    end
+
+    it "raises ArgumentError if passed something else than a String or an array of Strings" do
+      -> { Tempfile.create(:create_spec) }.should raise_error(ArgumentError, "unexpected prefix: :create_spec")
+      -> { Tempfile.create([:create_spec]) }.should raise_error(ArgumentError, "unexpected prefix: :create_spec")
+      -> { Tempfile.create(["create_spec", :temp]) }.should raise_error(ArgumentError, "unexpected suffix: :temp")
+    end
+  end
+
+  context "when called with a second positional argument" do
+    it "uses it as a directory for the tempfile" do
+      @tempfile = Tempfile.create("create_spec", "./")
+      @tempfile.path.should.start_with?("./create_spec")
+    end
+
+    it "raises TypeError if argument can not be converted to a String" do
+      -> { Tempfile.create("create_spec", :temp) }.should raise_error(TypeError, "no implicit conversion of Symbol into String")
+    end
+  end
+
+  context "when called with a mode option" do
+    it "ORs it with the default mode, forcing it to be readable and writable" do
+      @tempfile = Tempfile.create(mode: File::RDONLY)
+      @tempfile.puts "test"
+      @tempfile.rewind
+      @tempfile.read.should == "test\n"
+    end
+
+    it "raises NoMethodError if passed a String mode" do
+      -> { Tempfile.create(mode: "wb") }.should raise_error(NoMethodError, /undefined method ['`]|' for .+String/)
+    end
+  end
+
+  ruby_version_is "3.4" do
+    context "when called with anonymous: true" do
+      it "returns an already unlinked File without a proper path" do
+        @tempfile = Tempfile.create(anonymous: true)
+        @tempfile.should_not.closed?
+        @tempfile.path.should == "#{Dir.tmpdir}/"
+        File.file?(@tempfile.path).should be_false
+      end
+
+      it "unlinks file before calling the block" do
+        Tempfile.create(anonymous: true) do |tempfile|
+          @tempfile = tempfile
+          @tempfile.should_not.closed?
+          @tempfile.path.should == "#{Dir.tmpdir}/"
+          File.file?(@tempfile.path).should be_false
+        end
+        @tempfile.should.closed?
+      end
+    end
+
+    context "when called with anonymous: false" do
+      it "returns a usual File with a path" do
+        @tempfile = Tempfile.create(anonymous: false)
+        @tempfile.should_not.closed?
+        @tempfile.path.should.start_with?(Dir.tmpdir)
+        File.file?(@tempfile.path).should be_true
+      end
+    end
+  end
+
+  context "when called with other options" do
+    it "passes them along to File.open" do
+      @tempfile = Tempfile.create(encoding: "IBM037:IBM037", binmode: true)
+      @tempfile.external_encoding.should == Encoding.find("IBM037")
+      @tempfile.binmode?.should be_true
+    end
+  end
+end
diff --git a/spec/ruby/library/tempfile/initialize_spec.rb b/spec/ruby/library/tempfile/initialize_spec.rb
index 3b20e8ad4b..f2e786d7d8 100644
--- a/spec/ruby/library/tempfile/initialize_spec.rb
+++ b/spec/ruby/library/tempfile/initialize_spec.rb
@@ -12,7 +12,7 @@ describe "Tempfile#initialize" do
 
   it "opens a new tempfile with the passed name in the passed directory" do
     @tempfile.send(:initialize, "basename", tmp(""))
-    File.exist?(@tempfile.path).should be_true
+    File.should.exist?(@tempfile.path)
 
     tmpdir = tmp("")
     path = @tempfile.path
diff --git a/spec/ruby/library/tempfile/shared/unlink.rb b/spec/ruby/library/tempfile/shared/unlink.rb
index 2b575fd391..e821228d70 100644
--- a/spec/ruby/library/tempfile/shared/unlink.rb
+++ b/spec/ruby/library/tempfile/shared/unlink.rb
@@ -7,6 +7,6 @@ describe :tempfile_unlink, shared: true do
     @tempfile.close
     path = @tempfile.path
     @tempfile.send(@method)
-    File.exist?(path).should be_false
+    File.should_not.exist?(path)
   end
 end
diff --git a/spec/ruby/library/time/iso8601_spec.rb b/spec/ruby/library/time/iso8601_spec.rb
index 4a9eb45613..ab35ab25d6 100644
--- a/spec/ruby/library/time/iso8601_spec.rb
+++ b/spec/ruby/library/time/iso8601_spec.rb
@@ -2,6 +2,6 @@ require_relative '../../spec_helper'
 require_relative 'shared/xmlschema'
 require 'time'
 
-describe "Time.xmlschema" do
-  it_behaves_like :time_xmlschema, :iso8601
+describe "Time.iso8601" do
+  it_behaves_like :time_library_xmlschema, :iso8601
 end
diff --git a/spec/ruby/library/time/shared/rfc2822.rb b/spec/ruby/library/time/shared/rfc2822.rb
index d99f1f76de..e460d655a6 100644
--- a/spec/ruby/library/time/shared/rfc2822.rb
+++ b/spec/ruby/library/time/shared/rfc2822.rb
@@ -1,33 +1,33 @@
 describe :time_rfc2822, shared: true do
   it "parses RFC-822 strings" do
     t1 = (Time.utc(1976, 8, 26, 14, 30) + 4 * 3600)
-    t2 = Time.rfc2822("26 Aug 76 14:30 EDT")
+    t2 = Time.send(@method, "26 Aug 76 14:30 EDT")
     t1.should == t2
 
     t3 = Time.utc(1976, 8, 27, 9, 32) + 7 * 3600
-    t4 = Time.rfc2822("27 Aug 76 09:32 PDT")
+    t4 = Time.send(@method, "27 Aug 76 09:32 PDT")
     t3.should == t4
   end
 
   it "parses RFC-2822 strings" do
     t1 = Time.utc(1997, 11, 21, 9, 55, 6) + 6 * 3600
-    t2 = Time.rfc2822("Fri, 21 Nov 1997 09:55:06 -0600")
+    t2 = Time.send(@method, "Fri, 21 Nov 1997 09:55:06 -0600")
     t1.should == t2
 
     t3 = Time.utc(2003, 7, 1, 10, 52, 37) - 2 * 3600
-    t4 = Time.rfc2822("Tue, 1 Jul 2003 10:52:37 +0200")
+    t4 = Time.send(@method, "Tue, 1 Jul 2003 10:52:37 +0200")
     t3.should == t4
 
     t5 = Time.utc(1997, 11, 21, 10, 1, 10) + 6 * 3600
-    t6 = Time.rfc2822("Fri, 21 Nov 1997 10:01:10 -0600")
+    t6 = Time.send(@method, "Fri, 21 Nov 1997 10:01:10 -0600")
     t5.should == t6
 
     t7 = Time.utc(1997, 11, 21, 11, 0, 0) + 6 * 3600
-    t8 = Time.rfc2822("Fri, 21 Nov 1997 11:00:00 -0600")
+    t8 = Time.send(@method, "Fri, 21 Nov 1997 11:00:00 -0600")
     t7.should == t8
 
     t9 = Time.utc(1997, 11, 24, 14, 22, 1) + 8 * 3600
-    t10 = Time.rfc2822("Mon, 24 Nov 1997 14:22:01 -0800")
+    t10 = Time.send(@method, "Mon, 24 Nov 1997 14:22:01 -0800")
     t9.should == t10
 
     begin
@@ -36,11 +36,11 @@ describe :time_rfc2822, shared: true do
       # ignore
     else
       t11 = Time.utc(1969, 2, 13, 23, 32, 54) + 3 * 3600 + 30 * 60
-      t12 = Time.rfc2822("Thu, 13 Feb 1969 23:32:54 -0330")
+      t12 = Time.send(@method, "Thu, 13 Feb 1969 23:32:54 -0330")
       t11.should == t12
 
       t13 = Time.utc(1969, 2, 13, 23, 32, 0) + 3 * 3600 + 30 * 60
-      t14 = Time.rfc2822(" Thu,
+      t14 = Time.send(@method, " Thu,
       13
         Feb
           1969
@@ -50,16 +50,16 @@ describe :time_rfc2822, shared: true do
     end
 
     t15 = Time.utc(1997, 11, 21, 9, 55, 6)
-    t16 = Time.rfc2822("21 Nov 97 09:55:06 GMT")
+    t16 = Time.send(@method, "21 Nov 97 09:55:06 GMT")
     t15.should == t16
 
     t17 = Time.utc(1997, 11, 21, 9, 55, 6) + 6 * 3600
-    t18 = Time.rfc2822("Fri, 21 Nov 1997 09 :   55  :  06 -0600")
+    t18 = Time.send(@method, "Fri, 21 Nov 1997 09 :   55  :  06 -0600")
     t17.should == t18
 
     -> {
       # inner comment is not supported.
-      Time.rfc2822("Fri, 21 Nov 1997 09(comment):   55  :  06 -0600")
+      Time.send(@method, "Fri, 21 Nov 1997 09(comment):   55  :  06 -0600")
     }.should raise_error(ArgumentError)
   end
 end
diff --git a/spec/ruby/library/time/shared/xmlschema.rb b/spec/ruby/library/time/shared/xmlschema.rb
index 44d33cda7e..0002886ca5 100644
--- a/spec/ruby/library/time/shared/xmlschema.rb
+++ b/spec/ruby/library/time/shared/xmlschema.rb
@@ -1,24 +1,24 @@
-describe :time_xmlschema, shared: true do
+describe :time_library_xmlschema, shared: true do
   it "parses ISO-8601 strings" do
     t = Time.utc(1985, 4, 12, 23, 20, 50, 520000)
     s = "1985-04-12T23:20:50.52Z"
-    t.should == Time.xmlschema(s)
-    #s.should == t.xmlschema(2)
+    t.should == Time.send(@method, s)
+    #s.should == t.send(@method, 2)
 
     t = Time.utc(1996, 12, 20, 0, 39, 57)
     s = "1996-12-19T16:39:57-08:00"
-    t.should == Time.xmlschema(s)
+    t.should == Time.send(@method, s)
     # There is no way to generate time string with arbitrary timezone.
     s = "1996-12-20T00:39:57Z"
-    t.should == Time.xmlschema(s)
-    #assert_equal(s, t.xmlschema)
+    t.should == Time.send(@method, s)
+    #assert_equal(s, t.send(@method))
 
     t = Time.utc(1990, 12, 31, 23, 59, 60)
     s = "1990-12-31T23:59:60Z"
-    t.should == Time.xmlschema(s)
+    t.should == Time.send(@method, s)
     # leap second is representable only if timezone file has it.
     s = "1990-12-31T15:59:60-08:00"
-    t.should == Time.xmlschema(s)
+    t.should == Time.send(@method, s)
 
     begin
       Time.at(-1)
@@ -27,27 +27,27 @@ describe :time_xmlschema, shared: true do
     else
       t = Time.utc(1937, 1, 1, 11, 40, 27, 870000)
       s = "1937-01-01T12:00:27.87+00:20"
-      t.should == Time.xmlschema(s)
+      t.should == Time.send(@method, s)
     end
 
     # more
 
-    # (Time.utc(1999, 5, 31, 13, 20, 0) + 5 * 3600).should == Time.xmlschema("1999-05-31T13:20:00-05:00")
-    # (Time.local(2000, 1, 20, 12, 0, 0)).should == Time.xmlschema("2000-01-20T12:00:00")
-    # (Time.utc(2000, 1, 20, 12, 0, 0)).should == Time.xmlschema("2000-01-20T12:00:00Z")
-    # (Time.utc(2000, 1, 20, 12, 0, 0) - 12 * 3600).should == Time.xmlschema("2000-01-20T12:00:00+12:00")
-    # (Time.utc(2000, 1, 20, 12, 0, 0) + 13 * 3600).should == Time.xmlschema("2000-01-20T12:00:00-13:00")
-    # (Time.utc(2000, 3, 4, 23, 0, 0) - 3 * 3600).should == Time.xmlschema("2000-03-04T23:00:00+03:00")
-    # (Time.utc(2000, 3, 4, 20, 0, 0)).should == Time.xmlschema("2000-03-04T20:00:00Z")
-    # (Time.local(2000, 1, 15, 0, 0, 0)).should == Time.xmlschema("2000-01-15T00:00:00")
-    # (Time.local(2000, 2, 15, 0, 0, 0)).should == Time.xmlschema("2000-02-15T00:00:00")
-    # (Time.local(2000, 1, 15, 12, 0, 0)).should == Time.xmlschema("2000-01-15T12:00:00")
-    # (Time.utc(2000, 1, 16, 12, 0, 0)).should == Time.xmlschema("2000-01-16T12:00:00Z")
-    # (Time.local(2000, 1, 1, 12, 0, 0)).should == Time.xmlschema("2000-01-01T12:00:00")
-    # (Time.utc(1999, 12, 31, 23, 0, 0)).should == Time.xmlschema("1999-12-31T23:00:00Z")
-    # (Time.local(2000, 1, 16, 12, 0, 0)).should == Time.xmlschema("2000-01-16T12:00:00")
-    # (Time.local(2000, 1, 16, 0, 0, 0)).should == Time.xmlschema("2000-01-16T00:00:00")
-    # (Time.utc(2000, 1, 12, 12, 13, 14)).should == Time.xmlschema("2000-01-12T12:13:14Z")
-    # (Time.utc(2001, 4, 17, 19, 23, 17, 300000)).should == Time.xmlschema("2001-04-17T19:23:17.3Z")
+    # (Time.utc(1999, 5, 31, 13, 20, 0) + 5 * 3600).should == Time.send(@method, "1999-05-31T13:20:00-05:00")
+    # (Time.local(2000, 1, 20, 12, 0, 0)).should == Time.send(@method, "2000-01-20T12:00:00")
+    # (Time.utc(2000, 1, 20, 12, 0, 0)).should == Time.send(@method, "2000-01-20T12:00:00Z")
+    # (Time.utc(2000, 1, 20, 12, 0, 0) - 12 * 3600).should == Time.send(@method, "2000-01-20T12:00:00+12:00")
+    # (Time.utc(2000, 1, 20, 12, 0, 0) + 13 * 3600).should == Time.send(@method, "2000-01-20T12:00:00-13:00")
+    # (Time.utc(2000, 3, 4, 23, 0, 0) - 3 * 3600).should == Time.send(@method, "2000-03-04T23:00:00+03:00")
+    # (Time.utc(2000, 3, 4, 20, 0, 0)).should == Time.send(@method, "2000-03-04T20:00:00Z")
+    # (Time.local(2000, 1, 15, 0, 0, 0)).should == Time.send(@method, "2000-01-15T00:00:00")
+    # (Time.local(2000, 2, 15, 0, 0, 0)).should == Time.send(@method, "2000-02-15T00:00:00")
+    # (Time.local(2000, 1, 15, 12, 0, 0)).should == Time.send(@method, "2000-01-15T12:00:00")
+    # (Time.utc(2000, 1, 16, 12, 0, 0)).should == Time.send(@method, "2000-01-16T12:00:00Z")
+    # (Time.local(2000, 1, 1, 12, 0, 0)).should == Time.send(@method, "2000-01-01T12:00:00")
+    # (Time.utc(1999, 12, 31, 23, 0, 0)).should == Time.send(@method, "1999-12-31T23:00:00Z")
+    # (Time.local(2000, 1, 16, 12, 0, 0)).should == Time.send(@method, "2000-01-16T12:00:00")
+    # (Time.local(2000, 1, 16, 0, 0, 0)).should == Time.send(@method, "2000-01-16T00:00:00")
+    # (Time.utc(2000, 1, 12, 12, 13, 14)).should == Time.send(@method, "2000-01-12T12:13:14Z")
+    # (Time.utc(2001, 4, 17, 19, 23, 17, 300000)).should == Time.send(@method, "2001-04-17T19:23:17.3Z")
   end
 end
diff --git a/spec/ruby/library/time/to_date_spec.rb b/spec/ruby/library/time/to_date_spec.rb
deleted file mode 100644
index baeafe0847..0000000000
--- a/spec/ruby/library/time/to_date_spec.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-
-require_relative '../../spec_helper'
-require 'time'
-
-describe "Time#to_date" do
-  it "yields accurate julian date for ambiguous pre-Gregorian reform value" do
-    Time.utc(1582, 10, 4).to_date.jd.should == Date::ITALY - 11 # 2299150j
-  end
-
-  it "yields accurate julian date for Julian-Gregorian gap value" do
-    Time.utc(1582, 10, 14).to_date.jd.should == Date::ITALY - 1 # 2299160j
-  end
-
-  it "yields accurate julian date for post-Gregorian reform value" do
-    Time.utc(1582, 10, 15).to_date.jd.should == Date::ITALY # 2299161j
-  end
-
-  it "yields same julian day regardless of UTC time value" do
-    Time.utc(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
-    Time.utc(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
-  end
-
-  it "yields same julian day regardless of local time or zone" do
-
-    with_timezone("Pacific/Pago_Pago", -11) do
-      Time.local(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
-      Time.local(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
-    end
-
-    with_timezone("Asia/Kamchatka", +12) do
-      Time.local(1582, 10, 15, 00, 00, 00).to_date.jd.should == Date::ITALY
-      Time.local(1582, 10, 15, 23, 59, 59).to_date.jd.should == Date::ITALY
-    end
-
-  end
-
-  it "yields date with default Calendar reform day" do
-    Time.utc(1582, 10,  4).to_date.start.should == Date::ITALY
-    Time.utc(1582, 10, 14).to_date.start.should == Date::ITALY
-    Time.utc(1582, 10, 15).to_date.start.should == Date::ITALY
-  end
-end
diff --git a/spec/ruby/library/time/to_datetime_spec.rb b/spec/ruby/library/time/to_datetime_spec.rb
deleted file mode 100644
index 0e37a61108..0000000000
--- a/spec/ruby/library/time/to_datetime_spec.rb
+++ /dev/null
@@ -1,27 +0,0 @@
-require_relative '../../spec_helper'
-require 'time'
-
-describe "Time#to_datetime" do
-  it "returns a DateTime representing the same instant" do
-    time = Time.utc(3, 12, 31, 23, 58, 59)
-    datetime = time.to_datetime
-    datetime.year.should == 3
-    datetime.month.should == 12
-    datetime.day.should == 31
-    datetime.hour.should == 23
-    datetime.min.should == 58
-    datetime.sec.should == 59
-  end
-
-  it "roundtrips" do
-    time = Time.utc(3, 12, 31, 23, 58, 59)
-    datetime = time.to_datetime
-    datetime.to_time.utc.should == time
-  end
-
-  it "yields a DateTime with the default Calendar reform day" do
-    Time.utc(1582, 10,  4, 1, 2, 3).to_datetime.start.should == Date::ITALY
-    Time.utc(1582, 10, 14, 1, 2, 3).to_datetime.start.should == Date::ITALY
-    Time.utc(1582, 10, 15, 1, 2, 3).to_datetime.start.should == Date::ITALY
-  end
-end
diff --git a/spec/ruby/library/time/xmlschema_spec.rb b/spec/ruby/library/time/xmlschema_spec.rb
index 4279311199..ff3c864a02 100644
--- a/spec/ruby/library/time/xmlschema_spec.rb
+++ b/spec/ruby/library/time/xmlschema_spec.rb
@@ -3,5 +3,5 @@ require_relative 'shared/xmlschema'
 require 'time'
 
 describe "Time.xmlschema" do
-  it_behaves_like :time_xmlschema, :xmlschema
+  it_behaves_like :time_library_xmlschema, :xmlschema
 end
diff --git a/spec/ruby/library/timeout/timeout_spec.rb b/spec/ruby/library/timeout/timeout_spec.rb
index a9a60fdeb9..e16bcaea6a 100644
--- a/spec/ruby/library/timeout/timeout_spec.rb
+++ b/spec/ruby/library/timeout/timeout_spec.rb
@@ -18,9 +18,33 @@ describe "Timeout.timeout" do
     end.should raise_error(StandardError)
   end
 
+  it "raises specified error type with specified message when it times out" do
+    -> do
+      Timeout.timeout(1, StandardError, "foobar") do
+        sleep
+      end
+    end.should raise_error(StandardError, "foobar")
+  end
+
+  it "raises specified error type with a default message when it times out if message is nil" do
+    -> do
+      Timeout.timeout(1, StandardError, nil) do
+        sleep
+      end
+    end.should raise_error(StandardError, "execution expired")
+  end
+
   it "returns back the last value in the block" do
     Timeout.timeout(1) do
       42
     end.should == 42
   end
+
+  ruby_version_is "3.4" do
+    it "raises an ArgumentError when provided with a negative duration" do
+      -> {
+        Timeout.timeout(-1)
+      }.should raise_error(ArgumentError, "Timeout sec must be a non-negative number")
+    end
+  end
 end
diff --git a/spec/ruby/library/tmpdir/dir/mktmpdir_spec.rb b/spec/ruby/library/tmpdir/dir/mktmpdir_spec.rb
index eab86818bd..8165c2d8a8 100644
--- a/spec/ruby/library/tmpdir/dir/mktmpdir_spec.rb
+++ b/spec/ruby/library/tmpdir/dir/mktmpdir_spec.rb
@@ -39,7 +39,7 @@ describe "Dir.mktmpdir when passed a block" do
     Dir.mktmpdir do |path|
       @tmpdir = path
       called = true
-      path.start_with?(@real_tmp_root).should be_true
+      path.should.start_with?(@real_tmp_root)
     end
     called.should be_true
   end
diff --git a/spec/ruby/library/uri/generic/host_spec.rb b/spec/ruby/library/uri/generic/host_spec.rb
index f2076d2bc1..4a5a162512 100644
--- a/spec/ruby/library/uri/generic/host_spec.rb
+++ b/spec/ruby/library/uri/generic/host_spec.rb
@@ -2,7 +2,10 @@ require_relative '../../../spec_helper'
 require 'uri'
 
 describe "URI::Generic#host" do
-  it "needs to be reviewed for spec completeness"
+  # https://hackerone.com/reports/156615
+  it "returns empty string when host is empty" do
+    URI.parse('http:////foo.com').host.should == ''
+  end
 end
 
 describe "URI::Generic#host=" do
diff --git a/spec/ruby/library/uri/generic/to_s_spec.rb b/spec/ruby/library/uri/generic/to_s_spec.rb
index 8c90d7645b..c436ee3c03 100644
--- a/spec/ruby/library/uri/generic/to_s_spec.rb
+++ b/spec/ruby/library/uri/generic/to_s_spec.rb
@@ -2,5 +2,8 @@ require_relative '../../../spec_helper'
 require 'uri'
 
 describe "URI::Generic#to_s" do
-  it "needs to be reviewed for spec completeness"
+  # https://hackerone.com/reports/156615
+  it "preserves / characters when host is empty" do
+    URI('http:///foo.com').to_s.should == 'http:///foo.com'
+  end
 end
diff --git a/spec/ruby/library/uri/select_spec.rb b/spec/ruby/library/uri/select_spec.rb
index c2eb6f8733..839b68b3a1 100644
--- a/spec/ruby/library/uri/select_spec.rb
+++ b/spec/ruby/library/uri/select_spec.rb
@@ -15,12 +15,8 @@ describe "URI#select" do
   end
 
   it "raises an ArgumentError if a component is requested that isn't valid under the given scheme" do
-    [
-      -> {URI("mailto:spam@mailinator.com").select(:path)},
-      -> {URI("http://blog.blag.web").select(:typecode)},
-    ].each do |select_lambda|
-      select_lambda.should raise_error(ArgumentError)
-    end
+    -> { URI("mailto:spam@mailinator.com").select(:path) }.should raise_error(ArgumentError)
+    -> { URI("http://blog.blag.web").select(:typecode) }.should raise_error(ArgumentError)
   end
 
   it "raises an ArgumentError if given strings rather than symbols" do
diff --git a/spec/ruby/library/uri/set_component_spec.rb b/spec/ruby/library/uri/set_component_spec.rb
index 642a5d6fcf..1d4165c535 100644
--- a/spec/ruby/library/uri/set_component_spec.rb
+++ b/spec/ruby/library/uri/set_component_spec.rb
@@ -6,25 +6,27 @@ describe "URI#select" do
   it "conforms to the MatzRuby tests" do
     uri = URI.parse('http://foo:bar@baz')
     (uri.user = 'oof').should == 'oof'
-    uri.to_s.should == 'http://oof:bar@baz'
-    (uri.password = 'rab').should == 'rab'
-    uri.to_s.should == 'http://oof:rab@baz'
-    (uri.userinfo = 'foo').should == 'foo'
-    uri.to_s.should == 'http://foo:rab@baz'
-    (uri.userinfo = ['foo', 'bar']).should == ['foo', 'bar']
-    uri.to_s.should == 'http://foo:bar@baz'
-    (uri.userinfo = ['foo']).should == ['foo']
-    uri.to_s.should == 'http://foo:bar@baz'
-    (uri.host = 'zab').should == 'zab'
-    uri.to_s.should == 'http://foo:bar@zab'
-    (uri.port = 8080).should == 8080
-    uri.to_s.should == 'http://foo:bar@zab:8080'
-    (uri.path = '/').should == '/'
-    uri.to_s.should == 'http://foo:bar@zab:8080/'
-    (uri.query = 'a=1').should == 'a=1'
-    uri.to_s.should == 'http://foo:bar@zab:8080/?a=1'
-    (uri.fragment = 'b123').should == 'b123'
-    uri.to_s.should == 'http://foo:bar@zab:8080/?a=1#b123'
+    version_is(URI::VERSION, "1.0.4") do
+      uri.to_s.should == 'http://oof@baz'
+      (uri.password = 'rab').should == 'rab'
+      uri.to_s.should == 'http://oof:rab@baz'
+      (uri.userinfo = 'foo').should == 'foo'
+      uri.to_s.should == 'http://foo@baz'
+      (uri.userinfo = ['foo', 'bar']).should == ['foo', 'bar']
+      uri.to_s.should == 'http://foo:bar@baz'
+      (uri.userinfo = ['foo']).should == ['foo']
+      uri.to_s.should == 'http://foo@baz'
+      (uri.host = 'zab').should == 'zab'
+      uri.to_s.should == 'http://zab'
+      (uri.port = 8080).should == 8080
+      uri.to_s.should == 'http://zab:8080'
+      (uri.path = '/').should == '/'
+      uri.to_s.should == 'http://zab:8080/'
+      (uri.query = 'a=1').should == 'a=1'
+      uri.to_s.should == 'http://zab:8080/?a=1'
+      (uri.fragment = 'b123').should == 'b123'
+      uri.to_s.should == 'http://zab:8080/?a=1#b123'
+    end
 
     uri = URI.parse('http://example.com')
     -> { uri.password = 'bar' }.should raise_error(URI::InvalidURIError)
diff --git a/spec/ruby/library/uri/shared/parse.rb b/spec/ruby/library/uri/shared/parse.rb
index 87e1ee933e..c5057b6c4b 100644
--- a/spec/ruby/library/uri/shared/parse.rb
+++ b/spec/ruby/library/uri/shared/parse.rb
@@ -192,8 +192,15 @@ describe :uri_parse, shared: true do
     file.should be_kind_of(URI::Generic)
   end
 
-  it "raises errors on malformed URIs" do
-    -> { @object.parse('http://a_b:80/') }.should raise_error(URI::InvalidURIError)
-    -> { @object.parse('http://a_b/') }.should raise_error(URI::InvalidURIError)
+  if URI::DEFAULT_PARSER == URI::RFC2396_Parser
+    it "raises errors on malformed URIs" do
+      -> { @object.parse('http://a_b:80/') }.should raise_error(URI::InvalidURIError)
+      -> { @object.parse('http://a_b/') }.should raise_error(URI::InvalidURIError)
+    end
+  elsif URI::DEFAULT_PARSER == URI::RFC3986_Parser
+    it "does not raise errors on URIs contained underscore" do
+      -> { @object.parse('http://a_b:80/') }.should_not raise_error(URI::InvalidURIError)
+      -> { @object.parse('http://a_b/') }.should_not raise_error(URI::InvalidURIError)
+    end
   end
 end
diff --git a/spec/ruby/library/weakref/fixtures/classes.rb b/spec/ruby/library/weakref/fixtures/classes.rb
index 560c58b041..041afab14d 100644
--- a/spec/ruby/library/weakref/fixtures/classes.rb
+++ b/spec/ruby/library/weakref/fixtures/classes.rb
@@ -13,9 +13,11 @@ class WeakRefSpec
   def self.make_dead_weakref
     weaks = []
     weak = nil
-    10_000.times do
+    1000.times do
       weaks << make_weakref
-      GC.start
+    end
+
+    1000.times do
       GC.start
       break if weak = weaks.find { |w| !w.weakref_alive? }
     end
diff --git a/spec/ruby/library/weakref/weakref_alive_spec.rb b/spec/ruby/library/weakref/weakref_alive_spec.rb
index 173ea01485..1ebf9c1ee3 100644
--- a/spec/ruby/library/weakref/weakref_alive_spec.rb
+++ b/spec/ruby/library/weakref/weakref_alive_spec.rb
@@ -5,7 +5,7 @@ describe "WeakRef#weakref_alive?" do
   it "returns true if the object is reachable" do
     obj = Object.new
     ref = WeakRef.new(obj)
-    ref.weakref_alive?.should == true
+    ref.weakref_alive?.should be_true
   end
 
   it "returns a falsy value if the object is no longer reachable" do
diff --git a/spec/ruby/library/win32ole/fixtures/classes.rb b/spec/ruby/library/win32ole/fixtures/classes.rb
index f61cf6ba69..5a16fcca45 100644
--- a/spec/ruby/library/win32ole/fixtures/classes.rb
+++ b/spec/ruby/library/win32ole/fixtures/classes.rb
@@ -1,14 +1,25 @@
 require 'win32ole'
 
+# win32ole deprecated constants like WIN32OLE_TYPELIB in Ruby 3.4
+# but only added the replacements like WIN32OLE::TypeLib in Ruby 3.4.
+# So we use the new-style constants in specs to avoid deprecation warnings
+# and we define the new-style constants as the old ones if they don't exist yet.
+WIN32OLE::TypeLib ||= WIN32OLE_TYPELIB
+WIN32OLE::RuntimeError ||= WIN32OLERuntimeError
+WIN32OLE::Method ||= WIN32OLE_METHOD
+WIN32OLE::Type ||= WIN32OLE_TYPE
+WIN32OLE::Event ||= WIN32OLE_EVENT
+WIN32OLE::Param ||= WIN32OLE_PARAM
+
 module WIN32OLESpecs
-  MSXML_AVAILABLE = WIN32OLE_TYPELIB.typelibs.any? { |t| t.name.start_with?('Microsoft XML') }
-  SYSTEM_MONITOR_CONTROL_AVAILABLE = WIN32OLE_TYPELIB.typelibs.any? { |t| t.name.start_with?('System Monitor Control') }
+  MSXML_AVAILABLE = WIN32OLE::TypeLib.typelibs.any? { |t| t.name.start_with?('Microsoft XML') }
+  SYSTEM_MONITOR_CONTROL_AVAILABLE = WIN32OLE::TypeLib.typelibs.any? { |t| t.name.start_with?('System Monitor Control') }
 
   def self.new_ole(name)
     tries = 0
     begin
       WIN32OLE.new(name)
-    rescue WIN32OLERuntimeError => e
+    rescue WIN32OLE::RuntimeError => e
       if tries < 3
         tries += 1
         $stderr.puts "WIN32OLESpecs#new_ole retry (#{tries}): #{e.class}: #{e.message}"
diff --git a/spec/ruby/library/win32ole/win32ole/_getproperty_spec.rb b/spec/ruby/library/win32ole/win32ole/_getproperty_spec.rb
index 940eebfb91..52cb978bea 100644
--- a/spec/ruby/library/win32ole/win32ole/_getproperty_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/_getproperty_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/_invoke_spec.rb b/spec/ruby/library/win32ole/win32ole/_invoke_spec.rb
index 91f5091d24..994c2e6d36 100644
--- a/spec/ruby/library/win32ole/win32ole/_invoke_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/_invoke_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/codepage_spec.rb b/spec/ruby/library/win32ole/win32ole/codepage_spec.rb
index 4e0cf5ca55..07e93646ac 100644
--- a/spec/ruby/library/win32ole/win32ole/codepage_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/codepage_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/connect_spec.rb b/spec/ruby/library/win32ole/win32ole/connect_spec.rb
index 72dceb1572..ac0976ddc1 100644
--- a/spec/ruby/library/win32ole/win32ole/connect_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/connect_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/const_load_spec.rb b/spec/ruby/library/win32ole/win32ole/const_load_spec.rb
index cacc7a2b22..2099c4aa66 100644
--- a/spec/ruby/library/win32ole/win32ole/const_load_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/const_load_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/constants_spec.rb b/spec/ruby/library/win32ole/win32ole/constants_spec.rb
index 978b7ade92..8533741440 100644
--- a/spec/ruby/library/win32ole/win32ole/constants_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/constants_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/create_guid_spec.rb b/spec/ruby/library/win32ole/win32ole/create_guid_spec.rb
index 2e18b6ab11..8aa853df9e 100644
--- a/spec/ruby/library/win32ole/win32ole/create_guid_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/create_guid_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/invoke_spec.rb b/spec/ruby/library/win32ole/win32ole/invoke_spec.rb
index 08a5156e05..d6ff7fade3 100644
--- a/spec/ruby/library/win32ole/win32ole/invoke_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/invoke_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
diff --git a/spec/ruby/library/win32ole/win32ole/locale_spec.rb b/spec/ruby/library/win32ole/win32ole/locale_spec.rb
index 75a82ddd7f..89e84d8038 100644
--- a/spec/ruby/library/win32ole/win32ole/locale_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/locale_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -12,14 +13,14 @@ platform_is :windows do
       begin
         begin
           WIN32OLE.locale = 1041
-        rescue WIN32OLERuntimeError
+        rescue WIN32OLE::RuntimeError
           STDERR.puts("\n#{__FILE__}:#{__LINE__}:#{self.class.name}.test_s_locale_set is skipped(Japanese locale is not installed)")
           return
         end
 
         WIN32OLE.locale.should == 1041
         WIN32OLE.locale = WIN32OLE::LOCALE_SYSTEM_DEFAULT
-        -> { WIN32OLE.locale = 111 }.should raise_error WIN32OLERuntimeError
+        -> { WIN32OLE.locale = 111 }.should raise_error WIN32OLE::RuntimeError
         WIN32OLE.locale.should == WIN32OLE::LOCALE_SYSTEM_DEFAULT
       ensure
         WIN32OLE.locale.should == WIN32OLE::LOCALE_SYSTEM_DEFAULT
diff --git a/spec/ruby/library/win32ole/win32ole/new_spec.rb b/spec/ruby/library/win32ole/win32ole/new_spec.rb
index 6b717195f1..b2a0a5da18 100644
--- a/spec/ruby/library/win32ole/win32ole/new_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/new_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -16,8 +17,8 @@ platform_is :windows do
       -> { WIN32OLESpecs.new_ole(42) }.should raise_error( TypeError )
     end
 
-    it "raises WIN32OLERuntimeError if invalid string is given" do
-      -> { WIN32OLE.new('foo') }.should raise_error( WIN32OLERuntimeError )
+    it "raises WIN32OLE::RuntimeError if invalid string is given" do
+      -> { WIN32OLE.new('foo') }.should raise_error( WIN32OLE::RuntimeError )
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole/ole_func_methods_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_func_methods_spec.rb
index 75748182fe..b846685518 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_func_methods_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_func_methods_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -10,8 +11,8 @@ platform_is :windows do
       -> { @dict.ole_func_methods(1) }.should raise_error ArgumentError
     end
 
-    it "returns an array of WIN32OLE_METHODs" do
-      @dict.ole_func_methods.all? { |m| m.kind_of? WIN32OLE_METHOD }.should be_true
+    it "returns an array of WIN32OLE::Methods" do
+      @dict.ole_func_methods.all? { |m| m.kind_of? WIN32OLE::Method }.should be_true
     end
 
     it "contains a 'AddRef' method for Scripting Dictionary" do
diff --git a/spec/ruby/library/win32ole/win32ole/ole_get_methods_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_get_methods_spec.rb
index a991624a23..b6e7f960bb 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_get_methods_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_get_methods_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -7,8 +8,8 @@ platform_is :windows do
       @win32ole = WIN32OLESpecs.new_ole('Shell.Application')
     end
 
-    it "returns an array of WIN32OLE_METHOD objects" do
-      @win32ole.ole_get_methods.all? {|m| m.kind_of? WIN32OLE_METHOD}.should be_true
+    it "returns an array of WIN32OLE::Method objects" do
+      @win32ole.ole_get_methods.all? {|m| m.kind_of? WIN32OLE::Method}.should be_true
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole/ole_method_help_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_method_help_spec.rb
index 8a26d79a20..9cb3f9e6cf 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_method_help_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_method_help_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   require_relative 'shared/ole_method'
diff --git a/spec/ruby/library/win32ole/win32ole/ole_method_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_method_spec.rb
index f82a212f5d..e48ff8d905 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_method_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_method_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   require_relative 'shared/ole_method'
diff --git a/spec/ruby/library/win32ole/win32ole/ole_methods_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_methods_spec.rb
index 5ac9ae9cfa..92c4363f78 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_methods_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_methods_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -10,8 +11,8 @@ platform_is :windows do
       -> { @dict.ole_methods(1) }.should raise_error ArgumentError
     end
 
-    it "returns an array of WIN32OLE_METHODs" do
-      @dict.ole_methods.all? { |m| m.kind_of? WIN32OLE_METHOD }.should be_true
+    it "returns an array of WIN32OLE::Methods" do
+      @dict.ole_methods.all? { |m| m.kind_of? WIN32OLE::Method }.should be_true
     end
 
     it "contains a 'AddRef' method for Scripting Dictionary" do
diff --git a/spec/ruby/library/win32ole/win32ole/ole_obj_help_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_obj_help_spec.rb
index ef8944ee39..f298f19dba 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_obj_help_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_obj_help_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 
 platform_is :windows do
   require_relative '../fixtures/classes'
@@ -11,8 +12,8 @@ platform_is :windows do
       -> { @dict.ole_obj_help(1) }.should raise_error ArgumentError
     end
 
-    it "returns an instance of WIN32OLE_TYPE" do
-      @dict.ole_obj_help.kind_of?(WIN32OLE_TYPE).should be_true
+    it "returns an instance of WIN32OLE::Type" do
+      @dict.ole_obj_help.kind_of?(WIN32OLE::Type).should be_true
     end
   end
 end
diff --git a/spec/ruby/library/win32ole/win32ole/ole_put_methods_spec.rb b/spec/ruby/library/win32ole/win32ole/ole_put_methods_spec.rb
index 727291e9f0..2b46ae47de 100644
--- a/spec/ruby/library/win32ole/win32ole/ole_put_methods_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/ole_put_methods_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
@@ -10,8 +11,8 @@ platform_is :windows do
       -> { @dict.ole_put_methods(1) }.should raise_error ArgumentError
     end
 
-    it "returns an array of WIN32OLE_METHODs" do
-      @dict.ole_put_methods.all? { |m| m.kind_of? WIN32OLE_METHOD }.should be_true
+    it "returns an array of WIN32OLE::Methods" do
+      @dict.ole_put_methods.all? { |m| m.kind_of? WIN32OLE::Method }.should be_true
     end
 
     it "contains a 'Key' method for Scripting Dictionary" do
diff --git a/spec/ruby/library/win32ole/win32ole/setproperty_spec.rb b/spec/ruby/library/win32ole/win32ole/setproperty_spec.rb
index 7409823f20..bacdee63da 100644
--- a/spec/ruby/library/win32ole/win32ole/setproperty_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole/setproperty_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   require_relative 'shared/setproperty'
diff --git a/spec/ruby/library/win32ole/win32ole/shared/ole_method.rb b/spec/ruby/library/win32ole/win32ole/shared/ole_method.rb
index f1fd8713a4..bae424a604 100644
--- a/spec/ruby/library/win32ole/win32ole/shared/ole_method.rb
+++ b/spec/ruby/library/win32ole/win32ole/shared/ole_method.rb
@@ -10,9 +10,9 @@ platform_is :windows do
       -> { @dict.send(@method) }.should raise_error ArgumentError
     end
 
-    it "returns the WIN32OLE_METHOD 'Add' if given 'Add'" do
+    it "returns the WIN32OLE::Method 'Add' if given 'Add'" do
       result = @dict.send(@method, "Add")
-      result.kind_of?(WIN32OLE_METHOD).should be_true
+      result.kind_of?(WIN32OLE::Method).should be_true
       result.name.should == 'Add'
     end
   end
diff --git a/spec/ruby/library/win32ole/win32ole_event/new_spec.rb b/spec/ruby/library/win32ole/win32ole_event/new_spec.rb
index a1a1612393..4efd4c3e0f 100644
--- a/spec/ruby/library/win32ole/win32ole_event/new_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_event/new_spec.rb
@@ -1,8 +1,9 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
 
   guard -> { WIN32OLESpecs::MSXML_AVAILABLE } do
-    describe "WIN32OLE_EVENT.new" do
+    describe "WIN32OLE::Event.new" do
       before :all do
         @xml_dom = WIN32OLESpecs.new_ole('MSXML.DOMDocument')
       end
@@ -12,21 +13,21 @@ platform_is :windows do
       end
 
       it "raises TypeError given invalid argument" do
-        -> { WIN32OLE_EVENT.new "A" }.should raise_error TypeError
+        -> { WIN32OLE::Event.new "A" }.should raise_error TypeError
       end
 
       it "raises RuntimeError if event does not exist" do
-        -> { WIN32OLE_EVENT.new(@xml_dom, 'A') }.should raise_error RuntimeError
+        -> { WIN32OLE::Event.new(@xml_dom, 'A') }.should raise_error RuntimeError
       end
 
       it "raises RuntimeError if OLE object has no events" do
         dict = WIN32OLESpecs.new_ole('Scripting.Dictionary')
-        -> { WIN32OLE_EVENT.new(dict) }.should raise_error RuntimeError
+        -> { WIN32OLE::Event.new(dict) }.should raise_error RuntimeError
       end
 
-      it "creates WIN32OLE_EVENT object" do
-        ev = WIN32OLE_EVENT.new(@xml_dom)
-        ev.should be_kind_of WIN32OLE_EVENT
+      it "creates WIN32OLE::Event object" do
+        ev = WIN32OLE::Event.new(@xml_dom)
+        ev.should be_kind_of WIN32OLE::Event
       end
     end
   end
diff --git a/spec/ruby/library/win32ole/win32ole_event/on_event_spec.rb b/spec/ruby/library/win32ole/win32ole_event/on_event_spec.rb
index feb26b0637..acc7d2d6b6 100644
--- a/spec/ruby/library/win32ole/win32ole_event/on_event_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_event/on_event_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   guard -> { WIN32OLESpecs::MSXML_AVAILABLE } do
@@ -14,7 +15,7 @@ platform_is :windows do
       @event_spec_alt = "spec_alt"
     end
 
-    describe "WIN32OLE_EVENT#on_event" do
+    describe "WIN32OLE::Event#on_event" do
       before :all do
         @fn_xml = File.absolute_path "../fixtures/event.xml", __dir__
       end
@@ -22,7 +23,7 @@ platform_is :windows do
       before :each do
         @xml_dom = WIN32OLESpecs.new_ole 'MSXML.DOMDocument'
         @xml_dom.async = true
-        @ev = WIN32OLE_EVENT.new @xml_dom
+        @ev = WIN32OLE::Event.new @xml_dom
         @event_global   = ''
         @event_specific = ''
         @event_spec_alt = ''
@@ -36,21 +37,21 @@ platform_is :windows do
       it "sets global event handler properly, and the handler is invoked by event loop" do
         @ev.on_event { |*args| handler_global(*args) }
         @xml_dom.loadXML "<program><name>Ruby</name><version>trunk</version></program>"
-        WIN32OLE_EVENT.message_loop
+        WIN32OLE::Event.message_loop
         @event_global.should =~ /onreadystatechange/
       end
 
       it "accepts a String argument and the handler is invoked by event loop" do
         @ev.on_event("onreadystatechange") { |*args| @event = 'foo' }
         @xml_dom.loadXML "<program><name>Ruby</name><version>trunk</version></program>"
-        WIN32OLE_EVENT.message_loop
+        WIN32OLE::Event.message_loop
         @event.should =~ /foo/
       end
 
       it "accepts a Symbol argument and the handler is invoked by event loop" do
         @ev.on_event(:onreadystatechange) { |*args| @event = 'bar' }
         @xml_dom.loadXML "<program><name>Ruby</name><version>trunk</version></program>"
-        WIN32OLE_EVENT.message_loop
+        WIN32OLE::Event.message_loop
         @event.should =~ /bar/
       end
 
@@ -59,7 +60,7 @@ platform_is :windows do
         @ev.on_event("onreadystatechange") { |*args| handler_specific(*args) }
         @ev.on_event("onreadystatechange") { |*args| handler_spec_alt(*args) }
         @xml_dom.load @fn_xml
-        WIN32OLE_EVENT.message_loop
+        WIN32OLE::Event.message_loop
         @event_global.should == 'ondataavailable'
         @event_global.should_not =~ /onreadystatechange/
         @event_specific.should == ''
diff --git a/spec/ruby/library/win32ole/win32ole_method/dispid_spec.rb b/spec/ruby/library/win32ole/win32ole_method/dispid_spec.rb
index 69068683b7..e5f55f2d38 100644
--- a/spec/ruby/library/win32ole/win32ole_method/dispid_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/dispid_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#dispid" do
+  describe "WIN32OLE::Method#dispid" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m = WIN32OLE_METHOD.new(ole_type, "namespace")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m = WIN32OLE::Method.new(ole_type, "namespace")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/event_interface_spec.rb b/spec/ruby/library/win32ole/win32ole_method/event_interface_spec.rb
index 70c8b30cca..bea47348ee 100644
--- a/spec/ruby/library/win32ole/win32ole_method/event_interface_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/event_interface_spec.rb
@@ -1,13 +1,14 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   guard -> { WIN32OLESpecs::SYSTEM_MONITOR_CONTROL_AVAILABLE } do
 
-    describe "WIN32OLE_METHOD#event_interface" do
+    describe "WIN32OLE::Method#event_interface" do
       before :each do
-        ole_type = WIN32OLE_TYPE.new("System Monitor Control", "SystemMonitor")
-        @on_dbl_click_method = WIN32OLE_METHOD.new(ole_type, "OnDblClick")
-        ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-        @namespace_method = WIN32OLE_METHOD.new(ole_type, "namespace")
+        ole_type = WIN32OLE::Type.new("System Monitor Control", "SystemMonitor")
+        @on_dbl_click_method = WIN32OLE::Method.new(ole_type, "OnDblClick")
+        ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+        @namespace_method = WIN32OLE::Method.new(ole_type, "namespace")
       end
 
       it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/event_spec.rb b/spec/ruby/library/win32ole/win32ole_method/event_spec.rb
index c41f8fe99d..5a94cf5ce6 100644
--- a/spec/ruby/library/win32ole/win32ole_method/event_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/event_spec.rb
@@ -1,11 +1,12 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require_relative '../fixtures/classes'
   guard -> { WIN32OLESpecs::SYSTEM_MONITOR_CONTROL_AVAILABLE } do
 
-    describe "WIN32OLE_METHOD#event?" do
+    describe "WIN32OLE::Method#event?" do
       before :each do
-        ole_type = WIN32OLE_TYPE.new("System Monitor Control", "SystemMonitor")
-        @on_dbl_click_method = WIN32OLE_METHOD.new(ole_type, "OnDblClick")
+        ole_type = WIN32OLE::Type.new("System Monitor Control", "SystemMonitor")
+        @on_dbl_click_method = WIN32OLE::Method.new(ole_type, "OnDblClick")
       end
 
       it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/helpcontext_spec.rb b/spec/ruby/library/win32ole/win32ole_method/helpcontext_spec.rb
index 21b3ae8bde..83f34b9c10 100644
--- a/spec/ruby/library/win32ole/win32ole_method/helpcontext_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/helpcontext_spec.rb
@@ -1,12 +1,13 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#helpcontext" do
+  describe "WIN32OLE::Method#helpcontext" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      @get_file_version = WIN32OLE_METHOD.new(ole_type, "GetFileVersion")
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      @get_file_version = WIN32OLE::Method.new(ole_type, "GetFileVersion")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/helpfile_spec.rb b/spec/ruby/library/win32ole/win32ole_method/helpfile_spec.rb
index b6d0a19a37..9cf9d63d3b 100644
--- a/spec/ruby/library/win32ole/win32ole_method/helpfile_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/helpfile_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#helpfile" do
+  describe "WIN32OLE::Method#helpfile" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/helpstring_spec.rb b/spec/ruby/library/win32ole/win32ole_method/helpstring_spec.rb
index 9f940fd4a0..5ae4a5e090 100644
--- a/spec/ruby/library/win32ole/win32ole_method/helpstring_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/helpstring_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#helpstring" do
+  describe "WIN32OLE::Method#helpstring" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/invkind_spec.rb b/spec/ruby/library/win32ole/win32ole_method/invkind_spec.rb
index 7fff479daf..06acbb58a5 100644
--- a/spec/ruby/library/win32ole/win32ole_method/invkind_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/invkind_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#invkind" do
+  describe "WIN32OLE::Method#invkind" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/invoke_kind_spec.rb b/spec/ruby/library/win32ole/win32ole_method/invoke_kind_spec.rb
index e8638abd91..0e97ec3305 100644
--- a/spec/ruby/library/win32ole/win32ole_method/invoke_kind_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/invoke_kind_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#invoke_kind" do
+  describe "WIN32OLE::Method#invoke_kind" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/name_spec.rb b/spec/ruby/library/win32ole/win32ole_method/name_spec.rb
index cd5404fc54..6e2e233a62 100644
--- a/spec/ruby/library/win32ole/win32ole_method/name_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/name_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#name" do
+  describe "WIN32OLE::Method#name" do
     it_behaves_like :win32ole_method_name, :name
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_method/new_spec.rb b/spec/ruby/library/win32ole/win32ole_method/new_spec.rb
index 8ebf93b992..46186ae566 100644
--- a/spec/ruby/library/win32ole/win32ole_method/new_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/new_spec.rb
@@ -1,31 +1,32 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD.new" do
+  describe "WIN32OLE::Method.new" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     it "raises TypeError when given non-strings" do
-      -> { WIN32OLE_METHOD.new(1, 2) }.should raise_error TypeError
+      -> { WIN32OLE::Method.new(1, 2) }.should raise_error TypeError
     end
 
     it "raises ArgumentError if only 1 argument is given" do
-      -> { WIN32OLE_METHOD.new("hello") }.should raise_error ArgumentError
-      -> { WIN32OLE_METHOD.new(@ole_type) }.should raise_error ArgumentError
+      -> { WIN32OLE::Method.new("hello") }.should raise_error ArgumentError
+      -> { WIN32OLE::Method.new(@ole_type) }.should raise_error ArgumentError
     end
 
-    it "returns a valid WIN32OLE_METHOD object" do
-      WIN32OLE_METHOD.new(@ole_type, "Open").should be_kind_of WIN32OLE_METHOD
-      WIN32OLE_METHOD.new(@ole_type, "open").should be_kind_of WIN32OLE_METHOD
+    it "returns a valid WIN32OLE::Method object" do
+      WIN32OLE::Method.new(@ole_type, "Open").should be_kind_of WIN32OLE::Method
+      WIN32OLE::Method.new(@ole_type, "open").should be_kind_of WIN32OLE::Method
     end
 
-    it "raises WIN32OLERuntimeError if the method does not exist" do
-      -> { WIN32OLE_METHOD.new(@ole_type, "NonexistentMethod") }.should raise_error WIN32OLERuntimeError
+    it "raises WIN32OLE::RuntimeError if the method does not exist" do
+      -> { WIN32OLE::Method.new(@ole_type, "NonexistentMethod") }.should raise_error WIN32OLE::RuntimeError
     end
 
     it "raises TypeError if second argument is not a String" do
-      -> { WIN32OLE_METHOD.new(@ole_type, 5) }.should raise_error TypeError
+      -> { WIN32OLE::Method.new(@ole_type, 5) }.should raise_error TypeError
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_method/offset_vtbl_spec.rb b/spec/ruby/library/win32ole/win32ole_method/offset_vtbl_spec.rb
index 8e50c39787..3c80cb3c2a 100644
--- a/spec/ruby/library/win32ole/win32ole_method/offset_vtbl_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/offset_vtbl_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#offset_vtbl" do
+  describe "WIN32OLE::Method#offset_vtbl" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/params_spec.rb b/spec/ruby/library/win32ole/win32ole_method/params_spec.rb
index 2f8da3d45b..0b1b4595a3 100644
--- a/spec/ruby/library/win32ole/win32ole_method/params_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/params_spec.rb
@@ -1,12 +1,13 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#params" do
+  describe "WIN32OLE::Method#params" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
@@ -18,8 +19,8 @@ platform_is :windows do
       @m_file_name.params.should be_empty
     end
 
-    it "returns 4-element array of WIN32OLE_PARAM for Shell's 'BrowseForFolder' method" do
-      @m_browse_for_folder.params.all? { |p| p.kind_of? WIN32OLE_PARAM }.should be_true
+    it "returns 4-element array of WIN32OLE::Param for Shell's 'BrowseForFolder' method" do
+      @m_browse_for_folder.params.all? { |p| p.kind_of? WIN32OLE::Param }.should be_true
       @m_browse_for_folder.params.size == 4
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_method/return_type_detail_spec.rb b/spec/ruby/library/win32ole/win32ole_method/return_type_detail_spec.rb
index f8ce3e1b3a..c3725bfef2 100644
--- a/spec/ruby/library/win32ole/win32ole_method/return_type_detail_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/return_type_detail_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#return_type_detail" do
+  describe "WIN32OLE::Method#return_type_detail" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/return_type_spec.rb b/spec/ruby/library/win32ole/win32ole_method/return_type_spec.rb
index 58e26df77b..9e5a1eb1df 100644
--- a/spec/ruby/library/win32ole/win32ole_method/return_type_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/return_type_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#return_type" do
+  describe "WIN32OLE::Method#return_type" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/return_vtype_spec.rb b/spec/ruby/library/win32ole/win32ole_method/return_vtype_spec.rb
index dc159dd09e..34fd135b8c 100644
--- a/spec/ruby/library/win32ole/win32ole_method/return_vtype_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/return_vtype_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#return_vtype" do
+  describe "WIN32OLE::Method#return_vtype" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/shared/name.rb b/spec/ruby/library/win32ole/win32ole_method/shared/name.rb
index ddaff4011b..7e2197ca5a 100644
--- a/spec/ruby/library/win32ole/win32ole_method/shared/name.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/shared/name.rb
@@ -3,8 +3,8 @@ platform_is :windows do
 
   describe :win32ole_method_name, shared: true do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "File")
-      @m_file_name = WIN32OLE_METHOD.new(ole_type, "name")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "File")
+      @m_file_name = WIN32OLE::Method.new(ole_type, "name")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/size_opt_params_spec.rb b/spec/ruby/library/win32ole/win32ole_method/size_opt_params_spec.rb
index a38fe5c681..38cb21ccef 100644
--- a/spec/ruby/library/win32ole/win32ole_method/size_opt_params_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/size_opt_params_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#size_opt_params" do
+  describe "WIN32OLE::Method#size_opt_params" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/size_params_spec.rb b/spec/ruby/library/win32ole/win32ole_method/size_params_spec.rb
index 0c5a94c338..5d0a35a0ef 100644
--- a/spec/ruby/library/win32ole/win32ole_method/size_params_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/size_params_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#size_params" do
+  describe "WIN32OLE::Method#size_params" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_method/to_s_spec.rb b/spec/ruby/library/win32ole/win32ole_method/to_s_spec.rb
index ecb3c08038..cdcc4525b1 100644
--- a/spec/ruby/library/win32ole/win32ole_method/to_s_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/to_s_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#name" do
+  describe "WIN32OLE::Method#name" do
     it_behaves_like :win32ole_method_name, :to_s
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_method/visible_spec.rb b/spec/ruby/library/win32ole/win32ole_method/visible_spec.rb
index 918b6ef782..2f02c15c8b 100644
--- a/spec/ruby/library/win32ole/win32ole_method/visible_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_method/visible_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_METHOD#visible?" do
+  describe "WIN32OLE::Method#visible?" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      @m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      @m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_param/default_spec.rb b/spec/ruby/library/win32ole/win32ole_param/default_spec.rb
index af08c84782..a37b03866d 100644
--- a/spec/ruby/library/win32ole/win32ole_param/default_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/default_spec.rb
@@ -1,14 +1,15 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#default" do
+  describe "WIN32OLE::Param#default" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      m_browse_for_folder = WIN32OLE_METHOD.new(ole_type, "BrowseForFolder")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      m_browse_for_folder = WIN32OLE::Method.new(ole_type, "BrowseForFolder")
       @params = m_browse_for_folder.params
 
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type, "CopyFile")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
@@ -16,7 +17,7 @@ platform_is :windows do
       -> { @params[0].default(1) }.should raise_error ArgumentError
     end
 
-    it "returns nil for each of WIN32OLE_PARAM for Shell's 'BrowseForFolder' method" do
+    it "returns nil for each of WIN32OLE::Param for Shell's 'BrowseForFolder' method" do
       @params.each do |p|
         p.default.should be_nil
       end
diff --git a/spec/ruby/library/win32ole/win32ole_param/input_spec.rb b/spec/ruby/library/win32ole/win32ole_param/input_spec.rb
index a0022fef13..d7e27d7739 100644
--- a/spec/ruby/library/win32ole/win32ole_param/input_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/input_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#input?" do
+  describe "WIN32OLE::Param#input?" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type, "CopyFile")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
@@ -13,7 +14,7 @@ platform_is :windows do
     end
 
     it "returns true for 3rd parameter of FileSystemObject's 'CopyFile' method" do
-      @param_overwritefiles.input?.should == true
+      @param_overwritefiles.should.input?
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_param/name_spec.rb b/spec/ruby/library/win32ole/win32ole_param/name_spec.rb
index 0c20c24720..2c3474ffb3 100644
--- a/spec/ruby/library/win32ole/win32ole_param/name_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/name_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#name" do
+  describe "WIN32OLE::Param#name" do
     it_behaves_like :win32ole_param_name, :name
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_param/ole_type_detail_spec.rb b/spec/ruby/library/win32ole/win32ole_param/ole_type_detail_spec.rb
index e683d1c16e..e3379dbf3e 100644
--- a/spec/ruby/library/win32ole/win32ole_param/ole_type_detail_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/ole_type_detail_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#ole_type_detail" do
+  describe "WIN32OLE::Param#ole_type_detail" do
     before :each do
-      ole_type_detail = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type_detail, "CopyFile")
+      ole_type_detail = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type_detail, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_param/ole_type_spec.rb b/spec/ruby/library/win32ole/win32ole_param/ole_type_spec.rb
index b9a3639c3e..a7b6666807 100644
--- a/spec/ruby/library/win32ole/win32ole_param/ole_type_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/ole_type_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#ole_type" do
+  describe "WIN32OLE::Param#ole_type" do
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type, "CopyFile")
+      ole_type = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_param/optional_spec.rb b/spec/ruby/library/win32ole/win32ole_param/optional_spec.rb
index 3fb9dc1867..50e95fc77f 100644
--- a/spec/ruby/library/win32ole/win32ole_param/optional_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/optional_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#optional?" do
+  describe "WIN32OLE::Param#optional?" do
     before :each do
-      ole_type_detail = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type_detail, "CopyFile")
+      ole_type_detail = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type_detail, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_param/retval_spec.rb b/spec/ruby/library/win32ole/win32ole_param/retval_spec.rb
index f5546e79e5..fa4a09ea0c 100644
--- a/spec/ruby/library/win32ole/win32ole_param/retval_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/retval_spec.rb
@@ -1,10 +1,11 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#retval?" do
+  describe "WIN32OLE::Param#retval?" do
     before :each do
-      ole_type_detail = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type_detail, "CopyFile")
+      ole_type_detail = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type_detail, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_param/shared/name.rb b/spec/ruby/library/win32ole/win32ole_param/shared/name.rb
index 043bc32856..56ff24ddc8 100644
--- a/spec/ruby/library/win32ole/win32ole_param/shared/name.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/shared/name.rb
@@ -3,8 +3,8 @@ platform_is :windows do
 
   describe :win32ole_param_name, shared: true do
     before :each do
-      ole_type_detail = WIN32OLE_TYPE.new("Microsoft Scripting Runtime", "FileSystemObject")
-      m_copyfile = WIN32OLE_METHOD.new(ole_type_detail, "CopyFile")
+      ole_type_detail = WIN32OLE::Type.new("Microsoft Scripting Runtime", "FileSystemObject")
+      m_copyfile = WIN32OLE::Method.new(ole_type_detail, "CopyFile")
       @param_overwritefiles = m_copyfile.params[2]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_param/to_s_spec.rb b/spec/ruby/library/win32ole/win32ole_param/to_s_spec.rb
index 5b4b4c1c80..c59f426692 100644
--- a/spec/ruby/library/win32ole/win32ole_param/to_s_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_param/to_s_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_PARAM#to_s" do
+  describe "WIN32OLE::Param#to_s" do
     it_behaves_like :win32ole_param_name, :to_s
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/guid_spec.rb b/spec/ruby/library/win32ole/win32ole_type/guid_spec.rb
index 25907c8e32..e574a945ad 100644
--- a/spec/ruby/library/win32ole/win32ole_type/guid_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/guid_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#guid for Shell Controls" do
+  describe "WIN32OLE::Type#guid for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/helpcontext_spec.rb b/spec/ruby/library/win32ole/win32ole_type/helpcontext_spec.rb
index d436835188..35911fec52 100644
--- a/spec/ruby/library/win32ole/win32ole_type/helpcontext_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/helpcontext_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#helpcontext for Shell Controls" do
+  describe "WIN32OLE::Type#helpcontext for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/helpfile_spec.rb b/spec/ruby/library/win32ole/win32ole_type/helpfile_spec.rb
index 01e6945138..7bd61a1c40 100644
--- a/spec/ruby/library/win32ole/win32ole_type/helpfile_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/helpfile_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#helpfile for Shell Controls" do
+  describe "WIN32OLE::Type#helpfile for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/helpstring_spec.rb b/spec/ruby/library/win32ole/win32ole_type/helpstring_spec.rb
index 3bd2cbe5dd..940475b25e 100644
--- a/spec/ruby/library/win32ole/win32ole_type/helpstring_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/helpstring_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#helpstring for Shell Controls" do
+  describe "WIN32OLE::Type#helpstring for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/major_version_spec.rb b/spec/ruby/library/win32ole/win32ole_type/major_version_spec.rb
index 7dae16617d..598e5bcef8 100644
--- a/spec/ruby/library/win32ole/win32ole_type/major_version_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/major_version_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#major_version for Shell Controls" do
+  describe "WIN32OLE::Type#major_version for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/minor_version_spec.rb b/spec/ruby/library/win32ole/win32ole_type/minor_version_spec.rb
index ff412dd100..59cfb94012 100644
--- a/spec/ruby/library/win32ole/win32ole_type/minor_version_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/minor_version_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#minor_version for Shell Controls" do
+  describe "WIN32OLE::Type#minor_version for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/name_spec.rb b/spec/ruby/library/win32ole/win32ole_type/name_spec.rb
index b7a28c553a..4cc3426872 100644
--- a/spec/ruby/library/win32ole/win32ole_type/name_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/name_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#name" do
+  describe "WIN32OLE::Type#name" do
     it_behaves_like :win32ole_type_name, :name
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/new_spec.rb b/spec/ruby/library/win32ole/win32ole_type/new_spec.rb
index fab690c2dd..185a235940 100644
--- a/spec/ruby/library/win32ole/win32ole_type/new_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/new_spec.rb
@@ -1,36 +1,40 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE.new" do
+  describe "WIN32OLE::Type.new" do
     it "raises ArgumentError with no argument" do
-      -> { WIN32OLE_TYPE.new }.should raise_error ArgumentError
+      -> { WIN32OLE::Type.new }.should raise_error ArgumentError
     end
 
     it "raises ArgumentError with invalid string" do
-      -> { WIN32OLE_TYPE.new("foo") }.should raise_error ArgumentError
+      -> { WIN32OLE::Type.new("foo") }.should raise_error ArgumentError
     end
 
     it "raises TypeError if second argument is not a String" do
-      -> { WIN32OLE_TYPE.new(1,2) }.should raise_error TypeError
-      -> { WIN32OLE_TYPE.new('Microsoft Shell Controls And Automation',2) }.
-      should raise_error TypeError
+      -> { WIN32OLE::Type.new(1,2) }.should raise_error TypeError
+      -> {
+        WIN32OLE::Type.new('Microsoft Shell Controls And Automation',2)
+      }.should raise_error TypeError
     end
 
-    it "raise WIN32OLERuntimeError if OLE object specified is not found" do
-      -> { WIN32OLE_TYPE.new('Microsoft Shell Controls And Automation','foo') }.
-      should raise_error WIN32OLERuntimeError
-      -> { WIN32OLE_TYPE.new('Microsoft Shell Controls And Automation','Application') }.
-      should raise_error WIN32OLERuntimeError
+    it "raise WIN32OLE::RuntimeError if OLE object specified is not found" do
+      -> {
+        WIN32OLE::Type.new('Microsoft Shell Controls And Automation','foo')
+      }.should raise_error WIN32OLE::RuntimeError
+      -> {
+        WIN32OLE::Type.new('Microsoft Shell Controls And Automation','Application')
+      }.should raise_error WIN32OLE::RuntimeError
     end
 
-    it "creates WIN32OLE_TYPE object from name and valid type" do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
-      ole_type.should be_kind_of WIN32OLE_TYPE
+    it "creates WIN32OLE::Type object from name and valid type" do
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
+      ole_type.should be_kind_of WIN32OLE::Type
     end
 
-    it "creates WIN32OLE_TYPE object from CLSID and valid type" do
-      ole_type2 = WIN32OLE_TYPE.new("{13709620-C279-11CE-A49E-444553540000}", "Shell")
-      ole_type2.should be_kind_of WIN32OLE_TYPE
+    it "creates WIN32OLE::Type object from CLSID and valid type" do
+      ole_type2 = WIN32OLE::Type.new("{13709620-C279-11CE-A49E-444553540000}", "Shell")
+      ole_type2.should be_kind_of WIN32OLE::Type
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/ole_classes_spec.rb b/spec/ruby/library/win32ole/win32ole_type/ole_classes_spec.rb
index 0ce0fc98a4..ed14e37a95 100644
--- a/spec/ruby/library/win32ole/win32ole_type/ole_classes_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/ole_classes_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE.ole_classes for Shell Controls" do
+  describe "WIN32OLE::Type.ole_classes for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
@@ -11,7 +12,7 @@ platform_is :windows do
     end
 
     it "returns array of WIN32OLE_TYPEs" do
-      WIN32OLE_TYPE.ole_classes("Microsoft Shell Controls And Automation").all? {|e| e.kind_of? WIN32OLE_TYPE }.should be_true
+      WIN32OLE::Type.ole_classes("Microsoft Shell Controls And Automation").all? {|e| e.kind_of? WIN32OLE::Type }.should be_true
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/ole_methods_spec.rb b/spec/ruby/library/win32ole/win32ole_type/ole_methods_spec.rb
index 9265549d20..0c031abaa6 100644
--- a/spec/ruby/library/win32ole/win32ole_type/ole_methods_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/ole_methods_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#ole_methods for Shell Controls" do
+  describe "WIN32OLE::Type#ole_methods for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
@@ -11,7 +12,7 @@ platform_is :windows do
     end
 
     it "returns an Integer" do
-      @ole_type.ole_methods.all? { |m| m.kind_of? WIN32OLE_METHOD }.should be_true
+      @ole_type.ole_methods.all? { |m| m.kind_of? WIN32OLE::Method }.should be_true
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/ole_type_spec.rb b/spec/ruby/library/win32ole/win32ole_type/ole_type_spec.rb
index 2bc19aa85e..49c1902f8c 100644
--- a/spec/ruby/library/win32ole/win32ole_type/ole_type_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/ole_type_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#ole_type for Shell Controls" do
+  describe "WIN32OLE::Type#ole_type for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/progid_spec.rb b/spec/ruby/library/win32ole/win32ole_type/progid_spec.rb
index f0d80ba39e..9a700426d9 100644
--- a/spec/ruby/library/win32ole/win32ole_type/progid_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/progid_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#progid for Shell Controls" do
+  describe "WIN32OLE::Type#progid for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/progids_spec.rb b/spec/ruby/library/win32ole/win32ole_type/progids_spec.rb
index 19d8bf56e0..b1b57960cd 100644
--- a/spec/ruby/library/win32ole/win32ole_type/progids_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/progids_spec.rb
@@ -1,13 +1,14 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE.progids" do
+  describe "WIN32OLE::Type.progids" do
     it "raises ArgumentError if an argument is given" do
-      -> { WIN32OLE_TYPE.progids(1) }.should raise_error ArgumentError
+      -> { WIN32OLE::Type.progids(1) }.should raise_error ArgumentError
     end
 
     it "returns an array containing 'Shell.Explorer'" do
-      WIN32OLE_TYPE.progids().include?('Shell.Explorer').should be_true
+      WIN32OLE::Type.progids().include?('Shell.Explorer').should be_true
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/shared/name.rb b/spec/ruby/library/win32ole/win32ole_type/shared/name.rb
index 6f37446b23..efae7aeec1 100644
--- a/spec/ruby/library/win32ole/win32ole_type/shared/name.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/shared/name.rb
@@ -3,7 +3,7 @@ platform_is :windows do
 
   describe :win32ole_type_name, shared: true do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
     end
 
     it "raises ArgumentError if argument is given" do
diff --git a/spec/ruby/library/win32ole/win32ole_type/src_type_spec.rb b/spec/ruby/library/win32ole/win32ole_type/src_type_spec.rb
index 71e304d80a..3c7651cc1f 100644
--- a/spec/ruby/library/win32ole/win32ole_type/src_type_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/src_type_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#src_type for Shell Controls" do
+  describe "WIN32OLE::Type#src_type for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/to_s_spec.rb b/spec/ruby/library/win32ole/win32ole_type/to_s_spec.rb
index b713990ed2..03a0344fdb 100644
--- a/spec/ruby/library/win32ole/win32ole_type/to_s_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/to_s_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#to_s" do
+  describe "WIN32OLE::Type#to_s" do
     it_behaves_like :win32ole_type_name, :to_s
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/typekind_spec.rb b/spec/ruby/library/win32ole/win32ole_type/typekind_spec.rb
index 35f3562721..8b62f3e2eb 100644
--- a/spec/ruby/library/win32ole/win32ole_type/typekind_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/typekind_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#typekind for Shell Controls" do
+  describe "WIN32OLE::Type#typekind for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/typelibs_spec.rb b/spec/ruby/library/win32ole/win32ole_type/typelibs_spec.rb
index 369e0274f3..71d7cf00f7 100644
--- a/spec/ruby/library/win32ole/win32ole_type/typelibs_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/typelibs_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE.typelibs for Shell Controls" do
+  describe "WIN32OLE::Type.typelibs for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
@@ -11,11 +12,11 @@ platform_is :windows do
     end
 
     it "raises ArgumentError if any argument is give" do
-      -> { WIN32OLE_TYPE.typelibs(1) }.should raise_error ArgumentError
+      -> { WIN32OLE::Type.typelibs(1) }.should raise_error ArgumentError
     end
 
     it "returns array of type libraries" do
-      WIN32OLE_TYPE.typelibs().include?("Microsoft Shell Controls And Automation").should be_true
+      WIN32OLE::Type.typelibs().include?("Microsoft Shell Controls And Automation").should be_true
     end
 
   end
diff --git a/spec/ruby/library/win32ole/win32ole_type/variables_spec.rb b/spec/ruby/library/win32ole/win32ole_type/variables_spec.rb
index fbf3dd0341..b1a407523c 100644
--- a/spec/ruby/library/win32ole/win32ole_type/variables_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/variables_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#variables for Shell Controls" do
+  describe "WIN32OLE::Type#variables for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_type/visible_spec.rb b/spec/ruby/library/win32ole/win32ole_type/visible_spec.rb
index 403b2b843b..05c54c8838 100644
--- a/spec/ruby/library/win32ole/win32ole_type/visible_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_type/visible_spec.rb
@@ -1,9 +1,10 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
-  describe "WIN32OLE_TYPE#visible? for Shell Controls" do
+  describe "WIN32OLE::Type#visible? for Shell Controls" do
     before :each do
-      @ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "Shell")
+      @ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "Shell")
     end
 
     after :each do
diff --git a/spec/ruby/library/win32ole/win32ole_variable/name_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/name_spec.rb
index 8bac1a9891..dd9bfa594f 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/name_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/name_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
diff --git a/spec/ruby/library/win32ole/win32ole_variable/ole_type_detail_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/ole_type_detail_spec.rb
index dab4edabaa..89576ceedc 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/ole_type_detail_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/ole_type_detail_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -5,7 +6,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_variable/ole_type_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/ole_type_spec.rb
index d08acc9bde..441011f1e7 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/ole_type_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/ole_type_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -5,7 +6,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_variable/shared/name.rb b/spec/ruby/library/win32ole/win32ole_variable/shared/name.rb
index 033e830fac..d02942ce0a 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/shared/name.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/shared/name.rb
@@ -5,7 +5,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_variable/to_s_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/to_s_spec.rb
index 000ac14d7e..d4cab8e924 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/to_s_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/to_s_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/name'
 
 platform_is :windows do
diff --git a/spec/ruby/library/win32ole/win32ole_variable/value_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/value_spec.rb
index c15f64c2c5..d26273ebed 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/value_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/value_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -5,11 +6,11 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
-    it "returns a Integer" do
+    it "returns an Integer" do
       # according to doc, this could return nil
       @var.value.should be_kind_of Integer
     end
diff --git a/spec/ruby/library/win32ole/win32ole_variable/variable_kind_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/variable_kind_spec.rb
index 4cca7f8874..17bc47160a 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/variable_kind_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/variable_kind_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -5,7 +6,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_variable/varkind_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/varkind_spec.rb
index 56cd1c337a..c5f8164509 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/varkind_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/varkind_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -6,7 +7,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/win32ole/win32ole_variable/visible_spec.rb b/spec/ruby/library/win32ole/win32ole_variable/visible_spec.rb
index 7f7a557b57..ba53a81de0 100644
--- a/spec/ruby/library/win32ole/win32ole_variable/visible_spec.rb
+++ b/spec/ruby/library/win32ole/win32ole_variable/visible_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 platform_is :windows do
   require 'win32ole'
 
@@ -5,7 +6,7 @@ platform_is :windows do
     # not sure how WIN32OLE_VARIABLE objects are supposed to be generated
     # WIN32OLE_VARIABLE.new even seg faults in some cases
     before :each do
-      ole_type = WIN32OLE_TYPE.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
+      ole_type = WIN32OLE::Type.new("Microsoft Shell Controls And Automation", "ShellSpecialFolderConstants")
       @var = ole_type.variables[0]
     end
 
diff --git a/spec/ruby/library/yaml/add_builtin_type_spec.rb b/spec/ruby/library/yaml/add_builtin_type_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/add_builtin_type_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/add_domain_type_spec.rb b/spec/ruby/library/yaml/add_domain_type_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/add_domain_type_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/add_private_type_spec.rb b/spec/ruby/library/yaml/add_private_type_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/add_private_type_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/add_ruby_type_spec.rb b/spec/ruby/library/yaml/add_ruby_type_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/add_ruby_type_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/detect_implicit_spec.rb b/spec/ruby/library/yaml/detect_implicit_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/detect_implicit_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/dump_spec.rb b/spec/ruby/library/yaml/dump_spec.rb
index 5af794b7f8..97b665d6a5 100644
--- a/spec/ruby/library/yaml/dump_spec.rb
+++ b/spec/ruby/library/yaml/dump_spec.rb
@@ -1,17 +1,21 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
 
-# TODO: WTF is this using a global?
+require 'yaml'
+
 describe "YAML.dump" do
+  before :each do
+    @test_file = tmp("yaml_test_file")
+  end
+
   after :each do
-    rm_r $test_file
+    rm_r @test_file
   end
 
   it "converts an object to YAML and write result to io when io provided" do
-    File.open($test_file, 'w' ) do |io|
+    File.open(@test_file, 'w' ) do |io|
       YAML.dump( ['badger', 'elephant', 'tiger'], io )
     end
-    YAML.load_file($test_file).should == ['badger', 'elephant', 'tiger']
+    YAML.load_file(@test_file).should == ['badger', 'elephant', 'tiger']
   end
 
   it "returns a string containing dumped YAML when no io provided" do
@@ -35,9 +39,18 @@ describe "YAML.dump" do
   end
 
   it "dumps an OpenStruct" do
-    require "ostruct"
+    begin
+      require "ostruct"
+    rescue LoadError
+      skip "OpenStruct is not available"
+    end
     os = OpenStruct.new("age" => 20, "name" => "John")
-    YAML.dump(os).should match_yaml("--- !ruby/object:OpenStruct\ntable:\n  :age: 20\n  :name: John\n")
+    yaml_dump = YAML.dump(os)
+
+    [
+      "--- !ruby/object:OpenStruct\nage: 20\nname: John\n",
+      "--- !ruby/object:OpenStruct\ntable:\n  :age: 20\n  :name: John\n",
+    ].should.include?(yaml_dump)
   end
 
   it "dumps a File without any state" do
diff --git a/spec/ruby/library/yaml/dump_stream_spec.rb b/spec/ruby/library/yaml/dump_stream_spec.rb
index 9d30fef819..f0578fa800 100644
--- a/spec/ruby/library/yaml/dump_stream_spec.rb
+++ b/spec/ruby/library/yaml/dump_stream_spec.rb
@@ -1,5 +1,6 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
+
+require 'yaml'
 
 describe "YAML.dump_stream" do
   it "returns a YAML stream containing the objects passed" do
diff --git a/spec/ruby/library/yaml/each_node_spec.rb b/spec/ruby/library/yaml/each_node_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/each_node_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/emitter_spec.rb b/spec/ruby/library/yaml/emitter_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/emitter_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/fixtures/common.rb b/spec/ruby/library/yaml/fixtures/common.rb
deleted file mode 100644
index 1d868806f1..0000000000
--- a/spec/ruby/library/yaml/fixtures/common.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-begin
-  require 'syck'
-rescue LoadError
-  # do nothing
-end
-
-require 'yaml'
-
-$test_file = tmp("yaml_test_file")
-$test_parse_file = File.dirname(__FILE__) + "/test_yaml.yml"
diff --git a/spec/ruby/library/yaml/fixtures/strings.rb b/spec/ruby/library/yaml/fixtures/strings.rb
index 6f66dc3659..f478f89823 100644
--- a/spec/ruby/library/yaml/fixtures/strings.rb
+++ b/spec/ruby/library/yaml/fixtures/strings.rb
@@ -1,36 +1,26 @@
-$complex_key_1 = <<EOY
-    ? # PLAY SCHEDULE
-      - Detroit Tigers
-      - Chicago Cubs
-    :
-      - 2001-07-23
+module YAMLSpecs
+  COMPLEX_KEY_1 = <<~EOY
+      ? # PLAY SCHEDULE
+        - Detroit Tigers
+        - Chicago Cubs
+      :
+        - 2001-07-23
 
-    ? [ New York Yankees,
-        Atlanta Braves ]
-    : [ 2001-07-02, 2001-08-12,
-       2001-08-14 ]
-EOY
+      ? [ New York Yankees,
+          Atlanta Braves ]
+      : [ 2001-07-02, 2001-08-12,
+         2001-08-14 ]
+  EOY
 
-$to_yaml_hash =
-<<EOY
--
-  avg: 0.278
-  hr: 65
-  name: Mark McGwire
--
-  avg: 0.288
-  hr: 63
-  name: Sammy Sosa
-EOY
+  MULTIDOCUMENT = <<~EOY
+  ---
+  - Mark McGwire
+  - Sammy Sosa
+  - Ken Griffey
 
-$multidocument = <<EOY
----
-- Mark McGwire
-- Sammy Sosa
-- Ken Griffey
-
-# Team ranking
----
-- Chicago Cubs
-- St Louis Cardinals
-EOY
+  # Team ranking
+  ---
+  - Chicago Cubs
+  - St Louis Cardinals
+  EOY
+end
diff --git a/spec/ruby/library/yaml/generic_parser_spec.rb b/spec/ruby/library/yaml/generic_parser_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/generic_parser_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/load_documents_spec.rb b/spec/ruby/library/yaml/load_documents_spec.rb
deleted file mode 100644
index 27edbcaa86..0000000000
--- a/spec/ruby/library/yaml/load_documents_spec.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-require_relative 'fixtures/strings'
-require_relative 'shared/each_document'
-
-ruby_version_is ''...'2.5' do
-  describe "YAML.load_documents" do
-    it_behaves_like :yaml_each_document, :load_documents
-  end
-end
diff --git a/spec/ruby/library/yaml/load_file_spec.rb b/spec/ruby/library/yaml/load_file_spec.rb
index 2363c08120..4941d0485b 100644
--- a/spec/ruby/library/yaml/load_file_spec.rb
+++ b/spec/ruby/library/yaml/load_file_spec.rb
@@ -1,13 +1,18 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
+
+require 'yaml'
 
 describe "YAML.load_file" do
+  before :each do
+    @test_file = tmp("yaml_test_file")
+  end
+
   after :each do
-    rm_r $test_file
+    rm_r @test_file
   end
 
   it "returns a hash" do
-    File.open($test_file,'w' ){|io| YAML.dump( {"bar"=>2, "car"=>1}, io ) }
-    YAML.load_file($test_file).should == {"bar"=>2, "car"=>1}
+    File.open(@test_file,'w' ){|io| YAML.dump( {"bar"=>2, "car"=>1}, io ) }
+    YAML.load_file(@test_file).should == {"bar"=>2, "car"=>1}
   end
 end
diff --git a/spec/ruby/library/yaml/load_spec.rb b/spec/ruby/library/yaml/load_spec.rb
index 0b6bef2dac..56700a85f9 100644
--- a/spec/ruby/library/yaml/load_spec.rb
+++ b/spec/ruby/library/yaml/load_spec.rb
@@ -1,137 +1,10 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-require_relative 'fixtures/strings'
+require_relative 'shared/load'
 
 describe "YAML.load" do
-  after :each do
-    rm_r $test_file
-  end
-
-  it "returns a document from current io stream when io provided" do
-    File.open($test_file, 'w') do |io|
-      YAML.dump( ['badger', 'elephant', 'tiger'], io )
-    end
-    File.open($test_file) { |yf| YAML.load( yf ) }.should == ['badger', 'elephant', 'tiger']
-  end
-
-  it "loads strings" do
-    strings = ["str",
-               " str",
-               "'str'",
-               "str",
-               " str",
-               "'str'",
-               "\"str\"",
-                "\n str",
-                "---  str",
-                "---\nstr",
-                "--- \nstr",
-                "--- \n str",
-                "--- 'str'"
-              ]
-    strings.each do |str|
-      YAML.load(str).should == "str"
-    end
-  end
-
-  it "loads strings with chars from non-base Unicode plane" do
-    # We add these strings as bytes and force the encoding for safety
-    # as bugs in parsing unicode characters can obscure bugs in this
-    # area.
-
-    yaml_and_strings = {
-      # "--- 🌵" => "🌵"
-      [45, 45, 45, 32, 240, 159, 140, 181] =>
-      [240, 159, 140, 181],
-      # "--- 🌵 and some text" => "🌵 and some text"
-      [45, 45, 45, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116] =>
-      [240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116],
-      # "--- Some text 🌵 and some text" => "Some text 🌵 and some text"
-      [45, 45, 45, 32, 83, 111, 109, 101, 32, 116, 101, 120, 116, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116] =>
-      [83, 111, 109, 101, 32, 116, 101, 120, 116, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116]
-    }
-    yaml_and_strings.each do |yaml, str|
-      YAML.load(yaml.pack("C*").force_encoding("UTF-8")).should == str.pack("C*").force_encoding("UTF-8")
-    end
-  end
-
-  it "fails on invalid keys" do
-    if YAML.to_s == "Psych"
-      error = Psych::SyntaxError
-    else
-      error = ArgumentError
-    end
-    -> { YAML.load("key1: value\ninvalid_key") }.should raise_error(error)
-  end
-
-  it "accepts symbols" do
-    YAML.load( "--- :locked" ).should == :locked
-  end
-
-  it "accepts numbers" do
-    YAML.load("47").should == 47
-    YAML.load("-1").should == -1
-  end
-
-  it "accepts collections" do
-    expected = ["a", "b", "c"]
-    YAML.load("--- \n- a\n- b\n- c\n").should == expected
-    YAML.load("--- [a, b, c]").should == expected
-    YAML.load("[a, b, c]").should == expected
-  end
-
-  it "parses start markers" do
-    YAML.load("---\n").should == nil
-    YAML.load("--- ---\n").should == "---"
-    YAML.load("--- abc").should == "abc"
-  end
-
-  it "works with block sequence shortcuts" do
-    block_seq = "- - - one\n    - two\n    - three"
-    YAML.load(block_seq).should == [[["one", "two", "three"]]]
-  end
-
-  it "works on complex keys" do
-    require 'date'
-    expected = {
-      [ 'Detroit Tigers', 'Chicago Cubs' ] => [ Date.new( 2001, 7, 23 ) ],
-      [ 'New York Yankees', 'Atlanta Braves' ] => [ Date.new( 2001, 7, 2 ),
-                                                    Date.new( 2001, 8, 12 ),
-                                                    Date.new( 2001, 8, 14 ) ]
-    }
-    YAML.load($complex_key_1).should == expected
-  end
-
-  it "loads a symbol key that contains spaces" do
-    string = ":user name: This is the user name."
-    expected = { :"user name" => "This is the user name."}
-    YAML.load(string).should == expected
-  end
-
-  describe "with iso8601 timestamp" do
-    it "computes the microseconds" do
-      [ [YAML.load("2011-03-22t23:32:11.2233+01:00"),   223300],
-        [YAML.load("2011-03-22t23:32:11.0099+01:00"),   9900],
-        [YAML.load("2011-03-22t23:32:11.000076+01:00"), 76]
-      ].should be_computed_by(:usec)
-    end
-
-    it "rounds values smaller than 1 usec to 0 " do
-      YAML.load("2011-03-22t23:32:11.000000342222+01:00").usec.should == 0
-    end
-  end
-
-  it "loads an OpenStruct" do
-    require "ostruct"
-    os = OpenStruct.new("age" => 20, "name" => "John")
-    loaded = YAML.load("--- !ruby/object:OpenStruct\ntable:\n  :age: 20\n  :name: John\n")
-    loaded.should == os
-  end
+  it_behaves_like :yaml_load_safe, :load
 
-  it "loads a File but raise an error when used as it is uninitialized" do
-    loaded = YAML.load("--- !ruby/object:File {}\n")
-    -> {
-      loaded.read(1)
-    }.should raise_error(IOError)
+  guard -> { Psych::VERSION < "4.0.0" } do
+    it_behaves_like :yaml_load_unsafe, :load
   end
 end
diff --git a/spec/ruby/library/yaml/load_stream_spec.rb b/spec/ruby/library/yaml/load_stream_spec.rb
index 689653c8cd..31bc862f5e 100644
--- a/spec/ruby/library/yaml/load_stream_spec.rb
+++ b/spec/ruby/library/yaml/load_stream_spec.rb
@@ -1,8 +1,9 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
 require_relative 'fixtures/strings'
 require_relative 'shared/each_document'
 
+require 'yaml'
+
 describe "YAML.load_stream" do
   it_behaves_like :yaml_each_document, :load_stream
 end
diff --git a/spec/ruby/library/yaml/object_maker_spec.rb b/spec/ruby/library/yaml/object_maker_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/object_maker_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/parse_documents_spec.rb b/spec/ruby/library/yaml/parse_documents_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/parse_documents_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/parse_file_spec.rb b/spec/ruby/library/yaml/parse_file_spec.rb
index 8c59a2d7ef..7bffcdc62f 100644
--- a/spec/ruby/library/yaml/parse_file_spec.rb
+++ b/spec/ruby/library/yaml/parse_file_spec.rb
@@ -1,8 +1,10 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
 
-describe "YAML#parse_file" do
+require 'yaml'
+
+describe "YAML.parse_file" do
   it "returns a YAML::Syck::Map object after parsing a YAML file" do
-    YAML.parse_file($test_parse_file).should be_kind_of(Psych::Nodes::Document)
+    test_parse_file = fixture __FILE__, "test_yaml.yml"
+    YAML.parse_file(test_parse_file).should be_kind_of(Psych::Nodes::Document)
   end
 end
diff --git a/spec/ruby/library/yaml/parse_spec.rb b/spec/ruby/library/yaml/parse_spec.rb
index d5dbfdcee2..37e2b7fa0a 100644
--- a/spec/ruby/library/yaml/parse_spec.rb
+++ b/spec/ruby/library/yaml/parse_spec.rb
@@ -1,13 +1,14 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
 
-describe "YAML#parse with an empty string" do
+require 'yaml'
+
+describe "YAML.parse with an empty string" do
   it "returns false" do
     YAML.parse('').should be_false
   end
 end
 
-describe "YAML#parse" do
+describe "YAML.parse" do
   before :each do
     @string_yaml = "foo".to_yaml
   end
diff --git a/spec/ruby/library/yaml/parser_spec.rb b/spec/ruby/library/yaml/parser_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/parser_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/quick_emit_spec.rb b/spec/ruby/library/yaml/quick_emit_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/quick_emit_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/read_type_class_spec.rb b/spec/ruby/library/yaml/read_type_class_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/read_type_class_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/shared/each_document.rb b/spec/ruby/library/yaml/shared/each_document.rb
index 999123dc2a..6f00aee297 100644
--- a/spec/ruby/library/yaml/shared/each_document.rb
+++ b/spec/ruby/library/yaml/shared/each_document.rb
@@ -1,7 +1,7 @@
 describe :yaml_each_document, shared: true do
   it "calls the block on each successive document" do
     documents = []
-    YAML.send(@method, $multidocument) do |doc|
+    YAML.send(@method, YAMLSpecs::MULTIDOCUMENT) do |doc|
       documents << doc
     end
     documents.should == [["Mark McGwire", "Sammy Sosa", "Ken Griffey"],
@@ -9,7 +9,8 @@ describe :yaml_each_document, shared: true do
   end
 
   it "works on files" do
-    File.open($test_parse_file, "r") do |file|
+    test_parse_file = fixture __FILE__, "test_yaml.yml"
+    File.open(test_parse_file, "r") do |file|
       YAML.send(@method, file) do |doc|
         doc.should == {"project"=>{"name"=>"RubySpec"}}
       end
diff --git a/spec/ruby/library/yaml/shared/load.rb b/spec/ruby/library/yaml/shared/load.rb
new file mode 100644
index 0000000000..b8bb605b0a
--- /dev/null
+++ b/spec/ruby/library/yaml/shared/load.rb
@@ -0,0 +1,142 @@
+require_relative '../fixtures/strings'
+
+require 'yaml'
+
+describe :yaml_load_safe, shared: true do
+  it "returns a document from current io stream when io provided" do
+    @test_file = tmp("yaml_test_file")
+    File.open(@test_file, 'w') do |io|
+      YAML.dump( ['badger', 'elephant', 'tiger'], io )
+    end
+    File.open(@test_file) { |yf| YAML.send(@method,  yf ) }.should == ['badger', 'elephant', 'tiger']
+  ensure
+    rm_r @test_file
+  end
+
+  it "loads strings" do
+    strings = ["str",
+               " str",
+               "'str'",
+               "str",
+               " str",
+               "'str'",
+               "\"str\"",
+                "\n str",
+                "---  str",
+                "---\nstr",
+                "--- \nstr",
+                "--- \n str",
+                "--- 'str'"
+              ]
+    strings.each do |str|
+      YAML.send(@method, str).should == "str"
+    end
+  end
+
+  it "loads strings with chars from non-base Unicode plane" do
+    # We add these strings as bytes and force the encoding for safety
+    # as bugs in parsing unicode characters can obscure bugs in this
+    # area.
+
+    yaml_and_strings = {
+      # "--- 🌵" => "🌵"
+      [45, 45, 45, 32, 240, 159, 140, 181] =>
+      [240, 159, 140, 181],
+      # "--- 🌵 and some text" => "🌵 and some text"
+      [45, 45, 45, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116] =>
+      [240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116],
+      # "--- Some text 🌵 and some text" => "Some text 🌵 and some text"
+      [45, 45, 45, 32, 83, 111, 109, 101, 32, 116, 101, 120, 116, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116] =>
+      [83, 111, 109, 101, 32, 116, 101, 120, 116, 32, 240, 159, 140, 181, 32, 97, 110, 100, 32, 115, 111, 109, 101, 32, 116, 101, 120, 116]
+    }
+    yaml_and_strings.each do |yaml, str|
+      YAML.send(@method, yaml.pack("C*").force_encoding("UTF-8")).should == str.pack("C*").force_encoding("UTF-8")
+    end
+  end
+
+  it "fails on invalid keys" do
+    if YAML.to_s == "Psych"
+      error = Psych::SyntaxError
+    else
+      error = ArgumentError
+    end
+    -> { YAML.send(@method, "key1: value\ninvalid_key") }.should raise_error(error)
+  end
+
+  it "accepts symbols" do
+    YAML.send(@method,  "--- :locked" ).should == :locked
+  end
+
+  it "accepts numbers" do
+    YAML.send(@method, "47").should == 47
+    YAML.send(@method, "-1").should == -1
+  end
+
+  it "accepts collections" do
+    expected = ["a", "b", "c"]
+    YAML.send(@method, "--- \n- a\n- b\n- c\n").should == expected
+    YAML.send(@method, "--- [a, b, c]").should == expected
+    YAML.send(@method, "[a, b, c]").should == expected
+  end
+
+  it "parses start markers" do
+    YAML.send(@method, "---\n").should == nil
+    YAML.send(@method, "--- ---\n").should == "---"
+    YAML.send(@method, "--- abc").should == "abc"
+  end
+
+  it "works with block sequence shortcuts" do
+    block_seq = "- - - one\n    - two\n    - three"
+    YAML.send(@method, block_seq).should == [[["one", "two", "three"]]]
+  end
+
+  it "loads a symbol key that contains spaces" do
+    string = ":user name: This is the user name."
+    expected = { :"user name" => "This is the user name."}
+    YAML.send(@method, string).should == expected
+  end
+end
+
+describe :yaml_load_unsafe, shared: true do
+  it "works on complex keys" do
+    require 'date'
+    expected = {
+      [ 'Detroit Tigers', 'Chicago Cubs' ] => [ Date.new( 2001, 7, 23 ) ],
+      [ 'New York Yankees', 'Atlanta Braves' ] => [ Date.new( 2001, 7, 2 ),
+                                                    Date.new( 2001, 8, 12 ),
+                                                    Date.new( 2001, 8, 14 ) ]
+    }
+    YAML.send(@method, YAMLSpecs::COMPLEX_KEY_1).should == expected
+  end
+
+  describe "with iso8601 timestamp" do
+    it "computes the microseconds" do
+      [ [YAML.send(@method, "2011-03-22t23:32:11.2233+01:00"),   223300],
+        [YAML.send(@method, "2011-03-22t23:32:11.0099+01:00"),   9900],
+        [YAML.send(@method, "2011-03-22t23:32:11.000076+01:00"), 76]
+      ].should be_computed_by(:usec)
+    end
+
+    it "rounds values smaller than 1 usec to 0 " do
+      YAML.send(@method, "2011-03-22t23:32:11.000000342222+01:00").usec.should == 0
+    end
+  end
+
+  it "loads an OpenStruct" do
+    begin
+      require "ostruct"
+    rescue LoadError
+      skip "OpenStruct is not available"
+    end
+    os = OpenStruct.new("age" => 20, "name" => "John")
+    loaded = YAML.send(@method, "--- !ruby/object:OpenStruct\ntable:\n  :age: 20\n  :name: John\n")
+    loaded.should == os
+  end
+
+  it "loads a File but raise an error when used as it is uninitialized" do
+    loaded = YAML.send(@method, "--- !ruby/object:File {}\n")
+    -> {
+      loaded.read(1)
+    }.should raise_error(IOError)
+  end
+end
diff --git a/spec/ruby/library/yaml/tagurize_spec.rb b/spec/ruby/library/yaml/tagurize_spec.rb
deleted file mode 100644
index cc1b757ce9..0000000000
--- a/spec/ruby/library/yaml/tagurize_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-
-ruby_version_is ''...'2.5' do
-  describe "YAML.tagurize" do
-    it "converts a type_id to a taguri" do
-      YAML.tagurize('wtf').should == "tag:yaml.org,2002:wtf"
-      YAML.tagurize(1).should == 1
-    end
-  end
-end
diff --git a/spec/ruby/library/yaml/to_yaml_spec.rb b/spec/ruby/library/yaml/to_yaml_spec.rb
index 03ec4f6916..08c5451416 100644
--- a/spec/ruby/library/yaml/to_yaml_spec.rb
+++ b/spec/ruby/library/yaml/to_yaml_spec.rb
@@ -1,7 +1,8 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
 require_relative 'fixtures/example_class'
 
+require 'yaml'
+
 describe "Object#to_yaml" do
 
   it "returns the YAML representation of an Array object" do
@@ -12,13 +13,21 @@ describe "Object#to_yaml" do
     { "a" => "b"}.to_yaml.should match_yaml("--- \na: b\n")
   end
 
-  it "returns the YAML representation of a Class object" do
+  it "returns the YAML representation of an object" do
     YAMLSpecs::Example.new("baz").to_yaml.should match_yaml("--- !ruby/object:YAMLSpecs::Example\nname: baz\n")
   end
 
+  it "returns the YAML representation of a Class object" do
+    YAMLSpecs::Example.to_yaml.should match_yaml("--- !ruby/class 'YAMLSpecs::Example'\n")
+  end
+
+  it "returns the YAML representation of a Module object" do
+    Enumerable.to_yaml.should match_yaml("--- !ruby/module 'Enumerable'\n")
+  end
+
   it "returns the YAML representation of a Date object" do
     require 'date'
-    Date.parse('1997/12/30').to_yaml.should match_yaml("--- 1997-12-30\n")
+    Date.new(1997, 12, 30).to_yaml.should match_yaml("--- 1997-12-30\n")
   end
 
   it "returns the YAML representation of a FalseClass" do
@@ -56,6 +65,13 @@ describe "Object#to_yaml" do
   it "returns the YAML representation of a Struct object" do
     Person = Struct.new(:name, :gender)
     Person.new("Jane", "female").to_yaml.should match_yaml("--- !ruby/struct:Person\nname: Jane\ngender: female\n")
+  ensure
+    Object.send(:remove_const, :Person)
+  end
+
+  it "returns the YAML representation of an unnamed Struct object" do
+    person = Struct.new(:name, :gender)
+    person.new("Jane", "female").to_yaml.should match_yaml("--- !ruby/struct\nname: Jane\ngender: female\n")
   end
 
   it "returns the YAML representation of a Symbol object" do
@@ -72,16 +88,8 @@ describe "Object#to_yaml" do
     true_klass.to_yaml.should match_yaml("--- true\n")
   end
 
-  ruby_version_is ""..."2.7" do
-    it "returns the YAML representation of a Error object" do
-      StandardError.new("foobar").to_yaml.should match_yaml("--- !ruby/exception:StandardError\nmessage: foobar\n")
-    end
-  end
-
-  ruby_version_is "2.7" do
-    it "returns the YAML representation of a Error object" do
-      StandardError.new("foobar").to_yaml.should match_yaml("--- !ruby/exception:StandardError\nmessage: foobar\nbacktrace: \n")
-    end
+  it "returns the YAML representation of a Error object" do
+    StandardError.new("foobar").to_yaml.should match_yaml("--- !ruby/exception:StandardError\nmessage: foobar\nbacktrace: \n")
   end
 
   it "returns the YAML representation for Range objects" do
diff --git a/spec/ruby/library/yaml/transfer_spec.rb b/spec/ruby/library/yaml/transfer_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/transfer_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/try_implicit_spec.rb b/spec/ruby/library/yaml/try_implicit_spec.rb
deleted file mode 100644
index 44c820940f..0000000000
--- a/spec/ruby/library/yaml/try_implicit_spec.rb
+++ /dev/null
@@ -1,2 +0,0 @@
-require_relative '../../spec_helper'
-require_relative 'fixtures/common'
diff --git a/spec/ruby/library/yaml/unsafe_load_spec.rb b/spec/ruby/library/yaml/unsafe_load_spec.rb
new file mode 100644
index 0000000000..385cd2a6e2
--- /dev/null
+++ b/spec/ruby/library/yaml/unsafe_load_spec.rb
@@ -0,0 +1,9 @@
+require_relative '../../spec_helper'
+require_relative 'shared/load'
+
+guard -> { Psych::VERSION >= "4.0.0" } do
+  describe "YAML.unsafe_load" do
+    it_behaves_like :yaml_load_safe, :unsafe_load
+    it_behaves_like :yaml_load_unsafe, :unsafe_load
+  end
+end
diff --git a/spec/ruby/library/zlib/adler32_spec.rb b/spec/ruby/library/zlib/adler32_spec.rb
index 62240e2de7..226aa18522 100644
--- a/spec/ruby/library/zlib/adler32_spec.rb
+++ b/spec/ruby/library/zlib/adler32_spec.rb
@@ -22,7 +22,7 @@ describe "Zlib.adler32" do
     -> { Zlib.adler32(test_string, 2**128) }.should raise_error(RangeError)
   end
 
-  it "calculates the Adler checksum for string and initial Adler value for Bignums" do
+  it "calculates the Adler checksum for string and initial Adler value for Integers" do
     test_string = "This is a test string! How exciting!%?"
     Zlib.adler32(test_string, 2**30).should == 1137642779
   end
diff --git a/spec/ruby/library/zlib/crc32_spec.rb b/spec/ruby/library/zlib/crc32_spec.rb
index 4c1d6ce2e9..d5f5c199cc 100644
--- a/spec/ruby/library/zlib/crc32_spec.rb
+++ b/spec/ruby/library/zlib/crc32_spec.rb
@@ -29,7 +29,7 @@ describe "Zlib.crc32" do
     -> { Zlib.crc32(test_string, 2**128) }.should raise_error(RangeError)
   end
 
-  it "calculates the CRC checksum for string and initial CRC value for Bignums" do
+  it "calculates the CRC checksum for string and initial CRC value for Integers" do
     test_string = "This is a test string! How exciting!%?"
     # Zlib.crc32(test_string, -2**30).should == 277228695
     Zlib.crc32(test_string, 2**30).should == 46597132
diff --git a/spec/ruby/library/zlib/crc_table_spec.rb b/spec/ruby/library/zlib/crc_table_spec.rb
index f7fc2749fa..de8876086b 100644
--- a/spec/ruby/library/zlib/crc_table_spec.rb
+++ b/spec/ruby/library/zlib/crc_table_spec.rb
@@ -2,74 +2,79 @@ require_relative '../../spec_helper'
 require "zlib"
 
 describe "Zlib.crc_table" do
-
-  it "returns the same value as zlib's get_crc_table()" do
-    Zlib.crc_table.should == [
-      0, 1996959894, 3993919788, 2567524794,
-      124634137, 1886057615, 3915621685, 2657392035,
-      249268274, 2044508324, 3772115230, 2547177864,
-      162941995, 2125561021, 3887607047, 2428444049,
-      498536548, 1789927666, 4089016648, 2227061214,
-      450548861, 1843258603, 4107580753, 2211677639,
-      325883990, 1684777152, 4251122042, 2321926636,
-      335633487, 1661365465, 4195302755, 2366115317,
-      997073096, 1281953886, 3579855332, 2724688242,
-      1006888145, 1258607687, 3524101629, 2768942443,
-      901097722, 1119000684, 3686517206, 2898065728,
-      853044451, 1172266101, 3705015759, 2882616665,
-      651767980, 1373503546, 3369554304, 3218104598,
-      565507253, 1454621731, 3485111705, 3099436303,
-      671266974, 1594198024, 3322730930, 2970347812,
-      795835527, 1483230225, 3244367275, 3060149565,
-      1994146192, 31158534, 2563907772, 4023717930,
-      1907459465, 112637215, 2680153253, 3904427059,
-      2013776290, 251722036, 2517215374, 3775830040,
-      2137656763, 141376813, 2439277719, 3865271297,
-      1802195444, 476864866, 2238001368, 4066508878,
-      1812370925, 453092731, 2181625025, 4111451223,
-      1706088902, 314042704, 2344532202, 4240017532,
-      1658658271, 366619977, 2362670323, 4224994405,
-      1303535960, 984961486, 2747007092, 3569037538,
-      1256170817, 1037604311, 2765210733, 3554079995,
-      1131014506, 879679996, 2909243462, 3663771856,
-      1141124467, 855842277, 2852801631, 3708648649,
-      1342533948, 654459306, 3188396048, 3373015174,
-      1466479909, 544179635, 3110523913, 3462522015,
-      1591671054, 702138776, 2966460450, 3352799412,
-      1504918807, 783551873, 3082640443, 3233442989,
-      3988292384, 2596254646, 62317068, 1957810842,
-      3939845945, 2647816111, 81470997, 1943803523,
-      3814918930, 2489596804, 225274430, 2053790376,
-      3826175755, 2466906013, 167816743, 2097651377,
-      4027552580, 2265490386, 503444072, 1762050814,
-      4150417245, 2154129355, 426522225, 1852507879,
-      4275313526, 2312317920, 282753626, 1742555852,
-      4189708143, 2394877945, 397917763, 1622183637,
-      3604390888, 2714866558, 953729732, 1340076626,
-      3518719985, 2797360999, 1068828381, 1219638859,
-      3624741850, 2936675148, 906185462, 1090812512,
-      3747672003, 2825379669, 829329135, 1181335161,
-      3412177804, 3160834842, 628085408, 1382605366,
-      3423369109, 3138078467, 570562233, 1426400815,
-      3317316542, 2998733608, 733239954, 1555261956,
-      3268935591, 3050360625, 752459403, 1541320221,
-      2607071920, 3965973030, 1969922972, 40735498,
-      2617837225, 3943577151, 1913087877, 83908371,
-      2512341634, 3803740692, 2075208622, 213261112,
-      2463272603, 3855990285, 2094854071, 198958881,
-      2262029012, 4057260610, 1759359992, 534414190,
-      2176718541, 4139329115, 1873836001, 414664567,
-      2282248934, 4279200368, 1711684554, 285281116,
-      2405801727, 4167216745, 1634467795, 376229701,
-      2685067896, 3608007406, 1308918612, 956543938,
-      2808555105, 3495958263, 1231636301, 1047427035,
-      2932959818, 3654703836, 1088359270, 936918000,
-      2847714899, 3736837829, 1202900863, 817233897,
-      3183342108, 3401237130, 1404277552, 615818150,
-      3134207493, 3453421203, 1423857449, 601450431,
-      3009837614, 3294710456, 1567103746, 711928724,
-      3020668471, 3272380065, 1510334235, 755167117,
-    ]
+  # This spec fails when zlib.h and libz.so are not from the same version.
+  # In older zlib (< 1.2.7 it seems), get_crc_table() is stored as u64[],
+  # but in newer zlib, get_crc_table() is stored as u32[].
+  # Technically, there is ABI breakage between those zlib versions,
+  # but get_crc_table() is an "undocumented function" according to zlib.h.
+  guard -> { ENV["RUBY_SPEC_TEST_ZLIB_CRC_TABLE"] != "false" } do
+    it "returns the same value as zlib's get_crc_table()" do
+      Zlib.crc_table.should == [
+        0, 1996959894, 3993919788, 2567524794,
+        124634137, 1886057615, 3915621685, 2657392035,
+        249268274, 2044508324, 3772115230, 2547177864,
+        162941995, 2125561021, 3887607047, 2428444049,
+        498536548, 1789927666, 4089016648, 2227061214,
+        450548861, 1843258603, 4107580753, 2211677639,
+        325883990, 1684777152, 4251122042, 2321926636,
+        335633487, 1661365465, 4195302755, 2366115317,
+        997073096, 1281953886, 3579855332, 2724688242,
+        1006888145, 1258607687, 3524101629, 2768942443,
+        901097722, 1119000684, 3686517206, 2898065728,
+        853044451, 1172266101, 3705015759, 2882616665,
+        651767980, 1373503546, 3369554304, 3218104598,
+        565507253, 1454621731, 3485111705, 3099436303,
+        671266974, 1594198024, 3322730930, 2970347812,
+        795835527, 1483230225, 3244367275, 3060149565,
+        1994146192, 31158534, 2563907772, 4023717930,
+        1907459465, 112637215, 2680153253, 3904427059,
+        2013776290, 251722036, 2517215374, 3775830040,
+        2137656763, 141376813, 2439277719, 3865271297,
+        1802195444, 476864866, 2238001368, 4066508878,
+        1812370925, 453092731, 2181625025, 4111451223,
+        1706088902, 314042704, 2344532202, 4240017532,
+        1658658271, 366619977, 2362670323, 4224994405,
+        1303535960, 984961486, 2747007092, 3569037538,
+        1256170817, 1037604311, 2765210733, 3554079995,
+        1131014506, 879679996, 2909243462, 3663771856,
+        1141124467, 855842277, 2852801631, 3708648649,
+        1342533948, 654459306, 3188396048, 3373015174,
+        1466479909, 544179635, 3110523913, 3462522015,
+        1591671054, 702138776, 2966460450, 3352799412,
+        1504918807, 783551873, 3082640443, 3233442989,
+        3988292384, 2596254646, 62317068, 1957810842,
+        3939845945, 2647816111, 81470997, 1943803523,
+        3814918930, 2489596804, 225274430, 2053790376,
+        3826175755, 2466906013, 167816743, 2097651377,
+        4027552580, 2265490386, 503444072, 1762050814,
+        4150417245, 2154129355, 426522225, 1852507879,
+        4275313526, 2312317920, 282753626, 1742555852,
+        4189708143, 2394877945, 397917763, 1622183637,
+        3604390888, 2714866558, 953729732, 1340076626,
+        3518719985, 2797360999, 1068828381, 1219638859,
+        3624741850, 2936675148, 906185462, 1090812512,
+        3747672003, 2825379669, 829329135, 1181335161,
+        3412177804, 3160834842, 628085408, 1382605366,
+        3423369109, 3138078467, 570562233, 1426400815,
+        3317316542, 2998733608, 733239954, 1555261956,
+        3268935591, 3050360625, 752459403, 1541320221,
+        2607071920, 3965973030, 1969922972, 40735498,
+        2617837225, 3943577151, 1913087877, 83908371,
+        2512341634, 3803740692, 2075208622, 213261112,
+        2463272603, 3855990285, 2094854071, 198958881,
+        2262029012, 4057260610, 1759359992, 534414190,
+        2176718541, 4139329115, 1873836001, 414664567,
+        2282248934, 4279200368, 1711684554, 285281116,
+        2405801727, 4167216745, 1634467795, 376229701,
+        2685067896, 3608007406, 1308918612, 956543938,
+        2808555105, 3495958263, 1231636301, 1047427035,
+        2932959818, 3654703836, 1088359270, 936918000,
+        2847714899, 3736837829, 1202900863, 817233897,
+        3183342108, 3401237130, 1404277552, 615818150,
+        3134207493, 3453421203, 1423857449, 601450431,
+        3009837614, 3294710456, 1567103746, 711928724,
+        3020668471, 3272380065, 1510334235, 755167117,
+      ]
+    end
   end
-
 end
diff --git a/spec/ruby/library/zlib/deflate/append_spec.rb b/spec/ruby/library/zlib/deflate/append_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/deflate/append_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/deflate/deflate_spec.rb b/spec/ruby/library/zlib/deflate/deflate_spec.rb
index 828880f8d8..e16e6ad0ef 100644
--- a/spec/ruby/library/zlib/deflate/deflate_spec.rb
+++ b/spec/ruby/library/zlib/deflate/deflate_spec.rb
@@ -23,7 +23,7 @@ describe "Zlib::Deflate.deflate" do
 
   it "deflates chunked data" do
     random_generator = Random.new(0)
-    deflated         = ''
+    deflated         = +''
 
     Zlib::Deflate.deflate(random_generator.bytes(20000)) do |chunk|
       deflated << chunk
@@ -58,6 +58,11 @@ describe "Zlib::Deflate#deflate" do
                       Array.new(31, 0) +
                       [24, 128, 0, 0, 1]).pack('C*')
   end
+
+  it "has a binary encoding" do
+    @deflator.deflate("").encoding.should == Encoding::BINARY
+    @deflator.finish.encoding.should == Encoding::BINARY
+  end
 end
 
 describe "Zlib::Deflate#deflate" do
@@ -65,7 +70,7 @@ describe "Zlib::Deflate#deflate" do
   before :each do
     @deflator         = Zlib::Deflate.new
     @random_generator = Random.new(0)
-    @original         = ''
+    @original         = +''
     @chunks           = []
   end
 
diff --git a/spec/ruby/library/zlib/deflate/flush_spec.rb b/spec/ruby/library/zlib/deflate/flush_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/deflate/flush_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/deflate/new_spec.rb b/spec/ruby/library/zlib/deflate/new_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/deflate/new_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/deflate/params_spec.rb b/spec/ruby/library/zlib/deflate/params_spec.rb
index 0b1cca8c8a..0242653528 100644
--- a/spec/ruby/library/zlib/deflate/params_spec.rb
+++ b/spec/ruby/library/zlib/deflate/params_spec.rb
@@ -3,7 +3,7 @@ require 'zlib'
 
 describe "Zlib::Deflate#params" do
   it "changes the deflate parameters" do
-    data = 'abcdefghijklm'
+    data = +'abcdefghijklm'
 
     d = Zlib::Deflate.new Zlib::NO_COMPRESSION, Zlib::MAX_WBITS,
     Zlib::DEF_MEM_LEVEL, Zlib::DEFAULT_STRATEGY
diff --git a/spec/ruby/library/zlib/deflate_spec.rb b/spec/ruby/library/zlib/deflate_spec.rb
index 01538dd4e6..6eeaa164c5 100644
--- a/spec/ruby/library/zlib/deflate_spec.rb
+++ b/spec/ruby/library/zlib/deflate_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require "zlib"
 
-describe "Zlib#deflate" do
+describe "Zlib.deflate" do
   it "deflates some data" do
     Zlib.deflate("1" * 10).should == [120, 156, 51, 52, 132, 1, 0, 10, 145, 1, 235].pack('C*')
   end
diff --git a/spec/ruby/library/zlib/gunzip_spec.rb b/spec/ruby/library/zlib/gunzip_spec.rb
new file mode 100644
index 0000000000..2417fed57c
--- /dev/null
+++ b/spec/ruby/library/zlib/gunzip_spec.rb
@@ -0,0 +1,14 @@
+require_relative '../../spec_helper'
+require 'zlib'
+
+describe "Zlib.gunzip" do
+  before :each do
+    @data = '12345abcde'
+    @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
+            76, 74, 78, 73, 5, 0, 157, 5, 0, 36, 10, 0, 0, 0].pack('C*')
+  end
+
+  it "decodes the given gzipped string" do
+    Zlib.gunzip(@zip).should == @data
+  end
+end
diff --git a/spec/ruby/library/zlib/gzip_spec.rb b/spec/ruby/library/zlib/gzip_spec.rb
new file mode 100644
index 0000000000..35694264f0
--- /dev/null
+++ b/spec/ruby/library/zlib/gzip_spec.rb
@@ -0,0 +1,15 @@
+require_relative '../../spec_helper'
+require 'zlib'
+
+describe "Zlib.gzip" do
+  before :each do
+    @data = '12345abcde'
+    @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
+            76, 74, 78, 73, 5, 0, 157, 5, 0, 36, 10, 0, 0, 0].pack('C*')
+  end
+
+  it "gzips the given string" do
+    # skip gzip header for now
+    Zlib.gzip(@data)[10..-1].should == @zip[10..-1]
+  end
+end
diff --git a/spec/ruby/library/zlib/gzipfile/close_spec.rb b/spec/ruby/library/zlib/gzipfile/close_spec.rb
index 870870f2fa..964b5ffb4d 100644
--- a/spec/ruby/library/zlib/gzipfile/close_spec.rb
+++ b/spec/ruby/library/zlib/gzipfile/close_spec.rb
@@ -8,7 +8,7 @@ describe "Zlib::GzipFile#close" do
     Zlib::GzipWriter.wrap io do |gzio|
       gzio.close
 
-      gzio.closed?.should == true
+      gzio.should.closed?
 
       -> { gzio.orig_name }.should \
         raise_error(Zlib::GzipFile::Error, 'closed gzip stream')
diff --git a/spec/ruby/library/zlib/gzipfile/closed_spec.rb b/spec/ruby/library/zlib/gzipfile/closed_spec.rb
index b885add485..726f391b41 100644
--- a/spec/ruby/library/zlib/gzipfile/closed_spec.rb
+++ b/spec/ruby/library/zlib/gzipfile/closed_spec.rb
@@ -6,11 +6,11 @@ describe "Zlib::GzipFile#closed?" do
   it "returns the closed status" do
     io = StringIO.new
     Zlib::GzipWriter.wrap io do |gzio|
-      gzio.closed?.should == false
+      gzio.should_not.closed?
 
       gzio.close
 
-      gzio.closed?.should == true
+      gzio.should.closed?
     end
   end
 end
diff --git a/spec/ruby/library/zlib/gzipfile/crc_spec.rb b/spec/ruby/library/zlib/gzipfile/crc_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/crc_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/finish_spec.rb b/spec/ruby/library/zlib/gzipfile/finish_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/finish_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/level_spec.rb b/spec/ruby/library/zlib/gzipfile/level_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/level_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/mtime_spec.rb b/spec/ruby/library/zlib/gzipfile/mtime_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/mtime_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/os_code_spec.rb b/spec/ruby/library/zlib/gzipfile/os_code_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/os_code_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/sync_spec.rb b/spec/ruby/library/zlib/gzipfile/sync_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/sync_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/to_io_spec.rb b/spec/ruby/library/zlib/gzipfile/to_io_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/to_io_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipfile/wrap_spec.rb b/spec/ruby/library/zlib/gzipfile/wrap_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipfile/wrap_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/each_byte_spec.rb b/spec/ruby/library/zlib/gzipreader/each_byte_spec.rb
index d2c43ecaa4..48821dc833 100644
--- a/spec/ruby/library/zlib/gzipreader/each_byte_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/each_byte_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#each_byte" do
+describe "Zlib::GzipReader#each_byte" do
 
   before :each do
     @data = '12345abcde'
diff --git a/spec/ruby/library/zlib/gzipreader/each_char_spec.rb b/spec/ruby/library/zlib/gzipreader/each_char_spec.rb
new file mode 100644
index 0000000000..de6396da7e
--- /dev/null
+++ b/spec/ruby/library/zlib/gzipreader/each_char_spec.rb
@@ -0,0 +1,51 @@
+require_relative '../../../spec_helper'
+require 'stringio'
+require 'zlib'
+
+describe "Zlib::GzipReader#each_char" do
+
+  before :each do
+    @data = '12345abcde'
+    @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
+            76, 74, 78, 73, 5, 0, 157, 5, 0, 36, 10, 0, 0, 0].pack('C*')
+
+    @io = StringIO.new @zip
+    ScratchPad.clear
+  end
+
+  it "calls the given block for each char in the stream, passing the char as an argument" do
+    gz = Zlib::GzipReader.new @io
+
+    ScratchPad.record []
+    gz.each_char { |b| ScratchPad << b }
+
+    ScratchPad.recorded.should == ["1", "2", "3", "4", "5", "a", "b", "c", "d", "e"]
+  end
+
+  it "returns an enumerator, which yields each char in the stream, when no block is passed" do
+    gz = Zlib::GzipReader.new @io
+    enum = gz.each_char
+
+    ScratchPad.record []
+    while true
+      begin
+        ScratchPad << enum.next
+      rescue StopIteration
+        break
+      end
+    end
+
+    ScratchPad.recorded.should == ["1", "2", "3", "4", "5", "a", "b", "c", "d", "e"]
+  end
+
+  it "increments position before calling the block" do
+    gz = Zlib::GzipReader.new @io
+
+    i = 1
+    gz.each_char do |ignore|
+      gz.pos.should == i
+      i += 1
+    end
+  end
+
+end
diff --git a/spec/ruby/library/zlib/gzipreader/each_line_spec.rb b/spec/ruby/library/zlib/gzipreader/each_line_spec.rb
index b576788e27..6f17365879 100644
--- a/spec/ruby/library/zlib/gzipreader/each_line_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/each_line_spec.rb
@@ -1,5 +1,6 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/each'
 
-describe "GzipReader#each_line" do
+describe "Zlib::GzipReader#each_line" do
   it_behaves_like :gzipreader_each, :each_line
 end
diff --git a/spec/ruby/library/zlib/gzipreader/each_spec.rb b/spec/ruby/library/zlib/gzipreader/each_spec.rb
index f9b90be316..3b98391a87 100644
--- a/spec/ruby/library/zlib/gzipreader/each_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/each_spec.rb
@@ -1,5 +1,6 @@
+require_relative "../../../spec_helper"
 require_relative 'shared/each'
 
-describe "GzipReader#each" do
+describe "Zlib::GzipReader#each" do
   it_behaves_like :gzipreader_each, :each
 end
diff --git a/spec/ruby/library/zlib/gzipreader/eof_spec.rb b/spec/ruby/library/zlib/gzipreader/eof_spec.rb
index e33d8e3133..673220fdfd 100644
--- a/spec/ruby/library/zlib/gzipreader/eof_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/eof_spec.rb
@@ -2,8 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#eof?" do
-
+describe "Zlib::GzipReader#eof?" do
   before :each do
     @data = '{"a":1234}'
     @zip = [31, 139, 8, 0, 0, 0, 0, 0, 0, 3, 171, 86, 74, 84, 178, 50,
@@ -49,8 +48,7 @@ describe "GzipReader#eof?" do
       gz.read(1).should == @data[i, 1]
     end
     gz.eof?.should be_true
-    gz.read().should == ""
+    gz.read.should == ""
     gz.eof?.should be_true
   end
-
 end
diff --git a/spec/ruby/library/zlib/gzipreader/getc_spec.rb b/spec/ruby/library/zlib/gzipreader/getc_spec.rb
index 90b5ffe37a..e567231940 100644
--- a/spec/ruby/library/zlib/gzipreader/getc_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/getc_spec.rb
@@ -2,8 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#getc" do
-
+describe "Zlib::GzipReader#getc" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
@@ -37,5 +36,4 @@ describe "GzipReader#getc" do
     gz.getc.should be_nil
     gz.pos.should == pos
   end
-
 end
diff --git a/spec/ruby/library/zlib/gzipreader/gets_spec.rb b/spec/ruby/library/zlib/gzipreader/gets_spec.rb
index 8e4465e49c..d3a2e7d263 100644
--- a/spec/ruby/library/zlib/gzipreader/gets_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/gets_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'zlib'
 require 'stringio'
 
-describe 'GzipReader#gets' do
+describe 'Zlib::GzipReader#gets' do
   describe 'with "" separator' do
     it 'reads paragraphs skipping newlines' do
       # gz contains "\n\n\n\n\n123\n45\n\n\n\n\nabc\nde\n\n\n\n\n"
diff --git a/spec/ruby/library/zlib/gzipreader/lineno_spec.rb b/spec/ruby/library/zlib/gzipreader/lineno_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/lineno_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/mtime_spec.rb b/spec/ruby/library/zlib/gzipreader/mtime_spec.rb
new file mode 100644
index 0000000000..e8e71fa72e
--- /dev/null
+++ b/spec/ruby/library/zlib/gzipreader/mtime_spec.rb
@@ -0,0 +1,11 @@
+require_relative '../../../spec_helper'
+require 'zlib'
+require 'stringio'
+
+describe "Zlib::GzipReader#mtime" do
+  it "returns the timestamp from the Gzip header" do
+    io = StringIO.new "\x1f\x8b\x08\x00\x44\x33\x22\x11\x00\xff\x03\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+    gz = Zlib::GzipReader.new(io)
+    gz.mtime.to_i.should == 0x11223344
+  end
+end
diff --git a/spec/ruby/library/zlib/gzipreader/new_spec.rb b/spec/ruby/library/zlib/gzipreader/new_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/new_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/open_spec.rb b/spec/ruby/library/zlib/gzipreader/open_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/open_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/pos_spec.rb b/spec/ruby/library/zlib/gzipreader/pos_spec.rb
index df7c78ad8f..8586faec92 100644
--- a/spec/ruby/library/zlib/gzipreader/pos_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/pos_spec.rb
@@ -2,8 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#pos" do
-
+describe "Zlib::GzipReader#pos" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
@@ -22,5 +21,4 @@ describe "GzipReader#pos" do
     gz.read
     gz.pos.should == @data.length
   end
-
 end
diff --git a/spec/ruby/library/zlib/gzipreader/read_spec.rb b/spec/ruby/library/zlib/gzipreader/read_spec.rb
index a13f087fe9..b81954b5ce 100644
--- a/spec/ruby/library/zlib/gzipreader/read_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/read_spec.rb
@@ -2,8 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#read" do
-
+describe "Zlib::GzipReader#read" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
@@ -64,5 +63,4 @@ describe "GzipReader#read" do
       gz.read(2**16).should be_nil
     end
   end
-
 end
diff --git a/spec/ruby/library/zlib/gzipreader/readchar_spec.rb b/spec/ruby/library/zlib/gzipreader/readchar_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/readchar_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/readline_spec.rb b/spec/ruby/library/zlib/gzipreader/readline_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/readline_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/readlines_spec.rb b/spec/ruby/library/zlib/gzipreader/readlines_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/readlines_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/readpartial_spec.rb b/spec/ruby/library/zlib/gzipreader/readpartial_spec.rb
index a367e5b856..559ce9f841 100644
--- a/spec/ruby/library/zlib/gzipreader/readpartial_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/readpartial_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe 'GzipReader#readpartial' do
+describe "Zlib::GzipReader#readpartial" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
diff --git a/spec/ruby/library/zlib/gzipreader/rewind_spec.rb b/spec/ruby/library/zlib/gzipreader/rewind_spec.rb
index 2e22458b43..b31abb6abf 100644
--- a/spec/ruby/library/zlib/gzipreader/rewind_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/rewind_spec.rb
@@ -2,8 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipReader#rewind" do
-
+describe "Zlib::GzipReader#rewind" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
diff --git a/spec/ruby/library/zlib/gzipreader/shared/each.rb b/spec/ruby/library/zlib/gzipreader/shared/each.rb
index 11c15d8a66..71608e04ab 100644
--- a/spec/ruby/library/zlib/gzipreader/shared/each.rb
+++ b/spec/ruby/library/zlib/gzipreader/shared/each.rb
@@ -3,7 +3,6 @@ require 'stringio'
 require 'zlib'
 
 describe :gzipreader_each, shared: true do
-
   before :each do
     @data = "firstline\nsecondline\n\nforthline"
     @zip = [31, 139, 8, 0, 244, 125, 128, 88, 2, 255, 75, 203, 44, 42, 46, 201,
@@ -47,5 +46,4 @@ describe :gzipreader_each, shared: true do
       @gzreader.pos.should == i
     end
   end
-
 end
diff --git a/spec/ruby/library/zlib/gzipreader/tell_spec.rb b/spec/ruby/library/zlib/gzipreader/tell_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/tell_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb b/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb
index 6fb6915f15..7fa0608f9f 100644
--- a/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/ungetbyte_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe 'GzipReader#ungetbyte' do
+describe "Zlib::GzipReader#ungetbyte" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
diff --git a/spec/ruby/library/zlib/gzipreader/ungetc_spec.rb b/spec/ruby/library/zlib/gzipreader/ungetc_spec.rb
index d19ec61610..34f2a1a2ca 100644
--- a/spec/ruby/library/zlib/gzipreader/ungetc_spec.rb
+++ b/spec/ruby/library/zlib/gzipreader/ungetc_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe 'GzipReader#ungetc' do
+describe "Zlib::GzipReader#ungetc" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
diff --git a/spec/ruby/library/zlib/gzipreader/unused_spec.rb b/spec/ruby/library/zlib/gzipreader/unused_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipreader/unused_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/comment_spec.rb b/spec/ruby/library/zlib/gzipwriter/comment_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/comment_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/flush_spec.rb b/spec/ruby/library/zlib/gzipwriter/flush_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/flush_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/new_spec.rb b/spec/ruby/library/zlib/gzipwriter/new_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/new_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/open_spec.rb b/spec/ruby/library/zlib/gzipwriter/open_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/open_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/orig_name_spec.rb b/spec/ruby/library/zlib/gzipwriter/orig_name_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/orig_name_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/pos_spec.rb b/spec/ruby/library/zlib/gzipwriter/pos_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/pos_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/print_spec.rb b/spec/ruby/library/zlib/gzipwriter/print_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/print_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/printf_spec.rb b/spec/ruby/library/zlib/gzipwriter/printf_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/printf_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/putc_spec.rb b/spec/ruby/library/zlib/gzipwriter/putc_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/putc_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/puts_spec.rb b/spec/ruby/library/zlib/gzipwriter/puts_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/puts_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/tell_spec.rb b/spec/ruby/library/zlib/gzipwriter/tell_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/gzipwriter/tell_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/gzipwriter/write_spec.rb b/spec/ruby/library/zlib/gzipwriter/write_spec.rb
index f694ce7cb7..522ae7f2aa 100644
--- a/spec/ruby/library/zlib/gzipwriter/write_spec.rb
+++ b/spec/ruby/library/zlib/gzipwriter/write_spec.rb
@@ -2,7 +2,7 @@ require_relative '../../../spec_helper'
 require 'stringio'
 require 'zlib'
 
-describe "GzipWriter#write" do
+describe "Zlib::GzipWriter#write" do
   before :each do
     @data = '12345abcde'
     @zip = [31, 139, 8, 0, 44, 220, 209, 71, 0, 3, 51, 52, 50, 54, 49, 77,
diff --git a/spec/ruby/library/zlib/inflate/finish_spec.rb b/spec/ruby/library/zlib/inflate/finish_spec.rb
index f6e592fb6b..3e0663e265 100644
--- a/spec/ruby/library/zlib/inflate/finish_spec.rb
+++ b/spec/ruby/library/zlib/inflate/finish_spec.rb
@@ -1,3 +1,4 @@
+require_relative "../../../spec_helper"
 require 'zlib'
 
 describe "Zlib::Inflate#finish" do
diff --git a/spec/ruby/library/zlib/inflate/inflate_spec.rb b/spec/ruby/library/zlib/inflate/inflate_spec.rb
index cc33bd4c32..b308a4ba67 100644
--- a/spec/ruby/library/zlib/inflate/inflate_spec.rb
+++ b/spec/ruby/library/zlib/inflate/inflate_spec.rb
@@ -39,6 +39,13 @@ describe "Zlib::Inflate#inflate" do
     @inflator.finish.should == 'uncompressed_data'
   end
 
+  it "has a binary encoding" do
+    data = [120, 156, 99, 96, 128, 1, 0, 0, 10, 0, 1].pack('C*')
+    unzipped = @inflator.inflate data
+    @inflator.finish.encoding.should == Encoding::BINARY
+    unzipped.encoding.should == Encoding::BINARY
+  end
+
 end
 
 describe "Zlib::Inflate.inflate" do
@@ -65,7 +72,7 @@ describe "Zlib::Inflate.inflate" do
     data = [120, 156, 75, 203, 207, 7, 0, 2, 130, 1, 69].pack('C*')
     z = Zlib::Inflate.new
     # add bytes, one by one
-    result = ""
+    result = +""
     data.each_byte { |d| result << z.inflate(d.chr)}
     result << z.finish
     result.should == "foo"
@@ -75,7 +82,7 @@ describe "Zlib::Inflate.inflate" do
     data = [120, 156, 75, 203, 207, 7, 0, 2, 130, 1, 69].pack('C*')[0,5]
     z = Zlib::Inflate.new
     # add bytes, one by one, but not all
-    result = ""
+    result = +""
     data.each_byte { |d| result << z.inflate(d.chr)}
     -> { result << z.finish }.should raise_error(Zlib::BufError)
   end
@@ -83,7 +90,7 @@ describe "Zlib::Inflate.inflate" do
   it "properly handles excessive data, byte-by-byte" do
     main_data = [120, 156, 75, 203, 207, 7, 0, 2, 130, 1, 69].pack('C*')
     data =  main_data * 2
-    result = ""
+    result = +""
 
     z = Zlib::Inflate.new
     # add bytes, one by one
@@ -98,7 +105,7 @@ describe "Zlib::Inflate.inflate" do
   it "properly handles excessive data, in one go" do
     main_data = [120, 156, 75, 203, 207, 7, 0, 2, 130, 1, 69].pack('C*')
     data =  main_data * 2
-    result = ""
+    result = +""
 
     z = Zlib::Inflate.new
     result << z.inflate(data)
diff --git a/spec/ruby/library/zlib/inflate/new_spec.rb b/spec/ruby/library/zlib/inflate/new_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/inflate/new_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/inflate/set_dictionary_spec.rb b/spec/ruby/library/zlib/inflate/set_dictionary_spec.rb
index 251cec44bb..375ee3c765 100644
--- a/spec/ruby/library/zlib/inflate/set_dictionary_spec.rb
+++ b/spec/ruby/library/zlib/inflate/set_dictionary_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative '../../../spec_helper'
 require 'zlib'
 
diff --git a/spec/ruby/library/zlib/inflate/sync_point_spec.rb b/spec/ruby/library/zlib/inflate/sync_point_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/inflate/sync_point_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/inflate/sync_spec.rb b/spec/ruby/library/zlib/inflate/sync_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/inflate/sync_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/inflate_spec.rb b/spec/ruby/library/zlib/inflate_spec.rb
index 393bea4f3c..42c8dc5fbe 100644
--- a/spec/ruby/library/zlib/inflate_spec.rb
+++ b/spec/ruby/library/zlib/inflate_spec.rb
@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 require "zlib"
 
-describe "Zlib#inflate" do
+describe "Zlib.inflate" do
   it "inflates some data" do
     Zlib.inflate([120, 156, 51, 52, 132, 1, 0, 10, 145, 1, 235].pack('C*')).should == "1" * 10
   end
diff --git a/spec/ruby/library/zlib/zlib_version_spec.rb b/spec/ruby/library/zlib/zlib_version_spec.rb
index e724feaa39..f83dfae66d 100644
--- a/spec/ruby/library/zlib/zlib_version_spec.rb
+++ b/spec/ruby/library/zlib/zlib_version_spec.rb
@@ -1 +1,8 @@
 require_relative '../../spec_helper'
+require 'zlib'
+
+describe "Zlib.zlib_version" do
+  it "returns the version of the libz library" do
+    Zlib.zlib_version.should be_an_instance_of(String)
+  end
+end
diff --git a/spec/ruby/library/zlib/zstream/close_spec.rb b/spec/ruby/library/zlib/zstream/close_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/close_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/closed_spec.rb b/spec/ruby/library/zlib/zstream/closed_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/closed_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/end_spec.rb b/spec/ruby/library/zlib/zstream/end_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/end_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/ended_spec.rb b/spec/ruby/library/zlib/zstream/ended_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/ended_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/finish_spec.rb b/spec/ruby/library/zlib/zstream/finish_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/finish_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/finished_spec.rb b/spec/ruby/library/zlib/zstream/finished_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/finished_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/flush_next_in_spec.rb b/spec/ruby/library/zlib/zstream/flush_next_in_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/flush_next_in_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/flush_next_out_spec.rb b/spec/ruby/library/zlib/zstream/flush_next_out_spec.rb
index 59a0622903..63676a8203 100644
--- a/spec/ruby/library/zlib/zstream/flush_next_out_spec.rb
+++ b/spec/ruby/library/zlib/zstream/flush_next_out_spec.rb
@@ -8,7 +8,7 @@ describe "Zlib::ZStream#flush_next_out" do
     zs << [120, 156, 75, 203, 207, 7, 0, 2, 130, 1, 69].pack('C*')
 
     zs.flush_next_out.should == 'foo'
-    zs.finished?.should == true
+    zs.should.finished?
     zs.flush_next_out.should == ''
   end
 end
diff --git a/spec/ruby/library/zlib/zstream/reset_spec.rb b/spec/ruby/library/zlib/zstream/reset_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/reset_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/stream_end_spec.rb b/spec/ruby/library/zlib/zstream/stream_end_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/stream_end_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/total_in_spec.rb b/spec/ruby/library/zlib/zstream/total_in_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/total_in_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/library/zlib/zstream/total_out_spec.rb b/spec/ruby/library/zlib/zstream/total_out_spec.rb
deleted file mode 100644
index e15f14f95f..0000000000
--- a/spec/ruby/library/zlib/zstream/total_out_spec.rb
+++ /dev/null
@@ -1 +0,0 @@
-require_relative '../../../spec_helper'
diff --git a/spec/ruby/optional/capi/README b/spec/ruby/optional/capi/README
index 57b0c51f01..069ca3c106 100644
--- a/spec/ruby/optional/capi/README
+++ b/spec/ruby/optional/capi/README
@@ -8,9 +8,6 @@ specs:
     optional/capi/array_spec.rb
 2.  Put the C file containing the C functions for array_spec.rb in
     optional/capi/ext/array_spec.c
-3.  Add a '#define HAVE_RB_ARY_NEW  1' to rubyspec.h
-4.  Name the C extension class 'CApiArraySpecs'.
-5.  Name the C functions 'array_spec_rb_ary_new'.
-6.  Wrap the code in the optional/capi/ext/array_spec.c in
-    '#ifdef HAVE_RB_ARY_NEW'
-7.  Attach the C function to the class using the name 'rb_ary_new'
+3.  Name the C extension class 'CApiArraySpecs'.
+4.  Name the C functions 'array_spec_rb_ary_new'.
+5.  Attach the C function to the class using the name 'rb_ary_new'
diff --git a/spec/ruby/optional/capi/array_spec.rb b/spec/ruby/optional/capi/array_spec.rb
index acd225e0e0..7e87859856 100644
--- a/spec/ruby/optional/capi/array_spec.rb
+++ b/spec/ruby/optional/capi/array_spec.rb
@@ -83,8 +83,8 @@ describe "C-API Array function" do
       @s.rb_ary_cat([1, 2], 3, 4).should == [1, 2, 3, 4]
     end
 
-    it "raises a #{frozen_error_class} if the array is frozen" do
-      -> { @s.rb_ary_cat([].freeze, 1) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError if the array is frozen" do
+      -> { @s.rb_ary_cat([].freeze, 1) }.should raise_error(FrozenError)
     end
   end
 
@@ -130,8 +130,8 @@ describe "C-API Array function" do
       @s.rb_ary_rotate([1, 2, 3, 4], -3).should == [2, 3, 4, 1]
     end
 
-    it "raises a #{frozen_error_class} if the array is frozen" do
-      -> { @s.rb_ary_rotate([].freeze, 1) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError if the array is frozen" do
+      -> { @s.rb_ary_rotate([].freeze, 1) }.should raise_error(FrozenError)
     end
   end
 
@@ -190,6 +190,22 @@ describe "C-API Array function" do
     end
   end
 
+  describe "rb_ary_sort" do
+    it "returns a new sorted array" do
+      a = [2, 1, 3]
+      @s.rb_ary_sort(a).should == [1, 2, 3]
+      a.should == [2, 1, 3]
+    end
+  end
+
+  describe "rb_ary_sort_bang" do
+    it "sorts the given array" do
+      a = [2, 1, 3]
+      @s.rb_ary_sort_bang(a).should == [1, 2, 3]
+      a.should == [1, 2, 3]
+    end
+  end
+
   describe "rb_ary_store" do
     it "overwrites the element at the given position" do
       a = [1, 2, 3]
@@ -214,9 +230,9 @@ describe "C-API Array function" do
       a.should == [nil, nil, 7]
     end
 
-    it "raises a #{frozen_error_class} if the array is frozen" do
+    it "raises a FrozenError if the array is frozen" do
       a = [1, 2, 3].freeze
-      -> { @s.rb_ary_store(a, 1, 5) }.should raise_error(frozen_error_class)
+      -> { @s.rb_ary_store(a, 1, 5) }.should raise_error(FrozenError)
     end
   end
 
@@ -249,6 +265,14 @@ describe "C-API Array function" do
       @s.RARRAY_PTR_assign(a, :set)
       a.should == [:set, :set, :set]
     end
+
+    it "allows memcpying between arrays" do
+      a = [1, 2, 3]
+      b = [0, 0, 0]
+      @s.RARRAY_PTR_memcpy(a, b)
+      b.should == [1, 2, 3]
+      a.should == [1, 2, 3] # check a was not modified
+    end
   end
 
   describe "RARRAY_LEN" do
@@ -264,6 +288,16 @@ describe "C-API Array function" do
     end
   end
 
+  describe "RARRAY_ASET" do
+    # This macro does NOT do any bounds checking!
+    it "writes an element in the array" do
+      ary = [1, 2, 3]
+      @s.RARRAY_ASET(ary, 0, 0)
+      @s.RARRAY_ASET(ary, 2, 42)
+      ary.should == [0, 2, 42]
+    end
+  end
+
   describe "rb_assoc_new" do
     it "returns an array containing the two elements" do
       @s.rb_assoc_new(1, 2).should == [1, 2]
@@ -309,10 +343,46 @@ describe "C-API Array function" do
     end
   end
 
-  describe "rb_iterate" do
+  ruby_version_is ""..."4.0" do
+    describe "rb_iterate" do
+      it "calls an callback function as a block passed to an method" do
+        s = [1,2,3,4]
+        s2 = @s.rb_iterate(s)
+
+        s2.should == s
+
+        # Make sure they're different objects
+        s2.equal?(s).should be_false
+      end
+
+      it "calls a function with the other function available as a block" do
+        h = {a: 1, b: 2}
+
+        @s.rb_iterate_each_pair(h).sort.should == [1,2]
+      end
+
+      it "calls a function which can yield into the original block" do
+        s2 = []
+
+        o = Object.new
+        def o.each
+          yield 1
+          yield 2
+          yield 3
+          yield 4
+        end
+
+        @s.rb_iterate_then_yield(o) { |x| s2 << x }
+
+        s2.should == [1,2,3,4]
+      end
+    end
+  end
+
+  describe "rb_block_call" do
     it "calls an callback function as a block passed to an method" do
       s = [1,2,3,4]
-      s2 = @s.rb_iterate(s)
+      s2 = @s.rb_block_call(s)
 
       s2.should == s
 
@@ -323,7 +393,7 @@ describe "C-API Array function" do
     it "calls a function with the other function available as a block" do
       h = {a: 1, b: 2}
 
-      @s.rb_iterate_each_pair(h).sort.should == [1,2]
+      @s.rb_block_call_each_pair(h).sort.should == [1,2]
     end
 
     it "calls a function which can yield into the original block" do
@@ -337,7 +407,7 @@ describe "C-API Array function" do
         yield 4
       end
 
-      @s.rb_iterate_then_yield(o) { |x| s2 << x }
+      @s.rb_block_call_then_yield(o) { |x| s2 << x }
 
       s2.should == [1,2,3,4]
     end
diff --git a/spec/ruby/optional/capi/basic_object_spec.rb b/spec/ruby/optional/capi/basic_object_spec.rb
new file mode 100644
index 0000000000..2922a421da
--- /dev/null
+++ b/spec/ruby/optional/capi/basic_object_spec.rb
@@ -0,0 +1,24 @@
+require_relative 'spec_helper'
+
+load_extension("basic_object")
+
+describe "C-API basic object" do
+  before :each do
+    @s = CApiBasicObjectSpecs.new
+  end
+
+  describe "RBASIC_CLASS" do
+    it "returns the class of an object" do
+      c = Class.new
+      o = c.new
+      @s.RBASIC_CLASS(o).should == c
+    end
+
+    it "returns the singleton class" do
+      o = Object.new
+      @s.RBASIC_CLASS(o).should == Object
+      singleton_class = o.singleton_class
+      @s.RBASIC_CLASS(o).should == singleton_class
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/bignum_spec.rb b/spec/ruby/optional/capi/bignum_spec.rb
index b20275b8f7..179f053eec 100644
--- a/spec/ruby/optional/capi/bignum_spec.rb
+++ b/spec/ruby/optional/capi/bignum_spec.rb
@@ -7,21 +7,23 @@ def ensure_bignum(n)
   n
 end
 
-full_range_longs = (fixnum_max == 2**(0.size * 8 - 1) - 1)
+full_range_longs = (fixnum_max == max_long)
+max_ulong = begin
+  require 'rbconfig/sizeof'
+  RbConfig::LIMITS['ULONG_MAX']
+rescue LoadError
+  nil
+end
+# If the system doesn't offer ULONG_MAX, assume 2's complement and derive it
+# from LONG_MAX.
+max_ulong ||= 2 * (max_long + 1) - 1
 
 describe "CApiBignumSpecs" do
   before :each do
     @s = CApiBignumSpecs.new
-
-    if full_range_longs
-      @max_long = 2**(0.size * 8 - 1) - 1
-      @min_long = -@max_long - 1
-      @max_ulong = ensure_bignum(2**(0.size * 8) - 1)
-    else
-      @max_long = ensure_bignum(2**(0.size * 8 - 1) - 1)
-      @min_long = ensure_bignum(-@max_long - 1)
-      @max_ulong = ensure_bignum(2**(0.size * 8) - 1)
-    end
+    @max_long = max_long
+    @min_long = min_long
+    @max_ulong = ensure_bignum(max_ulong)
   end
 
   describe "rb_big2long" do
@@ -123,7 +125,7 @@ describe "CApiBignumSpecs" do
       val.should == @max_ulong
     end
 
-    platform_is wordsize: 64 do
+    platform_is c_long_size: 64 do
       it "packs max_ulong into 2 ulongs to allow sign bit" do
         val = @s.rb_big_pack_length(@max_ulong)
         val.should == 2
@@ -187,14 +189,14 @@ describe "CApiBignumSpecs" do
     it "returns a Fixnum for a Fixnum input value" do
       val = @s.rb_dbl2big(2)
 
-      val.kind_of?(Fixnum).should == true
+      val.kind_of?(Integer).should == true
       val.should == 2
     end
 
     it "returns a Fixnum for a Float input value" do
       val = @s.rb_dbl2big(2.5)
 
-      val.kind_of?(Fixnum).should == true
+      val.kind_of?(Integer).should == true
       val.should == 2
     end
 
@@ -202,7 +204,7 @@ describe "CApiBignumSpecs" do
       input = 219238102380912830988.5 # chosen by fair dice roll
       val   = @s.rb_dbl2big(input)
 
-      val.kind_of?(Bignum).should == true
+      val.kind_of?(Integer).should == true
 
       # This value is based on the output of a simple C extension that uses
       # rb_dbl2big() to convert the above input value to a Bignum.
diff --git a/spec/ruby/optional/capi/binding_spec.rb b/spec/ruby/optional/capi/binding_spec.rb
new file mode 100644
index 0000000000..5d0ef2efb8
--- /dev/null
+++ b/spec/ruby/optional/capi/binding_spec.rb
@@ -0,0 +1,16 @@
+require_relative 'spec_helper'
+
+load_extension("binding")
+
+describe "CApiBindingSpecs" do
+  before :each do
+    @b = CApiBindingSpecs.new
+  end
+
+  describe "Kernel#binding" do
+    it "raises when called from C" do
+      foo = 14
+      -> { @b.get_binding }.should raise_error(RuntimeError)
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/class_spec.rb b/spec/ruby/optional/capi/class_spec.rb
index 0b03fb9e6c..7abb5d4ed9 100644
--- a/spec/ruby/optional/capi/class_spec.rb
+++ b/spec/ruby/optional/capi/class_spec.rb
@@ -1,5 +1,6 @@
 require_relative 'spec_helper'
 require_relative 'fixtures/class'
+require_relative '../../core/module/fixtures/classes'
 
 load_extension("class")
 compile_extension("class_under_autoload")
@@ -11,6 +12,7 @@ autoload :ClassIdUnderAutoload, "#{object_path}/class_id_under_autoload_spec"
 describe :rb_path_to_class, shared: true do
   it "returns a class or module from a scoped String" do
     @s.send(@method, "CApiClassSpecs::A::B").should equal(CApiClassSpecs::A::B)
+    @s.send(@method, "CApiClassSpecs::A::M").should equal(CApiClassSpecs::A::M)
   end
 
   it "resolves autoload constants" do
@@ -26,7 +28,9 @@ describe :rb_path_to_class, shared: true do
   end
 
   it "raises a TypeError if the constant is not a class or module" do
-    -> { @s.send(@method, "CApiClassSpecs::A::C") }.should raise_error(TypeError)
+    -> {
+      @s.send(@method, "CApiClassSpecs::A::C")
+    }.should raise_error(TypeError, 'CApiClassSpecs::A::C does not refer to class/module')
   end
 
   it "raises an ArgumentError even if a constant in the path exists on toplevel" do
@@ -39,19 +43,100 @@ describe "C-API Class function" do
     @s = CApiClassSpecs.new
   end
 
+  describe "rb_class_instance_methods" do
+    it "returns the public and protected methods of self and its ancestors" do
+      methods = @s.rb_class_instance_methods(ModuleSpecs::Basic)
+      methods.should include(:protected_module, :public_module)
+
+      methods = @s.rb_class_instance_methods(ModuleSpecs::Basic, true)
+      methods.should include(:protected_module, :public_module)
+    end
+
+    it "when passed false as a parameter, returns the instance methods of the class" do
+      methods = @s.rb_class_instance_methods(ModuleSpecs::Child, false)
+      methods.should include(:protected_child, :public_child)
+    end
+  end
+
+  describe "rb_class_public_instance_methods" do
+    it "returns a list of public methods in module and its ancestors" do
+      methods = @s.rb_class_public_instance_methods(ModuleSpecs::CountsChild)
+      methods.should include(:public_3)
+      methods.should include(:public_2)
+      methods.should include(:public_1)
+
+      methods = @s.rb_class_public_instance_methods(ModuleSpecs::CountsChild, true)
+      methods.should include(:public_3)
+      methods.should include(:public_2)
+      methods.should include(:public_1)
+    end
+
+    it "when passed false as a parameter, should return only methods defined in that module" do
+      @s.rb_class_public_instance_methods(ModuleSpecs::CountsChild, false).should == [:public_1]
+    end
+  end
+
+  describe "rb_class_protected_instance_methods" do
+    it "returns a list of protected methods in module and its ancestors" do
+      methods = @s.rb_class_protected_instance_methods(ModuleSpecs::CountsChild)
+      methods.should include(:protected_3)
+      methods.should include(:protected_2)
+      methods.should include(:protected_1)
+
+      methods = @s.rb_class_protected_instance_methods(ModuleSpecs::CountsChild, true)
+      methods.should include(:protected_3)
+      methods.should include(:protected_2)
+      methods.should include(:protected_1)
+    end
+
+    it "when passed false as a parameter, should return only methods defined in that module" do
+      @s.rb_class_public_instance_methods(ModuleSpecs::CountsChild, false).should == [:public_1]
+    end
+  end
+
+  describe "rb_class_private_instance_methods" do
+    it "returns a list of private methods in module and its ancestors" do
+      @s.rb_class_private_instance_methods(ModuleSpecs::CountsChild).should == ModuleSpecs::CountsChild.private_instance_methods
+      @s.rb_class_private_instance_methods(ModuleSpecs::CountsChild, true).should == ModuleSpecs::CountsChild.private_instance_methods
+    end
+
+    it "when passed false as a parameter, should return only methods defined in that module" do
+      methods = @s.rb_class_private_instance_methods(ModuleSpecs::CountsChild, false)
+      methods.should == [:private_1]
+    end
+  end
+
   describe "rb_class_new_instance" do
     it "allocates and initializes a new object" do
-      o = @s.rb_class_new_instance(0, nil, CApiClassSpecs::Alloc)
+      o = @s.rb_class_new_instance([], CApiClassSpecs::Alloc)
       o.class.should == CApiClassSpecs::Alloc
       o.initialized.should be_true
     end
 
     it "passes arguments to the #initialize method" do
-      o = @s.rb_class_new_instance(2, [:one, :two], CApiClassSpecs::Alloc)
+      o = @s.rb_class_new_instance([:one, :two], CApiClassSpecs::Alloc)
       o.arguments.should == [:one, :two]
     end
   end
 
+  describe "rb_class_new_instance_kw" do
+    it "passes arguments and keywords to the #initialize method" do
+      obj = @s.rb_class_new_instance_kw([{pos: 1}, {kw: 2}], CApiClassSpecs::KeywordAlloc)
+      obj.args.should == [{pos: 1}]
+      obj.kwargs.should == {kw: 2}
+
+      obj = @s.rb_class_new_instance_kw([{}], CApiClassSpecs::KeywordAlloc)
+      obj.args.should == []
+      obj.kwargs.should == {}
+    end
+
+    it "raises TypeError if the last argument is not a Hash" do
+      -> {
+        @s.rb_class_new_instance_kw([42], CApiClassSpecs::KeywordAlloc)
+      }.should raise_error(TypeError, 'no implicit conversion of Integer into Hash')
+    end
+  end
+
   describe "rb_include_module" do
     it "includes a module into a class" do
       c = Class.new
@@ -109,16 +194,6 @@ describe "C-API Class function" do
     end
   end
 
-  describe "rb_define_method" do
-    it "defines a method taking variable arguments as a C array if the argument count is -1" do
-      @s.rb_method_varargs_1(1, 3, 7, 4).should == [1, 3, 7, 4]
-    end
-
-    it "defines a method taking variable arguments as a Ruby array if the argument count is -2" do
-      @s.rb_method_varargs_2(1, 3, 7, 4).should == [1, 3, 7, 4]
-    end
-  end
-
   describe "rb_class2name" do
     it "returns the class name" do
       @s.rb_class2name(CApiClassSpecs).should == "CApiClassSpecs"
@@ -127,6 +202,10 @@ describe "C-API Class function" do
     it "returns a string for an anonymous class" do
       @s.rb_class2name(Class.new).should be_kind_of(String)
     end
+
+    it "returns a string beginning with # for an anonymous class" do
+      @s.rb_class2name(Struct.new(:x, :y).new(1, 2).class).should.start_with?('#')
+    end
   end
 
   describe "rb_class_path" do
@@ -242,6 +321,15 @@ describe "C-API Class function" do
         @s.rb_define_class("ClassSpecDefineClass4", nil)
       }.should raise_error(ArgumentError)
     end
+
+    it "allows arbitrary names, including constant names not valid in Ruby" do
+      cls = @s.rb_define_class("_INVALID_CLASS", CApiClassSpecs::Super)
+      cls.name.should == "_INVALID_CLASS"
+
+      -> {
+        Object.const_get(cls.name)
+      }.should raise_error(NameError, /wrong constant name/)
+    end
   end
 
   describe "rb_define_class_under" do
@@ -277,6 +365,8 @@ describe "C-API Class function" do
                                         "ClassUnder6",
                                         Class.new)
       }.should raise_error(TypeError)
+    ensure
+      CApiClassSpecs.send(:remove_const, :ClassUnder6)
     end
 
     it "defines a class for an existing Autoload" do
@@ -286,6 +376,15 @@ describe "C-API Class function" do
     it "raises a TypeError if class is defined and its superclass mismatches the given one" do
       -> { @s.rb_define_class_under(CApiClassSpecs, "Sub", Object) }.should raise_error(TypeError)
     end
+
+    it "allows arbitrary names, including constant names not valid in Ruby" do
+      cls = @s.rb_define_class_under(CApiClassSpecs, "_INVALID_CLASS", CApiClassSpecs::Super)
+      cls.name.should == "CApiClassSpecs::_INVALID_CLASS"
+
+      -> {
+        CApiClassSpecs.const_get(cls.name)
+      }.should raise_error(NameError, /wrong constant name/)
+    end
   end
 
   describe "rb_define_class_id_under" do
@@ -313,6 +412,15 @@ describe "C-API Class function" do
     it "raises a TypeError if class is defined and its superclass mismatches the given one" do
       -> { @s.rb_define_class_id_under(CApiClassSpecs, :Sub, Object) }.should raise_error(TypeError)
     end
+
+    it "allows arbitrary names, including constant names not valid in Ruby" do
+      cls = @s.rb_define_class_id_under(CApiClassSpecs, :_INVALID_CLASS2, CApiClassSpecs::Super)
+      cls.name.should == "CApiClassSpecs::_INVALID_CLASS2"
+
+      -> {
+        CApiClassSpecs.const_get(cls.name)
+      }.should raise_error(NameError, /wrong constant name/)
+    end
   end
 
   describe "rb_define_class_variable" do
@@ -338,7 +446,7 @@ describe "C-API Class function" do
   end
 
   describe "rb_class_new" do
-    it "returns an new subclass of the superclass" do
+    it "returns a new subclass of the superclass" do
       subclass = @s.rb_class_new(CApiClassSpecs::NewClass)
       CApiClassSpecs::NewClass.should be_ancestor_of(subclass)
     end
@@ -381,4 +489,16 @@ describe "C-API Class function" do
       @s.rb_class_real(0).should == 0
     end
   end
+
+  describe "rb_class_get_superclass" do
+    it "returns parent class for a provided class" do
+      a = Class.new
+      @s.rb_class_get_superclass(Class.new(a)).should == a
+    end
+
+    it "returns false when there is no parent class" do
+      @s.rb_class_get_superclass(BasicObject).should == false
+      @s.rb_class_get_superclass(Module.new).should == false
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/constants_spec.rb b/spec/ruby/optional/capi/constants_spec.rb
index 11a328a91f..172d10a788 100644
--- a/spec/ruby/optional/capi/constants_spec.rb
+++ b/spec/ruby/optional/capi/constants_spec.rb
@@ -11,24 +11,42 @@ describe "C-API constant" do
     @s.rb_cArray.should == Array
   end
 
+  specify "rb_cBasicObject references the BasicObject class" do
+    @s.rb_cBasicObject.should == BasicObject
+  end
+
+  specify "rb_cBinding references the Binding class" do
+    @s.rb_cBinding.should == Binding
+  end
+
   specify "rb_cClass references the Class class" do
     @s.rb_cClass.should == Class
   end
 
+  specify "rb_cComplex references the Complex class" do
+    @s.rb_cComplex.should == Complex
+  end
+
   specify "rb_mComparable references the Comparable module" do
     @s.rb_mComparable.should == Comparable
   end
 
-  ruby_version_is ""..."2.5" do
-    specify "rb_cData references the Data class" do
-      @s.rb_cData.should == Data
-    end
+  specify "rb_cDir references the Dir class" do
+    @s.rb_cDir.should == Dir
+  end
+
+  specify "rb_cEncoding references the Encoding class" do
+    @s.rb_cEncoding.should == Encoding
   end
 
   specify "rb_mEnumerable references the Enumerable module" do
     @s.rb_mEnumerable.should == Enumerable
   end
 
+  specify "rb_cEnumerator references the Enumerator class" do
+    @s.rb_cEnumerator.should == Enumerator
+  end
+
   specify "rb_cFalseClass references the FalseClass class" do
     @s.rb_cFalseClass.should == FalseClass
   end
@@ -37,10 +55,18 @@ describe "C-API constant" do
     @s.rb_cFile.should == File
   end
 
+  specify "rb_mFileTest references the FileTest module" do
+    @s.rb_mFileTest.should == FileTest
+  end
+
   specify "rb_cFloat references the Float class" do
     @s.rb_cFloat.should == Float
   end
 
+  specify "rb_mGC references the GC module" do
+    @s.rb_mGC.should == GC
+  end
+
   specify "rb_cHash references the Hash class" do
     @s.rb_cHash.should == Hash
   end
@@ -57,10 +83,18 @@ describe "C-API constant" do
     @s.rb_mKernel.should == Kernel
   end
 
+  specify "rb_mMath references the Math module" do
+    @s.rb_mMath.should == Math
+  end
+
   specify "rb_cMatch references the MatchData class" do
     @s.rb_cMatch.should == MatchData
   end
 
+  specify "rb_cMethod references the Method class" do
+    @s.rb_cMethod.should == Method
+  end
+
   specify "rb_cModule references the Module class" do
     @s.rb_cModule.should == Module
   end
@@ -77,14 +111,34 @@ describe "C-API constant" do
     @s.rb_cObject.should == Object
   end
 
+  specify "rb_cProc references the Proc class" do
+    @s.rb_cProc.should == Proc
+  end
+
+  specify "rb_mProcess references the Process module" do
+    @s.rb_mProcess.should == Process
+  end
+
+  specify "rb_cRandom references the Random class" do
+    @s.rb_cRandom.should == Random
+  end
+
   specify "rb_cRange references the Range class" do
     @s.rb_cRange.should == Range
   end
 
+  specify "rb_cRational references the Rational class" do
+    @s.rb_cRational.should == Rational
+  end
+
   specify "rb_cRegexp references the Regexp class" do
     @s.rb_cRegexp.should == Regexp
   end
 
+  specify "rb_cStat references the File::Stat class" do
+    @s.rb_cStat.should == File::Stat
+  end
+
   specify "rb_cString references the String class" do
     @s.rb_cString.should == String
   end
@@ -109,18 +163,9 @@ describe "C-API constant" do
     @s.rb_cTrueClass.should == TrueClass
   end
 
-  specify "rb_cProc references the Proc class" do
-    @s.rb_cProc.should == Proc
-  end
-
-  specify "rb_cMethod references the Method class" do
-    @s.rb_cMethod.should == Method
-  end
-
-  specify "rb_cDir references the Dir class" do
-    @s.rb_cDir.should == Dir
+  specify "rb_cUnboundMethod references the UnboundMethod class" do
+    @s.rb_cUnboundMethod.should == UnboundMethod
   end
-
 end
 
 describe "C-API exception constant" do
@@ -132,6 +177,14 @@ describe "C-API exception constant" do
     @s.rb_eArgError.should == ArgumentError
   end
 
+  specify "rb_eEncodingError references the EncodingError class" do
+    @s.rb_eEncodingError.should == EncodingError
+  end
+
+  specify "rb_eEncCompatError references the Encoding::CompatibilityError" do
+    @s.rb_eEncCompatError.should == Encoding::CompatibilityError
+  end
+
   specify "rb_eEOFError references the EOFError class" do
     @s.rb_eEOFError.should == EOFError
   end
@@ -144,10 +197,20 @@ describe "C-API exception constant" do
     @s.rb_eException.should == Exception
   end
 
+  specify "rb_eFatal references the fatal class" do
+    fatal = @s.rb_eFatal
+    fatal.should be_kind_of(Class)
+    fatal.should < Exception
+  end
+
   specify "rb_eFloatDomainError references the FloatDomainError class" do
     @s.rb_eFloatDomainError.should == FloatDomainError
   end
 
+  specify "rb_eFrozenError references the FrozenError class" do
+    @s.rb_eFrozenError.should == FrozenError
+  end
+
   specify "rb_eIndexError references the IndexError class" do
     @s.rb_eIndexError.should == IndexError
   end
@@ -160,6 +223,10 @@ describe "C-API exception constant" do
     @s.rb_eIOError.should == IOError
   end
 
+  specify "rb_eKeyError references the KeyError class" do
+    @s.rb_eKeyError.should == KeyError
+  end
+
   specify "rb_eLoadError references the LoadError class" do
     @s.rb_eLoadError.should == LoadError
   end
@@ -172,10 +239,6 @@ describe "C-API exception constant" do
     @s.rb_eMathDomainError.should == Math::DomainError
   end
 
-  specify "rb_eEncCompatError references the Encoding::CompatibilityError" do
-    @s.rb_eEncCompatError.should == Encoding::CompatibilityError
-  end
-
   specify "rb_eNameError references the NameError class" do
     @s.rb_eNameError.should == NameError
   end
@@ -220,6 +283,10 @@ describe "C-API exception constant" do
     @s.rb_eStandardError.should == StandardError
   end
 
+  specify "rb_eStopIteration references the StopIteration class" do
+    @s.rb_eStopIteration.should == StopIteration
+  end
+
   specify "rb_eSyntaxError references the SyntaxError class" do
     @s.rb_eSyntaxError.should == SyntaxError
   end
diff --git a/spec/ruby/optional/capi/data_spec.rb b/spec/ruby/optional/capi/data_spec.rb
index c03b863678..d000eba6e3 100644
--- a/spec/ruby/optional/capi/data_spec.rb
+++ b/spec/ruby/optional/capi/data_spec.rb
@@ -1,45 +1,53 @@
 require_relative 'spec_helper'
+ruby_version_is ""..."3.4" do
+  load_extension("data")
 
-load_extension("data")
-
-describe "CApiAllocSpecs (a class with an alloc func defined)" do
-  it "calls the alloc func" do
-    @s = CApiAllocSpecs.new
-    @s.wrapped_data.should == 42 # not defined in initialize
-  end
-end
-
-describe "CApiWrappedStruct" do
-  before :each do
-    @s = CApiWrappedStructSpecs.new
+  describe "CApiAllocSpecs (a class with an alloc func defined)" do
+    it "calls the alloc func" do
+      @s = CApiAllocSpecs.new
+      @s.wrapped_data.should == 42 # not defined in initialize
+    end
   end
 
-  it "wraps with Data_Wrap_Struct and Data_Get_Struct returns data" do
-    a = @s.wrap_struct(1024)
-    @s.get_struct(a).should == 1024
-  end
+  describe "CApiWrappedStruct" do
+    before :each do
+      @s = CApiWrappedStructSpecs.new
+    end
 
-  describe "RDATA()" do
-    it "returns the struct data" do
+    it "wraps with Data_Wrap_Struct and Data_Get_Struct returns data" do
       a = @s.wrap_struct(1024)
-      @s.get_struct_rdata(a).should == 1024
+      @s.get_struct(a).should == 1024
     end
 
-    it "allows changing the wrapped struct" do
-      a = @s.wrap_struct(1024)
-      @s.change_struct(a, 100)
-      @s.get_struct(a).should == 100
+    describe "RDATA()" do
+      it "returns the struct data" do
+        a = @s.wrap_struct(1024)
+        @s.get_struct_rdata(a).should == 1024
+      end
+
+      it "allows changing the wrapped struct" do
+        a = @s.wrap_struct(1024)
+        @s.change_struct(a, 100)
+        @s.get_struct(a).should == 100
+      end
+
+      it "raises a TypeError if the object does not wrap a struct" do
+        -> { @s.get_struct(Object.new) }.should raise_error(TypeError)
+      end
     end
 
-    it "raises a TypeError if the object does not wrap a struct" do
-      -> { @s.get_struct(Object.new) }.should raise_error(TypeError)
+    describe "rb_check_type" do
+      it "does not raise an exception when checking data objects" do
+        a = @s.wrap_struct(1024)
+        @s.rb_check_type(a, a).should == true
+      end
     end
-  end
 
-  describe "DATA_PTR" do
-    it "returns the struct data" do
-      a = @s.wrap_struct(1024)
-      @s.get_struct_data_ptr(a).should == 1024
+    describe "DATA_PTR" do
+      it "returns the struct data" do
+        a = @s.wrap_struct(1024)
+        @s.get_struct_data_ptr(a).should == 1024
+      end
     end
   end
 end
diff --git a/spec/ruby/optional/capi/debug_spec.rb b/spec/ruby/optional/capi/debug_spec.rb
new file mode 100644
index 0000000000..14ba25609c
--- /dev/null
+++ b/spec/ruby/optional/capi/debug_spec.rb
@@ -0,0 +1,74 @@
+require_relative 'spec_helper'
+
+load_extension('debug')
+
+describe "C-API Debug function" do
+  before :each do
+    @o = CApiDebugSpecs.new
+  end
+
+  describe "rb_debug_inspector_open" do
+    it "creates a debug context and calls the given callback" do
+      @o.rb_debug_inspector_open(42).should be_kind_of(Array)
+      @o.debug_spec_callback_data.should == 42
+    end
+  end
+
+  describe "rb_debug_inspector_frame_self_get" do
+    it "returns self" do
+      @o.rb_debug_inspector_frame_self_get(0).should == @o
+      @o.rb_debug_inspector_frame_self_get(1).should == self
+    end
+  end
+
+  describe "rb_debug_inspector_frame_class_get" do
+    it "returns the frame class" do
+      @o.rb_debug_inspector_frame_class_get(0).should == CApiDebugSpecs
+    end
+  end
+
+  describe "rb_debug_inspector_frame_binding_get" do
+    it "returns the current binding" do
+      a = "test"
+      b = @o.rb_debug_inspector_frame_binding_get(1)
+      b.should be_an_instance_of(Binding)
+      b.local_variable_get(:a).should == "test"
+    end
+
+    it "matches the locations in rb_debug_inspector_backtrace_locations" do
+      frames = @o.rb_debug_inspector_open(42)
+      frames.each do |_s, klass, binding, iseq, backtrace_location|
+        if binding
+          # YJIT modifies Array#each backtraces but leaves its source_location as is
+          unless defined?(RubyVM::YJIT) && klass == Array && iseq.label == "each"
+            binding.source_location.should == [backtrace_location.path, backtrace_location.lineno]
+          end
+          method_name = binding.eval('__method__')
+          if method_name
+            method_name.should == backtrace_location.base_label.to_sym
+          end
+        end
+      end
+    end
+  end
+
+  describe "rb_debug_inspector_frame_iseq_get" do
+    it "returns an InstructionSequence" do
+      if defined?(RubyVM::InstructionSequence)
+        @o.rb_debug_inspector_frame_iseq_get(1).should be_an_instance_of(RubyVM::InstructionSequence)
+      else
+        @o.rb_debug_inspector_frame_iseq_get(1).should == nil
+      end
+    end
+  end
+
+  describe "rb_debug_inspector_backtrace_locations" do
+    it "returns an array of Thread::Backtrace::Location" do
+      bts = @o.rb_debug_inspector_backtrace_locations
+      bts.should_not.empty?
+      bts.each { |bt| bt.should be_kind_of(Thread::Backtrace::Location) }
+      location = "#{__FILE__}:#{__LINE__ - 3}"
+      bts[1].to_s.should include(location)
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/digest_spec.rb b/spec/ruby/optional/capi/digest_spec.rb
new file mode 100644
index 0000000000..65c5ecebb1
--- /dev/null
+++ b/spec/ruby/optional/capi/digest_spec.rb
@@ -0,0 +1,103 @@
+require_relative 'spec_helper'
+
+begin
+  require 'fiddle'
+rescue LoadError
+  return
+end
+
+load_extension('digest')
+
+describe "C-API Digest functions" do
+  before :each do
+    @s = CApiDigestSpecs.new
+  end
+
+  describe "rb_digest_make_metadata" do
+    before :each do
+      @metadata = @s.rb_digest_make_metadata
+    end
+
+    it "should store the block length" do
+      @s.block_length(@metadata).should == 40
+    end
+
+    it "should store the digest length" do
+      @s.digest_length(@metadata).should == 20
+    end
+
+    it "should store the context size" do
+      @s.context_size(@metadata).should == 129
+    end
+  end
+
+  describe "digest plugin" do
+    before :each do
+      @s = CApiDigestSpecs.new
+      @digest = Digest::TestDigest.new
+
+      # A pointer to the CTX type defined in the extension for this spec. Digest does not make the context directly
+      # accessible as part of its API. However, to ensure we are properly loading the plugin, it's useful to have
+      # direct access to the context pointer to verify its contents.
+      @context = Fiddle::Pointer.new(@s.context(@digest))
+    end
+
+    it "should report the block length" do
+      @digest.block_length.should == 40
+    end
+
+    it "should report the digest length" do
+      @digest.digest_length.should == 20
+    end
+
+    it "should initialize the context" do
+      # Our test plugin always writes the string "Initialized\n" when its init function is called.
+      verify_context("Initialized\n")
+    end
+
+    it "should update the digest" do
+      @digest.update("hello world")
+
+      # Our test plugin always writes the string "Updated: <data>\n" when its update function is called.
+      current = "Initialized\nUpdated: hello world"
+      verify_context(current)
+
+      @digest << "blah"
+
+      current = "Initialized\nUpdated: hello worldUpdated: blah"
+      verify_context(current)
+    end
+
+    it "should finalize the digest" do
+      @digest.update("")
+
+      finish_string = @digest.instance_eval { finish }
+
+      # We expect the plugin to write out the last `@digest.digest_length` bytes, followed by the string "Finished\n".
+      #
+      finish_string.should == "d\nUpdated: Finished\n"
+      finish_string.encoding.should == Encoding::ASCII_8BIT
+    end
+
+    it "should reset the context" do
+      @digest.update("foo")
+      verify_context("Initialized\nUpdated: foo")
+
+      @digest.reset
+
+      # The context will be recreated as a result of the `reset` so we must fetch the latest context pointer.
+      @context = Fiddle::Pointer.new(@s.context(@digest))
+
+      verify_context("Initialized\n")
+    end
+
+    def verify_context(current_body)
+      # In the CTX type, the length of the current context contents is stored in the first byte.
+      byte_count = @context[0]
+      byte_count.should == current_body.bytesize
+
+      # After the size byte follows a string.
+      @context[1, byte_count].should == current_body
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/encoding_spec.rb b/spec/ruby/optional/capi/encoding_spec.rb
index 003edc9669..c14983c7ea 100644
--- a/spec/ruby/optional/capi/encoding_spec.rb
+++ b/spec/ruby/optional/capi/encoding_spec.rb
@@ -1,8 +1,9 @@
 # -*- encoding: utf-8 -*-
+# frozen_string_literal: false
 require_relative 'spec_helper'
 require_relative 'fixtures/encoding'
 
-load_extension('encoding')
+extension_path = load_extension('encoding')
 
 describe :rb_enc_get_index, shared: true do
   it "returns the index of the encoding of a String" do
@@ -31,13 +32,11 @@ describe :rb_enc_set_index, shared: true do
     result.first.should == result.last
   end
 
-  ruby_version_is "2.6" do
-    it "raises an ArgumentError for a non-encoding capable object" do
-      obj = Object.new
-      -> {
-        result = @s.send(@method, obj, 1)
-      }.should raise_error(ArgumentError, "cannot set encoding on non-encoding capable object")
-    end
+  it "raises an ArgumentError for a non-encoding capable object" do
+    obj = Object.new
+    -> {
+      result = @s.send(@method, obj, 1)
+    }.should raise_error(ArgumentError, "cannot set encoding on non-encoding capable object")
   end
 end
 
@@ -48,12 +47,61 @@ describe "C-API Encoding function" do
     @s = CApiEncodingSpecs.new
   end
 
-  ruby_version_is "2.6" do
-    describe "rb_enc_alias" do
-      it "creates an alias for an existing Encoding" do
-        name = "ZOMGWTFBBQ#{@n += 1}"
-        @s.rb_enc_alias(name, "UTF-8").should >= 0
-        Encoding.find(name).name.should == "UTF-8"
+  describe "rb_enc_alias" do
+    it "creates an alias for an existing Encoding" do
+      name = "ZOMGWTFBBQ#{@n += 1}"
+      @s.rb_enc_alias(name, "UTF-8").should >= 0
+      Encoding.find(name).name.should == "UTF-8"
+    end
+  end
+
+  describe "rb_enc_codelen" do
+    it "returns the correct length for the given codepoint" do
+      @s.rb_enc_codelen(0x24, Encoding::UTF_8).should == 1
+      @s.rb_enc_codelen(0xA2, Encoding::UTF_8).should == 2
+      @s.rb_enc_codelen(0x20AC, Encoding::UTF_8).should == 3
+      @s.rb_enc_codelen(0x24B62, Encoding::UTF_8).should == 4
+    end
+  end
+
+  describe "rb_enc_strlen" do
+    before :each do
+      @str = 'こにちわ' # Each codepoint in this string is 3 bytes in UTF-8
+    end
+
+    it "returns the correct string length for the encoding" do
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::UTF_8).should == 4
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::BINARY).should == 12
+    end
+
+    it "returns the string length based on a fixed-width encoding's character length, even if the encoding is incompatible" do
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::UTF_16BE).should == 6
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::UTF_16LE).should == 6
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::UTF_32BE).should == 3
+      @s.rb_enc_strlen(@str, @str.bytesize, Encoding::UTF_32LE).should == 3
+    end
+
+    it "does not consider strings to be NUL-terminated" do
+      s = "abc\0def"
+      @s.rb_enc_strlen(s, s.bytesize, Encoding::US_ASCII).should == 7
+      @s.rb_enc_strlen(s, s.bytesize, Encoding::UTF_8).should == 7
+    end
+
+    describe "handles broken strings" do
+      it "combines valid character and invalid character counts in UTF-8" do
+        # The result is 3 because `rb_enc_strlen` counts the first valid character and then adds
+        # the byte count for the invalid character that follows for 1 + 2.
+        @s.rb_enc_strlen(@str, 5, Encoding::UTF_8).should == 3
+      end
+
+      it "combines valid character and invalid character counts in UTF-16" do
+        @s.rb_enc_strlen(@str, 5, Encoding::UTF_16BE).should == 3
+      end
+
+      it "rounds up for fixed-width encodings" do
+        @s.rb_enc_strlen(@str, 7, Encoding::UTF_32BE).should == 2
+        @s.rb_enc_strlen(@str, 7, Encoding::UTF_32LE).should == 2
+        @s.rb_enc_strlen(@str, 5, Encoding::BINARY).should == 5
       end
     end
   end
@@ -82,12 +130,72 @@ describe "C-API Encoding function" do
     end
   end
 
+  describe "rb_enc_isalnum" do
+    it "returns non-zero for alpha-numeric characters" do
+      @s.rb_enc_isalnum("a".ord, Encoding::US_ASCII).should == true
+      @s.rb_enc_isalnum("2".ord, Encoding::US_ASCII).should == true
+      @s.rb_enc_isalnum("a".ord, Encoding::UTF_8).should == true
+      @s.rb_enc_isalnum("2".ord, Encoding::UTF_8).should == true
+      @s.rb_enc_isalnum("é".encode(Encoding::ISO_8859_1).ord, Encoding::ISO_8859_1).should == true
+    end
+
+    it "returns zero for non alpha-numeric characters" do
+      @s.rb_enc_isalnum("-".ord, Encoding::US_ASCII).should == false
+      @s.rb_enc_isalnum(" ".ord, Encoding::US_ASCII).should == false
+      @s.rb_enc_isalnum("-".ord, Encoding::UTF_8).should == false
+      @s.rb_enc_isalnum(" ".ord, Encoding::UTF_8).should == false
+    end
+  end
+
+  describe "rb_enc_isspace" do
+    it "returns non-zero for space characters" do
+      @s.rb_enc_isspace(" ".ord, Encoding::US_ASCII).should == true
+      @s.rb_enc_isspace(" ".ord, Encoding::UTF_8).should == true
+    end
+
+    it "returns zero for non space characters" do
+      @s.rb_enc_isspace("-".ord, Encoding::US_ASCII).should == false
+      @s.rb_enc_isspace("A".ord, Encoding::US_ASCII).should == false
+      @s.rb_enc_isspace("3".ord, Encoding::US_ASCII).should == false
+      @s.rb_enc_isspace("-".ord, Encoding::UTF_8).should == false
+      @s.rb_enc_isspace("A".ord, Encoding::UTF_8).should == false
+      @s.rb_enc_isspace("3".ord, Encoding::UTF_8).should == false
+    end
+  end
+
   describe "rb_enc_from_index" do
     it "returns an Encoding" do
       @s.rb_enc_from_index(0).should be_an_instance_of(String)
     end
   end
 
+  describe "rb_enc_mbc_to_codepoint" do
+    it "returns the correct codepoint for the given character and size" do
+      @s.rb_enc_mbc_to_codepoint("é").should == 0xE9
+    end
+
+    it "returns 0 if p == e" do
+      @s.rb_enc_mbc_to_codepoint("").should == 0
+    end
+
+    it "returns the raw byte if incomplete character in UTF-8" do
+      @s.rb_enc_mbc_to_codepoint("\xC3").should == 0xC3
+      @s.rb_enc_mbc_to_codepoint("\x80").should == 0x80
+    end
+  end
+
+  describe "rb_enc_mbcput" do
+    it "writes the correct bytes to the buffer" do
+      @s.rb_enc_mbcput(0x24, Encoding::UTF_8).should == "$"
+      @s.rb_enc_mbcput(0xA2, Encoding::UTF_8).should == "¢"
+      @s.rb_enc_mbcput(0x20AC, Encoding::UTF_8).should == "€"
+      @s.rb_enc_mbcput(0x24B62, Encoding::UTF_8).should == "𤭢"
+
+      @s.rb_enc_mbcput(0x24, Encoding::UTF_16BE).bytes.should == [0, 0x24]
+      @s.rb_enc_mbcput(0x24B62, Encoding::UTF_16LE).bytes.should == [82, 216, 98, 223]
+    end
+  end
+
   describe "rb_usascii_encoding" do
     it "returns the encoding for Encoding::US_ASCII" do
       @s.rb_usascii_encoding.should == "US-ASCII"
@@ -131,6 +239,29 @@ describe "C-API Encoding function" do
     end
   end
 
+  describe "rb_enc_precise_mbclen" do
+    it "returns the correct length for single byte characters" do
+      @s.rb_enc_precise_mbclen("hello", 7).should == 1
+      @s.rb_enc_precise_mbclen("hello", 5).should == 1
+      @s.rb_enc_precise_mbclen("hello", 1).should == 1
+      @s.rb_enc_precise_mbclen("hello", 0).should == -2
+      @s.rb_enc_precise_mbclen("hello", -1).should == -2
+      @s.rb_enc_precise_mbclen("hello", -5).should == -2
+    end
+
+    it "returns the correct length for multi-byte characters" do
+      @s.rb_enc_precise_mbclen("ésumé", 2).should == 2
+      @s.rb_enc_precise_mbclen("ésumé", 3).should == 2
+      @s.rb_enc_precise_mbclen("ésumé", 0).should == -2
+      @s.rb_enc_precise_mbclen("ésumé", 1).should == -2
+      @s.rb_enc_precise_mbclen("あ", 20).should == 3
+      @s.rb_enc_precise_mbclen("あ", 3).should == 3
+      @s.rb_enc_precise_mbclen("あ", 2).should == -2
+      @s.rb_enc_precise_mbclen("あ", 0).should == -2
+      @s.rb_enc_precise_mbclen("あ", -2).should == -2
+    end
+  end
+
   describe "rb_obj_encoding" do
     it "returns the encoding associated with an object" do
       str = "abc".encode Encoding::BINARY
@@ -153,11 +284,9 @@ describe "C-API Encoding function" do
       @s.rb_enc_get_index(1).should == -1
     end
 
-    ruby_version_is "2.6" do
-      it "returns -1 for an object without an encoding" do
-        obj = Object.new
-        @s.rb_enc_get_index(obj).should == -1
-      end
+    it "returns -1 for an object without an encoding" do
+      obj = Object.new
+      @s.rb_enc_get_index(obj).should == -1
     end
   end
 
@@ -173,6 +302,26 @@ describe "C-API Encoding function" do
     end
   end
 
+  describe "rb_enc_str_new_cstr" do
+    it "creates a new ruby string from a c string literal" do
+      result = @s.rb_enc_str_new_cstr_constant(Encoding::US_ASCII)
+      result.should  == "test string literal"
+      result.encoding.should == Encoding::US_ASCII
+    end
+
+    it "creates a new ruby string from a c string variable" do
+      result = @s.rb_enc_str_new_cstr("test string", Encoding::US_ASCII)
+      result.should == "test string"
+      result.encoding.should == Encoding::US_ASCII
+    end
+
+    it "when null encoding is given with a c string literal, it creates a new ruby string with ASCII_8BIT encoding" do
+      result = @s.rb_enc_str_new_cstr_constant(nil)
+      result.should == "test string literal"
+      result.encoding.should == Encoding::ASCII_8BIT
+    end
+  end
+
   describe "rb_enc_str_coderange" do
     describe "when the encoding is BINARY" do
       it "returns ENC_CODERANGE_7BIT if there are no high bits set" do
@@ -217,6 +366,17 @@ describe "C-API Encoding function" do
     end
   end
 
+  describe "MBCLEN_CHARFOUND_P" do
+    it "returns non-zero for valid character" do
+      @s.MBCLEN_CHARFOUND_P("a".ord).should == 1
+    end
+
+    it "returns zero for invalid characters" do
+      @s.MBCLEN_CHARFOUND_P(0).should == 0
+      @s.MBCLEN_CHARFOUND_P(-1).should == 0
+    end
+  end
+
   describe "ENCODING_GET" do
     it_behaves_like :rb_enc_get_index, :ENCODING_GET
   end
@@ -257,6 +417,14 @@ describe "C-API Encoding function" do
 
       @s.rb_to_encoding(obj).should == "UTF-8"
     end
+
+    describe "when the rb_encoding struct is stored in native memory" do
+      it "can still read the name of the encoding" do
+        address = @s.rb_to_encoding_native_store(Encoding::UTF_8)
+        address.should be_kind_of(Integer)
+        @s.rb_to_encoding_native_name(address).should == "UTF-8"
+      end
+    end
   end
 
   describe "rb_to_encoding_index" do
@@ -312,7 +480,7 @@ describe "C-API Encoding function" do
     end
 
     it "sets the encoding of a Regexp to that of the second argument" do
-      @s.rb_enc_copy(/regexp/, @obj).encoding.should == Encoding::US_ASCII
+      @s.rb_enc_copy(/regexp/.dup, @obj).encoding.should == Encoding::US_ASCII
     end
   end
 
@@ -363,7 +531,7 @@ describe "C-API Encoding function" do
     end
 
     it "sets the encoding of a Regexp to the encoding" do
-      @s.rb_enc_associate(/regexp/, "BINARY").encoding.should == Encoding::BINARY
+      @s.rb_enc_associate(/regexp/.dup, "BINARY").encoding.should == Encoding::BINARY
     end
 
     it "sets the encoding of a String to a default when the encoding is NULL" do
@@ -380,7 +548,7 @@ describe "C-API Encoding function" do
 
     it "sets the encoding of a Regexp to the encoding" do
       index = @s.rb_enc_find_index("UTF-8")
-      enc = @s.rb_enc_associate_index(/regexp/, index).encoding
+      enc = @s.rb_enc_associate_index(/regexp/.dup, index).encoding
       enc.should == Encoding::UTF_8
     end
 
@@ -392,19 +560,19 @@ describe "C-API Encoding function" do
 
   describe "rb_ascii8bit_encindex" do
     it "returns an index for the ASCII-8BIT encoding" do
-      @s.rb_ascii8bit_encindex().should >= 0
+      @s.rb_ascii8bit_encindex().should == 0
     end
   end
 
   describe "rb_utf8_encindex" do
     it "returns an index for the UTF-8 encoding" do
-      @s.rb_utf8_encindex().should >= 0
+      @s.rb_utf8_encindex().should == 1
     end
   end
 
   describe "rb_usascii_encindex" do
     it "returns an index for the US-ASCII encoding" do
-      @s.rb_usascii_encindex().should >= 0
+      @s.rb_usascii_encindex().should == 2
     end
   end
 
@@ -479,4 +647,102 @@ describe "C-API Encoding function" do
       length.should == 4
     end
   end
+
+  describe "rb_enc_str_asciionly_p" do
+    it "returns true for an ASCII string" do
+      @s.rb_enc_str_asciionly_p("hello").should be_true
+    end
+
+    it "returns false for a non-ASCII string" do
+      @s.rb_enc_str_asciionly_p("hüllo").should be_false
+    end
+  end
+
+  describe "rb_enc_raise" do
+    it "forces exception message encoding to the specified one" do
+      utf_8_incompatible_string = "\x81".b
+
+      -> {
+        @s.rb_enc_raise(Encoding::UTF_8, RuntimeError, utf_8_incompatible_string)
+      }.should raise_error { |e|
+        e.message.encoding.should == Encoding::UTF_8
+        e.message.valid_encoding?.should == false
+        e.message.bytes.should == utf_8_incompatible_string.bytes
+      }
+    end
+  end
+
+  describe "rb_uv_to_utf8" do
+    it 'converts a Unicode codepoint to a UTF-8 C string' do
+      str = ' ' * 6
+      {
+        1  => "\x01",
+        0x80 => "\xC2\x80",
+        0x800 => "\xE0\xA0\x80",
+        0x10000 => "\xF0\x90\x80\x80",
+        0x200000 => "\xF8\x88\x80\x80\x80",
+        0x4000000 => "\xFC\x84\x80\x80\x80\x80",
+      }.each do |num, result|
+        len = @s.rb_uv_to_utf8(str, num)
+        str.byteslice(0, len).should == result
+      end
+    end
+  end
+
+  describe "rb_enc_left_char_head" do
+    it 'returns the head position of a character' do
+      @s.rb_enc_left_char_head("é", 1).should == 0
+      @s.rb_enc_left_char_head("éééé", 7).should == 6
+
+      @s.rb_enc_left_char_head("a", 0).should == 0
+
+      # unclear if this is intended to work
+      @s.rb_enc_left_char_head("a", 1).should == 1
+
+      # Works because for single-byte encodings rb_enc_left_char_head() just returns the pointer
+      @s.rb_enc_left_char_head("a".force_encoding(Encoding::US_ASCII), 88).should == 88
+      @s.rb_enc_left_char_head("a".b, 88).should == 88
+    end
+  end
+
+  describe "ONIGENC_MBC_CASE_FOLD" do
+    it "returns the correct case fold for the given string" do
+      @s.ONIGENC_MBC_CASE_FOLD("lower").should == ["l", 1]
+      @s.ONIGENC_MBC_CASE_FOLD("Upper").should == ["u", 1]
+      @s.ONIGENC_MBC_CASE_FOLD("ABC"[1..-1]).should == ["b", 1]
+    end
+
+    it "works with other encodings" do
+      @s.ONIGENC_MBC_CASE_FOLD("lower".force_encoding("binary")).should == ["l", 1]
+      @s.ONIGENC_MBC_CASE_FOLD("Upper".force_encoding("binary")).should == ["u", 1]
+      @s.ONIGENC_MBC_CASE_FOLD("É").should == ["é", 2]
+
+      str, length = @s.ONIGENC_MBC_CASE_FOLD('$'.encode(Encoding::UTF_16BE))
+      length.should == 2
+      str.bytes.should == [0, 0x24]
+    end
+  end
+
+  describe "rb_define_dummy_encoding" do
+    run = 0
+
+    it "defines the dummy encoding" do
+      @s.rb_define_dummy_encoding("FOO#{run += 1}")
+      enc = Encoding.find("FOO#{run}")
+      enc.should.dummy?
+    end
+
+    it "returns the index of the dummy encoding" do
+      index = @s.rb_define_dummy_encoding("BAR#{run += 1}")
+      index.should == Encoding.list.size - 1
+    end
+
+    it "raises EncodingError if too many encodings" do
+      code = <<-RUBY
+        require #{extension_path.dump}
+        1_000.times {|i| CApiEncodingSpecs.new.rb_define_dummy_encoding("R_\#{i}") }
+      RUBY
+      ruby_exe(code, args: "2>&1", exit_status: 1).should.include?('too many encoding (> 256) (EncodingError)')
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/exception_spec.rb b/spec/ruby/optional/capi/exception_spec.rb
index 62d7d3706e..5bc8e26c62 100644
--- a/spec/ruby/optional/capi/exception_spec.rb
+++ b/spec/ruby/optional/capi/exception_spec.rb
@@ -36,6 +36,50 @@ describe "C-API Exception function" do
       runtime_error.set_backtrace []
       -> { @s.rb_exc_raise(runtime_error) }.should raise_error(RuntimeError, '42')
     end
+
+    it "sets $! to the raised exception when not rescuing from an another exception" do
+      runtime_error = RuntimeError.new '42'
+      runtime_error.set_backtrace []
+      begin
+        @s.rb_exc_raise(runtime_error)
+      rescue
+        $!.should == runtime_error
+      end
+    end
+
+    it "sets $! to the raised exception when $! when rescuing from an another exception" do
+      runtime_error = RuntimeError.new '42'
+      runtime_error.set_backtrace []
+      begin
+        begin
+          raise StandardError
+        rescue
+          @s.rb_exc_raise(runtime_error)
+        end
+      rescue
+        $!.should == runtime_error
+      end
+    end
+  end
+
+  describe "rb_errinfo" do
+    it "is cleared when entering a C method" do
+      begin
+        raise StandardError
+      rescue
+        $!.class.should == StandardError
+        @s.rb_errinfo().should == nil
+      end
+    end
+
+    it "does not clear $! in the calling method" do
+      begin
+        raise StandardError
+      rescue
+        @s.rb_errinfo()
+        $!.class.should == StandardError
+      end
+    end
   end
 
   describe "rb_set_errinfo" do
@@ -55,4 +99,103 @@ describe "C-API Exception function" do
       -> { @s.rb_set_errinfo("error") }.should raise_error(TypeError)
     end
   end
+
+  describe "rb_error_frozen_object" do
+    it "raises a FrozenError regardless of the object's frozen state" do
+      # The type of the argument we supply doesn't matter. The choice here is arbitrary and we only change the type
+      # of the argument to ensure the exception messages are set correctly.
+      -> { @s.rb_error_frozen_object(Array.new) }.should raise_error(FrozenError, "can't modify frozen Array: []")
+      -> { @s.rb_error_frozen_object(Array.new.freeze) }.should raise_error(FrozenError, "can't modify frozen Array: []")
+    end
+
+    it "properly handles recursive rb_error_frozen_object calls" do
+      klass = Class.new(Object)
+      object = klass.new
+      s = @s
+      klass.define_method :inspect do
+        s.rb_error_frozen_object(object)
+      end
+
+      -> { @s.rb_error_frozen_object(object) }.should raise_error(FrozenError, "can't modify frozen #{klass}:  ...")
+    end
+  end
+
+  describe "rb_syserr_new" do
+    it "returns system error with default message when passed message is NULL" do
+      exception = @s.rb_syserr_new(Errno::ENOENT::Errno, nil)
+      exception.class.should == Errno::ENOENT
+      exception.message.should include("No such file or directory")
+      exception.should.is_a?(SystemCallError)
+    end
+
+    it "returns system error with custom message" do
+      exception = @s.rb_syserr_new(Errno::ENOENT::Errno, "custom message")
+
+      exception.message.should include("custom message")
+      exception.class.should == Errno::ENOENT
+      exception.should.is_a?(SystemCallError)
+    end
+  end
+
+  describe "rb_syserr_new_str" do
+    it "returns system error with default message when passed message is nil" do
+      exception = @s.rb_syserr_new_str(Errno::ENOENT::Errno, nil)
+
+      exception.message.should include("No such file or directory")
+      exception.class.should == Errno::ENOENT
+      exception.should.is_a?(SystemCallError)
+    end
+
+    it "returns system error with custom message" do
+      exception = @s.rb_syserr_new_str(Errno::ENOENT::Errno, "custom message")
+      exception.message.should include("custom message")
+      exception.class.should == Errno::ENOENT
+      exception.should.is_a?(SystemCallError)
+    end
+  end
+
+  describe "rb_make_exception" do
+    it "returns a RuntimeError when given a String argument" do
+      e = @s.rb_make_exception(["Message"])
+      e.class.should == RuntimeError
+      e.message.should == "Message"
+    end
+
+    it "returns the exception when given an Exception argument" do
+      exc = Exception.new
+      e = @s.rb_make_exception([exc])
+      e.should == exc
+    end
+
+    it "returns the exception with the given class and message" do
+      e = @s.rb_make_exception([Exception, "Message"])
+      e.class.should == Exception
+      e.message.should == "Message"
+    end
+
+    it "returns the exception with the given class, message, and backtrace" do
+      e = @s.rb_make_exception([Exception, "Message", ["backtrace 1"]])
+      e.class.should == Exception
+      e.message.should == "Message"
+      e.backtrace.should == ["backtrace 1"]
+    end
+
+    it "raises a TypeError for incorrect types" do
+      -> { @s.rb_make_exception([nil]) }.should raise_error(TypeError)
+      -> { @s.rb_make_exception([Object.new]) }.should raise_error(TypeError)
+      obj = Object.new
+      def obj.exception
+        "not exception type"
+      end
+      -> { @s.rb_make_exception([obj]) }.should raise_error(TypeError)
+    end
+
+    it "raises an ArgumentError for too many arguments" do
+      -> { @s.rb_make_exception([Exception, "Message", ["backtrace 1"], "extra"])  }.should raise_error(ArgumentError)
+    end
+
+    it "returns nil for empty arguments" do
+      @s.rb_make_exception([]).should == nil
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/ext/array_spec.c b/spec/ruby/optional/capi/ext/array_spec.c
index 69cb035e61..628c4df9d7 100644
--- a/spec/ruby/optional/capi/ext/array_spec.c
+++ b/spec/ruby/optional/capi/ext/array_spec.c
@@ -33,6 +33,19 @@ static VALUE array_spec_RARRAY_PTR_assign(VALUE self, VALUE array, VALUE value)
   return Qnil;
 }
 
+
+static VALUE array_spec_RARRAY_PTR_memcpy(VALUE self, VALUE array1, VALUE array2) {
+  VALUE *ptr1, *ptr2;
+  long size;
+  size = RARRAY_LEN(array1);
+  ptr1 = RARRAY_PTR(array1);
+  ptr2 = RARRAY_PTR(array2);
+  if (ptr1 != NULL && ptr2 != NULL) {
+    memcpy(ptr2, ptr1, size * sizeof(VALUE));
+  }
+  return Qnil;
+}
+
 static VALUE array_spec_RARRAY_LEN(VALUE self, VALUE array) {
   return INT2FIX(RARRAY_LEN(array));
 }
@@ -41,6 +54,11 @@ static VALUE array_spec_RARRAY_AREF(VALUE self, VALUE array, VALUE index) {
   return RARRAY_AREF(array, FIX2INT(index));
 }
 
+static VALUE array_spec_RARRAY_ASET(VALUE self, VALUE array, VALUE index, VALUE value) {
+  RARRAY_ASET(array, FIX2INT(index), value);
+  return value;
+}
+
 static VALUE array_spec_rb_ary_aref(int argc, VALUE *argv, VALUE self) {
   VALUE ary, args;
   rb_scan_args(argc, argv, "1*", &ary, &args);
@@ -144,6 +162,14 @@ static VALUE array_spec_rb_ary_shift(VALUE self, VALUE array) {
   return rb_ary_shift(array);
 }
 
+static VALUE array_spec_rb_ary_sort(VALUE self, VALUE array) {
+  return rb_ary_sort(array);
+}
+
+static VALUE array_spec_rb_ary_sort_bang(VALUE self, VALUE array) {
+  return rb_ary_sort_bang(array);
+}
+
 static VALUE array_spec_rb_ary_store(VALUE self, VALUE array, VALUE offset, VALUE value) {
   rb_ary_store(array, FIX2INT(offset), value);
 
@@ -170,6 +196,7 @@ static VALUE copy_ary(RB_BLOCK_CALL_FUNC_ARGLIST(el, new_ary)) {
   return rb_ary_push(new_ary, el);
 }
 
+#ifndef RUBY_VERSION_IS_4_0
 static VALUE array_spec_rb_iterate(VALUE self, VALUE ary) {
   VALUE new_ary = rb_ary_new();
 
@@ -177,11 +204,21 @@ static VALUE array_spec_rb_iterate(VALUE self, VALUE ary) {
 
   return new_ary;
 }
+#endif
+
+static VALUE array_spec_rb_block_call(VALUE self, VALUE ary) {
+  VALUE new_ary = rb_ary_new();
+
+  rb_block_call(ary, rb_intern("each"), 0, 0, copy_ary, new_ary);
+
+  return new_ary;
+}
 
 static VALUE sub_pair(RB_BLOCK_CALL_FUNC_ARGLIST(el, holder)) {
   return rb_ary_push(holder, rb_ary_entry(el, 1));
 }
 
+#ifndef RUBY_VERSION_IS_4_0
 static VALUE each_pair(VALUE obj) {
   return rb_funcall(obj, rb_intern("each_pair"), 0);
 }
@@ -193,16 +230,32 @@ static VALUE array_spec_rb_iterate_each_pair(VALUE self, VALUE obj) {
 
   return new_ary;
 }
+#endif
+
+static VALUE array_spec_rb_block_call_each_pair(VALUE self, VALUE obj) {
+  VALUE new_ary = rb_ary_new();
+
+  rb_block_call(obj, rb_intern("each_pair"), 0, 0, sub_pair, new_ary);
+
+  return new_ary;
+}
 
 static VALUE iter_yield(RB_BLOCK_CALL_FUNC_ARGLIST(el, ary)) {
   rb_yield(el);
   return Qnil;
 }
 
+#ifndef RUBY_VERSION_IS_4_0
 static VALUE array_spec_rb_iterate_then_yield(VALUE self, VALUE obj) {
   rb_iterate(rb_each, obj, iter_yield, obj);
   return Qnil;
 }
+#endif
+
+static VALUE array_spec_rb_block_call_then_yield(VALUE self, VALUE obj) {
+  rb_block_call(obj, rb_intern("each"), 0, 0, iter_yield, obj);
+  return Qnil;
+}
 
 static VALUE array_spec_rb_mem_clear(VALUE self, VALUE obj) {
   VALUE ary[1];
@@ -229,7 +282,9 @@ void Init_array_spec(void) {
   rb_define_method(cls, "RARRAY_LEN", array_spec_RARRAY_LEN, 1);
   rb_define_method(cls, "RARRAY_PTR_iterate", array_spec_RARRAY_PTR_iterate, 1);
   rb_define_method(cls, "RARRAY_PTR_assign", array_spec_RARRAY_PTR_assign, 2);
+  rb_define_method(cls, "RARRAY_PTR_memcpy", array_spec_RARRAY_PTR_memcpy, 2);
   rb_define_method(cls, "RARRAY_AREF", array_spec_RARRAY_AREF, 2);
+  rb_define_method(cls, "RARRAY_ASET", array_spec_RARRAY_ASET, 3);
   rb_define_method(cls, "rb_ary_aref", array_spec_rb_ary_aref, -1);
   rb_define_method(cls, "rb_ary_clear", array_spec_rb_ary_clear, 1);
   rb_define_method(cls, "rb_ary_delete", array_spec_rb_ary_delete, 2);
@@ -252,14 +307,21 @@ void Init_array_spec(void) {
   rb_define_method(cls, "rb_ary_reverse", array_spec_rb_ary_reverse, 1);
   rb_define_method(cls, "rb_ary_rotate", array_spec_rb_ary_rotate, 2);
   rb_define_method(cls, "rb_ary_shift", array_spec_rb_ary_shift, 1);
+  rb_define_method(cls, "rb_ary_sort", array_spec_rb_ary_sort, 1);
+  rb_define_method(cls, "rb_ary_sort_bang", array_spec_rb_ary_sort_bang, 1);
   rb_define_method(cls, "rb_ary_store", array_spec_rb_ary_store, 3);
   rb_define_method(cls, "rb_ary_concat", array_spec_rb_ary_concat, 2);
   rb_define_method(cls, "rb_ary_plus", array_spec_rb_ary_plus, 2);
   rb_define_method(cls, "rb_ary_unshift", array_spec_rb_ary_unshift, 2);
   rb_define_method(cls, "rb_assoc_new", array_spec_rb_assoc_new, 2);
+#ifndef RUBY_VERSION_IS_4_0
   rb_define_method(cls, "rb_iterate", array_spec_rb_iterate, 1);
   rb_define_method(cls, "rb_iterate_each_pair", array_spec_rb_iterate_each_pair, 1);
   rb_define_method(cls, "rb_iterate_then_yield", array_spec_rb_iterate_then_yield, 1);
+#endif
+  rb_define_method(cls, "rb_block_call", array_spec_rb_block_call, 1);
+  rb_define_method(cls, "rb_block_call_each_pair", array_spec_rb_block_call_each_pair, 1);
+  rb_define_method(cls, "rb_block_call_then_yield", array_spec_rb_block_call_then_yield, 1);
   rb_define_method(cls, "rb_mem_clear", array_spec_rb_mem_clear, 1);
   rb_define_method(cls, "rb_ary_freeze", array_spec_rb_ary_freeze, 1);
   rb_define_method(cls, "rb_ary_to_ary", array_spec_rb_ary_to_ary, 1);
diff --git a/spec/ruby/optional/capi/ext/basic_object_spec.c b/spec/ruby/optional/capi/ext/basic_object_spec.c
new file mode 100644
index 0000000000..1618670ceb
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/basic_object_spec.c
@@ -0,0 +1,19 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE basic_object_spec_RBASIC_CLASS(VALUE self, VALUE obj) {
+  return RBASIC_CLASS(obj);
+}
+
+void Init_basic_object_spec(void) {
+  VALUE cls = rb_define_class("CApiBasicObjectSpecs", rb_cObject);
+  rb_define_method(cls, "RBASIC_CLASS", basic_object_spec_RBASIC_CLASS, 1);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/bignum_spec.c b/spec/ruby/optional/capi/ext/bignum_spec.c
index 14a51f5099..a950d8b16f 100644
--- a/spec/ruby/optional/capi/ext/bignum_spec.c
+++ b/spec/ruby/optional/capi/ext/bignum_spec.c
@@ -65,7 +65,7 @@ static VALUE bignum_spec_rb_big_pack_array(VALUE self, VALUE val, VALUE len) {
   long long_len = NUM2LONG(len);
 
   VALUE ary = rb_ary_new_capa(long_len);
-  unsigned long *buf = malloc(long_len * SIZEOF_LONG);
+  unsigned long *buf = (unsigned long*) malloc(long_len * SIZEOF_LONG);
 
   /* The array should be filled with recognisable junk so we can check
      it is all cleared properly. */
@@ -102,5 +102,5 @@ void Init_bignum_spec(void) {
 }
 
 #ifdef __cplusplus
-extern "C" {
+}
 #endif
diff --git a/spec/ruby/optional/capi/ext/binding_spec.c b/spec/ruby/optional/capi/ext/binding_spec.c
new file mode 100644
index 0000000000..b2e3c88b6d
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/binding_spec.c
@@ -0,0 +1,19 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE binding_spec_get_binding(VALUE self) {
+  return rb_funcall(self, rb_intern("binding"), 0);
+}
+
+void Init_binding_spec(void) {
+  VALUE cls = rb_define_class("CApiBindingSpecs", rb_cObject);
+  rb_define_method(cls, "get_binding", binding_spec_get_binding, 0);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/boolean_spec.c b/spec/ruby/optional/capi/ext/boolean_spec.c
index 7bb6fe569d..081cffa103 100644
--- a/spec/ruby/optional/capi/ext/boolean_spec.c
+++ b/spec/ruby/optional/capi/ext/boolean_spec.c
@@ -29,5 +29,5 @@ void Init_boolean_spec(void) {
 }
 
 #ifdef __cplusplus
-extern "C" {
+}
 #endif
diff --git a/spec/ruby/optional/capi/ext/class_id_under_autoload_spec.c b/spec/ruby/optional/capi/ext/class_id_under_autoload_spec.c
index 64393a9397..cc5550f041 100644
--- a/spec/ruby/optional/capi/ext/class_id_under_autoload_spec.c
+++ b/spec/ruby/optional/capi/ext/class_id_under_autoload_spec.c
@@ -1,5 +1,13 @@
 #include "ruby.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void Init_class_id_under_autoload_spec(void) {
   rb_define_class_id_under(rb_cObject, rb_intern("ClassIdUnderAutoload"), rb_cObject);
 }
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/class_spec.c b/spec/ruby/optional/capi/ext/class_spec.c
index 6e5c02e657..8ac0e7a93f 100644
--- a/spec/ruby/optional/capi/ext/class_spec.c
+++ b/spec/ruby/optional/capi/ext/class_spec.c
@@ -37,31 +37,50 @@ static VALUE class_spec_rb_path_to_class(VALUE self, VALUE path) {
   return rb_path_to_class(path);
 }
 
+static VALUE class_spec_rb_class_instance_methods(int argc, VALUE* argv, VALUE self) {
+  VALUE mod = argv[0];
+  return rb_class_instance_methods(--argc, ++argv, mod);
+}
+
+static VALUE class_spec_rb_class_public_instance_methods(int argc, VALUE* argv, VALUE self) {
+  VALUE mod = argv[0];
+  return rb_class_public_instance_methods(--argc, ++argv, mod);
+}
+
+static VALUE class_spec_rb_class_protected_instance_methods(int argc, VALUE* argv, VALUE self) {
+  VALUE mod = argv[0];
+  return rb_class_protected_instance_methods(--argc, ++argv, mod);
+}
+
+static VALUE class_spec_rb_class_private_instance_methods(int argc, VALUE* argv, VALUE self) {
+  VALUE mod = argv[0];
+  return rb_class_private_instance_methods(--argc, ++argv, mod);
+}
+
 static VALUE class_spec_rb_class_new(VALUE self, VALUE super) {
   return rb_class_new(super);
 }
 
-static VALUE class_spec_rb_class_new_instance(VALUE self,
-                                      VALUE nargs, VALUE args,
-                                      VALUE klass) {
-  int c_nargs = FIX2INT(nargs);
-  VALUE *c_args = alloca(sizeof(VALUE) * c_nargs);
-  int i;
-
-  for (i = 0; i < c_nargs; i++)
-    c_args[i] = rb_ary_entry(args, i);
+static VALUE class_spec_rb_class_new_instance(VALUE self, VALUE args, VALUE klass) {
+  return rb_class_new_instance(RARRAY_LENINT(args), RARRAY_PTR(args), klass);
+}
 
-  return rb_class_new_instance(c_nargs, c_args, klass);
+static VALUE class_spec_rb_class_new_instance_kw(VALUE self, VALUE args, VALUE klass) {
+  return rb_class_new_instance_kw(RARRAY_LENINT(args), RARRAY_PTR(args), klass, RB_PASS_KEYWORDS);
 }
 
 static VALUE class_spec_rb_class_real(VALUE self, VALUE object) {
-  if(rb_type_p(object, T_FIXNUM)) {
+  if (rb_type_p(object, T_FIXNUM)) {
     return INT2FIX(rb_class_real(FIX2INT(object)));
   } else {
     return rb_class_real(CLASS_OF(object));
   }
 }
 
+static VALUE class_spec_rb_class_get_superclass(VALUE self, VALUE klass) {
+  return rb_class_get_superclass(klass);
+}
+
 static VALUE class_spec_rb_class_superclass(VALUE self, VALUE klass) {
   return rb_class_superclass(klass);
 }
@@ -99,19 +118,19 @@ VALUE class_spec_define_attr(VALUE self, VALUE klass, VALUE sym, VALUE read, VAL
 }
 
 static VALUE class_spec_rb_define_class(VALUE self, VALUE name, VALUE super) {
-  if(NIL_P(super)) super = 0;
+  if (NIL_P(super)) super = 0;
   return rb_define_class(RSTRING_PTR(name), super);
 }
 
 static VALUE class_spec_rb_define_class_under(VALUE self, VALUE outer,
                                                  VALUE name, VALUE super) {
-  if(NIL_P(super)) super = 0;
+  if (NIL_P(super)) super = 0;
   return rb_define_class_under(outer, RSTRING_PTR(name), super);
 }
 
 static VALUE class_spec_rb_define_class_id_under(VALUE self, VALUE outer,
                                                  VALUE name, VALUE super) {
-  if(NIL_P(super)) super = 0;
+  if (NIL_P(super)) super = 0;
   return rb_define_class_id_under(outer, SYM2ID(name), super);
 }
 
@@ -125,19 +144,6 @@ static VALUE class_spec_include_module(VALUE self, VALUE klass, VALUE module) {
   return klass;
 }
 
-static VALUE class_spec_method_var_args_1(int argc, VALUE *argv, VALUE self) {
-  VALUE ary = rb_ary_new();
-  int i;
-  for (i = 0; i < argc; i++) {
-    rb_ary_push(ary, argv[i]);
-  }
-  return ary;
-}
-
-static VALUE class_spec_method_var_args_2(VALUE self, VALUE argv) {
-  return argv;
-}
-
 void Init_class_spec(void) {
   VALUE cls = rb_define_class("CApiClassSpecs", rb_cObject);
   rb_define_method(cls, "define_call_super_method", class_spec_define_call_super_method, 2);
@@ -146,9 +152,15 @@ void Init_class_spec(void) {
   rb_define_method(cls, "rb_class2name", class_spec_rb_class2name, 1);
   rb_define_method(cls, "rb_path2class", class_spec_rb_path2class, 1);
   rb_define_method(cls, "rb_path_to_class", class_spec_rb_path_to_class, 1);
+  rb_define_method(cls, "rb_class_instance_methods", class_spec_rb_class_instance_methods, -1);
+  rb_define_method(cls, "rb_class_public_instance_methods", class_spec_rb_class_public_instance_methods, -1);
+  rb_define_method(cls, "rb_class_protected_instance_methods", class_spec_rb_class_protected_instance_methods, -1);
+  rb_define_method(cls, "rb_class_private_instance_methods", class_spec_rb_class_private_instance_methods, -1);
   rb_define_method(cls, "rb_class_new", class_spec_rb_class_new, 1);
-  rb_define_method(cls, "rb_class_new_instance", class_spec_rb_class_new_instance, 3);
+  rb_define_method(cls, "rb_class_new_instance", class_spec_rb_class_new_instance, 2);
+  rb_define_method(cls, "rb_class_new_instance_kw", class_spec_rb_class_new_instance_kw, 2);
   rb_define_method(cls, "rb_class_real", class_spec_rb_class_real, 1);
+  rb_define_method(cls, "rb_class_get_superclass", class_spec_rb_class_get_superclass, 1);
   rb_define_method(cls, "rb_class_superclass", class_spec_rb_class_superclass, 1);
   rb_define_method(cls, "rb_cvar_defined", class_spec_cvar_defined, 2);
   rb_define_method(cls, "rb_cvar_get", class_spec_cvar_get, 2);
@@ -161,8 +173,6 @@ void Init_class_spec(void) {
   rb_define_method(cls, "rb_define_class_id_under", class_spec_rb_define_class_id_under, 3);
   rb_define_method(cls, "rb_define_class_variable", class_spec_define_class_variable, 3);
   rb_define_method(cls, "rb_include_module", class_spec_include_module, 2);
-  rb_define_method(cls, "rb_method_varargs_1", class_spec_method_var_args_1, -1);
-  rb_define_method(cls, "rb_method_varargs_2", class_spec_method_var_args_2, -2);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/class_under_autoload_spec.c b/spec/ruby/optional/capi/ext/class_under_autoload_spec.c
index 120dec7327..e0b1f249c0 100644
--- a/spec/ruby/optional/capi/ext/class_under_autoload_spec.c
+++ b/spec/ruby/optional/capi/ext/class_under_autoload_spec.c
@@ -1,5 +1,13 @@
 #include "ruby.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void Init_class_under_autoload_spec(void) {
   rb_define_class_under(rb_cObject, "ClassUnderAutoload", rb_cObject);
 }
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/constants_spec.c b/spec/ruby/optional/capi/ext/constants_spec.c
index c8ae843016..05819ea476 100644
--- a/spec/ruby/optional/capi/ext/constants_spec.c
+++ b/spec/ruby/optional/capi/ext/constants_spec.c
@@ -5,310 +5,145 @@
 extern "C" {
 #endif
 
-static VALUE constants_spec_rb_cArray(VALUE self) {
-  return rb_cArray;
-}
-
-#ifndef RUBY_INTEGER_UNIFICATION
-static VALUE constants_spec_rb_cBignum(VALUE self) {
-  return rb_cBignum;
-}
-#endif
-
-static VALUE constants_spec_rb_cClass(VALUE self) {
-  return rb_cClass;
-}
-
-static VALUE constants_spec_rb_cData(VALUE self) {
-  return rb_cData;
-}
-
-static VALUE constants_spec_rb_cFalseClass(VALUE self) {
-  return rb_cFalseClass;
-}
-
-static VALUE constants_spec_rb_cFile(VALUE self) {
-  return rb_cFile;
-}
-
-#ifndef RUBY_INTEGER_UNIFICATION
-static VALUE constants_spec_rb_cFixnum(VALUE self) {
-  return rb_cFixnum;
-}
-#endif
-
-static VALUE constants_spec_rb_cFloat(VALUE self) {
-  return rb_cFloat;
-}
-
-static VALUE constants_spec_rb_cHash(VALUE self) {
-  return rb_cHash;
-}
-
-static VALUE constants_spec_rb_cInteger(VALUE self) {
-  return rb_cInteger;
-}
-
-static VALUE constants_spec_rb_cIO(VALUE self) {
-  return rb_cIO;
-}
-
-static VALUE constants_spec_rb_cModule(VALUE self) {
-  return rb_cModule;
-}
-
-static VALUE constants_spec_rb_cMatch(VALUE self) {
-  return rb_cMatch;
-}
-
-static VALUE constants_spec_rb_cNilClass(VALUE self) {
-  return rb_cNilClass;
-}
-
-static VALUE constants_spec_rb_cNumeric(VALUE self) {
-  return rb_cNumeric;
-}
-
-static VALUE constants_spec_rb_cObject(VALUE self) {
-  return rb_cObject;
-}
-
-static VALUE constants_spec_rb_cRange(VALUE self) {
-  return rb_cRange;
-}
-
-static VALUE constants_spec_rb_cRegexp(VALUE self) {
-  return rb_cRegexp;
-}
-
-static VALUE constants_spec_rb_cString(VALUE self) {
-  return rb_cString;
-}
-
-static VALUE constants_spec_rb_cStruct(VALUE self) {
-  return rb_cStruct;
-}
-
-static VALUE constants_spec_rb_cSymbol(VALUE self) {
-  return rb_cSymbol;
-}
-
-static VALUE constants_spec_rb_cTime(VALUE self) {
-  return rb_cTime;
-}
-
-static VALUE constants_spec_rb_cThread(VALUE self) {
-  return rb_cThread;
-}
-
-static VALUE constants_spec_rb_cTrueClass(VALUE self) {
-  return rb_cTrueClass;
-}
-
-static VALUE constants_spec_rb_cProc(VALUE self) {
-  return rb_cProc;
-}
-
-static VALUE constants_spec_rb_cMethod(VALUE self) {
-  return rb_cMethod;
-}
-
-static VALUE constants_spec_rb_cEnumerator(VALUE self) {
-  return rb_cEnumerator;
-}
-
-static VALUE constants_spec_rb_mComparable(VALUE self) {
-  return rb_mComparable;
-}
-
-static VALUE constants_spec_rb_mEnumerable(VALUE self) {
-  return rb_mEnumerable;
-}
-
-static VALUE constants_spec_rb_mKernel(VALUE self) {
-  return rb_mKernel;
-}
-
-static VALUE constants_spec_rb_eArgError(VALUE self) {
-  return rb_eArgError;
-}
-
-static VALUE constants_spec_rb_eEOFError(VALUE self) {
-  return rb_eEOFError;
-}
-
-static VALUE constants_spec_rb_mErrno(VALUE self) {
-  return rb_mErrno;
-}
-
-static VALUE constants_spec_rb_eException(VALUE self) {
-  return rb_eException;
-}
-
-static VALUE constants_spec_rb_eFloatDomainError(VALUE self) {
-  return rb_eFloatDomainError;
-}
-
-static VALUE constants_spec_rb_eIndexError(VALUE self) {
-  return rb_eIndexError;
-}
-
-static VALUE constants_spec_rb_eInterrupt(VALUE self) {
-  return rb_eInterrupt;
-}
-
-static VALUE constants_spec_rb_eIOError(VALUE self) {
-  return rb_eIOError;
-}
-
-static VALUE constants_spec_rb_eLoadError(VALUE self) {
-  return rb_eLoadError;
-}
-
-static VALUE constants_spec_rb_eLocalJumpError(VALUE self) {
-  return rb_eLocalJumpError;
-}
-
-static VALUE constants_spec_rb_eNameError(VALUE self) {
-  return rb_eNameError;
-}
-
-static VALUE constants_spec_rb_eNoMemError(VALUE self) {
-  return rb_eNoMemError;
-}
-
-static VALUE constants_spec_rb_eNoMethodError(VALUE self) {
-  return rb_eNoMethodError;
-}
-
-static VALUE constants_spec_rb_eNotImpError(VALUE self) {
-  return rb_eNotImpError;
-}
-
-static VALUE constants_spec_rb_eRangeError(VALUE self) {
-  return rb_eRangeError;
-}
-
-static VALUE constants_spec_rb_eRegexpError(VALUE self) {
-  return rb_eRegexpError;
-}
-
-static VALUE constants_spec_rb_eRuntimeError(VALUE self) {
-  return rb_eRuntimeError;
-}
-
-static VALUE constants_spec_rb_eScriptError(VALUE self) {
-  return rb_eScriptError;
-}
-
-static VALUE constants_spec_rb_eSecurityError(VALUE self) {
-  return rb_eSecurityError;
-}
-
-static VALUE constants_spec_rb_eSignal(VALUE self) {
-  return rb_eSignal;
-}
-
-static VALUE constants_spec_rb_eStandardError(VALUE self) {
-  return rb_eStandardError;
-}
-
-static VALUE constants_spec_rb_eSyntaxError(VALUE self) {
-  return rb_eSyntaxError;
-}
-
-static VALUE constants_spec_rb_eSystemCallError(VALUE self) {
-  return rb_eSystemCallError;
-}
-
-static VALUE constants_spec_rb_eSystemExit(VALUE self) {
-  return rb_eSystemExit;
-}
-
-static VALUE constants_spec_rb_eSysStackError(VALUE self) {
-  return rb_eSysStackError;
-}
-
-static VALUE constants_spec_rb_eTypeError(VALUE self) {
-  return rb_eTypeError;
-}
-
-static VALUE constants_spec_rb_eThreadError(VALUE self) {
-  return rb_eThreadError;
-}
-
-static VALUE constants_spec_rb_eZeroDivError(VALUE self) {
-  return rb_eZeroDivError;
-}
-
-static VALUE constants_spec_rb_eMathDomainError(VALUE self) {
-  return rb_eMathDomainError;
-}
-
-static VALUE constants_spec_rb_eEncCompatError(VALUE self) {
-  return rb_eEncCompatError;
-}
-
-static VALUE constants_spec_rb_mWaitReadable(VALUE self) {
-  return rb_mWaitReadable;
-}
-
-static VALUE constants_spec_rb_mWaitWritable(VALUE self) {
-  return rb_mWaitWritable;
-}
-
-static VALUE constants_spec_rb_cDir(VALUE self) {
-  return rb_cDir;
-}
+#define defconstfunc(name) \
+static VALUE constants_spec_##name(VALUE self) { return name; }
+
+defconstfunc(rb_cArray)
+defconstfunc(rb_cBasicObject)
+defconstfunc(rb_cBinding)
+defconstfunc(rb_cClass)
+defconstfunc(rb_cComplex)
+defconstfunc(rb_mComparable)
+defconstfunc(rb_cDir)
+defconstfunc(rb_cEncoding)
+defconstfunc(rb_mEnumerable)
+defconstfunc(rb_cEnumerator)
+defconstfunc(rb_cFalseClass)
+defconstfunc(rb_cFile)
+defconstfunc(rb_mFileTest)
+defconstfunc(rb_cFloat)
+defconstfunc(rb_mGC)
+defconstfunc(rb_cHash)
+defconstfunc(rb_cInteger)
+defconstfunc(rb_cIO)
+defconstfunc(rb_mKernel)
+defconstfunc(rb_mMath)
+defconstfunc(rb_cMatch)
+defconstfunc(rb_cMethod)
+defconstfunc(rb_cModule)
+defconstfunc(rb_cNilClass)
+defconstfunc(rb_cNumeric)
+defconstfunc(rb_cObject)
+defconstfunc(rb_cProc)
+defconstfunc(rb_mProcess)
+defconstfunc(rb_cRandom)
+defconstfunc(rb_cRange)
+defconstfunc(rb_cRational)
+defconstfunc(rb_cRegexp)
+defconstfunc(rb_cStat)
+defconstfunc(rb_cString)
+defconstfunc(rb_cStruct)
+defconstfunc(rb_cSymbol)
+defconstfunc(rb_cTime)
+defconstfunc(rb_cThread)
+defconstfunc(rb_cTrueClass)
+defconstfunc(rb_cUnboundMethod)
+defconstfunc(rb_eArgError)
+defconstfunc(rb_eEncodingError)
+defconstfunc(rb_eEncCompatError)
+defconstfunc(rb_eEOFError)
+defconstfunc(rb_mErrno)
+defconstfunc(rb_eException)
+defconstfunc(rb_eFatal)
+defconstfunc(rb_eFloatDomainError)
+defconstfunc(rb_eFrozenError)
+defconstfunc(rb_eIndexError)
+defconstfunc(rb_eInterrupt)
+defconstfunc(rb_eIOError)
+defconstfunc(rb_eKeyError)
+defconstfunc(rb_eLoadError)
+defconstfunc(rb_eLocalJumpError)
+defconstfunc(rb_eMathDomainError)
+defconstfunc(rb_eNameError)
+defconstfunc(rb_eNoMemError)
+defconstfunc(rb_eNoMethodError)
+defconstfunc(rb_eNotImpError)
+defconstfunc(rb_eRangeError)
+defconstfunc(rb_eRegexpError)
+defconstfunc(rb_eRuntimeError)
+defconstfunc(rb_eScriptError)
+defconstfunc(rb_eSecurityError)
+defconstfunc(rb_eSignal)
+defconstfunc(rb_eStandardError)
+defconstfunc(rb_eStopIteration)
+defconstfunc(rb_eSyntaxError)
+defconstfunc(rb_eSystemCallError)
+defconstfunc(rb_eSystemExit)
+defconstfunc(rb_eSysStackError)
+defconstfunc(rb_eTypeError)
+defconstfunc(rb_eThreadError)
+defconstfunc(rb_mWaitReadable)
+defconstfunc(rb_mWaitWritable)
+defconstfunc(rb_eZeroDivError)
 
 void Init_constants_spec(void) {
   VALUE cls = rb_define_class("CApiConstantsSpecs", rb_cObject);
   rb_define_method(cls, "rb_cArray", constants_spec_rb_cArray, 0);
-#ifndef RUBY_INTEGER_UNIFICATION
-  rb_define_method(cls, "rb_cBignum", constants_spec_rb_cBignum, 0);
-#endif
-
+  rb_define_method(cls, "rb_cBasicObject", constants_spec_rb_cBasicObject, 0);
+  rb_define_method(cls, "rb_cBinding", constants_spec_rb_cBinding, 0);
   rb_define_method(cls, "rb_cClass", constants_spec_rb_cClass, 0);
-  rb_define_method(cls, "rb_cData", constants_spec_rb_cData, 0);
+  rb_define_method(cls, "rb_cComplex", constants_spec_rb_cComplex, 0);
+  rb_define_method(cls, "rb_mComparable", constants_spec_rb_mComparable, 0);
+  rb_define_method(cls, "rb_cDir", constants_spec_rb_cDir, 0);
+  rb_define_method(cls, "rb_cEncoding", constants_spec_rb_cEncoding, 0);
+  rb_define_method(cls, "rb_mEnumerable", constants_spec_rb_mEnumerable, 0);
+  rb_define_method(cls, "rb_cEnumerator", constants_spec_rb_cEnumerator, 0);
   rb_define_method(cls, "rb_cFalseClass", constants_spec_rb_cFalseClass, 0);
   rb_define_method(cls, "rb_cFile", constants_spec_rb_cFile, 0);
-#ifndef RUBY_INTEGER_UNIFICATION
-  rb_define_method(cls, "rb_cFixnum", constants_spec_rb_cFixnum, 0);
-#endif
-
+  rb_define_method(cls, "rb_mFileTest", constants_spec_rb_mFileTest, 0);
   rb_define_method(cls, "rb_cFloat", constants_spec_rb_cFloat, 0);
+  rb_define_method(cls, "rb_mGC", constants_spec_rb_mGC, 0);
   rb_define_method(cls, "rb_cHash", constants_spec_rb_cHash, 0);
   rb_define_method(cls, "rb_cInteger", constants_spec_rb_cInteger, 0);
   rb_define_method(cls, "rb_cIO", constants_spec_rb_cIO, 0);
+  rb_define_method(cls, "rb_mKernel", constants_spec_rb_mKernel, 0);
+  rb_define_method(cls, "rb_mMath", constants_spec_rb_mMath, 0);
   rb_define_method(cls, "rb_cMatch", constants_spec_rb_cMatch, 0);
+  rb_define_method(cls, "rb_cMethod", constants_spec_rb_cMethod, 0);
   rb_define_method(cls, "rb_cModule", constants_spec_rb_cModule, 0);
   rb_define_method(cls, "rb_cNilClass", constants_spec_rb_cNilClass, 0);
   rb_define_method(cls, "rb_cNumeric", constants_spec_rb_cNumeric, 0);
   rb_define_method(cls, "rb_cObject", constants_spec_rb_cObject, 0);
+  rb_define_method(cls, "rb_cProc", constants_spec_rb_cProc, 0);
+  rb_define_method(cls, "rb_mProcess", constants_spec_rb_mProcess, 0);
+  rb_define_method(cls, "rb_cRandom", constants_spec_rb_cRandom, 0);
   rb_define_method(cls, "rb_cRange", constants_spec_rb_cRange, 0);
+  rb_define_method(cls, "rb_cRational", constants_spec_rb_cRational, 0);
   rb_define_method(cls, "rb_cRegexp", constants_spec_rb_cRegexp, 0);
+  rb_define_method(cls, "rb_cStat", constants_spec_rb_cStat, 0);
   rb_define_method(cls, "rb_cString", constants_spec_rb_cString, 0);
   rb_define_method(cls, "rb_cStruct", constants_spec_rb_cStruct, 0);
   rb_define_method(cls, "rb_cSymbol", constants_spec_rb_cSymbol, 0);
   rb_define_method(cls, "rb_cTime", constants_spec_rb_cTime, 0);
   rb_define_method(cls, "rb_cThread", constants_spec_rb_cThread, 0);
   rb_define_method(cls, "rb_cTrueClass", constants_spec_rb_cTrueClass, 0);
-  rb_define_method(cls, "rb_cProc", constants_spec_rb_cProc, 0);
-  rb_define_method(cls, "rb_cMethod", constants_spec_rb_cMethod, 0);
-  rb_define_method(cls, "rb_cEnumerator", constants_spec_rb_cEnumerator, 0);
-  rb_define_method(cls, "rb_mComparable", constants_spec_rb_mComparable, 0);
-  rb_define_method(cls, "rb_mEnumerable", constants_spec_rb_mEnumerable, 0);
-  rb_define_method(cls, "rb_mKernel", constants_spec_rb_mKernel, 0);
+  rb_define_method(cls, "rb_cUnboundMethod", constants_spec_rb_cUnboundMethod, 0);
   rb_define_method(cls, "rb_eArgError", constants_spec_rb_eArgError, 0);
+  rb_define_method(cls, "rb_eEncodingError", constants_spec_rb_eEncodingError, 0);
+  rb_define_method(cls, "rb_eEncCompatError", constants_spec_rb_eEncCompatError, 0);
   rb_define_method(cls, "rb_eEOFError", constants_spec_rb_eEOFError, 0);
   rb_define_method(cls, "rb_mErrno", constants_spec_rb_mErrno, 0);
   rb_define_method(cls, "rb_eException", constants_spec_rb_eException, 0);
+  rb_define_method(cls, "rb_eFatal", constants_spec_rb_eFatal, 0);
   rb_define_method(cls, "rb_eFloatDomainError", constants_spec_rb_eFloatDomainError, 0);
+  rb_define_method(cls, "rb_eFrozenError", constants_spec_rb_eFrozenError, 0);
   rb_define_method(cls, "rb_eIndexError", constants_spec_rb_eIndexError, 0);
   rb_define_method(cls, "rb_eInterrupt", constants_spec_rb_eInterrupt, 0);
   rb_define_method(cls, "rb_eIOError", constants_spec_rb_eIOError, 0);
+  rb_define_method(cls, "rb_eKeyError", constants_spec_rb_eKeyError, 0);
   rb_define_method(cls, "rb_eLoadError", constants_spec_rb_eLoadError, 0);
   rb_define_method(cls, "rb_eLocalJumpError", constants_spec_rb_eLocalJumpError, 0);
+  rb_define_method(cls, "rb_eMathDomainError", constants_spec_rb_eMathDomainError, 0);
   rb_define_method(cls, "rb_eNameError", constants_spec_rb_eNameError, 0);
   rb_define_method(cls, "rb_eNoMemError", constants_spec_rb_eNoMemError, 0);
   rb_define_method(cls, "rb_eNoMethodError", constants_spec_rb_eNoMethodError, 0);
@@ -320,18 +155,16 @@ void Init_constants_spec(void) {
   rb_define_method(cls, "rb_eSecurityError", constants_spec_rb_eSecurityError, 0);
   rb_define_method(cls, "rb_eSignal", constants_spec_rb_eSignal, 0);
   rb_define_method(cls, "rb_eStandardError", constants_spec_rb_eStandardError, 0);
+  rb_define_method(cls, "rb_eStopIteration", constants_spec_rb_eStopIteration, 0);
   rb_define_method(cls, "rb_eSyntaxError", constants_spec_rb_eSyntaxError, 0);
   rb_define_method(cls, "rb_eSystemCallError", constants_spec_rb_eSystemCallError, 0);
   rb_define_method(cls, "rb_eSystemExit", constants_spec_rb_eSystemExit, 0);
   rb_define_method(cls, "rb_eSysStackError", constants_spec_rb_eSysStackError, 0);
   rb_define_method(cls, "rb_eTypeError", constants_spec_rb_eTypeError, 0);
   rb_define_method(cls, "rb_eThreadError", constants_spec_rb_eThreadError, 0);
-  rb_define_method(cls, "rb_eZeroDivError", constants_spec_rb_eZeroDivError, 0);
-  rb_define_method(cls, "rb_eMathDomainError", constants_spec_rb_eMathDomainError, 0);
-  rb_define_method(cls, "rb_eEncCompatError", constants_spec_rb_eEncCompatError, 0);
   rb_define_method(cls, "rb_mWaitReadable", constants_spec_rb_mWaitReadable, 0);
   rb_define_method(cls, "rb_mWaitWritable", constants_spec_rb_mWaitWritable, 0);
-  rb_define_method(cls, "rb_cDir", constants_spec_rb_cDir, 0);
+  rb_define_method(cls, "rb_eZeroDivError", constants_spec_rb_eZeroDivError, 0);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/data_spec.c b/spec/ruby/optional/capi/ext/data_spec.c
index a41666f655..efefe37c3a 100644
--- a/spec/ruby/optional/capi/ext/data_spec.c
+++ b/spec/ruby/optional/capi/ext/data_spec.c
@@ -3,6 +3,7 @@
 
 #include <string.h>
 
+#ifndef RUBY_VERSION_IS_3_4
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -19,7 +20,7 @@ void sample_wrapped_struct_mark(void* st) {
 }
 
 VALUE sdaf_alloc_func(VALUE klass) {
-  struct sample_wrapped_struct* bar = malloc(sizeof(struct sample_wrapped_struct));
+  struct sample_wrapped_struct* bar = (struct sample_wrapped_struct*) malloc(sizeof(struct sample_wrapped_struct));
   bar->foo = 42;
   return Data_Wrap_Struct(klass, &sample_wrapped_struct_mark, &sample_wrapped_struct_free, bar);
 }
@@ -32,7 +33,7 @@ VALUE sdaf_get_struct(VALUE self) {
 }
 
 VALUE sws_wrap_struct(VALUE self, VALUE val) {
-  struct sample_wrapped_struct* bar = malloc(sizeof(struct sample_wrapped_struct));
+  struct sample_wrapped_struct* bar = (struct sample_wrapped_struct*) malloc(sizeof(struct sample_wrapped_struct));
   bar->foo = FIX2INT(val);
   return Data_Wrap_Struct(rb_cObject, &sample_wrapped_struct_mark, &sample_wrapped_struct_free, bar);
 }
@@ -58,15 +59,22 @@ VALUE sws_get_struct_data_ptr(VALUE self, VALUE obj) {
 
 VALUE sws_change_struct(VALUE self, VALUE obj, VALUE new_val) {
   struct sample_wrapped_struct *old_struct, *new_struct;
-  new_struct = malloc(sizeof(struct sample_wrapped_struct));
+  new_struct = (struct sample_wrapped_struct*) malloc(sizeof(struct sample_wrapped_struct));
   new_struct->foo = FIX2INT(new_val);
-  old_struct = RDATA(obj)->data;
+  old_struct = (struct sample_wrapped_struct*) RDATA(obj)->data;
   free(old_struct);
   RDATA(obj)->data = new_struct;
   return Qnil;
 }
 
+VALUE sws_rb_check_type(VALUE self, VALUE obj, VALUE other) {
+  rb_check_type(obj, TYPE(other));
+  return Qtrue;
+}
+#endif
+
 void Init_data_spec(void) {
+#ifndef RUBY_VERSION_IS_3_4
   VALUE cls = rb_define_class("CApiAllocSpecs", rb_cObject);
   rb_define_alloc_func(cls, sdaf_alloc_func);
   rb_define_method(cls, "wrapped_data", sdaf_get_struct, 0);
@@ -76,6 +84,8 @@ void Init_data_spec(void) {
   rb_define_method(cls, "get_struct_rdata", sws_get_struct_rdata, 1);
   rb_define_method(cls, "get_struct_data_ptr", sws_get_struct_data_ptr, 1);
   rb_define_method(cls, "change_struct", sws_change_struct, 2);
+  rb_define_method(cls, "rb_check_type", sws_rb_check_type, 2);
+#endif
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/debug_spec.c b/spec/ruby/optional/capi/ext/debug_spec.c
new file mode 100644
index 0000000000..9131eda78b
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/debug_spec.c
@@ -0,0 +1,93 @@
+#include "ruby.h"
+#include "rubyspec.h"
+#include "ruby/debug.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE callback_data = Qfalse;
+
+static VALUE rb_debug_inspector_open_callback(const rb_debug_inspector_t *dc, void *ptr) {
+    if (!dc) {
+      rb_raise(rb_eRuntimeError, "rb_debug_inspector_t should not be NULL");
+    }
+
+    VALUE locations = rb_debug_inspector_backtrace_locations(dc);
+    int len = RARRAY_LENINT(locations);
+    VALUE results = rb_ary_new2(len);
+    for (int i = 0; i < len; i++) {
+        VALUE ary = rb_ary_new2(5); // [self, klass, binding, iseq, backtrace_location]
+        rb_ary_store(ary, 0, rb_debug_inspector_frame_self_get(dc, i));
+        rb_ary_store(ary, 1, rb_debug_inspector_frame_class_get(dc, i));
+        rb_ary_store(ary, 2, rb_debug_inspector_frame_binding_get(dc, i));
+        rb_ary_store(ary, 3, rb_debug_inspector_frame_iseq_get(dc, i));
+        rb_ary_store(ary, 4, rb_ary_entry(locations, i));
+        rb_ary_push(results, ary);
+    }
+    callback_data = (VALUE)ptr;
+    return results;
+}
+
+static VALUE rb_debug_inspector_frame_self_get_callback(const rb_debug_inspector_t *dc, void *ptr) {
+  return rb_debug_inspector_frame_self_get(dc, NUM2LONG((VALUE) ptr));
+}
+
+static VALUE rb_debug_inspector_frame_class_get_callback(const rb_debug_inspector_t *dc, void *ptr) {
+  return rb_debug_inspector_frame_class_get(dc, NUM2LONG((VALUE) ptr));
+}
+
+static VALUE rb_debug_inspector_frame_binding_get_callback(const rb_debug_inspector_t *dc, void *ptr) {
+  return rb_debug_inspector_frame_binding_get(dc, NUM2LONG((VALUE) ptr));
+}
+
+static VALUE rb_debug_inspector_frame_iseq_get_callback(const rb_debug_inspector_t *dc, void *ptr) {
+  return rb_debug_inspector_frame_iseq_get(dc, NUM2LONG((VALUE) ptr));
+}
+
+static VALUE debug_spec_callback_data(VALUE self) {
+  return callback_data;
+}
+
+VALUE debug_spec_rb_debug_inspector_open(VALUE self, VALUE index) {
+  return rb_debug_inspector_open(rb_debug_inspector_open_callback, (void *)index);
+}
+
+VALUE debug_spec_rb_debug_inspector_frame_self_get(VALUE self, VALUE index) {
+  return rb_debug_inspector_open(rb_debug_inspector_frame_self_get_callback, (void *)index);
+}
+
+VALUE debug_spec_rb_debug_inspector_frame_class_get(VALUE self, VALUE index) {
+  return rb_debug_inspector_open(rb_debug_inspector_frame_class_get_callback, (void *)index);
+}
+
+VALUE debug_spec_rb_debug_inspector_frame_binding_get(VALUE self, VALUE index) {
+  return rb_debug_inspector_open(rb_debug_inspector_frame_binding_get_callback, (void *)index);
+}
+
+VALUE debug_spec_rb_debug_inspector_frame_iseq_get(VALUE self, VALUE index) {
+  return rb_debug_inspector_open(rb_debug_inspector_frame_iseq_get_callback, (void *)index);
+}
+
+static VALUE rb_debug_inspector_backtrace_locations_func(const rb_debug_inspector_t *dc, void *ptr) {
+  return rb_debug_inspector_backtrace_locations(dc);
+}
+
+VALUE debug_spec_rb_debug_inspector_backtrace_locations(VALUE self) {
+  return rb_debug_inspector_open(rb_debug_inspector_backtrace_locations_func, (void *)self);
+}
+
+void Init_debug_spec(void) {
+  VALUE cls = rb_define_class("CApiDebugSpecs", rb_cObject);
+  rb_define_method(cls, "rb_debug_inspector_open", debug_spec_rb_debug_inspector_open, 1);
+  rb_define_method(cls, "rb_debug_inspector_frame_self_get", debug_spec_rb_debug_inspector_frame_self_get, 1);
+  rb_define_method(cls, "rb_debug_inspector_frame_class_get", debug_spec_rb_debug_inspector_frame_class_get, 1);
+  rb_define_method(cls, "rb_debug_inspector_frame_binding_get", debug_spec_rb_debug_inspector_frame_binding_get, 1);
+  rb_define_method(cls, "rb_debug_inspector_frame_iseq_get", debug_spec_rb_debug_inspector_frame_iseq_get, 1);
+  rb_define_method(cls, "rb_debug_inspector_backtrace_locations", debug_spec_rb_debug_inspector_backtrace_locations, 0);
+  rb_define_method(cls, "debug_spec_callback_data", debug_spec_callback_data, 0);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/digest_spec.c b/spec/ruby/optional/capi/ext/digest_spec.c
new file mode 100644
index 0000000000..65c8defa20
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/digest_spec.c
@@ -0,0 +1,168 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#include "ruby/digest.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define DIGEST_LENGTH 20
+#define BLOCK_LENGTH 40
+
+const char *init_string = "Initialized\n";
+const char *update_string = "Updated: ";
+const char *finish_string = "Finished\n";
+
+#define PAYLOAD_SIZE 128
+
+typedef struct CTX {
+  uint8_t pos;
+  char payload[PAYLOAD_SIZE];
+} CTX;
+
+void* context = NULL;
+
+int digest_spec_plugin_init(void *raw_ctx) {
+    // Make the context accessible to tests. This isn't safe, but there's no way to access the context otherwise.
+    context = raw_ctx;
+
+    struct CTX *ctx = (struct CTX *)raw_ctx;
+    size_t len = strlen(init_string);
+
+    // Clear the payload since this init function will be invoked as part of the `reset` operation.
+    memset(ctx->payload, 0, PAYLOAD_SIZE);
+
+    // Write a simple value we can verify in tests.
+    // This is not what a real digest would do, but we're using a dummy digest plugin to test interactions.
+    memcpy(ctx->payload, init_string, len);
+    ctx->pos = (uint8_t) len;
+
+    return 1;
+}
+
+void digest_spec_plugin_update(void *raw_ctx, unsigned char *ptr, size_t size) {
+    struct CTX *ctx = (struct CTX *)raw_ctx;
+    size_t update_str_len = strlen(update_string);
+
+    if (ctx->pos + update_str_len + size >= PAYLOAD_SIZE) {
+        rb_raise(rb_eRuntimeError, "update size too large; reset the digest and write fewer updates");
+    }
+
+    // Write the supplied value to the payload so it can be easily verified in test.
+    // This is not what a real digest would do, but we're using a dummy digest plugin to test interactions.
+    memcpy(ctx->payload + ctx->pos, update_string, update_str_len);
+    ctx->pos += update_str_len;
+
+    memcpy(ctx->payload + ctx->pos, ptr, size);
+    ctx->pos += size;
+
+    return;
+}
+
+int digest_spec_plugin_finish(void *raw_ctx, unsigned char *ptr) {
+    struct CTX *ctx = (struct CTX *)raw_ctx;
+    size_t finish_string_len = strlen(finish_string);
+
+    // We're always going to write DIGEST_LENGTH bytes. In a real plugin, this would be the digest value. Here we
+    // write out a text string in order to make validation in tests easier.
+    //
+    // In order to delineate the output more clearly from an `Digest#update` call, we always write out the
+    // `finish_string` message. That leaves `DIGEST_LENGTH - finish_string_len` bytes to read out of the context.
+    size_t context_bytes = DIGEST_LENGTH - finish_string_len;
+
+    memcpy(ptr, ctx->payload + (ctx->pos - context_bytes), context_bytes);
+    memcpy(ptr + context_bytes, finish_string, finish_string_len);
+
+    return 1;
+}
+
+static const rb_digest_metadata_t metadata = {
+    // The RUBY_DIGEST_API_VERSION value comes from ruby/digest.h and may vary based on the Ruby being tested. Since
+    // it isn't publicly exposed in the digest gem, we ignore for these tests. Either the test hard-codes an expected
+    // value and is subject to breaking depending on the Ruby being run or we publicly expose `RUBY_DIGEST_API_VERSION`,
+    // in which case the test would pass trivially.
+    RUBY_DIGEST_API_VERSION,
+    DIGEST_LENGTH,
+    BLOCK_LENGTH,
+    sizeof(CTX),
+    (rb_digest_hash_init_func_t) digest_spec_plugin_init,
+    (rb_digest_hash_update_func_t) digest_spec_plugin_update,
+    (rb_digest_hash_finish_func_t) digest_spec_plugin_finish,
+};
+
+// The `get_metadata_ptr` function is not publicly available in the digest gem. However, we need to use
+// to extract the `rb_digest_metadata_t*` value set up by the plugin so we reproduce and adjust the
+// definition here.
+//
+// Taken and adapted from https://github.com/ruby/digest/blob/v3.2.0/ext/digest/digest.c#L558-L568
+static rb_digest_metadata_t * get_metadata_ptr(VALUE obj) {
+    rb_digest_metadata_t *algo;
+
+#ifdef DIGEST_USE_RB_EXT_RESOLVE_SYMBOL
+    // In the digest gem there is an additional data type check performed before reading the value out.
+    // Since the type definition isn't public, we can't use it as part of a type check here so we omit it.
+    // This is safe to do because this code is intended to only load digest plugins written as part of this test suite.
+    algo = (rb_digest_metadata_t *) RTYPEDDATA_DATA(obj);
+#else
+# undef RUBY_UNTYPED_DATA_WARNING
+# define RUBY_UNTYPED_DATA_WARNING 0
+    Data_Get_Struct(obj, rb_digest_metadata_t, algo);
+#endif
+
+    return algo;
+}
+
+VALUE digest_spec_rb_digest_make_metadata(VALUE self) {
+    return rb_digest_make_metadata(&metadata);
+}
+
+VALUE digest_spec_block_length(VALUE self, VALUE meta) {
+    rb_digest_metadata_t* algo = get_metadata_ptr(meta);
+
+    return SIZET2NUM(algo->block_len);
+}
+
+VALUE digest_spec_digest_length(VALUE self, VALUE meta) {
+    rb_digest_metadata_t* algo = get_metadata_ptr(meta);
+
+    return SIZET2NUM(algo->digest_len);
+}
+
+VALUE digest_spec_context_size(VALUE self, VALUE meta) {
+    rb_digest_metadata_t* algo = get_metadata_ptr(meta);
+
+    return SIZET2NUM(algo->ctx_size);
+}
+
+#ifndef PTR2NUM
+#define PTR2NUM(x) (rb_int2inum((intptr_t)(void *)(x)))
+#endif
+
+VALUE digest_spec_context(VALUE self, VALUE digest) {
+    return PTR2NUM(context);
+}
+
+void Init_digest_spec(void) {
+    VALUE cls;
+
+    cls = rb_define_class("CApiDigestSpecs", rb_cObject);
+    rb_define_method(cls, "rb_digest_make_metadata", digest_spec_rb_digest_make_metadata, 0);
+    rb_define_method(cls, "block_length", digest_spec_block_length, 1);
+    rb_define_method(cls, "digest_length", digest_spec_digest_length, 1);
+    rb_define_method(cls, "context_size", digest_spec_context_size, 1);
+    rb_define_method(cls, "context", digest_spec_context, 1);
+
+    VALUE mDigest, cDigest_Base, cDigest;
+
+    mDigest = rb_define_module("Digest");
+    mDigest = rb_digest_namespace();
+    cDigest_Base = rb_const_get(mDigest, rb_intern_const("Base"));
+
+    cDigest = rb_define_class_under(mDigest, "TestDigest", cDigest_Base);
+    rb_iv_set(cDigest, "metadata", rb_digest_make_metadata(&metadata));
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/encoding_spec.c b/spec/ruby/optional/capi/ext/encoding_spec.c
index 3cde884225..aa8662cfbd 100644
--- a/spec/ruby/optional/capi/ext/encoding_spec.c
+++ b/spec/ruby/optional/capi/ext/encoding_spec.c
@@ -7,8 +7,12 @@
 extern "C" {
 #endif
 
+static VALUE encoding_spec_MBCLEN_CHARFOUND_P(VALUE self, VALUE obj) {
+  return INT2FIX(MBCLEN_CHARFOUND_P(FIX2INT(obj)));
+}
+
 static VALUE encoding_spec_ENC_CODERANGE_ASCIIONLY(VALUE self, VALUE obj) {
-  if(ENC_CODERANGE_ASCIIONLY(obj)) {
+  if (ENC_CODERANGE_ASCIIONLY(obj)) {
     return Qtrue;
   } else {
     return Qfalse;
@@ -57,21 +61,19 @@ static VALUE encoding_spec_rb_filesystem_encindex(VALUE self) {
 
 static VALUE encoding_spec_rb_default_internal_encoding(VALUE self) {
   rb_encoding* enc = rb_default_internal_encoding();
-  if(enc == 0) return Qnil;
+  if (enc == 0) return Qnil;
   return rb_str_new2(enc->name);
 }
 
 static VALUE encoding_spec_rb_default_external_encoding(VALUE self) {
   rb_encoding* enc = rb_default_external_encoding();
-  if(enc == 0) return Qnil;
+  if (enc == 0) return Qnil;
   return rb_str_new2(enc->name);
 }
 
-#ifdef RUBY_VERSION_IS_2_6
 static VALUE encoding_spec_rb_enc_alias(VALUE self, VALUE alias, VALUE orig) {
   return INT2NUM(rb_enc_alias(RSTRING_PTR(alias), RSTRING_PTR(orig)));
 }
-#endif
 
 static VALUE encoding_spec_rb_enc_associate(VALUE self, VALUE obj, VALUE enc) {
   return rb_enc_associate(obj, NIL_P(enc) ? NULL : rb_enc_find(RSTRING_PTR(enc)));
@@ -84,7 +86,7 @@ static VALUE encoding_spec_rb_enc_associate_index(VALUE self, VALUE obj, VALUE i
 static VALUE encoding_spec_rb_enc_compatible(VALUE self, VALUE a, VALUE b) {
   rb_encoding* enc = rb_enc_compatible(a, b);
 
-  if(!enc) return INT2FIX(0);
+  if (!enc) return INT2FIX(0);
 
   return rb_enc_from_encoding(enc);
 }
@@ -102,10 +104,38 @@ static VALUE encoding_spec_rb_enc_find_index(VALUE self, VALUE name) {
   return INT2NUM(rb_enc_find_index(RSTRING_PTR(name)));
 }
 
+static VALUE encoding_spec_rb_enc_isalnum(VALUE self, VALUE chr, VALUE encoding) {
+  rb_encoding *e = rb_to_encoding(encoding);
+  return rb_enc_isalnum(FIX2INT(chr), e) ? Qtrue : Qfalse;
+}
+
+static VALUE encoding_spec_rb_enc_isspace(VALUE self, VALUE chr, VALUE encoding) {
+  rb_encoding *e = rb_to_encoding(encoding);
+  return rb_enc_isspace(FIX2INT(chr), e) ? Qtrue : Qfalse;
+}
+
 static VALUE encoding_spec_rb_enc_from_index(VALUE self, VALUE index) {
   return rb_str_new2(rb_enc_from_index(NUM2INT(index))->name);
 }
 
+static VALUE encoding_spec_rb_enc_mbc_to_codepoint(VALUE self, VALUE str) {
+  char *p = RSTRING_PTR(str);
+  char *e = RSTRING_END(str);
+  return INT2FIX(rb_enc_mbc_to_codepoint(p, e, rb_enc_get(str)));
+}
+
+static VALUE encoding_spec_rb_enc_mbcput(VALUE self, VALUE code, VALUE encoding) {
+  unsigned int c = FIX2UINT(code);
+  rb_encoding *enc = rb_to_encoding(encoding);
+  char buf[ONIGENC_CODE_TO_MBC_MAXLEN];
+  memset(buf, '\1', sizeof(buf));
+  int len = rb_enc_mbcput(c, buf, enc);
+  if (buf[len] != '\1') {
+    rb_raise(rb_eRuntimeError, "should not change bytes after len");
+  }
+  return rb_enc_str_new(buf, len, enc);
+}
+
 static VALUE encoding_spec_rb_enc_from_encoding(VALUE self, VALUE name) {
   return rb_enc_from_encoding(rb_enc_find(RSTRING_PTR(name)));
 }
@@ -114,6 +144,13 @@ static VALUE encoding_spec_rb_enc_get(VALUE self, VALUE obj) {
   return rb_str_new2(rb_enc_get(obj)->name);
 }
 
+static VALUE encoding_spec_rb_enc_precise_mbclen(VALUE self, VALUE str, VALUE offset) {
+  int o = FIX2INT(offset);
+  char *p = RSTRING_PTR(str);
+  char *e = p + o;
+  return INT2FIX(rb_enc_precise_mbclen(p, e, rb_enc_get(str)));
+}
+
 static VALUE encoding_spec_rb_obj_encoding(VALUE self, VALUE obj) {
   return rb_obj_encoding(obj);
 }
@@ -149,6 +186,21 @@ static VALUE encoding_spec_rb_enc_str_coderange(VALUE self, VALUE str) {
   }
 }
 
+static VALUE encoding_spec_rb_enc_str_new_cstr(VALUE self, VALUE str, VALUE enc) {
+  rb_encoding *e = rb_to_encoding(enc);
+  return rb_enc_str_new_cstr(StringValueCStr(str), e);
+}
+
+static VALUE encoding_spec_rb_enc_str_new_cstr_constant(VALUE self, VALUE enc) {
+  if (NIL_P(enc)) {
+    rb_encoding *e = NULL;
+    return rb_enc_str_new_static("test string literal", strlen("test string literal"), e);
+  } else {
+    rb_encoding *e = rb_to_encoding(enc);
+    return rb_enc_str_new_cstr("test string literal", e);
+  }
+}
+
 static VALUE encoding_spec_rb_enc_str_new(VALUE self, VALUE str, VALUE len, VALUE enc) {
   return rb_enc_str_new(RSTRING_PTR(str), FIX2INT(len), rb_to_encoding(enc));
 }
@@ -175,6 +227,21 @@ static VALUE encoding_spec_rb_to_encoding(VALUE self, VALUE obj) {
   return rb_str_new2(rb_to_encoding(obj)->name);
 }
 
+static rb_encoding** native_rb_encoding_pointer;
+
+static VALUE encoding_spec_rb_to_encoding_native_store(VALUE self, VALUE obj) {
+  rb_encoding* enc = rb_to_encoding(obj);
+  VALUE address = SIZET2NUM((size_t) native_rb_encoding_pointer);
+  *native_rb_encoding_pointer = enc;
+  return address;
+}
+
+static VALUE encoding_spec_rb_to_encoding_native_name(VALUE self, VALUE address) {
+  rb_encoding** ptr = (rb_encoding**) NUM2SIZET(address);
+  rb_encoding* enc = *ptr;
+  return rb_str_new2(enc->name);
+}
+
 static VALUE encoding_spec_rb_to_encoding_index(VALUE self, VALUE obj) {
   return INT2NUM(rb_to_encoding_index(obj));
 }
@@ -196,8 +263,72 @@ static VALUE encoding_spec_rb_enc_codepoint_len(VALUE self, VALUE str) {
   return rb_ary_new3(2, LONG2NUM(codepoint), LONG2NUM(len));
 }
 
+static VALUE encoding_spec_rb_enc_str_asciionly_p(VALUE self, VALUE str) {
+  if (rb_enc_str_asciionly_p(str)) {
+    return Qtrue;
+  } else {
+    return Qfalse;
+  }
+}
+
+static VALUE encoding_spec_rb_enc_raise(VALUE self, VALUE encoding, VALUE exception_class, VALUE format) {
+  rb_encoding *e = rb_to_encoding(encoding);
+  const char *f = RSTRING_PTR(format);
+
+  rb_enc_raise(e, exception_class, "%s", f);
+}
+
+static VALUE encoding_spec_rb_uv_to_utf8(VALUE self, VALUE buf, VALUE num) {
+  int len = rb_uv_to_utf8(RSTRING_PTR(buf), NUM2INT(num));
+  RB_ENC_CODERANGE_CLEAR(buf);
+  return INT2NUM(len);
+}
+
+static VALUE encoding_spec_ONIGENC_MBC_CASE_FOLD(VALUE self, VALUE str) {
+  char *beg = RSTRING_PTR(str);
+  char *beg_initial = beg;
+  char *end = beg + 2;
+  OnigUChar fold[ONIGENC_GET_CASE_FOLD_CODES_MAX_NUM];
+  memset(fold, '\1', sizeof(fold));
+  rb_encoding *enc = rb_enc_get(str);
+  int r = ONIGENC_MBC_CASE_FOLD(enc, ONIGENC_CASE_FOLD, &beg, (const OnigUChar *)end, fold);
+  if (r > 0 && fold[r] != '\1') {
+    rb_raise(rb_eRuntimeError, "should not change bytes after len");
+  }
+  VALUE str_result = r <= 0 ? Qnil : rb_enc_str_new((char *)fold, r, enc);
+  long bytes_used = beg - beg_initial;
+  return rb_ary_new3(2, str_result, INT2FIX(bytes_used));
+}
+
+static VALUE encoding_spec_rb_enc_codelen(VALUE self, VALUE code, VALUE encoding) {
+  unsigned int c = FIX2UINT(code);
+  rb_encoding *enc = rb_to_encoding(encoding);
+  return INT2FIX(rb_enc_codelen(c, enc));
+}
+
+static VALUE encoding_spec_rb_enc_strlen(VALUE self, VALUE str, VALUE length, VALUE encoding) {
+  int l = FIX2INT(length);
+  char *p = RSTRING_PTR(str);
+  char *e = p + l;
+
+  return LONG2FIX(rb_enc_strlen(p, e, rb_to_encoding(encoding)));
+}
+
+static VALUE encoding_spec_rb_enc_left_char_head(VALUE self, VALUE str, VALUE offset) {
+  char *ptr = RSTRING_PTR(str);
+  char *result = rb_enc_left_char_head(ptr, ptr + NUM2INT(offset), RSTRING_END(str), rb_enc_get(str));
+  return LONG2NUM(result - ptr);
+}
+
+static VALUE encoding_spec_rb_define_dummy_encoding(VALUE self, VALUE name) {
+  return INT2NUM(rb_define_dummy_encoding(RSTRING_PTR(name)));
+}
+
 void Init_encoding_spec(void) {
-  VALUE cls = rb_define_class("CApiEncodingSpecs", rb_cObject);
+  VALUE cls;
+  native_rb_encoding_pointer = (rb_encoding**) malloc(sizeof(rb_encoding*));
+
+  cls = rb_define_class("CApiEncodingSpecs", rb_cObject);
   rb_define_method(cls, "ENC_CODERANGE_ASCIIONLY",
                    encoding_spec_ENC_CODERANGE_ASCIIONLY, 1);
 
@@ -211,37 +342,48 @@ void Init_encoding_spec(void) {
   rb_define_method(cls, "rb_locale_encindex", encoding_spec_rb_locale_encindex, 0);
   rb_define_method(cls, "rb_filesystem_encoding", encoding_spec_rb_filesystem_encoding, 0);
   rb_define_method(cls, "rb_filesystem_encindex", encoding_spec_rb_filesystem_encindex, 0);
-  rb_define_method(cls, "rb_default_internal_encoding",
-                   encoding_spec_rb_default_internal_encoding, 0);
-
-  rb_define_method(cls, "rb_default_external_encoding",
-                   encoding_spec_rb_default_external_encoding, 0);
-
-#ifdef RUBY_VERSION_IS_2_6
+  rb_define_method(cls, "rb_default_internal_encoding", encoding_spec_rb_default_internal_encoding, 0);
+  rb_define_method(cls, "rb_default_external_encoding", encoding_spec_rb_default_external_encoding, 0);
   rb_define_method(cls, "rb_enc_alias", encoding_spec_rb_enc_alias, 2);
-#endif
-
+  rb_define_method(cls, "MBCLEN_CHARFOUND_P", encoding_spec_MBCLEN_CHARFOUND_P, 1);
   rb_define_method(cls, "rb_enc_associate", encoding_spec_rb_enc_associate, 2);
   rb_define_method(cls, "rb_enc_associate_index", encoding_spec_rb_enc_associate_index, 2);
   rb_define_method(cls, "rb_enc_compatible", encoding_spec_rb_enc_compatible, 2);
   rb_define_method(cls, "rb_enc_copy", encoding_spec_rb_enc_copy, 2);
+  rb_define_method(cls, "rb_enc_codelen", encoding_spec_rb_enc_codelen, 2);
+  rb_define_method(cls, "rb_enc_strlen", encoding_spec_rb_enc_strlen, 3);
   rb_define_method(cls, "rb_enc_find", encoding_spec_rb_enc_find, 1);
   rb_define_method(cls, "rb_enc_find_index", encoding_spec_rb_enc_find_index, 1);
+  rb_define_method(cls, "rb_enc_isalnum", encoding_spec_rb_enc_isalnum, 2);
+  rb_define_method(cls, "rb_enc_isspace", encoding_spec_rb_enc_isspace, 2);
   rb_define_method(cls, "rb_enc_from_index", encoding_spec_rb_enc_from_index, 1);
+  rb_define_method(cls, "rb_enc_mbc_to_codepoint", encoding_spec_rb_enc_mbc_to_codepoint, 1);
+  rb_define_method(cls, "rb_enc_mbcput", encoding_spec_rb_enc_mbcput, 2);
   rb_define_method(cls, "rb_enc_from_encoding", encoding_spec_rb_enc_from_encoding, 1);
   rb_define_method(cls, "rb_enc_get", encoding_spec_rb_enc_get, 1);
+  rb_define_method(cls, "rb_enc_precise_mbclen", encoding_spec_rb_enc_precise_mbclen, 2);
   rb_define_method(cls, "rb_obj_encoding", encoding_spec_rb_obj_encoding, 1);
   rb_define_method(cls, "rb_enc_get_index", encoding_spec_rb_enc_get_index, 1);
   rb_define_method(cls, "rb_enc_set_index", encoding_spec_rb_enc_set_index, 2);
   rb_define_method(cls, "rb_enc_str_coderange", encoding_spec_rb_enc_str_coderange, 1);
+  rb_define_method(cls, "rb_enc_str_new_cstr", encoding_spec_rb_enc_str_new_cstr, 2);
+  rb_define_method(cls, "rb_enc_str_new_cstr_constant", encoding_spec_rb_enc_str_new_cstr_constant, 1);
   rb_define_method(cls, "rb_enc_str_new", encoding_spec_rb_enc_str_new, 3);
   rb_define_method(cls, "ENCODING_GET", encoding_spec_ENCODING_GET, 1);
   rb_define_method(cls, "ENCODING_SET", encoding_spec_ENCODING_SET, 2);
   rb_define_method(cls, "rb_enc_to_index", encoding_spec_rb_enc_to_index, 1);
   rb_define_method(cls, "rb_to_encoding", encoding_spec_rb_to_encoding, 1);
+  rb_define_method(cls, "rb_to_encoding_native_store", encoding_spec_rb_to_encoding_native_store, 1);
+  rb_define_method(cls, "rb_to_encoding_native_name", encoding_spec_rb_to_encoding_native_name, 1);
   rb_define_method(cls, "rb_to_encoding_index", encoding_spec_rb_to_encoding_index, 1);
   rb_define_method(cls, "rb_enc_nth", encoding_spec_rb_enc_nth, 2);
   rb_define_method(cls, "rb_enc_codepoint_len", encoding_spec_rb_enc_codepoint_len, 1);
+  rb_define_method(cls, "rb_enc_str_asciionly_p", encoding_spec_rb_enc_str_asciionly_p, 1);
+  rb_define_method(cls, "rb_enc_raise", encoding_spec_rb_enc_raise, 3);
+  rb_define_method(cls, "rb_uv_to_utf8", encoding_spec_rb_uv_to_utf8, 2);
+  rb_define_method(cls, "ONIGENC_MBC_CASE_FOLD", encoding_spec_ONIGENC_MBC_CASE_FOLD, 1);
+  rb_define_method(cls, "rb_enc_left_char_head", encoding_spec_rb_enc_left_char_head, 2);
+  rb_define_method(cls, "rb_define_dummy_encoding", encoding_spec_rb_define_dummy_encoding, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/exception_spec.c b/spec/ruby/optional/capi/ext/exception_spec.c
index cdd86b183e..c3b94d7bcd 100644
--- a/spec/ruby/optional/capi/ext/exception_spec.c
+++ b/spec/ruby/optional/capi/ext/exception_spec.c
@@ -8,6 +8,10 @@
 extern "C" {
 #endif
 
+VALUE exception_spec_rb_errinfo(VALUE self) {
+  return rb_errinfo();
+}
+
 VALUE exception_spec_rb_exc_new(VALUE self, VALUE str) {
   char *cstr = StringValuePtr(str);
   return rb_exc_new(rb_eException, cstr, strlen(cstr));
@@ -23,7 +27,7 @@ VALUE exception_spec_rb_exc_new3(VALUE self, VALUE str) {
 }
 
 VALUE exception_spec_rb_exc_raise(VALUE self, VALUE exc) {
-    if (self != Qundef) rb_exc_raise(exc);
+  if (self != Qundef) rb_exc_raise(exc);
   return Qnil;
 }
 
@@ -32,13 +36,47 @@ VALUE exception_spec_rb_set_errinfo(VALUE self, VALUE exc) {
   return Qnil;
 }
 
+NORETURN(VALUE exception_spec_rb_error_frozen_object(VALUE self, VALUE object));
+
+VALUE exception_spec_rb_error_frozen_object(VALUE self, VALUE object) {
+  rb_error_frozen_object(object);
+  UNREACHABLE_RETURN(Qnil);
+}
+
+VALUE exception_spec_rb_syserr_new(VALUE self, VALUE num, VALUE msg) {
+  int n = NUM2INT(num);
+  char *cstr = NULL;
+
+  if (msg != Qnil) {
+    cstr = StringValuePtr(msg);
+  }
+
+  return rb_syserr_new(n, cstr);
+}
+
+VALUE exception_spec_rb_syserr_new_str(VALUE self, VALUE num, VALUE msg) {
+  int n = NUM2INT(num);
+  return rb_syserr_new_str(n, msg);
+}
+
+VALUE exception_spec_rb_make_exception(VALUE self, VALUE ary) {
+  int argc = RARRAY_LENINT(ary);
+  VALUE *argv = RARRAY_PTR(ary);
+  return rb_make_exception(argc, argv);
+}
+
 void Init_exception_spec(void) {
   VALUE cls = rb_define_class("CApiExceptionSpecs", rb_cObject);
+  rb_define_method(cls, "rb_errinfo", exception_spec_rb_errinfo, 0);
   rb_define_method(cls, "rb_exc_new", exception_spec_rb_exc_new, 1);
   rb_define_method(cls, "rb_exc_new2", exception_spec_rb_exc_new2, 1);
   rb_define_method(cls, "rb_exc_new3", exception_spec_rb_exc_new3, 1);
   rb_define_method(cls, "rb_exc_raise", exception_spec_rb_exc_raise, 1);
   rb_define_method(cls, "rb_set_errinfo", exception_spec_rb_set_errinfo, 1);
+  rb_define_method(cls, "rb_error_frozen_object", exception_spec_rb_error_frozen_object, 1);
+  rb_define_method(cls, "rb_syserr_new", exception_spec_rb_syserr_new, 2);
+  rb_define_method(cls, "rb_syserr_new_str", exception_spec_rb_syserr_new_str, 2);
+  rb_define_method(cls, "rb_make_exception", exception_spec_rb_make_exception, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/fiber_spec.c b/spec/ruby/optional/capi/ext/fiber_spec.c
new file mode 100644
index 0000000000..db54f7ad8c
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/fiber_spec.c
@@ -0,0 +1,64 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+VALUE fiber_spec_rb_fiber_current(VALUE self) {
+  return rb_fiber_current();
+}
+
+VALUE fiber_spec_rb_fiber_alive_p(VALUE self, VALUE fiber) {
+  return rb_fiber_alive_p(fiber);
+}
+
+VALUE fiber_spec_rb_fiber_resume(VALUE self, VALUE fiber, VALUE ary) {
+    long argc = RARRAY_LEN(ary);
+    VALUE *argv = (VALUE*) alloca(sizeof(VALUE) * argc);
+    int i;
+
+    for (i = 0; i < argc; i++) {
+      argv[i] = rb_ary_entry(ary, i);
+    }
+
+  return rb_fiber_resume(fiber, (int)argc, argv);
+}
+
+VALUE fiber_spec_rb_fiber_yield(VALUE self, VALUE ary) {
+  long argc = RARRAY_LEN(ary);
+  VALUE *argv = (VALUE*) alloca(sizeof(VALUE) * argc);
+  int i;
+
+  for (i = 0; i < argc; i++) {
+    argv[i] = rb_ary_entry(ary, i);
+  }
+  return rb_fiber_yield((int)argc, argv);
+}
+
+VALUE fiber_spec_rb_fiber_new_function(RB_BLOCK_CALL_FUNC_ARGLIST(args, dummy)) {
+  return rb_funcall(args, rb_intern("inspect"), 0);
+}
+
+VALUE fiber_spec_rb_fiber_new(VALUE self) {
+  return rb_fiber_new(fiber_spec_rb_fiber_new_function, Qnil);
+}
+
+VALUE fiber_spec_rb_fiber_raise(int argc, VALUE *argv, VALUE self) {
+  VALUE fiber = argv[0];
+  return rb_fiber_raise(fiber, argc-1, argv+1);
+}
+
+void Init_fiber_spec(void) {
+  VALUE cls = rb_define_class("CApiFiberSpecs", rb_cObject);
+  rb_define_method(cls, "rb_fiber_current", fiber_spec_rb_fiber_current, 0);
+  rb_define_method(cls, "rb_fiber_alive_p", fiber_spec_rb_fiber_alive_p, 1);
+  rb_define_method(cls, "rb_fiber_resume", fiber_spec_rb_fiber_resume, 2);
+  rb_define_method(cls, "rb_fiber_yield", fiber_spec_rb_fiber_yield, 1);
+  rb_define_method(cls, "rb_fiber_new", fiber_spec_rb_fiber_new, 0);
+  rb_define_method(cls, "rb_fiber_raise", fiber_spec_rb_fiber_raise, -1);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/finalizer_spec.c b/spec/ruby/optional/capi/ext/finalizer_spec.c
new file mode 100644
index 0000000000..83347da912
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/finalizer_spec.c
@@ -0,0 +1,25 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE define_finalizer(VALUE self, VALUE obj, VALUE finalizer) {
+  return rb_define_finalizer(obj, finalizer);
+}
+
+static VALUE undefine_finalizer(VALUE self, VALUE obj) {
+  return rb_undefine_finalizer(obj);
+}
+
+void Init_finalizer_spec(void) {
+  VALUE cls = rb_define_class("CApiFinalizerSpecs", rb_cObject);
+
+  rb_define_method(cls, "rb_define_finalizer", define_finalizer, 2);
+  rb_define_method(cls, "rb_undefine_finalizer", undefine_finalizer, 1);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/float_spec.c b/spec/ruby/optional/capi/ext/float_spec.c
index 34be917965..3db05cef8c 100644
--- a/spec/ruby/optional/capi/ext/float_spec.c
+++ b/spec/ruby/optional/capi/ext/float_spec.c
@@ -25,12 +25,21 @@ static VALUE float_spec_RFLOAT_VALUE(VALUE self, VALUE float_h) {
   return rb_float_new(RFLOAT_VALUE(float_h));
 }
 
+static VALUE float_spec_RB_FLOAT_TYPE_P(VALUE self, VALUE val) {
+  if (RB_FLOAT_TYPE_P(val)) {
+    return Qtrue;
+  } else {
+    return Qfalse;
+  }
+}
+
 void Init_float_spec(void) {
   VALUE cls = rb_define_class("CApiFloatSpecs", rb_cObject);
   rb_define_method(cls, "new_zero", float_spec_new_zero, 0);
   rb_define_method(cls, "new_point_five", float_spec_new_point_five, 0);
   rb_define_method(cls, "rb_Float", float_spec_rb_Float, 1);
   rb_define_method(cls, "RFLOAT_VALUE", float_spec_RFLOAT_VALUE, 1);
+  rb_define_method(cls, "RB_FLOAT_TYPE_P", float_spec_RB_FLOAT_TYPE_P, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/gc_spec.c b/spec/ruby/optional/capi/ext/gc_spec.c
index 0a76b9d40a..2637ad27ac 100644
--- a/spec/ruby/optional/capi/ext/gc_spec.c
+++ b/spec/ruby/optional/capi/ext/gc_spec.c
@@ -7,6 +7,16 @@ extern "C" {
 
 VALUE registered_tagged_value;
 VALUE registered_reference_value;
+VALUE registered_before_rb_gc_register_address;
+VALUE registered_before_rb_global_variable_string;
+VALUE registered_before_rb_global_variable_bignum;
+VALUE registered_before_rb_global_variable_float;
+VALUE registered_after_rb_global_variable_string;
+VALUE registered_after_rb_global_variable_bignum;
+VALUE registered_after_rb_global_variable_float;
+VALUE rb_gc_register_address_outside_init;
+
+VALUE rb_gc_register_mark_object_not_referenced_float;
 
 static VALUE registered_tagged_address(VALUE self) {
   return registered_tagged_value;
@@ -16,33 +26,122 @@ static VALUE registered_reference_address(VALUE self) {
   return registered_reference_value;
 }
 
-static VALUE gc_spec_rb_gc_enable() {
+static VALUE get_registered_before_rb_gc_register_address(VALUE self) {
+  return registered_before_rb_gc_register_address;
+}
+
+static VALUE get_registered_before_rb_global_variable_string(VALUE self) {
+  return registered_before_rb_global_variable_string;
+}
+
+static VALUE get_registered_before_rb_global_variable_bignum(VALUE self) {
+  return registered_before_rb_global_variable_bignum;
+}
+
+static VALUE get_registered_before_rb_global_variable_float(VALUE self) {
+  return registered_before_rb_global_variable_float;
+}
+
+static VALUE get_registered_after_rb_global_variable_string(VALUE self) {
+  return registered_after_rb_global_variable_string;
+}
+
+static VALUE get_registered_after_rb_global_variable_bignum(VALUE self) {
+  return registered_after_rb_global_variable_bignum;
+}
+
+static VALUE get_registered_after_rb_global_variable_float(VALUE self) {
+  return registered_after_rb_global_variable_float;
+}
+
+static VALUE gc_spec_rb_gc_register_address(VALUE self) {
+  rb_gc_register_address(&rb_gc_register_address_outside_init);
+  rb_gc_register_address_outside_init = rb_str_new_cstr("rb_gc_register_address() outside Init_");
+  return rb_gc_register_address_outside_init;
+}
+
+static VALUE gc_spec_rb_gc_unregister_address(VALUE self) {
+  rb_gc_unregister_address(&rb_gc_register_address_outside_init);
+  return Qnil;
+}
+
+static VALUE gc_spec_rb_gc_enable(VALUE self) {
   return rb_gc_enable();
 }
 
-static VALUE gc_spec_rb_gc_disable() {
+static VALUE gc_spec_rb_gc_disable(VALUE self) {
   return rb_gc_disable();
 }
 
-static VALUE gc_spec_rb_gc() {
+static VALUE gc_spec_rb_gc(VALUE self) {
   rb_gc();
   return Qnil;
 }
 
+static VALUE gc_spec_rb_gc_latest_gc_info(VALUE self, VALUE hash_or_key) {
+  return rb_gc_latest_gc_info(hash_or_key);
+}
+
+static VALUE gc_spec_rb_gc_adjust_memory_usage(VALUE self, VALUE diff) {
+  rb_gc_adjust_memory_usage(NUM2SSIZET(diff));
+  return Qnil;
+}
+
+static VALUE gc_spec_rb_gc_register_mark_object(VALUE self, VALUE obj) {
+  rb_gc_register_mark_object(obj);
+  return Qnil;
+}
+
+static VALUE gc_spec_rb_gc_register_mark_object_not_referenced_float(VALUE self) {
+  return rb_gc_register_mark_object_not_referenced_float;
+}
 
 void Init_gc_spec(void) {
   VALUE cls = rb_define_class("CApiGCSpecs", rb_cObject);
-  registered_tagged_value    = INT2NUM(10);
-  registered_reference_value = rb_str_new2("Globally registered data");
 
   rb_gc_register_address(&registered_tagged_value);
   rb_gc_register_address(&registered_reference_value);
+  rb_gc_register_address(&registered_before_rb_gc_register_address);
+  rb_global_variable(&registered_before_rb_global_variable_string);
+  rb_global_variable(&registered_before_rb_global_variable_bignum);
+  rb_global_variable(&registered_before_rb_global_variable_float);
+
+  registered_tagged_value    = INT2NUM(10);
+  registered_reference_value = rb_str_new2("Globally registered data");
+  registered_before_rb_gc_register_address = rb_str_new_cstr("registered before rb_gc_register_address()");
+
+  registered_before_rb_global_variable_string = rb_str_new_cstr("registered before rb_global_variable()");
+  registered_before_rb_global_variable_bignum = LL2NUM(INT64_MAX);
+  registered_before_rb_global_variable_float = DBL2NUM(3.14);
+
+  registered_after_rb_global_variable_string = rb_str_new_cstr("registered after rb_global_variable()");
+  rb_global_variable(&registered_after_rb_global_variable_string);
+  registered_after_rb_global_variable_bignum = LL2NUM(INT64_MAX);
+  rb_global_variable(&registered_after_rb_global_variable_bignum);
+  registered_after_rb_global_variable_float = DBL2NUM(6.28);
+  rb_global_variable(&registered_after_rb_global_variable_float);
+
+  rb_gc_register_mark_object_not_referenced_float = DBL2NUM(1.61);
+  rb_gc_register_mark_object(rb_gc_register_mark_object_not_referenced_float);
 
   rb_define_method(cls, "registered_tagged_address", registered_tagged_address, 0);
   rb_define_method(cls, "registered_reference_address", registered_reference_address, 0);
+  rb_define_method(cls, "registered_before_rb_gc_register_address", get_registered_before_rb_gc_register_address, 0);
+  rb_define_method(cls, "registered_before_rb_global_variable_string", get_registered_before_rb_global_variable_string, 0);
+  rb_define_method(cls, "registered_before_rb_global_variable_bignum", get_registered_before_rb_global_variable_bignum, 0);
+  rb_define_method(cls, "registered_before_rb_global_variable_float", get_registered_before_rb_global_variable_float, 0);
+  rb_define_method(cls, "registered_after_rb_global_variable_string", get_registered_after_rb_global_variable_string, 0);
+  rb_define_method(cls, "registered_after_rb_global_variable_bignum", get_registered_after_rb_global_variable_bignum, 0);
+  rb_define_method(cls, "registered_after_rb_global_variable_float", get_registered_after_rb_global_variable_float, 0);
+  rb_define_method(cls, "rb_gc_register_address", gc_spec_rb_gc_register_address, 0);
+  rb_define_method(cls, "rb_gc_unregister_address", gc_spec_rb_gc_unregister_address, 0);
   rb_define_method(cls, "rb_gc_enable", gc_spec_rb_gc_enable, 0);
   rb_define_method(cls, "rb_gc_disable", gc_spec_rb_gc_disable, 0);
   rb_define_method(cls, "rb_gc", gc_spec_rb_gc, 0);
+  rb_define_method(cls, "rb_gc_adjust_memory_usage", gc_spec_rb_gc_adjust_memory_usage, 1);
+  rb_define_method(cls, "rb_gc_register_mark_object", gc_spec_rb_gc_register_mark_object, 1);
+  rb_define_method(cls, "rb_gc_register_mark_object_not_referenced_float", gc_spec_rb_gc_register_mark_object_not_referenced_float, 0);
+  rb_define_method(cls, "rb_gc_latest_gc_info", gc_spec_rb_gc_latest_gc_info, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/globals_spec.c b/spec/ruby/optional/capi/ext/globals_spec.c
index f70622f66c..20dea1a05a 100644
--- a/spec/ruby/optional/capi/ext/globals_spec.c
+++ b/spec/ruby/optional/capi/ext/globals_spec.c
@@ -7,15 +7,29 @@ extern "C" {
 
 VALUE g_hooked_var;
 
+VALUE var_2x_getter(ID id, VALUE *data) {
+  return *data;
+}
+
 void var_2x_setter(VALUE val, ID id, VALUE *var) {
-    *var = INT2NUM(NUM2INT(val) * 2);
+  *var = INT2NUM(NUM2INT(val) * 2);
 }
 
 static VALUE sb_define_hooked_variable(VALUE self, VALUE var_name) {
-  rb_define_hooked_variable(StringValuePtr(var_name), &g_hooked_var, 0, var_2x_setter);
+  rb_define_hooked_variable(StringValuePtr(var_name), &g_hooked_var, var_2x_getter, var_2x_setter);
+  return Qnil;
+}
+
+static VALUE sb_define_hooked_variable_default_accessors(VALUE self, VALUE var_name) {
+  rb_define_hooked_variable(StringValuePtr(var_name), &g_hooked_var, (rb_gvar_getter_t*) NULL, (rb_gvar_setter_t*) NULL);
   return Qnil;
 }
 
+static VALUE sb_define_hooked_variable_null_var(VALUE self, VALUE var_name) {
+    rb_define_hooked_variable(StringValuePtr(var_name), NULL, (rb_gvar_getter_t*) NULL, (rb_gvar_setter_t*) NULL);
+    return Qnil;
+}
+
 VALUE g_ro_var;
 
 static VALUE sb_define_readonly_variable(VALUE self, VALUE var_name, VALUE val) {
@@ -36,6 +50,26 @@ static VALUE sb_define_variable(VALUE self, VALUE var_name, VALUE val) {
   return Qnil;
 }
 
+long virtual_var_storage;
+
+VALUE incrementing_getter(ID id, VALUE *data) {
+  return LONG2FIX(virtual_var_storage++);
+}
+
+void incrementing_setter(VALUE val, ID id, VALUE *data) {
+  virtual_var_storage = FIX2LONG(val);
+}
+
+static VALUE sb_define_virtual_variable_default_accessors(VALUE self, VALUE name) {
+  rb_define_virtual_variable(StringValuePtr(name), (rb_gvar_getter_t*) NULL, (rb_gvar_setter_t*) NULL);
+  return Qnil;
+}
+
+static VALUE sb_define_virtual_variable_incrementing_accessors(VALUE self, VALUE name) {
+  rb_define_virtual_variable(StringValuePtr(name), incrementing_getter, incrementing_setter);
+  return Qnil;
+}
+
 static VALUE sb_f_global_variables(VALUE self) {
   return rb_f_global_variables();
 }
@@ -64,6 +98,10 @@ static VALUE global_spec_rb_defout(VALUE self) {
   return rb_defout;
 }
 
+static VALUE global_spec_rb_fs(VALUE self) {
+  return rb_fs;
+}
+
 static VALUE global_spec_rb_rs(VALUE self) {
   return rb_rs;
 }
@@ -93,10 +131,14 @@ void Init_globals_spec(void) {
   VALUE cls = rb_define_class("CApiGlobalSpecs", rb_cObject);
   g_hooked_var = Qnil;
   rb_define_method(cls, "rb_define_hooked_variable_2x", sb_define_hooked_variable, 1);
+  rb_define_method(cls, "rb_define_hooked_variable_default_accessors", sb_define_hooked_variable_default_accessors, 1);
+  rb_define_method(cls, "rb_define_hooked_variable_null_var", sb_define_hooked_variable_null_var, 1);
   g_ro_var = Qnil;
   rb_define_method(cls, "rb_define_readonly_variable", sb_define_readonly_variable, 2);
   g_var = Qnil;
   rb_define_method(cls, "rb_define_variable", sb_define_variable, 2);
+  rb_define_method(cls, "rb_define_virtual_variable_default_accessors", sb_define_virtual_variable_default_accessors, 1);
+  rb_define_method(cls, "rb_define_virtual_variable_incrementing_accessors", sb_define_virtual_variable_incrementing_accessors, 1);
   rb_define_method(cls, "sb_get_global_value", sb_get_global_value, 0);
   rb_define_method(cls, "rb_f_global_variables", sb_f_global_variables, 0);
   rb_define_method(cls, "sb_gv_get", sb_gv_get, 1);
@@ -105,6 +147,7 @@ void Init_globals_spec(void) {
   rb_define_method(cls, "rb_stdout", global_spec_rb_stdout, 0);
   rb_define_method(cls, "rb_stderr", global_spec_rb_stderr, 0);
   rb_define_method(cls, "rb_defout", global_spec_rb_defout, 0);
+  rb_define_method(cls, "rb_fs", global_spec_rb_fs, 0);
   rb_define_method(cls, "rb_rs", global_spec_rb_rs, 0);
   rb_define_method(cls, "rb_default_rs", global_spec_rb_default_rs, 0);
   rb_define_method(cls, "rb_output_rs", global_spec_rb_output_rs, 0);
diff --git a/spec/ruby/optional/capi/ext/hash_spec.c b/spec/ruby/optional/capi/ext/hash_spec.c
index c8735cec2c..653917f2c4 100644
--- a/spec/ruby/optional/capi/ext/hash_spec.c
+++ b/spec/ruby/optional/capi/ext/hash_spec.c
@@ -105,6 +105,16 @@ VALUE hash_spec_rb_hash_new(VALUE self) {
   return rb_hash_new();
 }
 
+VALUE hash_spec_rb_hash_new_capa(VALUE self, VALUE capacity) {
+  return rb_hash_new_capa(NUM2LONG(capacity));
+}
+
+VALUE rb_ident_hash_new(void); /* internal.h, used in ripper */
+
+VALUE hash_spec_rb_ident_hash_new(VALUE self) {
+  return rb_ident_hash_new();
+}
+
 VALUE hash_spec_rb_hash_size(VALUE self, VALUE hash) {
   return rb_hash_size(hash);
 }
@@ -113,6 +123,29 @@ VALUE hash_spec_rb_hash_set_ifnone(VALUE self, VALUE hash, VALUE def) {
   return rb_hash_set_ifnone(hash, def);
 }
 
+VALUE hash_spec_compute_a_hash_code(VALUE self, VALUE seed) {
+  int int_seed = FIX2INT(seed);
+  st_index_t h = rb_hash_start(int_seed);
+  h = rb_hash_uint32(h, 540u);
+  h = rb_hash_uint32(h, 340u);
+  h = rb_hash_end(h);
+  return ULONG2NUM(h);
+}
+
+VALUE hash_spec_rb_hash_bulk_insert(VALUE self, VALUE array_len, VALUE array, VALUE hash) {
+  VALUE* ptr;
+
+  if (array == Qnil) {
+    ptr = NULL;
+  } else {
+    ptr = RARRAY_PTR(array);
+  }
+
+  long len = FIX2LONG(array_len);
+  rb_hash_bulk_insert(len, ptr, hash);
+  return Qnil;
+}
+
 void Init_hash_spec(void) {
   VALUE cls = rb_define_class("CApiHashSpecs", rb_cObject);
   rb_define_method(cls, "rb_hash", hash_spec_rb_hash, 1);
@@ -134,8 +167,12 @@ void Init_hash_spec(void) {
   rb_define_method(cls, "rb_hash_lookup2", hash_spec_rb_hash_lookup2, 3);
   rb_define_method(cls, "rb_hash_lookup2_default_undef", hash_spec_rb_hash_lookup2_default_undef, 2);
   rb_define_method(cls, "rb_hash_new", hash_spec_rb_hash_new, 0);
+  rb_define_method(cls, "rb_hash_new_capa", hash_spec_rb_hash_new_capa, 1);
+  rb_define_method(cls, "rb_ident_hash_new", hash_spec_rb_ident_hash_new, 0);
   rb_define_method(cls, "rb_hash_size", hash_spec_rb_hash_size, 1);
   rb_define_method(cls, "rb_hash_set_ifnone", hash_spec_rb_hash_set_ifnone, 2);
+  rb_define_method(cls, "compute_a_hash_code", hash_spec_compute_a_hash_code, 1);
+  rb_define_method(cls, "rb_hash_bulk_insert", hash_spec_rb_hash_bulk_insert, 3);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/integer_spec.c b/spec/ruby/optional/capi/ext/integer_spec.c
index 7e9e8b26bd..792fc0652a 100644
--- a/spec/ruby/optional/capi/ext/integer_spec.c
+++ b/spec/ruby/optional/capi/ext/integer_spec.c
@@ -6,13 +6,18 @@ extern "C" {
 #endif
 
 static VALUE integer_spec_rb_integer_pack(VALUE self, VALUE value,
-    VALUE words, VALUE numwords, VALUE wordsize, VALUE nails, VALUE flags)
-{
+    VALUE words, VALUE numwords, VALUE wordsize, VALUE nails, VALUE flags) {
   int result = rb_integer_pack(value, (void*)RSTRING_PTR(words), FIX2INT(numwords),
       FIX2INT(wordsize), FIX2INT(nails), FIX2INT(flags));
   return INT2FIX(result);
 }
 
+RUBY_EXTERN VALUE rb_int_positive_pow(long x, unsigned long y); /* internal.h, used in ripper */
+
+static VALUE integer_spec_rb_int_positive_pow(VALUE self, VALUE a, VALUE b) {
+  return rb_int_positive_pow(FIX2INT(a), FIX2INT(b));
+}
+
 void Init_integer_spec(void) {
   VALUE cls = rb_define_class("CApiIntegerSpecs", rb_cObject);
   rb_define_const(cls, "MSWORD", INT2NUM(INTEGER_PACK_MSWORD_FIRST));
@@ -27,8 +32,9 @@ void Init_integer_spec(void) {
   rb_define_const(cls, "NEGATIVE", INT2NUM(INTEGER_PACK_NEGATIVE));
 
   rb_define_method(cls, "rb_integer_pack", integer_spec_rb_integer_pack, 6);
+  rb_define_method(cls, "rb_int_positive_pow", integer_spec_rb_int_positive_pow, 2);
 }
 
 #ifdef __cplusplus
-extern "C" {
+}
 #endif
diff --git a/spec/ruby/optional/capi/ext/io_spec.c b/spec/ruby/optional/capi/ext/io_spec.c
index a8f5a29145..f3ede15729 100644
--- a/spec/ruby/optional/capi/ext/io_spec.c
+++ b/spec/ruby/optional/capi/ext/io_spec.c
@@ -21,16 +21,14 @@ static int set_non_blocking(int fd) {
   int flags = 1;
   return ioctl(fd, FIOBIO, &flags);
 #else
-# define SET_NON_BLOCKING_FAILS_ALWAYS 1
+#define SET_NON_BLOCKING_FAILS_ALWAYS 1
   errno = ENOSYS;
   return -1;
 #endif
 }
 
 static int io_spec_get_fd(VALUE io) {
-  rb_io_t* fp;
-  GetOpenFile(io, fp);
-  return fp->fd;
+  return rb_io_descriptor(io);
 }
 
 VALUE io_spec_GetOpenFile_fd(VALUE self, VALUE io) {
@@ -43,7 +41,7 @@ VALUE io_spec_rb_io_addstr(VALUE self, VALUE io, VALUE str) {
 
 VALUE io_spec_rb_io_printf(VALUE self, VALUE io, VALUE ary) {
   long argc = RARRAY_LEN(ary);
-  VALUE *argv = alloca(sizeof(VALUE) * argc);
+  VALUE *argv = (VALUE*) alloca(sizeof(VALUE) * argc);
   int i;
 
   for (i = 0; i < argc; i++) {
@@ -55,7 +53,7 @@ VALUE io_spec_rb_io_printf(VALUE self, VALUE io, VALUE ary) {
 
 VALUE io_spec_rb_io_print(VALUE self, VALUE io, VALUE ary) {
   long argc = RARRAY_LEN(ary);
-  VALUE *argv = alloca(sizeof(VALUE) * argc);
+  VALUE *argv = (VALUE*) alloca(sizeof(VALUE) * argc);
   int i;
 
   for (i = 0; i < argc; i++) {
@@ -67,7 +65,7 @@ VALUE io_spec_rb_io_print(VALUE self, VALUE io, VALUE ary) {
 
 VALUE io_spec_rb_io_puts(VALUE self, VALUE io, VALUE ary) {
   long argc = RARRAY_LEN(ary);
-  VALUE *argv = alloca(sizeof(VALUE) * argc);
+  VALUE *argv = (VALUE*) alloca(sizeof(VALUE) * argc);
   int i;
 
   for (i = 0; i < argc; i++) {
@@ -115,13 +113,13 @@ VALUE io_spec_rb_io_taint_check(VALUE self, VALUE io) {
 
 #define RB_IO_WAIT_READABLE_BUF 13
 
-#if SET_NON_BLOCKING_FAILS_ALWAYS
+#ifdef SET_NON_BLOCKING_FAILS_ALWAYS
 NORETURN(VALUE io_spec_rb_io_wait_readable(VALUE self, VALUE io, VALUE read_p));
 #endif
 
 VALUE io_spec_rb_io_wait_readable(VALUE self, VALUE io, VALUE read_p) {
   int fd = io_spec_get_fd(io);
-#if !SET_NON_BLOCKING_FAILS_ALWAYS
+#ifndef SET_NON_BLOCKING_FAILS_ALWAYS
   char buf[RB_IO_WAIT_READABLE_BUF];
   int ret, saved_errno;
 #endif
@@ -129,8 +127,8 @@ VALUE io_spec_rb_io_wait_readable(VALUE self, VALUE io, VALUE read_p) {
   if (set_non_blocking(fd) == -1)
     rb_sys_fail("set_non_blocking failed");
 
-#if !SET_NON_BLOCKING_FAILS_ALWAYS
-  if(RTEST(read_p)) {
+#ifndef SET_NON_BLOCKING_FAILS_ALWAYS
+  if (RTEST(read_p)) {
     if (read(fd, buf, RB_IO_WAIT_READABLE_BUF) != -1) {
       return Qnil;
     }
@@ -139,9 +137,9 @@ VALUE io_spec_rb_io_wait_readable(VALUE self, VALUE io, VALUE read_p) {
     errno = saved_errno;
   }
 
-  ret = rb_io_wait_readable(fd);
+  ret = rb_io_maybe_wait_readable(errno, io, Qnil);
 
-  if(RTEST(read_p)) {
+  if (RTEST(read_p)) {
     ssize_t r = read(fd, buf, RB_IO_WAIT_READABLE_BUF);
     if (r != RB_IO_WAIT_READABLE_BUF) {
       perror("read");
@@ -153,28 +151,80 @@ VALUE io_spec_rb_io_wait_readable(VALUE self, VALUE io, VALUE read_p) {
 
   return ret ? Qtrue : Qfalse;
 #else
-  UNREACHABLE;
+  UNREACHABLE_RETURN(Qnil);
 #endif
 }
 
 VALUE io_spec_rb_io_wait_writable(VALUE self, VALUE io) {
-  int ret = rb_io_wait_writable(io_spec_get_fd(io));
+  int ret = rb_io_maybe_wait_writable(errno, io, Qnil);
   return ret ? Qtrue : Qfalse;
 }
 
+VALUE io_spec_rb_io_maybe_wait_writable(VALUE self, VALUE error, VALUE io, VALUE timeout) {
+  int ret = rb_io_maybe_wait_writable(NUM2INT(error), io, timeout);
+  return INT2NUM(ret);
+}
+
+#ifdef SET_NON_BLOCKING_FAILS_ALWAYS
+NORETURN(VALUE io_spec_rb_io_maybe_wait_readable(VALUE self, VALUE error, VALUE io, VALUE timeout, VALUE read_p));
+#endif
+
+VALUE io_spec_rb_io_maybe_wait_readable(VALUE self, VALUE error, VALUE io, VALUE timeout, VALUE read_p) {
+  int fd = io_spec_get_fd(io);
+#ifndef SET_NON_BLOCKING_FAILS_ALWAYS
+  char buf[RB_IO_WAIT_READABLE_BUF];
+  int ret, saved_errno;
+#endif
+
+  if (set_non_blocking(fd) == -1)
+    rb_sys_fail("set_non_blocking failed");
+
+#ifndef SET_NON_BLOCKING_FAILS_ALWAYS
+  if (RTEST(read_p)) {
+    if (read(fd, buf, RB_IO_WAIT_READABLE_BUF) != -1) {
+      return Qnil;
+    }
+    saved_errno = errno;
+    rb_ivar_set(self, rb_intern("@write_data"), Qtrue);
+    errno = saved_errno;
+  }
+
+  // main part
+  ret = rb_io_maybe_wait_readable(NUM2INT(error), io, timeout);
+
+  if (RTEST(read_p)) {
+    ssize_t r = read(fd, buf, RB_IO_WAIT_READABLE_BUF);
+    if (r != RB_IO_WAIT_READABLE_BUF) {
+      perror("read");
+      return SSIZET2NUM(r);
+    }
+    rb_ivar_set(self, rb_intern("@read_data"),
+        rb_str_new(buf, RB_IO_WAIT_READABLE_BUF));
+  }
+
+  return INT2NUM(ret);
+#else
+  UNREACHABLE_RETURN(Qnil);
+#endif
+}
+
+VALUE io_spec_rb_io_maybe_wait(VALUE self, VALUE error, VALUE io, VALUE events, VALUE timeout) {
+  return rb_io_maybe_wait(NUM2INT(error), io, events, timeout);
+}
+
 VALUE io_spec_rb_thread_wait_fd(VALUE self, VALUE io) {
   rb_thread_wait_fd(io_spec_get_fd(io));
   return Qnil;
 }
 
 VALUE io_spec_rb_wait_for_single_fd(VALUE self, VALUE io, VALUE events, VALUE secs, VALUE usecs) {
-  int fd = io_spec_get_fd(io);
-  struct timeval tv;
+  VALUE timeout = Qnil;
   if (!NIL_P(secs)) {
-    tv.tv_sec = FIX2INT(secs);
-    tv.tv_usec = FIX2INT(usecs);
+      timeout = rb_float_new((double)FIX2INT(secs) + (0.000001 * FIX2INT(usecs)));
   }
-  return INT2FIX(rb_wait_for_single_fd(fd, FIX2INT(events), NIL_P(secs) ? NULL : &tv));
+  VALUE result = rb_io_wait(io, events, timeout);
+  if (result == Qfalse) return INT2FIX(0);
+  else return result;
 }
 
 VALUE io_spec_rb_thread_fd_writable(VALUE self, VALUE io) {
@@ -182,6 +232,46 @@ VALUE io_spec_rb_thread_fd_writable(VALUE self, VALUE io) {
   return Qnil;
 }
 
+VALUE io_spec_rb_thread_fd_select_read(VALUE self, VALUE io) {
+  int fd = io_spec_get_fd(io);
+
+  rb_fdset_t fds;
+  rb_fd_init(&fds);
+  rb_fd_set(fd, &fds);
+
+  int r = rb_thread_fd_select(fd + 1, &fds, NULL, NULL, NULL);
+  rb_fd_term(&fds);
+  return INT2FIX(r);
+}
+
+VALUE io_spec_rb_thread_fd_select_write(VALUE self, VALUE io) {
+  int fd = io_spec_get_fd(io);
+
+  rb_fdset_t fds;
+  rb_fd_init(&fds);
+  rb_fd_set(fd, &fds);
+
+  int r = rb_thread_fd_select(fd + 1, NULL, &fds, NULL, NULL);
+  rb_fd_term(&fds);
+  return INT2FIX(r);
+}
+
+VALUE io_spec_rb_thread_fd_select_timeout(VALUE self, VALUE io) {
+  int fd = io_spec_get_fd(io);
+
+  struct timeval timeout;
+  timeout.tv_sec = 10;
+  timeout.tv_usec = 20;
+
+  rb_fdset_t fds;
+  rb_fd_init(&fds);
+  rb_fd_set(fd, &fds);
+
+  int r = rb_thread_fd_select(fd + 1, NULL, &fds, NULL, &timeout);
+  rb_fd_term(&fds);
+  return INT2FIX(r);
+}
+
 VALUE io_spec_rb_io_binmode(VALUE self, VALUE io) {
   return rb_io_binmode(io);
 }
@@ -201,6 +291,21 @@ VALUE io_spec_rb_io_close(VALUE self, VALUE io) {
   return rb_io_close(io);
 }
 
+VALUE io_spec_rb_io_set_nonblock(VALUE self, VALUE io) {
+  rb_io_t* fp;
+#ifdef F_GETFL
+  int flags;
+#endif
+  GetOpenFile(io, fp);
+  rb_io_set_nonblock(fp);
+#ifdef F_GETFL
+  flags = fcntl(io_spec_get_fd(io), F_GETFL, 0);
+  return flags & O_NONBLOCK ? Qtrue : Qfalse;
+#else
+  return Qfalse;
+#endif
+}
+
 /*
  * this is needed to ensure rb_io_wait_*able functions behave
  * predictably because errno may be set to unexpected values
@@ -212,6 +317,51 @@ static VALUE io_spec_errno_set(VALUE self, VALUE val) {
   return val;
 }
 
+VALUE io_spec_mode_sync_flag(VALUE self, VALUE io) {
+  int mode;
+#ifdef RUBY_VERSION_IS_3_3
+  mode = rb_io_mode(io);
+#else
+  rb_io_t *fp;
+  GetOpenFile(io, fp);
+  mode = fp->mode;
+#endif
+  if (mode & FMODE_SYNC) {
+    return Qtrue;
+  } else {
+    return Qfalse;
+  }
+}
+
+#if defined(RUBY_VERSION_IS_3_3) || defined(TRUFFLERUBY)
+static VALUE io_spec_rb_io_mode(VALUE self, VALUE io) {
+  return INT2FIX(rb_io_mode(io));
+}
+
+static VALUE io_spec_rb_io_path(VALUE self, VALUE io) {
+  return rb_io_path(io);
+}
+
+static VALUE io_spec_rb_io_closed_p(VALUE self, VALUE io) {
+  return rb_io_closed_p(io);
+}
+
+static VALUE io_spec_rb_io_open_descriptor(VALUE self, VALUE klass, VALUE descriptor, VALUE mode, VALUE path, VALUE timeout, VALUE internal_encoding, VALUE external_encoding, VALUE ecflags, VALUE ecopts) {
+  struct rb_io_encoding io_encoding;
+
+  io_encoding.enc = rb_to_encoding(internal_encoding);
+  io_encoding.enc2 = rb_to_encoding(external_encoding);
+  io_encoding.ecflags = FIX2INT(ecflags);
+  io_encoding.ecopts = ecopts;
+
+  return rb_io_open_descriptor(klass, FIX2INT(descriptor), FIX2INT(mode), path, timeout, &io_encoding);
+}
+
+static VALUE io_spec_rb_io_open_descriptor_without_encoding(VALUE self, VALUE klass, VALUE descriptor, VALUE mode, VALUE path, VALUE timeout) {
+  return rb_io_open_descriptor(klass, FIX2INT(descriptor), FIX2INT(mode), path, timeout, NULL);
+}
+#endif
+
 void Init_io_spec(void) {
   VALUE cls = rb_define_class("CApiIOSpecs", rb_cObject);
   rb_define_method(cls, "GetOpenFile_fd", io_spec_GetOpenFile_fd, 1);
@@ -225,16 +375,36 @@ void Init_io_spec(void) {
   rb_define_method(cls, "rb_io_check_readable", io_spec_rb_io_check_readable, 1);
   rb_define_method(cls, "rb_io_check_writable", io_spec_rb_io_check_writable, 1);
   rb_define_method(cls, "rb_io_check_closed", io_spec_rb_io_check_closed, 1);
+  rb_define_method(cls, "rb_io_set_nonblock", io_spec_rb_io_set_nonblock, 1);
   rb_define_method(cls, "rb_io_taint_check", io_spec_rb_io_taint_check, 1);
   rb_define_method(cls, "rb_io_wait_readable", io_spec_rb_io_wait_readable, 2);
   rb_define_method(cls, "rb_io_wait_writable", io_spec_rb_io_wait_writable, 1);
+  rb_define_method(cls, "rb_io_maybe_wait_writable", io_spec_rb_io_maybe_wait_writable, 3);
+  rb_define_method(cls, "rb_io_maybe_wait_readable", io_spec_rb_io_maybe_wait_readable, 4);
+  rb_define_method(cls, "rb_io_maybe_wait", io_spec_rb_io_maybe_wait, 4);
   rb_define_method(cls, "rb_thread_wait_fd", io_spec_rb_thread_wait_fd, 1);
   rb_define_method(cls, "rb_thread_fd_writable", io_spec_rb_thread_fd_writable, 1);
+  rb_define_method(cls, "rb_thread_fd_select_read", io_spec_rb_thread_fd_select_read, 1);
+  rb_define_method(cls, "rb_thread_fd_select_write", io_spec_rb_thread_fd_select_write, 1);
+  rb_define_method(cls, "rb_thread_fd_select_timeout", io_spec_rb_thread_fd_select_timeout, 1);
   rb_define_method(cls, "rb_wait_for_single_fd", io_spec_rb_wait_for_single_fd, 4);
   rb_define_method(cls, "rb_io_binmode", io_spec_rb_io_binmode, 1);
   rb_define_method(cls, "rb_fd_fix_cloexec", io_spec_rb_fd_fix_cloexec, 1);
   rb_define_method(cls, "rb_cloexec_open", io_spec_rb_cloexec_open, 3);
   rb_define_method(cls, "errno=", io_spec_errno_set, 1);
+  rb_define_method(cls, "rb_io_mode_sync_flag", io_spec_mode_sync_flag, 1);
+#if defined(RUBY_VERSION_IS_3_3) || defined(TRUFFLERUBY)
+  rb_define_method(cls, "rb_io_mode", io_spec_rb_io_mode, 1);
+  rb_define_method(cls, "rb_io_path", io_spec_rb_io_path, 1);
+  rb_define_method(cls, "rb_io_closed_p", io_spec_rb_io_closed_p, 1);
+  rb_define_method(cls, "rb_io_open_descriptor", io_spec_rb_io_open_descriptor, 9);
+  rb_define_method(cls, "rb_io_open_descriptor_without_encoding", io_spec_rb_io_open_descriptor_without_encoding, 5);
+  rb_define_const(cls, "FMODE_READABLE", INT2FIX(FMODE_READABLE));
+  rb_define_const(cls, "FMODE_WRITABLE", INT2FIX(FMODE_WRITABLE));
+  rb_define_const(cls, "FMODE_BINMODE", INT2FIX(FMODE_BINMODE));
+  rb_define_const(cls, "FMODE_TEXTMODE", INT2FIX(FMODE_TEXTMODE));
+  rb_define_const(cls, "ECONV_UNIVERSAL_NEWLINE_DECORATOR", INT2FIX(ECONV_UNIVERSAL_NEWLINE_DECORATOR));
+#endif
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/kernel_spec.c b/spec/ruby/optional/capi/ext/kernel_spec.c
index 0e8827c613..a8fed21b59 100644
--- a/spec/ruby/optional/capi/ext/kernel_spec.c
+++ b/spec/ruby/optional/capi/ext/kernel_spec.c
@@ -7,16 +7,12 @@
 extern "C" {
 #endif
 
-VALUE kernel_spec_call_proc(VALUE arg_array) {
+static VALUE kernel_spec_call_proc(VALUE arg_array) {
   VALUE arg = rb_ary_pop(arg_array);
   VALUE proc = rb_ary_pop(arg_array);
   return rb_funcall(proc, rb_intern("call"), 1, arg);
 }
 
-VALUE kernel_spec_call_proc_raise(VALUE arg_array, VALUE raised_exc) {
-  return kernel_spec_call_proc(arg_array);
-}
-
 static VALUE kernel_spec_rb_block_given_p(VALUE self) {
   return rb_block_given_p() ? Qtrue : Qfalse;
 }
@@ -59,15 +55,32 @@ VALUE kernel_spec_rb_block_call_multi_arg(VALUE self, VALUE ary) {
   return rb_block_call(ary, rb_intern("inject"), 1, method_args, block_call_inject_multi_arg, Qnil);
 }
 
-VALUE kernel_spec_rb_block_call_no_func(VALUE self, VALUE ary) {
-  return rb_block_call(ary, rb_intern("map"), 0, NULL, NULL, Qnil);
+static VALUE return_extra_data(RB_BLOCK_CALL_FUNC_ARGLIST(yield_value, extra_data)) {
+  return extra_data;
 }
 
+VALUE rb_block_call_extra_data(VALUE self, VALUE object) {
+  return rb_block_call(object, rb_intern("instance_exec"), 0, NULL, return_extra_data, object);
+}
+
+VALUE kernel_spec_rb_block_call_no_func(VALUE self, VALUE ary) {
+  return rb_block_call(ary, rb_intern("map"), 0, NULL, (rb_block_call_func_t)NULL, Qnil);
+}
 
 VALUE kernel_spec_rb_frame_this_func(VALUE self) {
   return ID2SYM(rb_frame_this_func());
 }
 
+VALUE kernel_spec_rb_category_warn_deprecated(VALUE self) {
+  rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "foo");
+  return Qnil;
+}
+
+VALUE kernel_spec_rb_category_warn_deprecated_with_integer_extra_value(VALUE self, VALUE value) {
+  rb_category_warn(RB_WARN_CATEGORY_DEPRECATED, "foo %d", FIX2INT(value));
+  return Qnil;
+}
+
 VALUE kernel_spec_rb_ensure(VALUE self, VALUE main_proc, VALUE arg,
                             VALUE ensure_proc, VALUE arg2) {
   VALUE main_array, ensure_array;
@@ -97,13 +110,19 @@ VALUE kernel_spec_call_proc_with_catch_obj(RB_BLOCK_CALL_FUNC_ARGLIST(arg, data)
 }
 
 VALUE kernel_spec_rb_catch_obj(VALUE self, VALUE obj, VALUE main_proc) {
-  return rb_catch_obj(obj, kernel_spec_call_proc_with_catch, main_proc);
+  return rb_catch_obj(obj, kernel_spec_call_proc_with_catch_obj, main_proc);
 }
 
 VALUE kernel_spec_rb_eval_string(VALUE self, VALUE str) {
   return rb_eval_string(RSTRING_PTR(str));
 }
 
+#ifndef RUBY_VERSION_IS_4_0
+VALUE kernel_spec_rb_eval_cmd_kw(VALUE self, VALUE cmd, VALUE args, VALUE kw_splat) {
+  return rb_eval_cmd_kw(cmd, args, NUM2INT(kw_splat));
+}
+#endif
+
 VALUE kernel_spec_rb_raise(VALUE self, VALUE hash) {
   rb_hash_aset(hash, ID2SYM(rb_intern("stage")), ID2SYM(rb_intern("before")));
   if (self != Qundef)
@@ -122,7 +141,16 @@ VALUE kernel_spec_rb_throw_obj(VALUE self, VALUE obj, VALUE result) {
   return ID2SYM(rb_intern("rb_throw_failed"));
 }
 
-VALUE kernel_spec_call_proc_with_raised_exc(VALUE arg_array, VALUE raised_exc) {
+VALUE kernel_spec_rb_errinfo(VALUE self) {
+  return rb_errinfo();
+}
+
+VALUE kernel_spec_rb_set_errinfo(VALUE self, VALUE exc) {
+  rb_set_errinfo(exc);
+  return Qnil;
+}
+
+static VALUE kernel_spec_call_proc_with_raised_exc(VALUE arg_array, VALUE raised_exc) {
   VALUE argv[2];
   int argc;
 
@@ -134,7 +162,7 @@ VALUE kernel_spec_call_proc_with_raised_exc(VALUE arg_array, VALUE raised_exc) {
 
   argc = 2;
 
-  return rb_funcall2(proc, rb_intern("call"), argc, argv);
+  return rb_funcallv(proc, rb_intern("call"), argc, argv);
 }
 
 VALUE kernel_spec_rb_rescue(VALUE self, VALUE main_proc, VALUE arg,
@@ -145,6 +173,10 @@ VALUE kernel_spec_rb_rescue(VALUE self, VALUE main_proc, VALUE arg,
   rb_ary_push(main_array, main_proc);
   rb_ary_push(main_array, arg);
 
+  if (raise_proc == Qnil) {
+    return rb_rescue(kernel_spec_call_proc, main_array, NULL, arg2);
+  }
+
   raise_array = rb_ary_new();
   rb_ary_push(raise_array, raise_proc);
   rb_ary_push(raise_array, arg2);
@@ -165,7 +197,7 @@ VALUE kernel_spec_rb_rescue2(int argc, VALUE *args, VALUE self) {
   rb_ary_push(raise_array, args[3]);
 
   return rb_rescue2(kernel_spec_call_proc, main_array,
-      kernel_spec_call_proc_raise, raise_array, args[4], args[5], (VALUE)0);
+      kernel_spec_call_proc_with_raised_exc, raise_array, args[4], args[5], (VALUE)0);
 }
 
 static VALUE kernel_spec_rb_protect_yield(VALUE self, VALUE obj, VALUE ary) {
@@ -179,6 +211,18 @@ static VALUE kernel_spec_rb_protect_yield(VALUE self, VALUE obj, VALUE ary) {
   return res;
 }
 
+static VALUE kernel_spec_rb_protect_ignore_status(VALUE self, VALUE obj, VALUE ary) {
+  int status = 0;
+  VALUE res = rb_protect(rb_yield, obj, &status);
+  rb_ary_store(ary, 0, INT2NUM(23));
+  rb_ary_store(ary, 1, res);
+  return rb_errinfo();
+}
+
+static VALUE kernel_spec_rb_protect_null_status(VALUE self, VALUE obj) {
+  return rb_protect(rb_yield, obj, NULL);
+}
+
 static VALUE kernel_spec_rb_eval_string_protect(VALUE self, VALUE str, VALUE ary) {
   int status = 0;
   VALUE res = rb_eval_string_protect(RSTRING_PTR(str), &status);
@@ -192,8 +236,8 @@ static VALUE kernel_spec_rb_eval_string_protect(VALUE self, VALUE str, VALUE ary
 
 VALUE kernel_spec_rb_sys_fail(VALUE self, VALUE msg) {
   errno = 1;
-  if(msg == Qnil) {
-    rb_sys_fail(0);
+  if (msg == Qnil) {
+    rb_sys_fail(NULL);
   } else if (self != Qundef) {
     rb_sys_fail(StringValuePtr(msg));
   }
@@ -201,7 +245,7 @@ VALUE kernel_spec_rb_sys_fail(VALUE self, VALUE msg) {
 }
 
 VALUE kernel_spec_rb_syserr_fail(VALUE self, VALUE err, VALUE msg) {
-  if(msg == Qnil) {
+  if (msg == Qnil) {
     rb_syserr_fail(NUM2INT(err), NULL);
   } else if (self != Qundef) {
     rb_syserr_fail(NUM2INT(err), StringValuePtr(msg));
@@ -209,6 +253,13 @@ VALUE kernel_spec_rb_syserr_fail(VALUE self, VALUE err, VALUE msg) {
   return Qnil;
 }
 
+VALUE kernel_spec_rb_syserr_fail_str(VALUE self, VALUE err, VALUE msg) {
+  if (self != Qundef) {
+    rb_syserr_fail_str(NUM2INT(err), msg);
+  }
+  return Qnil;
+}
+
 VALUE kernel_spec_rb_warn(VALUE self, VALUE msg) {
   rb_warn("%s", StringValuePtr(msg));
   return Qnil;
@@ -254,10 +305,19 @@ static VALUE kernel_spec_rb_yield_values(VALUE self, VALUE obj1, VALUE obj2) {
   return rb_yield_values(2, obj1, obj2);
 }
 
+static VALUE kernel_spec_rb_yield_values2(VALUE self, VALUE ary) {
+  long len = RARRAY_LEN(ary);
+  VALUE *args = (VALUE*)alloca(sizeof(VALUE) * len);
+  for (int i = 0; i < len; i++) {
+    args[i] = rb_ary_entry(ary, i);
+  }
+  return rb_yield_values2((int)len, args);
+}
+
 static VALUE do_rec(VALUE obj, VALUE arg, int is_rec) {
-  if(is_rec) {
+  if (is_rec) {
     return obj;
-  } else if(arg == Qtrue) {
+  } else if (arg == Qtrue) {
     return rb_exec_recursive(do_rec, obj, Qnil);
   } else {
     return Qnil;
@@ -269,7 +329,7 @@ static VALUE kernel_spec_rb_exec_recursive(VALUE self, VALUE obj) {
 }
 
 static void write_io(VALUE io) {
-  rb_funcall(io, rb_intern("write"), 1, rb_str_new2("e"));
+  rb_funcall(io, rb_intern("write"), 1, rb_str_new2("in write_io"));
 }
 
 static VALUE kernel_spec_rb_set_end_proc(VALUE self, VALUE io) {
@@ -281,20 +341,52 @@ static VALUE kernel_spec_rb_f_sprintf(VALUE self, VALUE ary) {
   return rb_f_sprintf((int)RARRAY_LEN(ary), RARRAY_PTR(ary));
 }
 
+static VALUE kernel_spec_rb_str_format(VALUE self, VALUE count, VALUE ary, VALUE format) {
+  return rb_str_format(FIX2INT(count), RARRAY_PTR(ary), format);
+}
+
 static VALUE kernel_spec_rb_make_backtrace(VALUE self) {
   return rb_make_backtrace();
 }
 
-static VALUE kernel_spec_rb_obj_method(VALUE self, VALUE obj, VALUE method) {
-  return rb_obj_method(obj, method);
+static VALUE kernel_spec_rb_funcallv(VALUE self, VALUE obj, VALUE method, VALUE args) {
+  return rb_funcallv(obj, SYM2ID(method), RARRAY_LENINT(args), RARRAY_PTR(args));
 }
 
-static VALUE kernel_spec_rb_funcall3(VALUE self, VALUE obj, VALUE method) {
-  return rb_funcall3(obj, SYM2ID(method), 0, NULL);
+static VALUE kernel_spec_rb_funcallv_kw(VALUE self, VALUE obj, VALUE method, VALUE args) {
+  return rb_funcallv_kw(obj, SYM2ID(method), RARRAY_LENINT(args), RARRAY_PTR(args), RB_PASS_KEYWORDS);
 }
 
-static VALUE kernel_spec_rb_funcall_with_block(VALUE self, VALUE obj, VALUE method, VALUE block) {
-  return rb_funcall_with_block(obj, SYM2ID(method), 0, NULL, block);
+static VALUE kernel_spec_rb_keyword_given_p(int argc, VALUE *args, VALUE self) {
+  return rb_keyword_given_p() ? Qtrue : Qfalse;
+}
+
+static VALUE kernel_spec_rb_funcallv_public(VALUE self, VALUE obj, VALUE method) {
+  return rb_funcallv_public(obj, SYM2ID(method), 0, NULL);
+}
+
+static VALUE kernel_spec_rb_funcall_with_block(VALUE self, VALUE obj, VALUE method, VALUE args, VALUE block) {
+  return rb_funcall_with_block(obj, SYM2ID(method), RARRAY_LENINT(args), RARRAY_PTR(args), block);
+}
+
+static VALUE kernel_spec_rb_funcall_with_block_kw(VALUE self, VALUE obj, VALUE method, VALUE args, VALUE block) {
+  return rb_funcall_with_block_kw(obj, SYM2ID(method), RARRAY_LENINT(args), RARRAY_PTR(args), block, RB_PASS_KEYWORDS);
+}
+
+static VALUE kernel_spec_rb_funcall_many_args(VALUE self, VALUE obj, VALUE method) {
+  return rb_funcall(obj, SYM2ID(method), 15,
+                    INT2FIX(15), INT2FIX(14), INT2FIX(13), INT2FIX(12), INT2FIX(11),
+                    INT2FIX(10), INT2FIX(9), INT2FIX(8), INT2FIX(7), INT2FIX(6),
+                    INT2FIX(5), INT2FIX(4), INT2FIX(3), INT2FIX(2), INT2FIX(1));
+}
+
+static VALUE kernel_spec_rb_check_funcall(VALUE self, VALUE receiver, VALUE method, VALUE args) {
+  VALUE ret = rb_check_funcall(receiver, SYM2ID(method), RARRAY_LENINT(args), RARRAY_PTR(args));
+  if (ret == Qundef) {
+    return ID2SYM(rb_intern("Qundef"));
+  } else {
+    return ret;
+  }
 }
 
 void Init_kernel_spec(void) {
@@ -304,36 +396,55 @@ void Init_kernel_spec(void) {
   rb_define_method(cls, "rb_block_call", kernel_spec_rb_block_call, 1);
   rb_define_method(cls, "rb_block_call_multi_arg", kernel_spec_rb_block_call_multi_arg, 1);
   rb_define_method(cls, "rb_block_call_no_func", kernel_spec_rb_block_call_no_func, 1);
+  rb_define_method(cls, "rb_block_call_extra_data", rb_block_call_extra_data, 1);
   rb_define_method(cls, "rb_block_proc", kernel_spec_rb_block_proc, 0);
   rb_define_method(cls, "rb_block_lambda", kernel_spec_rb_block_lambda, 0);
   rb_define_method(cls, "rb_frame_this_func_test", kernel_spec_rb_frame_this_func, 0);
   rb_define_method(cls, "rb_frame_this_func_test_again", kernel_spec_rb_frame_this_func, 0);
+  rb_define_method(cls, "rb_category_warn_deprecated", kernel_spec_rb_category_warn_deprecated, 0);
+  rb_define_method(cls, "rb_category_warn_deprecated_with_integer_extra_value", kernel_spec_rb_category_warn_deprecated_with_integer_extra_value, 1);
   rb_define_method(cls, "rb_ensure", kernel_spec_rb_ensure, 4);
   rb_define_method(cls, "rb_eval_string", kernel_spec_rb_eval_string, 1);
+#ifndef RUBY_VERSION_IS_4_0
+  rb_define_method(cls, "rb_eval_cmd_kw", kernel_spec_rb_eval_cmd_kw, 3);
+#endif
   rb_define_method(cls, "rb_raise", kernel_spec_rb_raise, 1);
   rb_define_method(cls, "rb_throw", kernel_spec_rb_throw, 1);
   rb_define_method(cls, "rb_throw_obj", kernel_spec_rb_throw_obj, 2);
+  rb_define_method(cls, "rb_errinfo", kernel_spec_rb_errinfo, 0);
+  rb_define_method(cls, "rb_set_errinfo", kernel_spec_rb_set_errinfo, 1);
+  rb_define_method(cls, "rb_rescue", kernel_spec_rb_rescue, 4);
   rb_define_method(cls, "rb_rescue", kernel_spec_rb_rescue, 4);
   rb_define_method(cls, "rb_rescue2", kernel_spec_rb_rescue2, -1);
   rb_define_method(cls, "rb_protect_yield", kernel_spec_rb_protect_yield, 2);
+  rb_define_method(cls, "rb_protect_ignore_status", kernel_spec_rb_protect_ignore_status, 2);
+  rb_define_method(cls, "rb_protect_null_status", kernel_spec_rb_protect_null_status, 1);
   rb_define_method(cls, "rb_eval_string_protect", kernel_spec_rb_eval_string_protect, 2);
   rb_define_method(cls, "rb_catch", kernel_spec_rb_catch, 2);
   rb_define_method(cls, "rb_catch_obj", kernel_spec_rb_catch_obj, 2);
   rb_define_method(cls, "rb_sys_fail", kernel_spec_rb_sys_fail, 1);
   rb_define_method(cls, "rb_syserr_fail", kernel_spec_rb_syserr_fail, 2);
+  rb_define_method(cls, "rb_syserr_fail_str", kernel_spec_rb_syserr_fail_str, 2);
   rb_define_method(cls, "rb_warn", kernel_spec_rb_warn, 1);
   rb_define_method(cls, "rb_yield", kernel_spec_rb_yield, 1);
   rb_define_method(cls, "rb_yield_indirected", kernel_spec_rb_yield_indirected, 1);
   rb_define_method(cls, "rb_yield_define_each", kernel_spec_rb_yield_define_each, 1);
   rb_define_method(cls, "rb_yield_values", kernel_spec_rb_yield_values, 2);
+  rb_define_method(cls, "rb_yield_values2", kernel_spec_rb_yield_values2, 1);
   rb_define_method(cls, "rb_yield_splat", kernel_spec_rb_yield_splat, 1);
   rb_define_method(cls, "rb_exec_recursive", kernel_spec_rb_exec_recursive, 1);
   rb_define_method(cls, "rb_set_end_proc", kernel_spec_rb_set_end_proc, 1);
   rb_define_method(cls, "rb_f_sprintf", kernel_spec_rb_f_sprintf, 1);
+  rb_define_method(cls, "rb_str_format", kernel_spec_rb_str_format, 3);
   rb_define_method(cls, "rb_make_backtrace", kernel_spec_rb_make_backtrace, 0);
-  rb_define_method(cls, "rb_obj_method", kernel_spec_rb_obj_method, 2);
-  rb_define_method(cls, "rb_funcall3", kernel_spec_rb_funcall3, 2);
-  rb_define_method(cls, "rb_funcall_with_block", kernel_spec_rb_funcall_with_block, 3);
+  rb_define_method(cls, "rb_funcallv", kernel_spec_rb_funcallv, 3);
+  rb_define_method(cls, "rb_funcallv_kw", kernel_spec_rb_funcallv_kw, 3);
+  rb_define_method(cls, "rb_keyword_given_p", kernel_spec_rb_keyword_given_p, -1);
+  rb_define_method(cls, "rb_funcallv_public", kernel_spec_rb_funcallv_public, 2);
+  rb_define_method(cls, "rb_funcall_many_args", kernel_spec_rb_funcall_many_args, 2);
+  rb_define_method(cls, "rb_funcall_with_block", kernel_spec_rb_funcall_with_block, 4);
+  rb_define_method(cls, "rb_funcall_with_block_kw", kernel_spec_rb_funcall_with_block_kw, 4);
+  rb_define_method(cls, "rb_check_funcall", kernel_spec_rb_check_funcall, 3);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/language_spec.c b/spec/ruby/optional/capi/ext/language_spec.c
new file mode 100644
index 0000000000..749c188956
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/language_spec.c
@@ -0,0 +1,42 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE language_spec_switch(VALUE self, VALUE value) {
+  if (value == ID2SYM(rb_intern("undef"))) {
+    value = Qundef;
+  }
+
+  switch (value) {
+    case Qtrue:
+      return ID2SYM(rb_intern("true"));
+    case Qfalse:
+      return ID2SYM(rb_intern("false"));
+    case Qnil:
+      return ID2SYM(rb_intern("nil"));
+    case Qundef:
+      return ID2SYM(rb_intern("undef"));
+    default:
+      return ID2SYM(rb_intern("default"));
+  }
+}
+
+/* Defining a local variable rb_mProcess which already exists as a global variable
+ * For instance eventmachine does this in Init_rubyeventmachine() */
+static VALUE language_spec_global_local_var(VALUE self) {
+  VALUE rb_mProcess = rb_const_get(rb_cObject, rb_intern("Process"));
+  return rb_mProcess;
+}
+
+void Init_language_spec(void) {
+  VALUE cls = rb_define_class("CApiLanguageSpecs", rb_cObject);
+  rb_define_method(cls, "switch", language_spec_switch, 1);
+  rb_define_method(cls, "global_local_var", language_spec_global_local_var, 0);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/module_spec.c b/spec/ruby/optional/capi/ext/module_spec.c
index 3c8455a942..12bcf99983 100644
--- a/spec/ruby/optional/capi/ext/module_spec.c
+++ b/spec/ruby/optional/capi/ext/module_spec.c
@@ -76,6 +76,27 @@ static VALUE module_specs_rb_define_method(VALUE self, VALUE cls, VALUE str_name
   return Qnil;
 }
 
+static VALUE module_specs_method_var_args_1(int argc, VALUE *argv, VALUE self) {
+  VALUE ary = rb_ary_new();
+  int i;
+  for (i = 0; i < argc; i++) {
+    rb_ary_push(ary, argv[i]);
+  }
+  return ary;
+}
+
+static VALUE module_specs_method_var_args_2(VALUE self, VALUE argv) {
+  return argv;
+}
+
+static VALUE module_specs_rb_define_method_1required(VALUE self, VALUE arg1) {
+    return arg1;
+}
+
+static VALUE module_specs_rb_define_method_2required(VALUE self, VALUE arg1, VALUE arg2) {
+    return arg2;
+}
+
 static VALUE module_specs_rb_define_module_function(VALUE self, VALUE cls, VALUE str_name) {
   rb_define_module_function(cls, RSTRING_PTR(str_name), module_specs_test_method, 0);
   return Qnil;
@@ -128,21 +149,21 @@ void Init_module_spec(void) {
   rb_define_method(cls, "rb_define_module_under", module_specs_rb_define_module_under, 2);
   rb_define_method(cls, "rb_define_const", module_specs_define_const, 3);
   rb_define_method(cls, "rb_define_global_const", module_specs_define_global_const, 2);
-  rb_define_method(cls, "rb_define_global_function",
-      module_specs_rb_define_global_function, 1);
+  rb_define_method(cls, "rb_define_global_function", module_specs_rb_define_global_function, 1);
 
   rb_define_method(cls, "rb_define_method", module_specs_rb_define_method, 2);
-  rb_define_method(cls, "rb_define_module_function",
-      module_specs_rb_define_module_function, 2);
+  rb_define_method(cls, "rb_define_method_varargs_1", module_specs_method_var_args_1, -1);
+  rb_define_method(cls, "rb_define_method_varargs_2", module_specs_method_var_args_2, -2);
+  rb_define_method(cls, "rb_define_method_1required", module_specs_rb_define_method_1required, 1);
+  rb_define_method(cls, "rb_define_method_2required", module_specs_rb_define_method_2required, 2);
+
+  rb_define_method(cls, "rb_define_module_function", module_specs_rb_define_module_function, 2);
 
-  rb_define_method(cls, "rb_define_private_method",
-      module_specs_rb_define_private_method, 2);
+  rb_define_method(cls, "rb_define_private_method", module_specs_rb_define_private_method, 2);
 
-  rb_define_method(cls, "rb_define_protected_method",
-      module_specs_rb_define_protected_method, 2);
+  rb_define_method(cls, "rb_define_protected_method", module_specs_rb_define_protected_method, 2);
 
-  rb_define_method(cls, "rb_define_singleton_method",
-      module_specs_rb_define_singleton_method, 2);
+  rb_define_method(cls, "rb_define_singleton_method", module_specs_rb_define_singleton_method, 2);
 
   rb_define_method(cls, "rb_undef_method", module_specs_rb_undef_method, 2);
   rb_define_method(cls, "rb_undef", module_specs_rb_undef, 2);
diff --git a/spec/ruby/optional/capi/ext/module_under_autoload_spec.c b/spec/ruby/optional/capi/ext/module_under_autoload_spec.c
index c8f19a287b..b19466e555 100644
--- a/spec/ruby/optional/capi/ext/module_under_autoload_spec.c
+++ b/spec/ruby/optional/capi/ext/module_under_autoload_spec.c
@@ -1,7 +1,15 @@
 #include "ruby.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void Init_module_under_autoload_spec(void) {
   VALUE specs = rb_const_get(rb_cObject, rb_intern("CApiModuleSpecs"));
   rb_define_module_under(specs, "ModuleUnderAutoload");
   rb_define_module_under(specs, "RubyUnderAutoload");
 }
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/mutex_spec.c b/spec/ruby/optional/capi/ext/mutex_spec.c
index c2fdf917ac..d2c8f98e89 100644
--- a/spec/ruby/optional/capi/ext/mutex_spec.c
+++ b/spec/ruby/optional/capi/ext/mutex_spec.c
@@ -29,15 +29,34 @@ VALUE mutex_spec_rb_mutex_sleep(VALUE self, VALUE mutex, VALUE timeout) {
   return rb_mutex_sleep(mutex, timeout);
 }
 
-
 VALUE mutex_spec_rb_mutex_callback(VALUE arg) {
   return rb_funcall(arg, rb_intern("call"), 0);
 }
 
+VALUE mutex_spec_rb_mutex_naughty_callback(VALUE arg) {
+  int *result = (int *) arg;
+  return (VALUE) result;
+}
+
+VALUE mutex_spec_rb_mutex_callback_basic(VALUE arg) {
+  return arg;
+}
+
 VALUE mutex_spec_rb_mutex_synchronize(VALUE self, VALUE mutex, VALUE value) {
   return rb_mutex_synchronize(mutex, mutex_spec_rb_mutex_callback, value);
 }
 
+VALUE mutex_spec_rb_mutex_synchronize_with_naughty_callback(VALUE self, VALUE mutex) {
+  // a naughty callback accepts or returns not a Ruby object but arbitrary value
+  int arg = 42;
+  VALUE result = rb_mutex_synchronize(mutex, mutex_spec_rb_mutex_naughty_callback, (VALUE) &arg);
+  return INT2NUM(*((int *) result));
+}
+
+VALUE mutex_spec_rb_mutex_synchronize_with_native_callback(VALUE self, VALUE mutex, VALUE value) {
+  return rb_mutex_synchronize(mutex, mutex_spec_rb_mutex_callback_basic, value);
+}
+
 void Init_mutex_spec(void) {
   VALUE cls = rb_define_class("CApiMutexSpecs", rb_cObject);
   rb_define_method(cls, "rb_mutex_new", mutex_spec_rb_mutex_new, 0);
@@ -47,6 +66,8 @@ void Init_mutex_spec(void) {
   rb_define_method(cls, "rb_mutex_unlock", mutex_spec_rb_mutex_unlock, 1);
   rb_define_method(cls, "rb_mutex_sleep", mutex_spec_rb_mutex_sleep, 2);
   rb_define_method(cls, "rb_mutex_synchronize", mutex_spec_rb_mutex_synchronize, 2);
+  rb_define_method(cls, "rb_mutex_synchronize_with_naughty_callback", mutex_spec_rb_mutex_synchronize_with_naughty_callback, 1);
+  rb_define_method(cls, "rb_mutex_synchronize_with_native_callback", mutex_spec_rb_mutex_synchronize_with_native_callback, 2);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/numeric_spec.c b/spec/ruby/optional/capi/ext/numeric_spec.c
index 556c71a587..d3639580a8 100644
--- a/spec/ruby/optional/capi/ext/numeric_spec.c
+++ b/spec/ruby/optional/capi/ext/numeric_spec.c
@@ -54,13 +54,17 @@ static VALUE numeric_spec_NUM2INT(VALUE self, VALUE num) {
 }
 
 static VALUE numeric_spec_INT2NUM(VALUE self, VALUE num) {
-  return INT2NUM(NUM2LONG(num));
+  return INT2NUM(NUM2INT(num));
 }
 
 static VALUE numeric_spec_NUM2LONG(VALUE self, VALUE num) {
   return LONG2NUM(NUM2LONG(num));
 }
 
+static VALUE numeric_spec_NUM2SHORT(VALUE self, VALUE num) {
+  return LONG2NUM(NUM2SHORT(num));
+}
+
 static VALUE numeric_spec_NUM2UINT(VALUE self, VALUE num) {
   return ULONG2NUM(NUM2UINT(num));
 }
@@ -109,6 +113,7 @@ void Init_numeric_spec(void) {
   rb_define_method(cls, "NUM2DBL", numeric_spec_NUM2DBL, 1);
   rb_define_method(cls, "NUM2INT", numeric_spec_NUM2INT, 1);
   rb_define_method(cls, "NUM2LONG", numeric_spec_NUM2LONG, 1);
+  rb_define_method(cls, "NUM2SHORT", numeric_spec_NUM2SHORT, 1);
   rb_define_method(cls, "INT2NUM", numeric_spec_INT2NUM, 1);
   rb_define_method(cls, "NUM2UINT", numeric_spec_NUM2UINT, 1);
   rb_define_method(cls, "NUM2ULONG", numeric_spec_NUM2ULONG, 1);
diff --git a/spec/ruby/optional/capi/ext/object_spec.c b/spec/ruby/optional/capi/ext/object_spec.c
index cd32050f14..995bc38fcf 100644
--- a/spec/ruby/optional/capi/ext/object_spec.c
+++ b/spec/ruby/optional/capi/ext/object_spec.c
@@ -15,9 +15,7 @@ static VALUE object_spec_FL_ABLE(VALUE self, VALUE obj) {
 
 static int object_spec_FL_TEST_flag(VALUE flag_string) {
   char *flag_cstr = StringValueCStr(flag_string);
-  if (strcmp(flag_cstr, "FL_TAINT") == 0) {
-    return FL_TAINT;
-  } else if (strcmp(flag_cstr, "FL_FREEZE") == 0) {
+  if (strcmp(flag_cstr, "FL_FREEZE") == 0) {
     return FL_FREEZE;
   }
   return 0;
@@ -27,20 +25,6 @@ static VALUE object_spec_FL_TEST(VALUE self, VALUE obj, VALUE flag) {
   return INT2FIX(FL_TEST(obj, object_spec_FL_TEST_flag(flag)));
 }
 
-static VALUE object_spec_OBJ_TAINT(VALUE self, VALUE obj) {
-  OBJ_TAINT(obj);
-  return Qnil;
-}
-
-static VALUE object_spec_OBJ_TAINTED(VALUE self, VALUE obj) {
-  return OBJ_TAINTED(obj) ? Qtrue : Qfalse;
-}
-
-static VALUE object_spec_OBJ_INFECT(VALUE self, VALUE host, VALUE source) {
-  OBJ_INFECT(host, source);
-  return Qnil;
-}
-
 static VALUE object_spec_rb_any_to_s(VALUE self, VALUE obj) {
   return rb_any_to_s(obj);
 }
@@ -102,7 +86,7 @@ static VALUE so_rb_obj_dup(VALUE self, VALUE klass) {
 static VALUE so_rb_obj_call_init(VALUE self, VALUE object,
                                  VALUE nargs, VALUE args) {
   int c_nargs = FIX2INT(nargs);
-  VALUE *c_args = alloca(sizeof(VALUE) * c_nargs);
+  VALUE *c_args = (VALUE*) alloca(sizeof(VALUE) * c_nargs);
   int i;
 
   for (i = 0; i < c_nargs; i++)
@@ -113,11 +97,14 @@ static VALUE so_rb_obj_call_init(VALUE self, VALUE object,
   return Qnil;
 }
 
+static VALUE so_rb_obj_class(VALUE self, VALUE obj) {
+  return rb_obj_class(obj);
+}
+
 static VALUE so_rbobjclassname(VALUE self, VALUE obj) {
   return rb_str_new2(rb_obj_classname(obj));
 }
 
-
 static VALUE object_spec_rb_obj_freeze(VALUE self, VALUE obj) {
   return rb_obj_freeze(obj);
 }
@@ -142,8 +129,8 @@ static VALUE object_specs_rb_obj_method_arity(VALUE self, VALUE obj, VALUE mid)
   return INT2FIX(rb_obj_method_arity(obj, SYM2ID(mid)));
 }
 
-static VALUE object_spec_rb_obj_taint(VALUE self, VALUE obj) {
-  return rb_obj_taint(obj);
+static VALUE object_specs_rb_obj_method(VALUE self, VALUE obj, VALUE method) {
+  return rb_obj_method(obj, method);
 }
 
 static VALUE so_require(VALUE self) {
@@ -165,11 +152,7 @@ static VALUE object_spec_rb_method_boundp(VALUE self, VALUE obj, VALUE method, V
 }
 
 static VALUE object_spec_rb_special_const_p(VALUE self, VALUE value) {
-  if (rb_special_const_p(value)) {
-    return Qtrue;
-  } else {
-    return Qfalse;
-  }
+  return rb_special_const_p(value);
 }
 
 static VALUE so_to_id(VALUE self, VALUE obj) {
@@ -180,120 +163,132 @@ static VALUE object_spec_RTEST(VALUE self, VALUE value) {
   return RTEST(value) ? Qtrue : Qfalse;
 }
 
+static VALUE so_check_type(VALUE self, VALUE obj, VALUE other) {
+  rb_check_type(obj, TYPE(other));
+  return Qtrue;
+}
+
 static VALUE so_is_type_nil(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_NIL) {
+  if (TYPE(obj) == T_NIL) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_type_object(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_OBJECT) {
+  if (TYPE(obj) == T_OBJECT) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_type_array(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_ARRAY) {
+  if (TYPE(obj) == T_ARRAY) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_type_module(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_MODULE) {
+  if (TYPE(obj) == T_MODULE) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_type_class(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_CLASS) {
+  if (TYPE(obj) == T_CLASS) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_type_data(VALUE self, VALUE obj) {
-  if(TYPE(obj) == T_DATA) {
+  if (TYPE(obj) == T_DATA) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_nil(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_NIL)) {
+  if (rb_type_p(obj, T_NIL)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_object(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_OBJECT)) {
+  if (rb_type_p(obj, T_OBJECT)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_array(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_ARRAY)) {
+  if (rb_type_p(obj, T_ARRAY)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_module(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_MODULE)) {
+  if (rb_type_p(obj, T_MODULE)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_class(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_CLASS)) {
+  if (rb_type_p(obj, T_CLASS)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_rb_type_p_data(VALUE self, VALUE obj) {
-  if(rb_type_p(obj, T_DATA)) {
+  if (rb_type_p(obj, T_DATA)) {
+    return Qtrue;
+  }
+  return Qfalse;
+}
+
+static VALUE so_is_rb_type_p_file(VALUE self, VALUE obj) {
+  if (rb_type_p(obj, T_FILE)) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_builtin_type_object(VALUE self, VALUE obj) {
-  if(BUILTIN_TYPE(obj) == T_OBJECT) {
+  if (BUILTIN_TYPE(obj) == T_OBJECT) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_builtin_type_array(VALUE self, VALUE obj) {
-  if(BUILTIN_TYPE(obj) == T_ARRAY) {
+  if (BUILTIN_TYPE(obj) == T_ARRAY) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_builtin_type_module(VALUE self, VALUE obj) {
-  if(BUILTIN_TYPE(obj) == T_MODULE) {
+  if (BUILTIN_TYPE(obj) == T_MODULE) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_builtin_type_class(VALUE self, VALUE obj) {
-  if(BUILTIN_TYPE(obj) == T_CLASS) {
+  if (BUILTIN_TYPE(obj) == T_CLASS) {
     return Qtrue;
   }
   return Qfalse;
 }
 
 static VALUE so_is_builtin_type_data(VALUE self, VALUE obj) {
-  if(BUILTIN_TYPE(obj) == T_DATA) {
+  if (BUILTIN_TYPE(obj) == T_DATA) {
     return Qtrue;
   }
   return Qfalse;
@@ -315,6 +310,10 @@ static VALUE object_spec_rb_iv_set(VALUE self, VALUE obj, VALUE name, VALUE valu
   return rb_iv_set(obj, RSTRING_PTR(name), value);
 }
 
+static VALUE object_spec_rb_ivar_count(VALUE self, VALUE obj) {
+  return ULONG2NUM(rb_ivar_count(obj));
+}
+
 static VALUE object_spec_rb_ivar_get(VALUE self, VALUE obj, VALUE sym_name) {
   return rb_ivar_get(obj, SYM2ID(sym_name));
 }
@@ -345,14 +344,59 @@ static VALUE object_spec_rb_class_inherited_p(VALUE self, VALUE mod, VALUE arg)
   return rb_class_inherited_p(mod, arg);
 }
 
+static int foreach_f(ID key, VALUE val, VALUE ary) {
+  rb_ary_push(ary, ID2SYM(key));
+  rb_ary_push(ary, val);
+  return ST_CONTINUE;
+}
+
+static VALUE object_spec_rb_ivar_foreach(VALUE self, VALUE obj) {
+  VALUE ary = rb_ary_new();
+  rb_ivar_foreach(obj, foreach_f, ary);
+  return ary;
+}
+
+static VALUE speced_allocator(VALUE klass) {
+  VALUE super = rb_class_get_superclass(klass);
+  VALUE instance = rb_get_alloc_func(super)(klass);
+  rb_iv_set(instance, "@from_custom_allocator", Qtrue);
+  return instance;
+}
+
+static VALUE object_spec_rb_define_alloc_func(VALUE self, VALUE klass) {
+  rb_define_alloc_func(klass, speced_allocator);
+  return Qnil;
+}
+
+static VALUE object_spec_rb_undef_alloc_func(VALUE self, VALUE klass) {
+  rb_undef_alloc_func(klass);
+  return Qnil;
+}
+
+static VALUE object_spec_speced_allocator_p(VALUE self, VALUE klass) {
+  rb_alloc_func_t allocator = rb_get_alloc_func(klass);
+  return (allocator == speced_allocator) ? Qtrue : Qfalse;
+}
+
+static VALUE object_spec_custom_alloc_func_p(VALUE self, VALUE klass) {
+  rb_alloc_func_t allocator = rb_get_alloc_func(klass);
+  return allocator ? Qtrue : Qfalse;
+}
+
+static VALUE object_spec_redefine_frozen(VALUE self) {
+    // The purpose of this spec is to verify that `frozen?`
+    // and `RB_OBJ_FROZEN` do not mutually recurse infinitely.
+    if (RB_OBJ_FROZEN(self)) {
+        return Qtrue;
+    }
+
+    return Qfalse;
+}
 
 void Init_object_spec(void) {
   VALUE cls = rb_define_class("CApiObjectSpecs", rb_cObject);
   rb_define_method(cls, "FL_ABLE", object_spec_FL_ABLE, 1);
   rb_define_method(cls, "FL_TEST", object_spec_FL_TEST, 2);
-  rb_define_method(cls, "OBJ_TAINT", object_spec_OBJ_TAINT, 1);
-  rb_define_method(cls, "OBJ_TAINTED", object_spec_OBJ_TAINTED, 1);
-  rb_define_method(cls, "OBJ_INFECT", object_spec_OBJ_INFECT, 2);
   rb_define_method(cls, "rb_any_to_s", object_spec_rb_any_to_s, 1);
   rb_define_method(cls, "rb_attr_get", so_attr_get, 2);
   rb_define_method(cls, "rb_obj_instance_variables", object_spec_rb_obj_instance_variables, 1);
@@ -368,6 +412,7 @@ void Init_object_spec(void) {
   rb_define_method(cls, "rb_obj_alloc", so_rb_obj_alloc, 1);
   rb_define_method(cls, "rb_obj_dup", so_rb_obj_dup, 1);
   rb_define_method(cls, "rb_obj_call_init", so_rb_obj_call_init, 3);
+  rb_define_method(cls, "rb_obj_class", so_rb_obj_class, 1);
   rb_define_method(cls, "rb_obj_classname", so_rbobjclassname, 1);
   rb_define_method(cls, "rb_obj_freeze", object_spec_rb_obj_freeze, 1);
   rb_define_method(cls, "rb_obj_frozen_p", object_spec_rb_obj_frozen_p, 1);
@@ -375,15 +420,15 @@ void Init_object_spec(void) {
   rb_define_method(cls, "rb_obj_is_instance_of", so_instance_of, 2);
   rb_define_method(cls, "rb_obj_is_kind_of", so_kind_of, 2);
   rb_define_method(cls, "rb_obj_method_arity", object_specs_rb_obj_method_arity, 2);
-  rb_define_method(cls, "rb_obj_taint", object_spec_rb_obj_taint, 1);
+  rb_define_method(cls, "rb_obj_method", object_specs_rb_obj_method, 2);
   rb_define_method(cls, "rb_require", so_require, 0);
   rb_define_method(cls, "rb_respond_to", so_respond_to, 2);
   rb_define_method(cls, "rb_method_boundp", object_spec_rb_method_boundp, 3);
   rb_define_method(cls, "rb_obj_respond_to", so_obj_respond_to, 3);
   rb_define_method(cls, "rb_special_const_p", object_spec_rb_special_const_p, 1);
-
   rb_define_method(cls, "rb_to_id", so_to_id, 1);
   rb_define_method(cls, "RTEST", object_spec_RTEST, 1);
+  rb_define_method(cls, "rb_check_type", so_check_type, 2);
   rb_define_method(cls, "rb_is_type_nil", so_is_type_nil, 1);
   rb_define_method(cls, "rb_is_type_object", so_is_type_object, 1);
   rb_define_method(cls, "rb_is_type_array", so_is_type_array, 1);
@@ -396,6 +441,7 @@ void Init_object_spec(void) {
   rb_define_method(cls, "rb_is_rb_type_p_module", so_is_rb_type_p_module, 1);
   rb_define_method(cls, "rb_is_rb_type_p_class", so_is_rb_type_p_class, 1);
   rb_define_method(cls, "rb_is_rb_type_p_data", so_is_rb_type_p_data, 1);
+  rb_define_method(cls, "rb_is_rb_type_p_file", so_is_rb_type_p_file, 1);
   rb_define_method(cls, "rb_is_builtin_type_object", so_is_builtin_type_object, 1);
   rb_define_method(cls, "rb_is_builtin_type_array", so_is_builtin_type_array, 1);
   rb_define_method(cls, "rb_is_builtin_type_module", so_is_builtin_type_module, 1);
@@ -407,11 +453,21 @@ void Init_object_spec(void) {
   rb_define_method(cls, "rb_obj_instance_eval", object_spec_rb_obj_instance_eval, 1);
   rb_define_method(cls, "rb_iv_get", object_spec_rb_iv_get, 2);
   rb_define_method(cls, "rb_iv_set", object_spec_rb_iv_set, 3);
+  rb_define_method(cls, "rb_ivar_count", object_spec_rb_ivar_count, 1);
   rb_define_method(cls, "rb_ivar_get", object_spec_rb_ivar_get, 2);
   rb_define_method(cls, "rb_ivar_set", object_spec_rb_ivar_set, 3);
   rb_define_method(cls, "rb_ivar_defined", object_spec_rb_ivar_defined, 2);
   rb_define_method(cls, "rb_copy_generic_ivar", object_spec_rb_copy_generic_ivar, 2);
   rb_define_method(cls, "rb_free_generic_ivar", object_spec_rb_free_generic_ivar, 1);
+  rb_define_method(cls, "rb_define_alloc_func", object_spec_rb_define_alloc_func, 1);
+  rb_define_method(cls, "rb_undef_alloc_func", object_spec_rb_undef_alloc_func, 1);
+  rb_define_method(cls, "speced_allocator?", object_spec_speced_allocator_p, 1);
+  rb_define_method(cls, "custom_alloc_func?", object_spec_custom_alloc_func_p, 1);
+  rb_define_method(cls, "not_implemented_method", rb_f_notimplement, -1);
+  rb_define_method(cls, "rb_ivar_foreach", object_spec_rb_ivar_foreach, 1);
+
+  cls = rb_define_class("CApiObjectRedefinitionSpecs", rb_cObject);
+  rb_define_method(cls, "frozen?", object_spec_redefine_frozen, 0);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/proc_spec.c b/spec/ruby/optional/capi/ext/proc_spec.c
index 18fd1997ee..b7cd5d6262 100644
--- a/spec/ruby/optional/capi/ext/proc_spec.c
+++ b/spec/ruby/optional/capi/ext/proc_spec.c
@@ -11,10 +11,63 @@ VALUE proc_spec_rb_proc_new_function(RB_BLOCK_CALL_FUNC_ARGLIST(args, dummy)) {
   return rb_funcall(args, rb_intern("inspect"), 0);
 }
 
+VALUE proc_spec_rb_proc_new_function_arg(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  return arg;
+}
+
+VALUE proc_spec_rb_proc_new_function_argc(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  return INT2FIX(argc);
+}
+
+VALUE proc_spec_rb_proc_new_function_argv_n(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  int n = FIX2INT(arg);
+  if (n < argc) {
+    return argv[n];
+  } else {
+    rb_exc_raise(rb_exc_new2(rb_eArgError, "Arg index out of bounds."));
+  }
+}
+
+VALUE proc_spec_rb_proc_new_function_callback_arg(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  return callback_arg;
+}
+
+VALUE proc_spec_rb_proc_new_function_blockarg(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  return blockarg;
+}
+
+VALUE proc_spec_rb_proc_new_function_block_given_p(VALUE arg, VALUE callback_arg, int argc, const VALUE *argv, VALUE blockarg) {
+  return rb_block_given_p() ? Qtrue : Qfalse;
+}
+
 VALUE proc_spec_rb_proc_new(VALUE self) {
   return rb_proc_new(proc_spec_rb_proc_new_function, Qnil);
 }
 
+VALUE proc_spec_rb_proc_new_arg(VALUE self) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_arg, Qnil);
+}
+
+VALUE proc_spec_rb_proc_new_argc(VALUE self) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_argc, Qnil);
+}
+
+VALUE proc_spec_rb_proc_new_argv_n(VALUE self) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_argv_n, Qnil);
+}
+
+VALUE proc_spec_rb_proc_new_callback_arg(VALUE self, VALUE arg) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_callback_arg, arg);
+}
+
+VALUE proc_spec_rb_proc_new_blockarg(VALUE self) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_blockarg, Qnil);
+}
+
+VALUE proc_spec_rb_proc_new_block_given_p(VALUE self) {
+  return rb_proc_new(proc_spec_rb_proc_new_function_block_given_p, Qnil);
+}
+
 VALUE proc_spec_rb_proc_arity(VALUE self, VALUE prc) {
   return INT2FIX(rb_proc_arity(prc));
 }
@@ -23,6 +76,22 @@ VALUE proc_spec_rb_proc_call(VALUE self, VALUE prc, VALUE args) {
   return rb_proc_call(prc, args);
 }
 
+VALUE proc_spec_rb_proc_call_kw(VALUE self, VALUE prc, VALUE args) {
+  return rb_proc_call_kw(prc, args, RB_PASS_KEYWORDS);
+}
+
+VALUE proc_spec_rb_proc_call_with_block(VALUE self, VALUE prc, VALUE args, VALUE block) {
+  return rb_proc_call_with_block(prc, RARRAY_LENINT(args), RARRAY_PTR(args), block);
+}
+
+static VALUE proc_spec_rb_proc_call_with_block_kw(VALUE self, VALUE prc, VALUE args, VALUE block) {
+  return rb_proc_call_with_block_kw(prc, RARRAY_LENINT(args), RARRAY_PTR(args), block, RB_PASS_KEYWORDS);
+}
+
+VALUE proc_spec_rb_obj_is_proc(VALUE self, VALUE prc) {
+  return rb_obj_is_proc(prc);
+}
+
 /* This helper is not strictly necessary but reflects the code in wxRuby that
  * originally exposed issues with this Proc.new behavior.
  */
@@ -58,9 +127,19 @@ VALUE proc_spec_rb_Proc_new(VALUE self, VALUE scenario) {
 void Init_proc_spec(void) {
   VALUE cls = rb_define_class("CApiProcSpecs", rb_cObject);
   rb_define_method(cls, "rb_proc_new", proc_spec_rb_proc_new, 0);
+  rb_define_method(cls, "rb_proc_new_arg", proc_spec_rb_proc_new_arg, 0);
+  rb_define_method(cls, "rb_proc_new_argc", proc_spec_rb_proc_new_argc, 0);
+  rb_define_method(cls, "rb_proc_new_argv_n", proc_spec_rb_proc_new_argv_n, 0);
+  rb_define_method(cls, "rb_proc_new_callback_arg", proc_spec_rb_proc_new_callback_arg, 1);
+  rb_define_method(cls, "rb_proc_new_blockarg", proc_spec_rb_proc_new_blockarg, 0);
+  rb_define_method(cls, "rb_proc_new_block_given_p", proc_spec_rb_proc_new_block_given_p, 0);
   rb_define_method(cls, "rb_proc_arity", proc_spec_rb_proc_arity, 1);
   rb_define_method(cls, "rb_proc_call", proc_spec_rb_proc_call, 2);
+  rb_define_method(cls, "rb_proc_call_kw", proc_spec_rb_proc_call_kw, 2);
+  rb_define_method(cls, "rb_proc_call_with_block", proc_spec_rb_proc_call_with_block, 3);
+  rb_define_method(cls, "rb_proc_call_with_block_kw", proc_spec_rb_proc_call_with_block_kw, 3);
   rb_define_method(cls, "rb_Proc_new", proc_spec_rb_Proc_new, 1);
+  rb_define_method(cls, "rb_obj_is_proc", proc_spec_rb_obj_is_proc, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/range_spec.c b/spec/ruby/optional/capi/ext/range_spec.c
index 7a475ec695..9faed3e5ee 100644
--- a/spec/ruby/optional/capi/ext/range_spec.c
+++ b/spec/ruby/optional/capi/ext/range_spec.c
@@ -7,7 +7,7 @@ extern "C" {
 
 VALUE range_spec_rb_range_new(int argc, VALUE* argv, VALUE self) {
   int exclude_end = 0;
-  if(argc == 3) {
+  if (argc == 3) {
     exclude_end = RTEST(argv[2]);
   }
   return rb_range_new(argv[0], argv[1], exclude_end);
@@ -25,9 +25,9 @@ VALUE range_spec_rb_range_values(VALUE self, VALUE range) {
   return ary;
 }
 
-VALUE range_spec_rb_range_beg_len(VALUE self, VALUE range, VALUE begpv, VALUE lenpv, VALUE lenv, VALUE errv) {
-  long begp = FIX2LONG(begpv);
-  long lenp = FIX2LONG(lenpv);
+VALUE range_spec_rb_range_beg_len(VALUE self, VALUE range, VALUE lenv, VALUE errv) {
+  long begp = 0;
+  long lenp = 0;
   long len = FIX2LONG(lenv);
   int err = FIX2INT(errv);
   VALUE ary = rb_ary_new();
@@ -38,11 +38,51 @@ VALUE range_spec_rb_range_beg_len(VALUE self, VALUE range, VALUE begpv, VALUE le
   return ary;
 }
 
+VALUE range_spec_rb_arithmetic_sequence_extract(VALUE self, VALUE object) {
+  VALUE ary = rb_ary_new();
+  rb_arithmetic_sequence_components_t components;
+
+  int status = rb_arithmetic_sequence_extract(object, &components);
+
+  if (!status) {
+      rb_ary_store(ary, 0, LONG2FIX(status));
+      return ary;
+  }
+
+  rb_ary_store(ary, 0, LONG2FIX(status));
+  rb_ary_store(ary, 1, components.begin);
+  rb_ary_store(ary, 2, components.end);
+  rb_ary_store(ary, 3, components.step);
+  rb_ary_store(ary, 4, components.exclude_end ? Qtrue : Qfalse);
+  return ary;
+}
+
+VALUE range_spec_rb_arithmetic_sequence_beg_len_step(VALUE self, VALUE aseq, VALUE lenv, VALUE errv) {
+  long begp = 0;
+  long lenp = 0;
+  long stepp = 0;
+
+  long len = FIX2LONG(lenv);
+  int err = FIX2INT(errv);
+
+  VALUE success = rb_arithmetic_sequence_beg_len_step(aseq, &begp, &lenp, &stepp, len, err);
+
+  VALUE ary = rb_ary_new();
+  rb_ary_store(ary, 0, success);
+  rb_ary_store(ary, 1, LONG2FIX(begp));
+  rb_ary_store(ary, 2, LONG2FIX(lenp));
+  rb_ary_store(ary, 3, LONG2FIX(stepp));
+
+  return ary;
+}
+
 void Init_range_spec(void) {
   VALUE cls = rb_define_class("CApiRangeSpecs", rb_cObject);
   rb_define_method(cls, "rb_range_new", range_spec_rb_range_new, -1);
   rb_define_method(cls, "rb_range_values", range_spec_rb_range_values, 1);
-  rb_define_method(cls, "rb_range_beg_len", range_spec_rb_range_beg_len, 5);
+  rb_define_method(cls, "rb_range_beg_len", range_spec_rb_range_beg_len, 3);
+  rb_define_method(cls, "rb_arithmetic_sequence_extract", range_spec_rb_arithmetic_sequence_extract, 1);
+  rb_define_method(cls, "rb_arithmetic_sequence_beg_len_step", range_spec_rb_arithmetic_sequence_beg_len_step, 3);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/rbasic_spec.c b/spec/ruby/optional/capi/ext/rbasic_spec.c
new file mode 100644
index 0000000000..5a95b92804
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/rbasic_spec.c
@@ -0,0 +1,104 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef RBASIC_FLAGS
+#define RBASIC_FLAGS(obj) (RBASIC(obj)->flags)
+#endif
+
+#ifndef RBASIC_SET_FLAGS
+#define RBASIC_SET_FLAGS(obj, flags_to_set) (RBASIC(obj)->flags = flags_to_set)
+#endif
+
+#ifndef FL_SHAREABLE
+static const VALUE VISIBLE_BITS = FL_TAINT | FL_FREEZE;
+static const VALUE DATA_VISIBLE_BITS = FL_TAINT | FL_FREEZE | ~(FL_USER0 - 1);
+#else
+static const VALUE VISIBLE_BITS = FL_FREEZE;
+static const VALUE DATA_VISIBLE_BITS = FL_FREEZE | ~(FL_USER0 - 1);
+#endif
+
+#if SIZEOF_VALUE == SIZEOF_LONG
+#define VALUE2NUM(v) ULONG2NUM(v)
+#define NUM2VALUE(n) NUM2ULONG(n)
+#elif SIZEOF_VALUE == SIZEOF_LONG_LONG
+#define VALUE2NUM(v) ULL2NUM(v)
+#define NUM2VALUE(n) NUM2ULL(n)
+#else
+#error "unsupported"
+#endif
+
+VALUE rbasic_spec_freeze_flag(VALUE self) {
+  return VALUE2NUM(RUBY_FL_FREEZE);
+}
+
+static VALUE spec_get_flags(VALUE obj, VALUE visible_bits) {
+  VALUE flags = RB_FL_TEST(obj, visible_bits);
+  return VALUE2NUM(flags);
+}
+
+static VALUE spec_set_flags(VALUE obj, VALUE flags, VALUE visible_bits) {
+  flags &= visible_bits;
+
+  // Could also be done like:
+  // RB_FL_UNSET(obj, visible_bits);
+  // RB_FL_SET(obj, flags);
+  // But that seems rather indirect
+  RBASIC_SET_FLAGS(obj, (RBASIC_FLAGS(obj) & ~visible_bits) | flags);
+
+  return VALUE2NUM(flags);
+}
+
+static VALUE rbasic_spec_get_flags(VALUE self, VALUE obj) {
+  return spec_get_flags(obj, VISIBLE_BITS);
+}
+
+static VALUE rbasic_spec_set_flags(VALUE self, VALUE obj, VALUE flags) {
+  return spec_set_flags(obj, NUM2VALUE(flags), VISIBLE_BITS);
+}
+
+static VALUE rbasic_spec_copy_flags(VALUE self, VALUE to, VALUE from) {
+  return spec_set_flags(to, RBASIC_FLAGS(from), VISIBLE_BITS);
+}
+
+static VALUE rbasic_spec_get_klass(VALUE self, VALUE obj) {
+  return RBASIC_CLASS(obj);
+}
+
+static VALUE rbasic_rdata_spec_get_flags(VALUE self, VALUE structure) {
+  return spec_get_flags(structure, DATA_VISIBLE_BITS);
+}
+
+static VALUE rbasic_rdata_spec_set_flags(VALUE self, VALUE structure, VALUE flags) {
+  return spec_set_flags(structure, NUM2VALUE(flags), DATA_VISIBLE_BITS);
+}
+
+static VALUE rbasic_rdata_spec_copy_flags(VALUE self, VALUE to, VALUE from) {
+  return spec_set_flags(to, RBASIC_FLAGS(from), DATA_VISIBLE_BITS);
+}
+
+static VALUE rbasic_rdata_spec_get_klass(VALUE self, VALUE structure) {
+  return RBASIC_CLASS(structure);
+}
+
+void Init_rbasic_spec(void) {
+  VALUE cls = rb_define_class("CApiRBasicSpecs", rb_cObject);
+  rb_define_method(cls, "freeze_flag", rbasic_spec_freeze_flag, 0);
+  rb_define_method(cls, "get_flags", rbasic_spec_get_flags, 1);
+  rb_define_method(cls, "set_flags", rbasic_spec_set_flags, 2);
+  rb_define_method(cls, "copy_flags", rbasic_spec_copy_flags, 2);
+  rb_define_method(cls, "get_klass", rbasic_spec_get_klass, 1);
+
+  cls = rb_define_class("CApiRBasicRDataSpecs", rb_cObject);
+  rb_define_method(cls, "get_flags", rbasic_rdata_spec_get_flags, 1);
+  rb_define_method(cls, "set_flags", rbasic_rdata_spec_set_flags, 2);
+  rb_define_method(cls, "copy_flags", rbasic_rdata_spec_copy_flags, 2);
+  rb_define_method(cls, "get_klass", rbasic_rdata_spec_get_klass, 1);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/regexp_spec.c b/spec/ruby/optional/capi/ext/regexp_spec.c
index fc1c8b1e63..9de7982b50 100644
--- a/spec/ruby/optional/capi/ext/regexp_spec.c
+++ b/spec/ruby/optional/capi/ext/regexp_spec.c
@@ -9,8 +9,10 @@
 extern "C" {
 #endif
 
-VALUE regexp_spec_re(VALUE self) {
-  return rb_reg_new("a", 1, 0);
+VALUE regexp_spec_re(VALUE self, VALUE str, VALUE options) {
+  char *cstr = StringValueCStr(str);
+  int opts = FIX2INT(options);
+  return rb_reg_new(cstr, strlen(cstr), opts);
 }
 
 VALUE regexp_spec_reg_1st_match(VALUE self, VALUE md) {
@@ -33,19 +35,38 @@ VALUE regexp_spec_backref_get(VALUE self) {
   return rb_backref_get();
 }
 
+static VALUE regexp_spec_backref_set(VALUE self, VALUE backref) {
+  rb_backref_set(backref);
+  return Qnil;
+}
+
+VALUE regexp_spec_reg_match_backref_get(VALUE self, VALUE re, VALUE str) {
+  rb_reg_match(re, str);
+  return rb_backref_get();
+}
+
 VALUE regexp_spec_match(VALUE self, VALUE regexp, VALUE str) {
   return rb_funcall(regexp, rb_intern("match"), 1, str);
 }
 
+VALUE regexp_spec_memcicmp(VALUE self, VALUE str1, VALUE str2) {
+  long l1 = RSTRING_LEN(str1);
+  long l2 = RSTRING_LEN(str2);
+  return INT2FIX(rb_memcicmp(RSTRING_PTR(str1), RSTRING_PTR(str2), l1 < l2 ? l1 : l2));
+}
+
 void Init_regexp_spec(void) {
   VALUE cls = rb_define_class("CApiRegexpSpecs", rb_cObject);
   rb_define_method(cls, "match", regexp_spec_match, 2);
-  rb_define_method(cls, "a_re", regexp_spec_re, 0);
+  rb_define_method(cls, "a_re", regexp_spec_re, 2);
   rb_define_method(cls, "a_re_1st_match", regexp_spec_reg_1st_match, 1);
   rb_define_method(cls, "rb_reg_match", regexp_spec_reg_match, 2);
   rb_define_method(cls, "rb_backref_get", regexp_spec_backref_get, 0);
+  rb_define_method(cls, "rb_backref_set", regexp_spec_backref_set, 1);
+  rb_define_method(cls, "rb_reg_match_backref_get", regexp_spec_reg_match_backref_get, 2);
   rb_define_method(cls, "rb_reg_options", regexp_spec_rb_reg_options, 1);
   rb_define_method(cls, "rb_reg_regcomp", regexp_spec_rb_reg_regcomp, 1);
+  rb_define_method(cls, "rb_memcicmp", regexp_spec_memcicmp, 2);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/rubyspec.h b/spec/ruby/optional/capi/ext/rubyspec.h
index 78e298fddb..6c4bea5da0 100644
--- a/spec/ruby/optional/capi/ext/rubyspec.h
+++ b/spec/ruby/optional/capi/ext/rubyspec.h
@@ -1,34 +1,50 @@
 #ifndef RUBYSPEC_H
 #define RUBYSPEC_H
 
-/* Define convenience macros similar to the mspec guards to assist
- * with version incompatibilities.
- */
+/* Define convenience macros similar to the mspec
+ * guards to assist with version incompatibilities. */
 
 #include <ruby.h>
-#ifdef HAVE_RUBY_VERSION_H
-# include <ruby/version.h>
+#include <ruby/version.h>
+
+/* copied from ext/-test-/cxxanyargs/cxxanyargs.cpp */
+#if 0 /* Ignore deprecation warnings */
+
+#elif defined(_MSC_VER)
+#pragma warning(disable : 4996)
+
+#elif defined(__INTEL_COMPILER)
+#pragma warning(disable : 1786)
+
+#elif defined(__clang__)
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+
+#elif defined(__GNUC__)
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
+#elif defined(__SUNPRO_CC)
+#pragma error_messages (off,symdeprecated)
+
 #else
-# include <version.h>
-#endif
+// :FIXME: improve here for your compiler.
 
-#ifndef RUBY_VERSION_MAJOR
-#define RUBY_VERSION_MAJOR RUBY_API_VERSION_MAJOR
-#define RUBY_VERSION_MINOR RUBY_API_VERSION_MINOR
-#define RUBY_VERSION_TEENY RUBY_API_VERSION_TEENY
 #endif
 
-#define RUBY_VERSION_BEFORE(major,minor,teeny) \
-  ((RUBY_VERSION_MAJOR < (major)) || \
-   (RUBY_VERSION_MAJOR == (major) && RUBY_VERSION_MINOR < (minor)) || \
-   (RUBY_VERSION_MAJOR == (major) && RUBY_VERSION_MINOR == (minor) && RUBY_VERSION_TEENY < (teeny)))
+#define RUBY_VERSION_BEFORE(major,minor) \
+  ((RUBY_API_VERSION_MAJOR < (major)) || \
+   (RUBY_API_VERSION_MAJOR == (major) && RUBY_API_VERSION_MINOR < (minor)))
+#define RUBY_VERSION_SINCE(major,minor) (!RUBY_VERSION_BEFORE(major, minor))
+
+#if RUBY_VERSION_SINCE(4, 0)
+#define RUBY_VERSION_IS_4_0
+#endif
 
-#if RUBY_VERSION_MAJOR > 2 || (RUBY_VERSION_MAJOR == 2 && RUBY_VERSION_MINOR >= 6)
-#define RUBY_VERSION_IS_2_6
+#if RUBY_VERSION_SINCE(3, 4)
+#define RUBY_VERSION_IS_3_4
 #endif
 
-#if RUBY_VERSION_MAJOR > 2 || (RUBY_VERSION_MAJOR == 2 && RUBY_VERSION_MINOR >= 4)
-#define RUBY_VERSION_IS_2_4
+#if RUBY_VERSION_SINCE(3, 3)
+#define RUBY_VERSION_IS_3_3
 #endif
 
 #endif
diff --git a/spec/ruby/optional/capi/ext/set_spec.c b/spec/ruby/optional/capi/ext/set_spec.c
new file mode 100644
index 0000000000..11a271b361
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/set_spec.c
@@ -0,0 +1,65 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#ifdef RUBY_VERSION_IS_4_0
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define RBOOL(x) ((x) ? Qtrue : Qfalse)
+
+int yield_element_and_arg(VALUE element, VALUE arg) {
+  return RTEST(rb_yield_values(2, element, arg)) ? ST_CONTINUE : ST_STOP;
+}
+
+VALUE set_spec_rb_set_foreach(VALUE self, VALUE set, VALUE arg) {
+  rb_set_foreach(set, yield_element_and_arg, arg);
+  return Qnil;
+}
+
+VALUE set_spec_rb_set_new(VALUE self) {
+  return rb_set_new();
+}
+
+VALUE set_spec_rb_set_new_capa(VALUE self, VALUE capa) {
+  return rb_set_new_capa(NUM2INT(capa));
+}
+
+VALUE set_spec_rb_set_lookup(VALUE self, VALUE set, VALUE element) {
+  return RBOOL(rb_set_lookup(set, element));
+}
+
+VALUE set_spec_rb_set_add(VALUE self, VALUE set, VALUE element) {
+  return RBOOL(rb_set_add(set, element));
+}
+
+VALUE set_spec_rb_set_clear(VALUE self, VALUE set) {
+  return rb_set_clear(set);
+}
+
+VALUE set_spec_rb_set_delete(VALUE self, VALUE set, VALUE element) {
+  return RBOOL(rb_set_delete(set, element));
+}
+
+VALUE set_spec_rb_set_size(VALUE self, VALUE set) {
+  return SIZET2NUM(rb_set_size(set));
+}
+
+void Init_set_spec(void) {
+  VALUE cls = rb_define_class("CApiSetSpecs", rb_cObject);
+
+  rb_define_method(cls, "rb_set_foreach", set_spec_rb_set_foreach, 2);
+  rb_define_method(cls, "rb_set_new", set_spec_rb_set_new, 0);
+  rb_define_method(cls, "rb_set_new_capa", set_spec_rb_set_new_capa, 1);
+  rb_define_method(cls, "rb_set_lookup", set_spec_rb_set_lookup, 2);
+  rb_define_method(cls, "rb_set_add", set_spec_rb_set_add, 2);
+  rb_define_method(cls, "rb_set_clear", set_spec_rb_set_clear, 1);
+  rb_define_method(cls, "rb_set_delete", set_spec_rb_set_delete, 2);
+  rb_define_method(cls, "rb_set_size", set_spec_rb_set_size, 1);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/spec/ruby/optional/capi/ext/string_spec.c b/spec/ruby/optional/capi/ext/string_spec.c
index 6ad0b46ae4..094013e049 100644
--- a/spec/ruby/optional/capi/ext/string_spec.c
+++ b/spec/ruby/optional/capi/ext/string_spec.c
@@ -1,8 +1,10 @@
 #include "ruby.h"
 #include "rubyspec.h"
 
+#include <fcntl.h>
 #include <string.h>
 #include <stdarg.h>
+#include <errno.h>
 
 #include "ruby/encoding.h"
 
@@ -14,14 +16,9 @@ extern "C" {
  * On TruffleRuby RSTRING_PTR and the bytes remain in managed memory
  * until they must be written to native memory.
  * In some specs we want to test using the native memory. */
-char* NATIVE_RSTRING_PTR(VALUE str) {
-  char* ptr = RSTRING_PTR(str);
-  char** native = malloc(sizeof(char*));
-  *native = ptr;
-  ptr = *native;
-  free(native);
-  return ptr;
-}
+#ifndef NATIVE_RSTRING_PTR
+#define NATIVE_RSTRING_PTR(str) RSTRING_PTR(str)
+#endif
 
 VALUE string_spec_rb_cstr2inum(VALUE self, VALUE str, VALUE inum) {
   int num = FIX2INT(inum);
@@ -59,7 +56,7 @@ VALUE string_spec_rb_str_buf_new(VALUE self, VALUE len, VALUE str) {
 
   buf = rb_str_buf_new(NUM2LONG(len));
 
-  if(RTEST(str)) {
+  if (RTEST(str)) {
     snprintf(RSTRING_PTR(buf), NUM2LONG(len), "%s", RSTRING_PTR(str));
   }
 
@@ -74,12 +71,32 @@ VALUE string_spec_rb_str_buf_new2(VALUE self) {
   return rb_str_buf_new2("hello\0invisible");
 }
 
+VALUE string_spec_rb_str_tmp_new(VALUE self, VALUE len) {
+  VALUE str = rb_str_tmp_new(NUM2LONG(len));
+  rb_obj_reveal(str, rb_cString);
+  return str;
+}
+
+VALUE string_spec_rb_str_tmp_new_klass(VALUE self, VALUE len) {
+  return RBASIC_CLASS(rb_str_tmp_new(NUM2LONG(len)));
+}
+
+VALUE string_spec_rb_str_buf_append(VALUE self, VALUE str, VALUE two) {
+  return rb_str_buf_append(str, two);
+}
+
 VALUE string_spec_rb_str_buf_cat(VALUE self, VALUE str) {
   const char *question_mark = "?";
   rb_str_buf_cat(str, question_mark, strlen(question_mark));
   return str;
 }
 
+VALUE string_spec_rb_enc_str_buf_cat(VALUE self, VALUE str, VALUE other, VALUE encoding) {
+  char *cstr = StringValueCStr(other);
+  rb_encoding* enc = rb_to_encoding(encoding);
+  return rb_enc_str_buf_cat(str, cstr, strlen(cstr), enc);
+}
+
 VALUE string_spec_rb_str_cat(VALUE self, VALUE str) {
   return rb_str_cat(str, "?", 1);
 }
@@ -88,17 +105,29 @@ VALUE string_spec_rb_str_cat2(VALUE self, VALUE str) {
   return rb_str_cat2(str, "?");
 }
 
+VALUE string_spec_rb_str_cat_cstr(VALUE self, VALUE str, VALUE other) {
+  return rb_str_cat_cstr(str, StringValueCStr(other));
+}
+
+VALUE string_spec_rb_str_cat_cstr_constant(VALUE self, VALUE str) {
+  return rb_str_cat_cstr(str, "?");
+}
+
 VALUE string_spec_rb_str_cmp(VALUE self, VALUE str1, VALUE str2) {
   return INT2NUM(rb_str_cmp(str1, str2));
 }
 
+VALUE string_spec_rb_str_strlen(VALUE self, VALUE str) {
+  return LONG2NUM(rb_str_strlen(str));
+}
+
 VALUE string_spec_rb_str_conv_enc(VALUE self, VALUE str, VALUE from, VALUE to) {
   rb_encoding* from_enc;
   rb_encoding* to_enc;
 
   from_enc = rb_to_encoding(from);
 
-  if(NIL_P(to)) {
+  if (NIL_P(to)) {
     to_enc = 0;
   } else {
     to_enc = rb_to_encoding(to);
@@ -108,14 +137,13 @@ VALUE string_spec_rb_str_conv_enc(VALUE self, VALUE str, VALUE from, VALUE to) {
 }
 
 VALUE string_spec_rb_str_conv_enc_opts(VALUE self, VALUE str, VALUE from, VALUE to,
-                                       VALUE ecflags, VALUE ecopts)
-{
+                                       VALUE ecflags, VALUE ecopts) {
   rb_encoding* from_enc;
   rb_encoding* to_enc;
 
   from_enc = rb_to_encoding(from);
 
-  if(NIL_P(to)) {
+  if (NIL_P(to)) {
     to_enc = 0;
   } else {
     to_enc = rb_to_encoding(to);
@@ -124,6 +152,10 @@ VALUE string_spec_rb_str_conv_enc_opts(VALUE self, VALUE str, VALUE from, VALUE
   return rb_str_conv_enc_opts(str, from_enc, to_enc, FIX2INT(ecflags), ecopts);
 }
 
+VALUE string_spec_rb_str_drop_bytes(VALUE self, VALUE str, VALUE len) {
+  return rb_str_drop_bytes(str, NUM2LONG(len));
+}
+
 VALUE string_spec_rb_str_export(VALUE self, VALUE str) {
   return rb_str_export(str);
 }
@@ -165,7 +197,7 @@ VALUE string_spec_rb_str_new_offset(VALUE self, VALUE str, VALUE offset, VALUE l
 }
 
 VALUE string_spec_rb_str_new2(VALUE self, VALUE str) {
-  if(NIL_P(str)) {
+  if (NIL_P(str)) {
     return rb_str_new2("");
   } else {
     return rb_str_new2(RSTRING_PTR(str));
@@ -181,7 +213,7 @@ VALUE string_spec_rb_str_export_to_enc(VALUE self, VALUE str, VALUE enc) {
 }
 
 VALUE string_spec_rb_str_new_cstr(VALUE self, VALUE str) {
-  if(NIL_P(str)) {
+  if (NIL_P(str)) {
     return rb_str_new_cstr("");
   } else {
     return rb_str_new_cstr(RSTRING_PTR(str));
@@ -220,14 +252,6 @@ VALUE string_spec_rb_str_new5(VALUE self, VALUE str, VALUE ptr, VALUE len) {
   return rb_str_new5(str, RSTRING_PTR(ptr), FIX2INT(len));
 }
 
-VALUE string_spec_rb_tainted_str_new(VALUE self, VALUE str, VALUE len) {
-  return rb_tainted_str_new(RSTRING_PTR(str), FIX2INT(len));
-}
-
-VALUE string_spec_rb_tainted_str_new2(VALUE self, VALUE str) {
-  return rb_tainted_str_new2(RSTRING_PTR(str));
-}
-
 VALUE string_spec_rb_str_plus(VALUE self, VALUE str1, VALUE str2) {
   return rb_str_plus(str1, str2);
 }
@@ -250,6 +274,16 @@ VALUE string_spec_rb_str_resize_RSTRING_LEN(VALUE self, VALUE str, VALUE size) {
   return INT2FIX(RSTRING_LEN(modified));
 }
 
+VALUE string_spec_rb_str_resize_copy(VALUE self, VALUE str) {
+  rb_str_modify_expand(str, 5);
+  char *buffer = RSTRING_PTR(str);
+  buffer[1] = 'e';
+  buffer[2] = 's';
+  buffer[3] = 't';
+  rb_str_resize(str, 4);
+  return str;
+}
+
 VALUE string_spec_rb_str_split(VALUE self, VALUE str) {
   return rb_str_split(str, ",");
 }
@@ -285,6 +319,25 @@ VALUE string_spec_RSTRING_PTR_iterate(VALUE self, VALUE str) {
   return Qnil;
 }
 
+VALUE string_spec_RSTRING_PTR_iterate_uint32(VALUE self, VALUE str) {
+  uint32_t* ptr;
+  long i, l = RSTRING_LEN(str) / sizeof(uint32_t);
+
+  ptr = (uint32_t *)RSTRING_PTR(str);
+  for(i = 0; i < l; i++) {
+    rb_yield(UINT2NUM(ptr[i]));
+  }
+  return Qnil;
+}
+
+VALUE string_spec_RSTRING_PTR_short_memcpy(VALUE self, VALUE str) {
+  /* Short memcpy operations may be optimised by the compiler to a single write. */
+  if (RSTRING_LEN(str) >= 8) {
+    memcpy(RSTRING_PTR(str), "Infinity", 8);
+  }
+  return str;
+}
+
 VALUE string_spec_RSTRING_PTR_assign(VALUE self, VALUE str, VALUE chr) {
   int i;
   char c;
@@ -306,7 +359,7 @@ VALUE string_spec_RSTRING_PTR_set(VALUE self, VALUE str, VALUE i, VALUE chr) {
 
 VALUE string_spec_RSTRING_PTR_after_funcall(VALUE self, VALUE str, VALUE cb) {
   /* Silence gcc 4.3.2 warning about computed value not used */
-  if(RSTRING_PTR(str)) { /* force it out */
+  if (RSTRING_PTR(str)) { /* force it out */
     rb_funcall(cb, rb_intern("call"), 1, str);
   }
 
@@ -326,6 +379,39 @@ VALUE string_spec_RSTRING_PTR_after_yield(VALUE self, VALUE str) {
   return from_rstring_ptr;
 }
 
+VALUE string_spec_RSTRING_PTR_read(VALUE self, VALUE str, VALUE path) {
+  char *cpath = StringValueCStr(path);
+  int fd = open(cpath, O_RDONLY);
+  VALUE capacities = rb_ary_new();
+  if (fd < 0) {
+    rb_syserr_fail(errno, "open");
+  }
+
+  rb_str_modify_expand(str, 30);
+  rb_ary_push(capacities, SIZET2NUM(rb_str_capacity(str)));
+  char *buffer = RSTRING_PTR(str);
+  if (read(fd, buffer, 30) < 0) {
+    rb_syserr_fail(errno, "read");
+  }
+
+  rb_str_modify_expand(str, 53);
+  rb_ary_push(capacities, SIZET2NUM(rb_str_capacity(str)));
+  char *buffer2 = RSTRING_PTR(str);
+  if (read(fd, buffer2 + 30, 53 - 30) < 0) {
+    rb_syserr_fail(errno, "read");
+  }
+
+  rb_str_set_len(str, 53);
+  close(fd);
+  return capacities;
+}
+
+VALUE string_spec_RSTRING_PTR_null_terminate(VALUE self, VALUE str, VALUE min_length) {
+  char* ptr = RSTRING_PTR(str);
+  char* end = ptr + RSTRING_LEN(str);
+  return rb_str_new(end, FIX2LONG(min_length));
+}
+
 VALUE string_spec_StringValue(VALUE self, VALUE str) {
   return StringValue(str);
 }
@@ -338,11 +424,7 @@ static VALUE string_spec_SafeStringValue(VALUE self, VALUE str) {
 static VALUE string_spec_rb_str_hash(VALUE self, VALUE str) {
   st_index_t val = rb_str_hash(str);
 
-#if SIZEOF_LONG == SIZEOF_VOIDP || SIZEOF_LONG_LONG == SIZEOF_VOIDP
-  return LONG2FIX((long)val);
-#else
-#error unsupported platform
-#endif
+  return ST2FIX(val);
 }
 
 static VALUE string_spec_rb_str_update(VALUE self, VALUE str, VALUE beg, VALUE end, VALUE replacement) {
@@ -358,18 +440,46 @@ static VALUE string_spec_rb_str_free(VALUE self, VALUE str) {
 static VALUE string_spec_rb_sprintf1(VALUE self, VALUE str, VALUE repl) {
   return rb_sprintf(RSTRING_PTR(str), RSTRING_PTR(repl));
 }
+
 static VALUE string_spec_rb_sprintf2(VALUE self, VALUE str, VALUE repl1, VALUE repl2) {
   return rb_sprintf(RSTRING_PTR(str), RSTRING_PTR(repl1), RSTRING_PTR(repl2));
 }
 
 static VALUE string_spec_rb_sprintf3(VALUE self, VALUE str) {
-  return rb_sprintf("Result: %"PRIsVALUE".", str);
+  return rb_sprintf("Result: %" PRIsVALUE ".", str);
 }
 
 static VALUE string_spec_rb_sprintf4(VALUE self, VALUE str) {
-  return rb_sprintf("Result: %+"PRIsVALUE".", str);
+  return rb_sprintf("Result: %+" PRIsVALUE ".", str);
+}
+
+static VALUE string_spec_rb_sprintf5(VALUE self, VALUE width, VALUE precision, VALUE str) {
+  return rb_sprintf("Result: %*.*s.", FIX2INT(width), FIX2INT(precision), RSTRING_PTR(str));
+}
+
+static VALUE string_spec_rb_sprintf6(VALUE self, VALUE width, VALUE precision, VALUE str) {
+  return rb_sprintf("Result: %*.*" PRIsVALUE ".", FIX2INT(width), FIX2INT(precision), str);
 }
 
+static VALUE string_spec_rb_sprintf7(VALUE self, VALUE str, VALUE obj) {
+  VALUE results = rb_ary_new();
+  rb_ary_push(results, rb_sprintf(RSTRING_PTR(str), obj));
+  char cstr[256];
+  int len = snprintf(cstr, 256, RSTRING_PTR(str), obj);
+  rb_ary_push(results, rb_str_new(cstr, len));
+  return results;
+}
+
+static VALUE string_spec_rb_sprintf8(VALUE self, VALUE str, VALUE num) {
+  VALUE results = rb_ary_new();
+  rb_ary_push(results, rb_sprintf(RSTRING_PTR(str), FIX2LONG(num)));
+  char cstr[256];
+  int len = snprintf(cstr, 256, RSTRING_PTR(str), FIX2LONG(num));
+  rb_ary_push(results, rb_str_new(cstr, len));
+  return results;
+}
+
+PRINTF_ARGS(static VALUE string_spec_rb_vsprintf_worker(char* fmt, ...), 1, 2);
 static VALUE string_spec_rb_vsprintf_worker(char* fmt, ...) {
   va_list varargs;
   VALUE str;
@@ -394,6 +504,14 @@ static VALUE string_spec_rb_usascii_str_new(VALUE self, VALUE str, VALUE len) {
   return rb_usascii_str_new(RSTRING_PTR(str), NUM2INT(len));
 }
 
+static VALUE string_spec_rb_usascii_str_new_lit(VALUE self) {
+  return rb_usascii_str_new_lit("nokogiri");
+}
+
+static VALUE string_spec_rb_usascii_str_new_lit_non_ascii(VALUE self) {
+  return rb_usascii_str_new_lit("r\xc3\xa9sum\xc3\xa9");
+}
+
 static VALUE string_spec_rb_usascii_str_new_cstr(VALUE self, VALUE str) {
   return rb_usascii_str_new_cstr(RSTRING_PTR(str));
 }
@@ -412,6 +530,57 @@ static VALUE string_spec_rb_str_modify(VALUE self, VALUE str) {
   return str;
 }
 
+static VALUE string_spec_rb_utf8_str_new_static(VALUE self) {
+  return rb_utf8_str_new_static("nokogiri", 8);
+}
+
+static VALUE string_spec_rb_utf8_str_new(VALUE self) {
+  return rb_utf8_str_new("nokogiri", 8);
+}
+
+static VALUE string_spec_rb_utf8_str_new_cstr(VALUE self) {
+  return rb_utf8_str_new_cstr("nokogiri");
+}
+
+PRINTF_ARGS(static VALUE call_rb_str_vcatf(VALUE mesg, const char *fmt, ...), 2, 3);
+static VALUE call_rb_str_vcatf(VALUE mesg, const char *fmt, ...) {
+  va_list ap;
+  va_start(ap, fmt);
+  VALUE result = rb_str_vcatf(mesg, fmt, ap);
+  va_end(ap);
+  return result;
+}
+
+static VALUE string_spec_rb_str_vcatf(VALUE self, VALUE mesg) {
+  return call_rb_str_vcatf(mesg, "fmt %d %d number", 42, 7);
+}
+
+static VALUE string_spec_rb_str_catf(VALUE self, VALUE mesg) {
+  return rb_str_catf(mesg, "fmt %d %d number", 41, 6);
+}
+
+static VALUE string_spec_rb_str_locktmp(VALUE self, VALUE str) {
+  return rb_str_locktmp(str);
+}
+
+static VALUE string_spec_rb_str_unlocktmp(VALUE self, VALUE str) {
+  return rb_str_unlocktmp(str);
+}
+
+static VALUE string_spec_rb_enc_interned_str_cstr(VALUE self, VALUE str, VALUE enc) {
+  rb_encoding *e = NIL_P(enc) ? 0 : rb_to_encoding(enc);
+  return rb_enc_interned_str_cstr(RSTRING_PTR(str), e);
+}
+
+static VALUE string_spec_rb_enc_interned_str(VALUE self, VALUE str, VALUE len, VALUE enc) {
+  rb_encoding *e = NIL_P(enc) ? 0 : rb_to_encoding(enc);
+  return rb_enc_interned_str(RSTRING_PTR(str), FIX2LONG(len), e);
+}
+
+static VALUE string_spec_rb_str_to_interned_str(VALUE self, VALUE str) {
+  return rb_str_to_interned_str(str);
+}
+
 void Init_string_spec(void) {
   VALUE cls = rb_define_class("CApiStringSpecs", rb_cObject);
   rb_define_method(cls, "rb_cstr2inum", string_spec_rb_cstr2inum, 2);
@@ -421,12 +590,20 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_str_buf_new", string_spec_rb_str_buf_new, 2);
   rb_define_method(cls, "rb_str_capacity", string_spec_rb_str_capacity, 1);
   rb_define_method(cls, "rb_str_buf_new2", string_spec_rb_str_buf_new2, 0);
+  rb_define_method(cls, "rb_str_tmp_new", string_spec_rb_str_tmp_new, 1);
+  rb_define_method(cls, "rb_str_tmp_new_klass", string_spec_rb_str_tmp_new_klass, 1);
+  rb_define_method(cls, "rb_str_buf_append", string_spec_rb_str_buf_append, 2);
   rb_define_method(cls, "rb_str_buf_cat", string_spec_rb_str_buf_cat, 1);
+  rb_define_method(cls, "rb_enc_str_buf_cat", string_spec_rb_enc_str_buf_cat, 3);
   rb_define_method(cls, "rb_str_cat", string_spec_rb_str_cat, 1);
   rb_define_method(cls, "rb_str_cat2", string_spec_rb_str_cat2, 1);
+  rb_define_method(cls, "rb_str_cat_cstr", string_spec_rb_str_cat_cstr, 2);
+  rb_define_method(cls, "rb_str_cat_cstr_constant", string_spec_rb_str_cat_cstr_constant, 1);
   rb_define_method(cls, "rb_str_cmp", string_spec_rb_str_cmp, 2);
+  rb_define_method(cls, "rb_str_strlen", string_spec_rb_str_strlen, 1);
   rb_define_method(cls, "rb_str_conv_enc", string_spec_rb_str_conv_enc, 3);
   rb_define_method(cls, "rb_str_conv_enc_opts", string_spec_rb_str_conv_enc_opts, 5);
+  rb_define_method(cls, "rb_str_drop_bytes", string_spec_rb_str_drop_bytes, 2);
   rb_define_method(cls, "rb_str_export", string_spec_rb_str_export, 1);
   rb_define_method(cls, "rb_str_export_locale", string_spec_rb_str_export_locale, 1);
   rb_define_method(cls, "rb_str_dup", string_spec_rb_str_dup, 1);
@@ -449,13 +626,12 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_str_new3", string_spec_rb_str_new3, 1);
   rb_define_method(cls, "rb_str_new4", string_spec_rb_str_new4, 1);
   rb_define_method(cls, "rb_str_new5", string_spec_rb_str_new5, 3);
-  rb_define_method(cls, "rb_tainted_str_new", string_spec_rb_tainted_str_new, 2);
-  rb_define_method(cls, "rb_tainted_str_new2", string_spec_rb_tainted_str_new2, 1);
   rb_define_method(cls, "rb_str_plus", string_spec_rb_str_plus, 2);
   rb_define_method(cls, "rb_str_times", string_spec_rb_str_times, 2);
   rb_define_method(cls, "rb_str_modify_expand", string_spec_rb_str_modify_expand, 2);
   rb_define_method(cls, "rb_str_resize", string_spec_rb_str_resize, 2);
   rb_define_method(cls, "rb_str_resize_RSTRING_LEN", string_spec_rb_str_resize_RSTRING_LEN, 2);
+  rb_define_method(cls, "rb_str_resize_copy", string_spec_rb_str_resize_copy, 1);
   rb_define_method(cls, "rb_str_set_len", string_spec_rb_str_set_len, 2);
   rb_define_method(cls, "rb_str_set_len_RSTRING_LEN", string_spec_rb_str_set_len_RSTRING_LEN, 2);
   rb_define_method(cls, "rb_str_split", string_spec_rb_str_split, 1);
@@ -465,10 +641,14 @@ void Init_string_spec(void) {
   rb_define_method(cls, "RSTRING_LEN", string_spec_RSTRING_LEN, 1);
   rb_define_method(cls, "RSTRING_LENINT", string_spec_RSTRING_LENINT, 1);
   rb_define_method(cls, "RSTRING_PTR_iterate", string_spec_RSTRING_PTR_iterate, 1);
+  rb_define_method(cls, "RSTRING_PTR_iterate_uint32", string_spec_RSTRING_PTR_iterate_uint32, 1);
+  rb_define_method(cls, "RSTRING_PTR_short_memcpy", string_spec_RSTRING_PTR_short_memcpy, 1);
   rb_define_method(cls, "RSTRING_PTR_assign", string_spec_RSTRING_PTR_assign, 2);
   rb_define_method(cls, "RSTRING_PTR_set", string_spec_RSTRING_PTR_set, 3);
   rb_define_method(cls, "RSTRING_PTR_after_funcall", string_spec_RSTRING_PTR_after_funcall, 2);
   rb_define_method(cls, "RSTRING_PTR_after_yield", string_spec_RSTRING_PTR_after_yield, 1);
+  rb_define_method(cls, "RSTRING_PTR_read", string_spec_RSTRING_PTR_read, 2);
+  rb_define_method(cls, "RSTRING_PTR_null_terminate", string_spec_RSTRING_PTR_null_terminate, 2);
   rb_define_method(cls, "StringValue", string_spec_StringValue, 1);
   rb_define_method(cls, "SafeStringValue", string_spec_SafeStringValue, 1);
   rb_define_method(cls, "rb_str_hash", string_spec_rb_str_hash, 1);
@@ -478,13 +658,29 @@ void Init_string_spec(void) {
   rb_define_method(cls, "rb_sprintf2", string_spec_rb_sprintf2, 3);
   rb_define_method(cls, "rb_sprintf3", string_spec_rb_sprintf3, 1);
   rb_define_method(cls, "rb_sprintf4", string_spec_rb_sprintf4, 1);
+  rb_define_method(cls, "rb_sprintf5", string_spec_rb_sprintf5, 3);
+  rb_define_method(cls, "rb_sprintf6", string_spec_rb_sprintf6, 3);
+  rb_define_method(cls, "rb_sprintf7", string_spec_rb_sprintf7, 2);
+  rb_define_method(cls, "rb_sprintf8", string_spec_rb_sprintf8, 2);
   rb_define_method(cls, "rb_vsprintf", string_spec_rb_vsprintf, 4);
   rb_define_method(cls, "rb_str_equal", string_spec_rb_str_equal, 2);
   rb_define_method(cls, "rb_usascii_str_new", string_spec_rb_usascii_str_new, 2);
+  rb_define_method(cls, "rb_usascii_str_new_lit", string_spec_rb_usascii_str_new_lit, 0);
+  rb_define_method(cls, "rb_usascii_str_new_lit_non_ascii", string_spec_rb_usascii_str_new_lit_non_ascii, 0);
   rb_define_method(cls, "rb_usascii_str_new_cstr", string_spec_rb_usascii_str_new_cstr, 1);
   rb_define_method(cls, "rb_String", string_spec_rb_String, 1);
   rb_define_method(cls, "rb_string_value_cstr", string_spec_rb_string_value_cstr, 1);
   rb_define_method(cls, "rb_str_modify", string_spec_rb_str_modify, 1);
+  rb_define_method(cls, "rb_utf8_str_new_static", string_spec_rb_utf8_str_new_static, 0);
+  rb_define_method(cls, "rb_utf8_str_new", string_spec_rb_utf8_str_new, 0);
+  rb_define_method(cls, "rb_utf8_str_new_cstr", string_spec_rb_utf8_str_new_cstr, 0);
+  rb_define_method(cls, "rb_str_vcatf", string_spec_rb_str_vcatf, 1);
+  rb_define_method(cls, "rb_str_catf", string_spec_rb_str_catf, 1);
+  rb_define_method(cls, "rb_str_locktmp", string_spec_rb_str_locktmp, 1);
+  rb_define_method(cls, "rb_str_unlocktmp", string_spec_rb_str_unlocktmp, 1);
+  rb_define_method(cls, "rb_enc_interned_str_cstr", string_spec_rb_enc_interned_str_cstr, 2);
+  rb_define_method(cls, "rb_enc_interned_str", string_spec_rb_enc_interned_str, 3);
+  rb_define_method(cls, "rb_str_to_interned_str", string_spec_rb_str_to_interned_str, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/struct_spec.c b/spec/ruby/optional/capi/ext/struct_spec.c
index b9c3b902bf..756cfca8dd 100644
--- a/spec/ruby/optional/capi/ext/struct_spec.c
+++ b/spec/ruby/optional/capi/ext/struct_spec.c
@@ -15,13 +15,11 @@ static VALUE struct_spec_rb_struct_getmember(VALUE self, VALUE st, VALUE key) {
   return rb_struct_getmember(st, SYM2ID(key));
 }
 
-static VALUE struct_spec_rb_struct_s_members(VALUE self, VALUE klass)
-{
+static VALUE struct_spec_rb_struct_s_members(VALUE self, VALUE klass) {
   return rb_ary_dup(rb_struct_s_members(klass));
 }
 
-static VALUE struct_spec_rb_struct_members(VALUE self, VALUE st)
-{
+static VALUE struct_spec_rb_struct_members(VALUE self, VALUE st) {
   return rb_ary_dup(rb_struct_members(st));
 }
 
@@ -30,7 +28,7 @@ static VALUE struct_spec_rb_struct_aset(VALUE self, VALUE st, VALUE key, VALUE v
 }
 
 /* Only allow setting three attributes, should be sufficient for testing. */
-static VALUE struct_spec_struct_define(VALUE self, VALUE name,
+static VALUE struct_spec_rb_struct_define(VALUE self, VALUE name,
   VALUE attr1, VALUE attr2, VALUE attr3) {
 
   const char *a1 = StringValuePtr(attr1);
@@ -44,7 +42,7 @@ static VALUE struct_spec_struct_define(VALUE self, VALUE name,
 }
 
 /* Only allow setting three attributes, should be sufficient for testing. */
-static VALUE struct_spec_struct_define_under(VALUE self, VALUE outer,
+static VALUE struct_spec_rb_struct_define_under(VALUE self, VALUE outer,
   VALUE name, VALUE attr1, VALUE attr2, VALUE attr3) {
 
   const char *nm = StringValuePtr(name);
@@ -56,17 +54,33 @@ static VALUE struct_spec_struct_define_under(VALUE self, VALUE outer,
 }
 
 static VALUE struct_spec_rb_struct_new(VALUE self, VALUE klass,
-                                       VALUE a, VALUE b, VALUE c)
-{
-
+                                       VALUE a, VALUE b, VALUE c) {
   return rb_struct_new(klass, a, b, c);
 }
 
-#ifdef RUBY_VERSION_IS_2_4
-static VALUE struct_spec_rb_struct_size(VALUE self, VALUE st)
-{
+static VALUE struct_spec_rb_struct_size(VALUE self, VALUE st) {
   return rb_struct_size(st);
 }
+
+static VALUE struct_spec_rb_struct_initialize(VALUE self, VALUE st, VALUE values) {
+  return rb_struct_initialize(st, values);
+}
+
+#if defined(RUBY_VERSION_IS_3_3)
+/* Only allow setting three attributes, should be sufficient for testing. */
+static VALUE struct_spec_rb_data_define(VALUE self, VALUE superclass,
+  VALUE attr1, VALUE attr2, VALUE attr3) {
+
+  const char *a1 = StringValuePtr(attr1);
+  const char *a2 = StringValuePtr(attr2);
+  const char *a3 = StringValuePtr(attr3);
+
+  if (superclass == Qnil) {
+    superclass = 0;
+  }
+
+  return rb_data_define(superclass, a1, a2, a3, NULL);
+}
 #endif
 
 void Init_struct_spec(void) {
@@ -76,11 +90,13 @@ void Init_struct_spec(void) {
   rb_define_method(cls, "rb_struct_s_members", struct_spec_rb_struct_s_members, 1);
   rb_define_method(cls, "rb_struct_members", struct_spec_rb_struct_members, 1);
   rb_define_method(cls, "rb_struct_aset", struct_spec_rb_struct_aset, 3);
-  rb_define_method(cls, "rb_struct_define", struct_spec_struct_define, 4);
-  rb_define_method(cls, "rb_struct_define_under", struct_spec_struct_define_under, 5);
+  rb_define_method(cls, "rb_struct_define", struct_spec_rb_struct_define, 4);
+  rb_define_method(cls, "rb_struct_define_under", struct_spec_rb_struct_define_under, 5);
   rb_define_method(cls, "rb_struct_new", struct_spec_rb_struct_new, 4);
-#ifdef RUBY_VERSION_IS_2_4
   rb_define_method(cls, "rb_struct_size", struct_spec_rb_struct_size, 1);
+  rb_define_method(cls, "rb_struct_initialize", struct_spec_rb_struct_initialize, 2);
+#if defined(RUBY_VERSION_IS_3_3)
+  rb_define_method(cls, "rb_data_define", struct_spec_rb_data_define, 4);
 #endif
 }
 
diff --git a/spec/ruby/optional/capi/ext/symbol_spec.c b/spec/ruby/optional/capi/ext/symbol_spec.c
index 28da69ea3c..ba88635faa 100644
--- a/spec/ruby/optional/capi/ext/symbol_spec.c
+++ b/spec/ruby/optional/capi/ext/symbol_spec.c
@@ -7,6 +7,10 @@
 extern "C" {
 #endif
 
+VALUE symbol_spec_SYMBOL_P(VALUE self, VALUE obj) {
+  return SYMBOL_P(obj) ? Qtrue : Qfalse;
+}
+
 VALUE symbol_spec_rb_intern(VALUE self, VALUE string) {
   return ID2SYM(rb_intern(RSTRING_PTR(string)));
 }
@@ -43,14 +47,27 @@ VALUE symbol_spec_rb_id2name(VALUE self, VALUE symbol) {
   return rb_str_new(c_str, strlen(c_str));
 }
 
+VALUE symbol_spec_rb_id2name_id_zero(VALUE self) {
+  const char* c_str = rb_id2name((ID) 0);
+  return c_str ? rb_str_new(c_str, strlen(c_str)) : Qnil;
+}
+
 VALUE symbol_spec_rb_id2str(VALUE self, VALUE symbol) {
   return rb_id2str(SYM2ID(symbol));
 }
 
+VALUE symbol_spec_rb_id2str_id_zero(VALUE self) {
+  return rb_id2str((ID) 0);
+}
+
 VALUE symbol_spec_rb_intern_str(VALUE self, VALUE str) {
   return ID2SYM(rb_intern_str(str));
 }
 
+VALUE symbol_spec_rb_check_symbol_cstr(VALUE self, VALUE str) {
+  return rb_check_symbol_cstr(RSTRING_PTR(str), RSTRING_LEN(str), rb_enc_get(str));
+}
+
 VALUE symbol_spec_rb_is_class_id(VALUE self, VALUE sym) {
   return rb_is_class_id(SYM2ID(sym)) ? Qtrue : Qfalse;
 }
@@ -67,8 +84,13 @@ VALUE symbol_spec_rb_sym2str(VALUE self, VALUE sym) {
   return rb_sym2str(sym);
 }
 
+VALUE symbol_spec_rb_to_symbol(VALUE self, VALUE val) {
+  return rb_to_symbol(val);
+}
+
 void Init_symbol_spec(void) {
   VALUE cls = rb_define_class("CApiSymbolSpecs", rb_cObject);
+  rb_define_method(cls, "SYMBOL_P", symbol_spec_SYMBOL_P, 1);
   rb_define_method(cls, "rb_intern", symbol_spec_rb_intern, 1);
   rb_define_method(cls, "rb_intern2", symbol_spec_rb_intern2, 2);
   rb_define_method(cls, "rb_intern_const", symbol_spec_rb_intern_const, 1);
@@ -77,12 +99,16 @@ void Init_symbol_spec(void) {
   rb_define_method(cls, "rb_intern3", symbol_spec_rb_intern3, 3);
   rb_define_method(cls, "rb_intern3_c_compare", symbol_spec_rb_intern3_c_compare, 4);
   rb_define_method(cls, "rb_id2name", symbol_spec_rb_id2name, 1);
+  rb_define_method(cls, "rb_id2name_id_zero", symbol_spec_rb_id2name_id_zero, 0);
   rb_define_method(cls, "rb_id2str", symbol_spec_rb_id2str, 1);
+  rb_define_method(cls, "rb_id2str_id_zero", symbol_spec_rb_id2str_id_zero, 0);
   rb_define_method(cls, "rb_intern_str", symbol_spec_rb_intern_str, 1);
+  rb_define_method(cls, "rb_check_symbol_cstr", symbol_spec_rb_check_symbol_cstr, 1);
   rb_define_method(cls, "rb_is_class_id", symbol_spec_rb_is_class_id, 1);
   rb_define_method(cls, "rb_is_const_id", symbol_spec_rb_is_const_id, 1);
   rb_define_method(cls, "rb_is_instance_id", symbol_spec_rb_is_instance_id, 1);
   rb_define_method(cls, "rb_sym2str", symbol_spec_rb_sym2str, 1);
+  rb_define_method(cls, "rb_to_symbol", symbol_spec_rb_to_symbol, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/thread_spec.c b/spec/ruby/optional/capi/ext/thread_spec.c
index 139652e326..ac77e4e813 100644
--- a/spec/ruby/optional/capi/ext/thread_spec.c
+++ b/spec/ruby/optional/capi/ext/thread_spec.c
@@ -8,19 +8,24 @@
 #include <unistd.h>
 #endif
 #if defined(_WIN32)
-#define pipe(p) rb_w32_pipe(p)
+#include "ruby/win32.h"
+#define read rb_w32_read
+#define write rb_w32_write
+#define pipe rb_w32_pipe
+#endif
+
+#ifndef _WIN32
+#include <pthread.h>
 #endif
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-static VALUE thread_spec_rb_thread_alone() {
+static VALUE thread_spec_rb_thread_alone(VALUE self) {
   return rb_thread_alone() ? Qtrue : Qfalse;
 }
 
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-
 /* This is unblocked by unblock_func(). */
 static void* blocking_gvl_func(void* data) {
   int rfd = *(int *)data;
@@ -62,7 +67,7 @@ static VALUE thread_spec_rb_thread_call_without_gvl(VALUE self) {
 }
 
 /* This is unblocked by a signal. */
-static void* blocking_gvl_func_for_udf_io(void *data) {
+static void* blocking_gvl_func_for_ubf_io(void *data) {
   int rfd = (int)(size_t)data;
   char dummy;
 
@@ -82,14 +87,14 @@ static VALUE thread_spec_rb_thread_call_without_gvl_with_ubf_io(VALUE self) {
     rb_raise(rb_eRuntimeError, "could not create pipe");
   }
 
-  ret = rb_thread_call_without_gvl(blocking_gvl_func_for_udf_io,
+  ret = rb_thread_call_without_gvl(blocking_gvl_func_for_ubf_io,
                                   (void*)(size_t)fds[0], RUBY_UBF_IO, 0);
   close(fds[0]);
   close(fds[1]);
   return (VALUE)ret;
 }
 
-static VALUE thread_spec_rb_thread_current() {
+static VALUE thread_spec_rb_thread_current(VALUE self) {
   return rb_thread_current();
 }
 
@@ -113,7 +118,6 @@ static VALUE thread_spec_rb_thread_wait_for(VALUE self, VALUE s, VALUE ms) {
   return Qnil;
 }
 
-
 VALUE thread_spec_call_proc(void *arg_ptr) {
   VALUE arg_array = (VALUE)arg_ptr;
   VALUE arg = rb_ary_pop(arg_array);
@@ -129,6 +133,44 @@ static VALUE thread_spec_rb_thread_create(VALUE self, VALUE proc, VALUE arg) {
   return rb_thread_create(thread_spec_call_proc, (void*)args);
 }
 
+static VALUE thread_spec_ruby_native_thread_p(VALUE self) {
+  if (ruby_native_thread_p()) {
+    return Qtrue;
+  } else {
+    return Qfalse;
+  }
+}
+
+#ifndef _WIN32
+static VALUE false_result = Qfalse;
+static VALUE true_result = Qtrue;
+
+static void *new_thread_check(void *args) {
+  if (ruby_native_thread_p()) {
+    return &true_result;
+  } else {
+    return &false_result;
+  }
+}
+#endif
+
+static VALUE thread_spec_ruby_native_thread_p_new_thread(VALUE self) {
+#ifndef _WIN32
+    pthread_t t;
+    void *result = &true_result;
+    pthread_create(&t, NULL, new_thread_check, NULL);
+    pthread_join(t, &result);
+    return *(VALUE *)result;
+#else
+    return Qfalse;
+#endif
+}
+
+#ifdef RUBY_VERSION_IS_4_0
+static VALUE thread_spec_ruby_thread_has_gvl_p(VALUE self) {
+  return ruby_thread_has_gvl_p() ? Qtrue : Qfalse;
+}
+#endif
 
 void Init_thread_spec(void) {
   VALUE cls = rb_define_class("CApiThreadSpecs", rb_cObject);
@@ -141,6 +183,11 @@ void Init_thread_spec(void) {
   rb_define_method(cls,  "rb_thread_wakeup", thread_spec_rb_thread_wakeup, 1);
   rb_define_method(cls,  "rb_thread_wait_for", thread_spec_rb_thread_wait_for, 2);
   rb_define_method(cls,  "rb_thread_create", thread_spec_rb_thread_create, 2);
+  rb_define_method(cls,  "ruby_native_thread_p", thread_spec_ruby_native_thread_p, 0);
+  rb_define_method(cls,  "ruby_native_thread_p_new_thread", thread_spec_ruby_native_thread_p_new_thread, 0);
+#ifdef RUBY_VERSION_IS_4_0
+  rb_define_method(cls,  "ruby_thread_has_gvl_p", thread_spec_ruby_thread_has_gvl_p, 0);
+#endif
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/tracepoint_spec.c b/spec/ruby/optional/capi/ext/tracepoint_spec.c
new file mode 100644
index 0000000000..6666c8f85c
--- /dev/null
+++ b/spec/ruby/optional/capi/ext/tracepoint_spec.c
@@ -0,0 +1,49 @@
+#include "ruby.h"
+#include "rubyspec.h"
+
+#include <ruby/debug.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+static VALUE callback_called = Qnil;
+
+static void callback(VALUE tpval, void *data) {
+  callback_called = (VALUE) data;
+}
+
+static VALUE tracepoint_spec_rb_tracepoint_new(VALUE self, VALUE data) {
+  return rb_tracepoint_new(Qnil, RUBY_EVENT_LINE, callback, (void*) data);
+}
+
+static VALUE tracepoint_spec_callback_called(VALUE self) {
+  return callback_called;
+}
+
+static VALUE tracepoint_spec_rb_tracepoint_disable(VALUE self, VALUE trace) {
+  rb_tracepoint_disable(trace);
+  return rb_tracepoint_enabled_p(trace);
+}
+
+static VALUE tracepoint_spec_rb_tracepoint_enable(VALUE self, VALUE trace) {
+  rb_tracepoint_enable(trace);
+  return rb_tracepoint_enabled_p(trace);
+}
+
+static VALUE tracepoint_spec_rb_tracepoint_enabled_p(VALUE self, VALUE trace) {
+  return rb_tracepoint_enabled_p(trace);
+}
+
+void Init_tracepoint_spec(void) {
+  VALUE cls = rb_define_class("CApiTracePointSpecs", rb_cObject);
+  rb_define_method(cls, "rb_tracepoint_new", tracepoint_spec_rb_tracepoint_new, 1);
+  rb_define_method(cls, "rb_tracepoint_disable", tracepoint_spec_rb_tracepoint_disable, 1);
+  rb_define_method(cls, "rb_tracepoint_enable", tracepoint_spec_rb_tracepoint_enable, 1);
+  rb_define_method(cls, "rb_tracepoint_enabled_p", tracepoint_spec_rb_tracepoint_enabled_p, 1);
+  rb_define_method(cls, "callback_called?", tracepoint_spec_callback_called, 0);
+}
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/spec/ruby/optional/capi/ext/typed_data_spec.c b/spec/ruby/optional/capi/ext/typed_data_spec.c
index a2cc53f54d..221f1c8ac4 100644
--- a/spec/ruby/optional/capi/ext/typed_data_spec.c
+++ b/spec/ruby/optional/capi/ext/typed_data_spec.c
@@ -8,7 +8,7 @@ extern "C" {
 #endif
 
 struct sample_typed_wrapped_struct_parent {
-    int foo;
+  int foo;
 };
 
 void sample_typed_wrapped_struct_parent_free(void* st) {
@@ -32,7 +32,7 @@ static const rb_data_type_t sample_typed_wrapped_struct_parent_data_type = {
 };
 
 struct sample_typed_wrapped_struct {
-    int foo;
+  int foo;
 };
 
 void sample_typed_wrapped_struct_free(void* st) {
@@ -61,7 +61,7 @@ static const rb_data_type_t sample_typed_wrapped_struct_data_type = {
 };
 
 struct sample_typed_wrapped_struct_other {
-    int foo;
+  int foo;
 };
 
 void sample_typed_wrapped_struct_other_free(void* st) {
@@ -86,43 +86,53 @@ static const rb_data_type_t sample_typed_wrapped_struct_other_data_type = {
 
 
 VALUE sdaf_alloc_typed_func(VALUE klass) {
-    struct sample_typed_wrapped_struct* bar = (struct sample_typed_wrapped_struct *)malloc(sizeof(struct sample_typed_wrapped_struct));
-    bar->foo = 42;
-    return TypedData_Wrap_Struct(klass, &sample_typed_wrapped_struct_data_type, bar);
+  struct sample_typed_wrapped_struct* bar;
+  bar = (struct sample_typed_wrapped_struct *) malloc(sizeof(struct sample_typed_wrapped_struct));
+  bar->foo = 42;
+  return TypedData_Wrap_Struct(klass, &sample_typed_wrapped_struct_data_type, bar);
 }
 
 VALUE sdaf_typed_get_struct(VALUE self) {
-    struct sample_typed_wrapped_struct* bar;
-    TypedData_Get_Struct(self, struct sample_typed_wrapped_struct, &sample_typed_wrapped_struct_data_type, bar);
+  struct sample_typed_wrapped_struct* bar;
+  TypedData_Get_Struct(self, struct sample_typed_wrapped_struct, &sample_typed_wrapped_struct_data_type, bar);
 
-    return INT2FIX((*bar).foo);
+  return INT2FIX((*bar).foo);
 }
 
 VALUE sws_typed_wrap_struct(VALUE self, VALUE val) {
-    struct sample_typed_wrapped_struct* bar = (struct sample_typed_wrapped_struct *)malloc(sizeof(struct sample_typed_wrapped_struct));
-    bar->foo = FIX2INT(val);
-    return TypedData_Wrap_Struct(rb_cObject, &sample_typed_wrapped_struct_data_type, bar);
+  struct sample_typed_wrapped_struct* bar;
+  bar = (struct sample_typed_wrapped_struct *) malloc(sizeof(struct sample_typed_wrapped_struct));
+  bar->foo = FIX2INT(val);
+  return TypedData_Wrap_Struct(rb_cObject, &sample_typed_wrapped_struct_data_type, bar);
+}
+
+#undef RUBY_UNTYPED_DATA_WARNING
+#define RUBY_UNTYPED_DATA_WARNING 0
+VALUE sws_untyped_wrap_struct(VALUE self, VALUE val) {
+  int* data = (int*) malloc(sizeof(int));
+  *data = FIX2INT(val);
+  return Data_Wrap_Struct(rb_cObject, NULL, free, data);
 }
 
 VALUE sws_typed_get_struct(VALUE self, VALUE obj) {
-    struct sample_typed_wrapped_struct* bar;
-    TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct, &sample_typed_wrapped_struct_data_type, bar);
+  struct sample_typed_wrapped_struct* bar;
+  TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct, &sample_typed_wrapped_struct_data_type, bar);
 
-    return INT2FIX((*bar).foo);
+  return INT2FIX((*bar).foo);
 }
 
 VALUE sws_typed_get_struct_different_type(VALUE self, VALUE obj) {
-    struct sample_typed_wrapped_struct_other* bar;
-    TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct_other, &sample_typed_wrapped_struct_other_data_type, bar);
+  struct sample_typed_wrapped_struct_other* bar;
+  TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct_other, &sample_typed_wrapped_struct_other_data_type, bar);
 
-    return INT2FIX((*bar).foo);
+  return INT2FIX((*bar).foo);
 }
 
 VALUE sws_typed_get_struct_parent_type(VALUE self, VALUE obj) {
-    struct sample_typed_wrapped_struct_parent* bar;
-    TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct_parent, &sample_typed_wrapped_struct_parent_data_type, bar);
+  struct sample_typed_wrapped_struct_parent* bar;
+  TypedData_Get_Struct(obj, struct sample_typed_wrapped_struct_parent, &sample_typed_wrapped_struct_parent_data_type, bar);
 
-    return INT2FIX((*bar).foo);
+  return INT2FIX((*bar).foo);
 }
 
 VALUE sws_typed_get_struct_rdata(VALUE self, VALUE obj) {
@@ -138,27 +148,53 @@ VALUE sws_typed_get_struct_data_ptr(VALUE self, VALUE obj) {
 }
 
 VALUE sws_typed_change_struct(VALUE self, VALUE obj, VALUE new_val) {
-  struct sample_typed_wrapped_struct *old_struct, *new_struct;
-  new_struct = (struct sample_typed_wrapped_struct *)malloc(sizeof(struct sample_typed_wrapped_struct));
+  struct sample_typed_wrapped_struct *new_struct;
+  new_struct = (struct sample_typed_wrapped_struct *) malloc(sizeof(struct sample_typed_wrapped_struct));
   new_struct->foo = FIX2INT(new_val);
-  old_struct = RTYPEDDATA(obj)->data;
-  free(old_struct);
+  free(RTYPEDDATA(obj)->data);
   RTYPEDDATA(obj)->data = new_struct;
   return Qnil;
 }
 
+VALUE sws_typed_rb_check_type(VALUE self, VALUE obj, VALUE other) {
+  rb_check_type(obj, TYPE(other));
+  return Qtrue;
+}
+
+VALUE sws_typed_rb_check_typeddata_same_type(VALUE self, VALUE obj) {
+  return rb_check_typeddata(obj, &sample_typed_wrapped_struct_data_type) == DATA_PTR(obj) ? Qtrue : Qfalse;
+}
+
+VALUE sws_typed_rb_check_typeddata_same_type_parent(VALUE self, VALUE obj) {
+  return rb_check_typeddata(obj, &sample_typed_wrapped_struct_parent_data_type) == DATA_PTR(obj) ? Qtrue : Qfalse;
+}
+
+VALUE sws_typed_rb_check_typeddata_different_type(VALUE self, VALUE obj) {
+  return rb_check_typeddata(obj, &sample_typed_wrapped_struct_other_data_type) == DATA_PTR(obj) ? Qtrue : Qfalse;
+}
+
+VALUE sws_typed_RTYPEDDATA_P(VALUE self, VALUE obj) {
+  return RTYPEDDATA_P(obj) ? Qtrue : Qfalse;
+}
+
 void Init_typed_data_spec(void) {
   VALUE cls = rb_define_class("CApiAllocTypedSpecs", rb_cObject);
   rb_define_alloc_func(cls, sdaf_alloc_typed_func);
   rb_define_method(cls, "typed_wrapped_data", sdaf_typed_get_struct, 0);
   cls = rb_define_class("CApiWrappedTypedStructSpecs", rb_cObject);
   rb_define_method(cls, "typed_wrap_struct", sws_typed_wrap_struct, 1);
+  rb_define_method(cls, "untyped_wrap_struct", sws_untyped_wrap_struct, 1);
   rb_define_method(cls, "typed_get_struct", sws_typed_get_struct, 1);
   rb_define_method(cls, "typed_get_struct_other", sws_typed_get_struct_different_type, 1);
   rb_define_method(cls, "typed_get_struct_parent", sws_typed_get_struct_parent_type, 1);
   rb_define_method(cls, "typed_get_struct_rdata", sws_typed_get_struct_rdata, 1);
   rb_define_method(cls, "typed_get_struct_data_ptr", sws_typed_get_struct_data_ptr, 1);
   rb_define_method(cls, "typed_change_struct", sws_typed_change_struct, 2);
+  rb_define_method(cls, "rb_check_type", sws_typed_rb_check_type, 2);
+  rb_define_method(cls, "rb_check_typeddata_same_type", sws_typed_rb_check_typeddata_same_type, 1);
+  rb_define_method(cls, "rb_check_typeddata_same_type_parent", sws_typed_rb_check_typeddata_same_type_parent, 1);
+  rb_define_method(cls, "rb_check_typeddata_different_type", sws_typed_rb_check_typeddata_different_type, 1);
+  rb_define_method(cls, "RTYPEDDATA_P", sws_typed_RTYPEDDATA_P, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/ext/util_spec.c b/spec/ruby/optional/capi/ext/util_spec.c
index 50a5fcb095..b5bde420d2 100644
--- a/spec/ruby/optional/capi/ext/util_spec.c
+++ b/spec/ruby/optional/capi/ext/util_spec.c
@@ -1,4 +1,5 @@
 #include "ruby.h"
+#include "ruby/util.h"
 #include "rubyspec.h"
 
 #ifdef __cplusplus
@@ -6,17 +7,28 @@ extern "C" {
 #endif
 
 VALUE util_spec_rb_scan_args(VALUE self, VALUE argv, VALUE fmt, VALUE expected, VALUE acc) {
-  int i, result, argc = (int)RARRAY_LEN(argv);
-  VALUE args[6], failed, a1, a2, a3, a4, a5, a6;
-
-  failed = rb_intern("failed");
-  a1 = a2 = a3 = a4 = a5 = a6 = failed;
-
-  for(i = 0; i < argc; i++) {
-    args[i] = rb_ary_entry(argv, i);
+  int result, argc;
+  VALUE a1, a2, a3, a4, a5, a6;
+
+  argc = (int) RARRAY_LEN(argv);
+  VALUE* args = RARRAY_PTR(argv);
+  /* the line above can be replaced with this for Ruby implementations which do not support RARRAY_PTR() yet
+    VALUE args[6];
+    for(int i = 0; i < argc; i++) {
+      args[i] = rb_ary_entry(argv, i);
+    } */
+
+  a1 = a2 = a3 = a4 = a5 = a6 = INT2FIX(-1);
+
+#ifdef RB_SCAN_ARGS_KEYWORDS
+  if (*RSTRING_PTR(fmt) == 'k') {
+    result = rb_scan_args_kw(RB_SCAN_ARGS_KEYWORDS, argc, args, RSTRING_PTR(fmt)+1, &a1, &a2, &a3, &a4, &a5, &a6);
+  } else {
+#endif
+    result = rb_scan_args(argc, args, RSTRING_PTR(fmt), &a1, &a2, &a3, &a4, &a5, &a6);
+#ifdef RB_SCAN_ARGS_KEYWORDS
   }
-
-  result = rb_scan_args(argc, args, RSTRING_PTR(fmt), &a1, &a2, &a3, &a4, &a5, &a6);
+#endif
 
   switch(NUM2INT(expected)) {
   case 6:
@@ -50,22 +62,17 @@ static VALUE util_spec_rb_get_kwargs(VALUE self, VALUE keyword_hash, VALUE keys,
   int len = RARRAY_LENINT(keys);
 
   int values_len = req + (opt < 0 ? -1 - opt : opt);
-  int i = 0;
 
-  ID *ids = malloc(sizeof(VALUE) * len);
-  VALUE *results = malloc(sizeof(VALUE) * values_len);
-  int extracted = 0;
-  VALUE ary = Qundef;
+  ID *ids = (ID *)alloca(sizeof(VALUE) * len);
+  VALUE *results = (VALUE *)alloca(sizeof(VALUE) * values_len);
 
-  for (i = 0; i < len; i++) {
+  for (int i = 0; i < len; i++) {
     ids[i] = SYM2ID(rb_ary_entry(keys, i));
   }
 
-  extracted = rb_get_kwargs(keyword_hash, ids, req, opt, results);
-  ary = rb_ary_new_from_values(extracted, results);
-  free(results);
-  free(ids);
-  return ary;
+  int extracted = rb_get_kwargs(keyword_hash, ids, req, opt, results);
+
+  return rb_ary_new_from_values(extracted, results);
 }
 
 static VALUE util_spec_rb_long2int(VALUE self, VALUE n) {
@@ -85,6 +92,18 @@ static VALUE util_spec_rb_sourceline(VALUE self) {
   return INT2NUM(rb_sourceline());
 }
 
+static VALUE util_spec_strtod(VALUE self, VALUE string) {
+  char *endptr = NULL;
+  double value = strtod(RSTRING_PTR(string), &endptr);
+  return rb_ary_new_from_args(2, rb_float_new(value), endptr ? rb_str_new2(endptr) : Qnil);
+}
+
+static VALUE util_spec_ruby_strtod(VALUE self, VALUE string) {
+  char *endptr = NULL;
+  double value = ruby_strtod(RSTRING_PTR(string), &endptr);
+  return rb_ary_new_from_args(2, rb_float_new(value), endptr ? rb_str_new2(endptr) : Qnil);
+}
+
 void Init_util_spec(void) {
   VALUE cls = rb_define_class("CApiUtilSpecs", rb_cObject);
   rb_define_method(cls, "rb_scan_args", util_spec_rb_scan_args, 4);
@@ -93,6 +112,8 @@ void Init_util_spec(void) {
   rb_define_method(cls, "rb_iter_break", util_spec_rb_iter_break, 0);
   rb_define_method(cls, "rb_sourcefile", util_spec_rb_sourcefile, 0);
   rb_define_method(cls, "rb_sourceline", util_spec_rb_sourceline, 0);
+  rb_define_method(cls, "strtod", util_spec_strtod, 1);
+  rb_define_method(cls, "ruby_strtod", util_spec_ruby_strtod, 1);
 }
 
 #ifdef __cplusplus
diff --git a/spec/ruby/optional/capi/fiber_spec.rb b/spec/ruby/optional/capi/fiber_spec.rb
new file mode 100644
index 0000000000..05d867498c
--- /dev/null
+++ b/spec/ruby/optional/capi/fiber_spec.rb
@@ -0,0 +1,86 @@
+require_relative 'spec_helper'
+
+load_extension('fiber')
+
+describe "C-API Fiber function" do
+  before :each do
+    @s = CApiFiberSpecs.new
+  end
+
+  describe "rb_fiber_current" do
+    it "returns the current fiber" do
+      result = @s.rb_fiber_current()
+      result.should be_an_instance_of(Fiber)
+      result.should == Fiber.current
+    end
+  end
+
+  describe "rb_fiber_alive_p" do
+    it "returns the fibers alive status" do
+      fiber = Fiber.new { Fiber.yield }
+      fiber.resume
+      @s.rb_fiber_alive_p(fiber).should be_true
+      fiber.resume
+      @s.rb_fiber_alive_p(fiber).should be_false
+    end
+  end
+
+  describe "rb_fiber_resume" do
+    it "resumes the fiber" do
+      fiber = Fiber.new { |arg| Fiber.yield arg }
+      @s.rb_fiber_resume(fiber, [1]).should == 1
+      @s.rb_fiber_resume(fiber, [2]).should == 2
+    end
+  end
+
+  describe "rb_fiber_yield" do
+    it "yields the fiber" do
+      fiber = Fiber.new { @s.rb_fiber_yield([1]) }
+      fiber.resume.should == 1
+    end
+  end
+
+  describe "rb_fiber_new" do
+    it "returns a new fiber" do
+      fiber = @s.rb_fiber_new
+      fiber.should be_an_instance_of(Fiber)
+      fiber.resume(42).should == "42"
+    end
+  end
+
+  describe "rb_fiber_raise" do
+    it "raises an exception on the resumed fiber" do
+      fiber = Fiber.new do
+        begin
+          Fiber.yield
+        rescue => error
+          error
+        end
+      end
+
+      fiber.resume
+
+      result = @s.rb_fiber_raise(fiber, "Boom!")
+      result.should be_an_instance_of(RuntimeError)
+      result.message.should == "Boom!"
+    end
+
+    it "raises an exception on the transferred fiber" do
+      main = Fiber.current
+
+      fiber = Fiber.new do
+        begin
+          main.transfer
+        rescue => error
+          error
+        end
+      end
+
+      fiber.transfer
+
+      result = @s.rb_fiber_raise(fiber, "Boom!")
+      result.should be_an_instance_of(RuntimeError)
+      result.message.should == "Boom!"
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/file_spec.rb b/spec/ruby/optional/capi/file_spec.rb
index 96d731e4fa..12449b4e34 100644
--- a/spec/ruby/optional/capi/file_spec.rb
+++ b/spec/ruby/optional/capi/file_spec.rb
@@ -69,7 +69,7 @@ describe "C-API File function" do
     end
 
     it "does not call #to_str on a String" do
-      obj = "path"
+      obj = +"path"
       obj.should_not_receive(:to_str)
       @s.FilePathValue(obj).should eql(obj)
     end
diff --git a/spec/ruby/optional/capi/finalizer_spec.rb b/spec/ruby/optional/capi/finalizer_spec.rb
new file mode 100644
index 0000000000..162e8ea693
--- /dev/null
+++ b/spec/ruby/optional/capi/finalizer_spec.rb
@@ -0,0 +1,40 @@
+require_relative "spec_helper"
+
+extension_path = load_extension("finalizer")
+
+describe "CApiFinalizerSpecs" do
+  before :each do
+    @s = CApiFinalizerSpecs.new
+  end
+
+  describe "rb_define_finalizer" do
+    it "defines a finalizer on the object" do
+      code = <<~RUBY
+        require #{extension_path.dump}
+
+        obj = Object.new
+        finalizer = Proc.new { puts "finalizer run" }
+        CApiFinalizerSpecs.new.rb_define_finalizer(obj, finalizer)
+      RUBY
+
+      ruby_exe(code).should == "finalizer run\n"
+    end
+  end
+
+  describe "rb_undefine_finalizer" do
+    ruby_bug "#20981", "3.4.0"..."3.4.2" do
+      it "removes finalizers from the object" do
+        code = <<~RUBY
+          require #{extension_path.dump}
+
+          obj = Object.new
+          finalizer = Proc.new { puts "finalizer run" }
+          ObjectSpace.define_finalizer(obj, finalizer)
+          CApiFinalizerSpecs.new.rb_undefine_finalizer(obj)
+        RUBY
+
+        ruby_exe(code).should.empty?
+      end
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/fixnum_spec.rb b/spec/ruby/optional/capi/fixnum_spec.rb
index aa02a0543b..e691aa3893 100644
--- a/spec/ruby/optional/capi/fixnum_spec.rb
+++ b/spec/ruby/optional/capi/fixnum_spec.rb
@@ -25,7 +25,7 @@ describe "CApiFixnumSpecs" do
       end
     end
 
-    platform_is wordsize: 64 do # sizeof(long) > sizeof(int)
+    platform_is c_long_size: 64 do # sizeof(long) > sizeof(int)
       it "raises a TypeError if passed nil" do
         -> { @s.FIX2INT(nil) }.should raise_error(TypeError)
       end
@@ -74,7 +74,7 @@ describe "CApiFixnumSpecs" do
       end
     end
 
-    platform_is wordsize: 64 do # sizeof(long) > sizeof(int)
+    platform_is c_long_size: 64 do # sizeof(long) > sizeof(int)
       it "raises a TypeError if passed nil" do
         -> { @s.FIX2UINT(nil) }.should raise_error(TypeError)
       end
diff --git a/spec/ruby/optional/capi/fixtures/class.rb b/spec/ruby/optional/capi/fixtures/class.rb
index dbb0b69967..b463e3b4c3 100644
--- a/spec/ruby/optional/capi/fixtures/class.rb
+++ b/spec/ruby/optional/capi/fixtures/class.rb
@@ -15,6 +15,16 @@ class CApiClassSpecs
     end
   end
 
+  class KeywordAlloc
+    attr_reader :initialized, :args, :kwargs
+
+    def initialize(*args, **kwargs)
+      @initialized = true
+      @args = args
+      @kwargs = kwargs
+    end
+  end
+
   class Attr
     def initialize
       @foo, @bar, @baz = 1, 2, 3
@@ -87,5 +97,8 @@ class CApiClassSpecs
 
     class B
     end
+
+    module M
+    end
   end
 end
diff --git a/spec/ruby/optional/capi/fixtures/kernel.rb b/spec/ruby/optional/capi/fixtures/kernel.rb
new file mode 100644
index 0000000000..d3fc7c57e8
--- /dev/null
+++ b/spec/ruby/optional/capi/fixtures/kernel.rb
@@ -0,0 +1,19 @@
+class CApiKernelSpecs
+  class ClassWithPublicMethod
+    def public_method(*, **)
+      :public
+    end
+  end
+
+  class ClassWithPrivateMethod
+    private def private_method(*, **)
+      :private
+    end
+  end
+
+  class ClassWithProtectedMethod
+    protected def protected_method(*, **)
+      :protected
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/fixtures/module.rb b/spec/ruby/optional/capi/fixtures/module.rb
index ba90eb7181..aac8bfbfb3 100644
--- a/spec/ruby/optional/capi/fixtures/module.rb
+++ b/spec/ruby/optional/capi/fixtures/module.rb
@@ -13,6 +13,10 @@ class CApiModuleSpecs
     autoload :D, File.expand_path('../const_get.rb', __FILE__)
 
     X = 1
+    Q = 1
+    R = 2
+    S = 3
+    T = 5
   end
 
   class B < A
diff --git a/spec/ruby/optional/capi/fixtures/object.rb b/spec/ruby/optional/capi/fixtures/object.rb
new file mode 100644
index 0000000000..a59f2309d8
--- /dev/null
+++ b/spec/ruby/optional/capi/fixtures/object.rb
@@ -0,0 +1,29 @@
+class CApiObjectSpecs
+  class IVars
+    def initialize
+      @a = 3
+      @b = 7
+      @c = 4
+    end
+
+    def self.set_class_variables
+      @@foo = :a
+      @@bar = :b
+      @@baz = :c
+    end
+  end
+
+  module MVars
+    @@mvar = :foo
+    @@mvar2 = :bar
+
+    @ivar = :baz
+  end
+
+  module CVars
+    @@cvar = :foo
+    @@cvar2 = :bar
+
+    @ivar = :baz
+  end
+end
diff --git a/spec/ruby/optional/capi/fixtures/read.txt b/spec/ruby/optional/capi/fixtures/read.txt
new file mode 100644
index 0000000000..f7065a35d0
--- /dev/null
+++ b/spec/ruby/optional/capi/fixtures/read.txt
@@ -0,0 +1 @@
+fixture file contents to test read() with RSTRING_PTR
diff --git a/spec/ruby/optional/capi/float_spec.rb b/spec/ruby/optional/capi/float_spec.rb
index 8381945315..4b98902b59 100644
--- a/spec/ruby/optional/capi/float_spec.rb
+++ b/spec/ruby/optional/capi/float_spec.rb
@@ -27,4 +27,17 @@ describe "CApiFloatSpecs" do
       f.should eql(101.99)
     end
   end
+
+  describe "RB_FLOAT_TYPE_P" do
+    it "returns true for floats" do
+      @f.RB_FLOAT_TYPE_P(2.0).should == true
+    end
+
+    it "returns false for non-floats" do
+      @f.RB_FLOAT_TYPE_P(nil).should == false
+      @f.RB_FLOAT_TYPE_P(10).should == false
+      @f.RB_FLOAT_TYPE_P("string").should == false
+      @f.RB_FLOAT_TYPE_P(Object.new).should == false
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/gc_spec.rb b/spec/ruby/optional/capi/gc_spec.rb
index 1c34675f0d..d9661328ab 100644
--- a/spec/ruby/optional/capi/gc_spec.rb
+++ b/spec/ruby/optional/capi/gc_spec.rb
@@ -7,15 +7,60 @@ describe "CApiGCSpecs" do
     @f = CApiGCSpecs.new
   end
 
-  it "correctly gets the value from a registered address" do
-    @f.registered_tagged_address.should == 10
-    @f.registered_tagged_address.should equal(@f.registered_tagged_address)
-    @f.registered_reference_address.should == "Globally registered data"
-    @f.registered_reference_address.should equal(@f.registered_reference_address)
+  describe "rb_gc_register_address" do
+    it "correctly gets the value from a registered address" do
+      @f.registered_tagged_address.should == 10
+      @f.registered_tagged_address.should equal(@f.registered_tagged_address)
+      @f.registered_reference_address.should == "Globally registered data"
+      @f.registered_reference_address.should equal(@f.registered_reference_address)
+    end
+
+    it "keeps the value alive even if the value is assigned after rb_gc_register_address() is called" do
+      GC.start
+      @f.registered_before_rb_gc_register_address.should == "registered before rb_gc_register_address()"
+    end
+
+    it "can be called outside Init_" do
+      @f.rb_gc_register_address.should == "rb_gc_register_address() outside Init_"
+      @f.rb_gc_unregister_address
+    end
   end
 
-  describe "rb_gc_enable" do
+  describe "rb_global_variable" do
+    before :all do
+      GC.start
+    end
+
+    describe "keeps the value alive even if the value is assigned after rb_global_variable() is called" do
+      it "for a string" do
+        @f.registered_before_rb_global_variable_string.should == "registered before rb_global_variable()"
+      end
+
+      it "for a bignum" do
+        @f.registered_before_rb_global_variable_bignum.should == 2**63 - 1
+      end
 
+      it "for a Float" do
+        @f.registered_before_rb_global_variable_float.should == 3.14
+      end
+    end
+
+    describe "keeps the value alive when the value is assigned before rb_global_variable() is called" do
+      it "for a string" do
+        @f.registered_after_rb_global_variable_string.should == "registered after rb_global_variable()"
+      end
+
+      it "for a bignum" do
+        @f.registered_after_rb_global_variable_bignum.should == 2**63 - 1
+      end
+
+      it "for a Float" do
+        @f.registered_after_rb_global_variable_float.should == 6.28
+      end
+    end
+  end
+
+  describe "rb_gc_enable" do
     after do
       GC.enable
     end
@@ -42,13 +87,50 @@ describe "CApiGCSpecs" do
   end
 
   describe "rb_gc" do
-
     it "increases gc count" do
       gc_count = GC.count
       @f.rb_gc
       GC.count.should > gc_count
     end
+  end
+
+  describe "rb_gc_adjust_memory_usage" do
+    # Just check that it does not throw, as it seems hard to observe any effect
+    it "adjusts the amount of registered external memory" do
+      -> {
+        @f.rb_gc_adjust_memory_usage(8)
+        @f.rb_gc_adjust_memory_usage(-8)
+      }.should_not raise_error
+    end
+  end
+
+  describe "rb_gc_register_mark_object" do
+    it "can be called with an object" do
+      @f.rb_gc_register_mark_object(Object.new).should be_nil
+    end
 
+    it "keeps the value alive even if the value is not referenced by any Ruby object" do
+      @f.rb_gc_register_mark_object_not_referenced_float.should == 1.61
+    end
   end
 
+  describe "rb_gc_latest_gc_info" do
+    it "raises a TypeError when hash or symbol not given" do
+      -> { @f.rb_gc_latest_gc_info("foo") }.should raise_error(TypeError)
+    end
+
+    it "raises an ArgumentError when unknown symbol given" do
+      -> { @f.rb_gc_latest_gc_info(:unknown) }.should raise_error(ArgumentError)
+    end
+
+    it "returns the populated hash when a hash is given" do
+      h = {}
+      @f.rb_gc_latest_gc_info(h).should == h
+      h.size.should_not == 0
+    end
+
+    it "returns a value when symbol is given" do
+      @f.rb_gc_latest_gc_info(:state).should be_kind_of(Symbol)
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/globals_spec.rb b/spec/ruby/optional/capi/globals_spec.rb
index 84694b1375..4657293e15 100644
--- a/spec/ruby/optional/capi/globals_spec.rb
+++ b/spec/ruby/optional/capi/globals_spec.rb
@@ -9,7 +9,7 @@ describe "CApiGlobalSpecs" do
   end
 
   it "correctly gets global values" do
-    @f.sb_gv_get("$BLAH").should == nil
+    suppress_warning { @f.sb_gv_get("$BLAH") }.should == nil
     @f.sb_gv_get("$\\").should == nil
     @f.sb_gv_get("\\").should == nil # rb_gv_get should change \ to $\
   end
@@ -21,7 +21,7 @@ describe "CApiGlobalSpecs" do
   end
 
   it "correctly sets global values" do
-    @f.sb_gv_get("$BLAH").should == nil
+    suppress_warning { @f.sb_gv_get("$BLAH") }.should == nil
     @f.sb_gv_set("$BLAH", 10)
     begin
       @f.sb_gv_get("$BLAH").should == 10
@@ -41,10 +41,19 @@ describe "CApiGlobalSpecs" do
     @f.sb_get_global_value.should == "XYZ"
   end
 
+  run = 0
+
   it "rb_define_readonly_variable should define a new readonly global variable" do
-    @f.rb_define_readonly_variable("ro_gvar", 15)
-    $ro_gvar.should == 15
-    -> { $ro_gvar = 10 }.should raise_error(NameError)
+    name = "ro_gvar#{run += 1}"
+    eval <<~RUBY
+    # Check the gvar doesn't exist and ensure rb_gv_get doesn't implicitly declare the gvar,
+    # otherwise the rb_define_readonly_variable call will conflict.
+    suppress_warning { @f.sb_gv_get("#{name}") }.should == nil
+
+    @f.rb_define_readonly_variable("#{name}", 15)
+    $#{name}.should == 15
+    -> { $#{name} = 10 }.should raise_error(NameError)
+    RUBY
   end
 
   it "rb_define_hooked_variable should define a C hooked global variable" do
@@ -53,13 +62,78 @@ describe "CApiGlobalSpecs" do
     $hooked_gvar.should == 4
   end
 
+  it "rb_define_hooked_variable should use default accessors if NULL ones are supplied" do
+    @f.rb_define_hooked_variable_default_accessors("$hooked_gvar_default_accessors")
+    $hooked_gvar_default_accessors = 10
+    $hooked_gvar_default_accessors.should == 10
+  end
+
+  it "rb_define_hooked_variable with default accessors should return nil for NULL variables" do
+    @f.rb_define_hooked_variable_null_var("$hooked_gvar_null_value")
+    $hooked_gvar_null_value.should == nil
+  end
+
+  describe "rb_define_virtual_variable" do
+    describe "with default accessors" do
+      before :all do
+        @f.rb_define_virtual_variable_default_accessors("$virtual_variable_default_accessors")
+      end
+
+      it "is read-only" do
+        -> { $virtual_variable_default_accessors = 10 }.should raise_error(NameError, /read-only/)
+      end
+
+      it "returns false with the default getter" do
+        $virtual_variable_default_accessors.should == false
+        $virtual_variable_default_accessors.should == false
+      end
+    end
+
+    describe "with supplied accessors" do
+      before :all do
+        @f.rb_define_virtual_variable_incrementing_accessors("$virtual_variable_incrementing_accessors")
+      end
+
+      it "returns a dynamically changing value" do
+        $virtual_variable_incrementing_accessors = 20
+        $virtual_variable_incrementing_accessors.should == 20
+        $virtual_variable_incrementing_accessors.should == 21
+        $virtual_variable_incrementing_accessors.should == 22
+
+        $virtual_variable_incrementing_accessors = 100
+        $virtual_variable_incrementing_accessors.should == 100
+        $virtual_variable_incrementing_accessors.should == 101
+        $virtual_variable_incrementing_accessors.should == 102
+      end
+    end
+  end
+
+  describe "rb_fs" do
+    before :each do
+      @field_separator = $;
+    end
+
+    after :each do
+      suppress_warning { $; = @field_separator }
+    end
+
+    it "returns nil by default" do
+      @f.rb_fs.should == nil
+    end
+
+    it "returns the value of $;" do
+      suppress_warning { $; = "foo" }
+      @f.rb_fs.should == "foo"
+    end
+  end
+
   describe "rb_rs" do
     before :each do
       @dollar_slash = $/
     end
 
     after :each do
-      $/ = @dollar_slash
+      suppress_warning { $/ = @dollar_slash }
     end
 
     it "returns \\n by default" do
@@ -67,7 +141,7 @@ describe "CApiGlobalSpecs" do
     end
 
     it "returns the value of $/" do
-      $/ = "foo"
+      suppress_warning { $/ = "foo" }
       @f.rb_rs.should == "foo"
     end
   end
@@ -121,7 +195,7 @@ describe "CApiGlobalSpecs" do
         $stdout = STDOUT
       end
 
-      it "returns $stdout" do
+      it "is an alias of rb_stdout" do
         $stdout = @stream
         @f.rb_defout.should equal($stdout)
       end
@@ -140,7 +214,7 @@ describe "CApiGlobalSpecs" do
     end
 
     after :each do
-      $\ = @dollar_backslash
+      suppress_warning {$\ = @dollar_backslash}
     end
 
     it "returns nil by default" do
@@ -148,7 +222,7 @@ describe "CApiGlobalSpecs" do
     end
 
     it "returns the value of $\\" do
-      $\ = "foo"
+      suppress_warning {$\ = "foo"}
       @f.rb_output_rs.should == "foo"
     end
   end
diff --git a/spec/ruby/optional/capi/hash_spec.rb b/spec/ruby/optional/capi/hash_spec.rb
index 2923faf7de..3a27de3bfa 100644
--- a/spec/ruby/optional/capi/hash_spec.rb
+++ b/spec/ruby/optional/capi/hash_spec.rb
@@ -21,7 +21,7 @@ describe "C-API Hash function" do
 
       # The actual conversion is an implementation detail.
       # We only care that ultimately we get a Fixnum instance.
-      @s.rb_hash(obj).should be_an_instance_of(Fixnum)
+      @s.rb_hash(obj).should.between?(fixnum_min, fixnum_max)
     end
 
     it "calls #to_int to converts a value returned by #hash to a Fixnum" do
@@ -50,6 +50,28 @@ describe "C-API Hash function" do
     end
   end
 
+  describe "rb_hash_new_capa" do
+    it "returns a new hash" do
+      @s.rb_hash_new_capa(3).should == {}
+    end
+
+    it "creates a hash with no default proc" do
+      @s.rb_hash_new_capa(3) {}.default_proc.should be_nil
+    end
+
+    it "raises RuntimeError when negative index is provided" do
+      -> { @s.rb_hash_new_capa(-1) }.should raise_error(RuntimeError, "st_table too big")
+    end
+  end
+
+  describe "rb_ident_hash_new" do
+    it "returns a new compare by identity hash" do
+      result = @s.rb_ident_hash_new
+      result.should == {}
+      result.compare_by_identity?.should == true
+    end
+  end
+
   describe "rb_hash_dup" do
     it "returns a copy of the hash" do
       hsh = {}
@@ -170,6 +192,61 @@ describe "C-API Hash function" do
     end
   end
 
+  describe "rb_hash_bulk_insert" do
+    it 'inserts key-value pairs into the hash' do
+      arr = [:a, 1, :b, 2, :c, 3]
+      hash = {}
+
+      @s.rb_hash_bulk_insert(arr.length, arr, hash)
+
+      hash.should == {a: 1, b: 2, c: 3}
+    end
+
+    it 'overwrites existing keys' do
+      arr = [:a, 4, :b, 5, :c, 6]
+      hash = {a: 1, b: 2}
+
+      @s.rb_hash_bulk_insert(arr.length, arr, hash)
+
+      hash.should == {a: 4, b: 5, c: 6}
+    end
+
+    it 'uses the last key in the array if it appears multiple times' do
+      arr = [:a, 1, :b, 2, :a, 3]
+      hash = {}
+
+      @s.rb_hash_bulk_insert(arr.length, arr, hash)
+
+      hash.should == {a: 3, b: 2}
+    end
+
+    it 'allows the array to be NULL if the length is zero' do
+      hash = {}
+
+      @s.rb_hash_bulk_insert(0, nil, hash)
+
+      hash.should == {}
+    end
+
+    it 'does not include any keys after the given length' do
+      arr = [:a, 1, :b, 2, :c, 3, :d, 4]
+      hash = {}
+
+      @s.rb_hash_bulk_insert(arr.length - 2, arr, hash)
+
+      hash.should == {a: 1, b: 2, c: 3}
+    end
+
+    it 'does not modify the hash if the length is zero' do
+      arr = []
+      hash = {a: 1, b: 2}
+
+      @s.rb_hash_bulk_insert(arr.length, arr, hash)
+
+      hash.should == {a: 1, b: 2}
+    end
+  end
+
   describe "rb_hash_size" do
     it "returns the size of the hash" do
       hsh = {fast: 'car', good: 'music'}
@@ -254,4 +331,13 @@ describe "C-API Hash function" do
       -> { @s.rb_Hash(h) }.should raise_error(TypeError)
     end
   end
+
+  describe "hash code functions" do
+    it "computes a deterministic number" do
+      hash_code = @s.compute_a_hash_code(53)
+      hash_code.should be_an_instance_of(Integer)
+      hash_code.should == @s.compute_a_hash_code(53)
+      @s.compute_a_hash_code(90).should == @s.compute_a_hash_code(90)
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/integer_spec.rb b/spec/ruby/optional/capi/integer_spec.rb
index 56f7ca3034..f177374569 100644
--- a/spec/ruby/optional/capi/integer_spec.rb
+++ b/spec/ruby/optional/capi/integer_spec.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 require_relative 'spec_helper'
 
 load_extension("integer")
@@ -140,6 +140,23 @@ describe "CApiIntegerSpecs" do
               result.should == -1
               @words.should == "\x11\x32\x54\x76\x98\xBA\xDC\xFE"
             end
+
+            it "converts numbers near the fixnum limit successfully" do
+              result = @s.rb_integer_pack(0x7123_4567_89ab_cdef, @words, 1, 8, 0,
+                CApiIntegerSpecs::NATIVE|CApiIntegerSpecs::PACK_2COMP)
+              result.should == 1
+              @words.should == "\xEF\xCD\xAB\x89\x67\x45\x23\x71"
+
+              result = @s.rb_integer_pack(2**62-1, @words, 1, 8, 0,
+                CApiIntegerSpecs::NATIVE|CApiIntegerSpecs::PACK_2COMP)
+              result.should == 1
+              @words.should == "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x3F"
+
+              result = @s.rb_integer_pack(2**63-1, @words, 1, 8, 0,
+                CApiIntegerSpecs::NATIVE|CApiIntegerSpecs::PACK_2COMP)
+              result.should == 1
+              @words.should == "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x7F"
+            end
           end
         end
       end
@@ -272,4 +289,19 @@ describe "CApiIntegerSpecs" do
       end
     end
   end
+
+  describe "rb_int_positive_pow" do
+    it "raises an integer to given power" do
+      @s.rb_int_positive_pow(2, 3).should == 8
+    end
+
+    it "raises a negative integer to given power" do
+      @s.rb_int_positive_pow(-2, 3).should == -8
+      @s.rb_int_positive_pow(-2, 4).should == 16
+    end
+
+    it "overflows for large inputs" do
+      @s.rb_int_positive_pow(8, 23).should == 590295810358705651712
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/io_spec.rb b/spec/ruby/optional/capi/io_spec.rb
index 7947a48eac..ab7a7fc8f6 100644
--- a/spec/ruby/optional/capi/io_spec.rb
+++ b/spec/ruby/optional/capi/io_spec.rb
@@ -1,4 +1,5 @@
 require_relative 'spec_helper'
+require_relative '../../fixtures/io'
 
 load_extension('io')
 
@@ -151,6 +152,16 @@ describe "C-API IO function" do
     end
   end
 
+  describe "rb_io_set_nonblock" do
+    platform_is_not :windows do
+      it "returns true when nonblock flag is set" do
+        require 'io/nonblock'
+        @o.rb_io_set_nonblock(@io)
+        @io.nonblock?.should be_true
+      end
+    end
+  end
+
   # NOTE: unlike the name might suggest in MRI this function checks if an
   # object is frozen, *not* if it's tainted.
   describe "rb_io_taint_check" do
@@ -165,13 +176,18 @@ describe "C-API IO function" do
     end
   end
 
-  describe "GetOpenFile" do
+  describe "rb_io_descriptor or GetOpenFile" do
     it "allows access to the system fileno" do
       @o.GetOpenFile_fd($stdin).should == 0
       @o.GetOpenFile_fd($stdout).should == 1
       @o.GetOpenFile_fd($stderr).should == 2
       @o.GetOpenFile_fd(@io).should == @io.fileno
     end
+
+    it "raises IOError if the IO is closed" do
+      @io.close
+      -> { @o.GetOpenFile_fd(@io) }.should raise_error(IOError, "closed stream")
+    end
   end
 
   describe "rb_io_binmode" do
@@ -220,7 +236,7 @@ describe "C-API IO function" do
   end
 
   describe "rb_io_check_writable" do
-    it "does not raise an exeption if the IO is opened for writing" do
+    it "does not raise an exception if the IO is opened for writing" do
       # The MRI function is void, so we use should_not raise_error
       -> { @o.rb_io_check_writable(@w_io) }.should_not raise_error
     end
@@ -246,12 +262,62 @@ describe "C-API IO function" do
     end
   end
 
+  describe "rb_io_maybe_wait_writable" do
+    it "returns mask for events if operation was interrupted" do
+      @o.rb_io_maybe_wait_writable(Errno::EINTR::Errno, @w_io, nil).should == IO::WRITABLE
+    end
+
+    it "returns 0 if there is no error condition" do
+      @o.rb_io_maybe_wait_writable(0, @w_io, nil).should == 0
+    end
+
+    it "raises an IOError if the IO is closed" do
+      @w_io.close
+      -> { @o.rb_io_maybe_wait_writable(0, @w_io, nil) }.should raise_error(IOError, "closed stream")
+    end
+
+    it "raises an IOError if the IO is not initialized" do
+      -> { @o.rb_io_maybe_wait_writable(0, IO.allocate, nil) }.should raise_error(IOError, "uninitialized stream")
+    end
+
+    it "can be interrupted" do
+      IOSpec.exhaust_write_buffer(@w_io)
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+      t = Thread.new do
+        @o.rb_io_maybe_wait_writable(0, @w_io, 10)
+      end
+
+      Thread.pass until t.stop?
+      t.kill
+      t.join
+
+      finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (finish - start).should < 9
+    end
+  end
+
   describe "rb_thread_fd_writable" do
     it "waits til an fd is ready for writing" do
       @o.rb_thread_fd_writable(@w_io).should be_nil
     end
   end
 
+  describe "rb_thread_fd_select" do
+    it "waits until an fd is ready for reading" do
+      @w_io.write "rb_thread_fd_select"
+      @o.rb_thread_fd_select_read(@r_io).should == 1
+    end
+
+    it "waits until an fd is ready for writing" do
+      @o.rb_thread_fd_select_write(@w_io).should == 1
+    end
+
+    it "waits until an fd is ready for writing with timeout" do
+      @o.rb_thread_fd_select_timeout(@w_io).should == 1
+    end
+  end
+
   platform_is_not :windows do
     describe "rb_io_wait_readable" do
       it "returns false if there is no error condition" do
@@ -280,6 +346,53 @@ describe "C-API IO function" do
         thr.join
       end
     end
+
+    describe "rb_io_maybe_wait_readable" do
+      it "returns mask for events if operation was interrupted" do
+        @o.rb_io_maybe_wait_readable(Errno::EINTR::Errno, @r_io, nil, false).should == IO::READABLE
+      end
+
+      it "returns 0 if there is no error condition" do
+        @o.rb_io_maybe_wait_readable(0, @r_io, nil, false).should == 0
+      end
+
+      it "blocks until the io is readable and returns events that actually occurred" do
+        @o.instance_variable_set :@write_data, false
+        thr = Thread.new do
+          Thread.pass until @o.instance_variable_get(:@write_data)
+          @w_io.write "rb_io_wait_readable"
+        end
+
+        @o.rb_io_maybe_wait_readable(Errno::EAGAIN::Errno, @r_io, IO::READABLE, true).should == IO::READABLE
+        @o.instance_variable_get(:@read_data).should == "rb_io_wait_re"
+
+        thr.join
+      end
+
+      it "can be interrupted" do
+        start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+        t = Thread.new do
+          @o.rb_io_maybe_wait_readable(0, @r_io, 10, false)
+        end
+
+        Thread.pass until t.stop?
+        t.kill
+        t.join
+
+        finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+        (finish - start).should < 9
+      end
+
+      it "raises an IOError if the IO is closed" do
+        @r_io.close
+        -> { @o.rb_io_maybe_wait_readable(0, @r_io, nil, false) }.should raise_error(IOError, "closed stream")
+      end
+
+      it "raises an IOError if the IO is not initialized" do
+        -> { @o.rb_io_maybe_wait_readable(0, IO.allocate, nil, false) }.should raise_error(IOError, "uninitialized stream")
+      end
+    end
   end
 
   describe "rb_thread_wait_fd" do
@@ -319,10 +432,242 @@ describe "C-API IO function" do
       @o.rb_wait_for_single_fd(@r_io, 1, 0, 0).should == 0
     end
   end
+
+  describe "rb_io_maybe_wait" do
+    it "waits til an fd is ready for reading" do
+      start = false
+      thr = Thread.new do
+        start = true
+        sleep 0.05
+        @w_io.write "rb_io_maybe_wait"
+      end
+
+      Thread.pass until start
+
+      @o.rb_io_maybe_wait(Errno::EAGAIN::Errno, @r_io, IO::READABLE, nil).should == IO::READABLE
+
+      thr.join
+    end
+
+    it "returns mask for events if operation was interrupted" do
+      @o.rb_io_maybe_wait(Errno::EINTR::Errno, @w_io, IO::WRITABLE, nil).should == IO::WRITABLE
+    end
+
+    it "raises an IOError if the IO is closed" do
+      @w_io.close
+      -> { @o.rb_io_maybe_wait(0, @w_io, IO::WRITABLE, nil) }.should raise_error(IOError, "closed stream")
+    end
+
+    it "raises an IOError if the IO is not initialized" do
+      -> { @o.rb_io_maybe_wait(0, IO.allocate, IO::WRITABLE, nil) }.should raise_error(IOError, "uninitialized stream")
+    end
+
+    it "can be interrupted when waiting for READABLE event" do
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+      t = Thread.new do
+        @o.rb_io_maybe_wait(0, @r_io, IO::READABLE, 10)
+      end
+
+      Thread.pass until t.stop?
+      t.kill
+      t.join
+
+      finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (finish - start).should < 9
+    end
+
+    it "can be interrupted when waiting for WRITABLE event" do
+      IOSpec.exhaust_write_buffer(@w_io)
+      start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+
+      t = Thread.new do
+        @o.rb_io_maybe_wait(0, @w_io, IO::WRITABLE, 10)
+      end
+
+      Thread.pass until t.stop?
+      t.kill
+      t.join
+
+      finish = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+      (finish - start).should < 9
+    end
+  end
+
+  ruby_version_is "3.3" do
+    describe "rb_io_mode" do
+      it "returns the mode" do
+        (@o.rb_io_mode(@r_io) & 0b11).should == 0b01
+        (@o.rb_io_mode(@w_io) & 0b11).should == 0b10
+        (@o.rb_io_mode(@rw_io) & 0b11).should == 0b11
+      end
+    end
+
+    describe "rb_io_path" do
+      it "returns the IO#path" do
+        @o.rb_io_path(@r_io).should == @r_io.path
+        @o.rb_io_path(@rw_io).should == @rw_io.path
+        @o.rb_io_path(@rw_io).should == @name
+      end
+    end
+
+    describe "rb_io_closed_p" do
+      it "returns false when io is not closed" do
+        @o.rb_io_closed_p(@r_io).should == false
+        @r_io.closed?.should == false
+      end
+
+      it "returns true when io is closed" do
+        @r_io.close
+
+        @o.rb_io_closed_p(@r_io).should == true
+        @r_io.closed?.should == true
+      end
+    end
+
+    quarantine! do # "Errno::EBADF: Bad file descriptor" at closing @r_io, @rw_io etc in the after :each hook
+      describe "rb_io_open_descriptor" do
+        it "creates a new IO instance" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.is_a?(IO)
+        end
+
+        it "return an instance of the specified class" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.class.should == File
+
+          io = @o.rb_io_open_descriptor(IO, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.class.should == IO
+        end
+
+        it "sets the specified file descriptor" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.fileno.should == @r_io.fileno
+        end
+
+        it "sets the specified path" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should == "a.txt"
+        end
+
+        it "sets the specified mode" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_BINMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.binmode?
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, CApiIOSpecs::FMODE_TEXTMODE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should_not.binmode?
+        end
+
+        it "sets the specified timeout" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.timeout.should == 60
+        end
+
+        it "sets the specified internal encoding" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.internal_encoding.should == Encoding::US_ASCII
+        end
+
+        it "sets the specified external encoding" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.external_encoding.should == Encoding::UTF_8
+        end
+
+        it "does not apply the specified encoding flags" do
+          name = tmp("rb_io_open_descriptor_specs")
+          File.write(name, "123\r\n456\n89")
+          file = File.open(name, "r")
+
+          io = @o.rb_io_open_descriptor(File, file.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", CApiIOSpecs::ECONV_UNIVERSAL_NEWLINE_DECORATOR, {})
+          io.read_nonblock(20).should == "123\r\n456\n89"
+        ensure
+          file.close
+          rm_r name
+        end
+
+        it "ignores the IO open options" do
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {external_encoding: "windows-1251"})
+          io.external_encoding.should == Encoding::UTF_8
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {internal_encoding: "windows-1251"})
+          io.internal_encoding.should == Encoding::US_ASCII
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {encoding: "windows-1251:binary"})
+          io.external_encoding.should == Encoding::UTF_8
+          io.internal_encoding.should == Encoding::US_ASCII
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {textmode: false})
+          io.should_not.binmode?
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {binmode: true})
+          io.should_not.binmode?
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {autoclose: false})
+          io.should.autoclose?
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, "a.txt", 60, "US-ASCII", "UTF-8", 0, {path: "a.txt"})
+          io.path.should == "a.txt"
+        end
+
+        it "ignores the IO encoding options" do
+          io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_WRITABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {crlf_newline: true})
+
+          io.write("123\r\n456\n89")
+          io.flush
+
+          @r_io.read_nonblock(20).should == "123\r\n456\n89"
+        end
+
+        it "allows wrong mode" do
+          io = @o.rb_io_open_descriptor(File, @w_io.fileno, CApiIOSpecs::FMODE_READABLE, "a.txt", 60, "US-ASCII", "UTF-8", 0, {})
+          io.should.is_a?(File)
+
+          platform_is_not :windows do
+            -> { io.read_nonblock(1) }.should raise_error(Errno::EBADF)
+          end
+
+          platform_is :windows do
+            -> { io.read_nonblock(1) }.should raise_error(IO::EWOULDBLOCKWaitReadable)
+          end
+        end
+
+        it "tolerates NULL as rb_io_encoding *encoding parameter" do
+          io = @o.rb_io_open_descriptor_without_encoding(File, @r_io.fileno, 0, "a.txt", 60)
+          io.should.is_a?(File)
+        end
+
+        it "deduplicates path String" do
+          path = "a.txt".dup
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should_not equal(path)
+
+          path = "a.txt".freeze
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+          io.path.should_not equal(path)
+        end
+
+        it "calls #to_str to convert a path to a String" do
+          path = Object.new
+          def path.to_str; "a.txt"; end
+
+          io = @o.rb_io_open_descriptor(File, @r_io.fileno, 0, path, 60, "US-ASCII", "UTF-8", 0, {})
+
+          io.path.should == "a.txt"
+        end
+      end
+    end
+  end
+
+  ruby_version_is "3.4" do
+    describe "rb_io_maybe_wait" do
+      it "returns nil if there is no error condition" do
+        @o.rb_io_maybe_wait(0, @w_io, IO::WRITABLE, nil).should == nil
+      end
+    end
+  end
 end
 
 describe "rb_fd_fix_cloexec" do
-
   before :each do
     @o = CApiIOSpecs.new
 
@@ -365,3 +710,29 @@ describe "rb_cloexec_open" do
     @io.close_on_exec?.should be_true
   end
 end
+
+describe "rb_io_t modes flags" do
+  before :each do
+    @o = CApiIOSpecs.new
+    @name = tmp("c_api_rb_io_specs")
+    touch @name
+  end
+
+  after :each do
+    rm_r @name
+  end
+
+  it "has the sync flag set if the IO object is synced in Ruby" do
+    File.open(@name) { |io|
+      io.sync = true
+      @o.rb_io_mode_sync_flag(io).should == true
+    }
+  end
+
+  it "has the sync flag unset if the IO object is not synced in Ruby" do
+    File.open(@name) { |io|
+      io.sync = false
+      @o.rb_io_mode_sync_flag(io).should == false
+    }
+  end
+end
diff --git a/spec/ruby/optional/capi/kernel_spec.rb b/spec/ruby/optional/capi/kernel_spec.rb
index d123eb13ea..6633ee50c1 100644
--- a/spec/ruby/optional/capi/kernel_spec.rb
+++ b/spec/ruby/optional/capi/kernel_spec.rb
@@ -1,15 +1,24 @@
 require_relative 'spec_helper'
+require_relative 'fixtures/kernel'
 
-load_extension("kernel")
+kernel_path = load_extension("kernel")
+
+class CApiKernelSpecs::Exc < StandardError
+end
+exception_class = CApiKernelSpecs::Exc
 
 describe "C-API Kernel function" do
   before :each do
     @s = CApiKernelSpecs.new
   end
 
+  after :each do
+    @s.rb_errinfo.should == nil
+  end
+
   describe "rb_block_given_p" do
     it "returns false if no block is passed" do
-      @s.rb_block_given_p.should == false
+      @s.should_not.rb_block_given_p
     end
 
     it "returns true if a block is passed" do
@@ -53,6 +62,11 @@ describe "C-API Kernel function" do
         i + 1
       end.should == [2, 4, 6]
     end
+
+    it "can pass extra data to the function" do
+      ary = [3]
+      @s.rb_block_call_extra_data(ary).should equal(ary)
+    end
   end
 
   describe "rb_frame_this_func" do
@@ -72,6 +86,22 @@ describe "C-API Kernel function" do
       -> { @s.rb_raise(h) }.should raise_error(TypeError)
       h[:stage].should == :before
     end
+
+    it "re-raises a rescued exception" do
+      -> do
+        begin
+          raise StandardError, "aaa"
+        rescue Exception
+          begin
+            @s.rb_raise({})
+          rescue TypeError
+          end
+
+          # should raise StandardError "aaa"
+          raise
+        end
+      end.should raise_error(StandardError, "aaa")
+    end
   end
 
   describe "rb_throw" do
@@ -126,26 +156,16 @@ describe "C-API Kernel function" do
   end
 
   describe "rb_warn" do
-    before :each do
-      @stderr, $stderr = $stderr, IOStub.new
-      @verbose = $VERBOSE
-    end
-
-    after :each do
-      $stderr = @stderr
-      $VERBOSE = @verbose
-    end
-
     it "prints a message to $stderr if $VERBOSE evaluates to true" do
-      $VERBOSE = true
-      @s.rb_warn("This is a warning")
-      $stderr.should =~ /This is a warning/
+      -> {
+        @s.rb_warn("This is a warning")
+      }.should complain(/warning: This is a warning/, verbose: true)
     end
 
     it "prints a message to $stderr if $VERBOSE evaluates to false" do
-      $VERBOSE = false
-      @s.rb_warn("This is a warning")
-      $stderr.should =~ /This is a warning/
+      -> {
+        @s.rb_warn("This is a warning")
+      }.should complain(/warning: This is a warning/, verbose: false)
     end
   end
 
@@ -167,13 +187,35 @@ describe "C-API Kernel function" do
     it "raises an exception from the given error" do
       -> do
         @s.rb_syserr_fail(Errno::EINVAL::Errno, "additional info")
-      end.should raise_error(Errno::EINVAL, /additional info/)
+      end.should raise_error(Errno::EINVAL, "Invalid argument - additional info")
     end
 
     it "can take a NULL message" do
       -> do
         @s.rb_syserr_fail(Errno::EINVAL::Errno, nil)
-      end.should raise_error(Errno::EINVAL)
+      end.should raise_error(Errno::EINVAL, "Invalid argument")
+    end
+
+    it "uses some kind of string as message when errno is unknown" do
+      -> { @s.rb_syserr_fail(-10, nil) }.should raise_error(SystemCallError, /[[:graph:]]+/)
+    end
+  end
+
+  describe "rb_syserr_fail_str" do
+    it "raises an exception from the given error" do
+      -> do
+        @s.rb_syserr_fail_str(Errno::EINVAL::Errno, "additional info")
+      end.should raise_error(Errno::EINVAL, "Invalid argument - additional info")
+    end
+
+    it "can take nil as a message" do
+      -> do
+        @s.rb_syserr_fail_str(Errno::EINVAL::Errno, nil)
+      end.should raise_error(Errno::EINVAL, "Invalid argument")
+    end
+
+    it "uses some kind of string as message when errno is unknown" do
+      -> { @s.rb_syserr_fail_str(-10, nil) }.should raise_error(SystemCallError, /[[:graph:]]+/)
     end
   end
 
@@ -200,10 +242,8 @@ describe "C-API Kernel function" do
       @s.rb_yield(1) { break 73 }.should == 73
     end
 
-    platform_is_not :"solaris2.10" do # NOTE: i386-pc-solaris2.10
-      it "rb_yield through a callback to a block that breaks with a value returns the value" do
-        @s.rb_yield_indirected(1) { break 73 }.should == 73
-      end
+    it "rb_yield through a callback to a block that breaks with a value returns the value" do
+      @s.rb_yield_indirected(1) { break 73 }.should == 73
     end
 
     it "rb_yield to block passed to enumerator" do
@@ -233,6 +273,18 @@ describe "C-API Kernel function" do
     end
   end
 
+  describe "rb_yield_values2" do
+    it "yields passed arguments" do
+      ret = nil
+      @s.rb_yield_values2([1, 2]) { |x, y| ret = x + y }
+      ret.should == 3
+    end
+
+    it "returns the result from block evaluation" do
+      @s.rb_yield_values2([1, 2]) { |x, y| x + y }.should == 3
+    end
+  end
+
   describe "rb_yield_splat" do
     it "yields with passed array's contents" do
       ret = nil
@@ -256,28 +308,28 @@ describe "C-API Kernel function" do
   describe "rb_protect" do
     it "will run a function with an argument" do
       proof = [] # Hold proof of work performed after the yield.
-      res = @s.rb_protect_yield(7, proof) { |x| x + 1 }
-      res.should == 8
+      res = @s.rb_protect_yield(77, proof) { |x| x + 1 }
+      res.should == 78
       proof[0].should == 23
     end
 
     it "will allow cleanup code to run after break" do
       proof = [] # Hold proof of work performed after the yield.
-      @s.rb_protect_yield(7, proof) { |x| break }
+      @s.rb_protect_yield(77, proof) { |x| break }
       proof[0].should == 23
     end
 
     it "will allow cleanup code to run after break with value" do
       proof = [] # Hold proof of work performed after the yield.
-      res = @s.rb_protect_yield(7, proof) { |x| break x + 1 }
-      res.should == 8
+      res = @s.rb_protect_yield(77, proof) { |x| break x + 1 }
+      res.should == 78
       proof[0].should == 23
     end
 
     it "will allow cleanup code to run after a raise" do
       proof = [] # Hold proof of work performed after the yield.
       -> do
-        @s.rb_protect_yield(7, proof) { |x| raise NameError}
+        @s.rb_protect_yield(77, proof) { |x| raise NameError }
       end.should raise_error(NameError)
       proof[0].should == 23
     end
@@ -285,11 +337,31 @@ describe "C-API Kernel function" do
     it "will return nil if an error was raised" do
       proof = [] # Hold proof of work performed after the yield.
       -> do
-        @s.rb_protect_yield(7, proof) { |x| raise NameError}
+        @s.rb_protect_yield(77, proof) { |x| raise NameError }
       end.should raise_error(NameError)
       proof[0].should == 23
       proof[1].should == nil
     end
+
+    it "accepts NULL as status and returns nil if it failed" do
+      @s.rb_protect_null_status(42) { |x| x + 1 }.should == 43
+      @s.rb_protect_null_status(42) { |x| raise NameError }.should == nil
+      @s.rb_errinfo().should.is_a? NameError
+    ensure
+      @s.rb_set_errinfo(nil)
+    end
+
+    it "populates rb_errinfo() with the captured exception" do
+      proof = []
+      @s.rb_protect_ignore_status(77, proof) { |x| raise NameError }
+      @s.rb_errinfo().should.is_a? NameError
+      # Note: on CRuby $! is the NameError here, but not clear if that is desirable or bug
+      proof[0].should == 23
+      proof[1].should == nil
+    ensure
+      @s.rb_set_errinfo(nil)
+    end
+
   end
 
   describe "rb_eval_string_protect" do
@@ -311,49 +383,61 @@ describe "C-API Kernel function" do
   describe "rb_rescue" do
     before :each do
       @proc = -> x { x }
-      @raise_proc_returns_sentinel = -> *_ { :raise_proc_executed }
-      @raise_proc_returns_arg = -> *a { a }
+      @rescue_proc_returns_sentinel = -> *_ { :rescue_proc_executed }
+      @rescue_proc_returns_arg = -> *a { a }
       @arg_error_proc = -> *_ { raise ArgumentError, '' }
       @std_error_proc = -> *_ { raise StandardError, '' }
       @exc_error_proc = -> *_ { raise Exception, '' }
     end
 
     it "executes passed function" do
-      @s.rb_rescue(@proc, :no_exc, @raise_proc_returns_arg, :exc).should == :no_exc
+      @s.rb_rescue(@proc, :no_exc, @rescue_proc_returns_arg, :exc).should == :no_exc
     end
 
-    it "executes passed 'raise function' if a StandardError exception is raised" do
-      @s.rb_rescue(@arg_error_proc, nil, @raise_proc_returns_sentinel, :exc).should == :raise_proc_executed
-      @s.rb_rescue(@std_error_proc, nil, @raise_proc_returns_sentinel, :exc).should == :raise_proc_executed
+    it "executes the passed 'rescue function' if a StandardError exception is raised" do
+      @s.rb_rescue(@arg_error_proc, nil, @rescue_proc_returns_sentinel, :exc).should == :rescue_proc_executed
+      @s.rb_rescue(@std_error_proc, nil, @rescue_proc_returns_sentinel, :exc).should == :rescue_proc_executed
     end
 
-    it "passes the user supplied argument to the 'raise function' if a StandardError exception is raised" do
-      arg1, _ = @s.rb_rescue(@arg_error_proc, nil, @raise_proc_returns_arg, :exc1)
+    it "passes the user supplied argument to the 'rescue function' if a StandardError exception is raised" do
+      arg1, _ = @s.rb_rescue(@arg_error_proc, nil, @rescue_proc_returns_arg, :exc1)
       arg1.should == :exc1
 
-      arg2, _ = @s.rb_rescue(@std_error_proc, nil, @raise_proc_returns_arg, :exc2)
+      arg2, _ = @s.rb_rescue(@std_error_proc, nil, @rescue_proc_returns_arg, :exc2)
       arg2.should == :exc2
     end
 
-    it "passes the raised exception to the 'raise function' if a StandardError exception is raised" do
-      _, exc1 = @s.rb_rescue(@arg_error_proc, nil, @raise_proc_returns_arg, :exc)
+    it "passes the raised exception to the 'rescue function' if a StandardError exception is raised" do
+      _, exc1 = @s.rb_rescue(@arg_error_proc, nil, @rescue_proc_returns_arg, :exc)
       exc1.class.should == ArgumentError
 
-      _, exc2 = @s.rb_rescue(@std_error_proc, nil, @raise_proc_returns_arg, :exc)
+      _, exc2 = @s.rb_rescue(@std_error_proc, nil, @rescue_proc_returns_arg, :exc)
       exc2.class.should == StandardError
     end
 
     it "raises an exception if passed function raises an exception other than StandardError" do
-      -> { @s.rb_rescue(@exc_error_proc, nil, @raise_proc_returns_arg, nil) }.should raise_error(Exception)
+      -> { @s.rb_rescue(@exc_error_proc, nil, @rescue_proc_returns_arg, nil) }.should raise_error(Exception)
     end
 
-    it "raises an exception if any exception is raised inside 'raise function'" do
+    it "raises an exception if any exception is raised inside the 'rescue function'" do
       -> { @s.rb_rescue(@std_error_proc, nil, @std_error_proc, nil) }.should raise_error(StandardError)
     end
 
-    it "makes $! available only during 'raise function' execution" do
-      @s.rb_rescue(@std_error_proc, nil, -> *_ { $! }, nil).class.should == StandardError
+    it "sets $! and rb_errinfo() during the 'rescue function' execution" do
+      @s.rb_rescue(-> *_ { raise exception_class, '' }, nil, -> _, exc {
+        exc.should.is_a?(exception_class)
+        $!.should.equal?(exc)
+        @s.rb_errinfo.should.equal?(exc)
+      }, nil)
+
+      @s.rb_rescue(-> _ { @s.rb_raise({}) }, nil, -> _, exc {
+        exc.should.is_a?(TypeError)
+        $!.should.equal?(exc)
+        @s.rb_errinfo.should.equal?(exc)
+      }, nil)
+
       $!.should == nil
+      @s.rb_errinfo.should == nil
     end
 
     it "returns the break value if the passed function yields to a block with a break" do
@@ -363,19 +447,46 @@ describe "C-API Kernel function" do
 
       proc_caller { break :value }.should == :value
     end
+
+    it "returns nil if the 'rescue function' is null" do
+      @s.rb_rescue(@std_error_proc, nil, nil, nil).should == nil
+    end
   end
 
   describe "rb_rescue2" do
     it "only rescues if one of the passed exceptions is raised" do
-      proc = -> x { x }
+      proc = -> x, _exc { x }
       arg_error_proc = -> *_ { raise ArgumentError, '' }
       run_error_proc = -> *_ { raise RuntimeError, '' }
-      type_error_proc = -> *_ { raise TypeError, '' }
+      type_error_proc = -> *_ { raise Exception, 'custom error' }
       @s.rb_rescue2(arg_error_proc, :no_exc, proc, :exc, ArgumentError, RuntimeError).should == :exc
       @s.rb_rescue2(run_error_proc, :no_exc, proc, :exc, ArgumentError, RuntimeError).should == :exc
       -> {
         @s.rb_rescue2(type_error_proc, :no_exc, proc, :exc, ArgumentError, RuntimeError)
-      }.should raise_error(TypeError)
+      }.should raise_error(Exception, 'custom error')
+    end
+
+    it "raises TypeError if one of the passed exceptions is not a Module" do
+      -> {
+        @s.rb_rescue2(-> *_ { raise RuntimeError, "foo" }, :no_exc, -> x { x }, :exc, Object.new, 42)
+      }.should raise_error(TypeError, /class or module required/)
+    end
+
+    it "sets $! and rb_errinfo() during the 'rescue function' execution" do
+      @s.rb_rescue2(-> *_ { raise exception_class, '' }, :no_exc, -> _, exc {
+        exc.should.is_a?(exception_class)
+        $!.should.equal?(exc)
+        @s.rb_errinfo.should.equal?(exc)
+      }, :exc, exception_class, ScriptError)
+
+      @s.rb_rescue2(-> *_ { @s.rb_raise({}) }, :no_exc, -> _, exc {
+        exc.should.is_a?(TypeError)
+        $!.should.equal?(exc)
+        @s.rb_errinfo.should.equal?(exc)
+      }, :exc, TypeError, ArgumentError)
+
+      $!.should == nil
+      @s.rb_errinfo.should == nil
     end
   end
 
@@ -429,6 +540,40 @@ describe "C-API Kernel function" do
     end
   end
 
+  describe "rb_category_warn" do
+    it "emits a warning into stderr" do
+      Warning[:deprecated] = true
+
+      -> {
+        @s.rb_category_warn_deprecated
+      }.should complain(/warning: foo/, verbose: true)
+    end
+
+    it "supports printf format modifiers" do
+      Warning[:deprecated] = true
+
+      -> {
+        @s.rb_category_warn_deprecated_with_integer_extra_value(42)
+      }.should complain(/warning: foo 42/, verbose: true)
+    end
+
+    it "does not emits a warning when a category is disabled" do
+      Warning[:deprecated] = false
+
+      -> {
+        @s.rb_category_warn_deprecated
+      }.should_not complain(verbose: true)
+    end
+
+    it "does not emits a warning when $VERBOSE is nil" do
+      Warning[:deprecated] = true
+
+      -> {
+        @s.rb_category_warn_deprecated
+      }.should_not complain(verbose: nil)
+    end
+  end
+
   describe "rb_ensure" do
     it "executes passed function and returns its value" do
       proc = -> x { x }
@@ -445,12 +590,33 @@ describe "C-API Kernel function" do
 
     it "executes passed 'ensure function' when an exception is raised" do
       foo = nil
-      raise_proc = -> { raise '' }
+      raise_proc = -> _ { raise exception_class }
       ensure_proc = -> x { foo = x }
-      @s.rb_ensure(raise_proc, nil, ensure_proc, :foo) rescue nil
+      -> {
+        @s.rb_ensure(raise_proc, nil, ensure_proc, :foo)
+      }.should raise_error(exception_class)
       foo.should == :foo
     end
 
+    it "sets $! and rb_errinfo() during the 'ensure function' execution" do
+      -> {
+        @s.rb_ensure(-> _ { raise exception_class }, nil, -> _ {
+          $!.should.is_a?(exception_class)
+          @s.rb_errinfo.should.is_a?(exception_class)
+        }, nil)
+      }.should raise_error(exception_class)
+
+      -> {
+        @s.rb_ensure(-> _ { @s.rb_raise({}) }, nil, -> _ {
+          $!.should.is_a?(TypeError)
+          @s.rb_errinfo.should.is_a?(TypeError)
+        }, nil)
+      }.should raise_error(TypeError)
+
+      $!.should == nil
+      @s.rb_errinfo.should == nil
+    end
+
     it "raises the same exception raised inside passed function" do
       raise_proc = -> *_ { raise RuntimeError, 'foo' }
       proc = -> *_ { }
@@ -462,6 +628,32 @@ describe "C-API Kernel function" do
     it "evaluates a string of ruby code" do
       @s.rb_eval_string("1+1").should == 2
     end
+
+    it "captures local variables when called within a method" do
+      a = 2
+      @s.rb_eval_string("a+1").should == 3
+    end
+  end
+
+  ruby_version_is ""..."4.0" do
+    describe "rb_eval_cmd_kw" do
+      it "evaluates a string of ruby code" do
+        @s.rb_eval_cmd_kw("1+1", [], 0).should == 2
+      end
+
+      it "calls a proc with the supplied arguments" do
+        @s.rb_eval_cmd_kw(-> *x { x.map { |i| i + 1 } }, [1, 3, 7], 0).should == [2, 4, 8]
+      end
+
+      it "calls a proc with keyword arguments if kw_splat is non zero" do
+        a_proc = -> *x, **y {
+          res = x.map { |i| i + 1 }
+          y.each { |k, v| res << k; res << v }
+          res
+        }
+        @s.rb_eval_cmd_kw(a_proc, [1, 3, 7, {a: 1, b: 2, c: 3}], 1).should == [2, 4, 8, :a, 1, :b, 2, :c, 3]
+      end
+    end
   end
 
   describe "rb_block_proc" do
@@ -469,7 +661,7 @@ describe "C-API Kernel function" do
       proc = @s.rb_block_proc { 1+1 }
       proc.should be_kind_of(Proc)
       proc.call.should == 2
-      proc.lambda?.should == false
+      proc.should_not.lambda?
     end
 
     it "passes through an existing lambda and does not convert to a proc" do
@@ -477,7 +669,7 @@ describe "C-API Kernel function" do
       proc = @s.rb_block_proc(&b)
       proc.should equal(b)
       proc.call.should == 2
-      proc.lambda?.should == true
+      proc.should.lambda?
     end
   end
 
@@ -486,7 +678,7 @@ describe "C-API Kernel function" do
       proc = @s.rb_block_lambda { 1+1 }
       proc.should be_kind_of(Proc)
       proc.call.should == 2
-      proc.lambda?.should == true
+      proc.should.lambda?
     end
 
     it "passes through an existing Proc and does not convert to a lambda" do
@@ -494,7 +686,7 @@ describe "C-API Kernel function" do
       proc = @s.rb_block_lambda(&b)
       proc.should equal(b)
       proc.call.should == 2
-      proc.lambda?.should == false
+      proc.should_not.lambda?
     end
   end
 
@@ -505,25 +697,9 @@ describe "C-API Kernel function" do
     end
   end
 
-  platform_is_not :windows do
-    describe "rb_set_end_proc" do
-      before :each do
-        @r, @w = IO.pipe
-      end
-
-      after :each do
-        @r.close
-        @w.close
-        Process.wait @pid
-      end
-
-      it "runs a C function on shutdown" do
-        @pid = fork {
-          @s.rb_set_end_proc(@w)
-        }
-
-        @r.read(1).should == "e"
-      end
+  describe "rb_set_end_proc" do
+    it "runs a C function on shutdown" do
+      ruby_exe("require #{kernel_path.inspect}; CApiKernelSpecs.new.rb_set_end_proc(STDOUT)").should == "in write_io"
     end
   end
 
@@ -541,21 +717,82 @@ describe "C-API Kernel function" do
     end
   end
 
-  describe "rb_obj_method" do
-    it "returns the method object for a symbol" do
-      method = @s.rb_obj_method("test", :size)
-      method.owner.should == String
-      method.name.to_sym.should == :size
+  describe "rb_funcallv" do
+    def empty
+      42
+    end
+
+    def sum(a, b)
+      a + b
+    end
+
+    it "calls a method" do
+      @s.rb_funcallv(self, :empty, []).should == 42
+      @s.rb_funcallv(self, :sum, [1, 2]).should == 3
     end
 
-    it "returns the method object for a string" do
-      method = @s.rb_obj_method("test", "size")
-      method.owner.should == String
-      method.name.to_sym.should == :size
+    it "calls a private method" do
+      object = CApiKernelSpecs::ClassWithPrivateMethod.new
+      @s.rb_funcallv(object, :private_method, []).should == :private
+    end
+
+    it "calls a protected method" do
+      object = CApiKernelSpecs::ClassWithProtectedMethod.new
+      @s.rb_funcallv(object, :protected_method, []).should == :protected
     end
   end
 
-  describe "rb_funcall3" do
+  describe "rb_funcallv_kw" do
+    it "passes keyword arguments to the callee" do
+      def m(*args, **kwargs)
+        [args, kwargs]
+      end
+
+      @s.rb_funcallv_kw(self, :m, [{}]).should == [[], {}]
+      @s.rb_funcallv_kw(self, :m, [{a: 1}]).should == [[], {a: 1}]
+      @s.rb_funcallv_kw(self, :m, [{b: 2}, {a: 1}]).should == [[{b: 2}], {a: 1}]
+      @s.rb_funcallv_kw(self, :m, [{b: 2}, {}]).should == [[{b: 2}], {}]
+    end
+
+    it "calls a private method" do
+      object = CApiKernelSpecs::ClassWithPrivateMethod.new
+      @s.rb_funcallv_kw(object, :private_method, [{}]).should == :private
+    end
+
+    it "calls a protected method" do
+      object = CApiKernelSpecs::ClassWithProtectedMethod.new
+      @s.rb_funcallv_kw(object, :protected_method, [{}]).should == :protected
+    end
+
+    it "raises TypeError if the last argument is not a Hash" do
+      def m(*args, **kwargs)
+        [args, kwargs]
+      end
+
+      -> {
+        @s.rb_funcallv_kw(self, :m, [42])
+      }.should raise_error(TypeError, 'no implicit conversion of Integer into Hash')
+    end
+  end
+
+  describe "rb_keyword_given_p" do
+    it "returns whether keywords were given to the C extension method" do
+      h = {a: 1}
+      empty = {}
+      @s.rb_keyword_given_p(a: 1).should == true
+      @s.rb_keyword_given_p("foo" => "bar").should == true
+      @s.rb_keyword_given_p(**h).should == true
+
+      @s.rb_keyword_given_p(h).should == false
+      @s.rb_keyword_given_p().should == false
+      @s.rb_keyword_given_p(**empty).should == false
+
+      @s.rb_funcallv_kw(@s, :rb_keyword_given_p, [{a: 1}]).should == true
+      @s.rb_funcallv_kw(@s, :rb_keyword_given_p, [{}]).should == false
+    end
+  end
+
+  describe "rb_funcallv_public" do
     before :each do
       @obj = Object.new
       class << @obj
@@ -566,29 +803,121 @@ describe "C-API Kernel function" do
     end
 
     it "calls a public method" do
-      @s.rb_funcall3(@obj, :method_public).should == :method_public
+      @s.rb_funcallv_public(@obj, :method_public).should == :method_public
     end
+
     it "does not call a private method" do
-      -> { @s.rb_funcall3(@obj, :method_private) }.should raise_error(NoMethodError, /private/)
+      -> { @s.rb_funcallv_public(@obj, :method_private) }.should raise_error(NoMethodError, /private/)
     end
   end
 
-  describe 'rb_funcall_with_block' do
+  describe 'rb_funcall' do
     before :each do
       @obj = Object.new
       class << @obj
-        def method_public; yield end
-        def method_private; yield end
-        private :method_private
+        def many_args(*args)
+          args
+        end
       end
     end
 
+    it "can call a public method with 15 arguments" do
+      @s.rb_funcall_many_args(@obj, :many_args).should == 15.downto(1).to_a
+    end
+  end
+
+  describe 'rb_funcall_with_block' do
     it "calls a method with block" do
-      @s.rb_funcall_with_block(@obj, :method_public, proc { :result }).should == :result
+      @obj = Object.new
+      class << @obj
+        def method_public(*args); [args, yield] end
+      end
+
+      @s.rb_funcall_with_block(@obj, :method_public, [1, 2], proc { :result }).should == [[1, 2], :result]
     end
 
     it "does not call a private method" do
-      -> { @s.rb_funcall_with_block(@obj, :method_private, proc { :result }) }.should raise_error(NoMethodError, /private/)
+      object = CApiKernelSpecs::ClassWithPrivateMethod.new
+
+      -> {
+        @s.rb_funcall_with_block(object, :private_method, [], proc { })
+      }.should raise_error(NoMethodError, /private/)
+    end
+
+    it "does not call a protected method" do
+      object = CApiKernelSpecs::ClassWithProtectedMethod.new
+
+      -> {
+        @s.rb_funcall_with_block(object, :protected_method, [], proc { })
+      }.should raise_error(NoMethodError, /protected/)
+    end
+  end
+
+  describe 'rb_funcall_with_block_kw' do
+    it "calls a method with keyword arguments and a block" do
+      @obj = Object.new
+      class << @obj
+        def method_public(*args, **kw, &block); [args, kw, block.call] end
+      end
+
+      @s.rb_funcall_with_block_kw(@obj, :method_public, [1, 2, {a: 2}], proc { :result }).should == [[1, 2], {a: 2}, :result]
+    end
+
+    it "does not call a private method" do
+      object = CApiKernelSpecs::ClassWithPrivateMethod.new
+
+      -> {
+        @s.rb_funcall_with_block_kw(object, :private_method, [{}], proc { })
+      }.should raise_error(NoMethodError, /private/)
+    end
+
+    it "does not call a protected method" do
+      object = CApiKernelSpecs::ClassWithProtectedMethod.new
+
+      -> {
+        @s.rb_funcall_with_block_kw(object, :protected_method, [{}], proc { })
+      }.should raise_error(NoMethodError, /protected/)
+    end
+  end
+
+  describe "rb_check_funcall" do
+    it "calls a method" do
+      @s.rb_check_funcall(1, :+, [2]).should == 3
+    end
+
+    it "returns Qundef if the method is not defined" do
+      obj = Object.new
+      @s.rb_check_funcall(obj, :foo, []).should == :Qundef
+    end
+
+    it "uses #respond_to? to check if the method is defined" do
+      ScratchPad.record []
+      obj = Object.new
+      def obj.respond_to?(name, priv)
+        ScratchPad << name
+        name == :foo || super
+      end
+      def obj.method_missing(name, *args)
+        name == :foo ? [name, 42] : super
+      end
+      @s.rb_check_funcall(obj, :foo, []).should == [:foo, 42]
+      ScratchPad.recorded.should == [:foo]
+    end
+
+    it "calls a private method" do
+      object = CApiKernelSpecs::ClassWithPrivateMethod.new
+      @s.rb_check_funcall(object, :private_method, []).should == :private
+    end
+
+    it "calls a protected method" do
+      object = CApiKernelSpecs::ClassWithProtectedMethod.new
+      @s.rb_check_funcall(object, :protected_method, []).should == :protected
+    end
+  end
+
+  describe "rb_str_format" do
+    it "returns a string according to format and arguments" do
+      @s.rb_str_format(3, [10, 2.5, "test"], "%d %f %s").should == "10 2.500000 test"
     end
   end
 end
diff --git a/spec/ruby/optional/capi/language_spec.rb b/spec/ruby/optional/capi/language_spec.rb
new file mode 100644
index 0000000000..f59b87f2a1
--- /dev/null
+++ b/spec/ruby/optional/capi/language_spec.rb
@@ -0,0 +1,37 @@
+require_relative 'spec_helper'
+
+load_extension("language")
+
+describe "C language construct" do
+  before :each do
+    @s = CApiLanguageSpecs.new
+  end
+
+  describe "switch (VALUE)" do
+    it "works for Qtrue" do
+      @s.switch(true).should == :true
+    end
+
+    it "works for Qfalse" do
+      @s.switch(false).should == :false
+    end
+
+    it "works for Qnil" do
+      @s.switch(nil).should == :nil
+    end
+
+    it "works for Qundef" do
+      @s.switch(:undef).should == :undef
+    end
+
+    it "works for the default case" do
+      @s.switch(Object.new).should == :default
+    end
+  end
+
+  describe "local variable assignment with the same name as a global" do
+    it "works for rb_mProcess" do
+      @s.global_local_var.should.equal?(Process)
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/module_spec.rb b/spec/ruby/optional/capi/module_spec.rb
index 34e6db82d8..af39ec0192 100644
--- a/spec/ruby/optional/capi/module_spec.rb
+++ b/spec/ruby/optional/capi/module_spec.rb
@@ -22,6 +22,8 @@ describe "CApiModule" do
     it "sets a new constant on a module" do
       @m.rb_const_set(CApiModuleSpecs::C, :W, 7)
       CApiModuleSpecs::C::W.should == 7
+    ensure
+      CApiModuleSpecs::C.send(:remove_const, :W)
     end
 
     it "sets an existing constant's value" do
@@ -36,7 +38,7 @@ describe "CApiModule" do
         CApiModuleSpecs::C.const_set(:_INVALID, 1)
       }.should raise_error(NameError, /wrong constant name/)
 
-      @m.rb_const_set(CApiModuleSpecs::C, :_INVALID, 2)
+      suppress_warning { @m.rb_const_set(CApiModuleSpecs::C, :_INVALID, 2) }
       @m.rb_const_get(CApiModuleSpecs::C, :_INVALID).should == 2
 
       # Ruby-level should still not allow access
@@ -93,6 +95,8 @@ describe "CApiModule" do
     it "defines a new constant on a module" do
       @m.rb_define_const(CApiModuleSpecs::C, "V", 7)
       CApiModuleSpecs::C::V.should == 7
+    ensure
+      CApiModuleSpecs::C.send(:remove_const, :V)
     end
 
     it "sets an existing constant's value" do
@@ -134,8 +138,12 @@ describe "CApiModule" do
       @m.rb_const_get(CApiModuleSpecs::A, :X).should == 1
     end
 
+    it "returns a constant defined in the module for multiple constants" do
+      [:Q, :R, :S, :T].each { |x| @m.rb_const_get(CApiModuleSpecs::A, x).should == CApiModuleSpecs::A.const_get(x) }
+    end
+
     it "returns a constant defined at toplevel" do
-      @m.rb_const_get(CApiModuleSpecs::A, :Fixnum).should == Fixnum
+      @m.rb_const_get(CApiModuleSpecs::A, :Integer).should == Integer
     end
 
     it "returns a constant defined in a superclass" do
@@ -176,8 +184,8 @@ describe "CApiModule" do
     end
 
     it "calls #const_missing if the constant is not defined in the class or ancestors" do
-      CApiModuleSpecs::M.should_receive(:const_missing).with(:Fixnum)
-      @m.rb_const_get_from(CApiModuleSpecs::M, :Fixnum)
+      CApiModuleSpecs::M.should_receive(:const_missing).with(:Integer)
+      @m.rb_const_get_from(CApiModuleSpecs::M, :Integer)
     end
 
     it "resolves autoload constants" do
@@ -242,11 +250,49 @@ describe "CApiModule" do
       cls.new.test_method.should == :test_method
     end
 
+    it "returns the correct arity when argc of the method in class is 0" do
+      cls = Class.new
+      @m.rb_define_method(cls, "test_method")
+      cls.new.method(:test_method).arity.should == 0
+    end
+
+    it "returns the correct arity when argc of the method in class is 1" do
+      @m.rb_define_method_1required(42).should == 42
+      @m.method(:rb_define_method_1required).arity.should == 1
+    end
+
+    it "returns the correct arity when argc of the method in class is 2" do
+      @m.rb_define_method_2required(1, 2).should == 2
+      @m.method(:rb_define_method_2required).arity.should == 2
+    end
+
+    it "defines a method taking variable arguments as a C array if the argument count is -1" do
+      @m.rb_define_method_varargs_1(1, 3, 7, 4).should == [1, 3, 7, 4]
+    end
+
+    it "returns the correct arity when argc of the method in class is -1" do
+      @m.method(:rb_define_method_varargs_1).arity.should == -1
+    end
+
+    it "defines a method taking variable arguments as a Ruby array if the argument count is -2" do
+      @m.rb_define_method_varargs_2(1, 3, 7, 4).should == [1, 3, 7, 4]
+    end
+
+    it "returns the correct arity when argc of the method in class is -2" do
+      @m.method(:rb_define_method_varargs_2).arity.should == -1
+    end
+
     it "defines a method on a module" do
       mod = Module.new
       @m.rb_define_method(mod, "test_method")
       mod.should have_instance_method(:test_method)
     end
+
+    it "returns the correct arity of the method in module" do
+      mod = Module.new
+      @m.rb_define_method(mod, "test_method")
+      mod.instance_method(:test_method).arity.should == 0
+    end
   end
 
   describe "rb_define_module_function" do
@@ -259,12 +305,23 @@ describe "CApiModule" do
       @mod.test_module_function.should == :test_method
     end
 
+    it "returns the correct arity of the module function" do
+      @mod.method(:test_module_function).arity.should == 0
+    end
+
     it "defines a private instance method" do
       cls = Class.new
       cls.include(@mod)
 
       cls.should have_private_instance_method(:test_module_function)
     end
+
+    it "returns the correct arity for private instance method" do
+      cls = Class.new
+      cls.include(@mod)
+
+      @mod.instance_method(:test_module_function).arity.should == 0
+    end
   end
 
   describe "rb_define_private_method" do
@@ -322,6 +379,11 @@ describe "CApiModule" do
       @class.should_not have_instance_method(:ruby_test_method)
     end
 
+    it "undefines private methods also" do
+      @m.rb_undef_method @class, "initialize_copy"
+      -> { @class.new.dup }.should raise_error(NoMethodError)
+    end
+
     it "does not raise exceptions when passed a missing name" do
       -> { @m.rb_undef_method @class, "not_exist" }.should_not raise_error
     end
@@ -331,12 +393,12 @@ describe "CApiModule" do
         @frozen = @class.dup.freeze
       end
 
-      it "raises a #{frozen_error_class} when passed a name" do
-        -> { @m.rb_undef_method @frozen, "ruby_test_method" }.should raise_error(frozen_error_class)
+      it "raises a FrozenError when passed a name" do
+        -> { @m.rb_undef_method @frozen, "ruby_test_method" }.should raise_error(FrozenError)
       end
 
-      it "raises a #{frozen_error_class} when passed a missing name" do
-        -> { @m.rb_undef_method @frozen, "not_exist" }.should raise_error(frozen_error_class)
+      it "raises a FrozenError when passed a missing name" do
+        -> { @m.rb_undef_method @frozen, "not_exist" }.should raise_error(FrozenError)
       end
     end
   end
diff --git a/spec/ruby/optional/capi/mutex_spec.rb b/spec/ruby/optional/capi/mutex_spec.rb
index 34659974f5..71a2212e36 100644
--- a/spec/ruby/optional/capi/mutex_spec.rb
+++ b/spec/ruby/optional/capi/mutex_spec.rb
@@ -85,5 +85,18 @@ describe "C-API Mutex functions" do
       callback = -> { @m.locked?.should be_true }
       @s.rb_mutex_synchronize(@m, callback)
     end
+
+    it "returns a value returned from a callback" do
+      callback = -> { :foo }
+      @s.rb_mutex_synchronize(@m, callback).should == :foo
+    end
+
+    it "calls a C-function that accepts and returns non-VALUE values" do
+      @s.rb_mutex_synchronize_with_naughty_callback(@m).should == 42
+    end
+
+    it "calls a native function" do
+      @s.rb_mutex_synchronize_with_native_callback(@m, 42).should == 42
+    end
   end
 end
diff --git a/spec/ruby/optional/capi/numeric_spec.rb b/spec/ruby/optional/capi/numeric_spec.rb
index d76f353850..e9667da5ba 100644
--- a/spec/ruby/optional/capi/numeric_spec.rb
+++ b/spec/ruby/optional/capi/numeric_spec.rb
@@ -106,7 +106,7 @@ describe "CApiNumericSpecs" do
       @s.NUM2LONG(5).should == 5
     end
 
-    platform_is wordsize: 32 do
+    platform_is c_long_size: 32 do
       it "converts -1 to an signed number" do
         @s.NUM2LONG(-1).should == -1
       end
@@ -120,7 +120,7 @@ describe "CApiNumericSpecs" do
       end
     end
 
-    platform_is wordsize: 64 do
+    platform_is c_long_size: 64 do
       it "converts -1 to an signed number" do
         @s.NUM2LONG(-1).should == -1
       end
@@ -143,6 +143,34 @@ describe "CApiNumericSpecs" do
     end
   end
 
+  describe "NUM2SHORT" do
+    it "raises a TypeError if passed nil" do
+      -> { @s.NUM2SHORT(nil) }.should raise_error(TypeError)
+    end
+
+    it "converts a Float" do
+      @s.NUM2SHORT(4.2).should == 4
+    end
+
+    it "converts a Fixnum" do
+      @s.NUM2SHORT(5).should == 5
+    end
+
+    it "converts -1 to an signed number" do
+      @s.NUM2SHORT(-1).should == -1
+    end
+
+    it "raises a RangeError if the value is more than 32bits" do
+      -> { @s.NUM2SHORT(0xffff_ffff+1) }.should raise_error(RangeError)
+    end
+
+    it "calls #to_int to coerce the value" do
+      obj = mock("number")
+      obj.should_receive(:to_int).and_return(2)
+      @s.NUM2SHORT(obj).should == 2
+    end
+  end
+
   describe "INT2NUM" do
     it "raises a TypeError if passed nil" do
       -> { @s.INT2NUM(nil) }.should raise_error(TypeError)
@@ -182,7 +210,7 @@ describe "CApiNumericSpecs" do
       @s.NUM2ULONG(5).should == 5
     end
 
-    platform_is wordsize: 32 do
+    platform_is c_long_size: 32 do
       it "converts -1 to an unsigned number" do
         @s.NUM2ULONG(-1).should == 4294967295
       end
@@ -203,7 +231,7 @@ describe "CApiNumericSpecs" do
       end
     end
 
-    platform_is wordsize: 64 do
+    platform_is c_long_size: 64 do
       it "converts -1 to an unsigned number" do
         @s.NUM2ULONG(-1).should == 18446744073709551615
       end
@@ -236,52 +264,45 @@ describe "CApiNumericSpecs" do
   describe "rb_Integer" do
     it "creates an Integer from a String" do
       i = @s.rb_Integer("8675309")
-      i.should be_kind_of(Integer)
-      i.should eql(8675309)
+      i.should == 8675309
     end
   end
 
   describe "rb_ll2inum" do
     it "creates a Fixnum from a small signed long long" do
       i = @s.rb_ll2inum_14()
-      i.should be_kind_of(Fixnum)
-      i.should eql(14)
+      i.should == 14
     end
   end
 
   describe "rb_ull2inum" do
     it "creates a Fixnum from a small unsigned long long" do
       i = @s.rb_ull2inum_14()
-      i.should be_kind_of(Fixnum)
-      i.should eql(14)
+      i.should == 14
     end
 
     it "creates a positive Bignum from a negative long long" do
       i = @s.rb_ull2inum_n14()
-      i.should be_kind_of(Bignum)
-      i.should eql(2 ** (@s.size_of_long_long * 8) - 14)
+      i.should == (2 ** (@s.size_of_long_long * 8) - 14)
     end
   end
 
   describe "rb_int2inum" do
     it "creates a Fixnum from a long" do
       i = @s.rb_int2inum_14()
-      i.should be_kind_of(Fixnum)
-      i.should eql(14)
+      i.should == 14
     end
   end
 
   describe "rb_uint2inum" do
     it "creates a Fixnum from a long" do
       i = @s.rb_uint2inum_14()
-      i.should be_kind_of(Fixnum)
-      i.should eql(14)
+      i.should == 14
     end
 
     it "creates a positive Bignum from a negative long" do
       i = @s.rb_uint2inum_n14()
-      i.should be_kind_of(Bignum)
-      i.should eql(2 ** (@s.size_of_VALUE * 8) - 14)
+      i.should == (2 ** (@s.size_of_VALUE * 8) - 14)
     end
   end
 
@@ -409,23 +430,12 @@ describe "CApiNumericSpecs" do
       @s.rb_num_coerce_cmp(2, obj, :<=>).should == -1
     end
 
-    ruby_version_is ""..."2.5" do
-      it "returns nil if passed nil" do
-        -> {
-          @result = @s.rb_num_coerce_cmp(nil, 2, :<=>)
-        }.should complain(/comparison operators will no more rescue exceptions/)
-        @result.should be_nil
-      end
-    end
-
-    ruby_version_is "2.5" do
-      it "lets the exception go through if #coerce raises an exception" do
-        obj = mock("rb_num_coerce_cmp")
-        obj.should_receive(:coerce).with(2).and_raise(RuntimeError.new("my error"))
-        -> {
-          @s.rb_num_coerce_cmp(2, obj, :<=>)
-        }.should raise_error(RuntimeError, "my error")
-      end
+    it "lets the exception go through if #coerce raises an exception" do
+      obj = mock("rb_num_coerce_cmp")
+      obj.should_receive(:coerce).with(2).and_raise(RuntimeError.new("my error"))
+      -> {
+        @s.rb_num_coerce_cmp(2, obj, :<=>)
+      }.should raise_error(RuntimeError, "my error")
     end
 
     it "returns nil if #coerce does not return an Array" do
diff --git a/spec/ruby/optional/capi/object_spec.rb b/spec/ruby/optional/capi/object_spec.rb
index 43b74b9151..8b4d8a9bba 100644
--- a/spec/ruby/optional/capi/object_spec.rb
+++ b/spec/ruby/optional/capi/object_spec.rb
@@ -1,4 +1,5 @@
 require_relative 'spec_helper'
+require_relative 'fixtures/object'
 
 load_extension("object")
 
@@ -30,6 +31,7 @@ describe "CApiObject" do
   class ObjectTest
     def initialize
       @foo = 7
+      yield if block_given?
     end
 
     def foo
@@ -88,6 +90,15 @@ describe "CApiObject" do
       o.initialized.should be_true
       o.arguments.should == [:one, :two]
     end
+
+    it "passes the block to #initialize" do
+      v = nil
+      o = @o.rb_obj_alloc(ObjectTest)
+      @o.rb_obj_call_init(o, 0, []) do
+        v = :foo
+      end
+      v.should == :foo
+    end
   end
 
   describe "rb_is_instance_of" do
@@ -110,6 +121,16 @@ describe "CApiObject" do
       @o.rb_respond_to(ObjectTest.new, :foo).should == true
       @o.rb_respond_to(ObjectTest.new, :bar).should == false
     end
+
+    it "can be used with primitives" do
+      @o.rb_respond_to(true, :object_id).should == true
+      @o.rb_respond_to(14, :succ).should == true
+    end
+
+    it "returns 0 if the method has been defined as rb_f_notimplement" do
+      @o.respond_to?(:not_implemented_method).should == false
+      @o.rb_respond_to(@o, :not_implemented_method).should == false
+    end
   end
 
   describe "rb_obj_respond_to" do
@@ -151,6 +172,20 @@ describe "CApiObject" do
     end
   end
 
+  describe "rb_obj_method" do
+    it "returns the method object for a symbol" do
+      method = @o.rb_obj_method("test", :size)
+      method.owner.should == String
+      method.name.to_sym.should == :size
+    end
+
+    it "returns the method object for a string" do
+      method = @o.rb_obj_method("test", "size")
+      method.owner.should == String
+      method.name.to_sym.should == :size
+    end
+  end
+
   describe "rb_method_boundp" do
     it "returns true when the given method is bound" do
       @o.rb_method_boundp(Object, :class, true).should == true
@@ -184,7 +219,7 @@ describe "CApiObject" do
     end
 
     it "requires a ruby file" do
-      $:.unshift File.dirname(__FILE__)
+      $:.unshift __dir__
       @o.rb_require()
       $foo.should == 7
     end
@@ -313,8 +348,8 @@ describe "CApiObject" do
 
     it "does not rescue exceptions raised by #to_ary" do
       obj = mock("to_ary")
-      obj.should_receive(:to_ary).and_raise(frozen_error_class)
-      -> { @o.rb_check_array_type obj }.should raise_error(frozen_error_class)
+      obj.should_receive(:to_ary).and_raise(FrozenError)
+      -> { @o.rb_check_array_type obj }.should raise_error(FrozenError)
     end
   end
 
@@ -414,13 +449,6 @@ describe "CApiObject" do
   end
 
   describe "FL_TEST" do
-    it "returns correct status for FL_TAINT" do
-      obj = Object.new
-      @o.FL_TEST(obj, "FL_TAINT").should == 0
-      obj.taint
-      @o.FL_TEST(obj, "FL_TAINT").should_not == 0
-    end
-
     it "returns correct status for FL_FREEZE" do
       obj = Object.new
       @o.FL_TEST(obj, "FL_FREEZE").should == 0
@@ -441,7 +469,7 @@ describe "CApiObject" do
   describe "rb_class_of" do
     it "returns the class of an object" do
       @o.rb_class_of(nil).should == NilClass
-      @o.rb_class_of(0).should == Fixnum
+      @o.rb_class_of(0).should == Integer
       @o.rb_class_of(0.1).should == Float
       @o.rb_class_of(ObjectTest.new).should == ObjectTest
     end
@@ -454,12 +482,31 @@ describe "CApiObject" do
     end
   end
 
+  describe "rb_obj_class" do
+    it "returns the class of an object" do
+      @o.rb_obj_class(nil).should == NilClass
+      @o.rb_obj_class(0).should == Integer
+      @o.rb_obj_class(0.1).should == Float
+      @o.rb_obj_class(ObjectTest.new).should == ObjectTest
+    end
+
+    it "does not return the singleton class if it exists" do
+      o = ObjectTest.new
+      o.singleton_class
+      @o.rb_obj_class(o).should equal ObjectTest
+    end
+  end
+
   describe "rb_obj_classname" do
     it "returns the class name of an object" do
       @o.rb_obj_classname(nil).should == 'NilClass'
-      @o.rb_obj_classname(0).should == Fixnum.to_s
+      @o.rb_obj_classname(0).should == 'Integer'
       @o.rb_obj_classname(0.1).should == 'Float'
       @o.rb_obj_classname(ObjectTest.new).should == 'ObjectTest'
+
+      o = ObjectTest.new
+      o.singleton_class
+      @o.rb_obj_classname(o).should == 'ObjectTest'
     end
   end
 
@@ -473,20 +520,58 @@ describe "CApiObject" do
       @o.rb_is_type_array([]).should == true
       @o.rb_is_type_array(DescArray.new).should == true
       @o.rb_is_type_module(ObjectTest).should == false
+      @o.rb_is_type_module(Module.new).should == true
       @o.rb_is_type_class(ObjectTest).should == true
       @o.rb_is_type_data(Time.now).should == true
     end
+
+    it "returns T_FILE for instances of IO and subclasses" do
+      STDERR.class.should == IO
+      @o.rb_is_rb_type_p_file(STDERR).should == true
+
+      File.open(__FILE__) do |f|
+        f.class.should == File
+        @o.rb_is_rb_type_p_file(f).should == true
+      end
+
+      require 'socket'
+      TCPServer.open(0) do |s|
+        @o.rb_is_rb_type_p_file(s).should == true
+      end
+    end
+  end
+
+  describe "rb_check_type" do
+    it "checks if the object is of the given type" do
+      @o.rb_check_type(nil, nil).should == true
+      @o.rb_check_type(ObjectTest.new, Object.new).should == true
+      @o.rb_check_type([], []).should == true
+      @o.rb_check_type(Class.new(Array).new, []).should == true
+      @o.rb_check_type(ObjectTest, Object).should == true
+    end
+
+    it "raises an exception if the object is not of the expected type" do
+      -> {
+        @o.rb_check_type([], Object.new)
+      }.should raise_error(TypeError, 'wrong argument type Array (expected Object)')
+
+      -> {
+        @o.rb_check_type(ObjectTest, Module.new)
+      }.should raise_error(TypeError, 'wrong argument type Class (expected Module)')
+
+      -> {
+        @o.rb_check_type(nil, "string")
+      }.should raise_error(TypeError, 'wrong argument type nil (expected String)')
+    end
   end
 
   describe "rb_type_p" do
     it "returns whether object is of the given type" do
-      class DescArray < Array
-      end
       @o.rb_is_rb_type_p_nil(nil).should == true
       @o.rb_is_rb_type_p_object([]).should == false
       @o.rb_is_rb_type_p_object(ObjectTest.new).should == true
       @o.rb_is_rb_type_p_array([]).should == true
-      @o.rb_is_rb_type_p_array(DescArray.new).should == true
+      @o.rb_is_rb_type_p_array(Class.new(Array).new).should == true
       @o.rb_is_rb_type_p_module(ObjectTest).should == false
       @o.rb_is_rb_type_p_class(ObjectTest).should == true
       @o.rb_is_rb_type_p_data(Time.now).should == true
@@ -495,12 +580,10 @@ describe "CApiObject" do
 
   describe "BUILTIN_TYPE" do
     it "returns the type constant for the object" do
-      class DescArray < Array
-      end
       @o.rb_is_builtin_type_object([]).should == false
       @o.rb_is_builtin_type_object(ObjectTest.new).should == true
       @o.rb_is_builtin_type_array([]).should == true
-      @o.rb_is_builtin_type_array(DescArray.new).should == true
+      @o.rb_is_builtin_type_array(Class.new(Array).new).should == true
       @o.rb_is_builtin_type_module(ObjectTest).should == false
       @o.rb_is_builtin_type_class(ObjectTest).should == true
       @o.rb_is_builtin_type_data(Time.now).should == true
@@ -570,62 +653,12 @@ describe "CApiObject" do
   end
 
   describe "OBJ_TAINT" do
-    it "taints the object" do
-      obj = mock("tainted")
-      @o.OBJ_TAINT(obj)
-      obj.tainted?.should be_true
-    end
   end
 
   describe "OBJ_TAINTED" do
-    it "returns C true if the object is tainted" do
-      obj = mock("tainted")
-      obj.taint
-      @o.OBJ_TAINTED(obj).should be_true
-    end
-
-    it "returns C false if the object is not tainted" do
-      obj = mock("untainted")
-      @o.OBJ_TAINTED(obj).should be_false
-    end
   end
 
   describe "OBJ_INFECT" do
-    it "does not taint the first argument if the second argument is not tainted" do
-      host   = mock("host")
-      source = mock("source")
-      @o.OBJ_INFECT(host, source)
-      host.tainted?.should be_false
-    end
-
-    it "taints the first argument if the second argument is tainted" do
-      host   = mock("host")
-      source = mock("source").taint
-      @o.OBJ_INFECT(host, source)
-      host.tainted?.should be_true
-    end
-
-    it "does not untrust the first argument if the second argument is trusted" do
-      host   = mock("host")
-      source = mock("source")
-      @o.OBJ_INFECT(host, source)
-      host.untrusted?.should be_false
-    end
-
-    it "untrusts the first argument if the second argument is untrusted" do
-      host   = mock("host")
-      source = mock("source").untrust
-      @o.OBJ_INFECT(host, source)
-      host.untrusted?.should be_true
-    end
-
-    it "propagates both taint and distrust" do
-      host   = mock("host")
-      source = mock("source").taint.untrust
-      @o.OBJ_INFECT(host, source)
-      host.tainted?.should be_true
-      host.untrusted?.should be_true
-    end
   end
 
   describe "rb_obj_freeze" do
@@ -653,31 +686,31 @@ describe "CApiObject" do
     end
 
     it "returns false if object passed to it is not frozen" do
-      obj = ""
+      obj = +""
       @o.rb_obj_frozen_p(obj).should == false
     end
   end
 
-  describe "rb_obj_taint" do
-    it "marks the object passed as tainted" do
-      obj = ""
-      obj.tainted?.should == false
-      @o.rb_obj_taint(obj)
-      obj.tainted?.should == true
-    end
+  describe "redefining frozen? works" do
+    it "allows an object to override frozen?" do
+      obj = CApiObjectRedefinitionSpecs.new
 
-    it "raises a #{frozen_error_class} if the object passed is frozen" do
-      -> { @o.rb_obj_taint("".freeze) }.should raise_error(frozen_error_class)
+      obj.frozen?.should == false
+      obj.freeze
+      obj.frozen?.should == true
     end
   end
 
+  describe "rb_obj_taint" do
+  end
+
   describe "rb_check_frozen" do
-    it "raises a #{frozen_error_class} if the obj is frozen" do
-      -> { @o.rb_check_frozen("".freeze) }.should raise_error(frozen_error_class)
+    it "raises a FrozenError if the obj is frozen" do
+      -> { @o.rb_check_frozen("".freeze) }.should raise_error(FrozenError)
     end
 
     it "does nothing when object isn't frozen" do
-      obj = ""
+      obj = +""
       -> { @o.rb_check_frozen(obj) }.should_not raise_error(TypeError)
     end
   end
@@ -805,6 +838,15 @@ describe "CApiObject" do
       end
     end
 
+    describe "rb_ivar_count" do
+      it "returns the number of instance variables" do
+        obj = Object.new
+        @o.rb_ivar_count(obj).should == 0
+        obj.instance_variable_set(:@foo, 42)
+        @o.rb_ivar_count(obj).should == 1
+      end
+    end
+
     describe "rb_ivar_get" do
       it "returns the instance variable on an object" do
         @o.rb_ivar_get(@test, :@foo).should == @test.instance_eval { @foo }
@@ -816,6 +858,7 @@ describe "CApiObject" do
 
       it "returns nil if the instance variable has not been initialized and is not a valid Ruby name" do
         @o.rb_ivar_get(@test, :bar).should == nil
+        @o.rb_ivar_get(@test, :mesg).should == nil
       end
 
       it 'returns the instance variable when it is not a valid Ruby name' do
@@ -851,18 +894,19 @@ describe "CApiObject" do
 
       it "does not throw an error if the instance variable is not a valid Ruby name" do
         @o.rb_ivar_defined(@test, :bar).should == false
+        @o.rb_ivar_defined(@test, :mesg).should == false
       end
     end
 
-    # The `generic_iv_tbl` table and `*_generic_ivar` functions are for mutable
+    # The `generic_fields_tbl` table and `*_generic_ivar` functions are for mutable
     # objects which do not store ivars directly in MRI such as RString, because
     # there is no member iv_index_tbl (ivar table) such as in RObject and RClass.
 
     describe "rb_copy_generic_ivar for objects which do not store ivars directly" do
       it "copies the instance variables from one object to another" do
-        original = "abc"
+        original = +"abc"
         original.instance_variable_set(:@foo, :bar)
-        clone = "def"
+        clone = +"def"
         @o.rb_copy_generic_ivar(clone, original)
         clone.instance_variable_get(:@foo).should == :bar
       end
@@ -870,11 +914,110 @@ describe "CApiObject" do
 
     describe "rb_free_generic_ivar for objects which do not store ivars directly" do
       it "removes the instance variables from an object" do
-        o = "abc"
+        o = +"abc"
         o.instance_variable_set(:@baz, :flibble)
         @o.rb_free_generic_ivar(o)
         o.instance_variables.should == []
       end
     end
   end
+
+  describe "allocator accessors" do
+    describe "rb_define_alloc_func" do
+      it "sets up the allocator" do
+        klass = Class.new
+        @o.rb_define_alloc_func(klass)
+        obj = klass.allocate
+        obj.class.should.equal?(klass)
+        obj.should have_instance_variable(:@from_custom_allocator)
+      end
+
+      it "sets up the allocator for a subclass of String" do
+        klass = Class.new(String)
+        @o.rb_define_alloc_func(klass)
+        obj = klass.allocate
+        obj.class.should.equal?(klass)
+        obj.should have_instance_variable(:@from_custom_allocator)
+        obj.should == ""
+      end
+
+      it "sets up the allocator for a subclass of Array" do
+        klass = Class.new(Array)
+        @o.rb_define_alloc_func(klass)
+        obj = klass.allocate
+        obj.class.should.equal?(klass)
+        obj.should have_instance_variable(:@from_custom_allocator)
+        obj.should == []
+      end
+    end
+
+    describe "rb_get_alloc_func" do
+      it "gets the allocator that is defined directly on a class" do
+        klass = Class.new
+        @o.rb_define_alloc_func(klass)
+        @o.speced_allocator?(Object).should == false
+        @o.speced_allocator?(klass).should == true
+      end
+
+      it "gets the allocator that is inherited" do
+        parent = Class.new
+        @o.rb_define_alloc_func(parent)
+        klass = Class.new(parent)
+        @o.speced_allocator?(Object).should == false
+        @o.speced_allocator?(klass).should == true
+      end
+    end
+
+    describe "rb_undef_alloc_func" do
+      it "makes rb_get_alloc_func() return NULL for a class without a custom allocator" do
+        klass = Class.new
+        @o.rb_undef_alloc_func(klass)
+        @o.custom_alloc_func?(klass).should == false
+      end
+
+      it "undefs the allocator for the class" do
+        klass = Class.new
+        @o.rb_define_alloc_func(klass)
+        @o.speced_allocator?(klass).should == true
+        @o.rb_undef_alloc_func(klass)
+        @o.custom_alloc_func?(klass).should == false
+      end
+
+      it "undefs the allocator for a class that inherits a allocator" do
+        parent = Class.new
+        @o.rb_define_alloc_func(parent)
+        klass = Class.new(parent)
+        @o.speced_allocator?(klass).should == true
+        @o.rb_undef_alloc_func(klass)
+        @o.custom_alloc_func?(klass).should == false
+
+        @o.speced_allocator?(parent).should == true
+      end
+    end
+
+    describe "rb_ivar_foreach" do
+      it "calls the callback function for each instance variable on an object" do
+        o = CApiObjectSpecs::IVars.new
+        ary = @o.rb_ivar_foreach(o)
+        ary.should == [:@a, 3, :@b, 7, :@c, 4]
+      end
+
+      it "calls the callback function for each cvar and ivar on a class" do
+        exp = [:@@cvar, :foo, :@@cvar2, :bar, :@ivar, :baz]
+        exp.unshift(:__classpath__, 'CApiObjectSpecs::CVars') if RUBY_VERSION < "3.3"
+
+        ary = @o.rb_ivar_foreach(CApiObjectSpecs::CVars)
+        ary.should == exp
+      end
+
+      it "calls the callback function for each cvar and ivar on a module" do
+        exp = [:@@mvar, :foo, :@@mvar2, :bar, :@ivar, :baz]
+        exp.unshift(:__classpath__, 'CApiObjectSpecs::MVars') if RUBY_VERSION < "3.3"
+
+        ary = @o.rb_ivar_foreach(CApiObjectSpecs::MVars)
+        ary.should == exp
+      end
+
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/proc_spec.rb b/spec/ruby/optional/capi/proc_spec.rb
index 9f9a37cc98..8b94432f3e 100644
--- a/spec/ruby/optional/capi/proc_spec.rb
+++ b/spec/ruby/optional/capi/proc_spec.rb
@@ -7,6 +7,8 @@ describe "C-API Proc function" do
   before :each do
     @p = CApiProcSpecs.new
     @prc = @p.rb_proc_new
+    @prc2 = @p.rb_proc_new_argv_n
+    @prc3 = @p.rb_proc_new_argc
   end
 
   describe "rb_proc_new" do
@@ -15,6 +17,7 @@ describe "C-API Proc function" do
     end
 
     it "calls the C function wrapped by the Proc instance when sent #call" do
+      @p.rb_proc_new_arg.call().should == nil
       @prc.call(:foo_bar).should == ":foo_bar"
       @prc.call([:foo, :bar]).should == "[:foo, :bar]"
     end
@@ -24,6 +27,30 @@ describe "C-API Proc function" do
       @prc[[:foo, :bar]].should == "[:foo, :bar]"
     end
 
+    it "calls the C function with the arg count in argc" do
+      @prc3.call().should == 0
+      @prc3.call(:foo).should == 1
+      @prc3.call(:foo, :bar).should == 2
+    end
+
+    it "calls the C function with arguments in argv" do
+      @prc2.call(1, :foo).should == :foo
+      @prc2.call(2, :foo, :bar).should == :bar
+      -> { @prc2.call(3, :foo, :bar) }.should raise_error(ArgumentError)
+    end
+
+    it "calls the C function with the block passed in blockarg" do
+      a_block = :foo.to_proc
+      @p.rb_proc_new_blockarg.call(&a_block).should == a_block
+      @p.rb_proc_new_blockarg.call().should == nil
+    end
+
+    it "calls the C function and yields to the block passed in blockarg" do
+      @p.rb_proc_new_block_given_p.call() do
+      end.should == false
+      @p.rb_proc_new_block_given_p.call().should == false
+    end
+
     it "returns a Proc instance correctly described in #inspect without source location" do
       @prc.inspect.should =~ /^#<Proc:([^ :@]*?)>$/
     end
@@ -54,6 +81,78 @@ describe "C-API Proc function" do
       @p.rb_proc_call(prc, [6, 7]).should == 42
     end
   end
+
+  describe "rb_proc_call_kw" do
+    it "passes keyword arguments to the proc" do
+      prc = proc { |*args, **kw| [args, kw] }
+
+      @p.rb_proc_call_kw(prc, [{}]).should == [[], {}]
+      @p.rb_proc_call_kw(prc, [{a: 1}]).should == [[], {a: 1}]
+      @p.rb_proc_call_kw(prc, [{b: 2}, {a: 1}]).should == [[{b: 2}], {a: 1}]
+      @p.rb_proc_call_kw(prc, [{b: 2}, {}]).should == [[{b: 2}], {}]
+    end
+
+    it "raises TypeError if the last argument is not a Hash" do
+      -> {
+        @p.rb_proc_call_kw(proc {}, [42])
+      }.should raise_error(TypeError, 'no implicit conversion of Integer into Hash')
+    end
+  end
+
+  describe "rb_proc_call_with_block" do
+    it "calls the Proc and passes arguments and a block" do
+      prc = Proc.new { |a, b, &block| block.call(a * b) }
+      @p.rb_proc_call_with_block(prc, [6, 7], proc { |n| n * 2 }).should == 6 * 7 * 2
+    end
+
+    it "calls the Proc and passes arguments when a block is nil" do
+      prc = Proc.new { |a, b| a * b }
+      @p.rb_proc_call_with_block(prc, [6, 7], nil).should == 6 * 7
+    end
+  end
+
+  describe "rb_proc_call_with_block_kw" do
+    it "passes keyword arguments and a block to the proc" do
+      prc = proc { |*args, **kw, &block| [args, kw, block.call(42)] }
+      block = proc { |n| n }
+
+      @p.rb_proc_call_with_block_kw(prc, [{}], block).should == [[], {}, 42]
+      @p.rb_proc_call_with_block_kw(prc, [{a: 1}], block).should == [[], {a: 1}, 42]
+      @p.rb_proc_call_with_block_kw(prc, [{b: 2}, {a: 1}], block).should == [[{b: 2}], {a: 1}, 42]
+      @p.rb_proc_call_with_block_kw(prc, [{b: 2}, {}], block).should == [[{b: 2}], {}, 42]
+    end
+
+    it "raises TypeError if the last argument is not a Hash" do
+      -> {
+        @p.rb_proc_call_with_block_kw(proc {}, [42], proc {})
+      }.should raise_error(TypeError, 'no implicit conversion of Integer into Hash')
+    end
+
+    it "passes keyword arguments to the proc when a block is nil" do
+      prc = proc { |*args, **kw| [args, kw] }
+
+      @p.rb_proc_call_with_block_kw(prc, [{}], nil).should == [[], {}]
+    end
+  end
+
+  describe "rb_obj_is_proc" do
+    it "returns true for Proc" do
+      prc = Proc.new {|a,b| a * b }
+      @p.rb_obj_is_proc(prc).should be_true
+    end
+
+    it "returns true for subclass of Proc" do
+      prc = Class.new(Proc).new {}
+      @p.rb_obj_is_proc(prc).should be_true
+    end
+
+    it "returns false for non Proc instances" do
+      @p.rb_obj_is_proc("aoeui").should be_false
+      @p.rb_obj_is_proc(123).should be_false
+      @p.rb_obj_is_proc(true).should be_false
+      @p.rb_obj_is_proc([]).should be_false
+    end
+  end
 end
 
 describe "C-API when calling Proc.new from a C function" do
@@ -69,24 +168,11 @@ describe "C-API when calling Proc.new from a C function" do
   # For example: C -> Ruby <- C -> Ruby means a C function called into Ruby
   # code which returned to C, then C called into Ruby code again.
 
-  ruby_version_is ""..."2.7" do
-    #   Ruby -> C -> rb_funcall(Proc.new)
-    it "returns the Proc passed by the Ruby code calling the C function" do
-      prc = @p.rb_Proc_new(0) { :called }
-      prc.call.should == :called
-    end
-
-    #   Ruby -> C -> Ruby <- C -> rb_funcall(Proc.new)
-    it "returns the Proc passed to the Ruby method when the C function calls other Ruby methods before calling Proc.new" do
-      prc = @p.rb_Proc_new(1) { :called }
-      prc.call.should == :called
-    end
-  end
-
   # Ruby -> C -> Ruby -> Proc.new
   it "raises an ArgumentError when the C function calls a Ruby method that calls Proc.new" do
-    def @p.Proc_new() Proc.new end
-    -> { @p.rb_Proc_new(2) { :called } }.should raise_error(ArgumentError)
+    -> {
+      @p.rb_Proc_new(2) { :called }
+    }.should raise_error(ArgumentError)
   end
 
   # Ruby -> C -> Ruby -> C -> rb_funcall(Proc.new)
@@ -95,20 +181,6 @@ describe "C-API when calling Proc.new from a C function" do
     -> { @p.rb_Proc_new(3) { :called } }.should raise_error(ArgumentError)
   end
 
-  ruby_version_is ""..."2.7" do
-    # Ruby -> C -> Ruby -> C (with new block) -> rb_funcall(Proc.new)
-    it "returns the most recent Proc passed when the Ruby method called the C function" do
-      prc = @p.rb_Proc_new(4) { :called }
-      prc.call.should == :calling_with_block
-    end
-
-    # Ruby -> C -> Ruby -> C (with new block) <- Ruby <- C -> # rb_funcall(Proc.new)
-    it "returns the Proc passed from the original Ruby call to the C function" do
-      prc = @p.rb_Proc_new(5) { :called }
-      prc.call.should == :called
-    end
-  end
-
   # Ruby -> C -> Ruby -> block_given?
   it "returns false from block_given? in a Ruby method called by the C function" do
     @p.rb_Proc_new(6).should be_false
diff --git a/spec/ruby/optional/capi/range_spec.rb b/spec/ruby/optional/capi/range_spec.rb
index 7a52dc7ff8..80c052e79a 100644
--- a/spec/ruby/optional/capi/range_spec.rb
+++ b/spec/ruby/optional/capi/range_spec.rb
@@ -69,7 +69,7 @@ describe "C-API Range function" do
   describe "rb_range_beg_len" do
     it "returns correct begin, length and result" do
       r = 2..5
-      begp, lenp, result = @s.rb_range_beg_len(r, 0, 0, 10, 0)
+      begp, lenp, result = @s.rb_range_beg_len(r, 10, 0)
       result.should be_true
       begp.should == 2
       lenp.should == 4
@@ -77,19 +77,155 @@ describe "C-API Range function" do
 
     it "returns nil when not in range" do
       r = 2..5
-      begp, lenp, result = @s.rb_range_beg_len(r, 0, 0, 1, 0)
+      begp, lenp, result = @s.rb_range_beg_len(r, 1, 0)
       result.should be_nil
     end
 
     it "raises a RangeError when not in range and err is 1" do
       r = -5..-1
-      -> { @s.rb_range_beg_len(r, 0, 0, 1, 1) }.should raise_error(RangeError)
+      -> { @s.rb_range_beg_len(r, 1, 1) }.should raise_error(RangeError)
     end
 
     it "returns nil when not in range and err is 0" do
       r = -5..-1
-      begp, lenp, result =  @s.rb_range_beg_len(r, 0, 0, 1, 0)
+      begp, lenp, result =  @s.rb_range_beg_len(r, 1, 0)
       result.should be_nil
     end
   end
+
+  describe "rb_arithmetic_sequence_extract" do
+    it "returns begin, end, step, exclude end of an instance of an Enumerator::ArithmeticSequence" do
+      enum = (10..20).step(5)
+      enum.should.kind_of?(Enumerator::ArithmeticSequence)
+
+      @s.rb_arithmetic_sequence_extract(enum).should == [1, 10, 20, 5, false]
+    end
+
+    it "returns begin, end, step, exclude end of an instance of a Range" do
+      range = (10..20)
+      @s.rb_arithmetic_sequence_extract(range).should == [1, 10, 20, 1, false]
+    end
+
+    it "returns begin, end, step, exclude end of a non-Range object with Range properties" do
+      object = Object.new
+      def object.begin
+        10
+      end
+      def object.end
+        20
+      end
+      def object.exclude_end?
+        false
+      end
+
+      @s.rb_arithmetic_sequence_extract(object).should == [1, 10, 20, 1, false]
+    end
+
+    it "returns failed status if given object is not Enumerator::ArithmeticSequence or Range or Range-like object" do
+      object = Object.new
+      @s.rb_arithmetic_sequence_extract(object).should == [0]
+    end
+  end
+
+  describe "rb_arithmetic_sequence_beg_len_step" do
+    it "returns correct begin, length, step and result" do
+      as = (2..5).step(5)
+      error_code = 0
+
+      success, beg, len, step = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+
+      beg.should == 2
+      len.should == 4
+      step.should == 5
+    end
+
+    it "takes into account excluded end boundary" do
+      as = (2...5).step(1)
+      error_code = 0
+
+      success, _, len, _ = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+      len.should == 3
+    end
+
+    it "adds length to negative begin boundary" do
+      as = (-2..5).step(1)
+      error_code = 0
+
+      success, beg, len, _ = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+
+      beg.should == 4
+      len.should == 2
+    end
+
+    it "adds length to negative end boundary" do
+      as = (2..-1).step(1)
+      error_code = 0
+
+      success, beg, len, _ = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+
+      beg.should == 2
+      len.should == 4
+    end
+
+    it "truncates arithmetic sequence length if end boundary greater than specified length value" do
+      as = (2..10).step(1)
+      error_code = 0
+
+      success, _, len, _ = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+      len.should == 4
+    end
+
+    it "returns inverted begin and end boundaries when step is negative" do
+      as = (2..5).step(-2)
+      error_code = 0
+
+      success, beg, len, step = @s.rb_arithmetic_sequence_beg_len_step(as, 6, error_code)
+      success.should be_true
+
+      beg.should == 5
+      len.should == 0
+      step.should == -2
+    end
+
+    it "returns nil when not in range and error code = 0" do
+      as = (2..5).step(1)
+      error_code = 0
+
+      success, = @s.rb_arithmetic_sequence_beg_len_step(as, 1, error_code)
+      success.should be_nil
+    end
+
+    it "returns nil when not in range, negative boundaries and error code = 0" do
+      as = (-5..-1).step(1)
+      error_code = 0
+
+      success, = @s.rb_arithmetic_sequence_beg_len_step(as, 1, 0)
+      success.should be_nil
+    end
+
+    it "returns begin, length and step and doesn't raise a RangeError when not in range and error code = 1" do
+      as = (2..5).step(1)
+      error_code = 1
+
+      success, beg, len, step = @s.rb_arithmetic_sequence_beg_len_step(as, 1, error_code)
+      success.should be_true
+
+      beg.should == 2
+      len.should == 4
+      step.should == 1
+    end
+
+    it "returns nil and doesn't raise a RangeError when not in range, negative boundaries and error code = 1" do
+      as = (-5..-1).step(1)
+      error_code = 1
+
+      success, = @s.rb_arithmetic_sequence_beg_len_step(as, 1, error_code)
+      success.should be_nil
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/rbasic_spec.rb b/spec/ruby/optional/capi/rbasic_spec.rb
new file mode 100644
index 0000000000..7b5b5b2fed
--- /dev/null
+++ b/spec/ruby/optional/capi/rbasic_spec.rb
@@ -0,0 +1,48 @@
+require_relative 'spec_helper'
+require_relative 'shared/rbasic'
+load_extension("rbasic")
+ruby_version_is ""..."3.4" do
+  load_extension("data")
+end
+load_extension("array")
+
+describe "RBasic support for regular objects" do
+  before :all do
+    @specs = CApiRBasicSpecs.new
+    @data = -> { [Object.new, Object.new] }
+  end
+  it_should_behave_like :rbasic
+end
+
+ruby_version_is ""..."3.4" do
+  describe "RBasic support for RData" do
+    before :all do
+      @specs = CApiRBasicRDataSpecs.new
+      @wrapping = CApiWrappedStructSpecs.new
+      @data = -> { [@wrapping.wrap_struct(1024), @wrapping.wrap_struct(1025)] }
+    end
+    it_should_behave_like :rbasic
+
+    it "supports user flags" do
+      obj, _ = @data.call
+      initial = @specs.get_flags(obj)
+      @specs.set_flags(obj, 1 << 14 | 1 << 16 | initial).should == 1 << 14 | 1 << 16 | initial
+      @specs.get_flags(obj).should == 1 << 14 | 1 << 16 | initial
+      @specs.set_flags(obj, initial).should == initial
+    end
+
+    it "supports copying the flags from one object over to the other" do
+      obj1, obj2 = @data.call
+      initial = @specs.get_flags(obj1)
+      @specs.get_flags(obj2).should == initial
+      @specs.set_flags(obj1, 1 << 14 | 1 << 16 | initial)
+      @specs.get_flags(obj1).should == 1 << 14 | 1 << 16 | initial
+
+      @specs.copy_flags(obj2, obj1)
+      @specs.get_flags(obj2).should == 1 << 14 | 1 << 16 | initial
+      @specs.set_flags(obj1, initial)
+      @specs.copy_flags(obj2, obj1)
+      @specs.get_flags(obj2).should == initial
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/regexp_spec.rb b/spec/ruby/optional/capi/regexp_spec.rb
index 52aae6bb01..49ac79f5c4 100644
--- a/spec/ruby/optional/capi/regexp_spec.rb
+++ b/spec/ruby/optional/capi/regexp_spec.rb
@@ -9,12 +9,20 @@ describe "C-API Regexp function" do
 
   describe "rb_reg_new" do
     it "returns a new valid Regexp" do
-      my_re = @p.a_re
+      my_re = @p.a_re("a", 0)
       my_re.kind_of?(Regexp).should == true
       ('1a' =~ my_re).should == 1
       ('1b' =~ my_re).should == nil
       my_re.source.should == 'a'
     end
+
+    it "returns a Regexp with the given options" do
+      @p.a_re("a", 0).options == 0
+      @p.a_re("a", Regexp::IGNORECASE).options.should == Regexp::IGNORECASE
+      @p.a_re("a", Regexp::EXTENDED).options.should == Regexp::EXTENDED
+      @p.a_re("a", Regexp::EXTENDED | Regexp::IGNORECASE).options.should == Regexp::EXTENDED | Regexp::IGNORECASE
+      @p.a_re("a", Regexp::MULTILINE).options.should == Regexp::MULTILINE
+    end
   end
 
   describe "rb_reg_nth_match" do
@@ -67,5 +75,54 @@ describe "C-API Regexp function" do
       md = /c/.match('ab')
       @p.rb_backref_get.should == md
     end
+
+    it "returns MatchData when used with rb_reg_match" do
+      @p.rb_reg_match_backref_get(/a/, 'ab')[0].should == 'a'
+    end
+  end
+
+  describe "rb_backref_set" do
+    before :each do
+      @md = "foo".match(/foo/)
+      $~ = nil
+    end
+
+    it "sets the value of $~" do
+      @p.rb_backref_set(@md)
+      @p.rb_backref_get.should == @md
+      $~.should == @md
+    end
+
+    it "sets a Thread-local value" do
+      running = false
+
+      thr = Thread.new do
+        @p.rb_backref_set(@md)
+        @p.rb_backref_get.should == @md
+        $~.should == @md
+        running = true
+      end
+
+      Thread.pass while thr.status and !running
+      $~.should be_nil
+
+      thr.join
+    end
+  end
+
+  describe "rb_memcicmp" do
+    it "returns 0 for identical strings" do
+      @p.rb_memcicmp('Hello', 'Hello').should == 0
+    end
+
+    it "returns 0 for strings which only differ in case" do
+      @p.rb_memcicmp('Hello', 'HELLO').should == 0
+      @p.rb_memcicmp('HELLO', 'Hello').should == 0
+    end
+
+    it "returns the difference between the first non matching characters" do
+      @p.rb_memcicmp('Hello', 'HELLP').should == -1
+      @p.rb_memcicmp('HELLp', 'Hello').should == 1
+    end
   end
 end
diff --git a/spec/ruby/optional/capi/set_spec.rb b/spec/ruby/optional/capi/set_spec.rb
new file mode 100644
index 0000000000..3e35be0505
--- /dev/null
+++ b/spec/ruby/optional/capi/set_spec.rb
@@ -0,0 +1,96 @@
+require_relative 'spec_helper'
+
+ruby_version_is "4.0" do
+  load_extension("set")
+
+  describe "C-API Set function" do
+    before :each do
+      @s = CApiSetSpecs.new
+    end
+
+    describe "rb_set_foreach" do
+      it "calls function with each element and arg" do
+        a = []
+        @s.rb_set_foreach(Set[1, 2], 3) {|*args| a.concat(args) }
+        a.should == [1, 3, 2, 3]
+      end
+
+      it "respects function return value" do
+        a = []
+        @s.rb_set_foreach(Set[1, 2], 3) do |*args|
+          a.concat(args)
+          false
+        end
+        a.should == [1, 3]
+      end
+    end
+
+    describe "rb_set_new" do
+      it "returns a new set" do
+        @s.rb_set_new.should == Set[]
+      end
+    end
+
+    describe "rb_set_new_capa" do
+      it "returns a new set" do
+        @s.rb_set_new_capa(3).should == Set[]
+      end
+    end
+
+    describe "rb_set_lookup" do
+      it "returns whether the element is in the set" do
+        set = Set[1]
+        @s.rb_set_lookup(set, 1).should == true
+        @s.rb_set_lookup(set, 2).should == false
+      end
+    end
+
+    describe "rb_set_add" do
+      it "adds element to set" do
+        set = Set[]
+        @s.rb_set_add(set, 1).should == true
+        set.should == Set[1]
+        @s.rb_set_add(set, 2).should == true
+        set.should == Set[1, 2]
+      end
+
+      it "returns false if element is already in set" do
+        set = Set[1]
+        @s.rb_set_add(set, 1).should == false
+        set.should == Set[1]
+      end
+    end
+
+    describe "rb_set_clear" do
+      it "empties and returns self" do
+        set = Set[1]
+        @s.rb_set_clear(set).should equal(set)
+        set.should == Set[]
+      end
+    end
+
+    describe "rb_set_delete" do
+      it "removes element from set" do
+        set = Set[1, 2]
+        @s.rb_set_delete(set, 1).should == true
+        set.should == Set[2]
+        @s.rb_set_delete(set, 2).should == true
+        set.should == Set[]
+      end
+
+      it "returns false if element is not already in set" do
+        set = Set[2]
+        @s.rb_set_delete(set, 1).should == false
+        set.should == Set[2]
+      end
+    end
+
+    describe "rb_set_size" do
+      it "returns number of elements in set" do
+        @s.rb_set_size(Set[]).should == 0
+        @s.rb_set_size(Set[1]).should == 1
+        @s.rb_set_size(Set[1,2]).should == 2
+      end
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/shared/rbasic.rb b/spec/ruby/optional/capi/shared/rbasic.rb
new file mode 100644
index 0000000000..e3485d4b7b
--- /dev/null
+++ b/spec/ruby/optional/capi/shared/rbasic.rb
@@ -0,0 +1,27 @@
+describe :rbasic, shared: true do
+  before :all do
+    specs = CApiRBasicSpecs.new
+    @freeze = specs.freeze_flag
+  end
+
+  it "reports the appropriate FREEZE flag for the object when reading" do
+    obj, _ = @data.call
+    initial = @specs.get_flags(obj)
+    obj.freeze
+    (@specs.get_flags(obj) & 0xFFFF).should == (@freeze | initial) & 0xFFFF
+  end
+
+  it "supports setting the FREEZE flag" do
+    obj, _ = @data.call
+    initial = @specs.get_flags(obj)
+    @specs.set_flags(obj, @freeze | initial).should == @freeze | initial
+    obj.should.frozen?
+  end
+
+  it "supports retrieving the (meta)class" do
+    obj, _ = @data.call
+    @specs.get_klass(obj).should == obj.class
+    obj.singleton_class # ensure the singleton class exists
+    @specs.get_klass(obj).should == obj.singleton_class
+  end
+end
diff --git a/spec/ruby/optional/capi/spec_helper.rb b/spec/ruby/optional/capi/spec_helper.rb
index eda4964b69..e7abf46e6c 100644
--- a/spec/ruby/optional/capi/spec_helper.rb
+++ b/spec/ruby/optional/capi/spec_helper.rb
@@ -8,12 +8,17 @@ require 'rbconfig'
 OBJDIR ||= File.expand_path("../../../ext/#{RUBY_ENGINE}/#{RUBY_VERSION}", __FILE__)
 
 def object_path
-  mkdir_p(OBJDIR)
-  OBJDIR
+  path = OBJDIR
+  if ENV['SPEC_CAPI_CXX'] == 'true'
+    path = "#{path}/cxx"
+  end
+  mkdir_p(path)
+  path
 end
 
 def compile_extension(name)
   debug = false
+  cxx = ENV['SPEC_CAPI_CXX'] == 'true'
   run_mkmf_in_process = RUBY_ENGINE == 'truffleruby'
 
   core_ext_dir = File.expand_path("../ext", __FILE__)
@@ -24,14 +29,14 @@ def compile_extension(name)
 
   ext = "#{name}_spec"
   lib = "#{object_path}/#{ext}.#{RbConfig::CONFIG['DLEXT']}"
-  ruby_header = "#{RbConfig::CONFIG['rubyhdrdir']}/ruby.h"
+  rubyhdrdir = RbConfig::CONFIG['rubyhdrdir']
+  ruby_header = "#{rubyhdrdir}/ruby.h"
+  abi_header = "#{rubyhdrdir}/ruby/internal/abi.h"
 
   if RbConfig::CONFIG["ENABLE_SHARED"] == "yes"
-    if PlatformGuard.windows?
-      libruby_so = "#{RbConfig::CONFIG['bindir']}/#{RbConfig::CONFIG['LIBRUBY_SO']}"
-    else
-      libruby_so = "#{RbConfig::CONFIG['libdir']}/#{RbConfig::CONFIG['LIBRUBY_SO']}"
-    end
+    # below is defined since 2.1, except for mswin, and maybe other platforms
+    libdirname = RbConfig::CONFIG.fetch 'libdirname', 'libdir'
+    libruby = "#{RbConfig::CONFIG[libdirname]}/#{RbConfig::CONFIG['LIBRUBY']}"
   end
 
   begin
@@ -43,7 +48,8 @@ def compile_extension(name)
     when mtime <= File.mtime("#{core_ext_dir}/rubyspec.h")
     when mtime <= File.mtime("#{spec_ext_dir}/#{ext}.c")
     when mtime <= File.mtime(ruby_header)
-    when libruby_so && mtime <= File.mtime(libruby_so)
+    when (mtime <= File.mtime(abi_header) rescue nil)
+    when libruby && mtime <= File.mtime(libruby)
     else
       return lib # up-to-date
     end
@@ -54,7 +60,11 @@ def compile_extension(name)
   Dir.mkdir(tmpdir)
   begin
     ["#{core_ext_dir}/rubyspec.h", "#{spec_ext_dir}/#{ext}.c"].each do |file|
-      cp file, "#{tmpdir}/#{File.basename(file)}"
+      if cxx and file.end_with?('.c')
+        cp file, "#{tmpdir}/#{File.basename(file, '.c')}.cpp"
+      else
+        cp file, "#{tmpdir}/#{File.basename(file)}"
+      end
     end
 
     Dir.chdir(tmpdir) do
@@ -64,11 +74,21 @@ def compile_extension(name)
         init_mkmf unless required
         create_makefile(ext, tmpdir)
       else
-        File.write("extconf.rb", "require 'mkmf'\n" +
-          "$ruby = ENV.values_at('RUBY_EXE', 'RUBY_FLAGS').join(' ')\n" +
+        # Workaround for digest C-API specs to find the ruby/digest.h header
+        # when run in the CRuby repository via make test-spec
+        if MSpecScript.instance_variable_defined?(:@testing_ruby)
+          ruby_repository_extra_include_dir = "-I#{RbConfig::CONFIG.fetch("prefix")}/#{RbConfig::CONFIG.fetch("EXTOUT")}/include"
+        end
+
+        File.write("extconf.rb", <<-RUBY)
+          require 'mkmf'
+          $ruby = ENV.values_at('RUBY_EXE', 'RUBY_FLAGS').join(' ')
           # MRI magic to consider building non-bundled extensions
-          "$extout = nil\n" +
-          "create_makefile(#{ext.inspect})\n")
+          $extout = nil
+          append_cflags '-Wno-declaration-after-statement'
+          #{"append_cflags #{ruby_repository_extra_include_dir.inspect}" if ruby_repository_extra_include_dir}
+          create_makefile(#{ext.inspect})
+        RUBY
         output = ruby_exe("extconf.rb")
         raise "extconf failed:\n#{output}" unless $?.success?
         $stderr.puts output if debug
@@ -102,13 +122,9 @@ def setup_make
 
   opts = {}
   if /(?:\A|\s)--jobserver-(?:auth|fds)=(\d+),(\d+)/ =~ make_flags
-    begin
-      r = IO.for_fd($1.to_i(10), "rb", autoclose: false)
-      w = IO.for_fd($2.to_i(10), "wb", autoclose: false)
-    rescue Errno::EBADF
-    else
-      opts[r] = r
-      opts[w] = w
+    [$1, $2].each do |fd|
+      fd = fd.to_i(10)
+      opts[fd] = fd
     end
   end
 
@@ -116,7 +132,9 @@ def setup_make
 end
 
 def load_extension(name)
-  require compile_extension(name)
+  ext_path = compile_extension(name)
+  require ext_path
+  ext_path
 rescue LoadError => e
   if %r{/usr/sbin/execerror ruby "\(ld 3 1 main ([/a-zA-Z0-9_\-.]+_spec\.so)"} =~ e.message
     system('/usr/sbin/execerror', "#{RbConfig::CONFIG["bindir"]}/ruby", "(ld 3 1 main #{$1}")
diff --git a/spec/ruby/optional/capi/string_spec.rb b/spec/ruby/optional/capi/string_spec.rb
index 469a190abd..72f20ee6a5 100644
--- a/spec/ruby/optional/capi/string_spec.rb
+++ b/spec/ruby/optional/capi/string_spec.rb
@@ -1,4 +1,5 @@
 # encoding: utf-8
+# frozen_string_literal: false
 require_relative 'spec_helper'
 require_relative '../../shared/string/times'
 
@@ -47,7 +48,7 @@ describe "C-API String function" do
   [Encoding::BINARY, Encoding::UTF_8].each do |enc|
     describe "rb_str_set_len on a #{enc.name} String" do
       before :each do
-        @str = "abcdefghij".force_encoding(enc)
+        @str = "abcdefghij".dup.force_encoding(enc)
         # Make sure to unshare the string
         @s.rb_str_modify(@str)
       end
@@ -76,7 +77,7 @@ describe "C-API String function" do
 
       it "invalidates the code range" do
         @s.rb_str_set_len(@str, 4)
-        @str.ascii_only?.should == true
+        @str.should.ascii_only?
       end
 
       it "updates the string's attributes visible in C code" do
@@ -97,6 +98,32 @@ describe "C-API String function" do
     end
   end
 
+  describe "rb_str_set_len on a UTF-16 String" do
+    before :each do
+      @str = "abcdefghij".dup.force_encoding(Encoding::UTF_16BE)
+      # Make sure to unshare the string
+      @s.rb_str_modify(@str)
+    end
+
+    it "inserts two NULL bytes at the length" do
+      @s.rb_str_set_len(@str, 4).b.should == "abcd".b
+      @s.rb_str_set_len(@str, 8).b.should == "abcd\x00\x00gh".b
+    end
+  end
+
+  describe "rb_str_set_len on a UTF-32 String" do
+    before :each do
+      @str = "abcdefghijkl".dup.force_encoding(Encoding::UTF_32BE)
+      # Make sure to unshare the string
+      @s.rb_str_modify(@str)
+    end
+
+    it "inserts four NULL bytes at the length" do
+      @s.rb_str_set_len(@str, 4).b.should == "abcd".b
+      @s.rb_str_set_len(@str, 12).b.should == "abcd\x00\x00\x00\x00ijkl".b
+    end
+  end
+
   describe "rb_str_buf_new" do
     it "returns the equivalent of an empty string" do
       buf = @s.rb_str_buf_new(10, nil)
@@ -108,7 +135,7 @@ describe "C-API String function" do
 
     it "returns a string with the given capacity" do
       buf = @s.rb_str_buf_new(256, nil)
-      @s.rb_str_capacity(buf).should == 256
+      @s.rb_str_capacity(buf).should >= 256
     end
 
     it "returns a string that can be appended to" do
@@ -158,6 +185,28 @@ describe "C-API String function" do
     end
   end
 
+  describe "rb_str_tmp_new" do
+    it "returns a hidden string (RBasic->klass is NULL)" do
+      @s.rb_str_tmp_new_klass(4).should == false
+    end
+
+    it "returns a new String object filled with \\0 bytes" do
+      lens = [4]
+
+      ruby_version_is "4.0" do
+        lens << 100
+      end
+
+      lens.each do |len|
+        s = @s.rb_str_tmp_new(len)
+        s.encoding.should == Encoding::BINARY
+        s.bytesize.should == len
+        s.size.should == len
+        s.should == "\x00" * len
+      end
+    end
+  end
+
   describe "rb_str_new" do
     it "creates a new String with BINARY Encoding" do
       @s.rb_str_new("", 0).encoding.should == Encoding::BINARY
@@ -167,10 +216,6 @@ describe "C-API String function" do
       @s.rb_str_new("hello", 3).should == "hel"
     end
 
-    it "returns a non-tainted string" do
-      @s.rb_str_new("hello", 5).tainted?.should == false
-    end
-
     it "returns an empty string if len is 0" do
       @s.rb_str_new("hello", 0).should == ""
     end
@@ -195,16 +240,30 @@ describe "C-API String function" do
 
   describe "rb_usascii_str_new" do
     it "creates a new String with US-ASCII Encoding from a char buffer of len characters" do
-      str = "abc".force_encoding("us-ascii")
+      str = "abc".dup.force_encoding("us-ascii")
       result = @s.rb_usascii_str_new("abcdef", 3)
       result.should == str
       result.encoding.should == Encoding::US_ASCII
     end
   end
 
+  describe "rb_usascii_str_new_lit" do
+    it "returns a US-ASCII string of the correct characters" do
+      str = @s.rb_usascii_str_new_lit
+      str.should == "nokogiri"
+      str.encoding.should == Encoding::US_ASCII
+    end
+
+    it "returns US-ASCII string for non-US-ASCII string literal" do
+      str = @s.rb_usascii_str_new_lit_non_ascii
+      str.should == "r\xC3\xA9sum\xC3\xA9".dup.force_encoding(Encoding::US_ASCII)
+      str.encoding.should == Encoding::US_ASCII
+    end
+  end
+
   describe "rb_usascii_str_new_cstr" do
     it "creates a new String with US-ASCII Encoding" do
-      str = "abc".force_encoding("us-ascii")
+      str = "abc".dup.force_encoding("us-ascii")
       result = @s.rb_usascii_str_new_cstr("abc")
       result.should == str
       result.encoding.should == Encoding::US_ASCII
@@ -272,8 +331,8 @@ describe "C-API String function" do
       str2 = @s.rb_str_new4 str1
       str1.should == str2
       str1.should equal(str2)
-      str1.frozen?.should == true
-      str2.frozen?.should == true
+      str1.should.frozen?
+      str2.should.frozen?
     end
 
     it "returns a frozen copy of the string" do
@@ -281,7 +340,7 @@ describe "C-API String function" do
       str2 = @s.rb_str_new4 str1
       str1.should == str2
       str1.should_not equal(str2)
-      str2.frozen?.should == true
+      str2.should.frozen?
     end
   end
 
@@ -305,22 +364,6 @@ describe "C-API String function" do
     end
   end
 
-  describe "rb_tainted_str_new" do
-    it "creates a new tainted String" do
-      newstring = @s.rb_tainted_str_new("test", 4)
-      newstring.should == "test"
-      newstring.tainted?.should be_true
-    end
-  end
-
-  describe "rb_tainted_str_new2" do
-    it "creates a new tainted String" do
-      newstring = @s.rb_tainted_str_new2("test")
-      newstring.should == "test"
-      newstring.tainted?.should be_true
-    end
-  end
-
   describe "rb_str_append" do
     it "appends a string to another string" do
       @s.rb_str_append("Hello", " Goodbye").should == "Hello Goodbye"
@@ -346,6 +389,14 @@ describe "C-API String function" do
     it_behaves_like :string_times, :rb_str_times, -> str, times { @s.rb_str_times(str, times) }
   end
 
+  describe "rb_str_buf_append" do
+    it "concatenates a string to another string" do
+      str = "Your house "
+      @s.rb_str_buf_append(str, "is on fire?").should.equal?(str)
+      str.should == "Your house is on fire?"
+    end
+  end
+
   describe "rb_str_buf_cat" do
     it "concatenates a C string to a ruby string" do
       @s.rb_str_buf_cat("Your house is on fire").should == "Your house is on fire?"
@@ -364,6 +415,26 @@ describe "C-API String function" do
     end
   end
 
+  describe "rb_str_cat_cstr" do
+    it "concatenates a C string literal to a ruby string" do
+      @s.rb_str_cat_cstr_constant("Your house is on fire").should == "Your house is on fire?"
+    end
+
+    it "concatenates a variable C string to a ruby string" do
+      @s.rb_str_cat_cstr("Your house is on fire", "?").should == "Your house is on fire?"
+    end
+  end
+
+  describe "rb_enc_str_buf_cat" do
+    it "concatenates a C string literal to a ruby string with the given encoding" do
+      input = "hello ".dup.force_encoding(Encoding::US_ASCII)
+      result = @s.rb_enc_str_buf_cat(input, "résumé", Encoding::UTF_8)
+      result.should == "hello résumé"
+      result.encoding.should == Encoding::UTF_8
+      result.object_id.should == input.object_id
+    end
+  end
+
   describe "rb_str_cmp" do
     it "returns 0 if two strings are identical" do
       @s.rb_str_cmp("ppp", "ppp").should == 0
@@ -386,6 +457,20 @@ describe "C-API String function" do
     end
   end
 
+  describe "rb_str_strlen" do
+    it 'returns 0 as the length of an empty string' do
+      @s.rb_str_strlen('').should == 0
+    end
+
+    it 'returns the number of characters in a string' do
+      @s.rb_str_strlen('hello').should == 5
+    end
+
+    it 'returns the number of characters in a string with multi-byte characters' do
+      @s.rb_str_strlen('こんにちは').should == 5
+    end
+  end
+
   describe "rb_str_split" do
     it "splits strings over a splitter" do
       @s.rb_str_split("Hello,Goodbye").should == ["Hello", "Goodbye"]
@@ -438,8 +523,8 @@ describe "C-API String function" do
 
   describe "rb_str_subseq" do
     it "returns a byte-indexed substring" do
-      str = "\x00\x01\x02\x03\x04".force_encoding("binary")
-      @s.rb_str_subseq(str, 1, 2).should == "\x01\x02".force_encoding("binary")
+      str = "\x00\x01\x02\x03\x04".dup.force_encoding("binary")
+      @s.rb_str_subseq(str, 1, 2).should == "\x01\x02".dup.force_encoding("binary")
     end
   end
 
@@ -509,6 +594,40 @@ describe "C-API String function" do
       end
       chars.should == [55, 48, 227, 131, 145, 227, 130, 175]
     end
+
+    it "returns a pointer which can be cast and used as another type" do
+      s = "70パク".
+        encode(Encoding::UTF_16LE).
+        force_encoding(Encoding::UTF_16LE).
+        encode(Encoding::UTF_8)
+
+      ints = []
+      @s.RSTRING_PTR_iterate_uint32(s) do |i|
+        ints << i
+      end
+      ints.should == s.unpack('LL')
+    end
+
+    it "allows a short memcpy to the string which may be converted to a single write operation by the compiler" do
+      str = "        "
+      @s.RSTRING_PTR_short_memcpy(str).should == "Infinity"
+    end
+
+    it "allows read() to update the string contents" do
+      filename = fixture(__FILE__, "read.txt")
+      str = ""
+      capacities = @s.RSTRING_PTR_read(str, filename)
+      capacities[0].should >= 30
+      capacities[1].should >= 53
+      capacities[0].should < capacities[1]
+      str.should == "fixture file contents to test read() with RSTRING_PTR"
+    end
+
+    it "terminates the string with at least (encoding min length) \\0 bytes" do
+      @s.RSTRING_PTR_null_terminate("abc", 1).should == "\x00"
+      @s.RSTRING_PTR_null_terminate("abc".encode("UTF-16BE"), 2).should == "\x00\x00"
+      @s.RSTRING_PTR_null_terminate("abc".encode("UTF-32BE"), 4).should == "\x00\x00\x00\x00"
+    end
   end
 
   describe "RSTRING_LEN" do
@@ -558,41 +677,42 @@ describe "C-API String function" do
   end
 
   describe "SafeStringValue" do
-    it "raises for tained string when $SAFE is 1" do
-      begin
-        Thread.new {
-          $SAFE = 1
-          -> {
-            @s.SafeStringValue("str".taint)
-          }.should raise_error(SecurityError)
-        }.join
-      ensure
-        $SAFE = 0
-      end
-    end
+  end
 
-    it_behaves_like :string_value_macro, :SafeStringValue
+  describe "rb_str_modify" do
+    it "raises an error if the string is frozen" do
+      -> { @s.rb_str_modify("frozen".freeze) }.should raise_error(FrozenError)
+    end
   end
 
   describe "rb_str_modify_expand" do
     it "grows the capacity to bytesize + expand, not changing the bytesize" do
       str = @s.rb_str_buf_new(256, "abcd")
-      @s.rb_str_capacity(str).should == 256
+      @s.rb_str_capacity(str).should >= 256
 
       @s.rb_str_set_len(str, 3)
       str.bytesize.should == 3
       @s.RSTRING_LEN(str).should == 3
-      @s.rb_str_capacity(str).should == 256
+      @s.rb_str_capacity(str).should >= 256
 
       @s.rb_str_modify_expand(str, 4)
       str.bytesize.should == 3
       @s.RSTRING_LEN(str).should == 3
-      @s.rb_str_capacity(str).should == 7
+      @s.rb_str_capacity(str).should >= 7
 
       @s.rb_str_modify_expand(str, 1024)
       str.bytesize.should == 3
       @s.RSTRING_LEN(str).should == 3
-      @s.rb_str_capacity(str).should == 1027
+      @s.rb_str_capacity(str).should >= 1027
+
+      @s.rb_str_modify_expand(str, 1)
+      str.bytesize.should == 3
+      @s.RSTRING_LEN(str).should == 3
+      @s.rb_str_capacity(str).should >= 4
+    end
+
+    it "raises an error if the string is frozen" do
+      -> { @s.rb_str_modify_expand("frozen".freeze, 10) }.should raise_error(FrozenError)
     end
   end
 
@@ -609,8 +729,13 @@ describe "C-API String function" do
       @s.rb_str_resize_RSTRING_LEN("test", 2).should == 2
     end
 
+    it "copies the existing bytes" do
+      str = "t"
+      @s.rb_str_resize_copy(str).should == "test"
+    end
+
     it "increases the size of the string" do
-      expected = "test".force_encoding("US-ASCII")
+      expected = "test".dup.force_encoding("US-ASCII")
       str = @s.rb_str_resize(expected.dup, 12)
       str.size.should == 12
       str.bytesize.should == 12
@@ -681,10 +806,6 @@ describe :rb_external_str_new, shared: true do
     x80 = [0x80].pack('C')
     @s.send(@method, "#{x80}abc").encoding.should == Encoding::BINARY
   end
-
-  it "returns a tainted String" do
-    @s.send(@method, "abc").tainted?.should be_true
-  end
 end
 
 describe "C-API String function" do
@@ -745,11 +866,11 @@ describe "C-API String function" do
 #     it "transcodes a String to Encoding.default_internal if it is set" do
 #       Encoding.default_internal = Encoding::EUC_JP
 #
-#  -      a = "\xE3\x81\x82\xe3\x82\x8c".force_encoding("utf-8")
+#  -      a = "\xE3\x81\x82\xe3\x82\x8c".dup.force_encoding("utf-8")
 #  +      a = [0xE3, 0x81, 0x82, 0xe3, 0x82, 0x8c].pack('C6').force_encoding("utf-8")
 #         s = @s.rb_external_str_new_with_enc(a, a.bytesize, Encoding::UTF_8)
 #  -
-#  -      s.should == "\xA4\xA2\xA4\xEC".force_encoding("euc-jp")
+#  -      s.should == "\xA4\xA2\xA4\xEC".dup.force_encoding("euc-jp")
 #  +      x = [0xA4, 0xA2, 0xA4, 0xEC].pack('C4')#.force_encoding('binary')
 #  +      s.should == x
 #         s.encoding.should equal(Encoding::EUC_JP)
@@ -764,17 +885,12 @@ describe "C-API String function" do
       s.should == x
       s.encoding.should equal(Encoding::EUC_JP)
     end
-
-    it "returns a tainted String" do
-      s = @s.rb_external_str_new_with_enc("abc", 3, Encoding::US_ASCII)
-      s.tainted?.should be_true
-    end
   end
 
   describe "rb_locale_str_new" do
     it "returns a String with 'locale' encoding" do
       s = @s.rb_locale_str_new("abc", 3)
-      s.should == "abc".force_encoding(Encoding.find("locale"))
+      s.should == "abc".dup.force_encoding(Encoding.find("locale"))
       s.encoding.should equal(Encoding.find("locale"))
     end
   end
@@ -782,33 +898,37 @@ describe "C-API String function" do
   describe "rb_locale_str_new_cstr" do
     it "returns a String with 'locale' encoding" do
       s = @s.rb_locale_str_new_cstr("abc")
-      s.should == "abc".force_encoding(Encoding.find("locale"))
+      s.should == "abc".dup.force_encoding(Encoding.find("locale"))
       s.encoding.should equal(Encoding.find("locale"))
     end
   end
 
   describe "rb_str_conv_enc" do
     it "returns the original String when to encoding is not specified" do
-      a = "abc".force_encoding("us-ascii")
+      a = "abc".dup.force_encoding("us-ascii")
       @s.rb_str_conv_enc(a, Encoding::US_ASCII, nil).should equal(a)
     end
 
     it "returns the original String if a transcoding error occurs" do
-      a = [0xEE].pack('C').force_encoding("utf-8")
-      @s.rb_str_conv_enc(a, Encoding::UTF_8, Encoding::EUC_JP).should equal(a)
+      a = [0xEE].pack('C').force_encoding(Encoding::UTF_8)
+      @s.rb_str_conv_enc(a, Encoding::UTF_8, Encoding::EUC_JP).should.equal?(a)
+      a.encoding.should == Encoding::UTF_8
+
+      a = "\x80".b
+      @s.rb_str_conv_enc(a, Encoding::BINARY, Encoding::UTF_8).should.equal?(a)
+      a.encoding.should == Encoding::BINARY
     end
 
     it "returns a transcoded String" do
-      a = "\xE3\x81\x82\xE3\x82\x8C".force_encoding("utf-8")
+      a = "\xE3\x81\x82\xE3\x82\x8C".dup.force_encoding(Encoding::UTF_8)
       result = @s.rb_str_conv_enc(a, Encoding::UTF_8, Encoding::EUC_JP)
-      x = [0xA4, 0xA2, 0xA4, 0xEC].pack('C4').force_encoding('utf-8')
-      result.should == x.force_encoding("euc-jp")
-      result.encoding.should equal(Encoding::EUC_JP)
+      result.should == [0xA4, 0xA2, 0xA4, 0xEC].pack('C4').force_encoding(Encoding::EUC_JP)
+      result.encoding.should == Encoding::EUC_JP
     end
 
     describe "when the String encoding is equal to the destination encoding" do
       it "returns the original String" do
-        a = "abc".force_encoding("us-ascii")
+        a = "abc".dup.force_encoding("us-ascii")
         @s.rb_str_conv_enc(a, Encoding::US_ASCII, Encoding::US_ASCII).should equal(a)
       end
 
@@ -818,7 +938,7 @@ describe "C-API String function" do
       end
 
       it "returns the origin String if the destination encoding is BINARY" do
-        a = "abc".force_encoding("binary")
+        a = "abc".dup.force_encoding("binary")
         @s.rb_str_conv_enc(a, Encoding::US_ASCII, Encoding::BINARY).should equal(a)
       end
     end
@@ -826,7 +946,7 @@ describe "C-API String function" do
 
   describe "rb_str_conv_enc_opts" do
     it "returns the original String when to encoding is not specified" do
-      a = "abc".force_encoding("us-ascii")
+      a = "abc".dup.force_encoding("us-ascii")
       @s.rb_str_conv_enc_opts(a, Encoding::US_ASCII, nil, 0, nil).should equal(a)
     end
 
@@ -837,7 +957,7 @@ describe "C-API String function" do
     end
 
     it "returns a transcoded String" do
-      a = "\xE3\x81\x82\xE3\x82\x8C".force_encoding("utf-8")
+      a = "\xE3\x81\x82\xE3\x82\x8C".dup.force_encoding("utf-8")
       result = @s.rb_str_conv_enc_opts(a, Encoding::UTF_8, Encoding::EUC_JP, 0, nil)
       x = [0xA4, 0xA2, 0xA4, 0xEC].pack('C4').force_encoding('utf-8')
       result.should == x.force_encoding("euc-jp")
@@ -846,7 +966,7 @@ describe "C-API String function" do
 
     describe "when the String encoding is equal to the destination encoding" do
       it "returns the original String" do
-        a = "abc".force_encoding("us-ascii")
+        a = "abc".dup.force_encoding("us-ascii")
         @s.rb_str_conv_enc_opts(a, Encoding::US_ASCII,
                                 Encoding::US_ASCII, 0, nil).should equal(a)
       end
@@ -858,7 +978,7 @@ describe "C-API String function" do
       end
 
       it "returns the origin String if the destination encoding is BINARY" do
-        a = "abc".force_encoding("binary")
+        a = "abc".dup.force_encoding("binary")
         @s.rb_str_conv_enc_opts(a, Encoding::US_ASCII,
                                 Encoding::BINARY, 0, nil).should equal(a)
       end
@@ -876,7 +996,7 @@ describe "C-API String function" do
   describe "rb_str_export_locale" do
     it "returns the original String with the locale encoding" do
       s = @s.rb_str_export_locale("abc")
-      s.should == "abc".force_encoding(Encoding.find("locale"))
+      s.should == "abc".dup.force_encoding(Encoding.find("locale"))
       s.encoding.should equal(Encoding.find("locale"))
     end
   end
@@ -900,7 +1020,7 @@ describe "C-API String function" do
       result = @s.rb_str_export_to_enc(source, Encoding::UTF_8)
       source.bytes.should == [0, 255]
     end
-end
+  end
 
   describe "rb_sprintf" do
     it "replaces the parts like sprintf" do
@@ -929,9 +1049,64 @@ end
     end
 
     it "formats a TrueClass VALUE as 'true' if sign specified in format" do
-      s = 'Result: true.'
+      s = 'Result: TrueClass.'
       @s.rb_sprintf4(true.class).should == s
     end
+
+    it "formats nil using to_s if sign not specified in format" do
+      s = 'Result: .'
+      @s.rb_sprintf3(nil).should == s
+    end
+
+    it "formats nil using inspect if sign specified in format" do
+      s = 'Result: nil.'
+      @s.rb_sprintf4(nil).should == s
+    end
+
+    it "truncates a string to a supplied precision if that is shorter than the string" do
+      s = 'Result: Hel.'
+      @s.rb_sprintf5(0, 3, "Hello").should == s
+    end
+
+    it "does not truncates a string to a supplied precision if that is longer than the string" do
+      s = 'Result: Hello.'
+      @s.rb_sprintf5(0, 8, "Hello").should == s
+    end
+
+    it "pads a string to a supplied width if that is longer than the string" do
+      s = 'Result:    Hello.'
+      @s.rb_sprintf5(8, 5, "Hello").should == s
+    end
+
+    it "truncates a VALUE string to a supplied precision if that is shorter than the VALUE string" do
+      s = 'Result: Hel.'
+      @s.rb_sprintf6(0, 3, "Hello").should == s
+    end
+
+    it "does not truncates a VALUE string to a supplied precision if that is longer than the VALUE string" do
+      s = 'Result: Hello.'
+      @s.rb_sprintf6(0, 8, "Hello").should == s
+    end
+
+    it "pads a VALUE string to a supplied width if that is longer than the VALUE string" do
+      s = 'Result:    Hello.'
+      @s.rb_sprintf6(8, 5, "Hello").should == s
+    end
+
+    it "can format a nil VALUE as a pointer and gives the same output as sprintf in C" do
+      res = @s.rb_sprintf7("%p", nil);
+      res[0].should == res[1]
+    end
+
+    it "can format a string VALUE as a pointer and gives the same output as sprintf in C" do
+      res = @s.rb_sprintf7("%p", "Hello")
+      res[0].should == res[1]
+    end
+
+    it "can format a raw number a pointer and gives the same output as sprintf in C" do
+      res = @s.rb_sprintf7("%p", 0x223643);
+      res[0].should == res[1]
+    end
   end
 
   describe "rb_vsprintf" do
@@ -955,7 +1130,7 @@ end
     end
 
     it "tries to convert the passed argument to a string by calling #to_s" do
-      @s.rb_String({"bar" => "foo"}).should == '{"bar"=>"foo"}'
+      @s.rb_String({"bar" => "foo"}).should == {"bar" => "foo"}.to_s
     end
   end
 
@@ -977,4 +1152,225 @@ end
     end
 
   end
+
+  describe "rb_str_drop_bytes" do
+    it "drops N characters for an ASCII string" do
+      str = "12345678".encode("US-ASCII")
+      @s.rb_str_drop_bytes(str, 4)
+      str.should == "5678".encode("US-ASCII")
+    end
+
+    it "drop N/2 characters for a UTF-16 string" do
+      str = "12345678".encode("UTF-16LE")
+      @s.rb_str_drop_bytes(str, 4)
+      str.should == "345678".encode("UTF-16LE")
+    end
+
+    it "drop N/4 characters for a UTF-32 string" do
+      str = "12345678".encode("UTF-32LE")
+      @s.rb_str_drop_bytes(str, 4)
+      str.should == "2345678".encode("UTF-32LE")
+    end
+  end
+
+  describe "rb_utf8_str_new_static" do
+    it "returns a UTF-8 string of the correct characters and length" do
+      str = @s.rb_utf8_str_new_static
+      str.should == "nokogiri"
+      str.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  describe "rb_utf8_str_new" do
+    it "returns a UTF-8 string of the correct characters and length" do
+      str = @s.rb_utf8_str_new
+      str.should == "nokogiri"
+      str.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  describe "rb_utf8_str_new_cstr" do
+    it "returns a UTF-8 string of the correct characters and length" do
+      str = @s.rb_utf8_str_new_cstr
+      str.should == "nokogiri"
+      str.encoding.should == Encoding::UTF_8
+    end
+  end
+
+  describe "rb_str_vcatf" do
+    it "appends the message to the string" do
+      @s.rb_str_vcatf("").should == "fmt 42 7 number"
+
+      str = "test "
+      @s.rb_str_vcatf(str)
+      str.should == "test fmt 42 7 number"
+    end
+  end
+
+  describe "rb_str_catf" do
+    it "appends the message to the string" do
+      @s.rb_str_catf("").should == "fmt 41 6 number"
+
+      str = "test "
+      @s.rb_str_catf(str)
+      str.should == "test fmt 41 6 number"
+    end
+  end
+
+  describe "rb_str_locktmp" do
+    it "raises an error when trying to lock an already locked string" do
+      str = +"test"
+      @s.rb_str_locktmp(str).should == str
+      -> { @s.rb_str_locktmp(str) }.should raise_error(RuntimeError, 'temporal locking already locked string')
+    end
+
+    it "locks a string so that modifications would raise an error" do
+      str = +"test"
+      @s.rb_str_locktmp(str).should == str
+      -> { str.upcase! }.should raise_error(RuntimeError, 'can\'t modify string; temporarily locked')
+    end
+
+    ruby_version_is "4.0" do
+      it "raises FrozenError if string is frozen" do
+        str = -"rb_str_locktmp"
+        -> { @s.rb_str_locktmp(str) }.should raise_error(FrozenError)
+
+        str = +"rb_str_locktmp"
+        str.freeze
+        -> { @s.rb_str_locktmp(str) }.should raise_error(FrozenError)
+      end
+    end
+  end
+
+  describe "rb_str_unlocktmp" do
+    it "unlocks a locked string" do
+      str = +"test"
+      @s.rb_str_locktmp(str)
+      @s.rb_str_unlocktmp(str).should == str
+      str.upcase!.should == "TEST"
+    end
+
+    it "raises an error when trying to unlock an already unlocked string" do
+      -> { @s.rb_str_unlocktmp(+"test") }.should raise_error(RuntimeError, 'temporal unlocking already unlocked string')
+    end
+
+    ruby_version_is "4.0" do
+      it "raises FrozenError if string is frozen" do
+        str = -"rb_str_locktmp"
+        -> { @s.rb_str_unlocktmp(str) }.should raise_error(FrozenError)
+
+        str = +"rb_str_locktmp"
+        str.freeze
+        -> { @s.rb_str_unlocktmp(str) }.should raise_error(FrozenError)
+      end
+    end
+  end
+
+  describe "rb_enc_interned_str_cstr" do
+    it "returns a frozen string" do
+      str = "hello"
+      val = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+
+      val.should.is_a?(String)
+      val.encoding.should == Encoding::US_ASCII
+      val.should.frozen?
+    end
+
+    it "returns the same frozen string" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result1.should.equal?(result2)
+    end
+
+    it "returns different frozen strings for different encodings" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str_cstr(str, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str_cstr(str, Encoding::UTF_8)
+      result1.should_not.equal?(result2)
+    end
+
+    it "returns the same string as String#-@" do
+      @s.rb_enc_interned_str_cstr("hello", Encoding::UTF_8).should.equal?(-"hello")
+    end
+
+    ruby_bug "#20322", ""..."3.4" do
+      it "uses the default encoding if encoding is null" do
+        str = "hello"
+        val = @s.rb_enc_interned_str_cstr(str, nil)
+        val.encoding.should == Encoding::ASCII_8BIT
+      end
+    end
+  end
+
+  describe "rb_enc_interned_str" do
+    it "returns a frozen string" do
+      str = "hello"
+      val = @s.rb_enc_interned_str(str, str.bytesize, Encoding::US_ASCII)
+
+      val.should.is_a?(String)
+      val.encoding.should == Encoding::US_ASCII
+      val.should.frozen?
+    end
+
+    it "returns the same frozen string" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::US_ASCII)
+      result1.should.equal?(result2)
+    end
+
+    it "returns different frozen strings for different encodings" do
+      str = "hello"
+      result1 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::US_ASCII)
+      result2 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::UTF_8)
+      result1.should_not.equal?(result2)
+    end
+
+    it 'returns the same string when using non-ascii characters' do
+      str = 'こんにちは'
+      result1 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::UTF_8)
+      result2 = @s.rb_enc_interned_str(str, str.bytesize, Encoding::UTF_8)
+      result1.should.equal?(result2)
+    end
+
+    it "returns the same string as String#-@" do
+      str = "hello"
+      @s.rb_enc_interned_str(str, str.bytesize, Encoding::UTF_8).should.equal?(-str)
+    end
+
+    ruby_bug "#20322", ""..."3.4" do
+      it "uses the default encoding if encoding is null" do
+        str = "hello"
+        val = @s.rb_enc_interned_str(str, str.bytesize, nil)
+        val.encoding.should == Encoding::ASCII_8BIT
+      end
+    end
+  end
+
+  describe "rb_str_to_interned_str" do
+    it "returns a frozen string" do
+      str = "hello"
+      result = @s.rb_str_to_interned_str(str)
+      result.should.is_a?(String)
+      result.should.frozen?
+    end
+
+    it "returns the same frozen string" do
+      str = "hello"
+      result1 = @s.rb_str_to_interned_str(str)
+      result2 = @s.rb_str_to_interned_str(str)
+      result1.should.equal?(result2)
+    end
+
+    it "returns different frozen strings for different encodings" do
+      result1 = @s.rb_str_to_interned_str("hello".dup.force_encoding(Encoding::US_ASCII))
+      result2 = @s.rb_str_to_interned_str("hello".dup.force_encoding(Encoding::UTF_8))
+      result1.should_not.equal?(result2)
+    end
+
+    it "returns the same string as String#-@" do
+      @s.rb_str_to_interned_str("hello").should.equal?(-"hello")
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/struct_spec.rb b/spec/ruby/optional/capi/struct_spec.rb
index 6254b098a9..cc8d7f932e 100644
--- a/spec/ruby/optional/capi/struct_spec.rb
+++ b/spec/ruby/optional/capi/struct_spec.rb
@@ -62,7 +62,7 @@ describe "C-API Struct function" do
 end
 
 describe "C-API Struct function" do
-  before :each do
+  before :all do
     @s = CApiStructSpecs.new
     @struct = @s.rb_struct_define_under(CApiStructSpecs, "CAPIStructUnder", "a", "b", "c")
   end
@@ -188,9 +188,9 @@ describe "C-API Struct function" do
       -> { @s.rb_struct_aset(@struct, 3, 1) }.should raise_error(IndexError)
     end
 
-    it "raises a #{frozen_error_class} if the struct is frozen" do
+    it "raises a FrozenError if the struct is frozen" do
       @struct.freeze
-      -> { @s.rb_struct_aset(@struct, :a, 1) }.should raise_error(frozen_error_class)
+      -> { @s.rb_struct_aset(@struct, :a, 1) }.should raise_error(FrozenError)
     end
   end
 
@@ -208,4 +208,109 @@ describe "C-API Struct function" do
       @s.rb_struct_size(@struct).should == 3
     end
   end
+
+  describe "rb_struct_initialize" do
+    it "sets all members" do
+      @s.rb_struct_initialize(@struct, [1, 2, 3]).should == nil
+      @struct.a.should == 1
+      @struct.b.should == 2
+      @struct.c.should == 3
+    end
+
+    it "does not freeze the Struct instance" do
+      @s.rb_struct_initialize(@struct, [1, 2, 3]).should == nil
+      @struct.should_not.frozen?
+      @s.rb_struct_initialize(@struct, [4, 5, 6]).should == nil
+      @struct.a.should == 4
+      @struct.b.should == 5
+      @struct.c.should == 6
+    end
+
+    it "raises ArgumentError if too many values" do
+      -> { @s.rb_struct_initialize(@struct, [1, 2, 3, 4]) }.should raise_error(ArgumentError, "struct size differs")
+    end
+
+    it "treats missing values as nil" do
+      @s.rb_struct_initialize(@struct, [1, 2]).should == nil
+      @struct.a.should == 1
+      @struct.b.should == 2
+      @struct.c.should == nil
+    end
+  end
+end
+
+ruby_version_is "3.3" do
+  describe "C-API Data function" do
+    before :all do
+      @s = CApiStructSpecs.new
+      @klass = @s.rb_data_define(nil, "a", "b", "c")
+    end
+
+    describe "rb_data_define" do
+      it "returns a subclass of Data class when passed nil as the first argument" do
+        @klass.should.is_a? Class
+        @klass.superclass.should == Data
+      end
+
+      it "returns a subclass of a class when passed as the first argument" do
+        superclass = Class.new(Data)
+        klass = @s.rb_data_define(superclass, "a", "b", "c")
+
+        klass.should.is_a? Class
+        klass.superclass.should == superclass
+      end
+
+      it "creates readers for the members" do
+        obj = @klass.new(1, 2, 3)
+
+        obj.a.should == 1
+        obj.b.should == 2
+        obj.c.should == 3
+      end
+
+      it "returns the member names as Symbols" do
+        obj = @klass.new(0, 0, 0)
+
+        obj.members.should == [:a, :b, :c]
+      end
+
+      it "raises an ArgumentError if arguments contain duplicate member name" do
+        -> { @s.rb_data_define(nil, "a", "b", "a") }.should raise_error(ArgumentError)
+      end
+
+      it "raises when first argument is not a class" do
+        -> { @s.rb_data_define([], "a", "b", "c") }.should raise_error(TypeError, "wrong argument type Array (expected Class)")
+      end
+    end
+
+    describe "rb_struct_initialize" do
+      it "sets all members for a Data instance" do
+        data = @klass.allocate
+        @s.rb_struct_initialize(data, [1, 2, 3]).should == nil
+        data.a.should == 1
+        data.b.should == 2
+        data.c.should == 3
+      end
+
+      it "freezes the Data instance" do
+        data = @klass.allocate
+        @s.rb_struct_initialize(data, [1, 2, 3]).should == nil
+        data.should.frozen?
+        -> { @s.rb_struct_initialize(data, [1, 2, 3]) }.should raise_error(FrozenError)
+      end
+
+      it "raises ArgumentError if too many values" do
+        data = @klass.allocate
+        -> { @s.rb_struct_initialize(data, [1, 2, 3, 4]) }.should raise_error(ArgumentError, "struct size differs")
+      end
+
+      it "treats missing values as nil" do
+        data = @klass.allocate
+        @s.rb_struct_initialize(data, [1, 2]).should == nil
+        data.a.should == 1
+        data.b.should == 2
+        data.c.should == nil
+      end
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/symbol_spec.rb b/spec/ruby/optional/capi/symbol_spec.rb
index ddc748c8d8..12c93c9f27 100644
--- a/spec/ruby/optional/capi/symbol_spec.rb
+++ b/spec/ruby/optional/capi/symbol_spec.rb
@@ -8,6 +8,16 @@ describe "C-API Symbol function" do
     @s = CApiSymbolSpecs.new
   end
 
+  describe "SYMBOL_P" do
+    it "returns true for a Symbol" do
+      @s.SYMBOL_P(:foo).should == true
+    end
+
+    it "returns false for non-Symbols" do
+      @s.SYMBOL_P('bar').should == false
+    end
+  end
+
   describe "rb_intern" do
     it "converts a string to a symbol, uniquely" do
       @s.rb_intern("test_symbol").should == :test_symbol
@@ -51,6 +61,10 @@ describe "C-API Symbol function" do
     it "converts a symbol to a C char array" do
       @s.rb_id2name(:test_symbol).should == "test_symbol"
     end
+
+    it "returns (char*) NULL for (ID) 0" do
+      @s.rb_id2name_id_zero.should == nil
+    end
   end
 
   describe "rb_id2str" do
@@ -62,6 +76,10 @@ describe "C-API Symbol function" do
       str = "test_symbol".encode(Encoding::UTF_16LE)
       @s.rb_id2str(str.to_sym).encoding.should == Encoding::UTF_16LE
     end
+
+    it "returns (VALUE) 0 = Qfalse for (ID) 0" do
+      @s.rb_id2str_id_zero.should == false
+    end
   end
 
   describe "rb_intern_str" do
@@ -71,6 +89,19 @@ describe "C-API Symbol function" do
     end
   end
 
+  describe "rb_check_symbol_cstr" do
+    it "returns a Symbol if a Symbol already exists for the given C string" do
+      sym = :test_symbol
+      @s.rb_check_symbol_cstr('test_symbol').should == sym
+    end
+
+    it "returns nil if the Symbol does not exist yet and does not create it" do
+      str = "symbol_does_not_exist_#{Object.new.object_id}_#{rand}"
+      @s.rb_check_symbol_cstr(str).should == nil # does not create the Symbol
+      @s.rb_check_symbol_cstr(str).should == nil
+    end
+  end
+
   describe "rb_is_const_id" do
     it "returns true given a const-like symbol" do
       @s.rb_is_const_id(:Foo).should == true
@@ -130,4 +161,20 @@ describe "C-API Symbol function" do
       @s.rb_sym2str(:bacon).should == "bacon"
     end
   end
+
+  describe "rb_to_symbol" do
+    it "returns a Symbol for a Symbol" do
+      @s.rb_to_symbol(:foo).should == :foo
+    end
+
+    it "returns a Symbol for a String" do
+      @s.rb_to_symbol("foo").should == :foo
+    end
+
+    it "coerces to Symbol using to_str" do
+      o = mock('o')
+      o.should_receive(:to_str).and_return("foo")
+      @s.rb_to_symbol(o).should == :foo
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/thread_spec.rb b/spec/ruby/optional/capi/thread_spec.rb
index 8ff5b48536..117726f0e2 100644
--- a/spec/ruby/optional/capi/thread_spec.rb
+++ b/spec/ruby/optional/capi/thread_spec.rb
@@ -101,14 +101,24 @@ describe "C-API Thread function" do
     end
   end
 
+  describe "ruby_native_thread_p" do
+    it "returns non-zero for a ruby thread" do
+      @t.ruby_native_thread_p.should be_true
+    end
+
+    it "returns zero for a non ruby thread" do
+      @t.ruby_native_thread_p_new_thread.should be_false
+    end
+  end
+
   describe "rb_thread_call_without_gvl" do
-    it "runs a C function with the global lock unlocked" do
+    it "runs a C function with the global lock unlocked and can be woken by Thread#wakeup" do
       thr = Thread.new do
         @t.rb_thread_call_without_gvl
       end
 
       # Wait until it's blocking...
-      Thread.pass while thr.status and thr.status != "sleep"
+      Thread.pass until thr.stop?
 
       # The thread status is set to sleep by rb_thread_call_without_gvl(),
       # but the thread might not be in the blocking read(2) yet, so wait a bit.
@@ -121,13 +131,47 @@ describe "C-API Thread function" do
       thr.value.should be_true
     end
 
-    it "runs a C function with the global lock unlocked amd unlocks IO with the generic RUBY_UBF_IO" do
+    platform_is_not :windows do
+      it "runs a C function with the global lock unlocked and can be woken by a signal" do
+        # Ruby signal handlers run on the main thread, so we need to reverse roles here and have a thread interrupt us
+        thr = Thread.current
+        thr.should == Thread.main
+
+        going_to_block = false
+        interrupter = Thread.new do
+          # Wait until it's blocking...
+          Thread.pass until going_to_block and thr.stop?
+
+          # The thread status is set to sleep by rb_thread_call_without_gvl(),
+          # but the thread might not be in the blocking read(2) yet, so wait a bit.
+          sleep 0.1
+
+          # Wake it up by sending a signal
+          done = false
+          prev_handler = Signal.trap(:HUP) { done = true }
+          begin
+            Process.kill :HUP, Process.pid
+            sleep 0.001 until done
+          ensure
+            Signal.trap(:HUP, prev_handler)
+          end
+        end
+
+        going_to_block = true
+        # Make sure it stopped and we got a proper value
+        @t.rb_thread_call_without_gvl.should be_true
+
+        interrupter.join
+      end
+    end
+
+    it "runs a C function with the global lock unlocked and unlocks IO with the generic RUBY_UBF_IO" do
       thr = Thread.new do
         @t.rb_thread_call_without_gvl_with_ubf_io
       end
 
       # Wait until it's blocking...
-      Thread.pass while thr.status and thr.status != "sleep"
+      Thread.pass until thr.stop?
 
       # The thread status is set to sleep by rb_thread_call_without_gvl(),
       # but the thread might not be in the blocking read(2) yet, so wait a bit.
@@ -140,4 +184,12 @@ describe "C-API Thread function" do
       thr.value.should be_true
     end
   end
+
+  ruby_version_is "4.0" do
+    describe "ruby_thread_has_gvl_p" do
+      it "returns true if the current thread has the GVL" do
+        @t.ruby_thread_has_gvl_p.should be_true
+      end
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/time_spec.rb b/spec/ruby/optional/capi/time_spec.rb
index 2c824bb566..ca5fc5952a 100644
--- a/spec/ruby/optional/capi/time_spec.rb
+++ b/spec/ruby/optional/capi/time_spec.rb
@@ -165,30 +165,28 @@ describe "CApiTimeSpecs" do
       usec.should == 500000
     end
 
-    guard -> { platform_is_not :mingw or ruby_version_is '2.5' } do
-      it "creates a timeval for a negative Fixnum" do
-        sec, usec = @s.rb_time_timeval(-1232141421)
-        sec.should be_kind_of(Integer)
-        sec.should == -1232141421
-        usec.should be_kind_of(Integer)
-        usec.should == 0
-      end
+    it "creates a timeval for a negative Fixnum" do
+      sec, usec = @s.rb_time_timeval(-1232141421)
+      sec.should be_kind_of(Integer)
+      sec.should == -1232141421
+      usec.should be_kind_of(Integer)
+      usec.should == 0
+    end
 
-      it "creates a timeval for a negative Float" do
-        sec, usec = @s.rb_time_timeval(-1.5)
-        sec.should be_kind_of(Integer)
-        sec.should == -2
-        usec.should be_kind_of(Integer)
-        usec.should == 500000
-      end
+    it "creates a timeval for a negative Float" do
+      sec, usec = @s.rb_time_timeval(-1.5)
+      sec.should be_kind_of(Integer)
+      sec.should == -2
+      usec.should be_kind_of(Integer)
+      usec.should == 500000
+    end
 
-      it "creates a timeval for a negative Rational" do
-        sec, usec = @s.rb_time_timeval(Rational(-3, 2))
-        sec.should be_kind_of(Integer)
-        sec.should == -2
-        usec.should be_kind_of(Integer)
-        usec.should == 500000
-      end
+    it "creates a timeval for a negative Rational" do
+      sec, usec = @s.rb_time_timeval(Rational(-3, 2))
+      sec.should be_kind_of(Integer)
+      sec.should == -2
+      usec.should be_kind_of(Integer)
+      usec.should == 500000
     end
 
     it "creates a timeval from a Time object" do
@@ -224,30 +222,28 @@ describe "CApiTimeSpecs" do
       nsec.should == 500000000
     end
 
-    guard -> { platform_is_not :mingw or ruby_version_is '2.5' } do
-      it "creates a timespec for a negative Fixnum" do
-        sec, nsec = @s.rb_time_timespec(-1232141421)
-        sec.should be_kind_of(Integer)
-        sec.should == -1232141421
-        nsec.should be_kind_of(Integer)
-        nsec.should == 0
-      end
+    it "creates a timespec for a negative Fixnum" do
+      sec, nsec = @s.rb_time_timespec(-1232141421)
+      sec.should be_kind_of(Integer)
+      sec.should == -1232141421
+      nsec.should be_kind_of(Integer)
+      nsec.should == 0
+    end
 
-      it "creates a timespec for a negative Float" do
-        sec, nsec = @s.rb_time_timespec(-1.5)
-        sec.should be_kind_of(Integer)
-        sec.should == -2
-        nsec.should be_kind_of(Integer)
-        nsec.should == 500000000
-      end
+    it "creates a timespec for a negative Float" do
+      sec, nsec = @s.rb_time_timespec(-1.5)
+      sec.should be_kind_of(Integer)
+      sec.should == -2
+      nsec.should be_kind_of(Integer)
+      nsec.should == 500000000
+    end
 
-      it "creates a timespec for a negative Rational" do
-        sec, nsec = @s.rb_time_timespec(Rational(-3, 2))
-        sec.should be_kind_of(Integer)
-        sec.should == -2
-        nsec.should be_kind_of(Integer)
-        nsec.should == 500000000
-      end
+    it "creates a timespec for a negative Rational" do
+      sec, nsec = @s.rb_time_timespec(Rational(-3, 2))
+      sec.should be_kind_of(Integer)
+      sec.should == -2
+      nsec.should be_kind_of(Integer)
+      nsec.should == 500000000
     end
 
     it "creates a timespec from a Time object" do
@@ -287,6 +283,11 @@ describe "CApiTimeSpecs" do
       -> { @s.rb_time_timespec_new(1447087832, 476451125, 86400) }.should raise_error(ArgumentError)
       -> { @s.rb_time_timespec_new(1447087832, 476451125, -86400) }.should raise_error(ArgumentError)
     end
+
+    it "doesn't call Time.at directly" do
+      Time.should_not_receive(:at)
+      @s.rb_time_timespec_new(1447087832, 476451125, 32400).should be_kind_of(Time)
+    end
   end
 
   describe "rb_timespec_now" do
diff --git a/spec/ruby/optional/capi/tracepoint_spec.rb b/spec/ruby/optional/capi/tracepoint_spec.rb
new file mode 100644
index 0000000000..2043b7c941
--- /dev/null
+++ b/spec/ruby/optional/capi/tracepoint_spec.rb
@@ -0,0 +1,56 @@
+require_relative 'spec_helper'
+
+load_extension("tracepoint")
+
+describe "CApiTracePointSpecs" do
+  before :each do
+    @s = CApiTracePointSpecs.new
+  end
+
+  after :each do
+    @trace.disable if @trace and @trace.enabled?
+  end
+
+  describe "rb_tracepoint_new" do
+    it "returns a tracepoint object" do
+      @trace = @s.rb_tracepoint_new(7)
+      @trace.should be_an_instance_of(TracePoint)
+      @trace.should_not.enabled?
+    end
+
+    it "traces lines when given RUBY_EVENT_LINE" do
+      @trace = @s.rb_tracepoint_new(8)
+      @trace.enable
+      @s.callback_called?.should == 8
+    end
+  end
+
+  describe "rb_tracepoint_disable" do
+    it "disables an enabled TracePoint" do
+      @trace = @s.rb_tracepoint_new(9)
+      @trace.should_not.enabled?
+      @trace.enable
+      @trace.should.enabled?
+      @s.rb_tracepoint_disable(@trace).should == false
+      @trace.should_not.enabled?
+    end
+  end
+
+  describe "rb_tracepoint_enable" do
+    it "enables a disabled TracePoint" do
+      @trace = @s.rb_tracepoint_new(10)
+      @trace.should_not.enabled?
+      @s.rb_tracepoint_enable(@trace).should == true
+      @trace.should.enabled?
+    end
+  end
+
+  describe "rb_tracepoint_enabled_p" do
+    it "returns correct enabled status" do
+      @trace = @s.rb_tracepoint_new(11)
+      @s.rb_tracepoint_enabled_p(@trace).should == false
+      @trace.enable
+      @s.rb_tracepoint_enabled_p(@trace).should == true
+    end
+  end
+end
diff --git a/spec/ruby/optional/capi/typed_data_spec.rb b/spec/ruby/optional/capi/typed_data_spec.rb
index da56a050fd..6d1398a1a0 100644
--- a/spec/ruby/optional/capi/typed_data_spec.rb
+++ b/spec/ruby/optional/capi/typed_data_spec.rb
@@ -57,4 +57,44 @@ describe "CApiWrappedTypedStruct" do
       @s.typed_get_struct_data_ptr(a).should == 1024
     end
   end
+
+  describe "rb_check_type" do
+    it "raises an exception when checking typed data objects" do
+      -> {
+        a = @s.typed_wrap_struct(1024)
+        @s.rb_check_type(a, a)
+      }.should raise_error(TypeError) { |e|
+        e.message.should == 'wrong argument type Object (expected Data)'
+      }
+    end
+  end
+
+  describe "rb_check_typeddata" do
+    it "returns data pointer when the struct has the given type" do
+      a = @s.typed_wrap_struct(1024)
+      @s.rb_check_typeddata_same_type(a).should == true
+    end
+
+    it "returns data pointer when the parent struct has the given type" do
+      a = @s.typed_wrap_struct(1024)
+      @s.rb_check_typeddata_same_type_parent(a).should == true
+    end
+
+    it "raises an error for different types" do
+      a = @s.typed_wrap_struct(1024)
+      -> { @s.rb_check_typeddata_different_type(a) }.should raise_error(TypeError)
+    end
+  end
+
+  describe "RTYPEDDATA_P" do
+    it "returns true for a typed data" do
+      a = @s.typed_wrap_struct(1024)
+      @s.RTYPEDDATA_P(a).should == true
+    end
+
+    it "returns false for an untyped data object" do
+      a = @s.untyped_wrap_struct(1024)
+      @s.RTYPEDDATA_P(a).should == false
+    end
+  end
 end
diff --git a/spec/ruby/optional/capi/util_spec.rb b/spec/ruby/optional/capi/util_spec.rb
index ee48e2e0ea..6cf064bf97 100644
--- a/spec/ruby/optional/capi/util_spec.rb
+++ b/spec/ruby/optional/capi/util_spec.rb
@@ -15,8 +15,9 @@ describe "C-API Util function" do
     end
 
     it "assigns the required arguments scanned" do
-      @o.rb_scan_args([1, 2], "2", 2, @acc).should == 2
-      ScratchPad.recorded.should == [1, 2]
+      obj = Object.new
+      @o.rb_scan_args([obj, 2], "2", 2, @acc).should == 2
+      ScratchPad.recorded.should == [obj, 2]
     end
 
     it "raises an ArgumentError if there are insufficient arguments" do
@@ -47,7 +48,7 @@ describe "C-API Util function" do
       ScratchPad.recorded.should == [1, 2, [3, 4]]
     end
 
-    it "assigns the required and optional arguments and and empty Array when there are no arguments to splat" do
+    it "assigns the required and optional arguments and empty Array when there are no arguments to splat" do
       @o.rb_scan_args([1, 2], "11*", 3, @acc).should == 2
       ScratchPad.recorded.should == [1, 2, []]
     end
@@ -99,13 +100,13 @@ describe "C-API Util function" do
 
     it "assigns Hash arguments" do
       h = {a: 1, b: 2}
-      @o.rb_scan_args([h], "0:", 1, @acc).should == 0
+      @o.rb_scan_args([h], "k0:", 1, @acc).should == 0
       ScratchPad.recorded.should == [h]
     end
 
     it "assigns required and Hash arguments" do
       h = {a: 1, b: 2}
-      @o.rb_scan_args([1, h], "1:", 2, @acc).should == 1
+      @o.rb_scan_args([1, h], "k1:", 2, @acc).should == 1
       ScratchPad.recorded.should == [1, h]
     end
 
@@ -114,9 +115,11 @@ describe "C-API Util function" do
       ScratchPad.recorded.should == [1, nil]
     end
 
-    it "assigns required and Hash arguments with nil Hash" do
-      @o.rb_scan_args([1, nil], "1:", 2, @acc).should == 1
-      ScratchPad.recorded.should == [1, nil]
+    it "rejects the use of nil as a hash" do
+      -> {
+        @o.rb_scan_args([1, nil], "1:", 2, @acc).should == 1
+      }.should raise_error(ArgumentError)
+      ScratchPad.recorded.should == []
     end
 
     it "assigns required and optional arguments with no hash argument given" do
@@ -124,33 +127,41 @@ describe "C-API Util function" do
       ScratchPad.recorded.should == [1, 7, 4]
     end
 
+    it "assigns optional arguments with no hash argument given" do
+      @o.rb_scan_args([1, 7], "02:", 3, @acc).should == 2
+      ScratchPad.recorded.should == [1, 7, nil]
+    end
+
+    it "assigns optional arguments with no hash argument given and rejects the use of optional nil argument as a hash" do
+      -> {
+        @o.rb_scan_args([1, nil], "02:", 3, @acc).should == 2
+      }.should_not complain
+
+      ScratchPad.recorded.should == [1, nil, nil]
+    end
+
     it "assigns required, optional, splat, post-splat, Hash and block arguments" do
       h = {a: 1, b: 2}
-      @o.rb_scan_args([1, 2, 3, 4, 5, h], "11*1:&", 6, @acc, &@prc).should == 5
+      @o.rb_scan_args([1, 2, 3, 4, 5, h], "k11*1:&", 6, @acc, &@prc).should == 5
       ScratchPad.recorded.should == [1, 2, [3, 4], 5, h, @prc]
     end
 
-    # r43934
-    it "rejects non-keyword arguments" do
+    it "does not reject non-symbol keys in keyword arguments" do
       h = {1 => 2, 3 => 4}
-      -> {
-        @o.rb_scan_args([h], "0:", 1, @acc)
-      }.should raise_error(ArgumentError)
-      ScratchPad.recorded.should == []
+      @o.rb_scan_args([h], "k0:", 1, @acc).should == 0
+      ScratchPad.recorded.should == [h]
     end
 
-    it "rejects required and non-keyword arguments" do
+    it "does not reject non-symbol keys in keyword arguments with required argument" do
       h = {1 => 2, 3 => 4}
-      -> {
-        @o.rb_scan_args([1, h], "1:", 2, @acc)
-      }.should raise_error(ArgumentError)
-      ScratchPad.recorded.should == []
+      @o.rb_scan_args([1, h], "k1:", 2, @acc).should == 1
+      ScratchPad.recorded.should == [1, h]
     end
 
-    it "considers the hash as a post argument when there is a splat" do
+    it "considers keyword arguments with non-symbol keys as keywords when using splat and post arguments" do
       h = {1 => 2, 3 => 4}
-      @o.rb_scan_args([1, 2, 3, 4, 5, h], "11*1:&", 6, @acc, &@prc).should == 6
-      ScratchPad.recorded.should == [1, 2, [3, 4, 5], h, nil, @prc]
+      @o.rb_scan_args([1, 2, 3, 4, 5, h], "k11*1:&", 6, @acc, &@prc).should == 5
+      ScratchPad.recorded.should == [1, 2, [3, 4], 5, h, @prc]
     end
   end
 
@@ -198,7 +209,7 @@ describe "C-API Util function" do
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     describe "rb_long2int" do
       it "raises a RangeError if the value is outside the range of a C int" do
         -> { @o.rb_long2int(0xffff_ffff_ffff) }.should raise_error(RangeError)
@@ -247,7 +258,37 @@ describe "C-API Util function" do
 
   describe "rb_sourceline" do
     it "returns the current ruby file" do
-      @o.rb_sourceline.should be_kind_of(Fixnum)
+      @o.rb_sourceline.should be_kind_of(Integer)
+    end
+  end
+
+  # ruby/util.h redefines strtod as a macro calling ruby_strtod
+
+  describe "strtod" do
+    it "converts a string to a double and returns the remaining string" do
+      d, s = @o.strtod("14.25test")
+      d.should == 14.25
+      s.should == "test"
+    end
+
+    it "returns 0 and the full string if there's no numerical value" do
+      d, s = @o.strtod("test")
+      d.should == 0
+      s.should == "test"
+    end
+  end
+
+  describe "ruby_strtod" do
+    it "converts a string to a double and returns the remaining string" do
+      d, s = @o.ruby_strtod("14.25test")
+      d.should == 14.25
+      s.should == "test"
+    end
+
+    it "returns 0 and the full string if there's no numerical value" do
+      d, s = @o.ruby_strtod("test")
+      d.should == 0
+      s.should == "test"
     end
   end
 
diff --git a/spec/ruby/optional/thread_safety/fixtures/classes.rb b/spec/ruby/optional/thread_safety/fixtures/classes.rb
new file mode 100644
index 0000000000..4f0ad030e5
--- /dev/null
+++ b/spec/ruby/optional/thread_safety/fixtures/classes.rb
@@ -0,0 +1,39 @@
+module ThreadSafetySpecs
+  # Returns the number of processors, rounded up so it's always a multiple of 2
+  def self.processors
+    require 'etc'
+    n = Etc.nprocessors
+    raise "expected at least 1 processor" if n < 1
+    n += 1 if n.odd? # ensure it's a multiple of 2
+    n
+  end
+
+  class Counter
+    def initialize
+      @value = 0
+      @mutex = Mutex.new
+    end
+
+    def get
+      @mutex.synchronize { @value }
+    end
+
+    def increment
+      @mutex.synchronize do
+        @value += 1
+      end
+    end
+  end
+
+  class Barrier
+    def initialize(parties)
+      @parties = parties
+      @counter = Counter.new
+    end
+
+    def wait
+      @counter.increment
+      Thread.pass until @counter.get == @parties
+    end
+  end
+end
diff --git a/spec/ruby/optional/thread_safety/hash_spec.rb b/spec/ruby/optional/thread_safety/hash_spec.rb
new file mode 100644
index 0000000000..53127fc973
--- /dev/null
+++ b/spec/ruby/optional/thread_safety/hash_spec.rb
@@ -0,0 +1,210 @@
+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Hash thread safety" do
+  it "supports concurrent #[]=" do
+    n_threads = ThreadSafetySpecs.processors
+
+    n = 1_000
+    operations = n * n_threads
+
+    h = {}
+    barrier = ThreadSafetySpecs::Barrier.new(n_threads + 1)
+
+    threads = n_threads.times.map { |t|
+      Thread.new {
+        barrier.wait
+        base = t * n
+        n.times do |j|
+          h[base+j] = t
+        end
+      }
+    }
+
+    barrier.wait
+    threads.each(&:join)
+
+    h.size.should == operations
+    h.each_pair { |key, value|
+      (key / n).should == value
+    }
+  end
+
+  # can't add a new key into hash during iteration (RuntimeError) on CRuby.
+  # Yet it's good to test this for implementations that support it.
+  guard_not -> { PlatformGuard.standard? } do
+    it "supports concurrent #[]= and #delete and iteration" do
+      n_threads = ThreadSafetySpecs.processors
+
+      n = 1_000
+      operations = n * n_threads / 2
+
+      h = {}
+      barrier1 = ThreadSafetySpecs::Barrier.new(n_threads + 2)
+      barrier2 = ThreadSafetySpecs::Barrier.new(n_threads + 1)
+
+      threads = n_threads.times.map { |t|
+        Thread.new {
+          barrier1.wait
+          base = t * n
+          n.times do |j|
+            h[base+j] = t
+          end
+
+          barrier2.wait
+          n.times do |j|
+            # delete only even keys
+            h.delete(base+j).should == t if (base+j).even?
+          end
+        }
+      }
+
+      read = true
+      reader = Thread.new {
+        barrier1.wait
+        while read
+          h.each_pair { |k,v|
+            k.should.is_a?(Integer)
+            v.should.is_a?(Integer)
+            (k / n).should == v
+          }
+        end
+      }
+
+      barrier1.wait
+      barrier2.wait
+      threads.each(&:join)
+      read = false
+      reader.join
+
+      # odd keys are left
+      h.size.should == operations
+      h.each_pair { |key, value|
+        key.should.odd?
+        (key / n).should == value
+      }
+    end
+  end
+
+  it "supports concurrent #[]= and #[]" do
+    n_threads = ThreadSafetySpecs.processors
+
+    n = 1_000
+    operations = n * n_threads / 2
+
+    h = {}
+    barrier = ThreadSafetySpecs::Barrier.new(n_threads + 1)
+
+    threads = n_threads.times.map { |t|
+      Thread.new {
+        barrier.wait
+        base = (t / 2) * n
+
+        if t.even?
+          n.times do |j|
+            k = base + j
+            h[k] = k
+          end
+        else
+          n.times do |j|
+            k = base + j
+            Thread.pass until v = h[k]
+            v.should == k
+          end
+        end
+      }
+    }
+
+    barrier.wait
+    threads.each(&:join)
+
+    h.size.should == operations
+    h.each_pair { |key, value|
+      key.should == value
+    }
+  end
+
+  it "supports concurrent #[]= and #[] with change to #compare_by_identity in the middle" do
+    n_threads = ThreadSafetySpecs.processors
+
+    n = 1_000
+    operations = n * n_threads / 2
+
+    h = {}
+    barrier = ThreadSafetySpecs::Barrier.new(n_threads + 1)
+
+    threads = n_threads.times.map { |t|
+      Thread.new {
+        barrier.wait
+        base = (t / 2) * n
+
+        if t.even?
+          n.times do |j|
+            k = base + j
+            h[k] = k
+          end
+        else
+          n.times do |j|
+            k = base + j
+            Thread.pass until v = h[k]
+            v.should == k
+          end
+        end
+      }
+    }
+
+    changer = Thread.new {
+      Thread.pass until h.size >= operations / 2
+      h.should_not.compare_by_identity?
+      h.compare_by_identity
+      h.should.compare_by_identity?
+    }
+
+    barrier.wait
+    threads.each(&:join)
+    changer.join
+
+    h.size.should == operations
+    h.each_pair { |key, value|
+      key.should == value
+    }
+  end
+
+  it "supports repeated concurrent #[]= and #delete and always returns a #size >= 0" do
+    n_threads = ThreadSafetySpecs.processors
+
+    n = 1_000
+    operations = n * n_threads / 2
+
+    h = {}
+    barrier = ThreadSafetySpecs::Barrier.new(n_threads + 1)
+    deleted = ThreadSafetySpecs::Counter.new
+
+    threads = n_threads.times.map { |t|
+      Thread.new {
+        barrier.wait
+        key = t / 2
+
+        if t.even?
+          n.times {
+            Thread.pass until h.delete(key)
+            h.size.should >= 0
+            deleted.increment
+          }
+        else
+          n.times {
+            h[key] = key
+            Thread.pass while h.key?(key)
+          }
+        end
+      }
+    }
+
+    barrier.wait
+    threads.each(&:join)
+
+    deleted.get.should == operations
+    h.size.should == 0
+    h.should.empty?
+  end
+end
diff --git a/spec/ruby/security/cve_2010_1330_spec.rb b/spec/ruby/security/cve_2010_1330_spec.rb
index fa4c756c6d..2594439550 100644
--- a/spec/ruby/security/cve_2010_1330_spec.rb
+++ b/spec/ruby/security/cve_2010_1330_spec.rb
@@ -1,7 +1,6 @@
 require_relative '../spec_helper'
 
 describe "String#gsub" do
-
   it "resists CVE-2010-1330 by raising an exception on invalid UTF-8 bytes" do
     # This original vulnerability talked about KCODE, which is no longer
     # used. Instead we are forcing encodings here. But I think the idea is the
@@ -9,7 +8,7 @@ describe "String#gsub" do
     # #gsub on a string in the UTF-8 encoding but with invalid an UTF-8 byte
     # sequence.
 
-    str = "\xF6<script>"
+    str = +"\xF6<script>"
     str.force_encoding Encoding::BINARY
     str.gsub(/</, "&lt;").should == "\xF6&lt;script>".b
     str.force_encoding Encoding::UTF_8
@@ -17,5 +16,4 @@ describe "String#gsub" do
       str.gsub(/</, "&lt;")
     }.should raise_error(ArgumentError, /invalid byte sequence in UTF-8/)
   end
-
 end
diff --git a/spec/ruby/security/cve_2013_4164_spec.rb b/spec/ruby/security/cve_2013_4164_spec.rb
index 94578cc7ce..d223b8fd5e 100644
--- a/spec/ruby/security/cve_2013_4164_spec.rb
+++ b/spec/ruby/security/cve_2013_4164_spec.rb
@@ -3,17 +3,13 @@ require_relative '../spec_helper'
 require 'json'
 
 describe "String#to_f" do
-
   it "resists CVE-2013-4164 by converting very long Strings to a Float" do
     "1.#{'1'*1000000}".to_f.should be_close(1.1111111111111112, TOLERANCE)
   end
-
 end
 
 describe "JSON.parse" do
-
   it "resists CVE-2013-4164 by converting very long Strings to a Float" do
     JSON.parse("[1.#{'1'*1000000}]").first.should be_close(1.1111111111111112, TOLERANCE)
   end
-
 end
diff --git a/spec/ruby/security/cve_2014_8080_spec.rb b/spec/ruby/security/cve_2014_8080_spec.rb
deleted file mode 100644
index 64e22cf3a7..0000000000
--- a/spec/ruby/security/cve_2014_8080_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-require_relative '../spec_helper'
-
-require 'rexml/document'
-
-describe "REXML::Document.new" do
-
-  it "resists CVE-2014-8080 by raising an exception when entity expansion has grown too large" do
-    xml = <<XML
-    <?xml version="1.0" encoding="UTF-8" ?>
-      <!DOCTYPE x [
-        <!ENTITY % x0 "xxxxxxxxxx">
-        <!ENTITY % x1 "%x0;%x0;%x0;%x0;%x0;%x0;%x0;%x0;%x0;%x0;">
-        <!ENTITY % x2 "%x1;%x1;%x1;%x1;%x1;%x1;%x1;%x1;%x1;%x1;">
-        <!ENTITY % x3 "%x2;%x2;%x2;%x2;%x2;%x2;%x2;%x2;%x2;%x2;">
-        <!ENTITY % x4 "%x3;%x3;%x3;%x3;%x3;%x3;%x3;%x3;%x3;%x3;">
-        <!ENTITY % x5 "%x4;%x4;%x4;%x4;%x4;%x4;%x4;%x4;%x4;%x4;">
-        <!ENTITY % x6 "%x5;%x5;%x5;%x5;%x5;%x5;%x5;%x5;%x5;%x5;">
-        <!ENTITY % x7 "%x6;%x6;%x6;%x6;%x6;%x6;%x6;%x6;%x6;%x6;">
-        <!ENTITY % x8 "%x7;%x7;%x7;%x7;%x7;%x7;%x7;%x7;%x7;%x7;">
-        <!ENTITY % x9 "%x8;%x8;%x8;%x8;%x8;%x8;%x8;%x8;%x8;%x8;">
-      ]>
-      <x>
-        %x9;%x9;%x9;%x9;%x9;%x9;%x9;%x9;%x9;%x9;
-      </x>
-XML
-
-    -> {
-      REXML::Document.new(xml).doctype.entities['x9'].value
-    }.should raise_error(REXML::ParseException, /entity expansion has grown too large/)
-  end
-
-end
diff --git a/spec/ruby/security/cve_2017_17742_spec.rb b/spec/ruby/security/cve_2017_17742_spec.rb
deleted file mode 100644
index 72776cb497..0000000000
--- a/spec/ruby/security/cve_2017_17742_spec.rb
+++ /dev/null
@@ -1,34 +0,0 @@
-require_relative '../spec_helper'
-
-require "webrick"
-require "stringio"
-require "net/http"
-
-describe "WEBrick" do
-  describe "resists CVE-2017-17742" do
-    it "for a response splitting headers" do
-      config = WEBrick::Config::HTTP
-      res = WEBrick::HTTPResponse.new config
-      res['X-header'] = "malicious\r\nCookie: hack"
-      io = StringIO.new
-      res.send_response io
-      io.rewind
-      res = Net::HTTPResponse.read_new(Net::BufferedIO.new(io))
-      res.code.should == '500'
-      io.string.should_not =~ /hack/
-    end
-
-    it "for a response splitting cookie headers" do
-      user_input = "malicious\r\nCookie: hack"
-      config = WEBrick::Config::HTTP
-      res = WEBrick::HTTPResponse.new config
-      res.cookies << WEBrick::Cookie.new('author', user_input)
-      io = StringIO.new
-      res.send_response io
-      io.rewind
-      res = Net::HTTPResponse.read_new(Net::BufferedIO.new(io))
-      res.code.should == '500'
-      io.string.should_not =~ /hack/
-    end
-  end
-end
diff --git a/spec/ruby/security/cve_2018_16396_spec.rb b/spec/ruby/security/cve_2018_16396_spec.rb
index e462e0022d..6f8a5d2f5d 100644
--- a/spec/ruby/security/cve_2018_16396_spec.rb
+++ b/spec/ruby/security/cve_2018_16396_spec.rb
@@ -1,21 +1,7 @@
 require_relative '../spec_helper'
 
 describe "Array#pack" do
-
-  it "resists CVE-2018-16396 by tainting output based on input" do
-    "aAZBbHhuMmPp".each_char do |f|
-      ["123456".taint].pack(f).tainted?.should be_true
-    end
-  end
-
 end
 
 describe "String#unpack" do
-
-  it "resists CVE-2018-16396 by tainting output based on input" do
-    "aAZBbHhuMm".each_char do |f|
-      "123456".taint.unpack(f).first.tainted?.should be_true
-    end
-  end
-
 end
diff --git a/spec/ruby/security/cve_2018_6914_spec.rb b/spec/ruby/security/cve_2018_6914_spec.rb
index 1eab3b84cc..f0aedb0dc6 100644
--- a/spec/ruby/security/cve_2018_6914_spec.rb
+++ b/spec/ruby/security/cve_2018_6914_spec.rb
@@ -5,56 +5,51 @@ require 'tmpdir'
 
 describe "CVE-2018-6914 is resisted by" do
   before :each do
+    @tmpdir = ENV['TMPDIR']
     @dir = tmp("CVE-2018-6914")
-    Dir.mkdir(@dir)
-    touch "#{@dir}/bar"
-
-    @traversal_path = Array.new(@dir.count('/'), '..').join('/') + @dir + '/'
-    @traversal_path.delete!(':') if platform_is(:windows)
+    Dir.mkdir(@dir, 0700)
+    ENV['TMPDIR'] = @dir
+    @dir << '/'
 
     @tempfile = nil
   end
 
   after :each do
+    ENV['TMPDIR'] = @tmpdir
     @tempfile.close! if @tempfile
     rm_r @dir
   end
 
   it "Tempfile.open by deleting separators" do
-    expect = Dir.glob(@traversal_path + '*').size
-    @tempfile = Tempfile.open([@traversal_path, 'foo'])
-    actual = Dir.glob(@traversal_path + '*').size
-    actual.should == expect
+    @tempfile = Tempfile.open(['../', 'foo'])
+    actual = @tempfile.path
+    File.absolute_path(actual).should.start_with?(@dir)
   end
 
   it "Tempfile.new by deleting separators" do
-    expect = Dir.glob(@traversal_path + '*').size
-    @tempfile = Tempfile.new(@traversal_path + 'foo')
-    actual = Dir.glob(@traversal_path + '*').size
-    actual.should == expect
+    @tempfile = Tempfile.new('../foo')
+    actual = @tempfile.path
+    File.absolute_path(actual).should.start_with?(@dir)
   end
 
   it "Tempfile.create by deleting separators" do
-    expect = Dir.glob(@traversal_path + '*').size
-    Tempfile.create(@traversal_path + 'foo') do
-      actual = Dir.glob(@traversal_path + '*').size
-      actual.should == expect
+    actual = Tempfile.create('../foo') do |t|
+      t.path
     end
+    File.absolute_path(actual).should.start_with?(@dir)
   end
 
   it "Dir.mktmpdir by deleting separators" do
-    expect = Dir.glob(@traversal_path + '*').size
-    Dir.mktmpdir(@traversal_path + 'foo') do
-      actual = Dir.glob(@traversal_path + '*').size
-      actual.should == expect
+    actual = Dir.mktmpdir('../foo') do |path|
+      path
     end
+    File.absolute_path(actual).should.start_with?(@dir)
   end
 
   it "Dir.mktmpdir with an array by deleting separators" do
-    expect = Dir.glob(@traversal_path + '*').size
-    Dir.mktmpdir([@traversal_path, 'foo']) do
-      actual = Dir.glob(@traversal_path + '*').size
-      actual.should == expect
+    actual = Dir.mktmpdir(['../', 'foo']) do |path|
+      path
     end
+    File.absolute_path(actual).should.start_with?(@dir)
   end
 end
diff --git a/spec/ruby/security/cve_2018_8778_spec.rb b/spec/ruby/security/cve_2018_8778_spec.rb
index 628159a4db..62057faa53 100644
--- a/spec/ruby/security/cve_2018_8778_spec.rb
+++ b/spec/ruby/security/cve_2018_8778_spec.rb
@@ -1,12 +1,10 @@
 require_relative '../spec_helper'
 
 describe "String#unpack" do
-
   it "resists CVE-2018-8778 by raising an exception when a position indicator is larger than a native integer" do
     pos = (1 << PlatformGuard::POINTER_SIZE) - 99
     -> {
       "0123456789".unpack("@#{pos}C10")
     }.should raise_error(RangeError, /pack length too big/)
   end
-
 end
diff --git a/spec/ruby/security/cve_2018_8780_spec.rb b/spec/ruby/security/cve_2018_8780_spec.rb
index 555ce9365c..9942e07ee2 100644
--- a/spec/ruby/security/cve_2018_8780_spec.rb
+++ b/spec/ruby/security/cve_2018_8780_spec.rb
@@ -29,17 +29,15 @@ describe "CVE-2018-8780 is resisted by" do
     }.should raise_error(ArgumentError, /(path name|string) contains null byte/)
   end
 
-  ruby_version_is "2.5" do
-    it "Dir.children by raising an exception when there is a NUL byte" do
-      -> {
-        Dir.children(@root+"\0")
-      }.should raise_error(ArgumentError, /(path name|string) contains null byte/)
-    end
+  it "Dir.children by raising an exception when there is a NUL byte" do
+    -> {
+      Dir.children(@root+"\0")
+    }.should raise_error(ArgumentError, /(path name|string) contains null byte/)
+  end
 
-    it "Dir.each_child by raising an exception when there is a NUL byte" do
-      -> {
-        Dir.each_child(@root+"\0").to_a
-      }.should raise_error(ArgumentError, /(path name|string) contains null byte/)
-    end
+  it "Dir.each_child by raising an exception when there is a NUL byte" do
+    -> {
+      Dir.each_child(@root+"\0").to_a
+    }.should raise_error(ArgumentError, /(path name|string) contains null byte/)
   end
 end
diff --git a/spec/ruby/security/cve_2019_8321_spec.rb b/spec/ruby/security/cve_2019_8321_spec.rb
index affcd00e02..a8a86e7d97 100644
--- a/spec/ruby/security/cve_2019_8321_spec.rb
+++ b/spec/ruby/security/cve_2019_8321_spec.rb
@@ -3,20 +3,18 @@ require_relative '../spec_helper'
 require 'rubygems'
 require 'rubygems/user_interaction'
 
-ruby_version_is "2.5.5" do
-  describe "CVE-2019-8321 is resisted by" do
-    it "sanitising verbose messages" do
-      ui = Class.new {
-        include Gem::UserInteraction
-      }.new
-      ui.should_receive(:say).with(".]2;nyan.")
-      verbose_before = Gem.configuration.verbose
-      begin
-        Gem.configuration.verbose = :really_verbose
-        ui.verbose("\e]2;nyan\a")
-      ensure
-        Gem.configuration.verbose = verbose_before
-      end
+describe "CVE-2019-8321 is resisted by" do
+  it "sanitising verbose messages" do
+    ui = Class.new {
+      include Gem::UserInteraction
+    }.new
+    ui.should_receive(:say).with(".]2;nyan.")
+    verbose_before = Gem.configuration.verbose
+    begin
+      Gem.configuration.verbose = :really_verbose
+      ui.verbose("\e]2;nyan\a")
+    ensure
+      Gem.configuration.verbose = verbose_before
     end
   end
 end
diff --git a/spec/ruby/security/cve_2019_8322_spec.rb b/spec/ruby/security/cve_2019_8322_spec.rb
index 04fb1a7a26..b70d78c033 100644
--- a/spec/ruby/security/cve_2019_8322_spec.rb
+++ b/spec/ruby/security/cve_2019_8322_spec.rb
@@ -5,19 +5,17 @@ require 'rubygems'
 require 'rubygems/safe_yaml'
 require 'rubygems/commands/owner_command'
 
-ruby_version_is "2.5.5" do
-  describe "CVE-2019-8322 is resisted by" do
-    it "sanitising owner names" do
-      command = Gem::Commands::OwnerCommand.new
-      def command.rubygems_api_request(*args)
-        Struct.new(:body).new("---\n- email: \"\e]2;nyan\a\"\n  handle: handle\n  id: id\n")
-      end
-      def command.with_response(response)
-        yield response
-      end
-      command.should_receive(:say).with("Owners for gem: name")
-      command.should_receive(:say).with("- .]2;nyan.")
-      command.show_owners "name"
+describe "CVE-2019-8322 is resisted by" do
+  it "sanitising owner names" do
+    command = Gem::Commands::OwnerCommand.new
+    def command.rubygems_api_request(*args)
+      Struct.new(:body).new("---\n- email: \"\e]2;nyan\a\"\n  handle: handle\n  id: id\n")
     end
+    def command.with_response(response)
+      yield response
+    end
+    command.should_receive(:say).with("Owners for gem: name")
+    command.should_receive(:say).with("- .]2;nyan.")
+    command.show_owners "name"
   end
 end
diff --git a/spec/ruby/security/cve_2019_8323_spec.rb b/spec/ruby/security/cve_2019_8323_spec.rb
index af0b270880..49a31a6682 100644
--- a/spec/ruby/security/cve_2019_8323_spec.rb
+++ b/spec/ruby/security/cve_2019_8323_spec.rb
@@ -5,34 +5,42 @@ require 'optparse'
 require 'rubygems'
 require 'rubygems/gemcutter_utilities'
 
-ruby_version_is "2.5.5" do
-  describe "CVE-2019-8323 is resisted by" do
-    describe "sanitising the body" do
-      it "for success codes" do
-        cutter = Class.new {
-          include Gem::GemcutterUtilities
-        }.new
-        response = Net::HTTPSuccess.new(nil, nil, nil)
-        def response.body
-          "\e]2;nyan\a"
-        end
-        cutter.should_receive(:say).with(".]2;nyan.")
-        cutter.with_response response
+describe "CVE-2019-8323 is resisted by" do
+  describe "sanitising the body" do
+    it "for success codes" do
+      cutter = Class.new {
+        include Gem::GemcutterUtilities
+      }.new
+      klass = if defined?(Gem::Net::HTTPSuccess)
+                Gem::Net::HTTPSuccess
+              else
+                Net::HTTPSuccess
+              end
+      response = klass.new(nil, nil, nil)
+      def response.body
+        "\e]2;nyan\a"
       end
+      cutter.should_receive(:say).with(".]2;nyan.")
+      cutter.with_response response
+    end
 
-      it "for error codes" do
-        cutter = Class.new {
-          include Gem::GemcutterUtilities
-        }.new
-        def cutter.terminate_interaction(n)
-        end
-        response = Net::HTTPNotFound.new(nil, nil, nil)
-        def response.body
-          "\e]2;nyan\a"
-        end
-        cutter.should_receive(:say).with(".]2;nyan.")
-        cutter.with_response response
+    it "for error codes" do
+      cutter = Class.new {
+        include Gem::GemcutterUtilities
+      }.new
+      def cutter.terminate_interaction(n)
+      end
+      klass = if defined?(Gem::Net::HTTPNotFound)
+                Gem::Net::HTTPNotFound
+              else
+                Net::HTTPNotFound
+              end
+      response = klass.new(nil, nil, nil)
+      def response.body
+        "\e]2;nyan\a"
       end
+      cutter.should_receive(:say).with(".]2;nyan.")
+      cutter.with_response response
     end
   end
 end
diff --git a/spec/ruby/security/cve_2019_8325_spec.rb b/spec/ruby/security/cve_2019_8325_spec.rb
index dcdbe34210..bbddb3a6ce 100644
--- a/spec/ruby/security/cve_2019_8325_spec.rb
+++ b/spec/ruby/security/cve_2019_8325_spec.rb
@@ -3,36 +3,44 @@ require_relative '../spec_helper'
 require 'rubygems'
 require 'rubygems/command_manager'
 
-ruby_version_is "2.5.5" do
-  describe "CVE-2019-8325 is resisted by" do
-    describe "sanitising error message components" do
-      it "for the 'while executing' message" do
-        manager = Gem::CommandManager.new
-        def manager.process_args(args, build_args)
-          raise StandardError, "\e]2;nyan\a"
-        end
-        def manager.terminate_interaction(n)
-        end
-        manager.should_receive(:alert_error).with("While executing gem ... (StandardError)\n    .]2;nyan.")
-        manager.run nil, nil
+describe "CVE-2019-8325 is resisted by" do
+  describe "sanitising error message components" do
+    before :each do
+      @ui = Gem::SilentUI.new
+    end
+
+    after :each do
+      @ui.close
+    end
+
+    it "for the 'while executing' message" do
+      manager = Gem::CommandManager.new
+      manager.ui = @ui
+      def manager.process_args(args, build_args)
+        raise StandardError, "\e]2;nyan\a"
       end
+      def manager.terminate_interaction(n)
+      end
+      manager.should_receive(:alert_error).with("While executing gem ... (StandardError)\n    .]2;nyan.")
+      manager.run nil, nil
+    end
 
-      it "for the 'invalid option' message" do
-        manager = Gem::CommandManager.new
-        def manager.terminate_interaction(n)
-        end
-        manager.should_receive(:alert_error).with("Invalid option: --.]2;nyan.. See 'gem --help'.")
-        manager.process_args ["--\e]2;nyan\a"], nil
+    it "for the 'invalid option' message" do
+      manager = Gem::CommandManager.new
+      def manager.terminate_interaction(n)
       end
+      manager.should_receive(:alert_error).with("Invalid option: --.]2;nyan.. See 'gem --help'.")
+      manager.process_args ["--\e]2;nyan\a"], nil
+    end
 
-      it "for the 'loading command' message" do
-        manager = Gem::CommandManager.new
-        def manager.require(x)
-          raise 'foo'
-        end
-        manager.should_receive(:alert_error).with("Loading command: .]2;nyan. (RuntimeError)\n\tfoo")
-        manager.send :load_and_instantiate, "\e]2;nyan\a"
+    it "for the 'loading command' message" do
+      manager = Gem::CommandManager.new
+      manager.ui = @ui
+      def manager.require(x)
+        raise 'foo'
       end
+      manager.should_receive(:alert_error).with("Loading command: .]2;nyan. (RuntimeError)\n\tfoo")
+      manager.send :load_and_instantiate, "\e]2;nyan\a"
     end
   end
 end
diff --git a/spec/ruby/security/cve_2020_10663_spec.rb b/spec/ruby/security/cve_2020_10663_spec.rb
new file mode 100644
index 0000000000..c44a13a0dd
--- /dev/null
+++ b/spec/ruby/security/cve_2020_10663_spec.rb
@@ -0,0 +1,49 @@
+require_relative '../spec_helper'
+
+ruby_version_is ""..."4.0" do
+  require 'json'
+
+  module JSONSpecs
+    class MyClass
+      def initialize(foo)
+        @foo = foo
+      end
+
+      def self.json_create(hash)
+        new(*hash['args'])
+      end
+
+      def to_json(*args)
+        { 'json_class' => self.class.name, 'args' => [ @foo ] }.to_json(*args)
+      end
+    end
+  end
+
+  guard -> {
+    JSON.const_defined?(:Pure) or
+    version_is(JSON::VERSION, '2.3.0')
+  } do
+    describe "CVE-2020-10663 is resisted by" do
+      it "only creating custom objects if passed create_additions: true or using JSON.load" do
+        obj = JSONSpecs::MyClass.new("bar")
+        JSONSpecs::MyClass.should.json_creatable?
+        json = JSON.dump(obj)
+
+        JSON.parse(json, create_additions: true).class.should == JSONSpecs::MyClass
+        JSON(json, create_additions: true).class.should == JSONSpecs::MyClass
+        if version_is(JSON::VERSION, '2.8.0')
+          warning = /\Wcreate_additions:\s*true\W\s+is\s+deprecated/
+        else
+          warning = ''
+        end
+        -> {
+          JSON.load(json).class.should == JSONSpecs::MyClass
+        }.should output_to_fd(warning, STDERR)
+
+        JSON.parse(json).class.should == Hash
+        JSON.parse(json, nil).class.should == Hash
+        JSON(json).class.should == Hash
+      end
+    end
+  end
+end
diff --git a/spec/ruby/security/cve_2024_49761_spec.rb b/spec/ruby/security/cve_2024_49761_spec.rb
new file mode 100644
index 0000000000..c66b438eef
--- /dev/null
+++ b/spec/ruby/security/cve_2024_49761_spec.rb
@@ -0,0 +1,7 @@
+require_relative '../spec_helper'
+
+describe "CVE-2024-49761 is resisted by" do
+  it "the Regexp implementation handling that regular expression in linear time" do
+    Regexp.linear_time?(/&#0*((?:\d+)|(?:x[a-fA-F0-9]+));/).should == true
+  end
+end
diff --git a/spec/ruby/shared/enumerable/minmax.rb b/spec/ruby/shared/enumerable/minmax.rb
new file mode 100644
index 0000000000..8af2626d2a
--- /dev/null
+++ b/spec/ruby/shared/enumerable/minmax.rb
@@ -0,0 +1,24 @@
+describe :enumerable_minmax, shared: true do
+  it "min should return the minimum element" do
+    @enum.minmax.should == [4, 10]
+    @strs.minmax.should == ["1010", "60"]
+  end
+
+  it "returns the minimum when using a block rule" do
+    @enum.minmax {|a,b| b <=> a }.should == [10, 4]
+    @strs.minmax {|a,b| a.length <=> b.length }.should == ["2", "55555"]
+  end
+
+  it "returns [nil, nil] for an empty Enumerable" do
+    @empty_enum.minmax.should == [nil, nil]
+  end
+
+  it "raises a NoMethodError for elements without #<=>" do
+    -> { @incomparable_enum.minmax }.should raise_error(NoMethodError)
+  end
+
+  it "raises an ArgumentError when elements are incompatible" do
+    -> { @incompatible_enum.minmax }.should raise_error(ArgumentError)
+    -> { @enum.minmax{ |a, b| nil } }.should raise_error(ArgumentError)
+  end
+end
diff --git a/spec/ruby/shared/enumerator/enum_for.rb b/spec/ruby/shared/enumerator/enum_for.rb
deleted file mode 100644
index 9030ffbd7d..0000000000
--- a/spec/ruby/shared/enumerator/enum_for.rb
+++ /dev/null
@@ -1,50 +0,0 @@
-describe :enum_for, shared: true do
-  it "is defined in Kernel" do
-    Kernel.method_defined?(@method).should be_true
-  end
-
-  it "returns a new enumerator" do
-    "abc".send(@method).should be_an_instance_of(Enumerator)
-  end
-
-  it "defaults the first argument to :each" do
-    enum = [1,2].send(@method)
-    enum.map { |v| v }.should == [1,2].each { |v| v }
-  end
-
-  it "exposes multi-arg yields as an array" do
-    o = Object.new
-    def o.each
-      yield :a
-      yield :b1, :b2
-      yield [:c]
-      yield :d1, :d2
-      yield :e1, :e2, :e3
-    end
-
-    enum = o.send(@method)
-    enum.next.should == :a
-    enum.next.should == [:b1, :b2]
-    enum.next.should == [:c]
-    enum.next.should == [:d1, :d2]
-    enum.next.should == [:e1, :e2, :e3]
-  end
-
-  it "uses the passed block's value to calculate the size of the enumerator" do
-    Object.new.enum_for { 100 }.size.should == 100
-  end
-
-  it "defers the evaluation of the passed block until #size is called" do
-    ScratchPad.record []
-
-    enum = Object.new.enum_for do
-      ScratchPad << :called
-      100
-    end
-
-    ScratchPad.recorded.should be_empty
-
-    enum.size
-    ScratchPad.recorded.should == [:called]
-  end
-end
diff --git a/spec/ruby/shared/enumerator/with_index.rb b/spec/ruby/shared/enumerator/with_index.rb
deleted file mode 100644
index 89f40070e0..0000000000
--- a/spec/ruby/shared/enumerator/with_index.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :enum_with_index, shared: true do
-
-  require_relative '../../fixtures/enumerator/classes'
-
-  before :each do
-    @origin = [1, 2, 3, 4]
-    @enum = @origin.to_enum
-  end
-
-  it "passes each element and its index to block" do
-    a = []
-    @enum.send(@method) { |o, i| a << [o, i] }
-    a.should == [[1, 0], [2, 1], [3, 2], [4, 3]]
-  end
-
-  it "returns the object being enumerated when given a block" do
-    @enum.send(@method) { |o, i| :glark }.should equal(@origin)
-  end
-
-  it "binds splat arguments properly" do
-    acc = []
-    @enum.send(@method) { |*b| c,d = b; acc << c; acc << d }
-    [1, 0, 2, 1, 3, 2, 4, 3].should == acc
-  end
-
-  it "returns an enumerator if no block is supplied" do
-    ewi = @enum.send(@method)
-    ewi.should be_an_instance_of(Enumerator)
-    ewi.to_a.should == [[1, 0], [2, 1], [3, 2], [4, 3]]
-  end
-end
diff --git a/spec/ruby/shared/enumerator/with_object.rb b/spec/ruby/shared/enumerator/with_object.rb
deleted file mode 100644
index c2e3a79366..0000000000
--- a/spec/ruby/shared/enumerator/with_object.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :enum_with_object, shared: true do
-  before :each do
-    @enum = [:a, :b].to_enum
-    @memo = ''
-    @block_params = @enum.send(@method, @memo).to_a
-  end
-
-  it "receives an argument" do
-    @enum.method(@method).arity.should == 1
-  end
-
-  context "with block" do
-    it "returns the given object" do
-      ret = @enum.send(@method, @memo) do |elm, memo|
-        # nothing
-      end
-      ret.should equal(@memo)
-    end
-
-    context "the block parameter" do
-      it "passes each element to first parameter" do
-        @block_params[0][0].should equal(:a)
-        @block_params[1][0].should equal(:b)
-      end
-
-      it "passes the given object to last parameter" do
-        @block_params[0][1].should equal(@memo)
-        @block_params[1][1].should equal(@memo)
-      end
-    end
-  end
-
-  context "without block" do
-    it "returns new Enumerator" do
-      ret = @enum.send(@method, @memo)
-      ret.should be_an_instance_of(Enumerator)
-      ret.should_not equal(@enum)
-    end
-  end
-end
diff --git a/spec/ruby/shared/fiber/resume.rb b/spec/ruby/shared/fiber/resume.rb
deleted file mode 100644
index d3dc438ae2..0000000000
--- a/spec/ruby/shared/fiber/resume.rb
+++ /dev/null
@@ -1,79 +0,0 @@
-describe :fiber_resume, shared: true do
-  it "can be invoked from the root Fiber" do
-   fiber = Fiber.new { :fiber }
-   fiber.send(@method).should == :fiber
-  end
-
-  it "raises a FiberError if invoked from a different Thread" do
-    fiber = Fiber.new { 42 }
-    Thread.new do
-      -> {
-        fiber.send(@method)
-      }.should raise_error(FiberError)
-    end.join
-
-    # Check the Fiber can still be used
-    fiber.send(@method).should == 42
-  end
-
-  it "passes control to the beginning of the block on first invocation" do
-    invoked = false
-    fiber = Fiber.new { invoked = true }
-    fiber.send(@method)
-    invoked.should be_true
-  end
-
-  it "returns the last value encountered on first invocation" do
-    fiber = Fiber.new { 1+1; true }
-    fiber.send(@method).should be_true
-  end
-
-  it "runs until the end of the block" do
-    obj = mock('obj')
-    obj.should_receive(:do).once
-    fiber = Fiber.new { 1 + 2; a = "glark"; obj.do }
-    fiber.send(@method)
-  end
-
-  it "runs until Fiber.yield" do
-    obj = mock('obj')
-    obj.should_not_receive(:do)
-    fiber = Fiber.new { 1 + 2; Fiber.yield; obj.do }
-    fiber.send(@method)
-  end
-
-  it "resumes from the last call to Fiber.yield on subsequent invocations" do
-    fiber = Fiber.new { Fiber.yield :first; :second }
-    fiber.send(@method).should == :first
-    fiber.send(@method).should == :second
-  end
-
-  it "accepts any number of arguments" do
-    fiber = Fiber.new { |a| }
-    -> { fiber.send(@method, *(1..10).to_a) }.should_not raise_error
-  end
-
-  it "sets the block parameters to its arguments on the first invocation" do
-    first = mock('first')
-    first.should_receive(:arg).with(:first).twice
-    fiber = Fiber.new { |arg| first.arg arg; Fiber.yield; first.arg arg; }
-    fiber.send(@method, :first)
-    fiber.send(@method, :second)
-  end
-
-  it "raises a FiberError if the Fiber is dead" do
-    fiber = Fiber.new { true }
-    fiber.send(@method)
-    -> { fiber.send(@method) }.should raise_error(FiberError)
-  end
-
-  it "raises a LocalJumpError if the block includes a return statement" do
-    fiber = Fiber.new { return; }
-    -> { fiber.send(@method) }.should raise_error(LocalJumpError)
-  end
-
-  it "raises a LocalJumpError if the block includes a break statement" do
-    fiber = Fiber.new { break; }
-    -> { fiber.send(@method) }.should raise_error(LocalJumpError)
-  end
-end
diff --git a/spec/ruby/shared/file/executable.rb b/spec/ruby/shared/file/executable.rb
index 2987d0aabb..baa156de98 100644
--- a/spec/ruby/shared/file/executable.rb
+++ b/spec/ruby/shared/file/executable.rb
@@ -13,7 +13,7 @@ describe :file_executable, shared: true do
     rm_r @file1, @file2
   end
 
-  platform_is_not :windows do
+  platform_is_not :windows, :android do
     it "returns true if named file is executable by the effective user id of the process, otherwise false" do
       @object.send(@method, '/etc/passwd').should == false
       @object.send(@method, @file1).should == true
@@ -39,6 +39,41 @@ describe :file_executable, shared: true do
     -> { @object.send(@method, nil)   }.should raise_error(TypeError)
     -> { @object.send(@method, false) }.should raise_error(TypeError)
   end
+
+  platform_is_not :windows do
+    as_superuser do
+      context "when run by a superuser" do
+        before :each do
+          @file = tmp('temp3.txt')
+          touch @file
+        end
+
+        after :each do
+          rm_r @file
+        end
+
+        it "returns true if file owner has permission to execute" do
+          File.chmod(0766, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "returns true if group has permission to execute" do
+          File.chmod(0676, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "returns true if other have permission to execute" do
+          File.chmod(0667, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "return false if nobody has permission to execute" do
+          File.chmod(0666, @file)
+          @object.send(@method, @file).should == false
+        end
+      end
+    end
+  end
 end
 
 describe :file_executable_missing, shared: true do
diff --git a/spec/ruby/shared/file/executable_real.rb b/spec/ruby/shared/file/executable_real.rb
index ce3d5ca176..bf2734ea07 100644
--- a/spec/ruby/shared/file/executable_real.rb
+++ b/spec/ruby/shared/file/executable_real.rb
@@ -37,6 +37,41 @@ describe :file_executable_real, shared: true do
     -> { @object.send(@method, nil)   }.should raise_error(TypeError)
     -> { @object.send(@method, false) }.should raise_error(TypeError)
   end
+
+  platform_is_not :windows do
+    as_real_superuser do
+      context "when run by a real superuser" do
+        before :each do
+          @file = tmp('temp3.txt')
+          touch @file
+        end
+
+        after :each do
+          rm_r @file
+        end
+
+        it "returns true if file owner has permission to execute" do
+          File.chmod(0766, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "returns true if group has permission to execute" do
+          File.chmod(0676, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "returns true if other have permission to execute" do
+          File.chmod(0667, @file)
+          @object.send(@method, @file).should == true
+        end
+
+        it "return false if nobody has permission to execute" do
+          File.chmod(0666, @file)
+          @object.send(@method, @file).should == false
+        end
+      end
+    end
+  end
 end
 
 describe :file_executable_real_missing, shared: true do
diff --git a/spec/ruby/shared/file/exist.rb b/spec/ruby/shared/file/exist.rb
index 3bd97711b4..67424146c5 100644
--- a/spec/ruby/shared/file/exist.rb
+++ b/spec/ruby/shared/file/exist.rb
@@ -4,11 +4,6 @@ describe :file_exist, shared: true do
     @object.send(@method, 'a_fake_file').should == false
   end
 
-  it "returns true if the file exist using the alias exists?" do
-    @object.send(@method, __FILE__).should == true
-    @object.send(@method, 'a_fake_file').should == false
-  end
-
   it "raises an ArgumentError if not passed one argument" do
     -> { @object.send(@method) }.should raise_error(ArgumentError)
     -> { @object.send(@method, __FILE__, __FILE__) }.should raise_error(ArgumentError)
diff --git a/spec/ruby/shared/file/grpowned.rb b/spec/ruby/shared/file/grpowned.rb
index 91a6483030..24e84c28e3 100644
--- a/spec/ruby/shared/file/grpowned.rb
+++ b/spec/ruby/shared/file/grpowned.rb
@@ -26,8 +26,7 @@ describe :file_grpowned, shared: true do
 
         @object.send(@method, @file).should == true
       else
-        # No supplementary groups
-        1.should == 1
+        skip "No supplementary groups"
       end
     end
   end
diff --git a/spec/ruby/shared/file/identical.rb b/spec/ruby/shared/file/identical.rb
index ecc21727ca..b7a2904839 100644
--- a/spec/ruby/shared/file/identical.rb
+++ b/spec/ruby/shared/file/identical.rb
@@ -9,7 +9,11 @@ describe :file_identical, shared: true do
     touch(@file2) { |f| f.puts "file2" }
 
     rm_r @link
-    File.link(@file1, @link)
+    begin
+      File.link(@file1, @link)
+    rescue Errno::EACCES
+      File.symlink(@file1, @link)
+    end
   end
 
   after :each do
diff --git a/spec/ruby/shared/file/readable.rb b/spec/ruby/shared/file/readable.rb
index 74f58caaff..7b45e23e36 100644
--- a/spec/ruby/shared/file/readable.rb
+++ b/spec/ruby/shared/file/readable.rb
@@ -4,9 +4,12 @@ describe :file_readable, shared: true do
     platform_is :windows do
       @file2 = File.join(ENV["WINDIR"], "system32/drivers/etc/services").tr(File::SEPARATOR, File::ALT_SEPARATOR)
     end
-    platform_is_not :windows do
+    platform_is_not :windows, :android do
       @file2 = "/etc/passwd"
     end
+    platform_is :android do
+      @file2 = "/system/bin/sh"
+    end
   end
 
   after :each do
@@ -21,6 +24,22 @@ describe :file_readable, shared: true do
   it "accepts an object that has a #to_path method" do
     @object.send(@method, mock_to_path(@file2)).should == true
   end
+
+  platform_is_not :windows do
+    as_superuser do
+      context "when run by a superuser" do
+        it "returns true unconditionally" do
+          file = tmp('temp.txt')
+          touch file
+
+          File.chmod(0333, file)
+          @object.send(@method, file).should == true
+
+          rm_r file
+        end
+      end
+    end
+  end
 end
 
 describe :file_readable_missing, shared: true do
diff --git a/spec/ruby/shared/file/readable_real.rb b/spec/ruby/shared/file/readable_real.rb
index b6e53ac76d..32d38bc7a2 100644
--- a/spec/ruby/shared/file/readable_real.rb
+++ b/spec/ruby/shared/file/readable_real.rb
@@ -14,6 +14,22 @@ describe :file_readable_real, shared: true do
   it "accepts an object that has a #to_path method" do
     File.open(@file,'w') { @object.send(@method, mock_to_path(@file)).should == true }
   end
+
+  platform_is_not :windows do
+    as_real_superuser do
+      context "when run by a real superuser" do
+        it "returns true unconditionally" do
+          file = tmp('temp.txt')
+          touch file
+
+          File.chmod(0333, file)
+          @object.send(@method, file).should == true
+
+          rm_r file
+        end
+      end
+    end
+  end
 end
 
 describe :file_readable_real_missing, shared: true do
diff --git a/spec/ruby/shared/file/size.rb b/spec/ruby/shared/file/size.rb
index 880dfbb612..cba99fe6a5 100644
--- a/spec/ruby/shared/file/size.rb
+++ b/spec/ruby/shared/file/size.rb
@@ -72,7 +72,7 @@ describe :file_size_nil_when_missing, shared: true do
   end
 
   it "returns nil if file_name doesn't exist or has 0 size" do
-     @object.send(@method, @missing).should == nil
+    @object.send(@method, @missing).should == nil
   end
 end
 
diff --git a/spec/ruby/shared/file/socket.rb b/spec/ruby/shared/file/socket.rb
index 55a1cfd284..ef6c482d1c 100644
--- a/spec/ruby/shared/file/socket.rb
+++ b/spec/ruby/shared/file/socket.rb
@@ -1,3 +1,33 @@
 describe :file_socket, shared: true do
-  it "accepts an object that has a #to_path method"
+  it "returns false if the file is not a socket" do
+    filename = tmp("i_exist")
+    touch(filename)
+
+    @object.send(@method, filename).should == false
+
+    rm_r filename
+  end
+
+  it "returns true if the file is a socket" do
+    require 'socket'
+
+    # We need a really short name here.
+    # On Linux the path length is limited to 107, see unix(7).
+    name = tmp("s")
+    server = UNIXServer.new(name)
+
+    @object.send(@method, name).should == true
+
+    server.close
+    rm_r name
+  end
+
+  it "accepts an object that has a #to_path method" do
+    obj = Object.new
+    def obj.to_path
+      __FILE__
+    end
+
+    @object.send(@method, obj).should == false
+  end
 end
diff --git a/spec/ruby/shared/file/sticky.rb b/spec/ruby/shared/file/sticky.rb
index 38bb6ed26b..e07fa22fd7 100644
--- a/spec/ruby/shared/file/sticky.rb
+++ b/spec/ruby/shared/file/sticky.rb
@@ -8,7 +8,7 @@ describe :file_sticky, shared: true do
     Dir.rmdir(@dir) if File.exist?(@dir)
   end
 
-  platform_is_not :windows, :darwin, :freebsd, :netbsd, :openbsd, :solaris, :aix do
+  platform_is_not :windows, :darwin, :freebsd, :netbsd, :openbsd, :aix do
     it "returns true if the named file has the sticky bit, otherwise false" do
       Dir.mkdir @dir, 01755
 
diff --git a/spec/ruby/shared/file/world_readable.rb b/spec/ruby/shared/file/world_readable.rb
index 0fd5a28397..1dce7a580f 100644
--- a/spec/ruby/shared/file/world_readable.rb
+++ b/spec/ruby/shared/file/world_readable.rb
@@ -28,18 +28,18 @@ describe :file_world_readable, shared: true do
     end
   end
 
-  # We don't specify what the Fixnum is because it's system dependent
-  it "returns a Fixnum if the file is chmod 644" do
+  # We don't specify what the Integer is because it's system dependent
+  it "returns an Integer if the file is chmod 644" do
     File.chmod(0644, @file)
-    @object.world_readable?(@file).should be_an_instance_of(Fixnum)
+    @object.world_readable?(@file).should be_an_instance_of(Integer)
   end
 
-  it "returns a Fixnum if the file is a directory and chmod 644" do
-    dir = rand().to_s + '-ww'
+  it "returns an Integer if the file is a directory and chmod 644" do
+    dir = tmp(rand().to_s + '-ww')
     Dir.mkdir(dir)
-    Dir.exist?(dir).should be_true
+    Dir.should.exist?(dir)
     File.chmod(0644, dir)
-    @object.world_readable?(dir).should be_an_instance_of(Fixnum)
+    @object.world_readable?(dir).should be_an_instance_of(Integer)
     Dir.rmdir(dir)
   end
 
diff --git a/spec/ruby/shared/file/world_writable.rb b/spec/ruby/shared/file/world_writable.rb
index da8af0bc2a..7ed252dcf3 100644
--- a/spec/ruby/shared/file/world_writable.rb
+++ b/spec/ruby/shared/file/world_writable.rb
@@ -27,18 +27,18 @@ describe :file_world_writable, shared: true do
       @object.world_writable?(@file).should be_nil
     end
 
-    # We don't specify what the Fixnum is because it's system dependent
-    it "returns a Fixnum if the file is chmod 777" do
+    # We don't specify what the Integer is because it's system dependent
+    it "returns an Integer if the file is chmod 777" do
       File.chmod(0777, @file)
-      @object.world_writable?(@file).should be_an_instance_of(Fixnum)
+      @object.world_writable?(@file).should be_an_instance_of(Integer)
     end
 
-    it "returns a Fixnum if the file is a directory and chmod 777" do
-      dir = rand().to_s + '-ww'
+    it "returns an Integer if the file is a directory and chmod 777" do
+      dir = tmp(rand().to_s + '-ww')
       Dir.mkdir(dir)
-      Dir.exist?(dir).should be_true
+      Dir.should.exist?(dir)
       File.chmod(0777, dir)
-      @object.world_writable?(dir).should be_an_instance_of(Fixnum)
+      @object.world_writable?(dir).should be_an_instance_of(Integer)
       Dir.rmdir(dir)
     end
   end
diff --git a/spec/ruby/shared/file/writable.rb b/spec/ruby/shared/file/writable.rb
index 902d545da1..65ea2c1781 100644
--- a/spec/ruby/shared/file/writable.rb
+++ b/spec/ruby/shared/file/writable.rb
@@ -8,7 +8,7 @@ describe :file_writable, shared: true do
   end
 
   it "returns true if named file is writable by the effective user id of the process, otherwise false" do
-    platform_is_not :windows do
+    platform_is_not :windows, :android do
       as_user do
         @object.send(@method, "/etc/passwd").should == false
       end
@@ -19,6 +19,22 @@ describe :file_writable, shared: true do
   it "accepts an object that has a #to_path method" do
     File.open(@file,'w') { @object.send(@method, mock_to_path(@file)).should == true }
   end
+
+  platform_is_not :windows do
+    as_superuser do
+      context "when run by a superuser" do
+        it "returns true unconditionally" do
+          file = tmp('temp.txt')
+          touch file
+
+          File.chmod(0555, file)
+          @object.send(@method, file).should == true
+
+          rm_r file
+        end
+      end
+    end
+  end
 end
 
 describe :file_writable_missing, shared: true do
diff --git a/spec/ruby/shared/file/writable_real.rb b/spec/ruby/shared/file/writable_real.rb
index e9721fd379..b4a0a58c6e 100644
--- a/spec/ruby/shared/file/writable_real.rb
+++ b/spec/ruby/shared/file/writable_real.rb
@@ -24,6 +24,22 @@ describe :file_writable_real, shared: true do
     -> { @object.send(@method, nil)   }.should raise_error(TypeError)
     -> { @object.send(@method, false) }.should raise_error(TypeError)
   end
+
+  platform_is_not :windows do
+    as_real_superuser do
+      context "when run by a real superuser" do
+        it "returns true unconditionally" do
+          file = tmp('temp.txt')
+          touch file
+
+          File.chmod(0555, file)
+          @object.send(@method, file).should == true
+
+          rm_r file
+        end
+      end
+    end
+  end
 end
 
 describe :file_writable_real_missing, shared: true do
diff --git a/spec/ruby/shared/hash/key_error.rb b/spec/ruby/shared/hash/key_error.rb
index 061c88c483..54dcb89e91 100644
--- a/spec/ruby/shared/hash/key_error.rb
+++ b/spec/ruby/shared/hash/key_error.rb
@@ -5,21 +5,19 @@ describe :key_error, shared: true do
     }.should raise_error(KeyError)
   end
 
-  ruby_version_is "2.5" do
-    it "sets the Hash as the receiver of KeyError" do
-      -> {
-        @method.call(@object, 'foo')
-      }.should raise_error(KeyError) { |err|
-        err.receiver.should equal(@object)
-      }
-    end
+  it "sets the Hash as the receiver of KeyError" do
+    -> {
+      @method.call(@object, 'foo')
+    }.should raise_error(KeyError) { |err|
+      err.receiver.should equal(@object)
+    }
+  end
 
-    it "sets the unmatched key as the key of KeyError" do
-      -> {
-        @method.call(@object, 'foo')
-      }.should raise_error(KeyError) { |err|
-        err.key.to_s.should == 'foo'
-      }
-    end
+  it "sets the unmatched key as the key of KeyError" do
+    -> {
+      @method.call(@object, 'foo')
+    }.should raise_error(KeyError) { |err|
+      err.key.to_s.should == 'foo'
+    }
   end
 end
diff --git a/spec/ruby/shared/io/putc.rb b/spec/ruby/shared/io/putc.rb
index fac14886ee..cdf18ac9fd 100644
--- a/spec/ruby/shared/io/putc.rb
+++ b/spec/ruby/shared/io/putc.rb
@@ -1,4 +1,4 @@
-# -*- encoding: binary -*-
+# encoding: binary
 describe :io_putc, shared: true do
   after :each do
     @io.close if @io && !@io.closed?
@@ -6,7 +6,7 @@ describe :io_putc, shared: true do
     rm_r @name
   end
 
-  describe "with a Fixnum argument" do
+  describe "with an Integer argument" do
     it "writes one character as a String" do
       @io.should_receive(:write).with("A")
       @io_object.send(@method, 65).should == 65
diff --git a/spec/ruby/shared/kernel/at_exit.rb b/spec/ruby/shared/kernel/at_exit.rb
new file mode 100644
index 0000000000..29db79bb39
--- /dev/null
+++ b/spec/ruby/shared/kernel/at_exit.rb
@@ -0,0 +1,76 @@
+describe :kernel_at_exit, shared: true do
+  it "runs after all other code" do
+    ruby_exe("#{@method} { print 5 }; print 6").should == "65"
+  end
+
+  it "runs in reverse order of registration" do
+    code = "#{@method} { print 4 }; #{@method} { print 5 }; print 6; #{@method} { print 7 }"
+    ruby_exe(code).should == "6754"
+  end
+
+  it "allows calling exit inside a handler" do
+    code = "#{@method} { print 3 }; #{@method} { print 4; exit; print 5 }; #{@method} { print 6 }"
+    ruby_exe(code).should == "643"
+  end
+
+  it "gives access to the last raised exception - global variables $! and $@" do
+    code = <<-EOC
+      #{@method} {
+        puts "The exception matches: \#{$! == $exception && $@ == $exception.backtrace} (message=\#{$!.message})"
+      }
+
+      begin
+        raise "foo"
+      rescue => $exception
+        raise
+      end
+    EOC
+
+    result = ruby_exe(code, args: "2>&1", exit_status: 1)
+    result.lines.should.include?("The exception matches: true (message=foo)\n")
+  end
+
+  it "gives access to an exception raised in a previous handler" do
+    code = "#{@method} { print '$!.message = ' + $!.message }; #{@method} { raise 'foo' }"
+    result = ruby_exe(code, args: "2>&1", exit_status: 1)
+    result.lines.should.include?("$!.message = foo")
+  end
+
+  it "both exceptions in a handler and in the main script are printed" do
+    code = "#{@method} { raise 'at_exit_error' }; raise 'main_script_error'"
+    result = ruby_exe(code, args: "2>&1", exit_status: 1)
+    result.should.include?('at_exit_error (RuntimeError)')
+    result.should.include?('main_script_error (RuntimeError)')
+  end
+
+  it "decides the exit status if both at_exit and the main script raise SystemExit" do
+    ruby_exe("#{@method} { exit 43 }; exit 42", args: "2>&1", exit_status: 43)
+    $?.exitstatus.should == 43
+  end
+
+  it "runs all handlers even if some raise exceptions" do
+    code = "#{@method} { STDERR.puts 'last' }; #{@method} { exit 43 }; #{@method} { STDERR.puts 'first' }; exit 42"
+    result = ruby_exe(code, args: "2>&1", exit_status: 43)
+    result.should == "first\nlast\n"
+    $?.exitstatus.should == 43
+  end
+
+  it "runs handlers even if the main script fails to parse" do
+    script = fixture(__FILE__, "#{@method}.rb")
+    result = ruby_exe('{', options: "-r#{script}", args: "2>&1", exit_status: 1)
+    $?.should_not.success?
+    result.should.include?("handler ran\n")
+
+    # it's tempting not to rely on error message and rely only on exception class name,
+    # but CRuby before 3.2 doesn't print class name for syntax error
+    result.should include_any_of("syntax error", "SyntaxError")
+  end
+
+  it "calls the nested handler right after the outer one if a handler is nested into another handler" do
+    ruby_exe(<<~ruby).should == "last\nbefore\nafter\nnested\nfirst\n"
+        #{@method} { puts :first }
+        #{@method} { puts :before; #{@method} { puts :nested }; puts :after };
+        #{@method} { puts :last }
+    ruby
+  end
+end
diff --git a/spec/ruby/shared/kernel/complex.rb b/spec/ruby/shared/kernel/complex.rb
new file mode 100644
index 0000000000..98ee0b2b3f
--- /dev/null
+++ b/spec/ruby/shared/kernel/complex.rb
@@ -0,0 +1,133 @@
+# Specs shared by Kernel#Complex() and String#to_c()
+describe :kernel_complex, shared: true do
+
+  it "returns a Complex object" do
+    @object.send(@method, '9').should be_an_instance_of(Complex)
+  end
+
+  it "understands integers" do
+    @object.send(@method, '20').should == Complex(20)
+  end
+
+  it "understands negative integers" do
+    @object.send(@method, '-3').should == Complex(-3)
+  end
+
+  it "understands fractions (numerator/denominator) for the real part" do
+    @object.send(@method, '2/3').should == Complex(Rational(2, 3))
+  end
+
+  it "understands fractions (numerator/denominator) for the imaginary part" do
+    @object.send(@method, '4+2/3i').should == Complex(4, Rational(2, 3))
+  end
+
+  it "understands negative fractions (-numerator/denominator) for the real part" do
+    @object.send(@method, '-2/3').should == Complex(Rational(-2, 3))
+  end
+
+  it "understands negative fractions (-numerator/denominator) for the imaginary part" do
+    @object.send(@method, '7-2/3i').should == Complex(7, Rational(-2, 3))
+  end
+
+  it "understands floats (a.b) for the real part" do
+    @object.send(@method, '2.3').should == Complex(2.3)
+  end
+
+  it "understands floats (a.b) for the imaginary part" do
+    @object.send(@method, '4+2.3i').should == Complex(4, 2.3)
+  end
+
+  it "understands negative floats (-a.b) for the real part" do
+    @object.send(@method, '-2.33').should == Complex(-2.33)
+  end
+
+  it "understands negative floats (-a.b) for the imaginary part" do
+    @object.send(@method, '7-28.771i').should == Complex(7, -28.771)
+  end
+
+  it "understands an integer followed by 'i' to mean that integer is the imaginary part" do
+    @object.send(@method, '35i').should == Complex(0,35)
+  end
+
+  it "understands a negative integer followed by 'i' to mean that negative integer is the imaginary part" do
+    @object.send(@method, '-29i').should == Complex(0,-29)
+  end
+
+  it "understands an 'i' by itself as denoting a complex number with an imaginary part of 1" do
+    @object.send(@method, 'i').should == Complex(0,1)
+  end
+
+  it "understands a '-i' by itself as denoting a complex number with an imaginary part of -1" do
+    @object.send(@method, '-i').should == Complex(0,-1)
+  end
+
+  it "understands 'a+bi' to mean a complex number with 'a' as the real part, 'b' as the imaginary" do
+    @object.send(@method, '79+4i').should == Complex(79,4)
+  end
+
+  it "understands 'a-bi' to mean a complex number with 'a' as the real part, '-b' as the imaginary" do
+    @object.send(@method, '79-4i').should == Complex(79,-4)
+  end
+
+  it "understands 'a+i' to mean a complex number with 'a' as the real part, 1i as the imaginary" do
+    @object.send(@method, '79+i').should == Complex(79, 1)
+  end
+
+  it "understands 'a-i' to mean a complex number with 'a' as the real part, -1i as the imaginary" do
+    @object.send(@method, '79-i').should == Complex(79, -1)
+  end
+
+  it "understands i, I, j, and J imaginary units" do
+    @object.send(@method, '79+4i').should == Complex(79, 4)
+    @object.send(@method, '79+4I').should == Complex(79, 4)
+    @object.send(@method, '79+4j').should == Complex(79, 4)
+    @object.send(@method, '79+4J').should == Complex(79, 4)
+  end
+
+  it "understands scientific notation for the real part" do
+    @object.send(@method, '2e3+4i').should == Complex(2e3,4)
+  end
+
+  it "understands negative scientific notation for the real part" do
+    @object.send(@method, '-2e3+4i').should == Complex(-2e3,4)
+  end
+
+  it "understands scientific notation for the imaginary part" do
+    @object.send(@method, '4+2e3i').should == Complex(4, 2e3)
+  end
+
+  it "understands negative scientific notation for the imaginary part" do
+    @object.send(@method, '4-2e3i').should == Complex(4, -2e3)
+  end
+
+  it "understands scientific notation for the real and imaginary part in the same String" do
+    @object.send(@method, '2e3+2e4i').should == Complex(2e3,2e4)
+  end
+
+  it "understands negative scientific notation for the real and imaginary part in the same String" do
+    @object.send(@method, '-2e3-2e4i').should == Complex(-2e3,-2e4)
+  end
+
+  it "understands scientific notation with e and E" do
+    @object.send(@method, '2e3+2e4i').should == Complex(2e3, 2e4)
+    @object.send(@method, '2E3+2E4i').should == Complex(2e3, 2e4)
+  end
+
+  it "understands 'm@a' to mean a complex number in polar form with 'm' as the modulus, 'a' as the argument" do
+    @object.send(@method, '79@4').should == Complex.polar(79, 4)
+    @object.send(@method, '-79@4').should == Complex.polar(-79, 4)
+    @object.send(@method, '79@-4').should == Complex.polar(79, -4)
+  end
+
+  it "ignores leading whitespaces" do
+    @object.send(@method, '  79+4i').should == Complex(79, 4)
+  end
+
+  it "ignores trailing whitespaces" do
+    @object.send(@method, '79+4i  ').should == Complex(79, 4)
+  end
+
+  it "understands _" do
+    @object.send(@method, '7_9+4_0i').should == Complex(79, 40)
+  end
+end
diff --git a/spec/ruby/shared/kernel/fixtures/END.rb b/spec/ruby/shared/kernel/fixtures/END.rb
new file mode 100644
index 0000000000..cc8ac17c36
--- /dev/null
+++ b/spec/ruby/shared/kernel/fixtures/END.rb
@@ -0,0 +1,3 @@
+END {
+  STDERR.puts "handler ran"
+}
diff --git a/spec/ruby/shared/kernel/fixtures/at_exit.rb b/spec/ruby/shared/kernel/fixtures/at_exit.rb
new file mode 100644
index 0000000000..e7bc8baf52
--- /dev/null
+++ b/spec/ruby/shared/kernel/fixtures/at_exit.rb
@@ -0,0 +1,3 @@
+at_exit do
+  STDERR.puts "handler ran"
+end
diff --git a/spec/ruby/shared/kernel/object_id.rb b/spec/ruby/shared/kernel/object_id.rb
index 7acdb27554..099df8ff94 100644
--- a/spec/ruby/shared/kernel/object_id.rb
+++ b/spec/ruby/shared/kernel/object_id.rb
@@ -52,10 +52,30 @@ describe :object_id, shared: true do
     o1.send(@method).should_not == o2.send(@method)
   end
 
-  it "returns a different value for two String literals" do
-    o1 = "hello"
-    o2 = "hello"
-    o1.send(@method).should_not == o2.send(@method)
+  guard -> { "test".frozen? && "test".equal?("test") } do # --enable-frozen-string-literal in $RUBYOPT
+    it "returns the same value for two identical String literals" do
+      o1 = "hello"
+      o2 = "hello"
+      o1.send(@method).should == o2.send(@method)
+    end
+  end
+
+  guard -> { "test".frozen? && !"test".equal?("test") } do # chilled string literals
+    it "returns a different frozen value for two String literals" do
+      o1 = "hello"
+      o2 = "hello"
+      o1.send(@method).should_not == o2.send(@method)
+      o1.frozen?.should == true
+      o2.frozen?.should == true
+    end
+  end
+
+  guard -> { !"test".frozen? } do
+    it "returns a different value for two String literals" do
+      o1 = "hello"
+      o2 = "hello"
+      o1.send(@method).should_not == o2.send(@method)
+    end
   end
 
   it "returns a different value for an object and its dup" do
diff --git a/spec/ruby/shared/kernel/raise.rb b/spec/ruby/shared/kernel/raise.rb
index d4553775f4..2be06ea797 100644
--- a/spec/ruby/shared/kernel/raise.rb
+++ b/spec/ruby/shared/kernel/raise.rb
@@ -12,6 +12,43 @@ describe :kernel_raise, shared: true do
     ScratchPad.recorded.should be_nil
   end
 
+  it "accepts an exception that implements to_hash" do
+    custom_error = Class.new(StandardError) do
+      def to_hash
+        {}
+      end
+    end
+    error = custom_error.new
+    -> { @object.raise(error) }.should raise_error(custom_error)
+  end
+
+  it "allows the message parameter to be a hash" do
+    data_error = Class.new(StandardError) do
+      attr_reader :data
+      def initialize(data)
+        @data = data
+      end
+    end
+
+    -> { @object.raise(data_error, {data: 42}) }.should raise_error(data_error) do |ex|
+      ex.data.should == {data: 42}
+    end
+  end
+
+  # https://bugs.ruby-lang.org/issues/8257#note-36
+  it "allows extra keyword arguments for compatibility" do
+    data_error = Class.new(StandardError) do
+      attr_reader :data
+      def initialize(data)
+        @data = data
+      end
+    end
+
+    -> { @object.raise(data_error, data: 42) }.should raise_error(data_error) do |ex|
+      ex.data.should == {data: 42}
+    end
+  end
+
   it "raises RuntimeError if no exception class is given" do
     -> { @object.raise }.should raise_error(RuntimeError, "")
   end
@@ -22,59 +59,69 @@ describe :kernel_raise, shared: true do
   end
 
   it "raises a RuntimeError if string given" do
-    -> { @object.raise("a bad thing") }.should raise_error(RuntimeError)
+    -> { @object.raise("a bad thing") }.should raise_error(RuntimeError, "a bad thing")
+  end
+
+  it "passes no arguments to the constructor when given only an exception class" do
+    klass = Class.new(Exception) do
+      def initialize
+      end
+    end
+    -> { @object.raise(klass) }.should raise_error(klass) { |e| e.message.should == klass.to_s }
   end
 
   it "raises a TypeError when passed a non-Exception object" do
-    -> { @object.raise(Object.new) }.should raise_error(TypeError)
+    -> { @object.raise(Object.new) }.should raise_error(TypeError, "exception class/object expected")
+    -> { @object.raise(Object.new, "message") }.should raise_error(TypeError, "exception class/object expected")
+    -> { @object.raise(Object.new, "message", []) }.should raise_error(TypeError, "exception class/object expected")
   end
 
   it "raises a TypeError when passed true" do
-    -> { @object.raise(true) }.should raise_error(TypeError)
+    -> { @object.raise(true) }.should raise_error(TypeError, "exception class/object expected")
   end
 
   it "raises a TypeError when passed false" do
-    -> { @object.raise(false) }.should raise_error(TypeError)
+    -> { @object.raise(false) }.should raise_error(TypeError, "exception class/object expected")
   end
 
   it "raises a TypeError when passed nil" do
-    -> { @object.raise(nil) }.should raise_error(TypeError)
+    -> { @object.raise(nil) }.should raise_error(TypeError, "exception class/object expected")
   end
 
-  it "re-raises the previously rescued exception if no exception is specified" do
-    -> do
-      begin
-        @object.raise Exception, "outer"
-        ScratchPad.record :no_abort
-      rescue
-        begin
-          @object.raise StandardError, "inner"
-        rescue
-        end
+  it "raises a TypeError when passed a message and an extra argument" do
+    -> { @object.raise("message", {cause: RuntimeError.new()}) }.should raise_error(TypeError, "exception class/object expected")
+  end
 
-        @object.raise
-        ScratchPad.record :no_reraise
-      end
-    end.should raise_error(Exception, "outer")
+  it "raises TypeError when passed a non-Exception object but it responds to #exception method that doesn't return an instance of Exception class" do
+    e = Object.new
+    def e.exception
+      Array
+    end
 
-    ScratchPad.recorded.should be_nil
+    -> {
+      @object.raise e
+    }.should raise_error(TypeError, "exception object expected")
   end
 
   it "re-raises a previously rescued exception without overwriting the backtrace" do
+    exception = nil
+
     begin
-      initial_raise_line = __LINE__; @object.raise 'raised'
-    rescue => raised
-      begin
-        raise_again_line = __LINE__; @object.raise raised
-      rescue => raised_again
-        # This spec is written using #backtrace and matching the line number
-        # from the string, as backtrace_locations is a more advanced
-        # method that is not always supported by implementations.
+      raise "raised"
+    rescue => exception
+      # Ignore.
+    end
 
-        raised_again.backtrace.first.should include("#{__FILE__}:#{initial_raise_line}:")
-        raised_again.backtrace.first.should_not include("#{__FILE__}:#{raise_again_line}:")
-      end
+    backtrace = exception.backtrace
+
+    begin
+      raised_exception = @object.raise(exception)
+    rescue => raised_exception
+      # Ignore.
     end
+
+    raised_exception.backtrace.should == backtrace
+    raised_exception.should == exception
   end
 
   it "allows Exception, message, and backtrace parameters" do
@@ -82,4 +129,270 @@ describe :kernel_raise, shared: true do
       @object.raise(ArgumentError, "message", caller)
     end.should raise_error(ArgumentError, "message")
   end
+
+  ruby_version_is "3.4" do
+    locations = caller_locations(1, 2)
+    it "allows Exception, message, and backtrace_locations parameters" do
+      -> do
+        @object.raise(ArgumentError, "message", locations)
+      end.should raise_error(ArgumentError, "message") { |error|
+        error.backtrace_locations.map(&:to_s).should == locations.map(&:to_s)
+      }
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "allows cause keyword argument" do
+      cause = StandardError.new("original error")
+      result = nil
+
+      -> do
+        @object.raise("new error", cause: cause)
+      end.should raise_error(RuntimeError, "new error") do |error|
+        error.cause.should == cause
+      end
+    end
+
+    it "raises an ArgumentError when only cause is given" do
+      cause = StandardError.new("cause")
+      -> do
+        @object.raise(cause: cause)
+      end.should raise_error(ArgumentError, "only cause is given with no arguments")
+    end
+
+    it "raises an ArgumentError when only cause is given and is nil" do
+      -> do
+        @object.raise(cause: nil)
+      end.should raise_error(ArgumentError, "only cause is given with no arguments")
+    end
+
+    it "raises a TypeError when given cause is not an instance of Exception" do
+      cause = Object.new
+      -> do
+        @object.raise("message", cause: cause)
+      end.should raise_error(TypeError, "exception object expected")
+    end
+
+    it "doesn't set given cause when it equals the raised exception" do
+      cause = StandardError.new("cause")
+      result = nil
+
+      -> do
+        @object.raise(cause, cause: cause)
+      end.should raise_error(StandardError, "cause") do |error|
+        error.should == cause
+        error.cause.should == nil
+      end
+    end
+
+    it "accepts cause equal an exception" do
+      error = RuntimeError.new("message")
+      result = nil
+
+      -> do
+        @object.raise(error, cause: error)
+      end.should raise_error(RuntimeError, "message") do |e|
+        e.cause.should == nil
+      end
+    end
+
+    it "rejects circular causes" do
+      -> {
+        begin
+          raise "Error 1"
+        rescue => error1
+          begin
+            raise "Error 2"
+          rescue => error2
+            begin
+              raise "Error 3"
+            rescue => error3
+              @object.raise(error1, cause: error3)
+            end
+          end
+        end
+      }.should raise_error(ArgumentError, "circular causes")
+    end
+
+    it "supports exception class with message and cause" do
+      cause = StandardError.new("cause message")
+      result = nil
+
+      -> do
+        @object.raise(ArgumentError, "argument error message", cause: cause)
+      end.should raise_error(ArgumentError, "argument error message") do |error|
+        error.should be_kind_of(ArgumentError)
+        error.message.should == "argument error message"
+        error.cause.should == cause
+      end
+    end
+
+    it "supports exception class with message, backtrace and cause" do
+      cause = StandardError.new("cause message")
+      backtrace = ["line1", "line2"]
+      result = nil
+
+      -> do
+        @object.raise(ArgumentError, "argument error message", backtrace, cause: cause)
+      end.should raise_error(ArgumentError, "argument error message") do |error|
+        error.should be_kind_of(ArgumentError)
+        error.message.should == "argument error message"
+        error.cause.should == cause
+        error.backtrace.should == backtrace
+      end
+    end
+
+    it "supports automatic cause chaining" do
+      -> do
+        begin
+          raise "first error"
+        rescue
+          # No explicit cause - should chain automatically:
+          @object.raise("second error")
+        end
+      end.should raise_error(RuntimeError, "second error") do |error|
+        error.cause.should be_kind_of(RuntimeError)
+        error.cause.message.should == "first error"
+      end
+    end
+
+    it "supports cause: nil to prevent automatic cause chaining" do
+      -> do
+        begin
+          raise "first error"
+        rescue
+          # Explicit nil prevents chaining:
+          @object.raise("second error", cause: nil)
+        end
+      end.should raise_error(RuntimeError, "second error") do |error|
+        error.cause.should == nil
+      end
+    end
+  end
+end
+
+describe :kernel_raise_across_contexts, shared: true do
+  ruby_version_is "4.0" do
+    describe "with cause keyword argument" do
+      it "uses the cause from the calling context" do
+        original_cause = nil
+        result = nil
+
+        # We have no cause ($!) and we don't specify one explicitly either:
+        @object.raise("second error") do |&block|
+          begin
+            begin
+              raise "first error"
+            rescue => original_cause
+              # We have a cause here ($!) but we should ignore it:
+              block.call
+            end
+          rescue => result
+            # Ignore.
+          end
+        end
+
+        result.should be_kind_of(RuntimeError)
+        result.message.should == "second error"
+        result.cause.should == nil
+      end
+
+      it "accepts a cause keyword argument that overrides the last exception" do
+        original_cause = nil
+        override_cause = StandardError.new("override cause")
+        result = nil
+
+        begin
+          raise "outer error"
+        rescue
+          # We have an existing cause, but we want to override it:
+          @object.raise("second error", cause: override_cause) do |&block|
+            begin
+              begin
+                raise "first error"
+              rescue => original_cause
+                # We also have an existing cause here:
+                block.call
+              end
+            rescue => result
+              # Ignore.
+            end
+          end
+        end
+
+        result.should be_kind_of(RuntimeError)
+        result.message.should == "second error"
+        result.cause.should == override_cause
+      end
+
+      it "supports automatic cause chaining from calling context" do
+        result = nil
+
+        @object.raise("new error") do |&block|
+          begin
+            begin
+              raise "original error"
+            rescue
+              block.call # Let the context yield/sleep
+            end
+          rescue => result
+            # Ignore.
+          end
+        end
+
+        result.should be_kind_of(RuntimeError)
+        result.message.should == "new error"
+        # Calling context has no current exception:
+        result.cause.should == nil
+      end
+
+      it "supports explicit cause: nil to prevent cause chaining" do
+        result = nil
+
+        begin
+          raise "calling context error"
+        rescue
+          @object.raise("new error", cause: nil) do |&block|
+            begin
+              begin
+                raise "target context error"
+              rescue
+                block.call # Let the context yield/sleep
+              end
+            rescue => result
+              # Ignore.
+            end
+          end
+
+          result.should be_kind_of(RuntimeError)
+          result.message.should == "new error"
+          result.cause.should == nil
+        end
+      end
+
+      it "raises TypeError when cause is not an Exception" do
+        -> {
+          @object.raise("error", cause: "not an exception") do |&block|
+            begin
+              block.call # Let the context yield/sleep
+            rescue
+              # Ignore - we expect the TypeError to be raised in the calling context
+            end
+          end
+        }.should raise_error(TypeError, "exception object expected")
+      end
+
+      it "raises ArgumentError when only cause is given with no arguments" do
+        -> {
+          @object.raise(cause: StandardError.new("cause")) do |&block|
+            begin
+              block.call # Let the context yield/sleep
+            rescue
+              # Ignore - we expect the ArgumentError to be raised in the calling context
+            end
+          end
+        }.should raise_error(ArgumentError, "only cause is given with no arguments")
+      end
+    end
+  end
 end
diff --git a/spec/ruby/shared/process/exit.rb b/spec/ruby/shared/process/exit.rb
index 1820dd17fd..1e073614a3 100644
--- a/spec/ruby/shared/process/exit.rb
+++ b/spec/ruby/shared/process/exit.rb
@@ -21,6 +21,12 @@ describe :process_exit, shared: true do
     end
   end
 
+  it "raises a SystemExit with message 'exit'" do
+    -> { @object.exit }.should raise_error(SystemExit) { |e|
+      e.message.should == "exit"
+    }
+  end
+
   it "tries to convert the passed argument to an Integer using #to_int" do
     obj = mock('5')
     obj.should_receive(:to_int).and_return(5)
@@ -75,20 +81,46 @@ end
 
 describe :process_exit!, shared: true do
   it "exits with the given status" do
-    out = ruby_exe("#{@object}.send(:exit!, 21)", args: '2>&1')
+    out = ruby_exe("#{@object}.send(:exit!, 21)", args: '2>&1', exit_status: 21)
     out.should == ""
     $?.exitstatus.should == 21
   end
 
   it "exits when called from a thread" do
-    out = ruby_exe("Thread.new { #{@object}.send(:exit!, 21) }.join; sleep", args: '2>&1')
+    out = ruby_exe("Thread.new { #{@object}.send(:exit!, 21) }.join; sleep", args: '2>&1', exit_status: 21)
     out.should == ""
     $?.exitstatus.should == 21
   end
 
   it "exits when called from a fiber" do
-    out = ruby_exe("Fiber.new { #{@object}.send(:exit!, 21) }.resume", args: '2>&1')
+    out = ruby_exe("Fiber.new { #{@object}.send(:exit!, 21) }.resume", args: '2>&1', exit_status: 21)
+    out.should == ""
+    $?.exitstatus.should == 21
+  end
+
+  it "skips at_exit handlers" do
+    out = ruby_exe("at_exit { STDERR.puts 'at_exit' }; #{@object}.send(:exit!, 21)", args: '2>&1', exit_status: 21)
     out.should == ""
     $?.exitstatus.should == 21
   end
+
+  it "skips ensure clauses" do
+    out = ruby_exe("begin; STDERR.puts 'before'; #{@object}.send(:exit!, 21); ensure; STDERR.puts 'ensure'; end", args: '2>&1', exit_status: 21)
+    out.should == "before\n"
+    $?.exitstatus.should == 21
+  end
+
+  it "overrides the original exception and exit status when called from #at_exit" do
+    code = <<-RUBY
+    at_exit do
+      STDERR.puts 'in at_exit'
+      STDERR.puts "$! is \#{$!.class}:\#{$!.message}"
+      #{@object}.send(:exit!, 21)
+    end
+    raise 'original error'
+    RUBY
+    out = ruby_exe(code, args: '2>&1', exit_status: 21)
+    out.should == "in at_exit\n$! is RuntimeError:original error\n"
+    $?.exitstatus.should == 21
+  end
 end
diff --git a/spec/ruby/shared/process/fork.rb b/spec/ruby/shared/process/fork.rb
index cb863b42d8..8dbb3d0da4 100644
--- a/spec/ruby/shared/process/fork.rb
+++ b/spec/ruby/shared/process/fork.rb
@@ -23,31 +23,31 @@ describe :process_fork, shared: true do
     end
 
     it "returns status zero" do
-      pid = Process.fork { exit! 0 }
+      pid = @object.fork { exit! 0 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status zero" do
-      pid = Process.fork { exit 0 }
+      pid = @object.fork { exit 0 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status zero" do
-      pid = Process.fork {}
+      pid = @object.fork {}
       _, result = Process.wait2(pid)
       result.exitstatus.should == 0
     end
 
     it "returns status non-zero" do
-      pid = Process.fork { exit! 42 }
+      pid = @object.fork { exit! 42 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 42
     end
 
     it "returns status non-zero" do
-      pid = Process.fork { exit 42 }
+      pid = @object.fork { exit 42 }
       _, result = Process.wait2(pid)
       result.exitstatus.should == 42
     end
@@ -60,7 +60,7 @@ describe :process_fork, shared: true do
       else
         Process.waitpid(child_id)
       end
-      File.exist?(@file).should == true
+      File.should.exist?(@file)
     end
 
     it "runs a block in a child process" do
@@ -69,7 +69,7 @@ describe :process_fork, shared: true do
         Process.exit!
       }
       Process.waitpid(pid)
-      File.exist?(@file).should == true
+      File.should.exist?(@file)
     end
 
     it "marks threads from the parent as killed" do
diff --git a/spec/ruby/shared/queue/deque.rb b/spec/ruby/shared/queue/deque.rb
index 8b755dd9b7..a154da6274 100644
--- a/spec/ruby/shared/queue/deque.rb
+++ b/spec/ruby/shared/queue/deque.rb
@@ -37,6 +37,15 @@ describe :queue_deq, shared: true do
     q.send(@method).should == 1
   end
 
+  it "converts false-ish for non_blocking to boolean" do
+    q = @object.call
+    q << 1
+    q << 2
+
+    q.send(@method, false).should == 1
+    q.send(@method, nil).should == 2
+  end
+
   it "returns nil for a closed empty queue" do
     q = @object.call
     q.close
@@ -55,6 +64,68 @@ describe :queue_deq, shared: true do
     t.join
   end
 
+  describe "with a timeout" do
+    it "returns an item if one is available in time" do
+      q = @object.call
+
+      t = Thread.new {
+        q.send(@method, timeout: TIME_TOLERANCE).should == 1
+      }
+      Thread.pass until t.status == "sleep" && q.num_waiting == 1
+      q << 1
+      t.join
+    end
+
+    it "returns nil if no item is available in time" do
+      q = @object.call
+
+      Thread.new {
+        q.send(@method, timeout: 0.001).should == nil
+      }.join
+    end
+
+    it "does nothing if the timeout is nil" do
+      q = @object.call
+      t = Thread.new {
+        q.send(@method, timeout: nil).should == 1
+      }
+      Thread.pass until t.status == "sleep" && q.num_waiting == 1
+      q << 1
+      t.join
+    end
+
+    it "immediately returns nil if no item is available and the timeout is 0" do
+      q = @object.call
+      q << 1
+      q.send(@method, timeout: 0).should == 1
+      q.send(@method, timeout: 0).should == nil
+    end
+
+    it "raise TypeError if timeout is not a valid numeric" do
+      q = @object.call
+      -> {
+        q.send(@method, timeout: "1")
+      }.should raise_error(TypeError, "no implicit conversion to float from string")
+
+      -> {
+        q.send(@method, timeout: false)
+      }.should raise_error(TypeError, "no implicit conversion to float from false")
+    end
+
+    it "raise ArgumentError if non_block = true is passed too" do
+      q = @object.call
+      -> {
+        q.send(@method, true, timeout: 1)
+      }.should raise_error(ArgumentError, "can't set a timeout if non_block is enabled")
+    end
+
+    it "returns nil for a closed empty queue" do
+      q = @object.call
+      q.close
+      q.send(@method, timeout: 0).should == nil
+    end
+  end
+
   describe "in non-blocking mode" do
     it "removes an item from the queue" do
       q = @object.call
@@ -81,5 +152,13 @@ describe :queue_deq, shared: true do
       q.close
       -> { q.send(@method, true) }.should raise_error(ThreadError)
     end
+
+    it "converts true-ish non_blocking argument to true" do
+      q = @object.call
+
+      -> { q.send(@method, true) }.should raise_error(ThreadError)
+      -> { q.send(@method, 1) }.should raise_error(ThreadError)
+      -> { q.send(@method, "") }.should raise_error(ThreadError)
+    end
   end
 end
diff --git a/spec/ruby/shared/queue/freeze.rb b/spec/ruby/shared/queue/freeze.rb
new file mode 100644
index 0000000000..4c506a4235
--- /dev/null
+++ b/spec/ruby/shared/queue/freeze.rb
@@ -0,0 +1,18 @@
+describe :queue_freeze, shared: true do
+  ruby_version_is ""..."3.3" do
+    it "can be frozen" do
+      queue = @object.call
+      queue.freeze
+      queue.should.frozen?
+    end
+  end
+
+  ruby_version_is "3.3" do
+    it "raises an exception when freezing" do
+      queue = @object.call
+      -> {
+        queue.freeze
+      }.should raise_error(TypeError, "cannot freeze #{queue}")
+    end
+  end
+end
diff --git a/spec/ruby/shared/rational/Rational.rb b/spec/ruby/shared/rational/Rational.rb
deleted file mode 100644
index 2c36243dc3..0000000000
--- a/spec/ruby/shared/rational/Rational.rb
+++ /dev/null
@@ -1,143 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../../fixtures/rational'
-
-describe :kernel_Rational, shared: true do
-  describe "passed Integer" do
-    # Guard against the Mathn library
-    guard -> { !defined?(Math.rsqrt) } do
-      it "returns a new Rational number with 1 as the denominator" do
-        Rational(1).should eql(Rational(1, 1))
-        Rational(-3).should eql(Rational(-3, 1))
-        Rational(bignum_value).should eql(Rational(bignum_value, 1))
-      end
-    end
-  end
-
-  describe "passed two integers" do
-    it "returns a new Rational number" do
-      rat = Rational(1, 2)
-      rat.numerator.should == 1
-      rat.denominator.should == 2
-      rat.should be_an_instance_of(Rational)
-
-      rat = Rational(-3, -5)
-      rat.numerator.should == 3
-      rat.denominator.should == 5
-      rat.should be_an_instance_of(Rational)
-
-      rat = Rational(bignum_value, 3)
-      rat.numerator.should == bignum_value
-      rat.denominator.should == 3
-      rat.should be_an_instance_of(Rational)
-    end
-
-    it "reduces the Rational" do
-      rat = Rational(2, 4)
-      rat.numerator.should == 1
-      rat.denominator.should == 2
-
-      rat = Rational(3, 9)
-      rat.numerator.should == 1
-      rat.denominator.should == 3
-    end
-  end
-
-  describe "when passed a String" do
-    it "converts the String to a Rational using the same method as String#to_r" do
-      r = Rational(13, 25)
-      s_r = ".52".to_r
-      r_s = Rational(".52")
-
-      r_s.should == r
-      r_s.should == s_r
-    end
-
-    it "scales the Rational value of the first argument by the Rational value of the second" do
-      Rational(".52", ".6").should == Rational(13, 15)
-      Rational(".52", "1.6").should == Rational(13, 40)
-    end
-
-    it "does not use the same method as Float#to_r" do
-      r = Rational(3, 5)
-      f_r = 0.6.to_r
-      r_s = Rational("0.6")
-
-      r_s.should == r
-      r_s.should_not == f_r
-    end
-
-    describe "when passed a Numeric" do
-      it "calls #to_r to convert the first argument to a Rational" do
-        num = RationalSpecs::SubNumeric.new(2)
-
-        Rational(num).should == Rational(2)
-      end
-    end
-
-    describe "when passed a Complex" do
-      it "returns a Rational from the real part if the imaginary part is 0" do
-        Rational(Complex(1, 0)).should == Rational(1)
-      end
-
-      it "raises a RangeError if the imaginary part is not 0" do
-        -> { Rational(Complex(1, 2)) }.should raise_error(RangeError)
-      end
-    end
-
-    it "raises a TypeError if the first argument is nil" do
-      -> { Rational(nil) }.should raise_error(TypeError)
-    end
-
-    it "raises a TypeError if the second argument is nil" do
-      -> { Rational(1, nil) }.should raise_error(TypeError)
-    end
-
-    it "raises a TypeError if the first argument is a Symbol" do
-      -> { Rational(:sym) }.should raise_error(TypeError)
-    end
-
-    it "raises a TypeError if the second argument is a Symbol" do
-      -> { Rational(1, :sym) }.should raise_error(TypeError)
-    end
-  end
-
-  ruby_version_is "2.6" do
-    describe "when passed exception: false" do
-      describe "and [non-Numeric]" do
-        it "swallows an error" do
-          Rational(:sym, exception: false).should == nil
-          Rational("abc", exception: false).should == nil
-        end
-      end
-
-      describe "and [non-Numeric, Numeric]" do
-        it "swallows an error" do
-          Rational(:sym, 1, exception: false).should == nil
-          Rational("abc", 1, exception: false).should == nil
-        end
-      end
-
-      describe "and [anything, non-Numeric]" do
-        it "swallows an error" do
-          Rational(:sym, :sym, exception: false).should == nil
-          Rational("abc", :sym, exception: false).should == nil
-        end
-      end
-
-      describe "and non-Numeric String arguments" do
-        it "swallows an error" do
-          Rational("a", "b", exception: false).should == nil
-          Rational("a", 0, exception: false).should == nil
-          Rational(0, "b", exception: false).should == nil
-        end
-      end
-
-      describe "and nil arguments" do
-        it "swallows an error" do
-          Rational(nil, exception: false).should == nil
-          Rational(nil, nil, exception: false).should == nil
-        end
-      end
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/abs.rb b/spec/ruby/shared/rational/abs.rb
deleted file mode 100644
index 8beb20da7e..0000000000
--- a/spec/ruby/shared/rational/abs.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_abs, shared: true do
-  it "returns self's absolute value" do
-    Rational(3, 4).send(@method).should == Rational(3, 4)
-    Rational(-3, 4).send(@method).should == Rational(3, 4)
-    Rational(3, -4).send(@method).should == Rational(3, 4)
-
-    Rational(bignum_value, -bignum_value).send(@method).should == Rational(bignum_value, bignum_value)
-  end
-end
diff --git a/spec/ruby/shared/rational/arithmetic_exception_in_coerce.rb b/spec/ruby/shared/rational/arithmetic_exception_in_coerce.rb
deleted file mode 100644
index 9377814732..0000000000
--- a/spec/ruby/shared/rational/arithmetic_exception_in_coerce.rb
+++ /dev/null
@@ -1,33 +0,0 @@
-require_relative '../../fixtures/rational'
-
-describe :rational_arithmetic_exception_in_coerce, shared: true do
-  ruby_version_is ""..."2.5" do
-    it "rescues exception (StandardError and subclasses) raised in other#coerce and raises TypeError" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
-
-      # e.g. Rational(3, 4) + b
-      -> { Rational(3, 4).send(@method, b) }.should raise_error(TypeError, /MockObject can't be coerced into Rational/)
-    end
-
-    it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-      [Exception, NoMemoryError].each do |exception|
-        b = mock("numeric with failed #coerce")
-        b.should_receive(:coerce).and_raise(exception)
-
-        # e.g. Rational(3, 4) + b
-        -> { Rational(3, 4).send(@method, b) }.should raise_error(exception)
-      end
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not rescue exception raised in other#coerce" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
-
-      # e.g. Rational(3, 4) + b
-      -> { Rational(3, 4).send(@method, b) }.should raise_error(RationalSpecs::CoerceError)
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/ceil.rb b/spec/ruby/shared/rational/ceil.rb
deleted file mode 100644
index f1cf60d2be..0000000000
--- a/spec/ruby/shared/rational/ceil.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_ceil, shared: true do
-  before do
-    @rational = Rational(2200, 7)
-  end
-
-  describe "with no arguments (precision = 0)" do
-    it "returns an Integer" do
-      @rational.ceil.should be_kind_of(Integer)
-    end
-
-    it "returns the truncated value toward positive infinity" do
-      @rational.ceil.should == 315
-      Rational(1, 2).ceil.should == 1
-      Rational(-1, 2).ceil.should == 0
-    end
-  end
-
-  describe "with a precision < 0" do
-    it "returns an Integer" do
-      @rational.ceil(-2).should be_kind_of(Integer)
-      @rational.ceil(-1).should be_kind_of(Integer)
-    end
-
-    it "moves the truncation point n decimal places left" do
-      @rational.ceil(-3).should == 1000
-      @rational.ceil(-2).should == 400
-      @rational.ceil(-1).should == 320
-    end
-  end
-
-  describe "with precision > 0" do
-    it "returns a Rational" do
-      @rational.ceil(1).should be_kind_of(Rational)
-      @rational.ceil(2).should be_kind_of(Rational)
-    end
-
-    it "moves the truncation point n decimal places right" do
-      @rational.ceil(1).should == Rational(3143, 10)
-      @rational.ceil(2).should == Rational(31429, 100)
-      @rational.ceil(3).should == Rational(157143, 500)
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/coerce.rb b/spec/ruby/shared/rational/coerce.rb
deleted file mode 100644
index ffb118e2a7..0000000000
--- a/spec/ruby/shared/rational/coerce.rb
+++ /dev/null
@@ -1,29 +0,0 @@
-require_relative '../../spec_helper'
-
-require 'bigdecimal'
-
-describe :rational_coerce, shared: true do
-  it "returns the passed argument, self as Float, when given a Float" do
-    result = Rational(3, 4).coerce(1.0)
-    result.should == [1.0, 0.75]
-    result.first.is_a?(Float).should be_true
-    result.last.is_a?(Float).should be_true
-  end
-
-  it "returns the passed argument, self as Rational, when given an Integer" do
-    result = Rational(3, 4).coerce(10)
-    result.should == [Rational(10, 1), Rational(3, 4)]
-    result.first.is_a?(Rational).should be_true
-    result.last.is_a?(Rational).should be_true
-  end
-
-  it "returns [argument, self] when given a Rational" do
-    Rational(3, 7).coerce(Rational(9, 2)).should == [Rational(9, 2), Rational(3, 7)]
-  end
-
-  it "raises an error when passed a BigDecimal" do
-    -> {
-      Rational(500, 3).coerce(BigDecimal('166.666666666'))
-    }.should raise_error(TypeError, /BigDecimal can't be coerced into Rational/)
-  end
-end
diff --git a/spec/ruby/shared/rational/comparison.rb b/spec/ruby/shared/rational/comparison.rb
deleted file mode 100644
index 0c8b3d0ac1..0000000000
--- a/spec/ruby/shared/rational/comparison.rb
+++ /dev/null
@@ -1,117 +0,0 @@
-require_relative '../../spec_helper'
-require_relative '../../fixtures/rational'
-
-describe :rational_cmp_rat, shared: true do
-  it "returns 1 when self is greater than the passed argument" do
-    (Rational(4, 4) <=> Rational(3, 4)).should equal(1)
-    (Rational(-3, 4) <=> Rational(-4, 4)).should equal(1)
-  end
-
-  it "returns 0 when self is equal to the passed argument" do
-    (Rational(4, 4) <=> Rational(4, 4)).should equal(0)
-    (Rational(-3, 4) <=> Rational(-3, 4)).should equal(0)
-  end
-
-  it "returns -1 when self is less than the passed argument" do
-    (Rational(3, 4) <=> Rational(4, 4)).should equal(-1)
-    (Rational(-4, 4) <=> Rational(-3, 4)).should equal(-1)
-  end
-end
-
-describe :rational_cmp_int, shared: true do
-  it "returns 1 when self is greater than the passed argument" do
-    (Rational(4, 4) <=> 0).should equal(1)
-    (Rational(4, 4) <=> -10).should equal(1)
-    (Rational(-3, 4) <=> -1).should equal(1)
-  end
-
-  it "returns 0 when self is equal to the passed argument" do
-    (Rational(4, 4) <=> 1).should equal(0)
-    (Rational(-8, 4) <=> -2).should equal(0)
-  end
-
-  it "returns -1 when self is less than the passed argument" do
-    (Rational(3, 4) <=> 1).should equal(-1)
-    (Rational(-4, 4) <=> 0).should equal(-1)
-  end
-end
-
-describe :rational_cmp_float, shared: true do
-  it "returns 1 when self is greater than the passed argument" do
-    (Rational(4, 4) <=> 0.5).should equal(1)
-    (Rational(4, 4) <=> -1.5).should equal(1)
-    (Rational(-3, 4) <=> -0.8).should equal(1)
-  end
-
-  it "returns 0 when self is equal to the passed argument" do
-    (Rational(4, 4) <=> 1.0).should equal(0)
-    (Rational(-6, 4) <=> -1.5).should equal(0)
-  end
-
-  it "returns -1 when self is less than the passed argument" do
-    (Rational(3, 4) <=> 1.2).should equal(-1)
-    (Rational(-4, 4) <=> 0.5).should equal(-1)
-  end
-end
-
-describe :rational_cmp_coerce, shared: true do
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational <=> obj
-  end
-
-  it "calls #<=> on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:<=>).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    (rational <=> obj).should == :result
-  end
-end
-
-describe :rational_cmp_coerce_exception, shared: true do
-  ruby_version_is ""..."2.5" do
-    it "rescues exception (StandardError and subclasses) raised in other#coerce and returns nil" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
-
-      -> {
-        (Rational(3, 4) <=> b).should == nil
-      }.should complain(/Numerical comparison operators will no more rescue exceptions of #coerce/)
-    end
-
-    it "does not rescue Exception and StandardError siblings raised in other#coerce" do
-      [Exception, NoMemoryError].each do |exception|
-        b = mock("numeric with failed #coerce")
-        b.should_receive(:coerce).and_raise(exception)
-
-        -> { Rational(3, 4) <=> b }.should raise_error(exception)
-      end
-    end
-  end
-
-  ruby_version_is "2.5" do
-    it "does not rescue exception raised in other#coerce" do
-      b = mock("numeric with failed #coerce")
-      b.should_receive(:coerce).and_raise(RationalSpecs::CoerceError)
-
-      -> { Rational(3, 4) <=> b }.should raise_error(RationalSpecs::CoerceError)
-    end
-  end
-end
-
-describe :rational_cmp_other, shared: true do
-  it "returns nil" do
-    (Rational <=> mock("Object")).should be_nil
-  end
-end
diff --git a/spec/ruby/shared/rational/denominator.rb b/spec/ruby/shared/rational/denominator.rb
deleted file mode 100644
index 10d46aacb3..0000000000
--- a/spec/ruby/shared/rational/denominator.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_denominator, shared: true do
-  it "returns the denominator" do
-    Rational(3, 4).denominator.should equal(4)
-    Rational(3, -4).denominator.should equal(4)
-
-    Rational(1, bignum_value).denominator.should == bignum_value
-  end
-
-  it "returns 1 if no denominator was given" do
-    Rational(80).denominator.should == 1
-  end
-end
diff --git a/spec/ruby/shared/rational/div.rb b/spec/ruby/shared/rational/div.rb
deleted file mode 100644
index d5bd9e6644..0000000000
--- a/spec/ruby/shared/rational/div.rb
+++ /dev/null
@@ -1,54 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_div_rat, shared: true do
-  it "performs integer division and returns the result" do
-    Rational(2, 3).div(Rational(2, 3)).should == 1
-    Rational(-2, 9).div(Rational(-9, 2)).should == 0
-  end
-
-  it "raises a ZeroDivisionError when the argument has a numerator of 0" do
-    -> { Rational(3, 4).div(Rational(0, 3)) }.should raise_error(ZeroDivisionError)
-  end
-
-  it "raises a ZeroDivisionError when the argument has a numerator of 0.0" do
-    -> { Rational(3, 4).div(Rational(0.0, 3)) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_div_float, shared: true do
-  it "performs integer division and returns the result" do
-    Rational(2, 3).div(30.333).should == 0
-    Rational(2, 9).div(Rational(-8.6)).should == -1
-    Rational(3.12).div(0.5).should == 6
-  end
-
-  it "raises a ZeroDivisionError when the argument is 0.0" do
-    -> { Rational(3, 4).div(0.0) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_div_int, shared: true do
-  it "performs integer division and returns the result" do
-    Rational(2, 1).div(1).should == 2
-    Rational(25, 5).div(-50).should == -1
-  end
-
-  it "raises a ZeroDivisionError when the argument is 0" do
-    -> { Rational(3, 4).div(0) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_div, shared: true do
-  it "returns an Integer" do
-    Rational(229, 21).div(82).should be_kind_of(Integer)
-  end
-
-  it "raises an ArgumentError if passed more than one argument" do
-    -> { Rational(3, 4).div(2,3) }.should raise_error(ArgumentError)
-  end
-
-  # See http://redmine.ruby-lang.org/issues/show/1648
-  it "raises a TypeError if passed a non-numeric argument" do
-    -> { Rational(3, 4).div([]) }.should raise_error(TypeError)
-  end
-end
diff --git a/spec/ruby/shared/rational/divide.rb b/spec/ruby/shared/rational/divide.rb
deleted file mode 100644
index 7d6d66390f..0000000000
--- a/spec/ruby/shared/rational/divide.rb
+++ /dev/null
@@ -1,71 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_divide_rat, shared: true do
-  it "returns self divided by other as a Rational" do
-    Rational(3, 4).send(@method, Rational(3, 4)).should eql(Rational(1, 1))
-    Rational(2, 4).send(@method, Rational(1, 4)).should eql(Rational(2, 1))
-
-    Rational(2, 4).send(@method, 2).should == Rational(1, 4)
-    Rational(6, 7).send(@method, -2).should == Rational(-3, 7)
-  end
-
-  it "raises a ZeroDivisionError when passed a Rational with a numerator of 0" do
-    -> { Rational(3, 4).send(@method, Rational(0, 1)) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_divide_int, shared: true do
-  it "returns self divided by other as a Rational" do
-    Rational(3, 4).send(@method, 2).should eql(Rational(3, 8))
-    Rational(2, 4).send(@method, 2).should eql(Rational(1, 4))
-    Rational(6, 7).send(@method, -2).should eql(Rational(-3, 7))
-  end
-
-  it "raises a ZeroDivisionError when passed 0" do
-    -> { Rational(3, 4).send(@method, 0) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_divide_float, shared: true do
-  it "returns self divided by other as a Float" do
-    Rational(3, 4).send(@method, 0.75).should eql(1.0)
-    Rational(3, 4).send(@method, 0.25).should eql(3.0)
-    Rational(3, 4).send(@method, 0.3).should eql(2.5)
-
-    Rational(-3, 4).send(@method, 0.3).should eql(-2.5)
-    Rational(3, -4).send(@method, 0.3).should eql(-2.5)
-    Rational(3, 4).send(@method, -0.3).should eql(-2.5)
-  end
-
-  it "returns infinity when passed 0" do
-    Rational(3, 4).send(@method, 0.0).infinite?.should eql(1)
-    Rational(-3, -4).send(@method, 0.0).infinite?.should eql(1)
-
-    Rational(-3, 4).send(@method, 0.0).infinite?.should eql(-1)
-    Rational(3, -4).send(@method, 0.0).infinite?.should eql(-1)
-  end
-end
-
-describe :rational_divide, shared: true do
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-    obj = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational.send(@method, obj)
-  end
-
-  it "calls #/ on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:/).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    rational.send(@method, obj).should == :result
-  end
-end
diff --git a/spec/ruby/shared/rational/divmod.rb b/spec/ruby/shared/rational/divmod.rb
deleted file mode 100644
index 5b319a95ff..0000000000
--- a/spec/ruby/shared/rational/divmod.rb
+++ /dev/null
@@ -1,42 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_divmod_rat, shared: true do
-  it "returns the quotient as Integer and the remainder as Rational" do
-    Rational(7, 4).divmod(Rational(1, 2)).should eql([3, Rational(1, 4)])
-    Rational(7, 4).divmod(Rational(-1, 2)).should eql([-4, Rational(-1, 4)])
-    Rational(0, 4).divmod(Rational(4, 3)).should eql([0, Rational(0, 1)])
-
-    Rational(bignum_value, 4).divmod(Rational(4, 3)).should eql([1729382256910270464, Rational(0, 1)])
-  end
-
-  it "raises a ZeroDivisonError when passed a Rational with a numerator of 0" do
-    -> { Rational(7, 4).divmod(Rational(0, 3)) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_divmod_int, shared: true do
-  it "returns the quotient as Integer and the remainder as Rational" do
-    Rational(7, 4).divmod(2).should eql([0, Rational(7, 4)])
-    Rational(7, 4).divmod(-2).should eql([-1, Rational(-1, 4)])
-
-    Rational(bignum_value, 4).divmod(3).should == [768614336404564650, Rational(2, 1)]
-  end
-
-  it "raises a ZeroDivisionError when passed 0" do
-    -> { Rational(7, 4).divmod(0) }.should raise_error(ZeroDivisionError)
-  end
-end
-
-describe :rational_divmod_float, shared: true do
-  it "returns the quotient as Integer and the remainder as Float" do
-    Rational(7, 4).divmod(0.5).should eql([3, 0.25])
-  end
-
-  it "returns the quotient as Integer and the remainder as Float" do
-    Rational(7, 4).divmod(-0.5).should eql([-4, -0.25])
-  end
-
-  it "raises a ZeroDivisionError when passed 0" do
-    -> { Rational(7, 4).divmod(0.0) }.should raise_error(ZeroDivisionError)
-  end
-end
diff --git a/spec/ruby/shared/rational/equal_value.rb b/spec/ruby/shared/rational/equal_value.rb
deleted file mode 100644
index b2e7e09415..0000000000
--- a/spec/ruby/shared/rational/equal_value.rb
+++ /dev/null
@@ -1,39 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_equal_value_rat, shared: true do
-  it "returns true if self has the same numerator and denominator as the passed argument" do
-    (Rational(3, 4) == Rational(3, 4)).should be_true
-    (Rational(-3, -4) == Rational(3, 4)).should be_true
-    (Rational(-4, 5) == Rational(4, -5)).should be_true
-
-    (Rational(bignum_value, 3) == Rational(bignum_value, 3)).should be_true
-    (Rational(-bignum_value, 3) == Rational(bignum_value, -3)).should be_true
-  end
-end
-
-describe :rational_equal_value_int, shared: true do
-  it "returns true if self has the passed argument as numerator and a denominator of 1" do
-    # Rational(x, y) reduces x and y automatically
-    (Rational(4, 2) == 2).should be_true
-    (Rational(-4, 2) == -2).should be_true
-    (Rational(4, -2) == -2).should be_true
-  end
-end
-
-describe :rational_equal_value_float, shared: true do
-  it "converts self to a Float and compares it with the passed argument" do
-    (Rational(3, 4) == 0.75).should be_true
-    (Rational(4, 2) == 2.0).should be_true
-    (Rational(-4, 2) == -2.0).should be_true
-    (Rational(4, -2) == -2.0).should be_true
-  end
-end
-
-describe :rational_equal_value, shared: true do
-  it "returns the result of calling #== with self on the passed argument" do
-    obj = mock("Object")
-    obj.should_receive(:==).and_return(:result)
-
-    (Rational(3, 4) == obj).should_not be_false
-  end
-end
diff --git a/spec/ruby/shared/rational/exponent.rb b/spec/ruby/shared/rational/exponent.rb
deleted file mode 100644
index 1d808177e9..0000000000
--- a/spec/ruby/shared/rational/exponent.rb
+++ /dev/null
@@ -1,178 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_exponent, shared: true do
-  describe "when passed Rational" do
-    # Guard against the Mathn library
-    guard -> { !defined?(Math.rsqrt) } do
-      it "returns Rational(1) if the exponent is Rational(0)" do
-        (Rational(0) ** Rational(0)).should eql(Rational(1))
-        (Rational(1) ** Rational(0)).should eql(Rational(1))
-        (Rational(3, 4) ** Rational(0)).should eql(Rational(1))
-        (Rational(-1) ** Rational(0)).should eql(Rational(1))
-        (Rational(-3, 4) ** Rational(0)).should eql(Rational(1))
-        (Rational(bignum_value) ** Rational(0)).should eql(Rational(1))
-        (Rational(-bignum_value) ** Rational(0)).should eql(Rational(1))
-      end
-
-      it "returns self raised to the argument as a Rational if the exponent's denominator is 1" do
-        (Rational(3, 4) ** Rational(1, 1)).should eql(Rational(3, 4))
-        (Rational(3, 4) ** Rational(2, 1)).should eql(Rational(9, 16))
-        (Rational(3, 4) ** Rational(-1, 1)).should eql(Rational(4, 3))
-        (Rational(3, 4) ** Rational(-2, 1)).should eql(Rational(16, 9))
-      end
-
-      it "returns self raised to the argument as a Float if the exponent's denominator is not 1" do
-        (Rational(3, 4) ** Rational(4, 3)).should be_close(0.681420222312052, TOLERANCE)
-        (Rational(3, 4) ** Rational(-4, 3)).should be_close(1.46752322173095, TOLERANCE)
-        (Rational(3, 4) ** Rational(4, -3)).should be_close(1.46752322173095, TOLERANCE)
-      end
-
-      it "returns a complex number when self is negative and the passed argument is not 0" do
-        (Rational(-3, 4) ** Rational(-4, 3)).should be_close(Complex(-0.7337616108654732, 1.2709123906625817), TOLERANCE)
-      end
-    end
-  end
-
-  describe "when passed Integer" do
-    it "returns the Rational value of self raised to the passed argument" do
-      (Rational(3, 4) ** 4).should == Rational(81, 256)
-      (Rational(3, 4) ** -4).should == Rational(256, 81)
-      (Rational(-3, 4) ** -4).should == Rational(256, 81)
-      (Rational(3, -4) ** -4).should == Rational(256, 81)
-
-      (Rational(bignum_value, 4) ** 4).should == Rational(28269553036454149273332760011886696253239742350009903329945699220681916416, 1)
-      (Rational(3, bignum_value) ** -4).should == Rational(7237005577332262213973186563042994240829374041602535252466099000494570602496, 81)
-      (Rational(-bignum_value, 4) ** -4).should == Rational(1, 28269553036454149273332760011886696253239742350009903329945699220681916416)
-      (Rational(3, -bignum_value) ** -4).should == Rational(7237005577332262213973186563042994240829374041602535252466099000494570602496, 81)
-    end
-
-    # Guard against the Mathn library
-    guard -> { !defined?(Math.rsqrt) } do
-      it "returns Rational(1, 1) when the passed argument is 0" do
-        (Rational(3, 4) ** 0).should eql(Rational(1, 1))
-        (Rational(-3, 4) ** 0).should eql(Rational(1, 1))
-        (Rational(3, -4) ** 0).should eql(Rational(1, 1))
-
-        (Rational(bignum_value, 4) ** 0).should eql(Rational(1, 1))
-        (Rational(3, -bignum_value) ** 0).should eql(Rational(1, 1))
-      end
-    end
-  end
-
-  describe "when passed Bignum" do
-    # #5713
-    it "returns Rational(0) when self is Rational(0) and the exponent is positive" do
-      (Rational(0) ** bignum_value).should eql(Rational(0))
-    end
-
-    it "raises ZeroDivisionError when self is Rational(0) and the exponent is negative" do
-      -> { Rational(0) ** -bignum_value }.should raise_error(ZeroDivisionError)
-    end
-
-    it "returns Rational(1) when self is Rational(1)" do
-      (Rational(1) **  bignum_value).should eql(Rational(1))
-      (Rational(1) ** -bignum_value).should eql(Rational(1))
-    end
-
-    it "returns Rational(1) when self is Rational(-1) and the exponent is positive and even" do
-      (Rational(-1) ** bignum_value(0)).should eql(Rational(1))
-      (Rational(-1) ** bignum_value(2)).should eql(Rational(1))
-    end
-
-    it "returns Rational(-1) when self is Rational(-1) and the exponent is positive and odd" do
-      (Rational(-1) ** bignum_value(1)).should eql(Rational(-1))
-      (Rational(-1) ** bignum_value(3)).should eql(Rational(-1))
-    end
-
-    it "returns positive Infinity when self is > 1" do
-      (Rational(2) ** bignum_value).infinite?.should == 1
-      (Rational(fixnum_max) ** bignum_value).infinite?.should == 1
-    end
-
-    it "returns 0.0 when self is > 1 and the exponent is negative" do
-      (Rational(2) ** -bignum_value).should eql(0.0)
-      (Rational(fixnum_max) ** -bignum_value).should eql(0.0)
-    end
-
-    # Fails on linux due to pow() bugs in glibc: http://sources.redhat.com/bugzilla/show_bug.cgi?id=3866
-    platform_is_not :linux do
-      it "returns positive Infinity when self < -1" do
-        (Rational(-2) ** bignum_value).infinite?.should == 1
-        (Rational(-2) ** (bignum_value + 1)).infinite?.should == 1
-        (Rational(fixnum_min) ** bignum_value).infinite?.should == 1
-      end
-
-      it "returns 0.0 when self is < -1 and the exponent is negative" do
-        (Rational(-2) ** -bignum_value).should eql(0.0)
-        (Rational(fixnum_min) ** -bignum_value).should eql(0.0)
-      end
-    end
-  end
-
-  describe "when passed Float" do
-    it "returns self converted to Float and raised to the passed argument" do
-      (Rational(3, 1) ** 3.0).should eql(27.0)
-      (Rational(3, 1) ** 1.5).should be_close(5.19615242270663, TOLERANCE)
-      (Rational(3, 1) ** -1.5).should be_close(0.192450089729875, TOLERANCE)
-    end
-
-    it "returns a complex number if self is negative and the passed argument is not 0" do
-      (Rational(-3, 2) ** 1.5).should be_close(Complex(0.0, -1.8371173070873836), TOLERANCE)
-      (Rational(3, -2) ** 1.5).should be_close(Complex(0.0, -1.8371173070873836), TOLERANCE)
-      (Rational(3, -2) ** -1.5).should be_close(Complex(0.0, 0.5443310539518174), TOLERANCE)
-    end
-
-    it "returns Complex(1.0) when the passed argument is 0.0" do
-      (Rational(3, 4) ** 0.0).should == Complex(1.0)
-      (Rational(-3, 4) ** 0.0).should == Complex(1.0)
-      (Rational(-3, 4) ** 0.0).should == Complex(1.0)
-    end
-  end
-
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-    obj      = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational ** obj
-  end
-
-  it "calls #** on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:**).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    (rational ** obj).should == :result
-  end
-
-  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Integer" do
-    [-1, -4, -9999].each do |exponent|
-      -> { Rational(0, 1) ** exponent }.should raise_error(ZeroDivisionError, "divided by 0")
-    end
-  end
-
-  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Rational with denominator 1" do
-    [Rational(-1, 1), Rational(-3, 1)].each do |exponent|
-      -> { Rational(0, 1) ** exponent }.should raise_error(ZeroDivisionError, "divided by 0")
-    end
-  end
-
-  # #7513
-  it "raises ZeroDivisionError for Rational(0, 1) passed a negative Rational" do
-    -> { Rational(0, 1) ** Rational(-3, 2) }.should raise_error(ZeroDivisionError, "divided by 0")
-  end
-
-  platform_is_not :solaris do # See https://github.com/ruby/spec/issues/134
-    it "returns Infinity for Rational(0, 1) passed a negative Float" do
-      [-1.0, -3.0, -3.14].each do |exponent|
-        (Rational(0, 1) ** exponent).infinite?.should == 1
-      end
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/fdiv.rb b/spec/ruby/shared/rational/fdiv.rb
deleted file mode 100644
index 6911ade8ac..0000000000
--- a/spec/ruby/shared/rational/fdiv.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_fdiv, shared: true do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/shared/rational/floor.rb b/spec/ruby/shared/rational/floor.rb
deleted file mode 100644
index ddf7fdbd17..0000000000
--- a/spec/ruby/shared/rational/floor.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_floor, shared: true do
-  before do
-    @rational = Rational(2200, 7)
-  end
-
-  describe "with no arguments (precision = 0)" do
-    it "returns an integer" do
-      @rational.floor.should be_kind_of(Integer)
-    end
-
-    it "returns the truncated value toward negative infinity" do
-      @rational.floor.should == 314
-      Rational(1, 2).floor.should == 0
-      Rational(-1, 2).floor.should == -1
-    end
-  end
-
-  describe "with a precision < 0" do
-    it "returns an integer" do
-      @rational.floor(-2).should be_kind_of(Integer)
-      @rational.floor(-1).should be_kind_of(Integer)
-    end
-
-    it "moves the truncation point n decimal places left" do
-      @rational.floor(-3).should == 0
-      @rational.floor(-2).should == 300
-      @rational.floor(-1).should == 310
-    end
-  end
-
-  describe "with a precision > 0" do
-    it "returns a Rational" do
-      @rational.floor(1).should be_kind_of(Rational)
-      @rational.floor(2).should be_kind_of(Rational)
-    end
-
-    it "moves the truncation point n decimal places right" do
-      @rational.floor(1).should == Rational(1571, 5)
-      @rational.floor(2).should == Rational(7857, 25)
-      @rational.floor(3).should == Rational(62857, 200)
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/hash.rb b/spec/ruby/shared/rational/hash.rb
deleted file mode 100644
index 50f21cec20..0000000000
--- a/spec/ruby/shared/rational/hash.rb
+++ /dev/null
@@ -1,9 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_hash, shared: true do
-  # BUG: Rational(2, 3).hash == Rational(3, 2).hash
-  it "is static" do
-    Rational(2, 3).hash.should == Rational(2, 3).hash
-    Rational(2, 4).hash.should_not == Rational(2, 3).hash
-  end
-end
diff --git a/spec/ruby/shared/rational/inspect.rb b/spec/ruby/shared/rational/inspect.rb
deleted file mode 100644
index 19691a2f25..0000000000
--- a/spec/ruby/shared/rational/inspect.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_inspect, shared: true do
-  it "returns a string representation of self" do
-    Rational(3, 4).inspect.should == "(3/4)"
-    Rational(-5, 8).inspect.should == "(-5/8)"
-    Rational(-1, -2).inspect.should == "(1/2)"
-
-    # Guard against the Mathn library
-    guard -> { !defined?(Math.rsqrt) } do
-      Rational(bignum_value, 1).inspect.should == "(#{bignum_value}/1)"
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/marshal_dump.rb b/spec/ruby/shared/rational/marshal_dump.rb
deleted file mode 100644
index 09782b45a5..0000000000
--- a/spec/ruby/shared/rational/marshal_dump.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_marshal_dump, shared: true do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/shared/rational/marshal_load.rb b/spec/ruby/shared/rational/marshal_load.rb
deleted file mode 100644
index 20bdd6fdf4..0000000000
--- a/spec/ruby/shared/rational/marshal_load.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_marshal_load, shared: true do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/shared/rational/minus.rb b/spec/ruby/shared/rational/minus.rb
deleted file mode 100644
index 0a0946fdb9..0000000000
--- a/spec/ruby/shared/rational/minus.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_minus_rat, shared: true do
-  it "returns the result of subtracting other from self as a Rational" do
-    (Rational(3, 4) - Rational(0, 1)).should eql(Rational(3, 4))
-    (Rational(3, 4) - Rational(1, 4)).should eql(Rational(1, 2))
-
-    (Rational(3, 4) - Rational(2, 1)).should eql(Rational(-5, 4))
-  end
-end
-
-describe :rational_minus_int, shared: true do
-  it "returns the result of subtracting other from self as a Rational" do
-    (Rational(3, 4) - 1).should eql(Rational(-1, 4))
-    (Rational(3, 4) - 2).should eql(Rational(-5, 4))
-  end
-end
-
-describe :rational_minus_float, shared: true do
-  it "returns the result of subtracting other from self as a Float" do
-    (Rational(3, 4) - 0.2).should eql(0.55)
-    (Rational(3, 4) - 2.5).should eql(-1.75)
-  end
-end
-
-describe :rational_minus, shared: true do
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-    obj = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational - obj
-  end
-
-  it "calls #- on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:-).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    (rational - obj).should == :result
-  end
-end
diff --git a/spec/ruby/shared/rational/modulo.rb b/spec/ruby/shared/rational/modulo.rb
deleted file mode 100644
index 9e4b0c49e6..0000000000
--- a/spec/ruby/shared/rational/modulo.rb
+++ /dev/null
@@ -1,43 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_modulo, shared: true do
-  it "returns the remainder when this value is divided by other" do
-    Rational(2, 3).send(@method, Rational(2, 3)).should == Rational(0, 1)
-    Rational(4, 3).send(@method, Rational(2, 3)).should == Rational(0, 1)
-    Rational(2, -3).send(@method, Rational(-2, 3)).should == Rational(0, 1)
-    Rational(0, -1).send(@method, -1).should == Rational(0, 1)
-
-    Rational(7, 4).send(@method, Rational(1, 2)).should == Rational(1, 4)
-    Rational(7, 4).send(@method, 1).should == Rational(3, 4)
-    Rational(7, 4).send(@method, Rational(1, 7)).should == Rational(1, 28)
-
-    Rational(3, 4).send(@method, -1).should == Rational(-1, 4)
-    Rational(1, -5).send(@method, -1).should == Rational(-1, 5)
-  end
-
-  it "returns a Float value when the argument is Float" do
-    Rational(7, 4).send(@method, 1.0).should be_kind_of(Float)
-    Rational(7, 4).send(@method, 1.0).should == 0.75
-    Rational(7, 4).send(@method, 0.26).should be_close(0.19, 0.0001)
-  end
-
-  it "raises ZeroDivisionError on zero denominator" do
-    -> {
-      Rational(3, 5).send(@method, Rational(0, 1))
-    }.should raise_error(ZeroDivisionError)
-
-    -> {
-      Rational(0, 1).send(@method, Rational(0, 1))
-    }.should raise_error(ZeroDivisionError)
-
-    -> {
-      Rational(3, 5).send(@method, 0)
-    }.should raise_error(ZeroDivisionError)
-  end
-
-  it "raises a ZeroDivisionError when the argument is 0.0" do
-    -> {
-      Rational(3, 5).send(@method, 0.0)
-    }.should raise_error(ZeroDivisionError)
-  end
-end
diff --git a/spec/ruby/shared/rational/multiply.rb b/spec/ruby/shared/rational/multiply.rb
deleted file mode 100644
index 9c861cf79d..0000000000
--- a/spec/ruby/shared/rational/multiply.rb
+++ /dev/null
@@ -1,62 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_multiply_rat, shared: true do
-  it "returns self divided by other as a Rational" do
-    (Rational(3, 4) * Rational(3, 4)).should eql(Rational(9, 16))
-    (Rational(2, 4) * Rational(1, 4)).should eql(Rational(1, 8))
-
-    (Rational(3, 4) * Rational(0, 1)).should eql(Rational(0, 4))
-  end
-end
-
-describe :rational_multiply_int, shared: true do
-  it "returns self divided by other as a Rational" do
-    (Rational(3, 4) * 2).should eql(Rational(3, 2))
-    (Rational(2, 4) * 2).should eql(Rational(1, 1))
-    (Rational(6, 7) * -2).should eql(Rational(-12, 7))
-
-    (Rational(3, 4) * 0).should eql(Rational(0, 4))
-  end
-end
-
-describe :rational_multiply_float, shared: true do
-  it "returns self divided by other as a Float" do
-    (Rational(3, 4) * 0.75).should eql(0.5625)
-    (Rational(3, 4) * 0.25).should eql(0.1875)
-    (Rational(3, 4) * 0.3).should be_close(0.225, TOLERANCE)
-
-    (Rational(-3, 4) * 0.3).should be_close(-0.225, TOLERANCE)
-    (Rational(3, -4) * 0.3).should be_close(-0.225, TOLERANCE)
-    (Rational(3, 4) * -0.3).should be_close(-0.225, TOLERANCE)
-
-    (Rational(3, 4) * 0.0).should eql(0.0)
-    (Rational(-3, -4) * 0.0).should eql(0.0)
-
-    (Rational(-3, 4) * 0.0).should eql(0.0)
-    (Rational(3, -4) * 0.0).should eql(0.0)
-  end
-end
-
-describe :rational_multiply, shared: true do
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-    obj = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational * obj
-  end
-
-  it "calls #* on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:*).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    (rational * obj).should == :result
-  end
-end
diff --git a/spec/ruby/shared/rational/numerator.rb b/spec/ruby/shared/rational/numerator.rb
deleted file mode 100644
index 50d768168c..0000000000
--- a/spec/ruby/shared/rational/numerator.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_numerator, shared: true do
-  it "returns the numerator" do
-    Rational(3, 4).numerator.should equal(3)
-    Rational(3, -4).numerator.should equal(-3)
-
-    Rational(bignum_value, 1).numerator.should == bignum_value
-  end
-end
diff --git a/spec/ruby/shared/rational/plus.rb b/spec/ruby/shared/rational/plus.rb
deleted file mode 100644
index b126360ee4..0000000000
--- a/spec/ruby/shared/rational/plus.rb
+++ /dev/null
@@ -1,48 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_plus_rat, shared: true do
-  it "returns the result of subtracting other from self as a Rational" do
-    (Rational(3, 4) + Rational(0, 1)).should eql(Rational(3, 4))
-    (Rational(3, 4) + Rational(1, 4)).should eql(Rational(1, 1))
-
-    (Rational(3, 4) + Rational(2, 1)).should eql(Rational(11, 4))
-  end
-end
-
-describe :rational_plus_int, shared: true do
-  it "returns the result of subtracting other from self as a Rational" do
-    (Rational(3, 4) + 1).should eql(Rational(7, 4))
-    (Rational(3, 4) + 2).should eql(Rational(11, 4))
-  end
-end
-
-describe :rational_plus_float, shared: true do
-  it "returns the result of subtracting other from self as a Float" do
-    (Rational(3, 4) + 0.2).should eql(0.95)
-    (Rational(3, 4) + 2.5).should eql(3.25)
-  end
-end
-
-describe :rational_plus, shared: true do
-  it "calls #coerce on the passed argument with self" do
-    rational = Rational(3, 4)
-    obj = mock("Object")
-    obj.should_receive(:coerce).with(rational).and_return([1, 2])
-
-    rational + obj
-  end
-
-  it "calls #+ on the coerced Rational with the coerced Object" do
-    rational = Rational(3, 4)
-
-    coerced_rational = mock("Coerced Rational")
-    coerced_rational.should_receive(:+).and_return(:result)
-
-    coerced_obj = mock("Coerced Object")
-
-    obj = mock("Object")
-    obj.should_receive(:coerce).and_return([coerced_rational, coerced_obj])
-
-    (rational + obj).should == :result
-  end
-end
diff --git a/spec/ruby/shared/rational/quo.rb b/spec/ruby/shared/rational/quo.rb
deleted file mode 100644
index 53b32fed2f..0000000000
--- a/spec/ruby/shared/rational/quo.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_quo, shared: true do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/shared/rational/remainder.rb b/spec/ruby/shared/rational/remainder.rb
deleted file mode 100644
index dd907608db..0000000000
--- a/spec/ruby/shared/rational/remainder.rb
+++ /dev/null
@@ -1,5 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_remainder, shared: true do
-  it "needs to be reviewed for spec completeness"
-end
diff --git a/spec/ruby/shared/rational/round.rb b/spec/ruby/shared/rational/round.rb
deleted file mode 100644
index 5b159ee3e6..0000000000
--- a/spec/ruby/shared/rational/round.rb
+++ /dev/null
@@ -1,106 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_round, shared: true do
-  before do
-    @rational = Rational(2200, 7)
-  end
-
-  describe "with no arguments (precision = 0)" do
-    it "returns an integer" do
-      @rational.round.should be_kind_of(Integer)
-      Rational(0, 1).round(0).should be_kind_of(Integer)
-      Rational(124, 1).round(0).should be_kind_of(Integer)
-    end
-
-    it "returns the truncated value toward the nearest integer" do
-      @rational.round.should == 314
-      Rational(0, 1).round(0).should == 0
-      Rational(2, 1).round(0).should == 2
-    end
-
-    it "returns the rounded value toward the nearest integer" do
-      Rational(1, 2).round.should == 1
-      Rational(-1, 2).round.should == -1
-      Rational(3, 2).round.should == 2
-      Rational(-3, 2).round.should == -2
-      Rational(5, 2).round.should == 3
-      Rational(-5, 2).round.should == -3
-    end
-  end
-
-  describe "with a precision < 0" do
-    it "returns an integer" do
-      @rational.round(-2).should be_kind_of(Integer)
-      @rational.round(-1).should be_kind_of(Integer)
-      Rational(0, 1).round(-1).should be_kind_of(Integer)
-      Rational(2, 1).round(-1).should be_kind_of(Integer)
-    end
-
-    it "moves the truncation point n decimal places left" do
-      @rational.round(-3).should == 0
-      @rational.round(-2).should == 300
-      @rational.round(-1).should == 310
-    end
-  end
-
-  describe "with a precision > 0" do
-    it "returns a Rational" do
-      @rational.round(1).should be_kind_of(Rational)
-      @rational.round(2).should be_kind_of(Rational)
-      # Guard against the Mathn library
-      guard -> { !defined?(Math.rsqrt) } do
-        Rational(0, 1).round(1).should be_kind_of(Rational)
-        Rational(2, 1).round(1).should be_kind_of(Rational)
-      end
-    end
-
-    it "moves the truncation point n decimal places right" do
-      @rational.round(1).should == Rational(3143, 10)
-      @rational.round(2).should == Rational(31429, 100)
-      @rational.round(3).should == Rational(157143, 500)
-      Rational(0, 1).round(1).should == Rational(0, 1)
-      Rational(2, 1).round(1).should == Rational(2, 1)
-    end
-
-    it "doesn't alter the value if the precision is too great" do
-      Rational(3, 2).round(10).should == Rational(3, 2).round(20)
-    end
-
-    # #6605
-    it "doesn't fail when rounding to an absurdly large positive precision" do
-      Rational(3, 2).round(2_097_171).should == Rational(3, 2)
-    end
-  end
-
-  describe "with half option" do
-    it "returns an Integer when precision is not passed" do
-      Rational(10, 4).round(half: nil).should == 3
-      Rational(10, 4).round(half: :up).should == 3
-      Rational(10, 4).round(half: :down).should == 2
-      Rational(10, 4).round(half: :even).should == 2
-      Rational(-10, 4).round(half: nil).should == -3
-      Rational(-10, 4).round(half: :up).should == -3
-      Rational(-10, 4).round(half: :down).should == -2
-      Rational(-10, 4).round(half: :even).should == -2
-    end
-
-    it "returns a Rational when the precision is greater than 0" do
-      Rational(25, 100).round(1, half: nil).should == Rational(3, 10)
-      Rational(25, 100).round(1, half: :up).should == Rational(3, 10)
-      Rational(25, 100).round(1, half: :down).should == Rational(1, 5)
-      Rational(25, 100).round(1, half: :even).should == Rational(1, 5)
-      Rational(35, 100).round(1, half: nil).should == Rational(2, 5)
-      Rational(35, 100).round(1, half: :up).should == Rational(2, 5)
-      Rational(35, 100).round(1, half: :down).should == Rational(3, 10)
-      Rational(35, 100).round(1, half: :even).should == Rational(2, 5)
-      Rational(-25, 100).round(1, half: nil).should == Rational(-3, 10)
-      Rational(-25, 100).round(1, half: :up).should == Rational(-3, 10)
-      Rational(-25, 100).round(1, half: :down).should == Rational(-1, 5)
-      Rational(-25, 100).round(1, half: :even).should == Rational(-1, 5)
-    end
-
-    it "raise for a non-existent round mode" do
-      -> { Rational(10, 4).round(half: :nonsense) }.should raise_error(ArgumentError, "invalid rounding mode: nonsense")
-    end
-  end
-end
diff --git a/spec/ruby/shared/rational/to_f.rb b/spec/ruby/shared/rational/to_f.rb
deleted file mode 100644
index 56e0b61d68..0000000000
--- a/spec/ruby/shared/rational/to_f.rb
+++ /dev/null
@@ -1,10 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_to_f, shared: true do
-  it "returns self converted to a Float" do
-    Rational(3, 4).to_f.should eql(0.75)
-    Rational(3, -4).to_f.should eql(-0.75)
-    Rational(-1, 4).to_f.should eql(-0.25)
-    Rational(-1, -4).to_f.should eql(0.25)
-  end
-end
diff --git a/spec/ruby/shared/rational/to_i.rb b/spec/ruby/shared/rational/to_i.rb
deleted file mode 100644
index 9be1183aa4..0000000000
--- a/spec/ruby/shared/rational/to_i.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_to_i, shared: true do
-  it "converts self to an Integer by truncation" do
-    Rational(7, 4).to_i.should eql(1)
-    Rational(11, 4).to_i.should eql(2)
-  end
-
-  it "converts self to an Integer by truncation" do
-    Rational(-7, 4).to_i.should eql(-1)
-  end
-end
diff --git a/spec/ruby/shared/rational/to_r.rb b/spec/ruby/shared/rational/to_r.rb
deleted file mode 100644
index 372c086850..0000000000
--- a/spec/ruby/shared/rational/to_r.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_to_r, shared: true do
-  it "returns self" do
-    a = Rational(3, 4)
-    a.to_r.should equal(a)
-
-    a = Rational(bignum_value, 4)
-    a.to_r.should equal(a)
-  end
-end
diff --git a/spec/ruby/shared/rational/to_s.rb b/spec/ruby/shared/rational/to_s.rb
deleted file mode 100644
index e90c6e5e39..0000000000
--- a/spec/ruby/shared/rational/to_s.rb
+++ /dev/null
@@ -1,14 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_to_s, shared: true do
-  it "returns a string representation of self" do
-    # Guard against the Mathn library
-    guard -> { !defined?(Math.rsqrt) } do
-      Rational(1, 1).to_s.should == "1/1"
-      Rational(2, 1).to_s.should == "2/1"
-    end
-    Rational(1, 2).to_s.should == "1/2"
-    Rational(-1, 3).to_s.should == "-1/3"
-    Rational(1, -3).to_s.should == "-1/3"
-  end
-end
diff --git a/spec/ruby/shared/rational/truncate.rb b/spec/ruby/shared/rational/truncate.rb
deleted file mode 100644
index 761dd3113a..0000000000
--- a/spec/ruby/shared/rational/truncate.rb
+++ /dev/null
@@ -1,45 +0,0 @@
-require_relative '../../spec_helper'
-
-describe :rational_truncate, shared: true do
-  before do
-    @rational = Rational(2200, 7)
-  end
-
-  describe "with no arguments (precision = 0)" do
-    it "returns an integer" do
-      @rational.truncate.should be_kind_of(Integer)
-    end
-
-    it "returns the truncated value toward 0" do
-      @rational.truncate.should == 314
-      Rational(1, 2).truncate.should == 0
-      Rational(-1, 2).truncate.should == 0
-    end
-  end
-
-  describe "with a precision < 0" do
-    it "returns an integer" do
-      @rational.truncate(-2).should be_kind_of(Integer)
-      @rational.truncate(-1).should be_kind_of(Integer)
-    end
-
-    it "moves the truncation point n decimal places left" do
-      @rational.truncate(-3).should == 0
-      @rational.truncate(-2).should == 300
-      @rational.truncate(-1).should == 310
-    end
-  end
-
-  describe "with a precision > 0" do
-    it "returns a Rational" do
-      @rational.truncate(1).should be_kind_of(Rational)
-      @rational.truncate(2).should be_kind_of(Rational)
-    end
-
-    it "moves the truncation point n decimal places right" do
-      @rational.truncate(1).should == Rational(1571, 5)
-      @rational.truncate(2).should == Rational(7857, 25)
-      @rational.truncate(3).should == Rational(62857, 200)
-    end
-  end
-end
diff --git a/spec/ruby/shared/sizedqueue/enque.rb b/spec/ruby/shared/sizedqueue/enque.rb
index 6ef12349f8..6804af3fb3 100644
--- a/spec/ruby/shared/sizedqueue/enque.rb
+++ b/spec/ruby/shared/sizedqueue/enque.rb
@@ -37,7 +37,7 @@ describe :sizedqueue_enq, shared: true do
     q << 1
 
     t = Thread.new {
-      -> { q.send(@method, 2) }.should raise_error(ClosedQueueError)
+      -> { q.send(@method, 2) }.should raise_error(ClosedQueueError, "queue closed")
     }
 
     Thread.pass until q.num_waiting == 1
@@ -47,4 +47,83 @@ describe :sizedqueue_enq, shared: true do
     t.join
     q.pop.should == 1
   end
+
+  describe "with a timeout" do
+    it "returns self if the item was pushed in time" do
+      q = @object.call(1)
+      q << 1
+
+      t = Thread.new {
+        q.send(@method, 2, timeout: TIME_TOLERANCE).should == q
+      }
+      Thread.pass until t.status == "sleep" && q.num_waiting == 1
+      q.pop
+      t.join
+    end
+
+    it "does nothing if the timeout is nil" do
+      q = @object.call(1)
+      q << 1
+      t = Thread.new {
+        q.send(@method, 2, timeout: nil).should == q
+      }
+      t.join(0.2).should == nil
+      q.pop
+      t.join
+    end
+
+    it "returns nil if no space is available and timeout is 0" do
+      q = @object.call(1)
+      q.send(@method, 1, timeout: 0).should == q
+      q.send(@method, 2, timeout: 0).should == nil
+    end
+
+    it "returns nil if no space is available in time" do
+      q = @object.call(1)
+      q << 1
+      Thread.new {
+        q.send(@method, 2, timeout: 0.001).should == nil
+      }.join
+    end
+
+    it "raise TypeError if timeout is not a valid numeric" do
+      q = @object.call(1)
+      -> {
+        q.send(@method, 2, timeout: "1")
+      }.should raise_error(TypeError, "no implicit conversion to float from string")
+
+      -> {
+        q.send(@method, 2, timeout: false)
+      }.should raise_error(TypeError, "no implicit conversion to float from false")
+    end
+
+    it "raise ArgumentError if non_block = true is passed too" do
+      q = @object.call(1)
+      -> {
+        q.send(@method, 2, true, timeout: 1)
+      }.should raise_error(ArgumentError, "can't set a timeout if non_block is enabled")
+    end
+
+    it "raise ClosedQueueError when closed before enqueued" do
+      q = @object.call(1)
+      q.close
+      -> { q.send(@method, 2, timeout: 1) }.should raise_error(ClosedQueueError, "queue closed")
+    end
+
+    it "interrupts enqueuing threads with ClosedQueueError when the queue is closed" do
+      q = @object.call(1)
+      q << 1
+
+      t = Thread.new {
+        -> { q.send(@method, 1, timeout: TIME_TOLERANCE) }.should raise_error(ClosedQueueError, "queue closed")
+      }
+
+      Thread.pass until q.num_waiting == 1
+
+      q.close
+
+      t.join
+      q.pop.should == 1
+    end
+  end
 end
diff --git a/spec/ruby/shared/sizedqueue/new.rb b/spec/ruby/shared/sizedqueue/new.rb
index 713785fb50..2573194efb 100644
--- a/spec/ruby/shared/sizedqueue/new.rb
+++ b/spec/ruby/shared/sizedqueue/new.rb
@@ -1,7 +1,12 @@
 describe :sizedqueue_new, shared: true do
-  it "raises a TypeError when the given argument is not Numeric" do
-    -> { @object.call("foo") }.should raise_error(TypeError)
+  it "raises a TypeError when the given argument doesn't respond to #to_int" do
+    -> { @object.call("12") }.should raise_error(TypeError)
     -> { @object.call(Object.new) }.should raise_error(TypeError)
+
+    @object.call(12.9).max.should == 12
+    object = Object.new
+    object.define_singleton_method(:to_int) { 42 }
+    @object.call(object).max.should == 42
   end
 
   it "raises an argument error when no argument is given" do
diff --git a/spec/ruby/shared/string/end_with.rb b/spec/ruby/shared/string/end_with.rb
new file mode 100644
index 0000000000..08f43c1bce
--- /dev/null
+++ b/spec/ruby/shared/string/end_with.rb
@@ -0,0 +1,61 @@
+describe :end_with, shared: true do
+  # the @method should either be :to_s or :to_sym
+
+  it "returns true only if ends match" do
+    s = "hello".send(@method)
+    s.should.end_with?('o')
+    s.should.end_with?('llo')
+  end
+
+  it 'returns false if the end does not match' do
+    s = 'hello'.send(@method)
+    s.should_not.end_with?('ll')
+  end
+
+  it "returns true if the search string is empty" do
+    "hello".send(@method).should.end_with?("")
+    "".send(@method).should.end_with?("")
+  end
+
+  it "returns true only if any ending match" do
+    "hello".send(@method).should.end_with?('x', 'y', 'llo', 'z')
+  end
+
+  it "converts its argument using :to_str" do
+    s = "hello".send(@method)
+    find = mock('o')
+    find.should_receive(:to_str).and_return("o")
+    s.should.end_with?(find)
+  end
+
+  it "ignores arguments not convertible to string" do
+    "hello".send(@method).should_not.end_with?()
+    -> { "hello".send(@method).end_with?(1) }.should raise_error(TypeError)
+    -> { "hello".send(@method).end_with?(["o"]) }.should raise_error(TypeError)
+    -> { "hello".send(@method).end_with?(1, nil, "o") }.should raise_error(TypeError)
+  end
+
+  it "uses only the needed arguments" do
+    find = mock('h')
+    find.should_not_receive(:to_str)
+    "hello".send(@method).should.end_with?("o", find)
+  end
+
+  it "works for multibyte strings" do
+    "céréale".send(@method).should.end_with?("réale")
+  end
+
+  it "raises an Encoding::CompatibilityError if the encodings are incompatible" do
+    pat = "ア".encode Encoding::EUC_JP
+    -> do
+      "あれ".send(@method).end_with?(pat)
+    end.should raise_error(Encoding::CompatibilityError)
+  end
+
+  it "checks that we are starting to match at the head of a character" do
+    "\xC3\xA9".send(@method).should_not.end_with?("\xA9")
+    "\xe3\x81\x82".send(@method).should_not.end_with?("\x82")
+    "\xd8\x00\xdc\x00".dup.force_encoding("UTF-16BE").send(@method).should_not.end_with?(
+        "\xdc\x00".dup.force_encoding("UTF-16BE"))
+  end
+end
diff --git a/spec/ruby/shared/string/start_with.rb b/spec/ruby/shared/string/start_with.rb
new file mode 100644
index 0000000000..4b947a3bbf
--- /dev/null
+++ b/spec/ruby/shared/string/start_with.rb
@@ -0,0 +1,84 @@
+describe :start_with, shared: true do
+  # the @method should either be :to_s or :to_sym
+
+  it "returns true only if beginning match" do
+    s = "hello".send(@method)
+    s.should.start_with?('h')
+    s.should.start_with?('hel')
+    s.should_not.start_with?('el')
+  end
+
+  it "returns true only if any beginning match" do
+    "hello".send(@method).should.start_with?('x', 'y', 'he', 'z')
+  end
+
+  it "returns true if the search string is empty" do
+    "hello".send(@method).should.start_with?("")
+    "".send(@method).should.start_with?("")
+  end
+
+  it "converts its argument using :to_str" do
+    s = "hello".send(@method)
+    find = mock('h')
+    find.should_receive(:to_str).and_return("h")
+    s.should.start_with?(find)
+  end
+
+  it "ignores arguments not convertible to string" do
+    "hello".send(@method).should_not.start_with?()
+    -> { "hello".send(@method).start_with?(1) }.should raise_error(TypeError)
+    -> { "hello".send(@method).start_with?(["h"]) }.should raise_error(TypeError)
+    -> { "hello".send(@method).start_with?(1, nil, "h") }.should raise_error(TypeError)
+  end
+
+  it "uses only the needed arguments" do
+    find = mock('h')
+    find.should_not_receive(:to_str)
+    "hello".send(@method).should.start_with?("h",find)
+  end
+
+  it "works for multibyte strings" do
+    "céréale".send(@method).should.start_with?("cér")
+  end
+
+  it "supports regexps" do
+    regexp = /[h1]/
+    "hello".send(@method).should.start_with?(regexp)
+    "1337".send(@method).should.start_with?(regexp)
+    "foxes are 1337".send(@method).should_not.start_with?(regexp)
+    "chunky\n12bacon".send(@method).should_not.start_with?(/12/)
+  end
+
+  it "supports regexps with ^ and $ modifiers" do
+    regexp1 = /^\d{2}/
+    regexp2 = /\d{2}$/
+    "12test".send(@method).should.start_with?(regexp1)
+    "test12".send(@method).should_not.start_with?(regexp1)
+    "12test".send(@method).should_not.start_with?(regexp2)
+    "test12".send(@method).should_not.start_with?(regexp2)
+  end
+
+  it "sets Regexp.last_match if it returns true" do
+    regexp = /test-(\d+)/
+    "test-1337".send(@method).start_with?(regexp).should be_true
+    Regexp.last_match.should_not be_nil
+    Regexp.last_match[1].should == "1337"
+    $1.should == "1337"
+
+    "test-asdf".send(@method).start_with?(regexp).should be_false
+    Regexp.last_match.should be_nil
+    $1.should be_nil
+  end
+
+  ruby_version_is ""..."3.3" do
+    it "does not check that we are not matching part of a character" do
+      "\xC3\xA9".send(@method).should.start_with?("\xC3")
+    end
+  end
+
+  ruby_version_is "3.3" do # #19784
+    it "checks that we are not matching part of a character" do
+      "\xC3\xA9".send(@method).should_not.start_with?("\xC3")
+    end
+  end
+end
diff --git a/spec/ruby/shared/string/times.rb b/spec/ruby/shared/string/times.rb
index 0baefd25b1..4814f894cf 100644
--- a/spec/ruby/shared/string/times.rb
+++ b/spec/ruby/shared/string/times.rb
@@ -20,41 +20,37 @@ describe :string_times, shared: true do
   it "raises an ArgumentError when given integer is negative" do
     -> { @object.call("cool", -3)    }.should raise_error(ArgumentError)
     -> { @object.call("cool", -3.14) }.should raise_error(ArgumentError)
+    -> { @object.call("cool", min_long) }.should raise_error(ArgumentError)
   end
 
   it "raises a RangeError when given integer is a Bignum" do
     -> { @object.call("cool", 999999999999999999999) }.should raise_error(RangeError)
+    -> { @object.call("", 999999999999999999999) }.should raise_error(RangeError)
   end
 
-  it "returns subclass instances" do
-    @object.call(MyString.new("cool"), 0).should be_an_instance_of(MyString)
-    @object.call(MyString.new("cool"), 1).should be_an_instance_of(MyString)
-    @object.call(MyString.new("cool"), 2).should be_an_instance_of(MyString)
+  it "works with huge long values when string is empty" do
+    @object.call("", max_long).should == ""
   end
 
-  it "always taints the result when self is tainted" do
-    ["", "OK", MyString.new(""), MyString.new("OK")].each do |str|
-      str.taint
-
-      [0, 1, 2].each do |arg|
-        @object.call(str, arg).tainted?.should == true
-      end
-    end
+  it "returns String instances" do
+    @object.call(MyString.new("cool"), 0).should be_an_instance_of(String)
+    @object.call(MyString.new("cool"), 1).should be_an_instance_of(String)
+    @object.call(MyString.new("cool"), 2).should be_an_instance_of(String)
   end
 
   it "returns a String in the same encoding as self" do
-    str = "\xE3\x81\x82".force_encoding Encoding::UTF_8
+    str = "\xE3\x81\x82".dup.force_encoding Encoding::UTF_8
     result = @object.call(str, 2)
     result.encoding.should equal(Encoding::UTF_8)
   end
 
-  platform_is wordsize: 32 do
+  platform_is c_long_size: 32 do
     it "raises an ArgumentError if the length of the resulting string doesn't fit into a long" do
       -> { @object.call("abc", (2 ** 31) - 1) }.should raise_error(ArgumentError)
     end
   end
 
-  platform_is wordsize: 64 do
+  platform_is c_long_size: 64 do
     it "raises an ArgumentError if the length of the resulting string doesn't fit into a long" do
       -> { @object.call("abc", (2 ** 63) - 1) }.should raise_error(ArgumentError)
     end
diff --git a/spec/ruby/shared/time/strftime_for_time.rb b/spec/ruby/shared/time/strftime_for_time.rb
index 49cd09051a..9f4d08d72e 100644
--- a/spec/ruby/shared/time/strftime_for_time.rb
+++ b/spec/ruby/shared/time/strftime_for_time.rb
@@ -170,4 +170,12 @@ describe :strftime_time, shared: true do
     time.strftime("%-k%p").should == "8AM"
     time.strftime("%-l%p").should == "8AM"
   end
+
+  it "should be able to show default Logger format" do
+    default_logger_format = "%Y-%m-%dT%H:%M:%S.%6N "
+    @new_time[2001, 2, 3, 4, 5, 6].strftime(default_logger_format).should == "2001-02-03T04:05:06.000000 "
+    @new_time[2001, 12, 3, 4, 5, 6 + 1/10r].strftime(default_logger_format).should == "2001-12-03T04:05:06.100000 "
+    @new_time[2001, 2, 13, 4, 5, 6 + 1/100r].strftime(default_logger_format).should == "2001-02-13T04:05:06.010000 "
+    @new_time[2001, 2, 3, 14, 5, 6 + 1/1000r].strftime(default_logger_format).should == "2001-02-03T14:05:06.001000 "
+  end
 end
diff --git a/spec/ruby/shared/time/yday.rb b/spec/ruby/shared/time/yday.rb
new file mode 100644
index 0000000000..f81c45261c
--- /dev/null
+++ b/spec/ruby/shared/time/yday.rb
@@ -0,0 +1,18 @@
+describe :time_yday, shared: true do
+  it 'returns the correct value for each day of each month' do
+    mdays = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+    yday = 1
+    mdays.each_with_index do |days, month|
+      days.times do |day|
+        @method.call(2014, month+1, day+1).should == yday
+        yday += 1
+      end
+    end
+  end
+
+  it 'supports leap years' do
+    @method.call(2016, 2, 29).should == 31 + 29
+    @method.call(2016, 3, 1).should == 31 + 29 + 1
+  end
+end
diff --git a/spec/ruby/shared/types/rb_num2dbl_fails.rb b/spec/ruby/shared/types/rb_num2dbl_fails.rb
new file mode 100644
index 0000000000..ec7cc11986
--- /dev/null
+++ b/spec/ruby/shared/types/rb_num2dbl_fails.rb
@@ -0,0 +1,17 @@
+#
+# Shared tests for rb_num2dbl related conversion failures.
+#
+# Usage example:
+#   it_behaves_like :rb_num2dbl_fails, nil, -> v { o = A.new; o.foo(v) }
+#
+
+describe :rb_num2dbl_fails, shared: true do
+  it "fails if string is provided" do
+    -> { @object.call("123") }.should raise_error(TypeError, "no implicit conversion to float from string")
+  end
+
+  it "fails if boolean is provided" do
+    -> { @object.call(true) }.should raise_error(TypeError, "no implicit conversion to float from true")
+    -> { @object.call(false) }.should raise_error(TypeError, "no implicit conversion to float from false")
+  end
+end
diff --git a/spec/ruby/spec_helper.rb b/spec/ruby/spec_helper.rb
index c38965d3c5..af1c385878 100644
--- a/spec/ruby/spec_helper.rb
+++ b/spec/ruby/spec_helper.rb
@@ -1,5 +1,5 @@
 use_realpath = File.respond_to?(:realpath)
-root = File.dirname(__FILE__)
+root = __dir__
 dir = "fixtures/code"
 CODE_LOADING_DIR = use_realpath ? File.realpath(dir, root) : File.expand_path(dir, root)
 
@@ -14,8 +14,7 @@ else
   end
 end
 
-# Running directly with ruby some_spec.rb
-unless ENV['MSPEC_RUNNER']
+unless ENV['MSPEC_RUNNER'] # Running directly with ruby some_spec.rb
   mspec_lib = File.expand_path("../../mspec/lib", __FILE__)
   $LOAD_PATH << mspec_lib if File.directory?(mspec_lib)
 
@@ -26,7 +25,14 @@ unless ENV['MSPEC_RUNNER']
     puts "Please add -Ipath/to/mspec/lib or clone mspec as a sibling to run the specs."
     exit 1
   end
+end
+
+# Compare with SpecVersion directly here so it works even with --unguarded
+if VersionGuard::FULL_RUBY_VERSION < SpecVersion.new('2.7')
+  abort "This version of ruby/spec requires Ruby 2.7+"
+end
 
+unless ENV['MSPEC_RUNNER'] # Running directly with ruby some_spec.rb
   ARGV.unshift $0
   MSpecRun.main
 end